Research was conducted to determine the potential for allelopathy to occur in pastures infested with bitter sneezeweed. Aqueous extracts of bitter sneezeweed leaves reduced alfalfa and Italian ryegrass seedling growth as much as 50% at concentrations of 0.5% (w/v). Leaf extracts were more phytotoxic than either stem or root extracts and seedling growth was reduced more than seed germination. Bitter sneezeweed tissue mixed in potting soil at concentrations as low as 0.3% w/w reduced alfalfa seedling numbers by 43%, plant height by 26%, and foliage dry matter production by 54% compared to plants cultured in soil without bitter sneezeweed leaf tissue. The potential concentration of bitter sneezeweed leaf material in soil in the pasture ecosystem was determined to be 0.5% w/v in the liquid phase and 0.2% w/w in the solid phase. Alfalfa seedling growth was reduced by 70% when germinating seed were placed under a bell jar with a potted mature bitter sneezeweed plant compared to control seedlings. A potential exists for bitter sneezeweed interference with developing alfalfa and Italian ryegrass seedlings following fall interseeding into pastures infested with bitter sneezeweed.

Rhynchophorus ferrugineus, known as the Red Palm Weevil (RPW), is reported as a pest of up to 40 palm species. However, the susceptibility degree and the defense mechanisms of these species against this weevil are still poorly known. In Europe, the RPW is a major pest of Phoenix canariensis while other palm species, including the congeneric Phoenix dactylifera, seem to be less suitable hosts for this insect. The aim of our study was to compare the defensive response of P. dactylifera, Chamaerops humilis and Washingtonia filifera against R. ferrugineus and try to define the mechanisms of resistance that characterize these species. Bioassays were carried out to evaluate the mortality induced on RPW larvae by extracts from the leaf rachis of the studied palm species. Tests at semi-field scale were also conducted, based either on forced palm infestation, with larvae of RPW, or on natural infestation, with adult females. Rachis extracts from C. humilis and W. filifera caused 100% larval mortality after 2 days of exposure, while extracts of P. dactylifera did not impair larval survival. Independently of the effect of the leaf extracts, the weevils were unable to naturally infest the three palm species, although larval survival was high after forced infestation of the plants. We concluded that the observed lack of infestation of P. dactylifera by RPW is due to factors other than antibiosis. In W. filifera and C. humilis, although the presence of antixenosis mechanisms cannot be excluded, resistance to R. ferrugineus seems to rely on the presence of antibiosis compounds.

The toxicity of produced formation water (PFW) originating from four natural gas production platforms located in the Adriatic Sea (Italy), and of seawater samples collected near these installations is assessed by means of bioassays with Brachionus plicatilis, with the brine shrimp Artemia franciscana and with Paracentrotus lividus. The toxicological response of these specimens was evaluated in order to identify the most sensitive one, in the consumer compartment, and to design a bioassay battery specific for samples collected in the surroundings of a gas platform. Larval mortality of rotifers, larval immobilization of crustaceans, fertilization success/failure (sperm cell test) and larval (pluteus) development success/failure (embryo toxicity test) of sea urchins were taken as ecotoxicological endpoints. The PFW sampled on two platforms resulted toxic, while no toxicity was recorded in seawater samples collected in the vicinity of the platforms, even in coincidence with the PFW discharge operations. The species and bioassays employed have shown different responses to PFW: P. lividus turned out to be more sensitive than A. franciscana and B. plicatilis. In particular, the embryo toxicity test showed a higher toxicity than the sperm cell test.

