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"Cold-blooded Solutions
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Frozen wood frog
Frozen wood frog. [Click for a larger image.] Photo by Dr. Kenneth Storey.
Dr. Rubinsky explains how the old approach of attempting to freeze organs for transplant differs from the new approach.
The adaptations of the wood frog and other species led Dr. Rubinsky to his new model for organ preservation.
Dr. Kenneth Storey Dr. Kenneth Story
Boris Rubinsky Dr. Boris Rubinsky

or eight years now Rubinsky has sought to understand how the wood frog survives the formation of ice crystals inside its body. His efforts have paid off, for he has developed the world's first technology for preserving organs at subfreezing temperatures. Rubinsky credits the wood frog with leading him to success by causing him to reject traditionally accepted paradigms of organ preservation.

In the past, researchers have often sought to preserve organs by rapidly cooling them to -200°C in liquid nitrogen. The biggest problem with standard freezing is that expanding ice crystals wreak havoc upon delicate tissues, rupturing thousands of microscopic blood vessels and crushing billions of cells. Such damage is irreparable. But if cooling occurs quickly enough -- about 1,000°C per minute -- then water molecules simply don't have time to assemble into organized ice crystals. According to Rubinsky, the nagging problem is that organs are simply too large to cool uniformly at 1,000°C per minute. One could no sooner accomplish this feat than thaw a 15-pound turkey in a single second -- without either boiling the turkey's exterior or leaving its insides still half frozen. So far, no one has solved this problem. Based upon his studies of the wood frog, Rubinsky has chosen to forsake this approach in favor of the opposite one: cooling organs more slowly to temperatures only a few degrees below freezing.

A Remarkable Experiment
Freeze-tolerant frogs have only recently gained recognition for their potential contributions to medicine; however, their existence has long been known. According to Kenneth Storey, a Carleton University biologist and a relative old-timer to the study of freeze tolerant vertebrates, the first reports of freeze tolerant frogs came from 18th century European sailors exploring for a Northwest Passage through what is now Canada.

One such report appears in the travel log kept by Captain Francis Smith as his ship, the California, explored near the Arctic Circle. Touching land in May 1747, Smith noted the emergence of "an infinite Number of Frogs, with a great croaking." The frogs had passed the winter frozen in holes in the ground. "A remarkable Experiment," wrote Smith, "is to take the Earth in which the Frog is so froze, and to break that Earth in Pieces without thawing it, the Frog will then break with it as short as a Piece of Glass. But...lay that Earth at a small Distance from the Fire, so as to thaw it, the Frog will recover his Summer Activity, and leap as usual."


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