Hypothyroidism alters the rhythmicity of the central clock, body temperature and metabolism: evidence of Bmal1 transcriptional regulation by T3.

In mammals, the central circadian oscillator is located in the suprachiasmatic nucleus (SCN). Hypothalamus-pituitary-thyroid axis components exhibit circadian oscillation, regulated by both central clock innervation and intrinsic circadian clocks in the anterior pituitary and thyroid glands. Thyroid disorders alter the rhythmicity of peripheral clocks in a tissue-dependent response; however, whether these effects are influenced by alterations in the master clock remains unknown. This study aimed to characterize the effects of hypothyroidism on the rhythmicity of SCN, body temperature (BT) and metabolism, and the possible mechanisms involved in this signalling. C57BL/6J adult male mice were divided into Control and Hypothyroid groups. Profiles of spontaneous locomotor activity (SLA), BT, oxygen consumption ( V ̇ O 2 ${{\dot{V}}_{{{{\mathrm{O}}}_{\mathrm{2}}}}}$ ) and respiratory quotient (RQ) were determined under free-running conditions. Clock gene expression, and neuronal activity of the SCN and medial preoptic nucleus (MPOM) area were investigated in light-dark (LD) conditions. Triiodothyronine (T3) transcriptional regulation of Bmal1 promoter activity was evaluated in GH3-transfected cells. Hypothyroidism delayed the rhythmicity of SLA and BT, and altered the expression of core clock components in the SCN. The activity of SCN neurons and their outputs were also affected, as evidenced by the loss of circadian rhythmicity in V ̇ O 2 ${{\dot{V}}_{{{{\mathrm{O}}}_{\mathrm{2}}}}}$ and RQ and alterations in the neuronal activity pattern of MPOM. In GH3 cells, T3 increased Bmal1 promoter activity in a time-dependent manner. Thyroid hormone may act as a temporal cue for the central circadian clock, and the uncoupling of central and peripheral clocks might contribute to a wide range of metabolic and thermoregulatory impairments observed in hypothyroidism. KEY POINTS: Hypothyroidism alters clock gene expression in the suprachiasmatic nucleus (SCN). Thyroid hypofunction alters the phase of spontaneous locomotor activity and body temperature rhythms. Thyroid hormone deficiency alters the daily pattern of SCN and medial preoptic nucleus neuronal activities. Hypothyroidism alterations are extended to daily oscillations of oxygen consumption and metabolism, which might contribute to the development of metabolic syndrome. Triiodothyronine increases Bmal1 promoter activity acting as temporal cue for the central circadian clock.

The relevance of vascular adjustments to hemodynamic control in the face of temperature change in Crotalus durissus.

The presence of cardiac shunts in ectothermic tetrapods is thought to be consistent with active vascular modulations for proper hemodynamic support. Local control of blood flow modulates tissue perfusion and thus systemic conductance (Gsys) is assumed to increase with body temperature (Tb) to accommodate higher aerobic demand. However, the general increase of Gsys presses for a higher right-to-left (R-L) shunt, which reduces arterial oxygen concentration. In contrast, Tb reduction leads to a Gsys decrease and a left-to-right shunt, which purportedly increases pulmonary perfusion and plasma filtration in the respiratory area. This investigation addressed the role of compensatory vascular adjustments in the face of the metabolic alterations caused by Tb change in the South American rattlesnake (Crotalus durissus). Cardiovascular recordings were performed in decerebrated rattlesnake preparations at 10, 20 and 30°C. The rise in Tb increased metabolic demand, and correlated with an augmentation in heart rate. Although cardiac output increased, systemic stroke volume reduced while pulmonary stroke volume remained stable. Although that resulted in a proportionally higher increase in pulmonary blood flow, the R-L shunt was maintained. While the systemic compliance of large arteries was the most relevant factor in regulating arterial systemic blood pressure, peripheral conductance of pulmonary circulation was the major factor influencing the final cardiac shunt. Such dynamic adjustment of systemic compliance and pulmonary resistance for shunt modulation has not been demonstrated before and contrasts with previous knowledge on shunt control.

Transitional photoperiod induces a mania-like behavior in male mice.

