DES DIFFÉRENCES LIÉES AU SEXE DANS LES STRATÉGIES DE RÉPARTITION SPATIALE CHEZ DES POISSONS PORTE-ÉPÉE (XIPHOPHORUS HELLERi) MAINTENUS EN CAPTIVITÉ

The swordtail fish is a species particularly abundant in fresh water of Mexico and Central America. It is an ovoviviparous species, not really territorial which shows nipright order. In this research, significant differences of spatial distribution have been found according to the position in the nipright order and according to the sex of the fish. These differences bind with two external variables: the presence of sexual partners and the space available for the fish. The dominating males prefer a space partition allowing access to the females more than a compartment allowing access to more space in volume. They also chase their subordinates in the contiguous compartment of the aquarium. Females swordtails prefer the bigger compartment independently of the presence of conspecific males. These results are discussed in the light of reproductive strategies particular to each sex

ER stress affects processing of MHC class I-associated peptides

<p>Abstract</p> <p>Background</p> <p>Viral infection and neoplastic transformation trigger endoplasmic reticulum (ER) stress. Thus, a large proportion of the cells that must be recognized by the immune system are stressed cells. Cells respond to ER stress by launching the unfolded protein response (UPR). The UPR regulates the two key processes that control major histocompatibility complex class I (MHC I)-peptide presentation: protein synthesis and degradation. We therefore asked whether and how the UPR impinges on MHC I-peptide presentation.</p> <p>Results</p> <p>We evaluated the impact of the UPR on global MHC I expression and on presentation of the H2K^b-associated SIINFEKL peptide. EL4 cells stably transfected with vectors coding hen egg lysozyme (HEL)-SIINFEKL protein variants were stressed with palmitate or exposed to glucose deprivation. UPR decreased surface expression of MHC I but did not affect MHC I mRNA level nor the total amount of intracellular MHC I proteins. Impaired MHC I-peptide presentation was due mainly to reduced supply of peptides owing to an inhibition of overall protein synthesis. Consequently, generation of H2K^b-SIINFEKL complexes was curtailed during ER stress, illustrating how generation of MHC I peptide ligands is tightly coupled to ongoing protein synthesis. Notably, the UPR-induced decline of MHC I-peptide presentation was more severe when the protein source of peptides was localized in the cytosol than in the ER. This difference was not due to changes in the translation rates of the precursor proteins but to increased stability of the cytosolic protein during ER stress.</p> <p>Conclusion</p> <p>Our results demonstrate that ER stress impairs MHC I-peptide presentation, and that it differentially regulates expression of ER- vs. cytosol-derived peptides. Furthermore, this work illustrates how ER stress, a typical feature of infected and malignant cells, can impinge on cues for adaptive immune recognition.</p

Spray-assisted polyelectrolyte multilayer buildup: from step-by-step to single-step polyelectrolyte film constructions.

The alternate deposition of polyanions and polycations on a solid substrate leads to the formation of nanometer to micrometer films called Polyelectrolyte Multilayers. This step-by-step construction of organic films constitutes a method of choice to functionalize surfaces with applications ranging from optical to bioactive coatings. The method was originally developed by dipping the substrate in the different polyelectrolyte solutions. Recent advances show that spraying the polyelectrolyte solutions onto the substrate represents an appealing alternative to dipping because it is much faster and easier to adapt at an industrial level. Multilayer deposition by spraying is thus greatly gaining in interest. Here we review the current literature on this deposition method. After a brief history of polyelectrolyte multilayers to place the spraying method in its context, we review the fundamental issues that have been addresses so far. We then give an overview the different fields where the method has been applied.journal articlereview2012 Feb 212012 01 26importe

Non-perturbative Power Corrections to Ghost and Gluon Propagators

We study the dominant non-perturbative power corrections to the ghost and gluon propagators in Landau gauge pure Yang-Mills theory using OPE and lattice simulations. The leading order Wilson coefficients are proven to be the same for both propagators. The ratio of the ghost and gluon propagators is thus free from this dominant power correction. Indeed, a purely perturbative fit of this ratio gives smaller value ($\simeq 270$MeV) of \Lambda_{\ms} than the one obtained from the propagators separately($\simeq 320$MeV). This argues in favour of significant non-perturbative $\sim 1/q^2$ power corrections in the ghost and gluon propagators. We check the self-consistency of the method.Comment: 14 pages, 4 figures; replaced with revised version, to appear in JHE

Divergent IR gluon propagator from Ward-Slavnov-Taylor identities?

