X-Message-Number: 7673
From: Brian Wowk <>
Date: Sun, 9 Feb 1997 23:12:13 -0600 (CST)
Subject: Re: Cryo Journal Club 1

        Thanks to Jan Coetzee for posting the abstract on fracturing
damage during rapid cooling/rewarming of small vitreous samples.
An even more interesting work relevant to the problems of vitrifying
human cryopatients is the paper
        "Physical Problems with the Vitrification of Large
         Biological Systems" by Fahy, Saur, and Williams,
         Cryobiology 27, 492-510 (1990).
This work concludes that "fracturing depends strongly on cooling rate
and thermal uniformity and can be postponed to about 25'C below
Tg for a 482-ml sample if cooling is slow and uniform."  In general, 
it appears from this study that fracturing of large vitreous solutions
can be avoided above the glass transition temperature (Tg) with careful
cooling as Tg is approached.  Avoiding fracturing far below Tg (about
-110'C for typical cryoprotectants) appears to be a more difficult
problem that may necessitate the development of high-temperature
(-130'C) storage systems for vitrified cryopatients.
Brian Wowk          CryoCare Foundation               1-800-TOP-CARE
President           Human Cryopreservation Services   

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