Absence Of Thermal Stress Research Articles

A comprehensive study on the jet electrodeposition method for fabricating 3D structures with overhangs

Electrochemical additive manufacturing (ECAM) is gaining increasing attention in the fabrication of micro/nano-scale metal structures due to its advantages, such as high forming accuracy, low porosity, absence of thermal stress, etc. Among various ECAM techniques, interest is increasingly enhanced in jet electrochemical deposition (Jet ECD) approach due to its ultra-high deposition rate. Despite its inherent advantages as a high-efficiency ECAM process, Jet ECD still faces challenges for automated fabrication of complex 3D structures due to suitable control of the jetted flow. In the present study, a step-delay method based on Jet ECD is proposed. This approach allows for the automation of the fabrication process using commonly employed stepper motor translational stages, seamlessly integrating it into the current 3D printing framework. By adjusting the moving time of the stages and the delay time between two successive steps, agreement between the movement of the stages and the temporally nonlinear electrodeposition rate can be achieved. Consequently, complex 3D copper structures with overhangs, such as 3D helical structures, are successfully obtained. It is found the deposition rate can be as high as ∼25 µm/min, and the maximum overhanging angle that can be achieved by the automated step-delay method is ∼60°. The mechanical properties of the deposited copper using the proposed approach have been thoroughly characterized by various techniques. The average grain size of the deposited copper can be as small as 0.5 µm without preferred orientation. It also shows that highly dense structures with porosity of less than 0.1% can be obtained, and the elastic modulus of the deposited copper ranges from 3 - 20 GPa. In future studies, it is anticipated that larger overhanging angles can be achieved by incorporating image recognition techniques in the step-delay method.

Still standing: The heat protection delivered by a facultative symbiont to its aphid host is resilient to repeated thermal stress.

Insects have evolved diverse strategies to resist extreme high temperatures (EHT). The adaptive value of such strategies has to be evaluated when organisms experience multiple EHT events during their lifetime, as predicted in a changing climate. This is particularly the case for associations with facultative microbial partners involved in insect heat tolerance, the resilience of which to repeated heat stress has never been studied. We compared two artificial lines of the pea aphid (Acyrthosiphon pisum) differing by the absence or presence of the heat-protective facultative bacterium Serratia symbiotica. We exposed insect nymphs to a varying number of EHT events (between 0 and 3), and recorded fitness parameters. Except survival traits, fitness estimates were affected by the interaction between aphid infection status (absence/presence of S. symbiotica) and thermal treatment (number of heat shocks applied). Costs of bacterial infection were detected in the absence of thermal stress: symbiont-hosting aphids incurred longer development, decreased fecundity and body size. However, symbiotic infection turned neutral, and even beneficial for some traits (development and body size), as the number of heat shocks increased, and compared to the aposymbiotic strain. Conversely, symbiotic infection mediated aphid response to heat shock(s): fitness decreased only in the uninfected group. These findings suggest that (i) the facultative symbiont may alternatively act as a pathogen, commensal or mutualist depending on thermal environment, and (ii) the heat protection it delivered to its host persists under frequent EHT. We discuss eco-evolutionary implications and the role of potentially confounding factors (stage-specific effects, genetic polymorphism displayed by the obligate symbiont).

Antioxidant responses of triangle sail mussel Hyriopsis cumingii exposed to toxic Microcystis aeruginosa and thermal stress

Harmful algal blooms (HABs) and thermal stress as climate changes become more common in global water ecosystem, especially under eutrophic habitats. Here our study examined the combined impacts of bloom forming cyanobacteria Microcystis aeruginosa and thermal stress on the antioxidant responses of the ecologically important species triangle sail mussel Hyriopsis cumingii. The differential responses of a series of enzymes, e.g. superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione-S-transferase (GST), as well as signal metabolites including reactive oxygen species (ROS), malondialdehyde (MDA) and glutathione (GSH) involved in antioxidant defense mechanisms were analyzed during 14 d exposure to toxic cyanobacterium M. aeruginosa and 7 d depuration period. The activities of SOD and GPx as well as the content of ROS and MDA in H. cumingii increased, while CAT activity reduced due to M. aeruginosa exposure. Thermal stress resulted in decrease of CAT, the accumulation of GSH and the enhance of GST and SOD. Meanwhile, the interactive effects among M. aeruginosa, thermal stress and time were also observed on most parameters except for GST activity. The total amount of microcystins (MC) in sail mussels increased with concentrations of exposed M. aeruginosa, independently of the presence or absence of thermal stress. Although around 50% of MC in mussels dropped in the depuration period, most parameters showed alterations because of cyanobacteria exposure and thermal stress. Overall, these findings suggested that toxic cyanobacteria or thermal stress induces oxidative stress and severely affects the enzymes activities and intermediates level associated with antioxidant defense mechanisms in sail mussels respectively. More importantly, the toxic impacts on sail mussels could be intensified by their combination.

