Mechanisms of vasomotor sympathetic activity generation in the renovascular hypertension in Wistar rats

The renovascular arterial hypertension (AH) is associated with sympathetic hyperactivity and impaired baroreflex sensitivity determined by increase in circulating angiotensin II (Ang II). The aim of this thesis was to evaluate the role of oxidative stress in the generation and maintenance of the AH (2 Kidney – 1 Clip). Five series of experiments were performed in male Wistar. The results showed autonomic cardiovascular control changes characterized by increased sympathetic modulation in blood vessels, impaired baroreflex sensitivity and tachycardia from the fourth week. Furthermore, we observed that Ang II (via AT-1 receptor) and NO (produced by iNOS) in the rostral ventrolateral medulla (RVLM) are involved in the maintenance of AH and renal sympathetic nerve activity in the 2K-1C. Indeed, there is an imbalance between pro-oxidants and antioxidants in the RVL and hypothalamic paraventricular nucleus (PVN) of animals 2K-1C, because the increase in blood pressure (BP) and sympathetic hyperactivity was reversed in response to administration of the antioxidant (Tempol) into the RVLM and PVN. The over expression of CuZnSOD in the RVLM prevented the AH and reduced the production of superoxide in this region in 2K-1C. Furthermore, improved the impaired baroreflex sensitivity and inhibited the tachycardia observed from the fourth week of AH. Chronic Vitamin C treatment decreased BP and sympathetictactivation in hypertensive animals. In addition, reduced gene expression of subunits of NAD (P) H oxidase in the PVN and RVLM, but unchanged the expression of CuZnSOD. Oxidative stress also seems to influence the gene expression of AT-1 receptor, iNOS, nNOS, IL-1 â and Glut-1 in the PVN and RVL regions, because the treatment reduced the expression of these components. Based on our results, we suggest that the angiotensin system, NO and oxidative stress in the PVN and RVLM are involved in the maintenance of sympathetic tone and the AH 2K-1C. Oxidative stress in sympathetic premotor neurons is a major mechanism for the establishment and maintenance of Ang II – dependent hypertension.A Hipertensão arterial (HA) renovascular está associada com uma hiperatividade simpática e prejuízo na sensibilidade reflexa do barorreceptor determinadas por aumento na Angiotensina II (Ang II) circulante. O objetivo da presente Tese foi avaliar o papel do estresse oxidativo na geração e manutenção da HA 2 Rins-1Clipe. Ratos Machos Wistar foram utilizados em cinco séries de experimentos. Os resultados demonstraram uma alteração no controle autonômico cardíaco caracterizado por maior modulação simpática nos vasos, um prejuízo da sensibilidade reflexa do barorreceptor e taquicardia a partir da quarta semana. Além disso, observou-se que Ang II (via receptor AT-1) e o NO (produzido pela iNOS) na região rostro ventrolateral do bulbo (RVL), participam mantendo a HA e a atividade nervosa simpática renal em ratos 2R-1C. Evidenciou-se um desequilíbrio entre próoxidantes e antioxidantes, caracterizando um estado de estresse oxidativo nas regiões RVL e no núcleo paraventricular (PVN) dos animais 2R-1C, visto que o aumento de pressão arterial (PA) e a hiperatividade simpática são revertidos com a administração do antioxidante (Tempol) nessas regiões. A super expressão crônica de CuZnSOD na região RVL preveniu a HA e reduziu a produção de superóxidos nessa região em ratos 2R-1C. Além disso, melhorou a sensibilidade reflexa do barorreceptor e inibiu a taquicardia observada a partir da quarta semana de HA. O tratamento crônico com Vitamina C promoveu queda da PA e simpato-inibição nos animais hipertensos. Além disso, reduziu a expressão gênica das subunidades de NAD(P)H oxidase nas regiões RVL e PVN, mas não interferiu na expressão de CuZnSOD. O estresse oxidativo também parece influenciar na expressão gênica do receptor AT-1, iNOS, nNOS, IL-1 ƒÀ e Glut-1 nas regioes RVL e PVN, visto que o tratamento reduziu a expressao desses componentes. Baseado em nossos resultados, podemos sugerir que o sistema angiotensinergico, nitrergico e o estresse oxidativo nas regioes RVL e PVN estao envolvidos na manutencao do tonus simpatico e da HA 2R-1C. O estresse oxidativo em neuronios pre-motores do simpatico e um mecanismo essencial para o estabelecimento e manutencao da HA Ang II - dependente.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)FAPESP: 05/60151-6CAPES/BEX: 3496/07-4TEDEBV UNIFESP: Teses e dissertaçõe

A fast, simple active contour algorithm for biomedical images

NRC publication: Ye

The Registration of MR Images using Multiscale Robust Methods

Acquisition of MR images involves their registration against some pre-chosen reference image. Motion artifacts and misregistration can seriously flaw their interpretation and analysis. This paper provides a global registration method that is robust in the presence of noise and local distortions between pairs of images. It uses a two-stage approach, comprising an optional Fourier phase-matching method to carry out pre-registration, followed by an iterative procedure. The iterative stage uses a prescribed set of registration points, defined on the reference image, at which a robust nonlinear regression is computed from the squared residuals at these points. The method can readily accommodate general linear, or even nonlinear, registration transformations on the images. The algorithm was tested by recovering the registration transformation parameters when a 256 by 256 pixel T 2 *-weighted human brain image was scaled, rotated and translated by prescribed amounts, and to which different am..

Comparison of two classification methodologies on a real-world biomedical problem

We compare two diverse classification strategies on real-life biomedical data. One is based on a genetic algorithm-driven feature extraction method, combined with data fusion and the use of a simple, single classifier, such as linear discriminant analysis. The other exploits a single layer perceptron-based, data-driven evolution of the optimal classifier, and data fusion. We discuss the intricate interplay between dataset size, the number of features, and classifier complexity, and suggest different techniques to handle such problems.Peer reviewed: YesNRC publication: Ye

An Investigation of the Influence of Chain Length on the Interfacial Ordering of L-Lysine and L-Proline and Their Homopeptides at Hydrophobic and Hydrophilic Interfaces Studied by Sum Frequency Generation and Quartz Crystal Microbalance

Sum frequency generation vibrational spectroscopy (SFG) and quartz crystal microbalance with dissipation monitoring (QCM-D) are employed to study the interfacial structure and adsorbed amount of the amino acids l-lysine and l-proline and their corresponding homopeptides, poly-l-lysine and poly-l-proline, at two liquid-solid interfaces. SFG and QCM-D experiments of these molecules are carried out at the interface between phosphate buffered saline at pH 7.4 (PBS) and the hydrophobic deuterated polystyrene (d{sub 8}-PS) surface as well as the interface between PBS and hydrophilic fused silica (SiO{sub 2}). The SFG spectra of the amino acids studied here are qualitatively similar to their corresponding homopeptides; however, the SFG signal from amino acids at the solid/PBS interface is smaller in magnitude relative to their more massive homopeptides at the concentrations studied here. Substantial differences are observed in SFG spectra for each species between the hydrophobic d{sub 8}-PS and the hydrophilic SiO{sub 2} liquid-solid interfaces, suggesting surface-dependent interfacial ordering of the biomolecules. Over the range of concentrations used in this study, QCM-D measurements also indicate that on both surfaces poly-l-lysine adsorbs to a greater extent than its constituent amino acid l-lysine. The opposite trend is demonstrated by poly-l-proline which sticks to both surfaces less extensively than its corresponding amino acid, l-proline. Lastly, we find that the adsorption of the molecules studied here can have a strong influence on interfacial water structure as detected in the SFG spectra