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Sample records for metal stress induce

  1. Origin of yielding in metallic glass: Stress-induced flow

    NASA Astrophysics Data System (ADS)

    Liu, Z. Y.; Chen, M. W.; Liu, C. T.; Yang, Y.

    2014-06-01

    Yielding in crystalline metals is well known to be governed by dislocation dynamics; however, the structural origin of yielding in metallic glasses (MGs) still remains as an issue of intense debate despite that substantial research efforts have been expended. In this Letter, based on well-designed cyclic microcompression tests, we provide compelling experimental evidence revealing that yielding of MGs is essentially a stress-induced viscous flow process, during which the measured viscosity ranges from 1014 Pa.s to 1011 Pa.s and decreases with the increase of applied stress, resembling the "shear-thinning" behavior of non-Newtonian liquids. This stress-induced non-Newtonian flow finally leads to shear instability, which manifests itself as the phenomenon of delayed yielding common to a variety of MGs.

  2. Plant responses to abiotic stresses: heavy metal-induced oxidative stress and protection by mycorrhization.

    PubMed

    Schützendübel, Andres; Polle, Andrea

    2002-05-01

    cadmium results in unspecific necrosis. Plants in certain mycorrhizal associations are less sensitive to cadmium stress than non-mycorrhizal plants. Data about antioxidative systems in mycorrhizal fungi in pure culture and in symbiosis are scarce. The present results indicate that mycorrhization stimulated the phenolic defence system in the Paxillus-Pinus mycorrhizal symbiosis. Cadmium-induced changes in mycorrhizal roots were absent or smaller than those in non-mycorrhizal roots. These observations suggest that although changes in rhizospheric conditions were perceived by the root part of the symbiosis, the typical Cd-induced stress responses of phenolics were buffered. It is not known whether mycorrhization protected roots from Cd-induced injury by preventing access of cadmium to sensitive extra- or intracellular sites, or by excreted or intrinsic metal-chelators, or by other defence systems. It is possible that mycorrhizal fungi provide protection via GSH since higher concentrations of this thiol were found in pure cultures of the fungi than in bare roots. The development of stress-tolerant plant-mycorrhizal associations may be a promising new strategy for phytoremediation and soil amelioration measures. PMID:11997381

  3. The deformation units in metallic glasses revealed by stress-induced localized glass transition

    NASA Astrophysics Data System (ADS)

    Huo, L. S.; Ma, J.; Ke, H. B.; Bai, H. Y.; Zhao, D. Q.; Wang, W. H.

    2012-06-01

    We report that even in quasi-static cyclic compressions in the apparent elastic regimes of the bulk metallic glasses, the precisely measured stress-strain curve presents a mechanical hysteresis loop, which is commonly perceived to occur only in high-frequency dynamic tests. A phenomenological viscoelastic model is established to explain the hysteresis loop and demonstrate the evolutions of the viscous zones in metallic glasses during the cyclic compression. The declining of the viscosity of the viscous zones to at least 1 × 1012 Pa s when stress applied indicates that stress-induced localized glass to supercooled liquid transition occurs. We show that the deformation units of metallic glasses are evolved from the intrinsic heterogeneous defects in metallic glasses under stress and the evolution is a manifestation of the stress-induced localized glass transition. Our study might provide a new insight into the atomic-scale mechanisms of plastic deformation of metallic glasses.

  4. NRF2 Oxidative Stress Induced by Heavy Metals is Cell Type Dependent

    EPA Science Inventory

    Exposure to metallic environmental toxicants has been demonstrated to induce a variety of oxidative stress responses in mammalian cells. The transcription factor Nrf2 is activated in response to oxidative stress and coordinates the expression of antioxidant gene products. In this...

  5. Origin of stress gradients induced in capped, copper metallization

    SciTech Connect

    Murray, Conal E.

    2014-02-24

    Stress gradients generated near the top surface of Cu thin films by capping layers, as measured using a combination of conventional and glancing incidence x-ray diffraction, exhibit heterogeneous behavior that is directly related to plastic anisotropy within the Cu grains. A comparison of stress gradients measured from several x-ray reflections to their corresponding Schmid factors yields a consistent, critical resolved shear stress. The results experimentally verify that dislocation-mediated plasticity is responsible for the creation of stress gradients at the Cu film/cap interface. Depth-dependent measurements reveal that the observed gradients are localized to within 200 nm of this interface.

  6. Cadmium-tolerant bacteria induce metal stress tolerance in cereals.

    PubMed

    Ahmad, Iftikhar; Akhtar, Muhammad Javed; Zahir, Zahir Ahmad; Naveed, Muhammad; Mitter, Birgit; Sessitsch, Angela

    2014-09-01

    Cadmium usually hampers plant growth, but bacterial inoculation may improve stress tolerance in plants to Cd by involving various mechanisms. The objective was to characterize and identify bacteria that improve plant growth under Cd stress and reduce Cd uptake. Cadmium-tolerant bacteria were isolated from rhizosphere soil, which was irrigated with tannery effluent, and six strains were selected as highly tolerant to Cd, showing minimum inhibitory concentration as 500 mg L(-1) or 4.45 mmol L(-1). These strains were identified by 16S rRNA gene analysis and functional analysis in regard to plant growth promotion characteristics. To determine their effect on cereal growth under Cd stress, seeds were inoculated with these strains individually and grown in soil contaminated with three Cd levels (0, 40 and 80 mg kg(-1)). Biomass production, relative water content (RWC), electrolyte leakage (ELL) and tissue Cd concentration were measured. Biomass of both cereals was inhibited strongly when exposed to Cd; however, bacterial inoculation significantly reduced the suppressive effect of Cd on cereal growth and physiology. The bacterial isolates belonged to the genera Klebsiella, Stenotrophomonas, Bacillus and Serratia. Maize was more sensitive than wheat to Cd. Klebsiella sp. strain CIK-502 had the most pronounced effects in promoting maize and wheat growth and lowering Cd uptake under Cd stress. PMID:24849374

  7. NRF2 Oxidative Stress Induced by Heavy Metals is Cell Type Dependent

    PubMed Central

    Simmons, Steven O; Fan, Chun-Yang; Yeoman, Kim; Wakefield, John; Ramabhadran, Ram

    2011-01-01

    Exposure to metallic environmental toxicants has been demonstrated to induce a variety of oxidative stress responses in mammalian cells. The transcription factor Nrf2 is activated in response to oxidative stress and coordinates the expression of antioxidant gene products. In this study, we describe the development of an Nrf2-specific reporter gene assay that can be used to study the oxidative stress response in multiple cell types. Using five different cell lines, the Nrf2-activating potency of twenty metals was assessed across a range of concentrations. While ten of the metals tested (cadmium, cobalt, copper, gold, iron, lead, mercury, silver, sodium arsenite and zinc) stimulated Nrf2-dependent transcriptional activity in at least three of the engineered cell lines, only three (cadmium, copper and sodium arsenite) were active in all five cell lines. A comparison of metal-induced Nrf2 transcriptional activation revealed significant differences in the absolute magnitude of activation as well as the relative potencies between the cell lines tested. However, there was no direct correlation between activity and potency. Taken together, these results show that the capacity to stimulate Nrf2 activity and relative potencies of these test compounds are highly dependent on the cell type tested. Since oxidative stress is thought to be involved in the mode of action of many toxicological studies, this observation may inform the design of paradigms for toxicity testing for toxicant prioritization and characterization. PMID:21643505

  8. Environment-induced embrittlement: Stress corrosion cracking and metal-induced embrittlement; Environmental embrittlement of iron aluminide alloys

    SciTech Connect

    Heldt, L.A.; Milligan, W.W.; White, C.L.

    1991-01-01

    This research program has included two thrusts. The first addressed environment-induced embrittlement in a parallel study of stress corrosion cracking and metal-induced embrittlement. This work has examined (1) mechanical properties as influenced by embrittling environments, (2) fractography and crystallography or transgranular cracking, (3) the mechanics of cracking, (4) the extent and role of local plastic flow, and (5) local chemistry within stress corrosion and metal-induced cracks. The embrittlement of iron aluminide alloys by air was addressed by determining the effect of water and hydrogen upon the mechanical properties. Slow strain rate testing in aqueous environments was carried out at controlled anodic and cathodic potentials. The effect of cathodically charged hydrogen and the effect of subsequent baking were measured. Environmental susceptibility was measured as affected by alloy composition, microstructure and degree of ordering.

  9. Tight junction proteins and oxidative stress in heavy metals-induced nephrotoxicity.

    PubMed

    Reyes, José L; Molina-Jijón, Eduardo; Rodríguez-Muñoz, Rafael; Bautista-García, Pablo; Debray-García, Yazmin; Namorado, María Del Carmen

    2013-01-01

    Kidney is a target organ for heavy metals. They accumulate in several segments of the nephron and cause profound alterations in morphology and function. Acute intoxication frequently causes acute renal failure. The effects of chronic exposure have not been fully disclosed. In recent years increasing awareness of the consequences of their presence in the kidney has evolved. In this review we focus on the alterations induced by heavy metals on the intercellular junctions of the kidney. We describe that in addition to the proximal tubule, which has been recognized as the main site of accumulation and injury, other segments of the nephron, such as glomeruli, vessels, and distal nephron, show also deleterious effects. We also emphasize the participation of oxidative stress as a relevant component of the renal damage induced by heavy metals and the beneficial effect that some antioxidant drugs, such as vitamin A (all-trans-retinoic acid) and vitamin E ( α -tocopherol), depict on the morphological and functional alterations induced by heavy metals. PMID:23710457

  10. Tight Junction Proteins and Oxidative Stress in Heavy Metals-Induced Nephrotoxicity

    PubMed Central

    Reyes, José L.; Molina-Jijón, Eduardo; Rodríguez-Muñoz, Rafael; Bautista-García, Pablo; Debray-García, Yazmin; Namorado, María del Carmen

    2013-01-01

    Kidney is a target organ for heavy metals. They accumulate in several segments of the nephron and cause profound alterations in morphology and function. Acute intoxication frequently causes acute renal failure. The effects of chronic exposure have not been fully disclosed. In recent years increasing awareness of the consequences of their presence in the kidney has evolved. In this review we focus on the alterations induced by heavy metals on the intercellular junctions of the kidney. We describe that in addition to the proximal tubule, which has been recognized as the main site of accumulation and injury, other segments of the nephron, such as glomeruli, vessels, and distal nephron, show also deleterious effects. We also emphasize the participation of oxidative stress as a relevant component of the renal damage induced by heavy metals and the beneficial effect that some antioxidant drugs, such as vitamin A (all-trans-retinoic acid) and vitamin E (α-tocopherol), depict on the morphological and functional alterations induced by heavy metals. PMID:23710457

  11. Fine ambient particles induce oxidative stress and metal binding genes in human alveolar macrophages.

    PubMed

    Huang, Yuh-Chin T; Li, Zhuowei; Carter, Jacqueline D; Soukup, Joleen M; Schwartz, David A; Yang, Ivana V

    2009-11-01

    Exposure to pollutant particles increased respiratory morbidity and mortality. The alveolar macrophages (AMs) are one cell type in the lung directly exposed to particles. Upon contact with particles, AMs are activated and produce reactive oxygen species, but the scope of this oxidative stress response remains poorly defined. In this study, we determined the gene expression profile in human AMs exposed to particles, and sought to characterize the global response of pro- and antioxidant genes. We exposed AMs obtained by bronchoscopy from normal individuals to Chapel Hill particulate matter of 2.5-microm diameter or smaller (PM(2.5); 1 microg/ml) or vehicle for 4 hours (n = 6 independent samples). mRNAs were extracted, amplified, and hybridized to Agilent human 1A microarray. Significant genes were identified by significance analysis of microarrays (false discovery rate, 10%; P < or = 0.05) and mapped with Gene Ontology in the Database for Annotation, Visualization, and Integrated Discovery. We found 34 and 41 up- and down-regulated genes, respectively; 22 genes (approximately 30%) were involved in metal binding, and 11 were linked to oxidative stress, including up-regulation of five metallothionein (MT)-1 isoforms. Exogenous MT1 attenuated PM(2.5)-induced H2O2 release. PM(2.5) premixed with MT1 stimulated less H2O2 release. Knockdown of MT1F gene increased PM(2.5)-induced H2O2 release. PM(2.5) at 1 microg/ml did not increase H2O2 release. Mount St. Helens PM(2.5) and acid-extracted Chapel Hill PM(2.5), both poor in metals, did not induce MT1F or H2O2 release. Our results show that PM(2.5) induced a gene expression profile prevalent with genes related to metal binding and oxidative stress in human AMs, independent of oxidative stress. Metals associated with PM may play an important role in particle-induced gene changes. PMID:19251948

  12. Fine Ambient Particles Induce Oxidative Stress and Metal Binding Genes in Human Alveolar Macrophages

    PubMed Central

    Huang, Yuh-Chin T.; Li, Zhuowei; Carter, Jacqueline D.; Soukup, Joleen M.; Schwartz, David A.; Yang, Ivana V.

    2009-01-01

    Exposure to pollutant particles increased respiratory morbidity and mortality. The alveolar macrophages (AMs) are one cell type in the lung directly exposed to particles. Upon contact with particles, AMs are activated and produce reactive oxygen species, but the scope of this oxidative stress response remains poorly defined. In this study, we determined the gene expression profile in human AMs exposed to particles, and sought to characterize the global response of pro- and antioxidant genes. We exposed AMs obtained by bronchoscopy from normal individuals to Chapel Hill particulate matter of 2.5-μm diameter or smaller (PM2.5; 1 μg/ml) or vehicle for 4 hours (n = 6 independent samples). mRNAs were extracted, amplified, and hybridized to Agilent human 1A microarray. Significant genes were identified by significance analysis of microarrays (false discovery rate, 10%; P ≤ 0.05) and mapped with Gene Ontology in the Database for Annotation, Visualization, and Integrated Discovery. We found 34 and 41 up- and down-regulated genes, respectively; 22 genes (∼30%) were involved in metal binding, and 11 were linked to oxidative stress, including up-regulation of five metallothionein (MT)-1 isoforms. Exogenous MT1 attenuated PM2.5-induced H2O2 release. PM2.5 premixed with MT1 stimulated less H2O2 release. Knockdown of MT1F gene increased PM2.5-induced H2O2 release. PM2.5 at 1 μg/ml did not increase H2O2 release. Mount St. Helens PM2.5 and acid-extracted Chapel Hill PM2.5, both poor in metals, did not induce MT1F or H2O2 release. Our results show that PM2.5 induced a gene expression profile prevalent with genes related to metal binding and oxidative stress in human AMs, independent of oxidative stress. Metals associated with PM may play an important role in particle-induced gene changes. PMID:19251948

  13. Cytotoxicity and oxidative stress induced by different metallic nanoparticles on human kidney cells

    PubMed Central

    2011-01-01

    Background Some manufactured nanoparticles are metal-based and have a wide variety of applications in electronic, engineering and medicine. Until now, many studies have described the potential toxicity of NPs on pulmonary target, while little attention has been paid to kidney which is considered to be a secondary target organ. The objective of this study, on human renal culture cells, was to assess the toxicity profile of metallic nanoparticles (TiO2, ZnO and CdS) usable in industrial production. Comparative studies were conducted, to identify whether particle properties impact cytotoxicity by altering the intracellular oxidative status. Results Nanoparticles were first characterized by size, surface charge, dispersion and solubility. Cytotoxicity of NPs was then evaluated in IP15 (glomerular mesangial) and HK-2 (epithelial proximal) cell lines. ZnO and CdS NPs significantly increased the cell mortality, in a dose-dependent manner. Cytotoxic effects were correlated with the physicochemical properties of NPs tested and the cell type used. Analysis of reactive oxygen species and intracellular levels of reduced and oxidized glutathione revealed that particles induced stress according to their composition, size and solubility. Protein involved in oxidative stress such as NF-κb was activated with ZnO and CdS nanoparticles. Such effects were not observed with TiO2 nanoparticles. Conclusion On glomerular and tubular human renal cells, ZnO and CdS nanoparticles exerted cytotoxic effects that were correlated with metal composition, particle scale and metal solubility. ROS production and oxidative stress induction clearly indicated their nephrotoxic potential. PMID:21371295

  14. Polyhydroxyfullerene Binds Cadmium Ions and Alleviates Metal-Induced Oxidative Stress in Saccharomyces cerevisiae

    PubMed Central

    Pradhan, Arunava; Pinheiro, José Paulo; Seena, Sahadevan; Pascoal, Cláudia

    2014-01-01

    The water-soluble polyhydroxyfullerene (PHF) is a functionalized carbon nanomaterial with several industrial and commercial applications. There have been controversial reports on the toxicity and/or antioxidant properties of fullerenes and their derivatives. Conversely, metals have been recognized as toxic mainly due to their ability to induce oxidative stress in living organisms. We investigated the interactive effects of PHF and cadmium ions (Cd) on the model yeast Saccharomyces cerevisiae by exposing cells to Cd (≤5 mg liter−1) in the absence or presence of PHF (≤500 mg liter−1) at different pHs (5.8 to 6.8). In the absence of Cd, PHF stimulated yeast growth up to 10.4%. Cd inhibited growth up to 79.7%, induced intracellular accumulation of reactive oxygen species (ROS), and promoted plasma membrane disruption in a dose- and pH-dependent manner. The negative effects of Cd on growth were attenuated by the presence of PHF, and maximum growth recovery (53.8%) was obtained at the highest PHF concentration and pH. The coexposure to Cd and PHF decreased ROS accumulation up to 36.7% and membrane disruption up to 30.7% in a dose- and pH-dependent manner. Two mechanisms helped to explain the role of PHF in alleviating Cd toxicity to yeasts: PHF decreased Cd-induced oxidative stress and bound significant amounts of Cd in the extracellular medium, reducing its bioavailability to the cells. PMID:25038095

  15. Glutathione Is a Key Player in Metal-Induced Oxidative Stress Defenses

    PubMed Central

    Jozefczak, Marijke; Remans, Tony; Vangronsveld, Jaco; Cuypers, Ann

    2012-01-01

    Since the industrial revolution, the production, and consequently the emission of metals, has increased exponentially, overwhelming the natural cycles of metals in many ecosystems. Metals display a diverse array of physico-chemical properties such as essential versus non-essential and redox-active versus non-redox-active. In general, all metals can lead to toxicity and oxidative stress when taken up in excessive amounts, imposing a serious threat to the environment and human health. In order to cope with different kinds of metals, plants possess defense strategies in which glutathione (GSH; γ-glu-cys-gly) plays a central role as chelating agent, antioxidant and signaling component. Therefore, this review highlights the role of GSH in: (1) metal homeostasis; (2) antioxidative defense; and (3) signal transduction under metal stress. The diverse functions of GSH originate from the sulfhydryl group in cysteine, enabling GSH to chelate metals and participate in redox cycling. PMID:22489146

  16. Subcellular distributions of metals and metal induced stress: A field study

    SciTech Connect

    Jenkins, K.D.; Howe, S.; Sanders, B.M. )

    1988-09-01

    This paper reports the results of a field study which took place around an exploratory well located in the Santa Barbara Channel. This study was designed to test for significant temporal and spatial differences in the concentrations of a number of drilling fluid-associated metals in both the sediments and biota. Temporal changes in the distribution of Ba, Cd, Cr, Cu, Hg, Ni, Pb, and Zn were examined in the sediments, and the bioaccumulation and subcellular distribution of these metals were examined in three benthic invertebrate species before and after drilling. Statistically significant increases in the accumulation of several of the metals were found in the surface sediments down current from the site after drilling with Ba showing the most pronounced increase. Statistically significant increases in the bioaccumulation of Ba were also observed in two of the three species examined, Cyclocardia ventricosa and Pactinaria californiensis. Within these organisms the majority of the Ba was localized in the granular pellets (>97%) and less than 0.1% accumulated in the cytosol. These data indicate that although bioaccumulation of Ba occurs in some species immediately down current from the well, most of it remains in an insoluble for, presumably as BaSO{sub 4}.

  17. Heavy metals induce oxidative stress and genome-wide modulation in transcriptome of rice root.

    PubMed

    Dubey, Sonali; Shri, Manju; Misra, Prashant; Lakhwani, Deepika; Bag, Sumit Kumar; Asif, Mehar H; Trivedi, Prabodh Kumar; Tripathi, Rudro Deo; Chakrabarty, Debasis

    2014-06-01

    Industrial growth, ecological disturbances and agricultural practices have contaminated the soil and water with many harmful compounds, including heavy metals. These heavy metals affect growth and development of plants as well as cause severe human health hazards through food chain contamination. In past, studies have been made to identify biochemical and molecular networks associated with heavy metal toxicity and uptake in plants. Studies suggested that most of the physiological and molecular processes affected by different heavy metals are similar to those affected by other abiotic stresses. To identify common and unique responses by different metals, we have studied biochemical and genome-wide modulation in transcriptome of rice (IR-64 cultivar) root after exposure to cadmium (Cd), arsenate [As(V)], lead (Pb) and chromium [Cr(VI)] in hydroponic condition. We observed that root tissue shows variable responses for antioxidant enzyme system for different heavy metals. Genome-wide expression analysis suggests variable number of genes differentially expressed in root in response to As(V), Cd, Pb and Cr(VI) stresses. In addition to unique genes, each heavy metal modulated expression of a large number of common genes. Study also identified cis-acting regions of the promoters which can be determinants for the modulated expression of the genes in response to different heavy metals. Our study advances understanding related to various processes and networks which might be responsible for heavy metal stresses, accumulation and detoxification. PMID:24553786

  18. Stress-induced chemical detection using flexible metal-organic frameworks.

    PubMed

    Allendorf, Mark D; Houk, Ronald J T; Andruszkiewicz, Leanne; Talin, A Alec; Pikarsky, Joel; Choudhury, Arnab; Gall, Kenneth A; Hesketh, Peter J

    2008-11-01

    In this work we demonstrate the concept of stress-induced chemical detection using metal-organic frameworks (MOFs) by integrating a thin film of the MOF HKUST-1 with a microcantilever surface. The results show that the energy of molecular adsorption, which causes slight distortions in the MOF crystal structure, can be converted to mechanical energy to create a highly responsive, reversible, and selective sensor. This sensor responds to water, methanol, and ethanol vapors, but yields no response to either N2 or O2. The magnitude of the signal, which is measured by a built-in piezoresistor, is correlated with the concentration and can be fitted to a Langmuir isotherm. Furthermore, we show that the hydration state of the MOF layer can be used to impart selectivity to CO2. Finally, we report the first use of surface-enhanced Raman spectroscopy to characterize the structure of a MOF film. We conclude that the synthetic versatility of these nanoporous materials holds great promise for creating recognition chemistries to enable selective detection of a wide range of analytes. PMID:18841964

  19. In Situ TEM Nanoindentation Studies on Stress-Induced Phase Transformations in Metallic Materials

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Wang, H.; Zhang, X.

    2016-01-01

    Although abundant phase transformations are in general thermally driven processes, there are many examples wherein stresses can induce phase transformations. Numerous in situ techniques, such as in situ x-ray diffraction and neutron diffraction, have been applied to reveal phase transformations. Recently, an in situ nanoindentation technique coupled with transmission electron microscopy demonstrated the capability to directly correlating stresses with phase transformations and microstructural evolutions at a submicron length scale. Here we briefly review in situ studies on stress-induced diffusional and diffusionless phase transformations in amorphous CuZrAl alloy and NiFeGa shape memory alloy. In the amorphous CuZrAl, in situ nanoindentation studies show that the nucleation of nanocrystals (a diffusional process) occurs at ultra-low stresses manifested by a prominent stress drop. In the NiFeGa shape memory alloy, two distinctive types of martensitic (diffusionless) phase transformations accompanied by stress plateaus are observed, including a reversible gradual phase transformation at low stress levels, and an irreversible abrupt phase transition at higher stress levels.

  20. In Situ TEM Nanoindentation Studies on Stress-Induced Phase Transformations in Metallic Materials

    DOE PAGESBeta

    Liu, Y.; Wang, H.; Zhang, X.

    2015-11-30

    Though abundant phase transformations are in general thermally driven processes, there are many examples wherein stresses can induce phase transformations. We applied numerous in situ techniques, such as in situ x-ray diffraction and neutron diffraction in order to reveal phase transformations. Recently, an in situ nanoindentation technique coupled with transmission electron microscopy demonstrated the capability to directly correlating stresses with phase transformations and microstructural evolutions at a submicron length scale. We briefly review in situ studies on stress-induced diffusional and diffusionless phase transformations in amorphous CuZrAl alloy and NiFeGa shape memory alloy. Moreover, in the amorphous CuZrAl, in situ nanoindentationmore » studies show that the nucleation of nanocrystals (a diffusional process) occurs at ultra-low stresses manifested by a prominent stress drop. In the NiFeGa shape memory alloy, two distinctive types of martensitic (diffusionless) phase transformations accompanied by stress plateaus are observed, including a reversible gradual phase transformation at low stress levels, and an irreversible abrupt phase transition at higher stress levels.« less

  1. In Situ TEM Nanoindentation Studies on Stress-Induced Phase Transformations in Metallic Materials

    SciTech Connect

    Liu, Y.; Wang, H.; Zhang, X.

    2015-11-30

    Though abundant phase transformations are in general thermally driven processes, there are many examples wherein stresses can induce phase transformations. We applied numerous in situ techniques, such as in situ x-ray diffraction and neutron diffraction in order to reveal phase transformations. Recently, an in situ nanoindentation technique coupled with transmission electron microscopy demonstrated the capability to directly correlating stresses with phase transformations and microstructural evolutions at a submicron length scale. We briefly review in situ studies on stress-induced diffusional and diffusionless phase transformations in amorphous CuZrAl alloy and NiFeGa shape memory alloy. Moreover, in the amorphous CuZrAl, in situ nanoindentation studies show that the nucleation of nanocrystals (a diffusional process) occurs at ultra-low stresses manifested by a prominent stress drop. In the NiFeGa shape memory alloy, two distinctive types of martensitic (diffusionless) phase transformations accompanied by stress plateaus are observed, including a reversible gradual phase transformation at low stress levels, and an irreversible abrupt phase transition at higher stress levels.

  2. Length and Width Effects of Metal Films on Stress-Induced Bending of Surface Micromachined Cantilever Curved Grating

    NASA Astrophysics Data System (ADS)

    Kuo, Ju-Nan

    2012-02-01

    In this study, the length and width effects of metal films on the stress-induced bending of a surface micromachined cantilever curved grating are systematically investigated. A characterization of cantilever curved gratings with various lengths and widths was conducted to observe out-of-plane deformation. A finite element model was established to analyze the deformation. Finite element analysis and experimental results indicate that the commonly used beam theory formula for predicting the deformation of surface micromachined cantilever curved gratings is not valid for these devices. Experiments show that the shape of a cantilever curved grating and residual stress have a close relationship. As the length increases, the residual stress of the metal increases, resulting in a larger out-of-plane deformation of the cantilever curved grating. The tip deflection gradually decreases as the length-to-width ratio of the cantilever curved grating increases. A more reliable shape design of metal films on the stress-induced bending of surface micromachined cantilever curved gratings can thus be achieved.

  3. Stress-induced chemical detection using flexible metal-organic frameworks.

    SciTech Connect

    Allendorf, Mark D.; Hesketh, Peter J.; Gall, Kenneth A.; Choudhury, A.; Pikarsky, J.; Andruszkiewicz, Leanne; Houk, Ronald J. T.; Talin, Albert Alec

    2009-09-01

    In this work we demonstrate the concept of stress-induced chemical detection using metal-organic frameworks (MOFs) by integrating a thin film of the MOF HKUST-1 with a microcantilever surface. The results show that the energy of molecular adsorption, which causes slight distortions in the MOF crystal structure, can be efficiently converted to mechanical energy to create a highly responsive, reversible, and selective sensor. This sensor responds to water, methanol, and ethanol vapors, but yields no response to either N{sub 2} or O{sub 2}. The magnitude of the signal, which is measured by a built-in piezoresistor, is correlated with the concentration and can be fitted to a Langmuir isotherm. Furthermore, we show that the hydration state of the MOF layer can be used to impart selectivity to CO{sub 2}. We also report the first use of surface-enhanced Raman spectroscopy to characterize the structure of a MOF film. We conclude that the synthetic versatility of these nanoporous materials holds great promise for creating recognition chemistries to enable selective detection of a wide range of analytes. A force field model is described that successfully predicts changes in MOF properties and the uptake of gases. This model is used to predict adsorption isotherms for a number of representative compounds, including explosives, nerve agents, volatile organic compounds, and polyaromatic hydrocarbons. The results show that, as a result of relatively large heats of adsorption (> 20 kcal mol{sup -1}) in most cases, we expect an onset of adsorption by MOF as low as 10{sup -6} kPa, suggesting the potential to detect compounds such as RDX at levels as low as 10 ppb at atmospheric pressure.

  4. The effect of a constraining metal tube on flux pinning induced stress in a long cylindrical superconductor

    NASA Astrophysics Data System (ADS)

    Yang, Xiaobin; Tu, Shan-Tung

    2012-07-01

    The use of an alloy tube to impose pressure on a superconducting cylinder during magnetizing reduces pinning-induced tensile stress in high temperature superconductors has been well established. In this paper the natural contact state between the superconducting cylinder and the metal tube is modeled. An exact solution is obtained for the isotropic magnetoelastic problem with the superconductor behaving magnetically, and an expression for the contact pressure exerted on the superconductor by the metal tube is obtained. This expression explicitly gives the contribution of the ratio of Young's modulus of the superconductor to that of the metal and the ratio of the internal to external radii of the metal tube. The stress profile in the superconductor, subjected to the restriction of metal tube, with both field cooled activation and pulse field activation is analyzed in terms of the Bean critical-state model. The results show that the metal tube can prevent radial expansion of the superconductor and can reduce the maximum tension for field-cooled and pulsed-field activations. These results are important for the selection of materials as well as the optimization of sizes of the alloy tube.

  5. Environment-induced embrittlement: Stress corrosion cracking and metal-induced embrittlement; Environmental embrittlement of iron aluminide alloys. Final report, September 1, 1986--August 31, 1991

    SciTech Connect

    Heldt, L.A.; Milligan, W.W.; White, C.L.

    1991-12-31

    This research program has included two thrusts. The first addressed environment-induced embrittlement in a parallel study of stress corrosion cracking and metal-induced embrittlement. This work has examined (1) mechanical properties as influenced by embrittling environments, (2) fractography and crystallography or transgranular cracking, (3) the mechanics of cracking, (4) the extent and role of local plastic flow, and (5) local chemistry within stress corrosion and metal-induced cracks. The embrittlement of iron aluminide alloys by air was addressed by determining the effect of water and hydrogen upon the mechanical properties. Slow strain rate testing in aqueous environments was carried out at controlled anodic and cathodic potentials. The effect of cathodically charged hydrogen and the effect of subsequent baking were measured. Environmental susceptibility was measured as affected by alloy composition, microstructure and degree of ordering.

  6. Creep and stress relaxation induced by interface diffusion in metal matrix composites

    NASA Astrophysics Data System (ADS)

    Li, Yinfeng; Li, Zhonghua

    2013-03-01

    An analytical solution is developed to predict the creep rate induced by interface diffusion in unidirectional fiber-reinforced and particle reinforced composites. The driving force for the interface diffusion is the normal stress acting on the interface, which is obtained from rigorous Eshelby inclusion theory. The closed-form solution is an explicit function of the applied stress, volume fraction and radius of the fiber, as well as the modulus ratio between the fiber and the matrix. It is interesting that the solution is formally similar to that of Coble creep in polycrystalline materials. For the application of the present solution in the realistic composites, the scale effect is taken into account by finite element analysis based on a unit cell. Based on the solution, a closed-form solution is also given as a description of stress relaxation induced by interfacial diffusion under constant strain. In addition, the analytical solution for the interface stress presented in this study gives some insight into the relationship between the interface diffusion and interface slip. This work was supported by the financial support from the Nature Science Foundation of China (No. 10932007), the National Basic Research Program of China (No. 2010CB631003/5), and the Doctoral Program of Higher Education of China (No. 20100073110006).

  7. Alpha-Synuclein Oligomers Interact with Metal Ions to Induce Oxidative Stress and Neuronal Death in Parkinson's Disease

    PubMed Central

    Deas, Emma; Cremades, Nunilo; Angelova, Plamena R.; Ludtmann, Marthe H.R.; Yao, Zhi; Chen, Serene; Horrocks, Mathew H.; Banushi, Blerida; Little, Daniel; Devine, Michael J.; Gissen, Paul; Klenerman, David; Dobson, Christopher M.; Wood, Nicholas W.

    2016-01-01

    Abstract Aims: Protein aggregation and oxidative stress are both key pathogenic processes in Parkinson's disease, although the mechanism by which misfolded proteins induce oxidative stress and neuronal death remains unknown. In this study, we describe how aggregation of alpha-synuclein (α-S) from its monomeric form to its soluble oligomeric state results in aberrant free radical production and neuronal toxicity. Results: We first demonstrate excessive free radical production in a human induced pluripotent stem-derived α-S triplication model at basal levels and on application of picomolar doses of β-sheet-rich α-S oligomers. We probed the effects of different structural species of α-S in wild-type rat neuronal cultures and show that both oligomeric and fibrillar forms of α-S are capable of generating free radical production, but that only the oligomeric form results in reduction of endogenous glutathione and subsequent neuronal toxicity. We dissected the mechanism of oligomer-induced free radical production and found that it was interestingly independent of several known cellular enzymatic sources. Innovation: The oligomer-induced reactive oxygen species (ROS) production was entirely dependent on the presence of free metal ions as addition of metal chelators was able to block oligomer-induced ROS production and prevent oligomer-induced neuronal death. Conclusion: Our findings further support the causative role of soluble amyloid oligomers in triggering neurodegeneration and shed light into the mechanisms by which these species cause neuronal damage, which, we show here, can be amenable to modulation through the use of metal chelation. Antioxid. Redox Signal. 24, 376–391. PMID:26564470

  8. Pycnogenol (PYC) induces apoptosis in human fibrosarcoma (HFS) cells under metal-mediated oxidative stress.

    PubMed

    Park, Yeon Sun; Kim, Young Gon

    2011-01-01

    Pycnogenol (PYC), polyphenolic compounds with antioxidant activity, acted as a prooxidant. PYC caused oxidative stress in human fibrosarcoma cells (HFS) when administered following pretreatment with iron chloride. The generated reactive oxygen species (ROS) caused the formation of 8-hydroxy-2'-deoxyguanosine (8-OHdG) in DNA and resulted in more apoptosis in HFS cells than in the human fibroblastoma (HFB) cells. DNA damage and cellular viability at different PYC concentrations were closely consistent with cell growth, high performance liquid chromatography (HPLC), Enzyme Linked Immunosorbent Assay (ELISA) and assays of two major antioxidant enzymes, superoxide dismutase (SOD) and catalase. Although the presence of PYC induced total SOD and catalase activities under oxidative stress in dose dependent fashion, more apoptotic cells were induced in HFS cells with increased [8-OHdG] than in HFB cells. The results suggest that PYC selectively induced cell death in HFS cells. This further confirmed that PYC-induced apoptosis is mediated primarily through the activation of caspase-3 apoptotic marker in HFS cells but not in HFB cells. We conclude that PYC would behave as either antioxidant or prooxidant dependant upon the cellular types. PMID:22754951

  9. Effect of Centella asiatica on arsenic induced oxidative stress and metal distribution in rats.

    PubMed

    Gupta, Richa; Flora, S J S

    2006-01-01

    Concomitant oral supplementation of Centella asiatica (100, 200 or 300 mg kg(-1), orally once daily) during arsenic exposure (20 ppm in drinking water for 4 weeks) was investigated in rats for its protective value. The animals exposed to arsenic (III) showed a significant inhibition of delta-aminolevulinic acid dehydratase (ALAD) activity, a marginal decrease in glutathione (GSH) and an increase in zinc protoporphyrin (ZPP) level in blood. Hepatic and renal glutathione (GSH) decreased, while oxidized glutathione (GSSG) and thiobarbituric acid reactive substance (TBARS) levels increased significantly in the liver, kidney and brain. The activities of brain superoxide dismutase (SOD) and catalase decreased marginally on arsenic exposure. Concomitant administration of Centella asiatica showed a significant protective action on inhibited blood ALAD activity and restored the blood GSH level, whereas most of the other blood biochemical parameters remained unchanged on Centella asiatica supplementation. Interestingly, most of the hepatic biochemical variables indicative of oxidative stress showed protection. There was, however, a significant protection observed in the altered kidney GSSG level and hepatic and brain TBARS. Only a marginal beneficial effect of Centella asiatica on blood and liver arsenic concentration was noted, particularly at the highest dose studies (300 mg kg(-1)). No effect of Centella asiatica on most of the altered renal biochemical parameters was noted. The results thus lead to the conclusion that simultaneous supplementation of Centella asiatica significantly protects against arsenic-induced oxidative stress but does not influence the arsenic concentration in these organs. It can thus be suggested that co-administration of Centella asiatica protects animals from arsenic-induced oxidative stress but exhibits no chelating property. Further studies are recommended for determining the effect of co-administration of Centella asiatica during chelation

  10. Stress induced and nuclear localized HIPP26 from Arabidopsis thaliana interacts via its heavy metal associated domain with the drought stress related zinc finger transcription factor ATHB29.

