Hours Of Heat Stress Research Articles

Challenges for heat stress: Intestinal culturable bacteria of Lohmann Brown chickens

This study aimed to assess how heat stress, specifically within the range of 35–38 °C, affects the populations of culturable intestinal lactobacilli, enterococci, and Escherichia coli, as well as the expression of Heat Shock Proteins (HSP70), in Lohmann Brown chickens. It also explored the influence of the chickens' blood transferrin and ceruloplasmin genotypes on these responses. Thirty chickens underwent eight hours of heat stress, maintained at an average temperature of 37 °C and a relative humidity of 75–80%, with continuous access to food and water. Behavioral monitoring was conducted throughout to prevent excessive heat-related mortality. The Lohmann Brown chickens from the Yerevan “Arax” poultry farm were initially classified based on their blood transferrin and ceruloplasmin genotypes to investigate potential correlations between intestinal bacterial composition and variations in these polymorphisms. A significant correlation was found between heat stress and the abundance of culturable enterococci within the intestinal microbiota, regardless of chicken TfAB, TfBC, CpAB, CpCC and TfAB, TfBC, CpAB, CpCD genotypes. Heat stress led to nearly double the HSP70 levels in chicken blood, along with a reduction in the culturable enterococci population by at least 10,000-fold in the intestinal microbiota. These findings are significant for targeted management strategies to mitigate heat stress in chicken populations.

High-resolution projections of outdoor thermal stress in the twenty-first century: a Tasmanian case study

To adapt to Earth’s rapidly changing climate, detailed modelling of thermal stress is needed. Dangerous stress levels are becoming more frequent, longer, and more severe. While traditional measurements of thermal stress have focused on air temperature and humidity, modern measures including radiation and wind speed are becoming widespread. However, projecting such indices has presented a challenging problem, due to the need for appropriate bias correction of multiple variables that vary on hourly timescales. In this paper, we aim to provide a detailed understanding of changing thermal stress patterns incorporating modern measurements, bias correction techniques, and hourly projections to assess the impact of climate change on thermal stress at human scales. To achieve these aims, we conduct a case study of projected thermal stress in central Hobart, Australia for 2040–2059, compared to the historical period 1990–2005. We present the first hourly metre-scale projections of thermal stress driven by multivariate bias-corrected data. We bias correct four variables from six dynamically downscaled General Circulation Models. These outputs drive the Solar and LongWave Environmental Irradiance Geometry model at metre scale, calculating mean radiant temperature and the Universal Thermal Climate Index. We demonstrate that multivariate bias correction can correct means on multiple time scales while accurately preserving mean seasonal trends. Changes in mean air temperature and UTCI by hour of the day and month of the year reveal diurnal and annual patterns in both temporal trends and model agreement. We present plots of future median stress values in the context of historical percentiles, revealing trends and patterns not evident in mean data. Our modelling illustrates a future Hobart that experiences higher and more consistent numbers of hours of heat stress arriving earlier in the year and extending further throughout the day.

Impacts of climate change on slow metabolism mammals: An ecophysiological perspective

The particular metabolism of armadillos, anteaters and pangolins may have important consequences for their vulnerability to climate change, which have not been studied so far regarding in its ecophysiological aspects. Studies have emphasized that integrating correlative and mechanistic ecological niche models (ENM) is an efficient strategy to estimate species distribution under climate change as it provides a more complete picture of the species' response than if they were performed separately. We evaluate the vulnerability of three Xenarthrans and one Pholidota (animals from the neotropics and Southeast Asia, respectively), under climate change using an integrative approach. This is the first study that performed an integrative ENM for armadillos, anteaters, and pangolins, including thermal tolerance aspects into the model. For all species, the hours of heat stress in the future were greater than under current conditions, except for the anteater which remained stable. Inside of their thermal refuge, however, they will not be exposed to heat stress. Therefore, it is possible that the semi-fossorial species would spend more time inside their burrows in a warmer scenario, reducing their time and energy spent on reproductivity and foraging activities, for example. The species distributions might expand in the future for all species (increasing 6% to 164%, depending on the species). Considering the thermal pressure imposed by climate change on these animals, the range expansion would not be expected. However, the target species are non-endemic and are currently widely distributed, which normally indicate lower vulnerability to climate change. Despite the projected range expansion, the synergy between the increased heat stress we predicted and other threats such as hunting pressure and habitat loss are also a great concern for the conservation of these unique animals. Therefore, these results imply that even predicting a potential expansion of these species distribution, they need to be monitored because they might experience thermal stress in addition to other pressures from human activities.

