Suppression of mRNAs Encoding Tegument Tetraspanins from Schistosoma mansoni Results in Impaired Tegument Turnover

Schistosomes express a family of integral membrane proteins, called tetraspanins (TSPs), in the outer surface membranes of the tegument. Two of these tetraspanins, Sm-TSP-1 and Sm-TSP-2, confer protection as vaccines in mice, and individuals who are naturally resistant to S. mansoni infection mount a strong IgG response to Sm-TSP-2. To determine their functions in the tegument of S. mansoni we used RNA interference to silence expression of Sm-tsp-1 and Sm-tsp-2 mRNAs. Soaking of parasites in Sm-tsp dsRNAs resulted in 61% (p = 0.009) and 74% (p = 0.009) reductions in Sm-tsp-1 and Sm-tsp-2 transcription levels, respectively, in adult worms, and 67%–75% (p = 0.011) and 69%–89% (p = 0.004) reductions in Sm-tsp-1 and Sm-tsp-2 transcription levels, respectively, in schistosomula compared to worms treated with irrelevant control (luciferase) dsRNA. Ultrastructural morphology of adult worms treated in vitro with Sm-tsp-2 dsRNA displayed a distinctly vacuolated and thinner tegument compared with controls. Schistosomula exposed in vitro to Sm-tsp-2 dsRNA had a significantly thinner and more vacuolated tegument, and morphology consistent with a failure of tegumentary invaginations to close. Injection of mice with schistosomula that had been electroporated with Sm-tsp-1 and Sm-tsp-2 dsRNAs resulted in 61% (p = 0.005) and 83% (p = 0.002) reductions in the numbers of parasites recovered from the mesenteries four weeks later when compared to dsRNA-treated controls. These results imply that tetraspanins play important structural roles impacting tegument development, maturation or stability

Speciation and fate of trace metals in estuarine sediments under reduced and oxidized conditions, Seaplane Lagoon, Alameda Naval Air Station (USA)

We have identified important chemical reactions that control the fate of metal-contaminated estuarine sediments if they are left undisturbed (in situ) or if they are dredged. We combined information on the molecular bonding of metals in solids from X-ray absorption spectroscopy (XAS) with thermodynamic and kinetic driving forces obtained from dissolved metal concentrations to deduce the dominant reactions under reduced and oxidized conditions. We evaluated the in situ geochemistry of metals (cadmium, chromium, iron, lead, manganese and zinc) as a function of sediment depth (to 100 cm) from a 60 year record of contamination at the Alameda Naval Air Station, California. Results from XAS and thermodynamic modeling of porewaters show that cadmium and most of the zinc form stable sulfide phases, and that lead and chromium are associated with stable carbonate, phosphate, phyllosilicate, or oxide minerals. Therefore, there is minimal risk associated with the release of these trace metals from the deeper sediments contaminated prior to the Clean Water Act (1975) as long as reducing conditions are maintained. Increased concentrations of dissolved metals with depth were indicative of the formation of metal HS(- )complexes. The sediments also contain zinc, chromium, and manganese associated with detrital iron-rich phyllosilicates and/or oxides. These phases are recalcitrant at near-neutral pH and do not undergo reductive dissolution within the 60 year depositional history of sediments at this site. The fate of these metals during dredging was evaluated by comparing in situ geochemistry with that of sediments oxidized by seawater in laboratory experiments. Cadmium and zinc pose the greatest hazard from dredging because their sulfides were highly reactive in seawater. However, their dissolved concentrations under oxic conditions were limited eventually by sorption to or co-precipitation with an iron (oxy)hydroxide. About 50% of the reacted CdS and 80% of the reacted ZnS were bonded to an oxide-substrate at the end of the 90-day oxidation experiment. Lead and chromium pose a minimal hazard from dredging because they are bonded to relatively insoluble carbonate, phosphate, phyllosilicate, or oxide minerals that are stable in seawater. These results point out the specific chemical behavior of individual metals in estuarine sediments, and the need for direct confirmation of metal speciation in order to constrain predictive models that realistically assess the fate of metals in urban harbors and coastal sediments

