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Sample records for accelerated stress conditions

  1. Influence of Accelerated Cooling Condition on Welding Thermal Cycle, Residual Stress, and Deformation in SM490A Steel ESW Joint

    NASA Astrophysics Data System (ADS)

    Deng, Dean; Sun, Jiamin; Dai, Deping; Jiang, Xiaohua

    2015-09-01

    Electro-slag welding (ESW) has been widely used to join the box column because of high productivity. The heat input of ESW is far larger than those of other fusion welding processes, so ESW usually results in a long holding time over certain elevated temperature (∆ t H time), a long cooling time from 800 to 500 °C (∆ t 8/5 time), and a wide heat-affected zone (HAZ). It can be foreseen that the mechanical properties especially fracture toughness of the fusion zone and HAZ will be inferior to those of base metal. As a fundamental research, a computational approach based on MSC.Marc code was developed to simulate the thermo-mechanical behaviors in a typical SM490A steel ESW joint under different cooling conditions. Meanwhile, the thermal cycles computed by numerical model were compared with the experimental measurements. Moreover, the influence of accelerated cooling methods on welding residual stress and deformation was examined numerically. Simulation results show that accelerated cooling methods not only can largely shorten ∆ t H time as well as ∆ t 8/5 time and reduce the size of HAZ, but also can affect the residual stress distribution and deformation. It is believed that the accelerated cooling methods proposed by this study potentially improve the mechanical properties of ESW joint.

  2. Membrane Degradation Accelerated Stress Test

    SciTech Connect

    Mukundan, Rangachary; Borup, Rodney L.

    2015-01-21

    These are a set of slides that deal with membrane degradation accelerated stress test. Specifically, the following topics are covered: membrane degradation FCTT drive cycle; membrane ASTs; current membrane ASTs damage mechanisms; proposed membrane AST, RH cycling in H2/Air; current proposed AST; 2min/2min AST damage mechanism; 30sec/45sec RH cycling at OCV.

  3. A study on task difficulty and acceleration stress

    NASA Technical Reports Server (NTRS)

    Repperger, D. W.; Rogers, D. B.

    1981-01-01

    The results of two experiments which relate to task difficulty and the effects of environmental stress on tracking performance are discussed and compared to subjective evaluations. The first experiment involved five different sum of sine tracking tasks which humans tracked both in a static condition and under a 5 Gz acceleration stress condition. The second experiment involved similar environmental stress conditions but in this case the tasks were constructed from deterministic functions with specially designed velocity and acceleration profiles. Phase Plane performance analysis was conducted to study potential measures of workload or tracking difficulty.

  4. Acceleration of degradation by highly accelerated stress test and air-included highly accelerated stress test in crystalline silicon photovoltaic modules

    NASA Astrophysics Data System (ADS)

    Suzuki, Soh; Tanahashi, Tadanori; Doi, Takuya; Masuda, Atsushi

    2016-02-01

    We examined the effects of hyper-hygrothermal stresses with or without air on the degradation of crystalline silicon (c-Si) photovoltaic (PV) modules, to shorten the required duration of a conventional hygrothermal-stress test [i.e., the “damp heat (DH) stress test”, which is conducted at 85 °C/85% relative humidity for 1,000 h]. Interestingly, the encapsulant within a PV module becomes discolored under the air-included hygrothermal conditions achieved using DH stress test equipment and an air-included highly accelerated stress test (air-HAST) apparatus, but not under the air-excluded hygrothermal conditions realized using a highly accelerated stress test (HAST) machine. In contrast, the reduction in the output power of the PV module is accelerated irrespective of air inclusion in hyper-hygrothermal test atmosphere. From these findings, we conclude that the required duration of the DH stress test will at least be significantly shortened using air-HAST, but not HAST.

  5. Traumatic stress, oxidative stress and posttraumatic stress disorder: neurodegeneration and the accelerated-aging hypothesis

    PubMed Central

    Miller, Mark W.; Sadeh, Naomi

    2014-01-01

    Posttraumatic stress disorder (PTSD) is associated with elevated risk for a variety of age-related diseases and neurodegeneration. In this paper, we review evidence relevant to the hypothesis that chronic PTSD constitutes a form of persistent life stress that potentiates oxidative stress (OXS) and accelerates cellular aging. We provide an overview of empirical studies that have examined the effects of psychological stress on OXS, discuss the stress-perpetuating characteristics of PTSD, and then identify mechanisms by which PTSD might promote OXS and accelerated aging. We review studies on OXS-related genes and the role that they may play in moderating the effects of PTSD on neural integrity and conclude with a discussion of directions for future research on antioxidant treatments and biomarkers of accelerated aging in PTSD. PMID:25245500

  6. Accelerated glass reaction under PCT conditions

    SciTech Connect

    Ebert, W.L.; Bates, J.K.; Buck, E.C.; Bradley, C.R.

    1992-01-01

    Static leach tests similar to PCT (Product Consistency Test) were performed for up to 2 years to assess long-term reaction behavior of high-level nuclear waste glasses similar to those at Defense Waste Processing Facility. These tests show the reaction rate to decrease with the reaction time from an initially high rate to a low rate, but then to accelerate to a higher rate after reaction times of about 1 year, depending on glass surface area/leachant volume ratio used. Solution concentrations of soluble glass components increase as the reaction is accelerated, while release of other glass components into solution is controlled by secondary phases. Net result is that transformation of glass to stable phases is accelerated while the solution becomes enriched in soluble components not effectively contained in secondary phases. Rate becomes linear in time after the acceleration and may be similar to the initial forward rate. A current model of glass reaction predicts that the glass reaction will be accelerated upon the formation of secondary phases which lower the silicic acid solution concentration. These tests show total Si concentration to increase upon reaction acceleration, however, which may be due to the slightly higher pH attained with the acceleration. The sudden change in the reaction rate is likely due to secondary phase formation. 17 refs, 2 tabs, 3 figs.

  7. Accelerated glass reaction under PCT conditions

    SciTech Connect

    Ebert, W.L.; Bates, J.K.; Buck, E.C.; Bradley, C.R.

    1992-12-31

    Static leach tests similar to PCT (Product Consistency Test) were performed for up to 2 years to assess long-term reaction behavior of high-level nuclear waste glasses similar to those at Defense Waste Processing Facility. These tests show the reaction rate to decrease with the reaction time from an initially high rate to a low rate, but then to accelerate to a higher rate after reaction times of about 1 year, depending on glass surface area/leachant volume ratio used. Solution concentrations of soluble glass components increase as the reaction is accelerated, while release of other glass components into solution is controlled by secondary phases. Net result is that transformation of glass to stable phases is accelerated while the solution becomes enriched in soluble components not effectively contained in secondary phases. Rate becomes linear in time after the acceleration and may be similar to the initial forward rate. A current model of glass reaction predicts that the glass reaction will be accelerated upon the formation of secondary phases which lower the silicic acid solution concentration. These tests show total Si concentration to increase upon reaction acceleration, however, which may be due to the slightly higher pH attained with the acceleration. The sudden change in the reaction rate is likely due to secondary phase formation. 17 refs, 2 tabs, 3 figs.

  8. Step-Stress Accelerated Degradation Testing for Solar Reflectors: Preprint

    SciTech Connect

    Jones, W.; Elmore, R.; Lee, J.; Kennedy, C.

    2011-09-01

    To meet the challenge to reduce the cost of electricity generated with concentrating solar power (CSP) new low-cost reflector materials are being developed including metalized polymer reflectors and must be tested and validated against appropriate failure mechanisms. We explore the application of testing methods and statistical inference techniques for quantifying estimates and improving lifetimes of concentrating solar power (CSP) reflectors associated with failure mechanisms initiated by exposure to the ultraviolet (UV) part of the solar spectrum. In general, a suite of durability and reliability tests are available for testing a variety of failure mechanisms where the results of a set are required to understand overall lifetime of a CSP reflector. We will focus on the use of the Ultra-Accelerated Weathering System (UAWS) as a testing device for assessing various degradation patterns attributable to accelerated UV exposure. Depending on number of samples, test conditions, degradation and failure patterns, test results may be used to derive insight into failure mechanisms, associated physical parameters, lifetimes and uncertainties. In the most complicated case warranting advanced planning and statistical inference, step-stress accelerated degradation (SSADT) methods may be applied.

  9. Off-normal and failure condition analysis of the MITICA negative-ion accelerator

    NASA Astrophysics Data System (ADS)

    Chitarin, Giuseppe; Agostinetti, Piero; Aprile, Daniele; Marconato, Nicolò; Marcuzzi, Diego; Serianni, Gianluigi; Veltri, Pierluigi; Zaccaria, Pierluigi

    2016-02-01

    The negative-ion accelerator for the MITICA neutral beam injector has been designed and optimized in order to reduce the thermo-mechanical stresses in all components below limits compatible with the required fatigue life. However, deviation from the expected beam performances can be caused by "off-normal" operating conditions of the accelerator. The purpose of the present work is to identify and analyse all the "off-normal" operating conditions, which could possibly become critical in terms of thermo-mechanical stresses or of degradation of the optical performances of the beam.

  10. Off-normal and failure condition analysis of the MITICA negative-ion accelerator.

    PubMed

    Chitarin, Giuseppe; Agostinetti, Piero; Aprile, Daniele; Marconato, Nicolò; Marcuzzi, Diego; Serianni, Gianluigi; Veltri, Pierluigi; Zaccaria, Pierluigi

    2016-02-01

    The negative-ion accelerator for the MITICA neutral beam injector has been designed and optimized in order to reduce the thermo-mechanical stresses in all components below limits compatible with the required fatigue life. However, deviation from the expected beam performances can be caused by "off-normal" operating conditions of the accelerator. The purpose of the present work is to identify and analyse all the "off-normal" operating conditions, which could possibly become critical in terms of thermo-mechanical stresses or of degradation of the optical performances of the beam. PMID:26932039

  11. Improved Accelerated Stress Tests Based on Fuel Cell Vehicle Data

    SciTech Connect

    Patterson, Timothy; Motupally, Sathya

    2012-06-01

    UTC will led a top-tier team of industry and national laboratory participants to update and improve DOE’s Accelerated Stress Tests (AST’s) for hydrogen fuel cells. This in-depth investigation will focused on critical fuel cell components (e.g. membrane electrode assemblies - MEA) whose durability represented barriers for widespread commercialization of hydrogen fuel cell technology. UTC had access to MEA materials that had accrued significant load time under real-world conditions in PureMotion® 120 power plant used in transit buses. These materials are referred to as end-of-life (EOL) components in the rest of this document. Advanced characterization techniques were used to evaluate degradation mode progress using these critical cell components extracted from both bus power plants and corresponding materials tested using the DOE AST’s. These techniques were applied to samples at beginning-of-life (BOL) to serve as a baseline. These comparisons advised the progress of the various failure modes that these critical components were subjected to, such as membrane degradation, catalyst support corrosion, platinum group metal dissolution, and others. Gaps in the existing ASTs predicted the degradation observed in the field in terms of these modes were outlined. Using the gaps, new AST’s were recommended and tested to better reflect the degradation modes seen in field operation. Also, BOL components were degraded in a test vehicle at UTC designed to accelerate the bus field operation.

  12. Cerium migration during PEM fuel cell accelerated stress testing

    SciTech Connect

    Baker, Andrew M.; Mukundan, Rangachary; Borup, Rodney L.; Spernjak, Dusan; Judge, Elizabeth J.; Advani, Suresh G.; Prasad, Ajay K.

    2016-01-01

    Cerium is a radical scavenger which improves polymer electrolyte membrane (PEM) fuel cell durability. During operation, however, cerium rapidly migrates in the PEM and into the catalyst layers (CLs). In this work, membrane electrode assemblies (MEAs) were subjected to accelerated stress tests (ASTs) under different humidity conditions. Cerium migration was characterized in the MEAs after ASTs using X-ray fluorescence. During fully humidified operation, water flux from cell inlet to outlet generated in-plane cerium gradients. Conversely, cerium profiles were flat during low humidity operation, where in-plane water flux was negligible, however, migration from the PEM into the CLs was enhanced. Humidity cycling resulted in both in-plane cerium gradients due to water flux during the hydration component of the cycle, and significant migration into the CLs. Fluoride and cerium emissions into effluent cell waters were measured during ASTs and correlated, which signifies that ionomer degradation products serve as possible counter-ions for cerium emissions. Fluoride emission rates were also correlated to final PEM cerium contents, which indicates that PEM degradation and cerium migration are coupled. Lastly, it is proposed that cerium migrates from the PEM due to humidification conditions and degradation, and is subsequently stabilized in the CLs by carbon catalyst supports.

  13. Cerium migration during PEM fuel cell accelerated stress testing

    DOE PAGES

    Baker, Andrew M.; Mukundan, Rangachary; Borup, Rodney L.; Spernjak, Dusan; Judge, Elizabeth J.; Advani, Suresh G.; Prasad, Ajay K.

    2016-01-01

    Cerium is a radical scavenger which improves polymer electrolyte membrane (PEM) fuel cell durability. During operation, however, cerium rapidly migrates in the PEM and into the catalyst layers (CLs). In this work, membrane electrode assemblies (MEAs) were subjected to accelerated stress tests (ASTs) under different humidity conditions. Cerium migration was characterized in the MEAs after ASTs using X-ray fluorescence. During fully humidified operation, water flux from cell inlet to outlet generated in-plane cerium gradients. Conversely, cerium profiles were flat during low humidity operation, where in-plane water flux was negligible, however, migration from the PEM into the CLs was enhanced. Humiditymore » cycling resulted in both in-plane cerium gradients due to water flux during the hydration component of the cycle, and significant migration into the CLs. Fluoride and cerium emissions into effluent cell waters were measured during ASTs and correlated, which signifies that ionomer degradation products serve as possible counter-ions for cerium emissions. Fluoride emission rates were also correlated to final PEM cerium contents, which indicates that PEM degradation and cerium migration are coupled. Lastly, it is proposed that cerium migrates from the PEM due to humidification conditions and degradation, and is subsequently stabilized in the CLs by carbon catalyst supports.« less

  14. Using Uncertainty Analysis to Guide the Development of Accelerated Stress Tests (Presentation)

    SciTech Connect

    Kempe, M.

    2014-03-01

    Extrapolation of accelerated testing to the long-term results expected in the field has uncertainty associated with the acceleration factors and the range of possible stresses in the field. When multiple stresses (such as temperature and humidity) can be used to increase the acceleration, the uncertainty may be reduced according to which stress factors are used to accelerate the degradation.

  15. Can hydromorphic conditions accelerate soil development?

    NASA Astrophysics Data System (ADS)

    Ringer, Marianna; Kiss, Klaudia; Horváth-Szabó, Kata; Réka Balázs, Brigitta; Németh, Tibor; Sipos, Péter; Szabó, Máté; Jakab, Gergely; Madarász, Balázs; Szalai, Zoltán

    2016-04-01

    The formation and development of waterlogged (hydromorphic) soils are primarily determined by long-term water saturation. The presence of water in the profile can result increasing speed of soil forming processes including the accumulation of organic matter or other components and mineralogical transformations. Original papers refer more than hundreds of years for this kinds of mineral transformations. We suppose that this process could be more rapid. This study focuses on the mineralogical investigation of a sandy meadow soil (calcic, gleyic Phaeozem ferric, arenic) located in a swampy area in Central Hungary. The starting time of the soil formation is a well documented fact: the parent material deposited during an extremely heavy flood event in the 1960s. Therefore, the studied soil profile is the result of the last half century. Our aim was to explore the degree of mineral phase alteration via soil formation during a half-century under hydromorphic conditions. Routine laboratory measurements (selective dissolution methods for the determination of amorphous and crystalline Fe, and Mn content, X-ray fluorescence spectroscopy measurements for elemental composition determination, X-ray powder diffraction for mineralogical composition, and particle sizing by laser diffraction) were implemented. Morphological and chemical study of carbonate and iron nodules was carried out by electron microprobe. Simple chemical tests (eg. Fe2+ indication by dipiridil test) and morphological observations were performed on the field. Redox potential (Eh) and pH were measured in 20 cm and 40 cm depths by field monitoring station during the vegetation period. Results show that well developed horizons have emerged during fifty years in the studied soil profile. The most intense mineralogical transformations developed in the zone of the heaviest redox oscillation. Soil formation under hydromorphic conditions proceeds at higher speeds contrariwise to the century time scale reported in

  16. Stability of lysozyme in aqueous extremolyte solutions during heat shock and accelerated thermal conditions.

    PubMed

    Avanti, Christina; Saluja, Vinay; van Streun, Erwin L P; Frijlink, Henderik W; Hinrichs, Wouter L J

    2014-01-01

    The purpose of this study was to investigate the stability of lysozyme in aqueous solutions in the presence of various extremolytes (betaine, hydroxyectoine, trehalose, ectoine, and firoin) under different stress conditions. The stability of lysozyme was determined by Nile red Fluorescence Spectroscopy and a bioactivity assay. During heat shock (10 min at 70°C), betaine, trehalose, ectoin and firoin protected lysozyme against inactivation while hydroxyectoine, did not have a significant effect. During accelerated thermal conditions (4 weeks at 55°C), firoin also acted as a stabilizer. In contrast, betaine, hydroxyectoine, trehalose and ectoine destabilized lysozyme under this condition. These findings surprisingly indicate that some extremolytes can stabilize a protein under certain stress conditions but destabilize the same protein under other stress conditions. Therefore it is suggested that for the screening extremolytes to be used for protein stabilization, an appropriate storage conditions should also be taken into account.

  17. Measuring Science Teachers' Stress Level Triggered by Multiple Stressful Conditions

    ERIC Educational Resources Information Center

    Halim, Lilia; Samsudin, Mohd Ali; Meerah, T. Subahan M.; Osman, Kamisah

    2006-01-01

    The complexity of science teaching requires science teachers to encounter a range of tasks. Some tasks are perceived as stressful while others are not. This study aims to investigate the extent to which different teaching situations lead to different stress levels. It also aims to identify the easiest and most difficult conditions to be regarded…

  18. Comparison of the conditioning of high gradient accelerating structures

    NASA Astrophysics Data System (ADS)

    Degiovanni, Alberto; Wuensch, Walter; Giner Navarro, Jorge

    2016-03-01

    Accelerating gradients in excess of 100 MV /m , at very low breakdown rates, have been successfully achieved in numerous prototype CLIC accelerating structures. The conditioning and operational histories of several structures, tested at KEK and CERN, have been compared and there is clear evidence that the conditioning progresses with the number of rf pulses and not with the number of breakdowns. This observation opens the possibility that the optimum conditioning strategy, which minimizes the total number of breakdowns the structure is subject to without increasing conditioning time, may be to never exceed the breakdown rate target for operation. The result is also likely to have a strong impact on efforts to understand the physical mechanism underlying conditioning and may lead to preparation procedures which reduce conditioning time.

  19. Stress and adaptation responses to repeated acute acceleration.

    NASA Technical Reports Server (NTRS)

    Burton, R. R.; Smith, A. H.

    1972-01-01

    Study in which groups of adult male chickens (single-comb white leghorn) were exposed daily to acceleration (centrifugation) of 2 or 3 G for 10 min, 1, 4, 8, 12, 16, and 24 hr (continuously), or 0 time (controls). After approximately five months of this intermittent treatment (training), the birds were exposed to continuous accelerations of the same G force (intensity). The degree of stress and adaptation of each bird was determined by survival and relative lymphocyte count criteria. Intermittent training exposures of 2 G developed levels of adaptation in birds directly proportional to the duration of their daily exposure. Intermittent training periods at 3 G, however, produced a physiological deterioration in birds receiving daily exposures of 8 hr or more. Adaptive benefits were found only in the 1- and 4-hr-daily intermittent 3-G exposure groups. Exposure to 3 G produced an immediate stress response as indicated by a low relative lymphocyte count which returned to control (preexposed) values prior to the next daily acceleration period in the 10-min, 1-hr, and 4-hr groups. This daily recovery period from stress appeared to be necessary for adaptation as opposed to deterioration for the more severe environmental (3 G) alteration.

  20. Activation of NADPH-recycling systems in leaves and roots of Arabidopsis thaliana under arsenic-induced stress conditions is accelerated by knock-out of Nudix hydrolase 19 (AtNUDX19) gene.

    PubMed

    Corpas, Francisco J; Aguayo-Trinidad, Simeón; Ogawa, Takahisa; Yoshimura, Kazuya; Shigeoka, Shigeru

    2016-03-15

    NADPH is an important cofactor in cell growth, proliferation and detoxification. Arabidopsis thaliana Nudix hydrolase 19 (AtNUDX19) belongs to a family of proteins defined by the conserved amino-acid sequence GX5-EX7REUXEEXGU which has the capacity to hydrolyze NADPH as a physiological substrate in vivo. Given the importance of NADPH in the cellular redox homeostasis of plants, the present study compares the responses of the main NADPH-recycling systems including NADP-isocitrate dehydrogenase (ICDH), glucose-6-phosphate dehydrogenase (G6PDH), 6-phosphogluconate dehydrogenase (6PGDH) and NADP-malic enzyme (ME) in the leaves and roots of Arabidopsis wild-type (Wt) and knock-out (KO) AtNUDX19 mutant (Atnudx19) plants under physiological and arsenic-induced stress conditions. Two major features were observed in the behavior of the main NADPH-recycling systems: (i) under optimal conditions in both organs, the levels of these activities were higher in nudx19 mutants than in Wt plants; and, (ii) under 500μM AsV conditions, these activities increase, especially in nudx19 mutant plants. Moreover, G6PDH activity in roots was the most affected enzyme in both Wt and nudx19 mutant plants, with a 4.6-fold and 5.0-fold increase, respectively. In summary, the data reveals a connection between the absence of chloroplastic AtNUDX19 and the rise in all NADP-dehydrogenase activities under physiological and arsenic-induced stress conditions, particularly in roots. This suggests that AtNUDX19 could be a key factor in modulating the NADPH pool in plants and consequently in redox homeostasis. PMID:26878367

  1. Investigation of accelerated stress factors and failure/degradation mechanisms in terrestrial solar cells

    NASA Technical Reports Server (NTRS)

    Lathrop, J. W.

    1983-01-01

    Results of an ongoing research program into the reliability of terrestrial solar cells are presented. Laboratory accelerated testing procedures are used to identify failure/degradation modes which are then related to basic physical, chemical, and metallurgical phenomena. In the most recent tests, ten different types of production cells, both with and without encapsulation, from eight different manufacturers were subjected to a variety of accelerated tests. Results indicated the presence of a number of hitherto undetected failure mechanisms, including Schottky barrier formation at back contacts and loss of adhesion of grid metallization. The mechanism of Schottky barrier formation is explained by hydrogen, formed by the dissociation of water molecules at the contact surface, diffusing to the metal semiconductor interface. This same mechanism accounts for the surprising increase in sensitivity to accelerated stress conditions that was observed in some cells when encapsulated.

  2. Transport synthetic acceleration with opposing reflecting boundary conditions

    SciTech Connect

    Zika, M.R.; Adams, M.L.

    2000-02-01

    The transport synthetic acceleration (TSA) scheme is extended to problems with opposing reflecting boundary conditions. This synthetic method employs a simplified transport operator as its low-order approximation. A procedure is developed that allows the use of the conjugate gradient (CG) method to solve the resulting low-order system of equations. Several well-known transport iteration algorithms are cast in a linear algebraic form to show their equivalence to standard iterative techniques. Source iteration in the presence of opposing reflecting boundary conditions is shown to be equivalent to a (poorly) preconditioned stationary Richardson iteration, with the preconditioner defined by the method of iterating on the incident fluxes on the reflecting boundaries. The TSA method (and any synthetic method) amounts to a further preconditioning of the Richardson iteration. The presence of opposing reflecting boundary conditions requires special consideration when developing a procedure to realize the CG method for the proposed system of equations. The CG iteration may be applied only to symmetric positive definite matrices; this condition requires the algebraic elimination of the boundary angular corrections from the low-order equations. As a consequence of this elimination, evaluating the action of the resulting matrix on an arbitrary vector involves two transport sweeps and a transmission iteration. Results of applying the acceleration scheme to a simple test problem are presented.

  3. Light energy dissipation under water stress conditions

    SciTech Connect

    Stuhlfauth, T.; Scheuermann, R.; Fock, H.P. )

    1990-04-01

    Using {sup 14}CO{sub 2} gas exchange and metabolite analyses, stomatal as well as total internal CO{sub 2} uptake and evolution were estimated. Pulse modulated fluorescence was measured during induction and steady state of photosynthesis. Leaf water potential of Digitalis lanata EHRH. plants decreased to {minus}2.5 megapascals after withholding irrigation. By osmotic adjustment, leaves remained turgid and fully exposed to irradiance even at severe water stress. Due to the stress-induced reduction of stomatal conductance, the stomatal CO{sub 2} exchange was drastically reduced, whereas the total CO{sub 2} uptake and evolution were less affected. Stomatal closure induced an increase in the reassimilation of internally evolved CO{sub 2}. This CO{sub 2}-recycling consumes a significant amount of light energy in the form of ATP and reducing equivalents. As a consequence, the metabolic demand for light energy is only reduced by about 40%, whereas net photosynthesis is diminished by about 70% under severe stress conditions. By CO{sub 2} recycling, carbon flux, enzymatic substrate turnover and consumption of light energy were maintained at high levels, which enabled the plant to recover rapidly after rewatering. In stressed D. lanata plants a variable fluorescence quenching mechanism, termed coefficient of actinic light quenching, was observed. Besides water conservation, light energy dissipation is essential and involves regulated metabolic variations.

  4. Acceleration of visually cued conditioned fear through the auditory pathway.

    PubMed

    Newton, Jessica R; Ellsworth, Charlene; Miyakawa, Tsuyoshi; Tonegawa, Susumu; Sur, Mriganka

    2004-09-01

    Defensive responses elicited by sensory experiences are critical for survival. Mice acquire a conditioned fear response rapidly to an auditory cue but slowly to a visual cue, a difference in learned behavior that is likely to be mediated by direct projections to the lateral amygdala from the auditory thalamus but mainly indirect ones from the visual thalamus. Here, we show that acquisition of visually cued conditioned fear is accelerated in 'rewired' mice that have retinal projections routed to the auditory thalamus. Visual stimuli induce expression of the immediate early gene Fos (also known as c-fos) in the auditory thalamus and the lateral amygdala in rewired mice, similar to the way auditory stimuli do in control mice. Thus, the rewired auditory pathway conveys visual information and mediates rapid activity-dependent plasticity in central structures that influence learned behavior.

  5. Step-Stress Accelerated Degradation Testing (SSADT) for Photovoltaic (PV) Devices and Cells (Presentation)

    SciTech Connect

    Lee, J.; Elmore, R.; Suh, C.; Jones, W.

    2010-10-01

    Presentation on step-stress accelerated degradation testing (SSADT) for photovoltaics (PV). Developed are a step-stress degradation test (SSADT) for PV reliability tests and a lifetime prediction model for PV products.

  6. Accelerated atherosclerosis in patients with chronic inflammatory rheumatologic conditions

    PubMed Central

    Hong, Jison; Maron, David J; Shirai, Tsuyoshi; Weyand, Cornelia M

    2015-01-01

    Atherosclerosis is a complex inflammatory disease involving aberrant immune and tissue healing responses, which begins with endothelial dysfunction and ends with plaque development, instability and rupture. The increased risk for coronary artery disease in patients with rheumatologic diseases highlights how aberrancy in the innate and adaptive immune system may be central to development of both disease states and that atherosclerosis may be on a spectrum of immune-mediated conditions. Recognition of the tight association between chronic inflammatory disease and complications of atherosclerosis will impact the understanding of underlying pathogenic mechanisms and change diagnostic and therapeutic approaches in patients with rheumatologic syndromes as well as patients with coronary artery disease. In this review, we provide a summary of the role of the immune system in atherosclerosis, discuss the proposed mechanisms of accelerated atherosclerosis seen in association with rheumatologic diseases, evaluate the effect of immunosuppression on atherosclerosis and provide updates on available risk assessment tools, biomarkers and imaging modalities. PMID:27042216

  7. STOCHASTIC ACCELERATION OF SUPRATHERMAL PARTICLES UNDER PRESSURE BALANCE CONDITIONS

    SciTech Connect

    Antecki, T.; Schlickeiser, R.; Zhang, M. E-mail: rsch@tp4.rub.de

    2013-02-10

    The acceleration of suprathermal charged particles in the heliosphere under pressure balance conditions including for the first time the radial spatial particle diffusion and convection in the solar wind is investigated. The physical conditions are derived for which the stationary phase space distribution of suprathermal particles approaches the power-law distribution f{proportional_to}p {sup -5}, which is often seen in spacecraft observations. For separable source distributions in momentum and position we analytically solve the stationary particle transport equation for a radially constant solar wind speed V {sub 0} and a momentum-independent radial spatial diffusion coefficient. The resulting stationary solution at any position within the finite heliosphere is the superposition of an infinite sum of power laws in momentum below and above the (assumed mono-momentum) injection momentum p{sub I} . The smallest spatial eigenvalue determines the flattest power law, to which the full stationary solution approaches at large and small enough momenta. Only for the case of a reflecting inner and a free-escape outer spatial boundary, does one small eigenvalue exist, yielding the power-law distribution f{proportional_to}p {sup -5} at sufficiently large momentum values. The other three spatial boundary conditions imply steeper momentum spectra. Momentum spectra and radial profiles of suprathermal particles are calculated by adopting a uniform outer ring spatial source distribution.

  8. Rapid behavioral maturation accelerates failure of stressed honey bee colonies

    PubMed Central

    Perry, Clint J.; Myerscough, Mary R.; Barron, Andrew B.

    2015-01-01

    Many complex factors have been linked to the recent marked increase in honey bee colony failure, including pests and pathogens, agrochemicals, and nutritional stressors. It remains unclear, however, why colonies frequently react to stressors by losing almost their entire adult bee population in a short time, resulting in a colony population collapse. Here we examine the social dynamics underlying such dramatic colony failure. Bees respond to many stressors by foraging earlier in life. We manipulated the demography of experimental colonies to induce precocious foraging in bees and used radio tag tracking to examine the consequences of precocious foraging for their performance. Precocious foragers completed far fewer foraging trips in their life, and had a higher risk of death in their first flights. We constructed a demographic model to explore how this individual reaction of bees to stress might impact colony performance. In the model, when forager death rates were chronically elevated, an increasingly younger forager force caused a positive feedback that dramatically accelerated terminal population decline in the colony. This resulted in a breakdown in division of labor and loss of the adult population, leaving only brood, food, and few adults in the hive. This study explains the social processes that drive rapid depopulation of a colony, and we explore possible strategies to prevent colony failure. Understanding the process of colony failure helps identify the most effective strategies to improve colony resilience. PMID:25675508

  9. Rapid behavioral maturation accelerates failure of stressed honey bee colonies.

    PubMed

    Perry, Clint J; Søvik, Eirik; Myerscough, Mary R; Barron, Andrew B

    2015-03-17

    Many complex factors have been linked to the recent marked increase in honey bee colony failure, including pests and pathogens, agrochemicals, and nutritional stressors. It remains unclear, however, why colonies frequently react to stressors by losing almost their entire adult bee population in a short time, resulting in a colony population collapse. Here we examine the social dynamics underlying such dramatic colony failure. Bees respond to many stressors by foraging earlier in life. We manipulated the demography of experimental colonies to induce precocious foraging in bees and used radio tag tracking to examine the consequences of precocious foraging for their performance. Precocious foragers completed far fewer foraging trips in their life, and had a higher risk of death in their first flights. We constructed a demographic model to explore how this individual reaction of bees to stress might impact colony performance. In the model, when forager death rates were chronically elevated, an increasingly younger forager force caused a positive feedback that dramatically accelerated terminal population decline in the colony. This resulted in a breakdown in division of labor and loss of the adult population, leaving only brood, food, and few adults in the hive. This study explains the social processes that drive rapid depopulation of a colony, and we explore possible strategies to prevent colony failure. Understanding the process of colony failure helps identify the most effective strategies to improve colony resilience.

  10. Rapid behavioral maturation accelerates failure of stressed honey bee colonies.

    PubMed

    Perry, Clint J; Søvik, Eirik; Myerscough, Mary R; Barron, Andrew B

    2015-03-17

    Many complex factors have been linked to the recent marked increase in honey bee colony failure, including pests and pathogens, agrochemicals, and nutritional stressors. It remains unclear, however, why colonies frequently react to stressors by losing almost their entire adult bee population in a short time, resulting in a colony population collapse. Here we examine the social dynamics underlying such dramatic colony failure. Bees respond to many stressors by foraging earlier in life. We manipulated the demography of experimental colonies to induce precocious foraging in bees and used radio tag tracking to examine the consequences of precocious foraging for their performance. Precocious foragers completed far fewer foraging trips in their life, and had a higher risk of death in their first flights. We constructed a demographic model to explore how this individual reaction of bees to stress might impact colony performance. In the model, when forager death rates were chronically elevated, an increasingly younger forager force caused a positive feedback that dramatically accelerated terminal population decline in the colony. This resulted in a breakdown in division of labor and loss of the adult population, leaving only brood, food, and few adults in the hive. This study explains the social processes that drive rapid depopulation of a colony, and we explore possible strategies to prevent colony failure. Understanding the process of colony failure helps identify the most effective strategies to improve colony resilience. PMID:25675508

  11. Psychological stress associated with cardiogenetic conditions

    PubMed Central

    Hidayatallah, Nadia; Silverstein, Louise B; Stolerman, Marina; McDonald, Thomas; Walsh, Christine A; Paljevic, Esma; Cohen, Lilian L; Marion, Robert W; Wasserman, David; Hreyo, Sarah; Dolan, Siobhan M

    2014-01-01

    Aim Genetic testing now makes it possible to identify specific mutations that may lead to life-threatening cardiac arrhythmias. This article presents data from a qualitative research study that explored the subjective experiences of individuals and families with cardiogenetic conditions. We focus on describing patients’ experiences of psychological stresses associated with having a cardiogenetic condition, illustrating the importance of integrating psychological and medical care. This integration of care is particularly important as personalized genomic medicine continues to evolve and the implications of genetic testing have a profound effect on individuals and families. Methods The researchers interviewed 50 participants from 32 families. The research team used a systematic, grounded theory procedure to code and analyze interview and focus group transcripts, incorporating multiple coders at several stages of the data analysis process. Results Three major themes emerged: a bereavement trajectory associated with sudden death in the absence of prior symptoms; high anxiety about transmitting a genetic mutation; and resilience reflected in positive lifestyle changes and participation in support groups. Conclusion This article identifies patient perspectives on personalized genomic medicine in cardiogenetics that can improve clinical care, including: specialized bereavement counseling; improving education about cardiogenetic conditions for medical professionals; parent guidelines for discussing cardiogenetic conditions with their children; information about support groups; and the routine inclusion of clinical psychologists in interdisciplinary treatment teams. Given recent advances in technology and decreasing costs, whole-genome sequencing is likely to become common practice in the near future. Therefore, these recommendations are likely to be relevant for other genetic conditions, as well as the entire field of personalized genomic medicine. PMID:25431604

  12. Temperature and current accelerated lifetime conditions and testing of laser diodes for ESA BepiColombo space mission

    NASA Astrophysics Data System (ADS)

    Klumel, Genady; Karni, Yoram; Cohen, Shalom; Rech, Markus; Weidlich, Kai

    2011-03-01

    System designers and end users of diode pumped solid state lasers often require knowledge of the operability limits of QCW laser diode pump sources and their predicted reliability performance as a function of operating conditions. Accelerated ageing at elevated temperatures, duty cycles and/or currents allows extended lifetime testing of diode stacks to be executed on compressed timescales with high confidence. We present a novel, time-efficient technique for the determination of accelerated lifetime test conditions using degradation rate data, rather than the traditionally used failures against time data. To assess the effect of thermally accelerated ageing, 4 groups of 4 stacks each were operated for 60 million pulses at different temperature stress levels by varying the pulse repetition rate from 100Hz to 250Hz. The measured power degradation rates fitted to an Arrhenius type model, result in activation energy of 0.47- 0.74eV, apparently indicating two thermally activated degradation modes with different activation energies. Similarly, for current accelerated ageing, another 4 groups of 4 stacks were tested at operation currents from 120A to 150A. The optical power degradation rates due to current stress follow a power law behavior with a current acceleration factor of 1.7. The obtained acceleration parameters allowed considerable reduction of the lifetime test duration, which would have otherwise taken an unacceptably long time under nominal operating conditions. The successful results of the accelerated lifetime have been a major milestone enabling qualification of SCD stacks as pump sources for the laser altimeter in ESA Bepi-Colombo space mission. The presented reliability analysis allows life test qualification programs to be accelerated for generic QCW stacks and their lifetime to be predicted in various operating environments.

  13. Possible mechanism by which stress accelerates growth of virally derived tumors.

    PubMed Central

    Romero, L M; Raley-Susman, K M; Redish, D M; Brooke, S M; Horner, H C; Sapolsky, R M

    1992-01-01

    Stress accelerates the growth of certain types of tumors. Here we report a possible metabolic mechanism underlying this phenomenon. Some early features of transformation include increased number of glucose transporters and greatly enhanced rates of glucose uptake; this adaptation accommodates the vast energy demands needed for neoplastic growth. In contrast, glucocorticoids, a class of steroid hormones secreted during stress, inhibit glucose transport in various tissues; this is one route by which circulating glucose concentrations are raised during stress. We reasoned that should transformed cells become resistant to this inhibitory action of glucocorticoids, such cells would gain preferential access to these elevated concentrations of glucose. In agreement with this, we observed that Fujinami sarcoma virus-transformed fibroblasts became resistant to this glucocorticoid action both in vitro and in the rat. As a result, under conditions where glucocorticoids exerted catabolic effects upon nontransformed fibroblasts (inhibition of metabolism and ATP concentrations), the opposite occurred in the virally transformed cells. We observe that this glucocorticoid resistance upon transformation cannot be explained by depletion of glucocorticoid receptors; previous studies have suggested that transformation causes an alteration in trafficking of such receptors. Because of this resistance of transformed fibroblasts to the inhibitory effects of glucocorticoids upon glucose transport, glucose stores throughout the body are, in effect, preferentially shunted to such tumors during stress. Images PMID:1438318

  14. Control over stress accelerates extinction of drug seeking via prefrontal cortical activation

    PubMed Central

    Baratta, Michael V.; Pomrenze, Matthew B.; Nakamura, Shinya; Dolzani, Samuel D.; Cooper, Donald C.

    2015-01-01

    Extinction is a form of inhibitory learning viewed as an essential process in suppressing conditioned responses to drug cues, yet there is little information concerning experiential variables that modulate its formation. Coping factors play an instrumental role in determining how adverse life events impact the transition from casual drug use to addiction. Here we provide evidence in rat that prior exposure to controllable stress accelerates the extinction of cocaine-seeking behavior relative to uncontrollable or no stress exposure. Subsequent experimentation using high-speed optogenetic tools determined if the infralimbic region (IL) of the ventral medial prefrontal cortex mediates the impact of controllable stress on cocaine-seeking behavior. Photoinhibition of pyramidal neurons in the IL during coping behavior did not interfere with subject's ability to control the stressor, but prevented the later control-induced facilitation of extinction. These results provide strong evidence that the degree of behavioral control over adverse events, rather than adverse events per se, potently modulates the extinction of cocaine-seeking behavior, and that controllable stress engages prefrontal circuitry that primes future extinction learning. PMID:25954765

  15. MICROWAVE-ACCELERATED MULTICOMPONENT REACTIONS UNDER SOLVENT-FREE CONDITIONS

    EPA Science Inventory

    The application of microwave-accelerated solventless synthetic protocols in multicomponent (MCC) reactions will be exemplified by several condensation and cyclization reactions including the rapid one-pot assembly of valuable heterocyclic compounds from in situ generated intermed...

  16. Polarization Losses under Accelerated Stress Test Using Multiwalled Carbon Nanotube Supported Pt Catalyst in PEM Fuel Cells

    SciTech Connect

    Park, Seh K.; Shao, Yuyan; Kou, Rong; Viswanathan, Vilayanur V.; Towne, Silas A.; Rieke, Peter C.; Liu, Jun; Lin, Yuehe; Wang, Yong

    2011-03-01

    The electrochemical behavior for Pt catalysts supported on multiwalled carbon nanotubes and Vulcan XC-72 in proton exchange membrane fuel cells under accelerated stress test was examined by cyclic voltammetry, electrochemical impedance spectroscopy, and polarization technique. Pt catalyst supported on multiwalled carbon nanotubes exhibited highly stable electrochemical surface area, oxygen reduction kinetics, and fuel cell performance at a highly oxidizing condition, indicating multiwalled carbon nanotubes show high corrosion resistance and strong interaction with Pt nanoparticles. The Tafel slope, ohmic resistances, and limiting current density determined were used to differentiate kinetic, ohmic, mass-transfer polarization losses from the actual polarization curve. Kinetic contribution to the total overpotential was larger throughout the stress test. However, the fraction of kinetic overpotential decreased and mass-transfer overpotential portion remained quite constant during accelerated stress test, whereas the fraction of ohmic overpotential primarily originating from severe proton transport limitation in the catalyst layer increased under the anodic potential hold.

  17. Long-term moderate exercise accelerates the recovery of stress-evoked cardiovascular responses.

    PubMed

    Hsu, Yuan-Chang; Tsai, Sheng-Feng; Yu, Lung; Chuang, Jih-Ing; Wu, Fong-Sen; Jen, Chauying J; Kuo, Yu-Min

    2016-01-01

    Psychological stress is an important global health problem. It is well documented that stress increases the incidences of various cardiovascular disorders. Regular exercise is known to reduce resting blood pressure (BP) and heart rate (HR). This study was designed to clarify the effects of long-term exercise on stress-evoked cardiovascular responses and to emphasize post-stress recovery effects. Male Wistar rats underwent 8 weeks of moderate treadmill training, with cardiovascular responses, autonomic nervous system activities and local Fos reactivity changes in the cardiovascular regulation center were monitored before, during and after immobilization stress. A spectral analysis of cardiovascular parameters was used to examine autonomic nervous activities. We found that long-term exercise (i) lowered resting BP, HR and sympathetic activity, but increased resting parasympathetic activity and baroreflex sensitivity (BRS); (ii) accelerated post-stress recovery of stress-evoked cardiovascular and sympathetic responses along with increased BRS and (iii) accelerated post-stress recovery of stress-evoked neuron activations in the paraventricular nucleus, but delayed it in the nucleus of the tractus solitarius. We conclude that, in rats, long-term exercise accelerated recovery of stress-evoked cardiovascular responses differentially altering hypothalamic and medullar neuron activities.

  18. Maximum von Mises Stress in the Loading Environment of Mass Acceleration Curve

    NASA Technical Reports Server (NTRS)

    Glaser, Robert J.; Chen, Long Y.

    2006-01-01

    Method for calculating stress due to acceleration loading: 1) Part has been designed by FEA and hand calculation in one critical loading direction judged by the analyst; 2) Maximum stress can be due to loading in another direction; 3) Analysis procedure to be presented determines: a) The maximum Mises stress at any point; and b) The direction of maximum loading associated with the "stress". Concept of Mass Acceleration Curves (MAC): 1) Developed by JPL to perform preliminary structural sizing (i.e. Mariners, Voyager, Galileo, Pathfinder, MER,...MSL); 2) Acceleration of physical masses are bounded by a curve; 3) G-levels of vibro-acoustic and transient environments; 4) Convergent process before the couple loads cycle; and 5) Semi-empirical method to effectively bound the loads, not a simulation of the actual response.

  19. Fault stability under conditions of variable normal stress

    USGS Publications Warehouse

    Dieterich, J.H.; Linker, M.F.

    1992-01-01

    The stability of fault slip under conditions of varying normal stress is modelled as a spring and slider system with rate- and state-dependent friction. Coupling of normal stress to shear stress is achieved by inclining the spring at an angle, ??, to the sliding surface. Linear analysis yields two conditions for unstable slip. The first, of a type previously identified for constant normal stress systems, results in instability if stiffness is below a critical value. Critical stiffness depends on normal stress, constitutive parameters, characteristic sliding distance and the spring angle. Instability of the first type is possible only for velocity-weakening friction. The second condition yields instability if spring angle ?? <-cot-1??ss, where ??ss is steady-state sliding friction. The second condition can arise under conditions of velocity strengthening or weakening. Stability fields for finite perturbations are investigated by numerical simulation. -Authors

  20. Estimation of Attitude and External Acceleration Using Inertial Sensor Measurement During Various Dynamic Conditions

    PubMed Central

    Lee, Jung Keun; Park, Edward J.; Robinovitch, Stephen N.

    2012-01-01

    This paper proposes a Kalman filter-based attitude (i.e., roll and pitch) estimation algorithm using an inertial sensor composed of a triaxial accelerometer and a triaxial gyroscope. In particular, the proposed algorithm has been developed for accurate attitude estimation during dynamic conditions, in which external acceleration is present. Although external acceleration is the main source of the attitude estimation error and despite the need for its accurate estimation in many applications, this problem that can be critical for the attitude estimation has not been addressed explicitly in the literature. Accordingly, this paper addresses the combined estimation problem of the attitude and external acceleration. Experimental tests were conducted to verify the performance of the proposed algorithm in various dynamic condition settings and to provide further insight into the variations in the estimation accuracy. Furthermore, two different approaches for dealing with the estimation problem during dynamic conditions were compared, i.e., threshold-based switching approach versus acceleration model-based approach. Based on an external acceleration model, the proposed algorithm was capable of estimating accurate attitudes and external accelerations for short accelerated periods, showing its high effectiveness during short-term fast dynamic conditions. Contrariwise, when the testing condition involved prolonged high external accelerations, the proposed algorithm exhibited gradually increasing errors. However, as soon as the condition returned to static or quasi-static conditions, the algorithm was able to stabilize the estimation error, regaining its high estimation accuracy. PMID:22977288

  1. Stress differentially affects fear conditioning in men and women.

    PubMed

    Merz, Christian Josef; Wolf, Oliver Tobias; Schweckendiek, Jan; Klucken, Tim; Vaitl, Dieter; Stark, Rudolf

    2013-11-01

    Stress and fear conditioning processes are both important vulnerability factors in the development of psychiatric disorders. In behavioral studies considerable sex differences in fear learning have been observed after increases of the stress hormone cortisol. But neuroimaging experiments, which give insights into the neurobiological correlates of stress × sex interactions in fear conditioning, are lacking so far. In the current functional magnetic resonance imaging (fMRI) study, we tested whether a psychosocial stressor (Trier Social Stress Test) compared to a control condition influenced subsequent fear conditioning in 48 men and 48 women taking oral contraceptives (OCs). One of two pictures of a geometrical figure was always paired (conditioned stimulus, CS+) or never paired (CS-) with an electrical stimulation (unconditioned stimulus). BOLD responses as well as skin conductance responses were assessed. Sex-independently, stress enhanced the CS+/CS- differentiation in the hippocampus in early acquisition but attenuated conditioned responses in the medial frontal cortex in late acquisition. In early acquisition, stress reduced the CS+/CS- differentiation in the nucleus accumbens in men, but enhanced it in OC women. In late acquisition, the same pattern (reduction in men, enhancement in OC women) was found in the amygdala as well as in the anterior cingulate. Thus, psychosocial stress impaired the neuronal correlates of fear learning and expression in men, but facilitated them in OC women. A sex-specific modulation of fear conditioning after stress might contribute to the divergent prevalence of men and women in developing psychiatric disorders.

  2. Solar wind conditions leading to efficient radiation belt electron acceleration: A superposed epoch analysis

    SciTech Connect

    Li, W.; Thorne, R. M.; Bortnik, J.; Baker, D. N.; Reeves, G. D.; Kanekal, S. G.; Spence, H. E.; Green, J. C.

    2015-09-07

    In this study by determining preferential solar wind conditions leading to efficient radiation belt electron acceleration is crucial for predicting radiation belt electron dynamics. Using Van Allen Probes electron observations (>1 MeV) from 2012 to 2015, we identify a number of efficient and inefficient acceleration events separately to perform a superposed epoch analysis of the corresponding solar wind parameters and geomagnetic indices. By directly comparing efficient and inefficient acceleration events, we clearly show that prolonged southward Bz, high solar wind speed, and low dynamic pressure are critical for electron acceleration to >1 MeV energies in the heart of the outer radiation belt. We also evaluate chorus wave evolution using the superposed epoch analysis for the identified efficient and inefficient acceleration events and find that chorus wave intensity is much stronger and lasts longer during efficient electron acceleration events, supporting the scenario that chorus waves play a key role in MeV electron acceleration.

  3. Power-conditioning system for the Advanced Test Accelerator

    SciTech Connect

    Newton, M.A.; Smith, M.E.; Birx, D.L.; Branum, D.R.; Cook, E.G.; Copp, R.L.; Lee, F.D.; Reginato, L.L.; Rogers, D.; Speckert, G.C.

    1982-06-01

    The Advanced Test Accelerator (ATA) is a pulsed, linear induction, electron accelerator currently under construction and nearing completion at Lawrence Livermore National Laboratory's Site 300 near Livermore, California. The ATA is a 50 MeV, 10 kA machine capable of generating electron beam pulses at a 1 kHz rate in a 10 pulse burst, 5 pps average, with a pulse width of 70 ns FWHM. Ten 18 kV power supplies are used to charge 25 capacitor banks with a total energy storage of 8 megajoules. Energy is transferred from the capacitor banks in 500 microsecond pulses through 25 Command Resonant Charge units (CRC) to 233 Thyratron Switch Chassis. Each Thyratron Switch Chassis contains a 2.5 microfarad capacitor and is charged to 25 kV (780 joules) with voltage regulation of +- .05%. These capacitors are switched into 10:1 step-up resonant transformers to charge 233 Blumleins to 250 kV in 20 microseconds. A magnetic modulator is used instead of a Blumlein to drive the grid of the injector.

  4. Desipramine and restraint stress induce odor conditioned aversion in rats: suppression by repeated conditioning.

    PubMed

    Murua, V S; Molina, V A

    1990-01-01

    Rats exposed to one, three, or seven conditioning sessions defined by an olfactory conditioned stimulus and stress or antidepressant administration as unconditioned stimulus were later tested for their preference for the conditioned olfactory stimulus. A significant reduction of the time spent in the conditioned stimulus was observed in animals exposed to one and three pairings with stress or three pairings with desipramine. A lack of conditioned aversion was observed in animals exposed to seven pairings with either reinforcer. These data could indicate that the adaptative mechanisms elicited by repeated stress or desipramine may be involved in the decrease of conditioned aversion. PMID:2096407

  5. Forced degradation studies of biopharmaceuticals: Selection of stress conditions.

    PubMed

    Tamizi, Elnaz; Jouyban, Abolghasem

    2016-01-01

    Stability studies under stress conditions or forced degradation studies play an important role in different phases of development and production of biopharmaceuticals and biological products. These studies are mostly applicable to selection of suitable candidates and formulation developments, comparability studies, elucidation of possible degradation pathways and identification of degradation products, as well as, development of stability indicating methods. Despite the integral part of these studies in biopharmaceutical industry, there is no well-established protocol for the selection of stress conditions, timing of stress testing and required extent of degradation. Therefore, due to the present gap in the stability studies guidelines, it is the responsibility of researchers working in academia and biopharmaceutical industry to set up forced degradation experiments that could fulfill all the expectations from the stability studies of biopharmaceuticals under stress conditions. Concerning the importance of the function of desired stress conditions in forced degradation studies, the present review aims to provide a practical summary of the applicable stress conditions in forced degradation studies of biopharmaceuticals according to the papers published in a time period of 1992-2015 giving detailed information about the experimental conditions utilized to induce required stresses.

  6. Telomere Replication Stress Induced by POT1 Inactivation Accelerates Tumorigenesis.

    PubMed

    Pinzaru, Alexandra M; Hom, Robert A; Beal, Angela; Phillips, Aaron F; Ni, Eric; Cardozo, Timothy; Nair, Nidhi; Choi, Jaehyuk; Wuttke, Deborah S; Sfeir, Agnel; Denchi, Eros Lazzerini

    2016-06-01

    Genome sequencing studies have revealed a number of cancer-associated mutations in the telomere-binding factor POT1. Here, we show that when combined with p53 deficiency, depletion of murine POT1a in common lymphoid progenitor cells fosters genetic instability, accelerates the onset, and increases the severity of T cell lymphomas. In parallel, we examined human and mouse cells carrying POT1 mutations found in cutaneous T cell lymphoma (CTCL) patients. Inhibition of POT1 activates ATR-dependent DNA damage signaling and induces telomere fragility, replication fork stalling, and telomere elongation. Our data suggest that these phenotypes are linked to impaired CST (CTC1-STN1-TEN1) function at telomeres. Lastly, we show that proliferation of cancer cells lacking POT1 is enabled by the attenuation of the ATR kinase pathway. These results uncover a role for defective telomere replication during tumorigenesis.

  7. FEM Techniques for High Stress Detection in Accelerated Fatigue Simulation

    NASA Astrophysics Data System (ADS)

    Veltri, M.

    2016-09-01

    This work presents the theory and a numerical validation study in support to a novel method for a priori identification of fatigue critical regions, with the aim to accelerate durability design in large FEM problems. The investigation is placed in the context of modern full-body structural durability analysis, where a computationally intensive dynamic solution could be required to identify areas with potential for fatigue damage initiation. The early detection of fatigue critical areas can drive a simplification of the problem size, leading to sensible improvement in solution time and model handling while allowing processing of the critical areas in higher detail. The proposed technique is applied to a real life industrial case in a comparative assessment with established practices. Synthetic damage prediction quantification and visualization techniques allow for a quick and efficient comparison between methods, outlining potential application benefits and boundaries.

  8. Rubisco activase and wheat productivity under heat stress conditions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rubisco activase (RCA) constrains the photosynthetic potential of plants at high temperature (heat stress). We hypothesized that endogenous levels of RCA could serve as an important determinant of plant productivity under heat stress conditions. In this study, we investigated the possible relation...

  9. Modeling heat stress under different environmental conditions.

    PubMed

    Carabaño, M J; Logar, B; Bormann, J; Minet, J; Vanrobays, M-L; Díaz, C; Tychon, B; Gengler, N; Hammami, H

    2016-05-01

    Renewed interest in heat stress effects on livestock productivity derives from climate change, which is expected to increase temperatures and the frequency of extreme weather events. This study aimed at evaluating the effect of temperature and humidity on milk production in highly selected dairy cattle populations across 3 European regions differing in climate and production systems to detect differences and similarities that can be used to optimize heat stress (HS) effect modeling. Milk, fat, and protein test day data from official milk recording for 1999 to 2010 in 4 Holstein populations located in the Walloon Region of Belgium (BEL), Luxembourg (LUX), Slovenia (SLO), and southern Spain (SPA) were merged with temperature and humidity data provided by the state meteorological agencies. After merging, the number of test day records/cows per trait ranged from 686,726/49,655 in SLO to 1,982,047/136,746 in BEL. Values for the daily average and maximum temperature-humidity index (THIavg and THImax) ranges for THIavg/THImax were largest in SLO (22-74/28-84) and shortest in SPA (39-76/46-83). Change point techniques were used to determine comfort thresholds, which differed across traits and climatic regions. Milk yield showed an inverted U-shaped pattern of response across the THI scale with a HS threshold around 73 THImax units. For fat and protein, thresholds were lower than for milk yield and were shifted around 6 THI units toward larger values in SPA compared with the other countries. Fat showed lower HS thresholds than protein traits in all countries. The traditional broken line model was compared with quadratic and cubic fits of the pattern of response in production to increasing heat loads. A cubic polynomial model allowing for individual variation in patterns of response and THIavg as heat load measure showed the best statistical features. Higher/lower producing animals showed less/more persistent production (quantity and quality) across the THI scale. The

  10. Bayesian Analysis of Step-Stress Accelerated Life Test with Exponential Distribution

    SciTech Connect

    Lee, J.; Pan, R.

    2012-04-01

    In this article, we propose a general Bayesian inference approach to the step-stress accelerated life test with type II censoring. We assume that the failure times at each stress level are exponentially distributed and the test units are tested in an increasing order of stress levels. We formulate the prior distribution of the parameters of life-stress function and integrate the engineering knowledge of product failure rate and acceleration factor into the prior. The posterior distribution and the point estimates for the parameters of interest are provided. Through the Markov chain Monte Carlo technique, we demonstrate a nonconjugate prior case using an industrial example. It is shown that with the Bayesian approach, the statistical precision of parameter estimation is improved and, consequently, the required number of failures could be reduced.

  11. Measurements in Transitional Boundary Layers Under High Free-Stream Turbulence and Strong Acceleration Conditions

    NASA Technical Reports Server (NTRS)

    Volino, Ralph J.; Simon, Terrence W.

    1995-01-01

    Measurements from transitional, heated boundary layers along a concave-curved test wall are presented and discussed. A boundary layer subject to low free-stream turbulence intensity (FSTI), which contains stationary streamwise (Gortler) vortices, is documented. The low FSTI measurements are followed by measurements in boundary layers subject to high (initially 8%) free-stream turbulence intensity and moderate to strong streamwise acceleration. Conditions were chosen to simulate those present on the downstream half of the pressure side of a gas turbine airfoil. Mean flow characteristics as well as turbulence statistics, including the turbulent shear stress, turbulent heat flux, and turbulent Prandtl number, are documented. A technique called "octant analysis" is introduced and applied to several cases from the literature as well as to data from the present study. Spectral analysis was applied to describe the effects of turbulence scales of different sizes during transition. To the authors'knowledge, this is the first detailed documentation of boundary layer transition under such high free-stream turbulence conditions.

  12. Voltage stress effects on microcircuit accelerated life test failure rates

    NASA Technical Reports Server (NTRS)

    Johnson, G. M.

    1976-01-01

    The applicability of Arrhenius and Eyring reaction rate models for describing microcircuit aging characteristics as a function of junction temperature and applied voltage was evaluated. The results of a matrix of accelerated life tests with a single metal oxide semiconductor microcircuit operated at six different combinations of temperature and voltage were used to evaluate the models. A total of 450 devices from two different lots were tested at ambient temperatures between 200 C and 250 C and applied voltages between 5 Vdc and 15 Vdc. A statistical analysis of the surface related failure data resulted in bimodal failure distributions comprising two lognormal distributions; a 'freak' distribution observed early in time, and a 'main' distribution observed later in time. The Arrhenius model was shown to provide a good description of device aging as a function of temperature at a fixed voltage. The Eyring model also appeared to provide a reasonable description of main distribution device aging as a function of temperature and voltage. Circuit diagrams are shown.

  13. Setting up virgin stress conditions in discrete element models

    PubMed Central

    Rojek, J.; Karlis, G.F.; Malinowski, L.J.; Beer, G.

    2013-01-01

    In the present work, a methodology for setting up virgin stress conditions in discrete element models is proposed. The developed algorithm is applicable to discrete or coupled discrete/continuum modeling of underground excavation employing the discrete element method (DEM). Since the DEM works with contact forces rather than stresses there is a need for the conversion of pre-excavation stresses to contact forces for the DEM model. Different possibilities of setting up virgin stress conditions in the DEM model are reviewed and critically assessed. Finally, a new method to obtain a discrete element model with contact forces equivalent to given macroscopic virgin stresses is proposed. The test examples presented show that good results may be obtained regardless of the shape of the DEM domain. PMID:27087731

  14. Quantum corrections to the stress-energy tensor in thermodynamic equilibrium with acceleration

    NASA Astrophysics Data System (ADS)

    Becattini, F.; Grossi, E.

    2015-08-01

    We show that the stress-energy tensor has additional terms with respect to the ideal form in states of global thermodynamic equilibrium in flat spacetime with nonvanishing acceleration and vorticity. These corrections are of quantum origin and their leading terms are second order in the gradients of the thermodynamic fields. Their relevant coefficients can be expressed in terms of correlators of the stress-energy tensor operator and the generators of the Lorentz group. With respect to previous assessments, we find that there are more second-order coefficients and that all thermodynamic functions including energy density receive acceleration and vorticity dependent corrections. Notably, also the relation between ρ and p , that is, the equation of state, is affected by acceleration and vorticity. We have calculated the corrections for a free real scalar field—both massive and massless—and we have found that they increase, particularly for a massive field, at very high acceleration and vorticity and very low temperature. Finally, these nonideal terms depend on the explicit form of the stress-energy operator, implying that different stress-energy tensors of the scalar field—canonical or improved—are thermodynamically inequivalent.

  15. Influence of boundary conditions on the radiation emitted by an accelerated source

    SciTech Connect

    Alves, Danilo T.; Crispino, Luis C. B.; Lima, Marcelo C. de; Higuchi, Atsushi

    2010-03-15

    We analyze how the radiation emitted by an accelerated source minimally coupled to a massless real scalar field is influenced by the boundary conditions imposed on the field. We find that the response rate of the accelerated source in the presence of nearby boundaries parallel to the direction of the source's motion can be suppressed or enhanced depending on whether Dirichlet or Neumann boundary conditions are imposed on the field. We conclude that the response rate strongly depends on the kind of boundary conditions imposed, just as the sign of the Casimir force depends on the boundary conditions imposed on the field.

  16. Aerodynamic surface stress intermittency and conditionally averaged turbulence statistics

    NASA Astrophysics Data System (ADS)

    Anderson, William; Lanigan, David

    2015-11-01

    Aeolian erosion is induced by aerodynamic stress imposed by atmospheric winds. Erosion models prescribe that sediment flux, Q, scales with aerodynamic stress raised to exponent, n, where n > 1 . Since stress (in fully rough, inertia-dominated flows) scales with incoming velocity squared, u2, it follows that q ~u2n (where u is some relevant component of the flow). Thus, even small (turbulent) deviations of u from its time-mean may be important for aeolian activity. This rationale is augmented given that surface layer turbulence exhibits maximum Reynolds stresses in the fluid immediately above the landscape. To illustrate the importance of stress intermittency, we have used conditional averaging predicated on stress during large-eddy simulation of atmospheric boundary layer flow over an arid, bare landscape. Conditional averaging provides an ensemble-mean visualization of flow structures responsible for erosion `events'. Preliminary evidence indicates that surface stress peaks are associated with the passage of inclined, high-momentum regions flanked by adjacent low-momentum regions. We characterize geometric attributes of such structures and explore streamwise and vertical vorticity distribution within the conditionally averaged flow field. This work was supported by the National Sci. Foundation, Phys. and Dynamic Meteorology Program (PM: Drs. N. Anderson, C. Lu, and E. Bensman) under Grant # 1500224. Computational resources were provided by the Texas Adv. Comp. Center at the Univ. of Texas.

  17. Chronic stress impairs learning and hippocampal cell proliferation in senescence-accelerated prone mice.

    PubMed

    Yan, Weihong; Zhang, Ting; Jia, Weiping; Sun, Xiaojiang; Liu, Xueyuan

    2011-02-25

    Chronic stress can induce cognitive impairment. It is unclear whether a higher susceptibility to chronic stress is associated with the progression of pathological brain aging. Senescence-accelerated prone mouse 8 (SAMP8) is a naturally occurring animal model of accelerated brain aging. Senescence-accelerated resistant mouse 1 (SAMR1) is usually used as the normal control. In this study, we examined the effects of chronic restraint stress (CRS) on learning in the Y-maze, hippocampal cell proliferation, and the expression of brain-derived neurotrophic factor (BDNF) in the hippocampus of 4-month-old SAMP8 and SAMR1. The results showed that exposure to CRS impaired learning and hippocampal cell proliferation in SAMP8 and SAMR1 but to a much greater extent in SAMP8. Furthermore, CRS significantly decreased the expression of BDNF protein and mRNA in the hippocampus of SAMP8 and SAMR1. These data indicated that SAMP8 is more sensitive to the deleterious effects of CRS on learning than SAMR1. A greater decrease in hippocampal cell proliferation caused by chronic stress may be part of the underlying mechanism for the more severe learning deficit observed in SAMP8. In addition, our findings suggested a role of BDNF in the stress-induced impairment of learning and hippocampal cell proliferation in both strains.

  18. Investigation of reliability attributes and accelerated stress factors on terrestrial solar cells

    NASA Technical Reports Server (NTRS)

    Prince, J. L.; Lathrop, J. W.

    1979-01-01

    The results of accelerated stress testing of four different types of silicon terrestrial solar cells are discussed. The accelerated stress tests used included bias-temperature tests, bias-temperature-humidity tests, thermal cycle and thermal shock tests, and power cycle tests. Characterization of the cells was performed before stress testing and at periodic down-times, using electrical measurement, visual inspection, and metal adherence pull tests. Electrical parameters measured included short-circuit current, open circuit voltage, and output power, voltage, and current at the maximum power point. Incorporated in the report are the distributions of the prestress electrical data for all cell types. Data were also obtained on cell series and shunt resistance.

  19. Momentum transfer within a porous medium. II. Stress boundary condition

    NASA Astrophysics Data System (ADS)

    Minale, Mario

    2014-12-01

    In this paper, we derive a boundary condition at the interface between a free fluid and a porous medium stating that the stress is transferred both to the fluid within the porous medium and to the solid skeleton. A zero stress jump is obtained so that the total stress is preserved at the interface. The boundary condition is obtained with the volume averaging method following the approach of Ochoa-Tapia and Whitaker ["Momentum transfer at the boundary between a porous medium and a homogeneous fluid—I. Theoretical development," Int. J. Heat Mass Transfer 38(14), 2635-2646 (1995)], but starting from the momentum balances written on the fluid and on the solid of the porous region, the latter was derived in part I of this paper. In the same way, also the boundary condition at the interface between a porous medium and a homogeneous solid is obtained. Both boundary conditions describe the equilibrium of forces at the interface, where part of the stress is carried by the solid skeleton and part by the fluid within the porous medium. With the derived boundary conditions, together with the stress transfer equation within the solid skeleton, it is now possible to satisfy the overall force equilibrium on a shear cell partially filled with a porous medium.

  20. Leaf conductance and carbon gain under salt-stressed conditions

    NASA Astrophysics Data System (ADS)

    Volpe, V.; Manzoni, S.; Marani, M.; Katul, G.

    2011-12-01

    Exposure of plants to salt stress is often accompanied by reductions in leaf photosynthesis and in stomatal and mesophyll conductances. To separate the effects of salt stress on these quantities, a model based on the hypothesis that carbon gain is maximized subject to a water loss cost is proposed. The optimization problem of adjusting stomatal aperture for maximizing carbon gain at a given water loss is solved for both a non-linear and a linear biochemical demand function. A key novel theoretical outcome of the optimality hypothesis is an explicit relationship between the stomatal and mesophyll conductances that can be evaluated against published measurements. The approaches here successfully describe gas-exchange measurements reported for olive trees (Olea europea L.) and spinach (Spinacia oleraceaL.) in fresh water and in salt-stressed conditions. Salt stress affected both stomatal and mesophyll conductances and photosynthetic efficiency of both species. The fresh water/salt water comparisons show that the photosynthetic capacity is directly reduced by 30%-40%, indicating that reductions in photosynthetic rates under increased salt stress are not due only to a limitation of CO2diffusion. An increase in salt stress causes an increase in the cost of water parameter (or marginal water use efficiency) exceeding 100%, analogous in magnitude to findings from extreme drought stress studies. The proposed leaf-level approach can be incorporated into physically based models of the soil-plant-atmosphere system to assess how saline conditions and elevated atmospheric CO2 jointly impact transpiration and photosynthesis.

  1. Accelerated stress testing of thin film solar cells: Development of test methods and preliminary results

    NASA Technical Reports Server (NTRS)

    Lathrop, J. W.

    1985-01-01

    If thin film cells are to be considered a viable option for terrestrial power generation their reliability attributes will need to be explored and confidence in their stability obtained through accelerated testing. Development of a thin film accelerated test program will be more difficult than was the case for crystalline cells because of the monolithic construction nature of the cells. Specially constructed test samples will need to be fabricated, requiring committment to the concept of accelerated testing by the manufacturers. A new test schedule appropriate to thin film cells will need to be developed which will be different from that used in connection with crystalline cells. Preliminary work has been started to seek thin film schedule variations to two of the simplest tests: unbiased temperature and unbiased temperature humidity. Still to be examined are tests which involve the passage of current during temperature and/or humidity stress, either by biasing in the forward (or reverse) directions or by the application of light during stress. Investigation of these current (voltage) accelerated tests will involve development of methods of reliably contacting the thin conductive films during stress.

  2. Accelerated resolution therapy: an innovative mental health intervention to treat post-traumatic stress disorder.

    PubMed

    Finnegan, Alan; Kip, K; Hernandez, D; McGhee, S; Rosenzweig, L; Hynes, C; Thomas, M

    2016-04-01

    Post-traumatic stress disorder (PTSD) is a disabling trauma and stress-related disorder that may occur after a person experiences a traumatic event, and evokes a combination of intrusion and avoidance symptoms, negative alterations in cognitions and mood, and alterations in arousal and reactivity. Accelerated resolution therapy (ART) is an emerging psychotherapy that provides fast and lasting resolution for mental health problems such as PTSD. ART has been shown to achieve a positive result in one to five sessions, typically over a 2-week period, and requires no homework, skills practice or repeated exposure to targeted events. Initial research, including one randomised control trial, has demonstrated that ART interventions can significantly reduce symptoms of psychological trauma in both civilians and US service members and veterans. These results suggest that ART be considered as either a primary treatment option or for refractory PTSD in those with a suboptimal response to endorsed first-line therapies. Conservative estimates indicate substantial potential cost savings in PTSD treatment. Despite the need for more definitive clinical trials, there is increasing interest in ART in the USA, including in the US Army. The growing positive empirical evidence is compelling, and there appears to be sufficient evidence to warrant UK researchers undertaking ART research. The armed forces offer the potential for comparative international trials. However, equally important are veterans, emergency services personnel and those subjected to violence. ART appears to also have application in other conditions, including depression, anxiety disorders, and alcohol or drug misuse. ART can potentially help personnel traumatised by the unique challenges of war and conflict zones by providing brief psychotherapy in a readily accessible and culturally competent manner. ART facilitates the provision of interventions and resolutions in theatre, thus enhancing forces' fighting capability

  3. Accelerated resolution therapy: an innovative mental health intervention to treat post-traumatic stress disorder.

    PubMed

    Finnegan, Alan; Kip, K; Hernandez, D; McGhee, S; Rosenzweig, L; Hynes, C; Thomas, M

    2016-04-01

    Post-traumatic stress disorder (PTSD) is a disabling trauma and stress-related disorder that may occur after a person experiences a traumatic event, and evokes a combination of intrusion and avoidance symptoms, negative alterations in cognitions and mood, and alterations in arousal and reactivity. Accelerated resolution therapy (ART) is an emerging psychotherapy that provides fast and lasting resolution for mental health problems such as PTSD. ART has been shown to achieve a positive result in one to five sessions, typically over a 2-week period, and requires no homework, skills practice or repeated exposure to targeted events. Initial research, including one randomised control trial, has demonstrated that ART interventions can significantly reduce symptoms of psychological trauma in both civilians and US service members and veterans. These results suggest that ART be considered as either a primary treatment option or for refractory PTSD in those with a suboptimal response to endorsed first-line therapies. Conservative estimates indicate substantial potential cost savings in PTSD treatment. Despite the need for more definitive clinical trials, there is increasing interest in ART in the USA, including in the US Army. The growing positive empirical evidence is compelling, and there appears to be sufficient evidence to warrant UK researchers undertaking ART research. The armed forces offer the potential for comparative international trials. However, equally important are veterans, emergency services personnel and those subjected to violence. ART appears to also have application in other conditions, including depression, anxiety disorders, and alcohol or drug misuse. ART can potentially help personnel traumatised by the unique challenges of war and conflict zones by providing brief psychotherapy in a readily accessible and culturally competent manner. ART facilitates the provision of interventions and resolutions in theatre, thus enhancing forces' fighting capability.

  4. Measurements in Transitional Boundary Layers Under High Free-Stream Turbulence and Strong Acceleration Conditions.

    NASA Astrophysics Data System (ADS)

    Volino, Ralph John

    1995-01-01

    Measurements from transitional, heated boundary layers along a concave-curved test wall are presented and discussed. A boundary layer subject to low free-stream turbulence intensity (FSTI), which contains stationary streamwise (Gortler) vortices, is documented. The low FSTI measurements are followed by measurements in boundary layers subject to high (initially 8%) free-stream turbulence intensity and moderate to strong (K = {nuover U_sp{infty} {2}}{dUinftyover dx} as high as 9times 10^{ -6}) acceleration. The high FSTI experiments are the main focus of the work. Conditions were chosen to simulate those present on the downstream half of the pressure side of a gas turbine airfoil. The high FSTI boundary layers undergo transition from a strongly disturbed non-turbulent state to a fully-turbulent state. Due to the stabilizing effect of strong acceleration, the transition zones are of extended length in spite of the high FSTI. Transitional values of skin friction coefficients and Stanton numbers drop below flat-plate, low FSTI, turbulent flow correlations, but remain well above laminar flow values. Mean velocity and temperature profiles exhibit clear changes in shape as the flow passes through transition. Turbulence statistics, including the turbulent shear stress, turbulent heat flux, and turbulent Prandtl number, are documented. Turbulent transport is strongly suppressed below values in unaccelerated turbulent boundary layers. A technique called "octant analysis" is introduced and applied to several cases from the literature as well as to data from the present study. Octant analysis shows a fundamental difference between transitional and fully-turbulent boundary layers. Transitional boundary layers are characterized by incomplete mixing compared to fully-turbulent boundary layers. Similar octant analysis results are observed in both low and high FSTI cases. Spectral analysis suggests that the non-turbulent zone of the high FSTI flow is dominated by large scale

  5. In-situ diagnostics and degradation mapping of a mixed-mode accelerated stress test for proton exchange membranes

    NASA Astrophysics Data System (ADS)

    Lai, Yeh-Hung; Fly, Gerald W.

    2015-01-01

    With increasing availability of more durable membrane materials for proton exchange membrane fuel cells, there is a need for a more stressful test that combines chemical and mechanical stressors to enable accelerated screening of promising membrane candidates. Equally important is the need for in-situ diagnostic methods with sufficient spatial resolution that can provide insights into how membranes degrade to facilitate the development of durable fuel cell systems. In this article, we report an accelerated membrane stress test and a degradation diagnostic method that satisfy both needs. By applying high-amplitude cycles of electrical load to a fuel cell fed with low-RH reactant gases, a wide range of mechanical and chemical stressful conditions can be created within the cell which leads to rapid degradation of a mechanically robust Ion Power™ N111-IP membrane. Using an in-situ shorting/crossover diagnostic method on a segmented fuel cell fixture that provides 100 local current measurements, we are able to monitor the progression and map the degradation modes of shorting, thinning, and crossover leak over the entire membrane. Results from this test method have been validated by conventional metrics of fluoride release rates, physical crossover leak rates, pinhole mapping, and cross-sectional measurements.

  6. Sensitivity Analysis of the Off-Normal Conditions of the SPIDER Accelerator

    SciTech Connect

    Veltri, P.; Agostinetti, P.; Antoni, V.; Chitarin, G.; Marconato, N.; Pilan, N.; Sartori, E.; Serianni, G.; Cavenago, M.

    2011-09-26

    In the context of the development of the 1 MV neutral beam injector for the ITER tokamak, the study on beam formation and acceleration has considerable importance. This effort includes the ion source and accelerator SPIDER (Source for Production of Ions of Deuterium Extracted from an Rf plasma) ion source, planned to be built in Padova, and designed to extract and accelerate a 355 A/m{sup 2} current of H{sup -}(or 285 A/m{sup 2} D{sup -}) up to 100 kV. Exhaustive simulations were already carried out during the accelerator optimization leading to the present design. However, as it is expected that the accelerator shall operate also in case of pre-programmed or undesired off-normal conditions, the investigation of a large set of off-normal scenarios is necessary. These analyses will also be useful for the evaluation of the real performances of the machine, and should help in interpreting experimental results, or in identifying dangerous operating conditions.The present contribution offers an overview of the results obtained during the investigation of these off-normal conditions, by means of different modeling tools and codes. The results, showed a good flexibility of the device in different operating conditions. Where the consequences of the abnormalities appeared to be problematic further analysis were addressed.

  7. Engineering Area Investigation of Reliability Attributes and Accelerated Stress Factors on Terrestrial Solar Cells

    NASA Technical Reports Server (NTRS)

    Lathrop, J. W.; Prince, J. L.

    1979-01-01

    Results obtained include the definition of a simplified stress test schedule for terrestrial solar cells based on the work performed during the first program year, and the design and fabrication of improved jigs and fixtures for electrical measurement and stress testing. Implementation of these advanced techniques for accelerated stress testing is underway on three solar cell types. In addition, review of the literature on second quadrant phenomena was begun and some preliminary second-quadrant electrical measurements were performed. Results obtained at the first down time for 75 C B-T testing and biased and unbiased T-H pressure cooker testing of type F cells showed little or no degradation in electrical parameters. Significant physical effects (large solder bubbles) were noted for type F cells subjected to the pressure cooker stress test.

