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The transient receptor potential vanilloid 1 (TRPV1) channel is a heat-activated cation channel that plays a crucial role in ambient temperature detection and thermal homeostasis. Although several structural features of TRPV1 have been shown to be involved in heat-induced activation of the gating process, the physiological significance of only a few of these key elements has been evaluated in an evolutionary context. Here, using transient expression in HEK293 cells, electrophysiological recordings, and molecular modeling, we show that the pore turret contains both structural and functional determinants that set the heat activation thresholds of distinct TRPV1 orthologs in mammals whose body temperatures fluctuate widely. We found that TRPV1 from the bat Carollia brevicauda exhibits a lower threshold temperature of channel activation than does its human ortholog and three bat-specific amino acid substitutions located in the pore turret are sufficient to determine this threshold temperature. Furthermore, the structure of the TRPV1 pore turret appears to be of physiological and evolutionary significance for differentiating the heat-activated threshold among species-specific TRPV1 orthologs. These findings support a role for the TRPV1 pore turret in tuning the heat-activated threshold, and they suggest that its evolution was driven by adaption to specific physiological traits among mammals exposed to variable temperatures.

The aim of this study was to evaluate some physiological parameters as total locomotor activity and subcutaneous temperature in two different bovine breeds under tropical environment. In this study, total locomotor activity and subcutaneous temperature were evaluated in 18 clinically healthy female cows. All cows were divided into 3 groups: group A1 was constituted by 6 Holstein Bos taurus, group A2 was constituted by 6 female Herford Bos taurus cows, and group B was constituted by 6 female Bradford Bos indicus cows. Data recording of total locomotor activity (TLA) and subcutaneous temperature (ST) was performed by means of a subcutaneous thermometer (Thermocron) and an actimeter ACTIWATCH® (Cambridge Neurotechnology Ltd.) based on accelerometer technologies equipped on all subjects to record TLA. At the same time, thermal and hygrometric recording were carried out, considering the subtropical climate of Santa Fe. The application of GLM for statistical analysis showed a significant effect (P < 0.05) on statistical model and time of the day on TLA and ST for all groups; no significative effects on animal parameters were found for ST and TLA except for group B. Circadian parameters have been evaluated according to the single cosinor procedure of ST that showed a diurnal daily rhythmicity for all investigated groups and TLA which is focused almost during the photophase for groups A1 and A2 and during scotophase for group B. Considering different species and breeds, and different environmental conditions, this study suggested that some subjects may be much more able to adapt themselves to environmental stress than others. During their evolution from Bos taurus, zebu cattle (Bos indicus) have acquired genes that confer thermotolerance. Subjects from Bos indicus breeds are better able to regulate body temperature in response to heat stress than Bos taurus subjects. [ABSTRACT FROM AUTHOR]

Heat stress events in Australian flying-fox camps have resulted in significant numbers of flying-fox deaths. The frequency and intensity of such events have increased in recent decades, attributed to anthropogenic climate change. Evidence-based interventions are required to address this growing threat. Responders currently use different combinations of a range of intervention methods. We undertook a systematic review of heat stress interventions, which we classified as either 'camp-scale' or 'individual-scale'. Camp-scale interventions included manual and automated misting of roost vegetation, whereas individual-scale interventions included spraying individual animals or removing them for intensive cooling and rehydration procedures. Our study showed that to date, evaluation of the efficacy of heat stress interventions has been largely anecdotal rather than empirical. This highlights the need for dedicated rigorous studies to evaluate the effectiveness of all the intervention methods described here. It will be especially important to understand the relationship between camp temperature and humidity levels and their influence on flying-foxes' ability to regulate their body temperature, because high relative humidity reduces the ability of mammals to cool themselves using evaporative heat loss. The development of biophysiological measures such as temperature and humidity indices for different flying-fox species would enable meaningful interpretations of intervention trials under controlled conditions. Extreme heat events are responsible for the deaths of large numbers of flying-foxes. Responders use a range of interventions to minimise mortality, such as spraying water on roost vegetation or individual animals and procedures to cool and rehydrate animals in the hand. Our current understanding of how effective these methods are is largely anecdotal rather than built on scientific evidence. Further research is warranted, particularly for understanding how temperature and humidity influence flying-foxes' ability to regulate their body temperature. Photograph by Matthew Mo. [ABSTRACT FROM AUTHOR]

