Try oxidising in the 5% chromic acid for about an hour.  That was Bauer's
original recommendation (4% for 40-60 minutes).  Alternatively, many have
found a 10% solution for 10 minutes satisfactory.  You could also do a
double oxidation with periodic acid.  That is oxidise in 1% periodic acid
for 15 minutes, block aldehyde with aniline-acetic for 30 minutes, then
re-oxidise for 15 minutes.  This also reduces background positive PAS
staining.

Bryan Llewellyn

Bryan Llewellyn
----- Original Message -----
From: "Cindy DuBois" 
To: "Histonet" 
Sent: Tuesday, October 18, 2005 10:46 AM
Subject: [Histonet] PAS vs CAS


> My lab manager recently read the article by Vinnie Della Speranza et. al.
> on fungus staining.  He wanted us to try the Chromic Acid Schiff's (CAS)
> procedure and compare it to our PAS procedure.
>
> Although I get some staining with the CAS, only about half of the fungus
> is staining and it is very light.
>
>  I used the following procedure:
> 1.  Clear & Hydrate slides (standard protocol).
> 2.  Incubate slides in 5% Chromic acid in water bath (temp approx. 42C)
> for 10minutes.
>          Solution was pre-heated for 10 minutes.
> 3.  Rinse and incubate in Schiff's solution for 10 minutes.
> 4.  Rinse in hot water.
> (Our tap water has a lot of sulfur in it and therefore we do not normally
> do the sulfuric acid rinse).
> 5.  Counterstain in Working Light Green, dehydrate and coverslip.
>
> If any one is using this procedure for their fungus stain would you please
> send me your procedure?
>
> Cindy DuBois, HT ASCP
> Integrated Pathology Associates
> Stockton CA
>
>
>
>
>
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