  8. NRF2 Regulates PINK1 Expression under Oxidative Stress Conditions

    PubMed Central

    Murata, Hitoshi; Takamatsu, Hitoshi; Liu, Sulai; Kataoka, Ken; Huh, Nam-ho; Sakaguchi, Masakiyo

    2015-01-01

    Mutations of the PTEN-induced putative kinase 1 (PINK1) gene are a cause of autosomal recessive forms of Parkinson’s disease. Recent studies have revealed that PINK1 is an essential factor for controlling mitochondrial quality, and that it protects cells from oxidative stresses. Although there has been considerable progress in the elucidation of various aspects of PINK1 protein regulation such as activation, stability and degradation, the transcriptional regulation of PINK1 mRNA under stress conditions remains unclear. In this study, we found that nuclear factor (erythroid-derived 2)-like 2 (NRF2), an antioxidant transcription factor, regulates PINK1 expression under oxidative stress conditions. Damaged mitochondria arising from stress conditions induced NRF2-dependent transcription of the PINK1 gene through production of reactive oxygen species (ROS). Either an ROS scavenger or forced expression of KEAP1, a potent inhibitory partner to NRF2, restricted PINK1 expression induced by activated NRF2. Transcriptionally up-regulated PINK1 diminished oxidative stress-associated cell death. The results indicate that PINK1 expression is positively regulated by NRF2 and that the NRF2-PINK1 signaling axis is deeply involved in cell survival. PMID:26555609

  9. Solar wind conditions leading to efficient radiation belt electron acceleration: A superposed epoch analysis

    DOE PAGES

    Li, W.; Thorne, R. M.; Bortnik, J.; Baker, D. N.; Reeves, G. D.; Kanekal, S. G.; Spence, H. E.; Green, J. C.

    2015-09-07

    In this study by determining preferential solar wind conditions leading to efficient radiation belt electron acceleration is crucial for predicting radiation belt electron dynamics. Using Van Allen Probes electron observations (>1 MeV) from 2012 to 2015, we identify a number of efficient and inefficient acceleration events separately to perform a superposed epoch analysis of the corresponding solar wind parameters and geomagnetic indices. By directly comparing efficient and inefficient acceleration events, we clearly show that prolonged southward Bz, high solar wind speed, and low dynamic pressure are critical for electron acceleration to >1 MeV energies in the heart of the outermore » radiation belt. We also evaluate chorus wave evolution using the superposed epoch analysis for the identified efficient and inefficient acceleration events and find that chorus wave intensity is much stronger and lasts longer during efficient electron acceleration events, supporting the scenario that chorus waves play a key role in MeV electron acceleration.« less

  10. Corrosion behavior of modified nano carbon black/epoxy coating in accelerated conditions

    NASA Astrophysics Data System (ADS)

    Ghasemi-Kahrizsangi, Ahmad; Shariatpanahi, Homeira; Neshati, Jaber; Akbarinezhad, Esmaeil

    2015-03-01

    The electrochemical behavior and anticorrosion properties of modified carbon black (CB) nanoparticles in epoxy coatings were investigated in accelerated conditions. Nanoparticles of CB were modified by sodium dodecyl sulfate (SDS) as surfactant. Dispersion of nanoparticles into epoxy was confirmed by Transmission Electron Microscopy (TEM). The accelerated condition was prepared at 65 °C. CB nanoparticles improved corrosion resistance of the epoxy coating. The optimum concentration of CB in the epoxy coating was 0.75 wt%. Results showed that the CB hinder the corrosion due to its barrier properties. CB can decrease the diffusion coefficient of water in the coating with filling the micropores.

  11. On Spin-Statistics and Bogoliubov Transformations in Flat Space-Time with Acceleration Conditions

    NASA Astrophysics Data System (ADS)

    Good, Michael R. R.

    2013-01-01

    A single real scalar field of spin zero obeying the Klein-Gordon equation in flat space-time under external conditions is considered in the context of the spin-statistics connection. An imposed accelerated boundary on the field is made to become, in the far future, (1) asymptotically inertial and (2) asymptotically noninertial (with an infinite acceleration). The constant acceleration Unruh effect is also considered. The systems involving nontrivial Bogoliubov transformations contain dynamics which point to commutation relations. Particles described by in-modes obey the same statistics as particles described by out-modes. It is found in the nontrivial systems that the spin-statistics connection can be manifest from the acceleration. The equation of motion for the boundary which forever emits thermal radiation is revealed.

  12. Zymomonas with improved xylose utilization in stress conditions

    SciTech Connect

    Caimi, Perry G; Emptage, Mark; Li, Xu; Viitanen, Paul V; Chou, Yat-Chen; Franden, Mary Ann; Zhang, Min

    2013-06-18

    Strains of xylose utilizing Zymomonas with improved xylose utilization and ethanol production during fermentation in stress conditions were obtained using an adaptation method. The adaptation involved continuously growing xylose utilizing Zymomonas in media containing high sugars, acetic acid, ammonia, and ethanol.

  13. Accelerated Stress Testing of Thin-Film Modules with SnO2:F Transparent Conductors

    SciTech Connect

    Osterwald, C. R.; McMahon, T. J.; del Cueto, J. A.; Adelstein, J.; Puett, J.

    2003-05-01

    This paper reviews a testing program conducted at NREL for the past two years that applied voltage, water vapor, and light stresses to thin-film photovoltaic (PV) modules with SnO2:F transparent conducting oxides (TCOs) deposited on soda-lime glass superstrates. Electrochemical corrosion at the glass-TCO interface was observed to result in delamination of the thin-film layers. Experimental testing was directed toward accelerating the corrosion and understanding the nature of the resulting damage.

  14. Repeatable electrical measurement instrumentation for use in the accelerated stress testing of thin film solar cells

    NASA Technical Reports Server (NTRS)

    Davis, C. W.; Lathrop, J. W.

    1985-01-01

    Attention is given to the construction, calibration, and performance of a repeatable measurement system for use in conjunction with the accelerated stress testing of a-Si:H cells. A filtered diode array is utilized to approximate the spectral response of any type of solar cell in discrete portions of the spectrum. It is noted that in order to achieve the necessary degree of overall repeatability, it is necessary to pay particular attention to methods of contacting and positioning the cells.

  15. Optimal design of multiple stress constant accelerated life test plan on non-rectangle test region

    NASA Astrophysics Data System (ADS)

    Chen, Wenhua; Gao, Liang; Liu, Juan; Qian, Ping; Pan, Jun

    2012-11-01

    For optimal design of constant stress accelerated life test(CSALT) with two-stress, if the stresses could not reach the highest levels simultaneously, the test region becomes non-rectangular. For optimal CSALT design on non-rectangle test region, the present method is only focused on non-rectangle test region with simple boundary, and the optimization algorithm is based on experience which can not ensure to obtain the optimal plan. In this paper, considering the linear-extreme value model and the optimization goal to minimize the variance of lifetime estimate under normal stress, the optimal design method of two-stress type-I censored CSALT plan on general non-rectangular test region is proposed. First, two properties of optimal test plans are proved and the relationship of all the optimal test plans is determined analytically. Then, on the basis of the two properties, the optimal problem is simplified and the optimal design method of two-stress CSALT plan on general non-rectangular test region is proposed. Finally, a numerical example is used to illustrate the feasibility and effectiveness of the method. The result shows that the proposed method could obtain the optimal test plan on non-rectangular test regions with arbitrary boundaries. This research provides the theory and method for two-stress optimal CSALT planning on non-rectangular test regions.

  16. Development of an RF Conditioning System for Charged-Particle Accelerators

    SciTech Connect

    Kang, Yoon W; Howlader, Mostofa; Shajedul Hasan, Dr. S. M.

    2008-01-01

    Charged-particle accelerators use various vacuum windows on their accelerating radio-frequency (RF) cavities to throughput very high RF power. Before being placed on the cavities, the windows should be cleaned, baked, and fully RF conditioned to prevent a poor vacuum from outgassing, as well as other forms of contamination. An example is the coaxial fundamental power coupler (FPC) with an annular alumina ceramic window for each of the 81 superconducting RF cavities in the Spallation Neutron Source (SNS) linear accelerator. The FPCs needed to be tested up to 650-kW peak in a traveling wave and 2.6 MW with standing wave peaks in 1.3 and 60 pulses/s at 805 MHz. In this paper, an Experimental-Physics-and-Industrial-Control-System-based RF conditioning system for the SNS RF test facility is presented. This paper summarizes the hardware and software design strategies, provides the results obtained, and describes the future research scope.

  17. Behavior of Materials Under Conditions of Thermal Stress

    NASA Technical Reports Server (NTRS)

    Manson, S S

    1954-01-01

    A review is presented of available information on the behavior of brittle and ductile materials under conditions of thermal stress and thermal shock. For brittle materials, a simple formula relating physical properties to thermal-shock resistance is derived and used to determine the relative significance of two indices currently in use for rating materials. For ductile materials, thermal-shock resistance depends upon the complex interrelation among several metallurgical variables which seriously affect strength and ductility. These variables are briefly discussed and illustrated from literature sources. The importance of simulating operating conditions in tests for rating materials is especially to be emphasized because of the importance of testing conditions in metallurgy. A number of practical methods that have been used to minimize the deleterious effects of thermal stress and thermal shock are outlined.

  18. Effect of Ultrasonic Peening and Accelerated Corrosion Exposure on the Residual Stress Distribution in Welded Marine Steel

    NASA Astrophysics Data System (ADS)

    Ahmad, Bilal; Fitzpatrick, Michael E.

    2015-03-01

    Specimens of DH36 marine steel were prepared with welded attachments. Residual stress measurements were made on the samples as-welded, following an ultrasonic peening treatment, and following accelerated corrosion exposure after ultrasonic peening. Neutron diffraction and the contour method were used for determining the residual stress profiles. The welding introduces tensile near-surface residual stress, approaching the material yield strength, and the ultrasonic peening overlays this with a compressive residual stress. Material removal by corrosion decreases the peak surface compressive stress slightly, by removal of a layer of stressed material, but does not cause significant redistribution of the residual stress profile.

  19. Testing the accelerating moment release (AMR) hypothesis in areas of high stress

    NASA Astrophysics Data System (ADS)

    Guilhem, Aurélie; Bürgmann, Roland; Freed, Andrew M.; Ali, Syed Tabrez

    2013-11-01

    Several retrospective analyses have proposed that significant increases in moment release occurred prior to many large earthquakes of recent times. However, the finding of accelerating moment release (AMR) strongly depends on the choice of three parameters: (1) magnitude range, (2) area being considered surrounding the events and (3) the time period prior to the large earthquakes. Consequently, the AMR analysis has been criticized as being a posteriori data-fitting exercise with no new predictive power. As AMR has been hypothesized to relate to changes in the state of stress around the eventual epicentre, we compare here AMR results to models of stress accumulation in California. Instead of assuming a complete stress drop on all surrounding fault segments implied by a back-slip stress lobe method, we consider that stress evolves dynamically, punctuated by the occurrence of earthquakes, and governed by the elastic and viscous properties of the lithosphere. We study the seismicity of southern California and extract events for AMR calculations following the systematic approach employed in previous studies. We present several sensitivity tests of the method, as well as grid-search analyses over the region between 1955 and 2005 using fixed magnitude range, radius of the search area and period of time. The results are compared to the occurrence of large events and to maps of Coulomb stress changes. The Coulomb stress maps are compiled using the coseismic stress from all M > 7.0 earthquakes since 1812, their subsequent post-seismic relaxation, and the interseismic strain accumulation. We find no convincing correlation of seismicity rate changes in recent decades with areas of high stress that would support the AMR hypothesis. Furthermore, this indicates limited utility for practical earthquake hazard analysis in southern California, and possibly other regions.

  20. Resistance of functional Lactobacillus plantarum strains against food stress conditions.

    PubMed

    Ferrando, Verónica; Quiberoni, Andrea; Reinhemer, Jorge; Suárez, Viviana

    2015-06-01

    The survival of three Lactobacillus plantarum strains (Lp 790, Lp 813 and Lp 998) with functional properties was studied taking into account their resistance to thermal, osmotic and oxidative stress factors. Stress treatments applied were: 52 °C-15 min (Phosphate Buffer pH 7, thermal shock), H2O2 0.1% (p/v) - 30 min (oxidative shock) and NaCl aqueous solution at 17, 25 and 30% (p/v) (room temperature - 1 h, osmotic shock). The osmotic stress was also evaluated on cell growth in MRS broth added of 2, 4, 6, 8 and 10% (p/v) of NaCl, during 20 h at 30 °C. The cell thermal adaptation was performed in MRS broth, selecting 45 °C for 30 min as final conditions for all strains. Two strains (Lp 813 and Lp 998) showed, in general, similar behaviour against the three stress factors, being clearly more resistant than Lp 790. An evident difference in growth kinetics in presence of NaCl was observed between Lp 998 and Lp 813, Lp998 showing a higher optical density (OD570nm) than Lp 813 at the end of the assay. Selected thermal adaptation improved by 2 log orders the thermal resistance of both strains, but cell growth in presence of NaCl was enhanced only in Lp 813. Oxidative resistance was not affected with this thermal pre-treatment. These results demonstrate the relevance of cell technological resistance when selecting presumptive "probiotic" cultures, since different stress factors might considerably affect viability or/and performance of the strains. The incidence of stress conditions on functional properties of the strains used in this work are currently under research in our group.

  1. Sex, stress, and fear: individual differences in conditioned learning.

    PubMed

    Zorawski, Michael; Cook, Craig A; Kuhn, Cynthia M; LaBar, Kevin S

    2005-06-01

    It has long been recognized that humans vary in their conditionability, yet the factors that contribute to individual variation in emotional learning remain to be delineated. The goal of the present study was to investigate the relationship among sex, stress hormones, and fear conditioning in humans. Forty-five healthy adults (22 females) underwent differential delay conditioning, using fear-relevant conditioned stimuli and a shock unconditioned stimulus. Salivary cortisol samples were taken at baseline and after acquisition training and a 24-h-delayed retention test. The results showed that acquisition of conditioning significantly correlated with postacquisition cortisol levels in males, but not in females. This sex-specific relationship was found despite similar overall levels of conditioning, unconditioned responding, and cortisol. There was no effect of postacquisition cortisol on consolidation of fear learning in either sex. These findings have implications for the understanding of individual differences in fear acquisition and risk factors for the development of affective disorders.

  2. Understanding Vocalization Might Help to Assess Stressful Conditions in Piglets

    PubMed Central

    Cordeiro, Alexandra Ferreira da Silva; Nääs, Irenilza de Alencar; Oliveira, Stanley R. M.; Violaro, Fabio; de Almeida, Andréia C. M.; Neves, Diego Pereira

    2013-01-01

    Simple Summary This research aimed to analyze the possibility of assessing piglets’ welfare using the records of their vocalization. The trial was done in a pig commercial farm, and we recorded the vocal signals from piglets in several stressful exposure situations. Data mining techniques were applied to the processed signals in order to obtain a stress classification using the recorded data. We found that, using the piglets’ vocalization, it was possible to identify the most frequent stressful conditions at the farrowing phase, namely: pain, cold and hunger. Abstract Assessing pigs’ welfare is one of the most challenging subjects in intensive pig farming. Animal vocalization analysis is a noninvasive procedure and may be used as a tool for assessing animal welfare status. The objective of this research was to identify stress conditions in piglets reared in farrowing pens through their vocalization. Vocal signals were collected from 40 animals under the following situations: normal (baseline), feeling cold, in pain, and feeling hunger. A unidirectional microphone positioned about 15 cm from the animals’ mouth was used for recording the acoustic signals. The microphone was connected to a digital recorder, where the signals were digitized at the 44,100 Hz frequency. The collected sounds were edited and analyzed. The J48 decision tree algorithm available at the Weka® data mining software was used for stress classification. It was possible to categorize diverse conditions from the piglets’ vocalization during the farrowing phase (pain, cold and hunger), with an accuracy rate of 81.12%. Results indicated that vocalization might be an effective welfare indicator, and it could be applied for assessing distress from pain, cold and hunger in farrowing piglets. PMID:26479541

  3. Early Adversity, Elevated Stress Physiology, Accelerated Sexual Maturation and Poor Health in Females

    PubMed Central

    Belsky, Jay; Ruttle, Paula L.; Boyce, W. Thomas; Armstrong, Jeffrey M.; Essex, Marilyn J.

    2015-01-01

    Evolutionary-minded developmentalists studying predictive-adaptive-response processes linking childhood adversity with accelerated female reproductive development and health scientists investigating the developmental origins of health and disease (DOoHaD) may be tapping the same process, whereby longer-term health costs are traded off for increased probability of reproducing before dying via a process of accelerated reproductive maturation. Using data from 73 females, we test the following propositions using path analysis: (a) greater exposure to prenatal stress predicts greater maternal depression and negative parenting in infancy, (b) which predicts elevated basal cortisol at 4.5 years, (c) which predicts accelerated adrenarcheal development, (d) which predicts more physical and mental health problems at age 18. Results prove generally consistent with these propositions, including a direct link from cortisol to mental health problems. DOoHaD investigators should consider including early sexual maturation as a core component linking early adversity and stress physiology with poor health later in life in females. PMID:25915592

  4. Early adversity, elevated stress physiology, accelerated sexual maturation, and poor health in females.

    PubMed

    Belsky, Jay; Ruttle, Paula L; Boyce, W Thomas; Armstrong, Jeffrey M; Essex, Marilyn J

    2015-06-01

    Evolutionary-minded developmentalists studying predictive-adaptive-response processes linking childhood adversity with accelerated female reproductive development and health scientists investigating the developmental origins of health and disease (DOoHaD) may be tapping the same process, whereby longer-term health costs are traded off for increased probability of reproducing before dying via a process of accelerated reproductive maturation. Using data from 73 females, we test the following propositions using path analysis: (a) greater exposure to prenatal stress predicts greater maternal depression and negative parenting in infancy, (b) which predicts elevated basal cortisol at 4.5 years, (c) which predicts accelerated adrenarcheal development, (d) which predicts more physical and mental health problems at age 18. Results prove generally consistent with these propositions, including a direct link from cortisol to mental health problems. DOoHaD investigators should consider including early sexual maturation as a core component linking early adversity and stress physiology with poor health later in life in females.

  5. Poor maternal nutrition and accelerated postnatal growth induces an accelerated aging phenotype and oxidative stress in skeletal muscle of male rats

    PubMed Central

    Fernandez-Twinn, Denise S.; Chen, Jian Hua; Hargreaves, Iain P.; Neergheen, Viruna; Aiken, Catherine E.; Ozanne, Susan E.

    2016-01-01

    ABSTRACT ‘Developmental programming’, which occurs as a consequence of suboptimal in utero and early environments, can be associated with metabolic dysfunction in later life, including an increased incidence of cardiovascular disease and type 2 diabetes, and predisposition of older men to sarcopenia. However, the molecular mechanisms underpinning these associations are poorly understood. Many conditions associated with developmental programming are also known to be associated with the aging process. We therefore utilized our well-established rat model of low birth weight and accelerated postnatal catch-up growth (termed ‘recuperated’) in this study to establish the effects of suboptimal maternal nutrition on age-associated factors in skeletal muscle. We demonstrated accelerated telomere shortening (a robust marker of cellular aging) as evidenced by a reduced frequency of long telomeres (48.5-8.6 kb) and an increased frequency of short telomeres (4.2-1.3 kb) in vastus lateralis muscle from aged recuperated offspring compared to controls. This was associated with increased protein expression of the DNA-damage-repair marker 8-oxoguanine-glycosylase (OGG1) in recuperated offspring. Recuperated animals also demonstrated an oxidative stress phenotype, with decreased citrate synthase activity, increased electron-transport-complex activities of complex I, complex II-III and complex IV (all markers of functional mitochondria), and increased xanthine oxidase (XO), p67phox and nuclear-factor kappa-light-chain-enhancer of activated B-cells (NF-κB). Recuperated offspring also demonstrated increased antioxidant defense capacity, with increased protein expression of manganese superoxide dismutase (MnSOD), copper-zinc superoxide dismutase (CuZnSOD), catalase and heme oxygenase-1 (HO1), all of which are known targets of NF-κB and can be upregulated as a consequence of oxidative stress. Recuperated offspring also had a pro-inflammatory phenotype, as evidenced by

  6. Lifetime Prediction for Degradation of Solar Mirrors using Step-Stress Accelerated Testing (Presentation)

    SciTech Connect

    Lee, J.; Elmore, R.; Kennedy, C.; Gray, M.; Jones, W.

    2011-09-01

    This research is to illustrate the use of statistical inference techniques in order to quantify the uncertainty surrounding reliability estimates in a step-stress accelerated degradation testing (SSADT) scenario. SSADT can be used when a researcher is faced with a resource-constrained environment, e.g., limits on chamber time or on the number of units to test. We apply the SSADT methodology to a degradation experiment involving concentrated solar power (CSP) mirrors and compare the results to a more traditional multiple accelerated testing paradigm. Specifically, our work includes: (1) designing a durability testing plan for solar mirrors (3M's new improved silvered acrylic "Solar Reflector Film (SFM) 1100") through the ultra-accelerated weathering system (UAWS), (2) defining degradation paths of optical performance based on the SSADT model which is accelerated by high UV-radiant exposure, and (3) developing service lifetime prediction models for solar mirrors using advanced statistical inference. We use the method of least squares to estimate the model parameters and this serves as the basis for the statistical inference in SSADT. Several quantities of interest can be estimated from this procedure, e.g., mean-time-to-failure (MTTF) and warranty time. The methods allow for the estimation of quantities that may be of interest to the domain scientists.

  7. Absence of transient receptor potential vanilloid-1 accelerates stress-induced axonopathy in the optic projection.

    PubMed

    Ward, Nicholas J; Ho, Karen W; Lambert, Wendi S; Weitlauf, Carl; Calkins, David J

    2014-02-26

    How neurons respond to stress in degenerative disease is of fundamental importance for identifying mechanisms of progression and new therapeutic targets. Members of the transient receptor potential (TRP) family of cation-selective ion channels are candidates for mediating stress signals, since different subunits transduce a variety of stimuli relevant in both normal and pathogenic physiology. We addressed this possibility for the TRP vanilloid-1 (TRPV1) subunit by comparing how the optic projection of Trpv1(-/-) mice and age-matched C57 controls responds to stress from elevated ocular pressure, the critical stressor in the most common optic neuropathy, glaucoma. Over a 5 week period of elevated pressure induced by microbead occlusion of ocular fluid, Trpv1(-/-) accelerated both degradation of axonal transport from retinal ganglion cells to the superior colliculus and degeneration of the axons themselves in the optic nerve. Ganglion cell body loss, which is normally later in progression, occurred in nasal sectors of Trpv1(-/-) but not C57 retina. Pharmacological antagonism of TRPV1 in rats similarly accelerated ganglion cell axonopathy. Elevated ocular pressure resulted in differences in spontaneous firing rate and action potential threshold current in Trpv1(-/-) ganglion cells compared with C57. In the absence of elevated pressure, ganglion cells in the two strains had similar firing patterns. Based on these data, we propose that TRPV1 may help neurons respond to disease-relevant stressors by enhancing activity necessary for axonal signaling.

  8. Key conditions for stable ion radiation pressure acceleration by circularly polarized laser pulses

    NASA Astrophysics Data System (ADS)

    Qiao, B.; Zepf, M.; Gibbon, P.; Borghesi, M.; Schreiber, J.; Geissler, M.

    2011-05-01

    Radiation pressure acceleration (RPA) theoretically may have great potential to revolutionize the study of laserdriven ion accelerators due to its high conversion efficiency and ability to produce high-quality monoenergetic ion beams. However, the instability issue of ion acceleration has been appeared to be a fundamental limitation of the RPA scheme. To solve this issue is very important to the experimental realization and exploitation of this new scheme. In our recent work, we have identified the key condition for efficient and stable ion RPA from thin foils by CP laser pulses, in particular, at currently available moderate laser intensities. That is, the ion beam should remain accompanied with enough co-moving electrons to preserve a local "bunching" electrostatic field during the acceleration. In the realistic LS RPA, the decompression of the co-moving electron layer leads to a change of local electrostatic field from a "bunching" to a "debunching" profile, resulting in premature termination of acceleration. One possible scheme to achieve stable RPA is using a multi-species foil. Two-dimensional PIC simulations show that 100 MeV/u monoenergetic C6+ and/or proton beams are produced by irradiation of a contaminated copper foil with CP lasers at intensities 5 × 1020W/cm2, achievable by current day lasers.

  9. Investigation of reliability attributes and accelerated stress factors on terrestrial solar cells

    NASA Technical Reports Server (NTRS)

    Lathrop, J. W.

    1982-01-01

    The accelerated stress test results obtained on all terrestrial solar cells since the inception of the program are summarized. Tested cells were grouped according to the method used to form the conductive metallization layer: solder dipped, vacuum deposited, screen printed, and copper plated. Although metallization systems within each group were quite similar, they differed in numerous details according to the procedures employed by each manufacturer. Test results were summarized for all cells according to both electrical degradation and catastrophic mechanical changes. These results indicated a variability within each metallization category which was dependent on the manufacturer. Only one manufacturer was represented in the copper plated category and, although these showed no signs of detrimental copper diffusion during high temperature testing, their metallization was removed easily during high humidity pressure cooker testing. Preliminary testing of encapsulated cells showed no major differences between encapsulated and unencapsulated cells when subjected to accelerated testing.

  10. Investigation of reliability attributes and accelerated stress factors on terrestrial solar cells

    NASA Astrophysics Data System (ADS)

    Lathrop, J. W.

    1982-06-01

    The accelerated stress test results obtained on all terrestrial solar cells since the inception of the program are summarized. Tested cells were grouped according to the method used to form the conductive metallization layer: solder dipped, vacuum deposited, screen printed, and copper plated. Although metallization systems within each group were quite similar, they differed in numerous details according to the procedures employed by each manufacturer. Test results were summarized for all cells according to both electrical degradation and catastrophic mechanical changes. These results indicated a variability within each metallization category which was dependent on the manufacturer. Only one manufacturer was represented in the copper plated category and, although these showed no signs of detrimental copper diffusion during high temperature testing, their metallization was removed easily during high humidity pressure cooker testing. Preliminary testing of encapsulated cells showed no major differences between encapsulated and unencapsulated cells when subjected to accelerated testing.

  11. Aerodynamic Surface Stress Intermittency and Conditionally Averaged Turbulence Statistics

    NASA Astrophysics Data System (ADS)

    Anderson, W.

    2015-12-01

    Aeolian erosion of dry, flat, semi-arid landscapes is induced (and sustained) by kinetic energy fluxes in the aloft atmospheric surface layer. During saltation -- the mechanism responsible for surface fluxes of dust and sediment -- briefly suspended sediment grains undergo a ballistic trajectory before impacting and `splashing' smaller-diameter (dust) particles vertically. Conceptual models typically indicate that sediment flux, q (via saltation or drift), scales with imposed aerodynamic (basal) stress raised to some exponent, n, where n > 1. Since basal stress (in fully rough, inertia-dominated flows) scales with the incoming velocity squared, u^2, it follows that q ~ u^2n (where u is some relevant component of the above flow field, u(x,t)). Thus, even small (turbulent) deviations of u from its time-averaged value may play an enormously important role in aeolian activity on flat, dry landscapes. The importance of this argument is further augmented given that turbulence in the atmospheric surface layer exhibits maximum Reynolds stresses in the fluid immediately above the landscape. In order to illustrate the importance of surface stress intermittency, we have used conditional averaging predicated on aerodynamic surface stress during large-eddy simulation of atmospheric boundary layer flow over a flat landscape with momentum roughness length appropriate for the Llano Estacado in west Texas (a flat agricultural region that is notorious for dust transport). By using data from a field campaign to measure diurnal variability of aeolian activity and prevailing winds on the Llano Estacado, we have retrieved the threshold friction velocity (which can be used to compute threshold surface stress under the geostrophic balance with the Monin-Obukhov similarity theory). This averaging procedure provides an ensemble-mean visualization of flow structures responsible for erosion `events'. Preliminary evidence indicates that surface stress peaks are associated with the passage of

  12. Stress Conditions Induced by Carvacrol and Cinnamaldehyde on Acinetobacter baumannii.

    PubMed

    Montagu, Angélique; Joly-Guillou, Marie-Laure; Rossines, Elisabeth; Cayon, Jérome; Kempf, Marie; Saulnier, Patrick

    2016-01-01

    Acinetobacter baumannii has emerged as a major cause of nosocomial infections. The ability of A. baumannii to display various resistance mechanisms against antibiotics has transformed it into a successful nosocomial pathogen. The limited number of antibiotics in development and the disengagement of the pharmaceutical industry have prompted the development of innovative strategies. One of these strategies is the use of essential oils, especially aromatic compounds that are potent antibacterial molecules. Among them, the combination of carvacrol and cinnamaldehyde has already demonstrated antibacterial efficacy against A. baumannii. The aim of this study was to determine the biological effects of these two compounds in A. baumannii, describing their effect on the rRNA and gene regulation under environmental stress conditions. Results demonstrated rRNA degradation by the carvacrol/cinnamaldehyde mixture, and this effect was due to carvacrol. Degradation was conserved after encapsulation of the mixture in lipid nanocapsules. Results showed an upregulation of the genes coding for heat shock proteins, such as groES, groEL, dnaK, clpB, and the catalase katE, after exposure to carvacrol/cinnamaldehyde mixture. The catalase was upregulated after carvacrol exposure wich is related to an oxidative stress. The combination of thiourea (hydroxyl radical scavenger) and carvacrol demonstrated a potent bactericidal effect. These results underline the development of defense strategies of the bacteria by synthesis of reactive oxygen species in response to environmental stress conditions, such as carvacrol. PMID:27486453

  13. Stress Conditions Induced by Carvacrol and Cinnamaldehyde on Acinetobacter baumannii

    PubMed Central

    Montagu, Angélique; Joly-Guillou, Marie-Laure; Rossines, Elisabeth; Cayon, Jérome; Kempf, Marie; Saulnier, Patrick

    2016-01-01

    Acinetobacter baumannii has emerged as a major cause of nosocomial infections. The ability of A. baumannii to display various resistance mechanisms against antibiotics has transformed it into a successful nosocomial pathogen. The limited number of antibiotics in development and the disengagement of the pharmaceutical industry have prompted the development of innovative strategies. One of these strategies is the use of essential oils, especially aromatic compounds that are potent antibacterial molecules. Among them, the combination of carvacrol and cinnamaldehyde has already demonstrated antibacterial efficacy against A. baumannii. The aim of this study was to determine the biological effects of these two compounds in A. baumannii, describing their effect on the rRNA and gene regulation under environmental stress conditions. Results demonstrated rRNA degradation by the carvacrol/cinnamaldehyde mixture, and this effect was due to carvacrol. Degradation was conserved after encapsulation of the mixture in lipid nanocapsules. Results showed an upregulation of the genes coding for heat shock proteins, such as groES, groEL, dnaK, clpB, and the catalase katE, after exposure to carvacrol/cinnamaldehyde mixture. The catalase was upregulated after carvacrol exposure wich is related to an oxidative stress. The combination of thiourea (hydroxyl radical scavenger) and carvacrol demonstrated a potent bactericidal effect. These results underline the development of defense strategies of the bacteria by synthesis of reactive oxygen species in response to environmental stress conditions, such as carvacrol. PMID:27486453

  14. The role of oxidative and nitrosative stress in accelerated aging and major depressive disorder.

    PubMed

    Maurya, Pawan Kumar; Noto, Cristiano; Rizzo, Lucas B; Rios, Adiel C; Nunes, Sandra O V; Barbosa, Décio Sabbatini; Sethi, Sumit; Zeni, Maiara; Mansur, Rodrigo B; Maes, Michael; Brietzke, Elisa

    2016-02-01

    Major depressive disorder (MDD) affects millions of individuals and is highly comorbid with many age associated diseases such as diabetes mellitus, immune-inflammatory dysregulation and cardiovascular diseases. Oxidative/nitrosative stress plays a fundamental role in aging, as well as in the pathogenesis of neurodegenerative/neuropsychiatric disorders including MDD. In this review, we critically review the evidence for an involvement of oxidative/nitrosative stress in acceleration of aging process in MDD. There are evidence of the association between MDD and changes in molecular mechanisms involved in aging. There is a significant association between telomere length, enzymatic antioxidant activities (SOD, CAT, GPx), glutathione (GSH), lipid peroxidation (MDA), nuclear factor κB, inflammatory cytokines with MDD. Major depression also is characterized by significantly lower concentration of antioxidants (zinc, coenzyme Q10, PON1). Since, aging and MDD share a common biological base in their pathophysiology, the potential therapeutic use of antioxidants and anti-aging molecules in MDD could be promising.

  15. Accelerated Testing Methodology in Constant Stress-Rate Testing for Advanced Structural Ceramics: A Preloading Technique

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Gyekenyesi, John P.; Huebert, Dean; Bartlett, Allen; Choi, Han-Ho

    2001-01-01

    Preloading technique was used as a means of an accelerated testing methodology in constant stress-rate ('dynamic fatigue') testing for two different brittle materials. The theory developed previously for fatigue strength as a function of preload was further verified through extensive constant stress-rate testing for glass-ceramic and CRT glass in room temperature distilled water. The preloading technique was also used in this study to identify the prevailing failure mechanisms at elevated temperatures, particularly at lower test rate in which a series of mechanisms would be associated simultaneously with material failure, resulting in significant strength increase or decrease. Two different advanced ceramics including SiC whisker-reinforced composite silicon nitride and 96 wt% alumina were used at elevated temperatures. It was found that the preloading technique can be used as an additional tool to pinpoint the dominant failure mechanism that is associated with such a phenomenon of considerable strength increase or decrease.

  16. Accelerated Testing Methodology in Constant Stress-Rate Testing for Advanced Structural Ceramics: A Preloading Technique

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Gyekenyesi, John P.; Huebert, Dean; Bartlett, Allen; Choi, Han-Ho

    2001-01-01

    Preloading technique was used as a means of an accelerated testing methodology in constant stress-rate (dynamic fatigue) testing for two different brittle materials. The theory developed previously for fatigue strength as a function of preload was further verified through extensive constant stress-rate testing for glass-ceramic and CRT glass in room temperature distilled water. The preloading technique was also used in this study to identify the prevailing failure mechanisms at elevated temperatures, particularly at lower test rates in which a series of mechanisms would be associated simultaneously with material failure, resulting in significant strength increase or decrease. Two different advanced ceramics including SiC whisker-reinforced composite silicon nitride and 96 wt% alumina were used at elevated temperatures. It was found that the preloading technique can be used as an additional tool to pinpoint the dominant failure mechanism that is associated with such a phenomenon of considerable strength increase or decrease.

  17. Electron Acceleration in a Dynamically Evolved Current Sheet Under Solar Coronal Conditions

    NASA Astrophysics Data System (ADS)

    Zhang, Shaohua; Du, A. M.; Feng, Xueshang; Cao, Xin; Lu, Quanming; Yang, Liping; Chen, Gengxiong; Zhang, Ying

    2014-05-01

    Electron acceleration in a drastically evolved current sheet under solar coronal conditions is investigated via the combined 2.5-dimensional (2.5D) resistive magnetohydrodynamics (MHD) and test-particle approaches. Having a high magnetic Reynolds number (105), the long, thin current sheet is torn into a chain of magnetic islands, which grow in size and coalesce with each other. The acceleration of electrons is explored in three typical evolution phases: when several large magnetic islands are formed (phase 1), two of these islands are approaching each other (phase 2), and almost merging into a "monster" magnetic island (phase 3). The results show that for all three phases electrons with an initial Maxwell distribution evolve into a heavy-tailed distribution and more than 20 % of the electrons can be accelerated higher than 200 keV within 0.1 second and some of them can even be energized up to MeV ranges. The lower-energy electrons are located away from the magnetic separatrices and the higher-energy electrons are inside the magnetic islands. The most energetic electrons have a tendency to be around the outer regions of the magnetic islands or to appear in the small secondary magnetic islands. It is the trapping effect of the magnetic islands and the distributions of E p that determine the acceleration and spatial distributions of the energetic electrons.

  18. Investigation of reliability attributes and accelerated stress factors on terrestrial solar cells

    NASA Technical Reports Server (NTRS)

    Lathrop, J. W.; Prince, J. L.

    1980-01-01

    Three tasks were undertaken to investigate reliability attributes of terrestrial solar cells: (1) a study of the electrical behavior of cells in the second (reverse) quadrant; (2) the accelerated stress testing of three new state-of-the-art cells; and (3) the continued bias-temperature testing of four block 2 type silicon cells at 78 C and 135 C. Electrical characteristics measured in the second quadrant were determined to be a function of the cell's thermal behavior with breakdown depending on the initiation of localized heating. This implied that high breakdown cells may be more fault tolerant when forced to operate in the second quadrant, a result contrary to conventional thinking. The accelerated stress tests used in the first (power) quadrant were bias-temperature, bias-temperature-humidity, temperature-humidity, thermal shock, and thermal cycle. The new type cells measured included an EFG cell, a polycrystalline cell, and a Czochralski cell. Significant differences in the response to the various tests were observed between cell types. A microprocessed controlled, short interval solar cell tester was designed and construction initiated on a prototype.

  19. DNS evaluation of Reynolds stress models and Generalized Langevin models using velocity-acceleration correlation

    NASA Astrophysics Data System (ADS)

    Zhao, Xinyu; Mathioudakis, Alexandros

    2015-11-01

    Velocity-acceleration correlation is used to evaluate the pressure-rate-of-strain term for Reynolds-stress based models and the drift coefficient in the generalized Langevin model. The direct numerical simulations (DNS) of a non-premixed temporally-evolving slot jet flame and a premixed temporally-evolving slot jet flame are used. Both flames feature moderate Reynolds numbers, as well as highly anisotropic and inhomogeneous flow environment. Good agreement is achieved between turbulent statistics obtained from velocity-acceleration correlation and those obtained directly from DNS. Different filter sizes are then applied to the DNS database to further test the feasibility of representing pressure-rate-of-strain term and the drift coefficient using velocity-acceleration correlation in experiments or large eddy simulations. Behaviors of turbulent statistics obtained from the premixed flame and those from the nonpremixed flame are analyzed. Finally, the applicability of existing generalized Langevin model coefficients to flame simulations is discussed. The authors acknowledge Dr. Jacqueline Chen for providing access to the DNS database and computing resources.

  20. Analysis of translation initiation during stress conditions by polysome profiling.

    PubMed

    Coudert, Laëtitia; Adjibade, Pauline; Mazroui, Rachid

    2014-01-01

    Precise control of mRNA translation is fundamental for eukaryotic cell homeostasis, particularly in response to physiological and pathological stress. Alterations of this program can lead to the growth of damaged cells, a hallmark of cancer development, or to premature cell death such as seen in neurodegenerative diseases. Much of what is known concerning the molecular basis for translational control has been obtained from polysome analysis using a density gradient fractionation system. This technique relies on ultracentrifugation of cytoplasmic extracts on a linear sucrose gradient. Once the spin is completed, the system allows fractionation and quantification of centrifuged zones corresponding to different translating ribosomes populations, thus resulting in a polysome profile. Changes in the polysome profile are indicative of changes or defects in translation initiation that occur in response to various types of stress. This technique also allows to assess the role of specific proteins on translation initiation, and to measure translational activity of specific mRNAs. Here we describe our protocol to perform polysome profiles in order to assess translation initiation of eukaryotic cells and tissues under either normal or stress growth conditions.

  1. Separating Fluid Shear Stress from Acceleration during Vibrations in Vitro: Identification of Mechanical Signals Modulating the Cellular Response

    PubMed Central

    Uzer, Gunes; Manske, Sarah L; Chan, M Ete; Chiang, Fu-Pen; Rubin, Clinton T; Frame, Mary D; Judex, Stefan

    2012-01-01

    The identification of the physical mechanism(s) by which cells can sense vibrations requires the determination of the cellular mechanical environment. Here, we quantified vibration-induced fluid shear stresses in vitro and tested whether this system allows for the separation of two mechanical parameters previously proposed to drive the cellular response to vibration – fluid shear and peak accelerations. When peak accelerations of the oscillatory horizontal motions were set at 1g and 60Hz, peak fluid shear stresses acting on the cell layer reached 0.5Pa. A 3.5-fold increase in fluid viscosity increased peak fluid shear stresses 2.6-fold while doubling fluid volume in the well caused a 2-fold decrease in fluid shear. Fluid shear was positively related to peak acceleration magnitude and inversely related to vibration frequency. These data demonstrated that peak shear stress can be effectively separated from peak acceleration by controlling specific levels of vibration frequency, acceleration, and/or fluid viscosity. As an example for exploiting these relations, we tested the relevance of shear stress in promoting COX-2 expression in osteoblast like cells. Across different vibration frequencies and fluid viscosities, neither the level of generated fluid shear nor the frequency of the signal were able to consistently account for differences in the relative increase in COX-2 expression between groups, emphasizing that the eventual identification of the physical mechanism(s) requires a detailed quantification of the cellular mechanical environment. PMID:23074384

  2. A specific group of genes respond to cold dehydration stress in cut Alstroemeria flowers whereas ambient dehydration stress accelerates developmental senescence expression patterns.

    PubMed

    Wagstaff, Carol; Bramke, Irene; Breeze, Emily; Thornber, Sarah; Harrison, Elizabeth; Thomas, Brian; Buchanan-Wollaston, Vicky; Stead, Tony; Rogers, Hilary

    2010-06-01

    Petal development and senescence entails a normally irreversible process. It starts with petal expansion and pigment production, and ends with nutrient remobilization and ultimately cell death. In many species this is accompanied by petal abscission. Post-harvest stress is an important factor in limiting petal longevity in cut flowers and accelerates some of the processes of senescence such as petal wilting and abscission. However, some of the effects of moderate stress in young flowers are reversible with appropriate treatments. Transcriptomic studies have shown that distinct gene sets are expressed during petal development and senescence. Despite this, the overlap in gene expression between developmental and stress-induced senescence in petals has not been fully investigated in any species. Here a custom-made cDNA microarray from Alstroemeria petals was used to investigate the overlap in gene expression between developmental changes (bud to first sign of senescence) and typical post-harvest stress treatments. Young flowers were stressed by cold or ambient temperatures without water followed by a recovery and rehydration period. Stressed flowers were still at the bud stage after stress treatments. Microarray analysis showed that ambient dehydration stress accelerates many of the changes in gene expression patterns that would normally occur during developmental senescence. However, a higher proportion of gene expression changes in response to cold stress were specific to this stimulus and not senescence related. The expression of 21 transcription factors was characterized, showing that overlapping sets of regulatory genes are activated during developmental senescence and by different stresses.

  3. Accelerated hydration of the Earth's deep crust induced by stress perturbations.

    PubMed

    Jamtveit, B; Austrheim, H; Malthe-Sørenssen, A

    2000-11-01

    The metamorphic cycle associated with the formation of mountain belts produces a lower crust containing little or no free fluid. The introduction of external fluids to dry and impermeable volumes of the Earth's crust is thus a prerequisite for the retrogressive metamorphism later observed in such regimes. Such metamorphism can cause significant changes in the crust's physical properties, including its density, rheology and elastic properties. On a large scale, the introduction of fluids requires the presence of high-permeability channels, such as faults or fractures, which are the result of external tectonic stresses. But extensive interaction between externally derived fluids and the fractured rock requires efficient mass transport away from the initial fractures into the rock itself, and this transport often occurs over distances much longer than expected from grain-boundary diffusion. Here we present both field observations and a simple network model that demonstrate how the transport of fluids into initially dry rock can be accelerated by perturbations in the local stress field caused by reactions with fluids. We also show that the morphology of reaction fronts separating 'dry' from 'wet' rocks depends on the anisotropy of the external stress field. PMID:11081509

  4. Accelerated hydration of the Earth's deep crust induced by stress perturbations.

    PubMed

    Jamtveit, B; Austrheim, H; Malthe-Sørenssen, A

    2000-11-01

    The metamorphic cycle associated with the formation of mountain belts produces a lower crust containing little or no free fluid. The introduction of external fluids to dry and impermeable volumes of the Earth's crust is thus a prerequisite for the retrogressive metamorphism later observed in such regimes. Such metamorphism can cause significant changes in the crust's physical properties, including its density, rheology and elastic properties. On a large scale, the introduction of fluids requires the presence of high-permeability channels, such as faults or fractures, which are the result of external tectonic stresses. But extensive interaction between externally derived fluids and the fractured rock requires efficient mass transport away from the initial fractures into the rock itself, and this transport often occurs over distances much longer than expected from grain-boundary diffusion. Here we present both field observations and a simple network model that demonstrate how the transport of fluids into initially dry rock can be accelerated by perturbations in the local stress field caused by reactions with fluids. We also show that the morphology of reaction fronts separating 'dry' from 'wet' rocks depends on the anisotropy of the external stress field.

  5. Skeletal Involution by Age-associated Oxidative Stress and Its Acceleration by Loss of Sex Steroids*

    PubMed Central

    Almeida, Maria; Han, Li; Martin-Millan, Marta; Plotkin, Lilian I.; Stewart, Scott A.; Roberson, Paula K.; Kousteni, Stavroula; O’Brien, Charles A.; Bellido, Teresita; Parfitt, A. Michael; Weinstein, Robert S.; Jilka, Robert L.; Manolagas, Stavros C.

    2011-01-01

    Both aging and loss of sex steroids have adverse effects on skeletal homeostasis, but whether and how they may influence each others negative impact on bone remains unknown. We report herein that both female and male C57BL/6 mice progressively lost strength (as determined by load-to-failure measurements) and bone mineral density in the spine and femur between the ages of 4 and 31 months. These changes were temporally associated with decreased rate of remodeling as evidenced by decreased osteoblast and osteoclast numbers and decreased bone formation rate; as well as increased osteoblast and osteocyte apoptosis, increased reactive oxygen species levels, and decreased glutathione reductase activity and a corresponding increase in the phosphorylation of p53 and p66shc, two key components of a signaling cascade that are activated by reactive oxygen species and influences apoptosis and lifespan. Exactly the same changes in oxidative stress were acutely reproduced by gonadectomy in 5-month-old females or males and reversed by estrogens or androgens in vivo as well as in vitro.We conclude that the oxidative stress that underlies physiologic organismal aging in mice may be a pivotal pathogenetic mechanism of the age-related bone loss and strength. Loss of estrogens or androgens accelerates the effects of aging on bone by decreasing defense against oxidative stress. PMID:17623659

  6. The senescence-accelerated mouse (SAM): a higher oxidative stress and age-dependent degenerative diseases model.

    PubMed

    Chiba, Yoichi; Shimada, Atsuyoshi; Kumagai, Naoko; Yoshikawa, Keisuke; Ishii, Sanae; Furukawa, Ayako; Takei, Shiro; Sakura, Masaaki; Kawamura, Noriko; Hosokawa, Masanori

    2009-04-01

    The SAM strain of mice is actually a group of related inbred strains consisting of a series of SAMP (accelerated senescence-prone) and SAMR (accelerated senescence-resistant) strains. Compared with the SAMR strains, the SAMP strains show a more accelerated senescence process, a shorter lifespan, and an earlier onset and more rapid progress of age-associated pathological phenotypes similar to human geriatric disorders. The higher oxidative stress status observed in SAMP mice is partly caused by mitochondrial dysfunction, and may be a cause of this senescence acceleration and age-dependent alterations in cell structure and function. Based on our recent observations, we discuss a possible mechanism for mitochondrial dysfunction resulting in the excessive production of reactive oxygen species, and a role for the hyperoxidative stress status in neurodegeneration in SAMP mice. These SAM strains can serve as a useful tool to understand the cellular mechanisms of age-dependent degeneration, and to develop clinical interventions. PMID:18688709

  7. Influence of initial conditions on the flow patterns of a shock-accelerated thin fluid layer

    SciTech Connect

    Budzinski, J.M.; Benjamin, R.F. ); Jacobs, J.W. )

    1994-11-01

    Previous observations of three flow patterns generated by shock acceleration of a thin perturbed, fluid layer are now correlated with asymmetries in the initial conditions. Using a different diagnostic (planar laser Rayleigh scattering) than the previous experiments, upstream mushrooms, downstream mushrooms, and sinuous patterns are still observed. For each experiment the initial perturbation amplitude on one side of the layer can either be larger, smaller, or the same as the amplitude on the other side, as observed with two images per experiment, and these differences lead to the formation of the different patterns.

  8. In-Situ Monitoring of Particle Growth at PEMFC Cathode under Accelerated Cycling Conditions

    SciTech Connect

    Billinge S. J.; Redmond, E.L.; Setzler, B.P.; Juhas, P.; Fullera, T.F.

    2012-05-01

    An in-situ method to measure changes in catalyst particle size at the cathode of a proton exchange membrane fuel cell is demonstrated. Synchrotron X-rays, 58 keV, were used to measure the pair distribution function on an operating fuel cell and observe the growth of catalyst particles under accelerated degradation conditions. The stability of Pt/C and PtCo/C with different initial particle sizes was monitored over 3000 potential cycles. The increase in particle size was fit to a linear trend as a function of cycles. The most stable electrocatalyst was found to be the alloyed PtCo with the larger initial particle size.

  9. Cellular respiration: the nexus of stress, condition, and ornamentation.

    PubMed

    Hill, Geoffrey E

    2014-10-01

    A fundamental hypothesis for the evolution and maintenance of ornamental traits is that ornaments convey information to choosing females about the quality of prospective mates. A diverse array of ornaments (e.g., colors, morphological features, and behaviors) has been associated with a wide range of measures of individual quality, but decades of study of such indicator traits have failed to produce general mechanisms of honest signaling. Here, I propose that efficiency of cellular respiration, as a product of mitochondrial function, underlies the associations between ornamentation and performance for a broad range of traits across taxa. A large biomedical literature documents the fundamental biochemical links between oxidative phosphorylation (OXPHOS) and the production of reactive oxygen species (ROS), the process of metabolism, the function of the immune system, the synthesis of proteins, and the development and function of the nervous system. The production of virtually all ornaments whose expressions have been demonstrated to be condition-dependent is directly affected by the efficiency of cellular respiration, suggesting that the signaling of respiratory efficiency may be the primary function of such traits. Furthermore, the production of ornaments links to stress-response systems, including particularly the neuroendocrine system, through mitochondrial function, thereby makes ornamental traits effective signals of the capacity to withstand environmental perturbations. The identification of a unifying mechanism of honest signaling holds the potential to connect many heretofore-disparate fields of study related to stress and ornamentation, including neuroendocrinology, respiratory physiology, metabolic physiology, and immunology. PMID:24791751

  10. TUSC3 Loss Alters the ER Stress Response and Accelerates Prostate Cancer Growth in vivo

    NASA Astrophysics Data System (ADS)

    Horak, Peter; Tomasich, Erwin; Vaňhara, Petr; Kratochvílová, Kateřina; Anees, Mariam; Marhold, Maximilian; Lemberger, Christof E.; Gerschpacher, Marion; Horvat, Reinhard; Sibilia, Maria; Pils, Dietmar; Krainer, Michael

    2014-01-01

    Prostate cancer is the most prevalent cancer in males in developed countries. Tumor suppressor candidate 3 (TUSC3) has been identified as a putative tumor suppressor gene in prostate cancer, though its function has not been characterized. TUSC3 shares homologies with the yeast oligosaccharyltransferase (OST) complex subunit Ost3p, suggesting a role in protein glycosylation. We provide evidence that TUSC3 is part of the OST complex and affects N-linked glycosylation in mammalian cells. Loss of TUSC3 expression in DU145 and PC3 prostate cancer cell lines leads to increased proliferation, migration and invasion as well as accelerated xenograft growth in a PTEN negative background. TUSC3 downregulation also affects endoplasmic reticulum (ER) structure and stress response, which results in increased Akt signaling. Together, our findings provide first mechanistic insight in TUSC3 function in prostate carcinogenesis in general and N-glycosylation in particular.

  11. Investigation of accelerated stress factors and failure/degradation mechanisms in terrestrial solar cells

    NASA Technical Reports Server (NTRS)

    Lathrop, J. W.

    1984-01-01

    Research on the reliability of terrestrial solar cells was performed to identify failure/degradation modes affecting solar cells and to relate these to basic physical, chemical, and metallurgical phenomena. Particular concerns addressed were the reliability attributes of individual single crystalline, polycrystalline, and amorphous thin film silicon cells. Results of subjecting different types of crystalline cells to the Clemson accelerated test schedule are given. Preliminary step stress results on one type of thin film amorphous silicon (a:Si) cell indicated that extraneous degradation modes were introduced above 140 C. Also described is development of measurement procedures which are applicable to the reliability testing of a:Si solar cells as well as an approach to achieving the necessary repeatability of fabricating a simulated a:Si reference cell from crystalline silicon photodiodes.

  12. A fiber optics sensor for strain and stress management in superconducting accelerator magnets

    SciTech Connect

    van Oort, J.M.; ten Kate, H.H.J.

    1993-09-20

    A novel cryogenic interferometric fiber optics sensor for the measurement of strain and stress in the coil windings of superconducting accelerator magnets is described. The sensor can operate with two different readout sources, monochromatic laser light and white light respectively. The sensor head is built up as an extrinsic Fabry-Perot interferometer formed with two cleaved fiber surfaces, and can be mounted in several configurations. When read with laser light, the sensor is an extremely sensitive relative strain or temperature detector. When read with white light the absolute strain and pressure can be measured. Results are presented of tests in several configurations at 77 K and 4.2 K, both for the relative and absolute readout method. Finally, the possible use for quench localization using the temperature sensitivity is described.

  13. A fiber optics sensor for strain and stress measurements in superconducting accelerator magnets

    SciTech Connect

    Oort, J.M. van ); Kate, H.H.J. ten . Applied Superconductivity Centre)

    1994-07-01

    A novel cryogenic interferometric fiber optics sensor for the measurement of strain and stress in the coil windings of superconducting accelerator magnets is described. The sensor can operate with two different readout sources, monochromatic laser light and white light respectively. The sensor head is built up as an extrinsic Fabry-Perot interferometer formed with two cleaved fiber surfaces, and can be mounted in several configurations. When read with laser light, the sensor is an extremely sensitive relative strain or temperature detector. When read with white light the absolute strain and pressure can be measured. Results are presented of tests in several configurations at 77 K and 4.2 K, both for the relative and absolute readout method. Finally, the possible use for quench localization using the temperature sensitivity is described.

  14. Electron Acceleration in a Dynamically Evolved Current Sheet of Solar Coronal Conditions

    NASA Astrophysics Data System (ADS)

    Shaohua, Z.; Du, A.; Feng, X.

    2012-12-01

    Electron acceleration in a drastically evolved current sheet of solar coronal conditions is investigated via the combined resistive Magnetohydrodynamics (MHD) and test particle approaches. With high magnetic Reynolds number, the long-thin current sheet is tearing into a chain of magnetic islands, which grow in size and coalesce together. The acceleration of electrons are explored in three typical evolvement phases: when several large magnetic islands are formed (phase1), two of them are approaching each other (phase2) and almost merging into a "monster" magnetic island (phase3). The results show that for all the three phases electrons with an initially Maxwellian distribution evolve into a heavy-tailed distribution and more than 20% of the electrons can be accelerated higher than 200 keV within 0.1 second and some of them can even be energized up to MeV ranges. Most of the energetic electrons move around the magnetic islands in clockwise direction (anti-parallel to the magnetic field lines), drifting in the -Z direction. The energetic electrons with 10 keV < Ek < 200 keV are located outside the magnetic separatrices, where parallel electric field (Ep) is small. The electrons with 200 keV < Ek < 5000 keV are distributed inside the magnetic islands where Ep is moderate large but have complex structures. The electrons with Ek > 5000 keV are located around the outer regions of the magnetic islands or at the core regions of the magnetic islands. Some of the most energetic electrons even appear in the small secondary magnetic islands that are embedded in the diusion regions in between the magnetic islands. It is the trapping eect of the magnetic islands and the distributions of Ep that determine the acceleration processes and space distribution of the energetic electrons.

  15. Disparity between online and offline tests in accelerated aging tests of LED lamps under electric stress.

    PubMed

    Wang, Yao; Jing, Lei; Ke, Hong-Liang; Hao, Jian; Gao, Qun; Wang, Xiao-Xun; Sun, Qiang; Xu, Zhi-Jun

    2016-09-20

    The accelerated aging tests under electric stress for one type of LED lamp are conducted, and the differences between online and offline tests of the degradation of luminous flux are studied in this paper. The transformation of the two test modes is achieved with an adjustable AC voltage stabilized power source. Experimental results show that the exponential fitting of the luminous flux degradation in online tests possesses a higher fitting degree for most lamps, and the degradation rate of the luminous flux by online tests is always lower than that by offline tests. Bayes estimation and Weibull distribution are used to calculate the failure probabilities under the accelerated voltages, and then the reliability of the lamps under rated voltage of 220 V is estimated by use of the inverse power law model. Results show that the relative error of the lifetime estimation by offline tests increases as the failure probability decreases, and it cannot be neglected when the failure probability is less than 1%. The relative errors of lifetime estimation are 7.9%, 5.8%, 4.2%, and 3.5%, at the failure probabilities of 0.1%, 1%, 5%, and 10%, respectively. PMID:27661576

  16. Investigation of reliability attributes and accelerated stress factors on terrestrial solar cells. Third annual report

    SciTech Connect

    Lathrop, J.W.; Hartman, R.A.; Saylor, C.R.

    1981-01-01

    The third year of the accelerated reliability testing program concentrated on electrical measurement instrumentation and in modeling cell behavior in the second quadrant. In addition, some preliminary work was done on correlating cell color changes with electrical degradation. Not reported are results of continuing accelerated stress tests on state of the art cells. A number of new cells were added to the program, but not in time for sufficient data to be obtained, while the older cells are undergoing extended test periods and new data are not yet available on them. The all-digital, microprocessor controlled, short interval tester, which was designed and fabricated, has replaced the manual measurement procedure formerly used. This has improved measurement accuracy and repeatability, reduced measurement time, and through coordinated data management procedures, eliminated data errors. A complete description of the tester including schematics and software is given and its operating procedures described. A computer model, based on the thermal and electrical properties of the cells and encapsulating materials, was developed to relate cell temperature to electrical characteristics in the second quadrant. This model adequately predicted the behavior of both encapsulated and unencapsulated cells, although accurate temperature measurements on encapsulated cells were difficult to obtain. In addition, only cells of one type were used for comparison and other cell types may require different parameter values for fitting. Use of the model should permit the prediction of a cell's sensitivity to degradation in the second quadrant. The computer program is listed together with a description of its operation.

  17. Effects of psychological stress and housing conditions on the delay of wound healing.

    PubMed

    Vegas, Óscar; VanBuskirk, JoAnne; Richardson, Steven; Parfitt, David; Helmreich, Dana; Rempel, Max; Moynihan, Jan; Tausk, Francisco

    2012-11-01

    This study explores the effects of stress and housing conditions on the healing of cutaneous wounds and its relationship with circulating levels of corticosterone. Specifically, we set out to examine the effect of combined physical (restraint stress and ultrasound) and psychological (predator scent) stressors on the cutaneous wound healing of female mice that had been housed either in groups (with social support; n= 16) or individually (without social support; n= 16). In contrast with other studies, the model of multiple ethological mild stressors utilized in this study significantly increased the levels of corticosterone, but failed to dramatically alter the healing of skin wounds. However, the results of this study provide evidence of the importance of housing conditions, suggesting that positive social interactions in females accelerate the rate of wound healing, and reduce levels of anxiety and circulating corticosterone. The level of anxiety, as well as the basal levels of corticosterone, proved to be valid predictors of the healing rates during different stages of cutaneous wound healing.

  18. Accelerated Weathering of Fluidized Bed Steam Reformation Material Under Hydraulically Unsaturated Conditions

    SciTech Connect

    Pierce, Eric M.

    2007-09-16

    To predict the long-term fate of low- and high-level waste forms in the subsurface over geologic time scales, it is important to understand the behavior of the corroding waste forms under conditions the mimic to the open flow and transport properties of a subsurface repository. Fluidized bed steam reformation (FBSR), a supplemental treatment technology option, is being considered as a waste form for the immobilization of low-activity tank waste. To obtain the fundamental information needed to evaluate the behavior of the FBSR waste form under repository relevant conditions and to monitor the long-term behavior of this material, an accelerated weathering experiment is being conducted with the pressurized unsaturated flow (PUF) apparatus. Unlike other accelerated weathering test methods (product consistency test, vapor hydration test, and drip test), PUF experiments are conducted under hydraulically unsaturated conditions. These experiments are unique because they mimic the vadose zone environment and allow the corroding waste form to achieve its final reaction state. Results from this on-going experiment suggest the volumetric water content varied as a function of time and reached steady state after 160 days of testing. Unlike the volumetric water content, periodic excursions in the solution pH and electrical conductivity have been occurring consistently during the test. Release of elements from the column illustrates a general trend of decreasing concentration with increasing reaction time. Normalized concentrations of K, Na, P, Re (a chemical analogue for 99Tc), and S are as much as 1 × 104 times greater than Al, Cr, Si, and Ti. After more than 600 days of testing, the solution chemistry data collected to-date illustrate the importance of understanding the long-term behavior of the FBSR product under conditions that mimic the open flow and transport properties of a subsurface repository.

  19. Systems-level characterization and engineering of oxidative stress tolerance in Escherichia coli under anaerobic conditions.

    PubMed

    Kang, Aram; Tan, Mui Hua; Ling, Hua; Chang, Matthew Wook

    2013-02-01

    Despite many prior studies on microbial response to oxidative stress, our understanding of microbial tolerance against oxidative stress is currently limited to aerobic conditions, and few engineering strategies have been devised to resolve toxicity issues of oxidative stress under anaerobic conditions. Since biological processes, such as anaerobic fermentation, are frequently hampered by toxicity arising from oxidative stress, increased microbial tolerance against oxidative stress improves the overall productivity and yield of biological processes. Here, we show a systems-level analysis of oxidative stress response of Escherichia coli under anaerobic conditions, and present an engineering strategy to improve oxidative stress tolerance. First, we identified essential cellular mechanisms and regulatory factors underlying oxidative stress response under anaerobic conditions using a transcriptome analysis. In particular, we showed that nitrogen metabolisms and respiratory pathways were differentially regulated in response to oxidative stress under anaerobic and aerobic conditions. Further, we demonstrated that among transcription factors with oxidative stress-derived perturbed activity, the deletion of arcA and arcB significantly improved oxidative stress tolerance under aerobic and anaerobic conditions, respectively, whereas fnr was identified as an essential transcription factor for oxidative stress tolerance under anaerobic conditions. Moreover, we showed that oxidative stress increased the intracellular NADH : NAD(+) ratio under aerobic and anaerobic conditions, which indicates a regulatory role of NADH in oxidative stress tolerance. Based on this finding, we demonstrated that increased NADH availability through fdh1 overexpression significantly improved oxidative stress tolerance under aerobic conditions. Our results here provide novel insight into better understanding of cellular mechanisms underlying oxidative stress tolerance under anaerobic conditions, and

  20. Historic Seismicity, Computed Peak Ground Accelerations, and Seismic Site Conditions for Northeast Mexico

    NASA Astrophysics Data System (ADS)

    Montalvo-Arriet, J. C.; Galván-Ramírez, I. N.; Ramos-Zuñiga, L. G.; Navarro de León, I.; Ramírez-Fernández, J. A.; Quintanilla-López, Y.; Cavazos-Tovar, N. P.

    2007-05-01

    In this study we present the historic seismicity, computed peak ground accelerations, and mapping of seismic site conditions for northeast Mexico. We start with a compilation of the regional seismicity in northeast Mexico (24- 31°N, 87-106°W) for the 1787-2006 period. Our study area lies within three morphotectonic provinces: Basin and Range and Rio Grande rift, Sierra Madre Oriental and Gulf Coastal Plain. Peak ground acceleration (PGA) maps were computed for three different scenarios: 1928 Parral, Chihuahua (MW = 6.5); 1931 Valentine, Texas (MW = 6.4); and a hypothetical earthquake located in central Coahuila (MW = 6.5). Ground acceleration values were computed using attenuation relations developed for central and eastern North America and the Basin and Range province. The hypothetical earthquake in central Coahuila is considered a critical scenario for the main cities of northeast Mexico. The damage associated with this hypothetical earthquake could be severe because the majority of the buildings were constructed without allowance for seismic accelerations. The expected PGA values in Monterrey, Saltillo and Monclova range from 30 to 70 cm/s2 (0.03 to 0.07g). This earthquake might also produce or trigger significant landslides and rock falls in the Sierra Madre Oriental, where several cities are located (e.g. suburbs of Monterrey). Additionally, the Vs30 distribution for the state of Nuevo Leon and the cities of Linares and Monterrey are presented. The Vs30 data was obtained using seismic refraction profiling correlated with borehole information. According to NEHRP soil classification, sites classes A, B and C are dominant. Sites with class D occupy minor areas in both cities. Due to the semi-arid conditions in northeast Mexico, we obtained the highest values of Vs30 in Quaternary deposits (alluvium) cemented by caliche. Similar values of Vs30 were obtained in Reno and Las Vegas, Nevada. This work constitutes the first attempt at understanding and

  1. Changes in Stress and Psychological Adjustment during the Transition to High School among Freshmen in an Accelerated Curriculum

    ERIC Educational Resources Information Center

    Suldo, Shannon M.; Shaunessy-Dedrick, Elizabeth

    2013-01-01

    This study determined whether participation in an accelerated curriculum (specifically, the International Baccalaureate [IB] program) upon entry to high school is associated with increases in stress and/or associated with psychological problems. Data from self-report questionnaires were collected at two time points (summer after eighth grade, fall…

  2. Fast, transient cardiac accelerations and decelerations during fear conditioning in rats.

    PubMed

    Knippenberg, J M J; Barry, R J; Kuniecki, M J; van Luijtelaar, G

    2012-02-01

    The current study reports on a number of heart rate responses observed in rats subjected to a discriminatory Pavlovian fear conditioning procedure. Rats learned that a series of six auditory pips was followed by a footshock when presented alone, but not when the pip series was preceded by a visual safety signal. Each auditory pip in the series evoked a fast transient (<1s) cardiac deceleration. This was the case on both trials followed by shock and on trials not followed by shock. The onset of the safety light evoked a similar fast deceleration. We propose that these transient decelerations are similar to the human Evoked Cardiac Response 1 (ECR1), a brief modest deceleration evoked by simple sensory stimuli that is thought to reflect an early process of stimulus registration. Immediately following these pip-evoked decelerations, modest fast accelerations were observed. These accelerations were larger when the pip series was followed by shock than when it was not followed by shock. We propose a potential linkage between these accelerations and the human acceleratory ECR2 component, which is associated with more elaborate processing following stimulus registration; something likely to take place when the pip series predicts an aversive event. Both the ECR1- and ECR2-like responses were embedded within a slow, gradual heart rate increase across the entire pip series. This tonic increase was significantly larger on trials with footshock and is therefore probably associated with anticipatory fear of the upcoming shock. An additional special type of cardiac response was found to the first pip in the series not preceded by the safety signal; here, a much larger and more sustained deceleration was apparent. This response appears relatable to the prolonged deceleration reported in humans in response to aversive picture content. We discuss the cardiac responses found in rats in the current study in the context of heart rate responses known in the human literature.

  3. Conditioning nerve crush accelerates cytoskeletal protein transport in sprouts that form after a subsequent crush.

    PubMed

    McQuarrie, I G; Jacob, J M

    1991-03-01

    To examine the relationship between axonal outgrowth and the delivery of cytoskeletal proteins to the growing axon tip, outgrowth was accelerated by using a conditioning nerve crush. Because slow component b (SCb) of axonal transport is the most rapid vehicle for carrying cytoskeletal proteins to the axon tip, the rate of SCb was measured in conditioned vs. sham-conditioned sprouts. In young Sprague-Dawley rats, the conditioning crush was made to sciatic nerve branches at the knee; 14 days later, the test crush was made where the L4 and L5 spinal nerves join to form the sciatic nerve in the flank. Newly synthesized proteins were labeled in motor neurons by injecting 35S-methionine into the lumbar spinal cord 7 days before the test crush. The wave of pulse-labeled SCb proteins reached the crush by the time it was made and subsequently entered sprouts. The nerve was removed and sectioned for SDS-PAGE and fluorography 4-12 days after the crush. Tubulins, neurofilament proteins, and representative "cytomatrix" proteins (actin, calmodulin, and putative microtubule-associated proteins) were removed from gels for liquid scintillation counting. Labeled SCb proteins entered sprouts without first accumulating in parent axon stumps, presumably because sprouts begin to grow within hours after axotomy. The peak of SCb moved 11% faster in conditioned than in sham-conditioned sprouts: 3.0 vs. 2.7 mm/d (p less than 0.05). To confirm that sprouts elongate more rapidly when a test crush is preceded by a conditioning crush, outgrowth distances were measured in a separate group of rats by labeling fast axonal transport with 3H-proline 24 hours before nerve retrieval.(ABSTRACT TRUNCATED AT 250 WORDS)

  4. Stem cell-conditioned medium accelerates distraction osteogenesis through multiple regenerative mechanisms.

    PubMed

    Ando, Yuji; Matsubara, Kohki; Ishikawa, Jun; Fujio, Masahito; Shohara, Ryutaro; Hibi, Hideharu; Ueda, Minoru; Yamamoto, Akihito

    2014-04-01

    Distraction osteogenesis (DO) successfully induces large-scale skeletal tissue regeneration, but it involves an undesirably long treatment period. A high-speed DO mouse model (H-DO) with a distraction speed twice that of a control DO model failed to generate new bone callus in the distraction gap. Here we demonstrate that the local administration of serum-free conditioned medium from human mesenchymal stem cells (MSC-CM) accelerated callus formation in the mouse H-DO model. Secretomic analysis identified factors contained in MSC-CM that recruit murine bone marrow stromal cells (mBMSCs) and endothelial cells/endothelial progenitor cells (EC/EPCs), inhibit inflammation and apoptosis, and promote osteoblast differentiation, angiogenesis, and cell proliferation. Functional assays identified MCP-1/-3 and IL-3/-6 as essential factors in recruiting mBMSCs and EC/EPCs. IL-3/-6 also enhanced the osteogenic differentiation of mBMSCs. MSC-CM that had been depleted of MCP-1/-3 failed to recruit mBMSCs, and consequently failed to promote callus formation. Taken together, our data suggest that MSCs produce a broad repertoire of trophic factors with tissue-regenerative activities that accelerate healing in the DO process.

  5. Bioreactor Conditioning for Accelerated Remodeling of Fibrin-Based Tissue Engineered Heart Valves

    NASA Astrophysics Data System (ADS)

    Schmidt, Jillian Beth

    Fibrin is a promising scaffold material for tissue engineered heart valves, as it is completely biological, allows for engineered matrix alignment, and is able to be degraded and replaced with collagen by entrapped cells. However, the initial fibrin matrix is mechanically weak, and extensive in vitro culture is required to create valves with sufficient mechanical strength and stiffness for in vivo function. Culture in bioreactor systems, which provide cyclic stretching and enhance nutrient transport, has been shown to increase collagen production by cells entrapped in a fibrin scaffold, accelerating strengthening of the tissue and reducing the required culture time. In the present work, steps were taken to improve bioreactor culture conditions with the goal of accelerating collagen production in fibrin-based tissue engineered heart valves using two approaches: (i) optimizing the cyclic stretching protocol and (ii) developing a novel bioreactor system that permits transmural and lumenal flow of culture medium for improved nutrient transport. The results indicated that incrementally increasing strain amplitude cyclic stretching with small, frequent increments in strain amplitude was optimal for collagen production in our system. In addition, proof of concept studies were performed in the novel bioreactor system and increased cellularity and collagen deposition near the lumenal surface of the tissue were observed.

  6. Chronic stress accelerates ligature-induced periodontitis by suppressing glucocorticoid receptor-α signaling

    PubMed Central

    Lu, Huaixiu; Xu, Minguang; Wang, Feng; Liu, Shisen; Gu, Jing; Lin, Songshan; Zhao, Lisheng

    2016-01-01

    Periodontitis is a common chronic inflammatory disease. Recent studies have shown that chronic stress (CS) might modulate periodontal disease, but there are few models of CS-induced periodontitis, and the underlying mechanisms are unclear. The present study established a rat model of periodontitis associated with CS induced by nylon thread ligatures. The severity of periodontitis was evaluated in this model by radiographic and pathological examination. The inflammatory reaction indicated by the elevated serum levels of interleukin (IL)-1β, IL-6 and IL-8 was assessed by enzyme-linked immunosorbent assay. Toll-like receptor-4 (TLR4) and glucocorticoid receptor-α (GR-α) expressions were detected by reverse transcriptase-PCR and western blotting. Open-field tests and serum corticosterone were used to evaluate CS. The results showed that CS induced behavioral changes and increased corticosterone levels of the animals with periodontitis. CS stimulation markedly increased alveolar bone loss, periodontal pocket depth and the number of plaques. It also enhanced the inflammatory reaction. These results suggest that CS accelerated the ligature-induced pathological changes associated with periodontitis. Further analysis of the mechanisms involved showed that GR-α expression was significantly downregulated in periodontal tissues of the animals undergoing CS. Blocking GR-α signaling in lipopolysaccharide and corticosteroid-treated human periodontal ligament fibroblast cells in vitro significantly upregulated the expression of p-Akt (protein kinase B) and TLR4, promoted nuclear factor-κB activity and increased levels of IL-1β, IL-6 and IL-8. This research suggests that CS might accelerate the pathological progression of periodontitis by a GR-α signaling-mediated inflammatory response and that this may be a potential therapeutic target for the treatment of periodontal disease, particularly in patients with CS. PMID:27012709

  7. Chronic stress accelerates ligature-induced periodontitis by suppressing glucocorticoid receptor-α signaling.

    PubMed

    Lu, Huaixiu; Xu, Minguang; Wang, Feng; Liu, Shisen; Gu, Jing; Lin, Songshan; Zhao, Lisheng

    2016-03-25

    Periodontitis is a common chronic inflammatory disease. Recent studies have shown that chronic stress (CS) might modulate periodontal disease, but there are few models of CS-induced periodontitis, and the underlying mechanisms are unclear. The present study established a rat model of periodontitis associated with CS induced by nylon thread ligatures. The severity of periodontitis was evaluated in this model by radiographic and pathological examination. The inflammatory reaction indicated by the elevated serum levels of interleukin (IL)-1β, IL-6 and IL-8 was assessed by enzyme-linked immunosorbent assay. Toll-like receptor-4 (TLR4) and glucocorticoid receptor-α (GR-α) expressions were detected by reverse transcriptase-PCR and western blotting. Open-field tests and serum corticosterone were used to evaluate CS. The results showed that CS induced behavioral changes and increased corticosterone levels of the animals with periodontitis. CS stimulation markedly increased alveolar bone loss, periodontal pocket depth and the number of plaques. It also enhanced the inflammatory reaction. These results suggest that CS accelerated the ligature-induced pathological changes associated with periodontitis. Further analysis of the mechanisms involved showed that GR-α expression was significantly downregulated in periodontal tissues of the animals undergoing CS. Blocking GR-α signaling in lipopolysaccharide and corticosteroid-treated human periodontal ligament fibroblast cells in vitro significantly upregulated the expression of p-Akt (protein kinase B) and TLR4, promoted nuclear factor-κB activity and increased levels of IL-1β, IL-6 and IL-8. This research suggests that CS might accelerate the pathological progression of periodontitis by a GR-α signaling-mediated inflammatory response and that this may be a potential therapeutic target for the treatment of periodontal disease, particularly in patients with CS.

  8. Pivotal role of oxidative stress in tumor metastasis under diabetic conditions in mice.

    PubMed

    Ikemura, Mai; Nishikawa, Makiya; Kusamori, Kosuke; Fukuoka, Miho; Yamashita, Fumiyoshi; Hashida, Mitsuru

    2013-09-10

    Diabetic patients are reported to have a high incidence and mortality of cancer, but little is known about the linkage. In this study, we investigated whether high oxidative stress is involved in the acceleration of tumor metastasis in diabetic mice. Murine melanoma B16-BL6 cells stably labeled with firefly luciferase (B16-BL6/Luc) were inoculated into the tail vein of streptozotocin (STZ)-treated or untreated mice. A luciferase assay demonstrated that tumor cells were present largely in the lung of untreated mice, whereas large numbers of tumor cells were detected in both the lung and liver of STZ-treated mice. Repeated injections of polyethylene glycol-conjugated catalase (PEG-catalase), a long-circulating derivative, reduced the elevated fasting blood glucose levels and plasma lipoperoxide levels of STZ-treated mice, but had no significant effects on these parameters in untreated mice. In addition, the injections significantly reduced the number of tumor cells in the lung and liver in both untreated and STZ-treated mice. Culture of B16-BL6/Luc cells in medium containing over 45 mg/dl glucose hardly affected the proliferation of the cells, whereas the addition of plasma of STZ-treated mice to the medium significantly increased the number of cells. Plasma samples of STZ-treated mice receiving PEG-catalase exhibited no such effect on proliferation. These findings indicate that a hyperglycemia-induced increase in oxidative stress is involved in the acceleration of tumor metastasis, and the removal of systemic hydrogen peroxide by PEG-catalase can inhibit the progression of diabetic conditions and tumor metastasis in diabetes. PMID:23735571

  9. Apolipoprotein E4 impairs macrophage efferocytosis and potentiates apoptosis by accelerating endoplasmic reticulum stress.

