Premières observations sur les lésions provoquées chez les ruminants infestés massivement par Schistosoma curassoni

Des constatations faites tant aux abattoirs de Dakar que sur des animaux autopsiés au laboratoire et en brousse, il ressort que sur les bovins, ovins et caprins infestés par Schistosoma curassoni, des lésions importantes de fibrose hépatique sont toujours associées à un parasitisme massif. Cette schistosomiase peut être considérée comme une bilharziose à retentissement hépatique. Chez ces mêmes animaux, on note au niveau des poumons, d'importants dépôts de pigment (vraisemblablement mélanique) donnant à l'organe une coloration allant du gris clair au noir franc. Les coupes histologiques montrent que ce pigment se dépose sous forme de mottes d'inégale grosseur, localisées vraisemblablement au niveau des histiocytes. Le mécanisme de la formation et de la localisation de ce pigment n'est pas encore élucid

The contribution of age structure to cell population responses to targeted therapeutics

Cells grown in culture act as a model system for analyzing the effects of anticancer compounds, which may affect cell behavior in a cell cycle position-dependent manner. Cell synchronization techniques have been generally employed to minimize the variation in cell cycle position. However, synchronization techniques are cumbersome and imprecise and the agents used to synchronize the cells potentially have other unknown effects on the cells. An alternative approach is to determine the age structure in the population and account for the cell cycle positional effects post hoc. Here we provide a formalism to use quantifiable age distributions from live cell microscopy experiments to parameterize an age-structured model of cell population response

Determination of structural parameters characterizing thin films by optical methods: A comparison between scanning angle reflectometry and optical waveguide lightmode spectroscopy

International audienceWe present a comparative study of the structural parameters characterizing thin macromolecular adsorbed films that are obtained from two optical techniques: optical waveguide lightmode spectroscopy ͑OWLS͒ and scanning angle reflectometry ͑SAR͒. We use polyelectrolyte multilayers and polyelectrolyte multilayers/protein films to perform this study. The comparison between the information obtained with the two methods is possible because the buildup of the polyelectrolyte multilayers is known to become substrate independent after the deposition of the first few polyelectrolyte layers. The analysis of the optical data requires usually to postulate a refractive index profile for the interface. Two profiles have been used: the homogeneous and isotropic monolayer and the bilayer profiles. When the refractive index profile of an adsorbed film is well approximated by a homogeneous and isotropic monolayer, as shown by using an analysis of the deposited films in terms of optical invariants, the two optical techniques lead to similar values for the film thickness and the optical mass. The situation is more complex in the case of the multilayers/protein films for which the calculated parameters can strongly depend upon the refractive index profile that is postulated to analyze the optical data. Whereas the optical mass and, to a lesser extent, the thickness seem fairly model independent for OWLS, they appear to be extremely sensitive to the model for SAR. For proteins deposited on top of the polyelectrolyte film, optical mass and protein thickness were found to be comparable when determined by OWLS and by SAR using the bilayer model. The data analysis of the SAR curves with the monolayer model leads to much larger and even physically unreasonable film thicknesses and optical masses. This was particularly noticeable for proteins having a large size ͑human serum albumin and fibrinogen͒, whereas both models lead to similar results for small sized proteins. By means of the different refractive index profiles, we show that great care must be taken in the physicochemical interpretation of the structural parameters determined by these optical techniques

Aphosphorose et botulisme au Sénégal

L'affection animale observée au Sénégal, dans la région du Ferlo, et connue localement sous le nom de "Gniedio" ou de "maladie des forages" rappelle par son étiologie, sa symptomatologie et sa pathogénie le Lamsiekte décrit par THEILER en Afrique du Sud. Elle résulte de l'association d'un trouble nutritionnel, essentiellement une carence en phosphore, et d'une toxémie botulique. Les analyses biochimiques, au Laboratoire de Dakar, ont mis en évidence l'état d'aphosphorose chez les animaux. Les analyses chimiques des sols, des eaux et des fourrages reflètent la même insuffisance en cet élément. L'hypothèse de botulisme se voit confirmée par le succès de la sérothérapie spécifique et de la prophylaxie à l'aide des anatoxines botuliques C et D. La toxine botulique a été révélée par séro-neutralisation chez la souris, mais jusqu'à ce jour l'isolement de Clostridium botulinum n'a pu être réalis

Targeting of MuLV Gag to the plasma membrane is mediated by PI(4,5)P2 and PhosphatidylSerine

Oral presentationInternational audienceMembrane targeting by the modern human immunodeficiency viruses is dependent on the plasma membrane-located phospholipid PI(4,5)P2. In order to determine if evolutionarily distant retroviruses are targeted by a similar mechanism, we generated mutant Gag constructs in the matrix (MA) domain of the Murine Leukemia Virus (MuLV) and examined their binding to membrane models and phenotypes in cell culture. Mutations in the MA polybasic region altered Gag localization, membrane binding and virion production. In addition, we show that MA binds with good affinity to all the phosphatidylinositol phosphates but displays a strong specificity for PI(4,5)P2 only if enhanced by phophatidylserine. Virus production was strongly impaired by PI(4,5)P2 depletion under 5ptaseIV overexpression. Our results suggest that the N-terminal polybasic region of MA is essential for Gag targeting to the plasma membrane and Gag cellular trafficking. The binding of the MA domain to PI(4,5)P2 appears to be a conserved feature among retroviruses, despite the fact that the MuLV-MA domain is structurally different from that of HIV-1 and -2 and lacks a readily identifiable PI(4,5)P2 binding cleft

Polyelectrolyte multilayer films with pegylated polypeptides as a new type of anti-microbial protection for biomaterials.

Adhesion of bacteria at the surface of implanted materials is the first step in microbial infection, leading to post-surgical complications. In order to reduce this adhesion, we show that poly(L-lysine)/poly(L-glutamic acid) (PLL/PGA) multilayers ending by several PLL/PGA-g-PEG bilayers can be used, PGA-g-PEG corresponding to PGA grafted by poly(ethylene glycol). Streaming potential and quartz crystal microbalance-dissipation measurements were used to characterize the buildup of these films. The multilayer films terminated by PGA and PGA-g-PEG were found to adsorb an extremely small amount of serum proteins as compared to a bare silica surface but the PGA ending films do not reduce bacterial adhesion. On the other hand, the adhesion of Escherichia coli bacteria is reduced by 72% on films ending by one (PLL/PGA-g-PEG) bilayer and by 92% for films ending by three (PLL/PGA-g-PEG) bilayers compared to bare substrate. Thus, our results show the ability of PGA-g-PEG to be inserted into multilayer films and to drastically reduce both protein adsorption and bacterial adhesion. This kind of anti-adhesive films represents a new and very simple method to coat any type of biomaterials for protection against bacterial adhesion and therefore limiting its pathological consequences.comparative studyevaluation studiesjournal articleresearch support, non-u.s. gov't2004 Mayimporte