Thermoneutral Environment Research Articles

Cold Stress Protocol In Brown Adipose Tissue Activation In Obese Men

PURPOSE: To measure the activation of brown adipose tissue by cold stress protocol in obese men. METHODS: 24 male military from Brazilian Army were evaluated (38.5 ± 1.8 years, BMI:30.7 ± 2.9 kg/m2,body fat:31.0 ± .2%). The maximum and medium supraclavicular temperature (TScvMax/TScvMed) from right/left sides and the maximum and medium sternum temperature (TStrMax/TStrMed) were register using the infrared camera E75 FLIR®, in two moments. First, volunteers remain 30 min in a thermoneutral environment (22.6 ± 0.2 °C) for thermalization. Second, hands were submerged in a container with ice water at the temperature of 13.0 ± 0.4 °C, during 5 min after. The body composition was evaluated using double X-ray absorptiometry. Kolmogorov-Smirnov normality test applied and confirmed parametric approach. The data were analyzed by SPSS® 25.0, running Student’s t-test two paired samples. The effect-size (Cohen's d) was calculated with GPower software. Significance level at p < 0.05. The images were analyzed using FLIR Tools® software. RESULTS: On the TScvMax was observed a significant increase on the right side from 33.6 ± 0.4 °C to 34.1 ± 0.6 °C (p < 0.001;d = 0.787) and on the left side 33.3 ± 0.6 °C to 34.0 ± 06.4 °C (p < 0.001;d = 0.787). On the TScvMed also was observed a significant increase on the right side from 32.8 ± 0.4 °C to 33.4 ± 0.6 °C (p < 0.001;d = 0.787) and on the left side 32.5 ± 0.5 °C to 33.1 ± 0.5 °C (p < 0.001;d = 0.787). But it was not observed in the control region (Sternum) where there was no BAT for TMax and TMed (p = 0.923 and p = 0.869), respectively. CONCLUSIONS: Cold stress protocol proved to be effective in BAT activation, increasing the temperature in the supraclavicular region for the obesity men group. This protocol ican be used in the clinical evaluation. It is suggested that in future studies other protocols with less time of exposure to the cold be studied, thus reducing the discomfort of the evaluated individual.

Interventions to prevent hypothermia in extremely preterm low-weight infants undergoing cardiac catheterisation

BackgroundIn January 2019, a new device called the Amplatzer Piccolo Occluder was approved by the US Food and Drug Administration for percutaneous closure of patent ductus arteriosus in infants weighing...

Dietary L-citrulline modulates the growth performance, amino acid profile, and the growth hormone/insulin-like growth factor axis in broilers exposed to high temperature.

Heat stress adversely affects the growth performance, muscle development, and protein metabolism in poultry. l-Citrulline (L-Cit), is a non-essential amino acid that is known to stimulate muscle protein synthesis under stress conditions. This study investigated whether L-Cit could influence the growth performance, amino acid profile, and protein metabolism in broilers exposed to high ambient temperature. In a 2 × 2 factorial arrangement, Arbor acre broilers (288 chickens) were fed with basal diet (CON) or 1% L-Cit supplemented diet and later subjected to either thermoneutral (TNZ: 24°C, 24 h/d) or heat stress (HS: 35°C for 8 h/d) environment for 21 days. The results showed that L-Cit diet promoted the body weight and body weight gain of broilers higher than the CON diet, and it further alleviated HS suppression of body weight and feed intake at certain periods (p < 0.05). Plasma urea, uric acid, glucose, and total cholesterol were elevated during HS, whereas, the triglyceride content was decreased (p < 0.05). Serum amino acids including citrulline, alanine, aspartate, and taurine were decreased by HS. L-Cit supplementation restored the citrulline level and alleviated HS induction of 3-methylhistidine (p < 0.05). L-Cit supplementation increased the plasma growth hormone (GH) and insulin-like growth factor-1 (IGF-1) concentration, as well as the GH concentration in the breast muscle (p < 0.05). The mRNA expression showed that HS elicited tissue-specific responses by upregulating some growth factors in the breast muscle, but downregulated the GH receptor, GH binding protein, and IGF-1 expression in the hypothalamus. L-Cit supplementation upregulated the GHRH and IGFBP2 expression in the hypothalamus. L-Cit also upregulated the expression of IGF-1R and IGFBP2 in the breast muscle of HS broilers. The total mTOR protein level in the breast muscle of HS broilers was also increased by L-Cit diet (p < 0.05). Therefore, this study demonstrated that HS negatively affected the growth performance of broilers and dysregulated the expression of growth factors related to protein metabolism. Contrarily, L-Cit promoted the growth responses of broilers via its stimulation of circulating GH/IGF-1 concentration. To certain extents, L-Cit supplementation elicited protective effects on the growth performance of HS broilers by diminishing protein catabolism.

