142 PHYSIOLOGY OF INDUCED HYPOTHERMIA 



the kidney takes place only in the last phase of re warming (And jus and ^lorel, 

 1952). 



Rats reanimated from the state of suspended animation after cooling to zero or 

 below have a much longer period of convalescence. The BAIR is lower than 

 normal and the RQ is abnormally high. Heat regulation is greatly impaired so that 

 the behavior is poikilothermic during the first hours, even days, requiring warm 

 surroundings. There is a temporary fall of water and food intake and a significant 

 weight loss. There is also a temporary impairment of fertility (Andjus and Smith, 

 1955). Psychological tests showed that although retention is not significantly influ- 

 enced, the learning capacity (problem-solving performance) seems to be signifi- 

 cantly, although temporarily, impaired. One rat rewarmed after cooling to a body 

 temperature of -3° C, had to be fed artificially for days before its capability of 

 standing and locomotion was re-established and its growth resumed. 



Eifect of repeated cooling. Rats can tolerate repeated cooling to zero, as fre- 

 quently as ten times in the course of 43 days (Andjus, 1955). Repeated cooling, 

 however, has its specific physiological consequences. Repeated cooling to 15° C, for 

 instance, increases the hyperglycemic reaction. Cooling to this level can be done as 

 often as every second day for five weeks (Popovic, 1952). Of great interest are 

 the adaptive changes elicited by repeated cooling to 0° C, which result in signifi- 

 cantly improved recovery rates, including more immediate re-establishment of 

 thermoregulation, less weight loss, and a rapid resumption of growth. There is also 

 an indication that repeated exposures lengthen the survival times after suspended 

 animation (Andjus, 1955). The physiological mechanisms of these improvements 

 remain unknown, although such changes as an increased adrenal weight have been 

 recorded. 



REFERENCES 



1. Andjus, R. K. : L'application de I'anesthesie hypoxique en hypophysectomie, Arch. Biol. Sc, 



Belgrade 2: 19-31, 1950. 



2. Andjus, R. K. : Sur la possibilite de ranimer le rat adulte refroidi jusqu'a proximite du point 



de congelation, C. R. Acad. Sci., Paris 232: 1591-1593, 1951. 

 '• 3. Andjus, R. K. : Suspended animation in cooled, supercooled, and frozen rats, J. Physiol. 

 128: 547-556, 1955. 



4. Andjus, R. K., Knopfelmacher, F., Russell, R. W., and Smith, A. U. : Effects of hypothermia 



on behavior, Nature 176: 1015-1016, 1955. 



5. Andjus, R. K., Lachiver, F., and Olivereau, AI.: Fonctionnement thyriodien chez le rat en 



lethargic hypotlicrmique, C. R. Acad. Sci., Paris 238: 838-840, 1954. 



6. Andjus, R. K., and Lovelock, J. E. : Reanimation of rats from body temperatures between 



and 1° C. by microwave diathermy, J. Physiol. 128: 541-546, 1955. 



7. Andjus, R. K., and Morel, F. : L'excretion hydro-minerale au cours de I'hypothermie etudiee 



chez le rat a I'aide du radio-sodium Na^ C. R. Soc. Biol., Paris 146: 1477-1481, 1952. 



8. Andjus, R. K., and Smith, A. U. : Reanimation of adult rats from body temperatures be- 



tween and 2° C, J. Physiol. 128: 446-472, 1955. 



9. Giaja, J.: Etat semblable a la torpeur des hibernants obtcnu chez le rat par la depression 



barometrique, Piull. Acad. Beograd 6: 65-79, 1940. 



10. Giaja, J.: Letargicno stanje dobiveno u macke i psa dejstvnm razredjcnog vazdulia i 



hladnoce, Glas Akad. Beograd (1) 188:U2,-U6, 1941. 



11. Giaja, J.: Hypothermic, hibernation, et poikilothermie expcrimentale, Biol, med., Paris 



'Z^.- '545-580, 1953. 



