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To determine whether using nicotine exacerbates exertional heat strain through an increased metabolic heat production (Hprod) or decreased skin blood flow (SkBF), 10 nicotine-naïve trained males [37 ± 12 yr; peak oxygen consumption (V̇ o 2peak): 66 ± 10 mL·min−1·kg−1] completed four trials at 20°C and 30°C following overnight transdermal nicotine (7 mg·24 h−1) and placebo use in a crossover, double-blind design. They cycled for 60 min (55% V̇ o 2peak) followed by a time trial (∼75% V̇ o 2peak) during which measures of gastrointestinal (Tgi) and mean weighted skin ( T ¯ sk) temperatures, SkBF, Hprod, and mean arterial pressure (MAP) were made. The difference in ΔTgi between nicotine and placebo trials was greater during 30°C (0.4 ± 0.5°C) than 20°C (0.1 ± 0.7°C), with T ¯ sk higher during nicotine than placebo trials (0.5 ± 0.5°C, P = 0.02). SkBF became progressively lower during nicotine than placebo trials (P = 0.01) and progressively higher during 30°C than 20°C trials (P < 0.01); MAP increased from baseline (P < 0.01) and remained elevated in all trials. The difference in Hprod between 30°C and 20°C trials was lower during nicotine than placebo (P = 0.01) and became progressively higher during 30°C than 20°C trials with exercise duration (P = 0.03). Mean power output during the time trial was lower during 30°C than 20°C trials (24 ± 25 W, P = 0.02), and although no effect of nicotine was observed (P > 0.59), two participants (20%) were unable to complete their 30°C nicotine trials as one reached the ethical limit for Tgi (40.0°C), whereas the other withdrew due to "nausea and chills" (Tgi = 39.7°C). These results demonstrate that nicotine use increases thermal strain and risk of exertional heat exhaustion by reducing SkBF. NEW & NOTEWORTHY: In naïve participants, acute nicotine use exerts a hyperthermic effect that increases the risk of heat exhaustion during exertional heat strain, which is driven by a blunted skin blood flow response. This has implications for 1) populations that face exertional heat strain and demonstrate high nicotine use (e.g., athletes and military, 25%–50%) and 2) study design whereby screening and exclusion for nicotine use or standardization of prior use (e.g., overnight abstinence) is encouraged. [ABSTRACT FROM AUTHOR]

American football players might face challenges during a prolonged exercise in the heat which can lead to impairments in performance and induce heat-related illness. The purpose of this study was to verify the body temperature and sweating responses in American football players while exercising at a moderate-high intensity effort as prescribed by metabolic heat production. Seven heat-acclimatized players participated in the study. Players exercised 4×20-min bouts at moderate-high intensity as 8.0W.kg-1 of metabolic heat production, with 10min rest between them, totalizing 110min of heat exposure (39oC and 50% relative humidity). Rectal (Tre) and skin (Tsk) temperatures, heart rate (HR), metabolic heat production were measured continuously. Dehydration was calculated from Δbody mass pre-and postexercise. Initial Tre and HR were 37.0 ± 0.3 °C and 80 ± 9 beats.min-1, respectively. Players began the trial euhydrated according to the initial urine specific gravity (1.014 ± 0.008) and colour (2.4 ± 1.4). During experimental trial, core temperature increased overtime (p < .001) resulting in a ΔTre of 2.2 ± 0.6 °C. Average HR during exercise was 166 ± 11 beats.min-1 and weighted Tsk was 36.7 ± 0.5 °C. Sweat volume was 2.6 ± 0.3 L, resulting a % hypohydration of - 3.1 ± 0.4 % reflecting a moderate level of hypohydration. Final urine specific gravity and colour were 1.024 ± 0.009 and 5.0 ± 1.0, respectively. Experimental trials were interrupted at the end of the third and the fourth exercise bouts in two players due to the respective adverse conditions: leg muscle cramps, and excessive Tre increase (reached 39.9 °C). Thermoregulation and hydration must be a major concern, mainly related to greater exercise intensities and longtime practice, inducing high hypohydration levels and risk of hyperthermia. [ABSTRACT FROM AUTHOR]

