Heat Stress Temperature Research Articles

Effects of L-proline on cellular responses of hen erythrocytes subjected to thermal stress.

Little is known on the protective effects of L-proline on hen erythrocytes. The aim of the study was to determine the protective effects of this amino acid at concentrations of 50μg/mL, 100μg/mL, 200μg/mL in hen erythrocytes subjected to temperatures 41°C, 43°C and 45°C for 1h and 4h. The following cellular parameters were determined: viability, morphological alterations, caspase 3/7 activity, heat shock protein HSP70 1A activity and glutathione level. The results showed that exposure to 43°C and 45°C resulted in a decrease of viability and increased morphological alterations of the non-treated erythrocytes. Caspase 3/7 activity was increased only at 45°C, however HSP70 1A activity and glutathione level were increased in the temperature-dependent manner. On the other hand, erythrocytes additionally exposed to L-proline showed alterations of the parameters when compared to the non-treated cells. L-proline at 50μg/mL and 100μg/mL increased caspase 3/7 activity at both 41°C and 43°C, however it was less augmented at all the concentrations at 45°C. Glutathione level was decreased in heat-stressed (at 43°C and 45°C) hen erythrocytes treated with L-proline (at 50μg/mL and 100μg/mL) but it was increased at 200μg/mL. HSP70 1A activity was augmented in a concentration- and temperature-dependent manner. The results indicate that proapoptotic or antiapoptotic effects of L-proline depend on its concentration and temperature of heat stress and thermoprotective effects induced by the amino acid on some parameters in hen erythrocytes may be a result of stimulation of antioxidative defense and stimulation of HSP70 1A activity.

Phosphatidic acid and hydrogen peroxide coordinately enhance heat tolerance in tall fescue.

Phosphatidic acid (PA) and hydrogen peroxide (H2 O2 ) play roles in regulating plant responses to abiotic stress. The objective of this study was to determine effects of H2 O2 or PA, individually and interactively, with a H2 O2 scavenging molecule, N,N'-dimethylthoiurea (DMTU), on plant tolerance to heat stress in tall fescue (Festuca arundinacea). Plants were treated with PA (25µm), H2 O2 (5mm) and PA (25µm)+DMTU (5mm) by foliar application and then exposed to heat stress (38/33°C) or optimal temperature (23/18°C, day/night) for 28days. Foliar application of PA and H2 O2 alone resulted in increases in leaf fresh weight, chlorophyll content, photochemical efficiency and cellular membrane stability in plants exposed to heat stress, whereas addition of DMTU suppressed the positive effects of PA. Expression levels of genes encoding the PA synthesizing enzyme, FaPLDδ, were significantly up-regulated by H2 O2 . Phosphatidic acid- or H2 O2 -enhanced heat tolerance was associated with the activation of stress signalling components (FaCDPK3, FaMPK6, FaMPK3), transcription factors (FaMBF1 and FaHsfA2c) and heat shock proteins (FaHSP18, FaHSP70 and FaHSP90). Phosphatidic acid and H2 O2 may work in coordination to further improve heat tolerance, involving up-regulation of transcription factors in stress signalling cascades and heat protection systems.

The Effect of Heat Stress on Milk Yield, Milk Fat Rate and Rectal Temperature in Holstein-Friesian Dairy Cattle

Heat stress is an environmental factor that negatively affects the morphological and physiological properties of dairy cattle. The aim of this study is to investigate the relationship between heat stress and milk yield, milk fat ratio and body temperature in Holstein-Friesian dairy cattle. Data Southeastern Anatolia Region of Turkey's Siirt province was obtained from a special Kurtalan Farm. Milk yield and content of 13 head Holstein-Friesian dairy cattle were recorded in March, April, May, June, July, August and September. In addition, temperature and humidity records were recorded in the farm and in the parlor to be used for calculating the temperature humidity index value. In the analysis of data, correlation and regression methods were used in SAS 9.4 program. As a result, positive correlation (P <0.001), milk yield and milk fat ratio and negative correlation (P <0.05, P <0.01) were detected between heat stress and body temperature. In addition, a significant negative relationship was observed between rectal temperature and milk yield (P <0.01).