Thermoneutral Environment for Neonates: Back to the Basics.

Thermoregulation is an essential component to the stability and long-term outcomes of newborns and critically-ill neonates. A thermoneutral environment (TNE) is an environment in which a neonate maintains a normal body temperature while minimizing energy expenditure and oxygen consumption. Neonates who experience thermal stability within a TNE demonstrate enhanced growth, decreased respiratory support, decreased oxygen requirements, increased glucose stability, reduced mortality, and reduced morbidities associated with hyperthermia and hypothermia. Heat exchange occurs between the neonate and surrounding environment through four mechanisms: evaporation, conduction, convection, and radiation. By recognizing the methods by which heat is lost or gained, the neonatal provider can prevent adverse conditions related to abnormal thermal control and support a thermoneutral neonatal environment.

Effect of chronic heat stress on gastrointestinal histology and expression of feed intake-regulatory hormones in broiler chickens

Heat stress (HS) dramatically impairs the growth performance of broiler chickens, mainly as a consequence of reduced feed intake due to the loss of appetite. This study was aimed at evaluating the alterations induced by chronic HS conditions on the morphological and morphometric features of the gastrointestinal (GI) tract and on the expression of some enteroendocrine cells (EECs) involved in the regulation of feed intake in chickens. Three hundred male chickens (Ross 308) were divided into two experimental groups and raised either in thermoneutral environment for the whole fattening period (0–41 days) (TNT group) or subjected to chronic HS conditions (30 °C for 24 h/day) from 35 to 41 days (HS group). Samples of proventriculus, duodenum, jejunum and cecum were collected from 24 broilers (12/group). Haematoxylin-eosin was used for the morphometric evaluations, while immunohistochemistry was applied for the evaluation of EECs expressing ghrelin (GHR), cholecystokinin (CCK), neuropeptide Y (NPY), glucagon-like peptide-1 (GLP-1), and serotonin (5-HT). In the proventriculus, HS reduced total wall thickness and mucous layer height (P ≤ 0.01) as well as mean diameter, circumference, and area of the compound tubular glands (P ≤ 0.001) with respect to TNT. The small intestine of HS birds was characterised by decreased villous height and total thickness (duodenum, P ≤ 0.01; jejunum, P ≤ 0.001), whereas crypt depth and width were reduced only in the jejunum (P ≤ 0.01). HS had negligible effects on the morphological aspects of the cecum. In the proventriculus, an increase in GHR and NPY EECs was observed in response to HS (P ≤ 0.001). Similarly, the small intestine villi of the HS group showed greater GLP-1 (P ≤ 0.05), 5-HT (P ≤ 0.001) and CCK (P ≤ 0.01) EECs. Moreover, the expression of 5-HT EECs was higher in the duodenal (P ≤ 0.01) and jejunal (P ≤ 0.01) crypts of HS birds, whereas GLP-1 and CCK EECs increased only in jejunal crypts (P ≤ 0.05). Finally, 5-HT EEC expression was increased in the cecum of HS group (P ≤ 0.01). In conclusion, these outcomes demonstrate that chronic HS induces morphometric alterations not only in the small intestine but also in a key organ such as the proventriculus. Furthermore, HS conditions affect the presence and distribution of EECs, suggesting that some GI peptides and biogenic amine may be implicated in the regulation of appetite and voluntary feed intake in heat-stressed broiler chickens.

Heat Stress Alters the Effect of Eimeria maxima Infection on Ileal Amino Acids Digestibility and Transporters Expression in Meat-Type Chickens.

