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/ Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=5675