The sperm bank's founder, Ole Schou, even wore a silver spermatozoon lapel pin as he posed for a portrait.
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I get my "sample" in the cup—that's all you need to know about that—and manage to add the liquefying powder and turn my spermatozoon pink without having panic attack.
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"A living human child, from the moment of fertilization on fusion of a human spermatozoon with a human ovum, is entitled to the same rights, powers, and privileges as are secured or granted by the laws of this state to any other human child," the bill says.
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This is the only known insect in the world to feature a giant single spermatozoon. The giant spermatozoon is thought to have evolved in this manner so as to act like a mating plug.
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The spermatozoon that fertilizes an oocyte will contribute its pronucleus, the other half of the zygotic genome. In some species, the spermatozoon will also contribute a centriole, which will help make up the zygotic centrosome required for the first division. However, in some species, such as in the mouse, the entire centrosome is acquired maternally. Currently under investigation is the possibility of other cytoplasmic contributions made to the embryo by the spermatozoon.
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This process also involves meiosis occurring in the diploid primary spermatocyte to produce the haploid spermatozoon.
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Spermatozoon is the male gamete. After ejaculation this cell is not mature, so it can not fertilize the oocyte. To have the ability to fertilize the female gamete, this cell suffers capacitation and acrosome reaction in female reproductive tract. The signaling pathways best described for spermatozoon involve these processes.
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Each of these processes becomes a male gamete termed a microgamete which is equivalent to a mammalian spermatozoon.
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Another type of atypical type of centriole was discovered in human and bovine sperm. This is the distal centriole of the spermatozoon, which has atypical structure and composition. This spermatozoon distal centriole is composed of splayed microtubules surrounding previously undescribed rods of centriole luminal proteins, and it has only a subset of the protein found in a typical centriole. After fertilization, the atypical distal centriole that is attached to the sperm tail recruits pericentriolar material, forming a new centriole, and localizing to the spindle pole during mitosis.
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Introduced in 2001, the intracytoplasmic morphologically selected sperm injection (IMSI) procedure changed the perception of how a spermatozoon suitable for fertilization (via injection into the egg) should appear. A very high powered lens is used to see the sperm in greater detail during the selection process. The spermatozoon is selected at higher magnification; the aim of this is to improve the chance of pregnancy. The use of high magnification for morphological sperm selection prior to ICSI has been associated with higher pregnancy rates and lower miscarriage rate.
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By contrast, gametes of diploid organisms contain only half as many chromosomes. In humans, this is 23 unpaired chromosomes. When two gametes (i.e. a spermatozoon and an ovum) meet during conception, they fuse together, creating a zygote.
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Another significant advance in ART was the development of intracytoplasmic sperm injection (ICSI) in 1992.Palermo G, Joris H, Devroey P et al. Pregnancies after intracytoplasmic injection of single spermatozoon into an oocyte. Lancet 1992; 340: 17.
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Movement of sperm is called sperm motility. The middle of the mammalian spermatozoon contains mitochondria that power the movement of the flagellum of the sperm. The motor around the base produces torque, just like in bacteria for movement through the aqueous environment.
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His contributions are most well known to protozoa research. Hertwig, on the basis of examining sea urchins, discovered and explained the zygote fertilization process for the first time correctly as a fusion of egg and spermatozoon (sperm cell) penetrating the egg membrane.
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Sperm Spermiogenesis is the final stage of spermatogenesis, which sees the maturation of spermatids into mature spermatozoa. The spermatid is a more or less circular cell containing a nucleus, Golgi apparatus, centriole and mitochondria. All these components take part in forming the spermatozoon.
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USDA in conjunction with Lawrence Livermore National Laboratories, 'Beltsfield Sperm Sexing Technology' relies on the DNA difference between the X- and Y- chromosomes. Prior to flow cytometric sorting, semen is labeled with a fluorescent dye called Hoechst 33342 which binds to the DNA of each spermatozoon.
