Harold,

I haven't ever had 'gaping holes' but I have had cracks in frozen 
tissue. The cracks occured when the tissue was held in the isopentane 
(in LN2) bath too long. W always froze for about 25-30 seconds. More 
than that and we would get cracks. if the tissue is large you are more 
likely to get cracks, prabably due to uneven expansion. We always kept 
the tissue to less that a centimeter in one direction. These were muscle 
biopsies for the most part.

My only conjecture about 'gaping holes' is that air bubbles may be 
trapped in the tissue.

Tim Morken, B.A., EMT(MSA), HTL(ASCP) 
Infectious Disease Pathology
Centers for Disease Control
MS-G32
1600 Clifton Rd.
Atlanta, GA 30333
USA

email: tim9@cdc.gov
       timcdc@hotmail.com
FAX:  (404)639-3043


----Original Message Follows----
From: Harold Obiakor <HOBIAKOR@niaid.nih.gov>
To: 'HistoNet Server' <HistoNet@Pathology.swmed.edu>
Subject: Frozen Tissue
Date: Thu, 11 Mar 1999 17:46:26 -0500

Hi,
Does anyone Know the best method to freeze tissue without having holes 
or
cracks in them? Currently we freeze our tissues with OCT (embedding 
medium
for frozen tissue) in Isopentane/Liquid nitrogen or dry ice and 
occasionally
we have gaping holes or cracks in the tissue after sectioning. We are
convinced that these holes are not due to the process of sectioning, but 
due
to the freezing method. We have also noticed that freezing tissues with 
OCT
in Isopentane on dry ice was a little bit better than in Isopentane 
placed
in liquid nitrogen.

								Harold.
								NIAID, NIH.















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