Torpor and hibernation, two distinct forms of heterothermy, are physiological responses employed by many endotherms to save energy during periods of cold, climatic unpredictability and food shortage. Heterothermy is characterized by varying body temperature and has been found to occur in various subtropical mammals. However, studies on thermoregulatory capabilities of South African Microchiroptera remain relatively scant. In this study, the capacity for use of heterothermy, the seasonal metabolic rates, and capacity for non-shivering thermogenesis were studied in four species of bats, namely Rhinolophus clivosus, Rhinolophus capensis, Miniopterus natalensis and Myotis tricolor. Animals were collected from a group of three mines in Sleepy Hollow Farm, 30km from Port Elizabeth, South Africa. All species demonstrated bouts of torpor in the winter while R. clivosus interestingly established a high propensity for torpor in the summer and normothermia in the winter. To my knowledge, this is the first study that has shown the down-regulation of metabolism and body temperature in summer and constant maintenance of normothermic body temperature in winter in a species of Microchiroptera. M. natalensis was thermolabile in both summer and winter and body temperatures closely tracked ambient temperatures. Mean ± SD normothermic body temperature measured of wild-caught R. clivosus and M. natalensis was 38.6 ± 1.7°C and 37.3 ± 2.2°C, respectively. Mean torpid body temperature measured of wild-caught R. clivosus, R. capensis and M. natalensis was 22.7 ± 3.3°C, 21.1 ± 3.2 °C, and 22.6 ± 3.1°C, respectively. Non-shivering thermogenesis was measured in R. clivosus and M. natalensis to determine the role of endogenous heat production in a volant mammal. The mean noradrenalineinduced thermogenesis ± SD in R. clivosus and M. natalensis was 2.6 ± 0.8 ml g-1 hr-1 and 2.7 ± 0.6 ml O2 g-1 hr-1, respectively. Both species demonstrated capacity for non-shivering thermogenesis, and this is the first study that has quantified the maximal response to noradrenaline in an Afrotropical Microchiropteran species. Physiology of Afrotropical bats is understudied and the extent to which torpor and/or hibernation is utilized amongst them remains relatively unknown. Heterothermy clearly plays a significant role in the energetic savings and balance of all four species in the study.

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.

Six adult male volunteers of similar body composition and physical fitness were tested to determine plasma immunoreactive β-endorphin (Piβ-EN) response under three conditions of exercise thermoregulatory stress. The experimental protocol consisted of 120 min of stationary upright cycling at 50% Vo₂max under conditions of neutral (24ºC, 50% RH)/euhydration (NE), hot (35°C, 50% RH)/euhydration (HE), and hot/dehydration (HD). Piβ-EN was measured by radioimmunoassay at -30 min, 0 min, and at 15 min intervals thereafter. Change in plasma volume (ΔPV) was measured to determine its effect on Piβ-EN concentration. Preexercise Piβ-EN levels averaged 23.7 ± 2.6 pg•ml⁻¹ in all conditions. The greatest Piβ-EN response occurred at 105 min in HD conditions when levels rose to 43.2 ± 6.9 pg•ml⁻¹. Exercise in HD and HE conditions resulted in significantly (p < 0.05) elevated Piβ-EN above levels observed in NE. ΔPV did not account for more than 10% of Piβ-EN changes at any interval. The Piβ-EN response pattern closely resembled rectal temperature changes in all conditions. These data suggest that conditions of increasing exercise thermoregulatory stress are associated with increasing peripheral β-endorphin concentration. / Master of Science

