Toxicity Assays in Nanodrops Combining Bioassay and Morphometric Endpoints

BACKGROUND: Improved chemical hazard management such as REACH policy objective as well as drug ADMETOX prediction, while limiting the extent of animal testing, requires the development of increasingly high throughput as well as highly pertinent in vitro toxicity assays. METHODOLOGY: This report describes a new in vitro method for toxicity testing, combining cell-based assays in nanodrop Cell-on-Chip format with the use of a genetically engineered stress sensitive hepatic cell line. We tested the behavior of a stress inducible fluorescent HepG2 model in which Heat Shock Protein promoters controlled Enhanced-Green Fluorescent Protein expression upon exposure to Cadmium Chloride (CdCl(2)), Sodium Arsenate (NaAsO(2)) and Paraquat. In agreement with previous studies based on a micro-well format, we could observe a chemical-specific response, identified through differences in dynamics and amplitude. We especially determined IC50 values for CdCl(2) and NaAsO(2), in agreement with published data. Individual cell identification via image-based screening allowed us to perform multiparametric analyses. CONCLUSIONS: Using pre/sub lethal cell stress instead of cell mortality, we highlighted the high significance and the superior sensitivity of both stress promoter activation reporting and cell morphology parameters in measuring the cell response to a toxicant. These results demonstrate the first generation of high-throughput and high-content assays, capable of assessing chemical hazards in vitro within the REACH policy framework

Measurement of active species in a flowing oxygen electron beam generated plasma

The paper reports on measurements of oxygen atoms and metastable singlet O$_2(^1\Delta)$ molecules in the flowing afterglow of a negative glow type plasma. Two methods of vacuum ultraviolet absorption spectroscopy are used. Compared to available data in positive column, results exhibit about same atomic concentration but a much smaller metastable concentration. Corresponding creation and loss mechanisms are proposed.Les concentrations d'oxygène atomique et d'oxygène moléculaire dans son état singulet sont mesurées en utilisant deux techniques d'absorption VUV, dans la post décharge en écoulement d'un plasma créé par faisceau d'électrons. Comparées à des données publiées pour la colonne positive , les concentrations en atomes sont du même ordre mais les concentrations en métastables sont fortement réduites. Des mécanismes correspondants de création et de perte sont proposés

Evidence of production of H2CN+-N2. Application to the atmosphere of Titan

The molecule H2CN+-N2 has been observed in a mixture of N2-CH4 irradiated by alpha particles from a radioactive source. The equilibrium constant has been measured and the enthalpy of the reaction has been calculated (|ΔH0| = 7.65 ± 0.09 kcal . mole-1).La molécule H2CN+-N2 est mise en évidence dans un mélange N2-CH4 soumis au rayonnement alpha d'une source radioactive. La constante d'équilibre est mesurée et la valeur de l'enthalpie de la réaction a été déterminée (|ΔH0| = 7,65 ± 0,09 kcal.mole-1)

EFFETS NON LINÉAIRES ET COUPLAGES PARAMÉTRIQUES DANS UN PLASMA SANS CHAMP MAGNÉTIQUE

En faisant varier la puissance d'une onde H. F. à la fréquence ƒ0 située dans une bande de résonance de plasma électronique, au-delà d'une valeur critique Pc, trois ondes deviennent instables (F, f0 - F, f0 + F) où F est une onde plasma ionique (Pc ~ 200 mW), ou pseudosonore (1) (Pc ~ 1 W). Les courbes de résonance se déforment et présentent une allure de "déferlement" qui s'explique par une augmentation de la densité électronique. Les instabilités à la fréqüence plasma ionique apparaissent dans des zones de pente maximum de la courbe de résonance.The power of a high frequency wave (f0) lying in an electron plasma mode is varied over a critical value : three waves become unstable (F, f0 - F, f0 + F), where F is an ion plasma wave (Pc ~ 200 mW), or the ionic acoustic wave (1) (Pc ~ 1 W). The resonance curves lose their form until they have two points of discontinuity and jump of the amplitude. This can be explained by an increase of the density. The instabilities at the ion plasma frequency appear at the steepest point of the resonance curve