The narwhal (Monodon monoceros) is a high‐Arctic species inhabiting areas that are experiencing increases in sea temperatures, which together with reduction in sea ice are expected to modify the niches of several Arctic marine apex predators. The Scoresby Sound fjord complex in East Greenland is the summer residence for an isolated population of narwhals. The movements of 12 whales instrumented with Fastloc‐GPS transmitters were studied during summer in Scoresby Sound and at their offshore winter ground in 2017–2019. An additional four narwhals provided detailed hydrographic profiles on both summer and winter grounds. Data on diving of the whales were obtained from 20 satellite‐linked time‐depth recorders and 16 Acousonde™ recorders that also provided information on the temperature and depth of buzzes. In summer, the foraging whales targeted depths between 300 and 850 m where the preferred areas visited by the whales had temperatures ranging between 0.6 and 1.5°C (mean = 1.1°C, SD = 0.22). The highest probability of buzzing activity during summer was at a temperature of 0.7°C and at depths > 300 m. The whales targeted similar depths at their offshore winter ground where the temperature was slightly higher (range: 0.7–1.7°C, mean = 1.3°C, SD = 0.29). Both the probability of buzzing events and the spatial distribution of the whales in both seasons demonstrated a preferential selection of cold water. This was particularly pronounced in winter where cold coastal water was selected and warm Atlantic water farther offshore was avoided. It is unknown if the small temperature niche of whales while feeding is because prey is concentrated at these temperature gradients and is easier to capture at low temperatures, or because there are limitations in the thermoregulation of the whales. In any case, the small niche requirements together with their strong site fidelity emphasize the sensitivity of narwhals to changes in the thermal characteristics of their habitats. [ABSTRACT FROM AUTHOR]

Abstract Stressful lifelong events may influence psychiatric diseases, like depression and anxiety. Interestingly, depressed patients have dysfunction of thermoregulatory cooling mechanisms. Thus, understanding the mechanisms related to the thermoregulatory changes in stress-related pathologies is important to better understand the symptoms and treatments for those diseases. However, the influence of early-life stress on the thermoregulatory profile of adults is unknown. In this study, we aimed to evaluate the thermoregulatory profile of adult male Wistar rats submitted to early-life stress by maternal separation (MS). On postnatal days 2–14, rats were submitted daily to MS for 3 h per day. At 3–4 months of age, anxiety-like behavior was evaluated using the open field test and elevated plus maze, depression-like behavior was evaluated using the forced swim test and thermoregulatory profile were also evaluated. In the behavioral tests, MS animals exhibited anxiety- and depression-like behaviors, and had higher core body temperatures during dark period of the circadian cycle, when compared to controls. In addition, MS animals presented higher hyperthermic and vasoconstriction responses than control animals when exposed to the warmth environment, and engaged in cold-seeking behavior whenever possible to select their preferred ambient temperature. The results suggest that, besides emotional alterations, MS induces a change in the thermoregulatory profile of rats that persists into adulthood. Graphical abstract fx1 Highlights • Body temperature was elevated in adult rats submitted to maternal separation (MS). • The heat defense response was compromised in MS rats. • MS rats preferred colder environments than controls. • MS induces changes in the thermoregulation in rats that persists into adulthood. [ABSTRACT FROM AUTHOR]