This study aimed to investigate the behavioral responses and circadian rhythms of mice to both rapid and gradual increases in photoperiod, mimicking the transition from winter to summer, which is associated with a heightened prevalence of hospitalizations for mania and suicidal behavior. Behavioral tests were performed in C57BL/6 male mice exposed to a transitional photoperiod, from short to long durations. To determine if circadian rhythms are affected, we measured spontaneous locomotor activity and body temperature. Mice exhibited heightened exploratory and risk-taking behaviors compared with equatorial and static long (16:8 h of light-dark cycle for several days) groups. These behaviors were prevented by lithium. Spontaneous locomotor activity and body temperature rhythms persisted and were effectively synchronized; however, the relative amplitude of activity and interdaily stability were diminished. Additionally, the animals displayed increased activity during the light phase. Photoperiodic transition modulates behavior and circadian rhythms, mirroring certain features observed in bipolar disorder patients. This study introduces an animal model for investigating mania-like behavior induced by photoperiodic changes, offering potential insights for suicide prevention strategies and the management of mood disorders.

Thermal mapping: Assessing the optimal sites for temperature measurement in the human body and emerging technologies.

Numerous body locations have been utilized to obtain an accurate body temperature. While some are commonly used, their accuracy, response time, invasiveness varies greatly, and determines their potential clinical and/or research use. This review discusses human body temperature locations, their accuracy, ease of use, advantages, and drawbacks. We explain the concept of core body temperature and which of the locations achieve the best correlation to this temperature. The body locations include axilla, oral cavity, rectum, digestive and urinary tracts, skin, tympanic, nasopharynx, esophagus, and pulmonary artery. The review also discusses the latest temperature technologies, heat-flux technology and telemetric ingestible temperature pills, and the body locations used to validate these devices. Rectal and esophageal measurements are the most frequently used.

Effects of Optimal Temperature Control in Body Contouring Surgery: A Nonrandomized Controlled Clinical Trial.

BACKGROUND: Perioperative hypothermia in plastic surgery has underestimated risks, including increased risk of infection, cardiac events, blood loss, prolonged recovery time, and increased nausea, pain, and opioid usage. Inadequate preventive measures can result in up to 4 hours of normothermia restoration. OBJECTIVES: The aim was to compare the impact of different strategies for normothermia during plastic surgery procedures and their relationship with clinical outcomes. METHODS: A nonrandomized clinical trial was conducted in a single center in Bogota, Colombia. We enrolled adult patients undergoing body contouring surgery and divided them into 4 intervention groups with different measures to control body temperature. Univariate and bivariate analyses were performed, comparing several clinical symptoms to evaluate outcomes. RESULTS: A total of 197 patients were analyzed. Most of them were females (84.3%). Mean age was 38.6 years, and the median procedure duration was 260 minutes. Demographic and clinical characteristics did not exhibit significant differences between the groups. There were notable variations in temperature measurements at crucial moments during the surgical procedure among the groups, attributed to the implementation of distinct thermal protective strategies. Group comparisons showed a relationship between hypothermia and increased nausea, vomiting, shivering, pain, and additional analgesia requirements. CONCLUSIONS: Incorporation of active thermal protective measures, such as Blanketrol or HotDog, during body contouring procedures, markedly diminishes the risk of hypothermia and enhances overall clinical outcomes. Implementing these active measures to maintain the patient in a state of normothermia not only improves operating room efficiency but also leads to a reduction in recovery room duration.

Identifying physiological indicators of the cognitive, thermal, and combined (cognitive-thermal) stress conditions.

Physiologically based stress detection systems have proven to be effective in identifying different stress conditions in the body to determine the source of stress and be able to counteract it. However, some stress conditions have not been widely studied, including thermal stress, cognitive stress, and combined (thermal-cognitive) stress conditions, which are frequently encountered in work or school environments. In order to develop systems to detect and differentiate these conditions, it is necessary to identify the physiological indicators that characterize each of them. The present research aims to identify which physiological indicators (heart rate, respiratory rate, galvanic skin response, and local temperature) could differentiate different stress conditions (no-stress, cognitive stress, thermal stress, and combined (thermal-cognitive) stress conditions). Thirty participants were exposed to cognitive, thermal, and combined stress sources while recording their physiological signals. The findings indicate that both mean heart rate and mean galvanic skin response identify moderate thermal and cognitive stress conditions as distinct from a no-stress condition, yet they do not differentiate between the two stress conditions. Additionally, heart rate uniquely identifies the cognitive-thermal stress condition, effectively distinguishing this combined stress condition from the singular stress conditions and the no-stress condition. Mean local temperature specifically signals thermal stress conditions, whereas mean respiratory rate accurately identifies cognitive stress conditions, with both indicators effectively separating these conditions from each other and from the no-stress condition. This is the first basis for differentiating thermal and cognitive stress conditions through physiological indicators.