    PubMed

    Cash, James G; Kuhel, David G; Basford, Joshua E; Jaeschke, Anja; Chatterjee, Tapan K; Weintraub, Neal L; Hui, David Y

    2012-08-10

    Apolipoprotein (apo) E4 is a major genetic risk factor for a wide spectrum of inflammatory metabolic diseases, including atherosclerosis, diabetes, and Alzheimer disease. This study compared diet-induced adipose tissue inflammation as well as functional properties of macrophages isolated from human APOE3 and APOE4 mice to identify the mechanism responsible for the association between apoE4 and inflammatory metabolic diseases. The initial study confirmed previous reports that APOE4 gene replacement mice were less sensitive than APOE3 mice to diet-induced body weight gain but exhibited hyperinsulinemia, and their adipose tissues were similarly inflamed as those in APOE3 mice. Peritoneal macrophages isolated from APOE4 mice were defective in efferocytosis compared with APOE3 macrophages. Increased cell death was also observed in APOE4 macrophages when stimulated with LPS or oxidized LDL. Western blot analysis of cell lysates revealed that APOE4 macrophages displayed elevated JNK phosphorylation indicative of cell stress even under basal culturing conditions. Significantly higher cell stress due mainly to potentiation of endoplasmic reticulum (ER) stress signaling was also observed in APOE4 macrophages after LPS and oxidized LDL activation. The defect in efferocytosis and elevated apoptosis sensitivity of APOE4 macrophages was ameliorated by treatment with the ER chaperone tauroursodeoxycholic acid. Taken together, these results showed that apoE4 expression causes macrophage dysfunction and promotes apoptosis via ER stress induction. The reduction of ER stress in macrophages may be a viable option to reduce inflammation and inflammation-related metabolic disorders associated with the apoE4 polymorphism.

  10. Stress-responsive expression patterns and functional characterization of cold shock domain proteins in cabbage (Brassica rapa) under abiotic stress conditions.

    PubMed

    Choi, Min Ji; Park, Ye Rin; Park, Su Jung; Kang, Hunseung

    2015-11-01

    Although the functional roles of cold shock domain proteins (CSDPs) have been demonstrated during the growth, development, and stress adaptation of Arabidopsis (Arabidopsis thaliana), rice (Oryza sativa), and wheat (Triticum aestivum), the functions of CSDPs in other plants species, including cabbage (Brassica rapa), are largely unknown. To gain insight into the roles of CSDPs in cabbage under stress conditions, the genes encoding CSDPs in cabbage were isolated, and the functional roles of CSDPs in response to environmental stresses were analyzed. Real-time RT-PCR analysis revealed that the levels of BrCSDP transcripts increased during cold, salt, or drought stress, as well as upon ABA treatment. Among the five BrCSDP genes found in the cabbage genome, one CSDP (BRU12051), named BrCSDP3, was unique in that it is localized to the chloroplast as well as to the nucleus. Ectopic expression of BrCSDP3 in Arabidopsis resulted in accelerated seed germination and better seedling growth compared to the wild-type plants under high salt or dehydration stress conditions, and in response to ABA treatment. BrCSDP3 did not affect the splicing of intron-containing genes and processing of rRNAs in the chloroplast. BrCSDP3 had the ability to complement RNA chaperone-deficient Escherichia coli mutant cells under low temperatures as well as DNA- and RNA-melting abilities, suggesting that it possesses RNA chaperone activity. Taken together, these results suggest that BrCSDP3, harboring RNA chaperone activity, plays a role as a positive regulator in seed germination and seedling growth under stress conditions.

  11. Stress-responsive expression patterns and functional characterization of cold shock domain proteins in cabbage (Brassica rapa) under abiotic stress conditions.

    PubMed

    Choi, Min Ji; Park, Ye Rin; Park, Su Jung; Kang, Hunseung

    2015-11-01

    Although the functional roles of cold shock domain proteins (CSDPs) have been demonstrated during the growth, development, and stress adaptation of Arabidopsis (Arabidopsis thaliana), rice (Oryza sativa), and wheat (Triticum aestivum), the functions of CSDPs in other plants species, including cabbage (Brassica rapa), are largely unknown. To gain insight into the roles of CSDPs in cabbage under stress conditions, the genes encoding CSDPs in cabbage were isolated, and the functional roles of CSDPs in response to environmental stresses were analyzed. Real-time RT-PCR analysis revealed that the levels of BrCSDP transcripts increased during cold, salt, or drought stress, as well as upon ABA treatment. Among the five BrCSDP genes found in the cabbage genome, one CSDP (BRU12051), named BrCSDP3, was unique in that it is localized to the chloroplast as well as to the nucleus. Ectopic expression of BrCSDP3 in Arabidopsis resulted in accelerated seed germination and better seedling growth compared to the wild-type plants under high salt or dehydration stress conditions, and in response to ABA treatment. BrCSDP3 did not affect the splicing of intron-containing genes and processing of rRNAs in the chloroplast. BrCSDP3 had the ability to complement RNA chaperone-deficient Escherichia coli mutant cells under low temperatures as well as DNA- and RNA-melting abilities, suggesting that it possesses RNA chaperone activity. Taken together, these results suggest that BrCSDP3, harboring RNA chaperone activity, plays a role as a positive regulator in seed germination and seedling growth under stress conditions. PMID:26263516

  12. Further study of the effect of the downstream plasma condition on accelerator grid erosion in an ion thruster

    NASA Technical Reports Server (NTRS)

    Peng, Xiaohang; Ruyten, Wilhelmus M.; Keefer, Dennis

    1992-01-01

    Further numerical results are presented of earlier particle-in-cell/Monte Carlo calculations of accelerator grid erosion in an ion thruster. A comparison between numerical and experimental results suggests that the accelerator grid impingement is primarily due to ions created far downstream from the accelerator grid. In particular, for the same experimental conditions as those of Monheiser and Wilbur at Colorado State University, it is found that a downstream plasma density of 2 x 10 exp 14/cu m is required to give the same ratio of accelerator grid impingement current to beam current (5 percent). For this condition, a potential hill is found in the downstream region of 2.5 V.

  13. Development and Use of Mark Sense Record Cards for Recording Medical Data on Pilots Subjected to Acceleration Stress

    NASA Technical Reports Server (NTRS)

    Smedal, Harald A.; Havill, C. Dewey

    1962-01-01

    A TIME-HONORED system of recording medical histories and the data obtained on physical and laboratory examination has been that of writing the information on record sheets that go into a folder for each patient. In order to have information which would be more readily retrieved, 'a program was initiated in 1952 by the U. S. Naval School of Aviation Medicine in connection with their "Care of the Flyer" study to place this information on machine record cards. In 1958, a machine record card method was developed for recording medical data in connection with the astronaut selection program. Machine record cards were also developed by the Aero Medical Laboratory, Wright-Patterson AFB, Ohio, and the Aviation Medical Acceleration Laboratory, Naval Air Development Center, Johnsville, Pennsylvania, for use in connection with a variety of tests including acceleration stress.1 Therefore, a variety of systems resulted in which data of a medical nature could easily be recalled. During the NASA, Ames Research Center centrifuge studies/'S the pilot subjects were interviewed after each centrifuge run, or series of runs, and subjective information was recorded in a log book by the usual history taking methods referred to above. After the methods Were reviewed, it' was recognized that a card system would be very useful in recording data from our pilots after they had been exposed to acceleration stress. Since the acceleration stress cards already developed did not meet our requirements, it was decided a different card was needed.

  14. Recovery mechanisms in proton exchange membrane fuel cells after accelerated stress tests

    NASA Astrophysics Data System (ADS)

    Zhang, Xu; Guo, Liejin; Liu, Hongtan

    2015-11-01

    The mechanisms of performance recovery after accelerated stress test (AST) in proton exchange membrane fuel cells (PEMFCs) are systematically studied. Experiments are carried out by incorporating a well-designed performance recovery procedure right after the AST protocol. The experiment results show that the cell performance recovers significantly from the degraded state after the AST procedure. The results from cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements further show that the performance recovery can be divided into kinetic and mass transport recoveries. It is further determined that the kinetic recovery, i.e. the recovery of electrochemical active area (ECA), is due to two distinct mechanisms: the reduction of platinum oxide and the re-attachment of detached platinum nanoparticles onto the carbon surface. The mass transport resistance is probably due to reduction of hydrophilic oxide groups on the carbon surface and the microstructure change that alleviates flooding. Performance comparisons show that the recovery procedure is highly effective, indicating the results of AST significantly over-estimate the true degradation in a PEM fuel cell. Therefore, a recovery procedure is highly recommended when an AST protocol is used to evaluate cell degradations to avoid over-estimating true performance degradations in PEMFCs.

  15. Effects of Swim Stress on Neophobia and Reconditioning Using a Conditioned Taste Aversion Procedure

    ERIC Educational Resources Information Center

    Walker, Jennifer M.; Ramsey, Ashley K.; Fowler, Stephanie W.; Schachtman, Todd R.

    2012-01-01

    Previous research has found that swim stress during a classical conditioning trial attenuates conditioned taste aversion (CTA). In the current study, rats were used to examine the effects of inescapable swim stress on the habituation of neophobia to a flavored solution and reacquisition of an extinguished conditioned taste aversion. In Experiment…

  16. Constraining the detailed balance condition in Hořava gravity with cosmic accelerating expansion

    SciTech Connect

    Chiang, Chien-I; Chen, Pisin; Gu, Je-An E-mail: jagu@ntu.edu.tw

    2010-10-01

    In 2009 Hořava proposed a power-counting renormalizable quantum gravity theory. Afterwards a term in the action that softly violates the detailed balance condition has been considered with the attempt of obtaining a more realistic theory in its IR-limit. This term is proportional to ωR{sup (3)}, where ω is a constant parameter and R{sup (3)} is the spatial Ricci scalar. In this paper we derive constraints on this IR-modified Hořava theory using the late-time cosmic accelerating expansion observations. We obtain a lower bound of |ω| that is nontrivial and depends on Λ{sub W}, the cosmological constant of the three dimensional spatial action in the Hořava gravity. We find that to preserve the detailed balance condition, one needs to fine-tune Λ{sub W} such that −2.29 × 10{sup −4} < (c{sup 2}Λ{sub W})/(H{sup 2}{sub 0}Ω{sub DE})−2 < 0, where H{sub 0} and Ω{sub DE} are the Hubble parameter and dark energy density fraction in the present epoch, respectively. On the other hand, if we do not insist on the detailed balance condition, then the valid region for Λ{sub W} is much relaxed to −0.39 < (c{sup 2}Λ{sub W})/(H{sup 2}{sub 0}Ω{sub DE})−2 < 0.12. We find that although the detailed balance condition cannot be ruled out, it is strongly disfavored.

  17. Optimized conditions for the extraction of secondary volatile metabolites in Angelica roots by accelerated solvent extraction.

    PubMed

    Cho, S-K; Abd El-Aty, A M; Choi, J-H; Kim, M R; Shim, J H

    2007-09-01

    Accelerated solvent extraction (ASE) of three common Angelica species found in Asia: Angelica sinensis (Oliv.) Diels from China, Angelica acutiloba (Sieb. et Zucc.) Kitagawa from Japan, and Angelica gigas Nakai from Korea was investigated. Preliminary experiments, including the selection of the solvent, extraction time, pressure, static cycle and time were investigated to optimize experimental parameters. Kováts indices and mass spectra were used to identify the components in the various fractions. These were then confirmed using gas chromatography-mass spectrometry (GC-MS). A total of 18 compounds were identified, with qualitative differences and similarities observed among the cultivars. From the 18 compounds found in the ASE extract of danggui cultivars, the major components were decursin, decursinol angelate (A. gigas); butylidene dihydrophthalide, 4-hydroxy-4-methyl-2-pentanone (A. sinensis); and 9,12-octadecanoic acid in Angelica acutiloba. The optimum ASE operating conditions were n-hexane as extraction solvent, extraction temperature and pressure of 80 degrees C and 1500 atm, respectively, static cycle of 2 min, and static time of 10 min. Under these conditions, the percentages of main analytes were increased.

  18. Accelerated Biodegradation of Agriculture Film Based on Aromatic-Aliphatic Copolyester in Soil under Mesophilic Conditions.

    PubMed

    Šerá, Jana; Stloukal, Petr; Jančová, Petra; Verney, Vincent; Pekařová, Silvie; Koutný, Marek

    2016-07-20

    A study was conducted on the biodegradation of aromatic-aliphatic copolyester-based agricultural film in soil at 25 °C. The polymer is known to be biodegradable under composting conditions although rather recalcitrant under mesophilic conditions. The material investigated comprised of the copolyester filled with approximately 25% of starch containing biodegradable plasticizers, and its behavior was compared to the corresponding material without the filler. Mineralization followed by CO2 production merely reached the point of about 6% after 100 days of incubation in the pure copolyester film, whereas the value of around 53% was recorded for the filled copolyester film, which exceeded the readily biodegradable starch filler content in the material by more than 20% and could be accounted for biodegradation of the copolyester. It was suggested that the accelerated copolyester biodegradation in the starch-filled material was most likely explained by the increase in the active surface area of the material available for the microbial attack after biodegradation of the filler. The results were supported by changes in molecular weight distributions of the copolyester and observations made by several microscopic techniques. These findings encourage further development of biodegradable agricultural films based on this material. PMID:27367168

  19. Stability of β-Lapachone upon Exposure to Various Stress Conditions: Resultant Efficacy and Cytotoxicity.

    PubMed

    Kim, Ki Hyun; Park, So-Hyun; Adhikary, Pratik; Cho, Jin Hun; Kang, Nae-Gyu; Jeong, Seong Hoon

    2016-01-01

    Even though β-lapachone is a promising compound with antitumor, antiinflammatory, antineoplastic, and wound-healing effects, there are still issues concerning its chemical stability and degradation mechanisms. The objective of this study was to obtain degradation profiles of β-lapachone and evaluate its chemical stability under various stress conditions. Moreover, the correlation between stability and efficacy was evaluated. The degradation study of β-lapachone was performed using heat, acid, base, oxidation, and light conditions. Kinetics and degradation profiles were investigated with HPLC and LC-MS. The stability indicated in the LC method was validated according to the International Conference on Harmonization guidelines. Human dermal fibroblast (HDF) cells were cultured with the standard and its degraded samples in the cellular activity and cytotoxicity test. β-Lapachone was relatively unstable upon exposure to light, and its photodegradation was accelerated with high relative humidity. Three degradants were identified, and their degradation followed zero-order kinetics. It was shown to degrade to phthalic acid under oxidative conditions, and the degradation kinetics were dependent on the concentration of hydrogen peroxide. Two degradation products were identified upon exposure to basic conditions, which followed first-order kinetics. β-Lapachone was relatively stable under acidic and thermal conditions. It increased the synthesis of collagen compared with the control. However, as the contents decreased, the synthesis of collagen also decreased in the photodegraded samples. β-Lapachone did not exert cytotoxic effects at the effective concentration in the cytotoxicity test. Therefore, in order to ensure efficacy and safety, the chemical stability of β-lapachone needs to be controlled carefully while considering instability mechanisms. PMID:27150470

  20. Self-consistency conditions for elementary Reynolds stress closures

    NASA Astrophysics Data System (ADS)

    Rubinstein, Robert

    2016-02-01

    This paper summarizes the analytical representation of the correlation tensor in homogeneous anisotropic turbulence and sketches an application to Reynolds stress transport turbulence models. It is shown that the analytical approach can address some of the limitations of conventional modeling.

  1. Identification of key factors in Accelerated Low Water Corrosion through experimental simulation of tidal conditions: influence of stimulated indigenous microbiota.

    PubMed

    Marty, Florence; Gueuné, Hervé; Malard, Emilie; Sánchez-Amaya, José M; Sjögren, Lena; Abbas, Ben; Quillet, Laurent; van Loosdrecht, Mark C M; Muyzer, Gerard

    2014-01-01

    Biotic and abiotic factors favoring Accelerated Low Water Corrosion (ALWC) on harbor steel structures remain unclear warranting their study under controlled experimental tidal conditions. Initial stimulation of marine microbial consortia by a pulse of organic matter resulted in localized corrosion and the highest corrosion rates (up to 12-times higher than non-stimulated conditions) in the low water zone, persisting after nine months exposure to natural seawater. Correlations between corrosion severity and the abundance and composition of metabolically active sulfate-reducing bacteria (SRB) indicated the importance and persistence of specific bacterial populations in accelerated corrosion. One phylotype related to the electrogenic SRB Desulfopila corrodens appeared as the major causative agent of the accelerated corrosion. The similarity of bacterial populations related to sulfur and iron cycles, mineral and tuberculation with those identified in ALWC support the relevance of experimental simulation of tidal conditions in the management of steel corrosion exposed to harbor environments.

  2. Study of photon emission by electron capture during solar nuclei acceleration. 2: Delimitation of conditions for charge transfert establishment

    NASA Technical Reports Server (NTRS)

    Perez-Peraza, J.; Alvarez, M.; Gallegos, A.

    1985-01-01

    The conditions for establishment of charge transfer during acceleration of nuclei up to Fe, for typical conditions of solar flare regions T = 5 x 10 to the 3rd power to 2.5 x 10 to the 8th power degrees K were explored. Results show that such conditions are widely assorted, depending on the acceleration mechanism, the kind of projections and their velocity, the target elements, the source temperature and consequently on the degree of ionization of matter and the local charge state of the accelerated ions. Nevertheless, in spite of that assorted behavior, there are some general tendencies that can be summarized as follows. In atomic H electron capture is systematically established from thermal energies up to high energies, whatever the element and for both acceleration process. For a given element and fixed temperature (T), the probability and energy domain of electron capture and loss with Fermi are higher than with Betatron acceleration. For a given acceleration process the heavier the ion the higher the probability and the wider the energy range for electron capture and loss. For given acceleration mechanism and fixed element the importance and energy domain of capture and loss increase with T: for those reasons, the energy range of charge equilibrium (illustrated with solid lines on the next figs.) is wider with Fermi and increases with temperature and atomic number of projectiles. For the same reasons, electron loss is smaller while the lighter the element, the lower the temperature and the Betatron process, such that there are conditions for which electron loss is not allowed at low energies, but only electron capture is established.

  3. Properties of the shear stress peak radiated ahead of rapidly accelerating rupture fronts that mediate frictional slip.

    PubMed

    Svetlizky, Ilya; Pino Muñoz, Daniel; Radiguet, Mathilde; Kammer, David S; Molinari, Jean-François; Fineberg, Jay

    2016-01-19

    We study rapidly accelerating rupture fronts at the onset of frictional motion by performing high-temporal-resolution measurements of both the real contact area and the strain fields surrounding the propagating rupture tip. We observe large-amplitude and localized shear stress peaks that precede rupture fronts and propagate at the shear-wave speed. These localized stress waves, which retain a well-defined form, are initiated during the rapid rupture acceleration phase. They transport considerable energy and are capable of nucleating a secondary supershear rupture. The amplitude of these localized waves roughly scales with the dynamic stress drop and does not decrease as long as the rupture front driving it continues to propagate. Only upon rupture arrest does decay initiate, although the stress wave both continues to propagate and retains its characteristic form. These experimental results are qualitatively described by a self-similar model: a simplified analytical solution of a suddenly expanding shear crack. Quantitative agreement with experiment is provided by realistic finite-element simulations that demonstrate that the radiated stress waves are strongly focused in the direction of the rupture front propagation and describe both their amplitude growth and spatial scaling. Our results demonstrate the extensive applicability of brittle fracture theory to fundamental understanding of friction. Implications for earthquake dynamics are discussed. PMID:26729877

  4. Properties of the shear stress peak radiated ahead of rapidly accelerating rupture fronts that mediate frictional slip

    PubMed Central

    Svetlizky, Ilya; Pino Muñoz, Daniel; Radiguet, Mathilde; Kammer, David S.; Molinari, Jean-François; Fineberg, Jay

    2016-01-01

    We study rapidly accelerating rupture fronts at the onset of frictional motion by performing high-temporal-resolution measurements of both the real contact area and the strain fields surrounding the propagating rupture tip. We observe large-amplitude and localized shear stress peaks that precede rupture fronts and propagate at the shear-wave speed. These localized stress waves, which retain a well-defined form, are initiated during the rapid rupture acceleration phase. They transport considerable energy and are capable of nucleating a secondary supershear rupture. The amplitude of these localized waves roughly scales with the dynamic stress drop and does not decrease as long as the rupture front driving it continues to propagate. Only upon rupture arrest does decay initiate, although the stress wave both continues to propagate and retains its characteristic form. These experimental results are qualitatively described by a self-similar model: a simplified analytical solution of a suddenly expanding shear crack. Quantitative agreement with experiment is provided by realistic finite-element simulations that demonstrate that the radiated stress waves are strongly focused in the direction of the rupture front propagation and describe both their amplitude growth and spatial scaling. Our results demonstrate the extensive applicability of brittle fracture theory to fundamental understanding of friction. Implications for earthquake dynamics are discussed. PMID:26729877

  5. Properties of the shear stress peak radiated ahead of rapidly accelerating rupture fronts that mediate frictional slip.

    PubMed

    Svetlizky, Ilya; Pino Muñoz, Daniel; Radiguet, Mathilde; Kammer, David S; Molinari, Jean-François; Fineberg, Jay

    2016-01-19

    We study rapidly accelerating rupture fronts at the onset of frictional motion by performing high-temporal-resolution measurements of both the real contact area and the strain fields surrounding the propagating rupture tip. We observe large-amplitude and localized shear stress peaks that precede rupture fronts and propagate at the shear-wave speed. These localized stress waves, which retain a well-defined form, are initiated during the rapid rupture acceleration phase. They transport considerable energy and are capable of nucleating a secondary supershear rupture. The amplitude of these localized waves roughly scales with the dynamic stress drop and does not decrease as long as the rupture front driving it continues to propagate. Only upon rupture arrest does decay initiate, although the stress wave both continues to propagate and retains its characteristic form. These experimental results are qualitatively described by a self-similar model: a simplified analytical solution of a suddenly expanding shear crack. Quantitative agreement with experiment is provided by realistic finite-element simulations that demonstrate that the radiated stress waves are strongly focused in the direction of the rupture front propagation and describe both their amplitude growth and spatial scaling. Our results demonstrate the extensive applicability of brittle fracture theory to fundamental understanding of friction. Implications for earthquake dynamics are discussed.

  6. Investigation of Thermal Stress Convection in Nonisothermal Gases Under Microgravity Conditions

    NASA Technical Reports Server (NTRS)

    Mackowski, Daniel W.; Knight, Roy W.

    1996-01-01

    Microgravity conditions offer an environment in which convection in a nonisothermal gas could be driven primarily by thermal stress. A direct examination of thermal stress flows would be invaluable in assessing the accuracy of the Burnett terms in the fluid stress tensor. We present a preliminary numerical investigation of the competing effects of thermal stress, thermal creep at the side walls, and buoyancy on gas convection in nonuniformly heated containers under normal and reduced gravity levels. Conditions in which thermal stress convection becomes dominant are identified, and issues regarding the experimental measurement of the flows are discussed.

  7. Bacterial economics: adaptation to stress conditions via stage-wise changes in the response mechanism.

    PubMed

    Baranyi, J; Metris, A; George, S M

    2015-02-01

    Common features of microbial adaptation are analysed with mathematical models and extended to stress conditions when the bacterial population declines before growing again. A parallel is drawn between bacterial and human communities in terms of non-mutation-based adaptation (acclimation) to stress. For a case study, the behaviour of Escherichia coli under osmotic stress, is detailed. It is suggested that stress modelling adaptation should be the focus of further developments in predictive food microbiology.

  8. The Effectiveness of Rambutan (Nephelium lappaceum L.) Extract in Stabilization of Sunflower Oil under Accelerated Conditions.

    PubMed

    Mei, Winne Sia Chiaw; Ismail, Amin; Esa, Norhaizan Mohd; Akowuah, Gabriel Akyirem; Wai, Ho Chun; Seng, Yim Hip

    2014-05-09

    The oxidative properties of sunflower oil supplemented with rambutan extract, (crude extract and its fractionated fraction, SF II) in comparison with synthetic antioxidant were investigated. The supplemented sunflower oils were stored under accelerated conditions for 24 days at 60 °C. For every 6-day interval, the oxidative properties of the supplemented sunflower oil were evaluated based on the following tests, namely peroxide value, p-anisidine value, Thiobarbituric Acid Reactive Substances (TBARS) assay, iodine value and free fatty acids. The total oxidation (TOTOX) values were also calculated based on the peroxide values and p-anisidine values. Rambutan extract is a potential source of antioxidant. The oxidative activities of the extracts at all concentrations were significantly (p < 0.05) higher than the control. Generally, the partially fractionated fraction was more effective than the crude extract. With a 2-year storage period at ambient temperature, the fractionated fraction of the extract, SF II at 300 ppm, was observed to work more effectively than the synthetic antioxidant, t-Tocopherol, and it possessed a protective effect comparable with butylatedhydrioxynanisole (BHA). Therefore, rambutan extract could be used as a potential alternative source of antioxidant in the oil industry or other fat-based products to delay lipid oxidation.

  9. The Effectiveness of Rambutan (Nephelium lappaceum L.) Extract in Stabilization of Sunflower Oil under Accelerated Conditions

    PubMed Central

    Mei, Winne Sia Chiaw; Ismail, Amin; Mohd. Esa, Norhaizan; Akowuah, Gabriel Akyirem; Wai, Ho Chun; Seng, Yim Hip

    2014-01-01

    The oxidative properties of sunflower oil supplemented with rambutan extract, (crude extract and its fractionated fraction, SF II) in comparison with synthetic antioxidant were investigated. The supplemented sunflower oils were stored under accelerated conditions for 24 days at 60 °C. For every 6-day interval, the oxidative properties of the supplemented sunflower oil were evaluated based on the following tests, namely peroxide value, p-anisidine value, Thiobarbituric Acid Reactive Substances (TBARS) assay, iodine value and free fatty acids. The total oxidation (TOTOX) values were also calculated based on the peroxide values and p-anisidine values. Rambutan extract is a potential source of antioxidant. The oxidative activities of the extracts at all concentrations were significantly (p < 0.05) higher than the control. Generally, the partially fractionated fraction was more effective than the crude extract. With a 2-year storage period at ambient temperature, the fractionated fraction of the extract, SF II at 300 ppm, was observed to work more effectively than the synthetic antioxidant, t-Tocopherol, and it possessed a protective effect comparable with butylatedhydrioxynanisole (BHA). Therefore, rambutan extract could be used as a potential alternative source of antioxidant in the oil industry or other fat-based products to delay lipid oxidation. PMID:26784877

  10. The solid phase stress tensor in porous media mechanics and the Hill-Mandel condition

    NASA Astrophysics Data System (ADS)

    Gray, William G.; Schrefler, Bernhard A.; Pesavento, Francesco

    2009-03-01

    An assessment of the stress tensors used currently for the modeling of partially saturated porous media is made which includes concepts like total stress, solid phase stress, and solid pressure. Thermodynamically constrained averaging theory is used to derive the solid phase stress tensor. It is shown that in the upscaling procedure the Hill conditions are satisfied, which is not trivial. The stress tensor is then compared to traditional stress measures. The physical meaning of two forms of solid pressure and of the Biot coefficient is clarified. Finally, a Bishop-Skempton like form of the stress tensor is obtained and a form of the total stress tensor that does not make use of the effective stress concept.

  11. Not all stress is equal: CREB is not necessary for restraint stress reinstatement of cocaine-conditioned reward

    PubMed Central

    Briand, Lisa A.; Blendy, Julie A.

    2013-01-01

    Stress elicits relapse to cocaine seeking in humans and in animal models. Cyclic AMP response element binding protein (CREB) is required for swim stress-induced reinstatement of cocaine conditioned place preference. However, the role of CREB in other stress-induced reinstatement models has not been examined. To determine whether CREB is required across different stressors we examined the ability of restraint to elicit reinstatement of cocaine-conditioned place preference in wild type and CREBαΔ mutant mice. In contrast to previously published differences in swim stress-induced reinstatement, both wildtype and CREBαΔ mutant mice demonstrated restraint stress elicited reinstatement of cocaine-conditioned reward. While CREB is necessary for swim stress-elicited zif268 expression within the nucleus accubmens (NAc) shell & prelimbic cortex (PrL), restraint-stress-elicited comparable increases in zif268 expression within these regions in both wildtype and CREBαΔ mutant mice. Our findings suggest that not all stressors engage the same circuits or molecular mechanisms to elicit reinstatement behavior. PMID:23458740

  12. Communities of different plant diversity respond similarly to drought stress: experimental evidence from field non-weeded and greenhouse conditions

    NASA Astrophysics Data System (ADS)

    Lanta, Vojtěch; Doležal, Jiří; Zemková, Lenka; Lepš, Jan

    2012-06-01

    Accelerating rate of species loss has prompted researchers to study the role of species diversity in processes that control ecosystem functioning. Although negative impact of species loss has been documented, the evidence concerning its impact on ecosystem stability is still limited. Here, we studied the effects of declining species and functional diversity on plant community responses to drought in the field (open to weed colonization) and greenhouse conditions. Both species and functional diversity positively affected the average yields of field communities. However, this pattern was similar in both drought-stressed and control plots. No effect of diversity on community resistance, biomass recovery after drought and resilience was found because drought reduced biomass production similarly at each level of diversity by approximately 30 %. The use of dissimilarity (characterized by Euclidean distance) revealed higher variation under changing environments (drought-stressed vs. control) in more diverse communities compared to less species-rich assemblages. In the greenhouse experiment, the effect of species diversity affected community resistance, indicating that more diverse communities suffered more from drought than species-poor ones. We conclude that our study did not support the insurance hypothesis (stability properties of a community should increase with species richness) because species diversity had an equivocal effect on ecosystem resistance and resilience in an environment held under non-weeded practice, regardless of the positive relationship between sown species diversity and community biomass production. More species-rich communities were less resistant against drought-stressed conditions than species-poor ones grown in greenhouse conditions.

  13. [Cardioprotective properties of new glutamic acid derivative under stress conditions].

    PubMed

    Perfilova, V N; Sadikova, N V; Berestovitskaia, V M; Vasil'eva, O S

    2014-01-01

    The effect of new glutamic acid derivative on the cardiac ino- and chronotropic functions has been studied in experiments on rats exposed to 24-hour immobilization-and-pain stress. It is established that glutamic acid derivative RGPU-238 (glufimet) at a dose of 28.7 mg/kg increases the increment of myocardial contractility and relaxation rates and left ventricular pressure in stress-tested animals by 13 1,1, 72.4, and 118.6%, respectively, as compared to the control group during the test for adrenoreactivity. Compound RGPU-238 increases the increment of the maximum intensity of myocardium functioning by 196.5 % at 30 sec of isometric workload as compared to the control group. The cardioprotective effect of compound RGPU-238 is 1.5 - 2 times higher than that of the reference drug phenibut.

  14. Correlates and consequences of morale versus depression under stressful conditions.

    PubMed

    Britt, Thomas W; Dickinson, James M; Moore, DeWayne; Castro, Carl A; Adler, Amy B

    2007-01-01

    The role of morale as a positive psychological construct distinct from the construct of depression was examined using data from a longitudinal study of 1,685 U.S. soldiers on a peacekeeping mission to Kosovo. Structural equation modeling analyses revealed morale was best predicted by indices of engagement in meaningful work and confidence in unit functioning and leadership, whereas depression was best predicted by deployment stressors and negative events. Morale assessed during the deployment was related to perceiving benefits from deploying six months later, whereas depression was related to posttraumatic stress disorder and negative perceptions of deploying. The relationship between morale and benefits was a function of engagement in meaningful work. Discussion focuses on the importance of longitudinal research in specifying the antecedents of positive and negative outcomes of a stressful work environment. PMID:17257065

  15. Metabolic stress-like condition can be induced by prolonged strenuous exercise in athletes

    PubMed Central

    Hambraeus, Leif; Piehl-Aulin, Karin; Essén-Gustavsson, Birgitta; Åkerfeldt, Torbjörn; Olsson, Roger; Stridsberg, Mats; Ronquist, Gunnar

    2009-01-01

    Few studies have examined energy metabolism during prolonged, strenuous exercise. We wanted therefore to investigate energy metabolic consequences of a prolonged period of continuous strenuous work with very high energy expenditure. Twelve endurance-trained athletes (6 males and 6 females) were recruited. They performed a 7-h bike race on high work-load intensity. Physiological, biochemical, endocrinological, and anthropometric muscular compartment variables were monitored before, during, and after the race. The energy expenditure was high, being 5557 kcal. Work-load intensity (% of VO2 peak) was higher in females (77.7%) than in men (69.9%). Muscular glycogen utilization was pronounced, especially in type I fibres (>90%). Additionally, muscular triglyceride lipolysis was considerably accelerated. Plasma glucose levels were increased concomitantly with an unchanged serum insulin concentration which might reflect an insulin resistance state in addition to proteolytic glyconeogenesis. Increased reactive oxygen species (malondialdehyde (MDA)) were additional signs of metabolic stress. MDA levels correlated with glycogen utilization rate. A relative deficiency of energy substrate on a cellular level was indicated by increased intracellular water of the leg muscle concomitantly with increased extracellular levels of the osmoregulatory amino acid taurine. A kindred nature of a presumed insulin-resistant state with less intracellular availability of glucose for erythrocytes was also indicated by the findings of decreased MCV together with increased MCHC (haemoconcentration) after the race. This strenuous energy-demanding work created a metabolic stress-like condition including signs of insulin resistance and deteriorated intracellular glucose availability leading to compromised fuelling of ion pumps, culminating in a disturbed cellular osmoregulation indicated by taurine efflux and cellular swelling. PMID:19242868

  16. Stress states in nuclear operators under conditions of shiftwork.

    PubMed

    Dalbokova, D; Tzenova, B; Ognjanova, V

    1995-01-01

    This study examined the stress states experienced by nuclear power operators at work under an existing shift system, time-on-shift effects and the manner in which these states may be moderated by achievement motivation and a sense of coherence. The results show an incidence of stress states during evening shifts and night-shifts in the operators, which are primarily characterized by increased distraction as well as by enhanced sleepiness and low irritability. The night-shift was found to be the most problematic one in terms of increased sleepiness and distractibility, and reduced alertness. An abrupt fall in alertness during the evening shift and a considerably increased distractibility at its end was observed. These facts, as well as the lack of recuperation from daily domestic activities and caring for children at the start of the shift, suggest that besides the night duty, the evening one also constitutes a serious challenge to operational safety at this nuclear facility. Correlations found between personality characteristics and sleepiness, distractibility and irritability, indicate personal resources as important modifiers of stress states. A narrowing in the effects of motivation and sense of coherence was found in the evening shifts and night-shifts. The results have practical implications for intentional modifications of personal resources at nuclear facilities. PMID:11539392

  17. Distinct stress conditions result in aggregation of proteins with similar properties

    PubMed Central

    Weids, Alan J.; Ibstedt, Sebastian; Tamás, Markus J.; Grant, Chris M.

    2016-01-01

    Protein aggregation is the abnormal association of proteins into larger aggregate structures which tend to be insoluble. This occurs during normal physiological conditions and in response to age or stress-induced protein misfolding and denaturation. In this present study we have defined the range of proteins that aggregate in yeast cells during normal growth and after exposure to stress conditions including an oxidative stress (hydrogen peroxide), a heavy metal stress (arsenite) and an amino acid analogue (azetidine-2-carboxylic acid). Our data indicate that these three stress conditions, which work by distinct mechanisms, promote the aggregation of similar types of proteins probably by lowering the threshold of protein aggregation. The proteins that aggregate during physiological conditions and stress share several features; however, stress conditions shift the criteria for protein aggregation propensity. This suggests that the proteins in aggregates are intrinsically aggregation-prone, rather than being proteins which are affected in a stress-specific manner. We additionally identified significant overlaps between stress aggregating yeast proteins and proteins that aggregate during ageing in yeast and C. elegans. We suggest that similar mechanisms may apply in disease- and non-disease settings and that the factors and components that control protein aggregation may be evolutionary conserved. PMID:27086931

  18. Characterizing drought stress and trait influence on maize yield under current and future conditions.

    PubMed

    Harrison, Matthew T; Tardieu, François; Dong, Zhanshan; Messina, Carlos D; Hammer, Graeme L

    2014-03-01

    Global climate change is predicted to increase temperatures, alter geographical patterns of rainfall and increase the frequency of extreme climatic events. Such changes are likely to alter the timing and magnitude of drought stresses experienced by crops. This study used new developments in the classification of crop water stress to first characterize the typology and frequency of drought-stress patterns experienced by European maize crops and their associated distributions of grain yield, and second determine the influence of the breeding traits anthesis-silking synchrony, maturity and kernel number on yield in different drought-stress scenarios, under current and future climates. Under historical conditions, a low-stress scenario occurred most frequently (ca. 40%), and three other stress types exposing crops to late-season stresses each occurred in ca. 20% of cases. A key revelation shown was that the four patterns will also be the most dominant stress patterns under 2050 conditions. Future frequencies of low drought stress were reduced by ca. 15%, and those of severe water deficit during grain filling increased from 18% to 25%. Despite this, effects of elevated CO2 on crop growth moderated detrimental effects of climate change on yield. Increasing anthesis-silking synchrony had the greatest effect on yield in low drought-stress seasonal patterns, whereas earlier maturity had the greatest effect in crops exposed to severe early-terminal drought stress. Segregating drought-stress patterns into key groups allowed greater insight into the effects of trait perturbation on crop yield under different weather conditions. We demonstrate that for crops exposed to the same drought-stress pattern, trait perturbation under current climates will have a similar impact on yield as that expected in future, even though the frequencies of severe drought stress will increase in future. These results have important ramifications for breeding of maize and have implications for

  19. Estradiol accelerates extinction of lithium chloride-induced conditioned taste aversions through its illness-associated properties.

    PubMed

    Yuan, D L; Chambers, K C

    1999-12-01

    Estradiol accelerates extinction of LiCl-induced conditioned taste aversions when it is present during a period that starts 2-3 days after acquisition and extends throughout extinction (before and during extinction). It has been suggested that estradiol acts before, not during, extinction and that its effect on extinction is associated with its illness-inducing properties. This hypothesis is based on previous work which shows an attenuation of conditioned taste aversion learning when rats are exposed to illness-inducing agents during a period that starts 2 days after acquisition and ends 2 days before extinction trials are initiated. Four experiments were designed to test elements of this hypothesis. The first two experiments demonstrated that if an estradiol-filled Silastic capsule is implanted before extinction of a LiCl-induced aversion, when the conditioned taste is not present, it accelerates extinction, but if it is implanted during extinction, when the conditioned taste is present, it prolongs extinction. The third experiment showed that the same dose of estradiol that accelerates extinction of a LiCl-induced aversion was effective in producing a conditioned taste aversion when it was present for 18 h after consumption of a novel sucrose solution. The fourth experiment indicated that serum levels of estradiol were elevated during the 18 h. These results are consistent with the hypothesis that the acceleration of extinction by estradiol is associated with its illness-inducing properties. It is suggested that estradiol acts on neural areas that mediate illness information and that one of these areas, the area postrema is necessary for estradiol to accelerate extinction of a LiCl-induced aversion.

  20. Plant mitochondria under a variety of temperature stress conditions.

    PubMed

    Rurek, Michał

    2014-11-01

    The biogenesis of plant mitochondria is a multistep process that depends on a concerted expression of mitochondrial and nuclear genes. The balance between different steps of this process, embracing various fluctuations in mitochondrial transcriptome and proteome, may be affected by diverse temperature treatments. A plethora of genes with altered expression during the acting of these stimuli were identified and their expression characterized, including those encoding for classical components of energy dissipating system. Selected aspects of current interest, regarding the functioning of plant mitochondria under cold and heat stresses, are highlighted.

  1. Effect of certain psychopharmacological preparations on adaptation under stress conditions

    NASA Technical Reports Server (NTRS)

    Stanishevskaya, A. V.; Mezentseva, L. N.

    1980-01-01

    Experiments staged on rats demonstrated that the formation of pathological states caused by stress and accompanied by the development of ulcerative lesion of the gastric mucosa are associated with the degree of the catecholamines level drop in the mesencephalon and hypothalamus. The application of seduxen and also of combinations consisting of L-DOPA with seduxen, or with an L-adrenoblocking agent pyroxan tends to reduce the frequency of developing alcerative lesions of the stomach. The protective effect produced by the combination of L-DOPA with an L-adrenoblocking agent pyroxan is barred by an additional administration of an B-adrenoblocking agent, inderal.

  2. Understanding How Kurtosis Is Transferred from Input Acceleration to Stress Response and Its Influence on Fatigue Llife

    NASA Technical Reports Server (NTRS)

    Kihm, Frederic; Rizzi, Stephen A.; Ferguson, Neil S.; Halfpenny, Andrew

    2013-01-01

    High cycle fatigue of metals typically occurs through long term exposure to time varying loads which, although modest in amplitude, give rise to microscopic cracks that can ultimately propagate to failure. The fatigue life of a component is primarily dependent on the stress amplitude response at critical failure locations. For most vibration tests, it is common to assume a Gaussian distribution of both the input acceleration and stress response. In real life, however, it is common to experience non-Gaussian acceleration input, and this can cause the response to be non-Gaussian. Examples of non-Gaussian loads include road irregularities such as potholes in the automotive world or turbulent boundary layer pressure fluctuations for the aerospace sector or more generally wind, wave or high amplitude acoustic loads. The paper first reviews some of the methods used to generate non-Gaussian excitation signals with a given power spectral density and kurtosis. The kurtosis of the response is examined once the signal is passed through a linear time invariant system. Finally an algorithm is presented that determines the output kurtosis based upon the input kurtosis, the input power spectral density and the frequency response function of the system. The algorithm is validated using numerical simulations. Direct applications of these results include improved fatigue life estimations and a method to accelerate shaker tests by generating high kurtosis, non-Gaussian drive signals.

  3. Life prediction of 808nm high power semiconductor laser by accelerated life test of constant current stress

    NASA Astrophysics Data System (ADS)

    Yao, Nan; Li, Wei; Zhao, Yihao; Zhong, Li; Liu, Suping; Ma, Xiaoyu

    2015-10-01

    High power semiconductor laser is widely used because of its high transformation efficiency, good working stability, compact volume and simple driving requirements. Laser's lifetime is very long, but tests at high levels of stress can speed up the failure process and shorten the times to failure significantly. So accelerated life test is used here for forecasting the lifetime of 808nm CW GaAs/AlGaAs high power semiconductor laser that has an output power of 1W under 1.04A. Accelerated life test of constant current stress based on the Inverse Power Law Relationship was designed. Tests were conducted under 1.3A, 1.6A and 1.9A at room temperature. It is the first time that this method is used in the domestic research of laser's lifetime prediction. Applying Weibull Distribution to describe the lifetime distribution and analyzing the data of times to failure, characteristics lifetime's functional relationship model with current is achieved. Then the characteristics lifetime under normal current is extrapolated, which is 9473h. Besides, to confirm the validity of the functional relationship model, we conduct an additional accelerated life test under 1.75A. Based on this experimental data we calculated the characteristics lifetime corresponding to 1.75A that is 171h, while the extrapolated characteristics lifetime from the former functional relationship model is 162h. The two results shows 5% deviation that is very low and acceptable, which indicates that the test design is reasonable and authentic.

  4. Tremor frequency characteristics in Parkinson's disease under resting-state and stress-state conditions.

    PubMed

    Lee, Hong Ji; Lee, Woong Woo; Kim, Sang Kyong; Park, Hyeyoung; Jeon, Hyo Seon; Kim, Han Byul; Jeon, Beom S; Park, Kwang Suk

    2016-03-15

    Tremor characteristics-amplitude and frequency components-are primary quantitative clinical factors for diagnosis and monitoring of tremors. Few studies have investigated how different patient's conditions affect tremor frequency characteristics in Parkinson's disease (PD). Here, we analyzed tremor characteristics under resting-state and stress-state conditions. Tremor was recorded using an accelerometer on the finger, under resting-state and stress-state (calculation task) conditions, during rest tremor and postural tremor. The changes of peak power, peak frequency, mean frequency, and distribution of power spectral density (PSD) of tremor were evaluated across conditions. Patients whose tremors were considered more than "mild" were selected, for both rest (n=67) and postural (n=25) tremor. Stress resulted in both greater peak powers and higher peak frequencies for rest tremor (p<0.001), but not for postural tremor. Notably, peak frequencies were concentrated around 5 Hz under stress-state condition. The distributions of PSD of tremor were symmetrical, regardless of conditions. Tremor is more evident and typical tremor characteristics, namely a lower frequency as amplitude increases, are different in stressful condition. Patient's conditions directly affect neural oscillations related to tremor frequencies. Therefore, tremor characteristics in PD should be systematically standardized across patient's conditions such as attention and stress levels.

  5. Optical diagnostic test of stress conditions of aquatic organisms.

    PubMed

    Axenov-Gribanov, Denis V; Gurkov, Anton N; Shakhtanova, Nadezhda S; Bedulina, Daria S; Timofeyev, Maxim A; Meglinski, Igor

    2011-09-01

    Global climate change has become a dire reality and its impact is expected to rise dramatically in the near future. Combined with the day-to-day human activities the climatic changes heavily affect the environment. In particular, a global temperature increase accompanied by a number of anthropogenic chemicals falling within the freshwater ecosystem results in a dramatic enhancement of the overall stress for most aquatic organisms. This leads to a significant shift in the species inventory and potential breakdown of the water ecosystem with severe consequences for local economies and water supply. In order to understand and predict the influence of climatic changes on the physiological and biochemical processes that take place in living aquatic organisms we explore the application of optical spectroscopy for monitoring and quantitative assessment of antioxidant enzymes activity in benthic amphipods of Lake Baikal. We demonstrate that the changes of the enzymes activity in Baikal amphipods undergoing thermal and/or hypoxia stress can be observed and documented by UV and optical spectroscopy both in vivo and in vitro. PMID:21548104

  6. Design of a High Field Stress, Velvet Cathode for the Flash X-Ray (FXR) Induction Accelerator

    SciTech Connect

    Houck, T; Brown, C; Fleming, D; Kreitzer, B; Lewis, K; Ong, M; Zentler, J

    2007-06-08

    A new cathode design has been proposed for the Flash X-Ray (FXR) induction linear accelerator with the goal of lowering the beam emittance. The original design uses a conventional Pierce geometry and applies a peak field of 134 kV/cm (no beam) to the velvet emission surface. Voltage/current measurements indicate that the velvet begins emitting near this peak field value and images of the cathode show a very non-uniform distribution of plasma light. The new design has a flat cathode/shroud profile that allows for a peak field stress of 230 kV/cm on the velvet. The emission area is reduced by about a factor of four to generate the same total current due to the greater field stress. The relatively fast acceleration of the beam, approximately 2.5 MeV in 10 cm, reduces space charge forces that tend to hollow the beam for a flat, non-Pierce geometry. The higher field stress achieved with the same rise time is expected to lead to an earlier and more uniform plasma formation over the velvet surface. Simulations and initial testing are presented.

  7. Severe stress hormone conditions cause an extended window of excitability in the mouse basolateral amygdala.

    PubMed

    Karst, Henk; Joëls, Marian

    2016-11-01

    Shortly after stress, basolateral amygdala neurons are exposed to sequential yet partly overlapping waves of hormones. We examined how these hormonal waves can change activity of basolateral amygdala neurons such that emotional aspects of stress become so deeply ingrained. To this end, spontaneous glutamatergic transmission was recorded during and up to several hours after combined adrenergic and corticosteroid waves, targeting the time-window relevant for encoding of stress-related information. Hormonal waves mimicking moderately stressful conditions cause a transient enhancement followed by later suppression of glutamatergic transmission. However, this late phase flips from suppressed to enhanced glutamatergic transmission with conditions mimicking severe stress. Such a prolonged window of enhanced excitability may contribute to the excessively strong encoding seen after the experience of highly stressful or traumatic events.

  8. Severe stress hormone conditions cause an extended window of excitability in the mouse basolateral amygdala.

    PubMed

    Karst, Henk; Joëls, Marian

    2016-11-01

    Shortly after stress, basolateral amygdala neurons are exposed to sequential yet partly overlapping waves of hormones. We examined how these hormonal waves can change activity of basolateral amygdala neurons such that emotional aspects of stress become so deeply ingrained. To this end, spontaneous glutamatergic transmission was recorded during and up to several hours after combined adrenergic and corticosteroid waves, targeting the time-window relevant for encoding of stress-related information. Hormonal waves mimicking moderately stressful conditions cause a transient enhancement followed by later suppression of glutamatergic transmission. However, this late phase flips from suppressed to enhanced glutamatergic transmission with conditions mimicking severe stress. Such a prolonged window of enhanced excitability may contribute to the excessively strong encoding seen after the experience of highly stressful or traumatic events. PMID:27460963

  9. Oxidative stress and age-related changes in T cells: is thalassemia a model of accelerated immune system aging?

    PubMed Central

    Ghatreh-Samani, Mahdi; Esmaeili, Nafiseh; Soleimani, Masoud; Asadi-Samani, Majid; Ghatreh-Samani, Keihan

    2016-01-01

    Iron overload in β-thalassemia major occurs mainly due to blood transfusion, an essential treatment for β-thalassemia major patients, which results in oxidative stress. It has been thought that oxidative stress causes elevation of immune system senescent cells. Under this condition, cells normally enhance in aging, which is referred to as premature immunosenescence. Because there is no animal model for immunosenescence, most knowledge on the immunosenescence pattern is based on induction of immunosenescence. In this review, we describe iron overload and oxidative stress in β-thalassemia major patients and how they make these patients a suitable human model for immunosenescence. We also consider oxidative stress in some kinds of chronic virus infections, which induce changes in the immune system similar to β-thalassemia major. In conclusion, a therapeutic approach used to improve the immune system in such chronic virus diseases, may change the immunosenescence state and make life conditions better for β-thalassemia major patients. PMID:27095931

  10. Oxidative stress and age-related changes in T cells: is thalassemia a model of accelerated immune system aging?

    PubMed

    Ghatreh-Samani, Mahdi; Esmaeili, Nafiseh; Soleimani, Masoud; Asadi-Samani, Majid; Ghatreh-Samani, Keihan; Shirzad, Hedayatolah

    2016-01-01

    Iron overload in β-thalassemia major occurs mainly due to blood transfusion, an essential treatment for β-thalassemia major patients, which results in oxidative stress. It has been thought that oxidative stress causes elevation of immune system senescent cells. Under this condition, cells normally enhance in aging, which is referred to as premature immunosenescence. Because there is no animal model for immunosenescence, most knowledge on the immunosenescence pattern is based on induction of immunosenescence. In this review, we describe iron overload and oxidative stress in β-thalassemia major patients and how they make these patients a suitable human model for immunosenescence. We also consider oxidative stress in some kinds of chronic virus infections, which induce changes in the immune system similar to β-thalassemia major. In conclusion, a therapeutic approach used to improve the immune system in such chronic virus diseases, may change the immunosenescence state and make life conditions better for β-thalassemia major patients.

  11. Designing Accelerated Tests Of Electromigration

    NASA Technical Reports Server (NTRS)

    Buehler, Martin G.

    1991-01-01

    Method for design of accelerated tests of electromigration (as in microscopic conductors in integrated circuits) based partly on simplified mathematical model of electromigration and partly on error analysis. Objective to determine quickly operating life of tested components under normal operating conditions by extrapolation from lifetime measurements at operating stresses greater than normal. Involves compromise between reducing testing time by increasing stresses and reducing uncertainty in extrapolated lifetime by decreasing stresses.

  12. A Flight Evaluation of an Airborne Physiological Instrumentation System, Including Preliminary Results Under Conditions of Varying Accelerations

    NASA Technical Reports Server (NTRS)

    Smedal, Harald A.; Holden, George R.; Smith, Joseph R., Jr.

    1960-01-01

    A physiological instrumentation system capable of recording the electrocardiogram, pulse rate, respiration rate, and systolic and diastolic blood pressures during flight has been developed. This instrumentation system was designed for use during control studies at varied levels of acceleration in order to monitor the well-being of the pilot and at the same time to obtain data for study of the relationships between his various physiological functions and his performance capability. Flights, made in a T-33 aircraft, demonstrated the ability of the system to obtain the desired physiological data in flight. The data obtained in these flights, although limited in nature, indicate a slowing of the pulse rate under the subgravity conditions of brief duration. There appeared to be a proportional nearly in-phase relationship between pulse rate and acceleration. A decrease in diastolic blood pressure together with an increase in pulse pressure was noted during subgravity conditions and an elevation of the diastolic pressure together with a decrease in pulse pressure du-ring increased accelerations. No change worthy of note was seen in the records of the systolic blood pressure, the respiration rate, or the electrocardiogram over the range of acceleration studied (0 to 3 g).

  13. Stress and Self-Perceived Parenting Behaviors of Parents of Children with Autistic Spectrum Conditions

    ERIC Educational Resources Information Center

    Osborne, Lisa A.; Reed, Phil

    2010-01-01

    The relationships between parenting stress and self-perceived parenting behaviors in 138 parents of children with autistic spectrum conditions were studied over 9-10 months. Apart from perceived communication being attenuated, there were no major areas of self-perceived parenting weakness. Parenting stress closely interacted with self-perceived…

  14. Measurement of heat stress conditions at cow level and comparison to climate conditions at stationary locations inside a dairy barn.

    PubMed

    Schüller, Laura K; Heuwieser, Wolfgang

    2016-08-01

    The objectives of this study were to examine heat stress conditions at cow level and to investigate the relationship to the climate conditions at 5 different stationary locations inside a dairy barn. In addition, we compared the climate conditions at cow level between primiparous and multiparous cows for a period of 1 week after regrouping. The temperature-humidity index (THI) differed significantly between all stationary loggers. The lowest THI was measured at the window logger in the experimental stall and the highest THI was measured at the central logger in the experimental stall. The THI at the mobile cow loggers was 2·33 THI points higher than at the stationary loggers. Furthermore, the mean daily THI was higher at the mobile cow loggers than at the stationary loggers on all experimental days. The THI in the experimental pen was 0·44 THI points lower when the experimental cow group was located inside the milking parlour. The THI measured at the mobile cow loggers was 1·63 THI points higher when the experimental cow group was located inside the milking parlour. However, there was no significant difference for all climate variables between primiparous and multiparous cows. These results indicate, there is a wide range of climate conditions inside a dairy barn and especially areas with a great distance to a fresh air supply have an increased risk for the occurrence of heat stress conditions. Furthermore, the heat stress conditions are even higher at cow level and cows not only influence their climatic environment, but also generate microclimates within different locations inside the barn. Therefore climate conditions should be obtained at cow level to evaluate the heat stress conditions that dairy cows are actually exposed to. PMID:27600964

  15. Stress-related hormones and glycinebetaine interplay in protection of photosynthesis under abiotic stress conditions.

    PubMed

    Kurepin, Leonid V; Ivanov, Alexander G; Zaman, Mohammad; Pharis, Richard P; Allakhverdiev, Suleyman I; Hurry, Vaughan; Hüner, Norman P A

    2015-12-01

    Plants subjected to abiotic stresses such as extreme high and low temperatures, drought or salinity, often exhibit decreased vegetative growth and reduced reproductive capabilities. This is often associated with decreased photosynthesis via an increase in photoinhibition, and accompanied by rapid changes in endogenous levels of stress-related hormones such as abscisic acid (ABA), salicylic acid (SA) and ethylene. However, certain plant species and/or genotypes exhibit greater tolerance to abiotic stress because they are capable of accumulating endogenous levels of the zwitterionic osmolyte-glycinebetaine (GB). The accumulation of GB via natural production, exogenous application or genetic engineering, enhances plant osmoregulation and thus increases abiotic stress tolerance. The final steps of GB biosynthesis occur in chloroplasts where GB has been shown to play a key role in increasing the protection of soluble stromal and lumenal enzymes, lipids and proteins, of the photosynthetic apparatus. In addition, we suggest that the stress-induced GB biosynthesis pathway may well serve as an additional or alternative biochemical sink, one which consumes excess photosynthesis-generated electrons, thus protecting photosynthetic apparatus from overreduction. Glycinebetaine biosynthesis in chloroplasts is up-regulated by increases in endogenous ABA or SA levels. In this review, we propose and discuss a model describing the close interaction and synergistic physiological effects of GB and ABA in the process of cold acclimation of higher plants.

  16. The Photoelastic Investigation of Three-dimensional Stress and Strain Conditions

    NASA Technical Reports Server (NTRS)

    Oppel, G

    1937-01-01

    The present report contains the description and typical application of two photoelastic methods which are suitable for the study of stress and strain conditions in three dimensions, namely: the fixation method and the immersion method.

  17. FERTILITY INTENTIONS AND EARLY LIFE HEALTH STRESS AMONG WOMEN IN EIGHT INDIAN CITIES: TESTING THE REPRODUCTIVE ACCELERATION HYPOTHESIS.

    PubMed

    Kulathinal, Sangita; Säävälä, Minna

    2015-09-01

    In life history theory, early life adversity is associated with an accelerated reproductive tempo. In harsh and unpredictable conditions in developing societies fertility is generally higher and the reproductive tempo faster than in more secure environments. This paper examines whether differences in female anthropometry, particularly adult height, are associated with fertility intentions of women in urban environments in India. The study population consists of women aged 15-29 (N=4485) in slums and non-slums of eight Indian cities in the National Family Health Survey (NFHS) of 2005-2006. Adult height is taken as a proxy for early childhood health and nutritional condition. Fertility intentions are examined by using two variables: the desire to have a child or another child, and to have it relatively soon, as indicative of accelerated reproductive scheduling. Evidence supporting the acceleration hypothesis is found in two urban frames out of 26 examined in a two-staged multinomial logistic model. In three cases, the relationship between fertility intentions and height is the opposite than expected by the acceleration hypothesis: taller women have a higher predictive probability of desiring a(nother) child and/or narrower birth spacing. Potential explanations for the partly contradictory relationship between the childhood health indicator and fertility intentions are discussed. PMID:25115228

  18. [Role of micro-organisms in adapting plants to environmental stress conditions].

    PubMed

    Hirt, Heribert

    2012-01-01

    Due to their sessile nature, plants have always been confronted to various abiotic and biotic stresses in their immediate environment. As a consequence, the survival of plants depended on their ability to adjust rapidly their physiology, development and growth to escape or mitigate the impacts of stress. All plants are known to perceive and respond to stress signals such as drought, heat, salinity, attacks by herbivores and pathogens. Some biochemical processes are common to all plant stress responses including the production of certain stress proteins and metabolites, as well as the modification of the reactive oxygen species (ROS) metabolism. Although there has been extensive research in the plant stress response field, it is not yet known which factors are responsible for conferring to some plant species the capacity to colonize extreme habitats. Although considerable progress has been made in our understanding of plant stress physiology, the contribution of the plant-associated microbial community in the soil, commonly called the rhizosphere, has only recently received enhanced attention. Recent studies showed that some plant species in natural habitats require microbial associations for stress tolerance and survival. Since plants have colonized land, they have evolved mechanisms to respond to changing environmental conditions and settle in extreme habitats. Although many plants lack the adaptive capability to adapt to stress conditions, the ability of a variety of plants to adapt to stress conditions appears to depend on the association with microbes, raising a number of questions: can all plants improve stress tolerance when associated with their appropriate microbial partners? Did we miss identifying the right partners for a given plant species or variety? What distinguishes the microbes and plants that are adapted to extreme environmental conditions from those living in temperate zones? Answers to these questions are likely to revolutionize plant biology

  19. Accelerated Growth Rate and Increased Drought Stress Resilience of the Model Grass Brachypodium distachyon Colonized by Bacillus subtilis B26

    PubMed Central

    Charron, Jean-Benoit; Vali, Hojatollah; Bertrand, Annick; Jabaji, Suha

    2015-01-01

    Plant growth-promoting bacteria (PGB) induce positive effects in plants, for instance, increased growth and reduced abiotic stresses susceptibility. The mechanisms by which these bacteria impact the host plant are numerous, diverse and often specific. Here, we studied the agronomical, molecular and biochemical effects of the endophytic PGB Bacillus subtilis B26 on the full life cycle of Brachypodium distachyon Bd21, an established model species for functional genomics in cereal crops and temperate grasses. Inoculation of Brachypodium with B. subtilis strain B26 increased root and shoot weights, accelerated growth rate and seed yield as compared to control plants. B. subtilis strain B26 efficiently colonized the plant and was recovered from roots, stems and blades as well as seeds of Brachypodium, indicating that the bacterium is able to migrate, spread systemically inside the plant, establish itself in the aerial plant tissues and organs, and is vertically transmitted to seeds. The presence of B. subtilis strain B26 in the seed led to systemic colonization of the next generation of Brachypodium plants. Inoculated Brachypodium seedlings and mature plants exposed to acute and chronic drought stress minimized the phenotypic effect of drought compared to plants not harbouring the bacterium. Protection from the inhibitory effects of drought by the bacterium was linked to upregulation of the drought-response genes, DREB2B-like, DHN3-like and LEA-14-A-like and modulation of the DNA methylation genes, MET1B-like, CMT3-like and DRM2-like, that regulate the process. Additionally, total soluble sugars and starch contents increased in stressed inoculated plants, a biochemical indication of drought tolerance. In conclusion, we show a single inoculation of Brachypodium with a PGB affected the whole growth cycle of the plant, accelerating its growth rates, shortening its vegetative period, and alleviating drought stress effects. These effects are relevant to grasses and cereal

  20. Stress and opioids: role of opioids in modulating stress-related behavior and effect of stress on morphine conditioned place preference.

    PubMed

    Bali, Anjana; Randhawa, Puneet Kaur; Jaggi, Amteshwar Singh

    2015-04-01

    Research studies have defined the important role of endogenous opioids in modulating stress-associated behavior. The release of β-endorphins in the amygdala in response to stress helps to cope with a stressor by inhibiting the over-activation of HPA axis. Administration of mu opioid agonists reduces the risk of developing post-traumatic stress disorder (PTSD) following a traumatic event by inhibiting fear-related memory consolidation. Similarly, the release of endogenous enkephalin and nociceptin in the basolateral amygdala and the nucleus accumbens tends to produce the anti-stress effects. An increase in dynorphin levels during prolonged exposure to stress may produce learned helplessness, dysphoria and depression. Stress also influences morphine-induced conditioned place preference (CPP) depending upon the intensity and duration of the stressor. Acute stress inhibits morphine CPP, while chronic stress potentiates CPP. The development of dysphoria due to increased dynorphin levels may contribute to chronic stress-induced potentiation of morphine CPP. The activation of ERK/cyclic AMP responsive element-binding (CREB) signaling in the mesocorticolimbic area, glucocorticoid receptors in the basolateral amygdala, and norepinephrine and galanin system in the nucleus accumbens may decrease the acute stress-induced inhibition of morphine CPP. The increase in dopamine levels in the nucleus accumbens and augmentation of GABAergic transmission in the median prefrontal cortex may contribute in potentiating morphine CPP. Stress exposure reinstates the extinct morphine CPP by activating the orexin receptors in the nucleus accumbens, decreasing the oxytocin levels in the lateral septum and amygdala, and altering the GABAergic transmission (activation of GABAA and inactivation of GABAB receptors). The present review describes these varied interactions between opioids and stress along with the possible mechanism. PMID:25636946

  1. Effects of Acute Stress on Decision Making under Ambiguous and Risky Conditions in Healthy Young Men.

    PubMed

    Cano-López, Irene; Cano-López, Beatriz; Hidalgo, Vanesa; González-Bono, Esperanza

    2016-01-01

    Acute stress and decision making (DM) interact in life - although little is known about the role of ambiguity and risk in this interaction. The aim of this study is to clarify the effect of acute stress on DM under various conditions. Thirty-one young healthy men were randomly distributed into two groups: experimental and control. DM processes were evaluated before and after an experimental session. For the experimental group, the session consisted of an acute stress battery; and the protocol was similar for the control group but the instructions were designed to minimize acute stress. Cardiovascular variables were continuously recorded 30 minutes before the DM tasks and during the experimental session. Cortisol, glucose, mood responses, and personality factors were also assessed. Acute stress was found to enhance disadvantageous decisions under ambiguous conditions (F(1, 29) = 4.16, p = .05, η2 p = .13), and this was mainly explained by the stress induced cortisol response (26.1% of variance, F(1, 30) = 11.59, p = .002). While there were no significant effects under risky conditions, inhibition responses differed between groups (F(1, 29) = 4.21, p = .05, η2 p = .13) and these differences were explained by cardiovascular and psychological responses (39.1% of variance, F(3, 30) = 7.42, p < .001). Results suggest that DM tasks could compete with cognitive resources after acute stress and could have implications for intervention in acute stress effects on DM in contexts such as addiction or eating disorders. PMID:27644414

  2. Free vibrations of thermally stressed orthotropic plates with various boundary conditions

    NASA Technical Reports Server (NTRS)

    Bailey, C. D.; Greetham, J. C.

    1973-01-01

    An analytical investigation of the vibrations of thermally stressed orthotropic plates in the prebuckled region is presented. The investigation covers the broad class of trapezoidal plates with two opposite sides parallel. Each edge of the plate may be subjected to different uniform boundary conditions. variable thickness and arbitrary temperature distributions (analytical or experimental) for any desired combination of boundary conditions may be prescribed. Results obtained using this analysis are compared to experimental results obtained for isotropic plates with thermal stress, and to results contained in the literature for orthotropic plates without thermal stress. Good agreement exists for both sets of comparisons.

  3. Molecular response of Saccharomyces cerevisiae wine and laboratory strains to high sugar stress conditions.

    PubMed

    Jiménez-Martí, E; Zuzuarregui, A; Gomar-Alba, M; Gutiérrez, D; Gil, C; del Olmo, M

    2011-01-31

    One of the stress conditions that can affect Saccharomyces cerevisiae cells during their growth is osmotic stress. Under particular environments (for instance, during the production of alcoholic beverages) yeasts have to cope with osmotic stress caused by high sugar concentrations. Although the molecular changes and pathways involved in the response to saline or sorbitol stress are widely understood, less is known about how cells respond to high sugar concentrations. In this work we present a comprehensive study of the response to this form of stress which indicates important transcriptomic changes, especially in terms of the genes involved in both stress response and respiration, and the implication of the HOG pathway. We also describe several genes of an unknown function which are more highly expressed under 20% (w/v) glucose than under 2% (w/v) glucose. In this work we focus on the YHR087w (RTC3) gene and its encoded protein. Proteomic analysis of the mutant deletion strain reveals lower levels of several yeast Hsp proteins, which establishes a link between this protein and the response to several forms of stress. The relevance of YHR087W for the response to high sugar and other stress conditions and the relationship of the encoded protein with several Hsp proteins suggest applications of this gene in biotechnological processes in which response to stress is important.

  4. Conditions of endoplasmic reticulum stress stimulate lipid droplet formation in Saccharomyces cerevisiae.

    PubMed

    Fei, Weihua; Wang, Han; Fu, Xin; Bielby, Christopher; Yang, Hongyuan

    2009-11-15

    LDs (lipid droplets) are cellular organelles which can be found in nearly all eukaryotic cells. Despite their importance in cell biology, the mechanism underlying LD biogenesis remains largely unknown. In the present study we report that conditions of ER (endoplasmic reticulum) stress stimulate LD formation in Saccharomyces cerevisiae. We found that LDs accumulated in yeast mutants with compromised protein glycosylation or ER-associated protein degradation. Moreover, tunicamycin and Brefeldin A, agents which induce ER stress, were found to stimulate LD formation. In contrast, the restoration of protein glycosylation reduced LD accumulation. Interestingly, enhanced neutral lipids synthesis and LD formation under conditions of ER stress was not dependent on Ire1p. Lastly, we demonstrated that the absence of LDs did not compromise cell viability under ER stress. Our results suggest that although more LDs are produced, LDs are not essential to cell survival under ER stress. PMID:19708857

  5. Nondestructive Evaluation and Monitoring Results from COPV Accelerated Stress Rupture Testing

    NASA Astrophysics Data System (ADS)

    Saulsberry, Regor L.; Greene, Nathanael J.; Banks, Curtis E.; Madaras, Eric I.; Waller, Jess M.; Forth, Scott C.; Russell, Rick W.

    2010-09-01

    To project objective is to develop and demonstrate nondestructive evaluation(NDE) techniques capable of assessing stress rupture related strength degradation for carbon composite pressure vessels, either in a structural health monitoring(SHM) or periodic inspection mode.

  6. Changes in oxidative stress parameters and neurodegeneration markers in the brain of the senescence-accelerated mice SAMP-8.

    PubMed

    Sureda, Francesc X; Gutierrez-Cuesta, Javier; Romeu, Marta; Mulero, Miquel; Canudas, Anna Maria; Camins, Antoni; Mallol, Jordi; Pallàs, Mercè

    2006-04-01

    The senescence-accelerated strains of mice (SAMP) are well-characterized animal models of senescence. Senescence may be related to enhanced production or defective control of reactive oxygen species, which lead to neuronal damage. Therefore, the activity of various oxidative-stress related enzymes was determined in the cortex of 5 months-old senescence-accelerated mice prone-8 (SAMP-8) of both sexes and compared with senescence-accelerated mice-resistant-1 (SAMR-1). Glutathione reductase and peroxidase activities in SAMP-8 male mice were lower than in male SAMR-1, and a decreased catalase activity was found in both male and female SAMP-8 mice, which correlates with the lower catalase expression found by Western blotting. Nissl staining showed marked loss of neuronal cells in the cerebral cortex of five month-old SAMP-8 mice. SAMP-8 mice also had marked astrogliosis and microgliosis. We also found an increase in caspase-3 and calpain activity in the cortex. In addition, we observed morphological changes in the immunostaining of tau protein in SAMP-8, indicative of a loss of their structural function. Altogether, these results show that, at as early as 5 months of age, SAMP-8 mice have cytological and molecular alterations indicative of neurodegeneration in the cerebral cortex and suggestive of altered control of the production of oxidative species and hyper-activation of calcium-dependent enzymes. PMID:16542809

  7. Development of a Fatigue Crack Growth Coupon for Highly Plastic Stress Conditions

    NASA Technical Reports Server (NTRS)

    Allen, Phillip A.; Aggarwal, Pravin K.; Swanson, Gregory R.

    2003-01-01

    The analytical approach used to develop a novel fatigue crack growth coupon for highly plastic stress field condition is presented in this paper. The flight hardware investigated is a large separation bolt that has a deep notch, which produces a large plastic zone at the notch root when highly loaded. Four test specimen configurations are analyzed in an attempt to match the elastic-plastic stress field and crack constraint conditions present in the separation bolt. Elastic-plastic finite element analysis is used to compare the stress fields and critical fracture parameters. Of the four test specimens analyzed, the modified double-edge notch tension - 3 (MDENT-3) most closely approximates the stress field, J values, and crack constraint conditions found in the flight hardware. The MDENT-3 is also most insensitive to load misalignment and/or load redistribution during crack growth.

  8. Operator independent left ventricular function monitoring during pharmacological stress echo with the new peak transcutaneous acceleration signal

    PubMed Central

    Bombardini, T; Marcelli, E; Picano, E; Borghi, B; Fedriga, P; Garberoglio, B; Gaggini, G; Plicchi, G

    2001-01-01

    BACKGROUND—As the myocardium contracts isometrically, it generates vibrations that can be measured with an accelerometer. The vibration peak, peak endocardial acceleration (PEA), is an index of contractility.
OBJECTIVE—To evaluate the feasibility of PEA measured by the cutaneous precordial application of the accelerometer sensor; and to assess the usefulness of PEA monitoring during pharmacological stress echocardiography.
DESIGN—Feasibility study.
SETTING—Stress echo laboratory.
PATIENTS—34 consecutive patients underwent pharmacological stress (26 with dipyridamole; 8 with dobutamine) and PEA monitoring simultaneously.
INTERVENTIONS—A microaccelerometer was positioned in the precordial region and PEA was recorded. Dipyridamole was infused up to 0.84 mg/kg in 10 minutes, and dobutamine up to 40 µg/kg/min in 15 minutes.
RESULTS—A consistent PEA signal was obtained in all patients. Overall mean (SD) baseline PEA was 0.26 (0.15) g (g = 9.8 m/s2), increasing to 0.5 (0.36) g at peak stress (+0.24 g, 95% confidence interval (CI) 0.14 to 0.34 g; p < 0.01). PEA increased from 0.26 (0.16) to 0.37 (0.25) g in the dipyridamole group (+0.11 g, 95% CI 0.08 to 0.16 g; p < 0.01), and from 0.29 (0.1) to 0.93 (0.37) g in the dobutamine group (+0.64 g, 95% CI 0.37 to 0.91 g; p < 0.01).
CONCLUSIONS—Using precordial leads this method offers potential for diagnostic application in the short term monitoring of myocardial function. PEA monitoring is feasible during pharmacological stress and documents left ventricular inotropic response quantitatively in a non-invasive and operator independent fashion.


Keywords: ventricular function; contractility; peak endocardial acceleration; stress echo PMID:11179267

  9. Conditioned stress prevents cue-primed cocaine reinstatement only in stress-responsive rats.

    PubMed

    Hadad, Natalie A; Wu, Lizhen; Hiller, Helmut; Krause, Eric G; Schwendt, Marek; Knackstedt, Lori A

    2016-07-01

    Neurobiological mechanisms underlying comorbid posttraumatic stress disorder (PTSD) and cocaine use disorder (CUD) are unknown. We aimed to develop an animal model of PTSD + CUD to examine the neurobiology underlying cocaine-seeking in the presence of PTSD comorbidity. Rats were exposed to cat urine once for 10-minutes and tested for anxiety-like behaviors one week later. Subsequently, rats underwent long-access (LgA) cocaine self-administration and extinction training. Rats were re-exposed to the trauma context and then immediately tested for cue-primed reinstatement of cocaine-seeking. Plasma and brains were collected afterwards for corticosterone assays and real-time qPCR analysis. Urine-exposed (UE; n = 23) and controls not exposed to urine (Ctrl; n = 11) did not differ in elevated plus maze behavior, but UE rats displayed significantly reduced habituation of the acoustic startle response (ASR) relative to Ctrl rats. A median split of ASR habituation scores was used to classify stress-responsive rats. UE rats (n = 10) self-administered more cocaine on Day 1 of LgA than control rats (Ctrl + Coc; n = 8). Re-exposure to the trauma context prevented cocaine reinstatement only in stress-responsive rats. Ctrl + Coc rats had lower plasma corticosterone concentrations than Ctrls, and decreased gene expression of corticotropin releasing hormone (CRH) and Glcci1 in the hippocampus. Rats that self-administered cocaine displayed greater CRH expression in the amygdala that was independent of urine exposure. While we did not find that cat urine exposure induced a PTSD-like phenotype in our rats, the present study underscores the need to separate stressed rats into cohorts based on anxiety-like behavior in order to study individual vulnerability to PTSD + CUD.

  10. Conditioned stress prevents cue-primed cocaine reinstatement only in stress-responsive rats.

    PubMed

    Hadad, Natalie A; Wu, Lizhen; Hiller, Helmut; Krause, Eric G; Schwendt, Marek; Knackstedt, Lori A

    2016-07-01

    Neurobiological mechanisms underlying comorbid posttraumatic stress disorder (PTSD) and cocaine use disorder (CUD) are unknown. We aimed to develop an animal model of PTSD + CUD to examine the neurobiology underlying cocaine-seeking in the presence of PTSD comorbidity. Rats were exposed to cat urine once for 10-minutes and tested for anxiety-like behaviors one week later. Subsequently, rats underwent long-access (LgA) cocaine self-administration and extinction training. Rats were re-exposed to the trauma context and then immediately tested for cue-primed reinstatement of cocaine-seeking. Plasma and brains were collected afterwards for corticosterone assays and real-time qPCR analysis. Urine-exposed (UE; n = 23) and controls not exposed to urine (Ctrl; n = 11) did not differ in elevated plus maze behavior, but UE rats displayed significantly reduced habituation of the acoustic startle response (ASR) relative to Ctrl rats. A median split of ASR habituation scores was used to classify stress-responsive rats. UE rats (n = 10) self-administered more cocaine on Day 1 of LgA than control rats (Ctrl + Coc; n = 8). Re-exposure to the trauma context prevented cocaine reinstatement only in stress-responsive rats. Ctrl + Coc rats had lower plasma corticosterone concentrations than Ctrls, and decreased gene expression of corticotropin releasing hormone (CRH) and Glcci1 in the hippocampus. Rats that self-administered cocaine displayed greater CRH expression in the amygdala that was independent of urine exposure. While we did not find that cat urine exposure induced a PTSD-like phenotype in our rats, the present study underscores the need to separate stressed rats into cohorts based on anxiety-like behavior in order to study individual vulnerability to PTSD + CUD. PMID:27181613

  11. Does cyclic stress and accelerated ageing influence the wear behavior of highly crosslinked polyethylene?

    PubMed

    Affatato, Saverio; De Mattia, Jonathan Salvatore; Bracco, Pierangiola; Pavoni, Eleonora; Taddei, Paola

    2016-06-01

    First-generation (irradiated and remelted or annealed) and second-generation (irradiated and vitamin E blended or doped) highly crosslinked polyethylenes were introduced in the last decade to solve the problems of wear and osteolysis. In this study, the influence of the Vitamin-E addition on crosslinked polyethylene (XLPE_VE) was evaluated by comparing the in vitro wear behavior of crosslinked polyethylene (XLPE) versus Vitamin-E blended polyethylene XLPE and conventional ultra-high molecular weight polyethylene (STD_PE) acetabular cups, after accelerated ageing according to ASTM F2003-02 (70.0±0.1°C, pure oxygen at 5bar for 14 days). The test was performed using a hip joint simulator run for two millions cycles, under bovine calf serum as lubricant. Mass loss was found to decrease along the series XLPE_VE>STD_PE>XLPE, although no statistically significant differences were found between the mass losses of the three sets of cups. Micro-Raman spectroscopy was used to investigate at a molecular level the morphology changes induced by wear. The spectroscopic analyses showed that the accelerated ageing determined different wear mechanisms and molecular rearrangements during testing with regards to the changes in both the chain orientation and the distribution of the all-trans sequences within the orthorhombic, amorphous and third phases. The results of the present study showed that the addition of vitamin E was not effective to improve the gravimetric wear of PE after accelerated ageing. However, from a molecular point of view, the XLPE_VE acetabular cups tested after accelerated ageing appeared definitely less damaged than the STD_PE ones and comparable to XLPE samples. PMID:26970299

  12. Effects of Stress and Sex on Acquisition and Consolidation of Human Fear Conditioning

    ERIC Educational Resources Information Center

    Kuhn, Cynthia M.; LaBar, Kevin S.; Zorawski, Michael; Blanding, Nineequa Q.

