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Stress Generation (stress + generation)

Distribution by Scientific Domains
Medical Sciences33%

Selected Abstracts

Stress generation in depression: Reflections on origins, research, and future directions

JOURNAL OF CLINICAL PSYCHOLOGY, Issue 9 2006
Constance Hammen
Depressed individuals report higher rates of stressful life events, especially those that have occurred in part because of the person's characteristics and behaviors affecting interpersonal interactions. Termed stress generation, this phenomenon draws attention to the role of the individual as an active contributor rather than passive player in his or her environment, and is therefore an example of action theory. In this article, the author speculates about the intellectual origins of her stress generation perspective, and notes somewhat similar transactional approaches to the stress-disorder link outside of depression research. The literature on stress generation in depression is reviewed, including studies that attempt to explore its correlates and predictors, covering clinical, contextual, family, genetic, cognitive, interpersonal, and personality variables. Empirical and conceptual gaps in our understanding of processes contributing to stressors in the lives of depressed people remain. The author concludes with suggestions for further research, with the goal of furthering understanding both of mechanisms of depression and of dysfunctional interpersonal processes, as well as development of effective interventions to help break the stress-recurrence cycle of depression. © 2006 Wiley Periodicals, Inc. J Clin Psychol 62: 1065,1082, 2006. [source]

Stress generation in the tension wood of poplar is based on the lateral swelling power of the G-layer

THE PLANT JOURNAL, Issue 4 2008
Luna Goswami
Summary The mechanism of active stress generation in tension wood is still not fully understood. To characterize the functional interdependency between the G-layer and the secondary cell wall, nanostructural characterization and mechanical tests were performed on native tension wood tissues of poplar (Populus nigra × Populus deltoids) and on tissues in which the G-layer was removed by an enzymatic treatment. In addition to the well-known axial orientation of the cellulose fibrils in the G-layer, it was shown that the microfibril angle of the S2-layer was very large (about 36°). The removal of the G-layer resulted in an axial extension and a tangential contraction of the tissues. The tensile stress,strain curves of native tension wood slices showed a jagged appearance after yield that could not be seen in the enzyme-treated samples. The behaviour of the native tissue was modelled by assuming that cells deform elastically up to a critical strain at which the G-layer slips, causing a drop in stress. The results suggest that tensile stresses in poplar are generated in the living plant by a lateral swelling of the G-layer which forces the surrounding secondary cell wall to contract in the axial direction. [source]

Protective role of pigment epithelium-derived factor (PEDF) in early phase of experimental diabetic retinopathy

DIABETES/METABOLISM: RESEARCH AND REVIEWS, Issue 7 2009
Yumiko Yoshida
Abstract Background Pigment epithelium-derived factor (PEDF) is the most potent inhibitor of angiogenesis in the mammalian eye, thus suggesting that PEDF may protect against proliferative diabetic retinopathy. However, a role for PEDF in early diabetic retinopathy remains to be elucidated. We investigated here whether and how PEDF could prevent the development of diabetic retinopathy. Methods Streptozotocin-induced diabetic rats were treated with or without intravenous injection of PEDF for 4 weeks. Early neuronal derangements were evaluated by electroretinogram (ERG) and immunofluorescent staining of glial fibrillary acidic protein (GFAP). Expression of PEDF and 8-hydroxydeoxyguanosine (8-OHdG), a marker of oxidative stress, was localized by immunofluorescence. Vascular endothelial growth factor (VEGF) and p22phox expression were evaluated with western blots. Breakdown of blood retinal barrier (BRB) was quantified with fluorescein isothiocynate (FITC)-conjugated dextran. NADPH oxidase activity was measured with lucigenin luminescence. Results Retinal PEDF levels were reduced, and amplitudes of a- and b-wave in the ERG were decreased in diabetic rats, which were in parallel with GFAP overexpression in the Müller cells. Further, retinal 8-OHdG, p22phox and VEGF levels and NADPH oxidase activity were increased, and BRB was broken in diabetic rats. Administration of PEDF ameliorated all of the characteristic changes in early diabetic retinopathy. Conclusions Results suggest that PEDF could prevent neuronal derangements and vascular hyperpermeability in early diabetic retinopathy via inhibition of NADPH oxidase-driven oxidative stress generation. Substitution of PEDF may offer a promising strategy for halting the development of diabetic retinopathy. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Stress generation in depression: Reflections on origins, research, and future directions

