increasing normal stress: Topics by Science.gov

Sample records for increasing normal stress

Frictional response of simulated faults to normal stresses perturbations probed with ultrasonic waves

NASA Astrophysics Data System (ADS)

Shreedharan, S.; Riviere, J.; Marone, C.

2017-12-01

We report on a suite of laboratory friction experiments conducted on saw-cut Westerly Granite surfaces to probe frictional response to step changes in normal stress and loading rate. The experiments are conducted to illuminate the fundamental processes that yield friction rate and state dependence. We quantify the microphysical frictional response of the simulated fault surfaces to normal stress steps, in the range of 1% - 600% step increases and decreases from a nominal baseline normal stress. We measure directly the fault slip rate and account for changes in slip rate with changes in normal stress and complement mechanical data acquisition by continuously probing the faults with ultrasonic pulses. We conduct the experiments at room temperature and humidity conditions in a servo controlled biaxial testing apparatus in the double direct shear configuration. The samples are sheared over a range of velocities, from 0.02 - 100 μm/s. We report observations of a transient shear stress and friction evolution with step increases and decreases in normal stress. Specifically, we show that, at low shear velocities and small increases in normal stress (<5% increase), the shear stress on the fault does not increase instantaneously with the normal stress step while the ultrasonic wave amplitude and normal displacement do. In other words, the shear stress does not follow the load point stiffness curve. At high shear velocities and larger normal stress steps (> 5% increases), the shear stress evolves immediately with normal stress. We show that the excursions in slip rate resulting from the changes in normal stress must be accounted for in order to predict fault strength evolution. Ultrasonic wave amplitudes which first increase immediately in response to normal stress steps, then decrease approximately linearly to a new steady state value, in part due to changes in fault slip rate. Previous descriptions of frictional state evolution during normal stress perturbations have not adequately accounted for the effect of large slip velocity excursions. Here, we attempt to do so by using the measured ultrasonic amplitudes as a proxy for frictional state during transient shear stress evolution. Our work aims to improve understanding of induced and triggered seismicity with focus on simulating static triggering using rate and state friction.
Full-Scale Linear Cutting Tests in Chongqing Sandstone to Study the Influence of Confining Stress on Rock Cutting Forces by TBM Disc Cutter

NASA Astrophysics Data System (ADS)

Pan, Yucong; Liu, Quansheng; Liu, Jianping; Peng, Xingxin; Kong, Xiaoxuan

2018-06-01

In order to study the influence of confining stress on rock cutting forces by tunnel boring machine (TBM) disc cutter, full-scale linear cutting tests are conducted in Chongqing Sandstone (uniaxial compressive strength 60.76 MPa) using five equal biaxial confining stressed conditions, i.e. 0-0, 5-5, 10-10, 15-15 and 20-20 MPa; disc cutter normal force, rolling force, cutting coefficient and normalized resultant force are analysed. It is found that confining stress can greatly affect disc cutter resultant force, its proportion in normal and rolling directions and its acting point for the hard Chongqing Sandstone and the confining stress range used in this study. For every confining stressed condition, as cutter penetration depth increases, disc cutter normal force increases with decreasing speed, rolling force and cutting coefficient both increase linearly, and acting point of the disc cutter resultant force moves downward at some extent firstly and then upward back to its initial position. For same cutter penetration depth, as confining stress increases, disc cutter normal force, rolling force, cutting coefficient and normalized resultant force all increase at some extent firstly and then decrease rapidly to very small values (quite smaller than those obtained under the non-stressed condition) after some certain confining stress thresholds. The influence of confining stress on rock cutting by TBM disc cutter can be generally divided into three stages as confining stress increases, i.e. strengthening effect stage, damaging effect stage and rupturing effect stage. In the former two stages (under low confining stress), rock remains intact and rock cutting forces are higher than those obtained under the non-stressed condition, and thus rock cutting by TBM disc cutter is restrained; in the last stage (under high confining stress), rock becomes non-intact and rock slabbing failure is induced by confining stress before disc cutting, and thus rock cutting by TBM disc cutter is facilitated. Meanwhile, some critical values of confining stress and cutter penetration depth are identified to represent the changes of rock cutting state. This study provides better understanding of the influence of confining stress on disc cutter performance and can guide to optimize the TBM operation under stressed condition.
Rock friction under variable normal stress

USGS Publications Warehouse

Kilgore, Brian D.; Beeler, Nicholas M.; Lozos, Julian C.; Oglesby, David

2017-01-01

This study is to determine the detailed response of shear strength and other fault properties to changes in normal stress at room temperature using dry initially bare rock surfaces of granite at normal stresses between 5 and 7 MPa. Rapid normal stress changes result in gradual, approximately exponential changes in shear resistance with fault slip. The characteristic length of the exponential change is similar for both increases and decreases in normal stress. In contrast, changes in fault normal displacement and the amplitude of small high-frequency elastic waves transmitted across the surface follow a two stage response consisting of a large immediate and a smaller gradual response with slip. The characteristic slip distance of the small gradual response is significantly smaller than that of shear resistance. The stability of sliding in response to large step decreases in normal stress is well predicted using the shear resistance slip length observed in step increases. Analysis of the shear resistance and slip-time histories suggest nearly immediate changes in strength occur in response to rapid changes in normal stress; these are manifested as an immediate change in slip speed. These changes in slip speed can be qualitatively accounted for using a rate-independent strength model. Collectively, the observations and model show that acceleration or deceleration in response to normal stress change depends on the size of the change, the frictional characteristics of the fault surface, and the elastic properties of the loading system.
Thermal Stress

DTIC Science & Technology

2011-01-01

can have a significant impact on normal physiological functioning if precipitous increases in core temperature are not adequately controlled with...anterior hypothalamusIntroduction Thermal stress can have a significant impact on normal physiological functioning if precipitous increases in core...fat and skin). The regulation of a relatively constant internal temperature is critical for normal physiological functioning of tissues and cells, as
Effect of stress perturbation on frictional instability: an experimental study

NASA Astrophysics Data System (ADS)

Yuanmin, H.; Shengli, M.

2017-12-01

We have performed a series of frictional experiments with direct shear configuration of three granite blocks by using a servo-controlled biaxial loading machine. In the experiments, a small- amplitude sine wave is modulated to shear and normal loading in order to study the effects of stress perturbation on stick-slip instability. The main results are as follows. Under the constant average normal stress and the constant loading point velocity in shear direction, the sample shows regular stick-slip behavior. After the stress perturbation is modulated, the correlation between the timing of stick-slip events and the perturbation increases with increasing the perturbation amplitude, and stress drop and interval time of stick-slip events tend to be discrete. This results imply that the change in Coulomb stress caused by stress perturbation may obviously change not only the occurrence time of earthquakes but also the earthquake magnitude. Both shear and normal stress perturbation can affect the stick-slip behavior, shear stress perturbation can only change the driving stress along fault, while the normal stress perturbation can change the contact state of asperities on the fault, so it's effect is more obviously. The stress perturbation can obviously affect acoustic emission (AE) activity during fault friction, which can trigger some AE events so that AE activity before stick-slip becomes stronger and occurs earlier. The perturbation in shear stress is more evident than that in normal stress in affecting AE activity, so we should not only pay attention to the magnitude of Coulomb stress changes caused by the perturbation, but also try to distinguish the stress changes are the shear stress changes or the normal stress changes, when study the effect of stress perturbation on fault friction.
Creep behaviour and creep mechanisms of normal and healing ligaments

NASA Astrophysics Data System (ADS)

Thornton, Gail Marilyn

Patients with knee ligament injuries often undergo ligament reconstructions to restore joint stability and, potentially, abate osteoarthritis. Careful literature review suggests that in 10% to 40% of these patients the graft tissue "stretches out". Some graft elongation is likely due to creep (increased elongation of tissue under repeated or sustained load). Quantifying creep behaviour and identifying creep mechanisms in both normal and healing ligaments is important for finding clinically relevant means to prevent creep. Ligament creep was accurately predicted using a novel yet simple structural model that incorporated both collagen fibre recruitment and fibre creep. Using the inverse stress relaxation function to model fibre creep in conjunction with fibre recruitment produced a superior prediction of ligament creep than that obtained from the inverse stress relaxation function alone. This implied mechanistic role of fibre recruitment during creep was supported using a new approach to quantify crimp patterns at stresses in the toe region (increasing stiffness) and linear region (constant stiffness) of the stress-strain curve. Ligament creep was relatively insensitive to increases in stress in the toe region; however, creep strain increased significantly when tested at the linear region stress. Concomitantly, fibre recruitment was evident at the toe region stresses; however, recruitment was limited at the linear region stress. Elevating the water content of normal ligament using phosphate buffered saline increased the creep response. Therefore, both water content and fibre recruitment are important mechanistic factors involved in creep of normal ligaments. Ligament scars had inferior creep behaviour compared to normal ligaments even after 14 weeks. In addition to inferior collagen properties affecting fibre recruitment and increased water content, increased glycosaminoglycan content and flaws in scar tissue were implicated as potential mechanisms of scar creep. Similarly, ligament autografts had persistently abnormal creep behaviour and creep recovery after 2 years likely due to infiltration by scar tissue. Short-term immobilization of autografts had long-term detrimental consequences perhaps due to re-injury of the graft at remobilization. Treatments that restore normal properties to these mechanistic factors in order to control creep would improve joint healing by restoring joint kinematics and maintaining normal joint loading.
Strength of Wet and Dry Montmorillonite

NASA Astrophysics Data System (ADS)

Morrow, C. A.; Lockner, D. A.; Moore, D. E.

2015-12-01

Montmorillonite, an expandable smectite clay, is a common mineral in fault zones to a depth of around 3 km. Its low strength relative to other common fault gouge minerals is important in many models of fault rheology. However, the coefficient of friction is not well constrained in the literature due to the difficulty of establishing fully drained or fully dried states in the laboratory. For instance, in some reported studies, samples were either partially saturated or possibly over pressured, leading to wide variability in reported shear strength. In this study, the coefficient of friction, μ, of both saturated and oven-dried (at 150°C) Na-montmorillonite was measured at normal stresses up to 680 MPa at room temperature and shortening rates from 1.0 to 0.01 μm/s. Care was taken to shear saturated samples slowly enough to avoid pore fluid overpressure in the clay layers. Coefficients of friction are reported after 8 mm of axial displacement in a triaxial apparatus on saw-cut samples containing a layer of montmorillonite gouge, with either granite or sandstone driving blocks. For saturated samples, μ increased from around 0.1 at low pressure to 0.25 at the highest test pressures. In contrast, values for oven-dried samples decreased asymptotically from approximately 0.78 at 10 MPa normal stress to around 0.45 at 400-680 MPa. While wet and dry strengths approached each other with increasing effective normal stress, wet strength remained only about half of the dry strength at 600 MPa effective normal stress. The increased coefficient of friction can be correlated with a reduction in the number of loosely bound lubricating surface water layers on the clay platelets due to applied normal stress under saturated conditions. The steady-state rate dependence of friction, a-b, was positive and dependent on normal stress. For saturated samples, a-b increased linearly with applied normal stress from ~0 to 0.004, while for dry samples a-b decreased with increasing normal stress from 0.008 to 0.002. All values were either neutral or rate strengthening, indicating a tendency for stable sliding.
Instrumented roll technology for the design space development of roller compaction process.

PubMed

Nesarikar, Vishwas V; Vatsaraj, Nipa; Patel, Chandrakant; Early, William; Pandey, Preetanshu; Sprockel, Omar; Gao, Zhihui; Jerzewski, Robert; Miller, Ronald; Levin, Michael

2012-04-15

Instrumented roll technology on Alexanderwerk WP120 roller compactor was developed and utilized successfully for the measurement of normal stress on ribbon during the process. The effects of process parameters such as roll speed (4-12 rpm), feed screw speed (19-53 rpm), and hydraulic roll pressure (40-70 bar) on normal stress and ribbon density were studied using placebo and active pre-blends. The placebo blend consisted of 1:1 ratio of microcrystalline cellulose PH102 and anhydrous lactose with sodium croscarmellose, colloidal silicon dioxide, and magnesium stearate. The active pre-blends were prepared using various combinations of one active ingredient (3-17%, w/w) and lubricant (0.1-0.9%, w/w) levels with remaining excipients same as placebo. Three force transducers (load cells) were installed linearly along the width of the roll, equidistant from each other with one transducer located in the center. Normal stress values recorded by side sensors and were lower than normal stress values recorded by middle sensor and showed greater variability than middle sensor. Normal stress was found to be directly proportional to hydraulic pressure and inversely to screw to roll speed ratio. For active pre-blends, normal stress was also a function of compressibility. For placebo pre-blends, ribbon density increased as normal stress increased. For active pre-blends, in addition to normal stress, ribbon density was also a function of gap. Models developed using placebo were found to predict ribbon densities of active blends with good accuracy and the prediction error decreased as the drug concentration of active blend decreased. Effective angle of internal friction and compressibility properties of active pre blend may be used as key indicators for predicting ribbon densities of active blend using placebo ribbon density model. Feasibility of on-line prediction of ribbon density during roller compaction was demonstrated using porosity-pressure data of pre-blend and normal stress measurements. Effect of vacuum to de-aerate pre blend prior to entering the nip zone was studied. Varying levels of vacuum for de-aeration of placebo pre blend did not affect the normal stress values. However, turning off vacuum completely caused an increase in normal stress with subsequent decrease in gap. Use of instrumented roll demonstrated potential to reduce the number of DOE runs by enhancing fundamental understanding of relationship between normal stress on ribbon and process parameters. Copyright © 2012 Elsevier B.V. All rights reserved.
An Experimental Study on Normal Stress and Shear Rate Dependency of Basic Friction Coefficient in Dry and Wet Limestone Joints

NASA Astrophysics Data System (ADS)

Mehrishal, Seyedahmad; Sharifzadeh, Mostafa; Shahriar, Korosh; Song, Jae-Jon

2016-12-01

Among all parameters that affect the friction of rocks, variable normal stress and slip rate are the most important second-order parameters. The shear-rate- and normal-stress-dependent friction behavior of rock discontinuities may significantly influence the dynamic responses of rock mass. In this research, two limestone rock types, which were travertine and onyx marble with slickenside and grinded #80 surfaces, were prepared and CNL direct shear tests were performed on the joints under various shear conditions. The shearing rate varied from 0.1 to 50 mm/min under different normal stresses (from 2 to 30 % of UCS) in both dry and wet conditions. Experiments showed that the friction coefficient of slickensided and ground #80 surfaces of limestone increased with the increasing shear velocity and decreased with the increasing normal stress. Micro-asperity interlocking between ground #80 surfaces showed higher wear and an increase in friction coefficient ( µ) compared to slickensided surfaces. Slickensided samples with moist surfaces showed an increase in the coefficient of friction compared to dry surfaces; however, on ground #80 surfaces, the moisture decreased the coefficient of friction to a smaller value. Slickenside of limestone typically slides stably in a dry condition and by stick-slip on moist surfaces. The observed shear-rate- and normal-stress-dependent friction behavior can be explained by a similar framework to that of the adhesion theory of friction and a friction mechanism that involves the competition between microscopic dilatant slip and surface asperity deformation. The results have important implications for understanding the behavior of basic and residual friction coefficients of limestone rock surfaces.
Direct Shear Tests of Sandstone Under Constant Normal Tensile Stress Condition Using a Simple Auxiliary Device

NASA Astrophysics Data System (ADS)

Cen, Duofeng; Huang, Da

2017-06-01

Tension-shear failure is a typical failure mode in the rock masses in unloading zones induced by excavation or river incision, etc., such as in excavation-disturbed zone of deep underground caverns and superficial rocks of high steep slopes. However, almost all the current shear failure criteria for rock are usually derived on the basis of compression-shear failure. This paper proposes a simple device for use with a servo-controlled compression-shear testing machine to conduct the tension-shear tests of cuboid rock specimens, to test the direct shear behavior of sandstone under different constant normal tensile stress conditions ( σ = -1, -1.5, -2, -2.5 and -3 MPa) as well as the uniaxial tension behavior. Generally, the fracture surface roughness decreases and the proportion of comminution areas in fracture surface increases as the change of stress state from tension to tension-shear and to compression-shear. Stepped fracture is a primary fracture pattern in the tension-shear tests. The shear stiffness, shear deformation and normal deformation (except the normal deformation for σ = -1 MPa) decrease during shearing, while the total normal deformation containing the pre-shearing portion increases as the normal tensile stress level (| σ|) goes up. Shear strength is more sensitive to the normal tensile stress than to the normal compressive stress, and the power function failure criterion (or Mohr envelope form of Hoek-Brown criterion) is examined to be the optimal criterion for the tested sandstone in the full region of tested normal stress in this study.
Laboratory observations of fault strength in response to changes in normal stress

USGS Publications Warehouse

Kilgore, Brian D.; Lozos, Julian; Beeler, Nicholas M.; Oglesby, David

2012-01-01

Changes in fault normal stress can either inhibit or promote rupture propagation, depending on the fault geometry and on how fault shear strength varies in response to the normal stress change. A better understanding of this dependence will lead to improved earthquake simulation techniques, and ultimately, improved earthquake hazard mitigation efforts. We present the results of new laboratory experiments investigating the effects of step changes in fault normal stress on the fault shear strength during sliding, using bare Westerly granite samples, with roughened sliding surfaces, in a double direct shear apparatus. Previous experimental studies examining the shear strength following a step change in the normal stress produce contradictory results: a set of double direct shear experiments indicates that the shear strength of a fault responds immediately, and then is followed by a prolonged slip-dependent response, while a set of shock loading experiments indicates that there is no immediate component, and the response is purely gradual and slip-dependent. In our new, high-resolution experiments, we observe that the acoustic transmissivity and dilatancy of simulated faults in our tests respond immediately to changes in the normal stress, consistent with the interpretations of previous investigations, and verify an immediate increase in the area of contact between the roughened sliding surfaces as normal stress increases. However, the shear strength of the fault does not immediately increase, indicating that the new area of contact between the rough fault surfaces does not appear preloaded with any shear resistance or strength. Additional slip is required for the fault to achieve a new shear strength appropriate for its new loading conditions, consistent with previous observations made during shock loading.
Characteristics of Asperity Damage and Its Influence on the Shear Behavior of Granite Joints

NASA Astrophysics Data System (ADS)

Meng, Fanzhen; Zhou, Hui; Wang, Zaiquan; Zhang, Chuanqing; Li, Shaojun; Zhang, Liming; Kong, Liang

2018-02-01

Surface roughness significantly affects the shear behavior of rock joints; thus, studies on the asperity damage characteristics and its influence on the shear behavior of joints are extremely important. In this paper, shear tests were conducted on tensile granite joints; asperity damage was evaluated based on acoustic emission (AE) events; and the influence of asperity damage on joint shear behavior was analyzed. The results indicated that the total AE events tended to increase with normal stress. In addition, the asperity damage initiation shear stress, which is defined as the transition point from slow growth to rapid growth in the cumulative events curve, was approximately 0.485 of the peak shear strength regardless of the normal stress. Moreover, 63-85% of the AE events were generated after the peak shear stress, indicating that most of the damage occurred in this stage. Both the dilation and the total AE events decreased with shear cycles because of the damage inflicted on asperities during the previous shear cycle. Two stages were observed in the normal displacement curves under low normal stress, whereas three stages (compression, dilation and compression again) were observed at a higher normal stress; the second compression stage may be caused by tensile failure outside the shear plane. The magnitude of the normal stress and the state of asperity are two important factors controlling the post-peak stress drop and stick-slip of granite joints. Serious deterioration of asperities will stop stick-slip from recurring under the same normal stress because the ability to accumulate energy is decreased. The AE b-value increases with the number of shear cycles, indicating that the stress concentration inside the fault plane is reduced because of asperity damage; thus, the potential for dynamic disasters, such as fault-slip rockbursts, will be decreased.
Flux-pinning-induced interfacial shearing and transverse normal stress in a superconducting coated conductor long strip

NASA Astrophysics Data System (ADS)

Jing, Ze; Yong, Huadong; Zhou, Youhe

2012-08-01

In this paper, a theoretical model is proposed to analyze the transverse normal stress and interfacial shearing stress induced by the electromagnetic force in the superconducting coated conductor. The plane strain approach is used and a singular integral equation is derived. By assuming that the critical current density is magnetic field independent and the superconducting film is infinitely thin, the interfacial shearing stress and normal stress in the film are evaluated for the coated conductor during the increasing and decreasing in the transport current, respectively. The calculation results are discussed and compared for the conductor with different substrate and geometry. The results indicate that the coated conductor with stiffer substrate and larger width experiences larger interfacial shearing stress and less normal stress in the film.
Novel Monitoring Techniques for Characterizing Frictional Interfaces in the Laboratory

PubMed Central

Selvadurai, Paul A.; Glaser, Steven D.

2015-01-01

A pressure-sensitive film was used to characterize the asperity contacts along a polymethyl methacrylate (PMMA) interface in the laboratory. The film has structural health monitoring (SHM) applications for flanges and other precision fittings and train rail condition monitoring. To calibrate the film, simple spherical indentation tests were performed and validated against a finite element model (FEM) to compare normal stress profiles. Experimental measurements of the normal stress profiles were within −7.7% to 6.6% of the numerical calculations between 12 and 50 MPa asperity normal stress. The film also possessed the capability of quantifying surface roughness, an important parameter when examining wear and attrition in SHM applications. A high definition video camera supplied data for photometric analysis (i.e., the measure of visible light) of asperities along the PMMA-PMMA interface in a direct shear configuration, taking advantage of the transparent nature of the sample material. Normal stress over individual asperities, calculated with the pressure-sensitive film, was compared to the light intensity transmitted through the interface. We found that the luminous intensity transmitted through individual asperities linearly increased 0.05643 ± 0.0012 candelas for an increase of 1 MPa in normal stress between normal stresses ranging from 23 to 33 MPa. PMID:25923930
ATR-like kinase Mec1 facilitates both chromatin accessibility at DNA replication forks and replication fork progression during replication stress

PubMed Central

Rodriguez, Jairo; Tsukiyama, Toshio

2013-01-01

Faithful DNA replication is essential for normal cell division and differentiation. In eukaryotic cells, DNA replication takes place on chromatin. This poses the critical question as to how DNA replication can progress through chromatin, which is inhibitory to all DNA-dependent processes. Here, we developed a novel genome-wide method to measure chromatin accessibility to micrococcal nuclease (MNase) that is normalized for nucleosome density, the NCAM (normalized chromatin accessibility to MNase) assay. This method enabled us to discover that chromatin accessibility increases specifically at and ahead of DNA replication forks in normal S phase and during replication stress. We further found that Mec1, a key regulatory ATR-like kinase in the S-phase checkpoint, is required for both normal chromatin accessibility around replication forks and replication fork rate during replication stress, revealing novel functions for the kinase in replication stress response. These results suggest a possibility that Mec1 may facilitate DNA replication fork progression during replication stress by increasing chromatin accessibility around replication forks. PMID:23307868
The effect of glucose concentration and sodium phenylbutyrate treatment on mitochondrial bioenergetics and ER stress in 3T3-L1 adipocytes.

PubMed

Tanis, Ross M; Piroli, Gerardo G; Day, Stani D; Frizzell, Norma

2015-01-01

While the 3T3-L1 adipocyte model is routinely used for the study of obesity and diabetes, the mitochondrial respiratory profile in normal versus high glucose has not been examined in detail. We matured adipocytes in normal (5mM) or high (30 mM) glucose and insulin and examined the mitochondrial bioenergetics. We also assessed the requirement for the Unfolded Protein Response (UPR) and ER stress under these conditions. Basal respiration was ~1.7-fold greater in adipocytes that had matured in 30 mM glucose; however, their ability to increase oxygen consumption in response to stress was impaired. Adipogenesis proceeded in both normal and high glucose with concomitant activation of the UPR, but only high glucose was associated with increased levels of ER stress and mitochondrial stress as observed by parallel increases in CHOP and protein succination. Treatment of adipocytes with sodium phenylbutyrate relieved mitochondrial stress through a reduction in mitochondrial respiration. Our data suggests that mitochondrial stress, protein succination and ER stress are uniquely linked in adipocytes matured in high glucose. Copyright © 2014 Elsevier B.V. All rights reserved.
The Effect of Glucose Concentration and Sodium Phenylbutyrate Treatment on Mitochondrial Bioenergetics and ER Stress in 3T3-L1 Adipocytes

PubMed Central

Tanis, Ross M.; Piroli, Gerardo G.; Day, Stani D.; Frizzell, Norma

2016-01-01

While the 3T3-L1 adipocyte model is routinely used for the study of obesity and diabetes, the mitochondrial respiratory profile in normal versus high glucose has not been examined in detail. We matured adipocytes in normal (5 mM) or high (30 mM) glucose and insulin and examined the mitochondrial bioenergetics. We also assessed the requirement for the Unfolded Protein Response (UPR) and ER stress under these conditions. Basal respiration was ∼1.7-fold greater in adipocytes that had matured in 30 mM glucose; however, their ability to increase oxygen consumption in response to stress was impaired. Adipogenesis proceeded in both normal and high glucose with concomitant activation of the UPR, but only high glucose was associated with increased levels of ER stress and mitochondrial stress as observed by parallel increases in CHOP and protein succination. Treatment of adipocytes with sodium phenylbutyrate relieved mitochondrial stress through a reduction in mitochondrial respiration. Our data suggests that mitochondrial stress, protein succination and ER stress are uniquely linked in adipocytes matured in high glucose. PMID:25448036
Normal stresses in shear thickening granular suspensions.

PubMed

Pan, Zhongcheng; de Cagny, Henri; Habibi, Mehdi; Bonn, Daniel

2017-05-24

When subjected to shear, granular suspensions exhibit normal stresses perpendicular to the shear plane but the magnitude and sign of the different components of the normal stresses are still under debate. By performing both oscillatory and rotational rheology measurements on shear thickening granular suspensions and systematically varying the particle diameters and the gap sizes between two parallel-plates, we show that a transition from a positive to a negative normal stress can be observed. We find that frictional interactions which determine the shear thickening behavior of suspensions contribute to the positive normal stresses. Increasing the particle diameters or decreasing the gap sizes leads to a growing importance of hydrodynamic interactions, which results in negative normal stresses. We determine a relaxation time for the system, set by both the pore and the gap sizes, that governs the fluid flow through the inter-particle space. Finally, using a two-fluid model we determine the relative contributions from the particle phase and the liquid phase.
Curcumin induces ER stress-mediated apoptosis through selective generation of reactive oxygen species in cervical cancer cells.

PubMed

Kim, Boyun; Kim, Hee Seung; Jung, Eun-Ji; Lee, Jung Yun; K Tsang, Benjamin; Lim, Jeong Mook; Song, Yong Sang

2016-05-01

Prolonged accumulation of misfolded or unfolded proteins caused by cellular stress, including oxidative stress, induces endoplasmic reticulum stress, which then activates an unfolded protein response (UPR). ER stress is usually maintained at higher levels in cancer cells as compared to normal cells due to altered metabolism in cancer. Here, we investigated whether curcumin is ER stress-mediated apoptosis in cervical cancer cells, and ROS increased by curcumin are involved in the process as an upstream contributor. Curcumin inhibited proliferation of cervical cancer cells (C33A, CaSki, HeLa, and ME180) and induced apoptotic cell death. Curcumin activated ER-resident UPR sensors, such as PERK, IRE-1α, and ATF6, and their downstream-signaling proteins in cervical cancer cells, but not in normal epithelial cells and peripheral blood mononuclear cells (PBMCs). CHOP, a key factor involved in ER stress-mediated apoptosis, was also activated by curcumin. CHOP decreased the ratio of anti-apoptotic protein Bcl-2 to pro-apoptotic protein Bax expression, and subsequently increased the apoptotic population of cervical cancer cells. Furthermore, curcumin elevated levels of intracellular reactive oxygen species (ROS) in cervical cancer cells, but not in normal epithelial cells. Scavenging ROS resulted in inhibition of ER stress and partially restored cell viability in curcumin-treated cancer cells. Collectively, these observations show that curcumin promotes ER stress-mediated apoptosis in cervical cancer cells through increase of cell type-specific ROS generation. Therefore, modulation of these differential responses to curcumin between normal and cervical cancer cells could be an effective therapeutic strategy without adverse effects on normal cells. © 2015 Wiley Periodicals, Inc.
Viscoelastic flow past mono- and bidisperse random arrays of cylinders: flow resistance, topology and normal stress distribution.

PubMed

De, S; Kuipers, J A M; Peters, E A J F; Padding, J T

2017-12-13

We investigate creeping viscoelastic fluid flow through two-dimensional porous media consisting of random arrangements of monodisperse and bidisperse cylinders, using our finite volume-immersed boundary method introduced in S. De, et al., J. Non-Newtonian Fluid Mech., 2016, 232, 67-76. The viscoelastic fluid is modeled with a FENE-P model. The simulations show an increased flow resistance with increase in flow rate, even though the bulk response of the fluid to shear flow is shear thinning. We show that if the square root of the permeability is chosen as the characteristic length scale in the determination of the dimensionless Deborah number (De), then all flow resistance curves collapse to a single master curve, irrespective of the pore geometry. Our study reveals how viscoelastic stresses and flow topologies (rotation, shear and extension) are distributed through the porous media, and how they evolve with increasing De. We correlate the local viscoelastic first normal stress differences with the local flow topology and show that the largest normal stress differences are located in shear flow dominated regions and not in extensional flow dominated regions at higher viscoelasticity. The study shows that normal stress differences in shear flow regions may play a crucial role in the increase of flow resistance for viscoelastic flow through such porous media.

Influence of Normal and Shear Stress on the Hydraulic Transmissivity of Thin Cracks in a Tight Quartz Sandstone, a Granite, and a Shale

NASA Astrophysics Data System (ADS)

Rutter, Ernest H.; Mecklenburgh, Julian

2018-02-01

Transmissivity of fluids along fractures in rocks is reduced by increasing normal stress acting across them, demonstrated here through gas flow experiments on Bowland shale, and oil flow experiments on Pennant sandstone and Westerly granite. Additionally, the effect of imposing shear stress at constant normal stress was determined, until frictional sliding started. In all cases, increasing shear stress causes an accelerating reduction of transmissivity by 1 to 3 orders of magnitude as slip initiated, as a result of the formation of wear products that block fluid pathways. Only in the case of granite, and to a lesser extent in the sandstone, was there a minor amount of initial increase of transmissivity prior to the onset of slip. These results cast into doubt the commonly applied presumption that cracks with high resolved shear stresses are the most conductive. In the shale, crack transmissivity is commensurate with matrix permeability, such that shales are expected always to be good seals. For the sandstone and granite, unsheared crack transmissivity was respectively 2 and 2.5 orders of magnitude greater than matrix permeability. For these rocks crack transmissivity can dominate fluid flow in the upper crust, potentially enough to permit maintenance of a hydrostatic fluid pressure gradient in a normal (extensional) faulting regime.
CD4+ T cells are important mediators of oxidative stress that cause hypertension in response to placental ischemia.

PubMed

Wallace, Kedra; Cornelius, Denise C; Scott, Jeremy; Heath, Judith; Moseley, Janae; Chatman, Krystal; LaMarca, Babbette

2014-11-01

Preeclampsia is associated with oxidative stress, which is suspected to play a role in hypertension, placental ischemia, and fetal demise associated with the disease. Various cellular sources of oxidative stress, such as neutrophils, monocytes, and CD4(+) T cells have been suggested as culprits in the pathophysiology of preeclampsia. The objective of this study was to examine a role of circulating and placental CD4(+) T cells in oxidative stress in response to placental ischemia during pregnancy. CD4(+) T cells and oxidative stress were measured in preeclamptic and normal pregnant women, placental ischemic and normal pregnant rats, and normal pregnant recipient rats of placental ischemic CD4(+) T cells. Women with preeclampsia had significantly increased circulating (P=0.02) and placental CD4(+) T cells (P=0.0001); lymphocyte secretion of myeloperoxidase (P=0.004); and placental reactive oxygen species (P=0.0004) when compared with normal pregnant women. CD4(+) T cells from placental ischemic rats cause many facets of preeclampsia when injected into normal pregnant recipient rats on gestational day 13. On gestational day 19, blood pressure increased in normal pregnant recipients of placental ischemic CD4(+) T cells (P=0.002) compared with that in normal pregnant rats. Similar to preeclamptic patients, CD4(+) T cells from placental ischemic rats secreted significantly more myeloperoxidase (P=0.003) and induced oxidative stress in cultured vascular cells (P=0.003) than normal pregnant rat CD4(+)Tcells. Apocynin, a nicotinamide adenine dinucleotide phosphate inhibitor, attenuated hypertension and all oxidative stress markers in placental ischemic and normal pregnant recipient rats of placental ischemic CD4(+)Tcells (P=0.05). These data demonstrate an important role for CD4(+) T cells in mediating another factor, oxidative stress, to cause hypertension during preeclampsia. © 2014 American Heart Association, Inc.
Influence of left ventricular hypertrophy and geometry on diagnostic accuracy of wall motion and perfusion magnetic resonance during dobutamine stress.

PubMed

Gebker, Rolf; Mirelis, Jesus G; Jahnke, Cosima; Hucko, Thomas; Manka, Robert; Hamdan, Ashraf; Schnackenburg, Bernhard; Fleck, Eckart; Paetsch, Ingo

2010-09-01

The purpose of this study was to determine the influence of left ventricular (LV) hypertrophy and geometry on the diagnostic accuracy of wall motion and additional perfusion imaging during high-dose dobutamine/atropine stress magnetic resonance for the detection of coronary artery disease. Combined dobutamine stress magnetic resonance (DSMR)-wall motion and DSMR-perfusion imaging was performed in a single session in 187 patients scheduled for invasive coronary angiography. Patients were classified into 4 categories on the basis of LV mass (normal, ≤ 81 g/m(2) in men and ≤ 62 g/m(2) in women) and relative wall thickness (RWT) (normal, <0.45) as follows: normal geometry (normal mass, normal RWT), concentric remodeling (normal mass, increased RWT), concentric hypertrophy (increased mass, increased RWT), and eccentric hypertrophy (increased mass, normal RWT). Wall motion and perfusion images were interpreted sequentially, with observers blinded to other data. Significant coronary artery disease was defined as ≥ 70% stenosis. In patients with increased LV concentricity (defined by an RWT ≥ 0.45), sensitivity and accuracy of DSMR-wall motion were significantly reduced (63% and 73%, respectively; P<0.05) compared with patients without increased LV concentricity (90% and 88%, respectively; P<0.05). Although accuracy of DSMR-perfusion was higher than that of DSMR-wall motion in patients with concentric hypertrophy (82% versus 71%; P < 0.05), accuracy of DSMR-wall motion was superior to DSMR-perfusion (90% versus 85%; P < 0.05) in patients with eccentric hypertrophy. The accuracy of DSMR-wall motion is influenced by LV geometry. In patients with concentric remodeling and concentric hypertrophy, additional first-pass perfusion imaging during high-dose dobutamine stress improves the diagnostic accuracy for the detection of coronary artery disease.
Ultrasonic investigation of granular materials subjected to compression and crushing.

PubMed

Gheibi, Amin; Hedayat, Ahmadreza

2018-07-01

Ultrasonic wave propagation measurement has been used as a suitable technique for studying the granular materials and investigating the soil fabric structure, the grain contact stiffness, frictional strength, and inter-particle contact area. Previous studies have focused on the variations of shear and compressional wave velocities with effective stress and void ratio, and lesser effort has been made in understanding the variation of amplitude and dominant frequency of transmitted compressional waves with deformation of soil packing. In this study, continuous compressional wave transmission measurements during compaction of unconsolidated quartz sand are used to investigate the impact of soil layer deformation on ultrasonic wave properties. The test setup consisted of a loading machine to apply constant loading rate to a sand layer (granular quartz) of 6 mm thickness compressed between two forcing blocks, and an ultrasonic wave measurement system to continuously monitor the soil layer during compression up to 48 MPa normal stress. The variations in compressional wave attributes such as wave velocity, transmitted amplitude, and dominant frequency were studied as a function of the applied normal stress and the measured normal strain as well as void ratio and particle size. An increasing trend was observed for P-wave velocity, transmitted amplitude and dominant frequency with normal stress. In specimen with the largest particle size (D 50  = 0.32 mm), the wave velocity, amplitude and dominant frequency were found to increase about 230%, 4700% and 320% as the normal stress reached the value of 48 MPa. The absolute values of transmitted wave amplitude and dominant frequency were greater for specimens with smaller particle sizes while the normalized values indicate an opposite trend. The changes in the transmitted amplitude were linked to the changes in the true contact area between the particles with a transitional point in the slope of normalized amplitude, coinciding with the yield stress of the granular soil layer. The amount of grain crushing as a result of increase in the normal stress was experimentally measured and a linear correlation was found between the degree of grain crushing and the changes in the normalized dominant frequency of compressional waves. Copyright © 2018 Elsevier B.V. All rights reserved.
Evolution of Friction and Permeability in a Propped Fracture under Shear

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Fengshou; Fang, Yi; Elsworth, Derek

We explore the evolution of friction and permeability of a propped fracture under shear. We examine the effects of normal stress, proppant thickness, proppant size, and fracture wall texture on the frictional and transport response of proppant packs confined between planar fracture surfaces. The proppant-absent and proppant-filled fractures show different frictional strength. For fractures with proppants, the frictional response is mainly controlled by the normal stress and proppant thickness. The depth of shearing-concurrent striations on fracture surfaces suggests that the magnitude of proppant embedment is controlled by the applied normal stress. Under high normal stress, the reduced friction implies thatmore » shear slip is more likely to occur on propped fractures in deeper reservoirs. The increase in the number of proppant layers, from monolayer to triple layers, significantly increases the friction of the propped fracture due to the interlocking of the particles and jamming. Permeability of the propped fracture is mainly controlled by the magnitude of the normal stress, the proppant thickness, and the proppant grain size. Permeability of the propped fracture decreases during shearing due to proppant particle crushing and related clogging. Proppants are prone to crushing if the shear loading evolves concurrently with the normal loading.« less
Evolution of Friction and Permeability in a Propped Fracture under Shear

DOE PAGES

Zhang, Fengshou; Fang, Yi; Elsworth, Derek; ...

2017-12-04

We explore the evolution of friction and permeability of a propped fracture under shear. We examine the effects of normal stress, proppant thickness, proppant size, and fracture wall texture on the frictional and transport response of proppant packs confined between planar fracture surfaces. The proppant-absent and proppant-filled fractures show different frictional strength. For fractures with proppants, the frictional response is mainly controlled by the normal stress and proppant thickness. The depth of shearing-concurrent striations on fracture surfaces suggests that the magnitude of proppant embedment is controlled by the applied normal stress. Under high normal stress, the reduced friction implies thatmore » shear slip is more likely to occur on propped fractures in deeper reservoirs. The increase in the number of proppant layers, from monolayer to triple layers, significantly increases the friction of the propped fracture due to the interlocking of the particles and jamming. Permeability of the propped fracture is mainly controlled by the magnitude of the normal stress, the proppant thickness, and the proppant grain size. Permeability of the propped fracture decreases during shearing due to proppant particle crushing and related clogging. Proppants are prone to crushing if the shear loading evolves concurrently with the normal loading.« less
Does magmatism influence low-angle normal faulting?

USGS Publications Warehouse

Parsons, Thomas E.; Thompson, George A.

1993-01-01

Synextensional magmatism has long been recognized as a ubiquitous characteristic of highly extended terranes in the western Cordillera of the United States. Intrusive magmatism can have severe effects on the local stress field of the rocks intruded. Because a lower angle fault undergoes increased normal stress from the weight of the upper plate, it becomes more difficult for such a fault to slide. However, if the principal stress orientations are rotated away from vertical and horizontal, then a low-angle fault plane becomes more favored. We suggest that igneous midcrustal inflation occurring at rates faster than regional extension causes increased horizontal stresses in the crust that alter and rotate the principal stresses. Isostatic forces and continued magmatism can work together to create the antiformal or domed detachment surface commonly observed in the metamorphic core complexes of the western Cordillera. Thermal softening caused by magmatism may allow a more mobile mid-crustal isostatic response to normal faulting.
Magnetic field effects on shear and normal stresses in magnetorheological finishing.

PubMed

Lambropoulos, John C; Miao, Chunlin; Jacobs, Stephen D

2010-09-13

We use a recent experimental technique to measure in situ shear and normal stresses during magnetorheological finishing (MRF) of a borosilicate glass over a range of magnetic fields. At low fields shear stresses increase with magnetic field, but become field-independent at higher magnetic fields. Micromechanical models of formation of magnetic particle chains suggest a complex behavior of magnetorheological (MR) fluids that combines fluid- and solid-like responses. We discuss the hypothesis that, at higher fields, slip occurs between magnetic particle chains and the immersed glass part, while the normal stress is governed by the MRF ribbon elasticity.
Coseismic and postseismic stress changes in a subducting plate: Possible stress interactions between large interplate thrust and intraplate normal-faulting earthquakes

NASA Astrophysics Data System (ADS)

Mikumo, Takeshi; Yagi, Yuji; Singh, Shri Krishna; Santoyo, Miguel A.

2002-01-01

A large intraplate, normal-faulting earthquake (Mw = 7.5) occurred in 1999 in the subducting Cocos plate below the downdip edge of the ruptured thrust fault of the 1978 Oaxaca, Mexico, earthquake (Mw = 7.8). This situation is similar to the previous case of the 1997 normal-faulting event (Mw = 7.1) that occurred beneath the rupture area of the 1985 Michoacan, Mexico, earthquake (Mw = 8.1). We investigate the possibility of any stress interactions between the preceding 1978 thrust and the following 1999 normal-faulting earthquakes. For this purpose, we estimate the temporal change of the stress state in the subducting Cocos plate by calculating the slip distribution during the 1978 earthquake through teleseismic waveform inversion, the dynamic rupture process, and the resultant coseismic stress change, together with the postseismic stress variations due to plate convergence and the viscoelastic relaxation process. To do this, we calculate the coseismic and postseismic changes of all stress components in a three-dimensional space, incorporating the subducting slab, the overlying crust and uppermost mantle, and the asthenosphere. For the coseismic stress change we solve elastodynamic equations, incorporating the kinematic fault slip as an observational constraint under appropriate boundary conditions. To estimate postseismic stress accumulations due to plate convergence, a virtual backward slip is imposed to lock the main thrust zone. The effects of viscoelastic stress relaxations of the coseismic change and the back slip are also included. The maximum coseismic increase in the shear stress and the Coulomb failure stress below the downdip edge of the 1978 thrust fault is estimated to be in the range between 0.5 and 1.5 MPa, and the 1999 normal-faulting earthquake was found to take place in this zone of stress increase. The postseismic variations during the 21 years after the 1978 event modify the magnitude and patterns of the coseismic stress change to some extent but are not large enough to overcome the coseismic change. These results suggest that the coseismic stress increase due to the 1978 thrust earthquake may have enhanced the chance of occurrence of the 1999 normal-faulting event in the subducting plate. If this is the case, one of the possible mechanisms could be static fatigue of rock materials around preexisting weak planes involved in the subducting plate, and it is speculated that that one of these planes might have been reactivated and fractured because of stress corrosion cracking under the applied stress there for 21 years.
Insulin resistance is associated with diminished endoplasmic reticulum stress responses in adipose tissue of healthy and diabetic subjects.

PubMed

Boden, Guenther; Cheung, Peter; Kresge, Karen; Homko, Carol; Powers, Ben; Ferrer, Lucas

2014-09-01

We recently showed that insulin increased ER stress in human adipose tissue. The effect of insulin resistance on ER stress is not known. It could be decreased, unchanged, or increased, depending on whether insulin regulates ER stress via the metabolic/phosphoinositide 3-kinase (PI3K) or alternate signaling pathways. To address this question, we examined effects of lipid-induced insulin resistance on insulin stimulation of ER stress. mRNAs of several ER stress markers were determined in fat biopsies obtained before and after 8-h hyperglycemic-hyperinsulinemic clamping in 13 normal subjects and in 6 chronically insulin-resistant patients with type 2 diabetes mellitus (T2DM). In normal subjects, hyperglycemia-hyperinsulinemia increased after/before mRNA ratios of several ER stress markers (determined by ER stress pathway array and by individual RT-PCR). Lipid infusion was associated with inhibition of the PI3K insulin-signaling pathway and with a decrease of hyperinsulinemia-induced ER stress responses. In chronically insulin-resistant patients with T2DM, hyperglycemic-hyperinsulinemia did not increase ER stress response marker mRNAs. In summary, insulin resistance, either produced by lipid infusions in normal subjects or chronically present in T2DM patients, was associated with decreased hyperinsulinemia-induced ER stress responses. This suggests, but does not prove, that these two phenomena were causally related. © 2014 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.
Finite Element Study of a Lumbar Intervertebral Disc Nucleus Replacement Device.

PubMed

Coogan, Jessica S; Francis, W Loren; Eliason, Travis D; Bredbenner, Todd L; Stemper, Brian D; Yoganandan, Narayan; Pintar, Frank A; Nicolella, Daniel P

2016-01-01

Nucleus replacement technologies are a minimally invasive alternative to spinal fusion and total disc replacement that have the potential to reduce pain and restore motion for patients with degenerative disc disease. Finite element modeling can be used to determine the biomechanics associated with nucleus replacement technologies. The current study focuses on a new nucleus replacement device designed as a conforming silicone implant with an internal void. A validated finite element model of the human lumbar L3-L4 motion segment was developed and used to investigate the influence of the nucleus replacement device on spine biomechanics. In addition, the effect of device design changes on biomechanics was determined. A 3D, L3-L4 finite element model was constructed from medical imaging data. Models were created with the normal intact nucleus, the nucleus replacement device, and a solid silicone implant. Probabilistic analysis was performed on the normal model to provide quantitative validation metrics. Sensitivity analysis was performed on the silicone Shore A durometer of the device. Models were loaded under axial compression followed by flexion/extension, lateral bending, or axial rotation. Compressive displacement, endplate stresses, reaction moment, and annulus stresses were determined and compared between the different models. The novel nucleus replacement device resulted in similar compressive displacement, endplate stress, and annulus stress and slightly higher reaction moment compared with the normal nucleus. The solid implant resulted in decreased displacement, increased endplate stress, decreased annulus stress, and decreased reaction moment compared with the novel device. With increasing silicone durometer, compressive displacement decreased, endplate stress increased, reaction moment increased, and annulus stress decreased. Finite element analysis was used to show that the novel nucleus replacement device results in similar biomechanics compared with the normal intact nucleus.
Finite Element Study of a Lumbar Intervertebral Disc Nucleus Replacement Device

PubMed Central

Coogan, Jessica S.; Francis, W. Loren; Eliason, Travis D.; Bredbenner, Todd L.; Stemper, Brian D.; Yoganandan, Narayan; Pintar, Frank A.; Nicolella, Daniel P.

2016-01-01

Nucleus replacement technologies are a minimally invasive alternative to spinal fusion and total disc replacement that have the potential to reduce pain and restore motion for patients with degenerative disc disease. Finite element modeling can be used to determine the biomechanics associated with nucleus replacement technologies. The current study focuses on a new nucleus replacement device designed as a conforming silicone implant with an internal void. A validated finite element model of the human lumbar L3–L4 motion segment was developed and used to investigate the influence of the nucleus replacement device on spine biomechanics. In addition, the effect of device design changes on biomechanics was determined. A 3D, L3–L4 finite element model was constructed from medical imaging data. Models were created with the normal intact nucleus, the nucleus replacement device, and a solid silicone implant. Probabilistic analysis was performed on the normal model to provide quantitative validation metrics. Sensitivity analysis was performed on the silicone Shore A durometer of the device. Models were loaded under axial compression followed by flexion/extension, lateral bending, or axial rotation. Compressive displacement, endplate stresses, reaction moment, and annulus stresses were determined and compared between the different models. The novel nucleus replacement device resulted in similar compressive displacement, endplate stress, and annulus stress and slightly higher reaction moment compared with the normal nucleus. The solid implant resulted in decreased displacement, increased endplate stress, decreased annulus stress, and decreased reaction moment compared with the novel device. With increasing silicone durometer, compressive displacement decreased, endplate stress increased, reaction moment increased, and annulus stress decreased. Finite element analysis was used to show that the novel nucleus replacement device results in similar biomechanics compared with the normal intact nucleus. PMID:27990418
Negative Social Evaluation Impairs Executive Functions in Adolescents With Excess Weight: Associations With Autonomic Responses.

PubMed

Padilla, María Moreno; Fernández-Serrano, María J; Verdejo García, Antonio; Reyes Del Paso, Gustavo A

2018-06-22

Adolescents with excess weight suffer social stress more frequently than their peers with normal weight. To examine the impact of social stress, specifically negative social evaluation, on executive functions in adolescents with excess weight. We also examined associations between subjective stress, autonomic reactivity, and executive functioning. Sixty adolescents (aged 13-18 years) classified into excess weight or normal weight groups participated. We assessed executive functioning (working memory, inhibition, and shifting) and subjective stress levels before and after the Trier Social Stress Task (TSST). The TSST was divided into two phases according to the feedback of the audience: positive and negative social evaluation. Heart rate and skin conductance were recorded. Adolescents with excess weight showed poorer executive functioning after exposure to TSST compared with adolescents with normal weight. Subjective stress and autonomic reactivity were also greater in adolescents with excess weight than adolescents with normal weight. Negative social evaluation was associated with worse executive functioning and increased autonomic reactivity in adolescents with excess weight. The findings suggest that adolescents with excess weight are more sensitive to social stress triggered by negative evaluations. Social stress elicited deterioration of executive functioning in adolescents with excess weight. Evoked increases in subjective stress and autonomic responses predicted decreased executive function. Deficits in executive skills could reduce cognitive control abilities and lead to overeating in adolescents with excess weight. Strategies to cope with social stress to prevent executive deficits could be useful to prevent future obesity in this population.
Potassium up-regulates antioxidant metabolism and alleviates growth inhibition under water and osmotic stress in wheat (Triticum aestivum L).

PubMed

Ahanger, Mohammad Abass; Agarwal, R M

2017-07-01

Pot experiments were conducted to find out the effectivity of K on Triticum aestivum L cultivars. Polyethylene glycol 6000 (PEG 6000) was used as an osmoticum to induce osmotic stress under sand culture setting up the water potential of external solution at -3 and -5 bars. In pots, plants were raised under restricted and normal irrigation and K was applied in varying doses (0, 20, 40, 60 kg ha -1 ) and estimation of different physiological and biochemical parameters was done at two developmental stages, i.e., preflowering and flowering. Supplementation of K resulted in obvious increase in growth and activity of antioxidant enzymes in both normal and stressed plants. Added potassium increased total phenols and tannins thereby strengthening the components of both the enzymatic as well as non-enzymatic antioxidant system. Under both normal and stressed conditions, K-fed plants experienced significant increase in the synthesis of osmolytes like free proline, amino acids, and sugars which assumes special significance in growth under water stress conditions. Wheat plants accumulating greater K were able to counteract the water stress-induced changes by maintaining lower Na/K ratio.
A Digital Image-Based Discrete Fracture Network Model and Its Numerical Investigation of Direct Shear Tests

NASA Astrophysics Data System (ADS)

Wang, Peitao; Cai, Meifeng; Ren, Fenhua; Li, Changhong; Yang, Tianhong

2017-07-01

This paper develops a numerical approach to determine the mechanical behavior of discrete fractures network (DFN) models based on digital image processing technique and particle flow code (PFC2D). A series of direct shear tests of jointed rocks were numerically performed to study the effect of normal stress, friction coefficient and joint bond strength on the mechanical behavior of joint rock and evaluate the influence of micro-parameters on the shear properties of jointed rocks using the proposed approach. The complete shear stress-displacement curve of the DFN model under direct shear tests was presented to evaluate the failure processes of jointed rock. The results show that the peak and residual strength are sensitive to normal stress. A higher normal stress has a greater effect on the initiation and propagation of cracks. Additionally, an increase in the bond strength ratio results in an increase in the number of both shear and normal cracks. The friction coefficient was also found to have a significant influence on the shear strength and shear cracks. Increasing in the friction coefficient resulted in the decreasing in the initiation of normal cracks. The unique contribution of this paper is the proposed modeling technique to simulate the mechanical behavior of jointed rock mass based on particle mechanics approaches.
Increased plasma peroxides as a marker of oxidative stress in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS).

PubMed

Maes, Michael; Kubera, Marta; Uytterhoeven, Marc; Vrydags, Nicolas; Bosmans, Eugene

2011-04-01

There is evidence that myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is characterized by activation of immune, inflammatory, oxidative and nitrosative stress (IO&NS) pathways. The present study was carried out in order to examine whether ME/CFS is accompanied by increased levels of plasma peroxides and serum oxidized LDL (oxLDL) antibodies, two biomarkers of oxidative stress. Blood was collected from 56 patients with ME/CFS and 37 normal volunteers. Severity of ME/CFS was measured using the Fibromyalgia and Chronic Fatigue Syndrome (FF) Rating Scale. Plasma peroxide concentrations were significantly higher in patients with ME/CFS than in normal controls. There was a trend towards significantly higher serum oxLDL antibodies in ME/CFS than in controls. Both biomarkers contributed significantly in discriminating between patients with ME/CFS and normal controls. Plasma peroxide and serum oxLDL antibody levels were both significantly related to one of the FF symptoms. The results show that ME/CFS is characterized by increased oxidative stress.
Low-level laser therapy (LLLT) reduces oxidative stress in primary cortical neurons in vitro.

PubMed

Huang, Ying-Ying; Nagata, Kazuya; Tedford, Clark E; McCarthy, Thomas; Hamblin, Michael R

2013-10-01

Low-level laser (light) therapy (LLLT) involves absorption of photons being in the mitochondria of cells leading to improvement in electron transport, increased mitochondrial membrane potential (MMP), and greater ATP production. Low levels of reactive oxygen species (ROS) are produced by LLLT in normal cells that are beneficial. We exposed primary cultured murine cortical neurons to oxidative stressors: hydrogen peroxide, cobalt chloride and rotenone in the presence or absence of LLLT (3 J/cm², CW, 810 nm wavelength laser, 20 mW/cm²). Cell viability was determined by Prestoblue™ assay. ROS in mitochondria was detected using Mito-sox, while ROS in cytoplasm was detected with CellRox™. MMP was measured with tetramethylrhodamine. In normal neurons LLLT elevated MMP and increased ROS. In oxidatively-stressed cells LLLT increased MMP but reduced high ROS levels and protected cultured cortical neurons from death. Although LLLT increases ROS in normal neurons, it reduces ROS in oxidatively-stressed neurons. In both cases MMP is increased. These data may explain how LLLT can reduce clinical oxidative stress in various lesions while increasing ROS in cells in vitro. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Predicted lattice-misfit stresses in a gallium-nitride (GaN) film

NASA Astrophysics Data System (ADS)

Suhir, E.; Yi, S.

2017-02-01

Effective, easy-to-use and physically meaningful analytical predictive models are developed for the evaluation the lattice-misfit stresses (LMS) in a semiconductor film grown on a circular substrate (wafer). The two-dimensional (plane-stress) theory-of-elasticity approximation (TEA) is employed. First of all, the interfacial shearing stresses are evaluated. These stresses might lead to the occurrence and growth of dislocations, as well as to possible delaminations (adhesive strength of the assembly) and the elevated stress and strain in the buffering material, if any (cohesive strength of the assembly). Second of all, the normal radial and circumferential (tangential) stresses acting in the film cross-sections are determined. These stresses determine the short- and long-term strength (fracture toughness) of the film material. It is shown that while the normal stresses in the semiconductor film are independent of its thickness, the interfacial shearing stresses increase with an increase in the induced force (not stress!) acting in the film cross-sections, and that this force increases with an increase in the film thickness. This leads, for a thick enough film, to the occurrence, growth and propagation of dislocations. These start at the assembly ends and propagate, when the film thickness increases, inwards the structure. The TEA data are compared with the results obtained using a simplified strength-of-materials approach (SMA). This approach considers, instead of an actual circular assembly, an elongated bi-material rectangular strip of unit width and of finite length equal to the wafer diameter. The analysis, although applicable to any semiconductor crystal growth (SCG) technology is geared in this analysis to the Gallium-Nitride (GaN) technology. The numerical example is carried out for a GaN film grown on a Silicon Carbide (SiC) substrate. It is concluded that the SMA model is acceptable for understanding the physics of the state of stress and for the prediction of the normal stresses acting in the major mid-portion of the assembly. The SMA model underestimates, however, the maximum interfacial shearing stress at the assembly periphery, and, because of the very nature of the SMA, is unable to address the circumferential stress. This stress can be quite high at the circular boundary of the assembly. At the assembly edge the circumferential stress is as high as σθ = (2-ν1)σ1, i.e., by the factor of 2-ν1 higher than the normal stress, σ1, in the mid-portion of the film. In this formula, ν1 is Poisson's ratio of the film material.
Effects of inertia on the steady shear rheology of concentrated emulsions: sign reversal of normal stress differences

NASA Astrophysics Data System (ADS)

Srivastava, Priyesh; Sarkar, Kausik

2012-11-01

The shear rheology of moderately concentrated emulsions (5-27% volume fraction) in the presence of inertia is numerically investigated. Typically, an emulsion of viscous drops experiences positive first normal stress difference (N1) and negative second normal stress difference (N2) , as has also been predicted by perturbative analysis (Choi-Schowalter model) and numerical simulation. However, recently using single drop results we have shown [Li and Sarkar, 2005, J. Rheo, 49, 1377] that introduction of inertia reverses the signs of the normal stress difference in the dilute limit. Here, we numerically investigate the effects of interactions between drops in a concentrated system. The simulation is validated against the dilute results as well as analytical relations. It also shows the reversal of signs for N1 and N2 for small Capillary numbers above a critical Reynolds number. The physics is explained by the inertia-induced orientation of the individual drops in shear. Increasing volume fraction increases the critical Reynolds number at which N1 and N2change sign. The breakdown of linearity with volume fraction with increasing concentration is also analyzed. Partially supported by NSF.
Cortisol as a Biomarker of Stress in Term Human Labor: Physiological and Methodological Issues

PubMed Central

Newton, Edward R.; Tanner, Charles J.; Heitkemper, Margaret M.

2013-01-01

Literature on the use of plasma cortisol to quantify psychophysiological stress in humans is extensive. However, in parturition at term gestation the use of cortisol as a biomarker of stress is particularly complex. Plasma cortisol levels increase as labor progresses. This increase seems to be important for maintenance of maternal/fetal wellbeing and facilitation of normal labor progress. Unique physiological and methodological issues involved in the use of cortisol as a biomarker of stress in labor present challenges for researchers. This review examines these issues, suggests mixed methods and within-subject repeated measures designs, and offers recommendations for assay procedures for parturient sampling. Documentation of clinical interventions and delivery outcomes may elucidate relationships among psychophysiological stressors, cortisol and normal labor progress. With attention to these methodological issues, analysis of plasma cortisol may lead to clinical interventions that support normal labor physiology. PMID:23338011

Dietary sodium influences the effect of mental stress on heart rate variability: a randomized trial in healthy adults.

PubMed

Allen, Alexander R; Gullixson, Leah R; Wolhart, Sarah C; Kost, Susan L; Schroeder, Darrell R; Eisenach, John H

2014-02-01

Dietary sodium influences intermediate physiological traits in healthy adults independent of changes in blood pressure. The purpose of this study was to test the hypothesis that dietary sodium affects cardiac autonomic modulation during mental stress. In a prospective, randomized cross-over design separated by 1 month between diets, 70 normotensive healthy young adults (F/M: 44/26, aged 18-38 years) consumed a 5-day low (10 mmol/day), normal (150 mmol), and high (400 mmol) sodium diet followed by heart rate variability (HRV) recordings at rest and during 5-min computerized mental arithmetic. Women were studied in the low hormone phase of the menstrual cycle following each diet. Diet did not affect resting blood pressure, but heart rate (HR) (mean ± SE) was 66 ± 1, 64 ± 1, and 63 ± 1 bpm in low, normal, and high sodium conditions, respectively (analysis of variance P = 0.02). For HRV, there was a main effect of sodium on resting SD of normalized RR intervals (SDNN), square root of the mean squared difference of successive normalized RR intervals (RMSSD), high frequency, low-frequency normalized units (LFnu), and high-frequency normalized units (HFnu) (P < 0.01 for all). The response to low sodium was most marked and consistent with sympathetic activation and reduced vagal activity, with increased LFnu and decreased SDNN, RMSSD, and HFnu compared to both normal and high sodium conditions (P ≤0.05 for all). Dietary sodium-by-mental stress interactions were significant for mean NN, RMSSD, high-frequency power, LFnu, and low frequency/high frequency ratio (P < 0.05 for all). The interactions signify that sodium restriction evoked an increase in resting sympathetic activity and reduced vagal activity to the extent that mental stress caused modest additional disruptions in autonomic balance. Conversely, normal and high sodium evoked a reduction in resting sympathetic activity and incremental increase in resting vagal activity, which were disrupted to a greater extent during mental stress compared to low sodium. We conclude that autonomic control of HRV at rest and during mental stress is altered by dietary sodium in healthy normotensive young adult men and women.
An experimental study of the influence of stress history on fault slip during injection of supercritical CO2

NASA Astrophysics Data System (ADS)

Cuss, Robert J.; Wiseall, Andrew C.; Tamayo-Mas, Elena; Harrington, Jon F.

2018-04-01

The injection of super-critical CO2 into a depleted reservoir will alter the pore pressure of the basin, which if sufficiently perturbed could result in fault slip. Therefore, knowledge of the acceptable pressure limits is required in order to maintain fault stability. A two-part laboratory study was conducted on fully saturated kaolinite fault gouge to investigate this issue. Previously, we showed that fault slip occurred once pore-pressure within the gouge was sufficient to overcome the normal stress acting on the fault. For kaolinite, this behaviour occurred at a pressure similar to the yield stress. The current study shows that following a slow-reduction in the maximum principal stress, as would be expected through changes in effective stress, the reactivation pressure shows a stress memory. Consequently, the pressure necessary to initiate fault slip is similar to that required at the maximum stress encountered. Therefore, fault slip is at least partially controlled by the previous maximum stress and not the current stress state. During the slow reduction in normal stress, the flow characteristics of the fault remain unchanged until pore-pressure exceeds shear stress and does not increase significantly until it exceeds normal stress. This results in fault slip, which slows the rate of flow increase as shear is an effective self-sealing mechanism. These observations lead to the conclusion that stress history is a vital parameter when considering fault stability.
Stress inhibits PYY secretion in obese and normal weight women.

PubMed

Kiessl, Gundula R R; Laessle, Reinhold G

2016-06-01

The impact of stress on circulating levels of appetite-regulating hormones remains largely unknown. The aim of this study was to analyze the effect of acute psychosocial stress on the gut hormone peptide YY (PYY) secretion in obese and normal weight women. Therefore, we compared pre- and post-prandial plasma PYY secretion of 42 obese and 43 normal weight women in a repeated measure randomized controlled laboratory experiment. PYY and cortisol concentrations were measured and ratings of stress and satiety were also recorded in response to a psychological stressor (Trier Social Stress Test, TSST). PYY samples were collected in the fasting state both before participating in the TSST and before a control session. Participants had a standardized meal after the TSST and control session, respectively. PYY was measured both 30 and 60 min after the TSST and control session, respectively. Stress inhibited PYY secretion as well as food intake in all women, but did not influence subjective satiety perception. The present data indicate that despite of lower PYY levels the subjects' requirement to overeat was not increased. From an evolutionary perspective this finding is adaptive. After stress the organism is prepared for fight or flight reaction, whereas not primarily necessary functions are inhibited. Therefore, increased food intake during stress would be dysfunctional.
On factors controlling precursor slip fronts in the laboratory and their relation to slow slip events in nature

NASA Astrophysics Data System (ADS)

Selvadurai, Paul A.; Glaser, Steven D.; Parker, Jessica M.

2017-03-01

Spatial variations in frictional properties on natural faults are believed to be a factor influencing the presence of slow slip events (SSEs). This effect was tested on a laboratory frictional interface between two polymethyl methacrylate (PMMA) bodies. We studied the evolution of slip and slip rates that varied systematically based on the application of both high and low normal stress (σ0=0.8 or 0.4 MPa) and the far-field loading rate (VLP). A spontaneous, frictional rupture expanded from the central, weaker, and more compliant section of the fault that had fewer asperities. Slow rupture propagated at speeds Vslow˜0.8 to 26 mm s-1 with slip rates from 0.01 to 0.2 μm s-1, resulting in stress drops around 100 kPa. During certain nucleation sequences, the fault experienced a partial stress drop, referred to as precursor detachment fronts in tribology. Only at the higher level of normal stress did these fronts exist, and the slip and slip rates mimicked the moment and moment release rates during the 2013-2014 Boso SSE in Japan. The laboratory detachment fronts showed rupture propagation speeds Vslow/VR∈ (5 to 172) × 10-7 and stress drops ˜ 100 kPa, which both scaled to the aforementioned SSE. Distributions of asperities, measured using a pressure sensitive film, increased in complexity with additional normal stress—an increase in normal stress caused added complexity by increasing both the mean size and standard deviation of asperity distributions, and this appeared to control the presence of the detachment front.
The Role of Oxidative Stress in Nervous System Aging

PubMed Central

Sims-Robinson, Catrina; Hur, Junguk; Hayes, John M.; Dauch, Jacqueline R.; Keller, Peter J.; Brooks, Susan V.; Feldman, Eva L.

2013-01-01

While oxidative stress is implicated in aging, the impact of oxidative stress on aging in the peripheral nervous system is not well understood. To determine a potential mechanism for age-related deficits in the peripheral nervous system, we examined both functional and morphological changes and utilized microarray technology to compare normal aging in wild-type mice to effects in copper/zinc superoxide dismutase-deficient (Sod1−/−) mice, a mouse model of increased oxidative stress. Sod1−/− mice exhibit a peripheral neuropathy phenotype with normal sensory nerve function and deficits in motor nerve function. Our data indicate that a decrease in the synthesis of cholesterol, which is vital to myelin formation, correlates with the structural deficits in axons, myelin, and the cell body of motor neurons in the Sod1+/+ mice at 30 months and the Sod1−/− mice at 20 months compared with mice at 2 months. Collectively, we have demonstrated that the functional and morphological changes within the peripheral nervous system in our model of increased oxidative stress are manifested earlier and resemble the deficits observed during normal aging. PMID:23844146
The role of oxidative stress in nervous system aging.

PubMed

Sims-Robinson, Catrina; Hur, Junguk; Hayes, John M; Dauch, Jacqueline R; Keller, Peter J; Brooks, Susan V; Feldman, Eva L

2013-01-01

While oxidative stress is implicated in aging, the impact of oxidative stress on aging in the peripheral nervous system is not well understood. To determine a potential mechanism for age-related deficits in the peripheral nervous system, we examined both functional and morphological changes and utilized microarray technology to compare normal aging in wild-type mice to effects in copper/zinc superoxide dismutase-deficient (Sod1(-/-)) mice, a mouse model of increased oxidative stress. Sod1(-/-) mice exhibit a peripheral neuropathy phenotype with normal sensory nerve function and deficits in motor nerve function. Our data indicate that a decrease in the synthesis of cholesterol, which is vital to myelin formation, correlates with the structural deficits in axons, myelin, and the cell body of motor neurons in the Sod1(+/+) mice at 30 months and the Sod1(-/-) mice at 20 months compared with mice at 2 months. Collectively, we have demonstrated that the functional and morphological changes within the peripheral nervous system in our model of increased oxidative stress are manifested earlier and resemble the deficits observed during normal aging.
The onset of stress response in rainbow trout Oncorhynchus mykiss embryos subjected to density and handling.

PubMed

Ghaedi, Gholamreza; Falahatkar, Bahram; Yavari, Vahid; Sheibani, Mohammad T; Broujeni, Gholamreza Nikbakht

2015-04-01

The present study made an attempt to measure the cortisol content, as an indicator of stress response, in rainbow trout embryos which were exposed to different densities and handling stress (air exposure) during incubation. The three densities of experimental embryos at early development stages were considered as 2.55 embryos/cm(2) (low density), 5.10 embryos/cm(2) (normal density) and 7.65 embryos/cm(2) (high density). The cortisol content of eggs (5.09 ± 0.12 ng/g) decreased to 3.68 ± 0.14 ng/g in newly fertilized eggs. Resting level of cortisol dropped at three densities by day 18 of post fertilization. Then, cortisol increased at hatching stage to 1.16 ± 0.11, 1.20 ± 0.12 and 1.21 ± 0.14 ng/g at low, normal and high densities, respectively. There were no statistically significant differences between cortisol concentrations in three densities. The acute handling stress test (5-min out-of-water), conducted on embryos (48 h post fertilization, organogenesis and eyed stage) in three densities, revealed no differences in whole-body cortisol levels between stressed and unstressed experimental groups. At hatching stage in low-density group, level of cortisol increased but the difference with the pre-stress levels was not statistically significant. Furthermore, significant differences in cortisol levels of stressed and unstressed embryos were detected on hatching in normal and high density groups [1.20 ± 0.12 at time 0-1.49 ± 0.11 ng/g at 1 hps (hours post stress) and from 1.21 ± 0.14 at time 0 to 1.53 ± 0.10 ng/g at 3 hps, respectively]. The results showed no difference in profile of cortisol in different densities, but acute stress conducted on embryos, incubated in different densities, revealed differences in cortisol stress response at hatching between normal and high density, which lead to cortisol increase at hatching time. It indicates that the lag time in the cortisol response to stressors immediately after hatching does not occur when the siblings were stressed during the embryo stage. Results, finally, indicated that hypothalamus-pituitary-interrenal axis was active and responded to an acute stressor under normal and high density, but it is unresponsive to a stressor around hatching under low density.
Imaging surface contacts: Power law contact distributions and contact stresses in quartz, calcite, glass and acrylic plastic

USGS Publications Warehouse

Dieterich, J.H.; Kilgore, B.D.

1996-01-01

A procedure has been developed to obtain microscope images of regions of contact between roughened surfaces of transparent materials, while the surfaces are subjected to static loads or undergoing frictional slip. Static loading experiments with quartz, calcite, soda-lime glass and acrylic plastic at normal stresses to 30 MPa yield power law distributions of contact areas from the smallest contacts that can be resolved (3.5 ??m2) up to a limiting size that correlates with the grain size of the abrasive grit used to roughen the surfaces. In each material, increasing normal stress results in a roughly linear increase of the real area of contact. Mechanisms of contact area increase are by growth of existing contacts, coalescence of contacts and appearance of new contacts. Mean contacts stresses are consistent with the indentation strength of each material. Contact size distributions are insensitive to normal stress indicating that the increase of contact area is approximately self-similar. The contact images and contact distributions are modeled using simulations of surfaces with random fractal topographies. The contact process for model fractal surfaces is represented by the simple expedient of removing material at regions where surface irregularities overlap. Synthetic contact images created by this approach reproduce observed characteristics of the contacts and demonstrate that the exponent in the power law distributions depends on the scaling exponent used to generate the surface topography.
Rheological State Diagrams for Rough Colloids in Shear Flow.

PubMed

Hsiao, Lilian C; Jamali, Safa; Glynos, Emmanouil; Green, Peter F; Larson, Ronald G; Solomon, Michael J

2017-10-13

To assess the role of particle roughness in the rheological phenomena of concentrated colloidal suspensions, we develop model colloids with varying surface roughness length scales up to 10% of the particle radius. Increasing surface roughness shifts the onset of both shear thickening and dilatancy towards lower volume fractions and critical stresses. Experimental data are supported by computer simulations of spherical colloids with adjustable friction coefficients, demonstrating that a reduction in the onset stress of thickening and a sign change in the first normal stresses occur when friction competes with lubrication. In the quasi-Newtonian flow regime, roughness increases the effective packing fraction of colloids. As the shear stress increases and suspensions of rough colloids approach jamming, the first normal stresses switch signs and the critical force required to generate contacts is drastically reduced. This is likely a signature of the lubrication films giving way to roughness-induced tangential interactions that bring about load-bearing contacts in the compression axis of flow.
Rheological State Diagrams for Rough Colloids in Shear Flow

NASA Astrophysics Data System (ADS)

Hsiao, Lilian C.; Jamali, Safa; Glynos, Emmanouil; Green, Peter F.; Larson, Ronald G.; Solomon, Michael J.

2017-10-01

To assess the role of particle roughness in the rheological phenomena of concentrated colloidal suspensions, we develop model colloids with varying surface roughness length scales up to 10% of the particle radius. Increasing surface roughness shifts the onset of both shear thickening and dilatancy towards lower volume fractions and critical stresses. Experimental data are supported by computer simulations of spherical colloids with adjustable friction coefficients, demonstrating that a reduction in the onset stress of thickening and a sign change in the first normal stresses occur when friction competes with lubrication. In the quasi-Newtonian flow regime, roughness increases the effective packing fraction of colloids. As the shear stress increases and suspensions of rough colloids approach jamming, the first normal stresses switch signs and the critical force required to generate contacts is drastically reduced. This is likely a signature of the lubrication films giving way to roughness-induced tangential interactions that bring about load-bearing contacts in the compression axis of flow.
Differential effects of cyclic and constant stress on ATP release and mucociliary transport by human airway epithelia

PubMed Central

Button, Brian; Picher, Maryse; Boucher, Richard C

2007-01-01

In the lungs, the first line of defence against bacterial infection is the thin layer of airway surface liquid (ASL) lining the airway surface. The superficial airway epithelium exhibits complex regulatory pathways that blend ion transport to adjust ASL volume to maintain proper mucociliary clearance (MCC). We hypothesized that stresses generated by airflow and transmural pressures during breathing govern ASL volume by regulating the rate of epithelial ATP release. Luminal ATP, via interactions with apical membrane P2-purinoceptors, regulates the balance of active ion secretion versus absorption to maintain ASL volume at optimal levels for MCC. In this study we tested the hypothesis that cyclic compressive stress (CCS), mimicking normal tidal breathing, regulates ASL volume in airway epithelia. Polarized tracheobronchial epithelial cultures from normal and cystic fibrosis (CF) subjects responded to a range of CCS by increasing the rate of ATP release. In normal airway epithelia, the CCS-induced increase in ASL ATP concentration was sufficient to induce purinoceptor-mediated increases in ASL height and MCC, via inhibition of epithelial Na+-channel-mediated Na+ absorption and stimulation of Cl− secretion through CFTR and the Ca2+-activated chloride channels. In contrast, static, non-oscillatory stress did not stimulate ATP release, ion transport or MCC, emphasizing the importance of rhythmic mechanical stress for airway defence. In CF airway cultures, which exhibit basal ASL depletion, CCS was partially effective, producing less ASL volume secretion than in normal cultures, but a level sufficient to restore MCC. The present data suggest that CCS may (1) regulate ASL volume in the normal lung and (2) improve clearance in the lungs of CF patients, potentially explaining the beneficial role of exercise in lung defence. PMID:17317749
Influence of omega-6/omega-3 rich dietary oils on lipid profile and antioxidant enzymes in normal and stressed rats.

PubMed

Benson, M K; Devi, Kshama

2009-02-01

To evaluate the influence of omega-6/omega-3 poly unsaturated fatty acid (PUFA) containing oils on lipid profile and endogenous antioxidant enzymes in normal and stressed (immobilization) rats, 28 day old male Wistar rats were fed for 45 days with fat enriched special diet (10% fat) prepared with sunflower oil (SO)--omega-6 rich, mustard oil (MO)--omega-3 rich and groundnut oil--control respectively. SO treated normal rats have significantly reduced total cholesterol, high density lipoprotein-cholesterol (HDL-C) and catalase thereby significantly increased the atherogenic index (AI) and lipid peroxidation (LPO). However, treatment with MO increased superoxide dismutase; decreased LPO significantly. Under stress conditions AI and LPO were significantly high with SO and significantly less with MO. In addition, SO decreased HDL-C whereas MO decreased non-HDL-C significantly. Results suggest a protective role against AI and LPO in normal and stress conditions in MO. The quantity of omega-3 fatty acids in dietary oil may play a crucial role in the body against atherogenicity. The findings signify that not just PUFA, but type of PUFA present in dietary oil used is important.
Poromechanics of stick-slip frictional sliding and strength recovery on tectonic faults

DOE PAGES

Scuderi, Marco M.; Carpenter, Brett M.; Johnson, Paul A.; ...

2015-10-22

Pore fluids influence many aspects of tectonic faulting including frictional strength aseismic creep and effective stress during the seismic cycle. But, the role of pore fluid pressure during earthquake nucleation and dynamic rupture remains poorly understood. Here we report on the evolution of pore fluid pressure and porosity during laboratory stick-slip events as an analog for the seismic cycle. We sheared layers of simulated fault gouge consisting of glass beads in a double-direct shear configuration under true triaxial stresses using drained and undrained fluid conditions and effective normal stress of 5–10 MPa. Shear stress was applied via a constant displacementmore » rate, which we varied in velocity step tests from 0.1 to 30 µm/s. Here, we observe net pore pressure increases, or compaction, during dynamic failure and pore pressure decreases, or dilation, during the interseismic period, depending on fluid boundary conditions. In some cases, a brief period of dilation is attendant with the onset of dynamic stick slip. Our data show that time-dependent strengthening and dynamic stress drop increase with effective normal stress and vary with fluid conditions. For undrained conditions, dilation and preseismic slip are directly related to pore fluid depressurization; they increase with effective normal stress and recurrence time. Microstructural observations confirm the role of water-activated contact growth and shear-driven elastoplastic processes at grain junctions. These results indicate that physicochemical processes acting at grain junctions together with fluid pressure changes dictate stick-slip stress drop and interseismic creep rates and thus play a key role in earthquake nucleation and rupture propagation.« less
Room temperature shear properties of the strain isolator pad for the shuttle thermal protection system

NASA Technical Reports Server (NTRS)

Sawyer, J. W.; Waters, W. A., Jr.

1981-01-01

Tests were conducted at room temperature to determine the shear properties of the strain isolator pad (SIP) material used in the thermal protection system of the space shuttle. Tests were conducted on both the .23 cm and .41 cm thick SIP material in the virgin state and after fifty fully reversed shear cycles. The shear stress displacement relationships are highly nonlinear, exhibit large hysteresis effects, are dependent on material orientation, and have a large low modulus region near the zero stress level where small changes in stress can result in large displacements. The values at the higher stress levels generally increase with normal and shear force load conditioning. Normal forces applied during the shear tests reduces the low modulus region for the material. Shear test techniques which restrict the normal movement of the material give erroneous stress displacement results. However, small normal forces do not significantly effect the shear modulus for a given shear stress. Poisson's ratio values for the material are within the range of values for many common materials. The values are not constant but vary as a function of the stress level and the previous stress history of the material. Ultimate shear strengths of the .23 cm thick SIP are significantly higher than those obtained for the .41 cm thick SIP.
Increase of Chamazulene and α-Bisabolol Contents of the Essential Oil of German Chamomile (Matricaria chamomilla L.) Using Salicylic Acid Treatments under Normal and Heat Stress Conditions.

PubMed

Ghasemi, Mojtaba; Babaeian Jelodar, Nadali; Modarresi, Mohammad; Bagheri, Nadali; Jamali, Abbas

2016-08-27

The chamazulene and α-(-)-bisabolol contents and quality of the chamomile oil are affected by genetic background and environmental conditions. Salicylic acid (SA), as a signaling molecule, plays a significant role in the plant physiological processes. The aim of this study was to evaluate the chemical profile, quantity, and improve the essential oil quality as a consequence of the increase of chamazulene and α-(-)-bisabol using salicylic acid under normal and heat stress conditions by the gas chromatography-mass spectrometry (GC-MS) technique. The factorial experiments were carried out during the 2011-2012 hot season using a randomized complete block design with three replications. The factors include four salicylic acid concentrations (0 (control), 10, 25 and 100 mg·L -1 ), and three chamomile cultivars (Bushehr, Bona, Bodegold) were sown on two different planting dates under field conditions. Fourteen compounds were identified from the extracted oil of the samples treated with salicylic acid under normal and heat stress conditions. The major identified oil compositions from chamomile cultivars treated with salicylic acid were chamazulene, α-(-)-bisabolol, bisabolone oxide, β-farnesene, en-yn-dicycloether, and bisabolol oxide A and B. Analysis of variance showed that the simple effects (environmental conditions, cultivar and salicylic acid) and their interaction were significant on all identified compounds, but the environmental conditions had no significant effect on bisabolol oxide A. The greatest amount of chamazulene obtained was 6.66% at the concentration of 10 mg·L -1 SA for the Bona cultivar under heat stress conditions, whereas the highest α-(-)-bisabolol amount attained was 3.41% at the concentration of 100 mg·L -1 SA for the Bona cultivar under normal conditions. The results demonstrated that the application of exogenous salicylic acid increases the quantity and essential oil quality as a consequence of the increase of chamazulene and α-(-)-bisabolol under normal and heat stress conditions.
Stress-induced ascorbic acid depletion and cortisol production in two salmonid fishes

USGS Publications Warehouse

Wedemeyer, Gary

1969-01-01

Interrenal ascorbic acid and serum cortisol were measured in non-specificity stressed yearling coho salmon and rainbow trout.Interrenal ascorbate was markedly decreased during stress but increased to normal if adaptation occurred.Serum cortisol was elevated by non-specific stress and remained high after interrenal ascorbate had returned to initial levels.
Re‐estimated effects of deep episodic slip on the occurrence and probability of great earthquakes in Cascadia

USGS Publications Warehouse

Beeler, Nicholas M.; Roeloffs, Evelyn A.; McCausland, Wendy

2013-01-01

Mazzotti and Adams (2004) estimated that rapid deep slip during typically two week long episodes beneath northern Washington and southern British Columbia increases the probability of a great Cascadia earthquake by 30–100 times relative to the probability during the ∼58 weeks between slip events. Because the corresponding absolute probability remains very low at ∼0.03% per week, their conclusion is that though it is more likely that a great earthquake will occur during a rapid slip event than during other times, a great earthquake is unlikely to occur during any particular rapid slip event. This previous estimate used a failure model in which great earthquakes initiate instantaneously at a stress threshold. We refine the estimate, assuming a delayed failure model that is based on laboratory‐observed earthquake initiation. Laboratory tests show that failure of intact rock in shear and the onset of rapid slip on pre‐existing faults do not occur at a threshold stress. Instead, slip onset is gradual and shows a damped response to stress and loading rate changes. The characteristic time of failure depends on loading rate and effective normal stress. Using this model, the probability enhancement during the period of rapid slip in Cascadia is negligible (<10%) for effective normal stresses of 10 MPa or more and only increases by 1.5 times for an effective normal stress of 1 MPa. We present arguments that the hypocentral effective normal stress exceeds 1 MPa. In addition, the probability enhancement due to rapid slip extends into the interevent period. With this delayed failure model for effective normal stresses greater than or equal to 50 kPa, it is more likely that a great earthquake will occur between the periods of rapid deep slip than during them. Our conclusion is that great earthquake occurrence is not significantly enhanced by episodic deep slip events.
Theoretical Study on Stress Sensitivity of Fractal Porous Media with Irreducible Water

NASA Astrophysics Data System (ADS)

Lei, Gang; Dong, Zhenzhen; Li, Weirong; Wen, Qingzhi; Wang, Cai

The couple flow deformation behavior in porous media has drawn tremendous attention in various scientific and engineering fields. However, though the coupled flow deformation mechanism has been intensively investigated in the last decades, the essential controls on stress sensitivity are not determined. It is of practical significance to use analytic methods to study stress sensitivity of porous media. Unfortunately, because of the disordered and extremely complicated microstructures of porous media, the theoretical model for stress sensitivity is scarce. The goal of this work is to establish a novel and reasonable quantitative model to determine the essential controls on stress sensitivity. The predictions of the theoretical model, derived from the Hertzian contact theory and fractal geometry, agree well with the available experimental data. Compared with the previous models, our model takes into account more factors, including the influence of the water saturation and the microstructural parameters of the pore space. The proposed models can reveal more mechanisms that affect the coupled flow deformation behavior in fractal porous media. The results show that the irreducible water saturation increases with the increase of effective stress, and decreases with the increased rock elastic modulus (or increased power law index) at a given effective stress. The effect of stress variation on porosity is smaller than that on permeability. Under a given effective stress, the normalized permeability (or the normalized porosity) becomes smaller with the decrease of rock elastic modulus (or the decrease of power law index). And a lower capillary pressure will correspond to an increased rock elastic modulus (or an increased power law index) under a given water saturation.
High-fat diet with stress impaired islets' insulin secretion by reducing plasma estradiol and pancreatic GLUT2 protein levels in rats' proestrus phase.

PubMed

Salimi, M; Zardooz, H; Khodagholi, F; Rostamkhani, F; Shaerzadeh, F

2016-10-01

This study was conducted to determine whether two estrus phases (proestrus and diestrus) in female rats may influence the metabolic response to a high-fat diet and/or stress, focusing on pancreatic insulin secretion and content. Animals were divided into high-fat and normal diet groups, then each group was subdivided into stress and non-stress groups, and finally, each one of these was divided into proestrus and diestrus subgroups. At the end of high-fat diet treatment, foot-shock stress was applied to the animals. Then, blood samples were taken to measure plasma factors. Finally, the pancreas was removed for determination of glucose transporter 2 (GLUT2) protein levels and assessment of insulin content and secretion of the isolated islets. In the normal and high-fat diet groups, stress increased plasma corticosterone concentration in both phases. In both study phases, high-fat diet consumption decreased estradiol and increased leptin plasma levels. In the high-fat diet group in response to high glucose concentration, a reduction in insulin secretion was observed in the proestrus phase compared with the same phase in the normal diet group in the presence and absence of stress. Also, high-fat diet decreased the insulin content of islets in the proestrus phase compared with the normal diet. High-fat diet and/or stress caused a reduction in islet GLUT2 protein levels in both phases. In conclusion, it seems possible that high-fat diet alone or combined with foot-shock, predispose female rats to impaired insulin secretion, at least in part, by interfering with estradiol levels in the proestrus phase and decreasing pancreatic GLUT2 protein levels.
Rheology of concentrated suspensions of non-colloidal rigid fibers

NASA Astrophysics Data System (ADS)

Guazzelli, Elisabeth; Tapia, Franco; Shaikh, Saif; Butler, Jason E.; Pouliquen, Olivier

2017-11-01

Pressure and volume-imposed rheology is used to study suspensions of non-colloidal, rigid fibers in the concentrated regime for aspect ratios ranging from 3 to 15. The suspensions exhibit yield-stresses. Subtracting these apparent yield-stresses reveals a viscous scaling for both the shear and normal stresses. The variation in aspect ratio does not affect the friction coefficient (ratio of shear and normal stresses), but increasing the aspect ratio lowers the maximum volume fraction at which the suspension flows. Constitutive laws are proposed for the viscosities and the friction coefficient close to this maximum flowable fraction. The scaling of the stresses near this jamming transition are found to differ substantially from that of a suspension of spheres.

The Applicability of Nonlinear Systems Dynamics Chaos Measures to Cardiovascular Physiology Variables

NASA Technical Reports Server (NTRS)

Hooker, John C.

1991-01-01

Three measures of nonlinear chaos (fractal dimension, Approximate Entropy (ApEn), and Lyapunov exponents) were studied as potential measures of cardiovascular condition. It is suggested that these measures have potential in the assessment of cardiovascular condition in environments of normal cardiovascular stress (normal gravity on the Earth surface), cardiovascular deconditioning (microgravity of space), and increased cardiovascular stress (lower body negative pressure (LBNP) treatments).
Stress perturbation associated with the Amazonas and other ancient continental rifts

USGS Publications Warehouse

Zoback, M.L.; Richardson, R.M.

1996-01-01

The state of stress in the vicinity of old continental rifts is examined to investigate the possibility that crustal structure associated with ancient rifts (specifically a dense rift pillow in the lower crust) may modify substantially the regional stress field. Both shallow (2.0-2.6 km depth) breakout data and deep (20-45 km depth) crustal earthquake focal mechanisms indicate a N to NNE maximum horizontal compression in the vicinity of the Paleozoic Amazonas rift in central Brazil. This compressive stress direction is nearly perpendicular to the rift structure and represents a ???75?? rotation relative to a regional E-W compressive stress direction in the South American plate. Elastic two-dimensional finite element models of the density structure associated with the Amazonas rift (as inferred from independent gravity modeling) indicate that elastic support of this dense feature would generate horizontal rift-normal compressional stresses between 60 and 120 MPa, with values of 80-100 MPa probably most representative of the overall structure. The observed ???75?? stress rotation constrains the ratio of the regional horizontal stress difference to the rift-normal compressive stress to be between 0.25 and 1.0, suggesting that this rift-normal stress may be from 1 to 4 times larger than the regional horizontal stress difference. A general expression for the modification of the normalized local horizontal shear stress (relative to the regional horizontal shear stress) shows that the same ratio of the rift-normal compression relative to the regional horizontal stress difference, which controls the amount of stress rotation, also determines whether the superposed stress increases or decreases the local maximum horizontal shear stress. The potential for fault reactivation of ancient continental rifts in general is analyzed considering both the local stress rotation and modification of horizontal shear stress for both thrust and strike-slip stress regimes. In the Amazonas rift case, because the observed stress rotation only weakly constrains the ratio of the regional horizontal stress difference to the rift-normal compression to be between 0.25 and 1.0, our analysis is inconclusive because the resultant normalized horizontal shear stress may be reduced (for ratios >0.5) or enhanced (for ratios <0.5). Additional information is needed on all three stress magnitudes to predict how a change in horizontal shear stress directly influences the likelihood of faulting in the thrust-faulting stress regime in the vicinity of the Amazonas rift. A rift-normal stress associated with the seismically active New Madrid ancient rift may be sufficient to rotate the horizontal stress field consistent with strike-slip faults parallel to the axis of the rift, although this results in a 20-40% reduction in the local horizontal shear stress within the seismic zone. Sparse stress data in the vicinity of the seismically quiescent Midcontinent rift of the central United States suggest a stress state similar to that of New Madrid, with the local horizontal shear stress potentially reduced by as much as 60%. Thus the markedly different levels of seismic activity associated with these two subparallel ancient rifts is probably due to other factors than stress perturbations due to dense rift pillows. The modeling and analysis here demonstrate that rift-normal compressive stresses are a significant source of stress acting on the lithosphere and that in some cases may be a contributing factor to the association of intraplate seismicity with old zones of continental extension.
5,7-Dimethoxycoumarin prevents chronic mild stress induced depression in rats through increase in the expression of heat shock protein-70 and inhibition of monoamine oxidase-A levels.

PubMed

Yang, Wei; Wang, Huanlin

2018-02-01

The current study was aimed to investigate the role of 5,7-dimethoxycoumarin in the prevention of chronic mild stress induced depression in rats. The chronic mild stress rat model was prepared using the known protocols. The results from open-field test showed that rats in the chronic mild stress group scored very low in terms of crossings and rearings than those of the normal rats. However, pre-treatment of the rats with 10 mg/kg doses of 5,7-dimethoxycoumarin prevented decline in the locomotor activity by chronic mild stress. The level of monoamine oxidase-A in the chronic mild stress rat hippocampus was markedly higher. Chronic mild stress induced increase in the monoamine oxidase-A level was inhibited by pre-treatment with 10 mg/kg doses of 5,7-dimethoxycoumarin in the rats. Chronic mild stress caused a marked increase in the level of caspase-3 mRNA and proteins in rat hippocampus tissues. The increased level of caspase-3 mRNA and protein level was inhibited by treatment of rats with 5,7-dimethoxycoumarin (10 mg/kg). 5,7-Dimethoxycoumarin administration into the rats caused a marked increase in the levels of heat shock protein-70 mRNA and protein. The levels of heat shock protein-70 were markedly lower both in normal and chronic mild stress groups of rats compared to the 5,7-dimethoxycoumarin treated groups. Thus 5,7-dimethoxycoumarin prevented the chronic mild stress induced depression in rats through an increase in the expression of heat shock protein-70 and inhibition of monoamine oxidase-A levels.
Effect of vitamin C on male fertility in rats subjected to forced swimming stress.

