AW: [Histonet] Over fixation

Gudrun Lang gu.lang <@t>
Mon Nov 25 10:30:19 CST 2013

Formaldehyd binds as methylol-group to basic functional groups on proteins.
The longer the fixation the longer the possibility to bind. The same basic
groups bind acid dyes like eosin. 
On the other side leads acidic formalin to degradation of DNA. This can lead
to lower affinity of hematoxylin.
So in sum long fixed tissue should stain paler. In old literature you find
the recommendation to wash fixed tissue in tapwater as long as the fixation
has longed. Hmm ;-)

-----Ursprüngliche Nachricht-----
Von: histonet-bounces <@t>
[mailto:histonet-bounces <@t>] Im Auftrag von Sanjeet
Gesendet: Sonntag, 24. November 2013 21:33
An: histonet <@t>
Betreff: [Histonet] Over fixation

Hi Histo folks,
Tissue biopsy that are  not fixed properly do have an adverse effect on H &
E staining. Tissues can be kept in formalin for a period of 5 to 7 days as
per literature. But what happens to the tissues that are kept over for a
longer period of time. By that I mean 6 to 12 months. Would over fixed
tissues have any effect on H & E stain. Some of my colleagues say NO, but I
say YES. I find that the over fixed tissues lose their affinity towards the
dyes . Please advice. 

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