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Histology: Fixation

Histology ASCP Fixation information

QuestionAnswer
What is the definition of a fixative? A fixative alters tissue by stabilizing the protein so that it is resistant to further changes.
Fixative as a process of denaturation Changes the soluble content of the cell into insoluble substances so that those substances are not lost during subsequent processing steps.
What is additive fixation? A process in which denaturation causes the protein molecule to unfold and the internal bonds to become disrupted. This disruption enables the protein to combine chemically with a fixative molecule, and the protein then becomes insoluble.
What is nonadditive fixation? A process in which denaturation causes the protein to become less capable of maintaining a relationship with water and becomes more reactive, but the fixative molecule does not combine with the protein.
Functions of fixatives 1) Kills tissue to prevent putrefaction and autolysis 2) Maintain the proper relationship between cells and extracellular substances 3) Bring out differences in refractive indexes and to increase the visibility of different tissue elements
Actions of fixatives 1) Inactivates enzymes 2) Kills bacteria 3) Act as mordants 4) Modify tissue for form retention through processing
What is denaturation? A process in which the protein molecule unfolds and the internal bonds become disrupted.
Additive fixatives Chemically link to the tissue to stabilize the protein
Nonadditive fixatives Act on tissue without chemically combining with the tissue to stabilize the proteins.
Coagulation Establishes a network in tissue that allows solutions to readily penetrate or gain entry into the interior of the tissue.
What does a noncoagulant fixative do? Creates a gel that makes penetration by subsequent solutions difficult.
List the coagulant fixatives zinc salts, mercuric chloride, cupric sulfate, ethyl alcohol, methyl alcohol, acetone and picric acid.
List the noncoagulant fixatives Formaldehyde, gluataraldehyde, glyoxal, osmium tetroxide and potassium dichromate.
What are factors that affect fixation? Temperature, size, volume ratio, time, penetration, tissue storage, pH, osmolality and choice of fixative.
List aqueous fixatives Acetic acid, formaldehyde, glutaraldehyde, glyoxal, mercuric chloride, osmium tetroxide, picric acid, potassium dichromate and zinc salts.
Best fixatives for nucleus Carnoy and acetic alcohol.
Nuclear bubbling Coalescence of chromatin into strands with intervening clear spaces.
Primary structure Determined by the arrangement of covalent bonds in the amino acid sequence.
Secondary structure Determined by hydrogen bonding between various components of the peptide chain
Tertiary structure Total 3D structure. Hydrogen bonds, ionic bonds, hydrophobic bonds and disulfide bonds are responsible.
Best fixatives for lipids Osmium tetroxide and chromic acid
List compound fixatives B5, Bouin, Gendre, Hollande, Zenker and Helly, Orth, Zamboni, Zinc Formalin and Alcoholic Formalin
Does not fix carbohydrates Acetic Acid, Formaldehyde, Picric Acid
Does not fix lipids Acetic Acid, Picric Acid, Ethanol
Penetrates rapidly Acetic Acid, Formaldehyde, Glyoxal, Acetone, Carnoy, Alcohol, Mercuric Chloride, Potassium Dichromate
Increases protein swelling Acetic Acid
Red blood cells are lysed Acetic Acid, Formalin Ammonium Bromide, Glyoxal, Bouin, Zenker
Exposure limit of 10 ppm Acetic Acid
Used in electron microscopy Paraformaldehyde, Modified Millonig Formalin, Glutaraldehyde, Osmium tetroxide, Zamboni, Carnoy
Preserves lipids, but are not made insoluble Formaldehyde
Fixes very slowly Formaldehyde, Glutaraldehyde
Hardens tissue Formaldehyde, Acetone, Ethanol, Glutaraldehyde, Mercuric Chloride, Carnoy
Allows more special stains Formaldehyde, Glyoxal, B5, Hollande
Artifactual pigments 1) Black acid hematin, birefringent formalin pigment 2) Mercury pigment, birefrigent 3) Chromic pigment
Hypertonic Formaldehyde
Hypotonic 10% Aqueous Formalin, 10% NBF
Isotonic 10% Formalin Saline, Modified Millonig Formalin
Recommended fixative for phosphlipid Calcium formalin
Recommended fixative for CNS Formalin Ammonium Bromide
Causes false positive Schiff Reaction Formalin Ammonium Bromide, Glutaraldehyde
Fixes as well as dehydrates Alcoholic Formalin, Acetone
Exposure limit of .75 ppm in 8 hour period Formaldehyde
Exposure limit of 2 ppm over 15 minute period Formaldehyde
Cross-links proteins Formaldehyde, Glutaraldehyde, Glyoxal, Mercuric Chloride,
Penetrates poorly Glutaraldehyde, Mercuric Chloride,
Staining of H. Pylori unsatisfactory Glyoxal
Produces shrinkage Mercuric chloride, Picric Acid, Ethanol, Potassium Dichromate, Acetone, Carnoy
Exposure limit of .002 ppm Osmium Tetroxide
Both a fixative and dye Picric Acid
Recommended fixative for glycogen Picric Acid,Ethanol, Methanol, Acetone, Gendre, Carnoy
Will decalcify tissue Picric Acid, Bouin, Hollande, Zenker
Used for hematopoietic and lymphoreticular tissue B5
Leaches iron Bouin, Glyoxal, Zenker
Preserves tissue antigenicity Zinc Salts, B5
Cannot be used with Electron Microscopy Bouin
Recommended for GI Hollande
Cannot be used for silver stains Zenker, Helly
Preserves enzymes Acetone
Fixation for rabies demonstration on brain tissue Acetone
Fixative for touch prep and blood smears Alcohol
Fixative for urate crystals Alcohol
Recommended fixative over Carnoy Methacarn. Replaces methanol for ethanol, produces less shrinkage and hardening.
