Time filter

Source Type

Paredes-Santos T.C.,Federal University of Rio de Janeiro | Paredes-Santos T.C.,Instituto Nacional Of Ciencia E Tecnologia Em Biologia Estrutural E Bioimagem | de Souza W.,Federal University of Rio de Janeiro | de Souza W.,Instituto Nacional Of Ciencia E Tecnologia Em Biologia Estrutural E Bioimagem | And 3 more authors.
Journal of Structural Biology | Year: 2012

Micronemes, rhoptries and dense granules are secretory organelles of Toxoplasma gondii crucial for host cell invasion and formation of the parasitophorous vacuole (PV). We examined whether their relative volumes change during the intracellular cycle. Stereological analysis of random ultrathin sections taken at 5. min of interaction, 7 and 24 h post-infection demonstrated that the relative volume of each type of organelle decreases just after the respective peak of secretion. Micronemes are radially arranged below the polar ring, while rhoptries converge to but only a few reach the inside of the conoid. In contrast to the apical and polarized organelles, dense granules were found scattered throughout the cytoplasm, with no preferential location in the parasite cell body. Extensive observation of random sections indicated that each organelle probably secretes in a different region. Micronemes secrete just below the posterior ring and probably require that the conoid is extruded. The rhoptries passing through the conoid secrete at a porosome-like point at the most apical region. Dense granules secrete laterally, probably at fenestrations in the inner membrane complex. Immunocytochemistry showed that there are no subpopulations of rhoptries or dense granules, as a single organelle can contain more than one kind of its specific proteins. The vacuolar-like profiles observed at the apical portion of parasites just after invasion were confirmed to be empty rhoptries, as they were positively labeled for rhoptry proteins. These findings contribute for a better understanding of the essential behavior of secretory organelles. © 2011 Elsevier Inc.


Amaral R.J.F.C.D.,Federal University of Rio de Janeiro | Pedrosa C.D.S.G.,Instituto Nacional Of Metrologia Normalizacao E Qualidade Industrial Inmetro | Kochem M.C.L.,Federal University of Rio de Janeiro | Silva K.R.D.,Federal University of Rio de Janeiro | And 5 more authors.
Stem Cell Research | Year: 2012

In cartilaginous tissues, perichondrium cambium layer may be the source of new cartilage. Human nasal septal perichondrium is considered to be a homogeneous structure in which some authors do not recognize the perichondrium internal zone or the cambium layer as a layer distinct from adjacent cartilage surface. In the present study, we isolated a chondrogenic cell population from human nasal septal cartilage surface zone. Nasoseptal chondrogenic cells were positive for surface markers described for mesenchymal stem cells, with exception of CD146, a perivascular cell marker, which is consistent with their avascular niche in cartilage. Although only Sox-9 was constitutively expressed, they also revealed osteogenic and chondrogenic, but not adipogenic, potentials in vitro, suggesting a more restricted lineage potential compared to mesenchymal stem cells. Interestingly, even in absence of chondrogenic growth factors in the pellet culture system, nasoseptal chondrogenic cells had a capacity to synthesize sulfated glycosaminoglycans, large amounts of collagen type II and to a lesser extent collagen type I. The spontaneous chondrogenic potential of this population of cells indicates that they may be a possible source for cartilage tissue engineering. Besides, the pellet culture system using nasoseptal chondrogenic cells may also be a model for studies of chondrogenesis. © 2011 Elsevier B.V.


Santo Filho D.M.D.E.,Laboratorio Of Fluidos | De Abreu F.L.B.,Normalizacao e Qualidade Industrial Inmetro | De Abreu F.L.B.,Federal University of Fluminense | Pereira R.G.,Federal University of Fluminense | And 6 more authors.
ASTM Special Technical Publication | Year: 2011

Copyright © 2010 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. The world is looking for changes in its energetic matrix through the use of biofuels to reduce the dependence on oil derivatives. Currently, the number of studies concerning mixtures of triglycerides from animals or plants with diesel fuel has risen due to efforts to reduce the consumption of diesel oil. This paper studies the behavior of the density of plant oils mixed with diesel fuel in relation to temperature, which is essential to guarantee engine efficiency. The density is related to the mass and to the volume being a critical property to the assessment of the subministered energy to the engine by the injection system, which behaves like a pump of positive displacement. Samples of the diesel fuel mixture were made with plant triglycerides in proportion and range of ∼5-20%. The densities of the samples were measured in a density meter with temperature varying between 18 and 25°C, as well as at 15°C, according to ASTM standard. Afterwards, the uncertainties of measurement were calculated, and the density change with respect to temperature is presented and shown in density variation curves. An analysis of the density variation curves shows that.

Loading Instituto Nacional Of Metrologia Normalizacao E Qualidade Industrial Inmetro collaborators
Loading Instituto Nacional Of Metrologia Normalizacao E Qualidade Industrial Inmetro collaborators