Tang Chi-wing, Wendy = 飲品味道對炎熱中運動的華籍男女小童之體液平衡及體温調節之影響 / 鄧稚穎. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 74-86). / Text in English; abstracts in English and Chinese. / Tang Chi-wing, Wendy = Yin pin wei dao dui yan re zhong yun dong de hua ji nan nü xiao tong zhi ti ye ping heng ji ti wen diao jie zhi ying xiang / Deng Zhiying. / Dedication --- p.i / Acknowledgements --- p.ii / Abstract --- p.iii / Table of Contents --- p.vi / List of Tables --- p.viii / List of Figure --- p.ix / Chapter CHAPTER ONE --- INTRODUCTION --- p.1 / Chapter 1.1 --- Background --- p.1 / Chapter 1.2 --- Purpose of the Study --- p.4 / Chapter 1.3 --- Hypotheses --- p.5 / Chapter 1.4 --- Definition of Terms --- p.6 / Chapter 1.5 --- Assumptions --- p.7 / Chapter 1.6 --- Delimitations --- p.7 / Chapter 1.7 --- Limitations --- p.8 / Chapter 1.8 --- Significance of Study --- p.8 / Chapter CHAPTER TWO --- REVIEW OF LITERATURE --- p.9 / Chapter 2.1 --- Water Balance during Exercise --- p.9 / Chapter 2.2 --- Effect of Dehydration on Human Body during Exercise --- p.11 / Chapter 2.3 --- Physiological Responses of Dehydration for Children when Exercising in the Heat --- p.17 / Chapter 2.4 --- Effect of Fluid Ingestion during Exercise --- p.20 / Chapter 2.5 --- Drivers of Fluid Replacement --- p.23 / Chapter CHAPTER THREE --- METHODOLOGY --- p.30 / Chapter 3.1 --- Participants --- p.30 / Chapter 3.2 --- Equipment and Instrumentation --- p.31 / Chapter 3.3 --- Preliminary Measurement --- p.31 / Chapter 3.4 --- Study Design and Procedures --- p.35 / Chapter 3.5 --- Collection and Analysis of Blood Samples --- p.44 / Chapter 3.6 --- Statistical Analysis --- p.44 / Chapter CHAPTER FOUR --- RESULTS --- p.46 / Chapter 4.1 --- Exercise Intensity --- p.46 / Chapter 4.2 --- Body Fluid Balance --- p.50 / Chapter 4.3 --- Thermoregulatory Responses --- p.61 / Chapter 4.4 --- Taste Perception Analysis --- p.62 / Chapter 4.5 --- Summary of the Results --- p.66 / Chapter CHAPTER FIVE --- DISCUSSION --- p.67 / Recommendations and Applications --- p.73 / REFERENCES --- p.74 / APPENDIXES --- p.87

During flight missions, fighter pilots are in general exposed to vast amounts of stress including mild hypoxia, vibrations, high accelerations, and thermal discomfort. It is interesting to predict potential risks with a certain mission or flight case due to these stresses to increase safety for fighter pilots. The most predominant risk is typically thermal discomfort which can lead to serious health concerns. Extensive exposure to high or low temperature in combination with a demanding work situation weakens the physical and mental state of the pilot and can eventually lead to life-threatening conditions. One method to estimate the physical and mental state of a person is to measure the body core temperature. The body core temperature cannot be measured continuously during flight and needs to be estimated by using for instance a human thermoregulatory model. In this study, a model of the human thermoregulatory system and the cockpit environment is developed. Current thermoregulatory models are not customized for fighter pilots but a model developed by Fiala et al. in 2001, which has previously shown good performance in both cold and warm environments as well as for various activation levels for the studied person, is used as a theoretical foundation. Clothing layers are implemented in the model corresponding to clothes used by pilots in the Swedish air force flying the fighter aircraft Gripen E in warm outside conditions. Cooling garments and air conditioning systems as well as avionics, canopy, and cockpit air are included in the model to get a realistic description of the cockpit environment. Input to the model is a flight case containing data with altitude and velocity of the fighter during a mission. human heat transfer; body temperature regulation; physiological model;cooling garment; cockpit modeling

A skill instruction technique based on cognitive behavioral principles was applied to thermal imagery to determine if it could enhance either subjective or physiological responsiveness. The effects of imagery instruction were compared with the effects of muscle relaxation on imagery vividness, thermal imagery involvement, and the finger temperature response. The subjects were 39 male and 29 female volunteers from a minimum security federal prison. The personality characteristic of absorption was used as a classification variable to control for individual differences. It was hypothesized that high absorption individuals would reveal higher levels of imagery vividness, involvement, and finger temperature change; that imagery skill instruction and muscle relaxation would be more effective than a control condition; and that the low absorption group would derive the greatest benefit from the imagery task instruction condition. None of the hypotheses was supported. Finger temperature increased over time during the experimental procedure but remained stable during thermal imagery. The results suggest that nonspecific relaxation effects may best account for finger temperature increases during thermal imagery. Results were discussed in relation to cognitive-behavioral theory and the characteristic of absorption.

Serotonin syndrome (SS) is a drug-induced toxicity caused by an excess of serotonin (5-HT) in the central nervous system (CNS). The symptoms of the disorder range from mild to severe, with the severe state evoking life-threatening hyperthermia. Autonomic dysfunction is controlled in part by serotonin receptors, with the 5-HT2A receptor responsible for increasing core body temperature (Tcor). Our results show that the 5-HT2A receptors on the preoptic/anterior hypothalamus (PO/AH) and prefrontal cortex (PFC), in particular, are sensitive to changes in ambient temperature (Tamb). The toxic increase of 5-HT is postulated to occur due to the temperature-dependent activation of these receptors that promotes a positive feedback mechanism. Our results suggest that changes in Tamb can either exacerbate or alleviate the symptom and that this is mediated by the 5-HT2A receptors. Understanding the mechanism involved in elevating Tcor is imperative in treating and preventing the disorder. / by Swapna Krishnamoorthy. / Vita. / Thesis (M.S.)--Florida Atlantic University, 2008. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2008. Mode of access: World Wide Web.

