Long-term Heat Stress Research Articles

Climate anomalies, land degradation and rural out-migration in Uganda.

Globally, rural livelihoods are increasingly challenged by the dual threats of land degradation and climate change. These issues are of particular concern in sub-Saharan Africa, where land degradation is believed to be severe and where climate change will bring higher temperatures and shifts in rainfall. To date, however, we know little about the relative effects of these various potential environmental stressors on migration. To examine these processes, we link longitudinal data from 850 Ugandan households with environmental data on soils, forests, and climate, and then analyze these data using approaches that account for potential spatial and temporal confounders. Our findings reveal that climate anomalies, rather than land degradation, are the primary contributor to environmental migration in Uganda, with heat stress of particular importance. Short hot spells increase temporary migration, an element of a diversified household livelihood strategy, while long-term heat stress induces permanent migration through an agricultural livelihoods pathway.

Emerging Roles of Heat-Induced circRNAs Related to Lactogenesis in Lactating Sows.

Heat stress negatively influences milk production and disrupts normal physiological activity of lactating sows, but the precious mechanisms by which hyperthermia adversely affects milk synthesis in sows still remain for further study. Circular RNAs are a novel class of non-coding RNAs with regulatory functions in various physiological and pathological processes. The expression profiles and functions of circRNAs of sows in lactogenesis remain largely unknown. In the present study, long-term heat stress (HS) resulted in a greater concentration of serum HSP70, LDH, and IgG, as well as decreased levels of COR, SOD, and PRL. HS reduced the total solids, fat, and lactose of sow milk, and HS significantly depressed CSNαs1, CSNαs2, and CSNκ biosynthesis. Transcriptome sequencing of lactating porcine mammary glands identified 42 upregulated and 25 downregulated transcripts in HS vs. control. Functional annotation of these differentially-expressed transcripts revealed four heat-induced genes involved in lactation. Moreover, 29 upregulated and 21 downregulated circRNA candidates were found in response to HS. Forty-two positively correlated circRNA-mRNA expression patterns were constructed between the four lactogenic genes and differentially expressed circRNAs. Five circRNA-miRNA-mRNA post-transcriptional networks were identified involving genes in the HS response of lactating sows. In this study we establish a valuable resource for circRNA biology in sow lactation. Analysis of a circRNA-miRNA-mRNA network further uncovered a novel layer of post-transcriptional regulation that could be used to improve sow milk production.

Analyses of the function of DnaJ family proteins reveal an underlying regulatory mechanism of heat tolerance in honeybee.

There is clear evidence of severe honeybee declines in recent years, and parallel declines of plant community and crop productivity that rely on them. Different stresses, including heat stress, are among the primary drivers of this decline. However, the mechanisms by which honeybees respond to heat stress are elusive. Though heat shock proteins (Hsps) play important roles in heat stress response, the function of DnaJs (a subfamily of Hsps) is unclear. Here, we aimed to determine the underlying regulatory mechanism of honeybees to heat stress mediated by DnaJs. We found that several DnaJ genes, including DnaJA1, DnaJB12 and DnaJC8, are key for honeybee heat tolerance. DnaJA1 and DnaJB12 are cytoplasmic proteins, and DnaJC8 is a nuclear protein. The expression of DnaJA1, DnaJB12 and DnaJC8 was induced at different levels under short-term and long-term heat stress. Phenotypic analysis indicated that DnaJA1, DnaJB12 and DnaJC8 knockdown attenuated honeybee heat resistance. In addition, DnaJA1 participated in the heat stress response by upregulating many heat-inducible genes at the transcriptome-wide level, especially LOC108002668 and LOC107995148. Importantly, the upregulation of LOC108002668 and LOC107995148 was significantly repressed under heat stress when DnaJA1 was knocked down. We also found that knockdown of DnaJA1, DnaJB12 and DnaJC8 decreased antioxidant defense ability and increased the degree of oxidative damage in the honeybee. Taken together, our results indicate that DnaJ genes play important roles under heat stress in the honeybee. Overexpression of DnaJ genes may protect honeybees from heat stress-induced injuries and increase their survival rate.