PSI-9 Effect of Pen-Surface Temperature and Trace Mineral Source on Infrared Hide Temperature in Cattle Raised in Confinement Under a Natural-Feeding Protocol in Summer

Abstract Thirty-two pens housing between 249–282 beef cattle each were blocked by arrival date and sex and used to investigate effects of pen-surface temperature, trace mineral source and sex on hide temperature. A randomized complete block design was used with 2 treatments: 1) Control, with inorganic sources for all trace minerals of interest; and 2) Test, with ProPath (Zinpro Corporation, Eden Prairie, MN) used to provide additional AA complexes of Zn and Mn, complexed Co, and ruminally-protected folic acid to basal control diet. Cattle were fed to meet requirements of JBS “Aspen Ridge” and observed twice monthly from June–September. Three observations per observation day were made at these times: 1) 0700–1000; 2) 1015–1315; 3) 1430–1700 (all times ± 30 min). Hide temperatures were observed caudal to glenohumeral joints of 10 black-hided and, when available, 10 non-black-hided animals per pen. Within each pen, surface temperatures were observed at 3 locations on the cement bunk apron and 7 locations on the dirt surface. Temperatures were observed using a Fluke VT04 visual infrared thermometer. Temperatures were greater on black-hided cattle than non-black-hided cattle (P &amp;lt; 0.0001) and on steers than heifers (P &amp;lt; 0.0001). Temperatures on Test cattle were greater (P = 0.0008) than temperatures on Control cattle, but this effect was small (0.251o C) and inconsistent across observation days (treatment within date interaction: P &amp;lt; 0.0001). Pen-surface temperatures were greater in Time 2 than Time 1 (P &amp;lt; 0.0001), but not different between Time 2 and Time 3 (P = 0.37). Hide temperatures on all cattle were correlated with pen-surface temperature (R2 = 0.43). Trace mineral source had a small but statistically significant effect on hide temperature. Correlations between hide temperature and visible signs of heat stress are unclear and warrant further observation.

Salinity-Conveyed Thermotolerance in the Coral Model Aiptasia Is Accompanied by Distinct Changes of the Bacterial Microbiome

Coral bleaching, i.e., the loss of photosynthetic algal endosymbionts, caused by ocean warming is now among the main factors driving global reef decline, making the elucidation of factors that contribute to thermotolerance important. Recent studies implicate high salinity as a contributing factor in cnidarians, potentially explaining the high thermotolerance of corals from the Arabian Seas. Here we characterized bacterial community composition under heat stress at different salinities using the coral model Aiptasia. Exposure of two Aiptasia host-algal symbiont pairings (H2-SSB01 and CC7-SSA01) to ambient (25°C) and heat stress (34°C) temperatures at low (36 PSU), intermediate (39 PSU), and high (42 PSU) salinities showed that bacterial community composition at high salinity was significantly different, concomitant with reduced bleaching susceptibility in H2-SSB01, not observed in CC7-SSA01. Elucidation of bacteria that showed increased relative abundance at high salinity, irrespective of heat stress, revealed candidate taxa that could potentially contribute to the observed increased thermotolerance. We identified 4 (H2-SSB01) and 3 (CC7-SSA01) bacterial taxa belonging to the orders Alteromonadales (1 OTU), Oligoflexales (1 OTU), Rhizobiales (2 OTUs), and Rhodobacterales (2 OTUs), suggesting that only few bacterial taxa are potential contributors to an increase in thermal tolerance at high salinities. These taxa have previously been implicated in nitrogen and DMSP cycling, processes that are considered to affect thermotolerance. Our study demonstrates microbiome restructuring in symbiotic cnidarians under heat stress at different salinities. As such, it underlines how host-associated bacterial communities adapt to prevailing environmental conditions with putative consequences for the environmental stress tolerance of the emergent metaorganism.

Natural variation of physiological traits, molecular markers, and chlorophyll catabolic genes associated with heat tolerance in perennial ryegrass accessions

