X-Message-Number: 20360
From: "Basie" <>
Subject: Researchers Prevent Cell Death 
Date: Thu, 24 Oct 2002 20:01:29 -0400

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Researchers Prevent Cell Death in Rats with Stroke
2 hours, 33 minutes ago
By Alison McCook 


NEW YORK (Reuters Health) - A group of Canadian researchers have successfully 
prevented many brain cells from dying in rats who experience stroke, perhaps 
pointing the way to a new technique that would allow humans to preserve more of 
their brain functioning after stroke. 

      


"We see this as a proof of principle that this kind of approach could work," 
study author Dr. Michael W. Salter of the Hospital for Sick Children in Toronto 
told Reuters Health. "We're optimistic that this is potentially going to work in
humans. But we still need to do more work." 



Stroke occurs when the blood supply to a portion of the brain is cut off, either
by a blood clot blocking an artery or a hemorrhage within the brain. This 
starves brain cells of blood and oxygen, eventually killing them. 



In the current study, when the researchers induced a stroke in rats, they gave 
some a treatment that interrupted a signal within affected nerve cells that 
would otherwise tell them to die. 



This treatment allowed the rats to preserve 67% more brain tissue than they 
likely would have otherwise, the authors note. In subsequent experiments, rats 
that received the new technique completed behavior tests better than the rodents
who were not given the treatment after stroke, the researchers report in the 
October 25th issue of Science. 



Study author Dr. Michael Tymianski of the Toronto Western Hospital Research 
Institute and the University of Toronto told Reuters Health that since strokes 
occur relatively frequently in humans, researchers have long sought to develop 
treatments to save the brain cells damaged by stroke. Clot-busting drugs, for 
example, help open up the blood vessels of stroke patients by destroying the 
blood clot that, in most cases, is blocking blood flow to the brain. 



However, Tymianski said that clot-busting drugs can have serious side effects, 
such as brain hemorrhage, so a stroke patient must be seen by a number of health
professionals and be tested before he will receive the drug. Since there is 
only a small window of time before the drug's side effects outweigh its 
benefits, many stroke patients arrive at the hospital too late to undergo all 
the necessary tests and receive the treatment, the researcher noted. 



But Tymianski said that he and his colleagues have not noted any side effects in
the rats who received the new brain cell preserving treatment. If the technique
continues to appear safe, the author predicted that paramedics may one day be 
able to give stroke patients the drug immediately, before they reach the 
hospital. "It actually could have a tremendous impact on the number of patients 
that could benefit from stroke treatment," he said. 



In the current study, the investigators targeted the process by which cells 
instruct themselves to die when blood flow is cut off in the brain. 



Nerve cells often rely on a chemical known as glutamate to communicate with each
other, and the chemical is also involved with learning and memory. However, 
when stroke occurs, cellular structures known as receptors become overstimulated
by glutamate, and this will trigger a process within the nerve cell that 
eventually leads to its death. 



The receptors have important functions in the brain, the authors noted, so 
blocking their action completely would have both good and bad effects. Instead, 
in the current paper, the researchers designed a protein fragment that blocks an
early step in the process within nerve cells that leads to their death, thereby
impeding the process while preserving the receptor. 


In experiments with rats, the protein fragment preserved 67% more brain tissue 
in the rats who received it, relative to those who didn't. However, not all 
tissue was saved, and Salter speculated that the brain cells that are at the 
core of the tissue affected by the loss of blood may often be difficult to 
preserve. "They may be too damaged initially," Salter said. 

SOURCE: Science 2002;298:846-850. 





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