"This is likely because muscles in men with greater body mass have more contractile tissue and strength, whereas in women with greater body mass more non-contractile adipose tissue is deposited within the muscle and hence cannot produce as much force," Culvenor said.
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The soreness is associated with temporary damage to muscle contractile proteins and/or the muscle sarcolemma.
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By every measure, these cells are much too young to be called heart cells and lack the key machinery that turns calcium pulses into contractile force.
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When sensors on its cell membrane detect good sources of nutrients, contractile networks of proteins (closely related to the ones found in human muscle) start pumping streams of cytoplasm in that direction, advancing the slime mold toward what it needs.
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They possess rudimentary contractile filaments, but contract relatively weakly compared to the cardiac contractile cells. The pacemaker cells are connected to neighboring contractile cells via gap junctions, which enable them to locally depolarize adjacent cells. Gap junctions allow the passage of positive cations from the depolarization of the pacemaker cell to adjacent contractile cells. This starts the depolarization and eventual action potential in contractile cells.
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The contractile vacuole has several structures attached to it in most cells, such as membrane folds, tubules, water tracts and small vesicles. These structures have been termed the spongiome; the contractile vacuole together with the spongiome is sometimes called the "contractile vacuole complex" (CVC). The spongiome serves several functions in water transport into the contractile vacuole and in localization and docking of the contractile vacuole within the cell. Paramecium and Amoeba possess large contractile vacuoles (average diameter of 13 and 45 µm, respectively), which are relatively comfortable to isolate, manipulate and assay.
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This predicted model is closely related to tropomyosin - a contractile protein.
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In hyperosmotic environments, less water will be expelled and the contraction cycle will be longer. The best understood contractile vacuoles belong to the protists Paramecium, Amoeba, Dictyostelium and Trypanosoma, and to a lesser extent the green alga Chlamydomonas. Not all species that possess a contractile vacuole are freshwater organisms; some marine, soil microorganisms and parasites also have a contractile vacuole. The contractile vacuole is predominant in species that do not have a cell wall, but there are exceptions (notably Chlamydomonas) which do possess a cell wall.
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Protist Paramecium aurelia with contractile vacuoles A contractile vacuole (CV) is a sub-cellular structure (organelle) involved in osmoregulation. It is found predominantly in protists and in unicellular algae. It was previously known as pulsatile or pulsating vacuole.
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The endoplasm contains food vacuoles, a granular nucleus, and a clear contractile vacuole.
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A cholekinetic drug is a pharmaceutical drug which increases the contractile power of the bile duct.
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Intermicrovillous space increases with contractile activity of myosin II and tropomyosin, and decreases when contraction ceases.
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Tensiomyography (TMG) is a measuring method for detection of skeletal muscles’ contractile properties.Dahmane, Raja, et al. "Evaluation of the ability to make non-invasive estimation of muscle contractile properties on the basis of the muscle belly response." Medical and biological engineering and computing 39.1 (2001): 51-55.
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Like many other protists, species of Amoeba control osmotic pressures with the help of a membrane-bound organelle called the contractile vacuole. Amoeba proteus has one contractile vacuole which slowly fills with water from the cytoplasm (diastole), then, while fusing with the cell membrane, quickly contracts (systole), releasing water to the outside by exocytosis. This process regulates the amount of water present in the cytoplasm of the amoeba. Immediately after the contractile vacuole (CV) expels water, its membrane crumples.
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Native records of contractile activity of the left ventricle of isolated rat heart perfused under Langendorff technique. Curve A - contractile function of the heart is greatly depressed after ischemia-reperfusion. Curve B - a set of short ischemic episodes (ischemic preconditioning) before prolonged ischemia provides functional recovery of contractile activity of the heart at reperfusion. The Langendorff heart or isolated perfused heart assay is an ex vivo technique used in pharmacological and physiological research using animals and also humans.
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Upon injection of acetylcholine, a slower contractile response, which is drastically under action potential threshold, is elicited.
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In many organisms, the force that drives furrow ingression is the assembly and contraction of actomyosin filaments that often form a contractile ring. The contractile ring is a very dynamic structure in which actomyosin filaments are continuously assembled and disassembled. The small GTPase RhoA has been shown to be implicated, controlling CR assembly and dynamics during cytokinesis. This GTPase cycles between an inactive GDP-bound form and an active GTP-bound form, and this RhoA flux seems important for contractile ring dynamics.
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Langendorff technique. Curve A - contractile function of the heart is greatly depressed after ischemia-reperfusion. Curve B - a set of short ischemic episodes (ischemic preconditioning) before prolonged ischemia provides functional recovery of contractile activity of the heart at reperfusion. Ischemia results in tissue damage in a process known as ischemic cascade.
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Subsequently, in 1967, Michael Ross studied the fine structure of these cells in mice and proved that the smooth muscle-like cells are contractile. He called them ‘’peritubular contractile cells’’. In 1969, Don Wayne Fawcett et al. termed these cells ‘’peritubular myoid cells’’, because of their similarities to smooth muscle cells.
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Abnormal expression of TRPV2 results in reduced shortening length, shortening rate, and lengthening rate which ultimately compromise cardiac contractile function.
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This makes the pumping of calcium out of the cell less efficient, which leads to a more forceful contraction of the heart. For individuals with weak hearts, it is sometimes provided to pump the heart with heavier contractile force. However, it can also cause hypertension because it increases the contractile force of the heart.
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The contractile vacuole, as its name suggests, expels water out of the cell by contracting. The growth (water gathering) and contraction (water expulsion) of the contractile vacuole are periodical. One cycle takes several seconds, depending on the species and the environment's osmolarity. The stage in which water flows into the CV is called diastole.
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Through evolution, the contractile vacuole has typically been lost in multicellular organisms, but it still exists in the unicellular stage of several multicellular fungi, as well as in several types of cells in sponges (amoebocytes, pinacocytes, and choanocytes). The number of contractile vacuoles per cell varies, depending on the species. Amoeba have one, Dictyostelium discoideum, Paramecium aurelia and Chlamydomonas reinhardtii have two, and giant amoeba, such as Chaos carolinensis, have many. The number of contractile vacuoles in each species is mostly constant and is therefore used for species characterization in systematics.
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Cardiac muscle There are two types of cardiac muscle cells: autorhythmic and contractile. Autorhythmic cells do not contract, but instead set the pace of contraction for other cardiac muscle cells, which can be modulated by the autonomic nervous system. In contrast, contractile muscle cells (cardiomyocytes) constitute the majority of the heart muscle and are able to contract.
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One forms as diffuse sheets, which are not contractile and either lack or contain very little ECM. The presence of this type of membrane does not usually affect retinal reattachment surgery. The retina can be reattached even with the membrane in place. The other type forms as very thick contractile membranes which pull at the retina.
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The AH domain of human anillin is essential for its interaction with RhoA. Depletion of RhoA halts contractile ring assembly and ingression, whereas, anillin depletion leads to a less severe phenotype when the contractile ring forms and ingresses partially. Depletion of anillin in Drosophila spermatocytes greatly reduces the localization of Rho and F-actin to equatorial regions.
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Excess in protons displaces calcium ions which is used within the fibers in activating the sarcomere, resulting in a reduced contractile force.
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The contraction of the contractile vacuole and the expulsion of water out of the cell is called systole. Water always flows first from outside the cell into the cytoplasm, and is only then moved from the cytoplasm into the contractile vacuole for expulsion. Species that possess a contractile vacuole typically always use the organelle, even at very hypertonic (high concentration of solutes) environments, since the cell tends to adjust its cytoplasm to become even more hyperosmotic than the environment. The amount of water expelled from the cell and the rate of contraction are related to the osmolarity of the environment.
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The myosin and actin are the contractile parts of continuous chains of tensile structures that stretch both across and between smooth muscle cells. The actin filaments of contractile units are attached to dense bodies. Dense bodies are rich in α-actinin, and also attach intermediate filaments (consisting largely of vimentin and desmin), and thereby appear to serve as anchors from which the thin filaments can exert force. Dense bodies also are associated with β-actin, which is the type found in the cytoskeleton, suggesting that dense bodies may coordinate tensions from both the contractile machinery and the cytoskeleton.
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Climacostomum virens The body is somewhat flexible but non-contractile, roughly ovoid or harp- shaped, and flattened from back to front. It has a large posterior contractile vacuole, and a characteristic posterior indentation (more pronounced in underfed individuals). The posterior vacuole surrounds the cytoproct (anus), through which food waste is eliminated. The macronucleus of Climacostomum virens is normally long and wormlike (vermiform).
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Langendorff technique. Curve A - contractile function of the heart is greatly depressed after ischemia-reperfusion. Curve B - a set of short ischemic episodes (ischemic preconditioning) before prolonged ischemia provides functional recovery of contractile activity of the heart at reperfusion. A study of aortic cross-clamping, a common procedure in cardiac surgery, demonstrated a strong potential benefit with further research ongoing.
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The ability of anillin to bind to and bundle actin together is conversed through many species. It is hypothesized that by regulating actin bundling, anillin increases the efficiency of actomyosin contractility during cell division. Both anillin and F-actin are found in contractile structures. They are recruited independently to the contractile ring, but F-actin increases the efficiency of anillin targeting.
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This feature is associated to a lack of contractile vacuoles in all loxodids. The term Loxodidae derives from the ancient greek (), meaning "oblique, tilted".
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The foetus may be compromised if there is prolonged delivery because of the non-contractile uterus; severe bleeding may cause hypovolemic shock in the mother.
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Removal of Ca2+ after contraction induces relaxation of the smooth muscle, and restores the molecular structure of the sarcoplasmic reticulum for the next contractile stimulus.
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Tissue was regenerated and the patch was well incorporated into the heart tissue. This is thought to be due, in part, to improved angiogenesis and reduction of inflammation. Although cardiomyocytes were produced from the mesenchymal stem cells, they did not appear to be contractile. Other treatments that induced a cardiac fate in the cells before transplanting had greater success at creating contractile heart tissue.
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At the cytokinesis furrow, it is the actin-myosin contractile ring that drives the cleavage process, during which cell membrane and wall grow inward, which eventually pinches the mother cell in two. The key components of this ring are the filamentous protein actin and the motor protein myosin II. The contractile ring assembles equatorially (in the middle of the cell) at the cell cortex (adjacent to the cell membrane). Rho protein family (RhoA protein in mammalian cells) is a key regulator of contractile ring formation and contraction in animal cells. The RhoA pathway promotes assembly of the actin-myosin ring by two main effectors.
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The piston is capable of repetitive and dramatic contractile motion; its function is not clear, but roles in locomotion, prey capture, and defense have been suggested.
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They also moderately reduce contractile forces of the atrial cardiac muscle, and reduce conduction velocity of the atrioventricular node (AV node). It also serves to slightly decrease the contractile forces of the ventricular muscle. M2 muscarinic receptors act via a Gi type receptor, which causes a decrease in cAMP in the cell, inhibition of voltage-gated Ca2+ channels, and increasing efflux of K+, in general, leading to inhibitory-type effects.
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Cross section through skeletal muscle and a small nerve at high magnification (H&E; stain) Muscle cells (myocytes) form the active contractile tissue of the body. Muscle tissue functions to produce force and cause motion, either locomotion or movement within internal organs. Muscle is formed of contractile filaments and is separated into three main types; smooth muscle, skeletal muscle and cardiac muscle. Smooth muscle has no striations when examined microscopically.
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In 1931, von Euler and Gaddum discovered substance P (SP) in horse brain and intestine. The substance showed strong vasodilatory effects and contractile activity on the rabbit gut. A great effort was put into purifying this substance from diverse mammalian tissue, but 30 years of research were without success. Nonmammalian peptides that elicited the same vasodilatory and contractile effects as SP were discovered by Erspamer in the early 1960s.
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On the other hand, probiotics have been shown to influence intestinal motility and sensory neurons as well as contractile activity of the intestine and to exert anti- inflammatory effects.
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Lubbockviruses are nonenveloped, with a head and tail. The head has a diameter of about 50 nm. The tail is around 110 nm long, and is flexible and contractile.
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These contractile cells respond to impulses of action potential from the pacemaker cells and are responsible for the contractions that pump blood through the body. The pacemaker cells make up just (1% of cells) and form the conduction system of the heart. They are generally much smaller than the contractile cells and have few of the myofibrils or myofilaments which means that they have limited contractibility. Their function is similar in many respects to neurons.
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In complex strabismus cases, toxin can be injected diagnostically as an aid to planning surgical treatment. The force exerted by a muscle is the sum of its contractile force (“active force”, controlled mostly by neural innervation) and its elastic force (“passive” force, determined stretching). Both are affected by muscle length, which determines the degree of stretch in a given eye position. Botulinum toxin paralysis reduces total muscle force by removing, or reducing, the contractile component.
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The contractile vacuole is a specialized type of vacuole that regulates the quantity of water inside a cell. In freshwater environments, the concentration of solutes is hypotonic, lesser outside than inside the cell. Under these conditions, osmosis causes water to accumulate in the cell from the external environment. The contractile vacuole acts as part of a protective mechanism that prevents the cell from absorbing too much water and possibly lysing (rupturing) through excessive internal pressure.
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The smallest known contractile vacuoles belong to Chlamydomonas, with a diameter of 1.5 µm. In Paramecium, which has one of the most complex contractile vacuoles, the vacuole is surrounded by several canals, which absorb water by osmosis from the cytoplasm. After the canals fill with water, the water is pumped into the vacuole. When the vacuole is full, it expels the water through a pore in the cytoplasm which can be opened and closed.
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Water has been shown in at least some species to enter the CV through aquaporins. Acidocalcisomes have been implied to work alongside the contractile vacuole in responding to osmotic stress. They were detected in the vicinity of the vacuole in Trypanosoma cruzi and were shown to fuse with the vacuole when the cells were exposed to osmotic stress. Presumably the acidocalcisomes empty their ion contents into the contractile vacuole, thereby increasing the vacuole's osmolarity.
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Climacostomum virens, from Alfred Kahl, 1932 Climacostomum virens has a flexible but non-contractile body, long, roughly ovoid or harp- shaped, and flattened from back to front. It has a large posterior contractile vacuole, and a characteristic posterior indentation, or dimple, that is more pronounced in underfed individuals. The posterior vacuole surrounds the cytoproct (anus), through which food waste is eliminated. The macronucleus of Climacostomum virens is normally long and wormlike (vermiform).
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The M2 muscarinic receptors are located in the heart, where they act to slow the heart rate down to normal sinus rhythm after positive stimulatory actions of the sympathetic nervous system, by slowing the speed of depolarization. They also reduce contractile forces of the atrial cardiac muscle, and reduce conduction velocity of the atrioventricular node (AV node). However, they have little effect on the contractile forces of the ventricular muscle, slightly decreasing force.
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The exact effects on the smooth muscle depend on the specific characteristics of the receptor activated—both parasympathetic input and sympathetic input can be either excitatory (contractile) or inhibitory (relaxing).
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As latrunculin inhibits actin polymerization and actomyosin contractile ability, exposure to latrunculin may result in cellular relaxation, expansion of drainage tissues and decreased outflow resistance in e.g. the trabecular meshwork.
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As contractile proteins are what cause muscles to contract and give them their physical strength, NASA concluded that isometrics may not be the best way for astronauts to maintain muscle tissue.
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Hapunaviruses are nonenveloped, with a head and tail. The head has a diameter of about 50 nm. The tail is around 260 nm long, has a small baseplate, and is contractile.
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Ultrastructural aspects of the somatic cortex and contractile vacuole of the ciliate Ichthyophtirius multifiliis. Journal of Protozoology 30: 481–490.Fox, D. P., J. M. Kuzava, and G. B. Chapman. 1987.
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Pericytes are also associated with endothelial cell differentiation and multiplication, angiogenesis, survival of apoptotic signals and travel. Certain pericytes, known as microvascular pericytes, develop around the walls of capillaries and help to serve this function. Microvascular pericytes may not be contractile cells, as they lack alpha-actin isoforms, structures that are common amongst other contractile cells. These cells communicate with endothelial cells via gap junctions, and in turn cause endothelial cells to proliferate or be selectively inhibited.
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Haloplasma contractile is a halophilic, cell wall-less bacterium. It is the only known representative of a deep lineage, and is classified in its own family (Haloplasmataceae) and order (Haloplasmatales), in the class Mollicutes. In terms of genetics, the bacterium Haloplasma contractile contains a dcwgene cluster is responsible for containing all the genes of the organism and promoting peptidoglycan synthesis. Also, MreB/Mbl are specific homologous parts of this bacterium that are vital in the contractility of the cell.
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They behave differently in different organisms and therefore it may be possible to design drugs that target acidocalcisomes in parasites but not those in the host. Acidocalcisomes have been implied in osmoregulation. They were detected in vicinity of the contractile vacuole in Trypanosoma cruzi and were shown to fuse with the vacuole when the cells were exposed to osmotic stress. Presumably the acidocalcisomes empty their ion contents into the contractile vacuole, thereby increasing the vacuole's osmolarity.
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Six years later, the anillin gene was cloned from cDNA originating from a Drosophila ovary. Staining with anti-anillin (Antigen 8) antibody showed the anillin localizes to the nucleus during interphase and to the contractile ring during cytokinesis. These observations agree with further research that found anillin in high concentrations near the cleavage furrow coinciding with RhoA, a key regulator of contractile ring formation. The name of the protein anillin originates from a Spanish word, anillo.
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Pain with active range of motion in one direction and pain with passive range of motion in the opposite direction signal contractile tissue dysfunction. Cyriax's papers are held at the Wellcome Library.
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After their release from the sarcoplasmic reticulum, calcium ions interact with contractile proteins that utilize ATP to shorten the muscle fiber. The sarcoplasmic reticulum plays a major role in excitation-contraction coupling.
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The uterus frequently contracts throughout the entire menstrual cycle, and these contractions have been termed endometrial waves or contractile waves. These appear to involve only the sub-endometrial layer of the myometrium.
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There are 9 structural proteins. The tail is non-contractile and has 6 short subterminal fibers. It is thick and rod-shaped and built of stacked disks. The maximum length is ~17 nm.
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As of 2007, two knockout mouse models for nebulin have been developed to better understand its in vivo function. Bang and colleagues demonstrated that nebulin-knockout mice die postnatally, have reduced thin filament length, and impaired contractile function. Postnatal sarcomere disorganization and degeneration occurred rapidly in these mice, indicating the nebulin is essential for maintaining the structural integrity of myofibrils. Witt and colleagues had similar results in their mice, which also died postnatally with reduced thin filament length and contractile function.
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During metaphase, the chromosomes line up using the spindle apparatus in the middle of the cell along the equatorial plate. The chromosomes move to opposite poles during anaphase and remain attached to the spindle fibers by their centromeres. Animal cell cleavage furrow formation is caused by a ring of actin microfilaments called the contractile ring, which forms during early anaphase. Myosin is present in the region of the contractile ring as concentrated microfilaments and actin filaments are predominant in this region.
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These contractile cells are connected by intercalated discs which allow a rapid response to impulses of action potential from the pacemaker cells. The intercalated discs allow the cells to act as a syncytium and enable the contractions that pump blood through the heart and into the major arteries. The pacemaker cells make up 1% of cells and form the conduction system of the heart. They are generally much smaller than the contractile cells and have few myofibrils which gives them limited contractibility.
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Tensiomyography is a simple to use selective and non-invasive method for detecting skeletal muscle contractile parameters using the linear displacement sensor.Šimunič, Boštjan. "TENSIOMYOGRAPHY–PAST AND FUTURE DIRECTIONS?." 7TH INTERNATIONAL SCIENTIFIC CONFERENCE ON KINESIOLOGY.
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Bi, E., P. Maddox, D. Lew, E. Salmon, J. McMillan, E. Yeh, and J. Pringle. (1998). Involvement of an Actomyosin Contractile Ring in Saccharomyces cerevisiae Cytokinesis. Journal Of Cell Biology. 142(5):1301–1312.
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Within the nucleus are permanently condensed chromosomes, which can easily be viewed under a light microscope. Just like other Euglenids, several species of Phacus also possess many contractile vacuoles and have a red- pigmented eyespot.
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3\. Antunes, A., et al. “A New Lineage of Halophilic, Wall-Less, Contractile Bacteria from a Brine-Filled Deep of the Red Sea.” Journal of Bacteriology, vol. 190, no. 10, July 2008, pp. 3580–3587.
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Contraction band necrosis is thought to arise by two mechanisms: #a calcium-dependent mechanism - activation of the contractile machinery of the cell via its usual mechanism, calcium, which is in excess due to ischemia. #a calcium-independent mechanism, as seen in rigor mortis - activation of the contractile machinery in the setting of low ATP. Reperfusion associated cell death has been modulated (reduced) in animal studies and is an area of active research, which holds the potential to significantly reduce the morbidity and mortality of cardiovascular disease.
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The contractile activity of smooth muscle cells is influenced by multiple inputs such as spontaneous electrical activity, neural and hormonal inputs, local changes in chemical composition, and stretch. This is in contrast to the contractile activity of skeletal muscle cells, which relies on a single neural input. Some types of smooth muscle cells are able to generate their own action potentials spontaneously, which usually occur following a pacemaker potential or a slow wave potential. These action potentials are generated by the influx of extracellular , and not .
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Many corms produce two different types of roots. Those growing from the bottom of the corm are normal fibrous roots, they are formed as the shoots grow, and are produced from the basal area at the bottom of the corm. The second type of roots are thicker layered roots that form as the new corms are growing, they are called contractile roots and they pull the corm deeper into the soil. In some species contractile roots are produced in response to fluctuating soil temperatures and light levels.
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In such species, once the corm is deep enough within the soil where the temperature is more uniform and there is no light, the contractile roots no longer grow and the corm is no longer pulled deeper into the soil. In some other species however, contractile roots seem to be a defence against digging animals and can bury the corm surprisingly deeply over the years. Wurmbea marginata is one example of a small plant that can be challenging to dig unharmed out of a hard, clayey hillside.
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He highlighted some chemical and functional similarities between the muscle fiber cells of the ventricle of the heart and the skeletal flexor muscles. He discovered that in the walls of atria there were less contractile fibers than elastic and fibrous tissue. This causes the tendency of this part of the heart to dilate itself more than undergo hypertrophy. Through experiments on frogs' and snails' hearts, he demonstrated the direct relationship between the volume of the blood in the heart chambers and the contractile energy.
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5-Oxo-ETE also stimulates contractile responses in fresh bronchi, cultured bronchi, and cultured lung smooth muscle taken from guinea pigs but in direct contrast to these studies is reported to relax bronchi isolated from humans. The latter bronchi contractile responses were blocked by cyclooxygenase-2 inhibition or a thromboxane A2 receptor antagonist and therefore appear mediated by 5-oxo-ETE-induced production of this thromboxane. In all events, the relaxing action of 5-oxo-ETE on human bronchi does not appear to involve OXER1.
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At the point of attachment between the long tail and the head there is a base plate where short pins are attached, a contractile sheath, and an internal core, similar to other bacteriophages in the Myoviridae.
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Cited by Howey. The protist usually has two macronuclei and a single micronucleus. Its entire cell body is covered with cilia arranged in spirals. It has two contractile vacuoles, one at each end of the body.
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Studies on turkeys have, nevertheless, shown that during SSC, a performance enhancement associated with elastic energy storage still takes place but it is thought that the aponeurosis could be a major source of energy storage (Roleveld et al., 1994). The contractile component itself has also been associated with the ability to increase contractile performance through muscle potentiation while other studies have found that this ability is quite limited and unable to account for such enhancements (Lensel and Goubel, 1987, Lensel-Corbeil and Goubel, 1990; Ettema and Huijing, 1989).
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The endoplasm of actinophryids is often darker and denser than the outer layer, and can sometimes be seen as a sharp boundary under a light microscope. The organisms can be either mononucleate, with a single, well defined nucleus in the center of the cell body, or multinucleate, with 10 or more nuclei dispersed throughout the organism. The cytoplasm of actinophryids is often granular, similar to that of Amoeba. Video of a contractile vacuole collapse in Actinosphaerium Contractile vacuoles are common in these organisms, who use them to maintain homeostasis and control buoyancy.
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Therefore, the pressure increase is slight until the organ is relatively full. The bladder's smooth muscle has some inherent contractile activity; however, when its nerve supply is intact, stretch receptors in the bladder wall initiate a reflex contraction that has a lower threshold than the inherent contractile response of the muscle. Action potentials carried by sensory neurons from stretch receptors in the urinary bladder wall travel to the sacral segments of the spinal cord through the pelvic nerves. Since bladder wall stretch is low during the storage phase, these afferent neurons fire at low frequencies.
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The muscles responsible for accelerating the runner forward are required to contract with increasing speed to accommodate the increasing velocity of the body. During the acceleration phase of sprinting, the contractile component of muscles is the main component responsible for the power output. Once a steady state velocity has been reached and the sprinter is upright, a sizable fraction of the power comes from the mechanical energy stored in the ‘series elastic elements’ during stretching of the contractile muscles that is released immediately after the positive work phase.Cavagna, Giovanni A., L. Komarek, and Stefania Mazzoleni.
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Reports of human iPSC models of sarcomeric cardiomyopathies showed cellular hypertrophy in most of the cases, including one with the c.2995_3010del MYBPC3 mutation that exhibited in addition to hypertrophy contractile variability in the presence of endothelin-1.
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After being induced by SREBP-1, BHLHE41 and BHLHE40 have been shown to repress myogenesis by blocking MYOD1 transcription. BHLHE40 and BHLHE41 are also known to alter the expression of several contractile proteins and mitochondrial proteins in skeletal muscle.
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In the circulatory system the haemolymph circulates as follows: mantle → nephridium or nephridia → heart. These slugs breathe using a pallial lung. They have a contractile pneumostome.Barker G. M. (2001) Gastropods on Land: Phylogeny, Diversity and Adaptive Morphology. 1-146.
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Hymenophyllum contractile is a species of fern in the family Hymenophyllaceae. It is endemic to Ecuador. Its natural habitats are subtropical or tropical moist lowland forests and subtropical or tropical moist montane forests. It is threatened by habitat loss.
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Different cells and organisms have adapted different ways of preventing cytolysis from occurring. For example, the paramecium uses a contractile vacuole, which rapidly pumps out excessive water to prevent the build-up of water and the otherwise subsequent lysis.
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Vorticella is a genus of bell-shaped ciliates that have stalks to attach themselves to substrates. The stalks have contractile myonemes, allowing them to pull the cell body against substrates. The formation of the stalk happens after the free-swimming stage.
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Adherens junctions were, for many years, thought to share the characteristic of anchor cells through their cytoplasmic actin filaments. Adherens junctions may serve as a regulatory module to maintain the actin contractile ring with which it is associated in microscopic studies.
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Other protists, such as Amoeba, have CVs that move to the surface of the cell when full and undergo exocytosis. In Amoeba contractile vacuoles collect excretory waste, such as ammonia, from the intracellular fluid by both diffusion and active transport.
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Zallen, J., and Wieschaus, E. (2004). Patterned gene expression directs bipolar planar polarity in Drosophila. Dev. Cell 6, 343–355. One mechanism by which Myosin II might promote polarized cell remodeling is through contractile activity that creates tension orienting junctional disassembly.
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Uterine smooth muscle mechanisms of relaxation differ significantly from those of other human smooth muscles. Removal of Ca2+ after contraction induces relaxation of the smooth muscle, and restores the molecular structure of the sarcoplasmic reticulum for the next contractile stimulus.
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The number of action potentials during the plateau of a particular BER slow wave can vary. This variation in action potential generation does not impact the frequency of waves through the GI tract, only the strength of those contractile waves.
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Like in other ciliates, a contractile vacuole maintains osmotic balance for the cell, and allows it to survive the salt concentrations in both marine and brackish water. The vacuole is located in Z. niveum directly below the lip of the peristome.
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Regardless of the pathway, as the impulse reaches the atrioventricular septum, the connective tissue of the cardiac skeleton prevents the impulse from spreading into the myocardial cells in the ventricles except at the atrioventricular node. The electrical event, the wave of depolarization, is the trigger for muscular contraction. The wave of depolarization begins in the right atrium, and the impulse spreads across the superior portions of both atria and then down through the contractile cells. The contractile cells then begin contraction from the superior to the inferior portions of the atria, efficiently pumping blood into the ventricles.
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This sustained phase has been attributed to certain myosin crossbridges, termed latch-bridges, that are cycling very slowly, notably slowing the progression to the cycle stage whereby dephosphorylated myosin detaches from the actin, thereby maintaining the force at low energy costs. This phenomenon is of great value especially for tonically active smooth muscle. Isolated preparations of vascular and visceral smooth muscle contract with depolarizing high potassium balanced saline generating a certain amount of contractile force. The same preparation stimulated in normal balanced saline with an agonist such as endothelin or serotonin will generate more contractile force.
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Cardiac-specific overexpression of constitutively-active PKCε (9-fold increase in PKCε protein, 4-fold increase in activity) induced cardiac hypertrophy characterizes by enhanced anterior and posterior left ventricular wall thickness. A later study unveiled that the aging of PKCε transgenic mice brought on dilated cardiomyopathy and heart failure by 12 months of age,] characterized by a preserved Frank-Starling mechanism and exhausted contractile reserve. Crossing PKCε transgenic mice with mutant cTnI mice lacking PKCε phosphorylation sites (Serine-43/Serine-45 mutated to Alanine) attenuated the contractile dysfunction and hypertrophic marker expression, offering critical mechanistic insights.
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As PTMs became better characterized, the associated nomenclature underwent a series of changes. In very early literature these cells may be referred to as ‘modified connective tissue cells’ or ‘interlamellar cells’. Subsequent experiments resulted in renaming these cells to better reflect their contractile nature. The term ‘peritubular contractile cells’ was first used in 1967. In 1969, Don Fawcett labelled these cells as ‘peritubular myoid cells’. ‘Peritubular’ refers to their anatomical location: adjacent to the seminiferous tubule. ‘Myoid’ stems from the Greek ‘myo’ (/ˈmʌɪəʊ/), which means relating to muscle. (PTMs resemble smooth muscle cells under an electron microscope).
