Mary-Ann,

     If your blocks are exhibiting small cracks, you may want to freeze the
     blocks in hexane rather than isopentane (methyl butane). It freezes at a
     slightly higher temperature than isopentane (-90C), but still freezes
     almost instantaneously preventing ice-crystal artefact formation.

     We used this extensively in the Institute of Neurological Sciences,
     Glasgow.

     Ronnie Houston
     Regional Histology Operations Manager
     Bon Secours HealthPartners Laboratories
     5801 Bremo Road
     Richmond, VA 23226


______________________________ Reply Separator _________________________________
Subject: RE: Freezing brains
Author:  Mary-Ann S Crissey  at BSHSIBTW
Date:    5/10/02 11:05 AM






           While I am new to histology in general, we work with rat brains.  I
       understand this lab used to freeze the brains on dry ice.  The tissue
       always developed holes due to ice crystal formation.  Now we quickly
       freeze either the whole brain or pieces of the brain in dry ice chilled
       methyl butane for 20 seconds before mounting on the freezing stage of the
       sliding microtome or the chuck for the cryostat. Our formalin fixed
       brains get soaked in 10% DMSO for an hour or so first (instead
       of
       overnight in 30% sucrose), but fresh brains go right into the methyl
       butane.  Occasionally there are small cracks in the hypothalamus, but
       usually the sections are very nice.