Dehydration alters behavioral thermoregulation and the geography of climatic vulnerability in two Amazonian lizards.

High temperatures and low water availability often strike organisms concomitantly. Observing how organisms behaviorally thermohydroregulate may help us to better understand their climatic vulnerability. This is especially important for tropical forest lizards, species that are purportedly under greater climatic risk. Here, we observed the influence of hydration level on the Voluntary Thermal Maximum (VTmax) in two small Amazonian lizard species: Loxopholis ferreirai (semiaquatic and scansorial) and Loxopholis percarinatum (leaf litter parthenogenetic dweller), accounting for several potential confounding factors (handling, body mass, starting temperature and heating rate). Next, we used two modeling approaches (simple mapping of thermal margins and NicheMapR) to compare the effects of dehydration, decrease in precipitation, ability to burrow, and tree cover availability, on geographic models of climatic vulnerability. We found that VTmax decreased with dehydration, starting temperature, and heating rates in both species. The two modeling approaches showed that dehydration may alter the expected intensity, extent, and duration of perceived thermal risk across the Amazon basin for these forest lizards. Based on our results and previous studies, we identify new evidence needed to better understand thermohydroregulation and to model the geography of climatic risk using the VTmax.

Evaluation of the breathing mode by infrared thermography.

OBJECTIVES: To analyze breathing modes with infrared thermography. METHODS: Cross-sectional observational exploratory study conducted in 20 female participants with a mean age of 26.0-years. The thermograms were made following the principles of the American Academy of Thermology and the Brazilian Thermology Society. The camera FLIR A315 (FLIR Inc., Santa Barbara, CA) was used for the tests. The recordings consisted of the participants breathing normally through the nose for 2min and simulating oral/oronasal breathing for another 2min. The thermograms were analyzed with the FLIR Tools software. An ellipse was placed between the nostrils and the lip commissures to obtain the mean temperatures. The collection was made by two independent researchers, and the normalized non-dimensional temperature was calculated. RESULTS: The temperature in nasal breathing is higher than in oral/oronasal breathing both for inhaling and exhaling when measured in the region of the mouth. The exhaling temperatures were higher than the inhaling ones in oral/oronasal breathing (through the nose and the mouth) and nasal breathing (only through the nose). The temperature difference between exhaling and inhaling (ΔT) was greater in oral/oronasal breathing when measured in the region of the mouth. CONCLUSION: The thermographic assessment of breathing modes may be made by comparing the mean temperatures of the mouth, using an ellipse. LEVEL OF EVIDENCE: Study without consistently applied reference standards.

Infrared Imaging of the Brain-Eyelid Thermal Tunnel: A Promising Method for Measuring Body Temperature in Afebrile Children.

(1) Infrared thermography of the inner canthus of the eye has emerged as a promising tool for temperature screening and fever diagnosis. Its non-invasive nature lends itself well to mass screening in diverse settings such as schools, public transport, and healthcare facilities. Swift and accurate temperature assessment plays a pivotal role in the early identification of potential fever cases, facilitating timely isolation, testing, and treatment, thereby mitigating the risk of disease transmission. Nonetheless, the reliability of this approach in the pediatric population, especially when compared to conventional thermometry methods, remains unexplored. This preliminary study aimed to evaluate the concordance between the temperature of the inner canthus of the eye (Tic,eye), referred to as the brain-eyelid thermal tunnel (BTT°), with axillary and tympanic methods in afebrile children. (2) Methods: A cohort of 36 children, matched in a 1:1 ratio for gender and age, underwent comprehensive assessments encompassing anthropometric data, blood pressure evaluations, axillary (Tax) and tympanic (Tty) temperature measurements, as well as BTT° infrared thermography. (3) Results: The findings revealed a high level of concordance among the tympanic, axillary, and BTT° measurement methods. Bland-Altman plots showed that the bias was minimal, and no statistically significant differences were observed when comparing BTT° with axillary (p = 0.136) and tympanic (p = 0.268) measurements. Passing-Bablok regression scatter plots further confirmed the agreement, aligning the fitted regression line closely with the identity line for both axillary versus BTT° and tympanic (Tty) versus BTT° comparisons. (4) Conclusions: This study holds significant implications for public health, especially in the context of infectious disease outbreaks such as COVID-19. BTT° infrared thermography of the inner canthus of the eye (Tic,eye) reliably measures body temperature in afebrile children in controlled settings; nevertheless, its practical application necessitates the adaptation of biothermodynamic parameters to accommodate diverse environmental conditions.

