Parkinson's disease, a degenerative brain disorder, affects an estimated 0.25-0.50% of the population. Symptoms result from neuronal degeneration in the nigrostriatal dopaminergic pathway and include tremor, rigidity and gradual slow- ness of spontaneous movement. The cause of Parkinson's disease is only partially understood; both environmental factors and a genetic predisposition have been im- plicated in its etiopathogenesis. Neural transplantation is being used experimentally for providing an alternative biological source of dopamine both in animal studies and in experimental clinical...