Ambient Heat Stress Research Articles

Plasma epinephrine and norepinephrine responses to extreme heat exposures in young and older adults.

Hyperthermia is known as a hyperadrenergic state, yet there is a lack of data on the sympathetic responses to ambient heat stress in humans. Therefore, we investigated the plasma epinephrine and norepinephrine concentrations of healthy young and older adults exposed to 3 h of very hot and dry, as well as hot and humid, heat, both with accompanying activities of daily living. We hypothesized that older adults, compared with young adults, would have augmented increases in epinephrine and norepinephrine concentrations secondary to increased thermal strain. Young (n = 20) and older (n = 18) participants underwent two 3-h heat exposures on different days: very hot and dry [47°C and 15% relative humidity (RH)] and hot and humid (41°C and 40% RH). To mimic heat generation comparable to activities of daily living, participants performed seven 5-min bouts of light cycling (approximately 3 METS) dispersed throughout the heat exposure. We measured plasma concentrations of epinephrine and norepinephrine at baseline, end, and 2-h postheat exposure. There was a group-wide increase in epinephrine from baseline to the end of the heat exposure (Δ19 ± 27 pg/mL; P < 0.001) in the hot and humid condition, but not in the very hot and dry condition (Δ6 ± 19 pg/mL; P = 0.10). There were group-wide decreases in norepinephrine concentrations from baseline to the end of the heat exposure in both the very hot and dry (Δ-131 ± 169 pg/mL; P < 0.001) and the hot and humid (Δ-138 ± 157 pg/mL; P < 0.001) conditions, with both returning to near baseline at 2-h postexposure. These data suggest that ambient heating with accompanying bouts of light intermittent exercise may lead to decreases in circulating concentrations of norepinephrine.NEW & NOTEWORTHY Herein we present plasma epinephrine and norepinephrine concentrations to 3 h of very hot and dry, as well as hot and humid, heat exposures with accompanying activities of daily living in young and older participants. We found 1) increased plasma concentrations of epinephrine in young and older adults following the hot and humid, but not the very hot and dry exposures and 2) decreased concentrations of norepinephrine in both groups following exposure to both conditions.

The Effects of Heat Stress on Bakery Workers: A Systematic Review.

Working in hot environments can cause diseases and reduce performance by upsetting the balance of physiological parameters of workers' bodies. Bakers are among the people exposed to heat stress continuously and daily. This review study aimed to investigate the effect of heat stress on bakers. In this review study, the related articles based on keywords were reviewed using "IranMedex", "Science Direct", "PubMed", "Scopus", "Web of Science", "SID", "Google Scholar", and "Magiran" databases from the years 2000 to 2021. The used search terms were "Heat stress", "Heat strain", "Heat exposure", "Heat waves", "Workplace", "Baker", and "health effects". In order to extract the required data, all parts of the articles have been reviewed. Out of the 16 studies reviewed in this study, 43.75% were cross-sectional, 25% were descriptive cross-sectional, and 31.25% were performed according to other study designs. In all of the studies, the WBGT index was used to assess ambient heat stress. In most studies, the mean exposure temperature was higher than the WBGT-ACGIH limit, especially among traditional bakery workers. The findings showed that exposure to thermal stress significantly affects some hematological parameters of blood, oxidative stress, heart rate, and body temperature. The situation of heat stress in the bakery environment is worrying in terms of health and reduced productivity of employees. Therefore, it is essential to take the necessary preventive and control measures to reduce heat stress and the resulting strain.

Genetic diversity, transcript heterogeneity and allele mining of TaSKP1-6B-4 gene variants across diverse genotypes under terminal heat stress and genome wide characterization of TaSKP1 gene family from bread wheat (Triticum aestivum L.).

