Em mamíferos, a temperatura corporal (Tc) varia ao longo do dia, de forma rítmica, bem como a atividade locomotora. Essa ritmicidade diária é gerada endogenamente, por osciladores circadianos. Em geral, os valores mais elevados de Tc concentram-se nos mesmos horários em que há atividade locomotora. No entanto, variações diárias de Tc são observadas mesmo em indivíduos imóveis, evidenciando que o ritmo de Tc não é uma mera consequência dos efeitos agudos da atividade locomotora. Este trabalho teve o objetivo de estudar o ritmo circadiano de Tc no roedor Ctenomys aff. knighti (tuco-tuco) e sua relação temporal com o ritmo de atividade locomotora. A caracterização do ritmo de Tc nesse animal é particularmente interessante, pois ele habita o ambiente subterrâneo, que impõe desafios tanto à expressão rítmica (pois os ciclos ambientais são ausentes ou têm baixa amplitude) quanto à termorregulação (devido à características como alta umidade e atmosfera hipóxica e estagnada). Medimos a Tc e a atividade locomotora dos tuco-tucos em condições controladas de laboratório. Na caracterização inicial, constatamos que o ritmo de Tc dos tuco-tucos persiste mesmo em escuridão e temperatura constantes. Quando houve exposição a um ciclo diário de claro/escuro, o ritmo de Tc foi sincronizado, e os valores mais altos ocorreram na fase de escuro. Os ritmos de Tc e de atividade locomotora mostraram-se fortemente associados no tempo. Investigamos, então, se a corrida na roda de atividade modificaria a amplitude do ritmo de Tc, por envolver atividade muscular intensa. Observamos, no entanto, que a amplitude é pouco alterada com a retirada da roda e que na sua ausência os animais substituem a corrida por outras atividades que também causam efeitos agudos na Tc. Em seguida, estudamos a variação da sensibilidade da Tc aos efeitos agudos da atividade ao longo do dia. Através de um método estatístico, que também foi utilizado para filtrar os dados de Tc, verificamos que há maior correlação entre variações de Tc e de atividade no início da noite. Por fim, investigamos se o controle do ritmo de Tc é exercido pelos núcleos supraquiasmáticos, os quais são os osciladores circadianos do ritmo de atividade locomotora. Nossa abordagem utilizou animais neurologicamente intactos, comparando os padrões do ritmo de Tc e de atividade locomotora durante a ocorrência do fenômeno de \"partição do ritmo\". Constatamos que na maioria dos casos os padrões de partição, tanto da Tc como da atividade locomotora são idênticos, sugerindo um controle temporal comum. No entanto, em um dos animais observamos diferenças entre os dois ritmos, sugerindo que esse controle circadiano pode ser ainda mais complexo. / In mammals, body temperature (Tb), as well as locomotor activity, changes during the day, exhibiting a rhythmic pattern. This daily rhythmicity is generated endogenously by circadian oscillators. Usually, the highest Tb values occur simultaneously to locomotor activity. Nevertheless, daily Tb changes are observed even in immobile individuals. This fact is evidence that the Tb rhythm is not a mere consequence of the acute effects of locomotor activity. The present work,which os performed in the research center CRILAR, in Argentina, had the objective of studying the circadian rhythm of Tb. in the rodent Ctenomys aff. knighti (tuco-tuco) and its temporal relationship with the locomotor activity rhythm. The characterization of the Tb rhythm in this animal is especially interesting because it inhabits the subterranean environment, which poses challenges to both rhythmic expression (because environmental cycles are either absent or have low amplitude) and thermoregulation (due to high relative humidity, hypoxic atmosphere and limited ventilation). We measured Tb and locomotor activity of tuco-tucos under controlled laboratory conditions. An initial characterization showed that the tuco-tuco\'s Tb rhythm persisted even in constant darkness and constant temperature. This rhythm synchronized to a daily light/dark cycle, with highest values occurring during the dark phase. Tb and locomotor activity rhythm were robustly associated in time. Then, we investigated whether the wheel running would modify the Tb rhythm amplitude, because this behavior involves intense muscular activity. However, we observed that the amplitude is only slightly altered upon running-wheel removal and that in the absence of the wheel tuco-tucos substitute running with other behaviors which also have acute effects on Tb. Applying a statistical method, which was also used to filter Tb data, we verified that there is a stronger correlation between Tb changes and activity in the beginning of the night. Finally, we investigated whether the Tb rhythm is also under control of the suprachiasmatic nuclei, which are knowingly the circadian oscillators for the locomotor activity rhythm. We used an approach which involved neurally intact animals, by comparing the rhythmic patterns of Tb and locomotor activity rhythms during the occurrence of a phenomenon called \"splitting\". In most cases, splitting patterns of both Tb and locomotor activity rhythms were identical, indicating a common temporal control of these two variables. Nevertheless, we observed, in one animal, differences between the two rhythms, which suggest that the circadian control might be even more complex.

