(Press-News.org) New data offer hints to why Parkinson's disease so selectively harms brain cells that produce the chemical dopamine, say researchers at Washington University School of Medicine in St. Louis.
Dopamine is involved in brain cell communications including the signals that control movement. As Parkinson's kills the dopamine-producing cells, patients begin to develop tremors, problems moving and other symptoms.
The new research shows that a drug known to damage dopamine-producing nerve cells and mimic Parkinson's disease does so by rapidly damaging cellular energy generators called mitochondria. This damage impairs the ability of mitochondria to circulate around the cell as they normally would. As a result, axons, the extended arms nerve cells use to send messages, wither; a few days later, the body or main portion of the cell also dies.
"Much of the research into Parkinson's disease treatments is focused on saving the bodies of these cells, but our results suggest that keeping axons healthy also is essential,"says Karen O'Malley, PhD, of Washington University School of Medicine in St. Louis. "When axons die back, dopamine is no longer delivered to the neurons that need it. The cell body also has fewer connections to other cells, and it needs those connections to survive."
The results were published May 11 in The Journal of Neuroscience.
Many processes and facilities for cellular maintenance are in the body of the nerve cell, and their products sometimes have to travel a significant distance to reach the axon's end.
"If you think, for example, about one of your peripheral nerves, the cell body is located in the spinal column, but some of the axons extend as far as your big toe," says O'Malley, professor of neurobiology. "That's like the cell body sits in an office in St. Louis and the end of the axon is in Chicago."
O'Malley compares the axon's system for transporting supplies to a railroad. Mitochondria are part of the railroad's cargo. They supply the energy that allows the axon to do its work.
For the study, O'Malley gave cultured mouse nerve cells a toxin called MPP+ that causes Parkinson's-like symptoms.
"MPP+ is a derivative of a synthetic form of heroin developed in California in the early 1980s," O'Malley says. "It came to scientists' attention when teenage abusers of the drug went to the hospital with Parkinson's disease symptoms."
O'Malley found that the toxin stopped the movement of mitochondria in the axon in 30 minutes. The railroad still functioned, shipping other cargo to the end of the axon. But most mitochondria either stopped moving or were headed for the cell body instead of the axon.
O'Malley suspected that this meant the mitochondria were damaged by the changes caused by the toxin and being shipped back to the cell body for repair. Additional tests supported this theory, showing that the mitochondria had lost their ability to maintain their membrane potential, a measure of mitochondrial fitness.
The specificity of this toxin for dopamine-producing cells is reinforced by the finding that other types of nerve cells did not have problems transporting mitochondria after toxin exposure. In a comparison between different nerve cell types, O'Malley found mitochondria in dopamine-producing nerve cells are smaller in size and travel three times slower. But she can't yet definitively say that these distinctions play a role in the problems caused by the toxin.
Scientists screened several compounds to see if they could block the toxin's effects. Only two antioxidants worked, glutathione and N-acetyl cysteine. The latter compound has already been shown to be effective in animal models of Parkinson's disease and is used as a treatment for other disorders in patients.
O'Malley is currently studying whether two genes linked to Parkinson's disease affect mitochondria damaged by the toxin.
"We're going to continue to look for specific differences in these cells that might help scientists develop better treatments," O'Malley says.
###
Kim-Han JS, Antenor-Dorsey JA, O'Malley KL. The Parkinsonian mimetic, MPP+, specifically impairs mitochondrial transport in dopamine axons. The Journal of Neuroscience, May 11, 2011.
Washington University School of Medicine's 2,100 employed and volunteer faculty physicians also are the medical staff of Barnes-Jewish and St. Louis Children's hospitals. The School of Medicine is one of the leading medical research, teaching and patient care institutions in the nation, currently ranked fourth in the nation by U.S. News & World Report. Through its affiliations with Barnes-Jewish and St. Louis Children's hospitals, the School of Medicine is linked to BJC HealthCare.
Disruption of nerve cell supply chain may contribute to Parkinson's
2011-05-13
ELSE PRESS RELEASES FROM THIS DATE:
AAPS national biotechnology conference to highlight breakthrough cancer treatments
2011-05-13
ARLINGTON, VA (May 3, 2011) – Cancer studies from Mercer University (Ga.) headline groundbreaking research that will be unveiled at the American Association of Pharmaceutical Scientists' (AAPS) National Biotechnology Conference (NBC). The conference takes place Monday, May 16 -Wednesday, May 18 at the Hilton San Francisco Union Square.
Developing an Oral Vaccine for Cervical Cancer
Cervical cancer is the second most common cancer among women in the world . Two preventative vaccines are currently available, but are expensive, require complex storage, and trained personnel ...