Simple SummaryHeat stress (HS) and Eimeria (E.) maxima infection are the most common physical and pathological stressors in chicken houses, and both affect intestinal digestibility and absorption leading to reduction in growth, morbidity, and mortality, causing massive economic losses. This study identifies the impact of each stressor and their combined effects on apparent amino acid digestibility and molecular transporters expression in the ileum of broiler chicken. Heat-stressed chickens showed no change in amino acids digestibility, despite the reduction in feed intake. Combining HS and E. maxima infection modulated the reduction in amino acids digestibility observed in the infected chickens. The expression of the ileal amino acid transporters was severely impacted by E. maxima infection but not by HS. Interestingly, the infected group reared under HS exhibited significantly higher expression levels in all the enterocytic apical and about half of the basolateral amino acid transporters than the infected birds raised in thermoneutral environment. Thus, HS putatively curtailed the maldigestion effects of E. maxima.Eimeria (E.) maxima invades the midgut of chickens and destroys the intestinal mucosa, impacting nutrient digestibility and absorption. Heat stress (HS) commonly affects the broiler chicken and contributes to inflammation and oxidative stress. We examined the independent and combined effects of HS and E. maxima infection on apparent amino acid ileal digestibility (AID) and mRNA expression of amino acid transporters in broiler chickens (Ross 708). There were four treatment groups: thermoneutral-control (TNc) and infected (TNi), heat-stress control (HSc) and infected (HSi), six replicates of 10 birds/treatment. Ileal content and tissue were sampled at 6 d post infection to determine AID and transporters expression. Surprisingly, the HSi chickens exposed to two critical stressors exhibited normal AID. Only the TNi group displayed reduction in AID. Using TNc as control, the HSc group showed upregulated CAT1, LAT4, TAT1, SNAT1, and SNAT7. The HSi group showed upregulated CAT1 and LAT1, and downregulated b0,+AT, rBAT, SNAT1, and SNAT2. The TNi group showed upregulated CAT1, LAT1, and SNAT1 and downregulated B0AT1, b0,+AT, rBAT, LAT4, and TAT1. The expression of all enterocytic-apical and about half of the basolateral transporters was higher in the HSi group than in the TNi group, indicating that HS can putatively alleviate the E. maxima adverse effect on ileal digestion and absorption.

Effects of a Short-Term Heat Acclimation Protocol in Elite Amateur Boxers

Stone, BL, Ashley, JD, Skinner, RM, Polanco, JP, Walters, MT, Schilling, BK, and Kellawan, JM. Effects of a short-term heat acclimation protocol in elite amateur boxers. J Strength Cond Res 36(7): 1966-1971, 2022-Boxing requires proficient technical and tactical skills coupled with high levels of physiological capacity. Although heat and humidity negatively affect acute exercise performance, short-term exercise training in hot and humid environments can lead to physiological adaptations that enhance exercise performance in both hot and thermoneutral conditions. In highly trained endurance athletes, exercise-induced acclimation can occur in as little as 5 days (known as short-term heat acclimation [STHA]). However, the impact of a 5-day heat acclimation (5-DayHA) in combat athletes, such as elite amateur boxers, is unknown. The aim of the present investigation was to determine whether a 5-DayHA improves aerobic performance in a thermoneutral environment and causes positive physiological adaptations in elite boxers. Seven elite amateur boxers underwent a 5-DayHA protocol, consisting of 60-minute exercise sessions in an environmental chamber at 32 °C and 70% relative humidity. Repeat sprint test (RST) evaluated aerobic performance in a thermoneutral environment 24 hours before and after the 5-DayHA. Presession and postsession hydration status (urine specific gravity) and body mass were assessed. After a 5-DayHA period, boxers significantly improved RST performance (13 ± 7 to 19 ± 7 sprints, d = 0.92, p = 0.03) but not pre-exercise hydration status (1.02 ± 0.01 to 1.01 ± 0.01, d = 0.82, p = 0.07). Therefore, these findings suggest 5-DayHA enhances aerobic performance in elite-level amateur boxers and may provide a viable training option for elite combat athletes.

Cardiac Adjustments During a Hot and Humid Heatwave Simulation in Older Adults

Heatwaves cause disproportionately high morbidity and mortality rates in those aged ≥ 65 years. While the underlying pathologies are typically of cardiovascular origin, the cardiac specific responses to real‐world heatwave conditions are not well‐defined.PurposeWe tested the hypothesis that three hours exposure to a hot and humid heat wave would increase left ventricular systolic contractility (s’) and early propagation velocity of mitral inflow (Vp) and decrease isovolumetric relaxation time (IVRT).MethodsEight healthy older adults (5 female/3 male; 70 ± 4 years; 26 ± 3 kg·m‐2) were exposed to 41°C, 40% humidity (replicating the 1995 Chicago heat wave) for three‐hours, interspersed with seven 5‐minute work bouts at three METS to replicate daily living activities. Core temperature (telemetric pill or rectal thermistor), skin temperature, blood pressure and heart rate were monitored continuously during heating. Water was provided throughout the protocol to minimize dehydration. Echocardiograms were taken at baseline (in a thermoneutral environment) and at three hours into heat stress to assess cardiac function. Pre to post heatwave differences in all variables were compared using paired samples t‐tests.ResultsCore temperature increased (36.7 ± 0.3 to 37.7 ± 0.5°C, p &lt; 0.001), skin temperature increased (34.0 ± 1.1 to 36.2 ± 0.8°C, p = 0.002), heart rate increased (59 ± 9 to 78 ± 18 b·min‐1,p = 0.012), and mean arterial pressure decreased (90 ± 14 to 78 ± 12 mmHg, p= 0.034) from baseline to 3‐hours heat exposure. Left ventricular contractility (s’) increased (8.2 ± 1.0 to 10.4 ± 1.4 cm/s, p = 0.002), while measures of diastolic function were unchanged during heating (p &gt; 0.14 for Vp, IVRT, E, A, E/A, e’, E/e’).ConclusionsOur preliminary findings suggest that humid heatwave exposure increases left ventricular contractility without impacting diastolic function in healthy older adults.

