16 research outputs found

    LATE CARBONIFEROUS BRACHIOPODS FROM KARAKORUM, PAKISTAN

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    Carboniferous rocks from North Karakorum display sharp lateral variations in lithology and thickness suggesting accumulation in half-grabens during continental rifting between the Karakorum block and northern Gondwana. Different Carboniferous successions, belonging to distinct tectonic units, have been detected. Thin, poorly fossiliferous successions of arenites and crinoidal limestones contrast with very thick terrigenous-carbonate successions comprising two distinct fossiliferous horizons. The lower fossiliferous horizon yielded brachiopods (Pustula sp., Rhipidomella sp., Choristites sp., Martiniopsis sp., Afghanospirifer sp., Gypospirifer sp., Composita sp.) of Bashkirian age. The upper fossiliferous horizon, lying about 90 m above the former, contains corals, crinoids and brachiopods (Densepustula cf. losarensis, Dowhatania sulcata n. sp., Brachythyris sp., Rhipidomella sp., Septacamera dowhatensis, Alispirifer middlemissi) of Moscovian to Kasimovian age. The Carboniferous brachiopods of North Karakorum are similar to those collected in the Late Carboniferous of Central Afghanistan, Himalaya (Manang, Spiti, Tibet), and Lhasa Block (Xainza area).&nbsp

    Opening of the Neo-Tethys Ocean and the Pangea B to Pangea A transformation during the Permian

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    We studied the stratigraphy, composition, and paleomagnetic properties of lateritic weathering profiles of Permian age from northern Iran and western Karakoram, Pakistan. A limited set of samples deemed representative yielded stable low-inclination paleomagnetic components carried essentially by hematite of chemical origin isolated in massive, fine-grained, and homogeneous ferricrete facies. These laterites originated at equatorial paleolatitudes characterized by intense weathering processes under warm and humid climatic conditions. Paleomagnetic estimates of paleolatitude from Iran, Karakoram, and north Tibet from this study and the literature, albeit sparse, provide testable constraints on the motion of the Cimmerian terranes as the result of the opening of the Neo-Tethys Ocean along the eastern margin of Gondwana during the Permian. We confirm and help refine previous suggestions that the Cimmerian terranes migrated from southern Gondwanan paleolatitudes in the Early Permian to subequatorial paleolatitudes by the Middle Permian – Early Triassic. As a novel conclusion, we find that timing, rates, and geometry of Cimmerian tectonics are broadly compatible with the transformation of Pangea from an Irvingian B to a Wegenerian A-type configuration with Neo-Tethyan opening taking place contemporaneously essentially in the Permian

    Neuroendocrine characterization and anorexigenic effects of telmisartan in diet- and glitazone-induced weight gain.

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    Telmisartan is an angiotensin II receptor blocker with peroxisome proliferator-activated receptor-gamma agonistic properties. Telmisartan prevents weight gain and decreases food intake in models of obesity and in glitazone-treated rodents. This study further investigates the influence of telmisartan and pioglitazone and their association on weight gain and body composition by examining their influence on neuroendocrine mediators involved in food intake. Male C57/Black 6 mice were fed a high-fat diet, weight matched, and randomized in 4 treatment groups: vehicle, pioglitazone, telmisartan, and pioglitazone-telmisartan. Weight gain, food and water intake, body composition, plasma leptin levels, and the hypothalamic expression of neuroendocrine mediators were analyzed. Additional studies were performed with irbesartan and in angiotensin II 1(A) receptor-knockout mice. Telmisartan abolished weight and fat gain in vehicle- and pioglitazone-treated mice while decreasing food intake, the hypothalamic expression of the agouti-related protein, and plasma leptin levels. Modifications in neuropeptide Y and proopiomelanocortin were not consistent with changes in food intake. The effects on weight gain and expression of the agouti-related protein were intermediate with irbesartan. The effects of telmisartan on weight gain were even more pronounced in angiotensin II 1(A) receptor-knockout mice. This study confirms the anorexigenic effects of telmisartan in mice fed a high-fat diet and suggests for the first time a functional role of telmisartan on hypothalamic orexigenic agouti-related protein regulation. These anorexigenic properties abolish both weight gain and body composition modifications in fat-fed and glitazone-treated mice. The anorexigenic properties are independent from the angiotensin II 1(A) receptor

    Rhizospheric iron and arsenic bacteria affected by water regime: Implications for metalloid uptake by rice

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    Rice is characterized by high levels of arsenic accumulation, even if cultivated in non-contaminated soils. Given the limits for arsenic concentration in rice grain recently established by the European Community, it is essential to understand the mechanisms and find solutions to this issue. Arsenic bioavailability is strictly related to water management of the rice paddy as well as to iron- and arsenic-cycling bacterial populations inhabiting the rice rhizosphere. To evaluate the effect of different agronomic conditions on the root-soil microbiota involved in arsenic mobilization, rice plants were grown in macrocosms containing non contaminated field soil under either continuous flooding, aerobic rice regime or continuous flooding with a 14 day-period of drainage before flowering. Specific groups of iron- and arsenic-cycling bacteria were assessed by real time quantitative PCR and fluorescence in situ hybridization. Continuous flooding led to the release of arsenate and iron in soil solution and produced rice grains with arsenite and organic arsenic above the recently established limits, contrary to the other agronomic conditions. Iron-reducing bacteria affiliated to the family Geobacteraceae significantly increased under continuous flooding in rhizosphere soil, in concomitance to arsenate dissolution from iron minerals. The 14 day-period of drainage before flowering allowed the recycling of iron, with the increase of Gallionella-like iron-oxidizing bacteria. This phenomenon likely influenced the decrease of arsenic translocation in rice grains. Regardless of the water regime, genes for arsenite oxidation (aioA) were the most abundant arsenic-processing genes, explaining the presence of arsenate in soil solution. The presence of arsenite and organic arsenic in rice grains produced under continuous flooding might be related to the retrieval of genes for arsenate reduction (arsC) and for arsenite methylation (arsM) in the proximity of the roots. These outcomes indicate a potential active role of rhizospheric iron- and arsenic-cycling bacteria in determining arsenic accumulation in rice grains from plants cultivated under continuous flooding, even in soil with a low arsenic content
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