This is true, but the ice damage can also come from the warming from 
-70 to -20. The initial freezing may be OK, but if the tissue isn't 
cryoprotected, then ice crystals will grow and form when the tissue 
warms up to -20. This happens as long as there is free water in the 
tissue. There might even be crystal growth at -70.

Phil

>I think the problem is in the initial freezing of the brains. Ice crystals
>will grow if the tissue is not frozen fast enough i.e. snap frozen in liquid
>nitrogen.
>Rita.
>
>-----Original Message-----
>From: Anacko, Nancy L. [mailto:NAnacko@Lifespan.org]
>Sent: 06 December 2002 15:37
>To: 'Server, Histonet'
>Subject: brain question
>
>
>Hi,
>A research tech is having a problem.....she is doing stains on fresh frozen
>brain that she recieves from a brain bank. The problem is ice-artifact on
>her sections/stains. She told me that she recieves the brain at -70 and then
>cuts them on a cryostat at -20. Any suggestions....I only work with fixed
>brain in parrafin.
>Thanks Nancy

-- 
Philip Oshel
Supervisor, BBPIC microscopy facility
Department of Animal Sciences
University of Wisconsin
1675 Observatory Drive
Madison,  WI  53706 - 1284
voice: (608) 263-4162
fax: (608) 262-5157 (dept. fax)