Study of the ternary system Al–H– RE ( RE = Er, La and Y) in liquid state

International audienc

Angers – Abbaye Saint-Aubin

Il s’agit d’une opération d’urgence réalisée dans le cloître Saint Aubin, à l’occasion de l’ouverture d’une tranchée technique d’une largeur de 2,5 m qui a traversé l’aile ouest, le nord de la galerie ouest et la galerie nord à l’emplacement d’une tranchée de fondation des arcs-boutants de l’église. Compte tenu de l’état d’avancement du projet, seule une surveillance des travaux et une série de relevés ponctuels ont pu être effectués. Sous l’aile ouest, des caves médiévales ont été mises au j..

Optimizing filter trap assay for the detection of aggregated alpha-synuclein in brain samples

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Phospholipase D protects ECV304 cells against TNFα-induced apoptosis

AbstractTumor necrosis factor α (TNFα), a pleiotropic cytokine, activates both apoptotic and pro-survival signals depending on the cell model. Using ECV304 cells, which can be made TNFα-sensitive by cycloheximide (CHX) co-treatment, we evaluated the potential roles of ceramide and phospholipase D (PLD) in TNFα-induced apoptosis. TNFα/CHX induced a robust increase in ceramide levels after 16h of treatment when cell death was maximal. PLD activity was increased at early time point (1h) whereas both PLD activity and PLD1 protein were strongly decreased after 24h. TNFα/CHX-induced cell death was significantly lowered by exogenous bacterial PLD and phoshatidic acid, and in cells overexpressing PLD1. Conversely, cells depleted in PLD proteins by small interference RNA (siRNA) treatment exhibited higher susceptibility to apoptosis. These results show that PLD exerts a protective role against TNFα-induced cell death

The cAMP-specific Phosphodiesterase PDE4D3 Is Regulated by Phosphatidic Acid Binding CONSEQUENCES FOR cAMP SIGNALING PATHWAY AND CHARACTERIZATION OF A PHOSPHATIDIC ACID BINDING SITE

Hormones and growth factors induce in many cell types the production of phosphatidic acid (PA), which has been proposed to play a role as a second messenger. We have previously shown in an acellular system that PA selectively stimulates certain isoforms of type 4 cAMP-phosphodiesterases (PDE4). Here we studied the effect of endogenous PA on PDE activity of transiently transfected MA10 cells overexpressing the PA-sensitive isoform PDE4D3. Cell treatment with inhibitors of PA degradation, including propranolol, induced an accumulation of endogenous PA accompanied by a stimulation of PDE activity and a significant decrease in both cAMP levels and protein kinase A activity. Furthermore, in FRTL5 cells, which natively express PDE4D3, pretreatment with compounds inducing PA accumulation prevented both cAMP increase and cAMP-responsive element-binding protein phosphorylation triggered by thyroid-stimulating hormone. To determine the mechanism of PDE stimulation by PA, endogenous phospholipids were labeled by preincubating MA10 cells overexpressing PDE4D3 with [(32)P]orthophosphate. Immuno- precipitation experiments showed that PA was specifically bound to PDE4D3, supporting the hypothesis that PDE4D3 activation occurs through direct binding of PA to the protein. PA binding site on PDE4D3 was characterized by engineering deletions of selected regions in the N-terminal regulatory domain of the enzyme. Deletion of amino acid residues 31-59 suppressed both PA-activating effect and PA binding, suggesting that this region rich in basic and hydrophobic residues contains the PA binding site. These observations strongly suggest that endogenous PA can modulate cAMP levels in intact cells, through a direct activation of PDE4D3

Source X par agrégats : contrôle et optimisation des paramètres gouvernant línteraction laser de puissance - agrégats de gaz rare

National audienceLes expériences que nous avons réalisées sur le Laser Ultra Court Accordable du CEA Saclay permettent dóbserver l\'émission de photons X dans la gamme 1-5 keV lors de lírradiation dágrégats de gaz rare (Ar, Kr et Xe comprenant entre 10^3 et 10^6 atomes par agrégat) avec un laser femtoseconde de puissance (Ipic jusqu\'à 10^17 W/cm²). En plus de la distribution des états de charge des ions responsables de l\'émission X, la technique de spectroscopie X que nous utilisons permet de mesurer les taux absolus de photons émis dans 4π par impulsion laser en fonction des paramètres gouvernant línteraction dans des conditions contrôlées. Nous avons déterminé la sensibilité des paramètres physiques régissant la production du rayonnement X pendant línteraction, ce qui permet dáccéder à lóptimisation de cette source. Cet article est plus particulièrement dédié aux résultas relatifs à l\'évolution du taux d\'X avec l\'éclairement laser, dúne part, et avec la durée de límpulsion laser, dáutre part

Production and Characterisation of a Neutralising Chimeric Antibody against Botulinum Neurotoxin A

