Harmful Effects Of Heat Stress Research Articles

Mechanisms underlying reproductive responses of Japanese quails to heat stress conditions.

Exposure to heat stress can cause a significant increase in the death rate and disease susceptibility of poultry birds, ultimately impacting the profitability of the poultry industry. Despite being a more economical choice, Japanese quails (Coturnix japonica) are not immune to the harmful effects of heat stress. Quails may experience negative effects on their reproductive performance due to excessive reactive molecules caused by heat stress. However, they have developed various mechanisms to maintain their reproductive abilities in such conditions. The neuroendocrine system in birds plays a vital role in regulating their reproductive responses to thermal stress, and it is also connected to other environmental factors such as photoperiod that can impact their reproductive performance. Hormones are crucial in the complex interactions necessary for sexual maturation and reproductive responses to heat stress in Japanese quails living in stressful thermal conditions.

Melatonin Application Induced Physiological and Molecular Changes in Carnation (Dianthus caryophyllus L.) under Heat Stress

Carnation is one of the most important ornamental plants worldwide; however, heat stress is a problem, which affects carnation cultivation. The harmful effects of heat stress include impaired vegetative development and reduced floral induction. In this study, to enhance carnation growth under conditions of heat stress, various concentrations of melatonin were added to in vitro culture media. The mechanism by which melatonin reduced heat stress damage was then studied by taking measurements of morphological parameters, levels of reactive oxygen species (ROS), antioxidant enzymes, and malondialdehyde (MDA), as well as differential gene expression, in carnation plants during in vitro culture. These data revealed that untreated carnation plants were more harmed by conditions of heat stress than plants treated with melatonin. Melatonin at concentrations of 5 and 10 mM increased chlorophyll content, fresh weight, and plant height to a greater extent than other concentrations. Melatonin may, thus, be used to alleviate damage to carnations caused by heat stress. The application of melatonin was also found to reduce oxidative damage and enhance antioxidant defense mechanisms. In addition, the expression of heat-related genes was found to be upregulated; in melatonin-treated plants, an upregulation was recorded in the expression of GAPDH, DcPOD1, DcPOD2, DcPOD3, Gols1, MBF1c, HSF30, HSP101, HSP70, and sHSP (MT) genes. In short, we found that melatonin treatment increased heat tolerance in carnation plants. The data presented here may serve as a reference for those seeking to enhance the growth of plants in conditions of heat stress.

Protective effects of SCFAs on organ injury and gut microbiota modulation in heat-stressed rats

PurposeThis research was conducted to investigate the potential of short-chain fatty acids (SCFAs) in protecting organs from heat stress-induced injuries and gut microbiota modulation.MethodsSprague–Dawley rats were randomly assigned to various groups including a control group, a room temperature training group, a hyperthermia training group, SCFAs pretreatment group, and recipients received feces from the HT group. After strenuous training at high temperatures, the levels of plasma enzymes AST, ALT, BUN, and Cr were evaluated. The changes in gut microbiota and fecal metabolites were detected using 16S rRNA sequencing and GC–MS methods. Pathological examination of colon and liver tissues was conducted, and immunohistochemical techniques were employed to assess intestinal barrier function.ResultsThe findings indicate that SCFAs hold the potential for mitigating liver and colon damage caused by heat stress. With the intervention of SCFAs, there were observable changes in the structure and metabolites of the intestinal microbiota, as well as improvements in intestinal barrier function. Further support for the benefits of SCFAs was found through fecal microbiota transplantation, which demonstrated that modified gut microbiota can effectively reduce organ damage.ConclusionsThis study provides evidence that SCFAs, as metabolites of the gut microbiota, have a valuable role to play in regulating gut health and mitigating the harmful effects of heat stress.

