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The accumulation of protein fragments in the brain begins before dementia
symptoms start and increases as dementia becomes more severe. Based
on the findings, which suggest that the accumulation of these fragments,
called amyloid beta-peptides, is to blame for the dementia of Alzheimer's
disease, drugs that remove or block the peptides might help slow
down or even prevent the disease. Two types of abnormal growths
in the brain -- plaques made up of amyloid beta-peptides and tangles
composed of tau proteins -- are telltale signs of Alzheimer's disease.
But there's been a controversy about which comes first, plaques
or tangles.
The results of the study, however, appear to place the blame on
plaques. The beta amyloid is very probably responsible for the dementia.
The researchers speculate that the peptides cause nerve damage that
lead to dementia and, in turn, the formation of plaques and tangles.
And even though much of the focus has been on the collecting of
the peptides into plaques, the study shows that high levels of beta
amyloids are present in the brains of people with dementia even
before plaques develop. Treatment with drugs that block the production
of amyloid beta-peptides, which are about to be tested in human
trials, might prevent the disease.
The Journal of the American Medical
Association 2000;283:1571-1577, 1615-1616
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