Heat Stress Exposure Research Articles

Heat stress: adaptation measures in South African informal settlements

Globally extreme weather events are experienced most acutely in cities. While formal settlements can respond to such events, informal settlements are often vulnerable and ill-prepared. Sub-Saharan Africa is rapidly urbanising with informal settlements that require effective climate change adaptation measures. Two climate adaptation strategies for informal dwellings are considered for their success under 2100 Intergovernmental Panel on Climate Change (IPCC) climate scenarios. Using existing data collected from informal dwellings in South Africa, the findings from a digital simulation study reveal that cool roof paints can currently lower excessive heat stress conditions by 42–63% when applied to high thermal mass dwellings with poorly insulated lightweight corrugated sheeting roofing. However, for the future 2100 climate scenarios this strategy only lowers excessive heat stress conditions by 12–17%. This calls for the development of integrated multifaceted heat stress adaptation strategies for informal settlements in Sub-Saharan Africa. <em><strong>Practice relevance</strong></em> This study assessed heat stress conditions and the application of two financially and practically feasible heat stress adaptation strategies in informal dwellings in South Africa. This involved assessing the efficacy of using cool roof paints and improved thermal insulation under current and future climate change-affected conditions. The findings reveal that Southern African informal dwellings experience extreme heat stress 32% of the time. Predicted climate change-affected conditions will increase heat stress exposure up to 40% over a full year. The study reveals that cool roof paints can improve the performance of uninsulated, low thermal mass homes in temperate climates by lowering heat stress conditions by 42–63%, yet this climate change adaptation strategy is only an interim solution with limited success (12–17% improvement) under future 2100 climate change-affected conditions. As a result multilayered integrated heat amelioration strategies are needed in informal communities.

Dietary nano-selenium alleviates heat stress-induced intestinal damage through affecting intestinal antioxidant capacity and microbiota in rainbow trout (Oncorhynchus mykiss)

Heat stress-induced intestinal damage is a key event in fish pathology. Nano-selenium (nano-Se) shows remarkably high biological activity and low toxicity, making it an ideal and ecological Se formulation; however, to date, the protective effects of nano-Se against heat stress-induced intestinal injury and pertinent molecular mechanisms remain unknown. Herein, rainbow trout (Oncorhynchus mykiss) were fed either a basal diet or basal diet + 5 mg/kg nano-Se. Samples were collected before (18 °C for 9 days; CG18 and Se18 groups) and after (24 °C for 8 h; CG24 and Se24 groups) heat stress treatment. On heat stress exposure, intestinal villus height, muscularis thickness, and goblet cell number decreased, and expression of tight junction proteins (ZO-1, occludin, and claudin-8d) was downregulated; dietary supplementation with nano-Se alleviated these effects. Furthermore, in the presence of nano-Se, catalase activity was elevated, and expression of diverse heat shock proteins (Hsp70b, Hsp90α, and Hsp30), selenoproteins (Gpx1a, Gpx1b1, and Trx), and anti-inflammatory cytokine (TGF-β) was upregulated. In contrast, nano-Se supplementation significantly alleviated the increase of the expression of pro-inflammatory cytokines (IL-1β and TNF-α) and the malondialdehyde content. We also observed that heat stress markedly increased the relative abundance of Actinobacteria, Firmicutes, Methylobacterium, Akkermansia, and Deinococcus and decreased that of Proteobacteria; nano-Se supplementation restored these changes, making their distribution similar to that in the control group. Overall, our findings suggest that nano-Se plays a protective role against heat stress-induced intestinal damage in rainbow trout by promoting the recovery of antioxidant enzyme activity, enhancing protein repair, alleviating inflammatory responses, and restoring intestinal microbiota composition.

Assessment of Heat Stress Exposure among Outdoor Cleansing Workers in Helwan University

Assessment of Heat Stress Exposure among Outdoor Cleansing Workers in Helwan University

Exosomal microRNAs regulate the heat stress response in sea cucumber Apostichopus japonicus

