Fig. 3.

Time course of HDL internalization. Correlative HDL-Alexa⁵⁶⁸ localization after the indicated time points from 15 to 180 min shows in the fluorescence microscope a time-dependent increase in size and number of intracellular endocytic compartments (a–d). Electron microscopy after DAB-photooxidation reveals that HDL-positive compartments are preferentially MVBs even after the shortest time point of incubation (e–h). The shapes of the MVBs change, their surface becomes smoother, their sizes as well as the numbers of internal vesicles increase over time, MVBs become more compact, whereas the tubular appendices decrease in numbers and lengths and become more uniform. Primary magnifications: 1,000x (a–d), 75,000x (e), 55,000x (f), 85,000x (g), 45,000x (h). Bars 5 μm (a–d), 100 nm (e–h)