Dissertations / Theses on the topic 'Résistance aux parasites'
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Leignel, Vincent. "Diversité génétique et résistance aux benzimidazoles chez ""Teladorsagia circumcincta" (Nematoda, Trichostrongylidea) parasite de petits ruminants." Montpellier 2, 2000. http://www.theses.fr/2000MON20142.
Full textMartin, Thibaud. "La résistance aux insecticides de Heliccoverpa armigera (Hübner) en Afrique de l'Ouest : du mécanisme à la gestions." Toulouse 3, 2003. http://www.theses.fr/2003TOU30087.
Full textLecouls, Anne-Claire. "Spectre d'activité et marquage moléculaire du gène Ma1 contrôlant la résistance aux nématodes Meloidogyne chez Prunier myrobolan." Aix-Marseille 2, 2000. http://www.theses.fr/2000AIX22031.
Full textMenard, Sandie. "Plasmodium falciparum et résistance aux antipaludiques : aperçu et conséquences des facteurs impliqués dans la sélection et la diffusion des parasites résistants." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30116/document.
Full textMalaria remains one of the most terrible infectious diseases with more than 200 million infections and 430,000 deaths each year, mostly children under five years old in sub-Saharan Africa. Plasmodium falciparum is responsible for the vast majority of malaria mortality cases. Control of malaria still remains a major public health problem, in particular because of resistances to antimalarials that parasites developed. The apparition of these resistances is due to the drug pressure, and their progressive diffusion is mainly via the travelling of infected hosts. However, the dynamics of emergence, diffusion and persistence of resistant parasites result from complex interactions between the antimalarials, the Human, the parasite and the vector. The work presented here participates in the malaria control process by first proposing an inventory of Plasmodium resistance to antimalarials used in Cameroon, thanks to molecular, phenotypic and clinical tools. A second part explores the possible consequences of prolonged use of artemisinin derivatives on the P. falciparum phenotype, in areas where resistance to this molecule is already established. The in vitro model used showed that continuous artemisinin pressures induced a new pluri-resistance profile. Finally, a last part analyses the role of the mosquito in the epidemiology of resistances and shows that the sporogony favours the diffusion of minority alleles, resistant or not, presented in humans. All this work confirms the multiplicity of forces acting on the dynamics of resistances and the complexity of their interactions making any prediction very speculative. Even if better knowledge of the societal, epidemiological, biological and pharmacological phenomena involved in resistances is a priority, regular phenotypic and genotypic surveillance in the field remains the best tool for adapting malaria control strategies
Boudsocq-Silvestre, Anne. "Résistance aux benzimidazoles des communautés de nématodes parasites du tractus digestif des petits ruminants : mécanismes génétiques et facteurs environnementaux." Tours, 2000. http://www.theses.fr/2000TOUR3805.
Full textPoitrineau, Karine. "Evolution de la résistance aux ennemis naturels et intéractions multiples : théorie et système biologique drosophiles-parasitoi͏̈des." Montpellier 2, 2004. http://www.theses.fr/2004MON20016.
Full textBeveraggi, André. "Etude des interactions hôte-parasite chez les bananiers sensibles et résistants inoculés par "Cercospora fijiensis" responsable de la maladie des raies noires." Montpellier 2, 1992. http://www.theses.fr/1992MON20264.
Full textRiou, Mickaël. "Rôles et régulation des P-glycoprotéines de membrane impliquées dans les mécanismes de résistance multiple des nématodes parasites des petits ruminants aux anthelminthiques." Tours, 2005. http://www.theses.fr/2005TOUR4001.
Full textP-glycoproteins (Pgp) play an important role in the multiresistance to anthelmintics in the parasitic nematodes of small domestic ruminants. This work allowed to describe the first scheme for the transport of anthelmintics in nematode egg implying Pgp and to show the role of membrane environment in their activity. The anthelmintics could penetrate into eggs either by passive diffusion or by direct capture by Pgp (influx). The presence of anthelmintics would activate Pgp by changing their conformation. Once activated, Pgp eliminate the anthelmintics (efflux) and protect eggs from their toxic effects. The transport of anthelmintics is altered by changes in cholesterol content of eggs. Cholesterol could act either indirectly on the solubilisation of anthelmintics in membranes or directly on Pgp activity
Bonneaud, Camille. "Stratégies génétique, physiologique et comportementale de résistance aux parasites au sein de populations naturelles de moineaux domestiques (Passer domesticus)." Paris 6, 2004. http://www.theses.fr/2004PA066010.
Full textBoivin, Thomas. "Pléiotropie de la résistance aux insecticides : estimation, manifestations écologiques et modélisation chez le carpocapse des pommes Cydia pomonella (L.)." Avignon, 2003. http://www.theses.fr/2003AVIG0311.
Full textAdaptation of populations to a new environment through the involvement of mutations with large phenotypic effects may be strongly constrained by deleterious pleiotropic effects of the newly selected characters that may affect life-history traits. Insecticide resistance is a convenient model for studying the pleiotropic trade-offs associated with adaptation because both the nature of the environmental changes and the adaptive responses of populations can be clearly identified. This study was undertaken to characterize the pleiotropic effects of insecticide resistance in the codling moth Cydia pomonella. Here we suggest that (i) insecticide resistant alleles are associated with life-history trade-offs that result in selection against insecticide resistant phenotypes in the absence of insecticide, and (ii) these life-history trade-offs result in significant alterations of both phenology and voltinism, which may however contribute to the selection process of insecticide resistant alleles independently from chemical treatments. A modelling approach of the interactions between both insecticide resistance and phenology allows the assessment of the seasonal evolution of insecticide resistant alleles, and may shed a light on new resistance management tactics of this major pest species
Gaba, Sabrina. "Processus impliqués dans la résistance aux benzimidazoles chez les nematodes d'ovins : des données biologiques à la modelisation." Tours, 2005. http://www.theses.fr/2005TOUR4017.
