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- NEW YORK (Reuters) - When bears hibernate, levels of sugar and fat in
their blood are similar to those in humans with diabetes, yet they burn
4,000 calories a day -- as much as a human athlete. Hibernating bears stop
eating, drinking and eliminating waste but they continue to build bone
and grow lean muscle mass. Females give birth to and nurse cubs and, contrary
to popular belief, bears are not even hungry when they emerge after months
of slumber. Dr. Ralph Nelson of the University of Illinois thinks his studies
of bear metabolism can offer new therapies for human disease from diabetes
to obesity and ways for astronauts to deal with long stints cooped up in
spacecraft. ``The circumstances of denning should produce early death,''
he told a recent seminar on biodiversity and human health sponsored by
the American Museum of Natural History. ``But the bear survives over winter
by producing substances that, when developed as drugs, should treat serious
human disorders of osteoporosis, kidney failure, obesity, diabetes and
anxiety.'' Nelson said the bear is just one example of how the natural
environment offers valuable resources for human health. Yet bears are endangered.
Shot as nuisances in the United States and Canada, caged in Asia, those
that do not fall foul of tourists often fall prey to the traditional medicine
trade. The astonishing metabolic qualities of bears did not go unnoticed
by the Chinese, who use them to cure a range of disorders including gallstones.
``Bear gallbladders are worth 18 times their weight in gold,'' Dr. Eric
Chivian, director of the Center for Global Health at Harvard, told the
seminar.
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- POTENTIAL NEW DRUGS FACE 'MAJOR THREAT'
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- Bears are not the only natural resource
threatened by destruction just as scientists start to realize their potential.
Drug companies that are actively combing forests and deserts for plants
and animals that might offer leads for developing exciting new drugs are
painfully aware that this potentially lucrative resource is disappearing
virtually before their eyes -- burned for fuel, cleared for farms or developed
into cities, towns and even golf courses. The World Conservation Union
said in a report last month that more than one-tenth of all the world's
plant species were headed toward extinction. A survey this month by the
American Museum of Natural History found that 70 percent of biologists
polled believe the world is in the midst of a mass extinction of plants
and animals and that this loss will pose ``a major threat'' to human existence
in the next century. ``It's important to do as much as we can, as soon
as we can, to preserve global biodiversity. Nearly all antibiotics have
been based on natural products,'' Dennis Schmatz, who heads animal health
research at the Merck company, told the seminar. Aware of this, the pharmaceuticals
firm has agreements with countries such as Costa Rica that still have virgin
forest. Schmatz described one promising product brought back by a team
who literally sampled every plant they encountered but found no indication
of any potential products. Back in the lab, however, a twig yielded up
a fungus that produced a chemical called apicidin, known experimentally
as L-755,875, which in test tubes kills cryptosporidium parasites that
cause diarrhea and Plasmodium falciparum, which causes malaria. Injected
into mice, apicidin can protect them from malaria, something that excited
the Merck researchers. ``Whether we get a drug out of it remains a question,''
Schmatz cautioned.
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- CONE SNAILS LEAD TO PAIN KILLER Meanwhile,
California-based Neurex took an interest in cone snails, beautiful creatures
collected for their shells in the Philippines and elsewhere. Their beauty
comes at a price -- the snails are armed with tiny harpoons connected to
poison sacs that can stun and paralyze a fish in milliseconds. Each cone
snail secretes dozens of different toxins, which scientists have been analyzing.
One blocks calcium channels -- chemical doorways that are important to
communication between cells, and Neurex found it can specifically block
the kind of pain signals found in chronic, untreatable pain, such as that
suffered by cancer patients. They created a synthetic version now named
ziconotide. ``In the spinal cord, it blocks synaptic transmissions only
between pain-sensing and pain-transmitter nerve cells,'' George Miljanich,
senior director of biochemistry at Neurex, said. He said ziconotide is
1,000 times stronger than morphine but does not have the undesirable side
effects such as growing tolerance. The effects of morphine start wearing
off after about a week and patients need more and more to get the same
effect, but with ziconotide, ``the same dose works a year later,'' Miljanich
said. Neurex has completed Phase III clinical trials, which show the drug
is safe and works. They are now preparing to ask the U.S. Food and Drug
Administration (FDA) to license it.
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- TIME MAY BE RUNNING OUT FOR CURES
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- Miljanich hopes other creatures might
offer more such drugs. But he, too, is aware that time is running out.
``From which coral reef will come the next cone snail that will treat Parkinson's,
or Alzheimer's?'' he asked. ``Are we willing to lose that coral reef?''
Some experts think coral reefs offer a wealth of medicinal miracles, if
people take the time to go and find them. ``This could well develop into
the major source for new drugs,'' said William Fenical of the Scripps Institute
of Oceanography. ``The potential here is enormous. Microscopic organisms
alone, there are billions of them in the ocean,'' Fenical, thedirector
of the institute's Center for Marine Biotechnology and Biomedicine in San
Diego, said. Crowded into the busy underwater city that is a coral reef,
many of these organisms have developed chemical offenses and defenses that
could translate into important human drugs. One strange, bacteria-like
organism found three miles below the surface, where water pressure is 4,000
times air pressure at sea level, produced a protein called macrolactin
that, in test tubes, worked against HIV and colon tumors. The organism
is so mysterious it defies classification. ``I sent this to five different
people who are experts in bacterial taxonomy. They sent it back and said
'good luck,''' said Fenical, who calls the find C-237. The experts have
precious little to work with. The sample was small, and unfortunately,
Fenical's group can get no more of the protein. ``The organism underwent
a mutation and doesn't make the compound any more,'' he told Reuters. And
something discovered by accident three miles down is not easy to come by.
''We just haven't run across it again.'' Fenical becomes angry at the thought
that such potential miracles could be wiped out by something as carelessly
ordinary as pollution. ``To consider that the first site to dump our sewage
is the ocean is a frightening prospect to me,'' he said.
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