Suspended Animation for Worm Embryos: Life After Frozen Death
Molecular biologist Mark Roth has found a way to bring frozen worm embryos and yeast cells back from the dead: he makes them hold their breath. In a paper to appear in the July 1 issue of Molecular Biology of the Cell, Roth questions the relationship between low oxygen, low temperatures, and life after death.
Freezing almost any living thing means certain doom, but, on occasion, organisms inexplicably make it through the cold. Even some humans have come back from what seemed an icy demise, for example the Canadian toddler Erica Nordby. In 2001, Nordby’s heart stopped beating for two hours and her body temperature dropped to 61 degrees Fahrenheit before rescuers found her and brought her back to life. Apparent miracles like these inspired Roth to hunt for the biological mechanisms at work.
This study did not freeze humans. Instead, Roth looked for a common life-preserving link in two frozen organisms very different from each other. He chose the nematode embryo and the yeast cell, and found that successful resuscitation in both organisms required extreme oxygen deprivation before freezing.
Roth and colleagues found that under normal conditions, yeast and nematode embryos cannot survive extreme cold. After 24 hours of exposure to temperatures just above freezing, 99 percent of the creatures expire. In contrast, if the organisms are first deprived of oxygen and thus enter a state of anoxia-induced suspended animation, 66 percent of the yeast and 97 percent of the nematode embryos will survive the cold. Once normal growth conditions are resumed–upon rewarming and reintroduction of oxygen–the organisms will reanimate and go on to live a normal lifespan.[Science Daily]
A developing nematode embryo rapidly divides its cells. When frozen, the embryo cannot divide these cells properly–and errors mean death. Roth believes that first reducing the organism’s oxygen, pauses it (as seen in the video, below) and keeps it from carrying out its job incorrectly.
The mechanism … has to do with 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.” [Fred Hutchinson Cancer Research Center Release]
Though this research does not explain the medical mysteries of frozen children coming back to life, Roth believes that this line of research into slowing organisms’ natural functions might eventually help preserve human organs for transplant or help in surgery.
Roth’s laboratory studies the potential clinical benefits of metabolic flexibility–from anoxia-induced reversible suspended animation to metabolic hibernation brought on by exposure to agents such as hydrogen sulfide. The ultimate goal of this work is to find ways to temporarily lower metabolism–like dialing down a dimmer switch on a lamp–as a means to “buy time” for patients in trauma situations, such as victims of heart attack or blood-loss injury, by reducing their need for oxygen until definitive medical care can be given. [Science Daily]
Image: flickr / ianduffy