Full textMutation of a trait and selection of the new mutant form is the key step of adaptation to environmental selective pressure. The resistance to benzimidazoles (anthelmintic treatments) of the nematodes Teladorsagia circumcincta, parasites of small ruminants (sheep) in a suitable model to study this process. The genetics of the resistance is well documented (one gene with two alleles) but the mechanisms governing selection still need to be disentangled. The early stage of selection of resistant strains cannot be studied experimentally and modelling is the only available approach. To characterize the processes involved in the selection of the resistance to benzimidazoles in T. Circumcicta, (i) we used a meta-analysis to identify the main factors governing the establishment of nematodes in sheep populations, (ii) we promoted the Weibull distribution rather than the Negative Binomial to describe the large numbers of nematodes observed in the most infected hosts and (iii) we investigated the effect of hypobiosis (arrested development) on the host-parasite dynamics. A simulation study, aiming to aggregate the knowledge on the T. Cicumcincta-sheep system, proved that the selection of the resistance to benzimidazoles was mainly affected by (i) the ingestion of clumps of infective larvae in the early stage of resistance selection and (ii) the refuge constituted by susceptible infective larvae remaining on pasture and by susceptible nematodes not exposed to treatments in sheep. We propose management rules in order to maintain selection for resistance as low as possible. It remains to extend this study to other nematodes species by adapting the parameters involved in the models. A further investigation of other potential refuges is also needed, of which refuge-effect of hypobiosis is of particular interest
Hita, Meseguer Maria Teresa. "Caracterización genética y molecular de un gen de resistencia específica de Drosophila melanogaster al himenóptero parásito Leptopilina boulardi." Tours, 2001. http://www.theses.fr/2001TOUR4014.
Full textBrahmi, Inès. "Obtention et Caractérisation de nouveaux génotypes de pois chiche, par radio-mutagenèse, résistants à Orobanche foetida." Nantes, 2015. https://archive.bu.univ-nantes.fr/pollux/show/show?id=45659d0d-6b67-49d1-b028-2d8c9262ca9c.
Full textBroomrapes are parasitic weeds widespread in agricultural systems of the Mediterranean basin. In Tunisia, Orobanche foetida attacks on cultivated legumes cause significant losses. Currently proposed control methods are insufficient. The selection of resistant varieties is the most economic method of control. In this context, the induction of genetic mutations is used to increase the genetic variability in the medium term for propose new resistant lines. In our study, the effectiveness of radio mutagenesis was evaluated in chickpea. The effect of irradiation on the germination and growth of chickpea plants (cv. Amdoun) was studied. The 150 Gy dose was defined as the mutagen dose capable of causing genetic mutations in chickpea A first phenotypic selection in a naturally O. Foetida infested plot was used to select 30 genotypes (M2 progeny), because of their low sensitivity which resulted in a reduced number of emerged orobanche. These genotypes were then studied in the laboratory to appreciate first their ability to induce seed germination broomrape and also their degree of resistance under artificial infestation. None of the mutants has completely lost the ability to induce germination of Orobanche seeds but five of them displayed a significantly reduced capacity compared to Amdoun control. Additional resistance components were observed, such as early necrosis of the parasite which prevents haustorium formation, and late disturbance in the subterranean development of the floral shoot which reduced parasite emergence. All the radiomutagenesis induced characters were stable as kept in the following M3 generation. This study shows that the effectivness of radiomutagenenis for producing strong resistance is related to modulations of accumulation of phenolic compounds and expression patterns of peroxidases and polyphenoloxidase in chickpea roots under infestation
Garamszegi, László Zsolt. "Parasitism and the evolution of bird song." Paris 6, 2002. http://www.theses.fr/2002PA066149.
Full textIhabi, Mounia. "Les parasites de conservation des pommes, du verger au fruitier : étude épidémiologique, étude comparative des cuticules de variétés très sensibles et de variétés résistantes." Littoral, 1997. http://www.theses.fr/1997DUNK0006.
Full textBarjau, Michelle. "Isolement, purification, et essai de détermination de la structure de la toxine issue d'un champignon : Colletotrichum gloeosporidoides." Aix-Marseille 3, 1995. http://www.theses.fr/1995AIX30040.
Full textKanika-Kiamfu, Justin. "Etude expérimentale des potentialités bioéthologiques d'Exochomus flaviventris Mader (Coléoptère - Coccinellidae) prédateur de la cochenille du manioc, Phenacoccus manihoti Mat. -Ferrero (Homoptère - Pseudococcidae)." Toulouse 3, 1991. http://www.theses.fr/1991TOU30230.
Full textVittu, Anaïs. "Outils bioinformatiques pour l'analyse génétique de la résistance du moustique Anopheles gambiae vis-à-vis des parasites du paludisme." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAJ096/document.
Full textDuring my PhD, I developed and implemented new methods and tools using the latest technologies of the Next Generation Sequencing, bioinformatics tools and the « reciprocal allele-specific RNA interference » (rasRNAi) method with the aim of identifying genetic and non-genetic factors responsible for the resistance of the mosquito Anopheles gambiae to the mouse malaria parasites Plasmodium berghei. I have implemented a strategy for identifying polymorphisms in the resistant and susceptible lines to (1) select genetic markers for future genetic analysis and (2) list the polymorphicgenes. I contributed to the development of a new allele-specific dsRNA probe for the rasRNAi method by identifying how mosquitoes process the injected dsRNA by the analysis of sequenced small RNAs from the injected dsRNA. I developed a pipeline to identify the microbiota composition in susceptible and resistant lines in order to compare them
Fouchet, David. "Rôle des anticorps maternels dans le changement d' impact d'une maladie infectieuse : impact du choix du modèle sur la compréhension des relations hôte parasites." Lyon 1, 2006. http://www.theses.fr/2006LYO10151.
Full textLespinasse, Denis. "Cartographie génétique de l'"Hevea (Hevea spp)" et déterminisme de la résistance au champignon pathogène "Microcyclus ulei"." Montpellier 2, 1999. http://www.theses.fr/1999MON20053.
Full textVillain, Luc. "Caractérisation et bioécologie du complexe parasitaire du genre pratylenchus (nemata : pratylenchidae) présent sur caféiers (coffea spp. ) au Guatemala." Rennes, Agrocampus Ouest, 2000. http://www.theses.fr/2000NSARA033.
