Re: [Histonet] Re: Paraformaldehyde use question for geniuses

From:"Gayle Callis"

Dear Teri and Fellow Histonetters,

Teri's words of wisdom on fixation and storage of samples are well taken.

Please provide the vendor for the 16% paraformaldehyde in ampules so our 
FACS technician doesn't have to weigh out PFA powder anymore.   She is going 
to be delighted.

Gayle M. Callis

----- Original Message ----- 
From: "Johnson, Teri" 
Sent: Thursday, April 24, 2008 2:55 PM
Subject: [Histonet] Re: Paraformaldehyde use question for geniuses


Have you performed experiments that show more of a benefit for storing 
samples in formalin over 70% alcohol in your lab? I have one researcher who, 
based on their experience in cultured cells, knows that anything over 10 
minutes of fixation time causes their antibody staining to diminish using 
one particular antibody. I'm well aware of the current trend towards longer 
fixation times and generally believe that more is better. Because of 
evidence to the contrary, I cannot bring myself to recommend as a matter of 
routine, to store samples in formalin, especially for research purposes.

I much prefer to have the samples paraffin processed or cryo embedded after 
a defined period of time in fixative, and store the tissues in those two 
forms rather than anything aqueous or alcoholic.

Jackie - I'm not aware of any vendors who sell 4% formalin made from PFA in 
large quantities, simply due to the problem of re-polymerization upon 
storage. We get 16% solution in ampules, and then dilute in PBS to 4%. 
Perhaps that might work for you?

Teri Johnson, HT(ASCP)QIHC
Managing Director Histology Facility
Stowers Institute for Medical Research
1000 E. 50th St.
Kansas City, MO 64110

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