Severe Heat Stress Research Articles

Effect of neighbourhood courtyard design on the outdoor thermal comfort in a tropical city

In the tropical city of Ha Tinh (Vietnam), the number of new developed neighbourhoods in the courtyard layout is increasing while the city is experiencing annual severe heat stress. The paper quantitatively analyses, by means of ENVI-Met simulation, the effect of neighbourhood courtyard landscape on the outdoor thermal comfort (OTC) in the tropical city of Ha Tinh (Vietnam). A sample 9-ha residential block was at first experimentally configured with four scenarios of courtyard, including (1) bare grass and perimetry location of high plants, (2) grass ground, fully occupied high trees, (3) water body and perimetry location of high plants, and (4) mixed ground surfaces of water, hard pavement and grass, and partly occupied high trees. The adding of tree canopies to the entire courtyard, consequently sufficient shades, as in case 2, contributes to the better OTC among the chosen scenarios by triggering the reduction of mean radiant temperature (Tmrt) (2.9°C) and physiological equivalent temperature (PET) (3.5°C) at the hottest hours as compared to the original configuration (case 1) during the summer days. Application of perimetry plants with either water (case 1) or bare grass (case 3) results in higher PET though full occupation of water body lowers the air temperature by roughly 1°C. The limited impact on OTC of local water body is counter-intuitive, yet important result to the practice of urban design. The worst OTC was observed in case 4 where almost half of the garden was sun-exposed and intended for hard-paved playground and water body. Increasing shades against solar radiation is the most important measure to deal with intensive heat problem. The study is an essential part of translating academic knowledge on urban climate into interventions on urban design for better climate resilience of neighbourhoods in Vietnam and by extend in other tropical countries.

The use of percutaneous thermal sensing microchips for non-invasive measurement of body temperature in foals during summer seasons in a subtropical region

Continuous accurate attainment of the body temperature of foals is important to detect early stages of severe heat stress or fever due to a systemic illness. Among a number of methods to measure body temperature, measuring rectal temperature with a digital thermometer is most frequently used due to being relatively fast and simple method. It is also comparatively accurate and correlates well with the core body temperature. However, this method requires restraining the foal for a few seconds to obtain the temperature, and it can be dangerous for the handling person. Percutaneous thermal sensing microchips (PTSMs) are a means of monitoring the body temperature of horses, which offers a non-invasive, hygienic, quick, and accurate way to measure body temperature and provide an identification number for each individual, once it is implanted. This study tested the hypothesis that PTSM has a strong relationship with a conventional body temperature measurement, i.e., measuring rectal temperature with a digital thermometer of foals during summer seasons. Thirty-two foals in three consecutive foaling seasons (2018, 2019, and 2020 season) were implanted a PTSM into the right pectoral muscle, the right splenius muscle, the right gluteal muscle, and the nuchal ligament as early as two weeks after birth. The four PTSM temperatures, rectal temperature, and climate conditions (air temperature, relative humidity, and wet-bulb globe temperature) were obtained simultaneously during the three summer seasons and paired for comparison analysis. Among the PTSM temperatures, the pectoral muscle had the highest correlation and the least differences with rectal temperature. Using PTSM was safe, easy, and reliable for attaining body temperature in foals.

Effects of post‐flowering heat stress on chlorophyll content and yield components of a spring wheat diversity panel

AbstractHigh temperature has been a major limiting factor for wheat (Triticum aestivum L.) productivity and will become a significant driver of yield loss as global warming progresses. Many wheat‐growing regions worldwide experience terminal heat stress during the grain‐filling period, resulting in grain yield reduction. A sustainable solution to mitigate heat stress‐induced damage is to develop heat‐tolerant cultivars. To achieve this, identifying tolerant lines is essential to incorporate heat stress resilience into commercial varieties. Our working hypothesis was that retaining chlorophyll content during post‐flowering heat stress will reduce yield losses. In this study, we evaluated the terminal heat stress tolerance of 254 diverse spring wheat lines from North American and Australian wheat‐breeding programs in two independent experiments. The plants were grown in individual pots under controlled environments. Significant genetic variation was observed for the ability to retain post‐stress chlorophyll content and yield components. Grain yield per plant and individual grain weight were significantly correlated with chlorophyll content under heat stress. The reduction in grain yield per plant was contributed more by the reduction of the individual grain weight than by the grain number under heat stress. A highly tolerant line, cultivar Otis, retained 79.2% chlorophyll content relative to control, and also recorded 55% greater chlorophyll content than the average of all 254 lines, at the end of 16 d of severe heat stress treatment. Mapping populations are being developed using Otis, with an aim to identify the genetic basis of chlorophyll retention under terminal heat stress. Resilient wheat lines identified with high grain weight under stress will serve as useful resources for abiotic stress breeding programs.