The homeodomain-interacting protein kinase HPK-1 preserves protein homeostasis and longevity through master regulatory control of the HSF-1 chaperone network and TORC1-restricted autophagy in Caenorhabditis elegans

An extensive proteostatic network comprised of molecular chaperones and protein clearance mechanisms functions collectively to preserve the integrity and resiliency of the proteome. The efficacy of this network deteriorates during aging, coinciding with many clinical manifestations, including protein aggregation diseases of the nervous system. A decline in proteostasis can be delayed through the activation of cytoprotective transcriptional responses, which are sensitive to environmental stress and internal metabolic and physiological cues. The homeodomain-interacting protein kinase (hipk) family members are conserved transcriptional co-factors that have been implicated in both genotoxic and metabolic stress responses from yeast to mammals. We demonstrate that constitutive expression of the sole Caenorhabditis elegans Hipk homolog, hpk-1, is sufficient to delay aging, preserve proteostasis, and promote stress resistance, while loss of hpk-1 is deleterious to these phenotypes. We show that HPK-1 preserves proteostasis and extends longevity through distinct but complementary genetic pathways defined by the heat shock transcription factor (HSF-1), and the target of rapamycin complex 1 (TORC1). We demonstrate that HPK-1 antagonizes sumoylation of HSF-1, a post-translational modification associated with reduced transcriptional activity in mammals. We show that inhibition of sumoylation by RNAi enhances HSF-1-dependent transcriptional induction of chaperones in response to heat shock. We find that hpk-1 is required for HSF-1 to induce molecular chaperones after thermal stress and enhances hormetic extension of longevity. We also show that HPK-1 is required in conjunction with HSF-1 for maintenance of proteostasis in the absence of thermal stress, protecting against the formation of polyglutamine (Q35::YFP) protein aggregates and associated locomotory toxicity. These functions of HPK-1/HSF-1 undergo rapid down-regulation once animals reach reproductive maturity. We show that HPK-1 fortifies proteostasis and extends longevity by an additional independent mechanism: induction of autophagy. HPK-1 is necessary for induction of autophagosome formation and autophagy gene expression in response to dietary restriction (DR) or inactivation of TORC1. The autophagy-stimulating transcription factors pha-4/FoxA and mxl-2/Mlx, but not hlh-30/TFEB or the nuclear hormone receptor nhr-62, are necessary for extended longevity resulting from HPK-1 overexpression. HPK-1 expression is itself induced by transcriptional mechanisms after nutritional stress, and post-transcriptional mechanisms in response to thermal stress. Collectively our results position HPK-1 at a central regulatory node upstream of the greater proteostatic network, acting at the transcriptional level by promoting protein folding via chaperone expression, and protein turnover via expression of autophagy genes. HPK-1 therefore provides a promising intervention point for pharmacological agents targeting the protein homeostasis system as a means of preserving robust longevity.

Abstract 128: Mitochondrial CaMKII Plays Important Physiological and Pathological Roles

