X-Message-Number: 1425 Date: Fri, 11 Dec 92 23:17:54 CST From: Brian Wowk <> Subject: CRYONICS: freezing damage It is good to see a discussion of freezing damage underway on the net, and that this discussion is frank. Mike Darwin's brutal account of the damage done by current cryopreservation techniques serves as a strong argument for developing better ones. However Jeffrey Soreff's recent question about the possible superiority of chemical preservation over cryopreservation suggests that undue pessimism has been generated. According to a presentation made by Greg Fahy at the Alcor Anniversary Dinner earlier this year, the breaks produced by growing ice crystals are "clean" on an ultrastructural level. In other words, the broken edges are smooth, not frayed, when viewed on (freeze-substituted) electron micrographs. Additionally the broken bits are moved only microns, not off to parts unknown. Yes a frozen brain is a jigsaw puzzle; one with many disconnected pieces lying very close to where they ought to be, not one with badly jumbled or missing pieces. I, for one, am far from convinced that neural connectivity information is irreversibly lost in brains frozen with current (or even past) methods. It is important to keep information, both positive and negative, in perspective. On the positive side, it must be remembered that cryoprotected freezing is the only current means of maintaining the *functional viability* of individual brain cells indefinitely. It must also be remembered that freezing tends to *move things around*, not outright obliterate them (which is what chemical preservation does to all but the grossest level of neural anatomy). Freezing is not so bad that we need to look at entirely new modalities. As Mike says, what we need to do is make freezing even better by following promising leads on ways to reduce and eliminate ice formation. --- Brian Wowk Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=1425