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47 Cards in this Set

  • Front
  • Back
Define the purpose of fixation
stabilizing the protein so it is resistant to further changes
Define: Autolysis
destruction or digestion of tissues and cells by the enzymes normally present in the cells
Define: Fixation
the stabilization of protein
Define: Artifact
a structure or substance not normally present but produced my some external force or action ex. Tissue floaters, knife lines, air bubbles
Define: Pigment
a heterogeneous group of substances that contain enough natural color to be visible without further staining
Define: Nonaqueous fixative
ingredients are primarily acetone and either ethyl or methyl alcohol; they are nonadditive, coagulating fixatives
Define: Coagulating fixative
establishes a network in tissue that allows solutions to readily penetrate ore gain entry into the interior of the tissue
Define: Additive fixative
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
Define: Hypertonic
having a higher osmotic pressure than another solution; when surrounded by a hypertonic solution, the water leaves the cell and the cell shrinks
Define: Isotonic
fluids into which normal animal cells can be placed without causing either swelling or shrinkage of the cells
Identify the factors that affect the quality of fixation
temperature, size of tissue, time of fixation, or osmolality of fixative
describe the effect of temperature on fixation
affects the rate of fixation. An increase in temperature increases the rate of fixation, but also increases the rate of autolysis.
describe the effect of size on fixation
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.
describe the effect of time on fixation
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.
describe the effect of osmolality on fixation
important in terms of isotonic, hypertonic, and hypotonic such that the fixative will not swell, or shrink the cells of the tissue.
Acetic acid
noncoagulant; penetrates rapidly and leaves tissue very soft; precipitation and preservation of nucleoproteins (fixes nuclei) also precipitates DNA
Acetone
nonadditive protein coagulant; rapid acting fixative, can cause shrinkage; fixes and dehydrates; fixes brain tissue, frozen sections
Alcohols
nonaqueous fixative; preserves most pigments, dissolves fat, overhardens and shrinks tissue; fixes tissues, begins dehydration, preserves glycogen very well, penetrates quickly
B-5 fixative
fixative of hematopoietic and lymphoreticular tissues
Bouin solution
dissolves iron/small calcium deposits;excellent fixative for GI biopsy specimens
Carnoy and methacarn solutions
nonaqueous fixative; substitutes methyl alchohol for ethyl alcohol; fixative, used in cytology, rapid acting, preserves glycogen, good nuclear preservation
Aqueous Formalin
hypotonic, may cause formalin pigment; fixative
Buffered Formalin
hypotonic in the buffer ions present; routine fixation
Neutralized Formalin
solution becomes acidic after withdrawal from storage bottle; fixative
Acetate formalin
pseudocalcification of tissue can be caused; fixes phospholipids
Formalin alcohol
compound fixative used in tissue processors; fixes and dehydrates; tissue storage
Calcium formalin
calcium ions prevent gradual distortion; fixes/preserves phospholipids in tissues
Formalin ammonium bromide
very acidic, lyses red blood cells, causes nuclei to give positive Schiff reaction; fixes CNS tissue
Gendre solution
preservation of some carbohydrates, especially glycogen
Glutaraldehyde
dialdehyde; cross-linking proteins plus extra aldehyde reacts with Schiff reagent; fixation of specimens for electron microscopy
Helly solution
preserves eyrthrocytes
Hollande solution
Stable and will decalcify small specimens of bone
Mercuric chloride
corrosive chemical, protein coagulant; inhibits freezing, leaves tissue receptive to dyes; coagulant fixative, additive fixative
Orth solution
Not a good general purpose fixative; demonstrates chromaffin granules in the cytoplasm of cells of the adrenal medulla
Osmium tetroxide
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
Zamboni solution
primary fixative for electron microscopy
Zenker solution
lyses erythrocytes; fix and decalcify needle biopsy specimens of bone marrow; nuclear fixative
Zinc formalin
aqueous and alcoholic; zinc ions stabilize protein macromolecules against the changes and cross-linking induced by formaldehyde; superior nuclear detail and better paraffin infiltration
B-5 fixative
Fixative of hematopoietic and lymphoretiulat tissues
Bouin solution
Excellent for tissue that is to be trichrome stained and for preserving structures with soft and delicate textures
Carnoy and methacarn solutions
Rapid acting, preserves glycogen, exhibits good nuclear preservation but causes excessive shrinkage and hardening
Gendre solution
Excellent for the preservation of some carbohydrates, especially glycogen
Helly (working) solution
Preserves the erythrocytes but Zenker is better nuclear fixative
Hollande solution
Stable and will decalcify small specimens of bone
Orth solution
Not a good general purpose fixative; demonstrates chromaffin granules in the cytoplasm of cells of the adrenal medulla
Zamboni solution
Very stable, good general purpose fixative
Zenker (working) solution
Fix and decalcify needle biopsy specimens of bone marrow; nuclear fixative