X-Message-Number: 4999
From:  (Thomas Donaldson)
Subject: Re: CryoNet #4954 - #4962
Date: Mon, 16 Oct 1995 12:53:18 -0700 (PDT)

Hi!

For those who knew what had happened, it should be clear that my computer is
working again. It did take longer than I expected for me to get it back.

This is intended to be a short note to correct one thing Mike Perry said. 
There are TWO papers I gave references to, not just one. The Buell paper does
discuss a fixation method which may give better results than simply using the
Golgi method. In doing so it also raises the question of whether or not 
this destruction of dendritic spines was simply an artifact of the fixation
method used.

The other two papers (of which Mike mentions one) which I gave references to 
were two early cases in which experimenters, without providing any support,
recovered guinea pigs (after 4 hours close to 0 C) and rats (after 2 hours
close to 0 C). They are both in my old "Cryonics --- A Scientific Bibliography"
which is available from Alcor. The guinea pig experiment 
was done by a CE Huggins and appeared in SURGICAL FORUM 12(1961) 413. The
rat experiment was done by RN Andjus (an early cryobiologist) and published 
in PHYSIOLOGY 128(1955) 547.

Observations of chick brains after they have learned a simple task do show an
increase in dendritic spines. They also show an increase in the number of 
dendrites, the number of synapses, and the size of synapses. I do not know
which is the most important, but since dendritic spines form from the cell
membranes surrounding the synapse (not all synapses are on dendritic spines)
they might be much more subject to disruption than either dendrites or the
synapses they contain. (Which also suggests that the neuron will recreate 
them if they've been disrupted).

Neither of these experiments tested the memory of their animals, but again 
neither experimenter noticed any special signs of odd behavior afterwards.

Incidentally, before such experiments were done, many neuroscientists 
thought that our memories were maintained by the electrical currents in our
brain. Even given the primitive technology of the 50's, this idea was 
decisively refuted by cooling down trained animals until they showed no 
signs of electrical activity, bringing them back again, and testing them on
the same tasks they had learned before. With enough time between the first
training period and the cooldown, they remembered the task quite well.

			Best and long long life,

				Thomas Donaldson


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