180 research outputs found
La diversité génétique chez les plantes cultivées des régions tropicales = Genetic variability in tropical crops
Les activitĂ©s de l'ORSTOM sur les ressources gĂ©nĂ©tiques concernent une dizaine d'espĂšces tropicales d'intĂ©rĂȘt agricole principalement en Afrique. Les chercheurs ont tout d'abord contribuĂ© Ă l'enrichissement des banques de gĂšnes mondiales en matĂ©riel vĂ©gĂ©tal original ; prĂšs de 20 000 Ă©chantillons sont conservĂ©s par le Centre ORSTOM de Montpellier. L'analyse de la diversitĂ© gĂ©nĂ©tique des espĂšces a Ă©tĂ© privilĂ©giĂ©e afin de connaĂźtre sa structuration et de comprendre son organisation dans son contexte Ă©volutif (domestication, migration, sĂ©lection). Deux Ă©volutions fondamentales ont guidĂ© cette approche de la diversitĂ© gĂ©nĂ©tique : 1) les concepts de "pools gĂ©niques" et de "complexe d'espĂšces" pour rendre compte des rapports entre les espĂšces cultivĂ©es et les formes apparentĂ©es sauvages ; 2) l'Ă©tude du polymorphisme molĂ©culaire des protĂ©ines et de l'ADN, source quasi illimitĂ©e de marqueurs gĂ©nĂ©tiques, dans leur majoritĂ© sĂ©lectivement neutres. Ainsi, la description de l'organisation gĂ©nĂ©tique des espĂšces collectĂ©es a Ă©tĂ© rĂ©alisĂ©e et illustrĂ©e par l'exemple des riz. Afin de dĂ©velopper la conservation et la gestion des ressources gĂ©nĂ©tiques, les chercheurs ORSTOM participent au dĂ©veloppement de mĂ©thodologies adaptĂ©es : 1) la constitution de collections rĂ©duites (core collection) ; 2) la cryoconservation d'espĂšces Ă graines rĂ©calcitrantes et/ou Ă multiplication vĂ©gĂ©tative ; 3) la conservation #in situ$ des formes spontanĂ©es dans leurs Ă©cosystĂšmes et des formes cultivĂ©es dans leurs agrosystĂšmes. Les ressources gĂ©nĂ©tiques conservĂ©es prennent de la valeur ajoutĂ©e par leur Ă©valuation, leur gestion et leur utilisation en sĂ©lection. Quelques-unes des perspectives de valorisation des recherches ORSTOM sont prĂ©sentĂ©es, en particulier l'emploi de marqueurs molĂ©culaires cartographiĂ©s dans le pilotage de l'introgression des caractĂšres d'intĂ©rĂȘt agronomique. (RĂ©sumĂ© d'auteur
Investigation of grain orientations of melt-textured HTSC with addition of uranium oxide, Y2O3 and Y2BaCuO5
Local grain orientations were studied in melt-textured YBCO samples processed with various amounts of depleted uranuim oxide (DU) and Y 2O3 by means of electron backscatter diffraction (EBSD) analysis. The addition of DU leads to the formation of Ucontaining nanoparticles (Y2Ba4CuUOx) with sizes of around 200 nm, embedded in the superconducting Y-123 matrix. The orientation of the Y 2BaCuO5 (Y-211) particles, which are also present in the YBCO bulk microstructure, is generally random as is the case in other melttextured Y-123 samples. The presence of Y-211 particles, however, also affects the orientation of the Y-123 matrix in these samples
Le Clos-Henry : une ferme de La TÚne finale à Chùteau-Gontier (Mayenne)
La fouille du site du Clos-Henry Ă ChĂąteau-Gontier, outre la dĂ©couverte dâune fosse du nĂ©olithique ancien VSG a permis de mettre en Ă©vidence une ferme de La TĂšne finale dâemprise trĂšs modeste. Son enclos rectangulaire Ă partition interne nâoccupe en effet que 2 400 m2. malgrĂ© un nombre restreint de structures en creux, moins de quarante trous de poteau, quatre bĂątiments sur poteaux y ont Ă©tĂ© relevĂ©s. Lâoccupation relativement courte du site, une ou deux gĂ©nĂ©rations, permet dây distinguer une unitĂ© agricole constituĂ©e dâun bĂątiment principal associĂ© Ă quelques bĂątiments annexes de type grenier. Lâensemble est Ă©tabli au cours de la seconde moitiĂ© du second siĂšcle avant J.-C. et abandonnĂ© au milieu du siĂšcle suivant.The Clos-Henry excavation at ChĂąteau-Gontier (Mayenne) revealed â in addition to a âVSGâ early Neolithic pit â a modest late La Tene farmstead, a rectangular enclosure with internal partition 2400 sq. m. in area. In spite of the restricted number of features identified (less than 40 post-holes), four timber-framed buildings have been distinguished. The relatively short occupation of the site (one or two generations) visualises an agricultural unit consisting of a main building associated with some granary-type annexes. The whole is established during the second half of 2nd century BC and abandonned by the middle of the following century
5-hydroxytryptamine (5-HT)1A autoreceptor adaptive changes in substance P (neurokinin 1) receptor knock-out mice mimic antidepressant-induced desensitization