High post-flowering phosphorus status promotes the tolerance of soybean to terminal heat stress

Global air temperature is rising and resulting in higher frequency and intensity of extreme climatic events. This scenario threatens food security, requiring measures to mitigate the harmful effects of heat stress on agricultural production. Therefore, our study focused on understanding how phosphorus (P) availability during the reproductive period affects seed weight responses of soybean to terminal heat stress. The experiment was carried out in a complete 3 × 2 factorial design, with varying post-flowering P supply (severe deficiency: 20 μmol P L−1; mild deficiency: 100 μmol P L−1; sufficiency: 500 μmol P L−1) and thermal regimes imposed during the seed filling phase (control: 28.0/18.0 °C; heat stress: 42.0/28.5 °C). Our results revealed that seed weight and yield were unaffected by heat stress in the plants grown under P sufficiency, whereas a detrimental effect of warming on these traits was found in the plants facing post-flowering P deficiency. Sufficient post-flowering P supply alleviated also the harmful effects of heat stress on the integrity of the photosynthetic apparatus, which contributed to improve biomass partitioning to the harvestable organs by extending seed filling duration. Moreover, heat stress disturbed sink metabolism and caused reduction in the concentration of oil and starch solely in the seeds of the plants exposed to P limitation. In conclusion, maintaining adequate post-flowering P supply proves critical in enhancing soybean’s tolerance to terminal heat stress by supporting essential processes involved in effective seed filling. Consequently, implementing precise P nutritional management during the reproductive period of soybean might be a promising approach to improve crop yield stability in challenging environmental conditions.

Effect of heat stress on dairy cow production, reproduction, health, and potential mitigation strategies

Extreme weather events are becoming more common and more severe as a result of climate change, and this has serious implications for the future of livestock, farmer income and livelihoods, and food security worldwide. Dairy cattle have become more heat sensitive due to selective breeding for higher production and increased feedlot operations. The harmful effects of heat stress cause hyperthermia, oxidative stress, and other physiological changes in dairy cows. Environmental heat stress causes a decrease in feed intake, leading to a decrease in milk production in dairy cows. The main method to check for reductions in milk production in dairy cows during the summer is an accurate evaluation of heat stress and effective mitigation strategies. Three primary management strategies have been proposed to reduce heat stress and stabilize dairy cattle performance in increasingly hot and humid climates. Short-term management options include physical alteration of the environment and nutritional management, while long-term management strategy includes discovering heat-tolerant genetic traits and genomic selection for heat tolerance. This review looks at how heat stress has affected the dairy industry’s sustainability and elaborates on genomic selection for thermotolerance in dairy cattle as sustainable breeding practices to increase dairy cows’ ability to withstand high temperatures.

Thermopriming mitigates the effects of heat stress by modulating the expression of Heat shock factors in Brassica juncea (Indian mustard)

Brassica juncea (also known as Indian mustard) is an important vegetable oil seed crop whose growth and productivity is severely affected by heat stress. Interestingly, pre-exposure to sublethal heat stress, referred as thermopriming can remarkably enhance the plant heat stress tolerance. However, little is known about the impact of thermopriming on heat stress response of the important oil seed crop, B. juncea. In this study, we investigated the basal and thermopriming-induced heat stress response of 16 different cultivated, agronomically important varieties of Brassica juncea. Based on their basal heat stress response, we classify the varieties as heat sensitive, moderately tolerant or tolerant. Notably, almost all the varieties displayed enhanced heat stress tolerance upon thermopriming (acquired thermotolerance), albeit to varying magnitudes. Strikingly, the high oil-yielding, drought tolerant, heat sensitive variety Pusa Bold showed remarkable acquired thermotolerance upon thermopriming. Investigations in Pusa Bold indicate that the thermopriming-induced acquired thermotolerance predominantly correlates with the rapid activation of ROS scavenging mechanisms and differential expression of Heat Shock Family of transcription factors (BjHSFs). Taken together, our study reveals the positive impact of thermopriming in alleviating the harmful effects of heat stress on Brassica juncea seedlings and paves the path to enhance heat stress tolerance for improved productivity in the important oilseed crop Indian mustard.

