Synchronous and asynchronous DNA synthesis in multinucleated Ehrlich ascites tumor cells compared with multinucleated cells cultured from frog lung

Abstract

Monolayers from cultured explants of frog lung contained 10% binucleated and 0.2% multinucleated (3 or more nuclei) cells. Seven-day-old populations of Ehrlich ascites cells contained 1.6% binucleated and 0.4% multinucleated cells. Fourteen-day-old populations of Ehrlich ascites cells contained 11% binucleated and 4% multinucleated cells. The bi-and multi-nucleated frog lung cells synthesized their DNA synchronously, and during DNA synthesis all nuclei in the same cell incorporated 3 H-thymidine at an equal rate. Most of the bi-and multi-nucleated Ehrlich cells replicated their DNA synchronously in their 19th hour of newly initiated recurrent growth. However, 13% of all the binucleated and 18% of all multinucleated Ehrlich cells in recurrent growth replicated their DNA asynchronously. Some of the bi- and multi-nucleated cells in synchronous DNA synthesis incorporated 3 H-thymidine at different rates per nucleus. Nevertheless, almost all of the bi- and multi-nucleated Ehrlich cells studied entered mitosis synchronously. There were only two cases of multinucleated Ehrlich cells showing one nucleus in interphase with the rest in prophase. In no case, however, did an interphase nucleus appear in a cell with metaphase chromosomes in it.