45 resultados para Astrofísica nuclear


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Diabetic patients have increased susceptibility to infection, which may be related to impaired inflammatory response observed in experimental models of diabetes, and restored by insulin treatment. The goal of this study was to investigate whether insulin regulates transcription of cytokines and intercellular adhesion molecule 1 (ICAM-1) via nuclear factor-kappa B (NF-kappa B) signaling pathway in Escherichia coli LIPS-induced lung inflammation. Diabetic male Wistar rats (alloxan, 42 mg/kg, iv., 10 days) and controls were instilled intratracheally with saline containing LPS (750 mu g/0.4 mL) or saline only. Some diabetic rats were given neutral protamine Hagedorn insulin (4 IU, s.c.) 2 h before LIPS. Analyses performed 6 h after LPS included: (a) lung and mesenteric lymph node IL-1 beta, TNF-alpha, IL-10, and ICAM-1 messenger RNA (mRNA) were quantified by real-time reverse transcriptase-polymerase chain reaction; (b) number of neutrophils in the bronchoalveolar lavage (BAL) fluid, and concentrations of IL-1 beta, TNF-alpha, and IL-10 in the BAL were determined by the enzyme-linked immunosorbent assay; and (c) activation of NF-kappa B p65 subunit and phosphorylation of I-kappa B alpha were quantified by Western blot analysis. Relative to controls, diabetic rats exhibited a reduction in lung and mesenteric lymph node IL-1 beta (40%), TNF-alpha (similar to 30%), and IL-10 (similar to 40%) mRNA levels and reduced concentrations of IL-1 beta (52%), TNF-alpha (62%), IL-10 (43%), and neutrophil counts (72%) in the BAL. Activation of NF-kappa B p65 subunit and phosphorylation of I-kappa B alpha were almost suppressed in diabetic rats. Treatment of diabetic rats with insulin completely restored mRNA and protein levels of these cytokines and potentiated lung ICAM-1 mRNA levels (30%) and number of neutrophils (72%) in the BAL. Activation of NF-kappa B p65 subunit and phosphorylation of I-kappa B alpha were partially restored by insulin treatment. In conclusion, data presented suggest that insulin regulates transcription of proinflammatory (IL-1 beta, TNF-alpha) and anti-inflammatory (IL-10) cytokines, and expression of ICAM-1 via the NF-kappa B signaling pathway.

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This work investigated the functional role of nuclear factor-kappa B (NF-kappa B) in respiratory burst activity and in expression of the human phagocyte nicotinamide adenine dinucleotide phosphate (NADPH) oxidase genes CYBB, CYBA, NCF1, and NCF2. U937 cells with a stably transfected repressor of NF-kappa B (IKB alpha-S32A/S36A) demonstrated significantly lower superoxide release and lower CYBB and NCF1 gene expression compared with control U937 cells. We further tested Epstein-Barr virus (EBV)-transformed B cells from patients with anhidrotic ectodermal dysplasia with immunodeficiency (EDA-ID), an inherited disorderof NF-kappa B function. Superoxide release and CYBB gene expression by EDA-ID cells were significantly decreased compared with healthy cells and similar to cells from patients with X-linked chronic granulomatous disease (X91 degrees CGD). NCF1 gene expression in EDA-ID S321 cells was decreased compared with healthy control cells and similar to that in autosomal recessive (A47 degrees) CGD cells. Gel shift assays demonstrated loss of recombinant human p50 binding to a NF-kappa B site 5` to the CYBB gene in U937 cells treated with NF-kappa B inhibitors, repressor-transfected U937 cells, and EDA-ID patients cells. Zymosan phagocytosis was not affected by transfection of U937 cells with the NF-kappa B repressor. These studies show that NF-kappa B is necessary for CYBB and NCF1 gene expression and activation of the phagocyte NADPH oxidase in this model system.

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Mycoplasma genitalium (Mg) is a mollicute that causes a range of human urogenital infections. A hallmark of these bacteria is their ability to establish chronic infections that can persist despite completion of appropriate antibiotic therapies and intact and functional immune systems. Intimate adherence and surface colonization of mycoplasmas to host cells are important pathogenic features. However, their facultative intracellular nature is poorly understood, partly due to difficulties in developing and standardizing cellular interaction model systems. Here, we characterize growth and invasion properties of two Mg strains (G37 and 1019V). Mg G37 is a high-passage laboratory strain, while Mg 1019V is a low-passage isolate recovered from the cervix. The two strains diverge partially in gene sequences for adherence-related proteins and exhibit subtle variations in their axenic growth. However, with both strains and consistent with our previous studies, a subset of adherent Mg organisms invade host cells and exhibit perinuclear targeting. Remarkably, intranuclear localization of Mg proteins is observed, which occurred as early as 30 min after infection. Mg strains deficient in adherence were markedly reduced in their ability to invade and associate with perinuclear and nuclear sites.