Redox state and metabolic responses to severe heat stress in lenok Brachymystax lenok (Salmonidae).

In order to provide new insights into the physiological responses of lenok (Brachymystax lenok: Salmonidae) to acute and severe heat stress (25°C, 48h), dynamic changes in redox state and metabolic responses are studied combined biochemical index and non-targeted metabolome. Nicotinamide adenine dinucleotide (NAD+) consumption causes significant increases in ratio of reduced NADH to NAD+ and ratio of reduced nicotinamide adenine dinucleotide phosphate (NADPH) to NADP+, which induced the redox imbalance in heat stressed lenok. Lowered reduced glutathione/oxidized glutathione (GSH/GSSG) ratios suggested that more oxidized conditions occurred in heat-stressed lenok, leading to membrane lipid oxidation. The first few hours of heat stress promoted the activity of enzymes involved in anaerobic glycolysis (hexokinase, pyruvate kinase, lactic dehydrogenase) and glutamicpyruvic transaminase and glutamic oxaloacetic transaminase, which might lead to consumption of many carbohydrates and amino acid catabolism. These enzyme activities decreased with time in a possible compensatory strategy to manage anabolic and catabolic metabolism, maintaining the redox homeostasis. After 48 h of recovery, NAD+, carbohydrate levels and enzyme activities had returned to control levels, whereas many amino acids were consumed for repair and new synthesis. GSH remained at levels lower than controls, and the more oxidized conditions had not recovered, aggravating oxidative damage. Glutamic acid, glutamine, lysine and arginine may play important roles in survival of heat-stressed lenok.

Chloroplast-localized GUN1 contributes to the acquisition of basal thermotolerance in Arabidopsis thaliana.

Heat stress (HS) severely affects different cellular compartments operating in metabolic processes and represents a critical threat to plant growth and yield. Chloroplasts are crucial for heat stress response (HSR), signaling to the nucleus the environmental challenge and adjusting metabolic and biosynthetic functions accordingly. GENOMES UNCOUPLED 1 (GUN1), a chloroplast-localized protein, has been recognized as one of the main players of chloroplast retrograde signaling. Here, we investigate HSR in Arabidopsis wild-type and gun1 plantlets subjected to 2 hours of HS at 45°C. In wild-type plants, Reactive Oxygen Species (ROS) accumulate promptly after HS, contributing to transiently oxidize the cellular environment and acting as signaling molecules. After 3 hours of physiological recovery at growth temperature (22°C), the induction of enzymatic and non-enzymatic antioxidants prevents oxidative damage. On the other hand, gun1 mutants fail to induce the oxidative burst immediately after HS and accumulate ROS and oxidative damage after 3 hours of recovery at 22°C, thus resulting in enhanced sensitivity to HS. These data suggest that GUN1 is required to oxidize the cellular environment, participating in the acquisition of basal thermotolerance through the redox-dependent plastid-to-nucleus communication.

