Composition and properties of silver-containing calcium carbonate–calcium phosphate bone cement

The introduction of silver, either in the liquid phase (as silver nitrate solution: Ag(L)) or in the solid phase (as silver phosphate salt: Ag(S)) of calcium carbonate–calcium phosphate (CaCO₃–CaP) bone cement, its influence on the composition of the set cement (C-Ag(L) and C-Ag(S) cements with a Ca/Ag atomic ratio equal to 10.3) and its biological properties were investigated. The fine characterisation of the chemical setting of silver-doped and reference cements was performed using FTIR spectroscopy. We showed that the formation of apatite was enhanced from the first hours of maturation of C-Ag(L) cement in comparison with the reference cement, whereas a longer period of maturation (about 10 h) was required to observe this increase for C-Ag(S) cement, although in both cases, silver was present in the set cements mainly as silver phosphate. The role of silver nitrate on the setting chemical reaction is discussed and a chemical scheme is proposed. Antibacterial activity tests (S. aureus and S. epidermidis) and in vitro cytotoxicity tests (human bone marrow stromal cells (HBMSC)) showed that silver-loaded CaCO₃–CaP cements had antibacterial properties (anti-adhesion and anti-biofilm formation) without a toxic effect on HBMSC cells, making C-Ag(S) cement a promising candidate for the prevention of bone implant-associated infections.     

Kinetic Analysis of the Interaction of Mos1 Transposase with its Inverted Terminal Repeats Reveals New Insight into the Protein–DNA Complex Assembly

Transposases are specific DNA‐binding proteins that promote the mobility of discrete DNA segments. We used a combination of physicochemical approaches to describe the association of MOS1 (an eukaryotic transposase) with its specific target DNA, an event corresponding to the first steps of the transposition cycle. Because the kinetic constants of the reaction are still unknown, we aimed to determine them by using quartz crystal microbalance on two sources of recombinant MOS1: one produced in insect cells and the other produced in bacteria. The prokaryotic‐expressed MOS1 showed no cooperativity and displayed a K_d of about 300 nM . In contrast, the eukaryotic‐expressed MOS1 generated a cooperative system, with a lower K_d (～2 nm) . The origins of these differences were investigated by IR spectroscopy and AFM imaging. Both support the conclusion that prokaryotic‐ and eukaryotic‐expressed MOS1 are not similarly folded, thereby resulting in differences in the early steps of transposition.     

Harmful risks for workers in thermal spraying: A review completed by a survey in a French company

Thermal spray technologies are implemented in spray booths either manually or automatically. In both cases, workers can be exposed to several potential and real risks. The major risks are to workers’ respiratory systems and result from harmful feedstock materials. To the authors’ knowledge, very few specific studies have been conducted to assess the significance of these risks. This study describes the major risks encountered and reviews the results of a survey conducted in a French company that uses thermal spray technology on a large scale.     

Proton conducting PAMPS networks: From flexible to rigid materials

To elaborate tailor‐made proton conducting materials showing an interesting range of flexibility, a series of conetworks combining poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid) (PAMPS) and poly(ethylene oxide) dimethacrylate (PEGDM) with various chain lengths was synthesized. The homogeneity of these conetworks was checked by differential scanning calorimetry and dynamic mechanical thermal analysis. The swelling behavior of these materials is strongly influenced by the amount of sulfonic acid groups and the endothermal peak temperature, characteristic of the presence of bound water in the conetwork, increases from 65 to 120°C when AMPS amount increases from 10 to 75 wt %. In addition, the proton conductivity of these materials varies from 10^?3 to 10^?1 S cm^?1, depending on the AMPS amount. The storage moduli were found to be affected by both the AMPS content in the conetwork and its crosslinking density. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Amplitude et polarisation des ondes UBF détectées à bord du satellite GEOS-I. Méthodes d’analyse,problèmes rencontrés et solutions pratiques

