A three-dimensional model of the human blood-brain barrier to analyse the transport of nanoparticles and astrocyte/endothelial interactions

The aim of this study was to develop a three-dimensional (3D) model of the human blood-brain barrier in vitro, which mimics the cellular architecture of the CNS and could be used to analyse the delivery of nanoparticles to cells of the CNS. The model includes human astrocytes set in a collagen gel, which is overlaid by a monolayer of human brain endothelium (hCMEC/D3 cell line). The model was characterised by transmission electron microscopy (TEM), immunofluorescence microscopy and flow cytometry. A collagenase digestion method could recover the two cell types separately at 92-96% purity. Astrocytes grown in the gel matrix do not divide and they have reduced expression of aquaporin-4 and the endothelin receptor, type B compared to two-dimensional cultures, but maintain their expression of glial fibrillary acidic protein. The effects of conditioned media from these astrocytes on the barrier phenotype of the endothelium was compared with media from astrocytes grown conventionally on a two-dimensional (2D) substratum. Both induce the expression of tight junction proteins zonula occludens-1 and claudin-5 in hCMEC/D3 cells, but there was no difference between the induced expression levels by the two media. The model has been used to assess the transport of glucose-coated 4nm gold nanoparticles and for leukocyte migration. TEM was used to trace and quantitate the movement of the nanoparticles across the endothelium and into the astrocytes. This blood-brain barrier model is very suitable for assessing delivery of nanoparticles and larger biomolecules to cells of the CNS, following transport across the endothelium

Analyses of 32 Loci Clarify Phylogenetic Relationships among Trypanosoma cruzi Lineages and Support a Single Hybridization prior to Human Contact

Trypanosoma cruzi is the protozoan parasite that causes Chagas disease, a major health problem in Latin America. The genetic diversity of this parasite has been traditionally divided in two major groups: T. cruzi I and II, which can be further divided in six major genetic subdivisions (subgroups TcI-TcVI). T. cruzi I and II seem to differ in important biological characteristics, and are thought to represent a natural division relevant for epidemiological studies and development of prophylaxis. Having a correct reconstruction of the evolutionary history of T. cruzi is essential for understanding the potential connection between the genetic and phenotypic variability of T. cruzi with the different manifestations of Chagas disease. Here we present results from a comprehensive phylogenetic analysis of T. cruzi using more than 26 Kb of aligned sequence data. We show strong evidence that T. cruzi II (TcII-VI) is not a natural evolutionary group but a paraphyletic lineage and that all major lineages of T. cruzi evolved recently (<3 million years ago [mya]). Furthermore, the sequence data is consistent with one major hybridization event having occurred in this species recently (< 1 mya) but well before T. cruzi entered in contact with humans in South America

Blood-brain barrier-specific properties of a human adult brain endothelial cell line

Establishment of a human model of the blood-brain barrier has proven to be a difficult goal. Normal human brain endothelial cells were transduced by lentiviral vectors incorporating human telomerase and/or SV40 T antigen. Among the many stable immortalized clones obtained by sequential limiting dilution of the transduced cells, one was selected for its expression of normal endothelial markers such as CD31, VE Cadherin and von Willebrand Factor. This cell line, termed hCMEC/D3, showed a stable normal karyotype, maintained contact-inhibited monolayers in tissue culture, exhibited robust proliferation in response to endothelial growth factors and formed capillary tubes in matrix but no colonies in soft agar. hCMEC/D3 cells expressed telomerase and grew indefinitely without phenotypic dedifferentiation. These cells expressed chemokine receptors, upregulated adhesion molecules in response to inflammatory cytokines, and demonstrated blood-brain barrier characteristics including tight junctional proteins and capacity to actively exclude drugs. hCMEC/D3 are excellent candidates for studies of blood-brain barrier function, the responses of brain endothelium to inflammatory and infectious stimuli, and the interaction of brain endothelium with lymphocytes or tumor cells. Thus, hCMEC/D3 represents the first stable, fully characterized, well-differentiated human brain endothelial cell line and should serve as a widely utilizable research tool