Full textBonato, Olivier. "Dynamique des populations de l'acarien vert du manioc "Mononychellus progresivus" et de l'acarien rouge "Oligonychus gossypii" au Congo. Modélisation du sous-système acariens phytophages-manioc." Montpellier 2, 1993. http://www.theses.fr/1993MON20049.
Full textChylinski, Caroline. "Qu'est ce qui fait le succès des nématodes gastro-intestinaux chez leur hôte ? : Etude du rôle des nématodes, des moutons et des éleveurs." Thesis, Tours, 2014. http://www.theses.fr/2014TOUR4028/document.
Full textThe success of gastrointestinal nematodes in their sheep hosts is so extensive that they present one of the leading threats to ruminant health and production throughout the globe. This thesis research identified three key factors which influence their success including the gastrointestinal nematode biology, the sheep host protective response and the farmers control decisions. Using Haemonchus contortus as a model species, we demonstrated that the success of GIN biology is aided by their capacity to overcome numerous selective pressures that target both parasitic and free-living stages in their life cycle. This was achieved by amplifying life-history traits following challenge to recoup any costs in survival and reproduction. In turn, high levels of fitness were maintained and they remained stable in the face of numerous selective pressures. Sheep have the capacity to exert almost perfect control over GIN success by blocking their life cycle through via protective responses
Ali-Haimoud, Djamel-Eddine. "Contribution à l'étude de la lutte biologique contre Drechslera teres (Sacc. ) Shoem. , parasite de l'orge." Toulouse, INPT, 1994. http://www.theses.fr/1994INPT007A.
Full textGenois, Marie-Michelle. "Rôles de la recombinaison homologue dans la résistance aux drogues chez le parasite "Leishmania"." Doctoral thesis, Université Laval, 2015. http://hdl.handle.net/20.500.11794/26177.
Full textBien que l’on attribue généralement un effet néfaste à l’instabilité génomique, pour le parasite Leishmania, elle s’avère pourtant bénéfique. De façon étonnante, ce protozoaire possède la capacité de remanier le nombre de copies de ses gènes pour s’adapter à son environnement et résister aux drogues utilisées contre lui. La présence de séquences répétées identiques près des gènes essentiels à sa survie permet une recombinaison homologue (RH) efficace et entraîne subséquemment la formation d’une copie extrachromosomique supplémentaire du gène ciblé. Ce phénomène de réarrangement génique induit la formation d’amplicons circulaires ou linéaires et est, entre autres, responsable de la résistance aux agents thérapeutiques. À l’heure actuelle, les enzymes impliquées dans ce processus sont peu connues et l’émergence d’un nombre croissant de cas d’infections réfractaires aux traitements favorise l’étude des protéines médiant la RH dans des conditions de résistance. Il a été récemment montré que la formation d’amplicons circulaires est compromise en l’absence du gène LiRad51, mais n’est toutefois pas abolie. Cette observation suggère l’implication d’autres acteurs dans ce processus, alors que le mécanisme par lequel les amplicons linéaires sont formés demeure inconnu. Cette thèse présente la caractérisation biochimique et cellulaire des protéines clés de la RH impliquées dans l’amplification génique chez le parasite Leishmania infantum. Plus précisément, le rôle de LiBrca2, en tant que médiateur de LiRad51, est tout d'abord démontré en raison de son implication essentielle dans la localisation nucléaire de LiRad51 et dans la stimulation d’invasion de brins effectuée par la recombinase. De façon similaire, les paralogues de LiRad51 peuvent, possiblement grâce à leur capacité de lier et d’apparier de l’ADN, eux aussi, stimuler LiRad51 pour l’invasion d’un ADN simple-brin dans un duplex homologue. L’inactivation génique pour l’un d’entre eux (LiRad51-4) a montré un rôle considérable sur l'amplification circulaire, malgré le fait qu’aucune activité d’invasion n’a pu être observée en l’absence de LiRad51. Enfin, en accord avec son rôle bien établi chez l’humain, cette étude confirme que la protéine LiMre11 possède une activité exonucléase et qu’elle serait impliquée dans la production d’amplicons linéaires. Ces résultats mettent en évidence le potentiel thérapeutique des protéines de la réparation de l’ADN, domaine de recherche prometteur pour mieux lutter contre la leishmaniose.
Genomic instability is usually known as a harmful hallmark, although in the parasite Leishmania this represents a beneficial feature. Surprisingly, this protozoan takes advantage of its ability to reorganize its genome for adapting itself to different environments as well as for drug resistance. In fact, the presence of identical repeats near essential genes allows homologous recombination (HR) between them, and subsequently causes the formation of an additional extrachromosomally copy of the targeted gene. This phenomenon of gene rearrangement induces circular or linear amplicons which leads to drug resistance. However, little is known about the enzymes involved in this process. In addition, the increasing number of infection cases refractory to treatment promotes the study of proteins mediating HR in these circumstances. It has been shown recently by gene inactivation that LiRad51 recombinase plays an important role in circular amplicon formation but was not essential. This observation suggested the presence of other players involved in this process while the mechanism by which linear amplicons are formed is still unknown. This thesis presents biochemical and cellular characterization of key HR proteins involved in extrachromosomal DNA amplification. We first determine the role of LiBrca2 as a mediator of LiRad51. In particular, LiBrca2 is involved in LiRad51 nuclear localisation and stimulates the homology search performed by the recombinase. Secondly, we show evidence that the LiRad51 paralogs help LiRad51 to promote HR through their capacity to bind and anneal DNA. Similary to LiBrca2, they can stimulate LiRad51 to invade a resected DNA double-strand break in an undamaged template to form a D-loop structure. However, they cannot perform this key step on their own. We succeed to inactivate one paralog (LiRad51-4) and provide insights on circular gene amplification. Finally, we show that LiMre11 harbors both DNA binding and exonuclease activities while inactivation of this gene led to a reduction of linear amplicon formation after drug selection. These results highlight a novel LiMre11-dependent pathway used by Leishmania to amplify stochastically portions of its genome. The relevance of DNA repair for drug resistance and its potential as a drug target represent a promising area of research for future treatments of leishmaniasis.
