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JAWS
OF LIFE
Remarkably, an epaulette shark can survive
without oxygen for hours when it’s stranded
on coral reefs cut off from the ocean at low
tide. As the fish’s cells sense oxygen
levels dropping, the shark moves its gills rapidly
to take in more oxygen. Once oxygen levels fall
30% below normal, the shark slows its ventilation
and heartbeat and relaxes its arteries, reducing
resistance to blood being pumped to its brain.
Finally, neurons in the brain’s motor regions
release the inhibitory neurotransmitter gamma-aminobutyric
acid as a signal to power down nonessential functions,
and the shark becomes temporarily comatose.
Gillian Renshaw, a professor at the School of
Physiotherapy and Exercise Science at Griffith
University in Australia, wants to apply the principles
of this technique, known as hypoxic preconditioning,
to patients at risk of heart attacks and strokes.
By using intermittent hypoxia training on humans—administering
air with just 12% oxygen content for three- to
five-minute intervals during an hour—Renshaw
hopes to switch on genes that prompt blood-cell
production, capillary growth and the repair of
damaged proteins. She thinks these mechanisms
will not only help prevent heart attacks but
also minimize tissue damage when heart attacks
and strokes occur.
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BEARING
DROUGHT
Tardigrades, also known as water bears
or moss piglets, inhabit a vast range of aquatic
environments but are most commonly found on lichens
and moss, where they’re subjected to extreme
temperatures and cycles of wet and dry. To survive
arid and frozen spells, these half-millimeter-long
creatures have evolved an ability to exist in
a near-death state for as long as seven years.
One method the tardigrades use is anhydrobiosis,
in which they suspend their metabolism, replacing
water that has evaporated from their cells with
a type of sugar and curling into a ball to slow
the evaporation of their remaining moisture.
When water returns to their environment, tardigrades
rehydrate and spring back to life.
The water bear’s amazing adaptation inspired
scientists at Cambridge Biostability Limited
in the United Kingdom to develop a “stable
liquid” technology that allows vaccines
to be stored for long periods in temperatures
ranging from –4ºF to 158ºF. Vaccines
easily lose potency over time, and exposure to
high temperatures accelerates the degradation,
so proper storage necessitates either refrigerating
a liquid vaccine or reconstituting a powdered
one. That has stymied health-care efforts in
remote, developing regions where neither electricity
nor clean water is readily
available.
First, the Cambridge scientists spray-dried a liquid vaccine with sugar syrup,
making the vaccine viscous. As it thickens, the vaccine forms microscopic glasslike
beads called microspheres. Once a droplet of vaccine is embedded in the microsphere,
all chemical reactions stop, rendering the vaccine stable. When the serum is
injected into a patient, the body’s fluids dissolve the microspheres and
release the vaccine.
By mixing microspheres with different vaccines in the same liquid, the company
can deliver many vaccines in one dose. It has developed a vaccine against four
of the neurotoxins that cause botulism, and vaccines against hepatitis B, Haemophilus
influenzae and tetanus will enter trials in 2008. If approved, the three
would be combined with vaccines for diphtheria and pertussis in a single-dose
defense against these childhood diseases. 
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