Exosomes are small extracellular vesicles that contain nucleic acids such as microRNAs and may participate in important biological processes. We made the initial report of exosomes from sea cucumber Apostichopus japonicus, that were classically cup-shaped and had an average size of 74.65 nm, and identified specific exosome biomarkers (HSP70, TSG101, and CD9). We explored changes in the global expression of microRNAs in exosomes from the commercially important A. japonicus under normal conditions and heat-stressed conditions for 3 and 7 d. We found that heat stress increased exosome production and modified the expression profiles of the microRNAs that they contained. Novel_mir31, novel_mir132, novel_mir26, miR-92_1, and novel_mir27 were commonly found to be differentially expressed in three comparison groups, indicating their importance in the heat stress response. The microRNA expression levels were validated by qPCR. Function analysis of the target genes of these microRNAs indicated they were involved mainly in replication and repair in the initial response of A. japonicus to heat stress exposure. Conversely, during acclimation to the high temperature conditions, the target genes of the differentially expressed microRNAs were primarily involved in metabolism adjustments. Our results will contribute to a better understanding of the regulatory roles of exosomes in sea cucumber, and provide insights into the functions of sea cucumber exosome-shuttled microRNAs against environmental stresses exacerbated by global warming.

Group Outcomes for Time-Weighted Averaging in WBGT-Based Heat Stress Exposure Assessment.

The wet bulb globe temperature (WBGT)-based occupational exposure limits (OELs) were developed from steady exposures to heat stress at constant WBGT and metabolic rate (M). The exposure limits were based on compensable heat stress exposures at the upper limit of the prescriptive zone for most healthy people. Professional practice allows for using time-weighted averages (TWAs) of WBGT and M to account for heterogeneous heat stress exposures. The purpose of the current paper was to report on the effectiveness of time-weighted averaging to assess occupational heat stress using published studies. Our hypothesis was using TWA-WBGT and TWA-M was as protective as the recommended OELs for steady exposures. The current paper reports on 62 observations of work that alternate between at least two heat stress conditions (usually work and recovery) reported in 16 papers. The TWA-WBGT and TWA-M were determined for all observations. ΔLimit was the observed TWA-WBGT minus the exposure limit at the TWA-M based on acclimatization state. The observations were then classified as above or below ΔLimit = 0. Each observation was also classified as uncompensable if the mean core temperature for the group was greater than 38°C or a less tolerant individual was above 38.5°C. When comparing exposure classifications to outcome classifications using 2 × 2 tables, the sensitivity and specificity for all observations were 0.72 and 0.73, respectively. The sensitivity was much less than the expected value near 1.0, and the large difference called into question the ability of TWAs to represent actual heat stress. There was some suspicion that there were differences between acclimatized and unacclimatized observations. Before any of these findings are embedded in policy or practice, a more careful evaluation of TWAs is required. In conclusion, we believe that the use of TWAs for heat stress analysis was not fully evaluated, and we proposed a framework for evaluation.

Apparent and standardised ileal amino acid digestibilities in heat-stressed pigs fed wheat-soybean meal diets supplemented with l-arginine and dl-methionine.

Heat stress (HS) exposure may damage the small intestine epithelia of pigs affecting the digestibility and absorption of amino acids (AA). Arg and Met can enhance antioxidant and intestinal cell proliferation activity, thus supplementing them in diets might alleviate epithelial damage and correct the reduced AA digestibility. The effect of adding extra l-Arg and dl-Met to diets on the apparent (AID) and standardised ileal digestibility (SID) of AA was analysed in a 10-day experiment conducted with 10 ileal-cannulated HS pigs (25.3 ± 2.4 kg body weight). The pigs were divided into two treatments: Control, wheat-soybean meal diet supplemented with l-Lys, l-Thr, dl-Metand l-Trp; and control diet plus 0.20% l-Arg and 0.20% dl-Met (Arg + Met). Following an 8-day diet adaptation period, ileal digesta was continuously collected for 12 h, starting at 0700, on Days 9 and 10. All pigs were daily exposed to 29.6-36.1°C; ileal temperature was continuously monitored at 15-min intervals. Feed was provided twice a day. The ileal temperature ranged from 40.3 to 41.5°C. Daily ileal outflow of His, Ile, Leu, Phe, Thr, Serand Tyr decreased (p < 0.05), and that of Arg, Valand Pro tended to decrease (p < 0.10) in the Arg + Met pigs. The AID of Arg, His, Met, Thrand Tyr, and the SID of His, Met, and Thr increased in pigs fed the Arg + Met diet (p < 0.05). Thr and Val had the lowest AID values whereas Arg, Met, and Lys had the highest values. Arg (r = 0.64) and Met (r = 0.84) intake were highly correlated with their AID values; Met intake was highly correlated with its SID value (r = 0.72). Valine and Arg had the lowest whereas Arg had the highest SID values. In conclusion, supplementing l-Arg and dl-Met above the requirement decreases the ileal outflow of several AA, and increases the AID and SID of some essential AA in HS pigs.