Antagonists at substance P receptors of the neurokinin 1 (NK1) type have been shown to represent a novel class of antidepressant drugs, with comparable clinical efficacy to the selective serotonin (5-HT) reuptake inhibitors (SSRIs). Because 5-HT 1A receptors may be critically involved in the mechanisms of action of SSRIs, we examined whether these receptors could also be affected in a model of whole-life blockade of NK1 receptors, i.e. knock-out mice lacking the latter receptors (NK1ÏȘ/ÏȘ). 5-HT 1A receptor labeling by the selective antagonist radioligand receptor agonist ipsapirone to inhibit the discharge of serotoninergic neurons in the dorsal raphe nucleus within brainstem slices, and reduced hypothermic response to 8-OH-DPAT, were noted in NK1ÏȘ/ÏȘ versus NK1Ï©/Ï© mice. On the other hand, cortical 5-HT overflow caused by systemic injection of the SSRI paroxetine was four-to sixfold higher in freely moving NK1ÏȘ/ÏȘ mutants than in wild-type NK1Ï©/Ï© mice. Accordingly, the constitutive lack of NK1 receptors appears to be associated with a downregulation/functional desensitization of 5-HT 1A autoreceptors resembling that induced by chronic treatment with SSRI antidepressants. Double immunocytochemical labeling experiments suggest that such a heteroregulation of 5-HT 1A autoreceptors in NK1ÏȘ/ÏȘ mutants does not reflect the existence of direct NK1-5-HT 1A receptor interactions in normal mice
Polyamine Sharing between Tubulin Dimers Favours Microtubule Nucleation and Elongation via Facilitated Diffusion
We suggest for the first time that the action of multivalent cations on
microtubule dynamics can result from facilitated diffusion of GTP-tubulin to the
microtubule ends. Facilitated diffusion can promote microtubule assembly,
because, upon encountering a growing nucleus or the microtubule wall, random
GTP-tubulin sliding on their surfaces will increase the probability of
association to the target sites (nucleation sites or MT ends).
This is an original explanation for understanding the apparent discrepancy
between the high rate of microtubule elongation and the low rate of tubulin
association at the microtubule ends in the viscous cytoplasm. The mechanism of
facilitated diffusion requires an attraction force between two tubulins, which
can result from the sharing of multivalent counterions. Natural polyamines
(putrescine, spermidine, and spermine) are present in all
living cells and are potent agents to trigger tubulin self-attraction. By using
an analytical model, we analyze the implication of facilitated diffusion
mediated by polyamines on nucleation and elongation of microtubules. In
vitro experiments using pure tubulin indicate that the promotion of
microtubule assembly by polyamines is typical of facilitated diffusion. The
results presented here show that polyamines can be of particular importance for
the regulation of the microtubule network in vivo and provide
the basis for further investigations into the effects of facilitated diffusion
on cytoskeleton dynamics
The effect of phytostabilization on Zn speciation in a dredged contaminated sediment using scanning electron microscopy, X-ray fluorescence, EXAFS spectroscopy, and principal components analysis
De la genese a l'integration de l'information sensorielle dans le systeme cercal de la blatte: aspects electrophysiologiques
SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : T 80673 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc
Les fonctions des stigmates de la Passion du Christ
Les stigmatisés chrétiens fascinent. Au gré des époques et des discours, certains ont cru dissiper les ténÚbres inviolées du miracle des plaies de la Passion du Christ. Et malgré la raréfaction des cas de stigmatisation, la passion pour ce phénomÚne corporel insolite perdure. Pourtant une étude des cas Pio, Lebouc, Higginson, Beauvais et Galgani révÚle que les stigmates relÚvent soit d'une automutilation, soit d'une feinte suggérant leur présence. Là n'est cependant pas l'essentiel. Plus féconde s'avÚre une recherche axée sur ce mode original du rapport du sujet à son corps et ce d'autant qu'il se légitime dans le catholicisme et qu'il se soutient d'un rapport mystique à Jésus. A la faveur des enseignements freudiens et lacaniens, la thÚse démontre, à partir de la clinique, les deux fonctions principales des stigmates pour ces sujets. Soit le traitement d'une jouissance folle appartenant au corps propre et l'advenue d'un processus de représentation permettant de l'assumer et de la prendre en chargeStigmatized Christians are fascinating. According to different ages and views, some people believed they had cleared up the unpenetrated darkness surrounding the miracle of the wounds of