The Experts below are selected from a list of 5535 Experts worldwide ranked by ideXlab platform
Paul R Conlin - One of the best experts on this subject based on the ideXlab platform.
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protein kinase c activation stimulates Calcium transport in adrenal zona glomerulosa cells
Biochemical and Biophysical Research Communications, 1998Co-Authors: Massimo Cirillo, Mitzy Canessa, Stephen J Quinn, Paul R ConlinAbstract:Adrenal zona glomerulosa (ZG) cells produce aldosterone in response to angiotensin II and extracellular potassium through different mechanisms which involve changes in cytosolic free Calcium (Cai). Protein kinase C (PKC) activation is part of the angiotensin II signalling cascade but its effects on Caiare unknown. PKC activation with 1 μM phorbol 12-myristate 13-acetate (PMA) and 8 mM Kosignificantly increased the rate of Calcium influx (P < 0.001). Both the PKC- and the Ko-induced Calcium influx occurred via a nifedipine-sensitive pathway. When both were combined, PKC activation and 8 mM Kowere not additive over either agent alone. PKC activation and 8 mM Koalso stimulated Calcium efflux (P < 0.01). When combined together PKC activation and 8 mM Kohad additive effects on Calcium efflux (P < 0.05). PKC activation did not increase Cainor the Exchangeable Calcium pool in contrast to 8 mM Kowhich significantly increased both (P < 0.001). Thus, PKC activation in ZG cells induces a pattern of Calcium transport characterized by accelerated Calcium recycling across the cell membrane without increasing cell Calcium content.
Reiner Dohrmann - One of the best experts on this subject based on the ideXlab platform.
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three new quick cec methods for determining the amounts of Exchangeable Calcium cations in calcareous clays
Clays and Clay Minerals, 2009Co-Authors: Reiner Dohrmann, Stephan KaufholdAbstract:The cation exchange capacity (CEC) is one of the most important properties of clays in terms of their performance in both natural and technical processes. For decades, common methods for determining Exchangeable cations have failed when calcareous clays or soils were examined, because calcite is at least partly dissolved throughout the exchange experiment which in turn increases measureable Ca 2+ concentrations. As a result, Exchangeable Ca 2+ and the sum of Exchangeable cations by far exceed the amount of negative charges. In the past, the silver-thiourea method (AgTU) has been modified to overcome this problem (AgTU calcite ), but is unsatisfactory as the method is laborious. In the present study three new methods based on two alternative metal complexes, cobalt(III) hexamine (CoHex) and copper(II) triethylenetetramine (Cu-trien), are proposed. The optimum solid/liquid ratios of these methods and the optimum complex concentration of Cu-trien are reported, depending on the mineralogical composition of the samples. The key development is that the exchange solutions are saturated with respect to calcite prior to the experiment. Approximately 70―90% of the dissolution of calcite present as an admixture in a clay sample is suppressed in the subsequent cation exchange experiment, but not all. The Ca 2+ exchange is not suppressed and there is no evidence for any precipitation of this Ca 2+ . Three possibilities for how to handle this problem are discussed, one of which is to perform no further correction. The resulting error arises from the remaining calcite solubility of the different solutions after pre-treatment with calcite. This corresponds to errors of 0.2-1.3 (CoHex calcite ) and 0.7-8.4 (Cu-trien calcite ) -eq/100 g Ca 2+ for samples with small and large CEC values, respectively. As a consequence of the poor performance of Cu-trien calcile for samples with large CEC, a more concentrated Cu-trien 5 x calcite solution was developed which performed much better: 0.1-0.8 meq/100 g (Cu-trien 5 x calcite ). For Cu-trien 5 x calcite and CoHeX calcite at least, the errors are in the range of the non-systematic scattering for Exchangeable Ca 2+ determination. Therefore, the methods suggested provide 'operationally correct' Ca 2+ values without additional effort. Moreover, owing to the high selectivity of the index cations applied in the present study, only one exchange step is required, providing a significant advantage over the AgTU calcite method.
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cation exchange capacity methodology i an efficient model for the detection of incorrect cation exchange capacity and Exchangeable cation results
Applied Clay Science, 2006Co-Authors: Reiner DohrmannAbstract:Abstract In this study a model is proposed enabling the detection of incorrect cation exchange capacity (CEC) and Exchangeable cation values. Numerous CEC and Exchangeable cation analyses of clayey sediments, soils and bentonites were performed using triethanolamine-buffered barium chloride, ammonium acetate, silver thiourea and other exchange techniques. As long as these naturally clayey materials only contain adsorbents like clay minerals, organic substances and a group of mainly detrital minerals like quartz, feldspar and mica, results obtained with most procedures are correct. Problems arise when materials contain secondary phases like soluble Ca-carbonates and -sulphates. During the CEC-experiments, these phases interact with the exchange solution. According to expectations, results of Exchangeable Calcium values are incorrect but CEC is also affected [Deller, B., 1981. Determination of Exchangeable acidity, carbonate ions and change of buffer in triethanolamine-buffered solutions percolated through soil samples containing carbonates. Commun. Soil Sci. Plant Analysis 12, 161–177.]. Using the proposed Carbonate and Sulphate Field Model (CSF model) an evaluation of the accuracy of results is possible.
