Re: [Histonet] Proof that fixation in formaldehyde solution canbereversible?
One step further with this note. For straight morphology, 24-48 hours
of fixation in 10% formaldehyde followed by 70% ethanol, how long do
you feel comfortable keeping the tissue in 70% ethanol before
processing? If you canít process for whatever reason, any thoughts on
what to keep tissues in until processing occurs?
On Oct 4, 2006, at 1:33 PM, Patsy Ruegg wrote:
" Fixation is generally carried on by the alcohols used for the
Here in lies the problem for many antigens "unintended consequences"
you might say. If the sample is not adequately fixed-proteins
protected by crosslinking, the alcohols can destroy the protein of
interest. We need to fix for a minimum of 24 hours to allow for
crosslinking which will protect the proteins (especially surface
proteins) from processing so that they are still there and can be
accessed after unmasking the formalin fixation. If certain proteins
are not protected from tissue processing they will be lost forever
and no amount of epitope retrieval will restore them.
[mailto:firstname.lastname@example.org] On Behalf Of
Rittman, Barry R
Sent: Tuesday, October 03, 2006 10:49 AM
To: GT Hebert; email@example.com
Subject: RE: [Histonet] Proof that fixation in formaldehyde solution
can be reversible?
This is really opening a barrel of worms but...
Re formaldehyde solutions.
If tissues are fixed for a few hours in standard formalin solutions
then it is possible to reverse the fixation process by washing. It is
a reversible process in that the bonds that have been formed are
generally temporary and can be broken. Technically if you wish for
"adequate or true fixation" then Pearse provides the theory for why
this should be for about 1 week. (The fixation process does in fact
continue for years).
Of course no one fixes for one week except by accident. However the
fixation for 24 to 48 hours is only an initial fixation. Fixation is
generally carried on by the alcohols used for the processing.
A. G. E. Pearse "Histochemistry Theoretical and Applied: volume 1
Preparative and Optical Technology."Churchill Livingstone.
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