Impact of sodium citrate ingestion during recovery after strenuous exercise in the heat on heart rate variability: A randomized, crossover study

Changes in hydration status influence plasma volume (PV) which is associated with post‐exercise parasympathetic reactivation. The present study hypothesized that, after dehydrating cycling exercise in the heat (DE), stimulation of PV expansion with sodium citrate (CIT) supplementation would promote heart rate variability (HRV) recovery in endurance‐trained men. Twelve participants lost 4% of body mass during DE. During subsequent 16‐h recovery, participants consumed water ad libitum (CIT =5.5‐L, PLC =5.1‐L) and ate prescribed food supplemented with CIT or placebo in a randomized, double‐blind, crossover manner. Relative changes in PV were assessed across DE and 16‐h recovery. HRV was analyzed before and 16 h after DE in three conditions for altogether four 5‐min periods: supine in a thermoneutral environment, supine in the heat (32°C, 46% relative humidity; 2 periods), and standing in the heat. A larger expansion of PV across 16‐h recovery occurred in CIT compared to placebo trial (p < 0.0001). However, no between‐trial differences appeared in HRV parameters (lnRMSSD, lnSDNN, lnLF/HF) in any 5‐min period analyzed before or 16 h after DE (in all cases p > 0.05). Increases in HR (p < 0.001) and lnLF/HF (p = 0.005) and decreases in lnRMSSD (p < 0.001) and lnSDNN (p < 0.001) occurred following DE in both trials. Larger PV expansion induced by CIT supplementation after DE does not improve recovery of HRV at rest and has no influence on HRV responsiveness in endurance‐trained men.

The effects of exercise training in the cold on cerebral blood flow and cerebrovascular function in young healthy individuals.

Exercise elicits acute increases in cerebral blood flow velocity (CBFv) and provokes long-term beneficial effects on CBFv, thereby reducing cerebrovascular risk. Acute exposure to a cold stimulus also increases CBFv. We compared the impact of exercise training in cold and thermoneutral environments on CFBv, cerebrovascular function and peripheral endothelial function. Twenty-one (16 males, 22±5years) individuals were randomly allocated to either a cold (5°C) or thermoneutral (15°C) exercise intervention. Exercise consisted of 50-min cycling at 70% heart rate max, three times per week for eight weeks. Transcranial Doppler was used to determine pre and post intervention CBFv, dynamic cerebral autoregulation (dCA) and cerebrovascular reactivity (CVRCO2). Conduit endothelial function, microvascular function and cardiorespiratory fitness were also assessed. Cardiorespiratory fitness improved (2.91ml.min.kg-1, 95%CI 0.49, 5.3; P=0.02), regardless of exercise setting. Neither intervention had an impact on CBFv, CVRCO2, FMD or microvascular function (P>0.05). There was a significant interaction between time and condition for dCA normalised gain with evidence of a decrease by 0.192%cm.s-1.%mmHg-1 (95%CI -0.318, -0.065) following training in the cold and increase (0.129%cm.s-1.%mmHg-1, 95%CI 0.011, 0.248) following training in the thermoneutral environment (P=0.001). This was also evident for dCA phase with evidence of an increase by 0.072rad (95%CI -0.007, 0.152) following training in the cold and decrease by 0.065 (95%CI -0.144, 0.014) radians following training in the thermoneutral environment (P=0.02). Both training interventions improved fitness but CBFv, CVRCO2 and peripheral endothelial function were unaltered. Exercise training in the cold improved dCA whereas thermoneutral negated dCA.

Effect of Heat Stress, Dietary Electrolytes, and Vitamins E and C on Growth Performance and Blood Biochemistry of the Broiler Chicken

