X-Message-Number: 5915
From:  (David L Evens)
Newsgroups: sci.cryonics
Subject: Re: Freezing Damage
Date: 11 Mar 1996 15:39:13 GMT
Message-ID: <4i1hf1$>

References: <> 

Daniel Jacobs () wrote:
: In article <>,  (Brian Wowk) wrote:

: > In <>
:  (Daniel Jacobs) writes:
: > 
: > >Although I am generally very sympathetic to the concept of cryonics and
: > >can see no fundamental scientific reason for it not to succeed I was very
: > >worried by what I read in the BPI Tech Brief 16: "Canine Brain
: > >Cryopreservation"  by Charles Platt. To quote of the damage found in the
: > >canine brain:
: > 
: > (deleted)
: > 
: >         I too am disturbed by this damage, which is why I regard research
: > leading to reversible cryopreservation the brain as the most important
: > priority for cryonics today. 
: > 
: > >1. Has there been much thought been given to the protocol suggested  by
: > >Drexler  ie chemical fixation of the brain then subsequent vitrification?
: > >Would this not preserve maximum morphology and information?
: > 
: >         This has been investigated.  It was found that fixation
: > disrupted cell membrane integrity, causing ice crystals (which normally
: > form exclusively outside cells) to penetrate inside cells, causing
: > severe damage.

: Do you have any references that demonstrated this ice damage after
: fixation? Please forgive my ignorance ( I'm only a molecular biologist)
: but once a tissue was fixed couldn't the water be replaced by some solvent
: that doesn't cause freezing damage at -195C?

Certainly you could do that, and it would indeed aleviate the freezing 
damage.  (In fact, a number of suitable solvents are already in use in 
the preperation of specimens for electron microscopy.)  THe problem with 
this approach is that it is known to cause significant structural damage, 
and it is believed to cause severe chemical damage.  This would likely 
cause significant information loss, which is what we're trying to avoid.  
Given the apparent level of preservation using conventional techniques 
(the tissue is largely alive, and at least partially functional) it seems 
better to improve conventional tecniques at this time, rather than 
attempt to design radically different procedures.

As it stands now, it appears that there will soon be the posibility of 
organ level reversible vitrification to LN2 temperatures.  If we can 
achieve this, for all the organs, we will be able to produce true organ 
banking, with organs being kept until the best feasible match is 
available.  The next obvious step would be to try and generalise the 
technique to whole-body preservation so that organ recipients can be 
suspended (once they reach iminent death status) until a suitable donor 
organ comes along.  If vitrification works as well as it appears to, it 
may be that such people will, in some cases, remain suspended until the 
technology to repair or replace their existing organs is devloped.

They might not really LIKE suddenly finding themselves decades into the 
furute, but they would have had to conscent to the procedure, and that 
would have entailed being told of the risk of waking up in a distant 
future.  Most people who are willing to accept a donor organ are probably 
willing to take that risk, as well.

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