Effect of Heat Stress on Rumen Microbial Diversity and Fermentation Pattern in Buffalo

In this study, changes in rumen microbiome and fermentation were examined during heat stress (HS) in buffaloes. Six buffalo heifers were exposed to thermoneutral ( THI = 72 ) and HS ( THI = 87 – 90 ) conditions for 6 h between 10 AM and 4 PM for 21 days in the climatic chamber. A digestibility trial with four-day collection period was conducted at the end of the study, and rumen liquor was collected on day 21. At the phylum level, an increased ( p &lt; 0.05 ) abundance of Firmicutes and a decreased ( p &lt; 0.05 ) abundance of Proteobacteria and Planctomycetes were observed during HS compared to thermoneutral conditions. The abundance of 6 different genera of phylum Firmicutes, YRC22 (phylum Bacteroidetes), and Stenotrophomonas (phylum Proteobacteria) was increased ( p &lt; 0.05 ), whereas B. firmus, Lysinibacillus, Bacteroides unclassified genus (family Enterobacteriaceae), and Methanobrevibacter decreased ( p &lt; 0.05 ) during HS compared to control. Eight new genera from four different phyla were detected after HS exposure, whereas one genus was not detected in the rumen after HS exposure, which was present during thermoneutral conditions. Dry matter intake, volatile fatty acid concentration, and digestibility did not change ( p &gt; 0.05 ) during HS. It can be concluded that the resilience of the rumen microbial population invokes adaptive responses by changing their abundance to minimize the adverse effects on fermentation and digestibility in buffalo heifers.

Immune and intestinal microbiota responses to heat stress in Chinese mitten crab (Eriocheir sinensis)

Temperature is an important environmental stressor that affects the metabolism and immunity of Chinese mitten crab. In this study, we investigated immune-related enzyme activity, metabolism-related substances in haemolymph and intestinal microbiota responses of Eriocheir sinensis assigned to the control (24 °C) and heat stress (32 °C) groups. Based on the data obtained, the levels of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase and lactate dehydrogenase in the heat stress group exhibited a trend of increasing first and then decreasing, and all peaked at 12 h or 24 h. The metabolism-related substances in the haemolymph, including glucose, total cholesterol, and total protein, all showed significant differences between the control and heat stress groups from the mid to late period (P < 0.05). Under heat stress, the levels of alkaline phosphatase and acid phosphatase were both significantly higher than those of the control group from 12 h to 24 h and significantly lower at 72 h and 96 h (P < 0.05). The T-AOC of the heat stress group was significantly lower than that of the control group from 48 h to 96 h (P < 0.05). High-throughput 16S ribosomal DNA (rDNA) sequencing revealed that heat stress altered the composition of intestinal microbes of Eriocheir sinensis. Specifically, the abundance of the beneficial bacteria Candidatus, Hepatoplasma and Marinifilum decreased significantly, while the abundance of the pathogenic bacteria Rhodococcus and Morganella increased significantly (P < 0.05). The results revealed that acute heat stress exposure affected immune function and intestinal microbial community in E. sinensis. This work can help to uncover the mechanisms of heat stress responses in this species.

Meta-analysis and meta-regression of core body temperature in taurine and zebuine cattle under different environmental conditions