    2006-01-01

    We examined the relationship between stress hormone (cortisol) release and acquisition and consolidation of conditioned fear learning in healthy adults. Participants underwent acquisition of differential fear conditioning, and consolidation was assessed in a 24-h delayed extinction test. The acquisition phase was immediately followed by an 11-min…

  13. Polar 5 - An electron accelerator experiment within an aurora. I - Instrumentation and geophysical conditions

    NASA Technical Reports Server (NTRS)

    Maehlum, B. N.; Grandal, B.; Jacobsen, T. A.; Maseide, K.; Egeland, A.; Holtet, J.; Soraas, F.; Aarsnes, K.; Stadsnes, J.; Maynard, N. C.

    1980-01-01

    A mother-daughter rocket was launched over two auroral structures, which included a 10 keV electron accelerator and a series of diagnostic instruments for monitoring optical and wave effects generated through beam-atmospheric interactions and production of secondary electrons. The instrumentation, the ground and rocket background measurements obtained, and some of the beam effects on various geophysical parameters are presented. Attention is given to the rocket geometry, capacitance probe, particle counters, photometers, and the bremsstrahlung X-ray detector. Observations on the plasma environment, auroral particle precipitation, d.c. electric field, optical emissions, and auroral background HF and VLF emissions are also discussed.

  14. Nucleic acid aptamers stabilize proteins against different types of stress conditions.

    PubMed

    Jetani, Hardik C; Bhadra, Ankan Kumar; Jain, Nishant Kumar; Roy, Ipsita

    2014-01-01

    It has been observed that the same osmolyte cannot provide protection to a protein exposed to more than one stress condition. We wanted to study the effect of nucleic acid aptamers on the stabilization of proteins against a variety of stress conditions. Adjuvanted tetanus toxoid was exposed to thermal, freeze-thawing, and agitation stress. The stability and antigenicity of the toxoid were measured. Using nucleic acid aptamers selected against tetanus toxoid, we show that these specific RNA sequences were able to stabilize alumina-adsorbed tetanus toxoid against thermal-, agitation-, and freeze-thawing-induced stress. Binding affinity of the aptamer-protein complex did not show any significant change at elevated temperature as compared with that at room temperature, indicating that the aptamer protected the protein by remaining bound to it under stress conditions and did not allow either the protein to unfold or to promote protein-protein interaction. Thus, we show that by changing the stabilization strategy from a solvent-centric to a protein-centric approach, the same molecule can be employed as a stabilizer against more than one stress condition and thus probably reduce the cost of the product during its formulation.

  15. HPLC and HPLC/MS/MS Studies on Stress, Accelerated and Intermediate Degradation Tests of Antivirally Active Tricyclic Analog of Acyclovir.

    PubMed

    Lesniewska, Monika A; Dereziński, Paweł; Klupczyńska, Agnieszka; Kokot, Zenon J; Ostrowski, Tomasz; Zeidler, Joanna; Muszalska, Izabela

    2015-01-01

    The degradation behavior of a tricyclic analog of acyclovir [6-(4-MeOPh)-TACV] was determined in accordance with International Conference on Harmonization guidelines for good clinical practice under different stress conditions (neutral hydrolysis, strong acid/base degradation, oxidative decomposition, photodegradation, and thermal degradation). Accelerated [40±2°C/75%±5% relative humidity (RH)] and intermediate (30±2°C/65%±5% RH) stability tests were also performed. For observation of the degradation of the tested compound the RP-HPLC was used, whereas for the analysis of its degradation products HPLC/MS/MS was used. Degradation of the tested substance allowed its classification as unstable in neutral environment, acidic/alkaline medium, and in the presence of oxidizing agent. The tested compound was also light sensitive and was classified as photolabile both in solution and in the solid phase. However, the observed photodegradation in the solid phase was at a much lower level than in the case of photodegradation in solution. The study showed that both air temperature and RH had no significant effect on the stability of the tested substance during storage for 1 month at 100°C (dry heat) as well as during accelerated and intermediate tests. Based on the HPLC/MS/MS analysis, it can be concluded that acyclovir was formed as a degradation product of 6-(4-MeOPh)-TACV.

  16. Stress, deformation and micromorphological aspects of soil freezing under laboratory conditions

    NASA Astrophysics Data System (ADS)

    Jetchick, Elizabeth

    In this thesis, frost heave is viewed as a process resulting from the interactions between thermodynamic conditions, soil environment controls such as texture, stress/deformation conditions and soil microstructure. A series of laboratory experiments was devised to investigate the links between these aspects. Because a limited number of studies exist on the development of internal stresses and strains in freezing soil, the work focussed on obtaining rheological data using conventional soil strain gauges and prototype stress transducers. A fine-grained unstructured silt was placed in a column (30 cm diameter by 100 cm length) and subjected to freezing and freeze-thaw cycles from the top down, lasting up to three months. Heat and water flows, as well as stresses and strains were monitored. The frozen soil was sectioned at the end of four of the experiments to examine the soil fabrics that had developed. From the experimental results, schematic stress and strain curves are proposed. For a single freeze cycle, compressive normal and tensile normal stresses were recorded simultaneously by the measuring devices within the freezing soil profile. Ice lens inception took place when the stress field changed, a condition which occurred either at the frost front level or at the base of the growing ice lens. Negative and positive strains reflected the different stress states that were sustained below and above the freezing front. Negative strains or soil consolidation took place as stresses increased before the passage of the frost line. Negligible soil strains were recorded as maximum soil consolidation was attained, before soil expansion. Distinct positive strain patterns indicating secondary and continuing heave, were recorded simultaneously throughout a thickness of soil, over a range of temperatures. Ice lens growth mostly took place as secondary frost heave, but continuing heave was measured, and the temperature conditions for both types of heave were determined. During

  17. Investigation of reliability attributes and accelerated stress factors on terrestrial solar cells

    NASA Technical Reports Server (NTRS)

    Lathrop, J. W.; Hartman, R. A.; Saylor, C. R.

    1981-01-01

    Major effort during this reporting period was devoted to two tasks: improvement of the electrical measurement instrumentation through the design and construction of a microcomputer controlled short interval tester, and better understanding of second quadrant behavior by developing a mathematical model relating cell temperature to electrical characteristics. In addition, some preliminary work is reported on an investigation into color changes observed after stressing.

  18. Failure Engineering Study and Accelerated Stress Test Results for the Mars Global Surveyor Spacecraft's Power Shunt Assemblies

    NASA Technical Reports Server (NTRS)

    Gibbel, Mark; Larson, Timothy

    2000-01-01

    An Engineering-of-Failure approach to designing and executing an accelerated product qualification test was performed to support a risk assessment of a "work-around" necessitated by an on-orbit failure of another piece of hardware on the Mars Global Surveyor spacecraft. The proposed work-around involved exceeding the previous qualification experience both in terms of extreme cold exposure level and in terms of demonstrated low cycle fatigue life for the power shunt assemblies. An analysis was performed to identify potential failure sites, modes and associated failure mechanisms consistent with the new use conditions. A test was then designed and executed which accelerated the failure mechanisms identified by analysis. Verification of the resulting failure mechanism concluded the effort.

  19. Social defeat stress switches the neural system mediating benzodiazepine conditioned motivation.

    PubMed

    Riad-Allen, Lilian; van der Kooy, Derek

    2013-08-01

    Benzodiazepines have been demonstrated to have a high abuse liability in persons suffering from anxiety but have demonstrated mixed abuse liability findings in preclinical models. We hypothesized that by modeling anxiety in a male C57BL/6 mouse model it would be possible to reveal a preference for benzodiazepines within this subpopulation through negative reinforcement. Using the Tube Test of Social Dominance and the Resident/Intruder Paradigm we investigated whether animals identified as dominant or submissive/defeated would differentially display a preference for midazolam (a short acting benzodiazepine) in a conditioned place preference paradigm. Consistent with our hypotheses, benzodiazepine conditioned motivation was mediated by negative reinforcement as submissive but not dominant mice displayed a preference for midazolam. Furthermore, different neural systems mediated midazolam conditioned motivation depending on the stress status of the animal (single vs. repeated stress-as induced by the Resident/Intruder Paradigm). Singly stressed animals showed midazolam place preferences through a dopamine-independent pathway, whereas the place preferences of repeatedly stressed animals were mediated through a dopamine-dependent pathway. This demonstrates that stress is sufficient for switching the neural system mediating midazolam conditioned motivation. Finally, midazolam reinforcement in the conditioned place preference paradigm was shown to be predictive for dominance/submission status.

  20. A Transdiagnostic Minority Stress Treatment Approach for Gay and Bisexual Men’s Syndemic Health Conditions

    PubMed Central

    Pachankis, John E.

    2015-01-01

    Developing and deploying separate treatments for separate conditions seems ill-suited to intervening upon the co-occurring, and possibly functionally similar, psychosocial conditions facing gay and bisexual men. This article argues for the need to create transdiagnostic interventions that reduce multiple syndemic conditions facing gay and bisexual men at the level of their shared source in minority stress pathways. This article first reviews psychosocial syndemic conditions affecting gay and bisexual men, then suggests pathways that might link minority stress to psychosocial syndemics based on recent advancements in emotion science, psychiatric nosology, and cognitive-affective neuroscience, and finally suggests cross-cutting psychosocial treatment principles to reduce minority stress–syndemic pathways among gay and bisexual men. Because minority stress serves as a common basis of all psychosocial syndemic conditions reviewed here, locating the pathways through which minority stress generates psychosocial syndemics and employing overarching treatment principles capable of simultaneously alleviating these pathways will ultimately create a transdiagnostic approach to improving gay and bisexual men’s health. Clinical research and training approaches are suggested to further validate the pathways suggested here, establish the efficacy of treatment approaches tied to those pathways, and generate effective methods for disseminating a transdiagnostic minority stress treatment approach for gay and bisexual men’s psychosocial syndemic health. PMID:26123065

  1. Bulk stress distributions in the pore space of sphere-packed beds under Darcy flow conditions.

    PubMed

    Pham, Ngoc H; Voronov, Roman S; Tummala, Naga Rajesh; Papavassiliou, Dimitrios V

    2014-03-01

    In this paper, bulk stress distributions in the pore space of columns packed with spheres are numerically computed with lattice Boltzmann simulations. Three different ideally packed and one randomly packed configuration of the columns are considered under Darcy flow conditions. The stress distributions change when the packing type changes. In the Darcy regime, the normalized stress distribution for a particular packing type is independent of the pressure difference that drives the flow and presents a common pattern. The three parameter (3P) log-normal distribution is found to describe the stress distributions in the randomly packed beds within statistical accuracy. In addition, the 3P log-normal distribution is still valid when highly porous scaffold geometries rather than sphere beds are examined. It is also shown that the 3P log-normal distribution can describe the bulk stress distribution in consolidated reservoir rocks like Berea sandstone.

  2. Bulk stress distributions in the pore space of sphere-packed beds under Darcy flow conditions

    NASA Astrophysics Data System (ADS)

    Pham, Ngoc H.; Voronov, Roman S.; Tummala, Naga Rajesh; Papavassiliou, Dimitrios V.

    2014-03-01

    In this paper, bulk stress distributions in the pore space of columns packed with spheres are numerically computed with lattice Boltzmann simulations. Three different ideally packed and one randomly packed configuration of the columns are considered under Darcy flow conditions. The stress distributions change when the packing type changes. In the Darcy regime, the normalized stress distribution for a particular packing type is independent of the pressure difference that drives the flow and presents a common pattern. The three parameter (3P) log-normal distribution is found to describe the stress distributions in the randomly packed beds within statistical accuracy. In addition, the 3P log-normal distribution is still valid when highly porous scaffold geometries rather than sphere beds are examined. It is also shown that the 3P log-normal distribution can describe the bulk stress distribution in consolidated reservoir rocks like Berea sandstone.

  3. Proteomic analyses of the response of cyanobacteria to different stress conditions.

    PubMed

    Castielli, Ornella; De la Cerda, Berta; Navarro, José A; Hervás, Manuel; De la Rosa, Miguel A

    2009-06-01

    Cyanobacteria are significant contributors to global photosynthetic productivity, thus making it relevant to study how the different environmental stresses can alter their physiological activities. Here, we review the current research work on the response of cyanobacteria to different kinds of stress, mainly focusing on their response to metal stress as studied by using the modern proteomic tools. We also report a proteomic analysis of plastocyanin and cytochrome c(6) deletion mutants of the cyanobacterium Synechocystis sp. PCC 6803 grown under copper or iron deprivation, as compared to wild-type cells, so as to get a further understanding of the metal homeostasis in cyanobacteria and their response to changing environmental conditions.

  4. Proteomic study of a tolerant genotype of durum wheat under salt-stress conditions.

    PubMed

    Capriotti, Anna Laura; Borrelli, Grazia Maria; Colapicchioni, Valentina; Papa, Roberto; Piovesana, Susy; Samperi, Roberto; Stampachiacchiere, Serena; Laganà, Aldo

    2014-02-01

    Salinity is one of the major abiotic stress conditions limiting crop growth and productivity. Duilio is a wheat genotype that shows tolerant behavior in both salt-stress and drought-stress conditions. Toward better understanding of the biochemical response to salinity in this genotype of durum wheat, a comparative label-free shotgun proteomic analysis based on normalized spectral abundance factors was conducted on wheat leaf samples subjected to increasing salt-stress levels (100 and 200 mmol L(-1) NaCl) with respect to untreated samples. We found significant changes in 71 proteins for the first stress level, in 83 proteins at the higher salinity level, and in 88 proteins when comparing salt-stress levels with each other. The major changes concerned the proteins involved in primary metabolism and production of energy, followed by those involved in protein metabolism and cellular defense mechanisms. Some indications of different specific physiological and defense mechanisms implicated in increasing tolerance were obtained. The enhanced salinity tolerance in Duilio appeared to be governed by a higher capacity for osmotic homeostasis, a more efficient defense, and an improvement of protection from mechanical stress by increased cell wall lignifications, allowing a better potential for growth recovery.

  5. In Search of Concomitant Alterations of Dopaminergic and Neurotensinergic Systems in Stress Conditions.

    PubMed

    Rodríguez de Lores Arnaiz, Georgina; Antonelli, Marta C

    2016-02-01

    The aim of the present article is to review experimental evidence which suggest joint involvement of both the dopaminergic and neurotensinergic systems in stress conditions. At present, the concept of stress refers to an environmental demand exceeding the normal regulatory ability of an organism, particularly during unpredictable and uncontrollable situations. Chronic stress yields devastating effects including cognitive and working memory dysfunctions, for which neurotransmission mediated by the catecholamines dopamine and noradrenaline is crucial. Catecholamine synthesis depends on the rate-limiting enzyme, tyrosine hydroxylase, whose expression is associated with working memory and the response to chronic stress. Neurotensin is a tridecapeptide widely distributed in the nervous system, at both central and peripheral levels, which behaves as a neurotransmitter or neuromodulator. It mediates diverse biological actions including reward, locomotion, pain modulation and stress. Neurotensin and its high affinity NTS1 receptor are densely localized in areas that process emotion (amygdala nucleus), cognition (such as hippocampal nuclei and cortical areas) and the response to stress (hypothalamic nucleus). Experimental evidence indicates a crosstalk between the dopaminergic and the neurotensinergic systems either from an anatomical or a biochemical point of view. It is suggested that a concomitant alteration of dopaminergic and neurotensinergic systems takes place in diverse stress conditions.

  6. Conditioned Observation of Books and Accelerated Acquisition of Textual Responding by Preschool Children

    ERIC Educational Resources Information Center

    Tsai, Hshin-hui; Greer, R. Douglas

    2006-01-01

    We report an experiment investigating the effects of conditioning books as reinforcers for observing responses on the learning of textual responses by pre-school children. The independent variable was the acquisition of conditioned reinforcement of observing responses and choice of book stimuli in free play settings where children could choose to…

  7. Acceleration of vertical migration of corneal epithelial cells in albino rats during chronic immobilization stress

    SciTech Connect

    Timoshin, S.S.; Berezhnova, N.I.

    1986-01-01

    This paper studies the effect of chronic immobilization stress on the kinetics of corneal epithelial cells from the basal layer into higher layers. Experiments were carried out on 49 male rats. The animals were given an intraperitoneal injection of tritium-thymidine and an additional application of 5 microCi of tritium-thymidine was made to its surface because the cornea has no blood supply. The animals were killed and the cornea removed for investigation. Values of the index of labeled nuclei and intensity of thymidine labeling, characterizing DNA synthesis in the corneas of the control and experimental animals showed no significant change compared with their values in a pervious series of experiments. Chronic exposure to stress increased the velocity of vertical migration of the cells from the basal layer toward the outer layers of the cornea.

  8. Accelerated crack growth, residual stress, and a cracked zinc coated pressure shell

    NASA Technical Reports Server (NTRS)

    Dittman, Daniel L.; Hampton, Roy W.; Nelson, Howard G.

    1987-01-01

    During a partial inspection of a 42 year old, operating, pressurized wind tunnel at NASA-Ames Research Center, a surface connected defect 114 in. long having an indicated depth of a 0.7 in. was detected. The pressure shell, constructed of a medium carbon steel, contains approximately 10 miles of welds and is cooled by flowing water over its zinc coated external surface. Metallurgical and fractographic analysis showed that the actual detect was 1.7 in. deep, and originated from an area of lack of weld penetration. Crack growth studies were performed on the shell material in the laboratory under various loading rates, hold times, and R-ratios with a simulated shell environment. The combination of zinc, water with electrolyte, and steel formed an electrolytic cell which resulted in an increase in cyclic crack growth rate by as much as 500 times over that observed in air. It was concluded that slow crack growth occurred in the pressure shell by a combination of stress corrosion cracking due to the welding residual stress and corrosion fatigue due to the cyclic operating stress.

  9. Dynamics and correlation of serum cortisol and corticosterone under different physiological or stressful conditions in mice.

    PubMed

    Gong, Shuai; Miao, Yi-Long; Jiao, Guang-Zhong; Sun, Ming-Ju; Li, Hong; Lin, Juan; Luo, Ming-Jiu; Tan, Jing-He

    2015-01-01

    Although plasma corticosterone is considered the main glucocorticoid involved in regulation of stress responses in rodents, the presence of plasma cortisol and whether its level can be used as an indicator for rodent activation of stress remain to be determined. In this study, effects of estrous cycle stage, circadian rhythm, and acute and chronic (repeated or unpredictable) stressors of various severities on dynamics and correlation of serum cortisol and corticosterone were examined in mice. A strong (r = 0.6-0.85) correlation between serum cortisol and corticosterone was observed throughout the estrous cycle, all day long, and during acute or repeated restraints, chronic unpredictable stress and acute forced swimming or heat stress. Both hormones increased to the highest level on day 1 of repeated-restraint or unpredictable stresses, but after that, whereas the concentration of cortisol did not change, that of corticosterone showed different dynamics. Thus, whereas corticosterone declined dramatically during repeated restraints, it remained at the high level during unpredictable stress. During forced swimming or heat stress, whereas cortisol increased to the highest level within 3 min., corticosterone did not reach maximum until 40 min. of stress. Analysis with HPLC and HPLC-MS further confirmed the presence of cortisol in mouse serum. Taken together, results (i) confirmed the presence of cortisol in mouse serum and (ii) suggested that mouse serum cortisol and corticosterone are closely correlated in dynamics under different physiological or stressful conditions, but, whereas corticosterone was a more adaptation-related biomarker than cortisol during chronic stress, cortisol was a quicker responder than corticosterone during severe acute stress.

  10. Dynamics and Correlation of Serum Cortisol and Corticosterone under Different Physiological or Stressful Conditions in Mice

    PubMed Central

    Gong, Shuai; Miao, Yi-Long; Jiao, Guang-Zhong; Sun, Ming-Ju; Li, Hong; Lin, Juan; Luo, Ming-Jiu; Tan, Jing-He

    2015-01-01

    Although plasma corticosterone is considered the main glucocorticoid involved in regulation of stress responses in rodents, the presence of plasma cortisol and whether its level can be used as an indicator for rodent activation of stress remain to be determined. In this study, effects of estrous cycle stage, circadian rhythm, and acute and chronic (repeated or unpredictable) stressors of various severities on dynamics and correlation of serum cortisol and corticosterone were examined in mice. A strong (r = 0.6–0.85) correlation between serum cortisol and corticosterone was observed throughout the estrous cycle, all day long, and during acute or repeated restraints, chronic unpredictable stress and acute forced swimming or heat stress. Both hormones increased to the highest level on day 1 of repeated-restraint or unpredictable stresses, but after that, whereas the concentration of cortisol did not change, that of corticosterone showed different dynamics. Thus, whereas corticosterone declined dramatically during repeated restraints, it remained at the high level during unpredictable stress. During forced swimming or heat stress, whereas cortisol increased to the highest level within 3 min., corticosterone did not reach maximum until 40 min. of stress. Analysis with HPLC and HPLC-MS further confirmed the presence of cortisol in mouse serum. Taken together, results (i) confirmed the presence of cortisol in mouse serum and (ii) suggested that mouse serum cortisol and corticosterone are closely correlated in dynamics under different physiological or stressful conditions, but, whereas corticosterone was a more adaptation-related biomarker than cortisol during chronic stress, cortisol was a quicker responder than corticosterone during severe acute stress. PMID:25699675

  11. Stress concentration in the vicinity of a hole defect under conditions of Hertzian contact

    NASA Technical Reports Server (NTRS)

    Yamamoto, T.; Eguchi, M.; Murayama, K.

    1981-01-01

    Two dimensional photoelastic stress analyses were conducted for epoxy resin models containing a hole defect under the conditions of Hertzian contact. Stress concentrations around the defect were determined as a function of several parameters. The effect of tangential traction on the stress concentration was also determined. Sharp stress concentrations occur in the vicinity of both the left and the right side of the hole. The stress concentration becomes more distinct the larger the hole diameter and the smaller distance between the hole and the contact surface. The stress concentration is greatest when the disk imposing a normal load is located at the contact surface directly over the hole. The magnitude and the location of stress concentration varies with the distance between the Hertzian contact area and the hole. The area involved in a process of rolling contact fatigue is confined to a shallow region at both sides of the hole. It was found that the effect of tangential traction is comparatively small on the stress concentration around the hole.

  12. Unique genetic loci identified for emotional behavior in control and chronic stress conditions

    PubMed Central

    Carhuatanta, Kimberly A. K.; Shea, Chloe J. A.; Herman, James P.; Jankord, Ryan

    2014-01-01

    An individual's genetic background affects their emotional behavior and response to stress. Although studies have been conducted to identify genetic predictors for emotional behavior or stress response, it remains unknown how prior stress history alters the interaction between an individual's genome and their emotional behavior. Therefore, the purpose of this study is to identify chromosomal regions that affect emotional behavior and are sensitive to stress exposure. We utilized the BXD behavioral genetics mouse model to identify chromosomal regions that predict fear learning and emotional behavior following exposure to a control or chronic stress environment. 62 BXD recombinant inbred strains and C57BL/6 and DBA/2 parental strains underwent behavioral testing including a classical fear conditioning paradigm and the elevated plus maze. Distinct quantitative trait loci (QTLs) were identified for emotional learning, anxiety and locomotion in control and chronic stress populations. Candidate genes, including those with already known functions in learning and stress were found to reside within the identified QTLs. Our data suggest that chronic stress history reveals novel genetic predictors of emotional behavior. PMID:25374516

  13. CONDITIONAL β-CATENIN LOSS IN MICE PROMOTES CHEMICAL HEPATOCARCINOGENESIS: ROLE OF OXIDATIVE STRESS & PDGFRα/PIK3CA SIGNALING

    PubMed Central

    Zhang, Xu-Feng; Tan, Xinping; Zeng, Gang; Misse, Amalea; Singh, Sucha; Kim, Youngsoo; Klaunig, James E.; Monga, Satdarshan P. S.

    2011-01-01

    Activation of β-Catenin, the central effector of canonical Wnt pathway and a recognized oncogene, is implicated in hepatocellular carcinoma (HCC). Here, we examine N-nitrosodiethylamine (DEN)-induced tumorigenesis in hepatic β-catenin conditional knockout mice (β-cat KO). Only, male β-cat KO and age- and sex-matched littermate controls were given a single intraperitoneal DEN injection and followed for 6–12 months for hepatic tumors. Hepatic tumors were characterized for histology, proliferation, apoptosis, oxidative stress, and specific proteins by western blots, immunohistochemistry and coprecipitation studies. For in vivo tumor intervention studies, specific inhibitors were administered intraperitoneally or through drinking water. Intriguingly, β-cat KO mice show a paradoxical increase in the susceptibility to DEN-induced tumorigenesis. The accelerated tumorigenesis is due to increased injury and inflammation, unrestricted oxidative stress, fibrosis and compensatory increase in hepatocyte proliferation secondary to PDGFRα/phosphoinositide 3-kinase (PIK3CA)/Akt activation and c-Myc overexpression. In vitro suppression of β-catenin expression in hepatoma cells led to enhanced PDGFRα expression, which was abrogated in the presence of NF-κB inhibitor. Daily treatment of 6 months old DEN-exposed β-cat KO with PDGFRα inhibitor dramatically reduced tumor numbers and size. Inclusion of N-acetyl-L-cysteine (NAC), a known antioxidant and NF-κB-inhibitor, in the drinking water led to complete abolition of tumorigenesis in DEN-exposed β-cat KO. In conclusion, loss of β-catenin impairs the ability of liver to counteract DEN-induced oxidative stress and enhances tumorigenesis through PDGFRα/PIK3CA/Akt signaling. Blockade of PDGFRα or oxidative stress dramatically impacts β-catenin-deficient tumorigenesis. Also, hepatoma cells utilize PDGFRα/PIK3CA signaling as an escape mechanism following β-catenin suppression and their sequential suppression profoundly

  14. Accelerated adhesion of grafted skins by laser-induced stress wave-based gene transfer of hepatocyte growth factor

    NASA Astrophysics Data System (ADS)

    Aizawa, Kazuya; Sato, Shunichi; Saitoh, Daizoh; Tsuda, Hitoshi; Ashida, Hiroshi; Obara, Minoru

    2009-02-01

    In our previous study, we delivered plasmid DNA coding for human hepatocyto growth factor (hHGF) to rat skin grafts based on laser-induced stress wave (LISW), by which production of CD31-positive cells in the grafted skins was found to be enhanced, suggesting improved angiogenesis. In this study, we validated the efficacy of this method to accelerate adhesion of grafted skins; reperfusion and reepithelialization in the grafted skins were examined. As a graft, dorsal skin of a rat was exsected and its subcutaneous fat was removed. Plasmid DNA expression vector for hHGF was injected into the graft; on its back surface a laser target with a transparent sheet for plasma confinement was placed, and irradiated with three nanosecond laser pulses at a laser fluence of 1.2 J/cm2 (532 nm; spot diameter, 3 mm) to generate LISWs. After the application of LISWs, the graft was transplanted onto its donor site. We evaluated blood flow by laser Doppler imaging and analyzed reepithelialization based on immunohistochemistry as a function of postgrafting time. It was found that both reperfusion and reepithelialization were significantly enhanced for the grafts with gene transfection than for normal grafts; reepithelialization was completed within 7 days after transplantation with the transfected grafts. These findings demonstrate that adhesion of grafted skins can be accelerated by delivering HGF gene to the grafts based on LISWs.

  15. Brassinosteroids accelerate recovery of photosynthetic apparatus from cold stress by balancing the electron partitioning, carboxylation and redox homeostasis in cucumber.

    PubMed

    Jiang, Yu-Ping; Huang, Li-Feng; Cheng, Fei; Zhou, Yan-Hong; Xia, Xiao-Jian; Mao, Wei-Hua; Shi, Kai; Yu, Jing-Quan

    2013-05-01

    The aim of this study was to examine the role of brassinosteroids (BRs) in protecting the photosynthetic apparatus from cold-induced damage in cucumber (Cucumis sativus) plants. Recovery at both high light (HL) and low light (LL) after a cooling at 10/7°C induced irreversible inhibition of CO2 assimilation, photoinhibition at photosystem I (PSI) and inhibition of enzyme activities of Calvin cycle and ascorbate (AsA)-reduced glutathione (GSH) cycle, followed by accumulation of H2 O2 and malondialdehyde. However, cold-induced photoinhibition at PSII was fully recovered at LL but not at HL. Meanwhile, recovery at HL increased electron flux to O2 -dependent alternative pathway [Ja(O2 -dependent)]. Foliar application of 24-epibrassinolide (EBR) accelerated recovery from photoinhibition of PSII but not of PSI. EBR also significantly increased CO2 assimilation, activity of Calvin cycle enzymes and electron flux to carbon reduction [Je(PCR)], with a concomitant decrease in Ja(O2 -dependent); meanwhile EBR increased the activity of enzymes in AsA-GSH cycle and cellular redox states. However, the positive effect of EBR on plant recovery was observed only at HL, but not LL. These results indicate that BR accelerates the recovery of photosynthetic apparatus at HL by activation of enzymes in Calvin cycle and increasing the antioxidant capacity, which in turn mitigate the photooxidative stress and the inhibition of plant growth during the recovery.

  16. Bed Shear Stress under Complex Flow Conditions - The Case of Megech River, Ethiopia

    NASA Astrophysics Data System (ADS)

    Mehari, Michael; Dessie, Mekete; Abate, Mengiste

    2014-05-01

    Bed shear stress is a fundamental variable in river studies to link flow conditions to sediment transport. It is, however, difficult to estimate this variable accurately, particularly in complex flow conditions. This study compares shear stress estimated from the log profile, the depth-slope product and outputs from a two-dimensional hydraulic model. Vertical velocity profile observations from Megech River (one of the main rivers flowing into Lake Tana, upper Blue Nile Basin, Ethiopia) using SEBA Mini current meter M1attached with signal counter Z6-SEBA HAD under typical field conditions are used to evaluate the precision of different methods for estimating local boundary shear stress from velocity measurements. Results show that the velocity profile approach gives consistently lesser shear stress estimates. A comparison of the shear stress distributions derived using the two-dimensional hydraulic model and those estimated using the 1D reach-averaged equation (i.e. the depth-slope product) shows a close correspondence. Mean shear stresses determined using local depth and mean channel slope are only 14% greater than those values determined for the same data using local predictions of both depth and energy slope. As the overall mean shear stress provides a useful index of flow strength, this comparison suggests a good level of confidence in using the reach averaged one-dimensional equation, for which data can easily be collected from cross sectional surveys. However, the variance of the modelled shear stress distribution shows some differences by a factor of 3 to that calculated using the mean channel slope because of the larger uncertainity associated with point depth measurements. Although such models using 1D reach averaged equations are limited to different channel characteristics adhering to diverse model assumptions, they can still provide a useful tool for river-rehabilitation design and assessment, including sediment transport studies.

  17. Exposure to estradiol before but not during acquisition of LiCl-induced conditioned taste avoidance accelerates extinction.

    PubMed

    Chambers, Kathleen C; Hayes, Unja L

    2002-05-01

    Estradiol accelerates extinction of LiCl-induced conditioned taste avoidance when it is present continuously before and during acquisition. We have suggested that the effect of estradiol on extinction is due to its illness-associated, rather than learning-associated, properties. If this were the case, then one would expect estradiol to act before but not during acquisition. This expectation is based on previous work showing attenuation of learned taste avoidance when rats are given distal preexposure (greater than 24 h before conditioning) or proximal preexposure (less than 24 h before conditioning) to the illness-inducing agent LiCl before acquisition of a LiCl-induced conditioned taste avoidance. In three separate experiments, estradiol was administered during three different time periods via subcutaneous implantation of a 10-mm estradiol-filled capsule. In each experiment, the extinction of estradiol-treated females was compared to that of females implanted with empty capsules. In the first experiment, female rats were given distal exposure to estradiol before acquisition. Capsules were implanted 11 days before acquisition and were removed 2 days before acquisition. In the second experiment, female rats were given proximal exposure to estradiol before acquisition. Capsules were implanted 2.5 h before LiCl was paired with a sucrose solution and were removed 16.5 h later. In the third experiment, female rats were given exposure to estradiol during acquisition. Capsules were implanted at the same time as LiCl administration and were removed 18 h later. The only estradiol-treated females to show accelerated extinction were those given distal preexposure to estradiol in Experiment 1. These data do not support a learning-associated hypothesis and only partially support an illness-associated hypothesis. The failure to find accelerated extinction following proximal preexposure may reflect an inappropriate choice of the parameters used in the experiment or a difference

  18. Analysis of extinction acquisition to attenuated tones in prenatally stressed and non-stressed offspring following auditory fear conditioning.

    PubMed

    Salm, A K; Lally, B E; Borysiewicz, E; Fil, D; Konat, G

    2015-02-01

    Stimulus generalization occurs when stimuli with characteristics similar to a previously conditioned stimulus (CS) become able to evoke a previously conditioned response. Experimental data (Lissek et al., 2005) indicate that patients with post-traumatic stress disorder (PTSD), more often show stimulus generalization following fear conditioning when tested under laboratory conditions. Factors surrounding this observation may contribute to two common features of PTSD: 1) hyper-responsiveness to sensory stimuli reminiscent of those associated with the original trauma, and 2) resistance of PTSD to extinction-based therapies. Adverse early experience is considered a risk factor for the later development of PTSD and in the present experiments we hypothesized that stimulus generalization would occur in an animal model of adverse early experience, the prenatally stressed (PS) rat. Adult PS and control (CON) rats underwent extensive pre-habituation to a conditioning chamber followed by conventional auditory fear conditioning. The next day both groups began an extinction regimen where a series of quieter (attenuated), CSs were administered prior to the full 75 dB training CS. When tested in this manner, PS rats froze at significantly lower tone amplitudes than did CON offspring on the first day of extinction training. This suggests that the PS rats had stimulus-generalized the CS to lower decibel tones. In addition to this finding, we also observed that PS rats froze more often and longer during three ensuing days of extinction training to attenuated tones. Group differences vanished when PS and CON rats were extinguished under conventional conditions. Thus, it appears that the two extinction regimens differed in their aversive cue saliency for the PS vs. CON rats. Follow-up prefrontal cortex transcriptome probing suggests that cholinergic and dopaminergic alterations may be involved.

  19. Oxidative Stress and Low Glutathione in Common Ear, Nose, and Throat Conditions: A Systematic Review.

    PubMed

    Asher, Benjamin Finkelhor; Guilford, Frederick Timothy

    2016-09-01

    Context • Oxidative stress and tissue-damaging, oxygen (O2)-related, free-radical formation is inherent in human metabolism, and the tissues of the ear, nose, and throat (ENT) have an increased exposure to injury from those substances. Because glutathione (GSH) is a major component in an antioxidant defense against oxidative damage in ENT tissues, a review of the impact of lowered GSH and oxidative stress in conditions associated with the upper respiratory tract is warranted. Objective • The review intended to summarize the role that oxidative stress and GSH play. Design • The research team performed a literature review from 1980 to the present that was based on the following keywords: oxidative stress, oxidation, antioxidant, and GSH in common ENT conditions. The review found the following conditions: (1) rhinitis, (2) allergic rhinitis, (3) chronic rhinosinusitis (CRS), (4) CRS with polyps, (5) otitis media with effusion, (6) chronic otitis media (COM), (7) COM and cholesteatoma, (8) tympanic membrane sclerosis, (9) tonsillitis, (10) Meniere's disease, (11) laryngeal conditions, and (12) chronic cough. Results • ENT conditions have been found to be associated with oxidative stress and with low GSH. A limited number of the reviewed studies discussed antioxidant use or repletion of GSH. Although only a few reports support the use of GSH or antioxidants as adjuncts in the management of ENT conditions, no reports of side effects were found related to their use. Conclusions • Many ENT conditions are associated with oxidative stress and decreased GSH, both locally in the affected tissues and systemically. The oxidative stress of those conditions may be related to depletion of GSH, which is increased by the higher levels of O2 in the upper respiratory tract. A small number of studies have reported clinical benefits from the use of an antioxidant or GSH support. The findings of benefits and the lack of reports of side effects suggest that the clinical use of

  20. Oxidative Stress and Low Glutathione in Common Ear, Nose, and Throat Conditions: A Systematic Review.

    PubMed

    Asher, Benjamin Finkelhor; Guilford, Frederick Timothy

    2016-09-01

    Context • Oxidative stress and tissue-damaging, oxygen (O2)-related, free-radical formation is inherent in human metabolism, and the tissues of the ear, nose, and throat (ENT) have an increased exposure to injury from those substances. Because glutathione (GSH) is a major component in an antioxidant defense against oxidative damage in ENT tissues, a review of the impact of lowered GSH and oxidative stress in conditions associated with the upper respiratory tract is warranted. Objective • The review intended to summarize the role that oxidative stress and GSH play. Design • The research team performed a literature review from 1980 to the present that was based on the following keywords: oxidative stress, oxidation, antioxidant, and GSH in common ENT conditions. The review found the following conditions: (1) rhinitis, (2) allergic rhinitis, (3) chronic rhinosinusitis (CRS), (4) CRS with polyps, (5) otitis media with effusion, (6) chronic otitis media (COM), (7) COM and cholesteatoma, (8) tympanic membrane sclerosis, (9) tonsillitis, (10) Meniere's disease, (11) laryngeal conditions, and (12) chronic cough. Results • ENT conditions have been found to be associated with oxidative stress and with low GSH. A limited number of the reviewed studies discussed antioxidant use or repletion of GSH. Although only a few reports support the use of GSH or antioxidants as adjuncts in the management of ENT conditions, no reports of side effects were found related to their use. Conclusions • Many ENT conditions are associated with oxidative stress and decreased GSH, both locally in the affected tissues and systemically. The oxidative stress of those conditions may be related to depletion of GSH, which is increased by the higher levels of O2 in the upper respiratory tract. A small number of studies have reported clinical benefits from the use of an antioxidant or GSH support. The findings of benefits and the lack of reports of side effects suggest that the clinical use of

  1. Application of in situ stress estimation methods in wellbore stability analysis under isotropic and anisotropic conditions

    NASA Astrophysics Data System (ADS)

    Gholami, Raoof; Rasouli, Vamegh; Aadnoy, Bernt; Mohammadi, Ramin

    2015-08-01

    Estimation of in situ stresses is a key step in many petroleum engineering applications, ranging from wellbore stability to sanding analysis and hydraulic fracturing design. Direct techniques conventionally used to determine in situ stresses are indeed very time consuming and expensive. These measurements would also be restricted as to the depth of acquisition, and generalization of the results to entire rock masses may not yield representative results. In this paper, applications of three indirect methods-Zoback’s polygon, shear moduli, and poroelastic-are studied to assess their applicability in providing reliable stress estimation under isotropic and anisotropic conditions. Determination of elastic, strength, and in situ stress parameters according to the assumption of each method for one of the vertical wells drilled in south Iran indicated that the shear moduli method is an appropriate approach for prediction of maximum horizontal stress within an interval where sufficient field data including leak-off tests are acquired. However, the poroelastic method seems to be a better method in prediction of in situ stresses under anisotropic conditions. This might be due to the presence of excessive shale formations in subsurface layers, causing structural or intrinsic anisotropy-based methods such as poroelastic equations to deliver more accurate results. However, making general conclusions based on studying a single vertical wellbore may not be sufficient, and therefore further studies are required.

  2. Effects of far infrared rays irradiated from ceramic material (BIOCERAMIC) on psychological stress-conditioned elevated heart rate, blood pressure, and oxidative stress-suppressed cardiac contractility.

    PubMed

    Leung, Ting-Kai; Chen, Chien-Ho; Tsai, Shih-Ying; Hsiao, George; Lee, Chi-Ming

    2012-10-31

    The present study examined the effects of BIOCERAMIC on psychological stress-conditioned elevated heart rate, blood pressure and oxidative stress-suppressed cardiac contractility using in vivo and in vitro animal models. We investigated the effects of BIOCERAMIC on the in vivo cardiovascular hemodynamic parameters of rats by monitoring their heart rates, systolic blood pressure, mean blood pressure and diastolic blood pressure. Thereafter, we assayed its effects on the heart rate in an isolated frog heart with and without adrenaline stimulation, and on cardiac contractility under oxidative stress. BIOCERAMIC caused significant decreases in heart rates and systolic and mean blood pressure in the stress-conditioned heart rate rat models (P < 0.05), as well as in the experimental models of an isolated frog heart with and without adrenaline stimulation (P < 0.05), and normalized cardiac contractility under oxidative stress (P < 0.05). BIOCERAMIC may, therefore, normalize the effects of psychological stress and oxidative stress conditions.

  3. A QR accelerated volume-to-surface boundary condition for finite element solution of eddy current problems

    SciTech Connect

    White, D; Fasenfest, B; Rieben, R; Stowell, M

    2006-09-08

    We are concerned with the solution of time-dependent electromagnetic eddy current problems using a finite element formulation on three-dimensional unstructured meshes. We allow for multiple conducting regions, and our goal is to develop an efficient computational method that does not require a computational mesh of the air/vacuum regions. This requires a sophisticated global boundary condition specifying the total fields on the conductor boundaries. We propose a Biot-Savart law based volume-to-surface boundary condition to meet this requirement. This Biot-Savart approach is demonstrated to be very accurate. In addition, this approach can be accelerated via a low-rank QR approximation of the discretized Biot-Savart law.

  4. Unsteady heat dissipation in accelerator superconducting coils insulated with porous ceramic insulation in normal and supercritical helium conditions

    NASA Astrophysics Data System (ADS)

    Pietrowicz, S.; Four, A.; Baudouy, B.; Kimura, N.; Yamamoto, A.

    2014-01-01

    To investigate the unsteady heat dissipation in accelerator superconducting coils insulated with porous ceramic insulation, two experimental mock-ups reproducing the thermal and the mechanical conditions of a superconducting coils were produced. The mock-ups with compressive load of 10 MPa and 20 MPa were tested at normal (T = 4.23 K and p = 1 bar) and supercritical helium conditions (T = 4.23 K and p = 2.0 to 3.75 bar) during unsteady heat dissipation. The paper presents the experimental results of temperature rise in both superconducting coils as a function of time for a wide range of a localized heat load varying from 0.1 kJ/m3 up to 12.8 MJ m-3 per pulse. A numerical model of the transient process in these coils has been developed and the computations are compared with the experimental results.

  5. Role of cold shock proteins in growth of Listeria monocytogenes under cold and osmotic stress conditions.

    PubMed

    Schmid, Barbara; Klumpp, Jochen; Raimann, Eveline; Loessner, Martin J; Stephan, Roger; Tasara, Taurai

    2009-03-01

    The gram-positive bacterium Listeria monocytogenes is a food-borne pathogen of both public health and food safety significance. It possesses three small, highly homologous protein members of the cold shock protein (Csp) family. We used gene expression analysis and a set of mutants with single, double, and triple deletions of the csp genes to evaluate the roles of CspA, CspB, and CspD in the cold and osmotic (NaCl) stress adaptation responses of L. monocytogenes. All three Csps are dispensable for growth at optimal temperature (37 degrees C). These proteins are, however, required for efficient cold and osmotic stress tolerance of this bacterium. The hierarchies of their functional importance differ, depending on the environmental stress conditions: CspA>CspD>CspB in response to cold stress versus CspD>CspA/CspB in response to NaCl salt osmotic stress. The fact that Csps are promoting L. monocytogenes adaptation against both cold and NaCl stress has significant implications in view of practical food microbial control measures. The combined or sequential exposure of L. monocytogenes cells to these two stresses in food environments might inadvertently induce cross-protection responses.

  6. Chronic stress enhances microglia activation and exacerbates death of nigral dopaminergic neurons under conditions of inflammation

    PubMed Central

    2014-01-01

    Background Parkinson’s disease is an irreversible neurodegenerative disease linked to progressive movement disorders and is accompanied by an inflammatory reaction that is believed to contribute to its pathogenesis. Since sensitivity to inflammation is not the same in all brain structures, the aim of this work was to test whether physiological conditions as stress could enhance susceptibility to inflammation in the substantia nigra, where death of dopaminergic neurons takes place in Parkinson’s disease. Methods To achieve our aim, we induced an inflammatory process in nonstressed and stressed rats (subject to a chronic variate stress) by a single intranigral injection of lipopolysaccharide, a potent proinflammogen. The effect of this treatment was evaluated on inflammatory markers as well as on neuronal and glial populations. Results Data showed a synergistic effect between inflammation and stress, thus resulting in higher microglial activation and expression of proinflammatory markers. More important, the higher inflammatory response seen in stressed animals was associated with a higher rate of death of dopaminergic neurons in the substantia nigra, the most characteristic feature seen in Parkinson’s disease. This effect was dependent on glucocorticoids. Conclusions Our data demonstrate that stress sensitises midbrain microglia to further inflammatory stimulus. This suggests that stress may be an important risk factor in the degenerative processes and symptoms of Parkinson’s disease. PMID:24565378

  7. A Review & Assessment of Current Operating Conditions Allowable Stresses in ASME Section III Subsection NH

    SciTech Connect

    R. W. Swindeman

    2009-12-14

    The current operating condition allowable stresses provided in ASME Section III, Subsection NH were reviewed for consistency with the criteria used to establish the stress allowables and with the allowable stresses provided in ASME Section II, Part D. It was found that the S{sub o} values in ASME III-NH were consistent with the S values in ASME IID for the five materials of interest. However, it was found that 0.80 S{sub r} was less than S{sub o} for some temperatures for four of the materials. Only values for alloy 800H appeared to be consistent with the criteria on which S{sub o} values are established. With the intent of undertaking a more detailed evaluation of issues related to the allowable stresses in ASME III-NH, the availabilities of databases for the five materials were reviewed and augmented databases were assembled.

  8. Information on stress conditions in the oceanic crust from oval fractures in a deep borehole

    USGS Publications Warehouse

    Morin, R.H.

    1990-01-01

    Oval images etched into the wall of a deep borehole were detected in DSDP Hole 504B, eastern equatorial Pacific Ocean, from analysis of an acoustic televiewer log. A systematic inspection of these ovals has identified intriguing consistencies in appearance that cannot be explained satisfactorily by a random, coincidental distribution of pillow lavas. As an alternative hypothesis, Mohr-Coulomb failure criterion is used to account for the generation and orientation of similarly curved, stress-induced fractures. Consequently, these oval features can be interpreted as fractures and related directly to stress conditions in the oceanic crust at this site. The azimuth of the oval center corresponds to the orientation of maximum horizontal principal stress (SH), and the oval width, which spans approximately 180?? of the borehole, is aligned with the azimuth of minimum horizontal principal stress (Sh). The oval height is controlled by the fracture angle and thus is a function of the coefficient of internal friction of the rock. -from Author

  9. Reference Genes Selection and Normalization of Oxidative Stress Responsive Genes upon Different Temperature Stress Conditions in Hypericum perforatum L

    PubMed Central

    Velada, Isabel; Ragonezi, Carla; Arnholdt-Schmitt, Birgit; Cardoso, Hélia

    2014-01-01

    Reverse transcription-quantitative real-time PCR (RT-qPCR) is a widely used technique for gene expression analysis. The reliability of this method depends largely on the suitable selection of stable reference genes for accurate data normalization. Hypericum perforatum L. (St. John's wort) is a field growing plant that is frequently exposed to a variety of adverse environmental stresses that can negatively affect its productivity. This widely known medicinal plant with broad pharmacological properties (anti-depressant, anti-tumor, anti-inflammatory, antiviral, antioxidant, anti-cancer, and antibacterial) has been overlooked with respect to the identification of reference genes suitable for RT-qPCR data normalization. In this study, 11 candidate reference genes were analyzed in H. perforatum plants subjected to cold and heat stresses. The expression stability of these genes was assessed using GeNorm, NormFinder and BestKeeper algorithms. The results revealed that the ranking of stability among the three algorithms showed only minor differences within each treatment. The best-ranked reference genes differed between cold- and heat-treated samples; nevertheless, TUB was the most stable gene in both experimental conditions. GSA and GAPDH were found to be reliable reference genes in cold-treated samples, while GAPDH showed low expression stability in heat-treated samples. 26SrRNA and H2A had the highest stabilities in the heat assay, whereas H2A was less stable in the cold assay. Finally, AOX1, AOX2, CAT1 and CHS genes, associated with plant stress responses and oxidative stress, were used as target genes to validate the reliability of identified reference genes. These target genes showed differential expression profiles over time in treated samples. This study not only is the first systematic analysis for the selection of suitable reference genes for RT-qPCR studies in H. perforatum subjected to temperature stress conditions, but may also provide valuable information

  10. Hippocampal ripple-contingent training accelerates trace eyeblink conditioning and retards extinction in rabbits.

    PubMed

    Nokia, Miriam S; Penttonen, Markku; Wikgren, Jan

    2010-08-25

    There are at least two distinct oscillatory states of the hippocampus that are related to distinct behavioral patterns. Theta (4-12 Hz) oscillation has been suggested to indicate selective attention during which the animal concentrates on some features of the environment while suppressing reactivity to others. In contrast, sharp-wave ripples ( approximately 200 Hz) can be seen in a state in which the hippocampus is at its most responsive to any kind of afferent stimulation. In addition, external stimulation tends to evoke and reset theta oscillation, the phase of which has been shown to modulate synaptic plasticity in the hippocampus. Theoretically, training on a hippocampus-dependent learning task contingent upon ripples could enhance learning rate due to elevated responsiveness and enhanced phase locking of the theta oscillation. We used a brain-computer interface to detect hippocampal ripples in rabbits to deliver trace eyeblink conditioning and extinction trials selectively contingent upon them. A yoked control group was trained regardless of their ongoing neural state. Ripple-contingent training expedited acquisition of the conditioned response early in training and evoked stronger theta-band phase locking to the conditioned stimulus. Surprisingly, ripple-contingent training also resulted in slower extinction in well trained animals. We suggest that the ongoing oscillatory activity in the hippocampus determines the extent to which a stimulus can induce a phase reset of the theta oscillation, which in turn is the determining factor of learning rate in trace eyeblink conditioning.

  11. Granular assembly of alpha-synuclein leading to the accelerated amyloid fibril formation with shear stress.

    PubMed

    Bhak, Ghibom; Lee, Jung-Ho; Hahn, Ji-Sook; Paik, Seung R

    2009-01-01

    alpha-Synuclein participates in the Lewy body formation of Parkinson's disease. Elucidation of the underlying molecular mechanism of the amyloid fibril formation is crucial not only to develop a controlling strategy toward the disease, but also to apply the protein fibrils for future biotechnology. Discernable homogeneous granules of alpha-synuclein composed of approximately 11 monomers in average were isolated in the middle of a lag phase during the in vitro fibrillation process. They were demonstrated to experience almost instantaneous fibrillation during a single 12-min centrifugal membrane-filtration at 14,000 x g. The granular assembly leading to the drastically accelerated fibril formation was demonstrated to be a result of the physical influence of shear force imposed on the preformed granular structures by either centrifugal filtration or rheometer. Structural rearrangement of the preformed oligomomeric structures is attributable for the suprastructure formation in which the granules act as a growing unit for the fibril formation. To parallel the prevailing notion of nucleation-dependent amyloidosis, we propose a double-concerted fibrillation model as one of the mechanisms to explain the in vitro fibrillation of alpha-synuclein, in which two consecutive concerted associations of monomers and subsequent oligomeric granular species are responsible for the eventual amyloid fibril formation. PMID:19137068

  12. Comparison of online and offline tests in LED accelerated reliability tests under temperature stress.

    PubMed

    Ke, Hong-Liang; Jing, Lei; Gao, Qun; Wang, Yao; Hao, Jian; Sun, Qiang; Xu, Zhi-Jun

    2015-11-20

    Accelerated aging tests are the main method used in the evaluation of LED reliability, and can be performed in either online or offline modes. The goal of this study is to provide the difference between the two test modes. In the experiments, the sample is attached to different heat sinks to acquire the optical parameters under different junction temperatures of LEDs. By measuring the junction temperature in the aging process (Tj1), and the junction temperature in the testing process (Tj2), we achieve consistency with an online test of Tj1 and Tj2 and a difference with an offline test of Tj1 and Tj2. Experimental results show that the degradation rate of the luminous flux rises as Tj2 increases, which yields a difference of projected life L(70%) of 8% to 13%. For color shifts over 5000 h of aging, the online test shows a larger variation of the distance from the Planckian locus, about 40% to 50% more than the normal test at an ambient temperature of 25°C. PMID:26836556

  13. Surface Deformation of Sandstone during Stress Relaxation under Water-Saturated Condition

    NASA Astrophysics Data System (ADS)

    Anwar, A.; Choi, J. H.; Ichikawa, Y.

    2005-12-01

    Surface deformation characteristics of sandstone were evaluated during stress relaxation using newly developed equipment connected with a confocal laser scanning microscope (CLSM). Use of CLSM could provide the micro-scale measurement of surface deformation where the image was obtained pixel by pixel and line by line. Two types of sandstone according to their bedding plane were used for the uni-axial stress relaxation experiment under water saturated condition. Applied stress level was taken as 55-70% of the water saturated uni-axial strength of the sandstone considering that the maximum surface deformation may occur in this zone of loading. Relaxed stress and constant strain data were collected continuously by a strain gauge data recording system. Microphotographs of a selected grain contact point and several grain surfaces were obtained everyday using CLSM during the stress relaxation period. The grain contact deformation and inter-granular surface deformation were analyzed using a triangulation method drawn on the microphotographs. The strains of each triangle drawn on the surface were calculated through the B-matrix of a constant strain finite element approximation. Results revealed that vigorous grain contact and inter-granular surface deformation occurred during the stress relaxation. B-matrix results showed that the straining occurred higher near the grain boundary than the inter-granular surface. Surface deformation was found higher in the samples where the applied loads were parallel to the bedding plane indicating that the deformation characteristics depend on the internal energy and the stress concentration occurring on the inter-granular surface or the grain contact boundary. Internal energy may change under high stress and temperature condition offering so called dissolution process of rock forming minerals such as quartz and feldspar. However, these experiments were carried out under room temperature and we are currently planning to study this topic

  14. Exploring valid internal-control genes in Porphyra yezoensis (Bangiaceae) during stress response conditions

    NASA Astrophysics Data System (ADS)

    Wang, Wenlei; Wu, Xiaojie; Wang, Chao; Jia, Zhaojun; He, Linwen; Wei, Yifan; Niu, Jianfeng; Wang, Guangce

    2014-07-01

    To screen the stable expression genes related to the stress (strong light, dehydration and temperature shock) we applied Absolute real-time PCR technology to determine the transcription numbers of the selected test genes in P orphyra yezoensis, which has been regarded as a potential model species responding the stress conditions in the intertidal. Absolute real-time PCR technology was applied to determine the transcription numbers of the selected test genes in P orphyra yezoensis, which has been regarded as a potential model species in stress responding. According to the results of photosynthesis parameters, we observed that Y(II) and F v/ F m were significantly affected when stress was imposed on the thalli of P orphyra yezoensis, but underwent almost completely recovered under normal conditions, which were collected for the following experiments. Then three samples, which were treated with different grade stresses combined with salinity, irradiation and temperature, were collected. The transcription numbers of seven constitutive expression genes in above samples were determined after RNA extraction and cDNA synthesis. Finally, a general insight into the selection of internal control genes during stress response was obtained. We found that there were no obvious effects in terms of salinity stress (at salinity 90) on transcription of most genes used in the study. The 18S ribosomal RNA gene had the highest expression level, varying remarkably among different tested groups. RPS8 expression showed a high irregular variance between samples. GAPDH presented comparatively stable expression and could thus be selected as the internal control. EF-1α showed stable expression during the series of multiple-stress tests. Our research provided available references for the selection of internal control genes for transcripts determination of P. yezoensis.

  15. Transcriptomic and Proteomic Analysis of Oenococcus oeni Adaptation to Wine Stress Conditions

    PubMed Central

    Margalef-Català, Mar; Araque, Isabel; Bordons, Albert; Reguant, Cristina; Bautista-Gallego, Joaquín

    2016-01-01

    Oenococcus oeni, the main lactic acid bacteria responsible for malolactic fermentation in wine, has to adapt to stressful conditions, such as low pH and high ethanol content. In this study, the changes in the transcriptome and the proteome of O. oeni PSU-1 during the adaptation period before MLF start have been studied. DNA microarrays were used for the transcriptomic analysis and two complementary proteomic techniques, 2-D DIGE and iTRAQ labeling were used to analyze the proteomic response. One of the most influenced functions in PSU-1 due to inoculation into wine-like medium (WLM) was translation, showing the over-expression of certain ribosomal genes and the corresponding proteins. Amino acid metabolism and transport was also altered and several peptidases were up regulated both at gene and protein level. Certain proteins involved in glutamine and glutamate metabolism showed an increased abundance revealing the key role of nitrogen uptake under stressful conditions. A strong transcriptional inhibition of carbohydrate metabolism related genes was observed. On the other hand, the transcriptional up-regulation of malate transport and citrate consumption was indicative of the use of L-malate and citrate associated to stress response and as an alternative energy source to sugar metabolism. Regarding the stress mechanisms, our results support the relevance of the thioredoxin and glutathione systems in the adaptation of O. oeni to wine related stress. Genes and proteins related to cell wall showed also significant changes indicating the relevance of the cell envelop as protective barrier to environmental stress. The differences found between transcriptomic and proteomic data suggested the relevance of post-transcriptional mechanisms and the complexity of the stress response in O. oeni adaptation. Further research should deepen into the metabolisms mostly altered due to wine conditions to elucidate the role of each mechanism in the O. oeni ability to develop MLF. PMID

  16. [Emigration in hard conditions: the Immigrant Syndrome with chronic and multiple stress (Ulysses' Syndrome)].

    PubMed

    Achotegui, Joseba

    2005-01-01

    During the latest years, immigrant populations have been living in very hard conditions. To million people, migration is becoming a process with a high level of stress surpassing the human being capacity of adaptation. This people are prone to suffer the Immigrant Syndrome with chronic and multiple stress and the so called Ulysses Syndrome, what is becoming a serious health problem in the countries that receive the immigrants. This situation is the by-product of the unjust globalization and of the worsening of the living and health conditions of those undergoing such a displacement. In this article, the author postulates a relationship between the high level of stress suffered by the immigrants and their presentation of psychopathological symptoms. PMID:15912217

  17. [Emigration in hard conditions: the Immigrant Syndrome with chronic and multiple stress (Ulysses' Syndrome)].

    PubMed

    Achotegui, Joseba

    2005-01-01

    During the latest years, immigrant populations have been living in very hard conditions. To million people, migration is becoming a process with a high level of stress surpassing the human being capacity of adaptation. This people are prone to suffer the Immigrant Syndrome with chronic and multiple stress and the so called Ulysses Syndrome, what is becoming a serious health problem in the countries that receive the immigrants. This situation is the by-product of the unjust globalization and of the worsening of the living and health conditions of those undergoing such a displacement. In this article, the author postulates a relationship between the high level of stress suffered by the immigrants and their presentation of psychopathological symptoms.

  18. Curcumin Mitigates Accelerated Aging after Irradiation in Drosophila by Reducing Oxidative Stress

    PubMed Central

    Yu, Mira; Park, Sunhoo; Jin, Young Woo; Min, Kyung-Jin

    2015-01-01

    Curcumin, belonging to a class of natural phenol compounds, has been extensively studied due to its antioxidative, anticancer, anti-inflammatory, and antineurodegenerative effects. Recently, it has been shown to exert dual activities after irradiation, radioprotection, and radiosensitization. Here, we investigated the protective effect of curcumin against radiation damage using D. melanogaster. Pretreatment with curcumin (100 μM) recovered the shortened lifespan caused by irradiation and increased eclosion rate. Flies subjected to high-dose irradiation showed a mutant phenotype of outstretched wings, whereas curcumin pretreatment reduced incidence of the mutant phenotype. Protein carbonylation and formation of γH2Ax foci both increased following high-dose irradiation most likely due to generation of reactive oxygen species. Curcumin pretreatment reduced the amount of protein carbonylation as well as formation of γH2Ax foci. Therefore, we suggest that curcumin acts as an oxidative stress reducer as well as an effective protective agent against radiation damage. PMID:25815315

  19. Hippocampal Structural Plasticity Accompanies the Resulting Contextual Fear Memory Following Stress and Fear Conditioning

    ERIC Educational Resources Information Center

    Giachero, Marcelo; Calfa, Gaston D.; Molina, Victor A.

    2013-01-01

    The present research investigated the resulting contextual fear memory and structural plasticity changes in the dorsal hippocampus (DH) following stress and fear conditioning. This combination enhanced fear retention and increased the number of total and mature dendritic spines in DH. Intra-basolateral amygdala (BLA) infusion of midazolam prior to…

  20. Accelerated decolorization of reactive azo dyes under saline conditions by bacteria isolated from Arabian seawater sediment.

    PubMed

    Khalid, Azeem; Kausar, Farzana; Arshad, Muhammad; Mahmood, Tariq; Ahmed, Iftikhar

    2012-12-01

    Presence of huge amount of salts in the wastewater of textile dyeing industry is one of the major limiting factors in the development of an effective biotreatment system for the removal of azo dyes from textile effluents. Bacterial spp. capable of thriving under high salt conditions could be employed for the treatment of saline dyecontaminated textile wastewaters. The present study was aimed at isolating the most efficient bacterial strains capable of decolorizing azo dyes under high saline conditions. Fiftyeight bacterial strains were isolated from seawater, seawater sediment, and saline soil, using mineral salt medium enriched with 100 mg l−1 Reactive Black-5 azo dye and 50 g NaCl l−1 salt concentration. Bacterial strains KS23 (Psychrobacter alimentarius) and KS26 (Staphylococcus equorum) isolated from seawater sediment were able to decolorize three reactive dyes including Reactive Black 5, Reactive Golden Ovifix, and Reactive Blue BRS very efficiently in liquid medium over a wide range of salt concentration (0-100 g NaCl l)⁻¹. Time required for complete decolorization of 100 mg dye l ⁻¹ varied with the type of dye and salt concentration. In general, there was an inverse linear relationship between the velocity of the decolorization reaction (V) and salt concentration. This study suggested that bacteria isolated from saline conditions such as seawater sediment could be used in designing a bioreactor for the treatment of textile effluent containing high concentration of salts.

  1. Accelerated Stress Testing and Diagnostic Analysis of Degradation in CdTe Solar Cells

    SciTech Connect

    Albin, D. S.

    2008-11-01

    The primary goal of this study was to ascertain the presence and types of mechanisms affecting CdS/CdTe device stability in the temperature range of 60 to 120 ..deg..C. It should be noted that the results presented were specific to cells made using the specific growth conditions described.

  2. Biotic stress accelerates formation of climate-relevant aerosols in boreal forests

    NASA Astrophysics Data System (ADS)

    Joutsensaari, J.; Yli-Pirilä, P.; Korhonen, H.; Arola, A.; Blande, J. D.; Heijari, J.; Kivimäenpää, M.; Mikkonen, S.; Hao, L.; Miettinen, P.; Lyytikäinen-Saarenmaa, P.; Faiola, C. L.; Laaksonen, A.; Holopainen, J. K.

    2015-11-01

    Boreal forests are a major source of climate-relevant biogenic secondary organic aerosols (SOAs) and will be greatly influenced by increasing temperature. Global warming is predicted to not only increase emissions of reactive biogenic volatile organic compounds (BVOCs) from vegetation directly but also induce large-scale insect outbreaks, which significantly increase emissions of reactive BVOCs. Thus, climate change factors could substantially accelerate the formation of biogenic SOAs in the troposphere. In this study, we have combined results from field and laboratory experiments, satellite observations and global-scale modelling in order to evaluate the effects of insect herbivory and large-scale outbreaks on SOA formation and the Earth's climate. Field measurements demonstrated 11-fold and 20-fold increases in monoterpene and sesquiterpene emissions respectively from damaged trees during a pine sawfly (Neodiprion sertifer) outbreak in eastern Finland. Laboratory chamber experiments showed that feeding by pine weevils (Hylobius abietis) increased VOC emissions from Scots pine and Norway spruce seedlings by 10-50 fold, resulting in 200-1000-fold increases in SOA masses formed via ozonolysis. The influence of insect damage on aerosol concentrations in boreal forests was studied with a global chemical transport model GLOMAP and MODIS satellite observations. Global-scale modelling was performed using a 10-fold increase in monoterpene emission rates and assuming 10 % of the boreal forest area was experiencing outbreak. Results showed a clear increase in total particulate mass (local max. 480 %) and cloud condensation nuclei concentrations (45 %). Satellite observations indicated a 2-fold increase in aerosol optical depth over western Canada's pine forests in August during a bark beetle outbreak. These results suggest that more frequent insect outbreaks in a warming climate could result in substantial increase in biogenic SOA formation in the boreal zone and, thus

  3. Biotic stress accelerates formation of climate-relevant aerosols in boreal forests

    NASA Astrophysics Data System (ADS)

    Joutsensaari, J.; Yli-Pirilä, P.; Korhonen, H.; Arola, A.; Blande, J. D.; Heijari, J.; Kivimäenpää, M.; Mikkonen, S.; Hao, L.; Miettinen, P.; Lyytikäinen-Saarenmaa, P.; Faiola, C. L.; Laaksonen, A.; Holopainen, J. K.

    2015-04-01

    Boreal forests are a major source of climate-relevant biogenic secondary organic aerosols (SOA) and will be greatly influenced by increasing temperature. Global warming is predicted to increase emissions of reactive biogenic volatile organic compounds (BVOC) from vegetation directly, but will also induce large-scale insect outbreaks, which significantly increase emissions of reactive BVOC. Thus, climate change factors could substantially accelerate the formation of biogenic SOA in the troposphere. In this study, we have combined results from field and laboratory experiments, satellite observations and global scale modelling in order to evaluate the effects of insect herbivory and large-scale outbreaks on SOA formation and the Earth's climate. Field measurements demonstrated 11-fold and 20-fold increases in monoterpene and sesquiterpene emissions, respectively, from damaged trees during a pine sawfly (Neodiprion sertifer) outbreak in eastern Finland. Laboratory chamber experiments showed that feeding by pine weevils (Hylobius abietis) increased VOC emissions from Scots pine and Norway spruce seedlings by 10-50 fold resulting in 200-1000 fold increases in SOA masses formed via ozonolysis. The influence of insect damage on aerosol concentrations in boreal forests was studied with a global chemical transport model GLOMAP and MODIS satellite observations. Global scale modelling was performed using a 10-fold increase in monoterpene emission rates and assuming 10% of the boreal forest area was experiencing outbreak. Results showed a clear increase in total particulate mass (local max. 480%) and cloud condensation nuclei concentrations (45%). Satellite observations indicated a two-fold increase in aerosol optical depth (AOD) over western Canada's pine forests in August during a bark beetle outbreak. These results suggest that more frequent insect outbreaks in a warming climate could result in substantial increase in biogenic SOA formation in the boreal zone and, thus

  4. Formulation of boundary conditions for the multigrid acceleration of the Euler and Navier Stokes equations

    NASA Technical Reports Server (NTRS)

    Jentink, Thomas Neil; Usab, William J., Jr.

    1990-01-01

    An explicit, Multigrid algorithm was written to solve the Euler and Navier-Stokes equations with special consideration given to the coarse mesh boundary conditions. These are formulated in a manner consistent with the interior solution, utilizing forcing terms to prevent coarse-mesh truncation error from affecting the fine-mesh solution. A 4-Stage Hybrid Runge-Kutta Scheme is used to advance the solution in time, and Multigrid convergence is further enhanced by using local time-stepping and implicit residual smoothing. Details of the algorithm are presented along with a description of Jameson's standard Multigrid method and a new approach to formulating the Multigrid equations.

  5. Study Of Seed Yield Correlation With Different Traits Of Common Bean Under Stress Condition

    NASA Astrophysics Data System (ADS)

    Aminian, Roghayeh; Khodambashi, Mahmood; Yadegari, Mehrab

    2008-01-01

    In order to study seed yield and the most effective traits on seed yield of ten common been cultivars, a split plot in the form of complete block design was conducted at Shahrekord University. Among the characters studied, seed yield had the highest variation and the weight of plants had the lowest variation. the number of pods per plant had the highest correlation with seed yield in both stress and non stress conditions, while the number of seed per plant and 100 seeds weight had the lowest correlation with seed yield in non stress and stress conditions, respectively. Increase in stress intensity caused the increase in correlation between seed yield and the total weight of plant and the number of seed per pod. In principal components analysis, number of pods per plant, number of seeds per pods and seed yield had the highest correlation with the first component while 100 seeds weight and number of seeds per plant had the highest correlation with the second component.

  6. The effects of extrinsic stress on somatic markers and behavior are dependent on animal housing conditions.

    PubMed

    Huzard, Damien; Mumby, Dave G; Sandi, Carmen; Poirier, Guillaume L; van der Kooij, Michael A

    2015-11-01

    Properties of the environment play an important role in animal wellbeing and may modulate the effects of external threats. Whereas stressors can affect emotion and impair cognition, environmental enrichment may prevent the occurrence of such negative sequelae. Animals exposed to semi-natural group-housing experience a complex environment; whereas environmental enrichment might protect against stressors, a socially-enriched environment(SEE) could entail aggressive inter-male encounters with additive stress effects. In the present study, we investigated the effects of exposure to external stressors, footshocks and forced swimming, on adrenal gland and body weights as well as on behavior in rats housed under SEE or standard, non-enriched environment (NEE), conditions. We found that SEEs reduced the anxiogenic effects of stress. Moreover, SEEs improved the performance in an operant task and prevented the increase in impulsive behavior produced by external stressors on NEE animals. Whereas these findings are indicative of stress-buffering effects of SEEs, adrenal gland weights were increased while total body weights were decreased in SEE rats, suggesting that SEEs may simultaneously exacerbate physiological measurements of stress. Finally, in the SEE, total aggressive behaviors and body wounds were paradoxically reduced in animals that received external stressors in comparison to non-stressed controls. The consequences of the external stressors applied here are not uniform, varying according to the housing condition and the outcome considered.

  7. Nanoscale-alumina induces oxidative stress and accelerates amyloid beta (Aβ) production in ICR female mice

    NASA Astrophysics Data System (ADS)

    Shah, Shahid Ali; Yoon, Gwang Ho; Ahmad, Ashfaq; Ullah, Faheem; Amin, Faiz Ul; Kim, Myeong Ok

    2015-09-01

    The adverse effects of nanoscale-alumina (Al2O3-NPs) have been previously demonstrated in both in vitro and in vivo studies, whereas little is known about their mechanism of neurotoxicity. It is the goal of this research to determine the toxic effects of nano-alumina on human neuroblastoma SH-SY5Y and mouse hippocampal HT22 cells in vitro and on ICR female mice in vivo. Nano-alumina displayed toxic effects on SH-SY5Y cell lines in three different concentrations also increased aluminium abundance and induced oxidative stress in HT22 cells. Nano-alumina peripherally administered to ICR female mice for three weeks increased brain aluminium and ROS production, disturbing brain energy homeostasis, and led to the impairment of hippocampus-dependent memory. Most importantly, these nano-particles induced Alzheimer disease (AD) neuropathology by enhancing the amyloidogenic pathway of Amyloid Beta (Aβ) production, aggregation and implied the progression of neurodegeneration in the cortex and hippocampus of these mice. In conclusion, these data demonstrate that nano-alumina is toxic to both cells and female mice and that prolonged exposure may heighten the chances of developing a neurodegenerative disease, such as AD.

  8. Human-animal interaction, stress, and embryo production in Bos indicus embryo donors under tropical conditions.

    PubMed

    Macedo, Gustavo Guerino; Zúccari, Carmem Estefânia Serra Neto; de Abreu, Urbano Gomes Pinto; Negrão, João Alberto; da Costa e Silva, Eliane Vianna

    2011-08-01

    This study investigated the effect of human-animal interaction (HAI) and the stress response on the quality of embryo production in superovulated Nelore (Bos indicus) cattle, under tropical conditions. Thirty-two females underwent a superovulation protocol for 5 days. Cortisol concentrations were determined in blood plasma collected on days 0, 4, and 5. Artificial insemination was performed on days 4 and 5, and nonsurgical embryo flushing on day 11. Embryo production and viability were determined. Human stimulation, animal behaviors, accidents, and handling time were recorded to assess HAI. Cattle age was negatively correlated with accidents, frequency of aversive behaviors, and negative stimuli by stockperson during transit through corral compartments to receive superovulation treatments. The factor analysis revealed two distinct groups. The first group was called stressed and had higher cortisol concentration than the nonstressed group, 16.0 ± 2.1 and 12.5 ± 1.0 ng/mL, respectively. Comparisons between these groups showed that the frequency of voice emissions by the stockperson and the number of accidents were higher in the stressed group, and also, the mean handling time was longer in the stressed group than for the nonstressed. As a result, viability rate of the embryos was 19% lower in the stressed group (P < 0.05). This indicates that intensive negative HAI is likely related to stress, which affects embryo production in a superovulation program.

  9. Repeated social defeat stress enhances glutamatergic synaptic plasticity in the VTA and cocaine place conditioning.

    PubMed

    Stelly, Claire E; Pomrenze, Matthew B; Cook, Jason B; Morikawa, Hitoshi

    2016-01-01

    Enduring memories of sensory cues associated with drug intake drive addiction. It is well known that stressful experiences increase addiction vulnerability. However, it is not clear how repeated stress promotes learning of cue-drug associations, as repeated stress generally impairs learning and memory processes unrelated to stressful experiences. Here, we show that repeated social defeat stress in rats causes persistent enhancement of long-term potentiation (LTP) of NMDA receptor-mediated glutamatergic transmission in the ventral tegmental area (VTA). Protein kinase A-dependent increase in the potency of inositol 1,4,5-triphosphate-induced Ca(2+) signaling underlies LTP facilitation. Notably, defeated rats display enhanced learning of contextual cues paired with cocaine experience assessed using a conditioned place preference (CPP) paradigm. Enhancement of LTP in the VTA and cocaine CPP in behaving rats both require glucocorticoid receptor activation during defeat episodes. These findings suggest that enhanced glutamatergic plasticity in the VTA may contribute, at least partially, to increased addiction vulnerability following repeated stressful experiences. PMID:27374604

  10. Repeated social defeat stress enhances glutamatergic synaptic plasticity in the VTA and cocaine place conditioning

    PubMed Central

    Stelly, Claire E; Pomrenze, Matthew B; Cook, Jason B; Morikawa, Hitoshi

    2016-01-01

    Enduring memories of sensory cues associated with drug intake drive addiction. It is well known that stressful experiences increase addiction vulnerability. However, it is not clear how repeated stress promotes learning of cue-drug associations, as repeated stress generally impairs learning and memory processes unrelated to stressful experiences. Here, we show that repeated social defeat stress in rats causes persistent enhancement of long-term potentiation (LTP) of NMDA receptor-mediated glutamatergic transmission in the ventral tegmental area (VTA). Protein kinase A-dependent increase in the potency of inositol 1,4,5-triphosphate-induced Ca2+ signaling underlies LTP facilitation. Notably, defeated rats display enhanced learning of contextual cues paired with cocaine experience assessed using a conditioned place preference (CPP) paradigm. Enhancement of LTP in the VTA and cocaine CPP in behaving rats both require glucocorticoid receptor activation during defeat episodes. These findings suggest that enhanced glutamatergic plasticity in the VTA may contribute, at least partially, to increased addiction vulnerability following repeated stressful experiences. DOI: http://dx.doi.org/10.7554/eLife.15448.001 PMID:27374604

  11. Pseudomonas putida response in membrane bioreactors under salicylic acid-induced stress conditions.

    PubMed

    Collado, Sergio; Rosas, Irene; González, Elena; Gutierrez-Lavin, Antonio; Diaz, Mario

    2014-02-28

    Starvation and changing feeding conditions are frequently characteristics of wastewater treatment plants. They are typical causes of unsteady-state operation of biological systems and provoke cellular stress. The response of a membrane bioreactor functioning under feed-induced stress conditions is studied here. In order to simplify and considerably amplify the response to stress and to obtain a reference model, a pure culture of Pseudomonas putida was selected instead of an activated sludge and a sole substrate (salicylic acid) was employed. The system degraded salicylic acid at 100-1100mg/L with a high level of efficiency, showed rapid acclimation without substrate or product inhibition phenomena and good stability in response to unsteady states caused by feed variations. Under starvation conditions, specific degradation rates of around 15mg/gh were achieved during the adaptation of the biomass to the new conditions and no biofilm formation was observed during the first days of experimentation using an initial substrate to microorganisms ratio lower than 0.1. When substrate was added to the reactor as pulses resulting in rapidly changing concentrations, P. putida growth was observed only for substrate to microorganism ratios higher than 0.6, with a maximum YX/S of 0.5g/g. Biofilm development under changing feeding conditions was fast, biomass detachment only being significant for biomass concentrations on the membrane surface that were higher than 16g/m(2).

