Stable Body Temperature Research Articles

Origin and development of homoiothermy: A case study of avian energetics

The study is based on the results of the integrated measurement of the energy expenditure at rest and common activity in birds belonging to various systematic groups. Homeothermy has formed in birds and mammals independently and in different geological ages. However, in both groups it originated as a side effect of selection for aerobic metabolism improvement that provided a higher level of activity. Advantages of having high and stable body temperature, which were inevitably related with metabolism intensification, led to development of thermoregulatory adaptations such as fur and feathers. This made it possible to retain the metabolically generated heat and reduce heat absorption in hot environments. Emergence of homeothermy with aerobic supply of motion activity, possibilities to regulate the level of metabolism and thermal conductance, has opened a lot of opportunities for homoeothermic animals. Achieving such a level of energy utilization allowed them to maintain activity for a longer time, while its sensory support led to complication and diversification of birds’ behavioral repertoire (as well as that of mammals) facilitating the conquest of almost entire part of the biosphere that was suitable for living. This process was favored by the development of nurturing and passing on the information, collected throughout the life, to new generations. Formation of high levels of aerobic metabolism in birds and mammals was proceeding in parallel among different groups of reptilian ancestors. The level of homeothermy, at which aerobic metabolism was able to maintain prolonged activity, developed in birds and mammals in different ways: they had got dissimilar partitioning of venous and arterial networks, erythrocytes with or without a cell nucleus, different lungs design—but, at that, similar minimum metabolic power and rather close body temperatures which corresponded well to the environmental conditions on the Earth. Natural selection allowed animals with high energetic metabolism to increase their diversity and abundance, but only when homoeothermic animals could satisfy their demands for food resources, that had risen manifold. That happened in the middle of Cretaceous, in time with the appearance of angiosperms and expansion of related fauna of invertebrates.

Origin and development of homoiothermy: A case study of avian energetics

The study is based on the results of the integrated measurement of the energy expenditure at rest and common activity in birds belonging to various systematic groups. Homeothermy has formed in birds and mammals independently and in different geological ages. However, in both groups it originated as a side effect of selection for aerobic metabolism improvement that provided a higher level of activity. Advantages of having high and stable body temperature, which were inevitably related with metabolism intensification, led to development of thermoregulatory adaptations such as fur and feathers. This made it possible to retain the metabolically generated heat and reduce heat absorption in hot environments. Emergence of homeothermy with aerobic supply of motion activity, possibilities to regulate the level of metabolism and thermal conductance, has opened a lot of opportunities for homoeothermic animals. Achieving such a level of energy utilization allowed them to maintain activity for a longer time, while its sensory support led to complication and diversification of birds’ behavioral repertoire (as well as that of mammals) facilitating the conquest of almost entire part of the biosphere that was suitable for living. This process was favored by the development of nurturing and passing on the information, collected throughout the life, to new generations. Formation of high levels of aerobic metabolism in birds and mammals was proceeding in parallel among different groups of reptilian ancestors. The level of homeothermy, at which aerobic metabolism was able to maintain prolonged activity, developed in birds and mammals in different ways: they had got dissimilar partitioning of venous and arterial networks, erythrocytes with or without a cell nucleus, different lungs design—but, at that, similar minimum metabolic power and rather close body temperatures which corresponded well to the environmental conditions on the Earth. Natural selection allowed animals with high energetic metabolism to increase their diversity and abundance, but only when homoeothermic animals could satisfy their demands for food resources, that had risen manifold. That happened in the middle of Cretaceous, in time with the appearance of angiosperms and expansion of related fauna of invertebrates.

Does the variance of incubation temperatures always constitute a significant selective force for origin of reptilian viviparity?