BackgroundIdentification of genetic diversity in heat tolerance and associated traits is of great importance for improving heat tolerance in cool-season grass species. The objectives of this study were to determine genetic variations in heat tolerance associated with phenotypic and physiological traits and to identify molecular markers associated with heat tolerance in a diverse collection of perennial ryegrass (Lolium perenne L.).ResultsPlants of 98 accessions were subjected to heat stress (35/30 °C, day/night) or optimal growth temperature (25/20 °C) for 24 d in growth chambers. Overall heat tolerance of those accessions was ranked by principal component analysis (PCA) based on eight phenotypic and physiological traits. Among these traits, electrolyte leakage (EL), chlorophyll content (Chl), relative water content (RWC) had high correlation coefficients (− 0.858, 0.769, and 0.764, respectively) with the PCA ranking of heat tolerance. We also found expression levels of four Chl catabolic genes (CCGs), including LpNYC1, LpNOL, LpSGR, and LpPPH, were significant higher in heat sensitive ryegrass accessions then heat tolerant ones under heat stress. Furthermore, 66 pairs of simple sequence repeat (SSR) markers were used to perform association analysis based on the PCA result. The population structure of ryegrass can be grouped into three clusters, and accessions in cluster C were relatively more heat tolerant than those in cluster A and B. SSR markers significantly associated with above-mentioned traits were identified (R2 > 0.05, p < 0.01)., including two pairs of markers located on chromosome 4 in association with Chl content and another four pairs of markers in association with EL.ConclusionThe result not only identified useful physiological parameters, including EL, Chl content, and RWC, and their associated SSR markers for heat-tolerance breeding of perennial ryegrass, but also highlighted the involvement of Chl catabolism in ryegrass heat tolerance. Such knowledge is of significance for heat-tolerance breeding and heat tolerance mechanisms in perennial ryegrass as well as in other cool-season grass species.

Effect of selenium supplementation on productive performance and antioxidant status of broilers under heat stress: a meta-analysis and a meta-regression

Heat stress and a high metabolic rate of broilers increase the production of reactive oxygen species, which must be removed by antioxidants to prevent oxidative stress. Selenium (Se) is a potent antioxidant as it is a structural part of glutathione peroxidase (GPx). Dietary supplementation of Se can help reduce the oxidative stress caused by heat-stress conditions. The aim was to evaluate the effect of Se supplementation on the performance and antioxidant status of broilers under heat stress, by using a meta-analysis approach, and to quantify the contribution to heterogeneity of the explanatory variables through a meta-regression procedure. A database of 74 trials was created from 56 published studies that met the following inclusion criteria: papers that reported a measure of effect size, sample size, measure of variability and random procedure. The response variables were GPx and malondialdehyde concentrations, DM intake, average daily gain, and feed conversion rate. Broiler line, Se source, and dosage, heat-stress level, days of experimentation, sample source (blood, liver or meat) and basal Se concentration were considered to be explanatory variables. All statistical analyses were performed in R software, by using the ‘meta’ and ‘Metafor’ packages for meta-analysis and meta-regression respectively. High concentrations of GPx were found in Se-supplemented broilers (&amp;gt;1.76; P = 0.001), in comparison to control groups. However, when the random model was applied to GPx studies, it showed high heterogeneity (I2 = 95.4%), which was reduced (I2 = 61.5) when heat-stress temperature, Se source and its dosage and tissue sample were included as covariates in the meta-regression analysis. The highest standard mean difference of GPx was founded in studies that reported supplementation with inorganic Se sources (2.92), in comparison to supplementation with organic and nano-Se sources (1.66 and 1.44 respectively). The standard mean differences of malondialdehyde and feed conversion rate were significantly lower (&amp;lt;0.66 and &amp;lt;0.11 respectively) in supplemented broilers. Heterogeneity of all variables decreased when the explanatory variables were included in the mixed-regression model. Our findings confirmed that Se supplementation improves the broiler’s antioxidant status and productive performance. However, the response level was affected by dosage and source of Se and the level of heat stress.

Methyl donor supply to heat stress-challenged polymorphonuclear leukocytes from lactating Holstein cows enhances 1-carbon metabolism, immune response, and cytoprotective gene network abundance