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Spirostomum is a genus of free-living ciliate protists, belonging to the class Heterotrichea. Species of Spirostomum are found in both salt and fresh water. All are elongated, flexible and highly contractile. Although unicellular, members of some species can grow as long as .
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Tensiomyography assesses muscle mechanical response based on radial muscle belly displacement induced by a single electrical stimulus.Tous-Fajardo, Julio, et al. "Inter-rater reliability of muscle contractile property measurements using non-invasive tensiomyography." Journal of Electromyography and Kinesiology 20.4 (2010): 761-766.
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It assesses skeletal muscle thickeningPišot, Rado, et al. "Whole muscle contractile parameters and thickness loss during 35-day bed rest." European journal of applied physiology 104.2 (2008): 409-414. and low frequency lateral oscillations of active skeletal muscle fibers during twitch contractions.
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This escape mechanism requires a cytoskeleton regulator from the host plus an intact mycobacterial ESX-1 secretion system. Ejectosomes apparently exert a contractile force, forming a tight septum around the bacteria. Ejection of the bacteria occurs without host cell lysis.Hagedorn, M. et al.
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Each cell consists of a cell body from which 4-8 processes radiate and embrace the secretory unit. Myoepithelial cells have contractile functions. They help in expelling secretions from the lumen of secretory units and facilitate the movement of saliva in salivary ducts.
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The expression of CNN1 is specific to differentiated mature smooth muscle cells, suggesting a role in contractile functions. Calponin 1 is up-regulated in smooth muscle tissues during postnatal development with a higher content in phasic smooth muscle of the digestive tract.
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Extraglomerular mesangial cells are located in the junction between the afferent and efferent arterioles. These cells have a contractile property similar to vascular smooth muscles and thus play a role in “regulating GFR” by altering the vessel diameter. Renin is also found in these cells.
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The cell body is lens-shaped or half spherical when mature with two flagella. The chloroplast is dish- or bowl-shaped. Pyrenoids may be present or absent, the stigma large. The nucleus is centrally located and there may be 4 to 8 contractile vacuoles.
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The virus has a polyhedral head with a diameter of around 61 nm. The contractile tail is 100 nm long, and is attached to the head via a tail capital. The neck region bears fibres. The mature virus particle contains at least 19 proteins.
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There is a distinctly different electrical pattern involving the contractile cells. In this case, there is a rapid depolarization, followed by a plateau phase and then repolarization. This phenomenon accounts for the long refractory periods required for the cardiac muscle cells to pump blood effectively before they are capable of firing for a second time. These cardiac myocytes normally do not initiate their own electrical potential, although they are capable of doing so, but rather wait for an impulse to reach them. Contractile cells demonstrate a much more stable resting phase than conductive cells at approximately −80 mV for cells in the atria and −90 mV for cells in the ventricles.
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An efferent lymph vessel may directly drain into one of the (right or thoracic) lymph ducts, or may empty into another lymph node as its afferent lymph vessel. Both the lymph ducts return the lymph to the blood stream by emptying into the subclavian veins The functional unit of a lymph vessel is known as a lymphangion, which is the segment between two semilunar valves. Since it is contractile, depending upon the ratio of its length to its radius, it can act either like a contractile chamber propelling the fluid ahead, or as a resistance vessel tending to stop the lymph in its place.
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Lilliodeae genera are relatively homogeneous and distinct from the other two Liliaceae subfamilies (Calochortoideae and Streptopoideae). They are perennial herbaceous flowering plants that are mainly bulbous (Lilieae) with contractile roots, but may be rhizomatous (Medeoleae). Stems unbranched, leaves with parallel venation. Flowers are large and showy.
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The dead heart muscle is replaced by non- contractile fibrotic tissue, forming the myocardial scar. Scar tissue does not contract, and it does not help the heart pump blood. This persistently stresses the heart and increases the workload of the lasting myocardium as measured by MVO2.
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Haraldsson et al. The additive pulmonary vasodilatory effect of inhaled prostacyclin and inhaled milrinone in postcardiac surgical patients with pulmonary hypertension. Aesth Analg 2001;93:1439-45 Also, by causing the buildup of cAMP in the myocardium, Milrinone increases contractile force, heart rate and the extent of relaxation.
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The functional unit of a muscle fiber is called a sarcomere. Each myofiber is composed of actin and myosin myofibrils repeated as a sarcomere. Based on their contractile and metabolic phenotypes, skeletal muscle can be classified as slow-oxidative (Type I) or fast-oxidative (Type II).
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An example of a low [K+] low [Na+] solution is histidine-tryptophan- ketoglutarate. Conversely, increasing extracellular Ca2+ concentration enhances contractile force. Elevating Ca2+ concentration to a high enough level results in cardiac arrest in systole. This unfortunate irreversible event is referred to as "stone-heart" or rigor.
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Preload recruitable stroke work. During heart failure, myocardial contractility is reduced, which decreases the slope of the PRSW relationship. Recent studies also indicate that the volume axis intercept of the PRSW relationship (not the slope) may be a better indicator of the severity of contractile dysfunction.
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The T5 virion includes a 90 nanometer icosahedral capsid (head) and a 250 nanometer-long flexible, non-contractile tail. The capsid contains the phage's 121750 base pair, double-stranded DNA genome.Effantin G. et al.: Bacteriophage T5 structure reveals similarities with HK97 and T4 suggesting evolutionary relationships.
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Vorticella has an anterior peristomial lip which is short and narrow. An outward-curving peristomial disc is associated with the peristome. The peristomial disc, which may have ringed ridges or undulations, encloses rows of cilia. The contractile peristomal border closes over the disc and cilia during retraction of Vorticella.
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Excavated, hollowed out. Conchiolin. Conic. Shaped like a cone. Connective. A part connecting two other parts, as a muscle connecting two parts of the body, or a nerve connecting two ganglia. Constricted. Narrowed. Contractile. Capable of being contracted or drawn in, as the tentacle of a snail. Convex.
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An isolate of Erythropsidinium. The arrow indicates the piston; the double arrowhead indicates the ocelloid. Scale bar 20 µm. A piston (also known as a dart, prod, or tentacle) is a complex contractile organelle found in some dinoflagellates, namely the Erythropsidinium and Greuetodinium genera of the family Warnowiaceae.
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Strength training (resistance training) causes neural and muscular _adaptations_ which increase the capacity of an athlete to exert force through voluntary muscular contraction: After an initial period of neuro-muscular adaptation, the muscle tissue expands by creating sarcomeres (contractile elements) and increasing non-contractile elements like sarcoplasmic fluid. Muscular hypertrophy can be induced by progressive overload (a strategy of progressively increasing resistance or repetitions over successive bouts of exercise in order to maintain a high level of effort). However, the precise mechanisms are not clearly understood; currently accepted hypotheses involve some combination of mechanical tension, metabolic fatigue, and muscular damage. Muscular hypertrophy plays an important role in competitive bodybuilding and strength sports like powerlifting, football and Olympic weightlifting.
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Synemin is an intermediate filament (IF) and, like other IFs, primarily functions to integrate mechanical stress and maintain structural integrity in eukaryotic cells. While it has been observed in a variety of cell types, it has been best studied in the sarcomere of skeletal myocytes. It localizes at the Z-disk and has been shown to bind to α-dystrobrevin, α-actinin, and desmin to act as a mechanical linker in transmitting force laterally throughout the tissue, especially between the contractile myofibrils and extracellular matrix. Synemin contributes to linkage between costameres and the contractile apparatus in skeletal muscle of synemin null animals.. Synemin plays an important regulatory role in the heart and the consequences of its absence are profound.
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The stalk will finish growing in several hours. The stalk is made up of the spasmoneme, a contractile organelle, with rigid rod filaments, batonnets, surrounding it. The coiled spasmoneme and batonnets serve as a molecular spring, so that Vorticella can contract. The cell body can move hundreds of micrometers in milliseconds.
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A fossil Vorticella has been discovered inside a leech cocoon dating to the Triassic period, ca. 200 million years ago. The fossil was recovered from the Section Peak Formation at Timber Peak in East Antarctica, and has a recognizable peristome, helically-contractile stalk, and C-shaped macronucleus, like modern Vorticella species.
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Cystometry, also known as flow cystometry, is a clinical diagnostic procedure used to evaluate bladder function. Specifically, it measures contractile force of the bladder when voiding. The resulting chart generated from cystometric analysis is known as a cystometrogram (CMG), which plots volume of liquid emptied from bladder against intravesical pressure.
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As the fetal hypothalmus matures, activation of the HPA axis (hypothalmic- pituitary-adrenal axis) initiates labour though two hormonal mechanisms. The end pathway of both mechanisms leads to myometrial contractions a mechanical cause of placental separation, from the shear force, contractile and involution changes in the uterus distorting the placentome.
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The body of an organism is elongated and ovoided. It has a curved anterior apex that is over the peristome. It has a cytostome which is a two-layered undulating membrane, on the right front edge, and also contractile vacuole with cytopyge terminal. It is either brown or rose-coloured.
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Muscles are bundles of contractile fibers that are attached to bones by tendons. These bundles have different types of fibers within them, and horses have adapted over the years to produce different amounts of these fibers. "What Makes a Quarter Horse Different from a Thoroughbred"?] Tufts Cummings School of Veterinary Medicine.
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The peristome ranges from 55-75 μm in diameter. The rod-like, contractile stalk - the "spasmoneme" - is 25-300 μm long and 4 μm wide. It can collapse into a tightly coiled helix in less than 1/60th of a second.Bras, R., A. Upadhyaya, A. van Oudenaarden & C. Ortiz 2002.
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This neural training can cause several weeks of rapid gains in strength, which level off once the nerve is generating maximum contractions and the muscle reaches its physiological limit. Past this point, training effects increase muscular strength through myofibrillar or sarcoplasmic hypertrophy and metabolic fatigue becomes the factor limiting contractile force.
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Sketch of Collodictyon. The species in this genus range in size from 30 to 50 µm in length, can grow broad pseudopodia, and have four flagella and a ventral feeding groove or sulcus. They are devoid of cellulosic cell walls, chloroplasts or stigmata. There are two to several contractile vacuoles.
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Tropomyosin alpha-1 chain is a protein that in humans is encoded by the TPM1 gene. This gene is a member of the tropomyosin (Tm) family of highly conserved, widely distributed actin-binding proteins involved in the contractile system of striated and smooth muscles and the cytoskeleton of non- muscle cells.
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The failure to activate satellite cells upon injury or exercise is also thought to contribute to the pathophysiology of sarcopenia. Additionally, oxidized proteins can lead to a buildup of lipofuscin and cross-linked proteins causing an accumulation of non- contractile material in the skeletal muscle and contribute to sarcopenic muscle.
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When the cell enters mitosis, Cdr2 is distributed diffusely through the cytoplasm; there is no detectable cortical band in metaphase in anaphase. During septation at the end of anaphase, Cdr2 localizes to the contractile ring. After cytokinesis, Cdr2 is again distributed in a broad medial band centered on the nucleus.
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Contractile vacuoles are located between or beside the macronucleus and vestibule. The oral cilia contain the adoral zone of membranelles (AZM), which are compound ciliary organelles. The paroral membrane consists of a row of paired cilia. The cytostome has the AZM on one side and the paroral membrane on the other side.
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In 2004, a chemical known as blebbistatin was shown to inhibit the formation of blebs. This agent was discovered in a screen for small molecule inhibitors of nonmuscle myosin IIA and was shown to lower the affinity of myosin with actin, thus altering the contractile forces that impinge on the cytoskeleton-membrane interface.
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Gymnodoris subflava is a small size sea slug, it can reach a maximum size of 2,5 cm in length. Its stretched body is characterized by its bright yellow body color letting appear through its flanks the dark mass of its viscera especially close to the branchial plume. Its rhinophores and gills are contractile.
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The surface of the cell is uniformly covered with cilia arranged in longitudinal rows. The body may taper at the back end, forming something like a tail. Multiple contractile vacuoles lie in a row along the dorsal surface. Most Dileptus are colourless, but two nominal species carry symbiotic green algae in their cytoplasm.
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The pathophysiology of cardiomyopathies is better understood at the cellular level with advances in molecular techniques. Mutant proteins can disturb cardiac function in the contractile apparatus (or mechanosensitive complexes). Cardiomyocyte alterations and their persistent responses at the cellular level cause changes that are correlated with sudden cardiac death and other cardiac problems.
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Aagaard P, Andersen J, Dyhre-Poulsen P, Leffers A, Wagner A, Magnusson SP, Halkjaer-Kristensen J, Simonsen E. A mechanism for increased contractile strength of human pennate muscle in response to strength training: changes in muscle architecture. J of Physiol. 2001, 534.2: 613-623. A 2001 study, conducted by Aagaard et al.
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Mononucleated myoblasts can later fuse to form multinucleated myotubes under low serum conditions or starvation, leading to the precursors of contractile skeletal muscle cells in the process of myogenesis. C2C12 cells are used to study the differentiation of myoblasts, osteoblasts, and myogenesis, to express various target proteins, and to explore mechanistic biochemical pathways.
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Some protists do not have cell walls and cannot experience turgor pressure. These few protists are ones that use their contractile vacuole to regulate the quantity of water within the cell. Protist cells avoid lysing in solutions by utilizing a vacuole which pumps water out of the cells to maintain osmotic equilibrium.
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Just beneath the membranes of the cortex, the body shape of Halteria is stabilized by microtubules in a basket configuration. Within Halteria cells, a contractile vacuole is located approximately midway between the anterior and posterior ends of the cell. The mitochondria of Halteria are usually spherical with tubular cristae.Yamataka, S., & Hayashi, R. (1970).
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The leaflets are covered with a dense layer of silver hairs, angled forward at 70-80°. The basal leaflets are reduced to spines, similar to Cycas revoluta. The taproot is contractile, and tends to pull crown downwards. The female cones are open, with sporophylls 17–24 cm long, densely red-brown tomentose.
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Increasing evidence suggests that pericytes can regulate blood flow at the capillary level. For the retina, movies have been published showing that pericytes constrict capillaries when their membrane potential is altered to cause calcium influx, and in the brain it has been reported that neuronal activity increases local blood flow by inducing pericytes to dilate capillaries before upstream arteriole dilation occurs. This area is controversial, with a recent study claiming that pericytes do not express contractile proteins and are not capable of contraction in vivo, although the latter paper has been criticised for using a highly unconventional definition of pericyte which explicitly excludes contractile pericytes. It appears that different signaling pathways regulate the constriction of capillaries by pericytes and of arterioles by smooth muscle cells.
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This can lower the sensitivity of contractile apparatus to calcium ions (Ca2+) but also has the effect of increasing cytoplasmic Ca2+ concentration through an inhibition of the chemical pump that actively transports calcium out of the cell. This counters inhibiting effects of potassium ions (K+) on muscular action potentials. Lactic acid also has a negating effect on the chloride ions in the muscles, reducing their inhibition of contraction and leaving K+ as the only restricting influence on muscle contractions, though the effects of potassium are much less than if there were no lactic acid to remove the chloride ions. Ultimately, it is uncertain if lactic acid reduces fatigue through increased intracellular calcium or increases fatigue through reduced sensitivity of contractile proteins to Ca2+.
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Cardiac glycosides have long served as the main medical treatment to congestive heart failure and cardiac arrhythmia, due to their effects of increasing the force of muscle contraction while reducing heart rate. Heart failure is characterized by an inability to pump enough blood to support the body, possibly due to a decrease in the volume of the blood or its contractile force. Treatments for the condition thus focus on lowering blood pressure, so that the heart does not have to exert as much force to pump the blood, or directly increasing the heart's contractile force, so that the heart can overcome the higher blood pressure. Cardiac glycosides, such as the commonly used digoxin and digitoxin, deal with the latter, due to their positive inotropic activity.
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This can lower the sensitivity of contractile apparatus to Ca2+ but also has the effect of increasing cytoplasmic Ca2+ concentration through an inhibition of the chemical pump that actively transports calcium out of the cell. This counters inhibiting effects of potassium on muscular action potentials. Lactic acid also has a negating effect on the chloride ions in the muscles, reducing their inhibition of contraction and leaving potassium ions as the only restricting influence on muscle contractions, though the effects of potassium are much less than if there were no lactic acid to remove the chloride ions. Ultimately, it is uncertain if lactic acid reduces fatigue through increased intracellular calcium or increases fatigue through reduced sensitivity of contractile proteins to Ca2+.
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Between 1914 and 1915, Maestrini took part in a big scientific debate. Through experiments on the heart of snails and with a series of 19 observations on frog's heart, he was able to demonstrate the direct relationship between the volume of blood contained in the heart cavities and the contractile energy of the heart and consequently how, within certain limits, the lengthening of the heart fibers, cause of the dilatation of the heart, corresponds to a greater contractile energy. So he formulated his "Law of the Heart", challenging with valid arguments the conception of those who identified in the dilatation of the heart only a pathological event. Three years later, in 1918, Ernest Starling came at the same conclusions, publishing in London ″The law of the heart″.
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It is also hoped that recent findings from TFM will contribute to the design of optimal scaffolds for tissue engineering and regeneration of the peripheral nervous system, artery grafts,George, J. C., et al. "The contractile strength of vascular smooth muscle myocytes is shape dependent." Integrative Biology 6.2 (2014): 152-163. and epithelial skin cells.
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The late cicatricial phase of ARN includes changes in the way the vitreous is organized due to the cellular infiltration seen in the previous phase. In the vitreous and on top of the thinned necrotic retina, contractile membranes may form. Majority of patients with ARN will experience detachment of their retina in the affected eye.
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One is shorter and curled and the other one is longer and straight. The two flagella are fixed to the cell by four unique microtubular roots. In addition, the flagella are lined with small hairs that allow for better movement. There are also contractile vacuoles that control the flow of water in and out.
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It allows the examination of cardiac contractile strength and heart rate without the complications of an intact animal or human.Bell, R., Mocanu, M. & Yellon, D. Retrograde heart perfusion: The Langendorff technique of isolated heart perfusion. Journal of Molecular and Cellular Cardiology 50, 940-950 (2011). After 90 years this method is still being used.
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Beta-actin (human gene and protein abbreviation ACTB/ACTB) is one of six different actin isoforms which have been identified in humans. This is one of the two nonmuscle cytoskeletal actins. Actins are highly conserved proteins that are involved in cell motility, structure and integrity. Alpha actins are a major constituent of the contractile apparatus.
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The ZASP gene is located at chromosome 10, and encodes also-called Z-disk-associated protein.Mutation in this protein causes disintegration of the Z-disk of contractile elements (myofibrils) in muscle cells. Mutations of several other Z-disk related proteins, such as desmin, alfa-B-crystallin and myotilin can cause disorders similar to zaspopathy.
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When ingested, pulegone targets the liver and kidney, among other organs. Studies have been conducted on rats show that one of the main effects is the inhibition of contractile activity in the myometrium and death by kidney failure. Also found in the study, long term exposure to pennyroyal increased incidences of urinary bladder tumors.
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A contractile vacuole, often quite large, is located in the posterior. The Macronuclei can take a variety of forms. Depending on species and phase of life, they may be rod- shaped, ovoid, spherical, or moniliform (like a rosary, or string of beads). Blepharisma americanum swimming in a drop of pond water, with other microorganisms.
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3D rendering of a skeletal muscle fiber Skeletal muscle fibers show sarcomeres clearly. Muscle fibers are the individual contractile units within a muscle. A single muscle such as the biceps brachii contains many muscle fibers. Another group of cells, the myosatellite cells are found between the basement membrane and the sarcolemma of muscle fibers.
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With a pH of 6.4, there will be no glycolysis process existed, thus no energy will be produced. Higher concentration of H+ will also cause the loss of contractile force through the misplacement of calcium in muscle fiber, the misplacement of calcium in muscle fiber will disturb the formation of actin-myosin cross-bridge.
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This is due to there being the possibility of an asymmetric division. This as a result leads to cytokinesis producing unequal daughter cells containing completely different amounts or concentrations of fate- determining molecules. In animals the cytokinesis ends with formation of a contractile ring and thereafter a cleavage. But in plants it happen differently.
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Contractile vacuoles ("stars") were first observed by Spallanzani (1776) in protozoa, although mistaken for respiratory organs. Dujardin (1841) named these "stars" as vacuoles. In 1842, Schleiden applied the term for plant cells, to distinguish the structure with cell sap from the rest of the protoplasm. In 1885, de Vries named the vacuoule membrane as tonoplast.
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This is a fleshy, leathery plant growing from a small caudex with thin, corky roots. Unlike most ferns, S. multifidum has contractile roots, which are thought to help anchor the plant in the soil. It produces a single leaf which emerges directly from the ground. It is divided into a sterile and a fertile part.
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The trophozoites also contained tubular mitochondrial cristae, and a large contractile vacuole. All of these characteristics are distinguishing features of the genus Sappinia. The medical team sent the sample to the CDC, who confirmed that these characteristics do not coincide with any previously known pathogenic amoebae in humans. The patient was treated with several antimicrobials and recovered completely.
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The actual mechanism of septation of the outflow tract is poorly understood, but is recognized as a dynamic process with contributions from contractile, hemodynamic, and extracellular matrix interactions. Misalignment of the septum can cause the congenital heart conditions tetralogy of Fallot, persistent truncus arteriosus, dextro- Transposition of the great arteries, tricuspid atresia, and anomalous pulmonary venous connection.
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The cell body contains a contractile vacuole, a single large food vacuole, and several small granules. Also present is various numbers of mitochondria with flat shaped cristae. The periphery of the cell body is lined with extrusomes, and consists of an internal capsule that discharges and catches prey. Kraken has the ability to encyst when dormant.
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Bacteriophage P2, scientific name Escherichia virus P2, is a temperate phage that infects E. coli. It is a tailed virus with a contractile sheath and is thus classified in the genus Peduovirus (formerly P2likevirus), subfamily Peduovirinae, family Myoviridae within order Caudovirales. This genus of viruses includes many P2-like phages as well as the satellite phage P4.
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The bulb lies dormant after the leaves and flower stem die back and has contractile roots that pull it down further into the soil. The flower stem and leaves form in the bulb, to emerge the following season. Most species are dormant from summer to late winter, flowering in the spring, though a few species are autumn flowering.
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During the process, myocardial cells are stretched and stressed to produce new contractile elements. In colliquative myocytolysis, fluids accumulated within the cell dissolve myofibrils, resulting in vacuolization of the cell. It is considered an indicator of acute myocardial ischemia and can be used to confirm ischemia in the absence of other indicators of cause of death.
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Phage Mu is nonenveloped, with a head and a tail. The head has an icosahedral structure of about 54 nm in width. The neck is knob-like, and the tail is contractile with a base plate and six short terminal fibers. The genome has been fully sequenced and consists of 36,717 nucleotides, coding for 55 proteins.
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The genus is characterized by having large leaves and deep root systems with contractile roots used for changing the plant's level with the ground. Symplocarpus species grow from a rhizome and their leaves release a foul odor when crushed.Flora of North America Vol. 22, Symplocarpus foetidus (Linnaeus) Salisbury ex W. P. C. Barton, Veg. Mater. Med.
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It has a Golgi apparatus near the nucleus, mitochondria just inside the cell membrane (sarcolemma), and a smooth endoplasmic reticulum (specialized for muscle function and called the sarcoplasmic reticulum). While sarcoplasm and myoplasm, viewed etymologically, might seem to be synonyms, they are not. Whereas sarcoplasm is a type of cytoplasm, myoplasm is the entire contractile portion of muscle tissue.
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Carbetocin is to be used in the hospital by prescription only. It can be administered intravenously or intramuscularly. In both cases, the recommended dose for an average adult female is 100ug. Contractile effects of the uterus are apparent within two minutes and can be observed for approximately one hour, though maximum binding occurs about 30 minutes after intramuscular injection.
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Catecholamines levels increase due to increased sympathetic nervous system activity. Catecholamines can act on the alpha- adrenergic receptors and beta-adrenergic receptors which are G-protein coupled receptors. This binding initiates the same intracellular signalling pathways as angiotensin and endothelin. There is also activation of cAMP and an increase in intracellular Ca2+ which leads to contractile dysfunction and fibrosis.
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The message filters down to alter the pattern of gene expression. The additional contractile proteins appear to be incorporated into existing myofibrils (the chains of sarcomeres within a muscle cell). There appears to be some limit to how large a myofibril can become: at some point, they split. These events appear to occur within each muscle fiber.
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The first group is LPP, which belongs to the cyanopodoviruses. This group of viruses includes the original cyanophage isolate that infected "blue-green algae". Cyanophages in this group are easy to isolate from the environment. They carry short non-contractile tails and cause lysis of several species within three genera of cyanobacteria: Lyngbya, Plectonema and Phormidium.
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Tentaculata is a class of comb jellies. The common feature of this class is a pair of long, feathery, contractile tentacles, which can be retracted into specialised ciliated sheaths. In some species, the primary tentacles are reduced and they have smaller, secondary tentacles. The tentacles have colloblasts, which are sticky-tipped cells that trap small prey.
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Mitel Cédric, Corolla Jean-Pierre, Warren Lindsay, Leon Virginie, (2015) Goniobranchus fidelis (Kelaart, 1858). in : DORIS, 8/2/2015 The rhinophores are laminated, contractile and greyish in color with lighter colour at the tip. The shade of grey varies from one individual to another. The gills are the same colour as the rhinophores and they are retractable.
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The over expression of GRK2ct has been shown to significantly rescue cardiac function in murine models of heart failure by blocking Gβγ subunit signalling. In another study, biopsies were taken from patients with heart failure and virally induced overexpression of GRK2ct in the heart myocytes. Other tests showed an improvement in cardiac cell contractile function by inhibiting Gβγ.
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Holothuria hilla is a species of sea cucumber in the subgenus Mertensiothuria of the genus Holothuria. Some common names include the contractile sea cucumber, the sand sifting sea cucumber and the tigertail sea cucumber, and in Hawaii it is known as the light spotted sea cucumber. It is found in the Indo- Pacific region and the Red Sea.
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Peroxisomes are used to break down peroxide, which is otherwise toxic. Many protozoans have contractile vacuoles, which collect and expel excess water, and extrusomes, which expel material used to deflect predators or capture prey. In higher plants, most of a cell's volume is taken up by a central vacuole, which mostly contains water and primarily maintains its osmotic pressure.
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Opalina is a genus of parasitic heterokonts found in the intestines of frogs and toads. They lack mouths and contractile vacuoles, they are covered with nearly equal flagelliform cilia, and they have numerous nuclei, all similar. All the species are obligate endosymbionts, most likely commensal rather than parasitic, in cold-blooded vertebrates. Its body is leaflike in shape.
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This tissue is responsible for movements in our body. Muscles contain special proteins called contractile protein which contract and relax to cause movement. Muscle tissues vary with function and location in the body. In mammals the three types are: skeletal or striated muscle; smooth or non-striated muscle; and cardiac muscle, which is sometimes known as semi-striated.
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Sibernetic is a fluid mechanics simulator developed for simulations of C. elegans in the OpenWorm project developed for the OpenWorm project by Andrey Palyanov, Sergey Khayrulin and Mike Vella as part of the OpenWorm team. Sibernetic provides an implementation of the PCISPH contractile matter algorithm for simulating muscle tissue and is applied to C. elegans locomotion.
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Cytochalasin B, the name of which comes from the Greek cytos (cell) and chalasis (relaxation), is a cell-permeable mycotoxin. It was found that substoichimetric concentrations of cytochalasin B (CB) strongly inhibit network formation by actin filaments. Due to this, it is often used in cytological research. It inhibits cytoplasmic division by blocking the formation of contractile microfilaments.
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Peritubular myoid cells are responsible for the contractile nature of the seminiferous tubule. This contraction helps move the spermatozoa and fluid to the rete testes. There are a number of mediators involved in the regulation of contraction. Oxytocin produced by leydig cells has been shown to be a driving factor in the contractions by acting on peritubular myoid cells.
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As in other echinoderms, the radial canals give rise to lateral canals, but there are no ampullae, and clusters of three tube feet branch from the ends of each canal, except around the mouth, where they are found singly. In the absence of ampullae, water pressure is maintained by the ring canal, which is surrounded by contractile muscle fibres.
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Smoothelin is a protein that in humans is encoded by the SMTN gene. This gene encodes a structural protein that is found exclusively in contractile smooth muscle cells. It associates with stress fibers and constitutes part of the cytoskeleton. This gene is localized to chromosome 22q12.3, distal to the TUPLE1 locus and outside the DiGeorge syndrome deletion.
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Anillo means ring and shows that the name anillin references the observed enrichment of anillins at the contractile ring during cytokinesis. Anillins are also enriched at other actomyosin rings, most significantly, those at the leading edge of the Drosophila embryo during cellularization. These actomyosin rings invaginate to separate all nuclei for one another in the syncytial blastoderm.
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After having settled on a substrate for some time, Neocercomonas may also deploy pseudopodia from the posterior end of the cell. The anterior flagellum will continue to move after pseudopodia have been extended, though usually in a more erratic manner. Within the cell there is an anterior nucleus, accompanied by numerous contractile vacuoles spread throughout the cell.
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In anatomy, fascia adherens are ribbon-like structures that stabilize non- epithelial tissue. They are similar in function and structure to the zonula adherens or adherens junction of epithelial cells. It is a broad intercellular junction in the transversal sections of an intercalated disc of cardiac muscle anchoring actin filaments. It helps to transmit contractile forces.
