Browsing by Author "Opazo, JC"

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    Arousal from torpor in the chilean mouse-opposum (Thylamys elegans)
    (1999) Opazo, JC; Nespolo, RF; Bozinovic, F
    We examined the effect of norepinephrine injections on non-shivering thermogenesis (NST), rewarming rate, and metabolic cost during torpor arousal in warm- and cool-acclimated Chilean mouse-opposums, Thylamys elegans. Warm- and cool-acclimated animals did not display NST in response to NE injections. Values of VO2 (resting, after saline and NE injections) were not significantly different within treatments. Rewarming rates of warm-acclimated animals did not differ significantly from those in cool-acclimated animals. In contrast, the metabolic cost of torpor arousal was significantly affected by acclimation temperature. Warm-acclimated animals required more energy for arousal than cool-acclimated animals. Our study suggests that the main thermoregulatory mechanism during torpor arousal in this Chilean marsupial is shivering thermogenesis, and that its amount can be changed by thermal acclimation. (C) 1999 Elsevier Science B.V. All rights reserved.
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    Thermal acclimation, maximum metabolic rate, and nonshivering thermogenesis of Phyllotis xanthopygus (rodentia) in the Andes mountains
    (1999) Nespolo, RF; Opazo, JC; Rosenmann, M; Bozinovic, F
    We determined non-shivering thermogensis (NST) and maximum metabolic rate (MMR) as functions of thermal acclimation in a small mammal species in a seasonal environment. We studied the rodent Phyllotis xanthopygus (Muridae) living in the cool to cold climate of the high Andean Plateau of northern Chile. As expected, NST and MMR were constantly higher in cool-acclimated individuals. Nevertheless, the observed differences in shivering thermogenesis (ST) as a result of temperature acclimation (>200%) exceeded our expectations. The large contributions of ST was due to a 94% increase in MMR while a 49% of increased in NST Thus, changes in ST in P. xanthopygus account for most of the metabolic plasticity and thermogenic capability that enables this species to cope with thermal variations in the Andean environment.