ALCAM Regulates Motility, Invasiveness, and Adherens Junction Formation in Uveal Melanoma Cells

ALCAM, a member of the immunoglobulin superfamily, has been implicated in numerous developmental events and has been repeatedly identified as a marker for cancer metastasis. Previous studies addressing ALCAM’s role in cancer have, however, yielded conflicting results. Depending on the tumor cell type, ALCAM expression has been reported to be both positively and negatively correlated with cancer progression and metastasis in the literature. To better understand how ALCAM might regulate cancer cell behavior, we utilized a panel of defined uveal melanoma cell lines with high or low ALCAM levels, and directly tested the effects of manipulating these levels on cell motility, invasiveness, and adhesion using multiple assays. ALCAM expression was stably silenced by shRNA knockdown in a high-ALCAM cell line (MUM-2B); the resulting cells displayed reduced motility in gap-closure assays and a reduction in invasiveness as measured by a transwell migration assay. Immunostaining revealed that the silenced cells were defective in the formation of adherens junctions, at which ALCAM colocalizes with N-cadherin and ß-catenin in native cells. Additionally, we stably overexpressed ALCAM in a low-ALCAM cell line (MUM-2C); intriguingly, these cells did not exhibit any increase in motility or invasiveness, indicating that ALCAM is necessary but not sufficient to promote metastasis-associated cell behaviors. In these ALCAM-overexpressing cells, however, recruitment of ß-catenin and N-cadherin to adherens junctions was enhanced. These data confirm a previously suggested role for ALCAM in the regulation of adherens junctions, and also suggest a mechanism by which ALCAM might differentially enhance or decrease invasiveness, depending on the type of cadherin adhesion complexes present in tissues surrounding the primary tumor, and on the cadherin status of the tumor cells themselves

Biology of Streptococcus mutans-Derived Glucosyltransferases: Role in Extracellular Matrix Formation of Cariogenic Biofilms

The importance of Streptococcus mutans in the etiology and pathogenesis of dental caries is certainly controversial, in part because excessive attention is paid to the numbers of S. mutans and acid production while the matrix within dental plaque has been neglected. S. mutans does not always dominate within plaque; many organisms are equally acidogenic and aciduric. It is also recognized that glucosyltransferases from S. mutans (Gtfs) play critical roles in the development of virulent dental plaque. Gtfs adsorb to enamel synthesizing glucans in situ, providing sites for avid colonization by microorganisms and an insoluble matrix for plaque. Gtfs also adsorb to surfaces of other oral microorganisms converting them to glucan producers. S. mutans expresses 3 genetically distinct Gtfs; each appears to play a different but overlapping role in the formation of virulent plaque. GtfC is adsorbed to enamel within pellicle whereas GtfB binds avidly to bacteria promoting tight cell clustering, and enhancing cohesion of plaque. GtfD forms a soluble, readily metabolizable polysaccharide and acts as a primer for GtfB. The behavior of soluble Gtfs does not mirror that observed with surface-adsorbed enzymes. Furthermore, the structure of polysaccharide matrix changes over time as a result of the action of mutanases and dextranases within plaque. Gtfs at distinct loci offer chemotherapeutic targets to prevent caries. Nevertheless, agents that inhibit Gtfs in solution frequently have a reduced or no effect on adsorbed enzymes. Clearly, conformational changes and reactions of Gtfs on surfaces are complex and modulate the pathogenesis of dental caries in situ, deserving further investigation

Grounded theory - conceptual and operational aspects: a method possible to be applied in nursing research

