905 resultados para Potassium Channel


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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Introduction. Premature ejaculation is one of the most common male sexual dysfunctions. Current pharmacological treatments involve reduction in penile sensitivity by local anesthetics or increase of ejaculatory threshold by selective serotonin reuptake inhibitors. a1-Adrenoceptors (a1-ARs) and L-type calcium channels are expressed in the smooth muscles of the male reproductive tract, and their activations play an important role in the physiological events involved in the seminal emission phase of ejaculation.Aim. To evaluate if the inhibition of the contractility of the vas deferens and seminal vesicle by alpha(1)-AR antagonism or the L-type calcium channel blockade can delay ejaculation.Methods. The effects of the alpha(1)-AR antagonist tamsulosin and of the L-type calcium channel blockers, nifedipine and (S)-(+)-niguldipine, on contractions induced by norepinephrine in the rat vas deferens and seminal vesicles in vitro and on the ejaculation latency of male rats in behavioral mating tests were evaluated.Main Outcome Measure. Tension development of vas deferens and seminal vesicles in response to norepinephrine in vitro and behavioral mating parameters were quantified.Results. Tension development of vas deferens and seminal vesicle to alpha(1)-AR activation was significantly inhibited by tamsulosin, nifedipine, and (S)-(+)-niguldipine. Tamsulosin displayed insurmountable antagonism of contractions induced by norepinephrine in the rat vas deferens and seminal vesicle. Ejaculation latency of male rats was not modified by tamsulosin, nifedipine, or (S)-(+)-niguldipine; however, both the number and weight of the seminal plugs recovered from female rats mated with male rats treated with tamsulosin were significantly reduced.Conclusion. Seminal emission impairment by inhibition of vas deferens or seminal vesicle contractility by L-type calcium channel blockade or alpha(1)-AR antagonism is not able to delay the ejaculation. de Almeida Kiguti LR and Pupo AS. Investigation of the effects of alpha(1)-adrenoceptor antagonism and L-type calcium channel blockade on ejaculation and vas deferens and seminal vesicle contractility in vitro. J Sex Med 2012; 9: 159-168.

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Potassium (K) is required in high doses by the banana (Musa sp.) plant and interacts with other nutrient elements in which banana tissues are maintained under in vitro condition as a consequence modifications in the plant metabolism take place mainly in nitrogen (N) compounds, such as proteins, amino acids, and secondary compounds. When K is present in concentrations lower than that required, diamines such as putrescine and poliamines are formed. This metabolic disorder can also be correlated with the presence of different inorganic N forms, such as nitrate (NO3) and ammonium (NH4), and the ratios between both ions as well. In order to follow the physiological performance of the interrelationships, K/putrescine and of the NO3/NH4 ratio in the tissue of banana vitroplantlets, shoot apex of two banana cvs. Nanica and Prata Ana were maintained in modified MS medium in the presence of six different doses of K: 5, 10, 15, 20, 25, and 30 mM. After the period of tissue proliferation the cultures were transferred to rooting media containing the same different K doses. Dry matter, K, putrescine, and spermidine contents and their accumulation were determined in the shoots and roots of the vitroplantlets and in the shoot apex of the explant donor cultivar as well as the corresponding values for the whole vitroplantlets calculated. The data were statistically analyzed. The contents and accumulations of putrescine and spermidine in banana tissues were enhanced as K concentration decreased in the medium: four times (0.19% of the dry matter) for cv. Nanica and eight times (0.25% of the dry matter) for cv. Prata Ana. This behavior was not only related to the K depletion but to the NO3/NH4 ratio as well.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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The effects of silver insertion on the TiO(2) photocatalytic activity for the degradation of diclofenac potassium were reported here. Techniques such as X-ray diffraction, scanning electron microscopy and UV-Vis spectroscopy were used to comprehend the relation between structure and properties of the silver-modified TiO(2), thin films obtained by the sol-gel method. The lattice parameters and the crystallinity of TiO(2) anatase phase were affected by inserted silver, and the film thickness increased about 4 nm for each 1 wt.% of silver inserted. The degradation of diclofenac potassium and by-products reached an efficiency of 4.6 mg(C) W(-1) when the material was modified with silver. Although the first step of degradation involves only the photochemical process related to the loss of the chlorine and hydrogen atoms. This cyclization reaction leads to the formation of intermediate, which degradation is facilitated by the modified material. (C) 2007 Elsevier B.V. All rights reserved.