Maintenance of thermal homeostasis in rats fed a high-fat diet (HFD) is associated with changes in their thermal balance. The thermodynamic relationship between heat dissipation and energy storage is altered by the ingestion of high-energy diet content. Observation of thermal registers of core temperature behavior, in humans and rodents, permits identification of some characteristics of time series, such as autoreference and stationarity that fit adequately to a stochastic analysis. To identify this change, we used, for the first time, a stochastic autoregressive model, the concepts of which match those associated with physiological systems involved and applied in male HFD rats compared with their appropriate standard food intake age-matched male controls (n=7 per group). By analyzing a recorded temperature time series, we were able to identify when thermal homeostasis would be affected by a new diet. The autoregressive time series model (AR model) was used to predict the occurrence of thermal homeostasis, and this model proved to be very effective in distinguishing such a physiological disorder. Thus, we infer from the results of our study that maximum entropy distribution as a means for stochastic characterization of temperature time series registers may be established as an important and early tool to aid in the diagnosis and prevention of metabolic diseases due to their ability to detect small variations in thermal profile.

The objective of the present study was to evaluate the effects of different dietary crude protein (CP) and metabolizable energy (ME) levels on the performance, internal and external egg quality, and cloacal temperature of commercial layers reared in hot climate. In this trial, 100 commercial Hy-Line W-36 layers between 20 and 32 weeks of age were distributed according to a completely randomized experimental design with a 2 x 2 factorial arrangement, consisting of two CP levels (15 e 18%) and two ME contents (2700 and 3100 kcal/kg) with five replicates per treatment and 10 birds per replicate. Performance (feed intake, egg production, egg mass, and feed conversion ratio), internal (Haugh units and albumen and yolk percentage) and external (eggshell % and thickness) egg quality parameters were evaluated. Cloacal temperature was measured in two birds per replicate at 8:00 h and 13:00 h. The diet containing 2700 kcal ME/kg promoted the best performance, whereas the worse performance observed in birds fed the diet with 3100 ME/kg was partially recovered when the diet contained 18% CP. Haugh units worsened as dietary CP level increased. The other external and internal egg quality parameters were not affected by dietary CP or ME levels. The cloacal temperature of birds fed 15% CP was lower in the morning and higher in the afternoon relative to those fed 18% CP, which temperature did not change during the day. It was concluded that dietary CP and ME levels influenced the performance and the body temperature of commercial layers.

The aim of the present paper was to study the effect of shearing on some haematochemical parameters in ewes. Forty Valle del Belice ewes, clinically healthy and well-fed, were divided into two groups of twenty subjects each. Twenty ewes were let unshorn as a control group (Group A) and twenty ewes were shorn (Group B). After the blood collection by means of jugular venipuncture, some haematochemical parameters were assessed for each subject in the following experimental conditions: before shearing, 1st, 15th, 30th, 45th, 60 and 75th day after shearing. We studied the course of the following haematochemical parameters: glucose, β-hydroxybutyrate, NEFA, triglycerides, total cholesterol, total protein, urea and creatinine. Two-way repeated measures analysis of variance (ANOVA), followed by Bonferroni's test, was used to determine significant differences between the two groups in the studied parameters. The statistical analysis showed statistical differences (P < 0.05 was considered statistically significant) in β-hydroxybutyrate, NEFA, total protein and urea. Data analysis of variance showed a significant effect of time, with P < 0.0001, on all studied parameters. These results suggest that shearing induces adaptive metabolic responses in the ewes and exposure to elevated ambient temperature induces modifications of some haematochemical parameters.

Body temperature regulation under changes in ambient temperature involves adjustments in heat production and heat exchange rates between the animal and the environment. One mechanism involves the modulation of the surface temperature of specific areas of the body through vasomotor adjustment. In homeotherms, this thermoregulatory adjustment is essential for the maintenance of body temperature over a moderate temperature range, known as the thermal neutral zone (TNZ). The bill of the toco toucan (Ramphastos toco) has been described as a highly efficient thermal window and hypothesized to assist in the thermal homeostasis of this bird. Herein, we directly evaluated the contribution of heat exchange through the bill of the toco toucan and role of the bill in the delimitation of the TNZ. To do this, we measured metabolic rate (MR), via oxygen consumption, over a range of ambient temperatures from 0 to 35°C. MR measurements were made in birds with the bill intact and with the bill insulated. The limits of the TNZ did not differ between treatments, ranging from 10.8 to 25.0°C. The MR differed among treatments only at elevated temperatures (30 and 35°C), reaching 0.92±0.11 ml O2 g-1 h-1 (mean±s.d.) for the intact group and 1.13±0.13 ml O2 g-1 h-1 for the insulated group. These results indicate that although heat dissipation through the bill does not contribute significantly to widening of the TNZ, it may well be critically important in assisting body temperature regulation at higher temperatures extending above the upper limit of the TNZ., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2023. Published by The Company of Biologists Ltd.)

