[Histonet] Using chromic acid instead of periodic acid with Schiffs - for fungus staining ONLY!
I hope I didn't confuse people with my answer about PAS-F (what the F meant
escapes me??? for fungus, fluorescence?) where the person was asking about
using chromic acid instead of periodic acid i.e in PAS. Theoretically, one
could not call this PAS - maybe chromic acid-Schiff or CAS?? The key word
was the mention of Gridley staining, a method for fungus staining, and I
assumed this person wanted to use a chromic acid oxidizer followed by
Schiffs reagent for that purpose i.e fungus stain.
Whatever you do, do NOT use chromic acid for a standard PAS stain if
staining for mucosubstances, glycogen, basement membranes or other
components that are PAS positive. Chromic acid is a much stronger oxidizer
than periodic acid, and will over-oxidize these components to the point of
them NOT staining after Schiffs application - not a good idea. However
chromic acid with Schiffs does work for fungus staining. Freida Carson et
al wrote a publication on false negative fungus staining by using Periodic
acid -Schiffs reagent, and mentioned using chromic acid in place of
periodic acid. This can be found in J of Histotechnology, and an excellent
bit of information.
Chromic acid oxidation with Schiffs reagents is reserved for those who do
not want use periodic acid as the oxidizing agent for fungus staining.
Research Histopathology Supervisor
Veterinary Molecular Biology
Montana State University - Bozeman
PO Box 173610
Bozeman MT 59717-3610
406 994-4303 (FAX)
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