Nuclear-to-cytoplasm chromatin blebbing in senescent cells associated with depletion of lamin B1. (A) Extrusion of GFP-H2B-positive chromatin fragment from nonmitotic RS nucleus. Confocal time-lapse microscopy of transiently transfected GFP-H2B-expressing cell, 60× original magnification, 150 nm optical section, time in mins. Bars: 10 µm; (insert) 2 µm. 