Perioperative hypothermia is a serious complication of anaesthesia and is associated with many adverse consequences, including circulatory instability, respiratory depression and prolonged effects of the anaesthetics. The greatest caution should be applied to newborns and young children who are more prone to perioperative decrease in body temperature because of their relatively large body surface area and a thin layer of subcutaneous fat. The main mechanisms of heat loss in the operating theatre are conduction and radiation, convection and evaporation. Optimum thermal homeostasis during anaesthesia in children can be achieved through combining various procedures, e.g. using warming-up air mattresses, waterproof drapes, warming of infusion solutions, or preventing airflow around the patient. Perioperative body temperature can be measured using skin, oesophageal, rectal and tympanic thermometers, or the SpontOn device, which creates and uses an isothermal channel into the body core. Reliable body temperature measurement also helps to prevent iatrogenic hyperthermia. [ABSTRACT FROM AUTHOR]

Crop plants encounter thermal environments which fluctuate on a diurnal and seasonal basis. Future climate resilient cultivars will need to respond to thermal profiles reflecting more variable conditions, and harness plasticity that involves regulation of epigenetic processes and complex genomic regulatory networks. Compartmentalization within plant cells insulates the genomic central processing unit within the interphase nucleus. This review addresses the properties of the chromatin hardware in which the genome is embedded, focusing on the biophysical and thermodynamic properties of DNA, histones and nucleosomes. It explores the consequences of thermal and ionic variation on the biophysical behavior of epigenetic marks such as DNA cytosine methylation (5mC), and histone variants such as H2A.Z, and how these contribute to maintenance of chromatin integrity in the nucleus, while enabling specific subsets of genes to be regulated. Information is drawn from theoretical molecular in vitro studies as well as model and crop plants and incorporates recent insights into the role epigenetic processes play in mediating between environmental signals and genomic regulation. A preliminary speculative framework is outlined, based on the evidence of what appears to be a cohesive set of interactions at molecular, biophysical and electrostatic level between the various components contributing to chromatin conformation and dynamics. It proposes that within plant nuclei, general and localized ionic homeostasis plays an important role in maintaining chromatin conformation, whilst maintaining complex genomic regulation that involves specific patterns of epigenetic marks. More generally, reversible changes in DNA methylation appear to be consistent with the ability of nuclear chromatin to manage variation in external ionic and temperature environment. Whilst tentative, this framework provides scope to develop experimental approaches to understand in greater detail the internal environment of plant nuclei. It is hoped that this will generate a deeper understanding of the molecular mechanisms underlying genotype ⨰ environment interactions that may be beneficial for long-term improvement of crop performance in less predictable climates [ABSTRACT FROM AUTHOR]

The present study monitored daily and seasonal variations of rectal temperature in response to different environmental temperatures in alpacas bred in the Italian Apennines at 300 m a.s.l. In each season, the rectal temperature of 33 clinically healthy alpacas was measured three times/day (morning, midday, afternoon). Ambient temperatures were also recorded. Rectal temperatures ranged from a minimum value of 35.1 to a maximum of 39.4°C, with a maximum daily thermal excursion (ΔT) of 3.2°C. Temperatures increased throughout the day, with highly significant differences recorded in both young and adult animals between all the time bands ( P < 0.001). These differences were particularly dramatic for adults in summer, when the mean rectal temperature in the morning was 36.3 ± 0.13°C, probably as a consequence of recent shearing. Significant ΔT differences were recorded depending on the season in both young and adult animals ( P < 0.001), with the highest ΔT values recorded in summer (although the highest daily ambient excursion value was recorded in winter). In conclusion, similarly to alpacas bred in their natural environment, alpacas bred in Italy show a wide thermal neutrality zone, which is probably an adaptive response, that allows the animals to save energy. In the Italian Apennines, in order to prevent situations of hypothermia, with possible detrimental effects on alpacas' health and welfare, shearing should be carried out only in warm seasons. [ABSTRACT FROM AUTHOR]

