Journal of thermal biology最新文献

Urbanisation stands as a primary driver of biodiversity loss globally, reshaping natural landscapes and imposing novel environmental conditions upon organisms. This ecological novelty poses challenges, and species capable of thriving in urban environments are considered tolerant. Among vertebrates, anurans are the most susceptible to land-use changes, mainly due to their life history and morphological traits. They exhibit a great diversity of reproductive strategies and modes, among which the foam nest plays several important roles, such as moderating or buffering adverse conditions. In this study, we assessed the foam nest of Pleurodema borellii, an urban tolerant species, as a potential thermal insulator in the city of San Salvador de Jujuy, Argentina. We carried out our surveys within San Salvador and surrounding areas, focusing on urban and peri-urban environments. We measured the height, length, and internal temperature of 48 foam nests, as well as the temperature of their immediate environment (water and air at one cm above the nest), over consecutive days from the first day until the nest disappeared. Finally, we collected four to five embryos from each foam nest once a day to identify their developmental stage. Our results suggest that foam nests not only mitigate low temperatures but also buffer against the heat of urban environments. These findings suggest that the foam nest could be one of the traits that facilitates the occurrence of this anuran species in the city and therefore may explain its tolerance to urbanisation.

Type 2 diabetes mellitus (T2DM) is characterised by endothelial dysfunction, leading to increased risk of cardiovascular disease. Emerging evidence suggest that HWI may favourably improve vascular function but data are limited in individual with T2DM. The aim was to investigate whether repeated hot water immersion (HWI) improved macrovascular, microvascular and central haemodynamic function in individuals with T2DM. Fourteen individuals completed a pre-post experimental study where participants were assessed pre- and post-8-10 × 1 h HWI sessions (40 °C water) undertaken within a 14-day period. During HWIs, body position was adjusted to clamp rectal temperature at 38.5-39.0 °C for the duration of the immersion. Stroke volume index (SVi), cardiac index (Q˙ i), resting heart rate (HR), systolic blood pressure (SBP), diastolic BP (DBP), brachial flow-mediated dilation (FMD) and cutaneous microvascular endothelial function (via transdermal iontophoresis) and plasma [nitrate] and [nitrite] (NOX; via ozone chemiluminescence) were assessed pre- and post HWI. Neither brachial FMD measures of macrovascular endothelial function (p = 0.43) or forearm microvascular function (ACh max, p = 0.63; ACh area under curve (AUC), p = 0.63; insulin max, p = 0.51; insulin AUC, p = 0.86) or NOX (p = 0.38) were changed. Q˙ i (p < 0.01), SVi (p < 0.02) and resting HR (p < 0.01) were all significantly reduced following the 10-days HWI intervention. SBP was reduced (p = 0.03), whereas DBP was unchanged (p = 0.56). HWI may represent an appropriate intervention to improve Q˙ I, SVi and BP in individuals with T2DM, but not macrovascular endothelial or cutaneous microvascular function.

