Tim,
With reference to your PAS density problems, are you cutting your sections 
using a motorized microtome/cryostat? If not, that could well be your 
problem. No matter the experience of the tech, it is impossible to cut 
sections at the same speed, and thus the same thickness. The only way to 
confidently cut sections of the same thickness is to use a motorized cutting 
action.
We came across the same problems many years ago in Scotland when we were 
quantifying enzyme activities in individual muscle fibres using 
microdensitometry.
There is a whole text that mentions many of the problems associated with 
quantitative histochemistry with reference to enzyme histochemistry, but 
there is much useful information for anyone wanting to quantitate in 
pathology. I suspect it is out-of-print now, but it may be in your nearest 
Med School library.
"Trends in Enzyme Histochemistry and Cytochemistry" Ciba Foundation 
Symposium 73, Excerpta Medica 1980, ISBN 0 444 90135 3.

Ronnie Houston
Cytochemistry & Molecular Pathology
Texas Scottish Rite Hospital for Children
Dallas


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