Effect of heat stress on mitogen-activated protein kinases in the hypothalamic–pituitary–gonadal axis of developing Wenchang chicks

The regulatory roles of mitogen-activated protein kinase (MAPK) signaling pathways on the hypothalamic−pituitary−gonadal axis (HPG axis) of Wenchang chicks under heat stress (HS) were investigated. Additionally, the crosstalk between these signaling pathways was explored. Immunohistochemical experiments and Western blotting were employed to quantify extracellular regulated protein kinases (ERK), c-Jun N-terminal kinases (JNK), and p38MAPK (P38). In female chicks, hypothalamic ERKs were upregulated in Weeks 1 and 2 in the HS group compared with the control group (CK), while JNK and p38 were downregulated (P < 0.05). Pituitary MAPKs were all downregulated in the HS group compared with the CK group in Week 3, but p38 was upregulated in Week 4 (P < 0.01). In the HS group, ovarian MAPKs were all upregulated compared with the CK group during Week 5, whereas ERK was downregulated in Week 6 (P < 0.01). In contrast to the patterns of MAPK expression in female chicks in the HS and CK groups, ERK in male chicks showed a completely opposite pattern in Weeks 1, 2, and 5, while p38 and JNK were downregulated in both female and male chicks under HS during Weeks 2 and 3. In the HS group, pituitary and testis MAPKs showed a pattern opposite to that observed in female chicks under HS in Week 5; MAPKs were all downregulated (P < 0.05). Thus, there are gender differences in the MAPK signaling pathways in the HPG axis in chicks, and these pathways showed plasticity. Early HS can enhance chick growth and development as well as promote developing in the MAPK signaling pathways in the HPG axis. However, after heated brooding was discontinued in chicks, long-term HS obstructed chick development and caused tissue and function injury to the HPG axis.

Cross talk between heat shock protein 10 and a heat shock factor identified from Marsupenaeus japonicus

Heat shock factors (HSFs) and heat shock proteins (HSPs) are crucial regulators and effectors of the heat shock response (HSR). In this study, the full-length cDNA sequences of MjHSP10 and MjHSF1 were cloned by rapid amplification of cDNA ends (RACE). The deduced MjHSP10 and MjHSF1 amino acid (aa) sequences exhibited conserved structures and the functional features of HSP10 and HSF1, respectively. The tissue distributions and mRNA expression profiles of the two genes in response to heat stress were analyzed by quantitative real-time PCR (qRT-PCR). MjHSP10 and MjHSF1 were ubiquitously expressed in various tissues. Heat stress induced a significant increase in MjHSP10 expression that tend to positively correlate with temperature. Additionally, MjHSF1 transcription was up-regulated less than MjHSP10 transcription under heat stress. MjHSF1 expression in the hepatopancreas was up-regulated under only long-term (48 h) heat stress, and MjHSF1 transcription in the gill increased under only acute (34 °C) heat stress. MjHSF1 knockdown by RNA interference (RNAi) down-regulated MjHSP10 expression. Glutathione-S-transferase (GST) pull-down assays showed an interaction between MjHSP10 and the DNA-binding domain (DBD) of MjHSF1. This study provided new insights into cross talk between HSP10 and HSF1 in Marsupenaeus japonicus.

Immunolocalization of antioxidant enzymes in testis of rams submitted to long-term heat stress.

Long-term heat stress (HS) induced by testicular insulation generates oxidative stress (OS) on the testicular environment; consequently activating antioxidant enzymes such as superoxide dismutase (SOD), glutathione reductase (GR) and glutathione peroxidase (GPx). The aim of this work was to immunolocalize antioxidant enzymes present in different cells within the seminiferous tubule when rams were submitted to HS. Rams were divided into control (n = 6) and treated group (n = 6), comprising rams subjected to testicular insulation for 240 h. After the testicular insulation period, rams were subjected to orchiectomy. Testicular fragments were submitted to immunohistochemistry for staining against SOD, GR and GPx enzymes. We observed immunolocalization of GPx in more cell types of the testis after HS and when compared with other enzymes. In conclusion, GPx is the main antioxidant enzyme identified in testicular cells in an attempt to maintain oxidative balance when HS occurs.