It is important to be able to characterise foods and feedstuffs according to their available amino acid contents. This involves being able to determine amino acids chemically and the conduct of bioassays to determine amino acid digestibility and availability. The chemical analysis of amino acids is not straightforward and meticulousness is required to achieve consistent results. In particular and for accuracy, the effect of hydrolysis time needs to be accounted for. Some amino acids (for example, lysine) can undergo chemical modification during the processing and storage of foods, which interferes with amino acid analysis. Furthermore, the modified amino acids may also interfere with the determination of digestibility. A new approach to the determination of available lysine using a modified in vivo digestibility assay is discussed. Research is required into other amino acids susceptible to structural damage. There is recent compelling scientific evidence that bacterial activity in the small intestine of animals and man leads to the synthesis and uptake of dietary essential amino acids. This has implications for the accuracy of the ileal-based amino acid digestibility assay and further research is required to determine the extent of this synthesis, the source of nitrogenous material used for the synthesis and the degree of synthesis net of amino acid catabolism. Although there may be potential shortcomings in digestibility assays based on the determination of amino acids remaining undigested at the terminal ileum, there is abundant evidence in simple-stomached animals and growing evidence in human subjects that faecal-based amino acid digestibility coefficients are misleading. Hindgut microbial metabolism significantly alters the undigested dietary amino acid profile. The ileal amino acid digestibility bioassay is expected to be more accurate than its faecal-based counterpart, but correction of the ileal amino acid flow for amino acids of endogenous origin is necessary. Approaches to correcting for the endogenous component are discussed.

—Organophosphorus-derived pesticides are commonly used to control Culex quinquefasciatus, the principal vector of filariasis in India. This paper reports on the susceptibility of C. quinquefasciatus from Madurai city, Tamil Nadu and its environs, to the organophosphate Malathion. It was observed that both larval and adult mosquitoes had low levels of resistance to the pesticide, with resistance ratios at LC50, LC90, and LC95 varying from 0.94 to 3.07 in larvae, and 0.93 to 34.68 in adults. This observation indicates the possibility of higher resistance developing in C. quinquefasciatus populations, the limitation of organophosphorus compounds as larvicides in mosquito breeding sites as a measure to control filariasis, and the importance of research into alternative measures for managing C. quinquefasciatus.

L'effet de la salinité (0,3 - 0,45 et 2,45 g.L-1) et de la dureté (250 - 500 g.L-1 (CaCO3) sur la toxicité de Al, Cu, Cr, Cd, Ni, Zn vis-à-vis de Daphnia magna est étudiée en laboratoire. Les concentrations en ions métalliques varient entre 0,01 et 25 mg.L-1. Les résultats obtenus à 20°C montrent que la toxicité mesurée en CI50 24 h et CI50 48 h (CI = Concentration d'Inhibition) de Cd, Cu, Zn et Al augmente avec un accroissement de la salinité ou de la dureté. Par contre, la toxicité de Ni et Cr est atténuée malgré l'accroissement de la salinité du milieu. L'augmentation de la dureté entraîne une réduction de la toxicité du chrome.

Le rendement d'extraction de l'uranium a été étudié par extraction liquide-liquide, à l'aide d'une molécule macrocyclique, le calix[6]arène, 46, fonctionnalisé par des groupements acidecarboxylique. La phase aqueuse comprenait l'uranium en présence d'ions sodium et la phase organique le calixarène dissous dans le benzène. L' étude des paramètres d'extraction a permis deproposer un mécanisme d'extraction. Le rendement d'extraction augmente avec le pH et atteint un maximum voisin de 100% pour un pH>3,7. Sur des solutions contenant en plus de l'uranium desions sodium, marquées au 22-Na et/ou du plutonium 239, l'extraction de l'uranium reste optimale. Sur des échantillons d'urine, après minéralisation, environ 100% de l'uranium sont extraits par lecalixarène. Ces premiers résultats montrent que le calixarène choisi présente une structure adéquate vis-à-vis de la structure de coordination de l'ion uranyle, permettant ainsi une extractionsélective de l'uranium.

La méthode utilisée en routine pour déterminer une éventuelle contamination par des actinides, émetteurs alpha, est la mesure de la fraction éliminée dans les excreta (urine et/ou fèces). Laprocédure actuelle se compose de deux étapes, tout d'abord une séparation radiochimique sélective de chaque élément présent puis, après préparation d'une source électrodéposée, la mesure deson activité par spectrométrie alpha. Dans un souci de simplification de cette procédure, on évalue ici les performances de l'analyse des actinides par spectrométrie de masse, pour deuxtechniques particulières l'ICP-MS et le SIMS. L'utilisation des trois outils analytiques (spectrométrie alpha, ICP-MS, SIMS) est étudiée sur la base de résultats récents provenant de lalittérature et de ceux obtenus dans le laboratoire. Sur la base de ces résultats, le présent article analyse les avantages propres à chaque technique.

