X-Message-Number: 2299
Date: Sat, 5 Jun 93 23:21:19 CDT
From: Brian Wowk <>
Subject: CRYONICS dehydration

Ben Best:
 
> P.S. I believe Brian Wowk is wrong to claim that cryoprotectants act
> through dehydration. Dehydration occurs *without* cryoprotectant. The
> migration of water to the extracellular space during slow freezing is
> the reason that Audrey Smith was able to recover hamsters frozen to
> the point where 60% of brain water was ice. But too much cell
> dehydration results in denatured intracellular protein. The basis of
> cryoprotectant action is the vitrification of intracellular fluids,
> since intracellular ice is the worst source of freezing damage. My main
> concern about the use of glycerol is that it may not be perfusing into
> the cells adequately to vitrify and -- worse -- simply (osmotically)
> squeezing more water out of cell tissue rather than vitrifying.
 
        I was not suggesting that cryoprotectants operate 
*exculsively* by dehydration, only that dehyration by hypertonic 
cryoprotectant is beneficial inasmuch as it leaves less water in cells 
to be removed when freezing begins.  Assuming that the final amount of 
dehydration is the same (which may not be true, as you state) it seems 
better to start dehydration before freezing rather than during 
freezing since the concentration of hypertonic solution will be more 
uniform before freezing, and cell membrane conformations would be 
unconstrained by ice crystals.
 
                                                --- Brian Wowk

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