Effects of Dietary Betaine on Growth Performance, Digestive Function, Carcass Traits, and Meat Quality in Indigenous Yellow-Feathered Broilers under Long-Term Heat Stress

Simple SummaryHeat stress, one of the major problems in tropical and subtropical regions, adversely affects poultry production. This study was designed to evaluate the effects of dietary betaine on growth performance, digestive function, carcass traits, and meat quality in indigenous yellow-feathered broilers subjected to long-term heat stress. The results demonstrated that long-term heat exposure reduced the growth performance, digestive function, and carcass yield, and dietary betaine supplementation partially alleviated the adverse effects of heat stress on these parameters. These findings are useful for development of anti-heat stress feed additives in indigenous yellow-feathered broilers.Heat stress has a profound effect on poultry health and productivity. The present study evaluated whether feeding betaine could ameliorate long-term heat stress-induced impairment of productive performance in indigenous yellow-feathered broilers. A total of 240 five-week-old male broilers were randomly allocated to five treatments with six replicates of eight broilers each. The five treatments included a thermoneutral zone control group (TN, fed basal diet), a heat stress control group (HS, fed basal diet), and an HS control group supplemented 500, 1000, 2000 mg/kg betaine, respectively. The TN group was raised at 26 ± 1 °C during the whole study, HS groups exposed to 32 ± 1 °C for 8 h/day from 9:00 am to 17:00 pm. The results showed that heat stress decreased the body weight gain (BWG) and feed intake of broilers during 1–5, 6–10, and 1–10 weeks (p < 0.05). Dietary betaine tended to improve the BWG and feed intake of broilers under 5 weeks of heat stress (linear, p < 0.10), and betaine supplementation linearly increased the BWG and feed intake during 6–10 and 1–10 weeks (p < 0.05). Additionally, nitrogen retention was reduced by 5 weeks and 10 weeks of heat stress (p < 0.05), whereas dietary betaine could improve nitrogen retention in heat stressed broilers after both 5 and 10 weeks of heat stress (linear, p < 0.05). Moreover, this study observed that the trypsin activity of jejunum was decreased by 5 weeks of heat stress (p < 0.05), whereas betaine supplementation had quadratic effects on trypsin activity of jejunum in heat stressed broilers (p < 0.05). Furthermore, 10 weeks of heat stress induced a reduction of villus height of the duodenum and jejunum (p < 0.05), and decreased the villus height to crypt depth ratio of the jejunum (p < 0.05). Supplementation with betaine ameliorated the adverse effects of heat stress on these parameters (p < 0.05). Compared with the TN group, 10 weeks of heat stress reduced carcass and breast yield (p < 0.05) and betaine supplementation improved carcass and breast yield of heat stressed broilers (linear, p < 0.05). In conclusion, dietary supplementation of betaine could reduce the detrimental effects of long-term heat stress on growth performance, digestive function, and carcass traits in indigenous yellow-feathered broilers.