Energy and time optimization during exit from torpor in vertebrate endotherms.

Torpor is used in small sized birds and mammals as an energy conservation trait. Considerable effort has been put towards elucidating the mechanisms underlying its entry and maintenance, but little attention has been paid regarding the exit. Firstly, we demonstrate that the arousal phase has a stereotyped dynamic: there is a sharp increase in metabolic rate followed by an increase in body temperature and, then, a damped oscillation in body temperature and metabolism. Moreover, the metabolic peak is around two-fold greater than the corresponding euthermic resting metabolic rate. We then hypothesized that either time or energy could be crucial variables to this event and constructed a model from a collection of first principles of physiology, control engineering and thermodynamics. From the model, we show that the stereotyped pattern of the arousal is a solution to save both time and energy. We extended the analysis to the scaling of the use of torpor by endotherms and show that variables related to the control system of body temperature emerge as relevant to the arousal dynamics. In this sense, the stereotyped dynamics of the arousal phase necessitates a certain profile of these variables which is not maintained as body size increases.

Predicting the body core temperature of recreational athletes at the end of a 10 km self-paced run under environmental heat stress.

NEW FINDINGS: What is the central question of this study? The aim was to identify the factors predicting the body core temperature of athletes at the end of a 10 km self-paced run in a hot environment. What is the main finding and its importance? Hyperthermia in athletes subjected to self-paced running depends on several factors, highlighting the integrated control of core temperature during exercise under environmental heat stress. Five of the seven variables that significantly predicted core temperature are not invasive and, therefore, practical for use outside the laboratory environment: heart rate, sweat rate, wet-bulb globe temperature, running speed and maximal oxygen consumption. ABSTRACT: Measurement of body core temperature (Tcore ) is paramount to determining the thermoregulatory strain of athletes. However, standard measurement procedures of Tcore are not practical for extended use outside the laboratory environment. Therefore, determining the factors that predict Tcore during a self-paced run is crucial for creating more effective strategies to minimize the heat-induced impairment of endurance performance and reduce the occurrence of exertional heatstroke. The aim of this study was to identify the factors predicting Tcore values attained at the end of a 10 km time trial (end-Tcore ) under environmental heat stress. Initially, we extracted data obtained from 75 recordings of recreationally trained men and women. Next, we ran hierarchical multiple linear regression analyses to understand the predictive power of the following variables: wet-bulb globe temperature, average running speed, initial Tcore , body mass, differences between Tcore and skin temperature (Tskin ), sweat rate, maximal oxygen uptake, heart rate and change in body mass. Our data indicated that Tcore increased continuously during exercise, attaining 39.6 ± 0.5°C (mean ± SD) after 53.9 ± 7.5 min of treadmill running. This end-Tcore value was primarily predicted by heart rate, sweat rate, differences between Tcore and Tskin , wet-bulb globe temperature, initial Tcore , running speed and maximal oxygen uptake, in this order of importance (ß power values corresponded to 0.462, -0.395, 0.393, 0.327, 0.277, 0.244 and 0.228, respectively). In conclusion, several factors predict Tcore in athletes subjected to self-paced running under environmental heat stress. Moreover, considering the conditions investigated, heart rate and sweat rate, two practical (non-invasive) variables, have the highest predictive power.

Seasonal and elevational variation in thermal ecology of the crevice-dwelling knob-scaled lizard Xenosaurus fractus from central-eastern Mexico.