Mechanisms controlling immune function of dairy cows are dysregulated during heat stress (HS). Methyl donor supply-methionine (Met) and choline (Chol)-positively modulates innate immune function, particularly antioxidant systems of polymorphonuclear leukocytes (PMN). The objective of this study was to investigate the effect of Met and Chol supply in vitro on mRNA abundance of genes related to 1-carbon metabolism, inflammation, and immune function in short-term cultures of PMN isolated from mid-lactating Holstein cows in response to heat challenge. Blood PMN were isolated from 5 Holstein cows (153 ± 5 d postpartum, 34.63 ± 2.73 kg/d of milk production; mean ± SD). The PMN were incubated for 2 h at thermal-neutral (37°C; TN) or heat stress (42°C; HS) temperatures with 3 levels of Chol (0, 400, or 800 μg/mL) or 3 ratios of Lys:Met (Met; 3.6:1, 2.9:1, or 2.4:1). Supernatant concentrations of IL-1β, IL-6, and tumor necrosis factor-α were measured via bovine-specific ELISA. Fold-changes in mRNA abundance were calculated separately for Chol and Met treatments to obtain the fold-change response at 42°C (HS) relative to 37°C (TN). Data were subjected to ANOVA using PROC MIXED in SAS (SAS Institute Inc., Cary, NC). Orthogonal contrasts were used to determine the linear or quadratic effect of Met and Chol for mRNA fold-change and supernatant cytokine concentrations. Compared with PMN receiving 0 μg of Chol/mL, heat-stressed PMN supplemented with Chol at 400 or 800 μg/mL had greater fold-change in abundance of CBS, CSAD, GSS, GSR, and GPX1. Among genes associated with inflammation and immune function, fold-change in abundance of TLR2, TLR4, IRAK1, IL1B, and IL10 increased with 400 and 800 μg of Chol/mL compared with PMN receiving 0 μg of Chol/mL. Fold-change in abundance of SAHH decreased linearly at increasing levels of Met supply. A linear effect was detected for MPO, NFKB1, and SOD1 due to greater fold-change in abundance when Met was increased to reach Lys:Met ratios of 2.9:1 and 2.4:1. Although increasing Chol supply upregulated BAX, BCL2, and HSP70, increased Met supply only upregulated BAX. Under HS conditions, enhancing PMN supply of Chol to 400 μg/mL effectively increased fold-change in abundance of genes involved in antioxidant production (conferring cellular processes protection from free radicals and reactive oxygen species), inflammatory signaling, and innate immunity. Although similar outcomes were obtained with Met supply at Lys:Met ratios of 2.9:1 and 2.4:1, the response was less pronounced. Both Chol and Met supply enhanced the cytoprotective characteristics of PMN through upregulation of heat shock proteins. Overall, the modulatory effects detected in the present experiment highlight an opportunity to use Met and particularly Chol supplementation during thermal stress.

Dietary nitrate supplementation does not influence thermoregulatory or cardiovascular strain in older individuals during severe ambient heat stress.

What is the central question of this study? Does dietary nitrate supplementation with beetroot juice attenuate thermoregulatory and cardiovascular strain in older adults during severe heat stress? What is the main finding and its importance? A 7-day nitrate supplementation regimen lowered resting mean arterial pressure in thermoneutral conditions. During heat stress, core and mean skin temperatures, vasodilatory responses, sweat loss, heart rate and left ventricular function were unchanged, and mean arterial pressure was only transiently reduced, post-supplementation. These data suggest nitrate supplementation with beetroot juice does not mitigate thermoregulatory or cardiovascular strain in heat-stressed older individuals. This study tested the hypothesis that dietary nitrate supplementation with concentrated beetroot juice attenuates thermoregulatory and cardiovascular strain in older individuals during environmental heat stress. Nine healthy older individuals (six females, three males; aged 67±5years) were exposed to 42.5±0.1°C and 34.0±0.5% relative humidity conditions for 120min before (CON) and after 7days of dietary nitrate supplementation with concentrated beetroot juice (BRJ; 280ml, ∼16.8mmol of nitrate daily). Core and skin temperatures, body mass changes (indicative of whole-body sweat loss), skin blood flow and cutaneous vascular conductance, forearm blood flow and vascular conductance, heart rate, arterial blood pressures and indices of cardiac function were measured. The 7-day beetroot juice regimen increased plasma nitrate/nitrite levels from 27.4±15.2 to 477.0±102.5μmoll-1 (P<0.01) and lowered resting mean arterial pressure from 90±7 to 83±10mmHg at baseline under thermoneutral conditions (P=0.02). However, during subsequent heat stress, no differences in core and skin temperatures, skin blood flow and vascular conductance, forearm blood flow and vascular conductance, whole-body sweat loss, heart rate, and echocardiographic indices of systolic function and diastolic filling were evident following nitrate supplementation (all P>0.05). Mean arterial pressure was lower in BRJ vs. CON during heat stress (treatment-by-time interaction: P=0.02). Overall, these findings suggest that dietary nitrate supplementation with concentrated beetroot juice does not attenuate thermoregulatory or cardiovascular strain in older individuals exposed to severe ambient heat stress.