Abstract To test the hypothesis that the variance of incubation temperature may have constituted a significant selective force for reptilian viviparity, we incubated eggs of the slender forest skink Scincella modesta in five thermally different natural nests and at two constant temperatures (18 °C and 21 °C). Our manipulation of incubation temperature had significant effects on incubation length and several hatchling traits (snout-vent length, tail length, fore-limb length, and sprint speed), but not on hatching success and other hatchling traits examined (body mass, head size, and hind-limb length). Incubation length was nonlinearly sensitive to temperature, but it was not correlated with the thermal variance when holding the thermal mean constant. The 18 °C treatment not only produced smaller sized hatchlings but also resulted in decreased sprint speed. Eggs in the nest with the greatest proportion of temperatures higher than 28 °C also produced smaller sized hatchlings. None of the hatchling traits examined was affected by the thermal variance. Thermal fluctuations did result in longer incubation times, but females would benefit little from maintaining stable body temperatures or selecting thermally stable nests in terms of the reduced incubation length. Our data show that the mean rather than the variance of temperatures has a key role in influencing incubation length and hatchling phenotypes, and thus do not support the hypothesis tested.

Highly diluted medication reduces parasitemia and improves experimental infection evolution by Trypanosoma cruzi

BackgroundThere is no published information about the use of different protocols to administer a highly diluted medication.Evaluate the effect of different protocols for treatment with biotherapic T. cruzi 17 dH (BIOTTc17dH) on clinical/parasitological evolution of mice infected with T. cruzi-Y strain.MethodsA blind, randomized controlled trial was performed twice, using 60 28-day-old male Swiss mice infected with T. cruzi-Y strain, in five treatment groups: CI - treated with a 7% ethanol-water solution, diluted in water (10 μL/mL) ad libitum; BIOTPI - treated with BIOTTc17dH in water (10 μL/mL) ad libitum during a period that started on the day of infection; BIOT4DI - treated with BIOTTc17dH in water (10 μL/mL) ad libitum beginning on the 4th day of infection; BIOT4-5–6 - treated with BIOTTc17dH by gavage (0.2 mL/ animal/day) on the 4th, 5th and 6th days after infection; BIOT7-8–9 - treated with BIOTTc17dH by gavage (0.2 mL/ animal/day) on the 7th, 8th and 9th days after infection. We evaluated: parasitemia; total parasitemia (Ptotal); maximum peak of parasites; prepatent period (PPP) - time from infection to detection of the parasite in blood; patent period (PP) - period when the parasitemia can be detected in blood; clinical aspects; and mortality.ResultsParasitological parameters in the BIOTPI and mainly in the BIOT4PI group showed better evolution of the infection compared to the control group (CI), with lower Ptotal, lower maximum peak of parasites, higher PPP, lower PP and longer survival times. These animals showed stable body temperature and higher weight gain and water consumption, with more animals having normal-appearing fur for longer periods. In contrast, groups BIOT4-5–6 and BIOT7-8–9 showed worse evolution of the infection compared to the control group, considering both parasitological and clinical parameters. The correlation analysis combined with the other data from this study indicated that the prepatent period is the best parameter to evaluate the effect of a medication in this model.ConclusionsThe BIOT4DI group showed the best clinical and parasitological evolution, with lower parasitemia and a trend toward lower mortality and a longer survival period. The prepatent period was the best parameter to evaluate the effect of a medication in this model.

Flexibility in thermoregulatory physiology of two dunnarts, Sminthopsis macroura and Sminthopsis ooldea (Marsupialia; Dasyuridae)

Stripe-faced dunnarts (Sminthopsis macroura) and Ooldea dunnarts (S. ooldea) were acclimated for 2 weeks to ambient temperature (T(a)) regimes of 12-22°C, 18-28°C and 25-35°C, and then measured for standard, basal (BMR) and maximum (MMR) metabolic rate using flow-through respirometry. Sminthopsis macroura maintained a stable body temperature under all experimental T(a) and acclimation regimes. Although its BMR was not statistically different between the three acclimation regimes, the lower end of the thermoneutral zone (TNZ) shifted from 30°C under the 18-28°C and 12-22°C acclimation regimes to 35°C under the 25-35°C acclimation regime. MMR increased significantly at the cooler acclimation regimes. EWL increased at T(a)=35°C, compared with lower T(a), in all acclimation regimes, but an increase in evaporative water loss (EWL) at T(a)=10°C observed in cool acclimations did not occur at the 25-35°C regime. In contrast, S. ooldea had variable body temperature between experimental T(a) in all acclimation regimes, but no acclimational shift in TNZ, which was between 30 and 35°C. Neither BMR nor MMR was affected by exposure to the three acclimation regimes. EWL did not change across T(a) or with acclimation regime. Sminthopsis macroura was flexible in many aspects of its thermoregulation (involving energy and water balance) in response to thermal acclimation, presumably allowing it to balance its energy and water requirements over a broad range of climatic conditions. Sminthopsis ooldea seems to have an inflexible energetic and water balance in response to thermal acclimation, but has low nominal expenditure of either resource on thermoregulation because it thermoregulates less precisely than S. macroura. It seems that S. ooldea is adapted to a more narrow, stable climate.

