Animal physiology conference sheds light on human physiology

September 11, 2006

BETHESDA, MD (September 11, 2006) - If you're a bit weary of writing stories based on the latest press releases, consider covering The American Physiological Society's conference, Comparative Physiology 2006: Integrating Diversity, taking place October 8-11 in Virginia Beach, Virginia. There are plenty of fresh and interesting story lines you can develop, breaking away from the cookie cutter stories that everybody else is covering.

Comparative physiology is the study of all kinds of animals, finding general principles that may apply to humans, too. Working with frogs, snakes, squirrels, seals and a host of other animals not only answers the key question "How do they do that?" but may spur future biomedical advances to benefit people. The thought-provoking plenary speakers are: Do you feel a bit jittery before leaving on a big trip? If you do, then you have something in common with the Red Knot, which flies 7,500 miles from its summer home in the Arctic to its winter breeding grounds in New Zealand. Red Knots show signs of the jitters just before leaving on their arduous trek, said Piersma.

But there's a bigger change you can't see, a physiological packing of the bags: The Red Knot's pectoral muscle, which powers its wings, increases by 30-50% of its normal size in the weeks leading up to migration. Its heart grows bigger, fat stores balloon and digestive tracts shrink precipitously. The bird's blood thickens, making it possible to deliver more oxygen to the muscles. The end result? An animal built for the marathon, but not for eating.

One particularly interesting aspect of bird migration is related to obesity, said Piersma, who is also affiliated with the Royal Netherlands Institute for Sea Research. Even birds that don't make the seasonal trip will store fat in the weeks leading up to the migration, but they manage to lose it quickly, even when they don't expend the energy for migration.

Hear Piersma, an authority on migratory shorebirds talk on "The physiology of long-distance avian migration" on Sunday, Oct. 8. The details of the talk are embargoed until 3 p.m. that day. Hayes' research has fingered some herbicides and pesticides as disrupters of amphibian hormones and a threat to their survival. Early on, he focused on a popular herbicide, Atrazine, which his research found increases the estrogen level of male frogs while decreasing their testosterone levels - in essence, chemically castrating them, he said. His work has been featured in a variety of television and radio programs.

Hayes' talk, "Steroidal regulation of amphibian developmental physiology and behavior" will focus on his more recent research, which finds that pesticides and stressors (such as increased water temperature or falling pond levels), combine to lead to immune deficiency in frogs. In one experiment, Hayes injected yeast (a stressor) into frogs living upstream of an agricultural area. They were unaffected by the injection. But frogs downstream of the agricultural area -- where runoff contaminated the water with agricultural chemicals -- died.

The frogs where he did his dissertation work 10 years ago have disappeared. Ditto for the area he researched five years ago. His work translates to humans, he says. For instance, a clinical study in Missouri found a correlation between low fertility in men and the presence of Atrazine in their urine, Hayes said.

Hayes will speak on Monday, Oct. 9. The details of his talk is embargoed until 3 p.m. that day. Mammals that weigh more than 21 kilograms (about 46 pounds) are rare and becoming rarer, according to Terrie Williams, of the University's Center for Ocean Health. In her talk "Survival physiology: a reassessment of why big, fierce animals are rare," Williams says it all comes down to what these animals must eat to survive. Knowing what these animals need and when they need it is important to their survival.

"Physiology has a really critical role in species preservation and we think we've underplayed that," Williams said. Physiologists can define the daily and seasonal energy needs of these animals, information that help protect big, fierce animals.

In particular, Williams will look at marine animals, which live a relatively expensive lifestyle in terms of the energy they expend. Generally, they consume twice as many calories as carnivorous land animals of similar size. Killer whales, for example, consume 200,000 calories per day. Information about bioenergetics can be used to preserve these species, for example by creating marine reserves where human hunting and fishing is limited.

Williams is the author of "Hunter's Breath," a book about her research in Antarctica on the Weddell seal. She was named one of the top 50 women scientists in 2002 by Discover magazine.

Hear Williams speak on Tuesday, Oct. 10. Her talk is embargoed until 3 p.m. Hummingbirds live in the fast lane, but this pedal-to-the-metal lifestyle requires their little bodies to deliver enough fuel to stay ahead of the crowd. These remarkable birds can shut down their kidneys, a feat that would kill a human being, Martinez del Rio has found. His talk is entitled "The comparative/ecological physiology of nectar-feeding birds: the last 15 years."

Hummingbirds get their energy from sugar found in nectar. But nectar is mostly water, so the birds need to consume a lot of it to get enough sugar. Their kidneys must get rid of all that water by filtering it very fast. But because they have a very high respiration rate, they must conserve water when they are not feeding, or they will become dehydrated. How do they do that?

"When hummingbirds are fasting, their kidneys stop filtering altogether," Martinez del Rio explained. "In mammals, when the kidney stops filtering it is called acute kidney failure and can have dire consequences." Hummingbirds experience renal failure daily, an adaptation that allows them to live for a time without a functioning kidney. Hummingbirds have both the guts and the kidneys needed to face the challenges of their watery and sugary diets," he said.

Information embargoed until lecture is completed, 3 p.m., Wednesday, October 11. Jones' forehead-slapping moment of scientific insight may be remembered as an important step in the study of blood pressure. After 40 years of scientific work, Jones realized that it is possible to determine the blood pressure of fish after they have died.

The process, which he discovered with graduate student Marvin Braun, makes it much quicker, less expensive and less technically demanding to study fish blood pressure. This field not only provides insight into the physiology of fish, but can shed light on the evolution of blood pressure and may eventually provide some valuable information about our own circulatory system.

The technique, which works best when done within six hours of the animal's death, works for fish of all sizes. It is effective at determining the mean blood pressure of the living fish, Jones said. His talk is entitled "Necrophysiological determination of fish blood pressure: a lesson for us all?"

Material embargoed until his lecture is completed, 9 p.m., Wednesday, Oct. 11.

Please go to for a copy of the entire program.

The media can attend this fascinating conference by contacting Christine Guilfoy, or at (301) 634-7253.

For reporters who cannot attend, arrangements can be made in many cases for telephone interviews with scientists.
The American Physiological Society was founded in 1887 to foster basic and applied bioscience. The Bethesda, Maryland-based society has 10,500 members and publishes 14 peer-reviewed journals containing almost 4,000 articles annually.

APS provides a wide range of research, educational and career support and programming to further the contributions of physiology to understanding the mechanisms of diseased and healthy states. In 2004, APS received the Presidential Award for Excellence in Science, Mathematics and Engineering Mentoring.

American Physiological Society

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