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Histology

Fixative Characteristics

QuestionAnswer
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