Relation between trends in body temperature and outcome in incident hemodialysis patients

Various biochemical and physiological variables are related to outcome in hemodialysis (HD) patients. However, the prognostic implications of trends in body temperature (BT) in this population have not yet been studied. The aim of this study was to assess the relationship between trends in BT and outcome in incident HD patients. Six thousand seven hundred and forty-two incident HD patients without thyroid disease from the Renal Research Institute were followed for 1 year. Patients were divided into tertiles of initial pre-dialysis BT (Tertile 1: ≤ 36.47°C, Tertile 2: > 36.47 to 36.71°C and Tertile 3: > 36.7°C) and further classified according to the change in BT (increased: > 0.01°C/month, decreased: less than -0.01°C/month and stable, with change between - 0.01 and + 0.01°C/month) during the first year of treatment. The reference group is Tertile 2 of initial temperature with stable BT. Cox regression was used for survival analyses. Analyses were repeated for patients who survived the first year and were treated for ≥ 1 month in Year 2. BT decreased in 2903 patients, remained stable in 2238 patients and increased in 1601 patients. After adjustment for multiple risk factors, hazard ratios (HRs) for mortality were higher for those groups in whom, irrespective of the initial BT, BT increased or declined, as compared to the reference group during follow-up (HR between 1.46 and 2.27). The best survival was observed in the group with the highest BT at baseline and stable BT during the follow-up period (HR 0.50).

Quantifying heat balance components in neonates nursed under radiant warmers in neonatal intensive care

Neonatal intensive care units use radiant warmers (RW) to maintain stable body temperatures in many newborns. This study examined whether the rate of radiant heat required for heat balance (Rreq) is equal to the rate of radiant heat provided by the RW (Rprov). A systematic evaluation of time‐dependent changes in heat balance components was conducted in 10 newborns (mass: 2829±636 g; age: 9.2±11.0 days; BSA: 0.19±0.03 m2) nursed under RW. Metabolic rate, evaporative heat loss, convective and conductive heat flow, rectal temperature (Trec) and mean skin temperature (Tsk) were measured continuously for 105 min. The rate of body heat storage (S) was calculated using a two‐compartment model of ‘core’ (Trec) and ‘shell’ (Tsk) temperatures. Mean Rprov (1.28±2.59 W) and Rreq (1.25±2.51W) were not significantly different (P=0.63). However, while the resultant mean change in body heat content after 105 min was low (+0.46±2.79 kJ) and not significantly different from zero (P>0.05), an acute time‐dependent change in body heat storage was evidenced by a mean positive heat storage component of +6.64±2.98 kJ and a mean negative heat storage component of −6.17±2.64 kJ. Accordingly, the mean difference between maximum and minimum values for Trec and Tskwere 0.71±0.37°C and 2.18±0.81°C respectively. In conclusion, while RW maintain astable core temperature over a prolonged period, they induce acute bouts of heat imbalance.Supported by a NSERC Discovery Grant (O. Jay) & a CHEO Dept. of Surgery Research Grant (S. Chou).