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The crustacean species composition in the intertidal zones of 13 sheltered unconsolidated marine beaches in south-eastern Brazil is described. Fifty-three crustacean species were collected, adding 46 species to the total reported by previous studies in the same region. Decapods dominated the community, in contrast to exposed sandy beaches where peracarids normally predominate. The species were distributed irregularly among the beaches. Richness varied markedly among sites, and was positively related to a combination of factors such as fine sand grains, high organic matter content, and relatively low silt-clay content. The presence of rock fragments enabled both rocky shore and sandy beach crustaceans to occur oil the same beaches. Richness and abundance of crustaceans showed no clear relationship to sediment grain size and slope, in contrast to the norm for exposed sandy beaches. The dominance of the tanaid Kalliapseudes schubarti in sonic areas may be a result of organic matter pollution in the region. These beaches showed higher species richness than typical sheltered and exposed sandy beaches, indicating that this sheltered, highly heterogeneous seascape is an important area for conservation.

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A procedure to model optical diffused-channel waveguides is presented in this work. The dielectric waveguides present anisotropic refractive indexes which are calculated from the proton concentration. The proton concentration inside the channel is calculated by the anisotropic 2D-linear diffusion equation and converted to the refractive indexes using mathematical relations obtained from experimental data, the arbitrary refractive index profile is modeled by a. nodal expansion in the base functions. The TE and TM-like propagation properties (effective index) and the electromagnetic fields for well-annealed proton-exchanged (APE) LiNbO3 waveguides are computed by the finite element method.

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Anoplin, an antimicrobial, helical decapeptide from wasp venom, looses its biological activities by mere deamidation of its C-terminus. Secondary structure determination, by circular dichroism spectroscopy in amphipathic environments, and lytic activity in zwitterionic and anionic vesicles showed quite similar results for the amidated and the carboxylated forms of the peptide. The deamidation of the C-terminus introduced a negative charge at an all-positive charged peptide, causing a loss of amphipathicity, as indicated by molecular dynamics simulations in TFE/water mixtures and this subtle modification in a peptide's primary structure disturbed the interaction with bilayers and biological membranes. Although being poorly lytic, the amidated form, but not the carboxylated, presented ion channel-like activity on anionic bilayers with a well-defined conductance step; at approximately the same concentration it showed antimicrobial activity. The pores remain open at trans-negative potentials, preferentially conducting cations, and this situation is equivalent to the interaction of the peptide with bacterial membranes that also maintain a high negative potential inside. Copyright (C) 2007 European Peptide Society and John Wiley & Sons, Ltd.

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Using the exclusive decay B-s(0)-->J/psi(mu(+)mu(-))phi(K+K-), we report the most precise single measurement of the B-s(0) lifetime. The data sample corresponds to an integrated luminosity of approximately 220 pb(-1) collected with the D0 detector at the Fermilab Tevatron Collider in 2002-2004. We reconstruct 337 signal candidates, from which we extract the B-s(0) lifetime, tau(B-s(0))=1.444(-0.090)(+0.098)(stat)+/-0.020(sys) ps. We also report a measurement for the lifetime of the B-0 meson using the exclusive decay B-0-->J/psi(mu(+)mu(-))K-*0(892)(K(+)pi(-)). We reconstruct 1370 signal candidates, obtaining tau(B-0)=1.473(-0.050)(+0.052)(stat)+/-0.023(sys) ps, and the ratio of lifetimes, tau(B-s(0))/tau(B-0)=0.980(-0.071)(+0.076)(stat)+/-0.003(sys).

