Previous techniques often required the use of dyes or fixatives to help see these molecules.
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The brains are plucked from the mouse as fast as possible, which has been preserved with aldehyde fixatives in a race against the damage of death.
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And as long as a decade ago, the company had already introduced processes for producing chemical-free cloth dyed with things like tea, tobacco, mushrooms and crocus and made permanent without use of caustic fixatives.
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In drawing, a fixative is a liquid, similar to varnish, which is usually sprayed over a finished piece of artwork, usually a dry media artwork, to better preserve it and prevent smudging. Modern fixatives are usually alcohol based, and hydrocarbon propelled. Certain manufacturers produce fixatives specified for a certain media only, such as soft pastel fixatives. Modern fixatives are elevated in quality in terms of transparency, colourlessness, age-resistance and UV resistance, which prevents yellowing and fading caused by exposure to light.
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Precipitating (or denaturing) fixatives act by reducing the solubility of protein molecules and often by disrupting the hydrophobic interactions that give many proteins their tertiary structure. The precipitation and aggregation of proteins is a very different process from the crosslinking that occurs with aldehyde fixatives. The most common precipitating fixatives are ethanol and methanol. They are commonly used to fix frozen sections and smears.
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Radioactivity or radionuclide fixatives are specialized polymer coatings used to “fix” radioactive isotopes or radioactive material to surfaces. These fixatives, also known as permanent coatings in the radioactive contamination control field, have been used for many decades in facilities processing radioactive material to control radioactive contamination. There has been increased interest in these fixatives or coatings recently due to the growing concern of contamination from a radioactivity dispersal device (RDD also known as a dirty bomb) and because radioactivity fixatives in use today lose the ability to contain the radioactivity to the surface during a fire. Radioactivity fixatives reduce or eliminate the movement of radionuclides from surfaces thereby lowering the health risk of inhalation or other exposure to radioactive isotopes.
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A fixative is used to equalize the vapor pressures, and thus the volatilities, of the raw materials in a perfume oil, as well as to increase the tenacity. Natural fixatives are resinoids (benzoin, labdanum, myrrh, olibanum, storax, tolu balsam) and animal products (ambergris, castoreum, musk, and civetNew Perfume Fixatives - Chemical & Engineering News Archive / Chem. Eng. News, 1941, 19 (20), p 1134 "perfume fixatives, ...the four traditionally used by perfumers—musk, civet, ambergris, and castoreum."). Synthetic fixatives include substances of low volatility (diphenylmethane, cyclopentadecanolide, ambroxide, benzyl salicylate) and virtually odorless solvents with very low vapor pressures (benzyl benzoate, diethyl phthalate, triethyl citrate).
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Histologic section of a fossilized invertebrate. Ordovician bryozoan. Chemical fixatives are used to preserve and maintain the structure of tissues and cells; fixation also hardens tissues which aids in cutting the thin sections of tissue needed for observation under the microscope. Fixatives generally preserve tissues (and cells) by irreversibly cross-linking proteins.
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These crosslinking fixatives, especially formaldehyde, tend to preserve the secondary structure of proteins and may also preserve most tertiary structure.
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Fixatives are toxic to most common microorganisms (bacteria in particular) that might exist in a tissue sample or which might otherwise colonize the fixed tissue. In addition, many fixatives chemically alter the fixed material to make it less palatable (either indigestible or toxic) to opportunistic microorganisms. Finally, fixatives often alter the cells or tissues on a molecular level to increase their mechanical strength or stability. This increased strength and rigidity can help preserve the morphology (shape and structure) of the sample as it is processed for further analysis.
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There are many articles on the use of radioactive fixatives with a review article from 1983 often used as a reference. A more recent review article looks at the use of these radioactive fixatives for use after the detonation of a RDD. Current research is investigating new coatings that are effective at containing radioactive material to the surface during and after fires.
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In both immersion and perfusion fixation processes, chemical fixatives are used to preserve structures in a state (both chemically and structurally) as close to living tissue as possible. This requires a chemical fixative.
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The oxidizing fixatives can react with the side chains of proteins and other biomolecules, allowing the formation of crosslinks that stabilize tissue structure. However they cause extensive denaturation despite preserving fine cell structure and are used mainly as secondary fixatives. Osmium tetroxide is often used as a secondary fixative when samples are prepared for electron microscopy. (It is not used for light microscopy as it penetrates thick sections of tissue very poorly.) Potassium dichromate, chromic acid, and potassium permanganate all find use in certain specific histological preparations.