Infrared thermography (IRT) is a non-invasive method to estimate body temperature in many animal species. The eye has been indicated as the ideal region for IRT, potentially serving as an early indicator of variations in body temperature triggered by various events and stimuli. Studies are being conducted to understand sources of variation in IRT temperature of the eye and develop comprehensive guidelines for veterinary medicine and animal production purposes. The present study adds information about variation in temperature estimated from different eye regions in sheep due to analysers. Thirty-one thermal images, fifteen of the right and sixteen of the left eyes of a ewe, captured with a FLIR E8-XT camera, were analysed by each of three analysers, and minimum (Tmin), maximum (Tmax) and average (Tavg) temperature in lacrimal caruncle (R1), medial canthus of the eye (R2) and eyeball (R3) were estimated. Differences among analysers were analysed by ANOVA (normal distribution) or Friedman test (non-normal distribution), considering thermal images as blocks. Limits of Agreement with the Mean (LOAM) were estimated and agreement plots were drawn. There were no differences (P > 0.05) among analysers in temperature (°C, mean ± standard deviation or median and 2.5%-97.5% quantiles) estimated in R1 (Tmin = 36.3 ± 0.87, Tmax = 37.2 (35.9-37.7), Tavg = 36.7 ± 0.67), R2 (Tmax = 37.2 (36.0-37.8)) and R3 (Tavg = 36.1 (34.9-37.3)) for the right eye (n = 45), and in R1 (Tmin = 36.0 (34.3-37.3), Tmax = 36.8 ± 0.49, Tavg = 36.4 ± 0.53), R2 (Tmin = 35.9 ± 0.71, Tmax = 36.7 (35.8-37.7), Tavg = 36.3 (35.5-37.5)) and R3 (Tavg = 35.9 (34.8-36.6)) for the left eye (n = 48); but differences (P < 0.05) were present in R3 (Tmin, Tmax) for both eyes and in R2 (Tmin and Tavg) for the right eye. The highest mean differences in temperature (°C) (P < 0.05) among analysers were in R3 from the right eye (Tmin = 0.70, Tmax = 0.25) and the left eye (Tmin = 0.64, Tmax = 0.10), and in R2 from the right eye (Tmin = 0.54, Tavg = 0.50). Considering both eyes and all eye regions, the total range for the LOAM (°C) was lower for Tmax (0.42-0.93) and Tavg (0.63-1.17) than for Tmin (1.49-2.70), indicating a higher, medium, and lower agreement among analysers for Tmax, Tavg and Tmin, respectively. Considering the eyes, the total range for the LOAM (°C) was lower in all regions from the left eye (0.42-1.59) compared to the right eye (0.79-2.70), indicating a higher agreement among analysers from the left eye. Considering the eye regions, the total range for the LOAM (°C) was generally higher in R3 (0.84-3.70) than in R1 (0.61-1.79) and R2 (0.42-2.03), indicating the lowest agreement among analysers in R3 for Tmin (3.70). The present study shows that in sheep, the lacrimal caruncle confers the best agreement among analysers for all estimated temperatures, and that Tmax, across all eye regions, should be regarded as the most reliable estimation.

Many occupations, including military and industrial, cannot benefit from large-scale cooling strategies; therefore, personal cooling strategies may be more appropriate. We assessed the efficacy of a ventilated vest (Vest) based on participant' autonomic and cognitive responses during military-related activities in the heat. Male soldiers conducted 90-min trials in 35 °C ambient temperature and 40% relative humidity: i) March with/without Vest (N = 10), ii) Guard duty with/without Vest (N = 8). During each trial, we monitored their physiological (gastrointestinal temperature, T_gi; skin temperature, T_skin; torso microclimate temperature/humidity, M_T/M_RH; oxygen uptake, VO₂; Heart rate, HR) and cognitive (reaction time, number of errors) and subjective responses. While some elements of T_gi, T_skin, M_T, and HR reduction in the Vest trial were observed, these decrements were small and persisted only for a short period of time. VO₂ was significantly affected by the exercise but unaffected by the Vest (with vs. without) (p > 0.05). Cognitive performance did not improve significantly with the use of the Vest. However, reaction time improved after both trials. Sweat accumulation in the near-to-skin clothing layer was 2x (March) and 9x (Guard) higher (p < 0.001) without the vest, and participants reported feeling more comfortable and cooler when wearing the vest. The significantly lower sweat accumulation in the next-to-skin clothing layers when wearing the Vest improved thermal comfort and sensation, which was not reflected in the autonomic and cognitive response under the prevailing conditions. Possibly, a more powerful and upgraded concept of the vest could result in improved physiological and cognitive performance.

