X-Message-Number: 3557 Subject: SCI.CRYONICS: Low Temperature Cryonics From: (Ben Best) Date: Sat, 31 Dec 1994 09:52:00 -0500 I briefly mentioned an interest in liquid Helium storage several weeks ago and was quickly attacked by someone who showed little interest in hearing me out. Sometimes I wonder if there are not "fundamentalist cryonicists" who are as intolerant of deviant ideas as fundamentalist religionists -- and for the same reasons. Anyway, the time has come for me to explain my reasoning, beginning with a brief review of the "state of the art" of cryonic cryopreservation. In the 1950s Audrey Smith demonstrated that hamsters could be frozen to nearly -1 Celcius such that 60% of brain water is turned to crystalline ice -- with no loss of normal behavior upon rewarming. It is also known that 27.2% glycerol (3.72 Molar) in water results in no more than 60% of the water being frozen -- the rest is vitrified solid (i.e. a solid which has hardened like glass rather than formed ice crystals). To avoid the toxicity, viscosity and dehydration of higher glycerol concentrations, cryonic suspensions were performed fulfilling the "Smith Criterion" figure of 3.72 Molar glycerol. Light microscopy seemed to indicate that 3.72 Molar glycerol might not be causing freezing damage. Then 3 Trans Time whole-body patients were moved to Alcor and converted to neuro. Autopsy of the bodies indicated that large-scale cracking might be a problem, even if ice-crystal damage is not. Glass turns from a liquid to a solid by gradual increase in viscosity -- in distinction to the abrupt phase transition seen with crystal-formation. Nonetheless, the increase in viscosity is not completely uniform with temperature-drop. In particular, there tends to be a "glass transition temperature" at which solidification proceeds more rapidly for small temperature-change. For glycerol/water solutions this tends to be in the -90 to -130 degree Celcius range. When glasses are cooled, cooling proceeds from outside to inside, resulting in stresses from the warmer core which needs to contract more than the surface. Robert Ettinger has asserted that very slow cooling below glass transition temperature eliminates the cracking problem -- and the Cryonics Institute has contracted Ukrainian scientists to prove this point. Brian Wowk has investigated the feasibility of "cold room" storage just below glass transition (-130 Celcius) and has demonstrated that this could be considerably more economical than liquid nitrogen. All this concern with cracking made a great deal of sense when we believed (on the basis of light microscopy) that there is no freezing damage. If suspended animation of the brain were demonstrably achieved, I would be very interested in storage at -130 Celcius. But in the December 1991 issue of CRYONICS magazine, cryobiologist Dr. Greg Fahy wrote of the results of his ultramicroscopy examination of a rabbit brain frozen to -130 Celcius. He observed considerable freezing damage. The "Smith Criterion" has been abandoned by many cryonicists, and Alcor/Biopreservation patients are now being frozen with glycerol concentrations above 7 Molar. Unfortunately, perfusion of glycerol into cells is poor and considerable dehydration is occurring. With known freezing damage, extensive protein cross-linking due to dehydration, and cryoprotectant toxicity at the cellular level -- gross cracking is the least of our worries. Even without cracking, we are very dependent on future molecular repair technology for current cryonics patients. This picture could be very different if the vitrification solution that Dr. Fahy has used with kidneys proves to be a workable alternative to glycerol. In Hugh Hixon's classic essay "How Cold is Cold Enough" he says "... any temperature below -130 C to -135 C is probably safe due to elimination of translational molecular movement as a result of vitrification". Yet at the November 1994 Cryonics Conference Hugh indicated an interest in temperatures *above* glass transition as a means of avoiding the "brittleness" of glass. I think Hugh has made mistakes on both sides of the "glass transition" coin. What are the effects of freezing? Tissue is crushed, mangled and small pieces are broken-off. Yet this does not necessarily mean the kind of loss of structure that happens when a piece of tissue is dissolved in a bowl of acid. The crushing, mangling and breaking-off of small pieces are the result of deterministic vector forces. Some future computational and molecular-repair technology may well be able to deduce original structure on the basis of the evidence -- as long as the evidence is maintained. The worst thing that can happen is the "dissolution" of structure and small pieces. I believe Hugh's claim that translational motion does not exist below glass transition is mistaken. Molecules in an ice crystal may have vibrational rather than translational motion, but there is no reason for this to be true of a vitrified solid. Try looking at a window pane that is decades old -- the slow flow has visible effects. Above glass transition temperature the situation is worse -- risking dissolution of structure to avoid brittleness and cracking would be disastrous, in my mind. The very most conservative approach is the lowest possible temperature. Only 3 elements have boiling points below that of liquid nitrogen (which boils at 77 degrees Kelvin) -- namely Neon (27 Kelvin), Hydrogen (20 Kelvin) and Helium (4.2 Kelvin). Current dewars could not used Helium because it diffuses through steel and destroys the vacuum -- protective linings would have to be added. Neon is probably safer to use than Hydrogen, and is more plentiful than Helium. But all are probably at least an order of magnitude more expensive than liquid nitrogen. Liquid nitrogen is the best low temperature storage I can afford, but a lower temperature might not be a bad idea for a very wealthy person. It is difficult to do a cost/benefit analysis on this problem when there are so many questions concerning WHAT needs to be preserved. That is the motive behind my series "The Anatomical Basis of Mind" in CANADIAN CRYONICS NEWS. I believe it is important to consider the consequences of all biostasis options, whether or not they prove to be feasible. What seems impractical today may become very practical tomorrow -- or, at least, inspire ideas which are more practical. Also, I don't want anyone to think that criticism of a sentence in Hugh Hixon's essay means that I don't respect the man or his work. I respect the man and I think the essay deserves to be respected as a classic piece of analysis. -- Ben Best () Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=3557