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Different species of Arcella can have different number of nuclei, ranging from a single nucleus, as in some A. hemisphaerica, up to 200 nuclei, as in A. megastoma, though the majority is binucleate. They also have many contractile vacuoles, and can develop vacuoles of carbon dioxide in their cytoplasm to float up to the surface of the water.
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Occasional (pericyte)s (Rouget cells), which may have a contractile function, are found around the capillary wall. Pericytes have the ability to alter local blood flow. The choriocapillaris is densest in the macular area, where it is the sole blood supply for a small region of the retina. The choriocapillaris is unique to the choroid and does not continue into the ciliary body.
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This author uses an example of the contractile elements present in the porifera or sponges that do truly lack this striated muscle containing this protein. Furthermore, Steinmetz et al. present evidence for a polyphyletic origin of striated muscle cell development through their analysis of morphological and molecular markers that are present in bilaterians and absent in cnidarians, ctenophores, and bilaterians. Steimetz et al.
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The vestibule is a passage for both food entrance and waste exit. The vestibular membranes push the food inwards, where they then congregate in a spindle-shaped food vacuole in the pharynx. Once the food vacuoles leave the non-ciliated pharyngeal tube, they become rounded. When the water flows outwards, contractile vacuoles and full food vacuoles may empty their contents.
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Once the leaves die back in summer, the roots also wither. After some years, the roots shorten pulling the bulbs deeper into the ground (contractile roots). The bulbs develop from the inside, pushing the older layers outwards which become brown and dry, forming an outer shell, the tunic or skin. Up to 60 layers have been counted in some wild species.
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They regulate blood flow by their contractile activity and secrete extracellular matrix, prostaglandins, and cytokines. Mesangial cells also have phagocytic activity, removing proteins and other molecules trapped in the glomerular basement membrane or filtration barrier. The Bowman's capsule has an outer parietal layer composed of simple squamous epithelium. The visceral layer, composed of modified simple squamous epithelium, is lined by podocytes.
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The protoplast of the prey is then sucked out into a food vacuole. Remaining contents are then drawn out using pseudopodia. The vampyrellid uses its pseudopodia to move from cell to cell repeating the process. Excess water absorbed from prey cells is removed by numerous small contractile vacuoles on the periphery of the organism, maintaining an only slightly increased size after each meal.
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The maximal force depends on the contractile properties of the muscle fibers. Within a motor unit, all the muscle fibers are of the same type (e.g. type I (slow twitch) or Type II fibers (fast twitch)), and motor units of multiple types make up a given muscle. Motor units of a given muscle are collectively referred to as a motor pool.
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S. roeselii is found in still or slow-moving bodies of water, where it feeds on bacteria, flagellates, algae, and other ciliates. When feeding, the cell is fixed in place (sessile), attached by a posterior "holdfast" organelle to a firm surface such as plant stem or submerged detritus. Attached specimens are trumpet-shaped, and very contractile. When swimming freely, cells are compactly ovoid.
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Though not universally used, ‘metabolic fatigue’ is a common term for the reduction in contractile force due to the direct or indirect effects of two main factors: # Shortage of fuel (substrates) within the muscle fiber # Accumulation of substances (metabolites) within the muscle fiber, which interfere either with the release of calcium (Ca2+) or with the ability of calcium to stimulate muscle contraction.
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Actin, alpha skeletal muscle is a protein that in humans is encoded by the ACTA1 gene. Actin alpha 1 which is expressed in skeletal muscle is one of six different actin isoforms which have been identified. Actins are highly conserved proteins that are involved in cell motility, structure and integrity. Alpha actins are a major constituent of the contractile apparatus.
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After the insult occurs, a series of histopathological and structural changes occur in the left ventricular myocardium that lead to progressive decline in left ventricular performance. Ultimately, ventricular remodeling may result in diminished contractile (systolic) function and reduced stroke volume. Physiological remodeling is reversible while pathological remodeling is mostly irreversible. Remodeling of the ventricles under left/right pressure demand make mismatches inevitable.
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Two interdependent events drive cytokinesis in S. cerevisiae. The first event is contractile actomyosin ring (AMR) constriction and the second event is formation of the primary septum (PS), a chitinous cell wall structure that can only be formed during cytokinesis. The PS resembles in animals the process of extracellular matrix remodeling. When the AMR constricts, the PS begins to grow.
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Proper coordination and correct positional assembly of the contractile ring depends on septins, which is the precursor to the septum ring. These GTPases assemble complexes with other proteins. The septins form a ring at the site where the bud will be created during late G1. They help promote the formation of the actin-myosin ring, although this mechanism is unknown.
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PaSCs express the intermediate filament proteins desmin and glial fibrillary acidic protein. The expression of a diverse range of intermediate filament proteins enables the PaSC to harbour contractile abilities. Cellular extensions also enable the cells to sense their environment. Following inflammation or injury to the pancreas, quiescent PaSCs are activated to myofibroblast like cells, which expresses α- smooth muscle actin.
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ROCK1 is a protein serine/threonine kinase also known as rho-associated, coiled-coil-containing protein kinase 1. Other common names are ROKβ and P160ROCK. ROCK1 is a major downstream effecter of the small GTPase RhoA and is a regulator of the actomyosin cytoskeleton which promotes contractile force generation. ROCK1 plays a role in cancer and in particular cell motility, metastasis, and angiogenesis.
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The common ostrich heart is a closed system, contractile chamber. It is composed of myogenic muscular tissue associated with heart contraction features. There is a double circulatory plan in place possessing both a pulmonary circuit and systemic circuit. The common ostrich's heart has similar features to other avian species like having a conically shaped heart, and being enclosed by a pericardium layer.
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The cell is roughly oval or kidney-shaped in profile, with a distinct concavity on the anterior of the oral side. Cilia are arranged in 50-63 longitudinal rows. At the center of the cell is a large, ovoid macronucleus and a small spherical micronucleus. A single contractile vacuole is located slightly posterior to the middle of the body, near the right side.
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During pregnancy, both protein metabolism and carbohydrate metabolism are affected. One kilogram of extra protein is deposited, with half going to the fetus and placenta, and another half going to uterine contractile proteins, breast glandular tissue, plasma protein, and haemoglobin. An increased requirement for nutrients is given by fetal growth and fat deposition. Changes are caused by steroid hormones, lactogen, and cortisol.
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It is the earliest intracellular stage of parasite. It is elongated, slightly curved, microscopic unicellular organism with one end pointed and the other end blunt. The pellicle, forming external envelope, contains longitudinally arranged contractile microtubules which help in wriggling movements of organism. Cytoplasm includes a vesicular nucleus, a mitochondrion, golgi bodies, endoplasmic reticulum, ribosomes, lysosomes and vacuoles containing reserve food, etc.
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Most suctoria are around 15-30 μm in size, with a non-contractile stalk and often a lorica or shell. Suctoria sucking a colpidium. Suctoria reproduce primarily by budding, producing swarmers that lack both tentacles and stalks but have cilia. They may also reproduce through conjugation, which is peculiar in involving cells of different size and often involves total fusion.
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Most anillins can be sequestered to the nucleus during interphase, but there are exceptions – Drosophila anilins in the early embryo, C. elegans ANI-1 in early embryos, C. elegans ANI-2 in oogenic gonads, and Mid2p in fission yeast. These anillins that are not sequestered during interphase suggest that anillins may also regulate cytoskeletal dynamics outside the contractile ring during cytokinesis.
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This group is also well known for possessing other unusually complex subcellular structures such as the ocelloid and nematocyst. Observations of Erythropsidinium samples reveal that the length of the piston is highly variable across specimens. The piston is known to be capable of repetitive and dramatic contractile motion; although its function is unknown, roles in locomotion, prey capture, and defense have been suggested.
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Human gamma-actin is 41.8 kDa in molecular weight and 375 amino acids in length. Actins are highly conserved proteins that are involved in various types of cell motility, and maintenance of the cytoskeleton. In vertebrates, three main groups of actin isoforms, alpha, beta and gamma have been identified. The alpha actins are found in muscle tissues and are a major constituent of the sarcomere contractile apparatus.
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Both bundle branches descend and reach the apex of the heart where they connect with the Purkinje fibers. This passage takes approximately 25 ms. The Purkinje fibers are additional myocardial conductive fibers that spread the impulse to the myocardial contractile cells in the ventricles. They extend throughout the myocardium from the apex of the heart toward the atrioventricular septum and the base of the heart.
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The symptoms for PKD are varied from case to case, however, typically they consist of involuntary movements. Such contractile movements include dystonia, chorea, athetosis, and ballism. For example, “Her attacks were characterized as sudden unilateral stiffness of upper and lower limbs followed by an involuntary extrarotation of the arm and leg.” Another frequently occurring symptom is the presence of an aura before the attack.
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These arteries have two unique features: an intimal cushion and valves. Sympathetic stimulation maintains a tonic contractile state of the intimal cushion, smooth muscle lying in the center of the artery. This keeps the artery coiled and little blood flow occurs, instead routing to arteriovenous shunts to the deep dorsal vein. Parasympathetic stimulation removes the tonic state and allows vasodilation of the intimal cushion.
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Spirostomum reproduces by binary fission. Reproduction may be purely asexual, or it may follow conjugation, during which compatible mating individuals come together and transfer genetic material across a cytoplasmic link. Members of the genus are extremely contractile. When startled, Spirostomum ambiguum can contract its body length by more than 60% within a few milliseconds (a contraction speed similar to that of the ciliate Vorticella).
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It consists of a central tube, a contractile sheath, a collar, a base plate, six tail pins and six long fibers. It is similar to Tectiviridae, but differs in the fact that a myovirus' tail is permanent. Contractions of the tail require ATP. On contraction of the sheath, sheath subunits slide over each other and the tail shortens to 10–15 nm in length.
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On attaching to a host cell, the virus uses its contractile sheath like a syringe, piercing the cell wall with its central tube and injecting the genetic material into the host. The injected DNA takes over the host cell's mechanisms for transcription and translation and begins to manufacture new viruses. Replication follows the replicative transposition model. DNA-templated transcription is the method of transcription.
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Astrephomene gubernaculifera is a colonial, flagellated volvocine green algae. It consists of 16, 32, 64 or 128 cells, 2 to 7 of which are small and oriented such that their flagella form a rudder (Stein 1958). Each cell is surrounded by a gelatinous matrix and contains an eyespot, two flagella and 1-3 contractile vacuoles at the anterior end. Astrephomene gubernaculifera can reproduce sexually or asexually.
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Most Euglenozoa are photoautotrophic, but some are chemoorganotrophs (saprophytic). They are commonly found in freshwater. The members of the phylum Euglenozoa have a pellicle for support, a red eye spot called a stigma to orient the cell toward light, chlorophyll a and b to assist in the process of photosynthesis, contractile vacuoles, and flagella. 260x260px One major pathogen from the phylum Euglenozoa is Leishmania.
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Just below the plasma membrane, and in the inner fluid region, cytoplasm can be found. The pellicle structure in the protist is a thin layer of protein that helps provide the cell with some support and protection. In addition to the plasma membrane, protists contain two different types of vacuoles. Contractile vacuoles help to maintain osmoregulation, and phagocytic vacuoles allow select protists to ingest food.
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Most prefer a porous, loamy soil, and good drainage is essential. Most species bloom in July or August (northern hemisphere). The flowering periods of certain lily species begin in late spring, while others bloom in late summer or early autumn. They have contractile roots which pull the plant down to the correct depth, therefore it is better to plant them too shallowly than too deep.
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Like other ribbon worms, T. polymorphus is not divided into segments but is soft, smooth and contractile. It is up to long but just wide, with a rounded head slightly broader than the body. There is a proboscis pore and a mouth on the underside of the head but there are no eye- spots or cephalic slits. Fresh specimens are a dark reddish-brown or orangeish-brown.
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The iris is a contractile structure, consisting mainly of smooth muscle, surrounding the pupil. Light enters the eye through the pupil, and the iris regulates the amount of light by controlling the size of the pupil. This is known as the pupillary light reflex. The iris contains two groups of smooth muscles; a circular group called the sphincter pupillae, and a radial group called the dilator pupillae.
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There is some variation between individuals in this species, and the gills (retractile) and rhinophores (contractile) range in colour from a translucent straw-color, through to pink and light orange.Debelius, Helmut, 2001, Nudibranchs and Sea Snails: Indo-Pacific Field Guide, IKAN - Unterwasserarchiv, Frankfurt, Germany.P.L. Beesley, G.J.B. Ross, A. Wells, Mollusca - The southern synthesis, vol.5, CSIRO, 1998,David Behrens, Nudibranch behaviour, New World Publication INC.
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Species of Oziroe grow from bulbs, which have contractile roots as well as normal ones. Each bulb produces only a few leaves, which are thick and grooved. The flowering stem (scape) appears at the same time as the leaves. It has bract along its length, with generally one or two flowers on straight stalks (pedicels) appearing from the angle between each bract and the scape.
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Viruses in Spounavirinae are non-enveloped, with icosahedral and Head-tail geometries, and T=16 symmetry. The diameter is around 84-94 nm, with a length of 140-219 in length, contractile with globular structures at its tip, has 6 long terminal fibers, 6 short spikes and a double base platenm. Genomes are circular, around 130-160kb in length. The genome codes for 190 to 230 proteins.
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Pressure-volume area plot. There is a highly linear correlation between the PVA and cardiac oxygen consumption per beat. This relationship holds true under a variety of loading and contractile conditions. This estimation of myocardial oxygen consumption (MVO2) is used to study the coupling of mechanical work and the energy requirement of the heart in various disease states, such as diabetes, ventricular hypertrophy, and heart failure.
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Metabolites are the substances (generally waste products) produced as a result of muscular contraction. They include chloride, potassium, lactic acid, ADP, magnesium (Mg2+), reactive oxygen species, and inorganic phosphate. Accumulation of metabolites can directly or indirectly produce metabolic fatigue within muscle fibers through interference with the release of calcium (Ca2+) from the sarcoplasmic reticulum or reduction of the sensitivity of contractile molecules actin and myosin to calcium.
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Extrafusal muscle fibers are not to be confused with intrafusal muscle fibers, which are innervated by sensory nerve endings in central noncontractile parts and by gamma motor neurons in contractile ends and thus serve as a sensory proprioceptor. Extrafusal muscle fibers can be generated in vitro (in a dish) from pluripotent stem cells through directed differentiation. This allows study of their formation and physiology.
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Rottlerin increases in isolated heart contractility independent of its vascular effects, as well as enhanced perfusion through vasomotor activity. The activation of BKCa++ channels by rottlerin relaxes coronary smooth muscle and improves myocardial perfusion after cardioplegia. Myocardial stunning is associated with oxidant radical damage and calcium overload. Contractile abnormalities can occur through oxidant-dependent damage and also through calcium overload in the mitochondria resulting in mitochondrial damage.
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The atomic structure of monomeric actin was solved by Kabsch et al., and closely thereafter this same group published the structure of the actin filament. Actins are highly conserved proteins; the alpha actins are found in muscle tissues and are a major constituent of the contractile apparatus. Cardiac (ACTC1) and skeletal (ACTA1) alpha actins differ by only four amino acids (Asp4Glu, Glu5Asp, Leu301Met, Ser360Thr; cardiac/skeletal).
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The reactive oxygen species are capable of stressing the endoplasmic reticulum, which increases the amount of the unfolded protein response signals. This leads to inflammation, cell proliferation, and eventually to cell death. Another mechanism in which reactive oxygen species cause cell death would be through the cytoskeleton rearrangement, which affects the contractile proteins. The reactive nitrogen species arise once the reactive oxygen species destroy the mitochondria.
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Also, such mechanism relieves the tongue's musculature from physiological constraints such as limited peak power output - mechanical efficiency and thermal dependence by uncoupling the activation of the depressor mandibulae's contractile units from actual muscular movement. In other words, the kinematic parameters developed by contribution of the elastic structures differ from those developed by muscular projection, accounting for the difference in velocity, power output, and thermal dependence.
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"The Mechanics of Sprint Running." The Journal of Physiology 217 (1971): 709-21. As the velocity of the runner increases, inertia and air resistance effects become the limiting factors on the sprinter's top speed. It was previously believed that there was an intramuscular viscous force that increased proportionally to the velocity of muscle contraction that opposed the contractile force; this theory has since been disproved.
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In Drosophila, anillin is necessary to organize myosin into rings in the cellularization front. Depletion of anillin in Drosophila and humans leads to changes in the spatial and temporal stability of myosin during cytokinesis. In C. elegans, ANI-1 organizes myosin into foci during cytokinesis and establishment of polarity, whereas, ANI-2 is a requirement for the maintenance of myosin-rich contractile lining of oogenic gonads.
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Cytokinesis is defined by actomyosin-based contraction. RhoA-dependent diaphanous-related formins (DRFs) localize to the cleavage furrow during cytokinesis while stimulating local actin polymerization by coordinating microtubules with actin filaments at the site of the myosin contractile ring. Differences in effector binding distinguish RhoA amongst other related Ras homologs GTPases. Integrins can modulate RhoA activity depending on the extracellular matrix composition and other relevant factors.
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The cause of OAB is unclear, and indeed there may be multiple causes. It is often associated with overactivity of the detrusor urinae muscle, a pattern of bladder muscle contraction observed during urodynamics. It is also possible that the increased contractile nature originates from within the urothelium and lamina propria, and abnormal contractions in this tissue could stimulate dysfunction in the detrusor or whole bladder.
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People experiencing some forms of heart failure have a significant decrease in the contractile ability of muscle cells in the heart (cardiomyocytes). This impaired contractility occurs through a number of mechanisms. Some of the main problems associated with decreased contractility in those with heart failure are issues arising from imbalances in the concentration of calcium. Calcium permits myosin and actin to interact which allows initiation of contraction within the cardiomyocytes.
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Carukia barnesi is a small and extremely venomous jellyfish found near Australia. Stings can result in Irukandji syndrome, and this species is commonly known as Irukandji jellyfish, although this name does not distinguish it from other Irukandji jellyfish such as Malo kingi. A mature C. barnesi's bell is only in height. It has four contractile tentacles, one extending from each bottom "corner" of its bell, ranging in length from .
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In contractile bundles, the actin-bundling protein alpha-actinin separates each thin filament by ≈35 nm. This increase in distance allows thick filaments to fit in between and interact, enabling deformation or contraction. In deformation, one end of myosin is bound to the plasma membrane, while the other end "walks" toward the plus end of the actin filament. This pulls the membrane into a different shape relative to the cell cortex.
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Epelsiban was investigated for a potential role in benign prostatic hyperplasia also called prostate enlargement. Oxytocin treatment induces prostate enlargement in mice and produces contractions of the prostate through its specific receptor. Oxytocin concentrations are elevated in prostatic tissue from patients with benign prostatic hyperplasia. Epelsiban was found to inhibit the contractile effect of oxytocin in human prostatic tissue through its specific oxytocin receptors in a concentration-dependent manner.
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This chapter explores anal intercourse in Afro-Asian sexual culture. The chapter starts with the biological explanation of why a man would be drawn to the anus. The anal sphincter contains a greater contractile power than the vagina, and this allows the male greater pleasure through increased friction.Edwardes & Masters, The Cradle of Erotica, 104 The chapter continues to claim that anal intercourse is a routine practice among many Muslim women.
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This structure may function as a stopper, its digestion in the alimentary tract possibly triggering the discharge of the polar filaments. Two ideas have been proposed to explain the eversion of the polar filaments. Firstly, that the hydrostatic pressure in the polar capsule pushes the filament out, rather like the cnidocyst of jellyfish. The second is that extrusion is an active process involving contractile proteins and is calcium- dependent (Uspenskaya, 1982).
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Stress fibers are contractile actin bundles found in non-muscle cells. They are composed of actin (microfilaments) and non-muscle myosin II (NMMII), and also contain various crosslinking proteins, such as α-actinin, to form a highly regulated actomyosin structure within non-muscle cells. Stress fibers have been shown to play an important role in cellular contractility, providing force for a number of functions such as cell adhesion, migration and morphogenesis.
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Morphogenesis, at the cellular level, can be defined as giving shape to, or defining the architecture of a cell. The assembly of the cytoskeleton, including the actin cytoskeleton, is the determining factor in specifying cellular morphogenesis and conferring shape to cells. The contractility of stress fibers within the cell will therefore help to determine cellular morphogenesis. For example, the circumferential contractile actin belts of adherens junctions contribute to cellular morphogenesis.
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Approximately 300 myosin molecules constitute one thick filament. There are two isoforms of cardiac MHC, α and β, which display 93% homology. MHC-α and MHC-β display significantly different enzymatic properties, with α having 150-300% the contractile velocity and 60-70% actin attachment time as that of β. MHC-β is predominately expressed in the human ventricle, while MHC-α is predominantly expressed in human atria.
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Actin-associated LIM protein (ALP), also known as PDZ and LIM domain protein 3 is a protein that in humans is encoded by the PDLIM3 gene. ALP is highly expressed in cardiac and skeletal muscle, where it localizes to Z-discs and intercalated discs. ALP functions to enhance the crosslinking of actin by alpha actinin-2 and also appears to be essential for right ventricular chamber formation and contractile function.
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This can lead to degradation of the cytoskeleton and plasma membrane. Calpain may also break down sodium channels that have been damaged due to axonal stretch injury, leading to an influx of sodium into the cell. This, in turn, leads to the neuron's depolarization and the influx of more Ca2+. A significant consequence of calpain activation is the development of cardiac contractile dysfunction that follows ischemic insult to the heart.
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When the organism is fully extended, its macronucleus is long and worm-like. In contraction, the macronucleus may show distinct nodules separated by constricted areas, giving it the appearance of a string of beads. Cells have a single contractile vacuole, located to the left of the cell mouth (cytostome). The tail end of feeding organisms may be surrounded by a loose, mucilaginous lorica filled with debris and excreted matter.
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There are five known functions of intraglomerular mesangial cells: structural support of glomerular capillaries, regulation of the glomerular filtration rate, mesangial matrix formation, phagocytosis, and monitoring of capillary lumen glucose concentration. Intraglomerular mesangial cells have contractile activity. The initiation of contraction of mesangial cells is similar to that of smooth muscle. Contraction of mesangial cells is coupled with contraction of the basement membrane of the endothelium of glomerular capillaries.
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In consequence, the heart becomes rigid and poorly contractile while the heart valves may become stenotic or insufficient, i.e. reduced in ability to open or close, respectively. The damaged heart may also develop mural thrombi, i.e. clots which lay against ventricle walls, tend to break off, and flow through and block arteries; this condition often precedes the fibrotic stage of eosinophilic myocarditis and is termed the thrombotic stage.
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The zoospores are flattened cells that contain a cup- shaped green chromatophore and two flagella of equal length arising from the basal body and extending beyond the length of body. They contain one contractile vacuole, nucleus, dictyosome, chloroplast, and single mitochondrial reticulum or branched mitochondria linked to microbody. Some species have a stigma (eyespots) which helps orient zoospores towards high light intensity. There are two types of endoplasmic reticulum cisternae.
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The use of two other cations, Na+ and Ca2+, also can be used to arrest the heart. By removing extracellular Na+ from perfusate, the heart will not beat because the action potential is dependent upon extracellular Na+ ions. However, the removal of Na+ does not alter the resting membrane potential of the cell. Likewise, removal of extracellular Ca2+ results in a decreased contractile force, and eventual arrest in diastole.
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The actin filaments here are both pre-existing and new. Cleavage is driven by these motor proteins, actin and myosin, which are the same proteins involved with muscle contraction. During cellular cleavage, the contractile ring tightens around the cytoplasm of the cell until the cytoplasm is pinched into two daughter cells. During the final phase of mitosis, telophase, the furrow forms an intercellular bridge using mitotic spindle fibers.
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Besides actin and myosin II, the contractile ring contains the scaffolding protein anillin. Anillin binds to actin, myosin, RhoA, and CYK-4, and thereby links the equatorial cortex with the signals from the central spindle. It also contributes to the linkage of the actin-myosin ring to the plasma membrane. Another protein, septin, has also been speculated to serve as a structural scaffold on which the cytokinesis apparatus is organized.
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The adherens junctions are scattered around dense bands that are circumfering the smooth muscle cell in a rib-like pattern. The dense band (or dense plaques) areas alternate with regions of membrane containing numerous caveolae. When complexes of actin and myosin contract, force is transduced to the sarcolemma through intermediate filaments attaching to such dense bands. During contraction, there is a spatial reorganization of the contractile machinery to optimize force development.
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Of these, more than 10 differentially expressed genes belong to the Wnt family which are essential for differentiation. This coincides with the observation that without RYR1 present, muscle cells appear in smaller groups, are underdeveloped, and lack organization. Fiber type composition is also affected, with less type 1 muscle fibers when there are decreased amounts of RYR1. These findings demonstrate RYR1 has a non-contractile role during muscle development.
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The blood vessels consist of arteries, capillaries and veins and are lined with a cellular endothelium which is quite unlike that of most other invertebrates. The blood circulates through the aorta and capillary system, to the vena cavae, after which the blood is pumped through the gills by the auxiliary hearts and back to the main heart. Much of the venous system is contractile, which helps circulate the blood.
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The valves of the rosy razor clam are relatively small, thin and finely sculptured. At the anterior end of the animal there is a strong, protruding foot. At the posterior end, is the large mantle sac containing the gills; when relaxed, it protrudes and is twice the length of the valves, but it can be contracted back between the valves. Posterior to this are the two robust, contractile siphons.
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S100A1 gene transfer to engineered heart tissue was shown to augment contractile performance of the tissue implants, suggesting that S100A1 may be effective in facilitating cardiac tissue replacement therapy in heart failure patients. However, the clinical efficacy of this strategy remains to be determined. In addition, multiple drugs, including Pentamidine, Amlexanox, Olopatadine, Cromolyn, and Propanolol, are known to bind to S100A1, although their affinities are often in the mid-micromolar range.
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Actin, gamma-enteric smooth muscle is a protein that in humans is encoded by the ACTG2 gene. Actins are highly conserved proteins that are involved in various types of cell motility, and maintenance of the cytoskeleton. In vertebrates, three main groups of actin isoforms, alpha, beta and gamma have been identified. The alpha actins are found in muscle tissues and are a major constituent of the contractile apparatus.
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Myosin-11 is a smooth muscle myosin belonging to the myosin heavy chain family. Myosin-11 is a subunit of a hexameric protein that consists of two heavy chain subunits and two pairs of non-identical light chain subunits. It is a major contractile protein, converting chemical energy into mechanical energy through the hydrolysis of ATP. Alternative splicing generates isoforms that are differentially expressed, with ratios changing during muscle cell maturation.
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Neointimal Hyperplasia is the movement and proliferation of smooth muscle cells into the luminal area of a blood vessel. This generates a new inner structure that can block blood flow. This is commonly seen to cause failure of interventional clinical procedures that include placement of stents and bypass grafts. Due to changes in potassium channel type the vascular smooth muscle cells switch from the contractile to proliferating phenotype.
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Sponge cells have the ability to communicate with each other via calcium signaling or by other means. Sponge larvae differentiate sensory cells which respond to stimuli including light, gravity, and water movement, all of which increase the fitness of the organism. In addition to sensory cells differentiated during development, adult Porifera display contractile activity. The emergence of nervous systems has been linked to the evolution of voltage-gated sodium (Nav) channels.
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Some animals may experience vaginal secretions that could be bloody. The female is not yet sexually receptive; the old corpus luteum degenerates; the uterus and the vagina distend and fill with fluid, become contractile and secrete a sanguinous fluid; the vaginal epithelium proliferates and the vaginal cytology shows a large number of non-cornified nucleated epithelial cells. Variant terms for proestrus include pro-oestrus, proestrum, and pro-oestrum.
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ANI-1 and ANI-2 (proteins homologous to anillin) are essential for embryonic viability in both organisms. ANI-1 is required for cortical ruffling, pseudocleavage, and all contractile events that occur in embryos prior to mitosis. ANI-1 is also crucial for segregation of polar bodies during meiosis. ANI-2 functions in the maintenance of the structure of the central core of the cytoplasm, the rachis, during oogenesis.
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Anillin was first isolated from Drosophila by harnessing its interactions with both F-actin and microtubules. Furthermore, anillin-rich structures that form after Latrunculin A treatment of Drosophila cells localize to the plus-ends of microtubules. The interaction between anillin and microtubules suggest that anillin may serve as a signaling factor to relay the position of the mitotic spindle to the cortex to ensure appropriate contractile ring formation during cytokinesis.
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A myoneme (or spasmoneme) is a contractile structure found in some eukaryotic single-celled organisms, particularly Vorticella. It consists of a series of protein filaments that shorten rapidly upon exposure to calcium. Although the shortening can be up to 100 lengths per second, faster than any muscle, the relaxation time is several seconds (compared to approximately one tenth of a second for muscle). The myonemes of Acantharea also display slow contraction and undulation movements.
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The Type VI Secretion System (T6SS) is widely spread amongst Gram-negative bacteria and consists of a protein complex, encoded by several different genes, forming "needle-like" structure capable of injecting effector molecules into neighbouring target cells similar to the contractile tail of the T4 bacteriophage. One T6SS may have several different effectors such as PAAR-domain toxins or Hcp toxins and some species can deliver these toxins into both prokaryotes and eukaryotes.
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Decreases in the generation of contractile forces and whole muscle power have also been found in response to microgravity. To counter the effects of microgravity on the musculoskeletal system, aerobic exercise is recommended. This often takes the form of in-flight cycling. A more effective regimen includes resistive exercises or the use of a penguin suit (contains sewn-in elastic bands to maintain a stretch load on antigravity muscles), centrifugation, and vibration.
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The stimulation for these contractions likely originates in modified smooth muscle cells called interstitial cells of Cajal. These cells cause spontaneous cycles of slow wave potentials that can cause action potentials in smooth muscle cells. They are associated with the contractile smooth muscle via gap junctions. These slow wave potentials must reach a threshold level for the action potential to occur, whereupon Ca2+ channels on the smooth muscle open and an action potential occurs.