Abstract The use of regulatory and obligatory heat production mechanisms were studied in juvenile birds during the development of endothermy. The development of shivering thermogenesis was studied in the pectoral and gastrocnemius muscles of the altricial domestic pigeon and in three precocial galliforms (Japanese quail, grey partridge and domestic fowl). The development of shivering was the determinant for the beginning of endothermy. Homeothermy also necessitated avoidance of excess heat loss by insulation and behavioural thermoregulation. In the precocial species, shivering thermogenesis was present in the leg muscles of the youngest age groups (1-2 d) studied. Breast muscles contributed shivering from the second post-hatching week. In the altricial pigeons, significant thermogenesis was apparent later than in the precocials, at the age of 6 d. In contrast to the precocials, the pectoral muscles of the altricials were the most significant heat production tissues. In newly-hatched partridges and pigeons, incipient shivering did not result in significant heat production. The ability to produce heat in cold by putative nonshivering thermogenesis was studied in Japanese quail chicks and domestic ducklings. In both species, three-week cold acclimation resulted in morphometric and physiological changes, but there was no clear evidence of nonshivering thermogenesis. The lack of NST was evident because an increase in shivering amplitude at least in one of the muscles studied paralleled an increase in oxygen consumption. Consequently, shivering thermogenesis was probably the only mode of regulatory heat production. The amplitudes of shivering EMGs measured during cold exposure were dependent on the coexistence of postprandial thermogenesis or exercise. Japanese quail chicks were able to substitute shivering thermogenesis partially with postprandial heat production when nourished. Bipedal exercise both inhibited shivering in pectorals directly via inhibitory neural circuits and stimulated it indirectly via decreased body temperature. Because of increased heat loss, exercise was not used as a substitute for shivering. Shivering is a flexible mode of thermogenesis and its magnitude can be adjusted according to the magnitude of obligatory thermogenesis. The adjustment works towards energy saving by avoidance of the summation of different modes of heat production. The prerequisite for successful adjustment of shivering is adequate insulation, whose role in preventing excessive heat loss is pronounced during exercise. It is concluded that the energetics of posthatching thermoregulation includes the potential for optimizations in energy use in order to avoid dissipation of waste energy as heat.

Current knowledge indicates that nonthermal muscle metaboreflex activity plays a critical role in the modulation of skin vasodilation and sweating. However, the mechanisms of control have primarily been studied during isometric handgrip exercise in which muscle metaboreceptor activation is induced by a brief post-exercise ischemia of the upper limb. While the reflex increase in mean arterial pressure associated with this period of ischemia is consistent with the activation of muscle metaboreceptors, the change in baroreflex activity may in itself modulate the response. Thus, we sought to understand how these nonthermal stimuli interact in modulating the control of skin perfusion and sweating under conditions of elevated hyperthermia. Furthermore, we examined the mechanisms responsible for the maintenance of arterial blood pressure under varying levels of heat stress during isometric handgrip exercise. Our study findings indicate that the parallel activation of muscle metaboreceptors and baroreceptors during post-exercise ischemia causes divergent influences on the control of skin blood flow and sweating; and these nonthermal stimuli are dependent on the level of hyperthermia. Moreover, we report that heat stress reduces the increase in arterial blood pressure during isometric handgrip exercise and this attenuation is attributed to a blunted increase in peripheral resistance, since cardiac output increased to similar levels for all heat stress conditions. These results provide important insight and understanding into the role of muscle metabo- and baroreflex activity on the control of skin blood flow and sweating; along with further knowledge into the cardiovascular mechanisms responsible for the regulation of arterial blood pressure during hyperthermia.

Thermoregulation is considered a top priority in neonatology due to the fact that relative to adults, neonates have a morphological susceptibility to excessive heat exchange with the environment, and exhibit limited physiological/behavioural responses to thermal strain. Consequently, the environmental conditions in which they are nursed must be tightly regulated to maintain body temperature stable. Neonatal intensive care units (NICU) use radiant warmers (RW) to thermally manage many newborns. However, recent evidence suggests that RW induce intermittent bouts of thermal strain that could adversely affect patients. This warrants further investigation of neonatal heat balance and the pertinent factors affecting it. Conducting an exhaustive audit of heat exchanges affecting the body during standard care under a RW could yield important information that would lead to the improvement of clinical practice in NICUs. The present thesis focuses on neonatal thermoregulatory responses, various body heat exchange mechanisms and processes during standard care under RW.