Thermoregulatory behavior is a basic motivated behavior for body temperature homeostasis. Despite its fundamental importance, a forebrain region or defined neural population required for this process has yet to be established. Here, we show that Vgat -expressing neurons in the lateral hypothalamus (LH Vgat neurons) are required for diverse thermoregulatory behaviors. The population activity of LH Vgat neurons is increased during thermoregulatory behavior and bidirectionally encodes thermal punishment and reward (P&R). Although this population also regulates feeding and caloric reward, inhibition of parabrachial inputs selectively impaired thermoregulatory behaviors and encoding of thermal stimulus by LH Vgat neurons. Furthermore, two-photon calcium imaging revealed a subpopulation of LH Vgat neurons bidirectionally encoding thermal P&R, which is engaged during thermoregulatory behavior, but is largely distinct from caloric reward-encoding LH Vgat neurons. Our data establish LH Vgat neurons as a required neural substrate for behavioral thermoregulation and point to the key role of the thermal P&R-encoding LH Vgat subpopulation in thermoregulatory behavior. [Display omitted] • LH Vgat neurons are required for diverse thermoregulatory behaviors • They encode thermoregulatory behavior, as well as thermal punishment and reward • Thermoregulatory behavior and encoding of thermal reward require parabrachial inputs • Distinct LH Vgat subpopulations encode thermal and caloric rewards Jung et al. show that Vgat -expressing neurons in the lateral hypothalamus are generally required for diverse thermoregulatory behaviors. A subpopulation of these neurons encodes motivational properties of thermal stimuli as well as the behavior itself and is largely separate from caloric reward-encoding subpopulation. [ABSTRACT FROM AUTHOR]

• Dark respiration and photosynthesis were measured in leaves of poplar Populus deltoides × nigra (‘Veronese’) saplings to investigate the extent of respiratory and photosynthetic acclimation in pre-existing and newly emerged leaves to abrupt changes in air temperature. • The saplings were grown at three temperature regimes and at high and low nitrogen availabilities. Rates of photosynthesis and dark respiration ( Rd) were measured at the initial temperature and the saplings were then transferred to a different temperature regime, where the plants remained for a second and third round of measurements on pre-existing and newly emerged leaves. • Acclimation of photosynthesis was limited following transfer to warmer or cooler growing conditions. There was strong evidence of cold and warm acclimation of Rd to growth temperature, but this was limited in pre-existing leaves. Full acclimation of Rd was restricted to newly emerged leaves grown at the new growth temperature. • These findings indicate that the extent of thermal acclimation differs significantly between photosynthesis and respiration. Importantly, pre-existing leaves in poplar were capable of some respiratory acclimation, but full acclimation was observed only in newly emerged leaves. The Rd/ Amax ratio declined at higher growth temperatures, and nitrogen status of leaves had little impact on the degree of acclimation. [ABSTRACT FROM AUTHOR]

Abstract: [1.] With the derived free-run temperature of light paper nests the influence of the thermal capacity of the nest or the nest site, respectively, on thermal homeostasis is quantified. [2.] Gravimetric information from the continuous investigation of the nest weight coupled with temperature and humidity measurement allows the correlation of the colonies’ foraging behavior with their heat production inside the nest. [3.] Wasps (Vespa crabro) do not regulate their nest environment towards a specific and constant temperature but rather build nests adapted to their foraging behavior and general energy budget. [Copyright &y& Elsevier]