Acceleration data reveal the energy management strategy of a marine ectotherm during reproduction

Abstract1. Maintaining a high and stable body temperature is often critical for female ectotherms during reproduction. Yet this strategy may be energetically costly, and therefore challenging, during this period of already high‐energy demand.2. Here, the 6‐week deployment of tri‐axial accelerometers (n = 6) on a marine ectotherm, the loggerhead turtle (Caretta caretta), reproducing at the northern limit of the species’ breeding range (i.e. in a thermally dynamic environment) revealed the behavioural mechanisms underlying its energy management strategy during the breeding season.3. The estimated activity levels of female loggerheads using overall dynamic body acceleration (ODBA) were high during the breeding season, suggesting that marine turtles may not be able to remain inactive for long periods in the same manner as terrestrial ectotherms, because of the thermally dynamic nature of their environment.4. However, activity levels were not constant throughout the season, being impacted by both ambient water temperature and female reproductive status. In cold water at the beginning of the nesting season, high levels of activity suggested that females behaviourally thermoregulated by seeking out warm water patches along the shoreline. Interactions with male turtles (courtship and/or avoidance) may also explain this high level of activity. As sea temperatures warmed up and the amount of energy devoted to reproduction probably increased, the turtles spent more time resting during long sequential flat‐bottomed dives, and reduced any unnecessary locomotory activity.5. Turtles may therefore adjust their activity patterns in response to seasonal variations in abiotic (i.e. ambient temperature) and biotic (i.e. reproductive status) factors. This may help minimize activity‐linked metabolic rate and maximize reproductive output over a season while breeding in thermally dynamic environments.6. A mechanistic model gave support to these empirical results. The model revealed that actively maintaining high and stable body temperature is of clear benefit to female turtles at temperate breeding sites. While energetically costly, such active thermoregulatory behaviour may speed up egg maturation, allowing turtles to initiate nesting earlier in the season, and hence maximize reproductive output.

The naked mole rat genome: understanding aging through genome analysis

In the past 15 years, genomics has penetrated all areas of the life sciences [1], and this dramatic change in the way science is done is often viewed as genome revolution. However, application of genomics to study senescence and aging lagged behind. Until this year, no genomes have been sequenced explicitly to understand aging. In this regard, the recent completion of the genome of the naked mole rat [2] marks an important milestone, as this study was performed primarily to better understand the exceptional longevity of this rodent. Naked mole rats live in the subterranean niche in southeast Africa and are the longest-lived rodents (maximum lifespan of 32 years). Being the size of a mouse, naked mole rats can be conveniently studied in the laboratory setting and compared with other rodents. Delayed aging is not the only exceptional trait in naked mole rats. These animals are also not known to develop cancer, do not maintain stable body temperature, can live at low oxygen and high carbon dioxide concentrations in the atmosphere, do not feel certain types of pain, and represent one of only two known eusocial mammals [3]. What have we learned from the initial analysis of the genome of this remarkable animal? First, the genome is characterized by the reduced level of polymorphism, consistent with low DNA mutation rate (although other explanations are also possible). Second, an unusual thermogenesis of naked mole rats, which may be linked to longevity through metabolic rate, is consistent with the altered sequence of a key thermoregulator, UCP1, which modified its sequences that mediate regulation by nucleotides and fatty acids. Another interesting finding is the unique sequence of a tumor suppressor p16, a protein whose mutations were linked to a variety of human diseases associated with aging. In addition, analyses of gene expression as a function of age distinguished naked mole rats from other mammals. Each of these as well as several other findings reported in the genome paper [2] provides interesting leads which can now be examined experimentally. The availability of the genome of the naked mole rat should be viewed as the first step in the process of Editorial

The Mouse Cremaster Muscle Preparation for Intravital Imaging of the Microcirculation

