[Histonet] overfixation with formalin

[Geoff]

I agree with Rene, Barry, etc.

Geoff

On 11/3/2012 2:41 PM, Gudrun Lang wrote:
> 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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Geoff McAuliffe, Ph.D.
Neuroscience and Cell Biology
Robert Wood Johnson Medical School
675 Hoes Lane, Piscataway, NJ 08854
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mcauliff <@t> umdnj.edu
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