Calcium/calmodulin-dependent protein kinase II (CaMKII) is known for its roles in fight-or-flight responses, where it mobilizes ATP-consuming processes to maximize power output by regulating cellular Ca 2+ . We hypothesized that CaMKII may also influence ATP-generating processes in a feedforward mechanism to match ATP consumption with demand. Most cellular ATP is produced by oxidative phosphorylation (OXPHOS) in mitochondria; therefore, we generated transgenic animals whose mitochondrial CaMKII activity is boosted or inhibited by overexpressing mitochondrial targeted CaMKII (mtCaMKII), or a specific CaMKII inhibitor (mtCaMKII N ). We found that mitochondria from mtCaMKII mice have increased activity of pyruvate dehydrogenase and various TCA cycle enzymes. However, these mitochondria failed to provide sufficient ATP for cardiac function, likely due to detrimental remodeling of electron transport chain complex I. As a result, mtCaMKII mice develop a unique dilated cardiomyopathy soon after birth, which could be rescued by overexpressing the mitochondrial but not the myofibrillar form of creatine kinase. mtCaMKII N mice are protected against lipopolysaccharides (LPS)-induced mortality, ischemia/reperfusion injury, adverse cardiac remodeling after myocardial infarction and asthma. Furthermore, Drosophila melanogaster overexpressing mtCaMKII N have longer lifespan under heat stress (29 o C) and are resistant to paraquat, an ROS-inducing agent. However, in the mice, inhibiting mitochondrial CaMKII reduces metabolic fitness required to sustain the isoproterenol-induced fight-or-flight response, leading to elevated utilization of the cardiac glycogen store and increased lactate production. mtCaMKII N mice have reduced spontaneous activity and a higher tendency to gain fat mass when fed a high-fat diet; mtCaMKII N flies have a shorter lifespan in the absence of thermal stress (25 o C). We are using phosphoproteomics, metabolomics and in silico modeling approaches to determine the mechanisms by which mtCaMKII regulates energy metabolism and stress responses. Our results have provided important insights into the physiological and pathological roles of mitochondrial CaMKII.

Desempenho produtivo de coelhos criados em jaulas sob o efeito de duas densidades

The production of rabbit`s meat using the flat deck cage systems, should consider a minimum space per animal. The stocking density should be assessed considering the effect on the animal welfare and productive capacities. The objective of this work was to study the growth of rabbits through fattening submitted to different densities. In a commercial farm 300 rabbits were distributed in 40 cages with a floor area of 3600 cm2/cage, subjected to the following densities: 6 (6C) and 9 (9C) rabbits/cage. The animals were weighed at weaning, 37 days old (d), and at 64 d and 71 d. Also, the food consumption, the temperature (T) and relative humidity (RH) were registered. Data were analyzed by ANOVA, to evaluate the effect of density on body weight (BW), average daily gain (ADG) and conversion index (CI) and to assess the effect of two fattening periods in the environmental parameters. There were differences (P<0,05) in live weight at 64 and 71 d of age, with the group 6C presenting higher values relative to 9C. The stocking density for the three ages were respectively for 6C and 9C, 16.6 and 24.5 kg/m2 (37 d), 38.7 and 53.7 kg/m2 (64 d), 43.0 and 56.5 kg/m2 (71 d). The 37-64 d, 64-71 d and 37-71 d ADG were influenced by the density, with higher growth for 6C. Concerning feeding conversion it was not observed the effect of stocking density. Mortality was higher in 9C (P<0.01). These differences may be justified by the high density stocking and competition for access to food. The values of T, HR and temperature-humidity index-ITH were 21.0°C, 86.7% and 20.7. For ITH, 100.0% of the observations were less than 27.8, indicating the absence of thermal stress.

Regulation of embryonic development and apoptotic-related gene expression by brain-derived neurotrophic factor in two different culture conditions in ovine

In the present study, we aimed to evaluate effects of brain-derived neurotrophic factor (BDNF) which is a member of neurotrophic factor family on developmental competence of oocytes in sheep. In vitro maturation was performed in presence of various concentrations (0, 10, and 100 ng/mL) of BDNF. Meiotic maturation, levels of intracellular glutathione, embryonic developmental potential after parthenogenetic activation, number of total and apoptotic cells in blastocysts, and expression of Bax and Bcl-2 genes in blastocyst cells were determined. Under unstressed condition, while at 100 ng/mL concentration, BDNF increased the IVM rate; an increase of glutathione level was observed at 10 ng/mL concentration. Moreover, when BDNF-treated oocytes were used for parthenogenetic activation, more blastocyst at both 10 and 100 ng/mL levels was obtained in comparison with the untreated group. Under heat stress (HS), the blastocyst rate was dramatically reduced in untreated oocytes compared to that obtained from 10 ng/mL BDNF groups. Total cell number in blastocysts was not affected by the treatment groups. The mean of Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive nuclei in blastocysts was not influenced by addition of BDNF in medium and that presence or absence of thermal stress during IVM than the control group. Moreover, our data revealed that the expression of Bax and Bcl-2 genes in blastocysts was affected by both BDNF concentration and HS. Conclusively, supplementation of IVM medium with 10 ng/mL BDNF had a beneficial effect on sheep oocyte competence by increasing the rate of blastocyst especially when HS exists.