The current thesis examined whether sex-differences in local and whole-body heat loss are evident after accounting for confounding differences in physical characteristics and rate of metabolic heat production. Three experimental studies were performed: the first examined whole-body heat loss in males and females matched for body mass and surface area during exercise at a fixed rate of metabolic heat production; the second examined local and whole-body heat loss responses between sexes during exercise at increasing requirements for heat loss; the third examined sex-differences in local sweating and cutaneous vasodilation to given doses of pharmacological agonists, as well as during passive heating. The first study demonstrates that females exhibit a lower whole-body sudomotor thermosensitivity (553 ± 77 vs. 795 ± 85 W•°C-1, p=0.05) during exercise performed at a fixed rate of metabolic heat production. The second study shows that whole-body sudomotor thermosensitivity is similar between sexes at a requirement for heat loss of 250 W•m-2 (496 ± 139 vs. 483 ± 185 W•m-2•°C-1, p=0.91) and 300 W•m-2 (283 ± 70 vs. 211 ± 66 W•m-2•°C-1, p=0.17), only becoming greater in males at a requirement for heat loss of 350 W•m-2 (197 ± 61 vs. 82 ± 27 W•m-2•°C-1, p=0.007). In the third study, a lower sweat rate to the highest concentration of acetylcholine (0.27 ± 0.08 vs. 0.48 ± 0.13 mg•min-1•cm-2, p=0.02) and methylcholine (0.41 ± 0.09 vs. 0.57 ± 0.11 mg•min-1•cm-2, p=0.04) employed was evidenced in females, with no differences in cholinergic sensitivity. Taken together, the results of the current thesis show that sex itself can modulate sudomotor activity, specifically the thermosensitivity of the response, during both exercise and passive heat stress. Furthermore, the results of the third study point towards a peripheral modulation of the sweat gland as a mechanism responsible for the lower sudomotor thermosensitivity in females.

Heat acclimation increases the local heat loss responses of sweating and skin blood flow which is thought to persist for up to 3 weeks post-acclimation. However, the extent to which increases in local heat loss affect whole-body heat loss as a function of increasing levels of heat stress remains unresolved. Using direct calorimetry, we examined changes in whole-body evaporative heat loss (EHL) during progressive increases in metabolic heat production 1) prior to (Day 0), during (Day 7) and following a 14-day heat acclimation protocol (Day 14) – Induction phase, and; 2) at the end of a 1-week (Day 21) and 2-week decay period (Day 28) – Decay phase. Ten males performed intermittent exercise (3 x 30-min (min) bouts of cycling at 300 (Ex1), 350 (Ex2), and 400 watts•meters2 (W•m2) (Ex3) separated by 10 and 20 min rest periods, respectively). During the induction period, EHL at Day 7 was increased at each of the three exercise bouts (Ex1: + 6%; Ex2 +8%; Ex3: +13%, all p≤0.05) relative to Day 0 (EHL at Ex1: 529 W; Ex2: 625 W; Ex3: 666 W). At Day 14, EHL was increased for all three exercise bouts compared to Day 0 (Ex1: 9%; Ex2: 12%; Ex3: 18%, all p≤0.05). As a result, a lower cumulative change in body heat content (ΔHb) was measured at Day 7 (-30%, p≤0.001) and Day 14 (-47%, p≤0.001). During the decay phase, EHL at Day 21 and 28 was only reduced in Ex 3 (p≤0.05) compared to Day 14. In parallel, ΔHb increased by 39% (p=0.003) and 57% (p≤0.001) on Day 21 and Day 28 relative to Day 14, respectively. When Day 28 was compared to Day 0, EHL remained elevated in each of the exercise bouts (p≤0.05). As such, ΔHb remained significantly lower on Day 28 compared to Day 0 (-16%, p=0.042). We show that 14 days of heat acclimation increases whole-body EHL during exercise in the heat which is maintained 14 days post-acclimation.

Previous research has demonstrated that ingesting fluid of different temperatures results in different whole-body sweat losses (WBSL) and transient changes in local sweat rate (LSR) without any parallel differences in core or skin temperatures. The purpose of this thesis was to determine the potential location and relative contribution of gastrointestinal thermoreceptors that modify sudomotor activity. Eight participants cycled for 75 min while cold (1.5°C) and warm (50°C) water was either swilled in the mouth, or delivered directly to the stomach bypassing the mouth using a nasogastric tube, after 15, 30 and 45-min of exercise. Mouth-swilling warm or cold water did not alter sudomotor output, however delivering warm or cold water directly into the stomach led to a temperature-dependent change in sudomotor output, despite similar core and skin temperatures. These data indicate that thermoreceptors independently modulating sudomotor output probably reside within the abdominal area, but not the mouth.