Exploiting Wild Emmer Wheat Diversity to Improve Wheat A and B Genomes in Breeding for Heat Stress Adaptation.

Wheat is highly sensitive to temperature beyond the optimum. To improve wheat adaptation to heat stress, the best option is to exploit the diversity of wild wheat progenitors. This study aimed to identify germplasm and quantitative trait loci associated with heat stress tolerance from wild emmer wheat diversity. We evaluated a diverse set of multiple derivative lines harboring chromosome segments from nine wild emmer wheat parents under four environments: two optimum environments at Tottori, Japan and Dongola, Sudan, one moderate heat stress environment, and one severe heat stress environment at Wad Medani, Sudan. Genome-wide association analysis was conducted with 13,312 SNP markers. Strong marker-trait associations (MTAs) were identified for chlorophyll content at maturity on chromosomes 1A and 5B: these MTAs explained 28.8 and 26.8% of the variation, respectively. A region on chromosome 3A (473.7–638.4 Mbp) contained MTAs controlling grain yield, under optimum and severe heat stress. Under severe heat stress, regions on chromosomes 3A (590.4–713.3 Mbp) controlled grain yield, biomass, days to maturity and thousand kernel weight, and on 3B (744.0–795.2 Mbp) grain yield and biomass. Heat tolerance efficiency (HTE) was controlled by three MTAs, one each on chromosomes 2A, 2B, and 5A under moderate heat stress and one MTA on chromosome 3A under severe heat stress. Some of the MTAs found here were previously reported, but the new ones originated from the wild emmer wheat genomes. The favorable alleles identified from wild emmer wheat were absent or rare in the elite durum wheat germplasm being bred for heat stress tolerance. This study provides potential genetic materials, alleles, MTAs, and quantitative trait loci for enhancing wheat adaptation to heat stress. The derivative lines studied here could be investigated to enhance other stress tolerance such as drought and salinity.

Thermal stress and TiO2 nanoparticle-induced oxidative DNA damage and apoptosis in mouse hippocampus.

Titanium dioxide (nano-TiO2) is used abundantly in various industrial products and novel medical therapies. In addition, the impact of climate change on the health and safety will undoubtedly increase in the future. However, the effects of exposure to these nanoparticles and heat stress on hippocampal DNA damage and apoptosis remain unclear. This study was conducted to evaluate the DNA damage and apoptosis in the hippocampal tissue and the physiological responses in mice induced by intraperitoneal (i.p.) administration of TiO2 nanoparticles (NPs) and heat stress for 14 consecutive days. The results showed that heat stress and TiO2-NPs were induced in the mouse hippocampus that led to hippocampal reactive oxygen species generation, oxidative damage of DNA, and apoptosis in a partly dose-dependent manner, especially at very hot temperature. High doses of nanosized TiO2 and severe heat stress significantly damaged the function of the hippocampus, as shown in the comet assay and apoptosis tests. The results of this study may provide data for appropriate measures to control and assess the risk of nano-TiO2 and thermal stress hazards to human health, especially workers. Safety guidelines and policies should be considered when handling nanomaterials in a hot environment.

Thermoregulatory Response of Blackbelly Adult Ewes and Female Lambs during the Summer under Tropical Conditions in Southern Mexico.

