Self-assembled monolayers of bisphosphonates: Influence of side chain steric hindrance

Bisphosphonates form self-assembled monolayers (SAMs) spontaneously on stainless steel, silicon, and titanium oxidized surfaces. We used contact angle measurements, atomic force microscopy, and X-ray reflectivity analysis to study the formation of SAMs on a model surface of ultraflat titanium (rms=0.2 nm). The results were extended to standard materials (mechanically polished titanium, stainless steel, and silicon) and showed that water-soluble bisphosphonic perfluoropolyether can easily form SAMs, with 100% surface coverage and a layer thickness of less than 3 nm. Hydrophobic (water contact angle >110° on stainless steel or titanium) and lipophobic (methylene iodide contact angle >105° on titanium) properties are discussed in terms of industrial applications

Dendritic Cell-Mediated-Immunization with Xenogenic PrP and Adenoviral Vectors Breaks Tolerance and Prolongs Mice Survival against Experimental Scrapie

In prion diseases, PrPc, a widely expressed protein, is transformed into a pathogenic form called PrPSc, which is in itself infectious. Antibodies directed against PrPc have been shown to inhibit PrPc to PrPSc conversion in vitro and protect in vivo from disease. Other effectors with potential to eliminate PrPSc-producing cells are cytotoxic T cells directed against PrP-derived peptides but their ability to protect or to induce deleterious autoimmune reactions is not known. The natural tolerance to PrPc makes difficult to raise efficient adaptive responses. To break tolerance, adenovirus (Ad) encoding human PrP (hPrP) or control Ad were administered to wild-type mice by direct injection or by transfer of Ad-transduced dendritic cells (DCs). Control Ad-transduced DCs from Tg650 mice overexpressing hPrP were also used for immunization. DC-mediated but not direct administration of AdhPrP elicited antibodies that bound to murine native PrPc. Frequencies of PrP-specific IFNγ-secreting T cells were low and in vivo lytic activity only targeted cells strongly expressing hPrP. Immunohistochemical analysis revealed that CD3+ T cell infiltration was similar in the brain of vaccinated and unvaccinated 139A-infected mice suggesting the absence of autoimmune reactions. Early splenic PrPSc replication was strongly inhibited ten weeks post infection and mean survival time prolonged from 209 days in untreated 139A-infected mice to 246 days in mice vaccinated with DCs expressing the hPrP. The efficacy appeared to be associated with antibody but not with cytotoxic cell-mediated PrP-specific responses

Early detection of West Nile virus in France: quantitative assessment of syndromic surveillance system using nervous signs in horses

West Nile virus (WNV) is a growing public health concern in Europe and there is a need todevelop more efficient early detection systems. Nervous signs in horses are considered to be anearly indicator of WNV and, using them in a syndromic surveillance system, might be relevant.In our study, we assessed whether or not data collected by the passive French surveillance systemfor the surveillance of equine diseases can be used routinely for the detection of WNV. We testedseveral pre-processing methods and detection algorithms based on regression. We evaluatedsystem performances using simulated and authentic data and compared them to those of thesurveillance system currently in place. Our results show that the current detection algorithmprovided similar performances to those tested using simulated and real data. However, regressionmodels can be easily and better adapted to surveillance objectives. The detection performancesobtained were compatible with the early detection of WNV outbreaks in France (i.e. sensitivity98%, specificity >94%, timeliness 2·5 weeks and around four false alarms per year) but furtherwork is needed to determine the most suitable alarm threshold for WNV surveillance in Franceusing cost-efficiency analysis

Influence of water on the circulation of the West Nile Virus in horses in Southern France

National audienc

Oligosaccharide induced resistance in grapevine as affected by cuticle permeability

International audienceGrapevine is susceptible to many diseases such as downy mildew, caused by the oomycete Plasmopara viticola (Pv). Sulfated laminarin PS3 is obtained by chemical sulfation of laminarin, an oligosaccharide (OS) from the brown algae Laminaria digitata. PS3 has been shown to elicit plant defense reactions and to induce resistance against Pv in grapevine (1). Our aim is to understand the penetration of OS in the grapevine leaf and to correlate it with the resistance induced against Pv. For this purpose, we followed the uptake of labeled compounds in the leaf, the effect of different adjuvants on their penetration and PS3 efficacy in Pv resistance tests. 1. S. Trouvelot, A. Varnier, M. Allegre, L. Mercier, F. Baillieul, C. Arnould, V. Gianinazzi-Pearson, O. Klarzynski, J. M. Joubert, A. Pugin, X. Daire Mol Plant Microbe Interact. 21, 232-243 (2008)