La dosimétrie des expositions internes aux radionucléides incorporés repose sur une connaissance aussi complète que possible du comportement des substances radioactives dans l'organisme.Ceci est essentiel pour interpréter les mesures d'activité faites dans le corps et ses émonctoires et les exprimer sous forme de quantités incorporées et de doses engagées. On décrit ici entermes généraux les voies d'incorporation, les transferts au sang, la distribution et la rétention dans les organes puis l'excrétion des radionucléides. L'ensemble de ces processus biocinétiquescomplexes est schématisé de façon à pouvoir être représenté par des modèles mathématiques accessibles au calcul. Depuis une dizaine d'années, la Commission internationale de protectionradiologique a entrepris la révision systématique de toutes ses recommandations pour tenir compte de l'évolution des connaissances : révision des facteurs de pondération du risque stochastique,révision complète du modèle respiratoire, révision de nombreux facteurs d'absorption digestive, élaboration de modèles spécifiques de certains organes et de certains éléments. Cette démarche aconduit à réactualiser la plupart des coefficients de dose pour les travailleurs.

Several strains of Hyphomycetes fungi were assayed in the laboratory to determine their pathogenicity against second instar Chilo partellus Swinhoe larvae and fifth–sixth instar Busseola fusca Fuller larvae. Pathogenic activity to both stem borers was demonstrated with Beauveria bassiana (Balsamo) Vuillemin and Metarhizium anisopliae (Metschnikoff) Sorokin. B. bassiana isolates caused mortality of 3–100% of mortality in C. partellus larvae, and 30–84% in B.fusca. Strains of M.anisopliae showed a high level of virulence for both insect pests, causing mortality levels of 65–100%. Development of fungal infection appeared to take longer in B. fusca larvae (LT50 of 6.2–13.2 days) than in C. partellus (LT50 of 1.9–5.4 days). B. bassiana isolate ICIPE 4, and M. anisopliae isolates ICIPE 18 and 30, which were effective against both stem borers, outperformed the other pathogens tested. They appear to have potential for use asmicrobial agents in the control of C. partellus and B. fusca.

Studies conducted using laboratory and field bioassays showed that cypermethrin (b = −1.691) had a significantly (P < 0.05) higher and longer residual action at 7,14,21 and 28 days after application than did fenvalerate (b = −2.28) and permethrin (b = −1.871) against Dysdercus fasciatus Sign, and D. nigrofasciatus Stal. when coefficient regression analyses were performed. Residual action of fenvalerate and permethrin was regarded as being identical over the same experimental period in the field since their regression coefficients were not significantly (P > 0.05) different from each other.

It was also shown by these studies that the effective interval between applications was 21 days for cypermethrin and 14 days when fenvalerate and permethrin were applied. This finding has important practical implications in the adoption of an integrated approach aimed at minimizing damage to cotton by D. nigrofasciatus.

La dynamique de croissance du périphyton sur des substrats artificiels immergés à l'amont et à l'aval de secteurs de cours d'eau recevant des rejets polluants a été utilisée pour évaluer le niveau de pollution. La méthode est basée sur la détermination de paramètres globaux (matières organiques, pigments chlorophylliens, respiration, photosynthèse, assimilation hétérotrophe) qui permettent de caractériser le développement des communautés photoautotrophes et hétérotrophes sur les substrats. Le taux de croissance et l'activité hétérotrophe de ces communautés évoluent au cours de la durée d'immersion des substrats selon un modèle général qui est décrit à partir de séries de données recueillies sur trois cours d'eau. Les résultats obtenus sur 22 stations montrent que ces paramètres constituent des indicateurs de pollution plus sensibles que ceux basés sur la composition spécifique des communautés de périphyton.