Re: [Histonet] Using chromic acid instead of periodic acid with Schiffs - for fungus staining ONLY!
Apparently I screwed up. The concentration of chromic acid should be 4% for
1 hour (or 10% for 10 minutes - a much later modification). Sorry.
----- Original Message -----
From: "Bryan Llewellyn"
Sent: Tuesday, August 23, 2005 4:29 PM
Subject: 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.
> Bryan Llewellyn
> ----- 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)
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