Comparative analysis of heat‐stress‐induced abscisic acid and heat shock protein responses among pea varieties

AbstractHeat shock proteins (HSPs) and abscisic acid (ABA) play important roles in plant heat responses but have not been extensively studied in pea (Pisum sativum L.), whose heat susceptibility is well known. In this study, four pea varieties varying in heat tolerance based on field trials were evaluated. Plants were heat stressed for 3, 6, 12, or 24 h at 38 °C before pollination. Anther and stipule RNA from the same flowering node were sampled for transcriptional profiling of PsHSP18.1 and PsHSP71.2. Additional stipules were sampled for the quantification of ABA concentration and its five key catabolites from the four major ABA catabolic pathways by ultra‐high performance liquid chromatography–selected reaction monitoring mass spectrometry (UHPLC‐SRM/MS). The transcription of both HSP genes was upregulated because of heat stress (HS). In stipules, the upregulation was greatest at 3 h HS, whereas in anthers, the induced transcription was similar among different hours of HS. Likewise, more ABA accumulated in the ABA metabolism pool because of HS, and the ABA response started rapidly after 3 h of treatment. Heat‐tolerant varieties had a higher ABA synthesis and turnover rate at 3 h HS than their respective heat‐susceptible counterparts. This study provides new insights into different heat tolerance among Canadian pea varieties regarding HSP and ABA hormone regulation.

Two hours of heat stress induces MAP-kinase signaling and autophagasome accumulation in C2C12 myotubes.

Short bouts of heat can induce a hormetic stress response, whereas prolonged or excessive exposure can elicit detrimental effects. We previously demonstrated an increase in autophagic signaling in C2C12 myotubes in response to 1 h of heat at 40 °C. In opposition, longer durations of heat exposure (e.g., 12 and 24 h) lead to an accumulation of autophagasomes and elevations in markers of cellular inflammation, oxidative stress, and apoptosis. Whether a longer, yet moderate, duration of 2 h of heat further enhances autophagic flux and attenuates stress and inflammatory signaling, or transitions the cell toward a dysregulation of autophagy is unclear. In this study, C2C12 myotubes were maintained at 37 °C or exposed to 40 °C (HT) for 2 h, and harvested immediately or following 2, 8, or 24 h of recovery. Two hours of HT immediately increased pAMPK (T172; p = 0.001), and subsequently increased pULK1 (S555) at 2 h of recovery (p = 0.028). LC3 II was increased at 8 h (p = 0.043) and 24 h (p = 0.015) of recovery, whereas p62 was elevated at 2 h (p = 0.002) and 8 h (p < 0.001) of recovery, but returned to baseline by 24 h. In Bafilomycin A1 treated cells, p62 was further increased immediately following HT (p = 0.041). There was also a significant elevation in p-p38 (Thr180/Try182), pJNK (Thr183/Tyr185), and pNFκB (Ser536). These findings suggest that as short as 2 h of heat exposure contributes to cell stress and accumulation of autophagasomes in skeletal muscle.

THE EFFECT OF GLUCOSE AND SUCROSE ON THE PHOTOSYNTHETIC PIGMENTS CONTENT IN ARABIDOPSIS THALINA UPON HEAT STRESS

An increase in the Earth's average temperature has a negative effect on the development, growth and productivity of cultivated plants. One of the main metabolic damages caused by exposure to elevated temperatures is excessive production of reactive oxygen species (ROS). ROS, accumulating in chloroplasts, cause significant damage to the photosynthetic apparatus of plants, destroying the chloroplast membrane and damaging pigments. Carbohydrates play a key role in the regulation of the processes of photosynthesis, respiration, seed germination, flowering and aging of plants. Carbohydrates are chemical signaling and sensitive molecules that receive a specific signal under normal conditions and under the influence of stress factors. The aim of our work was to study the effect of exogenous sucrose and glucose on the content of photosynthetic pigments in A. thaliana plants under the influence of heat stress. Two lines of arabidopsiswere used for research: wild-type plants and cat2cat3 knockout line with lacking isoforms of catalase, the main antioxidant enzyme. The plants were grown under conditions of 16-hour daylight at a constant temperature of + 28º C, air humidity of 70% and illumination of 2.5 kL. Treatment was perfomed in the dark for 2 and 4 hours at temperatures of +37 (moderate stress) and +44°C (severe stress treatment). Contorl Plants were incubated in a potassium-phosphate buffer without the addition of sucrose and glucose at a temperature of +20° C. It was shown that the content of chlorophyll a, b and carotenoids in intact plants of the wild type and the knockout line was the same. Under the influence of heat stress, the content of the studied pigments in the presence of sucrose did not change in both lines. During heat stress in the presence of glucose, changes were noted during the 4-hour stress. It was shown that in the control plants incubated at room temperature in the presence of glucose, the content of chlorophyll a and carotenoids increased in wild type. Upon severe heat stress (+44°С), a decrease in the pigment content was jbserved. The data obtained indicate that in conditions of 4 hours of heat stress, exogenous glucose is involved in the plant cell stress response. No changes in the content of chlorophyll and carotenoids were observed in knockout line cat2cat3.

