BBC
Parkinson's patients have changes in their
brains
A commonly-used
organic pesticide produced symptoms similar to Parkinson's disease
when small amounts were injected into rats over time.
It adds weight to theories that repeated exposure to low levels
may also be causing cumulative damage to the human brain.
The pesticide
Rotenone, frequently used as an insecticide and as a method of
killing fish, is considered relatively benign compared to many
commercially-available chemicals.
But scientists
now believe it interferes with cells in the brain which produce
a chemical called dopamine.
Lack of dopamine
produces the well-known Parkinsonism symptoms such as tremor,
rigidity and difficulty moving.
The loss of
these key brain cells is presently irreversible, and worsens over
time, eventually leading to death.
The cause
of Parkinson's Disease is largely unknown, with cases appearing
sporadically and apparently at random, leading some scientists
to think it could be caused by long-term exposure to environmental
toxins.
Because of
the current lack of knowledge about the origins of the illness,
the only acknowledged risk factor is age - the older you are,
the more likely you are to get it.
Approximately
1% of people over the age of 65 develop the illness.
To test this,
Dr Tim Greenamyre from the Emory University in Georgia, US, administered
Rotenone intravenously over a period of weeks to rats.
Physical
symptoms
Not only did
the rats develop some of the physical symptoms of Parkinson's,
but scans revealed actual changes in their brains which appear
similar to changes in the brain of a Parkinson's patient.
The research
was published in the journal Nature Neuroscience.
The team believes
Rotenone may be causing cell components called mitochondriae to
release damaging molecules called free radicals, which go on to
affect the dopamine-producing brain cells.
Professor
Adrian Williams, chairman of the medical advisory panel of the
Parkinson's Disease Society, said it was possible that pesticides
did cause Parkinson's in some patients - but the likelihood was
it was only a small minority.
He said it
was possible a minority of patients had a genetic make-up which
made them more vulnerable to the effects of pesticides than normal.
He told BBC
News Online: "It is unlikely that all cases of Parkinson's
are caused by pesticides, but it may be that one or two in every
hundred are.
"It would
be wrong to expect that a condition such as Parkinson's is caused
by a single factor."
Prof Williams
also warned of the dangers of drawing conclusions based on experimental
research on animals.
Separate research,
published in the journal Science, supports the theory that this
type of damage is behind the development of Parkinson's.
A team from
the University of Pennsylvania School of Medicine has identified
a protein which, when damaged by free radicals, could trigger
the onset of Parkinson's.
When the physical
brain changes associated with Parkinson's were examined, a protein,
called alpha-synuclein, was found in an altered state there, but
not elsewhere.
This change
to the protein could have been caused by free radicals.
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