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Cold-blooded Solutions to Warm-blooded Problems

R.sylvatica, North American wood frog.[ Click for a larger image.] Photo by Dr. Kenneth Storey.
Dr. Boris Rubinsky explains why the wood frog is such an excellent model for his research.

P icking up where18th century Arctic explorers left off, Boris Rubinsky is discovering what the wood frog knew all along -- how to freeze and thaw. Rubinsky is an engineer at U.C. Berkeley. His goal is to revolutionize the logistics of organ transplantation through cryopreservation: to preserve for weeks donor organs which now last only hours.

The time-honored mantra of those who study cryopreservation is that a living organ can only be preserved if the formation of ice crystals is utterly avoided. But the wood frog and other denizens of the Great White North have led Rubinsky to reject this notion in favor of a new one: If ice crystals cannot be wholly prevented, at least their propagation can be controlled -- with startling results.


The North American wood frog belongs to a small group of animals that are freeze tolerant. As the temperature drops below freezing each winter, the wood frog drifts into a deep hibernation, its breathing and heartbeat grind to a halt, and as much as 65% of the water in its body gradually crystallizes into ice. Sound uncomfortable? The wood frog seems not to mind terribly much, as it spends two or three months of each winter frozen, with its body temperature ranging between -1°C and -6°C. When spring finally arrives, the ice melts, heartbeat and breathing return, and the frog continues on its happy-go-lucky way.