Dynamin-dependent endocytosis is necessary for convergent-extension movements in Xenopus animal cap explants

Cadherin cell-cell adhesion molecules are important determinants of morphogenesis and tissue patterning. C-cadherin plays a key role in the cell-upon-cell movements seen during Xenopus gastrulation. In particular, regulated changes in C-cadherin adhesion critically influence convergence-extension movements, thereby determining organization of the body plan. It is also predicted that remodelling of cadherin adhesive contacts is important for such cell-on-cell movements to occur. The recent demonstration that Epithelial (E-) cadherin is capable of undergoing endocytic trafficking to and from the cell surface presents a potential mechanism for rapid remodelling of such adhesive contacts. To test the potential role for C-cadherin endocytosis during convergence-extension, we expressed in early Xenopus embryos a dominantly-inhibitory mutant of the GTPase, dynamin, a key regulator of clathrin-mediated endocytosis. We report that this dynamin mutant significantly blocked the elongation of animal cap explants in response to activin, accompanied by inhibition of C-cadherin endocytosis. We propose that dynamin-dependent endocytosis of C-cadherin plays an important role in remodelling adhesive contacts during convergence-extension movements in the early Xenopus embryo.

Role of hlx1 in zebrafish brain morphogenesis

hlx1 is a related homeobox gene expressed in a dynamic spatiotemporal expression pattern during development of the zebrafish brain. The homologues of hlx1, mouse dbx1 and Xenopus Xdbx, are known to play a role in the specification of neurons in the spinal cord. However, the role of these molecules in the brain is less well known. We have used two different approaches to elucidate a putative function for hlx1 in the developing zebrafish brain. Blastomeres were injected with either synthetic hlx1 mRNA in gain-of-function experiments or with antisense morpholino oligonucleotides directed against hlx1 in loss-of-function experiments. Mis-expression of hlx1 produced severe defects in brain morphogenesis as a result of abnormal ventricle formation, a phenotype we referred to as fused-brain. These animals also showed a reduction in the size of forebrain neuronal clusters as well as abnormal axon pathfinding. hlx1 antisense morpholinos specifically perturbed hindbrain morphogenesis leading to defects in the integrity of the neuroepithelium. While hindbrain patterning was in the most part unaffected there were select disruptions to the expression pattern of the neurogenic gene Zash1B in specific rhombomeres. Our results indicate multiple roles for hlx1 during zebrafish brain morphogenesis.

Expression and role of roundabout-1 in embryonic Xenopus forebrain

The receptor Roundabout-1 (Robo1) and its ligand Slit are known to influence axon guidance and central nervous system (CNS) patterning in both vertebrate and nonvertebrate systems. Although Robo-Slit interactions mediate axon guidance in the Drosophila CNS, their role in establishing the early axon scaffold in the embryonic vertebrate brain remains unclear. We report here the identification and expression of a Xenopus Robo1 orthologue that is highly homologous to mammalian Robo1. By using overexpression studies and immunohistochemical and in situ hybridization techniques, we have investigated the role of Robo1 in the development of a subset of neurons and axon tracts in the Xenopus forebrain. Robo1 is expressed in forebrain nuclei and in neuroepithelial cells underlying the main axon tracts. Misexpression of Robo1 led to aberrant development of axon tracts as well as the ectopic differentiation of forebrain neurons. These results implicate Robo1 in both neuronal differentiation and axon guidance in embryonic vertebrate forebrain. (C) 2002 Wiley-Liss, Inc.

Novel genes regulated by Sonic Hedgehog in pluripotent mesenchymal cells

Sonic Hedgehog is a secreted morphogen involved in patterning a wide range of structures in the developing embryo. Disruption of the Hedgehog signalling cascade leads to a number of developmental disorders and plays a key role in the formation of a range of human cancers. The identification of genes regulated by Hedgehog is crucial to understanding how disruption of this pathway leads to neoplastic transformation. We have used a Sonic Hedgehog (Shh) responsive mouse cell line, C3H/10T1/2, to provide a model system for hedgehog target gene discovery. Following activation of cell cultures with Shh, RNA was used to interrogate microarrays to investigate downstream transcriptional consequences of hedgehog stimulation. As a result 11 target genes have been identified, seven of which are induced (Thrombomodulin, GILZ, BF-2, Nr4a1, IGF2, PMP22, LASP1) and four of which are repressed (SFRP-1, SFRP-2, Mip1-gamma, Amh) by Shh. These targets have a diverse range of putative functions and include transcriptional regulators and molecules known to be involved in regulating cell growth or apoptosis. The corroboration of genes previously implicated in hedgehog signalling, along with the finding of novel targets, demonstrates both the validity and power of the C3H/10T1/2 system for Shh target gene discovery.