SKP1 (S-phase kinase protein1) is an essential regulatory component of SCF (Skp1-cullin-F-box) E3 ubiquitin ligases involved in maintenance of cellular protein homeostasis through ubiquitin mediated proteasome system (UPS). UPS play a key role in stress response and grain yield. Earlier, we isolated TaSKP1-6B-4, highly induced in flag leaf tissues (Accession No. KJ830759.1) of developing wheat caryopses under heat stress. To further assess the functional role of SKP1, genetic variability analysis was carried out in a panel of 25 contrasting germplasm through extensive phenotyping and transcript profiling of TaSKP1-6B-4 during anthesis under ambient and terminal heat stress (THS) in field experiments for two consecutive years. The analysis of variance revealed significant variations for all the traits studied. Higher H2(%), GCV, PCV, GA and GA% mean observed in tiller number per plant (23.81, 17.65, 5.71, 28, 30.86%) and grain number per head (30.27, 82.79, 60.16, 105.00, 108.64%) under THS over ambient temperature. Higher fold induction of TaSKP1-6B-4 transcripts was recorded in 10 genotypes viz. HD2967 (9.9), IC145456 (6.18) in flag leaf; while C-306 (15.88), RAJ3765 (8.37) in ear head. Allele mining of SKP1-6B-4 showed genotypic sequence variations. Whole genome wide search of SKP1 gene family identified 95 SKP1 genes which were structurally characterized. Grain yield, leaf senescence and other agronomic-morpho-physiological parameters combined with transcript profiling, cvHD2967, was found to be the best positively responsive to THS which by pedigree was not heat tolerant. We report a novel 2 year comprehensive field based analysis on collective genetic variability and SKP1/UPS modulation under a natural environmental setting. The data reveals potential functional role of UPS under THS and tolerant cultivars can be further utilized for clarifying the role of UPS mechanistically at the molecular level and for developing terminal heat stress tolerant wheat.

Citizen and machine learning-aided high-resolution mapping of urban heat exposure and stress

Through conversion of land cover to more built-up, impervious surfaces, cities create hotter environments than their surroundings for urban residents, with large differences expected between different parts of the city. Existing measurements of ambient air temperature and heat stress, however, are often insufficient to capture the intra-urban variability in heat exposure. This study provides a replicable method for modeling air temperature, humidity, and moist heat stress over the urban area of Chapel Hill while engaging citizens to collect high-temporal and spatially-resolved air temperature and humidity measurements. We use low-cost, consumer-grade sensors combined with satellite remote sensing data and machine learning to map urban air temperature and relative humidity over various land-cover classes to understand intra-urban spatial variability of ambient heat exposure at a relatively high resolution (10 m). Our findings show that individuals may be exposed to higher levels of air temperature and moist heat stress than weather station data suggest, and that the ambient heat exposure varies according to land cover type, with tree-covered land the coolest and built-up areas the warmest, and time of day, with higher air temperatures observed during the early afternoon. Combining our resulting dataset with sociodemographic data, policymakers and urban planners in Chapel Hill can use data output from this method to identify areas exposed to high temperature and moist heat stress as a first step to design effective mitigation measures.

Ambient temperature, heat stress and fetal growth: A review of placenta-mediated mechanisms

Pregnancy is increasingly considered a period of vulnerability for extreme heat exposure. Multiple lines of evidence support that heat stress is associated with placental insufficiency, poor fetal growth and decreased birth weight. In this narrative review, we first summarize evidence linking ambient temperature or experimentally-induced heat stress with fetal and placental growth outcomes in humans, ruminants and murine species. We then synthesize the literature on putative underlying biological pathways with a focus on the placenta. Reviewed mechanisms include: reduced uterine-placental blood flow, impaired supply of metabolic substrates to the fetus, activation of the maternal stress-response system, and disruption of other endocrine and immune system endpoints. Taken together, this body of evidence supports that exposure to extreme ambient heat likely has adverse consequences for placental development and function. However, research investigating placenta-mediated pathophysiological mechanisms in humans remains extremely limited.

Residential segregation and outdoor urban moist heat stress disparities in the United States