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A paraxial rod also runs parallel to the axoneme of the single flagellum on one side, giving the flagella increased thickness, robustness, and strength. As mentioned earlier, these organisms also have glycosomes, which are specialized peroxisomes. Depending on the species examined, these glycosomes may take the form of two rows separated by filamentous fibres. Some isolates of the genus also have a contractile vacuole located at the anterior end, near the flagellar pocket.
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Lister wrote his first paper in 1853, Observations on the Contractile Tissue of the Iris that advanced the work of Albert von Kölliker, demonstrating the existence of two distinct muscles, the dilator and sphincter in the Iris. It was published in Quarterly Journal of Microscopical Science. His next paper was a similar work Observations on the Muscular Tissue of the Skin. More than 30 of his early school papers are still preserved.
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Myosin is a major contractile protein that converts chemical energy into mechanical energy through the hydrolysis of ATP. Class II Myosins are hexameric proteins composed of a pair of myosin heavy chains (MYH) and two pairs of nonidentical light chains. Myosin heavy chains are encoded by a multigene family. In mammals, at least ten different myosin heavy chain (MYH) isoforms have been described from striated, smooth, but rarely in non-muscle cells.
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Eastern skunk cabbage has contractile roots which contract after growing into the earth. This pulls the stem of the plant deeper into the mud, so that the plant in effect grows downward, not upward. Each year, the plant grows deeper into the earth, so that older plants are practically impossible to dig up. They reproduce by hard, pea-sized seeds which fall in the mud and are carried away by animals or by floods.
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The shells of testate amoebae may be composed of various substances, including calcium, silica, chitin, or agglutinations of found materials like small grains of sand and the frustules of diatoms. testate amoeba Difflugia acuminata. To regulate osmotic pressure, most freshwater amoebae have a contractile vacuole which expels excess water from the cell. This organelle is necessary because freshwater has a lower concentration of solutes (such as salt) than the amoeba's own internal fluids (cytosol).
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The macronucleus is long and sausage-shaped, and the spherical micronucleus is nested next to it, often hidden by the macronucleus. The opening, known as the peristome, at the pointed anterior end leads to the cytostome, or the mouth. Cysts are smaller than trophozoites and are round and have a tough, heavy cyst wall made of one or two layers. Usually only the macronucleus and sometimes cilia and contractile vacuoles are visible in the cyst.
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It is possible, to trace the origin of these elements in the blood of the marrow cells The high content of colorless elements in the blood of the marrow makes it likely that these is a migration of contractile marrow cells into the vessels. A thorough description of my observations will be published. In 1869, Neumann described the "lymphoid marrow cell" in the bone marrow.Neumann, E.: Über die Bedeutung des Knochenmarks f.d.
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For the body to keep moving properly and with finesse, the nervous system has to have a constant input of sensory data coming from areas such as the muscles and joints. In order to receive a continuous stream of sensory data, the body has developed special sensory receptors called proprioceptors. Muscle spindles are a type of proprioceptor, and they are found inside the muscle itself. They lie parallel with the contractile fibers.
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The mitotic apparatus is made up of a central spindle and polar asters made up of polymers of tubulin protein called microtubules. The asters are nucleated by centrosomes and the centrosomes are organized by centrioles brought into the egg by the sperm as basal bodies. Cytokinesis is mediated by the contractile ring made up of polymers of actin protein called microfilaments. Karyokinesis and cytokinesis are independent but spatially and temporally coordinated processes.
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A contractile vacuole is used to maintain osmotic equilibrium by excreting excess water from the cell (see Osmoregulation). An Amoeba obtains its food by phagocytosis, engulfing smaller organisms and particles of organic matter, or by pinocytosis, taking in dissolved nutrients through vesicles formed within the cell membrane. Food enveloped by the Amoeba is stored in digestive organelles called food vacuoles. Amoeba, like other unicellular eukaryotic organisms, reproduces asexually by mitosis and cytokinesis.
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It is commonly attached by a long highly contractile stalk to some submerged objects like weeds, animals, or stones. Vorticella campanula is often found in large groups. All the individuals in the group, however, remain free and independent of each other. Most Vorticella are found in abundance in stagnant water rich in decaying organic matter and feed largely on bacteria, but Vorticella campanula live only in uncontaminated water where bacterial growth is poor.
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If one identical twin is affected, there is a 33% chance the other one will be as well. Mutations in genes involved in muscle development are risk factors for clubfoot, specifically those encoding the muscle contractile complex (MYH3, TPM2, TNNT3, TNNI2 and MYH8). These can cause congenital contractures, including clubfoot, in distal arthrogryposis (DA) syndromes. Clubfoot can also be present in people with genetic conditions such as Loeys–Dietz syndrome and Ehlers-Danlos syndrome.
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As the heart fills with more blood than usual, there is an increase in the load experienced by each myocyte. This stretches the muscle fibers, increasing the affinity of troponin C to Ca2+ ions, causing a greater number of cross- bridges to form within the muscle fibers. This increases the contractile force of the cardiac muscle, resulting in increased stroke volume. Frank–Starling curves can be used as an indicator of muscle contractility (inotropy).
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NASA has researched the use of isometrics in preventing muscle atrophy experienced by astronauts as a result of living in a zero gravity environment. Isometrics, muscle lengthening and muscle shortening exercises were studied and compared. The outcome showed that while all three exercise types promoted muscle growth, isometrics failed to prevent a decrease in the amount of contractile proteins found in the muscle tissue. The result was muscle degradation at a molecular level.
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Phosphatidylethanolamine (PE) has been shown to be present during this time which indicates that is may play a role in movement between the plasma membrane and contractile ring. The bridge is then broken and resealed to form two identical daughter cells during cytokinesis. The breakage is formed by microtubules and the resealing is negated by Calcium dependent exocytosis using Golgi vesicles. In comparison, the plant cell septum and the animal cell mid-zone are analogous.
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Here, variant angina is taken to include typical and atypical cases. For a portion of patients, variant angina may be a manifestation of a more generalized episodic smooth muscle-contractile disorder such as migraine, Raynaud's phenomenon, or aspirin-induced asthma. Variant angina is also the major complication of eosinophilic coronary periarteritis, an extremely rare disorder caused by extensive eosinophilic infiltration of the adventitia and periadventitia, i.e. the soft tissues, surrounding the coronary arteries.
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The lymph capillaries drain the lymph to larger contractile lymphatics, which have valves as well as smooth muscle walls. These are called the collecting lymphatics. As the collecting lymph vessel accumulates lymph from more and more lymph capillaries in its course, it becomes larger and is called the afferent lymph vessel as it enters a lymphs node. Here the lymph percolates through the lymph node tissue and is removed by the efferent lymph vessel.
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Pandorina is a genus of green algae composed of 8, 16, or sometimes 32 cells, held together at their bases to form a sack globular colony surrounded by mucilage. The cells are ovoid or slightly narrowed at one end to appear keystone- or pear-shaped. Each cell has two flagella with two contractile vacuoles at their base, an eyespot, and a large cup-shaped chloroplast with at least one pyrenoid. Pandorina sp.
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MHC-α isoform is abundantly expressed in both cardiac atria and cardiac ventricles during embryonic development. Following birth, cardiac ventricles predominantly express the MHC-β isoform and cardiac atria predominantly express the MHC-α isoform. The two isoforms of cardiac MHC, α and β, display 93% homology. MHC-α and MHC-β display significantly different enzymatic properties, with α having 150-300% the contractile velocity and 60-70% actin attachment time as that of β.
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Phosphatidylethanolamines are found in all living cells, composing 25% of all phospholipids. In human physiology, they are found particularly in nervous tissue such as the white matter of brain, nerves, neural tissue, and in spinal cord, where they make up 45% of all phospholipids. Phosphatidylethanolamines play a role in membrane fusion and in disassembly of the contractile ring during cytokinesis in cell division. Additionally, it is thought that phosphatidylethanolamine regulates membrane curvature.
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Each cell contains myofibrils, specialized protein fibers that slide past each other. These are organized into sarcomeres, the fundamental contractile units of muscle cells. The regular organization of myofibrils into sarcomeres gives cardiac muscle cells a striped or striated appearance when looked at through a microscope, similar to skeletal muscle. These striations are caused by lighter I bands composed mainly of a protein called actin, and darker A bands composed mainly of myosin.
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Contractile forces are transmitted laterally within intramuscular connective tissue to the epimysium and then to the tendon. Due to the nature of skeletal muscle, direct measurements are not possible, but many indirect studies and analyses have shown that the ECM is an important part of force transmission during muscle contraction.Bloch, R.J., Gonzalez-Serratos, H. (2003). Lateral force transmission across costameres in skeletal muscle, Exercise and Sport Sciences Reviews, 31 (2), 73-78.Trotter, J.A., 1993.
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In the fruitfly, knock-down of nmr (neuromancer), Drosophila's Tbx20 homolog gene, led to slower heart rate, arrythmias and abnormal myofibrillar architecture. Heterozygous Tbx20 knockout adult mice displayed left ventricle dilation, decreased wall thickness and contractile abnormalities. Homozygous conditional cardiomyocyte Tbx20 knockout adult mice died within 15 days after knockout induction. Mice hearts presented with dilated cardiomyopathy and contraction-related dysfunctions such as abnormal atrioventricular conduction, slower heart rate, altered ventricular depolarization/repolarization and arrhythmias.
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Divisome and elongasome complexes responsible for peptidoglycan synthesis during lateral cell-wall growth and division. Bacterial cell division happens through binary fission or budding. The divisome is a protein complex in bacteria that is responsible for cell division, constriction of inner and outer membranes during division, and peptidoglycan (PG) synthesis at the division site. A tubulin like protein, FtsZ plays a critical role in formation of a contractile ring for the cell division.
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In active feeding stages, there is a slime coat surrounding the myxamoeba to which bacteria sink onto. The ultrastructure of Fonticula also includes small contractile vacuoles, which are mainly deposited towards the posterior end of the cell. An ultrastructural feature that is shared between Fonticula and certain Acrasidae is mitochondria with discoid cristae. The golgi apparatus lends a helping hand in the fruiting stage in Fonticula as numerous dictyosomes are involved in the sorogenesis process.
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The iris dilator muscle (pupil dilator muscle, pupillary dilator, radial muscle of iris, radiating fibers), is a smooth muscle of the eye, running radially in the iris and therefore fit as a dilator. The pupillary dilator consists of a spokelike arrangement of modified contractile cells called myoepithelial cells. These cells are stimulated by the sympathetic nervous system. When stimulated, the cells contract, widening the pupil and allowing more light to enter the eye.
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These latter are the giant axons that the work of Alan Hodgkin and Andrew Huxley made famous. Each secondary axon branches at the stellate ganglion and contacts all the tertiary axons; thus, information concerning relevant sensory input is relayed from the sense organs in the cephalic ganglion (the squid’s brain) to the contractile muscular mantle (which is activated directly by the tertiary giant axons). Fig 1. Upper left, side view of a squid.
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These two anillin-like proteins do not have any overlap in their functions. Mid1p has been characterized as a key regulator in cytokinesis, responsible for arranging contractile ring assembly and positioning. Mid2p acts later in cytokinesis to organize septins during septation, or the invagination of inner membranes, outer membranes, and the cell wall that occurs in order to separate daughter cells completely. Saccharomyces cerevisiae (budding yeast) also have two anillin-like proteins, Boi1p and Boi2p.
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Anillins are required for the faithfulness of cytokinesis and its F-actin-, myosin-, and septin-binding domains implicate anillin in actomyosin cytoskeletal organization. In agreement with this belief, anillin-mutant cells have disrupted contractile rings. Additionally, it is hypothesized that anillin couples the actomyosin cytoskeleton to microtubules by binding MgcRacGAP/CYK-4/RacGAP50C. Anillins have also been shown to organize the actomyosin cytoskeleton into syncytial structures observed in Drosophila embryos or C. elegans gonads.
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M. avidus cells are oval-shaped with a relatively pointed anterior end and a contractile vacuole toward the rounded posterior end of the cell. The cells feature several kineties, or rows of cilia along the major axis of the cell body, and a single caudal cilium. Descriptions vary on the number of kineties per cell, from as few as 10 to as many as 14. Each cell possesses one macronucleus and one micronucleus.
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ROS increases uncoupling proteins (UCPs) and potentiate proton leakage through the adenine nucleotide translocator (ANT), the combination of which uncouples the mitochondria. Uncoupling then increases oxygen consumption by the mitochondria, compounding the increase in fatty acid oxidation. This creates a vicious cycle of uncoupling; furthermore, even though oxygen consumption increases, ATP synthesis does not increase proportionally because the mitochondria are uncoupled. Less ATP availability ultimately results in an energy deficit presenting as reduced cardiac efficiency and contractile dysfunction.
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Numbers 1, 2, 3 and 5 are short tapering arms with two rows of suckers. The left 5th appendage of males is modified to form a hectocotylus arm which is used to transfer spermatophores into the female reproductive organ. The other pair of appendages are contractile tentacles and are much longer than the arms. These have clubs with four rows of suckers at the distal end and are used for capturing food which is then transferred to the arms.
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Actin participates in many important cellular processes, including muscle contraction, cell motility, cell division and cytokinesis, vesicle and organelle movement, cell signaling, and the establishment and maintenance of cell junctions and cell shape. Many of these processes are mediated by extensive and intimate interactions of actin with cellular membranes. In vertebrates, three main groups of actin isoforms, alpha, beta, and gamma have been identified. The alpha actins, found in muscle tissues, are a major constituent of the contractile apparatus.
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Muscle cells form the active contractile tissue of the body known as muscle tissue or muscular tissue. Muscle tissue functions to produce force and cause motion, either locomotion or movement within internal organs. Muscle tissue is separated into three distinct categories: visceral or smooth muscle, found in the inner linings of organs; skeletal muscle, typically attached to bones, which generate gross movement; and cardiac muscle, found in the heart, where it contracts to pump blood throughout an organism.
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Portions of the right bundle branch are found in the moderator band and supply the right papillary muscles. Because of this connection, each papillary muscle receives the impulse at approximately the same time, so they begin to contract simultaneously just prior to the remainder of the myocardial contractile cells of the ventricles. This is believed to allow tension to develop on the chordae tendineae prior to right ventricular contraction. There is no corresponding moderator band on the left.
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Taken together, the findings clearly indicate that when skeletal muscles, especially those having a large proportion of slow myofibers, undergo both atrophy and remodeling of the contractile phenotype, the functional capacity of the muscle is reduced along with its ability to sustain work output. If a sufficient mass of muscle tissue across several key muscle groups were similarly affected, this would most likely impair the fitness of the individual when challenged with moderate-intensity exercise scenarios.
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Costameres have several primary functions. First, they keep the sarcolemma in line with the sarcomere during contraction and subsequent relaxation. They are also responsible for the lateral transmission of the sarcomere-generated contractile force to the sarcolemma and the ECM. Only 20-30% of the total force generated by sarcomere contraction is transmitted longitudinally, suggesting that the majority of the force generated by sarcomeres is transduced in the lateral direction, perpendicular to the contracting myofibril fibers.
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Two flagella emanate from the anterior papilla of the cell, and cells have two contractile vacuoles at the flagellar base. Polytoma possesses a leukoplast in place of a chloroplast, in which many starch grains are concentrated; there is no pyrenoid. Since they lack photosynthetic capability, Polytoma species are entirely saprotrophic, obtaining nutrients from decaying organic matter. Some species possess an eyespot apparatus (stigma) in the anterior portion of the leucoplast, but in others this organelle is absent.
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Many vacuoles can sometimes be seen in the periphery of the organi in addition to large, bubble-like non-contractile vacuoles. Young trophozoites range from about 25-40um, while mature trophozoites can reach to about 70um. Organisms tend to have multiple spherical nuclei with a central compact nucleolus. Some species of Vampyrella have been observed to fuse with each other to form large plasmodia with the same structure and colouration as a single free-living cell.
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A significant study reports that the risk for recurrence of heart failure in recovered PPCM patients as a result of subsequent pregnancy is approximately 21% or better. The chance of relapse may be even smaller for those with normal contractile reserve as demonstrated by stress echocardiography. In any subsequent pregnancy, careful monitoring is necessary. Where relapse occurs, conventional treatment should be resumed, including hydralazine with nitrates plus beta-blockers during pregnancy, or ACE-inhibitors plus beta-blockers following pregnancy.
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Carbetocin inhibits endogenous oxytocin release, interrupting the uterine feedback loop with the hypothalamus and decreasing both central and peripheral release of oxytocin. During pregnancy, the synthesis of oxytocin receptors in the uterus greatly increases, reaching a peak during labor and delivery. Consequently, the administration of carbetocin or another oxytocin analog during or immediately following birth will have increased uterotonic and contractile effect. The application of carbetocin does not affect a non- pregnant uterus with lower oxytocin receptor expression.
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This depolarisation triggers the entry of calcium from the sarcoplasmic reticulum to cause contraction (tensing) of the muscle. To prevent the muscle from being perpetually contracted, the channel contains a fast inactivation gate that plugs the sodium pore very quickly after it opens. This prevents further entry of sodium. In time, potassium ions will leave the muscle cells, repolarising the cells and causing the pumping of calcium away from the contractile apparatus to relax the muscle.
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Pressure-Volume loops showing end-systolic pressure volume relationship End- systolic pressure volume relationship (ESPVR) describes the maximal pressure that can be developed by the ventricle at any given LV volume. This implies that the PV loop cannot cross over the line defining ESPVR for any given contractile state. The slope of ESPVR (Ees) represents the end-systolic elastance, which provides an index of myocardial contractility. The ESPVR is relatively insensitive to changes in preload, afterload, and heart rate.
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The pennation angle of the rotator cuff myofibers, the angle at which fibers connect to the associated tendon, affects the contractile properties and function of the whole pennate muscle. For example, the pennation angle determines the architectural gear ratio at which a pennate muscle operates. A large initial pennation angle results in a large AGR and velocity amplification. A 2011 study on human cadaveric shoulders suggests tendon tears may affect the pennation angle of the rotator cuff muscles.
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Dynamic microtubules regulate the levels of key G-proteins such as RhoA and Rac1, which regulate cell contractility and cell spreading. Dynamic microtubules are also required to trigger focal adhesion disassembly, which is necessary for migration. It has been found that microtubules act as “struts” that counteract the contractile forces that are needed for trailing edge retraction during cell movement. When microtubules in the trailing edge of cell are dynamic, they are able to remodel to allow retraction.
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Disrupting AMR misorients the PS, suggesting that both have a dependent role. Additionally, disrupting the PS also leads to disruptions in the AMR, suggesting both the actomyosin ring and primary septum have an interdependent relationship. The AMR, which is attached to the cell membrane facing the cytosol, consists of actin and myosin II molecules that coordinate the cells to split. The ring is thought to play an important role in ingression of the plasma membrane as a contractile force.
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Smooth muscle may contract phasically with rapid contraction and relaxation, or tonically with slow and sustained contraction. The reproductive, digestive, respiratory, and urinary tracts, skin, eye, and vasculature all contain this tonic muscle type. This type of smooth muscle can maintain force for prolonged time with only little energy utilization. There are differences in the myosin heavy and light chains that also correlate with these differences in contractile patterns and kinetics of contraction between tonic and phasic smooth muscle.
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The ectoplasm consists of cytoplasmic extensions used for prey capture and also contains food vacuoles for prey digestion. The ectoplasm is surrounded by a periplasmic cortex, also made up of microfibrils, but arranged into twenty plates, each with a hole through which one spicule projects. The cortex is linked to the spines by contractile myonemes, which assist in buoyancy control by allowing the ectoplasm to expand and contract, increasing and decreasing the total volume of the cell.
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Capitulum mitella has a short leathery stalk or peduncle supporting an upper region or capitulum, the whole being up to long. The peduncle is muscular and contractile and its surface is covered with fine scales. The capitulum is protected by eight large, sheathing scales and a ring of about twenty tiny scales surround the joint of capitulum and peduncle. Inside these scales is a cavity containing the head and thorax of the animal and its appendages.
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Fusion with more diploid stage cells, and even with other plasmodium of the same species, will continue to increase the size of the plasmodium. These macroscopic forms of the slime mold are the most well-known and best-studied stage of the life cycle. The plasmodium feeds on bacteria, other microorganisms and can even cannibalize other slime molds. The massive cytoplasm contains multiple nuclei, contractile vacuoles, mitochondria and food vacuoles found on the peripheral edge of the plasmodium.
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Under conditions of stress, including viral infection, cytotoxic agents, and oxidative stress, activation of NRG-1/ErbB signaling can protect myocardial cells against apoptosis. In contrast to embryonic and neonatal cardiomyocytes, adult myocardial cells are terminally differentiated and have lost the ability to proliferate. Therefore, growth of adult cardiac cells is commonly characterized by hypertrophy and an increased content of contractile proteins. However, studies have shown NRG-1 promotes myocardial regeneration through hyperplasia, and prevents hypertrophy surrounding infarcted areas.
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They are contractile cells which contain actin filaments and are primarily involved in transport of spermatozoa through the tubules. They provide structural integrity to the tubules through their involvement in laying down the basement membrane. This has also been shown to affect Sertoli cell function and PTM cells also communicate with Sertoli cells through the secretion of growth factors and ECM (extra-cellular matrix) components. Studies have shown PTM cells to be critical in achieving normal spermatogenesis.
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ACTA2 (actin alpha 2) is an actin protein with several aliases including alpha-actin, alpha-actin-2, aortic smooth muscle or alpha smooth muscle actin (α-SMA, SMactin, alpha-SM-actin, ASMA). Actins are a family of globular multi- functional proteins that form microfilaments. ACTA2 is one of 6 different actin isoforms and is involved in the contractile apparatus of smooth muscle. ACTA2 (as with all the actins) is extremely highly conserved and found in nearly all mammals.
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Phosphorylation: Ser118 of fsTnI, equivalent to Ser150 in cTnI, was reported as a phosphorylation substrate of AMPK. As AMPK is a key regulator of cellular energetics, phosphorylation of this site may provide an adaptive mechanism during energy deprivation in both skeletal and cardiac muscles. S-glutathionylation: fsTnI was found to be S-glutathionylated at Cys133 in rodent fast-twitch skeletal muscle and in human type II muscle fibers after exercise, which increased Ca2+ sensitivity of the contractile apparatus.
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Cytolysis occurs when a cell bursts due to an osmotic imbalance that has caused excess water to move into the cell. Cytolysis can be prevented by several different mechanisms, including the contractile vacuole that exists in some paramecia, which rapidly pump water out of the cell. Cytolysis does not occur under normal conditions in plant cells because plant cells have a strong cell wall that contains the osmotic pressure, or turgor pressure, that would otherwise cause cytolysis to occur.
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In drosophila, Sti (Sticky, ortholog of Citron-K) localizes to the cleavage furrow via association of a predicted coiled-coil region with actin and myosin. However, Sti depletion perturbs RhoA localization and causes excessive accumulation of phosphorylated MRLC (myosin regulatory light chain) at the cleavage site in late cytokinesis. Sti is believed to maintain correct RhoA localization at the cleavage site, which is in turn important for proper contractile ring organization at the end of cytokinesis.
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Schirmer was born in Bremen. He studied medicine and philosophy in Heidelberg and Basel from 1961 to 1966, receiving his doctorate at the Max Planck Institute for Medical Research under the tutelage of Swiss physiologist Johann Caspar Rüegg. The topic of his dissertation was "The Distinctive Features of Contractile Proteins in Arteries" (German: Die Besonderheiten der contractilen Proteine der Arterien). He received his university professor qualification (German Habilitation) in 1975 in biochemistry at the University of Heidelberg.
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Cardiac muscle cells or cardiomyocytes (also known as myocardiocytes or cardiac myocytes) are the muscle cells (myocytes) that make up the cardiac muscle (heart muscle). Each myocardial cell contains myofibrils, which are specialized organelles consisting of long chains of sarcomeres, the fundamental contractile units of muscle cells. Cardiomyocytes show striations similar to those on skeletal muscle cells. Unlike multinucleated skeletal cells, the majority of cardiomyocytes contain only one nucleus, although they may have as many as four.
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The linear, double-stranded DNA genome is 64,960 base pairs in length – only half the size of most phages with contractile tails, which typically fall in the range 161–231 kb. It has a GC-content of 35.4%. Of the 91 open reading frames (ORFs), only 33 show similarity to other known sequences. Remarkably, the genome of Cyanophage N1 encodes a functional CRISPR array, which has been suggested to protect the host against infection by competing viruses.
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The anterior end of the ciliates is covered in circular rows of cilia known as the somatic girdle. The main stalk that connects all of the ciliates branches is composed of a contractile spasmoneme, allowing stalk to contact as a single functioning unit. When contracting the colony can reduce its size by folding in as a single unit in a zig zag fashion. The protozoa can display polymorphism, or multiple physical forms of the same cell.
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Arranged in sheets or cylindrically, contractile myofibrils run the length of the muscle fiber. Myofibrils comprising a fine actin filament enclosed between a thick pair of myosin filaments slide past each other instigated by nerve impulses. Muscles can be divided into four categories: #Visceral: these muscles surround the tubes and ducts and produce peristalsis as demonstrated in the digestive system. #Segmental: causing telescoping of muscle segments required for moulting, increase in body pressure and locomotion in legless larvae.
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The effects of norbormide are caused by the endo-isomers, but the exo-isomers R, T and X showed no contractile effects on the rat arterio smooth muscle. There was only a relaxing effect on the muscle. In animal studies of Rozkowksi, he showed that the effects that are caused by NRB are irreversible. Another study has shown that there were respiratory depressions after the cardiovascular effects in the rats which were treated with norbormide in vivo.
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Since 2001, Thomas Lecuit has been studying how genes orchestrate the cellular movements that cause changes in the shape of embryonic tissues. His research includes characterization of the physical principles of morphogenesis, along the lines of the work begun by d'Arcy Thompson in On Growth and Form (1917)D’Arcy Wentworth Thompson, On Growth and Form, 1re éd., Cambridge (UK), Cambridge university Press, 1917; Forme et croissance, trad. de Dominique teyssié, seuil, coll. « science ouverte » 2009.His team first discovered the nature of the mechanical forces that cause tissue plasticity, namely the contractile forces that reshape the shape and cellular interactionsBertet C, Sulak L, Lecuit T, « Myosin-dependent junction remodelling controls planar cell intercalation and axis elongation », Nature, 2004 jun 10;429(6992), p. 667-71Rauzi, M., Verant, P., Lecuit, T. and Lenne, PF, « Nature and anisotropy of cortical forces orienting Drosophila tissue morphogenesis », Nature Cell Biology, 2008 dec;10(12), p. 1401-10Rauzi, M., Lenne PF., and Lecuit, T, « Planar polarized actomyosin contractile flows control epithelial junction remodelling », Nature, 2010.
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Myosin is a major contractile protein which converts chemical energy into mechanical energy through the hydrolysis of ATP. Myosin is a hexameric protein composed of a pair of myosin heavy chains (MYH) and two pairs of nonidentical light chains. This gene is a member of the MYH family and encodes a protein with an IQ domain and a myosin head-like domain. Mutations in this gene have been associated with two congenital contracture (arthrogryposis) syndromes, Freeman–Sheldon syndrome and Sheldon–Hall syndrome.
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The absolute refractory period for cardiac contractile muscle lasts approximately 200 ms, and the relative refractory period lasts approximately 50 ms, for a total of 250 ms. This extended period is critical, since the heart muscle must contract to pump blood effectively and the contraction must follow the electrical events. Without extended refractory periods, premature contractions would occur in the heart and would not be compatible with life. (a) There is long plateau phase due to the influx of calcium ions.
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The body and oral kinetids make up the infraciliature, an organization unique to the ciliates and important in their classification, and include various fibrils and microtubules involved in coordinating the cilia. The infraciliature is one of the main components of the cell cortex. Others are the alveoli, small vesicles under the cell membrane that are packed against it to form a pellicle maintaining the cell's shape, which varies from flexible and contractile to rigid. Numerous mitochondria and extrusomes are also generally present.
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This increases the speed of muscle relaxation, allowing the muscle to contract again sooner. Although parvalbumin is classified as a delayed calcium buffer, it quickly sequesters Ca2+, usually before the muscle is done fully contracting. Large amounts of parvalbumin allow rapid contractions of muscles at a high contractile speed with the trade-off of having relatively lower contraction force. This decreased force of contraction is due to the rapid sequestration of Ca2+, preventing prolonged contraction which is required for greater force.
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Colpoda inflata is 30-90 μm long and is characteristically L-shaped with its oral opening, the vestibule, lying in the corner of the "L". Very well-nourished individuals can also appear reniform. C. inflata has a macronucleus to which a micronucleus is attached, contractile vacuoles, an excretory pore and several extrusomes, although populations without extrusomes have been observed. The ciliature of C. inflata is holotrichous, meaning that it is regularly distributed over the whole cell surface in slightly spiralling lines.
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This increase in calcium activates calcium-sensitive contractile proteins that then use ATP to cause cell shortening. The mechanism for muscle contraction evaded scientists for years and requires continued research and updating. The sliding filament theory was independently developed by Andrew F. Huxley and Rolf Niedergerke and by Hugh Huxley and Jean Hanson. Their findings were published as two consecutive papers published in the 22 May 1954 issue of Nature under the common theme "Structural Changes in Muscle During Contraction".
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Protein catabolism (breakdown) has been estimated to supply 10% to 15% of the total energy requirement during a two-hour aerobic training session. This process could severely degrade the protein structures needed to maintain survival such as contractile properties of proteins in the heart, cellular mitochondria, myoglobin storage, and metabolic enzymes within muscles. The oxidative system (aerobic) is the primary source of ATP supplied to the body at rest and during low intensity activities and uses primarily carbohydrates and fats as substrates.
