Fig. 2. Ultrastructure of AVs in AD brain. (A-C) Dystrophic neurites are filled predominantly with (A) AVs, including large double-membrane limited immature AVs, such as autophagosomes containing multiple smaller compartments (B) or multilamellar structures (C, arrowhead), and single-membrane vesicles containing electron-dense intraluminal materical, which correspond to late AVs (autophagolysosomes, amphisomes) or lysosomes (C, arrow). The latter structures are immunogold labeled by antibodies to cathepsin D, which identifies them as autophagolysosomes. AVs in AD brain are similar to AVs isolated from livers of mice treated with vinblastine to slow autophagosome-lysosome fusion (panels D,E). Bars, 500 nm. Reprinted with permission (Nixon et al., 2005).