•Urban-resolving numerical model shows pervasive heat stress disparities in US cities •Present residential segregation strongly associated with heat stress inequities •Historically redlined neighborhoods show higher heat stress than other neighborhoods •Skin temperature overestimates disparities in ambient heat exposure and heat stress The combined impact of urbanization-induced warming and drying on large-scale heat stress disparities remains unknown, with multicity studies using satellite-derived land surface temperature as a proxy for these disparities. Here, using high-resolution urban-resolving numerical model simulations for 2014–2018, we find pervasive disparities in all-sky average maximum summertime air temperature and moist heat stress metrics across US cities, with higher outdoor heat stress exposure in poorer and primarily non-white census tracts. Ninety-four percent of the US urban population (228 million) live in cities where heat stress burdens the poor, with heat stress inequities between white and non-white populations strongly associated with residential segregation. Similarly, historically redlined neighborhoods show higher heat stress than their non-redlined counterparts, demonstrating how historical segregation relates to present-day environmental inequalities. Our results provide quantitative estimates of physiologically relevant heat stress disparities at the US national scale and highlight potential biases when using satellites as a proxy for these. The combined impact of urbanization-induced warming and drying on large-scale heat stress disparities remains unknown, with multicity studies using satellite-derived land surface temperature as a proxy for these disparities. Here, using high-resolution urban-resolving numerical model simulations for 2014–2018, we find pervasive disparities in all-sky average maximum summertime air temperature and moist heat stress metrics across US cities, with higher outdoor heat stress exposure in poorer and primarily non-white census tracts. Ninety-four percent of the US urban population (228 million) live in cities where heat stress burdens the poor, with heat stress inequities between white and non-white populations strongly associated with residential segregation. Similarly, historically redlined neighborhoods show higher heat stress than their non-redlined counterparts, demonstrating how historical segregation relates to present-day environmental inequalities. Our results provide quantitative estimates of physiologically relevant heat stress disparities at the US national scale and highlight potential biases when using satellites as a proxy for these.

Acute Encephalopathy in Children From Muzaffarpur, Bihar, India, and the Potential Role of Ambient Heat Stress-Induced Mitochondrial Dysfunction.

Periodic outbreaks of acute encephalopathy in children have been reported from Muzaffarpur, Bihar, India. No infectious cause has been identified for this. This study presents the clinical and metabolic profile of children hospitalized with acute encephalopathy and the potential role of ambient heat stress. This cross-sectional study included children (<15 years) with acute encephalopathy admitted from April 4, 2019, to July 4, 2019. The clinical and laboratory investigations included infections, metabolic abnormalities, and muscle tissue analysis. The children who had metabolic derangements but no infectious cause were labeled as acute metabolic encephalopathy.The descriptive analysis summarized the clinical, laboratory, and histopathology findings, and their association with the ambient heat parameters was explored. Out of the 450 children hospitalized (median age, four years), 94 (20.9%) died.Children had early morning onset (89%), seizures (99%), fever (82%), hypoglycemia at admission (64%), raised aminotransferases (60%), and high blood urea (66%). Blood lactate (50%), lactate dehydrogenase (84%), pyruvate (100%), ammonia (32%), and creatinine phosphokinase (69%) were raised. Viral marker tests were negative. The patients had abnormal metabolic markers like decreased blood-free carnitine, elevated blood acylcarnitines, and elevated urinary lactate, oxalate, maleate, adipate, and fatty acid metabolites. Blood carnitine and acylcarnitine levels normalized in 75% of the patients treated with carnitine and coenzyme-Q.Muscle tissues showed megamitochondria on electron microscopy and reduced respiratory enzyme complex-I activity. A significant correlation between the number of admissions and ambient heat indices was observed. The findings suggest secondary mitochondrial dysfunction as a possible mechanism for acute encephalopathy in children from Muzaffarpur, Bihar, and ambient heat stress as a possible risk factor.

Differing Responses of Three Scleractinian Corals from Phuket Coast in the Andaman Sea to Experimental Warming and Hypoxia

An unprecedented decline in the diversity and health of coral reefs is occurring around the world as they are threatened by multiple global and local stressors. Rising seawater temperature and low dissolved oxygen (DO) conditions are expected to intensify as a result of climate change. Understanding the responses of corals to these stressors is necessary for making predictions and devising mitigation strategies. The three coral species—Porites lutea, Montipora tuberculosa, and Pocillopora verrucosa—were sampled from Patong Bay, Phuket, Thailand, as representatives of different coral morphologies. Coral nubbins were subjected to experimental investigation under ambient conditions (29 °C, DO &gt; 6 mgL−1), heat stress (32 °C), hypoxia (DO &lt; 2 mgL−1), and heat stress + hypoxia treatments. Photosynthetic performance indicators Fv/Fm and Fv/F0 and physiological parameters Symbiodiniaceae density, pigment concentration, and growth rate were quantified. We found P. verrucosa (branching) to be the most sensitive and severely affected by heat stress or hypoxia, more so than P. lutea (massive) and M. tuberculosa (tabular). The combination of these stressors had less impact on these species, except for a decline in growth rate of M. tuberculosa. This study also suggests that the corals respond differently to high temperature and low oxygen, with their sensitivity depending on species. These responses, however, may differ according to the lighting, especially in hypoxic conditions. The results fill a research gap to help predict the vulnerability of these three coral species in shallow reef habitats under climate change scenarios.