A method for analysing polarized signals is briefly described. This method is applied to the instantaneous frequency, amplitude and polarization of Ulf waves detected in a frame of reference rotating at frequency close to the one of the waves being studied. This method is being applied to the data obtained from the European satellites Geos-1and 2,which are stabilized by rotation at about 0.17Hz. The local static magnetic field has a strong component perpendicular to the satellite rotation axis, therefore inducing in the antennas a strong component at the rotating frequency. Part of this parasitic signal is eliminated directly on board the satellite owing to a despinsystem. But the remaining disturbance affects all the frequencies of the power spectrum with a ratio depending on the relative value of the integration time and the rotation period. This modification of the spectrum is studied in detail and the authors demonstrate that it can be avoided with an easy method of signal processing at the ground. Both methods used jointly allow the production as a routine basis of experimenter summariesenabling to know at each moment the main characteristics of the waves being detected.     

Bacteria removal in septic effluent: influence of biofilm and protozoa

Numerous biological, physical and chemical parameters are involved in the retention and removal of bacteria in wastewater treatment systems. Biological parameters, such as biofilms and protozoa grazing activity, are often mentioned but few studies provide a better understanding of their influence. In this study, the effect of bacterivorous protozoa on pathogenic indicator bacteria removal was investigated in septic effluent and in the presence of a biofilm coating glass slides. Endogenous bacteria from septic effluent were quantified. First, bacteria removal was compared between septic effluents treated or not with an inhibitor of protozoa (cycloheximide). The mortality rates were 10 times lower in treated effluent (96 CFU mL(-1) d(-1)) than in untreated effluent (1100 CFU mL(-1) d(-1)). Secondly, the efficiency of bacteria removal was studied (i) with a biofilm surface and active protozoa, (ii) with a biofilm surface and inactivated protozoa, (iii) with a clean surface. Protozoa in the presence of a biofilm were responsible for 60% of bacteria removal. Biofilm without protozoa and a clean surface each removed similar quantities of bacteria. Grazing by protozoa could be an important biological mechanism for bacterial elimination in wastewater treatment systems.     

Investigating Pathogenicity and Virulence of Staphylococcus pettenkoferi: An Emerging Pathogen

Staphylococcus pettenkoferi is a coagulase-negative Staphylococcus identified in 2002 that has been implicated in human diseases as an opportunistic pathogenic bacterium. Its multiresistant character is becoming a major health problem, yet the pathogenicity of S. pettenkoferi is poorly characterized. In this study, the pathogenicity of a S. pettenkoferi clinical isolate from diabetic foot osteomyelitis was compared with a Staphylococcus aureus strain in various in vitro and in vivo experiments. Growth kinetics were compared against S. aureus, and bacteria survival was assessed in the RAW 264.7 murine macrophage cell line, the THP-1 human leukemia monocytic cell line, and the HaCaT human keratinocyte cell line. Ex vivo analysis was performed in whole blood survival assays and in vivo assays via the infection model of zebrafish embryos. Moreover, whole-genome analysis was performed. Our results show that S. pettenkoferi was able to survive in human blood, human keratinocytes, murine macrophages, and human macrophages. S. pettenkoferi demonstrated its virulence by causing substantial embryo mortality in the zebrafish model. Genomic analysis revealed virulence factors such as biofilm-encoding genes (e.g., icaABCD; rsbUVW) and regulator-encoding genes (e.g., agr, mgrA, sarA, saeS) well characterized in S. aureus. This study thus advances the knowledge of this under-investigated pathogen and validates the zebrafish infection model for this bacterium.     

GC and HPLC of grape monoterpenyl glycosides

The aim of the present study was to find a method alternative to enzymic hydrolysis for the analysis of grape terpenyl glycosides. GC after trimethylsilane derivatisation, and HPLC on four different stationary phases, ie bare silica, aminopropyl-, diol- and octadecyl-bonded silicas, were in turn considered for the separation of these aroma precursors extracted from grape juice, and specific enzymic hydrolyses with highly purified glycosidases showed which were the major components. These investigations show that reversed-phase liquid chromatography is better suited for both the direct and individual analysis of these glycosides.