Screaming Penguin - Source Does Matter

WASHINGTON, April 21 (Reuters) - Mice forced to breathe hydrogen sulfide -- known best for its rotten egg smell -- go into a kind of suspended animation, U.S. researchers said on Thursday in a finding that may help save human lives.

Although hydrogen sulfide gas is toxic in high doses, it may activate some of the mechanisms that cause other animals to go into hibernation, they wrote in this week's issue of the journal Science.

Finding a safe way to do this in humans could lead to new ways to treat cancer and prevent injury or death from blood loss, or help people undergo and recover from surgery better, said the team at Fred Hutchinson Cancer Research Center.

"We are, in essence, temporarily converting mice from warm-blooded to cold-blooded creatures, which is exactly the same thing that happens naturally when mammals hibernate," said Mark Roth, who led the study, in a statement.

"We think this may be a latent ability that all mammals have -- potentially even humans -- and we're just harnessing it and turning it on and off, inducing a state of hibernation on demand," said Roth, a biochemist.

Bears do it, amphibians do it, and people occasionally hibernate, too. Many cases have been documented of small children, and the occasional adult, reviving from near-drownings in icy water after their body temperatures had dropped and they had stopped breathing for more than an hour.

"Understanding the connections between random instances of seemingly miraculous, unexplained survival in so-called clinically dead humans and our ability to induce and reverse metabolic quiescence in model organisms could have dramatic implications for medical care," Roth said.

--Reuters

...and from the Beeb:

Astonishing drop

In the latest study, Dr Roth and his colleagues found that the mice stopped moving and appeared to lose consciousness within minutes of breathing the air and H2S mixture.

The animals' breathing rates dropped from the normal 120 breaths per minute to less than 10 breaths per minute.

During exposure their metabolic rates dropped by an astonishing 90%, and their core body temperatures fell from 37C to as low as 11C.

After six hours' exposure to the mixture, the mice were given fresh air. Their metabolic rate and core body temperature returned to normal, and tests showed they had suffered no ill effects.

Co-author Eric Blackstone said the next step would be to carry out studies in larger animals.

Mice do not normally hibernate, but they can reach a similar state called clinical torpor in conditions of food deprivation.

"If you can manipulate the metabolism of animals in this way with implications for humans then I could see very widespread applications," commented John Speakman, professor of zoology at the University of Aberdeen.

"There is military interest in short-duration hibernation for battlefield stabilisation of troops. If you have a soldier who is shot down, you want to be able to hibernate them on site until you can get a team in to rescue them."

Space travel

Scientists at the European Space Agency (Esa) are investigating the possibility of inducing hibernation-like states in astronauts sent on long trips to the outer planets such as Jupiter and Saturn. However, like other applications, this one may be some way off.

"The atmospheric approach to inducing torpor is a nice one because it would diffuse very quickly in the body and saves you having to administer something internally," explained Mark Ayre, of Esa's Advanced Concepts Team at Nordwijk in the Netherlands.

"We have been looking at suspended animation to cut consumables - food and water - on a journey that could take five years or longer. That is important because missions are driven by the mass of the spacecraft.

"The other thing is trying to avoid psychological problems. You can have people awake, in which case you need to keep them entertained. That means more volume and potentially a very large mass.

"Or you avoid all that by putting them to sleep."

Inducing hibernation-like states could also have potential in cancer research by allowing patients to tolerate higher radiation doses without damaging healthy tissue.

Cancer cells are not dependent on oxygen to grow, says Dr Roth, so they are more resistant to radiotherapy.

"Right now in most forms of cancer treatment we're killing off the normal cells long before we're killing off the tumour cells. By inducing metabolic hibernation in healthy tissue, we'd at least level the playing field," he explained.