We exploit the Ward-Slavnov-Taylor identity relating the 3-gluons to the ghost-gluon vertices to conclude either that the ghost dressing function is finite and non vanishing at zero momentum while the gluon propagator diverges (although it may do so weakly enough not to be in contradiction with current lattice data) or that the 3-gluons vertex is non-regular when one momentum goes to zero. We stress that those results should be kept in mind when one studies the Infrared properties of the ghost and gluon propagators, for example by means of Dyson-Schwinger equations.Comment: 6 pages, bibte

Polyelectrolyte multilayer films as substrates for photoreceptor cells.

Reconstruction of extracellular matrix substrates for delivery of functional photoreceptors is crucial in pathologies such as retinal degeneration and age-related macular degeneration. In this study, we assembled polyelectrolyte films using the layer-by-layer deposition method. The buildup of three different films composed of poly(L-lysine)/chondroitin sulfate (PLL/CSA), poly(L-lysine)/poly(styrenesulfonate) (PLL/PSS), or poly(L-lysine)/hyaluronic acid (PLL/HA) was followed by means of quartz crystal microbalance measurements, optical waveguide light mode spectroscopy, confocal microscopy, and atomic force microscopy. The exponential growth regime and the diffusion of PLL chains from the bulk through the PLL/CSA, PLL/PSS, and PLL/HA films was examined. Evaluation of photoreceptor cell viability was optimal on one layer of PLL (PLL(1)), followed by 10 bilayers of PLL/HA [(PLL/HA)(10)] and 10 bilayers of PLL/CSA [(PLL/CSA)(10)]. The number of bilayers and the type of terminating layer also had a significant influence on the number of photoreceptor cells attached. Functionalized polyelectrolyte multilayer films were obtained by adsorbing basic fibroblastic factor (bFGF) or the insoluble fraction of interphotoreceptor matrix (IPM) on or within polyelectrolyte multilayers. bFGF and IPM adsorption on top of the (PLL/CSA)(10)/PLL polyelectrolyte films increased the number of photoreceptor cells attached and maintained the differentiation of rod and cone cells.journal articleresearch support, non-u.s. gov't2006 Janimporte

Statics and dynamics of weakly coupled antiferromagnetic spin-1/2 ladders in a magnetic field

We investigate weakly coupled spin-1/2 ladders in a magnetic field. The work is motivated by recent experiments on the compound (C5H12N)2CuBr4 (BPCB). We use a combination of numerical and analytical methods, in particular the density matrix renormalization group (DMRG) technique, to explore the phase diagram and the excitation spectra of such a system. We give detailed results on the temperature dependence of the magnetization and the specific heat, and the magnetic field dependence of the nuclear magnetic resonance (NMR) relaxation rate of single ladders. For coupled ladders, treating the weak interladder coupling within a mean-field or quantum Monte Carlo approach, we compute the transition temperature of triplet condensation and its corresponding antiferromagnetic order parameter. Existing experimental measurements are discussed and compared to our theoretical results. Furthermore we compute, using time dependent DMRG, the dynamical correlations of a single spin ladder. Our results allow to directly describe the inelastic neutron scattering cross section up to high energies. We focus on the evolution of the spectra with the magnetic field and compare their behavior for different couplings. The characteristic features of the spectra are interpreted using different analytical approaches such as the mapping onto a spin chain, a Luttinger liquid (LL) or onto a t-J model. For values of parameters for which such measurements exist, we compare our results to inelastic neutron scattering experiments on the compound BPCB and find excellent agreement. We make additional predictions for the high energy part of the spectrum that are potentially testable in future experiments.Comment: 35 pages, 26 figure