Environmental heat stress creates a detriment to the welfare and performance in broiler chickens. While there are some dietary mineral and vitamin supplements that mitigate this condition, a rapid, plasma-based detection method would improve management response and broaden the scientific understanding of heat stress. A total of 960 broilers were used to determine the effect of heat stress and dietary electrolyte balance on blood biochemistry. Sex sorted chicks were allocated to 48 pens with 20 chicks per pen creating 6 treatments (3 diets x 2 house environments) with eight replicates and fed one of three dietary treatments: a control containing primarily sodium chloride (NaCl), a heat stress formulation containing bicarbonate (NaHCO3), or heat stress fortified with 200 ppm vitamin C and E (NaHCO3 Fortified). Birds were housed in two different temperature-controlled environments either a thermoneutral (Control) or heat stressed (Heat Stress) environment. At day 28, 35 and 42 venous blood was collected and analyzed using rapid detection methods followed by post-mortem veterinary evaluations. Performance was measured at weekly intervals. Mortality was significantly higher in broilers exposed to heat stress as compared to thermoneutral, while broilers that received dietary sodium chloride also had higher mortality than bicarbonate fed birds. Heat stress significantly impacted potassium, hematocrit, uric acid, total protein, globulin, hematocrit, lymphocytes, sodium, and glucose. This study demonstrates that blood biochemistry of broiler chickens is influenced by dietary intervention and changing environmental conditions. This pattern suggests a blood biomarker footprint of sub-optimal nutrition or poor environmental conditions that may provide valuable information into physiological changes in response to dietary electrolytes, vitamins, and heat stress. Furthermore, this footprint may potentiate the development of diagnostic tools, combining biomarkers to determine nutrition and health status of individual broiler flocks, for nutritionists, veterinarians, and live production managers to manage flocks for environmental, humane, and productive purposes.

Marine Survival in the Mediterranean: A Pilot Study on the Cognitive and Cardiorespiratory Response to Sudden Cool Water Immersion.

Background and Aim: The Mediterranean is one of the major gateways of human migratory fluxes from Northern Africa, the Middle East, and Central Asia to Europe. Sea accidents have become an urgent humanitarian crisis due to the high number of migrants on the move, but data on the physiological effects to sudden cool water immersion are not as extensive as cold-water studies. We wanted to evaluate to what extent cool water immersion (~18 °C) may detrimentally affect cognitive ability and cardiorespiratory strain compared to the more prevalent cold-water (<10–15 °C) studies. Methods: In this case, 10 active, healthy men participated in this study which consisted of completing one familiarization trial, and then a control (CON) or experimental (EXP) trial in a randomized, repeated-measures, cross-over fashion, separated by at least 7-days. Cognitive function was assessed via the Symbol Digit Modalities Test (SDMT), a code substitution test, performed at baseline, then repeated in either a thermoneutral (~25 °C room air) dry environment, or when immersed to the neck in 18 °C water. Testing consisted of six “Step” time-blocks 45-s each, with a 5-s pause between each Step. Cardiorespiratory measures, continuously recorded, included heart rate (beats per minute), minute ventilation (E, L∙min−1), oxygen consumption (O2, L∙min−1), and respiratory frequency (fR, count∙min−1). Results: Initial responses to cool water (<2 min) found that participants performed ~11% worse on the code substitution test (p = 0.025), consumed 149% greater amounts of oxygen (CI: 5.1 to 9.1 L∙min−1, p < 0.0001) and experienced higher cardiovascular strain (HR CI: 13 to 38 beats per minute, p = 0.001) than during the control trial. Physiological strain was in-line to those observed in much colder water temperature. Conclusion: Sudden, cool water immersion also negatively affects cognitive function and cardiorespiratory strain, especially during the first two minutes of exposure. The magnitude increase in heart rate is strongly associated with poorer cognitive function, even in (relatively) warmer water consistent with temperatures found in the Mediterranean Sea environment.

A conceptual model for changes in finger photoplethysmograph signals caused by hand posture and isothermic regulation

Objective. To observe changes in baseline position and pulsatile light absorbance (photoplethysmograph, PPG) in the finger-tip, by raising the hand above the horizontal plane in recumbent subjects. We applied current knowledge of the circulation to the finger-tip, particularly arteriovenous anastomoses (AVAs), and the physiology of the venous circulation. Approach.We studied healthy young volunteers in a quiet thermoneutral environment. A finger plethysmograph on the non-dominant hand recorded transmission of red and infra-red light, with observations expressed as absorbance to allow comparisons within and between subjects. Breathing movements were recorded unobtrusively to assess any effect on absorbance and the pulse amplitude of the signals. All body movements were passive: the study arm was elevated in a trough to about 40° above the horizontal plane. The following conditions were studied, each for 15 min, using the last 10 min for analysis: recumbent, study arm elevated, study arm horizontal, and both legs elevated by 40°. Main results. We found a substantial time-related effect, and considerable variation between subjects. Arm elevation reduced red light absorbance and increased the range of amplitudes of the PPG waveform: only in subjects with large absorbances, did waveform amplitude increase. Spontaneous, thermoregulatory decreases in absorbance were large and associated with decreases in waveform amplitude. Significance. Finger-tip vessels distend with blood and light absorbance increases when AVAs open. The vessels pulsate more strongly when the hand is raised: venous collapse allows the vessels to become more compliant. The postcapillary circulation is likely to be an important source of pulsation.

