What animals can tell us about hemorrhage, organ transplants and aging

BETHESDA, Md (September 25, 2006) The stereotype of a scientist as a man in a white lab coat hunched over a microscope in a laboratory is far from real life. Consider the scientists who will meet at The American Physiological Society's conference, Comparative Physiology 2006: Integrating Diversity, taking place October 8-11 in Virginia Beach, Virginia.

  • They spend time in the mountains studying bears, animals that hibernate for months without suffering significant muscle atrophy
  • They follow migrating birds thousands of miles to understand how they fuel their metabolisms for grueling transoceanic flights
  • They slog through wetlands, studying frogs that literally freeze during the winter, then hop away in the spring as though nothing unusual occurred

Comparative physiologists study all kinds of animals -- bears, frogs, snakes, squirrels, seals, oysters and a host of other animals to answer the question "How do they do that?" They uncover general physiological principles that may apply to humans, and may spur future medical advances to benefit people. These scientists exude an enthusiasm for their work and maintain a wonderment of the physiological adaptations in the animal world.

Science writers can meet and interview many of these scientists at the Comparative Physiology conference. (See the box at the end of this release for a link to the program.) If you can't make it to the conference but want to review the program and conduct interviews from your office, The American Physiological Society can help arrange that, in many cases.

With six plenary speakers, 20 symposia, and hundreds of poster presentations, there is much to choose from. Consider three symposia: "Biomedical applications of suspended animation," "Molecular aspects of the mechanisms of hibernation," and "Comparative biology of aging in long-lived animals." How is it that:

  • Hibernating squirrels can lose up to 60% of their blood volume and survive at least 10 hours?
  • Brine shrimp can lie on the shore like brittle skeletons, but snap back to life when placed in water?
  • Naked mole rats can live for 28 years but their mice cousins live only three?
  • Birds live longer than their ultra-high metabolic rates would predict?

Matthew T. Andrews of the University of Minnesota Duluth and Hannah V. Carey of the University of Wisconsin School of Veterinary Medicine are the organizers of the suspended animation symposium. This and a second symposium "Molecular aspects of the mechanisms of hibernation" will include studies of animal hibernators, a form of suspended animation.

Keeping their cool

When a person suffers a stroke, heart attack or severe hypothermia, it is not the loss of blood flow (ischemia) that causes the greatest damage to the organs and tissues, explained Andrews. Instead, the greatest damage occurs when the blood flow is restored (reperfusion). Hibernating animals have significantly reduced blood flow when they hibernate, but reperfuse without injury when emerging from hibernation.

"If we can figure out how the hibernating ground squirrel does that, we might be able to avoid the damage that strokes cause in humans," Andrews said.

The ground squirrel's remarkable physiological abilities change with the seasons, Carey said. The animal's liver and heart remain viable outside the body for much longer during the hibernation season and the squirrel can tolerate a much greater loss of blood during this time. And Carey has found that this is true even when the hibernating squirrel briefly arouses from hibernation during the winter and its physiology has returned to normal.

These findings could one day extend the time we can preserve organs for transplant and give doctors time to find a suitable recipient, Carey and Andrews said. The research could also profoundly change how we treat people who are severely hypothermic or have suffered massive blood loss.

No fountain of youth -- yet

Human life expectancy has been greatly enhanced by advances in disease prevention and treatment. But what do we know about how and why we age, and can we slow the aging process?

In the symposium, "Comparative biology of aging in long-lived animals" scientists will compare the physiology of a variety of long- and short-lived species to understand how they age at different rates, said Deborah Kristan of California State University at San Marcos. Kristan will co-chair the session with Rochelle Buffenstein of the City College of New York.

Much of the early aging research was done on short-lived animals, because it was easier to study a complete life span, Kristan said. But physiologists have recently turned their attention to long-lived animals. Some of the aging theories to be discussed during the symposium:

  • DNA damage and repair. Short-lived animals may suffer more damage to their genes and have a more difficult time repairing the damage than long-lived animals, the theory goes. Mice, a short-lived species, have a high occurrence of cancer, which is related to damage to the genes, while mole-rats appear to be cancer-resistant, Kristan said. On the other hand, long-lived animals, including humans, not only suffer less DNA damage when exposed to damaging agents, they have a greater ability to repair the damage when it occurs, Buffenstein said.

  • Oxidative stress. The prevailing theory has been that oxidative stress -- damage caused to cells by rogue oxygen atoms known as reactive oxygen species -- shortens lifespan. Animals that could best prevent reactive oxygen species (ROS) generation, neutralize them, or repair the damage it causes, would live the longest, the theory goes. Buffenstein's research with naked mole rats, the longest-lived rodent known, may cause physiologists to modify this theory.

  • Metabolic rate. In theory, the higher the species' metabolic rate, the shorter its life span should be because ROS are generated during aerobic metabolism as we use oxygen. But birds, which have a very high metabolic rate, live much longer than most similar-sized mammals with a lower metabolic rate. A study of birds, bats and rodents finds differences within their cells that may help explain the longer-than-expected life span of birds and bats, Kristan said.

These are just two of the symposia taking place at the conference. There are plenty of fresh and interesting story lines you can develop by going through the program or by calling The American Physiological Society.

Go to http://www.the-aps.org/meetings/aps/vabeach/index.htm and click on "Week at a glance" for the full Comparative Physiology program. Check out "Conference-Related Press Releases," for more program summaries. Members of the media who want to obtain a complete set of conference abstracts can contact Christine Guilfoy, cguilfoy@the-aps.org or at (301) 634-7253.


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.

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