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The diversity of characteristics complicates description of Liliaceae morphology, and confused taxonomic classification for centuries. The diversity is also of considerable evolutionary significance (see Evolution). The family Liliaceae are characterised as monocotyledonous, perennial, herbaceous, bulbous (or rhizomatous in the case of Medeoleae) flowering plants with simple trichomes (root hairs) and contractile roots. The flowers may be arranged along the stem, developing from the base, or as a single flower at the tip of the stem, or as a cluster of flowers.
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Unlike the atrial cells, SA node cells contain fewer mitochondria (the power plant of the cell), fewer myofibers (the contractile machinery of the cell), and a smaller sarcoplasmic reticulum (a calcium storage organelle that releases calcium for contraction). This means that the SA node cells are less equipped to contract compared to the atrial and ventricular cells. Action potentials pass from one cardiac cell to the next through pores known as gap junctions. These gap junctions are made of proteins called connexins.
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Cyanophages like other bacteriophages rely on Brownian motion to collide with bacteria, and then use receptor binding proteins to recognize cell surface proteins, which leads to adherence. Viruses with contractile tails then rely on receptors found on their tails to recognize highly conserved proteins on the surface of the host cell. Cyanophages also have several surface proteins with Ig like domains, which are used for adherence. Some cyanophages also produce a horn like structure, which projects from the vertex opposite of the tail.
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The apelin receptor is expressed early during the embryonic development of the heart, where it regulates the migration of cell progenitors fated to differentiate into cardiomyocytes, the contractile cells of the heart. Its expression is also detected in the cardiomyocytes of the adult where apelin behaves as one of the most potent stimulator of cardiac contractility. Aged apelin knockout mice develop progressive impairment of cardiac contractility. Apelin acts as a mediator of the cardiovascular control, including for blood pressure and blood flow.
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Part of the process of strength training is increasing the nerve's ability to generate sustained, high frequency signals which allow a muscle to contract with their greatest force. It is this "neural training" that causes several weeks worth of rapid gains in strength, which level off once the nerve is generating maximum contractions and the muscle reaches its physiological limit. Past this point, training effects increase muscular strength through myofibrillar or sarcoplasmic hypertrophy and metabolic fatigue becomes the factor limiting contractile force.
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Peripheral muscle fatigue' during physical work is an inability for the body to supply sufficient energy or other metabolites to the contracting muscles to meet the increased energy demand. This is the most common case of physical fatigue—affecting a national average of 72% of adults in the work force in 2002. This causes contractile dysfunction that manifests in the eventual reduction or lack of ability of a single muscle or local group of muscles to do work. The insufficiency of energy, i.e.
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Phosphodiesterases (PDE) degrades cAMP and cGMP and, within the respiratory system of a newborn with MAS, various isoforms of PDE may be involved due to their pro-inflammatory and smooth muscle contractile activity. Therefore, non-selective and selective inhibitors of PDE could potentially be used in MAS therapy. However, the use of PDE inhibitors can cause cardiovascular side effects. Non-selective PDE inhibitors, such as methylxanthines, increase concentrations of cAMP and cGMP in the cells leading to bronchodilation and vasodilation.
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Tropomyosin alpha-3 chain is a protein that in humans is encoded by the TPM3 gene. This gene encodes a member of the tropomyosin family of actin-binding proteins involved in the contractile system of striated and smooth muscles and the cytoskeleton of non-muscle cells. Tropomyosins are dimers of coiled-coil proteins that polymerize end-to-end along the major groove in most actin filaments. They provide stability to the filaments and regulate access of other actin-binding proteins.
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This makes the blood very viscous and it requires considerable pressure to pump it around the body; octopuses' blood pressures can exceed . In cold conditions with low oxygen levels, haemocyanin transports oxygen more efficiently than haemoglobin. The haemocyanin is dissolved in the plasma instead of being carried within blood cells, and gives the blood a bluish colour. The systemic heart has muscular contractile walls and consists of a single ventricle and two atria, one for each side of the body.
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Furthermore, it was found that CB causes the disorganization of the 50Å microfilaments of mouse epithelial cells which causes the cells to lose their shape. It also affects the appearance of young glands in cells and new gland formation in other cells. Another group found that CB inhibits the ability of HeLa cells to undergo cytokinesis by decomposition of the contractile ring. Research from 1971 showed that CB interferes with the release of iodine derived from thyroglobulin and blocks colloid endocytosis.
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Part of the process of strength training is increasing the nerve's ability to generate sustained, high frequency signals which allow a muscle to contract with their greatest force. It is this "neural training" that causes several weeks worth of rapid gains in strength, which level off once the nerve is generating maximum contractions and the muscle reaches its physiological limit. Past this point, training effects increase muscular strength through myofibrillar or sarcoplasmic hypertrophy and metabolic fatigue becomes the factor limiting contractile force.
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Osculum The osculum (plural "oscula") is an excretory structure in the living sponge, a large opening to the outside through which the current of water exits after passing through the spongocoel. Wastes diffuse into the water and the water is pumped through the osculum carrying away with it the sponge's wastes. Sponges pump large volumes of water: typically a volume of water equal to the sponge's body size is pumped every five seconds. The size of the osculum is regulated by contractile myocytes.
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In the long run, however, reduced availability of the SMN protein results in gradual death of motor neuron cells in the anterior horn of spinal cord and the brain. Muscles that depend on these motor neurons for neural input now have decreased innervation (also called denervation), and therefore have decreased input from the central nervous system (CNS). Decreased impulse transmission through the motor neurons leads to decreased contractile activity of the denervated muscle. Consequently, denervated muscles undergo progressive atrophy (waste away).
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Quantitative neuromuscular monitors can be subdivided into monitors that measure the electrical response, the compound evoked muscle action potential, and those that monitor the contractile response to stimulation. The measurement of the electrical response to muscle stimulation is called electromyography. The mechanical response to stimulation of the muscle can be measured by mechanomyography, kinemyography and acceleromyography Quantitative acceleromyographic neuromuscular monitor with stimulating electrodes over the ulnar nerve and the piezoelectric crystal that measures acceleration on the thumb with hand adapter.
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Melkonian has research interests that range from cell biology, Melkonian, M., Robenek, H. (1980): Eyespot membranes of Chlamydomonas reinhardii: a freeze-fracture study. J. Ultrastruct. Res. 72, 90-102Salisbury, J.L., Baron, A., Surek, B., Melkonian, M. (1984): Striated flagellar roots: isolation and partial characterization of a calcium-modulated contractile organelle. J. Cell Biol. 99, 962-970 Melkonian, M., Reize, I.B., Preisig, H.R. (1987): Maturation of a flagellum/basal body requires more than one cell cycle in algal flagellates: Studies on Nephroselmis olivacea (Prasinophyceae).
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Sea Challengers Natural History Books, Washington, 426 pp. page(s): 217 The rhinophores are lamellate and contractile, the base is white topped with blue to purple but they can also be white with a longitudinal blue to purple line. The branched gill has a whitish external side, the internal surface is golden.Warren, Lindsay , Corolla, Jean-Pierre , Sittler, Alain-Pierre, (2014) Chromodoris leopardus Rudman, 1987 in : DORIS, January 3, 2014Debelius, Helmut, 2001, Nudibranchs and Sea Snails: Indo-Pacific Field Guide, IKAN – Unterwasserarchiv, Frankfurt, Germany.
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In test with rabbits, significant improvement in protection against arrhythmic effects and infarct size reduction was observed after administrating exogenously SRTX-c (in dosage of 0.24 nmol/kg, i.v.) prior the coronary occlusion accident. That was achieved thanks to ability of SRTX-c to activate selected ETB receptors. In rat thoracic aorta, the contractile activity is grouped as follows: ET-1 > SRTX-b > SRTX-a > SRTX-c at lower concentrations, but SRTX-b > ET-1 > SRTX-a > SRTX-c at higher concentrations.
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On the microscopic level, the wave of depolarization propagates to adjacent cells via gap junctions located on the intercalated disc. The heart is a functional syncytium (not to be confused with a true "syncytium" in which all the cells are fused together, sharing the same plasma membrane as in skeletal muscle). In a functional syncytium, electrical impulses propagate freely between cells in every direction, so that the myocardium functions as a single contractile unit. This property allows rapid, synchronous depolarization of the myocardium.
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Colponema is a colorless biflagellate with a pronounced ventral feeding groove. Cell size ranges from 4-14 µm in width and 8-17 µm in length and they have an oval shape that narrows at the anterior end. The cells have 1 µm long toxicysts, a type of organelle that is extruded from the cell and are used to immobilize prey. Species of Colponema vary in the presence of a contractile vacuoles, degree of dorsoventral flattening, and the length of flagella.
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Diagram of esophageal motility study in nutcracker esophagus: The disorder shows peristalsis with high-pressure esophageal contractions exceeding 180 mmHg and contractile waves with a long duration exceeding 6 sec. The diagnosis of nutcracker esophagus is typically made with an esophageal motility study, which shows characteristic features of the disorder. Esophageal motility studies involve pressure measurements of the esophagus after a patient takes a wet (fluid-containing) or dry (solid-containing) swallow. Measurements are usually taken at various points in the esophagus.
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The scab temporarily restores the integrity of the epidermis and restricts the entry of microorganisms. After the scab is formed, cells of the stratum basale begin to divide by mitosis and migrate to the edges of the scab. A week after the injury, the edges of the wound are pulled together by contraction. Contraction is an important part of the healing process when damage has been extensive, and involves shrinking in size of underlying contractile connective tissue, which brings the wound margins toward one another.
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It links the myofibrils laterally by connecting the Z-disks. Through its connection to the sarcomere, desmin connects the contractile apparatus to the cell nucleus, mitochondria, and post-synaptic areas of motor endplates. These connections maintain the structural and mechanical integrity of the cell during contraction while also helping in force transmission and longitudinal load bearing. In human heart failure, desmin expression is upregulated, which has been hypothesized to be a defense mechanism in an attempt to maintain normal sarcomere alignment amidst disease pathogenesis.
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Alpha(1)-adrenergic stimulation by phenylephrine in atrial muscle strips showed an 80% increase in ALC-2 phosphorylation coordinate with enhanced contractile force, which was inhibited by both Rho kinase and myosin light chain kinase inhibition. In a canine model of atrial fibrillation, decreased atrial contractility was associated with decreased ALC-2 and myosin binding protein C phosphorylation. Moreover, the slow force response induced by stretch in human atrial muscle was shown to be modulated by enhanced phosphorylation of ALC-2 by myosin light chain kinase.
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Nicotinic acetylcholine receptor 5\. Mitochondrion Muscle relaxation and paralysis can theoretically occur by interrupting function at several sites, including the central nervous system, myelinated somatic nerves, unmyelinated motor nerve terminals, nicotinic acetylcholine receptors, the motor end plate, and the muscle membrane or contractile apparatus. Most neuromuscular blockers function by blocking transmission at the end plate of the neuromuscular junction. Normally, a nerve impulse arrives at the motor nerve terminal, initiating an influx of calcium ions, which causes the exocytosis of synaptic vesicles containing acetylcholine.
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Diagrammatic conduction system of the heart Normal sinus rhythm is established by the sinoatrial (SA) node, the heart's pacemaker. The SA node is a specialized grouping of cardiomyocytes in the upper and back walls of the right atrium very close to the opening of the superior vena cava. The SA node has the highest rate of depolarization. This impulse spreads from its initiation in the SA node throughout the atria through specialized internodal pathways, to the atrial myocardial contractile cells and the atrioventricular node.
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The tentacles are hollow and are extended via hydrostatic pressure in a similar manner as the introvert, but have a different mechanism from that of the rest of the introvert, being connected, via a system of ducts, to one or two contractile sacs next to the oesophagus. Hooks are often present near the mouth on the introvert. These are proteinaceous, non-chitinous specializations of the epidermis, either arranged in rings or scattered. They may be involved in scraping algae off rock, or alternatively provide anchorage.
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Blood flows forward in the dorsal vessel, above the gut, and returns down the body in the ventral vessel, beneath the gut. The blood vessels themselves are contractile, helping to push the blood along, so most species have no need of a heart. In a few cases, however, muscular pumps analogous to a heart are found in various parts of the system. Conversely, some species have little or no circulatory system at all, transporting oxygen in the coelomic fluid that fills their body cavities.
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The extraglomerular mesangial cells are found between the afferent and efferent arterioles towards the vascular pole of the glomerulus. The extraglomerular mesangial cells are adjacent to the intraglomerular mesangial cells that are located inside the glomerulus and in between the capillaries. The primary function of mesangial cells is to remove trapped residues and aggregated protein from the basement membrane thus keeping the filter free of debris. The contractile properties of mesangial cells have been shown to be insignificant in changing the filtration pressure of the glomerulus.
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In liposomes Osawa (2009) showed FtsZ is capable of exerting a contractile force with no other proteins present. Erickson (2009) proposed how the roles of tubulin-like proteins and actin-like proteins in cell division became reversed in an evolutionary mystery. The use of the FtsZ ring in dividing chloroplasts and some mitochondria further establishes their prokaryotic ancestry. L-form bacteria that lack a cell wall do not require FtsZ for division, which implies that bacteria may have retained components of an ancestral mode of cell division.
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In this model, FtsZ scission force comes from the relative lateral movement of subunits. Lines of FtsZ would line up together parallel and pull on each other creating a "cord" of many strings that tightens itself. In other models, FtsZ does not provide the contractile force but provides the cell a spatial scaffold for other proteins to execute the division of the cell. This is akin to the creating of a temporary structure by construction workers to access hard-to-reach places of a building.
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Similarly, in systemic hypertension, the left ventricle must work harder to overcome the higher pressures of the vascular system and responds by thickening to deal with increased wall stress. Concentric hypertrophy is characterized by an addition of sarcomeres (the contractile units of cardiac cells) in parallel. The result is an increase in thickness of the myocardium without a corresponding increase in ventricular size. This is maladaptive largely because there is not a corresponding proliferation of the vasculature supplying the myocardium, resulting in ischemic areas of the heart.
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Morphologically the subfamily is characterised by having 6 tepals and 6 stamens with a superior ovary, a characteristic which placed them within the older order of Liliales in many older classification systems, such as the Cronquist system, but they now separate from them within the Asparagales order. They have also been included in the family Liliaceae. Roots: contractile and mucilaginous. Leaves: fleshy and mucilaginous arranged in a basal rosette, alternate and spiral, simple, margin entire, with parallel venation, sheathing at the base, without stipules and hair simple.
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Trimastix were first described by William Kent in 1881 when he observed a Trimastix cell in a sample sourced from decaying fuci seaweed. He described the genera at the time as free-swimming naked animalcules that are oval, or pear shaped, with a membranous border and three flagella inserted on the anterior end. Kent observed one flagellum facing forwards and two facing backwards. It was also noted in this account that Trimastix had a visually apparent nucleus and contractile vacuole but no visual oral aperture.
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In vitro muscle testing can be done on any scale of muscle organization - entire groups of muscles (provided they share a common insertion or origin, as in the human quadriceps), a single muscle, a "bundle" of muscle fibers, a single muscle fiber, a single myofibril, a single sarcomere, a cardiomyocyte or even a half- sarcomere. Muscle fibers may be intact, or may be "skinned", a process which removes the cell membrane, sarcoplasmic reticulum, and cytoplasm, allowing greater access to the contractile components of the sarcomere.
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Whilst variation in gap junction channels do occur, their structure remains relatively standard, and this interaction ensures efficient communication without the escape of molecules or ions to the extracellular fluid. Gap junctions play vital roles in the human body, including their role in the uniform contractile of the heart muscle. They are also relevant in signal transfers in the brain, and their absence shows a decreased cell density in the brain. Retinal and skin cells are also dependent on gap junctions in cell differentiation and proliferation.
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Some biologists have proposed that the Hemichordates (specifically the Enteropneusta) may represent an intermediate body plan in the evolution of the "inverted" state of the chordates. Though they are considered deuterostomes, the dorsoventral axis of hemichordates retains features of both protostomes and chordates. For example, enteropneusts have an ectodermally-derived dorsal nerve cord in the collar region which has been proposed to be homologous to the chordate neural tube. However, they also have a ventral nerve cord and a dorsal contractile vessel similar to protostomes.
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Cytochalasin has found practical application in thromboelastometry (TEM) whole blood assays for the assessment of fibrinogen and fibrin polymerization disorders in the FIBTEM assay on ROTEM. This test is based on the principle that cytochalasin D very effectively inhibits platelet function by inhibition of the contractile elements. The platelet inhibition is more effective than when platelets are blocked by GPIIb/IIIa antagonists. In vitro and clinical data indicate that the clot strength in FIBTEM increases in a fibrinogen concentration-dependent manner independent of platelet count.
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Cell "sorting out" consists of cells moving so as to sort into clusters that maximize contact between cells of the same type. The ability of cells to do this has been proposed to arise from differential cell adhesion by Malcolm Steinberg through his differential adhesion hypothesis. Tissue separation can also occur via more dramatic cellular differentiation events during which epithelial cells become mesenchymal (see Epithelial–mesenchymal transition). Mesenchymal cells typically leave the epithelial tissue as a consequence of changes in cell adhesive and contractile properties.
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First, RhoA stimulates nucleation of unbranched actin filaments by activation of Diaphanous-related formins. This local generation of new actin filaments is important for the contractile ring formation. This actin filament formation process also requires a protein called profilin, which binds to actin monomers and helps load them onto the filament end. Second, RhoA promotes myosin II activation by the kinase ROCK, which activates myosin II directly by phosphorylation of the myosin light chain and also inhibits myosin phosphatase by phosphorylation of the phosphatase-targeting subunit MYPT.
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In support of the adenoviral experiments, S100A1 transgenic overexpressing mice subjected to myocardial infarction showed preserved contractile function, abrogated apoptosis, preserved sarcoplasmic reticulum calcium cycling and beta adrenergic signaling, prevention from cardiac hypertrophy and heart failure, as well as prolonged survival relative to non- transgenic controls. S100A1 has also been identified as a novel regulator of endothelial cell post-ischemic angiogenesis, as patients with limb ischemia exhibited downregulation of S100A1 expression in hypoxic tissue. In melanocytic cells, S100A1 gene expression may be regulated by MITF.
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As a result, the use of disopyramide may reduce contractile force up to 42% at low doses and up to 100% in higher doses leading to heart failure. Levites proposed a possible secondary mode of action for disopyramide, against reentrant arrhythmias after an ischemic insult. Disopyramide decreases the inhomogeneity between infarcted and normal myocardium refractory periods; in addition to lengthening the refractory period. This decreases the chance of re-entry depolarization, because signals are more likely to encounter tissue in a refractory state which cannot be excited.
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Species in the genus Dunaliella are morphogically similar to Chlamydomonas reinhardtii with the main exception being that Dunaliella lack both a cell wall and a contractile vacuole. Dunaliella has two flagella of equal length and has a single cup-like chloroplast that often contains a central pyrenoid. The chloroplast can hold large amounts of β-carotene, which makes it appear orange-red. The β-carotene appears to protect the organism from long-term UV radiation that D. salina is exposed to in its typical environments.
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When ACh is degraded by AChE, the receptors are no longer stimulated and the muscle can be repolarised. If enough Na+ enter the muscle fibre, it causes an increase in the membrane potential from its resting potential of -95mV to -50mV (above the threshold potential -55V) which causes an action potential to spread throughout the fibre. This potential travels along the surface of the sarcolemma. The sarcolemma is an excitable membrane that surrounds the contractile structures known as myofibrils that are located deep in the muscle fibre.
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Peripheral muscle fatigue during physical work is considered an inability for the body to supply sufficient energy or other metabolites to the contracting muscles to meet the increased energy demand. This is the most common case of physical fatigue—affecting a national average of 72% of adults in the work force in 2002. This causes contractile dysfunction that manifests in the eventual reduction or lack of ability of a single muscle or local group of muscles to do work. The insufficiency of energy, i.e.
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The Liliaceae are characterised as monocotyledonous, perennial, herbaceous, bulbous (or rhizomatous in the case of Medeoleae) flowering plants with simple trichomes (root hairs) and contractile roots. The flowers may be arranged (inflorescence) along the stem, developing from the base, or as a single flower at the tip of the stem, or as a cluster of flowers. They contain both male (androecium) and female (gynoecium) characteristics and are symmetric radially, but sometimes as a mirror image. Most flowers are large and colourful, except for Medeoleae.
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Numerous in vitro experimental data indicate that calponin 1 functions as an inhibitory regulator of smooth muscle contractility through inhibiting actomyosin interactions. In this regulation, binding of Ca2+-calmodulin and PKC phosphorylation dissociate calponin 1 from the actin filament and facilitate smooth muscle contraction. In vivo data also support the role of calponin 1 as regulator of smooth muscle contractility. While aortic smooth muscle of adult Wistar Kyoto rats, which naturally lacks calponin 1, is fully contractile, it has a decreased sensitivity to norepinephrine activation.
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Nebulette was identified in 1995 by Moncman and Wang using primary cultures of chicken embryonic cardiomyocytes by immunoprecipitations with certain anti-nebulin monoclonal antibodies. Normal expression of nebulette is essential for the assembly and contractile function of myofibrils. Specifically, nebulette appears to regulate the stability and length of actin thin filaments, as well as beating frequencies of cardiomyocytes; reduction of full-length nebulette protein in cardiomyocytes resulted in reduced thin filament lengths, depressed beating frequencies and loss of thin filament regulatory proteins troponin I and tropomyosin.
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Most vessels of the microcirculation are lined by flattened cells of the endothelium and many of them are surrounded by contractile cells called pericytes. The endothelium provides a smooth surface for the flow of blood and regulates the movement of water and dissolved materials in the interstitial plasma between the blood and the tissues. The endothelium also produces molecules that discourage the blood from clotting unless there is a leak. Pericyte cells can contract and decrease the size of the arterioles and thereby regulate blood flow and blood pressure.
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Though HFpEF is characterized by a normal ejection fraction, this parameter is a rather poor index of the heart's contractile function. Some studies have shown that metrics of load independent contractility (such as left ventricular stiffness) reveal diminished systolic function in HFpEF patients compared to healthy controls, and are corroborated by tissue Doppler findings that reveal changes in longitudinal contraction and motion abnormalities. While these systolic impairments may be minimal at rest, they become more exaggerated with increased demand, as seen in exercise.Borlaug, B. A., Kane, G. C., Melenovsky, V., & Olson, T. P. (2016).
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The terminal web is a filamentous structure found at the apical surface of epithelial cells that possess microvilli. It is composed primarily of actin filaments stabilized by spectrin, which also anchors the terminal web to the apical cell membrane. The presence of myosin II and tropomyosin helps to explain the contractile ability of the terminal web. When contracted, the terminal web causes a decrease in diameter of the apex of the cell, causing the microvilli, which are anchored into the terminal web through their stiff actin fibers, to spread apart.
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In most amphibian organs including the heart, the concentration of adrenaline far exceeds that of noradrenaline, and adrenaline is indeed the main transmitter. In mammals, however, difficulties arose. In a comprehensive structure-activity study of adrenaline-like compounds, Dale and the chemist George Barger in 1910 pointed out that Elliott's hypothesis assumed a stricter parallelism between the effects of sympathetic nerve impulses and adrenaline than actually existed. For example, sympathetic impulses shared with adrenaline contractile effects in the trigone but not relaxant effects in the fundus of the cat's urinary bladder.
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In addition, preeclampsia can result in thrombocytopenia, platelet dysfunction, and disseminated intravascular coagulation, which may also contribute to the observed association. Chorioamnionitis has repeatedly been shown to result in a poorly contractile uterus, likely in part due to inflammation. Retained placenta can also result in atony by rendering focal areas of uterine myometrium unable to contract. Cesarean delivery, often performed after a protracted labor, may predispose a patient to uterine atony as a result of uterine muscle fatigue or impaired contraction at the site of the uterine incision.
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A post-anal tail is present in juvenile member of the acorn worm family Harrimaniidae. The prosome of pterobranchs is specialized into a muscular and ciliated cephalic shield used in locomotion and in secreting the coenecium. The mesosome extends into one pair (in the genus Rhabdopleura) or several pairs (in the genus Cephalodiscus) of tentaculated arms used in filter feeding. The metasome, or trunk, contains a looped digestive tract, gonads, and extends into a contractile stalk that connects individuals to the other members of the colony, produced by asexual budding.
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Muscles contain many different systems on which the evolutionary selection of preflex stabilization can operate. The deltoid muscle, for example, consists of at least seven segments with different bone attachments and neural control. Within each muscle segment, there exists a complex internal structure that goes down to one in which each muscle unit consists of a tendon, aponeurosis, and a fascicle of active contractile and passive elements. Another source of variation is in the internal architecture of the fiber orientation relative to a muscle’s line of action, for example, as found in pennate muscles.
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Mesangial cells have irregular shapes with flattened-cylinder-like cell bodies and processes at both ends containing actin, myosin and actinin, giving mesangial cells contractile properties. The anchoring filaments from mesangial cells to the glomerular basement membrane can alter capillary flow by changing glomerular ultrafiltration surface area. Extraglomerular mesangial cells are in close connection to afferent and efferent arteriolar cells by gap junctions, allowing for intercellular communication. Mesangial cells are separated by intercellular spaces containing extracellular matrix called the mesangial matrix that is produced by the mesangial cells.
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The haloviruses HF1 and HF2 belong to the same genus but since they infect archaea rather than bacteria are likely to be placed in a separate genus once their classification has been settled. A dwarf group has been proposed on morphological and genomic grounds. This group includes the phages Aeromonas salmonicida phage 56, Vibrio cholerae phages 138 and CP-T1, Bdellovibrio phage φ1422 and Pectobacterium carotovorum phage ZF40. Their shared characteristics include an identical virion morphology, characterized by usually short contractile tails and all have genome sizes of approximately 45 kilobases.
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In 1897 Engelmann introduced four Greek terms to describe key physiological properties of the heart: inotropy, the ability to contract; chronotropy, the ability to initiate an electrical impulse; dromotropy, the ability to conduct an electrical impulse; and bathmotropy, the ability to respond to direct mechanical stimulation. A fifth term, lusitropy, was introduced in 1982 when relaxation was recognized to be an active process, and not simply dissipation of the contractile event. In an article in the American Journal of the Medical Sciences, these five terms were described as the five fundamental properties of the heart.
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The corms form in vertical chains with the youngest at the top and oldest and largest buried most deeply in the soil. The roots of the lowermost corm in a chain are contractile roots and drag the corm deeper into the ground where conditions allow. The chains of corms are fragile and easily separated, a quality that has enabled some species to become invasive and difficult to control in the garden. They have colourful inflorescences of 4 to 20 vivid red and orange subopposite flowers on a divaricately (horizontally) branched stem.
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Endurance training can increase the size of low force- producing slow twitch muscle by as much as resistance training can increase the size of high force-producing fast twitch muscle. These situations have the ability to result in two muscles of equal size, but the slow twitch muscle produces only a small fraction of the maximum contractile strength produced by the fast twitch muscle.Vanderheyden, M. J., Hilgevoord, A. A. J., Bour, L. J., & Devisser, B. W. O. (1994). MODELING MOTONEURON FIRING PROPERTIES - DEPENDENCY ON SIZE AND CALCIUM DYNAMICS.
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Sizes of the cells vary with environmental conditions such as light, salinity, and nutrient availability . Their two equal-length apical flagella are about 1.5X – 2X the length of the cell and beat rapidly, pulling the cell forward to cause abrupt turning motions and rotations along the longitudinal axis. The basal bodies of the flagella are interconnected by a distal fibre that is bilaterally cross-striated. The morphology of Dunaliella is very similar to that of Chlamydomonas, however it can be distinguished through its lack of cell wall and contractile vacuoles.
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This budding process involves multiple signaling pathways including the elevation of intracellular calcium and reorganization of the cell's structural scaffolding. The formation and release of microvesicles involve contractile machinery that draws opposing membranes together before pinching off the membrane connection and launching the vesicle into the extracellular space. Microvesicle budding takes place at unique locations on the cell membrane that are enriched with specific lipids and proteins reflecting their cellular origin. At these locations, proteins, lipids, and nucleic acids are selectively incorporated into microvesicles and released into the surrounding environment.
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The type species for Cyanomyovirus of the family Myoviridae is Cyanophage AS-1, which was isolated from a waste stabilization pond, and was also the first genus recognized. The tails have been observed as either contractile or noncontractile with lengths of 20 to 244 nm, widths of 15 to 23 nm, and a shrinking range of 93 nm. Cyanophages generally have isometric hexagonal heads with diameters ranging from 55 to 90 nm. There is large morphological variation in this group, which suggests that they infect a variety of host species.
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This builds an osmotic gradient across the vesicle membrane, leading to influx of water from the cytosol into the vesicles by osmosis, which is facilitated by aquaporins. Since these vesicles fuse with the central contractile vacuole, which expels the water, ions end up being removed from the cell, which is not beneficial for a freshwater organism. The removal of ions with the water has to be compensated by some yet-unidentified mechanism. Like other eukaryotes, Amoeba species are adversely affected by excessive osmotic pressure caused by extremely saline or dilute water.
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He has an equal skill with the poisons of Sarkoy, including the dreaded cluthe, a poison which acts within seconds to paralyze and minutes to kill by means of muscle contractions (including contractile paralysis of the respiratory muscles). He also employs at one point a gauntlet wired to deliver electric shocks and a pistol which discharges "slivers of explosive glass". As a civilian, his ships are unarmed. The armament of warships is not covered to any degree, but probably includes energy weapons similar to the projac but on a larger scale.
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Portion of a myofibril, showing sarcomere structure: S = Sarcomere, unit of muscle function A = A-band, region of myosin I = I-band, region of just actin H = H-zone, region of just myosin Z = Z-line, sarcomere boundary M = M-line, sarcomere center Each muscle fiber contains myofibrils, which are very long chains of sarcomeres, the contractile units of the cell. A cell from the biceps brachii muscle may contain 80,000 sarcomeres. The myofibrils of smooth muscle cells are not arranged into sarcomeres. The sarcomeres are composed of thin and thick filaments.
