Insecticidal and Repellent Activity of Siparuna guianensis Aubl. (Negramina) against Aedes aegypti and Culex quinquefasciatus

This study investigated the toxic effects of essential oils isolated from Siparuna guianensis against Aedes aegypti, Culex quinquefasciatus (eggs, larvae, pupae, and adult) and Aedes albopictus (C6/36) cells. The oviposition-deterring activity, egg viability, and repellence activity in the presence of different essential oils concentrations were determined. The essential oils showed high toxicity to all developmental stages of A. aegypti and C. quinquefasciatus. Furthermore, the oils also showed high repellent activity towards the adult stage of mosquitoes (0.025 to 0.550 μg/cm2 skin conferred 100% repellence up to 120 min) and in contact with cultured insect cells (C6/36) induced death possibly by necrosis. The results presented in this work show the potential of S. guianensis essential oils for the development of an alternative and effective method for the natural control of mosquitoes in homes and urban areas.     

Direct evidence for intra- and intermolecular disulfide bond formation in the human glucocorticoid receptor. Inhibition of DNA binding and identification of a new receptor-associated protein

We have investigated the potential for the steroid affinity-labeled human glucocorticoid receptor to form both intramolecular and intermolecular disulfide bonds. Glucocorticoid receptors labeled in intact HeLa S3 cells with the covalent affinity label [3H]dexamethasone mesylate ([3H]DM) were analyzed on denaturing 5-12% polyacrylamide gels under both nonreducing and reducing conditions. Under nonreducing conditions the affinity-labeled receptor migrated as a heterogeneous species having an average molecular mass of approximately 96 kDa whereas, under reducing conditions, the receptor migrated as a more discrete form. These data suggest that a reducing environment can influence the structure of the glucocorticoid receptor monomer and further imply that sulfhydryl groups within the affinity-labeled receptor are available for modification. To pursue this observation in greater detail, we tested the effect of oxidizing conditions on the structure of the glucocorticoid receptor. The presence of low concentrations (0.125-0.5 mM) of three oxidizing reagents (sodium tetrathionate, disulfiram, and iodosobenzoate) altered the migration of the affinity-labeled receptor resulting in forms of apparent lower molecular mass (as low as 78 kDa). This altered migration, not seen with most other cytosolic proteins, is consistent with the formation of intramolecular disulfide bonds within the receptor which presumably cause it to assume a folded conformation and migrate faster through the gel. At higher concentrations of these reagents (up to 5.0 mM), we also detect a saturably labeled [3H]DM band which has a higher molecular mass (approximately 140 kDa), indicating the formation of intermolecular disulfide bonds between the [3H]DM-labeled receptor and another closely associated protein(s) having a molecular mass of approximately 40 kDa. The effects which these oxidizing reagents have on glucocorticoid receptor structure are completely reversed upon the addition of dithiothreitol, indicating that the observed changes in migration do not reflect receptor proteolysis but rather a folding and unfolding within the receptor monomeric protein. We have also analyzed the effect of this oxidation/reduction on the function of the glucocorticoid receptor. Oxidation of the [3H]DM-labeled receptor complex with 0.5 mM sodium tetrathionate inhibited activation of receptor to a form capable of binding to DNA-cellulose. This inhibition can be reversed with dithiothreitol at 25 degrees C but not at 0 degrees C, suggesting that these oxidizing reagents are inhibitory at the transformation and/or activation steps.(ABSTRACT TRUNCATED AT 400 WORDS)     

Exploring the Factor Structure of Neurocognitive Measures in Older Individuals

Here we focus on factor analysis from a best practices point of view, by investigating the factor structure of neuropsychological tests and using the results obtained to illustrate on choosing a reasonable solution. The sample (n=1051 individuals) was randomly divided into two groups: one for exploratory factor analysis (EFA) and principal component analysis (PCA), to investigate the number of factors underlying the neurocognitive variables; the second to test the “best fit” model via confirmatory factor analysis (CFA). For the exploratory step, three extraction (maximum likelihood, principal axis factoring and principal components) and two rotation (orthogonal and oblique) methods were used. The analysis methodology allowed exploring how different cognitive/psychological tests correlated/discriminated between dimensions, indicating that to capture latent structures in similar sample sizes and measures, with approximately normal data distribution, reflective models with oblimin rotation might prove the most adequate.