Orientador: Alex Sandro Campos Maia / Banca: Marcos Chiquitelli Neto / Banca: Márcia Helena Machado da Rocha Fernandes / Resumo: O objetivo deste estudo foi validar o condicionamento dos animais e o desenvolvimento de pesquisas que visem entender as respostas do equilíbrio térmico de bovinos Guzerá (Bos indicus), em consequência das variações meteorológicas ao longo do dia, em ambiente tropical e a emissão de metano. Foram avaliados dez bovinos da raça Guzerá, cinco machos e cinco fêmeas, com média de vinte meses, alojados em baias individuais, protegidos da radiação solar. A frequência respiratória, volume respiratório corrente, a produção de calor metabólico e a perda de calor latente via sistema respiratório, foram determinados usando um sistema de calorimetria indireta, com o auxílio de uma máscara facial. Simultaneamente, foram analisadas a temperatura retal (TR), temperatura da epiderme (TEP), temperatura do pelame (TS), temperatura do ar expirado (TEXP), além das variáveis meteorológicas, temperatura do ar (TA), umidade relativa (UR), radiação solar (RS), e temperatura radiante média (TRM). Também foram determinados os fluxos de calor por radiação e convecção. As temperaturas do ar expirado, do pelame e da epiderme, se mostraram dependentes da temperatura do ar, aumentando de 28 a 35°C, 31 a 38°C e 33 a 38°C, respectivamente, quando a temperatura do ar aumentou de 25 para 34°C, enquanto que a temperatura retal foi dependente da hora do dia. A produção de calor metabólico apresentou média de 115 e 155 W m-2, para machos e fêmeas, respectivamente, e não se alterou com o aumento da temperatura do ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The aim of this study was to validate the conditioning of animals and the development of research aimed at understanding the responses of the thermal equilibrium of Guzerá cattle (Bos indicus), as a result of weather variations throughout the day in a tropical environment and the methane emission. Evaluated ten Guzerat cattle, five males and five females, with an average of twenty months, housed in individual pens, protected from direct solar radiation. The respiratory rate, tidal respiratory volume, metabolic heat production and loss of latent heat via the respiratory system, were determined using an indirect calorimetry system with the aid of a facial mask. At the same time, we analyzed the rectal temperature (TR), skin surface temperature (TEP), hair coat temperature (TS), expired air temperature (TEXP), besides meteorological variables, air temperature (TA), relative humidity (UR), solar radiation (RS), and mean radiant temperature (TRM). It was also determined heat flow by radiation and convection. The expired air temperature, hair coat temperature and skin surface temperature, proved to be dependent on air temperature, adding 28 to 35 ° C, 31 to 38 ° C and 33 to 38 ° C, respectively, when the air temperature increased from 25 to 34 ° C. While the rectal temperature is dependent on the time of day. The metabolic heat production averaged 115 and 155 W m-2 for males and females, respectively, and did not change with increasing air temperature (25-34 ° C), the same was tru... (Complete abstract click electronic access below) / Mestre

