Causes and Consequences of Microtubule Acetylation

International audienceAmong the different types of cytoskeletal components, microtubules arguably accumulate the greatest diversity of post-translational modifications (PTMs). Acetylation of lysine 40 (K40) of atubulin has received a particular attention because it is the only tubulin PTM to be found in the lumen of microtubules - most other tubulin PTMs are found at their outer surface. As a consequence, the enzyme catalyzing K40 acetylation needs to penetrate the narrow microtubules lumen to find its substrate. Acetylated microtubules have been considered as stable, long-lived microtubules, however until recently there was little information about whether the longevity of these microtubules is the cause or the consequence of acetylation. Current advances suggest that this PTM helps the microtubule lattice to cope with mechanical stress, thus facilitating microtubule self-repair. These observations now shed a new light on the structural integrity of microtubules, as well as on mechanisms and biological functions of tubulin acetylation. Here we discuss the recentunderstanding on how acetylation is generated in the lumen of microtubules, and how this ‘hidden’PTM can control microtubule properties and functions

Gradient Span Analysis Method: Application to the Multipoint Aerodynamic Shape Optimization of a Turbine Cascade

This paper presents the application of the gradient span analysis (GSA) method to the multipoint optimization of the two-dimensional LS89 turbine distributor. The cost function (total pressure loss) and the constraint (mass flow rate) are computed from the resolution of the Reynolds-averaged Navier-Stokes equations. The penalty method is used to replace the constrained optimization problem with an unconstrained problem. The optimization process is steered by a gradient-based quasi-Newton algorithm. The gradient of the cost function with respect to design variables is obtained with the discrete adjoint method, which ensures an efficient computation time independent of the number of design variables. The GSA method gives a minimal set of operating conditions to insert into the weighted sum model to solve the multipoint optimization problem. The weights associated to these conditions are computed with the utopia point method. The single-point optimization at the nominal condition and the multipoint optimization over a wide range of conditions of the LS89 blade are compared. The comparison shows the strong advantages of the multipoint optimization with the GSA method and utopia-point weighting over the traditional single-point optimization

Class III PI3K regulates organismal glucose homeostasis by providing negative feedback on hepatic insulin signalling.

Defective hepatic insulin receptor (IR) signalling is a pathogenic manifestation of metabolic disorders including obesity and diabetes. The endo/lysosomal trafficking system may coordinate insulin action and nutrient homeostasis by endocytosis of IR and the autophagic control of intracellular nutrient levels. Here we show that class III PI3K--a master regulator of endocytosis, endosomal sorting and autophagy--provides negative feedback on hepatic insulin signalling. The ultraviolet radiation resistance-associated gene protein (UVRAG)-associated class III PI3K complex interacts with IR and is stimulated by insulin treatment. Acute and chronic depletion of hepatic Vps15, the regulatory subunit of class III PI3K, increases insulin sensitivity and Akt signalling, an effect that requires functional IR. This is reflected by FoxO1-dependent transcriptional defects and blunted gluconeogenesis in Vps15 mutant cells. On depletion of Vps15, the metabolic syndrome in genetic and diet-induced models of insulin resistance and diabetes is alleviated. Thus, feedback regulation of IR trafficking and function by class III PI3K may be a therapeutic target in metabolic conditions of insulin resistance

A coupled implicit-explicit time integration method for compressible unsteady flows

This paper addresses how two time integration schemes, the Heun's scheme for explicit time integration and the second-order Crank-Nicolson scheme for implicit time integration, can be coupled spatially. This coupling is the prerequisite to perform a coupled Large Eddy Simulation / Reynolds Averaged Navier-Stokes computation in an industrial context, using the implicit time procedure for the boundary layer (RANS) and the explicit time integration procedure in the LES region. The coupling procedure is designed in order to switch from explicit to implicit time integrations as fast as possible, while maintaining stability. After introducing the different schemes, the paper presents the initial coupling procedure adapted from a published reference and shows that it can amplify some numerical waves. An alternative procedure, studied in a coupled time/space framework, is shown to be stable and with spectral properties in agreement with the requirements of industrial applications. The coupling technique is validated with standard test cases, ranging from one-dimensional to three-dimensional flows

