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Etude des relations entre compositions membranaires lipidiques et fonctions cellulaires : Cas des hémocytes de bivalves atteints de neoplasie disséminée

Abstract : The aim of the works presented in this PhD thesis was to evidence structure-functional characteristics of a precise cell type, bivalve hemocytes. Analytical tools such as high performance liquid chromatography (HPLC) and gas chromatography (GC) allowed an in-depth investigation of membrane lipid components. Detailed composition of phospholipid classes and subclasses and their respective specific fatty acid composition were evidenced. Moreover, use of flow cytometry allowed characterizing some hemocyte cell functions and ploidy. Membrane lipid composition of hemocytes was finely characterized in four bivalve species; the Pacific oyster Crassostrea gigas, the Manila clam, Ruditapes philippinarum, the edible cockle Cerastoderma edule and the soft-shell clam Mya arenaria. Among the main lipid particularities, a high content of plasmalogen enriched in non-methylene interrupted (NMI) fatty acids and in 20:1n-11 was evidenced for the first time in hemocytes. These fatty acids present the particularity to be biosynthesized de novo in marine bivalves. Hemocyte membranes were also found to be very rich in ceramide aminoethylphosphonate (CAEP) and in sterols. The second step consisted in the study of the modifications of membrane lipid composition and cell functions potentially induced by disseminated neoplasia, in order to emerge structuro-functional links at the membrane level. For this purpose, circulating cells originating from healthy animals and from animals affected by disseminated neoplasia were compared in cockle from Arcachon Bay and in soft-shell clam from Prince-Edward-Island (Canada). In the case of cockles, a highly lower proportion of plasmalogen-NMI FA molecular species was observed in neoplastic cell membranes. This observation was associated to a lower phagocytic activity and a subcellular origin of reactive oxygen species (ROS) different. In soft-shell clams, a lower proportion of plasmalogen phosphatidylserine-20:1n-11 molecular species was associated to a lower phagocytic activity in circulating cells of animals affected by disseminated neoplasia. Characteristics of disseminated neoplasia affecting cockles from Arcachon Bay appeared very different from the ones observed in soft-shell clam from Prince-Edward-Island, concerning particularly the ploidy of neoplastic cells but also their proliferation and the prevalence of the different development stages of the disease. A different progression of the pathology was suggested. These This could explain the observed differences in membrane lipid structure alterations of neoplastic cells between the two species.
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Fabienne Le Grand. Etude des relations entre compositions membranaires lipidiques et fonctions cellulaires : Cas des hémocytes de bivalves atteints de neoplasie disséminée. Chimie analytique. Université de Bretagne occidentale - Brest, 2010. Français. ⟨tel-00684750⟩

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