Stem cell transplants may someday be used to treat Parkinson's disease. Researchers are hopeful that these cells would alleviate the symptoms of Parkinson's disease by

Researchers are hopeful that these cells would alleviate the symptoms of Parkinson's disease by secreting the neurotransmitter dopamine.

Explanation:

Dopamine is a neurotransmitter released by the brain that plays a role in pain processing at various levels of the central nervous system. This includes the spinal cord, periaduectal gray matter, the thalamus, the basal ganglia, the insular cortex, and the cingulate cortex. Low dopamine levels are associated with the painful symptoms that frequently occur in Parkinson's disease. Parkinson's is generated from a neurodegenerative disorder that mainly affects dopaminergic neurons, responsible for producing and secreting dopamine within the brain. When these neurons degenerate, dopamine levels decrease and the consequences are tremor, muscle stiffness and difficulty making voluntary movements, among others.  In Parkinson's disease, there is a loss of dopaminergic neurons and a potential treatment would be that the lost neurons could somehow be replaced. One possibility is to transplant stem cells that differentiate into dopamine-producing nerve cells.

Explanation:

The law of conservation of mass or principle of mass conservation states that for any system closed to all transfers of matter and energy, the mass of the system must remain constant over time, as the system's mass cannot change, so quantity can neither be added nor be removed.