X-Message-Number: 26064
Date: Thu, 21 Apr 2005 15:43:23 -0700 (PDT)
From: Andrew Lynch <>
Subject: Mice in suspended animation


Mice put in 'suspended animation' 

By Paul Rincon 
BBC News science reporter 

 The mice showed no ill-effects when they were revived

Mice have been placed in a state of near suspended animation, raising the 
possibility that hibernation could one day be induced in humans. 

If so, it might be possible to put astronauts into hibernation-like states for 
long-haul space flights - as often depicted in science fiction films. 
A US team from Seattle reports its findings in Science magazine. 

In this case, suspended animation means the reversible cessation of all visible 
life processes in an organism. 

The researchers from the University of Washington and the Fred Hutchinson Cancer
Research Center in Seattle put the mice in a chamber filled with air laced with
80 parts per million (ppm) of hydrogen sulphide (H2S) - the malodorous gas that
give rotten eggs their stink. 

Hydrogen sulphide can be deadly in high concentrations. But it is also produced 
normally in humans and animals, and is believed to help regulate body 
temperature and metabolic activity. 
'Widespread uses' 

In addition to its possible use in space travel, the ability to induce a 
hibernation-like state could have widespread uses in medicine. 

Lead investigator Dr Mark Roth said this might ultimately lead to new ways of 
treating cancer, and preventing injury and death from insufficient blood supply 
to organs and tissues. 

During hibernation, activity in the body's cells slows to a near standstill, 
dramatically cutting the animal's need for oxygen. 

If humans could be freed from their dependence on oxygen, it could buy time for 
critically ill patients on organ-transplant lists and in operating rooms, said 
Dr Roth. 

"Manipulating this molecular mechanism for clinical benefit potentially could 
revolutionise treatment for a host of human ills related to ischaemia 
[deficiency of the blood supply], or damage to living tissue from lack of 
oxygen," he explained. 

But he added that any procedure in a clinical setting would likely be 
administered via injection rather than by getting patients to inhale a gas. 
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 

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 

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