[Histonet] re: overprocessing
Thank you for your comments, John.
My first post was under a guy called Ted Brain who was always looking into
processing /embeding protocols and reagents in an attempt to find the
"optimal " for our bone and teeth!
It was years ago when I taught Histopathology that I would use , in a simple
( OK, plagiarised) practical on "The effects of Fixation" , 1cm cubes of
gelatin, fixed using a range of coagulant/additive fixing fluids to
demonstrate the penetration rates and the physical effects that the
different fixing agents had on pure protein. A qualitative assessment
only....... wouldn't expect more from students at 7.30pm after they'd been
at college since 10am.
Regarding my initial remark: I didn't notice any shrinkage difference
between the short-time fixed gelatin blocks and the ones that had been fixed
for ages. But then again, there is the effect of alcohol in the processor
which is significant. I wasn't doing this comparison under rigid exptl
conditions: we have many perfused- formalin fixed specimens which have been
embedded in gelatin, vibratome-cut and that I then wished to process to
pwax. Would extended fixation time of the gelatin "stiffen" it sufficiently
to prevent shrinkage? The answer , for me, is "No". So, I take off the
gelatin, before processing.
No "exact science" there, Rene. Sorry!
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