Simple SummaryClimate change has intensified high environmental temperatures, subjecting farm animals to heat stress conditions. In this study, the thermoregulatory responses of Blackbelly adult ewes and female lambs, during the summer under tropical conditions, in southern Mexico were analyzed. The combination of temperature and relative humidity in summer in tropical conditions causes heat stress in hair ewes, resulting in thermoregulatory problems. To counteract these effects, females modify their physiological constants to avoid reproductive and productive problems under these production conditions.High environmental temperatures cause heat stress in ewes, resulting in thermoregulatory problems. In this study, the thermoregulatory responses of Blackbelly adult ewes (G1, n = 14) and female lambs (G2, n = 7), during the summer under tropical conditions, in southern Mexico were analyzed. Different physiological variables and skin temperatures (ST) of the ewes were recorded. Breathing frequency (BF) values were similar between groups at 116.73 ± 33.598 bpm (G1) and 113.661 ± 34.515 bpm (G2) (p > 0.05). In the case of skin elasticity (SE), there were no significant differences between the time of day and the age of the ewes (p > 0.05). Significant differences were observed between groups for BF, rectal temperature (RT), and heart rate (HR) values (p < 0.05). All ST values, for both groups, were significantly higher during the afternoon (p < 0.001). In general, all Blackbelly adult ewes and female lambs during the summer present severe heat stress conditions as a result of an increase in physiological constants and ST. It is concluded that all ewes thermoregulate body temperature by modifying different physiological variables to counteract the effect of heat stress.

The feeding behavior of dairy cattle under tropical heat stress conditions at smallholder urban farming

Abstract. Despal, Faresty C, Zahera R, Toharmat R. 2022. Title The feeding behavior of dairy cattle under tropical heat stress conditions at smallholder urban farming. Biodiversitas 23: 3771-3777. Dairy cattle (Bos taurus) feeding behavior influences feed intake and affect animal welfare and disease management. This study observed dairy cattle feeding behaviors under tropical smallholder urban farming environments. Thirty-six cattle at the Kebon Pedes area of Bogor City were observed during 12 h feeding (6 am-6 pm). These traits included eating, ruminating, resting duration, and frequencies, measured using a continuous method. Temperature, humidity, temperature-humidity index (THI), feed and nutrient intake, milk production, and components were measured. The results showed that the cattle were in mild to severe heat stress. The average cow daily eating, ruminating, and resting frequencies were 6.61, 7.61, and 22.33 times, while the average eating, ruminating, and resting durations per cow per 12 h were 129.64, 105.67, and 484.69 minutes, respectively. The dry matter intake was 11.17 kg with a roughage to concentrate ratio of 0.73:1. The protein, ash, ether extract, and crude fiber intake were 10.25, 6.62, 3.67, and 22.08% DM, respectively. The average milk productions and fat contents were 11.01 L/head/d and 5.44%. The results showed that eating and ruminating levels correlated positively with feed, and CF intakes while resting correlated negatively. It was concluded that the cattle were in heat-stressed (THI of &gt;78) condition, reduced DM intake, and deficient in energy and CP, which led to lower milk production but higher milk components, specifically milk fat. It is recommended to improve forage quality that promotes eating and ruminating and reduces resting durations, improving milk production.

Three years of warming and rainfall reduction alter leaf physiology but not relative abundance of an annual species in a Mediterranean savanna

Increasing air temperatures and decreasing rainfall can alter Mediterranean ecosystems, where summer heat and drought already limit plant regeneration. Manipulative field studies can help to understand and anticipate community responses to climate changes. In a Mediterranean oak wooded pasture, we have investigated the effects of warming (W, via open-top chambers increasing 1.4 °C mean air temperature), reduced rainfall (D, via gutters removing 33% of rainfall) and the combination of both factors (WD) on the winter-annual Geranium dissectum L. We measured reproductive phenology and output, leaf physiology during the reproductive phase, and plant relative abundance. Warming had a positive effect on plant height and little effects on leaf physiology. Rainfall reduction enhanced leaf water use efficiency. However, the most noticeable effects occurred in WD plants, which exhibited lower leaf predawn water potential and earlier flowering phenology in the first year of treatment, and a higher ratio of leaf dark respiration (R) to net CO2 assimilation (Pn) at comparable temperatures in the third year, compared to control plants. Leaf R at ambient temperature was similar across climatic treatments. The relative abundance of G. dissectum decreased by 23% over three years, but similarly across treatments. A short life cycle helps G. dissectum to escape severe late-spring heat and drought stress. Moreover, stomata closure and thermal acclimation of R can attenuate plant stress impact on reproduction. Adaptability of the short-lived annual G. dissectum could mitigate climate change impact on community composition over short periods (e.g. three years); however, a reduction in net carbon gain could eventually affect its reproductive success and persistence in the community.