Heat stress affects livestock productivity and is often determined by an increase in the core body temperature (CBT). To evaluate the latter, both vaginal and rectal temperatures can be used. The aims of this study were (1) to perform a meta-analysis in order to evaluate the impact of heat stress in comparison to thermoneutral conditions on CBT in Bos taurus and Bos taurus indicus cattle, and (2) to evaluate the effects of genetic group, sex, productive purpose, climate zone, and temperature-humidity index (THI class) heat stress on the vaginal and rectal temperatures of cattle. Eighty-nine studies were included in this meta-analysis. Systematic review and meta-analysis were performed following the PRISMA guidelines. The standardized mean difference (SMD) in CBT between the heat stress (HS) and thermoneutral (TN) environments was used as a measure of effect size, considering a 95% confidence interval (CI). Cochran's Q test and I² statistic indicated high variability among studies; thus, a random effects model was used. Subgroup and meta-regression analysis were performed to investigate the source of heterogeneity. Genetic group, sex, productive purpose, climate zone, and THI class were included as covariates. The SMD in CBT between the HS and TN environments was 7.45 °C (95%CI: 5.89;9.02 °C, P = 0.0001), indicating a physiological response to the heat stress condition. The SMD in CBT was 3.92 °C higher in Bos taurus than Bos taurus indicus animals (P < 0.05). Animals in climate zone D (warm temperate zone) showed a lower SMD in CBT than those in climate zone B (arid zone) (SMD = 4.04 ºC vs 12.38 ºC). The THI class affected the SMD in CBT (P < 0.05). The genetic group, climate zone, THI class and interaction between genetic group and climate zone explained 29.89% of the heterogeneity observed among studies. In conclusion, heat stress exposure affects the vaginal and rectal temperatures of cattle. The CBT measured by rectal and vaginal temperatures can be used to detect heat stress-induced changes in CBT. Bos taurus and Bos taurus indicus animals seem to respond differently to heat stress in terms of CBT.

Quantifying the impact of heat on human physical work capacity; part IV: interactions between work duration and heat stress severity

High workplace temperatures negatively impact physical work capacity (PWC). Although PWC loss models with heat based on 1-h exposures are available, it is unclear if further adjustments are required to accommodate repeated work/rest cycles over the course of a full work shift. Therefore, we examined the impact of heat stress exposure on human PWC during a simulated work shift consisting of six 1-h work-rest cycles. Nine healthy males completed six 50-min work bouts, separated by 10-min rest intervals and an extended lunch break, on four separate occasions: once in a cool environment (15 °C/50% RH) and in three different air temperature and relative humidity combinations (moderate, 35 °C/50% RH; hot, 40 °C/50% RH; and very hot, 40 °C/70%). To mimic moderate to heavy workload, work was performed on a treadmill at a fixed heart rate of 130 beats·min−1. During each work bout, PWC was quantified as the kilojoules expended above resting levels. Over the shift, work output per cycle decreased, even in the cool climate, with the biggest decrement after the lunch break and meal consumption. Expressing PWC relative to that achieved in the cool environment for the same work duration, there was an additional 5(± 4)%, 7(± 6)%, and 16(± 7)% decrease in PWC when work was performed across a full work shift for the moderate, hot, and very hot condition respectively, compared with 1-h projections. Empirical models to predict PWC based on the level of heat stress (Wet-Bulb Globe Temperature, Universal Thermal Climate Index, Psychrometric Wet-Bulb Temperature, Humidex, and Heat Index) and the number of work cycles performed are presented.

Symposium review: Environmental effects on mammary immunity and health.

Environmental effects on pathogen abundance and access are precursors to mastitis. Indeed, high heat and humidity, and unsanitary housing and equipment, are associated with greater pathogen load and exposure. Although less is known about effects of environment on a cow's ability to resist infection, several indicators suggest that it can affect pathogen responses. Mastitis incidence and bulk tank somatic cell count vary with season, typically peaking in summer. Recent controlled studies have revealed that heat stress exposure results in changes in the microbiome of the cow and her environment, which may relate to negative effects on milk quality and cow health. Alternatively, specific pathogen loads may vary based on housing dynamics rather than associations with physical environment. Indeed, housing-related stressors, such as overcrowding and social group challenge, influence secretion of glucocorticoids, thus affecting pathogen resistance in the cow. Two key seasonal variables are photoperiod and temperature, specifically the heat stress consequent to elevated temperature and humidity. Shifts in light duration regulate immune function in other species, but apparently have limited effect on udder health of lactating cows. In contrast, in dry cows, short days increase peripheral blood mononuclear cell number and are associated with lower somatic cell count in the next lactation, compared with long days. With heat stress, elevated body temperature directly affects expression of immune-related genes in mammary tissue. Responses depend on duration of exposure and feature acute upregulation of immune-signaling pathways, followed by enrichment of other immune-related pathways after prolonged exposure. Most responses are transient and recover within 1 wk. Functionally, heat stress impairs some aspects of acquired immunity in dry cows, including antigen responses and lymphocyte proliferation, but apparently not innate immune function. However, heat stress in late gestation reduces neutrophil phagocytosis and killing in vitro, and neutrophils in circulation are reduced in vivo as are responses to pathogen challenge in the subsequent lactation. A holistic understanding of the complex interplay of environment, pathogens, and host is needed to inform advances in this area.

