Fixatives Flashcards
If acidic (unbuffered), a dark brown precipitate may form in vascular tissue
Formalin
Fast penetration rate but fixation is slow
Formalin
Addition of methanol can reduce polymerization of this fixative
Formalin
May cause diffuse PAS reaction due to unbound aldehyde group
Glutaraldehyde
Yellow precipitate can be prevented by washing tissue prior to dehydration
Potassium dichromate
Tissues are left soft if used alone, so it is used as part of a compound fixative
Potassium dichromate
If concentrated form is purchased, it must be diluted to 10% (w/v) for use
Formalin
Its precipitate is difficult to remove but can be reduced with 1% acid alcohol
Potassium dichromate
While commonly used for routine fixation, it is a known carcinogen
Formalin
Its mode of action differs above and below pH 3.75
Potassium dichromate
It is used almost exclusively for electron microscopy, as it preserves the ultrastructure
Glutaraldehyde
It forms a black precipitate throughout the tissue
Mercuric chloride
Used as a component of compound fixatives in the fixation of blood films, cytology smears and enzymes for histochemistry
Ethyl alcohol
Its precipitate can be removed using alcoholic iodine followed by sodium thiosulfate
Mercuric chloride
As a component of a compound fixative its swelling effect can counteract shrinkage
Acetic acid
