Colony Size and Giant Cell Formation from Mammalian Cells Exposed to 1 MHz Ultrasound

Chinese hamster ovary (CHO) cells were exposed to continuous wave 1 MHz, 5 W/ cm² ultrasound for 5 min, plated, and allowed to grow for 7 days; colonies were then scored for size and for the presence of giant cells. Sonicated colonies contained fewer cells than controls by a factor 0.53 (P < 0.001), but contained more giant cells than sham controls by a factor of 1.30 (P < 0.001). On a per cell basis the frequency of giant cells was 2.47 times higher in the colonies arising from sonicated cells. Characteristics of giant cells varied; all were abnormally large cells with one large nucleus or several smaller nuclei and/or protoplasmic bridges.