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cation exchange capacity methodology iii correct Exchangeable Calcium determination of calcareous clays using a new silver thiourea method
Applied Clay Science, 2006Co-Authors: Reiner DohrmannAbstract:Abstract Cation exchange capacity (CEC) is a fundamental property of clays and soils. Determination of CEC for samples that contain Ca-carbonate minerals, such as calcite and dolomite, is problematic because Ca2+ released by dissolution of carbonates during CEC determinations interferes with the accuracy of CEC values. This paper describes a new method for the determination of correct Exchangeable Ca2+ values of calcareous clays and soils. For the method, a silver–thiourea exchange solution is saturated with Ca2+ by treatment with fine-grained calcite prior to the start of the exchange procedure. Using this exchange solution, calcite in the sample can no longer be dissolved but Exchangeable Ca2+ is desorbed quantitatively. The case for dolomite is similar, because dissolution of dolomite is minimised. However, the determination of reasonable Exchangeable Ca2+ values for samples containing gypsum is not possible because gypsum is soluble in the exchange solution.
Massimo Cirillo - One of the best experts on this subject based on the ideXlab platform.
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protein kinase c activation stimulates Calcium transport in adrenal zona glomerulosa cells
Biochemical and Biophysical Research Communications, 1998Co-Authors: Massimo Cirillo, Mitzy Canessa, Stephen J Quinn, Paul R ConlinAbstract:Adrenal zona glomerulosa (ZG) cells produce aldosterone in response to angiotensin II and extracellular potassium through different mechanisms which involve changes in cytosolic free Calcium (Cai). Protein kinase C (PKC) activation is part of the angiotensin II signalling cascade but its effects on Caiare unknown. PKC activation with 1 μM phorbol 12-myristate 13-acetate (PMA) and 8 mM Kosignificantly increased the rate of Calcium influx (P < 0.001). Both the PKC- and the Ko-induced Calcium influx occurred via a nifedipine-sensitive pathway. When both were combined, PKC activation and 8 mM Kowere not additive over either agent alone. PKC activation and 8 mM Koalso stimulated Calcium efflux (P < 0.01). When combined together PKC activation and 8 mM Kohad additive effects on Calcium efflux (P < 0.05). PKC activation did not increase Cainor the Exchangeable Calcium pool in contrast to 8 mM Kowhich significantly increased both (P < 0.001). Thus, PKC activation in ZG cells induces a pattern of Calcium transport characterized by accelerated Calcium recycling across the cell membrane without increasing cell Calcium content.
Yong Jiang - One of the best experts on this subject based on the ideXlab platform.
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base cations and micronutrients in soil aggregates as affected by enhanced nitrogen and water inputs in a semi arid steppe grassland
Science of The Total Environment, 2017Co-Authors: Ruzhen Wang, Yuge Zhang, Zhuwen Xu, Jennifer A J Dungait, Heather L. Buss, Shan Yang, Yong JiangAbstract:Abstract The intensification of grassland management by nitrogen (N) fertilization and irrigation may threaten the future integrity of fragile semi-arid steppe ecosystems by affecting the concentrations of base cation and micronutrient in soils. We extracted base cations of Exchangeable Calcium (Ca), magnesium (Mg), potassium (K), and sodium (Na) and extractable micronutrients of iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn) from three soil aggregate sizes classes (microaggregates, 2 mm) from a 9-year N and water field manipulation study. There were significantly more base cations (but not micronutrients) in microaggregates compared to macroaggregates which was related to greater soil organic matter and clay contents. Nitrogen addition significantly decreased Exchangeable Ca by up to 33% in large and small macroaggregates and Exchangeable Mg by up to 27% in three aggregates but significantly increased extractable Fe, Mn and Cu concentrations (by up to 262%, 150%, and 55%, respectively) in all aggregate size classes. However, water addition only increased Exchangeable Na, while available Fe and Mn were decreased by water addition when averaging across all N treatments and aggregate classes. The loss of Exchangeable Ca and Mg under N addition and extractable Fe and Mn in soil aggregates under water addition might potentially constrain the productivity of this semi-arid grassland ecosystem.
