X-Message-Number: 3371 Subject: SCI.CRYONICS: High Pressure Cryonics Reanimated From: (Ben Best) Date: Mon, 31 Oct 1994 04:04:00 -0500 I was even more disappointed than Ken Stone that the idea of High Pressure Cryonics evoked no discussion -- or even a display of comprehension. In conversation, Paul Wakfer told me that he and Mike Darwin simply dismissed the idea as "impractical". I am reminded of the adage that "a person with a hammer tends to view every problem as a nail" -- and I would add the comment that the person also tends to dismiss problems requiring a screwdriver as "impractical". To be "practical" for cryonics, high pressure would first have to be shown to be of benefit and second would have to be shown to be feasible to incorporate into cryopreservation procedures with manageable equipment at manageable costs. I am disappointed that despite his interest Ken Stone takes it to be self-evident that "quick changes in pressure would smush the patient". I wrote at length replying to this misconception and I am not inclined to repeat myself. There are two high pressure phenomena which are of potential benefit to cryonics. The first phenomenon is that High Pressure (2,000 atmospheres) depresses the freezing point of water to -22 degrees Celcius. The second phenomenon is that Very High Pressure (14,000 atmospheres) elevates the freezing point of water to +50 degrees Celcius. The effect of High Pressure is well-known in the cryobiological community, but has only been dabbled-with. The effect of Very High Pressure has not been discussed before in connection with cryobiology before, to my knowledge. I was hopeful of raising consciousness on Very High Pressure, but I would love to see more work on both High Pressure and Very High Pressure. Thanks to work by Ukrainian researchers, Robert Ettinger now feels confident that cracking is not a problem for liquid nitrogen cryostasis. Even if this is true, there remains the larger problems of freezing damage and loss of viability. I believe that immediate use of High Pressure would virtually guarantee reduction of freezing damage and increased viability. Unfortunately, the concept of *reduced freezing damage* and of *increased viability* seem alien to cryonics research. Viability and (even moreso) freezing damage are viewed as all-or-nothing. Greater use of electromicroscopy in connection with cryopreservation procedures will hopefully result in more appreciation of the distinctions between greater and lesser freezing damage. Cryoprotectant toxicity is reduced at lower temperature. Therefore, the use of High Pressure to maintain a liquid state at -20 degrees Celcius and below could mean introducing cryoprotectant at temperatures at which their toxicity is minimal. This could be of particular benefit for DMSO since it is far less toxic at low temperature and it perfuses cells so much better than glycerol. Freezing damage is not so much due to "puncturing of cells by ice crystals" as due to mechanical crushing resulting from the fact that ice is less dense than water. Very High Pressure could eliminate volume expansion if pressure can be applied so *rapidly* that ice crystal formation is prevented. Phase transition to a solid state produced by cooling depends upon conduction -- which means that it is necessarily so slow as to allow ice crystal formation. Phase transition produced by *rapid* application of Very High Pressure has the potential for producing vitrification by not allowing time for ice crystals (low density) to form. Such a procedure could conceivably be done without cryoprotectant -- and thus without cryoprotectant toxicity. I don't think that mechanical damage ("smushing" cells) is the crucial problem with Very High Pressure Cryonics. I believe the key problems needing investigation are heat-of-fusion and developing manageable equipment at a reasonable cost. And, of course, arousing the interest of people who have resources needed to investigate these questions. -- Ben Best () Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=3371