A team of surgeons at Scripps Clinic and Research Foundation in San Diego said they will begin treating Parkinson's disease with an experimental form of brain surgery. On Sept. 8, Scripps surgeons are scheduled to remove an adrenal gland from a 63-year-old man's flank and transplant it to his brain. A spokesman for the surgical team said the procedure, pioneered by doctors at Centro Medico La Raza in Mexico City, has resulted in dramatic improvement for most patients. Parkinson's disease is caused by a deficiency of the brain hormone dopamine, which helps transmit messages between brain cells. The adrenal gland produces dopamine, and researchers hope that by transplanting all or part of an adrenal gland to the brain they might make it possible for more dopamine to reach the brain cells.