    PubMed

    Barth, Olaf; Vogt, Sebastian; Uhlemann, Ria; Zschiesche, Wiebke; Humbeck, Klaus

    2009-01-01

    HIPP26 from Arabidopsis thaliana belongs to a novel class of plant proteins, characterized by a heavy metal associated domain and an additional isoprenylation motif. It is induced during cold, salt and drought stress. The nuclear localization of HIPP26, predicted by a NLS motif, could be confirmed in onion epidermal cells overexpressing GFP-HIPP26. Experiments with modified HIPP26 indicate that the isoprenylation plays a role in the spatial distribution in the nucleus. Using promoter-GUS constructs, a tissue specific expression pattern of HIPP26 could be shown, with high expression in the vascular tissue. By a yeast-two-hybrid approach a strong interaction of HIPP26 with the zinc finger homeodomain transcription factor ATHB29, which is known to play a role in dehydration stress response could be detected. This was confirmed by GST pull-down assays. When using a modified HIPP26 lacking the two central cysteines of the heavy metal associated domain, ATHB29 was not bound in the GST pull-down assay, indicating that this structure is necessary for the interaction. Further yeast-two-hybrid analyses testing interaction of different members of the HIPP family with related zinc finger transcription factors revealed a specific interaction of ATHB29 with several HIPP proteins. A functional relationship between HIPP26 and ATHB29 is also indicated by experiments with mutants of HIPP26 showing altered expression levels of such genes known to be regulated by ATHB29. PMID:18974936

  11. Analysis of Channel Stress Induced by NiPt-Silicide in Metal-Oxide-Semiconductor Field-Effect Transistor and Its Generation Mechanism

    NASA Astrophysics Data System (ADS)

    Mizuo, Mariko; Yamaguchi, Tadashi; Kudo, Shuichi; Hirose, Yukinori; Kimura, Hiroshi; Tsuchimoto, Jun-ichi; Hattori, Nobuyoshi

    2013-09-01

    Channel stress induced by NiPt-silicide films in metal-oxide-semiconductor field-effect transistors (MOSFETs) was demonstrated using UV-Raman spectroscopy, and its generation mechanism was revealed. It was possible to accurately measure the channel stress with the Raman test structure. The channel stress depends on the source/drain doping type and the second silicide annealing method. In order to discuss the channel stress generation mechanism, NiPt-silicide microstructure analyses were performed using X-ray diffraction analysis and scanning transmission electron microscopy. The channel stress generation mechanism can be elucidated by the following two factors: the change in the NiSi lattice spacing, which depends on the annealing temperature, and the NiSi crystal orientation. The analyses of these factors are important for controlling channel stress in stress engineering for high-performance transistors.

  12. Comparative Analysis of Stress Induced Gene Expression in Caenorhabditis elegans following Exposure to Environmental and Lab Reconstituted Complex Metal Mixture

    PubMed Central

    Kumar, Ranjeet; Pradhan, Ajay; Khan, Faisal Ahmad; Lindström, Pia; Ragnvaldsson, Daniel; Ivarsson, Per; Olsson, Per-Erik; Jass, Jana

    2015-01-01

    Metals are essential for many physiological processes and are ubiquitously present in the environment. However, high metal concentrations can be harmful to organisms and lead to physiological stress and diseases. The accumulation of transition metals in the environment due to either natural processes or anthropogenic activities such as mining results in the contamination of water and soil environments. The present study used Caenorhabditis elegans to evaluate gene expression as an indicator of physiological response, following exposure to water collected from three different locations downstream of a Swedish mining site and a lab reconstituted metal mixture. Our results indicated that the reconstituted metal mixture exerted a direct stress response in C. elegans whereas the environmental waters elicited either a diminished or abrogated response. This suggests that it is not sufficient to use the biological effects observed from laboratory mixtures to extrapolate the effects observed in complex aquatic environments and apply this to risk assessment and intervention. PMID:26168046

  13. Toxicity Induced by a Metal Mixture (Cd, Pb and Zn) in the Yeast Pichia kudriavzevii: The Role of Oxidative Stress.

    PubMed

    Mesquita, Vanessa A; Silva, Cristina F; Soares, Eduardo V

    2016-05-01

    The present work aims to contribute for the elucidation of the role of oxidative stress in the toxicity associated with the exposure of Pichia kudriavzevii to multi-metals (Cd, Pb and Zn). Cells of the non-conventional yeast P. kudriavzevii exposed for 6 h to the action of multi-metals accumulated intracellular reactive oxygen species (ROS), evaluated through the oxidation of the probe 2',7'-dichlorodihydrofluorescein diacetate. A progressive loss of membrane integrity (monitored using propidium iodide) was observed in multi-metal-treated cells. The triggering of intracellular ROS accumulation preceded the loss of membrane integrity. These results suggest that the disruption of membrane integrity can be attributed to the oxidative stress. The exposure of yeast cells to single metal showed that, under the concentrations tested, Pb was the metal responsible for the induction of the oxidative stress. Yeast cells coexposed to an antioxidant (ascorbic acid) and multi-metals did not accumulate intracellular ROS, but loss proliferation capacity. Together, the data obtained indicated that intracellular ROS accumulation contributed to metal toxicity, namely for the disruption of membrane integrity of the yeast P. kudriavzevii. It was proposed that Pb toxicity (the metal responsible for the toxic symptoms under the conditions tested) result from the combination of an ionic mechanism and the intracellular ROS accumulation. PMID:26781618

  14. Charge trapping induced drain-induced-barrier-lowering in HfO2/TiN p-channel metal-oxide-semiconductor-field-effect-transistors under hot carrier stress

    NASA Astrophysics Data System (ADS)

    Lo, Wen-Hung; Chang, Ting-Chang; Tsai, Jyun-Yu; Dai, Chih-Hao; Chen, Ching-En; Ho, Szu-Han; Chen, Hua-Mao; Cheng, Osbert; Huang, Cheng-Tung

    2012-04-01

    This letter studies the channel hot carrier stress (CHCS) behaviors on high dielectric constant insulator and metal gate HfO2/TiN p-channel metal-oxide-semiconductor field effect transistors. It can be found that the degradation is associated with electron trapping, resulting in Gm decrease and positive Vth shift. However, Vth under saturation region shows an insignificant degradation during stress. To compare that, the CHC-induced electron trapping induced DIBL is proposed to demonstrate the different behavior of Vth between linear and saturation region. The devices with different channel length are used to evidence the trapping-induced DIBL behavior.

  15. Chemometrics applied to the analysis of induced phytochelatins in Hordeum vulgare plants stressed with various toxic non-essential metals and metalloids.

    PubMed

    Dago, Àngela; González, Inmaculada; Ariño, Cristina; Díaz-Cruz, José Manuel; Esteban, Miquel

    2014-01-01

    Hordeum vulgare plants were stressed with Hg, Cd and As and their phytotoxicity was evaluated in terms of growth inhibition and total metal uptake by the plant. The synthesised phytochelatins ((γ-Glu-Cys)n-Gly, n=2-5; PCs) were determined by HPLC with amperometric detection at a glassy carbon electrode. The results indicate that H. vulgare is a good phytostabilisation plant due to its capacity to accumulate heavy metals in roots. Cd and Hg are the most uptake toxic elements, being Cd the most potent inducer of PCs. The data obtained on the different PCs and related peptides induced by each heavy metal were used to perform a Principal Component Analysis (PCA) of the results as a function of the contaminating toxic element or its concentration level. The nature of the stressor element could be predicted from the pattern of PCs and related peptides identified by PCA. PCs were the most strongly induced peptides under Cd and Hg stress, whereas As only tended to synthesise small thiols such as glutathione and γ-glutamylcysteine, both precursors of PCs synthesis. This finding indicates that PCs are induced at different rates depending on the metal stressor used. PMID:24274289

  16. Corrosion Product Film-Induced Stress Facilitates Stress Corrosion Cracking

    PubMed Central

    Wang, Wenwen; Zhang, Zhiliang; Ren, Xuechong; Guan, Yongjun; Su, Yanjing

    2015-01-01

    Finite element analyses were conducted to clarify the role of corrosion product films (CPFs) in stress corrosion cracking (SCC). Flat and U-shaped edge-notched specimens were investigated in terms of the CPF-induced stress in the metallic substrate and the stress in the CPF. For a U-shaped edge-notched specimen, the stress field in front of the notch tip is affected by the Young’s modulus of the CPF and the CPF thickness and notch geometry. The CPF-induced tensile stress in the metallic substrate is superimposed on the applied load to increase the crack tip strain and facilitate localized plasticity deformation. In addition, the stress in the CPF surface contributes to the rupture of the CPFs. The results provide physical insights into the role of CPFs in SCC. PMID:26066367

  17. Corrosion Product Film-Induced Stress Facilitates Stress Corrosion Cracking.

    PubMed

    Wang, Wenwen; Zhang, Zhiliang; Ren, Xuechong; Guan, Yongjun; Su, Yanjing

    2015-01-01

    Finite element analyses were conducted to clarify the role of corrosion product films (CPFs) in stress corrosion cracking (SCC). Flat and U-shaped edge-notched specimens were investigated in terms of the CPF-induced stress in the metallic substrate and the stress in the CPF. For a U-shaped edge-notched specimen, the stress field in front of the notch tip is affected by the Young's modulus of the CPF and the CPF thickness and notch geometry. The CPF-induced tensile stress in the metallic substrate is superimposed on the applied load to increase the crack tip strain and facilitate localized plasticity deformation. In addition, the stress in the CPF surface contributes to the rupture of the CPFs. The results provide physical insights into the role of CPFs in SCC. PMID:26066367

  18. Pressure-induced alpha to omega transition in titanium metal: a systematic study of the effects of uniaxial stress

    SciTech Connect

    Errandonea, D.; Meng, Y.; Somayazulu, M.; Hausermann, D.

    2010-07-13

    The effects of uniaxial stress on the pressure-induced {alpha} {yields} {omega} transition in pure titanium (Ti) are investigated by means of angle dispersive X-ray diffraction in a diamond-anvil cell. Experiments under four different pressure environments reveal that: (1) the onset of the transition depends on the pressure medium used, going from 4.9 GPa (no pressure medium) to 10.5 GPa (argon pressure medium); (2) the {alpha} and {omega} phases coexist over a rather large pressure range, which depends on the pressure medium employed; (3) the hysteresis and quenchability of the {omega} phase is affected by differences in the sample pressure environment; and (4) a short-term laser heating of Ti lowers the {alpha} {yields} {omega} transition pressure. Possible transition mechanisms are discussed in the light of the present results, which clearly demonstrate the influence of uniaxial stress in the {alpha} {yields} {omega} transition.

  19. Metal-sulfide mineral ores, Fenton chemistry and disease. Particle induced inflammatory stress response in lung cells

    SciTech Connect

    Harrington, Andrea D.; Smirnov, Alexander; Tsirka, Stella E.; Schoonen, Martin A. A.

    2014-07-10

    The inhalation of mineral particulates and other earth materials, such as coal, can initiate or enhance disease in humans. Workers in occupations with high particulate exposure, such as mining, are particularly at risk. The ability of a material to generate an inflammatory stress response (ISR), a measure of particle toxicity, is a useful tool in evaluating said exposure risk. ISR is defined as the upregulation of cellular reactive oxygen species (ROS) normalized to cell viability. This study compares the ISR of A549 human lung epithelial cells after exposure to well-characterized common metal-sulfide ore mineral separates. The evaluation of the deleterious nature of ore minerals is based on a range of particle loadings (serial dilutions of 0.002 m2/mL stock) and exposure periods (beginning at 30 min and measured systematically for up to 24 h). There is a wide range in ISR values generated by the ore minerals. The ISR values produced by the sphalerite samples are within the range of inert materials. Arsenopyrite generated a small ISR that was largely driven by cell death. Galena showed a similar, but more pronounced response. Copper-bearing ore minerals generated the greatest ISR, both by upregulating cellular ROS and generating substantial and sustained cell death. Chalcopyrite and bornite, both containing ferrous iron, generated the greatest ISR overall. Particles containing Fenton metals as major constituents produce the highest ISR, while other heavy metals mainly generate cell death. Furthermore, this study highlights the importance of evaluating the chemistry, oxidation states and structure of a material when assessing risk management.

  20. Metal-sulfide mineral ores, Fenton chemistry and disease. Particle induced inflammatory stress response in lung cells

    DOE PAGESBeta

    Harrington, Andrea D.; Smirnov, Alexander; Tsirka, Stella E.; Schoonen, Martin A. A.

    2014-07-10

    The inhalation of mineral particulates and other earth materials, such as coal, can initiate or enhance disease in humans. Workers in occupations with high particulate exposure, such as mining, are particularly at risk. The ability of a material to generate an inflammatory stress response (ISR), a measure of particle toxicity, is a useful tool in evaluating said exposure risk. ISR is defined as the upregulation of cellular reactive oxygen species (ROS) normalized to cell viability. This study compares the ISR of A549 human lung epithelial cells after exposure to well-characterized common metal-sulfide ore mineral separates. The evaluation of the deleteriousmore » nature of ore minerals is based on a range of particle loadings (serial dilutions of 0.002 m2/mL stock) and exposure periods (beginning at 30 min and measured systematically for up to 24 h). There is a wide range in ISR values generated by the ore minerals. The ISR values produced by the sphalerite samples are within the range of inert materials. Arsenopyrite generated a small ISR that was largely driven by cell death. Galena showed a similar, but more pronounced response. Copper-bearing ore minerals generated the greatest ISR, both by upregulating cellular ROS and generating substantial and sustained cell death. Chalcopyrite and bornite, both containing ferrous iron, generated the greatest ISR overall. Particles containing Fenton metals as major constituents produce the highest ISR, while other heavy metals mainly generate cell death. Furthermore, this study highlights the importance of evaluating the chemistry, oxidation states and structure of a material when assessing risk management.« less

  1. Metal-Sulfide Mineral Ores, Fenton Chemistry and Disease – Particle Induced Inflammatory Stress Response in Lung Cells

    PubMed Central

    Harrington, Andrea D.; Smirnov, Alexander; Tsirka, Stella E.; Schoonen, Martin A.A.

    2014-01-01

    The inhalation of mineral particulates and other earth materials, such as coal, can initiate or enhance disease in humans. Workers in occupations with high particulate exposure, such as mining, are particularly at risk. The ability of a material to generate an inflammatory stress response (ISR), a measure of particle toxicity, is a useful tool in evaluating said exposure risk. ISR is defined as the upregulation of cellular reactive oxygen species (ROS) normalized to cell viability. This study compares the ISR of A549 human lung epithelial cells after exposure to well-characterized common metal-sulfide ore mineral separates. The evaluation of the deleterious nature of ore minerals is based on a range of particle loadings (serial dilutions of 0.002 m2/mL stock) and exposure periods (beginning at 30 minutes and measured systematically for up to 24 hours). There is a wide range in ISR values generated by the ore minerals. The ISR values produced by the sphalerite samples are within the range of inert materials. Arsenopyrite generated a small ISR that was largely driven by cell death. Galena showed a similar, but more pronounced response. Copper-bearing ore minerals generated the greatest ISR, both by upregulating cellular ROS and generating substantial and sustained cell death. Chalcopyrite and bornite, both containing ferrous iron, generated the greatest ISR overall. Particles containing Fenton metals as major constituents produce the highest ISR, while other heavy metals mainly generate cell death. This study highlights the importance of evaluating the chemistry, oxidation states and structure of a material when assessing risk management. PMID:25107347

  2. Metal-sulfide mineral ores, Fenton chemistry and disease--particle induced inflammatory stress response in lung cells.

    PubMed

    Harrington, Andrea D; Smirnov, Alexander; Tsirka, Stella E; Schoonen, Martin A A

    2015-01-01

    The inhalation of mineral particulates and other earth materials, such as coal, can initiate or enhance disease in humans. Workers in occupations with high particulate exposure, such as mining, are particularly at risk. The ability of a material to generate an inflammatory stress response (ISR), a measure of particle toxicity, is a useful tool in evaluating said exposure risk. ISR is defined as the upregulation of cellular reactive oxygen species (ROS) normalized to cell viability. This study compares the ISR of A549 human lung epithelial cells after exposure to well-characterized common metal-sulfide ore mineral separates. The evaluation of the deleterious nature of ore minerals is based on a range of particle loadings (serial dilutions of 0.002m(2)/mL stock) and exposure periods (beginning at 30min and measured systematically for up to 24h). There is a wide range in ISR values generated by the ore minerals. The ISR values produced by the sphalerite samples are within the range of inert materials. Arsenopyrite generated a small ISR that was largely driven by cell death. Galena showed a similar, but more pronounced response. Copper-bearing ore minerals generated the greatest ISR, both by upregulating cellular ROS and generating substantial and sustained cell death. Chalcopyrite and bornite, both containing ferrous iron, generated the greatest ISR overall. Particles containing Fenton metals as major constituents produce the highest ISR, while other heavy metals mainly generate cell death. This study highlights the importance of evaluating the chemistry, oxidation states and structure of a material when assessing risk management. PMID:25107347

  3. State Transition of a Defect Causing Random-Telegraph-Noise Fluctuation in Stress-Induced Leakage Current of Thin SiO2 Films in a Metal-Oxide-Silicon Structure

    NASA Astrophysics Data System (ADS)

    Ishida, Takeshi; Tega, Naoki; Mori, Yuki; Miki, Hiroshi; Mine, Toshiyuki; Kume, Hitoshi; Torii, Kazuyoshi; Yamada, Ren-ichi; Shiraishi, Kenji

    2013-11-01

    Dynamic fluctuation in stress-induced leakage current - called “variable stress-induced leakage current” - in a gate oxide of a metal-oxide-semiconductor structure was investigated. Variable stress-induced leakage current is attributed to random telegraph noise, which is associated with the state-transition of a single defect. To analyze the mechanism of the state-transition, dependence of state-transition probabilities on gate current and on temperature were investigated. These dependences indicate that the state-transition mechanism is a defect-structure transition by charge collision.

  4. Laser Peening--Strengthening Metals to Improve Fatigue Lifetime and Retard Stress-Induced Corrosion Cracking in Gears, Bolts and Cutter

    SciTech Connect

    Hackel, L A; Chen, H-L

    2003-08-20

    Laser peening is an emerging modern process that impresses a compressive stress into the surfaces of metals. Treatment can reduce the rate of fatigue cracking and stress-corrosion-cracking in metals (such as gears, bolts and cutters) needed for tunnel boring and other construction & mining applications. Laser peening could also be used to form metals or alloys into a precise shape without yielding and leaving both sulfates in a crack resistant compressive state.

  5. The understanding on the evolution of stress-induced gate leakage in high-k dielectric metal-oxide-field-effect transistor by random-telegraph-noise measurement

    NASA Astrophysics Data System (ADS)

    Hsieh, E. R.; Chung, Steve S.

    2015-12-01

    The evolution of gate-current leakage path has been observed and depicted by RTN signals on metal-oxide-silicon field effect transistor with high-k gate dielectric. An experimental method based on gate-current random telegraph noise (Ig-RTN) technique was developed to observe the formation of gate-leakage path for the device under certain electrical stress, such as Bias Temperature Instability. The results show that the evolution of gate-current path consists of three stages. In the beginning, only direct-tunnelling gate current and discrete traps inducing Ig-RTN are observed; in the middle stage, interaction between traps and the percolation paths presents a multi-level gate-current variation, and finally two different patterns of the hard or soft breakdown path can be identified. These observations provide us a better understanding of the gate-leakage and its impact on the device reliability.

  6. Does stress induce bowel dysfunction?

    PubMed

    Chang, Yu-Ming; El-Zaatari, Mohamad; Kao, John Y

    2014-08-01

    Psychological stress is known to induce somatic symptoms. Classically, many gut physiological responses to stress are mediated by the hypothalamus-pituitary-adrenal axis. There is, however, a growing body of evidence of stress-induced corticotrophin-releasing factor (CRF) release causing bowel dysfunction through multiple pathways, either through the HPA axis, the autonomic nervous systems, or directly on the bowel itself. In addition, recent findings of CRF influencing the composition of gut microbiota lend support for the use of probiotics, antibiotics, and other microbiota-altering agents as potential therapeutic measures in stress-induced bowel dysfunction. PMID:24881644

  7. The surgically induced stress response.

    PubMed

    Finnerty, Celeste C; Mabvuure, Nigel Tapiwa; Ali, Arham; Kozar, Rosemary A; Herndon, David N

    2013-09-01

    The stress response to surgery, critical illness, trauma, and burns encompasses derangements of metabolic and physiological processes that induce perturbations in the inflammatory, acute phase, hormonal, and genomic responses. Hypermetabolism and hypercatabolism result, leading to muscle wasting, impaired immune function and wound healing, organ failure, and death. The surgery-induced stress response is largely similar to that triggered by traumatic injuries; the duration of the stress response, however, varies according to the severity of injury (surgical or traumatic). This spectrum of injuries and insults ranges from small lacerations to severe insults such as large poly-traumatic and burn injuries. Burn injuries provide an extreme model of trauma induced stress responses that can be used to study the long-term effects of a prolonged stress response. Although the stress response to acute trauma evolved to confer improved chances of survival following injury, in modern surgical practice the stress response can be detrimental. PMID:24009246

  8. Impact of additional Pt and NiSi crystal orientation on channel stress induced by Ni silicide film in metal-oxide-semiconductor field-effect transistors

    NASA Astrophysics Data System (ADS)

    Mizuo, Mariko; Yamaguchi, Tadashi; Kudo, Shuichi; Hirose, Yukinori; Kimura, Hiroshi; Tsuchimoto, Jun-ichi; Hattori, Nobuyoshi

    2014-01-01

    The impact of additional Pt and Ni monosilicide (NiSi) crystal orientation on channel stress from Ni silicide in metal-oxide-semiconductor field-effect transistors (MOSFETs) has been demonstrated. The channel stress generation mechanism can be explained by the NiSi crystal orientation. In pure Ni silicide films, the channel stress in the p-type substrate is much larger than that in the n-type one, since the NiSi a-axis parallel to the channel direction is strongly aligned on the p-type substrate compared with on the n-type one. On the other hand, in NiPt silicide films, the difference in the channel stress between the p- and n-type substrates is small, because the NiSi crystal orientation on the p-type substrate is similar to that on the n-type one. These results can be explained by the Pt segregation at the interface between the NiSi film and the Si surface. Segregated Pt atoms cause the NiSi b-axis to align normal to the Si(001) surface in the nucleation step owing to the expansion of the NiSi lattice spacing at the NiSi/Si interface. Furthermore, the Pt segregation mechanism is considered to be caused by the grain boundary diffusion in the Ni2Si film during NiSi formation. We confirmed that the grains of Ni2Si on the p-type substrate are smaller than those on the n-type one. The Ni2Si film on the p-type substrate has more grain boundary diffusion paths than that on the n-type one. Therefore, the amount of Pt segregation at the NiSi/Si interface on the p-type substrate is larger than that on the n-type one. Consequently, the number of NiSi grains with the b-axis aligned normal to the Si(001) in the p-type substrate is larger than that in the n-type one. As a result, the channel stress induced by NiPt silicide in PMOS is larger than that in NMOS. According to this mechanism, controlling the Pt concentration at the NiSi/Si interface is one of the key factors for channel stress engineering.

  9. The Surgically Induced Stress Response

    PubMed Central

    Finnerty, Celeste C.; Mabvuure, Nigel Tapiwa; Ali, Arham; Kozar, Rosemary A.; Herndon, David N.

    2013-01-01

    The stress response to surgery, critical illness, trauma, and burns encompasses derangements of metabolic and physiological processes which induce perturbations in the inflammatory, acute phase, hormonal, and genomic responses. Hypermetabolism and hypercatabolism result, leading to muscle wasting, impaired immune function and wound healing, organ failure, and death. The surgery-induced stress response is largely similar to that triggered by traumatic injuries; the duration of the stress response, however, varies according to the severity of injury (surgical or traumatic). This spectrum of injuries and insults ranges from small lacerations to severe insults such as large poly-traumatic and burn injuries. Although the stress response to acute trauma evolved to improve chances of survival following injury, in modern surgical practice the stress response can be detrimental. PMID:24009246

  10. Heavy metal stress detection and monitoring via LED-induced chlorophyll fluorescence analysis of Zea mays L. seedlings aimed at polluted soil phytoremediation

    NASA Astrophysics Data System (ADS)

    Gouveia-Neto, Artur S.; Silva, Elias A., Jr.; da Silva, Airon José; do Nascimento, Clístenes W. A.

    2012-03-01

    Chlorophyll fluorescence spectroscopy is employed to detect and study the time evolution of metal stress of Zea mays L. seedlings aiming polluted soil phytoremediation. The chlorophyll fluorescence spectra of intact leaves are analyzed using 405 nm LED excitation. Red (Fr) and far-red (FFr) emissions around 685 nm and 735 nm, respectively, are examined as a function of the heavy metal concentration. The fluorescence ratio Fr/FFr was employed to monitor the effect of heavy metal upon the physiological state of the plants before signs of visual stress became apparent. The chlorophyll fluorescence analysis permitted detection and evaluation of the damage caused by heavy metal soil contamination in the early stages of the plants growing process, which is not feasible using conventional in vitro spectral analysis.

  11. Method For Characterizing Residual Stress In Metals

    DOEpatents

    Jacobson, Loren A.; Michel, David J.; Wyatt, Jeffrey R.

    2002-12-03

    A method is provided for measuring the residual stress in metals. The method includes the steps of drilling one or more holes in a metal workpiece to a preselected depth and mounting one or more acoustic sensors on the metal workpiece and connecting the sensors to an electronic detecting and recording device. A liquid metal capable of penetrating into the metal workpiece placed at the bottom of the hole or holes. A recording is made over a period of time (typically within about two hours) of the magnitude and number of noise events which occur as the liquid metal penetrates into the metal workpiece. The magnitude and number of noise events are then correlated to the internal stress in the region of the workpiece at the bottom of the hole.

  12. Stress-corrosion cracking in metals

    NASA Technical Reports Server (NTRS)

    1971-01-01

    Criteria and recommended practices for preventing stress-corrosion cracking from impairing the structural integrity and flightworthiness of space vehicles are presented. The important variables affecting stress-corrosion cracking are considered to be the environment, including time and temperature; metal composition, and structure; and sustained tensile stress. For designing spacecraft structures that are free of stress-corrosion cracking for the service life of the vehicle the following rules apply: (1) identification and control of the environments to which the structure will be exposed during construction, storage, transportation, and use; (2) selection of alloy compositions and tempers which are resistant to stress-corrosion cracking in the identified environment; (3) control of fabrication and other processes which may introduce residual tensile stresses or damage the material; (4) limitation of the combined residual and applied tensile stresses to below the threshold stress level for the onset of cracking throughout the service life of the vehicle; and (5) establishment of a thorough inspection program.

  13. Stress-induced cervical lesions.

    PubMed

    Braem, M; Lambrechts, P; Vanherle, G

    1992-05-01

    The increasing occurrence of dental lesions at the cervical surfaces requires more knowledge of the causes of the process. Acidic and abrasive mechanisms have clearly been documented as causes but the stress theory by Lee and Eakle is still controversial. This report describes several incidences of possible stress-induced lesions according to the characteristics described by Lee and Eakle. The occurrences of subgingival lesions lend credence to the stress-induction theory by exclusion of other superimposing etiologic factors. With the current concepts, a perceptive approach to the treatment of cervical lesions can be executed. PMID:1527763

  14. Metal-induced stress in bivalves living along a gradient of Cd contamination: relating sub-cellular metal distribution to population-level responses.

    PubMed

    Perceval, Olivier; Couillard, Yves; Pinel-Alloul, Bernadette; Giguère, Anik; Campbell, Peter G C

    2004-09-20

    The use of biomarkers to assess the impacts of contaminants on aquatic ecosystems has noticeably increased over the past few years. Few of these studies, however, have contributed to the prediction of ecologically significant effects (i.e., at the population or community levels). The present field study was designed to evaluate the potential of metallothionein (MT) and sub-cellular metal partitioning measurements for predicting toxic effects at higher levels of the biological organization in freshwater bivalves (Pyganodon grandis) chronically exposed to Cd. For that purpose, we quantitatively sampled P. grandis populations in the littoral zone of nine lakes on the Precambrian Canadian Shield during two consecutive summers (1998 and 1999); lakes were characterized by contrasting Cd levels but similar trophic status. We tested relationships between the population status of P. grandis (i.e., growth parameters, density, biomass, secondary production, turnover ratio and cumulative fecundity) and (i) ambient Cd concentrations, (ii) sub-organismal responses (MT concentrations in the gill cytosol of individuals and Cd concentrations in three metal-ligand pools identified as M-HMW, the high molecular weight pool, M-MT, the metallothionein-like pool and M-LMW, the low molecular weight pool) and (iii) ecological confounding factors (food resources, presence of host fishes for the obligatory parasitic larval stage of P. grandis). Our results show that littoral density, live weight, dry viscera biomass, production and cumulative fecundity decreased with increasing concentrations of the free-cadmium ion in the environment (Pearson's r ranging from -0.63 to -0.78). On the other hand, theoretical maximum shell lengths (L( infinity )) in our populations were related to both the dissolved Ca concentration and food quality (sestonic C and N concentrations). Overall, Cd concentrations in the gill cytosolic HMW pool of the individual molluscs were the biomarker response that was most

  15. Biomedical Implications of Heavy Metals Induced Imbalances in Redox Systems

    PubMed Central

    Singh, Shweta; Siddiqi, Nikhat J.

    2014-01-01

    Several workers have extensively worked out the metal induced toxicity and have reported the toxic and carcinogenic effects of metals in human and animals. It is well known that these metals play a crucial role in facilitating normal biological functions of cells as well. One of the major mechanisms associated with heavy metal toxicity has been attributed to generation of reactive oxygen and nitrogen species, which develops imbalance between the prooxidant elements and the antioxidants (reducing elements) in the body. In this process, a shift to the former is termed as oxidative stress. The oxidative stress mediated toxicity of heavy metals involves damage primarily to liver (hepatotoxicity), central nervous system (neurotoxicity), DNA (genotoxicity), and kidney (nephrotoxicity) in animals and humans. Heavy metals are reported to impact signaling cascade and associated factors leading to apoptosis. The present review illustrates an account of the current knowledge about the effects of heavy metals (mainly arsenic, lead, mercury, and cadmium) induced oxidative stress as well as the possible remedies of metal(s) toxicity through natural/synthetic antioxidants, which may render their effects by reducing the concentration of toxic metal(s). This paper primarily concerns the clinicopathological and biomedical implications of heavy metals induced oxidative stress and their toxicity management in mammals. PMID:25184144

  16. Antioxidant-Induced Stress

    PubMed Central

    Villanueva, Cleva; Kross, Robert D.

    2012-01-01

    Antioxidants are among the most popular health-protecting products, sold worldwide without prescription. Indeed, there are many reports showing the benefits of antioxidants but only a few questioning the possible harmful effects of these “drugs”. The normal balance between antioxidants and free radicals in the body is offset when either of these forces prevails. The available evidence on the harmful effects of antioxidants is analyzed in this review. In summary, a hypothesis is presented that “antioxidant-induced stress” results when antioxidants overwhelm the body’s free radicals. PMID:22408440

  17. Overall evaluation of the effect of residual stress induced by shot peening in the improvement of fatigue fracture resistance for metallic materials

    NASA Astrophysics Data System (ADS)

    Wang, Renzhi; Ru, Jilai

    2015-03-01

    Before 1980s, the circular suspension spring in automobile subjected to torsion fatigue load, under the cyclic normal tensile stresses, the majority of fatigue fracture occurred was in normal tensile fracture mode(NTFM) and the fracture surface was under 45° diagonal. Because there exists the interaction between the residual stresses induced by shot peening and the applied cyclic normal tensile stresses in NTFM, which represents as "stress strengthening mechanism", shot peening technology could be used for improving the fatigue fracture resistance(FFR) of springs. However, since 1990s up to date, in addition to regular NTFM, the fatigue fractures occurred of peened springs from time to time are in longitudinal shear fracture mode(LSFM) or transverse shear fracture mode(TSFM) with the increase of applied cyclic shear stresses, which leads to a remarkable decrease of FFR. However, LSFM/TSFM can be avoided effectively by means of shot peening treatment again on the peened springs. The phenomena have been rarely happened before. At present there are few literatures concerning this problem. Based upon the results of force analysis of a spring, there is no interaction between the residual stresses by shot peening and the applied cyclic shear stresses in shear fracture. This means that the effect of "stress strengthening mechanism" for improving the FFR of LSFM/TSFM is disappeared basically. During shot peening, however, both of residual stress and cyclic plastic deformed microstructure are induced synchronously like "twins" in the surface layer of a spring. It has been found for the first time by means of force analysis and experimental results that the modified microstructure in the "twins" as a "structure strengthening mechanism" can improve the FFR of LSFM/TSFM. At the same time, it is also shown that the optimum technology of shot peening strengthening must have both "stress strengthening mechanism" and "structure strengthening mechanism" simultaneously so that the

  18. Matrix metalloproteinase-2 and -9 are induced differently by metal nanoparticles in human monocytes: The role of oxidative stress and protein tyrosine kinase activation

    SciTech Connect

    Wan Rong; Mo Yiqun; Zhang Xing; Chien Sufan; Tollerud, David J.; Zhang Qunwei

    2008-12-01

    Recently, many studies have shown that nanoparticles can translocate from the lungs to the circulatory system. As a particulate foreign body, nanoparticles could induce host responses such as reactive oxygen species (ROS) generation, inflammatory cytokine and matrix metalloproteinase (MMP) release which play a major role in tissue destruction and remodeling. However, the direct effects of nanoparticles on leukocytes, especially monocytes, are still unclear. The objective of the present study was to compare the ability of Nano-Co and Nano-TiO{sub 2} to cause alteration of transcription and activity of MMPs and to explore possible mechanisms. We hypothesized that non-toxic doses of some transition metal nanoparticles stimulate an imbalance of MMP/TIMP that cause MMP production that may contribute to their health effects. To test this hypothesis, U937 cells were treated with Nano-Co and Nano-TiO{sub 2} and cytotoxic effects and ROS generation were measured. The alteration of MMP-2 and MMP-9 expression and activity of MMP-2 and MMP-9 after exposure to these metal nanoparticles were subsequently determined. To investigate the potential signaling pathways involved in the Nano-Co-induced MMP activation, the ROS scavengers or inhibitors, AP-1 inhibitor, and protein tyrosine kinase (PTK) inhibitors were also used to pre-treat U937 cells. Our results demonstrated that exposure of U937 cells to Nano-Co, but not to Nano-TiO{sub 2}, at a dose that does not cause cytotoxicity, resulted in ROS generation and up-regulation of MMP-2 and MMP-9 mRNA expression{sub ..} Our results also showed dose- and time-related increases in pro-MMP-2 and pro-MMP-9 gelatinolytic activities in conditioned media after exposure of U937 cells to Nano-Co, but not to Nano-TiO{sub 2}. Nano-Co-induced pro-MMP-2 and pro-MMP-9 activity increases were inhibited by pre-treatment with ROS scavengers or inhibitors. We also demonstrated dose- and time-related decreases in tissue inhibitors of metalloproteinases 2

  19. Matrix metalloproteinase-2 and -9 are induced differently by metal nanoparticles in human monocytes: The role of oxidative stress and protein tyrosine kinase activation

    PubMed Central

    Wan, Rong; Mo, Yiqun; Zhang, Xing; Chien, Sufan; Tollerud, David J.; Zhang, Qunwei

    2009-01-01

    Recently, many studies have shown that nanoparticles can translocate from the lungs to the circulatory system. As a particulate foreign body, nanoparticles could induce host responses such as reactive oxygen species (ROS) generation, inflammatory cytokine and matrix metalloproteinase (MMP) release which play a major role in tissue destruction and remodeling. However, the direct effects of nanoparticles on leukocytes, especially monocytes, are still unclear. The objective of the present study was to compare the ability of Nano-Co and Nano-TiO2 to cause alteration of transcription and activity of MMPs and to explore possible mechanisms. We hypothesized that non-toxic doses of some transition metal nanoparticles stimulate an imbalance of MMP/TIMP that cause MMP production that may contribute to their health effects. To test this hypothesis, U937 cells were treated with Nano-Co and Nano-TiO2 and cytotoxic effects and ROS generation were measured. The alteration of MMP-2 and MMP-9 expression and activity of MMP-2 and MMP-9 after exposure to these metal nanoparticles were subsequently determined. To investigate the potential signaling pathways involved in the Nano-Co-induced MMP activation, the ROS scavengers or inhibitors, AP-1 inhibitor, and protein tyrosine kinase (PTK) inhibitors were also used to pre-treat U937 cells. Our results demonstrated that exposure of U937 cells to Nano-Co, but not to Nano-TiO2, at a dose that does not cause cytotoxicity, resulted in ROS generation and up-regulation of MMP-2 and MMP-9 mRNA expression.. Our results also showed dose- and time-related increases in pro-MMP-2 and pro-MMP-9 gelatinolytic activities in conditioned media after exposure of U937 cells to Nano-Co, but not to Nano-TiO2. Nano-Co-induced pro-MMP-2 and pro-MMP-9 activity increases were inhibited by pre-treatment with ROS scavengers or inhibitors. We also demonstrated dose- and time-related decreases in tissue inhibitors of metalloproteinases 2 (TIMP-2) in U937 cells after

  20. Is Neurotoxicity of Metallic Nanoparticles the Cascades of Oxidative Stress?

    PubMed

    Song, Bin; Zhang, YanLi; Liu, Jia; Feng, XiaoLi; Zhou, Ting; Shao, LongQuan

    2016-12-01

    With the rapid development of nanotechnology, metallic (metal or metal oxide) nanoparticles (NPs) are widely used in many fields such as cosmetics, the food and building industries, and bio-medical instruments. Widespread applications of metallic NP-based products increase the health risk associated with human exposures. Studies revealed that the brain, a critical organ that consumes substantial amounts of oxygen, is a primary target of metallic NPs once they are absorbed into the body. Oxidative stress (OS), apoptosis, and the inflammatory response are believed to be the main mechanisms underlying the neurotoxicity of metallic NPs. Other studies have disclosed that antioxidant pretreatment or co-treatment can reverse the neurotoxicity of metallic NPs by decreasing the level of reactive oxygen species, up-regulating the activities of antioxidant enzymes, decreasing the proportion of apoptotic cells, and suppressing the inflammatory response. These findings suggest that the neurotoxicity of metallic NPs might involve a cascade of events following NP-induced OS. However, additional research is needed to determine whether NP-induced OS plays a central role in the neurotoxicity of metallic NPs, to develop a comprehensive understanding of the correlations among neurotoxic mechanisms and to improve the bio-safety of metallic NP-based products. PMID:27295259

  1. Is Neurotoxicity of Metallic Nanoparticles the Cascades of Oxidative Stress?

    NASA Astrophysics Data System (ADS)

    Song, Bin; Zhang, YanLi; Liu, Jia; Feng, XiaoLi; Zhou, Ting; Shao, LongQuan

    2016-06-01

    With the rapid development of nanotechnology, metallic (metal or metal oxide) nanoparticles (NPs) are widely used in many fields such as cosmetics, the food and building industries, and bio-medical instruments. Widespread applications of metallic NP-based products increase the health risk associated with human exposures. Studies revealed that the brain, a critical organ that consumes substantial amounts of oxygen, is a primary target of metallic NPs once they are absorbed into the body. Oxidative stress (OS), apoptosis, and the inflammatory response are believed to be the main mechanisms underlying the neurotoxicity of metallic NPs. Other studies have disclosed that antioxidant pretreatment or co-treatment can reverse the neurotoxicity of metallic NPs by decreasing the level of reactive oxygen species, up-regulating the activities of antioxidant enzymes, decreasing the proportion of apoptotic cells, and suppressing the inflammatory response. These findings suggest that the neurotoxicity of metallic NPs might involve a cascade of events following NP-induced OS. However, additional research is needed to determine whether NP-induced OS plays a central role in the neurotoxicity of metallic NPs, to develop a comprehensive understanding of the correlations among neurotoxic mechanisms and to improve the bio-safety of metallic NP-based products.