Effects of short-term in vitro heat stress on bovine preantral follicles

Heat stress occurs when heat dissipation mechanisms are overwhelmed by external and internal heat production. Ovarian reserve is an important contributor to reproductive success in cattle. The effects of heat stress on antral follicle development have been well studied; the consequences on preantral follicles are still largely unknown. This study aimed to investigate and characterize the effects of a short in vitro heat stress exposure on bovine preantral follicles, with a special focus on primordial follicles. Bovine ovarian cortex fragments (3 × 3 × 1 mm) were isolated and incubated at different temperatures for 2 h. The incubation methodology was validated using a non-incubated group. Incubation groups consisted in physiological temperature (38.5 °C) or heat stress (41 °C). Data on follicle count, diameter of the primordial follicles, number of granulosa cells, and markers for follicle proliferation and degeneration were recorded. Heat stress caused a significant decrease in the number of primordial follicles (p < 0.0001) compared to control and non-incubated groups. The diameter of these follicles also decreased under heat stress (p < 0.0001), as did the number of granulosa cells. In addition, an increase in the number of degenerated follicles (p < 0.0001) and a decrease in granulosa cell proliferation (p < 0.0001) were found after exposure to heat stress. The results of this in vitro study show that a brief exposure to heat stress can affect the follicular reserve in the ovarian cortex and therefore, provide relevant information of its effects on the reproductive performance of cattle.

Dry-season variability in near-surface temperature measurements and landsat-based land surface temperature in Kenyatta University, Kenya

Understanding thermal gradients is essential for sustainability of built-up ecosystems, biodiversity conservation, and human health. Urbanized environments in the tropics have received little attention on underlying factors and processes governing thermal variability as compared to temperate environments, despite the worsening heat stress exposure from global warming. This study characterized near surface air temperature (NST) and land surface temperature (LST) profiles across Kenyatta University, main campus, located in the peri-urban using in situ traverse temperature measurements and satellite remote sensing methods respectively. The study sought to; (i) find out if the use of fixed and mobile temperature sensors in time-synchronized in situ traverses can yield statistically significant temperature gradients (ΔT) attributable to landscape features, (ii) find out how time of the day influences NST gradients, (iii) determine how NST clusters compare to LST values derived from analysis of ‘cloud-free’ Landsat 8 OLI (Operational Land Imager) satellite image, and (iv) determine how NST and LST values are related to biophysical properties of land cover features.. The Getis–Ord Gi* statistics of ΔT values indicate statistically significant clustering hot and cold spots, especially in the afternoon (3–5 PM). NST ‘hot spots’ and ‘cold spots’ coincide with hot and cold regions of Landsat-based LST map. Ordinary Least Square Regression (OLS) indicate statistically significant (p < 0.01) coefficients of MNDWI and NDBI explaining 15% of ΔT variation, and albedo, MNDWI, and NDBI explaining 46% of the variations in LST patterns. These findings demonstrate that under clear sky, late afternoon walking traverses records spatial variability in NST within tropical peri-urban environments during dry season. This study approach may be enhanced through collecting biophysical attributes and NST records simultaneously to improve reliability of regression models for urban thermal ecology.

Short- and Long-Term Exposure to Heat Stress Differently Affect Performance, Blood Parameters, and Integrity of Intestinal Epithelia of Growing Pigs.

Simple SummaryHigh ambient temperature provokes heat stress in animals. Observed signs of heat stress in pigs include altered physiological constants, changes in feeding behavior, reduced weight gain, or even body weight loss. Short-term exposition to heat stress has been associated with alterations in small intestine physiology, including digestion and absorption of nutrients. Those alterations reduce when pigs start the acclimation process to heat stress, which may occur at around one week of exposure to high ambient temperature. In this study, the short- (2 days) and long- (7 days) term exposure to natural heat stress on performance, blood components, and intestinal integrity of growing pigs were analyzed. Short-term heat stress reduced pig performance and altered blood components. Intestinal integrity was affected drastically at day 2 under heat stress conditions, but pigs started to recover most of their growth rate and intestinal integrity at day 7.The effect of short- and long-term exposure to heat stress (HS) was analyzed on blood components, performance, and intestinal epithelium integrity of pigs. Eighteen pigs (36.0 ± 3.5 kg BW) were assigned to three groups: thermo-neutral (TN); 2 d exposure to HS (2dHS); and 7 d exposure to HS (7dHS). Blood chemistry and hemogram analyses were performed; small intestine samples were analyzed for mRNA expression and histology. Compared to TN, 2dHS and 7dHS pigs reduced weight gain and feed intake; weight gain was higher in 7dHS than in 2dHS pigs (p < 0.05). White blood cells, platelet, and hematocrit were affected in 2dHS and 7dHS compared to TN pigs (p < 0.05). Short- and long-term exposure to HS affected blood concentration of triglycerides, urea, total protein, and albumin (p ≤ 0.05). Villi-height and crypt-depth decreased in HS pigs (p < 0.01). Mucin-producing and apoptotic cell number increased in 7dHS compared to TN pigs (p < 0.05). Expression of tight-junction-proteins decreased in 2dHS pigs compared to TN and 7dHS pigs (p < 0.05). Short-term exposure of pigs to HS dramatically affects performance, blood components, and integrity of the small intestine epithelia; nevertheless, pigs show signs of recovery at 7 d of HS exposure.