Buxton, Samuel. "Parasitic nematode ion channels : improving understanding of pharmacology and genetic composition." Thesis, Tours, 2012. http://www.theses.fr/2012TOUR4047/document.
Full textParasitic nematode infections of humans, plants and animals are of major economic impact. Anthelmintics are the main chemotherapeutic agents used for treatment and prophylaxis of nematode infections because there is presently no effective vaccine on the market. However, resistance has been reported to the mainstay anthelmintics. There is therefore the urgent need to understand the genetics of the receptors targeted by these anthelmintics and to find alternative targets for developing new anthelmintics. We have demonstrated the effects of the new novelacting cyclooctadepsipeptide anthelmintic, emodepside, on the membrane potential and voltageactivated currents in the pig parasite Ascaris suum. Finally, we show the cloning of four acetylcholine receptor subunit genes from another pig parasite, Oesophagostomum dentatum and the expression and characterization of four levamisole receptor subtypes in Xenopus laevis oocytes
Courtot, Élise. "Etude de la diversité des récepteurs à l'acétylcholine chez les nématodes : de l'identification à la caractérisation fonctionnelle." Thesis, Tours, 2015. http://www.theses.fr/2015TOUR4039.
Full textAcetylcholine receptors (AChRs) of parasitic nematodes are the major pharmacological targets for anthelmintics used in veterinary medicine. However, with the emergence of resistant isolates, the optimization of control strategies requires a better knowledge of the mode of action of anthelmintics and of the AChR repertoire for the identification of new therapeutic targets. Indeed, parasitic nematodes possess a large diversity of AChR subunits. In this context, we identified two AChR subunits: ACR-26 and ACR-27, specifically found in parasitic nematodes. By expressing these subunits in Xenopus oocytes and in the model nematode Caenorhabditis elegans, we identified a novel muscular AChR subtype sensitive to morantel: the M-AChR. Moreover, we performed a molecular and functional comparative study of the AChR subunits from ACR-16 group in different nematode species. The identification of these new receptors paves the way for the development of new anthelmintic drugs
Laffitte, Marie-Claude. "Caractérisation des mécanismes de réarrangements géniques chez le parasite Leishmania résistant aux drogues." Doctoral thesis, Université Laval, 2016. http://hdl.handle.net/20.500.11794/26690.
Full textNous avons pu établir un lien entre MRE11 et RAD50, deux protéines agissant au sein d’un même complexe MRN (MRE11-RAD50-NBS1), et l’instabilité génomique. En effet, l’inactivation de MRE11 et RAD50 a conduit à des réarrangements chromosomiques qui semblent être survenus par micro-homologie. Ces travaux ont donc permis de mettre en lumière qu’en l’absence des protéines majeures de la recombinaison homologue, un mécanisme de réparation par micro-homologie indépendant de MRE11 se met en place dans la cellule. De plus, l’inactivation du gène RAD50 dans une souche sauvage s’est révélée impossible alors qu’elle l’était dans une souche préalablement inactivée pour MRE11, suggérant une certaine hiérarchie dans le complexe MRN. Cette thèse présente également l’étude de l’acquisition de mutations ponctuelles dans le gène du transporteur de miltéfosine qui conduit à la résistance des parasites à cette drogue. La technologie de séquençage à profondeur élevée (« deep-sequencing ») nous a permis de séquencer ce gène à différents stades intermédiaires de la résistance, afin de déterminer la fréquence d’acquisition et la stabilité de ces mutations. Nous avons pu observer que les mutations ponctuelles dans le gène du transporteur de miltéfosine ne sont pas présentes dans les premiers stades de la résistance mais acquises à des concentrations plus élevées. L’analyse du gène a également démontré un plus grand nombre de mutations au fur et à mesure que la pression de sélection s’intensifie ainsi qu’une certaine stabilité des mutations après retrait de la pression de drogue, laissant entrevoir un maintien de la résistance. Ces résultats mettent en évidence l’implication des protéines de réparation de l’ADN dans la stabilité génomique chez Leishmania, mais surtout un rôle dans l’amplification extra-chromosomique liée à la résistance. L’utilisation des nouvelles technologies de séquençage nous a également permis d’étudier la dynamique d’acquisition de mutations ponctuelles impliquées dans la résistance.
Coqueret, Victoire. "How do plants defend themselves? : Study of the Tomato - Tuta absoluta pathosystem in interaction with nitrogen fertilization." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0234.
Full textThe identification of ecophysiological responses of plants is a prerequisite for improving the natural defences of plants and reducing the use of chemical inputs in crops. Plant responses to herbivorous attack involve defence and tolerance mechanisms. Plant responses to a leafminer larva are pourly documented, in contrast to chewing and piercing insects. The objective of my Ph.D. was to characterize the tomato trait responses to Tuta absoluta herbivory in order to determine the local and systemic responses in terms of soluble and volatile compounds. We looked at the responses of tomatoes subjected to two contrasting levels of nitrogen availability, knowing that nitrogen is a lever to promote the basal plant defence level. We worked on tomato, a Solanaceae, grown in hydroponics and subjected to Tuta absoluta. Our research strategy has focused on identifying and quantifying soluble and volatile defence compounds and determining the nutritional value of foliar tissues. We have shown that tomatoes establish an induced- resistance against the herbivore, which results in a concentration increase of chlorogenic acid, caffeoyl putrescine and tomatine locally at the level of the parasite zone and / or systemically in the others non-infested foliar compartments. The defence role of these molecules on Tuta absoluta has yet to be confirmed. We have also shown that tomatoes set up an indirect defence against Tuta absoluta, based on the emission of volatile compounds in the vicinity of plants. We have identified several new herbivore-induced VOCs (m-cymene, menthatriene, ß-cis-ocimene, ß-phellandrene, terpinolene, ß−caryophyllene, humulene). Some of the identified VOCs are known to be emitted in greater quantities during a herbivorous attack and to play a role in attracting predatory insects or repelling egg-laying females. Thus, their elicitation seems generic to herbivory and not specific to Tuta absoluta. The specificity of tomato - Tuta absoluta interactions could be enhanced by further analysis in metabolomics, transcriptomics (expression of RNAseq genes) and by investigating the induced signaling pathways. Contrary to what was expected, our results show little effect of the nitrogen limitation on the observed responses. Nevertheless, as demonstrated previously, nitrogen restriction affects larval development. My work has reinforced the “trophic“ hypothesis of slowing larval development by a limited nitrogen availability. Thus, the stoichiometry of the food bowl is highly modified and the larvae have to consume more material to acquire the nitrogen necessary for their development. Nevertheless, we can not exclude the hypothesis “compounds of defence“. Indeed, we have shown that the concentrations of phenolic compounds and tomatine and of the VOC emission supposed to be involved in the constitutive defence are increased in the case of nitrogen limitation. The diversity and complementarity of the experiments will allow the acquired data to feed a functional model of the attacked plant. This model might include plant nitrogen regimes as a reactive plant defence factor
Brotherton, Marie-Christine. "Études protéomiques chez le parasite protozoaire Leishmania." Thesis, Université Laval, 2013. http://www.theses.ulaval.ca/2013/29748/29748.pdf.