Single-variable analyses have limited ability to explain complex phenomena such as the regulation of prolonged physical (aerobic) performance. Our study aimed to identify predictors of performance in rats subjected to incremental-speed running exercise. Notably, most variables assessed were associated with rats' thermoregulation. We extracted data from 355 records obtained in 216 adult Wistar rats. Hierarchical multiple linear regression analyses were conducted to identify the predictive power of eight variables. The distance traveled, a performance index, was the dependent variable. The independent variables included body mass, biological sex, body core temperature (T_CORE) measurement site, and the following thermoregulation-related variables: ambient temperature (T_AMB), initial T_CORE, exercise-induced change in T_CORE (ΔT_CORE), ΔT_CORE from 0 to 10 min (ΔT_CORE 0-10; when T_CORE increase is fastest), and heat loss index (HLI). This analysis with eight variables revealed an adjusted R² of 0.495; T_AMB, ΔT_CORE, body mass, and ΔT_CORE 0-10 had the highest predictive powers (β values: -0.700, 0.463, -0.353, and -0.130, respectively). Additional analyses consisted of separate regressions for each T_CORE index measured: abdominal (T_ABD), brain (T_BRAIN), and colonic (T_COL) temperature. These analyses yielded adjusted R² values of 0.608 (T_ABD), 0.550 (T_BRAIN), and 0.437 (T_COL). Again, the distance traveled was primarily predicted by body mass and thermoregulation-related variables (T_AMB, ΔT_CORE, and ΔT_CORE 0-10). Among these four variables, ΔT_CORE was the only one with a positive β value (directly predicted performance), while the others had negative values. Collectively, these findings advance our understanding of performance regulation in rats, especially regarding the role of thermoregulation-related variables.

Heat stress (HS) disrupts water homeostasis in broiler chickens. Kidney aquaporins (AQPs) facilitate water permeability in the renal tubules, thereby maintaining homeostasis of body water and metabolites. We evaluated the mRNA expression of kidney AQPs 1, 2, 3 and 4, and the blood composition of broilers raised under thermoneutral (TN) or cyclic HS condition with or without glucose supplementation. The treatments were TN+0% glucose (TN0), TN+6% glucose (TN6), HS+0% glucose (HS0), and HS+6% glucose (HS6). Each treatment had 6 replicates of 19 birds each. Groups with glucose (Glu) supplementation continuously received 6% Glu in water, and HS groups were exposed to a cyclic HS regime involving 35 °C from 8am to 8pm, and subsequently retuned to 25 °C (thermoneutral) from 8pm to 8am. Both heat and glucose supplementation were applied from d28 to d35. Blood and kidney were collected from 1 bird/replicate on d35. AQP-1, -2, and -3 were highly expressed (p < 0.05) in HS0 relative to TN0, TN6, and HS6. Birds in the TN6 and HS6 had a lower expression of AQP2 while HS0 and HS6 had a lower expression of AQP4. Birds in the HS0 group had a higher water consumption relative to TN0, TN6 and HS6. HS0 and HS6 had a higher water conversion ratio relative to TN0 and TN6. Heat stress lowered (p < 0.05) blood PCO₂, TCO_2, and HCO₃. The blood pH, Na, K, and Cl composition were not affected (p > 0.05) with heat or glucose supplementation. Cyclic HS (p < 0.0001) and glucose supplementation (p = 0.0090) raised the blood glucose level. Kidney aquaporins 1, 2, and 3 are important indicators of water utilization in HS broiler chickens.