PSII-B-21 Does Prior Viral Infection Exacerbate the Response to Heat Stress?

Abstract In rodent models, prior immune activation appears to exacerbate the response to heat stress (HS), presumably by compounding an inflammatory response by both insults. Thus, study objectives were to investigate whether prior viral infection aggravates the physiological and feed intake (FI) responses to HS. Crossbred barrows (n=45; 75.5±4.8 kg BW) were enrolled in two experimental periods (P). During P1 (2 d), pigs were fed ad libitum and housed in thermoneutral (20ºC) conditions. During P2 (6 d), pigs were exposed to an increased heat load (28 to 31ºC). Rectal temperature (TR), skin temperature (TS), and respiration rate (RR) were obtained twice daily. FI was measured daily as feed disappearance. Unexpectedly, pigs became sick during the experiment and tested positive for influenza on d 6 of P2. Based on TR obtained during P1, animals were retrospectively categorized into 1 of 2 groups: 1) High-TR (HT; top third of pigs; TR&amp;gt;39.32ºC; x̅=39.38ºC; n=15), or 2) Low-TR (LT; bottom third of pigs; TR&amp;lt; 39.10ºC; x̅=38.95ºC; n=15). Pigs in the middle third tier were excluded from the analysis. This ostensibly categorized pigs into a “sick” and “healthy” status. Data were statistically analyzed using the MIXED procedure in SAS. As expected, HS increased TR in both groups; however, HT had elevated TR during P2 relative to LT pigs (+0.5ºC; P&amp;lt; 0.01). Skin temperature and RR increased during HS but remained similar between HT and LT pigs (P&amp;gt;0.41). During P1, FI was similar between groups (P&amp;gt;0.33). During P2, HS reduced FI in both groups; however, the decrease was more severe in HT than LT pigs (53 vs. 37%, respectively; P=0.01). Altogether, HT pigs, presumably infected before HS exposure, had increased TR and a more drastic reduction in FI during HS than LT pigs. A better understanding of how viral or bacterial infection influences the response to HS would have pragmatic implications for all segments of animal agriculture.

Within-population variability in coral heat tolerance indicates climate adaptation potential

Coral reefs are facing unprecedented mass bleaching and mortality events due to marine heatwaves and climate change. To avoid extirpation, corals must adapt. Individual variation in heat tolerance and its heritability underpin the potential for coral adaptation. However, the magnitude of heat tolerance variability within coral populations is largely unresolved. We address this knowledge gap by exposing corals from a single reef to an experimental marine heatwave. We found that double the heat stress dosage was required to induce bleaching in the most-tolerant 10%, compared to the least-tolerant 10% of the population. By the end of the heat stress exposure, all of the least-tolerant corals were dead, whereas the most-tolerant remained alive. To contextualize the scale of this result over the coming century, we show that under an ambitious future emissions scenario, such differences in coral heat tolerance thresholds equate to up to 17 years delay until the onset of annual bleaching and mortality conditions. However, this delay is limited to only 10 years under a high emissions scenario. Our results show substantial variability in coral heat tolerance which suggests scope for natural or assisted evolution to limit the impacts of climate change in the short-term. For coral reefs to persist through the coming century, coral adaptation must keep pace with ocean warming, and ambitious emissions reductions must be realized.