Transcriptomic insights into the roles of HSP70-16 in sepal’s responses to developmental and mild heat stress signals

Plant heat stress response (HSR) involves many heat shock proteins (HSPs), each might has distinct function. Thus, understanding of molecular bases of corresponding responses of each HSP in plant is essential for both basic and applied researches. While previous work focused dominantly on high temperature heat stress, studies on mild heat stress (about 5 °C over the optimal growth temperature) are rare. HSP70-16 is required for normal function of lateral sepals during flower opening at normal and mild heat stress, however, its underlying mechanism remains obscure. In this study, we compared transcriptomes of wild type and hsp70-16 sepals grown under normal (22 °C) and mild heat stress (27 °C) temperatures. Combined with weighted gene co-expression network analysis (WGCNA), we uncovered a HSP70-16 mediated molecular network that integrates both developmental and mild heat stress signals in Arabidopsis sepals, functioning to maintain protein homeostasis and metabolite homeostasis through a serial of network and hub genes including those encoding protein kinases, transcription factors, heat stress transcription factors, HSPs, hormones, reactive oxygen species, lipid/cuticle and cell wall components. Overall, the output of this study will provide an excellent resource for future characterization of HSPs to understand plant and heat stress interaction and obtain acquired thermos-tolerant plants.

Direct exposure to mild heat stress stimulates cell viability and heat shock protein expression in primary cultured broiler fibroblasts.

Fibroblasts produce collagen which is mainly essential for repairing tissue damage and maintaining the structural integrity of tissues. However, studies have given scientific evidence about harmful effect of thermal manipulation in fibroblast. Therefore, the aim of this study was to determine the mild heat stress temperature which increased broiler fibroblast viability. The experiment was divided into two groups (37°C and 41°C), and each group was divided into five subgroups based on different incubation times (6h, 12h, 24h, 48h, and 72h) with three replications. In experimental group (41°C), fibroblast viability increased significantly in 12h but decreased in 72h compared with control (37°C). At 41°C, live cell increased significantly in 24h and then declined in 48h as well as 72h than control. Moreover, the S phase lengthened in shorter incubation time of experimental group compared with control. Protein and mRNA (HSP70, HSP60, and HSP47) expressions were significantly higher at 41°C compared with 37°C, but at the end of the experiment, HSP expression level was higher in both groups. Finally, this study recommended 41°C as a mild heat stress temperature for increasing broiler fibroblast viability.

Suppression of heat-induced leaf senescence by γ-aminobutyric acid, proline, and ammonium nitrate through regulation of chlorophyll degradation in creeping bentgrass

Heat-induced leaf senescence may be regulated by nitrogen or nitrogen-enriched amino acids. The objectives of the current study were to examine whether exogenous application of у-aminobutyric acid (GABA), proline, and ammonium nitrate (N) could alleviate heat-induced leaf senescence in creeping bentgrass (Agrostis stolonifera L.) and to determine whether the effects of GABA, proline, and N on heat-induced leaf senescence were associated with the alteration of chlorophyll (Chl) metabolism. Plants were exposed to heat stress (35/30 °C, day/night) or non-stress (22/18 °C, day/night) temperature conditions for 35 d in controlled-environment growth chambers. Turf quality, Chl content, and photochemical efficiency declined whereas the activities of Chl-degrading enzymes (chlorophyllase and pheophytinase) increased in response to heat stress. Application of GABA, proline, or N significantly enhanced turf quality, Chl content, and photochemical efficiency, and suppressed Chl-degrading enzyme activities under heat stress. The activity of a Chl-synthesizing enzyme (porphobilinogen deaminase) was not affected by GABA, proline, or N application. These results indicate that heat-induced leaf senescence could be mainly due to heat-accelerated Chl degradation, and GABA, proline, or N could suppress Chl degradation, alleviating heat-induced leaf senescence in creeping bentgrass.

Modest reductions in face skin temperature do not improve tolerance to a simulated hemorrhagic challenge in exercise heat stressed individuals.

