[ExI] Another step towards uploading

Anders Sandberg 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!

Anders Sandberg,
Future of Humanity Institute
Oxford Martin School
Faculty of Philosophy
Oxford University

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