  12. Interactions between sleep, stress, and metabolism: From physiological to pathological conditions.

    PubMed

    Hirotsu, Camila; Tufik, Sergio; Andersen, Monica Levy

    2015-11-01

    Poor sleep quality due to sleep disorders and sleep loss is highly prevalent in the modern society. Underlying mechanisms show that stress is involved in the relationship between sleep and metabolism through hypothalamic-pituitary-adrenal (HPA) axis activation. Sleep deprivation and sleep disorders are associated with maladaptive changes in the HPA axis, leading to neuroendocrine dysregulation. Excess of glucocorticoids increase glucose and insulin and decrease adiponectin levels. Thus, this review provides overall view of the relationship between sleep, stress, and metabolism from basic physiology to pathological conditions, highlighting effective treatments for metabolic disturbances. PMID:26779321

  13. Interactions between sleep, stress, and metabolism: From physiological to pathological conditions

    PubMed Central

    Hirotsu, Camila; Tufik, Sergio; Andersen, Monica Levy

    2015-01-01

    Poor sleep quality due to sleep disorders and sleep loss is highly prevalent in the modern society. Underlying mechanisms show that stress is involved in the relationship between sleep and metabolism through hypothalamic–pituitary–adrenal (HPA) axis activation. Sleep deprivation and sleep disorders are associated with maladaptive changes in the HPA axis, leading to neuroendocrine dysregulation. Excess of glucocorticoids increase glucose and insulin and decrease adiponectin levels. Thus, this review provides overall view of the relationship between sleep, stress, and metabolism from basic physiology to pathological conditions, highlighting effective treatments for metabolic disturbances. PMID:26779321

  14. Behavioral and physiological responses of female prairie voles (Microtus ochrogaster) to various stressful conditions

    PubMed Central

    Smith, Adam S.; Lieberwirth, Claudia; Wang, Zuoxin

    2014-01-01

    Stressful life events elicit hypothalamic-pituitary-adrenal (HPA) axis activation, which may alter psychological states or behavioral routines. Therefore, the current study focused on the HPA axis response to better understand such manifestations in female prairie voles (Microtus ochrogaster). In Experiment 1, females were stressed for 1 h via one of four stressors: exposure to a novel environment, immobilization (‘plastic mesh’), brief social defeat, or prolonged social defeat. Following a 30 min recovery, the females received a 5-min elevated plus maze (EPM) test and, subsequently, blood was collected to measure plasma corticosterone concentrations. Only immobilization stress induced an anxiety-like behavioral response in the EPM test and elevated plasma corticosterone levels compared to the control groups. Corticosterone concentrations were also significantly elevated following exposure to prolonged social defeat compared to the control conditions, but not after novel environment stress or short social defeat. In Experiment 2, females were exposed to immobilization stress over 1, 3, or 7 days in a daily (predictable; pIMO) or irregular (unpredictable; uIMO) schedule. The biobehavioral stress response in females exposed to pIMO for 3 or 7 days did not differ significantly from controls, suggesting these females habituated. By comparison, females exposed to uIMO over 3 or 7 days did not habituate behaviorally or physiologically, even producing augmented corticosterone levels. In both experiments, positive correlations were found between corticosterone levels and anxiety-like behaviors in the EPM test. Together, our data suggest that the stress response by female prairie voles is dependent on stress intensity, source, previous experience, and predictability. Furthermore, the HPA axis response, as evident by corticosterone levels, is associated with the impact that these factors have on behavioral routine. PMID:23647082

  15. Accelerated aging phenotype in mice with conditional deficiency for mitochondrial superoxide dismutase in the connective tissue.

    PubMed

    Treiber, Nicolai; Maity, Pallab; Singh, Karmveer; Kohn, Matthias; Keist, Alexander F; Ferchiu, Florentina; Sante, Lea; Frese, Sebastian; Bloch, Wilhelm; Kreppel, Florian; Kochanek, Stefan; Sindrilaru, Anca; Iben, Sebastian; Högel, Josef; Ohnmacht, Michael; Claes, Lutz E; Ignatius, Anita; Chung, Jin H; Lee, Min J; Kamenisch, York; Berneburg, Mark; Nikolaus, Thorsten; Braunstein, Kerstin; Sperfeld, Anne-Dorte; Ludolph, Albert C; Briviba, Karlis; Wlaschek, Meinhard; Florin, Lore; Angel, Peter; Scharffetter-Kochanek, Karin

    2011-04-01

    The free radical theory of aging postulates that the production of mitochondrial reactive oxygen species is the major determinant of aging and lifespan. Its role in aging of the connective tissue has not yet been established, even though the incidence of aging-related disorders in connective tissue-rich organs is high, causing major disability in the elderly. We have now addressed this question experimentally by creating mice with conditional deficiency of the mitochondrial manganese superoxide dismutase in fibroblasts and other mesenchyme-derived cells of connective tissues in all organs. Here, we have shown for the first time that the connective tissue-specific lack of superoxide anion detoxification in the mitochondria results in reduced lifespan and premature onset of aging-related phenotypes such as weight loss, skin atrophy, kyphosis (curvature of the spine), osteoporosis and muscle degeneration in mutant mice. Increase in p16(INK4a) , a robust in vivo marker for fibroblast aging, may contribute to the observed phenotype. This novel model is particularly suited to decipher the underlying mechanisms and to develop hopefully novel connective tissue-specific anti-aging strategies.

  16. Hedgehog pathway maintains cell survival under stress conditions, and drives drug resistance in lung adenocarcinoma

    PubMed Central

    Lin, Erh-Hsuan; Kao, Yu-Rung; Lin, Chih-An; Kuo, Ting-Yu; Yang, Sheng-Ping; Hsu, Chiung-Fang; Chou, Teh-Ying; Ho, Chao-Chi; Wu, Cheng-Wen

    2016-01-01

    Hedgehog (HH) pathway plays an important role in embryonic development, but is largely inactive in adult except for tissue repair. Aberrant activation of HH pathway has been found in a variety of cancer types. In non-small cell lung cancer, however, the role and importance of HH pathway remain controversial. In the current study, we found that HH pathway was maintained in low activity in lung adenocarcinoma (LAC) cells under normal culture condition, but was highly induced in response to stress conditions. Activation of HH pathway promoted cell survival, growth, and invasion partially through HGF and MET signaling. Hedgehog-Interacting Protein (HHIP), a cell-surface negative regulator of HH pathway, was epigenetically silenced in LAC. Overexpression of HHIP blocked the activation of HH and HGF/MET pathways, and made cells significantly more susceptible to stress conditions. In LAC cells with acquired resistance to Epidermal Growth Factor Receptor Tyrosin Kinase Inhibitor (EGFR-TKI), we found that a part of tumor cells were much more sensitive to HH or HGF/MET inhibitors, suggesting an oncogenic addiction shift from EGFR to HH and HGF/MET pathways. In conclusion, this study showed that HH pathway is a survival signaling that drives LAC cell growth under stress conditions, and HHIP is a key regulator to block the induction of HH pathway. Targeting the HH pathway through inhibitors or HHIP thus holds promise to address EGFR-TKI resistance in LAC in clinic. PMID:27015549

  17. Hedgehog pathway maintains cell survival under stress conditions, and drives drug resistance in lung adenocarcinoma.

    PubMed

    Lin, Erh-Hsuan; Kao, Yu-Rung; Lin, Chih-An; Kuo, Ting-Yu; Yang, Sheng-Ping; Hsu, Chiung-Fang; Chou, Teh-Ying; Ho, Chao-Chi; Wu, Cheng-Wen

    2016-04-26

    Hedgehog (HH) pathway plays an important role in embryonic development, but is largely inactive in adult except for tissue repair. Aberrant activation of HH pathway has been found in a variety of cancer types. In non-small cell lung cancer, however, the role and importance of HH pathway remain controversial. In the current study, we found that HH pathway was maintained in low activity in lung adenocarcinoma (LAC) cells under normal culture condition, but was highly induced in response to stress conditions. Activation of HH pathway promoted cell survival, growth, and invasion partially through HGF and MET signaling. Hedgehog-Interacting Protein (HHIP), a cell-surface negative regulator of HH pathway, was epigenetically silenced in LAC. Overexpression of HHIP blocked the activation of HH and HGF/MET pathways, and made cells significantly more susceptible to stress conditions. In LAC cells with acquired resistance to Epidermal Growth Factor Receptor Tyrosin Kinase Inhibitor (EGFR-TKI), we found that a part of tumor cells were much more sensitive to HH or HGF/MET inhibitors, suggesting an oncogenic addiction shift from EGFR to HH and HGF/MET pathways. In conclusion, this study showed that HH pathway is a survival signaling that drives LAC cell growth under stress conditions, and HHIP is a key regulator to block the induction of HH pathway. Targeting the HH pathway through inhibitors or HHIP thus holds promise to address EGFR-TKI resistance in LAC in clinic. PMID:27015549

  18. Mesenchymal stem cell-conditioned medium accelerates skin wound healing: An in vitro study of fibroblast and keratinocyte scratch assays

    SciTech Connect

    Walter, M.N.M.; Wright, K.T.; Fuller, H.R.; MacNeil, S.; Johnson, W.E.B.

    2010-04-15

    We have used in vitro scratch assays to examine the relative contribution of dermal fibroblasts and keratinocytes in the wound repair process and to test the influence of mesenchymal stem cell (MSC) secreted factors on both skin cell types. Scratch assays were established using single cell and co-cultures of L929 fibroblasts and HaCaT keratinocytes, with wound closure monitored via time-lapse microscopy. Both in serum supplemented and serum free conditions, wound closure was faster in L929 fibroblast than HaCaT keratinocyte scratch assays, and in co-culture the L929 fibroblasts lead the way in closing the scratches. MSC-CM generated under serum free conditions significantly enhanced the wound closure rate of both skin cell types separately and in co-culture, whereas conditioned medium from L929 or HaCaT cultures had no significant effect. This enhancement of wound closure in the presence of MSC-CM was due to accelerated cell migration rather than increased cell proliferation. A number of wound healing mediators were identified in MSC-CM, including TGF-{beta}1, the chemokines IL-6, IL-8, MCP-1 and RANTES, and collagen type I, fibronectin, SPARC and IGFBP-7. This study suggests that the trophic activity of MSC may play a role in skin wound closure by affecting both dermal fibroblast and keratinocyte migration, along with a contribution to the formation of extracellular matrix.

  19. Non-thermal electron acceleration in low Mach number collisionless shocks. II. Firehose-mediated Fermi acceleration and its dependence on pre-shock conditions

    SciTech Connect

    Guo, Xinyi; Narayan, Ramesh; Sironi, Lorenzo

    2014-12-10

    Electron acceleration to non-thermal energies is known to occur in low Mach number (M{sub s} ≲ 5) shocks in galaxy clusters and solar flares, but the electron acceleration mechanism remains poorly understood. Using two-dimensional (2D) particle-in-cell (PIC) plasma simulations, we showed in Paper I that electrons are efficiently accelerated in low Mach number (M{sub s} = 3) quasi-perpendicular shocks via a Fermi-like process. The electrons bounce between the upstream region and the shock front, with each reflection at the shock resulting in energy gain via shock drift acceleration. The upstream scattering is provided by oblique magnetic waves that are self-generated by the electrons escaping ahead of the shock. In the present work, we employ additional 2D PIC simulations to address the nature of the upstream oblique waves. We find that the waves are generated by the shock-reflected electrons via the firehose instability, which is driven by an anisotropy in the electron velocity distribution. We systematically explore how the efficiency of wave generation and of electron acceleration depend on the magnetic field obliquity, the flow magnetization (or equivalently, the plasma beta), and the upstream electron temperature. We find that the mechanism works for shocks with high plasma beta (≳ 20) at nearly all magnetic field obliquities, and for electron temperatures in the range relevant for galaxy clusters. Our findings offer a natural solution to the conflict between the bright radio synchrotron emission observed from the outskirts of galaxy clusters and the low electron acceleration efficiency usually expected in low Mach number shocks.

  20. Non-thermal Electron Acceleration in Low Mach Number Collisionless Shocks. II. Firehose-mediated Fermi Acceleration and its Dependence on Pre-shock Conditions

    NASA Astrophysics Data System (ADS)

    Guo, Xinyi; Sironi, Lorenzo; Narayan, Ramesh

    2014-12-01

    Electron acceleration to non-thermal energies is known to occur in low Mach number (Ms <~ 5) shocks in galaxy clusters and solar flares, but the electron acceleration mechanism remains poorly understood. Using two-dimensional (2D) particle-in-cell (PIC) plasma simulations, we showed in Paper I that electrons are efficiently accelerated in low Mach number (Ms = 3) quasi-perpendicular shocks via a Fermi-like process. The electrons bounce between the upstream region and the shock front, with each reflection at the shock resulting in energy gain via shock drift acceleration. The upstream scattering is provided by oblique magnetic waves that are self-generated by the electrons escaping ahead of the shock. In the present work, we employ additional 2D PIC simulations to address the nature of the upstream oblique waves. We find that the waves are generated by the shock-reflected electrons via the firehose instability, which is driven by an anisotropy in the electron velocity distribution. We systematically explore how the efficiency of wave generation and of electron acceleration depend on the magnetic field obliquity, the flow magnetization (or equivalently, the plasma beta), and the upstream electron temperature. We find that the mechanism works for shocks with high plasma beta (gsim 20) at nearly all magnetic field obliquities, and for electron temperatures in the range relevant for galaxy clusters. Our findings offer a natural solution to the conflict between the bright radio synchrotron emission observed from the outskirts of galaxy clusters and the low electron acceleration efficiency usually expected in low Mach number shocks.

  1. Stress and body condition are associated with climate and demography in Asian elephants

    PubMed Central

    Mumby, Hannah S.; Mar, Khyne U.; Thitaram, Chatchote; Courtiol, Alexandre; Towiboon, Patcharapa; Min-Oo, Zaw; Htut-Aung, Ye; Brown, Janine L.; Lummaa, Virpi

    2015-01-01

    Establishing links between ecological variation, physiological markers of stress and demography is crucial for understanding how and why changes in environmental conditions affect population dynamics, and may also play a key role for conservation efforts of endangered species. However, detailed longitudinal studies of long-lived species are rarely available. We test how two markers of stress and body condition vary through the year and are associated with climatic conditions and large-scale mortality and fertility variation in the world's largest semi-captive population of Asian elephants employed in the timber industry in Myanmar. Glucocorticoid metabolites (used as a proxy for stress levels in 75 elephants) and body weight (used as a proxy for condition in 116 elephants) were monitored monthly across a typical monsoon cycle and compared with birth and death patterns of the entire elephant population over half a century (n = 2350). Our results show seasonal variation in both markers of stress and condition. In addition, this variation is correlated with population-level demographic variables. Weight is inversely correlated with population mortality rates 1 month later, and glucocorticoid metabolites are negatively associated with birth rates. Weight shows a highly positive correlation with rainfall 1 month earlier. Determining the factors associated with demography may be key to species conservation by providing information about the correlates of mortality and fertility patterns. The unsustainability of the studied captive population has meant that wild elephants have been captured and tamed for work. By elucidating the correlates of demography in captive elephants, our results offer management solutions that could reduce the pressure on the wild elephant population in Myanmar. PMID:27293715

  2. Stress and body condition are associated with climate and demography in Asian elephants.

    PubMed

    Mumby, Hannah S; Mar, Khyne U; Thitaram, Chatchote; Courtiol, Alexandre; Towiboon, Patcharapa; Min-Oo, Zaw; Htut-Aung, Ye; Brown, Janine L; Lummaa, Virpi

    2015-01-01

    Establishing links between ecological variation, physiological markers of stress and demography is crucial for understanding how and why changes in environmental conditions affect population dynamics, and may also play a key role for conservation efforts of endangered species. However, detailed longitudinal studies of long-lived species are rarely available. We test how two markers of stress and body condition vary through the year and are associated with climatic conditions and large-scale mortality and fertility variation in the world's largest semi-captive population of Asian elephants employed in the timber industry in Myanmar. Glucocorticoid metabolites (used as a proxy for stress levels in 75 elephants) and body weight (used as a proxy for condition in 116 elephants) were monitored monthly across a typical monsoon cycle and compared with birth and death patterns of the entire elephant population over half a century (n = 2350). Our results show seasonal variation in both markers of stress and condition. In addition, this variation is correlated with population-level demographic variables. Weight is inversely correlated with population mortality rates 1 month later, and glucocorticoid metabolites are negatively associated with birth rates. Weight shows a highly positive correlation with rainfall 1 month earlier. Determining the factors associated with demography may be key to species conservation by providing information about the correlates of mortality and fertility patterns. The unsustainability of the studied captive population has meant that wild elephants have been captured and tamed for work. By elucidating the correlates of demography in captive elephants, our results offer management solutions that could reduce the pressure on the wild elephant population in Myanmar. PMID:27293715

  3. Stress and body condition are associated with climate and demography in Asian elephants.

    PubMed

    Mumby, Hannah S; Mar, Khyne U; Thitaram, Chatchote; Courtiol, Alexandre; Towiboon, Patcharapa; Min-Oo, Zaw; Htut-Aung, Ye; Brown, Janine L; Lummaa, Virpi

    2015-01-01

    Establishing links between ecological variation, physiological markers of stress and demography is crucial for understanding how and why changes in environmental conditions affect population dynamics, and may also play a key role for conservation efforts of endangered species. However, detailed longitudinal studies of long-lived species are rarely available. We test how two markers of stress and body condition vary through the year and are associated with climatic conditions and large-scale mortality and fertility variation in the world's largest semi-captive population of Asian elephants employed in the timber industry in Myanmar. Glucocorticoid metabolites (used as a proxy for stress levels in 75 elephants) and body weight (used as a proxy for condition in 116 elephants) were monitored monthly across a typical monsoon cycle and compared with birth and death patterns of the entire elephant population over half a century (n = 2350). Our results show seasonal variation in both markers of stress and condition. In addition, this variation is correlated with population-level demographic variables. Weight is inversely correlated with population mortality rates 1 month later, and glucocorticoid metabolites are negatively associated with birth rates. Weight shows a highly positive correlation with rainfall 1 month earlier. Determining the factors associated with demography may be key to species conservation by providing information about the correlates of mortality and fertility patterns. The unsustainability of the studied captive population has meant that wild elephants have been captured and tamed for work. By elucidating the correlates of demography in captive elephants, our results offer management solutions that could reduce the pressure on the wild elephant population in Myanmar.

  4. Stress-induced activation of brown adipose tissue prevents obesity in conditions of low adaptive thermogenesis

    PubMed Central

    Razzoli, Maria; Frontini, Andrea; Gurney, Allison; Mondini, Eleonora; Cubuk, Cankut; Katz, Liora S.; Cero, Cheryl; Bolan, Patrick J.; Dopazo, Joaquin; Vidal-Puig, Antonio; Cinti, Saverio; Bartolomucci, Alessandro

    2015-01-01

    Background Stress-associated conditions such as psychoemotional reactivity and depression have been paradoxically linked to either weight gain or weight loss. This bi-directional effect of stress is not understood at the functional level. Here we tested the hypothesis that pre-stress level of adaptive thermogenesis and brown adipose tissue (BAT) functions explain the vulnerability or resilience to stress-induced obesity. Methods We used wt and triple β1,β2,β3−Adrenergic Receptors knockout (β-less) mice exposed to a model of chronic subordination stress (CSS) at either room temperature (22 °C) or murine thermoneutrality (30 °C). A combined behavioral, physiological, molecular, and immunohistochemical analysis was conducted to determine stress-induced modulation of energy balance and BAT structure and function. Immortalized brown adipocytes were used for in vitro assays. Results Departing from our initial observation that βARs are dispensable for cold-induced BAT browning, we demonstrated that under physiological conditions promoting low adaptive thermogenesis and BAT activity (e.g. thermoneutrality or genetic deletion of the βARs), exposure to CSS acted as a stimulus for BAT activation and thermogenesis, resulting in resistance to diet-induced obesity despite the presence of hyperphagia. Conversely, in wt mice acclimatized to room temperature, and therefore characterized by sustained BAT function, exposure to CSS increased vulnerability to obesity. Exposure to CSS enhanced the sympathetic innervation of BAT in wt acclimatized to thermoneutrality and in β-less mice. Despite increased sympathetic innervation suggesting adrenergic-mediated browning, norepinephrine did not promote browning in βARs knockout brown adipocytes, which led us to identify an alternative sympathetic/brown adipocytes purinergic pathway in the BAT. This pathway is downregulated under conditions of low adaptive thermogenesis requirements, is induced by stress, and elicits activation

  5. Modulation of phenolic metabolism under stress conditions in a Lotus japonicus mutant lacking plastidic glutamine synthetase

    PubMed Central

    García-Calderón, Margarita; Pons-Ferrer, Teresa; Mrázova, Anna; Pal'ove-Balang, Peter; Vilková, Mária; Pérez-Delgado, Carmen M.; Vega, José M.; Eliášová, Adriana; Repčák, Miroslav; Márquez, Antonio J.; Betti, Marco

    2015-01-01

    This paper was aimed to investigate the possible implications of the lack of plastidic glutamine synthetase (GS2) in phenolic metabolism during stress responses in the model legume Lotus japonicus. Important changes in the transcriptome were detected in a GS2 mutant called Ljgln2-2, compared to the wild type, in response to two separate stress conditions, such as drought or the result of the impairment of the photorespiratory cycle. Detailed transcriptomic analysis showed that the biosynthesis of phenolic compounds was affected in the mutant plants in these two different types of stress situations. For this reason, the genes and metabolites related to this metabolic route were further investigated using a combined approach of gene expression analysis and metabolite profiling. A high induction of the expression of several genes for the biosynthesis of different branches of the phenolic biosynthetic pathway was detected by qRT-PCR. The extent of induction was always higher in Ljgln2-2, probably reflecting the higher stress levels present in this genotype. This was paralleled by accumulation of several kaempferol and quercetine glycosides, some of them described for the first time in L. japonicus, and of high levels of the isoflavonoid vestitol. The results obtained indicate that the absence of GS2 affects different aspects of phenolic metabolism in L. japonicus plants in response to stress. PMID:26442073

  6. Emotional stress evoked by classical fear conditioning induces yawning behavior in rats.

    PubMed

    Kubota, Natsuko; Amemiya, Seiichiro; Yanagita, Shinya; Nishijima, Takeshi; Kita, Ichiro

    2014-04-30

    Yawning is often observed not only in a state of boredom or drowsiness but also in stressful emotional situations, suggesting that yawning is an emotional behavior. However, the neural mechanisms for yawning during stressful emotional situations have not been fully determined, though previous studies have suggested that both parvocellular oxytocin (OT) and corticotropin-releasing factor (CRF) neurons in the hypothalamic paraventricular nucleus (PVN) are responsible for induction of yawning. Thus, using ethological observations and c-Fos immunohistochemistry, we examined whether emotional stress evoked by classical fear conditioning is involved in induction of yawning behavior in freely moving rats. Emotional stress induced yawning behavior that was accompanied by anxiety-related behavior, and caused neuronal activation of the central nucleus of the amygdala (CeA), as well as increases in activity of both OT and CRF neurons in the PVN. These results suggest that emotional stress may induce yawning behavior, in which the neuronal activation of the CeA may have a key role.

  7. Tolerance of Mycorrhiza infected pistachio (Pistacia vera L.) seedling to drought stress under glasshouse conditions.

    PubMed

    Abbaspour, H; Saeidi-Sar, S; Afshari, H; Abdel-Wahhab, M A

    2012-05-01

    The influence of Glomus etunicatum colonization on plant growth and drought tolerance of 3-month-old Pistacia vera seedlings in potted culture was studied in two different water treatments. The arbuscular mycorrhiza (AM) inoculation and plant growth (including plant shoot and root weight, leaf area, and total chlorophyll) were higher for well-watered than for water-stressed plants. The growth of AM-treated seedlings was higher than non-AM-treatment regardless of water status. P, K, Zn and Cu contents in AM-treated shoots were greater than those in non-AM shoots under well-watered conditions and drought stress. N and Ca content were higher under drought stress, while AM symbiosis did not affect the Mg content. The contents of soluble sugars, proteins, flavonoid and proline were higher in mycorrhizal than non-mycorrhizal-treated plants under the whole water regime. AM colonization increased the activities of peroxidase enzyme in treatments, but did not affect the catalase activity in shoots and roots under well-watered conditions and drought stress. We conclude that AM colonization improved the drought tolerance of P. vera seedlings by increasing the accumulation of osmotic adjustment compounds, nutritional and antioxidant enzyme activity. It appears that AM formation enhanced the drought tolerance of pistachio plants, which increased host biomass and plant growth.

  8. Three Brassica rapa metallothionein genes are differentially regulated under various stress conditions.

    PubMed

    Ahn, Young Ock; Kim, Sun Ha; Lee, Jeongyeo; Kim, Hyeran; Lee, Haeng-Soon; Kwak, Sang-Soo

    2012-03-01

    The expression profiles of three Brassica rapa metallothionein genes (BrMT 1-3) were determined in 7-day-old seedlings exposed to various exogenous factors including plant hormones, heavy metals and abiotic stresses. BrMT1, BrMT2, and BrMT3 were representatives of MT gene type 1, type 2, and type 3, respectively, according to their cysteine alignment. BrMT2 showed a relatively higher basal expression level compared to BrMT1 and BrMT3 under normal conditions. The BrMT1 transcript was markedly increased by various factors including ethephon, polyethylene glycol and hydrogen peroxide, with no down-regulation evident. On the contrary, BrMT2 expression was down-regulated by abscisic acid, salicylic acid, and methyl jasmonate. Heavy metals did not increase BrMT2 expression. BrMT3 expression was only marginally and non-significantly up- and down-regulated by the stress conditions tested. Promoter regions of BrMT1 and BrMT2 display different cis-acting elements supporting the different responses of both genes against various stresses. The results demonstrate the differential regulation of BrMT1-3 by various plant exogenous factors, and indicate the utility of the BrMT1 promoter as a multiple stress inducible promoter.

  9. Antenatal Maternal Stress Alters Functional Brain Responses In Adult Offspring During Conditioned Fear

    PubMed Central

    Sadler, Theodore R.; Nguyen, Peter T.; Yang, Jun; Givrad, Tina K.; Mayer, Emeran A.; Maarek, Jean-Michel I.; Hinton, David R.; Holschneider, Daniel P.

    2011-01-01

    Antenatal maternal stress has been shown in rodent models and in humans to result in altered behavioral and neuroendocrine responses, yet little is known about its effects on functional brain activation. Pregnant female rats received a daily foot-shock stress or sham-stress two days after testing plug-positive and continuing for the duration of their pregnancy. Adult male offspring (age 14 weeks) with and without prior maternal stress (MS) were exposed to an auditory fear conditioning (CF) paradigm. Cerebral blood flow (CBF) was assessed during recall of the tone cue in the nonsedated, nontethered animal using the 14C-iodoantipyrine method, in which the tracer was administered intravenously by remote activation of an implantable minipump. Regional CBF distribution was examined by autoradiography and analyzed by statistical parametric mapping in the three-dimensionally reconstructed brains. Presence of fear memory was confirmed by behavioral immobility (‘freezing’). Corticosterone plasma levels during the CF paradigm were measured by ELISA in a separate group of rats. Antenatal MS exposure altered functional brain responses to the fear conditioned cue in adult offspring. Rats with prior MS exposure compared to those without demonstrated heightened fear responsivity, exaggerated and prolonged corticosterone release, increased functional cerebral activation of limbic/paralimbic regions (amygdala, ventral hippocampus, insula, ventral striatum, nucleus acumbens), the locus coeruleus, and white matter, and deactivation of medial prefrontal cortical regions. Dysregulation of corticolimbic circuits may represent risk factors in the future development of anxiety disorders and associated alterations in emotional regulation. PMID:21300034

  10. Accelerated adhesion of grafted skin by laser-induced stress wave-based gene transfer of hepatocyte growth factor

    NASA Astrophysics Data System (ADS)

    Aizawa, Kazuya; Sato, Shunichi; Terakawa, Mitsuhiro; Saitoh, Daizoh; Tsuda, Hitoshi; Ashida, Hiroshi; Obara, Minoru

    2009-11-01

    Gene therapy using wound healing-associated growth factor gene has received much attention as a new strategy for improving the outcome of tissue transplantation. We delivered plasmid DNA coding for human hepatocyte growth factor (hHGF) to rat free skin grafts by the use of laser-induced stress waves (LISWs); autografting was performed with the grafts. Systematic analysis was conducted to evaluate the adhesion properties of the grafted tissue; angiogenesis, cell proliferation, and reepithelialization were assessed by immunohistochemistry, and reperfusion was measured by laser Doppler imaging as a function of time after grafting. Both the level of angiogenesis on day 3 after grafting and the increased ratio of blood flow on day 4 to that on day 3 were significantly higher than those in five control groups: grafting with hHGF gene injection alone, grafting with control plasmid vector injection alone, grafting with LISW application alone, grafting with LISW application after control plasmid vector injection, and normal grafting. Reepithelialization was almost completed on day 7 even at the center of the graft with LISW application after hHGF gene injection, while it was not for the grafts of the five control groups. These findings demonstrate the validity of our LISW-based HGF gene transfection to accelerate the adhesion of grafted skins.

  11. Prognostics of Power Mosfets Under Thermal Stress Accelerated Aging Using Data-Driven and Model-Based Methodologies

    NASA Technical Reports Server (NTRS)

    Celaya, Jose; Saxena, Abhinav; Saha, Sankalita; Goebel, Kai F.

    2011-01-01

    An approach for predicting remaining useful life of power MOSFETs (metal oxide field effect transistor) devices has been developed. Power MOSFETs are semiconductor switching devices that are instrumental in electronics equipment such as those used in operation and control of modern aircraft and spacecraft. The MOSFETs examined here were aged under thermal overstress in a controlled experiment and continuous performance degradation data were collected from the accelerated aging experiment. Dieattach degradation was determined to be the primary failure mode. The collected run-to-failure data were analyzed and it was revealed that ON-state resistance increased as die-attach degraded under high thermal stresses. Results from finite element simulation analysis support the observations from the experimental data. Data-driven and model based prognostics algorithms were investigated where ON-state resistance was used as the primary precursor of failure feature. A Gaussian process regression algorithm was explored as an example for a data-driven technique and an extended Kalman filter and a particle filter were used as examples for model-based techniques. Both methods were able to provide valid results. Prognostic performance metrics were employed to evaluate and compare the algorithms.

  12. Functional analysis of stress protein data in a flor yeast subjected to a biofilm forming condition

    PubMed Central

    Moreno-García, Jaime; Mauricio, Juan Carlos; Moreno, Juan; García-Martínez, Teresa

    2016-01-01

    In this data article, an OFFGEL fractionator coupled to LTQ Orbitrap XL MS equipment and a SGD filtering were used to detect in a biofilm-forming flor yeast strain, the maximum possible number of stress proteins under the first stage of a biofilm formation conditions (BFC) and under an initial stage of fermentation used as reference, so-called non-biofilm formation condition (NBFC). Protein functional analysis – based on cellular components and biological process GO terms – was performed for these proteins through the SGD Gene Ontology Slim Mapper tool. A detailed analysis and interpretation of the data can be found in “Stress responsive proteins of a flor yeast strain during the early stages of biofilm formation” [1]. PMID:27104213

  13. Functional analysis of stress protein data in a flor yeast subjected to a biofilm forming condition.

    PubMed

    Moreno-García, Jaime; Mauricio, Juan Carlos; Moreno, Juan; García-Martínez, Teresa

    2016-06-01

    In this data article, an OFFGEL fractionator coupled to LTQ Orbitrap XL MS equipment and a SGD filtering were used to detect in a biofilm-forming flor yeast strain, the maximum possible number of stress proteins under the first stage of a biofilm formation conditions (BFC) and under an initial stage of fermentation used as reference, so-called non-biofilm formation condition (NBFC). Protein functional analysis - based on cellular components and biological process GO terms - was performed for these proteins through the SGD Gene Ontology Slim Mapper tool. A detailed analysis and interpretation of the data can be found in "Stress responsive proteins of a flor yeast strain during the early stages of biofilm formation" [1]. PMID:27104213

  14. RSS1 regulates the cell cycle and maintains meristematic activity under stress conditions in rice

    PubMed Central

    Ogawa, Daisuke; Abe, Kiyomi; Miyao, Akio; Kojima, Mikiko; Sakakibara, Hitoshi; Mizutani, Megumi; Morita, Haruka; Toda, Yosuke; Hobo, Tokunori; Sato, Yutaka; Hattori, Tsukaho; Hirochika, Hirohiko; Takeda, Shin

    2011-01-01

    Plant growth and development are sustained by continuous cell division in the meristems, which is perturbed by various environmental stresses. For the maintenance of meristematic functions, it is essential that cell division be coordinated with cell differentiation. However, it is unknown how the proliferative activities of the meristems and the coordination between cell division and differentiation are maintained under stressful conditions. Here we show that a rice protein, RSS1, whose stability is controlled by cell cycle phases, contributes to the vigour of meristematic cells and viability under salinity conditions. These effects of RSS1 are exerted by regulating the G1–S transition, possibly through an interaction of RSS1 with protein phosphatase 1, and are mediated by the phytohormone, cytokinin. RSS1 is conserved widely in plant lineages, except eudicots, suggesting that RSS1-dependent mechanisms might have been adopted in specific lineages during the evolutionary radiation of angiosperms. PMID:21505434

  15. Numerical Investigation of Thermal Stress Convention in Nonisothermal Gases Under Microgravity Conditions

    NASA Technical Reports Server (NTRS)

    Mackowski, D. W.

    1999-01-01

    Reported here are our results of our numerical/theoretical investigation into the effects of thermal stress in nonisothermal gases under microgravity conditions. The first part of the report consists of a brief summary of the accomplishments and conclusions of our work. The second part consists of two manuscripts, one being a paper presented at the 1998 MSAD Fluid Physics workshop, and the other to appear in Physics of Fluids.

  16. Influence of temper condition on the nonlinear stress-strain behavior of boron-aluminum

    NASA Technical Reports Server (NTRS)

    Kennedy, J. M.; Herakovich, E. T.; Tenney, D. R.

    1977-01-01

    The influence of temper condition on the tensile and compressive stress-strain behavior for six boron-aluminum laminates was investigated. In addition to monotonic tension and compression tests, tension-tension, compression-compression, and tension--compression tests were conducted to study the effects of cyclic loading. Tensile strength results are a function of the laminate configuration; unidirectional laminates were affected considerably more than other laminates with some strength values increasing and others decreasing.

  17. Frictional behavior and microstructures of calcite fault gouges deformed under extreme conditions of normal stress and sliding velocity

    NASA Astrophysics Data System (ADS)

    Smith, S. A.; Billi, A.; Spagnuolo, E.; Di Toro, G.; Nielsen, S. B.; Violay, M. E.

    2011-12-01

    In recent years several experimental studies have been performed using rotary-shear apparatus to investigate the frictional behavior of gouge materials at seismic slip rates. However, because of technical difficulties confining gouge layers, a majority of these experiments were conducted at normal stresses <2-3MPa, making extrapolation to natural conditions challenging. Here, we present results from an experimental study on calcite gouges (<250μm grain size) deformed in a purpose-built sample holder and using a rotary-shear apparatus at INGV, Rome. Ring-shaped (25/45mm int./ext. diameter), 2.8mm-thick layers of gouge were deformed up to 34MPa normal stress, at slip rates of 10μm/s - 3m/s, in both room-dry and water-present conditions. A peak slip rate of 3m/s was achieved after 0.5s, and total displacements were 1-3m. CO2 emissions were monitored using a mass spectrometer connected to a capillary tube positioned approximately 1cm from the gouge sample holder. Samples were preserved in ultra-low viscosity resin for optical and Field-Emission SEM observations. At slip rates >0.3m/s frictional strength, μ, increases to a peak value of 0.6-1.0 followed by a rapid decay to a lower steady-state value, μss, before finally undergoing dynamic strength recovery during decelerating slip. CO2 starts to be liberated almost instantaneously (within 500μm of slip) during acceleration and reaches a peak value during steady-state sliding of up to 10,000ppm, before decreasing to 380-420ppm within a few seconds following the experiment. μss decreases with increasing slip rate, but in contrast to previous experiments we find that extremely low values of μss<0.2 are only achieved at a slip rate of 1m/s for normal stresses >22MPa. An unexpected result is that steady-state shear stress at slip rates >1m/s does not increase monotonically (either linearly or not, e.g. in the presence of lubrication) with normal stress, but begins to decrease above a normal stress of 15-20MPa, a

  18. International perspectives on psychosocial working conditions, mental health, and stress of dairy farm operators.

    PubMed

    Lunner Kolstrup, Christina; Kallioniemi, Marja; Lundqvist, Peter; Kymäläinen, Hanna-Riitta; Stallones, Lorann; Brumby, Susan

    2013-01-01

    Dairy farm operators-farmers, workers, and family members-are faced with many demands and stressors in their daily work and these appear to be shared across countries and cultures. Dairy operators experience high psychosocial demands with respect to a hard work and production ethos, economic influences, and social and environmental responsibility. Furthermore, both traditional and industrial farms are highly dependent on external conditions, such as weather, fluctuating markets, and regulations from government authorities. Possible external stressors include disease outbreaks, taxes related to dairy production, and recent negative societal attitudes to farming in general. Dairy farm operators may have very few or no opportunities to influence and control these external conditions, demands, and expectations. High work demands and expectations coupled with low control and lack of social support can lead to a poor psychosocial work environment, with increased stress levels, ill mental health, depression, and, in the worst cases, suicide. Internationally, farmers with ill mental health have different health service options depending on their location. Regardless of location, it is initially the responsibility of the individual farmer and farm family to handle mental health and stress, which can be of short- or long-term duration. This paper reviews the literature on the topics of psychosocial working conditions, mental health, stress, depression, and suicide among dairy farm operators, farm workers, and farm family members in an international perspective. PMID:23844791

  19. Damage and Plastic Deformation Modeling of Beishan Granite Under Compressive Stress Conditions

    NASA Astrophysics Data System (ADS)

    Chen, L.; Wang, C. P.; Liu, J. F.; Liu, J.; Wang, J.; Jia, Y.; Shao, J. F.

    2015-07-01

    Based on experimental investigations, we propose a coupled elastoplastic damage model to simulate the mechanical behavior of granite under compressive stress conditions. The granite is taken from the Beishan area, a preferable region for China's high-level radioactive waste repository. Using a 3D acoustic emission monitoring system in mechanical tests, we focus on the cracking process and its influence on the macroscopic mechanical behavior of the granite samples. It is verified that the crack propagation coupled with fractional sliding along the cracks is the principal mechanism controlling the failure process and nonlinear mechanical behavior of granite under compressive stress conditions. Based on this understanding, the coupled elastoplastic damage model is formulated in the framework of the thermodynamics theory. In the model, the coupling between damage and plastic deformation is simulated by introducing the independent damage variable in the plastic yield surface. As a preliminary validation of the model, a series of numerical simulations are performed for compressive tests conducted under different confining pressures. Comparisons between the numerical and simulated results show that the proposed model can reproduce the main features of the mechanical behavior of Beishan granite, particularly the damage evolution under compressive stress conditions.

  20. A reliable preloaded cycling time trial for use in conditions of significant thermal stress.

    PubMed

    Che Jusoh, M R; Morton, R H; Stannard, S R; Mündel, T

    2015-06-01

    The purpose of this study was to assess the reliability of a 15-min time trial preloaded with 45 min of fixed-intensity cycling under laboratory conditions of thermal stress. Eight trained cyclists/triathletes (41 ± 10 years, VO2 peak: 69 ± 8 mL/kg/min, peak aerobic power: 391 ± 72 W) completed three trials (the first a familiarization) where they cycled at ∼ 55% VO2 peak for 45 min followed by a 15-min time trial (∼75% VO2 peak) under conditions of significant thermal stress (WBGT: 26.7 ± 0.8 °C, frontal convective airflow: 20 km/h). Seven days separated the trials, which were conducted at the same time of day following 24 h of exercise and dietary control. Reliability increased when a familiarization trial was performed, with the resulting coefficient of variation and intraclass correlation coefficient of the work completed during the 15-min time trial, 3.6% and 0.96, respectively. Therefore, these results demonstrate a high level of reliability for a 15-min cycling time trial following a 45-min preload when performed under laboratory conditions of significant thermal stress using trained cyclists/triathletes.

  1. Factors affecting stress assisted corrosion cracking of carbon steel under industrial boiler conditions

    NASA Astrophysics Data System (ADS)

    Yang, Dong

    Failure of carbon steel boiler tubes from waterside has been reported in the utility boilers and industrial boilers for a long time. In industrial boilers, most waterside tube cracks are found near heavy attachment welds on the outer surface and are typically blunt, with multiple bulbous features indicating a discontinuous growth. These types of tube failures are typically referred to as stress assisted corrosion (SAC). For recovery boilers in the pulp and paper industry, these failures are particularly important as any water leak inside the furnace can potentially lead to smelt-water explosion. Metal properties, environmental variables, and stress conditions are the major factors influencing SAC crack initation and propagation in carbon steel boiler tubes. Slow strain rate tests (SSRT) were conducted under boiler water conditions to study the effect of temperature, oxygen level, and stress conditions on crack initation and propagation on SA-210 carbon steel samples machined out of boiler tubes. Heat treatments were also performed to develop various grain size and carbon content on carbon steel samples, and SSRTs were conducted on these samples to examine the effect of microstructure features on SAC cracking. Mechanisms of SAC crack initation and propagation were proposed and validated based on interrupted slow strain tests (ISSRT). Water chemistry guidelines are provided to prevent SAC and fracture mechanics model is developed to predict SAC failure on industrial boiler tubes.

  2. Stress hormones are associated with the neuronal correlates of instructed fear conditioning.

    PubMed

    Merz, Christian Josef; Stark, Rudolf; Vaitl, Dieter; Tabbert, Katharina; Wolf, Oliver Tobias

    2013-01-01

    The effects of sex and stress hormones on classical fear conditioning have been subject of recent experimental studies. A correlation approach between basal cortisol concentrations and neuronal activation in fear-related structures seems to be a promising alternative approach in order to foster our understanding of how cortisol influences emotional learning. In this functional magnetic resonance imaging study, participants with varying sex hormone status (20 men, 15 women taking oral contraceptives, 15 women tested in the luteal phase) underwent an instructed fear conditioning protocol with geometrical figures as conditioned stimuli and an electrical stimulation as unconditioned stimulus. Salivary cortisol concentrations were measured and afterwards correlated with fear conditioned brain responses. Results revealed a positive correlation between basal cortisol levels and differential activation in the amygdala in men and OC women only. These results suggest that elevated endogenous cortisol levels are associated with enhanced fear anticipation depending on current sex hormone availability.

  3. Assessment of Initial Test Conditions for Experiments to Assess Irradiation Assisted Stress Corrosion Cracking Mechanisms

    SciTech Connect

    Busby, Jeremy T; Gussev, Maxim N

    2011-04-01

    Irradiation-assisted stress corrosion cracking is a key materials degradation issue in today s nuclear power reactor fleet and affects critical structural components within the reactor core. The effects of increased exposure to irradiation, stress, and/or coolant can substantially increase susceptibility to stress-corrosion cracking of austenitic steels in high-temperature water environments. . Despite 30 years of experience, the underlying mechanisms of IASCC are unknown. Extended service conditions will increase the exposure to irradiation, stress, and corrosive environment for all core internal components. The objective of this effort within the Light Water Reactor Sustainability program is to evaluate the response and mechanisms of IASCC in austenitic stainless steels with single variable experiments. A series of high-value irradiated specimens has been acquired from the past international research programs, providing a valuable opportunity to examine the mechanisms of IASCC. This batch of irradiated specimens has been received and inventoried. In addition, visual examination and sample cleaning has been completed. Microhardness testing has been performed on these specimens. All samples show evidence of hardening, as expected, although the degree of hardening has saturated and no trend with dose is observed. Further, the change in hardening can be converted to changes in mechanical properties. The calculated yield stress is consistent with previous data from light water reactor conditions. In addition, some evidence of changes in deformation mode was identified via examination of the microhardness indents. This analysis may provide further insights into the deformation mode under larger scale tests. Finally, swelling analysis was performed using immersion density methods. Most alloys showed some evidence of swelling, consistent with the expected trends for this class of alloy. The Hf-doped alloy showed densification rather than swelling. This observation may be

  4. Reference gene selection for qRT-PCR in Caragana korshinskii Kom. under different stress conditions.

    PubMed

    Yang, Qi; Yin, Jiajia; Li, Gao; Qi, Liwang; Yang, Feiyun; Wang, Ruigang; Li, Guojing

    2014-01-01

    Caragana korshinskii Kom., which is widely distributed in the northwest China and Mongolia, is an important forage bush belonging to the legume family with high economic and ecological value. Strong tolerance ability to various stresses makes C. korshinskii Kom. a valuable species for plant stress research. In this study, suitable reference genes for quantitative real-time reverse transcription PCR (qRT-PCR) were screened from 11 candidate reference genes, including ACT, GAPDH, EF1α, UBQ, TUA, CAP, TUB, TUB3, SKIP1, SKIP5-1 and SKIP5-2. A total of 129 samples under drought, heat, cold, salt, ABA and high pH treatment were profiled, and software such as geNORM, NormFinder and BestKeeper were used for reference gene evaluation and selection. Different suitable reference genes were selected under different stresses. Across all 129 samples, GAPDH, EF1α and SKIP5-1 were found to be the most stable reference genes, and EF1α+SKIP5-1 is the most stable reference gene combination. Conversely, TUA, TUB and SKIP1 were not suitable for using as reference genes owing to their great expression variation under some stress conditions. The relative expression levels of CkWRKY1 were detected using the stable and unstable reference genes and their applicability was confirmed. These results provide some stable reference genes and reference gene combinations for qRT-PCR under different stresses in C. korshinskii Kom. for future research work, and indicate that CkWRKY1 plays essential roles in response to stresses in C. korshinskii.

  5. Herbal Supplement Extends Life Span Under Some Environmental Conditions and Boosts Stress Resistance

    PubMed Central

    Villeponteau, Bryant; Matsagas, Kennedy; Nobles, Amber C.; Rizza, Cristina; Horwitz, Marc; Benford, Gregory; Mockett, Robin J.

    2015-01-01

    Genetic studies indicate that aging is modulated by a great number of genetic pathways. We have used Drosophila longevity and stress assays to test a multipath intervention strategy. To carry out this strategy, we supplemented the flies with herbal extracts (SC100) that are predicted to modulate the expression of many genes involved in aging and stress resistance, such as mTOR, NOS, NF-KappaB, and VEGF. When flies were housed in large cages with SC100 added, daily mortality rates of both male and female flies were greatly diminished in mid to late life. Surprisingly, SC100 also stabilized midlife mortality rate increases so as to extend the maximum life span substantially beyond the limits previously reported for D. melanogaster. Under these conditions, SC100 also promoted robust resistance to partial starvation stress and to heat stress. Fertility was the same initially in both treated and control flies, but it became significantly higher in treated flies at older ages as the fertility of control flies declined. Mean and maximum life spans of flies in vials at the same test site were also extended by SC100, but the life spans were short in absolute terms. In contrast, at an independent test site where stress was minimized, the flies exhibited much longer mean life spans, but the survival curves became highly rectangular and the effects of SC100 on both mean and maximum life spans declined greatly or were abolished. The data indicate that SC100 is a novel herbal mix with striking effects on enhancing Drosophila stress resistance and life span in some environments, while minimizing mid to late life mortality rates. They also show that the environment and other factors can have transformative effects on both the length and distribution of survivorship, and on the ability of SC100 to extend the life span. PMID:25879540

  6. Deficiency in the mitochondrial apoptotic pathway reveals the toxic potential of autophagy under ER stress conditions

    PubMed Central

    Deegan, Shane; Saveljeva, Svetlana; Logue, Susan E; Pakos-Zebrucka, Karolina; Gupta, Sanjeev; Vandenabeele, Peter; Bertrand, Mathieu JM; Samali, Afshin

    2014-01-01

    Endoplasmic reticulum (ER) stress-induced cell death is normally associated with activation of the mitochondrial apoptotic pathway, which is characterized by CYCS (cytochrome c, somatic) release, apoptosome formation, and caspase activation, resulting in cell death. In this study, we demonstrate that under conditions of ER stress cells devoid of CASP9/caspase-9 or BAX and BAK1, and therefore defective in the mitochondrial apoptotic pathway, still undergo a delayed form of cell death associated with the activation of caspases, therefore revealing the existence of an alternative stress-induced caspase activation pathway. We identified CASP8/caspase-8 as the apical protease in this caspase cascade, and found that knockdown of either of the key autophagic genes, ATG5 or ATG7, impacted on CASP8 activation and cell death induction, highlighting the crucial role of autophagy in the activation of this novel ER stress-induced death pathway. In line with this, we identified a protein complex composed of ATG5, FADD, and pro-CASP8 whose assembly coincides with caspase activation and cell death induction. Together, our results reveal the toxic potential of autophagy in cells undergoing ER stress that are defective in the mitochondrial apoptotic pathway, and suggest a model in which the autophagosome functions as a platform facilitating pro-CASP8 activation. Chemoresistance, a common problem in the treatment of cancer, is frequently caused by the downregulation of key mitochondrial death effector proteins. Alternate stress-induced apoptotic pathways, such as the one described here, may become of particular relevance for tackling the problem of chemoresistance in cancer cells. PMID:25470234

  7. Deficiency in the mitochondrial apoptotic pathway reveals the toxic potential of autophagy under ER stress conditions.

    PubMed

    Deegan, Shane; Saveljeva, Svetlana; Logue, Susan E; Pakos-Zebrucka, Karolina; Gupta, Sanjeev; Vandenabeele, Peter; Bertrand, Mathieu J M; Samali, Afshin

    2014-01-01

    Endoplasmic reticulum (ER) stress-induced cell death is normally associated with activation of the mitochondrial apoptotic pathway, which is characterized by CYCS (cytochrome c, somatic) release, apoptosome formation, and caspase activation, resulting in cell death. In this study, we demonstrate that under conditions of ER stress cells devoid of CASP9/caspase-9 or BAX and BAK1, and therefore defective in the mitochondrial apoptotic pathway, still undergo a delayed form of cell death associated with the activation of caspases, therefore revealing the existence of an alternative stress-induced caspase activation pathway. We identified CASP8/caspase-8 as the apical protease in this caspase cascade, and found that knockdown of either of the key autophagic genes, ATG5 or ATG7, impacted on CASP8 activation and cell death induction, highlighting the crucial role of autophagy in the activation of this novel ER stress-induced death pathway. In line with this, we identified a protein complex composed of ATG5, FADD, and pro-CASP8 whose assembly coincides with caspase activation and cell death induction. Together, our results reveal the toxic potential of autophagy in cells undergoing ER stress that are defective in the mitochondrial apoptotic pathway, and suggest a model in which the autophagosome functions as a platform facilitating pro-CASP8 activation. Chemoresistance, a common problem in the treatment of cancer, is frequently caused by the downregulation of key mitochondrial death effector proteins. Alternate stress-induced apoptotic pathways, such as the one described here, may become of particular relevance for tackling the problem of chemoresistance in cancer cells.

  8. Deficiency in the mitochondrial apoptotic pathway reveals the toxic potential of autophagy under ER stress conditions.

    PubMed

    Deegan, Shane; Saveljeva, Svetlana; Logue, Susan E; Pakos-Zebrucka, Karolina; Gupta, Sanjeev; Vandenabeele, Peter; Bertrand, Mathieu J M; Samali, Afshin

    2014-01-01

    Endoplasmic reticulum (ER) stress-induced cell death is normally associated with activation of the mitochondrial apoptotic pathway, which is characterized by CYCS (cytochrome c, somatic) release, apoptosome formation, and caspase activation, resulting in cell death. In this study, we demonstrate that under conditions of ER stress cells devoid of CASP9/caspase-9 or BAX and BAK1, and therefore defective in the mitochondrial apoptotic pathway, still undergo a delayed form of cell death associated with the activation of caspases, therefore revealing the existence of an alternative stress-induced caspase activation pathway. We identified CASP8/caspase-8 as the apical protease in this caspase cascade, and found that knockdown of either of the key autophagic genes, ATG5 or ATG7, impacted on CASP8 activation and cell death induction, highlighting the crucial role of autophagy in the activation of this novel ER stress-induced death pathway. In line with this, we identified a protein complex composed of ATG5, FADD, and pro-CASP8 whose assembly coincides with caspase activation and cell death induction. Together, our results reveal the toxic potential of autophagy in cells undergoing ER stress that are defective in the mitochondrial apoptotic pathway, and suggest a model in which the autophagosome functions as a platform facilitating pro-CASP8 activation. Chemoresistance, a common problem in the treatment of cancer, is frequently caused by the downregulation of key mitochondrial death effector proteins. Alternate stress-induced apoptotic pathways, such as the one described here, may become of particular relevance for tackling the problem of chemoresistance in cancer cells. PMID:25470234

  9. Early postnatal stress alters place conditioning to both mu- and kappa-opioid agonists.

    PubMed

    Michaels, Clifford C; Holtzman, Stephen G

    2008-04-01

    Clinical literature has established a link between early childhood incidents of neglect and trauma and adult problems with substance abuse. In rats, such early life stress has been modeled using a maternal separation (MS) paradigm in which rat pups were removed from their mothers for a few hours daily during the first two postnatal weeks. In this study, we used the MS model to investigate the effects of early postnatal stress on place conditioning to both mu- and kappa-opioid agonists in male and female Long-Evans rats. Offspring of both rearing conditions [MS or nonhandled (NH)] were conditioned using a biased procedure to saline, the mu-opioid agonist morphine (3.0, 5.6, and 10 mg/kg s.c.), or the kappa-opioid agonist spiradoline (0.3, 1.0, and 3.0 mg/kg) for 3 days, followed by a drug-free place-conditioning test 24 h later. Saline was administered in the morning, 30 min before confinement in one compartment, whereas morphine or spiradoline was administered in a similar manner 6 h later in the opposite compartment. MS offspring spent significantly more time in the morphine-paired compartment than NH offspring, indicating a greater place preference for the mu-opioid agonist. In the case of spiradoline, NH offspring spent significantly less time in the spiradoline-paired compartment, indicating a greater aversion to the kappa-opioid agonist in these animals than in MS offspring. These findings indicate that early postnatal stress can significantly alter the rewarding or aversive value of mu- and kappa-opioid agonists when measured using place conditioning. PMID:18203949

  10. Changes in seed water status as characterized by NMR in developing soybean seed grown under moisture stress conditions

    SciTech Connect

    Krishnan, P. Singh, Ravender; Verma, A.P.S.; Joshi, D.K.; Singh, Sheoraj

    2014-02-21

    Highlights: • In developing soybean seeds, moisture stress resulted in more proportion of water to bound state. • These changes are further corroborated by concomitant changes in seed metabolites. • Thus there exists a moisture stress and development stage dependence of seed tissue water status. - Abstract: Changes in water status of developing seeds of Soybean (Glycine max L. Merrill.) grown under different moisture stress conditions were characterized by proton nuclear magnetic resonance (NMR)- spin–spin relaxation time (T{sub 2}). A comparison of the seed development characteristics, composition and physical properties indicated that, characteristics like seed weight, seed number/ear, rate of seed filling increased with development stages but decreased with moisture stress conditions. The NMR- spin–spin relaxation (T{sub 2}) component like bound water increased with seed maturation (40–50%) but decreased with moisture stress conditions (30–40%). The changes in seed water status to increasing levels of moisture stress and seed maturity indicates that moisture stress resulted in more proportion of water to bound state and intermediate state and less proportion of water in free-state. These changes are further corroborated by significant changes in protein and starch contents in seeds under high moisture stress treatments. Thus seed water status during its development is not only affected by development processes but also by moisture stress conditions. This study strongly indicated a clear moisture stress and development stage dependence of seed tissue water status in developing soybean seeds.

  11. Inhibition of bacterial and leukocyte adhesion under shear stress conditions by material surface chemistry.

    PubMed

    Patel, Jasmine D; Ebert, Michael; Stokes, Ken; Ward, Robert; Anderson, James M

    2003-01-01

    Biomaterial-centered infections, initiated by bacterial adhesion, persist due to a compromised host immune response. Altering implant materials with surface modifying endgroups (SMEs) may enhance their biocompatibility by reducing bacterial and inflammatory cell adhesion. A rotating disc model, which generates shear stress within physiological ranges, was used to characterize adhesion of leukocytes and Staphylococcus epidermidis on polycarbonate-urethanes and polyetherurethanes modified with SMEs (polyethylene oxide, fluorocarbon and dimethylsiloxane) under dynamic flow conditions. Bacterial adhesion in the absence of serum was found to be mediated by shear stress and surface chemistry, with reduced adhesion exhibited on materials modified with polydimethylsiloxane and polyethylene oxide SMEs. In contrast, bacterial adhesion was enhanced on materials modified with fluorocarbon SMEs. In the presence of serum, bacterial adhesion was primarily neither material nor shear dependent. However, bacterial adhesion in serum was significantly reduced to < or = 10% compared to adhesion in serum-free media. Leukocyte adhesion in serum exhibited a shear dependency with increased adhesion occurring in regions exposed to lower shear-stress levels of < or = 7 dyne/cm2. Additionally, polydimethylsiloxane and polyethylene oxide SMEs reduced leukocyte adhesion on polyether-urethanes. In conclusion, these results suggest that surface chemistry and shear stress can mediate bacterial and cellular adhesion. Furthermore, materials modified with polyethylene oxide SMEs are capable of inhibiting bacterial adhesion, consequently minimizing the probability of biomaterial-centered infections.

  12. Development of a Fatigue Crack Growth Coupon for Highly Plastic Stress Conditions

    NASA Technical Reports Server (NTRS)

    Allen, Phillip A.; Aggarwal, Pravin K.; Swanson, Gregory R.

    2003-01-01

    This paper presents an analytical approach used to develop a novel fatigue crack growth coupon for a highly plastic 3-D stress field condition. The flight hardware investigated in this paper is a large separation bolt that fractures using pyrotechnics at the appointed time during the flight sequence. The separation bolt has a deep notch that produces a severe stress concentration and a large plastic zone when highly loaded. For this geometry, linear-elastic fracture mechanics (LEFM) techniques are not valid due to the large nonlinear stress field. Unfortunately, industry codes that are generally available for fracture mechanics analysis and fatigue crack growth (e.g. NASGRO (11) are limited to LEFM and are available for only a limited number of geometries. The results of LEFM based codes are questionable when used on geometries with significant plasticity. Therefore elastic-plastic fracture mechanics (EPFM) techniques using the finite element method (FEM) were used to analyze the bolt and test coupons. scale flight hardware is very costly in t e r n of assets, laboratory resources, and schedule. Therefore to alleviate some of these problems, a series of novel test coupons were developed to simulate the elastic-plastic stress field present in the bolt.

  13. Pharmacological models and approaches for pathophysiological conditions associated with hypoxia and oxidative stress.

    PubMed

    Farías, Jorge G; Herrera, Emilio A; Carrasco-Pozo, Catalina; Sotomayor-Zárate, Ramón; Cruz, Gonzalo; Morales, Paola; Castillo, Rodrigo L

    2016-02-01

    Hypoxia is the failure of oxygenation at the tissue level, where the reduced oxygen delivered is not enough to satisfy tissue demands. Metabolic depression is the physiological adaptation associated with reduced oxygen consumption, which evidently does not cause any harm to organs that are exposed to acute and short hypoxic insults. Oxidative stress (OS) refers to the imbalance between the generation of reactive oxygen species (ROS) and the ability of endogenous antioxidant systems to scavenge ROS, where ROS overwhelms the antioxidant capacity. Oxidative stress plays a crucial role in the pathogenesis of diseases related to hypoxia during intrauterine development and postnatal life. Thus, excessive ROS are implicated in the irreversible damage to cell membranes, DNA, and other cellular structures by oxidizing lipids, proteins, and nucleic acids. Here, we describe several pathophysiological conditions and in vivo and ex vivo models developed for the study of hypoxic and oxidative stress injury. We reviewed existing literature on the responses to hypoxia and oxidative stress of the cardiovascular, renal, reproductive, and central nervous systems, and discussed paradigms of chronic and intermittent hypobaric hypoxia. This systematic review is a critical analysis of the advantages in the application of some experimental strategies and their contributions leading to novel pharmacological therapies.

  14. Pharmacological models and approaches for pathophysiological conditions associated with hypoxia and oxidative stress.

    PubMed

    Farías, Jorge G; Herrera, Emilio A; Carrasco-Pozo, Catalina; Sotomayor-Zárate, Ramón; Cruz, Gonzalo; Morales, Paola; Castillo, Rodrigo L

    2016-02-01

    Hypoxia is the failure of oxygenation at the tissue level, where the reduced oxygen delivered is not enough to satisfy tissue demands. Metabolic depression is the physiological adaptation associated with reduced oxygen consumption, which evidently does not cause any harm to organs that are exposed to acute and short hypoxic insults. Oxidative stress (OS) refers to the imbalance between the generation of reactive oxygen species (ROS) and the ability of endogenous antioxidant systems to scavenge ROS, where ROS overwhelms the antioxidant capacity. Oxidative stress plays a crucial role in the pathogenesis of diseases related to hypoxia during intrauterine development and postnatal life. Thus, excessive ROS are implicated in the irreversible damage to cell membranes, DNA, and other cellular structures by oxidizing lipids, proteins, and nucleic acids. Here, we describe several pathophysiological conditions and in vivo and ex vivo models developed for the study of hypoxic and oxidative stress injury. We reviewed existing literature on the responses to hypoxia and oxidative stress of the cardiovascular, renal, reproductive, and central nervous systems, and discussed paradigms of chronic and intermittent hypobaric hypoxia. This systematic review is a critical analysis of the advantages in the application of some experimental strategies and their contributions leading to novel pharmacological therapies. PMID:26617218

  15. Responses to rotating linear acceleration vectors considered in relation to a model of the otolith organs. [human oculomotor response to transverse acceleration stress

    NASA Technical Reports Server (NTRS)

    Benson, A. J.; Barnes, G. R.

    1973-01-01

    Human subjects were exposed to a linear acceleration vector that rotated in the transverse plane of the skull without angular counterrotation. Lateral eye movements showed a sinusoidal change in slow phase velocity and an asymmetry or bias in the same direction as vector rotation. A model is developed that attributes the oculomotor response to otolithic mechanisms. It is suggested that the bias component is the manifestation of torsion of the statoconial plaque relative to the base of the utricular macula and that the sinusoidal component represents the translational oscillation of the statoconia. The model subsumes a hypothetical neural mechanism which allows x- and y-axis accelerations to be resolved. Derivation of equations of motion for the statoconial plaque in torsion and translation, which take into account forces acting in shear and normal to the macula, yield estimates of bias and sinusoidal components that are in qualitative agreement with the diverse experimental findings.

  16. Determination of internal controls for quantitative gene expression of Isochrysis zhangjiangensis at nitrogen stress condition

    NASA Astrophysics Data System (ADS)

    Wu, Shuang; Zhou, Jiannan; Cao, Xupeng; Xue, Song

    2016-02-01

    Isochrysis zhangjiangensis is a potential marine microalga for biodiesel production, which accumulates lipid under nitrogen limitation conditions, but the mechanism on molecular level is veiled. Quantitative real-time polymerase chain reaction (qPCR) provides the possibility to investigate the gene expression levels, and a valid reference for data normalization is an essential prerequisite for firing up the analysis. In this study, five housekeeping genes, actin (ACT), α-tubulin (TUA), ß-tubulin (TUB), ubiquitin (UBI), 18S rRNA (18S) and one target gene, diacylglycerol acyltransferase (DGAT), were used for determining the reference. By analyzing the stabilities based on calculation of the stability index and on operating the two types of software, geNorm and bestkeeper, it showed that the reference genes widely used in higher plant and microalgae, such as UBI, TUA and 18S, were not the most stable ones in nitrogen-stressed I. zhangjiangensis, and thus are not suitable for exploring the mRNA expression levels under these experimental conditions. Our results show that ACT together with TUB is the most feasible internal control for investigating gene expression under nitrogen-stressed conditions. Our findings will contribute not only to future qPCR studies of I. zhangjiangensis, but also to verification of comparative transcriptomics studies of the microalgae under similar conditions.

  17. Numerical Simulation of Rock Fracturing under Laboratory True-Triaxial Stress Conditions

    NASA Astrophysics Data System (ADS)

    Ghofrani Tabari, Mehdi; Hazzard, Jim; Young, R. Paul

    2016-04-01

    simulated at the final stages of the experiment at higher effective stresses where an M-shaped form of through-going fractures was developed and their spatial orientations and angles were measured under various polyaxial loading conditions. This study enhances our understanding about the nature of initiation and propagation of fractures under true-triaxial stress states.

  18. Stress of Kindergarten teachers: How we tried to detect and to reduce it by using a small and wearable ECG and acceleration measuring device?

    PubMed

    Shirouzu, Shigenori; Seno, Yumeka; Tobioka, Ken; Masaki, Takeo; Yasumatsu, Kiyotaka; Mishima, Norio; Sugano, Hisanobu

    2015-01-01

    In 2014 school year, four female teachers of Nazareth Kindergarten decided to resign (DRT) due to workplace stress caused by human relationships between themselves. Our preliminary interview investigation revealed there was a stressor (STR), a certain elder female teacher and her less polite words and attitude. Using small and wearable ECG and acceleration measuring device, we measured 24 hour's autonomic nervous system's activity (ASNA) and sleep behavior of the STR and surrounding teachers, and tried to evaluate their stress objectively and to understand the reason of STR's less polite behaviors. For comparison, we also measured female Mind-Body Medicine (MBM) patients suffering adjustment disorder and clinical depression. PMID:26737766

  19. Cell Wall Amine Oxidases: New Players in Root Xylem Differentiation under Stress Conditions.

    PubMed

    Ghuge, Sandip A; Tisi, Alessandra; Carucci, Andrea; Rodrigues-Pousada, Renato A; Franchi, Stefano; Tavladoraki, Paraskevi; Angelini, Riccardo; Cona, Alessandra

    2015-01-01

    Polyamines (PAs) are aliphatic polycations present in all living organisms. A growing body of evidence reveals their involvement as regulators in a variety of physiological and pathological events. They are oxidatively deaminated by amine oxidases (AOs), including copper amine oxidases (CuAOs) and flavin adenine dinucleotide (FAD)-dependent polyamine oxidases (PAOs). The biologically-active hydrogen peroxide (H₂O₂) is a shared compound in all of the AO-catalyzed reactions, and it has been reported to play important roles in PA-mediated developmental and stress-induced processes. In particular, the AO-driven H₂O₂ biosynthesis in the cell wall is well known to be involved in plant wound healing and pathogen attack responses by both triggering peroxidase-mediated wall-stiffening events and signaling modulation of defense gene expression. Extensive investigation by a variety of methodological approaches revealed high levels of expression of cell wall-localized AOs in root xylem tissues and vascular parenchyma of different plant species. Here, the recent progresses in understanding the role of cell wall-localized AOs as mediators of root xylem differentiation during development and/or under stress conditions are reviewed. A number of experimental pieces of evidence supports the involvement of apoplastic H₂O₂ derived from PA oxidation in xylem tissue maturation under stress-simulated conditions. PMID:27135338

  20. Statistical optimization of pigment production by Monascus sanguineus under stress condition.

    PubMed

    Dikshit, Rashmi; Tallapragada, Padmavathi

    2014-01-01

    Natural pigments are produced by the Monascus sp., which are used for coloring food substances. The intent of this study was to optimize the pigment yield and biomass produced from the unexplored Monascus sanguineus in submerged culture under stress conditions. For inducing thermal stress, the spores were incubated at various temperatures at higher ranges. For inducing osmotic stress, varied concentrations of NaCl, glycerol, and peptone were used. The medium components were optimized by response surface methodology (RSM). The combined effects of the four medium constituents mentioned were studied using a 2⁴ full factorial central composite design (CCD). The relationships between the predicted values and actual values, independent variable, and the response were calculated according to a second-order quadratic model. It was deduced that the variable with the leading effect was the linear effect of glycerol concentration. Furthermore, the quadratic effects of peptone and the interactive effects of temperature and glycerol were more noteworthy than other factors. The optimum values for the test variables in coded factors were found to be spores treated with 70°C for temperature, 0.25 M for glycerol, 0.51% (w/v) for peptone, and 1.25% (w/v) for NaCl, corresponding to a maximum red pigment yield of 55.67 color value units (CVU)/mL. With optimized conditions, the pigment yield was almost three times the yield observed with the control.

  1. Cyp11A1 canola plants under short time heat stress conditions.

    PubMed

    Sakhno, L O; Slyvets, M S; Kuchuk, M V

    2014-01-01

    In order to investigate the high temperature tolerance of spring canola plants (Brassica napus L.) constitutively expressing cyp11A1 gene which encodes bovine cytochrome P450(scc) the growth features were analyzed under short time heat stress (42 degrees C) in growth chamber. Earlier it was documented that results of the heat tolerance test positively correlated with improvement of high temperature resistance in field trial. Higher relative water content (by 13%) and superoxide dismutase (SOD) activity, lower electrolyte leakage (up 1.4-fold) and smaller increase in chlorophyll a and carotenoid contents in cyp11A1 canola leaves in comparison with wild-type plants under stress allowed to conclude cyp11A1 plants are more tolerant to high temperature than the control ones. We suppose that SOD activity increase which revealed in our transgenic canola in normal condition plays the defining role in the biochemical alterations in plant metabolism for the thermotolerance improvement. SOD activity increment could be caused by heterologous cytochrome P450(scc) activity which resulted in the superoxide radical formation. Cyp11A1 canola plants might be resistant to the other stress conditions of different origin.

  2. Distinct 5′ UTRs regulate XIAP expression under normal growth conditions and during cellular stress

    PubMed Central

    Riley, Alura; Jordan, Lindsay E.; Holcik, Martin

    2010-01-01

    X-chromosome linked inhibitor of apoptosis, XIAP, is cellular caspase inhibitor and a key regulator of apoptosis. We and others have previously shown that XIAP expression is regulated primarily at the level of protein synthesis; the 5′ untranslated region (UTR) of XIAP mRNA contains an Internal Ribosome Entry Site (IRES) that supports cap-independent expression of XIAP protein during conditions of pathophysiological stress, such as serum deprivation or gamma irradiation. Here, we show that XIAP is encoded by two distinct mRNAs that differ in their 5′ UTRs. We further show that the dominant, shorter, 5′ UTR promotes a basal level of XIAP expression under normal growth conditions. In contrast, the less abundant longer 5′ UTR contains an IRES and supports cap-independent translation during stress. Our data suggest that the combination of alternate regulatory regions and distinct translational initiation modes is critical in maintaining XIAP levels in response to cellular stress and may represent a general mechanism of cellular adaptation. PMID:20385593

  3. Association between oxidative stress and contextual fear conditioning in Carioca high- and low-conditioned freezing rats.

    PubMed

    Hassan, Waseem; Gomes, Vitor de Castro; Pinton, Simone; Batista Teixeira da Rocha, Joao; Landeira-Fernandez, J

    2013-05-28

    We recently reported two novel breeding lines of rats known as Carioca high-and low-conditioned freezing (CHF and CLF), based on defensive freezing responses to contextual cues previously associated with electric footshock. The anxiety-like profile of these animals from the 7th generation was tested in the elevated plus maze. The results indicated that CHF animals presented a significantly more "anxious" phenotype compared with CLF animals. Animals from the 12th generation were used to evaluate the oxidative stress status of the cortex, hippocampus, and cerebellum. Reactive oxidative species (ROS) were evaluated using 2,7-dichlorofluorescin diacetate (DCFH-DA; a sensor of reactive oxygen species [ROS]), and the levels of malondialdehyde (MDA), an early marker of lipid peroxidation, were assessed. The results indicated that free radical concentrations and MDA levels were significantly higher in all three brain structures in CHF rats compared with CLF rats. Our data also showed that the hippocampus had the highest reactive species and MDA concentrations compared with the cortex and cerebellum in CHF rats. Animals from the 16th generation were used to evaluate the antioxidant enzyme activity of catalase (CAT) and glutathione peroxidase (GPx) within these three brain structures. The results indicated that CAT activity was lower in the cortex and hippocampus in CHF rats compared with CLF rats. No significant difference was observed in the cerebellum. The enzymatic activity of GPx was significantly decreased in all three structures in CHF rats compared with CLF rats. The hippocampus exhibited the highest GPx activity compared with the other two brain structures. These findings suggest the involvement of a redox system in these two bidirectional lines, and the hippocampus might be one of the prime brain structures involved in this state of oxidative stress imbalance.

  4. Association between oxidative stress and contextual fear conditioning in Carioca high- and low-conditioned freezing rats.

    PubMed

    Hassan, Waseem; Gomes, Vitor de Castro; Pinton, Simone; Batista Teixeira da Rocha, Joao; Landeira-Fernandez, J

    2013-05-28

    We recently reported two novel breeding lines of rats known as Carioca high-and low-conditioned freezing (CHF and CLF), based on defensive freezing responses to contextual cues previously associated with electric footshock. The anxiety-like profile of these animals from the 7th generation was tested in the elevated plus maze. The results indicated that CHF animals presented a significantly more "anxious" phenotype compared with CLF animals. Animals from the 12th generation were used to evaluate the oxidative stress status of the cortex, hippocampus, and cerebellum. Reactive oxidative species (ROS) were evaluated using 2,7-dichlorofluorescin diacetate (DCFH-DA; a sensor of reactive oxygen species [ROS]), and the levels of malondialdehyde (MDA), an early marker of lipid peroxidation, were assessed. The results indicated that free radical concentrations and MDA levels were significantly higher in all three brain structures in CHF rats compared with CLF rats. Our data also showed that the hippocampus had the highest reactive species and MDA concentrations compared with the cortex and cerebellum in CHF rats. Animals from the 16th generation were used to evaluate the antioxidant enzyme activity of catalase (CAT) and glutathione peroxidase (GPx) within these three brain structures. The results indicated that CAT activity was lower in the cortex and hippocampus in CHF rats compared with CLF rats. No significant difference was observed in the cerebellum. The enzymatic activity of GPx was significantly decreased in all three structures in CHF rats compared with CLF rats. The hippocampus exhibited the highest GPx activity compared with the other two brain structures. These findings suggest the involvement of a redox system in these two bidirectional lines, and the hippocampus might be one of the prime brain structures involved in this state of oxidative stress imbalance. PMID:23566816

  5. Overexpression of AtGRDP2, a novel glycine-rich domain protein, accelerates plant growth and improves stress tolerance

    PubMed Central

    Ortega-Amaro, María A.; Rodríguez-Hernández, Aída A.; Rodríguez-Kessler, Margarita; Hernández-Lucero, Eloísa; Rosales-Mendoza, Sergio; Ibáñez-Salazar, Alejandro; Delgado-Sánchez, Pablo; Jiménez-Bremont, Juan F.

