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 Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=4999