PubMed

Vijayprasad, Sanghishetti; Bb, Ghongane; Bb, Nayak

2014-07-01

Stress is defined as a general body response to initially threatening external or internal demands, involving the mobilization of physiological and psychological resources to deal with them. Recently, oxidative stress has become the focus of interest as a potential cause of male infertility. Normally, equilibrium exists between reactive oxygen species (ROS) production and antioxidant scavenging activities in the male reproductive organs. The ascorbic acid is a known antioxidant present in the testis with the precise role of protecting the latter from the oxidative damage. It also contributes to the support of spermatogensis at least in part through its capacity to maintain antioxidant in an active state. Group1: Normal Control animal received Distilled water, Group 2: Positive control (Only Stress), Group 3: Normal rats received an intermediate dose of Vitamin C (20mg/kg/day), Group 4: Stress + Low dose Vitamin C (10mg/kg/day), Group 5: Stress+ Intermediate dose Vitamin C (20mg/kg/day), Group 6: High dose Vitamin C (30mg/kg/day). On 16(th) day effect of stress on body weight, Reproductive organ weight, sperm parameters, and hormonal assay was studied. In the present context, in stress group the sperm count, motility, testicular weight declined significantly. The intermediate dose and high dose of vitamin C showed significantly increased effect on the sperm count and motility. Various physiological changes produced force swimming indicates that swimming is an effective model for producing stress in albino rats. The results suggest that Vitamin C supplementation improves the stress induced reproductive infertility due to both their testosterone increase effect and their antioxidant effect.
Role of oxidative stress and nitric oxide in atherothrombosis

PubMed Central

Lubos, Edith; Handy, Diane E.; Loscalzo, Joseph

2008-01-01

During the last decade basic and clinical research has highlighted the central role of reactive oxygen species (ROS) in cardiovascular disease. Enhanced production or attenuated degradation of ROS leads to oxidative stress, a process that affects endothelial and vascular function, and contributes to vascular disease. Nitric oxide (NO), a product of the normal endothelium, is a principal determinant of normal endothelial and vascular function. In states of inflammation, NO production by the vasculature increases considerably and, in conjunction with other ROS, contributes to oxidative stress. This review examines the role of oxidative stress and NO in mechanisms of endothelial and vascular dysfunction with an emphasis on atherothrombosis. PMID:18508590
Stuy on Fatigue Life of Aluminum Alloy Considering Fretting

NASA Astrophysics Data System (ADS)

Yang, Maosheng; Zhao, Hongqiang; Wang, Yunxiang; Chen, Xiaofei; Fan, Jiali

2018-01-01

To study the influence of fretting on Aluminum Alloy, a global finite element model considering fretting was performed using the commercial code ABAQUS. With which a new model for predicting fretting fatigue life has been presented based on friction work. The rationality and effectiveness of the model were validated according to the contrast of experiment life and predicting life. At last influence factor on fretting fatigue life of aerial aluminum alloy was investigated with the model. The results revealed that fretting fatigue life decreased monotonously with the increasing of normal load and then became constant at higher pressures. At low normal load, fretting fatigue life was found to increase with increase in the pad radius. At high normal load, however, the fretting fatigue life remained almost unchanged with changes in the fretting pad radius. The bulk stress amplitude had the dominant effect on fretting fatigue life. The fretting fatigue life diminished as the bulk stress amplitude increased.
A stress sensitivity model for the permeability of porous media based on bi-dispersed fractal theory

NASA Astrophysics Data System (ADS)

Tan, X.-H.; Liu, C.-Y.; Li, X.-P.; Wang, H.-Q.; Deng, H.

A stress sensitivity model for the permeability of porous media based on bidispersed fractal theory is established, considering the change of the flow path, the fractal geometry approach and the mechanics of porous media. It is noted that the two fractal parameters of the porous media construction perform differently when the stress changes. The tortuosity fractal dimension of solid cluster DcTσ become bigger with an increase of stress. However, the pore fractal dimension of solid cluster Dcfσ and capillary bundle Dpfσ remains the same with an increase of stress. The definition of normalized permeability is introduced for the analyzation of the impacts of stress sensitivity on permeability. The normalized permeability is related to solid cluster tortuosity dimension, pore fractal dimension, solid cluster maximum diameter, Young’s modulus and Poisson’s ratio. Every parameter has clear physical meaning without the use of empirical constants. Predictions of permeability of the model is accordant with the obtained experimental data. Thus, the proposed model can precisely depict the flow of fluid in porous media under stress.
Size Dependence of Residual Thermal Stresses in Micro Multilayer Ceramic Capacitors by Using Finite Element Unit Cell Model Including Strain Gradient Effect

NASA Astrophysics Data System (ADS)

Jiang, W. G.; Xiong, C. A.; Wu, X. G.

2013-11-01

The residual thermal stresses induced by the high-temperature sintering process in multilayer ceramic capacitors (MLCCs) are investigated by using a finite-element unit cell model, in which the strain gradient effect is considered. The numerical results show that the residual thermal stresses depend on the lateral margin length, the thickness ratio of the dielectrics layer to the electrode layer, and the MLCC size. At a given thickness ratio, as the MLCC size is scaled down, the peak shear stress reduces significantly and the normal stresses along the length and thickness directions change slightly with the decrease in the ceramic layer thickness t d as t d > 1 μm, but as t d < 1 μm, the normal stress components increase sharply with the increase in t d. Thus, the residual thermal stresses induced by the sintering process exhibit strong size effects and, therefore, the strain gradient effect should be taken into account in the design and evaluation of MLCC devices
Segmentation of Slow Slip Events in South Central Alaska Possibly Controlled by a Subducted Oceanic Plateau

NASA Astrophysics Data System (ADS)

Li, Haotian; Wei, Meng; Li, Duo; Liu, Yajing; Kim, YoungHee; Zhou, Shiyong

2018-01-01

Recent GPS observations show that slow slip events in south central Alaska are segmented along strike. Here we review several mechanisms that might contribute to this segmentation and focus on two: along-strike variation of slab geometry and effective normal stress. We then test them by running numerical simulations in the framework of rate-and-state friction with a nonplanar fault geometry. Results show that the segmentation is most likely related to the along-strike variation of the effective normal stress on the fault plane caused by the Yakutat Plateau. The Yakutat Plateau could affect the effective normal stress by either lowering the pore pressure in Upper Cook Inlet due to less fluids release or increasing the normal stress due to the extra buoyancy caused by the subducted Yakutat Plateau. We prefer the latter explanation because it is consistent with the relative amplitudes of the effective normal stress in Upper and Lower Cook Inlet and there is very little along-strike variation in Vp/Vs ratio in the fault zone from receiver function analysis. However, we cannot exclude the possibility that the difference in effective normal stress results from along-strike variation of pore pressure due to the uncertainties in the Vp/Vs estimates. Our work implies that a structural anomaly can have a long-lived effect on the subduction zone slip behavior and might be a driving factor on along-strike segmentation of slow slip events.
Tumor vessel normalization after aerobic exercise enhances chemotherapeutic efficacy.

PubMed

Schadler, Keri L; Thomas, Nicholas J; Galie, Peter A; Bhang, Dong Ha; Roby, Kerry C; Addai, Prince; Till, Jacob E; Sturgeon, Kathleen; Zaslavsky, Alexander; Chen, Christopher S; Ryeom, Sandra

2016-10-04

Targeted therapies aimed at tumor vasculature are utilized in combination with chemotherapy to improve drug delivery and efficacy after tumor vascular normalization. Tumor vessels are highly disorganized with disrupted blood flow impeding drug delivery to cancer cells. Although pharmacologic anti-angiogenic therapy can remodel and normalize tumor vessels, there is a limited window of efficacy and these drugs are associated with severe side effects necessitating alternatives for vascular normalization. Recently, moderate aerobic exercise has been shown to induce vascular normalization in mouse models. Here, we provide a mechanistic explanation for the tumor vascular normalization induced by exercise. Shear stress, the mechanical stimuli exerted on endothelial cells by blood flow, modulates vascular integrity. Increasing vascular shear stress through aerobic exercise can alter and remodel blood vessels in normal tissues. Our data in mouse models indicate that activation of calcineurin-NFAT-TSP1 signaling in endothelial cells plays a critical role in exercise-induced shear stress mediated tumor vessel remodeling. We show that moderate aerobic exercise with chemotherapy caused a significantly greater decrease in tumor growth than chemotherapy alone through improved chemotherapy delivery after tumor vascular normalization. Our work suggests that the vascular normalizing effects of aerobic exercise can be an effective chemotherapy adjuvant.
The sex differences in nature of vascular endothelial stress: nitrergic mechanisms

NASA Astrophysics Data System (ADS)

Sindeev, Sergey; Gekaluyk, Artem; Ulanova, Maria; Agranovich, Ilana; Sharref, Ali Esmat; Semyachkina-Glushkovskaya, Oxana

2016-04-01

Here we studied the role of nitric oxide in cardiovascular regulation in male and female hypertensive rats under normal and stress conditions. We found that the severity of hypertension in females was lower than in males. Hypertensive females demonstrated more favorable pattern of cardiovascular responses to stress. Nitric oxide blockade by NG-nitro-L-arginine methyl ester (L-NAME) increased the mean arterial pressure and decreased the heart rate more effectively in females than in males. During stress, L-NAME modified the stress-induced cardiovascular responses more significantly in female compared with male groups. Our data show that hypertensive females demonstrated the more effective nitric oxide control of cardiovascular activity under normal and especially stress conditions than male groups. This sex differences may be important mechanism underlying greater in females vs. males stress-resistance of cardiovascular system and hypertension formation.
Changes in ventricular function during emotional stress and cold exposure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kiess, M.C.; Moore, R.A.; Dimsdale, J.

1984-01-01

Patients with cardiac disease frequently develop symptoms with emotional stress or cold exposure. To investigate the effects of these stresses in normal subjects, an ambulatory ventricular function monitor (VEST) (previously reported to measure EFs which correlate well with gamma camera measurements) was employed to record sequential 2 minute time activity curves from the left ventricles of 6 healthy men (ages 19-24) during a control period and during a 30 minute stress interview with a psychiatrist. Four of the subjects were also monitored in a cold room (1/sup 0/C) for 20 min. In addition to the left ventricular time-activity curve, heartmore » rate (HR), and BP (cuff) were recorded. All subjects had increases in HR, BP and EF during the stress interview. Cold, however, produced decreases in HR and EF and an increase in BP. The results (mean +- SD) are tabulated. End-systolic and end-diastolic counts and hence volume decreased during the interview and increased during cold exposure. The results suggest that (1) ambulatory changes in ventricular function can be measured with the VEST, and (2) significant changes in cardiovascular physiology are seen in normal subjects during a stress interview and exposure to cold.« less
Natural thermal adaptation increases heat shock protein levels and decreases oxidative stress.

PubMed

Oksala, Niku K J; Ekmekçi, F Güler; Ozsoy, Ergi; Kirankaya, Serife; Kokkola, Tarja; Emecen, Güzin; Lappalainen, Jani; Kaarniranta, Kai; Atalay, Mustafa

2014-01-01

Heat shock proteins (HSPs), originally identified as heat-inducible gene products, are a family of highly conserved proteins that respond to a wide variety of stress including oxidative stress. Although both acute and chronic oxidative stress have been well demonstrated to induce HSP responses, little evidence is available whether increased HSP levels provide enhanced protection against oxidative stress under elevated yet sublethal temperatures. We studied relationships between oxidative stress and HSPs in a physiological model by using Garra rufa (doctor fish), a fish species naturally acclimatized to different thermal conditions. We compared fish naturally living in a hot spring with relatively high water temperature (34.4±0.6°C) to those living in normal river water temperature (25.4±4.7°C), and found that levels of all the studied HSPs (HSP70, HSP60, HSP90, HSC70 and GRP75) were higher in fish living in elevated water temperature compared with normal river water temperature. In contrast, indicators of oxidative stress, including protein carbonyls and lipid hydroperoxides, were decreased in fish living in the elevated temperature, indicating that HSP levels are inversely associated with oxidative stress. The present results provide evidence that physiologically increased HSP levels provide protection against oxidative stress and enhance cytoprotection. Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.
Speckle Tracking Imaging in Normal Stress Echocardiography.

PubMed

Leitman, Marina; Tyomkin, Vladimir; Peleg, Eli; Zyssman, Izhak; Rosenblatt, Simcha; Sucher, Edgar; Gercenshtein, Vered; Vered, Zvi

2017-04-01

Exercise stress echocardiography is a widely used modality for the diagnosis and follow-up of patients with coronary artery disease. During the last decade, speckle tracking imaging has been used increasingly for accurate evaluation of cardiac function. This work aimed to assess speckle-tracking imaging parameters during nonischemic exercise stress echocardiography. During 2011 to 2014 we studied 46 patients without history of coronary artery disease, who completed exercise stress echocardiography protocol, had normal left ventricular function, a nonischemic response, and satisfactory image quality. These exams were analyzed with speckle-tracking imaging software at rest and at peak exercise. Peak strain and time-to-peak strain were measured at rest and after exercise. Clinical follow-up included a telephone contact 1 to 3 years after stress echo exam, confirming freedom from coronary events during this time. Global and regional peak strain increased following exercise. Time-to-peak global and regional strain and time-to-peak strain adjusted to the heart rate were significantly shorter in all segments after exercise. Rest-to-stress ratio of time-to-peak strain adjusted to the heart rate was 2.0 to 2.8. Global and regional peak strain rise during normal exercise echocardiography. Peak global and regional strain occur before or shortly after aortic valve closure at rest and after exercise, and the delay is more apparent at the basal segments. Time-to-peak strain normally shortens significantly during exercise; after adjustment to heart rate it shortens by a ratio of 2.0 to 2.8. These data may be useful for interpretation of future exercise stress speckle-tracking echocardiography studies. © 2016 by the American Institute of Ultrasound in Medicine.
Experimental study of the flow in the wake of a stationary sphere immersed in a turbulent boundary layer

NASA Astrophysics Data System (ADS)

van Hout, René; Eisma, Jerke; Elsinga, Gerrit E.; Westerweel, Jerry

2018-02-01

In many applications, finite-sized particles are immersed in a turbulent boundary layer (TBL) and it is of interest to study wall effects on the instantaneous shedding of turbulence structures and associated mean velocity and Reynolds stress distributions. Here, 3D flow field dynamics in the wake of a prototypical, small sphere (D+=50 , 692
Neonatal growth restriction-related leptin deficiency enhances leptin-triggered sympathetic activation and central angiotensin II receptor-dependent stress-evoked hypertension.

PubMed

Peotta, Veronica; Rahmouni, Kamal; Segar, Jeffrey L; Morgan, Donald A; Pitz, Kate M; Rice, Olivia M; Roghair, Robert D

2016-08-01

Neonatal growth restriction (nGR) leads to leptin deficiency and increases the risk of hypertension. Previous studies have shown nGR-related hypertension is normalized by neonatal leptin (nLep) and exacerbated by psychological stress. With recent studies linking leptin and angiotensin signaling, we hypothesized that nGR-induced nLep deficiency increases adult leptin sensitivity; leading to leptin- or stress-induced hypertension, through a pathway involving central angiotensin II type 1 receptors. We randomized mice with incipient nGR, by virtue of their presence in large litters, to vehicle or physiologic nLep supplementation (80 ng/g/d). Adult caloric intake and arterial pressure were monitored at baseline, during intracerebroventricular losartan infusion and during systemic leptin administration. nGR increased leptin-triggered renal sympathetic activation and hypertension with increased leptin receptor expression in the arcuate nucleus of the hypothalamus; all of those nGR-associated phenotypes were normalized by nLep. nGR mice also had stress-related hyperphagia and hypertension, but only the stress hypertension was blocked by central losartan infusion. nGR leads to stress hypertension through a pathway that involves central angiotensin II receptors, and nGR-associated leptin deficiency increases leptin-triggered hypertension in adulthood. These data suggest potential roles for preservation of neonatal growth and nLep supplementation in the prevention of nGR-related hypertension.
Stress does not affect ghrelin secretion in obese and normal weight women.

PubMed

Kiessl, Gundula R R; Laessle, Reinhold G

2017-03-01

Stress has been supposed to increase appetite. The biological basis of this phenomenon may be a stress-induced alteration of the secretion of GUT peptides such as ghrelin. Stress-induced changes in ghrelin secretion could be a biological basis of overeating and a factor contributing to the development of obesity. Aim of the study was to analyze the effect of acute psychosocial stress on ghrelin secretion in obese and normal weight women. We compared pre- and postprandial plasma ghrelin secretion of 42 obese and 43 normal weight women in a randomized crossover design. Ghrelin and cortisol concentrations were measured and ratings of stress were also recorded in response to a psychological stressor (Trier Social Stress Test, TSST). Ghrelin samples were collected in the fasting state one time before participating in the TSST and one time before a control session. After the TSST, respectively, control session participants had a standardized ad libitum meal. 30 and 60 min after the TSST, respectively, control session preprandial ghrelin was measured again. Obese women showed lower pre- and postprandial release of ghrelin than normal weight controls. Moreover, obese women showed inhibited postprandial decrease of ghrelin secretion. Stress did not affect postprandial ghrelin secretion, but inhibited food intake in all subjects. The present data provide further evidence of altered ghrelin release in obesity. Acute stress did not affect postprandial ghrelin secretion, but inhibited food intake in all subjects. Results are discussed with regard to biological and psychological regulation of hunger and satiety in obesity.
Characterization of the Differential Response of Endothelial Cells Exposed to Normal and Elevated Laminar Shear Stress

PubMed Central

White, Stephen J; Hayes, Elaine M; Lehoux, Stéphanie; Jeremy, Jamie Y; Horrevoets, Anton JG; Newby, Andrew C

2011-01-01

Most acute coronary events occur in the upstream region of stenotic atherosclerotic plaques that experience laminar shear stress (LSS) elevated above normal physiological levels. Many studies have described the atheroprotective effect on endothelial behavior of normal physiological LSS (approximately 15 dynes/cm2) compared to static or oscillatory shear stress (OSS), but it is unknown whether the levels of elevated shear stress imposed by a stenotic plaque would preserve, enhance or reverse this effect. Therefore we used transcriptomics and related functional analyses to compare human endothelial cells exposed to laminar shear stress of 15 (LSS15-normal) or 75 dynes/cm2 (LSS75-elevated). LSS75 upregulated expression of 145 and downregulated expression of 158 genes more than twofold relative to LSS15. Modulation of the metallothioneins (MT1-G, -M, -X) and NADPH oxidase subunits (NOX2, NOX4, NOX5, and p67phox) accompanied suppression of reactive oxygen species production at LSS75. Shear induced changes in dual specificity phosphatases (DUSPs 1, 5, 8, and 16 increasing and DUSPs 6 and 23 decreasing) were observed as well as reduced ERK1/2 but increased p38 MAP kinase phosphorylation. Amongst vasoactive substances, endothelin-1 expression decreased whereas vasoactive intestinal peptide (VIP) and prostacyclin expression increased, despite which intracellular cAMP levels were reduced. Promoter analysis by rVISTA identified a significant over representation of ATF and Nrf2 transcription factor binding sites in genes upregulated by LSS75 compared to LSS15. In summary, LSS75 induced a specific change in behavior, modifying gene expression, reducing ROS levels, altering MAP kinase signaling and reducing cAMP levels, opening multiple avenues for future study. J. Cell. Physiol. 226: 2841–2848, 2011. © 2011 Wiley-Liss, Inc. PMID:21302282
Significance of an Increase in Diastolic Blood Pressure during a Stress Test in Terms of Comorbidities and Long-term Total and CV Mortality.

PubMed

Sydó, Nóra; Sydó, Tibor; Gonzalez Carta, Karina A; Hussain, Nasir; Merkely, Béla; Murphy, Joseph G; Squires, Ray W; Lopez-Jimenez, Francisco; Allison, Thomas G

2018-05-15

A decrease in diastolic blood pressure (DBP) with exercise is considered normal, but the significance of an increase in DBP has not been validated. Our aim was to determine the relationship of DBP increasing on a stress test regarding comorbidities and mortality. Our database was reviewed from 1993-2010 using the first stress test of a patient. Non-Minnesota residence, baseline CV disease, rest DBP <60 or >100 mmHg, and age <30 or ≥80 were exclusion criteria. DBP response was classified Normal if peak DBP-rest DBP <0, Borderline 0-9, Abnormal ≥10mmHg. Mortality was determined from Mayo Clinic records and Minnesota Death Index. Logistic regression was used to determine the relationship of DBP response to presence of comorbidities. Cox regression was used to determine total and CV mortality risk by DBP response. All analyses were adjusted for age, sex and resting DBP. 20760 patients were included (51±11 years, female n=7314). Rest/peak averaged DBP 82±8/69 ±15 mmHg in normal vs 79±9/82±9 mmHg in borderline vs 76±9/92±11 mmHg in abnormal DBP response. There were 1582 deaths (8%) with 557 (3%) CV deaths over 12±5 years of follow-up. In patients with borderline and abnormal DBP response, odds ratios for obesity, hypertension, diabetes and current smoking were significant, while hazard ratios for total and CV death were not significant compared to patients with normal DBP response. DBP response to exercise is significantly associated with important comorbidities at the time of the stress test but does not add to the prognostic yield of stress test.
Characterization of the differential response of endothelial cells exposed to normal and elevated laminar shear stress.

PubMed

White, Stephen J; Hayes, Elaine M; Lehoux, Stéphanie; Jeremy, Jamie Y; Horrevoets, Anton J G; Newby, Andrew C

2011-11-01

Most acute coronary events occur in the upstream region of stenotic atherosclerotic plaques that experience laminar shear stress (LSS) elevated above normal physiological levels. Many studies have described the atheroprotective effect on endothelial behavior of normal physiological LSS (approximately 15 dynes/cm(2)) compared to static or oscillatory shear stress (OSS), but it is unknown whether the levels of elevated shear stress imposed by a stenotic plaque would preserve, enhance or reverse this effect. Therefore we used transcriptomics and related functional analyses to compare human endothelial cells exposed to laminar shear stress of 15 (LSS15-normal) or 75 dynes/cm(2) (LSS75-elevated). LSS75 upregulated expression of 145 and downregulated expression of 158 genes more than twofold relative to LSS15. Modulation of the metallothioneins (MT1-G, -M, -X) and NADPH oxidase subunits (NOX2, NOX4, NOX5, and p67phox) accompanied suppression of reactive oxygen species production at LSS75. Shear induced changes in dual specificity phosphatases (DUSPs 1, 5, 8, and 16 increasing and DUSPs 6 and 23 decreasing) were observed as well as reduced ERK1/2 but increased p38 MAP kinase phosphorylation. Amongst vasoactive substances, endothelin-1 expression decreased whereas vasoactive intestinal peptide (VIP) and prostacyclin expression increased, despite which intracellular cAMP levels were reduced. Promoter analysis by rVISTA identified a significant over representation of ATF and Nrf2 transcription factor binding sites in genes upregulated by LSS75 compared to LSS15. In summary, LSS75 induced a specific change in behavior, modifying gene expression, reducing ROS levels, altering MAP kinase signaling and reducing cAMP levels, opening multiple avenues for future study. Copyright © 2011 Wiley-Liss, Inc.

Expression of heat shock protein 70 in transport-stressed broiler pectoralis major muscle and its relationship with meat quality.

PubMed

Xing, T; Wang, M F; Han, M Y; Zhu, X S; Xu, X L; Zhou, G H

2017-09-01

Omics research has indicated that heat shock protein 70 (HSP70) is a potential biomarker of meat quality. However, the specific changes and the potential role of HSP70 in postmortem meat quality development need to be further defined. In this study, Arbor Acres broiler chickens (n=126) were randomly categorized into three treatment groups of unstressed control (C), 0.5-h transport (T) and subsequent water shower spray following transport (T/W). Each treatment consisted of six replicates with seven birds each. The birds were transported according to a designed protocol. The pectoralis major (PM) muscles of the transport-stressed broilers were categorized as normal and pale, soft and exudative (PSE)-like muscle samples according to L* and pH24 h values to test the expression and location of HSP70. Results revealed that the activities of plasma creatine kinase and lactate dehydrogenase increased significantly (P<0.05) in normal and PSE-like muscle samples after transportation. The mRNA expression of HSP70 in normal muscle samples increased significantly (P<0.05) compared with that in the controls after stress. The protein expression of HSP70 increased significantly in normal muscle samples and decreased significantly (P<0.05) in PSE-like muscles. Immuno-fluorescence showed that HSP70 was present in the cytoplasm and on surface membranes of PM muscle cells in the normal samples following stress. Meanwhile, HSP70 was present on the surface membranes and extracellular matrix but was barely visible in the cytoplasm of the PSE-like samples. Principal component analysis showed high correlations between HSP70 and meat quality and stress indicators. In conclusion, this research suggests that the variation in HSP70 expression may provide a novel insight into the pathways underlying meat quality development.
Relationship between screw sagittal angle and stress on endplate of adjacent segments after anterior cervical corpectomy and fusion with internal fixation: a Chinese finite element study.

PubMed

Zhang, Yu; Tang, Yibo; Shen, Hongxing

2017-12-01

In order to reduce the incidence of adjacent segment disease (ASD), the current study was designed to establish Chinese finite element models of normal 3rd~7th cervical vertebrae (C3-C7) and anterior cervical corpectomy and fusion (ACCF) with internal fixation , and analyze the influence of screw sagittal angle (SSA) on stress on endplate of adjacent cervical segments. Mimics 8.1 and Abaqus/CAE 6.10 softwares were adopted to establish finite element models. For C4 superior endplate and C6 inferior endplate, their anterior areas had the maximum stress in anteflexion position, and their posterior areas had the maximum stress in posterior extension position. As SSA increased, the stress reduced. With an increase of 10° in SSA, the stress on anterior areas of C4 superior endplate and C6 inferior endplate reduced by 12.67% and 7.99% in anteflexion position, respectively. With an increase of 10° in SSA, the stress on posterior areas of C4 superior endplate and C6 inferior endplate reduced by 9.68% and 10.22% in posterior extension position, respectively. The current study established Chinese finite element models of normal C3-C7 and ACCF with internal fixation , and demonstrated that as SSA increased, the stress on endplate of adjacent cervical segments decreased. In clinical surgery, increased SSA is able to play important role in protecting the adjacent cervical segments and reducing the incidence of ASD.
Activation of ATP-sensitive potassium channel by iptakalim normalizes stress-induced HPA axis disorder and depressive behaviour by alleviating inflammation and oxidative stress in mouse hypothalamus.

PubMed

Zhao, Xiao-Jie; Zhao, Zhan; Yang, Dan-Dan; Cao, Lu-Lu; Zhang, Ling; Ji, Juan; Gu, Jun; Huang, Ji-Ye; Sun, Xiu-Lan

2017-04-01

Stress-induced disturbance of the hypothalamic-pituitary-adrenal (HPA) axis is strongly implicated in incidence of mood disorders. A heightened neuroinflammatory response and oxidative stress play a fundamental role in the dysfunction of the HPA axis. We have previously demonstrated that iptakalim (Ipt), a new ATP-sensitive potassium (K-ATP) channel opener, could prevent oxidative injury and neuroinflammation against multiple stimuli-induced brain injury. The present study was to demonstrate the impacts of Ipt in stress-induced HPA axis disorder and depressive behavior. We employed 2 stress paradigms: 8 weeks of continuous restraint stress (chronic restraint stress, CRS) and 2h of restraint stress (acute restraint stress, ARS), to mimic both chronic stress and severe acute stress. Prolonged (4 weeks) and short-term (a single injection) Ipt treatment was administered 30min before each stress paradigm. We found that HPA axis was altered after stress, with different responses to CRS (lower ACTH and CORT, higher AVP, but normal CRH) and ARS (higher CRH, ACTH and CORT, but normal AVP). Both prolonged and short-term Ipt treatment normalized stress-induced HPA axis disorders and abnormal behaviors in mice. CRS and ARS up-regulated mRNA levels of inflammation-related molecules (TNFα, IL-1β, IL-6 and TLR4) and oxidative stress molecules (gp91phox, iNOS and Nrf2) in the mouse hypothalamus. Double immunofluorescence showed CRS and ARS increased microglia activation (CD11b and TNFα) and oxidative stress in neurons (NeuN and gp91phox), which were alleviated by Ipt. Therefore, the present study reveals that Ipt could prevent against stress-induced HPA axis disorders and depressive behavior by alleviating inflammation and oxidative stress in the hypothalamus. Copyright © 2017 Elsevier Inc. All rights reserved.
Maturation Stress Generation in Poplar Tension Wood Studied by Synchrotron Radiation Microdiffraction[C][W][OA

PubMed Central

Clair, Bruno; Alméras, Tancrède; Pilate, Gilles; Jullien, Delphine; Sugiyama, Junji; Riekel, Christian

2011-01-01

Tension wood is widespread in the organs of woody plants. During its formation, it generates a large tensile mechanical stress called maturation stress. Maturation stress performs essential biomechanical functions such as optimizing the mechanical resistance of the stem, performing adaptive movements, and ensuring the long-term stability of growing plants. Although various hypotheses have recently been proposed, the mechanism generating maturation stress is not yet fully understood. In order to discriminate between these hypotheses, we investigated structural changes in cellulose microfibrils along sequences of xylem cell differentiation in tension and normal wood of poplar (Populus deltoides × Populus trichocarpa ‘I45-51’). Synchrotron radiation microdiffraction was used to measure the evolution of the angle and lattice spacing of crystalline cellulose associated with the deposition of successive cell wall layers. Profiles of normal and tension wood were very similar in early development stages corresponding to the formation of the S1 layer and the outer part of the S2 layer. Subsequent layers were found with a lower microfibril angle (MFA), corresponding to the inner part of the S2 layer of normal wood (MFA approximately 10°) and the G layer of tension wood (MFA approximately 0°). In tension wood only, this steep decrease in MFA occurred together with an increase in cellulose lattice spacing. The relative increase in lattice spacing was found close to the usual value of maturation strains. Analysis showed that this increase in lattice spacing is at least partly due to mechanical stress induced in cellulose microfibrils soon after their deposition, suggesting that the G layer directly generates and supports the tensile maturation stress in poplar tension wood. PMID:21068364
Influence of polygonal wear of railway wheels on the wheel set axle stress

NASA Astrophysics Data System (ADS)

Wu, Xingwen; Chi, Maoru; Wu, Pingbo

2015-11-01

The coupled vehicle/track dynamic model with the flexible wheel set was developed to investigate the effects of polygonal wear on the dynamic stresses of the wheel set axle. In the model, the railway vehicle was modelled by the rigid multibody dynamics. The wheel set was established by the finite element method to analyse the high-frequency oscillation and dynamic stress of wheel set axle induced by the polygonal wear based on the modal stress recovery method. The slab track model was taken into account in which the rail was described by the Timoshenko beam and the three-dimensional solid finite element was employed to establish the concrete slab. Furthermore, the modal superposition method was adopted to calculate the dynamic response of the track. The wheel/rail normal forces and the tangent forces were, respectively, determined by the Hertz nonlinear contact theory and the Shen-Hedrick-Elkins model. Using the coupled vehicle/track dynamic model, the dynamic stresses of wheel set axle with consideration of the ideal polygonal wear and measured polygonal wear were investigated. The results show that the amplitude of wheel/rail normal forces and the dynamic stress of wheel set axle increase as the vehicle speeds rise. Moreover, the impact loads induced by the polygonal wear could excite the resonance of wheel set axle. In the resonance region, the amplitude of the dynamic stress for the wheel set axle would increase considerably comparing with the normal conditions.
Early Life Stress Differentially Modulates Distinct Forms of Brain Plasticity in Young and Adult Mice

PubMed Central

Reichardt, Wilfried; Clark, Kristin; Geiger, Julia; Gross, Claus M.; Heyer, Andrea; Neagu, Valentin; Bhatia, Harsharan; Atas, Hasan C.; Fiebich, Bernd L.; Bischofberger, Josef; Haas, Carola A.; Normann, Claus

2012-01-01

Background Early life trauma is an important risk factor for many psychiatric and somatic disorders in adulthood. As a growing body of evidence suggests that brain plasticity is disturbed in affective disorders, we examined the short-term and remote effects of early life stress on different forms of brain plasticity. Methodology/Principal Findings Mice were subjected to early deprivation by individually separating pups from their dam in the first two weeks after birth. Distinct forms of brain plasticity were assessed in the hippocampus by longitudinal MR volumetry, immunohistochemistry of neurogenesis, and whole-cell patch-clamp measurements of synaptic plasticity. Depression-related behavior was assessed by the forced swimming test in adult animals. Neuropeptides and their receptors were determined by real-time PCR and immunoassay. Early maternal deprivation caused a loss of hippocampal volume, which returned to normal in adulthood. Adult neurogenesis was unaffected by early life stress. Long-term synaptic potentiation, however, was normal immediately after the end of the stress protocol but was impaired in adult animals. In the forced swimming test, adult animals that had been subjected to early life stress showed increased immobility time. Levels of substance P were increased both in young and adult animals after early deprivation. Conclusion Hippocampal volume was affected by early life stress but recovered in adulthood which corresponded to normal adult neurogenesis. Synaptic plasticity, however, exhibited a delayed impairment. The modulation of synaptic plasticity by early life stress might contribute to affective dysfunction in adulthood. PMID:23071534
Analysis of space-time projection of differential and Michelson-type speckle-interferometer output signal for cardiovibration measurement

NASA Astrophysics Data System (ADS)

Ulyanov, Sergey S.; Tuchin, Valery V.

1993-06-01

The sex differences in cardiovascular system responses to a mild noise stress are established using the physiological and the dynamic systems theory methods. Lower levels of basal systolic arterial pressure and higher rates of its dropping and normalization under influence and after its cessation are typical for women. There are no hypertensive responses to stresses in women in contrast to men. The normalized entropy of the ECG signal, describing the physiological variability, increases in women and decreases in men. The advantages of female cardiovascular system response to mild stresses are discussed.
Normal force and drag force in magnetorheological finishing

NASA Astrophysics Data System (ADS)

Miao, Chunlin; Shafrir, Shai N.; Lambropoulos, John C.; Jacobs, Stephen D.

2009-08-01

The material removal in magnetorheological finishing (MRF) is known to be controlled by shear stress, λ, which equals drag force, Fd, divided by spot area, As. However, it is unclear how the normal force, Fn, affects the material removal in MRF and how the measured ratio of drag force to normal force Fd/Fn, equivalent to coefficient of friction, is related to material removal. This work studies, for the first time for MRF, the normal force and the measured ratio Fd/Fn as a function of material mechanical properties. Experimental data were obtained by taking spots on a variety of materials including optical glasses and hard ceramics with a spot-taking machine (STM). Drag force and normal force were measured with a dual load cell. Drag force decreases linearly with increasing material hardness. In contrast, normal force increases with hardness for glasses, saturating at high hardness values for ceramics. Volumetric removal rate decreases with normal force across all materials. The measured ratio Fd/Fn shows a strong negative linear correlation with material hardness. Hard materials exhibit a low "coefficient of friction". The volumetric removal rate increases with the measured ratio Fd/Fn which is also correlated with shear stress, indicating that the measured ratio Fd/Fn is a useful measure of material removal in MRF.
Normal Force and Drag Force in Magnetorheological Finishing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miao, C.; Shafrir, S.N.; Lambropoulos, J.C.

2010-01-13

The material removal in magnetorheological finishing (MRF) is known to be controlled by shear stress, tau, which equals drag force, Fd, divided by spot area, As. However, it is unclear how the normal force, Fn, affects the material removal in MRF and how the measured ratio of drag force to normal force Fd/Fn, equivalent to coefficient of friction, is related to material removal. This work studies, for the first time for MRF, the normal force and the measured ratio Fd/Fn as a function of material mechanical properties. Experimental data were obtained by taking spots on a variety of materials includingmore » optical glasses and hard ceramics with a spot-taking machine (STM). Drag force and normal force were measured with a dual load cell. Drag force decreases linearly with increasing material hardness. In contrast, normal force increases with hardness for glasses, saturating at high hardness values for ceramics. Volumetric removal rate decreases with normal force across all materials. The measured ratio Fd/Fn shows a strong negative linear correlation with material hardness. Hard materials exhibit a low “coefficient of friction”. The volumetric removal rate increases with the measured ratio Fd/Fn which is also correlated with shear stress, indicating that the measured ratio Fd/Fn is a useful measure of material removal in MRF.« less
Visual and psychological stress during computer work in healthy, young females-physiological responses.

PubMed

Mork, Randi; Falkenberg, Helle K; Fostervold, Knut Inge; Thorud, Hanne Mari S

2018-05-30

Among computer workers, visual complaints, and neck pain are highly prevalent. This study explores how occupational simulated stressors during computer work, like glare and psychosocial stress, affect physiological responses in young females with normal vision. The study was a within-subject laboratory experiment with a counterbalanced, repeated design. Forty-three females performed four 10-min computer-work sessions with different stress exposures: (1) minimal stress; (2) visual stress (direct glare); (3) psychological stress; and (4) combined visual and psychological stress. Muscle activity and muscle blood flow in trapezius, muscle blood flow in orbicularis oculi, heart rate, blood pressure, blink rate and postural angles were continuously recorded. Immediately after each computer-work session, fixation disparity was measured and a questionnaire regarding perceived workstation lighting and stress was completed. Exposure to direct glare resulted in increased trapezius muscle blood flow, increased blink rate, and forward bending of the head. Psychological stress induced a transient increase in trapezius muscle activity and a more forward-bent posture. Bending forward towards the computer screen was correlated with higher productivity (reading speed), indicating a concentration or stress response. Forward bent posture was also associated with changes in fixation disparity. Furthermore, during computer work per se, trapezius muscle activity and blood flow, orbicularis oculi muscle blood flow, and heart rate were increased compared to rest. Exposure to glare and psychological stress during computer work were shown to influence the trapezius muscle, posture, and blink rate in young, healthy females with normal binocular vision, but in different ways. Accordingly, both visual and psychological factors must be taken into account when optimizing computer workstations to reduce physiological responses that may cause excessive eyestrain and musculoskeletal load.
The effects of castration, preslaughter stress and zeranol implants on beef: Part 2-Cooking properties and flavor of loin steaks from bovine males.

PubMed

Jeremiah, L E; Newman, J A; Tong, A K; Gibson, L L

1988-01-01

A total of 144 male crossbred calves were allocated to four castration or implant treatments (unimplanted bulls; unimplanted steers; bulls implanted with zeranol at 100 days of age and reimplanted at intervals of 69, 93 and 56 days thereafter; bulls implanted with zeranol at 168 days of age and reimplanted at intervals of 93 and 56 days thereafter) and two preslaughter shipping treatments (minimum preslaughter stress, with cattle shipped and slaughtered within 4 h of leaving the feedlot pen; normal preslaughter stress, with cattle mixed, trucked 160 km, and slaughtered up to 24 h after leaving the feedlot pen). These cattle were slaughtered and striploin steaks were removed after 6 days of post-mortem aging. Evaluations of these steaks were then conducted using both an experienced laboratory taste panel and a highly trained professional flavor profile panel. Results indicated that: (1) steaks from bulls had higher cooking losses than their counterparts from steers, when minimum preslaughter stress was applied; and required longer cooking times under both preslaughter handling treatments; (2) steaks from unimplanted bulls had greater cooking losses and required longer cooking times than their counterparts from implanted bulls under normal preslaughter stress, but not under minimum preslaughter stress; (3) higher proportions of bull steaks than steer steaks contained inappropriate flavor character notes, under both minimum and normal levels of preslaughter stress; (4) both castration and preslaughter handling affected the intensity and order of appearance of specific flavor character notes; (5) the level of preslaughter stress significantly influenced the detection of specific flavor character notes in steaks from both bulls and steers; (6) steaks from steers under minimum preslaughter stress were rated significantly higher in flavor amplitude than their counterparts from bulls when under normal preslaughter stress, and steaks from steers under minimum preslaughter stress received higher flavor desirability scores than steaks from bulls under both minimum and normal preslaughter stress; (7) zeranol implants influenced the appearance and the order of appearance of specific flavor character notes under both minimum and normal levels of preslaughter stress; (8) both zeranol implants and the length of time animals were implanted appeared to increase the intensity of certain inappropriate character notes, and to decrease the intensity of certain appropriate character notes; (9) steaks from implanted bulls received lower flavor amplitude ratings than their counterparts from unimplanted bulls under normal preslaughter stress, but not under minimum preslaughter stress; (10) the level of preslaughter stress influenced both the appearance and order of appearance of specific flavor character notes in both implanted and unimplanted bull steaks; (11) the intensities of certain flavor character notes were influenced by differences in the level of preslaughter stress in both implanted and unimplanted bull steaks, and higher levels usually resulted in inappropriate character notes being more intense; (12) steaks from bulls in both implant groups received lower flavor amplitude ratings when normal preslaughter stress was applied, clearly indicating the deleterious effect of the combination of zeranol implants and normal preslaughter stress on bull beef flavor; and (13) the deleterious effect of the combination of zeranol implants and normal preslaughter stress on bull beef flavor could not be explaind on the basis of greater production of 'dark cutting' beef. Copyright © 1988. Published by Elsevier Ltd.
Resveratrol alleviates diabetes-induced testicular dysfunction by inhibiting oxidative stress and c-Jun N-terminal kinase signaling in rats

DOE Office of Scientific and Technical Information (OSTI.GOV)

Faid, Iman; Al-Hussaini, Heba; Kilarkaje, Narayana, E-mail: knarayana@hsc.edu.kw

Diabetes adversely affects reproductive functions in humans and animals. The present study investigated the effects of Resveratrol on diabetes-induced alterations in oxidative stress, c-Jun N-terminal kinase (JNK) signaling and apoptosis in the testis. Adult male Wistar rats (13–15 weeks; n = 6/group) were segregated into 1) normal control, 2) Resveratrol-treated (5 mg/kg; ip; given during last 3 weeks), 3) Streptozotocin-induced diabetic and, 4) Resveratrol-treated diabetic groups, and euthanized on day 42 after the confirmation of diabetes. Resveratrol did not normalize blood glucose levels in diabetic rats. Resveratrol supplementation recovered diabetes-induced decreases in reproductive organ weights, sperm count and motility, intra-testicularmore » levels of superoxide dismutase, catalase, and glutathione peroxidase and an increase in 4-hydroxynonenal activities (P < 0.05). Resveratrol also recovered diabetes-induced increases in JNK signaling pathway proteins, namely, ASK1 (apoptosis signal-regulating kinase 1), JNKs (46 and 54 kDa isoforms) and p-JNK to normal control levels (P < 0.05). Interestingly, the expression of a down-stream target of ASK1, MKK4 (mitogen-activated protein kinase kinase 4) and its phosphorylated form (p-MKK4) did not change in experimental groups. Resveratrol inhibited diabetes-induced increases in AP-1 (activator protein-1) components, c-Jun and ATF2 (activating transcription factor 2), but not their phosphorylated forms, to normal control levels (P < 0.05). Further, Resveratrol inhibited diabetes-induced increase in cleaved-caspase-3 to normal control levels. In conclusion, Resveratrol alleviates diabetes-induced apoptosis in testis by modulating oxidative stress, JNK signaling pathway and caspase-3 activities, but not by inhibiting hyperglycemia, in rats. These results suggest that Resveratrol supplementation may be a useful strategy to treat diabetes-induced testicular dysfunction. - Highlights: • Resveratrol up-regulates glutathione peroxidase and catalase levels in the testis. • Diabetes up-regulates oxidative stress and JNK pathway in the testis. • Resveratrol inhibits diabetes-induced oxidative stress and JNK pathway. • Resveratrol mitigates diabetes-induced apoptosis of testicular cells. • Resveratrol treatment alleviates diabetes-induced testicular dysfunction.« less
Increase of Chamazulene and α-Bisabolol Contents of the Essential Oil of German Chamomile (Matricaria chamomila L.) Using Salicylic Acid Treatments under Normal and Heat Stress Conditions

PubMed Central

Ghasemi, Mojtaba; Babaeian Jelodar, Nadali; Modarresi, Mohammad; Bagheri, Nadali; Jamali, Abbas

2016-01-01

The chamazulene and α-(−)-bisabolol contents and quality of the chamomile oil are affected by genetic background and environmental conditions. Salicylic acid (SA), as a signaling molecule, plays a significant role in the plant physiological processes. The aim of this study was to evaluate the chemical profile, quantity, and improve the essential oil quality as a consequence of the increase of chamazulene and α-(−)-bisabol using salicylic acid under normal and heat stress conditions by the gas chromatography-mass spectrometry (GC-MS) technique. The factorial experiments were carried out during the 2011–2012 hot season using a randomized complete block design with three replications. The factors include four salicylic acid concentrations (0 (control), 10, 25 and 100 mg·L−1), and three chamomile cultivars (Bushehr, Bona, Bodegold) were sown on two different planting dates under field conditions. Fourteen compounds were identified from the extracted oil of the samples treated with salicylic acid under normal and heat stress conditions. The major identified oil compositions from chamomile cultivars treated with salicylic acid were chamazulene, α-(−)-bisabolol, bisabolone oxide, β-farnesene, en-yn-dicycloether, and bisabolol oxide A and B. Analysis of variance showed that the simple effects (environmental conditions, cultivar and salicylic acid) and their interaction were significant on all identified compounds, but the environmental conditions had no significant effect on bisabolol oxide A. The greatest amount of chamazulene obtained was 6.66% at the concentration of 10 mg·L−1 SA for the Bona cultivar under heat stress conditions, whereas the highest α-(−)-bisabolol amount attained was 3.41% at the concentration of 100 mg·L−1 SA for the Bona cultivar under normal conditions. The results demonstrated that the application of exogenous salicylic acid increases the quantity and essential oil quality as a consequence of the increase of chamazulene and α-(−)-bisabolol under normal and heat stress conditions. PMID:28231151
Cytoskeletal role in the transition from compensated to decompensated hypertrophy during adult canine left ventricular pressure overloading

NASA Technical Reports Server (NTRS)

Tagawa, H.; Koide, M.; Sato, H.; Zile, M. R.; Carabello, B. A.; Cooper, G. 4th

1998-01-01

Increased microtubule density causes cardiocyte contractile dysfunction in right ventricular (RV) pressure-overload hypertrophy, and these linked phenotypic and contractile abnormalities persist and progress during the transition to failure. Although more severe in cells from failing than hypertrophied RVs, the mechanical defects are normalized in each case by microtubule depolymerization. To define the role of increased microtubule density in left ventricular (LV) pressure-overload hypertrophy and failure, in a given LV we examined ventricular mechanics, sarcomere mechanics, and free tubulin and microtubule levels in control dogs and in dogs with aortic stenosis both with LV hypertrophy alone and with initially compensated hypertrophy that had progressed to LV muscle failure. In comparing initial values with those at study 8 weeks later, dogs with hypertrophy alone had a very substantial increase in LV mass but preservation of a normal ejection fraction and mean systolic wall stress. Dogs with hypertrophy and associated failure had a substantial but lesser increase in LV mass and a reduction in ejection fraction, as well as a marked increase in mean systolic wall stress. Cardiocyte contractile function was equivalent, and unaffected by microtubule depolymerization, in cells from control LVs and those with compensated hypertrophy. In contrast, cardiocyte contractile function in cells from failing LVs was quite depressed but was normalized by microtubule depolymerization. Microtubules were increased only in failing LVs. These contractile and cytoskeletal changes, when assayed longitudinally in a given dog by biopsy, appeared in failing ventricles only when wall stress began to increase and function began to decrease. Thus, the microtubule-based cardiocyte contractile dysfunction characteristic of pressure-hypertrophied myocardium, originally described in the RV, obtains equally in the LV but is shown here to have a specific association with increased wall stress.
Numerical analysis of stress effects on Frank loop evolution during irradiation in austenitic Fe&z.sbnd;Cr&z.sbnd;Ni alloy

NASA Astrophysics Data System (ADS)

Tanigawa, Hiroyasu; Katoh, Yutai; Kohyama, Akira

1995-08-01

Effects of applied stress on early stages of interstitial type Frank loop evolution were investigated by both numerical calculation and irradiation experiments. The final objective of this research is to propose a comprehensive model of complex stress effects on microstructural evolution under various conditions. In the experimental part of this work, the microstructural analysis revealed that the differences in resolved normal stress caused those in the nucleation rates of Frank loops on {111} crystallographic family planes, and that with increasing external applied stress the total nucleation rate of Frank loops was increased. A numerical calculation was carried out primarily to evaluate the validity of models of stress effects on nucleation processes of Frank loop evolution. The calculation stands on rate equuations which describe evolution of point defects, small points defect clusters and Frank loops. The rate equations of Frank loop evolution were formulated for {111} planes, considering effects of resolved normal stress to clustering processes of small point defects and growth processes of Frank loops, separately. The experimental results and the predictions from the numerical calculation qualitatively coincided well with each other.
Stress distribution in two-dimensional silos

NASA Astrophysics Data System (ADS)

Blanco-Rodríguez, Rodolfo; Pérez-Ángel, Gabriel

2018-01-01

Simulations of a polydispersed two-dimensional silo were performed using molecular dynamics, with different numbers of grains reaching up to 64 000, verifying numerically the model derived by Janssen and also the main assumption that the walls carry part of the weight due to the static friction between grains with themselves and those with the silo's walls. We vary the friction coefficient, the radii dispersity, the silo width, and the size of grains. We find that the Janssen's model becomes less relevant as the the silo width increases since the behavior of the stresses becomes more hydrostatic. Likewise, we get the normal and tangential stress distribution on the walls evidencing the existence of points of maximum stress. We also obtained the stress matrix with which we observe zones of concentration of load, located always at a height around two thirds of the granular columns. Finally, we observe that the size of the grains affects the distribution of stresses, increasing the weight on the bottom and reducing the normal stress on the walls, as the grains are made smaller (for the same total mass of the granulate), giving again a more hydrostatic and therefore less Janssen-type behavior for the weight of the column.
[Biomechanical analysis on healing process of sagittal fracture of the mandibular condyle after rigid fixation].

PubMed

Jing, Jie; Qu, Ai-li; Ding, Xiao-mei; Hei, Yu-na

2015-04-01

To analyze the biomechanical healing process on rigid fixation of sagittal fracture of the mandibular condyle (SFMC), and to provide guidelines for surgical treatment. Three-dimensional finite element model (3D-FEAM) of mandible and condyle was established. The right condyle was simulated as SFMC with 0.1 mm space across the condyle length ways. The 3D-FEAM of rigid fixation was established. The biomechanical factors such as stress distribution of condylar surface, displacement around fracture, stress on the plate and stress shielding were calculated during 0, 4, 8 and 12-week after rigid fixation. The maximum equivalent stress of normal condyle was located at the area of middle 1/3 of condylar neck. The maximum equivalent stress at 0-week after fixation was 23 times than that on normal condyle. They were located at the condylar stump and the plate near inferior punctual areas of fracture line. There were little stress on the other areas. The maximum equivalent stress at 4, 8 and 12-week was approximately 6 times than that on normal condyle. They were located at the areas same as the area at 0-week. There were little stress on the other areas at the condyle. The maximum total displacement and maximum total corner were increased 0.57-0.75 mm and 0.01-0.09° respectively during healing process. The maximum equivalent stress at 0-week on the condylar trump was 5-6 times compared with that at 4, 8, and 12-week. The maximum equivalent stress, maximum total displacement and maximum total corner on the fractured fragment were not changed significantly during healing process. The maximum equivalent stress at 0-week on the plate was 7-9 times compared with that at 4, 8, 12-week. The stress of the condyle and stress shielding of the plate may be the reasons of absorbing and rebuilding on the condyle in healing process of SFMC. The biomechanical parameters increase obviously at 4-week after fixation. Elastic intermaxillary traction is necessary to decrease total displacement and total corner of the condyle, and liquid diet is necessary to decrease equivalent stress within 4 weeks. Rehabilitation training should be used to recover TMJ functions after 4 weeks because the condyle and mandible have the ability to carry out normal functions.
Strigolactone analogues induce apoptosis through activation of p38 and the stress response pathway in cancer cell lines and in conditionally reprogrammed primary prostate cancer cells.

PubMed

Pollock, Claire B; McDonough, Sara; Wang, Victor S; Lee, Hyojung; Ringer, Lymor; Li, Xin; Prandi, Cristina; Lee, Richard J; Feldman, Adam S; Koltai, Hinanit; Kapulnik, Yoram; Rodriguez, Olga C; Schlegel, Richard; Albanese, Christopher; Yarden, Ronit I

2014-03-30

Strigolactones are a novel class of plant hormones produced in roots and regulate shoot and root development. We have previously shown that synthetic strigolactone analogues potently inhibit growth of breast cancer cells and breast cancer stem cells. Here we show that strigolactone analogues inhibit the growth and survival of an array of cancer-derived cell lines representing solid and non-solid cancer cells including: prostate, colon, lung, melanoma, osteosarcoma and leukemic cell lines, while normal cells were minimally affected. Treatment of cancer cells with strigolactone analogues was hallmarked by activation of the stress-related MAPKs: p38 and JNK and induction of stress-related genes; cell cycle arrest and apoptosis evident by increased percentages of cells in the sub-G1 fraction and Annexin V staining. In addition, we tested the response of patient-matched conditionally reprogrammed primary prostate normal and cancer cells. The tumor cells exhibited significantly higher sensitivity to the two most potent SL analogues with increased apoptosis confirmed by PARP1 cleavage compared to their normal counterpart cells. Thus, Strigolactone analogues are promising candidates for anticancer therapy by their ability to specifically induce cell cycle arrest, cellular stress and apoptosis in tumor cells with minimal effects on growth and survival of normal cells.
A preclinical model of binge eating elicited by yo-yo dieting and stressful exposure to food: effect of sibutramine, fluoxetine, topiramate, and midazolam.

PubMed

Cifani, Carlo; Polidori, Carlo; Melotto, Sergio; Ciccocioppo, Roberto; Massi, Maurizio

2009-05-01

Preclinical models are needed to investigate the neurobiology and psychobiology of binge eating and to identify innovative pharmacotherapeutic strategies. A modification of the model based on the combination of cyclic caloric restrictions and acute stress was developed to further increase its face validity and reliability and, for the first time, to assess its predictive value. Four groups of female rats were employed: group 1 was normally fed and not stressed on the test day (25th); group 2 was fed normally but was exposed to an acute stress on day 25; group 3 was exposed to three cycles (4 days 66% of chow intake + 4 days food ad libitum) of yo-yo dieting but not stressed; and group 4 was exposed to cyclic yo-yo dieting and then stressed. All groups were fed highly palatable food (HPF) for 2 h on days 5-6 and 13-14. Acute stress was elicited by exposing rats to HPF, but preventing them from access to it for 15 min. The combination of cyclic food restriction and stressful exposure to food markedly increased HPF intake. Sibutramine and fluoxetine inhibited food intake in all conditions. Topiramate selectively inhibited compulsive HPF intake in rats submitted to caloric restriction and stress. Midazolam increased HPF intake. Pharmacological results suggest that this model, in addition to face validity as an isomorphic model of human binge eating, is endowed with good predictive validity.
Childhood socioeconomic status and serotonin transporter gene polymorphism enhance cardiovascular reactivity to mental stress.

PubMed

Williams, Redford B; Marchuk, Douglas A; Siegler, Ilene C; Barefoot, John C; Helms, Michael J; Brummett, Beverly H; Surwit, Richard S; Lane, James D; Kuhn, Cynthia M; Gadde, Kishore M; Ashley-Koch, Allison; Svenson, Ingrid K; Schanberg, Saul M

2008-01-01

To test the hypothesis that low socioeconomic status (SES) and the 5HTTLPR L allele are associated with increased cardiovascular reactivity (CVR) to stress in a larger sample and that SES and 5HTTLPR genotypes interact to enhance CVR to stress. CVR to mental stress has been proposed as one mechanism linking stress to the pathogenesis of cardiovascular disease. The more transcriptionally efficient long (L) allele of a polymorphism of the serotonin transporter gene promoter (5HTTLPR) has been found associated with increased risk of myocardial infarction. We found the long allele associated with larger CVR to mental stress in a preliminary study of 54 normal volunteers. Subjects included 165 normal community volunteers stratified for race, gender, and SES, who underwent mental stress testing. Childhood SES as indexed by Father's Education Level was associated with larger systolic blood pressure (SBP) (p < .05) and diastolic blood pressure (DBP) (p = .01) responses to mental stress. The L allele was associated with larger SBP (p = .04), DBP (p < .0001), and heart rate (p = .04) responses to mental stress compared with the short (S) allele. Subjects with the SS genotype and high Father's Education exhibited smaller SBP (5.2 mm Hg) and DBP (2.9 mm Hg) responses than subjects with LL genotype and low Father's Education (SBP = 13.3 mm Hg, p = .002; DBP = 9.7 mm Hg, p < .0001). Both the 5HTTLPR long allele and low SES, particularly during childhood, are associated with increased CVR to mental stress, which could account, at least in part, for the increased cardiovascular disease risk associated with these characteristics. If confirmed in further research, these characteristics could be used to identify persons who might benefit from preventive interventions.

Calnexin, an ER stress-induced protein, is a prognostic marker and potential therapeutic target in colorectal cancer.

PubMed

Ryan, Deborah; Carberry, Steven; Murphy, Áine C; Lindner, Andreas U; Fay, Joanna; Hector, Suzanne; McCawley, Niamh; Bacon, Orna; Concannon, Caoimhin G; Kay, Elaine W; McNamara, Deborah A; Prehn, Jochen H M

2016-07-01

Colorectal cancer (CRC) is a leading cause of cancer mortality in the Western world and commonly treated with genotoxic chemotherapy. Stress in the endoplasmic reticulum (ER) was implicated to contribute to chemotherapeutic resistance. Hence, ER stress related protein may be of prognostic or therapeutic significance. The expression levels of ER stress proteins calnexin, calreticulin, GRP78 and GRP94 were determined in n = 23 Stage II and III colon cancer fresh frozen tumour and matched normal tissue samples. Data were validated in a cohort of n = 11 rectal cancer patients treated with radiochemotherapy in the neoadjuvant setting. The calnexin gene was silenced using siRNA in HCT116 cells. There were no increased levels of ER stress proteins in tumour compared to matched normal tissue samples in Stage II or III CRC. However, increased calnexin protein levels were predictive of poor clinical outcome in the patient cohort. Data were validated in the rectal cancer cohort treated in the neoadjuvant setting. Calnexin gene-silencing significantly reduced cell survival and increased cancer cell susceptibility to 5FU chemotherapy. Increased tumour protein levels of calnexin may be of prognostic significance in CRC, and calnexin may represent a potential target for future therapies.
Elasto-optics in double-coated optical fibers induced by axial strain and hydrostatic pressure.

PubMed

Yang, Yu-Ching; Lee, Haw-Long; Chou, Huann-Ming

2002-04-01

Stresses, microbending loss, and refractive-index changes induced simultaneously by axial strain and hydrostatic pressure in double-coated optical fibers are analyzed. The lateral pressure and normal stresses in the optical fiber, primary coating, and secondary coating are derived. Also presented are the microbending loss and refractive-index changes in the glass fiber. The normal stresses are affected by axial strain, hydrostatic pressure, material properties, and thickness of the primary and secondary coatings. It is found that microbending loss decreases with increasing thickness, the Young's modulus, and the Poisson's ratio of the secondary coating but increases with the increasing Young's modulus and Poisson's ratio of the primary coating. Similarly, changes in refractive index in the glass fiber decrease with the increasing Young's modulus and Poisson's ratio of the secondary coating but increase with the increasing Young's modulus and Poisson's ratio of the primary coating. Therefore, to minimize microbending loss induced simultaneously by axial strain and hydrostatic pressure in the glass fiber, the polymeric coatings should be suitably selected. An optimal design procedure is also indicated.
Friction coefficient and effective interference at the implant-bone interface.

PubMed

Damm, Niklas B; Morlock, Michael M; Bishop, Nicholas E

2015-09-18

Although the contact pressure increases during implantation of a wedge-shaped implant, friction coefficients tend to be measured under constant contact pressure, as endorsed in standard procedures. Abrasion and plastic deformation of the bone during implantation are rarely reported, although they define the effective interference, by reducing the nominal interference between implant and bone cavity. In this study radial forces were analysed during simulated implantation and explantation of angled porous and polished implant surfaces against trabecular bone specimens, to determine the corresponding friction coefficients. Permanent deformation was also analysed to determine the effective interference after implantation. For the most porous surface tested, the friction coefficient initially increased with increasing normal contact stress during implantation and then decreased at higher contact stresses. For a less porous surface, the friction coefficient increased continually with normal contact stress during implantation but did not reach the peak magnitude measured for the rougher surface. Friction coefficients for the polished surface were independent of normal contact stress and much lower than for the porous surfaces. Friction coefficients were slightly lower for pull-out than for push-in for the porous surfaces but not for the polished surface. The effective interference was as little as 30% of the nominal interference for the porous surfaces. The determined variation in friction coefficient with radial contact force, as well as the loss of interference during implantation will enable a more accurate representation of implant press-fitting for simulations. Copyright © 2015 Elsevier Ltd. All rights reserved.
Combining Earthquake Focal Mechanism Inversion and Coulomb Friction Law to Yield Tectonic Stress Magnitudes in Strike-slip Faulting Regime

NASA Astrophysics Data System (ADS)

Soh, I.; Chang, C.

2017-12-01

The techniques for estimating present-day stress states by inverting multiple earthquake focal mechanism solutions (FMS) provide orientations of the three principal stresses and their relative magnitudes. In order to estimate absolute magnitudes of the stresses that are generally required to analyze faulting mechanics, we combine the relative stress magnitude parameter (R-value) derived from the inversion process and the concept of frictional equilibrium of stress state defined by Coulomb friction law. The stress inversion in Korean Peninsula using 152 FMS data (magnitude≥2.5) conducted at regularly spaced grid points yields a consistent strike-slip faulting regime in which the maximum (S1) and the minimum (S3) principal stresses act in horizontal planes (with an S1 azimuth in ENE-WSW) and the intermediate principal stress (S2) close to vertical. However, R-value varies from 0.28 to 0.75 depending on locations, systematically increasing eastward. Based on the assumptions that the vertical stress is lithostatic, pore pressure is hydrostatic, and the maximum differential stress (S1-S3) is limited by Byerlee's friction of optimally oriented faults for slip, we estimate absolute magnitudes of the two horizontal principal stresses using R-value. As R-value increases, so do the magnitudes of the horizontal stresses. Our estimation of the stress magnitudes shows that the maximum horizontal principal stress (S1) normalized by vertical stress tends to increase from 1.3 in the west to 1.8 in the east. The estimated variation of stress magnitudes is compatible with distinct clustering of faulting types in different regions. Normal faulting events are densely populated in the west region where the horizontal stress is relatively low, whereas numerous reverse faulting events prevail in the east offshore where the horizontal stress is relatively high. Such a characteristic distribution of distinct faulting types in different regions can only be explained in terms of stress magnitude variation.
Effect of restoration volume on stresses in a mandibular molar: a finite element study.

PubMed

Wayne, Jennifer S; Chande, Ruchi; Porter, H Christian; Janus, Charles

2014-10-01

There can be significant disagreement among dentists when planning treatment for a tooth with a failing medium-to-large--sized restoration. The clinician must determine whether the restoration should be replaced or treated with a crown, which covers and protects the remaining weakened tooth structure during function. The purpose of this study was to evaluate the stresses generated in different sized amalgam restorations via a computational modeling approach and reveal whether a predictable pattern emerges. A computer tomography scan was performed of an extracted mandibular first molar, and the resulting images were imported into a medical imaging software package for tissue segmentation. The software was used to separate the enamel, dentin, and pulp cavity through density thresholding and surface rendering. These tissue structures then were imported into 3-dimensional computer-aided design software in which material properties appropriate to the tissues in the model were assigned. A static finite element analysis was conducted to investigate the stresses that result from normal occlusal forces. Five models were analyzed, 1 with no restoration and 4 with increasingly larger restoration volume proportions: a normal-sized tooth, a small-sized restoration, 2 medium-sized restorations, and 1 large restoration as determined from bitewing radiographs and occlusal surface digital photographs. The resulting von Mises stresses for dentin-enamel of the loaded portion of the tooth grew progressively greater as the size of the restoration increased. The average stress in the normal, unrestored tooth was 4.13 MPa, whereas the smallest restoration size increased this stress to 5.52 MPa. The largest restoration had a dentin-enamel stress of 6.47 MPa. A linear correlation existed between restoration size and dentin-enamel stress, with an R(2) of 0.97. A larger restoration volume proportion resulted in higher dentin-enamel stresses under static loading. A comparison of the von Mises stresses to the yield strengths of the materials revealed a relationship between a tooth's restoration volume proportion and the potential for failure, although factors other than restoration volume proportion may also impact the stresses generated in moderate-sized restorations. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.
Early Mitochondrial Adaptations in Skeletal Muscle to Diet-Induced Obesity Are Strain Dependent and Determine Oxidative Stress and Energy Expenditure But Not Insulin Sensitivity

PubMed Central

Sena, Sandra; Sloan, Crystal; Tebbi, Ali; Han, Yong Hwan; O'Neill, Brian T.; Cooksey, Robert C.; Jones, Deborah; Holland, William L.; McClain, Donald A.; Abel, E. Dale

2012-01-01

This study sought to elucidate the relationship between skeletal muscle mitochondrial dysfunction, oxidative stress, and insulin resistance in two mouse models with differential susceptibility to diet-induced obesity. We examined the time course of mitochondrial dysfunction and insulin resistance in obesity-prone C57B and obesity-resistant FVB mouse strains in response to high-fat feeding. After 5 wk, impaired insulin-mediated glucose uptake in skeletal muscle developed in both strains in the absence of any impairment in proximal insulin signaling. Impaired mitochondrial oxidative capacity preceded the development of insulin resistant glucose uptake in C57B mice in concert with increased oxidative stress in skeletal muscle. By contrast, mitochondrial uncoupling in FVB mice, which prevented oxidative stress and increased energy expenditure, did not prevent insulin resistant glucose uptake in skeletal muscle. Preventing oxidative stress in C57B mice treated systemically with an antioxidant normalized skeletal muscle mitochondrial function but failed to normalize glucose tolerance and insulin sensitivity. Furthermore, high fat-fed uncoupling protein 3 knockout mice developed increased oxidative stress that did not worsen glucose tolerance. In the evolution of diet-induced obesity and insulin resistance, initial but divergent strain-dependent mitochondrial adaptations modulate oxidative stress and energy expenditure without influencing the onset of impaired insulin-mediated glucose uptake. PMID:22510273
Numerical simulation of the stress distribution in a coal mine caused by a normal fault

NASA Astrophysics Data System (ADS)

Zhang, Hongmei; Wu, Jiwen; Zhai, Xiaorong

2017-06-01

Luling coal mine was used for research using FLAC3D software to analyze the stress distribution characteristics of the two sides of a normal fault zone with two different working face models. The working faces were, respectively, on the hanging wall and the foot wall; the two directions of mining were directed to the fault. The stress distributions were different across the fault. The stress was concentrated and the influenced range of stress was gradually larger while the working face was located on the hanging wall. The fault zone played a negative effect to the stress transmission. Obviously, the fault prevented stress transmission, the stress concentrated on the fault zone and the hanging wall. In the second model, the stress on the two sides decreased at first, but then increased continuing to transmit to the hanging wall. The concentrated stress in the fault zone decreased and the stress transmission was obvious. Because of this, the result could be used to minimize roadway damage and lengthen the time available for coal mining by careful design of the roadway and working face.
Combined mode I stress intensity factors of slanted cracks

NASA Astrophysics Data System (ADS)

Ismail, A. E.; Rahman, M. Q. Abdul; Ghazali, M. Z. Mohd; Zulafif Rahim, M.; Rasidi Ibrahim, M.; Fahrul Hassan, Mohd; Nor, Nik Hisyamudin Muhd; Ariffin, A. M. T.; Zaini Yunos, Muhamad

2017-08-01

The solutions of stress intensity factors (SIFs) for slanted cracks in plain strain plate are hard to find in open literature. There are some previous solutions of SIFs available, however the studies are not completed except for the case of plain stress. The slanted cracks are modelled numerically using ANSYS finite element program. There are ten slanted angles and seven relative crack depths are used and the plate contains cracks which is assumed to fulfil the plain strain condition. The plate is then stressed under tension and bending loading and the SIFs are determined according to the displacement extrapolation method. Based on the numerical analysis, both slanted angles and relative crack length, a/L played an important role in determining the modes I and II SIFs. As expected the SIFs increased when a/L is increased. Under tension force, the introduction of slanted angles increased the SIFs. Further increment of angles reduced the SIFs however they are still higher than the SIFs obtained using normal cracks. Under bending moment, the present of slanted angles are significantly reduced the SIFs compared with the normal cracks. Under similar loading, mode II SIFs increased as function of a/L and slanted angles where increasing such parameters increasing the mode II SIFs.
Ecological comparison of cellular stress responses among populations - normalizing RT-qPCR values to investigate differential environmental adaptations.

PubMed

Koenigstein, Stefan; Pöhlmann, Kevin; Held, Christoph; Abele, Doris

2013-05-16

Rising temperatures and other environmental factors influenced by global climate change can cause increased physiological stress for many species and lead to range shifts or regional population extinctions. To advance the understanding of species' response to change and establish links between individual and ecosystem adaptations, physiological reactions have to be compared between populations living in different environments. Although changes in expression of stress genes are relatively easy to quantify, methods for reliable comparison of the data remain a contentious issue. Using normalization algorithms and further methodological considerations, we compare cellular stress response gene expression levels measured by RT-qPCR after air exposure experiments among different subpopulations of three species of the intertidal limpet Nacella. Reference gene assessment algorithms reveal that stable reference genes can differ among investigated populations and / or treatment groups. Normalized expression values point to differential defense strategies to air exposure in the investigated populations, which either employ a pronounced cellular stress response in the inducible Hsp70 forms, or exhibit a comparatively high constitutive expression of Hsps (heat shock proteins) while showing only little response in terms of Hsp induction. This study serves as a case study to explore the methodological prerequisites of physiological stress response comparisons among ecologically and phylogenetically different organisms. To improve the reliability of gene expression data and compare the stress responses of subpopulations under potential genetic divergence, reference gene stability algorithms are valuable and necessary tools. As the Hsp70 isoforms have been shown to play different roles in the acute stress responses and increased constitutive defenses of populations in their different habitats, these comparative studies can yield insight into physiological strategies of adaptation to environmental stress and provide hints for the prudent use of the cellular stress response as a biomarker to study environmental stress and stress adaptation of populations under changing environmental conditions.
Ecological comparison of cellular stress responses among populations – normalizing RT-qPCR values to investigate differential environmental adaptations

PubMed Central

2013-01-01

Background Rising temperatures and other environmental factors influenced by global climate change can cause increased physiological stress for many species and lead to range shifts or regional population extinctions. To advance the understanding of species’ response to change and establish links between individual and ecosystem adaptations, physiological reactions have to be compared between populations living in different environments. Although changes in expression of stress genes are relatively easy to quantify, methods for reliable comparison of the data remain a contentious issue. Using normalization algorithms and further methodological considerations, we compare cellular stress response gene expression levels measured by RT-qPCR after air exposure experiments among different subpopulations of three species of the intertidal limpet Nacella. Results Reference gene assessment algorithms reveal that stable reference genes can differ among investigated populations and / or treatment groups. Normalized expression values point to differential defense strategies to air exposure in the investigated populations, which either employ a pronounced cellular stress response in the inducible Hsp70 forms, or exhibit a comparatively high constitutive expression of Hsps (heat shock proteins) while showing only little response in terms of Hsp induction. Conclusions This study serves as a case study to explore the methodological prerequisites of physiological stress response comparisons among ecologically and phylogenetically different organisms. To improve the reliability of gene expression data and compare the stress responses of subpopulations under potential genetic divergence, reference gene stability algorithms are valuable and necessary tools. As the Hsp70 isoforms have been shown to play different roles in the acute stress responses and increased constitutive defenses of populations in their different habitats, these comparative studies can yield insight into physiological strategies of adaptation to environmental stress and provide hints for the prudent use of the cellular stress response as a biomarker to study environmental stress and stress adaptation of populations under changing environmental conditions. PMID:23680017
An Experimental Evaluation of Adaptogenic Potential of Standardized Epipremnum Aureum Leaf Extract.

PubMed

Das, Sreemoy Kanti; Sengupta, Pinaki; Mustapha, Mohd Shahimi; Sarker, Md Moklesur Rahman

2017-01-01

Stress is a normal part of everyday life but chronic stress can lead to a variety of stress-related illnesses including hypertension, anxiety, and depression. In the present investigation, standardized leaf extract of Epipremnumaureum was evaluated for its anti-stress potential. For the evaluation of anti-stress activity, groups of mice ( n = 6) were subjected to forced swim stress and anoxic stress tolerance test in mice 1h after daily treatment of E.aureumextract . Diazepam (5 mg/kg) was taken as a reference standard. Urinary vanillylmandelic acid (VMA) and ascorbic acid were selected as noninvasive biomarkers to assess the anti-stress activity and plasma cortisol, blood ascorbic acid, and weight of adrenal were measured. The 24 h urinary excretion of VMA and ascorbic acid were determined by spectrophotometric methods in all groups under normal and stressed conditions. The hematological parameters (neutrophils, lymphocytes, and eosinophils) were also determined. Administration of E.aureumat doses of 400 and 600 mg/kg wasfound to be effective in inhibiting the stress induced urinary biochemical changes in a dose-dependent manner. Treatment with E. aureum extract prevents the rise in blood ascorbic acid and plasma cortisol. Moreover, the extract prevented the increase in weight of adrenal gland also significantly increased the anoxia stress tolerance time. Dose-dependent significant reduction in white blood cell count was observed in anoxic stress tolerance test as compared to stressed group. Hence, the present study provides scientific support for the positiveadaptogenic effect of E. aureum extract.
The influence of emotional stress on Doppler-derived aortic peak velocity in boxer dogs.

PubMed

Pradelli, D; Quintavalla, C; Crosta, M C; Mazzoni, L; Oliveira, P; Scotti, L; Brambilla, P; Bussadori, C

2014-01-01

Subaortic stenosis (SAS) is a common congenital heart disease in Boxers. Doppler-derived aortic peak velocity (AoPV) is a diagnostic criterion for the disease. To investigate the influence of emotional stress during echocardiographic examination on AoPV in normal and SAS-affected Boxers. To evaluate the effects of aortic root diameters on AoPV in normal Boxers. DOGS: Two hundred and fifteen normal and 19 SAS-affected Boxers. The AoPV was recorded at the beginning of echocardiographic examination (T0), and when the emotional stress of the dog was assumed to decrease based on behavioral parameters and heart rate (T1). AoPV0-AoPV1 was calculated. In normal dogs, stroke volume index was calculated at T0 and T1. Aortic root diameters were measured and their relationship with AoPV and AoPV0-AoPV1 was evaluated. In normal dogs, AoPV was higher at T0 (median, 1.95 m/s; range, 1.60-2.50 m/s) than at T1 (median, 1.76 m/s; range, 1.40-2.20 m/s; P < .0001; reduction 9.2%). The stroke volume index at T0 also was greater than at T1 (P < .0001). Weak negative correlations were detected between aortic root size and aortic velocities. In SAS-affected dogs, AoPV0 was higher than AoPV1 (P < .0001; reduction 7.3%). Aortic peak velocity was affected by emotional stress during echocardiographic examination both in SAS-affected and normal Boxers. In normal Boxers, aortic root size weakly affected AoPVs, but did not affect AoPV0-AoPV1. Stroke volume seems to play a major role in stress-related AoPV increases in normal Boxers. Emotional stress should be taken into account when screening for SAS in the Boxer breed. Copyright © 2014 by the American College of Veterinary Internal Medicine.
Normal personality traits, rumination and stress generation among early adolescent girls

PubMed Central

Stroud, Catherine B.; Sosoo, Effua E.; Wilson, Sylia

2017-01-01

This study examined associations between personality and stress generation. Expanding upon prior work, we examined (a) the role of Positive Emotionality (PE), Negative Emotionality (NE), and Constraint (CON), and their lower-order facets, as predictors of acute and chronic interpersonal stress generation; (b) whether personality moderated effects of rumination on stress generation; and (c) whether personality increased exposure to independent (uncontrollable) stress. These questions were examined in a one-year study of 126 adolescent girls (M age = 12.39 years) using contextual stress interviews. NE predicted increases in acute and chronic interpersonal stress generation, but not independent stress. NE, CON and affiliative PE each moderated the effect of rumination on chronic interpersonal stress generation. These effects were driven by particular lower-order traits. PMID:28845067
Modeling and Studying the Effect of Texture and Elastic Anisotropy of Copper Microstructure in Nanoscale Interconnects on Reliability in Integrated Circuits

NASA Astrophysics Data System (ADS)

Basavalingappa, Adarsh

Copper interconnects are typically polycrystalline and follow a lognormal grain size distribution. Polycrystalline copper interconnect microstructures with a lognormal grain size distribution were obtained with a Voronoi tessellation approach. The interconnect structures thus obtained were used to study grain growth mechanisms, grain boundary scattering, scattering dependent resistance of interconnects, stress evolution, vacancy migration, reliability life times, impact of orientation dependent anisotropy on various mechanisms, etc. In this work, the microstructures were used to study the impact of microstructure and elastic anisotropy of copper on thermal and electromigration induced failure. A test structure with copper and bulk moduli values was modeled to do a comparative study with the test structures with textured microstructure and elastic anisotropy. By subjecting the modeled test structure to a thermal stress by ramping temperature down from 400 °C to 100 °C, a significant variation in normal stresses and pressure were observed at the grain boundaries. This variation in normal stresses and hydrostatic stresses at the grain boundaries was found to be dependent on the orientation, dimensions, surroundings, and location of the grains. This may introduce new weak points within the metal line where normal stresses can be very high depending on the orientation of the grains leading to delamination and accumulation sites for vacancies. Further, the hydrostatic stress gradients act as a driving force for vacancy migration. The normal stresses can exceed certain grain orientation dependent critical threshold values and induce delamination at the copper and cap material interface, thereby leading to void nucleation and growth. Modeled test structures were subjected to a series of copper depositions at 250 °C followed by copper etch at 25 °C to obtain initial stress conditions. Then the modeled test structures were subjected to 100,000 hours ( 11.4 years) of simulated thermal stress at an elevated temperature of 150 °C. Vacancy migration due to concentration gradients, thermal gradients, and mechanical stress gradients were considered under the applied thermal stress. As a result, relatively high concentrations of vacancies were observed in the test structure due to a driving force caused by the pressure gradients resulting from the elastic anisotropy of copper. The grain growth mechanism was not considered in these simulations. Studies with two grain analysis demonstrated that the stress gradients developed will be severe when (100) grains are adjacent to (111) grains, therefore making them the weak points for potentially reliability failures. Ilan Blech discovered that electromigration occurs above a critical product of the current density and metal length, commonly referred as Blech condition. Electromigration stress simulations in this work were carried out by subjecting test structures to scaled current densities to overcome the Blech condition of (jL)crit for small dimensions of test structure and the low temperature stress condition used. Vacancy migration under the electromigration stress conditions was considered along with the vacancy migration induced stress evolution. A simple void growth model was used which assumes voids start to form when vacancies reach a critical level. Increase of vacancies in a localized region increases the resistance of the metal line. Considering a 10% increase in resistance as a failure criterion, the distributions of failure times were obtained for given electromigration stress conditions. Bimodal/multimodal failure distributions were obtained as a result. The sigma values were slightly lower than the ones commonly observed from experiments. The anisotropy of the elastic moduli of copper leads to the development of significantly different stress values which are dependent on the orientation of the grains. This results in some grains having higher normal stress than the others. This grain orientation dependent normal stress can reach a critical stress necessary to induce delamination at the copper and cap interface. Time taken to reach critical stress was considered as time to fail and distributions of failure times were obtained for structures with different grain orientations in the microstructure for different critical stress values. The sigma values of the failure distributions thus obtained for different constant critical stress values had a strong dependence of on the critical stress. It is therefore critical to use the appropriate critical stress value for the delamination of copper and cap interface. The critical stress necessary to overcome the local adhesion of the copper and the cap material interface is dependent on grain orientation of the copper. Simulations were carried out by considering grain orientation dependent critical normal stress values as failure criteria. The sigma value thus obtained with selected critical stress values were comparable to sigma values commonly observed from experiments.
Impedance-Based Pre-Stress Monitoring of Rock Bolts Using a Piezoceramic-Based Smart Washer-A Feasibility Study.

PubMed

Wang, Bo; Huo, Linsheng; Chen, Dongdong; Li, Weijie; Song, Gangbing

2017-01-27

Pre-stress degradation or looseness of rock bolts in mining or tunnel engineering threatens the stability and reliability of the structures. In this paper, an innovative piezoelectric device named a "smart washer" with the impedance method is proposed with the aim of developing a real-time device to monitor the pre-stress level of rock bolts. The proposed method was verified through tests on a rock bolt specimen. By applying high-frequency sweep excitations (typically >30 kHz) to the smart washer that was installed on the rock bolt specimen, we observed that the variation in impedance signatures indicated the rock bolt pre-stress status. With the degradation of rock bolt pre-stress, the frequency in the dominating peak of the real part of the electrical impedance signature increased. To quantify the effectiveness of the proposed technique, a normalized root mean square deviation (RMSD) index was developed to evaluate the degradation level of the rock bolt pre-stress. The experimental results demonstrated that the normalized RMSD-based looseness index, which was computed from the impedance value detected by the "smart washer", increased with loss of the pre-stress of the rock bolt. Therefore, the proposed method can effectively detect the degradation of rock bolt pre-stress, as demonstrated by experiments.
Impedance-Based Pre-Stress Monitoring of Rock Bolts Using a Piezoceramic-Based Smart Washer—A Feasibility Study

PubMed Central

Wang, Bo; Huo, Linsheng; Chen, Dongdong; Li, Weijie; Song, Gangbing

2017-01-01

Pre-stress degradation or looseness of rock bolts in mining or tunnel engineering threatens the stability and reliability of the structures. In this paper, an innovative piezoelectric device named a “smart washer” with the impedance method is proposed with the aim of developing a real-time device to monitor the pre-stress level of rock bolts. The proposed method was verified through tests on a rock bolt specimen. By applying high-frequency sweep excitations (typically >30 kHz) to the smart washer that was installed on the rock bolt specimen, we observed that the variation in impedance signatures indicated the rock bolt pre-stress status. With the degradation of rock bolt pre-stress, the frequency in the dominating peak of the real part of the electrical impedance signature increased. To quantify the effectiveness of the proposed technique, a normalized root mean square deviation (RMSD) index was developed to evaluate the degradation level of the rock bolt pre-stress. The experimental results demonstrated that the normalized RMSD-based looseness index, which was computed from the impedance value detected by the “smart washer”, increased with loss of the pre-stress of the rock bolt. Therefore, the proposed method can effectively detect the degradation of rock bolt pre-stress, as demonstrated by experiments. PMID:28134811
Effective stress, friction and deep crustal faulting

USGS Publications Warehouse

Beeler, N.M.; Hirth, Greg; Thomas, Amanda M.; Burgmann, Roland

2016-01-01

Studies of crustal faulting and rock friction invariably assume the effective normal stress that determines fault shear resistance during frictional sliding is the applied normal stress minus the pore pressure. Here we propose an expression for the effective stress coefficient αf at temperatures and stresses near the brittle-ductile transition (BDT) that depends on the percentage of solid-solid contact area across the fault. αf varies with depth and is only near 1 when the yield strength of asperity contacts greatly exceeds the applied normal stress. For a vertical strike-slip quartz fault zone at hydrostatic pore pressure and assuming 1 mm and 1 km shear zone widths for friction and ductile shear, respectively, the BDT is at ~13 km. αf near 1 is restricted to depths where the shear zone is narrow. Below the BDT αf = 0 is due to a dramatically decreased strain rate. Under these circumstances friction cannot be reactivated below the BDT by increasing the pore pressure alone and requires localization. If pore pressure increases and the fault localizes back to 1 mm, then brittle behavior can occur to a depth of around 35 km. The interdependencies among effective stress, contact-scale strain rate, and pore pressure allow estimates of the conditions necessary for deep low-frequency seismicity seen on the San Andreas near Parkfield and in some subduction zones. Among the implications are that shear in the region separating shallow earthquakes and deep low-frequency seismicity is distributed and that the deeper zone involves both elevated pore fluid pressure and localization.
Comparisons between gouge and bare surface friction of serpentinite at seismic slip velocities: Implications for dynamic weakening of gouge-bearing faults

NASA Astrophysics Data System (ADS)

Proctor, B.; Mitchell, T. M.; Hirth, G.; Goldsby, D. L.; Di Toro, G.; Zorzi, F.

2013-12-01

High-velocity friction (HVF) experiments on bare rock surfaces have revealed various dynamic weakening processes (e.g., flash weakening, gel weakening, melt lubrication) that likely play a fundamental role in coseismic fault weakening. However, faults generally contain a thin layer of gouge separating the solid wallrocks, thus it is important to understand how the presence of gouge modifies the efficiency of these weakening processes at seismic slip rates. We explored the frictional behavior of bare surfaces and powdered samples of an antigorite-rich serpentinite (ARS) and a lizardite-rich serpentinite (LRS) at earthquake slip rates. HVF experiments were conducted with slip displacements ranging from ~0.5 to 2m, at velocities ranging from 0.002m/s to 6.5 m/s, and with normal stresses ranging from 2-22 MPa for gouge and 5-100MPa for bare surfaces. Our results demonstrate that the friction coefficient (μ) of powdered serpentine is significantly larger than that of bare surfaces under otherwise identical conditions. Bare surface friction decreases over a weakening distance of a few centimeters to a nominally steady-state value of ~0.1 at velocities greater than 0.1m/s. The nominal steady-state friction decreases non-linearly with increasing normal stress from 0.14 to 0.045 at 5 and ~100MPa respectfully at a slip velocity of 1m/s. Additionally, the recovery of frictional strength during deceleration depends on total displacement; samples slipped for ~50mm recover faster than samples slipped for ~0.5m. Microstructural analysis of bare surfaces deformed at the highest normal stresses revealed translucent glass-like material on the slip surfaces and XRD analysis of wear material revealed an increasing presence of olivine and enstatite with increasing normal stress. In contrast, gouge requires an order of magnitude higher velocity than bare surfaces to induce frictional weakening, has a larger weakening distance and higher steady state friction values for equivalent deformation conditions. Furthermore, we observe a strong normal stress dependence of the nominal steady state friction and the weakening distance of ARS and LRS gouge from 0.51 to 0.39 and from 25-10cm at 4MPa and 22MPa, respectfully, for at a slip velocity of 1m/s. Strain was localized onto a shear surface in the range of 100-300 microns wide in all gouge samples deformed at >10cm/s and XRD analyses revealed the presence of olivine and enstatite in samples with the most weakening and none in samples with no weakening. Our results indicate that dynamic weakening occurs in gouge at low normal stress in response to strain localization and shear heating of the slip surface. However, because more initial displacement is required to localize strain, weakening initiates at higher velocities and after larger weakening distances than bare surfaces. At higher normal stress, localization occurs after less displacement and the differences between gouge and bare-surface friction diminish; extrapolation of our data suggests that the behavior of serpentine gouge will approach that of bare surfaces at normal stresses ≥60 MPa.
Hydromechanical effects of continental glaciation on groundwater systems

USGS Publications Warehouse

Neuzil, C.E.

2012-01-01

Hydromechanical effects of continental ice sheets may involve considerably more than the widely recognized direct compression of overridden terrains by ice load. Lithospheric flexure, which lags ice advance and retreat, appears capable of causing comparable or greater stress changes. Together, direct and flexural loading may increase fluid pressures by tens of MPa in geologic units unable to drain. If so, fluid pressures in low-permeability formations subject to glaciation may have increased and decreased repeatedly during cycles of Pleistocene glaciation and can again in the future. Being asynchronous and normally oriented, direct and flexural loading presumably cause normal and shear stresses to evolve in a complex fashion through much or all of a glacial cycle. Simulations of fractured rock predict permeability might vary by two to three orders of magnitude under similar stress changes as fractures at different orientations are subjected to changing normal and shear stresses and some become critically stressed. Uncertainties surrounding these processes and their interactions, and the confounding influences of surface hydrologic changes, make it challenging to delineate their effects on groundwater flow and pressure regimes with any specificity. To date, evidence for hydromechanical changes caused by the last glaciation is sparse and inconclusive, comprising a few pressure anomalies attributed to the removal of direct ice load. This may change as more data are gathered, and understanding of relevant processes is refined.
AML cells have low spare reserve capacity in their respiratory chain that renders them susceptible to oxidative metabolic stress

PubMed Central

Sriskanthadevan, Shrivani; Jeyaraju, Danny V.; Chung, Timothy E.; Prabha, Swayam; Xu, Wei; Skrtic, Marko; Jhas, Bozhena; Hurren, Rose; Gronda, Marcela; Wang, Xiaoming; Jitkova, Yulia; Sukhai, Mahadeo A.; Lin, Feng-Hsu; Maclean, Neil; Laister, Rob; Goard, Carolyn A.; Mullen, Peter J.; Xie, Stephanie; Penn, Linda Z.; Rogers, Ian M.; Dick, John E.; Minden, Mark D.

2015-01-01

Mitochondrial respiration is a crucial component of cellular metabolism that can become dysregulated in cancer. Compared with normal hematopoietic cells, acute myeloid leukemia (AML) cells and patient samples have higher mitochondrial mass, without a concomitant increase in respiratory chain complex activity. Hence these cells have a lower spare reserve capacity in the respiratory chain and are more susceptible to oxidative stress. We therefore tested the effects of increasing the electron flux through the respiratory chain as a strategy to induce oxidative stress and cell death preferentially in AML cells. Treatment with the fatty acid palmitate induced oxidative stress and cell death in AML cells, and it suppressed tumor burden in leukemic cell lines and primary patient sample xenografts in the absence of overt toxicity to normal cells and organs. These data highlight a unique metabolic vulnerability in AML, and identify a new therapeutic strategy that targets abnormal oxidative metabolism in this malignancy. PMID:25631767

Normal Stress or Adjustment Disorder?

MedlinePlus

... Lifestyle Stress management What's the difference between normal stress and an adjustment disorder? Answers from Daniel K. Hall-Flavin, M.D. Stress is a normal psychological and physical reaction to ...
Inhibition of endoplasmic reticulum stress improves coronary artery function in type 2 diabetic mice.

PubMed

Choi, Soo-Kyoung; Lim, Mihwa; Yeon, Soo-In; Lee, Young-Ho

2016-06-01

What is the central question of this study? Endoplasmic reticulum (ER) stress has been reported to be involved in type 2 diabetes; however, the role of exacerbated ER stress in vascular dysfunction in type 2 diabetes remains unknown. What is the main finding and its importance? The main findings of this study are that ER stress is increased in the coronary arteries in type 2 diabetes, and inhibition of ER stress using taurine-conjugated ursodeoxycholic acid improves vascular function, which is associated with normalization of the myogenic response and endothelium-dependent relaxation. Vascular dysfunction is a major complication in type 2 diabetes. Although endoplasmic reticulum (ER) stress has been suggested to be a contributory factor in cardiovascular diseases, the relationship between ER stress and vascular dysfunction in type 2 diabetes remains unclear. Thus, in the present study, we examined whether ER stress contributes to coronary artery dysfunction and whether inhibition of ER stress ameliorates vascular function in type 2 diabetes. Type 2 diabetic mice and their control counterparts were treated with an ER stress inhibitor (taurine-conjugated ursodeoxycholic acid, 150 mg kg(-1) day(-1) , by i.p. injection) for 2 weeks or not treated. The myogenic response and endothelium-dependent relaxation were measured in pressurized coronary arteries. In type 2 diabetic mice, blood glucose and body weight were elevated compared with control mice. The myogenic response was potentiated and endothelium-dependent relaxation impaired in coronary arteries from the type 2 diabetic mice. Interestingly, treatment with the ER stress inhibitor normalized the myogenic responses and endothelium-dependent relaxation. These data were associated with an increase in ER stress marker expression or phosphorylation (IRE1-XBP-1 and PERK-eIF2α) in type 2 diabetic mice, which were reduced by treatment with the ER stress inhibitor. Inhibition of ER stress normalizes the myogenic response and improves vascular function in type 2 diabetes. Therefore, ER stress could be a potential target for cardiovascular diseases in diabetes mellitus. © 2016 The Authors. Experimental Physiology © 2016 The Physiological Society.
A pivotal role for starch in the reconfiguration of 14C-partitioning and allocation in Arabidopsis thaliana under short-term abiotic stress.

PubMed

Dong, Shaoyun; Zhang, Joshua; Beckles, Diane M

2018-06-18

Plant carbon status is optimized for normal growth but is affected by abiotic stress. Here, we used 14 C-labeling to provide the first holistic picture of carbon use changes during short-term osmotic, salinity, and cold stress in Arabidopsis thaliana. This could inform on the early mechanisms plants use to survive adverse environment, which is important for efficient agricultural production. We found that carbon allocation from source to sinks, and partitioning into major metabolite pools in the source leaf, sink leaves and roots showed both conserved and divergent responses to the stresses examined. Carbohydrates changed under all abiotic stresses applied; plants re-partitioned 14 C to maintain sugar levels under stress, primarily by reducing 14 C into the storage compounds in the source leaf, and decreasing 14 C into the pools used for growth processes in the roots. Salinity and cold increased 14 C-flux into protein, but as the stress progressed, protein degradation increased to produce amino acids, presumably for osmoprotection. Our work also emphasized that stress regulated the carbon channeled into starch, and its metabolic turnover. These stress-induced changes in starch metabolism and sugar export in the source were partly accompanied by transcriptional alteration in the T6P/SnRK1 regulatory pathway that are normally activated by carbon starvation.
Free-edge stress analysis of glass-epoxy laminates with matrix cracks

NASA Technical Reports Server (NTRS)

Fish, John C.; O'Brien, T. K.

