X-Message-Number: 12927
From: 
Date: Sun, 12 Dec 1999 10:59:27 EST
Subject: tubulin depolymerization in cryonics

  There are microtubules in dendrites and axons both; they are an important 
structural element and also provide a 'track' for the dynein and kinesin 
proteins to 'walk' on for vesicle transport. The protein that forms the 
central structure of the microtubules, tubulin, depolymerizes rapidly at 0 
Celsius (the polymerization is entropy-driven). Now obviously this is not a 
universal limitation, antarctic fish live below 0 Celsius their whole lives. 
But it seems conceivable that human neuron connections might retract quickly 
at low temperatures. Has this issue been addressed in freezing protocols, or 
for that matter, in low-temperature surgery? (Sorry if this is old hat, I 
don't get time to read Cryonet that often.) --Bill Walker

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