Bothering a Sleeping Bear

Once upon a time, Senator William Proxmire garnered praise and headlines by handing out Golden Fleece awards to people he thought guilty of conspicuously wasting taxpayers' money. Scientists were among his favorite targets. He could tell they were fleecing the public merely by reading the titles of their funded proposals.

Judging science takes more than laughing at a title. For example, how would you feel about watching your money go toward something titled, "Chemical Analysis of the Bladder Contents of Hibernating Black Bears?" It sounds rather like work fit only to keep biologists employed. Surely it would deserve a Golden Fleece.

Ah, but work covering exactly what that hypothetical title describes may help combat human ills as diverse as osteoporosis, kidney failure, and obesity. A sleeping black bear, it turns out, is a metabolic marvel.

If human beings lie around for months on end, such as during convalescence, their bones become brittle. Hibernating squirrels and other deep sleepers also lose bone mass while they rest. Bears don't.

Most animals that sleep through months of scarcity lower their metabolic rates and their body temperatures dramatically. They don't eat or drink. Light-sleeping bears also take in nothing, but they lower their body temperatures only slightly. They burn about 4000 calories a day while they hibernate.

Should disease or coma keep a human being from urinating for several days, that person will die from toxic urea building up in the blood. Animals in deep hibernation must rouse occasionally to void urine or the same fate befalls them. Hibernating black bears don't urinate, but their blood urea levels decline while they sleep.

According to a group of scientists working with Dr. Ralph A. Nelson of the Carle Foundation in Urbana, Illinois, the bears manage their biochemical tricks by means of an environmentally sound practice. They recycle.

In people and other animals that lose bone mass when they do not exercise, bone-building cells called osteoblasts slow down while the cells that get rid of old bone, the osteoclasts, keep on with their work of destruction. The calcium released by the osteoclasts is carried away by the blood, filtered off by the kidneys, and excreted in the urine. In hibernating bears, the osteoblasts don't slow down. Calcium reaching the bloodstream doesn't get filtered away into the bladder. It ends up at another part of the skeleton and is used in rebuilding bone at the new site. The bears' blood calcium levels stay fairly constant throughout the year.

Nelson and his colleagues think they are close to isolating the chemical in hibernating-bear blood responsible for calcium recycling, but they are giving few specifics. They hope to patent their work eventually, with an eye toward providing something useful for the millions of people whose bones weaken with age.

They are not so close to understanding the way bears recycle urea. Catheters inserted into the bladders of hibernating bears collected some urine, but it never accumulated. The urine and its chemical load were reabsorbed across the bladder wall.

The researchers concocted some synthetic urea dosed with radioisotopes so they could trace its travels. When this trackable urea was injected into a bear, it soon disappeared-but the radioactive molecules turned up in various proteins and neurotransmitters in the bear's body. Somehow bears are able to split urea and use its components to fabricate amino acids, the building blocks of proteins.

The energy source for this chemical wizardry is fat. Newly awakened bears may be groggy but they're fit. After sleeping for months, they have lost no bone nor protein but have burned off quantities of fat. The bears still hide this metabolic secret, an answer to a dieter's dream.

So, does such goofy-sounding but useful research deserve a Golden Fleece? Maybe. The original Golden Fleece, after all, was full of real gold.