Expanded single-mode fiber using graded index multimode fiber

International audienceA compact large Gaussian mode field diameter single-mode fiber is developed. This expanded single-mode fiber consists of splicing fibers with various lengths and characteristics. The principle of this optical arrangement is to excite the first mode of propagation of the multimode graded index to preserve a Gaussian field. The coupling properties are numerically analyzed, considering the effects of gap, radial offset, and tilt. The fiber connections loss between the same kinds of expanded single-mode fibers with a Gaussian mode field diameter of 18 µm is measured with an average of 0.55 dB. This large mode field diameter is preserved on a long length of fiber >20 cm

Dynamic behaviour of a monolithic suspension device for the French watt balance experiment

In the French watt balance experiment, in order to have a single point of application of a weight and an electromagnetic force balancing this weight, a system of double gimbals with flexure pivots was made out of copper-beryllium alloy. This allows the articulation of the suspension devices of the mass (generating the weight) and coil (on which the electromagnetic force acts) around four coplanar axes which intersect at one point (equivalent to a virtual centre of rotation). The study of the free dynamic behaviour under vacuum of this device dealt with resonance, damping due to internal friction of the material and coupling between the two systems of gimbals. The results obtained show that this novel device presents suitable characteristics for concentrating two different forces at a single point and aligning them around a common vertical axis. It can be used not only for watt balance experiments but also for any other mechanical applications where alignment and concentration of two forces are necessary

Phase transfer of monosaccharides through noncovalent interactions: Selective extraction of glucose by a lipophilic cage receptor

We have previously shown that macrotricyclic host 1a is a powerful receptor for glucopyranosyl units in the nonpolar medium of chloroform. However, the solubility properties of 1a did not permit studies of the extraction of carbohydrates from aqueous solution. This paper describes the synthesis of the new variant 1b, furnished with a highly lipophilic exterior array of 12 benzyloxy substituents. In homogeneous solution, 1b behaves much as 1a, binding n-octyl β-d-glucoside with K(a) = 720 M(−1) in CD(3)OH/CDCl(3) (8:92). In two-phase experiments, the improved solubility of 1b allows carbohydrate extraction to be observed. Three hexoses (glucose, galactose, and mannose), two pentoses (ribose and xylose), and the two methyl glucosides are all extracted substantially into chloroform from 1 M aqueous solutions. Among the hexoses, 1b shows notable affinity and selectivity for glucose, extracting detectable amounts even from 0.1 M aqueous solutions

An integrative eco-epidemiological analysis of West Nile Virus transmission

International audienceWest Nile disease, caused by the West Nile virus (WNV), is a mosquito-borne zoonotic disease affecting humans and horses that involves wild birds as amplifying hosts. The mechanisms of WNV transmission remain unclear in Europe where the occurrence of outbreaks has dramatically increased in recent years. We used a dataset on the competence, distribution, abundance, diversity and dispersal of wild bird hosts and mosquito vectors to test alternative hypotheses concerning the transmission of WNV in Southern France. We modelled the successive processes of introduction, amplification, dispersal and spillover of WNV to incidental hosts based on host-vector contact rates on various land cover types and over four seasons. We evaluated the relative importance of the mechanisms tested using two independent serological datasets of WNV antibodies collected in wild birds and horses. We found that the same transmission processes (seasonal virus introduction by migratory birds, Culex modestus mosquitoes as amplifying vectors, heterogeneity in avian host competence, absence of 'dilution effect') best explain the spatial variations in WNV seroprevalence in the two serological datasets. Our results provide new insights on the pathways of WNV introduction, amplification and spillover and the contribution of bird and mosquito species to WNV transmission in Southern France

Evidence for foliar uptake of sulfated laminarin into grapevine depending on surfactant use and leaf surface

Certains ß-1,3-glucanes, en particulier la laminarine sulfatée (PS3), sont connus pour être des inducteurs de résistance de la vigne contre l’agent pathogène Plasmopara viticola. Bien que leur efficacité soit incontestable, la protection induite reste variable au vignoble. Pour être perçue par la plante, ils nécessitent de franchir les barrières constitutives, et notamment la cuticule. Ainsi, leur faible efficacité au champ pourrait être liée par une pénétration limitée à travers la cuticule des feuilles, suite à leur pulvérisation. Dans cette étude, nous avons mis au point une méthode pour analyser les comportements de diffusion du PS3 dans les feuilles de Vitis vinifera, à l’aide d’un microscope biphotonique. Nos résultats ont révélé que ce polysaccharide est vraisemblablement capable de pénétrer à travers la cuticule des feuilles de vigne, lorsqu’il est formulé dans un adjuvant adéquat. Par ailleurs, les stomates, les parois anticlines et les trichomes se sont révélés être des zones de diffusion préférentielle pour cette molécule. Il a été intéressant de constater que son taux de pénétration était plus important sur la face abaxiale des feuilles (stomatique), que la face adaxiale (sans stomate). De plus, nous sommes parvenus à lier le taux de pénétration, avec l’efficacité de PS3 en tant qu’inducteur de résistance contre le mildiou