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A number of dicarbonyl compounds are bioactive. Diacetyl is known to cause the lung disease bronchiolitis obliterans in those individuals exposed to it in an occupational setting. Dialdehydes, e.g. glutaraldehyde and malonaldehyde, are fixatives or sterilizers.
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The most widely used fixative for light microscopy is 10% neutral buffered formalin, or NBF (4% formaldehyde in phosphate buffered saline). For electron microscopy, the most commonly used fixative is glutaraldehyde, usually as a 2.5% solution in phosphate buffered saline. Other fixatives used for electron microscopy are osmium tetroxide or uranyl acetate. The main action of these aldehyde fixatives is to cross-link amino groups in proteins through the formation of methylene bridges (-CH2-), in the case of formaldehyde, or by C5H10 cross-links in the case of glutaraldehyde.
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In addition to formalin, other chemical fixatives have been used. But, with the advent of immunohistochemistry (IHC) staining and diagnostic molecular pathology testing on these specimen samples, formalin has become the standard chemical fixative in human diagnostic histopathology. Fixation times for very small specimens are shorter, and standards exist in human diagnostic histopathology.
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The scent of a perfume that appears close to the departure of the middle notes. The base and middle notes together are the main theme of a perfume. Base notes bring depth and solidity to a perfume. Compounds of this class are often the fixatives used to hold and boost the strength of the lighter top and middle notes.
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In Panama, the Yaviza people mix the resin with honey and give it to newborns to impart knowledge and ward off hexes. Within the Peruvian Amazon near Iquitos, it is also used as an insect repellent. The balsam and its oil are used as fixatives in soap perfumes and fragrances. Copaiba is also used as an artist material, especially in oil paint recipes and in ceramic decoration.
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Fixation is done to not only preserve sample, but also to increase permeability of cells to stains. However, most common fixation agents have the capacity to alter cells by changing certain aspects such as size, how light is scattered, autofluorescence and nucleic acids. This is problematic as flow cytometric distinction of cells relies on these qualities. Some fixatives also lead to complete loss of cells.
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Artifacts are structures or features in tissue that interfere with normal histological examination. Artifacts interfere with histology by changing the tissues appearance and hiding structures. Tissue processing artifacts can include pigments formed by fixatives, shrinkage, washing out of cellular components, color changes in different tissues types and alterations of the structures in the tissue. An example is mercury pigment left behind after using Zenker's fixative to fix a section.
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Synthetic musks are a class of synthetic aroma compounds to emulate the scent of deer musk and other animal musks (castoreum and civet). Synthetic musks have a clean, smooth and sweet scent lacking the fecal notes of animal musks. They are used as flavorings and fixatives in cosmetics, detergents, perfumes and foods, supplying the base note of many perfume formulas. Most musk fragrance used in perfumery today is synthetic.
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Crosslinking fixatives act by creating covalent chemical bonds between proteins in tissue. This anchors soluble proteins to the cytoskeleton, and lends additional rigidity to the tissue. Preservation of transient or fine cytoskeletal structure such as contractions during embryonic differentiation waves is best achieved by a pretreatment using microwaves before the addition of a cross linking fixative.Rapid Microwave Fixation of Cell Monolayers Preserves Microtubule-associated Cell Structures J Histochem Cytochem. 2008 Jul; 56(7): 697–709.
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Charcoal can produce lines that are very light or intensely black, while being easily removable, yet vulnerable to leaving stains on paper. The dry medium can be applied to almost any surface from smooth to very coarse. Fixatives are often used with charcoal drawings to solidify the position to prevent erasing or rubbing off of charcoal dusts. The method used to create artists' charcoal is similar to that employed in other fields, such as producing gunpowder and cooking fuel.
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Glutaraldehyde and formaldehyde solutions (also used as fixatives) are accepted liquid sterilizing agents, provided that the immersion time is sufficiently long. To kill all spores in a clear liquid can take up to 22 hours with glutaraldehyde and even longer with formaldehyde. The presence of solid particles may lengthen the required period or render the treatment ineffective. Sterilization of blocks of tissue can take much longer, due to the time required for the fixative to penetrate.
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In performing their protective role, fixatives denature proteins by coagulation, by forming additive compounds, or by a combination of coagulation and additive processes. A compound that adds chemically to macromolecules stabilizes structure most effectively if it is able to combine with parts of two different macromolecules, an effect known as cross-linking. Fixation of tissue is done for several reasons. One reason is to kill the tissue so that postmortem decay (autolysis and putrefaction) is prevented.