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The large Sertoli cells (which are not dividing) function as supportive cells to the developing sperm. The second cell type are the cells belonging to the spermatogenic cell lineage. These develop to eventually become sperm cells (spermatozoon). Typically, the spermatogenic cells will make four to eight layers in the germinal epithelium.
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The spermatozoa of animals are produced through spermatogenesis inside the male gonads (testicles) via meiotic division. The initial spermatozoon process takes around 70 days to complete. The process starts with the production of spermatogonia from germ cell precursors. These divide and differentiate into spermatocytes, which undergo meiosis to form spermatids.
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The term zooid has historically also been used for an organic cell or organized body that has independent movement within a living organism, especially a motile gamete such as a spermatozoon (in the case of algae now zoid), or an independent animal- like organism produced asexually, as by budding or fission.
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Where the spermatozoan is about to pierce, the yolk (ooplasm) is drawn out into a conical elevation, termed the cone of attraction or reception cone. Once the spermatozoon has entered, the peripheral portion of the yolk changes into a membrane, the perivitelline membrane, which prevents the passage of additional spermatozoa.
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Lepadogaster species have semicystic spermatogenesis, which is a rare form of spermatogenesis in which the cyst breaks apart before the spermatozoon stage. The sperm of Lepadogaster also has an odd elongated shape to it.Hernández, M. R., Sàbat, M., Muñoz, M., & Casadevall, M. (2005). Semicystic spermatogenesis and reproductive strategy in Ophidion barbatum (Pisces, Ophidiidae).
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Although various mammals have been studied, mice represent the best studied animal models for understanding the cortical reaction in mammals. In mammals the cortical reaction leads to a modification of the zona pellucida that blocks polyspermy; enzymes released by cortical granules digest sperm receptor glycoproteins ZP2 and ZP3 so that they can no longer bind spermatozoon.
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The sex ratio is 1:1. The structure of the flagellum of the spermatozoon is unique: the flagellum is divided into two parts. T. fluviatilis eggs are usually laid in from mid-April to October, in temperatures above 10 °C. Eggs are laid in egg capsules deposited on stones and sometimes on shells of conspecific individuals.
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The ability to freeze and subsequently thaw and transfer embryos has significantly improved the feasibility of IVF use. The other very significant milestone in IVF was the development of the intracytoplasmic sperm injection (ICSI) of single sperms by Gianpiero D. Palermo et al.in Brussels (UZ Brussel), 1992.Pregnancies after intracytoplasmic injection of single spermatozoon into an oocyte.
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Diagram of stages of embryo development to a larval and adult stage. In developmental biology, embryonic development, also known as embryogenesis, is the development of an embryo. Embryonic development starts with the fertilization of an egg cell (ovum) by a sperm cell, (spermatozoon). Once fertilized, the ovum becomes a single diploid cell known as a zygote.
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Usually 23 chromosomes from spermatozoon and 23 chromosomes from egg cell fuse (half of spermatozoons carry X chromosome and the other half Y chromosome). Their membranes dissolve, leaving no barriers between the male and female chromosomes. During this dissolution, a mitotic spindle forms between them. The spindle captures the chromosomes before they disperse in the egg cytoplasm.
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The theory that located the homonculus in the egg was called ovism. But, when spermatozoa were discovered, a rival camp of spermists sprang up, claiming that the homunculus must come from the male. In fact, the term "spermatozoon," coined by Karl Ernst von Baer, means "seed animals." With the discovery of sperm and the concept of spermism came a religious quandary.
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The cellular reproduction process of meiosis was discovered by Oscar Hertwig in 1876. Mitosis was discovered several years later in 1882 by Walther Flemming. Hertwig studied sea urchins, and noticed that each egg contained one nucleus prior to fertilization and two nuclei after. This discovery proved that one spermatozoon could fertilize an egg, and therefore proved the process of meiosis.
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Fertilization by a spermatozoon, when it occurs, usually takes place in the ampulla, the widest section of the fallopian tubes. A fertilized egg immediately begins the process of embryogenesis, or development. The developing embryo takes about three days to reach the uterus and another three days to implant into the endometrium. It has usually reached the blastocyst stage at the time of implantation.