A less data demanding ecophysiological niche modeling approach for mammals with comparison to conventional correlative niche modeling

Ecophysiological models are more data demanding and, consequently, less used than correlative ecological niche models to predict species’ distribution under climate change, especially for endotherms. Hybrid models that integrate both approaches are even less used, and several aspects about their predictions (e.g. accuracy, geographic extent and uncertainty) have been poorly explored. We developed a hybrid model for mammals using hours of activity and hours of heat stress as mechanistic variables, fitted using macroclimatic data and applied to conventional correlative modeling. We then compared the outputs from conventional correlative models with our hybrid model for 58 tropical mammals in term of accuracy, uncertainty, and predicted geographic distribution under climate change. We expected that hybrid models to have higher accuracy than correlative ones, with difference in predicted geographic distribution extent. We found no substantial differences between correlative and hybrid predictions for accuracy, uncertainty, and extent. Although the area predicted as suitable did not differ in extent, they differ in location, with lower congruence between models for future prediction. This result challenged the widespread assumption that hybrid models are more accurate. The ecophysiological model approach proposed here ease ecophysiological data requirements. We propose, therefore, choosing model approach based on study's objective, rather than on data requirements or the assumption that hybrid models have better predictions. The main advantage of the hybrid model is in providing a more complete view of the species response, as proximal (causal) and distal (environment) aspects are combined.

Which factor is more important: Intensity or duration of episodic heat stress on broiler chickens?

With the current global warming, there is a predicted increase in frequency, intensity and duration of heat waves in future. Little is known of how this could affect the welfare of broiler chickens. Sixty-four broiler chickens were subjected to either high heat stress (HHS; 32°C, 70% RH for 3h), moderate heat stress (MHS; 30°C, 70% RH for 6h), or normal conditions (NC: 20°C, 50% RH for 6h) for two consecutive days. On both days, the temperature-ID chips on all chipped birds were scanned during pre-heat stress (PrHS), end of 3h (3HS) and 6h (6HS) of heat stress using a pocket reader. Half of the chip birds' CBT was measured at the end of each hour of heat stress (HS: 1st -3rd hour). Surface body temperatures (SBTs) from under the wing (WT), feet (FT), cloaca (CLT) and comb (CT) were measured. Blood samples, feed intake, daily weight gain and mortality was also monitored. Data was analysed using General Linear Model and simple linear regression. At 3HS, CBT/ΔCBT and all SBTs showed this trend: HHS>MHS>NC (P<0.001). The regression equations to predict ΔCBT in HHS and MHS are ΔCBT=0.917+0.663h, P<0.05 and ΔCBT=0.371+0.338h, P<0.05 respectively. Blood pH, pCO2, iCa, HCO3- and TCO2 showed same trend: HHS, MHS>NC (P<0.05). Comparing HHS for 3h with MHS and NC for 6h shows that CBT/ΔCBT, WT and CLT in HHS, MHS>control (P<0.001) while FT and CT showed a different trend (HHS > MHS > NC, P<0.001). pCO2, feed intake and daily weight gain showed same trend (HHS, MHS > control). Temperature-ID chip (a less invasive technique) gave CBT/ΔCBT values that corresponded with the degree of heat stress experienced by the birds. Broilers were more tolerant to MHS than HHS after 3h but MHS for 6h and HHS for 3h had similar impact.