Multiwavelength Raman spectroscopy of diamond nanowires present in n-type ultrananocrystalline films

Multiwavelength Raman spectroscopy is employed to investigate ultrananocrystalline diamond films deposited by the plasma enhanced chemical vapor deposition technique. Recently, we have shown that the addition of nitrogen in the gas source during synthesis induce the formation of diamond n-type films, exhibiting the highest electrical conductivity at ambient temperature. This point is related with the formation of elongated diamond nanostructures and the presence of sp2-bonded carbon in these films. The Raman results presented here confirm these aspects and provide a better and deeper understanding of the nature of these films and their related optical and electronic properties

Development of automated tools based on electronic identification for the improvement of organic livestock production systems

Technical constraints of livestock production in organic farming systems are numerous and require more attention than in conventional systems. The implementation of individual electronic identification that is planned in Europe offers the possibility of developing automated devices that may be well adapted to the practices of organic breeders. We developed an automated mounting detector, carried by a male, which makes it possible to detect any female in oestrus. Hence, this device is the unique solution for inseminating females when they are fertile, thus ensuring links with selection programmes. The second device developed is a dynamic sorting door based on respect for animal behaviour, preventing stress by allowing animals not to be unnecessarily confined. When associated with an electronic weighing device, it offers the possibility of adapting health treatments to the appropriate animals, in agreement with organic breeding specifications. Finally, electronic identification combined with GPS offers the breeder the possibility of simplifying the certification of animals in areas converted to organic farming. We believe that these technologies may greatly reduce the workload of breeders while improving animal welfare

Quantification of water content and speciation in natural silicic glasses (phonolite, dacite, rhyolite) by confocal microRaman spectrometry

International audienceThe determination of total water content (H2OT: 0.1-10 wt%) and water speciation (H2Omolecular/OH) in volcanic products by confocal microRaman spectrometry are discussed for alkaline (phonolite) and calcalkaline (dacite and rhyolite) silicic glasses. Shape and spectral distribution of the total water band (H2OT) at not, vert, similar3550 cm−1 show systematic evolution with glass H2OT, water speciation and NBO/T. In the studied set of silicic samples, calibrations based on internal normalization of the H2OT band to a band related to vibration of aluminosilicate network (TOT) at not, vert, similar490 cm−1 vary with glass peraluminosity. An external calibration procedure using well-characterized glass standards is less composition-dependent and provides excellent linear correlation between total dissolved water content and height or area of the H2OT Raman band. Accuracy of deconvolution procedure of the H2OT band to quantify water speciation in water-rich and depolymerized glasses depends on the strength of OH hydrogen bonding. System confocal performance, scattering from embedding medium and glass microcrystallinity have a crucial influence on accuracy of Raman analyses of water content in glass-bearing rocks and melt inclusions in crystals

Engineered Near and Far Field Optical Response of Dielectric Nanostuctures using Focused Cylindrical Vector Beams

Near- and far-field optical properties of silicon nanostructures under linear polarization (Gaussian beam), and azimuthally or radially focused cylindrical vector beams are investigated by finite-difference time-domain method (FDTD) in Meep open-source software. A python toolkit allowing FDTD simulations in Meep for using those excitation sources is provided. In addition to the preferential excitation of specific electric or magnetic resonance modes as function of the excitation beam polarization, it is shown in the case of spheroids that shape anisotropy affects the resonance wavelength and the dipole orientation of the magnetic or electric dipole mode. For radial or linear polarization, the electric dipole resonance is split by an anapole mode depending on the spheroid symmetry axis with respect to the electric field orientation. Finally, the optical properties in both far-field (scattering pattern) and near-field (electric and magnetic field hot spots) can be tuned by changing the excitation polarization at a fixed wavelength and selecting properly the spheroid shape and dimensions. These numerical simulations can be extended to more complex shapes, or fabrication-friendly nanostructures such as nanocylinders with circular or elliptic sections