[ExI] Another step towards uploading
anders at aleph.se
Mon Oct 7 19:42:12 UTC 2013
On 07/10/2013 15:45, John Clark wrote:
> On Mon, Oct 7, 2013 at 1:43 AM, Eugen Leitl <eugen at leitl.org
> <mailto:eugen at leitl.org>> wrote:
> > Perfusion by diffusion works only on cm^3 scale systems.
> OK, but how is that a problem? Just cut the big brain up into slices
> one centimeter thick or less; the gap between the slices could be made
> very thin indeed, on the order of 30 nanometers.
The problem is: how do you cut a brain? A fresh brain has the
consistency of stringy toothpaste: any cutting will do massive damage.
Methods for sectioning brains properly always start with putting them in
a bucket of formaline... for two weeks or more: http://goo.gl/9ueYjN
Think about what happens during that time. Yuck. As this paper shows,
diffusion is slow enough to produce noticeable gradients of immunostains:
Now, there seem to exist perfusion based methods, and fixing in situ
seems to be a great start for getting something that can be sliced well
Some aim at rapid fixation by injecting fixation liquid through basal
blood vessels and the ventricles, followed by the bucket for a few days:
It might even be applicable to whale brains (!):
"Due to limited space and supplies of fresh water on board, the fixative
usually had to be mixed for each whale using seawater instead of fresh
water. When seawater was used, NaCl was not added to the solution. To
prepare and open the skull, sharp painter scrapes, a circular bone saw
with an adjustable blade, chisels and hammers were needed. The use of
chemicals and saw on a very unstable working platform and the risk of
spatters of bone splints, necessitated that the operator wore protective
glasses, gasmask, chemical resistant industrial gloves, heavy oilskins
and strong boots." - ah, tough Norwegian science!
Future of Humanity Institute
Oxford Martin School
Faculty of Philosophy
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