  2. Redox Proteomics Changes in the Fungal Pathogen Trichosporon asahii on Arsenic Exposure: Identification of Protein Responses to Metal-Induced Oxidative Stress in an Environmentally-Sampled Isolate

    PubMed Central

    Ilyas, Sidra; Rehman, Abdul; Varela, Ana Coelho; Sheehan, David

    2014-01-01

    extensive proteomic alterations in response to metal-induced oxidative stress in T. asahii. Amino acid metabolism, protein folding and degradation are principally affected. PMID:25062082

  3. Flow stress model in metal cutting

    NASA Technical Reports Server (NTRS)

    Black, J. T.

    1978-01-01

    A model for the plastic deformation that occurs in metal cutting, based on dislocation mechanics, is presented. The model explains the fundamental deformation structure that develops during machining and is based on the well known Cottrell-Stokes Law, wherein the flow stress is partitioned into two parts; an athermal part which occurs in the shear fronts (or shear bands); and a thermal part which occurs in the lamella regions. The deformation envokes the presence of a cellular dislocation distribution which always exists in the material ahead of the shear process. This 'alien' dislocation distribution either exists in the metal prior to cutting or is produced by the compressive stress field which operates in front of the shear process. The magnitude of the flow stress and direction of the shear are shown to be correlated to the stacking fault energy of the metal being cut. The model is tested with respect to energy consumption rates and found to be consistent with observed values.

  4. Are metallothioneins equally good biomarkers of metal and oxidative stress?

    PubMed

    Figueira, Etelvina; Branco, Diana; Antunes, Sara C; Gonçalves, Fernando; Freitas, Rosa

    2012-10-01

    Several researchers investigated the induction of metallothioneins (MTs) in the presence of metals, namely Cadmium (Cd). Fewer studies observed the induction of MTs due to oxidizing agents, and literature comparing the sensitivity of MTs to different stressors is even more scarce or even nonexistent. The role of MTs in metal and oxidative stress and thus their use as a stress biomarker, remains to be clearly elucidated. To better understand the role of MTs as a biomarker in Cerastoderma edule, a bivalve widely used as bioindicator, a laboratory assay was conducted aiming to assess the sensitivity of MTs to metal and oxidative stressors. For this purpose, Cd was used to induce metal stress, whereas hydrogen peroxide (H2O2), being an oxidizing compound, was used to impose oxidative stress. Results showed that induction of MTs occurred at very different levels in metal and oxidative stress. In the presence of the oxidizing agent (H2O2), MTs only increased significantly when the degree of oxidative stress was very high, and mortality rates were higher than 50 percent. On the contrary, C. edule survived to all Cd concentrations used and significant MTs increases, compared to the control, were observed in all Cd exposures. The present work also revealed that the number of ions and the metal bound to MTs varied with the exposure conditions. In the absence of disturbance, MTs bound most (60-70 percent) of the essential metals (Zn and Cu) in solution. In stressful situations, such as the exposure to Cd and H2O2, MTs did not bind to Cu and bound less to Zn. When organisms were exposed to Cd, the total number of ions bound per MT molecule did not change, compared to control. However the sort of ions bound per MT molecule differed; part of the Zn and all Cu ions where displaced by Cd ions. For organisms exposed to H2O2, each MT molecule bound less than half of the ions compared to control and Cd conditions, which indicates a partial oxidation of thiol groups in the cysteine

  5. Metal-binding peptides: Their role in responses to metal stress

    SciTech Connect

    Rauser, W.E. )

    1989-04-01

    Excess metals are one stress that plants may encounter. The metals Cd, Cu, Ni, and Zn are considered because of concern for their entry into the foodchain of animals and man. Studies of metal tolerant plants and cell cultures suggest three types of responses: exclusion of metal from protoplasts by binding to cell walls, differential membrane transport reducing metal exposure of enzymes, and intracellular chelation of metal in innocuous forms. One group of compounds involved in the latter response are metal-binding peptides designated phytochelatins. They are a family of small peptides composed of five kinds of amino acids, including 2 to 11 cysteines which provide thiols for selective binding of metal. Metals induce the synthesis of phytochelatins through unknown enzymes involving glutathione. In plant cell cultures the peptides bind about 90% of the intracellular Cd. In roots of young plants up to half of the metal is bound by phytochelatins. Intact plants probably use a combination of responses to deal with excess metals, phytochelatins may dominate in certain cases.

  6. Sublethal Heavy Metal Stress Stimulates Innate Immunity in Tomato

    PubMed Central

    Chandra, Swarnendu; Acharya, Krishnendu

    2015-01-01

    Effect of sublethal heavy metal stress as plant biotic elicitor for triggering innate immunity in tomato plant was investigated. Copper in in vivo condition induced accumulation of defense enzymes like peroxidase (PO), polyphenol oxidase (PPO), phenylalanine ammonia-lyase (PAL), and β-1,3 glucanase along with higher accumulation of total phenol, antioxidative enzymes (catalase and ascorbate peroxidase), and total chlorophyll content. Furthermore, the treatment also induced nitric oxide (NO) production which was confirmed by realtime visualization of NO burst using a fluorescent probe 4,5-diaminofluorescein diacetate (DAF-2DA) and spectrophotometric analysis. The result suggested that the sublethal dose of heavy metal can induce an array of plant defense responses that lead to the improvement of innate immunity in plants. PMID:25729768

  7. Discontinuity stresses in metallic pressure vessels

    NASA Technical Reports Server (NTRS)

    1971-01-01

    The state of the art, criteria, and recommended practices for the theoretical and experimental analyses of discontinuity stresses and their distribution in metallic pressure vessels for space vehicles are outlined. The applicable types of pressure vessels include propellant tanks ranging from main load-carrying integral tank structure to small auxiliary tanks, storage tanks, solid propellant motor cases, high pressure gas bottles, and pressurized cabins. The major sources of discontinuity stresses are discussed, including deviations in geometry, material properties, loads, and temperature. The advantages, limitations, and disadvantages of various theoretical and experimental discontinuity analysis methods are summarized. Guides are presented for evaluating discontinuity stresses so that pressure vessel performance will not fall below acceptable levels.

  8. Stability of La2O3 Metal-Insulator-Metal Capacitors under Constant Voltage Stress

    NASA Astrophysics Data System (ADS)

    Shu-Hua Wu,; Chih-Kang Deng,; Tuo-Hung Hou,; Bi-Shiou Chiou,

    2010-04-01

    In this study, we demonstrate the stability of high-κ La2O3 metal-insulator-metal (MIM) capacitors under constant voltage stress (CVS). It was found that the variation in capacitance caused by CVS strongly depends on the injected charges regardless of stress biases. Furthermore, the quadratic voltage coefficient of capacitance (α) decreases with a logarithmic increase in dielectric loss. Charge trapping contributes to the relative capacitance variation under CVS while the reduced carrier mobility due to the stress-induced traps is responsible for the reduction of α. Additionally, high stability of 10-year lifetime is achieved for a 10-nm La2O3 MIM capacitor with an 11.4 fF/μm2 capacitance density.

  9. Stability of La2O3 Metal-Insulator-Metal Capacitors under Constant Voltage Stress

    NASA Astrophysics Data System (ADS)

    Wu, Shu-Hua; Deng, Chih-Kang; Hou, Tuo-Hung; Chiou, Bi-Shiou

    2010-04-01

    In this study, we demonstrate the stability of high-κ La2O3 metal-insulator-metal (MIM) capacitors under constant voltage stress (CVS). It was found that the variation in capacitance caused by CVS strongly depends on the injected charges regardless of stress biases. Furthermore, the quadratic voltage coefficient of capacitance (α) decreases with a logarithmic increase in dielectric loss. Charge trapping contributes to the relative capacitance variation under CVS while the reduced carrier mobility due to the stress-induced traps is responsible for the reduction of α. Additionally, high stability of 10-year lifetime is achieved for a 10-nm La2O3 MIM capacitor with an 11.4 fF/µm2 capacitance density.

  10. Proteomic responses to metal-induced oxidative stress in hydrothermal vent-living mussels, Bathymodiolus sp., on the Southwest Indian Ridge.

    PubMed

    Cole, Catherine; Coelho, Ana Varela; James, Rachael H; Connelly, Doug; Sheehan, David

    2014-05-01

    Bathymodiolin mussels are amongst the dominant fauna occupying hydrothermal vent ecosystems throughout the World's oceans. This subfamily inhabits a highly ephemeral and variable environment, where exceptionally high concentrations of reduced sulphur species and heavy metals necessitate adaptation of specialised detoxification mechanisms. Whilst cellular responses to common anthropogenic pollutants are well-studied in shallow-water species, they remain limited in deep-sea vent fauna. Bathymodiolus sp. were sampled from two newly-discovered vent sites on the Southwest Indian Ridge (Tiamat and Knuckers Gaff) by the remotely operated vehicle (ROV) Kiel 6000 during the RRS James Cook cruise, JC 067 in November 2011. Here, we use redox proteomics to investigate the effects of tissue metal accumulation on protein expression and thiol oxidation in gill. Following 2D PAGE, we demonstrate a significant difference in intensity in 30 protein spots in this organ between the two vent sites out of 205 matched spots. We also see significant variations in thiol oxidation in 15 spots, out of 143 matched. At Tiamat, 23 protein spots are up-regulated compared to Knuckers Gaff and we identify 5 of these with important roles in metabolism, cell structure, stress response, and redox homeostasis. We suggest that increased metal exposure triggers changes in the proteome, regulating tissue uptake. This is evident both between vent sites and across a chemical gradient within the Knuckers Gaff vent site. Our findings highlight the importance of proteomic plasticity in successful adaptation to the spatially and temporally fluctuating chemical environments that are characteristic of hydrothermal vent habitats. PMID:24080408

  11. Mechanisms of Metal-Induced Centrosome Amplification

    PubMed Central

    Holmes, Amie L.; Wise, John Pierce

    2014-01-01

    Exposure to toxic and carcinogenic metals is widespread; however, their mechanisms of action remain largely unknown. One potential mechanism for metal-induced carcinogenicity and toxicity is centrosome amplification. Here, we review the mechanisms for metal-induced centrosome amplification, including arsenic, chromium, mercury and nano-titanium dioxide. PMID:21118148

  12. Noble metal nanoparticle-induced oxidative stress modulates tumor associated macrophages (TAMs) from an M2 to M1 phenotype: An in vitro approach.

    PubMed

    Pal, Ramkrishna; Chakraborty, Biswajit; Nath, Anupam; Singh, Leichombam Mohindro; Ali, Mohammed; Rahman, Dewan Shahidur; Ghosh, Sujit Kumar; Basu, Abhishek; Bhattacharya, Sudin; Baral, Rathindranath; Sengupta, Mahuya

    2016-09-01

    Diagnosis of cancer and photothermal therapy using optoelectronic properties of noble metal nanoparticles (NPs) has established a new therapeutic approach for treating cancer. Here we address the intrinsic properties of noble metal NPs (gold and silver) as well as the mechanism of their potential antitumor activity. For this, the study addresses the functional characterization of tumor associated macrophages (TAMs) isolated from murine fibrosarcoma induced by a chemical carcinogen, 3-methylcholanthrene (MCA). We have previously shown antitumor activity of both gold nanoparticles (AuNPs) and silver nanoparticle (AgNPs) in vivo in a murine fibrosarcoma model. In the present study, it has been seen that AuNPs and AgNPs modulate the reactive oxygen species (ROS) and reactive nitrogen species (RNS) production, suppressing the antioxidant system of cells (TAMs). Moreover, the antioxidant-mimetic action of these NPs maintain the ROS and RNS levels in TAMs which act as second messengers to activate the proinflammatory signaling cascades. Thus, while there is a downregulation of tumor necrosis factor-α (TNF-α) and Interleukin-10 (IL-10) in the TAMs, the proinflammatory cytokine Interleukin-12 (IL-12) is upregulated resulting in a polarization of TAMs from M2 (anti-inflammatory) to M1 (pro-inflammatory) nature. PMID:27344639

  13. Nondestructive method for measuring residual stresses in metals, a concept

    NASA Technical Reports Server (NTRS)

    Schwebel, C. D.

    1968-01-01

    Nondestructive direct measurement of residual surface stresses in metals can be made because metal under stress has a different electrochemical solution potential than in the unstressed condition. The method uses two matched electrolytic cells to cancel extraneous effects on the actual solution potential of the metal specimen.

  14. Inductive measurements of the stress assisted and strain induced martensite transformations of Sandvik maraging steel 1RK91 before, during and after metal forming

    NASA Astrophysics Data System (ADS)

    Nolles, H.; Post, J.; Beyer, J.

    2003-10-01

    Measurements of transformation behaviour are very important to get a good knowledge of the material behaviour of metastable stainless steels during metal forming processes. A convenient way of measuring this kind of transformations is inductive measurment. This article describes a possible solution for this kind of measurements, together with the developed sensors and electronics. The first part of the article focuses on the electronics, calibration and the development of the sensors. The equipment is also used for multi sensor measurements. The second part of the article shows results of measurements on the Sandvik maraging steel 1RK91. The results are shown for three examples: A problem that occurs during inductive measurements is that more pararneters than the martensite content have influence on the output of the signal. Elastic stresses, temperature and plastic deformation have also a big influence on the signal output. Some results of measurements are shown to demonstrate the influence together with a calibration metho(l.Thieineasuring device is fully automatic and conriceted to a computer to make sample logging possible during testing.

  15. Laser induced surface stress on water droplets.

    PubMed

    Wang, Neng; Lin, Zhifang; Ng, Jack

    2014-10-01

    Laser induced stress on spherical water droplets is studied. At mechanical equilibrium, the body stress vanishes therefore we consider only the surface stress. The surface stress on sub-wavelength droplets is slightly weaker along the light propagation direction. For larger droplets, due to their light focusing effect, the forward stress is significantly enhanced. For a particle roughly 3 micron in radius, when it is excited at whispering gallery mode with Q ∼ 10⁴ by a 1 Watt Gaussian beam, the stress can be enhanced by two orders of magnitude, and can be comparable with the Laplace pressure. PMID:25321955

  16. Hydrostatic Stress Effects in Metal Plasticity

    NASA Technical Reports Server (NTRS)

    Wilson, Christopher D.

    1999-01-01

    Since the 1940s, the theory of plasticity has assumed that hydrostatic stress does not affect the yield or postyield behavior of metals. This assumption is based on the early work of Bridgman. Bridgman found that hydrostatic pressure (compressive stress) does not affect yield behavior until a substantial amount of pressure (greater than 100 ksi) is present. The objective of this study was to determine the effect of hydrostatic tension on yield behavior. Two different specimen geometries were examined: an equal-arm bend specimen and a double edge notch specimen. The presence of a notch is sufficient to develop high enough hydrostatic tensile stresses to affect yield. The von Mises yield function, which does not have a hydrostatic component, and the Drucker-Prager yield function, which includes a hydrostatic component, were used in finite element analyses of the two specimen geometries. The analyses were compared to test data from IN 100 specimens. For both geometries, the analyses using the Drucker-Prager yield function more closely simulated the test data. The von Mises yield function lead to 5-10% overprediction of the force-displacement or force-strain response of the test specimens.

  17. a Simple Interpretation of the Rice Spectral Indices Space for Assessment of Heavy Metal Stress

    NASA Astrophysics Data System (ADS)

    Wang, P.; Huang, F.; Liu, X. N.

    2016-06-01

    Heavy metal stress will induce the change of the bio-parameters like chlorophyll, nitrogen and water content of rice. In this paper, we analyzed the traditional spectral index which has strong relationship in general with the three bio-parameters using hyperspectral data acquired by ASD. It is found that some indies do not work well when the heavy metal stress exists, however, some indies still has ability to estimate the above three bio-parameters. A new interpretation is proposed to classify the stress level based on both the physical mechanism analysis and the statistic model after we describe and discuss studies on the expression of spectral indices of rice under heavy metal stress. The 3-axes spectral indices spaces, which are constructed of 3 spectral indices sensitive to rice's chlorophyll concentration, nitrogen concentration and water concentration respectively, are used to visualize the linkage between heavy metal stress and spectrum of rice canopy.

  18. Stress induced obesity: lessons from rodent models of stress

    PubMed Central

    Patterson, Zachary R.; Abizaid, Alfonso

    2013-01-01

    Stress was once defined as the non-specific result of the body to any demand or challenge to homeostasis. A more current view of stress is the behavioral and physiological responses generated in the face of, or in anticipation of, a perceived threat. The stress response involves activation of the sympathetic nervous system and recruitment of the hypothalamic-pituitary-adrenal (HPA) axis. When an organism encounters a stressor (social, physical, etc.), these endogenous stress systems are stimulated in order to generate a fight-or-flight response, and manage the stressful situation. As such, an organism is forced to liberate energy resources in attempt to meet the energetic demands posed by the stressor. A change in the energy homeostatic balance is thus required to exploit an appropriate resource and deliver useable energy to the target muscles and tissues involved in the stress response. Acutely, this change in energy homeostasis and the liberation of energy is considered advantageous, as it is required for the survival of the organism. However, when an organism is subjected to a prolonged stressor, as is the case during chronic stress, a continuous irregularity in energy homeostasis is considered detrimental and may lead to the development of metabolic disturbances such as cardiovascular disease, type II diabetes mellitus and obesity. This concept has been studied extensively using animal models, and the neurobiological underpinnings of stress induced metabolic disorders are beginning to surface. However, different animal models of stress continue to produce divergent metabolic phenotypes wherein some animals become anorexic and lose body mass while others increase food intake and body mass and become vulnerable to the development of metabolic disturbances. It remains unclear exactly what factors associated with stress models can be used to predict the metabolic outcome of the organism. This review will explore a variety of rodent stress models and discuss the

  19. Drug-Induced Oxidative Stress and Toxicity

    PubMed Central

    Deavall, Damian G.; Martin, Elizabeth A.; Horner, Judith M.; Roberts, Ruth

    2012-01-01

    Reactive oxygen species (ROS) are a byproduct of normal metabolism and have roles in cell signaling and homeostasis. Species include oxygen radicals and reactive nonradicals. Mechanisms exist that regulate cellular levels of ROS, as their reactive nature may otherwise cause damage to key cellular components including DNA, protein, and lipid. When the cellular antioxidant capacity is exceeded, oxidative stress can result. Pleiotropic deleterious effects of oxidative stress are observed in numerous disease states and are also implicated in a variety of drug-induced toxicities. In this paper, we examine the nature of ROS-induced damage on key cellular targets of oxidative stress. We also review evidence implicating ROS in clinically relevant, drug-related side effects including doxorubicin-induced cardiac damage, azidothymidine-induced myopathy, and cisplatin-induced ototoxicity. PMID:22919381

  20. Ethylene and Metal Stress: Small Molecule, Big Impact

    PubMed Central

    Keunen, Els; Schellingen, Kerim; Vangronsveld, Jaco; Cuypers, Ann

    2016-01-01

    The phytohormone ethylene is known to mediate a diverse array of signaling processes during abiotic stress in plants. Whereas many reports have demonstrated enhanced ethylene production in metal-exposed plants, the underlying molecular mechanisms are only recently investigated. Increasing evidence supports a role for ethylene in the regulation of plant metal stress responses. Moreover, crosstalk appears to exist between ethylene and the cellular redox balance, nutrients and other phytohormones. This review highlights our current understanding of the key role ethylene plays during responses to metal exposure. Moreover, particular attention is paid to the integration of ethylene within the broad network of plant responses to metal stress. PMID:26870052

  1. Ethylene and Metal Stress: Small Molecule, Big Impact.

    PubMed

    Keunen, Els; Schellingen, Kerim; Vangronsveld, Jaco; Cuypers, Ann

    2016-01-01

    The phytohormone ethylene is known to mediate a diverse array of signaling processes during abiotic stress in plants. Whereas many reports have demonstrated enhanced ethylene production in metal-exposed plants, the underlying molecular mechanisms are only recently investigated. Increasing evidence supports a role for ethylene in the regulation of plant metal stress responses. Moreover, crosstalk appears to exist between ethylene and the cellular redox balance, nutrients and other phytohormones. This review highlights our current understanding of the key role ethylene plays during responses to metal exposure. Moreover, particular attention is paid to the integration of ethylene within the broad network of plant responses to metal stress. PMID:26870052

  2. On the Stress-Temperature Scaling for Steady-State Flow in Metallic Glasses

    SciTech Connect

    Guan, Pengfei; Chen, Mingwei; Egami, T.

    2010-01-01

    Through computer simulation of steady-state flow in a Zr50Cu40Al10 metallic glass using a set of realistic potentials we found a simple scaling relationship between temperature and stress as they affect viscosity. The scaling relationship provides new insights for the microscopic mechanism of shear flow in the glassy state, in terms of the elastic energy of the applied stress modifying the local energy landscape. The results suggest that the plastic flow and mechanical failure in metallic glasses are consequences of stress-induced glass transition.

  3. Residual thermal stress control in composite reinforced metal structures. [by mechanical loading of metal component prior to bonding

    NASA Technical Reports Server (NTRS)

    Kelly, J. B.; June, R. R.

    1972-01-01

    Advanced composite materials, composed of boron or graphite fibers and a supporting matrix, make significant structural efficiency improvements available to aircraft and aerospace designers. Residual stress induced during bonding of composite reinforcement to metal structural elements can be reduced or eliminated through suitable modification to the manufacturing processes. The most successful method employed during this program used a steel tool capable of mechanically loading the metal component in compression prior to the adhesive bonding cycle. Compression loading combined with heating to 350 F during the bond cycle can result in creep deformation in aluminum components. The magnitude of the deformation increases with increasing stress level during exposure to 350 F.

  4. Mechanisms of Nanoparticle-Induced Oxidative Stress and Toxicity

    PubMed Central

    Wang, Liying

    2013-01-01

    The rapidly emerging field of nanotechnology has offered innovative discoveries in the medical, industrial, and consumer sectors. The unique physicochemical and electrical properties of engineered nanoparticles (NP) make them highly desirable in a variety of applications. However, these novel properties of NP are fraught with concerns for environmental and occupational exposure. Changes in structural and physicochemical properties of NP can lead to changes in biological activities including ROS generation, one of the most frequently reported NP-associated toxicities. Oxidative stress induced by engineered NP is due to acellular factors such as particle surface, size, composition, and presence of metals, while cellular responses such as mitochondrial respiration, NP-cell interaction, and immune cell activation are responsible for ROS-mediated damage. NP-induced oxidative stress responses are torch bearers for further pathophysiological effects including genotoxicity, inflammation, and fibrosis as demonstrated by activation of associated cell signaling pathways. Since oxidative stress is a key determinant of NP-induced injury, it is necessary to characterize the ROS response resulting from NP. Through physicochemical characterization and understanding of the multiple signaling cascades activated by NP-induced ROS, a systemic toxicity screen with oxidative stress as a predictive model for NP-induced injury can be developed. PMID:24027766

  5. Metal Gate (TiN, TiC, TaN) Film Stack Stress

    NASA Astrophysics Data System (ADS)

    Bello, A. F.; Paul, Abhijeet; Kim, Hoon

    2015-10-01

    Successful stress engineering in semiconductor device structures must consider all the contributions to the stress field including those not typically considered for stress, such as work function metal (WFM) gate layers that are used to tune to the desired work function level. These films induce stress especially since they are so close to the channel region. In this study we measure stress from blanket layer films and combinations of TiN, TiC, and TaN deposited on Hf oxide, at thicknesses that are typically used for advanced metal-oxide-semiconductor field-effect transistor (MOSFET) devices. Tungsten (W) deposited on top of the WFM layer stacks is also measured. For combination film stacks, the stress is measured after each deposition step. The induced stress from the WFM is significant, in the range of hundreds of MPa, and varies according to the thickness and processing conditions such as annealing temperature and time, etc. Results from these blanket film measurements were used as a guide for technology computer-aided design (TCAD) modeling of the stress field in FinFET structures with design rules comparable to 10-nm technology. The tensor stress components identify areas of compressive and tensile stress and with a magnitude similar to expected results. The stress field could be used to calculate the FinFET device performance, and in this case an example is provided with the relative improvement in drain current.

  6. Thermoelastic Stress Analysis: The Mean Stress Effect in Metallic Alloys

    NASA Technical Reports Server (NTRS)

    Gyekenyesi, Andrew L.; Baaklini, George Y.

    1999-01-01

    The primary objective of this study involved the utilization of the thermoelastic stress analysis (TSA) method to demonstrate the mean stress dependence of the thermoelastic constant. Titanium and nickel base alloys, commonly employed in aerospace gas turbines, were the materials of interest. The repeatability of the results was studied through a statistical analysis of the data. Although the mean stress dependence was well established, the ability to confidently quantify it was diminished by the experimental variations. If calibration of the thermoelastic response to mean stress can be successfully implemented, it is feasible to use the relationship to determine a structure's residual stress state.

  7. Can heavy metal pollution defend seed germination against heat stress? Effect of heavy metals (Cu(2+), Cd(2+) and Hg(2+)) on maize seed germination under high temperature.

    PubMed

    Deng, Benliang; Yang, Kejun; Zhang, Yifei; Li, Zuotong

    2016-09-01

    Heavy metal pollution, as well as greenhouse effect, has become a serious threat today. Both heavy metal and heat stresses can arrest seed germination. What response can be expected for seed germination under both stress conditions? Here, the effects of heavy metals (Cu(2+), Cd(2+) and Hg(2+)) on maize seed germination were investigated at 20 °C and 40 °C. Compared with 20 °C, heat stress induced thermodormancy. However, this thermodormancy could be significantly alleviated by the addition of a low concentration of heavy metals. Heavy metals, as well as heat stress induced H2O2 accumulation in germinating seeds. Interestingly, this low concentration of heavy metal that promoted seed germination could be partly blocked by DMTU (a specific ROS scavenger), irrespective of temperature. Accordingly, H2O2 addition reinforced this promoting effect on seed germination, which was induced by a low concentration of heavy metal. Furthermore, we found that the NADPH oxidase derived ROS was required for seed germination promoted by the heavy metals. Subsequently, treatment of seeds with fluridone (a specific inhibitor of ABA) or ABA significantly alleviated or aggravated thermodormancy, respectively. However, this alleviation or aggravation could be partly attenuated by a low concentration of heavy metals. In addition, germination that was inhibited by high concentrations of heavy metals was also partly reversed by fluridone. The obtained results support the idea that heavy metal-mediated ROS and hormone interaction can finally affect the thermodormancy release or not. PMID:27239687

  8. Gravity-induced stresses in finite slopes

    USGS Publications Warehouse

    Savage, W.Z.

    1994-01-01

    An exact solution for gravity-induced stresses in finite elastic slopes is presented. This solution, which is applied for gravity-induced stresses in 15, 30, 45 and 90?? finite slopes, has application in pit-slope design, compares favorably with published finite element results for this problem and satisfies the conditions that shear and normal stresses vanish on the ground surface. The solution predicts that horizontal stresses are compressive along the top of the slopes (zero in the case of the 90?? slope) and tensile away from the bottom of the slopes, effects which are caused by downward movement and near-surface horizontal extension in front of the slope in response to gravity loading caused by the additional material associated with the finite slope. ?? 1994.

  9. Morphological evolution of voids by surface drift diffusion driven by capillary, electromigration, and thermal-stress gradients induced by steady-state heat flow in passivated metallic thin films and flip chip solder joints. I. Theory

    NASA Astrophysics Data System (ADS)

    Ogurtani, Tarik Omer; Akyildiz, Oncu

    2008-07-01

    The morphological evolution of intragranular voids induced by surface drift diffusion under the actions of capillary and electromigration (EM) forces and thermal-stress gradients (TSGs) associated with steady-state heat flow is investigated in passivated metallic thin films and flip chip solder joints via computer simulation using the front-tracking method. In the mesoscopic nonequilibrium thermodynamic formulation of the generalized driving forces for the thermal-stress-induced surface drift diffusion, not only the usual elastic strain energy density contribution but also the elastic dipole tensor interaction (EDTI) between the thermal-stress field and the mobile atomic species (monovacancies) are considered using the concept of elastic interaction energy promoted in unified linear instability analysis (ULISA) [T. O. Ogurtani, Phys. Rev. B 74, 155422 (2006)]. According to extensive computer experiments performed on voids, which are initially cylindrical in shape, two completely different and topographically distinct behaviors are observed during the development of quasistationary state void surface morphologies, even in the presence of strong EM forces. These behaviors strictly depend on whether or not heat flux crowding occurs in the regions between the void surface layer and the sidewalls of the interconnect lines due to proximity effects of the insulating boundaries. In both morphological cases, however, one also observes two well-defined regimes, namely, the EM and TSG dominated regimes in EM versus EDTI parametric space. In the case of the TSG dominated regime, the void center of gravity (centroid) exhibits uniform displacement (drift) velocity proportional and opposite to the induced TSG exactly as predicted by ULISA theory. These domains are bounded by a threshold level curve for the EDTI parameter, above which an extremely sharp crack tip nucleation and propagation occurs in the highly localized minima in the triaxial stress regions (i.e., hot spots

  10. Stress Drops for Potentially Induced Earthquake Sequences

    NASA Astrophysics Data System (ADS)

    Huang, Y.; Beroza, G. C.; Ellsworth, W. L.

    2015-12-01

    Stress drop, the difference between shear stress acting across a fault before and after an earthquake, is a fundamental parameter of the earthquake source process and the generation of strong ground motions. Higher stress drops usually lead to more high-frequency ground motions. Hough [2014 and 2015] observed low intensities in "Did You Feel It?" data for injection-induced earthquakes, and interpreted them to be a result of low stress drops. It is also possible that the low recorded intensities could be a result of propagation effects. Atkinson et al. [2015] show that the shallow depth of injection-induced earthquakes can lead to a lack of high-frequency ground motion as well. We apply the spectral ratio method of Imanishi and Ellsworth [2006] to analyze stress drops of injection-induced earthquakes, using smaller earthquakes with similar waveforms as empirical Green's functions (eGfs). Both the effects of path and linear site response should be cancelled out through the spectral ratio analysis. We apply this technique to the Guy-Greenbrier earthquake sequence in central Arkansas. The earthquakes migrated along the Guy-Greenbrier Fault while nearby injection wells were operating in 2010-2011. Huang and Beroza [GRL, 2015] improved the magnitude of completeness to about -1 using template matching and found that the earthquakes deviated from Gutenberg-Richter statistics during the operation of nearby injection wells. We identify 49 clusters of highly similar events in the Huang and Beroza [2015] catalog and calculate stress drops using the source model described in Imanishi and Ellsworth [2006]. Our results suggest that stress drops of the Guy-Greenbrier sequence are similar to tectonic earthquakes at Parkfield, California (the attached figure). We will also present stress drop analysis of other suspected induced earthquake sequences using the same method.

  11. Diabetic Cardiovascular Disease Induced by Oxidative Stress

    PubMed Central

    Kayama, Yosuke; Raaz, Uwe; Jagger, Ann; Adam, Matti; Schellinger, Isabel N.; Sakamoto, Masaya; Suzuki, Hirofumi; Toyama, Kensuke; Spin, Joshua M.; Tsao, Philip S.

    2015-01-01

    Cardiovascular disease (CVD) is the leading cause of morbidity and mortality among patients with diabetes mellitus (DM). DM can lead to multiple cardiovascular complications, including coronary artery disease (CAD), cardiac hypertrophy, and heart failure (HF). HF represents one of the most common causes of death in patients with DM and results from DM-induced CAD and diabetic cardiomyopathy. Oxidative stress is closely associated with the pathogenesis of DM and results from overproduction of reactive oxygen species (ROS). ROS overproduction is associated with hyperglycemia and metabolic disorders, such as impaired antioxidant function in conjunction with impaired antioxidant activity. Long-term exposure to oxidative stress in DM induces chronic inflammation and fibrosis in a range of tissues, leading to formation and progression of disease states in these tissues. Indeed, markers for oxidative stress are overexpressed in patients with DM, suggesting that increased ROS may be primarily responsible for the development of diabetic complications. Therefore, an understanding of the pathophysiological mechanisms mediated by oxidative stress is crucial to the prevention and treatment of diabetes-induced CVD. The current review focuses on the relationship between diabetes-induced CVD and oxidative stress, while highlighting the latest insights into this relationship from findings on diabetic heart and vascular disease. PMID:26512646

  12. Heat Stress-Induced DNA Damage

    PubMed Central

    Kantidze, O.L.; Velichko, A.K.; Luzhin, A.V.; Razin, S.V.

    2016-01-01

    Although the heat-stress response has been extensively studied for decades, very little is known about its effects on nucleic acids and nucleic acid-associated processes. This is due to the fact that the research has focused on the study of heat shock proteins and factors (HSPs and HSFs), their involvement in the regulation of transcription, protein homeostasis, etc. Recently, there has been some progress in the study of heat stress effects on DNA integrity. In this review, we summarize and discuss well-known and potential mechanisms of formation of various heat stress-induced DNA damage. PMID:27437141

  13. Lead induced testicular hypersensitivity in stressed rats.

    PubMed

    Saxena, D K; Lal, B; Srivastava, R S; Chandra, S V

    1990-01-01

    Rats were immobilized for 2 h and treated i.p. with lead Pb2+ (8 mg/kg/day) for 45 d to investigate the testicular effects of lead on rats kept under immobilization stress. Marked alteration in SDH. G6PDH activity, cholesterol and ascorbic acid contents and reduced sperm counts associated with marked pathological changes in the testis of rats were observed after combined treatment with lead and immobilization stress in comparison to either alone. An increase in the disturbances of testicular androgen synthesis seems to be responsible for enhanced testicular injury in lead induced stressed rats. PMID:2401350

  14. Effect of Residual Stresses on the Hardness of Bulk Metallic Glasses

    SciTech Connect

    Wang, L.; Bei, Hongbin; Gao, Y. F.; Lu, Zhao Ping; Nieh, T. G.

    2011-01-01

    Nanoindentation experiments were conducted on Zr-based metallic glass samples, which were elastically and plastically bent in order to investigate the effect of residual stresses on hardness. It was found that tensile residual stress reduced the hardness significantly, while compressive residual stress produced only a small effect on the hardness. These observations are consistent with three-dimensional continuum-plasticity-based finite-element simulations. The hardness was also found to vary more significantly with residual stresses, in particular in tension, than that caused by shear-banding-induced softening, suggesting hardness measurement is a practical method for the evaluation of tensile residual stresses in a metallic glass. Hardness variation in the bent sample was correlated with the residual-stress induced volume dilatation through a free-volume-based model. In this paper, we also present a detailed stress analysis based on yield asymmetry under tension and compression to describe the distribution of residual stresses in bent metallic glass specimens. The calculations agree well with the hardness variations measured experimentally.

  15. Stress-Induced Nanoparticle Crystallization

    PubMed Central

    2015-01-01

    We demonstrate for the first time a new mechanical annealing method that can significantly improve the structural quality of self-assembled nanoparticle arrays by eliminating defects at room temperature. Using in situ high-pressure small-angle X-ray scattering, we show that deformation of nanoparticle assembly in the presence of gigapascal level stress rebalances interparticle forces within nanoparticle arrays and transforms the nanoparticle film from an amorphous assembly with defects into a quasi-single crystalline superstructure. Our results show that the existence of the hydrostatic pressure field makes the transformation both thermodynamically and kinetically possible/favorable, thus providing new insight for nanoparticle self-assembly and integration with enhanced mechanical performance. PMID:24829089

  16. Metallothionein Alleviates Oxidative Stress-Induced Endoplasmic Reticulum Stress and Myocardial Dysfunction

    PubMed Central

    Guo, Rui; Ma, Heng; Gao, Feng; Zhong, Li; Ren, Jun

    2009-01-01

    Oxidative stress and endoplasmic reticulum (ER) stress have been implicated in cardiovascular diseases although the interplay between the two is not clear. This study was designed to examine the influence of oxidative stress through glutathione depletion on myocardial ER stress and contractile function in the absence or presence of the heavy metal scavenger antioxidant metallothionein (MT). FVB and MT overexpression transgenic mice received the GSH synthase inhibitor buthionine sulfoximine (BSO, 30 mM) in drinking water for 2 weeks. Oxidative stress, ER stress, apoptosis, cardiac function and ultrastructure were assessed using GSH/GSSG assay, reactive oxygen species (ROS), immunoblotting, caspase-3 activity, Langendorff perfused heart function (LVDP and ± dP/dt), and transmission electron microscopy. BSO led to a robust decrease in the GSH/GSSG ratio and increased ROS production, consolidating oxidative stress. Cardiac function and ultrastructure were compromised following BSO treatment, the effect of which was obliterated by MT. BSO promoted overt ER stress as evidenced by upregulated BiP, calregulin, phospho-IRE1α and phospho-eIF2α without affecting total IRE1α and eIF2α. BSO treatment led to apoptosis manifested as elevated expression of CHOP/GADD153, caspase-12 and Bax as well as caspase-3 activity, reduced Bcl-2 expression and JNK phosphorylation, all of which was ablated by MT. Moreover, both antioxidant N-acetylcysteine and the ER stress inhibitor tauroursodeoxycholic acid reversed the oxidative stress inducer menadione-elicited depression in cardiomyocyte contractile function. Taken together, these data suggested that ER stress occurs likely downstream of oxidative stress en route to cardiac dysfunction. PMID:19344729

  17. Thermal-Stress Reducer For Metal/Composite Joint

    NASA Technical Reports Server (NTRS)

    Glinski, Robert L.

