X-Message-Number: 13865 Date: Wed, 07 Jun 2000 22:58:19 -0700 From: Mike Perry <> Subject: Hi-temp storage, calore restriction, FTL Ivan Snyder, #13850, says ... > >Considering the freezing point of glycerol, it seems to me that immersion >in liquid nitrogen defeats the purpose. Not so. You are trying mainly to preserve inferable structure, not cell viability, unlike what nature is "trying" to do. > I imagine that the vitrification >process is meant to get around this, but I understand that the chemicals >involved are toxic. Work is being done to reduce toxicity. > 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. There is no prospect presently known for longterm storage of brain tissue at -20. Suda found significant degradation of brain waves after storage of up to 7 years. (That he got brainwaves at all after such a long time is remarkable though.) This would not rule out some new protocol that would lead to viable storage at this temperature, but it has yet to be worked out. Once again, our goals are not identical to nature's, and we can't simply trust nature to provide the answers. > These seem like good reasons for re-examining >protocol. > Looking for better protocols is certainly worthwhile, but I think it would be a mistake to fixate too strongly on systems in which the organism is still slightly metabolizing, which is probably true at -20. Again, though, I am not ruling out a high-temperature protocol. There is certainly much in this area that we do not know. On the subject of calorie restriction (Doug Skrecky, #13853) this subject has come up before. I am not an expert, but I had to deal with it as part of the book I've written, which I hope to send off to a publisher (finally) in maybe a day or two. I ended up echoing the sentiments of advocates of CR, at least to the extent that it appears to have some beneficial effect and does tend to increase the lifespan when tested in lab animals, though its precise mechanism is unknown. The paper Doug cites does not appear to challenge that conclusion, only to suggest that certain observable changes in the skin of mice correlate well with life expectancies. It could certainly be the case that the lifespan increase is entirely due to the poor diets the lab mice have been exposed to, but this must be so for many, many experiments over the several decades that CR has been studied. I'm sure many diets were tried, and to me it seems unlikely that all of the observed increases in lifespan can be attributed entirely to poor food. Doug also says "Obesity also has no effect on mortality, provided physically fit obese humans are compared with physically fit lean humans." Well, as long as you are physically fit you aren't about to die (except for accidents, etc.). But the question can still can be raised whether obese people are as likely to *be* physically fit, and stay that way, as lean people. In any case, based on the previous debates on this forum my book now says "when effects of disease are accounted for, thinner people with adequate nutrition are longer-lived." A reference I was given on this is: NIH National Task Force on the Prevention of Obesity, "Very Low-Calorie Diets," JAMA 270 #8 (1993) 967-74. On faster-than-light travel and signalling (James Swayze, #13851) I think it is still holding up that no information can actually be sent and understood at the other end in time less than it would take light to travel the distance, and this I see as basically upholding relativity even if funny effects persist. (I like it that an object can be in two places at once though--shades of many-worlds!) Mike Perry Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=13865