141 research outputs found

    Stellar equilibrium configurations of white dwarfs in the f(R,T)f(R,T) gravity

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    In this work we investigate the equilibrium configurations of white dwarfs in a modified gravity theory, na\-mely, f(R,T)f(R,T) gravity, for which RR and TT stand for the Ricci scalar and trace of the energy-momentum tensor, respectively. Considering the functional form f(R,T)=R+2Tf(R,T)=R+2\lambda T, with \lambda being a constant, we obtain the hydrostatic equilibrium equation for the theory. Some physical properties of white dwarfs, such as: mass, radius, pressure and energy density, as well as their dependence on the parameter \lambda are derived. More massive and larger white dwarfs are found for negative values of \lambda when it decreases. The equilibrium configurations predict a maximum mass limit for white dwarfs slightly above the Chandrasekhar limit, with larger radii and lower central densities when compared to standard gravity outcomes. The most important effect of f(R,T)f(R,T) theory for massive white dwarfs is the increase of the radius in comparison with GR and also f(R)f(R) results. By comparing our results with some observational data of massive white dwarfs we also find a lower limit for \lambda, namely, >3104\lambda >- 3\times 10^{-4}.Comment: To be published in EPJ

    Exclusion of PAX9 and MSX1 mutation in six families affected by tooth agenesis. A genetic study and literature review

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    Objectives: In the present study, it is described the phenotypical analysis and the mutational screening, for genes PAX9 and MSX1, of six families affected by severe forms of tooth agenesis associated with other dental anomalies and systemic entities. Study Design: Six families affected by severe tooth agenesis associated with other dental anomalies and systemic entities were included. Oral exploration, radiological examination, medical antecedents consideration and muta - tional screening for PAX9 and MSX1 were carried out. Results: No mutations were discovered despite the fact that numerous teeth were missing. An important pheno - typical variability was observed within the probands, not being possible to establish a parallelism with the pat - terns associated to previously described PAX9 and MSX1 mutations. Conclusions: These results bring us to conclude that probably other genes can determine phenotypical patterns of dental agenesis in the families studied, different than the ones described in the mutations of PAX9 and MSX1. Moreover, epigenetic factors can be involved, as those that can reduce gene dosage and other post-transcriptional modulation agents, causing dental agenesis associated or not with systemic anomalies

    An谩lisis semicuantitativo del calcio y f贸sforo en los tejidos calcificados de la mand铆bula

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    El objetivo de nuestra investigaci贸n es realizar un estudio microanal铆tico semicuantitativo del calcio y el f贸sforo en los tejidos calcificados de la mand铆bula. Dentro de este estudio se pretende calcular el valor de la ratio Ca/P por m茅todos semicuantitativos y compararlo con los valores estequiom茅tricos de la ratio Ca/P de la hidroxiapatita referidos en la literatura; conocer los valores de la ratio Ca/P obtenidos para el tejido condroide, el hueso lamelar, el hueso fibrorreticular y el cart铆lago calcificado en las muestras fetales, por una parte, y adultas, por otra; y si existen o no diferencias significativas en la proporci贸n Ca/P obtenidos para feto y adulto. El an谩lisis morfol贸gico de los tejidos calcificados fue realizado por medio de Microrradiograf铆a Electr贸nica de Barrido (MEB) por electrones retrodispersados (Backscattering), y los resultados permiten afirmar que la ratio obtenida por an谩lisis semicuantitativo mediante dispersi贸n de rayos X de los tejidos calcificados (condroide, hueso lamelar y fibrorreticular) se encuentra m谩s pr贸xima a 1, y que no existen diferencias significativas entre las muestras fetales y de adulto en los tejidos analizados