    1993-01-01

    Simple insert called "thermal link" reduces stresses caused by mismatches between thermal expansions of metal part and nonmetallic part made of fiber/matrix composite material. Link conceived for use in casing of advanced jet engine.

  18. Investigation into stress wave propagation in metal foams

    NASA Astrophysics Data System (ADS)

    Li, Lang; Xue, Pu; Chen, Yue

    2015-09-01

    The aim of this study is to investigate stress wave propagation in metal foams under high-speed impact loading. Three-dimensional Voronoi model is established to represent real closed-cell foam. Based on the one-dimensional stress wave theory and Voronoi model, a numerical model is developed to calculate the velocity of elastic wave and shock wave in metal foam. The effects of impact velocity and relative density of metal foam on the stress wave propagation in metal foams are explored respectively. The results show that both elastic wave and shock wave propagate faster in metal foams with larger relative density; with increasing the impact velocity, the shock wave propagation velocity increase, but the elastic wave propagation is not sensitive to the impact velocity.

  19. Proteome changes induced by aluminium stress in tomato roots.

    PubMed

    Zhou, Suping; Sauvé, Roger; Thannhauser, Theodore W

    2009-01-01

    Growth inhibition in acid soils due to Al stress affects crop production worldwide. To understand mechanisms in sensitive crops that are affected by Al stress, a proteomic analysis of primary tomato root tissue, grown in Al-amended and non-amended liquid cultures, was performed. DIGE-SDS-MALDI-TOF-TOF analysis of these tissues resulted in the identification of 49 proteins that were differentially accumulated. Dehydroascorbate reductase, glutathione reductase, and catalase enzymes associated with antioxidant activities were induced in Al-treated roots. Induced enzyme proteins associated with detoxification were mitochondrial aldehyde dehydrogenase, catechol oxidase, quinone reductase, and lactoylglutathione lyase. The germin-like (oxalate oxidase) proteins, the malate dehydrogenase, wali7 and heavy-metal associated domain-containing proteins were suppressed. VHA-ATP that encodes for the catalytic subunit A of the vacuolar ATP synthase was induced and two ATPase subunit 1 isoforms were suppressed. Several proteins in the active methyl cycle, including SAMS, quercetin 3-O-methyltransferase and AdoHcyase, were induced by Al stress. Other induced proteins were isovaleryl-CoA dehydrogenase and the GDSL-motif lipase hydrolase family protein. NADPH-dependent flavin reductase and beta-hydroxyacyl-ACP dehydratase were suppressed. PMID:19336389

  20. Fault activation due to glacially induced stresses

    NASA Astrophysics Data System (ADS)

    Steffen, R.; Lund, B.; Wu, P. P.

    2013-12-01

    Melting glaciers worldwide have an effect on sea level, but also on the stability of pre-existing faults. The load due to continental ice sheets or glaciers depresses the surface below, leading to changes in the lithospheric stresses. The accumulation of ice mass increases the vertical stress, and the horizontal stresses increase due to the accompanying flexure of the lithosphere. During deglaciation, ice-mass loss causes a simultaneous decrease in vertical stress; however, horizontal stresses decrease only slowly due to the slow readjusting of the Earth. After the end of deglaciation, only the induced horizontal stresses remain as the process of glacial isostatic adjustment (GIA) proceeds visco-elastically. The modelling of this process and the estimation of fault slip is enabled by a new GIA-fault model. However, this finite-element model is only available in two dimensions, and the extension to three dimensions is a necessary step further to allow the comparison of obtained fault slips to observations of glacially induced faults in Europe and North America. The model has several input parameters, which affect the activation time of faults and their resulting slip (e.g. ice history, rheology of the Earth, frictional properties, pore-fluid pressure). We will present the results of the new 3D model and show the sensitivity of faults with respect to modelling parameters. Furthermore, a comparison to observations will be presented.

  1. Fault activation due to glacially induced stresses

    NASA Astrophysics Data System (ADS)

    Steffen, Rebekka; Lund, Björn

    2014-05-01

    Melting glaciers worldwide have an effect on sea level, but also on the stability of pre-existing faults. The load due to continental ice sheets or glaciers depresses the surface below, leading to changes in the lithospheric stresses. The accumulation of ice mass increases the vertical stress, and the horizontal stresses increase due to the accompanying flexure of the lithosphere. During deglaciation, ice-mass loss causes a simultaneous decrease in vertical stress; however, horizontal stresses decrease only slowly due to the slow readjusting of the Earth. After the end of deglaciation, only the induced horizontal stresses remain as the process of glacial isostatic adjustment (GIA) proceeds visco-elastically. The modelling of this process and the estimation of fault slip is enabled by a new GIA-fault model. However, this finite-element model is only available in two dimensions, and the extension to three dimensions is a necessary step further to allow the comparison of obtained fault slips to observations of glacially induced faults in Europe and North America. The model has several input parameters, which affect the activation time of faults and their resulting slip (e.g. ice history, rheology of the Earth, frictional properties, pore-fluid pressure). We will present the results of the new 3D model and show the sensitivity of faults with respect to modelling parameters. Furthermore, a comparison to observations will be presented.

  2. Stress-Induced Mutagenesis in Bacteria

    PubMed Central

    Foster, Patricia L.

    2009-01-01

    Bacteria spend their lives buffeted by changing environmental conditions. To adapt to and survive these stresses, bacteria have global response systems that result in sweeping changes in gene expression and cellular metabolism. These responses are controlled by master regulators, which include: alternative sigma factors, such as RpoS and RpoH; small molecule effectors, such as ppGpp; gene repressors such as LexA; and, inorganic molecules, such as polyphosphate. The response pathways extensively overlap and are induced to various extents by the same environmental stresses. These stresses include nutritional deprivation, DNA damage, temperature shift, and exposure to antibiotics. All of these global stress responses include functions that can increase genetic variability. In particular, up-regulation and activation of error-prone DNA polymerases, down-regulation of error-correcting enzymes, and movement of mobile genetic elements are common features of several stress responses. The result is that under a variety of stressful conditions, bacteria are induced for genetic change. This transient mutator state may be important for adaptive evolution. PMID:17917873

  3. Stress-Induced Cardiomyopathy Presenting as Shock

    PubMed Central

    Yoo, Tae Kyung; Lee, Jong-Young; Oh, Sam Sae; Song, Young Seok; Lee, Seung Jae; Ko, Kyung Jin

    2016-01-01

    Stress-induced cardiomyopathy has become a more recognized and reported entity. It can be caused by emotional or physical stress, which causes excessive catecholamine release. Typically, the clinical course is benign with conservative treatment being effective. However, stress-induced cardiomyopathy can be fatal. A 41-year-old female presented with cardiogenic shock followed by sudden back pain. Initial echocardiographic finding showed severely decreased ejection fraction with akinesia at all mid-to-apical walls with relatively preserved basal wall contractility. The coronary artery was intact on coronary angiography. Cardiac resuscitation and extra-corporeal membrane oxygenation was needed to manage the cardiogenic shock. Recovery was complete after 2 weeks. PMID:27081451

  4. Analysis of thermal stresses and metal movement during welding

    NASA Technical Reports Server (NTRS)

    Muraki, T.; Masubuchi, K.

    1973-01-01

    The research is reported concerning the development of a system of mathematical solutions and computer programs for one- and two-dimensional analyses for thermal stresses. Reports presented include: the investigation of thermal stress and buckling of tantalum and columbium sheet; and analysis of two dimensional thermal strains and metal movement during welding.

  5. Fatigue stress concentration and notch sensitivity in nanocrystalline metals

    DOE PAGESBeta

    Furnish, Timothy A.; Boyce, Brad L.; Sharon, John A.; O’Brien, Christopher J.; Clark, Blythe G.; Arrington, Christian L.; Pillars, Jamin R.

    2016-03-11

    Recent studies have shown the potential for nanocrystalline metals to possess excellent fatigue resistance compared to their coarse-grained counterparts. Although the mechanical properties of nanocrystalline metals are believed to be particularly susceptible to material defects, a systematic study of the effects of geometric discontinuities on their fatigue performance has not yet been performed. In the present work, nanocrystalline Ni–40 wt%Fe containing both intrinsic and extrinsic defects were tested in tension–tension fatigue. The defects were found to dramatically reduce the fatigue resistance, which was attributed to the relatively high notch sensitivity in the nanocrystalline material. Microstructural analysis within the crack-initiation zonesmore » underneath the defects revealed cyclically-induced abnormal grain growth (AGG) as a predominant deformation and crack initiation mechanism during high-cycle fatigue. Furthermore, the onset of AGG and the ensuing fracture is likely accelerated by the stress concentrations, resulting in the reduced fatigue resistance compared to the relatively defect-free counterparts.« less

  6. Phytochemicals Mediated Remediation of Neurotoxicity Induced by Heavy Metals.

    PubMed

    Gupta, Vivek Kumar; Singh, Shweta; Agrawal, Anju; Siddiqi, Nikhat Jamal; Sharma, Bechan

    2015-01-01

    Almost all the environmental components including both the abiotic and biotic factors have been consistently threatened by excessive contamination of heavy metals continuously released from various sources. Different heavy metals have been reported to generate adverse effects in many ways. Heavy metals induced neurotoxicity and impairment in signalling cascade leading to cell death (apoptosis) has been indicated by several workers. On one hand, these metals are required by the cellular systems to regulate various biological functions of normal cells, while on the other their biomagnification in the cellular systems produces adverse effects. The mechanism by which the heavy metals induce neurotoxicity follows free radicals production pathway(s) specially the generation of reactive oxygen species and reactive nitrogen species. These free radicals produced in excess have been shown to create an imbalance between the oxidative and antioxidative systems leading to emergence of oxidative stress, which may cause necrosis, DNA damage, and many neurodegenerative disorders. This mini review summarizes the current knowledge available on the protective role of varied natural products isolated from different herbs/plants in imparting protection against heavy metals (cadmium, lead, arsenic, and mercury) mediated neurotoxicity. PMID:26618004

  7. Phytochemicals Mediated Remediation of Neurotoxicity Induced by Heavy Metals

    PubMed Central

    Gupta, Vivek Kumar; Singh, Shweta; Agrawal, Anju; Siddiqi, Nikhat Jamal; Sharma, Bechan

    2015-01-01

    Almost all the environmental components including both the abiotic and biotic factors have been consistently threatened by excessive contamination of heavy metals continuously released from various sources. Different heavy metals have been reported to generate adverse effects in many ways. Heavy metals induced neurotoxicity and impairment in signalling cascade leading to cell death (apoptosis) has been indicated by several workers. On one hand, these metals are required by the cellular systems to regulate various biological functions of normal cells, while on the other their biomagnification in the cellular systems produces adverse effects. The mechanism by which the heavy metals induce neurotoxicity follows free radicals production pathway(s) specially the generation of reactive oxygen species and reactive nitrogen species. These free radicals produced in excess have been shown to create an imbalance between the oxidative and antioxidative systems leading to emergence of oxidative stress, which may cause necrosis, DNA damage, and many neurodegenerative disorders. This mini review summarizes the current knowledge available on the protective role of varied natural products isolated from different herbs/plants in imparting protection against heavy metals (cadmium, lead, arsenic, and mercury) mediated neurotoxicity. PMID:26618004

  8. Residual stress within nanoscale metallic multilayer systems during thermal cycling

    SciTech Connect

    Economy, David Ross; Cordill, Megan Jo; Payzant, E. Andrew; Kennedy, Marian S.

    2015-09-21

    Projected applications for nanoscale metallic multilayers will include wide temperature ranges. Since film residual stress has been known to alter system reliability, stress development within new film structures with high interfacial densities should be characterized to identify potential long-term performance barriers. To understand factors contributing to thermal stress evolution within nanoscale metallic multilayers, stress in Cu/Nb systems adhered to Si substrates was calculated from curvature measurements collected during cycling between 25 °C and 400 °C. Additionally, stress within each type of component layers was calculated from shifts in the primary peak position from in-situ heated X-ray diffraction. The effects of both film architecture (layer thickness) and layer order in metallic multilayers were tracked and compared with monolithic Cu and Nb films. Analysis indicated that the thermoelastic slope of nanoscale metallic multilayer films depends on thermal expansion mismatch, elastic modulus of the components, and also interfacial density. The layer thickness (i.e. interfacial density) affected thermoelastic slope magnitude while layer order had minimal impact on stress responses after the initial thermal cycle. When comparing stress responses of monolithic Cu and Nb films to those of the Cu/Nb systems, the nanoscale metallic multilayers show a similar increase in stress above 200 °C to the Nb monolithic films, indicating that Nb components play a larger role in stress development than Cu. Local stress calculations from X-ray diffraction peak shifts collected during heating reveal that the component layers within a multilayer film respond similarly to their monolithic counterparts.

  9. Residual stress within nanoscale metallic multilayer systems during thermal cycling

    DOE PAGESBeta

    Economy, David Ross; Cordill, Megan Jo; Payzant, E. Andrew; Kennedy, Marian S.

    2015-09-21

    Projected applications for nanoscale metallic multilayers will include wide temperature ranges. Since film residual stress has been known to alter system reliability, stress development within new film structures with high interfacial densities should be characterized to identify potential long-term performance barriers. To understand factors contributing to thermal stress evolution within nanoscale metallic multilayers, stress in Cu/Nb systems adhered to Si substrates was calculated from curvature measurements collected during cycling between 25 °C and 400 °C. Additionally, stress within each type of component layers was calculated from shifts in the primary peak position from in-situ heated X-ray diffraction. The effects ofmore » both film architecture (layer thickness) and layer order in metallic multilayers were tracked and compared with monolithic Cu and Nb films. Analysis indicated that the thermoelastic slope of nanoscale metallic multilayer films depends on thermal expansion mismatch, elastic modulus of the components, and also interfacial density. The layer thickness (i.e. interfacial density) affected thermoelastic slope magnitude while layer order had minimal impact on stress responses after the initial thermal cycle. When comparing stress responses of monolithic Cu and Nb films to those of the Cu/Nb systems, the nanoscale metallic multilayers show a similar increase in stress above 200 °C to the Nb monolithic films, indicating that Nb components play a larger role in stress development than Cu. Local stress calculations from X-ray diffraction peak shifts collected during heating reveal that the component layers within a multilayer film respond similarly to their monolithic counterparts.« less

  10. Transgenic nematodes as biosensors for metal stress in soil pore water samples.

    PubMed

    Anbalagan, Charumathi; Lafayette, Ivan; Antoniou-Kourounioti, Melissa; Haque, Mainul; King, John; Johnsen, Bob; Baillie, David; Gutierrez, Carmen; Martin, Jose A Rodriguez; de Pomerai, David

    2012-03-01

    Caenorhabditis elegans strains carrying stress-reporter green fluorescent protein transgenes were used to explore patterns of response to metals. Multiple stress pathways were induced at high doses by most metals tested, including members of the heat shock, oxidative stress, metallothionein (mtl) and xenobiotic response gene families. A mathematical model (to be published separately) of the gene regulatory circuit controlling mtl production predicted that chemically similar divalent metals (classic inducers) should show additive effects on mtl gene induction, whereas chemically dissimilar metals should show interference. These predictions were verified experimentally; thus cadmium and mercury showed additive effects, whereas ferric iron (a weak inducer) significantly reduced the effect of mercury. We applied a similar battery of tests to diluted samples of soil pore water extracted centrifugally after mixing 20% w/w ultrapure water with air-dried soil from an abandoned lead/zinc mine in the Murcia region of Spain. In addition, metal contents of both soil and soil pore water were determined by ICP-MS, and simplified mixtures of soluble metal salts were tested at equivalent final concentrations. The effects of extracted soil pore water (after tenfold dilution) were closely mimicked by mixtures of its principal component ions, and even by the single most prevalent contaminant (zinc) alone, though other metals modulated its effects both positively and negatively. In general, mixtures containing similar (divalent) metal ions exhibited mainly additive effects, whereas admixture of dissimilar (e.g. trivalent) ions often resulted in interference, reducing overall levels of stress-gene induction. These findings were also consistent with model predictions. PMID:22037694

  11. Acute stress may induce ovulation in women

    PubMed Central

    2010-01-01

    Background This study aims to gather information either supporting or rejecting the hypothesis that acute stress may induce ovulation in women. The formulation of this hypothesis is based on 2 facts: 1) estrogen-primed postmenopausal or ovariectomized women display an adrenal-progesterone-induced ovulatory-like luteinizing hormone (LH) surge in response to exogenous adrenocorticotropic hormone (ACTH) administration; and 2) women display multiple follicular waves during an interovulatory interval, and likely during pregnancy and lactation. Thus, acute stress may induce ovulation in women displaying appropriate serum levels of estradiol and one or more follicles large enough to respond to a non-midcycle LH surge. Methods A literature search using the PubMed database was performed to identify articles up to January 2010 focusing mainly on women as well as on rats and rhesus monkeys as animal models of interaction between the hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-gonadal (HPG) axes. Results Whereas the HPA axis exhibits positive responses in practically all phases of the ovarian cycle, acute-stress-induced release of LH is found under relatively high plasma levels of estradiol. However, there are studies suggesting that several types of acute stress may exert different effects on pituitary LH release and the steroid environment may modulate in a different way (inhibiting or stimulating) the pattern of response of the HPG axis elicited by acute stressors. Conclusion Women may be induced to ovulate at any point of the menstrual cycle or even during periods of amenorrhea associated with pregnancy and lactation if exposed to an appropriate acute stressor under a right estradiol environment. PMID:20504303

  12. Stress induced neuroendocrine-immune plasticity

    PubMed Central

    Liezmann, Christiane; Stock, Daniel; Peters, Eva M. J.

    2012-01-01

    Research over the past decade has revealed close interaction between the nervous and immune systems in regulation of peripheral inflammation linking psychosocial stress with chronic somatic disease and aging. Moreover emerging data suggests that chronic inflammations lead to a pro-inflammatory status underlying premature aging called inflammaging. In this context, the spleen can be seen as a switch board monitoring peripherally derived neuroendocrine-immune mediators in the blood and keeping up a close communication with the central stress response via its mainly sympathetic innervation. The effect aims at balanced and well-timed stress axis activation and immune adaptation in acute peripheral inflammatory events. Constant adjustment to the needs generated by environmental and endogenous challenges is provided by neuroendocrine-immune plasticity. However, maladaptive plasticity induced e.g., by chronic stress-axis activation and excessive non-neuronal derived neuroendocrine mediators may be at the heart of the observed stress sensitivity promote inflammaging under chronic inflammatory conditions. We here review the role of neurotransmitters, neuropeptides and neurotrophins as stress mediators modulating the immune response in the spleen and their potential role in inflammaging. PMID:23467333

  13. Shocked and Stressed, Metals Get Stronger

    SciTech Connect

    Hackel, L

    2002-03-12

    People who know their way around metalworking are no doubt familiar with peening--using a ball-peen hammer to pound a piece of metal into shape and strengthen it against fatigue failure. For the past 50 years, an industrialized equivalent has been shot peening, in which metal or ceramic beads as large as marbles or as small as salt and pepper grains pneumatically bombard a metal surface. Laser peening, a process based on a superior laser technology developed at Lawrence Livermore, replaces the hammer blows and streams of beads with short blasts of laser light. The end result is a piece of metal with significantly improved performance. Lawrence Livermore and Metal Improvement Company, Inc., won a coveted R and D 100 Award for their laser-peening process in 1998 (see S and TR, October 1998, pp. 12-13). Since that time, they've been developing uses for the technology with a number of industries, including automotive, medical, and aerospace. They've also developed an offshoot technique--laser peenmarking{trademark}--which provides a way to easily and clearly identify parts with a mark that is extremely difficult to counterfeit. Another outgrowth is a new peen-forming technology that allows complex contouring of problematic thick metal components such as the thick sections of large aircraft wings. There have also been spinback applications to the Department of Energy's programs for stockpile stewardship, fuel-efficient vehicles, and long-term nuclear waste storage.

  14. Influence of particle bombardment on microstructure and internal stresses of refractory metal suicides on silicon

    NASA Astrophysics Data System (ADS)

    Hardtke, Ch.; Schilling, W.; Ullmaier, H.

    1991-07-01

    First results on microstructural changes and stress relaxation in thin refractory metal suicide films (TaSi 2 and MoSi 2) caused by particle bombardment are reported. The polycrystalline films had initial tensile stresses of some 10 9 Pa. Exposed to irradiation with Ge ions of 400 keV, both suicides showed a similar stress relaxation behaviour as a function of dose. During room-temperature implantation the initial tensile stress rapidly decreased and turned into compressive stress. Continuous irradiation partly relaxed the compressive stress and resulted in a saturation value of some -10 8 Pa. With increasing implantation temperature, the buildup of compressive stress gradually vanished, leaving only the initial decrease of tensile stress which finally approached zero. Based on microstructural investigations (TEM and X-ray diffraction) it is proposed to explain this behaviour by the combined action of two processes: relaxation of tensile stress by a volume increase due to irradiation-induced amorphization, and Frenkel defect production and relaxation of compressive stress by irradiation-induced densification of amorphous regions and/or Frenkel defect elimination.

  15. Metal accumulation and oxidative stress biomarkers in octopus (Octopus vulgaris) from Northwest Atlantic.

    PubMed

    Semedo, Miguel; Reis-Henriques, Maria Armanda; Rey-Salgueiro, Ledicia; Oliveira, Marta; Delerue-Matos, Cristina; Morais, Simone; Ferreira, Marta

    2012-09-01

    Metals are ubiquitous in the environment and accumulate in aquatic organisms and are known for their ability to enhance the production of reactive oxygen species (ROS). In aquatic species, oxidative stress mechanisms have been studied by measuring antioxidant enzyme activities and oxidative damages in tissues. The aim of this study was to apply and validate a set of oxidative stress biomarkers and correlate responses with metal contents in tissues of common octopus (Octopus vulgaris). Antioxidant enzyme activity (catalase--CAT, superoxide dismutase--SOD and glutathione S-transferases--GST), oxidative damages (lipid peroxidation--LPO and protein carbonyl content--PCO) and metal content (Cu, Zn, Pb, Cd and As) in the digestive gland and arm of octopus, collected in the NW Portuguese coast in different periods, were assessed after capture and after 14 days in captivity. CAT and SOD activities were highly responsive to fluctuations in metal concentrations and able to reduce oxidative damage, LPO and PCO in the digestive gland. CAT activity was also positively correlated with SOD and GST activities, which emphasizes that the three enzymes respond in a coordinated way to metal induced oxidative stress. Our results validate the use of oxidative stress biomarkers to assess metal pollution effects in this ecological and commercial relevant species. Moreover, octopus seems to have the ability to control oxidative damage by triggering an antioxidant enzyme coordinated response in the digestive gland. PMID:22796413

  16. Potential/charge induced nanoporous metal actuators.

    PubMed

    Viswanath, R N

    2009-01-01

    The mechanical response to the electrochemical charging of nanoporous metals with their pore space wetted by electrolyte have been studied in-situ using dilatometry and wide angle x-ray diffractometry techniques. The actuation strain reported in this manuscript is purely elastic and completely reversible. The capacitive double layer charging became more effective near to the potential to zero charge (pzc) and contribute significantly to the variations of surface stress and crystal strain. In a suitable experimental setup, the actuator effect from porous metals can be amplified, where deliberate movements of the actuator parts are desirable with minimum external force, suggesting that metallic foam-like materials with high surface to volume ratio could be used to mimic natural muscles. PMID:19964917

  17. Expression of γ-tocopherol methyltransferase in chloroplasts results in massive proliferation of the inner envelope membrane and decreases susceptibility to salt and metal-induced oxidative stresses by reducing reactive oxygen species.

    PubMed

    Jin, Shuangxia; Daniell, Henry

    2014-12-01

    The γ-tocopherol methyltransferase (γ-TMT) is an important enzyme regulating synthesis of four tocopherols (α, γ, β and δ). In this report, we investigated the role of γ-TMT in regulating abiotic stress within chloroplasts. The At γ-tmt overexpressed via the tobacco chloroplast genome accumulated up to 7.7% of the total leaf protein, resulting in massive proliferation of the inner envelope membrane (IEM, up to eight layers). Such high-level expression of γ-TMT converted most of γ-tocopherol to α-tocopherol in transplastomic seeds (~10-fold higher) in the absence of abiotic stress. When grown in 400 mm NaCl, α-tocopherol content in transplastomic TMT leaves increased up to 8.2-fold and 2.4-fold higher than wild-type leaves. Likewise, under heavy metal stress, α-tocopherol content in the TMT leaves increased up to 7.5-fold, twice higher than in the wild type. Under extreme salt stress, the wild type accumulated higher starch and total soluble sugars, but TMT plants were able to regulate sugar transport. Hydrogen peroxide and superoxide content in wild type increased up to 3-fold within 48 h of NaCl stress when compared to TMT plants. The ion leakage from TMT leaves was significantly less than wild-type plants under abiotic stress and with less malondialdehyde, indicating lower lipid peroxidation. Taken together, these studies show that α-tocopherol plays a crucial role in the alleviation of salt and heavy metal stresses by decreasing ROS, lipid peroxidation and ion leakage, in addition to enhancing vitamin E conversion. Increased proliferation of the IEM should facilitate studies on retrograde signalling from chloroplast to the nucleus. PMID:25051898

  18. Expression of γ-tocopherol methyltransferase in chloroplasts results in massive proliferation of the inner envelope membrane and decreases susceptibility to salt and metal-induced oxidative stress by reducing reactive oxygen species

    PubMed Central

    Jin, Shuangxia; Daniell, Henry

    2014-01-01

    Summary The γ-tocopherol methyltransferase (γ-TMT) is an important enzyme regulating synthesis of four tocopherols (α, γ, β and δ). In this report, we investigated the role of γ-TMT in regulating abiotic stress within chloroplasts. The At γ-tmt overexpressed via the tobacco chloroplast genome accumulated up to 7.7% of the total leaf protein, resulting in massive proliferation of the inner envelope membrane (IEM, up to 8 layers). Such high level expression of γ-TMT converted most of γ-tocopherol to α-tocopherol in transplastomic seeds (~10 fold higher) in the absence of abiotic stress. When grown in 400 mM NaCl, α-tocopherol content in transplastomic TMT leaves increased up to 8.2-fold and 2.4-fold higher than wild-type leaves. Likewise, under heavy metal stress α-tocopherol content in the TMT leaves increased up to 7.5-fold, twice higher than in the wild-type. Under extreme salt stress, the wild-type accumulated higher starch and total soluble sugars but TMT plants were able to regulate sugar transport. Hydrogen peroxide and superoxide content in wild-type increased up to 3-fold within 48 hours of NaCl stress when compared to TMT plants. The ion leakage from TMT leaves was significantly less than wild-type plants under abiotic stress and with less malondialdehyde, indicating lower lipid peroxidation. Taken together, these studies show that α-tocopherol plays a crucial role in the alleviation of salt and heavy metal stresses by decreasing ROS, lipid peroxidation and ion leakage, in addition to enhancing vitamin E conversion. Increased proliferation of the IEM should facilitate studies on retrograde signaling from chloroplast to the nucleus. PMID:25051898

  19. Assessing Cd-induced stress from plant spectral response

    NASA Astrophysics Data System (ADS)

    Kancheva, Rumiana; Georgiev, Georgi

    2014-10-01

    Remote sensing plays a significant role in local, regional and global monitoring of land covers. Ecological concerns worldwide determine the importance of remote sensing applications for the assessment of soil conditions, vegetation health and identification of stress-induced changes. The extensive industrial growth and intensive agricultural land-use arise the serious ecological problem of environmental pollution associated with the increasing anthropogenic pressure on the environment. Soil contamination is a reason for degradation processes and temporary or permanent decrease of the productive capacity of land. Heavy metals are among the most dangerous pollutants because of their toxicity, persistent nature, easy up-take by plants and long biological half-life. This paper takes as its focus the study of crop species spectral response to Cd pollution. Ground-based experiments were performed, using alfalfa, spring barley and pea grown in Cd contaminated soils and in different hydroponic systems under varying concentrations of the heavy metal. Cd toxicity manifested itself by inhibition of plant growth and synthesis of photosynthetic pigments. Multispectral reflectance, absorbance and transmittance, as well as red and far red fluorescence were measured and examined for their suitability to detect differences in plant condition. Statistical analysis was performed and empirical relationships were established between Cd concentration, plant growth variables and spectral response Various spectral properties proved to be indicators of plant performance and quantitative estimators of the degree of the Cd-induced stress.

  20. Stress-enhanced swelling of metal during irradiation

    SciTech Connect

    Garner, F.A.; Gilbert, E.R.; Porter, D.L.

    1980-04-01

    Data are available which show that stress plays a major role in the development of radiation-induced void growth in AISI 316 and many other alloys. Earlier experiments came to the opposite conclusion and are shown to have investigated stress levels which inadvertantly cold-worked the material. Stress-affected swelling spans the entire temperature range in fast reactor irradiations and accelerates with increasing irradiatin temperature. It also appears to operate in all alloy starting conditions investigated. Two major microstructural mechanisms appear to be causing the enhancement of swelling, which for tensile stresses is manifested primarily as a decrease in the incubation period. These mechanisms are stress-induced changes in the interstitial capture efficiency of voids and stress-induced changes in the vacancy emission rate of various microstructural components. There also appears to be an enhancement of intermetallic phase formation with applied stress and this is shown to increase swelling by accelerating the microchemical evolution that precedes void growth at high temperature. This latter consideration complicates the extrapolation of these data to compressive stress states.

  1. Contaminant-induced oxidative stress in fish: a mechanistic approach.

    PubMed

    Lushchak, Volodymyr I

    2016-04-01

    The presence of reactive oxygen species (ROS) in living organisms was described more than 60 years ago and virtually immediately it was suggested that ROS were involved in various pathological processes and aging. The state when ROS generation exceeds elimination leading to an increased steady-state ROS level has been called "oxidative stress." Although ROS association with many pathological states in animals is well established, the question of ROS responsibility for the development of these states is still open. Fish represent the largest group of vertebrates and they inhabit a broad range of ecosystems where they are subjected to many different aquatic contaminants. In many cases, the deleterious effects of contaminants have been connected to induction of oxidative stress. Therefore, deciphering of molecular mechanisms leading to such contaminant effects and organisms' response may let prevent or minimize deleterious impacts of oxidative stress. This review describes general aspects of ROS homeostasis, in particular highlighting its basic aspects, modification of cellular constituents, operation of defense systems and ROS-based signaling with an emphasis on fish systems. A brief introduction to oxidative stress theory is accompanied by the description of a recently developed classification system for oxidative stress based on its intensity and time course. Specific information on contaminant-induced oxidative stress in fish is covered in sections devoted to such pollutants as metal ions (particularly iron, copper, chromium, mercury, arsenic, nickel, etc.), pesticides (insecticides, herbicides, and fungicides) and oil with accompanying pollutants. In the last section, certain problems and perspectives in studies of oxidative stress in fish are described. PMID:26607273

  2. Diffusion induced stresses in buckling battery electrodes

    NASA Astrophysics Data System (ADS)

    Bhandakkar, Tanmay K.; Johnson, Harley T.

    2012-06-01

    Highly networked nanostructured battery electrode materials offer the possibility of achieving both rapid battery charge-discharge rates and high storage capacity. Recently, lithium ion battery (LIB) electrodes based on a 2-D honeycomb architecture were shown to undergo remarkable and reversible morphological changes during the lithiation process. Charge-discharge rates in 3-D composite electrode have also been shown to benefit from sandwiching the electrolytically active material between highly conductive ion and electron transport pathways to reduce electrical resistance and solid-state diffusion lengths. In the present work we simulate and analyze the observed morphological changes in honeycomb electrodes, with and without the presence of conductive pathways, during the lithiation-delithiation process. Diffusion induced stresses are analyzed for such structures undergoing elastic-plastic deformation during cycling. The results show that such a periodic, nanostructured electrode geometry allows for the presence of buckling-like deformation modes, which effectively reduce the resulting mechanical stresses that lead to electrode failure.

  3. Pressure-induced metallization of silane

    SciTech Connect

    Chen,X.; Struzhkin, V.; Song, Y.; Goncharov, A.; Ahart, M.; Liu, Z.; Mao, H.; Hemley, R.

    2008-01-01

    There is a great interest in electronic transitions in hydrogen-rich materials under extreme conditions. It has been recently suggested that the group IVa hydrides such as methane (CH4), silane (SiH4), and germane (GeH4) become metallic at far lower pressures than pure hydrogen at equivalent densities because the hydrogen is chemically compressed in group IVa hydride compounds. Here we report measurements of Raman and infrared spectra of silane under pressure. We find that SiH4 undergoes three phase transitions before becoming opaque at 27-30 GPa. The vibrational spectra indicate the material transforms to a polymeric (framework) structure in this higher pressure range. Room-temperature infrared reflectivity data reveal that the material exhibits Drude-like metallic behavior above 60 GPa, indicating the onset of pressure-induced metallization.

  4. Pressure-Induced Foaming of Metals

    NASA Astrophysics Data System (ADS)

    García-Moreno, Francisco; Mukherjee, Manas; Jiménez, Catalina; Banhart, John

    2015-05-01

    Pressure-induced foaming (PIF) of metals is a foaming technique in which blowing agent free compacted metal powders are foamed. The method consists of heating hot-compacted metallic precursors to above their melting temperature under gas overpressure and foaming them by pressure release. This study focuses on PIF of Al99.7 and AlSi7 alloys under both air or Ar and overpressures up to 9 bar. In situ x-ray radioscopy allows us to follow the foaming process and to perform quantitative analyses of expansion, foam morphology, and coalescence rate. Mass spectrometry helps to identify hydrogen as the foaming gas. Adsorbates on the former powder particles are found to be the primary gas source. Various advantages of this new method are identified and discussed.

  5. Interfacial stress in a carbon-to-metal bond joint under thermal shock loading

    SciTech Connect

    You, J.H.

    1998-02-01

    The duplex bond joint consisting of a metallic substrate armored with carbon-base materials is a promising candidate configuration for application to high heat flux operations. When a bond joint is subjected to thermal loadings, significant thermal stresses may develop due to mismatch of the thermal expansion coefficients. Stress intensification occurs near the free surface edge of the interface, sometimes showing singularity. The singular stress fields are critical for understanding the loading nature of the bond interface in a joint system. In this paper, thermal stresses in the bond interface of a carbon-to-molybdenum joint element were investigated. A high heat flux (HHF) pulse was assumed as the reference load history to simulate the thermal shock condition. The thermomechanical behavior was described quantitatively in terms of the stress intensity factor. The stress solutions of the singular field computed by the theoretical approach showed a good agreement with the numerical results of the finite element analysis. The stress intensity factor of the singular stress fields near the free surface edge of the interface showed a time variation similar to that of the bulk stress. The temperature gradient induced by the transient HHF load affected the overall interfacial stress only slightly.

  6. Environmental-induced oxidative stress in neurodegenerative disorders and aging.

    PubMed

    Migliore, Lucia; Coppedè, Fabio

    2009-03-31

    The aetiology of most neurodegenerative disorders is multifactorial and consists of an interaction between environmental factors and genetic predisposition. Free radicals derived primarily from molecular oxygen have been implicated and considered as associated risk factors for a variety of human disorders including neurodegenerative diseases and aging. Damage to tissue biomolecules, including lipids, proteins and DNA, by free radicals is postulated to contribute importantly to the pathophysiology of oxidative stress. The potential of environmental exposure to metals, air pollution and pesticides as well as diet as risk factors via the induction of oxidative stress for neurodegenerative diseases and aging is discussed. The role of genetic background is discussed on the light of the oxidative stress implication, focusing on both complex neurodegenerative diseases (Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis) and monogenic neurological disorders (Huntington's disease, Ataxia telangiectasia, Friedreich Ataxia and others). Emphasis is given to role of the repair mechanisms of oxidative DNA damage in delaying aging and protecting against neurodegeneration. The emerging interplay between environmental-induced oxidative stress and epigenetic modifications of critical genes for neurodegeneration is also discussed. PMID:18952194

  7. Stress state in turbopump bearing induced by shrink fitting

    NASA Technical Reports Server (NTRS)

    Sims, P.; Zee, R.

    1991-01-01

    The stress generated by shrink fitting in bearing-like geometries is studied. The feasibility of using strain gages to determine the strain induced by shrink fitting process is demonstrated. Results from a ring with a uniform cross section reveal the validity of simple stress mechanics calculations for determining the stress state induced in this geometry by shrink fitting.

  8. Proper PWHT can stop stress-induced corrosion

    SciTech Connect

    Bloch, C.; Hill, J.; Connell, D.

    1997-05-01

    Postweld heat treatment of welded joints to improve the ductility of welds susceptible to cracking due to metal composition or wall thickness has become an essential component of standards generated by professional organizations. When properly applied, these procedures have proven to be quite effective in preventing premature weld-related failures. Recently, the welding industry has recognized that weld-induced stress also plays a role in certain localized corrosion phenomena. To address the cause of these long-term corrosion failures, it has become common practice to specify postweld heat treatment for thin-walled piping and vessels that would otherwise be exempt from code procedures. Corrosion often continues to be a problem even after post-weld heat treatment (PWHT) is performed on these relatively thin-walled weldments. The results of the extensive tests performed for the preparation of this paper indicate that surprisingly large through-wall radial temperature gradients often exist during the application of common PWHT practices. As a result of these radial temperature gradients, the standard application of heating elements to the pipe exterior does not always provide assurance that the interior surfaces at the edge of the heat-affected zone (HAZ) will achieve the temperatures necessary to adequately reduce weld-induced hardness. It is on these interior surfaces that the stress-induced corrosion phenomena is initiated.