Heat stress exposure changed liver lipid metabolism and abdominal fat deposition in broilers

To evaluate the effects of heat stress on lipid metabolism in the liver and abdominal adipose deposition in broilers, totally, 120 female 21-day old broilers were selected and randomly allocated to 2 groups with 6 replication and 10 broilers per each replication. Broilers in the control group (CON) were reared at 24 °C, and broilers in the heat stress group (HS) were reared at 34 °C. Heat stress exposure increased (P < 0.05) rectal temperature, relative weight of abdominal adipose and liver, serum triacylglycerol (TG) and total cholesterol (TC) level, liver TG, TC, and very low-density lipoprotein (VLDL) content. Hepatic mRNA expression level of fatty acid synthase (FAS), acetyl-coenzyme A carboxylase (ACC), and abdominal adipose mRNA expression level of ACC and CCAAT/enhancer-binding protein-α (C/EBPα) were up-regulated (P < 0.05) when compared with the CON group. Heat stress exposure increased serum and hepatic TC and TG content, up-regulated the mRNA expression of FAS and ACC in liver, and promoted preadipocytes differentiation by increasing C/EBPα mRNA expression in abdominal adipose. Therefore, heat stress exposure increased abdominal adipose deposition, which related to increase in hepatic de novo lipogenesis, and promoted preadipocytes differentiation in abdominal adipose. HIGHLIGHTS Heat stress increased abdominal adipose deposition Heat stress increased hepatic de novo lipogenesis Heat stress promoted preadipocytes differentiation in abdominal adipose

Trehalose Attenuates Oxidative Stress and Endoplasmic Reticulum Stress-Mediated Apoptosis in IPEC-J2 Cells Subjected to Heat Stress.

Simple SummaryAs global warming continues, the increased frequency and intensity of high ambient temperatures imposes heat stress (HS) on farm animals and human beings. Pigs are susceptible to heat exposure; decreased performance and increased morbidity due to HS give rise to economic losses for the swine industry. HS induces oxidative stress and apoptosis, both of which are associated with compromised intestinal barrier integrity. Trehalose (Tre) is a natural disaccharide that is considered a health-promoting food owing to its antioxidant and anti-inflammatory effects and its molecular chaperone ability to inhibit protein denaturation. The present study aimed to determine the optimum trehalose level for alleviating HS-induced intestinal porcine epithelial cell (IPEC-J2) insults and to uncover the molecular mechanism of the protective effects of Tre. This study demonstrated that 10 mM trehalose can significantly attenuate HS-induced IPEC-J2 cell impairment and that the mechanism is related to trehalose alleviating oxidative stress and endoplasmic reticulum stress-mediated apoptosis.This study was carried out to investigate the effects of trehalose (Tre) on antioxidant capacity, endoplasmic reticulum stress (ERS) response and apoptosis of heat-stressed intestinal porcine epithelial cells (IPEC-J2). IPEC-J2 cells were cultured at 37 °C until the end of the experiment (control, CON); exposed to heat stress for 2 h (43 °C, HS); or pretreated with 0.1, 1, 5, 10, and 15 mM trehalose at 37 °C for 4 h prior to heat stress exposure for 2 h. The optimum level of trehalose for protecting against HS-induced cell injuries was determined to be 10 mM, as evidenced by the highest cellular viability and lowest malondialdehyde (MDA) content and lactate dehydrogenase (LDH) activity. Based on these, IPEC-J2 cells were divided into three groups: the first group was cultured at 37 °C until the end of the experiment (control, CON); the second group was exposed to heat stress for 2 h (43 °C, HS); the third group was pretreated with 10 mM trehalose for 4 h at 37 °C prior to heat stress exposure for 2 h (Tre + HS). The reactive oxygen species (ROS) content, superoxide dismutase (SOD) activity, mitochondrial membrane potential (MMP) changes, and expressions of the manganese superoxide dismutase (SOD2), ERS and apoptosis-related proteins were determined. Compared to the CON group, HS significantly increased ROS generation (p < 0.01), decreased SOD activity (p < 0.05), and downregulated protein expression of SOD2 (p < 0.01). Compared to the HS group, Tre supplementation reduced ROS levels and increased SOD activity and SOD2 expression to the levels that were comparable to the control (p < 0.05). The HS-induced ERS response was evidenced by the increased protein expressions of glucose-regulated protein 78 (GRP78) (p < 0.01), eukaryotic translation initiation factor 2α (p-eif2α) (p < 0.01), transcription activator 4 (ATF4) (p < 0.01), and the protein expression of C/EBP homologous protein (CHOP) (p < 0.01), which were the four hallmarks of ERS. The Tre + HS group showed lower expressions of GRP78 (p < 0.01), p-eif2α (p < 0.01), ATF4 (p < 0.01), and CHOP (p < 0.01) than that of the HS group. Tre pretreatment attenuated HS-induced mitochondrial apoptosis in IPEC-J2 cells, demonstrated by the increased MMP and decreased proapoptotic proteins active caspase 3, Bax, and cytochrome c (Cyt c). Taken together, trehalose can protect against HS-induced oxidative damage and endoplasmic reticulum stress-mediated apoptosis in IPEC-J2 cells. These data may provide a nutritional strategy for alleviating heat stress in pig production.

