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