There is strong covariation between the thermal physiology of ectothermic animals and their thermal environment. Spatial and temporal differences in the thermal environment across a species' range may result in changes in thermal preferences between populations of that species. Alternatively, thermoregulatory-based microhabitat selection can allow individuals to maintain similar body temperatures across a broad thermal gradient. Which strategy a species adopts is often dependent on taxon-specific levels of physiological conservatism or ecological context. Identifying which strategies species use in response to spatial and temporal variation in environmental temperatures requires empirical evidence, which then can support predictions as to how a species might respond to a changing climate. Here we present findings of our analyses of the thermal quality, thermoregulatory accuracy and efficiency for the lizard, Xenosaurus fractus, across an elevation-thermal gradient and over the temporal thermal variation associated with seasonal changes. Xenosaurus fractus is a strict crevice-dweller, a habitat that can buffer this lizard from extreme temperatures and is a thermal conformer (body temperatures reflect air and substrate temperatures). We found populations of this species differed in their thermal preferences along an elevation gradient and between seasons. Specifically, we found that habitat thermal quality, thermoregulatory accuracy and efficiency (all measures of how well the lizards' body temperatures compared to their preferred body temperatures) varied along thermal gradients and with season. Our findings indicate that this species has adapted to local conditions and shows seasonal flexibility in those spatial adaptations. Along with their strict crevice-dwelling habitat, these adaptations may provide some protection against a warming climate.

Diagnostic applicability of infrared thermography in the evaluation of canine mammary tumors / Aplicabilidade diagnóstica da termografia infravermelha na avaliação dos tumores mamários caninos

Mammary tumors have a high prevalence in bitches and women, and are related to high rates of morbidity and mortality. For the human species, thermography has stood out as a diagnostic tool for breast cancer. However, its clinical benefit in bitches remains unknown. Thus, the goal of the present study was to evaluate the diagnostic applicability of infrared thermography for canine mammary tumors, as well as to correlate tumor temperature with mitotic index and tumor volume. Thermographic and digital images of eight bitches with mammary neoplasms were captured. Thermograms were entered into the FLIR tools software and the temperature of 15 tumor and 15 healthy glands from the contralateral mammary chain was analyzed. There was no significant difference (p = 0.786) between the mean temperature of neoplastic (33.71°C ± 1.86) and healthy (33.54°C ± 1.59) glands. There was a negative and moderate correlation between tumor temperature and mitotic index (ρ = -0.52 p = 0.049). However, no correlation was detected between mammary temperature and tumor volume (p = 0.10). Although thermography allowed no distinction between neoplastic and healthy mammary glands in bitches, it may be promising to assess the proliferative rate of tumors. In addition, malignant neoplasms may be more often hypothermic than healthy tissue.(AU)

Os tumores mamários apresentam alta prevalência em cadelas e mulheres, sendo relacionados a elevadas taxas de morbidade e mortalidade. Para a espécie humana, a termografia tem se destacado como ferramenta diagnóstica do câncer de mama. Entretanto, o seu benefício clínico em cadelas permanece desconhecido. Assim, o objetivo do presente estudo foi ava-liar a aplicabilidade diagnóstica da termografia infravermelha para os tumores mamários caninos, bem como correlacionar a temperatura tumoral com o índice mitótico e volume tumoral. Foram capturadas imagens termográficas e digitais de oito cadelas com neoplasias mamárias. Os termogramas foram inseridos no software FLIR tools e analisou-se a temperatura de 15 mamas tumorais e 15 hígidas da cadeia mamária contralateral. Não houve diferença significativa (p = 0,786) entre a tempera-tura média das glândulas neoplásicas (33,71°C ± 1,86) e saudáveis (33,54°C ± 1,59). Houve correlação negativa e moderada entre a temperatura tumoral e índice mitótico (ρ = -0,52 p = 0,049). Entretanto, não foi observada correlação entre tempe-ratura e volume tumoral (p = 0,10). Apesar da termografia não ter permitido a diferenciação das mamas neoplásicas e saudá-veis de cadelas, ela pode ser uma forma promissora para avaliação da taxa proliferativa dos tumores. Além disso, as neoplasias malignas podem apresentar-se mais frequentemente hipotérmicas em relação ao tecido saudável.(AU)

emperature, pH and sarcomere length of Caiman yacare in different body weight categories at slaughter / Temperatura, pH e comprimento de sarcômero de Caiman yacare em diferentes categorias de peso corporal ao abate