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The form of anisogamy that occurs in animals, including humans, is oogamy, where a large, non-motile egg (ovum) is fertilized by a small, motile sperm (spermatozoon). The egg is optimized for longevity, whereas the small sperm is optimized for motility and speed. The size and resources of the egg cell allow for the production of pheromones, which attract the swimming sperm cells.
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The cAMP/PKA signaling pathway leads to sperm cells capacitation; however, adenylyl cyclase in sperm cells is different from the somatic cells. Adenylyl cyclase in spermatozoon does not recognize G proteins, so it is stimulated by bicarbonate and Ca2+ ions. Then, it converts adenosine triphosphate into cyclic AMP, which activates Protein kinase A. PKA leads to protein tyrosine phosphorylation. Phospholipase C (PLC) is involved in acrosome reaction.
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ZP3 is a glycoprotein present in zona pelucida and it interacts with receptors in spermatozoon. So, ZP3 can activate G protein coupled receptors and tyrosine kinase receptors, that leads to production of PLC. PLC cleaves the phospholipid phosphatidylinositol 4,5-bisphosphate (PIP2) into diacyl glycerol (DAG) and inositol 1,4,5-trisphosphate. IP3 is released as a soluble structure into the cytosol and DAG remains bound to the membrane.
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Hermann Fol continued Hertwig's research by testing the effects of injecting several spermatozoa into an egg, and found that the process did not work with more than one spermatozoon. Flemming began his research of cell division starting in 1868. The study of cells was an increasingly popular topic in this time period. By 1873, Schneider had already begun to describe the steps of cell division.
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After the acrosome reaction, the sperm is believed to remain bound to the zona pellucida through exposed ZP2 receptors. These receptors are unknown in mice but have been identified in guinea pigs. In mammals, the binding of the spermatozoon to the GalT initiates the acrosome reaction. This process releases the hyaluronidase that digests the matrix of hyaluronic acid in the vestments around the oocyte.
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The spermatozoon of Chimaericola leptogaster (drawing) The first molecular sequences obtained from Chimaericola leptogaster suggested that the Chimaericolidae were a basal group within the Polyopisthocotylea. Chimaericola leptogaster was studied with transmission electron microscopy. Several organs have been investigated in details: vaginae, clamps, digestive system, and spermiogenesis and spermatozoa. These ultrastructural results have confirmed the basal position of the species in comparison to marine Polyopisthocotylea.
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Males release their sperm into sea water. While the released agglomerations of spermatozoa, referred to as spermatozeugmata, do not remain intact for more than 30 seconds in laboratory conditions, they may maintain integrity for longer periods of time in specific hydrothermal vent conditions. Usually, the spermatozeugmata swim into the female's tube. Movement of the cluster is conferred by the collective action of each spermatozoon moving independently.
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Spermatozoa develop in the seminiferous tubules of the testes. During their development the spermatogonia proceed through meiosis to become spermatozoa. Many changes occur during this process: the DNA in nuclei becomes condensed; the acrosome develops as a structure close to the nucleus. The acrosome is derived from the Golgi apparatus and contains hydrolytic enzymes important for fusion of the spermatozoon with an egg cell.
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As a graduate student of Hokkaido University in Japan Yanagimachi studied fish (herring) fertilization and the sexual organization of rhizocephalans (parasitic barnacles). In fish, he discovered calcium-dependent, chemotactic movement of spermatozoa into the micropyle through which the fertilizing spermatozoon enters the egg. This was the first discovery of sperm chemotaxis in vertebrate animals. In rhizocephala, he found that adults are not hermaphroditic as generally thought, but bisexual.
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He also wrote a leading textbook. By studying sea urchins he proved that fertilization occurs due to the fusion of a sperm and egg cell. He recognized the role of the cell nucleus during inheritance and chromosome reduction during meiosis: in 1876, he published his findings that fertilization includes the penetration of a spermatozoon into an egg cell. Hertwig's experiments with frog eggs revealed the 'long axis rule', or Hertwig rule.