京都大学 / 新制・課程博士 / 博士(地域研究) / 甲第23305号 / 地博第286号 / 新制||地||110(附属図書館) / 京都大学大学院アジア・アフリカ地域研究研究科アフリカ地域研究専攻 / (主査)准教授 佐藤 宏樹, 教授 山越 言, 准教授 安岡 宏和 / 学位規則第4条第1項該当 / Doctor of Area Studies / Kyoto University / DGAM

Bats inhabiting arid, subtropical environments face diverse challenges related to energy and water balance. First, they may have to conserve water and energy during cool, dry winters when water is scarce and insect availability reduced. Second, during hot summers when air temperature may routinely exceed body temperature, bats may need to avoid both hyperthermia and dehydration. A common response to the energetically challenging winter period in temperate, subtropical and tropical species is heterothermy (i.e. torpor and hibernation). Despite evidence suggesting that heterothermy is of major significance in the energy balance of tropical and subtropical bats, its occurrence in southern African species especially those in semi-arid subtropical regions have received relatively little attention. Moreover, the physiological and thermoregulatory responses of bats to high air temperatures (Ta) are relatively poorly known. The goal of my project was to investigate various seasonal physiological challenges imposed on bats in an arid, sub-tropical climate. I investigated the occurrence of winter heterothermy in Nycteris thebaica (Nycteridae) in the Limpopo Valley. Skin temperatures (Tskin) were measured using temperature-sensitive transmitters, and roost temperatures (Troost) were recorded using miniature temperature loggers. N. thebaica used multiple roosting sites, including a hollow baobab tree (Adansonia digitata) and several caves, and exhibited only moderate heterothermy. Tskin was maintained around normothermic levels, with differences of 3-9°C (7.5±1.7°C) between overall maximum and minimum Tbs. A minimum Tskin of 28.4°C occurred at Troost = 23.8°C, and patterns of thermoregulation did not appear to be influenced by prevailing weather conditions. Roost temperatures did not decrease below 10°C, and averaged 21.2±2.8°C and 23.3±2.9°C respectively. The lack of pronounced heterothermy in N. thebaica is surprising, particularly in view of the daily torpor cycles observed in many insectivorous bat species. I also investigated the physiological responses of three sympatric bat species during summer using an open-flow respirometry system to measure resting metabolic rates (RMR) and evaporative water loss (EWL) over a range of Tas ~ 10-42°C, with body temperatures (Tb) simultaneously recorded via temperature-sensitive passive integrated transponder (PIT) tags. Basal metabolic rates for Nycteris thebaica and Taphozous mauritianus were 8.9±2.7mW.g-1 and 6.6±2.2mW.g-1 respectively, falling within the 95% prediction intervals for bat BMR, whereas the value for Sauromys petrophilus (3.4±0.6mW.g-1) fell below the lower 95% prediction interval. Maximum EWL for N. thebaica, T. mauritianus and S. petrophilus were 18.6±2.1mg.g-1.h-1 (Ta=39.4°C), 14.7±3.1mg.g-1.h-1 (Ta=41.9°C) and 23.7±7.4mg.g-1.h-1 (Ta=41.7°C) respectively. Maximum individual Tbs recorded were 46.5°C in N. thebaica (Ta=39.3°C), 44.9°C in T. mauritianus (Ta=41.8°C) and 46.5°C in S. petrophilus (Ta=41.7°C). Overall, I found that N. thebaica was the least heat tolerant species, with T. mauritianus and S. petrophilus being more heat tolerant. In the face of climate change, heat tolerance together with specific thermal properties of a given roost may play a major role in the ability of a species to persist in a hot, arid environment. / Dissertation (MSc)--University of Pretoria, 2012. / Zoology and Entomology / unrestricted

Thermoregulation plays an important role in organisms' lives during foraging, escaping from predators, sexual selection or overwintering. Moreover, pressure on efficient thermoregulation could affect species on an evolutionary level and was recently hypothesized to maintain imperfect mimicry in hoverflies (Diptera, Syrphidae). We set these two aims: 1) to study relationships between thermoregulation, mimicry accuracy and resembled model, 2) to closely study effect of developmental temperature in an intermediately accurate honeybee mimic, Eristalis tenax. In the first part of the project, we examined temperature excess of 566 specimens in 47 species of hoverflies in the field. We did not find significant effect of mimicry accuracy on temperature excess in our data. However, we found a strong sexual dimorphism. Females had lower temperature excess, which was very resilient to internal and external factors, whereas males had higher temperature excess, influenced by activity at time of capture (flying > sitting) and resembled model (bumblebee-mimics > honeybee- mimics > wasp-mimics > solitary bee-mimics). We suggest, that males are pushed to higher temperature excess by sexual selection within lekking. In the second part of the project, we reared E. tenax in three different temperatures in laboratory...