Fig. 4. Fluorescence micrograph of atrial endocardial endothelial cells cultured on a glass coverslip (pooled cells from three fish) and incubated with fluorescein-labelled lipopolysaccharide for 1 h at 12°C. All endocardial cells in the monolayer cultures accumulated the probe. Note that fluorescence is confined to discrete vesicles probably representing endocytic vesicles. Scale bar, 10 µm.