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47 Cards in this Set
- Front
- Back
Define the purpose of fixation
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stabilizing the protein so it is resistant to further changes
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Define: Autolysis
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destruction or digestion of tissues and cells by the enzymes normally present in the cells
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Define: Fixation
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the stabilization of protein
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Define: Artifact
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a structure or substance not normally present but produced my some external force or action ex. Tissue floaters, knife lines, air bubbles
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Define: Pigment
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a heterogeneous group of substances that contain enough natural color to be visible without further staining
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Define: Nonaqueous fixative
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ingredients are primarily acetone and either ethyl or methyl alcohol; they are nonadditive, coagulating fixatives
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Define: Coagulating fixative
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establishes a network in tissue that allows solutions to readily penetrate ore gain entry into the interior of the tissue
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Define: Additive fixative
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denaturation causes the protein molecules to unfold and the internal bonds become disrupted, this disruption enables the protein to combine chemically with a fixative molecule and the protein then becomes insoluble
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Define: Hypertonic
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having a higher osmotic pressure than another solution; when surrounded by a hypertonic solution, the water leaves the cell and the cell shrinks
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Define: Isotonic
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fluids into which normal animal cells can be placed without causing either swelling or shrinkage of the cells
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Identify the factors that affect the quality of fixation
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temperature, size of tissue, time of fixation, or osmolality of fixative
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describe the effect of temperature on fixation
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affects the rate of fixation. An increase in temperature increases the rate of fixation, but also increases the rate of autolysis.
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describe the effect of size on fixation
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important because of its effect on reagent penetration. Large specimens must be opened to expose all layers or the fixative will not be able to penetrate the entire specimen. Sections should be no thicker than 3mm and should never touch the top and bottom of the cassette.
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describe the effect of time on fixation
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important because a) the tissue should be placed immediately in fixative to eliminate autolysis and b) the duration of fixation must be adequate to ensure that the tissue will not be distorted in subsequent processing steps.
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describe the effect of osmolality on fixation
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important in terms of isotonic, hypertonic, and hypotonic such that the fixative will not swell, or shrink the cells of the tissue.
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Acetic acid
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noncoagulant; penetrates rapidly and leaves tissue very soft; precipitation and preservation of nucleoproteins (fixes nuclei) also precipitates DNA
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Acetone
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nonadditive protein coagulant; rapid acting fixative, can cause shrinkage; fixes and dehydrates; fixes brain tissue, frozen sections
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Alcohols
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nonaqueous fixative; preserves most pigments, dissolves fat, overhardens and shrinks tissue; fixes tissues, begins dehydration, preserves glycogen very well, penetrates quickly
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B-5 fixative
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fixative of hematopoietic and lymphoreticular tissues
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Bouin solution
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dissolves iron/small calcium deposits;excellent fixative for GI biopsy specimens
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Carnoy and methacarn solutions
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nonaqueous fixative; substitutes methyl alchohol for ethyl alcohol; fixative, used in cytology, rapid acting, preserves glycogen, good nuclear preservation
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Aqueous Formalin
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hypotonic, may cause formalin pigment; fixative
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Buffered Formalin
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hypotonic in the buffer ions present; routine fixation
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Neutralized Formalin
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solution becomes acidic after withdrawal from storage bottle; fixative
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Acetate formalin
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pseudocalcification of tissue can be caused; fixes phospholipids
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Formalin alcohol
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compound fixative used in tissue processors; fixes and dehydrates; tissue storage
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Calcium formalin
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calcium ions prevent gradual distortion; fixes/preserves phospholipids in tissues
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Formalin ammonium bromide
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very acidic, lyses red blood cells, causes nuclei to give positive Schiff reaction; fixes CNS tissue
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Gendre solution
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preservation of some carbohydrates, especially glycogen
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Glutaraldehyde
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dialdehyde; cross-linking proteins plus extra aldehyde reacts with Schiff reagent; fixation of specimens for electron microscopy
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Helly solution
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preserves eyrthrocytes
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Hollande solution
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Stable and will decalcify small specimens of bone
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Mercuric chloride
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corrosive chemical, protein coagulant; inhibits freezing, leaves tissue receptive to dyes; coagulant fixative, additive fixative
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Orth solution
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Not a good general purpose fixative; demonstrates chromaffin granules in the cytoplasm of cells of the adrenal medulla
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Osmium tetroxide
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noncoagulant, carcinogen; rarely used alone for fixation, acts like chromic acid when used with acid solution; preserves mitochondria by rendering the lipid component insoluble in alchohol
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Zamboni solution
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primary fixative for electron microscopy
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Zenker solution
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lyses erythrocytes; fix and decalcify needle biopsy specimens of bone marrow; nuclear fixative
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Zinc formalin
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aqueous and alcoholic; zinc ions stabilize protein macromolecules against the changes and cross-linking induced by formaldehyde; superior nuclear detail and better paraffin infiltration
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B-5 fixative
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Fixative of hematopoietic and lymphoretiulat tissues
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Bouin solution
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Excellent for tissue that is to be trichrome stained and for preserving structures with soft and delicate textures
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Carnoy and methacarn solutions
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Rapid acting, preserves glycogen, exhibits good nuclear preservation but causes excessive shrinkage and hardening
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Gendre solution
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Excellent for the preservation of some carbohydrates, especially glycogen
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Helly (working) solution
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Preserves the erythrocytes but Zenker is better nuclear fixative
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Hollande solution
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Stable and will decalcify small specimens of bone
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Orth solution
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Not a good general purpose fixative; demonstrates chromaffin granules in the cytoplasm of cells of the adrenal medulla
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Zamboni solution
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Very stable, good general purpose fixative
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Zenker (working) solution
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Fix and decalcify needle biopsy specimens of bone marrow; nuclear fixative
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