Figure 8. Ultrastructural features of autophagic cell death.

R921 cells were treated with 0.5 mM SIN-1 in GD medium for 24 h, fixed and prepared for electron microscopy as described in the Materials and methods section. (A) Untreated control cells showing normal distribution of organelles. Arrowhead shows an autolysosome with a highly electron-dense myelin figure. (B) Features of early autophagic cell death in cells treated with GD+SIN-1. (C, D) Cup-shaped membranous structures in the cytoplasm or occasionally wrapping mitochondria. (E) An autophagosome, containing organelles undergoing degenerative changes and electron-dense myelin figures. (F) An autophagosome fusing with a lysosome (arrow) to form a single membrane vacuole containing phagocytosed cell fragments and myelin figures (arrowheads). (G) Autolysosomes found close to the plasma membrane. Arrow shows a mitochondrion in an autolysosome. (H) Crystalline structures. (I) A vacuole containing membrane whorls. (J) Features of late autophagic cell death showing membrane blebbing and increased number of vacuoles. Arrow shows sequestration of the cytoplasm. The remaining mitochondria seem to organize in the perinuclear area. Arrowhead shows mitochondria in small clusters. Nuclear chromatin is condensed and some detached from the nuclear envelope. (K) Features of very late autophagic cell death. The cell appears highly vacuolated and shows disappearance of all organelles. Nuclear chromatin appears condensed. Scale bars: (A, B), 5 μm; (C, D), 1 μm; (E, F), 1 μm; (G), 1 μm; (H, J and K), 3.3 μm; and (I), 0.83 μm.