Obesity occurs when nutrient intake exceeds energy expenditure over prolonged periods. In the modern world, obesity has reached epidemic proportions. Complications of obesity, including cardiovascular disease, non-alcoholic fatty liver disease, certain forms of cancer, and metabolic dysfunction contribute substantially to morbidity and death today. With 13% of the world’s population affected, the rising rates of obesity will grow as a public health burden. Until recently, pharmacologic attempts to treat obesity have focused on reducing food intake. However, motivated in part by recent studies in mice and by analyses of fat in humans, approaches to increasing energy expenditure, specifically thermogenic energy expenditure, may provide a new therapeutic avenue. Most simplistically, there are two classes of adipocytes: storage and thermogenic. Storage fat, typically composed of unilocular white adipocytes function as storage depots for excess calories. On the other hand, thermogenic fat containing brown or beige adipocytes, generate heat through uncoupled mitochondrial respiration, This regulated generation of heat, known as thermogenesis, is used by organisms to maintain or increase body temperature. Historically, thermogenesis has been divided into shivering and nonshivering thermogenesis. Repeated, rapid contraction of skeletal muscles generate heat and is the basis for shivering thermogenesis. Nonshivering thermogenesis (NST) describes all the other mechanisms by which an organism can generate regulated heat. Only two organelles are known to contribute to NST: the mitochondrion of brown and beige adipocytes and the sarcoplasmic reticulum of muscle. The role of other organelles has not been systematically studied. Here we show in mice that thermogenic stimuli, including a cold challenge and pyrogenic molecules, activate a lysosomal program in a known thermogenic tissue (BAT) as well as several “non-thermogenic” organs, including the spleen, liver and skeletal muscle. A similar program is activated by a cold challenge in the metazoan, Drosophila melanogaster, suggesting an evolutionarily ancient origin for this response. We show by both pharmacologic and genetic means that impairment of lysosomal function compromises the thermogenic response of individual cells ex vivo and of mice in vivo. Data from genetic manipulations find that impairment of lysosome function that leads to cold intolerance and death can modestly downregulate the classical Ucp1 thermogenic program. However, pharmacological inhibition reveals that impairment of lysosome function can compromise thermogenesis without altering the Ucp1 program. As part of our efforts to study lysosome function in thermogenesis we developed a new method of measuring thermogenesis in primary cells. Using isothermal titration calorimetry (ITC), we quantitatively measured the heat generated by cells isolated from mice. This permitted us to assess the effects of both genetic and pharmacologic manipulations on the generation of heat and allowed us, for the first time, to measure the heat (uCal/sec/cell) of BAT in the basal and stimulated state. With ITC, we demonstrated that the impairment of lysosome function had direct effects on the generation of cellular heat, independent of systemic modulators of temperature such as basal metabolic rate or circulatory dissipation. From these studies, we conclude that lysosomes are thermogenic organelles induced by cold and pyrogenic stimuli and contribute both directly and indirectly to thermogenesis. Our work also suggests that lysosome thermogenesis may provide a means of thermoregulation in non-homeotherms as well as in tissues previously not implicated in temperature regulation in mammals.

Background: Protection against cold is vitally important in prehospital trauma care to reduce heat loss and prevent body core cooling. Objectives: Evaluate the effect on cold stress and thermoregulation in volunteer subjects byutilising additional insulation on a spineboard (I). Determine thermal insulation properties of blankets and rescue bags in different wind conditions (II). Establish the utility of wet clothing removal or the addition of a vapour barrier by determining the effect on heat loss within different levels of insulation in cold and warm ambient temperatures (III) and evaluating the effect on cold stress and thermoregulation in volunteer subjects (IV). Methods: Aural canal temperature, sensation of shivering and cold discomfort was evaluated in volunteer subjects, immobilised on non-insulated (n=10) or insulated (n=9) spineboards in cold outdoor conditions (I). A thermal manikin was setup inside a climatic chamber and total resultant thermal insulation for the selected ensembles was determined in low, moderate and high wind conditions (II). Dry and wet heat loss and the effect of wet clothing removal or the addition of a vapour barrier was determined with the thermal manikin dressed in either dry, wet or no clothing; with or without a vapour barrier; and with three different levels of insulation in warm and cold ambient conditions (III). The effect on metabolic rate, oesophageal temperature, skin temperature, body heat storage, heart rate, and cold discomfort by wet clothing removal or the addition of a vapour barrier was evaluated in volunteer subjects (n=8), wearing wet clothing in a cold climatic chamber during four different insulation protocols in a cross-over design (IV). Results: Additional insulation on a spine board rendered a significant reduction of estimated shivering but there was no significant difference in aural canal temperature or cold discomfort (I). In low wind conditions, thermal insulation correlated to thickness of the insulation ensemble. In greater air velocities, thermal insulation was better preserved for ensembles that were windproof and resistant to the compressive effect of the wind (II). Wet clothing removal or the use of a vapour barrier reduced total heat loss by about one fourth in the cold environment and about one third in the warm environment (III). In cold stressed wet subjects, with limited insulation applied, wet clothing removal or the addition of a vapour barrier significantly reduced metabolic rate, increased skin rewarming rate, and improved total body heat storage but there was no significant difference in heart rate or oesophageal temperature cooling rate (IV). Similar effects on heat loss and cold stress was also achieved by increasing the insulation. Cold discomfort was significantly reduced with the addition of a vapour barrier and with an increased insulation but not with wet clothing removal. Conclusions: Additional insulation on a spine board might aid in reducing cold stress inprolonged transportations in a cold environment. In extended on scene durations, the use of a windproof and compression resistant outer cover is crucial to maintain adequate thermal insulation. In a sustained cold environment in which sufficient insulation is not available, wet clothing removal or the use of a vapour barrier might be considerably important reducing heat loss and relieving cold stress.