Characteristic Evolution and Matching

I review the development of numerical evolution codes for general relativity based upon the characteristic initial value problem. Progress in characteristic evolution is traced from the early stage of 1D feasibility studies to 2D axisymmetric codes that accurately simulate the oscillations and gravitational collapse of relativistic stars and to current 3D codes that provide pieces of a binary black hole spacetime. Cauchy codes have now been successful at simulating all aspects of the binary black hole problem inside an artificially constructed outer boundary. A prime application of characteristic evolution is to extend such simulations to null infinity where the waveform from the binary inspiral and merger can be unambiguously computed. This has now been accomplished by Cauchy-characteristic extraction, where data for the characteristic evolution is supplied by Cauchy data on an extraction worldtube inside the artificial outer boundary. The ultimate application of characteristic evolution is to eliminate the role of this outer boundary by constructing a global solution via Cauchy-characteristic matching. Progress in this direction is discussed.Comment: New version to appear in Living Reviews 2012. arXiv admin note: updated version of arXiv:gr-qc/050809

Expression of caspase-3, p53 and Bcl-2 in generalized aggressive periodontitis

BACKGROUND: Apoptosis, or programmed cell death is a form of physiological cell death. It is increased or decreased in the presence of infection, inflammation or tissue remodelling. Previous studies suggest that apoptosis is involved in the pathogenesis of inflammatory periodontal disease. The aim of the present study was to investigate the clinical features and known indicators of apoptosis (p53, Bcl-2, Caspase-3) in patients with generalized aggressive periodontitis (GAP) METHODS: Eight patients with GAP, who had sites with probing depths (PD) > 5 mm, and 10 periodontally-healthy persons were included in the study. Clinical examinations and PD were performed, and the plaque index and gingival index were recorded. Gingival tissues biopsies were obtained from active site of each patient and from healthy individuals. The expression of caspase-3, Bcl-2, and p53 was evaluated by immunohistochemistry RESULTS: There were no significant differences between GAP and control group with respect to levels of caspase-3 and p53 expression (P > 0.05). Contrary, the frequency of grade 3 expression of Bcl-2 was higher in GAP group than the control group. CONCLUSION: The higher frequency of Bcl-2 expression in GAP group indicates and delayed apoptosis can lead to increasing resident inflammatory cells in periodontal tissues and resulting in progressive periodontal destruction

Targeted p120-Catenin Ablation Disrupts Dental Enamel Development

Dental enamel development occurs in stages. The ameloblast cell layer is adjacent to, and is responsible for, enamel formation. When rodent pre-ameloblasts become tall columnar secretory-stage ameloblasts, they secrete enamel matrix proteins, and the ameloblasts start moving in rows that slide by one another. This movement is necessary to form the characteristic decussating enamel prism pattern. Thus, a dynamic system of intercellular interactions is required for proper enamel development. Cadherins are components of the adherens junction (AJ), and they span the cell membrane to mediate attachment to adjacent cells. p120 stabilizes cadherins by preventing their internalization and degradation. So, we asked if p120-mediated cadherin stability is important for dental enamel formation. Targeted p120 ablation in the mouse enamel organ had a striking effect. Secretory stage ameloblasts detached from surrounding tissues, lost polarity, flattened, and ameloblast E- and N-cadherin expression became undetectable by immunostaining. The enamel itself was poorly mineralized and appeared to be composed of a thin layer of merged spheres that abraded from the tooth. Significantly, p120 mosaic mouse teeth were capable of forming normal enamel demonstrating that the enamel defects were not a secondary effect of p120 ablation. Surprisingly, blood-filled sinusoids developed in random locations around the developing teeth. This has not been observed in other p120-ablated tissues and may be due to altered p120-mediated cell signaling. These data reveal a critical role for p120 in tooth and dental enamel development and are consistent with p120 directing the attachment and detachment of the secretory stage ameloblasts as they move in rows

Carbon Nanotubes in Tissue Engineering

For their peculiar features carbon nanotubes (CNTs) are emerging in many areas of nanotechnology applications. CNT-based technology has been increasingly proposed for biomedical applications, to develop biomolecule nanocarriers, bionanosensors and smart material for tissue engineering purposes. In the following chapter this latter application will be explored, describing why CNTs can be considered an ideal material able to support and boost the growth and the proliferation of many kind of tissues

Characteristic Evolution and Matching

I review the development of numerical evolution codes for general relativity based upon the characteristic initial value problem. Progress is traced from the early stage of 1D feasibility studies to 2D axisymmetric codes that accurately simulate the oscillations and gravitational collapse of relativistic stars and to current 3D codes that provide pieces of a binary black spacetime. A prime application of characteristic evolution is to compute waveforms via Cauchy-characteristic matching, which is also reviewed.Comment: Published version http://www.livingreviews.org/lrr-2005-1

Apoptotic signalling targets the post-endocytic sorting machinery of the death receptor Fas/CD95

Fas plays a major role in regulating ligand-induced apoptosis in many cell types. It is well known that several cancers demonstrate reduced cell surface levels of Fas and thus escape a potential control system via ligand-induced apoptosis, although underlying mechanisms are unclear. Here we report that the endosome associated trafficking regulator 1 (ENTR1), controls cell surface levels of Fas and Fas-mediated apoptotic signalling. ENTR1 regulates, via binding to the coiled coil domain protein Dysbindin, the delivery of Fas from endosomes to lysosomes thereby controlling termination of Fas signal transduction. We demonstrate that ENTR1 is cleaved during Fas-induced apoptosis in a caspase-dependent manner revealing an unexpected interplay of apoptotic signalling and regulation of endolysosomal trafficking resulting in a positive feedback signalling-loop. Our data provide insights into the molecular mechanism of Fas post-endocytic trafficking and signalling, opening possible explanations on how cancer cells regulate cell surface levels of death receptors

¿Psicología de la Educación o Psicología Escolar? Esa es la cuestión

Este artigo apresenta alguns dados oriundos da tese de doutorado sobre a história do campo de conhecimento e prática da Psicologia em sua relação com a Educação no Brasil. Este estudo foi conduzido baseado no fundamento epistêmico-filosófico do materialismo histórico dialético e na nova história, utilizando fontes bibliográficas históricas e cinco relatos orais de personagens da Psicologia Educacional e Escolar. Os depoimentos e o material das fontes escritas constituíram o corpus documental cuja organização seguiu a metodologia da história oral e historiografia plural. Foi realizada análise descritivo-analítica compreendida em duas etapas: a) análise documental (fontes não orais) e b) construção de indicadores e núcleos de significação dos registros orais. A partir das análises, compôs-se uma periodização da história da Psicologia Educacional e Escolar brasileira por meio de marcos históricos da área. No presente artigo destaca-se a discussão acerca da conceituação e terminologias utilizadas pela Psicologia Educacional e Escolar ao longo do tempo e de como essas mudanças nas nomenclaturas da área refletem questões epistemológicas, ideológicas e políticas