X-Message-Number: 13850 Date: Tue, 6 Jun 2000 10:09:34 -0700 Subject: re: Higher Temp Storage From: Ivan Snyder <> Hi Mike and all, >Message #13843 >Date: Mon, 05 Jun 2000 07:31:31 -0700 >From: Mike Perry <> >In view of Doug Skrecky's posting, #13841, we can ask of the higher >temperature storage that has been proposed as an accompaniment of a new >suspension protocol would really be best for longterm preservation of >identity-critical information. The higher-temperature storage may indeed >lead to reversible cryopreservation, yet over many decades it could still >promote degradation of memory information in the brain that would not occur >at liquid nitrogen temperature. The cracking that occurred in lowering to >this temperature might still be a favorable tradeoff. Something to >investigate. Actually, though, I am inclined to optimism about storage of >brain tissue at -130, in view of the successes Suda had with brainwave >recovery at the much higher storage temperature of -20. Ivan here, I offer my perspective as one who studies biology. I find it most easy to infer from nature to deduce what is feasible. We already know what cryosuspension protocol works; that which mimics already working systems. There are many creatures which naturally undergo seasonal freezing. These range from the most simple organisms to the more complex. The most complex and most similar physiologically to us which freeze and revive are I believe frogs. I can't recall for sure now what sort of cryoprotectant the frogs have, but I know that insects produce glycerol, which is what is also used in human cryosuspensions. I have read that although alot of insects do survive freezing and thawing, there is a minimum temperature limit which they can tolerate, lower and they are killed. This is because glycerol, like any other substance, has a freezing point. Glycerol merely lowers the freezing point. I think the insects would sustain internal freeze fractures at temps even higher than that at which dry ice sublimes. Considering the freezing point of glycerol, it seems to me that immersion in liquid nitrogen defeats the purpose. I imagine that the vitrification process is meant to get around this, but I understand that the chemicals involved are toxic. I see a benefit in the use of liquid nitrogen; the system is more easily maintained, less fear of breakdown, and is cheaper than with a refrigerator. Still, temperatures regulated by a refrigerator at -20 most closely matches the natural *working* cryosuspension systems seen in the insects. These seem like good reasons for re-examining protocol. Ivan Snyder Hermosa Beach California ________________________________________________________________ YOU'RE PAYING TOO MUCH FOR THE INTERNET! Juno now offers FREE Internet Access! Try it today - there's no risk! For your FREE software, visit: http://dl.www.juno.com/get/tagj. Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=13850