X-Message-Number: 1419
Date: 10 Dec 92 05:48:46 EST
From: Mike Darwin <>
Subject: CRYONICS Re: J. Krause's remarks on High Pressure Freezing

From: Mike Darwin
Date: 9 December, 1992
Re: J. Krause's remarks on high pressure freezing

     The amount of pressure required to inhibit ice formation down  to 
a safe and stable temperature is astronomical.  If you cool under many 
atmospheres of pressure you will eventually get freezing, but not with 
normal ice I.  Rather you get allotropes of ice which are more compact 
(and apparently more damaging). One reason for this appears to be that 
ice forms intracellularly under ultrahyperbaric conditions.

     This  brings to me to a point about your posting: cells  are  not 
exploded  by ice under conditions of slow to moderate cooling (< or  = 
to  1  degree  C per minute) at one  atmosphere.   Rather,  cells  are 
dehydrated  by ice forming outside the cells - the ice freezes out  as 
pure  water, raises the extracellular solute concentration -  and  the 
cells  dehydrate.   Why this happens requires more time and  space  to 
explain than I have of either.

     Finally,  ultrahyperbaria in the range of even 1,000  atmospheres 
results in serious injury to living systems.  This is a major headache 
for  organ  cryopreservationists who are trying to use  hyperbaria  to 
inhibit ice formation in organs loaded with multimolar  concentrations 
of   cryoprotectant   while  cooling  to  a   temperature   at   which 
vitrification  will occur (then the pressure can be released  and  the 
organ  stored  in  the glassy, ice-free  state).   The  cryobiological 
literature  contains  many  papers dealing with the  effects  of  high 
pressure  on organs.  Similarly, there is a rich literature  in  other 
disciplines documenting the damaging effects of ultrahigh pressure  on 
everything from enzymes to microorganisms.

     Alas,  the world is not a simple place and most  "obvious"  ideas 
have  been thought of and explored by the "experts."   However,  don't 
let  that  discourage you.  Every once in a while a  simple  new  idea 
comes  along  from someone who "doesn't known it can't  be  done"  and 
history is made.

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