Abstract Eggs are a vulnerable stage because they are sensitive to thermal and hydric conditions and yet cannot behaviourally avoid stressful environments. A general mechanistic model of egg development in natural nests requires microclimatic predictions of temperature, humidity, radiation (if above ground) and water potential (if buried in soil) to be integrated with models of heat and water exchange of the egg and the metabolism of the developmental process. Although all the required pieces for such a model now exist, they have not been integrated into a general modelling framework. We developed such an integration using NicheMapR package for mechanistic niche modelling. Specifically, we took an existing general model of egg water exchange and connected it with the microclimate model in NicheMapR to simulate nest thermal and hydric environments, including the effects of soil water potential on liquid and vapour exchange and moisture‐mediated soil thermal conductivity on heat exchange. We then used the Dynamic Energy Budget model within the ectotherm model of NicheMapR as the mechanistic engine for the developmental process, allowing the explicit computation of the dynamics of metabolic heat production and all aspects of mass exchange. We illustrate the modelling framework using existing laboratory and field data on reptiles, insects, and birds. We show that it can capture laboratory observations of water exchange and metabolic heat production and how it can be used to map potential development and water uptake under natural conditions at the continental scale. The modelling framework can be used to interpret laboratory experiments and allows strong inferences to be made about the abiotic constraints on egg development in natural nests under past, present, and future environmental change.

Eggs are a vulnerable stage because they are sensitive to thermal and hydric conditions and yet cannot behaviourally avoid stressful environments. A general mechanistic model of egg development in natural nests requires microclimatic predictions of temperature, humidity, radiation (if above ground) and water potential (if buried in soil) to be integrated with models of heat and water exchange of the egg and the metabolism of the developmental process. Although all the required pieces for such a model now exist, they have not been integrated into a general modelling framework.We developed such an integration using NicheMapR package for mechanistic niche modelling. Specifically, we took an existing general model of egg water exchange and connected it with the microclimate model in NicheMapR to simulate nest thermal and hydric environments, including the effects of soil water potential on liquid and vapour exchange and moisture‐mediated soil thermal conductivity on heat exchange. We then used the Dynamic Energy Budget model within the ectotherm model of NicheMapR as the mechanistic engine for the developmental process, allowing the explicit computation of the dynamics of metabolic heat production and all aspects of mass exchange.We illustrate the modelling framework using existing laboratory and field data on reptiles, insects, and birds. We show that it can capture laboratory observations of water exchange and metabolic heat production and how it can be used to map potential development and water uptake under natural conditions at the continental scale.The modelling framework can be used to interpret laboratory experiments and allows strong inferences to be made about the abiotic constraints on egg development in natural nests under past, present, and future environmental change. [ABSTRACT FROM AUTHOR]

The Burmese python has a remarkable digestive physiology with large elevations of metabolic rate and heart rate following feeding. Here, we investigated the relationship between heart rate, oxygen consumption and core body temperature during digestion in five pythons (Python bivittatus) by implantation of data loggers. The snakes were placed in respirometers at 30±0.1°C for 26 days and voluntarily ingested three meals of different size, whilst heart rate, core body temperature and oxygen consumption rate were measured continuously. Both oxygen consumption and heart rate increased severalfold during digestion, and metabolic heat production increased core body temperature by 2°C, explaining 12% of the observed tachycardia. The rise in core body temperature means that standard metabolic rate increased during digestion, and we estimate that failure to account for core body temperature leads to a 4% overestimation of the specific dynamic action (SDA) response. Our study reveals a close correlation between oxygen consumption and heart rate during digestion, further supporting the use of heart rate as a proxy for metabolism., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2024. Published by The Company of Biologists Ltd.)