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Reproduction has also been observed involving only a single spermatozoon reaching the female's tube. Generally, fertilization in R. pachyptila is considered internal. However, some argue that, as the sperm is released into sea water and only afterwards reaches the eggs in the oviducts, it should be defined as internal- external. R. pachyptila is completely dependent on the production of vulcanic gases and the presence of sulfide-oxidizing bacteria.
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During copulation, the male inseminates the female. The spermatozoon fertilizes an ovum or various ova in the uterus or fallopian tubes, and this results in one or multiple zygotes. Sometimes, a zygote can be created by humans outside of the animal's body in the artificial process of in-vitro fertilization. After fertilization, the newly formed zygote then begins to divide through mitosis, forming an embryo, which implants in the female's endometrium.
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The acrosome reaction for a sea urchin, a similar process. Note that the picture shows several stages of one and the same spermatozoon - only one penetrates the ovum Illustration depicting ovulation and fertilization. The sperm entering the ovum using acrosomal enzymes to dissolve the gelatinous envelope of the oocyte. Human fertilization is the union of a human egg and sperm, usually occurring in the ampulla of the fallopian tube.
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Prior to flow cytometric sorting, semen is labeled with a fluorescent dye called Hoechst 33342 which binds to the DNA of each spermatozoon. As the X chromosome is larger (i.e. has more DNA) than the Y chromosome, the "female" (X-chromosome bearing) spermatozoa will absorb a greater amount of dye than its male (Y-chromosome bearing) counterpart. As a consequence, when exposed to UV light during flow cytometry, X spermatozoa fluoresce brighter than Y- spermatozoa.
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In addition to the two pairs of book lungs, other synapomorphies of Tetrapulmonata include a large postcerebral pharynx (reduced in Uropygi), prosomal endosternite with four segmental components, subchelate chelicerae, a complex coxotrochanteral joint in the walking legs, a pretarsal depressor muscle arising in the patella (convergent with Dromopoda, lost in Amblypygi), a pedicel formed, in part, by ventral elements of the second opisthomal segment and a spermatozoon axoneme with a 9+3 microtubule arrangement.
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Culture of human embryonic stem cells in mitotically inactivated porcine ovarian fibroblasts (POF) causes differentiation into germ cells (precursor cells of oocytes and spermatozoa), as evidenced by gene expression analysis. Human embryonic stem cells have been stimulated to form Spermatozoon-like cells, yet still slightly damaged or malformed. It could potentially treat azoospermia. In 2012, oogonial stem cells were isolated from adult mouse and human ovaries and demonstrated to be capable of forming mature oocytes.
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Micromanipulators are usually used in conjunction with microscopes. Depending on the application, one or more micromanipulators may be fitted to a microscope stage or rigidly mounted to a bench next to a microscope. A typical application of micromanipulation is human intracytoplasmic sperm injection. Here, a spermatozoon measuring some 3 to 5 micrometres across is injected into an oocyte of approximately 100 micrometres in diameter, under the direct manual control of an embryologist.
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Prior to flow cytometric sorting, semen is labeled with a fluorescent dye called Hoechst 33342 which binds to the DNA of each spermatozoon. As the X chromosome is larger (i.e. has more DNA) than the Y chromosome, the "female" (X-chromosome bearing) spermatozoa will absorb a greater amount of dye than its male (Y-chromosome bearing) counterpart. As a consequence, when exposed to UV light during flow cytometry, X spermatozoa fluoresce brighter than Y- spermatozoa.
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As the spermatozoa pass through the flow cytometer in single file, each spermatozoon is encased by a single droplet of fluid and assigned an electric charge corresponding to its chromosome status (e.g. X-positive charge, Y-negative charge). The stream of X- and Y- droplets is then separated by means of electrostatic deflection and collected into separate collection tubes for subsequent processing.Seidel GE, Jr., Garner DL. Current status of sexing mammalian spermatozoa.
