Petropolis D.B.,Federal University of Rio de Janeiro |
Petropolis D.B.,Institute Pasteur Paris |
Rodrigues J.C.F.,Federal University of Rio de Janeiro |
Rodrigues J.C.F.,Instituto Nacional Of Ciencia |
And 6 more authors.
PeerJ | Year: 2014
Leishmania amazonensis is the causative agent of American cutaneous leishmaniasis, an important neglected tropical disease. Once Leishmania amazonensis is inoculated into the human host, promastigotes are exposed to the extracellular matrix (ECM) of the dermis. However, little is known about the interaction between the ECM and Leishmania promastigotes. In this study we established L. amazonensis promastigote culture in a three-dimensional (3D) environment mainly composed of Collagen I (COL I). This 3D culture recreates in vitro some aspects of the human host infection site, enabling the study of the interaction mechanisms of L. amazonensis with the host ECM. Promastigotes exhibited "freeze and run" migration in the 3D COL I matrix, which is completely different fromthe conventional in vitro swimming mode of migration. Moreover, L. amazonensis promastigotes were able to invade, migrate inside, and remodel the 3D COL I matrix. Promastigote trans-matrix invasion and the freeze and run migration mode were also observed when macrophages were present in the matrix. At least two classes of proteases, metallo- and cysteine proteases, are involved in the 3D COL I matrix degradation caused by Leishmania. Treatment with a mixture of protease inhibitors significantly reduced promastigote invasion and migration through this matrix. Together our results demonstrate that L. amazonensis promastigotes release proteases and actively remodel their 3D environment, facilitating their migration. This raises the possibility that promastigotes actively interact with their 3D environment during the search for their cellular "home"-macrophages. Supporting this hypothesis, promastigotes migrated faster than macrophages in a novel 3D co-culture model. © 2014 Petropolis et al.
Golbert D.R.,Laboratorio Nacional Of Computacao Cientifica |
Golbert D.R.,Instituto Nacional Of Ciencia |
Blanco P.J.,Laboratorio Nacional Of Computacao Cientifica |
Blanco P.J.,Instituto Nacional Of Ciencia |
And 3 more authors.
Journal of Computational Physics | Year: 2015
The von Neumann linear analysis, restricted by a heuristic selection of wave-number vectors was applied to the search of explicit lattice Boltzmann schemes which exhibit more stability than existing methods. The relative stability of the family members of quasi-incompressible collision kernels, for the Navier-Stokes equations in confined flows, was analyzed. The linear stability analysis was simplified by assuming a uniform velocity level over the whole domain, where only the wave numbers of the first harmonic normal to the flow direction were permitted. A singular equilibrium function that maximizes the critical velocity level was identified, which was afterwards tested in particular cases of confined flows of interest, validating the resulting procedure. © 2015 Elsevier Inc.
de Carvalho P.R.,Federal Rural University of Amazonia |
de Carvalho P.R.,Federal University of Para |
dos Santos W.G.,Federal University of Para |
dos Santos W.G.,Instituto Nacional Of Ciencia |
And 2 more authors.
Revista Brasileira de Geofisica | Year: 2010
Until about ten years ago, all commercial borehole induction devices were built up with the traditional coaxial coil arrays. Since then, those apparatus incorporated the unconventional coplanar coil arrays, in order to investigate thinly laminated reservoirs and to locate axially asymmetrical anomalies like vugs and fractures. In order to comprehend the fundamentals of the coplanar array in induction probes, we present a comparative study with the coaxial array through one-dimensional modeling of some borehole environments, like: 1) homogeneous, isotropic and unlimited conducting media; 2) invaded thick bed with annulus; 3) horizontal and dipping multilayer sequences; 4) gradational transition zone between two thick beds; and 5) thinly laminated formations. The comparative study allows us to conclude that: 1) the skin effect is strongest in the coplanar array responses; 2) the coplanar array responses are more sensitive to mud filtrate invasion and annulus zones, which are direct indicators of movable oil; 3) polarization"horns" on the coplanar array profiles can be good bed boundary indicators; 4) coplanar arrays present the greatest sensitivity to detect and delineate thinly laminated reservoirs. © 2010 Sociedade Brasileira de Geofísica.
De Oliveira Matos I.,Federal University of ABC |
Alves W.A.,Federal University of ABC |
Alves W.A.,Instituto Nacional Of Ciencia |
Nascimento O.R.,Federal University of ABC |
Nascimento O.R.,University of Sao Paulo
Quimica Nova | Year: 2011
In this work, we describe the immobilization of the dinuclear compound [Cu 2(apyhist) 2Cl 2](ClO 4) 2 (1) and its derived cations complexes, obtained in water solution or by deprotonation of the imidazolate moiety in the ligand leading to a cyclic tetranuclear species, in the Nafion ® membrane on glass carbon electrode surface. After that, we studied the influence of the equilibrium in the electrocatalytic activity towards the reduction of H 2O 2 in the development of an amperometric sensor for the analytical determination of hydrogen peroxide. This strategy proved successful, and the electrochemical behaviour of the all complexes formed within the Nafion ® coatings was characterized. We also provide evidence that its related cyclic tetranuclear imidazolate-bridged complex acts as a catalysts for the intramolecular, two-electron reduction of H 2O 2.
Prates D.B.,Federal University of Bahia |
Araujo-Santos T.,Federal University of Bahia |
Luz N.F.,Federal University of Bahia |
Andrade B.B.,National Institute of Allergy and Infectious Diseases |
And 10 more authors.
Journal of Leukocyte Biology | Year: 2011
Neutrophils are considered the host's first line of defense against infections and have been implicated in the immunopathogenesis of Leishmaniasis. Leishmania parasites are inoculated alongside vectors' saliva, which is a rich source of pharmacologically active substances that interfere with host immune response. In the present study, we tested the hypothesis that salivary components from Lutzomyia longipalpis, an important vector of visceral Leishmaniasis, enhance neutrophil apoptosis. Murine inflammatory peritoneal neutrophils cultured in the presence of SGS presented increased surface expression of FasL and underwent caspase-dependent and FasL-mediated apoptosis. This proapoptosis effect of SGS on neutrophils was abrogated by pretreatment with protease as well as preincubation with antisaliva antibodies. Furthermore, in the presence of Leishmania chagasi, SGS also increased apoptosis on neutrophils and increased PGE 2 release and decreased ROS production by neutrophils, while enhancing parasite viability inside these cells. The increased parasite burden was abrogated by treatment with z-VAD, a pan caspase inhibitor, and NS-398, a COX-2 inhibitor. In the presence of SGS, Leishmaniainfected neutrophils produced higher levels of MCP-1 and attracted a high number of macrophages by chemotaxis in vitro assays. Both of these events were abrogated by pretreatment of neutrophils with bindarit, an inhibitor of CCL2/MCP-1 expression. Taken together, our data support the hypothesis that vector salivary proteins trigger caspase-dependent and FasL-mediated apoptosis, thereby favoring Leishmania survival inside neutrophils, which may represent an important mechanism for the establishment of Leishmania infection. © Society for Leukocyte Biology.