1992-01-01

The effect of matrix cracks on the composite delamination and interlaminar stresses is investigated in (+15/90n/-15)s glass-epoxy laminates (with values of n equal to 0, 1, 2, or 3) subjected to monotonically increasing tension loads. Three-dimensional (3D) and quasi-3D (Q3D) finite-element analyses are used to model the free-edge stress states in the laminates with and without a matrix crack, respectively. The Q3D results show that in-plane transverse tensile stresses exist in the +15 deg plies near the free edges of all of the laminates used and that only the interlaminar shear stress is high at the +15/theta interface. The results of 3D analysis indicate that large tensile interlaminar normal as well as shear stresses develop at the intersection of the matrix crack and the free edge. This suggests that the interlaminar normal stress plays a significant role in the failure of these laminates.
Blood glucose may condition factor VII levels in diabetic and normal subjects.

PubMed

Ceriello, A; Giugliano, D; Quatraro, A; Dello Russo, P; Torella, R

1988-12-01

Increased factor VII levels have been reported in Type 1 (insulin-dependent) diabetic subjects. A direct correlation between fasting plasma glucose and factor VII level was found to exist in both diabetic and normal subjects. Induced-hyperglycaemia was able to increase factor VII levels in both diabetic patients and normal control subjects while, when euglycaemia was achieved in diabetic patients, factor VII values returned to normal range. This study shows that the level of factor VII may be directly conditioned by circulating blood glucose and, therefore, stresses the role of hyperglycaemia in conditioning coagulation abnormalities in diabetes mellitus.
Effect of pertussis toxin pretreated centrally on blood glucose level induced by stress.

PubMed

Suh, Hong-Won; Sim, Yun-Beom; Park, Soo-Hyun; Sharma, Naveen; Im, Hyun-Ju; Hong, Jae-Seung

2016-09-01

In the present study, we examined the effect of pertussis toxin (PTX) administered centrally in a variety of stress-induced blood glucose level. Mice were exposed to stress after the pretreatment of PTX (0.05 or 0.1 µg) i.c.v. or i.t. once for 6 days. Blood glucose level was measured at 0, 30, 60 and 120 min after stress stimulation. The blood glucose level was increased in all stress groups. The blood glucose level reached at maximum level after 30 min of stress stimulation and returned to a normal level after 2 h of stress stimulation in restraint stress, physical, and emotional stress groups. The blood glucose level induced by cold-water swimming stress was gradually increased up to 1 h and returned to the normal level. The intracerebroventricular (i.c.v.) or intrathecal (i.t.) pretreatment with PTX, a Gi inhibitor, alone produced a hypoglycemia and almost abolished the elevation of the blood level induced by stress stimulation. The central pretreatment with PTX caused a reduction of plasma insulin level, whereas plasma corticosterone level was further up-regulated in all stress models. Our results suggest that the hyperglycemia produced by physical stress, emotional stress, restraint stress, and the cold-water swimming stress appear to be mediated by activation of centrally located PTX-sensitive G proteins. The reduction of blood glucose level by PTX appears to due to the reduction of plasma insulin level. The reduction of blood glucose level by PTX was accompanied by the reduction of plasma insulin level. Plasma corticosterone level up-regulation by PTX in stress models may be due to a blood glucose homeostatic mechanism.
The activity of antioxidant enzymes in response to salt stress in safflower (Carthamus tinctorius L.) and sunflower (Helianthus annuus L.) seedlings raised from seed treated with chitosan.

PubMed

Jabeen, Nusrat; Ahmad, Rafiq

2013-05-01

Salt tolerance is a complex trait which involves the coordinated action of many genes that perform a variety of functions, such as ion sequestration, metabolic adjustment, osmotic adjustment and antioxidative defence. In this article, the growth and the generation and scavenging of reactive oxygen species (ROS) under normal (ECiw [Electrical conductivity of irrigation water] = 0.5 dS m(-1)) and salt stress conditions (ECiw = 3.4, 6.1, 8.6 and 10.8 dS m(-1) ) in relation to the priming of seeds of the two important oil yielding crops, i.e. safflower and sunflower, with different concentrations of chitosan [0% (control), 0.25%, 0.50%, 0.75%] is discussed. Induced salinity stress significantly decreased germination percentage, germination rate, length and weight of root and shoot, and protein content. Proline content, malondialdehyde content (MDA), catalase (CAT) and peroxidase (POX) activity increased at 10.8 dS m(-1). Under control conditions there were no significant differences in germination percentage among different concentrations of chitosan, whereas CAT and POX activity were increased by low concentrations of chitosan. With increasing salt stress, low concentrations of chitosan increased germination percentage but decreased MDA and proline contents and CAT and POX activity. Generation of ROS seems to be unavoidable under normal conditions and the activity of antioxidant enzymes in plants varies in terms of ROS generation under salt stress. However, the data indicate that plants subjected to salt stress-induced oxidative stress and the low concentrations of chitosan exhibited positive effects on salt stress alleviation through the reduction of enzyme activity in both crops. © 2012 Society of Chemical Industry.
Repressed SIRT1/PGC-1α pathway and mitochondrial disintegration in iPSC-derived RPE disease model of age-related macular degeneration.

PubMed

Golestaneh, Nady; Chu, Yi; Cheng, Shuk Kei; Cao, Hong; Poliakov, Eugenia; Berinstein, Daniel M

2016-12-20

Study of age related macular degeneration (AMD) has been hampered by lack of human models that represent the complexity of the disease. Here we have developed a human in vitro disease model of AMD to investigate the underlying AMD disease mechanisms. Generation of iPSCs from retinal pigment epithelium (RPE) of AMD donors, age-matched normal donors, skin fibroblasts of a dry AMD patient, and differentiation of iPSCs into RPE (AMD RPE-iPSC-RPE, normal RPE-iPSC-RPE and AMD Skin-iPSC-RPE, respectively). Immunostaining, cell viability assay and reactive oxygen species (ROS) production under oxidative stress conditions, electron microscopy (EM) imaging, ATP production and glycogen concentration assays, quantitative real time PCR, western blot, karyotyping. The AMD RPE-iPSC-RPE and AMD Skin-iPSC-RPE present functional impairment and exhibit distinct disease phenotypes compared to RPE-iPSC-RPE generated from normal donors (Normal RPE-iPSC-RPE). The AMD RPE-iPSC-RPE and AMD Skin-iPSC-RPE show increased susceptibility to oxidative stress and produced higher levels of reactive oxygen species (ROS) under stress in accordance with recent reports. The susceptibility to oxidative stress-induced cell death in AMD RPE-iPSC-RPE and Skin-iPSC-RPE was consistent with inability of the AMD RPE-iPSC-RPE and Skin-iPSC-RPE to increase SOD2 expression under oxidative stress. Phenotypic analysis revealed disintegrated mitochondria, accumulation of autophagosomes and lipid droplets in AMD RPE-iPSC-RPE and AMD Skin-iPSC-RPE. Mitochondrial activity was significantly lower in AMD RPE-iPSC-RPE and AMD Skin-iPSC-RPE compared to normal cells and glycogen concentration was significantly increased in the diseased cells. Furthermore, Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), a regulator of mitochondrial biogenesis and function was repressed, and lower expression levels of NAD-dependent deacetylase sirtuin1 (SIRT1) were found in AMD RPE-iPSC-RPE and AMD Skin-iPSC-RPE as compared to normal RPE-iPSC-RPE. Our studies suggest SIRT1/PGC-1α as underlying pathways contributing to AMD pathophysiology, and open new avenues for development of targeted drugs for treatment of this devastating neurodegenerative disease of the visual system.
Effect of friction on the rheology of dense suspensions

NASA Astrophysics Data System (ADS)

Gallier, Stany; Lemaire, Elisabeth; Peters, François; Lobry, Laurent

2014-11-01

This work reports three-dimensional numerical simulations of sheared non-Brownian concentrated suspensions using a fictitious domain method. Contacts between particles are modeled using a DEM-like approach (Discrete Element Method), which allows for a more physical description, including roughness and friction. This study emphasizes the effect of friction between particles and its role on rheological properties, especially on normal stress differences. Friction is shown to notably increase viscosity and second normal stress difference | N2 | and decrease | N1 | , in better agreement with experiments. The hydrodynamic and contact contributions to the overall particle stress are particularly investigated and this shows that the effect of friction is mostly due to the additional contact stress since the hydrodynamic stress remains unaffected by friction. Simulation results are also compared with experiments and the agreement is improved when friction is accounted for: this suggests that friction is operative in actual suspensions.
Growth of contact area between rough surfaces under normal stress

NASA Astrophysics Data System (ADS)

Stesky, R. M.; Hannan, S. S.

1987-05-01

The contact area between deforming rough surfaces in marble, alabaster, and quartz was measured from thin sections of surfaces bonded under load with low viscosity resin epoxy. The marble and alabaster samples had contact areas that increased with stress at an accelerating rate. This result suggests that the strength of the asperity contacts decreased progressively during the deformation, following some form of strain weakening relationship. This conclusion is supported by petrographic observation of the thin sections that indicate that much of the deformation was cataclastic, with minor twinning of calcite and kinking of gypsum. In the case of the quartz, the observed contact area was small and increased approximately linearly with normal stress. Only the irreversible cataclastic deformation was observed; however strain-induced birefringence and cracking of the epoxy, not observed with the other rocks, suggests that significant elastic deformation occurred, but recovered during unloading.
Antioxidant potential of the methanol-methylene chloride extract of Terminalia glaucescens leaves on mice liver in streptozotocin-induced stress.

PubMed

Njomen, Guy Bertrand Sabas Nya; Kamgang, René; Oyono, Jean Louis Essame; Njikam, Njifutie

2008-11-01

The antioxidant effect of the methanol-methylene chloride extract of Terminalia glaucescens (Combretaceae) leaves was investigated in streptozotocin (STZ)-induced oxidative stress. Oxidative stress was induced in mice by a daily dose of STZ (45 mg/kg body weight i.p.) for five days. From day one, before STZ injection, normal and diabetic-test mice received an oral dose of the extract (100 or 300 mg/kg b.w.) daily. Plasma metabolites, lipid peroxidation, and antioxidant enzymes in the liver were assessed and gain in body weight recorded. In normal mice the plant extract reduced food and water intake, blood glucose and LDL-C level and body weight gain, did not affect the lipid peroxidation in the liver, while the antioxidant enzyme activities seemed increased. Blood glucose was decreased (P < 0.05) in normal mice treated with 300 mg/kg extract. Diabetic mice pretreated with 100 mg/kg extract as diabetic control mice (DC) showed significant (P < 0.001) body weight loss, polyphagia and polydipsia, high plasma glucose level, decrease in the liver catalase, peroxidase, and superoxide dismutase activities, and increase in lipid peroxidation. The HDL-C level was lowered (P < 0.05) whereas LDL-C increased. In 300 mg/kg extract-pretreated diabetic mice the extract prevented body weight loss, increase of blood glucose level, lipid peroxidation in liver, food and water intake, and lowering of plasma HDL-C level and liver antioxidants; this extract prevented LDL-C level increase. These results indicate that T. glaucescens protects against STZ-induced oxidative stress and could thus explain its traditional use for diabetes and obesity treatment or management.
76 FR 1644 - Biweekly Notice; Applications and Amendments to Facility Operating Licenses Involving No...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-01-11

... tubesheet in that region. At normal operating pressures, leakage from primary water stress corrosion... cause failure. The EDG reliability will thereby be potentially increased by reducing the stresses on the..., ``Bases for Plugging Degraded PWR [pressurized-water reactor] Steam Generator Tubes,'' margins against...
HEAT SHOCK FACTOR 1-MEDIATED THERMOTOLERANCE PREVENTS CELL DEATH AND RESULTS IN G2/M CELL CYCLE ARREST

EPA Science Inventory

Mammalian cells respond to stress by activating heat shock transcription factors (e.g., HSF1) that regulate increased synthesis of heat shock proteins (HSPs). HSPs mediate protection from deleterious effects of stress by preventing permanent disruption of normal cellular mitosis...
Differential toxicity of arsenic on renal oxidative damage and urinary metabolic profiles in normal and diabetic mice.

PubMed

Yin, Jinbao; Liu, Su; Yu, Jing; Wu, Bing

2017-07-01

Diabetes is a common metabolic disease, which might influence susceptibility of the kidney to arsenic toxicity. However, relative report is limited. In this study, we compared the influence of inorganic arsenic (iAs) on renal oxidative damage and urinary metabolic profiles of normal and diabetic mice. Results showed that iAs exposure increased renal lipid peroxidation in diabetic mice and oxidative DNA damage in normal mice, meaning different effects of iAs exposure on normal and diabetic individuals. Nuclear magnetic resonance (NMR)-based metabolome analyses found that diabetes significantly changed urinary metabolic profiles of mice. Oxidative stress-related metabolites, such as arginine, glutamine, methionine, and β-hydroxybutyrate, were found to be changed in diabetic mice. The iAs exposure altered amino acid metabolism, lipid metabolism, carbohydrate metabolism, and energy metabolism in normal and diabetic mice, but had higher influence on metabolic profiles of diabetic mice than normal mice, especially for oxidative stress-related metabolites and metabolisms. Above results indicate that diabetes increased susceptibility to iAs exposure. This study provides basic information on differential toxicity of iAs on renal toxicity and urinary metabolic profiles in normal and diabetic mice and suggests that diabetic individuals should be considered as susceptible population in toxicity assessment of arsenic.
Nonlinear interaction of strong S-waves with the rupture front in the shallow subsurface

NASA Astrophysics Data System (ADS)

Sleep, N. H.

2017-12-01

Shallow deformation in moderate to large earthquakes is sometimes distributed rather than being concentrated on a single fault plane. Strong high-frequency S-waves interact with the rupture front to produce this effect. For strike-slip faults, the rupture propagation velocity is a fraction of the S-wave velocity. The rupture propagation vector refracts essentially vertically in the low (S-wave) velocity shallow subsurface. So does the propagation direction of S-waves. The shallow rupture front is essentially mode 3 near the surface. Strong S-waves arrive before the rupture front. They continue to arrive for several seconds in a large event. There are simple scaling relationships. The dynamic Coulomb stress ratio of horizontal stress on horizontal planes from S-waves is the normalized acceleration in g's. For fractured rock and gravel, frictional failure occurs when the normalized acceleration exceeds the effective coefficient of friction. Acceleration tends to saturate at that level as the anelastic strain rate increases rapidly with stress. For muddy materials, failure begins at a low normalized acceleration but increases slowly with dynamic stress. Dynamic accelerations sometimes exceed 1 g. In both cases, the rupture tip finds the shallow subsurface already in nonlinear failure down to a few to tens of meters depth. The material does not distinguish between S-wave and rupture tip stresses. Both stresses add to the stress invariant and hence to the anelastic strain rate tensor. Surface anelastic strain from fault slip is thus distributed laterally over a distance scaling to the depth of nonlinearity from S-waves. The environs of the fault anelastically accommodate the fault slip at depth. This process differs from blind faults where the shallow coseismic strain is mostly elastic and interseismic anelastic processes accommodate the long-term shallow deformation.
Age-dependent increase in oxidative stress in gastrocnemius muscle with unloading

PubMed Central

Siu, Parco M.; Pistilli, Emidio E.; Alway, Stephen E.

2008-01-01

Oxidative stress increases during unloading in muscle from young adult rats. The present study examined the markers of oxidative stress and antioxidant enzyme gene and protein expressions in medial gastrocnemius muscles of aged and young adult (30 and 6 mo of age) Fischer 344 × Brown Norway rats after 14 days of hindlimb suspension. Medial gastrocnemius muscle weight was decreased by ∼30% in young adult and aged rats following suspension. When muscle weight was normalized to animal body weight, it was reduced by 12% and 22% in young adult and aged rats, respectively, after suspension. Comparisons between young adult and aged control animals demonstrated a 25% and 51% decline in muscle mass when expressed as absolute muscle weight and muscle weight normalized to the animal body weight, respectively. H2O2 content was elevated by 43% while Mn superoxide dismutase (MnSOD) protein content was reduced by 28% in suspended muscles compared with control muscles exclusively in the aged animals. Suspended muscles had greater content of malondialdehyde (MDA)/4-hydroxyalkenals (4-HAE) (29% and 58% increase in young adult and aged rats, respectively), nitrotyrosine (76% and 65% increase in young adult and aged rats, respectively), and catalase activity (69% and 43% increase in young adult and aged rats, respectively) relative to control muscles. Changes in oxidative stress markers MDA/4-HAE, H2O2, and MnSOD protein contents in response to hindlimb unloading occurred in an age-dependent manner. These findings are consistent with the hypotheses that oxidative stress has a role in mediating disuse-induced and sarcopenia-associated muscle losses. Our data suggest that aging may predispose skeletal muscle to increased levels of oxidative stress both at rest and during unloading. PMID:18801960
Smoothing and roughening of slip surfaces in direct shear experiments

NASA Astrophysics Data System (ADS)

Sagy, Amir; Badt, Nir; Hatzor, Yossef H.

2015-04-01

Faults in the upper crust contain discrete slip surfaces which have absorbed a significant part of the shear displacement along them. Field measurements demonstrate that these surfaces are rough at all measurable scales and indicate that surfaces of relatively large-slip faults are statistically smoother than those of small-slip faults. However, post faulting and surface erosion process that might affect the geometry of outcrops cannot be discounted in such measurements. Here we present experimental results for the evolution of shear surface topography as function of slip distance and normal stress in direct shear experiments. A single prismatic fine grain limestone block is first fractured in tension mode using the four-point bending test methodology and then the fracture surface topography is scanned using a laser profilometer. We then shear the obtained tensile fracture surfaces in direct shear, ensuring the original fracture surfaces are in a perfectly matching configuration at the beginning of the shear test. First, shearing is conducted to distances varying from 5 to 15 mm under constant normal stress of 2MPa and a constant displacement rate of 0.05 mm/s using two closed-loop servo controlled hydraulic pistons, supplying normal and shear forces (Davidesko et al., 2014). In the tested configuration peak shear stress is typically attained after a shear displacement of about 2-3 mm, beyond which lower shear stress is required to continue shearing at the preset displacement rate of 0.05 mm/s as is typical for initially rough joints. Following some initial compression the interface begins to dilate and continues to do so until the end of the test. The sheared tensile fracture surface is then scanned again and the geometrical evolution, in term of RMS roughness and power spectral density (PSD) is analyzed. We show that shearing smooth the surface along all our measurements scales. The roughness ratio, measured by initial PSD / final PSD for each wavelength, increases as a function of slip amount. The roughness measured after slip can be fitted by a power-law similar to that of the initial tensile surface. In the next series of experiments a similar procedure is applied when the roughness evolution is measured as a function of increasing normal stress for a fixed displacement amount of 10 mm. While samples sheared under a constant normal stress of 5 MPa generated surface smoothing, shearing under normal stress of 7.5 MPa to 15 MPa exhibited surface roughening at the measured range of scales. We find that roughening is correlated with the attained peak shear stress values, stress drop (peak shear stress minus residual shear stress) and with wear accumulation, a novel measurement procedure of which is developed here. Analysis of the sheared samples shows that roughening is generated by sets of dense fractures that significantly damaged the sample in the immediate proximity to large asperities. This roughening is related to penetrative damage during transient wear in rough surfaces.
Effects of Lentinula edodes consumption on biochemical, hematologic and oxidative stress parameters in rats receiving high-fat diet.

PubMed

Spim, Sara Rosicler Vieira; de Oliveira, Bruna Giovanna Corrêa Chrispim; Leite, Fernanda Gomes; Gerenutti, Marli; Grotto, Denise

2017-10-01

Functional foods can prevent/reduce the risks related to obesity. Lentinula edodes is a highly nutritious mushroom rich in protein, vitamins and minerals. Some studies have demonstrated the hypocholesterolemic effects from L. edodes in high doses, which does not represent the consumption in humans. We evaluated ingestion of a realistic dose of L. edodes associated with a high-fat diet (HFD) on hematologic, biochemical and oxidative stress parameters. Eighteen male Wistar rats were divided into three groups: control (normal diet); HFD; and HFD + L. edodes (100 mg/kg/day). After 30 days, blood was collected. Biochemical and hematologic parameters were analyzed, as well as oxidative stress biomarkers. The HFD increased levels of total cholesterol and triglycerides. Lentinula edodes reduced these parameters significantly to concentrations found in the control group. The HFD increased levels of alanine transaminase and aspartate transaminase (markers of liver damage). Lentinula edodes returned the levels of these enzymes to normal levels and normalized serum levels of urea (which were also increased owing to consumption of the HFD). Lentinula edodes reduced levels of urea and glucose. Lipid peroxidation was increased in rats receiving the HFD, and L. edodes reduced malondialdehyde levels, thereby preventing oxidation of fatty acids. Lentinula edodes was shown to have hypolipidemic, hypoglycemic, hepatoprotective and renoprotective features in doses that are suitable for humans.
Discrete normal plantar stress variations with running speed.

PubMed

Gross, T S; Bunch, R P

1989-01-01

The distribution of force beneath the plantar foot surface during shod distance running, a kinetic descriptor of locomotion not previously reported, was recorded for ten rearfoot striking runners. Normal discrete stresses were assessed while the subjects ran on a treadmill at 2.98, 3.58, and 4.47 ms-1, with eight piezoceramic transducers secured inside the left shoe. Between 2.98 and 4.47 ms-1, mean peak stress increased significantly beneath the calcaneus (303.9-426.6 kPa), second metatarsal head (633.5-730.5 kPa), and hallux (575.1-712.4 kPa). Calcaneal stresses were notable for their rapid loading rate, averaging 10.1 kPa (ms)-1 at 3.58 ms-1. Highest stresses were measured beneath the second and third metatarsal heads and hallux. Peak first metatarsal head stress was less than peak second and third metatarsal head stresses in each of the 30 combinations of subjects and running speeds. However, lower stresses do not necessarily imply lower forces, as the force bearing surface area of each metatarsal head must be considered.
Mid-Crustal Stress Magnitude and Rotation Transients Related to the Seismic Cycle

NASA Astrophysics Data System (ADS)

Nüchter, J. A.; Ellis, S.

2008-12-01

Seismic slip causes a stress drop in the upper crust, and a major stress increase at the lower termination of the fault in the middle crust. Previous numerical models show how these stresses relax during an episode of postseismic creep. Natural evidence for postseismic stress and strain transients at depth is provided by 1) the geological record of exhumed metamorphic rocks, and 2) from postseismic surface deformation transients. In the present study, we use numerical models to investigate the changes in the geometry of the mid-crustal stress field caused by seismic slip along normal faults within an extensional tectonic setting. We model a 100x30km crustal section, with a fault reaching down to 20km and dipping at 60°. A non-linear thermal gradient and constant elastic parameters are applied. Thermally activated creep is described by values derived from laboratory creep experiments on wet quartzite. The crust is loaded by horizontal extension at a constant rate, and earthquakes are triggered by a short term decrease in the frictional coefficient of the fault. During the interseismic period, this coefficient is set to high values to lock the fault. A sequence of 30 earthquakes with a constant recurrence interval of 500y is simulated, and the results for the last seismic cycle are analyzed. In such a tectonic setting, the Anderson theory predicts that the maximum principal stress is vertical. A stress field consistent to this theory is reached after an initial stage of 15ka extension without earthquake activity. The results for the 30th seismic cycle imply that seismic slip causes a major stress increase of at least 50MPa at a depth level below the brittle ductile transition, which is in accordance to reports on seismic stress increase derived from the record of metamorphic rocks. In the hanging wall, the stress increase results mainly from an increase in the maximum principal stress and the stress tensor rotates counter-clockwise by 10-30°. In the footwall the stress increase results mainly from a drop in the minimum principal stress, and the stress tensor rotates clockwise by 45-60°. A change in the magnitude of differential stress can be addressed by the addition of an incremental stress tensor resulting from elastic strain to the preexisting stress tensor. In an isotropic medium, the orientation of the maximum and the minimum principal stress changes are controlled by the directions of maximum compression and maximum extension, respectively. The magnitude and the orientation of the resulting stress tensor depend: 1) on the absolute magnitudes and on the ratio of the magnitudes of pre-existing stress and incremental change in the stress tensor; and 2) on the mis-orientation between existing stress and stress change principal directions. The zone of coseismic loading correlates to the interval in which seismic slip tapers off with depth. For a normal fault, the crust here is subjected to fault-parallel compression in the hanging wall, and to extension in the footwall. The resulting orientation of the seismic principal compressive stress change parallel to the fault in the hanging wall and normal to the fault in the footwall causes the particular deflection of the resulting stress tensor . During the interseismic period, the stress peak relaxes by thermally activated creep, while the deflection of the stress tensor is persistent. We show that significant mis- orientations of the stress tensor can be preserved over timescales typical for a seismic cycle, in dependence on the far field extension rate. We conclude that seismic activity causes 1) a non-steady state mid-crustal stress field, and 2) a persistent deflection of the stress tensor orientation from the predictions of the Anderson theory.

Laying hen responses to acute heat stress and carbon dioxide supplementation: I. Blood gas changes and plasma lactate accumulation.

PubMed

Koelkebeck, K W; Odom, T W

1994-04-01

Exposure to heat stress lowered partial pressure of arterial blood carbon dioxide (paCO2), arterial blood bicarbonate ion (HCO3-), but increased arterial blood pH (pHa) and plasma lactate (LA). Increasing ambient carbon dioxide (CO2) to 1.5% increased paCO2 from hypocapnic levels to normocapnic levels, raised HCO3-, lowered pHa and plasma LA to pre-heat stress levels. Following CO2 treatment, respiratory alkalosis conditions returned. It was evident in this study that increasing ambient chamber CO2 to 1.5% was effective in ameliorating acid-base disturbances and reducing elevated levels of plasma LA which normally develops when laying hens are subjected to an acute heat stress exposure.
Fluid-structure interaction modeling of aneurysmal arteries under steady-state and pulsatile blood flow: a stability analysis.

PubMed

Sharzehee, Mohammadali; Khalafvand, Seyed Saeid; Han, Hai-Chao

2018-02-01

Tortuous aneurysmal arteries are often associated with a higher risk of rupture but the mechanism remains unclear. The goal of this study was to analyze the buckling and post-buckling behaviors of aneurysmal arteries under pulsatile flow. To accomplish this goal, we analyzed the buckling behavior of model carotid and abdominal aorta with aneurysms by utilizing fluid-structure interaction (FSI) method with realistic waveforms boundary conditions. FSI simulations were done under steady-state and pulsatile flow for normal (1.5) and reduced (1.3) axial stretch ratios to investigate the influence of aneurysm, pulsatile lumen pressure and axial tension on stability. Our results indicated that aneurysmal artery buckled at the critical buckling pressure and its deflection nonlinearly increased with increasing lumen pressure. Buckling elevates the peak stress (up to 118%). The maximum aneurysm wall stress at pulsatile FSI flow was (29%) higher than under static pressure at the peak lumen pressure of 130 mmHg. Buckling results show an increase in lumen shear stress at the inner side of the maximum deflection. Vortex flow was dramatically enlarged with increasing lumen pressure and artery diameter. Aneurysmal arteries are more susceptible than normal arteries to mechanical instability which causes high stresses in the aneurysm wall that could lead to aneurysm rupture.
Dynamic release and clearance of circulating microparticles during cardiac stress.

PubMed

Augustine, Daniel; Ayers, Lisa V; Lima, Eduardo; Newton, Laura; Lewandowski, Adam J; Davis, Esther F; Ferry, Berne; Leeson, Paul

2014-01-03

Microparticles are cell-derived membrane vesicles, relevant to a range of biological responses and known to be elevated in cardiovascular disease. To investigate microparticle release during cardiac stress and how this response differs in those with vascular disease. We measured a comprehensive panel of circulating cell-derived microparticles by a standardized flow cytometric protocol in 119 patients referred for stress echocardiography. Procoagulant, platelet, erythrocyte, and endothelial but not leukocyte, granulocyte, or monocyte-derived microparticles were elevated immediately after a standardized dobutamine stress echocardiogram and decreased after 1 hour. Twenty-five patients developed stress-induced wall motion abnormalities suggestive of myocardial ischemia. They had similar baseline microparticle levels to those who did not develop ischemia, but, interestingly, their microparticle levels did not change during stress. Furthermore, no stress-induced increase was observed in those without inducible ischemia but with a history of vascular disease. Fourteen patients subsequently underwent coronary angiography. A microparticle rise during stress echocardiography had occurred only in those with normal coronary arteries. Procoagulant, platelet, erythrocyte, and endothelial microparticles are released during cardiac stress and then clear from the circulation during the next hour. This stress-induced rise seems to be a normal physiological response that is diminished in those with vascular disease.
Improving prediction of outcomes in African Americans with normal stress echocardiograms using a risk scoring system.

PubMed

Sutter, David A; Thomaides, Athanasios; Hornsby, Kyle; Mahenthiran, Jothiharan; Feigenbaum, Harvey; Sawada, Stephen G

2013-06-01

Cardiovascular mortality is high in African Americans, and those with normal results on stress echocardiography remain at increased risk. The aim of this study was to develop a risk scoring system to improve the prediction of cardiovascular events in African Americans with normal results on stress echocardiography. Clinical data and rest echocardiographic measurements were obtained in 548 consecutive African Americans with normal results on rest and stress echocardiography and ejection fractions ≥50%. Patients were followed for myocardial infarction and death for 3 years. Predictors of cardiovascular events were determined with Cox regression, and hazard ratios were used to determine the number of points in the risk score attributed to each independent predictor. During follow-up of 3 years, 47 patients (8.6%) had events. Five variables-age (≥45 years in men, ≥55 years in women), history of coronary disease, history of smoking, left ventricular hypertrophy, and exercise intolerance (<7 METs in men, <5 METs in women, or need for dobutamine stress)-were independent predictors of events. A risk score was derived for each patient (ranging from 0 to 8 risk points). The area under the curve for the risk score was 0.82 with the optimum cut-off risk score of 6. Among patients with risk scores ≥6, 30% had events, compared with 3% with risk score <6 (p <0.001). In conclusion, African Americans with normal results on stress echocardiography remain at significant risk for cardiovascular events. A risk score can be derived from clinical and echocardiographic variables, which can accurately distinguish high- and low-risk patients. Copyright © 2013 Elsevier Inc. All rights reserved.
Frictional properties of the Nankai frontal thrust explain recurring shallow slow slip events

NASA Astrophysics Data System (ADS)

Saffer, D. M.; Ikari, M.; Kopf, A.; Roesner, A.

2017-12-01

Recent observations provide evidence for shallow slip reaching to the trench on subduction megathrusts, both in earthquakes and slow slip events (SSE). This is at odds with existing friction studies, which report primarily velocity-strengthening behavior (friction increases with slip velocity) for subduction fault material and synthetic analogs, which leads only to stable sliding. We report on direct shearing experiments on fault rocks from IODP Site C0007, which sampled the frontal thrust of the Nankai accretionary prism. This fault has been implicated in both coseimic slip and recurring SSE. We focus on material from 437.2 meters below seafloor, immediately above a localized shear zone near the base of the fault. In our experiments, a 25 mm diameter cylindrical specimen is loaded in an assembly of two steel plates. After application of normal stress (3, 10, or 17 MPa) and subsequent equilibration, the lower plate is driven at a constant velocity while the upper plate remains stationary; this configuration forces shear to localize between the two plates. After reaching a steady state residual friction coefficient (µss), we conducted velocity-stepping tests to measure the friction rate parameter (a-b), defined as the change in friction for a change in velocity: (a-b) = Δuss/ln(V/Vo), over a range of velocities from 0.1-100 µm s-1. We find that µss ranges from 0.26 to 0.32 and exhibits a slight decrease with normal stress. We observe velocity-weakening behavior at low normal stresses (3-10 MPa) and for low sliding velocities (< 3-10 µm s-1). Values of (a-b)_increase systematically from -0.007 to -0.005 at velocities of 0.3-1 µm s-1, to 0.001-0.045 at velocities >30 µm s-1. At higher normal stress (17 MPa), we observe dominantly velocity-strengthening, consistent with previously reported measurements for 25 MPa normal stress. Our observation of rate weakening at slip rates matching those of SSE in the outer Nankai forearc provide a potential explanation for periodic strain accumulation and subsequent release during SSE near the trench. The observation of rate weakening behavior only at low normal stresses also suggests that nucleation of these SSE should be restricted to shallow depths (< 2-5 km) or zones of elevated pore fluid pressure.
Frictional properties of the Nankai frontal thrust explain recurring shallow slow slip events

NASA Astrophysics Data System (ADS)

Scholz, J. R.; Davy, C.; Barruol, G.; Fontaine, F. R.; Cordier, E.

2016-12-01

Recent observations provide evidence for shallow slip reaching to the trench on subduction megathrusts, both in earthquakes and slow slip events (SSE). This is at odds with existing friction studies, which report primarily velocity-strengthening behavior (friction increases with slip velocity) for subduction fault material and synthetic analogs, which leads only to stable sliding. We report on direct shearing experiments on fault rocks from IODP Site C0007, which sampled the frontal thrust of the Nankai accretionary prism. This fault has been implicated in both coseimic slip and recurring SSE. We focus on material from 437.2 meters below seafloor, immediately above a localized shear zone near the base of the fault. In our experiments, a 25 mm diameter cylindrical specimen is loaded in an assembly of two steel plates. After application of normal stress (3, 10, or 17 MPa) and subsequent equilibration, the lower plate is driven at a constant velocity while the upper plate remains stationary; this configuration forces shear to localize between the two plates. After reaching a steady state residual friction coefficient (µss), we conducted velocity-stepping tests to measure the friction rate parameter (a-b), defined as the change in friction for a change in velocity: (a-b) = Δuss/ln(V/Vo), over a range of velocities from 0.1-100 µm s-1. We find that µss ranges from 0.26 to 0.32 and exhibits a slight decrease with normal stress. We observe velocity-weakening behavior at low normal stresses (3-10 MPa) and for low sliding velocities (< 3-10 µm s-1). Values of (a-b)_increase systematically from -0.007 to -0.005 at velocities of 0.3-1 µm s-1, to 0.001-0.045 at velocities >30 µm s-1. At higher normal stress (17 MPa), we observe dominantly velocity-strengthening, consistent with previously reported measurements for 25 MPa normal stress. Our observation of rate weakening at slip rates matching those of SSE in the outer Nankai forearc provide a potential explanation for periodic strain accumulation and subsequent release during SSE near the trench. The observation of rate weakening behavior only at low normal stresses also suggests that nucleation of these SSE should be restricted to shallow depths (< 2-5 km) or zones of elevated pore fluid pressure.
Mechanosensitive channels protect plastids from hypoosmotic stress during normal plant growth.

PubMed

Veley, Kira M; Marshburn, Sarah; Clure, Cara E; Haswell, Elizabeth S

2012-03-06

Cellular response to osmotic stress is critical for survival and involves volume control through the regulated transport of osmolytes. Organelles may respond similarly to abrupt changes in cytoplasmic osmolarity. The plastids of the Arabidopsis thaliana leaf epidermis provide a model system for the study of organellar response to osmotic stress within the context of the cell. An Arabidopsis mutant lacking two plastid-localized homologs of the bacteria mechanosensitive channel MscS (MscS-like [MSL] 2 and 3) exhibits large round epidermal plastids that lack dynamic extensions known as stromules. This phenotype is present under normal growth conditions and does not require exposure to extracellular osmotic stress. Here we show that increasing cytoplasmic osmolarity through a genetic lesion known to produce elevated levels of soluble sugars, exogenously providing osmolytes in the growth media, or withholding water rescues the msl2-1 msl3-1 leaf epidermal plastid phenotype, producing plastids that resemble the wild-type in shape and size. Furthermore, the epidermal plastids in msl2-1 msl3-1 leaves undergo rapid and reversible volume and shape changes in response to extracellular hypertonic or hypotonic challenges. We conclude that plastids are under hypoosmotic stress during normal plant growth and dynamic response to this stress requires MSL2 and MSL3. Copyright Â© 2012 Elsevier Ltd. All rights reserved.
Static-stress impact of the 1992 Landers earthquake sequence on nucleation and slip at the site of the 1999 M=7.1 Hector Mine earthquake, southern California

USGS Publications Warehouse

Parsons, Tom; Dreger, Douglas S.

2000-01-01

The proximity in time (∼7 years) and space (∼20 km) between the 1992 M=7.3 Landers earthquake and the 1999 M=7.1 Hector Mine event suggests a possible link between the quakes. We thus calculated the static stress changes following the 1992 Joshua Tree/Landers/Big Bear earthquake sequence on the 1999 M=7.1 Hector Mine rupture plane in southern California. Resolving the stress tensor into rake-parallel and fault-normal components and comparing with changes in the post-Landers seismicity rate allows us to estimate a coefficient of friction on the Hector Mine plane. Seismicity following the 1992 sequence increased at Hector Mine where the fault was unclamped. This increase occurred despite a calculated reduction in right-lateral shear stress. The dependence of seismicity change primarily on normal stress change implies a high coefficient of static friction (µ≥0.8). We calculated the Coulomb stress change using µ=0.8 and found that the Hector Mine hypocenter was mildly encouraged (0.5 bars) by the 1992 earthquake sequence. In addition, the region of peak slip during the Hector Mine quake occurred where Coulomb stress is calculated to have increased by 0.5–1.5 bars. In general, slip was more limited where Coulomb stress was reduced, though there was some slip where the strongest stress decrease was calculated. Interestingly, many smaller earthquakes nucleated at or near the 1999 Hector Mine hypocenter after 1992, but only in 1999 did an event spread to become a M=7.1 earthquake.
Investigations on GSK-3β/NF-kB signaling in stress and stress adaptive behavior in electric foot shock subjected mice.

PubMed

Bali, Anjana; Jaggi, Amteshwar Singh

2016-04-01

The present study was designed to explore the role of GSK-3β and NF-kB signaling in electric foot shock-induced stress and stress adaptation. Mice were subjected to foot shocks of 0.5mA intensity and 1s duration of 1h to produce acute stress. Animals were exposed to the same stressor for 5 days to induce stress adaptation. The behavioral alterations were assessed using the actophotometer, hole board, open field and social interaction tests. The serum corticosterone levels were assessed as a marker of the HPA axis. The levels of total GSK-3β, p-GSK-3β-S9 and p-NF-kB were determined in the hippocampus, frontal cortex and amygdala. Acute electric foot shock stress produced behavioral and biochemical changes; decreased the levels of p-GSK-3β-S9, produced no change in total GSK-3β levels and increased p-NF-kB levels in the brain. However, repeated exposure of foot shock stress restored the behavioral and biochemical changes along with normalization of p-GSK-3β-S9 and p-NF-kB levels. Administration of AR-A01, a selective GSK-3β inhibitor, or diethyldithiocarbamic acid (DDTC), a selective NF-kB inhibitor, diminished acute stress-induced behavioral and biochemical changes. Furthermore, AR-A014418 normalized acute stress-induced alterations in p-GSK-3β-S9 and p-NF-kB levels, however, DDTC selectively restored NF-kB levels without any change in p-GSK-3β-S9 levels. It probably suggests that NF-kB is a downstream mediator of the GSK-3 signaling cascade. It may conclude that acute stress associated decrease in p-GSK-3β-S9 and increase in p-NF-kB levels in the brain contribute in the development of behavioral and biochemical alterations and normalization of GSK-3β/NF-kB signaling may contribute in stress adaptive behavior in response to repeated electric foot shock-subjected mice. Copyright © 2016 Elsevier B.V. All rights reserved.
Stress responses at the endometrial-placental interface regulate labyrinthine placental differentiation from trophoblast stem cells.

PubMed

Rappolee, D A; Zhou, S; Puscheck, E E; Xie, Y

2013-05-01

Development can happen in one of two ways. Cells performing a necessary function can differentiate from stem cells before the need for it arises and stress does not develop. Or need arises before function, stress develops and stress signals are part of the normal stimuli that regulate developmental mechanisms. These mechanisms adjust stem cell differentiation to produce function in a timely and proportional manner. In this review, we will interpret data from studies of null lethal mutants for placental stress genes that suggest the latter possibility. Acknowledged stress pathways participate in stress-induced and -regulated differentiation in two ways. These pathways manage the homeostatic response to maintain stem cells during the stress. Stress pathways also direct stem cell differentiation to increase the first essential lineage and suppress later lineages when stem cell accumulation is diminished. This stress-induced differentiation maintains the conceptus during stress. Pathogenic outcomes arise because population sizes of normal stem cells are first depleted by decreased accumulation. The fraction of stem cells is further decreased by differentiation that is induced to compensate for smaller stem cell populations. Analysis of placental lethal null mutant genes known to mediate stress responses suggests that the labyrinthine placenta develops during, and is regulated by, hypoxic stress.
Coating thickness affects surface stress measurement of brush electro-plating nickel coating using Rayleigh wave approach.

PubMed

Liu, Bin; Dong, Shiyun; Xu, Binshi; He, Peng

2012-09-01

A surface ultrasonic wave approach was presented for measuring surface stress of brush electro-plating nickel coating specimen, and the influence of coating thickness on surface stress measurement was discussed. In this research, two Rayleigh wave transducers with 5MHz frequency were employed to collect Rayleigh wave signals of coating specimen with different static tensile stresses and different coating thickness. The difference in time of flight between two Rayleigh wave signals was determined based on normalized cross correlation function. The influence of stress on propagation velocity of Rayleigh wave and the relationship between the difference in time of flight and tensile stress that corresponded to different coating thickness were discussed. Results indicate that inhomogeneous deformation of coating affects the relationship between the difference in time of flight and tensile stress, velocity of Rayleigh wave propagating in coating specimen increases with coating thickness increasing, and the variation rate reduces of difference in time of flight with tensile stress increasing as coating thickness increases. Copyright © 2012 Elsevier B.V. All rights reserved.
Stress and strain analysis of contractions during ramp distension in partially obstructed guinea pig jejunal segments

PubMed Central

Zhao, Jingbo; Liao, Donghua; Yang, Jian; Gregersen, Hans

2011-01-01

Previous studies have demonstrated morphological and biomechanical remodeling in the intestine proximal to an obstruction. The present study aimed to obtain stress and strain thresholds to initiate contraction and the maximal contraction stress and strain in partially obstructed guinea pig jejunal segments. Partial obstruction and sham operations were surgically created in mid-jejunum of male guinea pigs. The animals survived 2, 4, 7, and 14 days, respectively. Animals not being operated on served as normal controls. The segments were used for no-load state, zero-stress state and distension analyses. The segment was inflated to 10 cmH2O pressure in an organ bath containing 37°C Krebs solution and the outer diameter change was monitored. The stress and strain at the contraction threshold and at maximum contraction were computed from the diameter, pressure and the zero-stress state data. Young’s modulus was determined at the contraction threshold. The muscle layer thickness in obstructed intestinal segments increased up to 300%. Compared with sham-obstructed and normal groups, the contraction stress threshold, the maximum contraction stress and the Young’s modulus at the contraction threshold increased whereas the strain threshold and maximum contraction strain decreased after 7 days obstruction (P<0.05 and 0.01). In conclusion, in the partially obstructed intestinal segments, a larger distension force was needed to evoke contraction likely due to tissue remodeling. Higher contraction stresses were produced and the contraction deformation (strain) became smaller. PMID:21632056
Salt geometry influence on present-day stress orientations in the Nile Delta: Insights from numerical modeling

NASA Astrophysics Data System (ADS)

Eckert, Andreas; Zhang, Weicheng

2016-02-01

The offshore Nile Delta displays sharply contrasting orientations of the maximum horizontal stress, SH, in regions above Messinian evaporites (suprasalt) and regions below Messinian evaporites (subsalt). Published stress orientation data predominantly show margin-normal suprasalt SH orientations but a margin-parallel subsalt SH orientation. While these data sets provide the first major evidence that evaporite sequences can act as mechanical detachment horizons, the cause for the stress orientation contrast remains unclear. In this study, 3D finite element analysis is used to investigate the causes for stress re-orientation based on two different hypotheses. The modeling study evaluates the influence of different likely salt geometries and whether stress reorientations are the result of basal drag forces induced by gravitational gliding or whether they represent localized variations due to mechanical property contrasts. The modeling results show that when salt is present as a continuous layer, gravitational gliding occurs and basal drag forces induced in the suprasalt layers result in the margin-normal principal stress becoming the maximum horizontal stress. With the margin-normal stress increase being confined to the suprasalt layers, the salt acts as a mechanical detachment horizon, resulting in different SH orientations in the suprasalt compared to the subsalt layers. When salt is present as isolated bodies localized stress variations occur due to the mechanical property contrasts imposed by the salt, also resulting in different SH orientations in the suprasalt compared to the subsalt layers. The modeling results provide additional quantitative evidence to confirm the role of evaporite sequences as mechanical detachment horizons.
A Thermo-Hydro-Mechanical coupled Numerical modeling of Injection-induced seismicity on a pre-existing fault

NASA Astrophysics Data System (ADS)

Kim, Jongchan; Archer, Rosalind

2017-04-01

In terms of energy development (oil, gas and geothermal field) and environmental improvement (carbon dioxide sequestration), fluid injection into subsurface has been dramatically increased. As a side effect of these operations, a number of injection-induced seismic activities have also significantly risen. It is known that the main causes of induced seismicity are changes in local shear and normal stresses and pore pressure as well. This mechanism leads to increase in the probability of earthquake occurrence on permeable pre-existing fault zones predominantly. In this 2D fully coupled THM geothermal reservoir numerical simulation of injection-induced seismicity, we investigate the thermal, hydraulic and mechanical behavior of the fracture zone, considering a variety of 1) fault permeability, 2) injection rate and 3) injection temperature to identify major contributing parameters to induced seismic activity. We also calculate spatiotemporal variation of the Coulomb stress which is a combination of shear stress, normal stress and pore pressure and lastly forecast the seismicity rate on the fault zone by computing the seismic prediction model of Dieterich (1994).
Evidence for initiation of frictional partial slip as the mechanism behind nonlinear stress-strain hysteresis in rock fractures under seismic-frequency torsion

NASA Astrophysics Data System (ADS)

Saltiel, S.; Bonner, B. P.; Delbridge, B. G.; Ajo Franklin, J. B.

2016-12-01

We have adapted a low-frequency (0.1 - 64 Hz) torsional apparatus to explore the pure shear behavior of rock fractures under low normal stresses, simulating low effective stress environments - shallow depths and/or under high pore pressures. The instrument is unique in this ability to measure under very low confinement as well as to probe partial slip on the outside of asperities, before full slip nucleation occurs. Using a sinusoidal oscillation around this condition, we can probe the stress-strain constitutive relation at a range of strain amplitudes and the rate-dependence of the initiation of asperity slip. We find different, nonlinear, stress-strain constitutive relations for dolomite, rhyolite, and granite fractured samples, but all show softening at high strain amplitudes (above microstrain or micron-scale displacement). All measured samples exhibit qualitatively similar time-series hysteresis loops and frequency-dependence. The low frequency stress-strain loops stiffen at the high strain static end of the sinusoidal oscillation. This shape is determined by harmonic generation in the strain, while the stress signal has low power in harmonics, confirming that the driver and electronics are not the source of this nonlinearity. We also observe that this stiffening cusp does not occur as frequency increases above 8 Hz (opposite to normal dispersion seen at higher normal stresses). We monitor the fracture surface wear with repeated cycles to show the extent of slip on mapped asperities. These observations suggest that a rate dependent, healing, process causes the nonlinear responce of fracture faces under low normal stress to periodic shear. We propose that static friction at the low strain-rate part of the cycle, when given enough time at low oscillation frequencies, causes this stiffening cusp shape in the hysteretic stress-strain curve. An analytic model with idealized contact area is used to constrain the rate-state friction constitutive model parameters needed to provide this dynamic behavior.
Investigation of secondary flows in turbulent pipe flows with three-dimensional sinusoidal walls

NASA Astrophysics Data System (ADS)

Chan, Leon; MacDonald, Michael; Chung, Daniel; Hutchins, Nicholas; Ooi, Andrew

2017-11-01

The occurrence of secondary flows is systematically investigated via Direct Numerical Simulations (DNS) of turbulent flow in a rough wall pipe at friction Reynolds numbers of 540. In this study, the peak-to-trough height of the roughness elements, which consist of three-dimensional sinusoidal roughness, is fixed at 120 viscous units while the wavelength of the roughness elements is varied. The solidity or effective slope (ES) of the roughness ranges from the sparse regime (ES = 0.18) to the closely packed roughness/dense regime (ES = 0.72). The time-independent dispersive stresses, which arise due to the stationary features of the flow, are analysed and are found to increase with increasing roughness wavelength. These dispersive stresses are related to the occurrence of secondary flows and are maximum within the roughness canopy. Above the crest of the roughness elements, the dispersive stresses reduce to zero at wall-normal heights greater than half of the roughness wavelength. This study has found that the size and wall-normal extent of the secondary flows scales with the roughness wavelength and can reach wall-normal heights of almost half of the pipe radius.
Analysis of Interface Properties of Hybrid Pre-stressed Strengthening RC Beams with Crack

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie Zhihong; Huang Peiyan; Guo Yongchang

2010-05-21

A finite element (FE) analysis model of interface layer is established for the pre-stressed CFS-GFS hybrid strengthened beams. An elastic solution for the interfacial stress in the adhesive layer of the retrofitted beams is developed as well. The analytical results were compared with the FE results of interfacial stresses in the beams with different thickness of the adhesive and the fibre sheet. Different heights of Cracks in the interfacial layer of the concrete beam are considered in FE Model. Analysis results show the strengthening pattern is of excellent interface performance and the strength of the fiber sheet can be effectivelymore » utilized. The results also indicate the shear and normal stresses in the interfacial layer of the concrete beam release at the locations of the cracks and reach the maximal value before the concrete cracked. The shear and normal stresses in the adhesive layer increase abruptly, and the cracks in the adhesive layer then appear. The axial stresses of hybrid fiber sheet near the cracks decrease locally at the sites of the concrete cracks.« less
A role for tyrosinase-related protein 1 in 4-tert-butylphenol-induced toxicity in melanocytes: Implications for vitiligo.

PubMed

Manga, Prashiela; Sheyn, David; Yang, Fan; Sarangarajan, Rangaprasad; Boissy, Raymond E

2006-11-01

Vitiligo presents with depigmented cutaneous lesions following localized melanocyte death. Multiple factors contribute to cell death, including genetically determined susceptibility to trauma, and environmental factors, such as exposure to 4-tert-butylphenol (4-TBP). We demonstrate that 4-TBP induces oxidative stress that is more readily overcome by melanocytes from normally pigmented individuals than from two individuals with vitiligo. The antioxidant catalase selectively and significantly reduced death of melanocytes derived from two individuals with vitiligo, indicating a role for oxidative stress in vitiligo pathogenesis. In normal melanocytes, oxidative stress results in reduced expression of microphthalmia-associated transcription factor (MITF). Melanocyte-stimulating hormone-induced expression of MITF protein caused increased sensitivity to 4-TBP, whereas sensitivity of melanomas correlated with MITF expression. MITF stimulates melanin synthesis by up-regulating expression of melanogenic enzymes such as tyrosinase-related protein-1 (Tyrp1). Although melanin content per se did not affect sensitivity to 4-TBP, expression of Tyrp1 significantly increased sensitivity. Melanocytes and melanomas that express functional Tyrp1 were significantly more sensitive to 4-TBP than Tyrp1-null cells. Thus, normal melanocytes respond to 4-TBP by reducing expression of MITF and Tyrp1. We hypothesize that melanocytes in vitiligo demonstrate reduced ability to withstand oxidative stress due, partly, to a disruption in MITF regulation of Tyrp1.
Acute vascular effects of carbonated warm water lower leg immersion in healthy young adults.

PubMed

Ogoh, Shigehiko; Nagaoka, Ryohei; Mizuno, Takamasa; Kimura, Shohei; Shidahara, Yasuhiro; Ishii, Tomomi; Kudoh, Michinari; Iwamoto, Erika

2016-12-01

Endothelial dysfunction is associated with increased cardiovascular mortality and morbidity; however, this dysfunction may be ameliorated by several therapies. For example, it has been reported that heat-induced increases in blood flow and shear stress enhance endothelium-mediated vasodilator function. Under these backgrounds, we expect that carbon dioxide (CO 2 )-rich water-induced increase in skin blood flow improves endothelium-mediated vasodilation with less heat stress. To test our hypothesis, we measured flow-mediated dilation (FMD) before and after acute immersion of the lower legs and feet in mild warm (38°C) normal or CO 2 -rich tap water (1000 ppm) for 20 min in 12 subjects. Acute immersion of the lower legs and feet in mild warm CO 2 -rich water increased FMD (P < 0.01) despite the lack of change in this parameter upon mild warm normal water immersion. In addition, FMD was positively correlated with change in skin blood flow regardless of conditions (P < 0.01), indicating that an increase in skin blood flow improves endothelial-mediated vasodilator function. Importantly, the temperature of normal tap water must reach approximately 43°C to achieve the same skin blood flow level as that obtained during mild warm CO 2 -rich water immersion (38°C). These findings suggest that CO 2 -rich water-induced large increases in skin blood flow may improve endothelial-mediated vasodilator function while causing less heat stress. © 2016 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.
ROLE OF NRF2 IN THE OXIDATIVE STRESS-DEPENDENT HYPERTENSION ASSOCIATED WITH THE DEPLETION OF DJ-1

PubMed Central

Cuevas, Santiago; Yang, Yu; Konkalmatt, Prasad; Asico, Laureano; Feranil, Jun; Jones, John; Villar, Van Anthony; Armando, Ines; Jose, Pedro A.

2015-01-01

Renal dopamine 2 receptor dysfunction is associated with oxidative stress and high blood pressure. We have reported that DJ-1, an oxidative stress response protein, is positively regulated by dopamine 2 receptor in the kidney. The transcription factor Nrf2 regulates the expression of several antioxidant genes. We tested the hypothesis that Nrf2 is involved in the renal DJ-1-mediated inhibition of reactive oxygen species production. We have reported that silencing dopamine 2 receptor in mouse renal proximal tubule cells decreases the expression of DJ-1. We now report that silencing DJ-1 or dopamine 2 receptor in mouse proximal tubule cells and mouse kidneys, decreases Nrf2 expression and activity and increases reactive oxygen species production; blood pressure is also increased in mice in which renal DJ-1 or dopamine 2 receptor is silenced. DJ-1−/− mice have decreased renal Nrf2 expression and activity, and increased nitro-tyrosine levels an dopamine 2 receptor d blood pressure. Silencing Nrf2 in mouse proximal tubule cells does not alter the expression of DJ-1 or dopamine 2 receptor, indicating that Nrf2 is downstream of dopamine 2 receptor and DJ-1. A Nrf2 inducer, bardoxolone, normalizes the systolic blood pressure and renal malondialdehyde levels in DJ-1−/− mice without affecting them in their wild-type littermates. Because Nrf2 ubiquitination is increased in DJ-1−/− mice, we conclude that the protective effect of DJ-1 on renal oxidative stress is mediated, in part, by preventing Nrf2 degradation. Moreover, renal dopamine 2 receptor and DJ-1 are necessary for normal Nrf2 activity to keep a normal redox balance and blood pressure. PMID:25895590

Transverse Stress Decay in a Specially Orthotropic Strip Under Localizing Normal Edge Loading

NASA Technical Reports Server (NTRS)

Fichter, W. B.

2000-01-01

Solutions are presented for the stresses in a specially orthotropic infinite strip which is subjected to localized uniform normal loading on one edge while the other edge is either restrained against normal displacement only, or completely fixed. The solutions are used to investigate the diffusion of load into the strip and in particular the decay of normal stress across the width of the strip. For orthotropic strips representative of a broad range of balanced and symmetric angle-ply composite laminates, minimum strip widths are found that ensure at least 90% decay of the normal stress across the strip. In addition, in a few cases where, on the fixed edge the peak shear stress exceeds the normal stress in magnitude, minimum strip widths that ensure 90% decay of both stresses are found. To help in putting these results into perspective, and to illustrate the influence of material properties on load 9 orthotropic materials, closed-form solutions for the stresses in similarly loaded orthotropic half-planes are obtained. These solutions are used to generate illustrative stress contour plots for several representative laminates. Among the laminates, those composed of intermediate-angle plies, i.e., from about 30 degrees to 60 degrees, exhibit marked changes in normal stress contour shape with stress level. The stress contours are also used to find 90% decay distances in the half-planes. In all cases, the minimum strip widths for 90% decay of the normal stress exceed the 90% decay distances in the corresponding half-planes, in amounts ranging from only a few percent to about 50% of the half-plane decay distances. The 90% decay distances depend on both material properties and the boundary conditions on the supported edge.
Perceived early-life maternal care and the cortisol response to repeated psychosocial stress.

PubMed

Engert, Veronika; Efanov, Simona I; Dedovic, Katarina; Duchesne, Annie; Dagher, Alain; Pruessner, Jens C

2010-11-01

In the past decade, a body of animal and human research has revealed a profound influence of early-life experiences, ranging from variations in parenting behaviour to severe adversity, on hypothalamic-pituitary-adrenal axis regulation in adulthood. In our own previous studies, we have shown how variations in early-life parental care influence the development of the hippocampus and modify the cortisol awakening response. In the present study, we investigated the influence of early-life maternal care on cortisol, heart rate and subjective psychological responses to the repeated administration of a psychosocial laboratory stressor in a population of 63 healthy young adults. Low, medium and high early-life maternal care groups were identified using the Parental Bonding Instrument. Controlling for the effect of sex, we found an inverted u-shaped relation between increasing levels of maternal care and cortisol stress responsivity. Specifically, overall and stress-induced cortisol levels went from below normal in the low maternal care, to normal in the medium care, back to below normal in the high maternal care groups. We found no group differences with respect to heart rate and subjective psychological stress measures. Whereas low and high maternal care groups exhibited similarly low endocrine stress responses, their psychological profiles were opposed with increased levels of depression and anxiety and decreased self-esteem in the low care group. Sex was unequally distributed among maternal care groups, whereby the number of men with low maternal care was too small to allow introducing sex as a second between-group variable. We discuss the potential significance of this dissociation between endocrine and psychological parameters with respect to stress vulnerability and resistance for each maternal care group.
Effects of berberine on the growth and immune performance in response to ammonia stress and high-fat dietary in blunt snout bream Megalobrama amblycephala.

PubMed

Chen, Qing-Qing; Liu, Wen-Bin; Zhou, Man; Dai, Yong-Jun; Xu, Chao; Tian, Hong-Yan; Xu, Wei-Na

2016-08-01

This study aimed to figure out the effects of berberine on growth performance, immunity, oxidative stress and hepatocyte apoptosis of blunt snout bream (Megalobrama amblycephala) fed with high-fat diet. 320 fish (80.00 ± 0.90 g) were divided randomly into four trial groups (each with four replicates) and fed with 4 diets (normal diet, normal diet with 50 mg/kg berberine, high-fat diet, high-fat diet with 50 mg/kg berberine), respectively. At the end of the feeding trial, ammonia stress test was carried out for 5 days. The result showed the growth performance, immune parameters including plasm acid phosphatase (ACP) activities, lysozyme (LYZ) activities and alternative complement C3 and C4 contents were suppressed in fish fed with high-fat diets but improved in berberine diets compared with control (normal diet). Hepatopancreas oxidative status, the malondialdehyde (MDA), protein carbonyl (PC) and lipid peroxide (LPO) were increased significantly (P < 0.05) when fish were fed with high-fat diets. Berberine could slow the progression of the oxidative stress induced by high-fat through increasing superoxide dismutase (SOD) activities and total sulfydryl (T-SH) levels of fish. And the hepatocyte apoptosis in the high-fat group could also be alleviated by berberine. After the ammonia stress test, the accumulative mortality was extremely (P < 0.05) low in fish fed high-fat diet with berberine compared to other groups. It was concluded berberine as a functional feed additive significantly inhibited the progression of oxidative stress, reduced the apoptosis and enhanced the immunity of fish fed with high-fat diet. Copyright © 2016 Elsevier Ltd. All rights reserved.
Perceived early-life maternal care and the cortisol response to repeated psychosocial stress

PubMed Central

Engert, Veronika; Efanov, Simona I.; Dedovic, Katarina; Duchesne, Annie; Dagher, Alain; Pruessner, Jens C.

2010-01-01

Background In the past decade, a body of animal and human research has revealed a profound influence of early-life experiences, ranging from variations in parenting behaviour to severe adversity, on hypothalamic–pituitary–adrenal axis regulation in adulthood. In our own previous studies, we have shown how variations in early-life parental care influence the development of the hippocampus and modify the cortisol awakening response. Methods In the present study, we investigated the influence of early-life maternal care on cortisol, heart rate and subjective psychological responses to the repeated administration of a psychosocial laboratory stressor in a population of 63 healthy young adults. Low, medium and high early-life maternal care groups were identified using the Parental Bonding Instrument. Results Controlling for the effect of sex, we found an inverted u-shaped relation between increasing levels of maternal care and cortisol stress responsivity. Specifically, overall and stress-induced cortisol levels went from below normal in the low maternal care, to normal in the medium care, back to below normal in the high maternal care groups. We found no group differences with respect to heart rate and subjective psychological stress measures. Whereas low and high maternal care groups exhibited similarly low endocrine stress responses, their psychological profiles were opposed with increased levels of depression and anxiety and decreased self-esteem in the low care group. Limitations Sex was unequally distributed among maternal care groups, whereby the number of men with low maternal care was too small to allow introducing sex as a second between-group variable. Conclusion We discuss the potential significance of this dissociation between endocrine and psychological parameters with respect to stress vulnerability and resistance for each maternal care group. PMID:20964960
Maternal stress during pregnancy increases neonatal allergy susceptibility: role of glucocorticoids.

PubMed

Lim, Robert; Fedulov, Alexey V; Kobzik, Lester

2014-07-15

We sought to test experimentally whether maternal stress can promote susceptibility to development of asthma-like allergic airways disease in offspring. Normal pregnant mice (day 15) were subjected to a single restraint stress exposure. We subsequently tested their offspring for the development of airway hyperreactivity (AHR) and allergic airway inflammation (AI), after an intentionally suboptimal sensitization protocol. The offspring of stressed mothers showed levels of AI and enhanced airway responses to methacholine comparable to those seen in fully sensitized and challenged positive control animals; in contrast, minimal effects were seen in control offspring. Restraint stress caused a rapid and large increase in plasma corticosterone levels. Maternal treatment with dexamethasone on day 15 of pregnancy mimicked the stress effect and reproduced the AI and AHR outcomes, whereas blockade of the stress-induced corticosterone surge with metyrapone pretreatment of pregnant mice abrogated the effect. We conclude that stress-triggered glucocorticoids during pregnancy can increase susceptibility to allergy in offspring. Because inflammation typically includes a stress hormone response, the results also suggest a common pathway by which various injurious exposures during pregnancy might increase offspring susceptibility to asthma. Copyright © 2014 the American Physiological Society.
Seismic evidence for a slab tear at the Puerto Rico Trench

NASA Astrophysics Data System (ADS)

Meighan, Hallie E.; Pulliam, Jay; ten Brink, Uri; López-Venegas, Alberto M.

2013-06-01

fore-arc region of the northeast Caribbean plate north of Puerto Rico and the Virgin Islands has been the site of numerous seismic swarms since at least 1976. A 6 month deployment of five ocean bottom seismographs recorded two such tightly clustered swarms, along with additional events. Joint analyses of the ocean bottom seismographs and land-based seismic data reveal that the swarms are located at depths of 50-150 km. Focal mechanism solutions, found by jointly fitting P wave first-motion polarities and S/P amplitude ratios, indicate that the broadly distributed events outside the swarm generally have strike- and dip-slip mechanisms at depths of 50-100 km, while events at depths of 100-150 km have oblique mechanisms. A stress inversion reveals two distinct stress regimes: The slab segment east of 65°W longitude is dominated by trench-normal tensile stresses at shallower depths (50-100 km) and by trench-parallel tensile stresses at deeper depths (100-150 km), whereas the slab segment west of 65°W longitude has tensile stresses that are consistently trench normal throughout the depth range at which events were observed (50-100 km). The simple stress pattern in the western segment implies relatively straightforward subduction of an unimpeded slab, while the stress pattern observed in the eastern segment, shallow trench-normal tension and deeper trench-normal compression, is consistent with flexure of the slab due to rollback. These results support the hypothesis that the subducting North American plate is tearing at or near these swarms. The 35 year record of seismic swarms at this location and the recent increase in seismicity suggest that the tear is still propagating.
Seismic evidence for a slab tear at the Puerto Rico Trench

USGS Publications Warehouse

Meighan, Hallie E.; Pulliam, Jay; ten Brink, Uri S.; López-Venegas, Alberto M.

2013-01-01

The fore-arc region of the northeast Caribbean plate north of Puerto Rico and the Virgin Islands has been the site of numerous seismic swarms since at least 1976. A 6 month deployment of five ocean bottom seismographs recorded two such tightly clustered swarms, along with additional events. Joint analyses of the ocean bottom seismographs and land-based seismic data reveal that the swarms are located at depths of 50–150 km. Focal mechanism solutions, found by jointly fitting P wave first-motion polarities and S/P amplitude ratios, indicate that the broadly distributed events outside the swarm generally have strike- and dip-slip mechanisms at depths of 50–100 km, while events at depths of 100–150 km have oblique mechanisms. A stress inversion reveals two distinct stress regimes: The slab segment east of 65°W longitude is dominated by trench-normal tensile stresses at shallower depths (50–100 km) and by trench-parallel tensile stresses at deeper depths (100–150 km), whereas the slab segment west of 65°W longitude has tensile stresses that are consistently trench normal throughout the depth range at which events were observed (50–100 km). The simple stress pattern in the western segment implies relatively straightforward subduction of an unimpeded slab, while the stress pattern observed in the eastern segment, shallow trench-normal tension and deeper trench-normal compression, is consistent with flexure of the slab due to rollback. These results support the hypothesis that the subducting North American plate is tearing at or near these swarms. The 35 year record of seismic swarms at this location and the recent increase in seismicity suggest that the tear is still propagating.
Stressed out or subjective acquisition of competence – how do veterinary students see their curative work placement?

PubMed Central

Dilly, Marc; Tipold, Andrea; Geuenich, Katja

2016-01-01

Veterinary studies in Germany are regulated by the Veterinary Certification Act (TAppV). The practical part of the education consists of 1,170 hours, whereby up to 850 hours can be spent on the curative work placement. A curative work placement can result in physical and psychological stress in the sense of a professional overload. It is the aim of this study to find out in what areas and to what extent competence is acquired and psychological stress exists in students during their work placement. Veterinary students (n=142) from all German education institutes participated in a voluntary online-study based on Burnout Screening Scales (BOSS) as well as a questionnaire regarding the acquisition of competence and excessive stress during the work placement (FKÜP). The distribution of values for work placement related stress show that such work placement related stress is generally slightly increased (T=60) and lies above that of occupational stresses within the normal population. Work placement related physical complaints also show a significant slight increase (T=61). A value (T=42) within the normal range was determined for the resource values. Few of the students questioned considered themselves to be excessively stressed in favour of a high subjective acquisition of competences. The largest increase regarding the acquisition of competence was noted for the areas of animal handling/restraint and application and injection techniques. In the sense of a perceived excessive demand regarding practical capabilities the areas of emergency management, surgery and medication dispensation were mentioned. With regard to the load structure and the acquisition of competence by veterinary students during their work placement, more support of the individual and a balancing of teaching/learning goals would be desirable and represents a promising approach. PMID:26958657
Housing in Pyramid Counteracts Neuroendocrine and Oxidative Stress Caused by Chronic Restraint in Rats

PubMed Central

Rao, Guruprasad; Murthy, K. Dilip; Bhat, P. Gopalakrishna

2007-01-01

The space within the great pyramid and its smaller replicas is believed to have an antistress effect. Research has shown that the energy field within the pyramid can protect the hippocampal neurons of mice from stress-induced atrophy and also reduce neuroendocrine stress, oxidative stress and increase antioxidant defence in rats. In this study, we have, for the first time, attempted to study the antistress effects of pyramid exposure on the status of cortisol level, oxidative damage and antioxidant status in rats during chronic restraint stress. Adult female Wistar rats were divided into four groups as follows: normal controls (NC) housed in home cage and left in the laboratory; restrained rats (with three subgroups) subject to chronic restraint stress by placing in a wire mesh restrainer for 6 h per day for 14 days, the restrained controls (RC) having their restrainers kept in the laboratory; restrained pyramid rats (RP) being kept in the pyramid; and restrained square box rats (RS) in the square box during the period of restraint stress everyday. Erythrocyte malondialdehyde (MDA) and plasma cortisol levels were significantly increased and erythrocyte-reduced glutathione (GSH) levels, erythrocyte glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) activities were significantly decreased in RC and RS rats as compared to NC. However, these parameters were maintained to near normal levels in RP rats which showed significantly decreased erythrocyte MDA and plasma cortisol and significantly increased erythrocyte GSH levels, erythrocyte GSH-Px and SOD activities when compared with RS rats. The results showed that housing in pyramid counteracts neuroendocrine and oxidative stress caused by chronic restraint in rats. PMID:17342239
Cardiovascular reactivity to acute psychological stress following sleep deprivation.

PubMed

Franzen, Peter L; Gianaros, Peter J; Marsland, Anna L; Hall, Martica H; Siegle, Greg J; Dahl, Ronald E; Buysse, Daniel J

2011-10-01

Psychological stress and sleep disturbances are highly prevalent and are both implicated in the etiology of cardiovascular diseases. Given the common co-occurrence of psychological distress and sleep disturbances including short sleep duration, this study examined the combined effects of these two factors on blood pressure reactivity to immediate mental challenge tasks after well-rested and sleep-deprived experimental conditions. Participants (n = 20) were healthy young adults free from current or past sleep, psychiatric, or major medical disorders. Using a within-subjects crossover design, we examined acute stress reactivity under two experimental conditions: after a night of normal sleep in the laboratory and after a night of total sleep deprivation. Two standardized psychological stress tasks were administered, a Stroop color-word naming interference task and a speech task, which were preceded by a prestress baseline period and followed by a poststress recovery period. Each period was 10 minutes in duration, and blood pressure recordings were collected every 2.5 minutes throughout each period. Mean blood pressure responses during stress and recovery periods were examined with a mixed-effects analysis of covariance, controlling for baseline blood pressure. There was a significant interaction between sleep deprivation and stress on systolic blood pressure (F(2,82.7) = 4.05, p = .02). Systolic blood pressure was higher in the sleep deprivation condition compared with the normal sleep condition during the speech task and during the two baseline periods. Sleep deprivation amplified systolic blood pressure increases to psychological stress. Sleep loss may increase cardiovascular risk by dysregulating stress physiology.
Short-term pre- and post-operative stress prolongs incision-induced pain hypersensitivity without changing basal pain perception.

PubMed

Cao, Jing; Wang, Po-Kai; Tiwari, Vinod; Liang, Lingli; Lutz, Brianna Marie; Shieh, Kun-Ruey; Zang, Wei-Dong; Kaufman, Andrew G; Bekker, Alex; Gao, Xiao-Qun; Tao, Yuan-Xiang

2015-12-02

Chronic stress has been reported to increase basal pain sensitivity and/or exacerbate existing persistent pain. However, most surgical patients have normal physiological and psychological health status such as normal pain perception before surgery although they do experience short-term stress during pre- and post-operative periods. Whether or not this short-term stress affects persistent postsurgical pain is unclear. In this study, we showed that pre- or post-surgical exposure to immobilization 6 h daily for three consecutive days did not change basal responses to mechanical, thermal, or cold stimuli or peak levels of incision-induced hypersensitivity to these stimuli; however, immobilization did prolong the duration of incision-induced hypersensitivity in both male and female rats. These phenomena were also observed in post-surgical exposure to forced swimming 25 min daily for 3 consecutive days. Short-term stress induced by immobilization was demonstrated by an elevation in the level of serum corticosterone, an increase in swim immobility, and a decrease in sucrose consumption. Blocking this short-term stress via intrathecal administration of a selective glucocorticoid receptor antagonist, RU38486, or bilateral adrenalectomy significantly attenuated the prolongation of incision-induced hypersensitivity to mechanical, thermal, and cold stimuli. Our results indicate that short-term stress during the pre- or post-operative period delays postoperative pain recovery although it does not affect basal pain perception. Prevention of short-term stress may facilitate patients' recovery from postoperative pain.
Gastroprotective Properties of Karanjin from Karanja (Pongamia pinnata) Seeds; Role as Antioxidant and H, K-ATPase Inhibitor.

PubMed

Vismaya; Belagihally, Srikanta M; Rajashekhar, Sindhu; Jayaram, Vinay B; Dharmesh, Shylaja M; Thirumakudalu, Sindhu Kanya C

2011-01-01

Plant extracts are the most attractive sources of newer drugs and have been shown to produce promising results for the treatment of gastric ulcers. Karanjin, a furano-flavonoid has been evaluated for anti-ulcerogenic property by employing adult male albino rats. Karanjin (>95% pure) was administered to these rats in two different concentrations, that is, 10 and 20 mg kg(-1) b.w. Ulcers were induced in the experimental animals by swim and ethanol stress. Serum, stomach and liver-tissue homogenates were assessed for biochemical parameters. Karanjin inhibited 50 and 74% of ulcers induced by swim stress at 10 and 20 mg kg(-1) b.w., respectively. Gastric mucin was protected up to 85% in case of swim stress, whereas only 47% mucin recovery was seen in ethanol stress induced ulcers. H(+), K(+)-ATPase activity, which was increased 2-fold in ulcer conditions, was normalized by Karanjin in both swim/ethanol stress-induced ulcer models. Karanjin could inhibit oxidative stress as evidenced by the normalization of lipid peroxidation and antioxidant enzyme (i.e., catalase, peroxidase and superoxide dismutase) levels. Karanjin at concentrations of 20 mg kg(-1) b.w., when administered orally for 14 days, did not indicate any lethal effects. There were no significant differences in total protein, serum glutamate pyruvate transaminase, serum glutamate oxaloacetate transaminase and alkaline phosphatase between normal and Karanjin-treated rats indicating no adverse effect on major organs. During treatment schedule, animals remained as healthy as control animals with normal food and water intake and body weight gain.
Gastroprotective Properties of Karanjin from Karanja (Pongamia pinnata) Seeds; Role as Antioxidant and H+, K+-ATPase Inhibitor

PubMed Central

Vismaya; Belagihally, Srikanta M.; Rajashekhar, Sindhu; Jayaram, Vinay B.; Dharmesh, Shylaja M.; Thirumakudalu, Sindhu Kanya C.

2011-01-01

Plant extracts are the most attractive sources of newer drugs and have been shown to produce promising results for the treatment of gastric ulcers. Karanjin, a furano-flavonoid has been evaluated for anti-ulcerogenic property by employing adult male albino rats. Karanjin (>95% pure) was administered to these rats in two different concentrations, that is, 10 and 20 mg kg−1 b.w. Ulcers were induced in the experimental animals by swim and ethanol stress. Serum, stomach and liver-tissue homogenates were assessed for biochemical parameters. Karanjin inhibited 50 and 74% of ulcers induced by swim stress at 10 and 20 mg kg−1 b.w., respectively. Gastric mucin was protected up to 85% in case of swim stress, whereas only 47% mucin recovery was seen in ethanol stress induced ulcers. H+, K+-ATPase activity, which was increased 2-fold in ulcer conditions, was normalized by Karanjin in both swim/ethanol stress-induced ulcer models. Karanjin could inhibit oxidative stress as evidenced by the normalization of lipid peroxidation and antioxidant enzyme (i.e., catalase, peroxidase and superoxide dismutase) levels. Karanjin at concentrations of 20 mg kg−1 b.w., when administered orally for 14 days, did not indicate any lethal effects. There were no significant differences in total protein, serum glutamate pyruvate transaminase, serum glutamate oxaloacetate transaminase and alkaline phosphatase between normal and Karanjin-treated rats indicating no adverse effect on major organs. During treatment schedule, animals remained as healthy as control animals with normal food and water intake and body weight gain. PMID:21799691
Where did the time go? Friction evolves with slip following large velocity steps, normal stress steps, and (?) during long holds

NASA Astrophysics Data System (ADS)

Rubin, A. M.; Bhattacharya, P.; Tullis, T. E.; Okazaki, K.; Beeler, N. M.

2016-12-01

The popular constitutive formulations of rate-and-state friction offer two end-member views on whether friction evolves only with slip (Slip law state evolution) or with time even without slip (Aging law state evolution). While rate stepping experiments show support for the Slip law, laboratory observed frictional behavior of initially bare rock surfaces near zero slip rate has traditionally been interpreted to show support for time-dependent evolution of frictional strength. Such laboratory derived support for time-dependent evolution has been one of the motivations behind the Aging law being widely used to model earthquake cycles on natural faults.Through a combination of theoretical results and new experimental data on initially bare granite, we show stronger support for the other end member view, i.e. that friction under a wide range of sliding conditions evolves only with slip. Our dataset is unique in that it combines up to 3.5 orders of magnitude rate steps, sequences of holds up to 10000s, and 5% normal stress steps at order of magnitude different sliding rates during the same experimental run. The experiments were done on the Brown rotary shear apparatus using servo feedback, making the machine stiff enough to provide very large departures from steady-state while maintaining stable, quasi-static sliding. Across these diverse sliding conditions, and in particular for both large velocity step decreases and the longest holds, the data are much more consistent with the Slip law version of slip-dependence than the time-dependence formulated in the Aging law. The shear stress response to normal stress steps is also consistently better explained by the Slip law when paired with the Linker-Dieterich type response to normal stress perturbations. However, the remarkable symmetry and slip-dependence of the normal stress step increases and decreases suggest deficiencies in the Linker-Dieterich formulation that we will probe in future experiments.High quality measurements of interface compaction from the normal-stress steps suggest that the instantaneous changes in state and contact area are opposite in sign, indicating that state evolution might be fundamentally connected to contact quality, and not quantity alone.
Cerebrospinal Fluid Concentration of Key Autophagy Protein Lamp2 Changes Little During Normal Aging

PubMed Central

Loeffler, David A.; Klaver, Andrea C.; Coffey, Mary P.; Aasly, Jan O.

2018-01-01

Autophagy removes both functional and damaged intracellular macromolecules from cells via lysosomal degradation. Three autophagic mechanisms, namely macroautophagy, chaperone-mediated autophagy (CMA), and microautophagy, have been described in mammals. Studies in experimental systems have found macroautophagy and CMA to decrease with normal aging, despite the fact that oxidative stress, which can activate both processes, increases with normal aging. Whether autophagic mechanisms decrease in the human brain during normal aging is unclear. The primary objective of this study was to examine the association of a major autophagy protein, lysosome-associated membrane glycoprotein (lamp2), with age in cerebrospinal fluid (CSF) samples from healthy subjects. Lamp2 consists of three isoforms, lamp2a, 2b and 2c, all of which participate in autophagy. Lamp2’s CSF concentration decreases in Parkinson’s disease (PD) and increases in Alzheimer’s disease (AD), but whether its CSF concentration changes during normal aging has not been investigated. Our secondary objectives were to examine the associations of lamp2’s CSF concentration with CSF levels of the molecular chaperone heat shock 70-kDa protein (HSPA8), which interacts with lamp2a in CMA, and oxidative stress markers 8-hydroxy-2′-deoxyguanosine (8-OHdG), 8-isoprostane (8-ISO) and Total Antioxidant Capacity (TAC) in healthy subjects. We found lamp2’s observed associations with these variables to be weak, with all Kendall’s tau-b absolute values ≤0.20. These results suggest that CSF lamp2 concentration changes little during normal aging and does not appear to be associated with HSPA8 or oxidative stress. Further studies are indicated to determine the relationship between CSF lamp2 concentration and brain autophagic processes.
A computational study of the respiratory airflow characteristics in normal and obstructed human airways.

PubMed

Sul, Bora; Wallqvist, Anders; Morris, Michael J; Reifman, Jaques; Rakesh, Vineet

2014-09-01

Obstructive lung diseases in the lower airways are a leading health concern worldwide. To improve our understanding of the pathophysiology of lower airways, we studied airflow characteristics in the lung between the 8th and the 14th generations using a three-dimensional computational fluid dynamics model, where we compared normal and obstructed airways for a range of breathing conditions. We employed a novel technique based on computing the Pearson׳s correlation coefficient to quantitatively characterize the differences in airflow patterns between the normal and obstructed airways. We found that the airflow patterns demonstrated clear differences between normal and diseased conditions for high expiratory flow rates (>2300ml/s), but not for inspiratory flow rates. Moreover, airflow patterns subjected to filtering demonstrated higher sensitivity than airway resistance for differentiating normal and diseased conditions. Further, we showed that wall shear stresses were not only dependent on breathing rates, but also on the distribution of the obstructed sites in the lung: for the same degree of obstruction and breathing rate, we observed as much as two-fold differences in shear stresses. In contrast to previous studies that suggest increased wall shear stress due to obstructions as a possible damage mechanism for small airways, our model demonstrated that for flow rates corresponding to heavy activities, the wall shear stress in both normal and obstructed airways was <0.3Pa, which is within the physiological limit needed to promote respiratory defense mechanisms. In summary, our model enables the study of airflow characteristics that may be impractical to assess experimentally. Published by Elsevier Ltd.
Late myocardial ischemia with ST-segment elevation after negative dobutamine stress echocardiography in a patient with normal coronary arteries.

PubMed

Cabani, Enrico; Lattanzi, Fabio; Paci, Anna Maria; Pieroni, Andrea; Baria, Luca; Tommasi, Salvatore Mario De

2009-04-01

Late complications after pharmacological stress echocardiography are infrequent but potentially dreadful events. We report the case of a 80-year-old woman admitted to hospital for rest chest pain with trivial troponin increase, normal left ventricular function and no significant ECG changes. A dobutamine stress echocardiography was performed for diagnostic purpose, with a negative result. About 30 min after the end of dobutamine infusion, she developed ST-segment elevation in inferior leads associated with chest pain and left ventricular dyssynergy, promptly resolved by sublingual nitrates. Subsequently, angiography documented the absence of significant coronary stenoses. The following clinical course was uneventful. Transient myocardial ischemia was likely due to dobutamine-induced coronary spasm. The case emphasizes the utility of routine, long-lasting monitoring of patients after stress echocardiography, even if negative, to counteract possible late life-threatening complications.
HPA axis response to social stress is attenuated in schizophrenia but normal in depression: evidence from a meta-analysis of existing studies.

PubMed

Ciufolini, Simone; Dazzan, Paola; Kempton, Matthew J; Pariante, Carmine; Mondelli, Valeria

2014-11-01

We conducted a meta-analysis to investigate the HPA axis response to social stress in studies that used the Trier Social Stress Test (TSST), or comparable distressing paradigms, in individuals with either depression or schizophrenia. Sample size-adjusted effect sizes (Hedge's g statistic) were calculated to estimate the HPA axis stress response to social stress. We used a meta-regression model to take into account the moderating effect of the baseline cortisol level. Participants with depression show an activation pattern to social stress similar to that of healthy controls. Despite a normal cortisol production rate, individuals with schizophrenia have lower cortisol levels than controls both in anticipation and after exposure to social stress. Participants with depression and higher cortisol levels before the task have an increased cortisol production and reached higher cortisol levels during the task. This may be explained by the presence of an impaired negative feedback. The activation pattern present in schizophrenia may explain the reduced ability to appropriately contextualize past experiences shown by individuals with psychosis in social stressful situation. Copyright © 2014 Elsevier Ltd. All rights reserved.
The Influence of Artificial Cervical Disc Prosthesis Height on the Cervical Biomechanics: A Finite Element Study.

PubMed

Yuan, Wei; Zhang, Haiping; Zhou, Xiaoshu; Wu, Weidong; Zhu, Yue

2018-05-01

Artificial cervical disc replacement is expected to maintain normal cervical biomechanics. At present, the effect of the Prestige LP prosthesis height on cervical biomechanics has not been thoroughly studied. This finite element study of the cervical biomechanics aims to predict how the parameters, like range of motion (ROM), adjacent intradiscal pressure, facet joint force, and bone-implant interface stress, are affected by different heights of Prestige LP prostheses. The finite element model of intact cervical spine (C3-C7) was obtained from our previous study, and the model was altered to implant Prestige LP prostheses at the C5-C6 level. The effects of the height of 5, 6, and 7 mm prosthesis replacement on ROM, adjacent intradiscal pressure, facet joint force, as well as the distribution of bone-implant interface stress were examined. ROM, adjacent intradiscal pressure, and facet joint force increased with the prosthesis height, whereas ROM and facet joint force decreased at C5-C6. The maximal stress on the inferior surface of the prostheses was greater than that on the superior surface, and the stresses increased with the prosthesis height. The biomechanical changes were slightly affected by the height of 5 and 6 mm prostheses, but were strongly affected by the 7-mm prosthesis. An appropriate height of the Prestige LP prosthesis can preserve normal ROM, adjacent intradiscal pressure, and facet joint force. Prostheses with a height of ≥2 mm than normal can lead to marked changes in the cervical biomechanics and bone-implant interface stress. Copyright © 2018 Elsevier Inc. All rights reserved.
Frictional stability and earthquake triggering during fluid pressure stimulation of an experimental fault

NASA Astrophysics Data System (ADS)

Scuderi, M. M.; Collettini, C.; Marone, C.

2017-11-01

It is widely recognized that the significant increase of M > 3.0 earthquakes in Western Canada and the Central United States is related to underground fluid injection. Following injection, fluid overpressure lubricates the fault and reduces the effective normal stress that holds the fault in place, promoting slip. Although, this basic physical mechanism for earthquake triggering and fault slip is well understood, there are many open questions related to induced seismicity. Models of earthquake nucleation based on rate- and state-friction predict that fluid overpressure should stabilize fault slip rather than trigger earthquakes. To address this controversy, we conducted laboratory creep experiments to monitor fault slip evolution at constant shear stress while the effective normal stress was systematically reduced via increasing fluid pressure. We sheared layers of carbonate-bearing fault gouge in a double direct shear configuration within a true-triaxial pressure vessel. We show that fault slip evolution is controlled by the stress state acting on the fault and that fluid pressurization can trigger dynamic instability even in cases of rate strengthening friction, which should favor aseismic creep. During fluid pressurization, when shear and effective normal stresses reach the failure condition, accelerated creep occurs in association with fault dilation; further pressurization leads to an exponential acceleration with fault compaction and slip localization. Our work indicates that fault weakening induced by fluid pressurization can overcome rate strengthening friction resulting in fast acceleration and earthquake slip. Our work points to modifications of the standard model for earthquake nucleation to account for the effect of fluid overpressure and to accurately predict the seismic risk associated with fluid injection.

Normal stresses in semiflexible polymer hydrogels

NASA Astrophysics Data System (ADS)

Vahabi, M.; Vos, Bart E.; de Cagny, Henri C. G.; Bonn, Daniel; Koenderink, Gijsje H.; MacKintosh, F. C.

2018-03-01

Biopolymer gels such as fibrin and collagen networks are known to develop tensile axial stress when subject to torsion. This negative normal stress is opposite to the classical Poynting effect observed for most elastic solids including synthetic polymer gels, where torsion provokes a positive normal stress. As shown recently, this anomalous behavior in fibrin gels depends on the open, porous network structure of biopolymer gels, which facilitates interstitial fluid flow during shear and can be described by a phenomenological two-fluid model with viscous coupling between network and solvent. Here we extend this model and develop a microscopic model for the individual diagonal components of the stress tensor that determine the axial response of semiflexible polymer hydrogels. This microscopic model predicts that the magnitude of these stress components depends inversely on the characteristic strain for the onset of nonlinear shear stress, which we confirm experimentally by shear rheometry on fibrin gels. Moreover, our model predicts a transient behavior of the normal stress, which is in excellent agreement with the full time-dependent normal stress we measure.
Does oxidative stress modulate left ventricular diastolic function in asymptomatic subjects with hereditary hemochromatosis?

PubMed

Shizukuda, Yukitaka; Bolan, Charles D; Tripodi, Dorothy J; Sachdev, Vandana; Nguyen, Tammy T; Botello, Gilberto; Yau, Yu-Ying; Sidenko, Stanislav; Inez, Ernst; Ali, Mir I; Waclawiw, Myron A; Leitman, Susan F; Rosing, Douglas R

2009-11-01

Little is known about the early mechanisms mediating left ventricular (LV) diastolic dysfunction in patients with hereditary hemochromatosis (HH). However, the increased oxidative stress related to iron overload may be involved in this process, and strain rate (SR), a sensitive echocardiography-derived measure of diastolic function, may detect such changes. we evaluated the relationship between left ventricular diastolic function measured with tissue Doppler SR and oxidative stress in asymptomatic HH subjects and control normal subjects. Ninety-four consecutive visits of 43 HH subjects, age 30-74 (50 +/- 10, mean +/- SD), and 37 consecutive visits of 21 normal volunteers, age 30-63 (48 +/- 8), were evaluated over a 3-year period. SR was obtained from the basal septum in apical four-chamber views. All patients had confirmed C282Y homozygosity, a documented history of iron overload, and were New York Heart Association functional class I. Normal volunteers lacked HFE gene mutations causing HH. In the HH subjects, the SR demonstrated moderate but significant correlations with biomarkers of oxidative stress; however, no correlations were noted in normal subjects. The biomarkers of iron overload per se did not show significant correlations with the SR. Although our study was limited by the relatively small subject number, these results suggest that a possible role of oxidative stress to affect LV diastolic function in asymptomatic HH subjects and SR imaging may be a sensitive measure to detect that effect.
One-pot three-component synthesis of novel heterocyclic steroids as a central antioxidant and anti-inflammatory agents.

PubMed

Mohamed, Nadia R; Abdelhalim, Mervat M; Khadrawy, Yasser A; Elmegeed, Gamal A; Abdel-Salam, Omar M E

2012-11-01

Oxidative stress and inflammation have been implicated in several neurodegenerative and developmental brain disorders. The present work was devoted to the design and synthesis of novel steroid derivatives bearing promising heterocyclic moiety that would act to reduce neuro-inflammation and oxidative stress in brain. The novel heterocyclic steroids were synthesized and their chemical structures were confirmed by studying their analytical and spectral data. The tested compounds were assayed in the model of neuro-inflammation produced in rats by cerebral lipopolysaccharide injection. The intracerebral administration of bacterial endotoxin resulted in cerebral inflammatory state evidenced by increased malondialdehyde (MDA), decreased reduced glutathione (GSH) level, increased nitric oxide as well as increased acetylcholinesterase (AChE) activity in the brain. Compounds 6, 10, 8b and 13a markedly increased reduced glutathione. Malondialadehyde and nitric oxide levels were reduced to normal values after treatment with all tested compounds. AChE activity was normalized by compound 8b and reduced to below normal values by compounds 10 and 14a. These results are exciting in that these agents might be useful candidates in treatment of cerebral inflammation. Copyright © 2012 Elsevier Inc. All rights reserved.
The protective effect of the Vacha rhizome extract on chronic stress-induced immunodeficiency in rat.

PubMed

Sarjan, H N; Divyashree, S; Yajurvedi, H N

2017-12-01

Chronic stress is an inevitable factor in the modern day society which affects cell mediated as well as humoral immunity. There is a need to prevent stress effects with traditionally used herbs. The present study was undertaken to investigate the immunoprotective effect of Vacha (Acorus calamus L. Acoraceae) rhizome under stressful condition. Soxlet extraction of Vacha rhizome was performed with increasing polarity of solvents, i.e., petroleum ether to ethanol. The extract was concentrated by distilling off the solvent in flash evaporator and dried in desiccators. The benzene extract was found to have anti-stress property in our earlier studies and hence it was used in the present experiment. Extract was administered every day for 4 weeks orally to adult female rats prior to exposure to stress, restraint (1 h) and forced swimming exercise (15 min). Vacha rhizome extract significantly prevented the stress induced reduction in total and differential leukocytes count, immunoglobulin content, bone marrow cellularity and viability, lymphocytes counts in lymphoid organs, islands of white pulp of spleen (ED 50 = 10 mg, p < 0.001) and a significant increase in circulating immune complexes and apoptotic index of lymphoid organs (ED 50 = 10 mg, p < 0.001) compared to controls. The present study clearly indicates that Vacha extract not only prevents stress-induced suppression of immunity and structural involution of lymphoid organs, but also boosts immunity in normal rats. Therefore, it is suggested that Vacha extract administration maintains normal immunity despite the body experiencing stress.
Use of a student support group to reduce student stress in a nurse anesthesia program.

PubMed

Kless, J R

1989-02-01

Stress in nurse anesthesia programs may be excessive at times, especially in new students. While some degree of stress is necessary to motivate learning, excessive or prolonged stress can interfere with the normal learning process, thereby prolonging a student's clinical and academic progress. In the extreme, excessive stress may even preclude a student's successful completion of the educational program. Active faculty intervention through a student support group is advocated as a method for controlling stress levels and facilitating student learning. The positive effects of such intervention also increase the overall productivity of a program and better prepare nurse anesthesia students for their future careers.
Shear-coupled grain-boundary migration dependence on normal strain/stress

NASA Astrophysics Data System (ADS)

Combe, N.; Mompiou, F.; Legros, M.