Face cooling is associated with autonomic and cardiovascular alterations that accompany an increased blood pressure. Following an exercise heat stress, even minor increases in heart rate and vascular resistance may permit an improved blood pressure control during a simulated hemorrhagic challenge (Lower Body Negative Pressure, LBNP) and improve tolerance. Our aim was to examine whether modest reductions in face skin temperature would improve LBNP tolerance in exercise heat stressed individuals. Ten healthy subjects (Age: 29 ± 13 yrs; Ht: 177 ± 9 cm; Wt: 72.4 ± 8.0 kg) completed two counterbalanced trials (Trial A and Trial B) cycling at 63 ± 6% of their predetermined VO2Max whilst wearing a warm water perfused suit and face mask until core temperature had increased 1.5°C. Participants then underwent LBNP to pre syncope. LBNP tolerance was quantified as cumulative stress index (CSI; mmHg*min). Face skin temperature represents the average of forehead, cheek and chin skin temperatures. Face skin temperature was maintained at exercise heat stress values throughout LBNP in Trial A but was reduced via facial fanning in Trial B after 1 minute of LBNP. Arterial blood pressure (MAP, Penaz method), heart rate (HR, ECG), stroke volume (SV, Pulse Contour Analysis) were continuously measured and total peripheral resistance (TPR) was calculated. Following exercise heat stress, core (38.6 ± 0.2 °C), mean skin (38.2 ± 0.6 °C) and face skin (36.4 ± 0.5 °C) temperatures were elevated relative to baseline (all P &lt; 0.05) and not different between trials (all P &gt; 0.05). Face skin temperature remained elevated throughout LBNP in Trial A (36.1 ± 0.5 °C) but was reduced in Trial B (31.3 ± 1.6°C, P = 0.0001 between trials). Following exercise and prior to LBNP, HR was increased (63 ± 8 to 121 ±15 BPM) while MAP (86 ± 7 to 70 ± 6 mmHg) and TPR (12.5 ± 2.0 to 7.7 ± 1.6 mmHg/L/min) were similarly lowered relative to baseline in both trials (all P &lt; 0.05). Mean arterial pressure was similarly reduced at pre syncope in both trials (54 ± 11 and 57 ± 5 mmHg; P &lt; 0.0001 relative to prior to LBNP). TPR and HR increased during LBNP in both trials relative to baseline (both P &lt; 0.05) but were not different between trials 2 minutes after the onset of LBNP (TPR: 7.8 ± 1.7 vs. 7.8 ± 1.8 mmHg/L/min and HR: 131 ± 17 vs. 137 ± 22 BPM, main effect of trial both P &gt; 0.05). CSI was not different between trials (Trial A: 332 ± 176 vs. Trial B: 393 ± 261 mmHg*min; P = 0.482). LBNP tolerance was not improved by face skin cooling in exercise heat stressed individuals. These results suggest that modest reductions in face skin temperature are not accompanied by an improved blood pressure control during a simulated hemorrhagic challenge in exercise heat stressed individuals.

Influence of heat stress on reference genes stability in heart and liver of two chickens genotypes.

Real-time polymerase chain reaction (RT-qPCR) is an important tool for analyzing gene expression. However, before analyzing the expression of target genes, it is crucial to normalize the reference genes, in order to find the most stable gene to be used as an endogenous control. A gene that remains stable in all samples under different treatments is considered a suitable normalizer. In this sense, we aimed to identify stable reference genes for normalization of target genes in the heart and liver tissues from two genetically divergent groups of chickens (Cobb 500® commercial line and Peloco backyard chickens) under comfort and acute heat stress environmental conditions. Eight reference genes (ACTB, HPRT1, RPL5, EEF1, MRPS27, MRPS30, TFRC and LDHA) were analyzed for expression stability. The samples were obtained from 24 chickens, 12 from the backyard Peloco and 12 from the Cobb 500® line, exposed to two environmental conditions (comfort and heat stress). Comfort temperature was 23°C and heat stress temperature was 39.5°C for one hour. Subsequently, the animals were euthanized, and heart and liver tissue fragments were collected for RNA extraction and amplification. To determine the stability rate of gene expression, three different statistical algorithms were applied: BestKeeper, geNorm and NormFinder, and to obtain an aggregated stability list, the RankAgregg package of R software was used. The most stable genes using BestKeeper tool, including the two factors (genetic group and environmental condition), were LDHA, RPL5 and MRPS27 for heart tissue, and TFRC, RPL5 and EEF1 for liver tissue. Applying geNorm algorithm, the best reference genes were RPL5, EEF1 and MRPS30 for heart tissue and LDHA, EEF1 and RPL5 for liver. Using the NormFinder algorithm, the best normalizer genes were EEF1, RPL5 and LDHA in heart, and EEF1, RPL5 and ACTB in liver tissue. In the overall ranking obtained by RankAggreg package, considering the three algorithms, the RPL5, EEF1 and LDHA genes were the most stable for heart tissue, whereas RPL5, EEF1 and ACTB were the most stable for liver tissue. According to the RankAggreg tool classification based on the three different algorithms (BestKeeper, geNorm and NormFinder), the most stable genes were RPL5, EEF1 and LDHA for heart tissue and RPL5, EEF1 and ACTB for liver tissue of chickens subjected to comfort and acute heat stress environmental conditions. However, the best reference genes may vary depending on the experimental conditions of each study, such as different breeds, environmental stressors, and tissues analyzed. Therefore, the need to perform priori studies to assay the best reference genes at the outset of each study is emphasized.