Inhibition of photosynthetic CO2 fixation in the coral Pocillopora damicornis and its relationship to thermal bleaching

Two inhibitors of the Calvin-Benson cycle [glycolaldehyde (GA) and potassium cyanide (KCN)] were used in cultured Symbiodinium cells and in nubbins of the coral Pocillopora damicornis to test the hypothesis that inhibition of the Calvin-Benson cycle triggers coral bleaching. Inhibitor concentration range-finding trials aimed to determine the appropriate concentration to generate inhibition of the Calvin-Benson cycle, but avoid other metabolic impacts to the symbiont and the animal host. Both 3 mmol l(-1) GA and 20 μmol l(-1) KCN caused minimal inhibition of host respiration, but did induce photosynthetic impairment, measured by a loss of photosystem II function and oxygen production. GA did not affect the severity of bleaching, nor induce bleaching in the absence of thermal stress, suggesting inhibition of the Calvin-Benson cycle by GA does not initiate bleaching in P. damicornis. In contrast, KCN did activate a bleaching response through symbiont expulsion, which occurred in the presence and absence of thermal stress. While KCN is an inhibitor of the Calvin-Benson cycle, it also promotes reactive oxygen species formation, and it is likely that this was the principal agent in the coral bleaching process. These findings do not support the hypothesis that temperature-induced inhibition of the Calvin-Benson cycle alone induces coral bleaching.

Investigation of the Interface Parameters of Fiber-Reinforced Composite Materials

Design of the interfacial properties is a significant fundamental issue in the field of composite materials. Much attention has been paid to the improvement of the interface strength, while there has been a little work concerning the mechanical design of the interface for fiber-reinforced polymers (FRPs) in which the fiber is transversely isotropic thanks to its orientation feature. Based on the conception of neutral inclusion and imperfect interface conditions, the interface parameters are obtained for the FRPs by using Kolosov constant. We demonstrate the effect of the thermal residual stresses on the neutrality for FRPs in this paper. If the interface has the properties of design parameters without consideration of thermal stress, the presence of thermal residual stress/strain would break the neutrality in the cases of equal-biaxial tension and pure shear. In particular, the neutral fiber does not exist unless the thermal stress is eliminated in the equal-biaxial tension. In the case of uniaxial tension, the neutral fiber does not exist in absence of thermal stress, while the neutrality would become possible by properly controlling the thermal residual stress. Because the large thermal residual stress will result in the formation of cracks in matrix, a trade-off design is necessary between the neutrality and the initiation of matrix cracking.

Plantation Forestry under Global Warming: Hybrid Poplars with Improved Thermotolerance Provide New Insights on the in Vivo Function of Small Heat Shock Protein Chaperones

Climate-driven heat stress is a key factor affecting forest plantation yields. While its effects are expected to worsen during this century, breeding more tolerant genotypes has proven elusive. We report here a substantial and durable increase in the thermotolerance of hybrid poplar (Populus tremula×Populus alba) through overexpression of a major small heat shock protein (sHSP) with convenient features. Experimental evidence was obtained linking protective effects in the transgenic events with the unique chaperone activity of sHSPs. In addition, significant positive correlations were observed between phenotype strength and heterologous sHSP accumulation. The remarkable baseline levels of transgene product (up to 1.8% of total leaf protein) have not been reported in analogous studies with herbaceous species. As judged by protein analyses, such an accumulation is not matched either by endogenous sHSPs in both heat-stressed poplar plants and field-grown adult trees. Quantitative real time-polymerase chain reaction analyses supported these observations and allowed us to identify the poplar members most responsive to heat stress. Interestingly, sHSP overaccumulation was not associated with pleiotropic effects that might decrease yields. The poplar lines developed here also outperformed controls under in vitro and ex vitro culture conditions (callus biomass, shoot production, and ex vitro survival), even in the absence of thermal stress. These results reinforce the feasibility of improving valuable genotypes for plantation forestry, a field where in vitro recalcitrance, long breeding cycles, and other practical factors constrain conventional genetic approaches. They also provide new insights into the biological functions of the least understood family of heat shock protein chaperones.

