X-Message-Number: 7812 From: Brian Wowk <> Date: Wed, 5 Mar 1997 13:15:02 -0600 (CST) Subject: Devitrification In Cryo Journal Club 4, Jan Coetzee writes: >One can conclude from this experiment that it would be difficult to avoid >crystallization during the rewarming of tissue from vitrification. Before >one stops other freezing procedures of cryo patients one might want to give >serious consideration to this problem. There are a variety things that can be done to increase the stability of vitreous solutions on rewarming. For example, years ago Boutron found that certain hydrophobic additives like n-propanol and methyl 1,2 propanediol significantly decreased critical warming rates necessary to avoid devitrification. For some CPAs, glass stability is also exquisitely sensitive to concentration. Increasingly the concentration of DMSO, for example, just a few percent above CNV produces glasses that are stable at almost any rewarming rate. The price of these stabilization techniques is added toxicity. But if our initial goal is better ultrastructure, then we can afford to add more toxicity than organ preservationists can tolerate. Another point is that fluorocarbon cooling also works in reverse: After an organ has been vitrified with fluorocarbon perfusion, fluorocarbon perfusion can also be used to warm it extremely rapidly. We (21st Century Medicine) expect rewarming rates of 50'C per minute for brains, and 300'C per minute for kidneys (the most vascular organ of the human body). These rates should be sufficient to avoid devitrification of solutions near CNV even without RF rewarming. Finally, an important point needs to be made with respect to cryonics. Even if cryonics patients are vitrified with solutions that devitrify easily on rewarming, then they are still better off than cryonics patients who are frozen. Both frozen patients and patients vitrified with unstable solutions will require nanotechnological repairs at deep sub-zero temperatures before they are rewarmed, but the repairs required for vitrified patients will be much less extensive. *************************************************************************** Brian Wowk CryoCare Foundation 1-800-TOP-CARE President Human Cryopreservation Services http://www.cryocare.org/cryocare/ Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=7812