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It is called zona pellucida in mammals. As soon as the spermatozoon fuses with the ovum, signal transduction occurs, resulting in an increase of cytoplasmic calcium ions. This itself triggers the cortical reaction, which results in depositing several substances onto the vitelline membrane through exocytosis of the cortical granules, transforming it into a hard layer called the “fertilization membrane”, which serves as a barrier inaccessible to other spermatozoa. This phenomenon is the slow block to polyspermy.
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The oocyte receives mitochondria from maternal cells, which will go on to control embryonic metabolism and apoptotic events. The partitioning of mitochondria is carried out by a system of microtubules that will localize mitochondria throughout the oocyte. In certain organisms, such as mammals, paternal mitochondria brought to the oocyte by the spermatozoon are degraded through the attachment of ubiquitinated proteins. The destruction of paternal mitochondria ensures the strictly maternal inheritance of mitochondria and mitochondrial DNA or mtDNA.
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ZP3 is then involved in the induction of the acrosome reaction, whereby a spermatozoon releases the contents of the acrosomal vesicle. The exact characterisation of what occurs in other species has become more complicated as further zona proteins have been identified. In humans, five days after the fertilization, the blastocyst performs zona hatching; the zona pellucida degenerates and decomposes, to be replaced by the underlying layer of trophoblastic cells. The zona pellucida is essential for oocyte growth and fertilization.
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Typical centrioles are made of 9 triplets of microtubules organized with radial symmetry. Centrioles can vary the number of microtubules and can be made of 9 doublets of microtubules (as in Drosophila melanogaster) or 9 singlets of microtubules as in C. elegans. Atypical centrioles are centrioles that do not have microtubules, such as the Proximal Centriole-Like found in D. melanogaster sperm, or that have microtubules with no radial symmetry, such as in the distal centriole of human spermatozoon.
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As the spermatozoa pass through the flow cytometer in single file, each spermatozoon is encased by a single droplet of fluid and assigned an electric charge corresponding to its chromosome status (e.g. X-positive charge, Y-negative charge). The stream of X- and Y- droplets is then separated by means of electrostatic deflection and collected into separate collection tubes for subsequent processing. Recently, a study published in 2006 indicated that mothers with toxoplasmosis have a significantly higher sex ratio of boys to girls.
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In somatic cells it binds to receptors in nucleus; however, in spermatozoon its receptors are present in plasmatic membrane. This hormone activates AKT that leads to activation of other protein kinases, involved in capacitation and acrosome reaction. When ROS (reactive oxygen species) are present in high concentration, they can affect the physiology of cells, but when they are present in moderated concentration they are important for acrosome reaction and capacitation. ROS can interact with cAMP/PKA and progesterone pathway, stimulating them.
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J. Reprod. Dev., 59, 59-65. and a gradient of natriuretic peptide precursor A, shown to be a chemoattractant for mouse spermatozoa, was found, in decreasing concentration order, in the ampulla, isthmus, and uterotubal junction.Bian, F., Mao, G., Guo, M., Mao, G., Wang, J., Li, J., Han, Y., Chen, X., Zhang, M. and Xia, G. (2012) Gradients of natriuretic peptide precursor A (NPPA) in oviduct and of natriuretic peptide receptor 1 (NPR1) in spermatozoon are involved in mouse sperm chemotaxis and fertilization.
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Fertilization and implantation in humans Through an interplay of hormones that includes follicle stimulating hormone that stimulates folliculogenesis and oogenesis creates a mature egg cell, the female gamete. Fertilization is the event where the egg cell fuses with the male gamete, spermatozoon. After the point of fertilization, the fused product of the female and male gamete is referred to as a zygote or fertilized egg. The fusion of female and male gametes usually occurs following the act of sexual intercourse.
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As the X chromosome is larger (i.e. has more DNA) than the Y chromosome, the "female" (X-chromosome bearing) spermatozoa will absorb a greater amount of dye than its male (Y-chromosome bearing) counterpart. As a consequence, when exposed to UV light during flow cytometry, X spermatozoa fluoresce brighter than Y- spermatozoa. As the spermatozoa pass through the flow cytometer in single file, each spermatozoon is encased by a single droplet of fluid and assigned an electric charge corresponding to its chromosome status (e.g.
