Figure 1.

Transmission electron microscopic images of SP94-LD and LD internalized by SK-HEP-1 cells. The SK-HEP-1 cells (1×10⁷ cells) were incubated with 10 µg/ml SP94-LD or LD at 37°C for 10 min, and then frozen and processed for TEM. Representative electron micrographs of the cells treated with SP94-LD (A) and LD (B) are shown. (C) Coated pit structures were visually identified by the presence of the electron-dense coating of the plasma membrane (arrows). (D) High magnification image of the coated pit structures, indicated by the boxed area in (C). (E) Image of SP94-LD in endosomes (arrows). (F) High magnification image of the endosomes, as shown in (E). (G) The late endosomes deliver their cargo, SP94-LD, to the lysosomes (arrows), resulting in the electron-dense, multivesicular appearance of late endosomes known as multivesicular bodies (MVBs). (H and I) High magnification images of the regions indicated by the boxed areas in (G). TEM photomicrographs were subjected to morphometric analysis with ImageJ software. (J) Vesicle number and area distribution of cells treated with SP94-LD or LD. (K) Statistical analysis of vesicle count per cell. (L) Statistical analysis of average area per vesicle. (M) Statistical analysis of total vesicle area per cell (n=16–18).