Full textPetitprez, Michel. "Pouvoir pathogène et épidemiologie de Exserohilum turcicum, parasite du mai͏̈s." Toulouse, INPT, 1989. http://www.theses.fr/1989INPT027A.
Full textJulien, de Zélicourt Axel de. "Les défensines de tournesol : implication dans la résistance à la plante parasite Orobanche cumana et mode d'action." Nantes, 2008. http://www.theses.fr/2008NANT2120.
Full textThe resistance of the LR1 sunflower to the parasitic plant Orobanche cumana is chracaterized by an overexpression of the defensin gene HaDef1. Defensins are small basic antifungal peptides of around 50 amino acids. To date, three genes had been identified in the sunflower. In order to better understand the defensin role in sunflower resistance to O. Cumana, a molecular study was conducted on this small multigenic family. Thus, two new genes were identified and among the five identified, three of them including HaDef1 are expressed in roots but response differently to defence activating molecules like SA or JA. On the other hand, only HaDef1 is highly overexpressed after O. Cumana infestation. A peptide production in an heterologous bacterial system was conducted to study the Ha-DEF1 activity. At micromolar concentrations, Ha-DEF1 induces cell death at the radicle apex of germinated seeds of O. Cumana or O. Ramosa, but has no effect on A. Thaliana or the parasitic plant Striga hermonthica. Ha-DEF1 is strongly inhibited by calcium addition and AAL toxin, a sphingolipid metabolism disruptant, provokes the same symptoms as this defensin. Ha-DEF1 triggers also an intracellular calcium increase by activating the IP3 pathway in orobanche cells which could explain cell death. Theses results highlight for the first time a toxic activity of plant defensins on plant cells and open up new perspectives in the comprehension. Of its mode of action
Moreira, Wilfried. "Stress oxydatif, différentiation et mort cellulaire chez le parasite Leishmania." Thesis, Université Laval, 2011. http://www.theses.ulaval.ca/2011/28186/28186.pdf.
Full textLeprohon, Philippe. "Caractérisation de la famille des protéines ABC et étude transcriptomique de la résistance à l'antimoine chez le parasite protozoaire Leishmania." Thesis, Université Laval, 2008. http://www.theses.ulaval.ca/2008/25561/25561.pdf.
Full textThe parasite Leishmania is responsible for considerable morbidity and mortality around the world. No effective vaccine is yet available against this parasite and treatment thus relies on chemotherapy. Few drugs are available and most of them are associated with limitations such as toxicity and high cost. Pentavalent antimonials have been used for decades in the treatment of leishmaniasis and remain the mainstay against all forms of Leishmania infections in most endemic regions. However, the efficacy of these compounds is compromised by the selection of resistant parasites that are now described on a frequent basis in several endemic regions. The mechanisms involved in antimony resistance are partly understood and have pinpointed the role of ATP-binding cassette (ABC) proteins. Moreover, drug resistance studies with different in vitro-selected mutants have suggested the presence of unidentified mechanisms involved in antimony resistance. The objectives of this thesis were i) to define the complete ABC protein family in Leishmania and to analaze their evolution by phylogenetic analyses, ii) to assess the role of the entire ABCC subfamily in antimony resistance, and iii) to take advantage of the availability of the Leishmania genome sequence to study the gene expression profile associated with an antimony resistance phenotype at the genomic level. Phylogenetic analyses revealed the magnitude of the ABC gene family in Leishmania, which seemed to have undergone gene duplication events following the divergence of the Leishmania lineage. Moreover, subcellular localization experiments indicated that the entire ABCC protein subfamily is located to intracellular compartments in Leishmania, and gene overexpression experiments revealed the involvement of two of these proteins in antimony resistance. Finally, a whole-genome transcriptomic study confirmed the involvement of MRPA in antimony resistance and revealed the recombination events associated with its amplification in the highly resistant L. infantum Sb2000.1 mutant. More importantly, the transcriptomic study revealed the presence of aneuploid chromosomes in at least two different antimony-resistant mutants and selection of a partial revertant strain allowed the observation of a good correlation between the antimony resistance levels and the copy number of the aneuploid chromosomes.
Chapuis, Laurence. "L'eutypiose de la vigne : contribution à l'étude des relations hôte-parasite." Bordeaux 2, 1995. http://www.theses.fr/1995BOR22002.
Full textAguerre, Sophie. "Résistance génétique aux nématodes gastro-intestinaux chez les ovins : évaluation des stratégies de sélection et de leur impact à l'échelle de l'élevage." Thesis, Toulouse, INPT, 2019. http://www.theses.fr/2019INPT0111.
