Bear Hibernation Implies Human Applications

Bear hibernation appears uniqueand suitable for application to human needs. It is obviously worthwhile to explore the biochemistry involved and toget all the answers to the questions implied.

Rather obviously this form ofhibernation is also applicable to spending a lot of time in space as we arelikely to face in the not too far distant future.  It is able to conserve all nutrients in theform of a closed loop, while also preserving muscle and bone mass.  In fact the method may be applicable toactive space travelers let alone those sleeping.

It is all very suggestive and I nonot understand why all this has not been picked up on a lot sooner.  Surely NASA has done work on this to work outthe metabolic pathways.

Bear hibernation study finds surprises in search for clues to helphuman health

An infrared camera captures an Alaskan black bear in deep hibernation.For the first time, researchers watched bears slumber all winter, discoveringthat the famous hibernators maintain a relatively high body temperature even astheir breathing, heart rate, and metabolism drop far below normal.

Washington Post Staff Writer 

Friday, February 18, 2011; 12:55 AM

Call this study "Big Brother" black bear.

In the woods of Alaska,five black bears snoozed all winter while researchers recorded every detail oftheir slow-motion daily drama for the first time.

Cameras caught them shuffling around every day or so.

Oxygen and carbon dioxide monitors kept tabs on their metabolism.

And sensors implanted in their abdomens recorded their heart rate andbreathing.

It's more than reality show contestants usually have to put up with.

And yet, these scientific stars performed perfectly, offering anunprecedented glimpse into the secrets of hibernation.

It turns out that Ursus americanus hibernates in a mannerunlike that of the dozens of other hibernating mammals. The biologists saw thatthe animals' heart rate dropped precipitously, they breathed just two or threetimes a minute and their metabolism slowed to a trickle as the animals slowlyburned the fat they spent all summer accumulating.

None of that was unexpected.

And yet, unlike other hibernators such as squirrels, chipmunks,raccoons and skunks, the bears maintained a high body temperature throughoutfive months of inactivity.

Further, when the bears emerged in mid-April, the researchers gotanother surprise. Like a fuzzy-headed human waking from a Sunday snooze, thebears stayed groggy, with their metabolic rate remaining at about half that ofsummer levels for two to three weeks.

"The slow emergence from hibernation was very surprising,"said Oivind Toien, a biologist at the Instituteof Arctic Biology at the University of Alaskaat Fairbanks,who cross-country skied to a control hut near the dens every morning for fivemonths.

Intrigued by the ability of black bears to snooze all winter - and withan eye toward one day putting injured or sick people into hibernation-likestates - Toien and colleagues rounded up five bears that had wandered too closeto people, lured them into ersatz dens in the woods, wired the animals andtheir hovels to the hilt, and then watched and waited.

Despite months of very little activity, other research has shown, blackbears maintain muscle tone and bone mass, both of which deteriorate rapidly inhumans confined to beds or astronauts floating in space.

How they do so remains a mystery that medical researchers want tounravel.

Barnes said his team euthanized the bears in the study to collecttissue samples. The researchers said the bears, chosen for the experimentbecause they appeared used to people, were also therefore too potentiallydangerous to be released back in the wild.

"Somehow the bears have tricked their tissue, their bones andmuscles, into thinking they're still doing work," said Brian Barnes,director of the Institute of Arctic Biology. "We're very interested inthat."

Barnes said the study, unveiled Thursday at the annual meeting of theAmerican Association for the Advancement of Science in Washington, marks thefirst time anyone has monitored black bears continuously throughout hibernationin a natural setting.

However, many other researchers have been probing the secrets of theanimals' slumber.
"They are metabolic marvels," said Lynn Rogers, a biologistat the nonprofit Wildlife Research Institute in Ely,Minn. Rogershas spent 44 years studying Minnesota'shibernating black bears.

His technique contrasts sharply with that of the Alaska researchers. Whereas the Alaskanswired their bears with high-tech monitors, Rogers peeks into dens and sometimessnuggles up to the beasts. "A wild bear will fall asleep next to me, and Ican have my hand on its femoral artery or something to get a heart rate," Rogers said.

He once even laid his head on a hibernating bear's chest to hear itsheart. "I know, stupid," he said, though he quickly added that he hasnever been attacked.

Rogers said skinny bears hibernate more soundly than fat ones, as theyhave less fat to draw on for energy.
One big hibernation mystery bear watchers are keen to understand:how the animals' bodies recycle key nutrients. "That's part of thewonder," Rogerssaid. "They go for months without urinating or defecating. Instead, theyare recycling calcium and nitrogen, so they end up with strong bones andmuscles."

Barnes said his team is now trying to understand the biological tricks thebears employ to lower their metabolism so dramatically.

Doing so could one day aid patients with strokes and serious injuries,he said.

"If we can uncover the way hibernators turn down their demand foroxygen, you can imagine developing a therapy . . . to put someone in stasis, aprotected state," Barnes said. "That would give you more time. Itwould expand the 'golden hour' where it's critical to reach medical care to agolden day or a golden week."

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