Interactions between the cannabinoid and the serotonergic systems in modulation of pain perception

The aim of our study was to evaluate the effects of cannabinoids and serotonergic system on nociception in intact rats and after heat stress. Cannabinoid receptor type 1 (CB1) and 5-hydroxytryptamine receptor (5НТ1А) agonists and antagonists have been administered according to different experimental designs (alone and in combinations) in intact male Wistar rats, as well in animals subjected to one hour of heat stress. Pain perception has been evaluated by Paw pressure test. Our results pointed out that cannabinoids and the serotonergic system interact in nociception in intact animals as well as after heat stress. Cannabinoids seemed to have less prominent role in such interaction in intact animals than after heat stress. The interplay between the two systems probably involves different mechanisms in intact animals and after heat stress with time-dependent effects. The interaction between the cannabinoid and the serotonergic systems exerts a modulating rather than mediating effect on h-SIA.

Interactions between the endogenous cannabinoid system and the peptides of the Tyr-MIF-1 family modulate heat stress-induced analgesia

The present study aimed at evaluating whether an interaction between the endocannabinoid system (ECS) and peptides from the Tyr-MIF-1 family modulates heat stress-induced analgesia. For this purpose, adult male rats were subjected to 1 hour of heat stress. Pain perception was estimated in vivo by Paw pressure test. Immunohistochemical evaluation of CB1 receptors was also performed in the periaqueductal grey (PAG). Our results showed that the application of CB1-receptor agonist anandamide at the end of the stress led to a tendency of decrease in heat-SIA. We also found that each of the four Tyr-MIF-1 peptides interacted with the ECS after acute heat stress, resulting in changes in the PP-thresholds with different direction, degree, and duration. In particular, the administration of MIF-1 and Tyr-K-MIF-1 after CB1-receptor agonist anandamide increased heat stress-induced analgesia (heat-SIA) after the 10th min, while Tyr-MIF-1 and Tyr-W-MIF-1 produced only short-lasting analgesia. CB1-expression in the PAG was also estimated, showing an increase after Tyr-MIF-1 and Tyr-W-MIF-1 administration with anandamide pretreatment, and a decrease after Tyr-W-MIF-1 administration with the CB1-receptor antagonist AM251- or the opioid receptor antagonist naloxone pretreatment. In summary, it can be inferred that under heat stress conditions the peptides from the Tyr-MIF-1 family, interacting with opioid and non-opioid receptors, differently relate with the cannabinoid system and such an interaction modulates heat stress-induced analgesia. It also seems that Tyr-MIF-1 and Tyr-W-MIF-1 have a direct impact on CB1-expression in the PAG, while MIF-1 and Tyr-K-MIF-1 probably act via second messengers or the activation of additional neurotransmitter system(s).

Effect of early age heat stress on growth performance and some blood parameters of two strains of rabbits

The main objective of the present study was to evaluate the effect of short term Heat Stress on productive performance and some blood parameters in two strains of growing rabbits. A total number of 60 weaned unsexed rabbits (6 weeks of age) were used in this study (30 from each of New Zealand White, NZW, and Local Baladi Black, BB rabbits). They were randomly divided into two experimental groups: a control group and heat stressed one. The latter group was exposed to four hours of heat stress at 36 ± 1 ⁰C and 55 – 60% RH for three consecutive days at 42 days of age. The same manner was applied after six weeks of age (at marketing). After HS exposure, three rabbits from each treatment were used to determine some blood parameters, heat shock protein (HSP 70, 90); Growth performance data were also recorded. Results showed that daily weight gain was significantly increased in heat stressed rabbits than control, while feed consumption was significantly reduced in NZW rabbits, resulting in an improvement in FCR of NZW rabbits than BB. Heat stress (p≤0.05) increased plasma total protein, albumin and Globulin than control group, while A/G ratio was not influenced. Baladi Black rabbits had significantly lower IGF and Corticosterone level compared by NZW rabbits, while T3 hormone level was not significantly affected. HS increased (p ≤ 0.05) IGF and Corticosterone levels. A significant interaction effect between HS and breed was recorded for all studied hormones. Heat shock protein were significantly increased in local BB rabbits compared to NZW ones. It is concluded that it is concluded that early age heat exposure of weaning rabbits could be used as an alternative tool to alleviate the negative impact of heat stress at older age. We chose two strains of rabbits (BB NZW) because they the most common types in our country.