Baicalin inhibits oxidative injures of mouse uterine tissue induced by acute heat stress through activating the Keap1/Nrf2 signaling pathway

Heat stress effect the physiological functions of body, and reproductive system is one of the most sensitive. It's imperative to find out suitable measures to alleviate harmful effects of heat stress. Baicalin is well-known with its antioxidative property. To examine whether Baicalin could reduce oxidative injures of uterine tissue in heat-stressed mice. The mice were divided into four groups: control (Con), Baicalin (Bai), heat stress (H) and heat stress plus Baicalin (H + Bai). The oxidative damage of uterine tissue was detected by ELISA, H&E staining, tunnel assay and immunohistochemical staining. The protein/mRNA expressions of Keap1/Nrf2 related factors were detected by Western blot or QPCR. The results showed that mice heat-stressed at 41 °C for 2 h induced macroscopic changes, significantly increased MDA content and reduced activities of antioxidant enzymes including SOD, CAT and GSH-Px of the uterine tissue. Compared with Con group, heat stress up-regulated caspase-3 and caspase-9, enhanced the apoptosis of endometrial epithelial and glandular epithelial cells, improved the HO-1 mRNA/protein and NQO1 protein expressions, while down-regulated the mRNA/protein of Keap1. Compared with H group, antioxidant enzyme activities, Nrf2 protein and Nrf2, NQO1 and GCLC mRNA expressions were significantly increased in the H + Bai group. While the uterine epithelial cells apoptosis, MDA contents, caspase-3, caspase-9 and Keap1 protein and HO-1 mRNA expressions were decreased in the H + Bai group of mice compared with that in H group. Briefly, acute heat stress causes oxidative injures and apoptosis of mouse uterine tissue and Baicalin protects uterine tissue from the damages possibly through Keap1/Nrf2 signaling pathway.

The effect of heat stress on the epidermal growth factor (EGF)-mediated intracellular signaling, and changes cell behavior on swine testicular cell

At present, high environmental temperature is the main factor endangering animal production, growth and development. Therefore, the harmful effects of heat stress led by hot environment on livestock have attracted much attention. In this work, the cellar property and signaling property of epidermal growth factor (EGF) below heat stress remains unclear in swine testicular cells. Here, the effect of heat stress on EGF-induced intracellular signaling and cell behavior was explored in the ST (a porcine testis cell line). A series of experiments were done to study the cellular behavior and signaling properties of EGF under heat stress. It can be discovered which high ambient temperature changed the cellular characteristics of EGF/EGFR. The eventuates displayed when cells were exposed to thermal environment, EGF/EGFR basically did not internalize, mainly gathered on the cell membrane. Our group also researched the effect of EGF’s signaling properties, and the results showed that the ability of EGF to activate EGFR-mediated intracellular signaling decreased significantly under heat stress. Finally, this study illustrated that EGF’s cell behavior and signaling profile are obviously altered, indicating that heat stress seriously affected the biological activity of EGF/EGFR, which establish a solid foundation for studying the effect of the EGF on testicular tissue under heat environment.

The role of antioxidant compounds in plant heat tolerance

Plants are sessile organisms, therefore cannot move to more favorable environments; consequently, plant growth and developmental processes are affected, often lethally by stress. High temperature or ‘Heat’ stress is known as major environmental stress that limits plant growth, metabolism, and productivity worldwide. Heat stress is often defined as the rise in temperature beyond a threshold level for a period of time sufficient to cause irreversible damage to plant growth and development. The increase of temperature up to a certain level increases plant growth, photosynthesis, respiration and enzyme activity and after that these parameters tend to decline. One of the ways to deal the with adverse effects of heat stress may involve exploring some molecules that have the potential to protect the plants from the harmful effects of heat stress In recent decades exogenous protectant such as osmoprotectants (proline, glycinebetaine, trehalose, etc.), plant hormone (gibberellic acids, jasmonic acids, brassinosterioids, salicylic acid, etc.), signaling molecules (nitric oxide, hydrogen peroxide, etc.), polyamines (spermidine, spermine, putrescine), trace elements (selenium, silicon, etc.) antioxidants (ascorbic acid, thiamine, glutathione, tocopherol, etc.), have been found effective in mitigating the abiotic stress induced damage in plant. Current report showed that several antioxidants compound such as ascorbic acid and thiamine perform positive effect to combat heat stress in plant is dose dependent manner.

In-Vivo Biophoton Emission, Physiological and Oxidative Responses of Biostimulant-Treated Winter Wheat (Triticum eastivum L.) as Seed Priming Possibility, for Heat Stress Alleviation.

