Différenciation génétique de quelques populations de Chrysichthys nigrodigitatus et de C. johnelsi (Pisces, Bagridae) de Côte d'Ivoire et du Mali

Le polymorphisme de 19 locus codant pour des enzymes a été étudié dans six populations de #Chrysichthys nigrodigitatus Lacépède 1803 (#Pisces, Bagridae), espèce utilisée en aquaculture africaine, et une population de #Chrysischthys johnelsi Daget 1959. La population de #C. nigrodigitatus du bassin du Niger (Bamako, Mali) est nettement différenciée des populations des bassins du Sassandra, du Bandama, de la Comoé et des lagunes Ebrié et Aby en Côte d'Ivoire (0,233 <D<0,266). Etant donné la grande répartition géographique de #C. nigrodigitatus$qui s'étend de l'Angola au Sénégal, Ces résultats laissent penser que l'espèce présente une forte différenciation génétique que l'on pourrait mettre à profit dans un programme d'amélioration génétique en aquaculture. Les échantillons des lagunes Ebrié et Aby (Côte d'Ivoire) présentent des taux de polymorphisme les plus importants (H = 4,5$ présente également un polymorphisme et cette espèce, proche de #C. nigrodigitatus$, pourrait être utilisée pour obtenir des hybrides ou des lignées gynogénétiques. (Résumé d'auteur

Proceedings of the 2nd international conference on insect pests in the urban environment

Larval susceptibility to organophosphates (OP), carbamates (CARB) and pyrethroids (PYR) was investigated in #Culex quinquefasciatus$ from Côte d'Ivoire and Burkina Faso. A total of 33 populations collected in 25 cities were tested. The resistance of these natural field populations was compared to a susceptible reference strain under the same conditions. In Côte d'Ivoire, populations showed a heterogeneous response to OP and CARB. A range of 40 %-98 % of larvae had a low resistance level to both chlorpyrifos (2-8x) and propoxur (1-4x). The remaining 2 % to 60 % of larvae displayed a high level of cross-resistance between chlorpyrifos (15-30x) and propoxur (>700x). Biochemical studies showed that low level resistance to OP was due to A2-B2 overproduced esterases and that cross-resistance to OP and CARB was conferred by an insensitive acetylcholinesterase (AChE). This AChE provided a lower resistance to temephos (10x). In Burkina Faso, populations were slightly resistant to OP (1-3x) and not to CARB. The esterases A2-B2 were only present at 50 % frequency. In contrast, PYR-resistance was similar between the two countries. All populations were resistant to either permethrin (20-80x) and deltamethrin (15-40x). Bioassays using piperonyl butoxide (PB) and biochemical studies showed that PYR-resistance involved increased metabolism by mixed function oxidases. Knowing that synergism of PB did not completely suppress resistance and that adults did not show a knockdown effect with high permethrin concentrations, it is likely that PYR-resistance was also due to a Kdr gene. (Résumé d'auteur

Genetic variability in Tetranychus urticae (Acari : Tetranychidae) from Greece : insecticide resistance and isozymes

Etude de la résistance au méthyl-parathion, au méthidathion et au méthomyl chez une population de #Tetranychus urticae$ Koch originaire de Grèce. A la CL 50 le taux de résistance est hautement variable avec le méthidathion (5 à 63 fois) et avec le méthomyl (6 à 34 fois). Les courbes de mortalité avec le méthyl-parathion présentent un plateau net à une mortalité d'environ 20% et le taux de résistance est d'environ 50 fois à CL 50, dans tous les échantillons. Par utilisation de la focalisation isoélectrique sur des membranes d'acétate de cellulose, les études électrophorétiques de 5 loci codant les estérases (Est-1 et Est-2), l'isomérase gluco-phosphate (Gpi), l'enzyme malique (Me) et la phosphoglucomutase (Pgm), indiquent les différences génétiques importantes parmi les échantillons. (Résumé d'auteur

Order and Frustration in Chiral Liquid Crystals

This paper reviews the complex ordered structures induced by chirality in liquid crystals. In general, chirality favors a twist in the orientation of liquid-crystal molecules. In some cases, as in the cholesteric phase, this favored twist can be achieved without any defects. More often, the favored twist competes with applied electric or magnetic fields or with geometric constraints, leading to frustration. In response to this frustration, the system develops ordered structures with periodic arrays of defects. The simplest example of such a structure is the lattice of domains and domain walls in a cholesteric phase under a magnetic field. More complex examples include defect structures formed in two-dimensional films of chiral liquid crystals. The same considerations of chirality and defects apply to three-dimensional structures, such as the twist-grain-boundary and moire phases.Comment: 39 pages, RevTeX, 14 included eps figure