Use of a Water‐soaked Garment, with and without an Electric Fan, to Mitigate Thermal Strain in Older Individuals under Heat Wave Conditions

As average global surface temperatures are projected to rise, and heat waves are expected to increase in frequency, duration, and intensity, exposure to high levels of heat stress will occur with greater regularity. Older individuals are particularly vulnerable to heat stress, evidenced by excess hospitalizations and mortality among individuals aged &gt;60 years. With the continue rise of electricity costs coupled with vulnerable regions that do not have easy access to air conditioning, it is imperative to find alternative cooling strategies that are cost‐effective and accessible for older individuals. The present study evaluated whether wearing a water‐soaked t‐shirt, with and without electric fan use, mitigates thermal and cardiovascular strain under heat wave conditions. Nine healthy older individuals (68 ± 4 years; five females) completed three, 120‐min heat exposures (42.4 ± 0.2°C, 34.2 ± 0.9% relative humidity) on separate occasions while wearing either a dry t‐shirt (CON), a t‐shirt soaked with 500 ml of tap water (WET), or a t‐shirt soaked with 500 ml of tap water while facing an electric fan forcing air at 2.4 ± 0.4 m/s (WET+FAN). Measurements included core and mean skin temperatures, evaporative mass loss, heart rate, and blood pressure. The rise in core temperature was attenuated by ~0.3°C in WET compared to DRY and WET+FAN during the first hour of heat stress (P &lt; 0.01). At 120 min, the rise in core temperature remained attenuated by ~0.2 °C in WET compared to DRY (P=0.0016), while other comparisons were not different. After the 120‐min heat exposure, changes in body mass, which largely reflect evaporation of sweat and moisture trapped in clothing, were greatest in WET+FAN, followed by WET, and then DRY (P &lt; 0.01). However, sweat losses were lowest in WET, followed by DRY, and then WET+FAN (P &lt; 0.01). Heart rate was lower during the first hour in WET vs. DRY, and at 30 min only in WET vs. WET+FAN (P &lt; 0.01). No differences in mean arterial pressure were found (P = 0.51). In conclusion, simply wearing a water‐soaked t‐shirt is an effective heat management strategy to mitigate thermal and cardiovascular strain and lower sweat losses in older people exposed to heat wave conditions. Conversely, the cooling benefits of a water‐soaked t‐shirt are eliminated when used in combination with a fan.Support or Funding InformationFunding: National Institutes of Health (R01GM068865) and Department of Defense – US Army (W81XWH‐15‐1‐0647)

Astaxanthin supplementation impacts the cellular HSP expression profile during passive heating.

Astaxanthin is a powerful carotenoid antioxidant prevalent in marine organisms and approved as a food supplement. Recent studies have demonstrated Astaxanthin's beneficial attributes in various health states. Following initial reports of potential heat protective properties in Astaxanthin supplemented rats, we present here results of a novel study examining the effect of Astaxanthin supplementation on the heat shock response in rats in relation to core temperature (Tc) and the ensuing physiological strain. Two hours of heat stress at 41°C during which rats developed their thermoregulatory hyperthermic plateau resulted in progressive increases in HSP72 and HSP27 in the Astaxanthin (Oleoresin)-treated group but not in the control (Olive oil) group. Enhanced elevation in HSPs suggests that Astaxanthin supplementation may augment the cellular stress protective response to heat stress.

Rosemary Reduces Heat Stress by Inducing CRYAB and HSP70 Expression in Broiler Chickens.