During incubation, embryonic growth and development are dependent on nutrients deposited in the egg. The content of the yolk can be transferred to the embryo in 2 ways: directly into the intestine via the yolk stalk or through the highly vascularized yolk sac membrane. It has been suggested that, as a result of genetic selection and improved management, the increase in posthatch growth rate and concurrently the increase in metabolic rate of broiler chickens during the last 50 yr has also increased embryonic metabolism. A higher metabolic rate during incubation would imply a lower residual yolk weight and possibly lower energy reserve for the hatchling. This might affect posthatch development and performance. This review examined scientific publications published between 1930 and 2018 to compare residual yolk weight at hatch, metabolic heat production, and yolk utilization throughout incubation. This review aimed to investigate 1) whether or not residual yolk weight and composition has been changed during the 88-yr period considered and 2) which abiotic and biotic factors affect yolk utilization in poultry during incubation and the early posthatch period. It can be concluded that 1) residual yolk weight and the total solid amount of the residual yolk at hatch seem to be decreased in the recent decades. It cannot be concluded whether the (lack of) differences between old and modern strains are due to genetic selection, changed management and incubation conditions, or moment of sampling (immediately after hatch or at pulling). It is remarkable that with the genetic progress and improved management and incubation conditions over the last 88 yr, effects on yolk utilization efficiency and embryonic metabolic heat production are limited; 2) factors specially affecting residual yolk weight at hatch include egg size and incubation temperature, whereas breeder age has more influence on nutrient composition of the residual yolk.

We compared two methods of partitional calorimetry to calculate heat storage and heat debt during cold air (0°C) exposure causing mild core cooling. Twelve participants performed a 5 min baseline in thermoneutral conditions (∼22.0°C, ∼50% relative humidity) followed by cold air exposure (∼0°C) until rectal temperature was reduced by ∆-0.5°C. Partitional calorimetry was used to calculate avenues of heat exchange (radiative, convective, and evaporative), heat storage, and heat debt continuously throughout cold exposure. We compared deriving these variables using prediction equations based on environmental and participant characteristics (PCAL Equation Method ) versus using measurement tools such as humidity sensors and heat flux discs (PCAL Heat Flux Method ). There were significant differences between methods (all p  ≤ 0.001) for determining heat exchange, heat storage, and heat debt. At ∆-0.5°C, PCAL Heat Flux Method had greater levels of radiative and convective heat exchange (PCAL Heat Flux Method : -143.0 ± 16.8 W∙m 2 vs PCAL Equation Method : -123.0 ± 12.9 W∙m 2 , p  ≤ 0.001), evaporative heat exchange (PCAL Heat Flux Method : -9.0 ± 1.7 W∙m 2 vs PCAL Equation Method : -4.1 ± 0.0 W∙m 2 , p  ≤ 0.001), heat storage (PCAL Heat Flux Method : -15.0 ± 31.0 W∙m 2 vs PCAL Equation Method : +6.0 ± 25.9 W∙m 2 , p  = 0.020), and heat debt (PCAL Heat Flux Method : -692.0 ± 315.0 kJ vs PCAL Equation Method : -422.0 ± 136.0 kJ, p  ≤ 0.001). Overall, this study found the largest discrepancies between the two methods were when the environmental conditions and skin temperature were in high flux, as well as when core temperature was reduced by ∆-0.5°C. The use of PCAL Heat Flux Method may be more advantageous to use in the cold to provide a higher resolution measurement of cold strain., Competing Interests: The authors declare there are no competing interests.

The objective of this study was to assess biothermal conditions in the selected Polish health resorts for specific forms of climatic therapy. We calculated Universal Thermal Climate Index (UTCI) for ten-year period (2008-2017) and then added adjustment terms, taking into account changes in metabolic rates during various physical activities from resting to vigorous exercise. The adjusted UTCI values increased with rising activity, implying that warmer parts of the year were unsuitable for intensive forms of climatotherapy. These results demonstrate that the UTCI adjustment procedure provides well-balanced assessments of bioclimatic conditions for the purpose of climatic treatment considering the level of activity. [ABSTRACT FROM AUTHOR]

