Impact of the L-arginine-Nitric Oxide Pathway and Oxidative Stress on the Pathogenesis of the Metabolic Syndrome

The discovery of the physiological roles of nitric oxide has revolutionized the understanding of regulation of vascular tone, platelet adhesion and aggregation, and immune activation. Perhaps the most intriguing aspect of nitric oxide (NO) is that it is a gas that, in the absence of receptors, can regulate both normal physiological events and mediate cytotoxicity under pathological conditions. NO is produced from L-arginine by NO synthases (NOS), yielding L-citrulline and NO. The regulation of L-arginine pathway activity occurs at the level of NO production. The metabolic syndrome is a cluster of insulin resistance, elevated blood pressure, and atherogenic dyslipidemia, a common basis of cardiovascular disease. It occurs in genetically susceptible individuals with environmental influences and has serious economic and social consequences. Pharmacological and non-pharmacological therapies should be individualized and targeted to normalize its alterations of blood pressure, HDL cholesterol, triglycerides and glucose values. Despite the increasing prevalence of the metabolic syndrome in the last decades, there has been little progress in the understanding of the precise mechanisms involved in the pathogenesis of this syndrome and its complications. Emerging evidence is available that NO, inflammation and oxidative stress play important roles in the physiopathology of this syndrome. This review summarizes and evaluates the participation of the L-arginine-NO pathway and oxidative stress in the physiopathology of the metabolic syndrome and cardiovascular events at the systemic level, as well as the effects of exercise on this syndrome

Radiation induced warping of protostellar accretion disks

We examine the consequences of radiatively driven warping of accretion disks surrounding pre-main-sequence stars. These disks are stable against warping if the luminosity arises from a steady accretion flow, but are unstable at late times when the intrinsic luminosity of the star overwhelms that provided by the disk. Warps can be excited for stars with luminosities of around 10 solar luminosities or greater, with larger and more severe warps in the more luminous systems. A twisted inner disk may lead to high extinction towards stars often viewed through their disks. After the disk at all radii becomes optically thin, the warp decays gradually on the local viscous timescale, which is likely to be long. We suggest that radiation induced warping may account for the origin of the warped dust disk seen in Beta Pictoris, if the star is only around 10-20 Myr old, and could lead to non-coplanar planetary systems around higher mass stars.Comment: 12 pages, including 3 figures. ApJ Letters, in pres

The Role of Exercise on L-Arginine Nitric Oxide Pathway in Chronic Heart Failure

Chronic heart failure (CHF) is a pathological state with high morbidity and mortality and the full understanding of its genesis remain to be elucidated. In this syndrome, a cascade of neurohormonal and hemodynamic mechanisms, as well as inflammatory mediators, are activated to improve the impaired cardiac function. Clinical and experimental observations have shown that CHF is associated with a generalized disturbance in endothelium-dependent vasodilation, which may contribute to the progression of ventricular and vascular remodelling in this syndrome. There is also accumulating evidence that disturbances in nitric oxide (NO) availability is involved in the development of heart failure at the systemic and cardiac levels. NO is a ubiquitous signalling molecule which causes potent vasodilation, inhibits platelet activation and regulates the contractile properties of cardiac myocytes. It is generated from the amino acid L-arginine via constitutive and inducible isoforms of the enzyme NO synthase (NOS). There is evidence that exercise, a nonpharmacological tool, improves symptoms, fitness (VO2peak), quality of life and NO bioavailability in CHF population. This review examines different aspects of the L-arginine-NO pathway and inflammation in the physiopathology of CHF and highlights the important beneficial effects of exercise in this disease

Dynamical evolution of escaped plutinos, another source of Centaurs

It was shown in previous works the existence of weakly chaotic orbits in the plutino population that diffuse very slowly. These orbits correspond to long-term plutino escapers and then represent the plutinos that are escaping from the resonance at present. In this paper we perform numerical simulations in order to explore the dynamical evolution of plutinos recently escaped from the resonance. The numerical simulations were divided in two parts. In the first one we evolved 20,000 test particles in the resonance in order to detect and select the long-term escapers. In the second one, we numerically integrate the selected escaped plutinos in order to study their dynamical post escaped behavior. Our main results include the characterization of the routes of escape of plutinos and their evolution in the Centaur zone. We obtained a present rate of escape of plutinos between 1 and 10 every 10 years. The escaped plutinos have a mean lifetime in the Centaur zone of 108 Myr and their contribution to the Centaur population would be a fraction of less than 6 % of the total Centaur population. In this way, escaped plutinos would be a secondary source of Centaurs.Comment: Accepted for publication in A&

Estudo do índice de área foliar de pastagens em diferentes níveis de degradação com aplicação de imagens Landsat 5 - TM e dados de campo.