Throughout the body, the maintenance of homeostasis requires the constant supply of oxygen and nutrients concomitant with removal of metabolic by-products. This balance is achieved by the movement of blood through the microcirculation, which encompasses the smallest branches of the vascular supply throughout all tissues and organs. Arterioles branch from arteries to form networks that control the distribution and magnitude of oxygenated blood flowing into the multitude of capillaries intimately associated with parenchymal cells. Capillaries provide a large surface area for diffusional exchange between tissue cells and the blood supply. Venules collect capillary effluent and converge as they return deoxygenated blood towards the heart. To observe these processes in real time requires an experimental approach for visualizing and manipulating the living microcirculation. The cremaster muscle of rats was first used as a model for studying inflammation using histology and electron microscopy post mortem. The first in vivo report of the exposed intact rat cremaster muscle investigated microvascular responses to vasoactive drugs using reflected light. However curvature of the muscle and lack of focused illumination limited the usefulness of this preparation. The major breakthrough entailed opening the muscle, detaching it from the testicle and spreading it radially as a flat sheet for transillumination under a compound microscope. While shown to be a valuable preparation to study the physiology of the microcirculation in rats and hamsters, the cremaster muscle in mice has proven particularly useful in dissecting cellular pathways involved in regulating microvascular function and real-time imaging of intercellular signaling. The cremaster muscle is derived from the internal oblique and transverse abdominus muscles as the testes descend through the inguinal canal. It serves to support (Greek: cremaster = suspender) and maintain temperature of the testes. As described here, the cremaster muscle is prepared as a thin flat sheet for outstanding optical resolution. With the mouse maintained at a stable body temperature and plane of anesthesia, surgical preparation involves freeing the muscle from surrounding tissue and the testes, spreading it onto transparent pedestal of silastic rubber and securing the edges with insect pins while irrigating it continuously with physiological salt solution. The present protocol utilizes transgenic mice expressing GCaMP2 in arteriolar endothelial cells. GCaMP2 is a genetically encoded fluorescent calcium indicator molecule. Widefield imaging and an intensified charge-coupled device camera enable in vivo study of calcium signaling in the arteriolar endothelium.

The Mouse Cremaster Muscle Preparation for Intravital Imaging of the Microcirculation

Throughout the body, the maintenance of homeostasis requires the constant supply of oxygen and nutrients concomitant with removal of metabolic by-products. This balance is achieved by the movement of blood through the microcirculation, which encompasses the smallest branches of the vascular supply throughout all tissues and organs. Arterioles branch from arteries to form networks that control the distribution and magnitude of oxygenated blood flowing into the multitude of capillaries intimately associated with parenchymal cells. Capillaries provide a large surface area for diffusional exchange between tissue cells and the blood supply. Venules collect capillary effluent and converge as they return deoxygenated blood towards the heart. To observe these processes in real time requires an experimental approach for visualizing and manipulating the living microcirculation. The cremaster muscle of rats was first used as a model for studying inflammation using histology and electron microscopy post mortem1,2. The first in vivo report of the exposed intact rat cremaster muscle investigated microvascular responses to vasoactive drugs using reflected light3. However curvature of the muscle and lack of focused illumination limited the usefulness of this preparation. The major breakthrough entailed opening the muscle, detaching it from the testicle and spreading it radially as a flat sheet for transillumination under a compound microscope4. While shown to be a valuable preparation to study the physiology of the microcirculation in rats5 and hamsters6, the cremaster muscle in mice7 has proven particularly useful in dissecting cellular pathways involved in regulating microvascular function8-11 and real-time imaging of intercellular signaling12. The cremaster muscle is derived from the internal oblique and transverse abdominus muscles as the testes descend through the inguinal canal13. It serves to support (Greek: cremaster = suspender) and maintain temperature of the testes. As described here, the cremaster muscle is prepared as a thin flat sheet for outstanding optical resolution. With the mouse maintained at a stable body temperature and plane of anesthesia, surgical preparation involves freeing the muscle from surrounding tissue and the testes, spreading it onto transparent pedestal of silastic rubber and securing the edges with insect pins while irrigating it continuously with physiological salt solution. The present protocol utilizes transgenic mice expressing GCaMP2 in arteriolar endothelial cells. GCaMP2 is a genetically encoded fluorescent calcium indicator molecule12. Widefield imaging and an intensified charge-coupled device camera enable in vivo study of calcium signaling in the arteriolar endothelium.

Single gene deletions of orexin, leptin, neuropeptide Y, and ghrelin do not appreciably alter food anticipatory activity in mice.