Lactating dairy cows exhibit a myriad of responses to heat stress. These responses partially facilitate the thermal balance between heat gain and heat loss, but also account for reduction in productivity. Decreased milk yield is the most recognized impact of heat stress on a dairy cow and results in significant economic loss to dairy producers. The reduced milk yield by heat stress is observed when daily average temperature-humidity index exceeds 68, above which the milk yield of a cow is negatively correlated with temperature-humidity index or dry bulb temperature. Milk yield is also positively correlated with body temperature of the cows under evaporative cooling, which reflects the positive relationship between metabolic heat production and milk yield. During summer, feed intake is positively correlated with milk yield, and the decreased intake explains at least half of the reduction in milk yield by heat stress. These emphasize the importance of maintaining intake on productivity during summer. Although not entirely clear, mechanisms that mediate the reduced milk yield by heat stress in addition to intake may be multifactorial. These could include but are not limited to altered metabolism, potential activation of immune system and inflammation, changes in behavior, and altered mammary gland development and function. • Summarized the threshold of heat stress. • Explored interrelationships between milk yield, body temperature, and climatic variables during summer. • Reviewed factors that influence milk yield responses to heat stress, and cow responses to heat stress. [ABSTRACT FROM AUTHOR]

During incubation, embryonic growth and development are dependent on nutrients deposited in the egg. The content of the yolk can be transferred to the embryo in 2 ways: directly into the intestine via the yolk stalk or through the highly vascularized yolk sac membrane. It has been suggested that, as a result of genetic selection and improved management, the increase in posthatch growth rate and concurrently the increase in metabolic rate of broiler chickens during the last 50 yr has also increased embryonic metabolism. A higher metabolic rate during incubation would imply a lower residual yolk weight and possibly lower energy reserve for the hatchling. This might affect posthatch development and performance. This review examined scientific publications published between 1930 and 2018 to compare residual yolk weight at hatch, metabolic heat production, and yolk utilization throughout incubation. This review aimed to investigate 1) whether or not residual yolk weight and composition has been changed during the 88-yr period considered and 2) which abiotic and biotic factors affect yolk utilization in poultry during incubation and the early posthatch period. It can be concluded that 1) residual yolk weight and the total solid amount of the residual yolk at hatch seem to be decreased in the recent decades. It cannot be concluded whether the (lack of) differences between old and modern strains are due to genetic selection, changed management and incubation conditions, or moment of sampling (immediately after hatch or at pulling). It is remarkable that with the genetic progress and improved management and incubation conditions over the last 88 yr, effects on yolk utilization efficiency and embryonic metabolic heat production are limited; 2) factors specially affecting residual yolk weight at hatch include egg size and incubation temperature, whereas breeder age has more influence on nutrient composition of the residual yolk. [ABSTRACT FROM AUTHOR]

Abstract Background Various individual characteristics affect environmental adaptability of a human. The present study evaluates the relationship between physical fitness and peripheral vasoconstriction in a cold environment. Methods Seven healthy male students (aged 22.0 years) participated in this study. Cold exposure tests consisted of supine rest for 60 min at 28 °C followed by 90 min at 10 °C. Rectal and skin temperatures at seven sites, oxygen consumption, and the diameter of a finger vein were measured during the experiment. Metabolic heat production, skin heat conductance, and the rate of vasoconstriction were calculated. Individual maximum oxygen consumption, a direct index of aerobic fitness, was measured on the day following the cold exposure test. Results Decreases in temperature of the hand negatively correlated with the changes in rectal temperature. Maximum oxygen consumption and the rate of vasoconstriction are positively correlated. Furthermore, pairs of the following three factors are also significantly correlated: rate of metabolic heat production, skin heat conductance, and the rate of vasoconstriction. Conclusion The results of this study suggested that the capacity for peripheral vasoconstriction can be improved by physical exercise. Furthermore, when exposed to a cold environment, fitter individuals could maintain metabolic heat production at the resting metabolic level of a thermoneutral condition, as they correspondingly lost less heat.

Blood glucose (BG) concentration monitoring is essential for controlling complications arising from diabetes, as well as digital management of the disease. At present, finger-prick glucometers are widely used to measure BG concentrations. In consideration of the challenges of invasive BG concentration measurements involving pain, risk of infection, expense, and inconvenience, we propose a noninvasive BG concentration detection method based on the conservation of energy metabolism. In this study, a multisensor integrated detection probe was designed and manufactured by 3D-printing technology to be worn on the wrist. Two machine-learning algorithms were also applied to establish the regression model for predicting BG concentrations. The results showed that the back-propagation neural network model produced better performance than the multivariate polynomial regression model, with a mean absolute relative difference and correlation coefficient of 5.453% and 0.936, respectively. Here, about 98.413% of the predicted values were within zone A of the Clarke error grid. The above results proved the potential of our method and device for noninvasive glucose concentration detection from the human wrist.

