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Using a pulse radiolysis approach to generate and observe superoxide anions (O2-.) in the absence and presence of calcium, we have attempted to verify the recent hypothesis of Babizhayev (Arch. Biochem. Biophys. 266, 446-451, 1988) of a Ca2(+)-O2-. interaction during lipid peroxidation. We could not observe rapid scavenging of O2-. or complex formation with Ca2+ to account for an inhibitory effect of this cation on lipid peroxidation. Neither could we agree that the stimulatory effect is due to liberation of catalytic ferrous iron from weak complexes by Ca2+. Drawing on reports in the literature, we propose an alternate explanation for the apparent stimulation of lipid peroxidation by low Ca2+ concentrations. In our view, this is not a direct effect, but reflects independently initiated processes of lipid peroxidation and Ca2+ translocation, which interact subsequently in a synergistic manner. The reported inhibition at high Ca2+ concentrations is considered an artifact as it was observed at levels far in excess of those relevant to animal systems (but not necessarily in some plant compartments). 相似文献
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Maria Wagenstaller Andrea Buettner 《Metabolomics : Official journal of the Metabolomic Society》2013,9(1):9-20
The volatile and odorous profile of human urine may be a rich source for physiological information and could increase our understanding of metabolization and excretion processes of low-molecular weight compounds originating from, for example, dietary or endogenous sources. However, the diagnostic potential of the urinary volatile fraction is not yet fully understood, probably due to the limited application of modern analytical tools in urine volatile analysis. Accordingly, the aim of this study was to evaluate a combined chemo-analytical and human-sensory approach for characterization of the human urine odorant composition. We used one- and two-dimensional high resolution gas chromatography–olfactometry/mass spectrometry to identify commonly occurring and potent odorants in human urine. The studies were carried out on both native urine and on urine that had been treated by glucuronidase assays, with analysis of the liberated odor-active compounds using the same techniques. Based on retention indices, odor qualities and intensities, and mass spectra compared to references, a total of 14 odorants were detected in the majority of the untreated urine samples, and 24 odorants in the glucuronidase-treated samples. A major part of the identified substances are reported here for the first time. Our results show that chemosensory approaches are a useful strategy for the characterization of the odorant profile of human urine. 相似文献
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Kondababu Kurakula Mariska Vos Iker Otermin Rubio Goran Marinkovi? Reinhard Buettner Lukas C. Heukamp Jan Stap Vivian de Waard Claudia M. van Tiel Carlie J.M. de Vries 《PloS one》2014,9(4)
The LIM-only protein FHL2, also known as DRAL or SLIM3, has a function in fine-tuning multiple physiological processes. FHL2 is expressed in the vessel wall in smooth muscle cells (SMCs) and endothelial cells and conflicting data have been reported on the regulatory function of FHL2 in SMC phenotype transition. At present the function of FHL2 in SMCs in vascular injury is unknown. Therefore, we studied the role of FHL2 in SMC-rich lesion formation. In response to carotid artery ligation FHL2-deficient (FHL2-KO) mice showed accelerated lesion formation with enhanced Ki67 expression compared with wild-type (WT)-mice. Consistent with these findings, cultured SMCs from FHL2-KO mice showed increased proliferation through enhanced phosphorylation of extracellular-regulated kinase-1/2 (ERK1/2) and induction of CyclinD1 expression. Overexpression of FHL2 in SMCs inhibited CyclinD1 expression and CyclinD1-knockdown blocked the enhanced proliferation of FHL2-KO SMCs. We also observed increased CyclinD1 promoter activity in FHL2-KO SMCs, which was reduced upon ERK1/2 inhibition. Furthermore, FHL2-KO SMCs showed enhanced migration compared with WT SMCs. In conclusion, FHL2 deficiency in mice results in exacerbated SMC-rich lesion formation involving increased proliferation and migration of SMCs via enhanced activation of the ERK1/2-CyclinD1 signaling pathway. 相似文献
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Impact of rainfall manipulations and biotic controls on soil respiration in Mediterranean and desert ecosystems along an aridity gradient 总被引:1,自引:0,他引:1