Effects of maternal methionine supplementation on the response of Japanese quail (Coturnix coturnix japonica) chicks to heat stress.

This study investigated the hypothesis that methionine supplementation of Japanese quail (Coturnix coturnix japonica) hens can reduce the effects of oxidative stress and improve the performance of the offspring exposed to heat stress during growth. For that, the quail hens were fed with three diets related to the methionine supplementation: methionine-deficient diet (Md); diet supplemented with the recommended methionine level (Met1); and diet supplemented with methionine above the recommended level (Met2). Their chicks were identified, weighed, and housed according to the maternal diet group from 1 to 14 d of age. On 15 d of age, chicks were weighed and divided into two groups: thermoneutral ambient (constant temperature of 23 °C) and intermittent heat stress ambient (daily exposure to 34 °C for 6 h). Methionine-supplemented (Met1 and Met2) hens had higher egg production, better feed conversion ratio, higher hatchability of total and fertile eggs, and offspring with higher body weight. Supplemented (Met1 and Met2) hens showed greater expression of glutathione synthase (GSS) and methionine sulfoxide reductase A (MSRA) genes, greater total antioxidant capacity, and lower lipid peroxidation in the liver. The offspring of hens fed the Met2 diet had lower death rate (1 to 14 d), higher weight on 15 d of age, weight gain, and better feed conversion ratio from 1 to 14 d of age. Among chicks reared under heat stress, the progeny of methionine-supplemented hens had higher weight on 35 d, weight gain, expression of GSS, MSRA, and thermal shock protein 70 (HSP70) genes, and total antioxidant capacity in the liver, as well as lower heterophil/lymphocyte ratio. Positive correlations between expression of glutathione peroxidase 7 (GPX7) and MSRA genes in hens and offspring were observed. Our results show that maternal methionine supplementation contributes to offspring development and performance in early stages and that, under conditions of heat stress during growth, chicks from methionine-supplemented hens respond better to hot environmental conditions than chicks from nonsupplemented hens. Supplementation of quail hens diets with methionine promoted activation of different metabolic pathways in offspring subjected to stress conditions.

Delineating the impacts of air temperature and humidity for endurance exercise.

What is the central question of this study? What are the independent effects of air temperature and humidity on performance, physiological and perceptual responses during endurance exercise? What is the main finding and its importance? When examined independently, elevated air temperature increased heat strain and impaired aerobic exercise performance, but to a lesser extent than has been reported previously. These findings highlight the importance of absolute humidity relative to temperature when exercising or working under severe heat stress. Many studies have reported that ambient heat stress increases physiological and perceptual strain and impairs endurance exercise, but effects of air temperature per se remain almost unexamined. Most studies have used matched relative humidity, thereby exponentially increasing absolute humidity (water content in air) concurrently with temperature. Absolute (not relative) humidity governs evaporative rate and is more important at higher work rates and air temperatures. Therefore, we examined the independent effects of air temperature and humidity on performance, thermal, cardiovascular and perceptual measures during endurance exercise. Utilizing a crossover design, 14 trained participants (7 females) completed 45min fixed-intensity cycling (70% ) followed by a 20-km time trial in each of four environments: three air temperatures at matched absolute humidity (Cool, 18°C; Moderate, 27°C; and Hot, 36°C; at 1.96kPa, air velocity ∼4.5m/s), and one at elevated humidity (Hot Humid, 36°C at 3.92kPa). Warmer air caused warmer skin (0.5°C/°C; P<0.001), higher heart rate (1bpm/°C; P<0.001), sweat rate (0.04l/h/°C; P<0.001) and thermal perceptions during fixed-intensity exercise, but minimally affected core temperature (<0.01°C/°C; P=0.053). Time-trial performance was comparable between Cool and Moderate (95% CI: -1.4, 5.9%; P=0.263), but 3.6-6% slower in Hot (95% CI: ±2.4%; P≤0.006). Elevated humidity increased core temperature (P<0.001), perceived temperature and discomfort but not skin temperature or heart rate, and reduced mean blood pressure (P=0.046) during fixed-intensity exercise. Elevated humidity impaired time-trial performance by 3.4% (95% CI: ±2.2%; P=0.006). In conclusion, these findings quantify the importance of absolute humidity alongside air temperature when exercising under severe heat stress.