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The TATA box is also found in 40% of the core promoters of genes that code for the actin cytoskeleton and contractile apparatus in cells. The type of core promoter affects the level of transcription and expression of a gene. TATA-binding protein (TBP) can be recruited in two ways, by SAGA, a cofactor for RNA polymerase II, or by TFIID. When promoters use the SAGA/TATA box complex to recruit RNA polymerase II, they are more highly regulated and display higher expression levels than promoters using the TFIID/TBP mode of recruitment.
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In a healthy heart, specialized cells in the sinoatrial node are responsible for the generation of contractile stimuli that are directed throughout the heart. A direct neural-like pathway propagates this electrical signal from the SA node through the atrial tissue to a central nodal point in the center of the heart, the atrioventricular node. From here, the signal travels down a signal conducting channel (the bundle of His) where it will diverge into a left and right branch that will control the left and right ventricle, respectively.
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ECG from a person taking digoxin, explaining ST depressions in mainly precordial leads V4 and V5. Digoxin's primary mechanism of action involves inhibition of the sodium potassium adenosine triphosphatase (Na+/K+ ATPase), mainly in the myocardium. This inhibition causes an increase in intracellular sodium levels, resulting in decreased activity of the sodium-calcium exchanger, which normally imports three extracellular sodium ions into the cell and transports one intracellular calcium ion out of the cell. The reversal of this exchanger causes an increase in the intracellular calcium concentration that is available to the contractile proteins.
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Pulmonary heart disease, also known as cor pulmonale, is the enlargement and failure of the right ventricle of the heart as a response to increased vascular resistance (such as from pulmonic stenosis) or high blood pressure in the lungs. Chronic pulmonary heart disease usually results in right ventricular hypertrophy (RVH), whereas acute pulmonary heart disease usually results in dilatation. Hypertrophy is an adaptive response to a long-term increase in pressure. Individual muscle cells grow larger (in thickness) and change to drive the increased contractile force required to move the blood against greater resistance.
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This gene, a muscle member of the immunoglobulin superfamily, encodes a myosin light-chain kinase, which is a calcium-/calmodulin-dependent enzyme. This kinase phosphorylates myosin regulatory light chains to facilitate myosin interaction with actin filaments to produce contractile activity. This gene encodes both smooth muscle and nonmuscle isoforms. In addition, using a separate promoter in an intron in the 3' region, it encodes telokin, a small protein identical in sequence to the C-terminus of myosin light chain kinase, that is independently expressed in smooth muscle and functions to stabilize unphosphorylated myosin filaments.
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It has also been proposed that microdomain interaction marks the formation of new focal adhesion sites at the cell periphery. The interaction of myosin with the actin network then generates membrane retraction/ruffling, retrograde flow, and contractile forces for forward motion. Finally, continuous application of stress on the old focal adhesion sites could result in the calcium-induced activation of calpain, and consequently the detachment of focal adhesions which completes the cycle. In addition to actin polymerization, microtubules may also play an important role in cell migration where the formation of lamellipodia is involved.
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The significance of each of these factors will depend on the nature of the fatigue-inducing work that is being performed. Though not universally used, "metabolic fatigue" is a common alternative term for peripheral muscle weakness, because of the reduction in contractile force due to the direct or indirect effects of the reduction of substrates or accumulation of metabolites within the muscle fiber. This can occur through a simple lack of energy to fuel contraction, or through interference with the ability of Ca2+ to stimulate actin and myosin to contract.
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The muscle architecture of pennate muscles, such as the human quadriceps, is highly plastic and strongly influences contractile properties. Changes to pennate muscle architectural properties, such as pennation angle and thereby the PCSA, can alter the muscle’s force producing capabilities as well as the AGR at which the muscle operates. Parallelogram models predict that total PCSA of bipennate muscles increases in proportion to sin(θpennation) while total force exerted on the associated aponeurosis decreases with cos(θpennation). This theorizes that pennate muscle force generation increases until a 45 degree pennation angle is achieved.
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Following its assembly, contraction of the actin-myosin ring leads to ingression of the attached plasma membrane, which partitions the cytoplasm into two domains of emerging sister cells. The force for the contractile processes is generated by movements along actin by the motor protein myosin II. Myosin II uses the free energy released when ATP is hydrolyzed to move along these actin filaments, constricting the cell membrane to form a cleavage furrow. Continued hydrolysis causes this cleavage furrow to ingress (move inwards), a striking process that is clearly visible through a light microscope.
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Dictyostelium aggregations on a culture plate Dictyostelium colony in process of aggregation Pseudoplasmodium or "slug" of a Dictyostelium Single amoeboid cell of Dictyostelium, showing the contractile vacuole Dictyostelium is a genus of single- and multi-celled eukaryotic, phagotrophic bacterivores. Though they are Protista and in no way fungal, they traditionally are known as "slime molds". They are present in most terrestrial ecosystems as a normal and often abundant component of the soil microflora, and play an important role in the maintenance of balanced bacterial populations in soils.Landolt. C. (2006) Dictyostelid Cellular Slime Molds from Caves.
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Herald Ecochem, established in May 2012, is an environmentally conscious company that manufactures plastic materials for food, electronics, and other products. In 2013 Ecochem received ISO 9001, a quality management certificate, and in 2014 it received ISO 14001, an environmental management certificate. In addition in 2015, Ecochem became the first Korean company to receive a “Green Label’, which is Singapore’s ecofriendly approval certificate. Ecochem is currently in the process of developing other high value films such as contractile film, special protection film, sun ray protecting film, and circuit board film.
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In the case of collective migration, tumor cells form protrusions (pseudopodia) at the leading edge, use integrins to form focal contacts with the actin cytoskeleton, and perform proteolytic degradation of the extracellular matrix, creating a space for invasion of the tumor tissue and extensively involving the actin-myosin contractile apparatus in the process to ensure successful migration. The differences in the polarity of collectively migrating cell groups are due to the features of expression of surface receptors, such as CXCR4 and CXCR7 chemokine receptors, in the “leader” cells.
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Rottlerin is a potent large conductance potassium channel (BKCa++) opener.Clements RT, Cordeiro B, Feng J, Bianchi C, Sellke FW. "Rottlerin increases cardiac contractile performance and coronary perfusion through BKCa++ channel activation after cold cardioplegic arrest in isolated hearts. Circulation 2011 Sep 13; 124(11 Suppl):S55-61 BKCa++ is found in the inner mitochondrial membrane of cardiomyocytes.Zakharov SI, Morrow JP, Liu G, Yang L, Marx SO. Activation of the BK (SLO1) potassium channel by mallotoxin" J Biol Chem 2005;280: 30882–30887 Opening these channels is beneficial for post-ischemic changes in vasodilation.
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Motor unit recruitment refers to the activation of additional motor units to accomplish an increase in contractile strength in a muscle. A motor unit consists of one motor neuron and all of the muscle fibers it stimulates. All muscles consist of a number of motor units and the fibers belonging to a motor unit are dispersed and intermingle amongst fibers of other units. The muscle fibers belonging to one motor unit can be spread throughout part, or most of the entire muscle, depending on the number of fibers and size of the muscle.
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Nonmuscle tropomyosin isoforms function in all cells, both muscle and nonmuscle cells, and are involved in a range of cellular pathways that control and regulate the cell's cytoskeleton and other key cellular functions. The actin filament system that is involved in regulating these cellular pathways is more complex than the actin filament systems that regulates muscle contraction. The contractile system relies upon 4 actin filament isoforms and 5 tropomyosin isoforms, whereas the actin filament system of the cytoskeleton uses two actin filament isoforms and over 40 tropomyosin isoforms.
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Microscopically, veins have a thick outer layer made of connective tissue, called the tunica externa or tunica adventitia. During procedures requiring venous access such as venipuncture, one may notice a subtle "pop" as the needle penetrates this layer. The middle layer of bands of smooth muscle are called tunica media and are, in general, much thinner than those of arteries, as veins do not function primarily in a contractile manner and are not subject to the high pressures of systole, as arteries are. The interior is lined with endothelial cells called tunica intima.
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It is not understood whether the physical opening of the L-type calcium channels or the presence of calcium causes the ryanodine receptors to open. The outflow of calcium allows the myosin heads access to the actin cross-bridge binding sites, permitting muscle contraction. Muscle contraction ends when calcium ions are pumped back into the sarcoplasmic reticulum, allowing the contractile apparatus and, thus, muscle cell to relax. Upon muscle contraction, the A-bands do not change their length (1.85 micrometer in mammalian skeletal muscle), whereas the I-bands and the H-zone shorten.
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From 1915, however, he suddenly changed ideas and strongly claimed the theses published in the Italian magazine by Maestrini. In 1923, on the advice of Silvestro Baglioni, director of the Institute of Physiology of the University of Rome, Maestrini wrote to Starling to claim the priority of the discovery. The response of the English physiologist was surprising. In a letter still kept by Maestrini’s family, Starling recognized that it wasn't the Italian scientist who first, in 1915, had shown a direct relationship between the length of the cardiac fiber and its contractile strength.
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Like other ribbon worms, A. lactifloreus is not divided into segments but is smooth and contractile. It is up to eight centimetres long with a head slightly broader than the body. The eyes are in four groups, two rows on either side of the front of the head and two more central clusters further back. There is a proboscis which can be extended forward from an opening above the mouth and which can be as long as the body and it is armed with a needle-like stylet.
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An axostyle is a sheet of microtubules found in certain protists. It arises from the bases of the flagella, sometimes projecting beyond the end of the cell, and is often flexible or contractile, and so may be involved in movement and provides support for the cell. Axostyles originate in association with a flagellar microtubular root and occur in two groups, the oxymonads and parabasalids; they have different structures and are not homologous. Within Trichomonads the axostyle has been theorised to participate in locomotion and cell adhesion, but also karyokinesis during cell division.
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Hypertrophic cardiomyopathy (HCM) is a common condition (prevalence >1:500) characterized by abnormal thickening of the ventricular muscle, classically in the intraventricular septal wall. HCM is described as a disease of the sarcomere, because mutations in the contractile proteins of the sarcomere have been identified in about half of patients with HCM. The cTnC mutations that have been associated with HCM are A8V, L29Q, A31S, C84Y, D145E. In all cases, the mutation was identified in a single patient, so additional genetic testing is needed to confirm or refute the clinical significance of these mutations.
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The significance of each of these factors will depend on the nature of the fatigue-inducing work that is being performed. Though not universally used, "metabolic fatigue" is a common alternative term for peripheral muscle weakness, because of the reduction in contractile force due to the direct or indirect effects of the reduction of substrates or accumulation of metabolites within the myocytes. This can occur through a simple lack of energy to fuel contraction, or through interference with the ability of Ca2+ to stimulate actin and myosin to contract.
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Excessive catecholamine stimulation has a toxic effect on cardiac muscle cells which creates necrosis of the contractile units of cells similarly seen during acute myocardial infarction. The increased workload of cardiac muscle created by the stimulation of catecholamines, increases the need for more blood and oxygen to these muscles to sustain function. When these demands are unable to be met, the heart is starved of blood and oxygen and begins to die. Included in the cytotoxic sequela of catecholamine toxicity is the molecular transformation of the cardiac myocyte to produce apical stunning.
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The Angiosperm Phylogeny Group (APG) made rapid progress in establishing a modern monophyletic classification of the flowering plants by 2009. Despite establishing this relative degree of monophyly (genetic homogeneity) for the family Liliaceae, their morphology remains diverse and there exists within the Liliaceae clade or grouping, a number of subclades (subgroups). Particularly enigmatic were Clintonia, Medeola, Scoliopus, and Tricyrtis. Of the fifteen genera within the Liliaceae, the ten genera of the Lilioideae subfamily form one morphological group that is characterised by contractile bulbs and roots, and a Fritillaria-type embryo-sac (megagametophyte with four megaspores).
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Since both the digestive system and the respiratory system are connected by the pharynx, there are many problems and diseases that occur when the body is unable to regulate passage of food and air into the appropriate tracts. Perhaps the most preventable cause of damage to these reflexes originates from smoking. One study has shown that, when compared to non-smokers, the threshold volumes (in other words the lowest volume at which one of these reflexes is triggered) for both the pharyngo-upper esophageal sphincter contractile reflex and reflexive pharyngeal swallowing is increased.
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The scaffold protein anillin is one of the most crucial partners of RhoA during cytokinesis and plays a fundamental role in the assembly and stabilization of the contractile ring by interacting with RhoA, septins, F-actin, myosin II, and mDia2 and it has been shown that its depletion results in cleavage furrow instability. Citron-K is capable of physically and functionally interacting with the actin-binding protein anillin. Like active RhoA, anillin is also displaced from the midbody in Citron-K-depleted cells. The overexpression of Citron-K and of anillin leads to abscission delay.
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Cells in the outer layer (epidermis) and the inner layer (gastrodermis) have microfilaments that group into contractile fibers. These fibers are not true muscles because they are not freely suspended in the body cavity as they are in more developed animals. Longitudinal fibres are found in the tentacles and oral disc, and also within the mesenteries, where they can contract the whole length of the body. Circular fibers are found in the body wall and, in some species, around the oral disc, allowing the animal to retract its tentacles into a protective sphincter.
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Since the anemone lacks a rigid skeleton, the contractile cells pull against the fluid in the gastrovascular cavity, forming a hydrostatic skeleton. The anemone stabilizes itself by flattening its pharynx which acts as a valve, keeping the gastrovascular cavity at a constant volume and making it rigid. When the longitudinal muscles relax, the pharynx opens and the cilia lining the siphonoglyphs beat, wafting water inwards and refilling the gastrovascular cavity. In general, the sea anemone inflates its body to extend its tentacles and feed, and deflates it when resting or disturbed.
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Muranotrichea is a class of free-living marine anaerobic ciliates, that, together with the classes Parablepharismea and Armophorea, form a major clade of obligate anaerobes within the SAL group (Spirotrichea, Armophorea, and Litostomatea). Muranotrichea are medium to large, elongated holotrichous ciliates with contractile body and somatic ciliature composed of dikinetids. Their oral ciliature includes an elongated key-hole shaped peristome, an adoral zone of membranelles spiraling rightward around distinctly neck-like anterior body part; and heteromorphic paroral membrane . They inhabit micro- oxic marine to brackish sediments and host prokaryotic ectosymbionts and endosymbionts.
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L-type calcium channel blockers can induce dilation of the coronary arteries while also decreasing the heart's demand for oxygen by reducing contractility, heart rate, and wall stress. The reduction of these latter three factors decreases the contractile force that the myocardium must exert in order to achieve the same level of cardiac output. Beta-receptor antagonists do not cause vasodilation, but like L-type calcium channel blockers, they do reduce the heart's demand for oxygen. This reduction similarly results from a decrease in heart rate, afterload, and wall stress.
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Frank's initial research was related to fat absorption. But in his postdoctoral work (Habilitationsschrift) Frank investigated the isometric and isotonic contractile behaviour of the heart and it is this work that he is best known for. Frank's work on this topic preceded that of Ernest Starling, but both are usually credited with providing the foundations of what is termed the Frank–Starling law of the heart. This law states that "Within physiological limits, the force of contraction is directly proportional to the initial length of the muscle fiber".
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This is true up to a point, however beyond this there is a loss of contractile ability due to loss of connection between myofibrils; see figure. Various pathologies, listed below, can lead to volume overload. Different mechanisms are involved depending on the cause, however the common theme is that of a high cardiac output with a low or normal afterload. The output may be high due to the inefficiency in valve disease, or it may be high due to shunting of blood in left-to-right shunts and arteriovenous malformations.
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In chemistry, 3,3,4,4-tetramethyltetrahydrofuran-2,5-dione is a heterocyclic compound with the formula , or (CH3)2(COC2COO)(CH3)2. It is a white crystalline solid with a pungent camphoraceous odor. The compound is also called 3,3,4,4-tetramethyloxolane-2,5-dione (its IUPAC name) or 3,3,4,4-tetramethylsuccinic anhydride, namely the anhydride of 2,2,3,3-tetramethylsuccinic acid, and sometimes abbreviated as TMSA.Subat Turdi, Peisheng Xu, Qun Li, Youqing Shen, Parhat Kerram, and Jun Ren (2008), Amidization of Doxorubicin Alleviates Doxorubicin-Induced Contractile Dysfunction and Reduced Survival in Murine Cardiomyocytes. Toxicology Letters volume 178, issue 3, pages 197–201.
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Additionally, the inductive effects resulting from signaling between cell populations in EBs results in spatially and temporally defined changes, which promote complex morphogenesis. Tissue-like structures are often exhibited within EBs, including the appearance of blood islands reminiscent of early blood vessel structures in the developing embryo, as well as the patterning of neurite extensions (indicative of neuron organization) and spontaneous contractile activity (indicative of cardiomyocyte differentiation) when EBs are plated onto adhesive substrates such as gelatin. More recently, complex structures, including optic cup-like structures were created in vitro resulting from EB differentiation.
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Dystrophin supports muscle fiber strength, and the absence of dystrophin reduces muscle stiffness, increases sarcolemmal deformability, and compromises the mechanical stability of costameres and their connections to nearby myofibrils. This has been shown in recent studies where biomechanical properties of the sarcolemma and its links through costameres to the contractile apparatus were measured, and helps to prevent muscle fiber injury. Movement of thin filaments (actin) creates a pulling force on the extracellular connective tissue that eventually becomes the tendon of the muscle. The dystrophin associated protein complex also helps scaffold various signalling and channel proteins, implicating the DAPC in regulation of signalling processes.
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The main functions of the microcirculation are the delivery of oxygen and nutrients and the removal of carbon dioxide (CO2). It also serves to regulate blood flow and tissue perfusion thereby affecting blood pressure and responses to inflammation which can include edema (swelling). Most vessels of the microcirculation are lined by flattened cells of the endothelium and many of them are surrounded by contractile cells called pericytes. The endothelium provides a smooth surface for the flow of blood and regulates the movement of water and dissolved materials in the interstitial plasma between the blood and the tissues.
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Sappinia species also contain tubular mitochondrial cristae, and have a large contractile vacuole that changes in shape during locomotion. S. pedata has erect, cyst-like, standing amoebae, while S. platani has dictyosomes . The erect standing amoebae were originally observed by Dangeard (1896) in S. pedata, and were originally called spores or pedicellate cysts, as they looked similar to the spore-bearing stalks seen in slime molds. Further studies have concluded that there is no cell wall present in these standing amoebae, and they continue to change shape while in the erect position, therefore they are not cysts or spores.
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The comb rows also function as chemical sense organs, serving the same role as insect antennae. Mertensia ovum is the major source of bioluminescence from Arctic gelatinous zooplankton. This species, like other ctenophores, has a large body cavity and is carnivorous, feeding on copepods and small crustaceans snagged by its two extremely sticky and robust tentacles (see Tentaculata). These are long and contractile with numerous lateral tentillae or side branches bearing colloblasts, each of which consists of a coiled spiral filament, structurally similar to a nematocyst, but instead of injecting a toxin, release an adhesive substance which ensnares the prey.
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The internodal pathways consist of three bands (anterior, middle, and posterior) that lead directly from the SA node to the next node in the conduction system, the atrioventricular node. The impulse takes approximately 50 ms (milliseconds) to travel between these two nodes. The relative importance of this pathway has been debated since the impulse would reach the atrioventricular node simply following the cell-by-cell pathway through the contractile cells of the myocardium in the atria. In addition, there is a specialized pathway called Bachmann's bundle or the interatrial band that conducts the impulse directly from the right atrium to the left atrium.
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The findings showed that the maximal strength of the muscle, as studied in situ using a computer-programmed ergometer system, was reduced by 24% after the 6-day flight and 37% after the 14-day flight. These changes were consistent with the degree of atrophy observed at both the gross and single-myofiber level. Also, shifts occurred in the force-frequency response of the soleus in the flight animals, suggesting a switch to a faster contractile phenotype. Maximal shortening velocities were increased by 14% and 24% in the 6-day and 14-day spaceflight groups, respectively.
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This first major discovery of Franzini- Armstrong's was that transverse tubules open at the cell surface, and this is an essential discovery in understanding how muscle is activated to contract. There are numerous additional scientists that greatly helped and influenced Franzini-Armstrong's work, including Richard Podolsky, Sir Andrew Huxley, and Paul Horowicz. From 1963 – 1964, Franzini-Armstrong worked as Richard Podolsky's research assistant at National Institutes of Health, and he improved her foundation on the physiology of muscle activation. From 1964 – 1966, Franzini-Armstrong worked in Sir Andrew Huxley's lab, and there she began to fully comprehend contractile machinery and appreciate optics.
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The increased performance benefit associated with muscle contractions that take place during SSCs has been the focus of much research in order to determine the true nature of this enhancement. At present, there is some debate as to where and how this performance enhancement takes place. It has been postulated that elastic structures in series with the contractile component can store energy like a spring after being forcibly stretched. Since the length of the tendon increases due to the active stretch phase, if the series elastic component acts as a spring, it would therefore be storing more potential energy.
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The tentacular coelom connects the tentacles at the tip of the introvert to a ring canal at their base, from which a contractile vessel runs along beside the esophagus and ends blindly posteriorly. Some evidence points towards the involvement of these structures in ultrafiltration. In crevice-dwelling sipunculans, respiration is mainly through the tentacular system, with oxygen diffusing into the trunk coelom from the tentacular coelom. However, in other species the skin is thin and respiration is mainly through the cuticle of the trunk, where oxygen uptake is assisted by the presence of dermal coelomic canals just beneath the epidermis.
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A wide spectrum of clinical features have been associated with ANKRD1/CARP. Mutations in ANKRD1 have been associated with dilated cardiomyopathy, two of which result in altered binding with TLN1 and FHL2. Mutations in ANKRD1 have also been associated with hypertrophic cardiomyopathy, and have shown to increase binding of CARP to Titin and MYPN. Examination of the functional effects of CARP hypertrophic cardiomyopathy mutations in engineered heart tissue demonstrated that Thr123Met was a gain-of-function mutation exhibiting augmented contractile properties; whereas Pro52Ala and Ile280Val were unstable and failed to incorporate into sarcomeres, an effect that was remedied upon proteasome inhibition via epoxomicin.
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Upon application of pressure to the internal end of the cervix, oxytocin is released (therefore increase in contractile proteins), which stimulates uterine contractions, which in turn increases pressure on the cervix (thereby increasing oxytocin release, etc.), until the baby is delivered. Sensory information regarding mechanical stretch of the cervix is carried in a sensory neuron, which synapses in the dorsal horn before ascending to the brain in the anterolateral columns (ipsilateral and contralateral routes). Via the median forebrain bundle, the efferent reaches the PVN and SON of the hypothalamus. The posterior pituitary releases oxytocin due to increased firing in the hypothalamo-hypophyseal tract.
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The muscle has "tension producing tissue comprising small contractile units referred to as sarcomeres" that each contain a "thick (myosin) and thin (actin) myofilament (muscle filaments or proteins) that overlaps to format a cross-bridge bond (attachment)". When in a concentric exercise, shortening of a muscle occurs as the myosin and actin cross bridges repeatedly attach and detach to draw the actin across the myosin — creating force. Each cross-bridge attachment and detachment cycle is powered by the splitting of one molecule of adenosine triphosphate (ATP). Examples of such exercises include kicking a ball or lifting a weight.
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The most dangerous side effect of doxorubicin is dilated cardiomyopathy, leading to congestive heart failure. The rate of cardiomyopathy is dependent on its cumulative dose, with an incidence about 4% when the dose of doxorubicin is 500–550 mg/m2, 18% when the dose is 551–600 mg/m2 and 36% when the dose exceeds 600 mg/m2. There are several ways in which doxorubicin is believed to cause cardiomyopathy, including oxidative stress, downregulation of genes for contractile proteins, and p53-mediated apoptosis. Doxorubicin-induced cardiomyopathy typically results in dilated cardiomyopathy, with all four cardiac chambers being enlarged.
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The cytoplasmic calcium binds to Troponin C, moving the tropomyosin complex off the actin binding site allowing the myosin head to bind to the actin filament. From this point on, the contractile mechanism is essentially the same as for skeletal muscle (above). Briefly, using ATP hydrolysis, the myosin head pulls the actin filament toward the centre of the sarcomere. Key proteins involved in cardiac calcium cycling and excitation-contraction coupling Following systole, intracellular calcium is taken up by the sarco/endoplasmic reticulum ATPase (SERCA) pump back into the sarcoplasmic reticulum ready for the next cycle to begin.
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Instead of a rigid cell wall, the plasmalemma of Dunaliella has a notable thick, mucilaginous coating. Olivera et al. noticed that the cell coating was affected by proteolytic enzymes and neuraminidase and concluded that its makeup must be mostly glycoproteid with some neuraminic acid residues. Instead of contractile vacuoles, marine species of Dunaliella replace the organelle’s usual spot in most other Chlorophyceae cells, with two to three dictyostomes that lie in a characteristic parabasal position with their forming faces toward the plasmalemma and ER. Dunaliella cells consist of a large, cup-shaped plastid that takes up the majority of the cell.
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The involvement of Polo kinases in the process of cytokinesis was first shown in fission yeast, in which the overexpression of Plo1 drives septation at any stage of the cell cycle and plo1 mutants fail to septate.Mulvihill, D. P., Petersen, J., Ohkura, H., Glover, D. M. & Hagan, I. M. Plo1 kinase recruitment to the spindle pole body and its role in cell division in Schizosaccharomyces pombe. Mol. Biol. Cell 10, 2771–2785 (1999). A protein called Mid1 determines where the contractile ring forms has been shown to shuttle out of the nucleus due to phosphorylation of Plk.
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Some research suggests that this chronic desensitization is due to the over activation of a kinase, G protein-coupled receptor kinase 2 (GRK2), which phosphorylates and deactivates certain G protein coupled receptors . When the G protein coupled receptor is activated, the Gβγ subunit recruits GRK2 which then phosphorylates and desensitizes GPCRs like the βAR. Preventing the interaction of the βγ subunit with GRK2 has therefore been studied as a potential target for increasing heart contractile function. The developed molecule GRK2ct is a protein inhibitor which inhibits the signalling properties of Gβγ subunit but does not interfere with alpha subunit signalling.
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However, as it progresses the LV volume increases and the contractile function deteriorates, thus leading to dysfunctional LV and a decrease in ejection fraction.Harrison's Internal Medicine 17th edition The increase in stroke volume is explained by the Frank–Starling mechanism, in which increased ventricular pre-load stretches the myocardium such that contractions are more forceful. The regurgitant volume causes a volume overload and a pressure overload of the left atrium and the left ventricle. The increased pressures in the left side of the heart may inhibit drainage of blood from the lungs via the pulmonary veins and lead to pulmonary congestion.
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This regional variability in strain was accompanied by a statistically significant increase in AGR and resting pennation angle from distal to proximal portions of the muscle. Furthermore, greater changes in pennation angle were visible at the proximal end of the MG. The experimental AGR values modulated positively with the pennation angle as well as the distance between the deep and superficial apopneuroses and may have been affected by regional patterns in orthogonal bulging. These trends highlight the complexity of muscle physiology, as different regions of muscles may contract with diverse contractile properties, such as strain and AGR.
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Classical (local) preconditioning has an early phase with an immediate onset lasting 2–3 hours that protects against myocardial infarction. The early phase involves post-translational modification of preexisting proteins, brought about by the activation of G protein-coupled receptors as well as downstream MAPK's and PI3/Akt. These signaling events act on the ROS-generating mitochondria, activate PKCε and the Reperfusion Injury Salvage Kinase (RISK) pathway, preventing mitochondrial permeability transition pore (MTP) opening. The late phase with an onset of 12–24 hours that lasts 3–4 days and protects against both infarction and reversible postischemic contractile dysfunction, termed myocardial stunning.
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Although the structure and function is basically the same in smooth muscle cells in different organs, their specific effects or end-functions differ. The contractile function of vascular smooth muscle regulates the lumenal diameter of the small arteries- arterioles called resistance vessels, thereby contributing significantly to setting the level of blood pressure and blood flow to vascular beds. Smooth muscle contracts slowly and may maintain the contraction (tonically) for prolonged periods in blood vessels, bronchioles, and some sphincters. Activating arteriole smooth muscle can decrease the lumenal diameter 1/3 of resting so it drastically alters blood flow and resistance.
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Activation of aortic smooth muscle doesn't significantly alter the lumenal diameter but serves to increase the viscoelasticity of the vascular wall. In the digestive tract, smooth muscle contracts in a rhythmic peristaltic fashion, rhythmically forcing foodstuffs through the digestive tract as the result of phasic contraction. A non-contractile function is seen in specialized smooth muscle within the afferent arteriole of the juxtaglomerular apparatus, which secretes renin in response to osmotic and pressure changes, and also it is believed to secrete ATP in tubuloglomerular regulation of glomerular filtration rate. Renin in turn activates the renin–angiotensin system to regulate blood pressure.
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Having cardiomyocytes connected via gap junctions allow all contractile cells of the heart to act in a coordinated fashion and contract as a unit. All the while being in sync with the pacemaker cells; this is the property that allows the pacemaker cells to control contraction in all other cardiomyocytes. Cells in the SA node spontaneously depolarize, ultimately resulting in contraction, approximately 100 times per minute. This native rate is constantly modified by the activity of sympathetic and parasympathetic nerve fibers via the autonomic nervous system, so that the average resting cardiac rate in adult humans is about 70 beats per minute.