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However, in the absence of an accurate understanding of human development, early notions about the timing and process of conception were often vague. Both the 1828 and 1913 editions of Webster's Dictionary said that to "conceive" meant "to receive into the womb and ... begin the formation of the embryo." However most references say that it was only in 1875 that Oskar Hertwig discovered that fertilization includes the penetration of a spermatozoon into an ovum. Thus, the term "conception" was in use long before the details of fertilization were discovered.
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A male typically inherits an X chromosome from ovum and a Y chromosome from spermatozoon. The presence of the sex-determining-region of the Y chromosome, or SRY gene, determines the embryo being a male. Internal and external male genitalia development from bipotential gonad in embryo. SRY gene encodes testis-determining SRY factor (TDF) protein that promotes expression of several other genes such as SRY-box 9 (SOX-9) gene and steroidogenic factor-1 (SF1) gene, causing differentiation of the medulla of bipotential gonad into testis by week six.
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Intracellular calcium influx contributes to sperm capacitation and hyperactivation, causing a more violent and rapid non-linear motility pattern as sperm approach the oocyte. The capacitated spermatozoon and the oocyte meet and interact in the ampulla of the fallopian tube. Rheotaxis, thermotaxis and chemotaxis are known mechanisms that guide sperm towards the egg during the final stage of sperm migration. Spermatozoa respond (see Sperm thermotaxis) to the temperature gradient of ~2 °C between the oviduct and the ampulla, and chemotactic gradients of progesterone have been confirmed as the signal emanating from the cumulus oophorus cells surrounding rabbit and human oocytes.
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Importantly, the fraction of capacitated (and, hence, chemotactically responsive) spermatozoa is low (~10% in humans), the life span of the capacitated/chemotactic state is short (1–4 hours in humans), a spermatozoon can be at this state only once in its lifetime, and sperm individuals become capacitated/chemotactic at different time points, resulting in continuous replacement of capacitated/chemotactic cells within the sperm population, i.e., prolonged availability of capacitated cells.Cohen-Dayag, A., Ralt, D., Tur-Kaspa, I., Manor, M., Makler, A., Dor, J., Mashiach, S. and Eisenbach, M. (1994) Sequential acquisition of chemotactic responsiveness by human spermatozoa. Biol. Reprod. 50, 786–790.
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Changes in pH both controls and activates the MSP polymerization throughout spermatogenesis by a pH gradient within the pseudopod of the spermatozoon: assembly occurs at the leading edge where the pH is high, and disassembly of the filaments occurs at the base where the pH is lowered. Degradation of the MSP filaments results in a traction force at the base of the pseudopod, which in turn pulls the cytoskeleton forward. The combination of these two forces is the motive force that allows sperm motility. Attachment of the cytoskeleton to the substratum is required to generate a directional movement.
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Protamines are small, arginine-rich, nuclear proteins that replace histones late in the haploid phase of spermatogenesis and are believed essential for sperm head condensation and DNA stabilization. They may allow for denser packaging of DNA in the spermatozoon than histones, but they must be decompressed before the genetic data can be used for protein synthesis. However, in humans and maybe other primates, 10-15% of the sperm's genome is packaged by histones thought to bind genes that are essential for early embryonic development. Protamine and protamine-like (PL) proteins are among the sperm specific nuclear basic proteins (SNBPs).
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Fertilization takes place when the spermatozoon has successfully entered the ovum and the two sets of genetic material carried by the gametes fuse together, resulting in the zygote (a single diploid cell). This usually takes place in the ampulla of one of the fallopian tubes. The zygote contains the combined genetic material carried by both the male and female gametes which consists of the 23 chromosomes from the nucleus of the ovum and the 23 chromosomes from the nucleus of the sperm. The 46 chromosomes undergo changes prior to the mitotic division which leads to the formation of the embryo having two cells.