The objective of this work was to characterize the internal temperature of the carcass, pH and sarcomere length in four categories of body weight at a slaughter. The categories were: category 1, animals up to 1.5 kg, category 2, animals from 1.501 to 2.5 kg, category 3, animals from 2.501 to 3.5 kg and category 4, animals over 3.501 kg. The time intervals evaluated were 0.5, 2, 4, 6, 8, 10, 12, 14, 16, 18, 24 and 36 hours after bleeding, therefore, a factorial scheme (4 x 12) was used, in which where four categories of pre-slaughter weight and the behavior of the carcasses during the post-slaughter time were evaluated. There was no interaction effect between the weight categories and the time for the variation of the carcass internal temperature, pH and sarcomere length, but when only the time of rigor was evaluated, there were significant differences for the analyzed parameters. The internal temperature of the initial average carcass (0.5 hours) was 16.02°C, reaching 3.80°C at 36 hours post-slaughter. In addition, the lowest average pH found was at 24 hours, with a value of 5.39. Regarding the sarcomere length, the smallest mean length observed was 1.41 µm at 16 hours post-slaughter and the final mean length (36 hours) was 1.89 µm. It was concluded that the analyzed margin of the categories of body weight at slaughter did not interfere in the variation of temperature, pH and sarcomere length during the post-mortem of the Pantanal caiman.(AU)

O objetivo do trabalho foi caracterizar a temperatura interna da carcaça, o pH e o comprimento de sarcômero em quatro categorias de peso corporal ao abate. As categorias foram: categoria 1, animais com até 1,5 kg, categoria 2, animais de 1,501 a 2,5 kg, categoria 3, animais de 2,501 a 3,5 kg e categoria 4, animais acima de 3,501 kg. Os intervalos de tempo avaliados foram 0,5, 2, 4, 6, 8, 10, 12, 14, 16, 18, 24 e 36 horas, após a sangria, portanto, foi utilizado um esquema fatorial (4 x 12) que avaliou quatro categorias de peso e o comportamento das carcaças ao decorrer do tempo. Não houve efeito de interação entre as categorias de peso e o tempo para a variação da temperatura interna da carcaça, pH e comprimento de sarcômero, mas quando avaliado apenas o tempo de rigor, houve diferenças significativas para os parâmetros analisados. A temperatura interna da carcaça média inicial (0,5 horas) foi de 16,02°C, chegando a 3,80°C nas 36 horas pós-abate. Além disso, o menor pH médio encontrado foi as 24 horas, com valor de 5,39. Em relação ao comprimento de sarcômero o menor comprimento médio observado foi de 1,41 µm nas 16 horas pós-abate e o comprimento médio final (36 horas) foi de 1,89 µm. Conclui-se que a margem analisada das categorias de peso corporal ao abate, não interferiram na variação de temperatura, pH e comprimento de sarcômero durante o post mortem do jacaré-do-Pantanal.(AU)

Normal gastrointestinal temperature values measured through ingestible capsules technology: a systematic review.

Climate change has amplified the importance of continuous and precise body core temperature (Tcore) monitoring in the everyday life. In this context, assessing Tcore through ingestible capsules technology, i.e., gastrointestinal temperature (Tgastrointestinal), emerges as a good alternative to prevent heat-related illness. Therefore, we conducted a systematic review to point out values of normal Tgastrointestinal measured through ingestible capsules in healthy humans. The study followed PRISMA guidelines and searched the PubMed and Scielo databases from 1971 to 2023. Our search strategy included the descriptors ("gastrointestinal temperature") AND ("measurement"), and eligible studies had to be written in English and measured Tgastrointestinal using ingestible capsules or sensors in healthy adults aged 18-59 at rest. Two pairs of researchers independently reviewed titles and abstracts and identified 35 relevant articles out of 1,088 in the initial search. An average value of 37.13 °C with a standard deviation of 0.24 °C was observed, independently of the gender. The values measured ranged from 36.70 °C to 37.69 °C. In conclusion, this systematic review pointed out the mean value of 37.13 ± 0.24 °C measured by ingestible capsules as reference for resting Tgastrointestinal in healthy adult individuals.

A 32-day long fieldwork in Antarctica improves heat tolerance during physical exercise.

We evaluated the influence of a 32-day camping in Antarctica on physical performance and exercise-induced thermoregulatory responses. In Brazil, before and after the Antarctic camping, the volunteers performed an incremental exercise at temperate conditions and, two days later, an exercise heat stress protocol (45-min running at 60% of maximum aerobic speed, at 31°C and 60% of relative humidity). In Antarctica, core temperature was assessed on a day of fieldwork, and average values higher than 38.5°C were reported. At pre- and post-Antarctica, physiological (whole-body and local sweat rate, number of active sweat glands, sweat gland output, core and skin temperatures) and perceptual (thermal comfort and sensation) variables were measured. The Antarctic camping improved the participants' performance and induced heat-related adaptations, as evidenced by sweat redistribution (lower in the chest but higher in grouped data from the forehead, forearm, and thigh) and reduced skin temperatures in the forehead and chest during the exercise heat stress protocol. Notwithstanding the acclimatization, the participants did not report differences of the thermal sensation and comfort. In conclusion, staying in an Antarctic camp for 32 days improved physical performance and elicited physiological adaptations to heat due to the physical exertion-induced hyperthermia in the field.

