Research News from the College of Veterinary Medicine
Excerpted from stories by Jim Barlow, UI News Bureau

Heavy consumption of tainted fish curbs adult learning and memory
Since 1992, researchers, led by Dr. Susan Schantz, veterinary biosciences, have studied Lake Michigan fish-eaters, many of whom regularly had eaten more than 24 pounds of sport-caught fish a year. The researchers' latest findings show that the heavy eaters who are now over age 49 have problems learning and remembering new verbal information.

"This study suggests, for the first time, that PCB body burdens in adulthood may be associated with impairments in certain aspects of memory and learning," Dr. Schantz says. "The focus has been almost exclusively on increased health risks of exposure to children and pregnant women. It had been assumed that mature adults are less susceptible than are developing fetuses. This may not be the case."

PCBs were widely used—until banned in the late 1970s—as electrical insulators and lubricants and as extenders in paints and varnishes. The chemicals decompose slowly and are virtually non-biodegradable. Large quantities remain in older electrical equipment still in use. In the Great Lakes, PCBs make their way up the food chain and accumulate at increasing levels in fatty tissue.

The findings were reported in the June 2001 issue of Environmental Health Perspectives, a journal of the National Institutes of Health. The study also found elevated levels of DDE (a breakdown product of DDT), lead, and mercury in the heavy fish-eaters, but the only negative effects were tied to blood serum levels of PCBs.

Fish-eaters with high blood PCB levels had difficulties recalling a story told just 30 minutes earlier. They also were less likely than their less-exposed peers to cluster words given orally into categories based on their meaning to boost recall, says Dr. Schantz.

Collaborators in the study were from Michigan State University, the State University of New York at Albany, and the University of Texas Health Science Center at Houston.

Newly found estrogen role in males might lead to contraceptive for men
Researchers tapping into the estrogen pathway that regulates fertility in males have found two independent roles of the hormone, and they may have uncovered a new approach for developing a male contraceptive.

Dr. Rex Hess, veterinary biosciences, and colleagues discovered that estrogen regulates fluid reabsorption in the male reproductive tract by triggering a protein involved in sodium transport. They also found that estrogen sustains the morphological architecture of the efferent ductules.

"We were not expecting this second role of estrogen," says Dr. Hess. "This structure-sustaining role appears to be independent of estrogen's molecular function of regulating ion transport. This tells us that estrogen is important for the expression of other genes with distinct physiological and morphological functions."

The overlay of the double staining of estrogen receptors a and b shows why the efferent ductule makes a likely target for a male contraceptive.

Dr. Hess and colleagues had documented in 1997 that estrogen was vital for fluid reabsorption during the transfer of sperm in fluid from the testis through the efferent ductules to the epididymis, where sperm matures and is stored. Their latest publication provides a molecular picture of what estrogen does.

Efferent ductules are small tubes that produce concentrated semen. In a series of experiments using mice lacking the estrogen receptor or proteins thought to be regulated by estrogen, the scientists showed that when sodium transport did not occur, excess fluid diluted the sperm, leaving mice infertile. However, when the estrogen receptor was present, epithelial cells were normal in appearance, even when sodium transport was abolished in the mice lacking the protein NHE3.

Hess and colleagues discovered that NHE3, which is responsible for the transport of sodium into and out of cells, was directly responsible for luminal fluid reabsorption under estrogen regulation. "Thus, blockage of the estrogen receptor could provide a new target for developing the perfect contraceptive in the male," Dr. Hess says.

The work was reported in the Proceedings of the National Academy of Science. Co-authors were veterinary biosciences research specialists Rong Nie and Kay Carnes and Dr. Benita S. Katzenellenbogen of the University of Illinois College of Medicine at Urbana-Champaign.

Other contributors were from the University of Missouri at Columbia, the University of Arizona Health Sciences Center, the University of California at San Francisco, and the Human Reproductive Sciences Unit in Edinburgh, Scotland.

The National Institutes of Health and Kenneth A. Scott Charitable Foundation funded the work.