    2015-01-01

    Proteins with glycine-rich signatures have been reported in a wide variety of organisms including plants, mammalians, fungi, and bacteria. Plant glycine-rich protein genes exhibit developmental and tissue-specific expression patterns. Herein, we present the characterization of the AtGRDP2 gene using Arabidopsis null and knockdown mutants and, Arabidopsis and lettuce over-expression lines. AtGRDP2 encodes a short glycine-rich domain protein, containing a DUF1399 domain and a putative RNA recognition motif (RRM). AtGRDP2 transcript is mainly expressed in Arabidopsis floral organs, and its deregulation in Arabidopsis Atgrdp2 mutants and 35S::AtGRDP2 over-expression lines produces alterations in development. The 35S::AtGRDP2 over-expression lines grow faster than the WT, while the Atgrdp2 mutants have a delay in growth and development. The over-expression lines accumulate higher levels of indole-3-acetic acid and, have alterations in the expression pattern of ARF6, ARF8, and miR167 regulators of floral development and auxin signaling. Under salt stress conditions, 35S::AtGRDP2 over-expression lines displayed higher tolerance and increased expression of stress marker genes. Likewise, transgenic lettuce plants over-expressing the AtGRDP2 gene manifest increased growth rate and early flowering time. Our data reveal an important role for AtGRDP2 in Arabidopsis development and stress response, and suggest a connection between AtGRDP2 and auxin signaling. PMID:25653657

  6. Accelerated Resolution Therapy for treatment of pain secondary to symptoms of combat-related posttraumatic stress disorder

    PubMed Central

    Kip, Kevin E.; Rosenzweig, Laney; Hernandez, Diego F.; Shuman, Amy; Diamond, David M.; Girling, Sue Ann; Sullivan, Kelly L.; Wittenberg, Trudy; Witt, Ann M.; Lengacher, Cecile A.; Anderson, Brian; McMillan, Susan C.

    2014-01-01

    Background As many as 70% of veterans with chronic pain treated within the US Veterans Administration (VA) system may have posttraumatic stress disorder (PTSD), and conversely, up to 80% of those with PTSD may have pain. We describe pain experienced by US service members and veterans with symptoms of PTSD, and report on the effect of Accelerated Resolution Therapy (ART), a new, brief exposure-based therapy, on acute pain reduction secondary to treatment of symptoms of PTSD. Methods A randomized controlled trial of ART versus an attention control (AC) regimen was conducted among 45 US service members/veterans with symptoms of combat-related PTSD. Participants received a mean of 3.7 sessions of ART. Results Mean age was 41.0 + 12.4 years and 20% were female. Most veterans (93%) reported pain. The majority (78%) used descriptive terms indicative of neuropathic pain, with 29% reporting symptoms of a concussion or feeling dazed. Mean pre-/post-change on the Pain Outcomes Questionnaire (POQ) was −16.9±16.6 in the ART group versus −0.7±14.2 in the AC group (p=0.0006). Among POQ subscales, treatment effects with ART were reported for pain intensity (effect size = 1.81, p=0.006), pain-related impairment in mobility (effect size = 0.69, p=0.01), and negative affect (effect size = 1.01, p=0.001). Conclusions Veterans with symptoms of combat-related PTSD have a high prevalence of significant pain, including neuropathic pain. Brief treatment of symptoms of combat-related PTSD among veterans by use of ART appears to acutely reduce concomitant pain. PMID:24959325

  7. Brief Treatment of Symptoms of Post-Traumatic Stress Disorder (PTSD) by Use of Accelerated Resolution Therapy (ART(®)).

    PubMed

    Kip, Kevin E; Elk, Carrie A; Sullivan, Kelly L; Kadel, Rajendra; Lengacher, Cecile A; Long, Christopher J; Rosenzweig, Laney; Shuman, Amy; Hernandez, Diego F; Street, Jennifer D; Girling, Sue Ann; Diamond, David M

    2012-06-01

    Post-Traumatic Stress Disorder (PTSD) is a prevalent, disabling anxiety disorder. This prospective cohort study reports on a new exposure-based therapy known as Accelerated Resolution Therapy (ART(®)) that incorporates the use of eye movements administered in a brief treatment period (1-5 one-hour sessions within three weeks). Eighty adults aged 21-60 years with symptoms of PTSD were recruited from the Tampa Bay area. The ART-based psychotherapy was designed to minimize anxiety and body sensations associated with recall of traumatic memories and to replace distressing images with favorable ones. Participants' mean age was 40 years, 77% were female, and 29% were Hispanic. Participants underwent a median of three ART sessions, 66 of 80 (82.5%) completed treatment, and 54 of 66 (81.8%) provided 2-month follow-up data. Mean scores pre- and post-ART and at 2-month follow-up were: PTSD Checklist: 54.5 ± 12.2 vs. 31.2 ± 11.4 vs. 30.0 ± 12.4; Brief Symptom Inventory: 30.8 ± 14.6 vs. 10.1 ± 10.8 vs. 10.1 ± 12.1; Center for Epidemiologic Studies Depression Scale: 29.5 ± 10.9 vs. 11.8 ± 11.1 vs. 13.5 ± 12.1; Trauma Related Growth Inventory-Distress scale: 18.9 ± 4.1 vs. 7.4 ± 5.9 vs. 8.2 ± 5.9 (p < 0.0001 for all pre-ART vs. post-ART and 2-month comparisons). No serious adverse events were reported. ART appears to be a brief, safe, and effective treatment for symptoms of PTSD.

  8. Transglutaminase type 2-dependent selective recruitment of proteins into exosomes under stressful cellular conditions.

    PubMed

    Diaz-Hidalgo, Laura; Altuntas, Sara; Rossin, Federica; D'Eletto, Manuela; Marsella, Claudia; Farrace, Maria Grazia; Falasca, Laura; Antonioli, Manuela; Fimia, Gian Maria; Piacentini, Mauro

    2016-08-01

    Numerous studies are revealing a role of exosomes in intercellular communication, and growing evidence indicates an important function for these vesicles in the progression and pathogenesis of cancer and neurodegenerative diseases. However, the biogenesis process of exosomes is still unclear. Tissue transglutaminase (TG2) is a multifunctional enzyme with different subcellular localizations. Particularly, under stressful conditions, the enzyme has been also detected in the extracellular matrix, but the mechanism(s) by which TG2 is released outside the cells requires further investigation. Therefore, the goal of the present study was to determine whether exosomes might be a vehicle for TG2 to reach the extracellular space, and whether TG2 could be involved in exosomes biogenesis. To address this issue, we isolated and characterized exosomes derived from cells either expressing or not TG2, under stressful conditions (i.e. proteasome impairment or expressing a mutated form of huntingtin (mHtt) containing 84 polyglutamine repeats). Our results show that TG2 is present in the exosomes only upon proteasome blockade, a condition in which TG2 interacts with TSG101 and ALIX, two key proteins involved in exosome biogenesis. Interestingly, we found that TG2 favours the assembly of a protein complex including mHtt, ALIX, TSG101 and BAG3, a co-chaperone involved in the clearance of mHtt. The formation of this complex is paralleled by the selective recruitment of mHtt and BAG3 in the exosomes derived from TG2 proficient cells only. Overall, our data indicate that TG2 is an important player in the biogenesis of exosomes controlling the selectivity of their cargo under stressful cellular conditions. In addition, these vesicles represent the way by which cells can release TG2 into the extracellular space under proteostasis impairment.

  9. Development of stress boundary conditions in smoothed particle hydrodynamics (SPH) for the modeling of solids deformation

    NASA Astrophysics Data System (ADS)

    Douillet-Grellier, Thomas; Pramanik, Ranjan; Pan, Kai; Albaiz, Abdulaziz; Jones, Bruce D.; Williams, John R.

    2016-10-01

    This paper develops a method for imposing stress boundary conditions in smoothed particle hydrodynamics (SPH) with and without the need for dummy particles. SPH has been used for simulating phenomena in a number of fields, such as astrophysics and fluid mechanics. More recently, the method has gained traction as a technique for simulation of deformation and fracture in solids, where the meshless property of SPH can be leveraged to represent arbitrary crack paths. Despite this interest, application of boundary conditions within the SPH framework is typically limited to imposed velocity or displacement using fictitious dummy particles to compensate for the lack of particles beyond the boundary interface. While this is enough for a large variety of problems, especially in the case of fluid flow, for problems in solid mechanics there is a clear need to impose stresses upon boundaries. In addition to this, the use of dummy particles to impose a boundary condition is not always suitable or even feasibly, especially for those problems which include internal boundaries. In order to overcome these difficulties, this paper first presents an improved method for applying stress boundary conditions in SPH with dummy particles. This is then followed by a proposal of a formulation which does not require dummy particles. These techniques are then validated against analytical solutions to two common problems in rock mechanics, the Brazilian test and the penny-shaped crack problem both in 2D and 3D. This study highlights the fact that SPH offers a good level of accuracy to solve these problems and that results are reliable. This validation work serves as a foundation for addressing more complex problems involving plasticity and fracture propagation.

  10. Transglutaminase type 2-dependent selective recruitment of proteins into exosomes under stressful cellular conditions.

    PubMed

    Diaz-Hidalgo, Laura; Altuntas, Sara; Rossin, Federica; D'Eletto, Manuela; Marsella, Claudia; Farrace, Maria Grazia; Falasca, Laura; Antonioli, Manuela; Fimia, Gian Maria; Piacentini, Mauro

    2016-08-01

    Numerous studies are revealing a role of exosomes in intercellular communication, and growing evidence indicates an important function for these vesicles in the progression and pathogenesis of cancer and neurodegenerative diseases. However, the biogenesis process of exosomes is still unclear. Tissue transglutaminase (TG2) is a multifunctional enzyme with different subcellular localizations. Particularly, under stressful conditions, the enzyme has been also detected in the extracellular matrix, but the mechanism(s) by which TG2 is released outside the cells requires further investigation. Therefore, the goal of the present study was to determine whether exosomes might be a vehicle for TG2 to reach the extracellular space, and whether TG2 could be involved in exosomes biogenesis. To address this issue, we isolated and characterized exosomes derived from cells either expressing or not TG2, under stressful conditions (i.e. proteasome impairment or expressing a mutated form of huntingtin (mHtt) containing 84 polyglutamine repeats). Our results show that TG2 is present in the exosomes only upon proteasome blockade, a condition in which TG2 interacts with TSG101 and ALIX, two key proteins involved in exosome biogenesis. Interestingly, we found that TG2 favours the assembly of a protein complex including mHtt, ALIX, TSG101 and BAG3, a co-chaperone involved in the clearance of mHtt. The formation of this complex is paralleled by the selective recruitment of mHtt and BAG3 in the exosomes derived from TG2 proficient cells only. Overall, our data indicate that TG2 is an important player in the biogenesis of exosomes controlling the selectivity of their cargo under stressful cellular conditions. In addition, these vesicles represent the way by which cells can release TG2 into the extracellular space under proteostasis impairment. PMID:27169926

  11. Influence of Bacillus spp. strains on seedling growth and physiological parameters of sorghum under moisture stress conditions.

    PubMed

    Grover, Minakshi; Madhubala, R; Ali, Sk Z; Yadav, S K; Venkateswarlu, B

    2014-09-01

    Microorganisms isolated from stressed ecosystem may prove as ideal candidates for development of bio-inoculants for stressed agricultural production systems. In the present study, moisture stress tolerant rhizobacteria were isolated from the rhizosphere of sorghum, pigeonpea, and cowpea grown under semiarid conditions in India. Four isolates KB122, KB129, KB133, and KB142 from sorghum rhizosphere exhibited plant growth promoting traits and tolerance to salinity, high temperature, and moisture stress. These isolates were identified as Bacillus spp. by 16S rDNA sequence analysis. The strains were evaluated for growth promotion of sorghum seedlings under two different moisture stress conditions (set-I, continuous 50% soil water holding capacity (WHC) throughout the experiment and set-II, 75% soil WHC for 27 days followed by no irrigation for 5 days) under greenhouse conditions. Plate count and scanning electron microscope studies indicated successful root surface colonization by inoculated bacteria. Plants inoculated with Bacillus spp. strains showed better growth in terms of shoot length and root biomass with dark greenish leaves due to high chlorophyll content while un-inoculated plants showed rolling of the leaves, stunted appearance, and wilting under both stress conditions. Inoculation also improved leaf relative water content and soil moisture content. However, variation in proline and sugar content in the different treatments under two stress conditions indicated differential effect of microbial treatments on plant physiological parameters under stress conditions.

  12. Reduced amygdala responsivity during conditioning to trauma-related stimuli in posttraumatic stress disorder.

    PubMed

    Diener, Slawomira J; Nees, Frauke; Wessa, Michèle; Wirtz, Gustav; Frommberger, Ulrich; Penga, Tina; Ruttorf, Michaela; Ruf, Matthias; Schmahl, Christian; Flor, Herta

    2016-10-01

    Exaggerated conditioned fear responses and impaired extinction along with amygdala overactivation have been observed in posttraumatic stress disorder (PTSD). These fear responses might be triggered by cues related to the trauma through higher-order conditioning, where reminders of the trauma may serve as unconditioned stimuli (US) and could maintain the fear response. We compared arousal, valence, and US expectancy ratings and BOLD brain responses using fMRI in 14 traumatized persons with PTSD and 14 without PTSD (NPTSD) and 13 matched healthy controls (HC) in a differential aversive conditioning paradigm. The US were trauma-specific pictures for the PTSD and NPTSD group and equally aversive and arousing for the HC; the conditioned stimuli (CS) were graphic displays. During conditioning, the PTSD patients compared to the NPTSD and HC indicated higher arousal to the conditioned stimulus that was paired with the trauma picture (CS+) compared to the unpaired (CS-), increased dissociation during acquisition and extinction, and failure to extinguish the CS/US-association compared to NPTSD. During early and late acquisition, the PTSD patients showed a significantly lower amygdala activation to CS+ versus CS- and a negative interaction between activation in the amygdala and dorsolateral prefrontal cortex (PFC), while NPTSD and HC displayed a negative interaction between amygdala and medial PFC. These findings suggest maladaptive anticipatory coping with trauma-related stimuli in patients with PTSD, indicated by enhanced conditioning, with related abnormal amygdala reactivity and connectivity, and delayed extinction. PMID:27412783

  13. Thermal signature of fear conditioning in mild post traumatic stress disorder.

    PubMed

    Di Giacinto, A; Brunetti, M; Sepede, G; Ferretti, A; Merla, A

    2014-04-25

    Fear conditioning has been proposed as an important factor involved in the etiology of posttraumatic stress disorder (PTSD). We examined fear processing in PTSD patients with mild symptoms and in individuals who did not develop symptoms (both groups consisting of victims of a bank robbery), through the study of fear-conditioned response. Conditioned responses were quantified by the skin conductance response (SCR) and the facial thermal response, the latter being measured by high-resolution functional thermal infrared (fIR) imaging. We found: (a) a change of the physiological parameters with respect to the baseline condition in both control subjects and PTSD patients during the conditioning phase; (b) the permanence of the conditioning effect in the maintenance phase in both control and PTSD patients; (c) patients and controls did differ for the variation across the phases of the physiological parameters rather than for their absolute values, showing that PTSD patients had a prolonged excitation and higher tonic component of autonomic activity. These results, although preliminary, indicate that the analysis of SCR and facial thermal response during the conditioning paradigm is a promising psychometric method of investigation, even in the case of low level of PTSD symptom severity. To the best of our knowledge, this study is the first attempt to discriminate between control subjects and PTSD patients with mild symptoms through infrared thermal imaging. It may suggest feasible approaches for diagnostic screening in the early phases of the disorder and in the assessment of preventive measures and therapies. PMID:24561216

  14. A Statistical Perspective on Highly Accelerated Testing.

    SciTech Connect

    Thomas, Edward V.

    2015-02-01

    Highly accelerated life testing has been heavily promoted at Sandia (and elsewhere) as a means to rapidly identify product weaknesses caused by flaws in the product's design or manufacturing process. During product development, a small number of units are forced to fail at high stress. The failed units are then examined to determine the root causes of failure. The identification of the root causes of product failures exposed by highly accelerated life testing can instigate changes to the product's design and/or manufacturing process that result in a product with increased reliability. It is widely viewed that this qualitative use of highly accelerated life testing (often associated with the acronym HALT) can be useful. However, highly accelerated life testing has also been proposed as a quantitative means for "demonstrating" the reliability of a product where unreliability is associated with loss of margin via an identified and dominating failure mechanism. It is assumed that the dominant failure mechanism can be accelerated by changing the level of a stress factor that is assumed to be related to the dominant failure mode. In extreme cases, a minimal number of units (often from a pre-production lot) are subjected to a single highly accelerated stress relative to normal use. If no (or, sufficiently few) units fail at this high stress level, some might claim that a certain level of reliability has been demonstrated (relative to normal use conditions). Underlying this claim are assumptions regarding the level of knowledge associated with the relationship between the stress level and the probability of failure. The primary purpose of this document is to discuss (from a statistical perspective) the efficacy of using accelerated life testing protocols (and, in particular, "highly accelerated" protocols) to make quantitative inferences concerning the performance of a product (e.g., reliability) when in fact there is lack-of-knowledge and uncertainty concerning the

  15. Inhibition of anandamide hydrolysis dampens the neuroendocrine response to stress in neonatal rats subjected to suboptimal rearing conditions.

    PubMed

    McLaughlin, Ryan Joseph; Verlezza, Silvanna; Gray, Jennifer Megan; Hill, Matthew Nicholas; Walker, Claire-Dominique

    2016-01-01

    Exposure to stress during early development can exert profound effects on the maturation of the neuroendocrine stress axis. The endocannabinoid (ECB) system has recently surfaced as a fundamental component of the neuroendocrine stress response; however, the effect of early-life stress on neonatal ECB signaling and the capacity to which ECB enhancement may modulate neonatal stress responses is relatively unknown. The present study assessed whether exposure to early-life stress in the form of limited access to nesting/bedding material (LB) from postnatal (PND) day 2 to 9 alters neuroendocrine activity and hypothalamic ECB content in neonatal rats challenged with a novel immobilization stressor. Furthermore, we examined whether inhibition of fatty acid amide hydrolase (FAAH), the enzyme responsible for the degradation of anandamide (AEA) affects neuroendocrine responses in PND10 pups as a function of rearing conditions. Neonatal rats showed a robust increase in corticosterone (CORT) and adrenocorticotropin hormone (ACTH) secretion in response to immobilization stress, which was significantly blunted in pups reared in LB conditions. Accordingly, LB pups exhibited reduced stress-induced Fos immunoreactivity in the paraventricular nucleus of the hypothalamus, with no significant differences in hypothalamic ECB content. Administration of the FAAH inhibitor URB597 (0.3 mg/kg, ip) 90 min prior to immobilization stress significantly dampened stress-induced CORT release, but only in pups reared in LB conditions. These results suggest that rearing in restricted bedding conditions dampens the neuroendocrine response to stress, while augmenting AEA mitigates stress-induced alterations in glucocorticoid secretion preferentially in pups subjected to early-life stress.

  16. The effects of acute stress exposure on striatal activity during Pavlovian conditioning with monetary gains and losses.

    PubMed

    Lewis, Andrea H; Porcelli, Anthony J; Delgado, Mauricio R

    2014-01-01

    Pavlovian conditioning involves the association of an inherently neutral stimulus with an appetitive or aversive outcome, such that the neutral stimulus itself acquires reinforcing properties. Across species, this type of learning has been shown to involve subcortical brain regions such as the striatum and the amygdala. It is less clear, however, how the neural circuitry involved in the acquisition of Pavlovian contingencies in humans, particularly in the striatum, is affected by acute stress. In the current study, we investigate the effect of acute stress exposure on Pavlovian conditioning using monetary reinforcers. Participants underwent a partial reinforcement conditioning procedure in which neutral stimuli were paired with high and low magnitude monetary gains and losses. A between-subjects design was used, such that half of the participants were exposed to cold stress while the remaining participants were exposed to a no stress control procedure. Cortisol measurements and subjective ratings were used as measures of stress. We observed an interaction between stress, valence, and magnitude in the ventral striatum, with the peak in the putamen. More specifically, the stress group exhibited an increased sensitivity to magnitude in the gain domain. This effect was driven by those participants who experienced a larger increase in circulating cortisol levels in response to the stress manipulation. Taken together, these results suggest that acute stress can lead to individual differences in circulating cortisol levels which influence the striatum during Pavlovian conditioning with monetary reinforcers.

  17. Cannabinoid modulation of chronic mild stress-induced selective enhancement of trace fear conditioning in adolescent rats.

    PubMed

    Reich, Christian G; Iskander, Anthony N; Weiss, Michael S

    2013-10-01

    History of stress is considered a major risk factor for the development of major depression and posttraumatic stress disorder (PTSD). Elucidating the neurobiological mechanisms of Pavlovian fear conditioning may provide insight into the etiology of PTSD. In the current study, adolescent male Sprague-Dawley rats were exposed to 3 weeks of a chronic-mild-unpredictable stress (CMS) protocol. Immediately following the CMS, the animals were subjected to hippocampal-dependent (trace and contextual) and hippocampal-independent (delay) fear conditioning. CMS exposure enhanced trace freezing behavior compared to non-stress controls. This effect was not observed in contextual or delay conditioned animals. Given that the endocannabinoid system is negatively affected by CMS procedures, separate groups of stressed rats were administered the CB1 receptor agonist, ACEA (0.1 mg/kg), prior to trace fear conditioning or a memory-recall test. Regardless of administration time, ACEA significantly reduced freezing behavior in stressed animals. Furthermore, when administered during the first memory recall test, ACEA enhanced long-term extinction in both stress and non-stress groups. The results demonstrate that chronic unpredictable stress selectively enhances hippocampal-dependent episodic fear memories. Pathologies of the episodic memory and fear response may increase the susceptibility of developing PTSD. Reduction in fear responses via exogenous activation of the CB1 receptor suggests that a deficiency in the endocannabinoid system contributes to this pathology.

  18. The effects of acute stress exposure on striatal activity during Pavlovian conditioning with monetary gains and losses

    PubMed Central

    Lewis, Andrea H.; Porcelli, Anthony J.; Delgado, Mauricio R.

    2014-01-01

    Pavlovian conditioning involves the association of an inherently neutral stimulus with an appetitive or aversive outcome, such that the neutral stimulus itself acquires reinforcing properties. Across species, this type of learning has been shown to involve subcortical brain regions such as the striatum and the amygdala. It is less clear, however, how the neural circuitry involved in the acquisition of Pavlovian contingencies in humans, particularly in the striatum, is affected by acute stress. In the current study, we investigate the effect of acute stress exposure on Pavlovian conditioning using monetary reinforcers. Participants underwent a partial reinforcement conditioning procedure in which neutral stimuli were paired with high and low magnitude monetary gains and losses. A between-subjects design was used, such that half of the participants were exposed to cold stress while the remaining participants were exposed to a no stress control procedure. Cortisol measurements and subjective ratings were used as measures of stress. We observed an interaction between stress, valence, and magnitude in the ventral striatum, with the peak in the putamen. More specifically, the stress group exhibited an increased sensitivity to magnitude in the gain domain. This effect was driven by those participants who experienced a larger increase in circulating cortisol levels in response to the stress manipulation. Taken together, these results suggest that acute stress can lead to individual differences in circulating cortisol levels which influence the striatum during Pavlovian conditioning with monetary reinforcers. PMID:24904331

  19. The role of the hok/sok locus in bacterial response to stressful growth conditions.

    PubMed

    Chukwudi, Chinwe U; Good, Liam

    2015-02-01

    The hok/sok locus is renowned for its plasmid stabilization effect via post-segregational killing of plasmid-free daughter cells. However, the function(s) of the chromosome-encoded loci, which are more abundant in pathogenic strains of a broad range of enteric bacteria, are yet to be understood. Also, the frequent occurrence of this toxin/antitoxin addiction system in multi-drug resistance plasmids suggests additional roles. In this study, the effects of the hok/sok locus on the growth of bacteria in stressful growth-limiting conditions such as high temperature and antibiotic burden were investigated using hok/sok plasmids. The results showed that the hok/sok locus prolonged the lag phase of host cell cultures, thereby enabling the cells to adapt, respond to the stress and eventually thrive in these growth-limiting conditions by increasing the growth rate at exponential phase. The hok/sok locus also enhanced the survival and growth of cells in low cell density cultures irrespective of unfavourable growth conditions, and may complement existing or defective SOS mechanism. In addition to the plasmid stabilization function, these effects would enhance the ability of pathogenic bacteria to establish infections and propagate the antibiotic resistance elements carried on these plasmids, thereby contributing to the virulence of such bacteria.

  20. Rice Root Architectural Plasticity Traits and Genetic Regions for Adaptability to Variable Cultivation and Stress Conditions.

    PubMed

    Sandhu, Nitika; Raman, K Anitha; Torres, Rolando O; Audebert, Alain; Dardou, Audrey; Kumar, Arvind; Henry, Amelia

    2016-08-01

    Future rice (Oryza sativa) crops will likely experience a range of growth conditions, and root architectural plasticity will be an important characteristic to confer adaptability across variable environments. In this study, the relationship between root architectural plasticity and adaptability (i.e. yield stability) was evaluated in two traditional × improved rice populations (Aus 276 × MTU1010 and Kali Aus × MTU1010). Forty contrasting genotypes were grown in direct-seeded upland and transplanted lowland conditions with drought and drought + rewatered stress treatments in lysimeter and field studies and a low-phosphorus stress treatment in a Rhizoscope study. Relationships among root architectural plasticity for root dry weight, root length density, and percentage lateral roots with yield stability were identified. Selected genotypes that showed high yield stability also showed a high degree of root plasticity in response to both drought and low phosphorus. The two populations varied in the soil depth effect on root architectural plasticity traits, none of which resulted in reduced grain yield. Root architectural plasticity traits were related to 13 (Aus 276 population) and 21 (Kali Aus population) genetic loci, which were contributed by both the traditional donor parents and MTU1010. Three genomic loci were identified as hot spots with multiple root architectural plasticity traits in both populations, and one locus for both root architectural plasticity and grain yield was detected. These results suggest an important role of root architectural plasticity across future rice crop conditions and provide a starting point for marker-assisted selection for plasticity. PMID:27342311

  1. Induction kinetics of a conditional pH stress response system in Escherichia coli.

    PubMed

    Fritz, Georg; Koller, Christiane; Burdack, Korinna; Tetsch, Larissa; Haneburger, Ina; Jung, Kirsten; Gerland, Ulrich

    2009-10-23

    The analysis of stress response systems in microorganisms can reveal molecular strategies for regulatory control and adaptation. In this study, we focused on the Cad module, a subsystem of Escherichia coli's response to acidic stress that is conditionally activated at low pH only when lysine is available. When expressed, the Cad system counteracts the elevated H(+) concentration by converting lysine to cadaverine under the consumption of H(+) and exporting cadaverine in exchange for external lysine. Surprisingly, the cad operon displays a transient response, even when the conditions for its induction persist. To quantitatively characterize the regulation of the Cad module, we experimentally recorded and theoretically modeled the dynamics of important system variables. We established a quantitative model that adequately describes and predicts the transient expression behavior for various initial conditions. Our quantitative analysis of the Cad system supports negative feedback by external cadaverine as the origin of the transient response. Furthermore, the analysis puts causal constraints on the precise mechanism of signal transduction via the regulatory protein CadC. PMID:19703467

  2. Dynamics of food availability, body condition and physiological stress response in breeding Black-legged Kittiwakes

    USGS Publications Warehouse

    Kitaysky, A.S.; Wingfield, J.C.; Piatt, J.F.

    1999-01-01

    1. The seasonal dynamics of body condition (BC), circulating corticosterone levels (baseline, BL) and the adrenocortical response to acute stress (SR) were examined in long-lived Black-legged Kittiwakes, Rissa tridactyla, breeding at Duck (food-poor colony) and Gull (food-rich colony) Islands in lower Cook Inlet, Alaska. It was tested whether the dynamics of corticosterone levels reflect a seasonal change in bird physiological condition due to reproduction and/or variation in foraging conditions. 2. BC declined seasonally, and the decline was more pronounced in birds at the food-poor colony. BL and SR levels of corticosterone rose steadily through the reproductive season, and BL levels were significantly higher in birds on Duck island compared with those on Gull Island. During the egg-laying and chick-rearing stages, birds had lower SR on Duck Island than on Gull Island. 3. The results suggest that, in addition to a seasonal change in bird physiology during reproduction, local ecological factors such as food availability affect circulating levels of corticosterone and adrenal response to acute stress.

  3. Mindfulness-Based Stress Reduction, Fear Conditioning, and The Uncinate Fasciculus: A Pilot Study.

    PubMed

    Hölzel, Britta K; Brunsch, Vincent; Gard, Tim; Greve, Douglas N; Koch, Kathrin; Sorg, Christian; Lazar, Sara W; Milad, Mohammed R

    2016-01-01

    Mindfulness has been suggested to impact emotional learning, but research on these processes is scarce. The classical fear conditioning/extinction/extinction retention paradigm is a well-known method for assessing emotional learning. The present study tested the impact of mindfulness training on fear conditioning and extinction memory and further investigated whether changes in white matter fiber tracts might support such changes. The uncinate fasciculus (UNC) was of particular interest in the context of emotional learning. In this pilot study, 46 healthy participants were quasi-randomized to a Mindfulness-Based Stress Reduction (MBSR, N = 23) or waitlist control (N = 23) group and underwent a two-day fear conditioning, extinction learning, and extinction memory protocol before and after the course or control period. Skin conductance response (SCR) data served to measure the physiological response during conditioning and extinction memory phases. Diffusion tensor imaging (DTI) data were analyzed with probabilistic tractography and analyzed for changes of fractional anisotropy in the UNC. During conditioning, participants were able to maintain a differential response to conditioned vs. not conditioned stimuli following the MBSR course (i.e., higher sensitivity to the conditioned stimuli), while controls dropped the response. Extinction memory results were not interpretable due to baseline differences. MBSR participants showed a significant increase in fractional anisotropy in the UNC, while controls did not (group by time interaction missed significance). Pre-post changes in UNC were correlated with changes in the response to the conditioned stimuli. The findings suggest effects of mindfulness practice on the maintenance of sensitivity of emotional responses and suggest underlying neural plasticity. (ClinicalTrials.gov, Identifier NCT01320969, https://clinicaltrials.gov/ct2/show/NCT01320969). PMID:27378875

  4. Mindfulness-Based Stress Reduction, Fear Conditioning, and The Uncinate Fasciculus: A Pilot Study.

    PubMed

    Hölzel, Britta K; Brunsch, Vincent; Gard, Tim; Greve, Douglas N; Koch, Kathrin; Sorg, Christian; Lazar, Sara W; Milad, Mohammed R

    2016-01-01

    Mindfulness has been suggested to impact emotional learning, but research on these processes is scarce. The classical fear conditioning/extinction/extinction retention paradigm is a well-known method for assessing emotional learning. The present study tested the impact of mindfulness training on fear conditioning and extinction memory and further investigated whether changes in white matter fiber tracts might support such changes. The uncinate fasciculus (UNC) was of particular interest in the context of emotional learning. In this pilot study, 46 healthy participants were quasi-randomized to a Mindfulness-Based Stress Reduction (MBSR, N = 23) or waitlist control (N = 23) group and underwent a two-day fear conditioning, extinction learning, and extinction memory protocol before and after the course or control period. Skin conductance response (SCR) data served to measure the physiological response during conditioning and extinction memory phases. Diffusion tensor imaging (DTI) data were analyzed with probabilistic tractography and analyzed for changes of fractional anisotropy in the UNC. During conditioning, participants were able to maintain a differential response to conditioned vs. not conditioned stimuli following the MBSR course (i.e., higher sensitivity to the conditioned stimuli), while controls dropped the response. Extinction memory results were not interpretable due to baseline differences. MBSR participants showed a significant increase in fractional anisotropy in the UNC, while controls did not (group by time interaction missed significance). Pre-post changes in UNC were correlated with changes in the response to the conditioned stimuli. The findings suggest effects of mindfulness practice on the maintenance of sensitivity of emotional responses and suggest underlying neural plasticity. (ClinicalTrials.gov, Identifier NCT01320969, https://clinicaltrials.gov/ct2/show/NCT01320969).

  5. Mindfulness-Based Stress Reduction, Fear Conditioning, and The Uncinate Fasciculus: A Pilot Study

    PubMed Central

    Hölzel, Britta K.; Brunsch, Vincent; Gard, Tim; Greve, Douglas N.; Koch, Kathrin; Sorg, Christian; Lazar, Sara W.; Milad, Mohammed R.

    2016-01-01

    Mindfulness has been suggested to impact emotional learning, but research on these processes is scarce. The classical fear conditioning/extinction/extinction retention paradigm is a well-known method for assessing emotional learning. The present study tested the impact of mindfulness training on fear conditioning and extinction memory and further investigated whether changes in white matter fiber tracts might support such changes. The uncinate fasciculus (UNC) was of particular interest in the context of emotional learning. In this pilot study, 46 healthy participants were quasi-randomized to a Mindfulness-Based Stress Reduction (MBSR, N = 23) or waitlist control (N = 23) group and underwent a two-day fear conditioning, extinction learning, and extinction memory protocol before and after the course or control period. Skin conductance response (SCR) data served to measure the physiological response during conditioning and extinction memory phases. Diffusion tensor imaging (DTI) data were analyzed with probabilistic tractography and analyzed for changes of fractional anisotropy in the UNC. During conditioning, participants were able to maintain a differential response to conditioned vs. not conditioned stimuli following the MBSR course (i.e., higher sensitivity to the conditioned stimuli), while controls dropped the response. Extinction memory results were not interpretable due to baseline differences. MBSR participants showed a significant increase in fractional anisotropy in the UNC, while controls did not (group by time interaction missed significance). Pre-post changes in UNC were correlated with changes in the response to the conditioned stimuli. The findings suggest effects of mindfulness practice on the maintenance of sensitivity of emotional responses and suggest underlying neural plasticity. (ClinicalTrials.gov, Identifier NCT01320969, https://clinicaltrials.gov/ct2/show/NCT01320969). PMID:27378875

  6. Residual stress analysis on tensile MMC specimens after loading/unloading tests in several conditions

    NASA Astrophysics Data System (ADS)

    Giuliani, Alessandra; Albertini, Gianni; Manescu, Adrian

    2004-07-01

    Residual stresses have been investigated in samples made of AA6061+22% Al2O3 in order to correlate microstructural characteristics with mechanical performances. In particular, the possible occurrence of a brittle fracture induced by an excessive load transfer from the matrix to the reinforcement was investigated. To this end, macrostresses and microstresses were analysed. A neutron diffraction test on 12 specimens submitted to several loading/unloading conditions at different temperatures was performed. These measurements aimed to establish the optimal temperature for the initial extruded billet in pre-heating stage, before forging the final wheel hub.

  7. Photoacoustic detection of ethylene released by biological samples under stress conditions

    NASA Astrophysics Data System (ADS)

    Cristescu, Simona M.; Dumitras, Dan C.; Dutu, Doru C. A.

    1998-07-01

    A high sensitive photoacoustic system has been developed to monitor the ethylene released by mature tomatoes and wheat seeds during germination as a response of fast effects of mechanical and thermal stress. Under normal conditions of temperature and pressure, the coronet removal yielded a significant increase of ethylene emission as compared to the local wounding of tomato tissues. To determine the temperature influence on ethylene emission rates, both tomatoes and germinating wheat seeds were investigated at cold treatment (4 degree(s)C) and at room temperature (22 degree(s)C). Early changes in ethylene released after imbibition in connection with the physiological results of germination were also monitored.

  8. Chronic social stress conditions differentially modify vulnerability to amphetamine self-administration.

    PubMed

    Lemaire, V; Deminière, J M; Mormède, P

    1994-06-27

    Using social instability and cohabitation with females as chronic stress, we observed that neuroendocrine systems were differentially activated according to the experimental design. We show here that amphetamine self-administration, a paradigm to study the reinforcing effects of psychostimulants, is also differentially affected by these conditions. Coexistence with females increases amphetamine self-administration and this effect is reduced when social instability is superimposed. On the other hand, locomotor response to amphetamine is not modified by either social factor, suggesting a specific involvement of a subset of dopaminergic neurons. PMID:7953651

  9. Micronized fibres affect in vitro fermentation under normal buffered and osmotic stress conditions using porcine inocula.

    PubMed

    Aumiller, T; Mosenthin, R; Rink, F; Hartung, K; Weiss, E

    2015-12-01

    In this in vitro study, the modified Hohenheim gas test was used to determine fermentation activity and bacterial composition of pig's faecal microbial inoculum, when fermenting a standard pig diet with varying levels of crude protein (CP; 20, 24 and 28% CP), and supplemented with one of three fibre sources manufactured by micronization treatment. These were wheat envelopes (MWE), pea fibre (MPF) and lupine fibre (MLF). For comparison, inulin was used. As intestinal bacteria have to cope with varying osmotic conditions in their ecosystem, fermentation was performed under normal buffered and osmotic stress conditions. After 24 h of fermentation, total gas production and ammonia production were measured. In addition, the effect of MWE and inulin on short-chain fatty acid (SCFA) production and numbers of total eubacteria, Lactobacillus spp., Bifidobacterium spp., Enterobacteriaceae, Enterococcus spp., Clostridium cluster XIVa and Clostridium cluster IV, were determined using quantitative real-time PCR. Under normal buffered conditions, supplementation of MWE resulted in increased (p < 0.05) SCFA, acetic, propionic and valerianic acid production at CP levels of 20 and 28%. There was an increase (p < 0.05) in ammonia production for the micronized supplements, and for MWE an increased (p < 0.05) branched-chain proportion was observed, possibly due to higher availability of protein for fermentation which was released during the micronization process. Osmotic stress conditions reduced (p < 0.05) total gas as well as total SCFA, acetic and propionic acid production for all treatments, while cell counts were increased (p < 0.05) for Bifidobacterium spp., Enterococcus spp. and Lactobacillus spp. Under normal buffered conditions in combination with 24 and 28% CP levels, lactobacilli were increased for MWE, compared to inulin (p < 0.05). In conclusion, micronized supplements such as MWE may beneficially modulate pigs' intestinal microbiota by increasing SCFA production in

  10. Velocity and stress jump conditions between a porous medium and a fluid

    NASA Astrophysics Data System (ADS)

    Valdés-Parada, Francisco J.; Aguilar-Madera, Carlos G.; Ochoa-Tapia, J. Alberto; Goyeau, Benoît

    2013-12-01

    Modeling transport phenomena in hierarchical systems can be carried out by either a one domain approach or a two domain approach. The first one involves assuming the system as a pseudo-continuum and is expressed in terms of position-dependent effective medium coefficients. In the two domain approach, the differential equations have position-independent coefficients but require accounting for the corresponding boundary conditions that couple the equations between each homogeneous region. For momentum transport between a porous medium and a fluid, stress boundary conditions have been derived in terms of a jump coefficient that needs to be predicted within a two-domain approach formulation. However, continuity of the velocity is postulated at the dividing surface. In this work, we propose a methodology for the derivation of boundary conditions for both the velocity and the stress. These conditions are expressed in terms of jump coefficients that are computed from the solution of an ancillary macroscopic closure problem. This problem accounts for the deviations from the one and two domain approaches. From the closure problem solution we were also able to determine the position at which the jump conditions should be applied, i.e., the dividing surface position. In addition, we used this methodology adopting the assumptions proposed by Ochoa-Tapia and Whitaker as well as those by Beavers and Joseph. We found that any version of the two domain approach was in agreement with the one domain approach in the bulk of the porous medium and the fluid. However, the same is not true for the process of capturing the essential information of the inter-region.

  11. The weight gain response to stress during adulthood is conditioned by both sex and prenatal stress exposure.

    PubMed

    García-Cáceres, Cristina; Diz-Chaves, Yolanda; Lagunas, Natalia; Calmarza-Font, Isabel; Azcoitia, Iñigo; Garcia-Segura, Luis M; Frago, Laura M; Argente, Jesús; Chowen, Julie A

    2010-04-01

    Food intake and weight gain are known to be affected by stress. However, the type and duration of the stress may have variable effects, with males and females responding differently. We report the short-term and long-term effects of prenatal and adult immobilization stress, as well as the combination of these two stresses, on weight gain and food intake in male and female rats and the role of post-pubertal gonadal hormones in this process. No long-term effect of prenatal stress on food intake or weight gain was found in either sex. However, during the period of adult stress [at postnatal day (P) 90; 10 days duration] stressed male rats gained significantly less weight than controls and previous exposure to prenatal stress attenuated this effect (control: 31.2+/-2.1g; prenatal stress: 24.6+/-3.8g; adult stress: 8.1+/-3.4g; prenatal and adult stress: 18.2+/-3.3g; p<0.0001). There was no change in food intake in response to either prenatal or adult stress. Adult stress increased circulating corticosterone levels during the initial part of the stress period, in both male and female rats with this rise being greater in male rats. No effect on corticosterone levels was observed on the last day of stress in either sex. No effect on weight gain or food intake was observed in female rats. Following adult stress, male rats increased their weight gain, with no change in food intake, such that 1 month later they reached control levels. At the time of sacrifice (P180), there were no differences in weight or circulating metabolic hormone levels between any of the male groups. Although castration alone modulated body weight in both male and female rats, it did not affect their weight gain response to adult stress. These results indicate that the weight gain response to adult stress is sexually dimorphic and that this is not dependent on post-pubertal gonadal steroids. Furthermore, the outcome of this response closely depends on the time at which the change in weight is analyzed

  12. Migratory management and environmental conditions affect lifespan and oxidative stress in honey bees

    PubMed Central

    Simone-Finstrom, Michael; Li-Byarlay, Hongmei; Huang, Ming H.; Strand, Micheline K.; Rueppell, Olav; Tarpy, David R.

    2016-01-01

    Most pollination in large-scale agriculture is dependent on managed colonies of a single species, the honey bee Apis mellifera. More than 1 million hives are transported to California each year just to pollinate the almonds, and bees are trucked across the country for various cropping systems. Concerns have been raised about whether such “migratory management” causes bees undue stress; however to date there have been no longer-term studies rigorously addressing whether migratory management is detrimental to bee health. To address this issue, we conducted field experiments comparing bees from commercial and experimental migratory beekeeping operations to those from stationary colonies to quantify effects on lifespan, colony health and productivity, and levels of oxidative damage for individual bees. We detected a significant decrease in lifespan of migratory adult bees relative to stationary bees. We also found that migration affected oxidative stress levels in honey bees, but that food scarcity had an even larger impact; some detrimental effects of migration may be alleviated by a greater abundance of forage. In addition, rearing conditions affect levels of oxidative damage incurred as adults. This is the first comprehensive study on impacts of migratory management on the health and oxidative stress of honey bees. PMID:27554200

  13. Migratory management and environmental conditions affect lifespan and oxidative stress in honey bees.

    PubMed

    Simone-Finstrom, Michael; Li-Byarlay, Hongmei; Huang, Ming H; Strand, Micheline K; Rueppell, Olav; Tarpy, David R

    2016-01-01

    Most pollination in large-scale agriculture is dependent on managed colonies of a single species, the honey bee Apis mellifera. More than 1 million hives are transported to California each year just to pollinate the almonds, and bees are trucked across the country for various cropping systems. Concerns have been raised about whether such "migratory management" causes bees undue stress; however to date there have been no longer-term studies rigorously addressing whether migratory management is detrimental to bee health. To address this issue, we conducted field experiments comparing bees from commercial and experimental migratory beekeeping operations to those from stationary colonies to quantify effects on lifespan, colony health and productivity, and levels of oxidative damage for individual bees. We detected a significant decrease in lifespan of migratory adult bees relative to stationary bees. We also found that migration affected oxidative stress levels in honey bees, but that food scarcity had an even larger impact; some detrimental effects of migration may be alleviated by a greater abundance of forage. In addition, rearing conditions affect levels of oxidative damage incurred as adults. This is the first comprehensive study on impacts of migratory management on the health and oxidative stress of honey bees. PMID:27554200

  14. Floridoside production by the red microalga Galdieria sulphuraria under different conditions of growth and osmotic stress.

    PubMed

    Martinez-Garcia, Marta; van der Maarel, Marc J E C

    2016-12-01

    Floridoside is a compatible solute synthesized by red algae that has attracted considerable attention due to its promising antifouling and therapeutic properties. However, research on industrial applications of floridoside is hampered by limited compound availability and the development of a production process yielding high amounts of this glycoside has not been explored yet. In the present work, floridoside accumulation by the red microalgae Galdieria sulphuraria under different conditions was investigated in order to optimize the production of this glycoside in this microalgae. G. sulphuraria shows consider advantages over other red algae as potential industrial producer of floridoside due to its unicellular nature, its ability to grow heterotrophically in complete darkness and its acidophilic lifestyle. The main compatible solute accumulated by G. sulphuraria under salt stress was purified, identified as floridoside by (1)H-NMR and used as standard for quantification. Our results showed that applying the osmotic stress after the cells had grown first in medium with no salt resulted in higher floridoside yields compared to those obtained in cells growing under osmotic stress from the beginning. Among several parameters tested, the use of glycerol as carbon source for cell growth showed the most significant impact on floridoside accumulation, which reached a maximum of 56.8 mg/g dry biomass. PMID:27620735

  15. Oxidative stress conditions increase the frequency of de novo formation of the yeast [PSI +] prion

    PubMed Central

    Doronina, Victoria A.; Staniforth, Gemma L.; Speldewinde, Shaun H.; Tuite, Mick F.

    2015-01-01

    Summary Prions are self‐perpetuating amyloid protein aggregates which underlie various neurodegenerative diseases in mammals and heritable traits in yeast. The molecular basis of how yeast and mammalian prions form spontaneously into infectious amyloid‐like structures is poorly understood. We have explored the hypothesis that oxidative stress is a general trigger for prion formation using the yeast [PSI +] prion, which is the altered conformation of the Sup35 translation termination factor. We show that the frequency of [PSI +] prion formation is elevated under conditions of oxidative stress and in mutants lacking key antioxidants. We detect increased oxidation of Sup35 methionine residues in antioxidant mutants and show that overexpression of methionine sulphoxide reductase abrogates both the oxidation of Sup35 and its conversion to the [PSI +] prion. [PSI +] prion formation is particularly elevated in a mutant lacking the Sod1 Cu,Zn‐superoxide dismutase. We have used fluorescence microscopy to show that the de novo appearance of [PSI +] is both rapid and increased in frequency in this mutant. Finally, electron microscopy analysis of native Sup35 reveals that similar fibrillar structures are formed in both the wild‐type and antioxidant mutants. Together, our data indicate that oxidative stress is a general trigger of [PSI +] formation, which can be alleviated by antioxidant defenses. PMID:25601439

  16. Non-coding RNAs in marine Synechococcus and their regulation under environmentally relevant stress conditions

    PubMed Central

    Gierga, Gregor; Voss, Björn; Hess, Wolfgang R

    2012-01-01

    Regulatory small RNAs (sRNAs) have crucial roles in the adaptive responses of bacteria to changes in the environment. Thus far, potential regulatory RNAs have been studied mainly in marine picocyanobacteria in genetically intractable Prochlorococcus, rendering their molecular analysis difficult. Synechococcus sp. WH7803 is a model cyanobacterium, representative of the picocyanobacteria from the mesotrophic areas of the ocean. Similar to the closely related Prochlorococcus it possesses a relatively streamlined genome and a small number of genes, but is genetically tractable. Here, a comparative genome analysis was performed for this and four additional marine Synechococcus to identify the suite of possible sRNAs and other RNA elements. Based on the prediction and on complementary microarray profiling, we have identified several known as well as 32 novel sRNAs. Some sRNAs overlap adjacent coding regions, for instance for the central photosynthetic gene psbA. Several of these novel sRNAs responded specifically to environmentally relevant stress conditions. Among them are six sRNAs changing their accumulation level under cold stress, six responding to high light and two to iron limitation. Target predictions suggested genes encoding components of the light-harvesting apparatus as targets of sRNAs originating from genomic islands and that one of the iron-regulated sRNAs might be a functional homolog of RyhB. These data suggest that marine Synechococcus mount adaptive responses to these different stresses involving regulatory sRNAs. PMID:22258101

  17. Migratory management and environmental conditions affect lifespan and oxidative stress in honey bees.

    PubMed

    Simone-Finstrom, Michael; Li-Byarlay, Hongmei; Huang, Ming H; Strand, Micheline K; Rueppell, Olav; Tarpy, David R

    2016-01-01

    Most pollination in large-scale agriculture is dependent on managed colonies of a single species, the honey bee Apis mellifera. More than 1 million hives are transported to California each year just to pollinate the almonds, and bees are trucked across the country for various cropping systems. Concerns have been raised about whether such "migratory management" causes bees undue stress; however to date there have been no longer-term studies rigorously addressing whether migratory management is detrimental to bee health. To address this issue, we conducted field experiments comparing bees from commercial and experimental migratory beekeeping operations to those from stationary colonies to quantify effects on lifespan, colony health and productivity, and levels of oxidative damage for individual bees. We detected a significant decrease in lifespan of migratory adult bees relative to stationary bees. We also found that migration affected oxidative stress levels in honey bees, but that food scarcity had an even larger impact; some detrimental effects of migration may be alleviated by a greater abundance of forage. In addition, rearing conditions affect levels of oxidative damage incurred as adults. This is the first comprehensive study on impacts of migratory management on the health and oxidative stress of honey bees.

  18. Two-way shape memory behavior of semi-crystalline elastomer under stress-free condition

    NASA Astrophysics Data System (ADS)

    Qian, Chen; Dong, Yubing; Zhu, Yaofeng; Fu, Yaqin

    2016-08-01

    Semi-crystalline shape memory polymers exhibit two-way shape memory effect (2W-SME) under constant stresses through crystallization-induced elongation upon cooling and melting-induced constriction upon heating. The applied constant stress influenced the prediction and usability of 2W-SME in practical applications without any external force. Here the reversible shape transition in EVA-shaped memory polymer was quantitative analyzed under a suitable temperature range and external stress-free condition. The fraction of reversible strain increased with increasing upper temperature (T high) within the temperature range and reached the maximum value of 13.62% at 70 °C. However, reversible strain transition was almost lost when T high exceeded 80 °C because of complete melting of crystalline scaffold, known as the latent recrystallization template. The non-isothermal annealing of EVA 2W-SMP under changing circulating temperatures was confirmed. Moreover, the orientation of crystallization was retained at high temperatures. These findings may contribute to design an appropriate shape memory protocol based on application-specific requirements.

  19. Oxidative stress conditions increase the frequency of de novo formation of the yeast [PSI+] prion.

    PubMed

    Doronina, Victoria A; Staniforth, Gemma L; Speldewinde, Shaun H; Tuite, Mick F; Grant, Chris M

    2015-04-01

    Prions are self-perpetuating amyloid protein aggregates which underlie various neurodegenerative diseases in mammals and heritable traits in yeast. The molecular basis of how yeast and mammalian prions form spontaneously into infectious amyloid-like structures is poorly understood. We have explored the hypothesis that oxidative stress is a general trigger for prion formation using the yeast [PSI(+)] prion, which is the altered conformation of the Sup35 translation termination factor. We show that the frequency of [PSI(+)] prion formation is elevated under conditions of oxidative stress and in mutants lacking key antioxidants. We detect increased oxidation of Sup35 methionine residues in antioxidant mutants and show that overexpression of methionine sulphoxide reductase abrogates both the oxidation of Sup35 and its conversion to the [PSI(+)] prion. [PSI(+)] prion formation is particularly elevated in a mutant lacking the Sod1 Cu,Zn-superoxide dismutase. We have used fluorescence microscopy to show that the de novo appearance of [PSI(+)] is both rapid and increased in frequency in this mutant. Finally, electron microscopy analysis of native Sup35 reveals that similar fibrillar structures are formed in both the wild-type and antioxidant mutants. Together, our data indicate that oxidative stress is a general trigger of [PSI(+) formation, which can be alleviated by antioxidant defenses.

  20. Fast screening of Bifidobacterium longum sublethal stress conditions in a novel two-stage continuous culture strategy.

    PubMed

    Mozzetti, V; Grattepanche, F; Berger, B; Rezzonico, E; Arigoni, F; Lacroix, C

    2013-06-01

    A central issue in the application of probiotics as food additives is their fastidious production and their sensitivity to many environmental stresses. The importance of inducible cell-protective mechanisms triggered by application of sublethal stresses for survival under stress conditions has been demonstrated. Continuous cultures could be a suitable and more efficient method to test stress factors on one culture instead of several repeated batch cultures. In this study, the application of a two-stage continuous culture of Bifidobacterium longum NCC2705 was investigated. The first reactor was operated under fixed conditions at 37 °C and pH 6.0 and used to produce cells with controlled physiology, mimicking cells in the late exponential growth phase. Stress pretreatment combinations of pH (6.0, 5.0 and 4.0), temperature (37, 45 and 47 °C) and NaCl (0, 5 and 10%) were tested in the second reactor. Of all tested combinations, only those of pH 4.0 significantly decreased cell viability in the second reactor compared to control conditions (37 °C, pH 6.0, 0% NaCl) and, therefore, could not be considered as sublethal stresses. Pretreatments with 5 or 10% NaCl had a negative effect on cell viability after gastric lethal stress. A significant improvement in cell resistance to heat lethal stress (56 °C, 5 min) was observed for cells pretreated at 47 °C. In contrast, heat pretreatment negatively affected cell viability after freeze drying and osmotic lethal stresses. The two-stage continuous culture allowed for efficient screening of several stress pretreatments during the same experiment with up to four different conditions tested per day. Optimal sublethal stress conditions can also be applied for producing cells with traditional batch cultures. PMID:23443949

  1. HflX is a ribosome-splitting factor rescuing stalled ribosomes under stress conditions.

    PubMed

    Zhang, Yanqing; Mandava, Chandra Sekhar; Cao, Wei; Li, Xiaojing; Zhang, Dejiu; Li, Ningning; Zhang, Yixiao; Zhang, Xiaoxiao; Qin, Yan; Mi, Kaixia; Lei, Jianlin; Sanyal, Suparna; Gao, Ning

    2015-11-01

    Adverse cellular conditions often lead to nonproductive translational stalling and arrest of ribosomes on mRNAs. Here, we used fast kinetics and cryo-EM to characterize Escherichia coli HflX, a GTPase with unknown function. Our data reveal that HflX is a heat shock-induced ribosome-splitting factor capable of dissociating vacant as well as mRNA-associated ribosomes with deacylated tRNA in the peptidyl site. Structural data demonstrate that the N-terminal effector domain of HflX binds to the peptidyl transferase center in a strikingly similar manner as that of the class I release factors and induces dramatic conformational changes in central intersubunit bridges, thus promoting subunit dissociation. Accordingly, loss of HflX results in an increase in stalled ribosomes upon heat shock. These results suggest a primary role of HflX in rescuing translationally arrested ribosomes under stress conditions. PMID:26458047

  2. HflX is a ribosome-splitting factor rescuing stalled ribosomes under stress conditions.

    PubMed

    Zhang, Yanqing; Mandava, Chandra Sekhar; Cao, Wei; Li, Xiaojing; Zhang, Dejiu; Li, Ningning; Zhang, Yixiao; Zhang, Xiaoxiao; Qin, Yan; Mi, Kaixia; Lei, Jianlin; Sanyal, Suparna; Gao, Ning

    2015-11-01

    Adverse cellular conditions often lead to nonproductive translational stalling and arrest of ribosomes on mRNAs. Here, we used fast kinetics and cryo-EM to characterize Escherichia coli HflX, a GTPase with unknown function. Our data reveal that HflX is a heat shock-induced ribosome-splitting factor capable of dissociating vacant as well as mRNA-associated ribosomes with deacylated tRNA in the peptidyl site. Structural data demonstrate that the N-terminal effector domain of HflX binds to the peptidyl transferase center in a strikingly similar manner as that of the class I release factors and induces dramatic conformational changes in central intersubunit bridges, thus promoting subunit dissociation. Accordingly, loss of HflX results in an increase in stalled ribosomes upon heat shock. These results suggest a primary role of HflX in rescuing translationally arrested ribosomes under stress conditions.

  3. Stress responses and conditioning effects in mesothelial cells exposed to peritoneal dialysis fluid.

    PubMed

    Kratochwill, Klaus; Lechner, Michael; Siehs, Christian; Lederhuber, Hans C; Rehulka, Pavel; Endemann, Michaela; Kasper, David C; Herkner, Kurt R; Mayer, Bernd; Rizzi, Andreas; Aufricht, Christoph

    2009-04-01

    Renal replacement therapy by peritoneal dialysis is frequently complicated by technical failure. Peritoneal dialysis fluids (PDF) cause injury to the peritoneal mesothelial cell layer due to their cytotoxicity. As only isolated elements of the involved cellular processes have been studied before, we aimed at a global assessment of the mesothelial stress response to PDF. Following single or repeated exposure to PDF or control medium, proteomics and bioinformatics techniques were combined to study effects in mesothelial cells (MeT-5A). Protein expression was assessed by two-dimensional gel electrophoresis, and significantly altered spots were identified by MALDI-TOF MS and MS2 techniques. The lists of experimentally derived candidate proteins were expanded by a next neighbor approach and analyzed for significantly enriched biological processes. To address the problem of an unknown portion of false positive spots in 2DGE, only proteins showing significant p-values on both levels were further interpreted. Single PDF exposure resulted in reduction of biological processes in favor of reparative responses, including protein metabolism, modification and folding, with chaperones as a major subgroup. The observed biological processes triggered by this acute PDF exposure mainly contained functionally interwoven multitasking proteins contributing as well to cytoskeletal reorganization and defense mechanisms. Repeated PDF exposure resulted in attenuated protein regulation, reflecting inhibition of stress responses by high levels of preinduced chaperones. The identified proteins were less attributable to acute cellular injury but rather to specialized functions with a reduced number of involved multitasking proteins. This finding agrees well with the concept of conditioning effects and cytoprotection. In conclusion, this study describes the reprogrammed proteome of mesothelial cells during recovery from PDF exposure and adaption to repetitive stress. A broad stress response with

  4. Effect of some antioxidants on canola plants grown under soil salt stress condition.

    PubMed

    Sakr, M T; Arafa, A A

    2009-04-01

    In this study, two field experiments were carried out during the two growing seasons (2005-2006 and 2006-2007) to investigate the role of some applied antioxidants (spermine 10 mg L(-1) and ascorbic acid 200 mg L(-1)) in counteracting the harmful effect of soil salinity stress (10.1 or 14.6 dS m(-1)) on canola plants. Growth characters, yield and its components as well as biochemical constituents were studied in the two growing seasons. The results showed that all growth characters including; plant height, leaves number and area/plant, shoot and root dry weight as well as yield and its components including; fruit number/plant, number of fruiting branches, seed number/fruit, seed yield/plant and seed oil content of canola plant were decreased with increasing soil salt level (A2) comparing with (A1). On the other hand, applied antioxidants spermine 10 mg L(-1) and ascorbic acid 200 mg L(-1)) increased growth and yield of canola plant during the two growing seasons. However, the applied antioxidants were more effective under the first soil salt condition (A1) soil salt stress levels (A2) decreased each of photosynthetic pigments, K and P contents, while increased proline, soluble sugar, ascorbic acid, Na and Cl contents compared with (A1). On the other hand, applied antioxidants increased each of photosynthetic pigments, proline, soluble sugar, N, K and P contents, while decreased Na and Cl contents in canola plant under soil salt stress (A1 and A2) during the two growing seasons. It could be concluded that applied antioxidants could counteract the harmful effect of salt soil stress on growth, yield and biochemical constituents of canola plant.

  5. Serial analysis of the vascular endothelial transcriptome under static and shear stress conditions.

    PubMed

    Chu, Tian Jiao; Peters, David G

    2008-07-15

    We have utilized serial analysis of gene expression (SAGE) to analyze the response of human coronary artery endothelial cells (HCAECs) to laminar shear stress (LSS). Primary cultures of HCAECs were exposed to 15 dyn/cm(2) LSS for 24 h in a parallel plate flow chamber and compared with identical same passage cells cultured under static conditions. The expression levels of a number of functional categories of genes were reduced by shear stress including those encoding proteins involved in cell proliferation (CDC10, CDC20, CDC23, CCND1, CCNB1), angiogenesis (ANGPTL4, CTGF, CYR61, ENG, EPAS1, EGFR, LGALS3, PGK1, and SPARC), extracellular matrix and cell-matrix adhesion (EFEMP1, LOXL2, P4HB, FBN1, FN1, ITGA5, ITGAE, ITGAV, ILK, LAMR1) and ATP synthesis (ATP5G3, ATP5J2, ATP5L, ATP5D). We also observed an increase in the LSS-responsive expression of genes encoding stress response proteins, including HMOX1, which is significant since HMOX1 may have anti-inflammatory and vasodilatory vascular effects. The autosomal dominant polycystic kidney disease (ADPKD) genes PKD1 and PKD2 were also elevated by LSS. ADPKD is associated with vascular malfunction, including the impairment of vasoreactive processes. To our knowledge, this is the first SAGE-based analysis of the shear stress-responsive endothelial cell transcriptome. These immortal data provide a resource for further analyses of the molecular mechanisms underlying the biological response to LSS and contribute to the expanding collection of publicly available SAGE data. PMID:18505769

  6. From microgravity to osmotic conditions: mechanical integration of plant cells in response to stress

    NASA Astrophysics Data System (ADS)

    Wojtaszek, Przemyslaw; Kasprowicz, Anna; Michalak, Michal; Janczara, Renata; Volkmann, Dieter; Baluska, Frantisek

    Chemical reactions and interactions between molecules are commonly thought of as being at the basis of Life. Research of recent years, however, is more and more evidently indicating that physical forces are profoundly affecting the functioning of life at all levels of its organiza-tion. To detect and to respond to such forces, plant cells need to be integrated mechanically. Cell walls are the outermost functional zone of plant cells. They surround the individual cells, and also form a part of the apoplast. In cell suspensions, cell walls are embedded in the cul-ture medium which can be considered as a superapoplast. Through physical and chemical interactions they provide a basis for the structural and functional cell wall-plasma membrane-cytoskeleton (WMC) continuum spanning the whole cell. Here, the working of WMC contin-uum, and the participation of signalling molecules, like NO, would be presented in the context of plant responses to stress. In addition, the effects of the changing composition of WMC continuum will be considered, with particular attention paid to the modifications of the WMC components. Plant cells are normally adapted to changing osmotic conditions, resulting from variable wa-ter availability. The appearance of the osmotic stress activates adaptory mechanisms. If the strength of osmotic stress grows relatively slowly over longer period of time, the cells are able to adapt to conditions that are lethal to non-adapted cells. During stepwise adaptation of tobacco BY-2 suspension cells to the presence of various osmotically active agents, cells diverged into independent, osmoticum type-specific lines. In response to ionic agents (NaCl, KCl), the adhe-sive properties were increased and randomly dividing cells formed clumps, while cells adapted to nonionic osmotica (mannitol, sorbitol, PEG) revealed ordered pattern of precisely positioned cell divisions, resulting in the formation of long cell files. Changes in the growth patterns were accompanied by

  7. Adolescent traumatic stress experience results in less robust conditioned fear and post-extinction fear cue responses in adult rats.

    PubMed

    Moore, Nicole L T; Gauchan, Sangeeta; Genovese, Raymond F

    2014-05-01

    Early exposure to a traumatic event may produce lasting effects throughout the lifespan. Traumatic stress during adolescence may deliver a distinct developmental insult compared with more-often studied neonatal or juvenile traumatic stress paradigms. The present study describes the lasting effects of adolescent traumatic stress upon adulthood fear conditioning. Adolescent rats were exposed to a traumatic stressor (underwater trauma, UWT), then underwent fear conditioning during adulthood. Fear extinction was tested over five conditioned suppression extinction sessions three weeks later. The efficacies of two potential extinction-enhancing compounds, endocannabinoid reuptake inhibitor AM404 (10mg/kg) and M1 muscarinic positive allosteric modulator BQCA (10mg/kg), were also assessed. Finally, post-extinction fear responses were examined using a fear cue (light) as a prepulse stimulus. Rats traumatically stressed during adolescence showed blunted conditioned suppression on day 1 of extinction training, and AM404 reversed this effect. Post-extinction startle testing showed that fear conditioning eliminates prepulse inhibition to the light cue. Startle potentiation was observed only in rats without adolescent UWT exposure. AM404 and BQCA both ameliorated this startle potentiation, while BQCA increased startle in the UWT group. These results suggest that exposure to a traumatic stressor during adolescence alters developmental outcomes related to stress response and fear extinction compared to rats without adolescent traumatic stress exposure, blunting the adulthood fear response and reducing residual post-extinction fear expression. Efficacy of pharmacological interventions may also vary as a factor of developmental traumatic stress exposure.

  8. Does habitat disturbance affect stress, body condition and parasitism in two sympatric lemurs?

    PubMed

    Rakotoniaina, Josué H; Kappeler, Peter M; Ravoniarimbinina, Pascaline; Pechouskova, Eva; Hämäläinen, Anni M; Grass, Juliane; Kirschbaum, Clemens; Kraus, Cornelia

    2016-01-01

    Understanding how animals react to human-induced changes in their environment is a key question in conservation biology. Owing to their potential correlation with fitness, several physiological parameters are commonly used to assess the effect of habitat disturbance on animals' general health status. Here, we studied how two lemur species, the fat-tailed dwarf lemur (Cheirogaleus medius) and the grey mouse lemur (Microcebus murinus), respond to changing environmental conditions by comparing their stress levels (measured as hair cortisol concentration), parasitism and general body condition across four habitats ordered along a gradient of human disturbance at Kirindy Forest, Western Madagascar. These two species previously revealed contrasting responses to human disturbance; whereas M. murinus is known as a resilient species, C. medius is rarely encountered in highly disturbed habitats. However, neither hair cortisol concentrations nor parasitism patterns (prevalence, parasite species richness and rate of multiple infections) and body condition varied across the gradient of anthropogenic disturbance. Our results indicate that the effect of anthropogenic activities at Kirindy Forest is not reflected in the general health status of both species, which may have developed a range of behavioural adaptations to deal with suboptimal conditions. Nonetheless, a difference in relative density among sites suggests that the carrying capacity of disturbed habitat is lower, and both species respond differently to environmental changes, with C. medius being more negatively affected. Thus, even for behaviourally flexible species, extended habitat deterioration could hamper long-term viability of populations. PMID:27656285

  9. Eyeblink Classical Conditioning and Post-Traumatic Stress Disorder – A Model Systems Approach

    PubMed Central

    Schreurs, Bernard G.; Burhans, Lauren B.

    2015-01-01

    Not everyone exposed to trauma suffers flashbacks, bad dreams, numbing, fear, anxiety, sleeplessness, hyper-vigilance, hyperarousal, or an inability to cope, but those who do may suffer from post-traumatic stress disorder (PTSD). PTSD is a major physical and mental health problem for military personnel and civilians exposed to trauma. There is still debate about the incidence and prevalence of PTSD especially among the military, but for those who are diagnosed, behavioral therapy and drug treatment strategies have proven to be less than effective. A number of these treatment strategies are based on rodent fear conditioning research and are capable of treating only some of the symptoms because the extinction of fear does not deal with the various forms of hyper-vigilance and hyperarousal experienced by people with PTSD. To help address this problem, we have developed a preclinical eyeblink classical conditioning model of PTSD in which conditioning and hyperarousal can both be extinguished. We review this model and discuss findings showing that unpaired stimulus presentations can be effective in reducing levels of conditioning and hyperarousal even when unconditioned stimulus intensity is reduced to the point where it is barely capable of eliciting a response. These procedures have direct implications for the treatment of PTSD and could be implemented in a virtual reality environment. PMID:25904874

  10. Does habitat disturbance affect stress, body condition and parasitism in two sympatric lemurs?

    PubMed Central

    Rakotoniaina, Josué H.; Kappeler, Peter M.; Ravoniarimbinina, Pascaline; Pechouskova, Eva; Hämäläinen, Anni M.; Grass, Juliane; Kirschbaum, Clemens; Kraus, Cornelia

    2016-01-01

    Understanding how animals react to human-induced changes in their environment is a key question in conservation biology. Owing to their potential correlation with fitness, several physiological parameters are commonly used to assess the effect of habitat disturbance on animals’ general health status. Here, we studied how two lemur species, the fat-tailed dwarf lemur (Cheirogaleus medius) and the grey mouse lemur (Microcebus murinus), respond to changing environmental conditions by comparing their stress levels (measured as hair cortisol concentration), parasitism and general body condition across four habitats ordered along a gradient of human disturbance at Kirindy Forest, Western Madagascar. These two species previously revealed contrasting responses to human disturbance; whereas M. murinus is known as a resilient species, C. medius is rarely encountered in highly disturbed habitats. However, neither hair cortisol concentrations nor parasitism patterns (prevalence, parasite species richness and rate of multiple infections) and body condition varied across the gradient of anthropogenic disturbance. Our results indicate that the effect of anthropogenic activities at Kirindy Forest is not reflected in the general health status of both species, which may have developed a range of behavioural adaptations to deal with suboptimal conditions. Nonetheless, a difference in relative density among sites suggests that the carrying capacity of disturbed habitat is lower, and both species respond differently to environmental changes, with C. medius being more negatively affected. Thus, even for behaviourally flexible species, extended habitat deterioration could hamper long-term viability of populations.

  11. Does habitat disturbance affect stress, body condition and parasitism in two sympatric lemurs?

    PubMed Central

    Rakotoniaina, Josué H.; Kappeler, Peter M.; Ravoniarimbinina, Pascaline; Pechouskova, Eva; Hämäläinen, Anni M.; Grass, Juliane; Kirschbaum, Clemens; Kraus, Cornelia

    2016-01-01

    Understanding how animals react to human-induced changes in their environment is a key question in conservation biology. Owing to their potential correlation with fitness, several physiological parameters are commonly used to assess the effect of habitat disturbance on animals’ general health status. Here, we studied how two lemur species, the fat-tailed dwarf lemur (Cheirogaleus medius) and the grey mouse lemur (Microcebus murinus), respond to changing environmental conditions by comparing their stress levels (measured as hair cortisol concentration), parasitism and general body condition across four habitats ordered along a gradient of human disturbance at Kirindy Forest, Western Madagascar. These two species previously revealed contrasting responses to human disturbance; whereas M. murinus is known as a resilient species, C. medius is rarely encountered in highly disturbed habitats. However, neither hair cortisol concentrations nor parasitism patterns (prevalence, parasite species richness and rate of multiple infections) and body condition varied across the gradient of anthropogenic disturbance. Our results indicate that the effect of anthropogenic activities at Kirindy Forest is not reflected in the general health status of both species, which may have developed a range of behavioural adaptations to deal with suboptimal conditions. Nonetheless, a difference in relative density among sites suggests that the carrying capacity of disturbed habitat is lower, and both species respond differently to environmental changes, with C. medius being more negatively affected. Thus, even for behaviourally flexible species, extended habitat deterioration could hamper long-term viability of populations. PMID:27656285

  12. Validation of reference genes from Eucalyptus spp. under different stress conditions

    PubMed Central

    2012-01-01

    Background The genus Eucalyptus consists of approximately 600 species and subspecies and has a physiological plasticity that allows some species to propagate in different regions of the world. Eucalyptus is a major source of cellulose for paper manufacturing, and its cultivation is limited by weather conditions, particularly water stress and low temperatures. Gene expression studies using quantitative reverse transcription polymerase chain reaction (qPCR) require reference genes, which must have stable expression to facilitate the comparison of the results from analyses using different species, tissues, and treatments. Such studies have been limited in eucalyptus. Results Eucalyptus globulus Labill, Eucalyptus urograndis (hybrid from Eucalyptus urophylla S.T. Blake X Eucalyptus grandis Hill ex-Maiden) and E. uroglobulus (hybrid from E. urograndis X E. globulus) were subjected to different treatments, including water deficiency and stress recovery, low temperatures, presence or absence of light, and their respective controls. Except for treatment with light, which examined the seedling hypocotyl or apical portion of the stem, the expression analyses were conducted in the apical and basal parts of the stem. To select the best pair of genes, the bioinformatics tools GeNorm and NormFinder were compared. Comprehensive analyses that did not differentiate between species, treatments, or tissue types, showed that IDH (isocitrate dehydrogenase), SAND (SAND protein), ACT (actin), and A-Tub (α-tubulin) genes were the most stable. IDH was the most stable gene in all of the treatments. Conclusion Comparing these results with those of other studies on eucalyptus, we concluded that five genes are stable in different species and experimental conditions: IDH, SAND, ACT, A-Tub, and UBQ (ubiquitin). It is usually recommended a minimum of two reference genes is expression analysis; therefore, we propose that IDH and two others genes among the five identified genes in this study

  13. Influence of conditioned psychological stress on immunological recovery in mice exposed to low-dose x irradiation

    SciTech Connect

    Sato, K.; Flood, J.F.; Makinodan, T.

    1984-05-01

    A study was initiated to determine the effects of psychological stress on the immune response in BALB/c mice recovering from exposure to a low dose of ionizing radiation. Mice were first subjected to conditioning training for 12 days, then exposed to 200 R, subjected to psychological stress for 14 days, and assessed for peak anti-sheep RBC response. The seven treatment groups included two unirradiated groups and five irradiated groups. Mice exposed to 200 R and then subjected to conditioned psychological stress responded less vigorously to antigenic stimulation than those of the other irradiated groups. The psychological stress imposed upon these mice did not influence the antibody-forming capacity of unirradiated mice. These results indicate that a psychological stress which did not affect the immunological activity of unirradiated mice can curtail the immunological recovery of mice exposed to low doses of ionizing radiation.

  14. Over-representation of repeats in stress response genes: a strategy to increase versatility under stressful conditions?

    PubMed Central

    Rocha, Eduardo P. C.; Matic, Ivan; Taddei, François

    2002-01-01

    The survival of individual organisms facing stress is enhanced by the induction of a set of changes. As the intensity, duration and nature of stress is highly variable, the optimal response to stress may be unpredictable. To face such an uncertain future, it may be advantageous for a clonal population to increase its phenotypic heterogeneity (bet-hedging), ensuring that at least a subset of cells would survive the current stress. With current techniques, assessing the extent of this variability experimentally remains a challenge. Here, we use a bioinformatic approach to compare stress response genes with the rest of the genome for the presence of various kinds of repeated sequences, elements known to increase variability during the transfer of genetic information (i.e. during replication, but also during gene expression). We investigated the potential for illegitimate and homologous recombination of 296 Escherichia coli genes related to repair, recombination and physiological adaptations to different stresses. Although long repeats capable of engaging in homologous recombination are almost absent in stress response genes, we observed a significant high number of short close repeats capable of inducing phenotypic variability by slipped-mispair during DNA, RNA or protein synthesis. PMID:11972324

  15. Down-regulation of the autophagy gene, ATG7, protects bone marrow-derived mesenchymal stem cells from stressful conditions

    PubMed Central

    Molaei, Sedigheh; Amiri, Fatemeh; Harati, Mozhgan Dehghan; Bahadori, Marzie; Jaleh, Fatemeh; Jalili, Mohammad Ali; Mohammadi Roushandeh, Amaneh

    2015-01-01

    Background Mesenchymal stem cells (MSCs) are valuable for cell-based therapy. However, their application is limited owing to their low survival rate when exposed to stressful conditions. Autophagy, the process by which cells recycle the cytoplasm and dispose of defective organelles, is activated by stress stimuli to adapt, tolerate adverse conditions, or trigger the apoptotic machinery. This study aimed to determine whether regulation of autophagy would affect the survival of MSCs under stress conditions. Methods Autophagy was induced in bone marrow-derived MSCs (BM-MSCs) by rapamycin, and was inhibited via shRNA-mediated knockdown of the autophagy specific gene, ATG7. ATG7 expression in BM-MSCs was evaluated by reverse transcription polymerase chain reaction (RT-PCR), western blot, and quantitative PCR (qPCR). Cells were then exposed to harsh microenvironments, and a water-soluble tetrazolium salt (WST)-1 assay was performed to determine the cytotoxic effects of the stressful conditions on cells. Results Of 4 specific ATG7-inhibitor clones analyzed, only shRNA clone 3 decreased ATG7 expression. Under normal conditions, the induction of autophagy slightly increased the viability of MSCs while autophagy inhibition decreased their viability. However, under stressful conditions such as hypoxia, serum deprivation, and oxidative stress, the induction of autophagy resulted in cell death, while its inhibition potentiated MSCs to withstand the stress conditions. The viability of autophagy-suppressed MSCs was significantly higher than that of relevant controls (P<0.05, P<0.01 and P<0.001). Conclusion Autophagy modulation in MSCs can be proposed as a new strategy to improve their survival rate in stressful microenvironments. PMID:26157777

  16. Ultra-short laser-accelerated proton pulses have similar DNA-damaging effectiveness but produce less immediate nitroxidative stress than conventional proton beams

    PubMed Central

    Raschke, S.; Spickermann, S.; Toncian, T.; Swantusch, M.; Boeker, J.; Giesen, U.; Iliakis, G.; Willi, O.; Boege, F.

    2016-01-01

    Ultra-short proton pulses originating from laser-plasma accelerators can provide instantaneous dose rates at least 107-fold in excess of conventional, continuous proton beams. The impact of such extremely high proton dose rates on A549 human lung cancer cells was compared with conventionally accelerated protons and 90 keV X-rays. Between 0.2 and 2 Gy, the yield of DNA double strand breaks (foci of phosphorylated histone H2AX) was not significantly different between the two proton sources or proton irradiation and X-rays. Protein nitroxidation after 1 h judged by 3-nitrotyrosine generation was 2.5 and 5-fold higher in response to conventionally accelerated protons compared to laser-driven protons and X-rays, respectively. This difference was significant (p < 0.01) between 0.25 and 1 Gy. In conclusion, ultra-short proton pulses originating from laser-plasma accelerators have a similar DNA damaging potential as conventional proton beams, while inducing less immediate nitroxidative stress, which probably entails a distinct therapeutic potential. PMID:27578260

  17. Ultra-short laser-accelerated proton pulses have similar DNA-damaging effectiveness but produce less immediate nitroxidative stress than conventional proton beams

    NASA Astrophysics Data System (ADS)

    Raschke, S.; Spickermann, S.; Toncian, T.; Swantusch, M.; Boeker, J.; Giesen, U.; Iliakis, G.; Willi, O.; Boege, F.