2017-08-01

In specific conditions, grain-boundary (GB) migration occurs in polycrystalline materials as an alternative vector of plasticity compared to the usual dislocation activity. The shear-coupled GB migration, the expected most efficient GB based mechanism, couples the GB motion to an applied shear stress. Stresses on GB in polycrystalline materials seldom have, however, a unique pure shear component. This work investigates the influence of a normal strain on the shear coupled migration of a Σ 13 (320 )[001 ] GB in a copper bicrystal using atomistic simulations. We show that the yield shear stress inducing the GB migration strongly depends on the applied normal stress. Beyond, the application of a normal stress on this GB qualitatively modifies the GB migration: while the Σ 13 (320 )[001 ] GB shear couples following the 〈110 〉 migration mode without normal stress, we report the observation of the 〈010 〉 mode under a sufficiently high tensile normal stress. Using the nudge elastic band method, we uncover the atomistic mechanism of this 〈010 〉 migration mode and energetically characterize it.
Wrinkle-like slip pulse on a fault between different materials

USGS Publications Warehouse

Andrews, D.J.; Ben-Zion, Y.

1997-01-01

Pulses of slip velocity can propagate on a planar interface governed by a constant coefficient of friction, where the interface separates different elastic materials. Such pulses have been found in two-dimensional plane strain finite difference calculations of slip on a fault between elastic media with wave speeds differing by 20%. The self-sustaining propagation of the slip pulse arises from interaction between normal and tangential deformation that exists only with a material contrast. These calculations confirm the prediction of Weertman [1980] that a dislocation propagating steadily along a material interface has a tensile change of normal traction with the same pulse shape as slip velocity. The self-sustaining pulse is associated with a rapid transition from a head wave traveling along the interface with the S wave speed of the faster material, to an opposite polarity body wave traveling with the slower S speed. Slip occurs during the reversal of normal particle velocity. The pulse can propagate in a region with constant coefficient of friction and an initial stress state below the frictional criterion. Propagation occurs in only one direction, the direction of slip in the more compliant medium, with rupture velocity near the slower S wave speed. Displacement is larger in the softer medium, which is displaced away from the fault during the passage of the slip pulse. Motion is analogous to a propagating wrinkle in a carpet. The amplitude of slip remains approximately constant during propagation, but the pulse width decreases and the amplitudes of slip velocity and stress change increase. The tensile change of normal traction increases until absolute normal traction reaches zero. The pulse can be generated as a secondary effect of a drop of shear stress in an asperity. The pulse shape is unstable, and the initial slip pulse can change during propagation into a collection of sharper pulses. Such a pulse enables slip to occur with little loss of energy to friction, while at the same time increasing irregularity of stress and slip at the source. Copyright 1997 by the American Geophysical Union.
Differential modulatory effects of morphine on acute and chronic stress induced neurobehavioral and cellular markers in rats.

PubMed

Joshi, Jagdish C; Ray, Arunabha; Gulati, Kavita

2014-04-15

The present study evaluated the effects of morphine treatments on elevated plus maze test parameters, oxidative stress markers and Hsp70 expression in normal and stressed rats. Acute and chronic stress caused neurobehavioral suppression, altered prooxidant-antioxidant balance and increased Hsp70 expression in brain homogenates in a differential manner. Morphine (1 and 5mg/kg) attenuated RS induced anxiogenesis, changes in MDA and GSH but further enhanced Hsp70 expression. Similar anxiolytic and Hsp70 enhancing effects were seen after morphine in normal rats (no RS). Exposure to chronic RS did not elicit any appreciable neurobehavioral response in EPM but enhanced MDA, lowered GSH and exaggerated the Hsp70 expression. Pretreatment with morphine did not affect the neurobehavioral response to chronic RS, but reverted the GSH and Hsp70 expression. The results suggest that morphine differentially influences acute and chronic stress induced changes in anxiety behavior and complex interactions between oxidative stress markers and Hsp70 expression which may contribute to these effects. Copyright © 2014 Elsevier B.V. All rights reserved.
Effect of radiation on red cell membrane and intracellular oxidative defense systems.

PubMed

Katz, D; Mazor, D; Dvilansky, A; Meyerstein, N

1996-03-01

Ionizing radiation is currently used for prevention of transfusion associated graft versus host disease (TAGVHD). As radiation damage is associated with the production of activated oxygen species, the aim of this study was to observe the immediate effect of ionizing radiation on red cell membrane and intracellular oxidative defense systems. Neonatal and iron deficiency (IDA) cells, known for their increased sensitivity to oxidative stress, were chosen and compared with normal cells. Irradiation was performed in doses of 1500 cGy, 3000 cGy and 5000 cGy. GSH and methemoglobin levels and the activity of different antioxidant enzymes, measured under optimal in vitro conditions, were preserved in all cells after irradiation. Only radiation at the highest does of 5000 cGy, caused significant potassium leakage in neonatal cells and insignificant increase in IDA cells. Thus, cells with increased sensitivity to oxidative stress are more susceptible to damage by ionizing radiation than normal cells.
Wear Enhancement of Wheel-Rail Interaction by Ultrasonic Nanocrystalline Surface Modification Technique.

PubMed

Chang, Seky; Pyun, Young-Sik; Amanov, Auezhan

2017-02-16

In this study, an ultrasonic nanocrystalline surface modification (UNSM) technique was applied to normal and heat-treated rails made of 60 kgK steel to enhance the wear resistance of the wheel-rail interaction. The hardness and compressive residual stress values of the untreated and UNSM-treated rails were measured by the Brinell hardness tester and X-ray diffraction technique, respectively. It was found, according to the measurement results, that the hardness was increased by about 20% and 8%, whereas the compressive residual stress was induced by about 52% and 62% for the UNSM-treated normal and heat-treated rails, respectively. The UNSM-treated normal rail showed a slightly higher hardness than the heat-treated rail. The wear resistance of rails with respect to rotating speed and rolling time was assessed using a rolling contact wear (RCW) tester under dry conditions. The RCW test results revealed that the wear of the UNSM-treated rails was enhanced in comparison with those of the untreated rails. Also, the wear amount of the rails was increased with increasing the rotation speed. The UNSM-treated normal rail exhibited the highest wear resistance with respect to the rotation speed. The wear mechanisms of the rails are also discussed based on microscopic images of the worn out surfaces.
Wear Enhancement of Wheel-Rail Interaction by Ultrasonic Nanocrystalline Surface Modification Technique

PubMed Central

Chang, Seky; Pyun, Young-Sik; Amanov, Auezhan

2017-01-01

In this study, an ultrasonic nanocrystalline surface modification (UNSM) technique was applied to normal and heat-treated rails made of 60 kgK steel to enhance the wear resistance of the wheel-rail interaction. The hardness and compressive residual stress values of the untreated and UNSM-treated rails were measured by the Brinell hardness tester and X-ray diffraction technique, respectively. It was found, according to the measurement results, that the hardness was increased by about 20% and 8%, whereas the compressive residual stress was induced by about 52% and 62% for the UNSM-treated normal and heat-treated rails, respectively. The UNSM-treated normal rail showed a slightly higher hardness than the heat-treated rail. The wear resistance of rails with respect to rotating speed and rolling time was assessed using a rolling contact wear (RCW) tester under dry conditions. The RCW test results revealed that the wear of the UNSM-treated rails was enhanced in comparison with those of the untreated rails. Also, the wear amount of the rails was increased with increasing the rotation speed. The UNSM-treated normal rail exhibited the highest wear resistance with respect to the rotation speed. The wear mechanisms of the rails are also discussed based on microscopic images of the worn out surfaces. PMID:28772549
Estimating Stresses, Fault Friction and Fluid Pressure from Topography and Coseismic Slip Models

NASA Astrophysics Data System (ADS)

Styron, R. H.; Hetland, E. A.

2014-12-01

Stress is a first-order control on the deformation state of the earth. However, stress is notoriously hard to measure, and researchers typically only estimate the directions and relative magnitudes of principal stresses, with little quantification of the uncertainties or absolute magnitude. To improve upon this, we have developed methods to constrain the full stress tensor field in a region surrounding a fault, including tectonic, topographic, and lithostatic components, as well as static friction and pore fluid pressure on the fault. Our methods are based on elastic halfspace techniques for estimating topographic stresses from a DEM, and we use a Bayesian approach to estimate accumulated tectonic stress, fluid pressure, and friction from fault geometry and slip rake, assuming Mohr-Coulomb fault mechanics. The nature of the tectonic stress inversion is such that either the stress maximum or minimum is better constrained, depending on the topography and fault deformation style. Our results from the 2008 Wenchuan event yield shear stresses from topography up to 20 MPa (normal-sinistral shear sense) and topographic normal stresses up to 80 MPa on the faults; tectonic stress had to be large enough to overcome topography to produce the observed reverse-dextral slip. Maximum tectonic stress is constrained to be >0.3 * lithostatic stress (depth-increasing), with a most likely value around 0.8, trending 90-110°E. Minimum tectonic stress is about half of maximum. Static fault friction is constrained at 0.1-0.4, and fluid pressure at 0-0.6 * total pressure on the fault. Additionally, the patterns of topographic stress and slip suggest that topographic normal stress may limit fault slip once failure has occurred. Preliminary results from the 2013 Balochistan earthquake are similar, but yield stronger constraints on the upper limits of maximum tectonic stress, as well as tight constraints on the magnitude of minimum tectonic stress and stress orientation. Work in progress on the Wasatch fault suggests that maximum tectonic stress may also be able to be constrained, and that some of the shallow rupture segmentation may be due in part to localized topographic loading. Future directions of this work include regions where high relief influences fault kinematics (such as Tibet).
[Effect of the thyroid status on the proteinases/inhibitors system under stress].

PubMed

Gorodetskaya, I V; Gusakova, E A

2015-01-01

Тhe alarm-stage of stress reaction (аn hour after the stress of swimming of rats in a cage during an hour) is characterized by the stimulation of trypsinе-like activity (TLA) in the liver, and especially in the blood. At the resistance stage (48 hours after the stress) there is normalization of TLA in the blood and limitation of its growth in the liver. At the stage of exhaustion (an hour of stress during 10 days) the most significant increase of TLA in the liver and blood develops. Experimental hypothyroidism (25 mg/kg merkazolil within 20 days) per se causes a reduction of TLA, defines more pronounced stimulation of proteolysis in the alarm-stage, prevents its normalization at the resistance-stage, and promotes its excessive activation at the stage of exhaustion. Introduction of small doses of L-thyroxine (1.5-3.0 g/kg during 28 days) does not affect the system of proteolysis, limitis the increase of TLA at the alarm- and exhaustion stages, prevents its stimulation at the resistance-stage. The dependence of the changes in the proteases/inhibitors system under stress from the level of iodine-containing thyroid hormones in the blood is due to their influence on the activity of endogenous proteinase inhibitors (a1-antitrypsin and a2-macroglobulin) and on the permeability of lysosomes membranes.
[Adaptation to hypoxia and hyperoxia improves physical endurance: the role of reactive oxygen species and redox-signaling].

PubMed

Sazontova, T G; Glazachev, O S; Bolotova, A V; Dudnik, E N; Striapko, N V; Bedareva, I V; Anchishkina, N A; Arkhipenko, Iu V

2012-06-01

We have conducted theoretical foundation, experimental analysis and a pilot study of a new method of adaptation to hypoxia and hyperoxia in the prevention of hypoxic and stress-induced disorders and improving the body's tolerance to physical stress. It has been shown in the experimental part that a combination of physical exercise with adaptation to hypoxia-hyperoxia significantly increased tolerance to acute physical load (APL) and its active phase. Analysis of lipid peroxidation processes, antioxidant enzymes and HSPs showed that short-term training for physical exercise by itself compensates the stressor, but not the hypoxic component of the APL, the combination of training with adaptation to hypoxia-hyperoxia completely normalizes the stressor and hypoxic components of APL. The pilot study has been performed to evaluate the effectiveness of hypoxic-hyperoxic training course in qualified young athletes with over-training syndrome. After completing the course of hypoxia-hyperoxia adaptation, 14 sessions, accompanied by light mode sports training, the athletes set the normalization of autonomic balance, increased resistance to acute hypoxia in hypoxic test, increased physical performance--increased PWC170, maximal oxygen consumption (VO2max) parameters, their relative values to body mass, diminished shift of rate pressure product in the load. Thus, we confirmed experimental findings that hypoxic-hyperoxic training optimizes hypoxic (increased athletes resistance to proper hypoxia) and stress (myocardium economy in acute physical stress testing) components in systemic adaptation and restoration of athletes' with over-training syndrome.
Nicotine Enhances High-Fat Diet-Induced Oxidative Stress in the Kidney.

PubMed

Arany, Istvan; Hall, Samuel; Reed, Dustin K; Reed, Caitlyn T; Dixit, Mehul

2016-07-01

Life expectancy of an obese smoker is 13 years less than a normal weight smoker, which could be linked to the increased renal risk imposed by smoking. Both smoking-through nicotine (NIC)-and obesity-by free fatty acid overload-provoke oxidative stress in the kidney, which ultimately results in development of chronic kidney injury. Their combined renal risk, however, is virtually unknown. We tested the hypothesis that chronic NIC exposure worsens renal oxidative stress in mice on high-fat diet (HFD) by altering the balance between expression of pro-oxidant and antioxidant genes. Nine-week-old male C57Bl/6J mice consumed normal diet (ND) or HFD and received either NIC (200 μg/ml) or vehicle (2% saccharine) in their drinking water. Body weight, plasma clinical parameters, renal lipid deposition, markers of renal oxidative stress and injury, as well as renal expression of the pro-oxidant p66shc and the antioxidant MnSOD were determined after 12 weeks. NIC significantly augmented levels of circulating free fatty acid, as well as lipid deposition, oxidative stress and sublethal injury in the kidneys of mice on HFD. In addition, NIC exposure suppressed HFD-mediated induction of MnSOD while increased expression of p66shc in the kidney. Tobacco smoking or the increasingly popular E-cigarettes-via NIC exposure-could worsen obesity-associated lipotoxicity in the kidney. Hence, our findings could help to develop strategies that mitigate adverse effects of NIC on the obese kidney. Life expectancy of an obese smoker is 13 years less than a normal weight smoker, which could be linked to the increased renal risk imposed by smoking. NIC-the main component of tobacco smoke, E-cigarettes and replacement therapies-links smoking to renal injury via oxidative stress, which could superimpose renal oxidative stress caused by obesity. Our results substantiate this scenario using a mouse model of diet induced obesity and NIC exposure and imply the augmented long-term renal risk in obese smokers. Also, our study may help to develop strategies that mitigate adverse effects of NIC on the obese kidney. © The Author 2016. Published by Oxford University Press on behalf of the Society for Research on Nicotine and Tobacco. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.
Low-salt diet enhances vascular reactivity and Ca(2+) entry in pregnant rats with normal and reduced uterine perfusion pressure.

PubMed

Giardina, Jena B; Cockrell, Kathy L; Granger, Joey P; Khalil, Raouf A

2002-02-01

Salt moderation is often recommended to prevent excessive increases in blood pressure during pregnancy, particularly in women who are prone to pregnancy-induced hypertension; however, the vascular effects of low dietary salt intake during pregnancy are unclear. We investigated whether a low-salt diet during pregnancy alters the mechanisms of vascular smooth muscle contraction. Active stress and (45)Ca(2+) influx were measured in endothelium-denuded aortic strips of virgin and normal pregnant Sprague-Dawley rats and a hypertensive pregnant rat model produced by reduction in uterine perfusion pressure (RUPP), fed either a normal-sodium (NS, 1% NaCl) or low-sodium diet (LS, 0.2% NaCl) for 7 days. The mean arterial pressure was as follows: virgin/NS 108 +/- 8, virgin/LS 117 +/- 7, pregnant/NS 102 +/- 3, pregnant/LS 117 +/- 4, RUPP/NS 119 +/- 3, and RUPP/LS 133 +/- 6 mm Hg. Phenylephrine (Phe) caused concentration-dependent increases in active stress and (45)Ca(2+) influx that were greater in RUPP rats than in normal pregnant or virgin rats and were enhanced in pregnant/LS and RUPP/LS compared with pregnant/NS and RUPP/NS, respectively. High KCl (16 to 96 mmol/L), which stimulates Ca(2+) entry from the extracellular space, also caused increases in active stress that were greater in RUPP than in normal pregnant, in pregnant/LS than in pregnant/NS, and in RUPP/LS than in RUPP/NS rats. The Phe-induced (45)Ca(2+) influx--active stress relation was greater in RUPP/NS than in pregnant/NS and was enhanced in pregnant/LS and RUPP/LS compared with pregnant/NS and RUPP/NS, respectively. In Ca(2+)-free (2 mmol/L ethylene glycol bis(beta-aminoethylether)-N,N,N',N'-tetra-acetic acid) Krebs, stimulation of intracellular Ca(2+) release by Phe (10(-5) mol/L) or caffeine (25 mmol/L) caused a transient contraction that was not significantly different in all groups of rats. Thus, a low-salt diet in pregnant and RUPP rats is associated with increases in vascular reactivity that involves Ca(2+) entry from the extracellular space but not Ca(2+) release from the intracellular stores. The enhancement of the Phe-induced Ca(2+) influx--active stress relation in pregnant and RUPP rats on a low-salt diet suggests activation of other vascular contraction mechanisms in addition to Ca(2+) entry. Although it is difficult to extrapolate the experimental data in rats to clinical data in women, the increased vascular reactivity and Ca(2+) entry and the possible enhancement of additional vascular contraction mechanisms with a low-salt diet suggest that reduction of dietary salt intake should be carefully monitored during pregnancy and pregnancy-induced hypertension.
The Yeast Forkhead Transcription Factors Fkh1 and Fkh2 Regulate Lifespan and Stress Response Together with the Anaphase-Promoting Complex

PubMed Central

Postnikoff, Spike D. L.; Malo, Mackenzie E.; Wong, Berchman; Harkness, Troy A. A.

2012-01-01

Forkhead box O (FOXO) transcription factors have a conserved function in regulating metazoan lifespan. A key function in this process involves the regulation of the cell cycle and stress responses including free radical scavenging. We employed yeast chronological and replicative lifespan assays, as well as oxidative stress assays, to explore the potential evolutionary conservation of function between the FOXOs and the yeast forkhead box transcription factors FKH1 and FKH2. We report that the deletion of both FKH genes impedes normal lifespan and stress resistance, particularly in stationary phase cells, which are non-responsive to caloric restriction. Conversely, increased expression of the FKHs leads to extended lifespan and improved stress response. Here we show the Anaphase-Promoting Complex (APC) genetically interacts with the Fkh pathway, likely working in a linear pathway under normal conditions, as fkh1Δ fkh2Δ post-mitotic survival is epistatic to that observed in apc5CA mutants. However, under stress conditions, post-mitotic survival is dramatically impaired in apc5CA fkh1Δ fkh2Δ, while increased expression of either FKH rescues APC mutant growth defects. This study establishes the FKHs role as evolutionarily conserved regulators of lifespan in yeast and identifies the APC as a novel component of this mechanism under certain conditions, likely through combined regulation of stress response, genomic stability, and cell cycle regulation. PMID:22438832
Focal mechanisms and tidal modulation for tectonic tremors in Taiwan

NASA Astrophysics Data System (ADS)

Ide, S.; Yabe, S.; Tai, H. J.; Chen, K. H.

2015-12-01

Tectonic tremors in Taiwan have been discovered beneath the southern Central Range, but their hosting structure has been unknown. Here we constrain the focal mechanism of underground deformation related to tremors, using moment tensor inversion in the very low frequency band and tidal stress analysis. Three types of seismic data are used for two analysis steps: detection of tremors and the moment tensor inversion. Short-period seismograms from CWBSN are used for tremor detection. Broadband seismograms from BATS and the TAIGER project are used for both steps. About 1000 tremors were detected using an envelope correlation method in the high frequency band (2-8 Hz). Broadband seismograms are stacked relative to the tremor timing, and inverted for a moment tensor in the low frequency band (0.02-0.05 Hz). The best solution was obtained at 32 km depth, as a double-couple consistent with a low-angle thrust fault dipping to the east-southeast, or a high-angle thrust with a south-southwest strike. Almost all tremors occur when tidal shear stress is positive and normal stress is negative (clamping). Since the clamping stress is high for a high-angle thrust fault, the low-angle thrust fault is more likely to be the fault plane. Tremor rate increases non-linearly with increasing shear stress, suggesting a velocity strengthening friction law. The high tidal sensitivity is inconsistent with horizontal slip motion suggested by previous studies, and normal faults that dominates regional shallow earthquakes. Our results favor thrust slip on a low-angle fault dipping to the east-southeast, consistent with the subduction of the Eurasian plate. The tremor region is characterized by a deep thermal anomaly with decrease normal stress. This region has also experienced enough subduction to produce metamorphic fluids. A large amount of fluid and low vertical stress may explain the high tidal sensitivity.
Annular dilatation and loss of sino-tubular junction in aneurysmatic aorta: implications on leaflet quality at the time of surgery. A finite element study†

PubMed Central

Weltert, Luca; de Tullio, Marco D.; Afferrante, Luciano; Salica, Andrea; Scaffa, Raffaele; Maselli, Daniele; Verzicco, Roberto; De Paulis, Ruggero

2013-01-01

OBJECTIVES In the belief that stress is the main determinant of leaflet quality deterioration, we sought to evaluate the effect of annular and/or sino-tubular junction dilatation on leaflet stress. A finite element computer-assisted stress analysis was used to model four different anatomic conditions and analyse the consequent stress pattern on the aortic valve. METHODS Theoretical models of four aortic root configurations (normal, with dilated annulus, with loss of sino-tubular junction and with both dilatation simultaneously) were created with computer-aided design technique. The pattern of stress and strain was then analysed by means of finite elements analysis, when a uniform pressure of 100 mmHg was applied to the model. Analysis produced von Mises charts (colour-coded, computational, three-dimensional stress-pattern graphics) and bidimensional plots of compared stress on arc-linear line, which allowed direct comparison of stress in the four different conditions. RESULTS Stresses both on the free margin and on the ‘belly’ of the leaflet rose from 0.28 MPa (normal conditions) to 0.32 MPa (+14%) in case of isolated dilatation of the sino-tubular junction, while increased to 0.42 MPa (+67%) in case of isolated annular dilatation, with no substantial difference whether sino-tubular junction dilatation was present or not. CONCLUSIONS Annular dilatation is the key element determining an increased stress on aortic leaflets independently from an associated sino-tubular junction dilatation. The presence of annular dilatation associated with root aneurysm greatly decreases the chance of performing a valve sparing procedure without the need for additional manoeuvres on leaflet tissue. This information may lead to a refinement in the optimal surgical strategy. PMID:23536020
Central neuropeptide Y plays an important role in mediating the adaptation mechanism against chronic stress in male rats.

PubMed

Yang, Yu; Babygirija, Reji; Zheng, Jun; Shi, Bei; Sun, Weinan; Zheng, Xiaojiao; Zhang, Fan; Cao, Yu

2018-02-07

Exposure to continuous life stress often causes gastrointestinal (GI) symptoms. Studies have shown that neuropeptide Y (NPY) counteracts the biological actions of corticotrophin-releasing factor (CRF), and is involved in the termination of the stress response. However, in chronic repeated restraint stress (CRS) conditions, the actions of NPY on GI motility remain controversial. To evaluate the role of NPY in mediation of the adaptation mechanism and GI motility in CRS conditions, a CRS rat model was set up. Central CRF and NPY expression levels were analyzed, serum corticosterone and NPY concentrations were measured, and GI motor function was evaluated. The NPY Y1 receptor antagonist BIBP-3226 was centrally administered before stress loading, and on days, 1-5, of repeated stress, the central CRF and the serum corticosterone concentrations were measured. In addition, gastric and colonic motor functions were evaluated. The elevated central CRF expression and corticosterone concentration caused by acute stress began to fall after 3 days of stress loading, while central NPY expression and serum NPY began to increase. GI dysmotility also returned to a normal level. Pretreatment with BIBP-3226 abolished the adaptation mechanism, and significantly increased CRF expression and the corticosterone concentration, which resulted in delayed gastric emptying and accelerated fecal pellet output. Inhibited gastric motility and enhanced distal colonic motility were also recorded. CRS-produced adaptation, over-expressed central CRF, and GI dysmotility observed in acute restraint stress were restored to normal levels. Central NPY via the Y1 receptor plays an important role in mediating the adaptation mechanism against chronic stress. Copyright © 2018 Endocrine Society.

Speech perception in older listeners with normal hearing:conditions of time alteration, selective word stress, and length of sentences.

PubMed

Cho, Soojin; Yu, Jyaehyoung; Chun, Hyungi; Seo, Hyekyung; Han, Woojae

2014-04-01

Deficits of the aging auditory system negatively affect older listeners in terms of speech communication, resulting in limitations to their social lives. To improve their perceptual skills, the goal of this study was to investigate the effects of time alteration, selective word stress, and varying sentence lengths on the speech perception of older listeners. Seventeen older people with normal hearing were tested for seven conditions of different time-altered sentences (i.e., ±60%, ±40%, ±20%, 0%), two conditions of selective word stress (i.e., no-stress and stress), and three different lengths of sentences (i.e., short, medium, and long) at the most comfortable level for individuals in quiet circumstances. As time compression increased, sentence perception scores decreased statistically. Compared to a natural (or no stress) condition, the selectively stressed words significantly improved the perceptual scores of these older listeners. Long sentences yielded the worst scores under all time-altered conditions. Interestingly, there was a noticeable positive effect for the selective word stress at the 20% time compression. This pattern of results suggests that a combination of time compression and selective word stress is more effective for understanding speech in older listeners than using the time-expanded condition only.
Change of salivary stress marker concentrations during pregnancy: maternal depressive status suppress changes of those levels.

PubMed

Tsubouchi, Hiroaki; Nakai, Yuichiro; Toda, Masahiro; Morimoto, Kanehisa; Chang, Yang Sil; Ushioda, Norichika; Kaku, Shoji; Nakamura, Takafumi; Kimura, Tadashi; Shimoya, Koichiro

2011-08-01

The aim of the present study was to show changes in salivary cortisol and chromogranin A/protein concentrations as stress markers during pregnancy and to clarify the effect of chronic stress on stress markers. Salivary samples were collected from 69 pregnant women during pregnancy. Salivary cortisol levels and chromogranin A/protein titers were determined. We surveyed the women's chronic stress using the Zung self-rating depression scale and General Health Questionnaire-28. Cortisol levels in the saliva of pregnant women showed biphasic change during pregnancy. Chromogranin A/protein levels in the saliva of pregnant women increased in the second and the early third trimesters and decreased to the puerperal period. Salivary cortisol concentrations of the chronic high stress group were significantly lower compared with those of the normal group. Salivary chromogranin A/protein concentrations of the chronic high stress group were also significantly lower than those of the normal group. The titration of salivary cortisol concentrations and chromogranin A/protein levels is a useful tool to determine maternal stress levels. The elevation of cortisol and chromogranin A/protein in the saliva was suppressed in the chronic high stress group during pregnancy. © 2011 The Authors. Journal of Obstetrics and Gynaecology Research © 2011 Japan Society of Obstetrics and Gynecology.
Dependence of intramyocardial pressure and coronary flow on ventricular loading and contractility: a model study.

PubMed

Bovendeerd, Peter H M; Borsje, Petra; Arts, Theo; van De Vosse, Frans N

2006-12-01

The phasic coronary arterial inflow during the normal cardiac cycle has been explained with simple (waterfall, intramyocardial pump) models, emphasizing the role of ventricular pressure. To explain changes in isovolumic and low afterload beats, these models were extended with the effect of three-dimensional wall stress, nonlinear characteristics of the coronary bed, and extravascular fluid exchange. With the associated increase in the number of model parameters, a detailed parameter sensitivity analysis has become difficult. Therefore we investigated the primary relations between ventricular pressure and volume, wall stress, intramyocardial pressure and coronary blood flow, with a mathematical model with a limited number of parameters. The model replicates several experimental observations: the phasic character of coronary inflow is virtually independent of maximum ventricular pressure, the amplitude of the coronary flow signal varies about proportionally with cardiac contractility, and intramyocardial pressure in the ventricular wall may exceed ventricular pressure. A parameter sensitivity analysis shows that the normalized amplitude of coronary inflow is mainly determined by contractility, reflected in ventricular pressure and, at low ventricular volumes, radial wall stress. Normalized flow amplitude is less sensitive to myocardial coronary compliance and resistance, and to the relation between active fiber stress, time, and sarcomere shortening velocity.
Alpha-mangostin attenuates diabetic nephropathy in association with suppression of acid sphingomyelianse and endoplasmic reticulum stress.

PubMed

Liu, Tingting; Duan, Wang; Nizigiyimana, Paul; Gao, Lin; Liao, Zhouning; Xu, Boya; Liu, Lerong; Lei, Minxiang

2018-02-05

Diabetic nephropathy is a common complication of diabetes, but there are currently few treatment options. The aim of this study was to gain insight into the effect of alpha-mangostin on diabetic nephropathy and possible related mechanisms. Goto-Kakizaki rats were used as a diabetic model and received alpha-mangostin or desipramine treatment with normal saline as a control. Ten age-matched Sprague Dawley rats were used as normal controls and treated with normal saline. At week 12, blood glucose, albuminuria, apoptosis and renal pathologic changes were assessed. Protein levels for acid sphingomyelinase, glucose-regulated protein 78, phosphorylated PKR-like ER-resident kinase, activated transcription factor 4, CCAAT/enhancer-binding protein, homologous protein), and cleaved-caspase12 were measured. The level of acid sphingomyelinase was significantly increased, and ER stress was activated in diabetic rat kidneys when compared to the control animals. When acid sphingomyelinase was inhibited by alpha-mangostin, the expression of ER stress-related proteins was down-regulated in association with decreased levels of diabetic kidney injury. Alpha-mangostin, an acid sphingomyelinase inhibitor plays a protective role in diabetic neuropathy by relieving ER stress induced-renal cell apoptosis. Copyright © 2018 Elsevier Inc. All rights reserved.
Cold hardiness in relation to trace metal stress in the freeze-avoiding beetle Tenebrio molitor.

PubMed

Pedersen, Sindre A; Kristiansen, Erlend; Hansen, Bjørn H; Andersen, Rolf A; Zachariassen, Karl E

2006-08-01

The antifreeze proteins (AFPs) are a family of proteins characterised by their ability to inhibit the growth of ice. These proteins have evolved as a protection against lethal freezing in freeze avoiding species. Metal stress has been shown to reduce the cold hardening in invertebrates, but no study has investigated how this type of stress affects the production of AFPs. This study demonstrates that exposure to cadmium (Cd), copper (Cu) and zinc (Zn) reduces the normal developmental increase in AFP levels in Tenebrio molitor larvae reared under summer conditions. Exposure to winter conditions, however stimulated the production of AFPs in the metal exposed larvae, and raised the concentrations of AFPs to normal winter levels. The reduced level of AFPs in metal-stressed animals acclimated to summer conditions seems to arise from alterations in the normal gene expression of AFPs. The results indicate that metal exposure may cause freeze avoiding insects to become more susceptible to lethal freezing, as they enter the winter with lowered levels of AFPs. Such an effect cannot be revealed by ordinary toxicological tests, but may nevertheless be of considerable ecological importance.
Beneficial effect of fluoxetine treatment aganist psychological stress is mediated by increasing BDNF expression in selected brain areas

PubMed Central

Li, Gongying; Jing, Ping; Liu, Zhidong; Li, Zhiruo; Ma, Hongxia; Tu, Wenzhen; Zhang, Wei; Zhuo, Chuanjun

2017-01-01

SSRI antidepressant fluoxetine is widely used to treat psychological stress related disorders, however the underlying working mechanisms is not fully understood, as SSRIs can rapidly increase the extracellular serotonin levels but it normally takes weeks to reveal their therapeutic effect in the stress-related psychological disorders. Our previous study demonstrated that purely psychological stress without any physic stimuli induces a biphasic change in the expression of brain-derived neurotrophic factor (BDNF), which immediately decrease and then gradually increase after the stress; and that the latter BDNF increase in response to the psychological stress involves the activation of serotonin system. To investigate the role of BDNF in the fluoxetine treatment for stress-related psychological disorders, we examined the mRNA and protein levels of BDNF in the brain of Sprague-Dawley (SD) rats, which were pretreated with fluoxetine at 10 mg/kg or vehicle solution for 14 days, over 24 hour after an acute psychological stress exposure. In situ hybridization and immunohistochemistry were performed to detect the expression of BDNF at different time points in various brain regions after the psychological stress. We found that fluoxetine treatment completely blocked the BDNF decrease induced by the psychological stress, and also enhanced the gradual increase in the expression of BDNF in most of the brain regions except VTA after the psychological stress. The results suggest that the enhancement in BDNF levels induced by chronic fluoxetine treatment mediates the therapeutic effect against psychological stress. PMID:29050222
Haploid parthenotes express differential response to in vitro exposure of ammonia compared to normally fertilized embryos.

PubMed

Nair, Ramya; Mutalik, Srinivas; Dasappa, Jagadeesh Prasad; Kalthur, Guruprasad; Adiga, Satish Kumar

2017-04-22

In the present study, we assessed whether absence of paternal genome imparts any differential response in embryos to chemical stress such as ammonia. Parthenogenesis was induced in MII stage oocytes using 10 mM SrCl 2 in M16 medium. Parthenotes and normally fertilized embryos at 2 cell stage were exposed to different concentrations of ammonia and cultured till blastocyst. Exposure of ammonia to normally fertilized embryos resulted in significant decrease in the developmental potential (p < 0.0001) and blastocyst quality (p < 0.001). Whereas, in parthenotes, even though lower concentrations of ammonia did not have any effect, at 200 μM concentration the blastocyst rate was two times higher than control. The baseline apoptotic index was higher in parthenotes compared to normally fertilized embryos, which further increased after ammonium exposure (p < 0.001). Unlike in normally fertilized embryos ammonia exposure altered the mitochondrial distribution pattern and lead to increased expression of Oct4, Nanog and Na + /K + ion exchange channel, while the cytochrome C expression was downregulated. This indicates that haploidy and/or absence of paternal factors in the embryo results in differential tolerance to stress induced by ammonia. Copyright © 2017 Elsevier Inc. All rights reserved.
Effect of housing rats within a pyramid on stress parameters.

PubMed

Bhat, Surekha; Rao, Guruprasad; Murthy, K Dilip; Bhat, P Gopalakrishna

2003-11-01

The Giza pyramids of Egypt have been the subject of much research. Pyramid models with the same base to height ratio as of the Great Pyramid of Giza, when aligned on a true north-south axis, are believed to generate, transform and transmit energy. Research done with such pyramid models has shown that they induced greater relaxation in human subjects, promoted better wound healing in rats and afforded protection against stress-induced neurodegnerative changes in mice. The present study was done to assess the effects of housing Wistar rats within the pyramid on the status of oxidative damage and antioxidant defense in their erythrocytes and cortisol levels in their plasma. Rats were housed in cages under standard laboratory conditions. Cages were left in the open (normal control), under a wooden pyramid model (experimental rats) or in a cubical box of comparable dimensions (6 hr/day for 14 days). Erythrocyte malondialdehyde and plasma cortisol levels were significantly decreased in rats kept within the pyramid as compared to the normal control and those within the square box. Erythrocyte reduced glutathione levels, erythrocyte glutathione peroxidase and superoxide dismutase activities were significantly increased in the rats kept in the pyramid as compared to the other two groups. There was no significant difference in any of the parameters between the normal control and rats kept in the square box. The results showed that exposure of adult female Wistar rats to pyramid environment reduces stress oxidative stress and increases antioxidant defense in them.
Some physiological aspects of sublethal heat stress in the juvenile steelhead trout (Salmo gairdneri) and coho salmon (Oncorhynchus kisutch)

USGS Publications Warehouse

Wedemeyer, Gary

1973-01-01

A rapid (3 min) but sublethal temperature increase from 10 to 20 imposed a greater stress on juvenile coho salmon (Oncorhynchus kisutch) than on juvenile steelhead trout (Salmo gairdneri). Both species suffered hyperglycemia, hypocholesterolemia, increased blood hemoglobin, and decreased blood sugar regulatory precision, but the steelhead recovered more quickly. Acid–base equilibrium was essentially unaffected, and only the coho suffered any significant interrenal vitamin C depletion. Vitamin C normalization required about 24 hr.
Glucose metabolism in different regions of the rat brain under hypokinetic stress influence

NASA Technical Reports Server (NTRS)

Konitzer, K.; Voigt, S.

1980-01-01

Glucose metabolism in rats kept under long term hypokinetic stress was studied in 7 brain regions. Determination was made of the regional levels of glucose, lactate, glutamate, glutamine, aspartate, gamma-aminobutyrate and the incorporation of C-14 from plasma glucose into these metabolites, in glycogen and protein. From the content and activity data the regional glucose flux was approximated quantitatively. Under normal conditions the activity gradient cortex and frontal pole cerebellum, thalamus and mesencephalon, hypothalamus and pons and medulla is identical with that of the regional blood supply (measured with I131 serum albumin as the blood marker). Within the first days of immobilization a functional hypoxia occurred in all brain regions and the utilization of cycle amino acids for protein synthesis was strongly diminished. After the first week of stress the capillary volumes of all regions increased, aerobic glucose metabolism was enhanced (factors 1.3 - 2.0) and the incorporation of glucose C-14 via cycle amino acids into protein was considerably potentiated. The metabolic parameters normalized between the 7th and 11th week of stress. Blood supply and metabolic rate increased most in the hypothalamus.
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
Ethephon increases photosynthetic-nitrogen use efficiency, proline and antioxidant metabolism to alleviate decrease in photosynthesis under salinity stress in mustard.

PubMed

Iqbal, Noushina; Umar, Shahid; Per, Tasir S; Khan, Nafees A

2017-05-04

Salinity is a serious threat to plant growth and development worldwide reducing agricultural productivity each year. Ethylene is an important phytohormone that affects plants performance under normal and abiotic stress conditions. In this study, role of ethylene was investigated in mitigating salinity stress (100 mM NaCl) effects on photosynthesis in mustard plants subjected to different nitrogen (N; 5 and 10 mM) levels. Plants under salinity stress exhibited marked increase in proline and reduced glutathione (GSH) content and activity of antioxidant enzymes. Nitrogen supplementation at 10 mM was better than 200 µl l -1 ethephon treatment under no stress. However, under salinity stress, both N and ethephon were equally effective. The combined application of 10 mM N and ethephon to salinity stressed plants produced greatest increase in photosynthesis by increasing proline and antioxidant metabolism. Ethylene evolution was high under salinity stress, but treatment of 10 mM N and 200 µl l -1 ethephon greatly decreased ethylene evolution that was equivalent to the 10 mM N treatment alone. This concentration of ethylene decreased the oxidative stress and increased the photosynthetic nitrogen use efficiency (NUE) maximally to increase photosynthesis. The use of ethylene action inhibitor, norbornadiene (NBD) showed reduction in ethylene mediated effects in alleviating salinity. Norbornadiene decreased the photosynthetic-NUE, proline and GSH content that resulted in decrease in photosynthesis under salinity stress. This study indicated that ethylene regulated the proline and antioxidant metabolism under salinity stress to increase photosynthetic functions of mustard grown with low and optimum N. The modulation of ethylene could be adopted in agricultural practices to increase photosynthesis under salinity stress.
[Assessment of parental stress using the "Eltern-Belastungs-Screening zur Kindeswohlgefährdung" (EBSK) - association with emotional and behavioral problems in children].

PubMed

Eichler, Anna K; Glaubitz, Katharina A; Hartmann, Luisa C; Spangler, Gottfried

2014-07-01

Parental stress is increased in clinical contexts (e.g., child psychiatry) and correlates with behavioral and emotional problems of children. In addition, parental stress can result in a biased parental perception of child's behavior and emotions. These interrelations were examined in a normal (N = 320) and a clinical (N = 75) sample. The "Eltern-Belastungs-Screening zur Kindeswohlgefährdung" (EBSK; Deegener, Spangler, Körner & Becker, 2009) was used for the assessment of parental stress. As expected, increased EBSK scores were overrepresented in the clinical sample. In both samples stressed parents reported having children with more behavioral and emotional problems. Children of stressed parents in turn reported significantly less problems than their parents did. The rating of independent third persons, e.g. teachers, was not available and should be added in future research. Restrictions in methodology and conclusions for practice are discussed.
Combating photooxidative stress in green hairy roots of Daucus carota cultivated under light irradiation.

PubMed

Mukherjee, Chiranjit; Sircar, Debabrata; Chatterjee, Moniya; Das, Sampa; Mitra, Adinpunya

2014-01-15

The light-dependent generation of active oxygen species, which can disrupt normal metabolic process of plant, is termed as photo-oxidative stress. Plants are equipped with enzymatic and non-enzymatic antioxidative defence system to reduce the effect of such stress. Hairy root culture of Daucus carota when cultivated under continuous illumination (250 μmol m(-2)s(-1)) turned green. To know the reason behind that and photo-oxidative stress response in green hairy roots, activities of several antioxidant enzymes were measured. When compared with normal hairy roots, green hairy roots showed an enhanced superoxide dismutase (SOD) activity. Treatment with a SOD inhibitor diethyldithiocarbamate led to suppression of SOD activity in a concentration-dependent manner in green hairy roots. Interestingly, SOD-suppressed root showed three-fold enhanced caffeic acid glucoside accumulation in the soluble fraction as compared to untreated ones. While ascorbate peroxidase activity showed marginal increase in green hairy roots, a decrease in the activities of guaiacol peroxidase and catalase were observed. SDS-PAGE of crude protein profile from green hairy roots showed a distinct band, which was absent in normal hairy roots. MALDI-TOF-MS/MS analysis of the extracted protein confirmed it as the large subunit of RuBisCO. RT-PCR based expression analysis of betaine aldehyde dehydrogenase showed enhanced transcript levels in green hairy roots as compared to normal hairy roots, whereas reverse trends were observed with the transcripts accumulation for phenylalanine ammonia-lyase and chalcone synthase. These findings corroborate with the in vitro BADH activities in hairy roots, and thus indicate an important role of this stress enzyme in combating photo-oxidative stress in green hairy roots upon continuous light exposure. Copyright © 2013 Elsevier GmbH. All rights reserved.
Gravity-driven groundwater flow and slope failure potential: 1. Elastic effective-stress model

USGS Publications Warehouse

Iverson, Richard M.; Reid, Mark E.

1992-01-01

Hilly or mountainous topography influences gravity-driven groundwater flow and the consequent distribution of effective stress in shallow subsurface environments. Effective stress, in turn, influences the potential for slope failure. To evaluate these influences, we formulate a two-dimensional, steady state, poroelastic model. The governing equations incorporate groundwater effects as body forces, and they demonstrate that spatially uniform pore pressure changes do not influence effective stresses. We implement the model using two finite element codes. As an illustrative case, we calculate the groundwater flow field, total body force field, and effective stress field in a straight, homogeneous hillslope. The total body force and effective stress fields show that groundwater flow can influence shear stresses as well as effective normal stresses. In most parts of the hillslope, groundwater flow significantly increases the Coulomb failure potential Φ, which we define as the ratio of maximum shear stress to mean effective normal stress. Groundwater flow also shifts the locus of greatest failure potential toward the slope toe. However, the effects of groundwater flow on failure potential are less pronounced than might be anticipated on the basis of a simpler, one-dimensional, limit equilibrium analysis. This is a consequence of continuity, compatibility, and boundary constraints on the two-dimensional flow and stress fields, and it points to important differences between our elastic continuum model and limit equilibrium models commonly used to assess slope stability.
OsNucleolin1-L Expression in Arabidopsis Enhances Photosynthesis via Transcriptome Modification under Salt Stress Conditions.

PubMed

Udomchalothorn, Thanikarn; Plaimas, Kitiporn; Sripinyowanich, Siriporn; Boonchai, Chutamas; Kojonna, Thammaporn; Chutimanukul, Panita; Comai, Luca; Buaboocha, Teerapong; Chadchawan, Supachitra

2017-04-01

OsNUC1 encodes rice nucleolin, which has been shown to be involved in salt stress responses. Expression of the full-length OsNUC1 gene in Arabidopsis resulted in hypersensitivity to ABA during germination. Transcriptome analysis of the transgenic lines, in comparison with the wild type, revealed that the RNA abundance of >1,900 genes was significantly changed under normal growth conditions, while under salt stress conditions the RNAs of 999 genes were found to be significantly regulated. Gene enrichment analysis showed that under normal conditions OsNUC1 resulted in repression of genes involved in photosynthesis, while in salt stress conditions OsNUC1 increased expression of the genes involved in the light-harvesting complex. Correspondingly, the net rate of photosynthesis of the transgenic lines was increased under salt stress. Transgenic rice lines with overexpression of the OsNUC1-L gene were generated and tested for photosynthetic performance under salt stress conditions. The transgenic rice lines treated with salt stress at the booting stage had a higher photosynthetic rate and stomatal conductance in flag leaves and second leaves than the wild type. Moreover, higher contents of Chl a and carotenoids were found in flag leaves of the transgenic rice. These results suggest a role for OsNUC1 in the modification of the transcriptome, especially the gene transcripts responsible for photosynthesis, leading to stabilization of photosynthesis under salt stress conditions. © The Author 2017. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.
Tudor-SN, a component of stress granules, regulates growth under salt stress by modulating GA20ox3 mRNA levels in Arabidopsis

PubMed Central

Yan, Chunxia; Yan, Zongyun; Wang, Yizheng; Yan, Xiaoyuan; Han, Yuzhen

2014-01-01

The Tudor-SN protein (TSN) is universally expressed and highly conserved in eukaryotes. In Arabidopsis, TSN is reportedly involved in stress adaptation, but the mechanism involved in this adaptation is not understood. Here, we provide evidence that TSN regulates the mRNA levels of GA20ox3, a key enzyme for gibberellin (GA) biosynthesis. The levels of GA20ox3 transcripts decreased in TSN1/TSN2 RNA interference (RNAi) transgenic lines and increased in TSN1 over-expression (OE) transgenic lines. The TSN1 OE lines displayed phenotypes that may be attributed to the overproduction of GA. No obvious defects were observed in the RNAi transgenic lines under normal conditions, but under salt stress conditions these lines displayed slower growth than wild-type (WT) plants. Two mutants of GA20ox3, ga20ox3-1 and -2, also showed slower growth under stress than WT plants. Moreover, a higher accumulation of GA20ox3 transcripts was observed under salt stress. The results of a western blot analysis indicated that higher levels of TSN1 accumulated after salt treatment than under normal conditions. Subcellular localization studies showed that TSN1 was uniformly distributed in the cytoplasm under normal conditions but accumulated in small granules and co-localized with RBP47, a marker protein for stress granules (SGs), in response to salt stress. The results of RNA immunoprecipitation experiments indicated that TSN1 bound GA20ox3 mRNA in vivo. On the basis of these findings, we conclude that TSN is a novel component of plant SGs that regulates growth under salt stress by modulating levels of GA20ox3 mRNA. PMID:25205572
Ketogenic diets as an adjuvant cancer therapy: History and potential mechanism

PubMed Central

Allen, Bryan G.; Bhatia, Sudershan K.; Anderson, Carryn M.; Eichenberger-Gilmore, Julie M.; Sibenaller, Zita A.; Mapuskar, Kranti A.; Schoenfeld, Joshua D.; Buatti, John M.; Spitz, Douglas R.; Fath, Melissa A.

2014-01-01

Cancer cells, relative to normal cells, demonstrate significant alterations in metabolism that are proposed to result in increased steady-state levels of mitochondrial-derived reactive oxygen species (ROS) such as O2•−and H2O2. It has also been proposed that cancer cells increase glucose and hydroperoxide metabolism to compensate for increased levels of ROS. Given this theoretical construct, it is reasonable to propose that forcing cancer cells to use mitochondrial oxidative metabolism by feeding ketogenic diets that are high in fats and low in glucose and other carbohydrates, would selectively cause metabolic oxidative stress in cancer versus normal cells. Increased metabolic oxidative stress in cancer cells would in turn be predicted to selectively sensitize cancer cells to conventional radiation and chemotherapies. This review summarizes the evidence supporting the hypothesis that ketogenic diets may be safely used as an adjuvant therapy to conventional radiation and chemotherapies and discusses the proposed mechanisms by which ketogenic diets may enhance cancer cell therapeutic responses. PMID:25460731
Modeling and stress analyses of a normal foot-ankle and a prosthetic foot-ankle complex.

PubMed

Ozen, Mustafa; Sayman, Onur; Havitcioglu, Hasan

2013-01-01

Total ankle replacement (TAR) is a relatively new concept and is becoming more popular for treatment of ankle arthritis and fractures. Because of the high costs and difficulties of experimental studies, the developments of TAR prostheses are progressing very slowly. For this reason, the medical imaging techniques such as CT, and MR have become more and more useful. The finite element method (FEM) is a widely used technique to estimate the mechanical behaviors of materials and structures in engineering applications. FEM has also been increasingly applied to biomechanical analyses of human bones, tissues and organs, thanks to the development of both the computing capabilities and the medical imaging techniques. 3-D finite element models of the human foot and ankle from reconstruction of MR and CT images have been investigated by some authors. In this study, data of geometries (used in modeling) of a normal and a prosthetic foot and ankle were obtained from a 3D reconstruction of CT images. The segmentation software, MIMICS was used to generate the 3D images of the bony structures, soft tissues and components of prosthesis of normal and prosthetic ankle-foot complex. Except the spaces between the adjacent surface of the phalanges fused, metatarsals, cuneiforms, cuboid, navicular, talus and calcaneus bones, soft tissues and components of prosthesis were independently developed to form foot and ankle complex. SOLIDWORKS program was used to form the boundary surfaces of all model components and then the solid models were obtained from these boundary surfaces. Finite element analyses software, ABAQUS was used to perform the numerical stress analyses of these models for balanced standing position. Plantar pressure and von Mises stress distributions of the normal and prosthetic ankles were compared with each other. There was a peak pressure increase at the 4th metatarsal, first metatarsal and talus bones and a decrease at the intermediate cuneiform and calcaneus bones, in prosthetic ankle-foot complex compared to normal one. The predicted plantar pressures and von Misses stress distributions for a normal foot were consistent with other FE models given in the literature. The present study is aimed to open new approaches for the development of ankle prosthesis.
Nickel-regulated heart rate variability: The roles of oxidative stress and inflammation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chuang, Hsiao-Chi, E-mail: r92841005@ntu.edu.tw; Division of Pulmonary Medicine, Department of Internal Medicine, Shuang Ho Hospital, Taipei Medical University, Taipei, Taiwan; Hsueh, Tzu-Wei, E-mail: r95841015@ntu.edu.tw

Heart rate variability (HRV) has been reported to be a putative marker of cardiac autonomic imbalance caused by exposure to ambient particulate matter (PM). Our objective in this study was to determine the effects on HRV from exposure to nickel, an important chemical component of ambient PM that results in oxidative stress and inflammation. HRV data were collected for 72 h before lung exposure (baseline) and 72 h after intratracheal exposure (response) to nickel sulphate (NiSO{sub 4}; 526 μg) in Wistar Kyoto (WKY) and spontaneously hypertensive (SH) rats. The antioxidant N-acetyl-L-cysteine (NAC) and the anti-inflammatory celecoxib were intraperitoneally injected tomore » examine post-exposure oxidative and inflammatory responses. Self-controlled experiments examined the effects of NiSO{sub 4} exposure on average normal-to-normal intervals (ANN), natural logarithm-transformed standard deviation of the normal-to-normal intervals (LnSDNN) and root mean square of successive differences of adjacent normal-to-normal intervals (LnRMSSD); the resulting data were sequentially analysed using the generalised estimating equation model. HRV effects on NiSO{sub 4}-exposed SH rats were greater than those on NiSO{sub 4}-exposed WKY rats. After adjusted the HRV responses in the WKY rats as control, ANN and LnRMSSD were found to be quadratically increased over 72 h after exposure to NiSO{sub 4}. Both NAC and celecoxib mitigated the NiSO{sub 4}-induced alterations in HRV during the exposure period. The results suggest that concurrent Ni-induced oxidative stress and inflammatory responses play important roles in regulating HRV. These findings help bridge the gap between epidemiological and clinical studies on the plausible mechanisms of the cardiovascular consequences induced by chemical components in ambient PM. -- Highlights: ► To determine the effects on HRV from exposure to nickel. ► ANN and LnRMSSD were found to be quadratically increased after exposure to Ni. ► NAC and celecoxib mitigated the Ni-induced alterations in HRV. ► Ni-induced oxidative stress and inflammation play the roles in regulating HRV.« less

[Autonomic regulation at emotional stress under hypoxic conditions in the elderly with physiological and accelerated aging: effect of hypoxic training].

PubMed

Os'mak, E D; Asanov, É O

2014-01-01

The effect of hypoxic training on autonomic regulation in psycho-emotional stress conditions in hypoxic conditions in older people with physiological (25 people) and accelerated (28 people) aging respiratory system. It is shown that hypoxic training leads to an increase in vagal activity indicators (HF) and reduced simpatovagal index (LF/HF), have a normalizing effect on the autonomic balance during stress loads in older people with different types of aging respiratory system.
Probiotics normalize the gut-brain-microbiota axis in immunodeficient mice

PubMed Central

Smith, Carli J.; Emge, Jacob R.; Berzins, Katrina; Lung, Lydia; Khamishon, Rebecca; Shah, Paarth; Rodrigues, David M.; Sousa, Andrew J.; Reardon, Colin; Sherman, Philip M.; Barrett, Kim E.

2014-01-01

The gut-brain-microbiota axis is increasingly recognized as an important regulator of intestinal physiology. Exposure to psychological stress causes activation of the hypothalamic-pituitary-adrenal (HPA) axis and causes altered intestinal barrier function, intestinal dysbiosis, and behavioral changes. The primary aim of this study was to determine whether the effects of psychological stress on intestinal physiology and behavior, including anxiety and memory, are mediated by the adaptive immune system. Furthermore, we wanted to determine whether treatment with probiotics would normalize these effects. Here we demonstrate that B and T cell-deficient Rag1−/− mice displayed altered baseline behaviors, including memory and anxiety, accompanied by an overactive HPA axis, increased intestinal secretory state, dysbiosis, and decreased hippocampal c-Fos expression. Both local (intestinal physiology and microbiota) and central (behavioral and hippocampal c-Fos) changes were normalized by pretreatment with probiotics, indicating an overall benefit on health conferred by changes in the microbiota, independent of lymphocytes. Taken together, these findings indicate a role for adaptive immune cells in maintaining normal intestinal and brain health in mice and show that probiotics can overcome this immune-mediated deficit in the gut-brain-microbiota axis. PMID:25190473
Probiotics normalize the gut-brain-microbiota axis in immunodeficient mice.

PubMed

Smith, Carli J; Emge, Jacob R; Berzins, Katrina; Lung, Lydia; Khamishon, Rebecca; Shah, Paarth; Rodrigues, David M; Sousa, Andrew J; Reardon, Colin; Sherman, Philip M; Barrett, Kim E; Gareau, Mélanie G

2014-10-15

The gut-brain-microbiota axis is increasingly recognized as an important regulator of intestinal physiology. Exposure to psychological stress causes activation of the hypothalamic-pituitary-adrenal (HPA) axis and causes altered intestinal barrier function, intestinal dysbiosis, and behavioral changes. The primary aim of this study was to determine whether the effects of psychological stress on intestinal physiology and behavior, including anxiety and memory, are mediated by the adaptive immune system. Furthermore, we wanted to determine whether treatment with probiotics would normalize these effects. Here we demonstrate that B and T cell-deficient Rag1(-/-) mice displayed altered baseline behaviors, including memory and anxiety, accompanied by an overactive HPA axis, increased intestinal secretory state, dysbiosis, and decreased hippocampal c-Fos expression. Both local (intestinal physiology and microbiota) and central (behavioral and hippocampal c-Fos) changes were normalized by pretreatment with probiotics, indicating an overall benefit on health conferred by changes in the microbiota, independent of lymphocytes. Taken together, these findings indicate a role for adaptive immune cells in maintaining normal intestinal and brain health in mice and show that probiotics can overcome this immune-mediated deficit in the gut-brain-microbiota axis. Copyright © 2014 the American Physiological Society.
Quantitative real-time PCR normalization for gene expression studies in the plant pathogenic fungi Lasiodiplodia theobromae.

PubMed

Paolinelli-Alfonso, Marcos; Galindo-Sánchez, Clara Elizabeth; Hernandez-Martinez, Rufina

2016-08-01

Lasiodiplodia theobromae is a highly virulent plant pathogen. It has been suggested that heat stress increases its virulence. The aim of this work was to evaluate, compare, and recommend normalization strategies for gene expression analysis of the fungus growing with grapevine wood under heat stress. Using RT-qPCR-derived data, reference gene stability was evaluated through geNorm, NormFinder and Bestkeeper applications. Based on the geometric mean using the ranking position obtained for each independent analysis, genes were ranked from least to most stable as follows: glyceraldehyde-3-phosphate dehydrogenase (GAPDH), actin (ACT), β-tubulin (TUB) and elongation factor-1α (EF1α). Using RNAseq-derived data based on the calculated tagwise dispersion these genes were ordered by increasing stability as follows: GAPDH, ACT, TUB, and EF1α. The correlation between RNAseq and RTqPCR results was used as criteria to identify the best RT-qPCR normalization approach. The gene TUB is recommended as the best option for normalization among the commonly used reference genes, but alternative fungal reference genes are also suggested. Copyright © 2016 Elsevier B.V. All rights reserved.
Effects of Parsley (Petroselinum crispum) and its Flavonol Constituents, Kaempferol and Quercetin, on Serum Uric Acid Levels, Biomarkers of Oxidative Stress and Liver Xanthine Oxidoreductase Aactivity inOxonate-Induced Hyperuricemic Rats.

PubMed

Haidari, Fatemeh; Keshavarz, Seid Ali; Mohammad Shahi, Majid; Mahboob, Soltan-Ali; Rashidi, Mohammad-Reza

2011-01-01

Increased serum uric acid is known to be a major risk related to the development of several oxidative stress diseases. The aim of this study was to investigate the effect of parsley, quercetin and kaempferol on serum uric acid levels, liver xanthine oxidoreductase activity and two non-invasive biomarkers of oxidative stress (total antioxidant capacity and malondialdehyde concentration) in normal and oxonate-induced hyperuricemic rats. A total of 60 male Wistar rats were randomly divided into ten equal groups; including 5 normal groups (vehicle, parsley, quercetin, kaempferol and allopurinol) and 5 hyperuricemic groups (vehicle, parsley, quercetin, kaempferol and allopurinol). Parsley (5 g/Kg), quercetin (5 mg/Kg), kaempferol (5 mg/Kg) and allopurinol (5 mg/Kg) were administrated to the corresponding groups by oral gavage once a day for 2 weeks. The results showed that parsley and its flavonol did not cause any significant reduction in the serum uric acid levels in normal rats, but significantly reduced the serum uric acid levels of hyperuricemic rats in a time-dependent manner. All treatments significantly inhibited liver xanthine oxidoreductase activity. Parsley, kaempferol and quercetin treatment led also to a significant increase in total antioxidant capacity and decrease in malondialdehyde concentration in hyperuricemic rats. Although the hypouricemic effect of allopurinol was much higher than that of parsley and its flavonol constituents, it could not significantly change oxidative stress biomarkers. These features of parsley and its flavonols make them as a possible alternative for allopurinol, or at least in combination therapy to minimize the side effects of allopurinol to treat hyperuricemia and oxidative stress diseases.
Effects of Parsley (Petroselinum crispum) and its Flavonol Constituents, Kaempferol and Quercetin, on Serum Uric Acid Levels, Biomarkers of Oxidative Stress and Liver Xanthine Oxidoreductase Aactivity inOxonate-Induced Hyperuricemic Rats

PubMed Central

Haidari, Fatemeh; Keshavarz, Seid Ali; Mohammad Shahi, Majid; Mahboob, Soltan-Ali; Rashidi, Mohammad-Reza

2011-01-01

Increased serum uric acid is known to be a major risk related to the development of several oxidative stress diseases. The aim of this study was to investigate the effect of parsley, quercetin and kaempferol on serum uric acid levels, liver xanthine oxidoreductase activity and two non-invasive biomarkers of oxidative stress (total antioxidant capacity and malondialdehyde concentration) in normal and oxonate-induced hyperuricemic rats. A total of 60 male Wistar rats were randomly divided into ten equal groups; including 5 normal groups (vehicle, parsley, quercetin, kaempferol and allopurinol) and 5 hyperuricemic groups (vehicle, parsley, quercetin, kaempferol and allopurinol). Parsley (5 g/Kg), quercetin (5 mg/Kg), kaempferol (5 mg/Kg) and allopurinol (5 mg/Kg) were administrated to the corresponding groups by oral gavage once a day for 2 weeks. The results showed that parsley and its flavonol did not cause any significant reduction in the serum uric acid levels in normal rats, but significantly reduced the serum uric acid levels of hyperuricemic rats in a time-dependent manner. All treatments significantly inhibited liver xanthine oxidoreductase activity. Parsley, kaempferol and quercetin treatment led also to a significant increase in total antioxidant capacity and decrease in malondialdehyde concentration in hyperuricemic rats. Although the hypouricemic effect of allopurinol was much higher than that of parsley and its flavonol constituents, it could not significantly change oxidative stress biomarkers. These features of parsley and its flavonols make them as a possible alternative for allopurinol, or at least in combination therapy to minimize the side effects of allopurinol to treat hyperuricemia and oxidative stress diseases. PMID:24250417
46 CFR Appendix B to Part 154 - Stress Analyses Definitions

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 5 2010-10-01 2010-10-01 false Stress Analyses Definitions B Appendix B to Part 154...—Stress Analyses Definitions The following are the standard definitions of stresses for the analysis of an independent tank type B: Normal stress means the component of stress normal to the plane of reference...
46 CFR Appendix B to Part 154 - Stress Analyses Definitions

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 5 2012-10-01 2012-10-01 false Stress Analyses Definitions B Appendix B to Part 154...—Stress Analyses Definitions The following are the standard definitions of stresses for the analysis of an independent tank type B: Normal stress means the component of stress normal to the plane of reference...
46 CFR Appendix B to Part 154 - Stress Analyses Definitions

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 5 2013-10-01 2013-10-01 false Stress Analyses Definitions B Appendix B to Part 154...—Stress Analyses Definitions The following are the standard definitions of stresses for the analysis of an independent tank type B: Normal stress means the component of stress normal to the plane of reference...
46 CFR Appendix B to Part 154 - Stress Analyses Definitions

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 5 2014-10-01 2014-10-01 false Stress Analyses Definitions B Appendix B to Part 154...—Stress Analyses Definitions The following are the standard definitions of stresses for the analysis of an independent tank type B: Normal stress means the component of stress normal to the plane of reference...
46 CFR Appendix B to Part 154 - Stress Analyses Definitions

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 5 2011-10-01 2011-10-01 false Stress Analyses Definitions B Appendix B to Part 154...—Stress Analyses Definitions The following are the standard definitions of stresses for the analysis of an independent tank type B: Normal stress means the component of stress normal to the plane of reference...
Depression and stressful environments: identifying gaps in conceptualization and measurement.

PubMed

Hammen, Constance

2016-07-01

Stress is well known as a trigger of depressive reactions, fear, anxiety, and behavioral disorders. However, there are many gaps in the conceptualization and measurement of environmental stress. Exciting developments in the neuroscience of stress have increasingly expanded our knowledge of mechanisms by which stress may affect emotional and behavioral adjustment. Ironically, environmental stress has often been a silent player in human studies of stress processes. There is a significant need for increased efforts to include environmental stress variables in models of internalizing and other disorders. Measurement and conceptualization issues are prominent, and this article makes the case for improved methods of measuring acute, chronic, and early life stress, and for additional conceptualization of the dynamically changing and bidirectional effects of stress on disorder over time. There is a critical need for greater focus on and better measurement of the environment and its impact on emotional and other disorders, with emphasis on developmentally informed hypotheses. Empirical findings and new perspectives may contribute enormously to our understanding of normal and abnormal outcomes, and also to the challenge of effective interventions to promote mental health and optimal functioning.
Cardiac Energy Metabolism and Oxidative Stress Biomarkers in Diabetic Rat Treated with Resveratrol

PubMed Central

Carolo dos Santos, Klinsmann; Pereira Braga, Camila; Octavio Barbanera, Pedro; Rodrigues Ferreira Seiva, Fábio; Fernandes Junior, Ary; Fernandes, Ana Angélica Henrique

2014-01-01

Resveratrol (RSV), polyphenol from grape, was studied to evaluate its effects on calorimetric parameters, energy metabolism, and antioxidants in the myocardium of diabetic rats. The animals were randomly divided into four groups (n = 8): C (control group): normal rats; C-RSV: normal rats receiving RSV; DM: diabetic rats; and DM-RSV: diabetics rats receiving RSV. Type 1 diabetes mellitus was induced with administration of streptozotocin (STZ; 60 mg−1 body weight, single dose, i.p.). After 48 hours of STZ administration, the animals received RSV (1.0 mg/kg/day) for gavage for 30 days. Food, water, and energy intake were higher in the DM group, while administration of RSV caused decreases (p<0.05) in these parameters. The glycemia decreased and higher final body weight increased in DM-RSV when compared with the DM group. The diabetic rats showed higher serum-free fatty acid, which was normalized with RSV. Oxygen consumption (VO2) and carbon dioxide production (VCO2) decreased (p<0.05) in the DM group. This was accompanied by reductions in RQ. The C-RSV group showed higher VO2 and VCO2 values. Pyruvate dehydrogenase activity was lower in the DM group and normalizes with RSV. The DM group exhibited higher myocardial β-hydroxyacyl coenzyme-A dehydrogenase and citrate synthase activity, and RSV decreased the activity of these enzymes. The DM group had higher cardiac lactate dehydrogenase compared to the DM-RSV group. Myocardial protein carbonyl was increased in the DM group. RSV increased reduced glutathione in the cardiac tissue of diabetic animals. The glutathione reductase activity was higher in the DM-RSV group compared to the DM group. In conclusion, diabetes is accompanied by cardiac energy metabolism dysfunction and change in the biomarkers of oxidative stress. The cardioprotective effect may be mediated through RVS's ability to normalize free fatty acid oxidation, enhance utilization glucose, and control the biomarkers' level of oxidative stress under diabetic conditions. PMID:25050809
Thermal effects on shearing resistance of fractures in Tak granite

NASA Astrophysics Data System (ADS)

Khamrat, S.; Thongprapha, T.; Fuenkajorn, K.

2018-06-01

Triaxial shear tests have been performed on tension-induced fractures and smooth saw-cut surfaces in Tak granite under temperatures up to 773 K. The objective is to gain an understanding of the movement of shallow faults that cause seismic activities in the Tak batholith in the north of Thailand. The results indicate that the peak and residual shear strengths and fracture dilations notably decrease as the temperatures increase. The thermal effect is enhanced under higher confining pressures. The areas of the sheared-off asperities increase with temperature and confining pressure. A power equation can describe the increase of shear strengths with normal stress where the normal stress exponent is a linear function of the temperature. The strain energy principle is applied to incorporate the principal stresses and strains into a strength criterion. A linear relation between the distortional strain energy (Wd) and the mean strain energy (Wm) of the fractures is obtained. The Wd-Wm slope depends on the fracture roughness and strength of the asperities, which can be defined as a function of shear and mean strains and dilation of the fractures. This may allow predicting the peak strength of the shallow faults in the Tak batholith.
a Predictive Model of Permeability for Fractal-Based Rough Rock Fractures during Shear

NASA Astrophysics Data System (ADS)

Huang, Na; Jiang, Yujing; Liu, Richeng; Li, Bo; Zhang, Zhenyu

This study investigates the roles of fracture roughness, normal stress and shear displacement on the fluid flow characteristics through three-dimensional (3D) self-affine fractal rock fractures, whose surfaces are generated using the modified successive random additions (SRA) algorithm. A series of numerical shear-flow tests under different normal stresses were conducted on rough rock fractures to calculate the evolutions of fracture aperture and permeability. The results show that the rough surfaces of fractal-based fractures can be described using the scaling parameter Hurst exponent (H), in which H = 3 - Df, where Df is the fractal dimension of 3D single fractures. The joint roughness coefficient (JRC) distribution of fracture profiles follows a Gauss function with a negative linear relationship between H and average JRC. The frequency curves of aperture distributions change from sharp to flat with increasing shear displacement, indicating a more anisotropic and heterogeneous flow pattern. Both the mean aperture and permeability of fracture increase with the increment of surface roughness and decrement of normal stress. At the beginning of shear, the permeability increases remarkably and then gradually becomes steady. A predictive model of permeability using the mean mechanical aperture is proposed and the validity is verified by comparisons with the experimental results reported in literature. The proposed model provides a simple method to approximate permeability of fractal-based rough rock fractures during shear using fracture aperture distribution that can be easily obtained from digitized fracture surface information.
The influence of normal fault geometry on porous sandstone deformation: Insights from mechanical models into conditions leading to Coulomb failure and shear-enhanced compaction

NASA Astrophysics Data System (ADS)

Allison, K.; Reinen, L. A.

2011-12-01

Slip on non-planar faults produces stress perturbations in the surrounding host rock that can yield secondary faults at a scale too small to be resolved on seismic surveys. Porosity changes during failure may affect the ability of the rock to transmit fluids through dilatant cracking or, in porous rocks, shear-enhanced compaction (i.e., cataclastic flow). Modeling the mechanical behavior of the host rock in response to slip on non-planar faults can yield insights into the role of fault geometry on regions of enhanced or inhibited fluid flow. To evaluate the effect of normal fault geometry on deformation in porous sandstones, we model the system as a linear elastic, homogeneous, whole or half space using the boundary-element modeling program Poly3D. We consider conditions leading to secondary deformation using the maximum Coulomb shear stress (MCSS) as an index of brittle deformation and proximity to an elliptical yield envelope (Y), determined experimentally for porous sandstone (Baud et al., JGR, 2006), for cataclastic flow. We model rectangular faults consisting of two segments: an upper leg with a constant dip of 60° and a lower leg with dips ranging 15-85°. We explore far-field stress models of constant and gradient uniaxial strain. We investigate the potential damage in the host rock in two ways: [1] the size of the damage zone, and [2] regions of enhanced deformation indicated by elevated MCSS or Y. Preliminary results indicate that, along a vertical transect passing through the fault kink, [1] the size of the damage zone increases in the footwall with increasing lower leg dip and remains constant in the hanging wall. [2] In the footwall, the amount of deformation does not change as a function of lower leg dip in constant stress models; in gradient stress models, both MCSS and Y increase with dip. In the hanging wall, Y decreases with increasing lower leg dip for both constant and gradient stress models. In contrast, MCSS increases: as lower leg dip increases for constant stress models, and as the difference between lower leg dip and 60° increases for gradient stress models. These preliminary results indicate that the dip of the lower fault segment significantly affects the amount and style of deformation in the host rock.
46 CFR Appendix A to Part 154 - Equivalent Stress

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 5 2010-10-01 2010-10-01 false Equivalent Stress A Appendix A to Part 154 Shipping...—Equivalent Stress I. Equivalent stress (σ c) is calculated by the following formula or another formula... normal stress in “x” direction. σy=total normal stress in “y” direction. τxy=total shear stress in “xy...
46 CFR Appendix A to Part 154 - Equivalent Stress

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 5 2013-10-01 2013-10-01 false Equivalent Stress A Appendix A to Part 154 Shipping...—Equivalent Stress I. Equivalent stress (σ c) is calculated by the following formula or another formula... normal stress in “x” direction. σy=total normal stress in “y” direction. τxy=total shear stress in “xy...
46 CFR Appendix A to Part 154 - Equivalent Stress

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 5 2014-10-01 2014-10-01 false Equivalent Stress A Appendix A to Part 154 Shipping...—Equivalent Stress I. Equivalent stress (σ c) is calculated by the following formula or another formula... normal stress in “x” direction. σy=total normal stress in “y” direction. τxy=total shear stress in “xy...
46 CFR Appendix A to Part 154 - Equivalent Stress

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 5 2012-10-01 2012-10-01 false Equivalent Stress A Appendix A to Part 154 Shipping...—Equivalent Stress I. Equivalent stress (σ c) is calculated by the following formula or another formula... normal stress in “x” direction. σy=total normal stress in “y” direction. τxy=total shear stress in “xy...

46 CFR Appendix A to Part 154 - Equivalent Stress

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 5 2011-10-01 2011-10-01 false Equivalent Stress A Appendix A to Part 154 Shipping...—Equivalent Stress I. Equivalent stress (σ c) is calculated by the following formula or another formula... normal stress in “x” direction. σy=total normal stress in “y” direction. τxy=total shear stress in “xy...
Caffeine affects cardiovascular and neuroendocrine activation at work and home.

PubMed

Lane, James D; Pieper, Carl F; Phillips-Bute, Barbara G; Bryant, John E; Kuhn, Cynthia M

2002-01-01

This study investigated the effects of moderate doses of caffeine on ambulatory blood pressure and heart rate, urinary excretion of epinephrine, norepinephrine, and cortisol, and subjective measures of stress during normal activities at work and at home in the evening. Healthy, nonsmoking, habitual coffee drinkers (N = 47) participated in 3 days of ambulatory study. After a day of ad lib caffeine consumption, caffeine (500 mg) and placebo were administered double-blind in counter-balanced order on separate workdays. Ambulatory blood pressure and heart rate were monitored from the start of the workday until bedtime. Urinary excretion of catecholamines and cortisol was assessed during the workday and evening. Caffeine administration significantly raised average ambulatory blood pressure during the workday and evening by 4/3 mm Hg and reduced average heart rate by 2 bpm. Caffeine also increased by 32% the levels of free epinephrine excreted during the workday and the evening. In addition, caffeine amplified the increases in blood pressure and heart rate associated with higher levels of self-reported stress during the activities of the day. Effects were undiminished through the evening until bedtime. Caffeine has significant hemodynamic and humoral effects in habitual coffee drinkers that persist for many hours during the activities of everyday life. Furthermore, caffeine may exaggerate sympathetic adrenal-medullary responses to the stressful events of normal daily life. Repeated daily blood pressure elevations and increases in stress reactivity caused by caffeine consumption could contribute to an increased risk of coronary heart disease in the adult population.
Observed source parameters for dynamic rupture with non-uniform initial stressand relatively high fracture energy

USGS Publications Warehouse

Beeler, Nicholas M.; Kilgore, Brian D.; McGarr, Arthur F.; Fletcher, Jon Peter B.; Evans, John R.; Steven R. Baker,

2012-01-01

We have conducted dynamic rupture propagation experiments to establish the relations between in-source stress drop, fracture energy and the resulting particle velocity during slip of an unconfined 2 m long laboratory fault at normal stresses between 4 and 8 MPa. To produce high fracture energy in the source we use a rough fault that has a large slip weakening distance. An artifact of the high fracture energy is that the nucleation zone is large such that precursory slip reduces fault strength over a large fraction of the total fault length prior to dynamic rupture, making the initial stress non-uniform. Shear stress, particle velocity, fault slip and acceleration were recorded coseismically at multiple locations along strike and at small fault-normal distances. Stress drop increases weakly with normal stress. Average slip rate depends linearly on the fault strength loss and on static stress drop, both with a nonzero intercept. A minimum fracture energy of 1.8 J/m2 and a linear slip weakening distance of 33 μm are inferred from the intercept. The large slip weakening distance also affects the average slip rate which is reduced by in-source energy dissipation from on-fault fracture energy.Because of the low normal stress and small per event slip (∼86 μm), no thermal weakening such as melting or pore fluid pressurization occurs in these experiments. Despite the relatively high fracture energy, and the very low heat production, energy partitioning during these laboratory earthquakes is very similar to typical earthquake source properties. The product of fracture energy and fault area is larger than the radiated energy. Seismic efficiency is low at ∼2%. The ratio of apparent stress to static stress drop is ∼27%, consistent with measured overshoot. The fracture efficiency is ∼33%. The static and dynamic stress drops when extrapolated to crustal stresses are 2–7.3 MPa and in the range of typical earthquake stress drops. As the relatively high fracture energy reduces the slip velocities in these experiments, the extrapolated average particle velocities for crustal stresses are 0.18–0.6 m/s. That these experiments are consistent with typical earthquake source properties suggests, albeit indirectly, that thermal weakening mechanisms such as thermal pressurization and melting which lead to near complete stress drops, dominate earthquake source properties only for exceptional events unless crustal stresses are low.
On the continuity of mean total normal stress in geometrical multiscale cardiovascular problems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blanco, Pablo J., E-mail: pjblanco@lncc.br; INCT-MACC, Instituto Nacional de Ciência e Tecnologia em Medicina Assistida por Computação Científica, Petrópolis; Deparis, Simone, E-mail: simone.deparis@epfl.ch

2013-10-15

In this work an iterative strategy to implicitly couple dimensionally-heterogeneous blood flow models accounting for the continuity of mean total normal stress at interface boundaries is developed. Conservation of mean total normal stress in the coupling of heterogeneous models is mandatory to satisfy energetic consistency between them. Nevertheless, existing methodologies are based on modifications of the Navier–Stokes variational formulation, which are undesired when dealing with fluid–structure interaction or black box codes. The proposed methodology makes possible to couple one-dimensional and three-dimensional fluid–structure interaction models, enforcing the continuity of mean total normal stress while just imposing flow rate data or evenmore » the classical Neumann boundary data to the models. This is accomplished by modifying an existing iterative algorithm, which is also able to account for the continuity of the vessel area, when required. Comparisons are performed to assess differences in the convergence properties of the algorithms when considering the continuity of mean normal stress and the continuity of mean total normal stress for a wide range of flow regimes. Finally, examples in the physiological regime are shown to evaluate the importance, or not, of considering the continuity of mean total normal stress in hemodynamics simulations.« less
Stress anisotropy and velocity anisotropy in low porosity shale

NASA Astrophysics Data System (ADS)

Kuila, U.; Dewhurst, D. N.; Siggins, A. F.; Raven, M. D.

2011-04-01

Shales are known for often marked intrinsic anisotropy of many of their properties, including strength, permeability and velocity for example. In addition, it is well known that anisotropic stress fields can also have a significant impact on anisotropy of velocity, even in an isotropic medium. This paper sets out to investigate the ultrasonic velocity response of well-characterised low porosity shales from the Officer Basin in Western Australia to both isotropic and anisotropic stress fields and to evaluate the velocity response to the changing stress field. During consolidated undrained multi-stage triaxial tests on core plugs cut normal to bedding, V pv increases monotonically with increasing effective stress and V s1 behaves similarly although with some scatter. V ph and V sh remain constant initially but then decrease within each stage of the multi-stage test, although velocity from stage to stage at any given differential stress increases. This has the impact of decreasing both P-wave (ɛ) and S-wave anisotropy (γ) through application of differential stress within each loading stage. However, increasing the magnitude of an isotropic stress field has little effect on the velocity anisotropies. The intrinsic anisotropy of the shale remains reasonably high at the highest confining pressures. The results indicate the magnitude and orientation of the stress anisotropy with respect to the shale microfabric has a significant impact on the velocity response to changing stress fields.
The mitochondria targeted antioxidant MitoQ protects against fluoroquinolone-induced oxidative stress and mitochondrial membrane damage in human Achilles tendon cells.

PubMed

Lowes, Damon A; Wallace, Carol; Murphy, Michael P; Webster, Nigel R; Galley, Helen F

2009-04-01

Tendinitis and tendon rupture during treatment with fluoroquinolone antibiotics is thought to be mediated via oxidative stress. This study investigated whether ciprofloxacin and moxifloxacin cause oxidative stress and mitochondrial damage in cultured normal human Achilles' tendon cells and whether an antioxidant targeted to mitochondria (MitoQ) would protect against such damage better than a non-mitochondria targeted antioxidant. Human tendon cells from normal Achilles' tendons were exposed to 0-0.3 mM antibiotic for 24 h and 7 days in the presence of 1 microM MitoQ or an untargeted form, idebenone. Both moxifloxacin and ciprofloxacin resulted in up to a 3-fold increase in the rate of oxidation of dichlorodihydrofluorescein, a marker of general oxidative stress in tenocytes (p<0.0001) and loss of mitochondrial membrane permeability (p<0.001). In cells treated with MitoQ the oxidative stress was less and mitochondrial membrane potential was maintained. Mitochondrial damage to tenocytes during fluoroquinolone treatment may be involved in tendinitis and tendon rupture.
Job stress and productivity increase.

PubMed

Adaramola, Samson Sunday

2012-01-01

This paper examines mental and physical pressures that workers bear at work. The authors discuss how on the-job stress affects a person's capabilities and productivity, and how such pressures lend to higher incidences of accidents at work. The paper also discuss methods of reducing job-related stress and increasing productivity. An intervention was conducted amongst workers in a private firm. It shows mental and emotional pressure can affect performance and productivity of a worker on the job. One of the biggest influences of today's worker is on the-job stress. Job stress occurs when the requirements of the job do not match the capabilities, resources, or needs of the worker. This consequently affects how a person would normally deal with customer service problems, grievances, violence, conflict, and decisions on the job. Stress is an inevitable part of everyday life, and is therefore a distinct part of a person's job. To properly control the outcome of stress, there are certain precautions and methods that should be taken that will boost productivity.
Role of oxytocin in improving the welfare of farm animals - A review.

PubMed

Chen, Siyu; Sato, Shusuke

2017-04-01

Recently, increasing attention has been paid to the welfare of farm animals, which have been evaluated using behavioral and physiological measures. However, so far, the measures have almost always been used to estimate poor welfare. In this review, firstly we focus on how oxytocin (OT) relates to positive social behavior, pleasure, and stress tolerance, and second on which management factors stimulate OT release. OT induces maternal and affiliative behaviors and has an anti-stress effect. Further, OT is produced during enjoyable events, and has positive feedback on its own release as well. Therefore, to some extent, the relationship of OT to positive normal behavior was mutually beneficial-heightened OT concentration owing to comfortable rearing conditions induces positive social behavior, which in turn may increase OT concentration. Hence, studies on animal welfare should pay more attention to increasing comfort and the stress tolerance, rather than only focusing on when stress occurs in farm animals.
Coordinated regulation of photosynthesis in rice increases yield and tolerance to environmental stress

PubMed Central

Ambavaram, Madana M. R.; Basu, Supratim; Krishnan, Arjun; Ramegowda, Venkategowda; Batlang, Utlwang; Rahman, Lutfor; Baisakh, Niranjan; Pereira, Andy

2014-01-01

Plants capture solar energy and atmospheric carbon dioxide (CO2) through photosynthesis, which is the primary component of crop yield, and needs to be increased considerably to meet the growing global demand for food. Environmental stresses, which are increasing with climate change, adversely affect photosynthetic carbon metabolism (PCM) and limit yield of cereals such as rice (Oryza sativa) that feeds half the world. To study the regulation of photosynthesis, we developed a rice gene regulatory network and identified a transcription factor HYR (HIGHER YIELD RICE) associated with PCM, which on expression in rice enhances photosynthesis under multiple environmental conditions, determining a morpho-physiological programme leading to higher grain yield under normal, drought and high-temperature stress conditions. We show HYR is a master regulator, directly activating photosynthesis genes, cascades of transcription factors and other downstream genes involved in PCM and yield stability under drought and high-temperature environmental stress conditions. PMID:25358745
Disrupted cortical function underlies behavior dysfunction due to social isolation

PubMed Central

Miyazaki, Tomoyuki; Takase, Kenkichi; Nakajima, Waki; Tada, Hirobumi; Ohya, Daisuke; Sano, Akane; Goto, Takahisa; Hirase, Hajime; Malinow, Roberto; Takahashi, Takuya

2012-01-01

Stressful events during early childhood can have a profound lifelong influence on emotional and cognitive behaviors. However, the mechanisms by which stress affects neonatal brain circuit formation are poorly understood. Here, we show that neonatal social isolation disrupts molecular, cellular, and circuit developmental processes, leading to behavioral dysfunction. Neonatal isolation prevented long-term potentiation and experience-dependent synaptic trafficking of α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptors normally occurring during circuit formation in the rodent barrel cortex. This inhibition of AMPA receptor trafficking was mediated by an increase of the stress glucocorticoid hormone and was associated with reduced calcium/calmodulin-dependent protein kinase type II (CaMKII) signaling, resulting in attenuated whisker sensitivity at the cortex. These effects led to defects in whisker-dependent behavior in juvenile animals. These results indicate that neonatal social isolation alters neuronal plasticity mechanisms and perturbs the initial establishment of a normal cortical circuit, which potentially explains the long-lasting behavioral effects of neonatal stress. PMID:22706303
Ginseng and the hypothalamic-pituitary control of stress.

PubMed

Fulder, S J

1981-01-01

There are a group of so-called tonic remedies in Far Eastern medicine which are traditionally viewed as harmonizing or adjustive. Ginseng and eleutherococcus are the best known, and there is evidence that they increase arousal, stamina and stress resistance. We have attempted to explore the relationship between the behavioral and the stress effects, and to relate this to traditional concepts. In one series of experiments mice were given ginseng throughout their lifespan. At intervals their behavior response to mild stress was examined and found to be exaggerated compared to controls without ginseng. However, normal ambulatory behavior in the absence of stress was unaffected. A second series of experiments indicated that the binding of corticosteroid to certain brain regions was increased in adrenalectomized rats given ginseng saponin, compared to saline treated controls. This can be interpreted as a result of an increase in hypothalamic-pituitary-adrenal sensitivity caused by ginseng saponin. This is in accord with traditional concepts of the use of these remedies.
β-Cell Dysfunction Due to Increased ER Stress in a Stem Cell Model of Wolfram Syndrome

PubMed Central

Shang, Linshan; Hua, Haiqing; Foo, Kylie; Martinez, Hector; Watanabe, Kazuhisa; Zimmer, Matthew; Kahler, David J.; Freeby, Matthew; Chung, Wendy; LeDuc, Charles; Goland, Robin; Leibel, Rudolph L.; Egli, Dieter

2014-01-01

Wolfram syndrome is an autosomal recessive disorder caused by mutations in WFS1 and is characterized by insulin-dependent diabetes mellitus, optic atrophy, and deafness. To investigate the cause of β-cell failure, we used induced pluripotent stem cells to create insulin-producing cells from individuals with Wolfram syndrome. WFS1-deficient β-cells showed increased levels of endoplasmic reticulum (ER) stress molecules and decreased insulin content. Upon exposure to experimental ER stress, Wolfram β-cells showed impaired insulin processing and failed to increase insulin secretion in response to glucose and other secretagogues. Importantly, 4-phenyl butyric acid, a chemical protein folding and trafficking chaperone, restored normal insulin synthesis and the ability to upregulate insulin secretion. These studies show that ER stress plays a central role in β-cell failure in Wolfram syndrome and indicate that chemical chaperones might have therapeutic relevance under conditions of ER stress in Wolfram syndrome and other forms of diabetes. PMID:24227685
Supplementation of Ascorbic Acid in Weanling Horses Following Prolonged Transportation

PubMed Central

Ralston, Sarah; Stives, Michelle

2012-01-01

Simple Summary Horses normally synthesize adequate amounts of ascorbic acid (vitamin C) in their liver to meet their needs for the vitamin. However, prolonged stress results in low plasma concentrations and reduced immune function. Weanling horses were supplemented with ascorbic acid for 5 or 10 days or no ascorbic acid (4 per group) following 50+ hours of transportation. Supplementation caused increases in plasma concentrations but both supplemented groups had decreased plasma ascorbic acid for 1 to 3 weeks following cessation of supplementation, possibly due to suppressed synthesis. Supplementation of ascorbic acid following prolonged stress will increase plasma concentrations, but prolonged supplementation should be avoided. Abstract Though horses synthesize ascorbic acid in their liver in amounts that meet their needs under normal circumstances, prolonged stress results in low plasma concentrations due to enhanced utilization and renal excretion and can reduce immune function. It was hypothesized that plasma ascorbic acid could be maintained in weanling horses by oral supplementation following prolonged transportation. Weanlings were supplemented with no ascorbic acid (Tx 0: n = 4), 5 grams ascorbic acid twice daily for 5 days (Tx 1: n = 4) or for 10 days (Tx 2: n = 4) following >50 hours of transportation. Supplementation caused slight (P < 0.2) increases in plasma ascorbic acid concentrations. Both supplemented groups had decreased (P < 0.05) plasma concentrations for 1 to 3 weeks following cessation of supplementation, possibly due to increased renal excretion or suppressed hepatic synthesis. Supplementation of ascorbic acid following prolonged stress will increase plasma concentrations, but prolonged supplementation should be avoided. PMID:26486916
Accurate Thermal Stresses for Beams: Normal Stress

NASA Technical Reports Server (NTRS)

Johnson, Theodore F.; Pilkey, Walter D.

2002-01-01

Formulations for a general theory of thermoelasticity to generate accurate thermal stresses for structural members of aeronautical vehicles were developed in 1954 by Boley. The formulation also provides three normal stresses and a shear stress along the entire length of the beam. The Poisson effect of the lateral and transverse normal stresses on a thermally loaded beam is taken into account in this theory by employing an Airy stress function. The Airy stress function enables the reduction of the three-dimensional thermal stress problem to a two-dimensional one. Numerical results from the general theory of thermoelasticity are compared to those obtained from strength of materials. It is concluded that the theory of thermoelasticity for prismatic beams proposed in this paper can be used instead of strength of materials when precise stress results are desired.
Accurate Thermal Stresses for Beams: Normal Stress

NASA Technical Reports Server (NTRS)

Johnson, Theodore F.; Pilkey, Walter D.

2003-01-01

Formulations for a general theory of thermoelasticity to generate accurate thermal stresses for structural members of aeronautical vehicles were developed in 1954 by Boley. The formulation also provides three normal stresses and a shear stress along the entire length of the beam. The Poisson effect of the lateral and transverse normal stresses on a thermally loaded beam is taken into account in this theory by employing an Airy stress function. The Airy stress function enables the reduction of the three-dimensional thermal stress problem to a two-dimensional one. Numerical results from the general theory of thermoelasticity are compared to those obtained from strength of materials. It is concluded that the theory of thermoelasticity for prismatic beams proposed in this paper can be used instead of strength of materials when precise stress results are desired.
Characterization and modeling of the stress and pore-fluid dependent acoustic properties of fractured porous rocks

NASA Astrophysics Data System (ADS)

Almrabat, Abdulhadi M.

The thesis presents the results of a study of the characterization and modeling of the stress and pore-fluid dependent acoustic properties of fractured porous rocks. A new laboratory High Pressure and High Temperature (HPHT) triaxial testing system was developed to characterize the seismic properties of sandstone under different levels of effective stress confinement and changes in pore-fluid composition. An intact and fractured of Berea sandstones core samples were used in the experimental studies. The laboratory test results were used to develop analytical models for stress-level and pore-fluid dependent seismic velocity of sandstones. Models for stress-dependent P and S-wave seismic velocities of sandstone were then developed based on the assumption that stress-dependencies come from the nonlinear elastic response of micro-fractures contained in the sample under normal and shear loading. The contact shear stiffness was assumed to increase linearly with the normal stress across a micro-fracture, while the contact normal stiffness was assumed to vary as a power law with the micro-fracture normal stress. Both nonlinear fracture normal and shear contact models were validated by experimental data available in the literature. To test the dependency of seismic velocity of sandstone on changes in pore-fluid composition, another series of tests were conducted where P and S-wave velocities were monitored during injection of supercritical CO 2 in samples of Berea sandstone initially saturated with saline water and under constant confining stress. Changes in seismic wave velocity were measured at different levels of supercritical CO2 saturation as the initial saline water as pore-fluid was displaced by supercritical CO 2. It was found that the P- iv wave velocity significantly decreased while the S-wave velocity remained almost constant as the sample supercritical CO2 saturation increased. The dependency of the seismic velocity on changes on pore fluid composition during injection of supercritical CO 2 in Berea sandstone was modeled using a re-derived Biot-Gassmann substitution theory. In using the Biot-Gassmann substitution theory, it was found necessary to account for the changes in the pore-fluid compressibility in terms of the volumetric proportion and distribution of saline water and supercritical CO 2 in the sample pore space. This was done by using the empirical model of Brie et al. to account for the compressibility of mixtures of two-phase immiscible fluids. The combined Biot-Gassman and Brie et al. models were found to represent adequately the changes in P-wave velocity of Berea sandstone during displacement of saline water by supercritical CO2. The third experimental and modeling study addressed shear-wave splitting due to the presence of fractures in a rock mass. Tests were conducted using the high temperature and high pressure (HPHT) triaxial device on samples of Berea sandstone, containing a single induced tensile fracture running along the height of the sample. The fracture was created via a modified Brazilian Split Test loading where the edges of cylindrical samples were loaded on diametrically opposite two points by sharp guillotines. The Joint Roughness Coefficient (JRC) values of the fractured core samples were determined by profilometry and tilt test. The effect of mismatching of the fracture surfaces on shear wave splitting was investigated by applying different amounts of shear displacements to three core samples. The degree of mismatching of the fracture surfaces in the core samples was evaluated using the Joint Matching Coefficient (JMC). Shear-wave splitting, as measured by the difference in magnitudes of shear-wave velocities parallel and perpendicular to the fracture, Vs1 and Vs2 respectively, increases with increasing mismatch of the fracture surfaces and decreases with increasing effective stress, and approaches zero in the effective stress range tested. A model for the stress and JMC dependent shear-wave splitting was developed based on the experimental observations. Finally, the magnitude of shear-wave splitting was correlated with the permeability of the fractured porous sandstone for fluid flow parallel to the induced fracture. (Abstract shortened by UMI.)
Fault strength in Marmara region inferred from the geometry of the principle stress axes and fault orientations: A case study for the Prince's Islands fault segment

NASA Astrophysics Data System (ADS)

Pinar, Ali; Coskun, Zeynep; Mert, Aydin; Kalafat, Dogan

2015-04-01

The general consensus based on historical earthquake data point out that the last major moment release on the Prince's islands fault was in 1766 which in turn signals an increased seismic risk for Istanbul Metropolitan area considering the fact that most of the 20 mm/yr GPS derived slip rate for the region is accommodated mostly by that fault segment. The orientation of the Prince's islands fault segment overlaps with the NW-SE direction of the maximum principle stress axis derived from the focal mechanism solutions of the large and moderate sized earthquakes occurred in the Marmara region. As such, the NW-SE trending fault segment translates the motion between the two E-W trending branches of the North Anatolian fault zone; one extending from the Gulf of Izmit towards Çınarcık basin and the other extending between offshore Bakırköy and Silivri. The basic relation between the orientation of the maximum and minimum principal stress axes, the shear and normal stresses, and the orientation of a fault provides clue on the strength of a fault, i.e., its frictional coefficient. Here, the angle between the fault normal and maximum compressive stress axis is a key parameter where fault normal and fault parallel maximum compressive stress might be a necessary and sufficient condition for a creeping event. That relation also implies that when the trend of the sigma-1 axis is close to the strike of the fault the shear stress acting on the fault plane approaches zero. On the other hand, the ratio between the shear and normal stresses acting on a fault plane is proportional to the coefficient of frictional coefficient of the fault. Accordingly, the geometry between the Prince's islands fault segment and a maximum principal stress axis matches a weak fault model. In the frame of the presentation we analyze seismological data acquired in Marmara region and interpret the results in conjuction with the above mentioned weak fault model.
Mental stress and hypertension, an evolutionary framework: some historical perspectives of the 1960 World Health Organization Prague Hypertension Meeting.

