Fig. 7.

Electron micrograph illustrating the heterogeneity of late endosomes (LE). HepG2 cells were allowed to internalize bovine serum albumin (BSA) conjugated to 5 nm gold particles (abundant labeling) for 3 h and processed for immuno-EM of cathepsin D (10 nm gold particles, scarce labeling). Three seemingly identical late endosomes containing multiple ILVs and partially degraded material are shown, two of which are heavily loaded with BSA-gold, whereas the upper one is devoid of the endocytic tracer. G Golgi stacks; Bar 200 nm