    2016-08-01

    Ultra-short proton pulses originating from laser-plasma accelerators can provide instantaneous dose rates at least 107-fold in excess of conventional, continuous proton beams. The impact of such extremely high proton dose rates on A549 human lung cancer cells was compared with conventionally accelerated protons and 90 keV X-rays. Between 0.2 and 2 Gy, the yield of DNA double strand breaks (foci of phosphorylated histone H2AX) was not significantly different between the two proton sources or proton irradiation and X-rays. Protein nitroxidation after 1 h judged by 3-nitrotyrosine generation was 2.5 and 5-fold higher in response to conventionally accelerated protons compared to laser-driven protons and X-rays, respectively. This difference was significant (p < 0.01) between 0.25 and 1 Gy. In conclusion, ultra-short proton pulses originating from laser-plasma accelerators have a similar DNA damaging potential as conventional proton beams, while inducing less immediate nitroxidative stress, which probably entails a distinct therapeutic potential.

  18. Ultra-short laser-accelerated proton pulses have similar DNA-damaging effectiveness but produce less immediate nitroxidative stress than conventional proton beams.

    PubMed

    Raschke, S; Spickermann, S; Toncian, T; Swantusch, M; Boeker, J; Giesen, U; Iliakis, G; Willi, O; Boege, F

    2016-01-01

    Ultra-short proton pulses originating from laser-plasma accelerators can provide instantaneous dose rates at least 10(7)-fold in excess of conventional, continuous proton beams. The impact of such extremely high proton dose rates on A549 human lung cancer cells was compared with conventionally accelerated protons and 90 keV X-rays. Between 0.2 and 2 Gy, the yield of DNA double strand breaks (foci of phosphorylated histone H2AX) was not significantly different between the two proton sources or proton irradiation and X-rays. Protein nitroxidation after 1 h judged by 3-nitrotyrosine generation was 2.5 and 5-fold higher in response to conventionally accelerated protons compared to laser-driven protons and X-rays, respectively. This difference was significant (p < 0.01) between 0.25 and 1 Gy. In conclusion, ultra-short proton pulses originating from laser-plasma accelerators have a similar DNA damaging potential as conventional proton beams, while inducing less immediate nitroxidative stress, which probably entails a distinct therapeutic potential. PMID:27578260

  19. Acid back-diffusion and mucosal H+ handling in the rat stomach under normal and stress-induced conditions.

    PubMed

    Takeuchi, K; Okabe, S

    1983-02-01

    We determined acid back-diffusion and pepsin output simultaneously in vagotomized rats after instillation of HCl into the stomach under normal and stress-induced conditions. With exposure to 6 ml of 100 mM HCl, spontaneous acid back-diffusion increased with the duration of the experiment under both conditions, and the magnitude of the acid back-diffusion was decreased significantly by stress. There was no change in the output of pepsin. While disappearance of luminal acid caused by aspirin or taurocholic acid was not altered by stress, the pepsin output in response to H+ increased significantly in the stressed rats. With exposure to various concentrations of HCl for 3 hr, disappearance of the luminal acid increased linearly with the grade of HCl under both conditions. Except for the concentration of 300 mM, the magnitude of the acid back-diffusion was triple in the normal condition, and the ratio of pepsin output/net flux of H+ was significantly increased by stress. Thus, (1) spontaneous acid back-diffusion decreased with stress, while diffusion induced by chemical barrier breakers remained the same; (2) the action of H+ diffused back into the mucosa did not always parallel the amount of diffusion determined from the loss of H+ in the lumen; (3) intramucosal H+ may be largely dissipated in normal mucosa; and (4) the initiation or aggravation of drug-induced mucosal damages by stress may be related to insufficiency of the H+ dissipating mechanisms. PMID:6410110

  20. Acceleration of Fatigue Crack Growth after Overload in Carbon Steel

    NASA Astrophysics Data System (ADS)

    Yamauchi, A.; Miyahara, H.; Makabe, C.; Miyazaki, T.

    The effects of an overload on fatigue crack growth behavior have been investigated by using carbon steel. Delayed retardation and acceleration of crack growth were both observed. These phenomena depended not only on overload conditions but also on the baseline stress conditions. Moreover, the mechanical properties of the materials affected the crack growth rate after overload. It was found that crack growth accelerated when tensile residual stress was distributed in front of the crack tip. The residual stress distribution is related to the crack opening geometry at the overload stage.

  1. Timing of favorable conditions, competition and fertility interact to govern recruitment of invasive Chinese tallow tree in stressful environments.

    PubMed

    Gabler, Christopher A; Siemann, Evan

    2013-01-01

    The rate of new exotic recruitment following removal of adult invaders (reinvasion pressure) influences restoration outcomes and costs but is highly variable and poorly understood. We hypothesize that broad variation in average reinvasion pressure of Triadica sebifera (Chinese tallow tree, a major invader) arises from differences among habitats in spatiotemporal availability of realized recruitment windows. These windows are periods of variable duration long enough to permit establishment given local environmental conditions. We tested this hypothesis via a greenhouse mesocosm experiment that quantified how the duration of favorable moisture conditions prior to flood or drought stress (window duration), competition and nutrient availability influenced Triadica success in high stress environments. Window duration influenced pre-stress seedling abundance and size, growth during stress and final abundance; it interacted with other factors to affect final biomass and germination during stress. Stress type and competition impacted final size and biomass, plus germination, mortality and changes in size during stress. Final abundance also depended on competition and the interaction of window duration, stress type and competition. Fertilization interacted with competition and stress to influence biomass and changes in height, respectively, but did not affect Triadica abundance. Overall, longer window durations promoted Triadica establishment, competition and drought (relative to flood) suppressed establishment, and fertilization had weak effects. Interactions among factors frequently produced different effects in specific contexts. Results support our 'outgrow the stress' hypothesis and show that temporal availability of abiotic windows and factors that influence growth rates govern Triadica recruitment in stressful environments. These findings suggest that native seed addition can effectively suppress superior competitors in stressful environments. We also describe

  2. Synechococcus sp. Strain PCC 7002 Transcriptome: Acclimation to Temperature, Salinity, Oxidative Stress, and Mixotrophic Growth Conditions

    PubMed Central

    Ludwig, Marcus; Bryant, Donald A.

    2012-01-01

    Synechococcus sp. strain PCC 7002 is a unicellular, euryhaline cyanobacterium. It is a model organism for studies of cyanobacterial metabolism and has great potential for biotechnological applications. It exhibits an exceptional tolerance of high-light irradiation and shows very rapid growth. The habitats from which this and closely related strains were isolated are subject to changes in several environmental factors, including light, nutrient supply, temperature, and salinity. In this study global transcriptome profiling via RNAseq has been used to perform a comparative and integrated study of global changes in cells grown at different temperatures, at different salinities, and under mixotrophic conditions, when a metabolizable organic carbon source was present. Furthermore, the transcriptomes were investigated for cells that were subjected to a heat shock and that were exposed to oxidative stress. Lower growth temperatures caused relatively minor changes of the transcriptome; the most prominent changes affected fatty acid desaturases. A heat shock caused severe changes of the transcriptome pattern; transcripts for genes associated with major metabolic pathways declined and those for different chaperones increased dramatically. Oxidative stress, however, left the transcript pattern almost unaffected. When grown at high salinity, Synechococcus sp. PCC 7002 had increased expression of genes involved in compatible solute biosynthesis and showed increased mRNA levels for several genes involved in electron transport. Transcripts of two adjacent genes dramatically increased upon growth at high salinity; the respective proteins are putatively involved in coping with oxidative stress and in triggering ion channels. Only minor changes were observed when cells were grown at low salinity or when the growth medium was supplemented with glycerol. However, the transcriptome data suggest that cells must acclimate to excess reducing equivalents when a reduced C-source is present

  3. Hydrogen sulfide protects endothelial nitric oxide function under conditions of acute oxidative stress in vitro.

    PubMed

    Al-Magableh, Mohammad R; Kemp-Harper, Barbara K; Ng, Hooi H; Miller, Alyson A; Hart, Joanne L

    2014-01-01

    The aim of this study was to examine the ability of H2S, released from NaHS to protect vascular endothelial function under conditions of acute oxidative stress by scavenging superoxide anions (O2(-)) and suppressing vascular superoxide anion production. O2(-) was generated in Krebs' solution by reacting hypoxanthine with xanthine oxidase (Hx-XO) or with the O2(-) generator pyrogallol to model acute oxidative stress in vitro. O2(-) generation was measured by lucigenin-enhanced chemiluminescence. Functional responses in mouse aortic rings were assessed using a small vessel myograph. NaHS scavenged O2(-) in a concentration-dependent manner. Isolated aortic rings exposed to either Hx-XO or pyrogallol displayed significantly attenuated maximum vasorelaxation responses to the endothelium-dependent vasodilator acetylcholine, and significantly reduced NO bioavailability, which was completely reversed if vessels were pre-incubated with NaHS (100 μM). NADPH-stimulated aortic O2(-) production was significantly attenuated by the NADPH oxidase inhibitor diphenyl iodonium. Prior treatment of vessels with NaHS (100 nM-100 μM; 30 min) inhibited NADPH-stimulated aortic O2(-) production in a concentration-dependent manner. This effect persisted when NaHS was washed out prior to measuring NADPH-stimulated O2(-) production. These data show for the first time that NaHS directly scavenges O2(-) and suppresses vascular NADPH oxidase-derived O2(-) production in vitro. Furthermore, these properties protect endothelial function and NO bioavailability in an in vitro model of acute oxidative stress. These results suggest that H2S can elicit vasoprotection by both scavenging O2(-) and by reducing vascular NADPH oxidase-derived O2(-) production.

  4. Job-Related Stress and Chronic Health Conditions Among Filipino Immigrants

    PubMed Central

    de Castro, A. B.; Gee, Gilbert C.; Takeuchi, David T.

    2009-01-01

    Objectives We investigate how duration in the US impacts the relationship between job-related stress and health conditions among Filipino immigrants. Methods Using data from the Filipino American Community Epidemiologic Study, a cross-sectional sample of 1,381 immigrant Filipinos was obtained. Negative binomial regression was used to examine the interaction between years residing in the US and job concerns on number of self-reported health conditions. Results Job concern is positively associated with health conditions for all immigrants no matter what length of time they have spent in the US. This association is strongest for recent immigrants and the strength of the association weakened with increasing time spent in the US. Conclusions Findings suggest that job-related stressors are associated with adverse health outcomes among Filipino immigrants and that this relationship is strongest for newer immigrants. New immigrants should be recognized as a vulnerable group with regard to the impact of work on their well-being. PMID:18373275

  5. Trauma and Conditional Risk of Posttraumatic Stress Disorder in Two American Indian Reservation Communities

    PubMed Central

    Beals, Janette; Belcourt-Dittloff, Annjeanette; Garroutte, Eva M.; Croy, Calvin; Jervis, Lori L.; Whitesell, Nancy Rumbaugh; Mitchell, Christina M.; Manson, Spero M.

    2012-01-01

    Purpose To determine conditional risk of posttraumatic stress disorder (PTSD) in two culturally distinct American Indian reservation communities. Method Data from the American Indian Service Utilization, Psychiatric Epidemiology, Risk and Protective Factors Project, a cross-sectional population-based survey completed between 1997 and 2000. This study focused on 1,967 participants meeting the DSM-IV criteria for trauma exposure. Traumas were grouped into interpersonal, non-interpersonal, witnessed, and “trauma to close others” categories. Analyses examined distribution of worst traumas, conditional rates of PTSD following exposure, and distributions of PTSD cases deriving from these events. Bivariate and multivariate logistic regressions estimated associations of lifetime PTSD with trauma type. Results Overall, 15.9% of those exposed to DSM-IV trauma qualified for lifetime PTSD, a rate comparable to similar U.S. studies. Women were more likely to develop PTSD than were men. The majority (60%) of cases of PTSD among women derived from interpersonal trauma exposure (in particular, sexual and physical abuse); among men, cases were more evenly distributed across trauma categories. Conclusions Previous research has demonstrated higher rates of both trauma exposure and PTSD in American Indian samples compared to other Americans. This study shows that conditional rates of PTSD are similar to those reported elsewhere, suggesting that the elevated prevalence of this disorder in American Indian populations is largely due to higher rates of trauma exposure. PMID:23135256

  6. Stress and body condition in a population of largemouth bass: implications for red-sore disease

    SciTech Connect

    Esch, G.W.; Hazen, T.C.

    1980-09-01

    The body conditions, K = 10/sup 5/(weight, g)/(standard length)/sup 3/, and various hematological characters were examined for largemouth bass (Micropterus salmoides) taken from Par Pond, a reservoir heated by effluent from a nuclear production reactor at the Savannah River Plant near Aiken, South Carolina. Largemouth bass with K less than 2.0 had significantly lower (P < 0.05) hematocrits, hemoglobin concentrations, total red blood cell counts, total white blood cell counts, and lymphocyte fractions, and significantly higher granulocyte fractions and cortisol concentrations, than those with K greater than 2.0; monocyte, thrombocyte, and reticulocyte fractions were not different between the two K-factor groupings. When data were pooled, all blood variables except the reticulocyte fraction were significantly correlated with K. Hematocrit, the lymphocyte fraction, and cortisol concentration account for 20.5% of the variation in K. These data support a previous hypothesis that elevated water temperature promotes stress. Stress within the Par Pond largemouth bass population may play an important role in the epizootiology of red-sore disease caused by the gram-negative bacterium, Aeromonas hydrophila.

  7. Expression of tissue transglutaminase on primary olfactory ensheathing cells cultures exposed to stress conditions.

    PubMed

    Campisi, Agata; Spatuzza, Michela; Russo, Antonella; Raciti, Giuseppina; Vanella, Angelo; Stanzani, Stefania; Pellitteri, Rosalia

    2012-04-01

    Tissue transglutaminase (TG2), a multifunctional enzyme implicated in cellular proliferation and differentiation processes, plays a modulatory role in the cell response to stressors. Herein, we used olfactory ensheathing cells (OECs), representing an unusual population of glial cells to promote axonal regeneration and to provide trophic support, as well as to assess whether the effect of some Growth Factors (GFs), NGF, bFGF or GDNF, on TG2 overexpression induced by stress conditions, such as glutamate or lipopolysaccaride (LPS). Glial Fibrillary Acidic Protein (GFAP) and vimentin were used as markers of astroglial differentiation and cytoskeleton component, respectively. Glutamate or LPS treatment induced a particular increase of TG2 expression. A pre-treatment of the cells with the GFs restored the levels of the protein to that of untreated ones. Our results demonstrate that the treatment of OECs with the GFs was able to restore the OECs oxidative status as modified by stress, also counteracting TG2 overexpression. It suggests that, in OECs, TG2 modulation or inhibition induced by GFs might represent a therapeutic target to control the excitotoxicity and/or inflammation, which are involved in several acute and chronic brain diseases.

  8. Microcystin Production and Regulation under Nutrient Stress Conditions in Toxic Microcystis Strains

    PubMed Central

    Pimentel, Juliana S. M.

    2014-01-01

    Microcystin is a common and well-known cyanobacterial toxin whose intracellular role is still under investigation. Increasing knowledge on microcystin gene expression and regulation can contribute to the understanding of its putative cellular function. In this work, reverse transcription-quantitative PCR (RT-qPCR) was used to investigate the transcriptional response of the mcyD gene to nitrogen (nitrate and ammonium) and phosphorus limitation in two toxic Microcystis strains. The existence of a direct correlation between transcripts of mcyD and ntcA genes was also identified. In previous studies, NtcA (global nitrogen regulator) has been described as a potential component in the control of microcystin biosynthesis. This research showed that stress agents linked to nutrient deprivation could lead to a significant increase of microcystin production in both strains studied. The more toxic strain proved to be more resistant to nutrient limitation. The similar outcomes of mcyD regulation observed for all nutrients suggest that this response can be linked to oxidative stress of cells undergoing adverse growth conditions. PMID:25038094

  9. A uniaxial stress capacitive dilatometer for high-resolution thermal expansion and magnetostriction under multiextreme conditions.

    PubMed

    Küchler, R; Stingl, C; Gegenwart, P

    2016-07-01

    Thermal expansion and magnetostriction are directional dependent thermodynamic quantities. For the characterization of novel quantum phases of matter, it is required to study materials under multi-extreme conditions, in particular, down to very low temperatures, in very high magnetic fields or under high pressure. We developed a miniaturized capacitive dilatometer suitable for temperatures down to 20 mK and usage in high magnetic fields, which exerts a large spring force between 40 to 75 N on the sample. This corresponds to a uniaxial stress up to 3 kbar for a sample with cross section of (0.5 mm)(2). We describe design and performance test of the dilatometer which resolves length changes with high resolution of 0.02 Å at low temperatures. The miniaturized device can be utilized in any standard cryostat, including dilution refrigerators or the commercial physical property measurement system. PMID:27475567

  10. Cyclic-stress analysis of notches for supersonic transport conditions. [using finite element method

    NASA Technical Reports Server (NTRS)

    1974-01-01

    The feasibility of using the finite element method to account for the effects of cyclic load and temperature on local stresses and strains at a notch was demonstrated. The behavior of a notched titanium panel was studied under variable loads and temperatures representative of flight conditions for the lower wing surface of a Supersonic Transport (SST). The analysis was performed with the use of the BOPACE finite-element computer program which provides capability to determine high temperature and large viscoplastic effects caused by cyclic thermal and mechanical loads. The analysis involves the development of the finite-element model as well as determination of the structural behavior of the notched panel. Results are presented for twelve SST flights comprised of five different load-temperature cycles. The results show the approach is feasible, but material response to cyclic loads, temperatures, and hold times requires improved understanding to allow proper modeling of the material.

  11. Photosynthesis and transpiration of loblolly pine seedlings as influenced by moisture-stress conditioning

    SciTech Connect

    Seiler, J.R.; Johnson, J.D.

    1985-01-01

    One-yr-old seedlings were exposed to 8 wk of moisture stress conditioning (MSC); seedlings were watered only when pre-dawn needle water potential fell below -1.4 MPa. Water was then withheld and photosynthesis and transpiration rates recorded. Photosynthesis in well-watered controls and MSC seedlings was reduced to zero in 12 and 17 days respectively. Seedlings were harvested and water use efficiency calculated using photosynthesis and transpiration data; it was expressed as mg of CO/sub 2/ fixed per g of water lost. Seedlings exposed to MSC continued to photosynthesize to much lower needle water potentials. This response is at least partly attributed to the significant decrease (0.45 MPa) in needle osmotic potential found in MSC seedlings, which were able to maintain turgor to lower needle water potentials. Transpiration rate decreased 30% and water use efficiency increased 67% as a result of MSC. 26 references.

  12. Functions of Nitric Oxide (NO) in Roots during Development and under Adverse Stress Conditions

    PubMed Central

    Corpas, Francisco J.; Barroso, Juan B.

    2015-01-01

    The free radical molecule, nitric oxide (NO), is present in the principal organs of plants, where it plays an important role in a wide range of physiological functions. Root growth and development are highly regulated by both internal and external factors such as nutrient availability, hormones, pattern formation, cell polarity and cell cycle control. The presence of NO in roots has opened up new areas of research on the role of NO, including root architecture, nutrient acquisition, microorganism interactions and the response mechanisms to adverse environmental conditions, among others. Additionally, the exogenous application of NO throughout the roots has the potential to counteract specific damages caused by certain stresses. This review aims to provide an up-to-date perspective on NO functions in the roots of higher plants. PMID:27135326

  13. Stress responses of Calluna vulgaris to reduced and oxidised N applied under 'real world conditions'.

    PubMed

    Sheppard, Lucy J; Leith, Ian D; Crossley, A; Van Dijk, N; Fowler, D; Sutton, M A; Woods, C

    2008-08-01

    Effects and implications of reduced and oxidised N, applied under 'real world' conditions, since May 2002, are reported for Calluna growing on an ombrotrophic bog. Ammonia has been released from a 10 m line source generating monthly concentrations of 180-6 microg m(-3), while ammonium chloride and sodium nitrate are applied in rainwater at nitrate and ammonium concentrations below 4mM and providing up to 56 kg N ha(-1) year(-1) above a background deposition of 10 kg N ha(-1) year(-1). Ammonia concentrations, >8 microg m(-3) have significantly enhanced foliar N concentrations, increased sensitivity to drought, frost and winter desiccation, spring frost damage and increased the incidence of pathogen outbreaks. The mature Calluna bushes nearest the NH3 source have turned bleached and moribund. By comparison the Calluna receiving reduced and oxidised N in rain has shown no significant visible or stress related effects with no significant increase in N status.

  14. Stress responses of Calluna vulgaris to reduced and oxidised N applied under 'real world conditions'.

    PubMed

    Sheppard, Lucy J; Leith, Ian D; Crossley, A; Van Dijk, N; Fowler, D; Sutton, M A; Woods, C

    2008-08-01

    Effects and implications of reduced and oxidised N, applied under 'real world' conditions, since May 2002, are reported for Calluna growing on an ombrotrophic bog. Ammonia has been released from a 10 m line source generating monthly concentrations of 180-6 microg m(-3), while ammonium chloride and sodium nitrate are applied in rainwater at nitrate and ammonium concentrations below 4mM and providing up to 56 kg N ha(-1) year(-1) above a background deposition of 10 kg N ha(-1) year(-1). Ammonia concentrations, >8 microg m(-3) have significantly enhanced foliar N concentrations, increased sensitivity to drought, frost and winter desiccation, spring frost damage and increased the incidence of pathogen outbreaks. The mature Calluna bushes nearest the NH3 source have turned bleached and moribund. By comparison the Calluna receiving reduced and oxidised N in rain has shown no significant visible or stress related effects with no significant increase in N status. PMID:18177985

  15. A uniaxial stress capacitive dilatometer for high-resolution thermal expansion and magnetostriction under multiextreme conditions

    NASA Astrophysics Data System (ADS)

    Küchler, R.; Stingl, C.; Gegenwart, P.

    2016-07-01

    Thermal expansion and magnetostriction are directional dependent thermodynamic quantities. For the characterization of novel quantum phases of matter, it is required to study materials under multi-extreme conditions, in particular, down to very low temperatures, in very high magnetic fields or under high pressure. We developed a miniaturized capacitive dilatometer suitable for temperatures down to 20 mK and usage in high magnetic fields, which exerts a large spring force between 40 to 75 N on the sample. This corresponds to a uniaxial stress up to 3 kbar for a sample with cross section of (0.5 mm)2. We describe design and performance test of the dilatometer which resolves length changes with high resolution of 0.02 Å at low temperatures. The miniaturized device can be utilized in any standard cryostat, including dilution refrigerators or the commercial physical property measurement system.

  16. Stability of CIGS solar cells and component materials evaluated by a step-stress accelerated degradation test method

    NASA Astrophysics Data System (ADS)

    Pern, F. J.; Noufi, R.

    2012-10-01

    A step-stress accelerated degradation testing (SSADT) method was employed for the first time to evaluate the stability of CuInGaSe2 (CIGS) solar cells and device component materials in four Al-framed test structures encapsulated with an edge sealant and three kinds of backsheet or moisture barrier film for moisture ingress control. The SSADT exposure used a 15°C and then a 15% relative humidity (RH) increment step, beginning from 40°C/40%RH (T/RH = 40/40) to 85°C/70%RH (85/70) as of the moment. The voluminous data acquired and processed as of total DH = 3956 h with 85/70 = 704 h produced the following results. The best CIGS solar cells in sample Set-1 with a moisture-permeable TPT backsheet showed essentially identical I-V degradation trend regardless of the Al-doped ZnO (AZO) layer thickness ranging from standard 0.12 μm to 0.50 μm on the cells. No clear "stepwise" feature in the I-V parameter degradation curves corresponding to the SSADT T/RH/time profile was observed. Irregularity in I-V performance degradation pattern was observed with some cells showing early degradation at low T/RH < 55/55 and some showing large Voc, FF, and efficiency degradation due to increased series Rs (ohm-cm2) at T/RH >= 70/70. Results of (electrochemical) impedance spectroscopy (ECIS) analysis indicate degradation of the CIGS solar cells corresponded to increased series resistance Rs (ohm) and degraded parallel (minority carrier diffusion/recombination) resistance Rp, capacitance C, overall time constant Rp*C, and "capacitor quality" factor (CPE-P), which were related to the cells' p-n junction properties. Heating at 85/70 appeared to benefit the CIGS solar cells as indicated by the largely recovered CPE-P factor. Device component materials, Mo on soda lime glass (Mo/SLG), bilayer ZnO (BZO), AlNi grid contact, and CdS/CIGS/Mo/SLG in test structures with TPT showed notable to significant degradation at T/RH >= 70/70. At T/RH = 85/70, substantial blistering of BZO layers on CIGS

  17. Stability of CIGS Solar Cells and Component Materials Evaluated by a Step-Stress Accelerated Degradation Test Method: Preprint

    SciTech Connect

    Pern, F. J.; Noufi, R.

    2012-10-01

    A step-stress accelerated degradation testing (SSADT) method was employed for the first time to evaluate the stability of CuInGaSe2 (CIGS) solar cells and device component materials in four Al-framed test structures encapsulated with an edge sealant and three kinds of backsheet or moisture barrier film for moisture ingress control. The SSADT exposure used a 15oC and then a 15% relative humidity (RH) increment step, beginning from 40oC/40%RH (T/RH = 40/40) to 85oC/70%RH (85/70) as of the moment. The voluminous data acquired and processed as of total DH = 3956 h with 85/70 = 704 h produced the following results. The best CIGS solar cells in sample Set-1 with a moisture-permeable TPT backsheet showed essentially identical I-V degradation trend regardless of the Al-doped ZnO (AZO) layer thickness ranging from standard 0.12 μm to 0.50 μm on the cells. No clear 'stepwise' feature in the I-V parameter degradation curves corresponding to the SSADT T/RH/time profile was observed. Irregularity in I-V performance degradation pattern was observed with some cells showing early degradation at low T/RH < 55/55 and some showing large Voc, FF, and efficiency degradation due to increased series Rs (ohm-cm2) at T/RH ≥ 70/70. Results of (electrochemical) impedance spectroscopy (ECIS) analysis indicate degradation of the CIGS solar cells corresponded to increased series resistance Rs (ohm) and degraded parallel (minority carrier diffusion/recombination) resistance Rp, capacitance C, overall time constant Rp*C, and 'capacitor quality' factor (CPE-P), which were related to the cells? p-n junction properties. Heating at 85/70 appeared to benefit the CIGS solar cells as indicated by the largely recovered CPE-P factor. Device component materials, Mo on soda lime glass (Mo/SLG), bilayer ZnO (BZO), AlNi grid contact, and CdS/CIGS/Mo/SLG in test structures with TPT showed notable to significant degradation at T/RH ≥ 70/70. At T/RH = 85/70, substantial blistering of BZO layers on CIGS

  18. A mouse model of posttraumatic stress disorder that distinguishes between conditioned and sensitised fear.

    PubMed

    Siegmund, Anja; Wotjak, Carsten T

    2007-11-01

    The pathomechanisms of posttraumatic stress disorder (PTSD) are still unknown, but both fear conditioning and stress sensitisation are supposed to play a crucial role. Hence, valid animal models that model both associative and non-associative components of fear will facilitate elucidation of the biological substrates of the illness, and to develop novel and specific approaches for its prevention and therapy. Here we applied a single electric footshock to C57BL/6N (B6N) and C57BL/6JOla (B6JOla) mice and recorded the conditioned response to contextual trauma reminders (associative fear), the sensitised reaction to a neutral tone in a novel environment (non-associative fear, hyperarousal), social interaction and various emotional behaviours using Modified Holeboard, Test for Novelty-Induced Suppression of Feeding and Forced Swimming Test, after different incubation times (1, 14, 28 days). Freezing generally increased as a function of shock intensity. In B6N mice, sensitised fear was maximal 28 days after trauma and was accompanied by signs of emotional blunting and social withdrawal. B6JOla mice, in contrast, were less susceptible to develop PTSD-like symptoms. The phenotype of B6N exhibited high behavioural variance, allowing distinction between vulnerable and resilient individuals. Only in vulnerable B6N mice, chronic fluoxetine treatment - initiated after an incubation period of 28 days - ameliorated sensitised fear. This new mouse model fulfils common criteria for face and predictive validity and can be used to investigate the biological correlates of individual fear susceptibility, as well as the impact and interrelationship of associative and non-associative fear components in the development and maintenance of PTSD. PMID:17027033

  19. Alkaline phosphatase activity related to phosphorus stress of microphytoplankton in different trophic conditions

    NASA Astrophysics Data System (ADS)

    Ivančić, Ingrid; Pfannkuchen, Martin; Godrijan, Jelena; Djakovac, Tamara; Marić Pfannkuchen, Daniela; Korlević, Marino; Gašparović, Blaženka; Najdek, Mirjana

    2016-08-01

    The northern Adriatic (NA) is a favorable basin for studying the adaptive strategies of plankton to a variety of conditions along the steep gradients of environmental parameters over the year. Earlier studies identified phosphorus (P)-limitation as one of the key stresses within the NA that shape the biological response in terms of biodiversity and metabolic adjustments. A wide range of reports supports the notion that P-limitation is a globally important phenomenon in aquatic ecosystems. In this study P stress of marine microphytoplankton was determined at species level along a trophic gradient in the NA. In P-limitation all species with considerable contributions to the diatom community expressed alkaline phosphatase activity (APA), compared to only a few marginal dinoflagellate species. Nevertheless, APA expressing species did not always dominate the phytoplankton community, suggesting that APA is also an important strategy for species to survive and maintain active metabolism outside of their mass abundances. A symbiotic relationship could be supposed for diatoms that did not express APA themselves and probably benefited from APA expressed by attached bacteria. APA was not expressed by any microphytoplankton species during the autumn when P was not limiting, while most of the species did express APA during the P-limitation. This suggests that APA expression is regulated by orthophosphate availability. The methods employed in this study allowed the microscopic detection of APA for each microphytoplankton cell with simultaneous morphologic/taxonomic analysis. This approach uncovered a set of strategies to compete in P-limited conditions within the marine microphytoplankton community. This study confirms the role of P-limitation as a shaping factor in marine ecosystems.

  20. Severe early life stress hampers spatial learning and neurogenesis, but improves hippocampal synaptic plasticity and emotional learning under high-stress conditions in adulthood.

    PubMed

    Oomen, Charlotte A; Soeters, Heleen; Audureau, Nathalie; Vermunt, Lisa; van Hasselt, Felisa N; Manders, Erik M M; Joëls, Marian; Lucassen, Paul J; Krugers, Harm

    2010-05-12

    Early life stress increases the risk for developing stress-related pathologies later in life. Recent studies in rats suggest that mild early life stress, rather than being overall unfavorable, may program the hippocampus such that it is optimally adapted to a stressful context later in life. Here, we tested whether this principle of "adaptive programming" also holds under severely adverse early life conditions, i.e., 24 h of maternal deprivation (MD), a model for maternal neglect. In young adult male rats subjected to MD on postnatal day 3, we observed reduced levels of adult hippocampal neurogenesis as measured by cell proliferation, cell survival, and neuronal differentiation. Also, mature dentate granule cells showed a change in their dendritic morphology that was most noticeable in the proximal part of the dendritic tree. Lasting structural changes due to MD were paralleled by impaired water maze acquisition but did not affect long-term potentiation in the dentate gyrus. Importantly, in the presence of high levels of the stress hormone corticosterone, even long-term potentiation in the dentate gyrus of MD animals was facilitated. In addition to this, contextual learning in a high-stress environment was enhanced in MD rats. These morphological, electrophysiological, and behavioral observations show that even a severely adverse early life environment does not evolve into overall impaired hippocampal functionality later in life. Rather, adversity early in life can prepare the organism to perform optimally under conditions associated with high corticosteroid levels in adulthood.

  1. Coenzyme Q10 prevents hepatic fibrosis, inflammation, and oxidative stress in a male rat model of poor maternal nutrition and accelerated postnatal growth1

    PubMed Central

    Tarry-Adkins, Jane L; Fernandez-Twinn, Denise S; Hargreaves, Iain P; Neergheen, Viruna; Aiken, Catherine E; Martin-Gronert, Malgorzata S; McConnell, Josie M; Ozanne, Susan E

    2016-01-01

    Background: It is well established that low birth weight and accelerated postnatal growth increase the risk of liver dysfunction in later life. However, molecular mechanisms underlying such developmental programming are not well characterized, and potential intervention strategies are poorly defined. Objectives: We tested the hypotheses that poor maternal nutrition and accelerated postnatal growth would lead to increased hepatic fibrosis (a pathological marker of liver dysfunction) and that postnatal supplementation with the antioxidant coenzyme Q10 (CoQ10) would prevent this programmed phenotype. Design: A rat model of maternal protein restriction was used to generate low-birth-weight offspring that underwent accelerated postnatal growth (termed “recuperated”). These were compared with control rats. Offspring were weaned onto standard feed pellets with or without dietary CoQ10 (1 mg/kg body weight per day) supplementation. At 12 mo, hepatic fibrosis, indexes of inflammation, oxidative stress, and insulin signaling were measured by histology, Western blot, ELISA, and reverse transcriptase–polymerase chain reaction. Results: Hepatic collagen deposition (diameter of deposit) was greater in recuperated offspring (mean ± SEM: 12 ± 2 μm) than in controls (5 ± 0.5 μm) (P < 0.001). This was associated with greater inflammation (interleukin 6: 38% ± 24% increase; P < 0.05; tumor necrosis factor α: 64% ± 24% increase; P < 0.05), lipid peroxidation (4-hydroxynonenal, measured by ELISA: 0.30 ± 0.02 compared with 0.19 ± 0.05 μg/mL per μg protein; P < 0.05), and hyperinsulinemia (P < 0.05). CoQ10 supplementation increased (P < 0.01) hepatic CoQ10 concentrations and ameliorated liver fibrosis (P < 0.001), inflammation (P < 0.001), some measures of oxidative stress (P < 0.001), and hyperinsulinemia (P < 0.01). Conclusions: Suboptimal in utero nutrition combined with accelerated postnatal catch-up growth caused more hepatic fibrosis in adulthood, which was

  2. Stress-induced hyperthermia depends on both time of day and light condition.

    PubMed

    Peloso, Elizabeth; Wachulec, Maciej; Satinoff, Evelyn

    2002-04-01

    Rats placed in an environment other than their home cage increase their body temperature (Tb) by more than 1 degree C. This stress-induced hyperthermia is considered to be a fever, in the sense that the Tb rise seems to reflect an upward shift in the level of regulated Tb (set point). The circadian rhythm of Tb also reflects changes in set point. One might therefore expect to see differences in response to such stress during various phases of the light-dark (LD) cycle as Tb fluctuates between L and D. To test this, 3- to 6-month-old male Long-Evans rats were taken from their home cages (12:12 LD) and placed individually in a Plexiglas container for 30 min. Tb and activity were measured via telemetry. In the first experiment, rats were placed in the container during day (from 1 to 3 h after lights on) and night (from 1 to 3 h after lights off), with light on or off during the test. There was a significant Tb rise in response to placement in the container at all times except when the rats were tested during the night with light on in the container; in that condition there was no Tb rise. In the second experiment, the authors determined that 30 min of light in the home cage before the test did not affect Tb: If the light was on in the test situation, hyperthermia was inhibited, and if it was off, hyperthermia was as high as control levels. In the third experiment, to determine whether this effect was time dependent, the test was performed at 4-h intervals, with light on or off during the test. The strongest inhibiting effect of light was in early night. In the fourth experiment, the authors turned the lights on during early night while the rats were in their home cages. This reduced their Tb significantly by less than 0.3 degrees C. The authors conclude that both clock time and light condition during testing are factors affecting the Tb rise in response to stress. PMID:12002163

  3. Timing of Favorable Conditions, Competition and Fertility Interact to Govern Recruitment of Invasive Chinese Tallow Tree in Stressful Environments

    PubMed Central

    Gabler, Christopher A.; Siemann, Evan

    2013-01-01

    The rate of new exotic recruitment following removal of adult invaders (reinvasion pressure) influences restoration outcomes and costs but is highly variable and poorly understood. We hypothesize that broad variation in average reinvasion pressure of Triadica sebifera (Chinese tallow tree, a major invader) arises from differences among habitats in spatiotemporal availability of realized recruitment windows. These windows are periods of variable duration long enough to permit establishment given local environmental conditions. We tested this hypothesis via a greenhouse mesocosm experiment that quantified how the duration of favorable moisture conditions prior to flood or drought stress (window duration), competition and nutrient availability influenced Triadica success in high stress environments. Window duration influenced pre-stress seedling abundance and size, growth during stress and final abundance; it interacted with other factors to affect final biomass and germination during stress. Stress type and competition impacted final size and biomass, plus germination, mortality and changes in size during stress. Final abundance also depended on competition and the interaction of window duration, stress type and competition. Fertilization interacted with competition and stress to influence biomass and changes in height, respectively, but did not affect Triadica abundance. Overall, longer window durations promoted Triadica establishment, competition and drought (relative to flood) suppressed establishment, and fertilization had weak effects. Interactions among factors frequently produced different effects in specific contexts. Results support our ‘outgrow the stress’ hypothesis and show that temporal availability of abiotic windows and factors that influence growth rates govern Triadica recruitment in stressful environments. These findings suggest that native seed addition can effectively suppress superior competitors in stressful environments. We also describe

  4. Wheel running can accelerate or delay extinction of conditioned place preference for cocaine in male C57BL/6J mice, depending on timing of wheel access.

    PubMed

    Mustroph, Martina L; Stobaugh, Derrick J; Miller, Daniel S; DeYoung, Erin K; Rhodes, Justin S

    2011-10-01

    Aerobic exercise may represent a useful intervention for drug abuse in predisposed individuals. Exercise increases plasticity in the brain that could be used to reverse learned drug associations. Previous studies have reported that exposing mice to a complex environment including running wheels after drug conditioning abolishes conditioned place preference (CPP) for cocaine, whereas running can enhance CPP when administered before conditioning. The purpose of the present study was to test the hypothesis that timing of exercise relative to conditioning has opposing effects on cocaine CPP. Male C57BL/6J mice experienced 30 days of running or sedentary treatments either before or after cocaine conditioning. Control animals always received saline and never cocaine, but otherwise underwent the same conditioning and exercise treatments. Animals were given bromodeoxyuridine injections at the onset of conditioning or exercise, and euthanized at the end of the study to quantify survival of new neurons in the hippocampus as a marker of plasticity. Wheel running accelerated extinction of CPP when running occurred entirely after drug conditioning, whereas running delayed extinction when administered before conditioning. A single conditioning day after running was sufficient to abolish the accelerated extinction observed when all conditioning preceded running. Running approximately doubled adult hippocampal neurogenesis, whereas cocaine had no effect. These results suggest that exercise-induced plasticity can facilitate learning that context is no longer associated with drug. However, if drug exposure occurs after exercise, running-induced plasticity may strengthen drug associations. The results provide insights into the interaction between exercise and drug conditioning that could have implications for drug abuse treatments.

  5. Stress symptoms among adolescents: the role of subjective psychosocial conditions, lifestyle, and self-esteem.

    PubMed

    Schraml, Karin; Perski, Aleksander; Grossi, Giorgio; Simonsson-Sarnecki, Margareta

    2011-10-01

    Stress-related problems are increasing among Swedish adolescents, especially among females. The aims of this study were to survey the incidence of stress symptoms among 16-year-olds, to investigate the related gender differences, and to understand the factors that may contribute to stress symptoms. The study is questionnaire based, and the sample included 304 first-year high school students from two comparable schools. More than 30% of the high school students reported serious stress symptoms. Almost every second girl and every fifth boy reported that they felt stressed to a high degree. 8.2% were found to have severe stress symptoms, which would be considered a sign of chronic stress in adults. Besides the perception of high demands, low levels of global self-esteem, sleep disturbances, and poor social support played a crucial role in the prediction of stress symptoms. The findings highlight the need to develop and implement adequate stress prevention measures for adolescents.

  6. The impact of scaled boundary conditions on wall shear stress computations in atherosclerotic human coronary bifurcations.

    PubMed

    Schrauwen, Jelle T C; Schwarz, Janina C V; Wentzel, Jolanda J; van der Steen, Antonius F W; Siebes, Maria; Gijsen, Frank J H

    2016-05-15

    The aim of this study was to determine if reliable patient-specific wall shear stress (WSS) can be computed when diameter-based scaling laws are used to impose the boundary conditions for computational fluid dynamics. This study focused on mildly diseased human coronary bifurcations since they are predilection sites for atherosclerosis. Eight patients scheduled for percutaneous coronary intervention were imaged with angiography. The velocity proximal and distal of a bifurcation was acquired with intravascular Doppler measurements. These measurements were used for inflow and outflow boundary conditions for the first set of WSS computations. For the second set of computations, absolute inflow and outflow ratios were derived from geometry-based scaling laws based on angiography data. Normalized WSS maps per segment were obtained by dividing the absolute WSS by the mean WSS value. Absolute and normalized WSS maps from the measured-approach and the scaled-approach were compared. A reasonable agreement was found between the measured and scaled inflows, with a median difference of 0.08 ml/s [-0.01; 0.20]. The measured and the scaled outflow ratios showed a good agreement: 1.5 percentage points [-19.0; 4.5]. Absolute WSS maps were sensitive to the inflow and outflow variations, and relatively large differences between the two approaches were observed. For normalized WSS maps, the results for the two approaches were equivalent. This study showed that normalized WSS can be obtained from angiography data alone by applying diameter-based scaling laws to define the boundary conditions. Caution should be taken when absolute WSS is assessed from computations using scaled boundary conditions. PMID:26945083

  7. Intermittent hypoxia conditioning protects mitochondrial cytochrome c oxidase of rat cerebellum from ethanol withdrawal stress.

    PubMed

    Ju, Xiaohua; Mallet, Robert T; Downey, H Fred; Metzger, Daniel B; Jung, Marianna E

    2012-05-01

    Intermittent hypoxia (IH) conditioning minimizes neurocognitive impairment and stabilizes brain mitochondrial integrity during ethanol withdrawal (EW) in rats, but the mitoprotective mechanism is unclear. We investigated whether IH conditioning protects a key mitochondrial enzyme, cytochrome c oxidase (COX), from EW stress by inhibiting mitochondrially directed apoptotic pathways involving cytochrome c, Bax, or phosphor-P38 (pP38). Male rats completed two cycles of a 4-wk ethanol diet (6.5%) and 3 wk of EW. An IH program consisting of 5-10 bouts of 5-8 min of mild hypoxia (9.5-10% inspired O(2)) and 4 min of reoxygenation for 20 consecutive days began 3 days before the first EW period. For some animals, vitamin E replaced IH conditioning to test the contributions of antioxidant mechanisms to IH's mitoprotection. During the second EW, cerebellar-related motor function was evaluated by measuring latency of fall from a rotating rod (Rotarod test). After the second EW, COX activity in cerebellar mitochondria was measured by spectrophotometry, and COX, cytochrome c, Bax, and pP38 content were analyzed by immunoblot. Mitochondrial protein oxidation was detected by measuring carbonyl contents and by immunochemistry. Earlier IH conditioning prevented motor impairment, COX inactivation, depletion of COX subunit 4, protein carbonylation, and P38 phosphorylation during EW. IH did not prevent cytochrome c depletion during EW, and Bax content was unaffected by EW ± IH. Vitamin E treatment recapitulated IH protection of COX, and P38 inhibition attenuated protein oxidation during EW. Thus IH protects COX and improves cerebellar function during EW by limiting P38-dependent oxidative damage.

  8. The impact of scaled boundary conditions on wall shear stress computations in atherosclerotic human coronary bifurcations.

    PubMed

    Schrauwen, Jelle T C; Schwarz, Janina C V; Wentzel, Jolanda J; van der Steen, Antonius F W; Siebes, Maria; Gijsen, Frank J H

    2016-05-15

    The aim of this study was to determine if reliable patient-specific wall shear stress (WSS) can be computed when diameter-based scaling laws are used to impose the boundary conditions for computational fluid dynamics. This study focused on mildly diseased human coronary bifurcations since they are predilection sites for atherosclerosis. Eight patients scheduled for percutaneous coronary intervention were imaged with angiography. The velocity proximal and distal of a bifurcation was acquired with intravascular Doppler measurements. These measurements were used for inflow and outflow boundary conditions for the first set of WSS computations. For the second set of computations, absolute inflow and outflow ratios were derived from geometry-based scaling laws based on angiography data. Normalized WSS maps per segment were obtained by dividing the absolute WSS by the mean WSS value. Absolute and normalized WSS maps from the measured-approach and the scaled-approach were compared. A reasonable agreement was found between the measured and scaled inflows, with a median difference of 0.08 ml/s [-0.01; 0.20]. The measured and the scaled outflow ratios showed a good agreement: 1.5 percentage points [-19.0; 4.5]. Absolute WSS maps were sensitive to the inflow and outflow variations, and relatively large differences between the two approaches were observed. For normalized WSS maps, the results for the two approaches were equivalent. This study showed that normalized WSS can be obtained from angiography data alone by applying diameter-based scaling laws to define the boundary conditions. Caution should be taken when absolute WSS is assessed from computations using scaled boundary conditions.

  9. The senescence-accelerated mouse-prone 8 is not a suitable model for the investigation of cardiac inflammation and oxidative stress and their modulation by dietary phytochemicals.

    PubMed

    Schiborr, Christina; Schwamm, Dorothea; Kocher, Alexa; Rimbach, Gerald; Eckert, Gunter P; Frank, Jan

    2013-08-01

    Aging is associated with chronic inflammation and oxidative stress, which both may promote age-associated disorders including cardiovascular diseases. The cardiovascular system suffers from the life-long impact of stressors, such as reactive oxygen and nitrogen species. A diet rich in vegetables and fruits, and thus phytochemicals, may extend healthy lifespan in humans, in part by improving heart health by lowering of oxidative stress and modulating signal transduction pathways. To investigate the potential impact of dietary anthocyanin-rich bilberry extract and curcumin on oxidative stress and inflammatory markers in the heart, two groups of senescence-accelerated mouse-resistant 1 (SAMR1) and senescence-accelerated mouse-prone 8 (SAMP8) mice, respectively, were fed a Western-type diet (normal control and aged control, respectively) and two groups of SAMP8 mice were fed either bilberry extract (20g/kg diet) or curcumin (500mg/kg diet) over a period of 5 months. An activation of the transcription factor nuclear factor κ B (NFκB), but no differences in the gene and protein expression of NFκB-regulated pro-inflammatory mediators, was observed in the hearts of SAMP8 compared to SAMR1 control mice. Cardiac concentrations of protein and lipid oxidation parameters were similar in SAMR1 and SAMP8 control mice and the phytochemical-fed SAMP8 mice. Our data question the suitability of the SAMP8 and SAMR1 strains as a model for age-dependent changes of pro-inflammatory cytokines and oxidative stress in the heart.

  10. Dopamine receptor antagonists impair place conditioning after acute stress in rats.

    PubMed

    Shen, Ying-Ling; Chen, Yao-Chu; Liao, Ruey-Ming

    2010-02-01

    An immediate and robust release of dopamine appears in the brain under an acute stressor, but the functional role of dopamine under stress remains elusive. We recently showed conditioned place preference (CPP) induced by the acute application of a stressor such as being placed on an elevated stand or immobilized in a restraint holder. This study tested whether dopamine is involved in such CPP. The selective dopamine D1 and D2 receptor antagonists, SCH23390 and raclopride, respectively, were injected before stressor manipulation. The doses of SCH23390 (0.025 and 0.05 mg/kg) and raclopride (0.05 and 0.1 mg/kg) used to test for stressor-induced CPP were verified to be ineffective on spontaneous locomotor activity. The results showed that both drugs attenuated the development of stressor-induced CPP. Such a CPP blocking effect by pretreatment of dopamine receptor antagonist was true for either kind of stressor manipulated. These findings indicate that an acute stressor can facilitate a follow-up place conditioning, and that dopamine is involved in the present type of CPP formation.

  11. Transcriptional Response of Desulfovibrio vulgaris Hildenborough to Oxidative Stress Mimicking Environmental Conditions

    SciTech Connect

    Pereira, Patricia M.; He, Qiang; Xavier, Antonio V.; Zhou, Jizhong; Pereira, Ines A.C.; Louro, Ricardo O.

    2008-03-12

    Sulphate-reducing bacteria are anaerobes readily found in oxic-anoxic interfaces. Multiple defence pathways against oxidative conditions were identified in these organisms and proposed to be differentially expressed under different concentrations of oxygen, contributing to their ability to survive oxic conditions. In this study, Desulfovibrio vulgaris Hildenborough cells were exposed to the highest concentration of oxygen that sulphate-reducing bacteria are likely to encounter in natural habitats, and the global transcriptomic response was determined. 307 genes were responsive, with cellular roles in energy metabolism, protein fate, cell envelope and regulatory functions, including multiple genes encoding heat shock proteins, peptidases and proteins with heat shock promoters. Of the oxygen reducing mechanisms of D. vulgaris only the periplasmic hydrogen-dependent mechanism is up-regulated, involving the [NiFeSe]hydrogenase, formate dehydrogenase(s) and the Hmc membrane complex. The oxidative defence response concentrates on damage repair by metal-free enzymes. These data, together with the down regulation of the Fur operon, which restricts the availability of iron, and the lack of response of the PerR operon, suggest that a major effect of this oxygen stress is the inactivation and/or degradation of multiple metalloproteins present in D. vulgaris as a consequence of oxidative damage to their metal clusters.

  12. Effects of environmental stress on the condition of Littorina littorea along the Scheldt estuary (The Netherlands).

    PubMed

    Van den Broeck, Heidi; De Wolf, Hans; Backeljau, Thierry; Blust, Ronny

    2007-04-15

    The condition of the periwinkle Littorina littorea, expressed in terms of its shell morphology, reproductive impairment (i.e. female sterility/intersex, male penis shedding), trematode infestation load, lipid reserves and dry/wet weight ratio, was determined in function of environmental stress along the polluted Western and relatively clean Eastern Scheldt estuary (The Netherlands). The upstream increasing pollution and decreasing salinity levels along the Western Scheldt estuary (Fig. 1) are reflected in the dry/wet weight ratio and lipid content of the periwinkles. Compared to the Eastern Scheldt, female intersex (i.e. indicator of TBT pollution) and sterility occurred more frequently in the Western Scheldt estuary, while male penis shedding was even restricted to the latter estuary. The highest population intersex and sterility incidence was found near the harbour of Vlissingen and reflects potential nautical activities. The number of trematode infested periwinkles did not differ between both estuaries, although local sampling site differences were detected within each estuary, reflecting the complex interactions that exist among parasites, hosts and the local environment. Finally, both estuaries were maximally discriminated from each other based on the shell weight of the periwinkles using a canonical discriminant analysis. Periwinkles with the heaviest shells were found in the Western Scheldt estuary and may reflect growth rate or structural population differences caused by the less favourable living conditions in the Western Scheldt estuary. PMID:17343899

  13. Captive European starlings (Sturnus vulgaris) in breeding condition show an increased cardiovascular stress response to intruders.

    PubMed

    Dickens, Molly J; Nephew, Benjamin C; Romero, L Michael

    2006-01-01

    European starlings (Sturnus vulgaris) alter their physiology and behavior between seasons, becoming territorial during the spring/summer and flocking during the fall/winter. We used captive male starlings in breeding (photostimulated to 18L : 6D) and nonbreeding (11L : 13D) conditions to determine whether changing physiology and behavior alters their reaction to crowding. One or five intruders entered a resident's cage without human disturbance. A subcutaneous heart rate transmitter recorded cardiovascular output in residents. Corticosterone and testosterone were measured in plasma samples taken before and after the intrusion. While corticosterone concentrations did not change, heart rate changed significantly, indicating that these responses can be regulated independently. Long-day birds showed a significantly elevated heart rate response to the single-bird intrusion compared to short-day birds. Whereas five intruders elicited an identical peak response in both groups, long-day birds also demonstrated an equivalent response to one intruder. In addition, one intruder induced longer elevation in heart rate for long-day birds. Male starlings in breeding condition, therefore, demonstrate an increased sensitivity to additional conspecifics. This seasonal shift in response suggests that a higher tolerance for intrusion (i.e., considering a nearby starling as less stressful) may facilitate flocking behavior, while a lower tolerance may aid in territoriality. PMID:16927240

  14. Maxwell-Faraday Stresses in Electromagnetic Fields and the Self-Force on a Uniformly Accelerating Point Charge

    ERIC Educational Resources Information Center

    Rowland, D. R.

    2007-01-01

    The physical analysis of a uniformly accelerating point charge provides a rich problem to explore in advanced courses in electrodynamics and relativity since it brings together fundamental concepts in relation to electromagnetic radiation, Einstein's equivalence principle and the inertial mass of field energy in ways that reveal subtleties in each…

  15. Peroxisomal Monodehydroascorbate Reductase. Genomic Clone Characterization and Functional Analysis under Environmental Stress Conditions1

    PubMed Central

    Leterrier, Marina; Corpas, Francisco J.; Barroso, Juan B.; Sandalio, Luisa M.; del Río, Luis A.

    2005-01-01

    In plant cells, ascorbate is a major antioxidant that is involved in the ascorbate-glutathione cycle. Monodehydroascorbate reductase (MDAR) is the enzymatic component of this cycle involved in the regeneration of reduced ascorbate. The identification of the intron-exon organization and the promoter region of the pea (Pisum sativum) MDAR 1 gene was achieved in pea leaves using the method of walking polymerase chain reaction on genomic DNA. The nuclear gene of MDAR 1 comprises nine exons and eight introns, giving a total length of 3,770 bp. The sequence of 544 bp upstream of the initiation codon, which contains the promoter and 5′ untranslated region, and 190 bp downstream of the stop codon were also determined. The presence of different regulatory motifs in the promoter region of the gene might indicate distinct responses to various conditions. The expression analysis in different plant organs by northern blots showed that fruits had the highest level of MDAR. Confocal laser scanning microscopy analysis of pea leaves transformed with Agrobacterium tumefaciens having the binary vectors pGD, which contain the autofluorescent proteins enhanced green fluorescent protein and enhanced yellow fluorescent protein with the full-length cDNA for MDAR 1 and catalase, indicated that the MDAR 1 encoded the peroxisomal isoform. The functional analysis of MDAR by activity and protein expression was studied in pea plants grown under eight stress conditions, including continuous light, high light intensity, continuous dark, mechanical wounding, low and high temperature, cadmium, and the herbicide 2,4-dichlorophenoxyacetic acid. This functional analysis is representative of all the MDAR isoforms present in the different cell compartments. Results obtained showed a significant induction by high light intensity and cadmium. On the other hand, expression studies, performed by semiquantitative reverse transcription-polymerase chain reaction demonstrated differential expression patterns

  16. Stress-relaxation response of human menisci under confined compression conditions.

    PubMed

    Martin Seitz, Andreas; Galbusera, Fabio; Krais, Carina; Ignatius, Anita; Dürselen, Lutz

    2013-10-01

    The objective of this study was to determine the viscoelastic properties of human meniscal tissue during stress-relaxation under confined compression conditions. Lateral and medial longitudinal meniscus plugs of 25 donor knees (ntotal=150) were exposed to stress-relaxation tests under confined compression conditions at three compression levels (ε=0.1; 0.15; 0.2). Mathematical modelling using an exponential 1D-diffusion equation was used to predict the viscoelastic properties. Subsequently, finite element (FE) models were created using identical geometry, properties and test conditions as used for the in-vitro tests. Two constitutively different underlying mathematical formulations were applied to the FE models to reveal possible differences in their predictions for the relaxation response. While the first FE model mimicked the analytical model (FE1), the second FE model used a different biphasic, non-linear approach (FE2). Regression analyses showed promising coefficients of determination (R(2)>0.73) between the experimental data and the predictions obtained from the diffusion equation and the two FE models. Mean aggregate modulus, predicted with the diffusion equation (HA=64.0 kPa) was lower than those obtained with the two FE analyses (HA,FE1=91.9 kPa; HA,FE2=81.5 kPa). Mean hydraulic permeability (kFE2=1.5×10(-15)m(4)/Ns) of the second FE2 approach was statistically lower (p<0.01) than the other permeability values (k=3.9×10(-15)m(4)/Ns; kFE1=3.4×10(-15)m(4)/Ns). These differences are mainly due to the different underlying mathematical models used. However, when compared with corresponding literature, the results of the present study indicated good agreement. The results of the present study contribute to a better understanding of the complex nature of meniscal tissue and might also have an impact on the design of future meniscal substitutes. PMID:23811278

  17. Osmosis-induced swelling of Eurobitum bituminized radioactive waste in constant total stress conditions

    NASA Astrophysics Data System (ADS)

    Valcke, E.; Marien, A.; Smets, S.; Li, X.; Mokni, N.; Olivella, S.; Sillen, X.

    2010-11-01

    In geological disposal conditions, contact of Eurobitum bituminized radioactive waste, which contains high amounts of the hygroscopic and highly soluble NaNO 3, with groundwater will result in water uptake and swelling of the waste, and in subsequent leaching of the embedded NaNO 3 and radionuclides. The swelling of and the NaNO 3 leaching from non-radioactive Eurobitum samples, comprised between two stainless steel filters and in contact with 0.1 M KOH, was studied in restricted (semi-confined) swelling conditions, i.e. under a constant total stress, or counterpressure, of 2.2, 3.3, or 4.4 MPa ( i.e. oedometer conditions). Four tests were stopped after hydration times between 800 and 1500 days, and the samples were analyzed by micro-focus X-ray Computer Tomography (μCT) and by Environmental Scanning Electron Microscopy (ESEM). The complete set of data enabled a consistent interpretation of the observations and lead to an improved understanding of the phenomenology of the water uptake, swelling, and NaNO 3 leaching in restricted swelling conditions. Under the studied conditions, the bituminous matrix surrounding the NaNO 3 crystals and pores with NaNO 3 solution behaved as a highly efficient semi-permeable membrane, i.e. osmotic processes occurred. In the main part of the leached layers, a high average NaNO 3 concentration and related to this a high osmotic pressure prevailed, explaining why in the studied range the swelling was not measurably affected by the counterpressure. At the interface with the stainless steel filters, a low permeable re-compressed bitumen layer was formed, contributing to the slow release of NaNO 3 compared to the water uptake rate. A fully coupled Chemo-Hydro-Mechanical (CHM) constitutive model has been developed that integrates the key processes involved and that reproduces satisfactorily the results; this is presented in another work. Combination of the experimental and the modelling study allow to conclude that under semi

  18. Effect of thermal exposure on the residual stress relaxation in a hardened cylindrical sample under creep conditions

    NASA Astrophysics Data System (ADS)

    Radchenko, V. P.; Saushkin, M. N.; Tsvetkov, V. V.

    2016-05-01

    This paper describes the effect of thermal exposure (high-temperature exposure) ( T = 675°C) on the residual creep stress relaxation in a surface hardened solid cylindrical sample made of ZhS6UVI alloy. The analysis is carried out with the use of experimental data for residual stresses after micro-shot peening and exposures to temperatures equal to T = 675°C during 50, 150, and 300 h. The paper presents the technique for solving the boundary-value creep problem for the hardened cylindrical sample with the initial stress-strain state under the condition of thermal exposure. The uniaxial experimental creep curves obtained under constant stresses of 500, 530, 570, and 600 MPa are used to construct the models describing the primary and secondary stages of creep. The calculated and experimental data for the longitudinal (axial) tensor components of residual stresses are compared, and their satisfactory agreement is determined.

  19. Velocity acceleration as a determinant of flow-mediated dilation.

    PubMed

    Stoner, Lee; McCully, Kevin K

    2012-04-01

    Shear stress is the established stimulus for flow-mediated dilation (FMD). In vivo, shear stress is typically estimated using mean blood velocity. However, mean blood velocity may not adequately characterize the shear stimulus. Pulsatile flow results in large shear gradients (velocity acceleration) at the onset of flow. The purpose of this study was to determine the importance of velocity acceleration to FMD. We define FMD as the brachial artery shear rate-diameter slope. Fourteen physically active, young (26 ± 5 years), male subjects were tested. Progressive forearm heating and handgrip exercise elicited steady-state increases in shear rate. FMD was measured prior to and following induced increases in velocity acceleration. Velocity acceleration was increased by inflating a tourniquet around the forearm to 40 mm Hg. Hierarchical linear modeling was used to estimate change in diameter with repeated measures of shear stress nested within each subject. Averaged across conditions, the 40 mm Hg cuff resulted in a 14% increase in velocity acceleration (p = 0.001). FMD was attenuated by 11.0% (p = 0.015) for the acceleration vs. control condition. However, after specifying velocity acceleration as a covariate, FMD was no longer significantly (p = 0.619) different between acceleration and control conditions. This finding suggests that mean blood velocity alone may not adequately characterize the shear stimulus.

  20. Impact of Mental and Physical Stress on Blood Pressure and Pulse Pressure under Normobaric versus Hypoxic Conditions

    PubMed Central

    Trapp, Michael; Trapp, Eva-Maria; Egger, Josef W.; Domej, Wolfgang; Schillaci, Giuseppe; Avian, Alexander; Rohrer, Peter M.; Hörlesberger, Nina; Magometschnigg, Dieter; Cervar-Zivkovic, Mila; Komericki, Peter; Velik, Rosemarie; Baulmann, Johannes

    2014-01-01

    Objective Hypobaric hypoxia, physical and psychosocial stress may influence key cardiovascular parameters including blood pressure (BP) and pulse pressure (PP). We investigated the effects of mild hypobaric hypoxia exposure on BP and PP reactivity to mental and physical stress and to passive elevation by cable car. Methods 36 healthy volunteers participated in a defined test procedure consisting of a period of rest 1, mental stress task (KLT-R), period of rest 2, combined mental (KLT-R) and physical task (bicycle ergometry) and a last period of rest both at Graz, Austria (353 m asl) and at the top station Dachstein (2700 m asl). Beat-to-beat heart rate and BP were analysed both during the test procedures at Graz and at Dachstein and during passive 1000 m elevation by cable car (from 1702 m to 2700 m). Results A significant interaction of kind of stress (mental vs. combined mental and physical) and study location (Graz vs. Dachstein) was found in the systolic BP (p = .007) and PP (p = .002) changes indicating that during the combined mental and physical stress task sBP was significantly higher under hypoxic conditions whereas sBP and PP were similar during mental stress both under normobaric normoxia (Graz) and under hypobaric hypoxia (Dachstein). During the passive ascent in cable car less trivialization (psychological coping strategy) was associated with an increase in PP (p = .004). Conclusion Our data show that combined mental and physical stress causes a significant higher raise in sBP and PP under hypoxic conditions whereas isolated mental stress did not affect sBP and PP under hypoxic conditions. PP-reaction to ascent in healthy subjects is not uniform. BP reactions to ascent that represents an accumulation of physical (mild hypobaric hypoxia) and psychological stressors depend on predetermined psychological traits (stress coping strategies). Thus divergent cardiovascular reactions can be explained by applying the multidimensional aspects of the

  1. Selection of reference genes for quantitative reverse-transcription polymerase chain reaction normalization in Brassica napus under various stress conditions.

    PubMed

    Wang, Zheng; Chen, Yu; Fang, Hedi; Shi, Haifeng; Chen, Keping; Zhang, Zhiyan; Tan, Xiaoli

    2014-10-01

    Data normalization is essential for reliable output of quantitative real-time reverse-transcription polymerase chain reaction (qRT-PCR) assays, as the unsuitable choice of reference gene(s), whose expression might be influenced by exogenous treatments in plant tissues, could cause misinterpretation of results. To date, no systematic studies on reference genes have been performed in stressed Brassica napus. In this study, we investigated the expression variations of nine candidate reference genes in 40 samples of B. napus leaves subjected to various exogenous treatments. Parallel analyses by geNorm and NormFinder revealed that optimal reference genes differed across the different sets of samples. The best-ranked reference genes were PP2A and TIP41 for salt stress, TIP41 and ACT7 for heavy metal (Cr(6+)) stress, PP2A and UBC21 for drought stress, F-box and SAND for cold stress, F-box and ZNF for salicylic acid stress, TIP41, ACT7, and PP2A for methyl jasmonate stress, TIP41 and ACT7 for abscisic acid stress, and TIP41, UBC21, and PP2A for Sclerotinia sclerotiorum stress. Two newly employed reference genes, TIP41 and PP2A, showed better performances, suggesting their suitability in multiple conditions. To further validate the suitability of the reference genes, the expression patterns of BnWRKY40 and BnMKS1 were studied in parallel. This study is the first systematic analysis of reference gene selection for qRT-PCR normalization in B. napus, an agriculturally important crop, under different stress conditions. The results will contribute toward more accurate and widespread use of qRT-PCR in gene analysis of the genus Brassica. PMID:24770781

  2. Modulation of antioxidant machinery in α-tocopherol-enriched transgenic Brassica juncea plants tolerant to abiotic stress conditions.

    PubMed

    Kumar, Deepak; Yusuf, Mohd Aslam; Singh, Preeti; Sardar, Meryam; Sarin, Neera Bhalla

    2013-10-01

    The antioxidant machinery in plants consists of several components with unique or overlapping functions that combat the deleterious production of reactive oxygen species (ROS) induced by stress conditions. Tocopherols are a group of powerful antioxidants having additional roles in signaling and gene expression, with α-tocopherol being the most potent form. In the present study, we used wild-type (WT) and α-tocopherol-enriched transgenic (TR) Brassica juncea plants grown under salt, heavy metal, and osmotic stress to compare their relative tolerance to these stresses and to assess the effects of increased α-tocopherol content on the other antioxidative enzymes and molecules. The oxidative damage caused by induced stress was lower in TR plants compared to WT plants as assessed by their higher relative water content and lower electrolyte leakage, malondialdehyde content as well as H(2)O(2) accumulation. Lesser superoxide and H(2)O(2) accumulation was also observed by histochemical staining in TR seedlings exposed to stress. Though no significant differences were evident under normal growth conditions, TR plants showed higher activities and transcript levels of antioxidant enzymes superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase than WT plants under similar stress conditions. A decrease in ascorbate and glutathione content with marginally higher reductive ratios of these compounds was also observed in TR plants under the stress conditions. Our findings implicate the role of higher α-tocopherol levels in conferring better tolerance against salt, heavy metal, and osmotic stresses and also establish the existence of interplay between this lipid-soluble antioxidant and other water-soluble components of plant antioxidant defense.

  3. Chronic stress, cyclic 17β-estradiol, and daily handling influences on fear conditioning in the female rat.

    PubMed

    Hoffman, Ann N; Armstrong, Charles E; Hanna, Jeffery J; Conrad, Cheryl D

    2010-10-01

    Chronic stress and estrogens alter many forebrain regions in female rats that affect cognition. In order to investigate how chronic stress and estrogens influence fear learning and memory, we ovariectomized (OVX) female Sprague-Dawley rats and repeatedly injected them (s.c.) with 17β-estradiol (E, 10 μg/250 g or sesame oil vehicle, VEH). Concurrently, rats were restrained for 6 h/d/21 d (STR) or left undisturbed (CON). Rats were then fear conditioned with 4 tone-footshock pairings and then after 1 h and 24 h delays, given 15 tone extinction trials. Regardless of E treatment, chronic stress (VEH, E) facilitated freezing to tone during acquisition and extinction following a 1h delay, but not during extinction after a 24 h delay. E did not influence freezing to tone during any phase of fear conditioning for either the control or chronically stressed rats, but did influence contextual conditioning that may have been carried predominately by the STR group. In the second experiment, we investigated "handling" influences on fear conditioning acquisition, given the disparate findings from the current study and previous work (Baran, Armstrong, Niren, & Conrad, 2010; Baran, Armstrong, Niren, Hanna, & Conrad, 2009). Female rats remained gonadally-intact since E did not influence tone fear conditioning. Indeed, brief daily handling (1-3 m/d/21 d) facilitated acquisition of fear conditioning in chronically stressed female rats, and either had no effect or slightly attenuated fear conditioning in controls. Thus, chronic stress impacts amygdala-mediated fear learning in both OVX- and gonadally-intact females as found previously in males, with handling significantly influencing these outcomes.

  4. Chronic Psychological Stress Disrupted the Composition of the Murine Colonic Microbiota and Accelerated a Murine Model of Inflammatory Bowel Disease

    PubMed Central

    Watanabe, Yohei; Arase, Sohei; Nagaoka, Noriko; Kawai, Mitsuhisa; Matsumoto, Satoshi

    2016-01-01

    The effect of psychological stress on the gastrointestinal microbiota is widely recognized. Chronic psychological stress may be associated with increased disease activity in inflammatory bowel disease, but the relationships among psychological stress, the gastrointestinal microbiota, and the severity of colitis is not yet fully understood. Here, we examined the impact of 12-week repeated water-avoidance stress on the microbiota of two inbred strains of T cell receptor alpha chain gene knockout mouse (background, BALB/c and C57BL/6) by means of next-generation sequencing of bacterial 16S rRNA genes. In both mouse strains, knockout of the T cell receptor alpha chain gene caused a loss of gastrointestinal microbial diversity and stability. Chronic exposure to repeated water-avoidance stress markedly altered the composition of the colonic microbiota of C57BL/6 mice, but not of BALB/c mice. In C57BL/6 mice, the relative abundance of genus Clostridium, some members of which produce the toxin phospholipase C, was increased, which was weakly positively associated with colitis severity, suggesting that expansion of specific populations of indigenous pathogens may be involved in the exacerbation of colitis. However, we also found that colitis was not exacerbated in mice with a relatively diverse microbiota even if their colonic microbiota contained an expanded phospholipase C-producing Clostridium population. Exposure to chronic stress also altered the concentration of free immunoglobulin A in colonic contents, which may be related to both the loss of bacterial diversity in the colonic microbiota and the severity of the colitis exacerbation. Together, these results suggest that long-term exposure to psychological stress induces dysbiosis in the immunodeficient mouse in a strain-specific manner and also that alteration of microbial diversity, which may be related to an altered pattern of immunoglobulin secretion in the gastrointestinal tract, might play a crucial role in the

  5. Chronic Psychological Stress Disrupted the Composition of the Murine Colonic Microbiota and Accelerated a Murine Model of Inflammatory Bowel Disease.

    PubMed

    Watanabe, Yohei; Arase, Sohei; Nagaoka, Noriko; Kawai, Mitsuhisa; Matsumoto, Satoshi

    2016-01-01

    The effect of psychological stress on the gastrointestinal microbiota is widely recognized. Chronic psychological stress may be associated with increased disease activity in inflammatory bowel disease, but the relationships among psychological stress, the gastrointestinal microbiota, and the severity of colitis is not yet fully understood. Here, we examined the impact of 12-week repeated water-avoidance stress on the microbiota of two inbred strains of T cell receptor alpha chain gene knockout mouse (background, BALB/c and C57BL/6) by means of next-generation sequencing of bacterial 16S rRNA genes. In both mouse strains, knockout of the T cell receptor alpha chain gene caused a loss of gastrointestinal microbial diversity and stability. Chronic exposure to repeated water-avoidance stress markedly altered the composition of the colonic microbiota of C57BL/6 mice, but not of BALB/c mice. In C57BL/6 mice, the relative abundance of genus Clostridium, some members of which produce the toxin phospholipase C, was increased, which was weakly positively associated with colitis severity, suggesting that expansion of specific populations of indigenous pathogens may be involved in the exacerbation of colitis. However, we also found that colitis was not exacerbated in mice with a relatively diverse microbiota even if their colonic microbiota contained an expanded phospholipase C-producing Clostridium population. Exposure to chronic stress also altered the concentration of free immunoglobulin A in colonic contents, which may be related to both the loss of bacterial diversity in the colonic microbiota and the severity of the colitis exacerbation. Together, these results suggest that long-term exposure to psychological stress induces dysbiosis in the immunodeficient mouse in a strain-specific manner and also that alteration of microbial diversity, which may be related to an altered pattern of immunoglobulin secretion in the gastrointestinal tract, might play a crucial role in the

  6. Nondestructive Evaluation and Monitoring Results from COPV Accelerated Stress Rupture Testing, NASA White Sands Test Facility (WSTF)

    NASA Technical Reports Server (NTRS)

    Saulsberry Regor

    2010-01-01

    Develop and demonstrate NDE techniques for real-time characterization of CPVs and, where possible, identification of NDE capable of assessing stress rupture related strength degradation and/or making vessel life predictions (structural health monitoring or periodic inspection modes). Secondary: Provide the COPV user and materials community with quality carbon/epoxy (C/Ep) COPV stress rupture progression rate data. Aid in modeling, manufacturing, and application of COPVs for NASA spacecraft.

  7. Determination of Creep Behavior of Thermal Barrier Coatings Under Laser Imposed High Thermal and Stress Gradient Conditions

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Miller, Robert A.

    1999-01-01

    A laser sintering/creep technique has been established to determine the creep behavior of thermal barrier coatings under steady-state high heat flux conditions. For a plasma sprayed zirconia-8 wt. % yttria coating, a significant primary creep strain and a low apparent creep activation energy were observed. Possible creep mechanisms involved include stress induced mechanical sliding and temperature and stress enhanced cation diffusion through the splat and grain boundaries. The elastic modulus evolution, stress response, and total accumulated creep strain variation across the ceramic coating are simulated using a finite difference approach. The modeled creep response is consistent with experimental observations.

  8. Pituitary-adrenocortical adjustments to transport stress in horses with previous different handling and transport conditions

    PubMed Central

    Fazio, E.; Medica, P.; Cravana, C.; Ferlazzo, and A.

    2016-01-01

    Aim: The changes of the hypothalamic pituitary adrenal (HPA) axis response to a long distance transportation results in increase of adrenocorticotropic hormone (ACTH) and cortisol levels. The purpose of the study was to quantify the level of short-term road transport stress on circulating ACTH and cortisol concentrations, related to the effect of previous handling and transport experience of horses. Materials and Methods: The study was performed on 56 healthy horses after short-term road transport of 30 km. The horses were divided into four groups, Groups A, B, C, and D, with respect to the handling quality: Good (Groups A and B), bad (Group D), and minimal handling (Group C) conditions. According to the previous transport, experience horses were divided as follows: Horses of Groups A and D had been experienced long-distance transportation before; horses of Groups B and C had been limited experience of transportation. Results: One-way RM-ANOVA showed significant effects of transport on ACTH changes in Groups B and C and on cortisol changes in both Groups A and B. Groups A and B showed lower baseline ACTH and cortisol values than Groups C and D; Groups A and B showed lower post-transport ACTH values than Groups C and D. Groups A, B, and C showed lower post-transport cortisol values than Group D. Only Groups A and B horses have shown an adequate capacity of stress response to transportation. Conclusion: The previous transport experience and quality of handling could influence the HPA axis physiological responses of horses after short-term road transport.

  9. Pituitary-adrenocortical adjustments to transport stress in horses with previous different handling and transport conditions

    PubMed Central

    Fazio, E.; Medica, P.; Cravana, C.; Ferlazzo, and A.