Physiological parameters of F1 Holstein × Zebu cows fed with banana peel / Parâmetros fisiológicos de vacas F1 Holandês × Zebu alimentadas com inclusão de casca de banana

The objective was to evaluate the effects of different levels of banana peel inclusion on the physiological variables of lactating F1 Holstein × Zebu cows. Ten cows distributed in two 5 × 5 Latin squares were used. Five experimental diets were tested: sorghum silage (control group); and the addition of 15%, 30%, 45%, and 60% of banana peel to replace sorghum silage. The experiment lasted 80 days. The environmental and physiological variables of the animals were measured. The Black Globe-Humidity Index presented an alert situation in the morning shift and a dangerous situation in the afternoon shift. The respiratory rate was not influenced by the levels of banana peel inclusion (P > 0.05) in the morning shift. However, it was influenced (P < 0.05) in the afternoon shift. The levels of banana peel inclusion in the diet did not affect the rectal temperature. Under the study environmental conditions, the level of up to 60% of banana peel replacing sorghum silage did not alter the physiological variables of thermoregulation in F1 Holstein × Zebu cows.

Objetivou-se avaliar níveis de inclusão da casca de banana sobre as variáveis fisiológicas de vacas F1 Holandesas × Zebu em lactação. Foram utilizadas 10 vacas distribuídas em dois quadrados latinos 5×5. Sendo cinco dietas experimentais: silagem de sorgo (grupo controle); e a inserção de 15, 30, 45 e 60% da casca de banana em substituição a silagem de sorgo. O experimento teve duração de 80 dias. Mensuraram-se as variáveis ambientais e fisiológicas dos animais. O índice de temperatura de globo negro e umidade encontrada no turno matutino apresentou uma situação de alerta e no turno vespertino uma situação perigosa. A frequência respiratória foi influenciada pelos níveis de inclusão de casca de banana no turno vespertino. A temperatura retal não foi influenciada pelos níveis de inclusão de casca de banana na dieta. Sob as condições ambientais estudadas, o nível de até 60% de casca de banana, em substituição a silagem de sorgo, não alterou as variáveis fisiológicas de termorregulação em vacas F1 Holandesas × Zebu.

Temperature should not be measured on forearm with infrared thermometers for Covid-19 screening.

Not available.

Head pre-cooling improves 5-km time-trial performance in male amateur runners in the heat.

This study aimed to evaluate the effect of head pre-cooling on the 5-km time-trial performance of amateur runners in the heat. In a counterbalanced design, 15 male amateur runners (22.6 ± 3.5 y; VO2 max in heat 42.3 ± 4.4 mLO2 /kg/min) completed two 5-km time trials performed in the heat (35°C, 50% relative humidity). In one trial (HCOOL), participants underwent 20 min of head cooling in a temperate environment (23°C, 70% relative humidity) prior to exercise. In another trial (CON), exercise was preceded by 20 min of rest under the same temperature conditions. Exercise time was shorter in HCOOL (25 min and 36 s ± 3 min) compared to CON (27 ± 3 min; p = 0.02). Rectal temperature was reduced during the pre-exercise intervention in HCOOL (p < 0.001), but not in CON (p = 0.55). Relative changes in rectal temperature and mean head temperature were lower throughout HCOOL when compared with CON condition (p = 0.005 and p = 0.022, respectively). Mean skin temperature, heart rate, and rating of perceived exertion did not differ between HCOOL and CON conditions throughout exercise (p = 0.20, p = 0.52 and 0.31, respectively). Thermal comfort was lower in HCOOL condition in pre-exercise (p = 0.014) with no differences observed throughout exercise (p = 0.61). 5-km running performance in a hot environment was improved after a 20-min head cooling intervention, suggesting that this method may be practical as pre-cooling strategy and easily administered to both professional and amateur runners alike.