High temperature induces oxidative processes in wheat, the alleviation of which is promising using biostimulants. Priming has been used for enhancing stress tolerance of seedlings. However, the usage of biostimulants for priming is an unexplored area under either normal or stress conditions. Therefore, the aim of our study was to evaluate the heat stress alleviation capability of differentially applied biostimulant treatments on wheat seedlings. The investigation included stress parameters (fresh/dry weight ratio, chlorophyll content estimation, antioxidant capacity and lipid oxidation) combined with biophoton emission measurement, since with this latter non-invasive technique, it is possible to measure and elucidate in vivo stress conditions in real-time using lipid oxidation-related photon emissions. We confirmed that a single biostimulant pretreatment increased antioxidant capacity and decreased biophoton release and lipid oxidation, indicating the reduction of the harmful effects of heat stress. Therefore, biophoton emission proved to be suitable for detecting and imaging the effects of heat stress on wheat seedlings for the first time. Two-way analysis of variance (ANOVA) revealed that biostimulant (p = 4.01 × 10−7) treatments, temperature (p = 9.07 × 10−8), and the interaction of the two factors (p = 2.07 × 10−5) had a significant effect on the overall count per second values of biophoton emission, predicting more efficient biostimulant utilization practices, even for seed priming purposes.

The Effects of Heat Shock Protein 70 Addition in the Culture Medium on the Development and Quality of In Vitro Produced Heat Shocked Bovine Embryos.

Simple SummaryEuropean dairy cows are extremely sensitive to heat stress. During hot summers milk yield is suppressed, welfare status of the cows is aggravated, and their fertility is seriously compromised. The observed subfertility is attributed to endocrinological alterations and mainly to inability of the early embryo to develop uneventfully until the implantation stages. To protect the integrity and the functionality of their cells, all mammals have inherent defense mechanisms against external insults. A major representative of these molecules are the heat shock proteins (HSPs) that are secreted by almost all cells. In this study, we examined the effects of exogenous HSP70 on the developmental competence and quality of early embryos produced in vitro, after 24-h exposure to slightly elevated temperature. Our findings imply that the temperature rise is detrimental for the developmental potential of the early embryos, and that the HSP70 can partly mitigate the harmful effects of heat stress, by improving the embryo yield and by reducing the adverse effects of heat stress on some embryo quality characteristics.The aims of the present study were to examine the effects of HSP70 addition in the in vitro culture medium of day 3 embryos on their developmental competence and quality. Bovine oocytes (n = 1442) were in vitro matured, inseminated and cultured for the first two days according to standardized methods. The presumptive zygotes were randomly allocated in three experimental groups: Control, C (embryos cultured at 39 °C throughout the culture period), group C41 (temperature was raised to 41 °C from the 48th to 72nd h post insemination (p.i.) and then it returned at 39 °C for the remaining culture period), and group H41 (the temperature modification was the same as in C41 and during heat exposure, HSP70 was added in the culture medium). Cleavage and embryo yield were assessed 48 h p.i. and on days 7, 8, 9, respectively and gene expression in day 7 blastocysts was assessed by RT-PCR. Blastocyst yield was the highest in group C39; and higher in group H41 compared to group C41. From the gene expression analyses, altered expression of 11 genes was detected among groups. The analysis of the orchestrated patterns of gene expression differed between groups. The results of this study confirm the devastating effects of heat stress on embryo development and provide evidence that HSP70 addition at the critical stages can partly counterbalance, without neutralizing, the negative effects of the heat insult on embryos, acting mainly through mechanisms related to energy deployment.

Comparison of the effects of Presynch-Ovsynch, Presynch- Ovsynch+CIDR, and G6G protocols on the reproductive performance of lactating Holstein cows in the postpartum period

