11.   With that disease, Langston said, patients need not just nerve cells but brain cells that will make the nerve chemical dopamine.

12.   Without them, the brain cannot produce enough of a chemical called dopamine, a messenger that transmits signals within the brain.

13.   Just like the native brain cells they joined, the transplanted cells gained the ability to signal neighbors with bursts of the chemical dopamine.

14.   One brain cell signals another by releasing the chemical dopamine, which then attaches to receptors on the receiving cell.

15.   The disease involves gradual deterioration of nerve cell clusters that make the chemical dopamine, which helps control muscle movements.

16.   The work focused on a brain system in which brain cells signal each other by releasing bursts of a chemical called dopamine.