Rapid assessments of Pacific Ocean net coral reef carbonate budgets and net calcification following the 2014–2017 global coral bleaching event

AbstractThe 2014–2017 global coral bleaching event caused widespread coral mortality; however, its impact on the capacity for coral reefs to maintain calcium carbonate structures has not been determined. Here, we quantified remotely sensed maximum heat stress during the 2014–2017 bleaching event, census‐based net carbonate budgets from benthic imagery and fish survey data, and net reef calcification from salinity normalized seawater total alkalinity anomalies collected from 2017–2019 for 56 Pacific coral reef sites (Mariana Islands, Northwestern Hawaiian Islands, Pacific Remote Island Areas, and American Samoa). We incorporated the census‐based and chemistry‐based metrics to determine a calcification vulnerability index for each site to maintain calcium carbonate balance to provide accessible information to managers and policy makers. Most coral reef sites likely experienced ecologically severe (79%, n = 44) or significant (9%, n = 7) heat stress during the 2014–2017 coral bleaching event. Census‐based net carbonate budgets (mean ± 95% = 2.1 ± 0.6 kg CaCO3 m−2 yr−1) were positive for 77% of sites (n = 43), neutral for 16% of sites (n = 9), and negative for 7% of sites (n = 4). Chemistry‐based relative net reef calcification (mean ± 95% = 22 ± 10 μmol kg−1) was positive for 84% of sites (n = 47), neutral for 11% of sites (n = 6), and negative for 5% of sites (n = 3). The calcification vulnerability index suggested the Pacific Ocean reef sites surveyed were of minimal (68%, n = 38) to moderate (32%, n = 18) concern for maintaining calcium carbonate balance following the bleaching event. This suggests that many reefs maintained positive calcium carbonate balance, but that a large number of reefs may be approaching a potential threshold for maintaining their calcium carbonate balance under the climate crisis.

Amplified risk of compound heat stress-dry spells in Urban India.

Compound warm-dry spells over land, which is expected to occur more frequently and expected to cover a much larger spatial extent in a warming climate, result from the simultaneous or successive occurrence of extreme heatwaves, low precipitation, and synoptic conditions, e.g., low surface wind speeds. While changing patterns of weather and climate extremes cannot be ameliorated, effective mitigation requires an understanding of the multivariate nature of interacting drivers that influence the occurrence frequency and predictability of these extremes. However, risk assessments are often focused on univariate statistics, incorporating either extreme temperature or low precipitation; or at the most bivariate statistics considering concurrence of temperature versus precipitation, without accounting for synoptic conditions influencing their joint dependency. Based on station-based daily meteorological records from 23 urban and peri-urban locations of India, covering the 1970–2018 period, this study identifies four distinct regions that show temporal clustering of the timing of heatwaves. Further, combining joint probability distributions of interacting drivers, this analysis explored compound warm-dry potentials that result from the co-occurrence of warmer temperature, scarcer precipitation, and synoptic wind patterns. The results reveal 50-year severe heat stress solely based on the temperature at each location tends to be more frequent and is expected to become 5 to 17-year compound warm-dry events considering interdependence between attributes. Notably, considering dependence among drivers, a median 6-fold amplification (ranging from 3 to 10-fold) in compound warm-dry spell frequency is apparent relative to the expected annual number of a local (univariate) 50-year severe heatwave episode, indicating warming-induced desiccation is already underway over most of the urbanized areas of the country.Supplementary informationThe online version contains supplementary material available at 10.1007/s00382-022-06324-y.

Macroalgal canopies provide corals limited protection from bleaching and impede post-bleaching recovery

