<div dir="ltr"><div>Someone mentioned a Cryonics magazine article on plastic embedding vs cryopreservation. You can find the article here:<br><br><a href="http://www.alcor.org/magazine/2013/01/16/chemical-brain-preservation-and-human-suspended-animation/">http://www.alcor.org/magazine/2013/01/16/chemical-brain-preservation-and-human-suspended-animation/</a><br>
<br></div>--Max<br><br></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Mon, Oct 7, 2013 at 12:42 PM, Anders Sandberg <span dir="ltr"><<a href="mailto:anders@aleph.se" target="_blank">anders@aleph.se</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div text="#000000" bgcolor="#FFFFFF"><div class="im">
<div>On 07/10/2013 15:45, John Clark wrote:<br>
</div>
</div><blockquote type="cite">
<div dir="ltr"><div class="im">On Mon, Oct 7, 2013 at 1:43 AM, Eugen Leitl <span dir="ltr"><<a href="mailto:eugen@leitl.org" target="_blank">eugen@leitl.org</a>></span>
wrote:<br>
</div><div class="im"><div class="gmail_extra">
<div class="gmail_quote"><br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">> Perfusion by
diffusion works only on cm^3 scale systems.<br>
</blockquote>
<div><br>
</div>
<div>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. </div>
</div>
</div>
</div></div>
</blockquote>
<br>
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:
<a href="http://goo.gl/9ueYjN" target="_blank">http://goo.gl/9ueYjN</a><br>
Think about what happens during that time. Yuck. As this paper
shows, diffusion is slow enough to produce noticeable gradients of
immunostains:<br>
<a href="https://www.sciencedirect.com/science/article/pii/S0165027087800018" target="_blank">https://www.sciencedirect.com/science/article/pii/S0165027087800018</a><br>
<br>
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 later:<br>
<a href="http://www.ncbi.nlm.nih.gov/pubmed/9372749" target="_blank">http://www.ncbi.nlm.nih.gov/pubmed/9372749</a><br>
<a href="http://www.abcam.com/ps/pdf/protocols/perfusion.pdf" target="_blank">http://www.abcam.com/ps/pdf/protocols/perfusion.pdf</a><br>
Some aim at rapid fixation by injecting fixation liquid through
basal blood vessels and the ventricles, followed by the bucket for a
few days:<br>
<a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1860363/" target="_blank">http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1860363/</a><br>
<br>
It might even be applicable to whale brains (!):<br>
<a href="https://www.sciencedirect.com/science/article/pii/S0165027002001826" target="_blank">https://www.sciencedirect.com/science/article/pii/S0165027002001826</a><br>
<br>
"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!<span class="HOEnZb"><font color="#888888"><br>
<br>
<br>
<pre cols="72">--
Anders Sandberg,
Future of Humanity Institute
Oxford Martin School
Faculty of Philosophy
Oxford University </pre>
</font></span></div>
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<br></blockquote></div><br><br clear="all"><br>-- <br><div>Max More, PhD</div><div>Strategic Philosopher</div><div>Co-editor, <i>The Transhumanist Reader</i></div><div><a href="http://www.amazon.com/Transhumanist-Reader-Contemporary-Technology-Philosophy/dp/1118334310/ref=sr_1_1?s=books&ie=UTF8&qid=1372225570&sr=1-1&keywords=the+transhumanist+reader" target="_blank">http://www.amazon.com/Transhumanist-Reader-Contemporary-Technology-Philosophy/dp/1118334310/ref=sr_1_1?s=books&ie=UTF8&qid=1372225570&sr=1-1&keywords=the+transhumanist+reader</a><br>
President & CEO, Alcor Life Extension Foundation</div>
</div>