From AJC.com: "More than a million Americans who suffer from the debilitating neurological disorder Parkinson's disease are likely to be among the first to benefit from promising advances in embryonic stem cell research ... We want to replenish the population of nerve cells that are dying in the brains of Parkinson's victims. The encouraging recent scientific finding is that human embryo [embryonic] stem cells can be grown into the specific dopamine neuron that dies in Parkinson's, and we know that it can be transplanted and restore function in animal models [rats]. ... "If we manage to grow stem cells at will, we could have a supply that could help a large number of patients and reconstitute their [brain] circuitry."
Link: http://www.ajc.com/news/content/news/stories/2006/10/16/1017brains.html