Cryonics

[Trilobyte]

The obvious initial problem with cryogenic suspended animation (cooling organisms from a living state to preserve them and revive them at a later date) is that when cooled below the freezing point of body fluid ice forms which bursts all cells, vessels, membranes and bones. This problem can be solved by increasing the pressure of a sleep chamber an organism is placed in such that expanding ice is forced to shrink in volume and become a fluid at very low temperature (eg -100 degrees) thus not causing freeze damage.
My quiry is of the properties of blood at very low temperatures. Will it for example coagulate irreversibly or anything else, or the effects on brain tissue at very low temperatures and even higher compensation pressures.
I don't see a reason for why this cannot already be done with, say, live mice. (artificially increased blood glucose levels could be used as an antifreeze and means that a slightly lower pressure is possible - so lower requirements on the pump (etc) system.

 

[zyncod]

Nope. Glucose is not an antifreeze - but if you're thinking sugar, trehalose is probably the one you want. The problem is not with the blood - blood, as you probably know, is routinely frozen in blood banks (although there is a significant loss in cell viability during freezing). The major problem is the neurons. Even a 1% loss in neuronal function could affect not only higher-order cognitive processes but also sympathetic nerve systems - thus the heart would stop bleeding. And we don't even know enough about cryogenics to freeze "simple" organs like kidneys - hence the image of some rushed medical courier with a cooler containing an organ. If cryonics ever happens, we'll know enough about biology at that point to make it useless.
All this aside, I was doing a research study a few years ago to determine which cryoprotectants (chemicals - like trehalose) protected DNA best in D. melanogaster (fruit flies) for a biorepository. Out of a few thousand flies frozen, one or two woke up after a couple of weeks at -161C!! The cryoprotectant in that case, if memory serves, was ethylene glycol - the antifreeze for cars without the radioactive-type colorant.

 

[Trilobyte]

What makes you say that cryonics will be a useless technology?
In terms of long distance space travel as an example it would be very useful, since you will be using up less energy to keep the body in its stasis than if you keep the body alive and active for the whole time. The other benefits are psychological - as an alternative to being awake through the tedium of being in a confined space for a long time.

Freeze damage is eliminated altogether if there is no freezing, so there is no brain damage due to ice crystal formation because of the pressure and no damage due to chemical decomposition because of the low temperature.
There is also a known protein found in some animals (perhaps frogs or a reptile?) that acts as an antifreeze and is less toxic than artificial antifreeze - this could allow a lower pressure to be used. Are there actually any problems with this method?

 

[zyncod]

The antifreeze proteins found in animals are used to allow them to survive cold temperatures in the slightly subfreezing range - to about -4C. These proteins would have no real use in cryonics, as cryonics involves temperatures about -161C. The only real way for effective cryonics would be to instantly perfuse every tissue in the body with a chemical cryoprotectant, freeze the entire person instantly, and then instantly remove the toxic cryoprotectant from all tissues (the cryoprotectant would not necessarily be "toxic" per se but the changes in osmolarity for bodily cells would be toxic).

The problem people are having in cryogenics right now (ie, freezing a kidney) is mainly dealing with the fact that the organ cannot be instantly frozen. So as the "wave" of cold moves through the tissue, you have fatal changes in the architecture of the organ. The toxicity of the cryoprotectant is not so important in cryogenics because, for a kidney, not every cell needs to survive. However, when you are dealing with a whole person, the neural architecture must be preserved to an incredibly high degree. I don't know - there might be some very special chemical and a way of freezing the body with lasers or something that could possibly make cryonics workable. My point is only that by the time that comes around, you'll probably be able to download your mind into a robot or something which would kind of make the cryonic sleep on spaceships not that useful. Not that I really think mankind is going to be around long enough to do any of these things.

 

[Trilobyte]

Which seems more feasable in the near future; "dowloading" an interpretation of the equivalent processes that occur in the entire brain for a group of many individuals, or cooling them to a very low temperature WITHOUT the involvement of freezing?(Because of high pressure, nothing else is required to prevent any damage that would be done if you were to freeze someone.)

The initial cooling process would only occur once sufficient pressure has been applied such that it would be impossible for the water molecules to grow large ice clusters and expand by anything measurable( so waves of solidification as ice is formed is not relevant with this method. Any temporary hydrogen bonds that form between water and non-water molecules will break off again as soon as the body is reheated (then depressurised and awoken by electrical stimulation as a precaution incase the heart and lungs do not restart by themself).

(I only added antifreeze as a suggestion, it is not actually necessary.)

"Not that I really think mankind is going to be around long enough to do any of these things."

Do you really expect it to take that long to make long promised technology possible? Or are you expecting us to be wiped out in about another decade or two?

High intensity ultrasound would also make it possible to use lower compensation pressures by continuously shearing large ice crystals into ever smaller fragments (but this is unnecessary and energy expensive since it would have to be always on ).

My question is still why would the process I suggest not work? Surely there are SOME disadvantages or side effects that someone could point out to me...from a biology stand point, like any effects of high pressure on bones or neurons...or should I take this question elsewhere?