[ExI] Another step towards uploading
rafal.smigrodzki at gmail.com
Sat Oct 5 23:07:27 UTC 2013
On Friday, October 4, 2013, John Clark wrote:
> Right now the most detailed scans of entire brains were not obtained by
> freezing but by chemical fixation and then cutting the brain into thin
> slices, some only 30 nanometers or about 100 atoms thick and photographing
> the slices. I wish the good people at Alcor would say something about
> chemical fixation, the same process Drexler advocated in "Engines of
> Creation". I haven't heard any mention of chemopreservation from Alcor
> since a short 2009 article that I didn't think was very good.
### Max wrote about the choices between vitrification vs. fixation recently
(or was it somebody else at Alcor?). The problem is that suspension usually
takes place under non-optimal conditions - instead of live perfusion as in
the case of animals used for the scans you mentioned, the cryonauts are
treated typically after many hours of warm ischemia and this means the
perfusion can be rather poor. Freezing here at least stops further damage.
Keeping a poorly perfused brain at room temp makes it turn into a mush.
This said, one of my greatest worries regarding suspension is
organizational failure at Alcor - could happen during civil war, major
economic downturn or even due to mismanagement (not to say that the current
team is likely to fail but rather, you can never trust the younger
generations to stay faithful to the ideas of their predecessors). If I
could have elective live perfusion while still fully functional, followed
by polymer embedding (this might require some technology development ) and
room temperature storage, I might prefer it over cryoprotectant and helium
persufflation. I'm assuming that nanoscale MRI would still work in polymer
embedded tissue, so there would be no need for heavy metal staining.
I do think that both approaches, vitrification and fixation, should
be further researched, as much as our limited resources allow but for
now vitrification is still the better way to go.
Rafal Smigrodzki, MD-PhD
706 B Forest St.
Charlottesville, VA 22903
tel: (434) 295-4800
fax: (434) 295-4951
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