Physiological differences between individuals can significantly affect human thermal response to the environment. In practice, most thermal models use a single set of physiological data to represent an average person. We have developed a model to translate descriptive data about an individual into a set of physiological parameters which may be used in thermal models. We have incorporated these parameters into a model of human thermoregulation and comfort, which may be used to predict variations in thermal response between individuals. This paper presents this model and examples of its use in thermal simulation. r 2001 Elsevier Science Ltd. All rights reserved.

The intravenous administration of an amino acid (AA) mixture during general anesthesia reduces anesthesia-induced hypothermia. AA-induced skeletal muscle protein synthesis and thermogenesis play important roles in the antihypothermic effects of AAs. We hypothesized that a preanesthetic dietary protein deficiency impairs the antihypothermic effects of AAs during general anesthesia due to a reduction in thermogenesis caused by a decrease in muscle protein synthesis. Sprague-Dawley rats were divided into 4 groups: fed a control diet plus saline (CON-SAL) or the AA mixture (CON-AA), and fed a protein-free diet plus saline (PF-SAL) or the AA mixture (PF-AA). SAL solution or AA mixture solution was infused for 180 minutes during sevoflurane anesthesia, and rectal temperatures were measured. Rectal temperatures were significantly higher in the CON-AA group than in the PF-AA group 90 to 180 minutes after initiating the intravenous infusion of the test solutions. There was no significant difference between the PF-SAL and PF-AA groups. Plasma insulin concentrations were significantly higher in the CON-AA group than in the PF-AA group (P <.05). The phosphorylation states of protein kinase B, mammalian target of rapamycin, and eukaryotic initiation factor 4E-binding protein 1 were significantly greater in the CON-AA group than in the PF-AA group (P <.05, P <.05, and P <.01, respectively). Our results indicated that a dietary protein deficiency before general anesthesia impaired the antihypothermic effects of an AA mixture infusion during general anesthesia by decreasing muscle protein synthesis through the insulin-stimulated phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin complex 1 signaling pathway followed by metabolic heat production. [ABSTRACT FROM AUTHOR]

• Presented the variation in metabolic rate of Chinese subjects in different activities considering gender and age factors. • Women have lower metabolic rates than men in various activities and ages, emphasizing the importance of gender in studying metabolic rate and thermal comfort. • No age-related declines in metabolic heat production during lower activities, but an increase in production rates with age. • Differences compared to international standards suggest the need for potential modifications when applying them to the Chinese population. Metabolic rate is an essential factor in determining human thermal comfort. Existing metabolic rates for common activities in the current standards are based on mean adult values and do not include values for the middle-aged and the elderly. This study examines the metabolic rate of 151 Chinese male and female subjects aged 20 ∼ 69 during eighteen activities (reclining, 7 types of office work including seated and standing, 5 types of housework, and 5 walking speeds) using an indirect calorimeter in lab studies. The results show that women exhibited lower metabolic heat production rates (6–9% for sedentary and standing activities, 9–13% for household activities, and 4–9% for walking activities) than men across all activities, regardless of age. No age-related declines in metabolic heat production during lower activities (reclining, sedentary, standing, and household). Rather, metabolic heat production rates increased at a rate of 5–7 W/m2 per decade with age, which is contrary to popular beliefs. Women demonstrated a distinct pattern of changes compared to men, with significant declines observed in sitting and standing activities, at a rate of 2–3 W/m2 per decade. The ISO and ASHRAE standards tended to overestimate the metabolic rate for standing position activities and significantly underestimate the metabolic rate during walking. Some simple household activities, such as folding cloth, wiping windows, and vacuuming, had a moderate metabolic rate level, significantly higher than standing quiet. These findings could inform the development of interventions to promote healthy ageing and the design of more effective strategies for managing thermal comfort in different populations. It is suggested that the metabolic rate reference table or prediction method in international standards needs modification when applied to the Chinese population. [ABSTRACT FROM AUTHOR]

