FIXATIVES Flashcards
for routine paraffin sections, em, histochemical and enzymes
Aldehyde Fixatives
commonly used Aldehyde
10% Formalin
Fixation time of Aldehyde Fixatives
24 hours
Advantage of Aldehyde Fixative
cheap, readily available, easy to prepare, stable especially if stored in buffered solutions
Compatible w/ many stains
Does not overharden tissues
Penetrates tissues well
Preserve fat and mucin
Preserves glycogen
Does not precipitate proteins, for nervous tissue
For frozen tissue, does nor require washing out
Tolerant fixative
Advantage of Formaldehyde
Irritating fumes
Shrinkage of tissue
Soft fixative-does not harden some cytoplasmic structures
If unbuffered: reduces basophilic and eosinophilic stains; produce brown pigment granules on bld-contng tissue( spleen)
Prolonged: bleaching, fat dispersal, glycogen and biurate of sodium crystals dissolution
Disadvantage of Formaldehyde
Made up of saturated formaldehyde (40% by weight volume) diluted to 10% with NaCl
10% Formol-Saline
10% Formol-Saline is used for..
For CNS and general post mortem tis for histochemical exams
Fixation time of 10% Formol-Saline
Fixation time:
24 hrs at 35oC (95oF)
48 hrs at 20-25oC (65-77oF)
Preserves enzymes and nucleopoteins
Demonstrates fats and mucin
advantage of 10% Formol-Saline
Disadvantages are similar to formaldehyde with the ff addition:
It is slow fixative
Metachromatic reaction of amyloid is reduced
Acid dye stains less brightly than when fixed with Mercuric chloride
disavantage of 10% Formol-Saline
used for preservation and storage of surgical, post mortem and research specimens
10% Neutral Buffered Formalin or Phosphate-Buffered Formalin (pH 7)
Prevent pption of acid pigments on post mortem tissue and Best fixative for Iron pigments and elastic fibers
advantages of 10% Neutral Buffered Formalin or Phosphate-Buffered Formalin (pH 7)
fixation time of 10% Neutral Buffered Formalin or Phosphate-Buffered Formalin (pH 7)
4 to 24 hours
Time consuming
Positivity of mucin to PAS is reduced
Raecativty to Weigert’s Fe hematoxylin stain is reduced
Inert to lipids
disadvantage of 10% Neutral Buffered Formalin or Phosphate-Buffered Formalin (pH 7)
used For routine post mortem tissues
Formol-Corrosive (formol-sublimate)
Formol-Corrosive (formol-sublimate) fixation time
3 to 24 hours
Excelelnt for silver reticulin
Cytologic structures and blood cells are well preserved
NO need for washing out, tissues can be directly transferred to alcohol
Fixes lipids, neutral fats and phospholipids
advantage of Formol-Corrosive (formol-sublimate)
Penetration is slow, (not more than 1 cm)
Forms Mercuric chloride deposits
Does not allow frozen tissue sections
Inhibits tissue decalcification
disadvantage of Formol-Corrosive (formol-sublimate)
In alcoholic formalin, the post-fixation with …
Post fixation with phenol-formalin for 6 hrs or more can enhance immunoperoxidase studies on the tissues
Fixation is faster
Fixes and dehydrates
Preserves glycogen and for micro-incineration technique
Fix sputum
advantage of alcoholic formalin
Cause partial Lysis of RBC
disadvantage of alcoholic formalin
used For enzyme histochem and EM
Glutaraldehyde
fixation time in glutaraldehyde
2.5% (small tissue fragments)-2-4 hrs
4% Large- 6-8 to 24 hrs (4mm)
More pleasant and less irritating to the nose
Specimen vial should be refrigerated
Does not cause dermatitis
More expensive, less stable
Glutaraldehyde.
5-7% included in compound fixatives
Penetrates and hardens tissue rapidly
Routine fixative of choice in Tx photography
Metallic Fixatives
common metallic fixative
Mercuric Chloride
Metallic fixatives May produce black granular deposits except
Heidenhens susa
in metallic fixatives, Removal can be done by addition of ____
saturated iodine solution of 96% Alcohol
fluids/solutions under mercuric chloride
Zenker’s
Zenker-Formol
Heidenhain’s Susa
B5 Fixative
Contains Glacial Acetic acid
For small pieces of liver, spleen, CT fibers and Nuclei
Recommended for trichrome staining
Zenker
Dezenkeration is removal of ___ deposits using ____ and _____
Mercury ; Lugol’s Iodine and Na Thiosulfate