PubMed

Kuchel, Otto

2003-03-01

Emotional stress acutely and repetitively causing blood pressure increase or aggravating existing hypertension is usually not reflected by norepinephrine and epinephrine increase but by a sudden rise of dopamine, the third "defensive" catecholamine coping with the damaging neuropsychological and cardiovascular actions of the first two. This double-edged sympathetic response to emotional stress evolves during human lifespan and long-term evolution of hypertension. In the course of philogenesis it carries a potential mismatch between the normal physiology of the human dopaminergic system and current environmental (emotional particularly) conditions in industrialized countries. This offers a rational support to a mental stress-cardiovascular diseases relationship proposed 40 years ago in a WHO report which followed a memorable 1960 Prague Hypertension Meeting.
Estimation of stress relaxation time for normal and abnormal breast phantoms using optical technique

NASA Astrophysics Data System (ADS)

Udayakumar, K.; Sujatha, N.

2015-03-01

Many of the early occurring micro-anomalies in breast may transform into a deadliest cancer tumor in future. Probability of curing early occurring abnormalities in breast is more if rightly identified. Even in mammogram, considered as a golden standard technique for breast imaging, it is hard to pick up early occurring changes in the breast tissue due to the difference in mechanical behavior of the normal and abnormal tissue when subjected to compression prior to x-ray or laser exposure. In this paper, an attempt has been made to estimate the stress relaxation time of normal and abnormal breast mimicking phantom using laser speckle image correlation. Phantoms mimicking normal breast is prepared and subjected to precise mechanical compression. The phantom is illuminated by a Helium Neon laser and by using a CCD camera, a sequence of strained phantom speckle images are captured and correlated by the image mean intensity value at specific time intervals. From the relation between mean intensity versus time, tissue stress relaxation time is quantified. Experiments were repeated for phantoms with increased stiffness mimicking abnormal tissue for similar ranges of applied loading. Results shows that phantom with more stiffness representing abnormal tissue shows uniform relaxation for varying load of the selected range, whereas phantom with less stiffness representing normal tissue shows irregular behavior for varying loadings in the given range.
Screening study of select cotton-based hydromulch blends produced using the cross-linked biofiber process

USDA-ARS?s Scientific Manuscript database

As global populations continue to expand, stresses placed on our renewable resources are increasing. Disturbance of native landscapes from agriculture, urbanization, or by natural evolution brings the potential for soil erosion caused by normal rain events. Increasing regulatory pressure has resulte...

Caspase-12 ablation preserves muscle function in the mdx mouse

PubMed Central

Moorwood, Catherine; Barton, Elisabeth R.

2014-01-01

Duchenne muscular dystrophy (DMD) is a devastating muscle wasting disease caused by mutations in dystrophin. Several downstream consequences of dystrophin deficiency are triggers of endoplasmic reticulum (ER) stress, including loss of calcium homeostasis, hypoxia and oxidative stress. During ER stress, misfolded proteins accumulate in the ER lumen and the unfolded protein response (UPR) is triggered, leading to adaptation or apoptosis. We hypothesized that ER stress is heightened in dystrophic muscles and contributes to the pathology of DMD. We observed increases in the ER stress markers BiP and cleaved caspase-4 in DMD patient biopsies, compared with controls, and an increase in multiple UPR pathways in muscles of the dystrophin-deficient mdx mouse. We then crossed mdx mice with mice null for caspase-12, the murine equivalent of human caspase-4, which are resistant to ER stress. We found that deleting caspase-12 preserved mdx muscle function, resulting in a 75% recovery of both specific force generation and resistance to eccentric contractions. The compensatory hypertrophy normally found in mdx muscles was normalized in the absence of caspase-12; this was found to be due to decreased fibre sizes, and not to a fibre type shift or a decrease in fibrosis. Fibre central nucleation was not significantly altered in the absence of caspase-12, but muscle fibre degeneration found in the mdx mouse was reduced almost to wild-type levels. In conclusion, we have identified heightened ER stress and abnormal UPR signalling as novel contributors to the dystrophic phenotype. Caspase-4 is therefore a potential therapeutic target for DMD. PMID:24879640
Stress induction in the bacteria Shewanella oneidensis and Deinococcus radiodurans in response to below-background ionizing radiation.

PubMed

Castillo, Hugo; Schoderbek, Donald; Dulal, Santosh; Escobar, Gabriela; Wood, Jeffrey; Nelson, Roger; Smith, Geoffrey

2015-01-01

The 'Linear no-threshold' (LNT) model predicts that any amount of radiation increases the risk of organisms to accumulate negative effects. Several studies at below background radiation levels (4.5-11.4 nGy h(-1)) show decreased growth rates and an increased susceptibility to oxidative stress. The purpose of our study is to obtain molecular evidence of a stress response in Shewanella oneidensis and Deinococcus radiodurans grown at a gamma dose rate of 0.16 nGy h(-1), about 400 times less than normal background radiation. Bacteria cultures were grown at a dose rate of 0.16 or 71.3 nGy h(-1) gamma irradiation. Total RNA was extracted from samples at early-exponential and stationary phases for the rt-PCR relative quantification (radiation-deprived treatment/background radiation control) of the stress-related genes katB (catalase), recA (recombinase), oxyR (oxidative stress transcriptional regulator), lexA (SOS regulon transcriptional repressor), dnaK (heat shock protein 70) and SOA0154 (putative heavy metal efflux pump). Deprivation of normal levels of radiation caused a reduction in growth of both bacterial species, accompanied by the upregulation of katB, recA, SOA0154 genes in S. oneidensis and the upregulation of dnaK in D. radiodurans. When cells were returned to background radiation levels, growth rates recovered and the stress response dissipated. Our results indicate that below-background levels of radiation inhibited growth and elicited a stress response in two species of bacteria, contrary to the LNT model prediction.
Effect of second to first normal stress difference ratio at the die exit on neck-in phenomenon in polymeric flat film production

NASA Astrophysics Data System (ADS)

Barborik, Tomas; Zatloukal, Martin

2017-05-01

In this study, viscoelastic modeling of the extrusion film casting process, based on the lD membrane model and modified Leonov constitutive equation, was conducted and the effect of the viscoelastic stress state at the die exit (captured here via second to first normal stress difference ratio) on the unwanted neck-in phenomenon has been analyzed for wide range of Deborah numbers and materials having different level of uniaxial and planar extensional strain hardening. Relevant experimental data for LDPE and theoretical predictions based on multimode eXtended Pom-Pom model acquired from the open literature were used for the validation purposes. It was found that firstly, the predicting capabilities of both constitutive equations for given material and processing conditions are comparable even if the single mode modified Leonov model was used and secondly, the agreement between theoretical and experimental data on neck-in is fairly good. Results of the theoretical study revealed that the viscoelastic stress state at the die exit (i.e. -N2/N1 ratio) increases the level of neck-in if uniaxial extensional strain hardening, planar to uniaxial extensional viscosity ratio and Deborah number increases. It has also been revealed that there exists threshold value for Deborah number and extensional strain hardening below which the neck-in becomes independent on the die exit stress state.
Osteogenesis potential of different titania nanotubes in oxidative stress microenvironment.

PubMed

Yu, Yonglin; Shen, Xinkun; Luo, Zhong; Hu, Yan; Li, Menghuan; Ma, Pingping; Ran, Qichun; Dai, Liangliang; He, Ye; Cai, Kaiyong

2018-06-01

Oxidative stress is commonly existed in bone degenerative disease (osteoarthritis, osteoporosis etc.) and some antioxidants had great potential to enhance osteogenesis. In this study, we aim to investigate the anti-oxidative properties of various TiO 2 nanotubes (TNTs) so to screen the desirable size for improved osteogenesis and reveal the underlying molecular mechanism in vitro. Comparing cellular behaviors under normal and oxidative stress conditions, an interesting conclusion was obtained. In normal microenvironment, small TNTs were beneficial for adhesion and proliferation of osteoblasts, but large TNTs greatly increased osteogenic differentiation. However, after H 2 O 2 (300 μM) treatment (mimicking oxidative stress), only large TNTs samples demonstrated superior cellular behaviors of increased osteoblasts' adhesion, survival and differentiation when comparing with those of native titanium (control). Molecular results revealed that oxidative stress resistance of large nanotubes was closely related to the high expression of integrin α5β1 (ITG α5β1), which further up-regulated the production of anti-apoptotic proteins (p-FAK, p-Akt, p-FoxO3a and Bcl2) and down-regulated the expression of pro-apoptotic protein (Bax). Moreover, we found that Wnt signals (Wnt3a, Wnt5a, Lrp5, Lrp6 and β-catenin) played an important role in promoting osteogenic differentiation of osteoblasts under oxidative condition. Copyright © 2018 Elsevier Ltd. All rights reserved.
[Loss of capture by myocardial ischemia: A case report].

PubMed

Sonou, A; Adjagba, P M; Hounkponou, M; Codjo, L; Houéhanou-Sonou, C; Assani, S; Yessoufou, T; Sacca, J; Houénassi, M

2017-02-01

We report the case of a patient with pacemaker who presented chest pain during exercise followed by fainting. He has a history of arterial hypertension and diabetes. The initial examination was normal; the ventricular stimulation threshold was 1.125 volts (V) and cardiac enzymes were normal. Stress test has reproduced chest pain followed by loss of pacemaker capture and asystole. Coronary angiography showed a tight stenosis of the proximal anterior interventricular artery dilated by a drug-eluting stent. The control of stress test was normal. A stent thrombosis eight days later led to an acute coronary syndrome with recurrent syncope due to the loss of ventricular capture. The ventricular pacing threshold was then 2.25V. After revascularization and stabilization of the patient's clinical status, this threshold returned to 1.125V. This clinic case has confirmed that coronary artery disease could increase pacing threshold. It also highlights the usefulness of automatic capture algorithms in coronary patients. The stress test cannot only help to detect coronary artery disease but also allows the optimization of programming the pacemaker. Copyright © 2016 Elsevier Masson SAS. All rights reserved.
Frictional strength and heat flow of southern San Andreas Fault

NASA Astrophysics Data System (ADS)

Zhu, P. P.

2016-01-01

Frictional strength and heat flow of faults are two related subjects in geophysics and seismology. To date, the investigation on regional frictional strength and heat flow still stays at the stage of qualitative estimation. This paper is concentrated on the regional frictional strength and heat flow of the southern San Andreas Fault (SAF). Based on the in situ borehole measured stress data, using the method of 3D dynamic faulting analysis, we quantitatively determine the regional normal stress, shear stress, and friction coefficient at various seismogenic depths. These new data indicate that the southern SAF is a weak fault within the depth of 15 km. As depth increases, all the regional normal and shear stresses and friction coefficient increase. The former two increase faster than the latter. Regional shear stress increment per kilometer equals 5.75 ± 0.05 MPa/km for depth ≤15 km; regional normal stress increment per kilometer is equal to 25.3 ± 0.1 MPa/km for depth ≤15 km. As depth increases, regional friction coefficient increment per kilometer decreases rapidly from 0.08 to 0.01/km at depths less than ~3 km. As depth increases from ~3 to ~5 km, it is 0.01/km and then from ~5 to 15 km, and it is 0.002/km. Previously, frictional strength could be qualitatively determined by heat flow measurements. It is difficult to obtain the quantitative heat flow data for the SAF because the measured heat flow data exhibit large scatter. However, our quantitative results of frictional strength can be employed to investigate the heat flow in the southern SAF. We use a physical quantity P f to describe heat flow. It represents the dissipative friction heat power per unit area generated by the relative motion of two tectonic plates accommodated by off-fault deformation. P f is called "fault friction heat." On the basis of our determined frictional strength data, utilizing the method of 3D dynamic faulting analysis, we quantitatively determine the regional long-term fault friction heat at various seismogenic depths in the southern SAF. The new data show that as depth increases, regional friction stress increases within the depth of 15 km; its increment per kilometer equals 5.75 ± 0.05 MPa/km. As depth increases, regional long-term fault friction heat increases; its increment per kilometer is equal to 3.68 ± 0.03 mW/m2/km. The values of regional long-term fault friction heat provided by this study are always lower than those from heat flow measurements. The difference between them and the scatter existing in the measured heat flow data are mainly caused by the following processes: (i) heat convection, (ii) heat advection, (iii) stress accumulation, (iv) seismic bursts between short-term lull periods in a long-term period, and (v) influence of seismicity in short-term periods upon long-term slip rate and heat flow. Fault friction heat is a fundamental parameter in research on heat flow.
Regulative roles of glutathione reductase and four glutaredoxins in glutathione redox, antioxidant activity, and iron homeostasis of Beauveria bassiana.

PubMed

Zhang, Long-Bin; Tang, Li; Ying, Sheng-Hua; Feng, Ming-Guang

2016-07-01

Multiple glutaredoxins (Grx) and glutathione reductase (Glr) are vital for the thiol-disulfide redox system in budding yeast but generally unexplored in filamentous fungi. Here we characterized the Beauveria bassiana redox system comprising dithiol Grx1, monothiol Grx2-4, Grx-like Grx5, and Glr orthologue. Each grx or glr deletion was compensated by increased transcripts of some other grx genes in normal cultures. Particularly, grx3 compensated the absence of grx1, grx2, grx5, or glr under oxidative stress while its absence was compensated only by undeletable grx4 under normal conditions but by most of other undeleted grx and glr genes in response to menadione. Consequently, the redox state was disturbed in Δglr more than in Δgrx3 but not in Δgrx1/2/5. Superoxide dismutases were more active in normal Δgrx1-3 cultures but less in Δgrx5 or Δglr response to menadione. Total catalase activity increased differentially in all the mutant cultures stressed with or without H2O2 while total peroxidase activity decreased more in the normal or H2O2-stressed culture of Δglr than of Δgrx3. Among the mutants, Δgrx3 showed slightly increased sensitivity to menadione or H2O2; Δglr exhibited greater sensitivity to thiol-oxidizing diamide than thiol-reducing 1-chloro-2,4-dinitrobenzene as well as increased sensitivity to the two oxidants. Intriguingly, all the mutants grew slower in a Fe(3+)-inclusive medium perhaps due to elevated transcripts of two Fe(3+) transporter genes. More or fewer phenotypes linked with biocontrol potential were altered in four deletion mutants excluding Δgrx5. All the changes were restored by targeted gene complementation. Overall, Grx3 played more critical role than other Grx homologues in the Glr-dependent redox system of the fungal entomopathogen.
Persistent oxidative stress following renal ischemia-reperfusion injury increases ANG II hemodynamic and fibrotic activity

PubMed Central

Leonard, Ellen C.; Beal, Alisa G.; Schleuter, Devin; Friedrich, Jessica

2012-01-01

ANG II is a potent renal vasoconstrictor and profibrotic factor and its activity is enhanced by oxidative stress. We sought to determine whether renal oxidative stress was persistent following recovery from acute kidney injury (AKI) induced by ischemia-reperfusion (I/R) injury in rats and whether this resulted in increased ANG II sensitivity. Rats were allowed to recover from bilateral renal I/R injury for 5 wk and renal blood flow responses were measured. Post-AKI rats showed significantly enhanced renal vasoconstrictor responses to ANG II relative to sham-operated controls and treatment of AKI rats with apocynin (15 mM, in the drinking water) normalized these responses. Recovery from AKI for 5 wk resulted in sustained oxidant stress as indicated by increased dihydroethidium incorporation in renal tissue slices and was normalized in apocynin-treated rats. Surprisingly, the renal mRNA expression for common NADPH oxidase subunits was not altered in kidneys following recovery from AKI; however, mRNA screening using PCR arrays suggested that post-AKI rats had decreased renal Gpx3 mRNA and an increased expression other prooxidant genes such as lactoperoxidase, myeloperoxidase, and dual oxidase-1. When rats were infused for 7 days with ANG II (100 ng·kg−1·min−1), renal fibrosis was not apparent in sham-operated control rats, but it was enhanced in post-AKI rats. The profibrotic response was significantly attenuated in rats treated with apocynin. These data suggest that there is sustained renal oxidant stress following recovery from AKI that alters both renal hemodynamic and fibrotic responses to ANG II, and may contribute to the transition to chronic kidney disease following AKI. PMID:22442209
Inner and outer layer turbulence over a superhydrophobic surface with low roughness level at low Reynolds number

NASA Astrophysics Data System (ADS)

Abu Rowin, W.; Hou, J.; Ghaemi, S.

2017-09-01

The inner and outer layers of a turbulent channel flow over a superhydrophobic surface (SHS) are characterized using simultaneous long-range microscopic particle tracking velocimetry (micro-PTV) and particle image velocimetry, respectively. The channel flow is operated at a low Reynolds number of ReH = 4400 (based on full channel height and 0.174 m/s bulk velocity), equivalent to Reτ = 140 (based on half channel height and friction velocity). The SHS is produced by spray coating, and the root-mean-square of wall roughness normalized by wall-unit is k+rms = 0.11. The micro-PTV shows 0.023 m/s slip velocity over the SHS (about 13% of the bulk velocity), which corresponds to a slip-length of ˜200 μm. A drag reduction of ˜19% based on the slope of the linear viscous sublayer and 22% based on an analytical expression of Rastegari and Akhavan [J. Fluid Mech. 773, R4 (2015)] realized. The reduced Reτ over the SHS based on the corresponding friction velocity is ˜125, which is in the lower limit of a turbulence regime. The results show the increase of streamwise Reynolds stresses for the SHS in the linear viscous sublayer due to the slip boundary condition. The peak does not change in magnitude while it is displaced closer to the wall in physical distance. The wall-normal Reynolds stress over the SHS and smooth surface is observed to overlap near the wall at y+ < 10, while for the SHS is smaller further away from the wall in physical dimensions. At y+ = 30, is 30% smaller for the SHS. A small increase of Reynolds shear stress for the SHS is observed at y+ < 10, while about 30% reduction is observed at y+ = 30. The observed variation of Reynolds stresses is associated with the relatively small roughness of the surface. If Reynolds stresses are normalized based on the corresponding friction velocity, the non-dimensional stresses show a large increase of and a small increase of over the SHS at y+ < 20. Farther away from the wall at y+ > 20, the scaling of Reynolds stresses based on the corresponding uτ results in their overlap for the smooth and SHSs. The drag reduction is mainly associated with the reduction of viscous wall-shear stress, while the variation in Reynolds shear stress at the wall is negligible. The quadrant analysis of turbulent fluctuations shows attenuation of stronger sweep motions at y+ < 15, while ejections are attenuated in the buffer layer at y+ = 20 until 30.
Shin splints: MR appearance in a preliminary study.

PubMed

Anderson, M W; Ugalde, V; Batt, M; Gacayan, J

1997-07-01

To investigate the magnetic resonance (MR) imaging appearance of activity-related lower leg pain (shin splints syndrome) and evaluate the relative involvement of bone and soft tissues. Nineteen patients with activity-related lower leg pain and tenderness on palpation along the posteromedial tibia (shin splints) underwent clinical examination and MR imaging. Five also underwent plain radiography. MR findings were compared with patient demographics, clinical findings, and plain radiographs when available. Four MR patterns were identified: normal appearance (n = 7), periosteal fluid only (n = 5), abnormal marrow signal intensity (n = 5), and stress fracture (n = 2). Increased symptom duration correlated strongly with a normal MR image (P = .002). Plain radiographs appeared normal in all five patients for whom they were available. Patients with acute shin splints have a spectrum of MR findings, which suggests this clinical entity is part of a continuum of stress response in bone. The strong association between chronic symptoms and a normal-appearing MR image implies that this modality has less utility in these patients.
Shear Stress Partitioning in Large Patches of Roughness in the Atmospheric Inertial Sublayer

NASA Technical Reports Server (NTRS)

Gillies, John A.; Nickling, William G.; King, James

2007-01-01

Drag partition measurements were made in the atmospheric inertial sublayer for six roughness configurations made up of solid elements in staggered arrays of different roughness densities. The roughness was in the form of a patch within a large open area and in the shape of an equilateral triangle with 60 m long sides. Measurements were obtained of the total shear stress (tau) acting on the surfaces, the surface shear stress on the ground between the elements (tau(sub S)) and the drag force on the elements for each roughness array. The measurements indicated that tau(sub S) quickly reduced near the leading edge of the roughness compared with tau, and a tau(sub S) minimum occurs at a normalized distance (x/h, where h is element height) of approx. -42 (downwind of the roughness leading edge is negative), then recovers to a relatively stable value. The location of the minimum appears to scale with element height and not roughness density. The force on the elements decreases exponentially with normalized downwind distance and this rate of change scales with the roughness density, with the rate of change increasing as roughness density increases. Average tau(sub S): tau values for the six roughness surfaces scale predictably as a function of roughness density and in accordance with a shear stress partitioning model. The shear stress partitioning model performed very well in predicting the amount of surface shear stress, given knowledge of the stated input parameters for these patches of roughness. As the shear stress partitioning relationship within the roughness appears to come into equilibrium faster for smaller roughness element sizes it would also appear the shear stress partitioning model can be applied with confidence for smaller patches of smaller roughness elements than those used in this experiment.
Seismic and aseismic deformations and impact on reservoir permeability: The case of EGS stimulation at The Geysers, California, USA

NASA Astrophysics Data System (ADS)

Jeanne, Pierre; Rutqvist, Jonny; Rinaldi, Antonio Pio; Dobson, Patrick F.; Walters, Mark; Hartline, Craig; Garcia, Julio

2015-11-01

In this paper, we use the Seismicity-Based Reservoir Characterization approach to study the spatiotemporal dynamics of an injection-induced microseismic cloud, monitored during the stimulation of an enhanced geothermal system, and associated with the Northwest Geysers Enhanced Geothermal System (EGS) Demonstration project (California). We identified the development of a seismically quiet domain around the injection well surrounded by a seismically active domain. Then we compare these observations with the results of 3-D Thermo-Hydro-Mechanical simulations of the EGS, which accounts for changes in permeability as a function of the effective normal stress and the plastic strain. The results of our modeling show that (1) the aseismic domain is caused by both the presence of the injected cold water and by thermal processes. These thermal processes cause a cooling-stress reduction, which prevent shear reactivation and favors fracture opening by reducing effective normal stress and locally increasing the permeability. This process is accompanied by aseismic plastic shear strain. (2) In the seismic domain, microseismicity is caused by the reactivation of the preexisting fractures, resulting from an increase in injection-induced pore pressure. Our modeling indicates that in this domain, permeability evolves according to the effective normal stress acting on the shear zones, whereas shearing of preexisting fractures may have a low impact on permeability. We attribute this lack of permeability gain to the fact that the initial permeabilities of these preexisting fractures are already high (up to 2 orders of magnitude higher than the host rock) and may already be fully dilated by past tectonic straining.
Antioxidant activity and induction of mechanisms of resistance to stresses related to the inoculation with Azospirillum brasilense.

PubMed

Fukami, Josiane; Ollero, Francisco Javier; de la Osa, Clara; Valderrama-Fernández, Rocio; Nogueira, Marco Antonio; Megías, Manuel; Hungria, Mariangela

2018-06-07

We investigated the effects of Azospirillum brasilense strains Ab-V5 and Ab-V6 in the induction of mechanisms of systemic acquired resistance (SAR) and induced system resistance (ISR) on maize (Zea mays L.) plants. Under normal growth conditions, the treatments consisted of the standard inoculation of cells at sowing, and leaf spray of cells or their metabolites at the V2.5 growth stage; under saline stress (170 mM NaCl), the treatment consisted of standard single and co-inoculation of A. brasilense and Rhizobium tropici. The main compounds in the Azospirillum metabolites were identified as indole-3-acetic acid (IAA) and salicylic acid (SA). Under normal conditions, A. brasilense cells applied at sowing or by leaf spray increased the activities of catalase (CAT), superoxide dismutase (SOD), and malondialdehyde (MDA) in leaves, and of ascorbate peroxidase (APX) in roots; however, interestingly, in general the highest activities were observed by leaf spray of metabolites. Under normal conditions, the highest levels of salicylic acid (SA) and jasmonic acid (JA) were achieved in leaves by leaf spray of metabolites, of SA in roots by leaf spray of cells, and of JA in roots by standard inoculation and leaf spray of metabolites. Under saline stress, plant protection occurred via SA and abscisic acid (ABA), but not JA. In general, inoculation resulted in further increases in SA in leaves and roots, and ABA in leaves. We hypothesize that A. brasilense confers protection to maize plants by simultaneous induction of JA and SA pathways, and, under saline stressing conditions, by SA and ABA pathways.
The effects of adrenalectomy and corticsteroid injection on the fibrinolytic activity of complex heparin compounds in the blood during immobilization

NASA Technical Reports Server (NTRS)

Kudryashov, B. A.; Lomovskaya, E. G.; Shapiro, F. B.; Lyapina, L. Y.

1980-01-01

Total non-enzymatic fibrinolytic activity in the blood of rats increased three times in response to stress caused by 30 minute immobilization, and the activity of epinephrine-heparin complex increased nine times. In adrenalectomized animals, which showed a weak response to the same stress, intraperitoneal injection of hydrocortisone 30 minutes prior to immobilization normalized the response. Obtained results indicate that adrenalectomy leads to sharp reduction of heparin complexing with thromogenic proteins and epinephrine, while substitution therapy with hydrocortisone restores anticoagulation system function.
Nonlinear dynamics applied to the study of cardiovascular effects of stress

NASA Astrophysics Data System (ADS)

Anishchenko, T. G.; Igosheva, N. B.

1998-03-01

We study cardiovascular responses to emotional stresses in humans and rats using traditional physiological parameters and methods of nonlinear dynamics. We found that emotional stress results in significant changes of chaos degree of ECG and blood pressure signals, estimated using a normalized entropy. We demonstrate that the normalized entropy is a more sensitive indicator of the stress-induced changes in cardiovascular systems compared with traditional physiological parameters Using the normalized entropy we discovered the significant individual differences in cardiovascular stress-reactivity that was impossible to obtain by traditional physiological methods.
Experimental evidence of non-Amontons behaviour at a multi-contact interface

NASA Astrophysics Data System (ADS)

Scheibert, J.; Prevost, A.; Frelat, J.; Rey, P.; Debrégeas, G.

2008-08-01

We report on normal stress field measurements at the multicontact interface between a rough elastomeric film and a smooth glass sphere under normal load, using an original MEMS-based stress-sensing device. These measurements are compared to Finite-Elements Method (FEM) calculations with boundary conditions obeying locally Amontons' rigid-plastic-like friction law with a uniform friction coefficient. In dry contact conditions, significant deviations are observed which decrease with increasing load. In lubricated conditions, the measured profile recovers almost perfectly the predicted profile. These results are interpreted as a consequence of the finite compliance of the multicontact interface, a mechanism which is not taken into account in Amontons' law.
Dependence of Intramyocardial Pressure and Coronary Flow on Ventricular Loading and Contractility: A Model Study

PubMed Central

Borsje, Petra; Arts, Theo; van De Vosse, Frans N.

2006-01-01

The phasic coronary arterial inflow during the normal cardiac cycle has been explained with simple (waterfall, intramyocardial pump) models, emphasizing the role of ventricular pressure. To explain changes in isovolumic and low afterload beats, these models were extended with the effect of three-dimensional wall stress, nonlinear characteristics of the coronary bed, and extravascular fluid exchange. With the associated increase in the number of model parameters, a detailed parameter sensitivity analysis has become difficult. Therefore we investigated the primary relations between ventricular pressure and volume, wall stress, intramyocardial pressure and coronary blood flow, with a mathematical model with a limited number of parameters. The model replicates several experimental observations: the phasic character of coronary inflow is virtually independent of maximum ventricular pressure, the amplitude of the coronary flow signal varies about proportionally with cardiac contractility, and intramyocardial pressure in the ventricular wall may exceed ventricular pressure. A parameter sensitivity analysis shows that the normalized amplitude of coronary inflow is mainly determined by contractility, reflected in ventricular pressure and, at low ventricular volumes, radial wall stress. Normalized flow amplitude is less sensitive to myocardial coronary compliance and resistance, and to the relation between active fiber stress, time, and sarcomere shortening velocity. PMID:17048105
Gene expression of regulatory enzymes of glycolysis/gluconeogenesis in regenerating rat liver.

PubMed Central

Rosa, J L; Bartrons, R; Tauler, A

1992-01-01

Levels of mRNA for glucokinase, L-pyruvate kinase, fructose-1,6-bisphosphatase and phosphoenolpyruvate carboxykinase were analysed during liver regeneration. Levels of mRNA for glycolytic enzymes (glucokinase and L-pyruvate kinase) decreased rapidly after partial hepatectomy. Glucokinase mRNA increased at 16-24 h, returning to normal values after this time. L-pyruvate kinase mRNA recovered control levels at 168 h. In contrast, phosphoenolpyruvate carboxykinase mRNA increased rapidly after liver resection and remained high during the regenerative process. However, the levels of fructose-1,6-bisphosphatase mRNA were not modified significantly. These results correlate with the reported increased rate of gluconeogenesis and changes in enzyme levels after partial hepatectomy. The effect of stress on the mRNA levels was also studied. All enzymes showed variations in their mRNA levels after the surgical stress. In general, the differences were more pronounced in regenerating liver than in sham-operated animals, being practically normalized at 24 h. Images Fig. 2. Fig. 3. PMID:1329724
Variability of Slip Behavior in Simulations of Dynamic Rupture Interaction With Stronger Fault Patches Over Long-Term Deformation Histories

NASA Astrophysics Data System (ADS)

Lapusta, N.; Liu, Y.

2007-12-01

Heterogeneity in fault properties can have significant effect on dynamic rupture propagation and aseismic slip. It is often assumed that a fixed heterogeneity would have similar effect on fault slip throughout the slip history. We investigate dynamic rupture interaction with a fault patch of higher normal stress over several earthquake cycles in a three-dimensional model. We find that the influence of the heterogeneity on dynamic events has significant variation and depends on prior slip history. We consider a planar strike-slip fault governed by rate and state friction and driven by slow tectonic loading on deeper extension of the fault. The 30 km by 12 km velocity-weakening region, which is potentially seismogenic, is surrounded by steady-state velocity-strengthening region. The normal stress is constant over the fault, except in a circular patch of 2 km in diameter located in the seismogenic region, where normal stress is higher than on the rest of the fault. Our simulations employ the methodology developed by Lapusta and Liu (AGU, 2006), which is able to resolve both dynamic and quasi-static stages of spontaneous slip accumulation in a single computational procedure. The initial shear stress is constant on the fault, except in a small area where it is higher and where the first large dynamic event initiates. For patches with 20%, 40%, 60% higher normal stress, the first event has significant dynamic interaction with the patch, creating a rupture speed decrease followed by a supershear burst and larger slip around the patch. Hence, in the first event, the patch acts as a seismic asperity. For the case of 100% higher stress, the rupture is not able to break the patch in the first event. In subsequent dynamic events, the behavior depends on the strength of heterogeneity. For the patch with 20% higher normal stress, dynamic rupture in subsequent events propagates through the patch without any noticeable perturbation in rupture speed or slip. In particular, supershear propagation and additional slip accumulation around the patch are never repeated in the simulated history of the fault, and the patch stops manifesting itself as a seismic asperity. This is due to higher shear stress that is established at the patch after the first earthquake cycle. For patches with higher normal stress, shear stress redistribution also occurs, but it is less effective. The patches with 40% and 60% higher normal stress continue to affect rupture speed and fault slip in some of subsequent events, although the effect is much diminished with respect to the first event. For example, there are no supershear bursts. The patch with 100% higher normal stress is first broken in the second large event, and it retains significant influence on rupture speed and slip throughout the fault history, occasionally resulting in supershear bursts. Additional slip complexity emerges for patches with 40% and higher normal stress contrast. Since higher normal stress corresponds to a smaller nucleation size, nucleation of some events moves from the rheological transitions (where nucleation occurs in the cases with no stronger patch and with the patch of 20% higher normal stress) to the patches of higher normal stress. The patches nucleate both large, model-spanning, events, and small events that arrest soon after exiting the patch. Hence not every event that originates at the location of a potential seismic asperity is destined to be large, as its subsequent propagation is significantly influenced by the state of stress outside the patch.
[Blood lipids and adaptation to stress as risk factors for stroke prevention].

PubMed

Anders, I; Esterbauer, E; Fink, A; Ladurner, G; Huemer, M; Wranek, U

2000-01-01

Do stroke prevention patients with increased blood-fat-protein compounds (total cholesterol, HDL- and LDL cholesterol and triglyceride) have a different method of coping than patients with normal blood fat? 1159 stroke prevention patients participated in the following stroke risk investigations at this hospital: biographical and risk factor-orientated anamnesis, a neurological status investigation, a laboratory investigation, a sonographic investigation and a psychological investigation. The differences in the coping strategies of those patients with normal and those with higher blood-fat-protein compounds were investigated. Patients with higher total cholesterol showed significantly higher values in the avoidance of stress situations (sig. 0.041) and a stronger tendency towards escapist behaviour (sig. 0.05). Patients with normal HDL cholesterol values indicated a tendency (sig. 0.07) to higher values in positive self-instruction in comparison to patients with reduced HDL cholesterol values. Those prevention patients with higher LDL values showed a tendency (sig. 0.08) to higher values in the intake of narcotic substances (nicotine, alcohol, tranquillisers, pharmaceutical agents). Patients with increased triglyceride indicated significantly higher values in coping by compensation (eating, shopping, reward behaviour, watching TV; sig. 0.037) and the intake of narcotic substances (sig. 0.044). Prevention patients with higher total cholesterol, LDL/HDL, or triglyceride values showed significantly different coping strategies in comparison to those patients with normal values. Increased avoidance and escapism behaviour and also compensation and the abuse of narcotic substances could be seen in connection with an increase in the risk of a stroke. In contrast, a constructive coping strategy such as positive self-instruction could reduce the risk of a stroke, which goes along with normal HDL cholesterol.

Impact of early life stress on the pathogenesis of mental disorders: relation to brain oxidative stress.

PubMed

Schiavone, Stefania; Colaianna, Marilena; Curtis, Logos

2015-01-01

Stress is an inevitable part of human life and it is experienced even before birth. Stress to some extent could be considered normal and even necessary for the survival and the regular psychological development during childhood or adolescence. However, exposure to prolonged stress could become harmful and strongly impact mental health increasing the risk of developing psychiatric disorders. Recent studies have attempted to clarify how the human central nervous system (CNS) reacts to early life stress, focusing mainly on neurobiological modifications. Oxidative stress, defined as a disequilibrium between the oxidant generation and the antioxidant response, has been recently described as a candidate for most of the observed modifications. In this review, we will discuss how prolonged stressful events during childhood or adolescence (such as early maternal separation, parental divorce, physical violence, sexual or psychological abuses, or exposure to war events) can lead to increased oxidative stress in the CNS and enhance the risk to develop psychiatric diseases such as anxiety, depression, drug abuse or psychosis. Defining the sources of oxidative stress following exposure to early life stress might open new beneficial insights in therapeutic approaches to these mental disorders.
Transform push, oblique subduction resistance, and intraplate stress of the Juan de Fuca plate

USGS Publications Warehouse

Wang, K.; He, J.; Davis, E.E.

1997-01-01

The Juan de Fuca plate is a small oceanic plate between the Pacific and North America plates. In the southernmost region, referred to as the Gorda deformation zone, the maximum compressive stress a, constrained by earthquake focal mechanisms is N-S. Off Oregon, and possibly off Washington, NW trending left-lateral faults cutting the Juan de Fuca plate indicate a a, in a NE-SW to E-W direction. The magnitude of differential stress increases from north to south; this is inferred from the plastic yielding and distribution of earthquakes throughout the Gorda deformation zone. To understand how tectonic forces determine the stress field of the Juan de Fuca plate, we have modeled the intraplate stress using both elastic and elastic-perfectly plastic plane-stress finite element models. We conclude that the right-lateral shear motion of the Pacific and North America plates is primarily responsible for the stress pattern of the Juan de Fuca plate. The most important roles are played by a compressional force normal to the Mendocino transform fault, a result of the northward push by the Pacific plate and a horizontal resistance operating against the northward, or margin-parallel, component of oblique subduction. Margin-parallel subduction resistance results in large N-S compression in the Gorda deformation zone because the force is integrated over the full length of the Cascadia subduction zone. The Mendocino transform fault serves as a strong buttress that is very weak in shear but capable of transmitting large strike-normal compressive stresses. Internal failure of the Gorda deformation zone potentially places limits on the magnitude of the fault-normal stresses being transmitted and correspondingly on the magnitude of strike-parallel subduction resistance. Transform faults and oblique subduction zones in other parts of the world can be expected to transmit and create stresses in the same manner. Copyright 1997 by the American Geophysical Union.
Melanoma Inhibition by Anthocyanins Is Associated with the Reduction of Oxidative Stress Biomarkers and Changes in Mitochondrial Membrane Potential.

PubMed

Diaconeasa, Zoriţa; Ayvaz, Huseyin; Ruginǎ, Dumitriţa; Leopold, Loredana; Stǎnilǎ, Andreea; Socaciu, Carmen; Tăbăran, Flaviu; Luput, Lavinia; Mada, Diana Carla; Pintea, Adela; Jefferson, Andrew

2017-12-01

Anthocyanins are water soluble pigments which have been proved to exhibit health benefits. Several studies have investigated their effects on several types of cancer, but little attention has been given to melanoma. The phytochemical content of nine different berry samples was assessed by liquid chromatography followed by electrospray ionization mass spectrometry (LC-ESI + -MS). Twenty-six anthocyanins were identified, after a previous C 18 Sep-pak clean-up procedure. Chokeberry and red grape anthocyanins rich extracts (C-ARE and RG-ARE) were selected to be tested on normal and melanoma cell lines, due to their different chemical pattern. C-ARE composition consists of cyanidin aglycone glycosylated with different sugars; while RG-ARE contains glucosylated derivatives of five different aglycones. Both C-ARE and RG-ARE anthocyanins reduced proliferation, increased oxidative stress biomarkers and diminished mitochondrial membrane potential in melanoma cells, having no negative influence on normal cells. A synergistic response may be attributed to the five different aglycones present in RG-ARE, which proved to exert greater effects on melanoma cells than the mixture of cyanidin derivatives with different sugars (C-ARE). In conclusion, C-ARE and RG-ARE anthocyanins may inhibit melanoma cell proliferation and increase the level of oxidative stress, with opposite effect on normal cells. Therefore, anthocyanins might be recommended as active ingredients for cosmetic and nutraceutical industry. Graphical Abstract ᅟ.
Computational fluid dynamics simulation of transcatheter aortic valve degeneration.

PubMed

Dwyer, Harry A; Matthews, Peter B; Azadani, Ali; Jaussaud, Nicolas; Ge, Liang; Guy, T Sloane; Tseng, Elaine E

2009-08-01

Studied under clinical trials, transcatheter aortic valves (TAV) have demonstrated good short-term feasibility and results in high-risk surgical patients with severe aortic stenosis. However, their long-term safety and durability are unknown. The objective of this study is to evaluate hemodynamic changes within TAV created by bioprosthetic leaflet degeneration. Computational fluid dynamics (CFD) simulations were performed to evaluate the hemodynamics through TAV sclerosis (35% orifice reduction) and stenosis (78% orifice reduction). A three-dimensional surface mesh of the TAV within the aortic root was generated for each simulation. Leaflets were contained within an open, cylindrical body without attachment to the sinus commissures representing the stent. A continuous surface between the annulus and TAV excluded the geometry of the native calcified leaflets and prevented paravalvular leak. Unsteady control volume analysis throughout systole was used to calculate leaflet shear stress and total force on the TAV. Sclerosis increased total force on the TAV by 63% (0.602-0.98 N). Advancement of degeneration from sclerosis to stenosis was accompanied by an 86% increase in total force (1.82 N) but only a 32% increase in peak wall shear stress on the leaflets. Of the total force exerted on the TAV, 99% was in the direction of axial flow. Shear stresses on the TAV were greatest during peak systolic flow with stress concentrations on the tips of the leaflets. In the normal TAV, the aortic root geometry and physiologic flow dominate location and magnitude of shear stress. Following leaflet degeneration, the specific geometry of the stenosis dictates the profile of axial velocity leaving the TAV and shear stress on the leaflets. A dramatic increase in peak leaflet shear stress was observed (115 Pa stenosis vs. 87 Pa sclerosis and 29 Pa normal). CFD simulations in this study provide the first of its kind data quantifying hemodynamics within stenosed TAV. Stenosis leads to significant forces of TAV during systole; however, diastolic forces predominate even with significant stenosis. Substantial changes in peak shear stress occur with TAV degeneration. As the first implanted TAV begin to stenose, the authors recommend watchful examination for device failure.
Early gut colonizers shape parasite susceptibility and microbiota composition in honey bee workers

PubMed Central

Schwarz, Ryan S.; Moran, Nancy A.; Evans, Jay D.

2016-01-01

Microbial symbionts living within animal guts are largely composed of resident bacterial species, forming communities that often provide benefits to the host. Gut microbiomes of adult honey bees (Apis mellifera) include core residents such as the betaproteobacterium Snodgrassella alvi, alongside transient parasites such as the protozoan Lotmaria passim. To test how these species affect microbiome composition and host physiology, we administered S. alvi and/or L. passim inocula to newly emerged worker bees from four genetic backgrounds (GH) and reared them in normal (within hives) or stressed (protein-deficient, asocial) conditions. Microbiota acquired by normal bees were abundant but quantitatively differed across treatments, indicating treatment-associated dysbiosis. Pretreatment with S. alvi made normal bees more susceptible to L. passim and altered developmental and detoxification gene expression. Stressed bees were more susceptible to L. passim and were depauperate in core microbiota, yet supplementation with S. alvi did not alter this susceptibility. Microbiomes were generally more variable by GH in stressed bees, which also showed opposing and comparatively reduced modulation of gene expression responses to treatments compared with normal bees. These data provide experimental support for a link between altered gut microbiota and increased parasite and pathogen prevalence, as observed from honey bee colony collapse disorder. PMID:27482088
Respective effects of oxygen and energy substrate deprivation on beta cell viability.

PubMed

Lablanche, Sandrine; Cottet-Rousselle, Cécile; Argaud, Laurent; Laporte, Camille; Lamarche, Frédéric; Richard, Marie-Jeanne; Berney, Thierry; Benhamou, Pierre-Yves; Fontaine, Eric

2015-01-01

Deficit in oxygen and energetic substrates delivery is a key factor in islet loss during islet transplantation. Permeability transition pore (PTP) is a mitochondrial channel involved in cell death. We have studied the respective effects of oxygen and energy substrate deprivation on beta cell viability as well as the involvement of oxidative stress and PTP opening. Energy substrate deprivation for 1h followed by incubation in normal conditions led to a cyclosporin A (CsA)-sensitive-PTP-opening in INS-1 cells and human islets. Such a procedure dramatically decreased INS-1 cells viability except when transient removal of energy substrates was performed in anoxia, in the presence of antioxidant N-acetylcysteine (NAC) or when CsA or metformin inhibited PTP opening. Superoxide production increased during removal of energy substrates and increased again when normal energy substrates were restored. NAC, anoxia or metformin prevented the two phases of oxidative stress while CsA prevented the second one only. Hypoxia or anoxia alone did not induce oxidative stress, PTP opening or cell death. In conclusion, energy substrate deprivation leads to an oxidative stress followed by PTP opening, triggering beta cell death. Pharmacological prevention of PTP opening during islet transplantation may be a suitable option to improve islet survival and graft success. Copyright © 2015 Elsevier B.V. All rights reserved.
Enhanced nitrogen diffusion induced by atomic attrition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ochoa, E.A.; Figueroa, C.A.; Czerwiec, T.

2006-06-19

The nitrogen diffusion in steel is enhanced by previous atomic attrition with low energy xenon ions. The noble gas bombardment generates nanoscale texture surfaces and stress in the material. The atomic attrition increases nitrogen diffusion at lower temperatures than the ones normally used in standard processes. The stress causes binding energy shifts of the Xe 3d{sub 5/2} electron core level. The heavy ion bombardment control of the texture and stress of the material surfaces may be applied to several plasma processes where diffusing species are involved.
Hyperglycemia: a bad signature on the vascular system

PubMed Central

Costantino, Sarah; Paneni, Francesco

2015-01-01

Experimental work has clearly demonstrated that hyperglycemia is able to derail molecular pathways favouring oxidative stress, inflammation and endothelial dysfunction. Consistently, pooled analyses from prospective studies provide strong evidence that glycemic markers, namely glycated haemoglobin (HbA1c), predict cardiovascular risk, with an increase of about 18% in risk for each 1% absolute increase in HbA1c concentration, regardless of classical risk factors. Although the importance of hyperglycemic burden on cardiovascular phenotype, normalization of blood glucose levels in patients with long-standing hyperglycemia does not seem to reduce macrovascular complications. These data suggest that hyperglycemia may exert long-lasting detrimental effects on the cardiovascular system. This emerging phenomenon is defined metabolic or hyperglycemic memory to indicate a long-term persistence of hyperglycemic stress, even after blood glucose normalization. Here, we discuss clinical evidence and potential molecular mechanisms implicated in metabolic memory and, hence, diabetes-related cardiovascular complications. PMID:26543827
Finite Element Simulation and Experimental Verification of Internal Stress of Quenched AISI 4140 Cylinders

NASA Astrophysics Data System (ADS)

Liu, Yu; Qin, Shengwei; Hao, Qingguo; Chen, Nailu; Zuo, Xunwei; Rong, Yonghua

2017-03-01

The study of internal stress in quenched AISI 4140 medium carbon steel is of importance in engineering. In this work, the finite element simulation (FES) was employed to predict the distribution of internal stress in quenched AISI 4140 cylinders with two sizes of diameter based on exponent-modified (Ex-Modified) normalized function. The results indicate that the FES based on Ex-Modified normalized function proposed is better consistent with X-ray diffraction measurements of the stress distribution than FES based on normalized function proposed by Abrassart, Desalos and Leblond, respectively, which is attributed that Ex-Modified normalized function better describes transformation plasticity. Effect of temperature distribution on the phase formation, the origin of residual stress distribution and effect of transformation plasticity function on the residual stress distribution were further discussed.
Effects of chronic stress and high-fat diet on metabolic and nutritional parameters in Wistar rats.

PubMed

Bruder-Nascimento, Thiago; Campos, Dijon Henrique Salomé; Alves, Carlos; Thomaz, Samuel; Cicogna, Antônio Carlos; Cordellini, Sandra

2013-11-01

The aim of this study was assess the role of chronic stress on the metabolic and nutritional profile of rats exposed to a high-fat diet. Thirty-day-old male Wistar rats (70-100 g) were distributed into four groups: normal-diet (NC), chronic stress (St), high-fat diet (HD), and chronic stress/high-fat diet (HD/St). Stress consisted at immobilization during 15 weeks, 5 times per week, 1h per day; and exposure to the high-fat diet lasted 15 weeks. Nutritional and metabolic parameters were assessed. The level of significance was 5%. The HD group had final body weight, total fat, as well as insulin and leptin increased, and they were insulin resistant. The St and HD/St had arterial hypertension and increased levels of corticosterone. Stress blocked the effects of the high-fat diet. Chronic stress prevented the appearance of obesity. Our results help to clarify the mechanisms involved in metabolic and nutritional dysfunction, and contribute to clinical cases linked to stress and high-fat diet.
Distance-from-the-wall scaling of turbulent motions in wall-bounded flows

NASA Astrophysics Data System (ADS)

Baidya, R.; Philip, J.; Hutchins, N.; Monty, J. P.; Marusic, I.

2017-02-01

An assessment of self-similarity in the inertial sublayer is presented by considering the wall-normal velocity, in addition to the streamwise velocity component. The novelty of the current work lies in the inclusion of the second velocity component, made possible by carefully conducted subminiature ×-probe experiments to minimise the errors in measuring the wall-normal velocity. We show that not all turbulent stress quantities approach the self-similar asymptotic state at an equal rate as the Reynolds number is increased, with the Reynolds shear stress approaching faster than the streamwise normal stress. These trends are explained by the contributions from attached eddies. Furthermore, the Reynolds shear stress cospectra, through its scaling with the distance from the wall, are used to assess the wall-normal limits where self-similarity applies within the wall-bounded flow. The results are found to be consistent with the recent prediction from the work of Wei et al. ["Properties of the mean momentum balance in turbulent boundary layer, pipe and channel flows," J. Fluid Mech. 522, 303-327 (2005)], Klewicki ["Reynolds number dependence, scaling, and dynamics of turbulent boundary layers," J. Fluids Eng. 132, 094001 (2010)], and others that the self-similar region starts and ends at z+˜O (√{δ+}) and O (δ+) , respectively. Below the self-similar region, empirical evidence suggests that eddies responsible for turbulent stresses begin to exhibit distance-from-the-wall scaling at a fixed z+ location; however, they are distorted by viscous forces, which remain a leading order contribution in the mean momentum balance in the region z+≲O (√{δ+}) , and thus result in a departure from self-similarity.
Gel stretch method: a new method to measure constitutive properties of cardiac muscle cells

NASA Technical Reports Server (NTRS)

Zile, M. R.; Cowles, M. K.; Buckley, J. M.; Richardson, K.; Cowles, B. A.; Baicu, C. F.; Cooper G, I. V.; Gharpuray, V.

1998-01-01

Diastolic dysfunction is an important cause of congestive heart failure; however, the basic mechanisms causing diastolic congestive heart failure are not fully understood, especially the role of the cardiac muscle cell, or cardiocyte, in this process. Before the role of the cardiocyte in this pathophysiology can be defined, methods for measuring cardiocyte constitutive properties must be developed and validated. Thus this study was designed to evaluate a new method to characterize cardiocyte constitutive properties, the gel stretch method. Cardiocytes were isolated enzymatically from normal feline hearts and embedded in a 2% agarose gel containing HEPES-Krebs buffer and laminin. This gel was cast in a shape that allowed it to be placed in a stretching device. The ends of the gel were held between a movable roller and fixed plates that acted as mandibles. Distance between the right and left mandibles was increased using a stepper motor system. The force applied to the gel was measured by a force transducer. The resultant cardiocyte strain was determined by imaging the cells with a microscope, capturing the images with a CCD camera, and measuring cardiocyte and sarcomere length changes. Cardiocyte stress was characterized with a finite-element method. These measurements of cardiocyte stress and strain were used to determine cardiocyte stiffness. Two variables affecting cardiocyte stiffness were measured, the passive elastic spring and viscous damping. The passive spring was assessed by increasing the force on the gel at 1 g/min, modeling the resultant stress vs. strain relationship as an exponential [sigma = A/k(ekepsilon - 1)]. In normal cardiocytes, A = 23.0 kN/m2 and k = 16. Viscous damping was assessed by examining the loop area between the stress vs. strain relationship during 1 g/min increases and decreases in force. Normal cardiocytes had a finite loop area = 1.39 kN/m2, indicating the presence of viscous damping. Thus the gel stretch method provided accurate measurements of cardiocyte constitutive properties. These measurements have allowed the first quantitative assessment of passive elastic spring properties and viscous damping in normal mammalian cardiocytes.
Cardiac Responses to Thermal, Physical, and Emotional Stress

PubMed Central

Taggart, Peter; Parkinson, Peter; Carruthers, Malcolm

1972-01-01

We have studied the effect of a short period of exposure to the intense heat of a sauna bath on the electrocardiogram and plasma catecholamine, free fatty acid, and triglyceride concentrations in 17 subjects with apparently normal hearts and 18 persons with coronary heart disease. Similar observations were made on 11 of the 17 normal subjects and on 7 of the persons with coronary heart disease in response to exercise. Exposure to heat was associated with an increase in plasma adrenaline with no change in noradrenaline, free fatty acid, or triglyceride concentrations. Exercise was associated with the expected increase in both plasma noradrenaline and adrenaline concentrations. A heart rate up to 180 beats/min was observed in response to both heat and exercise. Apart from the ST-T changes inherent to sinus tachycardia, ST-T segment abnormalities were frequent in response to heat in both the subjects with normal and abnormal hearts, but little change occurred in the ST-T configuration when the subjects were exercised to produce comparable heart rates. Ectopic beats, sometimes numerous and multifocal, were observed in some subjects of both groups in response to heat, but not to exercise. It seems likely that the net unbalanced adrenaline component of the increased plasma catecholamine concentrations (which is also seen in certain emotional stress situations) is predominantly responsible for ischaemic-like manifestations of the electrocardiogram in susceptible subjects. The observations provide further validation for previously reported studies that it is the increased plasma noradrenaline in response to emotional stress that is associated with the release of free fatty acids and ultimate hypertriglyceridaemia, of probable importance in the aetiology of atheroma. ImagesFIG. 1FIG. 2FIG. 3FIG. 4FIG. 5FIG. 6 PMID:4114377
Comparisons of amino acids, body constituents and antioxidative response between long-time HD and normal HD.

PubMed

Torigoe, Akira; Sato, Emiko; Mori, Takefumi; Ieiri, Norio; Takahashi, Chika; Ishida, Yoko; Hotta, Osamu; Ito, Sadayoshi

2016-10-01

Introduction Oxidative stress is one of the main mediators of progression of chronic kidney diseases (CKD). Nuclear factor E2-related factor 2 (Nrf2) is the transcription factor of antioxidant and detoxifying enzymes and related proteins which play an important role in cellular defense. Long-time hemodialysis (HD) therapy (8 hours) has been considered to be more beneficial compared to normal HD therapy (4 hours). We investigated oxidative response related to Nrf2 in peripheral blood mononuclear cells (PBMCs) of long-time HD and normal HD patients. Methods Eight adult long-time HD therapy patients (44.5 ± 3.0 years) and 10 normal HD therapy patients (68.1 ± 2.7 years) were enrolled. PBMCs were isolated and processed for expression of Nrf2 and its related genes by qRT-PCR. Plasma indoxyl sulfate, amino acids, and body constituents were measured. Findings Plasma indoxyl sulfate was significantly low after long-time HD therapy compare to that of normal HD therapy. Although, skeletal muscle mass, lean body mass, mineral and protein were significantly decreased 2 months in normal HD patients, those in long-time HD patients were significantly increased after 2 months. Almost of amino acids were significantly decreased after HD therapy in both HD therapies. Plasma amino acids were significantly low in long-time HD patients compared to normal HD patients. In PBMCs, the expression of Nrf2 was significantly decreased and hemooxygenase-1 expression was significantly increased in long-time HD compared to normal HD. Conclusion These observations indicate the beneficial effects of in long-time HD in improving oxidative stress in patients. © 2016 International Society for Hemodialysis.
Obesity-induced endoplasmic reticulum stress causes chronic inflammation in adipose tissue.

PubMed

Kawasaki, Noritaka; Asada, Rie; Saito, Atsushi; Kanemoto, Soshi; Imaizumi, Kazunori

2012-01-01

Adipose tissue plays a central role in maintaining metabolic homeostasis under normal conditions. Metabolic diseases such as obesity and type 2 diabetes are often accompanied by chronic inflammation and adipose tissue dysfunction. In this study, we observed that endoplasmic reticulum (ER) stress and the inflammatory response occurred in adipose tissue of mice fed a high-fat diet for a period of 16 weeks. After 16 weeks of feeding, ER stress markers increased and chronic inflammation occurred in adipose tissue. We found that ER stress is induced by free fatty acid (FFA)-mediated reactive oxygen species (ROS) generation and up-regulated gene expression of inflammatory cytokines in 3T3-L1 adipocytes. Oral administration to obese mice of chemical chaperons, which alleviate ER stress, improved chronic inflammation in adipose tissue, followed by the suppression of increased body weight and improved insulin signaling. These results indicate that ER stress plays important pathophysiological roles in obesity-induced adipose tissue dysfunction.
Low body temperature in long-lived Ames dwarf mice at rest and during stress.

PubMed

Hunter, W S; Croson, W B; Bartke, A; Gentry, M V; Meliska, C J

1999-09-01

Among homeothermic animals, larger species generally have lower metabolic rates and live longer than do smaller species. Because Ames dwarf mice (dwarfs) live approximately 1 year longer than their larger normal sex- and age-matched siblings (normals), we hypothesized that they would have lower body core temperature (Tco). We, therefore, measured Tco of six dwarfs and six normals during 24-h periods of ad lib feeding, 24-h food deprivation, and emotional stress induced by cage switching. With ad lib feeding, Tco of dwarfs averaged 1.6 degrees C lower than normals; during food deprivation, Tco of both dwarfs and controls was significantly lower than when food was available ad lib; and following cage switch, Tco was elevated in both groups. However, during all three experiments, Tco was significantly lower in dwarfs than in normals. These data support the hypothesis that Ames dwarf mice, which live longer than normal size controls, maintain lower Tco than normals. Because dwarfs are deficient in thyroid stimulating hormone (TSH) and growth hormone (GH), their low Tco may be a result of reduced thermogenesis due to lack of those hormones. However, whether low Tco per se is related to the increased longevity of the dwarf mice remains an interesting possibility to be investigated.
Exploratory results from a new rotary shear designed to reproduce the extreme deformation conditions of crustal earthquakes

NASA Astrophysics Data System (ADS)

Di Toro, G.; Nielsen, S. B.; Spagnuolo, E.; Smith, S.; Violay, M. E.; Niemeijer, A. R.; Di Felice, F.; Di Stefano, G.; Romeo, G.; Scarlato, P.

2011-12-01

A challenging goal in experimental rock deformation is to reproduce the extreme deformation conditions typical of coseismic slip in crustal earthquakes: large slip (up to 50 m), slip rates (0.1-10 m/s), accelerations (> 10 m/s2) and normal stress (> 50 MPa). Moreover, fault zones usually contain non-cohesive rocks (gouges) and fluids. The integration of all these deformation conditions is such a technical challenge that there is currently no apparatus in the world that can reproduce seismic slip. Yet, the determination of rock friction at seismic slip rates remains one of the main unknowns in earthquake physics, as it cannot be determined (or very approximately) by seismic wave inversion analysis. In the last thirty years, rotary shear apparatus were designed that combine large normal stresses and slip but low slip rates (high-pressure rotary shears first designed by Tullis) or low normal stresses but large slip rates and slip (rotary shears first designed by Shimamoto). Here we present the results of experiments using a newly-constructed Slow to HIgh Velocity Apparatus (SHIVA), installed at INGV in Rome, which extends the combination of normal stress, slip and slip rate achieved by previous apparatus and reproduces the conditions likely to occur during an earthquake in the shallow crust. SHIVA uses two brushless engines (max power 300 kW, max torque 930 Nm) and an air actuator (thrust 5 tons) in a rotary shear configuration (nominally infinite displacement) to slide hollow rock cylinders (30/50 mm int./ext. diameter) at slip rates ranging from 10 micron/s up to 6.5 m/s, accelerations up to 80 m/s2 and normal stresses up to 50 MPa. SHIVA can also perform experiments in which the torque on the sample (rather than the slip rate) is progressively increased until spontaneous failure occurs: this experimental capability should better reproduce natural conditions. The apparatus is equipped with a sample chamber to carry out experiments in the presence of fluids (up to 15 MPa fluid pressure), devices to determine the fluid composition during sliding, a gouge sample holder (tested up to 34 MPa in normal stress), and an environmental/vacuum chamber connected to a mass spectrometer to measure gas release during frictional sliding. In particular, we will show: 1) the extremely low friction coefficients (often approaching zero) and short (few cm is some cases) slip weakening distances measured in experiments performed at large normal stress (<40MPa) and accelerations on cohesive rocks (carbonatic marbles and gabbros); 2) the spontaneous creep episodes, lasting a few mm to a few cm in slip, that precede the large stress drops typical of earthquake instabilities, observed in torque-controlled experiments on gabbro and marbles; 3) how the presence of free fluids (H2O) delays the onset of dynamic weakening in carbonatic rocks; 4) the experimental microstructures, produced at normal stresses up to 34 MPa and slip rates of 1-3 m/s, in calcite gouges that closely resemble those found in exhumed seismic fault zones.
Salt-tolerant and -sensitive alfalfa (Medicago sativa) cultivars have large variations in defense responses to the lepidopteran insect Spodoptera litura under normal and salt stress condition

PubMed Central

Lei, Yunting; Liu, Qing; Hettenhausen, Christian; Cao, Guoyan; Tan, Qing; Zhao, Weiye; Lin, Honghui

2017-01-01

In nature, plants are often exposed to multiple stress factors at the same time. Yet, little is known about how plants modulate their physiology to counteract simultaneous abiotic and biotic stresses, such as soil salinity and insect herbivory. In this study, insect performance bioassays, phytohormone measurements, quantification of transcripts, and protein determination were employed to study the phenotypic variations of two alfalfa (Medicago sativa) cultivars in response to insect Spodoptera litura feeding under normal and salt stress condition. When being cultivated in normal soil, the salt-tolerant alfalfa cultivar Zhongmu-1 exhibited lower insect resistance than did the salt-sensitive cultivar Xinjiang Daye. Under salinity stress, the defense responses of Xinjiang Daye were repressed, whereas Zhongmu-1 did not show changes in resistance levels. It is likely that salinity influenced the resistance of Xinjiang Daye through suppressing the accumulation of jasmonic acid-isoleucine (JA-Ile), which is the bioactive hormone inducing herbivore defense responses, leading to attenuated trypsin proteinase inhibitor (TPI) activity. Furthermore, exogenous ABA supplementation suppressed the insect herbivory-induced JA/JA-Ile accumulation and levels of JAR1 (jasmonate resistant 1) and TPI, and further decreased the resistance of Xinjiang Daye, whereas Zhongmu-1 showed very little response to the increased ABA level. We propose a mechanism, in which high levels of abscisic acid induced by salt treatment may affect the expression levels of JAR1 and consequently decrease JA-Ile accumulation and thus partly suppress the defense of Xinjiang Daye against insects under salt stress. This study provides new insight into the mechanism by which alfalfa responds to concurrent abiotic and biotic stresses. PMID:28719628
Salt-tolerant and -sensitive alfalfa (Medicago sativa) cultivars have large variations in defense responses to the lepidopteran insect Spodoptera litura under normal and salt stress condition.

PubMed

Lei, Yunting; Liu, Qing; Hettenhausen, Christian; Cao, Guoyan; Tan, Qing; Zhao, Weiye; Lin, Honghui; Wu, Jianqiang

2017-01-01

In nature, plants are often exposed to multiple stress factors at the same time. Yet, little is known about how plants modulate their physiology to counteract simultaneous abiotic and biotic stresses, such as soil salinity and insect herbivory. In this study, insect performance bioassays, phytohormone measurements, quantification of transcripts, and protein determination were employed to study the phenotypic variations of two alfalfa (Medicago sativa) cultivars in response to insect Spodoptera litura feeding under normal and salt stress condition. When being cultivated in normal soil, the salt-tolerant alfalfa cultivar Zhongmu-1 exhibited lower insect resistance than did the salt-sensitive cultivar Xinjiang Daye. Under salinity stress, the defense responses of Xinjiang Daye were repressed, whereas Zhongmu-1 did not show changes in resistance levels. It is likely that salinity influenced the resistance of Xinjiang Daye through suppressing the accumulation of jasmonic acid-isoleucine (JA-Ile), which is the bioactive hormone inducing herbivore defense responses, leading to attenuated trypsin proteinase inhibitor (TPI) activity. Furthermore, exogenous ABA supplementation suppressed the insect herbivory-induced JA/JA-Ile accumulation and levels of JAR1 (jasmonate resistant 1) and TPI, and further decreased the resistance of Xinjiang Daye, whereas Zhongmu-1 showed very little response to the increased ABA level. We propose a mechanism, in which high levels of abscisic acid induced by salt treatment may affect the expression levels of JAR1 and consequently decrease JA-Ile accumulation and thus partly suppress the defense of Xinjiang Daye against insects under salt stress. This study provides new insight into the mechanism by which alfalfa responds to concurrent abiotic and biotic stresses.
Oxidative stress biomarkers and their relationship with cytokine concentrations in overweight/obese pregnant women and their neonates.

PubMed

Hernández-Trejo, María; Montoya-Estrada, Araceli; Torres-Ramos, Yessica; Espejel-Núñez, Aurora; Guzmán-Grenfell, Alberto; Morales-Hernández, Rosa; Tolentino-Dolores, Maricruz; Laresgoiti-Servitje, Estibalitz

2017-01-07

Oxidative damage present in obese/overweight mothers may lead to further oxidative stress conditions or inflammation in maternal and cord blood samples. Thirty-four pregnant women/newborn pairs were included in this study to assess the presence of oxidative stress biomarkers and their relationship with serum cytokine concentrations. Oxidative stress biomarkers and antioxidant enzymes were compared between the mother/offspring pairs. The presence of 27 cytokines was measured in maternal and cord blood samples. Analyses were initially performed between all mothers and newborns and later between normal weight and mothers with overweight and obesity, and diabetic/non-diabetic women. Significant differences were found in biomarker concentrations between mothers and newborns. Additionally, superoxide-dismutase activity was higher in pre-pregnancy overweight mothers compared to those with normal weight. Activity for this enzyme was higher in neonates born from mothers with normal pregestational weight compared with their mothers. Nitrites in overweight/obese mothers were statistically lower than in their offspring. Maternal free fatty acids, nitrites, carbonylated proteins, malondialdehyde and superoxide dismutase predicted maternal serum concentrations of IL-4, IL-13, IP-10 and MIP-1β. Arginase activity in maternal plasma was related to decreased concentrations of IL-4 and IL-1β in cord arterial blood. Increased maternal malondialdehyde plasma was associated with higher levels of IL-6 and IL-7 in the offspring. Oxidative stress biomarkers differ between mothers and offspring and can predict maternal and newborn cytokine concentrations, indicating a potential role for oxidative stress in foetal metabolic and immunologic programming. Moreover, maternal obesity and diabetes may affect maternal microenvironments, and oxidative stress related to these can have an impact on the placenta and foetal growth.

Psychological Health and Overweight and Obesity Among High Stressed Work Environments

PubMed Central

Faghri, Pouran D; Mignano, Christina; Huedo- Medina, Tania B; Cherniack, Martin

2016-01-01

Correctional employees are recognized to underreport stress and stress symptoms and are known to have a culture that discourages appearing “weak” and seeking psychiatric help. This study assesses underreporting of stress and emotions. Additionally, it evaluates the relationships between stress and emotions on health behaviors. Correctional employees (n=317) completed physical assessments to measure body mass index (BMI), and surveys to assess perceived stress, emotions, and health behavior (diet, exercise, and sleep quality). Stress and emotion survey items were evaluated for under-reporting via skewness, kurtosis, and visual assessment of histograms. Structural equation modeling evaluated relationships between stress/emotion and health behaviors. Responses to stress and negatively worded emotions were non-normally distributed whereas responses to positively-worded emotions were normally distributed. Emotion predicted diet, exercise, and sleep quality whereas stress predicted only sleep quality. As stress was a poor predictor of health behaviors and responses to stress and negatively worded emotions were non-normally distributed it may suggests correctional employees are under-reporting stress and negative emotions. PMID:27547828
Psychological Health and Overweight and Obesity Among High Stressed Work Environments.

PubMed

Faghri, Pouran D; Mignano, Christina; Huedo-Medina, Tania B; Cherniack, Martin

2015-07-01

Correctional employees are recognized to underreport stress and stress symptoms and are known to have a culture that discourages appearing "weak" and seeking psychiatric help. This study assesses underreporting of stress and emotions. Additionally, it evaluates the relationships between stress and emotions on health behaviors. Correctional employees (n=317) completed physical assessments to measure body mass index (BMI), and surveys to assess perceived stress, emotions, and health behavior (diet, exercise, and sleep quality). Stress and emotion survey items were evaluated for under-reporting via skewness, kurtosis, and visual assessment of histograms. Structural equation modeling evaluated relationships between stress/emotion and health behaviors. Responses to stress and negatively worded emotions were non-normally distributed whereas responses to positively-worded emotions were normally distributed. Emotion predicted diet, exercise, and sleep quality whereas stress predicted only sleep quality. As stress was a poor predictor of health behaviors and responses to stress and negatively worded emotions were non-normally distributed it may suggests correctional employees are under-reporting stress and negative emotions.
Transient oxidative stress and inflammation after intraperitoneal administration of multiwalled carbon nanotubes functionalized with single strand DNA in rats

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clichici, Simona, E-mail: simonaclichici@yahoo.com; Biris, Alexandru Radu; Tabaran, Flaviu

2012-03-15

Multi-walled carbon nanotubes (MWCNTs) are widely used for nanotechnology. Their impact on living organisms is, however, not entirely clarified. Oxidative stress and inflammation seem to be the key mechanisms involved in MWCNTs' cytotoxicity. Until present, pulmonary and skin models were the main tested experimental designs to assess carbon nanotubes' toxicity. The systemic administration of MWCNTs is essential, with respect for future medical applications. Our research is performed on Wistar rats and is focused on the dynamics of oxidative stress parameters in blood and liver and pro-inflammatory cytokines in liver, after single dose (270 mg l{sup −1}) ip administration of MWCNTsmore » (exterior diameter 15–25 nm, interior diameter 10–15 nm, surface 88 m{sup 2} g{sup −1}) functionalized with single strand DNA (ss-DNA). The presence of MWCNTs in blood was assessed by Raman spectroscopy, while in liver histological examination and confocal microscopy were used. It was found that ss-DNA-MWCNTs induce oxidative stress in plasma and liver, with the return of the tested parameters to normal values, 6 h after ip injection of nanotubes, with the exception of reduced glutathione in plasma. The inflammatory cytokines (TNF-α, IL-1β) had a similar pattern of evolution. We also assessed the level of ERK1/2 and the phosphorylation of p65 subunit of NF-kB in liver that had a transient increase and returned to normal at the end of the tested period. Our results demonstrate that ss-DNA-MWCNTs produce oxidative stress and inflammation, but with a transient pattern. Given the fact that antioxidants modify the profile not only for oxidative stress, but also of inflammation, the dynamics of these alterations may be of practical importance for future protective strategies. -- Highlights: ► ss-DNA-MWCNTs ip administration induce oxidative stress in plasma and liver. ► ss-DNA-MWCNTs ip administration determine liver inflammation. ► ERK1/2 and p65 phosphorylated NF-KB increase in liver after MWCNTs ip injection. ► All the alterations, except plasma GSH, return to normal within 6 days.« less
Prevention of psychological stress-induced immune suppression by aged garlic extract.

PubMed

Kyo, E; Uda, N; Ushijima, M; Kasuga, S; Itakura, Y

1999-11-01

We determined the effect of Aged Garlic Extract (AGE) on damage caused to immune function by a psychological stress using a communication box. After four days of a psychological stress, a decrease in spleen weight and spleen cells was observed in the psychological stress-exposed mice as compared normal mice (non-stress). AGE significantly prevented the decreases in spleen weight and cells. Additionally, AGE significantly prevented the reduction of hemolytic plaque-forming-cells in spleen cells and anti-SRBC antibody titer in serum caused by this psychological stress. Moreover, a reduction in NK activities was observed in the psychological stress-exposed mice as compared with normal mice (non-stress), whereas NK activities in the AGE administered mice were almost the same as normal mice (non-stress). These results indicate that psychological stress qualitatively and quantitatively impairs immune function, and that AGE is extremely useful for preventing psychologically-induced damage.
Fertility of male adult rats submitted to forced swimming stress.

PubMed

Mingoti, G Z; Pereira, R N; Monteiro, C M R

2003-05-01

We investigated whether stress interferes with fertility during adulthood. Male Wistar rats (weighing 220 g in the beginning of the experiment) were forced to swim for 3 min in water at 32 degrees C daily for 15 days. Stress was assessed by the hot-plate test after the last stressing session. To assess fertility, control and stressed males (N = 15 per group) were mated with sexually mature normal females. Males were sacrificed after copulation. Stress caused by forced swimming was demonstrated by a significant increase in the latency of the pain response in the hot-plate test (14.6 +/- 1.25 s for control males vs 26.0 +/- 1.53 s for stressed males, P = 0.0004). No changes were observed in body weight, testicular weight, seminal vesicle weight, ventral prostate weight or gross histological features of the testes of stressed males. Similarly, no changes were observed in fertility rate, measured by counting live fetuses in the uterus of normal females mated with control and stressed males; no dead or incompletely developed fetuses were observed in the uterus of either group. In contrast, there was a statistically significant decrease in spermatid production demonstrated by histometric evaluation (154.96 +/- 5.41 vs 127.02 +/- 3.95 spermatids per tubular section for control and stressed rats, respectively, P = 0.001). These data demonstrate that 15 days of forced swimming stress applied to adult male rats did not impair fertility, but significantly decreased spermatid production. This suggests that the effect of stress on fertility should not be assessed before at least the time required for one cycle of spermatogenesis.
Alteration in Memory and Electroencephalogram Waves with Sub-acute Noise Stress in Albino Rats and Safeguarded by Scoparia dulcis.

PubMed

Loganathan, Sundareswaran; Rathinasamy, Sheeladevi

2016-01-01

Noise stress has different effects on memory and novelty and the link between them with an electroencephalogram (EEG) has not yet been reported. To find the effect of sub-acute noise stress on the memory and novelty along with EEG and neurotransmitter changes. Eight-arm maze (EAM) and Y-maze to analyze the memory and novelty by novel object test. Four groups of rats were used: Control, control treated with Scoparia dulcis extract, noise exposed, and noise exposed which received Scoparia extract. The results showed no marked difference observed between control and control treated with Scoparia extract on EAM, Y-maze, novel object test, and EEG in both prefrontal and occipital region, however, noise stress exposed rats showed significant increase in the reference memory and working memory error in EAM and latency delay, triad errors in Y-maze, and prefrontal and occipital EEG frequency rate with the corresponding increase in plasma corticosterone and epinephrine, and significant reduction in the novelty test, and significant reduction in the novelty test, amplitude of prefrontal, occipital EEG, and acetylcholine. These noise stress induced changes in EAM, Y-maze, novel object test, and neurotransmitters were significantly prevented when treated with Scoparia extract and these changes may be due to the normalizing action of Scoparia extract on the brain, which altered due to noise stress. Noise stress exposure causes EEG, behavior, and neurotransmitter alteration in the frontoparietal and occipital regions mainly involved in planning and recognition memoryOnly the noise stress exposed animals showed the significant alteration in the EEG, behavior, and neurotransmittersHowever, these noise stress induced changes in EEG behavior and neurotransmitters were significantly prevented when treated with Scoparia extractThese changes may be due to the normalizing action of Scoparia dulcis (adoptogen) on the brain which altered by noise stress. Abbreviations used: EEG: Electroencephalogram, dB: Decibel, EPI: Epinephrine, ACH: Acetylcholine, EAM: Eight-arm maze.
Alteration in Memory and Electroencephalogram Waves with Sub-acute Noise Stress in Albino Rats and Safeguarded by Scoparia dulcis

PubMed Central

Loganathan, Sundareswaran; Rathinasamy, Sheeladevi

2016-01-01

Background: Noise stress has different effects on memory and novelty and the link between them with an electroencephalogram (EEG) has not yet been reported. Objective: To find the effect of sub-acute noise stress on the memory and novelty along with EEG and neurotransmitter changes. Materials and Methods: Eight-arm maze (EAM) and Y-maze to analyze the memory and novelty by novel object test. Four groups of rats were used: Control, control treated with Scoparia dulcis extract, noise exposed, and noise exposed which received Scoparia extract. Results: The results showed no marked difference observed between control and control treated with Scoparia extract on EAM, Y-maze, novel object test, and EEG in both prefrontal and occipital region, however, noise stress exposed rats showed significant increase in the reference memory and working memory error in EAM and latency delay, triad errors in Y-maze, and prefrontal and occipital EEG frequency rate with the corresponding increase in plasma corticosterone and epinephrine, and significant reduction in the novelty test, and significant reduction in the novelty test, amplitude of prefrontal, occipital EEG, and acetylcholine. Conclusion: These noise stress induced changes in EAM, Y-maze, novel object test, and neurotransmitters were significantly prevented when treated with Scoparia extract and these changes may be due to the normalizing action of Scoparia extract on the brain, which altered due to noise stress. SUMMARY Noise stress exposure causes EEG, behavior, and neurotransmitter alteration in the frontoparietal and occipital regions mainly involved in planning and recognition memoryOnly the noise stress exposed animals showed the significant alteration in the EEG, behavior, and neurotransmittersHowever, these noise stress induced changes in EEG behavior and neurotransmitters were significantly prevented when treated with Scoparia extractThese changes may be due to the normalizing action of Scoparia dulcis (adoptogen) on the brain which altered by noise stress. Abbreviations used: EEG: Electroencephalogram, dB: Decibel, EPI: Epinephrine, ACH: Acetylcholine, EAM: Eight-arm maze PMID:27041862
Impact of chronic maternal stress during early gestation on maternal-fetal stress transfer and fetal stress sensitivity in sheep.

PubMed

Dreiling, Michelle; Schiffner, Rene; Bischoff, Sabine; Rupprecht, Sven; Kroegel, Nasim; Schubert, Harald; Witte, Otto W; Schwab, Matthias; Rakers, Florian

2018-01-01

Acute stress-induced reduction of uterine blood flow (UBF) is an indirect mechanism of maternal-fetal stress transfer during late gestation. Effects of chronic psychosocial maternal stress (CMS) during early gestation, as may be experienced by many working women, on this stress signaling mechanism are unclear. We hypothesized that CMS in sheep during early gestation augments later acute stress-induced decreases of UBF, and aggravates the fetal hormonal, cardiovascular, and metabolic stress responses during later development. Six pregnant ewes underwent repeated isolation stress (CMS) between 30 and 100 days of gestation (dGA, term: 150 dGA) and seven pregnant ewes served as controls. At 110 dGA, ewes were chronically instrumented and underwent acute isolation stress. The acute stress decreased UBF by 19% in both the CMS and control groups (p < .05), but this was prolonged in CMS versus control ewes (74 vs. 30 min, p < .05). CMS increased fetal circulating baseline and stress-induced cortisol and norepinephrine concentrations indicating a hyperactive hypothalamus-pituitary-adrenal (HPA)-axis and sympathetic-adrenal-medullary system. Increased fetal norepinephrine is endogenous as maternal catecholamines do not cross the placenta. Cortisol in the control but not in the CMS fetuses was correlated with maternal cortisol blood concentrations; these findings indicate: (1) no increased maternal-fetal cortisol transfer with CMS, (2) cortisol production in CMS fetuses when the HPA-axis is normally inactive, due to early maturation of the fetal HPA-axis. CMS fetuses were better oxygenated, without shift towards acidosis compared to the controls, potentially reflecting adaptation to repeated stress. Hence, CMS enhances maternal-fetal stress transfer by prolonged reduction in UBF and increased fetal HPA responsiveness.
D1 Receptors Regulate Dendritic Morphology in Normal and Stressed Prelimbic Cortex

PubMed Central

Lin, Grant L.; Borders, Candace B.; Lundewall, Leslie J.; Wellman, Cara L.

2014-01-01

Both stress and dysfunction of prefrontal cortex are linked to psychological disorders, and structure and function of medial prefrontal cortex (mPFC) are altered by stress. Chronic restraint stress causes dendritic retraction in the prelimbic region (PL) of mPFC in rats. Dopamine release in mPFC increases during stress, and chronic administration of dopaminergic agonists results in dendritic remodeling. Thus, stress-induced alterations in dopaminergic transmission in PL may contribute to dendritic remodeling. We examined the effects of dopamine D1 receptor (D1R) blockade in PL during daily restraint stress on dendritic morphology in PL. Rats either underwent daily restraint stress (3 h/day, 10 days) or remained unstressed. In each group, rats received daily infusions of either the D1R antagonist SCH23390 or vehicle into PL prior to restraint; unstressed and stressed rats that had not undergone surgery were also examined. On the final day of restraint, rats were euthanized and brains were processed for Golgi histology. Pyramidal neurons in PL were reconstructed and dendritic morphology was quantified. Vehicle-infused stressed rats demonstrated dendritic retraction compared to unstressed rats, and D1R blockade in PL prevented this effect. Moreover, in unstressed rats, D1R blockade produced dendritic retraction. These effects were not due to attenuation of the HPA axis response to acute stress: plasma corticosterone levels in a separate group of rats that underwent acute restraint stress with or without D1R blockade were not significantly different. These findings indicate that dopaminergic transmission in mPFC during stress contributes directly to the stress-induced retraction of apical dendrites, while dopamine transmission in the absence of stress is important in maintaining normal dendritic morphology. PMID:25305546
D1 receptors regulate dendritic morphology in normal and stressed prelimbic cortex.

PubMed

Lin, Grant L; Borders, Candace B; Lundewall, Leslie J; Wellman, Cara L

2015-01-01

Both stress and dysfunction of prefrontal cortex are linked to psychological disorders, and structure and function of medial prefrontal cortex (mPFC) are altered by stress. Chronic restraint stress causes dendritic retraction in the prelimbic region (PL) of mPFC in rats. Dopamine release in mPFC increases during stress, and chronic administration of dopaminergic agonists results in dendritic remodeling. Thus, stress-induced alterations in dopaminergic transmission in PL may contribute to dendritic remodeling. We examined the effects of dopamine D1 receptor (D1R) blockade in PL during daily restraint stress on dendritic morphology in PL. Rats either underwent daily restraint stress (3h/day, 10 days) or remained unstressed. In each group, rats received daily infusions of either the D1R antagonist SCH23390 or vehicle into PL prior to restraint; unstressed and stressed rats that had not undergone surgery were also examined. On the final day of restraint, rats were euthanized and brains were processed for Golgi histology. Pyramidal neurons in PL were reconstructed and dendritic morphology was quantified. Vehicle-infused stressed rats demonstrated dendritic retraction compared to unstressed rats, and D1R blockade in PL prevented this effect. Moreover, in unstressed rats, D1R blockade produced dendritic retraction. These effects were not due to attenuation of the HPA axis response to acute stress: plasma corticosterone levels in a separate group of rats that underwent acute restraint stress with or without D1R blockade were not significantly different. These findings indicate that dopaminergic transmission in mPFC during stress contributes directly to the stress-induced retraction of apical dendrites, while dopamine transmission in the absence of stress is important in maintaining normal dendritic morphology. Copyright © 2014 Elsevier Ltd. All rights reserved.
The Modulatory Properties of Chronic Antidepressant Drugs Treatment on the Brain Chemokine - Chemokine Receptor Network: A Molecular Study in an Animal Model of Depression.

PubMed

Trojan, Ewa; Ślusarczyk, Joanna; Chamera, Katarzyna; Kotarska, Katarzyna; Głombik, Katarzyna; Kubera, Marta; Basta-Kaim, Agnieszka

2017-01-01

An increasing number of studies indicate that the chemokine system may be the third major communication system of the brain. Therefore, the role of the chemokine system in the development of brain disorders, including depression, has been recently proposed. However, little is known about the impact of the administration of various antidepressant drugs on the brain chemokine - chemokine receptor axis. In the present study, we used an animal model of depression based on the prenatal stress procedure. We determined whether chronic treatment with tianeptine, venlafaxine, or fluoxetine influenced the evoked by prenatal stress procedure changes in the mRNA and protein levels of the homeostatic chemokines, CXCL12 (SDF-1α), CX3CL1 (fractalkine) and their receptors, in the hippocampus and frontal cortex. Moreover, the impact of mentioned antidepressants on the TGF-β, a molecular pathway related to fractalkine receptor (CX3CR1), was explored. We found that prenatal stress caused anxiety and depressive-like disturbances in adult offspring rats, which were normalized by chronic antidepressant treatment. Furthermore, we showed the stress-evoked CXCL12 upregulation while CXCR4 downregulation in hippocampus and frontal cortex. CXCR7 expression was enhanced in frontal cortex but not hippocampus. Furthermore, the levels of CX3CL1 and CX3CR1 were diminished by prenatal stress in the both examined brain areas. The mentioned changes were normalized with various potency by chronic administration of tested antidepressants. All drugs in hippocampus, while tianeptine and venlafaxine in frontal cortex normalized the CXCL12 level in prenatally stressed offspring. Moreover, in hippocampus only fluoxetine enhanced CXCR4 level, while fluoxetine and tianeptine diminished CXCR7 level in frontal cortex. Additionally, the diminished by prenatal stress levels of CX3CL1 and CX3CR1 in the both examined brain areas were normalized by chronic tianeptine and partially fluoxetine administration. Tianeptine modulate also brain TGF-β signaling in the prenatal stress-induced animal model of depression. Our results provide new evidence that not only prenatal stress-induced behavioral disturbances but also changes of CXCL12 and their receptor and at less extend in CX3CL1-CX3CR1 expression may be normalized by chronic antidepressant drug treatment. In particular, the effect on the CXCL12 and their CXCR4 and CXCR7 receptors requires additional studies to elucidate the possible biological consequences.
Stress sensitivity of fault seismicity: A comparison between limited-offset oblique and major strike-slip faults

USGS Publications Warehouse

Parsons, T.; Stein, R.S.; Simpson, R.W.; Reasenberg, P.A.

1999-01-01

We present a new three-dimensional inventory of the southern San Francisco Bay area faults and use it to calculate stress applied principally by the 1989 M = 7.1 Loma Prieta earthquake and to compare fault seismicity rates before and after 1989. The major high-angle right-lateral faults exhibit a different response to the stress change than do minor oblique (right-lateral/thrust) faults. Seismicity on oblique-slip faults in the southern Santa Clara Valley thrust belt increased where the faults were unclamped. The strong dependence of seismicity change on normal stress change implies a high coefficient of static friction. In contrast, we observe that faults with significant offset (>50-100 km) behave differently; microseismicity on the Hayward fault diminished where right-lateral shear stress was reduced and where it was unclamped by the Loma Prieta earthquake. We observe a similar response on the San Andreas fault zone in southern California after the Landers earthquake sequence. Additionally, the offshore San Gregorio fault shows a seismicity rate increase where right-lateral/oblique shear stress was increased by the Loma Prieta earthquake despite also being clamped by it. These responses are consistent with either a low coefficient of static friction or high pore fluid pressures within the fault zones. We can explain the different behavior of the two styles of faults if those with large cumulative offset become impermeable through gouge buildup; coseismically pressurized pore fluids could be trapped and negate imposed normal stress changes, whereas in more limited offset faults, fluids could rapidly escape. The difference in behavior between minor and major faults may explain why frictional failure criteria that apply intermediate coefficients of static friction can be effective in describing the broad distributions of aftershocks that follow large earthquakes, since many of these events occur both inside and outside major fault zones.
Creep to inertia dominated stick-slip behavior in sliding friction modulated by tilted non-uniform loading

NASA Astrophysics Data System (ADS)

Tian, Pengyi; Tao, Dashuai; Yin, Wei; Zhang, Xiangjun; Meng, Yonggang; Tian, Yu

2016-09-01

Comprehension of stick-slip motion is very important for understanding tribological principles. The transition from creep-dominated to inertia-dominated stick-slip as the increase of sliding velocity has been described by researchers. However, the associated micro-contact behavior during this transition has not been fully disclosed yet. In this study, we investigated the stick-slip behaviors of two polymethyl methacrylate blocks actively modulated from the creep-dominated to inertia-dominated dynamics through a non-uniform loading along the interface by slightly tilting the angle of the two blocks. Increasing the tilt angle increases the critical transition velocity from creep-dominated to inertia-dominated stick-slip behaviors. Results from finite element simulation disclosed that a positive tilt angle led to a higher normal stress and a higher temperature on blocks at the opposite side of the crack initiating edge, which enhanced the creep of asperities during sliding friction. Acoustic emission (AE) during the stick-slip has also been measured, which is closely related to the different rupture modes regulated by the distribution of the ratio of shear to normal stress along the sliding interface. This study provided a more comprehensive understanding of the effect of tilted non-uniform loading on the local stress ratio, the local temperature, and the stick-slip behaviors.
Creep to inertia dominated stick-slip behavior in sliding friction modulated by tilted non-uniform loading.

PubMed

Tian, Pengyi; Tao, Dashuai; Yin, Wei; Zhang, Xiangjun; Meng, Yonggang; Tian, Yu

2016-09-19

Comprehension of stick-slip motion is very important for understanding tribological principles. The transition from creep-dominated to inertia-dominated stick-slip as the increase of sliding velocity has been described by researchers. However, the associated micro-contact behavior during this transition has not been fully disclosed yet. In this study, we investigated the stick-slip behaviors of two polymethyl methacrylate blocks actively modulated from the creep-dominated to inertia-dominated dynamics through a non-uniform loading along the interface by slightly tilting the angle of the two blocks. Increasing the tilt angle increases the critical transition velocity from creep-dominated to inertia-dominated stick-slip behaviors. Results from finite element simulation disclosed that a positive tilt angle led to a higher normal stress and a higher temperature on blocks at the opposite side of the crack initiating edge, which enhanced the creep of asperities during sliding friction. Acoustic emission (AE) during the stick-slip has also been measured, which is closely related to the different rupture modes regulated by the distribution of the ratio of shear to normal stress along the sliding interface. This study provided a more comprehensive understanding of the effect of tilted non-uniform loading on the local stress ratio, the local temperature, and the stick-slip behaviors.
Creep to inertia dominated stick-slip behavior in sliding friction modulated by tilted non-uniform loading

PubMed Central

Tian, Pengyi; Tao, Dashuai; Yin, Wei; Zhang, Xiangjun; Meng, Yonggang; Tian, Yu

2016-01-01

Comprehension of stick-slip motion is very important for understanding tribological principles. The transition from creep-dominated to inertia-dominated stick-slip as the increase of sliding velocity has been described by researchers. However, the associated micro-contact behavior during this transition has not been fully disclosed yet. In this study, we investigated the stick-slip behaviors of two polymethyl methacrylate blocks actively modulated from the creep-dominated to inertia-dominated dynamics through a non-uniform loading along the interface by slightly tilting the angle of the two blocks. Increasing the tilt angle increases the critical transition velocity from creep-dominated to inertia-dominated stick-slip behaviors. Results from finite element simulation disclosed that a positive tilt angle led to a higher normal stress and a higher temperature on blocks at the opposite side of the crack initiating edge, which enhanced the creep of asperities during sliding friction. Acoustic emission (AE) during the stick-slip has also been measured, which is closely related to the different rupture modes regulated by the distribution of the ratio of shear to normal stress along the sliding interface. This study provided a more comprehensive understanding of the effect of tilted non-uniform loading on the local stress ratio, the local temperature, and the stick-slip behaviors. PMID:27641908
A stress-induced phase transition model for semi-crystallize shape memory polymer

NASA Astrophysics Data System (ADS)

Guo, Xiaogang; Zhou, Bo; Liu, Liwu; Liu, Yanju; Leng, Jinsong

2014-03-01

The developments of constitutive models for shape memory polymer (SMP) have been motivated by its increasing applications. During cooling or heating process, the phase transition which is a continuous time-dependent process happens in semi-crystallize SMP and the various individual phases form at different temperature and in different configuration. Then, the transformation between these phases occurred and shape memory effect will emerge. In addition, stress applied on SMP is an important factor for crystal melting during phase transition. In this theory, an ideal phase transition model considering stress or pre-strain is the key to describe the behaviors of shape memory effect. So a normal distributed model was established in this research to characterize the volume fraction of each phase in SMP during phase transition. Generally, the experiment results are partly backward (in heating process) or forward (in cooling process) compared with the ideal situation considering delay effect during phase transition. So, a correction on the normal distributed model is needed. Furthermore, a nonlinear relationship between stress and phase transition temperature Tg is also taken into account for establishing an accurately normal distributed phase transition model. Finally, the constitutive model which taking the stress as an influence factor on phase transition was also established. Compared with the other expressions, this new-type model possesses less parameter and is more accurate. For the sake of verifying the rationality and accuracy of new phase transition and constitutive model, the comparisons between the simulated and experimental results were carried out.
Exercise-induced heat stress disrupts the shear-dilatory relationship.

