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 investigation. 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 Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=4439