This is a descriptive-reflective study based on literature and qualitative design. It aimed to discuss conceptual aspects of Grounded Theory (GT) and to present the applicability of this methodology within the nursing field. GT consists of an interpretative and systematic framework that extracts significant aspects from experiences of social actors and which enables researchers to construct theoretical frameworks and intensify expansion of knowledge. It has been shown to be an important and consistent framework for objects of study that involve human interactions and which include phenomena concerning professional practice and which have not yet been properly examined and understood according to the rigor required for the construction of knowledge in qualitative designs.Se trata de estudio de naturaleza descriptiva reflexiva, apoyado en la literatura y de abordaje cualitativa. Tiene por objetivos discutir aspectos conceptuales de la teoría fundamentada en los datos y presentar la aplicabilidad de esa metodología en el área de enfermería. Consiste en marco teórico interpretativo y sistemático que extrae de las experiencias experimentadas por actores sociales aspectos significativos que posibilitan construir bases teóricas, potencializando la expansión del conocimiento. Se muestra una importante y consistente metodología para objetos de estudio que envuelven interacciones humanas y que conforman fenómenos de la práctica de la profesión todavía no desvelados y debidamente comprendidos, mediante el rigor requerido para la construcción de conocimientos de abordaje cualitativa.Trata-se de estudo de natureza descritivo-reflexiva, apoiado na literatura e de abordagem qualitativa. Tem por objetivos discutir aspectos conceituais da teoria fundamentada nos dados e apresentar a aplicabilidade dessa metodologia na área da enfermagem. Consiste em referencial interpretativo e sistemático que extrai das experiências vivenciadas por atores sociais aspectos significativos que possibilitam construir alicerces teóricos, potencializando a expansão do conhecimento. Mostra-se importante e consistente metodologia para objetos de estudo que envolvem interações humanas e que conformam fenômenos da prática da profissão ainda não desvelados e devidamente compreendidos, mediante o rigor requerido para a construção de conhecimentos de abordagem qualitativa

Rendimento e teores de macronutrientes em alface americana em função de doses de nitrogênio e molibdênio Nitrogen and molybdenum rates on the yield and macronutrients content in crisphead lettuce

O trabalho foi conduzido no município de Três Pontas, sul de Minas Gerais, de abril a julho de 2003, com o objetivo de avaliar a influência de doses de nitrogênio e molibdênio no rendimento e teor de macronutrientes da alface americana. Utilizou-se o delineamento de blocos ao acaso em arranjo fatorial 4 x 5, compreendendo quatro doses de nitrogênio em cobertura (0, 60, 120 e 180 kg ha-1) e cinco doses de molibdênio via foliar (0,0; 35,1; 70,2; 105,3 e 140,4 g ha-1) e três repetições. A massa fresca evidenciou efeitos significativos para doses de nitrogênio e de molibdênio, assim como para sua interação, enquanto os teores de nitrogênio e magnésio agiram de forma independente. Os teores de potássio reduziram-se com o aumento das doses de nitrogênio e molibdênio, sendo que para a maior dose de molibdênio (140,4 kg ha-1), estabeleceu-se um efeito quadrático no qual a dose de 76,1 kg ha-1 de nitrogênio em cobertura propiciou o maior teor de potássio. Para os teores de fósforo, cálcio e enxofre verificaram-se efeito significativo da interação N x Mo, cujas concentrações na parte aérea aumentaram com as doses de nitrogênio e molibdênio.<br>The trial was carried out at Três Pontas, Minas Gerais state, Brazil, from April to July 2003, to evaluate the influence of nitrogen and molybdenum rates on yield and macronutrients uptake of crisphead lettuce. A randomized complete blocks design with three replications was used. The treatments consisted of a factorial combination of four top dressing nitrogen levels (0.0; 60.0; 120.0 and 180.0 kg ha-1) and five foliar molybdenum levels (0.0, 35.1; 70.2; 105.3 and 140.4 g ha-1). The marketable fresh mass showed significant effect for levels of nitrogen and of molybdenum, as well as for their interaction, while the content of nitrogen and magnesium acted independently. The levels of potassium were reduced with the increase of the doses of nitrogen and molybdenum, and for the highest level of molybdenum (140.4 g ha-1) occurred a quadratic effect in which the dose of 76.1 kg ha-1 of N in top dressing showed the highest level of potassium. For the content of P, Ca and S a significant effect from the interaction N x K was verified, which had their content increased in the plant tops with the levels of nitrogen and molybdenum