VOA常速英语:Gene therapy to treat Parkinson's disease

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U.S. researchers are using gene therapy to treat the neurological condition Parkinson's disease, and they say the results so far are promising. VOA's Jessica Berman reports.

Successful gene therapy to correct a host of devastating diseases has been elusive. But researchers may have gotten a step closer with a treatment for Parkinson's disease, the second most common neuro-degenerative condition after Alzheimer's disease.

Neurologist Michael Kaplitt at the Weill College Medicine at Cornell University in New York says Parkinson's limits the ability of patients to move, and the gene therapy helped them to move.

"The symptoms are tremors and stiffness, freezing, you know, muscle stiffness," he said. "So, when you put that all together as sort of a composite, we saw there was a significant improvement in these patients over time that lasted for the full one year of the study."

Kaplitt says there is a group of cells in the region of the brain that controls movement through production of a chemical called dopamine. In Parkinson's disease, Kaplitt says, the cells stop producing dopamine and the movement control center becomes hyperactive.

In the onset of the disease, Parkinson's symptoms can be quieted with drugs that replace dopamine. But as the disease progresses, the drugs make the symptoms worse. So, Kaplitt and colleagues decided to try to bypass the dopamine-producing cells to see if they could alter regulation of movement at a higher brain level.

Researchers developed a therapy in which they attached a modified gene to viral particles and infused the treatment into one side of the brain of 12 participants with varying degrees of Parkinson's symptoms.

The gene, called GABA, helps in the production of a chemical that has a calming effect over a wider area of the brain.

Kaplitt says investigators were hoping for lasting results.

"The idea was, with a single surgery at a single site, putting in this one gene there, that you would create a little factory that would essentially reestablish the normal neuro-chemical balance of a large part of this circuit to normalize the flow of information to the rest of the brain and thereby hopefully improve symptoms," he explained.

Kaplitt says it took three months for the therapy to kick in, but once it did, most patients showed significant improvement of their symptoms up to one year after the therapy. He says for some patients, the improvements were not as marked or did not last as long.

The study was completed in May 2006 and its results were published in the latest issue of The Lancet.

A larger trial is being planned.

elusive :difficult to define or describe（难以定义的；难以描述的）