JOURNAL OF CLINICAL PSYCHOLOGY, Issue 9 2006
Constance Hammen
Depressed individuals report higher rates of stressful life events, especially those that have occurred in part because of the person's characteristics and behaviors affecting interpersonal interactions. Termed stress generation, this phenomenon draws attention to the role of the individual as an active contributor rather than passive player in his or her environment, and is therefore an example of action theory. In this article, the author speculates about the intellectual origins of her stress generation perspective, and notes somewhat similar transactional approaches to the stress-disorder link outside of depression research. The literature on stress generation in depression is reviewed, including studies that attempt to explore its correlates and predictors, covering clinical, contextual, family, genetic, cognitive, interpersonal, and personality variables. Empirical and conceptual gaps in our understanding of processes contributing to stressors in the lives of depressed people remain. The author concludes with suggestions for further research, with the goal of furthering understanding both of mechanisms of depression and of dysfunctional interpersonal processes, as well as development of effective interventions to help break the stress-recurrence cycle of depression. © 2006 Wiley Periodicals, Inc. J Clin Psychol 62: 1065,1082, 2006. [source]

Stress generation in the tension wood of poplar is based on the lateral swelling power of the G-layer

THE PLANT JOURNAL, Issue 4 2008
Luna Goswami
Summary The mechanism of active stress generation in tension wood is still not fully understood. To characterize the functional interdependency between the G-layer and the secondary cell wall, nanostructural characterization and mechanical tests were performed on native tension wood tissues of poplar (Populus nigra × Populus deltoids) and on tissues in which the G-layer was removed by an enzymatic treatment. In addition to the well-known axial orientation of the cellulose fibrils in the G-layer, it was shown that the microfibril angle of the S2-layer was very large (about 36°). The removal of the G-layer resulted in an axial extension and a tangential contraction of the tissues. The tensile stress,strain curves of native tension wood slices showed a jagged appearance after yield that could not be seen in the enzyme-treated samples. The behaviour of the native tissue was modelled by assuming that cells deform elastically up to a critical strain at which the G-layer slips, causing a drop in stress. The results suggest that tensile stresses in poplar are generated in the living plant by a lateral swelling of the G-layer which forces the surrounding secondary cell wall to contract in the axial direction. [source]

BEHAVIOUR OF THE ANTI-OXIDANT DEFENCE SYSTEM AND HEME OXYGENASE-1 PROTEIN EXPRESSION IN FRUCTOSE-HYPERTENSIVE RATS

CLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 8 2006
Ariel H Polizio
SUMMARY 1Addition of fructose to a rat diet for various periods of time leads to hypertension, hyperinsulinaemia and dyslipidaemia and provides a model for testing oxidative stress parameters in the animals. 2In the present study, oxidative stress generation, the soluble and enzymatic defence system and heme oxygenase-1 (HO-1) protein expression were investigated in the heart, liver and kidney of rats fed fructose for a period of 1 or 8 months. 3Compared with the control group, fructose-hypertensive rats showed increased in lipid peroxidation only in the heart after both 1 and 8 months of fructose treatment. Changes in the behaviour of the soluble and enzymatic defence system and HO-1 protein expression were different depending on the organ. Increased or unaltered activities of anti-oxidant enzymes were found in the liver and kidney, respectively. Induction of HO-1 prevented the generation of oxidative stress in the liver, where the activity of anti-oxidant defence enzymes was not reduced. Increased expression of HO-1 protein was not able to prevent the generation of oxidative stress in the heart, where fructose treatment diminished the activity of anti-oxidant enzymes. 4The results of the present study demonstrate that upregulation of HO-1 may prevent the generation of oxidative stress only when the anti-oxidant defence system is still operative. [source]