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nitrogen addition alters elemental stoichiometry within soil aggregates in a temperate steppe
Solid Earth, 2016Co-Authors: Jinfei Yin, Ruzhen Wang, Heyong Liu, Xue Feng, Yong JiangAbstract:Abstract. Ongoing increases in anthropogenic nitrogen (N) inputs have largely affected soil carbon (C) and nutrient cycling in most terrestrial ecosystems. Numerous studies have concerned the effects of elevated N inputs on soil dissolved organic carbon (DOC), dissolved inorganic N (DIN), available phosphorus (AP), Exchangeable Calcium (Ca) and magnesium (Mg), and available iron (Fe) and manganese (Mn). However, few have emphasized the stoichiometric traits of these soil parameters, especially within different soil aggregate fractions. In a semiarid grassland of Inner Mongolia, we studied the effect of N addition on the ratios of DOC : DIN, DOC : AP, DIN : AP, Exchangeable Ca : Mg, available Fe : Mn within three soil aggregate classes of large macroaggregates (> 2000 µm), small macroaggregates (250–2000 µm), and microaggregates (
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profile distribution of Exchangeable Calcium and magnesium in an aquic brown soil as affected by land use type
Journal of Applied Ecology, 2008Co-Authors: Yuge Zhang, Wenju Liang, Yong JiangAbstract:A comparative study was made on the profile distribution of Exchangeable Ca and Mg and Ca/Mg ratio at the depth of 0-150 cm in an aquic brown soil under four land use patterns, i. e., paddy field, maize field, fallow field, and woodland. The results showed that less difference was observed in the soil Exchangeable Ca content and storage among different land use patterns. For soil Exchangeable Mg, it was significantly higher in woodland than in paddy field, and its storage was in the sequence of woodland > maize field > fallow field > paddy field (P <0.05). The Exchangeable Ca/Mg ratio tended to decrease with soil depth, and was significantly lower in paddy field than in other three land use patterns in the soil layers below 40 cm (P <0.05). The preferential retention of Mg in soil ecosystem, soil management practices, and plant characteristics, e. g., biomass cycling rate, biomass above- and below-ground allocation, root distribution, and maximum rooting depth) might play important roles in shaping soil Exchangeable Ca and Mg profiles and in reconstructing soil Exchangeable Ca and Mg pools.
Henrique Soares Koehler - One of the best experts on this subject based on the ideXlab platform.
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acidity variables and Exchangeable Calcium and magnesium on an oxisol treated with phosphate alkaline biosolid
Scientia Agraria, 2010Co-Authors: Luiz Carlos Da Silva, Luiz Antonio Correa Lucchesi, Henrique Soares KoehlerAbstract:Resumen en: The alkaline biosolid enriched by phosphorus (P) can increase the soil extractable P4 and and exert further effects about soil acidity variables and exch...
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acidity variables and Exchangeable Calcium and magnesium on an oxisol treated with phosphate alkaline biosolid variaveis de acidez e calcio e magnesio trocaveis num latossolo tratado com um biossolido alcalinizado e fosfatado
2010Co-Authors: Luiz Carlos Da Silva, Luiz Antonio, Correa Lucchesi, Henrique Soares KoehlerAbstract:The alkaline biosolid enriched by phosphorus (P) can increase the soil extractable P 4 and and exert further effects about soil acidity variables and Exchangeable Calcium and magnesium. This fact can also contributes to the reduction of problems related to its final destination and attract farmers to the use of adequate quantities of these biosolids in agriculture by reduce his costs with soil fertilizers and liming operations. This work aimed to evaluate the acidity variables and Exchangeable Calcium and magnesium on an Oxisol treated with an alkaline biosolid that received different levels of phosphorus (P) from three sources after common bean grown under greenhouse condition. An alkaline biosolid received 0% P, 0.436% P, 0.872% P and 1.745% P from the partially acidulated rock phosphate Alvorada, single superphosphate and triple superphosphate. To the treatment establishment was recommended 45.85 kg P ha -1 from the treatments, except from the 0% P. Four levels and 3 sources of P addition generated 12 treatments with 4 replications. Treatments were applied 2.5 kg dry weight of an Oxisol from Contenda, PR, Brazil, in vases which was cultivated with 6 common bean plants (cv. IPR Uirapuru). After the plant harvest the soil analysis showed increases in the soil pH (CaCl2 0.01 mol dm -3 ), Exchangeable Calcium, magnesium and decreases in aluminum and potential acidity due to the treatments. The assessed variables showed the larger alterations due to the levels 0.436% of P addition in alkaline biosolid from partially acidulated rock phosphate Alvorada and single superphosphate.