  9. Melamine Induces Oxidative Stress in Mouse Ovary

    PubMed Central

    Dai, Xiao-Xin; Duan, Xing; Cui, Xiang-Shun; Kim, Nam-Hyung; Xiong, Bo; Sun, Shao-Chen

    2015-01-01

    Melamine is a nitrogen heterocyclic triazine compound which is widely used as an industrial chemical. Although melamine is not considered to be acutely toxic with a high LD50 in animals, food contaminated with melamine expose risks to the human health. Melamine has been reported to be responsible for the renal impairment in mammals, its toxicity on the reproductive system, however, has not been adequately assessed. In the present study, we examined the effect of melamine on the follicle development and ovary formation. The data showed that melamine increased reactive oxygen species (ROS) levels, and induced granulosa cell apoptosis as well as follicle atresia. To further analyze the mechanism by which melamine induces oxidative stress, the expression and activities of two key antioxidant enzymes superoxide dismutase (SOD) and glutathi-one peroxidase (GPX) were analyzed, and the concentration of malondialdehyde (MDA) were compared between control and melamine-treated ovaries. The result revealed that melamine changed the expression and activities of SOD and GPX in the melamine-treated mice. Therefore, we demonstrate that melamine causes damage to the ovaries via oxidative stress pathway. PMID:26545251

  10. DHEA administration modulates stress-induced analgesia in rats.

    PubMed

    Cecconello, Ana Lúcia; Torres, Iraci L S; Oliveira, Carla; Zanini, Priscila; Niches, Gabriela; Ribeiro, Maria Flávia Marques

    2016-04-01

    An important aspect of adaptive stress response is the pain response suppression that occurs during or following stress exposure, which is often referred to as acute stress-induced analgesia. Dehydroepiandrosterone (DHEA) participates in the modulation of adaptive stress response, changing the HPA axis activity. The effect of DHEA on the HPA axis activity is dependent on the state and uses the same systems that participate in the regulation of acute stress-induced analgesia. The impact of DHEA on nociception has been studied; however, the effect of DHEA on stress-induced analgesia is not known. Thus, the aim of the present study was to evaluate the effect of DHEA on stress-induced analgesia and determine the best time for hormone administration in relation to exposure to stressor stimulus. The animals were stressed by restraint for 1h in a single exposure and received treatment with DHEA by a single injection before the stress or a single injection after the stress. Nociception was assessed with a tail-flick apparatus. Serum corticosterone levels were measured. DHEA administered before exposure to stress prolonged the acute stress-induced analgesia. This effect was not observed when the DHEA was administered after the stress. DHEA treatment in non-stressed rats did not alter the nociceptive threshold, suggesting that the DHEA effect on nociception is state-dependent. The injection of DHEA had the same effect as exposure to acute stress, with both increasing the levels of corticosterone. In conclusion, acute treatment with DHEA mimics the response to acute stress indexed by an increase in activity of the HPA axis. The treatment with DHEA before stress exposure may facilitate adaptive stress response, prolonging acute stress-induced analgesia, which may be a therapeutic strategy of interest to clinics. PMID:26852948

  11. Oxidative stress in pied flycatcher (Ficedula hypoleuca) nestlings from metal contaminated environments in northern Sweden

    SciTech Connect

    Berglund, A.M.M. Sturve, J.; Foerlin, L.; Nyholm, N.E.I.

    2007-11-15

    Metals have been shown to induce oxidative stress in animals. One of the most metal polluted terrestrial environments in Sweden is the surroundings of a sulfide ore smelter plant located in the northern part of the country. Pied flycatcher nestlings (Ficedula hypoleuca) that grew up close to the industry had accumulated amounts of arsenic, cadmium, mercury, lead, iron and zinc in their liver tissue. The aim of this study was to investigate if pied flycatcher nestlings in the pollution gradient of the industry were affected by oxidative stress using antioxidant molecules and enzyme activities. The antioxidant assays were also evaluated in search for useful biomarkers in pied flycatchers. This study indicated that nestlings in metal contaminated areas showed signs of oxidative stress evidenced by up regulated hepatic antioxidant defense given as increased glutathione reductase (GR) and catalase (CAT) activities and slightly but not significantly elevated lipid peroxidation and glutathione-S-transferase (GST) activities. Stepwise linear regression indicated that lipid peroxidation and CAT activities were influenced mostly by iron, but iron and lead influenced the CAT activity to a higher degree. Positive relationships were found between GST and lead as well as GR activities and cadmium. We conclude that GR, CAT, GST activities and lipid peroxidation levels may function as useful biomarkers for oxidative stress in free-living pied flycatcher nestlings exposed to metal contaminated environments.

  12. Phenotypic plasticity in Scenedesmus incrassatulus (Chlorophyceae) in response to heavy metals stress.

    PubMed

    Peña-Castro, Julián Mario; Martínez-Jerónimo, Fernando; Esparza-García, Fernando; Cañizares-Villanueva, Rosa Olivia

    2004-12-01

    The microalgae genus Scenedesmus is commonly found in freshwater bodies, wastewater facilities and water polluted with heavy metals. Phenotypic plasticity in Scenedesmus has been documented in response to a wide variety of conditions; however, heavy metals have not been comprehensively documented as phenotypic plasticity inducers. In this study, we report the phenotypic plasticity of Scenedesmus incrassatulus (a non-spiny, four-cell coenobium forming species) in response to EC(50) value of copper, cadmium and hexavalent chromium. S. incrassatulus was grown in batch cultures in the presence of each metal. Chlorophyll-a content, cell size, parameters derived from the schematic energy-flux model for photosystem II, and morphotype expressions were recorded. Divalent cation metals induced unicellular forms, and hexavalent chromium produced out-of-shape coenobia corresponding to various stages of autospore formation. The changes induced by divalent metals were interpreted as phenotypic plasticity, because they were always associated to population doublings and were reversible when toxicant pressure was removed (only for Cu). Copper was the best inductor of unicellular forms and also affected significantly all the photosynthetic parameters measured. The developed morphotypes could confer ecological advantages to S. incrassatulus in metal stressed environments. PMID:15519408

  13. Bi-Metallic Composite Structures With Designed Internal Residual Stress Field

    NASA Technical Reports Server (NTRS)

    Brice, Craig A.

    2014-01-01

    Shape memory alloys (SMA) have a unique ability to recover small amounts of plastic strain through a temperature induced phase change. For these materials, mechanical displacement can be accomplished by heating the structure to induce a phase change, through which some of the plastic strain previously introduced to the structure can be reversed. This paper introduces a concept whereby an SMA phase is incorporated into a conventional alloy matrix in a co-continuous reticulated arrangement forming a bi-metallic composite structure. Through memory activation of the mechanically constrained SMA phase, a controlled residual stress field is developed in the interior of the structure. The presented experimental data show that the memory activation of the SMA composite component significantly changes the residual stress distribution in the overall structure. Designing the structural arrangement of the two phases to produce a controlled residual stress field could be used to create structures that have much improved durability and damage tolerance properties.

  14. The stress analysis of a heavy liquid metal pump impeller

    NASA Astrophysics Data System (ADS)

    Ma, X. D.; Li, X. L.; Zhu, Z. Q.; Li, C. J.; Gao, S.

    2016-05-01

    Lead-based coolant reactor is a promising Generation-IV reactor. In the lead-based coolant reactor, the coolant is liquid lead or lead-bismuth eutectic. The main pump in the reactor is a very important device. It supplies force for the coolant circulation. The liquid metal has a very large density which is about ten times of the water. Also, the viscosity of the coolant is small which is about one sixth of the water. When the pump transports heavy liquid, the blade loading is heavy. The large force can cause the failure of the blade when the fatigue stress exceeds the allowable stress. The impeller fraction is a very serious accident which is strictly prohibited in the nuclear reactor. In this paper, the numerical method is used to simulate the flow field of a heavy liquid metal pump. The SST k-w turbulent model is used in the calculation to get a more precise flow structure. The hydraulic force is obtained with the one way fluid solid coupling. The maximum stress in the impeller is analyzed. The stress in the liquid metal pump is compared with that in the water pump. The calculation results show that the maximum stress of the impeller blade increases with increase of flow rate. In the design of the impeller blade thickness, the impeller strength in large operating condition should be considered. The maximum stress of the impeller blade located in the middle and near the hub of the leading edge. In this position, the blade is easy to fracture. The maximum deformation of the impeller firstly increase with increase of flow rate and then decrease with increase of flow rate. The maximum deformation exists in the middle of the leading edge when in small flow rate and in the out radius of the impeller when in large flow rate. Comparing the stress of the impeller when transporting water and LBE, the maximum stress is almost one-tenth of that in the LBE impeller which is the same ratio of the density. The static stress in different medium is proportional to the pressure

  15. Reliability of HfO2 metal-insulator-metal capacitors under AC stress

    NASA Astrophysics Data System (ADS)

    Kassmi, M.; Jomni, F.; Gonon, P.; Khaldi, O.; Latu-Romain, L.; Mannequin, C.; Bsiesy, A.; Basrour, S.; Yangui, B.

    2016-04-01

    The electrical reliability of HfO2 based metal-insulator-metal capacitors is investigated under AC stress voltage. The capacitance-time (C-t) and conductance-time (G-t) responses are studied for different stress amplitudes and frequencies. Time-to-breakdown is observed to strongly depend on the electrode nature. Electrical degradation is discussed via a model based on oxygen vacancy/oxygen ions generation. Defect generation is controlled by the injecting nature of electrodes. Partial recovery, and so time-to-breakdown, are controlled by the ability of electrodes to store oxygen.

  16. Stress-induced voiding study in integrated circuit interconnects

    NASA Astrophysics Data System (ADS)

    Hou, Yuejin; Tan, Cher Ming

    2008-07-01

    An analytical equation for an ultralarge-scale integration interconnect lifetime due to stress-induced voiding (SIV) is derived from the energy perspective. It is shown that the SIV lifetime is strongly dependent on the passivation quality at the cap layer/interconnect interface, the confinement effect by the surrounding materials to the interconnects, and the available diffusion paths in the interconnects. Contrary to the traditional power-law creep model, we find that the temperature exponent in SIV lifetime formulation is determined by the available diffusion paths for the interconnect atoms and the interconnect geometries. The critical temperature for the SIV is found to be independent of passivation integrity and dielectric confinement effect. Actual stress-free temperature (SFT) during the SIV process is also found to be different from the dielectric/cap layer deposition temperature or the final annealing temperature of the metallization, and it can be evaluated analytically once the activation energy, temperature exponent and critical temperature are determined experimentally. The smaller actual SFT indicates that a strong stress relaxation occurs before the high temperature storage test. Our results show that our SIV lifetime model can be used to predict the SIV lifetime in nano-interconnects.

  17. Modeling of Laser-Induced Metal Combustion

    SciTech Connect

    Boley, C D; Rubenchik, A M

    2008-02-20

    Experiments involving the interaction of a high-power laser beam with metal targets demonstrate that combustion plays an important role. This process depends on reactions within an oxide layer, together with oxygenation and removal of this layer by the wind. We present an analytical model of laser-induced combustion. The model predicts the threshold for initiation of combustion, the growth of the combustion layer with time, and the threshold for self-supported combustion. Solutions are compared with detailed numerical modeling as benchmarked by laboratory experiments.

  18. Biomonitor of Environmental Stress: Coral Trace Metal Analysis

    NASA Astrophysics Data System (ADS)

    Grumet, N.; Hughen, K.

    2006-12-01

    Tropical reef corals are extremely sensitive to changes in environmental conditions and, as a result of environmental degradation and global climate change, coral reefs around the globe are severely threatened. Increased human population and development in tropical regions is leading to higher turbidity and silt loading from terrestrial runoff, increased pesticides and nutrients from agricultural land-use and sewage, and the release of toxic trace metals to coastal waters from industrial pollution. The uptake of these metals and nutrients within the coral skeletal aragonite is a sensitive biomonitor of environmental stresses on coral health. We analyzed 18 trace metals from the surface of coral skeletons collected in Bermuda, Indonesia and Belize to assess a range of threats to coral reef health - including climate change, agricultural runoff and pesticides, and coastal development and tourism. This surface sample network also includes samples representing 4 different coral species. Trace metal analysis was performed on an inductively coupled plasma mass spectrometer (ICP-MS) to a high degree of accuracy and precision at extremely low (ppb) concentrations using a protocol we developed for samples less than 2 mg. Proper cleaning techniques were employed to minimize blank level concentrations for ultra-trace metal ICP-MS solution analysis. However, Zn/Ca and Ni/Ca concentrations remain below analytical detection limits. Initial results indicate that sea surface temperature proxies (e.g., Sr/Ca, B/Ca and Mg/Ca) display similar ratios between the different sites, whereas those metals associated with anthropogenic activities, such as Co, Pb and Cu, are site-specific and are linked to individual environmental stressors. Results from this study will be applied to down core trace metal records in the future. In doing so, we aim to understand the impacts of compounding environmental stresses on coral health, and to identify regional threshold values beyond which corals

  19. Unusual Cyclodextrin Derivatives as a New Avenue to Modulate Self- and Metal-Induced Aβ Aggregation.

    PubMed

    Oliveri, Valentina; Bellia, Francesco; Pietropaolo, Adriana; Vecchio, Graziella

    2015-09-28

    Mounting evidence suggests an important role of cyclodextrins in providing protection in neurodegenerative disorders. Metal dyshomeostasis is reported to be a pathogenic factor in neurodegeneration because it could be responsible for damage involving oxidative stress and protein aggregation. As such, metal ions represent an effective target. To improve the metal-binding ability of cyclodextrin, we synthesized three new 8-hydroxyquinoline-cyclodextrin conjugates with difunctionalized cyclodextrins. In particular, the 3-difunctionalized regioisomer represents the first example of cyclodextrin with two pendants at the secondary rim, resulting in a promising compound. The derivatives have significant antioxidant capacity and the powerful activity in inhibiting self-induced amyloid-β aggregation seems to be led by synergistic effects of both cyclodextrin and hydroxyquinoline. Moreover, the derivatives are also able to complex metal ions and to inhibit metal-induced protein aggregation. Therefore, these compounds could have potential as therapeutic agents in diseases related to protein aggregation and metal dyshomeostasis. PMID:26298549

  20. Structure design and film process optimization for metal-gate stress in 20 nm nMOS devices

    NASA Astrophysics Data System (ADS)

    Zuozhen, Fu; Huaxiang, Yin; Xiaolong, Ma; Shumin, Chai; Jianfeng, Gao; Dapeng, Chen

    2013-06-01

    The optimizations to metal gate structure and film process were extensively investigated for great metal-gate stress (MGS) in 20 nm high-k/metal-gate-last (HK/MG-last) nMOS devices. The characteristics of advanced MGS technologies on device performances were studied through a process and device simulation by TCAD tools. The metal gate electrode with different stress values (0 to -6 GPa) was implemented in the device simulation along with other traditional process-induced-strain (PIS) technologies like e-SiC and nitride capping layer. The MGS demonstrated a great enhancing effect on channel carriers transporting in the device as device pitch scaling down. In addition, the novel structure for a tilted gate electrode was proposed and relationships between the tilt angle and channel stress were investigated. Also with a new method of fully stressed replacement metal gate (FSRMG) and using plane-shape-HfO to substitute U-shape-HfO, the effect of MGS was improved. For greater film stress in the metal gate, the process conditions for physical vapor deposition (PVD) TiNx were optimized. The maximum compressive stress of -6.5 GPa TiNx was achieved with thinner film and greater RF power as well as about 6 sccm N ratio.

  1. Thermoelastic Stress Analysis: An NDE Tool for the Residual Stress Assessment of Metallic Alloys

    NASA Technical Reports Server (NTRS)

    Gyekenyesi, Andrew L.; Baaklini, George Y.

    2000-01-01

    During manufacturing, certain propulsion components that will be used in a cyclic fatigue environment are fabricated to contain compressive residual stresses on their surfaces because these stresses inhibit the nucleation of cracks. Overloads and elevated temperature excursions cause the induced residual stresses to dissipate while the component is still in service, lowering its resistance to crack initiation. Research at the NASA Glenn Research Center at Lewis Field has focused on employing the Thermoelastic Stress Analysis technique (TSA, also recognized as SPATE: Stress Pattern Analysis by Thermal Emission) as a tool for monitoring the residual stress state of propulsion components. TSA is based on the fact that materials experience small temperature changes when they are compressed or expanded. When a structure is cyclically loaded (i.e., cyclically compressed and expanded), the resulting surface-temperature profile correlates to the stress state of the structure s surface. The surface-temperature variations resulting from a cyclic load are measured with an infrared camera. Traditionally, the temperature amplitude of a TSA signal has been theoretically defined to be linearly dependent on the cyclic stress amplitude. As a result, the temperature amplitude resulting from an applied cyclic stress was assumed to be independent of the cyclic mean stress.

  2. Stress and Reliability Analysis of a Metal-Ceramic Dental Crown

    NASA Technical Reports Server (NTRS)

    Anusavice, Kenneth J; Sokolowski, Todd M.; Hojjatie, Barry; Nemeth, Noel N.

    1996-01-01

    Interaction of mechanical and thermal stresses with the flaws and microcracks within the ceramic region of metal-ceramic dental crowns can result in catastrophic or delayed failure of these restorations. The objective of this study was to determine the combined influence of induced functional stresses and pre-existing flaws and microcracks on the time-dependent probability of failure of a metal-ceramic molar crown. A three-dimensional finite element model of a porcelain fused-to-metal (PFM) molar crown was developed using the ANSYS finite element program. The crown consisted of a body porcelain, opaque porcelain, and a metal substrate. The model had a 300 Newton load applied perpendicular to one cusp, a load of 30ON applied at 30 degrees from the perpendicular load case, directed toward the center, and a 600 Newton vertical load. Ceramic specimens were subjected to a biaxial flexure test and the load-to-failure of each specimen was measured. The results of the finite element stress analysis and the flexure tests were incorporated in the NASA developed CARES/LIFE program to determine the Weibull and fatigue parameters and time-dependent fracture reliability of the PFM crown. CARES/LIFE calculates the time-dependent reliability of monolithic ceramic components subjected to thermomechanical and/Or proof test loading. This program is an extension of the CARES (Ceramics Analysis and Reliability Evaluation of Structures) computer program.

  3. Salubrious effects of oxytocin on social stress-induced deficits

    PubMed Central

    Smith, Adam S.; Wang, Zuoxin

    2012-01-01

    Social relationships are a fundamental aspect of life, affecting social, psychological, physiological, and behavioral functions. While social interactions can attenuate stress and promote health, disruption, confrontations, isolation, or neglect in the social environment can each be major stressors. Social stress can impair the basal function and stress-induced activation of the hypothalamic-pituitary-adrenal (HPA) axis, impairing function of multiple biological systems and posing a risk to mental and physical health. In contrast, social support can ameliorate stress-induced physiological and immunological deficits, reducing the risk of subsequent psychological distress and improving an individual's overall well-being. For better clinical treatment of these physiological and mental pathologies, it is necessary to understand the regulatory mechanisms of stress-induced pathologies as well as determine the underlying biological mechanisms that regulate social buffering of the stress system. A number of ethologically relevant animal models of social stress and species that form strong adult social bonds have been utilized to study the etiology, treatment, and prevention of stress-related disorders. While undoubtedly a number of biological pathways contribute to the social buffering of the stress response, the convergence of evidence denotes the regulatory effects of oxytocin in facilitating social bond-promoting behaviors and their effect on the stress response. Thus, oxytocin may be perceived as a common regulatory element of the social environment, stress response, and stress-induced risks on mental and physical health. PMID:22178036

  4. TIA1 oxidation inhibits stress granule assembly and sensitizes cells to stress-induced apoptosis

    PubMed Central

    Arimoto-Matsuzaki, Kyoko; Saito, Haruo; Takekawa, Mutsuhiro

    2016-01-01

    Cytoplasmic stress granules (SGs) are multimolecular aggregates of stalled translation pre-initiation complexes that prevent the accumulation of misfolded proteins, and that are formed in response to certain types of stress including ER stress. SG formation contributes to cell survival not only by suppressing translation but also by sequestering some apoptosis regulatory factors. Because cells can be exposed to various stresses simultaneously in vivo, the regulation of SG assembly under multiple stress conditions is important but unknown. Here we report that reactive oxygen species (ROS) such as H2O2 oxidize the SG-nucleating protein TIA1, thereby inhibiting SG assembly. Thus, when cells are confronted with a SG-inducing stress such as ER stress caused by protein misfolding, together with ROS-induced oxidative stress, they cannot form SGs, resulting in the promotion of apoptosis. We demonstrate that the suppression of SG formation by oxidative stress may underlie the neuronal cell death seen in neurodegenerative diseases. PMID:26738979

  5. Effect of stress at dosing on organophosphate and heavy metal toxicity

    SciTech Connect

    Jortner, Bernard S.

    2008-11-15

    This paper reviews recent studies assessing the effect of well-defined, severe, transient stress at dosing on two classical models of toxicity. These are the acute (anticholinesterase) toxicity seen following exposure to the organophosphate insecticide chlorpyrifos, and the nephrotoxicity elicited by the heavy metal depleted uranium, in rats. Stress was induced by periods of restraint and forced swimming in days to weeks preceding toxicant exposure. Forced swimming was far more stressful, as measured by marked, if transient, elevation of plasma corticosterone. This form of stress was administered immediately prior to administration of chlorpyrifos or depleted uranium. Chlorpyrifos (single 60 mg/kg subcutaneously) elicited marked inhibition of brain acetylcholinesterase 4-day post-dosing. Depleted uranium (single intramuscular doses of 0.1, 0.3 or 1.0 mg/kg uranium) elicited dose-dependent increase in kidney concentration of the metal, with associated injury to proximal tubular epithelium and increases in serum blood urea nitrogen and creatinine during the 30-day post-dosing period. Stress at dosing had no effect on these toxicologic endpoints.

  6. Stress, stress-induced cortisol responses, and eyewitness identification performance.

    PubMed

    Sauerland, Melanie; Raymaekers, Linsey H C; Otgaar, Henry; Memon, Amina; Waltjen, Thijs T; Nivo, Maud; Slegers, Chiel; Broers, Nick J; Smeets, Tom

    2016-07-01

    In the eyewitness identification literature, stress and arousal at the time of encoding are considered to adversely influence identification performance. This assumption is in contrast with findings from the neurobiology field of learning and memory, showing that stress and stress hormones are critically involved in forming enduring memories. This discrepancy may be related to methodological differences between the two fields of research, such as the tendency for immediate testing or the use of very short (1-2 hours) retention intervals in eyewitness research, while neurobiology studies insert at least 24 hours. Other differences refer to the extent to which stress-responsive systems (i.e., the hypothalamic-pituitary-adrenal axis) are stimulated effectively under laboratory conditions. The aim of the current study was to conduct an experiment that accounts for the contemporary state of knowledge in both fields. In all, 123 participants witnessed a live staged theft while being exposed to a laboratory stressor that reliably elicits autonomic and glucocorticoid stress responses or while performing a control task. Salivary cortisol levels were measured to control for the effectiveness of the stress induction. One week later, participants attempted to identify the thief from target-present and target-absent line-ups. According to regression and receiver operating characteristic analyses, stress did not have robust detrimental effects on identification performance. Copyright © 2016 John Wiley & Sons, Ltd. © 2016 The Authors Behavioral Sciences & the Law Published by John Wiley & Sons Ltd. PMID:27417874

  7. Detection of Infrared Photons Using the Electronic Stress in Metal-Semiconductor Interfaces

    SciTech Connect

    Datskos, P.G.; Datskou, I.; Egert, C.M.; Rjic, S.

    1999-04-05

    It is well known that the work function of metals decreases when they are placed in a nonpolar liquid. A similar decrease occurs when the metal is placed into contact with a semiconductor forming a Schottky barrier. We report on a new method for detecting photons using the stress caused by photo-electrons emitted from a metal film surface in contact with a semiconductor microstructure. The photoelectrons diffuse into the microstructure and produce an electronic stress. The photon detection results from the measurement of the photo-induced bending of the microstructure. Internal photoemission has been used in the past to detect photons, however, in those cases the detection was accomplished by measuring the current due to photoelectrons and not due to electronic stress. Small changes in position (displacement) of microstructures are routinely measured in atomic force microscopy (AFM) where atomic imaging of surfaces relies on the measurement of small changes (< l0{sup -9} m) in the bending of microcantilevers. In the present work we studied the photon response of Si microcantilevers coated with a thin film of Pt. The Si microcantilevers were 500 nm thick and had a 30 nm layer of Pt. Photons with sufficient energies produce electrons from the platinum-silicon interface which diffuse into the Si and produce an electronic stress. Since the excess charge carriers cause the Si microcantilever to contract in length but not the Pt layer, the bimaterial microcantilever bends. In our present studies we used the optical detection technique to measure the photometric response of Pt-Si microcantilevers as a function of photon energy. The charge carriers responsible for the photo-induced stress in Si, were produced via internal photoemission using a diode laser with wavelength {lambda} = 1550 nm.

  8. A systems view of haloarchaeal strategies to withstand stress from transition metals

    PubMed Central

    Kaur, Amardeep; Pan, Min; Meislin, Megan; Facciotti, Marc T.; El-Gewely, Raafat; Baliga, Nitin S.

    2006-01-01

    Given that transition metals are essential cofactors in central biological processes, misallocation of the wrong metal ion to a metalloprotein can have resounding and often detrimental effects on diverse aspects of cellular physiology. Therefore, in an attempt to characterize unique and shared responses to chemically similar metals, we have reconstructed physiological behaviors of Halobacterium NRC-1, an archaeal halophile, in sublethal levels of Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II). Over 20% of all genes responded transiently within minutes of exposure to Fe(II), perhaps reflecting immediate large-scale physiological adjustments to maintain homeostasis. At steady state, each transition metal induced growth arrest, attempts to minimize oxidative stress, toxic ion scavenging, increased protein turnover and DNA repair, and modulation of active ion transport. While several of these constitute generalized stress responses, up-regulation of active efflux of Co(II), Ni(II), Cu(II), and Zn(II), down-regulation of Mn(II) uptake and up-regulation of Fe(II) chelation, confer resistance to the respective metals. We have synthesized all of these discoveries into a unified systems-level model to provide an integrated perspective of responses to six transition metals with emphasis on experimentally verified regulatory mechanisms. Finally, through comparisons across global transcriptional responses to different metals, we provide insights into putative in vivo metal selectivity of metalloregulatory proteins and demonstrate that a systems approach can help rapidly unravel novel metabolic potential and regulatory programs of poorly studied organisms. PMID:16751342

  9. Stress corrosion cracking of metal matrix composites: Modeling and experiment

    SciTech Connect

    Jones, R.H.

    1990-10-01

    The stress corrosion crack growth ate of metal matrix composites has been described by a model which is dependent on the length-to- diameter ({ell}/d) ratio and volume fraction of the reinforcing phase and matrix creep component. The model predicts a large dependence of the stress corrosion crack growth rate of a metal matrix composite on {ell}/d and matrix creep component and a small dependence on the volume fraction of reinforcement. Experimentally determined crack growth rates for 7090 Al/SiC tested in 3.5% NcCl solution, 6061 Al/SiC tested in moist air with NaCl and immersed in NaCl solution, and Mg/Al{sub 2}0{sub 3} tested in a chloride/chromate solution are all consistent with the model. The close correspondence between the model and experiment for a matrix creep stress exponent of 3 suggest that there is little corrosion damage to the reinforcing phase in these systems. 16 refs., 5 figs.

  10. Glucagon orchestrates stress-induced hyperglycaemia.

    PubMed

    Harp, J B; Yancopoulos, G D; Gromada, J

    2016-07-01

    Hyperglycaemia is commonly observed on admission and during hospitalization for medical illness, traumatic injury, burn and surgical intervention. This transient hyperglycaemia is referred to as stress-induced hyperglycaemia (SIH) and frequently occurs in individuals without a history of diabetes. SIH has many of the same underlying hormonal disturbances as diabetes mellitus, specifically absolute or relative insulin deficiency and glucagon excess. SIH has the added features of elevated blood levels of catecholamines and cortisol, which are not typically present in people with diabetes who are not acutely ill. The seriousness of SIH is highlighted by its greater morbidity and mortality rates compared with those of hospitalized patients with normal glucose levels, and this increased risk is particularly high in those without pre-existing diabetes. Insulin is the treatment standard for SIH, but new therapies that reduce glucose variability and hypoglycaemia are desired. In the present review, we focus on the key role of glucagon in SIH and discuss the potential use of glucagon receptor blockers and glucagon-like peptide-1 receptor agonists in SIH to achieve target glucose control. PMID:27027662

  11. Differentiating stress to wheat fields induced by Diuraphis noxia from other stress causing factors

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this study was to develop a method to differentiate two categories of stress to wheat fields, stress induced by the Russian wheat aphid, Diuraphis noxia (Mordvilko), and stress caused by other factors. The study used a set of 11 spatial pattern metrics derived from multispectral im...

  12. Stress-induced Sn Nanowires from Si-Sn Nanocomposite Coatings

    NASA Astrophysics Data System (ADS)

    Xiao, X.; Sachdev, A. K.; Haddad, D.; Li, Y.; Sheldon, B. W.; Soni, S. K.

    2010-10-01

    The growth of stress-induced tin (Sn) whiskers has been considered responsible for the failure of many electronic devices and many approaches have been developed to mitigate their growth. In this report, however, we describe a simple approach based on the same mechanism to promote the growth of Sn nanowires. The thermal expansion induced stress was utilized as the driving force to initiate the growth of Sn nanowires from Si-Sn phase-separated nanocomposite coatings. The nanostructure of the Si-Sn matrix was the key to controlling the shape and diameter of Sn nanowires. This approach provides additional flexibility for making desirable metallic nanowires with controlled dimensions.

  13. Electrode-stress-induced nanoscale disorder in Si quantum electronic devices

    NASA Astrophysics Data System (ADS)

    Park, J.; Ahn, Y.; Tilka, J. A.; Sampson, K. C.; Savage, D. E.; Prance, J. R.; Simmons, C. B.; Lagally, M. G.; Coppersmith, S. N.; Eriksson, M. A.; Holt, M. V.; Evans, P. G.

    2016-06-01

    Disorder in the potential-energy landscape presents a major obstacle to the more rapid development of semiconductor quantum device technologies. We report a large-magnitude source of disorder, beyond commonly considered unintentional background doping or fixed charge in oxide layers: nanoscale strain fields induced by residual stresses in nanopatterned metal gates. Quantitative analysis of synchrotron coherent hard x-ray nanobeam diffraction patterns reveals gate-induced curvature and strains up to 0.03% in a buried Si quantum well within a Si/SiGe heterostructure. Electrode stress presents both challenges to the design of devices and opportunities associated with the lateral manipulation of electronic energy levels.

  14. Metal surface nitriding by laser induced plasma

    NASA Astrophysics Data System (ADS)

    Thomann, A. L.; Boulmer-Leborgne, C.; Andreazza-Vignolle, C.; Andreazza, P.; Hermann, J.; Blondiaux, G.

    1996-10-01

    We study a nitriding technique of metals by means of laser induced plasma. The synthesized layers are composed of a nitrogen concentration gradient over several μm depth, and are expected to be useful for tribological applications with no adhesion problem. The nitriding method is tested on the synthesis of titanium nitride which is a well-known compound, obtained at present by many deposition and diffusion techniques. In the method of interest, a laser beam is focused on a titanium target in a nitrogen atmosphere, leading to the creation of a plasma over the metal surface. In order to understand the layer formation, it is necessary to characterize the plasma as well as the surface that it has been in contact with. Progressive nitrogen incorporation in the titanium lattice and TiN synthesis are studied by characterizing samples prepared with increasing laser shot number (100-4000). The role of the laser wavelength is also inspected by comparing layers obtained with two kinds of pulsed lasers: a transversal-excited-atmospheric-pressure-CO2 laser (λ=10.6 μm) and a XeCl excimer laser (λ=308 nm). Simulations of the target temperature rise under laser irradiation are performed, which evidence differences in the initial laser/material interaction (material heated thickness, heating time duration, etc.) depending on the laser features (wavelength and pulse time duration). Results from plasma characterization also point out that the plasma composition and propagation mode depend on the laser wavelength. Correlation of these results with those obtained from layer analyses shows at first the important role played by the plasma in the nitrogen incorporation. Its presence is necessary and allows N2 dissociation and a better energy coupling with the target. Second, it appears that the nitrogen diffusion governs the nitriding process. The study of the metal nitriding efficiency, depending on the laser used, allows us to explain the differences observed in the layer features

  15. Unpredictable chronic mild stress not chronic restraint stress induces depressive behaviours in mice.

    PubMed

    Zhu, Shenghua; Shi, Ruoyang; Wang, Junhui; Wang, Jun-Feng; Li, Xin-Min

    2014-10-01

    The chronic stress model was developed on the basis of the stress-diathesis hypothesis of depression. However, these behavioural responses associated with different stress paradigms are quite complex. This study examined the effects of two chronic stress regimens on anxiety-like and depressive behaviours. C57BL/6 mice were subjected to unpredictable chronic mild stress or to chronic restraint stress for 4 weeks. Subsequently, both anxiety-like behaviours (open field, elevated plus maze and novelty suppressed feeding) and depression-like behaviours (tail suspension, forced swim and sucrose preference) were evaluated. Both chronic stress models generated anxiety-like behaviours, whereas only unpredictable chronic mild stress could induce depressive behaviours such as increased immobility and decreased sucrose consumption. These results of the present study provide additional evidence on how chronic stress affects behavioural responses and point to the importance of the validity of animal models of chronic stress in studying depression. PMID:25089805

  16. Surface-Stress-Induced Phase Transformation of Ultrathin FeCo Nanowires.

    PubMed

    Shen, Jian; Gong, Maogang; Dai, Qilin; Ren, Shenqiang

    2016-01-13

    Ultrathin metal nanowires have attracted wide attention becau se oftheir unique anisotropy and surface-to-volume effects. In this study, we use ultrathin Au nanowires as the templating core to epitaxially grow magnetic iron-cobalt (FeCo) shell through metal-redox with the control on their thickness and stoichiometry. Large surface-stress-induced phase transformation in Au nanowires triggers and stabilizes metastable tetragonal FeCo nanostructure to enhance its magnetic anisotropy and coercivity. Meanwhile, under illumination, plasmon-induced hotspot in ultrathin Au nanowires enables the light-control on magnetic characteristics of FeCo shell. This study demonstrates the feasibility of surface-stress-induced phase transformation to stabilize and control metastable nanostructures for enhanced magnetic anisotropy, which is one of the key properties of functional magnetic materials. PMID:26709528

  17. Stress- and Allostasis-Induced Brain Plasticity

    PubMed Central

    McEwen, Bruce S.; Gianaros, Peter J.

    2014-01-01

    The brain is the key organ of stress processes. It determines what individuals will experience as stressful, it orchestrates how individuals will cope with stressful experiences, and it changes both functionally and structurally as a result of stressful experiences. Within the brain, a distributed, dynamic, and plastic neural circuitry coordinates, monitors, and calibrates behavioral and physiological stress response systems to meet the demands imposed by particular stressors. These allodynamic processes can be adaptive in the short term (allostasis) and maladaptive in the long term (allostatic load). Critically, these processes involve bidirectional signaling between the brain and body. Consequently, allostasis and allostatic load can jointly affect vulnerability to brain-dependent and stress-related mental and physical health conditions. This review focuses on the role of brain plasticity in adaptation to, and pathophysiology resulting from, stressful experiences. It also considers interventions to prevent and treat chronic and prevalent health conditions via allodynamic brain mechanisms. PMID:20707675

  18. Experimentally Induced Stress Validated by EMG Activity

    PubMed Central

    Luijcks, Rosan; Hermens, Hermie J.; Bodar, Lonneke; Vossen, Catherine J.; Os, Jim van.; Lousberg, Richel

    2014-01-01

    Experience of stress may lead to increased electromyography (EMG) activity in specific muscles compared to a non-stressful situation. The main aim of this study was to develop and validate a stress-EMG paradigm in which a single uncontrollable and unpredictable nociceptive stimulus was presented. EMG activity of the trapezius muscles was the response of interest. In addition to linear time effects, non-linear EMG time courses were also examined. Taking into account the hierarchical structure of the dataset, a multilevel random regression model was applied. The stress paradigm, executed in N = 70 subjects, consisted of a 3-minute baseline measurement, a 3-minute pre-stimulus stress period and a 2-minute post-stimulus phase. Subjects were unaware of the precise moment of stimulus delivery and its intensity level. EMG activity during the entire experiment was conform a priori expectations: the pre-stimulus phase showed a significantly higher mean EMG activity level compared to the other two phases, and an immediate EMG response to the stimulus was demonstrated. In addition, the analyses revealed significant non-linear EMG time courses in all three phases. Linear and quadratic EMG time courses were significantly modified by subjective anticipatory stress level, measured just before the start of the stress task. Linking subjective anticipatory stress to EMG stress reactivity revealed that subjects with a high anticipatory stress level responded with more EMG activity during the pre-stimulus stress phase, whereas subjects with a low stress level showed an inverse effect. Results suggest that the stress paradigm presented here is a valid test to quantify individual differences in stress susceptibility. Further studies with this paradigm are required to demonstrate its potential use in mechanistic clinical studies. PMID:24736740

  19. Induced stresses due to fluid extraction from axisymmetric reservoirs

    USGS Publications Warehouse

    Segall, P.

    1992-01-01

    Earthquakes can be induced by fluid extraction, as well as by fluid injection. Segall (1989) proposed that poroelastic stresses are responsible for inducing earthquakes associated with fluid extraction. Here, I present methods for computing poroelastic stress changes due to fluid extraction for general axisymmetric reservoir geometries. The results of Geertsma (1973) for a thin disk reservoir with uniform pressure drop are recovered as a special case. Predicted surface subsidence agrees very well with measured leveling changes over the deep Lacq gas field in southwestern France. The induced stresses are finite if the reservoir pressure changes are continuous. Computed stress changes are on the order of several bars, suggesting that the preexisting stress states in regions of extraction induced seismicity are very close to frictional instability prior to production. ?? 1992 Birkha??user Verlag.

  20. Horizontal stresses induced by vertical processes in planetary lithospheres

    NASA Technical Reports Server (NTRS)

    Banerdt, W. B.

    1993-01-01

    Understanding the state of stress in the elastic lithosphere is of fundamental importance for planetary geophysics, as it is the link between the observed geologic structures on the surface and the processes which form and modify these structures. As such, it can provide valuable constraints for the difficult problem of determining interior structure and processes. On the Earth, most large scale, organized deformation can be related to lateral tectonics associated with plate dynamics; however, the tectonics on many extraterrestrial bodies (such as the Moon, Mars, and most of the outer-planet satellites) appears to be primarily vertical in nature, and the horizontal stresses induced by vertical motions and loads are expected to dominate the deformation of their lithospheres. The largest stress contributions from vertical loading come from the flexure of the lithosphere, which induces both bending moments and membrane stresses. We are concerned here only with nonflexural changes in the state of stress induced by processes such as sedimentary and volcanic deposition, erosional denudation, and changes in the thermal gradient that induce uplift or subsidence. This analysis is important both for evaluating stresses for specific regions in which the vertical stress history can be estimated, as well as for applying the proper loading conditions to global stress models. It is also of interest for providing a reference state of stress for interpreting stress measurements in the crust of the Earth.