Coral bleaching, the result of loss of endosymbiotic dinoflagellates, as well as post-bleaching recovery can be exacerbated or mitigated by a range of local factors such as depth, turbidity, and natural or artificial shading providing protection for corals during thermal anomalies. On many reefs, losses in coral cover coincide with increases in upright macroalgae growth. Such shifts in benthic communities are generally viewed as negative, whereby macroalgae can outcompete corals for space, and affect adult coral health and fitness. However, the canopy provided by upright macroalgae could reduce solar irradiance and provide refuge for understorey corals during heat events, decreasing coral bleaching and subsequent mortality. To test this hypothesis, this study manually removed macroalgae from experimental plots on a macroalgae-dominated fringing reef at Magnetic Island in the central inshore region of the Great Barrier Reef, comparing the subsequent bleaching during and recovery following a severe heat stress event. In March 2020, sea surface temperature at Magnetic Island reached 31.4 °C, leading to bleaching. Surveys of coral communities undertaken at the peak of accumulated severe heat stress (DHW of 9.3 °C-weeks) in control and macroalgae removal plots showed that, averaged across coral morphological groups, there was no overall difference in bleaching prevalence in algal-removal and control plots (21.1% and 20.8% of the community bleached; respectively). However, bleaching prevalence varied within morphological groups, with massive morphology corals demonstrating higher probability of bleaching in removal plots compared to controls (0.26 and 0.09, respectively). Bleaching severity (i.e. percent of the colony tissue bleached) was consistent across control and removal plots (83.2% and 80.4% of colony area, respectively, averaged across morphologies), with branching corals demonstrating the lowest severity. Surveys were repeated in July after heat stress had dissipated, with coral communities in algal-removal plots displaying greater recovery than controls (i.e. 86.1% and 75.6% healthy, respectively, model estimated mean averaged across morphologies). Encrusting corals in control plots were the slowest to recover. We conclude that macroalgae provided limited refuge for branching and encrusting corals at the height of the thermal event, likely due to the severity of the accumulated heat stress, while massive corals enjoyed some degree of protection from the canopy. Greater recovery of coral communities in removal plots may potentially be explained by reduced competition with adjacent macroalgae. This study provides important insights into the interactions between these two dominant benthic groups and supports previous work finding macroalgae inhibits coral recovery after severe bleaching events.

Move, migrate, or tolerate: Quantifying three tactics for cold‐water fish coping with warm summers in a large river

AbstractMainstem rivers are important for provisioning cold‐water fisheries and often support fluvial life histories that grow much larger than resident counterparts in tributaries. However, mainstem rivers are also warmer than tributaries during summer and more tightly coupled to regional climate. A key challenge is to understand how fluvial life histories cope with summer temperatures in mainstem rivers, both now and in a warmer future. Here, we outline three options: tolerance, exploitation of cool microhabitats, or migration to cooler tributaries. We quantified the relative prevalence of these responses in the wild using a Lagrangian approach. Specifically, we used temperature transmitting radio‐tags to track coastal cutthroat trout (Oncorhynchus clarkii clarkii) habitat use across 100 km of the Willamette River, which exhibited a maximum temperature of 22°C. We found that 89.8% of fish stayed in the mainstem and tolerated high temperatures; 6.5% of the population exploited cool floodplain alcoves; and 3.7% moved into a cool tributary, the McKenzie River. We also found that on average, larger fish opted to use cold‐water refuge habitats rather than tolerate mainstem river temperatures. The expression of all three coping tactics suggests this population has adaptive capacity to respond to future warming. More work is needed to understand how the relative expression of these tactics change depending on the severity of heat stress or nontemperature attributes of mainstem, floodplain, and tributary habitat.

Robust increase in population exposure to heat stress with increasing global warming

Extreme heat, particularly if combined with humidity, poses a severe risk to human health. To estimate future global risk of extreme heat with humidity on health, we calculate indicators of heat stress that have been commonly used: the Heat Index, the Wet-Bulb Globe Temperature and the Wet-Bulb Temperature, from the latest Climate Model Intercomparison Project (CMIP6) projections. We analyse how and where different levels of heat stress hazards will change, from severe to deadly, and how results are sensitive to the choice of the index used. We evaluate this risk at country-level and use population and GDPPPP growth scenario to estimate the vulnerability of each nation. Consistent with previous studies, we find that South and East Asia, and the Middle-East, are highly exposed to heat stress hazards, and that this exposure increases by 20%–60% with global mean temperature change from 1.5 to 3 ∘C. However, we also find substantial increases in heat health risk for some vulnerable countries with less adaptive capacity, such as West Africa, and Central and South America. For these regions, about 20 to more than 50% of the population could be exposed to severe heat stress each year on average, independent of the index used. For global warming of 3∘, European countries and the USA will also be exposed several times per year to conditions with daily mean heat stress level equal to the maximum heat stress of the 2003 heat wave.

PIF4 Promotes Expression of HSFA2 to Enhance Basal Thermotolerance in Arabidopsis.

