Correlations between effective permeability and marrow contact channels surface of vertebral endplates

Homeostasis of the intervertebral disc relies on nutrient supply and waste clearance through the dense capillary network that is in contact with the cartilage endplate (CEP). We developed a micro-computerized tomography (micro-CT) method to quantify the marrow contact channel surface (MCCS) with the CEP and to validate the hypothesis according to which MCCS was correlated to the effective permeability of the vertebral endplate (VEP) and influenced by the mechanical stimuli. The influence of compression loading on local vascularization was investigated. Six 4-week-old skeletally immature pigs were instrumented with left pedicle screws and rod at both T5-T6 and L1-L2 levels to create asymmetrical spine tethers. After 3 months of growth, three cylindrical specimens of the VEP (one central and two lateral right and left) were obtained from both the instrumented and the control levels. We used a previously validated method for measuring permeability. Micro-CT analysis (resolution 12 mu m) yielded a gray-scale 2D-image of the discal end of each specimen converted into a binary 2D-image to derive the MCCS. Correlations between MCCS and effective permeability were assessed. Effective permeability and MCCS were significantly decreased compared to the control group especially on the tethered side (-41..5%, p = 0.004 and -52.5%, p = 0.0009, respectively). Correlations were significant and showed maximal value (r(2) = 0.430, p < 0.0001) on the tethered side involving maximal compressive loadings. Mechanical stimuli, due to unbalanced growth, altered the vascularization and the convective properties of the CEP. The cascade of mechanobiological events should offer perspectives for research on disc degeneration and attempted treatment. (C) 2010 Orthopaedic Research Society

Homologous Recombination Is Stimulated by a Decrease in dUTPase in Arabidopsis

Deoxyuridine triphosphatase (dUTPase) enzyme is an essential enzyme that protects DNA against uracil incorporation. No organism can tolerate the absence of this activity. In this article, we show that dUTPase function is conserved between E. coli (Escherichia coli), yeast (Saccharomyces cerevisiae) and Arabidopsis (Arabidopsis thaliana) and that it is essential in Arabidopsis as in both micro-organisms. Using a RNA interference strategy, plant lines were generated with a diminished dUTPase activity as compared to the wild-type. These plants are sensitive to 5-fluoro-uracil. As an indication of DNA damage, inactivation of dUTPase results in the induction of AtRAD51 and AtPARP2, which are involved in DNA repair. Nevertheless, RNAi/DUT1 constructs are compatible with a rad51 mutation. Using a TUNEL assay, DNA damage was observed in the RNAi/DUT1 plants. Finally, plants carrying a homologous recombination (HR) exclusive substrate transformed with the RNAi/DUT1 construct exhibit a seven times increase in homologous recombination events. Increased HR was only detected in the plants that were the most sensitive to 5-fluoro-uracils, thus establishing a link between uracil incorporation in the genomic DNA and HR. Our results show for the first time that genetic instability provoked by the presence of uracils in the DNA is poorly tolerated and that this base misincorporation globally stimulates HR in plants

Groupes partiels, prégroupes et réalisabilité des systèmes de fusion

In this article, we compare two different notions of partially defined group strutures, namely partial groups and pregroups, as introduced by Chermak and Stallings respectively. In particular we prove that the category of pregroups can be seen as a full subcategory of the category of partial groups. We also bring out some conjugation properties about elements and subgroups of finite order in pregroups and their universal groups. We then use these to investigate the question of realisability of fusion systems in finite pregroups

Théolepte de Philadelphie. Lettres à une princesse et discours monastiques

International audienc

Théolepte de Philadelphie. Lettres à une princesse et discours monastiques

International audienc

Théolepte de Philadelphie, Lettres et Discours monastiques

MH Congourdeau: auteur de l'introduction, traductrice des Discours N. Molinier: traducteur des lettrestraduction française des lettres et des discours adressés à sa disciple la princesse-moniale Irène-Eulogia Palaiologina par Théolepte de Philadelphie, évêque byzantin du 14e siècle, maître spirituel de Grégoire Palamas

A new statistical study of the magnetopause features seen by Cluster

International audienceThe BV method is based on both magnetic field and velocity measurements to determine the magnetopause normal with an improved accuracy from data of one spacecraft. It makes possible a reliable determination of the normal magnetic field and therefore to disentangle a tangential magnetopause from a reconnected one. We will show statistics on the determination of the normal component of the magnetic field and on other properties such as the magnetic shear angle of the tangential component. One of the byproducts of the method is the thickness of the boundary. We will discuss the similarities and differences with the statistics obtained by multi-spacecraft methods when both methods are reliable. The role in particular of a flow going through the magnetopause will be evidenced

Additional costs of polymyalgia rheumatica with giant-cell arteritis

International audienc

Microalgae as Soft Permeable Particles

International audienceThe colloidal stability of non-motile algal cells in water drives their distribution in space. An accurate description of the interfacial properties of microalgae is therefore critical to understand how microalgae concentrations can change in their biotope or during harvesting processes. Here, we probe the surface charges of three unicellular algae─Chlorella vulgaris, Nannochloropsis oculata, and Tetraselmis suecica─through their electrophoretic mobility. Ohshima’s soft particle theory describes the electrokinetic properties of particles covered by a permeable polyelectrolyte layer, a usual case for biological particles. The results appear to fit the predictions of Ohshima’s theory, proving that all three microalgae behave electrokinetically as soft particles. This allowed us to estimate two characteristic parameters of the polyelectrolyte external layer of microalgae: the volume charge density and the hydrodynamic penetration length. Results were compared with transmission electron microscopy observations of the algal cells’ surfaces, and in particular of their extracellular polymeric layer, which was identified with the permeable shell evidenced by electrophoretic measurements. Noticeably, the algal surface potentials estimated from electrophoretic mobility using the soft particle theory are less negative than the apparent zeta potentials. This finding indicates that electrostatics are expected to play a minor role in phenomena of environmental and industrial importance, such as microalgae aggregation or adhesion

Straightforward Assessment of Wettability Changes by Washburn Capillary Rise: Toward a Screening Tool for Selecting Water Compositions for Improved Oil Recovery

Evaluating the wettability state of reservoir rocks is key for understanding and optimizing waterflooding and improved oil recovery techniques that imply the use of low-salinity water. Aside from established petrophysical techniques, such as Amott imbibition tests, we evaluated the Washburn capillary rise method as a low-cost, easy-to-implement, and rapid screening tool for probing the wettability state of rock samples. The well-known limitations of this method are discussed and circumvented. We show that measuring the capillary rise of two liquids brine and n-octaneis required to assess the evolution of the wettability state of a material induced by various treatments. The wettability state is quantified by the adhesion tension of brine to the solid. The higher the adhesion tension of brine, the more water-wet the sample. An increase in oil-wetness is observed when the sample is contacted with a crude oil or its released waters; an increase in water-wetness is obtained by postcontacting the oil-wet sample with low-salinity brine or surfactant solutions. The Washburn capillary rise is revealed to be a robust method for screening wettability alteration. With a typical duration of 1–10 min, it allows reproducibility check and screening of a wide range of brine compositions in a reasonable time frame. Therefore, it is a relevant tool to identify the most favorable brine compositions to be tested afterward with more time-consuming techniques, such as Amott tests and corefloods