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The scattering of ortho-positronium (Ps) by H-2 has been investigated using a three-Ps-state (Ps(1s,2s, 2p)H-2(X (1)Sigma(g)(+))) coupled-channel model and using the Born approximation for higher excitations and ionization of Ps and B (1)Sigma(u)(+) and b (3)Sigma(u)(+) excitations of H-2. We employ a recently proposed time-reversal-symmetric non-local electron-exchange model potential. We present a calculational scheme for solving the body-frame fixed-nuclei coupled-channel scattering equations for Ps-H-2, which simplifies the numerical solution technique considerably. Ps ionization is found to have the leading contribution to target-elastic and all target-inelastic processes. The total cross sections at low and medium energies are in good agreement with experiment.

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Scattering of positronium (Ps) from atoms (H, He, Ne, Ar), molecule (H(2)) and ion (He(+)) have been investigated using a coupled-channel (CC) formalism with a regularised non-local exchange potential. The advantage of using such a regularized exchange potential in the close-coupling formalism and the normalizability aspect of the solution at low energies with a minimum effective coupling are discussed. Results for the elastic and total scattering cross-sections, resonance and binding energies in Ps-H, and pick-off annihilation results in Ps-He are found to be in excellent agreement with measurements and variational predictions. (C) 2000 Elsevier B.V. B.V. All rights reserved.

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A measurement of the top quark mass using events with one charged lepton, missing transverse energy, and jets in the final state, collected by the D0 detector from p (p) over bar collisions at root s=1.96 TeV at the Fermilab Tevatron collider, is presented. A constrained fit is used to fully reconstruct the kinematics of the events. For every event a top quark mass likelihood is calculated taking into account all possible jet assignments and the probability that an event is signal or background. Lifetime-based identification of b jets is employed to enhance the separation between t (t) over bar signal and background from other physics processes and to improve the assignment of the observed jets to the quarks in the t (1) over bar hypothesis. We extract a multiplicative jet energy scale (JES) factor in situ, greatly reducing the systematic effect related to the jet energy measurement. In a data sample with an integrated luminosity of 425 pb(-1), we observe 230 candidate events, with an estimated background of 123 events, and measure m(t)=173.7 +/- 4.4(stat+JES)(-2.0)(+2.1)(syst) GeV. This result represents the first application of the ideogram technique to the measurement of the top quark mass in lepton+jets events.

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A measurement of the top quark pair production cross section in proton antiproton collisions at an interaction energy of root s=1.96 TeV is presented. This analysis uses 405 +/- 25 pb(-1) of data collected with the D0 detector at the Fermilab Tevatron Collider. Fully hadronic t (t) over bar decays with final states of six or more jets are separated from the multijet background using secondary vertex tagging and a neural network. The t (t) over bar cross section is measured as sigma(t (t) over bar)=4.5(-1.9)(+2.0)(stat)(-1.1)(+1.4)(syst)+/- 0.3(lumi) pb for a top quark mass of m(t)=175 GeV/c(2).

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We present a measurement of the top quark mass in the dilepton channel based on approximately 370 pb(-1) of data collected by the DO experiment during Run R of the Fermilab Tevatron collider. We employ two different methods to extract the top quark mass. We show that both methods yield consistent results using ensemble tests of events generated with the DO Monte Carlo simulation. We combine the results from the two methods to obtain a top quark mass m(t) = 178.1 +/- 8.2 GeV. The statistical uncertainty is 6.7 GeV and the systematic uncertainty is 4.8 GeV. (c) 2007 Elsevier B.V. All rights reserved.

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We report a search for the standard model (SM) Higgs boson based on data collected by the D0 experiment at the Fermilab Tevatron Collider, corresponding to an integrated luminosity of 260 pb(-1). We study events with missing transverse energy and two acoplanar b jets, which provide sensitivity to the ZH production cross section in the nu nu bb channel, and to WH production when the lepton from the W ->center dot nu decay is undetected. The data are consistent with the SM background expectation, and we set 95% C.L. upper limits on sigma(pp -> ZH/WH) x B(H -> bb) from 3.4/8.3 to 2.5/6.3 pb, for Higgs-boson masses between 105 and 135 GeV.