Scientists believe they may be able to explain how some people who apparently freeze to death can be revived after a form of suspended animation.
Cell biologist Mark B Roth and his team at the Fred Hutchinson Cancer Research Center examined two very different organisms – yeast and nematodes, or garden worms.
They showed that both can survive hypothermia if they are first put into a state of suspended animation by means of anoxia, or extreme oxygen deprivation.
Under normal conditions, they found, yeast and nematode embryos cannot survive extreme cold. After 24 hours of exposure to temperatures just above freezing, 99 percent of the creatures die.
In contrast, if the organisms are first deprived of oxygen, a state of anoxia-induced suspended animation is induced, and 66 percent of the yeast and 97 percent of the nematode embryos survive.
Once normal growth conditions are resumed – upon rewarming and reintroduction of oxygen – the organisms reanimate and go on to live a normal lifespan.
There have been several documented cases in which humans have managed to make complete recoveries after apparently freezing to death.
Canadian toddler Erica Nordby wandered outside wearing only a diaper in winter 2001. Her heart had stopped beating for two hours and her body temperature had plummeted to 61 degrees Fahreneit before she was discovered, rewarmed and resuscitated.
In another notable incident, a Japanese man, Mitsutaka Uchikoshi, fell asleep in 2006 on a snowy mountain and was found by rescuers 23 days later with a core body temperature of 71 degrees Fahrenheit. He, too, made a full recovery.
Anoxia-induced suspended animation protects against extreme cold by preventing the cascade of events that lead to biological instability and, ultimately, death.
"When an organism is suspended its biological processes cannot do anything wrong," Roth said. "Under conditions of extreme cold, sometimes that is the correct thing to be doing; when you can’t do it right, don’t do it at all."