X-Message-Number: 5675
From:  (Brian Wowk)
Newsgroups: sci.cryonics
Subject: Re: Rat hearts - Pretoria
Date: 27 Jan 96 06:26:37 GMT
Message-ID: <>
References: <4e7c0g$>

	I want to thank Dr. du Plessis very much for sharing this
abbreviated account of his group's work with us, and helping clear
the air in the aftermath of the intense media coverage.  After being 
innundated for the past couple of months with newsgroup messages and 
private emails asking me about the significance of this work, and having
no concrete information to respond with, it's good to have a first-hand
report.

	My most important comment concerns the extraordinary means
of cooling used-- direct immersion of the rat heart in liquid
nitrogen.  With a specimen as small as a rat heart, the cooling
rate would be extremely high (probably in excess of 1000'C per minute).
This is in stark contrast to the slow cooling rates (<1'C per minute)
usually used in tissue cryopreservation to avoid the formation of
fatal intracellular ice.  Why then don't the rat hearts freeze 
intracellularly?  They probably do, but with cooling rates so high
(essentially flash freezing) the crystals may be too small to do any
damage.

	The pig heart experiments will be the real test of the
applicability of this work to human organs.  Except perhaps for
the very outermost layers, flash freezing of the pig heart will
not be possible.  Freezing will occur in a different cryobiological 
regime than the rat heart work, and it will be interesting to see
how well the perfusate protects under these conditions.

	I have to be honest.  As a long-time Greg Fahy fan, my
emotional preference would be for Greg to win any future Nobel
prizes that might be awarded for organ cryopreservation breakthroughs. :)
Intellectually, however, I know that the sooner *anyone* achieves 
a breakthrough in this field, the better off we will all be-- 
particularly if the work is extendable to the human brain.  I therefore
wish Dr. du Plessis and his group good luck and godspeed.
       
***************************************************************************
Brian Wowk          CryoCare Foundation               1-800-TOP-CARE
President           Your Gateway to the Future        
   http://www.cryocare.org/cryocare/

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