Spatially heterogeneous ecosystems form a majority of land types in the vast drylands of the globe. To evaluate climate‐change effects on CO2 fluxes in such ecosystems, it is critical to understand the relative responses of each ecosystem component (microsite). We investigated soil respiration (Rs) at four sites along an aridity gradient (90–780 mm mean annual precipitation, MAP) during almost 2 years. In addition, Rs was measured in rainfall manipulations plots at the two central sites where ~30% droughting and ~30% water supplementation treatments were used over 5 years. Annual Rs was higher by 23% under shrub canopies compared with herbaceous gaps between shrubs, but Rs at both microsites responded similarly to rainfall reduction. Decreasing precipitation and soil water content along the aridity gradient and across rainfall manipulations resulted in a progressive decline in Rs at both microsites, i.e. the drier the conditions, the larger was the effect of reduction in water availability on Rs. Annual Rs on the ecosystem scale decreased at a slope of 256/MAP g C m?2 yr?1 mm?1 (r2=0.97). The reduction in Rs amounted to 77% along the aridity gradient and to 16% across rainfall manipulations. Soil organic carbon (SOC) decreased with declining precipitation, and variation in SOC stocks explained 77% of the variation in annual Rs across sites, rainfall manipulations and microsites. This study shows that rainfall manipulations over several years are a useful tool for experimentally predicting climate‐change effects on CO2 fluxes for time scales (such as approximated by aridity gradients) that are beyond common research periods. Rainfall reduction decreases rates of Rs not only by lowering biological activity, but also by drastically reducing shrub cover. We postulate that future climate change in heterogeneous ecosystems, such as Mediterranean and deserts shrublands will have a major impact on Rs by feedbacks through changes in vegetation structure. 相似文献
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Dissolved carbon leaching from soil is a crucial component of the net ecosystem carbon balance 总被引:4,自引:0,他引:4
REIMO KINDLER KLAUS KAISER DAVID C. WALMSLEY CHRISTIAN BERNHOFER NINA BUCHMANN PIERRE CELLIER WERNER EUGSTER GERD GLEIXNER THOMAS GRŨNWALD ALEXANDER HEIM ANDREAS IBROM STEPHANIE K. JONES MIKE JONES KATJA KLUMPP WERNER KUTSCH KLAUS STEENBERG LARSEN SIMON LEHUGER BENJAMIN LOUBET REBECCA MCKENZIE EDDY MOORS BRUCE OSBORNE KIM PILEGAARD CORINNA REBMANN MATTHEW SAUNDERS MICHAEL W. I. SCHMIDT MARION SCHRUMPF JANINE SEYFFERTH UTE SKIBA JEAN‐FRANCOIS SOUSSANA MARK A. SUTTON CINDY TEFS BERNHARD VOWINCKEL MATTHIAS J. ZEEMAN MARTIN KAUPENJOHANN 《Global Change Biology》2011,17(2):1167-1185
Estimates of carbon leaching losses from different land use systems are few and their contribution to the net ecosystem carbon balance is uncertain. We investigated leaching of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and dissolved methane (CH4), at forests, grasslands, and croplands across Europe. Biogenic contributions to DIC were estimated by means of its δ13C signature. Leaching of biogenic DIC was 8.3±4.9 g m?2 yr?1 for forests, 24.1±7.2 g m?2 yr?1 for grasslands, and 14.6±4.8 g m?2 yr?1 for croplands. DOC leaching equalled 3.5±1.3 g m?2 yr?1 for forests, 5.3±2.0 g m?2 yr?1 for grasslands, and 4.1±1.3 g m?2 yr?1 for croplands. The average flux of total biogenic carbon across land use systems was 19.4±4.0 g C m?2 yr?1. Production of DOC in topsoils was positively related to their C/N ratio and DOC retention in subsoils was inversely related to the ratio of organic carbon to iron plus aluminium (hydr)oxides. Partial pressures of CO2 in soil air and soil pH determined DIC concentrations and fluxes, but soil solutions were often supersaturated with DIC relative to soil air CO2. Leaching losses of biogenic carbon (DOC plus biogenic DIC) from grasslands equalled 5–98% (median: 22%) of net ecosystem exchange (NEE) plus carbon inputs with fertilization minus carbon removal with harvest. Carbon leaching increased the net losses from cropland soils by 24–105% (median: 25%). For the majority of forest sites, leaching hardly affected actual net ecosystem carbon balances because of the small solubility of CO2 in acidic forest soil solutions and large NEE. Leaching of CH4 proved to be insignificant compared with other fluxes of carbon. Overall, our results show that leaching losses are particularly important for the carbon balance of agricultural systems. 相似文献
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