X-Message-Number: 14853
From: "Jan Coetzee" <>
Subject: Avoiding Brain Freeze:
Date: Sun, 5 Nov 2000 22:35:59 -0500

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Avoiding Brain Freeze:
Hibernating Ground Squirrel Brains Weather the Cold 

October 9, 2000

 The brisk air and changing color of leaves tell you that winter is on its way. 
 Although we humans go about our business as usual during the winter, some 
 animals engage in a special kind of sleep called hibernation. Hibernation helps
 animals survive the cold winter when it is difficult for them to find food. 
 The body temperature of some animals drops to near freezing as they prepare to 
 hibernate when heart rate and other body functions slow. Although body 
 temperature gets quite low, these hibernating animals wake up and warm up in 
 the spring without any damage. New research provides some clues about how their
 brains survive such cold temperatures.

 Scientists at the National Institutes of Health (NIH) examined the brains of 
 ground squirrels at different stages of hibernation. Using light and electron 
 microscopes, the researchers saw "slits" inside neurons and glial cells of 
 hibernating ground squirrels. These slits were never seen in tissue from 
 non-hibernating animals. The slits appeared to be hardened patches on the 
 endoplasmic reticulum without any protein. The endoplasmic reticulum is a 
 structure in the cell that is responsible for producing proteins, lipids and 
 other materials for cell metabolism. 

 The NIH scientists believe that the lipids and proteins that make up the 
 membrane of the endoplasmic reticulum were rearranged during hibernation to 
 form areas with and without proteins. Because the proteins moved to areas that 
 were not hardened, it is possible that they continued to function and keep the 
 cells alive.

Exactly how the proteins and lipids became rearranged is not known. Further 
studies may provide a better understanding of the changes that occur during 
hibernation and may uncover ways to preserve and protect tissue from cold 


Azzam, N.A., Hallenbeck, J.M. and Kachar, B. "Membrane changes during 
hibernation," Nature, Vol. 407, September 21, 2000, pp. 317-318. 


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