Gene delivery and immunomodulatory effects of plasmid DNA associated with Branched Amphiphilic Peptide Capsules.

We recently reported on a new class of branched amphiphilic peptides that associate with double stranded DNA and promote in vitro transfection of eukaryotic cells. In the present study, we tested a different formulation in which plasmid DNA associates with the surface of preformed 20-30nm cationic capsules formed through the self-assembly of the two branched amphiphilic peptides. Under these conditions, the negatively charged DNA interacts with the cationic surface of the Branched Amphiphilic Peptide Capsules (BAPCs) through numerous electrostatic interactions generating peptide-DNA complexes with sizes ranging from 50 to 250nm. The BAPCs-DNA nanoparticles are capable of delivering plasmid DNA of different size into cells in culture, yielding high transfection rates and minimal cytotoxicity. Furthermore, BAPCs were tested for in vivo delivery of a DNA vaccine previously designed to activate immune responses and capable of controlling tumors induced by type 16 human papilloma virus (HPV-16). The BAPCs-DNA nanoparticles enhanced the vaccine-induced antitumor protection and promoted activation of murine dendritic cells without significant toxic effects. These results indicate that branched amphiphilic oligo-peptides nanoparticles represent a new and promising nonviral DNA/gene delivery approach endowing immunomodulatory properties for DNA vaccines.

Differential protein expression in the midgut of Culex quinquefasciatus mosquitoes induced by the insecticide temephos.

Mosquitoes are vectors for pathogens of malaria, lymphatic filariasis, dengue, chikungunya, yellow fever and Japanese encephalitis. Culex quinquefasciatus Say, 1823 (Diptera: Culicidae) is a known vector of lymphatic filariasis. Its control in Brazil has been managed using the organophosphate temephos. Studies examining the proteins of Cx. quinquefasciatus that are differentially expressed in response to temephos further understanding of the modes of action of the insecticide and may potentially identify resistance factors in the mosquito. In the present study, a comparative proteomic analysis, using 2-dimensional electrophoresis coupled with matrix-assisted laser desorption/ionization (MALDI) time of flight (TOF)/TOF mass spectrometry, and bioinformatics analyses were performed to identify midgut proteins in Cx. quinquefasciatus larvae that were differentially expressed in response to exposure to temephos relative to those in untreated controls. A total of 91 protein spots were differentially expressed; 40 were upregulated and 51 were downregulated by temephos. A total of 22 proteins, predominantly upregulated, were identified as known to play a role in the immune response, whereas the downregulated proteins were involved in energy and protein catabolism. This is the first proteome study of the midgut of Cx. quinquefasciatus and it provides insights into the molecular mechanisms of insecticide-induced responses in the mosquito.

Rationale, Detection, and Implications of Interactions Between Independent Variables and Unmeasured Variables in Linear Models.

Conceptual rationales from five research contexts are presented which share the similarity that all posit unmeasured variables which interact with observed independent variables to produce a complete model of the dependent variable. For the class of linear underspecified models involving only observed effects, it is shown that estimated effects of the observed independent variables are overestimated, that squared error of the misspecified model overestimates true error, and that this misspecified squared error is a function of at least the square of the measured independent variable(s). A statistical test for this last relationship is presented (Cook & Weisberg, 1983). The effect of this phenomenon on statistical power is discussed. Possible analytic and design strategies to overcome the effect of such unmeasured interactions include use of the rank transform (Conover & Iman, 1981), use of several longitudinal assessments, and oversampling of levels of independent variables where variance heterogeneity is large relative to other levels. Limitations of these strategies are discussed.

Problems with step-wise regression in research on aging and recommended alternatives.

The use of step-wise regression techniques in aging research brings with it certain interpretative difficulties. Both geometric and algebraic approaches are used to demonstrate that although step-wise procedures pose little difficulty if predictors are orthogonal, these same procedures, when used with correlated predictors, can lead to poor tests of the predictor regression weights. Techniques that are useful in the detection of multicollinearity are discussed. Principal components regression, ridge regression, and hierarchical regression are evaluated as potential techniques for assessing the relative importance of predictors when these variables are correlated, as is common in aging research. Hierarchical regression is the most recommended technique in that it is theory-driven rather than dependent on empirical relations that may be sample-specific and unstable.