Body size of organisms is a key trait influencing nearly all aspects of their life history. Despite growing evidence of Bergmann's rule, there is considerably less known about the links between body size and the maximum capacity to thermoregulate of an animal in response to extreme cold or hot environment. Thermal characteristics such as resting metabolic rate (RMR) and non-shivering thermogenesis (NST), and the upper- and lower-critical temperatures of the thermal neutral zone (TNZ) were investigated in small and large body sized striped hamsters (Cricetulus barabensis). The maximum capacity to thermoregulate in response to extreme cold (-15 °C) or hot temperature (38 °C) was also examined, where both, different sized hamsters had similar RMR and NST regardless of temperature exposure. The large hamsters had 29.9% more body mass compared to small hamsters. The large hamsters showed a wider TNZ, with lower, lower-critical temperature, and showed considerable hyperthermia at the end of a 17-h hot exposure. In contrast, the small hamsters showed hypothermia following a 17-h cold exposure relative to large hamsters. In addition, the large hamsters showed 17.2% lower basal thermal conductance, and 14.9% lower maximum thermal conductance than the small hamsters after cold exposure, and 22.6% lower thermal conductance following heat exposure. Several molecular markers indicative of thermogenesis and oxidative stress did not differ significantly between the large and small hamsters. These findings suggest that individuals with larger body sizes have greater capacity to thermoregulate to cope with extreme cold, and a reduced capacity in response to extreme hot. In contrast, smaller individuals demonstrated the opposite trend. Body size may decide the capacity to thermoregulate to cope with extreme cold and heat, within which body heat dissipation is likely more important than heat production.

The use of thermography to measure skin temperature (Tsk) is typically assessed in a standing position; however, the differences of Tsk in different body positions have not been adequately studied. This study aimed to analyze the influence of body position (sitting, standing, and supine) on Tsk. Twenty-nine trained men (age 23.52 ± 0.34 years) spent 10 minutes in each of the three positions in random order. During these postures, the heart rate (HR) response and systolic and diastolic blood pressure were measured as influential cardiovascular variables. Tsk was measured in the trapezius, shoulder, chest, biceps, costal, elbow, abdomen, and forearm. Covariance analysis (ANCOVA), intraclass correlation (ICC), typical error, and effect size (ES) were applied. When comparing the three positions, greater variations in Tsk were observed in the shoulder (0.74-1.31 %), biceps (-0.36 - 1.33 %), elbow (0.46-1.20%) and forearm (0.58-1.41%). HR varied significantly between the different positions (p < 0.05), influencing Tsk in the chest (ES = 0.71), the biceps (ES = 0.56) and abdominal regions (ES = 0.91) in the sitting position compared to the supine position, and in the abdominal region (ES = 1.12) in the standing position compared to the supine position. The reliability of the measurement was excellent in the chest (ICC = 0.91), costal (ICC = 0.91), and abdominal (ICC = 0.89) regions. Although many studies traditionally measure Tsk in a standing position, the results of this study support that the Tsk distribution varies with body position, and this factor should be considered in any study using thermography.

Climate change is causing extreme short-term warming with greater intensity and more frequent occurrence. Reproduction and subsequent recruitment of coastal ecosystem engineers, such as the blue mussel, may be impacted by the extreme temperatures because these vital functions are sensitive to the timing of short-term changes in abiotic factors. We exposed intertidal blue mussels, Mytilus edulis, to a thermal challenge from 10 to 29 °C using an ecologically relevant heating rate of 4 °C/h. We assessed their reproductive status by observing spawning activity and by analyzing histological sections of their gonad tissue. In addition, we monitored their heart rates and valve gaping behavior to determine their thermal performance. We identified three spawning groups: non-spawners that had mature gonads but did not release gametes, post-spawners that released mature gametes prior to the thermal challenge, and active spawners that released mature gametes during the thermal challenge. Across temperatures, active spawners had significantly higher heart rates and their heart rate peaked at the temperatures 3.9 and 3.2 °C higher compared to those of non-spawners or post-spawners, respectively. Post-spawners had significantly narrower valve gapes across temperatures compared to both other spawning groups. Hence, the metabolic response to warming strongly depends on the reproductive status, with active spawners experiencing increased thermal stress due to heightened metabolism, non-spawners showing heat-induced metabolic depression, and post-spawners adopting an energy-conserving strategy indicated by reduced gaping. Considered together, spawning during recurring short-term warming events may elevate mortality risk with potential consequences for the local biodiversity in a future climate.