Hi Lynn,

Hmm, I can think of two things that could have happened. Was there a white
plaque in the freezing cup (container for isopentane)? If not, perhaps the
isopentane was not cold enough and the muscle tissue absorbed the isopentane
making it more difficult to freeze. Or there could have been a air pocket
that formed between the tissue and the OCT which would slow down freezing of
the tissue.
Sometimes, I do freeze muscle without OCT- but the OCT should not really
cause any problems except in the case of freezing large blocks which tend to
crack. I use 12 inch forceps cooled in liquid nitrogen to move the tissue to
a piece of plastic wrap resting on powdered dry ice. The tissue is quickly
wrapped in plastic and foil while resting on the dry ice. Then, it can be
transferred to -80C. Of course, cryomolds filled with OCT make handy vessels
that are easy to pluck from isopentane, bury in dry ice, then store at -80C.

Happy Freezing!


Lorraine Gibbs
Physiology &  Biophysics
University of Washington
-----Original Message-----
From: Lynn Gardner <lynn-gardner@uiowa.edu>
To: Histonet@pathology.swmed.edu <Histonet@pathology.swmed.edu>
Date: Thursday, January 11, 2001 9:00 AM
Subject: Frozen problem


>Dear Histonetters,
>
>We experienced an interesting problem when working with some muscle tissue
>the other day and was wondering if anyone out there has experienced it and
>if so how did they correct for it.
>
>We frozen some muscle tissue in isopentane cooled in liquid nitrogen to a
>temperature of -160. The tissue looked compeletly frozen when removed. We
>immediately placed the tissue in a vial and put in the -80 freezer. We
>embedded in OCT and tried to cut and all we got was a big hole in the OCT.
>The tissue seemed as though it was not frozen. Any idea of what happened??
>We have done this with other tissue and it worked fine. We know the freezer
>did not thaw out. So we are at a loss.
>
>I would appreciate any input! Thanks in advance gang!
>Lynn Gardner, HT(ASCP)
>
>