This study was performed on an industrial dairy farm near Tehran province, Iran, on 666 lactating Holstein cows from September 2019 to June 2020 in order to eliminate the harmful effects of heat stress on the reproductive performance of the cows. The hypothesis of the recent study was that by increasing the serum concentration of progesterone (P4) in the luteal phase before insemination in the form of Presynch-Ovsynch+CIDR (POC) and G6G protocols, the pregnancy rate of cows would be increased compared to the Presynch-Ovsynch (PO) protocol. The aim of the present study was to evaluate the effects of Presynch-Ovsynch (PGF2α-14d- PGF2α-12d-Ovsynch (OVS: GnRH(GnRH1)- 7d-PGF2α(PG)-2d-GnRH)-18h-Fixed-time artificial insemination (FTAI), n=212), Presynch-Ovsynch+CIDR (similar to the PO protocol, plus the use of a CIDR for 7 days, from the start of the OVS+FTAI protocol to the time of PG injection, n=230), and G6G (PGF2α- 2d-GnRH-6d-OVS+FTAI, n=224) protocols on the reproductive performance and pregnancy rate of lactating Holstein cows. The average body condition score (BCS) for the cows was about 2.5 at the time of the onset of the OVS+FTAI program. The average daily milk production for cows at the time of the start of the OVS+FTAI program was 38.3 kg/day. On average, the studied cows were inseminated 86 days postpartum. Implementation of the G6G protocol in comparison to the PO and POC protocols increased the serum concentration of P4 at GnRH1 (P=0.04). The cows that received the G6G protocol had a greater number of corpuses luteum (CL) on their ovaries at PG in comparison to the cows in the PO and POC protocols (P=0.03 and P=0.05, respectively). For all treatment protocols, the pregnancy rate of cows with >2 CLs on their ovaries at PG was significantly higher than for cows with ≤2 CLs on their ovaries at this time. The overall pregnancy rate for all cows studied was 42%. Separately, pregnancy rates for cows in PO, POC, and G6G protocols were calculated at 36.7%, 41.7%, and 47.3% respectively. The highest and the lowest pregnancy rates were obtained in the G6G and PO protocols, respectively (P=0.03). It can be concluded that the G6G protocol increased the pregnancy rate of cows in comparison to the PO but not to the POC protocol. This result can be attributed to the increase in serum concentration of P4 at GnRH1 and the greater number of CLs at PG following implementation of the G6G compared to the PO protocol. Although CIDR administration in the POC protocol led to an increase in the pregnancy rate of cows compared to the PO protocol, possibly by increasing the synchrony rate and the quality of the ovulatory follicle, this increase was not statistically significant (P=0.09).

EFFECTS OF TERMINAL HEAT STRESS AND THEIR RESPONSIVE MECHANISMS IN ELITE WHEAT GENOTYPES: A REVIEW

Wheat is the most important cereal crop in the world that ranks first position in terms of production and trade. In Nepal this is the third most cultivated crop after rice and maize. Various environmental constraints including heat stress have been determined to be a great factor to limit world wheat production. High temperature leaves a devastating impact in wheat production by affecting different stages including germination, plant growth, anthesis and grain filling etc. heat stress also affects photosynthesis process and responsible for the lower biomass yield. Various studies have shown that the reproductive stages of wheat plant are more susceptible to heat stress than vegetative stages. Heat stress hinders germination, reduce plant growth, decrease number of plant population per unit area and causes leaf senescence. Water relation disturbance and oxidative damage to plants are other harmful effects of heat stress in wheat plants. Plant also has tolerance mechanism against such heat induced stresses. Such mechanisms include avoidance against heat stress, production of heat shock protein and antioxidant mechanisms.

Behavioural, physiological, neuro-endocrine and molecular responses of cattle against heat stress: an updated review

The negative impact of heat stress on cattle growth, development, reproduction and production has been quite alarming across the world. Climate change elevates earth surface temperature which exacerbates the wrath of heat stress on cattle. Moreover, cattle in tropical and sub-tropical countries are most commonly affected by the menace of heat stress which severely wane their production and productivity. In general, cattle exhibit variousthermoregulatory responses such as behavioural, physiological, neuro-endocrine and molecular responses to counteract the terrible effects of heat stress. Amongst the aforementioned thermoregulatory responses, behavioural, physiological and neuro-endocrine responses are regarded as most conventional and expeditious responses shown by cattle against heat stress. Furthermore, molecular responses serve as the major adaptive response to attenuate the harmful effects of heat stress. Therefore, present review highlights the significance of behavioural, physiological, neuro-endocrine and molecular responses which act synergistically to combat the deleterious effects of heat stress thereby confer thermo-tolerance in cattle.

