X-Message-Number: 7836
From: "Jan Coetzee" <>
Subject: Cryo Journal Club 5
Date: Tue, 11 Mar 1997 12:11:14 -0500

Cryo Journal Club 5.


An Experimental Study of the Mechanical Response of Frozen Biological
Tissues at Cryogenic Temperatures

YOED RABIN, Paul S. Steif, Michael J. Taylor, Thomas B. Julian, Norman
Wolmark


An experimental study of the mechanical response of frozen soft biological
tissues to applied compressive stresses is presented. This study is related
to the mechanical stresses that develop due to the contraction of frozen
tissues in cryopreservation as well as in cryosurgical procedures. The main
concept in this study is that the stresses associated with the constrained
contraction of the frozen tissue, i.e., due to temperature variations
within the frozen tissue, can be simulated by an external mechanical load
which is applied to the frozen tissue while the tissue is maintained at a
uniform temperature. A new apparatus for measuring compressive stresses and
strains of frozen biological tissues in cryogenic temperature range is
presented. A new technique for processing the fresh biological tissue into
a cylindrical frozen sample for mechanical testing is introduced. Results
of compression tests on rabbit liver, kidney, and brain are presented and
are compared with available data from the literature on sea ice and single
ice crystals. An unusual response of frozen biological tissues to
compressive stress was observed: after the initial, roughly linear elastic
portion there was a series of sudden stress drops at constant strain, each
followed by a linear increase of stress with strain to the next drop. This
phenomenon, which is attributed to the accumulation of microcracks, broadly
resembles plastic deformation, and thus provides some support for simple
mechanical models invoked in theoretical studies.



Cryobiology, v 33, n 4, August 1996.



Cryo Journal club response:


One could conclude that under the conditions that these tissue samples were
preserved micro cracks can occur. If one selected a procedure to preserve a
cryo patient such as vitrification would micro cracks be more or less of a
problem? I do not refer to major cracks. I think because vitrification is a
"glass" condition the micro cracks would not occur but long linear cracks
would. Which would be easier to repair micro cracks or long linear cracks?

J.C.

Your participation will be appreciated.


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