Chapter 1: Fixation Flashcards
An example of an additive fixative is:
Picric Acid. The reaction with proteins is not entirely understood
When compared with tissue fixed in formalin, tissue fixed in zinc-formalin will show:
Superior nuclear detail. Zinc is also a less toxic additive to formalin than mercury.
Microscopic examination of an H&E stained section in formalin shows marked nuclear bubbling. One would most often see this artefact if:
The tissue has been incompletely fixed before processing.
Microscopic examination of an H&E stained section of GI shows marked absence of epithelium in otherwise normal tissue. This is likely resulted from:
Delayed fixation. GI needs to be instantly put in formalin to prevent post-mortem changes occuring.
A specimen of kidney must be shipped to another city for Immunoflourescence (IF) studies. Which fixative would you use?
Michel solution.
A certain project requires a fixative that contains acetic acid yet stabilizes erythrocytic membranes. Which fixative would you use?
Hollande solution. The cupric acetate in this solution stabilizes RBC membranes.
When the microwave oven is used for fixation, what is the most critical factor?
Temperature control.
To adequately remove the calcium from a specimen containing areas of microcalcifications, the tissue should be fixed in:
Hollande solution because it is acidic.
What fixative contains copper acetate?
Hollande solution which stabilized RBS membranes
A specimen is submitted with a note that it was fixed in formalin. Microscopic sections show marked RBC lysis. What happened?
The tissue was acidified with acetic acid.
Fixatives are classified as an additive because they:
Addition, or binding of the fixative to tissue proteins.
Kidney biopsy tissue has been fixed in phosphate buffered glutaraldehyde for 2 hours then placed in phosphate buffer solution. If a portion of this tissue is processed for light microscopy, sections would most likely show:
Nonspecific PAS staining which would lead to a false positive.
Uric acid crystals are preserved ONLY when tissue is fixed in:
Absolute (100%) alcohol.
Improper preservation of tissue will result if there is:
A delay in fixation
A good fixative will:
Protect tissue against alteration during subsequent processing.
The function of methanol in commercial formalin is to:
Prevent the polymerization of formaldehyde.
What does incomplete fixation look like?
Excessive cracks in tissue and smudging nucleii
In Electron Microscopy (EM), Zamboni fluid, glutaraldehyde and osmium tetroxide function as:
Fixative solutions
Tissue will remain unfixed if placed in:
Sodium borate.
Bouin solution is recommended for:
Tissue to be stained for the Feulgen reaction.
Formalin pigment can be removed by treatment with 10%
Ammonium hydroxide in 70% alcohol.
Stock neutralized formalin is prepared in the lab by storing the solution over a layer of calcium carbonate. The solution in this carboy will be:
Acidic.
Microscopic evaluation reveals a poorly stained H&E spleen section. This will be difficult to fix if the issue is involving:
Poor fixation.
To make a 10% formalin solution, how many mL of water should be added to 300 mL of 37%-40% formalin solution?
2700mL