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Rotten Eggs: Secret Ingredient for Suspended Animation?

March 26, 2008

Science
fiction usually sticks hibernating spaceflyers in glowing capsules of goo, but
a real-life ingredient for suspended animation may not be too far off,
scientists say.

Hydrogen
sulfide is the key stinky compound in rotting eggs and swamp
gas
. New research shows it can slow down a mouse’s metabolism, or the
consumption of oxygen, without dampening the flow of blood.

“A little hydrogen
sulfide gas is a way to reversibly and, apparently, safely cut metabolism in
mice,” Dr. Warren Zapol, a medical researcher at Massachusetts General
Hospital, told LiveScience. “There seemed to be no side harmful
effects to the mice after hours of breathing it in. They got sluggish, but
still responded to a pinch on the tail.”

Zapol, also
chief of anesthesia and critical care at the hospital, and his colleagues will
detail their findings in the April issue of the journal Anesthesiology.

Heart of
the problem

Previous
studies showed hydrogen sulfide gas could slow down metabolism but never
examined what happens to the circulatory system, the network of blood
distribution commanded by the heart.

Zapol’s
team used ultrasound technology to view the hearts of mice as they inhaled
hydrogen sulfide. After six hours, the heart rate of the mice halved, but their
blood pressure remained
normal, crucial to keeping blood adequately flowing through the body.

“When
you make everything sluggish, you’d think the heart would become sluggish, but
it didn’t,” Zapol said.

He said
that respiratory failure and other problems he expected to see weren’t
observed.

“I was
surprised how well it worked,” Zapol said. “You’d think poisoning the
metabolism would dangerously slow it down, but it didn’t really seem to
interfere.”

Suspended
animation?

Zapol
expects that combining hydrogen sulfide inhalation with chilling the body,
another method of slowing down the body’s machinery, could cut metabolism by up
to 90 percent.

“Nine
months in a spaceship heading out to Mars takes a lot of oxygen to burn, food
and water to consume, and produces a lot of waste [carbon dioxide],” said
Zapol, who is on the Institute of Medicine’s Committee on Aerospace Medicine
and the Medicine of Extreme Environments.

Theoretically,
cutting metabolism would reduce the need for consumables and produce less
waste, enabling spacecraft to travel lighter and faster.

“Wouldn’t
it be nice to arrest metabolism safely for long
periods of time
and reverse it when you wanted to?” Zapol said.

Before any
spaceflyers benefit from hydrogen sulfide research, Zapol thinks severely
injured people will.

“If
someone loses a lot of blood, we might be able to safely reduce their need for
oxygen,” he said. “That would feasibly extend limited windows to
perform life-saving operations.”

Much to
learn

For now,
however, Zapol says an incredible amount of research remains before any work on
humans can start.

“The
next thing we need to do is scale this up to animals bigger than a mouse,”
he said, explaining that larger creatures can react very differently to
experiments.

People, for
example, have reported headaches and nausea from doses of hydrogen sulfide gas
2,700 times less concentrated than those used in the team’s experiments. Ten
weeks of continuous exposure to the same levels Zapol and others used has been
shown to cause nose lesions, or ulcers, in mice.

But Zapol
thinks that hydrogen sulfide may not be the key ingredient for inducing a suspended
animation-like state
in mice – a less-toxic compound may form after the gas
is inhaled. If so, the toxicity of hydrogen sulfide could be circumvented.

“Chemistry
of the blood is very complex,” Zapol said. “We need to find out what,
exactly, is circulating in the blood and causing what we’ve observed.”

The National
Institute of Health and Linde Gas Therapeutics in Lidingo, Sweden, funded the team’s research.


Source: imaginova



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