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Lost in the Funhouse opens with a "story" which can be cut and pasted to form an endless Möbius strip The book opens with "Frame-Tale", a "story" in which "ONCE UPON A TIME THERE" and "WAS A STORY THAT BEGAN" are printed vertically, one on each side of the page. This is intended to be cut out by the reader, and its ends being fastened together, after being twisted once in a Möbius strip. This results in a regressus ad infinitum, a loop with no beginning or end. "Night-Sea Journey" follows, the first-person story of a human spermatozoon on its way to fertilize an egg.
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When the fetus is developed enough to survive outside of the uterus, the cervix dilates and contractions of the uterus propel it through the birth canal, which is the vagina. The ova, which are the female sex cells, are much larger than the spermatozoon and are normally formed within the ovaries of the female fetus before its birth. They are mostly fixed in location within the ovary until their transit to the uterus, and contain nutrients for the later zygote and embryo. Over a, usually, regular interval known as the menstrual cycle, in response to hormonal signals, a process of oogenesis matures one ovum which is released and sent down the Fallopian tube.
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This raised the possibility that, in mammals, chemotaxis is not solely a guidance mechanism but it is also a mechanism of sperm selection. Importantly, the fraction of capacitated (and, hence, chemotactically responsive) spermatozoa is low (~10% in humans), the life span of the capacitated/chemotactic state is short (1–4 hours in humans), a spermatozoon can be at this state only once in its lifetime, and sperm individuals become capacitated/chemotactic at different time points, resulting in continuous replacement of capacitated/chemotactic cells within the sperm population, i.e., prolonged availability of capacitated cells.Cohen-Dayag, A., Ralt, D., Tur-Kaspa, I., Manor, M., Makler, A., Dor, J., Mashiach, S. and Eisenbach, M. (1994) Sequential acquisition of chemotactic responsiveness by human spermatozoa. Biol. Reprod.
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In 1878, he obtained a post of professor at the University of Geneva where in the following year, he observed the penetration of a spermatozoon into an egg becoming thus a pioneer of the microscopic studies of fertilisation and cellular division. In 1886, he resigned from his post in Geneva to devote himself entirely to his research in Villefranche-sur- Mer where, in 1880, he had established a small marine laboratory with Jules Henri Barrois (1852–1943). Then, financially aided by the French government to carry out a study of distribution of sponges on the Tunisian and Greek coasts, he departed Le Havre on his new yacht, l' Aster on March 13, 1892, accompanied by several team members. After a stopover in Bénodet, the yacht disappeared at sea, and Fol was never seen again.
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They use the "mouths" to manipulate objects, as a humanoid uses hands. The Puppeteer's native language sounds like highly complex orchestral music, but they seem to be able to reproduce human language without difficulty or device, as well as the Heroes' Tongue (Kzinti), suggesting their vocal arrangement may resemble a pair of avian-like syrinxes rather than vocal cords. Biologically, Puppeteers are highly intelligent herbivores; a herd animal, Puppeteers prefer the company (and smell) of their own kind. Their cycle of reproduction is similar to that of Earth's digger wasps: the Puppeteers consider themselves to have three genders (two male, one female): the two "male" genders are the equivalent of human female and male (one has an ovipositor, the other produces sperm) and the "female" is a (non- sentient) parasitized host into which the ovum and spermatozoon are deposited.
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In 1977, Dale joined the Stazione Zoologica in Naples as a post-doctoral fellow of the Royal Society of Pathology, London where he joined the team of Alberto Monroy to study mechanisms of fertilization. One of his first discoveries, with Louis J De Felice from the US, was a novel non specific ion channel, the fertilization channel, that was gated by the spermatozoon, and later led to the hypothesis of a soluble sperm borne activating factor, that is now known to be ubiquitous. Using invertebrate and vertebrate gametes, the next two decades led to unifying concepts in the mechanism and kinetics of fertilization across the animal kingdom(8). In the early 1990s, thanks to the availability of human gametes and embryos for basic research, Dale launched research projects that led to the identification of the first activation event in the human oocyte(9) and the role of cell-cell interactions in the human embryo(6).
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