Heat stress (HS) seriously restricts the growth and development of plants. When plants are exposed to extreme high temperature, the heat stress response (HSR) is activated to enable plants to survive. Sessile plants have evolved multiple strategies to sense and cope with HS. Previous studies have established that PHYTOCHROME INTERACTING FACTOR 4 (PIF4) acts as a key component in thermomorphogenesis; however, whether PIF4 regulates plant thermotolerance and the molecular mechanism linking this light transcriptional factor and HSR remain unclear. Here, we show that the overexpression of PIF4 indeed provides plants with a stronger basal thermotolerance and greatly improves the survival ability of Arabidopsis under severe HS. Via phylogenetic analysis, we identified two sets (six) of PIF4 homologs in wheat, and the expression patterns of the PIF4 homologs were conservatively induced by heat treatment in both wheat and Arabidopsis. Furthermore, the PIF4 protein was accumulated under heat stress and had an identical expression level. Additionally, we found that the core regulator of HSR, HEAT SHOCK TRANSCRIPTION FACTOR A2 (HSFA2), was highly responsive to light and heat. Followed by promoter analysis and ChIP-qPCR, we further found that PIF4 can bind directly to the G-box motifs of the HSFA2 promoter. Via effector–reporter assays, we found that PIF4 binding could activate HSFA2 gene expression, thereby resulting in the activation of other HS-inducible genes, such as heat shock proteins. Finally, the overexpression of PIF4 led to a stronger basal thermotolerance under non-heat-treatment conditions, thereby resulting in an enhanced tolerance to severe heat stress. Taken together, our findings propose that PIF4 is linked to heat stress signaling by directly binding to the HSFA2 promoter and triggering the HSR at normal temperature conditions to promote the basal thermotolerance. These functions of PIF4 provide a candidate direction for breeding heat-resistant crop cultivars.

Ocean Acidification Alleviates Dwarf Eelgrass (Zostera noltii) Lipid Landscape Remodeling under Warming Stress.

Simple SummaryExpected climate change scenarios will have inevitable and important impacts on key foundation marine species such as seagrasses. This study was aimed to understand how the dwarf eelgrass Zostera noltii leaf lipid landscapes are altered under predicted ocean warming (+4 °C) and acidification (ΔpH 0.4) conditions. A severe reduction in the leaf total fatty acid (FA) content was observed in seagrasses individually exposed to hypercapnic or warming conditions, and this depletion was ameliorated under combined exposure to ocean warming and acidification conditions. The tested treatments also impacted the FA composition of all lipid classes, with warming exposure leading to decreases in polyunsaturated fatty acids (PUFAs). Galactolipid remodeling seems to have key roles in the physiological changes observed in seagrasses under these tested conditions, highlighting the higher impact of warming and that the proposed stress alleviation effect induced by increased water-dissolved CO2 availability. Neutral lipids were substantially increased under warming conditions, mainly with increases in C18 FA, impairing their use as substrates to maintain the osmotic balance of the cells. Nonetheless, the pace at which ocean warming is occurring can overcome the ameliorative capacity induced by higher CO2 availability, leaving seagrasses under severe heat stress beyond their lipid-remodeling capacity.Coastal seagrass meadows provide a variety of essential ecological and economic services, including nursery grounds, sediment stabilization, nutrient cycling, coastal protection, and blue carbon sequestration. However, these ecosystems are highly threatened by ongoing climatic change. This study was aimed to understand how the dwarf eelgrass Zostera noltii leaf lipid landscapes are altered under predicted ocean warming (+4 °C) and hypercapnic (ΔpH 0.4) conditions. Warming and hypercapnic conditions were found to induce a severe reduction in the leaf total fatty acid, though the combined treatment substantially alleviated this depletion. The lipid discrimination revealed a significant increase in the relative monogalactosyldiacylglycerol (MGDG) content in both hypercapnic and warming conditions, allied to plastidial membrane stabilization mechanisms. Hypercapnia also promoted enhanced phosphatidylglycerol (PG) leaf contents, a mechanism often associated with thylakoid reinvigoration. In addition to changing the proportion of storage, galacto- and phospholipids, the tested treatments also impacted the FA composition of all lipid classes, with warming exposure leading to decreases in polyunsaturated fatty acids (PUFAs); however, the combination of both stress conditions alleviated this effect. The observed galactolipid and phospholipid PUFA decreases are compatible with a homeoviscous adaptation, allowing for the maintenance of membrane stability by counteracting excessive membrane fluidity. Neutral lipid contents were substantially increased under warming conditions, especially in C18 fatty acids (C18), impairing their use as substrates for fatty acylated derivatives essential for maintaining the osmotic balance of cells. An analysis of the phospholipid and galactolipid fatty acid profiles as a whole revealed a higher degree of discrimination, highlighting the higher impact of warming and the proposed stress alleviation effect induced by increased water-dissolved CO2 availability. Still, it is essential to remember that the pace at which the ocean is warming can overcome the ameliorative capacity induced by higher CO2 availability, leaving seagrasses under severe heat stress beyond their lipid remodeling capacity.

