MADISON, Wis. -- Stem cell scientists at the University of Wisconsin-Madison will use a $7 million grant from the National Institutes of Health to study rats with Lou Gehrig's disease.

About 30,000 Americans have the disease, also known as ALS. The disease usually causes death within a few years of diagnosis because it weakens the muscles to the point that sufferers can't breathe.

Scientists will inject stem cells into the brains of rats with the disease to see whether the cells improve muscle control and breathing.

The scientists will run tests using both fetal and embryonic stem cells.