Fan Cooling Improves Submaximal Exercise Capacity in an Indoor Thermoneutral Environment

ABSTRACT Purpose: We compared physiological and perceptual responses to submaximal, moderate-vigorous, heart rate-based cycle ergometry with and without a fan. Methods: Sixteen recreationally active adults (25 ± 3 years; 8 men and 8 women) participated in the study. After an initial visit to assess cardiorespiratory fitness, each participant performed two 40-min training sessions on a cycle ergometer, either with or without a fan (~4 m/s), while workload was continually adjusted to elicit and maintain 70% of heart rate reserve. Workload, oxygen cost, and respiratory exchange ratio were monitored throughout, and rating of perceived exertion (RPE) and thermal sensation were recorded every 5 min. Blood lactate was recorded pre-, mid-, and post-sessions and nude body mass was obtained pre-post. Results: Greater (p < .01) mean workload (+15%) and oxygen consumption (+9%) yielded significantly greater (p < .01) energy expenditure with fan cooling (344 ± 124 kcals) compared to without fan cooling (302 ± 103 kcals). Thermal sensation, but not RPE (p = .09), was lower (p < .01) with fan cooling (3.8 ± 0.7) compared to without fan cooling (5.5 ± 0.8), and body mass loss was attenuated (p < .05) with fan cooling (−0.4 ± 0.2 kg) compared to the non-fan trial (−0.6 ± 0.3 kg). Significantly higher (p < .05) blood lactate values were observed in Fan (3.0 ± 1.9 mmol/l) vs. No Fan (2.5 ± 1.4 mmol/l) trials. Conclusions: Fan cooling during submaximal, moderate–vigorous intensity cycle ergometry significantly enhanced work capacity and energy expenditure without increasing perceived exertion. These data highlight the utility of fan cooling as a means to increase the effectiveness of indoor, heart rate-based cycle training.

Feed form and nutritional level for rearing growing broilers in thermoneutral or heat stress environments

The present study aimed to investigate the effects of different physical forms of feed and feeding programs on nutrient digestibility and performance of grower-finisher broilers under thermoneutrality or thermal stress. Three experiments were conducted using male broiler chickens (n=720) aged 19-42d. The design of two of the experiments was fully randomized in a 2×2 factorial arrangement with two forms of feed (mash and pellet) and two nutritional levels (13.19MJ/kg and 194.8g/kg CP - normal level and 13.61MJ/kg and 210.3g/kg CP - high level). The experiments took place in a climate-controlled room: Experiment 1 at thermoneutrality (21-23°C and 58-60% relative humidity) for 24h/day; Experiment 2 under thermal stress cycle (31-32°C and 63-65% relative humidity), for 6h/day and thermoneutrality (21-23°C, 58-60% relative humidity) for 18h/day. The nutrient digestibility and performance was analyzed. The design of the third experiment was fully randomized with two ambient condition treatments (thermoneutral and thermal stress) on heat production, caloric increment and net energy. Pellet feed obtained higher digestibility of dry matter, digestibility of crude protein, AME and AMEn (P<0.05) than mash feed for broilers reared in the thermoneutral environment. At the high nutritional level there was no effect of treatments on the coefficient of dry matter and crude protein (DCCP) (P>0.05), while the highest digestibility of AME and AMEn were obtained by the high nutritional level diet (P<0.05). Pellet feed had higher DCCP (P<0.05) than mash feed for broilers reared under cyclic heat stress. Broiler chickens under cyclic stress experienced increased caloric increment, rectal temperature and respiratory rate. The appropriate strategy to minimize these effects in both ambient conditions is to pellet feed.

Prevalence and risk factors for admission hypothermia in neonates in a Tertiary Hospital in Jos, Nigeria