Effects of different protein levels on growth performance and stress parameters in beef calves under heat stress

This study investigated the effects of dietary protein levels under various heat stress (HS) conditions on the growth performance and stress parameters in Korean native beef calves. Male calves (n = 40; initial BW = 202.2 ± 3.31 kg) were randomly assigned to climatic-controlled chambers with 3 × 3 factorial arrangements. Calves were assigned into three dietary protein levels (low protein; LP = 12.5%, medium protein; MP = 15%, and high protein; HP = 17.5%) and three HS levels [mild: temperature-humidity index (THI) = 74 to 76, moderate: THI = 81 to 83, and severe: THI = 89 to 91] with control (threshold: THI = 70 to 73 and dietary protein level 12.5%). The calves were subjected to ambient temperature (22 °C) for 7 days and subsequently to the temperature and humidity corresponding to the target THI level for 21 days. The data were analyzed using the repeated-measures analysis by the GLM procedure of SAS. As a result, average daily gain (ADG) was decreased (P < 0.05) under severe HS level compared to the mild and moderate HS stress levels. However, HP increased ADG (P < 0.05) than moderate levels (LP) and severe levels (LP and MP). Under different HS levels (mild, moderate, and severe), HR, RT, and blood cortisol were increased (P < 0.05) compared to a threshold level, but no differences were observed in the parameters among various protein levels. Varied HS levels decreased the levels of blood glucose, NEFA, and amino acids (AAs) (lysine and glutamic acid) compared to a threshold (P < 0.05). But, the HP group resulted in increased (P < 0.05) levels of blood glucose, NEFA, and AAs (lysine and glutamic acid) compared to LP and MP groups under severe HS stress. The expression level of the HSP70 gene in peripheral blood mononuclear cell (PBMC) and hair follicles was increased (P < 0.05) following an increase in moderate and severe HS levels. Also, HSP70 gene expression in the HP group was decreased (P < 0.05) compared with LP and MP groups under intense HS level. Overall, HS in Korean native beef calves exhibited negative effects on ADG, blood glucose, NEFA, and AA profile. However, 17.5% of dietary protein (HP) could compensate for the growth of heat-exposed Korean native beef calves through the regulation of homeostasis by protein and energy metabolism. Also, it was evident that adequate protein (HP) is used as a major nutrient for HSP70 synthesis in PBMC and hair follicles causing, a boost in the immune system of heat-exposed Korean native beef calves.

Experimental Cyclic Heat Stress on Intestinal Permeability, Bone Mineralization, Leukocyte Proportions and Meat Quality in Broiler Chickens.