Effect of summer heat stress on gene expression in bovine uterine endometrial tissues.

Heat stress negatively affects reproductive functions in cows. Increased temperature disturbs fetal development in utero. However, the effect of heat stress on uterine endometrial tissues has not been fully examined. Using qPCR analysis, we measured the mRNA expression of various molecular markers in uterine endometrial tissue of dairy cows from Hokkaido, Japan, in winter and summer. Markers examined were heat shock proteins (HSPs), antioxidant enzymes (catalase, copper/zinc superoxide dismutase, manganese superoxide dismutase, and glutathione peroxidase 4), inflammatory cytokines, and interferon stimulated genes. Our results showed heat stress, body and milk temperatures were higher during summer than during winter. Expression levels of HSP27, HSP60, and HSP90 mRNA, and of catalase and copper/zinc superoxide dismutase mRNA were lower in summer than in winter. Tumor necrosis factor alpha expression was higher in summer than in winter. In conclusion, summer heat stress may reduce the expression of HSPs, affecting the levels of inflammatory cytokines in bovine uterine endometrial tissue.

Interaction between Indoor Occupational Heat Stress and Environmental Temperature Elevations during Heat Waves

Abstract Occupational heat strain is a public health threat, and for outdoor industries there is a direct influence from elevated environmental temperatures during heat waves. However, the impact in indoor settings is more complex as industrial heat production and building architecture become factors of importance. Therefore, this study evaluated effects of heat waves on manufacturing productivity. Production halls in a manufacturing company were instrumented with 33 dataloggers to track air temperature and humidity. In addition, outdoor thermal conditions collected from a weather station next to the factory and daily productivity evaluated as overall equipment efficiency (OEE) were obtained, with interaction between productivity and thermal conditions analyzed before, during, and after four documented heat waves (average daily air temperature above 24°C on at least three consecutive days). Outdoor (before: 21.3° ± 4.6°C, during: 25.5° ± 4.3°C, and after: 19.8° ± 3.8°C) and indoor air temperatures (before: 30.4° ± 1.3°C, during: 32.8° ± 1.4°C, and after: 30.1° ± 1.4°C) were significantly elevated during the heat waves (p &amp;lt; 0.05). OEE was not different during the heat waves when compared with control, pre-heat-wave, and post-heat-wave OEE. Reduced OEE was observed in 3-day periods following the second and fourth heat wave (p &amp;lt; 0.05). Indoor workers in settings with high industrial heat production are exposed to a significant thermal stress that may increase during heat waves, but the impact on productivity cannot be directly derived from outdoor factors. The significant decline in productivity immediately following two of the documented heat waves could relate to a cumulative effect of the thermal strain experienced during work combined with high heat stress in the recovery time between work shifts.

Morpho-physiological traits associated with heat stress tolerance in tropical maize (Zea mays L.) at reproductive stage

Heat stress resilience has emerged as an important trait in maize hybrids targeted for post–monsoon spring cultivation in large parts of South Asia and many other parts of the tropics. Selection based on grain yield alone under heat stress is often misleading, and therefore an approach involving stress-adaptive secondary traits along with grain yield could help in the development of improved, stable heat stress tolerant cultivars. We attempted to identify reliable and effective secondary traits associated with heat stress tolerance in tropical maize and sources of heat stress tolerant germplasm. A panel of 99 elite maize inbred lines representing the wider genetic diversity of tropical maize and a set of 58 elite hybrids were phenotyped under natural heat stress and optimal temperature for grain yield and 15 secondary traits including 10 morpho-physiological traits and 5 yield attributes. Evaluation under natural heat stress was done during the spring season by adjusting the planting date so that the complete reproductive stage (from tassel emergence to late grain filling) was exposed to heat stress. The optimal temperature trial was planted during the monsoon season with no exposure to heat stress at any crop stage. Heat stress significantly affected most of the observed traits. Among the traits studied two yield attributing traits, i.e.- ears per plant (EPP) and kernel per row (KPR), and three morpho-physiological traits, i.e.- chlorophyll content (CC), leaf firing (LF) and tassel blast (TB) were found to be the key secondary traits associated with grain yield under heat stress. In addition, low anthesis-silking internal (ASI) is an important trait that needs to be added in the index selection for heat stress tolerance. The study identified nine promising heat stress tolerant maize inbred lines with desirable secondary traits and grain yield under severe heat stress, which could be used as source germplasm in heat stress tolerance maize breeding program.