Full textGastrointestinal nematodes are a major constraint on the health of grazing ruminants and cause significant production losses. The systematic use of anthelmintics has been questioned for several years due to the development of parasite resistance to these molecules, their impact on the environment and consumer concerns about livestock industry. A major research effort is being made to find strategies that, combined with a rational use of anthelmintics, would allow sustainable control of gastrointestinal nematodes. The genetic selection of more resistant animals is one of the most promising. This thesis aims to study the implementation of this selection and to evaluate the impacts it could have on the other traits under selection and on the different biological functions of the animal (growth, production, reproduction). An experimental infestation protocol has been developed to evaluate the resistance capacities of animals to the hematophagus nematode Haemonchus contortus by measuring the number of parasite eggs excreted in the faeces and the hematocrit. The genetic parameters of these parasite resistance traits show that resistance is heritable and that a very good correlation exists between experimentally infested rams and ewes infested on pasture in the Blond-faced Manech dairy breed. These results validated the effectiveness of the use of experimental infestation protocols in selection schemes to predict parasite resistance in natural conditions of infestation. The search for genome regions involved in resistance to gastrointestinal nematodes has revealed a polygenic determinism of this trait. Concomitant selection for milk production traits and low fecal egg counts is recommended in the future. It is feasible since low, although unfavourable, genetic correlations have been estimated between the number of eggs excreted in faeces and milk production traits. Finally, the long-term effects of the selection were evaluated in a study involving divergent lines selected in Romane breed for increased resistance or sensitivity to H. contortus. The effectiveness of the selection has been demonstrated in young growing females. The results showed that this selection could be associated with a higher energy cost of the immune response in resistant animals during the first weeks after infestation. But we have to evaluate this energy cost at a later time post infestation and for different physiological status of the animal. In conclusion, a selection for effective parasite resistance can be put in place but additional studies must be carried out in order to estimate its long-term impacts
Tey-Rulh, Patricia. "Métabolites toxiques secrètes in vitro par Eutypa lata (Pers. : Fr. ) tul. : parasite de la vigne : isolement et activité biologique." Toulouse, INPT, 1988. http://www.theses.fr/1988INPT019A.
Full textGauthier, Mathieu. "Etude et caractérisation des mécanismes de résistance de Brassica napus (colza, Brassicaceae) vis-à-vis de la plante parasite Phelipanche ramosa (L. ) Pomel (Orobanchaceae)." Nantes, 2012. http://archive.bu.univ-nantes.fr/pollux/show.action?id=eccc5cb9-1665-449d-ba79-cd8e9ba06f72.
Full textOver the past decade, Phelipanche ramosa, a weedy parasitic plant (broomrape), has been increasingly infesting winter oilseed rape fields in France. Elite lines have shown different responses in P. Ramosa infested fields, suggesting that genetic variability might be available for breeding programmes. Ten WOSR genotypes selected for their contrasting response in field experiments were analysed using hydroponic and greenhouse co-culture experiments to determine the components of resistance. While no total resistance was identified, some partial resistance mechanisms were observed : a low induction of P. Ramosa seed germination by host roots, a limitation of parasite attachments on root systems, and the induction of a delayed or even disturbed growth of tubercles, minimising and delaying parasite emergence from the soil. The possible induction of resistance mechanisms in oilseed rape by BTH, an elicitor of natural plant defences, was also studied in order to identify defence pathways induced in roots upon leaf treatment. The cDNA-AFLP expriment revealed that BTH signal applied on leaves did not induce a transcriptomic response in oilseed rape roots. However, BTH, directly applied on roots, induced the expression of PR1, a gene marker of the SA signalling pathway, and prevented P. Ramosa attachments. Similarly, another elicitor compound, the laminarin extracted from the algae Laminaria digitata, induced a reduction of broomrape attachments when applied by soil drench but not by leaf spray
Dwivedi, Ankit. "Functional analysis of genomic variations associated with emerging artemisinin resistant P. falciparum parasite populations and human infecting piroplasmida B. microti." Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT073/document.
Full textThe undergoing WHO Malaria elimination program is threatened by the emergenceand potential spread of the Plasmodium falciparum artemisinin resistant parasite.Recent reports have shown (a) SNPs in region of chromosome 13 to be understrong recent positive selection in Cambodia, (b) presence of P. falciparum parasiteresistant and sensitive subpopulations in Cambodia, (c) the evidence that mutationsin the Kelch propeller domain of the k13 gene are major determinants ofartemisinin resistance in Cambodian parasite population and (d) parasite subpopulations in Northern Cambodia near Thailand and Laos with mefloquine drugresistance and carrying R539T allele of the k13 gene.Identifying the genetic basis of resistance is important to monitor and control thetransmission of resistant parasites and to understand parasite metabolism for the development of new drugs. This thesis focuses on analysis of P. falciparum population structure in Cambodia and description of metabolic properties of these subpopulations and gene flow among them. This could help in identifying the genetic evidence associated to transmission and acquisition of artemisinin resistance over the country.First, a barcode approach was used to identify parasite subpopulations using smallnumber of loci. A mid-throughput PCR-LDR-FMA approach based on LUMINEXtechnology was used to screen for SNPs in 537 blood samples (2010 - 2011) from 16health centres in Cambodia. Based on successful typing of 282 samples, subpopulations were characterized along the borders of the country. Gene flow was described based on the gradient of alleles at the 11 loci in the barcode. The barcode successfully identifies recently emerging parasite subpopulations associated to artemisinin and mefloquine resistance.In the second approach, the parasite population structure was defined based on167 parasite NGS genomes (2008 - 2011) originating from four locations in Cambodia,recovered from the ENA database. Based on calling of 21257 SNPs, eight parasite subpopulations were described. Presence of admixture parasite subpopulation couldbe supporting artemisinin resistance transmission. Functional analysis based on significant genes validated similar background for resistant isolates and revealed PI3K pathway in resistant populations supporting acquisition of resistance by assisting the parasite in ring stage form.Our findings question the origin and the persistence of the P. falciparum subpopulations in Cambodia, provide evidence of gene flow among subpopulations anddescribe a model of artemisinin resistance acquisition.The variant calling approach was also implemented on the Babesia microti genome.This is a malaria like syndrome, and is endemic in the North-Eastern USA. Theobjective was to validate the taxonomic position of B. microti as out-group amongpiroplasmida and improve the functional genome annotation based on genetic variation, gene expression and protein antigenicity. We identified new proteins involved in parasite host interactions
Delamasure, Servane. "Activation et signalisation de la réponse immunitaire innée chez la drosophile : Rôle des recepteurs Toll." Université Louis Pasteur (Strasbourg) (1971-2008), 2003. https://publication-theses.unistra.fr/public/theses_doctorat/2003/DELAMASURE_Servane_2003.pdf.