    An谩lisis semicuantitativo del calcio y f贸sforo en el esmalte y la dentina

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    Existe una serie de caracter铆sticas comunes asociadas al proceso biol贸gico de formaci贸n de los tejidos calcificados a pesar de que los productos finales sean estructuralmente distintos. La presente investigaci贸n tiene como prop贸sito determinar si la ratio Ca/P ratio es la misma para los tejidos calcificados dentales tanto del feto como del adulto y si dicha ratio es diferente al valor de la ratio Ca/P de la hidroxiapatita pura calculada por estequiometr铆a. Se escogi贸 como material de observaci贸n el esmalte y la dentina, en muestras de fetos humanos y en un total de 30 ratas adultas de raza Wistar y 20 dientes humanos sanos. Las observaciones se llevaron a cabo por medio de Microscopia Electr贸nica de Barrido y Microan谩lisis por separaci贸n de energ铆a de rayos X. Los valores totales de la ratio Ca/P para el esmalte oscilaron en un intervalo de 0,9 y 1,2, con una media que se encuentra entre 1,07 y 1,08. Los valores totales de la ratio Ca/P para la dentina oscilan entre 1,03 y 1,12 y la media entre 1,07 y 1,075. No se encontraron diferencias estad铆sticamente significativas entre esmalte fetal y adulto ni entre la dentina fetal y adulta. A煤n no pudiendo definir la existencia de precursores espec铆ficos en los tejidos calcificados del diente (esmalte y dentina), nuestros resultados sugieren que no toda la cristalizaci贸n de estos tejidos corre a cargo de la hidroxiapatita sino que deben haber otros compuestos que expliquen la disminuci贸n del valor de la ratio Ca/P en las muestras estudiadas

    Upregulation of ERK1/2-eNOS via AT2 Receptors Decreases the Contractile Response to Angiotensin II in Resistance Mesenteric Arteries from Obese Rats

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    It has been clearly established that mitogen-activated protein kinases (MAPKS) are important mediators of angiotensin II (Ang II) signaling via AT1 receptors in the vasculature. However, evidence for a role of these kinases in changes of Ang II-induced vasoconstriction in obesity is still lacking. Here we sought to determine whether vascular MAPKs are differentially activated by Ang II in obese animals. the role of AT2 receptors was also evaluated. Male monosodium glutamate-induced obese (obese) and non-obese Wistar rats (control) were used. the circulating concentrations of Ang I and Ang II, determined by HPLC, were increased in obese rats. Ang II-induced isometric contraction was decreased in endothelium-intact resistance mesenteric arteries from obese compared with control rats and exhibited a retarded AT1 receptor antagonist response. Blocking of AT2 receptors and inhibition of either endothelial nitric oxide synthase (eNOS) or extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) restored Ang II-induced contraction in obese rats. Western blot analysis revealed increased protein expression of AT2 receptors in arteries from obese rats. Basal and Ang II-induced ERK1/2 phosphorylation was also increased in obese rats. Blockade of either AT1 or AT2 receptors corrected the increased ERK1/2 phosphorylation in arteries from obese rats to levels observed in control preparations. Phosphorylation of eNOS was increased in obese rats. Incubation with the ERK1/2 inhibitor before Ang II stimulation did not affect eNOS phosphorylation in control rats; however, it corrected the increased phosphorylation of eNOS in obese rats. These results clearly demonstrate that enhanced AT2 receptor and ERK1/2-induced, NO-mediated vasodilation reduces Ang II-induced contraction in an endothelium-dependent manner in obese rats.Funda莽茫o de Amparo 脿 Pesquisa do Estado de S茫o Paulo (FAPESP)Conselho Nacional de Desenvolvimento Cient铆fico e Tecnol贸gico (CNPq)Coordena莽茫o de Aperfei莽oamento de Pessoal de N铆vel Superior (CAPES)Univ S茫o Paulo, Inst Biomed Sci, Dept Pharmacol, S茫o Paulo, BrazilUniv Fed Goias, Div Cardiovasc Physiol, Dept Biol Sci, Jatai, BrazilUniversidade Federal de S茫o Paulo, Div Nephrol, Dept Med, Escola Paulista Med, S茫o Paulo, BrazilUniversidade Federal de S茫o Paulo, Div Nephrol, Dept Med, Escola Paulista Med, S茫o Paulo, BrazilFAPESP: 2007/58311-0FAPESP: 2008/51622-3FAPESP: 2010/03642-5Web of Scienc
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