HuR–hnRNP interactions and the effect of cellular stress

The heterogeneous nuclear ribonucleoproteins (hnRNPs) constitute an important group of RNA-binding proteins (RBPs) that play an active role in post-transcriptional gene regulation. Here, we focus on representative members of the hnRNP group of RBPs, namely hnRNP A1 and hnRNP C1/C2, which participate mainly in RNA splicing, as well as on HuR, a prototype of the AU-rich element-binding proteins (ARE-BP), which has an established role in regulating the stability and translation of target mRNAs. HuR and most hnRNPs are primarily localized in the nucleoplasm, and they can shuttle between the nucleus and the cytoplasm. Herein, we have extended our recently reported findings on the ability of HuR to associate with the immunopurified from mammalian cell extracts hnRNP and mRNP complexes by the application of an anti-HuR antibody that selects HuR-RNP complexes. We find that the protein components precipitated by the anti-HuR antibody are very similar to the hnRNP-HuR complexes reported previously. The in vivo association of HuR and hnRNP proteins is examined in the presence and the absence of thermal stress by confocal microscopy of intact cells and by in situ nuclear matrix preparation. We find notable heat-induced changes of HuR and of hnRNP A1, which exit the nucleus and co-localize to large cytoplasmic foci that represent heat-induced stress granules. The functional implications of HuR-hnRNP interactions in stressed and unstressed cells are discussed.

Effect of short-term pre-hatch heat shock of incubating eggs on subsequent

The aim of this study was to investigate the effect of thermal conditioning of broiler chickens during embryonic development on subsequent performance under standard rearing conditions. During incubation eggs from 32-, 45- and 56-week old Ross 308 broiler parent stock were subjected to a 2 h heat shock of 39 °C on days 14 and 15 of incubation. Eggs in the control were incubated throughout incubation at 37 °C. Chicks were feather sexed and equal numbers of each sex were placed in each pen per treatment, and reared for 42 days. Live weight, mortality and feed conversion ratio (FCR) were used as measures of performance. The final (six-week) live weights of broilers from young, mid and older parents for the treatment and control groups were 2113 ± 13.8 vs. 2159 ± 20.0, 2084 ± 29.2 vs. 2139 ± 20.0 and 2096 ± 17.6 vs. 2131 ± 24.3 g, respectively. The six-week live weight of the heat-treated group (2098 ± 12.0 g) was significantly lower than that of the control (2143 ± 12.2 g). The 1-6 week mortality figure was significantly lower in the heat-treated group of chickens from the young (83) and mid parent (77) groups compared to their controls (130 and 119), respectively. However, in the treatment group the incidence of mortality in broilers from the older parent group was significantly higher (105) than that of the control (79). The overall mortality without considering the parent age group was significantly lower in the treatment group (265) than in the control group (328). Mean FCR (g feed/g gain) of the chickens of the three parent groups was 1.79 ± 0.02 vs. 1.75 ± 0.03, 1.85 ± 0.03 vs. 1.77 ± 0.02 and 1.80 ± 0.03 vs. 1.77 ± 0.03 for the treatment vs. control groups, respectively, but the difference was significant only in the mid age parent group. These results suggest that prenatal thermal conditioning is not detrimental to broiler growth under standard rearing conditions in the absence of thermal stress. However, survival rate was improved but live weight and FCR were in some cases significantly poorer. Keywords: Heat stress, incubation, parent age, live weight, mortalitySouth African Journal of Animal Science Vol. 38 (1) 2008: pp. 58-64

Improved Resistance to Controlled Deterioration in Transgenic Seeds

We show that seed-specific overexpression of the sunflower (Helianthus annuus) HaHSFA9 heat stress transcription factor (HSF) in tobacco (Nicotiana tabacum) enhances the accumulation of heat shock proteins (HSPs). Among these proteins were HSP101 and a subset of the small HSPs, including proteins that accumulate only during embryogenesis in the absence of thermal stress. Levels of late embryogenesis abundant proteins or seed oligosaccharides, however, were not affected. In the transgenic seeds, a high basal thermotolerance persisted during the early hours of imbibition. Transgenic seeds also showed significantly improved resistance to controlled deterioration in a stable and transgene-dependent manner. Furthermore, overexpression of HaHSFA9 did not have detrimental effects on plant growth or development, including seed morphology and total seed yield. Our results agree with previous work tentatively associating HSP gene expression with phenotypes important for seed longevity. These findings might have implications for improving seed longevity in economically important crops.

