Tim,

I do a lot of I.A. some of which is similar to what you are doing.   Ran into the
same problem you are having and while investigating the cause, doing some
densitomitry on some of the H&E's (we knew there was a problem with the special's)
and finding the same problem I went to the lab. and checked the microtomes with a
micrometer.  One of the microtomes used to cut our sections had a variance of up to
3 um when set at 5 um.  They  started cutting the sections on an other (newer)
microtome aand we have not had that problem since.  They also replaced the older
microtome (gray 820) with a new one.

Densitomitry, system dependent, is very sensitive to section thickness.  The better
the system the more sensitive it is.

best regards,
Bob
Robert Schoonhoven
Laboratory of Molecular Carcinogenesis and Mutagenesis
Dept. of Environmental Sciences and Engineering
University of North Carolina
CB#7400
Chapel Hill, NC 27599
Phone 
office 919-966-6343
   Lab 919-966-6140
   Fax 919-966-6123 

Don't go around saying the world owes you a living; the world owes you
nothing; it was here first. 
Mark Twain [Samuel Langhornne Clemens] (1835-1910) 

-- Begin original message --

> From: Tim Fairchild <timf@cyllene.uwa.edu.au>
> Date: Thu, 22 Jul 1999 17:45:21 +0800
> Subject: PAS stain
> To: HistoNet Server <HistoNet@Pathology.swmed.edu>
> 
> When we are cutting our muscle block and subsequently staining for PAS, I have
> noticed that a difference in staining intensity exists, even on the same slide
> (i.e. same block, simply the next section).  Since we are using the staining
> intensity as an indicator of glycogen stores (via densitometry) it is important
> to ensure standardisation across all samples measured.  There is no streaking
> evident, it is just that some sections come out darker than the others.
> 
> Any thoughts on this?
> 
> Thanks in advance
> Tim.
> -----------------------------------------------------------------
> Timothy J. Fairchild B.Sc. (Hons)
> PhD Candidate
> Co-ordinator for Centre of Athletic Testing
> Department of Human Movement and Exercise Science
> Nedlands, Western Australia 6907
> Telephone: (+61 8) 9380 2793
> Facsimile:  (+61 8) 9380 1039
> Email: timf@cyllene.uwa.edu.au
> http://www.general.uwa.edu.au/~hmweb/index.htm
> 
> 
> 
> 
> 

-- End original message --