868 resultados para Potassium uptake selectivity


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Haloesterification of diverse diols with various carboxylic acids was achieved using potassium halides (KX) as the only halide source in ionic liquids. The best yield was obtained in [BMIM][PF6] when 1,2-octanediol, palmitic acid and KBr were used. This yield was 85% and the regioisomer with the bromine in primary position was present in a 75:25 ratio. The regioisomeric ratio could be improved using either KCl or some phenylcarboxylic acids. [BMIM][PF6] acts as both reaction media and catalyst of the reaction. To the best of our knowledge, this type of combined reaction using an ionic liquid is unprecedented. The other solvents tested did not lead either to the same yield or to the same regioisomeric ratio.

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Pig slurry is a valuable nutrient resource but constitutes a waste disposal problem in areas of high animal density. In the semiarid area of Pla d’Urgell, in the Ebro Valley, North-East Spain, irrigated crops receive large amounts of nutrients in the form of manure and mineral fertilizers. We studied the effect of pig slurry and additional side-dress mineral fertilizers on irrigated wheat, Triticum aestivum L., on a coarse loam soil, with high soil P and K levels. Yields increased by 62.3% when using pig slurry. The application of ammonium sulfate nitrate sidedress did not significantly increase wheat production. The average apparent recoveries were higher for potassium (88.7%) than for nitrogen (51.3%) and phosphorus (36.3%). Greater amounts of soil NO3-N were measured over the four growing seasons, which was consistent with the amount of N applied. Macronutrient and micronutrient uptake was significant higher for pig slurry treatments, but only small differences were found between the pig slurry and pig slurry plus ammonium sulfate nitrate treatments. The unfertilized treatment showed significantly lower soil P, K, Cu and Zn content than pig slurry treatments; 34%, 21%, 34%, and 26% respectively. These findings could be used to develop a nutrient management plan based on knowledge of soil test results and crop nutrient removal. This could help to improve the use of pig slurry and mineral fertilizers on limited available land areas and prevent the accumulation of potentially toxic elements in soils and the export of nutrients through agricultural drainage.

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One aim of this study is to determine the impact of water velocity on the uptake of indicator polychlorinated biphenyls (iPCBs) by silicone rubber (SR) and low-density polyethylene (LDPE) passive samplers. A second aim is to assess the efficiency of performance reference compounds (PRCs) to correct for the impact of water velocity. SR and LDPE samplers were spiked with 11 or 12 PRCs and exposed for 6 weeks to four different velocities (in the range of 1.6 to 37.7 cm s−1) in river-like flow conditions using a channel system supplied with river water. A relationship between velocity and the uptakewas found for each iPCB and enables to determine expected changes in the uptake due to velocity variations. For both samplers, velocity increases from 2 to 10 cm s−1, 30 cm s−1 (interpolated data) and 100 cm s−1 (extrapolated data) lead to increases of the uptake which do not exceed a factor of 2, 3 and 4.5, respectively. Results also showed that the influence of velocity decreased with increasing the octanol-water coefficient partition (log Kow) of iPCBs when SR is used whereas the opposite effect was observed for LDPE. Time-weighted average (TWA) concentrations of iPCBs in water were calculated from iPCB uptake and PRC release. These calculations were performed using either a single PRC or all the PRCs. The efficiency of PRCs to correct the impact of velocity was assessed by comparing the TWA concentrations obtained at the four tested velocities. For SR, a good agreement was found among the four TWA concentrations with both methods (average RSD b 10%). Also for LDPE, PRCs offered a good correction of the impact of water velocity (average RSD of about 10 to 20%). These results contribute to the process of acceptance of passive sampling in routine regulatory monitoring programs.

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Yield and physical and chemical characteristics of 'Paluma' guava fruit were evaluated as a function of the harvest at different maturity stages, under influence of nitrogen and potassium fertilization, in Petrolina, State of Pernambuco, Brazil. Fertilizer rates were 67 kg N + 33 kg K2O, 133 kg N + 67 kg K2O, 200 kg N + 100 kg K2O and 267 kg N + 133 kg K2O per hectare. Fruits were evaluated at maturity stages 2, 3, 4 and 5, established according to peel color. Higher doses of N and K induced higher yields. Nevertheless, fertilization with 200 kg of N + 100 kg of K per hectare improved fruit quality, delaying ascorbic acid breakdown and conserving pulp firmness. Main changes took place at maturity stages 4 and 5, when the fruit should present ideal conditions for consumption, namely the increase on soluble solids and soluble sugars content.

