Talk:Cryonics/Archive1

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This is an archive page, last updated 7 July 2017. Please do not make edits to this page.
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Long term notes (sticky)[edit]

  • "Freezing": Let it be taken as a given that when someone refers to freezing living/recently dead tissue, they mean reducing its temperature to the liquid nitrogen range, using all available means to prevent the formation of destructive ice crystals (such as the "vitrification" process).

I wanted to add the first note to reduce silly correction battles over terminology; the second got archived and without the link here no one will ever go mock my essay. Thank you. ħumanUser talk:Human 19:19, 6 March 2010 (UTC)

Do any of these people matter?[edit]

Can someone who knows what they're doing review this webpage:

http://www.evidencebasedcryonics.org/scientists-open-letter-on-cryonics/Ike (talk) 03:18, 21 November 2014 (UTC)

A few actual neuroscientists amongst a whole lot of unrelated fields - David Gerard (talk) 17:22, 16 April 2015 (UTC)

PZ on cryonicists again[edit]

[1] - includes comment from cryobiologist who apparently talks about this at length in a podcast (no transcript).

Also: A lot of the reference links here have gone stale and need refreshing - David Gerard (talk) 17:21, 16 April 2015 (UTC)

need to expand on the rabbit kidney[edit]

Cryonics advocates LOVE the rabbit kidney example. Here's a paper: [2] The nine days "surviving" rabbit showed plenty of signs of kidney failure (despite claims the rabbit could have survived indefinitely); they killed it and dissected it and found the kidney was way messed up, probably by cracks from freezing. This was a tiny object frozen with a best-case protocol. Apparently there's a case with a 45 days surviving rabbit? - David Gerard (talk) 09:13, 9 September 2015 (UTC)

new source[edit]

[3] - David Gerard (talk) 08:21, 16 September 2015 (UTC)

Preserving neurons. 99% won't cut it... or will it?[edit]

Having 'worked with stroke victims', the figure used for neuron loss following a severe stroke of "about 1%" sounds too low. Large mature strokes are usually pretty obvious on CT or MRI (as in "oh dear, there is a big hole where your temporal lobe used to be") which suggests volume loss more than 1%. I've checked the citations used currently (two blog posts and an article in the journal Stroke). I think the data is being misinterpreted.

The data is mainly in the Stroke article (Time Is Brain—Quantified. Saver JL. Stroke 2006; 37: 263-266). Saver analyzed the literature to determine "The typical final volume of large vessel, supratentorial ischemic stroke". (NB. a large vessel stroke is different from a large stroke). The answer is 54ml (findings ranging from 19 to 138ml). The total volume of the supratentorial brain quoted in the paper is 1020ml (excluding CSF). So the typical supratentorial brain loss is ~5% with some patients losing more than 10%! To be fair, size is probably less important than location e.g. a small stroke in the brainstem could stop you breathing; a large occipital stroke could blind you but leave other functions intact.

The total neuron count in the human brain is ~130 billion. However, surprisingly, most of them are in the cerebellum. The split (quoted in the paper) is 109 billion in the cerebellum to 21.5 in the neocortex (neocortex = 86% of supratentorial brain volume). The Wikipedia cerebellum article agrees with a 3.6:1 ratio [so it must be true...]. Presumably this reflects different architectures, glial numbers, white matter tracts, etc.

The Saver paper only looked at supratentorial strokes (i.e. not including the cerebellum). The total brain neuron count is skewed by the disproportionately large number of neurons in the cerebellum. Therefore using the total brain neuron count as the denominator for calculating %loss is misleading. I'm going to revise the 'Preserving neurons' section to better reflect the Saver paper data. Pantrog (talk) 01:12, 17 June 2016 (UTC)

I wrote that years ago and recall looking up the numbers ... if you have better cites, go for it - David Gerard (talk) 13:47, 17 June 2016 (UTC)