From: /G=Gerhard/S=Nebe-von-Caron/OU=1890CHPE/O=TMGB.URC/@LANGATE.gb.sprint.com
Date: Wed Nov 08 1995 - 06:30:00 EST
My memory worked and I found the note I made on the last
ISAC. We had some discussion about fixatives in the cell
proliferation workshop. Old PFA builds up formic acid when
degrading. Apart form people who used commercial reagents
from flow manufacturers, somebody mentioned that
Polysciences sells "fresh PFA" alliquoted probably under
argon or so. This would be similar to the approach described
by Calman, so probably more expensive.
Two other things I picked up at the meeting were to check
osmotic strenght of the PFA solutions and the fact that
formalin usually contains 15% MeOH for stabilisation.
Gerhard Nebe-v.Caron
Unilever Research, Colworth Laboratory Sharnbrook,
Bedfordshire
GB - MK44 1LQ
Tel: +44(0)1234-222066
FAX: +44(0)1234-222344
E.mail: gerhard.nebe-von-caron@urcgb.sprint.com
______________________________ Reply Separator _________________________________
Subject: Old Parformaldehyde
Author: Calman_Prussin@d10.niaid.pc.niaid.nih.gov at INTERNET
Date: 08/11/95 03:49
I think it depends on what you are using the paraformaldehyde (PFA) for. The
constraints on using PFA for fixation of already stained cells (for later
analysis) is less than that for uses with intracellular staining. For the
former, I think PFA in the frig for months should be fine.
A lot of the fears may simply be that, however a number of investigators I have
talked to make up fresh PFA for each use. I think the concern is old PFA causes
overfixation leading to increased nonspecific binding.
Considering how much trouble it is to make fresh PFA, we make up a couple of
litres at a time, aliquot them into 15 ml tubes and freeze the whole lot. I
will use thawed PFA for a week or two after thawing. I have heard that Ulf
Andersson's group in Stockholm use a similar approach, except they don't hold
on to the thawed PFA for 2 weeks.
Calman Prussin
Laboratory of Allergic Diseases
NIAID, NIH
---------------------- Replied Message Body ----------------------
Date: 11-2-95 6:48am
From: {herro001@maroon.tc.umn.edu}:unix:niaid
To: calman prussin:10:niaid,
karin hartmann:10:niaid,
barbara butcher:4:niaid,
ramya gopinath:4:niaid
Subj: Old Parformaldehyde
Also-to: cytometry mailing list <cytometry@flowcyt.cyto.purdue.edu>
--------------------------------------------------------------------
I have read the warnings to only use "fresh" parformaldehyde for fixation, but
I
don't recall ever hearing why.
Could someone explain the sorts of artifacts that old paraformaldehyde will
introduce? And what exactly IS old?
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