X-Message-Number: 4574 From: (Brian Wowk) Newsgroups: sci.cryonics Subject: Re: why is deep freezing necessary? Date: 26 Jun 1995 21:09:45 GMT Message-ID: <3sn7mp$> References: <3sep83$> In <3sep83$> (Adam Dingle) writes: >I read the Cryonics FAQ with curiosity. However one question remains quite >unclear to me: why is it necessary to store >the suspended individuals at a sub-freezing temperature? Given that dogs >and even a baboon have been revived after >being at cool, but above-freezing temperatures, for a number of hours, it >would seem to me that a suspended person >could be kept indefinitely at a temperature of, say, 1 degree Celsius, >without freezing damage. Is the fundamental >problem that bacterial decomposition would occur at such a temperature? >Or is there some other problem? Chemistry proceeds *furiously* at 1'C. Worst of all, it does so in an imbalanced manner (with some reactions suppressed by the cold, while others continue unabated). This problem has been faced by organ transplant surgeons for years as they race organs around the country on ice before they lose viability. The best preservative solutions around today will keep hearts good for about 12 hours, and kidneys for 36 hours, then that's it. This problem can be viewed in more familiar terms. Foods do not stay fresh indefinitely in refrigerators or even deep freezers. Traces of liquid water within which diffusion can occur remain inside cells all the way down to -120'C. Below this temperature the last traces of liquid water will vitrify (become as viscous as glass), and only then will all molecules be locked in place and unable to react. Long-term storage of biological materials therefore requires temperatures of -130'C or lower. Liquid nitrogen (cheap and convenient) is -196'C. ---Brian Wowk Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=4574