Botulinum neurotoxins, produced by Clostridium botulinum bacteria, are the causative agent of botulism. This disease only affects a few hundred people each year, thus ranking it among the orphan diseases. However, botulinum toxin type A (BoNT/A) is the most potent toxin known to man. Due to their potency and ease of production, these toxins were classified by the Centers for Disease Control and Prevention (CDC) as Category A biothreat agents. For several biothreat agents, like BoNT/A, passive immunotherapy remains the only possible effective treatment allowing in vivo neutralization, despite possible major side effects. Recently, several mouse monoclonal antibodies directed against a recombinant fragment of BoNT/A were produced in our laboratory and most efficiently neutralised the neurotoxin. In the present work, the most powerful one, TA12, was selected for chimerisation. The variable regions of this antibody were thus cloned and fused with the constant counterparts of human IgG1 (kappa light and gamma 1 heavy chains). Chimeric antibody production was evaluated in mammalian myeloma cells (SP2/0-Ag14) and insect cells (Sf9). After purifying the recombinant antibody by affinity chromatography, the biochemical properties of chimeric and mouse antibody were compared. Both have the same very low affinity constant (close to 10 pM) and the chimeric antibody exhibited a similar capacity to its parent counterpart in neutralising the toxin in vivo. Its strong affinity and high neutralising potency make this chimeric antibody interesting for immunotherapy treatment in humans in cases of poisoning, particularly as there is a probable limitation of the immunological side effects observed with classical polyclonal antisera from heterologous species

Émission X(L) du xénon par interaction laser -agrégats

National audienceNous avons étudié le rayonnement X provenant d'ions fortement multichargés (" 24+) présentant des lacunes en couche L produits lors de l'irradiation d'agrégats de xénon par des impulsions lumineuses issues d'un laser femtoseconde de puissance. Les résultats obtenus lors de la toute dernière campagne d'expériences réalisée auprès du serveur LUCA du SPAM/DRECAM au CEA/Saclay mettent en cause certains travaux antérieurs. Des divergences marquées apparaissent tant au niveau de l'interprétation des spectres X que sur la variation du taux d'émission en fonction de l'éclairement et de la longueur d'onde

The Mechanism of Docosahexaenoic Acid-induced Phospholipase D Activation in Human Lymphocytes Involves Exclusion of the Enzyme from Lipid Rafts

Docosahexaenoic acid (DHA), an n-3 polyunsaturated fatty acid that inhibits T lymphocyte activation, has been shown to stimulate phospholipase D (PLD) activity in stimulated human peripheral blood mononuclear cells (PBMC). To elucidate the mechanisms underlying the DHA-induced PLD activation, we first characterized the PLD expression pattern of PBMC. We show that these cells express PLD1 and PLD2 at the protein and mRNA level and are devoid of oleate-dependent PLD activity. DHA enrichment of PBMC increased the DHA content of cell phospholipids, which was directly correlated with the extent of PLD activation. The DHA-induced PLD activation was independent of conventional protein kinase C but inhibited by brefeldin A, which suggests ADP-ribosylation factor (ARF)-dependent mechanism. Furthermore, DHA enrichment dose-dependently stimulated ARF translocation to cell membranes. Whereas 50% of the guanosine 5'-3-O-(thio)triphosphate plus ARF-dependent PLD activity and a substantial part of PLD1 protein were located to the detergent-insoluble membranes, so-called rafts, of non-enriched PBMC, DHA treatment strongly displaced them toward detergent-soluble membranes where ARF is present. Collectively, these results suggest that the exclusion of PLD1 from lipid rafts, due to their partial disorganization by DHA, and its relocalization in the vicinity of ARF, is responsible for its activation. This PLD activation might be responsible for the immunosuppressive effect of DHA because it is known to transmit antiproliferative signals in lymphoid cells

Dynamique sub-picoseconde de l'interaction laser de puissance – agrégats de gaz rare : émission intense de rayons X et production d'ions multichargés.

National audienceLors de campagnes d'expériences réalisées sur le Laser Ultra Court Accordable du CEA/Saclay, nous avons étudié le rayonnement X, tant qualitativement (spectroscopie et énergie moyenne des photons) que quantitativement (taux absolus et lois d'évolution), émis lors de l'interaction d'un jet effusif d'agrégats de gaz rare (Ar, Kr, Xe comprenant entre 10^4 et 10^6 atomes/agrégat) avec un laser femtoseconde de puissance (éclairement jusqu'à quelques 10^17 W/cm2). Les résultats présentés dans ce manuscrit sont uniquement dédiés aux agrégats d'Ar pour lesquels nous avons observé un rayonnement X issu d'ions fortement multichargés (jusqu'à l'Ar16+) présentant des lacunes en couches K. La technique de spectroscopie X utilisée a permis de déterminer pour la première fois des taux absolus ainsi que les lois d'évolution de l'émission X en fonction de l'ensemble des paramètres gouvernant l'interaction (intensité, polarisation, longueur d'onde et durée du pulse laser aussi bien que taille, densité et numéro atomique des agrégats)