10 Finishing beef cattle under cover reduces heat load and improves efficiency during the summer

Abstract Heat-stress in finishing cattle presents a significant risk to efficiency and economic viability. The project objective was to quantify the effects of long-term heat stress when finishing cattle during the summer in the southeastern United States. Forty-five Angus crossbred steers (446±23 kg) were blocked by weight and randomly assigned to environmental finishing treatments including: covered with fan (CWF), covered without fan (CNF), or outside without shade (OUT). For 92 d steers were individually fed a typical feedlot ration. Environmental data were continuously recorded including: black globe temperature (BG), heat load index (HLI), and accumulated heat load units (AHLU). Feed intake was recorded daily, and steers were weighed every 20–25 days. When the first treatment averaged 613-kg all steers were slaughtered, and carcass data were collected. Data were analyzed as a Mixed Model (JMP V13; SAS Inst.) and means were separated (Least Squares Means). Average maximal BG was lower for covered finishing than OUT (P &lt; 0.01) however for HLI CWFCNF&gt;OUT, while G:F was similar (P = 0.22) between CWF and CNF, which were greater (P &lt; 0.01) than OUT. Hot carcass weights were heavier for CWF than OUT (P &lt; 0.01) and CNF was similar to both (P ≥ 0.11). There was no difference for USDA Yield Grade (2.6; P = 0.44), or marbling score (Modest20; P = 0.76). Steers finished under cover were more efficient than steers finished in open dry-lots. The addition of cooling fans further improved steer gains over those that were covered without fans.

124 Finishing beef cattle under cover reduces heat load and improves efficiency during the summer

Abstract Heat-stress in finishing cattle presents a significant risk to efficiency and economic viability. The project objective was to quantify the effects of long-term heat-stress when finishing cattle during the summer in the southeastern United States. Forty-five Angus crossbred steers (446±23 kg) were blocked by weight and randomly assigned to environmental finishing treatments including: covered with fan (CWF), covered without fan (CNF), or outside without shade (OUT). For 92 d steers were individually fed a typical feedlot ration. Environmental data were continuously recorded including: black globe temperature (BG), heat load index (HLI), and accumulated heat load units (AHLU). Feed intake was recorded daily, and steers were weighed every 20–25 days. When the first treatment averaged 613-kg all steers were slaughtered, and carcass data were collected. Data were analyzed as a Mixed Model (JMP V13; SAS Inst.) and means were separated (Least Squares Means). Average maximal BG was lower for covered finishing than OUT (P &lt; 0.01); however, for HLI CWFCNF&gt;OUT, while G:F was similar (P = 0.22) between CWF and CNF which were greater (P &lt; 0.01) than OUT. Hot carcass weights were heavier for CWF than OUT (P &lt; 0.01) and CNF was similar to both (P ≥ 0.11). There was no difference for USDA Yield Grade (2.6; P = 0.44), or marbling score (Modest20; P = 0.76). Steers finished under cover were more efficient than steers finished in open dry-lots. The addition of cooling fans further improved steer gains over those that were covered without fans.

Korean Red Ginseng alleviates neuroinflammation and promotes cell survival in the intermittent heat stress-induced rat brain by suppressing oxidative stress via estrogen receptor beta and brain-derived neurotrophic factor upregulation

BackgroundHeat stress orchestrates neurodegenerative disorders and results in the formation of reactive oxygen species that leads to cell death. Although the immunomodulatory effects of ginseng are well studied, the mechanism by which ginseng alleviates heat stress in the brain remains elusive. MethodsRats were exposed to intermittent heat stress for 6 months, and brain samples were examined to elucidate survival and antiinflammatory effect after Korean Red Ginseng (KRG) treatment. ResultsIntermittent long-term heat stress (ILTHS) upregulated the expression of cyclooxygenase 2 and inducible nitric oxide synthase, increasing infiltration of inflammatory cells (hematoxylin and eosin staining) and the level of proinflammatory cytokines [tumor necrosis factor α, interferon gamma (IFN-γ), interleukin (IL)-1β, IL-6], leading to cell death (terminal deoxynucleotidyl transferase–mediated dUTP nick-end labeling assay) and elevated markers of oxidative stress damage (myeloperoxidase and malondialdehyde), resulting in the downregulation of antiapoptotic markers (Bcl-2 and Bcl-xL) and expression of estrogen receptor beta and brain-derived neurotrophic factor, key factors in regulating neuronal cell survival. In contrast, KRG mitigated ILTHS-induced release of proinflammatory mediators, upregulated the mRNA level of the antiinflammatory cytokine IL-10, and increased myeloperoxidase and malondialdehyde levels. In addition, KRG significantly decreased the expression of the proapoptotic marker (Bax), did not affect caspase-3 expression, but increased the expression of antiapoptotic markers (Bcl-2 and Bcl-xL). Furthermore, KRG significantly activated the expression of both estrogen receptor beta and brain-derived neurotrophic factor. ConclusionILTHS induced oxidative stress responses and inflammatory molecules, which can lead to impaired neurogenesis and ultimately neuronal death, whereas, KRG, being the antioxidant, inhibited neuronal damage and increased cell viability.