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The dactylozooids make up the tentacles that are typically in length, but can reach over . The long tentacles "fish" continuously through the water, and each tentacle bears stinging, venom-filled nematocysts (coiled, thread-like structures), which sting, paralyze, and kill adult or larval squids and fishes. Large groups of Portuguese man o' war, sometimes over 1,000 individuals, may deplete fisheries. Contractile cells in each tentacle drag the prey into range of the digestive polyps, the gastrozooids, which surround and digest the food by secreting enzymes that break down proteins, carbohydrates, and fats, while the gonozooids are responsible for reproduction.
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The bulbs produce contractile roots; when these roots contract, they draw the bulbs down into deeper layers of the soil where there is greater moisture, reaching depths of . This may explain the absence of H. non-scripta from some thin soils over chalk in South East England, since the bulbs are unable to penetrate into sufficiently deep soils. H. non-scripta differs from H. hispanica, which occurs as an introduced species in the British Isles, in a number of ways. H. hispanica has paler flowers which are borne in radially symmetrical racemes; their tepals are less recurved, and are only faintly scented.
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Tansey found, early on in her PhD, that cellular mechanisms other than myosin light chain phosphorylation regulate contractile tension in smooth muscle cells. She later found that calcium dependent phosphorylation of MLCK in smooth muscle lead to decreased calcium sensitivity of phosphorylated myosin light chains. Tansey also proposed a model to understand the regulation of myosin light chain kinase phosphorylation by limited calmodulin availability. Following the completion of her graduate studies in 1992, Tansey moved to Washington University in St. Louis, Missouri, where she worked under the mentorship of Eugene M. Johnson in the Department of Molecular Pharmacology.
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In invertebrates, depending on the neurotransmitter released and the type of receptor it binds, the response in the muscle fiber could be either excitatory or inhibitory. For vertebrates, however, the response of a muscle fiber to a neurotransmitter can only be excitatory, in other words, contractile. Muscle relaxation and inhibition of muscle contraction in vertebrates is obtained only by inhibition of the motor neuron itself. This is how muscle relaxants work by acting on the motor neurons that innervate muscles (by decreasing their electrophysiological activity) or on cholinergic neuromuscular junctions, rather than on the muscles themselves.
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Prey is ensnared in long tentacles containing nematocysts, and ingested with a highly contractile mouth that can expand to consume organisms half the medusae's size. Due to their voracious nature, Aequorea victoria density can be inversely correlated to zooplankton density, indicating a competitive presence in shared environments. The swimming velocity of Aequorea victoria does not increase as their body size increases which deems them as inefficient swimmers. Therefore, they require direct contact with their prey in order to feed which is effectively done through energetic propulsion in which pressure allows them to passively move in their environment.
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When the central nervous system sends out signals to alpha neurons to fire, signals are also sent to gamma motor neurons to do the same. This process maintains the tautness of muscle spindles and is called alpha gamma co-activation. The nuclei of spindle muscle cells are located in the middle of these spindles, but unlike extrafusal muscle fibers, the myofibril contractile apparati of spindle fibers are located only at both ends of spindle. Efferent stimulation of the spindle by gamma motor neurons contracts the myofibrils, tautening the central region of spindle -- which maintains the muscle spindle's sensitivity to muscle's length change.
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ALC-1 is expressed very early in skeletal muscle and cardiac muscle development; two E-boxes and CArG box in the MYL4 promoter region regulate transcription. ALC-1 expression in cardiac ventricles decreases in early postnatal development, but is highly expressed in atria throughout all of adulthood. Normal atrial function is essential for embryogenesis, as inactivation of the MYL7 gene was embryonic lethal at ED10.5-11.5. Evidence of ALC-1 isoform expression on contractile mechanics of sarcomeres came from experiments studying fibers from patients expressing a higher level of ALC-1 relative to VLC-1 in cardiac left ventricular tissue.
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This is problematic for some organisms with pervious skins or with gill membranes, whose cell membranes may burst if excess water is not excreted. Some protists accomplish this using contractile vacuoles, while freshwater fish excrete excess water via the kidney. Although most aquatic organisms have a limited ability to regulate their osmotic balance and therefore can only live within a narrow range of salinity, diadromous fish have the ability to migrate between fresh water and saline water bodies. During these migrations they undergo changes to adapt to the surroundings of the changed salinities; these processes are hormonally controlled.
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This interaction is prevented by the MLCK-dependent light chain phosphorylation, resulting in the unfolding of myosin monomers and their rapid polymerization into filaments. The binding of KRP to the neck region folded, ATP-bound dephosphorylated myosin also promotes unfolding and filament formation, thus looking like light chain phosphorylation. This could be a physiologically significant phenomenon considering the high concentration of ATP always present in smooth muscle cells. Thus, Kinase-related protein may have a very important role in relaxed smooth muscle by keeping dephosphorylated myosin in the filamentous state ready for the next rapid contractile response.
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In the SAN cAMP binds to an ion channel involved in action potential initiation, speeding up the production of the action potential (see sinoatrial node for more detail). cAMP also, activates a protein called protein kinase A (PKA). PKA affects both the DHPR and RyR, increasing the rise in Ca 2+ within the contractile cells and therefore increasing rate of muscle contraction. PKA also affects the myofilaments as well as a protein called phospholamban (PLB; see sarcoplasmic reticulum for more details), speeding up the rate of Ca2+decline in the cell and so speeding up muscle relaxation.
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The bending of a muscular hydrostat can occur in two ways, both of which require the use of antagonistic muscles. The unilateral contraction of a longitudinal muscle will produce little or no bending and will serve to increase the diameter of the muscular hydrostat because of the constant volume principle that must be met. To bend the hydrostat structure, the unilateral contraction of longitudinal muscle must be accompanied by contractile activity of transverse, radial, or circular muscles to maintain a constant diameter. Bending of a muscular hydrostat can also occur by the contraction of transverse, radial, or circular muscles which decreases the diameter.
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Alpha-motor neurons can further be divided into three separate subclasses, distinguished according to the contractile properties of the motor units that they form: fast-twitch fatigable (FF), fast-twitch fatigue-resistant (FR), and slow-twitch fatigue- resistant (S). The composition of a motor pool may consist of multiple classes and subclasses of motor neurons. Motor pools in the spinal cord are clustered in distinct columns of motor neurons extending over multiple spinal cord segments; although, there is significant overlap. Motor pools that control proximal muscles are generally located medial to the ventral horn, while those that control distal muscles are located laterally.
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The Correspondence of Charles Darwin:, Volume 20; Volume 1872 by Charles Darwin Rouget is largely remembered for his correlation of physiology to microscopic anatomical structure. He was the first to discover the branching contractile cells on the external wall of the capillaries in amphibians, structures that are now known as "Rouget cells".The Inflammatory Process edited by Benjamin W. Zweifach, Lester Grant, Robert T. McCluskey Also the eponymous "Rouget's muscle" was described by him, which are circular fibers of the ciliary muscle of the eye. These fibers are sometimes called "Müller's muscle" after German anatomist Heinrich Müller (1820–1864).
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FtsZ, the first identified prokaryotic cytoskeletal element, forms a filamentous ring structure located in the middle of the cell called the Z-ring that constricts during cell division, similar to the actin-myosin contractile ring in eukaryotes. The Z-ring is a highly dynamic structure that consists of numerous bundles of protofilaments that extend and shrink, although the mechanism behind Z-ring contraction and the number of protofilaments involved are unclear. FtsZ acts as an organizer protein and is required for cell division. It is the first component of the septum during cytokinesis, and it recruits all other known cell division proteins to the division site.
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So when the chloride and potassium move out of the cells, the water will flux out which results in the leaves facing vertically. This movement of the leaves drooping takes only a couple of seconds as we saw in the video. However, when the leaves or the tree is shaken, this will activate contractile proteins that are in the pulvinus, and they will cause the leaves to droop. There are a few benefits of the drooping of the leaves: one is that it has been hypothesized that when the leaves droop it makes the plant look malnourished and unappealing, so herbivores are compelled to eat a different plant.
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In the genus Cephalodiscus, asexually produced individuals stay attached to the contractile stalk of the parent individual until completing their development. In the genus Rhabdopleura, zooids are permanently connected to the rest of the colony via a common stolon system. They have a diverticulum of the foregut called a stomochord, previously thought to be related to the chordate notochord, but this is most likely the result of convergent evolution rather than a homology. A hollow neural tube exists among some species (at least in early life), probably a primitive trait that they share with the common ancestor of chordata and the rest of the deuterostomes.
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The classical explanation of HPV involves inhibition of hypoxia-sensitive voltage-gated potassium channels in pulmonary artery smooth muscle cells leading to depolarization. This depolarization activates voltage-dependent calcium channels, which increases intracellular calcium and activates smooth muscle contractile machinery which in turn causes vasoconstriction. However, later studies have reported additional ion channels and mechanisms that contribute to HPV, such as transient receptor potential canonical 6 (TRPC6) channels, and transient receptor potential vanilloid 4 (TRPV4) channels. Recently it was proposed that hypoxia is sensed at the alveolar/capillary level, generating an electrical signal that is transduced to pulmonary arterioles through gap junctions in the pulmonary endothelium to cause HPV.
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Moyle's first major research, in collaboration with Dorothy L. Foster, focused on the interconversion of lactic acid and glycogen in muscle, recapitulating the work of Otto Fritz Meyerhof. After that, she studied the roles of succinic acid, fumaric acid, and malic acid in muscle metabolism, as well as the biochemical differences and relationships between aerobic and anaerobic pathways.Teich, p. 354-355 She subsequently worked on cyclic phosphate transfer in muscle contraction and, with collaborators, established for the first time a direct correlation of structure and function in muscle by confirming in 1939 that myosin, the contractile protein of muscle, behaves as the enzyme ATPase (adenosine triphosphatase).
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EGR/Nerve Growth factor is a transcription factor with a potential binding site in the REEP5 promoter, which promotes neural plasticity, and therefore potentially provides an explanation for elevated levels of Receptor Expression Enhancing Protein 5 in the brain. Additionally, two transcription factors related to heart development and function have possible binding sites in the promoter. Transcription Box 20 (TBX20) is related to heart development, with protein deficiencies linked to poor heart function in adult mice, and death in infants before gestation. MyoD is a Myogenic regulator which has been detected in the embryonic hearts of some birds in Purkinje cells, which are related to contractile function.
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During skeletal myogenesis, cycling progenitor cells known as myoblasts differentiate and fuse together into non-cycling muscle cells called myocytes that remain in a terminal G0 phase.page 395, Biology, Fifth Edition, Campbell, 1999 As a result, the fibers that make up skeletal muscle (myofibers) are cells with multiple nuclei, referred to as myonuclei, since each myonucleus originated from a single myoblast. Skeletal muscle cells continue indefinitely to provide contractile force through simultaneous contractions of cellular structures called sarcomeres. Importantly, these cells are kept in a terminal G0 phase since disruption of muscle fiber structure after myofiber formation would prevent proper transmission of force through the length of the muscle.
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Muscle growth can be stimulated by growth or injury and involves the recruitment of muscle stem cells – also known as satellite cells – out of a reversible quiescent state. These stem cells differentiate and fuse to generate new muscle fibers both in parallel and in series to increase force generation capacity. Cardiac muscle is also formed through myogenesis but instead of recruiting stem cells to fuse and form new cells, heart muscle cells – known as cardiomyocytes – simply increase in size as the heart grows larger. Similarly to skeletal muscle, if cardiomyocytes had to continue dividing to add muscle tissue the contractile structures necessary for heart function would be disrupted.
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Species in the genus Tetraspora contain two pseduoflagella as a part of the pseudociliary apparatus, two cup-shaped chloroplasts with chlorophyll A and B pigments, a single pyrenoid and contractile vacuoles located inside the cytoplasm. Additionally, starch grains can be seen covering the pyrenoid and the walls of the cells are noted to be thin. Tetraspora species do not possess a flagellum of the 9+2 microtubular fibre configuration, instead they have pseudoflagellum with a 9+0 fibre confirmation; where the central two tubular fibres are absent. There are two pseduoflagelulla that exist in a pair and both protrude from the anterior region of the cell and into the gelatinous matrix.
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Normal function of the heart involves proper coordination between the contraction and relaxation of cardiomyocytes. Proper contraction and relaxation depends on the coordinated rise and fall of Ca2+ in the cytosol of the cardiomyocytes.del Monte F, Harding SE, Schmidt U, Matsui T, Bin Kang Z, Dec GW, et al. (1999). "Restoration of contractile function in isolated cardiomyocytes from failing human hearts by gene transfer of SERCA2a". Circulation. 100:2308–2311. The SERCA2a transporter is found in the membrane of the SR and plays an important role in this cycle by removing cytosolic Ca2+ from the cardiomyocyte and pumping it back into the SR during relaxation of the heart (diastole).
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Plant cells do not perform cytokinesis through this exact method but the two procedures are not totally different. Animal cells form an actin-myosin contractile ring within the equatorial region of the cell membrane that constricts to form the cleavage furrow. In plant cells, Golgi vesicle secretions form a cell plate or septum on the equatorial plane of the cell wall by the action of microtubules of the phragmoplast. The cleavage furrow in animal cells and the phragmoplast in plant cells are complex structures made up of microtubules and microfilaments that aide in the final separation of the cells into two identical daughter cells.
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The bulk of new tissue production is carried by the smooth muscles of the media, which transform their phenotype from a contractile into a synthetic and proliferative one. Important roles are played by actin binding proteins like actin-binding Rho-activating protein (ABRA), cofilin, and thymosin beta 4 which determine actin polymerization and maturation. Integrins and connexins are markedly up-regulated. A key role in this concerted action, which leads to a 2-to-20 fold increase in vascular diameter, depending on species size (mouse versus human), are the transcription factors AP-1, egr-1, carp, ets, by the Rho pathway and by the mitogen activated kinases ERK-1 and -2.
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Cytokinesis illustration Cilliate undergoing cytokinesis, with the cleavage furrow being clearly visible Cytokinesis is not a phase of mitosis but rather a separate process, necessary for completing cell division. In animal cells, a cleavage furrow (pinch) containing a contractile ring develops where the metaphase plate used to be, pinching off the separated nuclei. In both animal and plant cells, cell division is also driven by vesicles derived from the Golgi apparatus, which move along microtubules to the middle of the cell. In plants, this structure coalesces into a cell plate at the center of the phragmoplast and develops into a cell wall, separating the two nuclei.
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PKCε translocation to sarcomeres and phosphorylation of cTnI and cMyBPC is involved in the κ-opioid- and α-adrenergic-dependent preconditioning that slows myosin cycling rate, thus protecting the contractile apparatus from damage. Activation of PKCε by εRACK prior to ischemia was also found to phosphorylate Ventricular myosin light chain-2, however the functional significance remains elusive. Actin-capping protein, CapZ appears to affect the localization of PKCε to Z-lines and modulates the cardiomyocyte response to ischemic injury. Cardioprotection in mice with reduction of CapZ showed enhancement in PKCε translocation to sarcomeres, thus suggesting that CapZ may compete with PKCε for the binding of RACK2.
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Ventral view with hyperiid amphipod Almost entirely transparent and colorless, and sometimes difficult to resolve, Aequorea victoria possess a highly contractile mouth and manubrium at the center of up to 100 radial canals that extend to the bell margin. The bell margin is surrounded by uneven tentacles, up to 150 of them in fully-grown specimens. The tentacles possess nematocysts that aid in prey capture, although they have no effect on humans. Specimens larger than 3 cm usually possess gonads for sexual reproduction, which run most of the length of the radial canals and are visible in the photos in this article as whitish thickenings along the radial canals.
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The sarcoplasmic reticulum is a network of tubules that extend throughout muscle cells, wrapping around (but not in direct contact with) the myofibrils (contractile units of the cell). Cardiac and skeletal muscle cells contain structures called transverse tubules (T-tubules), which are extensions of the cell membrane that travel into the centre of the cell. T-tubules are closely associated with a specific region of the SR, known as the terminal cisternae in skeletal muscle, with a distance of roughly 12 nanometers, separating them. This is the primary site of calcium release.The anatomy of the sarcoplasmic reticulum in vertebrate skeletal muscle: Its implications for excitation contraction coupling’, Zeitschrift fur Naturforschung.
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Specifically, the affected muscle cells have slower contractile velocities, have depressed actin-activated ATPase rates, and have increased stiffness. Due to the fact that the cause of the R403Q mutation lies within the region that encodes for the globular myosin head, alterations in the myosin head structure greatly impairs its ability to strongly interact with actin and form a stable cross-bridge. The development of HCM is multifaceted, but the R403Q mutation is one of the most influential risk factors. Of the hundreds of pathogenic mutations that give rise to HCM, R403Q mutations in myosin heavy chain genes are present in over half of them.
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A gradient in the levels of both MLC2v phosphorylation and its kinase, cardiac MLCK, has been shown to exist across the human heart from endocardium (low phosphorylation) to epicardium (high phosphorylation). The existence of this gradient has been proposed to impact cardiac torsion due to the relative spatial orientation of endocardial versus epicardial myofibers. In support of this, recent studies have shown that MLC-2v phosphorylation is critical in regulating left ventricular torsion. Variations in myosin cycling kinetics and contractile properties as a result of differential MLC-2v phosphorylation (Ser14/15) influence both epicardial and endocardial myofiber tension development and recovery to control cardiac torsion and myofiber strain mechanics.
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Fibers expressing high ALC-1 exhibited a higher maximal velocity and rate of shortening compared to fibers with low amounts of ALC-1, suggesting that ALC-1 increases cycling kinetics of myosin cross-bridges and regulates cardiac contractility. Further biochemical studies unveiled a weaker binding of the Alanine-Proline-rich N-terminus of ALC-1 to the C-terminus of actin relative to VLC-1, which may explain the mechanism underlying the differences in cycling kinetics. The importance of this region has however raised skepticism. Further evidence for the contractile-enhancing properties of ALC-1 came from studies employing transgenesis to replace VLC-1 with ALC-1 in the mouse ventricle.
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Calponin 3 was found in stress fibers of skin fibroblasts and myofibroblasts during wound healing. Cnn3 knockdown in primary fibroblasts impaired stress fiber formation, resulting in decreased cell motility and contractile ability.> Calponin 3 in the brain has a potential function in regulating actin filaments during neuronal remodeling. Calponin 3 was also found in dendritic spines of adult hippocampal neurons to regulate dendritic spine plasticity. While mice with systemic knockout of Cnn1 or Cnn2, or both Cnn1 and Cnn2 survive to adulthood and fertile, systemic knockout of calponin 3 in mice results in embryonic and neonatal lethality due to defect in the development of central nervous system.
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Mimosa pudica It has been concluded that loss of turgor pressure within the leaves of Mimosa pudica is responsible for the reaction the plant has when touched. Other factors such as changes in osmotic pressure, protoplasmic contraction and increase in cellular permeability have been observed to affect this response. It has also been recorded that turgor pressure is different in the upper and lower pulvinar cells of the plant, and the movement of potassium and calcium ions throughout the cells cause the increase in turgor pressure. When touched, the pulvinus is activated and exudes contractile proteins, which in turn increases turgor pressure and closes the leaves of the plant.
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The fibroblast involved in scarring and contraction is the myofibroblast, which is a specialized contractile fibroblast. These cells express α-smooth muscle actin (α-SMA). The myofibroblasts are absent in the first trimester in the embryonic stage where damage heals scar free; in small incisional or excision wounds less than 2 mm that also heal without scarring; and in adult unwounded tissues where the fibroblast in itself is arrested; however, the myofibroblast is found in massive numbers in adult wound healing which heals with a scar. The myofibroblasts make up a high proportion of the fibroblasts proliferating in the postembryonic wound at the onset of healing.
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Furthermore, Steinmetz et all showed that the localization of this duplicated set of genes that serve both the function of facilitating the formation of striated muscle genes and cell regulation and movement genes were already separated into striated myhc and non-muscle myhc. This separation of the duplicated set of genes is shown through the localization of the striated myhc to the contractile vacuole in sponges while the non-muscle myhc was more diffusely expressed during developmental cell shape and change. Steinmetz et al. found a similar pattern of localization in cnidarians with except with the cnidarian N. vectensis having this striated muscle marker present in the smooth muscle of the digestive track.
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The fall in arterial blood pressure results from pericardial fluid accumulation increasing pressure on the outside of the heart that limits the maximum size the ventricles can stretch to. This limits diastolic expansion (filling) which results in a lower EDV (End Diastolic Volume) which reduces stroke volume, a major determinant of systolic blood pressure. This is in accordance with the Frank-Starling law of the heart, which explains that as the ventricles fill with larger volumes of blood, they stretch further, and their contractile force increases, thus causing a related increase in systolic blood pressure. The rising central venous pressure is evidenced by distended jugular veins while in a non-supine position.
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Cell-based in vivo therapies may provide a transformative approach to augment vascular and muscle growth and to prevent non-contractile scar formation by delivering transcription factors or microRNAs to the heart. Cardiac fibroblasts, which represent 50% of the cells in the mammalian heart, can be reprogrammed into cardiomyocyte-like cells in vivo by local delivery of cardiac core transcription factors ( GATA4, MEF2C, TBX5 and for improved reprogramming plus ESRRG, MESP1, Myocardin and ZFPM2) after coronary ligation. These results implicated therapies that can directly remuscularize the heart without cell transplantation. However, the efficiency of such reprogramming turned out to be very low and the phenotype of received cardiomyocyte-like cells does not resemble those of a mature normal cardiomyocyte.
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CapZ binds the barbed end of actin filaments and prevents addition or loss of actin monomers to filaments. It has also been observed that CapZ functions to organize myofilaments during myofibrillogenesis and is present at Z-discs in muscle prior to the striation of actin filaments, suggesting that CapZ may function to direct the polarity and organization of sarcomeric actin during I-band formation. The function of CapZ-alpha2 may be modulated by the calcium-binding protein S100A in skeletal and cardiac muscle tissues, as crosslinking studies have shown S100A to directly interact with the C-terminal region of CapZ-alpha in the presence of calcium. CapZ appears to regulate intracellular signaling of contractile proteins in cardiac muscle.
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Lambda phage J protein interaction with the LamB porin Lambda phage is a non-contractile tailed phage, meaning during an infection event it cannot 'force' its DNA through a bacterial cell membrane. It must instead use an existing pathway to invade the host cell, having evolved the tip of its tail to interact with a specific pore to allow entry of its DNA to the hosts. # Bacteriophage Lambda binds to an E. coli cell by means of its J protein in the tail tip. The J protein interacts with the maltose outer membrane porin (the product of the lamB gene) of E. coli, a porin molecule, which is part of the maltose operon.
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Food vacuoles are formed through phagocytosis and typically follow a particular path through the cell as their contents are digested and broken down by lysosomes so the substances the vacuole contains are then small enough to diffuse through the membrane of the food vacuole into the cell. Anything left in the food vacuole by the time it reaches the cytoproct (anal pore) is discharged by exocytosis. Most ciliates also have one or more prominent contractile vacuoles, which collect water and expel it from the cell to maintain osmotic pressure, or in some function to maintain ionic balance. In some genera, such as Paramecium, these have a distinctive star shape, with each point being a collecting tube.
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This 'low' level of contraction is a protective mechanism to prevent avulsion of the tendon--the force generated by a 95% contraction of all fibers is sufficient to damage the body. In multiple fiber summation, if the central nervous system sends a weak signal to contract a muscle, the smaller motor units, being more excitable than the larger ones, are stimulated first. As the strength of the signal increases, more motor units are excited in addition to larger ones, with the largest motor units having as much as 50 times the contractile strength as the smaller ones. As more and larger motor units are activated, the force of muscle contraction becomes progressively stronger.
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Mural cells were described for the first time in the late 19th century as contractile cells lining up around the endothelium. In reality, it was a variety of cells that had been observed and bundled up under the common name of Rouget cells. Later studies brought controversy about their contractility, and this remains an elusive point today. Pericytes, vSMCs, and many other perivascular cell types express very similar markers such as Platelet Derived Growth Factor Receptor Beta (PDGFR-B), aminopeptidase-N (CD13), chondroitin sulfate proteoglycan 4 (Ng2), or desmin, which makes their identification difficult and requires a combination of markers: for example vSMCs but not pericytes express alpha-smooth muscle actin (ACTA2).
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Studies have shown that ALP is present at the first stage of myofibrilogenesis where it is bound to alpha actinin-2, and this association remains intact in mature myofibrils where ALP is localized to Z-discs and intercalated discs. Alpha actinin-2 is however not required for targeting ALP to Z-lines. Studies in ALP knockout mice have shown that ALP facilitates the cross-linking of actin filaments by alpha actinin-2, and absence of ALP induces abnormal right ventricular chamber formation, dysplasia and cardiomyopathy. Further studies using right ventricular epicardial systolic strain and geometric remodeling analysis in these animals unveiled that absence of ALP diminishes right ventricular contractile function and alters the pattern of cardiac hypertrophic remodeling.
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In an ideal scenario, regenerated tissue would reproduce sophisticated asymmetric helicodoidal architecture of the myocardium with the production of specialized extracellilar matrix to stimulate vascularization in the implanted tissue. From a cellular perspective, available techniques are monolayer cell construct onto temperature-sensitive polymer, where their detachment is driven by behavior of the mechanical properties of the synthetic support without the need of any enzymatic digestion such as trypsin. Cardiomyocites sheets have also been successfully implanted with an observed contractile function as a result of inter-cellular communication between the host and graft. However, from a practical point of view, such approach lacks of translational character as all studies share the lack of reproducibility, i.e.
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The scaffold retains regenerative activity provided that it has been prepared with appropriate levels of the specific surface (pore size in range 20-125 µm), degradation rate (degradation half-life 14 ± 7 days) and surface chemical features (ligand densities for integrins α1β1 and α2β1 must exceed approximately 200 μΜ α1β1 and α2β1 ligands). It has been hypothesized that specific binding of a sufficient number of contractile cells (myofibroblasts) on the scaffold surface, occurring within a narrow time window, is required for induction of skin regeneration in the presence of this scaffold. Studies with skin wounds have been extended to transected peripheral nerves, and the combined evidence supports a common regeneration mechanism for skin and peripheral nerves using this scaffold.
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Excessive vasoconstriction can cause cardiac output reduction or even fatal heart complication particularly in those with weak myocardial function. In those whose vasodilatory shock is caused by hypocalcemic cardiomyopathy in the context of dilated cardiomyopathy with documented both reduced heart ejection fraction and contractile performance, the uses of calcium and active vitamin D or recombinant human parathyroid hormone treatment are viable since there were many successful cases reported while given the physiological role of calcium on muscle contraction. A successful treatment requires leveraging the respective unique contributions of a multi-disciplinary team not only critical care doctors and often, infectious disease specialists but also respiratory therapy, nursing, pharmacy and others in collaboration.
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Another lab-on-a-chip similarly combined a microfluidic network in PDMS with planar microelectrodes, this time to measure extracellular potentials from single adult murine cardiomyocytes. A reported design of a heart-on-a-chip claims to have built "an efficient means of measuring structure-function relationships in constructs that replicate the hierarchical tissue architectures of laminar cardiac muscle." This chip determines that the alignment of the myocytes in the contractile apparatus made of cardiac tissue and the gene expression profile (affected by shape and cell structure deformation) contributes to the force produced in cardiac contractility. This heart-on-a-chip is a biohybrid construct: an engineered anisotropic ventricular myocardium is an elastomeric thin film.
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It postulates that active actin-myosin bundles are distributed throughout the cell cortex, and inhibition of their contraction near the spindle poles results in a gradient of contractile activity that is highest at the midpoint between poles. In other words, astral microtubules generate a negative signal that increases cortical relaxation close to the poles. Genetic and laser-micromanipulation studies in C. elegans embryos have shown that the spindle sends two redundant signals to the cell cortex, one originating from the central spindle, and a second signal deriving from the spindle aster, suggesting the involvement of multiple mechanisms combined in the positioning of the cleavage furrow. The predominance of one particular signal varies between cell types and organisms.
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Smooth muscles and skeletal muscles (and probably to a lower extent in cardiac muscle) in their well-differentiated (contractile) state co- express (along with vinculin) a splice variant carrying an extra exon in the 3' coding region, thus encoding a longer isoform meta-vinculin (meta VCL) of ~150KD molecular weight — a protein whose existence has been known since the 1980s. Translation of the extra exon causes a 68- to 79-amino acid acid-rich insert between helices I and II within the C-terminal tail domain. Mutations within the insert region correlate with hereditary idiopathic dilated cardiomyopathy. The length of the insert in metavinculin is 68 AA in mammals and 79 in frog.
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The idea of an electromagnetic nature of matter, however, had to be given up. Abraham (1904, 1905) argued that non-electromagnetic forces were necessary to prevent Lorentz's contractile electrons from exploding. He also showed that different results for the longitudinal electromagnetic mass can be obtained in Lorentz's theory, depending on whether the mass is calculated from its energy or its momentum, so a non-electromagnetic potential (corresponding to of the electron's electromagnetic energy) was necessary to render these masses equal. Abraham doubted whether it was possible to develop a model satisfying all of these properties. To solve those problems, Henri Poincaré in 1905 and 1906 introduced some sort of pressure ("Poincaré stresses") of non-electromagnetic nature.
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Poole-Wilson was interested in heart failure, coronary heart disease and the global prevention of heart disease and stroke. Heart failure was his major research focus and his work covered both basic science (laboratory studies) and clinical research. He was an enthusiastic supporter of high-quality fundamental research and a strong advocate of translational research so that what was learnt in the laboratory could be implemented more quickly and efficiently in medical practice. Following his early interest in the movement of K, Na and Ca ions across cardiac cell membranes and how these altered contraction, he became interested in studying similar processes that lead to the decline of contractile function as the heart started to fail.
