Liquid Nitrogen Affecting Cells

Kernel

Was just wondering, if I froze some cells, or an appendage, say my finger, with liquid nitrogen - would the cells be killed? If I waited for the liquid nitrogen to thaw out would my finger be normal again?

If the answer is yes, then if I was completely frozen in liquid nitrogen and thawed out, would it be possible to shock my heart back into action and for me to live? Ala, cryonics?

John

It doesn't really work like that. If you dipped your finger in liquid nitrogen it will probably die (look at people losing toes, fingers and limbs in arctic expeditions).

Gurgle

As far as I understand it, the problem with practical cryonics is:

Freeze too fast (e.g. with liquid nitrogen): A large proportion of the individual cells are destroyed as they 'break' rather than stretching with expanding
water.

Freeze too slow: Irreversible brain damage sets in due to oxygen starvation.

The best practical solution I've heard is a scene-of-accident treatment where you're filled up with saline at ~4°C, causing almost instant hypothermia, so you can be got back to hospital, patched up, refilled with blood, heated up and your heart started without brain damage.

I'd imagine a successful cryogenic freezeing will involve something similar but using a liquid which doesn't expand when its frozen.

John

Just to add a bit I forgot earlier, when we work with tissue in liquid nitrogen (if you freeze tissue you can cut very thin sections of it) it has to be treated first with a cryoprotectant which stops the cells from rupturing. I think finding a way to successfully pickle an entire person in a cryoprotectant without killing them first would be a major hurdle in cyrogenesis. Saline will only let you go down to a certain temperature before it freezes and expands and I think to successfully freeze someone you might want to make it a bit colder (bacterial cell stocks are kept at -80 C, iirc)