Criblage in vitro des graines d’accessions locales de ricin (Ricinus communis L.) en conditions de stress salin

Le ricin (Ricinus communis L.) est une plante peu exigeante dont la culture offre d’énormes potentialités économiques pour les exploitants agricoles sénégalais. L’identification de génotypes performants avec des rendements acceptables en conditions de stress salin constitue une des solutions pour promouvoir cette culture sur des sols inaffectés aux cultures vivrières. Quatre accessions locales de ricin ont été cultivées durant un mois sur le milieu de Murashige et Skoog (MS) modifié et additionné de 0 ; 25 ; 50 ; 100 et 150 mM de chlorure de sodium (NaCl). Les réponses des accessions ont été évaluées en conditions in vitro sur la base de paramètres morphologiques, biochimiques et de survie des vitroplants. L’effet de la salinité sur ces paramètres mesurés a permis de classer les accessions en groupe tolérant (acc1), moyennement tolérant (acc7) et sensible (acc3 et acc4). La concentration 50 mM de NaCl a été identifiée comme un seuil de tolérance critique et discriminant permettant une classification des accessions de ricin selon leur sensibilité au NaCl. La biomasse aérienne est apparue comme un critère pertinent pour classer les accessions de ricin. Les mesures des teneurs en chlorophylle des feuilles des vitroplants ont permis d’aboutir à la même classification des groupes.Mots clés: criblage, Ricinus communis, salinité, SénégalEnglish Title:  In vitro screening of local accessions of castor bean seeds (Ricinus communis l.) Under conditions of salinity stressEnglish AbstractCastor bean (Ricinus communis L.) is an undemanding plant whose cultivation has enormous economic potential for Seneg alese farmers. The identification of efficient genotypes tolerant to salt stress condition could constitute a significant result to promote ricin culture specifically in margin soils. Four local accessions of castor were cultivated, using in vitro conditions for four weeks on MS modified medium supplemented with 0, 25, 50, 100, 150 mM NaCl. In vitro plants responses to salinity were recorded in terms of morphological and biochemical parameters and the rate of plant survival. The effect of different levels of salinity on these parameters was used to classify the accessions in tolerant group (acc1), moderately tolerant (acc7) and sensitive (acc3 and acc4). The concentration 50 mM of NaCl was identified as a discriminant level for castor accessions classification and a critical level of tolerance. The in vitro plants shoot biomass, appeared a relevant parameter to be used for classification of castor accessions under in vitro conditions. The content of leaf chlorophyll for in vitro plants confirmed the classification of Castor bean accessions obtained with morphological parameters according to their sensitivity to the salinity.Keywords: screening, Ricinus communis, salinity, Senega

Le lymphome primitif de la prostate : à propos d’un cas avec revue de la literature

Le lymphome primitif de la prostate est une affection maligne rare. Les patients présentent initialement des signes urinaires locaux et des signes généraux. Plusieurs traitements ont été utilisés comme la prostatectomie radicale, la radiothérapie ou des associations de chimiothérapie et de radiothérapie. Une revue de la littérature fait état du mauvais pronostic du lymphome de la prostate, le diagnostic se faisant souvent à un stade tardif. Nous rapportons le cas d’un patient âgé de 73 ans présentant une rétention aiguë d’urines dans un contexte de constipation opiniâtre avec amaigrissement sévère. Il était diabétique, aux antécédents de carcinome urothélial de stade pT1 et de grade G3, traité par résection transurétrale et BCG thérapie. L’examen clinique a révélé une prostate très augmentée de volume, ce qui a été confirmé par les examens d’imagerie. L’analyseanatomo-pathologique des biopsies réalisées par voie transrectale a mis en évidence un lymphome malin non Hodgkinien de type B primitif de la prostate. La prise en charge a consisté en une chimiothérapie. Malgré une régression considérable du volume tumoral à partir de la troisièmesemaine, le patient est décédé au lendemain de son 5ème cycle de chimiothérapie

No effect of subthalamic deep brain stimulation on metacognition in Parkinson’s disease

Deep brain stimulation of the subthalamic nucleus (STN-DBS) is a powerful treatment in Parkinson’s disease (PD), which provides a positive effect on motor symptoms although the way it operates on high cognitive processes such as metacognition remains unclear. To address this issue, we recorded electroencephalogram (EEG) of PD patients treated with STN-DBS that performed a reversal learning (RL) paradigm endowed with metacognitive self-assessment. We considered two stimulation conditions, namely DBS-ON (stimulation on) and DBS-OFF (stimulation off), and focused our EEG-analysis on the frontal brain region due to its involvement on high cognitive processes. We found a trend towards a significant difference in RL ability between stimulation conditions. STN-DBS showed no effect on metacognition, although a significant association between accuracy and decision confidence level held for DBS OFF, but not in the case of DBS ON. In summary, our study revealed no significant effect of STN-DBS on RL or metacognition

Hydrogen-induced reversible spin-reorientation transition and magnetic stripe domain phase in bilayer Co on Ru(0001)

