Jr. Layne et al., FREEZE DURATION INFLUENCES POSTFREEZE SURVIVAL IN THE FROG RANA-SYLVATICA, The Journal of experimental zoology, 280(2), 1998, pp. 197-201
Survival, cryoprotection, and the time course for recovery of vital fu
nctions were studied in autumn-collected juvenile wood frogs (Rana syl
vatica) following freezing at -1.5 degrees C for various periods. Frog
s readily tolerated freezing for 3 or 9 d, but only 50% survived a 28-
d freezing trial. Generally, the postfreeze return of vital functions
(vascular circulation, pulmonary breathing, righting reflex, jumping r
eflex) occurred later in frogs frozen for longer periods. Augmenting e
ndogenous levels of the cryoprotectant glucose (via injections) prior
to freezing substantially increased freeze endurance, as these frogs h
ad excellent survival after remaining frozen for as long as 49 d. The
improved freeze endurance of glucose-loaded frogs apparently was not a
ssociated with a reduction in ice content but rather may reflect the g
reater availability of energy substrate needed to support metabolism o
f frozen ischemic tissues. (C) 1998 Wiley-Liss,Inc.