Doctors at the University of Pittsburgh Medical Center said they have performed the first transplant of human nerve cells into a patient's brain in an effort to reverse paralysis and other effects of stroke. The procedure involves a novel technique for manufacturing human neurons. If it proves safe and effective, researchers say it could set the stage for new treatments not only of the debilitating effects of stroke, but also of other neurological disorders, such as Parkinson's disease and spinal cord injury.