They're not made immediately better, but they improve over time as the graft matures. Schumacher stressed that the transplant results are only preliminary. It's very early. It's like the little Wright brothers' plane has gotten off the ground. More than a half-million Americans have Parkinson's, which produces such symptoms as tremors, rigidity and slowing of movement.
Medicines can help, but often lose effectiveness over time.
So scientists have been looking at ways to fix the basic problem, which is a deficit of a chemical messenger called dopamine in a particular part of the brain. For a decade, scientists have been studying transplants of human fetal brain cells into patients' brains. The cells pump out dopamine. But using human fetal tissue is controversial, and Schumacher said it's also logistically hard to round up enough fetal brain cells of just the right age to work. So he and colleagues have turned to pig cells, doing the first transplant three years ago.