A área foliar é um parâmetro chave na avaliação do crescimento das plantas, podendo ser tanto medida quanto estimada (Figueredo Júnior et al., 2005). Segundo Pereira e Machado (1987) a área foliar é um fator que depende do número e tamanho das folhas e de seu estádio fenológico. A relação entre a área foliar de toda vegetação e a unidade de área de solo ocupada por essa vegetação é denominada de índice de área foliar (IAF). Como a fotossíntese depende da área foliar, a produtividade de uma cultura será tanto maior quanto mais próximo for do IAF máximo potencial e quanto mais tempo permanecer ativa; retardando a senescência (Figueredo Júnior et al., 2005). Zanchi et al. (2009) afirmam existir poucas informações referentes a variação espacial da biomassa vegetal, altura da pastagem e do índice de área foliar de pastagens. Estes autores sugerem que as variações naturais no IAF, altura e biomassa de algumas espécies, respondem às variações sazonais e interanuais do clima e da umidade do solo. Neste sentido, a análise espacial do IAF com uso dados de satélite pode ser um importante indicador da biomassa em áreas extensas. Diante do exposto, este trabalho teve como objetivo a aplicação de técnicas de sensoriamento remoto e dados de campo no estudo do índice de área foliar de pastagens de Brachiaria em diferentes níveis de degradação na região de Guararapes, SP

On the dynamics of multiple systems of hot super-Earths and Neptunes: Tidal circularization, resonance and the HD 40307 system

[Abridged] We consider the dynamics of a system of hot super-Earths or Neptunes such as HD 40307. We show that, as tidal interaction with the central star leads to small eccentricities, the planets in this system could be undergoing resonant coupling even though the period ratios depart significantly from very precise commensurability. In a three planet system, this is indicated by the fact that resonant angles librate or are associated with long term changes to the orbital elements. We propose that the planets in HD 40307 were in a strict Laplace resonance while they migrated through the disc. After entering the disc inner cavity, tidal interaction would cause the period ratios to increase from two but with the inner pair deviating less than the outer pair, counter to what occurs in HD 40307. However, the relationship between these pairs that occurs in HD 40307 might be produced if the resonance is impulsively modified by an event like a close encounter shortly after the planetary system decouples from the disc. We find this to be in principle possible for a small relative perturbation on the order of a few 1.d-3 but then we find that evolution to the present system in a reasonable time is possible only if the masses are significantly larger than the minimum masses and tidal dissipation is very effective. On the other hand we found that a system like HD 40307 with minimum masses and more realistic tidal dissipation could be produced if the eccentricity of the outermost planet was impulsively increased to about 0.15. The form of resonantly coupled tidal evolution we consider here is quite general and could be of greater significance for systems with inner planets on significantly shorter orbital periods characteristic of for example CoRoT 7 b.Comment: 38 pages, 12 figures, accepted for publication in MNRA

S-system theory applied to array-based GNSS ionospheric sensing

The GPS carrier-phase and code data have proven to be valuable sources of measuring the Earth’s ionospheric total electron content (TEC). With the development of new GNSSs with multi frequency data, many more ionosphere-sensing combinations of different precision can be formed as input of ionospheric modelling. We present the general way of interpreting such combinations through an application of S-system theory and address how their precision propagates into that of the unbiased TEC solution. Presenting the data relevant to TEC determination, we propose the usage of an array of GNSS antennas to improve the TEC precision and to expedite the rather long observational time-span required for high-precision TEC determination

Planetesimal fragmentation and giant planet formation: the role of planet migration

In the standard model of core accretion, the cores of the giant planets form by the accretion of planetesimals. In this scenario, the evolution of the planetesimal population plays an important role in the formation of massive cores. Recently, we studied the role of planetesimal fragmentation in the in situ formation of a giant planet. However, the exchange of angular momentum between the planet and the gaseous disk causes the migration of the planet in the disk. In this new work, we incorporate the migration of the planet and study the role of planet migration in the formation of a massive core when the population of planetesimals evolves by planet accretion, migration, and fragmentatio