Long-Term Temperature Stress in the Coral Model Aiptasia Supports the "Anna Karenina Principle" for Bacterial Microbiomes.

The understanding of host-microbial partnerships has become a hot topic during the last decade as it has been shown that associated microbiota play critical roles in the host physiological functions and susceptibility to diseases. Moreover, the microbiome may contribute to host resilience to environmental stressors. The sea anemone Aiptasia is a good laboratory model system to study corals and their microbial symbiosis. In this regard, studying its bacterial microbiota provides a better understanding of cnidarian metaorganisms as a whole. Here, we investigated the bacterial communities of different Aiptasia host-symbiont combinations under long-term heat stress in laboratory conditions. Following a 16S rRNA gene sequencing approach we were able to detect significant differences in the bacterial composition and structure of Aiptasia reared at different temperatures. A higher number of taxa (i.e., species richness), and consequently increased α-diversity and β-dispersion, were observed in the microbiomes of heat-stressed individuals across all host strains and experimental batches. Our findings are in line with the recently proposed Anna Karenina principle (AKP) for animal microbiomes, which states that dysbiotic or stressed organisms have a more variable and unstable microbiome than healthy ones. Microbial interactions affect the fitness and survival of their hosts, thus exploring the AKP effect on animal microbiomes is important to understand host resilience. Our data contributes to the current knowledge of the Aiptasia holobiont and to the growing field of study of host-associated microbiomes.

Analysis of production traits and microclimate parameters on dairy cattle farms

Aiming determination of the variability of production traits (daily milk yield and composition) and microclimate parameters (ambient temperature and humidity) in the barns; as well as the correlation between the analyzed groups of traits, 1,636,192 test-day records from Simmentals and 1,275,713 test-day records from Holsteins were analysed. Performed analysis indicate high variability of production traits due to cow?s breed, parity as well as breeding region. Also, high variability of microclimate parameters in the barns due to season and breeding region was found. Furthermore, statistically highly significant (p &lt; 0.001) correlations between the production traits and microclimate parameters were determined. Finally, the negative effect of inadequate microclimate on daily milk production was determined in both breeds in all breeding regions. Since genetic evaluation and selection of dairy cattle for heat resistance is only long-term method for heat stress managing, determined effect will be taken into account in the statistical model for estimation of genetic parameters and breeding values.

PARP Inhibitor Affects Long-term Heat-stress Response via Changes in DNA Methylation

Resilience to stress can be obtained by adjusting the stress-response set point during postnatal sensory development. Recent studies have implemented epigenetic mechanisms to play leading roles in improving resilience. We previously found that better resilience to heat stress in chicks can be achieved by conditioning them to moderate heat stress during their critical developmental period of thermal control establishment, 3 days posthatch. Furthermore, the expression level of corticotropin-releasing hormone (CRH) was found to play a direct role in determining future resilience or vulnerability to heat stress by alterations in its DNA-methylation and demethylation pattern. Here we demonstrate how intraperitoneal injection of poly (ADP-ribose) polymerase (PARP) inhibitor (PARPi) influences the DNA methylation pattern, thereby affecting the long-term heat-stress response. Single PARPi administration, induced a reduction in both 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC), without affecting body temperature. The accumulated effect of three PARPi doses brought about a long-term decrease in 5mC% and 5hmC%. These changes coincided with a reduction in body temperature in non-conditioned chicks, similar to that occurring in moderately conditioned heat-stress-resilient chicks. The observed changes in DNA methylation can be explained by decreased activity of the enzyme DNA methyltransferase as a result of the PARPi injection. Furthermore, evaluation of the DNA-methylation pattern along the CRH intron showed a reduction in 5mC% as a result of PARPi treatment, alongside a reduction in CRH mRNA expression. Thus, PARPi treatment can affect DNA methylation, which can alter hypothalamic–pituitary–adrenal (HPA) axis anchors such as CRH, thereby potentially enhancing long-term resilience to heat stress.

