X-Message-Number: 3986 From: Ralph Merkle <> Subject: Re: Reversal of freezing injury Date: Fri, 10 Mar 1995 13:14:55 PST Thomas Donaldson said: >To Ralph Merkle: For someone who believes that no work on better means of >preservation is needed, you seem remarkably leery of the damage which present *Sigh*. I hope everyone realizes by now that Thomas is prone to attribute statements, opinions, and beliefs to me that I do not hold, have never held, and which I view as foolish. >cracking may be quite sufficient to destroy those memories: nanotechnology An interesting claim. I must confess that fractures created at low temperature are not high on my list of concerns. Freeze fracture methods are used today as a method of providing high resolution imaging of tissue. Hayat (in "Principles and Techniques of Electron Microscopy: Biological Applications," Third edition, by M. A. Hayat, CRC Press, 1989) says "Membranes split during freeze-fracturing along their central hydrophobic plane, exposing intramembranous surfaces. ... The fracture plane often follows the contours of membranes and leaves bumps or depressions where it passes around vesicles and other cell organelles. ... The fracturing process provides more accurate insight into the molecular architecture of membranes than any other ultrastructural method." It does not seem likely that this mechanism will result in significant information loss. Subsequent rewarming of fractured tissue to a liquid state would seem likely to result in significant disruption. It would seem desirable, therefore, to avoid such rewarming. The presence of fractures would make any method that involved rewarming as a first step substantially less plausible than methods which involve analysis while the tissue remains frozen. Direct analysis and repair of frozen tissue would seem entirely feasible using a medical technology based on a mature nanotechnology. Those who view the development of such a technology as either unlikely or problematic might view fractures with grave concern. Obviously, I am not a member of this group. An effective method of demonstrating that cryonics works would be to freeze a brain, thaw it, and demonstrate the retention of memory (and other behavioral responses). With today's technology, this implies that we must preserve function in order to show that learned behavioral responses are present (we can't demonstrate much of anything, today, with a non-functional brain). Thus, an important objective is to eliminate cracking damage in order to preserve function in order to demonstrate retention of long term memory. I (and many others!) would be very pleased by such a demonstration. Further, such a demonstration would be a major step in gaining acceptance in the medical community (which, for reasons that are obscure to me, seems to require proof that cryonics will work before supporting it's widespread use. Requiring proof that a lifesaving treatment will work prior to using it on a patient who will certainly die without it is not consistent with the Hippocratic oath, evidently a point of such surpassing subtlety that it eludes many people today). The value of eliminating cracking for furthering this goal is entirely independent of the likelihood that cracking results in information loss. Eliminating cracking would remain a valuable objective even if we had absolute proof that it resulted in no significant information loss. Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=3986