GATA proteins identify a novel ventral interneuron subclass in the developing chick spinal cord

Members of the GATA transcription factor gene family have been implicated in a variety of developmental processes, including that of the vertebrate central nervous system. However, the role of GATA proteins in spinal cord development remains unresolved. In this study, we investigated the expression and function of two GATA proteins, GATA2 and GATA3, in the developing chick spinal cord. We show that both proteins are expressed by a distinct subpopulation of ventral interneurons that share the same dorsoventral position as CHX10-positive V2 interneurons. However, no coexpression is observed between the two GATA proteins and CHX10. By in vivo notochord grafting and cyclopamine treatment, we demonstrate that the spatially restricted pattern of GATA3 expression is regulated, at least in part, by the signaling molecule Sonic hedgehog. In addition, we further show that Sonic hedgehog induces GATA3 expression in a dose-dependent manner. Using in ovo electroporations, we also demonstrate that GATA2 is upstream of GATA3 in the same epigenetic cascade and that GATA3 is capable of inducing GATA2 expression in vivo. Furthermore, the ectopically expressed GATA proteins can repress differentiation of other ventral cell fates, but not the development of progenitor populations identified by PAX protein expression. Taken together, our findings strongly suggest an important role for GATA2 and GATA3 proteins in the establishment of a distinct ventral interneuron subpopulation in the developing chick spinal cord. (C) 2002 Elsevier Science (USA).

Cadherin-directed actin assembly: E-cadherin physically associates with the Arp2/3 complex to direct actin assembly in nascent adhesive contacts

Cadherin cell adhesion molecules are major determinants of tissue patterning which function in cooperation with the actin cytoskeleton [1-4]. In the context of stable adhesion [1], cadherin/catenin complexes are often envisaged to passively scaffold onto cortical actin filaments. However, cadherins also form dynamic adhesive contacts during wound healing and morphogenesis [2]. Here actin polymerization has been proposed to drive cell surfaces together [5], although F-actin reorganization also occurs as cell contacts mature [6]. The interaction between cadherins and actin is therefore likely to depend on the functional state of adhesion. We sought to analyze the relationship between cadherin homophilic binding and cytoskeletal activity during early cadherin adhesive contacts. Dissecting the specific effect of cadherin ligation alone on actin regulation is difficult in native cell-cell contacts, due to the range of juxtacrine signals that can arise when two cell surfaces adhere [7]. We therefore activated homophilic ligation using a specific functional recombinant protein. We report the first evidence that E-cadherin associates with the Arp2/3 complex actin nucleator and demonstrate that cadherin binding can exert an active, instructive influence on cells to mark sites for actin assembly at the cell surface.

Microstructural evidence for the mechanism of the alpha-beta phase transformation in ytterbium SiAlON ceramics

Detailed microstructural evidence for the mechanism of the alpha-beta phase transformation in ytterbium SiAlON ceramics is presented. Grains, which show partial transformation, have been examined using transmission electron microscopy. We suggest that the transformation proceeds as a discernable reaction front and the accompanying lattice mismatch is accommodated be a series of complex dislocations. The stabilizing cation is ejected from the transformed alpha- phase and diffuse along the dislocation to accumulate as isolated pockets in a way similar to that observed in metal systems and termed pipe diffusion. High-resolution electron microscopy reveals the details of each of these features.