Mercuric Chloride, Anhydrous Sodium Acetate, Distilled Water, Formaldehyde B5
Picric Acid, Formaldehyde, Glacial Acetic Acid Bouin
95% Alcohol saturated with Picric Acid, Formaldehyde, Glacial Acetic Acid Gendre
Copper Acetate, Picric Acid, Formaldehyde, Acetic Acid, Distilled Water Hollande
Mercuric Chloride, Potassium Dichromate, Sodium Sulfate, Distilled Water, Glacial Acetic Acid Zenker
Mercuric Chloride, Potassium Dichromate, Sodium Sulfate, Distilled Water, Formaldehyde Helly
Potassium Dichromate, Sodium Sulfate, Distilled Water, Formaldehyde Orth
Paraformaldehyde, Picric Acid, Sodium Hydroxide, Phosphate Buffer, Distilled Water Zamboni
Absolute Ethyl Alcohol, Chloroform, Glacial Acetic Acid Carnoy
Absolute Methyl Alcohol, Chloroform, Glacial Acetic Acid Methacarn
Not reactive with proteins Acetic Acid
Reactive with nucleic acids Acetic Acid,Glyoxal, Glutaraldehyde, Mercuric Chloride, Potassium Dichromate, Osmium Tetroxide, Picric Acid
Oxidizes carbohydrates to aldehydes Potassium Dichromate
Penetrates slowly Glutaraldehyde, Potassium Dichromate, Osmium Tetroxide, Picric Acid, Zinc Salts
Preservation of nucleoproteins Acetic Acid
Mordant for trichrome Picric Acid
Preserves chromatin and membranes Glyoxal
Avoid Bouin Feulgen Reaction
B5 satisfactory Methyl Green-Pyronin Y
Helly satisfactory Methyl Green-Pyronin Y
Zenker satisfactory Methyl Green-Pyronin Y, Congo Red
Zenker is preferred May-Grunwald Giemsa, Alcian Blue-PAS-Hematoxylin, Verhoeff, Mallory PTAH, Hotchikiss McManus PAS
B5 is preferred May-Grunwald Giemsa
10% NBF satisfactory May-Grunwald Giemsa, Congo Red, Masson Trichrome, Mallory PTAH,
Bouin is preferred PAS, Alcian Blue, Masson Trichrome, Hotchkiss-McManus PAS
Methyl alcohol is required Blood smears for PAS
Alcoholic Formalin is preferred PAS D, Muller Mowry Colloidal Iron, Alizarin Red S
Absolute alcohol is preferred PAS D, Best Carmine, Congo Red, Crystal Violet, Turnbull Blue, Von Kossa
Carnoy is satisfactory Best Carmine
Bouin is satisfactory Best Carmine, Congo Red
Carnoy is preferred Muller Mowry Colloidal Iron, Congo Red
Avoid Helly Muller Mowry Colloidal Iron, Aldehyde Fuchsin, Periodic Acid-Methenamine Silver, Steiner and Steiner
Avoid Zenker Muller Mowry Colloidal Iron, Aldehyde Fuchsin, Periodic Acid-Methenamine Silver, Steiner and Steiner
Any well fixed tissue Gomori 1-Step Trichrome, Van Gieson Picric Acid-Acid Fuchsin, Verhoeff, Ziehl-Neelsen
Avoid B5 Periodic Acid-Methenamine Silver, Steiner and Steiner
Calcium Formalin preferred Oil Red O, Sudan Black B
Avoid Alcohol Oil Red O, Sudan Black B, Fontana Masson
Avoid Carnoy Oil Red O, Sudan Black B, Ziehl-Neelsen, Fite, Fontana Masson
Avoid Methacarn Oil Red O, Sudan Black B, Fontana Masson
Avoid Gendre Oil Red O, Sudan Black B, Fontana Masson
Alcohol is required Gomori Methenamine-Silver
Avoid Glutarldehyde Grocott Methenamine Silver
Created by: impossiblesum