Imaging the change in the magnetization vector in real time by spin-polarized low-energy electron microscopy, we observed a hydrogen-induced, reversible spin-reorientation transition in a cobalt bilayer on Ru(0001). Initially, hydrogen sorption reduces the size of out-of-plane magnetic domains and leads to the formation of a magnetic stripe domain pattern, which can be understood as a consequence of reducing the out-of-plane magnetic anisotropy. Further hydrogen sorption induces a transition to an in-plane easy-axis. Desorbing the hydrogen by heating the film to 400 K recovers the original out-of-plane magnetization. By means of ab-initio calculations we determine that the origin of the transition is the local effect of the hybridization of the hydrogen orbital and the orbitals of the Co atoms bonded to the absorbed hydrogen.Comment: 5 figure

Oxidation of graphene on metals

We use low-energy electron microscopy to investigate how graphene is removed from Ru(0001) and Ir(111) by reaction with oxygen. We find two mechanisms on Ru(0001). At short times, oxygen reacts with carbon monomers on the surrounding Ru surface, decreasing their concentration below the equilibrium value. This undersaturation causes a flux of carbon from graphene to the monomer gas. In this initial mechanism, graphene is etched at a rate that is given precisely by the same non-linear dependence on carbon monomer concentration that governs growth. Thus, during both growth and etching, carbon attaches and detaches to graphene as clusters of several carbon atoms. At later times, etching accelerates. We present evidence that this process involves intercalated oxygen, which destabilizes graphene. On Ir, this mechanism creates observable holes. It also occurs mostly quickly near wrinkles in the graphene islands, depends on the orientation of the graphene with respect to the Ir substrate, and, in contrast to the first mechanism, can increase the density of carbon monomers. We also observe that both layers of bilayer graphene islands on Ir etch together, not sequentially.Comment: 15 pages, 10 figures. Manuscript revised to improve discussion, following referee comments. Accepted for publication in Journal of Physical Chemistry C, Feb. 11, 201

Evidence for Surface Effects on the Intermolecular Interactions in Fe (II) Spin Crossover Coordination Polymers

From X-ray absorption spectroscopy (XAS) and X-ray photoemission spectroscopy (XPS) it is evident that the spin state transition behavior of Fe(II) spin crossover coordination polymer crystallites at the surface differs from the bulk. A comparison of four different coordination polymers reveals that the observed surface properties may differ from bulk for a variety of reasons. There are Fe(II) spin crossover coordination polymers with either almost complete switching of the spin state at the surface or no switching at all. Oxidation, differences in surface packing, and changes in coordination could all contribute to making the surface very different from the bulk. Some Fe(II) spin crossover coordination polymers may be sufficiently photoactive so that X-ray spectroscopies cannot discern the spin state transition

Localization of Dirac electrons by Moire patterns in graphene bilayers

We study the electronic structure of two Dirac electron gazes coupled by a periodic Hamiltonian such as it appears in rotated graphene bilayers. Ab initio and tight-binding approaches are combined and show that the spatially periodic coupling between the two Dirac electron gazes can renormalize strongly their velocity. We investigate in particular small angles of rotation and show that the velocity tends to zero in this limit. The localization is confirmed by an analysis of the eigenstates which are localized essentially in the AA zones of the Moire patterns.Comment: 4 pages, 5 figure

Effects of proton versus photon irradiation on (lymph) angiogenic, inflammatory, proliferative and anti-tumor immune responses in head and neck squamous cell carcinoma

International audienceThe proximity of organs at risk makes the treatment of head and neck squamous cell carcinoma (HNSCC) challenging by standard radiotherapy. The higher precision in tumor targeting of proton (P) therapy could promote it as the treatment of choice for HNSCC. Besides the physical advantage in dose deposition, few is known about the biological impact of P versus photons (X) in this setting. To investigate the comparative biological effects of P versus X radiation in HNSCC cells, we assessed the relative biological effectiveness (RBE), viability, proliferation and mRNA levels for genes involved in (lymph)angiogenesis, inflammation, proliferation and anti-tumor immunity. These parameters, particularly VEGF-C protein levels and regulations, were documented in freshly irradiated and/or long-term surviving cells receiving low/high-dose, single (SI)/multiple (MI) irradiations with P/X. The RBE was found to be 1.1 Key (lymph)angiogenesis and inflammation genes were downregulated (except for vegf-c) after P and upregulated after X irradiation in MI surviving cells, demonstrating a more favorable profile after P irradiation. Both irradiation types stimulated vegf-c promoter activity in a NF-κB-dependent transcriptional regulation manner, but at a lesser extent after P, as compared to X irradiation, which correlated with mRNA and protein levels. The cells surviving to MI by P or X generated tumors with higher volume, anarchic architecture and increased density of blood vessels. Increased lymphangiogenesis and a transcriptomic analysis in favor of a more aggressive phenotype were observed in tumors generated with X-irradiated cells. Increased detection of lymphatic vessels in relapsed tumors from patients receiving X radiotherapy was consistent with these findings. This study provides new data about the biological advantage of P, as compared to X irradiation. In addition to its physical advantage in dose deposition, P irradiation may help to improve treatment approaches for HNSCC