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 Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=2299