RayPortals: a light transport editing framework

International audiencePhysically based rendering, using path-space formulation of global illumination, has become a standard technique for high-quality computer-generated imagery. Nonetheless, being able to control and edit the resulting picture so that it corresponds to the artist vision is still a tedious trial-and-error process. We show how the manipulation of light transport translates into the path-space integral formulation of the rendering equation. We introduce portals as a path-space manipulation tool to edit and control renderings and show how our editing tool unifies and extends previous work on lighting editing. Portals allow the artist to precisely control the final aspect of the image without modifying neither scene geometry nor lighting setup. According to the setup of two geometric handles and a simple path selection filter, portals capture specific lightpaths and teleport them through 3D space. We implement portals in major path-based algorithms (Photon Mapping, Progressive Photon Mapping and Bi-directional Path Tracing) and demonstrate the wide range of control this technique allows on various lighting effects, from low-frequency color bleeding to high-frequency caustics as well as view-dependent reflections

A amostragem na avaliação das lixas-do-coqueiro Sampling in the evaluation of the coconut verrucoses

A avaliação das doenças foliares do coqueiro (Cocos nucifera L.), conhecidas como lixa-grande e lixa-pequena (verrugoses), causadas por Sphaeredothis acrocomiae e Phyllachora torrendiella, respectivamente, depara-se com o problema do método de amostragem, uma vez que não existe um método consensual em uso. Este trabalho foi realizado com o objetivo de comparar dois métodos de coleta de amostras mais utilizados na avaliação dessas doenças: método A: coleta de seis folíolos/planta, em uma única folha; método B: coleta de seis folíolos/planta, um em cada folha. O estudo foi desenvolvido a partir de três amostras de 300 folíolos (dez plantas x cinco folhas x seis folíolos), coletados em três genótipos de coqueiro, nos quais foi determinado o número de estromas da lixa-grande e da lixa-pequena. Com base nesses dados, estimaram-se as variâncias de folhas dentro de plantas e folíolos dentro de folhas e plantas, necessárias para os cálculos das estimativas das médias amostrais nos dois métodos em comparação, além de outras alternativas formuladas. Em ambas as lixas, em todos os genótipos, as estimativas da variância da média amostral calculadas pelo método A foram superiores às calculadas pelo método B, o que comprova que este último é mais eficaz que o primeiro. Outros tamanhos de amostra também foram avaliados e comparados ao método B, e constatou-se que amostras de seis folhas/planta, coletando-se, em cada uma, dois ou três folíolos, reduzem a variância amostral em 20% ou 30%, respectivamente, podendo, portanto, ser utilizadas com mais eficiência.<br>The evaluation of leaf diseases of coconuts, Cocos nucifera L., known as large verrucose and small verrucose, caused by Sphaerodothis acrocomiae and Phyllachora torrendiella, respectively, come upon the problem of sampling method. Since there is not a consensual method for measuring coconut verrucose incidence, the present work was done with the objective of comparing two sampling methods of common use: method A: sampling six leaflets/plant in a single leaf; method B: sampling six leaflets/plant, from different leaves. The study was developed starting from three samples of 300 leaflets (ten plants x five leaves x six leaflets) collected in three coconut genotypes, in which the stromata number of large verrucose and of small verrucose were counted. Throughout these data the variance was calculated from the leaf in the plant and the leaflet in the leaf and plant, necessary for the estimated sample average in the two compared methods, as well in the other formulated alternatives. For the two diseases, in all the genotypes, the estimate of variance of the sample mean calculated by the A method was higher than the one calculated by the B method, showing that the last method is more appropriate than the first one. Other sample sizes were also studied and compared by the B method, resulting that sample of two or three leaflets collected in six leaves per plant decreased sample variance on respectively 20% or 30%, probably being of more accurate applicability

A Contextual Analysis of Electoral Participation Sequences

This chapter presents an ongoing research project based on a seldom-used and particularly interesting source for the longitudinal, multilevel study of electoral participation: signature lists. We have been able to observe turnout in 44 ballots in one French polling station in the Paris region, between 1982 and 2007 (ca. 30,000 acts of turnout or abstention) and to link turnout data with various attributes of voters. We used sequence analysis to emphasize the correlation of participation patterns inside “electorate households” and to study the effect on turnout of the individual position in these households. This chapter discusses the ways in which this type of data and sequence methods makes it possible to take into account not only this social context of electoral participation, but also its temporal and political contexts. More generally, it exemplifies the uses of peculiar sequence data, with a very limited set of possible states but many dimensions to analyze