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Stress Leads (stress + lead)
Selected AbstractsReactive species and early manifestation of insulin resistance in type 2 diabetesDIABETES OBESITY & METABOLISM, Issue 2 2006L. E. Fridlyand The early stages of type 2 diabetes mellitus are characterized by the development of insulin resistance (IRe) in muscle cells and adipocytes with the concomitant loss of ,-cell compensation. We have extensively reviewed the literature related to metabolic and signalling pathways of reactive oxygen species (ROS) in regard to the coordinated development of oxidative stress and IRe. We considered the hypothesis that oxidative stress leads to IRe in muscle cells and adipocytes, but found that the data are more consistent with the hypothesis that the cellular mechanisms that protect against oxidative stress per se are capable of creating an ROS-dependent insulin-resistant state. Furthermore, ROS-induced mitochondrial dysfunction can lead to disruptions of lipid metabolism, increasing the intracellular lipid content, and, in addition, contribute to lipid-dependent IRe in myocytes. Together, these two ROS-activated pathways to IRe can contribute to a global state of profound resistance to insulin action. Therapeutic strategies should, therefore, be directed towards reducing insulin resistance without an increase in ROS production or concentration. Pharmacological or other approaches to IRe that result in the activation of mitochondrial biogenesis in particular could be highly beneficial in the prevention or treatment of both insulin resistance and type 2 diabetes. [source] Early transcriptional response of Saccharomyces cerevisiae to stress imposed by the herbicide 2,4-dichlorophenoxyacetic acidFEMS YEAST RESEARCH, Issue 2 2006Miguel Cacho Teixeira Abstract The global gene transcription pattern of the eukaryotic experimental model Saccharomyces cerevisiae in response to sudden aggression with the widely used herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) was analysed. Under acute stress, 14% of the yeast transcripts suffered a greater than twofold change. The yeastract database was used to predict the transcription factors mediating the response registered in this microarray analysis. Most of the up-regulated genes in response to 2,4-D are known targets of Msn2p, Msn4p, Yap1p, Pdr1p, Pdr3p, Stp1p, Stp2p and Rpn4p. The major regulator of ribosomal protein genes, Sfp1p, is known to control 60% of the down-regulated genes, in particular many involved in the transcriptional and translational machinery and in cell division. The yeast response to the herbicide includes the increased expression of genes involved in the oxidative stress response, the recovery or degradation of damaged proteins, cell wall remodelling and multiple drug resistance. Although the protective role of TPO1 and PDR5 genes was confirmed, the majority of the responsive genes encoding multidrug resistance do not confer resistance to 2,4-D. The increased expression of genes involved in alternative carbon and nitrogen source metabolism, fatty acid ,-oxidation and autophagy was also registered, suggesting that acute herbicide stress leads to nutrient limitation. [source] Behaviours of Medicago truncatula,Sinorhizobium meliloti Symbioses Under Osmotic Stress in Relation with the Symbiotic Partner Input: Effects on Nodule Functioning and ProtectionJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 3 2009H. Mhadhbi Abstract Three genotypes of the model legume Medicago truncatula were assessed for symbiotic effectiveness in cross inoculation with two strains of Sinorhizobium meliloti under mannitol-mediated osmotic stress. Symbioses showed different tolerance levels revealed on plant growth, nitrogen-fixing capacity and indices of nodule functioning and protection. The variability of stress response was essentially correlated with performance at non-stressful conditions. Symbiosis attitude depended on bacterial partner, host-plant genotype and their interaction. Plant genotype manifested the highest contribution to symbiotic efficiency indices under osmotic stress, even for nodulation and nitrogen fixation where the bacterial strain effect is highly pronounced. Contrasting (tolerant/sensitive) associations were identified for tolerance behaviours, involving the same plant genotype with different rhizobial strains and vice versa. In nodules, osmotic stress leads to accumulation of oxidized lipids and decrease in total protein and leghaemoglobin contents. Antioxidant responses were manifested as induction of guaiacol peroxidase (POX, E.C. 1.11.1.7) and superoxide dismutase (E.C. 1.15.1.1). POX induction was higher in tolerant symbioses and both enzymes were suggested as contributors to the protection of nodule integrity and functioning under osmotic stress. In conclusion, symbiotic efficiency in M. truncatula,S. meliloti combinations