Emission of constitutive isoprene, induced monoterpenes, and other volatiles under high temperatures in Eucalyptus camaldulensis: A 13 C labelling study.

Eucalypts are major emitters of biogenic volatile organic compounds (BVOCs), especially volatile isoprenoids. Emissions and incorporation of 13 C in BVOCs were measured in Eucalyptus camaldulensis branches exposed to rapid heat stress or progressive temperature increases, in order to detect both metabolic processes and their dynamics. Isoprene emission increased and photosynthesis decreased with temperatures rising from 30°C to 45°C, and an increasing percentage of unlabelled carbon was incorporated into isoprene in heat-stressed leaves. Intramolecular labelling was also incomplete in isoprene emitted by heat-stressed leaves, suggesting increasing contribution of respiratory (and possibly also photorespiratory) carbon. At temperature above 45°C, a drop of isoprene emission was mirrored by the appearance of unlabelled monoterpenes, green leaf volatiles, methanol, and ethanol, indicating that the emission of stored volatiles was mainly induced by cellular damage. Emission of partially labelled acetaldehyde was also observed at very high temperatures, suggesting a double source of carbon, with a large unlabelled component likely transported from roots and associated to the surge of transpiration at very high temperatures. Eucalypt plantations cover large areas worldwide, and our findings may dramatically change forecast and modelling of future BVOC emissions at planetary level, especially considering climate warming and frequent heat waves.

Integrating miRNA and mRNA expression profiles in plasma of laying hens associated with heat stress.

High temperature is one of the most common environmental stressors plaguing animal husbandry worldwide. Little is known about the regulatory roles of miRNAs in response to heat stress in laying hens. To systematically identify heat stress-responsive miRNAs and their targets in laying hens, the differential expression of miRNAs and mRNAs was compared under heat stress and normal temperature. We identified 16 miRNAs and 502 genes that were significantly changed in heat-stressed laying hens. By comparing the differentially expressed genes (DEGs) and the putative targets of the altered miRNAs based on bioinformatics prediction, 82 coordinated genes were identified. Gene ontology classification analyses of the 82 putative target genes showed that the biological category 'cellular response to stress' was prominently annotated. Notably, the response-related gene autophagy-related protein 9A was most likely controlled by the upregulated miRNAs gga-miR-92-5p, gga-miR-1618-5p, gga-miR-1737, and gga-miR-6557 in response to heat stress. Analysis of DEGs also revealed an increase in lipid metabolism in heat-stressed laying hens. Some of these genes were negatively correlated with the altered miRNAs, suggesting that they are potential targets of the miRNAs. Taken together, our results advance our understanding of the regulatory mechanism of heat-stress-induced injury in laying hens, specifically with regard to miRNAs.

Effects of heat shock and ambient temperature on female soldier production in a polyembryonic parasitic wasp

AbstractLarval castes are well known in both sexes of polyembryonic parasitic wasps, in which sterile soldier larvae are clonally produced from a single egg and thousands of reproductive larvae develop into adults. The proportion of soldier larvae in Copidosoma floridanum is first determined genetically in both sexes but subsequently increases in females as a result of environmental disturbances, such as the presence of competitive parasitoids. Because temperature is the most influential environmental factor affecting ectotherms, we hypothesize that an increase in ambient temperature also affects the production of female soldier larvae. Conversely, we hypothesize that there would be no effect of temperature on the production of male soldier larvae. In the present study, we show that heat stress experienced by C. floridanum at an early stage in host development increases the number of female soldier larvae produced during the last instar stage of the host. We also show that rearing at extreme (high and low) temperatures induces an increase in the number of female soldiers produced. The effect of heat stress and ambient temperature on soldier production is found only in females, as is the response to heterospecific competitors. By contrast, no responses are detected in males for either heat stress or ambient temperature. The adaptive effect of these phenomena is not known, although the results of the present study imply the existence of a common physiological cascade that causes an increase in the number of soldier larvae in females.