these cells die, less dopamine is produced, therefore leading to the movement difficulties associated with Parkinson's. (Stem Cells: Scientific Progress and Future Research Directions, 2001, p. 80)
             Over the last ten years, scientists have been experimenting with transplanting neuronal cells from a donor to a Parkinson's infected patient; however, this method has had limited success. Obtaining the significant number of cells needed for implantation is extremely difficult and often unlikely. (Chemistry & Industry, No. 5, p. 133) Researchers are hoping to find in stem cells a renewable source that can operate as dopamine neurons. As of now, laboratory-grown cells derived from stem cells are the best potential source. One way to get these cells to the point of dopamine production is to find the right combination of growth factors and cell-culture conditions where they are committed to being dopamine neurons and then injecting them directly into the brain. Another method is to place less committed cells into a damaged brain and rely on "environmental" signals to guide the cell into becoming a dopamine neuron. (Stem Cells: Scientific Progress and Future Research Directions, 2001, p.83) The present research has shown that both human fetal cells and embryonic stem cells can become fully functional dopamine neurons; however, whether adult stem cells will have a similar effect is presently unknown.
             Researchers of Parkinson's disease are also searching for a way to ignite the stem cell repair mechanisms already in a patient's brain to fix the problems the mechanisms couldn't otherwise manage. In a study conducted by James Fallon and colleagues, it was discovered that injecting a protein called transforming growth factor (TGFa) will trigger the brain's repair process, which is otherwise not triggered by a slowly developing degenerative disease like Parkinson's. (Stem Cells: Scientific Progress and Future Research Directions, 2001, p....