X-Message-Number: 6926
Date: Tue, 17 Sep 96 16:55:17
From: Steve Bridge <>
Subject: Hugh Hixon replies on research
To CryoNet
>From Steve Bridge, Alcor
September 17, 1996
The following message is from Hugh Hixon, Alcor's biochemist and head
researcher, in response to Brian Wowk's Message #6893 and some other recent
questions. It was hard to get Hugh to sit down and write this and I cannot
guarantee (rather the opposite, I suspect) that he will answer any follow-
up questions soon.
Steve
******************************************************
Brian Wowk's Cryonet #6893
1) We don't have a Visser heart model up and running at this
date (17 Sept '96) What we have had is a persuasive (but partial)
demonstration by Visser that she can in fact cryoprotect a rat heart,
cool it to very near LN2 temperature, rewarm it, decryoprotect it,
and get it to beat again. This means that at least most of the
muscle cells, the vasculature, and the heart's autonomic nervous
system are all functional, as are the cell membranes and portions of
the protein biochemistry. Given the limitations of the beating heart
preparation, this is very good performance.
Up to this point, all that has been taken to LN2 temperature and
survived are many types of individual cells, some vascular structures like
heart valves where the underlying structure is more important than the
cells that make it up, and arctic beetles that, while they have about a 65%
survival rate at dry ice temperature for a couple of months, die after
exposure to LN2 temperature. (But they stagger around a bit before
they die, which used to be the most impressive performance anybody
knew about.) (Someone recently posted on frog hearts surviving
freezing. I don't know about that. Could someone please provide a
*citation*, and perhaps a summary?)
2) Cooling rate. It is not clear to me from the question
whether and why fast cooling might be more advantageous than the slow
cooling that must be done in order to cool an object as large
as an entire human body. However, in order to prevent the
crystallization of pure water during cooling, it is calculated that
it must be cooled at at least 10**12 degrees C/second. Visser's
maximum cooling rate is in the neighborhood of tens of degrees a
second, and bodies are cooled roughly 10**4 slower than that. On
this scale, Visser's cooling rate is already fairly close to cryonic
procedure. Visser's procedure is at this point only a laboratory
procedure. Larger organs and slower cooling rates remain to be
explored.
3) It is rather unlikely that Visser has discovered some
idealized perfect cryoprotectant. (Of, say, science fiction
quality.) Cryonics for practical people has never been about
"perfect". The people who insist on perfection before being
suspended are not going to be suspended. Cryonics has always been
about what can be done with the resources at hand. Embalming is
better than rotting. Straight freezing is better than embalming.
Cryoprotection is better than straight freezing. And if Visser's
cryoprotectant is better than glycerol, one of the previous best
cryoprotectants, guess what we're going to do to try to survive?
4) A great deal remains to be determined about Visser's
cryoprotectant and its practical application, and yes, a lot of
fairly inexpensive basic research needs to be done. The pace will
probably pick up once her paper is published.
Re the "informal comparison" of the rat brains about which Dave Pizer
remarked, and Charles Platt immediately had a bunch of questions (Cryonet
#6885):
The event in question was definitely informal, absolutely not
scientific, produced no observations or conclusions worthy of
mention, and can't even serve as a bad example. It should not have been
reported. Our apologies for disturbing your curiosity.
Hugh Hixon
**********************************
Stephen Bridge, President ()
Alcor Life Extension Foundation
Non-profit cryonic suspension services since 1972.
7895 E. Acoma Dr., Suite 110, Scottsdale AZ 85260-6916
Phone (602) 922-9013 (800) 367-2228 FAX (602) 922-9027
for general requests
http://www.alcor.org
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