Homoeolog-specific activation of genes for heat acclimation in the allopolyploid grass Brachypodium hybridum.

BackgroundAllopolyploid plants often show wider environmental tolerances than their ancestors; this is expected to be due to the merger of multiple distinct genomes with a fixed heterozygosity. The complex homoeologous gene expression could have been evolutionarily advantageous for the adaptation of allopolyploid plants. Despite multiple previous studies reporting homoeolog-specific gene expression in allopolyploid species, there are no clear examples of homoeolog-specific function in acclimation to a long-term stress condition.ResultsWe found that the allopolyploid grass Brachypodium hybridum and its ancestor Brachypodium stacei show long-term heat stress tolerance, unlike its other ancestor, Brachypodium distachyon. To understand the physiological traits of B. hybridum, we compared the transcriptome of the 3 Brachypodium species grown under normal and heat stress conditions. We found that the expression patterns of approximately 26% and approximately 38% of the homoeolog groups in B. hybridum changed toward nonadditive expression and nonancestral expression, respectively, under normal condition. Moreover, we found that B. distachyon showed similar expression patterns between normal and heat stress conditions, whereas B. hybridum and B. stacei significantly altered their transcriptome in response to heat after 3 days of stress exposure, and homoeologs that were inherited from B. stacei may have contributed to the transcriptional stress response to heat in B. hybridum. After 15 days of heat exposure, B. hybridum and B. stacei maintained transcriptional states similar to those under normal conditions. These results suggest that an earlier response to heat that was specific to homoeologs originating from B. stacei contributed to cellular homeostasis under long-term heat stress in B. hybridum.ConclusionsOur results provide insights into different regulatory events of the homoeo-transcriptome that are associated with stress acclimation in allopolyploid plants.

Physiological responses of artificial moss biocrusts to dehydration-rehydration process and heat stress on the Loess Plateau, China

Ex-situ cultivation of biological soil crusts (biocrusts) is a promising technology to produce materials that can induce the recovery of biocrusts in the field for the purposes of preventing soil erosion and improving hydrological function in degraded ecosystems. However, the ability of artificially cultivated biocrusts to survive under adverse field conditions, including drought and heat stresses, is still relatively unknown. Mosses can bolster biocrust resistance to the stresses (e.g., drought and heat) and the resistance may be introduced prior to field cultivation. In this study, we subjected the well-developed artificial moss biocrusts (dominant species of Didymodon vinealis (Brid.) Zand.) that we cultivated in the phytotron to a dehydration-rehydration experiment and also a heat stress experiment and measured the activities of protective enzymes (including peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT)) and the contents of osmoregulatory substances (including soluble proteins and soluble sugars) and malondialdehyde (MDA, an indicator of oxidative stress) in the stem and leaf fragments of mosses. The results showed that, during the dehydration process, the activities of protective enzymes and the contents of osmoregulatory substances and MDA gradually increased with increasing duration of drought stress (over 13 days). During the rehydration process, values of these parameters decreased rapidly after 1 d of rehydration. The values then showed a gradual decrease for 5 days, approaching to the control levels. Under heat stress (45°C), the activities of protective enzymes and the content of soluble proteins increased rapidly within 2 h of heat exposure and then decreased gradually with increasing duration of heat exposure. In contrast, the contents of soluble sugars and MDA always increased gradually with increasing duration of heat exposure. This study indicates that artificial moss biocrusts possess a strong drought resistance and this resistance can be enhanced after a gradual dehydration treatment. This study also indicates that artificial moss biocrusts can only resist short-term heat stress (not long-term heat stress). These findings suggest that short-term heat stress or prolonged drought stress could be used to elevate the resistance of artificial moss biocrusts to adverse conditions prior to field reintroduction.