Prompt Proofing Blog Post: How to Improve Your Writing - Part 6
2011-05-13
This is the last of a six-part series on improving your writing style. Whether you write for business or academic purposes, there are a few golden rules that will help you sharpen up your prose.
Part 6 - Adjust your style to fit your audience
"Well, duh!", I hear you say; unfortunately this is not as obvious as it might seem. Basic rule of thumb: professional documents require a professional writing style whereas informal documents allow you to be more relaxed. That said, if an informal document is being written in a professional or business related environment, ...
Photosynthesis or photovoltaics: Weighing the impact
2011-05-13
Which is more efficient at harvesting the sun's energy, plants or solar cells? This salient question and an answer are the subject of an article published in the May 13 issue of the journal Science.
Although both photosynthesis and photovoltaics harvest energy from the sun, they operate in distinctly different ways producing different fuels. It is not a simple task to find common ground between the two in order to compare energy conversion efficiency.
"In order to make meaningful comparisons between photosynthesis (which provides stored chemical potential) and photovoltaic ...
Henry J. Miller, III Appointed Managing Director at Locust Capital Management
2011-05-13
Locust Capital Management is proud to announce the appointment of Henry J. Miller III, "Doc" as a Managing Director. Mr. Miller's responsibilities include Sales, Marketing, and Relationship Management for the firm. Prior to Locust Capital Mr. Miller was President of Miller & Company, LLC, a strategic Investment Consultant to institutional investors and Asset Management companies. Mr. Miller has held senior leadership positions with Wachovia Wealth Management, Neuberger Berman, Mellon Financial, CoreStates Bank, and Fidelity. Mr. Miller's Clients have included ...
States vary in children's health, gaps exist in insurance, quality care across sectors
2011-05-13
PORTLAND, Ore. — A comprehensive report based on the National Survey of Children's Health conducted by children's health researchers at Oregon Health & Science University and the Maternal and Child Health Bureau finds insurance duration, consistency and adequacy, and the corresponding access to health care, are lacking for many U.S. children and have a detrimental effect on their health and well-being.
The researchers cite a need for improvement in all states, with wide variations across states that can inform improvement efforts. The results especially support national ...
Study finds youth-mentor relationships particularly helpful for those experiencing hardship
2011-05-13
Athens, Ga. – In a time of transition for rural African-American young adults, natural mentors in the community help them stay focused on their goals and avoid potential difficulties associated with emerging adulthood, according to findings from an ongoing University of Georgia study.
The study, published in the early online edition of American Journal of Community Psychology, is part of a broader research program called the Adults in the Making project, which is aimed at helping rural African Americans transition to adulthood. The researchers found that behaviors such ...
The power of placebos
2011-05-13
This press release is available in French.
They may be uncomfortable talking about it, but it's definitely going on.
A recent survey, led by McGill Psychiatry Professor and Senior Lady Davis Institute Researcher Amir Raz, reports that one in five respondents – physicians and psychiatrists in Canadian medical schools – have administered or prescribed a placebo. Moreover, an even higher proportion of psychiatrists (more than 35 per cent) reported prescribing subtherapeutic doses of medication (that is, doses that are below, sometimes considerably below, the minimal recommended ...
Pets Best Insurance Reimburses Over $2,300 on Rattlesnake Bite Claim
2011-05-13
Pets Best Insurance says it has seen an alarming trend in the number of snakebite claims in the past few years--and the most notable claim of the season so far was for a dog who was bitten on the tongue by a rattlesnake in early April.
Although this dog's owner had pet insurance, many owners end up incurring huge costs for snake bites.
That's why the company wants to remind pet owners to practice caution when outdoors with pets this spring--as rattlesnake season is now in full swing.
President and Founder of Pets Best Insurance, Dr. Jack Stephens, said the bites ...
University of Alaska Fairbanks installs ocean acidification buoy in Alaska waters
2011-05-13
A new set of buoys in Alaska waters will help scientists understand how climate change may be affecting the pH level of northern seas. Researchers placed the first buoy last month.
"This is the first dedicated ocean acidification mooring to be deployed in a high-latitude coastal sea," said Jeremy Mathis, principal investigator for the project and an assistant professor of chemical oceanography at the University of Alaska Fairbanks. "Other moorings have been deployed with ocean acidification sensors, but this is the first complete package in Alaska."
The first buoy is ...
Findings could lead to a blood test for lung cancer
2011-05-13
COLUMBUS, Ohio – Researchers have identified characteristic patterns of molecules called microRNA (miRNA) in the blood of people with lung cancer that might reveal both the presence and aggressiveness of the disease, and perhaps who is at risk of developing it. These patterns may be detectable up to two years before the tumor is found by computed tomography (CT) scans.
The findings could lead to a blood test for lung cancer, according to a researcher with the Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research ...