Asynchrony of Nuclear Development in Cytochalasin-induced Multinucleate Cells

Synchrony of mitotic nuclei within a multinucleate cell is more of a biological rule than an exception (13) . Synchronized division of nuclei in multinucleate cells has been reported in slime molds (10), protozoa (12, 15, 16), insects (18), and mammalian germ and somatic cells (2, 6, 7, 13) . The influence of a cytoplasmic humoral factor which controls nuclear division has been supported by observations on the synchrony in cells joined by cytoplasmic bridges (2, 6, 7) and by experiments on nuclear transplantation (5, 8) . However, a few rare exceptions to the general rule are known (9, 13, 19) . Cytochalasin B, a mould metabolite from Helminthosporium dematioideum isolated by Aldridge et al . (1), causes multinucleate cell formation by suppressing daughter cell separation following an otherwise normal nuclear division (4, 14, 17) . In time-lapse cinematographic observations,' the mitotic cells round up, chromosomes segregate, and a normal cleavage furrow is seen to develop . The two resulting daughter cells move away from each other, but remain connected by a thin intercon-