Bilan de l’azote et du phosphore dans les exploitations agricoles de la région de Thiès au Sénégal

Dans la zone des Niayes de Thiès au Sénégal, un système d’exploitation agricole intégrant l’agriculture et l’élevage est largement adopté. L’aviculture est généralement associée au maraîchage avec une utilisation simultanée des engrais chimiques et des déchets organiques issus des élevages. Le bilan des minéraux essentiels (azote et phosphore) à l’échelle de l’exploitation agricole et de ses indicateurs de fonctionnement ont été estimés à l’aide d’enquêtes et d’analyses de laboratoire. Les bilans positifs obtenus au niveau de toutes les exploitations prospectées ont montré des excédents d'azote (N) et de phosphore (P) élevés avec des valeurs moyennes de 1455,38 et 76,59 kg/ha/an, respectivement. Les pertes de N et de P sont importantes et restent indépendants de l’effectif des sujets. Les indicateurs de fonctionnement calculés pour l’azote et le phosphore traduisent leur mauvaise gestion dans les exploitations avec des indices de gaspillage respectifs de 12,74 et de 1,90 kg.Mot clés : Minéraux, indicateurs de fonctionnement, exploitations agricoles, Sénégal

Direct Observation of Single Amyloid-β(1-40) Oligomers on Live Cells: Binding and Growth at Physiological Concentrations

Understanding how amyloid-β peptide interacts with living cells on a molecular level is critical to development of targeted treatments for Alzheimer's disease. Evidence that oligomeric Aβ interacts with neuronal cell membranes has been provided, but the mechanism by which membrane binding occurs and the exact stoichiometry of the neurotoxic aggregates remain elusive. Physiologically relevant experimentation is hindered by the high Aβ concentrations required for most biochemical analyses, the metastable nature of Aβ aggregates, and the complex variety of Aβ species present under physiological conditions. Here we use single molecule microscopy to overcome these challenges, presenting direct optical evidence that small Aβ(1-40) oligomers bind to living neuroblastoma cells at physiological Aβ concentrations. Single particle fluorescence intensity measurements indicate that cell-bound Aβ species range in size from monomers to hexamers and greater, with the majority of bound oligomers falling in the dimer-to-tetramer range. Furthermore, while low-molecular weight oligomeric species do form in solution, the membrane-bound oligomer size distribution is shifted towards larger aggregates, indicating either that bound Aβ oligomers can rapidly increase in size or that these oligomers cluster at specific sites on the membrane. Calcium indicator studies demonstrate that small oligomer binding at physiological concentrations induces only mild, sporadic calcium leakage. These findings support the hypothesis that small oligomers are the primary Aβ species that interact with neurons at physiological concentrations

Intermittent preventive treatment for malaria in pregnancy in Africa: What's new, what's needed?

Falciparum malaria is an important cause of maternal, perinatal and neonatal morbidity in high transmission settings in Sub-Saharan Africa. Intermittent preventive treatment with sulphadoxine-pyrimethamine (SP-IPT) has proven efficacious in reducing the burden of pregnancy-associated malaria but increasing levels of parasite resistance mean that the benefits of national SP-IPT programmes may soon be seriously undermined in much of the region. Hence, there is an urgent need to develop alternative drug regimens for IPT in pregnancy. This paper reviews published safety and efficacy data on various antimalarials and proposes several candidate combination regimens for assessment in phase II/III clinical trials

Evidence that interferon-gamma plays a protective role during cerebral malaria

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