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dicofol spill in 1980, there has been a 90- percent reduction in the number of juve- nile alligators at the lake. And in a popula- tion of animals that can live to be 60 years old, that's not healthy, he says. A nother reluctant toxicologist, Brent Palmer of Ohio University in Athens, has begun studying a sub- stance in the blood of egg-laying verte- brates that he suspects will one day prove a sensitive biomarker of exposure to estrogenic pollutants, at least in males. It's vitellogenin, the egg-yolk protein. When stimulated by estrogen, the liver produces this protein, then dumps it into the blood. From there it circulates to the ovaries, where it is deposited in an egg. Though males can produce vitellogenin, usually only females possess sufficient estrogen to do so. That's good, Guillette points out, be- cause "if you have enough estrogen in a male to turn on vitellogenin, then you probably have enough to shut off the normal functioning of the testes" Working with the red-eared slider, America's most common turtle, Palmer has demonstrated that DDT can turn on vitellogenin production in males. But DDT doesn't elicit the same broad suite of changes that estrogen does. For instance, it fails to trigger the liver's production of two other proteins and it turns on the production of some other substances that estrogen doesn't. "So even though DDT is mimicking estrogen in some ways," Pal- mer points out, "it's not exactlythe same." "Certainly, if we can find vitellogenin in males in the wild, that's a sign they've been exposed to an environmental estro- gen," he says. How- ever, Palmer is not yet sure whether the converse also holds: that the lack of vi- tellogenin proves no estrogen was en- countered. He says his new data "make me wonder if there might not still be an environmental estro- gen present, just one that's having some other effect" Indeed, he says, interpreting the lack of vitello- genin "could prove a very sticky problem" Pallid sturgeon, an endangered fish native to the Missouri and Mississippi Rivers. Though most U.S. sturgeons aren't faring well, "there hasn't been any record of reproduction in the pallid sturgeon for 10 years," notes Richard Ruelle of the U.S. Fish and Wildlife Service in Pierre, S.D. Indeed, he says, any pallid sturgeon seen these days are usually 30 to 40 years old. Altering the river - chiefly, damming and straightening its path - has reduced the fish's habitat. But the high concentrations of PCBs and DDT that have been found in some pallid sturgeon have led Ruelle to suspect that environmental estrogens might also be is not a problem jeopardizing its John Sumpter has for 15 years re had to cope with. gonads `aren't The rainbow trout Currently, Ruel and carp that he and in the gonadal his colleagues have confiscated fro studied throughout the waterways of England and Wales have displayed plenty of vitellogenin - even the males. Sumpter and Charles R. Tyler, biolo- gists at Brunel University in Uxbridge, England, collaborated with scientists from Britain's Ministry of Agriculture, EMI's - another environmental feminizer? If electromagnetic fields (EMFs) can affect the amount of estrogen in ani- mals-and their susceptibility to breast cancer (SN: 7/3/93, p.10) - might they also alter the fetal development of a male? Two studies investigating the topic suggest the answer may be a qualified yes. Robert F. McGivern of Harbor-UCLA Medical Center in Torrance, Calif., and his co-workers exposed pregnant rats to low-level, pulsed magnetic fields twice daily for six days during the period when the fetal brain is undergoing sex- ual differentiation. In the January 1990 TERATOLOGY the team reported finding that these low-frequency (15 hertz) pre- natal exposures demasculinized the scent-marking behavior of mature males. The study was notable for another reason, asserts McGivern, now at San Diego State University. Prenatal expo- sures led to "really huge" testes and prostate glands in the adult animal. The researchers have no explanation for the unexpected effect. In 1972, researchers at the University of Manitoba in Winnipeg conducted a similar experiment. "We exposed male rats chronically to magnetic fields - either pre- or postnatally," notes study leader Klaus-Peter Ossenkopp, now at the University of Western Ontario in London. His team found that "if the rats were prenatally exposed, they devel- oped heavier testicles. If you exposed them as adults, testicle size actually decreased" "The reproductive system of the rat is built like a Sherman tank," McGivern says. As a result, he maintains, "any disruption in the rat becomes interest- ing because the human is usually much more susceptible to the same things." And because EMFs appear capable of altering susceptibility to estrogen-me- diated tumors in female laboratory ani- mals, Ossenkopp asserts, these findings may represent EMFs' male reproductive corollary. Neither group has followed up on the work nor knows of others investigating the reproductive effects of EMFs. reproductive health. Indeed, he notes, searchers have reported that sturgeon distinctly male or female anymore." le is awaiting lab results on vitellogenin tissues saved from sturgeon that were m anglers who caught the fish illegally.. Fisheries, and Food to measure vi- tellogenin concentrations in fish that were caged and suspended for three weeks in the river outfalls of 30 different sewage treatment plants. In the January CHEMISTRY AND ECOLOGY, these researchers describe finding widely varied production of vitellogenin by the fish. However, "in all cases," they say," exposure of trout to effluent resulted in a very pronounced increase (500- to 100,000-fold, depending on the site) in the [blood] plasma vitellogenin concentra- tion" In some cases, male trout exhibited vitellogenin concentrations in their bloodstreams typical of mature females during egg production. Carp showed sim- ilar, though far smaller, increases. Attempts to isolate the agent respon- sible for these increases proved fruitless. However, at least one of the researchers strongly suspected that ethynylestradiol (EE) - the main estrogenic compound in birth-control pills - was responsible for much of the vitellogenin effect they ob- served. He reasoned that women on the pill excreted the EE in their urine and that some share of this chemical may have passed through the water-treatment plants. To test the theory, the researchers incubated fish in aquariums containing dilute concentrations of either estradiol- the animal kingdom's primary estrogen - or EE. Concentrations of EE as low as 0.1 nanogram per liter of water caused a significant spike in the animals' produc- tion of vitellogenin - proving EE "very x a x J T Cn 26 SCIENCE NEWS, VOL.145