PubMed

Ives, Stephen J; Lefferts, Wesley K; Wharton, Margret; Fehling, Patricia C; Smith, Denise L

2016-12-01

What is the central question of this study? Although heat stress is known to increase cardiovascular strain, no study, to date, had explored the potential impact of exercise-induced heat stress on vascular function. What is the main finding and its importance? We found that acute exercise tended to reduce flow-mediated dilatation (FMD), owing in part to reduced reactive hyperaemia/shear stimulus; thus, when FMD is normalized to shear no postexercise deficit exists. Exercise-induced heat stress increased reactive hyperaemia, shear rate, coupled with a sustained FMD postexercise, suggests that exercise-induced heat stress increases the amount of shear stimulus to elicit a similar response, indicating reduced vascular responsiveness, or reserve, which might increase cardiovascular susceptibility. Heat stress increases cardiovascular strain and is of particular concern in occupations, such as firefighting, in which individuals are required to perform strenuous work while wearing personal protective equipment. Sudden cardiac events are associated with strenuous activity and are the leading cause of duty-related death among firefighters, accounting for ∼50% of duty-related fatalities per year. Understanding the acute effects of exercise-induced heat stress (EIHS) on vascular endothelial function may provide insight into the mechanisms precipitating acute coronary events in firefighters. The purpose of this study, therefore, was to determine the effects of EIHS on vascular endothelial function. Using a balanced crossover design, 12 healthy men performed 100 min of moderate-intensity, intermittent exercise with and without EIHS (personal protective equipment or cooling vest, respectively). Measurements of flow-mediated dilatation (FMD), reactive hyperaemia and shear rate area under the curve (SR AUC ) were performed pre- and postexercise. During EIHS, core temperature was significantly higher (38 ± 0.1 versus 37 ± 0.1°C). Postexercise FMD tended to be suppressed in both conditions, but was not different from pre-exercise. Reactive hyperaemia was reduced after no-EIHS but increased after EIHS. Thus, normalizing FMD to the shear stimulus (FMD/SR AUC ) revealed a significant reduction in FMD after EIHS only (pre-exercise 0.15 ± 0.04 and 0.13 ± 0.02 s -1 versus postexercise, 0.13 ± 0.02 and 0.06 ± 0.02 s -1 , no-EIHS and EIHS, respectively). We conclude that moderate heat stress superimposed on moderate-intensity exercise resulted in reduced vascular endothelial function. This heat stress-induced alteration in the shear-dilatory relationship may relate to the increased risk of acute coronary events associated with activities that combine physical exertion and heat stress (i.e. firefighting). © 2016 The Authors. Experimental Physiology © 2016 The Physiological Society.
Oxidative stress and Na,K-ATPase activity differential regulation in brainstem and forebrain of Wistar Audiogenic rats may lead to increased seizure susceptibility.

PubMed

Parreira, Gabriela Machado; Resende, Maria Daniela Aparecida; Garcia, Israel José Pereira; Sartori, Daniela Bueno; Umeoka, Eduardo Henrique de Lima; Godoy, Lívea Dornela; Garcia-Cairasco, Norberto; Barbosa, Leandro Augusto; Santos, Hérica de Lima; Tilelli, Cristiane Queixa

2018-01-15

The Wistar Audiogenic Rat (WAR) is a well-characterized seizure-prone, inbred rodent strain that, when acutely stimulated with high-intensity sounds, develops brainstem-dependent tonic-clonic seizures that can evolve to limbic-like, myoclonic (forebrain) seizures when the acoustic stimuli are presented chronically (audiogenic kindling). In order to investigate possible mechanisms underlying WAR susceptibility to seizures, we evaluated Na,K-ATPase activity, Ca-ATPase activity, Mg-ATPase activity, lipid membrane composition and oxidative stress markers in whole forebrain and whole brainstem samples of naïve WAR, as compared to samples from control Wistar rats. We also evaluated the expression levels of α1 and α3 isoforms of Na,K-ATPase in forebrain samples. We observed increased Na,K-ATPase activity in forebrain samples and increased oxidative stress markers (lipid peroxidation, glutathione peroxidase and superoxide dismutase) in brainstem samples of WAR. The Ca-ATPase activity, Mg-ATPase activity, lipid membrane composition and expression levels of α1 and α3 isoforms of Na,K-ATPase were unaltered. In view of previous data showing that the membrane potentials from naïve WAR's neurons are less negative than that from neurons from Wistar rats, we suggest that Na,K-ATPase increased activity might be involved in a compensatory mechanism necessary to maintain WAR's brains normal activity. Additionally, ongoing oxidative stress in the brainstem could bring Na,K-ATPase activity back to normal levels, which may explain why WAR's present increased susceptibility to seizures triggered by high-intensity sound stimulation. Copyright © 2017 Elsevier B.V. All rights reserved.
Salt and nitric oxide synthase inhibition-induced hypertension: kidney dysfunction and brain anti-oxidant capacity.

PubMed

Oktar, Süleyman; Ilhan, Selçuk; Meydan, Sedat; Aydin, Mehmet; Yönden, Zafer; Gökçe, Ahmet

2010-01-01

The specific aim of this study was to examine the effects of salt-loading on kidney function and brain antioxidant capacity. Wistar rats were divided into four groups: Control rats were given normal drinking water and no drug treatment for 2 weeks. LNNA group: rats were given normal drinking water and the nitric oxide (NO) inhibitor NG-nitro-L-arginine (L-NNA), 3 mg/kg/day. LNNA + Salt group: rats were given drinking water containing salt 2% and 3 mg/kg L-NNA. Salt group: rats were given drinking water containing salt 2% and no drug treatment. Basal blood pressure and the levels of serum BUN, creatinine, uric acid, cortisol, electrolyte, serum antioxidant capacity, and oxidative stress were measured. NO, superoxide dismutase (SOD), and catalase (CAT) levels were measured in the hypothalamus, brainstem, and cerebellum. Salt overload increased the blood pressure of the LNNA + Salt group. Salt-loading enhanced BUN, creatinine, sodium retention. High salt produced an increase in uric acid levels and a decrease in cortisol levels in serum. Additionally, the oxidative stress index in serum increased in the LNNA + Salt group. Salt-loading enhanced brain NO levels, but not SOD and CAT activity. L-NNA increased brain SOD activity, but not CAT and NO levels. In conclusion, salt-loading causes hypertension, kidney dysfunction, and enhances oxidative stress in salt-sensitive rats.
Inhibition of hormonal and behavioral effects of stress by tryptophan in rats.

PubMed

Gul, Sumera; Saleem, Darakhshan; Haleem, Muhammad A; Haleem, Darakhshan Jabeen

2017-11-03

Stress in known to alter hormonal systems. Pharmacological doses of tryptophan, the essential amino acid precursor of serotonin, increase circulating leptin and decrease ghrelin in normal healthy adults. Because systemically injected leptin inhibits stress-induced behavioral deficits and systemically injected serotonin modulates leptin release from the adipocytes, we used tryptophan as a pharmacological tool to modulate hormonal and behavioral responses in unstressed and stressed rats. Leptin, ghrelin, serotonin, tryptophan, and behavior were studied in unstressed and stressed rats following oral administration of 0, 100, 200, and 300 mg/kg of tryptophan. Following oral administration of tryptophan at a dose of 300 mg/kg, circulating levels of serotonin and leptin increased and those of ghrelin decreased in unstressed animals. No effect occurred on 24-hours cumulative food intake and elevated plus maze performance. Exposure to 2 hours immobilization stress decreased 24 hours cumulative food intake and impaired performance in elevated plus maze monitored next day. Serum serotonin decreased, leptin increased, and no effect occurred on ghrelin. Stress effects on serotonin, leptin, food intake, and elevated plus maze performance did not occur in tryptophan-pretreated animals. Tryptophan-induced decreases of ghrelin also did not occur in stressed animals. The findings show an important role of serum serotonin, leptin, and ghrelin in responses to stress and suggest that the essential amino acid tryptophan can improve therapeutics in stress-induced hormonal and behavioral disorders.

Suppression of endoplasmic reticulum stress improves endothelium-dependent contractile responses in aorta of the spontaneously hypertensive rat

PubMed Central

Matsumoto, Takayuki; Webb, R. Clinton

2013-01-01

A contributing factor to increased peripheral resistance seen during hypertension is an increased production of endothelium-derived contractile factors (EDCFs). The main EDCFs are vasoconstrictor prostanoids, metabolites of arachidonic acid (AA) produced by Ca2+-dependent cytosolic phospholipase A2 (cPLA2) following phosphorylation (at Ser505) mediated by extracellular signal-regulated kinase (ERK1/2) and cyclooxygenase (COX) activations. Although endoplasmic reticulum (ER) stress has been shown to contribute to pathophysiological alterations in cardiovascular diseases, the relationship between ER stress and EDCF-mediated responses remains unclear. We tested the hypothesis that ER stress plays a role in EDCF-mediated responses via activation of the cPLA2/COX pathway in the aorta of the spontaneously hypertensive rat (SHR). Male SHR and Wistar-Kyoto rats (WKY) were treated with ER stress inhibitor, tauroursodeoxycholic acid or 4-phenlybutyric acid (TUDCA or PBA, respectively, 100 mg·kg−1·day−1 ip) or PBS (control, 300 μl/day ip) for 1 wk. There was a decrease in systolic blood pressure in SHR treated with TUDCA or PBA compared with control SHR (176 ± 3 or 181 ± 5, respectively vs. 200 ± 2 mmHg). In the SHR, treatment with TUDCA or PBA normalized aortic (vs. control SHR) 1) contractions to acetylcholine (ACh), AA, and tert-butyl hydroperoxide, 2) ACh-stimulated releases of prostanoids (thromboxane A2, PGF2α, and prostacyclin), 3) expression of COX-1, 4) phosphorylation of cPLA2 and ERK1/2, and 5) production of H2O2. Our findings demonstrate a novel interplay between ER stress and EDCF-mediated responses in the aorta of the SHR. Moreover, ER stress inhibition normalizes such responses by suppressing the cPLA2/COX pathway. PMID:23709602
Pulmonary blood flow and pulmonary hypertension: Is the pulmonary circulation flowophobic or flowophilic?

PubMed Central

Kulik, Thomas J.

2012-01-01

Increased pulmonary blood flow (PBF) is widely thought to provoke pulmonary vascular obstructive disease (PVO), but the impact of wall shear stress in the lung is actually poorly defined. We examined information from patients having cardiac lesions which impact the pulmonary circulation in distinct ways, as well as experimental studies, asking how altered hemodynamics impact the risk of developing PVO. Our results are as follows: (1) with atrial septal defect (ASD; increased PBF but low PAP), shear stress may be increased but there is little tendency to develop PVO; (2) with normal PBF but increased pulmonary vascular resistance (PVR; mitral valve disease) shear stress may also be increased but risk of PVO still low; (3) with high PVR and PBF (e.g., large ventricular septal defect), wall shear stress is markedly increased and the likelihood of developing PVO is much higher than with high PBF or PAP only; and (4) with ASD, experimental and clinical observations suggest that increased PBF plus another stimulus (e.g., endothelial inflammation) may be required for PVO. We conclude that modestly increased wall shear stress (e.g., ASD) infrequently provokes PVO, and likely requires other factors to be harmful. Likewise, increased PAP seldom causes PVO. Markedly increased wall shear stress may greatly increase the likelihood of PVO, but we cannot discriminate its effect from the combined effects of increased PAP and PBF. Finally, the age of onset of increased PAP may critically impact the risk of PVO. Some implications of these observations for future investigations are discussed. PMID:23130101
Aerobic exercise reduces oxidative stress and improves vascular changes of small mesenteric and coronary arteries in hypertension

PubMed Central

Roque, Fernanda R; Briones, Ana M; García-Redondo, Ana B; Galán, María; Martínez-Revelles, Sonia; Avendaño, Maria S; Cachofeiro, Victoria; Fernandes, Tiago; Vassallo, Dalton V; Oliveira, Edilamar M; Salaices, Mercedes

2013-01-01

Background and Purpose Regular physical activity is an effective non-pharmacological therapy for prevention and control of hypertension. We investigated the effects of aerobic exercise training in vascular remodelling and in the mechanical and functional alterations of coronary and small mesenteric arteries from spontaneously hypertensive rats (SHR). Experimental Approach Normotensive Wistar Kyoto (WKY), SHR and SHR trained on a treadmill for 12 weeks were used to evaluate vascular structural, mechanical and functional properties. Key Results Exercise did not affect lumen diameter, wall thickness and wall/lumen ratio but reduced vascular stiffness of coronary and mesenteric arteries from SHR. Exercise also reduced collagen deposition and normalized altered internal elastic lamina organization and expression of MMP-9 in mesenteric arteries from SHR. Exercise did not affect contractile responses of coronary arteries but improved the endothelium-dependent relaxation in SHR. In mesenteric arteries, training normalized the increased contractile responses induced by U46619 and by high concentrations of acetylcholine. In vessels from SHR, exercise normalized the effects of the NADPH oxidase inhibitor apocynin and the NOS inhibitor l-NAME in vasodilator or vasoconstrictor responses, normalized the increased O2− production and the reduced Cu/Zn superoxide dismutase expression and increased NO production. Conclusions and Implications Exercise training of SHR improves endothelial function and vascular stiffness in coronary and small mesenteric arteries. This might be related to the concomitant decrease of oxidative stress and increase of NO bioavailability. Such effects demonstrate the beneficial effects of exercise on the vascular system and could contribute to a reduction in blood pressure. PMID:22994554
Aerobic exercise reduces oxidative stress and improves vascular changes of small mesenteric and coronary arteries in hypertension.

PubMed

Roque, Fernanda R; Briones, Ana M; García-Redondo, Ana B; Galán, María; Martínez-Revelles, Sonia; Avendaño, Maria S; Cachofeiro, Victoria; Fernandes, Tiago; Vassallo, Dalton V; Oliveira, Edilamar M; Salaices, Mercedes

2013-02-01

Regular physical activity is an effective non-pharmacological therapy for prevention and control of hypertension. We investigated the effects of aerobic exercise training in vascular remodelling and in the mechanical and functional alterations of coronary and small mesenteric arteries from spontaneously hypertensive rats (SHR). Normotensive Wistar Kyoto (WKY), SHR and SHR trained on a treadmill for 12 weeks were used to evaluate vascular structural, mechanical and functional properties. Exercise did not affect lumen diameter, wall thickness and wall/lumen ratio but reduced vascular stiffness of coronary and mesenteric arteries from SHR. Exercise also reduced collagen deposition and normalized altered internal elastic lamina organization and expression of MMP-9 in mesenteric arteries from SHR. Exercise did not affect contractile responses of coronary arteries but improved the endothelium-dependent relaxation in SHR. In mesenteric arteries, training normalized the increased contractile responses induced by U46619 and by high concentrations of acetylcholine. In vessels from SHR, exercise normalized the effects of the NADPH oxidase inhibitor apocynin and the NOS inhibitor l-NAME in vasodilator or vasoconstrictor responses, normalized the increased O(2) (-) production and the reduced Cu/Zn superoxide dismutase expression and increased NO production. Exercise training of SHR improves endothelial function and vascular stiffness in coronary and small mesenteric arteries. This might be related to the concomitant decrease of oxidative stress and increase of NO bioavailability. Such effects demonstrate the beneficial effects of exercise on the vascular system and could contribute to a reduction in blood pressure. © 2012 The Authors. British Journal of Pharmacology © 2012 The British Pharmacological Society.
The antidepressant fluoxetine normalizes the nuclear glucocorticoid receptor evoked by psychosocial stress

NASA Astrophysics Data System (ADS)

Mitić, M.; Simić, I.; Djordjević, J.; Radojčić, M. B.; Adžić, M.

2011-12-01

Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis has been implicated in the pathophysiology of depression and stress disorders. Glucocorticoids, key regulators of the stress response, exert diverse effects on cellular processes in the hippocampus. Beside non-genomic pathways, glucocorticoid effects are mediated through activation of the glucocorticoid receptor (GR), a ligand activated transcriptional factor that belongs to the nuclear hormone receptor superfamily. We analysed the GR protein levels both in the cytoplasmic and nuclear compartments of the hippocampus of Wistar rats exposed to chronic psychosocial isolation stress upon chronic fluoxetine (FLU) treatment. Under chronic stress, corticosterone levels (CORT) were decreased compared to the control, and treatment with FLU did not change its level in the stressed rats. At the molecular level, FLU normalized the level of nuclear GR protein in the hippocampus of the stressed rats. Discrepancy between normalization of nuclear GR in the hippocampus and lack of normalization of HPA axis activity judged by CORT, suggests that other brain structures such as the amygdale and prefrontal cortex that also regulate HPA axis activity, seem not to be normalized by the FLU treatment used in our study.
High-frequency imaging of elastic contrast and contact area with implications for naturally observed changes in fault properties

USGS Publications Warehouse

Nagata, Kohei; Kilgore, Brian D.; Beeler, Nicholas M.; Nakatani, Masao

2014-01-01

During localized slip of a laboratory fault we simultaneously measure the contact area and the dynamic fault normal elastic stiffness. One objective is to determine conditions where stiffness may be used to infer changes in area of contact during sliding on nontransparent fault surfaces. Slip speeds between 0.01 and 10 µm/s and normal stresses between 1 and 2.5 MPa were imposed during velocity step, normal stress step, and slide-hold-slide tests. Stiffness and contact area have a linear interdependence during rate stepping tests and during the hold portion of slide-hold-slide tests. So long as linearity holds, measured fault stiffness can be used on nontransparent materials to infer changes in contact area. However, there are conditions where relations between contact area and stiffness are nonlinear and nonunique. A second objective is to make comparisons between the laboratory- and field-measured changes in fault properties. Time-dependent changes in fault zone normal stiffness made in stress relaxation tests imply postseismic wave speed changes on the order of 0.3% to 0.8% per year in the two or more years following an earthquake; these are smaller than postseismic increases seen within natural damage zones. Based on scaling of the experimental observations, natural postseismic fault normal contraction could be accommodated within a few decimeter wide fault core. Changes in the stiffness of laboratory shear zones exceed 10% per decade and might be detectable in the field postseismically.
The organization of the stress system and its dysregulation in depressive illness.

PubMed

Gold, P W

2015-02-01

Stressors are imminent or perceived challenges to homeostasis. The stress response is an innate, stereotypic, adaptive response to stressors that has evolved in the service of restoring the nonstressed homeostatic set point. It is encoded in specific neuroanatomical sites that activate a specific repertoire of cognitive, behavioral and physiologic phenomena. Adaptive responses, though essential for survival, can become dysregulated and result in disease. A clear example is autoimmune disease. I postulate that depression, like autoimmunity, represents a dysregulated adaptive response: a stress response that has gone awry. The cardinal manifestation of the normal stress response is anxiety. Cognitive programs shift from complex associative operations to rapid retrieval of unconscious emotional memories acquired during prior threatening situations. These emerge automatically to promote survival. To prevent distraction during stressful situations, the capacity to seek and experience pleasure is reduced, food intake is diminished and sexual activity and sleep are held in abeyance. Monoamines, cytokines, glutamate, GABA and other central mediators have key roles in the normal stress response. Many central loci are involved. The subgenual prefrontal cortex restrains the amygdala, the corticotropin-releasing hormone/hypothalamic-pituitary-adrenal (CRH/HPA) axis and the sympathomedullary system. The function of the subgenual prefrontal cortex is moderately diminished during normal stress to disinhibit these loci. This disinhibition promotes anxiety and physiological hyperarousal, while diminishing appetite and sleep. The dorsolateral prefrontal cortex is downregulated, diminishing cognitive regulation of anxiety. The nucleus accumbens is also downregulated, to reduce the propensity for distraction by pleasurable stimuli or the capacity to experience pleasure. Insulin resistance, inflammation and a prothrombotic state acutely emerge. These provide increased glucose for the brain and establish premonitory, proinflammatory and prothrombotic states in anticipation of either injury or hemorrhage during a threatening situation. Essential adaptive intracellular changes include increased neurogenesis, enhancement of neuroplasticity and deployment of a successful endoplasmic reticulum stress response. In melancholic depression, the activities of the central glutamate, norepinephrine and central cytokine systems are significantly and persistently increased. The subgenual prefrontal cortex is functionally impaired, and its size is reduced by as much as 40%. This leads to sustained anxiety and activations of the amygdala, CRH/HPA axis, the sympathomedullary system and their sequella, including early morning awakening and loss of appetite. The sustained activation of the amygdala, in turn, further activates stress system neuroendocrine and autonomic functions. The activity of the nucleus accumbens is further decreased and anhedonia emerges. Concomitantly, neurogenesis and neuroplasticity fall significantly. Antidepressants ameliorate many of these processes. The processes that lead to the behavioral and physiological manifestations of depressive illness produce a significant decrease in lifespan, and a doubling of the incidence of premature coronary artery disease. The incidences of premature diabetes and osteoporosis are also substantially increased. Six physiological processes that occur during stress and that are markedly increased in melancholia set into motion six different mechanisms to produce inflammation, as well as sustained insulin resistance and a prothrombotic state. Clinically, melancholic and atypical depression seem to be antithesis of one another. In melancholia, depressive systems are at their worst in the morning when arousal systems, such as the CRH/HPA axis and the noradrenergic systems, are at their maxima. In atypical depression, depressive symptoms are at their worst in the evening, when these arousal systems are at their minima. Melancholic patients experience anorexia and insomnia, whereas atypical patients experience hyperphagia and hypersomnia. Melancholia seems like an activation and persistence of the normal stress response, whereas atypical depression resembles a stress response that has been excessively inhibited. It is important that we stratify clinical studies of depressed patients to compare melancholic and atypical subtypes and establish their differential pathophysiology. Overall, it is important to note that many of the major mediators of the stress response and melancholic depression, such as the subgenual prefrontal cortex, the amygdala, the noradrenergic system and the CRH/HPA axis participate in multiple reinforcing positive feedback loops. This organization permits the establishment of the markedly exaggerated, persistent elevation of the stress response seen in melancholia. Given their pronounced interrelatedness, it may not matter where in this cascade the first abnormality arises. It will spread to the other loci and initiate each of their activations in a pernicious vicious cycle.
Laforin prevents stress-induced polyglucosan body formation and Lafora disease progression in neurons.

PubMed

Wang, Yin; Ma, Keli; Wang, Peixiang; Baba, Otto; Zhang, Helen; Parent, Jack M; Zheng, Pan; Liu, Yang; Minassian, Berge A; Liu, Yan

2013-08-01

Glycogen, the largest cytosolic macromolecule, is soluble because of intricate construction generating perfect hydrophilic-surfaced spheres. Little is known about neuronal glycogen function and metabolism, though progress is accruing through the neurodegenerative epilepsy Lafora disease (LD) proteins laforin and malin. Neurons in LD exhibit Lafora bodies (LBs), large accumulations of malconstructed insoluble glycogen (polyglucosans). We demonstrated that the laforin-malin complex reduces LBs and protects neuronal cells against endoplasmic reticulum stress-induced apoptosis. We now show that stress induces polyglucosan formation in normal neurons in culture and in the brain. This is mediated by increased glucose-6-phosphate allosterically hyperactivating muscle glycogen synthase (GS1) and is followed by activation of the glycogen digesting enzyme glycogen phosphorylase. In the absence of laforin, stress-induced polyglucosans are undigested and accumulate into massive LBs, and in laforin-deficient mice, stress drastically accelerates LB accumulation and LD. The mechanism through which laforin-malin mediates polyglucosan degradation remains unclear but involves GS1 dephosphorylation by laforin. Our work uncovers the presence of rapid polyglucosan metabolism as part of the normal physiology of neuroprotection. We propose that deficiency in the degradative phase of this metabolism, leading to LB accumulation and resultant seizure predisposition and neurodegeneration, underlies LD.
Geothermal production and reduced seismicity: Correlation and proposed mechanism

NASA Astrophysics Data System (ADS)

Cardiff, Michael; Lim, David D.; Patterson, Jeremy R.; Akerley, John; Spielman, Paul; Lopeman, Janice; Walsh, Patrick; Singh, Ankit; Foxall, William; Wang, Herbert F.; Lord, Neal E.; Thurber, Clifford H.; Fratta, Dante; Mellors, Robert J.; Davatzes, Nicholas C.; Feigl, Kurt L.

2018-01-01

At Brady Hot Springs, a geothermal field in Nevada, heated fluids have been extracted, cooled, and re-injected to produce electrical power since 1992. Analysis of daily pumping records and catalogs of microseismicity between 2010 and 2015 indicates a statistically significant correlation between days when the daily volume of production was at or above its long-term average rate and days when no seismic event was detected. Conversely, shutdowns in pumping for plant maintenance correlate with increased microseismicity. We hypothesize that the effective stress in the subsurface has adapted to the long-term normal operations (deep extraction) at the site. Under this hypothesis, extraction of fluids inhibits fault slip by increasing the effective stress on faults; in contrast, brief pumping cessations represent times when effective stress is decreased below its long-term average, increasing the likelihood of microseismicity.
Influence of ACTG4-7-PGP (Semax) on Morphofunctional State of Hepatocytes in Chronic Emotional and Painful Stress.

PubMed

Ivanov, A V; Bobyntsev, I I; Shepeleva, O M; Kryukov, A A; Andreeva, L A; Myasoedov, N F

2017-05-01

We studied the effect of intraperitoneal administration of peptide ACTG 4-7 -PGP to male Wistar rats in doses of 5, 50, 150, and 450 μg/kg on the morphofunctional state of hepatocytes in chronic emotional and painful stress. A dose-dependent stress-limiting effect of the peptide was observed: it normalized the protein synthesis function of the liver and serum activity of ALT. The anticytolytic effect of the peptide increased with increasing its dose against the background of the increase in the relative number of multinucleated and multinucleolated cells and deceleration of the recovery of serum protein concentration. The decrease of hepatocyte cytolysis against the background of more intense morphological signs of protein synthesis processes attests to activation of reparative processes in the liver parenchyma via enhanced constitutional synthesis of protein.
Typhoon-driven landsliding induces earthquakes: example of the 2009 Morakot typhoon

NASA Astrophysics Data System (ADS)

Steer, Philippe; Jeandet, Louise; Cubas, Nadaya; Marc, Odin; Meunier, Patrick; Hovius, Niels; Simoes, Martine; Cattin, Rodolphe; Shyu, J. Bruce H.; Liang, Wen-Tzong; Theunissen, Thomas; Chiang, Shou-Hao

2017-04-01

Extreme rainfall events can trigger numerous landslides in mountainous areas and a prolonged increase of river sediment load. The resulting mass transfer at the Earth surface in turn induces stress changes at depth, which could be sufficient to trigger shallow earthquakes. The 2009 Morakot typhoon represents a good case study as it delivered 3 m of precipitation in 3 days and caused some of the most intense erosion ever recorded. Analysis of seismicity time-series before and after the Morakot typhoon reveals a systematic increase of shallow (i.e. 0-15 km of depth) earthquake frequency in the vicinity of the areas displaying a high spatial density of landslides. This step-like increase in frequency lasts for at least 2-3 years and does not follow an Omori-type aftershock sequence. Rather, it is associated to a step change of the Gutenberg-Richter b-value of the earthquake catalog. Both changes occurred in mountainous areas of southwest Taiwan, where typhoon Morakot caused extensive landsliding. These spatial and temporal correlations strongly suggest a causal relationship between the Morakot-triggered landslides and the increase of earthquake frequency and their associated b-value. We propose that the progressive removal of landslide materials from the steep mountain landscape by river sediment transport acts as an approximately constant increase of the stress rate with respect to pre-typhoon conditions, and that this in turn causes a step-wise increase in earthquake frequency. To test this hypothesis, we investigate the response of a rate-and-state fault to stress changes using a 2-D continuum elasto-dynamic model. Consistent with the results of Ader et al. (2013), our preliminary results show a step-like increase of earthquake frequency in response to a step-like decrease of the fault normal stress. We also investigate the sensitivity of the amplitude and time-scale of the earthquake frequency increase to the amplitude of the normal stress change and to rheological parameters. Our study offers new insights on the potential influence of extreme erosional events on the short-time scale dynamics of faults and earthquakes.
Zero-stress states of human pulmonary arteries and veins.

PubMed

Huang, W; Yen, R T

1998-09-01

The zero-stress states of the pulmonary arteries and veins from order 3 to order 9 were determined in six normal human lungs within 15 h postmortem. The zero-stress state of each vessel was obtained by cutting the vessel transversely into a series of short rings, then cutting each ring radially, which caused the ring to spring open into a sector. Each sector was characterized by its opening angle. The mean opening angle varied between 92 and 163 degrees in the arterial tree and between 89 and 128 degrees in the venous tree. There was a tendency for opening angles to increase as the sizes of the arteries and veins increased. We computed the residual strains based on the experimental measurements and estimated the residual stresses according to Hooke's law. We found that the inner wall of a vessel at the state in which the internal pressure, external pressure, and longitudinal stress are all zero was under compression and the outer wall was in tension, and that the magnitude of compressive stress was greater than the magnitude of tensile stress.
Effect of long-term stress on H3Ser10 histone phosphorylation in neuronal nuclei of the sensorimotor cortex and midbrain reticular formation in rats with different nervous system excitability.

PubMed

Pavlova, M B; Dyuzhikova, N A; Shiryaeva, N V; Savenko, Yu N; Vaido, A I

2013-07-01

The effects of long-term mental and pain stress on H3Ser10 histone phosphorylation in neurons of the the sensorimotor corex and midbrain reticular formation were studied 24 h, 2 weeks, and 2 months after exposure of rats differing by the nervous system excitability. Rats with high excitability threshold exhibited higher basal level of H3Ser10 histone phosphorylation in the midbrain reticular formation neurons than rats with low excitability threshold. The sensorimotor cortical neurons of the two strains did not differ by this parameter. Stress led to a significant increase in the counts of immunopositive neuronal nuclei in rats with low excitability threshold: the parameter increased significantly in the sensorimotor cortex 24 h after exposure and normalized in 2 weeks after neurotization. In the midbrain reticular formation of this rat strain stress stimulated H3Ser10 histone phosphorylation after 24 h and after 2 weeks; the parameter normalized after neurotization in 2 months. Hence, genetically determined level of the nervous system excitability was essential for the basal level of neuron phosphorylation and for the time course of this process after long-term exposure to mental and pain stress, depending on the brain structure. A probable relationship between H3Ser10 histone phosphorylation process and liability to obsessive compulsive mental disorders in humans was discussed.
Anti-Apoptotic Protein Bcl-xL Expression in the Midbrain Raphe Region Is Sensitive to Stress and Glucocorticoids.

PubMed

Shishkina, Galina T; Kalinina, Tatyana S; Bulygina, Veta V; Lanshakov, Dmitry A; Babluk, Ekaterina V; Dygalo, Nikolay N

2015-01-01

Anti-apoptotic proteins are suggested to be important for the normal health of neurons and synapses as well as for resilience to stress. In order to determine whether stressful events may influence the expression of anti-apoptotic protein Bcl-xL in the midbrain and specifically in the midbrain serotonergic (5-HT) neurons involved in neurobehavioral responses to adverse stimuli, adult male rats were subjected to short-term or chronic forced swim stress. A short-term stress rapidly increased the midbrain bcl-xl mRNA levels and significantly elevated Bcl-xL immunoreactivity in the midbrain 5-HT cells. Stress-induced increase in glucocorticoid secretion was implicated in the observed effect. The levels of bcl-xl mRNA were decreased after stress when glucocorticoid elevation was inhibited by metyrapone (MET, 150 mg/kg), and this decrease was attenuated by glucocorticoid replacement with dexamethasone (DEX; 0.2 mg/kg). Both short-term stress and acute DEX administration, in parallel with Bcl-xL, caused a significant increase in tph2 mRNA levels and slightly enhanced tryptophan hydroxylase immunoreactivity in the midbrain. The increasing effect on the bcl-xl expression was specific to the short-term stress. Forced swim repeated daily for 2 weeks led to a decrease in bcl-xl mRNA in the midbrain without any effects on the Bcl-xL protein expression in the 5-HT neurons. In chronically stressed animals, an increase in tph2 gene expression was not associated with any changes in tryptophan hydroxylase protein levels. Our findings are the first to demonstrate that both short-term stress and acute glucocorticoid exposures induce Bcl-xL protein expression in the midbrain 5-HT neurons concomitantly with the activation of the 5-HT synthesis pathway in these neurons.
Evaluation of Residual Stress Measurements Before and After Post-Weld Heat Treatment in the Weld Repairs

NASA Astrophysics Data System (ADS)

Pardowska, Anna M.; Price, John W. H.; Finlayson, Trevor R.; Ibrahim, R.

2010-11-01

Welding repairs are increasingly a structural integrity concern for aging pressure vessel and piping components. It has been demonstrated that the residual stress distribution near repair welds can be drastically different from that of the original weld. Residual stresses have a significant effect on the lifetime performance of a weld, and a reduction of these stresses is normally desirable. The aim of this paper is to investigate residual stresses in various weld repair arrangements using the non-destructive neutron diffraction technique. This research is focused on characterization of the residual stress distribution: (i) in the original weld; (ii) in a shallow toe weld repair; and (iii) after conventional post-weld heat treatment. The focus of the measurements is on the values of the subsurface strain/stress variations across the weld.
Real time expression of ACC oxidase and PR-protein genes mediated by Methylobacterium spp. in tomato plants challenged with Xanthomonas campestris pv. vesicatoria.

PubMed

Yim, W J; Kim, K Y; Lee, Y W; Sundaram, S P; Lee, Y; Sa, T M

2014-07-15

Biotic stress like pathogenic infection increases ethylene biosynthesis in plants and ethylene inhibitors are known to alleviate the severity of plant disease incidence. This study aimed to reduce the bacterial spot disease incidence in tomato plants caused by Xanthomonas campestris pv. vesicatoria (XCV) by modulating stress ethylene with 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity of Methylobacterium strains. Under greenhouse condition, Methylobacterium strains inoculated and pathogen challenged tomato plants had low ethylene emission compared to pathogen infected ones. ACC accumulation and ACC oxidase (ACO) activity with ACO related gene expression increased in XCV infected tomato plants over Methylobacterium strains inoculated plants. Among the Methylobacterium spp., CBMB12 resulted lowest ACO related gene expression (1.46 Normalized Fold Expression), whereas CBMB20 had high gene expression (3.42 Normalized Fold Expression) in pathogen challenged tomato. But a significant increase in ACO gene expression (7.09 Normalized Fold Expression) was observed in the bacterial pathogen infected plants. In contrast, Methylobacterium strains enhanced β-1,3-glucanase and phenylalanine ammonia-lyase (PAL) enzyme activities in pathogen challenged tomato plants. The respective increase in β-1,3-glucanase related gene expressions due to CBMB12, CBMB15, and CBMB20 strains were 66.3, 25.5 and 10.4% higher over pathogen infected plants. Similarly, PAL gene expression was high with 0.67 and 0.30 Normalized Fold Expression, in pathogen challenged tomato plants inoculated with CBMB12 and CBMB15 strains. The results suggest that ethylene is a crucial factor in bacterial spot disease incidence and that methylobacteria with ACC deaminase activity can reduce the disease severity with ultimate pathogenesis-related protein increase in tomato. Copyright © 2014 Elsevier GmbH. All rights reserved.
A minimal titration model of the mammalian dynamical heat shock response

NASA Astrophysics Data System (ADS)

Sivéry, Aude; Courtade, Emmanuel; Thommen, Quentin

2016-12-01

Environmental stress, such as oxidative or heat stress, induces the activation of the heat shock response (HSR) and leads to an increase in the heat shock proteins (HSPs) level. These HSPs act as molecular chaperones to maintain cellular proteostasis. Controlled by highly intricate regulatory mechanisms, having stress-induced activation and feedback regulations with multiple partners, the HSR is still incompletely understood. In this context, we propose a minimal molecular model for the gene regulatory network of the HSR that reproduces quantitatively different heat shock experiments both on heat shock factor 1 (HSF1) and HSPs activities. This model, which is based on chemical kinetics laws, is kept with a low dimensionality without altering the biological interpretation of the model dynamics. This simplistic model highlights the titration of HSF1 by chaperones as the guiding line of the network. Moreover, by a steady states analysis of the network, three different temperature stress regimes appear: normal, acute, and chronic, where normal stress corresponds to pseudo thermal adaption. The protein triage that governs the fate of damaged proteins or the different stress regimes are consequences of the titration mechanism. The simplicity of the present model is of interest in order to study detailed modelling of cross regulation between the HSR and other major genetic networks like the cell cycle or the circadian clock.
Failure of Castlegate Sandstone under True Triaxial Loading

NASA Astrophysics Data System (ADS)

Ingraham, M. D.; Issen, K. A.; Holcomb, D. J.

2011-12-01

Understanding the stress conditions that cause deformation bands to form can provide insight into the geologic processes in a given location. In particular, understanding the relationship of the intermediate principal stress with respect to maximum and minimum compression when bands form, could provide useful information about the intermediate principal stress in field settings. Therefore, a series of tests were performed to investigate the effect of the intermediate principal stress on the mechanical response and failure of Castlegate sandstone under true triaxial states of stress. Constant mean stress tests were run at five different stress states ranging from: 1) intermediate principal stress equal to minimum compression to 2) intermediate principal stress equal to maximum compression. Failure occurred either through deformation band formation or apparent bulk compaction. Specimens that formed a deformation band experienced a stress drop at band formation. For a given level of intermediate principal stress, the peak stress increases with increasing mean stress. Additionally, as intermediate principal stress increases, the peak stress decreases for a given mean stress. Acoustic emissions (AE) recorded during testing were used to locate failure events in three-dimensional space within the sample. This allowed for more detailed investigation of the formation and propagation of the band(s) within the specimen. In specimens that appear to have undergone bulk compaction, AE events were randomly distributed throughout the sample. For specimens with bands, the band angles were measured as the angle between the maximum principal stress direction and the normal to the band that formed. Band angles tend to increase with increasing intermediate principal stress, and decrease with increasing mean stress. Results from the AE data shows that the band angle evolves during testing and the band that is expressed on the surface of the specimen at the conclusion of testing is not always the band that initially formed. AE results also show that low angle bands tend to be more diffuse than higher angle bands. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
Mass Transfer and Rheology of Fiber Suspensions

NASA Astrophysics Data System (ADS)

Wang, Jianghui

Rheological and mass transfer properties of non-Brownian fiber suspensions are affected by fiber characteristics, fiber interactions, and processing conditions. In this thesis we develop several simulation methods to study the dynamics of single fibers in simple shear flow, as well as the rheology and mass transfer of fiber suspensions. Isolated, rigid, neutrally-buoyant, non-Brownian, slightly curved, nonchiral fibers in simple shear flow of an incompressible Newtonian fluid at low Reynolds number can drift steadily in the gradient direction without external forces or torques. The average drift velocity and direction depend on the fiber aspect ratio, curvature and initial orientation. The drift results from the coupling of rotational and translational dynamics, and the combined effects of flipping, scooping, and spinning motions of the fiber. Irreversible fiber collisions in the suspensions cause shear-induced diffusion. The shear-induced self-diffusivity of dilute suspensions of fibers increases with increasing concentration and increasing static friction between contacts. The diffusivities in both the gradient and vorticity directions are larger for suspensions of curved fibers than for suspensions of straight fibers. For suspensions of curved fibers, significant enhancements in the diffusivity in the gradient direction are attributed to fiber drift in the gradient direction. The shear-induced self-diffusivity of concentrated suspensions of fibers increases with increasing concentration before fiber networks or flocs are formed, after which the diffusivity decreases with increasing concentration. The diffusivity increases with increasing fiber equilibrium bending angle, effective stiffness, coefficient of static friction, and rate of collisions. The specific viscosity of fiber suspensions increases with increasing fiber curvature, friction coefficient between mechanical contacts, and solids concentration. The specific viscosity increases linearly with concentration in the dilute regime, and increases with the cube of the concentration in the semi-dilute regime. Concentrated fiber suspensions are highly viscous, shear thinning, and exhibit significant yield stresses and normal stress differences. Yield stresses scale with volume concentration and fiber aspect ratio in the same way as that observed in experiments. The first normal stress difference increases linearly with shear rate. The shear-induced diffusivity increases linearly with the derivative of the particle contribution to stress for dilute suspensions with respective to concentration. This correlation between rheology and shear-induced diffusion makes it possible to predict diffusivity from easily measured rheological properties.
Remote sensing of drought and salinity stressed turfgrass

NASA Astrophysics Data System (ADS)

Ikemura, Yoshiaki

The ability to detect early signs of stress in turfgrass stands using a rapid, inexpensive, and nondestructive method would be a valuable management tool. Studies were conducted to determine if digital image analysis and spectroradiometric readings obtained from drought- and salinity-stressed turfgrasses accurately reflected the varying degrees of stress and correlated strongly with visual ratings, relative water content (RWC) and leaf osmolality, standard methods for measuring stress in plants. Greenhouse drought and salinity experiments were conducted on hybrid bluegrass [Poa arachnifera (Torn.) x pratensis (L.)] cv. Reveille and bermudagrass [Cynodon dactylon (L.)] cv. Princess 77. Increasing drought and salinity stress led to decreased RWC, increased leaf osmolality, and decreased visual ratings for both species. Percent green cover and hue values obtained from digital image analysis, and Normalized Difference Vegetation Index (NDVI), calculated from spectroradiometric readings, were moderately to highly correlated with visual ratings, RWC, and leaf osmolality. Similarly, in a field validation study conducted on hybrid bluegrass, spectral reflectance ratios were moderately to highly correlated with visual ratings. In addition, percent green cover obtained from digital image analysis was strongly correlated with most of the spectral ratios, particularly the ratio of fluorescence peaks (r = -0.88 to -0.99), modified triangular vegetation index (MTVI) (r = 0.82 to 0.98), and NDVI (r = 0.84 to 0.99), suggesting that spectral reflectance and digital image analysis are equally effective at detecting changes in color brought on by stress. The two methods differed in their ability to distinguish between drought salinity stress. Hue values obtained from digital image analysis responded differently to increasing drought stress than to increasing salinity stress. Whereas the onset of drought stress was reflected by increased hue values followed by a decrease in values as drought stress increased, there was no increase in hue values at the onset of salinity stress. Thus, changes in hue could be a key to distinguish drought and salinity stress. Both digital image analysis and spectroradiometry effectively detected drought and salinity stress and may have applications in turfgrass management as rapid and quantitative methods to determine drought and salinity stress in turf.

Investigation of the Influence of Shapes-Texture on Surface Deformation of UHMWPE as a Bearing Material in Static Normal Load and Rolling Contact

NASA Astrophysics Data System (ADS)

Lestari, W. D.; Ismail, R.; Jamari, J.; Bayuseno, A. P.

2017-05-01

Surface texture is a common method for improving wear properties of a tribo-pair of soft and hard bearing material. The reduction of wear rates on the contacting surface material is becoming important issues. In the present study, analysis of the contact pressure on the flat surface of UHMWPE (Ultra High Molecular Weight Polyethylene) under the static- and rolling motion with the surface of steel ball used the 3D finite element method (FEM) (the ABAQUS software version 6.12). Five shaped-texture models (square, circle, ellipse, triangle, and chevron) were presented on the flat surface for analysis. The normal load of 17, 30 and 50 N was deliberately set-up for static and rolling contact analysis. The contact pressure was determined to predict the wear behavior of the shaped-texture on the flat surface of UHMWPE. The results have shown that the static normal load yielded the lowest von-Mises stress distribution on the shaped-texture of the ellipse for all values applied a load, while the square shape experienced the highest stress distribution. Under rolling contact, however, the increasing load yielded the increasing von Mises stress distribution for the texture with a triangle shape. Moreover, the texture shapes for circle, ellipse, and chevron respectively, may undergo the lowest stress distribution for all load. The wear calculation provided that the circle and square shape may undergo the highest wear rates. Obviously, the surface texture of circle, ellipse, and chevron may experience the lowest wear rates and is potential for use in the surface engineering of bearing materials.
Seismic and aseismic deformations and impact on reservoir permeability: The case of EGS stimulation at The Geysers, California, USA

DOE PAGES

Jeanne, Pierre; Rutqvist, Jonny; Rinaldi, Antonio Pio; ...

2015-10-27

In this paper, we use the Seismicity-Based Reservoir Characterization approach to study the spatiotemporal dynamics of an injection-induced microseismic cloud, monitored during the stimulation of an enhanced geothermal system, and associated with the Northwest Geysers Enhanced Geothermal System (EGS) Demonstration project (California). We identified the development of a seismically quiet domain around the injection well surrounded by a seismically active domain. Then we compare these observations with the results of 3-D Thermo-Hydro-Mechanical simulations of the EGS, which accounts for changes in permeability as a function of the effective normal stress and the plastic strain. The results of our modeling showmore » that the aseismic domain is caused by both the presence of the injected cold water and by thermal processes. These thermal processes cause a cooling-stress reduction, which prevent shear reactivation and favors fracture opening by reducing effective normal stress and locally increasing the permeability. This process is accompanied by aseismic plastic shear strain. In the seismic domain, microseismicity is caused by the reactivation of the preexisting fractures, resulting from an increase in injection-induced pore pressure. Our modeling indicates that in this domain, permeability evolves according to the effective normal stress acting on the shear zones, whereas shearing of preexisting fractures may have a low impact on permeability. We attribute this lack of permeability gain to the fact that the initial permeabilities of these preexisting fractures are already high (up to 2 orders of magnitude higher than the host rock) and may already be fully dilated by past tectonic straining.« less
Seismic and aseismic deformations and impact on reservoir permeability: The case of EGS stimulation at The Geysers, California, USA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jeanne, Pierre; Rutqvist, Jonny; Rinaldi, Antonio Pio

In this paper, we use the Seismicity-Based Reservoir Characterization approach to study the spatiotemporal dynamics of an injection-induced microseismic cloud, monitored during the stimulation of an enhanced geothermal system, and associated with the Northwest Geysers Enhanced Geothermal System (EGS) Demonstration project (California). We identified the development of a seismically quiet domain around the injection well surrounded by a seismically active domain. Then we compare these observations with the results of 3-D Thermo-Hydro-Mechanical simulations of the EGS, which accounts for changes in permeability as a function of the effective normal stress and the plastic strain. The results of our modeling showmore » that the aseismic domain is caused by both the presence of the injected cold water and by thermal processes. These thermal processes cause a cooling-stress reduction, which prevent shear reactivation and favors fracture opening by reducing effective normal stress and locally increasing the permeability. This process is accompanied by aseismic plastic shear strain. In the seismic domain, microseismicity is caused by the reactivation of the preexisting fractures, resulting from an increase in injection-induced pore pressure. Our modeling indicates that in this domain, permeability evolves according to the effective normal stress acting on the shear zones, whereas shearing of preexisting fractures may have a low impact on permeability. We attribute this lack of permeability gain to the fact that the initial permeabilities of these preexisting fractures are already high (up to 2 orders of magnitude higher than the host rock) and may already be fully dilated by past tectonic straining.« less
Effects of exercise on biomechanical properties of the superficial digital flexor tendon in foals.

PubMed

Cherdchutham, W; Meershoek, L S; van Weeren, P R; Barneveld, A

2001-12-01

To determine the effects of exercise on biomechanical properties of the superficial digital flexor tendon (SDFT) in foals. 43 Dutch Warmblood foals. From 1 week until 5 months of age, 14 foals were housed in stalls and not exercised, 14 foals were housed in stalls and exercised daily, and 15 foals were maintained at pasture. Eight foals in each group were euthanatized at 5 months, and remaining foals were housed together in a stall and paddock until euthanatized at 11 months. After euthanasia, SDFT were isolated and fit in a material testing system. Mean cross-sectional area (CSA) was measured and traction forces recorded. Normalized force at rupture (force(rup)), normalized force at 4% strain, strain at rupture, stress at 4% strain (stress(4%stain)), and stress at rupture were compared among and within groups. At 5 months, mean CSA and normalized force(rup) were significantly greater and stress(4%strain) significantly less in the pastured group, compared with the other groups. At 11 months, CSA and normalized force(rup) were not significantly different among groups, because force(rup) increased significantly from 5 to 11 months in the nonexercised group and decreased significantly in the pastured group. Exercise significantly affected the biomechanical properties of the SDFT in foals. Evenly distributed moderate- and low-intensity exercise at a young age may be more effective for development of strong, flexible tendons in horses than single episodes of high-intensity exercise superimposed on stall rest. This effect may impact later susceptibility to SDFT injury.
The Interaction of Motor Performance and Psycho-Physiological Effects During Acceleration to Hypergravity

NASA Astrophysics Data System (ADS)

Guardiera, Simon; Schneider, Stefan

2008-06-01

Several studies reported that human motor performance is impaired during acceleration to hypergravity. While physiological explanations (e.g. vestibular activity) are widely discussed, psycho-physiological reasons (e.g. stress) are less considered. The present study therefore evaluates the interaction between psycho-physiological effects and motor performance in hypergravity. Eleven subjects performed a manual tracking task. Additionally, stress hormone concentration, EEG and subjective mood were evaluated. All measurements were performed in normal (+1Gz), and in (or directly after) three times gravitational acceleration (+3Gz). Motor performance decreased, while all determined stress hormone concentrations increased in +3Gz. EEG analysis revealed an increase of brain cortical activity in right frontal lobe in +3Gz. Subjective mood decreased due to +3Gz. Our data confirm, that motor performance is decreased in hypergravity, whereas an increase in psychophysiological stress markers could be obtained. We conclude that psycho-physiological changes have to be regarded as a possible explanation for deficits in motor performance in hypergravity.
Protective effects of azelaic acid against high-fat diet-induced oxidative stress in liver, kidney and heart of C57BL/6J mice.

PubMed

Muthulakshmi, Shanmugam; Saravanan, Ramalingam

2013-05-01

Excess fat intake induces hyperinsulinaemia, increases nutrient uptake and lipid accumulation, amplifies ROS generation, establishes oxidative stress and morphological changes leading to tissue injury in the liver, kidney and heart of high-fat diet (HFD)-fed mice. The effect of azelaic acid (AzA), a C9 α,ω-dicarboxylic acid, against HFD-induced oxidative stress was investigated by assaying the activities and levels of antioxidants and oxidative stress markers in the liver, kidney and heart of C57BL/6J mice. Mice were segregated into two groups, one fed standard diet (NC) and the other fed high-fat diet (HFD) for 15 weeks. HFD-fed mice were subjected to intragastric administration of AzA (80 mg/kg BW)/RSG (10 mg/kg BW) during 11-15 weeks. Glucose, insulin, triglycerides, hepatic and nephritic markers were analysed in the plasma and the activity of enzymatic, non-enzymatic antioxidants and lipid peroxidation markers were examined in the plasma/erythrocytes, liver, kidney and heart of normal and experimental mice. We inferred significant decrease in enzymatic and non-enzymatic antioxidants along with significant increase in glucose, insulin, hepatic and nephritic markers, triglycerides and lipid peroxidation markers in HFD-fed mice. Administration of AzA could positively restore the levels of plasma glucose, insulin, triglycerides, hepatic and nephritic markers to near normal. AzA increased the levels of enzymatic and nonenzymatic antioxidants with significant reduction in the levels of lipid peroxidation markers. Histopathological examination of liver, kidney and heart substantiated these results. Hence, we put forward that AzA could counteract the potential injurious effects of HFD-induced oxidative stress in C57BL/6J mice.
Response of Velocity Anisotropy of Shale Under Isotropic and Anisotropic Stress Fields

NASA Astrophysics Data System (ADS)

Li, Xiaying; Lei, Xinglin; Li, Qi

2018-03-01

We investigated the responses of P-wave velocity and associated anisotropy in terms of Thomsen's parameters to isotropic and anisotropic stress fields on Longmaxi shales cored along different directions. An array of piezoelectric ceramic transducers allows us to measure P-wave velocities along numerous different propagation directions. Anisotropic parameters, including the P-wave velocity α along a symmetry axis, Thomsen's parameters ɛ and δ, and the orientation of the symmetry axis, could then be extracted by fitting Thomsen's weak anisotropy model to the experimental data. The results indicate that Longmaxi shale displays weakly intrinsic velocity anisotropy with Thomsen's parameters ɛ and δ being approximately 0.05 and 0.15, respectively. The isotropic stress field has only a slight effect on velocity and associated anisotropy in terms of Thomsen's parameters. In contrast, both the magnitude and orientation of the anisotropic stress field with respect to the shale fabric are important in controlling the evolution of velocity and associated anisotropy in a changing stress field. For shale with bedding-parallel loading, velocity anisotropy is enhanced because velocities with smaller angles relative to the maximum stress increase significantly during the entire loading process, whereas those with larger angles increase slightly before the yield stress and afterwards decrease with the increasing differential stress. For shale with bedding-normal loading, anisotropy reversal is observed, and the anisotropy is progressively modified by the applied differential stress. Before reaching the yield stress, velocities with smaller angles relative to the maximum stress increase more significantly and even exceed the level of those with larger angles. After reaching the yield stress, velocities with larger angles decrease more significantly. Microstructural features such as the closure and generation of microcracks can explain the modification of the velocity anisotropy due to the applied stress anisotropy.
Parenting stress and affective symptoms in parents of autistic children.

PubMed

Gong, Yun; Du, YaSong; Li, HuiLin; Zhang, XiYan; An, Yu; Wu, Bai-Lin

2015-10-01

We examined parenting stress and mental health status in parents of autistic children and assessed factors associated with such stress. Participants were parents of 188 autistic children diagnosed with DSM-IV criteria and parents of 144 normally developing children. Parents of autistic children reported higher levels of stress, depression, and anxiety than parents of normally developing children. Mothers of autistic children had a higher risk of depression and anxiety than that did parents of normally developing children. Mothers compared to fathers of autistic children were more vulnerable to depression. Age, behavior problems of autistic children, and mothers' anxiety were significantly associated with parenting stress.
Tea polyphenol epigallocatechin 3-gallate impedes the anti-apoptotic effects of low-grade repetitive stress through inhibition of Akt and NFkappaB survival pathways.

PubMed

Sen, Prosenjit; Chakraborty, Prabir Kumar; Raha, Sanghamitra

2006-01-09

V79 Chinese Hamster lung fibroblasts were subjected to repetitive low-grade stress through multiple exposures to 30 microM H2O2 in culture for 4 weeks. Akt/protein kinase B became phosphorylated at serine473 and threonine308 during this period of repetitive stress. Concurrent exposure of the cells to LY294002 (5 microM), a phosphoinositide-3 kinase inhibitor or 4.5 microM epigallocatechin 3-gallate (EGCG), a tea polyphenol almost completely blocked Akt activation by repetitive stress. Phosphorylation of I kappa B kinase (IKK) and transcriptional activity driven by nuclear factor kappa B (NFkappaB) were significantly enhanced by repetitive oxidative stress. These increases were largely abolished by simultaneous exposure to EGCG. The repetitively stressed cells demonstrated a significant resistance to apoptosis by subsequent acute stress in the form of ultraviolet radiation at 5 J/m2 or H2O2 (7.5 mM). The resistance to apoptosis conferred by repetitive stress was drastically reduced (>80%) by constant exposure to EGCG during the stress period while the presence of LY294002 or the NFkappaB inhibitor SN50 brought about a relatively moderate effect (about 50-65%). Our data indicate that activation of Akt and NFkappaB pro-survival pathways by repetitive low-grade stress results in a strong inhibition of the normal apoptotic response after subsequent acute stress. The tea polyphenol EGCG impedes the activation of both Akt and NFkappaB by repetitive stress and as a result preserves the normal apoptotic response during subsequent acute stress.
High Temperature Uniaxial Compression and Stress-Relaxation Behavior of India-Specific RAFM Steel

NASA Astrophysics Data System (ADS)

Shah, Naimish S.; Sunil, Saurav; Sarkar, Apu

2018-07-01

India-specific reduced activity ferritic martensitic steel (INRAFM), a modified 9Cr-1Mo grade, has been developed by India as its own structural material for fabrication of the Indian Test Blanket Module (TBM) to be installed in the International Thermonuclear Energy Reactor (ITER). The extensive study on mechanical and physical properties of this material has been currently going on for appraisal of this material before being put to use in the ITER. High temperature compression, stress-relaxation, and strain-rate change behavior of the INRAFM steel have been investigated. The optical microscopic and scanning electron microscopic characterizations were carried out to observe the microstructural changes that occur during uniaxial compressive deformation test. Comparable true plastic stress values at 300 °C and 500 °C and a high drop in true plastic stress at 600 °C were observed during the compression test. Stress-relaxation behaviors were investigated at 500 °C, 550 °C, and 600 °C at a strain rate of 10-3 s-1. The creep properties of the steel at different temperatures were predicted from the stress-relaxation test. The Norton's stress exponent ( n) was found to decrease with the increasing temperature. Using Bird-Mukherjee-Dorn relationship, the temperature-compensated normalized strain rate vs stress was plotted. The stress exponent ( n) value of 10.05 was obtained from the normalized plot. The increasing nature of the strain rate sensitivity ( m) with the test temperature was found from strain-rate change test. The low plastic stability with m 0.06 was observed at 600 °C. The activation volume ( V *) values were obtained in the range of 100 to 300 b3. By comparing the experimental values with the literature, the rate-controlling mechanisms at the thermally activated region of high temperature were found to be the nonconservative movement of jogged screw dislocations and thermal breaking of attractive junctions.
High Temperature Uniaxial Compression and Stress-Relaxation Behavior of India-Specific RAFM Steel

NASA Astrophysics Data System (ADS)

Shah, Naimish S.; Sunil, Saurav; Sarkar, Apu

2018-05-01

India-specific reduced activity ferritic martensitic steel (INRAFM), a modified 9Cr-1Mo grade, has been developed by India as its own structural material for fabrication of the Indian Test Blanket Module (TBM) to be installed in the International Thermonuclear Energy Reactor (ITER). The extensive study on mechanical and physical properties of this material has been currently going on for appraisal of this material before being put to use in the ITER. High temperature compression, stress-relaxation, and strain-rate change behavior of the INRAFM steel have been investigated. The optical microscopic and scanning electron microscopic characterizations were carried out to observe the microstructural changes that occur during uniaxial compressive deformation test. Comparable true plastic stress values at 300 °C and 500 °C and a high drop in true plastic stress at 600 °C were observed during the compression test. Stress-relaxation behaviors were investigated at 500 °C, 550 °C, and 600 °C at a strain rate of 10-3 s-1. The creep properties of the steel at different temperatures were predicted from the stress-relaxation test. The Norton's stress exponent (n) was found to decrease with the increasing temperature. Using Bird-Mukherjee-Dorn relationship, the temperature-compensated normalized strain rate vs stress was plotted. The stress exponent (n) value of 10.05 was obtained from the normalized plot. The increasing nature of the strain rate sensitivity (m) with the test temperature was found from strain-rate change test. The low plastic stability with m 0.06 was observed at 600 °C. The activation volume (V *) values were obtained in the range of 100 to 300 b3. By comparing the experimental values with the literature, the rate-controlling mechanisms at the thermally activated region of high temperature were found to be the nonconservative movement of jogged screw dislocations and thermal breaking of attractive junctions.
Social Stress Increases Cortisol and Hampers Attention in Adolescents with Excess Weight

PubMed Central

Verdejo-Garcia, Antonio; Moreno-Padilla, Maria; Garcia-Rios, M. Carmen; Lopez-Torrecillas, Francisca; Delgado-Rico, Elena; Schmidt-Rio-Valle, Jacqueline; Fernandez-Serrano, Maria J.

2015-01-01

Objective To experimentally examine if adolescents with excess weight are more sensitive to social stress and hence more sensitive to harmful effects of stress in cognition. Design and Methods We conducted an experimental study in 84 adolescents aged 12 to 18 years old classified in two groups based on age adjusted Body Mass Index percentile: Normal weight (n=42) and Excess weight (n=42). Both groups were exposed to social stress as induced by the virtual reality version of the Trier Social Stress Task --participants were requested to give a public speech about positive and negative aspects of their personalities in front of a virtual audience. The outcome measures were salivary cortisol levels and performance in cognitive tests before and after the social stressor. Cognitive tests included the CANTAB Rapid Visual Processing Test (measuring attention response latency and discriminability) and the Iowa Gambling Task (measuring decision-making). Results Adolescents with excess weight compared to healthy weight controls displayed increased cortisol response and less improvement of attentional performance after the social stressor. Decision-making performance decreased after the social stressor in both groups. Conclusion Adolescents who are overweight or obese have increased sensitivity to social stress, which detrimentally impacts attentional skills. PMID:25898204
Chronic Heat Stress Impairs the Quality of Breast-Muscle Meat in Broilers by Affecting Redox Status and Energy-Substance Metabolism.

PubMed

Lu, Zhuang; He, Xiaofang; Ma, Bingbing; Zhang, Lin; Li, Jiaolong; Jiang, Yun; Zhou, Guanghong; Gao, Feng

2017-12-27

We investigated the molecular mechanisms by which chronic heat stress impairs the breast-meat quality of broilers. Broilers were assigned to three groups: the normal control (NC) group, heat-stress (HS) group, and pair-fed (PF) group. After 7 days of heat exposure (32 °C), the high temperature had caused oxidative stress; elevated the activity of citrate synthase (CS), the mRNA expression of M-CPT1, and the phosphorylation level of AMPKα; and reduced the mRNA expression of avUCP. After 14 days of heat exposure, the heat stress had increased the lightness and drip loss and decreased the pH and shear force of the breast meat. Additionally, the heat exposure had increased the mRNA expressions of FAS, ACC, and PDK4; the content of lipids; and the activities of lactic dehydrogenase and pyruvate kinase, and it had decreased the mRNA expression of M-CPT1 and the activity of CS. In conclusion, chronic heat stress impairs meat quality by causing mitochondria to malfunction and affecting energy-substance aerobic metabolism, resulting in increased glycolysis and intramuscular fat deposition.
An Analytical Model for Two-Order Asperity Degradation of Rock Joints Under Constant Normal Stiffness Conditions

NASA Astrophysics Data System (ADS)

Li, Yingchun; Wu, Wei; Li, Bo

2018-05-01

Jointed rock masses during underground excavation are commonly located under the constant normal stiffness (CNS) condition. This paper presents an analytical formulation to predict the shear behaviour of rough rock joints under the CNS condition. The dilatancy and deterioration of two-order asperities are quantified by considering the variation of normal stress. We separately consider the dilation angles of waviness and unevenness, which decrease to zero as the normal stress approaches the transitional stress. The sinusoidal function naturally yields the decay of dilation angle as a function of relative normal stress. We assume that the magnitude of transitional stress is proportionate to the square root of asperity geometric area. The comparison between the analytical prediction and experimental data shows the reliability of the analytical model. All the parameters involved in the analytical model possess explicit physical meanings and are measurable from laboratory tests. The proposed model is potentially practicable for assessing the stability of underground structures at various field scales.
The effect of inertia, viscous damping, temperature and normal stress on chaotic behaviour of the rate and state friction model

NASA Astrophysics Data System (ADS)

Sinha, Nitish; Singh, Arun K.; Singh, Trilok N.

2018-04-01

A fundamental understanding of frictional sliding at rock surfaces is of practical importance for nucleation and propagation of earthquakes and rock slope stability. We investigate numerically the effect of different physical parameters such as inertia, viscous damping, temperature and normal stress on the chaotic behaviour of the two state variables rate and state friction (2sRSF) model. In general, a slight variation in any of inertia, viscous damping, temperature and effective normal stress reduces the chaotic behaviour of the sliding system. However, the present study has shown the appearance of chaos for the specific values of normal stress before it disappears again as the normal stress varies further. It is also observed that magnitude of system stiffness at which chaotic motion occurs, is less than the corresponding value of critical stiffness determined by using the linear stability analysis. These results explain the practical observation why chaotic nucleation of an earthquake is a rare phenomenon as reported in literature.
PtrA/NINV, an alkaline/neutral invertase gene of Poncirus trifoliata, confers enhanced tolerance to multiple abiotic stresses by modulating ROS levels and maintaining photosynthetic efficiency.

PubMed

Dahro, Bachar; Wang, Fei; Peng, Ting; Liu, Ji-Hong

2016-03-29

Alkaline/neutral invertase (A/N-INV), an enzyme that hydrolyzes sucrose irreversibly into glucose and fructose, is essential for normal plant growth,development, and stress tolerance. However, the physiological and/or molecular mechanism underpinning the role of A/N-INV in abiotic stress tolerance is poorly understood. In this report, an A/N-INV gene (PtrA/NINV) was isolated from Poncirus trifoliata, a cold-hardy relative of citrus, and functionally characterized. PtrA/NINV expression levels were induced by cold, salt, dehydration, sucrose, and ABA, but decreased by glucose. PtrA/NINV was found to localize in both chloroplasts and mitochondria. Overexpression of PtrA/NINV conferred enhanced tolerance to multiple stresses, including cold, high salinity, and drought, as supported by lower levels of reactive oxygen species (ROS), reduced oxidative damages, decreased water loss rate, and increased photosynthesis efficiency, relative to wild-type (WT). The transgenic plants exhibited higher A/N-INV activity and greater reducing sugar content under normal and stress conditions. PtrA/NINV is an important gene implicated in sucrose decomposition, and plays a positive role in abiotic stress tolerance by promoting osmotic adjustment, ROS detoxification and photosynthesis efficiency. Thus, PtrA/NINV has great potential to be used in transgenic breeding for improvement of stress tolerance.
A simple model for the prediction of the discrete stiffness states of a homogeneous electrostatically tunable multi-layer beam

NASA Astrophysics Data System (ADS)

Bergamini, A.; Christen, R.; Motavalli, M.

2007-04-01

The adaptive modification of the mechanical properties of structures has been described as a key to a number of new or enhanced technologies, ranging from prosthetics to aerospace applications. Previous work reported the electrostatic tuning of the bending stiffness of simple sandwich structures by modifying the shear stress transfer parameters at the interface between faces and the compliant core of the sandwich. For this purpose, the choice of a sandwich structure presented considerable experimental advantages, such as the ability to obtain a large increase in stiffness by activating just two interfaces between the faces and the core of the beam. The hypothesis the development of structures with tunable bending stiffness is based on, is that by applying a normal stress at the interface between two layers of a multi-layer structure it is possible to transfer shear stresses from one layer to the other by means of adhesion or friction forces. The normal stresses needed to generate adhesion or friction can be generated by an electrostatic field across a dielectric layer interposed between the layers of a structure. The shear stress in the cross section of the structure (e.g. a beam) subjected to bending forces is transferred in full, if sufficiently large normal stresses and an adequate friction coefficient at the interface are given. Considering beams with a homogeneous cross-section, in which all layers are made of the same material and have the same width, eliminates the need to consider parameters such as the shear modulus of the material and the shear stiffness of the core, thus making the modelling work easier and the results more readily understood. The goal of the present work is to describe a numerical model of a homogeneous multi-layer beam. The model is validated against analytical solutions for the extreme cases of interaction at the interface (no friction and a high level of friction allowing for full shear stress transfer). The obtained model is used to better understand the processes taking place at the interfaces between layers, demonstrate the existence of discrete stiffness states and to find guidance for the selection of suitable dielectric layers for the generation of the electrostatic normal stresses needed for the shear stress transfer at the interface.
Tidal triggering of low frequency earthquakes near Parkfield, California: Implications for fault mechanics within the brittle-ductile transition

USGS Publications Warehouse

Thomas, A.M.; Burgmann, R.; Shelly, David R.; Beeler, Nicholas M.; Rudolph, M.L.

2012-01-01

Studies of nonvolcanic tremor (NVT) have established the significant impact of small stress perturbations on NVT generation. Here we analyze the influence of the solid earth and ocean tides on a catalog of ∼550,000 low frequency earthquakes (LFEs) distributed along a 150 km section of the San Andreas Fault centered at Parkfield. LFE families are identified in the NVT data on the basis of waveform similarity and are thought to represent small, effectively co-located earthquakes occurring on brittle asperities on an otherwise aseismic fault at depths of 16 to 30 km. We calculate the sensitivity of each of these 88 LFE families to the tidally induced right-lateral shear stress (RLSS), fault-normal stress (FNS), and their time derivatives and use the hypocentral locations of each family to map the spatial variability of this sensitivity. LFE occurrence is most strongly modulated by fluctuations in shear stress, with the majority of families demonstrating a correlation with RLSS at the 99% confidence level or above. Producing the observed LFE rate modulation in response to shear stress perturbations requires low effective stress in the LFE source region. There are substantial lateral and vertical variations in tidal shear stress sensitivity, which we interpret to reflect spatial variation in source region properties, such as friction and pore fluid pressure. Additionally, we find that highly episodic, shallow LFE families are generally less correlated with tidal stresses than their deeper, continuously active counterparts. The majority of families have weaker or insignificant correlation with positive (tensile) FNS. Two groups of families demonstrate a stronger correlation with fault-normal tension to the north and with compression to the south of Parkfield. The families that correlate with fault-normal clamping coincide with a releasing right bend in the surface fault trace and the LFE locations, suggesting that the San Andreas remains localized and contiguous down to near the base of the crust. The deep families that have high sensitivity to both shear and tensile normal stress perturbations may be indicative of an increase in effective fault contact area with depth. Synthesizing our observations with those of other LFE-hosting localities will help to develop a comprehensive understanding of transient fault slip below the “seismogenic zone” by providing constraints on parameters in physical models of slow slip and LFEs.
Obesity-Associated Oxidative Stress: Strategies Finalized to Improve Redox State

PubMed Central

Savini, Isabella; Catani, Maria Valeria; Evangelista, Daniela; Gasperi, Valeria; Avigliano, Luciana

2013-01-01

Obesity represents a major risk factor for a plethora of severe diseases, including diabetes, cardiovascular disease, non-alcoholic fatty liver disease, and cancer. It is often accompanied by an increased risk of mortality and, in the case of non-fatal health problems, the quality of life is impaired because of associated conditions, including sleep apnea, respiratory problems, osteoarthritis, and infertility. Recent evidence suggests that oxidative stress may be the mechanistic link between obesity and related complications. In obese patients, antioxidant defenses are lower than normal weight counterparts and their levels inversely correlate with central adiposity; obesity is also characterized by enhanced levels of reactive oxygen or nitrogen species. Inadequacy of antioxidant defenses probably relies on different factors: obese individuals may have a lower intake of antioxidant- and phytochemical-rich foods, such as fruits, vegetables, and legumes; otherwise, consumption of antioxidant nutrients is normal, but obese individuals may have an increased utilization of these molecules, likewise to that reported in diabetic patients and smokers. Also inadequate physical activity may account for a decreased antioxidant state. In this review, we describe current concepts in the meaning of obesity as a state of chronic oxidative stress and the potential interventions to improve redox balance. PMID:23698776
Fault trends on the seaward slope of the Aleutian Trench: Implications for a laterally changing stress field tied to a westward increase in oblique convergence

USGS Publications Warehouse

Mortera-Gutierrez, C. A.; Scholl, D. W.; Carlson, R.L.

2003-01-01

Normal faults along the seaward trench slope (STS) commonly strike parallel to the trench in response to bending of the oceanic plate into the subduction zone. This is not the circumstance for the Aleutian Trench, where the direction of convergence gradually changes westward, from normal to transform motion. GLORIA side-scan sonar images document that the Aleutian STS is dominated by faults striking oblique to the trench, west of 179??E and east of 172??W. These images also show a pattern of east-west trending seafloor faults that are aligned parallel to the spreading fabric defined by magnetic anomalies. The stress-strain field along the STS is divided into two domains west and east, respectively, of 179??E. Over the western domain, STS faults and nodal planes of earthquakes are oriented oblique (9??-46??) to the trench axis and (69??-90??) to the magnetic fabric. West of 179??E, STS fault strikes change by 36?? from the E-W trend of STS where the trench-parallel slip gets larger than its orthogonal component of convergence. This rotation indicates that horizontal stresses along the western domain of the STS are deflected by the increasing obliquity in convergence. An analytical model supports the idea that strikes of STS faults result from a superposition of stresses associated with the dextral shear couple of the oblique convergence and stresses caused by plate bending. For the eastern domain, most nodal planes of earthquakes strike parallel to the outer rise, indicating bending as the prevailing mechanism causing normal faulting. East of 172??W, STS faults strike parallel to the magnetic fabric but oblique (10??-26??) to the axis of the trench. On the basis of a Coulomb failure criterion the trench-oblique strikes probably result from reactivation of crustal faults generated by spreading. Copyright 2003 by the American Geophysical Union.

Selective effects of citalopram in a mouse model of stress-induced anhedonia with a control for chronic stress.

PubMed

Strekalova, Tatyana; Gorenkova, Natalia; Schunk, Edward; Dolgov, Oleg; Bartsch, Dusan

2006-05-01

A stress-induced decrease in sucrose preference in rodents is regarded as an analog of anhedonia, a key symptom of depression. We investigated the effects of citalopram, administrated via drinking water (15 mg/kg/day), in a mouse model of stress-induced anhedonia. In this model, chronic stress induces anhedonia in a subset of C57BL/6N mice, while the remaining animals do not show a hedonic deficit or other depressive-like behaviors, although they are exposed to the same stressors as the anhedonic mice. Pre-stress and post-stress treatment with citalopram counteracted the development and maintenance of anhedonia and rescued normal floating in the forced swim test, demonstrating an antidepressant-like action. During the post-stress treatment, citalopram selectively increased sucrose preference and intake on the fourth week of treatment in anhedonic mice without affecting non-anhedonic animals. Citalopram also decreased elevated water consumption in the anhedonic group. Citalopram, administered 1 week before and during a 4-week stress procedure, decreased the percentage of anhedonic mice and reduced the increase of water intake in stressed mice. This study suggests that our chronic stress paradigm can serve as a model of anhedonia, in which antidepressant treatment is selectively effective in animals with a hedonic deficit.
Dietary choline supplementation to dams during pregnancy and lactation mitigates the effects of in utero stress exposure on adult anxiety-related behaviors.

PubMed

Schulz, Kalynn M; Pearson, Jennifer N; Gasparrini, Mary E; Brooks, Kayla F; Drake-Frazier, Chakeer; Zajkowski, Megan E; Kreisler, Alison D; Adams, Catherine E; Leonard, Sherry; Stevens, Karen E

2014-07-15

Brain cholinergic dysfunction is associated with neuropsychiatric illnesses such as depression, anxiety, and schizophrenia. Maternal stress exposure is associated with these same illnesses in adult offspring, yet the relationship between prenatal stress and brain cholinergic function is largely unexplored. Thus, using a rodent model, the current study implemented an intervention aimed at buffering the potential effects of prenatal stress on the developing brain cholinergic system. Specifically, control and stressed dams were fed choline-supplemented or control chow during pregnancy and lactation, and the anxiety-related behaviors of adult offspring were assessed in the open field, elevated zero maze and social interaction tests. In the open field test, choline supplementation significantly increased center investigation in both stressed and nonstressed female offspring, suggesting that choline-supplementation decreases female anxiety-related behavior irrespective of prenatal stress exposure. In the elevated zero maze, prenatal stress increased anxiety-related behaviors of female offspring fed a control diet (normal choline levels). However, prenatal stress failed to increase anxiety-related behaviors in female offspring receiving supplemental choline during gestation and lactation, suggesting that dietary choline supplementation ameliorated the effects of prenatal stress on anxiety-related behaviors. For male rats, neither prenatal stress nor diet impacted anxiety-related behaviors in the open field or elevated zero maze. In contrast, perinatal choline supplementation mitigated prenatal stress-induced social behavioral deficits in males, whereas neither prenatal stress nor choline supplementation influenced female social behaviors. Taken together, these data suggest that perinatal choline supplementation ameliorates the sex-specific effects of prenatal stress. Published by Elsevier B.V.
Dietary choline supplementation to dams during pregnancy and lactation mitigates the effects of in utero stress exposure on adult anxiety-related behaviors

PubMed Central

Schulz, Kalynn M.; Pearson, Jennifer N.; Gasparrini, Mary E.; Brooks, Kayla F.; Drake-Frazier, Chakeer; Zajkowski, Megan E.; Kreisler, Alison D.; Adams, Catherine E.; Leonard, Sherry; Stevens, Karen E.

2014-01-01

Brain cholinergic dysfunction is associated with neuropsychiatric illnesses such as depression, anxiety, and schizophrenia. Maternal stress exposure is associated with these same illnesses in adult offspring, yet the relationship between prenatal stress and brain cholinergic function is largely unexplored. Thus, using a rodent model, the current study implemented an intervention aimed at buffering the potential effects of prenatal stress on the developing brain cholinergic system. Specifically, control and stressed dams were fed choline-supplemented or control chow during pregnancy and lactation, and the anxiety-related behaviors of adult offspring were assessed in the open field, elevated zero maze and social interaction tests. In the open field test, choline supplementation significantly increased center investigation in both stressed and nonstressed female offspring, suggesting that choline-supplementation decreases female anxiety-related behavior irrespective of prenatal stress exposure. In the elevated zero maze, prenatal stress increased anxiety-related behaviors of female offspring fed a control diet (normal choline levels). However, prenatal stress failed to increase anxiety-related behaviors in female offspring receiving supplemental choline during gestation and lactation, suggesting that dietary choline supplementation ameliorated the effects of prenatal stress on anxiety-related behaviors. For male rats, neither prenatal stress nor diet impacted anxiety-related behaviors in the open field or elevated zero maze. In contrast, perinatal choline supplementation mitigated prenatal stress-induced social behavioral deficits in males, whereas neither prenatal stress nor choline supplementation influenced female social behaviors. Taken together, these data suggest that perinatal choline supplementation ameliorates the sex-specific effects of prenatal stress. PMID:24675162
Redox balance signalling in occupational stress: modification by nutraceutical intervention.

PubMed

Marotta, F; Naito, Y; Padrini, F; Xuewei, X; Jain, S; Soresi, V; Zhou, L; Catanzaro, R; Zhong, K; Polimeni, A; Chui, D H

2011-01-01

There is increasing evidence that psychosocial stress can be viewed as a system-wide derangement of cellular homeostasis, with heightened oxidative stress and triggered proinflammatory mechanisms. The aim of this study is twofold: a) to replicate findings that psychological stress increases oxidative damage and b) to determine whether a fermented papaya preparation known to exert significant protective antioxidant properties could buffer such increases in nuclear DNA damage while also inducing epigenetic protective mechanisms. Twenty-eight sedentary men and women (age range: 28-52), who reported living a stressful lifestyle but with an overall positive attitude, were recruited for this study. Chronic diseases as well as severe burnout and use of drugs for anxiety constituted exclusion criteria. Subjects were supplemented for 1 month with 9 g/day (4.5 g twice a day) of a certified fermented papaya preparation. All subjects were given a stress and sleep quality questionnaire together with a diet and life style assessment. Blood was collected at 2 and 4 week, erythrocyte and leukocyte were separated to assess redox balance and heme oxygenase-1 (HO-1) gene expression while bilirubin oxidized metabolites (BOMs) were tested in the urine. Stressed individuals showed a significant abnormality of redox status with increased MDA of erythrocyte and increased level of 8-0HdG in leukocyte and BOMs excretion (p<0.05). Nutraceutical supplementation brought about a normalization of such values already at the 2 week observation (p<0.05) together with a significant upregulation of HO-1 (p<0.01). Taken together, the results of this study confirm that stressful occupational life per se, without any overt psychiatric illness, may be associated to increased oxidative stress. Supplementation with functional food affecting redox regulation may be part of the therapeutic armamentarium to be considered in this clinical setting.
Rock-avalanche Deposits Record Quantitative Information On Internal Deformation During Runout

NASA Astrophysics Data System (ADS)

McSaveney, M. J.; Zhang, M.

2016-12-01

The rock avalanche deposit at Wenjiagou Creek, China, shows grain-size changes with distance from source and with depth below the surface. To see what quantitative information on internal deformation might be able to be inferred from such information, we conducted a series of laboratory tests using a conventional ring-shear apparatus (Torshear Model 27-WF2202) at GNS Science, Lower Hutt, NZ. Lacking ready access to the limestone of the Wenjiagou Creek deposit, we used locally sourced 0.5-2 mm sand sieved from the greywacke-derived gravel bed of the Hutt River. To keep within the reliable operating limits of the apparatus, we conducted 38 dry tests using the combinations of normal stress, shear rate and shear displacement listed in Table 1. Size distributions were determined over the range 0.1 - 2000 µm using a laser sizer. Results showed that the number of grain breakages increased systematically with increasing normal stress and shear displacement, while shear rate had no significant influence. We concluded that if calibrated using appropriate materials, we would be able to quantify amounts of internal shear deformation in a rock avalanche by analysis of grain-size variations in the deposit. Table 1 Ring-shear test program Normal stress (kPa) Shear rate (mm/min) Shear displacement (mm) 200 100 74.2 37.1 0 100 200 500 1000 3000 400 100 74.2 37.1 0 100 200 500 1000 600 100 74.2 0 100 200 500 1000
The cellular immunity and oxidative stress markers in early pregnancy loss.

PubMed

Daglar, Korkut; Biberoglu, Ebru; Kirbas, Ayse; Dirican, Aylin Onder; Genc, Metin; Avci, Aslihan; Biberoglu, Kutay

2016-01-01

We investigated whether changes in cellular immunity and oxidative stress in pregnancy have any association with spontaneous miscarriage. Circulating adenosine deaminase (ADA) activity as a marker of cellular immunity and malondialdehyde (MDA) and catalase (CAT), glutathione peroxidase (GPx) as markers of T lymphocyte activation and parameters of oxidative stress and antioxidant defense were compared between 40 women with early pregnancy loss and another 40 women with ungoing healthy pregnancy. Women with miscarriage had higher serum ADA and GPx levels when compared with women with normal pregnancy (p = 0.034 and p < 0.001, respectively). Although serum MDA level was slightly higher in women with miscarriage, the difference was not significant (p = 0.083). CAT levels were alike in both groups. We have demonstrated an increased cellular immunity and perhaps a compensated oxidative stress related to increased antioxidant activation in women with early spontaneous pregnancy loss.
Stress-induced hyperlocomotion as a confounding factor in anxiety and depression models in mice.

PubMed

Strekalova, T; Spanagel, R; Dolgov, O; Bartsch, D

2005-05-01

Chronic stress is broadly used to model anxiety and depression. However, in chronic stress models, anxiety- and depression-like behaviors might be masked by unspecific effects of stress. We tested whether chronic stress in mice can induce unspecific changes in locomotion, and whether these changes interfere with the measurement of anxiety and forced-swimming behaviors. Also, we studied these latter behaviors in relation to the duration of stress, the lighting conditions during testing, and after the injection of diazepam. We employed a 4-week chronic stress paradigm, adopted from a model of stress-induced anhedonia and a 1-week subchronic stress, both consisting of rat exposure, restraint stress and tail suspension. Chronically stressed mice, tested under bright and moderate illumination, exhibited 'anxiolytic-like' behavior along with prolonged swimming and hyperactivity. These behaviors were not detectable under weak illumination or after the injection of diazepam (0.25 mg/kg). Instead, normal locomotion, increased anxiety and inhibited swimming were revealed under these conditions. Thus, chronic stress can induce hyperlocomotion in mice, which is triggered by acute stressors such as light, and interferes with the evaluation of anxiety and forced swimming. One week of stress did not change locomotion and forced swimming, and increased anxiety irrespective of illumination applied during testing. Our data can possibly explain previously reported contradictions in the behavioral testing of mice with chronic stress models of anxiety and depression.
Investigation of high-speed free shear flows using improved pressure-strain correlated Reynolds stress turbulence model

NASA Technical Reports Server (NTRS)

Tiwari, S. N.; Lakshmanan, B.

1993-01-01

A high-speed shear layer is studied using compressibility corrected Reynolds stress turbulence model which employs newly developed model for pressure-strain correlation. MacCormack explicit prediction-corrector method is used for solving the governing equations and the turbulence transport equations. The stiffness arising due to source terms in the turbulence equations is handled by a semi-implicit numerical technique. Results obtained using the new model show a sharper reduction in growth rate with increasing convective Mach number. Some improvements were also noted in the prediction of the normalized streamwise stress and Reynolds shear stress. The computed results are in good agreement with the experimental data.
Sleep restriction alters plasma endocannabinoids concentrations before but not after exercise in humans.

PubMed

Cedernaes, Jonathan; Fanelli, Flaminia; Fazzini, Alessia; Pagotto, Uberto; Broman, Jan-Erik; Vogel, Heike; Dickson, Suzanne L; Schiöth, Helgi B; Benedict, Christian

2016-12-01

Following binding to cannabinoid receptors, endocannabinoids regulate a variety of central nervous system processes including appetite and mood. Recent evidence suggests that the systemic release of these lipid metabolites can be altered by acute exercise and that their levels also vary across the 24-h sleep-wake cycle. The present study utilized a within-subject design (involving 16 normal-weight men) to determine whether daytime circulating endocannabinoid concentrations differ following three nights of partial sleep deprivation (4.25-h sleep opportunity, 2:45-7a.m. each night) vs. normal sleep (8.5-h sleep opportunity, 10:30p.m.-7a.m. each night), before and after an acute bout of ergometer cycling in the morning. In addition, subjective hunger and stress were measured. Pre-exercise plasma concentrations of 2-arachidonoylglycerol (2AG) were 80% higher 1.5h after awakening (vs. normal sleep, p<0.05) when participants were sleep-deprived. This coincided with increased hunger ratings (+25% vs. normal sleep, p<0.05). Moreover, plasma 2AG was elevated 15min post-exercise (+44%, p<0.05). Sleep duration did not however modulate this exercise-induced rise. Finally, subjective stress was generally lower on the day after three nights of short sleep vs. normal sleep, especially after exercise (p<0.05). Given that activation of the endocannabinoid system has been previously shown to acutely increase appetite and mood, our results could suggest that behavioral effects of acute sleep loss, such as increased hunger and transiently improved psychological state, may partially result from activation of this signaling pathway. In contrast, more pronounced exercise-induced elevations of endocannabinoids appear to be less affected by short sleep duration. Copyright © 2016 The Author(s). Published by Elsevier Ltd.. All rights reserved.
Validation of reference genes for accurate normalization of gene expression for real time-quantitative PCR in strawberry fruits using different cultivars and osmotic stresses.

PubMed

Galli, Vanessa; Borowski, Joyce Moura; Perin, Ellen Cristina; Messias, Rafael da Silva; Labonde, Julia; Pereira, Ivan dos Santos; Silva, Sérgio Delmar Dos Anjos; Rombaldi, Cesar Valmor

2015-01-10

The increasing demand of strawberry (Fragaria×ananassa Duch) fruits is associated mainly with their sensorial characteristics and the content of antioxidant compounds. Nevertheless, the strawberry production has been hampered due to its sensitivity to abiotic stresses. Therefore, to understand the molecular mechanisms highlighting stress response is of great importance to enable genetic engineering approaches aiming to improve strawberry tolerance. However, the study of expression of genes in strawberry requires the use of suitable reference genes. In the present study, seven traditional and novel candidate reference genes were evaluated for transcript normalization in fruits of ten strawberry cultivars and two abiotic stresses, using RefFinder, which integrates the four major currently available software programs: geNorm, NormFinder, BestKeeper and the comparative delta-Ct method. The results indicate that the expression stability is dependent on the experimental conditions. The candidate reference gene DBP (DNA binding protein) was considered the most suitable to normalize expression data in samples of strawberry cultivars and under drought stress condition, and the candidate reference gene HISTH4 (histone H4) was the most stable under osmotic stresses and salt stress. The traditional genes GAPDH (glyceraldehyde-3-phosphate dehydrogenase) and 18S (18S ribosomal RNA) were considered the most unstable genes in all conditions. The expression of phenylalanine ammonia lyase (PAL) and 9-cis epoxycarotenoid dioxygenase (NCED1) genes were used to further confirm the validated candidate reference genes, showing that the use of an inappropriate reference gene may induce erroneous results. This study is the first survey on the stability of reference genes in strawberry cultivars and osmotic stresses and provides guidelines to obtain more accurate RT-qPCR results for future breeding efforts. Copyright © 2014 Elsevier B.V. All rights reserved.
Effect of gravitational overloads, hypokinesia and hypodynamia on the vessels of the pulmonary blood circuit

NASA Technical Reports Server (NTRS)

Kasimtsev, A. A.

1980-01-01

Vessels of the pulmonary circuit are studied under normal conditions, in exposure to single stress or continuous threshold endurable chestspine gravitational stresses, and one to eight weak hypokinesia and hypodynamic effects followed by stress. Examination methods include rentgenography and microrentgenography, clearing, and histology. In exposure to gravitational stress the distal portions of the arterial vessels of the 3 and 4 orders constrict, while all veins dilate. Sinuosity of all vessels is noted. The volume of the capillary bed increases and signs of perivascular edema occur. Due to hypokinesia and hypodynamia the arteries constricted and the arterial bed becomes poor. The veins of all orders dilate and the volume of the capillary bed increases. The changes grew greater the longer the terms of hypodyamic effects. Successive combination of hypokinesia and hypodynamia and gravitational stresses cause more pronounced changes than separate effects of these two factors and result in great deformity of the vascular walls, including their rupture and penetration of formed elements beyond the limits of the vascular bed.
Iodinated contrast media can induce long-lasting oxidative stress in hemodialysis patients.

PubMed

Hwang, Seun Deuk; Kim, Yoon Ji; Lee, Sang Heun; Cho, Deok Kyu; Cho, Yun Hyeong; Moon, Sung Jin; Lee, Sang Choel; Yoon, Soo Young

2013-11-01

Due to their comorbidities, dialysis patients have many chances to undergo radiologic procedures using iodinated contrast media. We aimed to assess time-sequenced blood oxidative stress level after contrast exposure in hemodialysis (HD) patients compared to those in the non-dialysis population. We included 21 anuric HD patients [HD-coronary angiography (CAG) group] and 23 persons with normal renal function (nonHD-CAG group) scheduled for CAG, and assessed 4 oxidative stress markers [advanced oxidation protein products (AOPP); catalase; 8-hydroxydeoxyguanosine; and malondialdehyde] before and after CAG, and subsequently up to 28 days. In the nonHD-CAG group, only AOPP increased immediately after CAG and returned to baseline within one day. However, in the HD-CAG group, all four oxidative stress markers were significantly increased starting one day after CAG, and remained elevated longer than those in the nonHD-CAG group. Especially, AOPP level remained elevated for a month after contrast exposure. Our study showed that iodinated contrast media induces severe and prolonged oxidative stress in HD patients.
Controls on Earthquake Rupture and Triggering Mechanisms in Subduction Zones

DTIC Science & Technology

2010-06-01

weaken the fault [Wibber- ley and Shimamoto, 2005]. Song and Simons [2003] infer that strongly negative TPGA values correlate with increases in the...and Y. Hu (2006), Accretionary prisms in subduction earthquake cycles: The theory of dynamic Coulomb wedge, J. Geophys. Res., 111, B06410, doi:10.1029...modified Coulomb stress function, γ is a state variable, and A is a fault constitutive parameter. We assume that the normal stress σ remains constant, and
Co-ordinated stage-dependent enhancement of Plasmodium falciparum antioxidant enzymes and heat shock protein expression in parasites growing in oxidatively stressed or G6PD-deficient red blood cells.

PubMed

Akide-Ndunge, Oscar Bate; Tambini, Elisa; Giribaldi, Giuliana; McMillan, Paul J; Müller, Sylke; Arese, Paolo; Turrini, Francesco

2009-05-29

Plasmodium falciparum-parasitized red blood cells (RBCs) are equipped with protective antioxidant enzymes and heat shock proteins (HSPs). The latter are only considered to protect against thermal stress. Important issues are poorly explored: first, it is insufficiently known how both systems are expressed in relation to the parasite developmental stage; secondly, it is unknown whether P. falciparum HSPs are redox-responsive, in view of redox sensitivity of HSP in eukaryotic cells; thirdly, it is poorly known how the antioxidant defense machinery would respond to increased oxidative stress or inhibited antioxidant defense. Those issues are interesting as several antimalarials increase the oxidative stress or block antioxidant defense in the parasitized RBC. In addition, numerous inhibitors of HSPs are currently developed for cancer therapy and might be tested as anti-malarials. Thus, the joint disruption of the parasite antioxidant enzymes/HSP system would interfere with parasite growth and open new perspectives for anti-malaria therapy. Stage-dependent mRNA expression of ten representative P. falciparum antioxidant enzymes and hsp60/70-2/70-3/75/90 was studied by quantitative real-time RT-PCR in parasites growing in normal RBCs, in RBCs oxidatively-stressed by moderate H2O2 generation and in G6PD-deficient RBCs. Protein expression of antioxidant enzymes was assayed by Western blotting. The pentosephosphate-pathway flux was measured in isolated parasites after Sendai-virus lysis of RBC membrane. In parasites growing in normal RBCs, mRNA expression of antioxidant enzymes and HSPs displayed co-ordinated stage-dependent modulation, being low at ring, highest at early trophozoite and again very low at schizont stage. Additional exogenous oxidative stress or growth in antioxidant blunted G6PD-deficient RBCs indicated remarkable flexibility of both systems, manifested by enhanced, co-ordinated mRNA expression of antioxidant enzymes and HSPs. Protein expression of antioxidant enzymes was also increased in oxidatively-stressed trophozoites. Results indicated that mRNA expression of parasite antioxidant enzymes and HSPs was co-ordinated and stage-dependent. Secondly, both systems were redox-responsive and showed remarkably increased and co-ordinated expression in oxidatively-stressed parasites and in parasites growing in antioxidant blunted G6PD-deficient RBCs. Lastly, as important anti-malarials either increase oxidant stress or impair antioxidant defense, results may encourage the inclusion of anti-HSP molecules in anti-malarial combined drugs.
Disruption of Fatty Acid Amide Hydrolase Activity Prevents the Effects of Chronic Stress on Anxiety and Amygdalar Microstructure

PubMed Central

Hill, Matthew N.; Kumar, Shobha Anil; Filipski, Sarah B.; Iverson, Moriah; Stuhr, Kara L.; Keith, John M.; Cravatt, Benjamin F.; Hillard, Cecilia J.; Chattarji, Sumantra; McEwen, Bruce S.