Simple SummaryRecently, our laboratory published a heat stress model to induce gastrointestinal leakage in broiler chickens. Nevertheless, the model describes continuous heat stress (HS) conditions from day 21 until 42 days of age. The current brief report intends to present an alternative model (12 h/day), particularly more in accordance with real-world conditions, to evaluate nutraceuticals or products that can reduce the severity of HS under experimental conditions. Results of this study confirm what has been extensively reported by numerous scientists. Cyclic HS increased leaky gut, reduced performance, bone mineralization, and meat quality in broiler chickens.The goal of this research was to assess cyclic heat stress on gut permeability, bone mineralization, and meat quality in chickens. Two separate trials were directed. 320 day-of-hatch Cobb 500 male chicks were randomly assigned to four thermoneutral (TN) and four cyclic heat stress (HS) chambers with two pens each, providing eight replicates per treatment in each trial (n = 20 chicks/replicate). Environmental conditions in the TN group were established to simulate commercial production settings. Heat stress chickens were exposed to cyclic HS at 35 °C for 12 h/day from days 7–42. Performance parameters, intestinal permeability, bone parameters, meat quality, and leukocyte proportions were estimated. There was a significant (p < 0.05) reduction in body weight (BW), BW gain, and feed intake, but the feed conversion ratio increased in chickens under cyclic HS. Moreover, HS chickens had a significantly higher gut permeability, monocyte and basophil levels, but less bone mineralization than TN chickens. Nevertheless, the TN group had significant increases in breast yield, woody breast, and white striping in breast fillets compared to HS. These results present an alternative model to our previously published continuous HS model to better reflect commercial conditions to evaluate commercially available nutraceuticals or products with claims of reducing the severity of heat stress.

Effect on physiological parameters and semen quality upon oral administration of fresh onion juice to V-line rabbit buck during severe heat stress

Severe heat stress is recognized as a factor that severely influences the semen quality and antioxidant status of rabbits. In this context, fresh onion juice (FOJ) may be a safe and useful option to improve reproductive performance. This research was designed to evaluate the anti-stress effects of FOJ on physiological and semen parameters in heat-stressed bucks. Thirty-six V-line rabbit bucks were randomly distributed into three groups. The bucks received FOJ orally at different doses [0 (water), 1.5, and 3 ml/kg live body weight] every 2 days over a period of 2 months, with 3 weeks as an adaptation period. FOJ treatments significantly improved semen characteristics, such as libido, mass and individual sperm motility, semen concentration, sperm viability, and acrosome reaction with increased initial seminal fructose, via the oral administration of 1.5 and 3 mL FOJ/kg body weight, compared with the findings in control bucks. Seminal plasma antioxidant status was significantly enhanced by FOJ treatments. It was concluded that the oral administration of FOJ under severe heat stress can improve bucks’ semen characteristics and sex hormone concentrations except for testosterone, and it is considered a good strategy for improving the heat resistance of rabbit bucks, possibly due to its antioxidant activity.

The Functional Interplay between Ethylene, Hydrogen Sulfide, and Sulfur in Plant Heat Stress Tolerance.

Plants encounter several abiotic stresses, among which heat stress is gaining paramount attention because of the changing climatic conditions. Severe heat stress conspicuously reduces crop productivity through changes in metabolic processes and in growth and development. Ethylene and hydrogen sulfide (H2S) are signaling molecules involved in defense against heat stress through modulation of biomolecule synthesis, the antioxidant system, and post-translational modifications. Other compounds containing the essential mineral nutrient sulfur (S) also play pivotal roles in these defense mechanisms. As biosynthesis of ethylene and H2S is connected to the S-assimilation pathway, it is logical to consider the existence of a functional interplay between ethylene, H2S, and S in relation to heat stress tolerance. The present review focuses on the crosstalk between ethylene, H2S, and S to highlight their joint involvement in heat stress tolerance.

High-Throughput Screening of Microbial Isolates with Impact on &lt;em&gt;Caenorhabditis elegans&lt;/em&gt; Health

With its small size, short lifespan, and easy genetics, Caenorhabditis elegans offers a convenient platform to study the impact of microbial isolates on host physiology. It also fluoresces in blue when dying, providing a convenient means of pinpointing death. This property has been exploited to develop high-throughput label-free C. elegans survival assays (LFASS). These involve time-lapse fluorescence recording of worm populations set in multiwell plates, from which population median time of death can be derived. The present study adopts the LFASS approach to screen multiple microbial isolates at once for the effects on C. elegans susceptibility to severe heat and oxidative stresses. Such microbial screening pipeline, which can notably be used to prescreen probiotics, using severe stress resistance as a proxy for host health is reported here. The protocol describes how to grow both C. elegans gut microbiota isolate collections and synchronous worm populations in multiwell arrays before combining them for the assays. The example provided covers the testing of 47 bacterial isolates and one control strain on two worm strains, in two stress assays in parallel. However, the approach pipeline is readily scalable and applicable to the screening of many other modalities. Thus, it provides a versatile setup to rapidly survey a multiparametric landscape of biological and biochemical conditions that impact C. elegans health.