Full textCeriac, Steve. "Impacts des interactions entre le statut nutritionnel et parasitisme gastro-intestinal sur les réponses animales chez les petits ruminants." Thesis, Antilles, 2018. http://www.theses.fr/2018ANTI0284/document.
Full textGastrointestinal nematode (GIN) infections are a major cause of morbidity and mortality in small ruminants at pasture and therefore lead to production losses. Due to the emergence of anthelmintic resistance and consumer concerns about chemical residues in animal products, alternative control strategies are needed. The objective is no longer the total eradication of the parasite population, but rather a better control of these populations to achieve a favorable balance between the host and the parasites to improve animal production. A promising strategy for NGI control is to improve the host response through the nutritional status of the animals. Although goats are more susceptible than sheep to NGI infestations, most research programs to characterize host-NGI interactions are conducted in sheep. In contrast with the idea that the results obtained in sheep will be applicable to goats because of their proximity, many studies highlight significant differences between these models. The objective of this research project was to study the impact of nutritional status in terms of protein and energy quantity and protein quality provided by the diet on the responses (production vs response against parasitism) of Creole goats experimentally infested by Haemonchus contortus. We have shown that nutritional status reduces the severity and duration of regenerative anemia and H. contortus-induced thrombocytopenia in Creole goats. The protein-enriched diet was associated with resilience to infection rather than resistance
Renault, Patricia. "Méthodes de réduction de réseaux RC appliquées aux outils de vérification de circuits submicroniques." Paris 6, 2003. http://www.theses.fr/2003PA066579.
Full textLi, Hua. "Etude de la relation entre le mildiou de la vigne (Plasmopara viticola (B. Et C) Berl. Et de Toni) et l'espèce Vitis vinifera L. : variabilité de l'agent pathogène et de la sensibilité de l'hôte." Bordeaux 2, 1985. http://www.theses.fr/1985BOR20007.
Full textManga, Bella. "Etude de la diversité de "Colletotrichum kahawae" responsable de l'anthracnose des baies et caractérisation de la résistance du caféier Arabica à cet agent pathogène." Montpellier 2, 1999. http://www.theses.fr/1999MON20088.
Full textMac-Daniel, Laura. "Etude immunobiologique de la phase cutanéo-ganglionnaire du paludisme murin." Paris 7, 2013. http://www.theses.fr/2013PA077290.
Full textMalaria is one of the most deadly infectious diseases in the world, being responsible for nearly 700,000 deaths per year. The infection by Plasmodium, the causal agent of the disease, begins with the pre-erythrocytic (PE) phase, during which the sporozoite deposited in the skin by the mosquito reaches the liver via the bloodstream where it differentiates into the form that will infect red blood cells and cause the symptoms of the disease. The PE stages of Plasmodium represent a privileged target for anti-malaria vaccination. Indeed, the live attenuated vaccines against these stages have demonstrated their superiority in terms of efficiency of protection in both rodents and humans. The recent description of a new cutaneous-lymph node step has completely changed our vision of the PE phase, in particular in the context of immunisation in the skin. Most studies have concentrated on the characterisation of the effectors implicated in establishing a protective immune response after intravenous immunisation, whereas there is much less information concerning the fate of the parasite after intradermal immunisation, especially the interactions with the innate immune system. Furthermore, the capacity of the parasite to initiate intracellular development in the skin and gain the draining lymph node by its motility poses the question of the importance of the different antigenic forms of the parasite in the initiation of a protective response in the draining lymph nodes. My thesis consisted in dissecting the early steps that lead to a protective immune response via intradermal immunisation with irradiated sporozoites. At the tissue level, the irradiated parasite targets the same tissues as the non-irradiated sporozoites but their development is arrested in the skin and in the liver. At the cellular level, the inoculation of a high number of sporozoites in the skin gives rise to an important inflammatory response in the skin and draining lymph nodes, characterised by the recruitment of polynuclear neutrophils and inflammatory monocytes. This inflammation is correlated with a local elimination of the parasites and is associated with a Thl polarisation of the immune response in the draining lymph node. In both tissues, the parasite interacts preferentially with recruited polymorphonuclear neutrophils and the resident myeloid cells. In vitro, we have confirmed that the parasite can actively invade phagocytic cells and have shown for the first time that it can remain in the skin within myeloid cells. We next evaluated the importance of the antigens of these skin parasites in the initiation of a protective immune response. In this context, we established an efficient protocol for intradermal immunisation and its evaluation using bioluminescence imaging. We have shown that the antigens derived from the motile sporozoites that gain access to the draining lymph node play a predominant role in the initiation of this response compared to the cutaneous antigenic reservoir
Maillot, Gaétan. "Étude d’effecteurs de l’oomycète pathogène Phytophthora capsici exprimés au cours de l’interaction avec le piment et la tomate." Thesis, Avignon, 2018. http://www.theses.fr/2018AVIG0350.
