843 resultados para tomografia variazione totale norma L1 minimo alternato


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O aspecto da moralidade: a sua forma legal nas Constituições brasileiras -- A Constituição de 1988 e a explicitação de princípios. O princípio da moralidade -- A concreção do princípio da moralidade no Poder Judiciário; o art. 10 da Lei 9.421, de 24 de dezembro de 1996. O regime federativo e os princípios constitucionais -- O art. 10 da lei 9.421 e os Estados Federados

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Estudos em homenagem a Anna Maria Villela

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The cell adhesion molecule L1 regulates axonal guidance and fasciculation during development. We previously identified the regulatory region of the L1 gene and showed that it was sufficient for establishing the neural pattern of L1 expression in transgenic mice. In the present study, we characterize a DNA element within this region called the HPD that contains binding motifs for both homeodomain and Pax proteins and responds to signals from bone morphogenetic proteins (BMPs). An ATTA sequence within the core of the HPD was required for binding to the homeodomain protein Barx2 while a separate paired domain recognition motif was necessary for binding to Pax-6. In cellular transfection experiments, L1-luciferase reporter constructs containing the HPD were activated an average of 4-fold by Pax-6 in N2A cells and 5-fold by BMP-2 and BMP-4 in Ng108 cells. Both of these responses were eliminated on deletion of the HPD from L1 constructs. In transgenic mice, deletion of the HPD from an L1-lacZ reporter resulted in a loss of β-galactosidase expression in the telencephalon and mesencephalon. Collectively, our experiments indicate that the HPD regulates L1 expression in neural tissues via homeodomain and Pax proteins and is likely to be a target of BMP signaling during development.

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"Artigo produzido com base no trabalho de conclusão do Curso de Especialização em Análise e Controle de Constitucionalidade, promovido pela Unilegis - Universidade do Legislativo em parceria com a Universidade de Brasília - UnB, como requisito para a obtenção do título de Especialista. Orientador: Prof. Leonardo Augusto de Andrade Barbosa".

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Inclui notas bibliograficas.

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L1 elements are human transposons which replicate via an RNA intermediate. At least 15% of the human genome is composed of L1 sequence. An important initial step in the transposition reaction is nicking of the genomic DNA by L1 endonuclease (L1 EN). In vivo much of the genome exists in the form of chromatin or is undergoing biochemical transactions such as transcription, replication or repair, which may alter the accessibility of the L1 transposition machinery to DNA. To investigate this possibility we have examined the effect of substrate chromatinization on the ability of L1 EN to nick DNA. We find that DNA incorporated into nucleosomes is generally refractory to nicking by L1 EN. Interestingly, nicking of a minority of DNA sequences is enhanced when included in chromatin. Thus, dynamic epigenetic factors such as chromatinization are likely to influence the relatively permanent placement of L1 and other retroelements in the human genome.

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A novel imaging technology, high-speed microscopy, has been used to visualize the process of GLUT4 translocation in response to insulin in single 3T3-L1 adipocytes. A key advantage of this technology is that it requires extremely low light exposure times, allowing the quasi-continuous capture of information over 20–30 min without photobleaching or photodamage. The half-time for the accumulation of GLUT4-eGFP (enhanced green fluorescent protein) at the plasma membrane in a single cell was found to be of 5–7 min at 37°C. This half-time is substantially longer than that of exocytic vesicle fusion in neuroendocrine cells, suggesting that additional regulatory mechanisms are involved in the stimulation of GLUT4 translocation by insulin. Analysis of four-dimensional images (3-D over time) revealed that, in response to insulin, GLUT4-eGFP-enriched vesicles rapidly travel from the juxtanuclear region to the plasma membrane. In nontransfected adipocytes, impairment of microtubule and actin filament function inhibited insulin-stimulated glucose transport by 70 and 50%, respectively. When both filament systems were impaired insulin-stimulated glucose transport was completely inhibited. Taken together, the data suggest that the regulation of long-range motility of GLUT4-containing vesicles through the interaction with microtubule- and actin-based cytoskeletal networks plays an important role in the overall effect of insulin on GLUT4 translocation.

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We have investigated the structure of the cell adhesion molecule L1 by electron microscopy. We were particularly interested in the conformation of the four N-terminal immunoglobulin domains, because x-ray diffraction showed that these domains are bent into a horseshoe shape in the related molecules hemolin and axonin-1. Surprisingly, rotary-shadowed specimens showed the molecules to be elongated, with no indication of the horseshoe shape. However, sedimentation data suggested that these domains of L1 were folded into a compact shape in solution; therefore, this prompted us to look at the molecules by an alternative technique, negative stain. The negative stain images showed a compact shape consistent with the expected horseshoe conformation. We speculate that in rotary shadowing the contact with the mica caused a distortion of the protein, weakening the bonds forming the horseshoe and permitting the molecule to extend. We have thus confirmed that the L1 molecule is primarily in the horseshoe conformation in solution, and we have visualized for the first time its opening into an extended conformation. Our study resolves conflicting interpretations from previous electron microscopy studies of L1.