[Histonet] overfixation with formalin

[Rene J Buesa]

Gudrun:
I think you should ask for a refund for the cost of the course and try to be contracted to teach the next course.
You are right in all you said, and the "professor" is wrong.
René J.



________________________________
From: Gudrun Lang <gu.lang <@t> gmx.at>
To: histonet <@t> lists.utsouthwestern.edu 
Sent: Saturday, November 3, 2012 2:41 PM
Subject: [Histonet] overfixation with formalin

Hi histonetters!

I'm just attending a histo-course, where the teacher told us his opinion
about overfixation.

For him overfixation takes place in any formaldehyde solution with a
concentration above 5%. This should cause the margin-artefact, that leads to
false-positive IHC at the margins of the tissue and to false-negative
results in the center. The higher concetrated fixative should harden and
shrink the surface, so it cant be penetrated any more by the fixative.



I told him about the publication of Cecil Fox, who saw shrinkage only in
solutions with formaldehyde concentration above 30% (I think) and said, that
the methanol-part is responsible for that.

I believe, that these margin-artefacts are due to drying at the time of
biopsy or an effect of the needle-shot itself. (But believing is no
evidence)



In our lab we use 8% formaldehyde as standard fixative, buffered with
low-molar phosphatebuffer. There are no complains from the doctors about
margins.



Please help me with the histonet-wisdom. What's your opinion? 



Bye

Gudrun Lang



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