- NEW YORK (Reuters Health) - The elements copper and zinc may prompt prions
-- the infectious proteins that cause "mad cow disease" and similar
fatal neurological diseases -- to change shape, leading to the generation
of different strains of prions.
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- The finding, from a study conducted by
Dr. Jonathan D.F. Wadsworth of the Imperial College School of Medicine
at St. Mary's in London, UK, and colleagues, suggests that drugs that control
copper levels in the brain might be useful in treating prion disorders,
such as Creutzfeldt-Jakob disease (CJD), which currently have no known
treatment or cure, according to the report in the May issue of Nature Cell
Biology.
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- Prion disorders -- including bovine spongiform
encephalopathy, or "mad cow disease" in cattle, CJD in humans,
and scrapie in sheep -- are all characterized by progressive neurological
degeneration resulting in death.
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- These diseases are caused by a prion,
an abnormal version of a naturally-occurring protein, but researchers have
recognized different strains of prions that differ in incubation times,
symptoms, and severity of illness.
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- The researchers came to the conclusion
by studying two different human prion types that result in subtypes of
CJD. There are four different types of CJD, including a new variant that
has appeared in young adults in recent years in the UK and France, and
is believed by some experts to be linked to consumption of cattle infected
with bovine spongiform encephalopathy.
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- Wadsworth's team studied types 1 and
2 of classical CJD -- rare disorders that tend to strike in middle-age
or later, causing dementia, muscle wasting, and involuntary movements.
Type 1 tends to be more aggressive and death often occurs about 2 months
after symptoms begin, while people with type 2 tend to survive for about
8 months.
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- In laboratory studies, the researchers
found that one prion type could be converted into another in the presence
of the copper or zinc ions.
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- The finding has "widespread implications"
for both the classification and the study of prion diseases in humans and
animals, the authors conclude.
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- SOURCE: Nature Cell Biology 1999;1:55-59.
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