Identification of heat stress-susceptible and -tolerant phenotypes in goats in semiarid tropics

The production performance of livestock is influenced by short-term variation in weather pattern. Goat adapts to varied ecological conditions and maintains productivity; however, wide variation has been observed among individual animals in response to environmental stimuli in a population. The objective of the present study was to identify the contrasting phenotypes on the basis of the physiological response in goats during heat stress. The study utilised 138 Jamunapari and 242 Barbari goats during peak heat-stress period and 82 Jamunapari and Barbari goats under thermo-neutral conditions. The physiological response of goats to different environmental conditions was evaluated by recording various parameters such as rectal temperature (RT), respiration rate (RR) and heart rate (HR). The temperature humidity index varied from 85.36 to 89.80 and from 65.32 to 73.12 during heat-stress and thermo-neutral assessments respectively. There was direct increase in HR and RR (&gt;25%) due to heat stress in the animals, as compared with those in thermo-neutral conditions. On the basis of the distribution of RR and HR values across the breed in the population, the individuals having a RR of ≥50 and a HR of ≥130 are recognised as heat stress-susceptible phenotypes and those having a RR of ≤30 and a HR of ≤100 are recognised as heat stress-tolerant individuals. Different biomarkers were analysed in plasma, while heat-shock proteins and leptin were analysed in tissue extracts by ELISA. C-reactive protein and HSP90 concentrations were significantly (P &lt; 0.05) different between heat stress-susceptible and heat stress-tolerant individuals. Heat-shock proteins HSP70, HSP 90, and C-reactive protein and triiodothyronine were reliable indicators of long-term heat stress. Identification of contrasting phenotypes in regard to heat stress is necessary so as to evaluate the expression pattern at a cellular level, as well as physiological and biochemical parameters.

Erythrocyte nuclear abnormalities and leukocyte profile in the Antarctic fish Notothenia coriiceps after exposure to short- and long-term heat stress

Several studies suggest that Antarctic endemic stenothermic fish species, such as Notothenia coriiceps, have a limited ability to acclimate to warmer conditions. In the present study, we evaluated the effects of exposure to short- and long-term temperature increases on the occurrence of erythrocytic nuclear abnormalities (ENAs) and changes in the leukocyte profile of N. coriiceps. For the experiments, 30 specimens of N. coriiceps were captured in Admiralty Bay and transferred to the Commandant Ferraz Brazilian Antarctic Station where they were acclimated to water at 0 °C for 6 days and subsequently subjected to treatments of temperature increases (2–4 °C) on a short- (1 day) or long- (6 days) term basis. At the end of exposure, peripheral blood samples were collected and blood smears were prepared for qualitative and quantitative analysis of the ENAs and the leukocyte profile. Significant responses were observed for both ENAs and leukocyte profile. The responses of ENAs were characterized by an increased incidence of bilobed nuclei in erythroblasts following 1-day exposure to water at 2–4 °C, as well as increased incidence of bilobed nuclei in erythrocytes following 1-day and 6-day exposure to water at 4 °C. In the leukocyte profile, 1-day exposure to water at 2 °C promoted a stress response characterized by diminished levels of circulating lymphocytes (lymphopenia) and elevated levels of circulating monocytes (monocytosis). In conclusion, our results indicate that elevation of water temperature during short periods provoked cellular and physiological stress in N. coriiceps. Furthermore, we conclude that in terms of nuclear alterations, erythrocytes and erythroblasts respond differently to thermal stress. Finally, we conclude that the methodology proposed was efficient in quantifying thermal stress in N. coriiceps and we recommend the utilization of this technique in the biomonitoring of thermal stress in this species and other notothenioids.

Expression dynamics of HSP90 and nitric oxide synthase (NOS) isoforms during heat stress acclimation in Tharparkar cattle.

