Research roundup

30 October 2002 |

Weed killer may affect amphibians worldwide
Native male leopard frogs throughout the nation’s Corn Belt are being feminized by an herbicide, atrazine, used extensively to kill weeds on the country’s leading export crops, corn and soybeans, according to a survey conducted by Berkeley biologists.

The scientists also showed that male leopard frogs raised in laboratory tanks contaminated with atrazine develop egg cells in their testes and essentially turn into hermaphrodites. These sexual abnormalities were observed at atrazine levels as low as 0.1 parts per billion, 30 times lower than the current allowable limit for atrazine in drinking water set by the EPA.

These findings, added to earlier evidence that atrazine demasculinizes two other species of frog, suggest that the herbicide could be a factor in the decline of frogs and other amphibians in the United States and around the world, the authors say. Atrazine has been used on crops since 1956 and currently is the most widely used herbicide in the nation. It is so widespread that it can be found far from agricultural areas and even in rainwater and snow.

“These studies clearly indicate that atrazine is detrimental to amphibians,” says study author Tyrone Hayes, associate professor of integrative biology. Persuaded that atrazine is potentially destroying biodiversity, Hayes is now engaged in studies to determine the ultimate fate of these feminized tadpoles.

Hayes and his colleagues sampled leopard-frog tadpoles in eight separate ponds, ditches, rivers and streams in the Midwest during the summer of 2001 and found feminized male frogs at every site with measurable levels of atrazine. The sites were scattered through the Corn Belt and beyond.

The new experiment, reported in the Oct. 31 issue of “Nature,” is a repeat of earlier experiments using the leopard frog.

“The current data raise concern about the effects of atrazine on amphibians in general and the potential role of atrazine and other endocrine-disrupting pesticides in amphibian declines,” the authors write.
— Robert Sanders

New study explores terrorist-insurance market post-Sept. 11
The collapse of the U.S. terrorist-insurance market after September 11, 2001, was the result of insurance firms’ aversion to covering large-scale catastrophies, according to a new joint study by professors at Berkeley’s Haas School of Business and Santa Clara University’s Leavey School of Business.

The study, “Extreme Events and the Market for Terrorist Insurance,” says that temporary government intervention would both help revive the terrorist-insurance market after an event as extreme as the September 11 attacks and help stabilize affected industries. The real-estate and airline industries were hurt significantly by turmoil in the insurance market after 9/11.

Even as insurance premiums skyrocketed after September 11, coverage was severely limited or cancelled, leaving “trophy” office buildings without required coverage and potentially disrupting new construction projects. Yet the insurance industry had sufficient reserves to cover the insured losses — in excess of $50 billion — incurred on the day of the attacks, according to study co-authors Dwight Jaffee, Berkeley’s Willis Booth Professor of Banking, Finance and Real Estate, and Thomas Russell, professor of economics at Santa Clara University.

“Insurance firms,” Jaffee says, “shy away from large risks if the size of the risks are uncertain. But insurance firms are willing to provide auto insurance, since the size of the risks are well known.”

The authors conclude that aversion to providing catastrophic event insurance has also been observed following natural disasters such as Hurricane Andrew in 1992 and the 1994 Northridge earthquake. This tends to dissipate over time if no further events occur, they say.
— Ute Frey

Can the brain teach the nose new tricks?
Any wine connoisseur knows the nose can learn to recognize subtle new aromas, but where does that learning take place?

A new study by a team of Berkeley scientists has determined that we learn new smells in an area of our brains, not just in our noses. The latter has neural receptors previously thought to be solely responsible for a person’s ability to detect new odors.

Based on this new finding, the team, led by graduate student Joel Mainland and Noam Sobel, assistant professor of psychology, argues that the adult brain has more capabilities to change than previously thought. Its study appears in the Oct. 24 issue of “Nature.”

The discovery may have implications for how the brain recovers from injury. Recent evidence indicates that activity in damaged regions of the body results in regeneration in the brain. In stroke patients, for example, tying down unaffected limbs — to force patients to use their affected arms or legs — has resulted in partial recovery of affected limbs.

The researchers conducted their research using the chemical androstenone, a steroid hormone that approximately 30 percent of the population is unable to detect.

However, with repeated exposure to the odorant, about half of such non-detectors can develop the ability to detect it. For those who can smell androstenone, there is a wide range of reactions to its odor. Those most sensitive to it find the smell extremely foul and reminiscent, Sobel says, “of dirty laundry.”

Sobel and his colleagues found 12 subjects who could not detect the smell. In their study, one nostril was completely blocked, and the open nostril was exposed to androstenone for 21 days, after which both nostrils were tested. They found that both nostrils doubled their detection accuracy as a result of this exposure. The researchers concluded that this exposure-induced learning must have occurred in the olfactory structures in the brain that share information from both nostrils.

“Since the unexposed nostril learned just as well, the brain is definitely involved,” says Sobel. “This contradicts a previous theory that olfactory learning occurred in the nose only. Our results suggest there must be a central component in the brain at work.”
— Carol Hyman

New center to apply optics to medicine
Despite recent breakthroughs involving the use of light to treat and study disease, those techniques only scratch the surface of what is possible in the emerging field of biophotonics.

A new research effort aims to change all that. Scientists at 10 institutions around the country, including Berkeley, announced Oct. 24 a new Center for Biophotonics Science and Techno-logy to accelerate the application of state-of-the-art optical tools to biology and medicine.

The National Science Foundation is providing $40 million over 10 years to establish the center at UC Davis, in collaboration with researchers from Berkeley, Lawrence Livermore National Laboratory, UC San Francisco, Stanford University, and other universities. An additional $12 million in matching funds from federal and state grants and private sources will bring total funding to about $52 million.
“Biophotonics refers to the application of advanced optical technology to study biological processes,” says Jay Groves, assistant professor of chemistry at Berkeley, a faculty scientist at Lawrence Berkeley Laboratory, and a principal investigator with the center.

Lasers, for example, are widely used today in medicine and surgery. The center hopes to spur the development of new applications. Its researchers also hope to develop new technologies for detecting anthrax and other biological wea-pons, new tools to diagnose and treat cancer, and new technology to help scientists and physicians see what takes place in living cells.

Groves himself uses sophisticated optically coupled atomic-force microscopes to manipulate individual cell membranes only two molecules thick. “There is much more to light than an image,” he says. “Conventional microscopes use only a small fraction of the optical information from our samples; there is infinitely more we can do.”

The center will collaborate with industry to accelerate biophotonics technology development.
— Robert Sanders


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