The Dallas Morning News

DALLAS – For some scientists, every day is Groundhog Day. But these researchers aren’t looking for a shadow.

They’re trying to figure out how groundhogs – or any other hibernating creatures – annually put themselves into a state of near biological standstill. Body temperature plummets, metabolism nearly shuts down, and heart rate slows to something just shy of dead. Something transforms these normally warm-blooded, scurrying animals into cool, limp balls.

But what?

The answers could have profound implications for humans. Unraveling the mystery of hibernation is necessary for the alluring prospect of deep-space travel. If future generations are to endure an interplanetary journey, researchers must learn how to use the tools of a hibernationlike suspended animation.

More immediately, scientists believe the secrets of hibernation could drive dramatic advances in organ transplantation, stroke treatment, injury survival and even weight control.

“Why is it that this animal can eat like an obese person for several months and then shut off for a number of months?” asked Gregory Florant of Colorado State University. Florant studies groundhogs – with their day coming Thursday, this is the time of year his phone rings a lot – trying to understand how their energy regulation can shift so dramatically.

Contrary to popular perception, hibernating animals don’t doze off for the winter and wake up in the spring. Hibernation is not sleep. An animal will periodically rouse and then slip back down into a dormant state known as torpor.

The hallmark of hibernation is a dramatic rise and fall in metabolism – wild swings in body temperature and blood flow that a person could not withstand. One reason that strokes and heart attacks are so damaging, or that organs harvested for transplant last only hours, is that the tissues can’t survive when they’re choked of circulation, then flooded again with blood.

Since so many different mammals can hibernate, scientists believe the ability for human tissue to survive similar ebbs and flows of metabolism is probably buried in the genetic code.

“We are mammals, therefore we share genes with other mammals that can do this,” Florant said. In 2004, German scientists writing in the journal Nature described the hibernation of a lemur species in Madagascar, the first primate discovered to have this ability.

The genetics – or the biochemical explanation – of hibernation remains a mystery. “We haven’t discovered what complex of genes are directly involved,” Florant said.

But researchers have recently discovered important insights to the process. For example, Hannah Carey and her colleagues at the University of Wisconsin School of Veterinary Medicine have examined how long a liver from a rat can survive outside the body, compared with a liver harvested from a hibernating ground squirrel.

Last year, she reported that a rat liver showed considerable decline after being outside the body for 72 hours. But a liver from a hibernating squirrel could last an astonishing 96 hours with minimal damage.

One reason, she says, is that the liver from the ground squirrel was embedded with a healthier density of microscopic blood vessels after cold storage. The organ also appears to have a muted inflammatory response – a natural reaction to injury that damages tissues that have been subjected to low blood flow.

The next step, she says, is to find the biochemical mechanisms that enable these protections. “We want to learn how they do it,” she said.

Scientists have also recently reported findings that help explain the protection of brains of hibernating animals, and even some of the tools their bodies use to survive without food. Researchers from the University of Minnesota Duluth, for instance, reported last year that hibernating squirrels’ hearts produce enzymes that enhance the breakdown of fat for fuel and ease the movement of calcium within cells. Heart cells need calcium to contract.

With these and other discoveries, scientists hope to eventually understand one of the animal kingdom’s most remarkable feats.

“We have clues, but we don’t know how it all fits together,” said Sandra Martin of the University of Colorado School of Medicine.

One day, however, the inner workings of the groundhog may come out of hiding for good.

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(c) 2006, The Dallas Morning News.

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