  1. Salicylic acid-induced abiotic stress tolerance and underlying mechanisms in plants

    PubMed Central

    Khan, M. Iqbal R.; Fatma, Mehar; Per, Tasir S.; Anjum, Naser A.; Khan, Nafees A.

    2015-01-01

    Abiotic stresses (such as metals/metalloids, salinity, ozone, UV-B radiation, extreme temperatures, and drought) are among the most challenging threats to agricultural system and economic yield of crop plants. These stresses (in isolation and/or combination) induce numerous adverse effects in plants, impair biochemical/physiological and molecular processes, and eventually cause severe reductions in plant growth, development and overall productivity. Phytohormones have been recognized as a strong tool for sustainably alleviating adverse effects of abiotic stresses in crop plants. In particular, the significance of salicylic acid (SA) has been increasingly recognized in improved plant abiotic stress-tolerance via SA-mediated control of major plant-metabolic processes. However, the basic biochemical/physiological and molecular mechanisms that potentially underpin SA-induced plant-tolerance to major abiotic stresses remain least discussed. Based on recent reports, this paper: (a) overviews historical background and biosynthesis of SA under both optimal and stressful environments in plants; (b) critically appraises the role of SA in plants exposed to major abiotic stresses; (c) cross-talks potential mechanisms potentially governing SA-induced plant abiotic stress-tolerance; and finally (d) briefly highlights major aspects so far unexplored in the current context. PMID:26175738

  2. Stress-induced somatic embryogenesis in vegetative tissues of Arabidopsis thaliana.

    PubMed

    Ikeda-Iwai, Miho; Umehara, Mikihisa; Satoh, Shinobu; Kamada, Hiroshi

    2003-04-01

    Somatic embryogenesis is an obvious experimental evidence of totipotency, and is used as a model system for studying the mechanisms of de-differentiation and re-differentiation of plant cells. Although Arabidopsis is widely used as a model plant for genetic and molecular biological studies, there is no available tissue culture system for inducing somatic embryogenesis from somatic cells in this plant. We established a new tissue culture system using stress treatment to induce somatic embryogenesis in Arabidopsis. In this system, stress treatment induced formation of somatic embryos from shoot-apical-tip and floral-bud explants. The somatic embryos grew into young plantlets with normal morphology, including cotyledons, hypocotyls, and roots, and some embryo-specific genes (ABI3 and FUS3) were expressed in these embryos. Several stresses (osmotic, heavy metal ion, and dehydration stress) induced somatic embryogenesis, but the optimum stress treatment differed between different stressors. When we used mannitol to cause osmotic stress, the optimal conditions for somatic embryogenesis were 6-9 h of culture on solid B5 medium containing 0.7 m mannitol, after which the explants were transferred to B5 medium containing 2,4-dichlorophenoxyacetic acid (2,4-D, 4.5 microm), but no mannitol. Using this tissue culture system, we induced somatic embryogenesis in three major ecotypes of Arabidopsis thaliana-Ws, Col, and Ler. PMID:12662313

  3. Biological effects of laser-induced stress waves

    SciTech Connect

    Doukas, A.; Lee, S.; McAuliffe, D.

    1995-12-31

    Laser-induced stress waves can be generated by one of the following mechanisms: Optical breakdown, ablation or rapid heating of an absorbing medium. These three modes of laser interaction with matter allow the investigation of cellular and tissue responses to stress waves with different characteristics and under different conditions. The most widely studied phenomena are those of the collateral damage seen in photodisruption in the eye and in 193 run ablation of cornea and skin. On the other hand, the therapeutic application of laser-induced stress waves has been limited to the disruption of noncellular material such as renal stones, atheromatous plaque and vitreous strands. The effects of stress waves to cells and tissues can be quite disparate. Stress waves can fracture tissue, damage cells, and increase the permeability of the plasma membrane. The viability of cell cultures exposed to stress waves increases with the peak stress and the number of pulses applied. The rise time of the stress wave also influences the degree of cell injury. In fact, cell viability, as measured by thymidine incorporation, correlates better with the stress gradient than peak stress. Recent studies have also established that stress waves induce a transient increase of the permeability of the plasma membrane in vitro. In addition, if the stress gradient is below the damage threshhold, the cells remain viable. Thus, stress waves can be useful as a means of drug delivery, increasing the intracellular drug concentration and allowing the use of drugs which are impermeable to the cell membrane. The present studies show that it is important to create controllable stress waves. The wavelength tunability and the micropulse structure of the free electron laser is ideal for generating stress waves with independently adjustable parameters, such as rise time, duration and peak stress.

  4. Stress antagonizes morphine-induced analgesia in rats

    NASA Technical Reports Server (NTRS)

    Vernikos, J.; Shannon, L.; Heybach, J. P.

    1981-01-01

    Exposure to restraint stress resulted in antagonism of the analgesic effect of administered morphine in adult male rats. This antagonism of morphine-induced analgesia by restraint stress was not affected by adrenalectomy one day prior to testing, suggesting that stress-induced secretion of corticosteroids is not critical to this antagonism. In addition, parenteral administration of exogenous adrenocorticotropin (ACTH) mimicked the effect of stress in antagonizing morphine's analgesic efficacy. The hypothesis that ACTH is an endogenous opiate antagonist involved in modulating pain sensitivity is supported.

  5. Laser-Induced Breakdown Spectroscopy of Trace Metals

    NASA Technical Reports Server (NTRS)

    Simons, Stephen (Technical Monitor); VanderWal, Randall L.; Ticich, Thomas M.; West, Joseph R., Jr.

    2004-01-01

    An alternative approach for laser-induced breakdown spectroscopy (LIBS) determination of trace metal determination in liquids is demonstrated. The limits of detection (LOD) for the technique ranged from 10 ppb to 10 ppm for 15 metals metals (Mg, Al, Si, Ca, Ti, Cr, Fe, Co, Ni, Cu, Zn, As, Cd, Hg, Pb) tested.

  6. Optimizing phytoremediation of heavy metal-contaminated soil by exploiting plants' stress adaptation.

    PubMed

    Barocsi, Attila; Csintalan, Zsolt; Kocsanyi, Laszlo; Dushenkov, Slavik; Kuperberg, J Michael; Kucharski, Rafal; Richter, Peter I

    2003-01-01

    Soil phytoextraction is based on the ability of plants to extract contaminants from the soil. For less bioavailable metals, such as Pb, a chelator is added to the soil to mobilize the metal. The effect can be significant and in certain species, heavy metal accumulation can rapidly increase 10-fold. Accumulation of high levels of toxic metals may result in irreversible damage to the plant. Monitoring and controlling the phytotoxicity caused by EDTA-induced metal accumulation is crucial to optimize the remedial process, i.e. to achieve maximum uptake. We describe an EDTA-application procedure that minimizes phytotoxicity by increasing plant tolerance and allows phytoextraction of elevated levels of Pb and Cd. Brassica juncea is tested in soil with typical Pb and Cd concentrations of 500 mg kg-1 and 15 mg kg-1, respectively. Instead of a single dose treatment, the chelator is applied in multiple doses, that is, in several small increments, thus providing time for plants to initiate their adaptation mechanisms and raise their damage threshold. In situ monitoring of plant stress conditions by chlorophyll fluorescence recording allows for the identification of the saturating heavy metal accumulation process and of simultaneous plant deterioration. PMID:12710232

  7. Psychological Stress, Cocaine and Natural Reward Each Induce Endoplasmic Reticulum Stress Genes in Rat Brain

    PubMed Central

    Pavlovsky, Ashly A.; Boehning, Darren; Li, Dingge; Zhang, Yafang; Fan, Xiuzhen; Green, Thomas A.

    2013-01-01

    Our prior research has shown that the transcription of endoplasmic reticulum (ER) stress transcription factors Activating Transcription Factor 3 (ATF3) and ATF4 are induced by amphetamine and restraint stress in rat striatum. However, presently it is unknown the full extent of ER stress responses to psychological stress or cocaine, and which of the three ER stress pathways is activated. The current study examines transcriptional responses of key ER stress target genes subsequent to psychological stress or cocaine. Rats were subjected to acute or repeated restraint stress or cocaine treatment and mRNA was isolated from dorsal striatum, medial prefrontal cortex and nucleus accumbens brain tissue. ER stress gene mRNA expression was measured using quantitative PCR and RNA sequencing. Restraint stress and cocaine induced transcription of the classic ER stress-induced genes (BIP, CHOP, ATF3 and GADD34) and of two other ER stress components XBP1 and ATF6. In addition, rats living in an enriched environment (large group cage with novel toys changed daily) exhibited rapid induction of GADD34 and ATF3 after 30 min of exploring novel toys, suggesting these genes are also involved in normal non-pathological signaling. However, environmental enrichment, a paradigm that produces protective addiction and depression phenotypes in rats, attenuated the rapid induction of ATF3 and GADD34 after restraint stress. These experiments provide a sensitive measure of ER stress and, more importantly, these results offer good evidence of the activation of ER stress mechanisms from psychological stress, cocaine and natural reward. Thus, ER stress genes may be targets for novel therapeutic targets for depression and addiction. PMID:23644055

  8. Psychological stress, cocaine and natural reward each induce endoplasmic reticulum stress genes in rat brain.

    PubMed

    Pavlovsky, A A; Boehning, D; Li, D; Zhang, Y; Fan, X; Green, T A

    2013-08-29

    Our prior research has shown that the transcription of endoplasmic reticulum (ER) stress transcription factors activating transcription factor 3 (ATF3) and ATF4 are induced by amphetamine and restraint stress in rat striatum. However, presently the full extent of ER stress responses to psychological stress or cocaine, and which of the three ER stress pathways is activated is unknown. The current study examines transcriptional responses of key ER stress target genes subsequent to psychological stress or cocaine. Rats were subjected to acute or repeated restraint stress or cocaine treatment and mRNA was isolated from dorsal striatum, medial prefrontal cortex and nucleus accumbens brain tissue. ER stress gene mRNA expression was measured using quantitative polymerase chain reaction (PCR) and RNA sequencing. Restraint stress and cocaine-induced transcription of the classic ER stress-induced genes (BIP, CHOP, ATF3 and GADD34) and of two other ER stress components x-box binding protein 1 (XBP1) and ATF6. In addition, rats living in an enriched environment (large group cage with novel toys changed daily) exhibited rapid induction of GADD34 and ATF3 after 30 min of exploring novel toys, suggesting these genes are also involved in normal non-pathological signaling. However, environmental enrichment, a paradigm that produces protective addiction and depression phenotypes in rats, attenuated the rapid induction of ATF3 and GADD34 after restraint stress. These experiments provide a sensitive measure of ER stress and, more importantly, these results offer good evidence of the activation of ER stress mechanisms from psychological stress, cocaine and natural reward. Thus, ER stress genes may be targets for novel therapeutic targets for depression and addiction. PMID:23644055

  9. A tomato stem cell extract, containing antioxidant compounds and metal chelating factors, protects skin cells from heavy metal-induced damages.

    PubMed

    Tito, Annalisa; Carola, Antonietta; Bimonte, Marida; Barbulova, Ani; Arciello, Stefania; de Laurentiis, Francesco; Monoli, Irene; Hill, Jacqueline; Gibertoni, Simone; Colucci, Gabriella; Apone, Fabio

    2011-12-01

    Heavy metals can cause several genotoxic effects on cells, including oxidative stress, DNA sequence breakage and protein modification. Among the body organs, skin is certainly the most exposed to heavy metal stress and thus the most damaged by the toxic effects that these chemicals cause. Moreover, heavy metals, in particular nickel, can induce the over-expression of collagenases (enzymes responsible for collagen degradation), leading to weakening of the skin extracellular matrix. Plants have evolved sophisticated mechanisms to protect their cells from heavy metal toxicity, including the synthesis of metal chelating proteins and peptides, such as metallothioneins and phytochelatins (PC), which capture the metals and prevent the damages on the cellular structures. To protect human skin cells from heavy metal toxicity, we developed a new cosmetic active ingredient from Lycopersicon esculentum (tomato) cultured stem cells. This product, besides its high content of antioxidant compounds, contained PC, effective in the protection of skin cells towards heavy metal toxicity. We have demonstrated that this new product preserves nuclear DNA integrity from heavy metal damages, by inducing genes responsible for DNA repair and protection, and neutralizes the effect of heavy metals on collagen degradation, by inhibiting collagenase expression and inducing the synthesis of new collagen. PMID:21609336

  10. Macroscopic tensile plasticity by scalarizating stress distribution in bulk metallic glass.

    PubMed

    Gao, Meng; Dong, Jie; Huan, Yong; Wang, Yong Tian; Wang, Wei-Hua

    2016-01-01

    The macroscopic tensile plasticity of bulk metallic glasses (BMGs) is highly desirable for various engineering applications. However, upon yielding, plastic deformation of BMGs is highly localized into narrow shear bands and then leads to the "work softening" behaviors and subsequently catastrophic fracture, which is the major obstacle for their structural applications. Here we report that macroscopic tensile plasticity in BMG can be obtained by designing surface pore distribution using laser surface texturing. The surface pore array by design creates a complex stress field compared to the uniaxial tensile stress field of conventional glassy specimens, and the stress field scalarization induces the unusual tensile plasticity. By systematically analyzing fracture behaviors and finite element simulation, we show that the stress field scalarization can resist the main shear band propagation and promote the formation of larger plastic zones near the pores, which undertake the homogeneous tensile plasticity. These results might give enlightenment for understanding the deformation mechanism and for further improvement of the mechanical performance of metallic glasses. PMID:26902264

  11. Macroscopic tensile plasticity by scalarizating stress distribution in bulk metallic glass

    NASA Astrophysics Data System (ADS)

    Gao, Meng; Dong, Jie; Huan, Yong; Wang, Yong Tian; Wang, Wei-Hua

    2016-02-01

    The macroscopic tensile plasticity of bulk metallic glasses (BMGs) is highly desirable for various engineering applications. However, upon yielding, plastic deformation of BMGs is highly localized into narrow shear bands and then leads to the “work softening” behaviors and subsequently catastrophic fracture, which is the major obstacle for their structural applications. Here we report that macroscopic tensile plasticity in BMG can be obtained by designing surface pore distribution using laser surface texturing. The surface pore array by design creates a complex stress field compared to the uniaxial tensile stress field of conventional glassy specimens, and the stress field scalarization induces the unusual tensile plasticity. By systematically analyzing fracture behaviors and finite element simulation, we show that the stress field scalarization can resist the main shear band propagation and promote the formation of larger plastic zones near the pores, which undertake the homogeneous tensile plasticity. These results might give enlightenment for understanding the deformation mechanism and for further improvement of the mechanical performance of metallic glasses.

  12. Macroscopic tensile plasticity by scalarizating stress distribution in bulk metallic glass

    PubMed Central

    Gao, Meng; Dong, Jie; Huan, Yong; Wang, Yong Tian; Wang, Wei-Hua

    2016-01-01

    The macroscopic tensile plasticity of bulk metallic glasses (BMGs) is highly desirable for various engineering applications. However, upon yielding, plastic deformation of BMGs is highly localized into narrow shear bands and then leads to the “work softening” behaviors and subsequently catastrophic fracture, which is the major obstacle for their structural applications. Here we report that macroscopic tensile plasticity in BMG can be obtained by designing surface pore distribution using laser surface texturing. The surface pore array by design creates a complex stress field compared to the uniaxial tensile stress field of conventional glassy specimens, and the stress field scalarization induces the unusual tensile plasticity. By systematically analyzing fracture behaviors and finite element simulation, we show that the stress field scalarization can resist the main shear band propagation and promote the formation of larger plastic zones near the pores, which undertake the homogeneous tensile plasticity. These results might give enlightenment for understanding the deformation mechanism and for further improvement of the mechanical performance of metallic glasses. PMID:26902264

  13. Drilling-induced core fractures and in situ stress

    NASA Astrophysics Data System (ADS)

    Li, Yongyi; Schmitt, Douglas R.

    1998-03-01

    The relationship between the shapes of drilling-induced core fractures and the in situ state of stress is developed. The stress concentrations at the well bore bottom are first determined using a complete three-dimensional finite element analysis. Existing in situ compressional stresses generate large tensions in the immediate vicinity of the bottom hole which are sufficient to rupture the rock. Tensile fracture trajectories within these concentrated stress fields are predicted using a simple model of fracture propagation. These modeled fracture trajectories resemble well the observed shapes of drilling-induced core disking, petal, and petal-centerline fractures. Further, this agreement suggests that both the shape of the drilling-induced fracture and the location at which it initiates depends on the in situ stress state existing in the rock mass prior to drilling; the core fractures contain substantial information on in situ stress conditions. In all faulting regimes the coring-induced fractures initiate near the bit cut except for most cases under thrust faulting regime where the fracture initiates on the well bore axis. Further, under thrust faulting conditions only disk fractures appear possible. Both petal and disking fractures can be produced in strike-slip and normal faulting regimes depending upon the relative magnitudes between the least compressive horizontal principal stress and the vertical overburden stress. The predicted fracture shapes are in good qualitative agreement with observations of drilling-induced fractures described in the literature from laboratory experiments and field programs in which in situ stresses are measured by other means. The relationship of the morphology of coring induced fractures and in situ stresses suggests that the fractures can be used as independent complementary indicators in identifying stress regimes.

  14. Neurobiology of Stress-Induced Reproductive Dysfunction In Female Macaques

    PubMed Central

    Bethea, Cynthia L.; Centeno, Maria Luisa; Cameron, Judy L.

    2012-01-01

    It is now well accepted that stress can precipitate mental and physical illness. However, it is becoming clear that given the same stress, some individuals are very vulnerable and will succumb to illness while others are more resilient and cope effectively, rather than becoming ill. This difference between individuals is called stress sensitivity. Stress-sensitivity of an individual appears to be influenced by genetically inherited factors, early life (even prenatal) stress, and by the presence or absence of factors that provide protection from stress. In comparison to other stress-related diseases, the concept of sensitivity versus resilience to stress-induced reproductive dysfunction has received relatively little attention. The studies presented herein were undertaken to begin to identify stable characteristics and the neural underpinnings of individuals with sensitivity to stress-induced reproductive dysfunction. Female cynomolgus macaques with normal menstrual cycles either stop ovulating (Stress Sensitive) or to continue to ovulate (Stress Resilient) upon exposure to a combined metabolic and psychosocial stress. However, even in the absence of stress, the stress sensitive animals have lower secretion of the ovarian steroids, estrogen and progesterone, have higher heart rates, have lower serotonin function, have fewer serotonin neurons and lower expression of pivotal serotonin-related genes, have lower expression of 5HT2A and 2C genes in the hypothalamus, have higher gene expression of GAD67 and CRH in the hypothalamus and have reduced GnRH transport to the anterior pituitary. Altogether, the results suggest that the neurobiology of reproductive circuits in stress sensitive individuals is compromised. We speculate that with the application of stress, the dysfunction of these neural systems becomes exacerbated and reproductive function ceases. PMID:18931961

  15. Social factors modulate restraint stress induced hyperthermia in mice.

    PubMed

    Watanabe, Shigeru

    2015-10-22

    Stress-induced hyperthermia (SIH) was examined in three different social conditions in mice by thermographic measurement of the body surface temperature. Placing animals in cylindrical holders induced restraint stress. I examined the effect of the social factors in SIH using the thermograph (body surface temperature). Mice restrained in the holders alone showed SIH. Mice restrained in the holders at the same time as other similarly restrained cage mates (social equality condition) showed less hyperthermia. Interestingly, restrained mice with free moving cage mates (social inequality condition) showed the highest hyperthermia. These results are consistent with a previous experiment measuring the memory-enhancing effects of stress and the stress-induced elevation of corticosterone, and suggest that social inequality enhances stress. PMID:26232073

  16. Oxidative stress in the mollusk Echinolittorina peruviana (Gasteropoda: Littorinidae, Lamarck, 1822) and trace metals in coastal sectors with mining activity.

    PubMed

    Jara, C; Gaete, H; Lobos, G; Hidalgo, M E

    2014-08-01

    The aim of the study was to evaluate the effect of coastal waters of sites with mining activity in Echinolittorina peruviana, through oxidative stress biomarkers and heavy metals determination both in water and in tissue. Organisms were collected in the intertidal zone in areas with and without mining activity. Metal concentrations in the water and tissues, and also, the following biomarkers of oxidative stress: antioxidant enzyme activity, superoxide dismutase and catalase, non-enzymatic oxidative capacity (TRAP), oxidative damage to proteins (carbonyls) and TBARS, were measured The concentrations of accumulated metals had the following order Fe > Cu > Cd > Zn > Cr > Mo > As; the highest concentrations of metals in water and tissues were found in Caleta Palito and Chañaral. Results suggest that the coastal waters with mining activity and greatest concentrations of copper and iron induced the greater antioxidant response and oxidative damage to lipids in E. peruviana. PMID:24829115

  17. Possible Biomarkers of Chronic Stress Induced Exhaustion - A Longitudinal Study

    PubMed Central

    Wallensten, Johanna; Åsberg, Marie; Nygren, Åke; Szulkin, Robert; Wallén, Håkan; Mobarrez, Fariborz; Nager, Anna

    2016-01-01

    Background Vascular endothelial growth factor (VEGF), epidermal growth factor (EGF) and monocyte chemotactic protein-1 (MCP-1) have previously been suggested to be potential biomarkers for chronic stress induced exhaustion. The knowledge about VEGF has increased during the last decades and supports the contention that VEGF plays an important role in stress and depression. There is scarce knowledge on the possible relationship of EGF and MCP-1 in chronic stress and depression. This study further examines the role of VEGF, EGF and MCP-1 in women with chronic stress induced exhaustion and healthy women during a follow-up period of two years. Methods and Findings Blood samples were collected from 105 women with chronic stress induced exhaustion on at least 50% sick leave for at least three months, at inclusion (T0), after 12 months (T12) and after 24 months (T24). Blood samples were collected at inclusion (T0) in 116 physically and psychiatrically healthy women. The plasma levels of VEGF, EGF and MCP-1 were analyzed using Biochip Array Technology. Women with chronic stress induced exhaustion had significantly higher plasma levels of VEGF and EGF compared to healthy women at baseline, T12 and at T24. There was no significant difference in plasma levels of MCP-1. Plasma levels of VEGF and EGF decreased significantly in women with chronic stress induced exhaustion during the two years follow-up. Conclusions The replicated findings of elevated levels of VEGF and EGF in women with chronic stress induced exhaustion and decreasing plasma levels of VEGF and EGF during the two years follow-up add important knowledge to the pathophysiology of chronic stress induced exhaustion. PMID:27145079

  18. Thermal- and electromigration-induced stresses in passivated Al- and AlSiCu-interconnects

    SciTech Connect

    Beckers, D.; Schroeder, H.; Schilling, W.; Eppler, I.

    1997-05-01

    Mechanical stresses in microelectronic devices are of special interest because of degradation effects in microelectronic circuits such as stress induced voiding or electromigration. Al and al-alloys are commonly used as interconnect materials in integrated electronic devices. Stress induced voiding and degradation of metal lines by electromigration are closely related to the stresses in the lines. The authors have studied the strain and stress evolution during thermal cycling, isothermal relaxation and due to electromigration in passivated Al and AlSi(1%)Cu(0.5%) lines by X-Ray diffraction with variation of experimental parameters such as the aspect ratio and the electrical current density. Furthermore the extent of voiding and plastic shear deformation has been determined from the experimental metal strains with the help of finite element calculations. Main results are: (1) During thermal cycling the voiding is less than 2 {center_dot} 10{sup {minus}3}. The extent of plastic shear deformation increases with increasing line width and with decreasing flowstress. (2) During isothermal relaxation void growth occurs but no significant change in the plastic shear deformation. (3) An electric current in the lines causes no measurable additional change of the volume averaged stresses up to line failure.

  19. Altered Gravity Induces Oxidative Stress in Drosophila Melanogaster

    NASA Technical Reports Server (NTRS)

    Bhattacharya, Sharmila; Hosamani, Ravikumar

    2015-01-01

    Altered gravity environments can induce increased oxidative stress in biological systems. Microarray data from our previous spaceflight experiment (FIT experiment on STS-121) indicated significant changes in the expression of oxidative stress genes in adult fruit flies after spaceflight. Currently, our lab is focused on elucidating the role of hypergravity-induced oxidative stress and its impact on the nervous system in Drosophila melanogaster. Biochemical, molecular, and genetic approaches were combined to study this effect on the ground. Adult flies (2-3 days old) exposed to acute hypergravity (3g, for 1 hour and 2 hours) showed significantly elevated levels of Reactive Oxygen Species (ROS) in fly brains compared to control samples. This data was supported by significant changes in mRNA expression of specific oxidative stress and antioxidant defense related genes. As anticipated, a stress-resistant mutant line, Indy302, was less vulnerable to hypergravity-induced oxidative stress compared to wild-type flies. Survival curves were generated to study the combined effect of hypergravity and pro-oxidant treatment. Interestingly, many of the oxidative stress changes that were measured in flies showed sex specific differences. Collectively, our data demonstrate that altered gravity significantly induces oxidative stress in Drosophila, and that one of the organs where this effect is evident is the brain.

  20. Emotional Intelligence, Personality, and Task-Induced Stress

    ERIC Educational Resources Information Center

    Matthews, Gerald; Emo, Amanda K.; Funke, Gregory; Zeidner, Moshe; Roberts, Richard D.; Costa, Paul T.; Schulze, Ralf

    2006-01-01

    Emotional intelligence (EI) may predict stress responses and coping strategies in a variety of applied settings. This study compares EI and the personality factors of the Five Factor Model (FFM) as predictors of task-induced stress responses. Participants (N = 200) were randomly assigned to 1 of 4 task conditions, 3 of which were designed to be…

  1. Influence of the drying medium parameters on drying induced stresses

    SciTech Connect

    Musielak, G.

    2000-03-01

    A thermomechanical model of drying of capillary-porous materials whose material constants depend on moisture content and temperature is presented in the paper. The finite element method is used for the solution of two-dimensional problem of convective drying of a prismatic bar. The moisture distributions, temperature distributions, drying induced strains and stresses for various drying medium parameters are determined. The effect of these parameters on moisture distribution and in particular on drying induced stresses is discussed.

  2. ATR inhibition rewires cellular signaling networks induced by replication stress.

    PubMed

    Wagner, Sebastian A; Oehler, Hannah; Voigt, Andrea; Dalic, Denis; Freiwald, Anja; Serve, Hubert; Beli, Petra

    2016-02-01

    The slowing down or stalling of replication forks is commonly known as replication stress and arises from multiple causes such as DNA lesions, nucleotide depletion, RNA-DNA hybrids, and oncogene activation. The ataxia telangiectasia and Rad3-related kinase (ATR) plays an essential role in the cellular response to replication stress and inhibition of ATR has emerged as therapeutic strategy for the treatment of cancers that exhibit high levels of replication stress. However, the cellular signaling induced by replication stress and the substrate spectrum of ATR has not been systematically investigated. In this study, we employed quantitative MS-based proteomics to define the cellular signaling after nucleotide depletion-induced replication stress and replication fork collapse following ATR inhibition. We demonstrate that replication stress results in increased phosphorylation of a subset of proteins, many of which are involved in RNA splicing and transcription and have previously not been associated with the cellular replication stress response. Furthermore, our data reveal the ATR-dependent phosphorylation following replication stress and discover novel putative ATR target sites on MCM6, TOPBP1, RAD51AP1, and PSMD4. We establish that ATR inhibition rewires cellular signaling networks induced by replication stress and leads to the activation of the ATM-driven double-strand break repair signaling. PMID:26572502

  3. Potential role of punicalagin against oxidative stress induced testicular damage

    PubMed Central

    Rao, Faiza; Tian, Hui; Li, Wenqing; Hung, Helong; Sun, Fei

    2016-01-01

    Punicalagin is isolated from pomegranate and widely used for the treatment of different diseases in Chinese traditional medicine. This study aimed to evaluate the effect of Punicalagin (purity ≥98%) on oxidative stress induced testicular damage and its effect on fertility. We detected the antioxidant potential of punicalagin in lipopolysaccharide (LPS) induced oxidative stress damage in testes, also tried to uncover the boosting fertility effect of Punicalagin (PU) against oxidative stress-induced infertility. Results demonstrated that 9 mg kg−1 for 7 days treatment significantly decreases LPS induced oxidative damage in testes and nitric oxide production. The administration of oxidative stress resulted in a significant reduction in testes antioxidants GSH, T-SOD, and CAT raised LPO, but treatment with punicalagin for 7 days increased antioxidant defense GSH, T-SOD, and CAT by the end of the experiment and reduced LPO level as well. PU also significantly activates Nrf2, which is involved in regulation of antioxidant defense systems. Hence, the present research categorically elucidates the protective effect of punicalagin against LPS induced oxidative stress induced perturbation in the process of spermatogenesis and significantly increased sperm health and number. Moreover, fertility success significantly decreased in LPS-injected mice compared to controls. Mice injected with LPS had fertility indices of 12.5%, while others treated with a combination of PU + LPS exhibited 75% indices. By promoting fertility and eliminating oxidative stress and inflammation, PU may be a useful nutrient for the treatment of infertility. PMID:26763544

  4. Potential role of punicalagin against oxidative stress induced testicular damage.

    PubMed

    Rao, Faiza; Tian, Hui; Li, Wenqing; Hung, Helong; Sun, Fei

    2016-01-01

    Punicalagin is isolated from pomegranate and widely used for the treatment of different diseases in Chinese traditional medicine. This study aimed to evaluate the effect of Punicalagin (purity ≥98%) on oxidative stress induced testicular damage and its effect on fertility. We detected the antioxidant potential of punicalagin in lipopolysaccharide (LPS) induced oxidative stress damage in testes, also tried to uncover the boosting fertility effect of Punicalagin (PU) against oxidative stress-induced infertility. Results demonstrated that 9 mg kg-1 for 7 days treatment significantly decreases LPS induced oxidative damage in testes and nitric oxide production. The administration of oxidative stress resulted in a significant reduction in testes antioxidants GSH, T-SOD, and CAT raised LPO, but treatment with punicalagin for 7 days increased antioxidant defense GSH, T-SOD, and CAT by the end of the experiment and reduced LPO level as well. PU also significantly activates Nrf2, which is involved in regulation of antioxidant defense systems. Hence, the present research categorically elucidates the protective effect of punicalagin against LPS induced oxidative stress induced perturbation in the process of spermatogenesis and significantly increased sperm health and number. Moreover, fertility success significantly decreased in LPS-injected mice compared to controls. Mice injected with LPS had fertility indices of 12.5%, while others treated with a combination of PU + LPS exhibited 75% indices. By promoting fertility and eliminating oxidative stress and inflammation, PU may be a useful nutrient for the treatment of infertility. PMID:26763544

  5. Heavy-metal-induced reactive oxygen species: phytotoxicity and physicochemical changes in plants.

    PubMed

    Shahid, Muhammad; Pourrut, Bertrand; Dumat, Camille; Nadeem, Muhammad; Aslam, Muhammad; Pinelli, Eric

    2014-01-01

    As a result of the industrial revolution, anthropogenic activities have enhanced there distribution of many toxic heavy metals from the earth's crust to different environmental compartments. Environmental pollution by toxic heavy metals is increasing worldwide, and poses a rising threat to both the environment and to human health.Plants are exposed to heavy metals from various sources: mining and refining of ores, fertilizer and pesticide applications, battery chemicals, disposal of solid wastes(including sewage sludge), irrigation with wastewater, vehicular exhaust emissions and adjacent industrial activity.Heavy metals induce various morphological, physiological, and biochemical dysfunctions in plants, either directly or indirectly, and cause various damaging effects. The most frequently documented and earliest consequence of heavy metal toxicity in plants cells is the overproduction of ROS. Unlike redox-active metals such as iron and copper, heavy metals (e.g, Pb, Cd, Ni, AI, Mn and Zn) cannot generate ROS directly by participating in biological redox reactions such as Haber Weiss/Fenton reactions. However, these metals induce ROS generation via different indirect mechanisms, such as stimulating the activity of NADPH oxidases, displacing essential cations from specific binding sites of enzymes and inhibiting enzymatic activities from their affinity for -SH groups on the enzyme.Under normal conditions, ROS play several essential roles in regulating the expression of different genes. Reactive oxygen species control numerous processes like the cell cycle, plant growth, abiotic stress responses, systemic signalling, programmed cell death, pathogen defence and development. Enhanced generation of these species from heavy metal toxicity deteriorates the intrinsic antioxidant defense system of cells, and causes oxidative stress. Cells with oxidative stress display various chemical,biological and physiological toxic symptoms as a result of the interaction between ROS and

  6. Effect of salt, drought and metal stress on essential oil yield and quality in plants.

    PubMed

    Biswas, Shreyasee; Koul, Monika; Bhatnagar, Ashok Kumar

    2011-10-01

    Essential oil extracted from plants is of high commercial value in medicine, cosmetics and perfumery. Enhancing yield and maintaining the quality of oil is of significant commercial importance. Production of oil in plants is dependent on various biotic and abiotic factors to which the plants are subjected during their growth. Plants are exposed to various degrees of stress on account of natural and human-induced factors. Salinization, drought and presence of heavy metals in the substratum cause substantial effect on the yield and quality of bioactive constituents in the oil. In many plants, the level and kind of stress have detrimental effects on the growth and development. This review provides an account of the studies on some common abiotic stresses to which essential oil plants are exposed during their growth period and their influence on quality and quantity of oil. The yield and quality vary in different plants and so is the response. Enhancing essential oil productivity is an important challenge, and understanding the role played by stress may offer significant advantages to the essential oil farmers and processing industry. Scientific evaluation of the data on many important but unexplored essential oil plants will also help in mitigating, ameliorating and minimizing the harmful effects caused by stress. PMID:22164806

  7. Effect of incompatibility stress on the fit of metal-ceramic crowns.

    PubMed

    Anusavice, K J; Carroll, J E

    1987-08-01

    The interactive effect of coping thickness and a positive thermal contraction mismatch between metal and porcelain on the fit of metal-ceramic crowns has not yet been experimentally determined. Previous studies have suggested that marginal distortion may be due to contraction differences, although finite element analyses indicate that these distortion effects should be negligible. The marginal gap between metal-ceramic crowns and prepared dies was determined under conditions designed to exaggerate distortion effects. These included the use of thin metal copings (0.1 and 0.2 mm), a chamfer preparation, an alloy with relatively poor creep resistance, and a large thermal contraction mismatch between the alloy and porcelain layers. Gap changes which resulted during porcelain firing cycles were relatively small, but larger marginal discrepancies developed in crowns prepared with a compatible porcelain during grinding and abrasive blasting procedures. This study conclusively demonstrates that incompatibility stress induced by a positive contraction mismatch is not a primary cause of marginal or generalized distortion of metal-ceramic crowns and suggests that external grinding and internal abrasive blasting of crowns are more likely causes of this effect. PMID:3305635

  8. A new paradigm to induce mental stress: the Sing-a-Song Stress Test (SSST)

    PubMed Central

    Brouwer, Anne-Marie; Hogervorst, Maarten A.

    2014-01-01

    We here introduce a new experimental paradigm to induce mental stress in a quick and easy way while adhering to ethical standards and controlling for potential confounds resulting from sensory input and body movements. In our Sing-a-Song Stress Test, participants are presented with neutral messages on a screen, interleaved with 1-min time intervals. The final message is that the participant should sing a song aloud after the interval has elapsed. Participants sit still during the whole procedure. We found that heart rate and skin conductance during the 1-min intervals following the sing-a-song stress message are substantially higher than during intervals following neutral messages. The order of magnitude of the rise is comparable to that achieved by the Trier Social Stress Test. Skin conductance increase correlates positively with experienced stress level as reported by participants. We also simulated stress detection in real time. When using both skin conductance and heart rate, stress is detected for 18 out of 20 participants, approximately 10 s after onset of the sing-a-song message. In conclusion, the Sing-a-Song Stress Test provides a quick, easy, controlled and potent way to induce mental stress and could be helpful in studies ranging from examining physiological effects of mental stress to evaluating interventions to reduce stress. PMID:25120425

  9. The effect of weld stresses on weld quality. [stress fields and metal cracking

    NASA Technical Reports Server (NTRS)

    Chihoski, R. A.

    1972-01-01

    A narrow heat source raises the temperature of a spot on a solid piece of material like metal. The high temperature of the spot decreases with distance from the spot. This is true whether the heat source is an arc, a flame, an electron beam, a plasma jet, a laser beam, or any other source of intense, narrowly defined heat. Stress and strain fields around a moving heat source are organized into a coherent visible system. It is shown that five stresses act across the weld line in turn as an arc passes. Their proportions and positions are considerably altered by weld parameters or condition changes. These pushes and pulls affect the metallurgical character and integrity of the weld area even when there is no apparent difference between after-the-fact examples.

  10. Environmental stress induces trinucleotide repeat mutagenesis in human cells.

    PubMed

    Chatterjee, Nimrat; Lin, Yunfu; Santillan, Beatriz A; Yotnda, Patricia; Wilson, John H

    2015-03-24

    The dynamic mutability of microsatellite repeats is implicated in the modification of gene function and disease phenotype. Studies of the enhanced instability of long trinucleotide repeats (TNRs)-the cause of multiple human diseases-have revealed a remarkable complexity of mutagenic mechanisms. Here, we show that cold, heat, hypoxic, and oxidative stresses induce mutagenesis of a long CAG repeat tract in human cells. We show that stress-response factors mediate the stress-induced mutagenesis (SIM) of CAG repeats. We show further that SIM of CAG repeats does not involve mismatch repair, nucleotide excision repair, or transcription, processes that are known to promote TNR mutagenesis in other pathways of instability. Instead, we find that these stresses stimulate DNA rereplication, increasing the proportion of cells with >4 C-value (C) DNA content. Knockdown of the replication origin-licensing factor CDT1 eliminates both stress-induced rereplication and CAG repeat mutagenesis. In addition, direct induction of rereplication in the absence of stress also increases the proportion of cells with >4C DNA content and promotes repeat mutagenesis. Thus, environmental stress triggers a unique pathway for TNR mutagenesis that likely is mediated by DNA rereplication. This pathway may impact normal cells as they encounter stresses in their environment or during development or abnormal cells as they evolve metastatic potential. PMID:25775519

  11. Environmental stress induces trinucleotide repeat mutagenesis in human cells

    PubMed Central

    Chatterjee, Nimrat; Lin, Yunfu; Santillan, Beatriz A.; Yotnda, Patricia; Wilson, John H.