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Nucleoside transporters (NTs) mediate the uptake of nucleosides and nucleobases across the plasma membrane, mostly for salvage purposes. The canonical NTs belong to two gene families, SLC29 and SLC28. The former encode equilibrative nucleoside transporter proteins (ENTs), which mediate the facilitative diffusion of natural nucleosides with broad selectivity, whereas the latter encode concentrative nucleoside transporters (CNTs), which are sodium-coupled and show high affinity for substrates with variable selectivity. These proteins are expressed in most cell types, exhibiting apparent functional redundancy. This might indicate that CNTs play specific roles in the physiology of the cell beyond nucleoside salvage. Here, we addressed this possibility using adenoviral vectors to restore tumor cell expression of hCNT1 or a polymorphic variant (hCNT1S546P) lacking nucleoside translocation ability. We found that hCNT1 restoration in pancreatic cancer cells significantly altered cell-cycle progression and phosphorylation status of key signal-transducing kinases, promoted poly-(ADP ribose) polymerase hyperactivation and cell death, and reduced tumor growth and cell migration. Importantly, the translocation-defective transporter triggered these same effects on cell physiology. These data predict a novel and totally unexpected biological role for the nucleoside transporter protein hCNT1 that appears to be independent of its role as mediator of nucleoside uptake by cells, thereby suggesting a transceptor function. Cell Death & Disease Anastasis Stephanou Receiving Editor Cell Death & Disease 19th Apr 2013 Dr Perez-Torras Av/ Diagonal 643. Edif. Prevosti, Pl -1 Barcelona 08028 Spain RE: Manuscript CDDIS-13-0136R, 'CDDIS-13-0136R' Dear Dr Perez-Torras, It is a pleasure to inform you that your manuscript has been evaluated at the editorial level and has now been officially accepted for publication in Cell Death & Disease, pending you meet the following editorial requirements: 1) the list of the abbreviations is missing please include Could you send us the revised text as word file via e-mail and we will proceed and transfer the paper onto our typesetters. Please download, print, sign, and return the Licence to Publish Form using the link below. This must be returned via FAX to ++ 39 06 7259 6977 before your manuscript can be published:

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A field experiment with pineapple (Smooth Cayenne) was carried out on an Ultisol located in the city of Agudos (22º30'S; 49º03'W), in the state of São Paulo, Brazil, with the objective of investigating the effects of rates and sources of potassium fertilizer on plant growth and fruit yield. The experiment was a complete factorial design (4x3) with four rates (0, 175, 350, and 700 kg ha-1 of K2O) and three combinations of K sources (100% KCl, 100% K2SO4, and 40% K2SO4 + 60% KCl). Plant growth and fruit yield were evaluated. Biomass accumulation of pineapple plants was impaired by chlorine added with potassium chloride. Fruit yield increased with potassium fertilization. At high rates of K application, fertilization with K2SO4 showed better results than with KCl. Detrimental effects of KCl were associated with excess of chlorine.

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Genetic diversity of rootstocks can affect nutrient uptake and the nutrient status of grapevines. The rootstock influence on nutrient content in grape petioles was evaluated on three rootstocks competition experiments carried out at Vale do Rio do Peixe region, in the state of Santa Catarina, Brazil, with the cultivars Niagara Rosada, Concord, and Isabella, grafted on different rootstocks. Two soil liming depths were also evaluated in the Isabella experiment. The greatest rootstock effect was observed on K and Mg content and K/Mg ratio in the petioles. The Vitis vinifera x V. rotundifolia hybrid rootstocks VR 043-43 and VR 044-4 provided the highest K/Mg values and self rooted Isabella the lowest K/Mg ratio. The other tested rootstocks resulted in intermediate values. There was also significant effect on P content, but only in Niagara Rosada and Concord experiments. The depth of soil liming did not significantly affect K and Mg content in the Isabella experiment. The results indicate that rootstock must be considered for nutritional status evaluation and fertilizer recommendation regarding to K and Mg.