the Passion of Christ. And although cases of stigmatization have become rare, the passion for this unusual physical phenomenon endures. Yet a study of the Pio, Lebouc, Higginson, Beauvais and Galgani cases reveals that the stigmata proceed either from self-mutilation or from a ruse suggesting their presence. However, the main point does not lie here. Research into this peculiar form taken by the relationship between the subject and his or her body proves to be more fruitful, and this all the more so since the phenomenon finds legitimacy in Catholicism and is upheld by a mystic relation to Jesus. Following the Freudian and Lacanian theories, the thesis, based on clinical elements, demonstrates the two main functions of stigmata for these subjects. That is to say the treatment of uncontrollable pleasure belonging to the body itself and the appearance of a process of representation enabling the subject to accept it and deal with itRENNES2-BU Centrale (352382101) / SudocSudocFranceF
Analyse électrophysiologique, pharmacologique et moléculaire de facteurs modulant les effets d'un insecticide, le fipronil, sur des récepteurs gabaergiques d'insectes
Les rĂ©cepteurs ionotropes du GABA (GABARs) sont inhibĂ©s par des insecticides tels que les phĂ©nylpyrazoles (fipronil). Deux facteurs susceptibles de modifier leur sensibilitĂ© au fipronil ont Ă©tĂ© examinĂ©s : 1) l'Ă©dition de l'ARNm d'une sous-unitĂ© de GABAR (RDL) et 2) la phosphorylation par la PKC. La sous-unitĂ© RDL de drosophile prĂ©sente des mutations (A301ĂȘS/G et/ou T350ĂȘM) induisant une rĂ©sistance aux insecticides, ainsi que des sites d'Ă©dition dont un dans le domaine N-terminal (R122ĂȘG). Les effets fonctionnels de l'Ă©dition R122ĂȘG ont Ă©tĂ© testĂ©s par expression de divers isoformes de la sous-unitĂ© RDL (mutĂ©s ou non, Ă©ditĂ©s ou non) dans des ovocytes de xĂ©nope. Les rĂ©sultats montrent que l'Ă©dition R122ĂȘG entraĂźne une rĂ©duction de la sensibilitĂ© des rĂ©cepteurs RDL au GABA et au fipronil. Deux types de rĂ©cepteurs (GABAR1 et GABAR2) sont exprimĂ©s Ă la surface des neurones DUM isolĂ©s de Periplaneta americana, les GABAR2 Ă©tant rĂ©gulĂ©s positivement par la CaMKII. Ce modĂšle cellulaire a Ă©tĂ© utilisĂ© pour Ă©tudier, par la technique du patch-clamp, la rĂ©gulation des GABARs par la PKC et ses consĂ©quences sur les effets du fipronil. Les GABAR2 apparaissent plus sensibles Ă l'inhibition par des PKC que les GABAR1, et la potentialisation de l'activitĂ© des GABAR2 par la CaMKII s'exerce via l'inhibition d'une PKC. Les GABAR2 Ă©tant plus sensibles au fipronil que les GABAR1, leur blocage sĂ©lectif par une PKC entraĂźne une rĂ©duction importante de l'inhibition exercĂ©e par le fipronil. Le clonage de la sous-unitĂ© RDL dans la chaĂźne nerveuse de la blatte et dans les neurones DUM rĂ©vĂšle la prĂ©sence de sites potentiels de phosphorylation par la PKC et la CaMKII ainsi que l'existence de deux variants diffĂ©rant par vingt rĂ©sidus dans la boucle M3-M4.Ionotropic GABA receptors (GABARs) are inhibited by insecticides such as phenylpyrazoles (fipronil). Two factors that might alter their sensitivity to fipronil were examined: 1) mRNA editing of a GABAR subunit, RDL and 2) PKC phosphorylation. Drosophila RDL subunit presents mutations (A301ĂȘS/G or T350ĂȘM) that result in insecticide resistance, as well as an editing site (R122ĂȘG) in the N-terminal domain. Functional effects of the R122ĂȘG editing were assessed by expressing several isoforms of the RDL subunit (mutated or not, edited or not) in Xenopus oocytes. The results show that R122ĂȘG editing leads to a decrease of RDL receptors to both GABA and fipronil. Two GABARs subtypes (GABAR1 and GABAR2) are expressed at the surface of Periplaneta americana isolated DUM neurons, GABAR2 being positively modulated by the CaMKII. This cellular model has been used to study, by the patch-clamp technique, GABARs regulation by PKC and its consequences on fipronil effects. GABAR2 appear to be more sensitive to PKC inhibition than GABAR1, and CaMKII potentiation occurs through PKC inhibition. GABAR2 being more sensitive to fipronil than GABAR1, its selective blockade by PKC induces an important decrease in the inhibition exerted by fipronil. The cloning of the RDL subunit in Periplaneta americana nerve cord and in DUM neurons reveals the presence of potential phosphorylation sites by PKC and CaMKII, as well as the existence of two RDL variants that differ by a twenty residues insertion in the M3-M4 loop.ANGERS-BU Lettres et Sciences (490072106) / SudocSudocFranceF
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