Timing activity to match resource availability is a widely conserved ability in nature. Scheduled feeding of a limited amount of food induces increased activity prior to feeding time in animals as diverse as fish and rodents. Typically, food anticipatory activity (FAA) involves temporally restricting unlimited food access (RF) to several hours in the middle of the light cycle, which is a time of day when rodents are not normally active. We compared this model to calorie restriction (CR), giving the mice 60% of their normal daily calorie intake at the same time each day. Measurement of body temperature and home cage behaviors suggests that the RF and CR models are very similar but CR has the advantage of a clearly defined food intake and more stable mean body temperature. Using the CR model, we then attempted to verify the published result that orexin deletion diminishes food anticipatory activity (FAA) but observed little to no diminution in the response to CR and, surprisingly, that orexin KO mice are refractory to body weight loss on a CR diet. Next we tested the orexigenic neuropeptide Y (NPY) and ghrelin and the anorexigenic hormone, leptin, using mouse mutants. NPY deletion did not alter the behavior or physiological response to CR. Leptin deletion impaired FAA in terms of some activity measures, such as walking and rearing, but did not substantially diminish hanging behavior preceding feeding time, suggesting that leptin knockout mice do anticipate daily meal time but do not manifest the full spectrum of activities that typify FAA. Ghrelin knockout mice do not have impaired FAA on a CR diet. Collectively, these results suggest that the individual hormones and neuropepetides tested do not regulate FAA by acting individually but this does not rule out the possibility of their concerted action in mediating FAA.

Unique Aspects of the Elderly Surgical Population

Increasing life expectancies paired with age-related comorbidities have resulted in the continued growth of the elderly surgical population. In this group, age-associated changes and decreased physiological reserve impede the body's ability to maintain homeostasis during times of physiological stress, with a subsequent decrease in physiological reserve. This can lead to age-related physiological and cognitive dysfunction resulting in perioperative complications. Changes in the cardiovascular, pulmonary, nervous, hepatorenal, endocrine, skin, and soft tissue systems are discussed as they are connected to the perioperative experience. Alterations affect both the pharmacodynamics and pharmacokinetics of administered drugs. Elderly patients with coexisting diseases are at a greater risk for polypharmacy that can further complicate anesthetic management. Consequently, the importance of conducting a focused preoperative evaluation and identifying potential risk factors is strongly emphasized. Efforts to maintain intraoperative normothermia have been shown to be of great importance. Procedures to maintain stable body temperature throughout the perioperative period are presented. The choice of anesthetic technique, in regard to a regional versus general anesthetic approach, is debated widely in the literature. The type of anesthesia to be administered should be assessed on a case-by-case basis, with special consideration given to the health status of the patient, the type of operation being conducted, and the expertise of the anesthesiologist. Specifically addressed in this article are age-related cognitive issues such as postoperative cognitive dysfunction and postoperative delirium. Strategies are suggested for avoiding these pitfalls.

Seasonal changes of thermogenic capacity in Melano-bellied oriental voles ( Eothenomysmelanogaster)