Ambient heat stress and urolithiasis attacks in China: Implication for climate change

BackgroundAlthough the existing studies have suggested a significant association between high temperatures and urolithiasis, no nationwide studies have quantified the burden attributable to environmental heat stress and explored how the urolithiasis burden would vary in a warming climate. MethodsWe collected data on urolithiasis attacks from 137 hospitals in 59 main cities from 20 provincial regions of China from 2000 to 2020. An individual-level case-crossover analysis was conducted to estimate the effect of daily wet-bulb globe temperature (WBGT), a heat stress index combining temperature and humidity, on urolithiasis attacks. Stratified analyses were performed by region, age, and sex. We further quantified the future WBGT-related burden of urolithiasis from the Coupled Model Intercomparison Project Phase 6 under three Shared Socioeconomic Pathway (SSP) scenarios. ResultsIn total, 118,180 urolithiasis patients were evaluated. The exposure-response curve for the association between WBGT and urolithiasis attacks was J-shaped, with a significantly increased risk for WBGT higher than 14.8 °C. The middle-aged and elderly group (≥45 years old) had a higher risk of WBGT-related urolithiasis attacks than in the younger group, while no significant sex difference was observed. The attributable fraction (AF) due to high WBGT would increase from 10.1% in the 2010s to 16.1% in the 2090s under the SSP585 scenario. Warm regions were projected to experience disproportionately higher AFs and larger increments in the future. ConclusionsThis nationwide investigation provides novel evidence on the acute effect of high WBGT on urolithiasis attacks and demonstrates the increasing disease burden in a warming climate.

Objectively-assessed physical activity and heat stress and the association with kidney function in female harvest workers in Spain

BACKGROUND AND AIM: Physical activity (PA) in hot environments has been associated with kidney damage. In harvest workers, PA has been primarily assessed by questionnaires in males. We aimed to study the association between objectively-measured PA intensity and incidence of acute kidney injury (AKI) over the course of one work shift, in female harvest workers in Spain. METHODS: Ninety women working in greenhouses wore a Zephyr chest harness to measure PA intensity during one regular work shift in June 2020. We determined the mean (PA_mean), standard deviation (PA_sd), and 3-minute-maximum (PA_max, a proxy of peak PA intensity) of PA intensity (vector magnitude units). We estimated heat stress (HS) in greenhouses based on wet bulb globe temperature index (ISO 7243:2017). Serum creatinine and neutrophil gelatinase associated lipocalin (NGAL) levels were measured before and after the work shift. AKI was defined as an increase in post-shift serum creatinine by at least 0.3 mg/dl or at least 1.5 times the pre-shift serum creatinine levels. Additionally, we calculated pre-post-shift differences in NGAL. We used logistic regressions adjusted for age, body mass index, and HS. HS was also assessed as an effect modifier. RESULTS: PA_sd and PA_max seemed to be associated with AKI (OR=1.57 (95%CI=0.82;3.21) and 1.41 (0.71;2.85), respectively), but not PA_mean. There was no interaction between any of the PA variables and HS (p-value LRT&amp;#x3e;0.1). Mean (SD) increase in NGAL levels over the course of a work shift was higher among participants with AKI (27.8 (7.5)) compared to those without AKI (12.2 (2.7)). CONCLUSIONS: Results suggest that large changes and peaks in PA intensity should be avoided to protect renal function of harvest workers. Increased levels of NGAL among those with AKI are indicative of kidney damage among those with increased serum creatinine levels. KEYWORDS: Occupational physical activity, acute kidney injury, ambient heat stress

Ingestion of carbonated water increases middle cerebral artery blood velocity and improves mood states in resting humans exposed to ambient heat stress