Metabolic rate is one of the important factors determining human thermal comfort. However, in current standards, metabolic rates are based on average values for adults and do not include values for children. Children are in a phase of growth and development, with different body characteristics and composition, and their metabolic rates may differ from those of adults. This can lead to inaccurate estimations of thermal sensation. This study analyzed an open database on children's oxygen consumption during daily activities to determine metabolic heat production and rate for ages 6–18. Age and gender significantly influence the metabolic heat production (W) of children and adolescents. As individuals grow older, their metabolic heat production increases, with boys consistently showing higher values than girls. Using segmented regression analysis, the turning points of metabolic heat production growth in children and adolescents during watching television and walking activities were identified. It was determined that girls reach a stable state earlier than boys. Regarding metabolic rate (W/m2), the impact of gender and age varies across different activities but is generally modest. Males tend to have higher metabolic rates than females, and this difference tends to increase with age and activity. Throughout the entire age range, the metabolic rate remains relatively stable, without any significant inflection point observed. To optimize thermal environment designs in primary and middle schools, standards should focus on children and adolescents' specific metabolic data across genders and ages for common activities. Incorporating these reference values is crucial for designer guidelines and standards. • Examined the variation in metabolic rate among children and adolescents during common activities, taking into account factors such as gender and age. • Metabolic heat production tends to increase as individuals grow older, with boys consistently exhibiting higher values than girls. • Metabolic rate remains relatively stable across the entire age range, without any significant inflection points observed. • Provided data on metabolic heat production and metabolic rate for different age stages. [ABSTRACT FROM AUTHOR]

This work aimed at characterizing the thermal balance of Nellore cattle from the system of indirect calorimetry using a facial mask. The study was conducted at the Animal Biometeorology Laboratory of the São Paulo State University, Jaboticabal, Brazil. Five male Nellore weighing 750 ± 62 kg, at similar ages and body conditions were distributed in four 5 × 5 Latin squares (5 days of records and five schedules) during 20 days. Physiological and environmental measurements were obtained from the indirect calorimetry system using a facial mask. Respiratory parameters, hair coat, skin, and rectal temperature were continuously recorded. From this, metabolic heat production, sensible and latent ways of heat transfer were calculated. Metabolic heat production had an average value of 146.7 ± 0.49 W m−2 and did not change (P > 0.05) over the range of air temperature (24 to 35 °C). Sensible heat flow reached 60.08 ± 0.81 W m−2 when air temperature ranged from 24 to 25 °C, being negligible in conditions of temperature above 33 °C. Most of the heat produced by metabolism was dissipated by cutaneous evaporation when air temperature was greater than 30 °C. Respiratory parameters like respiratory rate and ventilation remained stable (P > 0.05) in the range of temperature studied. Under shade conditions and air temperature range from 24 to 35 °C, metabolic heat production, respiratory rate, and ventilation of mature Nellore cattle remain stable, which is indicative of low energetic cost to the thermoregulation. [ABSTRACT FROM AUTHOR]

The recruitment of thermoeffectors, including thermoregulatory behavior, relative to changes in body temperature has not been quantified in humans. We tested the hypothesis that changes in skin blood flow, behavior, and sweating or metabolic rate are initiated with increasing changes in mean skin temperature (Tskin) in resting humans. While wearing a water-perfused suit, 12 healthy young adults underwent heat (Heat) and cold stress (Cold) that induced gradual changes in Tskin. Subjects controlled the temperature of their dorsal neck to their perceived thermal comfort. Thus neck skin temperature provided an index of thermoregulatory behavior. Neck skin temperature (Tskin), core temperature (Tcore), metabolic rate, sweat rate, and nonglabrous skin blood flow were measured continually. Data were analyzed using segmental regression analysis, providing an index of thermoeffector activation relative to changes in Tskin. In Heat, increases in skin blood flow were observed with the smallest elevations in Tskin (P < 0.01). Thermal behavior was initiated with an increase in Tskin of 2.4±1.3°C (mean±SD, P = 0.04), while sweating was observed with further elevations in Tskin (3.4±0.5°C, P = 0.04), which coincided with increases in Tcore (P = 0.98). In Cold, reductions in skin blood flow occurred with the smallest decrease in Tskin (P < 0.01). Thermal behavior was initiated with a Tskin decrease of 1.5±1.3°C, while metabolic rate (P = 0.10) and Tcore (P = 0.76) did not change throughout. These data indicate that autonomic and behavioral thermoeffectors are recruited in coordination with one another and likely in an orderly manner relative to the comparative physiological cost. [ABSTRACT FROM AUTHOR]

