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Coelomocytes of Nereis diversicolor synthesize and secrete vitellogenin in vitro. Using a monoclonal antibody which specifically recognized vitellogenin, we showed by immunocytochemistry that among the coelomocytes only a subpopulation, called eleocytes, countained vitellogenin. These results assert that eleocytes are the vitellogenin producing cells in nereids.

We attempted to identify the nature and origin of the pigment produced by the marine worm Nereis diversicolor in order to isolate, in inert brown capsules, foreign objects introduced into its body cavity. This brown pigment, characterized by cytochemical techniques, could be a melanin. The activity of the enzyme phenoloxidase responsible for melanin biosynthesis was detected by enzyme cytochemistry techniques in vacuoles and the Golgi apparatus of coelomocytes activated by the presence of foreign bodies. Morphological techniques combined with a monoclonal immunological probe enabled us to establish that the "G2" granulocytes contain both the precursor of the pigment in dense bodies and the capacity for phenoloxidase synthesis when activated to encapsulate foreign bodies. The "G2" granulocyte may therefore be compared to a melanocyte in which melanin is not stored as in mammals, but immediately extruded following synthesis in the form of a thick fluid.

International audience; Incubation of mouse thymocytes with 10 μM monensin for 1 hour induces morphological alterations characterized by the extensive dilatation and vacuolization of the Golgi complex. This effect is used to study the transport and utilization of labelled sugar nucleotides into intracellular vesicles by using thymocytes whose plasma membrane has been permeabilized by ammonium chloride treatment. It is demonstrated that monensin stimulates the incorporation of labelled sialyl, fucosyl, galactosyl, and N-acetylglucosaminyl residues. This enhanced incorporation is not due to a direct effect of monensin on glycosyltransferase activities themselves but is a consequence of a higher entry and accumulation of labelled sugar nucleotides in the dilated vesicles.