AJP - Regulatory, Integrative and Comparative Physiology, Vol 266, Issue 6 1771-R1777, Copyright © 1994 by American Physiological Society
1H magnetic resonance imaging of freezing and thawing in freeze-tolerant frogs
B. Rubinsky, S. T. Wong, J. S. Hong, J. Gilbert, M. Roos and K. B. Storey
Department of Mechanical Engineering, University of California at Berkeley 94720.
Proton magnetic resonance imaging (MRI) of the processes of freezing and
thawing in the wood frog Rana sylvatica provided noninvasive and real-time
analysis of the mode of ice propagation through the body of a
freeze-tolerant vertebrate. MRI revealed a directional movement of ice from
the exterior inward that required several hours to reach completion.
Freezing in core organs such as liver, which produces and exports
cryoprotectant, and heart, which circulates it, was delayed and occurred
well after the organs were surrounded by extraorgan ice. Natural thawing
was a very different process; thawing began uniformly throughout the body,
but core organs melted more rapidly than peripheral ones, an adaptation
that may be key to the early restoration of heartbeat and breathing. The
images presented demonstrate the sensitivity and power of MRI and its
potential to become a critical monitoring technology in the development of
cryopreservation techniques for mammalian organ explants.