    2015-01-01

    The dynamic mutability of microsatellite repeats is implicated in the modification of gene function and disease phenotype. Studies of the enhanced instability of long trinucleotide repeats (TNRs)—the cause of multiple human diseases—have revealed a remarkable complexity of mutagenic mechanisms. Here, we show that cold, heat, hypoxic, and oxidative stresses induce mutagenesis of a long CAG repeat tract in human cells. We show that stress-response factors mediate the stress-induced mutagenesis (SIM) of CAG repeats. We show further that SIM of CAG repeats does not involve mismatch repair, nucleotide excision repair, or transcription, processes that are known to promote TNR mutagenesis in other pathways of instability. Instead, we find that these stresses stimulate DNA rereplication, increasing the proportion of cells with >4 C-value (C) DNA content. Knockdown of the replication origin-licensing factor CDT1 eliminates both stress-induced rereplication and CAG repeat mutagenesis. In addition, direct induction of rereplication in the absence of stress also increases the proportion of cells with >4C DNA content and promotes repeat mutagenesis. Thus, environmental stress triggers a unique pathway for TNR mutagenesis that likely is mediated by DNA rereplication. This pathway may impact normal cells as they encounter stresses in their environment or during development or abnormal cells as they evolve metastatic potential. PMID:25775519

  12. Folate levels modulate oncogene-induced replication stress and tumorigenicity

    PubMed Central

    Lamm, Noa; Maoz, Karin; Bester, Assaf C; Im, Michael M; Shewach, Donna S; Karni, Rotem; Kerem, Batsheva

    2015-01-01

    Chromosomal instability in early cancer stages is caused by replication stress. One mechanism by which oncogene expression induces replication stress is to drive cell proliferation with insufficient nucleotide levels. Cancer development is driven by alterations in both genetic and environmental factors. Here, we investigated whether replication stress can be modulated by both genetic and non-genetic factors and whether the extent of replication stress affects the probability of neoplastic transformation. To do so, we studied the effect of folate, a micronutrient that is essential for nucleotide biosynthesis, on oncogene-induced tumorigenicity. We show that folate deficiency by itself leads to replication stress in a concentration-dependent manner. Folate deficiency significantly enhances oncogene-induced replication stress, leading to increased DNA damage and tumorigenicity in vitro. Importantly, oncogene-expressing cells, when grown under folate deficiency, exhibit a significantly increased frequency of tumor development in mice. These findings suggest that replication stress is a quantitative trait affected by both genetic and non-genetic factors and that the extent of replication stress plays an important role in cancer development. PMID:26197802

  13. Multiple Stress Signals Induce p73β Accumulation1

    PubMed Central

    Lin, Kai Wei; Nam, Shin Yuen; Toh, Wen Hong; Dulloo, Iqbal; Sabapathy, Kanaga

    2004-01-01

    Abstract Although p73 is a structural and functional homologue of the tumor-suppressor gene p53, it is not mutated in many human cancers as p53. Besides, p73 was shown to be activated by only a subset of signals that activate p53, such as γ-irradiation and cisplatin, but not by other common genotoxic stress-inducing agents such as ultraviolet (UV) irradiation, although many of these signals are also capable of inducing p53-independent cell death. Using a p73-specific antibody, we confirmed that c-Abl is required for cisplatin-induced p73 upregulation, and further demonstrate that the p73 protein is upregulated by UV irradiation and other stress stimuli including sorbitol, hydrogen peroxide, nocodazol, and taxol. These stress signals upregulate both p73 mRNA and increases the stability of p73, indicating that p73 is regulated transcriptionally and posttranslationally. Cells stably expressing the dominant-negative p73 inhibitor protein (p73DD) and p73-/- fibroblasts are more resistant than control cells to apoptosis induced by these stress signals, suggesting that p73 contributes to apoptosis induction. Together, the data demonstrate that several stress signals can signal to p73 in vivo, which raises the possibility of eradicating cancers with an unmutated p73 gene by activating them with stress-inducing agents or their mimetics. PMID:15548364

  14. Role of endoplasmic reticulum stress in drug-induced toxicity.

    PubMed

    Foufelle, Fabienne; Fromenty, Bernard

    2016-02-01

    Drug-induced toxicity is a key issue for public health because some side effects can be severe and life-threatening. These adverse effects can also be a major concern for the pharmaceutical companies since significant toxicity can lead to the interruption of clinical trials, or the withdrawal of the incriminated drugs from the market. Recent studies suggested that endoplasmic reticulum (ER) stress could be an important event involved in drug liability, in addition to other key mechanisms such as mitochondrial dysfunction and oxidative stress. Indeed, drug-induced ER stress could lead to several deleterious effects within cells and tissues including accumulation of lipids, cell death, cytolysis, and inflammation. After recalling important information regarding drug-induced adverse reactions and ER stress in diverse pathophysiological situations, this review summarizes the main data pertaining to drug-induced ER stress and its potential involvement in different adverse effects. Drugs presented in this review are for instance acetaminophen (APAP), arsenic trioxide and other anticancer drugs, diclofenac, and different antiretroviral compounds. We also included data on tunicamycin (an antibiotic not used in human medicine because of its toxicity) and thapsigargin (a toxic compound of the Mediterranean plant Thapsia garganica) since both molecules are commonly used as prototypical toxins to induce ER stress in cellular and animal models. PMID:26977301

  15. Stress-induced obesity and the emotional nervous system

    PubMed Central

    Dallman, Mary F

    2009-01-01

    Stress and emotional brain networks foster eating behaviors that may lead to obesity. The neural networks underlying the complex interactions among stressors, body, brain and food intake are now better understood. Stressors, by activating a neural stress-response network, bias cognition toward increased emotional activity and degraded executive function. This causes formed habits to be used rather than a cognitive appraisal of responses. Stress also induces secretion of both glucocorticoids, which increases motivation for food, and insulin, which promotes food intake and obesity. Pleasurable feeding then reduces activity in the stress-response network, reinforcing the feeding habit. These effects of stressors emphasize the importance of teaching mental reappraisal techniques to restore responses from habitual to thoughtful, thus battling stress-induced obesity. PMID:19926299

  16. Oxidative stress-induced autophagy: Role in pulmonary toxicity

    SciTech Connect

    Malaviya, Rama; Laskin, Jeffrey D.; Laskin, Debra L.

    2014-03-01

    Autophagy is an evolutionarily conserved catabolic process important in regulating the turnover of essential proteins and in elimination of damaged organelles and protein aggregates. Autophagy is observed in the lung in response to oxidative stress generated as a consequence of exposure to environmental toxicants. Whether autophagy plays role in promoting cell survival or cytotoxicity is unclear. In this article recent findings on oxidative stress-induced autophagy in the lung are reviewed; potential mechanisms initiating autophagy are also discussed. A better understanding of autophagy and its role in pulmonary toxicity may lead to the development of new strategies to treat lung injury associated with oxidative stress. - Highlights: • Exposure to pulmonary toxicants is associated with oxidative stress. • Oxidative stress is known to induce autophagy. • Autophagy is upregulated in the lung following exposure to pulmonary toxicants. • Autophagy may be protective or pathogenic.

  17. HCV-Induced Oxidative Stress: Battlefield-Winning Strategy

    PubMed Central

    Rebbani, Khadija; Tsukiyama-Kohara, Kyoko

    2016-01-01

    About 150 million people worldwide are chronically infected with hepatitis C virus (HCV). The persistence of the infection is controlled by several mechanisms including the induction of oxidative stress. HCV relies on this strategy to redirect lipid metabolism machinery and escape immune response. The 3β-hydroxysterol Δ24-reductase (DHCR24) is one of the newly discovered host markers of oxidative stress. This protein, as HCV-induced oxidative stress responsive protein, may play a critical role in the pathogenesis of HCV chronic infection and associated liver diseases, when aberrantly expressed. The sustained expression of DHCR24 in response to HCV-induced oxidative stress results in suppression of nuclear p53 activity by blocking its acetylation and increasing its interaction with MDM2 in the cytoplasm leading to its degradation, which may induce hepatocarcinogenesis. PMID:27293514

  18. Stress proteins are induced by space environment

    NASA Astrophysics Data System (ADS)

    Takahashi, Akihisa; Ohnishi, Takeo

    The space environment contains two major biologically significant influences such as space radiations and microgravity. Almost all organisms possess essential recognition and response systems for environmental changes. The famous one of cellular stress responses is the gene induction of heat shock protein (HSP). HSP expression is increased under elevated temperatures, and also increased by other sources of cellular stress, including ionizing radiation, oxidative injury, osmotic stress and the unfolded protein response. HSPs assist in the folding and maintenance of newly translated proteins, the refolding of denatured proteins and the further unfolding of misfolded or destabilized proteins to protect the cell from crisis. Based on our space experiment, we report the results and discussion from the viewpoint of HSP expression after exposure to space environment.

  19. Heavy Metal Induced Antibiotic Resistance in Bacterium LSJC7.

    PubMed

    Chen, Songcan; Li, Xiaomin; Sun, Guoxin; Zhang, Yingjiao; Su, Jianqiang; Ye, Jun

    2015-01-01

    Co-contamination of antibiotics and heavy metals prevails in the environment, and may play an important role in disseminating bacterial antibiotic resistance, but the selective effects of heavy metals on bacterial antibiotic resistance is largely unclear. To investigate this, the effects of heavy metals on antibiotic resistance were studied in a genome-sequenced bacterium, LSJC7. The results showed that the presence of arsenate, copper, and zinc were implicated in fortifying the resistance of LSJC7 towards tetracycline. The concentrations of heavy metals required to induce antibiotic resistance, i.e., the minimum heavy metal concentrations (MHCs), were far below (up to 64-fold) the minimum inhibition concentrations (MIC) of LSJC7. This finding indicates that the relatively low heavy metal levels in polluted environments and in treated humans and animals might be sufficient to induce bacterial antibiotic resistance. In addition, heavy metal induced antibiotic resistance was also observed for a combination of arsenate and chloramphenicol in LSJC7, and copper/zinc and tetracycline in antibiotic susceptible strain Escherichia coli DH5α. Overall, this study implies that heavy metal induced antibiotic resistance might be ubiquitous among various microbial species and suggests that it might play a role in the emergence and spread of antibiotic resistance in metal and antibiotic co-contaminated environments. PMID:26426011

  20. Heavy Metal Induced Antibiotic Resistance in Bacterium LSJC7

    PubMed Central

    Chen, Songcan; Li, Xiaomin; Sun, Guoxin; Zhang, Yingjiao; Su, Jianqiang; Ye, Jun

    2015-01-01

    Co-contamination of antibiotics and heavy metals prevails in the environment, and may play an important role in disseminating bacterial antibiotic resistance, but the selective effects of heavy metals on bacterial antibiotic resistance is largely unclear. To investigate this, the effects of heavy metals on antibiotic resistance were studied in a genome-sequenced bacterium, LSJC7. The results showed that the presence of arsenate, copper, and zinc were implicated in fortifying the resistance of LSJC7 towards tetracycline. The concentrations of heavy metals required to induce antibiotic resistance, i.e., the minimum heavy metal concentrations (MHCs), were far below (up to 64-fold) the minimum inhibition concentrations (MIC) of LSJC7. This finding indicates that the relatively low heavy metal levels in polluted environments and in treated humans and animals might be sufficient to induce bacterial antibiotic resistance. In addition, heavy metal induced antibiotic resistance was also observed for a combination of arsenate and chloramphenicol in LSJC7, and copper/zinc and tetracycline in antibiotic susceptible strain Escherichia coli DH5α. Overall, this study implies that heavy metal induced antibiotic resistance might be ubiquitous among various microbial species and suggests that it might play a role in the emergence and spread of antibiotic resistance in metal and antibiotic co-contaminated environments. PMID:26426011

  1. Juvenile stress impairs body temperature regulation and augments anticipatory stress-induced hyperthermia responses in rats.

    PubMed

    Yee, Nicole; Plassmann, Kerstin; Fuchs, Eberhard

    2011-09-01

    Clinical studies have implicated adolescence as an important and vulnerable period during which traumatic experiences can predispose individuals to anxiety and mood disorders. As such, a stress model in juvenile rats (age 27-29 d) was previously developed to investigate the long-term effects of stress exposure during adolescence on behavior and physiology. This paradigm involves exposing rats to different stressors on consecutive days over a 3-day period. Here, we studied the effects of juvenile stress on long-term core body temperature regulation and acute stress-induced hyperthermia (SIH) responses using telemetry. We found no differences between control and juvenile stress rats in anxiety-related behavior on the elevated plus maze, which we attribute to stress associated with surgical implantation of telemetry devices. This highlights the severe impact of surgical stress on the results of subsequent behavioral measurements. Nonetheless, juvenile stress disrupted the circadian rhythmicity of body temperature and decreased circadian amplitude. It also induced chronic hypothermia during the dark phase of the day, when rats are most active. When subjected to acute social defeat stress as adults, juvenile stress had no impact on the SIH response relative to controls. However, 24 h later, juvenile stress rats displayed an elevated SIH response in anticipation of social defeat when re-exposed to the social defeat environment. Taken together, our findings indicate that juvenile stress can induce long-term alterations in body temperature regulation and heighten the increase in temperature associated with anticipation of social defeat. The outcomes of behavioral measurements in these experiments, however, are severely affected by surgical stress. PMID:21557956

  2. Isolation and characterisation of cDNA encoding a wheat heavy metal-associated isoprenylated protein involved in stress responses.

    PubMed

    Zhang, X; Feng, H; Feng, C; Xu, H; Huang, X; Wang, Q; Duan, X; Wang, X; Wei, G; Huang, L; Kang, Z

    2015-11-01

    In cells, metallochaperones are important proteins that safely transport metal ions. Heavy metal-associated isoprenylated plant proteins (HIPPs) are metallochaperones that contain a metal binding domain and a CaaX isoprenylation motif at the carboxy-terminal end. To investigate the roles of wheat heavy metal-associated isoprenylated plant protein (TaHIPP) genes in plant development and in stress responses, we isolated cDNA encoding the wheat TaHIPP1 gene, which contains a heavy metal-associated domain, nuclear localisation signals and an isoprenylation motif (CaaX motif). Quantitative real-time PCR analysis indicated that the TaHIPP1 gene was differentially expressed under biotic and abiotic stresses. Specifically, TaHIPP1 expression was up-regulated by ABA exposure or wounding. Additionally, TaHIPP1 over-expression in yeast (Schizosaccharomyces pombe) significantly increased the cell growth rate under Cu(2+) and high salinity stresses. The nuclear localisation of the protein was confirmed with confocal laser scanning microscopy of epidermal onion cells after particle bombardment with chimeric TaHIPP1-GFP constructs. In addition, TaHIPP1 was shown to enhance the susceptibility of wheat to Pst as determined by virus-induced gene silencing. These data indicate that TaHIPP1 is an important component in defence signalling pathways and may play a crucial role in the defence response of wheat to biotic and certain abiotic stresses. PMID:25951496

  3. Phloroglucinol Attenuates Free Radical-induced Oxidative Stress

    PubMed Central

    So, Mi Jung; Cho, Eun Ju

    2014-01-01

    The protective role of phloroglucinol against oxidative stress and stress-induced premature senescence (SIPS) was investigated in vitro and in cell culture. Phloroglucinol had strong and concentration-dependent radical scavenging effects against nitric oxide (NO), superoxide anions (O2−), and hydroxyl radicals. In this study, free radical generators were used to induce oxidative stress in LLC-PK1 renal epithelial cells. Treatment with phloroglucinol attenuated the oxidative stress induced by peroxyl radicals, NO, O2−, and peroxynitrite. Phloroglucinol also increased cell viability and decreased lipid peroxidation in a concentration-dependent manner. WI-38 human diploid fibroblast cells were used to investigate the protective effect of phloroglucinol against hydrogen peroxide (H2O2)-induced SIPS. Phloroglucinol treatment attenuated H2O2-induced SIPS by increasing cell viability and inhibited lipid peroxidation, suggesting that treatment with phloroglucinol should delay the aging process. The present study supports the promising role of phloroglucinol as an antioxidative agent against free radical-induced oxidative stress and SIPS. PMID:25320709

  4. Angina and Mental Stress-Induced Myocardial Ischemia

    PubMed Central

    Pimple, Pratik; Shah, Amit J.; Rooks, Cherie; Bremner, J. Douglas; Nye, Jonathon; Ibeanu, Ijeoma; Raggi, Paolo; Vaccarino, Viola

    2015-01-01

    Objective Mental stress-induced myocardial ischemia is a common phenomenon in patients with coronary artery disease (CAD) and an emerging prognostic factor. Mental stress ischemia is correlated with ambulatory ischemia. However, whether it is related to angina symptoms during daily life has not been examined. Methods We assessed angina-frequency (past month) in 98 post-myocardial infarction (MI) subjects (age 18-60 years) using the Seattle Angina Questionnaire. Patients underwent [99mTc]sestamibi SPECT perfusion imaging at rest, after mental stress, and after exercise/pharmacological stress. Summed scores of perfusion abnormalities were obtained by observer-independent software. A summed-difference score (SDS), the difference between stress and rest scores, was used to quantify myocardial ischemia under both stress conditions. Results The mean age was 50 years, 50% were female and 60% were non-white. After adjustment for age, sex, smoking, CAD-severity, depressive, anger and anxiety symptoms, each 1-point increase in mental-stress SDS was associated with 1.73-unit increase in the angina-frequency score (95% CI: 0.09-3.37) and 17% higher odds of being in a higher angina-frequency category (OR: 1.17, 95% CI: 1.00-1.38). Depressive symptoms were associated with 12% higher odds of being in a higher angina-frequency category (OR: 1.12, 95% CI: 1.03-1.21). In contrast, exercise/pharmacological stress-induced SDS was not associated with angina-frequency. Conclusion Among young and middle-aged post-MI patients, myocardial ischemia induced by mental stress in the lab, but not by exercise/pharmacological stress, is associated with higher frequency of retrospectively reported angina during the day. Psychosocial stressors related to mental stress ischemia may be important contributory factor to daily angina. PMID:25727240

  5. Oxidative stress induced carbonylation in human plasma.

    PubMed

    Madian, Ashraf G; Diaz-Maldonado, Naomi; Gao, Qiang; Regnier, Fred E

    2011-10-19

    The focus of this study was on the assessment of technology that might be of clinical utility in identification, quantification, characterization of carbonylation in human plasma proteins. Carbonylation is widely associated with oxidative stress diseases. Breast cancer patient samples were chosen as a stress positive case based on the fact that oxidative stress has been reported to be elevated in this disease. Measurements of 8-isoprostane in plasma confirmed that breast cancer patients in this study were indeed experiencing significant oxidative stress. Carbonyl groups in proteins from freshly drawn blood were derivatized with biotin hydrazide after which the samples were dialyzed and the biotinylated proteins subsequently selected, digested and labeled with iTRAQ™ heavy isotope coding reagent(s). Four hundred sixty proteins were identified and quantified, 95 of which changed 1.5 fold or more in concentration. Beyond confirming the utility of the analytical method, association of protein carbonylation was examined as well. Nearly one fourth of the selected proteins were of cytoplasmic, nuclear, or membrane origin. Analysis of the data by unbiased knowledge assembly methods indicated the most likely disease associated with the proteins was breast neoplasm. Pathway analysis showed the proteins which changed in carbonylation were strongly associated with Brca1, the breast cancer type-1 susceptibility protein. Pathway analysis indicated the major molecular functions of these proteins are defense, immunity and nucleic acid binding. PMID:21856457

  6. Water deficit stress induced gene expression

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Water deficit stress is one of the most challenging agricultural issues limiting sustainable cotton production. Many efforts have been incorporated using genetic and genomic approaches to identify valuable molecular resources. In this study, we aimed to identify a global set of transcript fragments ...

  7. Oxidative stress induced carbonylation in human plasma

    PubMed Central

    Madian, Ashraf G.; Diaz-Maldonado, Naomi; Gao, Qiang; Regnier, Fred E.

    2011-01-01

    The focus of this study was on the assessment of technology that might be of clinical utility in identification, quantification, characterization of carbonylation in human plasma proteins. Carbonylation is widely associated with oxidative stress diseases. Breast cancer patient samples were chosen as a stress positive case based on the fact that oxidative stress has been reported to be elevated in this disease. Measurements of 8-isoprostane in plasma confirmed that breast cancer patients in this study were indeed experiencing significant oxidative stress. Carbonyl groups in proteins from freshly drawn blood were derivatized with biotin hydrazide after which the samples were dialyzed and the biotinylated proteins subsequently selected, digested and labeled with iTRAQ™ heavy isotope coding reagent(s). Four hundred sixty proteins were identified and quantified, 95 of which changed 1.5 fold or more in concentration. Beyond confirming the utility of the analytical method, association of protein carbonylation was examined as well. Nearly one fourth of the selected proteins were of cytoplasmic, nuclear, or membrane origin. Analysis of the data by unbiased knowledge assembly methods indicated the most likely disease associated with the proteins was breast neoplasm. Pathway analysis showed the proteins which changed in carbonylation were strongly associated with Brca1, the breast cancer type-1 susceptibility protein. Pathway analysis indicated the major molecular functions of these proteins are defense, immunity and nucleic acid binding. PMID:21856457

  8. Physiological and biochemical mechanisms associated with trehalose-induced copper-stress tolerance in rice

    PubMed Central

    Mostofa, Mohammad Golam; Hossain, Mohammad Anwar; Fujita, Masayuki; Tran, Lam-Son Phan

    2015-01-01

    In this study, we examined the possible mechanisms of trehalose (Tre) in improving copper-stress (Cu-stress) tolerance in rice seedlings. Our findings indicated that pretreatment of rice seedlings with Tre enhanced the endogenous Tre level and significantly mitigated the toxic effects of excessive Cu on photosynthesis- and plant growth-related parameters. The improved tolerance induced by Tre could be attributed to its ability to reduce Cu uptake and decrease Cu-induced oxidative damage by lowering the accumulation of reactive oxygen species (ROS) and malondialdehyde in Cu-stressed plants. Tre counteracted the Cu-induced increase in proline and glutathione content, but significantly improved ascorbic acid content and redox status. The activities of major antioxidant enzymes were largely stimulated by Tre pretreatment in rice plants exposed to excessive Cu. Additionally, increased activities of glyoxalases I and II correlated with reduced levels of methylglyoxal in Tre-pretreated Cu-stressed rice plants. These results indicate that modifying the endogenous Tre content by Tre pretreatment improved Cu tolerance in rice plants by inhibiting Cu uptake and regulating the antioxidant and glyoxalase systems, and thereby demonstrated the important role of Tre in mitigating heavy metal toxicity. Our findings provide a solid foundation for developing metal toxicity-tolerant crops by genetic engineering of Tre biosynthesis. PMID:26073760

  9. Salicylic acid-induced abiotic stress tolerance and underlying mechanisms in plants.

    PubMed

    Khan, M Iqbal R; Fatma, Mehar; Per, Tasir S; Anjum, Naser A; Khan, Nafees A

    2015-01-01

    Abiotic stresses (such as metals/metalloids, salinity, ozone, UV-B radiation, extreme temperatures, and drought) are among the most challenging threats to agricultural system and economic yield of crop plants. These stresses (in isolation and/or combination) induce numerous adverse effects in plants, impair biochemical/physiological and molecular processes, and eventually cause severe reductions in plant growth, development and overall productivity. Phytohormones have been recognized as a strong tool for sustainably alleviating adverse effects of abiotic stresses in crop plants. In particular, the significance of salicylic acid (SA) has been increasingly recognized in improved plant abiotic stress-tolerance via SA-mediated control of major plant-metabolic processes. However, the basic biochemical/physiological and molecular mechanisms that potentially underpin SA-induced plant-tolerance to major abiotic stresses remain least discussed. Based on recent reports, this paper: (a) overviews historical background and biosynthesis of SA under both optimal and stressful environments in plants; (b) critically appraises the role of SA in plants exposed to major abiotic stresses; PMID:26175738

  10. Improved Photo-Induced Stability in Amorphous Metal-Oxide Based TFTs for Transparent Displays.

    PubMed

    Koo, Sang-Mo; Ha, Tae-Jun

    2015-10-01

    In this paper, we investigate the origin of photo-induced instability in amorphous metal-oxide based thin-film transistors (oxide-TFTs) by exploring threshold voltage (Vth) shift in transfer characteristics. The combination of photo irradiation and prolonged gate bias stress enhanced the shift in Vth in amorphous hafnium-indium-zinc-oxide (a-HfIZO) TFTs. Such results stem from the extended trapped charges at the localized defect states related to oxygen vacancy which play a role in a screening effect on the electric field induced by gate voltage. We also demonstrate the chemically clean interface in oxide-TFTs by employing oxygen annealing which reduces the density of trap states, thereby resulting in improved photo-induced stability. We believe that this work stimulates the research society of transparent electronics by providing a promising approach to suppress photo-induced instability in metal-oxide TFTs. PMID:26726416

  11. Temporal pore pressure induced stress changes during injection and depletion

    NASA Astrophysics Data System (ADS)

    Müller, Birgit; Heidbach, Oliver; Schilling, Frank; Fuchs, Karl; Röckel, Thomas

    2016-04-01

    Induced seismicity is observed during injection of fluids in oil, gas or geothermal wells as a rather immediate response close to the injection wells due to the often high-rate pressurization. It was recognized even earlier in connection with more moderate rate injection of fluid waste on a longer time frame but higher induced event magnitudes. Today, injection-related induced seismicity significantly increased the number of events with M>3 in the Mid U.S. However, induced seismicity is also observed during production of fluids and gas, even years after the onset of production. E.g. in the Groningen gas field production was required to be reduced due to the increase in felt and damaging seismicity after more than 50 years of exploitation of that field. Thus, injection and production induced seismicity can cause severe impact in terms of hazard but also on economic measures. In order to understand the different onset times of induced seismicity we built a generic model to quantify the role of poro-elasticity processes with special emphasis on the factors time, regional crustal stress conditions and fault parameters for three case studies (injection into a low permeable crystalline rock, hydrothermal circulation and production of fluids). With this approach we consider the spatial and temporal variation of reservoir stress paths, the "early" injection-related induced events during stimulation and the "late" production induced ones. Furthermore, in dependence of the undisturbed in situ stress field conditions the stress tensor can change significantly due to injection and long-term production with changes of the tectonic stress regime in which previously not critically stressed faults could turn to be optimally oriented for fault reactivation.

  12. Physiological characterization of Chlamydomonas reinhardtii acclimated to chronic stress induced by Ag, Cd, Cr, Cu and Hg ions.

    PubMed

    Nowicka, Beatrycze; Pluciński, Bartosz; Kuczyńska, Paulina; Kruk, Jerzy

    2016-08-01

    Acclimation to heavy metal-induced stress is a complex phenomenon. Among the mechanisms of heavy metal toxicity, an important one is the ability to induce oxidative stress, so that the antioxidant response is crucial for providing tolerance to heavy metal ions. The effect of chronic stress induced by ions of five heavy metals, Ag, Cu, Cr (redox-active metals) Cd, Hg (nonredox-active metals) on the green microalga Chlamydomonas reinhardtii was examined at two levels - the biochemical (content of photosynthetic pigments and prenyllipid antioxidants, lipid peroxidation) and the physiological (growth rate, photosynthesis and respiration rates, induction of nonphotochemical quenching of chlorophyll fluorescence). The expression of the genes which encode the enzymes participating in the detoxification of reactive oxygen species (APX1, CAT1, FSD1, MSD1) was measured. The other gene measured was one required for plastoquinone and α-tocopherol biosynthesis (VTE3). The application of heavy metal ions partly inhibited growth and biosynthesis of chlorophyll. The growth inhibition was accompanied by enhanced lipid peroxidation. An increase in the content of prenyllipid antioxidants was observed in cultures exposed to Cr2O7(2-), Cd(2+) (α- and γ-tocopherol and plastoquinone) and Cu(2+) (only tocopherols). The induction of nonphotochemical quenching was enhanced in cultures exposed to Cu(2+), Cr2O7(2-) and Cd(2+), as compared to the control. Chronic heavy metal-induced stress led to changes in gene expression dependent on the type and concentration of heavy metal ions. The up-regulation of antioxidant enzymes was usually accompanied by the up-regulation of the VTE3 gene. PMID:27104807

  13. Analysis of thermal stresses and metal movement during welding. I - Analytical study

    NASA Technical Reports Server (NTRS)

    Muraki, T.; Masubuchi, K.; Bryan, J. J.

    1974-01-01

    This is the first part of a study of thermal stresses and metal movement during welding. This part discusses analysis of two-dimensional thermal stresses and metal movement during bead-on-plate and butt welding. A finite-element formulation has been derived, based on the variational principle. The formulation includes temperature dependence of material properties as well as the yield criterion.

  14. Gravity-induced stresses in stratified rock masses

    USGS Publications Warehouse

    Amadei, B.; Swolfs, H.S.; Savage, W.Z.

    1988-01-01

    This paper presents closed-form solutions for the stress field induced by gravity in anisotropic and stratified rock masses. These rocks are assumed to be laterally restrained. The rock mass consists of finite mechanical units, each unit being modeled as a homogeneous, transversely isotropic or isotropic linearly elastic material. The following results are found. The nature of the gravity induced stress field in a stratified rock mass depends on the elastic properties of each rock unit and how these properties vary with depth. It is thermodynamically admissible for the induced horizontal stress component in a given stratified rock mass to exceed the vertical stress component in certain units and to be smaller in other units; this is not possible for the classical unstratified isotropic solution. Examples are presented to explore the nature of the gravity induced stress field in stratified rock masses. It is found that a decrease in rock mass anisotropy and a stiffening of rock masses with depth can generate stress distributions comparable to empirical hyperbolic distributions previously proposed in the literature. ?? 1988 Springer-Verlag.

  15. Improved Stress Reliability of Analog TiHfO Metal-Insulator-Metal Capacitors Using High-Work-Function Electrode

    NASA Astrophysics Data System (ADS)

    Cheng, Chun-Hu; Chiang, Kuo-Cheng; Pan, Han-Chang; Hsiao, Chien-Nan; Chou, Chang-Pin; McAlister, Sean P.; Chin, Albert

    2007-11-01

    We have studied the reliability of high-κ (κ ˜ 49) TixHf1-xO (x ˜ 0.67) metal-insulator-metal (MIM) capacitors after constant voltage stress induction. The use of a high-work-function Ni top electrode improves not only the leakage current, and temperature- and voltage-coefficients of capacitance, but also the long-term capacitance variation after stress induction.

  16. Ethanol Induces Endoplasmic Reticulum Stress in the Developing Brain

    PubMed Central

    Ke, Zunji; Wang, Xin; Liu, Ying; Fan, Zhiqin; Chen, Gang; Xu, Mei; Bower, Kimberley A.; Frank, Jacqueline A.; Li, Mingtao; Fang, Shengyun; Shi, Xianglin; Luo, Jia

    2016-01-01

    Background Ethanol exposure during brain development causes profound damages to the central nervous system (CNS). The underlying cellular/molecular mechanisms remain unclear. The endoplasmic reticulum (ER) is involved in posttranslational protein processing and transport. The accumulation of unfolded or misfolded proteins in the ER lumen triggers ER stress, which is characterized by translational attenuation, synthesis of ER chaperone proteins, and activation of transcription factors. Sustained ER stress ultimately leads to cell death. ER stress is implicated in various neurodegenerative processes. Methods Using a third trimester equivalent mouse model of ethanol exposure, we tested the hypothesis that ethanol induces ER stress in the developing brain. Seven-day-old C57BL/6 mice were acutely exposed to ethanol by subcutaneous injection and the expression of ER stress-inducible proteins (ERSIPs) and signaling pathways associated with ER stress were examined. Results Ethanol exposure significantly increased the expression of ERSIPs and activated signaling pathways associated with ER stress; these include ATF6, CHOP/GADD153, GRP78, and mesencephalic astrocyte-derived neurotrophic factor as well as the phosphorylation of IRE1α, eIF2α, PERK, and PKR. The ethanol-induced increase in ERSIPs occurred within 4 hours of ethanol injection, and levels of some ERSIPs remained elevated after 24 hours of ethanol exposure. Ethanol-induced increase in phosphorylated eIF2α, caspase-12, and CHOP was distributed in neurons of specific areas of the cerebral cortex, hippocampus, and thalamus. Conclusions Our finding indicates that ethanol induces ER stress in immature neurons, providing novel insight into ethanol’s detrimental effect on the developing CNS. PMID:21599712

  17. Influence of engineered interfaces on residual stresses and mechanical response in metal matrix composites

    SciTech Connect

    Arnold, S.M.; Wilt, T.E.

    1992-03-01

    Because of the inherent coefficient of thermal expansion (CTE) mismatch between fiber and matrix within metal and intermetallic matrix composite systems, high residual stresses can develop under various thermal loading conditions. These conditions include cooling from processing temperature to room temperature as well as subsequent thermal cycling. As a result of these stresses, within certain composite systems, radial, circumferential, and/or longitudinal cracks have been observed to form at the fiber matrix interface region. A number of potential solutions for reducing this thermally induced residual stress field have been proposed recently. Examples of some potential solutions are high CTE fibers, fiber preheating, thermal anneal treatments, and an engineered interface. Here the focus is on designing an interface (by using a compensating/compliant layer concept) to reduce or eliminate the thermal residual stress field and, therefore, the initiation and propagation of cracks developed during thermal loading. Furthermore, the impact of the engineered interface on the composite's mechanical response when subjected to isothermal mechanical load histories is examined.

  18. Influence of engineered interfaces on residual stresses and mechanical response in metal matrix composites

    NASA Technical Reports Server (NTRS)

    Arnold, Steven M.; Wilt, Thomas E.

    1992-01-01

    Because of the inherent coefficient of thermal expansion (CTE) mismatch between fiber and matrix within metal and intermetallic matrix composite systems, high residual stresses can develop under various thermal loading conditions. These conditions include cooling from processing temperature to room temperature as well as subsequent thermal cycling. As a result of these stresses, within certain composite systems, radial, circumferential, and/or longitudinal cracks have been observed to form at the fiber matrix interface region. A number of potential solutions for reducing this thermally induced residual stress field have been proposed recently. Examples of some potential solutions are high CTE fibers, fiber preheating, thermal anneal treatments, and an engineered interface. Here the focus is on designing an interface (by using a compensating/compliant layer concept) to reduce or eliminate the thermal residual stress field and, therefore, the initiation and propagation of cracks developed during thermal loading. Furthermore, the impact of the engineered interface on the composite's mechanical response when subjected to isothermal mechanical load histories is examined.

  19. (+)-Catechin protects dermal fibroblasts against oxidative stress-induced apoptosis

    PubMed Central

    2014-01-01

    Background Oxidative stress has been suggested as a mechanism underlying skin aging, as it triggers apoptosis in various cell types, including fibroblasts, which play important roles in the preservation of healthy, youthful skin. Catechins, which are antioxidants contained in green tea, exert various actions such as anti-inflammatory, anti-bacterial, and anti-cancer actions. In this study, we investigated the effect of (+)-catechin on apoptosis induced by oxidative stress in fibroblasts. Methods Fibroblasts (NIH3T3) under oxidative stress induced by hydrogen peroxide (0.1 mM) were treated with either vehicle or (+)-catechin (0–100 μM). The effect of (+)-catechin on cell viability, apoptosis, phosphorylation of c-Jun terminal kinases (JNK) and p38, and activation of caspase-3 in fibroblasts under oxidative stress were evaluated. Results Hydrogen peroxide induced apoptotic cell death in fibroblasts, accompanied by induction of phosphorylation of JNK and p38 and activation of caspase-3. Pretreatment of the fibroblasts with (+)-catechin inhibited hydrogen peroxide-induced apoptosis and reduced phosphorylation of JNK and p38 and activation of caspase-3. Conclusion (+)-Catechin protects against oxidative stress-induced cell death in fibroblasts, possibly by inhibiting phosphorylation of p38 and JNK. These results suggest that (+)-catechin has potential as a therapeutic agent for the prevention of skin aging. PMID:24712558

  20. ER Stress-induced Aberrant Neuronal Maturation and Neurodevelopmental Disorders.

    PubMed

    Kawada, Koichi; Iekumo, Takaaki; Kaneko, Masayuki; Nomura, Yasuyuki; Okuma, Yasunobu

    2016-01-01

    Neurodevelopmental disorders, which include autism spectrum disorder, are congenital impairments in the growth and development of the central nervous system. They are mainly accentuated during infancy and childhood. Autism spectrum disorder may be caused by environmental factors, genomic imprinting of chromosome 15q11-q13 regions, and gene defects such as those in genes encoding neurexin and neuroligin, which are involved in synaptogenesis and synaptic signaling. However, regardless of the many reports on neurodevelopmental disorders, the pathogenic mechanism and treatment of neurodevelopmental disorders remain unclear. Conversely, it has been reported that endoplasmic reticulum (ER) stress is involved in neurodegenerative diseases. ER stress is increased by environmental factors such as alcohol consumption and smoking. Here we show the recent results on ER stress-induced neurodevelopmental disorders. ER stress led to a decrease in the mRNA levels of the proneural factors Hes1/5 and Pax6, which maintain an undifferentiated state of the neural cells. This stress also led to a decrease in nestin expression and an increase in beta-III tubulin expression. In addition, dendrite length was shortened by ER stress in microtubule-associated protein-2 (MAP-2) positive cells. However, the ubiquitin ligase HRD1 expression was increased by ER stress. By suppressing HRD1 expression, the ER stress-induced decrease in nestin and MAP-2 expression and increase in beta-III tubulin returned to control levels. Therefore, we suggest that ER stress induces abnormalities in neuronal differentiation and maturation via HRD1 expression. These results suggest that targeting ER stress may facilitate quicker approaches toward the prevention and treatment of neurodevelopmental disorders. PMID:27252060

  1. Mechanical Stress Induces Biotic and Abiotic Stress Responses via a Novel cis-Element

    PubMed Central

    Walley, Justin W; Coughlan, Sean; Hudson, Matthew E; Covington, Michael F; Kaspi, Roy; Banu, Gopalan; Harmer, Stacey L; Dehesh, Katayoon

    2007-01-01

    Plants are continuously exposed to a myriad of abiotic and biotic stresses. However, the molecular mechanisms by which these stress signals are perceived and transduced are poorly understood. To begin to identify primary stress signal transduction components, we have focused on genes that respond rapidly (within 5 min) to stress signals. Because it has been hypothesized that detection of physical stress is a mechanism common to mounting a response against a broad range of environmental stresses, we have utilized mechanical wounding as the stress stimulus and performed whole genome microarray analysis of Arabidopsis thaliana leaf tissue. This led to the identification of a number of rapid wound responsive (RWR) genes. Comparison of RWR genes with published abiotic and biotic stress microarray datasets demonstrates a large overlap across a wide range of environmental stresses. Interestingly, RWR genes also exhibit a striking level and pattern of circadian regulation, with induced and repressed genes displaying antiphasic rhythms. Using bioinformatic analysis, we identified a novel motif overrepresented in the promoters of RWR genes, herein designated as the Rapid Stress Response Element (RSRE). We demonstrate in transgenic plants that multimerized RSREs are sufficient to confer a rapid response to both biotic and abiotic stresses in vivo, thereby establishing the functional involvement of this motif in primary transcriptional stress responses. Collectively, our data provide evidence for a novel cis-element that is distributed across the promoters of an array of diverse stress-responsive genes, poised to respond immediately and coordinately to stress signals. This structure suggests that plants may have a transcriptional network resembling the general stress signaling pathway in yeast and that the RSRE element may provide the key to this coordinate regulation. PMID:17953483

  2. Magnetic-field-induced liquid metal droplet manipulation

    NASA Astrophysics Data System (ADS)

    Kim, Daeyoung; Lee, Jeong-Bong

    2015-01-01

    We report magnetic-field-induced liquid metal droplet on-demand manipulation by coating a liquid metal with ferromagnetic materials. The gallium-based liquid metal alloy has a challenging drawback that it is instantly oxidized in ambient air, resulting in surface wetting on most surfaces. When the oxidized surface of the droplet is coated with ferromagnetic materials, it is non-wettable and can be controlled by applying an external magnetic field. We coated the surface of a liquid metal droplet with either an electroplated CoNiMnP layer or an iron (Fe) particle by simply rolling the liquid metal droplet on an Fe particle bed. For a paper towel, the minimum required magnetic flux density to initiate movement of the ~8 μL Fe-particle-coated liquid metal droplet was 50 gauss. Magnetic-field-induced liquid metal droplet manipulation was investigated under both horizontal and vertical magnetic fields. Compared to the CoNiMnP-electroplated liquid metal droplet, the Fe-particle-coated droplet could be well controlled because Fe particles were uniformly coated on the surface of the droplet. With a maximum applied magnetic flux density of ~1,600 gauss, the CoNiMnP layer on the liquid metal broke down, resulting in fragmentation of three smaller droplets, and the Fe particle was detached from the liquid metal surface and was re-coated after the magnetic field had been removed.

