BLACKSBURG - The U.S. Army recently awarded Virginia Tech researchers additional money to study whether a combination of stress and exposure to uranium from military ammunition could cause some of the myriad health problems affecting veterans of the first war in Iraq.

The U.S. military as well as some NATO forces frequently use depleted uranium in armor-piercing ammunition because of its density. Although far less radioactive than natural uranium, which is used for nuclear weapons and fuel for nuclear power plants, depleted uranium can still pose a health risk to those who come into direct contact with it. Environmental groups and some health advocates claim that exposure to depleted uranium - whether in the form of radioactive dust ingested after detonation, in the form of shrapnel in the body or through contact with spent munitions and their targets - could be causing Gulf War Syndrome, the name given to the assorted health problems suffered by veterans of the first Gulf War.

Others have said depleted uranium ammunition caused a rise in cancer rates and birth defects among Iraqi citizens. Medical studies have offered conflicting results on the potential dangers of depleted uranium, but research into the subject is intensifying.

Researchers at the Virginia-Maryland Regional College of Veterinary Medicine in Blacksburg have been testing depleted uranium's effects of laboratory rats for the past several years. The Tech team is paying particular attention to the toxicity of the uranium and whether stress - often in the form of forced swimming - affects the rats' reaction to heavy metal.

Bernie Jortner, a professor in the vet school's Department of Biomedical Science and an expert in neurotoxicity, said rats in one study who received an injection of a soluble uranium and were stressed once showed reduced motor activity skills for several days.

They also exhibited kidney damage and changes in levels of dopamine, a neurotransmitter essential to healthyfunction of the central nervous system.

But the rats' motor functions returned after the kidneys repaired themselves a week later, making it difficult for the researchers to determine whether it was the uranium directly or the kidney damage that affected the rats.

Jortner said the meaning of the dopamine changes is as yet unclear - pointing out, however, that reduced dopamine levels are associated with Parkinson's disease.

The Army recently extended a second study by Jortner and his two principal colleagues, Tech's Marion Ehrich and the University of Florida's David Barber, in which uranium pellets are implanted in rats to simulate shrapnel. These rats are kept longer and stressed more often.

Jortner said the second study is much more complex and comprehensive. "We'll have much more data ... and be much closer to the situation" faced by soldiers wounded by depleted uranium ammunition, Jortner said.

To date, the Army has invested in excess of $1 million in the research programs.