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The genetic diversity and phylogeographical patterns of Trypanosoma species that infect Brazilian bats were evaluated by examining 1043 bats from 63 species of seven families captured in Amazonia, the Pantanal, Cerrado and the Atlantic Forest biomes of Brazil. The prevalence of trypanosonne-infected bats, as estimated by haemoculture, was 12.9%, resulting in 77 Cultures of isolates, most morphologically identified as Trypanosoma cf. cruzi, classified by barcoding using partial sequences from ssrRNA gene into the subgenus Schizotrypanum and identified as T. cruzi (15), T cruzi marinkellei (37) or T. cf. dionisii (25). Phylogenetic analyses using nuclear ssrRNA, glycosomal glyceraldehyde 3-phosphate dehydrogenase (gGAPDH) and mitochondrial cytochrome b (Cyt b) gene sequences generated three clades, which clustered together forming the subgenus Schizotrypanum. In addition to vector association, bat trypanosomes were related by the evolutionary history, ecology and phylogeography of the bats. Tryponosoma cf. dionisii trypanosomes (32.4%) infected 12 species from four bat families captured in all biomes, from North to South Brazil, and clustered with T. dionisii from Europe despite being separated by some genetic distance. Trypanosoma cruzi marinkellei (49.3%) was restricted to phyllostomid bats from Amazonia to the Pantanal (North to Central). Trypanosoma cruzi (18.2%) was found mainly in vespertilionid and phyllostomid bats from the Pantanal/Cerrado and the Atlantic Forest (Central to Southeast), with a few isolates from Amazonia. (C) 2009 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.

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Protein kinase C (PKC) plays a key role in embryonic stem cell (ESC) proliferation, self-renewal and differentiation However, the function of specific PKC Isoenzymes have yet to be determined Of the PKCs expressed in undifferentiated ESCs, beta IPKC was the only isoenzyme abundantly expressed in the nuclei To investigate the role of beta IPKC in these cells, we employed a phosphoproteomics strategy and used two classical (cPKC) peptide modulators and one beta IPKC-specific inhibitor peptide We identified 13 nuclear proteins that are direct or indirect beta IPKC substrates in undifferentiated ESCs These proteins are known to be involved in regulating transcription, splicing, and chromatin remodeling during proliferation and differentiation Inhibiting beta IPKC had no effect on DNA synthesis in undifferentiated ESCs However, upon differentiation many cells seized to express beta IPKC and beta IPKC was frequently found in the cytoplasm Taken together, our results suggest that beta IPKC takes part in the processes that maintain ESCs in their undifferentiated state

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In this paper, we report results of a quantitative analysis of the effects of neutrons on DNA, and, specifically, the production of simple and double breaks of plasmid DNA in aqueous solutions with different concentrations of free-radical scavengers. The radiation damage to DNA was evaluated by electrophoresis through agarose gels. The neutron and gamma doses were measured separately with thermoluminescent detectors. In this work, we have also demonstrated usefulness of a new system for positioning and removing samples in channel BH#3 of the IEA-R1 reactor at the Instituto de Pesquisas Energeticas e Nucleares (Brazil) without necessity of interrupting the reactor operation. (C) 2010 Elsevier Ltd. All rights reserved.

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This paper describes a new mechanical samples positioning system that allows the safe placement and removal of biological samples for prolonged irradiation, in a nuclear reactor during full-power continuous operation. Also presented herein the materials of construction and operating principles. Additionally, this sample positioning system is compared with an existing pneumatic and automated transfer system, already available at the research reactors. The system consists of a mechanical arm with a claw, which can deliver the samples for irradiations without reactor shutdown. It was installed in the lEA-R1 research reactor at Instituto de Pesquisas Energeticas e Nucleares (IPEN), Sao Paulo, Brazil, and for the past 5 years, the system has successfully operated and allowed the conducting of important experiments. As a result of its introduction, the facility has been in a position to positively respond to the increased demand in studies of biology, medicine, physics, engineering, detector/dosimeter calibrations, etc. It is one example of the appropriated technologies that save energy and resources. (C) 2010 Elsevier Ltd. All rights reserved.

