Peggy et al,
	How does glyoxal fix??? I am not sure but to me the most obvious
explanation is that there is a reaction still occurring after the tissue is
blocked, most likely continuing fixation. This suggests to me that the
fixative is not completely removed during the processing. Possibly an
extended rinse before processing would help. Interesting situation and
probably more complex than I am thinking.
Cynthia Favara
Rocky Mountain Laboratories
903 S. 4th Street
Hamilton, MT 59840
406-363-9317
FAX 406-363-9286
 

-----Original Message-----
From: Lee & Peggy Wenk [mailto:lpwenk@mail.netquest.com]
Sent: Friday, November 17, 2000 3:11 AM
To: Histonet
Subject: GLYOXAL AND IHC


Need some help again.

Received a call. A histo lab has switched to a glyoxal fixative.

When they first perform an IHC on any of the tissues, for any antibody,
it works great.

If the lab goes back to the same BLOCK a couple of weeks later, and
cuts some more slides, the intensity of the staining is less.

If the labs waits a couple more weeks and cuts more slides from the
BLOCK, there is NO IHC staining.

Yet, the new BLOCKS (just processed) are staining great. So they know
that the antibodies are fine. But wait a couple of weeks on the new BLOCKS,
and the same decrease in staining pattern repeats.

They thought it might be underfixation, so they have increased the
time in fixation, but the pattern is still repeating.

I know about decrease of staining on previously cut/stored SLIDES.
But has anyone experienced this on BLOCKS, for any antibody,
in just a couple of weeks time? Is it a fixation/processing problem
in general, or is it specific to glyoxal fixatives?

Any and all thoughts from the collective minds of Histonet are welcomed.
(and appreciated)

Peggy A. Wenk, HTL(ASCP)
William Beaumont Hospital
Royal Oak, MI 48073