X-Message-Number: 5915 From: (David L Evens) Newsgroups: sci.cryonics Subject: Re: Freezing Damage Date: 11 Mar 1996 15:39:13 GMT Message-ID: <4i1hf1$> References: <> <> Daniel Jacobs () wrote: : In article <>, (Brian Wowk) wrote: : > In <> : (Daniel Jacobs) writes: : > : > >Although I am generally very sympathetic to the concept of cryonics and : > >can see no fundamental scientific reason for it not to succeed I was very : > >worried by what I read in the BPI Tech Brief 16: "Canine Brain : > >Cryopreservation" by Charles Platt. To quote of the damage found in the : > >canine brain: : > : > (deleted) : > : > I too am disturbed by this damage, which is why I regard research : > leading to reversible cryopreservation the brain as the most important : > priority for cryonics today. : > : > >1. Has there been much thought been given to the protocol suggested by : > >Drexler ie chemical fixation of the brain then subsequent vitrification? : > >Would this not preserve maximum morphology and information? : > : > This has been investigated. It was found that fixation : > disrupted cell membrane integrity, causing ice crystals (which normally : > form exclusively outside cells) to penetrate inside cells, causing : > severe damage. : Do you have any references that demonstrated this ice damage after : fixation? Please forgive my ignorance ( I'm only a molecular biologist) : but once a tissue was fixed couldn't the water be replaced by some solvent : that doesn't cause freezing damage at -195C? Certainly you could do that, and it would indeed aleviate the freezing damage. (In fact, a number of suitable solvents are already in use in the preperation of specimens for electron microscopy.) THe problem with this approach is that it is known to cause significant structural damage, and it is believed to cause severe chemical damage. This would likely cause significant information loss, which is what we're trying to avoid. Given the apparent level of preservation using conventional techniques (the tissue is largely alive, and at least partially functional) it seems better to improve conventional tecniques at this time, rather than attempt to design radically different procedures. As it stands now, it appears that there will soon be the posibility of organ level reversible vitrification to LN2 temperatures. If we can achieve this, for all the organs, we will be able to produce true organ banking, with organs being kept until the best feasible match is available. The next obvious step would be to try and generalise the technique to whole-body preservation so that organ recipients can be suspended (once they reach iminent death status) until a suitable donor organ comes along. If vitrification works as well as it appears to, it may be that such people will, in some cases, remain suspended until the technology to repair or replace their existing organs is devloped. They might not really LIKE suddenly finding themselves decades into the furute, but they would have had to conscent to the procedure, and that would have entailed being told of the risk of waking up in a distant future. Most people who are willing to accept a donor organ are probably willing to take that risk, as well. ---------------------------+------------------------------------------------ Ring around the neutron, | "OK, so he's not terribly fearsome. A pocket full of positrons,| But he certainly took us by surprise!" A fission, a fusion, +------------------------------------------------ We all fall down! | "Was anybody in the Maqui working for me?" ---------------------------+------------------------------------------------ "I'd cut down ever Law in England to get at the Devil!" "And what man could stand up in the wind that would blow once you'd cut down all the laws?" ---------------------------------------------------------------------------- e-mail will be posted as I see fit. ---------------------------------------------------------------------------- Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=5915