In ovo electroporation of Crim1 in the developing chick spinal cord

The novel mammalian gene Crim1 encodes a transmembrane bound protein with similarity to the secreted bone morphogenetic protein (BMP) antagonists, vertebrate Chordin, and its Drosophila homologue short gastrulation. Crim1 is expressed in the neural tube in mouse in a restricted pattern, but its function in central nervous system development is largely unknown. We isolated the chicken Crim1 orthologue and analyzed its expression in the developing neural tube. Chicken CRIM1 shares strong homology to human/mouse CRIM1 and C. elegans CRIM1-like proteins. Crim1 is expressed in a similar but not identical pattern to that in the developing spinal cord of mouse, including the notochord, floor plate, motor neurons, and the roof plate. Unlike follistatin, a secreted inhibitor of BMPs, in ovo electroporation of CRIM1, as a full-length transmembrane bound or secreted ectodomain was not sufficient to disrupt early patterning of the neural tube. However, ectodomain CRIM1 overexpression leads to an approximate 50% decrease in populations of specific ventral neuronal populations, including ISL-1(+) motor neurons, CHX-10(+) V1, and EN-1(+) V2 interneurons.

The validity of publication and citation counts for Sociology and other selected disciplines

The use of bibliometric data is a means of comparing. research productivity and scholarly. impact for individuals, work groups, institutions and nations within and between disciplines. Central to this debate is the notion that disciplines differ in the ways in which,they exchange ideas and disseminate information and therefore have diverse publishing and citation patterns. In this article we use two different approaches to compiling bibliometric data to compare publishing patterns of five different disciplines that encompass Molecular Biology; Administration/Political Science, Psychology,. Philosophy and Sociology/Anthropology. We find that the social sciences differ from each other as well as from the physical sciences in their publication and citation patterns. Further, while the different ways of organizing the data produce somewhat different results, the substantive findings for the general patterning of publications and citations of disciplines are consistent for both data sets. Sociology/Anthropology, when compared with the other disciplines, shows substantial differences across universities.

Local piezoelectric response of single poly(vinylidene fluoride) electrospun fibers

It is shown that electrospun poly(vynilidene fluoride) nanofibers are fully poled right after preparation and show b-phase contents of 70%, therefore being able to be implemented into electroactive devices without further processing steps. Further,the local piezoelectric properties of individual electrospun fibers have been studied by piezoresponse force microscopy. Piezoelectric response, polarization switching, and nanoscale patterning of the fibers have been demonstrated.

Análise dos métodos de medição dos parâmetros geométricos de via e correlação entre os dados obtidos

A razão atribuída à escolha do tema do T.F.M. em Caminhos-de-ferro, tem a ver com o facto de ser uma via de comunicação específica. Contrariamente ao que acontece na execução de auto-estradas, no caminho-de-ferro, a gestora da infra-estrutura responsabiliza-se pela execução, exploração (sinalização e controlo de circulação), abastecimento de energia fornecida às vias que dispõem de catenária (tracção eléctrica), manutenção e conservação da via. O processo de análise e inspecção de geometria de via, é usado quando e necessário preservar a infra-estrutura. Este processo iniciou-se nos caminhos-de-ferro portugueses, há muitos anos, depois da inauguração do primeiro troco de linha férrea. A primeira viagem ocorre em Outubro de 1856, sendo o início do processo em 1968, com a dresina “Matisa PV-6”. Em 1991 a C.P. adquiriu outro veículo de inspecção de via, tendo sido escolhido o VIV02 EM 120 da marca Plasser & Theurer, para substituir “Matisa PV-6”. O tema Análise dos Métodos de Medição dos Parâmetros Geométricos de Via e Correlação entre os Dados Obtidos está directamente relacionado com a manutenção e conservação de via. Na Unidade Operacional Sul (hoje ROS – Região Operacional Sul), local onde desenvolvi o T.F.M., não existem obras de construção de caminhos-de-ferro que pudesse acompanhar e constituir tema para o meu trabalho. Na realidade, com a falta de investimento que se perspectiva no futuro próximo, a manutenção da infra-estrutura passa a ser a actividade principal desenvolvida pela REFER, de modo a assegurar a comodidade, segurança e rapidez na deslocação de cargas e pessoas. A Analise Geométrica de Via e actualmente uma das principais actividades no âmbito da manutenção, que é feita por diagnóstico, contrariamente ao que acontecia no passado em que a conservação metódica era realizada num determinado ano num troço seleccionado independentemente da necessidade ou não da mesma. Uma ajuda preciosa, no que se refere à decisão de se realizar um determinado trabalho de conservação, e a do veículo VIV02 EM 120 que faz inspeções ao longo de toda a rede ferroviária e permite recolher dados e classificar através do desvio padrão, troços com extensão de 200 metros, obtendo os dados relevantes sobre a necessidade de intervenção. Para além do referido veículo existem também equipamentos ligeiros de inspecção dos parâmetros geométricos de via. Um desses equipamentos designa-se por Trólei, não sendo motorizado, pois o mesmo é movido manualmente por um operador. Obviamente que este equipamento não faz a inspecção a toda a rede pois a operação de medição é morosa, sendo contudo utilizado para análise de defeitos geométricos em pequenos trocos, tornando-se assim uma mais-valia, evitando o deslocar de um equipamento “pesado” como o VIV 02 EM 120. Para atingir os objectivos deste trabalho realizaram-se testes de medição com ambos (veiculo e equipamento ligeiro), no mesmo espaço temporal e com as mesmas características físicas, como a temperatura, humidade etc. Os resultados, de acordo com os objectivos, são a comparação entre as medições de ambos, com vista a comprovar a sua utilidade e necessidade, de acordo com os vários tipos de superstruturas constituintes da rede ferroviária nacional.