Background: Hypothermia on admission in neonatal units is a well-recognized contributor of neonatal mortality and morbidity. This study aimed to identify risk factors for hypothermia on admission in a resource-poor setting which will help provide targeted preventive interventions. Methods: A retrospective cross-sectional descriptive study was conducted from July 1, 2020 to January 31, 2022. A total of 567 neonates were included in the study, data were collected from the unit electronic database. The axillary temperature of each neonate was measured using a digital thermometer at the point of admission. Bivariate and multiple logistic regressions were used to assess associated risk factors. Results: The prevalence of admission hypothermia (AH) in the study population was 42.4% with mild and moderate hypothermia accounting for 46.3% and 53.7%, respectively. Maternal ages 20–29 years (adjusted odds ratio [aOR] 0.28, 95% confidence interval [CI] 0.09–0.93) and 30–39 years (aOR 0.27, 95% CI 0.08–0.88) and primary education (aOR 0.44, 95% CI 0.21–0.92) were associated with reduced risk of AH. Age <24 h (aOR 3.61, 95% CI 1.70–7.66), gestational age 28–32 weeks (aOR 3.90, 95% CI 1.41–10.79) and 33–36 weeks (aOR 2.835, 95% CI 1.52–5.28), admission weight <2.5 kg (aOR 2.01, 95% CI 1.18–3.43), and cold season (aOR 1.85, 95% CI 1.06–3.14) were associated with increased risk of AH. Mortality in those with AH was 3 folds (crude odds ratio 3.38, 95% CI 1.6–6.82). Conclusion: Hypothermia on admission is common in neonates in resource-poor settings. Training of newborn care-providers in maintaining thermoneutral environment and temperature at delivery and postnatal periods will be a cost-effective intervention in reducing neonatal mortality.

Comparison of the Effect of Hot and Thermo-Neutral Environments on Fat Oxidation during Post-Exercise Recovery in Exercise-Trained Obese Women: A Preliminary Report

Exercise training is recommended to promote energy expenditure. Fat utilization occurs during exercise and continues for an extended period of time after the exercise session. The environmental temperatures can influence whole body substrate oxidation. The present study aimed to address the impacts of environmental temperature on fat oxidation during post-exercise recovery in exercise-trained obese women. Eleven sedentary obese women (age: 18 - 50 y, BMI: 27.5 - 40 kg/m2) with regular menstruation participated in the study. All subjects underwent a 4-week moderate-intensity aerobic exercise program. After training, each subject completed 2 occasions of post-exercise recovery testing in hot (31 - 32 °C) and thermo-neutral (22 - 23 °C) conditions in a randomized crossover fashion with 3 - 4 days of washout period. Two exercise bouts preceding each recovery condition were identically performed for 60 min at 60 % of heart rate reserve (HRreserve) in the thermo-neutral condition. Both experiments were conducted during the follicular phase of menstrual cycle. Substrate oxidations were determined during 1 h of post-exercise recovery using indirect calorimetry. The results showed that the fat oxidation during recovery in thermo-neutral environment (52.8 ± 26.5 mg.kg-1.h-1) was significantly greater than recovery in hot environment (32.3 ± 27.9 mg.kg-1.h-1, p = 0.0002). Total energy from substrate oxidation was not different between hot and thermo-neutral environments. Thus, in obese women with 4-week exercise training, recovery in the thermo-neutral condition has a higher fat oxidation than in the hot condition. This result may be implicated in weight management for temperature of choice to recover after routine exercise training sessions.&#x0D; HIGHLIGHTS&#x0D; &#x0D; Fat oxidation was greater during recovery in thermo-neutral environment after moderate-intensity exercise in trained obese women&#x0D; Recovery carbohydrate oxidation was greater in hot environment than in thermo-neutral environment after moderate-intensity exercise&#x0D; Energy expenditure from substrate oxidations during recovery in both thermo-neutral and hot environments were similar&#x0D; &#x0D; GRAPHICAL ABSTRACT

Hydroxy Selenomethionine Improves Meat Quality through Optimal Skeletal Metabolism and Functions of Selenoproteins of Pigs under Chronic Heat Stress.

Chronic heat stress (CHS) induces metabolic changes in skeletal muscle from growth to maintenance that jeopardizes growth performance, carcass traits, and meat quality of pigs. We investigated the protective effect of dietary organic selenium (hydroxy-4-methylselenobutanoic acid, OH-SeMet) on CHS-induced skeletal muscle damages of growing pigs, and the corresponding responses of selenoproteins. A total of 40 ((Landrace ×Yorkshire) × Duroc) pigs with an average live weight of 49.64 ± 2.48 kg were used in this 4-week trial. Pigs were randomly allotted to 5 groups: The control group was raised on a basal diet in a thermoneutral environment (22 ± 2 °C); and four CHS groups were raised on a basal diet and supplemented with Se 0.0, 0.2, 0.4, and 0.6 mg/kg as OH-SeMet, respectively, in hyperthermal condition (33 ± 2 °C). CHS resulted in significant decrease of growth performance, carcass traits, and meat quality, which were associated with reduced (p < 0.05) serum alkaline phosphatase (ALP) and total superoxide dismutase (T-SOD) and increased (p < 0.05) serum creatine (CK), sarcous heat shock protein 70 (HSP70), glucokinase (GCK), phosphoenolpyruvate carboxykinase (PEPCK), and malondialdehyde (MDA) contents. Meanwhile, four metabolism-related genes and seven selenoprotein encoding genes were abnormally expressed in skeletal muscle. Dietary OH-SeMet addition partially alleviated the negative impact of CHS on carcass traits and improved meat quality. These improvements were accompanied by the increase in Se deposition, the anti-oxidative capacity of serum and muscle, and protein abundance of GPX1, GPX3, GPX4, and SELENOP. Supplementation with 0.6 mg Se/kg (OH-SeMet) restored the sarcous PEPCK, and 0.4 and 0.6 mg Se/kg (OH-SeMet) restored all abnormally expressed metabolism-related and selenoprotein encoding genes. In summary, dietary supplementation with OH-SeMet beyond Se requirement mitigated CHS-induced depression of carcass traits and meat quality of pigs associated with optimal skeletal metabolism, enhanced antioxidant capacity, and regulation of selenoproteins in skeletal muscle of pigs.

