Fig. 7. Assembly and disassembly of myosin-II thick filaments. Two time series of fluorescence micrographs of live, flattened amoebas expressing EGFP-myosin-II tail fragment. Time points are given in seconds. (A) Appearance of new filaments. When this cell changed its direction of movement from upper right to lower left at about 20 seconds, new thick filaments (arrows) appeared within seconds at the new tail end as the new lammellipodium (arrowheads) emerged at lower left. The fluorescent intensity of these new filaments increased with time. (B) Disappearance of filaments. The filament marked with an arrow disappeared while a neighboring filament (arrowhead) moved toward the rear (upper right). Bar, 10 µm.