[Histonet] Using chromic acid instead of periodic acid with Schiffs - for fungus staining ONLY!

[Bryan Llewellyn]

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.

Bryan Llewellyn


----- Original Message ----- 
From: "Bryan Llewellyn" <llewllew <@t> shaw.ca>
To: "Histonet" <histonet <@t> lists.utsouthwestern.edu>
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 
> minutes).
> 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" <gcallis <@t> montana.edu>
> To: <Histonet <@t> lists.utsouthwestern.edu>
> Sent: Tuesday, August 23, 2005 3:06 PM
> Subject: [Histonet] Using chromic acid instead of periodic acid with 
> Schiffs - for fungus staining ONLY!
>
>
>> Histonetters,
>>
>> 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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>