Tissue Fixation and Decalcification Flashcards
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Read the first 7 Tissue Fixation and Decalcification flashcards as text
Which fixative type is most likely to mask antigenic epitopes, necessitating antigen retrieval before immunohistochemistry?
Answer: 10% neutral buffered formalin
Formalin cross-links proteins and masks antigenic epitopes; heat-induced or proteolytic antigen retrieval must be performed to unmask these epitopes before IHC staining.
Zenker's fixative contains which hazardous heavy metal component?
Answer: Mercuric chloride
Zenker's fixative contains mercuric chloride, which is highly toxic and requires special handling and disposal procedures, contributing to its decline in modern laboratories.
Which fixative is preferred when preservation of glycogen in tissue is the primary concern?
Answer: Absolute alcohol (ethanol)
Absolute alcohol preserves glycogen by precipitating surrounding proteins through dehydration without dissolving the water-soluble glycogen molecules.
What is the ideal pH range for neutral buffered formalin to prevent artifact formation?
Answer: 6.8–7.4
NBF should be maintained between pH 6.8 and 7.4 to prevent the formation of formalin pigment (acid formaldehyde hematin) and optimize tissue preservation.
What is formalin pigment and how is it prevented?
Answer: A brown artifact from acidic formalin reacting with hemoglobin; prevented by using buffered formalin
Formalin pigment (acid formaldehyde hematin) is a brown refractile artifact that forms when acidic, unbuffered formalin reacts with hemoglobin in bloody tissue; buffering the formalin to neutral pH prevents its formation.
What is the recommended tissue-to-fixative volume ratio to ensure adequate fixation?
Answer: 1:10
A 1:10 tissue-to-fixative ratio ensures sufficient fixative volume to penetrate the specimen completely and maintain fixative concentration throughout the process.
Ethanol (absolute alcohol) is classified as which type of fixative based on its mechanism of action?
Answer: Non-additive coagulant fixative
Ethanol is a non-additive coagulant fixative that fixes tissue by precipitating and denaturing proteins through dehydration, without forming covalent cross-links.