  3. Copper Oxide Nanoparticles Induce Oxidative Stress and Cytotoxicity in Airway Epithelial Cells

    PubMed Central

    Fahmy, Baher; Cormier, Stephania A.

    2009-01-01

    Metal oxide nanoparticles are often used as industrial catalysts and elevated levels of these particles have been clearly demonstrated at sites surrounding factories. To date, limited toxicity data on metal oxide nanoparticles are available. To understand the impact of these airborne pollutants on the respiratory system, airway epithelial (HEp-2) cells were exposed to increasing doses of silicon oxide (SiO2), ferric oxide (Fe2O3) and copper oxide (CuO) nanoparticles, the leading metal oxides found in ambient air surrounding factories. CuO induced the greatest amount of cytotoxicity in a dose dependent manner; while even high doses (400 µg/cm2) of SiO2 and Fe2O3 were non-toxic to HEp-2 cells. Although all metal oxide nanoparticles were able to generate ROS in HEp-2 cells, CuO was better able to overwhelm antioxidant defenses (e.g. catalase and glutathione reductase). A significant increase in the level of 8-isoprostanes and in the ratio of GSSG to total glutathione in cells exposed to CuO suggested that ROS generated by CuO induced oxidative stress in HEp-2 cells. Co-treatment of cells with CuO and the antioxidant resveratrol increased cell viability suggesting that oxidative stress may be the cause of the cytotoxic effect of CuO. These studies demonstrated that there is a high degree of variability in the cytotoxic effects of metal oxides, that this variability is not due to the solubility of the transition metal, and that this variability appears to involve sustained oxidative stress possibly due to redox cycling. PMID:19699289

  4. Pneumococcal Hydrogen Peroxide–Induced Stress Signaling Regulates Inflammatory Genes

    PubMed Central

    Loose, Maria; Hudel, Martina; Zimmer, Klaus-Peter; Garcia, Ernesto; Hammerschmidt, Sven; Lucas, Rudolf; Chakraborty, Trinad; Pillich, Helena

    2015-01-01

    Microbial infections can induce aberrant responses in cellular stress pathways, leading to translational attenuation, metabolic restriction, and activation of oxidative stress, with detrimental effects on cell survival. Here we show that infection of human airway epithelial cells with Streptococcus pneumoniae leads to induction of endoplasmic reticulum (ER) and oxidative stress, activation of mitogen-associated protein kinase (MAPK) signaling pathways, and regulation of their respective target genes. We identify pneumococcal H2O2 as the causative agent for these responses, as both catalase-treated and pyruvate oxidase-deficient bacteria lacked these activities. Pneumococcal H2O2 induced nuclear NF-κB translocation and transcription of proinflammatory cytokines. Inhibition of translational arrest and ER stress by salubrinal or of MAPK signaling pathways attenuate cytokine transcription. These results provide strong evidence for the notion that inhibition of translation is an important host pathway in monitoring harmful pathogen-associated activities, thereby enabling differentiation between pathogenic and nonpathogenic bacteria. PMID:25183769

  5. Intermittent Noise Induces Physiological Stress in a Coastal Marine Fish

    PubMed Central

    Nichols, Tye A.; Anderson, Todd W.; Širović, Ana

    2015-01-01

    Anthropogenic noise in the ocean has increased substantially in recent decades, and motorized vessels produce what is likely the most common form of underwater noise pollution. Noise has the potential to induce physiological stress in marine fishes, which may have negative ecological consequences. In this study, physiological effects of increased noise (playback of boat noise recorded in the field) on a coastal marine fish (the giant kelpfish, Heterostichus rostratus) were investigated by measuring the stress responses (cortisol concentration) of fish to increased noise of various temporal dynamics and noise levels. Giant kelpfish exhibited acute stress responses when exposed to intermittent noise, but not to continuous noise or control conditions (playback of recorded natural ambient sound). These results suggest that variability in the acoustic environment may be more important than the period of noise exposure for inducing stress in a marine fish, and provide information regarding noise levels at which physiological responses occur. PMID:26402068

  6. Intermittent Noise Induces Physiological Stress in a Coastal Marine Fish.

    PubMed

    Nichols, Tye A; Anderson, Todd W; Širović, Ana

    2015-01-01

    Anthropogenic noise in the ocean has increased substantially in recent decades, and motorized vessels produce what is likely the most common form of underwater noise pollution. Noise has the potential to induce physiological stress in marine fishes, which may have negative ecological consequences. In this study, physiological effects of increased noise (playback of boat noise recorded in the field) on a coastal marine fish (the giant kelpfish, Heterostichus rostratus) were investigated by measuring the stress responses (cortisol concentration) of fish to increased noise of various temporal dynamics and noise levels. Giant kelpfish exhibited acute stress responses when exposed to intermittent noise, but not to continuous noise or control conditions (playback of recorded natural ambient sound). These results suggest that variability in the acoustic environment may be more important than the period of noise exposure for inducing stress in a marine fish, and provide information regarding noise levels at which physiological responses occur. PMID:26402068

  7. Study of inducer load and stress, volume 2

    NASA Technical Reports Server (NTRS)

    1972-01-01

    A program of analysis, design, fabrication and testing has been conducted to develop computer programs for predicting rocket engine turbopump inducer hydrodynamic loading, stress magnitude and distribution, and vibration characteristics. Methods of predicting blade loading, stress, and vibration characteristics were selected from a literature search and used as a basis for the computer programs. An inducer, representative of typical rocket engine inducers, was designed, fabricated, and tested with special instrumentation selected to provide measurements of blade surface pressures and stresses. Data from the tests were compared with predicted values and the computer programs were revised as required to improve correlation. For Volume 1 see N71-20403. For Volume 2 see N71-20404.

  8. Overlapping double etch technique for evaluation of metallic alloys to stress corrosion cracking

    DOEpatents

    Not Available

    1980-05-28

    A double overlapping etch zone technique for evaluation of the resistance of metallic alloys to stress corrosion cracking is described. The technique involves evaluating the metallic alloy along the line of demarcation between an overlapping double etch zone and single etch zone formed on the metallic alloy surface.

  9. Overlapping double etch technique for evaluation of metallic alloys to stress corrosion cracking

    DOEpatents

    Steeves, Arthur F.; Stewart, James C.

    1981-01-01

    A double overlapping etch zone technique for evaluation of the resistance of metallic alloys to stress corrosion cracking. The technique involves evaluating the metallic alloy along the line of demarcation between an overlapping double etch zone and single etch zone formed on the metallic alloy surface.

  10. Stress induced telomere shortening: longer life with less mutations?

    PubMed Central

    2014-01-01

    Background Mutations accumulate as a result of DNA damage and imperfect DNA repair machinery. In higher eukaryotes the accumulation and spread of mutations is limited in two primary ways: through p53-mediated programmed cell death and cellular senescence mediated by telomeres. Telomeres shorten at every cell division and cell stops dividing once the shortest telomere reaches a critical length. It has been shown that the rate of telomere attrition is accelerated when cells are exposed to DNA damaging agents. However the implications of this mechanism are not fully understood. Results With the help of in silico model we investigate the effect of genotoxic stress on telomere attrition and apoptosis in a population of non-identical replicating cells. When comparing the populations of cells with constant vs. stress-induced rate of telomere shortening we find that stress induced telomere shortening (SITS) increases longevity while reducing mutation rate. Interestingly, however, the effect takes place only when genotoxic stresses (e.g. reactive oxygen species due to metabolic activity) are distributed non-equally among cells. Conclusions Our results for the first time show how non-equal distribution of metabolic load (and associated genotoxic stresses) combined with stress induced telomere shortening can delay aging and minimize mutations. PMID:24580844

  11. Biomarkers of oxidative stress and metal accumulation in marsh frog (Pelophylax ridibundus).

    PubMed

    Borković-Mitić, Slavica S; Prokić, Marko D; Krizmanić, Imre I; Mutić, Jelena; Trifković, Jelena; Gavrić, Jelena; Despotović, Svetlana G; Gavrilović, Branka R; Radovanović, Tijana B; Pavlović, Slađan Z; Saičić, Zorica S

    2016-05-01

    To understand the effect of metals on the marsh frog Pelophylax ridibundus and the possible environment-induced changes in oxidative stress enzymes, we determined the concentrations of 18 metals: Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, Ga, Hg, In, Li, Mn, Ni, Pb, Sr, and Zn, in the tissues (liver, skin, and muscle) and water samples collected from different locations in Serbia. The activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR), glutathione S-transferase (GST), acetylcholinesterase (AChE), and changes in concentrations of reduced glutathione (GSH) and sulfhydryl groups (SH) were analyzed in the tissues of the sampled frogs. The concentrations of Al, Cd, Co, Cr, Cu, Fe, Ga, Hg, and Ni were highest in the liver, whereas those of Ba, Ca, Li, Mn, Pb, Sr, and Zn were highest in the skin. Hg correlated positively with liver SOD (in frogs from Danube-Tisza-Danube Canal (DTD)), muscle CAT (DTD), and muscle GST Ponjavica River (PO); Pb demonstrated a strong positive correlation with liver GR in frogs from Mt. Fruška Gora (FG); Cd only exhibited a positive correlation with AChE in the skin of frogs from DTD. In the skin, Zn correlated positively with AChE (DTD), SH groups (PO), and CAT (FG), and negatively with CAT, GST, and SH in the liver of frogs from DTD. Examination of these oxidative stress biomarkers, together with analysis of metal accumulation in the liver and skin of marsh frogs, provides a powerful tool for the assessment of metal pollution. PMID:26846240

  12. Silver nanoparticles induce endoplasmatic reticulum stress response in zebrafish

    SciTech Connect

    Christen, Verena; Capelle, Martinus; Fent, Karl

    2013-10-15

    Silver nanoparticles (AgNPs) find increasing applications, and therefore humans and the environment are increasingly exposed to them. However, potential toxicological implications are not sufficiently known. Here we investigate effects of AgNPs (average size 120 nm) on zebrafish in vitro and in vivo, and compare them to human hepatoma cells (Huh7). AgNPs are incorporated in zebrafish liver cells (ZFL) and Huh7, and in zebrafish embryos. In ZFL cells AgNPs lead to induction of reactive oxygen species (ROS), endoplasmatic reticulum (ER) stress response, and TNF-α. Transcriptional alterations also occur in pro-apoptotic genes p53 and Bax. The transcriptional profile differed in ZFL and Huh7 cells. In ZFL cells, the ER stress marker BiP is induced, concomitant with the ER stress marker ATF-6 and spliced XBP-1 after 6 h and 24 h exposure to 0.5 g/L and 0.05 g/L AgNPs, respectively. This indicates the induction of different pathways of the ER stress response. Moreover, AgNPs induce TNF-α. In zebrafish embryos exposed to 0.01, 0.1, 1 and 5 mg/L AgNPs hatching was affected and morphological defects occurred at high concentrations. ER stress related gene transcripts BiP and Synv are significantly up-regulated after 24 h at 0.1 and 5 mg/L AgNPs. Furthermore, transcriptional alterations occurred in the pro-apoptotic genes Noxa and p21. The ER stress response was strong in ZFL cells and occurred in zebrafish embryos as well. Our data demonstrate for the first time that AgNPs lead to induction of ER stress in zebrafish. The induction of ER stress can have several consequences including the activation of apoptotic and inflammatory pathways. - Highlights: • Effects of silver nanoparticles (120 nm AgNPs) are investigated in zebrafish. • AgNPs induce all ER stress reponses in vitro in zebrafish liver cells. • AgNPs induce weak ER stress in zebrafish embryos. • AgNPs induce oxidative stress and transcripts of pro-apoptosis genes.

  13. Ionic imbalance induced self-propulsion of liquid metals

    PubMed Central

    Zavabeti, Ali; Daeneke, Torben; Chrimes, Adam F.; O'Mullane, Anthony P.; Zhen Ou, Jian; Mitchell, Arnan; Khoshmanesh, Khashayar; Kalantar-zadeh, Kourosh

    2016-01-01

    Components with self-propelling abilities are important building blocks of small autonomous systems and the characteristics of liquid metals are capable of fulfilling self-propulsion criteria. To date, there has been no exploration regarding the effect of electrolyte ionic content surrounding a liquid metal for symmetry breaking that generates motion. Here we show the controlled actuation of liquid metal droplets using only the ionic properties of the aqueous electrolyte. We demonstrate that pH or ionic concentration gradients across a liquid metal droplet induce both deformation and surface Marangoni flow. We show that the Lippmann dominated deformation results in maximum velocity for the self-propulsion of liquid metal droplets and illustrate several key applications, which take advantage of such electrolyte-induced motion. With this finding, it is possible to conceive the propulsion of small entities that are constructed and controlled entirely with fluids, progressing towards more advanced soft systems. PMID:27488954

  14. Ionic imbalance induced self-propulsion of liquid metals

    NASA Astrophysics Data System (ADS)

    Zavabeti, Ali; Daeneke, Torben; Chrimes, Adam F.; O'Mullane, Anthony P.; Zhen Ou, Jian; Mitchell, Arnan; Khoshmanesh, Khashayar; Kalantar-Zadeh, Kourosh

    2016-08-01

    Components with self-propelling abilities are important building blocks of small autonomous systems and the characteristics of liquid metals are capable of fulfilling self-propulsion criteria. To date, there has been no exploration regarding the effect of electrolyte ionic content surrounding a liquid metal for symmetry breaking that generates motion. Here we show the controlled actuation of liquid metal droplets using only the ionic properties of the aqueous electrolyte. We demonstrate that pH or ionic concentration gradients across a liquid metal droplet induce both deformation and surface Marangoni flow. We show that the Lippmann dominated deformation results in maximum velocity for the self-propulsion of liquid metal droplets and illustrate several key applications, which take advantage of such electrolyte-induced motion. With this finding, it is possible to conceive the propulsion of small entities that are constructed and controlled entirely with fluids, progressing towards more advanced soft systems.

  15. Ionic imbalance induced self-propulsion of liquid metals.

    PubMed

    Zavabeti, Ali; Daeneke, Torben; Chrimes, Adam F; O'Mullane, Anthony P; Zhen Ou, Jian; Mitchell, Arnan; Khoshmanesh, Khashayar; Kalantar-Zadeh, Kourosh

    2016-01-01

    Components with self-propelling abilities are important building blocks of small autonomous systems and the characteristics of liquid metals are capable of fulfilling self-propulsion criteria. To date, there has been no exploration regarding the effect of electrolyte ionic content surrounding a liquid metal for symmetry breaking that generates motion. Here we show the controlled actuation of liquid metal droplets using only the ionic properties of the aqueous electrolyte. We demonstrate that pH or ionic concentration gradients across a liquid metal droplet induce both deformation and surface Marangoni flow. We show that the Lippmann dominated deformation results in maximum velocity for the self-propulsion of liquid metal droplets and illustrate several key applications, which take advantage of such electrolyte-induced motion. With this finding, it is possible to conceive the propulsion of small entities that are constructed and controlled entirely with fluids, progressing towards more advanced soft systems. PMID:27488954

  16. Aneuploidy-induced cellular stresses limit autophagic degradation

    PubMed Central

    Santaguida, Stefano; Vasile, Eliza; White, Eileen; Amon, Angelika

    2015-01-01

    An unbalanced karyotype, a condition known as aneuploidy, has a profound impact on cellular physiology and is a hallmark of cancer. Aneuploid cells experience a number of stresses that are caused by aneuploidy-induced proteomic changes. How the aneuploidy-associated stresses affect cells and whether cells respond to them are only beginning to be understood. Here we show that autophagosomal cargo such as protein aggregates accumulate within lysosomes in aneuploid cells. This causes a lysosomal stress response. Aneuploid cells activate the transcription factor TFEB, a master regulator of autophagic and lysosomal gene expression, thereby increasing the expression of genes needed for autophagy-mediated protein degradation. Accumulation of autophagic cargo within the lysosome and activation of TFEB-responsive genes are also observed in cells in which proteasome function is inhibited, suggesting that proteotoxic stress causes TFEB activation. Our results reveal a TFEB-mediated lysosomal stress response as a universal feature of the aneuploid state. PMID:26404941

  17. Calculation of radiation-induced creep and stress relaxation

    NASA Astrophysics Data System (ADS)

    Nagakawa, Johsei

    1995-08-01

    Numerical calculation based on a computer simulation of point defect kinetics under stress was performed to predict radiation-induced deformation in an Inconel X-750 bolt in a LWR core and for a 316 stainless steel blanket in experimental fusion reactors with the water-coolant scenario. Although the displacement rate is rather low, modest irradiation creep with nearly linear stress dependence was predicted below 200 MPa at 300°C in the LWR core. This low stress dependence causes significant stress relaxation, which coincides with the experimental data to 2 dpa. An almost equal amount of enhanced irradiation creep strain was predicted at 60°C in both solution annealed and cold worker 316 stainless steel in the water-cooled blanket. The stress relaxation is practically not expected without irradiation in both the cases, but the calculation predicts that it is definitely expected under irradiation.

  18. Tau protein is essential for stress-induced brain pathology.

    PubMed

    Lopes, Sofia; Vaz-Silva, João; Pinto, Vitor; Dalla, Christina; Kokras, Nikolaos; Bedenk, Benedikt; Mack, Natalie; Czisch, Michael; Almeida, Osborne F X; Sousa, Nuno; Sotiropoulos, Ioannis

    2016-06-28

    Exposure to chronic stress is frequently accompanied by cognitive and affective disorders in association with neurostructural adaptations. Chronic stress was previously shown to trigger Alzheimer's-like neuropathology, which is characterized by Tau hyperphosphorylation and missorting into dendritic spines followed by memory deficits. Here, we demonstrate that stress-driven hippocampal deficits in wild-type mice are accompanied by synaptic missorting of Tau and enhanced Fyn/GluN2B-driven synaptic signaling. In contrast, mice lacking Tau [Tau knockout (Tau-KO) mice] do not exhibit stress-induced pathological behaviors and atrophy of hippocampal dendrites or deficits of hippocampal connectivity. These findings implicate Tau as an essential mediator of the adverse effects of stress on brain structure and function. PMID:27274066

  19. Gravity-induced stresses near a vertical cliff

    USGS Publications Warehouse

    Savage, W.Z.

    1993-01-01

    The exact solution for gravity-induced stresses beneath a vertical cliff presented here has application to the design of cut slopes in rock, compares favorably with published photoelastic and finite-element results for this problem, and satisfies the condition that shear and normal stresses vanish on the ground surface, except at the bottom corner where stress concentrations exist. The solution predicts that horizontal stresses are tensile away from the bottom of the cliff-effects caused by movement below the cliff in response to the gravity loading of the cliff. Also, it is shown that along the top of the cliff normal stresses reduce to those predicted for laterally constrained flat-lying topography. ?? 1993.

  20. OGG1 is essential in oxidative stress induced DNA demethylation.

    PubMed

    Zhou, Xiaolong; Zhuang, Ziheng; Wang, Wentao; He, Lingfeng; Wu, Huan; Cao, Yan; Pan, Feiyan; Zhao, Jing; Hu, Zhigang; Sekhar, Chandra; Guo, Zhigang

    2016-09-01

    DNA demethylation is an essential cellular activity to regulate gene expression; however, the mechanism that triggers DNA demethylation remains unknown. Furthermore, DNA demethylation was recently demonstrated to be induced by oxidative stress without a clear molecular mechanism. In this manuscript, we demonstrated that 8-oxoguanine DNA glycosylase-1 (OGG1) is the essential protein involved in oxidative stress-induced DNA demethylation. Oxidative stress induced the formation of 8-oxoguanine (8-oxoG). We found that OGG1, the 8-oxoG binding protein, promotes DNA demethylation by interacting and recruiting TET1 to the 8-oxoG lesion. Downregulation of OGG1 makes cells resistant to oxidative stress-induced DNA demethylation, while over-expression of OGG1 renders cells susceptible to DNA demethylation by oxidative stress. These data not only illustrate the importance of base excision repair (BER) in DNA demethylation but also reveal how the DNA demethylation signal is transferred to downstream DNA demethylation enzymes. PMID:27251462

  1. Stress Induces Pain Transition by Potentiation of AMPA Receptor Phosphorylation

    PubMed Central

    Li, Changsheng; Yang, Ya; Liu, Sufang; Fang, Huaqiang; Zhang, Yong; Furmanski, Orion; Skinner, John; Xing, Ying; Johns, Roger A.

    2014-01-01

    Chronic postsurgical pain is a serious issue in clinical practice. After surgery, patients experience ongoing pain or become sensitive to incident, normally nonpainful stimulation. The intensity and duration of postsurgical pain vary. However, it is unclear how the transition from acute to chronic pain occurs. Here we showed that social defeat stress enhanced plantar incision-induced AMPA receptor GluA1 phosphorylation at the Ser831 site in the spinal cord and greatly prolonged plantar incision-induced pain. Interestingly, targeted mutation of the GluA1 phosphorylation site Ser831 significantly inhibited stress-induced prolongation of incisional pain. In addition, stress hormones enhanced GluA1 phosphorylation and AMPA receptor-mediated electrical activity in the spinal cord. Subthreshold stimulation induced spinal long-term potentiation in GluA1 phosphomimetic mutant mice, but not in wild-type mice. Therefore, spinal AMPA receptor phosphorylation contributes to the mechanisms underlying stress-induced pain transition. PMID:25297100

  2. [Physiological responses of tubificidae to heavy metal chromium stress].

    PubMed

    Lou, Ju-Qing; Yang, Dong-Ye; Cao, Yong-Qing; Sun, Pei-De; Zheng, Ping

    2014-11-01

    Tubificidae is now used in the wastewater treatment systems to successfully minimize the sludge production, which has been proved an effective, economical and sustainable technology. But the excess sludge inevitably contains a variety of heavy metals, especially the sludge from industrial wastewater treatment plant. In order to apply tubificidae to these systems, Chromium was selected as pollutant object and the physiological responses of tubificidae to Chromium were studied in this paper. Acute toxicity was analyzed and Median lethal concentrations (LC50) were determined over 96 h periods for Cr. Results indicated that 24 h LC50 and 96 h LC50 were 7.94 mg x L(-1) and 0.49 mg x L(-1), respectively. The duration f tubificidae in Cr solution decreased with increasing Cr concentration. Under the Cr stress, a highest respiration rate was obtained when the concentration of Cr(VI), temperature, pH and DO was 2.50 mg x L(-1), 26 degrees C, 6.0 and 6.0 mg x L(-1), respectively. The order of these factors was the concerntration of Cr(VI), temperature, DO and pH. The respiration experiments demonstrated that low concentration (< 2.50 mg x L(-1)) of Cr could promote the respiration rate of tubificidaes. On the other hand, when the concentration of Cr was 8.00 mg x L(-1), it could remarkably inhibit the respiratory rates of tubificidae. PMID:25639096

  3. Asg1 is a stress-inducible gene which increases stomatal resistance in salt stressed potato.

    PubMed

    Batelli, Giorgia; Massarelli, Immacolata; Van Oosten, Michael; Nurcato, Roberta; Vannini, Candida; Raimondi, Giampaolo; Leone, Antonella; Zhu, Jian-Kang; Maggio, Albino; Grillo, Stefania

    2012-12-15

    The identification of critical components in plant salt stress adaptation has greatly benefitted, in the last two decades, from fundamental discoveries in Arabidopsis and close model systems. Nevertheless, this approach has also highlighted a non-complete overlap between stress tolerance mechanisms in Arabidopsis and agricultural crops. Within a long-running research program aimed at identifying salt stress genetic determinants in potato by functional screening in Escherichia coli, we isolated Asg1, a stress-related gene with an unknown function. Asg1 is induced by salt stress in both potato and Arabidopsis and by abscisic acid in Arabidopsis. Asg1 is actively transcribed in all plant tissues. Furthermore, Asg1 promoter analysis confirmed its ubiquitous expression, which was remarkable in pollen, a plant tissue that undergoes drastic dehydration/hydration processes. Fusion of Asg1 with green fluorescent protein showed that the encoded protein is localized close to the plasma membrane with a non-continuous pattern of distribution. In addition, Arabidopsis knockout asg1 mutants were insensitive to both NaCl and sugar hyperosmotic environments during seed germination. Transgenic potato plants over-expressing the Asg1 gene revealed a stomatal hypersensitivity to NaCl stress which, however, did not result in a significantly improved tuber yield in stress conditions. Altogether, these data suggest that Asg1 might interfere with components of the stress signaling pathway by promoting stomatal closure and participating in stress adaptation. PMID:22854180

  4. Asg1 is a stress-inducible gene which increases stomatal resistance in salt stressed potato

    PubMed Central

    Batelli, Giorgia; Massarelli, Immacolata; Van Oosten, Michael; Nurcato, Roberta; Vannini, Candida; Raimondi, Giampaolo; Leone, Antonella; Zhu, Jian-Kang; Maggio, Albino; Grillo, Stefania

    2013-01-01

    The identification of critical components in plant salt stress adaptation has greatly benefitted, in the last two decades, from fundamental discoveries in Arabidopsis and close model systems. Nevertheless, this approach has also highlighted a non-complete overlap between stress tolerance mechanisms in Arabidopsis and agricultural crops. Within a long-running research program aimed at identifying salt stress genetic determinants in potato by functional screening in Escherichia coli, we isolated Asg1, a stress-related gene with an unknown function. Asg1 is induced by salt stress in both potato and Arabidopsis and by abscisic acid in Arabidopsis. Asg1 is actively transcribed in all plant tissues. Furthermore, Asg1 promoter analysis confirmed its ubiquitous expression, which was remarkable in pollen, a plant tissue that undergoes drastic dehydration/hydration processes. Fusion of Asg1 with green fluorescent protein showed that the encoded protein is localized close to the plasma membrane with a non-continuous pattern of distribution. In addition, Arabidopsis knockout asg1 mutants were insensitive to both NaCl and sugar hyperosmotic environments during seed germination. Transgenic potato plants over-expressing the Asg1 gene revealed a stomatal hypersensitivity to NaCl stress which, however, did not result in a significantly improved tuber yield in stress conditions. Altogether, these data suggest that Asg1 might interfere with components of the stress signaling pathway by promoting stomatal closure and participating in stress adaptation. PMID:22854180

  5. Endoplasmic reticulum stress and oxidative stress are involved in ZnO nanoparticle-induced hepatotoxicity

    PubMed Central

    Yang, Xia; Shao, Huali; Liu, Weirong; Gu, Weizhong; Shu, Xiaoli; Mo, Yiqun; Chen, Xuejun; Zhang, Qunwei; Jiang, Mizu

    2015-01-01

    Zinc oxide nanoparticles (Nano-ZnO) are widely used in sunscreens, clothes, medicine and electronic devices. However, the potential risks of human exposure and the potential for adverse health impacts are not well understood. Previous studies have demonstrated that exposure to Nano-ZnO caused liver damage and hepatocyte apoptosis through oxidative stress, but the molecular mechanisms that are involved in Nano-ZnO-induced hepatotoxicity are still unclear. Endoplasmic reticulum (ER) is sensitive to oxidative stress, and also plays a crucial role in oxidative stress-induced damage. Previous studies showed that ER stress was involved in many chemical-induced liver injuries. We hypothesized that exposure to Nano-ZnO caused oxidative stress and ER stress that were involved in Nano-ZnO-induced liver injury. To test our hypothesis, mice were gavaged with 200 mg/kg or 400 mg/kg of Nano-ZnO once a day for a period of 90 days, and blood and liver tissues were obtained for study. Our results showed that exposure to Nano-ZnO caused liver injury that was reflected by focal hepatocellular necrosis, congestive dilation of central veins, and significantly increased alanine transaminase (ALT) and aspartate transaminase (AST) levels. Exposure to Nano-ZnO also caused depletion of glutathione (GSH) the liver tissues. In addition, our electron microscope results showed that ER swelling and ribosomal degranulation were observed in the liver tissues from mice treated with Nano-ZnO. The mRNA expression levels of ER stress-associated genes (grp78, grp94, pdi-3, xbp-1) were also up-regulated in Nano-ZnO-treated mice. Nano-ZnO caused increased phosphorylation of RNA-dependent protein kinase-like ER kinase (PERK) and eukaryotic initiation factor 2α (eIF2α). Finally, we found that exposure to Nano-ZnO caused increased ER stress-associated apoptotic protein levels, such as caspase-3, caspase-9, caspase-12, phosphorylation of JNK, and CHOP/GADD153, and up-regulation of pro-apoptotic genes (chop

  6. Association between Anger and Mental Stress-Induced Myocardial Ischemia

    PubMed Central

    Pimple, Pratik; Shah, Amit; Rooks, Cherie; Bremner, J. Douglas; Nye, Jonathon; Ibeanu, Ijeoma; Murrah, Nancy; Shallenberger, Lucy; Kelley, Mary; Raggi, Paolo; Vaccarino, Viola

    2014-01-01

    Background Mental stress-induced myocardial ischemia is associated with adverse prognosis in coronary artery disease patients. Anger is thought to be a trigger of acute coronary syndromes and is associated with increased cardiovascular risk; however, little direct evidence exists for a link between anger and myocardial ischemia. Methods [99mTc]sestamibi single-photon emission tomography was performed at rest, after mental stress (a social stressor with a speech task), and after exercise/pharmacological stress. Summed scores of perfusion abnormalities were obtained by observer-independent software. A summed difference score, the difference between stress and rest scores, was used to quantify myocardial ischemia under both stress conditions. The Spielberger's State-Trait Anger Expression Inventory was used to assess different anger dimensions. Results The mean age was 50 years, 50% were female and 60% were non-white. After adjusting for demographic factors, smoking, coronary artery disease severity, depressive and anxiety symptoms, each interquartile range increment in state-anger score was associated with 0.36 units adjusted increase in ischemia as measured by the summed difference score (95% CI: 0.14-0.59); the corresponding association for trait-anger was 0.95 (95% CI: 0.21-1.69). Anger expression scales were not associated ischemia. None of the anger dimensions were related to ischemia during exercise/pharmacological stress. Conclusion Anger, both as an emotional state and as a personality trait, is significantly associated with propensity to develop myocardial ischemia during mental stress, but not during exercise/pharmacological stress. Patients with this psychological profile may be at increased risk for silent ischemia induced by emotional stress and this may translate into worse prognosis. PMID:25497256

  7. Oxidative stress induces mitochondrial fragmentation in frataxin-deficient cells

    SciTech Connect

    Lefevre, Sophie; Sliwa, Dominika; Rustin, Pierre; Camadro, Jean-Michel; Santos, Renata

    2012-02-10

    Highlights: Black-Right-Pointing-Pointer Yeast frataxin-deficiency leads to increased proportion of fragmented mitochondria. Black-Right-Pointing-Pointer Oxidative stress induces complete mitochondrial fragmentation in {Delta}yfh1 cells. Black-Right-Pointing-Pointer Oxidative stress increases mitochondrial fragmentation in patient fibroblasts. Black-Right-Pointing-Pointer Inhibition of mitochondrial fission in {Delta}yfh1 induces oxidative stress resistance. -- Abstract: Friedreich ataxia (FA) is the most common recessive neurodegenerative disease. It is caused by deficiency in mitochondrial frataxin, which participates in iron-sulfur cluster assembly. Yeast cells lacking frataxin ({Delta}yfh1 mutant) showed an increased proportion of fragmented mitochondria compared to wild-type. In addition, oxidative stress induced complete fragmentation of mitochondria in {Delta}yfh1 cells. Genetically controlled inhibition of mitochondrial fission in these cells led to increased resistance to oxidative stress. Here we present evidence that in yeast frataxin-deficiency interferes with mitochondrial dynamics, which might therefore be relevant for the pathophysiology of FA.

  8. Stress stimulus induced resistance to Cladosporium cucumerinum in cucumber seeding.

    PubMed

    Zhao, Huan; Wang, Bo-Chu; Zhao, Hu-Cheng; Wang, Jing Bo

    2005-07-25

    Up to date, the studies of plant induced resistance have become the focus in plant pathology and physiology. During the course of pathogens penetrating the plant cell, besides of chemical secretion, the pathogens may generate mechanical signal caused by the physical pressure on the plant cell. In the non-host resistance, both the chemical signal and the mechanical stress signal are considered to have contribution to the entire defense reaction acted by the plant. The penetration of pathogen Cladosporium cucumerinum to cucumber is thought to be one of the model in research of plant induced resistance. In the current study, as a mechanical signal elicitor, the appropriate stress stimulus was proved to effectually induce the resistance of cucumber seedling to C. cucumerinum. After the treatment of the stress stimulus on leaves, the activities of resistance-related enzymes were significantly increased, such as phenylanine ammonia lyase (PAL), peroxidase (POD). Also, we found that stress stimulation may cause synthesis of lignin, which acts as the physical barrier to defense the pathogens. The results suggest that stress stimulation may not only enhance ability of the plant cell resistance to pathogen penetration but also elicit the accumulation of pathogens suppression or antimicrobial chemical substance in the plant cell. PMID:16002268

  9. Activation of the hypothalamic-pituitary-adrenal stress axis induces cellular oxidative stress

    PubMed Central

    Spiers, Jereme G.; Chen, Hsiao-Jou Cortina; Sernia, Conrad; Lavidis, Nickolas A.

    2015-01-01

    Glucocorticoids released from the adrenal gland in response to stress-induced activation of the hypothalamic-pituitary-adrenal (HPA) axis induce activity in the cellular reduction-oxidation (redox) system. The redox system is a ubiquitous chemical mechanism allowing the transfer of electrons between donor/acceptors and target molecules during oxidative phosphorylation while simultaneously maintaining the overall cellular environment in a reduced state. The objective of this review is to present an overview of the current literature discussing the link between HPA axis-derived glucocorticoids and increased oxidative stress, particularly focussing on the redox changes observed in the hippocampus following glucocorticoid exposure. PMID:25646076

  10. Diaphragmatic breathing reduces exercise-induced oxidative stress.

    PubMed

    Martarelli, Daniele; Cocchioni, Mario; Scuri, Stefania; Pompei, Pierluigi

    2011-01-01

    Diaphragmatic breathing is relaxing and therapeutic, reduces stress, and is a fundamental procedure of Pranayama Yoga, Zen, transcendental meditation and other meditation practices. Analysis of oxidative stress levels in people who meditate indicated that meditation correlates with lower oxidative stress levels, lower cortisol levels and higher melatonin levels. It is known that cortisol inhibits enzymes responsible for the antioxidant activity of cells and that melatonin is a strong antioxidant; therefore, in this study, we investigated the effects of diaphragmatic breathing on exercise-induced oxidative stress and the putative role of cortisol and melatonin hormones in this stress pathway. We monitored 16 athletes during an exhaustive training session. After the exercise, athletes were divided in two equivalent groups of eight subjects. Subjects of the studied group spent 1 h relaxing performing diaphragmatic breathing and concentrating on their breath in a quiet place. The other eight subjects, representing the control group, spent the same time sitting in an equivalent quite place. Results demonstrate that relaxation induced by diaphragmatic breathing increases the antioxidant defense status in athletes after exhaustive exercise. These effects correlate with the concomitant decrease in cortisol and the increase in melatonin. The consequence is a lower level of oxidative stress, which suggests that an appropriate diaphragmatic breathing could protect athletes from long-term adverse effects of free radicals. PMID:19875429