There is limited and inconclusive evidence surrounding the physiological and perceptual responses to heat stress while sleep deprived, especially for females. This study aimed to quantify the effect of 24 h sleep deprivation on physiological strain and perceptual markers of heat-related illness in females. Nine females completed two 30-min heat stress tests (HST) separated by 48 h in 39°C, 41% relative humidity at a metabolic heat production of 10 W · kg−1. The non-sleep deprived HST was followed by the sleep deprivation (SDHST) trial for all participants during the follicular phase of the menstrual cycle. Physiological and perceptual measures were recorded at 5 min intervals during the HSTs. On the cessation of the HSTs, heat illness symptom index (HISI) was completed. HISI scores increased after sleep deprivation by 28 ± 16 versus 20 ± 16 (P = 0.01). Peak (39.40 ± 0.35°C vs. 39.35 ± 0.33°C) and change in rectal temperature (1.91 ± 0.21 vs. 1.93 ± 0.34°C), and whole body sweat rate (1.08 ± 0.31 vs. 1.15 ± 0.36 L · h−1) did not differ (P > 0.05) between tests. No difference was observed in peak, nor rise in: heart rate, mean skin temperature, perceived exertion or thermal sensation during the HSTs. Twenty-four hours sleep deprivation increased perceptual symptoms associated with heat-related illness; however, no thermoregulatory alterations were observed. [ABSTRACT FROM PUBLISHER]

We tested the hypotheses that older adults with cardiovascular co-morbidities will demonstrate greater changes in body temperature and exaggerated changes in blood pressure before initiating thermal behavior. We studied twelve healthy younger adults (Younger, 25 ± 4 y) and six older adults ('At Risk', 67 ± 4 y) taking prescription medications for at least two of the following conditions: hypertension, type II diabetes, hypercholesterolemia. Subjects underwent a 90-min test in which they voluntarily moved between cool (18.1 ± 1.8°C, RH: 29 ± 5%) and warm (40.2 ± 0.3°C, RH: 20 ± 0%) rooms when they felt 'too cool' (C→W) or 'too warm' (W→C). Mean skin and intestinal temperatures and blood pressure were measured. Data were analyzed as a change from pretest baseline. Changes in mean skin temperature were not different between groups at C→W (Younger: +0.2 ± 0.8°C, 'At Risk': +0.7 ± 1.8°C, P = 0.51) or W→C (Younger: +2.7 ± 0.6°C, 'At Risk': +2.9 ± 1.9°C, P = 0.53). Changes in intestinal temperature were not different at C→W (Younger: 0.0 ± 0.1°C, 'At Risk': +0.1 ± 0.2, P = 0.11), but differed at W→C (-0.1 ± 0.2°C vs. +0.1 ± 0.3°C, P = 0.02). Systolic pressure at C→W increased (Younger: +10 ± 9 mmHg, 'At Risk': +24 ± 17 mmHg) and at W→C decreased (Younger: −4 ± 13 mmHg, 'At Risk': -23 ± 19 mmHg) to a greater extent in 'At Risk' (P ≤ 0.05). Differences were also apparent for diastolic pressure at C→W (Younger: −2 ± 4 mmHg, 'At Risk': +17 ± 23 mmHg, P < 0.01), but not at W→C (Younger Y: +4 ± 13 mmHg, 'At Risk': −1 ± 6 mmHg, P = 0.29). Despite little evidence for differential control of thermal behavior, the initiation of behavior in 'at risk' older adults is preceded by exaggerated blood pressure responses. [ABSTRACT FROM AUTHOR]

