Re: [Histonet] Using chromic acid instead of periodic acid with Schiffs - for fungus staining ONLY!
I think the person wanted the details for Bauer's stain, or CAS (chromic
acid Schiff). It was originally published for glycogen, I believe, but PAS
is better for that. The method is simple.
Oxidise with 1% chromium trioxide in water for 1 hour (or 5% for 10
Bleach with 5% metabisulphite and wash.
Schiff's reagent 20 minutes or so.
Finish off as you would a PAS.
----- Original Message -----
From: "Gayle Callis"
Sent: Tuesday, August 23, 2005 3:06 PM
Subject: [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.
> Gayle Callis
> Research Histopathology Supervisor
> Veterinary Molecular Biology
> Montana State University - Bozeman
> PO Box 173610
> Bozeman MT 59717-3610
> 406 994-6367
> 406 994-4303 (FAX)
> Histonet mailing list
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