X-Message-Number: 12419
Date: Tue, 14 Sep 1999 16:27:01 -0400
From: Jan Coetzee <>
Subject: Aged brains restored

<p><font color="#000000" size="2" face="arial">Washington - Aged brains
have been restored to youthful vigour in a gene therapy experiment with
monkeys that may soon be tested in humans with Alzheimer's disease,
researchers report. Scientists hope the treatment will reinvigorate
thinking and memory.
<P>
"To our surprise, this technique nearly completely reversed"
the effects of ageing on a group of key brain cells that had
shrunken in elderly Rhesus monkeys, said Dr Mark H. Tuszynski of
the University of California, San Diego.
<P>
Tuszynski is senior author of a study appearing on Tuesday in
the Proceedings of the National Academy of Sciences.
<P>
Tuszynski said that the studies reinforce a new understanding
of how the brain ages and suggests that neurons in the older brain
don't die at first, but actually go into shrunken atrophy.
<P>
"We've all heard the dogma that we lose 10 000 neurons a day
after the age of 20," said Tuszynski. "Well, that is false. That
doesn't happen."
<P>
He said that an actual count of the cells in the cortex, a key
area in the thinking part of the brain, shows that very few cells
are actually lost with age.
<P>
Instead, he said his team found that it was control neurons in
another part of the brain, called the basal forebrain, that were
most dramatically affected by ageing. These cells, Tuszynski said,
had shrunk in size and had stopped making some regulatory
chemicals, a change that seriously affects the thinking cortex.
<P>
"These cells are like the air traffic controllers of the
brain," said the researcher. "They are on the ground, deeper in the
brain, controlling the activities of cells up there in the cortex.
They control the flow of information in the cortex."
<P>
The researchers found that about 40 percent of the basal
forebrain cells could not be detected in old monkeys, and that the
other 60 percent of the cells had shrunken in size by 10 percent.
<P>
But, said Tuszynski, they found the cells were not dead. By
inserting genes for nerve growth into the brain, he said, the cells
were revived and restored to nearly full vigour.
<P>
Dr Bradley Wise of the National Institute of Ageing said the
study is important because it suggests that "the decline in the
numbers and size of neurons with ageing may be reversible."
<P>
"A lot of studies have been done in rats in this area, but this
is a step forward because it used primates (Rhesus monkeys)," said
Wise. He cautioned, however, "at lot of work will have to be done",
including determining how long the gene treatment lasts, before the
technique could be used routinely in humans.
<P>
In their experiment, the University of California, San Diego
researchers used eight monkeys with an average age of 23, roughly
the monkey equivalent of the late 60s to 70s in humans.
<P>
Skin cells were taken from each of the monkeys. Into these
cells, the researchers inserted a gene that makes human nerve
growth factor, an essential chemical found in the brain. The
modified cells where then injected into the forebrain of four of
the monkeys. Four others, acting as controls, got injections of
skin cells without the nerve growth factor, or NGF, gene.
<P>
Once in the brain, the modified cells began making NGF.
<P>
After three months, the researchers examined the brains of the
eight monkeys. The control monkeys showed a brain cell loss
expected for animals their age. But the brains of the monkeys with
the NGF genes injections had an almost youthful appearance, said
Tuszynski.
<P>
"We restored the number of cells we could detect to about 92
percent of normal for a young monkey and size of the cells was
restored to within three percent," he said.
<P>
Tuszynski said it isn't know yet if the restored cells also
reinvigorated the thinking and memory of the old monkeys. That is
being tested now in a new group of old monkeys, he said.
<P>
But the therapy is so promising that the researchers last June
applied to the Food and Drug Administration to test the gene
therapy technique in humans with Alzheimer's disease. -
Sapa-AP<P></font></p>

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