Heat stress negatively affects poultry production and animal health. In response, animals invoke a heat stress response by inducing heat shock proteins (HSPs). Scientists are actively seeking natural products that can enhance the heat shock response. The present study aimed at assessing the effects of a purified rosemary extract comprising antioxidant compounds on the heat shock response and HSP expression profile in broiler chickens. The response of broilers to HS in the presence of purified rosemary extract was assessed using an in vivo myocardial cell model. Pathological lesions of heart tissue were examined microscopically. The levels and activities of enzymes associated with heart damage and oxidative damage were detected. Immunohistochemical staining was performed for HSPs in myocardial cells. The results showed that lactate dehydrogenase (LDH), creatine kinase (CK), and myocardial CK (CKMB) levels were reduced by the purified rosemary extract before and during heat stress. Heat stress alone increased CK and CKMB levels. The levels of oxidative damage-associated enzymes were compared between the rosemary + heat stress and heat stress-alone groups. The results indicated that in terms of these enzymes, the purified rosemary extract induced a more antioxidative state. Pathological examinations showed that heat stress caused myocardial fiber fracture, karyopyknosis, and degeneration. The addition of purified rosemary extract ameliorated these lesions to some degree, preserving more of the basic structure. Heat stress decreased the cellular levels of crystallin alpha B (CRYAB) and HSP70. The addition of the purified rosemary extract significantly increased the levels of CRYAB and HSP70 during heat stress (p < 0.0001). Immunohistochemistry showed that after rosemary treatment, CRYAB and HSP70 showed more intense staining compared with the no heat stress control group. In the rosemary + heat group, after 10 hours of heat stress, the staining intensity of these two proteins remained higher than in the heat stress group. Thus, purified rosemary extract could induce high levels of HSP70 and CRYAB in chicken hearts before and during heat stress. Purified rosemary extract could be used to alleviate heat stress in broiler chickens.

Temporal dynamics of gene expression in heat-stressed Caenorhabditis elegans.

There is considerable insight into pathways and genes associated with heat-stress conditions. Most genes involved in stress response have been identified using mutant screens or gene knockdowns. Yet, there is limited understanding of the temporal dynamics of global gene expression in stressful environments. Here, we studied global gene expression profiles during 12 hours of heat stress in the nematode C. elegans. Using a high-resolution time series of increasing stress exposures, we found a distinct shift in gene expression patterns between 3–4 hours into the stress response, separating an initially highly dynamic phase from a later relatively stagnant phase. This turning point in expression dynamics coincided with a phenotypic turning point, as shown by a strong decrease in movement, survival and, progeny count in the days following the stress. Both detectable at transcriptional and phenotypic level, this study pin-points a relatively small time frame during heat stress at which enough damage is accumulated, making it impossible to recover the next few days.

Effects of heat stress on the renal and branchial carbohydrate metabolism and antioxidant system of Antarctic fish.

The objective of the present study was to assess the effect of short-term (2-144h) heat stress (8 °C) on energy production processes and antioxidant defense systems in the kidneys and gills of Notothenia rossii and Notothenia coriiceps. Heat stress affected energy metabolism and oxidative stress parameters in a time-, tissue-, and species-dependent manner, and gills were more sensitive than kidneys to heat stress. N. rossii kidneys were able to stabilize carbohydrate metabolism after 12h of heat stress, whereas the glycogen levels in N. coriiceps kidneys fluctuated in response to varying glucose-6-phosphatase (G6Pase) levels. The gills of N. rossii were able to stabilize their energy demand and aerobic metabolism under heat stress, whereas in the gills of N. coriiceps, changes in carbohydrate metabolic pathways depended on the exposure time: initially, anaerobiosis was activated after 6h; the energy demand, characterized by glycogen consumption, increased after 72h, and aerobic metabolism was activated within 144h. With regard to the antioxidant defenses of the N. rossii kidney, it was found that levels of antioxidant enzymes were reduced during the first hours of heat stress, contributing to increased lipid peroxidation, whereas N. coriiceps kidneys did not show signs of oxidative damage. The gills of N. rossii exhibited more pronounced oxidative damage in response to heat stress than those of N. coriiceps despite the presence of increasing levels of antioxidants, likely due to tissue hypoxia.