Heat Stress in Broiler Chickens and the Effect of Dietary Polyphenols, with Special Reference to Willow (Salix spp.) Bark Supplements-A Review.

Over the last decade, there has been a growing interest in the use of a wide range of phytoadditives to counteract the harmful effects of heat stress in poultry. Willow (Salix spp.) is a tree with a long history. Among various forms, willow bark is an important natural source of salicin, β-O-glucoside of saligenin, but also of polyphenols (flavonoids and condensed tannins) with antioxidant, antimicrobial, and anti-inflammatory activity. In light of this, the current review presents some literature data aiming to: (1) describe the relationship between heat stress and oxidative stress in broilers, (2) present or summarize literature data on the chemical composition of Salix species, (3) summarize the mechanisms of action of willow bark in heat-stressed broilers, and (4) present different biological effects of the extract of Salix species in different experimental models.

An updated review on cattle thermoregulation: physiological responses, biophysical mechanisms, and heat stress alleviation pathways.

Heat stress is one of the main obstacles to achieving efficient cattle production systems, and it may have numerous adverse effects on cattle. As the planet undergoes climatic changes, which is predicted to raise the earth's average temperature by 1.5 °C between 2030 and 2052, its impact may trigger several stressful factors for livestock. Among these, an increase in core body temperature would trigger physiological imbalance, consequently affecting reproduction, animal health, and dry matter intake adversely. Core body temperature increase is commonly observed and poses challenges to livestock farmers. In cattle farming, thermal stress severely affects milk production and weight gain, and can compromise food security in the coming years. This review presents an updated approach to the physiological and thermoregulatory responses of cattle under various environmental conditions. Strategies for mitigating the harmful effects of heat stress on livestock are suggested as viable alternatives for the betterment of production systems.

Variability of malondialdehyde content and yield elements in Triticum aestivum L. under heat stress conditions

Heat stress has a significant effect on the growth and development of cereals and affects cereals production by reducing the total yield. High temperatures in plants lead to oxidative stress, which creates reactive oxygen species that are specific to cause damage to the cell membrane. Due to the action of reactive oxygen species, lipid peroxidation can occur. For that reason, it is important to find cultivars that are more resistant to the harmful effects of heat stress and thus enable higher productivity. The aim of this study was to determine the effect of heat stress on the degree of lipid peroxidation and yield elements in leaves of 10 wheat cultivars, in order to select cultivars more resistant to heat stress. The degree of lipid peroxidation was determined spectrophotometrically by measuring the concentration of reactive substances of thiobarbiturate acid (mainly malondialdehyde - MDA). The cultivar Renesansa with the largest increase in MDA in conditions of high air temperature (2.848 µmol/g fw) was also characterized by the lowest yield (2870 kg/ha). On the other hand, the cultivar Talas with the smallest increase in MDA content (1800 µmol/g fw) in conditions of high air temperature showed significantly higher yield (3830 kg/ha). In this paper was shown that lipid peroxidation has a significant effect on yield reduction in the investigated wheat cultivars. Cultivars Talas, Apač, Hyfi, Mila and Salasar were characterized as cultivars more resistant to heat stress with higher yields. These results suggest that wheat cultivars were significantly different in their ability to respond to heat stress, which could be useful for the development of tolerant wheat cultivars in the breeding programs.

Impacts of Strain Variation on Response to Heat Stress and Boldo Extract Supplementation to Broiler Chickens.

