Fig. 5. Transmission electron microscopy of late blebs in apoptotic HeLa cells. In ultrathin sections, late apoptotic cells were identified by their asymmetric profile due to the presence of few, large surface blebs containing condensed chromatin. (A) An example of a chromatin-containing surface bleb. Chromatin (Ch) is loosely enclosed by a continuous double membrane (arrowheads) that closely abuts the plasma membrane, with its outer leaflet following the surface topography of the plasma membrane (arrowhead in zoom panel [i]). On the outer leaflet of the surrounding membrane, ribosomes are apparent (arrowheads in [ii]), and a nuclear pore is also evident (arrowhead in [iii]). (B) A membrane sheet, probably ER, running close to the underside of the plasma membrane of an apoptotic bleb (its tip is marked by an arrowhead). Bars, 1 µm (A); Ai-iii, 100 nm (Ai-iii); 200 nm (B).