Fig. 1. Internalization of EGF-coated microspheres. Shown are stereo-images of GFP fluorescence of E-CHO cells (expressing the EGFR-GFP fusion protein) after 2 minutes (A), 5 minutes (B), 8 minutes (C) and 20 minutes (D) incubation with the microspheres. By 2 minutes most microspheres were completely engulfed by the plasma membrane. At 8 minutes, the distribution of fluorescence around the microspheres appeared less fuzzy. At 20 minutes some microspheres had translocated to the basal side of the cell. The stereo-images were processed in such a way that the cell-coverslip contact is oriented towards the observer. The microspheres themselves were not fluorescent, but could be visualized in the confocal reflection mode. The fluorescence stacks were deconvoluted as described in Materials and Methods.