2014-01-01

Hyperactivation of the amygdala following chronic stress is believed to be one of the primary mechanisms underlying the increased propensity for anxiety-like behaviors and pathological states; however, the mechanisms by which chronic stress modulates amygdalar function are not well characterized. The aim of the current study was to determine the extent to which the endocannabinoid system, which is known to regulate emotional behavior and neuroplasticity, contributes to changes in amygdalar structure and function following chronic stress. To examine the hypothesis, we have exposed C57/Bl6 mice to chronic restraint stress which results in an increase in fatty acid amide hydrolase (FAAH) activity and a reduction in the concentration of the endocannabinoid N-arachidonylethanolamine (AEA) within the amygdala. Chronic restraint stress also increased dendritic arborization, complexity and spine density of pyramidal neurons in the basolateral nucleus of the amygdala (BLA) and increased anxiety-like behavior in wild-type mice. All of the stress-induced changes in amygdalar structure and function were absent in mice deficient in FAAH. Further, the anti-anxiety effect of FAAH deletion was recapitulated in rats treated orally with a novel pharmacological inhibitor of FAAH, JNJ5003 (50 mg/kg/day), during exposure to chronic stress. These studies suggest that FAAH is required for chronic stress to induce hyperactivity and structural remodeling of the amygdala. Collectively, these studies indicate that FAAH-mediated decreases in AEA occur following chronic stress and that this loss of AEA signaling is functionally relevant to the effects of chronic stress. These data support the hypothesis that inhibition of FAAH has therapeutic potential in the treatment of anxiety disorders, possibly by maintaining normal amygdalar function in the face of chronic stress. PMID:22776900
On the expected relationships among apparent stress, static stress drop, effective shear fracture energy, and efficiency

USGS Publications Warehouse

Beeler, N.M.; Wong, T.-F.; Hickman, S.H.

2003-01-01

We consider expected relationships between apparent stress ??a and static stress drop ????s using a standard energy balance and find ??a = ????s (0.5 - ??), where ?? is stress overshoot. A simple implementation of this balance is to assume overshoot is constant; then apparent stress should vary linearly with stress drop, consistent with spectral theories (Brune, 1970) and dynamic crack models (Madariaga, 1976). Normalizing this expression by the static stress drop defines an efficiency ??sw = ??sa/????s as follows from Savage and Wood (1971). We use this measure of efficiency to analyze data from one of a number of observational studies that find apparent stress to increase with seismic moment, namely earthquakes recorded in the Cajon Pass borehole by Abercrombie (1995). Increases in apparent stress with event size could reflect an increase in seismic efficiency; however, ??sw for the Cajon earthquakes shows no such increase and is approximately constant over the entire moment range. Thus, apparent stress and stress drop co-vary, as expected from the energy balance at constant overshoot. The median value of ??sw for the Cajon earthquakes is four times lower than ??sw for laboratory events. Thus, these Cajon-recorded earthquakes have relatively low and approximately constant efficiency. As the energy balance requires ??sw = 0.5 - ??, overshoot can be estimated directly from the Savage-Wood efficiency; overshoot is positive for Cajon Pass earthquakes. Variations in apparent stress with seismic moment for these earthquakes result primarily from systematic variations in static stress drop with seismic moment and do not require a relative decrease in sliding resistance with increasing event size (dynamic weakening). Based on the comparison of field and lab determinations of the Savage-Wood efficiency, we suggest the criterion ??sw > 0.3 as a test for dynamic weakening in excess of that seen in the lab.
Increased resistance to oxidative stress in normal and glucose-6-phosphate dehydrogenase-deficient hemolysates in the presence of enzyme substrates.

PubMed

Yücel, G; Yeşilkaya, A; Aksu, T A; Yeğin, A; Alicigüzel, Y

1997-01-01

Erythrocytes and hemolysates from 10 normal and 10 glucose-6-phosphate dehydrogenase-deficient individuals were incubated with cumene hydroperoxide, and free radical-induced lipid peroxidation was monitored by chemiluminescence. Chemiluminescence intensities in erythrocytes of normal and deficient subjects were similar in the presence or absence of glucose-6-phosphate dehydrogenase substrates. Hemolysates of normal and deficient subjects also showed similar chemiluminescence in the absence of substrates. However, with the addition of substrates to the incubation medium, deficient hemolysates reached maximum chemiluminescence intensity within a shorter period, and maximum values were higher than in normal hemolysates. We believe this offers a new means of detection of glucose-6-phosphate dehydrogenase-deficient patients.
Glutamine prevents gastric oxidative stress in an animal model of portal hypertension gastropathy.

PubMed

Marques, Camila; Mauriz, José L; Simonetto, Douglas; Marroni, Claudio A; Tuñon, María J; González-Gallego, Javier; Marrón, Norma P

2011-01-01

Portal hypertension (PHI) is a clinical syndrome characterized by increases of the blood flow and/or of the vascular resistance in the portal system. A direct consequence of PHI can appearance different lesions on the gastric mucosa and submucosa, cumulatively termed portal hypertensive gastropathy (PHG). To investigate the effects of glutamine on oxidative stress in an experimental model of PHG induced by partial portal vein ligation (PPVL). Portal pressure, transaminase and alkaline phosphatase activity were quantified. Gastric tissue damage was assessed by histological analysis. Oxidative stress was measured by quantification of cytosolic concentration of thiobarbituric acid reactive substances (TBARS), hydroperoxide-initiated chemiluminescence (QL), and nitric oxide (NO) production. Moreover, activities of the antioxidant enzymes superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) were analyzed. Transaminase and alkaline phosphatase activities were not significantly modified by PPVL, indicating absence of liver injury. Histological analysis of gastric sections showed a lost of normal architecture, with edema and vasodilatation. TBARS, QL, and NO production were significantly increased in PPVL animals. A reduction of SOD activity was found. Glutamine administration markedly alleviated histological abnormalities and oxidative stress, normalized SOD activity, and blocked NO overproduction. Our results confirm that the use of molecules with antioxidant capacity can provide protection of the gastric tissue in portal hypertension. Glutamine treatment can be useful to reduce the oxidative damage induced by PHI on gastric tissue.
The Lcn2-engineered HEK-293 cells show senescence under stressful condition

PubMed Central

Bahmani, Bahareh; Amiri, Fatemeh; Mohammadi Roushandeh, Amaneh; Bahadori, Marzie; Harati, Mozhgan Dehghan; Habibi Roudkenar, Mehryar

2015-01-01

Objective(s): Lipocalin2 (Lcn2) gene is highly expressed in response to various types of cellular stresses. The precise role of Lcn2 has not been fully understood yet. However, it plays a key role in controlling vital cellular processes such as proliferation, apoptosis and metabolism. Recently it was shown that Lcn2 decreases senescence and increases proliferation of mesenchymal stem cells (MSC) with finite life span under either normal or oxidative stress conditions. However, Lcn2 effects on immortal cell line with infinite proliferation are not defined completely. Materials and Materials and Methods: HEK-293 cells were transfected with recombinant pcDNA3.1 containing Lcn2 fragment (pcDNA3.1-Lcn2). Expression of lipocalin2 in transfected cells was evaluated by RT-PCR, real time RT-PCR, and ELISA. Different cell groups were treated with H2O2 and WST-1 assay was performed to determine their proliferation rate. Senescence was studied by β-galactosidase and gimsa staining methods as well as evaluation of the expression of senescence-related genes by real time RT-PCR. Results: Lcn2 increased cell proliferation under normal culture condition, while the proliferation slightly decreased under oxidative stress. This decrease was further found to be attributed to senescence. Conclusion: Our findings indicated that under harmful conditions, Lcn2 gene is responsible for the regulation of cell survival through senescence. PMID:26124931
Psychological stress exerts an adjuvant effect on skin dendritic cell functions in vivo.

PubMed

Saint-Mezard, Pierre; Chavagnac, Cyril; Bosset, Sophie; Ionescu, Marius; Peyron, Eric; Kaiserlian, Dominique; Nicolas, Jean-Francois; Bérard, Frédéric

2003-10-15

Psychological stress affects the pathophysiology of infectious, inflammatory, and autoimmune diseases. However, the mechanisms by which stress could modulate immune responses in vivo are poorly understood. In this study, we report that application of a psychological stress before immunization exerts an adjuvant effect on dendritic cell (DC), resulting in increased primary and memory Ag-specific T cell immune responses. Acute stress dramatically enhanced the skin delayed-type hypersensitivity reaction to haptens, which is mediated by CD8(+) CTLs. This effect was due to increased migration of skin DCs, resulting in augmented CD8(+) T cell priming in draining lymph nodes and enhanced recruitment of CD8(+) T cell effectors in the skin upon challenge. This adjuvant effect of stress was mediated by norepinephrine (NE), but not corticosteroids, as demonstrated by normalization of the skin delayed-type hypersensitivity reaction and DC migratory properties following selective depletion of NE. These results suggest that release of NE by sympathetic nerve termini during a psychological stress exerts an adjuvant effect on DC by promoting enhanced migration to lymph nodes, resulting in increased Ag-specific T cell responses. Our findings may open new ways in the treatment of inflammatory diseases, e.g., psoriasis, allergic contact dermatitis, and atopic dermatitis.

Stress management at the worksite: reversal of symptoms profile and cardiovascular dysregulation.

PubMed

Lucini, Daniela; Riva, Silvano; Pizzinelli, Paolo; Pagani, Massimo

2007-02-01

Work stress may increase cardiovascular risk either indirectly, by inducing unhealthy life styles, or directly, by affecting the autonomic nervous system and arterial pressure. We hypothesized that, before any apparent sign of disease, work-related stress is already accompanied by alterations of RR variability profile and that a simple onsite stress management program based on cognitive restructuring and relaxation training could reduce the level of stress symptoms, revert stress-related autonomic nervous system dysregulation, and lower arterial pressure. We compared 91 white-collar workers, enrolled at a time of work downsizing (hence, in a stress condition), with 79 healthy control subjects. Psychological profiles were assessed by questionnaires and autonomic nervous system regulation by spectral analysis of RR variability. We also tested a simple onsite stress management program (cognitive restructuring and relaxation training) in a subgroup of workers compared with a sham subgroup (sham program). Workers presented an elevated level of stress-related symptoms and an altered variability profile as compared with control subjects (low-frequency component of RR variability was, respectively, 65.2+/-2 versus 55.3+/-2 normalized units; P<0.001; opposite changes were observed for the high-frequency component). These alterations were largely reverted (low-frequency component of RR variability from 63.6+/-3.9 to 49.3+/-3 normalized units; P<0.001) by the stress management program, which also slightly lowered systolic arterial pressure. No changes were observed in the sham program group. This noninvasive study indicates that work stress is associated with unpleasant symptoms and with an altered autonomic profile and suggests that a stress management program could be implemented at the worksite, with possible preventive advantages for hypertension.
Oxidative stress equilibrium during obstetric event in normal pregnancy.

PubMed

Salas-Pacheco, Jose Manuel; Lourenco-Jaramillo, Diana Lelidett; Mendez-Hernandez, Edna Madai; Sandoval-Carrillo, Ada Agustina; Hernandez Rayon, Yessica Ivonne; Llave-Leon, Osmel La; Aguilar-Duran, Marisela; Lopez-Terrones, Marcos Alonso; Barraza-Salas, Marcelo; Vazquez-Alaniz, Fernando

2017-08-01

The aim of this study was to determine malondialdehyde (MDA) concentration as an oxidative stress marker and total antioxidant capacity (TAC) in pregnancy before and after perinatal event. This study was performed on 200 healthy full-term pregnant women admitted to pregnancy resolution in Maternal-Child Hospital of Durango, Mexico. Oxidative stress and TAC were assessed through detection of lipid peroxidation by quantitation of thiobarbituric acid-reactive substances (TBARS) and TAC through ferric reducing ability of the plasma (FRAP). Our results showed increased levels of MDA after vaginal delivery (VD). TAC was also increased after obstetric event, but it did not differ between VD and caesarean section. We demonstrated that MDA concentrations are increased two hours after obstetric event, and this increase correlates with VD. The TAC was increased as a compensatory mechanism during obstetric event. Another important finding is that women receiving analgesia administration in VD, as well as dexamethasone administration in caesarean section, experienced a protector effect that decreased MDA levels.
Effects of Music Therapy on the Cardiovascular and Autonomic Nervous System in Stress-Induced University Students: A Randomized Controlled Trial.

PubMed

Lee, Kyoung Soon; Jeong, Hyeon Cheol; Yim, Jong Eun; Jeon, Mi Yang

2016-01-01

Stress is caused when a particular relationship between the individual and the environment emerges. Specifically, stress occurs when an individual's abilities are challenged or when one's well-being is threatened by excessive environmental demands. The aim of this study was to measure the effects of music therapy on stress in university students. Randomized controlled trial. Sixty-four students were randomly assigned to the experimental group (n = 33) or the control group (n = 31). Music therapy. Initial measurement included cardiovascular indicators (blood pressure and pulse), autonomic nervous activity (standard deviation of the normal-to-normal intervals [SDNN], normalized low frequency, normalized high frequency, low/high frequency), and subjective stress. After the first measurement, participants in both groups were exposed to a series of stressful tasks, and then a second measurement was conducted. The experimental group then listened to music for 20 minutes and the control group rested for 20 minutes. A third and final measurement was then taken. There were no significant differences between the two groups in the first or second measurement. However, after music therapy, the experimental group and the control group showed significant differences in all variables, including systolic blood pressure (p = .026), diastolic blood pressure (p = .037), pulse (p < .001), SDNN (p = .003), normalized low frequency (p < .001), normalized high frequency (p = .010), and subjective stress (p = .026). Classical music tends to relax the body and may stimulate the parasympathetic nervous system. These results suggest music therapy as an intervention for stress reduction.
The influence of topographic stresses on faulting, emphasizing the 2008 Wenchuan, China earthquake rupture

NASA Astrophysics Data System (ADS)

Styron, R. H.; Hetland, E. A.; Zhang, G.

2013-12-01

The weight of large mountains produces stresses in the crust that locally may be on the order of tectonic stresses (10-100 MPa). These stresses have a significant and spatially-variable deviatoric component that may be resolved as strong normal and shear stresses on range-bounding faults. In areas of high relief, the shear stress on faults can be comparable to inferred stress drops in earthquakes, and fault-normal stresses may be greater than 50 MPa, and thus may potentially influence fault rupture. Additionally, these stresses may be used to make inferences about the orientation and magnitude of tectonic stresses, for example by indicating a minimum stress needed to be overcome by tectonic stress. We are studying these effects in several tectonic environments, such as the Longmen Shan (China), the Denali fault (Alaska, USA) and the Wasatch Fault Zone (Utah, USA). We calculate the full topographic stress tensor field in the crust in a study region by convolution of topography with Green's functions approximating stresses from a point load on the surface of an elastic halfspace, using the solution proposed by Liu and Zoback [1992]. The Green's functions are constructed from Boussinesq's solutions for a vertical point load on an elastic halfspace, as well as Cerruti's solutions for a horizontal surface point load, accounting for irregular surface boundary and topographic spreading forces. The stress tensor field is then projected onto points embedded in the halfspace representing the faults, and the fault normal and shear stresses at each point are calculated. Our primary focus has been on the 2008 Wenchuan earthquake, as this event occurred at the base of one of Earth's highest and steepest topographic fronts and had a complex and well-studied coseismic slip distribution, making it an ideal case study to evaluate topographic influence on faulting. We calculate the topographic stresses on the Beichuan and Pengguan faults, and compare the results to the coseismic slip distribution, considering several published fault models. These models differ primarily in slip magnitude and planar vs. listric fault geometry at depth. Preliminary results indicate that topographic stresses are generally resistive to tectonic deformation, especially above ~10 km depth, where the faults are steep in all models. Down-dip topographic shear stresses on the fault are normal sense where the faults dip steeply, and reach 20 MPa on the fault beneath the Pengguan massif. Reverse-sense shear up to ~15 MPa is present on gently-dipping thrust flats at depth on listric fault models. Strike-slip shear stresses are sinistral on the steep, upper portions of faults but may be dextral on thrust flats. Topographic normal stress on the faults reaches ~80 MPa on thrust ramps and may be higher on flats. Coseismic slip magnitude is negatively correlated with topographic normal and down-dip shear stresses. The spatial patterns of topographic stresses and slip suggest that topographic stresses have significantly suppressed slip in certain areas: slip maxima occur in areas of locally lower topographic stresses, while areas of higher down-dip shear and normal stress show less slip than adjacent regions.
Viscous pressure correction in the irrotational flow outside Prandtl's boundary layer

NASA Astrophysics Data System (ADS)

Joseph, Daniel; Wang, Jing

2004-11-01

We argue that boundary layers on solid with irrotational motion outside are like a gas bubble because the shear stress vanishes at the edge of the boundary layer but the irrotational shear stress does not. This discrepancy induces a pressure correction and an additional drag which can be advertised as due to the viscous dissipation of the irrotational flow. Typically, this extra correction to the drag would be relatively small. A much more interesting implication of the extra pressure theory arises from the consideration of the effects of viscosity on the normal stress on a solid boundary which are entirely neglected in Prandtl's theory. It is very well known and easily demonstrated that as a consequence of the continuity equation the viscous normal stress must vanish on a rigid solid. It follows that all the greatly important effects of viscosity on the normal stress are buried in the pressure and the leading order effects of viscosity on the normal stress can be obtained from the viscous correction of viscous potential flow.
Genetic and environmental factors interact to influence anxiety.

PubMed

Gross, Cornelius; Hen, René

2004-01-01

Both genetic and environmental factors influence normal anxiety traits as well as anxiety disorders. In addition it is becoming increasingly clear that these factors interact to produce specific anxiety-related behaviors. For example, in humans and in monkeys mutations in the gene encoding for the serotonin transporter result in increased anxiety in adult life when combined with a stressful environment during development. Another recent example comes from twin studies suggesting that a small hippocampus can be a predisposing condition that renders individuals susceptible to post traumatic stress disorder. Such examples illustrate how specific mutations leading to abnormal brain development may increase vulnerability to environmental insults which may in turn lead to specific anxiety disorders.
A study of the effect of oral glucose loading on plasma oxidant:antioxidant balance in normal subjects.

PubMed

Ma, Shuk-Woon; Tomlinson, Brian; Benzie, Iris F F

2005-06-01

Antioxidant defence has been reported to decrease, and oxidative stress to increase, after oral glucose loading in both normal and diabetic subjects. If confirmed in normal subjects, glucose-induced antioxidant depletion has important implications for health in relation to the modern, sugar-rich diet. To investigate changes in plasma biomarkers of oxidant:antioxidant balance in non-diabetic subjects following oral glucose loading. Baseline inter-relationships between biomarkers of glycaemic control, oxidant:antioxidant balance and inflammation were also explored. A single-blinded, placebo-controlled, crossover intervention trial involving 10 healthy, consenting subjects. Venous blood was collected after ingestion of 75 g glucose in 300 mL water, or of water alone. Blood was collected at 0 time (fasting) and 30, 60, 90, 120 min post-ingestion. Within 2 weeks the procedure was repeated with volunteers crossed-over onto the other treatment. Plasma total antioxidant capacity (as the FRAP value), ascorbic acid, alpha-tocopherol, uric acid, malondialdehyde (MDA), allantoin and high sensitivity C-reactive protein (hsCRP), glucose and insulin, were measured in all samples. Paired results post-glucose and post-water at each time interval were compared using the Wilcoxon matched-pairs signed-ranks test. Normal glucose tolerance was observed in all subjects, although, as expected, plasma glucose and insulin increased significantly (p < 0.05, n = 10) after glucose loading. Post-glucose responses in plasma FRAP and the individual antioxidants tested were not significantly different to the responses seen post-water, although both FRAP and alpha-tocopherol decreased slightly. Neither were post-glucose changes in plasma MDA and allantoin, putative biomarkers of oxidative stress, significantly different to those after intake of water alone. Plasma FRAP and alpha-tocopherol also decreased slightly, but not significantly, after intake of water. A significant direct correlation (r = 0.867, p < 0.001, n = 10) was found between fasting allantoin and (log transformed) hsCRP concentrations. These new data from a controlled intervention trial indicate that acute, transient increases in plasma glucose following oral intake of a large glucose load do not, as previously reported, cause a significant decrease in plasma antioxidants or increase oxidative stress in non-diabetic subjects. This is reassuring given the large quantities of sugar ingested by children and adolescents. However, a small decrease in plasma antioxidant capacity was seen after ingestion of water and of glucose, and it is possible that intake of glucose without concomitant intake of antioxidants in susceptible individuals may cause oxidative stress. Further work is needed in relation to diabetic subjects and a possible glucose threshold for this. The finding of a direct relationship between allantoin, a biomarker of oxidative stress, and hsCRP, a marker of inflammation and CHD predictor, in healthy subjects is interesting and indicates a link between sub-clinical inflammation and oxidative stress.
Psychological Stress Induces Temporary Masticatory Muscle Mechanical Sensitivity in Rats

PubMed Central

Huang, Fei; Zhang, Min; Chen, Yong-Jin; Li, Qiang; Wu, An-Zhen

2011-01-01

To explore the relationship between psychological stress and masticatory muscle pain, we created a communication stress animal model to determine whether psychological stress could induce increased mechanical sensitivity in masticatory muscles and to study the changes of mechanical nociceptive thresholds after stress removal. Forty-eight male Sprague-Dawley rats were divided into a control group (CON), a foot-shocked group (FS, including 3 subgroups recorded as FS-1, FS-2, and FS-3), a psychological stress group (PS), and a drug treatment group (DT). PS and DT rats were confined in a communication box for one hour a day to observe the psychological responses of neighboring FS rats.Measurements of the mechanical nociceptive thresholds of the bilateral temporal and masseter muscles showed a stimulus-response relationship between psychological stress and muscle mechanical sensitivity. The DT rats, who received a diazepam injection, showed almost the same mechanical sensitivity of the masticatory muscles to that of the control in response to psychological stress. Fourteen days after the psychological stressor was removed, the mechanical nociceptive thresholds returned to normal. These findings suggest that psychological stress is directly related to masticatory muscle pain. Removal of the stressor could be a useful method for relieving mechanical sensitivity increase induced by psychological stress. PMID:21331360
Interactions between creep, fatigue and strain aging in two refractory alloys

NASA Technical Reports Server (NTRS)

Sheffler, K. D.

1972-01-01

The application of low-amplitude, high-frequency fatigue vibrations during creep testing of two strain-aging refractory alloys (molybdenum-base TZC and tantalum-base T-111) significantly reduced the creep strength of these materials. This strength reduction caused dramatic increases in both the first stage creep strain and the second stage creep rate. The magnitude of the creep rate acceleration varied directly with both frequency and A ratio (ratio of alternating to mean stress), and also varied with temperature, being greatest in the range where the strain-aging phenomenon was most prominent. It was concluded that the creep rate acceleration resulted from a negative strain rate sensitivity which is associated with the strain aging phenomenon in these materials. (A negative rate sensitivity causes flow stress to decrease with increasing strain rate, instead of increasing as in normal materials). By combining two analytical expressions which are normally used to describe creep and strain aging behavior, an expression was developed which correctly described the influence of temperature, frequency, and A ratio on the TZC creep rate acceleration.
Bidisperse and polydisperse suspension rheology at large solid fraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pednekar, Sidhant; Chun, Jaehun; Morris, Jeffrey F.

At the same solid volume fraction, bidisperse and polydisperse suspensions display lower viscosities, and weaker normal stress response, compared to monodisperse suspensions. The reduction of viscosity associated with size distribution can be explained by an increase of the maximum flowable, or jamming, solid fraction. In this work, concentrated or "dense" suspensions are simulated under strong shearing, where thermal motion and repulsive forces are negligible, but we allow for particle contact with a mild frictional interaction with interparticle friction coefficient of 0.2. Aspects of bidisperse suspension rheology are first revisited to establish that the approach reproduces established trends; the study ofmore » bidisperse suspensions at size ratios of large to small particle radii (2 to 4) shows that a minimum in the viscosity occurs for zeta slightly above 0.5, where zeta=phi_{large}/phi is the fraction of the total solid volume occupied by the large particles. The simple shear flows of polydisperse suspensions with truncated normal and log normal size distributions, and bidisperse suspensions which are statistically equivalent with these polydisperse cases up to third moment of the size distribution, are simulated and the rheologies are extracted. Prior work shows that such distributions with equivalent low-order moments have similar phi_{m}, and the rheological behaviors of normal, log normal and bidisperse cases are shown to be in close agreement for a wide range of standard deviation in particle size, with standard correlations which are functionally dependent on phi/phi_{m} providing excellent agreement with the rheology found in simulation. The close agreement of both viscosity and normal stress response between bi- and polydisperse suspensions demonstrates the controlling in influence of the maximum packing fraction in noncolloidal suspensions. Microstructural investigations and the stress distribution according to particle size are also presented.« less
Physical Modeling of Shear Behavior of Infilled Rock Joints Under CNL and CNS Boundary Conditions

NASA Astrophysics Data System (ADS)

Shrivastava, Amit Kumar; Rao, K. Seshagiri

2018-01-01

Despite their frequent natural occurrence, filled discontinuities under constant normal stiffness (CNS) boundary conditions have been studied much less systematically, perhaps because of the difficulties arising from the increased number of variable parameters. Because of the lack of reliable and realistic theoretical or empirical relations and the difficulties in obtaining and testing representative samples, engineers rely on judgment and often consider the shear strength of the infilled material itself as shear strength of rock joints. This assumption leads to uneconomical and also sometimes the unsafe design of underground structures, slopes, rock-socketed piles and foundations. To study the effect of infill on the shear behavior of rock joints, tests were performed on the modeled infilled rock joint having different joint roughness under constant normal load (CNL) and CNS boundary conditions at various initial normal stress and varying thickness of the infilled material. The test results indicate that shear strength decreases with an increase in t/ a ratio for both CNL and CNS conditions, but the reduction in shear strength is more for CNL than for CNS condition for a given initial normal stress. The detailed account of the effect of thickness of infilled material on shear and deformation behavior of infilled rock joint is discussed in this paper, and a model is proposed to predict shear strength of infilled rock joint.
Pressure Dependence of the Peierls Stress in Aluminum

NASA Astrophysics Data System (ADS)

Dang, Khanh; Spearot, Douglas

2018-03-01

The effect of pressure applied normal to the {111} slip plane on the Peierls stress in Al is studied via atomistic simulations. Edge, screw, 30°, and 60° straight dislocations are created using the Volterra displacement fields for isotropic elasticity. For each dislocation character angle, the Peierls stress is calculated based on the change in the internal energy, which is an invariant measure of the dislocation driving force. It is found that the Peierls stress for dislocations under zero pressure is in general agreement with previous results. For screw and 60° dislocations, the Peierls stress versus pressure relationship has maximum values associated with stacking fault widths that are multiples of the Peierls period. For the edge dislocation, the Peierls stress decreases with increasing pressure from tension to compression. Compared with the Mendelev potential, the Peierls stress calculated from the Mishin potential is more sensitive to changes in pressure.
Geothermal production and reduced seismicity: Correlation and proposed mechanism

DOE PAGES

Cardiff, Michael; Lim, David D.; Patterson, Jeremy R.; ...

2018-01-15

At Brady Hot Springs, a geothermal field in Nevada, heated fluids have been extracted, cooled, and re-injected to produce electrical power since 1992. Analysis of daily pumping records and catalogs of microseismicity between 2010 and 2015 indicates a statistically significant correlation between days when the daily volume of production was at or above its long-term average rate and days when no seismic event was detected. Conversely, shutdowns in pumping for plant maintenance correlate with increased microseismicity. Our hypothesis is that the effective stress in the subsurface has adapted to the long-term normal operations (deep extraction) at the site. Under thismore » hypothesis, extraction of fluids inhibits fault slip by increasing the effective stress on faults; in contrast, brief pumping cessations represent times when effective stress is decreased below its long-term average, increasing the likelihood of microseismicity.« less
An evaluation of the effects of bed rest, sleep deprivation and discontinuance of training on the physical fitness of highly trained young men

NASA Technical Reports Server (NTRS)

Olree, H. D.; Corbin, B.; Dugger, G.; Smith, C.

1973-01-01

This experiment was conducted to determine what physiological effects result when highly trained subjects are confined to bed, deprived of sleep, or allowed to discontinue training. Results indicated: (1) There was a moderate increase in strength variables due to the training in this experiment but the stress which the subjects received caused a negligible change in strength variables. (2) The training program resulted in highly significant changes in specific bicycle ergometer variables indicating good increases in cardiopulmonary fitness. Five days of bed rest or fifty hours of sleep deprivation caused comparable drastic decreases in cardiopulmonary fitness. Post stress the subjects reverted to a normal daily schedule and after two weeks they had recovered about half of what they lost. (3) Cardiac output remains relatively constant at a constant work load, but stroke volume increases with conditioning and decreases with deconditioning due to stress.
Geothermal production and reduced seismicity: Correlation and proposed mechanism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cardiff, Michael; Lim, David D.; Patterson, Jeremy R.

At Brady Hot Springs, a geothermal field in Nevada, heated fluids have been extracted, cooled, and re-injected to produce electrical power since 1992. Analysis of daily pumping records and catalogs of microseismicity between 2010 and 2015 indicates a statistically significant correlation between days when the daily volume of production was at or above its long-term average rate and days when no seismic event was detected. Conversely, shutdowns in pumping for plant maintenance correlate with increased microseismicity. Our hypothesis is that the effective stress in the subsurface has adapted to the long-term normal operations (deep extraction) at the site. Under thismore » hypothesis, extraction of fluids inhibits fault slip by increasing the effective stress on faults; in contrast, brief pumping cessations represent times when effective stress is decreased below its long-term average, increasing the likelihood of microseismicity.« less
Chronic and acute effects of stress on energy balance: are there appropriate animal models?

PubMed Central

2014-01-01

Stress activates multiple neural and endocrine systems to allow an animal to respond to and survive in a threatening environment. The corticotropin-releasing factor system is a primary initiator of this integrated response, which includes activation of the sympathetic nervous system and the hypothalamic-pituitary-adrenal (HPA) axis. The energetic response to acute stress is determined by the nature and severity of the stressor, but a typical response to an acute stressor is inhibition of food intake, increased heat production, and increased activity with sustained changes in body weight, behavior, and HPA reactivity. The effect of chronic psychological stress is more variable. In humans, chronic stress may cause weight gain in restrained eaters who show increased HPA reactivity to acute stress. This phenotype is difficult to replicate in rodent models where chronic psychological stress is more likely to cause weight loss than weight gain. An exception may be hamsters subjected to repeated bouts of social defeat or foot shock, but the data are limited. Recent reports on the food intake and body composition of subordinate members of group-housed female monkeys indicate that these animals have a similar phenotype to human stress-induced eaters, but there are a limited number of investigators with access to the model. Few stress experiments focus on energy balance, but more information on the phenotype of both humans and animal models during and after exposure to acute or chronic stress may provide novel insight into mechanisms that normally control body weight. PMID:25519732
Type 2 diabetes mellitus induces congenital heart defects in murine embryos by increasing oxidative stress, endoplasmic reticulum stress, and apoptosis.

PubMed

Wu, Yanqing; Reece, E Albert; Zhong, Jianxiang; Dong, Daoyin; Shen, Wei-Bin; Harman, Christopher R; Yang, Peixin

2016-09-01

Maternal type 1 and 2 diabetes mellitus are strongly associated with high rates of severe structural birth defects, including congenital heart defects. Studies in type 1 diabetic embryopathy animal models have demonstrated that cellular stress-induced apoptosis mediates the teratogenicity of maternal diabetes leading to congenital heart defect formation. However, the mechanisms underlying maternal type 2 diabetes mellitus-induced congenital heart defects remain largely unknown. We aim to determine whether oxidative stress, endoplasmic reticulum stress, and excessive apoptosis are the intracellular molecular mechanisms underlying maternal type 2 diabetes mellitus-induced congenital heart defects. A mouse model of maternal type 2 diabetes mellitus was established by feeding female mice a high-fat diet (60% fat). After 15 weeks on the high-fat diet, the mice showed characteristics of maternal type 2 diabetes mellitus. Control dams were either fed a normal diet (10% fat) or the high-fat diet during pregnancy only. Female mice from the high-fat diet group and the 2 control groups were mated with male mice that were fed a normal diet. At E12.5, embryonic hearts were harvested to determine the levels of lipid peroxides and superoxide, endoplasmic reticulum stress markers, cleaved caspase 3 and 8, and apoptosis. E17.5 embryonic hearts were harvested for the detection of congenital heart defect formation using India ink vessel patterning and histological examination. Maternal type 2 diabetes mellitus significantly induced ventricular septal defects and persistent truncus arteriosus in the developing heart, along with increasing oxidative stress markers, including superoxide and lipid peroxidation; endoplasmic reticulum stress markers, including protein levels of phosphorylated-protein kinase RNA-like endoplasmic reticulum kinase, phosphorylated-IRE1α, phosphorylated-eIF2α, C/EBP homologous protein, and binding immunoglobulin protein; endoplasmic reticulum chaperone gene expression; and XBP1 messenger RNA splicing, as well as increased cleaved caspase 3 and 8 in embryonic hearts. Furthermore, maternal type 2 diabetes mellitus triggered excessive apoptosis in ventricular myocardium, endocardial cushion, and outflow tract of the embryonic heart. Similar to those observations in type 1 diabetic embryopathy, maternal type 2 diabetes mellitus causes heart defects in the developing embryo manifested with oxidative stress, endoplasmic reticulum stress, and excessive apoptosis in heart cells. Copyright © 2016 Elsevier Inc. All rights reserved.
Stress-strain analysis of contractility in the ileum in response to flow and ramp distension in streptozotocin-induced diabetic rats--association with advanced glycation end product formation.

PubMed

Zhao, Jingbo; Chen, Pengmin; Gregersen, Hans

2015-04-13

This study compared the ileal contractility and analyzed the association between contractility with advanced glycation end product (AGE) formation in normal and streptozotocin (STZ)-induced diabetic rats. Nine STZ-induced diabetic rats (Diabetes group) and 9 normal rats (Normal group) were used. The motility experiments were carried out on ileums in organ baths containing physiological Krebs solution. Ileal pressure and diameter changes were obtained from basic, flow-induced and ramp distension-induced contractions. The frequency and amplitude of contractions were analyzed from pressure-diameter curves. Distension-induced contraction thresholds and maximum contraction amplitude of basic and flow-induced contractions were calculated in terms of stress and strain. AGE and its receptor (RAGE) in the layers were detected by immunohistochemistry staining. The maximum stress of flow-induced contractions was lowest in the Diabetes Group (P<0.05). During ramp distension, the pressure and stress thresholds and Young's modulus to induce phasic contraction were lowest in the Diabetes Group (P<0.05 and P<0.01). AGE and RAGE expressions in the different ileum layers were highest in the Diabetes group. The contraction pressure and stress thresholds were significantly associated with AGE expression in the muscle layer and RAGE expression in mucosa epithelium and neurons. The diabetic intestine was hypersensitive to distension for contraction induction. However, the contraction force produced by smooth muscle was lowest in diabetic rats. Increased AGE/RAGE expression was associated with the contractility changes in diabetic rats. Copyright © 2015 Elsevier Ltd. All rights reserved.
Slip behaviour of carbonate-bearing faults subjected to fluid pressure stimulations

NASA Astrophysics Data System (ADS)

Collettini, Cristiano; Scuderi, Marco; Marone, Chris

2017-04-01

Earthquakes caused by fluid injection within reservoir have become an important topic of political and social discussion as new drilling and improved technologies enable the extraction of oil and gas from previously unproductive formations. During reservoir stimulation, the coupled interactions of frictional and fluid flow properties together with the stress state control both the onset of fault slip and fault slip behaviour. However, currently, there are no studies under controlled, laboratory conditions for which the effect of fluid pressure on fault slip behaviour can be deduced. To cover this gap, we have developed laboratory experiments where we monitor fault slip evolution at constant shear stress but with increasing fluid pressure, i.e. reducing the effective normal stress. Experiments have been conducted in the double direct shear configuration within a pressure vessel on carbonate fault gouge, characterized by a slightly velocity strengthening friction that is indicative of stable aseismic creep. In our experiments fault slip history can be divided in three main stages: 1) for high effective normal stress the fault is locked and undergoes compaction; 2) when the shear and effective normal stress reach the failure condition, accelerated creep is associated to fault dilation; 3) further pressurization leads to an exponential acceleration during fault compaction and slip localization. Our results indicate that fault weakening induced by fluid pressurization overcomes the velocity strengthening behaviour of calcite gouge, resulting in fast acceleration and earthquake slip. As applied to tectonic faults our results suggest that a larger number of crustal faults, including those slightly velocity strengthening, can experience earthquake slip due to fluid pressurization.
Adaptogens exert a stress-protective effect by modulation of expression of molecular chaperones.

PubMed

Panossian, Alexander; Wikman, Georg; Kaur, Punit; Asea, Alexzander

2009-06-01

Adaptogens are medicinal plants that augment resistance to stress, and increase concentration, performance and endurance during fatigue. Experiments were carried out with BALB/c mice taking ADAPT-232 forte, a fixed combination of three genuine (native) extracts of Eleutherococcus senticocus, Schisandra chinensis and Rhodiola rosea, characterised for the content of active markers eleutherosides, schisandrins, salidroside, tyrosol and rosavin and in doses of about 30, 90 and 180 mg/kg for seven consecutive days followed by forced swimming test to exhaustion. ADAPT-232 forte strongly augments endurance of mice, increasing the time taken to exhaustion (TTE) in a dose-dependent manner from 3.0+/-0.5 to 21.1+/-1.7 min, approximately seven fold. Serum Hsp72 was measured by EIA both in normal and stressful conditions before and after swimming test. Repeated administration of adaptogen dose dependently increases basal level of Hsp72 in serum of mice from 0.8-1.5 to 5.5-6.3 pg/ml. This effect is even stronger than the effect of stress, including both physical (swimming) and emotional impacts: 3.2+/-1.2 pg/ml. Cumulative effect of stress and adaptogen was clearly observed in groups of animals treated with adaptogen after swimming to exhaustion, when serum Hsp72 increased to 15.1+/-1 pg/ml and remained at almost the same level during the 7 days. It can be concluded that adaptogens induce increase of serum Hsp72, regarded as a defense response to stress, and increase tolerance to stress (in our model combination of physical and emotional stresses). It can be suggested that increased tolerance to stress induced by adaptogen is associated with its stimulation of expression of Hsp70 and particularly with Hsp72 production and release into systemic circulation, which is known as a mediator of stress response involved in reparation of proteins during physical load. Our studies suggest that this could be one of the mechanisms of action of plant adaptogens.

Deformability analysis of sickle blood using ektacytometry.

PubMed

Rabai, Miklos; Detterich, Jon A; Wenby, Rosalinda B; Hernandez, Tatiana M; Toth, Kalman; Meiselman, Herbert J; Wood, John C

2014-01-01

Sickle cell disease (SCD) is characterized by decreased erythrocyte deformability, microvessel occlusion and severe painful infarctions of different organs. Ektacytometry of SCD red blood cells (RBC) is made difficult by the presence of rigid, poorly-deformable irreversibly sickled cells (ISC) that do not align with the fluid shear field and distort the elliptical diffraction pattern seen with normal RBC. In operation, the computer software fits an outline to the diffraction pattern, then reports an elongation index (EI) at each shear stress based on the length and width of the fitted ellipse: EI=(length-width)/(length+width). Using a commercial ektacytometer (LORCA, Mechatronics Instruments, The Netherlands) we have approached the problem of ellipse fitting in two ways: (1) altering the height of the diffraction image on a computer monitor using an aperture within the camera lens; (2) altering the light intensity level (gray level) used by the software to fit the image to an elliptical shape. Neither of these methods affected deformability results (elongation index-shear stress relations) for normal RBC but did markedly affect results for SCD erythrocytes: (1) decreasing image height by 15% and 30% increased EI at moderate to high stresses; (2) progressively increasing the light level increased EI over a wide range of stresses. Fitting data obtained at different image heights using the Lineweaver-Burke routine yielded percentage ISC results in good agreement with microscopic cell counting. We suggest that these two relatively simple approaches allow minimizing artifacts due to the presence of rigid discs or ISC and also suggest the need for additional studies to evaluate the physiological relevance of deformability data obtained via these methods.
Effects of the Bacterial Extract OM-85 on Phagocyte Functions and the Stress Response

PubMed Central

Baladi, S.; Kantengwa, S.; Donati, Y. R. A.; Polla, B. S.

1994-01-01

The effects of the bacterial extract OM-85 on the respiratory burst, intracellular calcium and the stress response have been investigated in human peripheral blood monocytes from normal donors. Activation of the respiratory burst during bacterial phagocytosis has been previously associated with heat shock/stress proteins synthesis. Whereas OM-85 stimulated superoxide production and increased Ca2+ mobilization, it fared to induce synthesis of classical HSPs. The lack of stress protein induction was observed even in the presence of iron which potentiates both oxidative injury and stress protein induction during bacterial phagocytosis. However OM-85 induced a 75–78 kDa protein, which is likely to be a glucose regulated protein (GRP78), and enhanced intracellular expression of interleukin-lβ precursor. PMID:18472933
Early in vivo changes in calcium ions, oxidative stress markers, and ion channel immunoreactivity following partial injury to the optic nerve.

PubMed

Wells, Jonathan; Kilburn, Matthew R; Shaw, Jeremy A; Bartlett, Carole A; Harvey, Alan R; Dunlop, Sarah A; Fitzgerald, Melinda

2012-03-01

CNS injury is often localized but can be followed by more widespread secondary degenerative events that usually result in greater functional loss. Using a partial transection model in rat optic nerve (ON). we recently demonstrated in vivo increases in the oxidative stress-associated enzyme MnSOD 5 min after injury. However, mechanisms by which early oxidative stress spreads remain unclear. In the present study, we assessed ion distributions, additional oxidative stress indicators, and ion channel immunoreactivity in ON in the first 24 hr after partial transection. Using nanoscale secondary ion mass spectroscopy (NanoSIMS), we demonstrate changes in the distribution pattern of Ca ions following partial ON transection. Regions of elevated Ca ions in normal ON in vivo rapidly decrease following partial ON transection, but there is an increasingly punctate distribution at 5 min and 24 hr after injury. We also show rapid decreases in catalase activity and later increases in immunoreactivity of the advanced glycation end product carboxymethyl lysine in astrocytes. Increased oxidative stress in astrocytes is accompanied by significantly increased immunoreactivity of the AMPA receptor subunit GluR1 and aquaporin 4 (AQP4). Taken together, the results indicate that Ca ion changes and oxidative stress are early events following partial ON injury that are associated with changes in GluR1 AMPA receptor subunits and altered ionic balance resulting from increased AQP4. Copyright © 2011 Wiley Periodicals, Inc.
Placental dysfunction in Suramin-treated rats: impact of maternal diabetes and effects of antioxidative treatment.

PubMed

Nash, Peppi; Olovsson, Matts; Eriksson, Ulf J

2005-04-01

The aim of the present study was to evaluate a rat model of placental dysfunction/preeclampsia in pregnancies complicated by maternal diabetes. A second objective was to evaluate the effects of vitamin E treatment in this model. Normal and streptozotocin-induced diabetic rats of two different strains (U and H) were given intraperitoneal (IP) injections of the angiogenesis inhibitor Suramin (Sigma Chemical Co, St Louis, MO) or saline in early pregnancy, and fed standard or vitamin E-enriched food. The outcome of pregnancy was evaluated on gestational day 20. In both rat strains Suramin caused fetal growth retardation, decreased placental blood flow, and increased placental concentration of the isoprostane 8-iso-PGF(2alpha). In the U rats Suramin also caused increased fetal resorption rate, increased maternal blood pressure, decreased renal blood flow, and diminished maternal growth. Diabetes caused severe maternal and fetal growth retardation, increased resorption rate, and increased placental 8-iso-PGF(2alpha) concentration independent of Suramin administration. The maternal and fetal effects of Suramin and diabetes were more pronounced in the U strain than in the H strain. Vitamin E treatment improved the status of Suramin-injected diabetic rats: in U rats the blood pressure increase was normalized; and in both U and H rats the decreased placental blood flow was marginally enhanced, and the increase in placental 8-iso-PGF(2alpha) was partly normalized by vitamin E. Suramin injections to pregnant rats cause a state of placental insufficiency, which in U rats resembles human preeclampsia. The induction of this condition is at least partly mediated by oxidative stress, and antagonized by antioxidative treatment. Maternal diabetes involves increased oxidative stress, and causes both maternal and fetal morbidity, which are only marginally affected by additional Suramin treatment.
Aerobic Glycolysis Is Essential for Normal Rod Function and Controls Secondary Cone Death in Retinitis Pigmentosa.

PubMed

Petit, Lolita; Ma, Shan; Cipi, Joris; Cheng, Shun-Yun; Zieger, Marina; Hay, Nissim; Punzo, Claudio

2018-05-29

Aerobic glycolysis accounts for ∼80%-90% of glucose used by adult photoreceptors (PRs); yet, the importance of aerobic glycolysis for PR function or survival remains unclear. Here, we further established the role of aerobic glycolysis in murine rod and cone PRs. We show that loss of hexokinase-2 (HK2), a key aerobic glycolysis enzyme, does not affect PR survival or structure but is required for normal rod function. Rods with HK2 loss increase their mitochondrial number, suggesting an adaptation to the inhibition of aerobic glycolysis. In contrast, cones adapt without increased mitochondrial number but require HK2 to adapt to metabolic stress conditions such as those encountered in retinitis pigmentosa, where the loss of rods causes a nutrient shortage in cones. The data support a model where aerobic glycolysis in PRs is not a necessity but rather a metabolic choice that maximizes PR function and adaptability to nutrient stress conditions. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.
Clinical significance of stress-related increase in blood pressure: current evidence in office and out-of-office settings.

PubMed

Munakata, Masanori

2018-05-29

High blood pressure is the most significant risk factor of cardiovascular and cerebrovascular diseases worldwide. Blood pressure and its variability are recognized as risk factors. Thus, hypertension control should focus not only on maintaining optimal levels but also on achieving less variability in blood pressure. Psychosocial stress is known to contribute to the development and worsening of hypertension. Stress is perceived by the brain and induces neuroendocrine responses in either a rapid or long-term manner. Moreover, endothelial dysfunction and inflammation might be further involved in the modulation of blood pressure elevation associated with stress. White-coat hypertension, defined as high clinic blood pressure but normal out-of-office blood pressure, is the most popular stress-related blood pressure response. Careful follow-up is necessary for this type of hypertensive patients because some show organ damage or a worse prognosis. On the other hand, masked hypertension, defined as high out-of-office blood pressure but normal office blood pressure, has received considerable interest as a poor prognostic condition. The cause of masked hypertension is complex, but evidence suggests that chronic stress at the workplace or home could be involved. Chronic psychological stress could be associated with distorted lifestyle and mental distress as well as long-lasting allostatic load, contributing to the maintenance of blood pressure elevation. Stress issues are common in patients in modern society. Considering psychosocial stress as the pathogenesis of blood pressure elevation is useful for achieving an individual-focused approach and 24-h blood pressure control.
Effects of topically applied tocotrienol on cataractogenesis and lens redox status in galactosemic rats.

PubMed

Abdul Nasir, Nurul Alimah; Agarwal, Renu; Vasudevan, Sushil; Tripathy, Minaketan; Alyautdin, Renad; Ismail, Nafeeza Mohd

2014-01-01

Oxidative and nitrosative stress underlies cataractogenesis, and therefore, various antioxidants have been investigated for anticataract properties. Several vitamin E analogs have also been studied for anticataract effects due to their antioxidant properties; however, the anticataract properties of tocotrienols have not been investigated. In this study, we investigated the effects of topically applied tocotrienol on the onset and progression of cataract and lenticular oxidative and nitrosative stress in galactosemic rats. In the first part of this study, we investigated the effects of topically applied microemulsion formulation of tocotrienol (TTE) using six concentrations ranging from 0.01% to 0.2%. Eight groups of Sprague-Dawley rats (n = 9) received distilled water, vehicle, or one of the six TTE concentrations as pretreatment topically twice daily for 3 weeks while on a normal diet. After pretreatment, animals in groups 2-8 received a 25% galactose diet whereas group 1 continued on the normal diet for 4 weeks. During this 4-week period, topical treatment continued as for pretreatment. Weekly slit-lamp examination was conducted to assess cataract progression. At the end of the experimental period, the animals were euthanized, and the proteins and oxidative stress parameters were estimated in the lenses. In the second part of the study, we compared the anticataract efficacy of the TTE with the liposomal formulation of tocotrienol (TTL) using five groups of Sprague-Dawley rats (n = 15) that received distilled water, TTE, TTL, or corresponding vehicle. The mode of administration and dosing schedule were the same as in study 1. Weekly ophthalmic examination and lens protein and oxidative stress estimates were performed as in study 1. Lens nitrosative stress was also estimated. During the 4-week treatment period, the groups treated with 0.03% and 0.02% tocotrienol showed slower progression of cataract compared to the vehicle-treated group (p<0.05), whereas the group treated with 0.2% tocotrienol showed faster progression of cataract compared to the vehicle-treated group (p<0.05). The lenticular protein content, malondialdehyde, superoxide dismutase, and catalase levels were normalized in the groups that received 0.03% and 0.02% tocotrienol. The lenticular reduced glutathione also showed a trend toward normalization in these groups. In contrast, the group treated with 0.2% tocotrienol showed increased lenticular oxidative stress. When the microemulsion and liposomal formulations were compared, the effects on cataract progression, lens oxidative and nitrosative stress, and lens protein content did not show significant differences. Topically applied tocotrienol within the concentration range of less than 0.05% and more than 0.01% tends to delay the onset and progression of cataract in galactose-fed rats by reducing lenticular oxidative and nitrosative stress. However, topical tocotrienol at a concentration of 0.2% and higher aggravates cataractogenesis in galactose-fed rats by increasing lens oxidative stress. The anticataract efficacy of 0.03% microemulsion of tocotrienol did not differ from its liposomal formulations at the same concentration.
Effects of topically applied tocotrienol on cataractogenesis and lens redox status in galactosemic rats

PubMed Central

Agarwal, Renu; Vasudevan, Sushil; Tripathy, Minaketan; Alyautdin, Renad; Ismail, Nafeeza Mohd

2014-01-01

Purpose Oxidative and nitrosative stress underlies cataractogenesis, and therefore, various antioxidants have been investigated for anticataract properties. Several vitamin E analogs have also been studied for anticataract effects due to their antioxidant properties; however, the anticataract properties of tocotrienols have not been investigated. In this study, we investigated the effects of topically applied tocotrienol on the onset and progression of cataract and lenticular oxidative and nitrosative stress in galactosemic rats. Methods In the first part of this study, we investigated the effects of topically applied microemulsion formulation of tocotrienol (TTE) using six concentrations ranging from 0.01% to 0.2%. Eight groups of Sprague-Dawley rats (n = 9) received distilled water, vehicle, or one of the six TTE concentrations as pretreatment topically twice daily for 3 weeks while on a normal diet. After pretreatment, animals in groups 2–8 received a 25% galactose diet whereas group 1 continued on the normal diet for 4 weeks. During this 4-week period, topical treatment continued as for pretreatment. Weekly slit-lamp examination was conducted to assess cataract progression. At the end of the experimental period, the animals were euthanized, and the proteins and oxidative stress parameters were estimated in the lenses. In the second part of the study, we compared the anticataract efficacy of the TTE with the liposomal formulation of tocotrienol (TTL) using five groups of Sprague-Dawley rats (n = 15) that received distilled water, TTE, TTL, or corresponding vehicle. The mode of administration and dosing schedule were the same as in study 1. Weekly ophthalmic examination and lens protein and oxidative stress estimates were performed as in study 1. Lens nitrosative stress was also estimated. Results During the 4-week treatment period, the groups treated with 0.03% and 0.02% tocotrienol showed slower progression of cataract compared to the vehicle-treated group (p<0.05), whereas the group treated with 0.2% tocotrienol showed faster progression of cataract compared to the vehicle-treated group (p<0.05). The lenticular protein content, malondialdehyde, superoxide dismutase, and catalase levels were normalized in the groups that received 0.03% and 0.02% tocotrienol. The lenticular reduced glutathione also showed a trend toward normalization in these groups. In contrast, the group treated with 0.2% tocotrienol showed increased lenticular oxidative stress. When the microemulsion and liposomal formulations were compared, the effects on cataract progression, lens oxidative and nitrosative stress, and lens protein content did not show significant differences. Conclusions Topically applied tocotrienol within the concentration range of less than 0.05% and more than 0.01% tends to delay the onset and progression of cataract in galactose-fed rats by reducing lenticular oxidative and nitrosative stress. However, topical tocotrienol at a concentration of 0.2% and higher aggravates cataractogenesis in galactose-fed rats by increasing lens oxidative stress. The anticataract efficacy of 0.03% microemulsion of tocotrienol did not differ from its liposomal formulations at the same concentration. PMID:24940038
Preliminary Thermal Stress Analysis of a High-Pressure Cryogenic Storage Tank

NASA Technical Reports Server (NTRS)

Baker, J. Mark

2003-01-01

The thermal stresses on a cryogenic storage tank strongly affect the condition of the tank and its ability to withstand operational stresses. These thermal stresses also affect the growth of any surface damage that might occur in the tank walls. These stresses are particularly of concern during the initial cooldown period for a new tank placed into service, and during any subsequent thermal cycles. A preliminary thermal stress analysis of a high-pressure cryogenic storage tank was performed. Stresses during normal operation were determined, as well as the transient temperature distribution. An elastic analysis was used to determine the thermal stresses in the inner wall based on the temperature data. The results of this elastic analysis indicate that the inner wall of the storage tank will experience thermal stresses of approximately 145,000 psi (1000 MPa). This stress level is well above the room-temperature yield strength of 304L stainless steel, which is about 25,000 psi (170 MPa). For this preliminary analysis, several important factors have not yet been considered. These factors include increased strength of 304L stainless steel at cryogenic temperatures, plastic material behavior, and increased strength due to strain hardening. In order to more accurately determine the thermal stresses and their affect on the tank material, further investigation is required, particularly in the area of material properties and their relationship to stress.
Data Collection and Simulation of Ecological Habitat and Recreational Habitat in the Shenandoah River, Virginia

USGS Publications Warehouse

Krstolic, Jennifer L.

2015-01-01

Time-series analyses were used to investigate changes in habitat availability with increased water withdrawals of 10, 20, and almost 50 percent (48.6 percent) up to the 2040 amounts projected by local water supply plans. Adult and sub-adult smallmouth bass frequently had habitat availability outside the normal range for habitat conditions during drought years, yet 10- or 20-percent increases in withdrawals did not contribute to a large reduction in habitat. When withdrawals were increased by 50 percent, there was an additional decrease in habitat. During 2002 drought scenarios, reduced habitat availability for sub-adult redbreast sunfish or river chub was only slightly evident with 50-percent increased withdrawal scenarios. Recreational habitat represented by canoeing decreased lower than normal during the 2002 drought. For a recent normal year, like 2012, increased water-withdrawal scenarios did not affect habitat availability for fish such as adult and sub-adult smallmouth bass, sub-adult redbreast sunfish, or river chub. Canoeing habitat availability was within the normal range most of 2012, and increased water-withdrawal scenarios showed almost no affect. For both ecological fish habitat and recreational canoeing habitat, the antecedent conditions (habitat within normal range of habitat or below normal) appear to govern whether additional water withdrawals will affect habitat availability. As human populations and water demands increase, many of the ecological or recreational stresses may be lessened by managing the timing of water withdrawals from the system.
Regular voluntary exercise cures stress-induced impairment of cognitive function and cell proliferation accompanied by increases in cerebral IGF-1 and GST activity in mice.

PubMed

Nakajima, Sanae; Ohsawa, Ikuroh; Ohta, Shigeo; Ohno, Makoto; Mikami, Toshio

2010-08-25

Chronic stress impairs cognitive function and hippocampal neurogenesis. This impairment is attributed to increases in oxidative stress, which result in the accumulation of lipid peroxide. On the other hand, voluntary exercise enhances cognitive function, hippocampal neurogenesis, and antioxidant capacity in normal animals. However, the effects of voluntary exercise on cognitive function, neurogenesis, and antioxidants in stressed mice are unclear. This study was designed to investigate whether voluntary exercise cures stress-induced impairment of cognitive function accompanied by improvement of hippocampal neurogenesis and increases in antioxidant capacity. Stressed mice were exposed to chronic restraint stress (CRS), which consisted of 12h immobilization daily and feeding in a small cage, for 8 weeks. Exercised mice were allowed free access to a running wheel during their exposure to CRS. At the 6th week, cognitive function was examined using the Morris water maze (MWM) test. Daily voluntary exercise restored stress-induced impairment of cognitive function and the hippocampal cell proliferation of newborn cells but not cell survival. Voluntary exercise increased insulin-like growth factor 1 (IGF-1) protein and mRNA expression in the cerebral cortex and liver, respectively. In addition, CRS resulted in a significant increase in the number of 4-hydrosynonenal (4-HNE)-positive cells in the hippocampal dentate gyrus; whereas, voluntary exercise inhibited it and enhanced glutathione s-transferases (GST) activity in the brain. These findings suggest that voluntary exercise attenuated the stress-induced impairment of cognitive function accompanied by improvement of cell proliferation in the dentate gyrus. This exercise-induced improvement was attributed to exercise-induced enhancement of IGF-1 protein and GST activity in the brain. Copyright 2010 Elsevier B.V. All rights reserved.
Biomechanical study of tarsometatarsal joint fusion using finite element analysis.

PubMed

Wang, Yan; Li, Zengyong; Zhang, Ming

2014-11-01

Complications of surgeries in foot and ankle bring patients with severe sufferings. Sufficient understanding of the internal biomechanical information such as stress distribution, contact pressure, and deformation is critical to estimate the effectiveness of surgical treatments and avoid complications. Foot and ankle is an intricate and synergetic system, and localized intervention may alter the functions to the adjacent components. The aim of this study was to estimate biomechanical effects of the TMT joint fusion using comprehensive finite element (FE) analysis. A foot and ankle model consists of 28 bones, 72 ligaments, and plantar fascia with soft tissues embracing all the segments. Kinematic information and ground reaction force during gait were obtained from motion analysis. Three gait instants namely the first peak, second peak and mid-stance were simulated in a normal foot and a foot with TMT joint fusion. It was found that contact pressure on plantar foot increased by 0.42%, 19% and 37%, respectively after TMT fusion compared with normal foot walking. Navico-cuneiform and fifth meta-cuboid joints sustained 27% and 40% increase in contact pressure at second peak, implying potential risk of joint problems such as arthritis. Von Mises stress in the second metatarsal bone increased by 22% at midstance, making it susceptible to stress fracture. This study provides biomechanical information for understanding the possible consequences of TMT joint fusion. Copyright © 2014 IPEM. Published by Elsevier Ltd. All rights reserved.
Physical Properties Of Acupuncture Needles: Do Disposable Acupuncture Needles Break With Normal Use

DTIC Science & Technology

2016-06-01

Lamb shank, which has complexity of tendon, fascia, and bone, was used to mimic human tissue. The needles (n=10) were stressed in the tissue substitute...needles were re-imaged after stressing and visually assessed. RESULTS: Only one manufacturing scuff mark was noted out of 90 needles before stress ...testing. Needles buckled but did not break when they were stressed beyond normal clinical use. No cracks or fractures were noted after stress
Risk stratification using stress echocardiography: incremental prognostic value over historic, clinical, and stress electrocardiographic variables across a wide spectrum of bayesian pretest probabilities for coronary artery disease.

PubMed

Bangalore, Sripal; Gopinath, Devi; Yao, Siu-Sun; Chaudhry, Farooq A

2007-03-01

We sought to evaluate the risk stratification ability and incremental prognostic value of stress echocardiography over historic, clinical, and stress electrocardiographic (ECG) variables, over a wide spectrum of bayesian pretest probabilities of coronary artery disease (CAD). Stress echocardiography is an established technique for the diagnosis of CAD. However, data on incremental prognostic value of stress echocardiography over historic, clinical, and stress ECG variables in patients with known or suggested CAD is limited. We evaluated 3259 patients (60 +/- 13 years, 48% men) undergoing stress echocardiography. Patients were grouped into low (<15%), intermediate (15-85%), and high (>85%) pretest CAD likelihood subgroups using standard software. The historical, clinical, stress ECG, and stress echocardiographic variables were recorded for the entire cohort. Follow-up (2.7 +/- 1.1 years) for confirmed myocardial infarction (n = 66) and cardiac death (n = 105) was obtained. For the entire cohort, an ischemic stress echocardiography study confers a 5.0 times higher cardiac event rate than the normal stress echocardiography group (4.0% vs 0.8%/y, P < .0001). Furthermore, Cox proportional hazard regression model showed incremental prognostic value of stress echocardiography variables over historic, clinical, and stress ECG variables across all pretest probability subgroups (global chi2 increased from 5.1 to 8.5 to 20.1 in the low pretest group, P = .44 and P = .01; from 20.9 to 28.2 to 116 in the intermediate pretest group, P = .47 and P < .0001; and from 17.5 to 36.6 to 61.4 in the high pretest group, P < .0001 for both groups). A normal stress echocardiography portends a benign prognosis (<1% event rate/y) in all pretest probability subgroups and even in patients with high pretest probability and yields incremental prognostic value over historic, clinical, and stress ECG variables across all pretest probability subgroups. The best incremental value is, however, in the intermediate pretest probability subgroup.
Static and kinetic friction of granite at high normal stress

USGS Publications Warehouse

Byerlee, J.D.

1970-01-01

Frictional sliding on ground surfaces of granite, angle of sliding planes 30?? and 45??, was investigated as a function of confining pressure. Over the normal stress range of 2-12 kb, the static frictional shear stress ??s follows the relationship ??s = 0??5 + 0?? ??n and the kinetic frictional shear stress ??k was calculated to be ??k = 0??25 + 0??47 ??n. ?? 1970.
Surplus dietary tryptophan reduces plasma cortisol and noradrenaline concentrations and enhances recovery after social stress in pigs.

PubMed

Koopmans, Sietse Jan; Ruis, Marko; Dekker, Ruud; van Diepen, Hans; Korte, Mechiel; Mroz, Zdzislaw

2005-07-21

Social stress occurs in intensive pig farming due to aggressive behavior. This stress may be reduced at elevated dietary levels of tryptophan (TRP). In this study, we compared the effects of high (13.2%) vs. normal (3.4%) dietary TRP to large neutral amino acid (LNAA) ratios on behavior and stress hormones in catheterized pigs ( approximately 50 kg BW), which were exposed to social stress by placing them twice into the territory of a dominant pig ( approximately 60 kg) for 15 min. Pre-stress plasma TRP concentrations were 156+/-15 vs. 53+/-6 micromol/l (p<0.01) in pigs on the high vs. normal TRP diets, respectively. Pre-stress plasma cortisol and noradrenaline concentrations were twofold (p<0.01) and 1.4-fold (p<0.05) lower but plasma adrenaline concentration was similar in pigs on the high vs. normal TRP diets, respectively. During the social confrontations, pigs on the high vs. normal TRP diets show a tendency towards reduced active avoidance behavior (3.2+/-1.1 vs. 6.7+/-1.2 min, p<0.1) but their physical activity (8.5+/-0.6 vs. 10.2+/-0.8 min) and aggressive attitude towards the dominant pig (11+/-3 vs. 7+/-2 times biting) were similar. Immediate (+5 min) post-stress plasma cortisol, noradrenaline and adrenaline responses were similar among dietary groups. After the social confrontations, the post-stress plasma cortisol, noradrenaline and adrenaline concentrations and/or curves (from +5 min to 2 h) were lower/steeper (p<0.05) in pigs on the high vs. normal TRP diets. In summary, surplus TRP in diets for pigs (1) does not significantly affect behavior when exposed to social stress, (2) reduces basal plasma cortisol and noradrenaline concentrations, (3) does not affect the immediate hormonal response to stress, and (4) reduces the long-term hormonal response to stress. In general, pigs receiving high dietary TRP were found to be less affected by stress.
What is eating you? Stress and the drive to eat.

PubMed

Groesz, Lisa M; McCoy, Shannon; Carl, Jenna; Saslow, Laura; Stewart, Judith; Adler, Nancy; Laraia, Barbara; Epel, Elissa

2012-04-01

Non-human animal studies demonstrate relationships between stress and selective intake of palatable food. In humans, exposure to laboratory stressors and self-reported stress are associated with greater food intake. Large studies have yet to examine chronic stress exposure and eating behavior. The current study assessed the relationship between stress (perceived and chronic), drive to eat, and reported food frequency intake (nutritious food vs. palatable non-nutritious food) in women ranging from normal weight to obese (N=457). Greater reported stress, both exposure and perception, was associated with indices of greater drive to eat-including feelings of disinhibited eating, binge eating, hunger, and more ineffective attempts to control eating (rigid restraint; r's from .11 to .36, p's<.05). These data suggest that stress exposure may lead to a stronger drive to eat and may be one factor promoting excessive weight gain. Relationships between stress and eating behavior are of importance to public health given the concurrent increase in reported stress and obesity rates. Copyright Â© 2011 Elsevier Ltd. All rights reserved.
Enhancement of allergic skin wheal responses in patients with atopic eczema/dermatitis syndrome by playing video games or by a frequently ringing mobile phone.

PubMed

Kimata, H

2003-06-01

Playing video games causes physical and psychological stress, including increased heart rate and blood pressure and aggression-related feelings. Use of mobile phones is very popular in Japan, and frequent ringing is a common and intrusive part of Japanese life. Atopic eczema/dermatitis syndrome is often exacerbated by stress. Stress increases serum IgE levels, skews cytokine pattern towards Th2 type, enhances allergen-induced skin wheal responses, and triggers mast cell degranulation via substance P, vasoactive intestinal peptide and nerve growth factor. (1). In the video game study, normal subjects (n = 25), patients with allergic rhinitis (n = 25) or atopic eczema/dermatitis syndrome (n = 25) played a video game (STREET FIGHTER II) for 2 h. Before and after the study, allergen-induced wheal responses, plasma levels of substance P, vasoactive intestinal peptide and nerve growth factor, and in vitro production of total IgE, antihouse dust mite IgE and cytokines were measured. (2). In the mobile phone study, normal subjects (n = 27), patients with allergic rhinitis (n = 27) or atopic eczema/dermatitis syndrome (n = 27) were exposed to 30 incidences of ringing mobile phones during 30 min. Before and after the study, allergen-induced wheal responses, plasma levels of substance P, vasoactive intestinal peptide and nerve growth factor were measured. Playing video games had no effect on the normal subjects or the patients with allergic rhinitis. In contrast, playing video games significantly enhanced allergen-induced skin wheal responses and increased plasma levels of substance P, vasoactive intestinal peptide and nerve growth factors in the patients with atopic eczema/dermatitis syndrome. Moreover, playing video games enhanced in vitro production of total IgE and anti-house dust mite IgE with concomitant increased production of IL-4, IL-10 and IL-13 and decreased production of IFN-gamma and IL-12 in the patients with atopic eczema/dermatitis syndrome. However, exposure to frequently ringing mobile phones significantly enhanced allergen-induced skin wheal responses, plasma levels of substance P, vasoactive intestinal peptide and nerve growth factors in the patients with atopic eczema/dermatitis syndrome, but not in the normal subjects or the patients with allergic rhinitis. Playing video games enhanced allergic responses with a concomitant increased release of substance P, vasoactive intestinal peptide and nerve growth factor, and skewing of the cytokine pattern toward Th2 type in the patients with atopic eczema/dermatitis syndrome. In addition, exposure to frequently ringing mobile phones also enhanced allergic responses with a concomitant increased release of substance P, vasoactive intestinal peptide and nerve growth factor Collectively, high technology causes stress, which in turn may aggravate symptoms of atopic eczema/dermatitis syndrome.
Acute Knockdown of Uncoupling Protein-2 Increases Uncoupling via the Adenine Nucleotide Transporter and Decreases Oxidative Stress in Diabetic Kidneys

PubMed Central

Friederich-Persson, Malou; Aslam, Shakil; Nordquist, Lina; Welch, William J.; Wilcox, Christopher S.; Palm, Fredrik

2012-01-01

Increased O2 metabolism resulting in chronic hypoxia is common in models of endstage renal disease. Mitochondrial uncoupling increases O2 consumption but the ensuing reduction in mitochondrial membrane potential may limit excessive oxidative stress. The present study addressed the hypothesis that mitochondrial uncoupling regulates mitochondria function and oxidative stress in the diabetic kidney. Isolated mitochondria from kidney cortex of control and streptozotocin-induced diabetic rats were studied before and after siRNA knockdown of uncoupling protein-2 (UCP-2). Diabetes resulted in increased UCP-2 protein expression and UCP-2-mediated uncoupling, but normal mitochondria membrane potential. This uncoupling was inhibited by GDP, which also increased the membrane potential. siRNA reduced UCP-2 protein expression in controls and diabetics (−30–50%), but paradoxically further increased uncoupling and markedly reduced the membrane potential. This siRNA mediated uncoupling was unaffected by GDP but was blocked by ADP and carboxyatractylate (CAT). Mitochondria membrane potential after UCP-2 siRNA was unaffected by GDP but increased by CAT. This demonstrated that further increased mitochondria uncoupling after siRNA towards UCP-2 is mediated through the adenine nucleotide transporter (ANT). The increased oxidative stress in the diabetic kidney, manifested as increased thiobarbituric acids, was reduced by knocking down UCP-2 whereas whole-body oxidative stress, manifested as increased circulating malondialdehyde, remained unaffected. All parameters investigated were unaffected by scrambled siRNA. In conclusion, mitochondrial uncoupling via UCP-2 regulates mitochondria membrane potential in diabetes. However, blockade of the diabetes-induced upregulation of UCP- 2 results in excessive uncoupling and reduced oxidative stress in the kidney via activation of ANT. PMID:22768304
Accelerated deflation promotes homogeneous airspace liquid distribution in the edematous lung.

PubMed

Wu, You; Nguyen, Tam L; Perlman, Carrie E

2017-04-01

Edematous lungs contain regions with heterogeneous alveolar flooding. Liquid is trapped in flooded alveoli by a pressure barrier-higher liquid pressure at the border than in the center of flooded alveoli-that is proportional to surface tension, T Stress is concentrated between aerated and flooded alveoli, to a degree proportional to T Mechanical ventilation, by cyclically increasing T , injuriously exacerbates stress concentrations. Overcoming the pressure barrier to redistribute liquid more homogeneously between alveoli should reduce stress concentration prevalence and ventilation injury. In isolated rat lungs, we test whether accelerated deflation can overcome the pressure barrier and catapult liquid out of flooded alveoli. We generate a local edema model with normal T by microinfusing liquid into surface alveoli. We generate a global edema model with high T by establishing hydrostatic edema, which does not alter T , and then gently ventilating the edematous lungs, which increases T at 15 cmH 2 O transpulmonary pressure by 52%. Thus ventilation of globally edematous lungs increases T , which should increase stress concentrations and, with positive feedback, cause escalating ventilation injury. In the local model, when the pressure barrier is moderate, accelerated deflation causes liquid to escape from flooded alveoli and redistribute more equitably. Flooding heterogeneity tends to decrease. In the global model, accelerated deflation causes liquid escape, but-because of elevated T -the liquid jumps to nearby, aerated alveoli. Flooding heterogeneity is unaltered. In pulmonary edema with normal T , early ventilation with accelerated deflation might reduce the positive feedback mechanism through which ventilation injury increases over time. NEW & NOTEWORTHY We introduce, in the isolated rat lung, a new model of pulmonary edema with elevated surface tension. We first generate hydrostatic edema and then ventilate gently to increase surface tension. We investigate the mechanical mechanisms through which 1 ) ventilation injures edematous lungs and 2 ) ventilation with accelerated deflation might lessen ventilation injury. Copyright © 2017 the American Physiological Society.

Accelerated deflation promotes homogeneous airspace liquid distribution in the edematous lung

PubMed Central

Wu, You; Nguyen, Tam L.

2017-01-01

Edematous lungs contain regions with heterogeneous alveolar flooding. Liquid is trapped in flooded alveoli by a pressure barrier—higher liquid pressure at the border than in the center of flooded alveoli—that is proportional to surface tension, T. Stress is concentrated between aerated and flooded alveoli, to a degree proportional to T. Mechanical ventilation, by cyclically increasing T, injuriously exacerbates stress concentrations. Overcoming the pressure barrier to redistribute liquid more homogeneously between alveoli should reduce stress concentration prevalence and ventilation injury. In isolated rat lungs, we test whether accelerated deflation can overcome the pressure barrier and catapult liquid out of flooded alveoli. We generate a local edema model with normal T by microinfusing liquid into surface alveoli. We generate a global edema model with high T by establishing hydrostatic edema, which does not alter T, and then gently ventilating the edematous lungs, which increases T at 15 cmH2O transpulmonary pressure by 52%. Thus ventilation of globally edematous lungs increases T, which should increase stress concentrations and, with positive feedback, cause escalating ventilation injury. In the local model, when the pressure barrier is moderate, accelerated deflation causes liquid to escape from flooded alveoli and redistribute more equitably. Flooding heterogeneity tends to decrease. In the global model, accelerated deflation causes liquid escape, but—because of elevated T—the liquid jumps to nearby, aerated alveoli. Flooding heterogeneity is unaltered. In pulmonary edema with normal T, early ventilation with accelerated deflation might reduce the positive feedback mechanism through which ventilation injury increases over time. NEW & NOTEWORTHY We introduce, in the isolated rat lung, a new model of pulmonary edema with elevated surface tension. We first generate hydrostatic edema and then ventilate gently to increase surface tension. We investigate the mechanical mechanisms through which 1) ventilation injures edematous lungs and 2) ventilation with accelerated deflation might lessen ventilation injury. PMID:27979983
Effect of the combination of metformin hydrochloride and melatonin on oxidative stress before and during pregnancy, and biochemical and histopathological analysis of the livers of rats after treatment for polycystic ovary syndrome

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lemos, Ana Janaina Jeanine M.; Unit of Medical and Health Sciences, Universidade Federal de Campina Grande; Peixoto, Christina A.

The aim of the present study was to analyze the effect of a combination of metformin hydrochloride and melatonin on oxidative stress together with a biochemical and histopathological analysis of the livers of Wistar rats induced with PCOS. The results indicated that a combination of the drugs was more effective in the reduction of plasmatic levels of liver enzyme alanine aminotransferase, nitric oxide and total glutathione, and decreased the inflammatory response and histopathological damage, producing results that were significantly similar to animals from the control group. A mixture of the drugs produced more effective results against liver toxicity caused bymore » PCOS, encouraging the normalization of biochemical parameters. During pregnancy, there was reduced oxidative stress compared to monotherapeutic use of these drugs. Interestingly, the combination of the drugs caused a physiological reaction similar to responses identified in healthy rats without induction of the PCOS control group. However, the clinical and physiological effectiveness of the combination should be further explored, especially with respect to the possible side effects on offspring. - Highlights: • Studies have documented increased oxidative stress in patients with PCOS. • It has been noted that women with PCOS have a high prevalence of liver alterations. • Liver disease in pregnancy may be pre-existing increasing the newborn mortality. • Metformin/melatonin associated reduced oxidative stress in liver in pregnant rats. • Association of metformin/melatonin normalizes hepatic biochemical parameters.« less
Tenascin-C and mechanotransduction in the development and diseases of cardiovascular system

PubMed Central

Imanaka-Yoshida, Kyoko; Aoki, Hiroki

2014-01-01

Living tissue is composed of cells and extracellular matrix (ECM). In the heart and blood vessels, which are constantly subjected to mechanical stress, ECM molecules form well-developed fibrous frameworks to maintain tissue structure. ECM is also important for biological signaling, which influences various cellular functions in embryonic development, and physiological/pathological responses to extrinsic stimuli. Among ECM molecules, increased attention has been focused on matricellular proteins. Matricellular proteins are a growing group of non-structural ECM proteins highly up-regulated at active tissue remodeling, serving as biological mediators. Tenascin-C (TNC) is a typical matricellular protein, which is highly expressed during embryonic development, wound healing, inflammation, and cancer invasion. The expression is tightly regulated, dependent on the microenvironment, including various growth factors, cytokines, and mechanical stress. In the heart, TNC appears in a spatiotemporal-restricted manner during early stages of development, sparsely detected in normal adults, but transiently re-expressed at restricted sites associated with tissue injury and inflammation. Similarly, in the vascular system, TNC is strongly up-regulated during embryonic development and under pathological conditions with an increase in hemodynamic stress. Despite its intriguing expression pattern, cardiovascular system develops normally in TNC knockout mice. However, deletion of TNC causes acute aortic dissection (AAD) under strong mechanical and humoral stress. Accumulating reports suggest that TNC may modulate the inflammatory response and contribute to elasticity of the tissue, so that it may protect cardiovascular tissue from destructive stress responses. TNC may be a key molecule to control cellular activity during development, adaptation, or pathological tissue remodeling. PMID:25120494
5-HT1A/1B Receptors as Targets for Optimizing Pigmentary Responses in C57BL/6 Mouse Skin to Stress

PubMed Central

Wu, Hua-Li; Pang, Si-Lin; Liu, Qiong-Zhen; Wang, Qian; Cai, Min-Xuan; Shang, Jing

2014-01-01

Stress has been reported to induce alterations of skin pigmentary response. Acute stress is associated with increased turnover of serotonin (5-hydroxytryptamine; 5-HT) whereas chronic stress causes a decrease. 5-HT receptors have been detected in pigment cells, indicating their role in skin pigmentation. To ascertain the precise role of 5-HT in stress-induced pigmentary responses, C57BL/6 mice were subjected to chronic restraint stress and chronic unpredictable mild stress (CRS and CUMS, two models of chronic stress) for 21 days, finally resulting in abnormal pigmentary responses. Subsequently, stressed mice were characterized by the absence of a black pigment in dorsal coat. The down-regulation of tyrosinase (TYR) and tyrosinase-related proteins (TRP1 and TRP2) expression in stressed skin was accompanied by reduced levels of 5-HT and decreased expression of 5-HT receptor (5-HTR) system. In both murine B16F10 melanoma cells and normal human melanocytes (NHMCs), 5-HT had a stimulatory effect on melanin production, dendricity and migration. When treated with 5-HT in cultured hair follicles (HFs), the increased expression of melanogenesis-related genes and the activation of 5-HT1A, 1B and 7 receptors also occurred. The serum obtained from stressed mice showed significantly decreased tyrosinase activity in NHMCs compared to that from nonstressed mice. The decrease in tyrosinase activity was further augmented in the presence of 5-HTR1A, 1B and 7 antagonists, WAY100635, SB216641 and SB269970. In vivo, stressed mice received 5-HT precursor 5-hydroxy-l-tryptophan (5-HTP), a member of the class of selective serotonin reuptake inhibitors (fluoxetine; FX) and 5-HTR1A/1B agonists (8-OH-DPAT/CP94253), finally contributing to the normalization of pigmentary responses. Taken together, these data strongly suggest that the serotoninergic system plays an important role in the regulation of stress-induced depigmentation, which can be mediated by 5-HT1A/1B receptors. 5-HT and 5-HTR1A/1B may constitute novel targets for therapy of skin hypopigmentation disorders, especially those worsened with stress. PMID:24586946
Fluid Pressure in the Shallow Plate Interface at the Nankai Trough Subduction Zone

NASA Astrophysics Data System (ADS)

Tobin, H. J.; Saffer, D.

2003-12-01

The factors controlling the occurrence, magnitude, and other characteristics of great earthquakes is a fundamental outstanding question in fault physics. Pore fluid pressure is perhaps the most critical yet poorly known parameter governing the strength and seismogenic character of plate boundary faults, but unfortunately cannot be directly inferred through available geophysical sensing methods. Moreover, true in situ fluid pressure has proven difficult to measure even in boreholes. At the Nankai Trough, several hundred meters of sediment are subducted beneath the frontal portion of the accretionary prism. The up-dip portion of the plate interface is therefore hosted in these fine-grained marine sedimentary rocks. ODP Leg 190 and 196 showed that these rapidly-loaded underthrust sediments are significantly overpressured near the deformation front. Here, we attempt to quantitatively infer porosity, pore pressure, and effective normal stress at the plate interface at depths currently inaccessible to drilling. Using seismic reflection interval velocity calibrated at the boreholes to porosity, we quantitatively infer pore pressure to ˜ 20 km down-dip of the deformation front, to a plate interface depth of ˜ 6 km. We have developed a Nankai-specific velocity-porosity transform using ODP cores and logs. We use this function to derive a porosity profile for each of two down-dip seismic sections extracted from a 3-D dataset from the Cape Muroto region. We then calculate pore fluid pressure and effective vertical (fault-normal) stress for the underthrust sediment section using a compaction disequilibrium approach and core-based consolidation test data. Because the pore fluid pressure at the fault interface is likely controlled by that of the top of the underthrust section, this calculation represents a quantitative profile of effective stress and pore pressure at the plate interface. Results show that seismic velocity and porosity increase systematically downdip in the underthrust section, but the increase is suppressed relative to that expected from normally consolidating sediments. The computed pore pressure increases landward from an overpressure ratio (λ * = hydrostatic pressure divided by the lithostatic overburden) of ˜ 0.6 at the deformation front to ˜ 0.77 where sediments have been subducted 15 km. The results of this preliminary analysis suggest that a 3-dimensional mapping of predicted effective normal stress in the seismic data volume is possible.
Partial Genetic Deletion of Neuregulin 1 Modulates the Effects of Stress on Sensorimotor Gating, Dendritic Morphology, and HPA Axis Activity in Adolescent Mice

PubMed Central

Chohan, Tariq W.; Boucher, Aurelie A.; Spencer, Jarrah R.; Kassem, Mustafa S.; Hamdi, Areeg A.; Karl, Tim; Fok, Sandra Y.; Bennett, Maxwell R.; Arnold, Jonathon C.

2014-01-01

Stress has been linked to the pathogenesis of schizophrenia. Genetic variation in neuregulin 1 (NRG1) increases the risk of developing schizophrenia and may help predict which high-risk individuals will transition to psychosis. NRG1 also modulates sensorimotor gating, a schizophrenia endophenotype. We used an animal model to demonstrate that partial genetic deletion of Nrg1 interacts with stress to promote neurobehavioral deficits of relevance to schizophrenia. Nrg1 heterozygous (HET) mice displayed greater acute stress-induced anxiety-related behavior than wild-type (WT) mice. Repeated stress in adolescence disrupted the normal development of higher prepulse inhibition of startle selectively in Nrg1 HET mice but not in WT mice. Further, repeated stress increased dendritic spine density in pyramidal neurons of the medial prefrontal cortex (mPFC) selectively in Nrg1 HET mice. Partial genetic deletion of Nrg1 also modulated the adaptive response of the hypothalamic-pituitary-adrenal axis to repeated stress, with Nrg1 HET displaying a reduced repeated stress-induced level of plasma corticosterone than WT mice. Our results demonstrate that Nrg1 confers vulnerability to repeated stress-induced sensorimotor gating deficits, dendritic spine growth in the mPFC, and an abberant endocrine response in adolescence. PMID:24442851
Environmental stress induces trinucleotide repeat mutagenesis in human cells

PubMed Central

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

2015-01-01

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

PubMed

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

2015-03-24

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

PubMed

Hunter, Ian; Soler, Amanda; Joseph, Gregory; Hutcheson, Brenda; Bradford, Chastity; Zhang, Frank Fan; Potter, Barry; Proctor, Spencer; Rocic, Petra

2017-04-01

Thirty percent of the world population is diagnosed with metabolic syndrome. High-fat/high-sucrose (HF/HS) diet (Western diet) correlates with metabolic syndrome prevalence. We characterized effects of the HF/HS diet on vascular (arterial stiffness, vasoreactivity, and coronary collateral development) and cardiac (echocardiography) function, oxidative stress, and inflammation in a rat model of metabolic syndrome (JCR rats). Furthermore, we determined whether male versus female animals were affected differentially by the Western diet. Cardiovascular function in JCR male rats was impaired versus normal Sprague-Dawley (SD) rats. HF/HS diet compromised cardiovascular (dys)function in JCR but not SD male rats. In contrast, cardiovascular function was minimally impaired in JCR female rats on normal chow. However, cardiovascular function in JCR female rats on the HF/HS diet deteriorated to levels comparable to JCR male rats on the HF/HS diet. Similarly, oxidative stress was markedly increased in male but not female JCR rats on normal chow but was equally exacerbated by the HF/HS diet in male and female JCR rats. These results indicate that the Western diet enhances oxidative stress and cardiovascular dysfunction in metabolic syndrome and eliminates the protective effect of female sex on cardiovascular function, implying that both males and females with metabolic syndrome are at equal risk for cardiovascular disease. NEW & NOTEWORTHY Western diet abolished protective effect of sex against cardiovascular disease (CVD) development in premenopausal animals with metabolic syndrome. Western diet accelerates progression of CVD in male and female animals with preexisting metabolic syndrome but not normal animals. Exacerbation of baseline oxidative stress correlates with accelerated progression of CVD in metabolic syndrome animals on Western diet. Copyright © 2017 the American Physiological Society.
Cardiovascular function in male and female JCR:LA-cp rats: effect of high-fat/high-sucrose diet

PubMed Central

Hunter, Ian; Soler, Amanda; Joseph, Gregory; Hutcheson, Brenda; Bradford, Chastity; Zhang, Frank Fan; Potter, Barry; Proctor, Spencer

2017-01-01

Thirty percent of the world population is diagnosed with metabolic syndrome. High-fat/high-sucrose (HF/HS) diet (Western diet) correlates with metabolic syndrome prevalence. We characterized effects of the HF/HS diet on vascular (arterial stiffness, vasoreactivity, and coronary collateral development) and cardiac (echocardiography) function, oxidative stress, and inflammation in a rat model of metabolic syndrome (JCR rats). Furthermore, we determined whether male versus female animals were affected differentially by the Western diet. Cardiovascular function in JCR male rats was impaired versus normal Sprague-Dawley (SD) rats. HF/HS diet compromised cardiovascular (dys)function in JCR but not SD male rats. In contrast, cardiovascular function was minimally impaired in JCR female rats on normal chow. However, cardiovascular function in JCR female rats on the HF/HS diet deteriorated to levels comparable to JCR male rats on the HF/HS diet. Similarly, oxidative stress was markedly increased in male but not female JCR rats on normal chow but was equally exacerbated by the HF/HS diet in male and female JCR rats. These results indicate that the Western diet enhances oxidative stress and cardiovascular dysfunction in metabolic syndrome and eliminates the protective effect of female sex on cardiovascular function, implying that both males and females with metabolic syndrome are at equal risk for cardiovascular disease. NEW & NOTEWORTHY Western diet abolished protective effect of sex against cardiovascular disease (CVD) development in premenopausal animals with metabolic syndrome. Western diet accelerates progression of CVD in male and female animals with preexisting metabolic syndrome but not normal animals. Exacerbation of baseline oxidative stress correlates with accelerated progression of CVD in metabolic syndrome animals on Western diet. PMID:28087518
Transcriptome-Wide Identification of Reference Genes for Expression Analysis of Soybean Responses to Drought Stress along the Day.

PubMed

Marcolino-Gomes, Juliana; Rodrigues, Fabiana Aparecida; Fuganti-Pagliarini, Renata; Nakayama, Thiago Jonas; Ribeiro Reis, Rafaela; Bouças Farias, Jose Renato; Harmon, Frank G; Correa Molinari, Hugo Bruno; Correa Molinari, Mayla Daiane; Nepomuceno, Alexandre

2015-01-01

The soybean transcriptome displays strong variation along the day in optimal growth conditions and also in response to adverse circumstances, like drought stress. However, no study conducted to date has presented suitable reference genes, with stable expression along the day, for relative gene expression quantification in combined studies on drought stress and diurnal oscillations. Recently, water deficit responses have been associated with circadian clock oscillations at the transcription level, revealing the existence of hitherto unknown processes and increasing the demand for studies on plant responses to drought stress and its oscillation during the day. We performed data mining from a transcriptome-wide background using microarrays and RNA-seq databases to select an unpublished set of candidate reference genes, specifically chosen for the normalization of gene expression in studies on soybean under both drought stress and diurnal oscillations. Experimental validation and stability analysis in soybean plants submitted to drought stress and sampled during a 24 h timecourse showed that four of these newer reference genes (FYVE, NUDIX, Golgin-84 and CYST) indeed exhibited greater expression stability than the conventionally used housekeeping genes (ELF1-β and β-actin) under these conditions. We also demonstrated the effect of using reference candidate genes with different stability values to normalize the relative expression data from a drought-inducible soybean gene (DREB5) evaluated in different periods of the day.
Molecular imaging of enhanced Na + expression in the liver of total sleep deprived rats by TOF-SIMS

NASA Astrophysics Data System (ADS)

Chang, Hung-Ming; Chen, Bo-Jung; Wu, Un-In; Huang, Yi-Lun; Mai, Fu-Der

2008-12-01

Sleep disorder is associated with metabolic disturbances, which was related to oxidative stress and subsequently sodium overload. Since liver plays important roles in metabolic regulation, present study is aimed to determine whether hepatic sodium, together with oxidative stress, would significantly alter after total sleep deprivation (TSD). Sodium ion was investigated by time-of-flight secondary ion mass spectrometry (TOF-SIMS). Parameter for oxidative stress was examined by heat shock protein-25 (HSP-25) immunohistochemistry. TOF-SIMS spectrum indicated that hepatic Na +/K + ratio counting as 82.41 ± 9.5 was obtained in normal rats. Sodium ions were distributed in hepatocytes with several aggregations. However, following TSD, the intensity for Na +/K + ratio was relatively increased (101.94 ± 6.9) and signals for sodium image were strongly expressed throughout hepatocytes without spatial localization. Quantitative analysis revealed that HSP-25 staining intensity is 1.78 ± 0.27 in TSD rats, which was significantly higher than that of normal ones (0.68 ± 0.15). HSP-25 augmentation suggests that hepatocytes suffer from oxidative stress following TSD. Concerning oxidative stress induced sodium overload would impair metabolic function; enhanced hepatic sodium expression after TSD may be a major cause of TSD relevant metabolic diseases.
Laforin Prevents Stress-Induced Polyglucosan Body Formation and Lafora Disease Progression in Neurons

PubMed Central

Wang, Yin; Ma, Keli; Wang, Peixiang; Baba, Otto; Zhang, Helen; Parent, Jack M.; Zheng, Pan; Liu, Yang; Minassian, Berge A; Liu, Yan

2013-01-01

Glycogen, the largest cytosolic macromolecule, is soluble because of intricate construction generating perfect hydrophilic-surfaced spheres. Little is known about neuronal glycogen function and metabolism, though progress is accruing through the neurodegenerative epilepsy Lafora disease (LD) proteins laforin and malin. Neurons in LD exhibit Lafora bodies (LBs), large accumulations of malconstructed insoluble glycogen (polyglucosans). We demonstrated that the laforin-malin complex reduces LBs and protects neuronal cells against endoplasmic reticulum stress-induced apoptosis. We now show that stress induces polyglucosan formation in normal neurons in culture and in brain. This is mediated by increased glucose-6-phosphate allosterically hyperactivating muscle glycogen synthase (GS1), and is followed by activation of the glycogen digesting enzyme glycogen phosphorylase. In the absence of laforin, stress-induced polyglucosans are undigested and accumulate into massive LBs, and in laforin-deficient mice stress drastically accelerates LB accumulation and LD. The mechanism through which laforin-malin mediates polyglucosan degradation remains unclear but involves GS1 dephosphorylation by laforin. Our work uncovers the presence of rapid polyglucosan metabolism as part of the normal physiology of neuroprotection. We propose that deficiency in the degradative phase of this metabolism, leading to LB accumulation and resultant seizure predisposition and neurodegeneration, underlies LD. PMID:23546741
Stress response in Caenorhabditis elegans caused by optical tweezers: wavelength, power, and time dependence.

