GENE THERAPY USED TO TREAT PATIENT WITH PARKINSON'S
Gene therapy is used for first time to treat patient with Parkinson's disease; procedure is performed on 55-year-old man; goal is to relieve tremors, shuffling gait and other abnormal movements caused by the disease; Food and Drug Adm has approved procedure for 12 people with severe Parkinson's; experiment is Phase 1 trial, meaning its main goal is to determine safety, not efficacy; hope is that first subjects will show signs that treatment works; Dr Michael G Kaplitt, who performs procedure on Nathan Klein at New York-Presbyterian Hospital, bores hole through top of Klein's skull, then infuses into brain 3.5 billion viral particles, each bearing copy of human gene meant to help relieve symptoms of Parkinson's; some leading experts in gene therapy and Parkinson's express concern, noting that experiment is going forward without evidence in monkeys that it could work; cite possibility of harm from viruses spreading in brain; photo (M)