In what could be a major breakthrough in the race for a Parkinson's disease cure, researchers announced this week that embryonic stem cells injected into the brains of rats with the disorder helped alleviate symptoms. Harvard Medical School researchers and doctors at McLean Hospital in Massachusetts found that embryonic cells injected into infected rats converted to neurons that make dopamine, a chemical Parkinson's sufferers lack. The process reportedly took nine months.

According to researchers, blood flow was restored to damaged areas of the brain and Parkinson's plagued rats that previously turned "aimlessly in their cages" returned to normal. Scientists warned, though, that five rats developed brain tumors, a side effect that researchers must resolve before human testing can begin.

Research involving embryonic stem cells may hold the key to curing Alzheimer's, diabetes, and the rejuvenation of ailing organs.