under osmotic stress is determined by each symbiont's input as well as the plant,microbe genotype interaction, and POX induction could prove a sensitive marker of tolerant symbioses. [source] Repeated stress alters the ability of nicotine to activate the hypothalamic,pituitary,adrenal axisJOURNAL OF NEUROCHEMISTRY, Issue 5 2006Kabirullah Lutfy Abstract Acute nicotine administration has been shown to activate the hypothalamic,pituitary,adrenal (HPA) axis and stimulate secretion of adrenocorticotrophic hormone (ACTH), corticosterone/cortisol and ,-endorphin (beta-END) in both rodents and humans, raising the possibility that activation of the HPA axis by nicotine may mediate some of the effects of nicotine. Since stress can increase the risk of drug use and abuse, we hypothesized that repeated stress would increase the ability of nicotine to stimulate the secretion of HPA hormones. To test our hypothesis, mice were exposed to repeated stress (swimming in 15°C water for 3 min/day for 5 days) and killed 15 min after injection of saline or nicotine (0.1 mg/kg, s.c.). Repeated exposure to stress increased the ability of nicotine to stimulate plasma ACTH (p < 0.05) and beta-END (p < 0.05), but not corticosterone secretion. In contrast, repeated exposure to stress increased the post-saline injection levels of corticosterone (p < 0.05), but not ACTH and beta-END. The present results suggest that chronic stress leads to an enhanced sensitivity of some components of the HPA axis to a subsequent nicotine challenge. [source] Oxidative stress in the pathogenesis of experimental diabetic neuropathyJOURNAL OF NEUROCHEMISTRY, Issue 2003P. A. Low We evaluated the effects of chronic hyperglycemia on L5 DRG neurons. Experimental diabetic neuropathy (EDN) was induced by streptozotocin. We studied peripheral nerve after 1, 3, 12 months of diabetes. A conduction deficit was present from the first month and persisted over 12 months, affecting mainly sensory fibers. 8-Hydroxy-deoxyguanosine labeling was significantly increased at all time points in DRG neurons, indicating oxidative injury. Caspase-3 labeling was increased at all three time-points, indicating commitment to the efferent limb of the apoptotic pathway. Apoptosis was confirmed by a significant increase in the percent of neurons undergoing apoptosis (TUNEL staining) at 1 month (8%), 3 months (7%) and 12 months (11%). Morphometry of DRG showed a selective loss (42%) of the largest neurons. These findings support the concept that oxidative stress leads to oxidative injury of DRG neurons, with mitochondrium as a specific target, leading to apoptosis and a predominantly sensory neuropathy. [source] A peroxide-induced zinc uptake system plays an important role in protection against oxidative stress in Bacillus subtilisMOLECULAR MICROBIOLOGY, Issue 4 2002Ahmed Gaballa Summary In Bacillus subtilis, hydrogen peroxide (H2O2) induces expression of the PerR regulon including catalase (KatA), alkyl hydroperoxide reductase and the DNA-binding protein MrgA. We have identified the P-type metal-transporting ATPase ZosA (formerly YkvW) as an additional member of the perR regulon. Expression of zosA is induced by H2O2 and repressed by the PerR metalloregulatory protein, which binds to two Per boxes in the promoter region. Physiological studies implicate ZosA in Zn(II) uptake. ZosA functions together with two Zur-regulated uptake systems and one known efflux system to maintain Zn(II) homeostasis. ZosA is the major pathway for zinc uptake in cells growing with micromolar levels of Zn(II) that are known to repress the two Zur-regulated transporters. A perR mutant is sensitive to high levels of zinc, and this sensitivity is partially suppressed by a zosA mutation. ZosA is important for resistance to both H2O2 and the thiol-oxidizing agent diamide. This suggests that increased intracellular Zn(II) may protect thiols from oxidation. In contrast, catalase is critical for H2O2 resistance but does not contribute significantly to diamide resistance. Growth of cells with elevated zinc significantly increases resistance to high concentrations of H2O2, and this effect requires ZosA. Our results indicate that peroxide stress leads to the upregulation of a dedicated Zn(II) uptake system that plays an important role in H2O2 and disulphide stress resistance. [source] Effects of uniaxial stress on the magnetic properties of thin films and GMR sensors prepared on polyimide substratesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2008Berkem Özkaya Abstract The effects of externally applied uniaxial stress on the magnetic properties of Co thin films and pseudo-spin-valve (PSV) structures on flexible polyimide substrates were investigated. The advantage of the polyimide substrate is its flexibility and high elasticity (,1%), which cannot be achieved using conventional crystalline substrates. The Co layers exhibit a macroscopic easy