Bryan,

Thank you for the historical and technical info on this, I was not aware of 
the Bauer reaction, for glycogen (no apologies needed as it makes perfect 
sense!)  - still learning after all these years.

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)



At 08:32 PM 8/23/2005, you wrote:
>What  Rita was asking about PAS-F, I don't know (what does the -F stand 
>for Rita?).
>However, the Bauer reaction (chromic acid oxidation-Schiff) in 1933
>was the first ever use in histochemistry of a glycol to aldehyde oxidation 
>reaction.
>This produces a positive Schiff result in a variety of mucosubstances,
>including cellulose, starch and (sorry Gayle) GLYCOGEN!
>It also gives a positive result with fungal cell walls.
>In fact the Bauer-Schiff was for many years the method of choice for the 
>demonstration of glycogen and other mucosubstances.
>
>As Gayle correctly pointed out, chromic acid further oxidizes the 
>aldehydes , probably to carboxyl groups and then to carbon dioxide.
>Mucosubstances with a high glycol density (glycogen, starch, fungal cell 
>walls) are more resistant to this effect.
>The resulting Schiff reaction is somewhat paler than a PAS, how much paler 
>depends on oxidation time, but still positive.
>Gomori (1946) used chromic acid oxidation in his method for glycogen and 
>mucin(sic).
>He detected the resulting aldehydes with hexamine-silver.
>Grocott (1955) optimized the Gomori technique for fungal cell walls.
>The Gridley stain (1953) was just a Bauer-Schiff/aldehyde fuchsine 
>combination stain.
>Periodic oxidation-Schiff was introduced by both Hotchkiss and McManus in 
>1945-46.
>Periodic acid does not further oxidize the aldehydes produced (at least 
>not in any reasonable time frame) and rapidly became the oxidation-Schiff 
>method of choice.
>
>Bryan


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