Sugar-free carbonated water is consumed worldwide. The consumption of carbonated water is high in summer, when the heat loss responses of sweating and skin vasodilation are activated, and thermal perceptions (thermal sensation and comfort) and mood states are negatively modulated. However, whether ingesting carbonated water under ambient heat exposure modulates cerebral blood flow index, heat loss responses, thermal perceptions, and mood states remains to be determined. In this study, 17 healthy, habitually active, young adults (eight women) ingested 4 °C noncarbonated or carbonated water under 37 °C ambient heat-stressed resting conditions. Both drinks increased the middle cerebral artery mean blood velocity, an index of cerebral blood flow, and mean arterial pressure, with carbonated water exhibiting higher elevations than noncarbonated water (P < 0.05). However, the heart rate, sweat rate, and skin blood flow during and after drinking remained unchanged between the two conditions (P > 0.05). The thermal sensation and comfort after drinking remained unchanged between the two conditions (P > 0.05); but, a drink-induced reduction in sleepiness was higher, and drink-induced elevations in motivation and exhilaration were higher after ingesting carbonated water than those after ingesting noncarbonated water (P < 0.05). The analyses suggest that in humans under ambient heat-stressed resting conditions, ingestion of cold carbonated water increases the cerebral blood flow index, blood pressure, motivation, and exhilaration, whereas it decreases sleepiness relative to ingestion of noncarbonated cold water. However, ingestion of cold carbonated water fails to modulate thermoregulatory responses and thermal perception as opposed to noncarbonated cold water.

Exogenously Applied GA3 Enhances Morphological Parameters of Tolerant and Sensitive Cyclamen persicum Genotypes under Ambient Temperature and Heat Stress Conditions.

Cyclamen genus is part of the Primulaceae family consisting of 24 species widely cultivated as ornamental and medicinal plants. They also possess high plasticity in terms of adaptability to alternating environmental conditions. In this regard, the present study investigates the germination and morphological parameters of heat-tolerant and heat-sensitive Cyclamen persicum accessions in the presence of different GA3 solutions (0, 30, 70 and 90 mg/L) under ambient temperature and heat stress conditions. Heat-tolerant genotypes, mainly C3-Smartiz Victoria (6.42%), C15-Merengue magenta (6.47%) and C16-Metis silverleaf (5.12%) had the highest germination rate with 90 mg/L GA3 treatment compared with control. Regarding heat-sensitive genotypes, C11-Verano (5.11%) and C13-Metis Origami (4.28%) had the lowest values in mean germination time, along with the Petticoat genotypes C1 (73.3%) and C2 (80.0%) with a high germination percentage. Heat-tolerant genotypes positively responded to GA3 (70 and 90 mg/L) even under heat stress conditions, by their higher values in plant height, an ascending trend also seen in heat-sensitive genotypes under GA3 treatment (70 and 90 mg/L). According to the hierarchical clustering, several heat-tolerant genotypes showed peculiar behavior under heat stress conditions, namely C3 (Smartiz Victoria), C7 (Halios falbala) and C8 (Latinia pipoca) which proved to be susceptible to heat stress even under GA3 application, compared with the other genotypes which showed tolerance to higher temperatures. In the case of heat-sensitive genotypes, C4 (Smartiz violet fonce), C6 (Metis blank pur), C11 (Verano) and C13 (Metis origami) possessed higher positive or negative values compared with the other heat-sensitive genotypes with increased doses of GA3. These genotypes were shown to be less affected by heat stress, suggesting their positive response to hormone treatment. In conclusion, the above-mentioned genotypes, particularly heat-tolerant C15 and heat-sensitive C2 with the highest germination capacity and development can be selected as heat-resistant genotypes to be deposited in gene banks and used in further amelioration programs under biotic and/or abiotic stresses to develop resistant genotypes.

Nicotinamide mononucleotide supplementation improves the quality of porcine oocytes under heat stress