Prenatal acute thermophysiological stress and spontaneous preterm birth in Western Australia, 2000-2015: A space-time-stratified case-crossover analysis.

Epidemiologic evidence on acute heat and cold stress and preterm birth (PTB) is inconsistent and based on ambient temperature rather than a thermophysiological index. The aim of this study was to use a spatiotemporal thermophysiological index (Universal Thermal Climate Index, UTCI) to investigate prenatal acute heat and cold stress exposures and spontaneous PTB. We conducted a space-time-stratified case-crossover analysis of 15,576 singleton live births with spontaneous PTB between January 1, 2000 and December 31, 2015 in Western Australia. The association between UTCI and spontaneous PTB was examined with distributed lag nonlinear models and conditional quasi-Poisson regression. Relative to the median UTCI, there was negligible evidence for associations at the lower range of exposures (1st to 25th percentiles). We found positive associations in the 95th and 99th percentiles, which increased with increasing days of heat stress in the first week of delivery. The relative risk (RR) and 95% confidence interval (CI) for the immediate (delivery day) and cumulative short-term (up to six preceding days) exposures to heat stress (99th percentile, 31.2°C) relative to no thermal stress (median UTCI, 13.8°C) were 1.01 (95% CI: 1.01, 1.02) and 1.05 (95% CI: 1.04, 1.06), respectively. Elevated effect estimates for heat stress were observed for the transition season, the year 2005-2009, male infants, women who smoked, unmarried, ≤ 19 years old, non-Caucasians, and high socioeconomic status. Effect estimates for cold stress (1st percentile, 0.7°C) were highest in the transition season, during 2005-2009, and for married, non-Caucasian, and high socioeconomic status women. Acute heat stress was associated with an elevated risk of spontaneous PTB with sociodemographic vulnerability. Cold stress was associated with risk in a few vulnerable subgroups. Awareness and mitigation strategies such as hydration, reducing outdoor activities, affordable heating and cooling systems, and climate change governance may be beneficial. Further studies with the UTCI are required.

Increased risk of heat stress conditions during the 2022 Comrades Marathon

The Comrades Marathon is South Africa’s – and the world’s – most recognised and largest ultra-marathon event, with over 15 000 participants from across the globe competing in the 89-km road running event each year. Historically, the event has been held before the start of austral winter (20 May – 17 June). However, in 2022, organisers of the race moved the event to 28 August, when austral spring commences. We explore the climate, in particular the Universal Thermal Comfort Index (UTCI), of past Comrades events (1980-2019) and compare these data to UTCI data of the new proposed date (28 August) for the same period. The climatology for May, June, July and August was determined to identify periods with the lowest risk for ‘strong’ to ‘very strong’ heat stress. Results show that participants’ risk of exposure to ‘strong’ heat stress and ‘very strong’ heat stress periods will be more likely if the event is held in August as compared to the original event dates. Therefore, it is concluded that mid-June to mid-July has the lowest risk of heat stress exposure along the route. Runners and organisers should be aware of the higher risk of exertional heat illness during the 2022 Comrades Marathon to ensure safe participation. Significance: The new proposed date for the Comrades Marathon will increase the risk of exposure to ‘strong’ and ‘very strong’ heat stress conditions, as defined by the Universal Thermal Comfort Index (UTCI). The UTCI indicates that mid-June to mid-July has the lowest risk of heat stress exposure at the three reference points along the route. Organisers should warn runners of the higher risk of exertional heat illness due to the possible exposure to high UTCI values or more unfavourable climatological conditions. Furthermore, runners should be informed of a variety of preventative strategies to ensure safe participation.