X-Message-Number: 8418
Date: Thu, 24 Jul 1997 09:32:53 -0700 (PDT)
From: Doug Skrecky <>
Subject: "hot" cryonics

In Message #8417 yvan Bozzonetti <> wrote:
>         That technology could be termed "hot" cryonics. In a first place we
> would look at temperature near -130 deg. C, the next step would be to look
> at dry ice temperature and so on until we have near room temperature
> conservation.
>
Many cryoprotectants are stable at dry ice temperatures. These are "solid"
cryoprotectants that do not melt at room temperature when dry. An example
of one of these is sorbitol which melts at 110 C. However even completely
dry sorbitol is not inert at room temperature. This only occurs when it
hardens to a glass at what is called the glass transition temperature or
"Tg". For sorbitol this is -9 C. As for stability of frozen tissue this
occurs at the annealed glass transition temperature or Tg'. For sorbitol
this is -64 C, so sorbitol treated frozen tissue can be expected to be
inert at dry ice temperatures. However there is a price to be paid for
this tremendous increase in stability & safety relative to "liquid"
cryoprotectants like glycerol & DMSO, with Tg's below -100 C. As far as I
am aware all potential cryoprotectants that could be used in conjunction
with dry ice storage suffer from relatively slow permeation into tissue.
So preparation of tissue with sorbitol and other "solid" cryoprotectants
would be time consuming relative to current procedures, which use
glycerol.
  One cryoprotectant that shows promise here is adonitol, which
permeates cell membranes over 30 times as quickly as sorbitol 
yet still melts at a warm and toasty 102 C. For those concerned about
safety or expense of cryonic storage, adonitol might be close to being the
optimal choice of cryoprotectant for use in conjunction with dry ice
storage.

References:
 "Melting and Glass Transitions of Low Molecular Weight
 Carbohydrates" Carbohydrate Research 238: 39-48 1993
 "Permeability Coefficients of Bull Speratozoa for water and polyhydric
 Alcohols" Experimental Cell Research 69: 212-216 1971

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