SARS-CoV-2 (Covid-19) workplace temperature screening: Seasonal concerns for thermal detection in northern regions

Workplace temperature screening has become standard practice during the SARS-CoV-2 pandemic. The objective was to determine the consistency of four temperature devices during exposure to simulated and actual environmental conditions reflective of a workplace. An infrared (IR) digital thermometer (accuracy(A)±0.2), IR laser thermometer (A±1), and thermal imaging camera (A±0.3) were used to measure forehead and tympanic (digital only) temperatures. The first experiment was conducted in a controlled simulated environment (−20 to 20 °C) with three participants (32-YOF, 27-YOM, 20-YOF). The second experiment used actual outdoor conditions (−0.48 to 45.6 °C) with two participants (32-YOF, 27-YOM). The tympanic measurement was the least impacted by environmental temperature (mean(±SD)): simulated (36.8(±0.18) °C) and actual (36.9(±0.16) °C). The thermal imaging camera had the lowest RMSE values (0.81–0.97 °C), with outdoor temperatures ranging from 0 to 45 °C. Environmental temperature influenced forehead temperature readings and required a resting period in a thermoneutral environment (5–9 min (−20 to −10 °C) to immediate (15–20 °C)).

Physiological Effects Observed In Police Academy Cadets During Simulated Occupational Stress In A Hyperthermic Environment

First responders (e.g., police) may be exposed to physical occupational stressors in the line of duty which may place them at risk for acute cardio-metabolic events (e.g., myocardial infarction). Environmental challenges may exacerbate this risk. PURPOSE: To observe the impact of a hyperthermic versus thermoneutral environment on physiological responses in police cadets performing a simulated occupational task. METHODS: Using an environmental chamber, 10 police cadets (22.2 ± 2.3 years), completed two occupational task exercise conditions in hyperthermic (HT, 380C) and thermoneutral (TN, 220C) environments on separate days. During each condition, participants completed a 10-minute treadmill walk at 70%-80% of their maximal heart rate followed by a 5-minute 50 lb sandbag lift. Participants had 10 seconds to lift the sandbag onto a table then another 10 seconds to place it back on the ground. The walk and lift were completed two times each per condition. Heart rate (HR), ratings of perceived exertion (RPE), and core temperature (T) were recorded immediately before entering the chamber (baseline), in the chamber at the conclusion of the occupational task (post-exercise), and outside the chamber after 10 min of rest (recovery). Two condition (HT, TN) by three time point (baseline, post-exercise, recovery) repeated measures ANOVAs were utilized to assess all dependent variables. Post-hoc analyses were performed using t-tests. RESULTS: Significant (F ≥ 8.6, p ≤ 0.003) condition by time interactions were observed for all dependent variables. There were no differences (t ≤ 2.0, p ≥ 0.07) across conditions in HR (76 ± 11 bpm TN, 82 ± 14 HT), RPE (6.4 ± 1 TN, 7.1 ± 2.4 HT), or T (37.2 ± 0.30C TN, 37.5 ± 0.20C HT) at baseline. However, each of these variables were significantly (t ≥ 2.3, p ≤ 0.05) greater post-exercise (104 ± 12 bpm TN, 146 ± 16 bpm HT; 8.9 ± 2.4 RPE TN, 13.4 ± 3.1 RPE HT; 37.6 ± 0.30C TN, 38.3 ± 0.30C HT) and during recovery (78 ± 12 bpm TN, 92 ± 13 HT; 6.7 ± 1.2 RPE TN, 7.7 ± 2.2 RPE HT; 37.4 ± 0.20C TN, 38.0 ± 0.30C HT) in the HT versus the TN condition. CONCLUSION: Concomitant occupational tasks and heat stressors increased physiologic and perceived measures of exertion and body temperature in police cadets beyond that of the occupational tasks alone.