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Bullfrogs are able to jump distances 10 times their body length due to the ability of activating muscular contractile units prior to extension of the plantaris muscle. In this process, sarcomeric contraction generates strain in elastic structures such as tendons, which in turn "catch" the energy generated by the strain. Such is subsequently released as the plantaris actively stretched during jumping, adding to the energy generated by muscular action alone, thus generating supramaximal powers that allow the bullfrog to jump great distances. Thus, the catch mechanism relies on elastic structures acting as muscle power amplifiers and their ability to absorb elastic strain energy and retain it for later explosive release during jumping.
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Pulseless electrical activity, it is possible to observe by invasive blood pressure (red) the transition from a normal mechanical activity of the heart, which progressively changes in rhythm and contractile quality to asystolia, even in the presence of normal electrical activity (green), also confirmed by the pulse oximeter detection even if with artifacts (blue) The absence of a pulse confirms a clinical diagnosis of cardiac arrest, but PEA can only be distinguished from other causes of cardiac arrest with a device capable of electrocardiography (ECG/EKG). In PEA, there is organised or semi-organised electrical activity in the heart as opposed to asystole (flatline) or to the disorganised electrical activity of either ventricular fibrillation or ventricular tachycardia.
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This vasodilation does not decrease the volume of blood the heart pumps, but rather it decreases the force the heart muscle must exert to pump the same volume of blood. Nitroglycerin pills, taken sublingually (under the tongue), are used to prevent or treat acute chest pain. The nitroglycerin reacts with a sulfhydryl group (–SH) to produce nitric oxide, which eases the pain by causing vasodilation. There is a potential role for the use of nitric oxide in alleviating bladder contractile dysfunctions, and recent evidence suggests that nitrates may be beneficial for treatment of angina due to reduced myocardial oxygen consumption both by decreasing preload and afterload and by some direct vasodilation of coronary vessels.
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Actin is a family of globular multi-functional proteins that form microfilaments. It is found in essentially all eukaryotic cells, where it may be present at a concentration of over 100 μM; its mass is roughly 42-kDa, with a diameter of 4 to 7 nm. An actin protein is the monomeric subunit of two types of filaments in cells: microfilaments, one of the three major components of the cytoskeleton, and thin filaments, part of the contractile apparatus in muscle cells. It can be present as either a free monomer called G-actin (globular) or as part of a linear polymer microfilament called F-actin (filamentous), both of which are essential for such important cellular functions as the mobility and contraction of cells during cell division.
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It has been proposed that the action potential arising from a touch stimulus leads to an increase of auxin in the cell, which causes the production of an contractile protein on the side of the touch that allows the plant to grip onto an object. Further, it has been shown that when auxin (typically leading to growth away from the side of its localization) and a touch stimulus (causing a tropic response toward its localization) were applied on the same side of a cucumber hypocotyl, the stem will curve towards the touch. Ethylene, another plant hormone, has also been shown to be an important regulator to the thigmotropic response in Arabidopsis thaliana roots. Under normal circumstances, high ethylene concentrations in the roots promote straight growth.
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Considerable information has accumulated covering a large number of spaceflight and HS experiments that span a time frame of ~4 to 22 days for spaceflight and from 1 to 56 days for HS. These experiments have primarily focused on extensor muscles used extensively for postural support and locomotor activity. The review by Roy, Baldwin, and Edgerton provides one of the most comprehensive reviews on rodents in the space environment. Additional reviews on this topic have been published. The collective observations clearly show that these types of muscle undergo significant reductions in muscle mass (muscle weight) along with a concomitant loss in total protein and myofibrillar (the fraction that is composed of the contractile machinery of structural proteins) protein content of the targeted muscles.
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In contrast to the contractile apparatus, studies on various rodent skeletal muscle metabolic enzymes have revealed a variety of responses with no clear-cut adaptive changes in oxidative enzyme expression. These observations are consistent with the results of studies focusing on mitochondrial function after 9 days of spaceflight in which no reduction in the capacity of skeletal muscle mitochondria to metabolize pyruvate (a carbohydrate derivative) was observed. These analyses were carried out under state 3 metabolic conditions, that is, non-limiting amounts of substrate and cofactors to simulate an energy turnover demand similar to that of high-intensity exercise. However, when a fatty acid substrate was tested, a reduction in the capacity of different muscle types to oxidize the long-chain fatty acid, palmitate, was observed.
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While other ectothermic animals become sluggish as their body temperatures decline, due to a reduction in the contractile velocity of their muscles, chameleons are able to project their tongues at high performance even at low body temperatures. The thermal sensitivity of tongue retraction in chameleons, however, is not a problem, as chameleons have a very effective mechanism of holding onto their prey once the tongue has come into contact with it, including surface phenomena, such as wet adhesion and interlocking, and suction. The thermal insensitivity of tongue projection thus enables chameleons to feed effectively on cold mornings prior to being able to behaviorally elevate their body temperatures through thermoregulation, when other sympatric lizards species are still inactive, likely temporarily expanding their thermal niche as a result.
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The importance of vascular elasticity in the circulatory system of the cephalopod Octopus vulgaris. The Journal of Experimental Biology, 152, 471–484 theorized that all octopus blood vessels may use smooth-muscle contractions to help move blood through the body, which would make sense in the context of them living under water with the attendant pressure. The elasticity and contractile nature of the octopus aorta serves to smooth out the pulsing nature of blood flow from the heart as the pulses travel the length of the vessel, while the vena cava serves in an energy-storage capacity. Stroke volume of the systemic heart changes inversely with the difference between the input blood pressure through the vena cava and the output back pressure through the aorta.
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ET-1 In addition to its direct vasoconstrictor effects, it causes changes in visceral and perivascular adipose tissue (PVAT), and may contribute to the pathogenesis of both insulin resistance and vascular dysfunction/damage. Perivascular adipose tissue seems to have anti contractile effect and this dilator effect was lost in obese patients. secondary to obesity, ET-1 high level changes on PVAT will lead to PVAT hypertrophy which will be associated with reduced partial oxygen pressure, an increase in the production of inflammatory cytokines such as TNF-α and IL-6, and elevation of reactive oxygen species. Thus, oxidative stress and hypoxia may promote imbalance in the production of vasoactive compounds and may affect vascular homeostasis by activating the ET-1 system.
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The myometrium is located between the endometrium (the inner layer of the uterine wall) and the serosa or perimetrium (the outer uterine layer). In non-primate species, the myometrium consists of two distinct layers, an outer longitudinal layer and an inner circular layer. However, in the human, the myometrial substructure is not so well defined as a new structure has emerged called the sub-endometrial layer of the myometrium also called the endometrial–myometrial junction. The inner one-third of the myometrium (termed the junctional or sub-endometrial layer) appears to be derived from the Müllerian duct, while the outer, more predominant layer of the myometrium appears to originate from non-Müllerian tissue and is the major contractile tissue during parturition and abortion.
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51 (1975) 244-250 For example, certain situations of excessive or reduced heart rate (tachycardia or bradycardia, respectively) can cause a BBB known as a rate-dependent bundle branch block (RDBBB). This manifests in a similar fashion to a regular bundle branch block, but occurs only under conditions that affect contractile rate. Tachycardia- dependent bundle branch block (TDBBB) can affect either ventricle in the heart, and occurs when the heart's rate of contraction reaches an elevated level and becomes uncoupled from the heart's refractory period (the time it takes for a cardiac cell to "reset" for future contraction). Thus the cell is unable to contract by the time the next electrical stimuli is present, and a blocking of this signal occurs.
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Highland herbfield on Macquarie Island dominated by the silver-leafed Pleurophyllum hookeri. Pleurophyllum hookeri, also known as the silver-leaf daisy or sage-green rosette herb, is a herbaceous plant in the daisy family, a megaherb native to the subantarctic Auckland and Campbell Islands of New Zealand and Australia’s Macquarie Island. It grows up to 900 mm in height and has crimson button flowers and long, silky, silver leaves, with a large carrot-like tuber and long roots. It also has the unusual feature of a vertically contractile stem, most of which is underground, which serves to keep the leaf rosette close to the ground surface and the plant anchored securely against the very strong winds typical of subantarctic islands.
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The ANK1 protein belongs to the ankyrin family that are believed to link the integral membrane proteins to the underlying spectrin-actin cytoskeleton and play key roles in activities such as cell motility, activation, proliferation, contact, and maintenance of specialized membrane domains. Multiple isoforms of ankyrin with different affinities for various target proteins are expressed in a tissue-specific, developmentally regulated manner. Most ankyrins are typically composed of three structural domains: an amino-terminal domain containing multiple ankyrin repeats; a central region with a highly conserved spectrin-binding domain; and a carboxy-terminal regulatory domain, which is the least conserved and subject to variation. The small ANK1 (sAnk1) protein splice variants makes contacts with obscurin, a giant protein surrounding the contractile apparatus in striated muscle.
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Erythropsidinium cells are a relatively large by dinoflagellate standards (50-120μm in longest dimension) and possess two flagella and two unusual organelles, the ocelloid and the piston. The ocelloid is light-responsive structure organized similarly to a multicellular organism's eye, considered a synapomorphic character for the Warnowiaceae; cells typically contain one ocelloid but occasional examples have been reported of cells containing two, without other indications of ongoing cell division. The piston is a long contractile structure protruding from the cell body, which is highly variable in length and morphology, and may contain prominent nodules along its length. As with the ocelloid, most cells possess a single piston, but in some cases specimens have been observed with two pistons on the same cell.
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When initially bound to PGE2 or other stimulating ligand, EP1 mobilizes G proteins containing the Gq alpha subunit (Gαq/11)-G beta-gamma complex. These two subunits in turn stimulate the Phosphoinositide 3-kinase pathway that raises cellular cytosolic Ca2+ levels thereby regulating Ca2+-sensitive cell signal pathways which include, among several others, those that promote the activation of certain protein kinase C isoforms. Since, this rise in cytosolic Ca2+ can also contract muscle cells, EP1 has been classified as a contractile type of prostanoid receptor. The activation of protein kinases C feeds back to phosphorylate and thereby desensitizes the activated EP1 receptor (see homologous desensitization but may also desensitize other types of prostanoid and non-prostanoid receptors (see heterologous desensitization).
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FP is classified as a contractile type of prostenoid receptor based on its ability, upon activation, to contract certain smooth muscle preparations and smooth muscle-containing tissues such as those of the uterus. When bound to PGF2α or other of its agonists, FP mobilizes primarily G proteins containing the Gq alpha subunit bound to of the Gq-Gβγ complex(i.e. Gqβγ). Gqβγ then dissociate into its Gq and Gβγ components which act to regulate cell signaling pathways. In particular, Gq stimulates cell signal pathways involving a) phospholipase C/IP3/cell Ca2+ mobilization/diacylglycerol/protein kinase Cs; calmodulin-modulated myosin light chain kinase; RAF/MEK/Mitogen-activated protein kinases; PKC/Ca2+/Calcineurin/Nuclear factor of activated T-cells; and the EGF cellular receptor.
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Ischemic preconditioning of the heart (B) provides functional recovery of the heart contractile activity at reperfusion If the blood supply to an organ or a tissue is impaired for a short time (usually less than five minutes) then restored so that blood flow is resumed, and the process repeated two or more times, the cells downstream of the tissue or organ are robustly protected from a final ischemic insult when the blood supply is cut off entirely and permanently. The protective effect which is imparted by IPC has two windows of protection. The first, lasts between 4–6 hours and has been named classical or early preconditioning. The second window begins at 24 hours lasting up to 72 hours post the ischaemia and reperfusion stimulus.
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Myosin-9 also known as myosin, heavy chain 9, non-muscle or non-muscle myosin heavy chain IIa (NMMHC-IIA) is a protein which in humans is encoded by the MYH9 gene. Non-muscle myosin IIA (NM IIA) is expressed in most cells and tissues where it participates in a variety of processes requiring contractile force, such as cytokinesis, cell migration, polarization and adhesion, maintenance of cell shape, and signal transduction. Myosin IIs are motor proteins that are part of a superfamily composed of more than 30 classes. Class II myosins include muscle and non-muscle myosins that are organized as hexameric molecules consisting of two heavy chains (230 kDa), two regulatory light chains (20 KDa) controlling the myosin activity, and two essential light chains (17 kDa), which stabilize the heavy chain structure.
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M-protein functions to stabilize the M-line cross-linking titin and myosin; the central portion of M-protein is around the M1-line, and the N-terminal and C-terminal regions are arranged along thick filaments. An animal model of thyroid hormone (T3)-induced cardiac hypertrophy showed that T3 rapidly reduced levels of M-protein; and siRNA reduction of M-protein in neonatal cardiomyocytes showed that the absence of M-protein causes significant contractile dysfunction (77% reduction in contraction velocity), thus illuminating the importance of M-protein for normal sarcomere function. M-protein can be post-translationally modified in vivo. M-protein fragments generated via cleavage by matrix metalloproteinase 2 in left ventricular myocardium have been identified as a factor in the development of pulmonary hypertension and ascites in broiler chickens.
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The patient is then instructed to go to the nearest bathroom and to attempt to defecate the balloon, where the time it takes is recorded by the doctors. An abnormal or prolonged time of expulsion of the balloon is seen as a problem in the anorectum region of the body and may lead to the diagnosis of dyssynergia, since the patient has a lack of control over their anorectal muscle contractions. Another technique used by doctors to test for dyssynergia is the anal sphincter EMG. This test involves the insertion of an electrode into the patient’s anal cavity, where they are asked to relax and push, as if they are trying to defecate. The electrical activity and contractile pressures of the patient’s anorectal contractions are recorded on a computer monitor and examined by the doctor.
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Some forms of strabismus can be corrected by weakening an extraocular muscle. Botulinum toxin blocks the neuromuscular transmission and thus paralyzes injected muscles. Paralysis is temporary, and it might seem that injections would always need to be repeated, except that muscles adapt to the lengths at which they are chronically held, so that a paralyzed muscle tends to get stretched-out by its antagonist and grows longer by addition of serial sarcomeres (the contractile units of skeletal muscles), while the antagonist tends to grow shorter by deletion of sarcomeres, thereby maintaining re-alignment when the toxin-caused paralysis has resolved. If there is good binocular vision, once muscular imbalance is sufficiently reduced, the brain mechanism of motor fusion (which points the eyes to a target visible to both) can stabilize eye alignment.
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The myometrium stretches (the smooth muscle cells expand in both size and numberSteven's and Lowe Histology p352) during pregnancy to allow for the uterus to become several times its non-gravid size, and contracts in a coordinated fashion, via a positive feedback effect on the "Ferguson reflex", during the process of labor. After delivery, the myometrium contracts to expel the placenta, and crisscrossing fibres of middle layer compress the blood vessels to minimize blood loss. A positive benefit to early breastfeeding is a stimulation of this reflex to reduce further blood loss and facilitate a swift return to prepregnancy uterine and abdominal muscle tone. Uterine smooth muscle has a phasic pattern, shifting between a contractile pattern and maintenance of a resting tone with discrete, intermittent contractions of varying frequency, amplitude and duration.
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In order to understand how these nerve and muscle cells work, she needed to be able to stimulate the cells properly and be able to record the results of the change in the currents of the individual cells occurring. Ida's microelectrode can be used for stimulating cells at the micro level while recording electrical activity within the cell without disturbing the cellular wall. This device was a revolutionary invention in neurophysiology and the study of contractile nerve tissue, however, the micro electrode was never officially attributed to Ida as being its first inventor. Though Dr. Hyde's possible microelectrode invention was reported in 1921, several others also created electrodes similar to Ida's, while scientific historians, like G. Kass-Simon have accredited Hyde's invention as being the original and revolutionary.
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Injuries to the spinal cord interfere with electrical signals between the brain and the muscles, resulting in paralysis below the level of injury. Restoration of limb function as well as regulation of organ function are the main application of FES, although FES is also used for treatment of pain, pressure, sore prevention, etc. Some examples of FES applications involve the use of neuroprostheses that allow the people with paraplegia to walk, stand, restore hand grasp function in people with quadriplegia, or restore bowel and bladder function. High intensity FES of the quadriceps muscles allows patients with complete lower motor neuron lesion to increase their muscle mass, muscle fiber diameter, improve ultrastructural organization of contractile material, increase of force output during electrical stimulation and perform FES assisted stand-up exercises.
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Rounding forces are driven by reorganization of F-actin and myosin (actomyosin) into a contractile homogeneous cell cortex that 1) rigidifies the cell periphery and 2) facilitates generation of intracellular hydrostatic pressure (up to 10 fold higher than interphase). The generation of intracellular pressure is particularly critical under confinement, such as would be important in a tissue scenario, where outward forces must be produced to round up against surrounding cells and/or the extracellular matrix. Generation of pressure is dependent on formin-mediated F-actin nucleation and Rho kinase (ROCK)-mediated myosin II contraction, both of which are governed upstream by signaling pathways RhoA and ECT2 through the activity of Cdk1. Due to its importance in mitosis, the molecular components and dynamics of the mitotic actomyosin cortex is an area of active research.
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In muscle, CAP/Ponsin plays a role in the formation of mature costameres from focal adhesion-like contacts during assembly of the contractile apparatus, as overexpression of CAP/Ponsin disrupted normal cell-matrix contact morphology. In a mouse model of viral myocarditis due to Coxsackievirus infection, CAP/Ponsin stabilized antiviral type I interferon production and was protective against apoptosis and cytotoxicity. CAP/Ponsin has also been shown to be a major regulator of insulin-stimulated signaling and regulation of glucose uptake, by potentiating insulin-induced phosphorylation and recruitment of CBL to a lipid raft signaling complex involving flotillin. A role for CAP/Ponsin in macrophage function was illuminated by the finding that mice harboring SORBS1-deficient macrophages in bone marrow was protective against high-fat diet-induced insulin resistance and showed reduced inflammation.
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Cheney's long histories of cardiovascular disease and periodic need for urgent health care raised questions of whether he was medically fit to serve in public office. Having smoked approximately 3 packs of cigarettes per day for nearly 20 years, Cheney had his first of five heart attacks on 18 June 1978, at age 37. Subsequent attacks in 1984, 1988, on 22 November 2000 and on 22 February 2010 resulted in moderate contractile dysfunction of his left ventricle. He underwent four-vessel coronary artery bypass grafting in 1988, coronary artery stenting in November 2000, urgent coronary balloon angioplasty in March 2001, and the implantation of a cardioverter-defibrillator in June 2001. On September 24, 2005, Cheney underwent a six-hour endo-vascular procedure to repair popliteal artery aneurysms bilaterally, a catheter treatment technique used in the artery behind each knee.
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The first use of ergoline alkaloids in modern medicine was described in 1808 by John Stearns, an American physician, who had reported on the uterine contractile actions of a preparation of ergot as a remedy for "quickening birth". Attempts to characterize the activity of ergoline alkaloids began in 1907, with the isolation of ergotoxine by G. Barger and F. H. Carrin. However, the industrial production of ergot alkaloids didn't begin until 1918, when Arthur Stoll patented the isolation of ergotamine tartrate, which was marketed by Sandoz in 1921. Following the determination of the basic chemical structure chemical structure of the ergot alkaloids in 1930, an era of intensive exploration of synthetic derivatives began and industrial production of ergoline alkaloids exploded, with Sandoz continuing to be the leading company in their production worldwide, up until 1950 when other competitors arose.
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This, in turn, means that eukaryotic organisms express different genes that give rise to: α-actin, which is found in contractile structures; β-actin, found at the expanding edge of cells that use the projection of their cellular structures as their means of mobility; and γ-actin, which is found in the filaments of stress fibres. In addition to the similarities that exist between an organism's isoforms there is also an evolutionary conservation in the structure and function even between organisms contained in different eukaryotic domains. In bacteria the actin homologue MreB has been identified, which is a protein that is capable of polymerizing into microfilaments; and in archaea the homologue Ta0583 is even more similar to the eukaryotic actins. Cellular actin has two forms: monomeric globules called G-actin and polymeric filaments called F-actin (that is, as filaments made up of many G-actin monomers).
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CARP was originally identified as a YB-1-associating, cardiac- restricted transcription co-repressor in the homeobox NKX2-5 pathway that is involved in cardiac ventricular chamber specification, maturation and morphogenesis, and whose mRNA levels are exquisitely sensitive to Doxorubicin, mediated through a hydrogen peroxide/ERK/p38MAP kinase-dependent as well as M-CAT cis-element-dependent mechanism. Subsequent studies showed that CARP expression in cardiomyocytes is regulated by alpha-adrenergic signaling, in part via the transcription factor GATA4. An additional study showed that beta- adrenergic signaling via protein kinase A and CaM kinase induces the expression of CARP, and that CARP may have a negative effect on contractile function. CARP has also been identified as a transcriptional co-activator of tumor suppressor protein p53 for stimulating gene expression in muscle; p53 was found to be an upstream effector of CARP via upregulation of the proximal ANKRD1 promoter.
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Closely related to the gag reflex, in which food or other foreign substances are forced back out of the pharynx, swallowing generally pushes food through the digestive system into the stomach. This reflex in particular functions as a protective system for the upper respiratory tract as it not only forces the glottis to close, thereby preventing any substances getting into the airways, but also clears the pharynx of any residual substances by a swallow. This particular reflex is simply one of several aero digestive reflexes, including also the pharyngoglottal closure reflex (in which no swallowing occurs yet the glottis still closes) and the pharyngo-upper esophageal sphincter contractile reflex, which occurs mainly during gastroesophageal reflux episodes. All either forcibly close the glottis or allow the pharynx to remove particles into the digestive tract that may have been forced back up by both this tract and the upper respiratory tract.
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Other risk factors that contributes to the formation of aneurysm are: cigarette smoking, hypertension, female gender, family history of cerebral aneurysm, infection, and trauma. Damage to structural integrity of the arterial wall by shear stress causes an inflammatory response with the recruitment of T cells, macrophages, and mast cells. The inflammatory mediators are: Interleukin 1 beta, Interleukin 6, Tumor necrosis factor alpha (TNF alpha), MMP1, MMP2, MMP9, prostaglandin E2, complement system, reactive oxygen species (ROS), and angiotensin II. On the other hand, smooth muscle cells from the tunica media layer of the artery moved into the tunica intima, where the function of the smooth muscle cells changed from contractile function into pro-inflammatory function. This causes the fibrosis of the arterial wall, with reduction of number of smooth muscle cells, abnormal collagen synthesis, resulting in thinning of arterial wall and formation of aneurysm and rupture.
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In the bodybuilding and fitness community and even in some academic books skeletal muscle hypertrophy is described as being in one of two types: Sarcoplasmic or myofibrillar. According to this hypothesis, during sarcoplasmic hypertrophy, the volume of sarcoplasmic fluid in the muscle cell increases with no accompanying increase in muscular strength, whereas during myofibrillar hypertrophy, actin and myosin contractile proteins increase in number and add to muscular strength as well as a small increase in the size of the muscle. Sarcoplasmic hypertrophy is greater in the muscles of bodybuilders because studies suggest sarcoplasmic hypertrophy shows a greater increase in muscle size while myofibrillar hypertrophy proves to increase overall muscular strength making it more dominant in Olympic weightlifters. These two forms of adaptations rarely occur completely independently of one another; one can experience a large increase in fluid with a slight increase in proteins, a large increase in proteins with a small increase in fluid, or a relatively balanced combination of the two.
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The intestines were probably shorter, to lighten the animal, and muscles not used for running were reduced. The diaphragm was likely connected to the movement of its gait and with the stretching phase of a stride, the expansion of space in the abdominal cavity pulled the diaphragm down and forced the animal to inhale, while the contractile phase compressed the lungs and forced air out, so it had no control over its breathing while running, a commonality of most quadruped sprinters. Analysis of its skeleton indicates that the giant cheetah was intermediate in morphology between the swift-moving cheetahs and slower big cats; for one, its head was more proportionate to that of the cheetah's cougar-like ancestors in appearance and its limbs were relatively more robust than the modern cheetah. Indeed, the giant cheetah may have less resembled its modern cousin and instead have had more in common in regards to morphology with the modern snow leopard, whose skeletal proportions are very similar.
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Activation of ERK induces expression of EGR1, a transcription factor which controls transcription of genes involved in cellular differentiation and mitogenesis. EP4 also interacts with Prostaglandin E receptor 4-associated protein (EPRAP) to inhibit phosphorylation of the proteasome protein, p105, thereby suppressing a cells ability to activate nuclear factor kappa B, a transcription factor that controls genes coding for cytokines and other elements that regulate inflammation, cell growth, and cell survival (see NF-κB#Structure). The activation of these pathways lead to variety of different types of functional responses depending on cell type, the pathways available in different cell types, and numerous other factors; EP4 activation may therefore have diverse effects on cell function depending on these factors. In many respects, EP4 actions resemble those of another type of another relaxant prostanoid receptor, EP2 but differs from the contractile prostanoid receptors, EP1 and EP3 receptors which mobilize G proteins containing the Gαq-Gβγ complex.
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A Dictyostelium discoideum (slime mold) cell exhibiting a prominent contractile vacuole on its left side The way in which water enters the CV had been a mystery for many years, but several discoveries since the 1990s have improved understanding of this issue. Water could theoretically cross the CV membrane by osmosis, but only if the inside of the CV is hyperosmotic (higher solute concentration) to the cytoplasm. The discovery of proton pumps in the CV membrane and the direct measurement of ion concentrations inside the CV using microelectrodes led to the following model: the pumping of protons either into or out of the CV causes different ions to enter the CV. For example, some proton pumps work as cation exchangers, whereby a proton is pumped out of the CV and a cation is pumped at the same time into the CV. In other cases, protons pumped into the CV drag anions with them (carbonate, for example), to balance the pH. This ion flux into the CV causes an increase in CV osmolarity and as a result water enters the CV by osmosis.
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Treatment is usually surgical, performed at the insertional ends of extraocular muscles (where they attach to the globe). Resection surgery removes tissue in order to stretch a muscle, increasing its elastic force; recession moves an insertion so as to reduce stretch, and so reduce elastic force; transposition moves an insertion “sideways”, sacrificing one direction of muscle action for another; posterior fixation relocates a muscle’s effective insertion to a mechanically disadvantageous position. All are kinds of compensatory impairment. Pharmacologic injection treatments, in contrast, offer the possibility of directly increasing or decreasing contractile muscle strength and elastic stiffness, as well as changing muscle length, without removing tissue or otherwise compromising orbital mechanics. The idea of treating strabismus by cutting some of the extraocular muscle fibers was published in American newspapers by New York oculist John Scudder in 1837 Spherical lenses and miotic eye drops can provide relief in some types of horizontal strabismus by biasing the neural link between convergence (orienting the lines of sight for near objects) and accommodation (focusing), and prism lenses can relieve diplopia (double vision) by refracting the visual axis, but these treatments don’t address the underlying muscular imbalance, and are not further considered here.
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Due to the presence of a cell wall, cytokinesis in plant cells is significantly different from that in animal cells, Rather than forming a contractile ring, plant cells construct a cell plate in the middle of the cell. The stages of cell plate formation include (1) creation of the phragmoplast, an array of microtubules that guides and supports the formation of the cell plate; (2) trafficking of vesicles to the division plane and their fusion to generate a tubular-vesicular network; (3) continued fusion of membrane tubules and their transformation into membrane sheets upon the deposition of callose, followed by deposition of cellulose and other cell wall components; (4) recycling of excess membrane and other material from the cell plate; and (5) fusion with the parental cell wall The phragmoplast is assembled from the remnants of the mitotic spindle, and serves as a track for the trafficking of vesicles to the phragmoplast midzone. These vesicles contain lipids, proteins and carbohydrates needed for the formation of a new cell boundary. Electron tomographic studies have identified the Golgi apparatus as the source of these vesicles, but other studies have suggested that they contain endocytosed material as well.
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G protein-coupled receptors (GPCRs) such as DP2 are integral membrane proteins that, when bound by their cognate ligands (or, in some cases, even when not ligand-bound and thereby acting continuously in a constitutive manner {see Receptor (biochemistry)#Constitutive activity}), mobilize one or more types of Heterotrimeric G proteins. DP2 is classified as a "contractile" prostanoid receptor in that it can cause the contraction of smooth muscle. As evidenced by its initial discovery as a receptor for PGD2 in T-helper type 2 cells, activated DP2 triggers Gi alpha subunit-linked heterotrimeric G proteins to dissociate into their component a) Gi alpha subunits (also termed Giα subunits) inhibit adenylyl cyclase b) G beta-gamma complex of subunits (Gβγ) have many potential functions, including simulation of phospholipase C to cleave phosphatidylinositol triphosphate into inositol triphosphate (IP3) and diacylglycerol (DAG), inhibition or stimulation of adenylyl cyclase depending on the isoform, activation of GIRK channels and activation of GRK. IP3 raises cytosolic Ca2 levels thereby regulating Ca2-sensitive signal pathways; DAG activates certain protein kinase C enzymes )PKCs) that phosphorylate and thereby regulate target proteins involved in cell signaling; and adenyl cyclase converts AMP into cyclic AMP (cAMP) thereby down-regulating cAMP- responsive proteins involved in cell signalling.
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From these observations it is apparent that the myofibrillar fraction, which is a key component of the muscle, is targeted for net degradation (as noted above) for two reasons: # degradation of this fraction allows smaller-diameter fibers to become manifest to meet the reduced requirements for force generation, and # the unraveling of the myofibrillar system allows faster MHC isoforms to become incorporated into the contractile machinery to replace the slower ones so that the muscle is able to function more effectively under a reduced state of gravitational loading. Providing further insight is the observation that the unloading state of spaceflight and of HS also increases the expression of fast type II sarcoplasmic reticulum (SR) ATPase-driven calcium pumps (SERCA II) while repressing the slower type I SERCA calcium pump. Since calcium cycling is used to regulate fiber activation and relaxation, the SR component of the muscle fiber controls the synchrony of contraction-relaxation processes. Since calcium cycling and crossbridge cycling are the two major systems that account for the vast majority of the energy expended during muscle contraction to support movement, when this property of the muscle is switched to a faster system the muscle can function more effectively in the unloaded environment.
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