Six male Tharparkar cattle of 2-3years old were selected for the study. After 15-day acclimation at thermoneutral zone (TNZ) in psychrometric chamber, animals were exposed at 42°C for 6h up to 23days followed by 12days of recovery period. Blood samples were collected during control period at TNZ (days 1, 5, and 12), after heat stress exposure (day 1, immediate heat stress acclimation (IHSA); days 2 to 10, short-term heat stress acclimation (STHSA); days 15 to 23, long-term heat stress acclimation (LTHSA); days 7 and 12, recovery period), and peripheral blood mononuclear cells (PBMCs) were isolated for RNA and protein extraction. The messenger RNA (mRNA) and protein expression in PBMCs were determined by qPCR and western blot, respectively. Samples at TNZ were taken as control. The mRNA expression of HSP90, iNOS, and eNOS was significantly upregulated (P<0.05) on day 1 (ISHA) as compared to control, remained consistent during STHSA, again increased during LTHSA, and finally reduced to basal level during recovery period. The protein expression of HSP90, iNOS, and eNOS were akin to their transcript pattern. PBMC culture study was conducted to study transcriptional abundance of HSP90, iNOS, and eNOS at different temperature-time combinations. The present findings indicate that HSP90, iNOS, and eNOS could possibly play an important role in mitigating thermal insults and confer thermotolerance during long-term heat stress exposure in Tharparkar cattle.

Phenotypic and genome‐wide association analysis of spike ethylene in diverse wheat genotypes under heat stress

The gaseous phytohormone ethylene plays an important role in spike development in wheat (Triticum aestivum). However, the genotypic variation and the genomic regions governing spike ethylene (SET) production in wheat under long-term heat stress remain unexplored. We investigated genotypic variation in the production of SET and its relationship with spike dry weight (SDW) in 130 diverse wheat elite lines and landraces under heat-stressed field conditions. We employed an Illumina iSelect 90K single nucleotide polymorphism (SNP) genotyping array to identify the genetic loci for SET and SDW through a genome-wide association study (GWAS) in a subset of the Wheat Association Mapping Initiative (WAMI) panel. The SET and SDW exhibited appreciable genotypic variation among wheat genotypes at the anthesis stage. There was a strong negative correlation between SET and SDW. The GWAS uncovered five and 32 significant SNPs for SET, and 22 and 142 significant SNPs for SDW, in glasshouse and field conditions, respectively. Some of these SNPs closely localized to the SNPs for plant height, suggesting close associations between plant height and spike-related traits. The phenotypic and genetic elucidation of SET and its relationship with SDW supports future efforts toward gene discovery and breeding wheat cultivars with reduced ethylene effects on yield under heat stress.

Effects of long-term heat stress and dietary restriction on the expression of genes of steroidogenic pathway and small heat-shock proteins in rat testicular tissue

The aim was to investigate the effects of long-term heat stress and dietary restriction on the expression of certain genes involving in steroidogenic pathway and small heat-shock proteins (sHSPs) in rat testis. Sprague Dawley rats (n=24) were equally divided into four groups. Group I and II were kept at an ambient temperature of 22°C, while Groups III and IV were reared at 38°C for 9weeks. Feed was freely available for Group I and Group III, while Group II and Group IV were fed 60% of the diet consumed by their ad libitum counterparts. At the end of 9weeks, testicles were collected under euthanasia. Total RNA was isolated from testis tissue samples. Expression profiles of the genes encoding androgen-binding protein, follicle-stimulating hormone receptor, androgen receptor, luteinising hormone receptor, steroidogenic acute regulatory protein (StAR), cyclooxygenase-2 and sHSP genes were assessed at mRNA levels using qPCR. Long-term heat stress decreased the expression of StAR and HspB10 genes while dietary restriction upregulated StAR gene expression. The results suggested that long-term heat stress negatively affected the expression of StAR and HspB10 genes and the dietary restriction was able to reverse negative effect of heat stress on the expression of StAR gene in rat testis.