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Histology
Fixative Characteristics
| Question | Answer |
|---|---|
| Ethanol, Methanol & Acetone | Coagulant, nonadditive for proteins,Some extraction of lipids, Rapid penetration, Preserves some enyzymes if cold, Poor for electron microscopy, Used when urates are to be demonstrated Overhardens tissue, shrinks tissue markedly and usually used alone. |
| Acetic Acid | Coagulant of nucleoprotein and Dna, rapid penetration, poor for electron microscopy, used in mixtures for fixation and preservation of nucleoprotein, swells tissue markedly, not used alone |
| Formaldehyde, Paraformaldehyde | Noncoagulant,Additive of protein, nil below 45C for nucleic acids, preserves lipids but w/ gradual loss, Rapid penetration but slow cross linking, preserves some enzymes if cold and brief, good w/ Millonig or paraformaldehyde, usually post fixed w/ osmium |
| Glyoxal:forms N-hydroxymethyl adducts with 2 carbon atoms | Additive of proteins and nucleic acids, rapid penetration w/ little cross linking, inferior to formaldehyde, antigen retrieval not needed unless arginine is in epitope, chromatin & membranes preserved w/ great clarity, hp stains poorly |
| Glutaraldehyde | Coagulant,additive of protein, coagulant of nucleic acid,preserves lipids but w/ gradual loss,slow penetration w/ rapid cross linking, enzyme activity better than CH2O,great for electron micro, usually postfixed w/ osmium, may give false + Schiff reaction |
| Mercuric Chloride | Coagulant, Additive of protein,coagulant of nucleic acid, unmask some lipids, rapid penetration,inhibits enzyme activity, promotes staining, produces an artifactual pigment, not used alone |
| Potassium Dichromate (pH <3.5) | Coagulant,additive(acts like chromic acid),Coagulant of nucleic acid,oxidizes to aldehydes,slow r.o.p., inhibits enzyme activity,poor electron micro cause distortion,can produce pigment,not used alone |
| Potassium Dichromate (pH >3.5) | Noncoagulant,additive of protein,dissolves DNA & percipitates nucleoprotein,attaches to some lipids makes them insoluble,rapid r.o.p,inhibits enzyme activity,poor electron micro b/c distortion,preserves chromaffin granules,produces pigment,not used alone |
| Osmium Tetroxide | Noncoag,additive of protein, noncoag of nucleic acids, reacts w/ and adds to double bond in lipids & makes them insoluble, slow r.o.p.,inhibits enzyme,excellent for electron micro,used to demostrate fat,penetrates a few cell layers, used allon usually |
| Picric Acid | Coagulant,additive of protein,precipitates nucleoprotein leaves dna soluble & partly hydrolyzed, slow penetration,inhibits enzymes,poor electron micro..causes distortion,mordant for trichrome,should not be used w/ Feulgen reaction, not used alone |
| Zinc Salts | Coagulant,additive of protein, slow rate of penetration,inhibits enzyme activity, poor electron mircoscopy, Preserves immuno-reactivity, gives good morphological preservation, can precipitate in the processor |
Created by:
kmajor316
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