PubMed Central

Leitz, Guenther; Fällman, Erik; Tuck, Simon; Axner, Ove

2002-01-01

Optical tweezers have emerged as a powerful technique for micromanipulation of living cells. Although the technique often has been claimed to be nonintrusive, evidence has appeared that this is not always the case. This work presents evidence that near-infrared continuous-wave laser light from optical tweezers can produce stress in Caenorhabditis elegans. A transgenic strain of C. elegans, carrying an integrated heat-shock-responsive reporter gene, has been exposed to laser light under a variety of illumination conditions. It was found that gene expression was most often induced by light of 760 nm, and least by 810 nm. The stress response increased with laser power and irradiation time. At 810 nm, significant gene expression could be observed at 360 mW of illumination, which is more than one order of magnitude above that normally used in optical tweezers. In the 700-760-nm range, the results show that the stress response is caused by photochemical processes, whereas at 810 nm, it mainly has a photothermal origin. These results give further evidence that the 700-760-nm wavelength region is unsuitable for optical tweezers and suggest that work at 810 nm at normal laser powers does not cause stress at the cellular level. PMID:11916877
Acoustic microscopy analyses to determine good vs. failed tissue engineered oral mucosa under normal or thermally stressed culture conditions.

PubMed

Winterroth, Frank; Lee, Junho; Kuo, Shiuhyang; Fowlkes, J Brian; Feinberg, Stephen E; Hollister, Scott J; Hollman, Kyle W

2011-01-01

This study uses scanning acoustic microscopy (SAM) ultrasonic profilometry to determine acceptable vs. failed tissue engineered oral mucosa. Specifically, ex vivo-produced oral mucosal equivalents (EVPOMEs) under normal or thermally stressed culture conditions were scanned with the SAM operator blinded to the culture conditions. As seeded cells proliferate, they fill in and smooth out the surface irregularities; they then stratify and produce a keratinized protective upper layer. Some of these transformations could alter backscatter of ultrasonic signals and in the case of the thermally stressed cells, produce backscatter similar to an unseeded device. If non-invasive ultrasonic monitoring could be developed, then tissue cultivation could be adjusted to measure biological variations in the stratified surface. To create an EVPOME device, oral mucosa keratinocytes were seeded onto acellular cadaveric dermis. Two sets of EVPOMEs were cultured: one at physiological temperature 37 °C and the other at 43 °C. The specimens were imaged with SAM consisting of a single-element transducer: 61 MHz center frequency, 32 MHz bandwidth, 1.52 f#. Profilometry for the stressed and unseeded specimens showed higher surface irregularities compared to unstressed specimens. Elevated thermal stress retards cellular differentiation, increasing root mean square values; these results show that SAM can potentially monitor cell/tissue development.
A Bed-Deformation Experiment Beneath Engabreen, Norway

NASA Astrophysics Data System (ADS)

Iverson, N. R.; Hooyer, T. S.; Fischer, U. H.; Cohen, D.; Jackson, M.; Moore, P. L.; Lappegard, G.; Kohler, J.

2001-12-01

Although deformation of sediment beneath ice masses may contribute to their motion and may sometimes enable fast glacier flow, both the kinematics and mechanics of deformation are controversial. This controversy stems, in part, from subglacial measurements that are difficult to interpret. Measurements have been made either beneath ice margins or remotely through boreholes with interpretive limitations caused by uncertain instrument position and performance, uncertain sediment thickness and bed geometry, and unknown disturbance of the bed and stress state by drilling. We have used a different approach made possible by the Svartisen Subglacial Laboratory, which enables human access to the bed of Engabreen, Norway, beneath 230 m of temperate ice. A trough (2 m x 1.5 m x 0.4 m deep) was blasted in the rock bed and filled with sediment (75 percent sand and gravel, 20 percent silt, 5 percent clay). Instruments were placed in the sediment to record shear deformation (tiltmeters), dilation and contraction, total normal stress, and pore-water pressure. Pore pressure was manipulated by feeding water to the base of the sediment with a high-pressure pump, operated in a rock tunnel 4 m below the bed surface. After irregular deformation during closure of ice on the sediment, shear deformation and volume change stopped, and total normal stress became constant at 2.2 MPa. Subsequent pump tests, which lasted several hours, induced pore-water pressures greater than 70 percent of the total normal stress and resulted in shear deformation over most of the sediment thickness with attendant dilation. Ice separated from the sediment when effective normal stress was lowest, arresting shear deformation. Displacement profiles during pump tests were similar to those observed by Boulton and co-workers at Breidamerkurjökull, Iceland, with rates of shear strain increasing upward toward the glacier sole. Such deformation does not require viscous deformation resistance and is expected in a Coulomb material, a model for till advocated by B. Kamb.
Microbubbles and Blood Brain Barrier Opening: A Numerical Study on Acoustic Emissions and Wall Stress Predictions

PubMed Central

Goertz, David E.; Hynynen, Kullervo

2015-01-01

Focused ultrasound with microbubbles is an emerging technique for blood brain barrier (BBB) opening. Here, a comprehensive theoretical model of a bubble-fluid-vessel system has been developed which accounts for the bubble’s non-spherical oscillations inside a microvessel, and its resulting acoustic emissions. Numerical simulations of unbound and confined encapsulated bubbles were performed to evaluate the effect of the vessel wall on acoustic emissions and vessel wall stresses. Using a Marmottant shell model, the normalized second harmonic to fundamental emissions first decreased as a function of pressure (>50 kPa) until reaching a minima ("transition point") at which point they increased. The transition point of unbound compared to confined bubble populations occurred at different pressures and was associated with an accompanying increase in shear and circumferential wall stresses. As the wall stresses depend on the bubble to vessel wall distance, the stresses were evaluated for bubbles with their wall at a constant distance to a flat wall. As a result, the wall stresses were bubble size and frequency dependent and the peak stress values induced by bubbles larger than resonance remained constant versus frequency at a constant mechanical index. PMID:25546853
Electrical and mechanical characteristics of fully transparent IZO thin-film transistors on stress-relieving bendable substrates

NASA Astrophysics Data System (ADS)

Park, Sukhyung; Cho, Kyoungah; Oh, Hyungon; Kim, Sangsig

2016-10-01

In this study, we report the electrical and mechanical characteristics of fully transparent indium zinc oxide (IZO) thin-film transistors (TFTs) fabricated on stress-relieving bendable substrates. An IZO TFT on a stress-relieving substrate can operate normally at a bending radius of 6 mm, while an IZO TFT on a normal plastic substrate fails to operate normally at a bending radius of 15 mm. A plastic island with high Young's modulus embedded on a soft elastomer layer with low Young's modulus plays the role of a stress-relieving substrate for the operation of the bent IZO TFT. The stress and strain distributions over the IZO TFT will be analyzed in detail in this paper.
Airplane Stress Analysis

NASA Technical Reports Server (NTRS)

Zahm, A F; Crook, L H

1918-01-01

Report presents stress analysis of individual components of an airplane. Normal and abnormal loads, sudden loads, simple stresses, indirect simple stresses, resultant unit stress, repetitive and equivalent stress, maximum steady load and stress are considered.
Impact of composite plates: Analysis of stresses and forces

NASA Technical Reports Server (NTRS)

Moon, F. C.; Kim, B. S.; Fang-Landau, S. R.

1976-01-01

The foreign object damage resistance of composite fan blades was studied. Edge impact stresses in an anisotropic plate were first calculated incorporating a constrained layer damping model. It is shown that a very thin damping layer can dramatically decrease the maximum normal impact stresses. A multilayer model of a composite plate is then presented which allows computation of the interlaminar normal and shear stresses. Results are presented for the stresses due to a line impact load normal to the plane of a composite plate. It is shown that significant interlaminar tensile stresses can develop during impact. A computer code was developed for this problem using the fast Fourier transform. A marker and cell computer code were also used to investigate the hydrodynamic impact of a fluid slug against a wall or turbine blade. Application of fluid modeling of bird impact is reviewed.

Stress promotes generalization of older but not recent threat memories

PubMed Central

Dunsmoor, Joseph E.; Otto, A. Ross; Phelps, Elizabeth A.

2017-01-01

Stress broadly affects the ability to regulate emotions and may contribute to generalization of threat-related behaviors to harmless stimuli. Behavioral generalization also tends to increase over time as memory precision for recent events gives way to more gist-like representations. Thus, acute stress coupled with a delay in time from a negative experience may be a strong predictor of the transition from normal to generalized fear expression. Here, we investigated the effect of a single-episode acute stressor on generalization of aversive learning when stress is administered either immediately after an aversive learning event or following a delay. In a between-subjects design, healthy adult volunteers underwent threat (fear) conditioning using a tone-conditioned stimulus paired with an electric shock to the wrist and another tone not paired with shock. Behavioral generalization was tested to a range of novel tones either on the same day (experiment 1) or 24 h later (experiment 2) and was preceded by either an acute stress induction or a control task. Anticipatory sympathetic arousal [i.e., skin conductance responses (SCRs)] and explicit measures of shock expectancy served as dependent measures. Stress administered shortly after threat conditioning did not affect behavioral generalization. In contrast, stress administered following a delay led to heightened arousal and increased generalization of SCRs and explicit measures of shock expectancy. These findings show that acute stress increases generalization of older but not recent threat memories and have clinical relevance to understanding overgeneralization characteristics of anxiety and stress-related disorders. PMID:28784793
High efficiency versus maximal performance--the cause of oxidative stress in eukaryotes: a hypothesis.

PubMed

Kadenbach, Bernhard; Ramzan, Rabia; Vogt, Sebastian

2013-01-01

Degenerative diseases are in part based on elevated production of ROS (reactive oxygen species) in mitochondria, mainly during stress and excessive work under stress (strenuous exercise). The production of ROS increases with increasing mitochondrial membrane potential (ΔΨ(m)). A mechanism is described which is suggested to keep ΔΨ(m) at low values under normal conditions thus preventing ROS formation, but is switched off under stress and excessive work to maximize the rate of ATP synthesis, accompanied by decreased efficiency. Low ΔΨ(m) and low ROS production are suggested to occur by inhibition of respiration at high [ATP]/[ADP] ratios. The nucleotides interact with phosphorylated cytochrome c oxidase (COX), representing the step with the highest flux-control coefficient of mitochondrial respiration. At stress and excessive work neural signals are suggested to dephosphorylate the enzyme and abolish the control of COX activity (respiration) by the [ATP]/[ADP] ratio with consequent increase of ΔΨ(m) and ROS production. The control of COX by the [ATP]/[ADP] ratio, in addition, is proposed to increase the efficiency of ATP production via a third proton pumping pathway, identified in eukaryotic but not in prokaryotic COX. We conclude that 'oxidative stress' occurs when the control of COX activity by the [ATP]/[ADP] ratio is switched off via neural signals. 2012 Elsevier B.V. All rights reserved
Metabolic and oxidative stress markers in Wistar rats after 2 months on a high-fat diet.

PubMed

Auberval, Nathalie; Dal, Stéphanie; Bietiger, William; Pinget, Michel; Jeandidier, Nathalie; Maillard-Pedracini, Elisa; Schini-Kerth, Valérie; Sigrist, Séverine

2014-01-01

Metabolic syndrome is associated with an increased risk of cardiovascular and hepatic complications. Oxidative stress in metabolic tissues has emerged as a universal feature of metabolic syndrome and its co-morbidities. We aimed to develop a rapidly and easily induced model of metabolic syndrome in rats to evaluate its impact on plasma and tissue oxidative stress. Metabolic syndrome was induced in rats using a high-fat diet (HFD), and these rats were compared to rats fed a normal diet (ND) for 2 months. Metabolic control was determined by measuring body weight, blood glucose, triglycerides, lipid peroxidation and protein carbonylation in plasma. Insulinemia was evaluated through the measure of C-peptide. Histological analysis was performed on the pancreas, liver and blood vessels. After 2 months, the HFD induced an increase in body weight, insulin and triglycerides. Liver steatosis was also observed in the HFD group, which was associated with an increase in glycogen storage. In the pancreas, the HFD induced islet hyperplasia. Tissue oxidative stress was also increased in the liver, pancreas and blood vessels, but plasma oxidative stress remained unchanged. This paper reports the development of a fast and easy model of rat metabolic syndrome associated with tissue oxidative stress. This model may be a good tool for the biological validation of drugs or antioxidants to limit or prevent the complications of metabolic syndrome.
INDUCED SEISMICITY MECHANISM AT THE GEYSERS, CALIFORNIA.

USGS Publications Warehouse

Oppenheimer, David

1985-01-01

Induced microearthquake activity at The Geysers geothermal reservoir is observed in the vicinity of eight geothermal steam power units. The earthquakes do not align with mapped faults but occur adjacent to steam wells. The sense of motion as deduced from focal mechanisms is strike-slip to reverse in the upper 1 km of the reservoir and changes to strike-slip to oblique normal slip at greater depth because of the increased lithostatic load. Below 1 km the reservoir is undergoing horizontal extension. Alignment of P and T axes with the regional stress field suggests that contraction of the reservoir contributes the incremental stress perturbation to the regional stress field and causes microearthquakes.
Which is Superior, Doppler Velocimetry or Non-stress Test or Both in Predicting the Perinatal Outcome of High-Risk Pregnancies.

PubMed

Subramanian, Vijaya; Venkat, Janani; Dhanapal, Mohana

2016-10-01

To analyze which is superior, Doppler velocimetry or non-stress test or both by means of categorization into four groups and comparing the prediction of perinatal outcome in high-risk pregnancies like anemia, hypertensive disorders of pregnancies. This was a prospective study conducted at the Department of Obstetrics and Gynaecology, ISO KGH, Madras Medical College, Chennai, in the year 2014. Two hundred high-risk pregnancies like anemia, hypertensive disorders of pregnancy were included in the study. They were examined systematically, and Doppler velocimetry and non-stress test were done. The main vessels studied by Doppler were umbilical artery and middle cerebral artery, and the indices were calculated. The results of the non-stress test were interpreted as reactive and non-reactive. Based on the results of Doppler and non-stress test, the 200 cases were categorized into four groups and the results were analyzed. Among the 200 cases of high-risk pregnancies, those with a normal Doppler study and a reactive non-stress test had good perinatal outcome. When both were abnormal, there was a higher percentage of adverse outcome as compared to that of either Doppler alone being abnormal or non-stress test alone being non-reactive. It was also found that abnormal Doppler but with a reactive non-stress test had the advantage of prolonging the pregnancy and bringing a better outcome indicating that non-stress test is surely a good test of well-being. When Doppler was normal, but non-stress test was non-reactive, there was an increase in the rate of cesarean section. Each method of fetal surveillance reflects different aspect of maternal and fetal pathophysiology. Hence, combining these will help to bring out better perinatal outcome.
The expression of heat shock proteins 70 and 90 in pea seedlings under simulated microgravity conditions

NASA Astrophysics Data System (ADS)

Kozeko, L.

Microgravity is an abnormal and so stress factor for plants. Expression of known stress-related genes is appeared to implicate in the cell response to different kinds of stress. Heat shock proteins HSP70 and HSP90 are present in plant cells under the normal growth conditions and their quantity increases during stress. The effect of simulated microgravity on expression of HSP70 and HSP90 was studied in etiolated Pisum sativum seedlings grown on the horizontal clinostat (2 rpm) from seed germination for 3 days. Seedlings were also subjected to two other types of stressors: vertical clinorotatoin (2 rpm) and 2 h temperature elevation (40°C). HSPs' level was measured by ELISA. The quantity of both HSPs increased more than in three times in the seedlings on the horizontal clinostat in comparison with the stationary 1 g control. Vertical clinorotation also increased HSPs' level but less at about 20% than horizontal one. These effects were comparable with the influence of temperature elevation. The data presented suggest that simulated microgravity upregulate HSP70 and HSP90 expression. The increased HSPs' level might evidence the important functional role of these proteins in plant adaptation to microgravity. We are currently investigating the contribution of constitutive or inducible forms of the HSPs in this stress response.
Effects of roughness height, pressure and streamwise distance on stress profiles in the inner part of turbulent boundary layer over super-hydrophobic surfaces

NASA Astrophysics Data System (ADS)

Ling, Hangjian; Katz, Joseph; Srinivasan, Siddarth; McKinley, Gareth; Golovin, Kevin; Tuteja, Anish; Pillutla, Venkata; Abhijeet, Abhijeet; Choi, Wonjae

2016-11-01

Digital holographic microscopy is used for measuring the mean velocity and stress in the inner part of turbulent boundary layers over sprayed or etched super-hydrophobic surfaces (SHSs). The slip velocity and wall friction are calculated directly from the mean velocity and its gradient along with the Reynolds shear stress at the top of SHSs "roughness". Effects of the normalized rms roughness height krms+, facility pressure p and streamwise distance x from the beginning of SHSs on mean flow are examined. For krms+<1 and pkrms / σ <1 (σ is surface tension), the SHSs show 10-28% wall friction reduction, 15-30% slip velocity and λ+ = 3-10 slip length. Increasing Reynolds number and/or krms to establish krms+>1, and increasing p to achieve pkrms / σ >1 suppress the drag reduction, as roughness effects and associated near wall Reynolds stress increase. When the roughness effect is not dominant, the measurements agree with previous theoretical predictions of the relationships between drag reduction and slip velocity. The significance of spanwise slip relative to streamwise slip varies with the SHSs texture. Transitions from a smooth wall to a SHS involve overshoot of Reynolds stress and undershoot of viscous stress, trends that diminish with x. Sponsored by ONR.
Degradation and Characterization of Antimisting Kerosene (AMK).

DTIC Science & Technology

1982-12-01

EXECUTIVE SUMMARY ................................................... I. INTRODUCTION ............................................... 2 II. DEGRADER...P - density Pll-P22 - normal stress difference P12 - shear stress x EXECUTIVE SI-9ARY CSingle pass degradation of Antinmisting Kerosene (ANIK) has...While the jet thrust experiment is more difficult to execute and interpret than flow experiments, a quality control test based on normal stresses would
Effects of stress in early life on immune functions in rats with asthma and the effects of music therapy.

PubMed

Lu, Yanxia; Liu, Meng; Shi, Shousen; Jiang, Hong; Yang, Lejin; Liu, Xin; Zhang, Qian; Pan, Fang

2010-06-01

Although studies have shown that psychological stress has detrimental effects on bronchial asthma, there are few objective data on whether early-life stress, as early postnatal psychosocial environment, has a long-lasting effect on adult asthma and the potential pathophysiologic mechanism. This study aims to examine the effects on immune function and hypothalamic-pituitary-adrenal (HPA) axis responses in adult asthmatic rats that experienced stress in early life and the potential ameliorative effects of music therapy on these parameters. Forty male Wistar rat pups were randomly assigned to the asthma group, the adulthood-stressed asthma group, the childhood-stressed asthma group, the music group, and the control group. Restraint stress and Mozart's Sonata K.448 were applied to ovalbumin (OVA)-induced asthmatic rats to establish psychological stress and music therapy models. The levels of serum corticosterone were examined in both childhood after stress and adulthood after OVA challenge. Immune indicators in blood, lung, and brain tissues were measured after the last OVA challenge. Stress in both childhood and adulthood resulted in increases in leukocyte and eosinophil numbers and serum interleukin (IL)-4 levels. The adulthood-stressed group demonstrated increased corticosterone levels after challenge, whereas the childhood-stressed group showed increased corticosterone concentration in childhood but decreased level in adulthood. Central IL-1beta exhibited a similar tendency. Music group rats showed reduced serum IL-4 and corticosterone. Stress in childhood and adulthood resulted in different HPA axis responsiveness in the exacerbation of markers of asthma. These data provide the first evidence of the long-term normalizing effects of music on asthmatic rats.
Boron attenuates malathion-induced oxidative stress and acetylcholinesterase inhibition in rats.

PubMed

Coban, Funda Karabag; Ince, Sinan; Kucukkurt, Ismail; Demirel, Hasan Huseyin; Hazman, Omer

2015-10-01

Organophosphorus compounds cause oxidative stress and lead to alterations in antioxidant status in organisms. In this study, the effects of subchronic exposure to malathion and the protective effects of boron (B) were evaluated in 48 Wistar rats, which were divided equally into six groups. For 28 d, the control group received a normal diet and tap water, the corn oil group received a normal diet and 0.5 mL of corn oil by gastric gavage and the malathion group received a normal diet and malathion (100 mg/kg/d) by gastric gavage. During the same period, each of the three other groups received a different dosage of B (5, 10 and 20 mg/kg/d, respectively) and malathion (100 mg/kg/d) by gastric gavage. Malathion administration during the period increased malondialdehyde, nitric oxide and 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels, as well as markers of liver function, yet decreased acetylcholinesterase, reduced glutathione, superoxide dismutase, and catalase activities in blood, liver, kidney and brain tissues. Administration of B in a dose-dependent manner also reversed malathion-induced oxidative stress, lipid peroxidation (LPO) and antioxidant enzyme activity. Moreover, B exhibited protective action against malathion-induced histopathological changes in liver, kidney and brain tissues. These results demonstrate that, if used in a dose-dependent manner, B decreases malathion-induced oxidative stress, enhances the antioxidant defense mechanism and regenerates tissues in rats.
Use of hydrogen peroxide to assess the sperm susceptibility to oxidative stress in subjects presenting a normal semen profile.

PubMed

Misro, M M; Choudhury, L; Upreti, K; Gautam, D; Chaki, S P; Mahajan, A S; Babbar, R

2004-04-01

Human sperm susceptibility to oxidative stress is vital as it affects various characteristics of sperm function. In the present study, we report a simple, sensitive and quick method of assessing the capacity of the sperms to withstand increased oxidative stress. The basis for the test was derived from the fact that human sperms suspended in Ham's F-10 medium tend to lose the forward progressive motility when co-incubated with H(2)O(2) (600 microm). Replacement of the medium with seminal plasma (1: 1) was able to reduce the loss of sperm motility (40%). Retention of sperm motility in semen (0-30%) following 10 min of H(2)O(2) (600 microm) exposure was taken as the criteria for delineating the quality of sperm as poor, moderate, good and excellent types. The protocol was tested in 87 subjects presenting a normal semen profile. On the basis of this test, 44% of the semen samples were classified as poor and the rest as moderate, good or excellent. Lipid peroxidation was found higher in the sperms from the 'poor' category. Activities of superoxide dismutase and catalase were also significantly elevated in the seminal plasma of these subjects as compared with combined categories of good or excellent. The test described here can be used routinely in laboratory investigations to assess sperm susceptibility to oxidative stress in subjects presenting a normal semen profile.
Determination of stress intensity factors for interface cracks under mixed-mode loading

NASA Technical Reports Server (NTRS)

Naik, Rajiv A.; Crews, John H., Jr.

1992-01-01

A simple technique was developed using conventional finite element analysis to determine stress intensity factors, K1 and K2, for interface cracks under mixed-mode loading. This technique involves the calculation of crack tip stresses using non-singular finite elements. These stresses are then combined and used in a linear regression procedure to calculate K1 and K2. The technique was demonstrated by calculating three different bimaterial combinations. For the normal loading case, the K's were within 2.6 percent of an exact solution. The normalized K's under shear loading were shown to be related to the normalized K's under normal loading. Based on these relations, a simple equation was derived for calculating K1 and K2 for mixed-mode loading from knowledge of the K's under normal loading. The equation was verified by computing the K's for a mixed-mode case with equal and normal shear loading. The correlation between exact and finite element solutions is within 3.7 percent. This study provides a simple procedure to compute K2/K1 ratio which has been used to characterize the stress state at the crack tip for various combinations of materials and loadings. Tests conducted over a range of K2/K1 ratios could be used to fully characterize interface fracture toughness.
Dietary antioxidents and oxidative stress in predialysis chronic kidney disease patients

PubMed Central

L Gupta, Krishan; Sahni, Nancy

2012-01-01

Context Dietary antioxidants are important in protecting against human diseases. Oxidative stress, a non- traditional risk factors of cardio-vascular disease is far more prevalent in chronic kidney disease (CKD) patients than in normal subjects. Evidence Acquisitions Directory of Open Access Journals (DOAJ), Google Scholar, Pubmed (NLM), LISTA (EBSCO) and Web of Science have been searched. Results Oxidative stress could be a consequence of an increase in reactive oxygen species as well as a decrease in antioxidant defenses. Among the important factors that can be involved in triggering oxidative stress is insufficient dietary intake of antioxidants. Malnourished CKD patients are reported to have more oxidative stress than well nourished ones. Conclusions Moving beyond the importance of assessment of dietary protein and energy in pre dialysis CKD patients to the assessment of dietary antioxidants is of utmost importance to help combat enhanced oxidative stress levels in such patients. PMID:24475404
Dietary antioxidents and oxidative stress in predialysis chronic kidney disease patients.

PubMed

L Gupta, Krishan; Sahni, Nancy

2012-10-01

Dietary antioxidants are important in protecting against human diseases. Oxidative stress, a non- traditional risk factors of cardio-vascular disease is far more prevalent in chronic kidney disease (CKD) patients than in normal subjects. Directory of Open Access Journals (DOAJ), Google Scholar, Pubmed (NLM), LISTA (EBSCO) and Web of Science have been searched. Oxidative stress could be a consequence of an increase in reactive oxygen species as well as a decrease in antioxidant defenses. Among the important factors that can be involved in triggering oxidative stress is insufficient dietary intake of antioxidants. Malnourished CKD patients are reported to have more oxidative stress than well nourished ones. Moving beyond the importance of assessment of dietary protein and energy in pre dialysis CKD patients to the assessment of dietary antioxidants is of utmost importance to help combat enhanced oxidative stress levels in such patients.
Direct numerical simulation of particle alignment in viscoelastic fluids

NASA Astrophysics Data System (ADS)

Hulsen, Martien; Jaensson, Nick; Anderson, Patrick

2016-11-01

Rigid particles suspended in viscoelastic fluids under shear can align in string-like structures in flow direction. To unravel this phenomenon, we present 3D direct numerical simulations of the alignment of two and three rigid, non-Brownian particles in a shear flow of a viscoelastic fluid. The equations are solved on moving, boundary-fitted meshes, which are locally refined to accurately describe the polymer stresses around and in between the particles. A small minimal gap size between the particles is introduced. The Giesekus model is used and the effect of the Weissenberg number, shear thinning and solvent viscosity is investigated. Alignment of two and three particles is observed. Morphology plots have been created for various combinations of fluid parameters. Alignment is mainly governed by the value of the elasticity parameter S, defined as half of the ratio between the first normal stress difference and shear stress of the suspending fluid. Alignment appears to occur above a critical value of S, which decreases with increasing shear thinning. This result, together with simulations of a shear-thinning Carreau fluid, leads us to the conclusion that normal stress differences are essential for particle alignment to occur, but it is also strongly promoted by shear thinning.
High-fat diet effects on metabolic responses to chronic stress.

PubMed

Nemati, Marzieh; Zardooz, Homeira; Rostamkhani, Fatemeh; Abadi, Alireza; Foroughi, Forough

2017-07-01

High-fat diets and chronic stress are prevalent risk factors for various chronic diseases in modern societies. This study investigated the effect of high-fat diet on glucose-related metabolic responses to chronic foot-shock stress. Male rats were divided into high-fat diet (containing 54.21% saturated and 44.89% unsaturated fatty acids) and normal diet groups and then into stress and non-stress subgroups. The diets were applied for 5 weeks, and stress was induced during the last week of the diet course. Plasma levels of metabolic parameters, HOMA-IR index, intra-abdominal fat weight, and islets' insulin secretion were assessed. High-fat diet increased abdominal fat weight and plasma leptin, and insulin levels in response to stress without affecting HOMA-IR index and islets' insulin secretion. High proportion of unsaturated fat may not lead to deleterious metabolic responses; however combined with chronic stress has a synergistic and adverse effect on visceral adiposity and results in elevated plasma leptin.
Regulation of Adult Neurogenesis and Plasticity by (Early) Stress, Glucocorticoids, and Inflammation

PubMed Central

Lucassen, Paul J.; Oomen, Charlotte A.; Naninck, Eva F.G.; Fitzsimons, Carlos P.; van Dam, Anne-Marie; Czeh, Boldizsár; Korosi, Aniko

2015-01-01

Exposure to stress is one of the best-known negative regulators of adult neurogenesis (AN). We discuss changes in neurogenesis in relation to exposure to stress, glucocorticoid hormones, and inflammation, with a particular focus on early development and on lasting effects of stress. Although the effects of acute and mild stress on AN are generally brief and can be quickly overcome, chronic exposure or more severe forms of stress can induce longer lasting reductions in neurogenesis that can, however, in part, be overcome by subsequent exposure to exercise, drugs targeting the stress system, and some antidepressants. Exposure to stress, particularly during the sensitive period of early life, may (re)program brain plasticity, in particular, in the hippocampus. This may increase the risk to develop cognitive or anxiety symptoms, common to brain diseases like dementia and depression in which plasticity changes occur, and a normalization of neurogenesis may be required for a successful treatment response and recovery. PMID:26330520
Evaluation of In-Situ Stress Assessment from Deep Borehole in the Middle Coastal Plain and Its implication for Taiwan Tectonics

NASA Astrophysics Data System (ADS)

Yeh, E. C.; Li, W. C.; Chiang, T. C.; Lin, W.; Wang, T. T.; Yu, C. W.; Chiao, C. H.; Yang, M. W.

2014-12-01

Scientific study in deep boreholes has paid more attention as the demand of natural resources and waste disposal and risk evaluation of seismic hazard dramatically increases, such as petroleum exploitation, geothermal energy, carbon sequestration, nuclear waste disposal and seismogenic faulting. In the deep borehole geoengineering, knowledge of in-situ stress is essential for the design of drilling-casing plan. Understanding the relationship between fracture and in-situ stress is the key information to evaluate the potential of fracture seal/conduit and fracture reactivity. Also, assessment of in-situ stress can provide crucial information to investigate mechanism of earthquake faulting and stress variationfor earthquake cycles. Formations under the Coastal Plain in Taiwan have evaluated as saline-water formations with gently west-dipping and no distinct fractures endured by regional tectonics of arc-continental collision with N35W compression. The situation is characterized as a suitable place for carbon sequestration. In this study, we will integrate results from different in-situ stress determinations such as anelastic strain recovery (ASR), borehore breakout, hydraulic fracturing from a 3000m borehole of carbon sequestration testing site and further evaluate the seal feasibility and tectonic implication. Results of 30 ASR experiments between the depth of 1500m and 3000m showed the consistent normal faulting stress regime. Stress gradient of vertical stress, horizontal maximum stress and horizontal minimum stress with depth is estimated. Borehole breakout is not existed throughout 1500-3000m. The mean orientation of breakout is about 175deg and mean width of breakout is 84 deg. Based on rock mechanical data, maximum injection pressure of carbon sequestration can be evaulated. Furthermore, normal faulting stress regime is consistent with core observations and image logging, the horizontal maximum stress of 85deg inferred from breakout suggested that this place has been affected by the compression of oblique collision. The comparison of stress magnitudes estimated from ASR, breakout and hydraulic fracturing cab further verified current results.
Interacting Effects Induced by Two Neighboring Pits Considering Relative Position Parameters and Pit Depth

PubMed Central

Huang, Yongfang; Gang, Tieqiang; Chen, Lijie

2017-01-01

For pre-corroded aluminum alloy 7075-T6, the interacting effects of two neighboring pits on the stress concentration are comprehensively analyzed by considering various relative position parameters (inclination angle θ and dimensionless spacing parameter λ) and pit depth (d) with the finite element method. According to the severity of the stress concentration, the critical corrosion regions, bearing high susceptibility to fatigue damage, are determined for intersecting and adjacent pits, respectively. A straightforward approach is accordingly proposed to conservatively estimate the combined stress concentration factor induced by two neighboring pits, and a concrete application example is presented. It is found that for intersecting pits, the normalized stress concentration factor Ktnor increases with the increase of θ and λ and always reaches its maximum at θ = 90°, yet for adjacent pits, Ktnor decreases with the increase of λ and the maximum value appears at a slight asymmetric location. The simulations reveal that Ktnor follows a linear and an exponential relationship with the dimensionless depth parameter Rd for intersecting and adjacent cases, respectively. PMID:28772758
Anti-Apoptotic Protein Bcl-xL Expression in the Midbrain Raphe Region Is Sensitive to Stress and Glucocorticoids

PubMed Central

Kalinina, Tatyana S.; Bulygina, Veta V.; Lanshakov, Dmitry A.; Babluk, Ekaterina V.

2015-01-01

Anti-apoptotic proteins are suggested to be important for the normal health of neurons and synapses as well as for resilience to stress. In order to determine whether stressful events may influence the expression of anti-apoptotic protein Bcl-xL in the midbrain and specifically in the midbrain serotonergic (5-HT) neurons involved in neurobehavioral responses to adverse stimuli, adult male rats were subjected to short-term or chronic forced swim stress. A short-term stress rapidly increased the midbrain bcl-xl mRNA levels and significantly elevated Bcl-xL immunoreactivity in the midbrain 5-HT cells. Stress-induced increase in glucocorticoid secretion was implicated in the observed effect. The levels of bcl-xl mRNA were decreased after stress when glucocorticoid elevation was inhibited by metyrapone (MET, 150 mg/kg), and this decrease was attenuated by glucocorticoid replacement with dexamethasone (DEX; 0.2 mg/kg). Both short-term stress and acute DEX administration, in parallel with Bcl-xL, caused a significant increase in tph2 mRNA levels and slightly enhanced tryptophan hydroxylase immunoreactivity in the midbrain. The increasing effect on the bcl-xl expression was specific to the short-term stress. Forced swim repeated daily for 2 weeks led to a decrease in bcl-xl mRNA in the midbrain without any effects on the Bcl-xL protein expression in the 5-HT neurons. In chronically stressed animals, an increase in tph2 gene expression was not associated with any changes in tryptophan hydroxylase protein levels. Our findings are the first to demonstrate that both short-term stress and acute glucocorticoid exposures induce Bcl-xL protein expression in the midbrain 5-HT neurons concomitantly with the activation of the 5-HT synthesis pathway in these neurons. PMID:26624017

Changes in turbulence with rotation of the omnicarbon prosthesis.

PubMed

Travis, Brandon R; Nyboe, Camilla; Christensen, Thomas D; Smerup, Morten; Johansen, Peter; Nygaard, Hans; Hasenkam, J Michael

2007-01-01

This study was performed to determine whether annular plane orientation of the Omnicarbon aortic valve influences forward flow turbulence. The Omnicarbon prostheses was modified to allow in situ manual rotation of the valve when implanted in the aortic position of eight 90 kg pigs. Pulsed Doppler ultrasound was used to acquire velocity measurements at 17 locations within the cross-sectional area of the ascending aorta. In each animal, 12 valve rotations were tested in this manner. Reynolds normal stresses were estimated from the velocity measurements. High Reynolds normal stresses were concentrated between left and posterior-right sides of the aortic wall for all orientations studied. No trends in mean or maximum Reynolds normal stresses with respect to valve rotation were consistent in the experiments. Unlike previous experiments with the Medtronic-Hall tilting disc valve, these experiments showed no notable changes in Reynolds normal stress with respect to orientation of the Omnicarbon valve. This suggests that the tendency of turbulent stresses to change with tilting disc valve orientation may be dependent on valve design.
Evidence of an inflammatory-like response in non-normally pigmented tissues of two scleractinian corals

PubMed Central

Palmer, Caroline V; Mydlarz, Laura D; Willis, Bette L

2008-01-01

Increasing evidence of links between climate change, anthropogenic stress and coral disease underscores the importance of understanding the mechanisms by which reef-building corals resist infection and recover from injury. Cellular inflammation and melanin-producing signalling pathway are two mechanisms employed by invertebrates to remove foreign organisms such as pathogens, but they have not been recorded previously in scleractinian corals. This study demonstrates the presence of the phenoloxidase (PO) activating melanin pathway in two species of coral, Acropora millepora and a massive species of Porites, which both develop local pigmentation in response to interactions with a variety of organisms. l-DOPA (3-(3,4-dihydroxyphenyl)-l-alanine) substrate-based enzyme activation assays demonstrated PO activity in healthy tissues of both species and upregulation in pigmented tissues of A. millepora. Histological staining conclusively identified the presence of melanin in Porites tissues. These results demonstrate that the PO pathway is active in both coral species. Moreover, the upregulation of PO activity in areas of non-normal pigmentation in A. millepora and increased melanin production in pigmented Porites tissues suggest the presence of a generalized defence response to localized stress. Interspecific differences in the usage of pathways involved in innate immunity may underlie the comparative success of massive Porites sp. as long-lived stress tolerators. PMID:18700208
High self-perceived stress and many stressors, but normal diurnal cortisol rhythm, in adults with ADHD (attention-deficit/hyperactivity disorder).

PubMed

Hirvikoski, Tatja; Lindholm, Torun; Nordenström, Anna; Nordström, Anna-Lena; Lajic, Svetlana

2009-03-01

Attention-deficit/hyperactivity disorder (ADHD) in adults is associated with significant impairment in many life activities and may thus increase the risk of chronic stress in everyday life. We compared adults with a DSM-IV ADHD diagnosis (n=28) with healthy controls (n=28) regarding subjective stress and amounts of stressors in everyday life, diurnal salivary cortisol in the everyday environment and salivary cortisol before and after cognitive stress in a laboratory setting. The association between cortisol concentrations and impulsivity was also investigated. Consistent with assumptions, individuals with ADHD reported significantly more self-perceived stress than controls, and subjective stress correlated with the amount of stressors in everyday life. The two groups were comparable with respect to overall diurnal cortisol levels and rhythm, as well as in pre- and post-stress cortisol concentrations. Post-stress cortisol (but not baseline cortisol) concentration was positively correlated with impulsivity. The group with high post-stress cortisol also reported more symptoms of depression and anxiety, as well as self-perceived stress and stressors in every-day life. The diagnosis of ADHD significantly increased the risk of belonging to the group with high post-stress cortisol levels. The results in this study warrant a focus not only on the primary diagnosis of ADHD, but also calls for a broader assessment of stressors and subjective stress in everyday life, as well as support comprising stress management and coping skills.
Anti-oxidative effects of curcumin on immobilization-induced oxidative stress in rat brain, liver and kidney.

PubMed

Samarghandian, Saeed; Azimi-Nezhad, Mohsen; Farkhondeh, Tahereh; Samini, Fariborz

2017-03-01

Restraint stress has been indicated to induce oxidative damage in tissues. Several investigations have reported that curcumin (CUR) may have a protective effect against oxidative stress. The present study was designed to investigate the protective effects of CUR on restraint stress induced oxidative stress damage in the brain, liver and kidneys. For chronic restraint stress, rats were kept in the restrainers for 1h every day, for 21 consecutive days. The animals received systemic administrations of CUR daily for 21days. In order to evaluate the changes of the oxidative stress parameters following restraint stress, the levels of malondialdehyde (MDA), reduced glutathione (GSH), as well as antioxidant enzyme activities superoxide dismutase (SOD) glutathione peroxidase (GPx), glutathione reductase (GR) and catalase (CAT) were measured in the brain, liver and kidney of rats after the end of restraint stress. The restraint stress significantly increased MDA level, but decreased the level of GSH and activists of SOD, GPx, GR, and CAT the brain, liver and kidney of rats in comparison to the normal rats (P<0.001). Intraperitoneal administration of CUR significantly attenuated oxidative stress and lipid peroxidation, prevented apoptosis, and increased antioxidant defense mechanism activity in the tissues versus the control group (P<0.05). This study shows that CUR can prevent restraint stress-induced oxidative damage in the brain, liver and kidney of rats and propose that CUR may be useful agents against oxidative stress in the tissues. Copyright © 2016 Elsevier Masson SAS. All rights reserved.
The Chemical Chaperone, PBA, Reduces ER Stress and Autophagy and Increases Collagen IV α5 Expression in Cultured Fibroblasts From Men With X-Linked Alport Syndrome and Missense Mutations.

PubMed

Wang, Dongmao; Mohammad, Mardhiah; Wang, Yanyan; Tan, Rachel; Murray, Lydia S; Ricardo, Sharon; Dagher, Hayat; van Agtmael, Tom; Savige, Judy

2017-07-01

X-linked Alport syndrome (OMIM 301050) is caused by COL4A5 missense variants in 40% of families. This study examined the effects of chemical chaperone treatment (sodium 4-phenylbutyrate) on fibroblast cell lines derived from men with missense mutations. Dermal fibroblast cultures were established from 2 affected men and 3 normals. Proliferation rates were examined, the collagen IV α5 chain localized with immunostaining, and levels of the intra- and extracellular chains quantitated with an in-house enzyme-linked immunosorbent assay. COL4A5 mRNA was measured using quantitative reverse transcriptase polymerase chain reaction. Endoplasmic reticulum (ER) size was measured on electron micrographs and after HSP47 immunostaining. Markers of ER stress (ATF6, HSPA5, DDIT3), autophagy (ATG5, BECN1, ATG7), and apoptosis (CASP3, BAD, BCL 2 ) were also quantitated by quantitative reverse transcriptase polymerase chain reaction. Measurements were repeated after 48 hours of incubation with 10 mM sodium 4-phenylbutyrate acid. Both COL4A5 missense variants were associated with reduced proliferation rates on day 6 ( P = 0.01 and P = 0.03), ER enlargement, and increased mRNA for ER stress and autophagy (all P values < 0.05) when compared with normal. Sodium 4-phenylbutyrate treatment increased COL4A5 transcript levels ( P < 0.01), and reduced ER size ( P < 0.01 by EM and P < 0.001 by immunostaining), ER stress (p HSPA5 and DDIT3, all P values < 0.01) and autophagy (ATG7, P < 0.01). Extracellular collagen IV α5 chain was increased in the M1 line only ( P = 0.06). Sodium 4-phenylbutyrate increases collagen IV α5 mRNA levels, reduces ER stress and autophagy, and possibly facilitates collagen IV α5 extracellular transport. Whether these actions delay end-stage renal failure in men with X-linked Alport syndrome and missense mutations will only be determined with clinical trials.
Effect of hepatitis B virus infection on sperm quality and oxidative stress state of the semen of infertile males.

PubMed

Qian, Li; Li, Qiong; Li, Haibo

2016-09-01

The effects of hepatitis B virus (HBV) infection on sperm quality and oxidative stress state of the semen of infertile males remain undetermined. Normal males and 60 semen samples from infertile males (with or without HBV infection) were subjected to semen analysis. Semen volume, semen pH, sperm density, percentage of forward, movement of sperm, sperm activation rate, sperm survival rate, rate of normal sperm morphology of infertile males with HBV infection were significantly lower than those of infertile males without genital infection and of normal males (P<.05), while interleukin (IL)-17, IL-18, and malondialdehyde (MDA) levels in subjects with HBV infection were significantly higher than those of infertile males without genital infection and of normal males (P<.05). In patients with HBV infection, MDA level was found to be negatively correlated with semen quality, but positively correlated with semen IL-17 and IL-18 concentrations. HBV infection increased MDA level, induced abnormal expression of IL-17 and IL-18, and negatively affected male reproductive capacity, resulting in male infertility. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
TLR-2 IS INVOLVED IN AIRWAY EPITHELIAL CELL RESPONE TO AIR POLLUTION PARTICLES

EPA Science Inventory

Primary cultures of normal human airway epithelial cells (NHBE) respond to ambient air pollution particulate matter (PM) by increased production of the cytokine IL-8, and the induction of a number of oxidant stress response genes. Components of ambient air PM responsible for stim...
Chronic and acute effects of stress on energy balance: are there appropriate animal models?

PubMed

Harris, Ruth B S

2015-02-15

Stress activates multiple neural and endocrine systems to allow an animal to respond to and survive in a threatening environment. The corticotropin-releasing factor system is a primary initiator of this integrated response, which includes activation of the sympathetic nervous system and the hypothalamic-pituitary-adrenal (HPA) axis. The energetic response to acute stress is determined by the nature and severity of the stressor, but a typical response to an acute stressor is inhibition of food intake, increased heat production, and increased activity with sustained changes in body weight, behavior, and HPA reactivity. The effect of chronic psychological stress is more variable. In humans, chronic stress may cause weight gain in restrained eaters who show increased HPA reactivity to acute stress. This phenotype is difficult to replicate in rodent models where chronic psychological stress is more likely to cause weight loss than weight gain. An exception may be hamsters subjected to repeated bouts of social defeat or foot shock, but the data are limited. Recent reports on the food intake and body composition of subordinate members of group-housed female monkeys indicate that these animals have a similar phenotype to human stress-induced eaters, but there are a limited number of investigators with access to the model. Few stress experiments focus on energy balance, but more information on the phenotype of both humans and animal models during and after exposure to acute or chronic stress may provide novel insight into mechanisms that normally control body weight. Copyright © 2015 the American Physiological Society.
Nonlinear Reynolds stress model for turbulent shear flows

NASA Technical Reports Server (NTRS)

Barton, J. Michael; Rubinstein, R.; Kirtley, K. R.

1991-01-01

A nonlinear algebraic Reynolds stress model, derived using the renormalization group, is applied to equilibrium homogeneous shear flow and fully developed flow in a square duct. The model, which is quadratically nonlinear in the velocity gradients, successfully captures the large-scale inhomogeneity and anisotropy of the flows studied. The ratios of normal stresses, as well as the actual magnitudes of the stresses are correctly predicted for equilibrium homogeneous shear flow. Reynolds normal stress anisotropy and attendant turbulence driven secondary flow are predicted for a square duct. Profiles of mean velocity and normal stresses are in good agreement with measurements. Very close to walls, agreement with measurements diminishes. The model has the benefit of containing no arbitrary constants; all values are determined directly from the theory. It seems that near wall behavior is influenced by more than the large scale anisotropy accommodated in the current model. More accurate near wall calculations may well require a model for anisotropic dissipation.
Personality dimensions of people who suffer from visual stress.

PubMed

Hollis, J; Allen, P M; Fleischmann, D; Aulak, R

2007-11-01

Personality dimensions of participants who suffer from visual stress were compared with those of normal participants using the Eysenck Personality Inventory. Extraversion-Introversion scores showed no significant differences between the participants who suffered visual stress and those who were classified as normal. By contrast, significant differences were found between the normal participants and those with visual stress in respect of Neuroticism-Stability. These differences accord with Eysenck's personality theory which states that those who score highly on the neuroticism scale do so because they have a neurological system with a low threshold such that their neurological system is easily activated by external stimuli. The findings also relate directly to the theory of visual stress proposed by Wilkins which postulates that visual stress results from an excess of neural activity. The data may indicate that the excess activity is likely to be localised at particular neurological regions or neural processes.
Stress-strain state of the lithosphere in the southern Baikal region and northern Mongolia from data on seismic moments of earthquakes

NASA Astrophysics Data System (ADS)

Klyuchevskii, A. V.; Dem'yanovich, V. M.

2006-05-01

Investigation and understanding of the present-day geodynamic situation are of key importance for the elucidation of the laws and evolution of the seismic process in a seismically active region. In this work, seismic moments of nearly 26000 earthquakes with K p ≥ 7 ( M LH ≥ 2) that occurred in the southern Baikal region and northern Mongolia (SBNM) (48° 54°N, 96° 108°E) from 1968 through 1994 are determined from amplitudes and periods of maximum displacements in transverse body waves. The resulting set of seismic moments is used for spatial-temporal analysis of the stress-strain state of the SBNM lithosphere. The stress fields of the Baikal rift and the India-Asia collision zone are supposed to interact in the region studied. Since the seismic moment of a tectonic earthquake depends on the type of motion in the source, seismic moments and focal mechanisms of earthquakes belonging to four long-term aftershock and swarm clusters of shocks in the Baikal region were used to “calibrate” average seismic moments in accordance with the source faulting type. The study showed that the stress-strain state of the SBNM lithosphere is spatially inhomogeneous and nonstationary. A space-time discrepancy is observed in the formation of faulting types in sources of weak ( K p = 7 and 8) and stronger ( K p ≥ 9) earthquakes. This discrepancy is interpreted in terms of rock fracture at various hierarchical levels of ruptures on differently oriented general, regional, and local faults. A gradual increase and an abrupt, nearly pulsed, decrease in the vertical component of the stress field S v is a characteristic feature of time variations. The zones where the stress S v prevails are localized at “singular points” of the lithosphere. Shocks of various energy classes in these zones are dominated by the normal-fault slip mechanism. For earthquakes with K p = 9, the source faulting changes with depth from the strike-slip type to the normal-strike-slip and normal types, suggesting an increase in S v . On the whole, the results of this study are well consistent with the synergism of open unstable dissipative systems and are usable for interpreting the main observable variations in the stress-strain state of the lithosphere in terms of spatiotemporal variations in the vertical component of the stress field S v . This suggests the influence of rifting on the present-day geodynamic processes in the SBNM lithosphere.
2,3-Dihydro-3β-methoxy Withaferin-A Protects Normal Cells against Stress: Molecular Evidence of Its Potent Cytoprotective Activity.

PubMed

Chaudhary, Anupama; Kalra, Rajkumar S; Huang, Chuang; Prakash, Jay; Kaul, Sunil C; Wadhwa, Renu

2017-10-27

2,3-Dihydro-3β-methoxy withaferin-A (3βmWi-A) is a natural withanolide that is structurally close to withaferin-A (Wi-A), is cytotoxic to human cancer cells, and is a candidate anticancer natural compound. Using cell-based biochemical, molecular, and imaging assays, we report that Wi-A and 3βmWi-A possess contrasting activities. Whereas Wi-A caused oxidative stress to normal cells, 3βmWi-A was well tolerated at even 10-fold higher concentrations. Furthermore, it promoted survival and protected normal cells against oxidative, UV radiation, and chemical stresses. We provide molecular evidence that 3βmWi-A induces antistress and pro-survival signaling through activation of the pAkt/MAPK pathway. We demonstrate that 3βmWi-A (i) contrary to Wi-A is safe and possesses stress-relieving activity, (ii) when given subsequent to a variety of stress factors including Wi-A, protects normal cells against their toxicity, and (iii) is a vital compound that may guard normal cells against the toxicity associated with various targeted therapeutic regimes in clinical practice.
Oxidative Stress, Antioxidant Status and Neurodevelopmental Outcome in Neonates Born to Pre-eclamptic Mothers.

PubMed

Bharadwaj, Shruthi K; Vishnu Bhat, B; Vickneswaran, V; Adhisivam, B; Bobby, Zachariah; Habeebullah, S

2018-05-01

To measure the oxidative stress and antioxidant status in preeclamptic mother-newborn dyads and correlate them with neurodevelopmental outcome at one year of corrected age. This cohort study conducted in a tertiary care teaching hospital, south India included 71 preeclamptic and 72 normal mother-newborn dyads. Biochemical parameters including total antioxidant status (TAS), protein carbonyls and malondialdehyde levels (MDA) were measured in both maternal and cord blood. Infants in both the groups were followed up to one year of corrected age and neurodevelopmental assessment was done using Developmental Assessment Scale for Indian Infants (DASII). Correlation and multivariate regression analysis was done to evaluate the oxidative stress markers in relation to neurodevelopmental outcome. All oxidative stress markers were higher in maternal and cord blood of pre-ecclampsia group compared to the normal group. Maternal Total antioxidant status (M-TAS) was lower in pre-eclampsia group than normal group. More neonates in the pre-ecclampsia group were preterm and intrauterine growth restriction (IUGR) and had higher incidence of morbidities like respiratory distress syndrome (RDS) and early onset sepsis (EOS). Infants in the preeclampsia group had lower motor age, motor score and motor developmental quotient (MoDQ). On multivariate logistic regression analyses, lower M-TAS levels were strongly associated with poor neuro-motor outcomes at 1 y of corrected age. Maternal TAS with a cut-off value of 0.965 mmol/L had a sensitivity of 77.8% and specificity of 55.3% in predicting MoDQ <70 at one year corrected age in infants born to preeclamptic mothers. Oxidative stress is increased in preeclamptic mother-newborn dyads. Low maternal TAS levels are associated with poor neuro-motor outcomes. Maternal TAS in preeclampsia is useful in predicting poor motor development at one year corrected age.
Rupture Dynamics along Thrust Dipping Fault: Inertia Effects due to Free Surface Wave Interactions

NASA Astrophysics Data System (ADS)

Vilotte, J. P.; Scala, A.; Festa, G.

2017-12-01

We numerically investigate the dynamic interaction between free surface and up-dip, in-plane rupture propagation along thrust faults, under linear slip-weakening friction. With reference to shallow along-dip rupture propagation during large subduction earthquakes, we consider here low dip-angle fault configurations with fixed strength excess and depth-increasing initial stress. In this configuration, the rupture undergoes a break of symmetry with slip-induced normal stress perturbations triggered by the interaction with reflected waves from the free surface. We found that both body-waves - behind the crack front - and surface waves - at the crack front - can trigger inertial effects. When waves interact with the rupture before this latter reaches its asymptotic speed, the rupture can accelerate toward the asymptotic speed faster than in the unbounded symmetric case, as a result of these inertial effects. Moreover, wave interaction at the crack front also affects the slip rate generating large ground motion on the hanging wall. Imposing the same initial normal stress, frictional strength and stress drop while varying the static friction coefficient we found that the break of symmetry makes the rupture dynamics dependent on the absolute value of friction. The higher the friction the stronger the inertial effect both in terms of rupture acceleration and slip amount. When the contact condition allows the fault interface to open close to the free surface, the length of the opening zone is shown to depend on the propagation length, the initial normal stress and the static friction coefficient. These new results are shown to agree with analytical results of rupture propagation in bounded media, and open new perspectives for understanding the shallow rupture of large subduction earthquakes and tsunami sources.
Transcriptional targets of DAF-16 insulin signaling pathway protect C. elegans from extreme hypertonic stress.

PubMed

Lamitina, S Todd; Strange, Kevin

2005-02-01

All cells adapt to hypertonic stress by regulating their volume after shrinkage, by accumulating organic osmolytes, and by activating mechanisms that protect against and repair hypertonicity-induced damage. In mammals and nematodes, inhibition of signaling from the DAF-2/IGF-1 insulin receptor activates the DAF-16/FOXO transcription factor, resulting in increased life span and resistance to some types of stress. We tested the hypothesis that inhibition of insulin signaling in Caenorhabditis elegans also increases hypertonic stress resistance. Genetic inhibition of DAF-2 or its downstream target, the AGE-1 phosphatidylinositol 3-kinase, confers striking resistance to a normally lethal hypertonic shock in a DAF-16-dependent manner. However, insulin signaling is not inhibited by or required for adaptation to hypertonic conditions. Microarray studies have identified 263 genes that are transcriptionally upregulated by DAF-16 activation. We identified 14 DAF-16-upregulated genes by RNA interference screening that are required for age-1 hypertonic stress resistance. These genes encode heat shock proteins, proteins of unknown function, and trehalose synthesis enzymes. Trehalose levels were elevated approximately twofold in age-1 mutants, but this increase was insufficient to prevent rapid hypertonic shrinkage. However, age-1 animals unable to synthesize trehalose survive poorly under hypertonic conditions. We conclude that increased expression of proteins that protect eukaryotic cells against environmental stress and/or repair stress-induced molecular damage confers hypertonic stress resistance in C. elegans daf-2/age-1 mutants. Elevated levels of solutes such as trehalose may also function in a cytoprotective manner. Our studies provide novel insights into stress resistance in animal cells and a foundation for new studies aimed at defining molecular mechanisms underlying these essential processes.
Influence of environmental temperature on prolificacy of pigs.

PubMed

Wettemann, R P; Bazer, F W

1985-01-01

Exposure of male and female pigs to elevated ambient temperatures can result in reduced reproductive efficiency. When boars and gilts are exposed to heat stress, respiratory rates increase to enhance evaporative cooling because minimal sweating occurs. During early pregnancy, gilts are especially susceptible to heat stress. Decreased conception rates and reduced litter size occur when gilts are exposed to elevated ambient temperature during Days 0 to 16 after mating. Concentrations of progesterone in peripheral plasma were reduced during Days 13-19 after mating and luteal function was extended to Day 25 in heat-stressed gilts that did not conceive. Increased concentrations of oestradiol during Day 10 to 12 of heat stress may interfere with normal maternal recognition of pregnancy. Heat stress reduced the amount of embryonic tissue present at Day 16 of pregnancy but the protein synthetic activity of the tissue was not altered. Thus some embryos may be lost and a reduction in litter size may occur. The production of oestrogen by the conceptus and uterus is not altered on Day 16, after exposure to heat stress for the previous 8 days. These studies suggest that heat stress during early pregnancy can alter the reproductive endocrine system, especially the control of luteal function. In addition, heat stress may have a direct effect on embryo or conceptus development. Exposure of boars to elevated ambient temperatures causes reductions in semen quality, sperm output and fertility. About 5 weeks are required for boars to recover from the detrimental effects of heat stress and to produce semen with potential for maximal fertility. Increased temperature has an inhibitory effect on spermatid maturation and on testicular androgen biosynthesis. Improvements in reproductive performance can be achieved by increasing evaporative cooling of boars.
Fatigue behavior of a 2XXX series aluminum alloy reinforced with 15 vol Pct SiCp

NASA Astrophysics Data System (ADS)

Bonnen, J. J.; Allison, J. E.; Jones, J. W.

1991-05-01

The fatigue behavior of a naturally aged powder metallurgy 2xxx series aluminum alloy (Alcoa MB85) and a composite made of this alloy with 15 vol pct SiCp, has been investigated. Fatigue lives were determined using load-controlled axial testing of unnotched cylindrical samples. The influence of mean stress was determined at stress ratios of -1, 0.1, and 0.7. Mean stress had a significant influence on fatigue life, and this influence was consistent with that normally observed in metals. At each stress ratio, the incorporation of SiC reinforcement led to an increase in fatigue life at low and intermediate stresses. When considered on a strain-life basis, however, the composite materials had a somewhat inferior resistance to fatigue. Fatigue cracks initiated from several different microstructural features or defect types, but fatigue life did not vary significantly with the specific initiation site. As the fatigue crack advanced away from the fatigue crack initiation site, increasing numbers of SiC particles were fractured, in agreement with crack-tip process zone models.
Modeling viscous dissipation during vocal fold contact: the influence of tissue viscosity and thickness with implications for hydration.

PubMed

Erath, Byron D; Zañartu, Matías; Peterson, Sean D

2017-06-01

The mechanics of vocal fold contact during phonation is known to play a crucial role in both normal and pathological speech production, though the underlying physics is not well understood. Herein, a viscoelastic model of the stresses during vocal fold contact is developed. This model assumes the cover to be a poroelastic structure wherein interstitial fluid translocates in response to mechanical squeezing. The maximum interstitial fluid pressure is found to generally increase with decreasing viscous dissipation and/or decreasing tissue elasticity. A global minimum in the total contact stress, comprising interstitial fluid pressure and elastic stress in the tissue, is observed over the studied dimensionless parameter range. Interestingly, physiologically reasonable estimates for the governing parameters fall within this global minimum region. The model is validated against prior experimental and computational work, wherein the predicted contact stress magnitude and impact duration agree well with published results. Lastly, observations of the potential relationship between vocal fold hydration and increased risk of tissue damage are discussed based upon model predictions of stress as functions of cover layer thickness and viscosity.
Interference assembly and fretting wear analysis of hollow shaft.

PubMed

Han, Chuanjun; Zhang, Jie

2014-01-01

Fretting damage phenomenon often appears in the interference fit assembly. The finite element model of hollow shaft and shaft sleeve was established, and the equivalent stress and contact stress were computed after interference assembly. The assembly body of hollow shaft and shaft sleeve was in whirling bending load, and the contact status (sticking, sliding, and opening) and the distribution of stress along one typical contact line were computed under different loads, interferences, hollow degrees, friction coefficient, and wear quantity. Judgment formula of contact state was fixed by introducing the corrected coefficient k. The computation results showed that the "edge effect" appears in the contact surface after interference fit. The size of slip zone is unchanged along with the increase of bending load. The greater the interference value, the bigger the wear range. The hollow degree does not influence the size of stick zone but controls the position of the junction point of slip-open. Tangential contact stress increases with the friction coefficient, which has a little effect on normal contact stress. The relationship between open size and wear capacity is approximately linear.
Iodinated Contrast Media Can Induce Long-Lasting Oxidative Stress in Hemodialysis Patients

PubMed Central

Hwang, Seun Deuk; Kim, Yoon Ji; Lee, Sang Heun; Cho, Deok Kyu; Cho, Yun Hyeong; Moon, Sung Jin; Lee, Sang Choel

2013-01-01

Purpose Due to their comorbidities, dialysis patients have many chances to undergo radiologic procedures using iodinated contrast media. We aimed to assess time-sequenced blood oxidative stress level after contrast exposure in hemodialysis (HD) patients compared to those in the non-dialysis population. Materials and Methods We included 21 anuric HD patients [HD-coronary angiography (CAG) group] and 23 persons with normal renal function (nonHD-CAG group) scheduled for CAG, and assessed 4 oxidative stress markers [advanced oxidation protein products (AOPP); catalase; 8-hydroxydeoxyguanosine; and malondialdehyde] before and after CAG, and subsequently up to 28 days. Results In the nonHD-CAG group, only AOPP increased immediately after CAG and returned to baseline within one day. However, in the HD-CAG group, all four oxidative stress markers were significantly increased starting one day after CAG, and remained elevated longer than those in the nonHD-CAG group. Especially, AOPP level remained elevated for a month after contrast exposure. Conclusion Our study showed that iodinated contrast media induces severe and prolonged oxidative stress in HD patients. PMID:24142649

Calculation methods study on hot spot stress of new girder structure detail

NASA Astrophysics Data System (ADS)

Liao, Ping; Zhao, Renda; Jia, Yi; Wei, Xing

2017-10-01

To study modeling calculation methods of new girder structure detail's hot spot stress, based on surface extrapolation method among hot spot stress method, a few finite element analysis models of this welded detail were established by finite element software ANSYS. The influence of element type, mesh density, different local modeling methods of the weld toe and extrapolation methods was analyzed on hot spot stress calculation results at the toe of welds. The results show that the difference of the normal stress in the thickness direction and the surface direction among different models is larger when the distance from the weld toe is smaller. When the distance from the toe is greater than 0.5t, the normal stress of solid models, shell models with welds and non-weld shell models tends to be consistent along the surface direction. Therefore, it is recommended that the extrapolated point should be selected outside the 0.5t for new girder welded detail. According to the results of the calculation and analysis, shell models have good grid stability, and extrapolated hot spot stress of solid models is smaller than that of shell models. So it is suggested that formula 2 and solid45 should be carried out during the hot spot stress extrapolation calculation of this welded detail. For each finite element model under different shell modeling methods, the results calculated by formula 2 are smaller than those of the other two methods, and the results of shell models with welds are the largest. Under the same local mesh density, the extrapolated hot spot stress decreases gradually with the increase of the number of layers in the thickness direction of the main plate, and the variation range is within 7.5%.
BDNF in sleep, insomnia, and sleep deprivation.

PubMed

Schmitt, Karen; Holsboer-Trachsler, Edith; Eckert, Anne

2016-01-01

The protein brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin family of growth factors involved in plasticity of neurons in several brain regions. There are numerous evidence that BDNF expression is decreased by experiencing psychological stress and that, accordingly, a lack of neurotrophic support causes major depression. Furthermore, disruption in sleep homeostatic processes results in higher stress vulnerability and is often associated with stress-related mental disorders. Recently, we reported, for the first time, a relationship between BDNF and insomnia and sleep deprivation (SD). Using a biphasic stress model as explanation approach, we discuss here the hypothesis that chronic stress might induce a deregulation of the hypothalamic-pituitary-adrenal system. In the long-term it leads to sleep disturbance and depression as well as decreased BDNF levels, whereas acute stress like SD can be used as therapeutic intervention in some insomniac or depressed patients as compensatory process to normalize BDNF levels. Indeed, partial SD (PSD) induced a fast increase in BDNF serum levels within hours after PSD which is similar to effects seen after ketamine infusion, another fast-acting antidepressant intervention, while traditional antidepressants are characterized by a major delay until treatment response as well as delayed BDNF level increase. Key messages Brain-derived neurotrophic factor (BDNF) plays a key role in the pathophysiology of stress-related mood disorders. The interplay of stress and sleep impacts on BDNF level. Partial sleep deprivation (PSD) shows a fast action on BDNF level increase.
Vascular Nox (NADPH Oxidase) Compartmentalization, Protein Hyperoxidation, and Endoplasmic Reticulum Stress Response in Hypertension.

PubMed

Camargo, Livia L; Harvey, Adam P; Rios, Francisco J; Tsiropoulou, Sofia; Da Silva, Renée de Nazaré Oliveira; Cao, Zhenbo; Graham, Delyth; McMaster, Claire; Burchmore, Richard J; Hartley, Richard C; Bulleid, Neil; Montezano, Augusto C; Touyz, Rhian M

2018-07-01

Vascular Nox (NADPH oxidase)-derived reactive oxygen species and endoplasmic reticulum (ER) stress have been implicated in hypertension. However, relationships between these processes are unclear. We hypothesized that Nox isoforms localize in a subcellular compartment-specific manner, contributing to oxidative and ER stress, which influence the oxidative proteome and vascular function in hypertension. Nox compartmentalization (cell fractionation), O 2 - (lucigenin), H 2 O 2 (amplex red), reversible protein oxidation (sulfenylation), irreversible protein oxidation (protein tyrosine phosphatase, peroxiredoxin oxidation), and ER stress (PERK [protein kinase RNA-like endoplasmic reticulum kinase], IRE1α [inositol-requiring enzyme 1], and phosphorylation/oxidation) were studied in spontaneously hypertensive rat (SHR) vascular smooth muscle cells (VSMCs). VSMC proliferation was measured by fluorescence-activated cell sorting, and vascular reactivity assessed in stroke-prone SHR arteries by myography. Noxs were downregulated by short interfering RNA and pharmacologically. In SHR, Noxs were localized in specific subcellular regions: Nox1 in plasma membrane and Nox4 in ER. In SHR, oxidative stress was associated with increased protein sulfenylation and hyperoxidation of protein tyrosine phosphatases and peroxiredoxins. Inhibition of Nox1 (NoxA1ds), Nox1/4 (GKT137831), and ER stress (4-phenylbutyric acid/tauroursodeoxycholic acid) normalized SHR vascular reactive oxygen species generation. GKT137831 reduced IRE1α sulfenylation and XBP1 (X-box binding protein 1) splicing in SHR. Increased VSMC proliferation in SHR was normalized by GKT137831, 4-phenylbutyric acid, and STF083010 (IRE1-XBP1 disruptor). Hypercontractility in the stroke-prone SHR was attenuated by 4-phenylbutyric acid. We demonstrate that protein hyperoxidation in hypertension is associated with oxidative and ER stress through upregulation of plasmalemmal-Nox1 and ER-Nox4. The IRE1-XBP1 pathway of the ER stress response is regulated by Nox4/reactive oxygen species and plays a role in the hyperproliferative VSMC phenotype in SHR. Our study highlights the importance of Nox subcellular compartmentalization and interplay between cytoplasmic reactive oxygen species and ER stress response, which contribute to the VSMC oxidative proteome and vascular dysfunction in hypertension. © 2018 American Heart Association, Inc.
Further insights into normal aortic valve function: role of a compliant aortic root on leaflet opening and valve orifice area.

PubMed

Sripathi, Vangipuram Canchi; Kumar, Ramarathnam Krishna; Balakrishnan, Komarakshi R

2004-03-01

This study aims to find the fundamental differences in the mechanism of opening and closing of a normal aortic valve and a valve with a stiff root, using a dynamic finite element model. A dynamic, finite element model with time varying pressure was used in this study. Shell elements with linear elastic properties for the leaflet and root were used. Two different cases were analyzed: (1) normal leaflets inside a compliant root, and (2) normal leaflets inside a stiff root. A compliant aortic root contributes substantially to the smooth and symmetrical leaflet opening with minimal gradients. In contrast, the leaflet opening inside a stiff root is delayed, asymmetric, and wrinkled. However, this wrinkling is not associated with increased leaflet stresses. In compliant roots, the effective valve orifice area can substantially increase because of increased root pressure and transvalvular gradients. In stiff roots this effect is strikingly absent. A compliant aortic root contributes substantially to smooth and symmetrical leaflet opening with minimal gradients. The compliance also contributes much to the ability of the normal aortic valve to increase its effective valve orifice in response to physiologic demands of exercise. This effect is strikingly absent in stiff roots.
Tectonic implications of the 2017 Ayvacık (Çanakkale) earthquakes, Biga Peninsula, NW Turkey

NASA Astrophysics Data System (ADS)

Özden, Süha; Över, Semir; Poyraz, Selda Altuncu; Güneş, Yavuz; Pınar, Ali

2018-04-01

The west to southwestward motion of the Anatolian block results from the relative motions between the Eurasian, Arabian and African plates along the right-lateral North Anatolian Fault Zone in the north and left-lateral East Anatolian Fault Zone in the east. The Biga Peninsula is tectonically influenced by the Anatolian motion originating along the North Anatolian Fault Zone which splits into two main (northern and southern) branches in the east of Marmara region: the southern branch extends towards the Biga Peninsula which is characterized by strike-slip to oblique normal faulting stress regime in the central to northern part. The southernmost part of peninsula is characterized by a normal to oblique faulting stress regime. The analysis of both seismological and structural field data confirms the change of stress regime from strike-slip character in the center and north to normal faulting character in the south of peninsula where the earthquake swarm recently occurred. The earthquakes began on 14 January 2017 (Mw: 4.4) on Tuzla Fault and migrated southward along the Kocaköy and Babakale's stepped-normal faults of over three months. The inversion of focal mechanisms yields a normal faulting stress regime with an approximately N-S (N4°E) σ3 axis. The inversion of earthquakes occurring in central and northern Biga Peninsula and the north Aegean region gives a strike-slip stress regime with approximately WNW-ESE (N85°W) σ1 and NNE-SSW (N17°E) σ3 axis. The strike-slip stress regime is attributed to westward Anatolian motion, while the normal faulting stress regime is attributed to both the extrusion of Anatolian block and the slab-pull force of the subducting African plate along the Hellenic arc.
Stress distribution in composite flatwise tension test specimens

NASA Technical Reports Server (NTRS)

Scott, Curtis A.; Pereira, J. Michael

1993-01-01

A finite element analysis was conducted to determine the stress distribution in typical graphite/epoxy composite flat wise tension (FWT) specimens under normal loading conditions. The purpose of the analysis was to determine the relationship between the applied load and the stress in the sample to evaluate the validity of the test as a means of measuring the out-of-plane strength of a composite laminate. Three different test geometries and three different material lay ups were modeled. In all cases, the out-of-plane component of stress in the test section was found to be uniform, with no stress concentrations, and very close to the nominal applied stress. The stress in the sample was found to be three-dimensional, and the magnitude of in-plane normal and shear stresses varied with the anisotropy of the test specimen. However, in the cases considered here, these components of stress were much smaller than the out-of-plane normal stress. The geometry of the test specimen had little influence on the results. It was concluded that the flat wise tension test provides a good measure of the out-of-plane strength for the representative materials that were studied.
Interactions between Polygonal Normal Faults and Larger Normal Faults, Offshore Nova Scotia, Canada

NASA Astrophysics Data System (ADS)

Pham, T. Q. H.; Withjack, M. O.; Hanafi, B. R.

2017-12-01

Polygonal faults, small normal faults with polygonal arrangements that form in fine-grained sedimentary rocks, can influence ground-water flow and hydrocarbon migration. Using well and 3D seismic-reflection data, we have examined the interactions between polygonal faults and larger normal faults on the passive margin of offshore Nova Scotia, Canada. The larger normal faults strike approximately E-W to NE-SW. Growth strata indicate that the larger normal faults were active in the Late Cretaceous (i.e., during the deposition of the Wyandot Formation) and during the Cenozoic. The polygonal faults were also active during the Cenozoic because they affect the top of the Wyandot Formation, a fine-grained carbonate sedimentary rock, and the overlying Cenozoic strata. Thus, the larger normal faults and the polygonal faults were both active during the Cenozoic. The polygonal faults far from the larger normal faults have a wide range of orientations. Near the larger normal faults, however, most polygonal faults have preferred orientations, either striking parallel or perpendicular to the larger normal faults. Some polygonal faults nucleated at the tip of a larger normal fault, propagated outward, and linked with a second larger normal fault. The strike of these polygonal faults changed as they propagated outward, ranging from parallel to the strike of the original larger normal fault to orthogonal to the strike of the second larger normal fault. These polygonal faults hard-linked the larger normal faults at and above the level of the Wyandot Formation but not below it. We argue that the larger normal faults created stress-enhancement and stress-reorientation zones for the polygonal faults. Numerous small, polygonal faults formed in the stress-enhancement zones near the tips of larger normal faults. Stress-reorientation zones surrounded the larger normal faults far from their tips. Fewer polygonal faults are present in these zones, and, more importantly, most polygonal faults in these zones were either parallel or perpendicular to the larger faults.
Placental Induced Growth Factor (PIGf) in Coronary Artery Disease

NASA Technical Reports Server (NTRS)

Sundaresan, Alamelu; Carabello, Blaise; Mehta, Satish; Schlegel, Todd; Pellis, Neal; Ott, Mark; Pierson, Duane

2010-01-01

Our previous studies on normal human lymphocytes have shown a five-fold increase (p less than 0.001) in angiogenic inducers such as Placental Induced Growth Factor (PIGf) in physiologically stressful environments such as modeled microgravity, a space analog. This suggests de-regulation of cardiovascular signalling pathways indicated by upregulation of PIGf. In the current study, we measured PIGf in the plasma of 33 patients with and without coronary artery disease (CAD) to investigate whether such disease is associated with increased levels of PIGf. A control consisting of 31 sex matched apparently healthy subjects was also included in the study. We observed that the levels of PIGf in CAD patients were significantly increased compared to those in healthy control subjects (p less than 0.001) and usually increased beyond the clinical threshold level (greater than 27ng/L). The mechanisms leading to up-regulation of angiogenic factors and the adaptation of organisms to stressful environments such as isolation, high altitude, hypoxia, ischemia, microgravity, increased radiation, etc are presently unknown and require further investigation in spaceflight and these other physiologically stressed environments.
Insulin/IGF-1 signaling mutants reprogram ER stress response regulators to promote longevity.

PubMed

Henis-Korenblit, Sivan; Zhang, Peichuan; Hansen, Malene; McCormick, Mark; Lee, Seung-Jae; Cary, Michael; Kenyon, Cynthia

2010-05-25

When unfolded proteins accumulate in the endoplasmic reticulum (ER), the unfolded protein response is activated. This ER stress response restores ER homeostasis by coordinating processes that decrease translation, degrade misfolded proteins, and increase the levels of ER-resident chaperones. Ribonuclease inositol-requiring protein-1 (IRE-1), an endoribonuclease that mediates unconventional splicing, and its target, the XBP-1 transcription factor, are key mediators of the unfolded protein response. In this study, we show that in Caenorhabditis elegans insulin/IGF-1 pathway mutants, IRE-1 and XBP-1 promote lifespan extension and enhance resistance to ER stress. We show that these effects are not achieved simply by increasing the level of spliced xbp-1 mRNA and expression of XBP-1's normal target genes. Instead, in insulin/IGF-1 pathway mutants, XBP-1 collaborates with DAF-16, a FOXO-transcription factor that is activated in these mutants, to enhance ER stress resistance and to activate new genes that promote longevity.
Stress corrosion cracking of Alloy 600 and Alloy 690 in all volatile treated water at elevated temperatures. Final report. [PWR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Theus, G.J.; Emanuelson, R.H.

1983-05-01

This report describes a continuing study of stress corrosion cracking (SCC) of Inconel alloys 600 and 690 in all-volatile treated (AVT) water. Specimens of alloys 600 and 690 are being exposed to AVT water at 288/sup 0/, 332/sup 0/, 343/sup 0/, and 360/sup 0/C. Alloy 600 generally resists SCC in high-purity water under normal service conditions but is susceptible under other specific conditions. In general, mill-annealed alloy 600 is more susceptible than stress-relieved material. Susceptibility to SCC increases rapidly with increasing exposure temperature. Very high stresses (near or above yield) are required to induce cracking in AVT or other high-puritymore » waters. Most of the data presented in this report are for alloy 600; alloy 690 has not yet cracked. However, the program is being continued and will subsequently characterize the high-purity water cracking behavior, if any, of alloy 690.« less
Predictive value of myocardial perfusion single-photon emission computed tomography and the impact of renal function on cardiac death.

PubMed

Hakeem, Abdul; Bhatti, Sabha; Dillie, Kathryn Sullivan; Cook, Jeffrey R; Samad, Zainab; Roth-Cline, Michelle D; Chang, Su Min

2008-12-09

Patients with chronic kidney disease (CKD) have worse cardiovascular outcomes than those without CKD. The prognostic utility of myocardial perfusion single-photon emission CT (MPS) in patients with varying degrees of renal dysfunction and the impact of CKD on cardiac death prediction in patients undergoing MPS have not been investigated. We followed up 1652 consecutive patients who underwent stress MPS (32% exercise, 95% gated) for cardiac death for a mean of 2.15+/-0.8 years. MPS defects were defined with a summed stress score (normal summed stress score <4, abnormal summed stress score>or=4). Ischemia was defined as a summed stress score >or=4 plus a summed difference score >or=2, and scar was defined as a summed difference score <2 plus a summed stress score >or=4. Renal function was calculated with the Modified Diet in Renal Disease equation. CKD (estimated glomerular filtration rate <60 mL . min(-1) . 1.73 m(-2)) was present in 36%. Cardiac death increased with worsening levels of perfusion defects across the entire spectrum of renal function. Presence of ischemia was independently predictive of cardiac death, all-cause mortality, and nonfatal myocardial infarction. Patients with normal MPS and CKD had higher unadjusted cardiac death event rates than those with no CKD and normal MPS (2.7% versus 0.8%, P=0.001). Multivariate Cox proportional hazards models revealed that both perfusion defects (hazard ratio 1.90, 95% CI 1.47 to 2.46) and CKD (hazard ratio 1.96, 95% CI 1.29 to 2.95) were independent predictors of cardiac death after accounting for risk factors, left ventricular dysfunction, pharmacological stress, and symptom status. Both MPS and CKD had incremental power for cardiac death prediction over baseline risk factors and left ventricular dysfunction (global chi(2) 207.5 versus 169.3, P<0.0001). MPS provides effective risk stratification across the entire spectrum of renal function. Renal dysfunction is also an important independent predictor of cardiac death in patients undergoing MPS. Renal function and MPS have additive value in risk stratisfying patients with suspected coronary artery disease. Patients with CKD appear to have a relatively less benign prognosis than those without CKD, even in the presence of a normal scan.
The knockdown of chloroplastic ascorbate peroxidases reveals its regulatory role in the photosynthesis and protection under photo-oxidative stress in rice.

PubMed

Caverzan, Andréia; Bonifacio, Aurenivia; Carvalho, Fabricio E L; Andrade, Claudia M B; Passaia, Gisele; Schünemann, Mariana; Maraschin, Felipe Dos Santos; Martins, Marcio O; Teixeira, Felipe K; Rauber, Rafael; Margis, Rogério; Silveira, Joaquim Albenisio Gomes; Margis-Pinheiro, Márcia

2014-01-01

The inactivation of the chloroplast ascorbate peroxidases (chlAPXs) has been thought to limit the efficiency of the water-water cycle and photo-oxidative protection under stress conditions. In this study, we have generated double knockdown rice (Oryza sativa L.) plants in both OsAPX7 (sAPX) and OsAPX8 (tAPX) genes, which encode chloroplastic APXs (chlAPXs). By employing an integrated approach involving gene expression, proteomics, biochemical and physiological analyses of photosynthesis, we have assessed the role of chlAPXs in the regulation of the protection of the photosystem II (PSII) activity and CO2 assimilation in rice plants exposed to high light (HL) and methyl violagen (MV). The chlAPX knockdown plants were affected more severely than the non-transformed (NT) plants in the activity and structure of PSII and CO2 assimilation in the presence of MV. Although MV induced significant increases in pigment content in the knockdown plants, the increases were apparently not sufficient for protection. Treatment with HL also caused generalized damage in PSII in both types of plants. The knockdown and NT plants exhibited differences in photosynthetic parameters related to efficiency of utilization of light and CO2. The knockdown plants overexpressed other antioxidant enzymes in response to the stresses and increased the GPX activity in the chloroplast-enriched fraction. Our data suggest that a partial deficiency of chlAPX expression modulate the PSII activity and integrity, reflecting the overall photosynthesis when rice plants are subjected to acute oxidative stress. However, under normal growth conditions, the knockdown plants exhibit normal phenotype, biochemical and physiological performance. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.
Exercise training prevents the attenuation of anesthetic pre-conditioning-mediated cardioprotection in diet-induced obese rats.

PubMed

Li, L; Meng, F; Li, N; Zhang, L; Wang, J; Wang, H; Li, D; Zhang, X; Dong, P; Chen, Y

2015-01-01

Obesity abolishes anesthetic pre-conditioning-induced cardioprotection due to impaired reactive oxygen species (ROS)-mediated adenosine monophosphate-activated protein kinase (AMPK) pathway, a consequence of increased basal myocardial oxidative stress. Exercise training has been shown to attenuate obesity-related oxidative stress. This study tests whether exercise training could normalize ROS-mediated AMPK pathway and prevent the attenuation of anesthetic pre-conditioning-induced cardioprotection in obesity. Male Sprague-Dawley rats were divided into lean rats fed with control diet and obese rats fed with high-fat diet. After 4 weeks of feeding, lean and obese rats were assigned to sedentary conditions or treadmill exercise for 8 weeks. There was no difference in infarct size between lean sedentary and obese sedentary rats after 25 min of myocardial ischemia followed by 120 min reperfusion. In lean rats, sevoflurane equally reduced infarct size in lean sedentary and lean exercise-trained rats. Molecular studies revealed that AMPK activity, endothelial nitric oxide synthase, and superoxide production measured at the end of ischemia in lean rats were increased in response to sevoflurane. In obese rats, sevoflurane increased the above molecular parameters and reduced infarct size in obese exercise-trained rats but not in obese sedentary rats. Additional study showed that obese exercise-trained rats had decreased basal oxidative stress than obese sedentary rats. The results indicate that exercise training can prevent the attenuation of anesthetic cardioprotection in obesity. Preventing the attenuation of this strategy may be associated with reduced basal oxidative stress and normalized ROS-mediated AMPK pathway, but the causal relationship remains to be determined. © 2014 The Acta Anaesthesiologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.
Impact of wall thickness and saccular geometry on the computational wall stress of descending thoracic aortic aneurysms.

PubMed

Shang, Eric K; Nathan, Derek P; Sprinkle, Shanna R; Fairman, Ronald M; Bavaria, Joseph E; Gorman, Robert C; Gorman, Joseph H; Jackson, Benjamin M

2013-09-10

Wall stress calculated using finite element analysis has been used to predict rupture risk of aortic aneurysms. Prior models often assume uniform aortic wall thickness and fusiform geometry. We examined the effects of including local wall thickness, intraluminal thrombus, calcifications, and saccular geometry on peak wall stress (PWS) in finite element analysis of descending thoracic aortic aneurysms. Computed tomographic angiography of descending thoracic aortic aneurysms (n=10 total, 5 fusiform and 5 saccular) underwent 3-dimensional reconstruction with custom algorithms. For each aneurysm, an initial model was constructed with uniform wall thickness. Experimental models explored the addition of variable wall thickness, calcifications, and intraluminal thrombus. Each model was loaded with 120 mm Hg pressure, and von Mises PWS was computed. The mean PWS of uniform wall thickness models was 410 ± 111 kPa. The imposition of variable wall thickness increased PWS (481 ± 126 kPa, P<0.001). Although the addition of calcifications was not statistically significant (506 ± 126 kPa, P=0.07), the addition of intraluminal thrombus to variable wall thickness (359 ± 86 kPa, P ≤ 0.001) reduced PWS. A final model incorporating all features also reduced PWS (368 ± 88 kPa, P<0.001). Saccular geometry did not increase diameter-normalized stress in the final model (77 ± 7 versus 67 ± 12 kPa/cm, P=0.22). Incorporation of local wall thickness can significantly increase PWS in finite element analysis models of thoracic aortic aneurysms. Incorporating variable wall thickness, intraluminal thrombus, and calcifications significantly impacts computed PWS of thoracic aneurysms; sophisticated models may, therefore, be more accurate in assessing rupture risk. Saccular aneurysms did not demonstrate a significantly higher normalized PWS than fusiform aneurysms.
Abandoned prairie vole mothers show normal maternal care but altered emotionality: Potential influence of the brain corticotropin-releasing factor system.

PubMed

Bosch, Oliver J; Pohl, Tobias T; Neumann, Inga D; Young, Larry J

2018-04-02

When fathers leave the family, mothers are at increased risk of developing depression and anxiety disorders. In biparental, socially monogamous prairie voles (Microtus ochrogaster), sudden bond disruption increases passive stress-coping, indicative of depressive-like behavior, and acts as chronic stressor in both males and females. However, the consequences of separation in lactating prairie vole mothers are unknown. In the present study, following 18 days of cohousing, half of the prairie vole pairs were separated by removing the male. In early lactation, maternal care was unaffected by separation, whereas anxiety-related behavior and passive stress-coping were significantly elevated in separated mothers. Separation significantly increased corticotropin-releasing factor (CRF) mRNA expression in the paraventricular nucleus of the hypothalamus under basal conditions, similar to levels of paired females after acute exposure to forced swim stress. A second cohort of lactating prairie voles was infused intracerebroventricularly with either vehicle or the CRF receptor antagonist D-Phe just prior to behavioral testing. The brief restraining during acute infusion significantly decreased arched back nursing in vehicle-treated paired and separated groups, whereas in the D-Phe-treated separated group the behavior was not impaired. Furthermore, in the latter, anxiety-related behavior and passive stress-coping were normalized to levels similar to vehicle-treated paired mothers. In conclusion, maternal investment is robust enough to withstand loss of the partner, whereas the mother's emotionality is affected, which may be - at least partly - mediated by a CRF-dependent mechanism. This animal model has potential for mechanistic studies of behavioral and physiological consequences of partner loss in single mothers. Copyright © 2017 Elsevier B.V. All rights reserved.
Experimental investigation of the effect of Reynolds number on flow structures in the wake of a circular parachute canopy

NASA Astrophysics Data System (ADS)

Jin, Zhe-Yan; Pasqualini, Sylvio; Qin, Bo

2014-06-01

In the present study, an experimental study was conducted to characterize the effect of Reynolds number on flow structures in the turbulent wake of a circular parachute canopy by utilizing stereoscopic particle image velocimetry (Stereo-PIV) technique. The parachute model tested in the present study was attached by 28 nylon suspension lines and placed horizontally at the test section center of the wind tunnel. The obtained results showed that with the increase of Reynolds number, the intensities of the vortices near the downstream region of the canopy skirt were found to increase accordingly. However, the increase of Reynolds number did not result in a significant change in ensembleaveraged normalized x-component of the velocity, ensembleaveraged normalized vorticity, normalized Reynolds stress, and normalized turbulent kinetic energy distributions in the turbulent wake of the circular parachute canopy. The obtained results are very useful to further our understanding about the unsteady aerodynamics in the wake of flexible circular parachute canopies and to constitute a reference for CFD computation.
Static stress changes associated with normal faulting earthquakes in South Balkan area

NASA Astrophysics Data System (ADS)

Papadimitriou, E.; Karakostas, V.; Tranos, M.; Ranguelov, B.; Gospodinov, D.

2007-10-01

Activation of major faults in Bulgaria and northern Greece presents significant seismic hazard because of their proximity to populated centers. The long recurrence intervals, of the order of several hundred years as suggested by previous investigations, imply that the twentieth century activation along the southern boundary of the sub-Balkan graben system, is probably associated with stress transfer among neighbouring faults or fault segments. Fault interaction is investigated through elastic stress transfer among strong main shocks ( M ≥ 6.0), and in three cases their foreshocks, which ruptured distinct or adjacent normal fault segments. We compute stress perturbations caused by earthquake dislocations in a homogeneous half-space. The stress change calculations were performed for faults of strike, dip, and rake appropriate to the strong events. We explore the interaction between normal faults in the study area by resolving changes of Coulomb failure function ( ΔCFF) since 1904 and hence the evolution of the stress field in the area during the last 100 years. Coulomb stress changes were calculated assuming that earthquakes can be modeled as static dislocations in an elastic half-space, and taking into account both the coseismic slip in strong earthquakes and the slow tectonic stress buildup associated with major fault segments. We evaluate if these stress changes brought a given strong earthquake closer to, or sent it farther from, failure. Our modeling results show that the generation of each strong event enhanced the Coulomb stress on along-strike neighbors and reduced the stress on parallel normal faults. We extend the stress calculations up to present and provide an assessment for future seismic hazard by identifying possible sites of impending strong earthquakes.
Heart rate variability (HRV): an indicator of stress

NASA Astrophysics Data System (ADS)

Kaur, Balvinder; Durek, Joseph J.; O'Kane, Barbara L.; Tran, Nhien; Moses, Sophia; Luthra, Megha; Ikonomidou, Vasiliki N.

2014-05-01

Heart rate variability (HRV) can be an important indicator of several conditions that affect the autonomic nervous system, including traumatic brain injury, post-traumatic stress disorder and peripheral neuropathy [3], [4], [10] & [11]. Recent work has shown that some of the HRV features can potentially be used for distinguishing a subject's normal mental state from a stressed one [4], [13] & [14]. In all of these past works, although processing is done in both frequency and time domains, few classification algorithms have been explored for classifying normal from stressed RRintervals. In this paper we used 30 s intervals from the Electrocardiogram (ECG) time series collected during normal and stressed conditions, produced by means of a modified version of the Trier social stress test, to compute HRV-driven features and subsequently applied a set of classification algorithms to distinguish stressed from normal conditions. To classify RR-intervals, we explored classification algorithms that are commonly used for medical applications, namely 1) logistic regression (LR) [16] and 2) linear discriminant analysis (LDA) [6]. Classification performance for various levels of stress over the entire test was quantified using precision, accuracy, sensitivity and specificity measures. Results from both classifiers were then compared to find an optimal classifier and HRV features for stress detection. This work, performed under an IRB-approved protocol, not only provides a method for developing models and classifiers based on human data, but also provides a foundation for a stress indicator tool based on HRV. Further, these classification tools will not only benefit many civilian applications for detecting stress, but also security and military applications for screening such as: border patrol, stress detection for deception [3],[17], and wounded-warrior triage [12].
Effects of routine handling and tagging procedures on physiological stress responses in juvenile chinook salmon

USGS Publications Warehouse

Sharpe, C.S.; Thompson, D.A.; Blankenship, H.L.; Schreck, C.B.

1998-01-01

Juvenile chinook salmon Oncorhynchus tshawytscha were subjected to handling and tagging protocols typical of normal hatchery operations and monitored for their physiological response to stress. Treatments included coded-wire-tagging, counting, ventral fin clipping, adipose fin clipping, and a procedure simulating a pond split. Treatment fish were also subjected to a standardized stress challenge (1 h confinement) to evaluate their ability to deal with disturbances subsequent to a handling or tagging procedure. Circulating levels of cortisol and glucose were used as indicators of stress. Each of the treatments elicited very similar responses among treatment groups. Cortisol increased from resting levels of about 20 ng/mL to about 90 ng/mL by 1 h poststress and returned to near resting levels by 8 h poststress. Glucose levels increased from 50 mg/dL to about 80 mg/dL by 1 h poststress and remained elevated for much of the experiment. The cortisol and glucose responses to the confinement stress did not differ over time or among treatments. However, the confinement stress results do suggest a small but significant cumulative response, indicating small residual effects of the original handling protocols. No deaths were noted among treatment groups.
Shear Stress-Normal Stress (Pressure) Ratio Decides Forming Callus in Patients with Diabetic Neuropathy

PubMed Central

Noguchi, Hiroshi; Takehara, Kimie; Ohashi, Yumiko; Suzuki, Ryo; Yamauchi, Toshimasa; Kadowaki, Takashi; Sanada, Hiromi

2016-01-01

Aim. Callus is a risk factor, leading to severe diabetic foot ulcer; thus, prevention of callus formation is important. However, normal stress (pressure) and shear stress associated with callus have not been clarified. Additionally, as new valuables, a shear stress-normal stress (pressure) ratio (SPR) was examined. The purpose was to clarify the external force associated with callus formation in patients with diabetic neuropathy. Methods. The external force of the 1st, 2nd, and 5th metatarsal head (MTH) as callus predilection regions was measured. The SPR was calculated by dividing shear stress by normal stress (pressure), concretely, peak values (SPR-p) and time integral values (SPR-i). The optimal cut-off point was determined. Results. Callus formation region of the 1st and 2nd MTH had high SPR-i rather than noncallus formation region. The cut-off value of the 1st MTH was 0.60 and the 2nd MTH was 0.50. For the 5th MTH, variables pertaining to the external forces could not be determined to be indicators of callus formation because of low accuracy. Conclusions. The callus formation cut-off values of the 1st and 2nd MTH were clarified. In the future, it will be necessary to confirm the effect of using appropriate footwear and gait training on lowering SPR-i. PMID:28050567

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