Organic cation transport in rat choroid plexus cells studied by fluorescence microscopy

Quinacrine uptakeand distribution were studied in a primary culture of rat choroidplexus epithelial cells using conventional and confocal fluorescencemicroscopy and image analysis. Quinacrine rapidly accumulated in cells,with steady-state levels being achieved after 10-20 min. Uptakewas reduced by other organic cations, e.g., tetraethylammonium (TEA),and by KCN. Quinacrine fluorescence was distributed in two cytoplasmiccompartments, one diffuse and the other punctate. TEA effluxexperiments indicated that more than one-half of intracellular organiccation was in a slowly emptying compartment. The protonophore monensinboth emptied that TEA compartment and abolished punctate quinacrinefluorescence, suggesting that a large fraction of total intracellularorganic cation was sequestered in acidic vesicles, e.g., endosomes.Finally, quinacrine-loaded vesicles were seen to move within thecytoplasm and to abruptly release their contents at the blood side ofthe cell; the rate of release was greatly reduced by the microtubule disrupter nocodazole.     

Opuntia micropropagation by axillary proliferation

Cladode explants of Opuntia amyclaea were cultivated in Murashige and Skoog medium with different supplements. Benzyladenine was necessary for shoot development from pre-existing buds. Axillary proliferation was also stimulated in subsequent subcultures in the presence of benzyladenine and when the apical meristem was not present in the explant. The number of shoots and the total dry weight were maximum with 5% of sucrose in the medium. It was found that satisfactory rooting occurred when 5×10^-5 M indole butyric acid was added to the medium. Vascular contact between roots and shoots was clearly shown by histological observations. The micropropagation system developed here allows the production in 100 days of 25 000 rooted plantlets from a single cladode, by the stimulation of axillary proliferation in the absence of apical dominance.