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The goal of this research was evaluated the effects of potassium and nitrogen fertilization on the plum (Prunus salicina) fresh fruit quality and after cold storage. The experiment was carried out in a five year-old plum orchard 'Reubennel', located at Araucaria County, Parana State, Southern Brazil, in a Haplumbrept Soil. Potassium fertilizer was applied at 55 and 110 kg/ha/year of K2O, as KCl. Nitrogen fertilizer was applied at 40, 80, 120, 160 and 200 kg/ha/year of N, as urea. It was used a split-plot design in a factorial scheme (2x5). One hundred plum fruits were harvested from each plot, in the same day, when 25 to 50% of the peel presented yellow-reddish color. At harvest and after 17, 27 and 37 days of storage at 0 ± 0.5 ºC, the flesh firmness, the total soluble solids, and the titratable acidity were assessed. Fresh fruit quality was affected by N application, with the best results obtained by applying 40 kg/ha/year of N. The N and K rate of 40 and 110 kg/ha/year, respectively, kept superior fruit quality during the storage. 'Reubennel' cold storage can not exceed 27 days. Fresh and stored 'Reubennel' plum fruit qualities depend on the N and K fertilizer rates.

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The objective of this work was to combine the advantages of the dried blood spot (DBS) sampling process with the highly sensitive and selective negative-ion chemical ionization tandem mass spectrometry (NICI-MS-MS) to analyze for recent antidepressants including fluoxetine, norfluoxetine, reboxetine, and paroxetine from micro whole blood samples (i.e., 10 microL). Before analysis, DBS samples were punched out, and antidepressants were simultaneously extracted and derivatized in a single step by use of pentafluoropropionic acid anhydride and 0.02% triethylamine in butyl chloride for 30 min at 60 degrees C under ultrasonication. Derivatives were then separated on a gas chromatograph coupled with a triple-quadrupole mass spectrometer operating in negative selected reaction monitoring mode for a total run time of 5 min. To establish the validity of the method, trueness, precision, and selectivity were determined on the basis of the guidelines of the "Société Française des Sciences et des Techniques Pharmaceutiques" (SFSTP). The assay was found to be linear in the concentration ranges 1 to 500 ng mL(-1) for fluoxetine and norfluoxetine and 20 to 500 ng mL(-1) for reboxetine and paroxetine. Despite the small sampling volume, the limit of detection was estimated at 20 pg mL(-1) for all the analytes. The stability of DBS was also evaluated at -20 degrees C, 4 degrees C, 25 degrees C, and 40 degrees C for up to 30 days. Furthermore, the method was successfully applied to a pharmacokinetic investigation performed on a healthy volunteer after oral administration of a single 40-mg dose of fluoxetine. Thus, this validated DBS method combines an extractive-derivative single step with a fast and sensitive GC-NICI-MS-MS technique. Using microliter blood samples, this procedure offers a patient-friendly tool in many biomedical fields such as checking treatment adherence, therapeutic drug monitoring, toxicological analyses, or pharmacokinetic studies.

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G protein-gated inwardly rectifying potassium (GIRK) channels play an important role in regulating neuronal excitability. Sorting nexin 27b (SNX27b), which reduces surface expression of GIRK channels through a PDZ domain interaction, contains a putative Ras-association (RA) domain with unknown function. Deleting the RA domain in SNX27b (SNX27b-DRA) prevents the down-regulation of GIRK2c/GIRK3 channels. Similarly, a point mutation (K305A) in the RA domain disrupts regulation of GIRK2c/GIRK3 channels and reduces H-Ras binding in vitro. Finally, the dominant-negative H-Ras (S17N) occludes the SNX27b-dependent decrease in surface expression of GIRK2c/GIRK3 channels. Thus, the presence of a functional RA domain and the interaction with Ras-like G proteins comprise a novel mechanism for modulating SNX27b control of GIRK channel surface expression and cellular excitability.