Vacuum impregnation (VI) has been widely used as pre-treatment prior to, e.g., minimal processing, freezing, or drying of fruit and vegetables. Most of the investigations have focused on the applicability of VI to modify physicochemical, sensory, and nutritive characteristics. However, little attention has been paid to the metabolic consequences of impregnating different substances into the plant tissue. This study explores short- and long-term metabolic responses of baby spinach leaves at 5 °C after impregnation with several substances that are commonly used in food industry, e.g., sucrose, calcium lactate, citric acid, and ascorbic acid. Short-term metabolic response of impregnated spinach leaves was measured with isothermal calorimetry for 7 h. Results demonstrated that leaves impregnated with calcium lactate and sucrose showed a drastic increase in metabolic heat production, but no change was recorded in leaves impregnated with solutions of ascorbic acid or citric acid. Long-term metabolic responses were evaluated by measuring sugars and starch. The different impregnation solutes provoked specific changes in the carbohydrate composition during cold storage and the concentrations at each time point are likely to be the result of mobilization of starch, which sharply decreased during storage, and solute-specific differences in metabolization and interconversion of sugars. [ABSTRACT FROM AUTHOR]

Seo, Yongsuk, Hayden D. Gerhart, Jeremiah Vaughan, Jung-Hyun Kim, and Ellen L. Glickman. Does acute normobaric hypoxia induce anapyrexia in adult humans? High Alt Med Biol. 18:185-190, 2017.-Exposure to hypoxia is known to induce a reduction in core body temperature as a protective mechanism, which has been shown in both animals and humans. The purpose of this study was to test if acute exposure to normobaric hypoxia (NH) induces anapyrexia in adult humans in association with decreased peripheral oxygen saturation (SpO2). Ten healthy male subjects were seated in atmospheres of normobaric normoxia 21% (NN21), NH 17% (NH17), and 13% (NH13) O2 for 60 minutes in a counterbalanced manner. Rectal temperature (Tre) was continuously monitored together with the quantification of metabolic heat production (MHP) and body heat storage (S). Baseline physiological measurements showed no differences between the three conditions. SpO2 was significantly decreased in NH17 and NH13 compared with NN21 ( p ≤ 0.001). Tre decreased following 60 minutes of resting in all conditions, but, independent of the conditions, showed no association between Tre and levels of hypoxic SpO2. There was also no significant difference in either MHP or S between conditions. The present results showed no evidence of hypoxia-induced anapyrexia in adult humans during 1 hour of resting after exposure to NH either at 13% or 17% O2. [ABSTRACT FROM AUTHOR]

In the presented paper, the capability of segmented flow chip calorimeters for the analysis of time-dependent pharmaceutical effects on differently complex biological systems is demonstrated. Due to the noninvasive nature of calorimetric measurements, the dynamics of metabolic changes in living material can be analyzed more precisely compared to endpoint methods, in particular in case of highly inhomogeneous sample material. In comparison to batch and conventional flow-through calorimeters, the segmented flow technology enables increased throughput and defined cultivation conditions of the investigated material. Samples of 1 mm of colorectal cancer tissue were treated with 5-Fluorouracil or staurosporine and subsequently analyzed by segmented flow chip calorimetry. The observed dynamics of the drug effects is characterized by defined inflection points in the heat rate curves. All data of the onset time were similar for a given drug. In contrast, the rate of metabolic deactivation of the tissue affected by the treatment was strongly dependent on the biology of the tumor from individual patients. The heat evolution of fibroblast spheroids treated with staurosporine showed a similar dynamics as observed in treated colorectal cancer tissue samples. However, the heat production of synthetic micro-tissues was more uniform than the heat production of the highly inhomogeneous cancer tissue, directly derived from surgical patients. The investigation of the effect of adrenalin and noradrenalin on the metabolism of daphnia demonstrated the excellent real-time capabilities of the used segmented flow chip calorimeter. An increased heat production rate could be measured already few minutes after start of treatment. The small thermal time constant of the calorimeter of only 25 s enabled the detection of drug-caused changes in the motility of the daphnia in a frequency bandwidth of 0.02 Hz. [ABSTRACT FROM AUTHOR]