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Cryonic freezing

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Cryonic freezing

Postby wheel » Fri Apr 11, 2008 2:54 pm

I read some facts from the Internet that this cryonic freezing technology is used to freeze dead bodies at very low temperature around the boiling point of liquid nitrogen. At such temperature, dead bodies can definitely be prevented from being decomposed. According to the resources, this preservation of dead bodies is done because future technology might be able to revive the dead people. Is this one of the purposes of preserving the dead bodies using cryonic freezing?

I understand that human sperms are also froze using this technique in the sperm bank. When cells freeze under normal condition, the frozen water inside the cells will cause the rupture of cells. My doubt is, how can cryonic freezing helps to prevent the sperms from rupturing?
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Postby canalon » Fri Apr 11, 2008 6:21 pm

To store sperm or cells you add antifreeze to the mix (DMSO, glycerol,...) that will prevent the formation of big ice crystals, by creating multiple nucleation sites (so plenty of very small crystals) and hence reduce the risk of membrane rupturing.

As for the freezing of whole body, I listened a few months ago a conference from someone studying how frogs and other animals can survive freezing temperature. And at the end he explained why cryonics is a joke (besides the fact that you might wonder why the hell anyone would care resuscitating you in the future...). The main points were:
- a human body is too big to freeze fast enough
- a frog brain is good for ribit ribit, but not much more, hence it seems to be able to withstand much more damage than any mammal, or ape.
- The mechanisms used to protect frog cells would kill your cells quite fast
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Postby wheel » Sun Apr 13, 2008 4:51 am

Do you mean only small ice crystals may form inside sperms stored in sperm bank?
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Re: Cryonic freezing

Postby biohazard » Tue Apr 15, 2008 1:08 pm

Yeah, you have to do it like Canalon said and use certain additives (cryopreservants) in order to freeze sperm without rupturing the cell membranes by ice crystals. In cell size-scale, small crystals are okay, huge crystals puncture the membrane.

And since this applies pretty much to all animal cells, large animals (here, humans) cannot be frozen that way, since you cannot A) distribute the cryoprservants efficiently, and B) freeze (or thaw) the body fast enough from all parts. Although you can freeze cells too fast also: if you simply toss your cells into the liquid nitrogen, they probably die regardless of cryoprservants, but if you first freeze them a bit slower (e.g. in a freezer), the results are better.

(Some) bacterial cells, on the other hand, are more robust and can often be succesfully frozen even without cryopreservants.
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Re: Cryonic freezing

Postby Anonymous13 » Thu Jul 30, 2009 12:03 pm

I dont know much about this "Cryonic Freezing" but what i have hurd of it gets me to thinking of a few things I have been trying to study in the last year.
*Please bare with me Im new to the science stuff*
Anyway, If you can freze a cell without it rupturing outside if the body, then could you do that inside the body too? I know you could not freze a human, am i correct? My question is more under the lines of, could you freze a organisum inside the human body? I mean like a worm something of that sort. Could we try to stop the creature in its track of distruction to give us enough time to save that human? Im not sure if it is posible, or if there could be a posible compound to create for this, but dose anyone think it could just happen? I belive that if you could freze a cell inside the body then you could freze a organisum too. Can you freze a cell inside the body? My questions are ramdom, but they will come to a point when I getr all the Information I need.
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Postby biohazard » Mon Aug 03, 2009 3:21 pm

You cannot freeze anything even moderately biggish for several reasons: first, you cannot spread the cryoprservant equally to all parts of the organism and not in an even concentration. Second, you cannot freeze big bodies in a constant rate, which means that the outer and/or extreme parts tend to freeze too fast and the internal parts too slowly - or if you get one of those pretty much right, the other will surely be wrong. Third, you cannot start the big internal systems inside large organisms after thawing: circulation, neural systems, digestion etc. There are probably quite a few other reasons as well why you'll fail to freeze even a mouse and thaw it alive, but those three are probably the biggest obstacles.

Certain largish amphibians seem to be able to cryopreserve themselves to some degree (getting back to "life" is much easier with cold-blooded animals), but those are the biggest things there are that survive some degree of cryoprservation - and even that is not a real thing, since they do not get completely frozen, but instead alter their cellular fluids in a way that prevents them from completely freezing over. That is, you cannot store a frog in a liquid nitrogen and bring it back to life.

I'm not sure which creature is the largest thing that you can actually freeze to -200 or so Celsius (which would be required for any proper cryopreservation), but I'd guess something on a scale of a nematode is already almost as big as you can get with today's technology.
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