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Des feuilles de #Guatteria ouregou$, Annonacée guyanaise, ont été isolés 22 alcaloïdes aporphiniques, dont 6 nouveaux, et appartiennent à des types structuraux originaux. Les résultats mettent en évidence une grande différence dans la composition en alcaloïdes entre les différents organes de la plante, dont la signification chimiotaxonomique est ici discutée. (Résumé d'auteur)

Zircaloy-4 has been oxidised in environmental scanning electron microscope (ESEM), at a temperature of 700 °C and the surface of the material has been observed during the oxidation, directly in the ESEM. The material has been subsequently analysed by atomic force microscopy (AFM) and transmission electron microscopy (TEM). Several aspects of the oxidation were revealed in these experiments. Zircaloy-4 oxidises at a different rate depending on the crystallographic orientation of the grains at the surface. The iron and chromium in the secondary phase particles (SPP) diffuse to the surface and oxidise to produce a profile at the surface of the material. The in situ observations reveal no cracks at the surface during the oxidation. Subsequent examination of the surface (ex situ) by AFM reveals the presence of pores in the oxide. TEM examinations indicate the presence of weak internal planes in the oxide layer, inducing cracks parallel to the metal-oxide interface. © 2003 Elsevier B.V. All rights reserved.

We measured the bidirectional reflectance in the VIS–NIR spectral range of different surfaces prepared from small-grained spherical water–ice particles over a wide range of incidence and emission geometries, including opposition. We show that coherent backscattering is dominating the opposition effect on fresh sample material, but its contribution decreases when particles become more irregularly shaped and the bulk porosity increases. Strong temporal evolution of the photometric properties of icy samples, caused by particle sintering and resulting in a decrease of backscattering, is shown. The sintering of the ice particles is documented using cryo-SEM micrographs of fresh and evolved samples. To complement the photometric characterization of ices, multiple high albedo laboratory analogs were investigated to study the effects of shape, grain size distribution, wavelength and surface roughness. In addition to the main backscattering peak, the phase curves also display the effect of glory in the case of surfaces of granular surfaces formed by either spherical ice or glass particles. We show that the angular position of the glory can be used to determine accurately the average size of the particles. Reflectance data are fitted by the Hapke photometric model, the Minnaert model and three morphological models. The resulting parameters can be used to reproduce our data and compare them to the results of other laboratory experiments and astronomical observations.

We have developed a gene therapy project for haemophilia B which aims to express factor IX (FIX) in haematopoietic lineage. Haematopoietic stem cells and subsequent megakaryocyte-derived cells represent the target cells of this approach. Our speculation is that platelets can deliver the coagulation factor at the site of injury, and subsequently correct the haemostasis defect. In order to direct FIX expression in cells from the megakaryocytic lineage, we designed a FIX cassette where the FIX cDNA was placed under the control of the tissue-specific glycoprotein IIb (GPIIb) promoter. In stably transfected HEL cells, FIX production was higher when driven by the GPIIb promoter compared to the CMV promoter. Using a cassette containing both the GPIIb promoter and a truncated FIX intron 1, FIX synthesis was dramatically increased in HEL cells. Northern blot analysis demonstrated an increase in FIX mRNA amounts, which paralleled with an increase of FIX antigen in the culture supernatants. Using a one-stage clotting assay and an activation by FXIa and FVIIa/TF, the HEL-derived recombinant FIX was shown to be a biologically active protein. This recombinant protein exhibited a 60-kDa molecular mass and was more heterogeneous than plasma immunopurified FIX (Mononine). The molecular mass difference could be partly explained by a different glycosylation pattern. The GPIIb promoter appears therefore to be a very attractive sequence to specifically direct FIX production in the megakaryocytic compartment of hematopoietic cells. These data also demonstrate that hematopoietic cells may represent potential target cells in an approach to gene therapy of haemophilia B.