From: Robina Suwol
Date: 21 Sep 2001
Remote Name: 18.104.22.168
--David Wallinga, M.D.
Excerpt: "ESSENTIALLY three lines of evidence have led researchers to believe that chemical exposures, particularly to pesticides, play a role in some cases of Parkinson's. One is that people who live in farming areas, especially those who drink well water, and have a history of exposure to pesticides are more likely to contract Parkinson's. Another is that several studies have shown that those who die of Parkinson's disease have higher levels of organochlorine pesticides in their brains than the general population. A third is that in the early 1980s, a group of young people developed Parkinson's symptoms after taking an illegal drug called MPTP (1-methyl-4-phenyl-1,2,3,6- etrahydropyridine), whose structure is similar to meperidine, trade named Demerol. The structure of its metabolite MPP+ is also similar to the pesticide paraquat."
----------------------------------------------------------- GOVERNMENT September 17, 2001 Volume 79, Number 38 CENEAR 79 38 pp. 35-37 ISSN 0009-2347
THE ENVIRONMENT AND PARKINSON'S If exposure to chemicals causes this dread disease, regulators may have to alter approaches to neurotoxicity testing and risk assessment
BETTE HILEMAN,C&EN WASHINGTON
The number of people with Parkinson's disease in the U.S. will surely rise as the population ages. Already, more than a million people, about 1% of the population over age 60, live with the disease. Despite years of effort, neither definitive causes of the disease nor effective long-term treatments have been found. Research efforts are increasing, however, and work on the combination of inheritance, age, and environmental exposures implicated in Parkinson's is starting to come together for a clearer picture--one that might ultimately alter regulations of some chemicals.
A conference held late last month in Colorado Springs made it clear that such research into causes and treatments for Parkinson's disease has reached an exciting stage of development. "A new optimism that Parkinson's can be defeated is energizing the research community," said meeting organizer Joan M. Cranmer of the department of pediatrics at the University of Arkansas for Medical Sciences (UAMS).
The meeting was sponsored by UAMS with support from the National Institute of Environmental Health Sciences (NIEHS), the Environmental Protection Agency (EPA), the Centers for Disease Control & Prevention (CDC), the Parkinson's Institute, and several other foundations and corporations. It brought together scientists from a wide variety of disciplines--toxicologists, chemists, neurologists, geneticists, epidemiologists, and clinicians.
PARKINSON'S DISEASE is a progressive, incurable ailment, and the second most common neurodegenerative disorder in the U.S. It begins when a class of brain cells that produce dopamine start to die. Symptoms become apparent only after 60 to 80% of the cells are dead. The disease is characterized by resting tremor, rigidity, slow movement, postural instability, and progressively involuntary writhing movements, paralysis, and an inability to talk or even swallow. Dopamine is a chemical messenger that helps control muscles. Although the medication levodopa--a dopamine precursor--relieves many Parkinson's symptoms, its effectiveness declines as the disease progresses.
Speakers explained that many scientific pieces of the Parkinson's puzzle have been identified. "But assembling the elements into a coherent theory of the cause of Parkinson's disease still remains a major challenge," said J. William Langston, scientific director and founder of the Parkinson's Institute.
NIEHS Director Kenneth Olden announced at the meeting an NIEHS initiative that may accelerate progress in the field--a Consortium Centers Program. It will provide a formal mechanism for interactions between clinicians, basic research scientists, and patient advocates. It will seek to identify and support novel approaches and research ventures that might not otherwise be pursued by scientists working in isolation, he said.
Only about 10% of Parkinson's cases are familial--that is, clearly caused by genes. The remainder result from unknown factors such as insults from the environment or some interaction between genetic susceptibility and the environment. "Parkinson's disease appears to arise from the interaction of three events--the patients' inherited genetic susceptibility, their subsequent environmental exposures, and their age," Olden said at the meeting.
WHATEVER THE CAUSE, Parkinson's is found in every country and very little is known about incidence patterns over time, said Caroline M. Tanner, director of clinical research at the Parkinson's Institute.
In addition to Parkinson's disease, there is a condition called Parkinsonism that resembles Parkinson's. Parkinsonism is sometimes caused by exposure to manganese, carbon monoxide, or other toxicants and, unlike Parkinson's, is often reversible, Tanner said.
Several speakers at the meeting pointed out that regulators may need to alter their approaches to neurotoxicity testing and risk assessment because of evidence that some kinds of chemical exposures in the womb, during early childhood, or later may increase susceptibility to Parkinson's in old age. Under current government guidelines for two-generation assays, lab rodents are sacrificed at 60 days, long before susceptibilities induced in early life could result in the types of illnesses that might show up during the equivalent of a rodent's old age--1.5 to 2 years.
"Relatively little research has focused on adult or aging animals which may be differentially sensitive to toxicants due to a history of prior exposure," said Virginia C. Moser, toxicologist at the EPA National Health & Environmental Effects Research Laboratory in Research Triangle Park, N.C. Research on rodents during old age is critical to understanding the potential influences of exposures in early life, she said.
ESSENTIALLY three lines of evidence have led researchers to believe that chemical exposures, particularly to pesticides, play a role in some cases of Parkinson's. One is that people who live in farming areas, especially those who drink well water, and have a history of exposure to pesticides are more likely to contract Parkinson's. Another is that several studies have shown that those who die of Parkinson's disease have higher levels of organochlorine pesticides in their brains than the general population. A third is that in the early 1980s, a group of young people developed Parkinson's symptoms after taking an illegal drug called MPTP (1-methyl-4- henyl-1,2,3,6-tetrahydropyridine), whose structure is similar to meperidine, trade named Demerol. The structure of its metabolite MPP+ is also similar to the pesticide paraquat........
(full article) http://pubs.acs.org/email/cen/html/091801045059.html