Field observations indicated a difference in the ability to locomote at low body temperatures in two closely related species of lizards from very different habitats and with radically different seasonal behavior. I measured the critical thermal minimum (the body temperature at which a cooling lizard just loses the ability to right itself) in both species. The winter-active, montane Sceloporus jarrovi had a significantly lower critical thermal minimum in both summer and winter than the winter-hibernating, lowland S. magister. Critical thermal minima were significantly lower in winter than in summer for both species. To determine a physiological basis for these differences, I examined the activity of myosin ATPase, which plays the limiting role in the velocity of muscle contraction, and the energetics of muscle as reflected by high energy phosphate compounds. Microenvironmental conditions were correlated with behavior, constraints on winter activity, and muscle physiology. Ca²⁺-activated myosin ATPase activity in S. magister of valley bottoms is greater than that in the vertical rock-dwelling S. jarrovi. No seasonal acclimatization occurs in myosin ATPase activity in either species. Changes in the muscle metabolism of hibernating animals has been attributed to the lack of muscular contractions in the dormant animals. I measured levels of phosphorylated compounds in a hindlimb muscle from summer and winter lizards of both species. Significant seasonal changes occur in some of the phosphate compounds in both species even though, within a given season, respective levels of phosphorylated compounds are similar in both species. Phosphorylcreatine and total acid-soluble phosphate levels increased in winter animals of both species. Apparently the high levels of phosphorylcreatine in winter S. magister are not simply due to inactivity; winter-active S. jarrovi contain similar amounts. Seasonal cycling of phosphate compounds may relate more to parathyroid status than to muscle activity. Winter activity in S. jarrovi was site-specific and highly dependent on a favorable microclimate. Winter dormancy in S. magister apparently is not dictated by the severity of the microclimate nor physiological limitations of skeletal muscle, but may be strongly influenced by the thermal inertia of that relatively large species.

No description available.

No description available.

Saccostomus campestris display sexual disparity in the use of summer daily torpor in response to energy stress. The hypothesis that males may compensate for a limited heterothermic capacity with lower normothermic body temperatures by maintaining lower resting metabolic rates relative to females was tested. Furthermore, the influence of testosterone on torpor incidence in males was investigated. Body temperature (T[b]) and oxygen consumption (VO₂) were measured at various ambient temperatures (Tₐ) and were compared between the sexes under food ad libitum and food restriction treatments. There were no significant differences in T[b] and VO₂ between sexes under food ad libitum treatment. Under food restriction there were pronounced sex differences in the employment of heterothermy. Females defended a lower setpoint T[b] for torpor (ca. 25°C), than males (ca. 29°C), and also employed torpor more frequently than males. Non-torpid males did, however show slight reductions in VO₂ under food restriction. The effect of testosterone on daily torpor was investigated by comparing minimum T[b]and torpor frequency of castrated mice implanted with testosterone-filled (experimental) and saline-filled (control) silastic capsules in response to food ad libitum and food restriction treatments. Testosterone inhibited torpor in males. The majority of control animals employed torpor under both food ad libitum and food restriction diets. It was concluded that although the animals were capable of shallow, summer torpor, it was confined to moderate ambient temperatures and was not used at low Tₐ's where several animals became pathologically hypothermic. Females derive energetic benefits from the use of torpor whereas males may partially compensate for their limited heterothennic capacity by a reduction in resting metabolic rates, accompanied by moderate reductions in body temperature during energetically stressful periods. The difference in the capacity for daily heterothenny between sexes was attributed to differences in their reproductive physiology. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2000.

No description available.

京都大学 / 新制・課程博士 / 博士(薬科学) / 甲第23841号 / 薬科博第156号 / 新制||薬科||17(附属図書館) / 京都大学大学院薬学研究科医薬創成情報科学専攻 / (主査)教授 土居 雅夫, 教授 中山 和久, 教授 竹島 浩 / 学位規則第4条第1項該当 / Doctor of Pharmaceutical Sciences / Kyoto University / DGAM

Thesis (MPsy(Clinical))--University of South Australia, 2005.

Bibliography: leaves 162-197. / vii, 216 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / To determine the effects of melatonin on sleepiness and body temperature under conditions that better approximated the endogenous melatonin profile. / Thesis (Ph.D.)--University of Adelaide, Dept. of Obstetrics and Gynaecology, 1998?

Thesis (MPsy(Clinical))--University of South Australia, 2005.

Diss. (sammanfattning) Linköping : Univ., 2002. / Härtill 5 uppsatser.