(From News-Medical.net). Researchers are getting closer to demonstrating a gene therapy for Parkinson's disease: "Parkinson's disease is caused by the death of brain cells that produce a vital chemical known as dopamine, which carries messages that tell the body how and when to move. In tests with 31 monkeys, including a control group, scientists inserted copies of a gene to produce [the protective protein] GDNF into a region in the front part of the brain called the striatum. They then induced Parkinson-like conditions by introducing a drug to destroy the dopamine-producing cells. Seventeen weeks after that, not only did the GDNF-treated monkeys show improvement in performing tasks, analysis of brain tissue showed the animals' dopamine systems were actually spared by the treatment."