Simple SummaryOne of the common approaches to alleviating heat-stress in poultry is nutritional manipulation using herbal extracts or their derivatives to maintain the health, welfare, and performance of birds. The present study investigated the protective effect of boldo leaf extract against the harmful effects of cyclic heat stress in two broiler strains (Arbor Acres; AA and Avian-48; AV). Administration of boldo in drinking water was able to restore growth and health traits to nearly normal values. Generally, AA chicks were better able to withstand heat stress and were also more likely to utilize boldo extract than AV chicks. The use of boldo leaf extract in poultry production can assist in mitigating the effect of heat stress, improving the antioxidant defense system, and increasing productivity and profitability.There is increasing interest in the use of natural antioxidant supplements in poultry diets as protection against the adverse effects of heat stress. The potential protective effect of boldo (Peumus boldus molina) leaf extract, which have antioxidant activity, were investigated against the harmful effects of heat stress in two broiler strains. Arbor Acres (AA) and Avian-48 (AV) chicks were divided into thermoneutral (TN) and heat stress (HS) groups and treated with 1 g boldo leaf extract/4 L drinking water during the heat stress period. HS reduced growth performance in both strains. The phagocytic index, phagocytic activity, and eosinophil and lymphocytes counts were significantly elevated in TN and HS AV birds but not altered in AA birds. Boldo extract treatment partially eliminated the previous negative impacts of heat stress. AA chicks were better able to withstand HS than AV chicks. Serum concentrations of total lipids and cholesterol were reduced in HS birds of both strains. Malondialdehyde, superoxide dismutase, and glutathione peroxidase levels were elevated but restored with the administration of boldo leaf extract in HS birds of both strains. Economic parameters were negatively affected by HS but restored to values close to those of the control group in boldo-treated HS birds. In conclusion, the administration of boldo leaf extract in drinking water was effective in neutralizing the harmful effects of heat stress on growth performance, blood indices, and economic parameters and improved the antioxidant defense system in heat-stressed birds.

Plant growth-regulating molecules as thermoprotectants: functional relevance and prospects for improving heat tolerance in food crops.

Among various abiotic stresses, heat stress is one of the most damaging, threatening plant productivity and survival all over the world. Warmer temperatures due to climatic anomalies above optimum growing temperatures have detrimental impacts on crop yield potential as well as plant distribution patterns. Heat stress affects overall plant metabolism in terms of physiology, biochemistry, and gene expression. Membrane damage, protein degradation, enzyme inactivation, and the accumulation of reactive oxygen species are some of the harmful effects of heat stress that cause injury to various cellular compartments. Although plants are equipped with various defense strategies to counteract these adversities, their defensive means are not sufficient to defend against the ever-rising temperatures. Hence, substantial yield losses have been observed in all crop species under heat stress. Here, we describe the involvement of various plant growth-regulators (PGRs) (hormones, polyamines, osmoprotectants, antioxidants, and other signaling molecules) in thermotolerance, through diverse cellular mechanisms that protect cells under heat stress. Several studies involving the exogenous application of PGRs to heat-stressed plants have demonstrated their role in imparting tolerance, suggesting the strong potential of these molecules in improving the performance of food crops grown under high temperature.

The adaptogenic anti-ageing potential of resveratrol against heat stress-mediated liver injury in aged rats: Role of HSP70 and NF-kB signalling.

Heat stress (HS) is a major international problem which has attracted a considerable attention due to its oxidative tissue effects and high morbidity and mortality rates, especially among elderly people. Discovering an effective antioxidant is pivotal for overcoming HS-induced injury. Therefore, the aim of this study was to estimate the hepatic protective effects of orally supplemented resveratrol (RES) against HS-mediated liver injury in young and old male Wistar albino rats. Compared to control rats, RES administered orally at a dose of 20 mg/kg BW for 21 successive days efficiently ameliorated HS-induced oxidative damage by significantly increasing (P ≤ 0.05) the level of reduced glutathione and glutathione peroxidase, and decreasing the levels of malondialdehyde and TNF-α in hepatic tissue of both young and aged rats. However, level of NF-κB was downregulated significantly in aged rats rather than young rats. Moreover, RES significantly decreased (P ≤ 0.05) the serum levels of aspartate transaminase and alkaline phosphatase in both ages of rats compared to their corresponding HS-stressed rats. Furthermore, RES upregulated the immunohistochemical expression of caspase 3 and heat shock protein 70 in young and aged rats, however it was more pronounced in young one. In addition, RES administration moderately normalized (P ≤ 0.0001) the harmful effects of HS on the hepatic architecture of both young and aged rats. In conclusion, this study reveals for the first time that RES exerts promising hepato-ameliorative effects against HS-induced oxidative stress in the young and aged rats via its antioxidant, anti-inflammatory, and anti-apoptotic effect, as well as via its inhibitory effect against the NF-κB signalling in a cellular system.