The source of the 1722 Algarve earthquake: evidence from MCS and tsunami data

The 27 December 1722 Algarve earthquake destroyed a large area in southern Portugal generating a local tsunami that inundated the shallow areas of Tavira. It is unclear whether its source was located onshore or offshore and, in any case, what was the tectonic source responsible for the event. We analyze available historical information concerning macroseismicity and the tsunami to discuss the most probable location of the source. We also review available seismotectonic knowledge of the offshore region close to the probable epicenter, selecting a set of four candidate sources. We simulate tsunamis produced by these candidate sources assuming that the sea bottom displacement is caused by a compressive dislocation over a rectangular fault, as given by the half-space homogeneous elastic approach, and we use numerical modeling to study wave propagation and run-up. We conclude that the 27 December 1722 Tavira earthquake and tsunami was probably generated offshore, close to 37 degrees 01'N, 7 degrees 49'W.

A non-pixel image reader for continuous image detection based on tandem heterostructures

An optically addressed read-write sensor based on two stacked p-i-n heterojunctions is analyzed. The device is a two terminal image sensing structure. The charge packets are injected optically into the p-i-n writer and confined at the illuminated regions changing locally the electrical field profile across the p-i-n reader. An optical scanner is used for charge readout. The design allows a continuous readout without the need for pixel-level patterning. The role of light pattern and scanner wavelengths on the readout parameters is analyzed. The optical-to-electrical transfer characteristics show high quantum efficiency, broad spectral response, and reciprocity between light and image signal. A numerical simulation supports the imaging process. A black and white image is acquired with a resolution around 20 mum showing the potentiality of these devices for imaging applications.

Radiographic outcomes and evaluation of developmental dysplasia of the hip in children

The Developmental Dysplasia of the Hip (DDH), also know as Congenital Dislocation of the Hip, is common in infants and children and may persist into adulthood. The radiographic interpretation is highly conditioned by appropriate patient positioning and image quality criteria. The main goal of this study is to demonstrate the value of radiographic evaluation of DDH. Through the retrospective analysis of 65 radiographs of the hips, only 2 (3.1%) female patients with 1-2 years of age presented radiographic findings of DDH. The inappropriate field size and the improper placement and size of the gonadal shields, were the most common errors observed.

Sub-micron structuring of silicon using femtosecond laser interferometry

We report the fabrication of planar sub-micron gratings in silicon with a period of 720 nm using a modified Michelson interferometer and femtosecond laser radiation. The gratings consist of alternated stripes of laser ablated and unmodified material. Ablated stripes are bordered by parallel ridges which protrude above the unmodified material. In the regions where ridges are formed, the laser radiation intensity is not sufficient to cause ablation. Nevertheless, melting and a significant temperature increase are expected, and ridges may be formed due to expansion of silicon during resolidification or silicon oxidation. These conclusions are consistent with the evolution of the stripes morphology as a function of the distance from the center of the grating. (C) 2013 Elsevier Ltd. All rights reserved.