New therapies involving transplants of stem cells, the body's master cells from which all tissues grow, have been slowed by federal funding restrictions on experiments using embryonic tissues. These rare cases probably are caused by inherited genetic abnormalities. However, most patients show their first Parkinson's symptoms after age 60. Researchers believe that older patients may have suffered brain damage from chronic exposure to unspecified toxins. In the experiment conducted at Emory University in Atlanta, neurologists implanted tiny pumps in the rats to continuously administer low doses of rotenone through the jaguar vein for as long as five weeks.
Rotenone is an organic product made from extracts of tropical plants.
It is widely used as an agricultural pesticide and to kill unwanted fish in reservoirs. People most frequently would be exposed to rotenone by ingesting residue in food or by handling the compound. Scientists acknowledged the pump method used in the experiment did not duplicate rotenone exposure in the real world, but said it was a more direct and reliable method for research purposes. Half of the rats gradually showed Parkinson's symptoms. Examination revealed that large numbers of dopamine-producing cells in the rats' brains had died or were damaged.