Seasonal changes of thermogenic capacity in Melano-bellied oriental voles ( Eothenomys melanogaster) were studied by measurements of body mass, basal metabolic rate (BMR), non-shivering thermogenesis (NST), thermogenic properties of brown adipose tissue (BAT), relative weight of liver mass, mitochondrial protein (MP) content, and activities of mitochondrial cytochrome C oxidase (COX) in autumn (October), winter (December), spring (April) and summer (July), respectively. Results showed that: (1) Body mass of E. melanogaster was the highest in autumn, and the lowest in summer. The seasonal change in body mass was subject not only by environment temperature but also to other factors such as reproduction, feeding habit and climate in the habitat. Reproductive periods of E. melanogaster were in early spring (February–March) and late autumn (September–October), and therefore, the body mass was higher in spring and autumn. In addition, E. melanogaster feeds on leaves and stems of plants in spring and summer, whereas mainly on fruits in autumn and winter as they contain more energy. The difference in the feeding habit could result in higher body mass in the late half of the year, but lower body mass in winter. The lower body mass in winter provides E. melanogaster with an advantage in motility. (2) The BMR and NST of E. melanogaster was higher in winter than in other seasons, which suggests that the regulating thermogenic capacity is an important adaptive strategy for E. melanogaster. However, there was no difference in relative oxygen consumption (NST–BMR/BMR), suggesting that the regulative capacity of BMR is approximately equal to NST in E. melanogaster. This is different from some small mammal species in north China, which have higher regulative capacity in NST than E. melanogaster. Melano-bellied oriental voles live in mountainous area with subtropical zone monsoon climate and abundant food resource, and therefore have lower regulative capacity in NST, which can reduce an absolute request for energy. The low regulative capacity in NST can also help E. melanogaster to maintain energy balance and stable body temperature. (3) The relative mass of BAT in winter was significantly higher than that in summer. Different seasons significantly affected the MP content of BAT. The MP content of BAT was in the following order: winter > fall > spring > summer. The trend as following was observed for the mitochondrial COX activity of BAT: winter > spring > fall > summer. In experimental conditions, the thermogenic rate of many small mammal species increased under cold acclimation. Short photoperiod alone could also induce E. melanogaster to increase NST and mitochondrial COX activity of BAT. Therefore, ambient temperature and photoperiod are important environmental cues to induce seasonal changes in thermogenic capacity in E. melanogaster. (4) The relative mass of liver in summer was higher than that in other seasons, but no seasonal changes were found among other seasons. The MP contents of liver showed highest level in winter and lowest in spring and summer. Significant seasonal changes were also observed in the mitochondrial COX activity of liver. It increased significantly in winter, but not in other seasons. This indicates that liver participate in adjustment of thermogenesis. These data indicate that both increasing whole-animal thermogenesis rate and thermogenic capacity at the cells of BAT and liver play an important role in the adaption of E. melanogaster to seasonal changes, and they are also closely correlated with the habitat condition and their life habit.

Disturbance of the Florida Manatee by an Invasive Catfish

Abstract During the winter, Trichechus manatus latirostris (Florida Manatee) depends on long periods of rest in comparatively warm thermal refuges to help conserve energy and maintain stable body temperatures. Pterygoplichthys disjunctivus (Vermiculated Suckermouth Sailfin Catfish) has been observed attached to, and grazing algae from, Florida Manatee in Volusia Blue Spring. We hypothesized that the disturbance caused by grazing armored catfish would significantly alter Florida Manatee behavior. Analyses of 6 hours of underwater video of Florida Manatee behavior, with and without attached armored catfish, revealed that during each observation period, Florida Manatees with attached catfish demonstrated significantly higher activity levels and numbers of active behaviors. Increased Florida Manatee activity caused by the armored catfish may compound the impact of other known threat effects.

Effects of repeated surgical stress on daily changes of body core temperature in mice

Daily body core temperature rhythm has been known to become blunted for several days following intra-abdominal implantation of biotelemetry transmitters in small rodents and about a week is required for re-establishment of stable body core temperature oscillation. In the present study carried out on mice it was found that a repetition of the same minor surgical intervention (laparotomy) several days apart could speed up the stabilization of body temperature oscillations. Melatonin supplied with the drinking water continuously was found to speed up the return of stable daily body temperature rhythm further on consecutive laparotomies, while daily injections of methylprednisolone resulted in some delay in the development of stable body core temperature oscillations. It is concluded that in C57BL/6 mice possessing low plasma levels of melatonin exhibit an adaptive response to repeated stresses influencing the dynamics of daily body temperature rhythm.

Responses to temperature variation: integration of thermoregulation and metabolism in vertebrates

Many vertebrates regulate their body temperature in response to thermal variability of the environment. Endotherms maintain relatively stable body temperatures by adjusting metabolic heat production in response to varying environmental heat loads. Although most ectotherms do not display adaptive thermogenesis, they do acclimate cellular metabolism to compensate for environmental temperature variation. The components of the thermoregulatory systems in endotherms and ectotherms are evolutionarily conserved, and I suggest that metabolic acclimation in ectotherms relies on the same regulatory pathways as adaptive thermogenesis in endotherms. Both groups rely on transient receptor potential ion channels to sense environmental temperatures. Thermosensory (afferent) information is relayed to the hypothalamus, which initiates a sympathetic efferent response. Cardiovascular responses to heat are similar in ectothermic crocodiles and in mammals, and are mediated by the autonomic nervous system in both cases. The sympathetic nervous system also modulates cellular metabolism by inducing expression of the transcriptional regulator peroxisome proliferator activated receptor gamma coactivator 1alpha (PGC-1alpha), which interacts with a range of transcription factors that control glycolysis, fatty acid oxidation, gluconeogenesis, mitochondrial biogenesis and bioenergetics, and metabolic rate. PGC-1alpha is best known from mammalian model species but there is increasing evidence that it is also instrumental in non-mammalian vertebrates. Hence, endothermic adaptive thermogenesis may result from the same regulatory pathways as ectothermic metabolic acclimation, and both could be considered as adaptive metabolic responses to temperature variation.