Heat Stress Affects Pi-related Genes Expression and Inorganic Phosphate Deposition/Accumulation in Barley

Phosphorus (P) in plants is taken from soil as an inorganic phosphate (Pi) and is one of the most important macroelements in growth and development. Plants actively react to Pi starvation by the induced expression of Pi transporters, MIR399, MIR827, and miR399 molecular sponge – IPS1 genes and by the decreased expression of the ubiquitin-conjugating enzyme E2 (PHOSPHATE2 – PHO2) and Pi sensing and transport SPX-MFS genes. The PHO2 protein is involved in the degradation of Pi transporters PHT1;1 (from soil to roots) and PHO1 (from roots to shoots). The decreased expression of PHO2 leads to Pi accumulation in shoots. In contrast, the pho1 mutant shows a decreased level of Pi concentration in shoots. Finally, Pi starvation leads to decreased Pi concentration in all plant tissues. Little is known about plant Pi homeostasis in other abiotic stress conditions. We found that, during the first hour of heat stress, Pi accumulated in barley shoots but not in the roots, and transcriptomic data analysis as well as RT-qPCR led us to propose an explanation for this phenomenon. Pi transport inhibition from soil to roots is balanced by lower Pi efflux from roots to shoots directed by the PHO1 transporter. In shoots, the PHO2 mRNA level is decreased, leading to an increased Pi level. We concluded that Pi homeostasis in barley during heat stress is maintained by dynamic changes in Pi-related genes expression.

Chronology of Early Heat Stress Mediated Changes in Oxidative Skeletal Muscle

We have previously reported that 24 hours of heat stress (HS) induced free radical injury in oxidative skeletal muscle. In addition, we found widespread aberrant intracellular signaling following 12h of HS. The aim of this investigation was to extend our knowledge regarding the early chronology of HS‐mediated intracellular signalling in oxidative skeletal muscle. We hypothesized that 2, 4, and 6 hours of HS would result in increased autophagy and decreased mitochondrial content in oxidative skeletal muscle compared to muscle maintained under thermoneutral (TN) conditions. To address this hypothesis, pigs were assigned to four groups (n=8/group) and housed under TN conditions (21°C) or exposed to HS (37°C) for 2, 4, or 6 hours. Next, animals were euthanized and the semitendinosus red (STR) was collected and analyzed. Compared to TN, relative protein abundance of autophagy initiators phosphoinositide 3‐kinase Class III and Beclin‐1 were increased by 57% and 56%, respectively (p&lt;0.05), following 6 hours of HS. At the same time point, relative abundance of the pre‐autophagosomal structure stabilizer, autophagy‐related protein 16‐1 (ATG16), was increased 59% (p&lt;0.05). Microtubule‐associated protein A/B light chain 3 (LC3)‐I was similar between all four groups but the autophagosome formation marker LC3‐II was increased by 94% (p&lt;0.05) following 6 hours of HS compared to TN. This resulted in a 2‐fold increase in the LC3II/I ratio (p&lt;0.05), which is indicative of increased autophagic flux, though sequstome‐1 (p62) protein abundance was similar between groups. In addition, the mitophagy marker, BCL2/adenovirus E1B protein‐interacting protein 3‐like (BNIP3), was increased by 41% (p&lt;0.05) following 6 hours of HS compared to TN. Relative protein abundance of TCA enzymes, electron transport chain components, and mitochondrial markers was similar between groups. These data demonstrate that short‐term HS induced autophagy/mitophagy. Together with our previous work we also suggest thatbetween 6 and 12 hours of HS the intracellular environment of oxidative skeletal muscle switches from one that promotes autophagy to one that inhibits it.Support or Funding InformationThis work supported by USDA grants 2014‐67015‐21627 and 2011‐67003‐30007.