[LINK] blog on cryonics by someone who freezes things in a cell bio lab

mwengler

http://www.strike-the-root.com/51/walker/walker12.html

Came across it pretty randomly, I found it quite intriguing. Cryonics is "routine" for human embryos, not far-fetched for humans at all. Makes the whole thing seem potentially very reasonable (and me someone who hasn't signed up and doesn't plan to).

http://www.strike-the-root.com/51/walker/walker12.html

Per PZ Myers, the state of the art in neural preservation doesn't recoverably preserve usable amounts of state in zebrafish brains, which are a few hundred microns on a side. How thin slices were you thinking of? And how fast were you going to be slicing?

I’ve worked with tiny little zebrafish brains, things a few hundred microns long on one axis, and I’ve done lots of EM work on them. You can’t fix them into a state resembling life very accurately: even with chemical perfusion with strong aldehyedes of small tissue specimens that takes hundreds of milliseconds, you get degenerative changes. There’s a technique where you slam the specimen into a block cooled to liquid helium temperatures — even there you get variation in preservation, it still takes 0.1ms to cryofix the tissue, and what they’re interested in preserving is cell states in a single cell layer, not whole multi-layered tissues. With the most elaborate and careful procedures, they report excellent fixation within 5 microns of the surface, and disruption of the tissue by ice crystal formation within 20 microns. So even with the best techniques available now, we could possibly preserve the thinnest, outermost, single cell layer of your brain…but all the fine axons and dendrites that penetrate deeper? Forget those.

Clarification: the current state of the art in neural preservation doesn't preserve amounts of state in zebrafish brains that are recoverable in usable form by the current state of the art.

If we had the ability to recover the information in usable form today, there would be no need for cryonics to exist.

2Dolores198414y

Which is obvious nonsense. PZ Meyers thinks we need atom-scale accuracy in our preservation. Were that the case, a sharp blow to the head or a hot cup of coffee would render you information theoretically-dead. If you want to study living cell biology, frozen to nanosecond accuracy, then, no, we can't do that for large systems. If you want extremely accurate synaptic and glial structural preservation, with maintenance of gene expressions and approximate internal chemical state (minus some cryoprotectant-induced denaturing), then we absolutely can do that, and there's a very strong case to be made that that's adequate for a full functional reconstruction of a human mind.

31986ED5214y

Odd. Human embryos are routinely cryogenically preserved, can be thawed and reimplanted to birth healthy human beings. Yet a blastocyst is roughly spherical, not homogenous, about 150-200 micrometers large, totals about 60 cells. Also, even rabbit kidneys, which are a few centimeters large, can be preserved. Not very often, not very reliably so, but some could still function and sustain life for days after being thawed.