BackgroundElevated ambient temperature-caused heat stress is a major concern for livestock production due to its negative impact on animal feed intake, growth, reproduction, and health. Particularly, the germ cells are extremely sensitive to the heat stress. However, the effective approach and strategy regarding how to protect mammalian oocytes from heat stress-induced defects have not been determined.MethodsGerminal vesicle (GV) porcine oocytes were cultured at 41.5 °C for 24 h to induce heat stress, and then cultured at 38.5 °C to the specific developmental stage for subsequent analysis. Nicotinamide mononucleotide (NMN) was dissolved in water to 1 mol/L for a stock solution and further diluted with the maturation medium to the final concentrations of 10 μmol/L, 20 μmol/L, 50 μmol/L or 100 μmol/L, respectively, during heat stress. Immunostaining and fluorescence intensity quantification were applied to assess the effects of heat stress and NMN supplementation on the key processes during the oocyte meiotic maturation.ResultsHere, we report that NMN supplementation improves the quality of porcine oocytes under heat stress. Specifically, we found that heat stress resulted in oocyte maturation failure by disturbing the dynamics of meiotic organelles, including the cytoskeleton assembly, cortical granule distribution and mitochondrial function. In addition, heat stress induced the production of excessive reactive oxygen species (ROS) and DNA damage, leading to the occurrence of apoptosis in oocytes and subsequent embryonic development arrest. More importantly, we validated that supplementation of NMN during heat stress restored the meiotic defects during porcine oocyte maturation.ConclusionsTaken together, our study documents that NMN supplementation is an effective approach to improve the quality of oocytes under heat stress by promoting both nuclear and cytoplasmic maturation.

Lipidomic Remodeling in Begonia grandis Under Heat Stress.

Characterization of the alterations in leaf lipidome in Begonia (Begonia grandis Dry subsp. sinensis) under heat stress will aid in understanding the mechanisms of stress adaptation to high-temperature stress often occurring during hot seasons at southern areas in China. The comparative lipidomic analysis was performed using leaves taken from Begonia plants exposed to ambient temperature or heat stress. The amounts of total lipids and major lipid classes, including monoacylglycerol (MG), diacylglycerol (DG), triacylglycerols (TG), and ethanolamine-, choline-, serine-, inositol glycerophospholipids (PE, PC, PS, PI) and the variations in the content of lipid molecular species, were analyzed and identified by tandem high-resolution mass spectrometry. Upon exposure to heat stress, a substantial increase in three different types of TG, including 18:0/16:0/16:0, 16:0/16:0/18:1, and 18:3/18:3/18:3, was detected, which marked the first stage of adaptation processes. Notably, the reduced accumulation of some phospholipids, including PI, PC, and phosphatidylglycerol (PG) was accompanied by an increased accumulation of PS, PE, and phosphatidic acid (PA) under heat stress. In contrast to the significant increase in the abundance of TG, all of the detected lysophospholipids and sphingolipids were dramatically reduced in the Begonia leaves exposed to heat stress, suggesting that a very dynamic and specified lipid remodeling process is highly coordinated and synchronized in adaptation to heat stress in Begonia plants.

Effect of Organic Fertilization on the Physiological Status of Tomatoes under Abiotic Stress

Abstract During the vegetation period of the years 2020 and 2021 in the experimental field at Agricultural University - Plovdiv it was conducted a physiological study of tomato cultivar (Rugby) with determined growth under the treatment with chemical and organic fertilizers. The aims of the study were to determine the changes in physiological behaviour and productivity of field tomatoes depending on the fertilization and dates of planting. The physiological assessment included the measuring of some parameters of chlorophyll fluorescence and chlorophyll content index. Chlorophyll fluorescence has proved to have the potential to detect abiotic stress effects on photosynthetic efficiency. This technique was used to assess growth intensity in tomato plants (Solanum lycopersicum), grown in different types of fertilizer treatment and planted in three additional dates – 30.04, 07.05 and 14.05 in conditions of ambient heat stress. Results have shown the slight effect of the applied organic fertilizer upon fluorescence parameters but significantly improved chlorophyll content index compared to no treatment variant. Additionally, it was measured higher chlorophyll content index for the second and third planting dates. The highest average yield was calculated for the NPK variant, as the statistically significant differences of the yield between control and fertilization variants were calculated in 2021. It possessed the highest average yield for second planting compared to the third date of planting.