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Zenker's fixative contains mercuric chloride ("corrosive sublimate"), potassium dichromate, sodium sulfate, water, and acetic acid. Fixatives containing mercuric chloride or potassium dichromate are toxic, making disposal as hazardous waste costly. Mercuric chloride can be replaced with the same weight of less toxic zinc chloride but the resulting "zinc-Zenker" may not give the same quality of fixation as the original mixture. This fixative is named after Konrad Zenker, a German histologist, who died in 1894 (Baker 1958).
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In recent years, studies have suggested that polycarbonates, made from bisphenol A (BPA) and phosgene (), such as the ones Nalgene used, may leach endocrine disruptors including BPA. Nalgene denies that the quantity leached from their products posed a significant threat to health. Among the secreted chemicals, BPA is a concern, as it binds to estrogen receptors, thus altering gene expression. Other research has found that fixatives in polycarbonate plastics can cause chromosomal error in cell division called aneuploidy.
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Oakmoss is commercially harvested in countries of South-Central Europe and usually exported to the Grasse region of France where its fragrant compounds are extracted as oakmoss absolutes and extracts. These raw materials are often used as perfume fixatives and form the base notes of many fragrances. They are also key components of Fougère and Chypre class perfumes. The lichen has a distinct and complex odor and can be described as woody, sharp and slightly sweet.
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The tissue is then placed into a reducing solution of hydroquinone. Lastly, the stain contrast and color is enhanced through the toning step with gold, in the form of gold chloride. This stain will appear as a dark brown color on parts of the nervous tissue such as the end-feet, myelinated fibers, and unmyelinated fibers. Bodian would go on in 1937 to refine the selectivity of the staining process through adjusting the formulations for the fixatives used.
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They are superior to the previously used animal tissues because of their large size and the high rate of mitosis (cell division) in the cell line. This allows the detection of antibodies to mitosis-specific antigens, such as centromere antibodies. They also allow identification of anti-Ro antibodies, because acetone is used for fixation of the cells (other fixatives can wash the antigen away). There are many nuclear staining patterns seen on HEp-2 cells: homogeneous, speckled, nucleolar, nuclear membranous, centromeric, nuclear dot and pleomorphic.
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In 1951 his research included histochemistry of viral and non-viral inclusion bodies and he continued to study chemical fixatives and fixation techniques. He showed that proteoglycans and polysaccharides of different pK values in their end groups can be differently stained which resulted in the development of Bi-Col procedure (Wolman, 1956). In fact, advances in our understanding of the chemical nature of ground substance remained largely neglected for a generation. Wolman also studied chemical factors underlying various impregnation procedures for the nervous system.
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Many new monomeric versions of EosFP have been developed that offer advantages over wild type EosFP. Developed by a team at the Janelia Farm Research Campus at Howard Hughes Medical Institute, mEos4 has higher photostability and longer imaging abilities than EosFP. It is also highly resistant to chemical fixatives such as PFA, gluteraldehyde and OsO4 which are used to preserve samples. mEos4 is effective at higher temperatures than EosFP, phot-converts at an increased rate and has a higher emission amplitude in both green and red fluorescent states.
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The main challenge in applying the technology to biological material was to invent a sample preparation procedure that would ensure that the atom and 3D structure remained stable while argon nano-etching occurred. During the NanoSAM scanning electron microscope visualisation, an electron beam at 25 kV is used instead of the normal 5 kV beam. Sample fixation and dehydration methods had to be developed and optimised to fit NanoSAM without creating sample distortions. Dehydration regimes based on alcohol extraction procedures were installed and optimised, while fixation using various fixatives was included.
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Synizesis refers to a phenomenon sometimes observed in one of the subphases of meiosis. This phenomenon, sometimes referred to as a "synizetic knot", and contrasted with the chromosome "bouquet" more typically observed, is characterized by the localization of the meiotic chromosomes in a tight clump on one side of the nucleus. The term synizesis seems to have been coined by McClung in 1905. The synizetic knot (Synizesis) was later found to be a technical artifact induced by the feature of strong acidic fixatives used during that time (e.g.
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In situ hybridization is a powerful technique for identifying specific mRNA species within individual cells in tissue sections, providing insights into physiological processes and disease pathogenesis. However, in situ hybridization requires that many steps be taken with precise optimization for each tissue examined and for each probe used. In order to preserve the target mRNA within tissues, it is often required that crosslinking fixatives (such as formaldehyde) be used. In addition, in-situ hybridization on tissue sections require that tissue slices be very thin, usually 3 µm to 7 µm in thickness.