Stress in hard metal films

In the absence of thermal stress, tensile stress in hard metal films is caused by grain boundary shrinkage and compressive stress is caused by ion peening. It is shown that the two contributions are additive. Moreover tensile stress generated at the grain boundaries does not relax by ion bombardment. In polycrystalline hard metal films the grain structure evolves during growth, leading to wider grains higher up in the film. The tensile component of the stress in the film is generated at the grain boundaries and therefore depends on film thickness. The effect of ion bombardment is independent of grain size, therefore compressive stress does not depend on film thickness. As a result in polycrystalline films deposited under a bias voltage a stress gradient exists from tensile at the interface to compressive at the top of the film.

Physiological tolerances of three sympatric riparian wolf spiders (Araneae: Lycosidae) correspond with microhabitat distributions

Coexisting species from the same ecological guild often exhibit different adaptations to discontinuous, abiotic environmental factors. In the laboratory, we compared tolerance to thermal and desiccation stress among three sympatric wolf spiders (Pirata sedentarius Montgomery, 1904, Pardosa lapidicina Emerton, 1885, and Pardosa fuscula Thorell, 1875). In the field, we examined spatial structure across a microhabitat (moisture) gradient in a streamside cobble habitat where these three species are abundant. Female P. sedentarius succumbed more quickly to desiccation stress than females of either Pardosa species. In the absence of thermal stress, desiccation tolerance was high for both Pardosa species. However, P. fuscula appears to be more resistant to combined thermal and desiccation stress than P. lapidicina. These findings correspond with the results of the field survey; the distribution of P. sedentarius was the most restricted (by proximity to the shoreline) among the three species. Contingency analyses also revealed greater relative abundance of P. fuscula than P. lapidicina farther away from the creek. Further examination of spatial structure suggests that neither of these two species was restricted by proximity to the shoreline within the sampling grid.

Microwave exposure induces Hsp70 and confers protection against hypoxia in chick embryos.

To determine if microwave exposure could elicit a biological effect in the absence of thermal stress, studies were designed in which chick embryos were exposed to athermal microwave radiation (915 MHz) to look for induction of Hsp70, a protein produced during times of cellular stress that aids in the protection of cellular components. Levels of Hsp70 were found to increase within 2 h, with maximum expression ( approximately 30% higher than controls) typically occurring by 3 h from the start of exposure. Other embryos were exposed to microwave radiation prior to being subjected to hypoxic stress, and were found to have significantly higher survival (P < 0.05) following re-oxygenation than non-exposed controls. The results of these studies indicate that not only can athermal microwave exposures activate the stress protein response pathway; they can also enhance survivability following exposure to a subsequent, potentially lethal stress. From a public health standpoint, it is important that more studies be performed to determine if repeated exposures, a condition likely to be found in cell phone use, are still beneficial.

Influence of bioenergetic stress on heat shock protein gene expression in nucleated red blood cells of fish.

The physiological and biochemical signals that induce stress protein (HSP) synthesis remain conjectural. In this study, we used the nucleated red blood cells from rainbow trout, Oncorhynchus mykiss, to address the interaction between energy status and HSP gene expression. Heat shock (25 degrees C) did not significantly affect ATP levels but resulted in an increase in HSP70 mRNA. Hypoxia alone did not induce HSP transcription in these cells despite a significant depression in ATP. Inhibition of oxidative phosphorylation with azide, in the absence of thermal stress, decreased ATP by 56% and increased lactate production by 62% but did not induce HSP gene transcription. Inhibition of oxidative phosphorylation and glycolysis with azide and iodoacetic acid respectively, decreased ATP by 79% and prevented lactate production, but did not induce either HSP70 or HSP30 gene transcription in these cells. This study demonstrates that a reduction in the cellular energy status will not induce stress protein gene transcription in rainbow trout red blood cells and may, in fact, limit induction during extreme metabolic inhibition.