Heat stress affects fetal brain and intestinal function associated with the alterations of placental barrier in late pregnant mouse

High ambient temperature-induced heat stress (HS) during pregnancy may affect the placental function and fetal development. Late gestation is a critical period of the developing fetal brain and intestine. The study aimed to investigate the effects of HS during late pregnancy on the function of placenta, fetal brain and intestine in a mouse model. We found that the number of stillborn fetal mice were increased due to maternal HS. Transcriptome analysis revealed that the expression of genes enriched in nutrients transport and metabolism of HS group were up-regulated in the placenta, but down-regulated in the fetal duodenum and jejunum. Interestingly, the concentration of triglyceride (TG) in the HS group was raised in the placenta, but reduced both in the fetal duodenum and jejunum compared with the thermal-neutral (TN) group. Additionally, maternal HS also reduced total cholesterol (TC) contents in the fetal duodenum. The mRNA expression and protein levels of placental fatty acid binding protein 2 and 4 (fabp2 and fabp4) were not affected by maternal HS, but the mRNA expression and protein levels of cluster of differentiation 36 (CD36) and diacylglycerol acyltransferase-2 (Dgat2) were decreased in the fetal intestine. Furthermore, maternal HS reduced the mRNA expression and protein levels of the placental 11beta-hydroxysteroid dehydrogenase type 2 (Hsd11b2) and 5-hydroxytryptamine receptor 1D (Htr1d). The concentrations of corticosterone and the expression of heat shock protein 90 beta family member 1 (hsp90b1), hypoxia up-regulated 1 (hyou1) and corticotropin releasing hormone receptor 1 (crhr1) enriched in response to glucocorticoids in the fetal brain were increased by maternal HS. Taken together, our findings demonstrated that maternal HS disrupted the placental glucocorticoid barrier and serotonin system associated with the raised corticosterone levels in the fetal brain, which might contribute to the decreased capacity of nutrients transport and metabolism in the fetal intestine.

The cardio-respiratory effects of passive heating and the human thermoneutral zone.

The thermoneutral zone (TNZ) defines the range of ambient temperatures at which resting metabolic rate (MR) is at a minimum. While the TNZ lower limit has been characterized, it is still unclear whether there is an upper limit, that is, beyond which MR during rest increases, and if so, what physiological upregulations explain this. We take the first step to fill this knowledge gap by measuring MR and multiple physiological variables in participants exposed to ambient heat stress while resting. Thirteen participants were exposed for an hour to 28℃‐50% relative humidity (RH) air, and both 40 and 50℃ each in 25% RH and humid (50% RH) conditions. Core and skin temperatures, blood pressure, sweat‐, heart‐, and breathing‐rate, minute ventilation, and movement levels were recorded throughout each condition. MR increased 35% (p = .015) during exposure to 40℃‐25% RH compared to baseline and a further 13% (p = .000) at in 50℃‐50%RH. This was not explained by increased fidgeting (p = .26), suggesting physiological upregulation. However, while greater heat stress invoked increases in heart rate (64%, p = .000), minute ventilation (78%, p = .000), and sweat rate (74%. p = .000) when comparing 50℃‐50% RH with baseline, the exact size of their relative energy cost is unclear and, therefore, so is their contribution to this increase in MR. Our study shows clear evidence that resting MR increases in humans at high temperature—there is a metabolic upper critical temperature, at least as low as 40℃. Further studies should pinpoint this value and fully explain this increased MR.

The effect of tree shade on ambient conditions and heat stress indicator traits of new-born South African Mutton Merino and Dormer lambs: Preliminary results.

This preliminary study investigated the provision of shade on heat stress indicators of South African Mutton Merino (SAMM) and Dormer lambs shortly after birth, during the autumn 2017 and 2018 lambing seasons. Newborn lambs were assessed to determine whether welfare, as assessed by respiratory response and rectal temperature as heat stress indicators, survival and early growth benefitted from the provision of shade. Groups consisting of 4-17 pregnant SAMM and Dormer ewes were randomly allocated to 5-10 paddocks with natural shade from trees and 5-9 paddocks that were directly in the sun with no shade available. The lambs were recorded within 24h of birth at noon. Climate data were obtained from a nearby weather station. The lambs were also weighed at 12 (SD=2) days of age at tail-docking. Tree shade had a moderating effect on temperature, resulting in lower maximum daytime and higher minimum night-time temperatures. There was an interaction between a temperature-humidity index (THI) and the treatments (access to shade or no access to shade) for respiration and rectal temperature (P<0.01). Both traits were relatively unaffected by the THI at values below 77. Unshaded lambs exhibited a pronounced upwards trend following a THI-threshold of 77-78. Tailing weight tended to be higher while lamb survival of live-born lambs to tail-docking was lower in lambs born in shaded paddocks but these trends did not persist to weaning. Shade is needed to enhance animal welfare by alleviating the effect of high THI-values on hot days in an autumn lambing season.