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Reactions taking place in the nucleus can be more difficult, and the extracellular fluids can create unique obstacles in the performance of immunocytochemistry. In this situation, permeabilizing cells using detergent (Triton X-100 or Tween-20) or choosing organic fixatives (acetone, methanol, or ethanol) becomes necessary. Antibodies are an important tool for demonstrating both the presence and the subcellular localization of an antigen. Cell staining is a very versatile technique and, if the antigen is highly localized, can detect as few as a thousand antigen molecules in a cell.
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There was also a limited number of dyes and fixatives available prior to the middle of the 19th century. A landmark development came from Camillo Golgi who invented a silver staining technique in 1873 which he called la reazione nera (black reaction), but more popularly known as Golgi stain or Golgi method, in his honour. Using this technique nerve cells with their highly branched dendrites and axon could be clearly visualised against a yellow background. Unfortunately Golgi described the nervous system as a continuous single network, in support of a notion called reticular theory.
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Acetone is also used and has been shown to produce better histological preservation than frozen sections when employed in the Acetone Methylbenzoate Xylene (AMEX) technique. Protein-denaturing methanol, ethanol and acetone are rarely used alone for fixing blocks unless studying nucleic acids. Acetic acid is a denaturant that is sometimes used in combination with the other precipitating fixatives, such as Davidson's AFA. The alcohols, by themselves, are known to cause considerable shrinkage and hardening of tissue during fixation while acetic acid alone is associated with tissue swelling; combining the two may result in better preservation of tissue morphology.
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A bottle of perfume by Yves Saint Laurent Perfume (, ; ) is a mixture of fragrant essential oils or aroma compounds, fixatives and solvents, used to give the human body, animals, food, objects, and living-spaces an agreeable scent. It is usually in liquid form and used to give a pleasant scent to a person's body. Ancient texts and archaeological excavations show the use of perfumes in some of the earliest human civilizations. Modern perfumery began in the late 19th century with the commercial synthesis of aroma compounds such as vanillin or coumarin, which allowed for the composition of perfumes with smells previously unattainable solely from natural aromatics alone.
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Flow cytometry is most frequently used to detect apoptotic DNA fragmentation. Analysis of DNA content by flow cytometry can identify apoptotic cells with fragmented DNA as the cells with fractional DNA content, often called the sub-G1 cells. The flow-cytometric assay utilizing the fluorochrome acridine orange shows that DNA fragmentation within individual cells is discontinuous likely reflecting different levels of restriction in accessibility of DNA to DNase, by the supranucleosomal and nucleosomal levels of chromatin structure. The presence of apoptotic "sub-G1cells" can also be detected in cells pre-fixed in ethanol but not after fixation in the crosslinking fixatives such as formaldehyde.
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Contamination control products have been used by the U.S. Department of Energy (DOE) and the commercial nuclear industry for decades to minimize contamination on radioactive equipment and surfaces and fix contamination in place. "Contamination control products" is a broad term that includes fixatives, strippable coatings, and decontamination gels. A fixative product functions as a permanent coating to stabilize residual loose/transferable radioactive contamination by fixing it in place; this aids in preventing the spread of contamination and reduces the possibility of the contamination becoming airborne, reducing workforce exposure and facilitating future deactivation and decommissioning (D&D;) activities. Strippable coating products are loosely adhered paint-like films and are used for their decontamination abilities.
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The simplest way to gain information about brain anatomy is by visual inspection, but many more sophisticated techniques have been developed. Brain tissue in its natural state is too soft to work with, but it can be hardened by immersion in alcohol or other fixatives, and then sliced apart for examination of the interior. Visually, the interior of the brain consists of areas of so-called grey matter, with a dark color, separated by areas of white matter, with a lighter color. Further information can be gained by staining slices of brain tissue with a variety of chemicals that bring out areas where specific types of molecules are present in high concentrations.
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An 1823 recipe for dying 60 pounds (lbs) - about 27 kg - of military woollen cloth lists: 1 lb of cochineal, 3 lbs madder, 6 lbs argol (potassium tartrate), 3 lbs alum, 4 pints tin liquor (stannous chloride), 6 lbs cudbear (orcein) and two buckets of urine. The alum, argol and tin liquor, which acted as mordants or dye fixatives were boiled together for half an hour, the madder and cochineal was added for another ten minutes. The cloth was added and boiled for two hours; after that, the cloth was drained and immersed in cudbear and urine for another two hours. The cloth was stretched out to dry on tenters, then finally brushed with teasels and tightly rolled to produce a sheen.
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