CENTRIOLAR CYCLE OF FUSED CELLS

Ultrastructure of centrioles of fused cells containing heterophasic in terphase nuclei, premature chromosome condensation, and a telophase-li ke nucleus were studied. The study indicated that the heterophasic cel lular environments contributed by the different cell partners exert a mutually opposite effect on the structure of centrioles. The G(1)-cell partner suppresses replication of S-centrioles. Asynchronous replicat ions of G(1) and S-stage centrioles were observed in some G(1)-S, G(1) -G(2) and S-G(2) fused cells. In interphase-mitotic fused cells, centr ioles of interphase stages underwent mitotic activation when their nuc lei were induced to premature chromosome condensation. Daughter centri oles of G(1)-, S-, and G(2)-stages were also capable of mitotic activa tion independently if they were separated from their mother centriole. Inactive centrioles were observed in some cells containing G(1)-prema ture chromosome condensation. When mitotic nuclei were induced to telo phase-like nucleus formation, their centrioles were also inactivated. Concomitant events of induced nuclear and centriolar changes suggest t hat they might have been controlled by the heterophasic cytoplasmic fa ctors through similar pathways.