A comparative ultrastructural study of a new type of autoschizis versus a survival cellular mechanism that involves cell membranes of cerebral arteries in humans.

The authors analyzed by transmission electron microscopy the modifications of plasmalemma and nuclear envelope in the cerebral arterial wall in humans. Their ultrastructural observations are performed on the tunica media and endothelium. During autoschizis, some smooth muscle cells showed deep invaginations of the nuclear envelope with multiple craters that disintegrate the nucleus, whereas in the endothelium repetitive invaginations of plasmalemma lead to cell demise by cytoplasmic self-excisions. During survival mechanism, a perinuclear constriction of plasmalemma occurs, which conserves nucleus and cytoskeleton, and only a segregated cytoplasmic area, without organelles, is removed in lumen.