The BRICS (Bronchiectasis Radiologically Indexed CT Score)- a multi-center study score for use in idiopathic and post infective bronchiectasis

OBJECTIVES: The goal of this study was to develop a simplified radiological score that could assess clinical disease severity in bronchiectasis. METHODS: The Bronchiectasis Radiologically Indexed CT Score (BRICS) was devised based on a multivariable analysis of the Bhalla score and its ability in predicting clinical parameters of severity. The score was then externally validated in six centers in 302 patients. RESULTS: A total of 184 high-resolution CT scans were scored for the validation cohort. In a multiple logistic regression model, disease severity markers significantly associated with the Bhalla score were percent predicted FEV1, sputum purulence, and exacerbations requiring hospital admission. Components of the Bhalla score that were significantly associated with the disease severity markers were bronchial dilatation and number of bronchopulmonary segments with emphysema. The BRICS was developed with these two parameters. The receiver operating-characteristic curve values for BRICS in the derivation cohort were 0.79 for percent predicted FEV1, 0.71 for sputum purulence, and 0.75 for hospital admissions per year; these values were 0.81, 0.70, and 0.70, respectively, in the validation cohort. Sputum free neutrophil elastase activity was significantly elevated in the group with emphysema on CT imaging. CONCLUSIONS: A simplified CT scoring system can be used as an adjunct to clinical parameters to predict disease severity in patients with idiopathic and postinfective bronchiectasis

DNA barcode assessment and population structure of aphidophagous hoverfly <i>Sphaerophoria scripta</i>:Implications for conservation biological control

With the advent of integrated pest management, the conservation of indigenous populations of natural enemies of pest species has become a relevant practice, necessitating the accurate identification of beneficial species and the inspection of evolutionary mechanisms affecting the long-time persistence of their populations. The long hoverfly,Sphaerophoria scripta, represents one of the most potent aphidophagous control agents due to a worldwide distribution and a favorable constellation of biological traits. Therefore, we assessed five EuropeanS. scriptapopulations by combining molecular (cytochromecoxidase subunit I-COI, internal transcribed spacer 2-ITS2, and allozyme loci) and morphological (wing size and shape) characters.COIsequences retrieved in this study were conjointly analyzed with BOLD/GenBank sequences of the otherSphaerophoriaspecies to evaluate whetherCOIpossessed a sufficient diagnostic value as a DNA barcode marker to consistently delimit allospecific individuals. Additionally, the aforementioned characters were used to inspect the population structure ofS. scriptain Europe using methods based on individual- and population-based genetic differences, as well as geometric morphometrics of wing traits. The results indicate numerous sharedCOIhaplotypes among differentSphaerophoriaspecies, thus disqualifying this marker from being an adequate barcoding region in this genus. Conversely, the analyses of population structuring revealed high population connectivity across Europe, therefore indicating strong tolerance ofS. scriptato environmental heterogeneity. The results imply a multilocus approach as the next step in molecular identification of differentSphaerophoriaspecies, while confirming the status ofS. scriptaas a powerful biocontrol agent of economically relevant aphid pests

Punctuated Chirality

Most biomolecules occur in mirror, or chiral, images of each other. However, life is homochiral: proteins contain almost exclusively levorotatory (L) amino acids, while only dextrorotatory (R) sugars appear in RNA and DNA. The mechanism behind this fundamental asymmetry of life remains an open problem. Coupling the spatiotemporal evolution of a general autocatalytic polymerization reaction network to external environmental effects, we show through a detailed statistical analysis that high intensity and long duration events may drive achiral initial conditions towards chirality. We argue that life's homochirality resulted from sequential chiral symmetry breaking triggered by environmental events, thus extending the theory of punctuated equilibrium to the prebiotic realm. Applying our arguments to other potentially life-bearing planetary platforms, we predict that a statistically representative sampling will be racemic on average.Comment: 13 pages, 4 color figures. Final version published in Origins of Life and Evolution of Biospheres. Typos corrected, figures improved, and a few definitions and word usage clarifie