X-Message-Number: 4439
Date: Tue, 23 May 1995 18:45:54 +0200 (MET DST)
From: Eugen Leitl <>
Subject: Cool Flies & Chilled Mice.

Hiya cryoprevisionists,

Some time ago there has been some discussion on very high pressure
vitrification. Since water has a density maximum at 4 deg Celsius
and ice swims on water, a _very_ high pressure can reduce volume
extension, so at further cooling the system would freeze in glass
state. Unfortunately, that high a pressure would scramble protein
structure irreversibly. But still, this method requires some further 

Such high pressures (and much higher) are accessible with a diamond
anvil press. Has anybody on this list access to such an equipment?
(I probably could, but it would require time and some considerable
energy on my part). The pressure chamber should be chillable up
to several degrees below 0 celsius to counteract instant 
reliquification upon pressure reversal. Since diamond is
a great heat conductor this should not pose such a problem.

A second thought. Metals are known to exist in glass state if cooled
at some billion degrees/s. The equivalent for cerebral tissue would
require extremely fast contact of a tiny tissue specimen with a 
cryofluid or a LN2fied metal block. Fluid gases will not do since
they have Leidenfrost and low heat capacity. A supercold fluid
(e.g. carbon tetrachloride or sumpn) is definitely better. I dimly
recall reading in Nature about a fast freezer based on a LN2fied copper
block and a probe guillotine bringing specimen slice into tight
contact of the heat sink. Even if we would reach no much glass state 
(xRay diffraction pattern as a probe), this should eliminate freeze
artefacts considerably. Anybody care to investigate that?

Another thought. Why not starting with tiny organisms, e.g. Drosophila
m. over Etruscan/lab mice to cats and then larger beasties with
cryoperfusion & vitrification? This scaling up would help to optimize 
cryoperfusion temp programme ramp for freeze artefact minimisation. 
Moreover, small organisms could be microwave-warmed up much faster and 
checked for generic neuro firing pattern restauration. Sheep & Co. right
from the start do not make much sense, imo.

-- Eugene

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