X-Message-Number: 4630
From: 
Date: Sat, 15 Jul 1995 23:34:48 -0400
Subject: SCI. CRYONICS clarifications

CLARIFICATIONS--

--to last month's comments in THE IMMORTALIST on BPI research:

1. I said that Mike Darwin at BioPreservation Inc. thinks the dog is a better
experimental model (reacting more like humans) than rodents, sheep, or even
other primates. However, he says that this refers only to resuscitation and
warm ischemia damage etc., not cryopreservation.

2. I remarked on the potential importance of the BPI finding of very good
ultra-structural
preservation in dog brains perfused with a solution including 7.4 M glycerine
and stored at around - 80'C for a year or more. However, I didn't remark
specifically on the novelty of good preservation after that length of time at
dry ice temperature.       

Going back quite a few years, several researchers had reported varying
degrees of deterioration, sometimes very considerable deterioration, after
storage in dry ice, sometimes after only a few weeks. I had always been
unconvinced that long term storage in dry ice was necessarily
hopeless--first, because the deterioration, even though substantial, was
probably self-limiting and not progressive to dissolution; and second because
it might depend sensitively on details of preparation. The BPI results now
suggest that, using their procedures, and specifically with a high
concentration of glycerol, storage at dry ice temperature produces no
noticeable additional damage to dog brains over a year to 18 months.

3. Mike agrees that his procedure essentially buys good ultrastructural
preservation at the cost of using glycerol levels that (so far) are
irreversibly toxic even when used without freezing.

4. I said his (and colleagues') study didn't address the cracking question.
Actually, they report no cracking; but cracking was not expected to occur at
these relatively high temperatures, rather to begin in the - 130'C to - 140'C
range. The Cryonics Institute sheep brains showed no cracking after rewarming
from liquid nitrogen temperature, and BPI and CryoSpan are running trials
with the CI slow cooling rates to see if this makes the difference.
                                                
Robert Ettinger
Cryonics Institute


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