axis induced by the preparation process. When the stress is applied perpendicular to the induced in-plane easy axis, the magnetic domains in the film rotate towards the applied stress direction, which was confirmed using Kerr microscopy and magneto-optical Kerr effect (MOKE) magnetometer measurements. A Co/Cu/Ni PSV system was prepared on polyimide substrate with dc magnetron sputtering. Applying uniaxial stress leads to opposite rotation of the magnetisation directions in both layers to each other due to different signs of the magnetostriction coefficients of Co and Ni. The magnetisation and giant magnetoresistance (GMR) curves under applied stress were recorded using in situ MOKE and current in-plane four-point probe techniques, respectively. When the stress is applied perpendicular to the external magnetic field (Hext), the operating range of the GMR sensor increases, whereas the sensitivity decreases. Anisotropy energies and saturation magnetostriction values of the Co and Ni layer were determined by fitting the GMR and magnetisation curves using a micromagnetic model. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Implications of Genotypic Diversity and Phenotypic Plasticity in the Ecophysiological Success of CAM Plants, Examined by Studies on the Vegetation of Madagascar,PLANT BIOLOGY, Issue 3 2001M. Kluge Abstract: On the basis of ,13C-values, genotypic diversity and phenotypic plasticity of CAM behaviour in plants of the Malagasy vegetation is surveyed. The study compares CAM patterns performed in the wild on the levels of genera (Kalanchoë [Crassulaceae], Angraecum [Orchidaceae], Lissochilus [Orchidaceae] and Rhipsalis [Cactaceae]), on the level of a family (Didiereaceae) and finally on the level of a common growth form, namely in leafless orchids. For Rhipsalis, also non-Malagasy species were included in the comparison. The genus Kalanchoë was found to be dominated by species representing the CAM-physiotype with CO2 fixation taking place only during the night, whereas the CAM/C3- and the C3-physiotypes (with limited intrinsic CAM potential) were less frequent. The opposite holds true for Angraecum. In the genus Rhipsalis, in the Didiereacean family and in the leafless orchids only the CAM-physiotype is represented. The photosynthetic physiotypes of CAM plants were found to be related to the environmental conditions of the habitat. That is, strong CAM performers are typically abundant in the dry climatic zones or at otherwise dry niches, species of the C3-physiotype (possibly with weak intrinsic capability of CAM performance) are distributed at humid sites and those of the CAM/C3-physiotype occupy sites with medium and changing exposure to stress. Phenotypic plasticity of CAM, as indicated by the intraspecific variability of the ,13C-values, was lower in the CAM-physiotype compared with the CAM/C3-physiotype. Our data support the view that strong stress leads to the dominance of highly adapted specialists among the CAM plants, with low phenotypic plasticity of the photosynthetic behaviour, whereas medium stress advances the unfolding of plastic CAM behaviour. Moreover, the data suggest that genera comprising all three physiotypes (Kalanchoë, Angraecum) are dispersed all over Madagascar, whilst groups comprising only strong CAM performers are restricted to limited areas or special types of habitats. This suggests that both genotypic diversity and phenotypic plasticity are important factors for the ecophysiological success of CAM. [source] The Influence of Shear Stress on Crystallization in an Ultrasound LevitatorCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 10 2007S. Sacher Abstract Industrial precipitation processes often use chemical agents to influence crystal morphology and size distribution. This experimental study deals with the investigation of physical parameters including an alternative method to affect crystal growth, thus, avoiding the presence of additives as intrinsic impurities. The influence of shear stress acting on growing crystals within a droplet is investigated in an ultrasound levitator. An ultrasound levitator enables the suspension of a single droplet against gravity and the study of containerless precipitation with specific mechanical forces acting on crystals. The levitator is used as a three-phase reactor with precipitation from the gas and liquid, and as a reactor for precipitation from two different solutions. Calcium carbonate is used as a model system. The variation of temperature and the amount of applied shear stress leads to different amounts of calcium carbonate morphologies. An increase in the shear stress results in more rounded or spherical crystals. The intensity of the shear stress also influences the particle size distributions of the precipitated crystals, i.e., with increasing shear stress, particle size distributions are shifted to smaller sizes. [source] | ||||||||||