    2016-01-01

    Aim: The changes of the hypothalamic pituitary adrenal (HPA) axis response to a long distance transportation results in increase of adrenocorticotropic hormone (ACTH) and cortisol levels. The purpose of the study was to quantify the level of short-term road transport stress on circulating ACTH and cortisol concentrations, related to the effect of previous handling and transport experience of horses. Materials and Methods: The study was performed on 56 healthy horses after short-term road transport of 30 km. The horses were divided into four groups, Groups A, B, C, and D, with respect to the handling quality: Good (Groups A and B), bad (Group D), and minimal handling (Group C) conditions. According to the previous transport, experience horses were divided as follows: Horses of Groups A and D had been experienced long-distance transportation before; horses of Groups B and C had been limited experience of transportation. Results: One-way RM-ANOVA showed significant effects of transport on ACTH changes in Groups B and C and on cortisol changes in both Groups A and B. Groups A and B showed lower baseline ACTH and cortisol values than Groups C and D; Groups A and B showed lower post-transport ACTH values than Groups C and D. Groups A, B, and C showed lower post-transport cortisol values than Group D. Only Groups A and B horses have shown an adequate capacity of stress response to transportation. Conclusion: The previous transport experience and quality of handling could influence the HPA axis physiological responses of horses after short-term road transport. PMID:27651674

  10. Plasma cortisol activity in rats under conditions of chronic stress supplemented with resveratrol

    PubMed Central

    Hurtado Salazar, Alejandro; Uribe-Velásquez, Luis F

    2012-01-01

    Objective: To determine the activity of cortisol in rats treated with exogenous adrenocorticotropic hormone (ACTH) and a resveratrol supplement. Methods: Forty-eight adult female rats and 16 male rats of the strain (Rattus norvegicus) that were three months old and with body weights ranging from 200 to 250 g for females and 300 to 350 g for males were used and kept in controlled environmental conditions: temperature of 20±2° C and light-dark cycles of 14 and 10 hours. They were fed a balanced diet and had free access to water. The rats were randomly divided into four groups: group 1 - was treated with 5 µg/kg of ACTH i.p. every twelve hours; group 2 - received the same treatment with ACTH plus a grape extract supplement (resveratrol) of 40 mg/kg; group 3 - only received grape extract (resveratrol); and group 4 - received a saline solution (0.9%) i.p. and oral, and served as controls. The experimental design was a 2×2 factorial with two levels ACTH and two polyphenol levels (grape extract). Results: No significant differences were found in blood cortisol concentrations, by day and gender, or by treatment effects (0.75 µg/dL ± 0.11; p <0.001). Conclusion: Results suggest that chronic stress and consumption of resveratrol did not directly alter levels of plasmatic cortisol in either stressed or unstressed rats. It was concluded that the given dosage levels of ACTH possibly did not produce sufficient stimulation of the adrenal gland for these animals. PMID:24893196

  11. Detritus-based assemblage responses under salinity stress conditions in a disused aquatic artificial ecosystem

    PubMed Central

    2013-01-01

    Background Despite the plethora of approaches, the sensitivity of the methods to measure the relationship between the abundance and biomass curves in stressed detritus-based ecosystems still remain to be refined. In this work, we report the comparison between biomass and abundance in a set of detritus-based macrozoobenthic assemblages located in six sampling pools with different salinity in an artificial aquatic ecosystem (disused Tarquinia Saltworks), using two diversity/dominance approaches (Abundance/Biomass Comparisons, or ABC, and Whittaker plots). We also evaluated the contribution of abundances and biomasses diversity (Simpson index) and nestedness, which measures the order by which macroinvertebrates colonized the detrital resource. Results The outputs obtained by both ABC curves and Whittaker plots highlight two different thresholds in assemblage structure: between about 44 and 50 practical salinity unit (psu) and between 50 and 87 psu, respectively. The first threshold was due to a turnover in taxon composition between assemblages, the second threshold (evidenced by Whittaker plots) was due to a change in taxon richness (lower in pools with higher salinity: i.e. > 50 psu). Moreover, a normal-shaped pattern in diversity (Simpson index) emerged, suggestive of an intermediate disturbance effect. The nested pattern did not show significant differences when considering the density and biomass of the sampled taxa, providing similar threshold of salinity in the relative contribution of macrozoobenthos on nestedness. Conclusions The use of detailed (ABC and Whittaker plots) and macroscopic (Simpson index and nestedness) approaches is proposed to identify thresholds in the structuring and functioning of detritus-based community of disused aquatic ecosystems: in particular, the inclusion of the parameter of biomass (scarcely utilized in community-based research) appears crucial. The responses of macrozoobenthic assemblages to the salinity stress conditions, in term

  12. [Effect of exogenous sucrose on growth and active ingredient content of licorice seedlings under salt stress conditions].

    PubMed

    Liu, Fu-zhi; Yang, Jun

    2015-11-01

    Licorice seedlings were taken as experimental materials, an experiment was conducted to study the effects of exogenous sucrose on growth and active ingredient content of licorice seedlings under NaCl stress conditions. The results of this study showed that under salt stress conditions, after adding a certain concentration of exogenous sucrose, the licorice seedlings day of relative growth rate was increasing, and this stress can be a significant weakening effect, indicating that exogenous sucrose salt stress-relieving effect. The total flavonoids and phenylalanine ammonia lyase (PAL) activity were significantly increased, the exogenous sucrose can mitigated the seedling roots under salt stress, the licorice flavonoid content in the enhanced growth was largely due to the activity of PAL an increased, when the concentration of exogenous sucrose wae 10 mmol x L(-1), PAL activity reaching a maximum, when the concentration of exogenous sucrose was 15 mmol x L(-1), PAL activity turned into a downward trend, the results indicating that this mitigation has concentration effect. After applying different concentrations of exogenous sugar, the contents of liquiritin changes with the change of flavonoids content was similar. After applying different concentrations of exogenous sucrose, the content of licorice acid under salt stress was higher than the levels were not reached during salt stress, the impact of exogenous sucrose concentration gradient of licorice acid accumulation was not obvious. PMID:27097411

  13. [Effect of exogenous sucrose on growth and active ingredient content of licorice seedlings under salt stress conditions].

    PubMed

    Liu, Fu-zhi; Yang, Jun

    2015-11-01

    Licorice seedlings were taken as experimental materials, an experiment was conducted to study the effects of exogenous sucrose on growth and active ingredient content of licorice seedlings under NaCl stress conditions. The results of this study showed that under salt stress conditions, after adding a certain concentration of exogenous sucrose, the licorice seedlings day of relative growth rate was increasing, and this stress can be a significant weakening effect, indicating that exogenous sucrose salt stress-relieving effect. The total flavonoids and phenylalanine ammonia lyase (PAL) activity were significantly increased, the exogenous sucrose can mitigated the seedling roots under salt stress, the licorice flavonoid content in the enhanced growth was largely due to the activity of PAL an increased, when the concentration of exogenous sucrose wae 10 mmol x L(-1), PAL activity reaching a maximum, when the concentration of exogenous sucrose was 15 mmol x L(-1), PAL activity turned into a downward trend, the results indicating that this mitigation has concentration effect. After applying different concentrations of exogenous sugar, the contents of liquiritin changes with the change of flavonoids content was similar. After applying different concentrations of exogenous sucrose, the content of licorice acid under salt stress was higher than the levels were not reached during salt stress, the impact of exogenous sucrose concentration gradient of licorice acid accumulation was not obvious.

  14. The tomato res mutant which accumulates JA in roots in non-stressed conditions restores cell structure alterations under salinity.

    PubMed

    Garcia-Abellan, José O; Fernandez-Garcia, Nieves; Lopez-Berenguer, Carmen; Egea, Isabel; Flores, Francisco B; Angosto, Trinidad; Capel, Juan; Lozano, Rafael; Pineda, Benito; Moreno, Vicente; Olmos, Enrique; Bolarin, Maria C

    2015-11-01

    Jasmonic acid (JA) regulates a wide spectrum of plant biological processes, from plant development to stress defense responses. The role of JA in plant response to salt stress is scarcely known, and even less known is the specific response in root, the main plant organ responsible for ionic uptake and transport to the shoot. Here we report the characterization of the first tomato (Solanum lycopersicum) mutant, named res (restored cell structure by salinity), that accumulates JA in roots prior to exposure to stress. The res tomato mutant presented remarkable growth inhibition and displayed important morphological alterations and cellular disorganization in roots and leaves under control conditions, while these alterations disappeared when the res mutant plants were grown under salt stress. Reciprocal grafting between res and wild type (WT) (tomato cv. Moneymaker) indicated that the main organ responsible for the development of alterations was the root. The JA-signaling pathway is activated in res roots prior to stress, with transcripts levels being even higher in control condition than in salinity. Future studies on this mutant will provide significant advances in the knowledge of JA role in root in salt-stress tolerance response, as well as in the energy trade-off between plant growth and response to stress.

  15. Stress Symptoms among Adolescents: The Role of Subjective Psychosocial Conditions, Lifestyle, and Self-Esteem

    ERIC Educational Resources Information Center

    Schraml, Karin; Perski, Aleksander; Grossi, Giorgio; Simonsson-Sarnecki, Margareta

    2011-01-01

    Stress-related problems are increasing among Swedish adolescents, especially among females. The aims of this study were to survey the incidence of stress symptoms among 16-year-olds, to investigate the related gender differences, and to understand the factors that may contribute to stress symptoms. The study is questionnaire based, and the sample…

  16. [Activation of the neuroendocrine system during changes in homeostasis during stress conditions].

    PubMed

    Vigas, M; Jezová, D

    1996-02-01

    Neuroendocrine response to stress stimuli is aimed to maintain body homeostasis. The activation of the neuroendocrine system is accomplished mainly by two ways: by feedback regulation based on the recognition of altered metabolic homeostasis by appropriate receptors sending the signal into the CNS, and by forward regulation involving a direct stimulation of the neuroendocrine system by a central command coming from an activated brain regulatory center. With regard to mechanisms of neuroendocrine activation, the signal specificity and site of its origin are of particular importance. The significance of the signal in neuroendocrine responses has been evaluated in three different stress conditions: hypoglycemia, surgical trauma and dynamic physical exercise. The stimulus inducing neuroendocrine response during hypoglycemia is the glucopenia. The signal for the activation of the neuroendocrine response is generated in glucosensitive cells which are not located in a single brain structure (hypothetical glucostat). The signal for growth hormone, vasopressin and oxytocin release is produced in brain structures protected by the blood-brain barrier, that for ACTH release in regions both protected and unprotected by the barrier, while the signal for prolactin release is generated in tissues lacking the blood-brain barrier. The neuroendocrine response during surgical trauma is activated by a signal formed in the damaged tissue reaching the CNS by neural pathways. Moreover, cytokins may participate on endocrine stimulation in those surgical interventions in which a large amount of bacterial endotoxins is released. During a complicated surgery, e.g. during a bypass other signals and modifying factors, such as hypothermia, dilution of blood, hypoperfusion of organs, rewarming of the body and hormone degradation in the oxygenator are important. On the On the other hand, during a short-term dynamic exercise, a forward regulation by a central signal from the activated CNS motor

  17. Determination of the stress conditions of the ductile-to-brittle regime along the Asuke Shear Zone, SW Japan

    NASA Astrophysics Data System (ADS)

    Kanai, Takuto; Takagi, Hideo

    2016-04-01

    The stress conditions of the ductile-to-brittle regime have been assessed along the Asuke Shear Zone (ASZ), which strikes NE-SW in the Cretaceous Ryoke granite terrain in SW Japan. Along the ASZ, pseudotachylyte and mylonitized pseudotachylyte are locally developed together with cataclasite. The simultaneous operation of dislocation creep and grain-size-sensitive creep, as indicated by the coexistence of the Z-maximum and relatively random c-axis lattice preferred orientations as well as the sizes of dynamically recrystallized quartz grains (6.40-7.79 μm) in the mylonitized pseudotachylyte, suggest differential stresses of 110-130 MPa at ∼300 °C. The e-twin morphology, twinning ratio, and distribution of the glide direction on the e-twin plane of the twinned calcite in the amygdules of the pseudotachylyte suggest the stress conditions of the σ1 and σ3 axes trend 228° and 320° and plunge 55° and 1°, respectively, and indicate differential stresses of 40-80 MPa at 150-200 °C. Based on kinematic indicators in the fault rocks, the stress conditions estimated from calcite twins, and the cooling history of the granitic protolith, the ASZ is inferred to have been activated under a stress state that caused sinistral normal movements before and after pseudotachylyte formation at 70-50 Ma.

  18. Screening of microRNAs associated with Alzheimer's disease using oxidative stress cell model and different strains of senescence accelerated mice.

    PubMed

    Zhang, Rui; Zhang, Qingfu; Niu, Jingya; Lu, Kang; Xie, Bing; Cui, Dongsheng; Xu, Shunjiang

    2014-03-15

    Oxidative stress plays a critical role in the etiology and pathogenesis of Alzheimer's disease (AD), and the molecular mechanisms that control the neuron response to oxidative stress have been extensively studied. However, the effects of oxidative stress on miRNA expression in hippocampal neurons has not been investigated, and little is known about the roles of ROS-modulated miRNAs in cell function as yet. In this study, miRNA microarray technology was used to analyze the expression of miRNAs in the oxidative stressed primary hippocampal neurons, hippocampus of senescence accelerated mouse prone 8 (SAMP8) and prone 10 (SAMP10). The targets of co-regulated microRNAs were also selected for computational prediction using miRWalk software and functional analysis by the DAVID software. In addition, the changes of co-regulated microRNA expression were validated by quantitative real-time PCR. The results of microarray analysis showed that miR-329, miR-193b, miR-20a, miR-296, and miR-130b were all upregulated in H2O2-induced primary hippocampal neurons and different strains of senescence accelerated mice. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that these co-regulated microRNAs may be involved in the regulation of cell growth, apoptosis, signal transmission and cancer development. In which, mitogen-activated protein kinase (MAPK) signaling pathway was one of the most significant pathways to be affected by 83 target genes of miR-329, miR-193b, miR-20a miR-296, and miR-130b. The quantitative real-time PCR data confirmed the alterations of the co-upregulated miRNAs. These results suggested that oxidative stress alters the miRNA expression profile of hippocampal neurons, and the deregulated miRNAs might play potential roles in the pathogenesis of neurodegenerative diseases, such as Alzheimer's disease (AD). This study provided a strong basis for the future study aiming at contributions of miRNAs induced by oxidative stress in AD.

  19. Temporal versus spatial variation in leaf reflectance under changing water stress conditions

    NASA Technical Reports Server (NTRS)

    Cohen, Warren B.

    1991-01-01

    Leaf reflectance changes associated with changes in water stress were analyzed in two separate experiments. Results indicate that the variation in reflectance among collections of leaves of a given species all at the same level of water stress is at least as great as the variation in reflectance associated with changes in water stress for a given leaf collection of that species. The implications is that results from leaf reflectance-water stress studies have only limited applicability to the remote sensing of plant canopy water stress.

  20. AgRISTARS: Early warning and crop condition assessment. Plant cover, soil temperature, freeze, water stress, and evapotranspiration conditions

    NASA Technical Reports Server (NTRS)

    Wiegand, C. L. (Principal Investigator); Nixon, P. R.; Gausman, H. W.; Namken, L. N.; Leamer, R. W.; Richardson, A. J.

    1981-01-01

    Emissive (10.5 to 12.5 microns) and reflective (0.55 to 1.1 microns) data for ten day scenes and infrared data for six night scenes of southern Texas were analyzed for plant cover, soil temperature, freeze, water stress, and evapotranspiration. Heat capacity mapping mission radiometric temperatures were: within 2 C of dewpoint temperatures, significantly correlated with variables important in evapotranspiration, and related to freeze severity and planting depth soil temperatures.

  1. Inactivation model equations and their associated parameter values obtained under static acid stress conditions cannot be used directly for predicting inactivation under dynamic conditions.

    PubMed

    Janssen, M; Verhulst, A; Valdramidis, V; Devlieghere, F; Van Impe, J F; Geeraerd, A H

    2008-11-30

    Organic acids (e.g., lactic acid, acetic acid and citric acid) are popular preservatives. In this study, the Listeria innocua inactivation is investigated under dynamic conditions of pH and undissociated lactic acid ([LaH]). A combined primary (Weibull-type) and secondary model developed for the L. innocua inactivation under static conditions [Janssen, M., Geeraerd, A.H., Cappuyns, A., Garcia-Gonzalez, L., Schockaert, G., Van Houteghem, N., Vereecken, K.M., Debevere, J., Devlieghere, F., Van Impe, J.F., 2007. Individual and combined effects of pH and lactic acid concentration on L. innocua inactivation: development of a predictive model and assessment of experimental variability. Applied and Environmental Microbiology 73(5), 1601-1611] was applied to predict the microbial inactivation under dynamic conditions. Because of its non-autonomous character, two approaches were proposed for the application of the Weibull-type model to dynamic conditions. The results quantitatively indicated that the L. innocua cell population was able to develop an induced acid stress resistance under dynamic conditions of pH and [LaH]. From a modeling point of view, it needs to be stressed that (i) inactivation model equations and associated parameter values, derived under static conditions, may not be suitable for use as such under dynamic conditions, and (ii) non-autonomous dynamic models reveal additional technical intricacies in comparison with autonomous models.

  2. Expression profiling of the bloom-forming cyanobacterium Nodularia CCY9414 under light and oxidative stress conditions

    PubMed Central

    Kopf, Matthias; Möke, Fred; Bauwe, Hermann; Hess, Wolfgang R; Hagemann, Martin

    2015-01-01

    Massive blooms of toxic cyanobacteria frequently occur in the central Baltic Sea during the summer. In the surface scum, cyanobacterial cells are exposed to high light (HL) intensity, high oxygen partial pressure and other stresses. To mimic these conditions, cultures of Nodularia spumigena CCY9414, which is a strain isolated from a cyanobacterial summer bloom in the Baltic Sea, were incubated at a HL intensity of 1200 μmol photons m−2 s−1 or a combination of HL and increased oxygen partial pressure. Using differential RNA sequencing, we compared the global primary transcriptomes of control and stressed cells. The combination of oxidative and light stresses induced the expression of twofold more genes compared with HL stress alone. In addition to the induction of known stress-responsive genes, such as psbA, ocp and sodB, Nodularia cells activated the expression of genes coding for many previously unknown light- and oxidative stress-related proteins. In addition, the expression of non-protein-coding RNAs was found to be stimulated by these stresses. Among them was an antisense RNA to the phycocyanin-encoding mRNA cpcBAC and the trans-encoded regulator of photosystem I, PsrR1. The large genome capacity allowed Nodularia to harbor more copies of stress-relevant genes such as psbA and small chlorophyll-binding protein genes, combined with the coordinated induction of these and many additional genes for stress acclimation. Our data provide a first insight on how N. spumigena became adapted to conditions relevant for a cyanobacterial bloom in the Baltic Sea. PMID:25689027

  3. Numerical modeling of physical vapor transport under microgravity conditions: Effect of thermal creep and stress

    NASA Technical Reports Server (NTRS)

    Mackowski, Daniel W.; Knight, Roy W.

    1993-01-01

    One of the most promising applications of microgravity (micro-g) environments is the manufacture of exotic and high-quality crystals in closed cylindrical ampoules using physical vapor transport (PVT) processes. The quality enhancements are believed to be due to the absence of buoyant convection in the weightless environment - resulting in diffusion-limited transport of the vapor. In a typical experiment, solid-phase sample material is initially contained at one end of the ampoule. The sample is made to sublime into the vapor phase and deposit onto the opposite end by maintaining the source at an elevated temperature with respect to the deposit. Identification of the physical factors governing both the rates and uniformity of crystal growth, and the optimization of the micro-g technology, will require an accurate modeling of the vapor transport within the ampoule. Previous micro-g modeling efforts have approached the problem from a 'classical' convective/diffusion formulation, in which convection is driven by the action of buoyancy on thermal and solutal density differences. The general conclusion of these works have been that in low gravity environments the effect of buoyancy on vapor transport is negligible, and vapor transport occurs in a diffusion-limited mode. However, it has been recently recognized than in the non-isothermal (and often low total pressure) conditions encountered in ampoules, the commonly-assumed no-slip boundary condition to the differential equations governing fluid motion can be grossly unrepresentative of the actual situation. Specifically, the temperature gradients can give rise to thermal creep flows at the ampoule side walls. In addition, temperature gradients in the vapor itself can, through the action of thermal stress, lead to bulk fluid convection.

  4. Global analysis of protein aggregation in yeast during physiological conditions and arsenite stress

    PubMed Central

    Ibstedt, Sebastian; Sideri, Theodora C.; Grant, Chris M.; Tamás, Markus J.

    2014-01-01

    ABSTRACT Protein aggregation is a widespread phenomenon in cells and associated with pathological conditions. Yet, little is known about the rules that govern protein aggregation in living cells. In this study, we biochemically isolated aggregation-prone proteins and used computational analyses to identify characteristics that are linked to physiological and arsenite-induced aggregation in living yeast cells. High protein abundance, extensive physical interactions, and certain structural properties are positively correlated with an increased aggregation propensity. The aggregated proteins have high translation rates and are substrates of ribosome-associated Hsp70 chaperones, indicating that they are susceptible for aggregation primarily during translation/folding. The aggregation-prone proteins are enriched for multiple chaperone interactions, thus high protein abundance is probably counterbalanced by molecular chaperones to allow soluble expression in vivo. Our data support the notion that arsenite interferes with chaperone activity and indicate that arsenite-aggregated proteins might engage in extensive aberrant protein–protein interactions. Expression of aggregation-prone proteins is down-regulated during arsenite stress, possibly to prevent their toxic accumulation. Several aggregation-prone yeast proteins have human homologues that are implicated in misfolding diseases, suggesting that similar mechanisms may apply in disease- and non-disease settings. PMID:25217615

  5. Optical stimulation of the hearing and deaf cochlea under thermal and stress confinement condition

    NASA Astrophysics Data System (ADS)

    Schultz, M.; Baumhoff, P.; Kallweit, N.; Sato, M.; Krüger, A.; Ripken, T.; Lenarz, T.; Kral, A.

    2014-03-01

    There is a controversy, to which extend cochlear stimulation with near infrared laser pulses at a wavelength of 1860 nm is based on optoacoustic stimulation of intact hair cells or -in contrast- is based on direct stimulation of the nerve cells in absence of functional hair cells. Thermal and stress confinement conditions apply, because of the pulse duration range (5 ns, 10 μs-20 ms) of the two lasers used. The dependency of the signal characteristics on pulse peak power and pulse duration was investigated in this study. The compound action potential (CAP) was measured during stimulation of the cochlea of four anaesthetized guinea pigs, which were hearing at first and afterwards acutely deafened using intracochlear neomycin-rinsing. For comparison hydrophone measurements in a water tank were performed to investigate the optoacoustic signals at different laser interaction regimes. With rising pulse peak power CAPs of the hearing animals showed first a threshold, then a positively correlated and finally a saturating dependency. CAPs also showed distinct responses at laser onset and offset separated with the pulse duration. At pulse durations shorter than physiological response times the signals merged. Basically the same signal characteristics were observed in the optoacoustic hydrophone measurements, scaled with the sensitivity and response time of the hydrophone. Taking together the qualitative correspondence in the signal response and the absence of any CAPs in deafened animals our results speak in favor of an optoacoustic stimulation of intact hair cells rather than a direct stimulation of nerve cells.

  6. IFNα/βR Signaling Promotes Regulatory T Cell Development and Function Under Stress Conditions

    PubMed Central

    Metidji, Amina; Rieder, Sadiye Amcaoglu; Glass, Deborah Dacek; Cremer, Isabelle; Punkosdy, George A.; Shevach, Ethan M.

    2015-01-01

    Type I IFNs are a family of cytokines with antiviral and immunomodulatory properties. While the antiviral effects of IFNs are well characterized, their immunomodulatory properties are less clear. To specifically address the effects of type I IFNs on Treg, we studied mixed bone morrow (BM) chimeras between wild-type (WT) and IFNα/βR (IFNAR) knockout (KO) mice, and heterozygous female mice expressing a Treg-specific deletion of the IFNAR. In these two models, IFNAR signaling promotes the development of the Treg lineage in the thymus and their survival in the periphery. IFNAR KO Treg had a higher expression of the pro-apoptotic gene Bim and higher frequency of active caspase positive cells. IFNAR KO Treg from chimeric mice displayed a more naïve phenotype, accompanied by lower levels of CD25 and phosphorylated STAT5. Therefore, in Treg IFNAR signaling may directly or indirectly affect phosphorylation of STAT5. In mixed chimeras with Scurfy fetal liver, Treg derived from IFNAR KO BM were unable to control T effector cell activation and tissue inflammation. Under stress conditions or in a competitive environment, IFNAR signaling may be required to maintain Treg homeostasis and function. PMID:25795758

  7. Leader length and secondary structure modulate mRNA function under conditions of stress

    SciTech Connect

    Kozak, M.

    1988-07-01

    Simina virus 40-based plasmids that direct the synthesis of preproinsulin in cultured monkey cells were used to study the effects of mRNA structure on translational efficiency. Lengthening the leader sequence enhanced translation in this system. The enhancement was most obvious when an unstructured sequence (two, four, or eight copies of the oligonculeotide AGCTAAGTAAGTAAGTA) was inserted upstream from a region of deliberate secondary structure; the degree of enhancement was proportional to the number of copies of the inserted oligonucleotide. Lengthening the leader sequence on the 3' side of a stem-and-loop structure, in contrast, did not offset the potentially inhibitory effect of the hairpin structure. Both the facilitating effect of length and the inhibitory effect of secondary structure were demonstrated most easily under conditions of mRNA competition, which was brought about by an abrupt shift in the tonicity of the culture medium. These experiments suggest a simple structural basis for the long-recognized differential response of viral and cellular mRNAs to hypertonic stress. The fact that the translatability of structure-prone mRNAs varies with changes in the environment may also have general implications for gene expression in eucaryotic cells.

  8. A Review on the Assessment of Stress Conditions for Simultaneous Production of Microalgal Lipids and Carotenoids.

    PubMed

    Minhas, Amritpreet K; Hodgson, Peter; Barrow, Colin J; Adholeya, Alok

    2016-01-01

    Microalgal species are potential resource of both biofuels and high-value metabolites, and their production is growth dependent. Growth parameters can be screened for the selection of novel microalgal species that produce molecules of interest. In this context our review confirms that, autotrophic and heterotrophic organisms have demonstrated a dual potential, namely the ability to produce lipids as well as value-added products (particularly carotenoids) under influence of various physico-chemical stresses on microalgae. Some species of microalgae can synthesize, besides some pigments, very-long-chain polyunsaturated fatty acids (VL-PUFA,>20C) such as docosahexaenoic acid and eicosapentaenoic acid, those have significant applications in food and health. Producing value-added by-products in addition to biofuels, fatty acid methyl esters (FAME), and lipids has the potential to improve microalgae-based biorefineries by employing either the autotrophic or the heterotrophic mode, which could be an offshoot of biotechnology. The review considers the potential of microalgae to produce a range of products and indicates future directions for developing suitable criteria for choosing novel isolates through bioprospecting large gene pool of microalga obtained from various habitats and climatic conditions. PMID:27199903

  9. Examination of the interaction of different lighting conditions and chronic mild stress in animal model.

    PubMed

    Muller, A; Gal, N; Betlehem, J; Fuller, N; Acs, P; Kovacs, G L; Fusz, K; Jozsa, R; Olah, A

    2015-09-01

    We examined the effects of different shift work schedules and chronic mild stress (CMS) on mood using animal model. The most common international shift work schedules in nursing were applied by three groups of Wistar-rats and a control group with normal light-dark cycle. One subgroup from each group was subjected to CMS. Levels of anxiety and emotional life were evaluated in light-dark box. Differences between the groups according to independent and dependent variables were examined with one- and two-way analysis of variance, with a significance level defined at p < 0.05. Interaction of lighting regimen and CMS was proved to be significant according to time spent in the light compartment and the average number of changes between the light and dark compartments. Results of our examination confirm that the changes of lighting conditions evocate anxiety more prominently than CMS. No significant differences were found between the results of the low rotating group and the control group, supposing that this schedule is the least harmful to health. Our results on the association between the use of lighting regimens and the level of CMS provide evidence that the fast rotating shift work schedule puts the heaviest load on the organism of animals.

  10. Interaction of S-nitrosoglutathione with methemoglobin under conditions of modeling carbonyl stress.

    PubMed

    Kosmachevskaya, Olga V; Shumaev, Konstantin B; Nasybullina, Elvira I; Gubkina, Svetlana A; Topunov, Alexey F

    2013-01-01

    The Maillard reaction is the key process in protein modification during pathologies connected with carbonyl stress. It was shown in system modeling that Maillard reaction interaction of L-lysine (L-lys) with methylglyoxal (MG) led to the formation of compounds reducing methemoglobin (metHb). Under the above conditions and in the presence of S-nitrosoglutathione (GSNO), metHb nitrosylation took place. Processes of metHb reduction and nitrosylation had the lag phase that was dependent on the presence of oxygen (O2) in the reaction mixture. Oxygen interacting with organic free radicals of the Maillard reaction inhibited hemoglobin (Hb) reduction and hence Hb nitrosylation during the first minutes of the reaction. It was also shown that the yield of organic free-radical intermediates of the L-lys with MG was increased in the presence of GSNO and metHb. All effects described could be a result of the formation of active red-ox GSNO derivates in the Maillard reaction. These derivates are probably mediators of one-electron oxidation of dialkylimine by MG. Anion radicals of S-nitrosothiols can function as such mediators. PMID:23662713

  11. A Review on the Assessment of Stress Conditions for Simultaneous Production of Microalgal Lipids and Carotenoids

    PubMed Central

    Minhas, Amritpreet K.; Hodgson, Peter; Barrow, Colin J.; Adholeya, Alok

    2016-01-01

    Microalgal species are potential resource of both biofuels and high-value metabolites, and their production is growth dependent. Growth parameters can be screened for the selection of novel microalgal species that produce molecules of interest. In this context our review confirms that, autotrophic and heterotrophic organisms have demonstrated a dual potential, namely the ability to produce lipids as well as value-added products (particularly carotenoids) under influence of various physico-chemical stresses on microalgae. Some species of microalgae can synthesize, besides some pigments, very-long-chain polyunsaturated fatty acids (VL-PUFA,>20C) such as docosahexaenoic acid and eicosapentaenoic acid, those have significant applications in food and health. Producing value-added by-products in addition to biofuels, fatty acid methyl esters (FAME), and lipids has the potential to improve microalgae-based biorefineries by employing either the autotrophic or the heterotrophic mode, which could be an offshoot of biotechnology. The review considers the potential of microalgae to produce a range of products and indicates future directions for developing suitable criteria for choosing novel isolates through bioprospecting large gene pool of microalga obtained from various habitats and climatic conditions. PMID:27199903

  12. The protein targeting factor Get3 functions as ATP-independent chaperone under oxidative stress conditions.

    PubMed

    Voth, Wilhelm; Schick, Markus; Gates, Stephanie; Li, Sheng; Vilardi, Fabio; Gostimskaya, Irina; Southworth, Daniel R; Schwappach, Blanche; Jakob, Ursula

    2014-10-01

    Exposure of cells to reactive oxygen species (ROS) causes a rapid and significant drop in intracellular ATP levels. This energy depletion negatively affects ATP-dependent chaperone systems, making ROS-mediated protein unfolding and aggregation a potentially very challenging problem. Here we show that Get3, a protein involved in ATP-dependent targeting of tail-anchored (TA) proteins under nonstress conditions, turns into an effective ATP-independent chaperone when oxidized. Activation of Get3's chaperone function, which is a fully reversible process, involves disulfide bond formation, metal release, and its conversion into distinct, higher oligomeric structures. Mutational studies demonstrate that the chaperone activity of Get3 is functionally distinct from and likely mutually exclusive with its targeting function, and responsible for the oxidative stress-sensitive phenotype that has long been noted for yeast cells lacking functional Get3. These results provide convincing evidence that Get3 functions as a redox-regulated chaperone, effectively protecting eukaryotic cells against oxidative protein damage.

  13. Context-dependent memory under stressful conditions: the case of skydiving.

    PubMed

    Thompson, L A; Williams, K L; L'Esperance, P; Cornelius, J

    2001-01-01

    Two experiments examined the effect of differing levels of emotional arousal on learning and memory for words in matching and mismatching contexts. In Experiment 1, experienced skydivers learned words either in the air or on the ground and recalled them in the same context or in the other context. Experiment 2 replicated the stimuli and design of the first experiment except that participants were shown a skydiving video in lieu of skydiving. Recall was poor in air-learning conditions with actual skydiving, but when lists were learned on land, recall was higher in the matching context than in the mismatching context. In the skydiving video experiment, recall was higher in matching learn-recall contexts regardless of the situation in which learning occurred. We propose that under extremely emotionally arousing circumstances, environmental and/or mood cues are unlikely to become encoded or linked to newly acquired information and thus cannot serve as cues to retrieval. Results can be applied to understanding variations in context-dependent memory in occupations (e.g., police, military special operations, and Special Weapons and Tactics teams) in which the worker experiences considerable emotional stress while learning or recalling new information.

  14. Proteins involved in biophoton emission and flooding-stress responses in soybean under light and dark conditions.

    PubMed

    Kamal, Abu Hena Mostafa; Komatsu, Setsuko

    2016-02-01

    To know the molecular systems basically flooding conditions in soybean, biophoton emission measurements and proteomic analyses were carried out for flooding-stressed roots under light and dark conditions. Photon emission was analyzed using a photon counter. Gel-free quantitative proteomics were performed to identify significant changes proteins using the nano LC-MS along with SIEVE software. Biophoton emissions were significantly increased in both light and dark conditions after flooding stress, but gradually decreased with continued flooding exposure compared to the control plants. Among the 120 significantly identified proteins in the roots of soybean plants, 73 and 19 proteins were decreased and increased in the light condition, respectively, and 4 and 24 proteins were increased and decreased, respectively, in the dark condition. The proteins were mainly functionally grouped into cell organization, protein degradation/synthesis, and glycolysis. The highly abundant lactate/malate dehydrogenase proteins were decreased in flooding-stressed roots exposed to light, whereas the lysine ketoglutarate reductase/saccharopine dehydrogenase bifunctional enzyme was increased in both light and dark conditions. Notably, however, specific enzyme assays revealed that the activities of these enzymes and biophoton emission were sharply increased after 3 days of flooding stress. This finding suggests that the source of biophoton emission in roots might involve the chemical excitation of electron or proton through enzymatic or non-enzymatic oxidation and reduction reactions. Moreover, the lysine ketoglutarate reductase/saccharopine dehydrogenase bifunctional enzyme may play important roles in responses in flooding stress of soybean under the light condition and as a contributing factor to biophoton emission.

  15. Reactive Oxygen Species Generation-Scavenging and Signaling during Plant-Arbuscular Mycorrhizal and Piriformospora indica Interaction under Stress Condition

    PubMed Central

    Nath, Manoj; Bhatt, Deepesh; Prasad, Ram; Gill, Sarvajeet S.; Anjum, Naser A.; Tuteja, Narendra

    2016-01-01

    A defined balance between the generation and scavenging of reactive oxygen species (ROS) is essential to utilize ROS as an adaptive defense response of plants under biotic and abiotic stress conditions. Moreover, ROS are not only a major determinant of stress response but also act as signaling molecule that regulates various cellular processes including plant-microbe interaction. In particular, rhizosphere constitutes the biologically dynamic zone for plant–microbe interactions which forms a mutual link leading to reciprocal signaling in both the partners. Among plant–microbe interactions, symbiotic associations of arbuscular mycorrhizal fungi (AMF) and arbuscular mycorrhizal-like fungus especially Piriformospora indica with plants are well known to improve plant growth by alleviating the stress-impacts and consequently enhance the plant fitness. AMF and P. indica colonization mainly enhances ROS-metabolism, maintains ROS-homeostasis, and thereby averts higher ROS-level accrued inhibition in plant cellular processes and plant growth and survival under stressful environments. This article summarizes the major outcomes of the recent reports on the ROS-generation, scavenging and signaling in biotic-abiotic stressed plants with AMF and P. indica colonization. Overall, a detailed exploration of ROS-signature kinetics during plant-AMF/P. indica interaction can help in designing innovative strategies for improving plant health and productivity under stress conditions.

  16. Deep transcriptomic profiling reveals the similarity between endothelial cells cultured under static and oscillatory shear stress conditions.

    PubMed

    Qiao, Congzhen; Meng, Fan; Jang, Inhwan; Jo, Hanjoong; Chen, Y Eugene; Zhang, Jifeng

    2016-09-01

    Atherosclerosis is a multifactorial disease that preferentially develops in specific regions in the arterial tree. This characteristic is mainly attributed to the unique pattern of hemodynamic shear stress in vivo. High laminar shear stress (LS) found in straight lumen exerts athero-protective effects. Low or oscillatory shear stress (OS) present in regions of lesser curvature and arterial bifurcations predisposes arterial intima to atherosclerosis. Shear stress-regulated endothelial function plays an important role in the process of atherosclerosis. Most in vitro research studies focusing on the molecular mechanisms of endothelial function are performed in endothelial cells (ECs) under cultured static (ST) condition. Some findings, however, are not recapitulated in subsequent translational studies, mostly likely due to the missing biomechanical milieu. Here, we profiled the whole transcriptome of primary human coronary arterial endothelial cells (HCAECs) under different shear stress conditions with RNA sequencing. Among 16,313 well-expressed genes, we detected 8,177 that were differentially expressed in OS vs. LS conditions and 9,369 in ST vs. LS conditions. Notably, only 1,618 were differentially expressed in OS vs. ST conditions. Hierarchical clustering of ECs demonstrated a strong similarity between ECs under OS and ST conditions at the transcriptome level. Subsequent pairwise heat mapping and principal component analysis gave further weight to the similarity. At the individual gene level, expressional analysis of representative well-known genes as well as novel genes showed a comparable amount at mRNA and protein levels in ECs under ST and OS conditions. In conclusion, the present work compared the whole transcriptome of HCAECs under different shear stress conditions at the transcriptome level as well as at the individual gene level. We found that cultured ECs are significantly different from those under LS conditions. Thus using cells under ST conditions is

  17. Effects of Extinction Treatments on the Reduction of Conditioned Responding and Conditioned Hyperarousal in a Rabbit Model of Posttraumatic Stress Disorder (PTSD)

    PubMed Central

    Burhans, Lauren B.; Smith-Bell, Carrie A.; Schreurs, Bernard G.

    2015-01-01

    We have previously characterized a model of posttraumatic stress disorder (PTSD), based on classical conditioning of the rabbit nictitating membrane response (NMR), that focuses on 2 key PTSD-like features: conditioned responses to trauma-associated cues and hyperarousal. In addition to the development of conditioned NMRs (CRs) to a tone conditioned stimulus (CS) associated with a periorbital shock unconditioned stimulus (US), we have observed that rabbits also exhibit a conditioning-specific reflex modification (CRM) of the NMR that manifests as an exaggerated and more complex reflexive NMR to presentations of the US by itself, particularly to intensities that elicited little response prior to conditioning. Previous work has demonstrated that unpaired presentations of the CS and US are successful at extinguishing CRs and CRM simultaneously, even when a significantly weakened version of the US is utilized. In the current study, additional extinction treatments were tested, including continued pairings of the CS with a weakened US and exposure to the training context alone, and these treatments were contrasted with the effects of unpaired extinction with a weakened US and remaining in home cages with no further treatment. Results showed that continued pairings only slightly decreased CRs and CRM, while context exposure had no effect on CRs and marginal effects on reducing CRM. Unpaired extinction was still the most effective treatment for reducing both. Findings are discussed in terms of applications to cognitive–behavioral therapies for treatment of PTSD, such as incorporating mild, innately stressful stimuli into virtual reality therapy. PMID:26348715

  18. Effects of extinction treatments on the reduction of conditioned responding and conditioned hyperarousal in a rabbit model of posttraumatic stress disorder (PTSD).

    PubMed

    Burhans, Lauren B; Smith-Bell, Carrie A; Schreurs, Bernard G

    2015-10-01

    We have previously characterized a model of posttraumatic stress disorder (PTSD), based on classical conditioning of the rabbit nictitating membrane response (NMR), that focuses on 2 key PTSD-like features: conditioned responses to trauma-associated cues and hyperarousal. In addition to the development of conditioned NMRs (CRs) to a tone conditioned stimulus (CS) associated with a periorbital shock unconditioned stimulus (US), we have observed that rabbits also exhibit a conditioning-specific reflex modification (CRM) of the NMR that manifests as an exaggerated and more complex reflexive NMR to presentations of the US by itself, particularly to intensities that elicited little response prior to conditioning. Previous work has demonstrated that unpaired presentations of the CS and US are successful at extinguishing CRs and CRM simultaneously, even when a significantly weakened version of the US is utilized. In the current study, additional extinction treatments were tested, including continued pairings of the CS with a weakened US and exposure to the training context alone, and these treatments were contrasted with the effects of unpaired extinction with a weakened US and remaining in home cages with no further treatment. Results showed that continued pairings only slightly decreased CRs and CRM, while context exposure had no effect on CRs and marginal effects on reducing CRM. Unpaired extinction was still the most effective treatment for reducing both. Findings are discussed in terms of applications to cognitive-behavioral therapies for treatment of PTSD, such as incorporating mild, innately stressful stimuli into virtual reality therapy.

  19. Investigation of Thermal Stress Convection in Nonisothermal Gases under Microgravity Conditions

    NASA Technical Reports Server (NTRS)

    Mackowski, Daniel W.

    1999-01-01

    The project has sought to ascertain the veracity of the Burnett relations, as applied to slow moving, highly nonisothermal gases, by comparison of convection and stress predictions with those generated by the DSMC method. The Burnett equations were found to provide reasonable descriptions of the pressure distribution and normal stress in stationary gases with a 1-D temperature gradient. Continuum/Burnett predictions of thermal stress convection in 2-D heated enclosures, however, are not quantitatively supported by DSMC results. For such situations, it appears that thermal creep flows, generated at the boundaries of the enclosure, will be significantly larger than the flows resulting from thermal stress in the gas.

  20. Influence of linear profile modification and loading conditions on the dynamic tooth load and stress of high contact ratio gears

    NASA Technical Reports Server (NTRS)

    Lee, Chinwai; Lin, Hsiang Hsi; Oswald, Fred B.; Townsend, Dennis P.

    1990-01-01

    A computer simulation for the dynamic response of high-contact-ratio spur gear transmissions is presented. High contact ratio gears have the potential to produce lower dynamic tooth loads and minimum root stress but they can be sensitive to tooth profile errors. The analysis presented examines various profile modifications under realistic loading conditions. The effect of these modifications on the dynamic load (force) between mating gear teeth and the dynamic root stress is presented. Since the contact stress is dependent on the dynamic load, minimizing dynamic loads will also minimize contact stresses. It is shown that the combination of profile modification and the applied load (torque) carried by a gear system has a significant influence on gear dynamics. The ideal modification at one value of applied load will not be the best solution for a different load. High-contact-ratio gears were found to require less modification than standard low-contact-ratio gears. High-contact-ratio gears are more adversely affected by excess modification than by under modification. In addition, the optimal profile modification required to minimize the dynamic load (hence the contact stress) on a gear tooth differs from the optimal modification required to minimize the dynamic root (bending) stress. Computer simulation can help find the design tradeoffs to determine the best profile modification to satisfy the conflicting constraints of minimizing both the load and root stress in gears which must operate over a range of applied loads.

  1. Objective measurement of human tolerance to +G sub z acceleration stress. Ph.D. Thesis - Univ. of N. Indiana

    NASA Technical Reports Server (NTRS)

    Rositano, S. A.

    1980-01-01

    The efficacy of a new objective technique using a transcutaneous Doppler flowmeter to monitor superficial temporal artery blood flow velocity during acceleration was investigated. The results were correlated with current objective and subjective G tolerance end points. In over 1300 centrifuge runs, retrograde eye level blood flow leading to total flow cessation was consistently recorded and preceded visual field deterioration leading to blackout by 3 to 23 seconds. The new method was successfully applied as an objective indication of tolerance in a variety of test situations including evaluation of g-suits, straining maneuvers, and 13 deg, 45 deg and 65 deg set back angles.

  2. Metabolic profiling of Lolium perenne shows functional integration of metabolic responses to diverse subtoxic conditions of chemical stress

    PubMed Central

    Serra, Anne-Antonella; Couée, Ivan; Renault, David; Gouesbet, Gwenola; Sulmon, Cécile

    2015-01-01

    Plant communities are confronted with a great variety of environmental chemical stresses. Characterization of chemical stress in higher plants has often been focused on single or closely related stressors under acute exposure, or restricted to a selective number of molecular targets. In order to understand plant functioning under chemical stress conditions close to environmental pollution conditions, the C3 grass Lolium perenne was subjected to a panel of different chemical stressors (pesticide, pesticide degradation compound, polycyclic aromatic hydrocarbon, and heavy metal) under conditions of seed-level or root-level subtoxic exposure. Physiological and metabolic profiling analysis on roots and shoots revealed that all of these subtoxic chemical stresses resulted in discrete physiological perturbations and complex metabolic shifts. These metabolic shifts involved stressor-specific effects, indicating multilevel mechanisms of action, such as the effects of glyphosate and its degradation product aminomethylphosphonic acid on quinate levels. They also involved major generic effects that linked all of the subtoxic chemical stresses with major modifications of nitrogen metabolism, especially affecting asparagine, and of photorespiration, especially affecting alanine and glycerate. Stress-related physiological effects and metabolic adjustments were shown to be integrated through a complex network of metabolic correlations converging on Asn, Leu, Ser, and glucose-6-phosphate, which could potentially be modulated by differential dynamics and interconversion of soluble sugars (sucrose, trehalose, fructose, and glucose). Underlying metabolic, regulatory, and signalling mechanisms linking these subtoxic chemical stresses with a generic impact on nitrogen metabolism and photorespiration are discussed in relation to carbohydrate and low-energy sensing. PMID:25618145

  3. Comparison of estimated core body temperature measured with the BioHarness and rectal temperature under several heat stress conditions.

    PubMed

    Seo, Yongsuk; DiLeo, Travis; Powell, Jeffrey B; Kim, Jung-Hyun; Roberge, Raymond J; Coca, Aitor

    2016-08-01

    Monitoring and measuring core body temperature is important to prevent or minimize physiological strain and cognitive dysfunction for workers such as first responders (e.g., firefighters) and military personnel. The purpose of this study is to compare estimated core body temperature (Tco-est), determined by heart rate (HR) data from a wearable chest strap physiology monitor, to standard rectal thermometry (Tre) under different conditions.  Tco-est and Tre measurements were obtained in thermoneutral and heat stress conditions (high temperature and relative humidity) during four different experiments including treadmill exercise, cycling exercise, passive heat stress, and treadmill exercise while wearing personal protective equipment (PPE).  Overall, the mean Tco-est did not differ significantly from Tre across the four conditions. During exercise at low-moderate work rates under heat stress conditions, Tco-est was consistently higher than Tre at all-time points. Tco-est underestimated temperature compared to Tre at rest in heat stress conditions and at a low work rate under heat stress while wearing PPE. The mean differences between the two measurements ranged from -0.1 ± 0.4 to 0.3 ± 0.4°C and Tco-est correlated well with HR (r = 0.795 - 0.849) and mean body temperature (r = 0.637 - 0.861).  These results indicate that, the comparison of Tco-est to Tre may result in over- or underestimation which could possibly lead to heat-related illness during monitoring in certain conditions. Modifications to the current algorithm should be considered to address such issues.

  4. Permeability of coal to CH4 under fixed volume boundary conditions: the effect of stress-strain-sorption behaviour

    NASA Astrophysics Data System (ADS)

    Liu, Jinfeng; Fokker, Peter; Spiers, Christopher

    2016-04-01

    Permeability evolution in coal reservoirs during CO2-Enhanced Coalbed Methane (ECBM) production is strongly influenced by swelling/shrinkage effects related to sorption and desorption of CO2 and CH4, respectively. Numerous permeability models, coupling the swelling response of coal to gas sorption, have been developed to predict in-situ coal seam permeability evolution during (E)CBM. However, experimental studies, aimed at testing such models, have mainly focused on the permeability changes occurring under constant lateral stress conditions, which are inconsistent with the in-situ boundary condition of (near) zero lateral strain. We performed CH4 permeability measurements, using the steady-state method, on a cylindrical sample of high volatile bituminous coal (25mm in diameter), under (near) fixed volume versus fixed stress conditions. The sample possessed a clearly visible cleat system. To isolate the effect of sorption on permeability evolution, helium (non-sorbing gas) was used as a control fluid. The bulk sample permeability to helium, under stress control conditions, changed from 4.07×10‑17to 7.5×10‑18m2, when the effective stress increased from 19.1 to 35.2MPa. Sorption of CH4 at a constant pressure of 10MPa, under fixed volume boundary conditions, resulted in a confining pressure increase from a poroelastically supported value of 29.3MPa to a near-equilibrium value of 38.6MPa over 171 hours. This is caused by the combined effect of the sorption-induced swelling and the self-compression of the sample. The concentration of CH4 adsorbed by the sample was 0.113 mmol/gcoal. During the adsorption process, the permeability to CH4 also decreased from 2.38×10‑17 to 4.91×10‑18m2, proving a strong influence of stress-strain-sorption behavior (c.f. Hol et al., 2012) on fracture permeability evolution. The CH4 permeability subsequently measured under stress controlled conditions varied from 1.37×10‑17 to 4.33×10‑18m2, for same change in confining

  5. Stress tolerance and virulence of insect-pathogenic fungi are determined by environmental conditions during conidial formation.

    PubMed

    Rangel, Drauzio E N; Braga, Gilberto U L; Fernandes, Éverton K K; Keyser, Chad A; Hallsworth, John E; Roberts, Donald W

    2015-08-01

    The virulence to insects and tolerance to heat and UV-B radiation of conidia of entomopathogenic fungi are greatly influenced by physical, chemical, and nutritional conditions during mycelial growth. This is evidenced, for example, by the stress phenotypes of Metarhizium robertsii produced on various substrates. Conidia from minimal medium (Czapek's medium without sucrose), complex medium, and insect (Lepidoptera and Coleoptera) cadavers had high, moderate, and poor tolerance to UV-B radiation, respectively. Furthermore, conidia from minimal medium germinated faster and had increased heat tolerance and were more virulent to insects than those from complex medium. Low water-activity or alkaline culture conditions also resulted in production of conidia with high tolerance to heat or UV-B radiation. Conidia produced on complex media exhibited lower stress tolerance, whereas those from complex media supplemented with NaCl or KCl (to reduce water activity) were more tolerant to heat and UV-B than those from the unmodified complex medium. Osmotic and nutritive stresses resulted in production of conidia with a robust stress phenotype, but also were associated with low conidial yield. Physical conditions such as growth under illumination, hypoxic conditions, and heat shock before conidial production also induced both higher UV-B and heat tolerance; but conidial production was not decreased. In conclusion, physical and chemical parameters, as well as nutrition source, can induce great variability in conidial tolerance to stress for entomopathogenic fungi. Implications are discussed in relation to the ecology of entomopathogenic fungi in the field, and to their use for biological control. This review will cover recent technologies on improving stress tolerance of entomopathogenic fungi for biological control of insects. PMID:25791499

  6. Stress tolerance and virulence of insect-pathogenic fungi are determined by environmental conditions during conidial formation.

    PubMed

    Rangel, Drauzio E N; Braga, Gilberto U L; Fernandes, Éverton K K; Keyser, Chad A; Hallsworth, John E; Roberts, Donald W

    2015-08-01

    The virulence to insects and tolerance to heat and UV-B radiation of conidia of entomopathogenic fungi are greatly influenced by physical, chemical, and nutritional conditions during mycelial growth. This is evidenced, for example, by the stress phenotypes of Metarhizium robertsii produced on various substrates. Conidia from minimal medium (Czapek's medium without sucrose), complex medium, and insect (Lepidoptera and Coleoptera) cadavers had high, moderate, and poor tolerance to UV-B radiation, respectively. Furthermore, conidia from minimal medium germinated faster and had increased heat tolerance and were more virulent to insects than those from complex medium. Low water-activity or alkaline culture conditions also resulted in production of conidia with high tolerance to heat or UV-B radiation. Conidia produced on complex media exhibited lower stress tolerance, whereas those from complex media supplemented with NaCl or KCl (to reduce water activity) were more tolerant to heat and UV-B than those from the unmodified complex medium. Osmotic and nutritive stresses resulted in production of conidia with a robust stress phenotype, but also were associated with low conidial yield. Physical conditions such as growth under illumination, hypoxic conditions, and heat shock before conidial production also induced both higher UV-B and heat tolerance; but conidial production was not decreased. In conclusion, physical and chemical parameters, as well as nutrition source, can induce great variability in conidial tolerance to stress for entomopathogenic fungi. Implications are discussed in relation to the ecology of entomopathogenic fungi in the field, and to their use for biological control. This review will cover recent technologies on improving stress tolerance of entomopathogenic fungi for biological control of insects.

  7. Loading and Boundary Condition Influences in a Poroelastic Finite Element Model of Cartilage Stresses in a Triaxial Compression Bioreactor

    PubMed Central

    Kallemeyn, Nicole A; Grosland, Nicole M; Pedersen, Doug R; Martin, James A; Brown, Thomas D

    2006-01-01

    Background: We developed a poroelastic finite element (FE) model of cartilage in dynamic triaxial compression to parametrically analyze the effects of loading and boundary conditions on a baseline model. Conventional mechanical tests on articular cartilage such as confined and unconfined compression, indentation, etc., do not fully allow for modulation of compression and shear at physiological levels whereas triaxial compression does. A Triaxial Compression Bioreactor, or TRIAX, has been developed to study chondrocyte responses to multi-axial stress conditions under cyclic loading. In the triaxial setting, however, a cartilage explant's physical testing environment departs from the ideal homogeneous stress state that would occur from strict linear superposition of the applied axial and transverse pressure. Method of Approach: An axisymmetric poroelastic FE model of a cartilage explant (4 mm diameter, 1.5 mm thick) in cyclic triaxial compression was created. Axial and transverse loads (2 MPa at 1 Hz.) were applied via a platen and containment sheath. Parameters of interest included the rise time and magnitude of the applied load, in addition to the containment sheath modulus and the friction coefficient at the cartilage/platen interfaces. Metrics of interest in addition to whole explant axial strain included axial (surface normal) stress, shear stress, pore pressure, and the fluid load carriage fraction within the explant. Results: Strain results were compared to experimental data from explants tested in the TRIAX under conditions similar to the baseline model. Explant biomechanics varied considerably over numbers of load cycles and parameter values. Cyclic loading caused an increase in accumulated strain for the various loading and boundary conditions. Conclusions: Unlike what would be expected from linear superposition of the homogeneous stresses from the applied axial and transverse pressure, we have shown that the stress state within the TRIAX is considerably

  8. Associations of Caregiver Stress with Working Conditions, Caregiving Practices, and Child Behaviour in Home-Based Child Care

    ERIC Educational Resources Information Center

    Rusby, Julie C.; Jones, Laura Backen; Crowley, Ryann; Smolkowski, Keith

    2013-01-01

    Home-based child caregivers face unique stressors related to the nature of their work. One hundred and fifty-five home-based child care providers in Oregon, USA, participated in this cross-sectional correlational study. We investigated associations between indicators of caregiver stress and child care working conditions, the quality of caregiver…

  9. Statistical analysis of short-term water stress conditions at Riggs Creek OzFlux tower site

    NASA Astrophysics Data System (ADS)

    Azmi, Mohammad; Rüdiger, Christoph; Walker, Jeffrey P.

    2016-08-01

    A large range of indices and proxies are available to describe the water stress conditions of an area subject to different applications, which have varying capabilities and limitations depending on the prevailing local climatic conditions and land cover. The present study uses a range of spatio-temporally high-resolution (daily and within daily) data sources to evaluate a number of drought indices (DIs) for the Riggs Creek OzFlux tower site in southeastern Australia. Therefore, the main aim of this study is to evaluate the statistical characteristics of individual DIs subject to short-term water stress conditions. In order to derive a more general and therefore representative DI, a new criterion is required to specify the statistical similarity between each pair of indices to allow determining the dominant drought types along with their representative DIs. The results show that the monitoring of water stress at this case study area can be achieved by evaluating the individual behaviour of three clusters of (i) vegetation conditions, (ii) water availability and (iii) water consumptions. This indicates that it is not necessary to assess all individual DIs one by one to derive a comprehensive and informative data set about the water stress of an area; instead, this can be achieved by analysing one of the DIs from each cluster or deriving a new combinatory index for each cluster, based on established combination methods.

  10. Adaptive Coping under Conditions of Extreme Stress: Multilevel Influences on the Determinants of Resilience in Maltreated Children

    ERIC Educational Resources Information Center

    Cicchetti, Dante; Rogosch, Fred A.

    2009-01-01

    The study of resilience in maltreated children reveals the possibility of coping processes and resources on multiple levels of analysis as children strive to adapt under conditions of severe stress. In a maltreating context, aspects of self-organization, including self-esteem, self-reliance, emotion regulation, and adaptable yet reserved…

  11. Identification of differentially expressed genes in Fiskeby III under ozone stress conditions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    As the global climate changes, plants will be challenged by environmental stresses that are more extreme and more frequent leading to increased yield loss. Specifically, ozone stress is an increasing problem in both urban and rural areas. Soybeans are one of the plant species that are quite ozone se...

  12. Acute social defeat stress increases the conditioned rewarding effects of cocaine in adult but not in adolescent mice.

    PubMed

    Montagud-Romero, S; Aguilar, M A; Maldonado, C; Manzanedo, C; Miñarro, J; Rodríguez-Arias, M

    2015-08-01

    Stressful experiences modify activity in areas of the brain involved in the rewarding effects of psychostimulants. In the present study we evaluated the influence of acute social defeat (ASD) on the conditioned rewarding effects of cocaine in adolescent (PND 29-32) and adult (PND 50-53) male mice in the conditioned place preference (CPP) paradigm. Experimental mice were exposed to social defeat in an agonistic encounter before each session of conditioning with 1mg/kg or 25mg/kg of cocaine. The effects of social defeat on corticosterone levels were also evaluated. Adult mice exposed to ASD showed an increase in the conditioned reinforcing effects of cocaine. Only these mice developed cocaine-induced CPP with the subthreshold dose of cocaine, and they needed a higher number of extinction sessions for the 25mg/kg cocaine-induced CPP to be extinguished. In adolescent mice, on the other hand, ASD reduced the conditioned reinforcing effects of cocaine, since CPP was not produced with the lower dose of cocaine and was extinguished faster when they were conditioned with 25mg/kg. Adult mice exposed to social defeat displayed higher levels of corticosterone than their controls and adolescent mice. Our results confirm that the effect of social defeat stress on the acquisition and reinstatement of the CPP induced by cocaine varies depending on the age at which this stress is experienced.

  13. Bayes Analysis and Reliability Implications of Stress-Rupture Testing a Kevlar/Epoxy COPV Using Temperature and Pressure Acceleration

    NASA Technical Reports Server (NTRS)

    Phoenix, S. Leigh; Kezirian, Michael T.; Murthy, Pappu L. N.

    2009-01-01

    Composite Overwrapped Pressure Vessels (COPVs) that have survived a long service time under pressure generally must be recertified before service is extended. Flight certification is dependent on the reliability analysis to quantify the risk of stress rupture failure in existing flight vessels. Full certification of this reliability model would require a statistically significant number of lifetime tests to be performed and is impractical given the cost and limited flight hardware for certification testing purposes. One approach to confirm the reliability model is to perform a stress rupture test on a flight COPV. Currently, testing of such a Kevlar49 (Dupont)/epoxy COPV is nearing completion. The present paper focuses on a Bayesian statistical approach to analyze the possible failure time results of this test and to assess the implications in choosing between possible model parameter values that in the past have had significant uncertainty. The key uncertain parameters in this case are the actual fiber stress ratio at operating pressure, and the Weibull shape parameter for lifetime; the former has been uncertain due to ambiguities in interpreting the original and a duplicate burst test. The latter has been uncertain due to major differences between COPVs in the database and the actual COPVs in service. Any information obtained that clarifies and eliminates uncertainty in these parameters will have a major effect on the predicted reliability of the service COPVs going forward. The key result is that the longer the vessel survives, the more likely the more optimistic stress ratio model is correct. At the time of writing, the resulting effect on predicted future reliability is dramatic, increasing it by about one "nine," that is, reducing the predicted probability of failure by an order of magnitude. However, testing one vessel does not change the uncertainty on the Weibull shape parameter for lifetime since testing several vessels would be necessary.

  14. Impact of oxidative stress defense on bacterial survival and morphological change in Campylobacter jejuni under aerobic conditions.

    PubMed

    Oh, Euna; McMullen, Lynn; Jeon, Byeonghwa

    2015-01-01

    Campylobacter jejuni, a microaerophilic foodborne pathogen, inescapably faces high oxygen tension during its transmission to humans. Thus, the ability of C. jejuni to survive under oxygen-rich conditions may significantly impact C. jejuni viability in food and food safety as well. In this study, we investigated the impact of oxidative stress resistance on the survival of C. jejuni under aerobic conditions by examining three mutants defective in key antioxidant genes, including ahpC, katA, and sodB. All the three mutants exhibited growth reduction under aerobic conditions compared to the wild-type (WT), and the ahpC mutant showed the most significant growth defect. The CFU reduction in the mutants was recovered to the WT level by complementation. Higher levels of reactive oxygen species were accumulated in C. jejuni under aerobic conditions than microaerobic conditions, and supplementation of culture media with an antioxidant recovered the growth of C. jejuni. The levels of lipid peroxidation and protein oxidation were significantly increased in the mutants compared to WT. Additionally, the mutants exhibited different morphological changes under aerobic conditions. The ahpC and katA mutants developed coccoid morphology by aeration, whereas the sodB mutant established elongated cellular morphology. Compared to microaerobic conditions, interestingly, aerobic culture conditions substantially induced the formation of coccoidal cells, and antioxidant treatment reduced the emergence of coccoid forms under aerobic conditions. The ATP concentrations and PMA-qPCR analysis supported that oxidative stress is a factor that induces the development of a viable-but-non-culturable state in C. jejuni. The findings in this study clearly demonstrated that oxidative stress resistance plays an important role in the survival and morphological changes of C. jejuni under aerobic conditions. PMID:25914692

  15. Metabolic analysis of antibody producing Chinese hamster ovary cell culture under different stresses conditions.

    PubMed

    Badsha, Md Bahadur; Kurata, Hiroyuki; Onitsuka, Masayoshi; Oga, Takushi; Omasa, Takeshi

    2016-07-01

    Chinese hamster ovary (CHO) cells are commonly used as the host cell lines concerning their ability to produce therapeutic proteins with complex post-translational modifications. In this study, we have investigated the time course extra- and intracellular metabolome data of the CHO-K1 cell line, under a control and stress conditions. The addition of NaCl and trehalose greatly suppressed cell growth, where the maximum viable cell density of NaCl and trehalose cultures were 2.2-fold and 2.8-fold less than that of a control culture. Contrariwise, the antibody production of both the NaCl and trehalose cultures was sustained for a longer time to surpass that of the control culture. The NaCl and trehalose cultures showed relatively similar dynamics of cell growth, antibody production, and substrate/product concentrations, while they indicated different dynamics from the control culture. The principal component analysis of extra- and intracellular metabolome dynamics indicated that their dynamic behaviors were consistent with biological functions. The qualitative pattern matching classification and hierarchical clustering analyses for the intracellular metabolome identified the metabolite clusters whose dynamic behaviors depend on NaCl and trehalose. The volcano plot revealed several reporter metabolites whose dynamics greatly change between in the NaCl and trehalose cultures. The elastic net identified some critical, intracellular metabolites that are distinct between the NaCl and trehalose. While a relatively small number of intracellular metabolites related to the cell growth, glucose, glutamine, lactate and ammonium ion concentrations, the mechanism of antibody production was suggested to be very complicated or not to be explained by elastic net regression analysis. PMID:26803706

  16. The influence of boundary conditions on wall shear stress distribution in patients specific coronary trees.

    PubMed

    van der Giessen, Alina G; Groen, Harald C; Doriot, Pierre-André; de Feyter, Pim J; van der Steen, Antonius F W; van de Vosse, Frans N; Wentzel, Jolanda J; Gijsen, Frank J H

    2011-04-01

    Patient specific geometrical data on human coronary arteries can be reliably obtained multislice computer tomography (MSCT) imaging. MSCT cannot provide hemodynamic variables, and the outflow through the side branches must be estimated. The impact of two different models to determine flow through the side branches on the wall shear stress (WSS) distribution in patient specific geometries is evaluated. Murray's law predicts that the flow ratio through the side branches scales with the ratio of the diameter of the side branches to the third power. The empirical model is based on flow measurements performed by Doriot et al. (2000) in angiographically normal coronary arteries. The fit based on these measurements showed that the flow ratio through the side branches can best be described with a power of 2.27. The experimental data imply that Murray's law underestimates the flow through the side branches. We applied the two models to study the WSS distribution in 6 coronary artery trees. Under steady flow conditions, the average WSS between the side branches differed significantly for the two models: the average WSS was 8% higher for Murray's law and the relative difference ranged from -5% to +27%. These differences scale with the difference in flow rate. Near the bifurcations, the differences in WSS were more pronounced: the size of the low WSS regions was significantly larger when applying the empirical model (13%), ranging from -12% to +68%. Predicting outflow based on Murray's law underestimates the flow through the side branches. Especially near side branches, the regions where atherosclerotic plaques preferentially develop, the differences are significant and application of Murray's law underestimates the size of the low WSS region.

  17. Developmental significance of cyanide-resistant respiration under stressed conditions: experiments in Dictyostelium cells.

    PubMed

    Kimura, Kei; Kuwayama, Hidekazu; Amagai, Aiko; Maeda, Yasuo

    2010-09-01

    We have previously reported that benzohydroxamic acid (BHAM), a potent inhibitor of cyanide (CN)-resistant respiration mediated by alternative oxidase (AOX), induces formation of unique cell masses (i.e., stalk-like cells with a large vacuole and thick cell wall) in starved Dictyostelium cells. Unexpectedly, however, aox-null cells prepared by homologous recombination exhibited normal development under normal culture conditions on agar, indicating that BHAM-induced stalk formation is not solely attributable to inhibition of CN-resistant respiration. This also suggests that a series of pharmacological approaches in the field of life science has serious limitations. Under stress (e.g., in submerged culture), starved aox-null cells exhibited slightly delayed aggregation compared with parental Ax-2 cells; most cells remained as loose aggregates even after prolonged incubation. Also, the developmental defects of aox-null cells became more marked upon incubation for 30 min just after starvation in the presence of ≥ 1.75 mmol/L H(2)O(2). This seems to indicate that CN-resistant respiration could mitigate cellular damage through reactive oxygen species (ROS), because AOX has a potential role in reduction of ROS production. Starved aox-null cells did not develop in the presence of 5 mmol/L KCN (which completely inhibited the conventional cytochrome-mediated respiration) and remained as non-aggregated single cells on agar even after prolonged incubation. Somewhat surprisingly, however, parental Ax-2 cells were found to develop normally, forming fruiting bodies even in the presence of 10 mmol/L KCN. Taken together, these results suggest that CN-resistant respiration might compensate for the production of adenosine tri-phosphate via oxidative phosphorylation.

  18. Chronic stress accelerates pancreatic cancer growth and invasion: a critical role for beta-adrenergic signaling in the pancreatic microenvironment.

    PubMed

    Kim-Fuchs, Corina; Le, Caroline P; Pimentel, Matthew A; Shackleford, David; Ferrari, Davide; Angst, Eliane; Hollande, Frédéric; Sloan, Erica K

    2014-08-01

    Pancreatic cancer cells intimately interact with a complex microenvironment that influences pancreatic cancer progression. The pancreas is innervated by fibers of the sympathetic nervous system (SNS) and pancreatic cancer cells have receptors for SNS neurotransmitters which suggests that pancreatic cancer may be sensitive to neural signaling. In vitro and non-orthotopic in vivo studies showed that neural signaling modulates tumour cell behavior. However the effect of SNS signaling on tumor progression within the pancreatic microenvironment has not previously been investigated. To address this, we used in vivo optical imaging to non-invasively track growth and dissemination of primary pancreatic cancer using an orthotopic mouse model that replicates the complex interaction between pancreatic tumor cells and their microenvironment. Stress-induced neural activation increased primary tumor growth and tumor cell dissemination to normal adjacent pancreas. These effects were associated with increased expression of invasion genes by tumor cells and pancreatic stromal cells. Pharmacological activation of β-adrenergic signaling induced similar effects to chronic stress, and pharmacological β-blockade reversed the effects of chronic stress on pancreatic cancer progression. These findings indicate that neural β-adrenergic signaling regulates pancreatic cancer progression and suggest β-blockade as a novel strategy to complement existing therapies for pancreatic cancer.

  19. Effect of solution and solid-phase conditions on the Fe(II)-accelerated transformation of ferrihydrite to lepidocrocite and goethite.

    PubMed

    Boland, Daniel D; Collins, Richard N; Miller, Christopher J; Glover, Chris J; Waite, T David

    2014-05-20

    Aqueous ferrous iron (Fe(II)) accelerates the transformation of ferrihydrite into secondary, more crystalline minerals however the factors controlling the rate and, indeed, the underlying mechanism of this transformation process remain unclear. Here, we present the first detailed study of the kinetics of the Fe(II)-accelerated transformation of ferrihydrite to goethite, via lepidocrocite, for a range of pH and Fe(II) concentrations and, from the results obtained, provide insight into the factors controlling the transformation rate and the processes responsible for transformation. A reaction scheme for the Fe(II)-accelerated secondary mineralization of ferrihydrite is developed in which an Fe(II) atom attaches to the ferrihydrite surface where it is immediately oxidized to Fe(III) with the resultant electron transferred, sequentially, to other iron oxyhydroxide Fe(III) atoms before release to solution as Fe(II). This freshly precipitated Fe(III) forms the nuclei for the formation of secondary minerals and also facilitates the ongoing uptake of Fe(II) from solution by creation of fresh surface sites. The concentration of solid-associated Fe(II) and the rate of transport of Fe(II) to the oxyhydroxide surface appear to determine which particular secondary minerals form and their rates of formation. Lepidocrocite growth is enhanced at lower solid-associated Fe(II) concentrations while conditions leading to more rapid uptake of Fe(II) from solution lead to higher goethite growth rates.

  20. Conditions for efficient and stable ion acceleration by moderate circularly polarized laser pulses at intensities of 10{sup 20} W/cm{sup 2}

    SciTech Connect

    Qiao, B.; Zepf, M.; Borghesi, M.; Dromey, B.; Kar, S.; Geissler, M.; Gibbon, P.; Schreiber, J.

    2011-04-15

    Conditions for efficient and stable ion radiation pressure acceleration (RPA) from thin foils by circularly polarized laser pulses at moderate intensities are theoretically and numerically investigated. It is found that the unavoidable decompression of the co-moving electron layer in Light-Sail RPA leads to a change of the local electrostatic field from a ''bunching'' to a ''debunching'' profile, ultimately resulting in premature termination of ion acceleration. One way to overcome this instability is the use of a multispecies foil where the high-Z ions act as a sacrificial species to supply excess co-moving electrons for preserving stable acceleration of the lower-Z ion species. It is shown by 2D particle-in-cell simulations that 100 MeV/u monoenergetic C{sup 6+} ion beams are produced by irradiation of a Cu-C-mixed foil with laser pulses at intensities 5 x 10{sup 20} W/cm{sup 2}, which can be easily achieved by current day lasers.

  1. Evaluation and validation of housekeeping genes as reference for gene expression studies in pigeonpea (Cajanus cajan) under drought stress conditions.

    PubMed

    Sinha, Pallavi; Singh, Vikas K; Suryanarayana, V; Krishnamurthy, L; Saxena, Rachit K; Varshney, Rajeev K

    2015-01-01

    Gene expression analysis using quantitative real-time PCR (qRT-PCR) is a very sensitive technique and its sensitivity depends on the stable performance of reference gene(s) used in the study. A number of housekeeping genes have been used in various expression studies in many crops however, their expression were found to be inconsistent under different stress conditions. As a result, species specific housekeeping genes have been recommended for different expression studies in several crop species. However, such specific housekeeping genes have not been reported in the case of pigeonpea (Cajanus cajan) despite the fact that genome sequence has become available for the crop. To identify the stable housekeeping genes in pigeonpea for expression analysis under drought stress conditions, the relative expression variations of 10 commonly used housekeeping genes (EF1α, UBQ10, GAPDH, 18SrRNA, 25SrRNA, TUB6, ACT1, IF4α, UBC and HSP90) were studied on root, stem and leaves tissues of Asha (ICPL 87119). Three statistical algorithms geNorm, NormFinder and BestKeeper were used to define the stability of candidate genes. geNorm analysis identified IF4α and TUB6 as the most stable housekeeping genes however, NormFinder analysis determined IF4α and HSP90 as the most stable housekeeping genes under drought stress conditions. Subsequently validation of the identified candidate genes was undertaken in qRT-PCR based gene expression analysis of uspA gene which plays an important role for drought stress conditions in pigeonpea. The relative quantification of the uspA gene varied according to the internal controls (stable and least stable genes), thus highlighting the importance of the choice of as well as validation of internal controls in such experiments. The identified stable and validated housekeeping genes will facilitate gene expression studies in pigeonpea especially under drought stress conditions. PMID:25849964

  2. Effects of reproductive condition and dominance rank on cortisol responsiveness to stress in free-ranging female rhesus macaques

    PubMed Central

    Hoffman, Christy L.; Ayala, James E.; Mas-Rivera, Adaris; Maestripieri, Dario

    2014-01-01

    The hypothalamic-pituitary-adrenal (HPA) axis modulates individuals’ physiological responses to social stress, which is an inevitable aspect of the daily lives of group-living animals. Previous nonhuman primate studies have reported that sex, age, rank and reproductive condition influence cortisol levels under stressful conditions. In this study we investigated cortisol responses to stress among 70 multiparous, free-ranging female rhesus macaques (Macaca mulatta) on the island of Cayo Santiago, PR. Plasma cortisol samples were collected in two consecutive years under similar conditions. Twenty-two females were sampled both years, and most of those females were lactating in only one of the years. Individual differences in cortisol levels were stable across years, even though reproductive condition changed for most individuals. No relationship was found between age or social rank and cortisol levels. Of the females that changed reproductive conditions, cortisol levels were higher when they were lactating than when they were cycling, and the amount of change in cortisol from cycling to lactating was greatest for low-ranking individuals. Heightened reactivity to stress during lactation may be the result of concerns about infant safety, and such concerns may be higher among low-ranking mothers than among higher ranking mothers. Psychosocial stress and hyperactivation of the HPA axis during lactation can suppress immune function and increase vulnerability to infectious diseases, thus explaining why adult females in the free-ranging rhesus macaque population on Cayo Santiago have a higher probability of mortality during the birth season than during the mating season. PMID:20039328

  3. Evaluation and Validation of Housekeeping Genes as Reference for Gene Expression Studies in Pigeonpea (Cajanus cajan) Under Drought Stress Conditions

    PubMed Central

    Sinha, Pallavi; Singh, Vikas K.; Suryanarayana, V.; Krishnamurthy, L.; Saxena, Rachit K.; Varshney, Rajeev K.

    2015-01-01

    Gene expression analysis using quantitative real-time PCR (qRT-PCR) is a very sensitive technique and its sensitivity depends on the stable performance of reference gene(s) used in the study. A number of housekeeping genes have been used in various expression studies in many crops however, their expression were found to be inconsistent under different stress conditions. As a result, species specific housekeeping genes have been recommended for different expression studies in several crop species. However, such specific housekeeping genes have not been reported in the case of pigeonpea (Cajanus cajan) despite the fact that genome sequence has become available for the crop. To identify the stable housekeeping genes in pigeonpea for expression analysis under drought stress conditions, the relative expression variations of 10 commonly used housekeeping genes (EF1α, UBQ10, GAPDH, 18SrRNA, 25SrRNA, TUB6, ACT1, IF4α, UBC and HSP90) were studied on root, stem and leaves tissues of Asha (ICPL 87119). Three statistical algorithms geNorm, NormFinder and BestKeeper were used to define the stability of candidate genes. geNorm analysis identified IF4α and TUB6 as the most stable housekeeping genes however, NormFinder analysis determined IF4α and HSP90 as the most stable housekeeping genes under drought stress conditions. Subsequently validation of the identified candidate genes was undertaken in qRT-PCR based gene expression analysis of uspA gene which plays an important role for drought stress conditions in pigeonpea. The relative quantification of the uspA gene varied according to the internal controls (stable and least stable genes), thus highlighting the importance of the choice of as well as validation of internal controls in such experiments. The identified stable and validated housekeeping genes will facilitate gene expression studies in pigeonpea especially under drought stress conditions. PMID:25849964

  4. Evaluation and validation of housekeeping genes as reference for gene expression studies in pigeonpea (Cajanus cajan) under drought stress conditions.

    PubMed

    Sinha, Pallavi; Singh, Vikas K; Suryanarayana, V; Krishnamurthy, L; Saxena, Rachit K; Varshney, Rajeev K

    2015-01-01

    Gene expression analysis using quantitative real-time PCR (qRT-PCR) is a very sensitive technique and its sensitivity depends on the stable performance of reference gene(s) used in the study. A number of housekeeping genes have been used in various expression studies in many crops however, their expression were found to be inconsistent under different stress conditions. As a result, species specific housekeeping genes have been recommended for different expression studies in several crop species. However, such specific housekeeping genes have not been reported in the case of pigeonpea (Cajanus cajan) despite the fact that genome sequence has become available for the crop. To identify the stable housekeeping genes in pigeonpea for expression analysis under drought stress conditions, the relative expression variations of 10 commonly used housekeeping genes (EF1α, UBQ10, GAPDH, 18SrRNA, 25SrRNA, TUB6, ACT1, IF4α, UBC and HSP90) were studied on root, stem and leaves tissues of Asha (ICPL 87119). Three statistical algorithms geNorm, NormFinder and BestKeeper were used to define the stability of candidate genes. geNorm analysis identified IF4α and TUB6 as the most stable housekeeping genes however, NormFinder analysis determined IF4α and HSP90 as the most stable housekeeping genes under drought stress conditions. Subsequently validation of the identified candidate genes was undertaken in qRT-PCR based gene expression analysis of uspA gene which plays an important role for drought stress conditions in pigeonpea. The relative quantification of the uspA gene varied according to the internal controls (stable and least stable genes), thus highlighting the importance of the choice of as well as validation of internal controls in such experiments. The identified stable and validated housekeeping genes will facilitate gene expression studies in pigeonpea especially under drought stress conditions.