Doctors reported that by extracting dopamine-producing neurons from aborted fetuses and injecting them into the brain to replace neurons destroyed by the disease, they were able to restore some patients' mobility. New studies reveal that fetal neuron implants can survive a decade or more but in some cases appear to acquire signs of Parkinson's disease, a surprising finding that could shed light on the disease's mechanisms. Studies found that many transplanted cells were apparently alive and well integrated in the patients' brains. But in certain cases it was found that a small proportion of the surviving cells showed a hallmark of Parkinson's pathology, clumps of protein containing alpha-synuclein and ubiquitin. Differences in surgical techniques or differences in the patients' immune reactions to the transplanted fetal cells might be important factors.