Full textPlants have developed complex defense mechanisms against pathogens, providing partial to total resistance. Nonetheless, some pathogens effector genes disrupt these mechanisms and help breaking down plant host defenses. Effectors are diverse proteins, with diverse range of evolution constraints. Pathogenomic approaches, such as transcriptomic studies and high-throughput screens of plant resistance factors by effectors, provide information on the effectors molecular functions and their role during the interaction in planta. Quantitative resistances are supposed to be more durable, even though some of them have been overcome by pathogens. This PhD is focused on effectors of Phytophthora capsici deployed during its interaction with pepper (Capsicum annuum) and tomato (Solanum lycopersicum). In Chapter I, I analysed the impact of the plant host genotype on the molecular mechanisms deployed by P. capsici when interacting with pepper, comparing two pathogen’s aggressiveness level and two plant resistance levels. These comparisons revealed differentials expression of genes associated with transport, metabolism and genes encoding pathogenicity effectors. In Chapter II, the avirulence activity of the differentially expressed cytoplasmic effectors was tested. The screening of pepper accessions with in planta transient expression assays revealed a link between expression differences and the ability of the effector to induce the pepper immune responses. Chapter III is focused on analysing effectors polymorphism within 33 isolates P. capsici isolates collected on different hosts and from different geographic regions, using RNA Seq samples at 24 and 72 hours post infection of a susceptible tomato genotype. Effectors showed high levels of diversity, with no correlation between polymorphism and the host on which they were collected. Some expression changes were observed between isolates collected on different hosts or in different geographic regions. Altogether, these results revealed 53 "core" effectors, bringing new insight into P. capsici and pepper/tomato interaction, and providing tools toward durable resistance breeding
Ponte, Costa Sónia Catarina Da. "Etude de l'interaction des bactéries du genre Photorhabdus avec les cellules du système immunitaire." Montpellier 2, 2008. http://www.theses.fr/2008MON20197.
Full textAs enterobactérias do género Photorhabdus são patogénicas para os insectos e recentemente foram descritas estirpes clínicas da espécies P. Asymbiotica isoladas nos Estados Unidos da América e na Austrália. Consagramo-nos ao estudo de alguns mecanismos de virulência utilizados por Photorhabdus. O genoma P. Luminescens subsp laumondii, estirpe TT01, apresenta um locus que codifica para o sistema de secreção do tipo três e um efector, LopT. Estudamos um novo efector de virulência de P. Luminescens, homólogo de LopT e designado LopT2, mas codificado sobre um vestígio de prófago. Como LopT, LopT2 apresenta uma actividade protease de cisteína, tendo como alvo as proteínas da família das Rho GTPases. LopT2 é produzido in vivo especificamente em órgãos de defesa, sugerindo que este factor de virulência desempenha um papel essencial na inibição das reacções de defesa imunitárias do insecto. Em relação a P. Asymbiotica, o nosso trabalho mostra, pela primeira vez, que se trata de uma bactéria de crescimento intracelular facultativa. As estirpes americanas são fracamente interiorizadas pelos macrófagos THP-1, enquanto que as estirpes australianas penetram facilmente em THP-1 bem como em células não fagocitárias (HeLa). Além disso, apenas as estirpes australianas induzem uma rápida e forte apoptose das células do sistema imunitário de insectos e de mamíferos. Mostramos que a maior virulência das estirpes australianas em relação às células, in vivo, pode estar correlacionada com a maior gravidade dos casos clínicos detectados na Australia, relativamente aos Estados Unidos da América
Missoh, Claudia. "Division of labor in anti-parasite defense strategies in ant colonies." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066450/document.
Full textDivision of labor is a key characteristic of social insects and contributes to their ecological success. Especially in disease defense, the intra-colony partitioning of sanitary work can reduce disease transmission, keep nestmates available for other tasks and reduce costs associated with sanitary task performance (i.e. at the behavioral and physiological level). Factors internal and external to the individual affecting sanitary task allocation are not well known and most studies investigated genetic differences between workers performing behavioral sanitary work. In the first two studies I addressed whether individual experience (through repeated exposure to a sanitary hazard or performance of the task) can generate interindividual differences in the performance of behavioral sanitary tasks. Repeated parasite exposure is a common threat in colonies of social insects, posing selection pressures on colony members to respond with improved disease-defense performance. In the clonal ant Platythyrea punctata, I tested whether experience gained by repeated tending of low-level fungus-exposed (Metarhizium robertsii) larvae alters the performance of sanitary brood care. I found that ants trained both with sham- and fungus-treated larvae groomed the brood longer than naive ants. Increased grooming of fungus-treated larvae resulted in more effective fungal removal, thus making trained ants better caretakers under parasite attack of the colony. Decomposing cadavers pose a sanitary risk to social insect colonies, necessitating cadaver management. In the second study I investigated whether cadaver management (i.e. cadaver grooming and transports) is divided among workers and task allocation affected by recent individual experience or worker size in the polymorphic and polygynous ant Cataglyphis velox. Many individuals performed cadaver management infrequently and few individuals dominated task performance. Our results suggested low division of labor for cadaver grooming and transport and a reduced modulation of these behaviors by recurrent exposure to nestmate cadavers
Boëte, Christophe. "Ecologie évolutive de la réponse de mélanisation chez le moustique Aedes aegypti et utilisation des moustiques génétiquement modifiés pour le contrôle du paludisme." Paris 6, 2003. http://www.theses.fr/2003PA066028.
Full textBaron, Olga. "Functional analysis of lipopolysaccharide binding proteins/Bactericidal permeability increasing proteins in immune responses of the freshwater snail, Biomphalaria glabrata." Thesis, Strasbourg, 2012. http://www.theses.fr/2012STRAJ016.
Full textLBP/BPIs are important immune factors of the mammalian antimicrobial response,poorly characterized in invertebrates. The aim of this work was to elucidate the role of LBP/BPIs in the immune response of the fresh-water snail B. glabrata. Firstly, we showed that one member, BgLBP/BPI1, was highly abundant in the albumen gland and the egg masses. Importantly, in addition to the expected activities of BPIs, such as the induction of bacterial permeability, we discovered a novel biocidal (antioomycete) activity that was unsuspected so far. We demonstrated that BgLBP/BPI1 is a major fitness-related protein, acting on both egg production and offspring protection against oomycete infections. Then, we investigated the sequence diversity and evolution of this LBP/BPI protein family and showed that at least 5 LBP/BPIs were expressed in B. glabrata, belonging to three distinct phylogenetic clades. Expression studies of representatives of the three clades showed that they are expressed in different tissues, differently regulated, and therefore supported the hypothesis of the acquisition of functional specificities by the members of this multigenic family