Optional strategies for reduced metabolism in gray mouse lemurs

Among the order of primates, torpor has been described only for the small Malagasy cheirogaleids Microcebus and Cheirogaleus. The nocturnal, gray mouse lemur, Microcebus murinus (approx. 60 g), is capable of entering into and spontaneously arousing from apparently daily torpor during the dry season in response to reduced temperatures and low food and water sources. Mark-recapture studies indicated that this primate species might also hibernate for several weeks, although physiological evidence is lacking. In the present study, we investigated patterns of body temperature in two free-ranging M. murinus during the austral winter using temperature-sensitive data loggers implanted subdermally. One lemur hibernated and remained inactive for 4 weeks. During this time, body temperature followed the ambient temperature passively with a minimum body temperature of 11.5 degrees C, interrupted by irregular arousals to normothermic levels. Under the same conditions, the second individual displayed only short bouts of torpor in the early morning hours but maintained stable normothermic body temperatures throughout its nocturnal activity. Reduction of body temperature was less pronounced in the mouse lemur that utilized short bouts of torpor with a minimum value of 27 degrees C. Despite the small sample size, our findings provide the first physiological confirmation that free-ranging individuals of M. murinus from the humid evergreen littoral rain forest have the option to utilize short torpor bouts or hibernation under the same conditions as two alternative energy-conserving physiological solutions to environmental constraints.

THE INFLUENCE OF NO-SYNTASA INHIBITOR ENTERED IN NEONATAL PERIOD ON BECOMING THE HEAT EXCHANGE MECHANISMS IN POSTNATAL ONTOGENY OF MAMMALS

The aim of the work was is to study the influence of NO-synthase inhibitor, introduced in the neonatal period, on the oxygen consumption as an indirect measure of the heat exchange. In the course of conducted experiments, it was found out that in the neonatal period NO takes part in the development of organisms responsible for the formation of stable body temperature and its changes during the day and intensity of the heat output.

Thermoregulation during gravidity in the children's python (Antaresia childreni): a test of the preadaptation hypothesis for maternal thermophily in snakes

Pregnant squamate reptiles (i.e. lizards and snakes) often maintain higher and more stable body temperatures than their nonpregnant conspecifics, and this maternal thermophily enhances developmental rate and can lead to increased offspring quality. However, it is unclear when this behaviour evolved relative to the evolution of viviparity. A preadaptation hypothesis suggests that maternal thermophily was a preadaptation to viviparity. Oviparous squamates are unique among oviparous reptiles for generally retaining their eggs until the embryos achieve one fourth of their development. As a result, maternal thermophily by gravid squamates may provide the same thermoregulatory benefits, at least during early development, that have been associated with viviparity. Thus, the evolution of viviparity in squamates may reflect an expanded duration of a pre-existing maternal thermoregulatory behaviour. Despite its evolutionary relevance, thermoregulation during gravidity in oviparous squamates has not yet been explored in depth. In the present study, we examined whether gravidity was associated with thermoregulatory changes in the oviparous children's python, Antaresia childreni. First, we discovered that, compared to most snakes, A. childreni is at an advanced stage of embryonic development at oviposition. Second, using surgically implanted temperature loggers, we detected a significant influence of reproductive status on thermoregulation. Reproductive females maintained higher and less variable body temperatures than nonreproductive females and this difference was most pronounced during the last 3 weeks of gravidity. Overall, these results highlight the continuum between oviparity and viviparity in squamate reptiles and emphasize the importance of thermal control of early embryonic development independent of reproductive mode.