Postterm and growth-retarded fetuses share a common problem which can be characterized by a discrepancy between the supply of oxygen and nutrients to, and the demand of the fetus. But, this "insufficient" placental exchange function may also extend to and affect its thermal homeostasis; e.g. when the capacity of convective (placenta) pathways is shifted towards conductive (surface) pathways for heat loss. Therefore, fetal scalp heat flux measurements, where heat serves as an intrinsic tracer for metabolic activity and placental exchange function, promised a new kind of information. In 81 pregnant women during labor we measured fetal scalp heat flux by means of an heat flux transducer attached to the fetal head and after the cervix had dilated to 3 cm. In the healthy fetuses we found a positive linear relationship between scalp heat flux and different anthropometric variables such as body length (r = 0.432, n = 65, P less than 0.01), head circumference and gestational age. In comparison, postmature and growth-retarded fetuses showed higher heat flux values than appropriately grown fetuses of the same length head size and gestational age. Moreover, in those fetuses scalp heat flux decreased by approximately 4 watt/m2 during the second stage and differed in this regard from the control group who showed stable values during labor and delivery. We conclude that scalp heat flux measurements may indicate disturbances of placental exchange before acute hypoxia occurs. [ABSTRACT FROM AUTHOR]

Passive radiative cooling includes using the atmospheric window to emit heat energy to the cold outer space and hence reduce the temperature of objects on Earth. In most cases, radiative cooling is required in summer and suppressed in winter for thermal comfort. Recent radiative cooling materials cannot self-adjust cooling capacity according to season and environment, thus limiting their applications. In this study, we have designed a temperature-controlled phase change structure (TCPCS). The TCPCS benefits radiative coolers to adjust their cooling ability according to the ambient temperature. In the outdoor test, the TCPCS can help the cooler to turn off at low temperatures and turn on at high temperatures automatically; the coolers with and without TCPCS have maximal temperature differences of 9.7 and 19.6 °C, respectively, in a whole day. Furthermore, we have further improved and designed a V-shaped TCPCS that can simultaneously achieve the dual functions of cooling in summer and heating in winter. The TCPCS assembled here is a simple, feasible, and scalable structure for self-adaptive cooling.

Crop plants encounter thermal environments which fluctuate on a diurnal and seasonal basis. Future climate resilient cultivars will need to respond to thermal profiles reflecting more variable conditions, and harness plasticity that involves regulation of epigenetic processes and complex genomic regulatory networks. Compartmentalization within plant cells insulates the genomic central processing unit within the interphase nucleus. This review addresses the properties of the chromatin hardware in which the genome is embedded, focusing on the biophysical and thermodynamic properties of DNA, histones and nucleosomes. It explores the consequences of thermal and ionic variation on the biophysical behavior of epigenetic marks such as DNA cytosine methylation (5mC), and histone variants such as H2A.Z, and how these contribute to maintenance of chromatin integrity in the nucleus, while enabling specific subsets of genes to be regulated. Information is drawn from theoretical molecular in vitro studies as well as model and crop plants and incorporates recent insights into the role epigenetic processes play in mediating between environmental signals and genomic regulation. A preliminary speculative framework is outlined, based on the evidence of what appears to be a cohesive set of interactions at molecular, biophysical and electrostatic level between the various components contributing to chromatin conformation and dynamics. It proposes that within plant nuclei, general and localized ionic homeostasis plays an important role in maintaining chromatin conformation, whilst maintaining complex genomic regulation that involves specific patterns of epigenetic marks. More generally, reversible changes in DNA methylation appear to be consistent with the ability of nuclear chromatin to manage variation in external ionic and temperature environment. Whilst tentative, this framework provides scope to develop experimental approaches to understand in greater detail the internal environment of plant nuclei. It is hoped that this will generate a deeper understanding of the molecular mechanisms underlying genotype × environment interactions that may be beneficial for long-term improvement of crop performance in less predictable climates.