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Using data taken by SELEX during the 1996-1997 fixed target run at Fermilab, we study the production of charmed hadrons on copper and carbon targets with Sigma(-), p, pi(-), and pi(+) beams. Parametrizing the dependence of the inclusive production cross section on the atomic number A as A(alpha), we determine alpha for D(+), D(0), D(s)(+), D(+)(2010), Lambda(+)(c), and their respective anti-particles, as a function of their transverse momentum p(t) and scaled longitudinal momentum x(F). Within our statistics there is no dependence of alpha on x(F) for any charm species for the interval 0.1 < x(F) < 1.0. The average value of alpha for charm production by pion beams is alpha(meson) = 0.850 +/- 0.028. This is somewhat larger than the corresponding average alpha(baryon) = 0.755 +/- 0.016 for charm production by baryon beams (Sigma(-), p).

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Assuming that nuclear matter can be treated as a perfect fluid, we study the propagation of perturbations in the baryon density. The equation of state is derived from a relativistic mean field model, which is a variant of the non-linear Walecka model. The expansion of the Euler and continuity equations of relativistic hydrodynamics around equilibrium configurations leads to differential equations for the density perturbation. We solve them numerically for linear and spherical perturbations and follow the propagation of the initial pulses. For linear perturbations we find single soliton solutions and solutions with one or more solitons followed by ""radiation"". Depending on the equation of state a strong damping may occur. We consider also the evolution of perturbations in a medium without dispersive effects. In this case we observe the formation and breaking of shock waves. We study all these equations also for matter at finite temperature. Our results may be relevant for the analysis of RHIC data. They suggest that the shock waves formed in the quark gluon plasma phase may survive and propagate in the hadronic phase. (C) 2009 Elseiver. B.V. All rights reserved.

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A systematic determination of the gluon distribution is of fundamental interest in understanding the parton structure Of nuclei and the QCD dynamics. Currently, the behavior of this distribution at small x (high energy) is completely undefined. In this Letter we analyze the possibility of constraining the nuclear effects present in Xg(A) using the inclusive observables which would be measured in the future electron-nucleus collider at RHIC. We demonstrate that the Study of nuclear longitudinal and charm structure functions allows to estimate the magnitude of shadowing and antishadowing effects in the nuclear gluon distribution. (C) 2008 Elsevier B.V. All rights reserved.

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Difficulties in cross-section measurements at very low energies, when charged particles are involved, led to the development of some indirect methods. The Trojan horse method (THM) allows us to bypass the Coulomb effects and has been successfully applied to several reactions of astrophysical interest. A brief review of the THM applications is reported together with some of the most recent results.

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We present a large-scale systematics of charge densities, excitation energies and deformation parameters For hundreds of heavy nuclei The systematics is based on a generalized rotation vibration model for the quadrupole and octupole modes and takes into account second-order contributions of the deformations as well as the effects of finite diffuseness values for the nuclear densities. We compare our results with the predictions of classical surface vibrations in the hydrodynamical approximation. (C) 2010 Elsevier B V All rights reserved.

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The University of Notre Dame, USA (Becchetti et al, Nucl. Instrum. Metho ds Res. A505, 377 (2003)) and later the University of Sao Paulo, Brazil (Lichtenthaler et al, Eur. Phys. J. A25, S-01, 733 (2005)) adopted a system based on superconducting solenoids to produce low-energy radioactive nuclear beams. In these systems the solenoids act as thick lenses to collect, select, and focus the secondary beam into a scattering chamb er. Many experiments with radioactive light particle beams (RNB) such as (6)He, (7)Be, (8)Li, (8)B have been performed at these two facilities. These low-energy RNB have been used to investigate low-energy reactions such as elastic scattering, transfer and breakup, providing useful information on the structure of light nuclei near the drip line and on astrophysics. Total reaction cross-sections, derived from elastic scattering analysis, have also been investigated for light system as a function of energy and the role of breakup of weakly bound or exotic nuclei is discussed.

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The scalar-isoscalar term in the two-pion exchange NN potential is abnormally large and does not respect the hierarchy of effects predicted by chiral perturbation theory. We argue that this anomaly is associated with non-perturbative effects, which are also present in the pi N scalar form factor.