The semistability of centric chromatin bodies during long-term passage of multidrug resistant mouse-Chinese hamster cell hybrids

In a cell fusion experiment with multidrug resistant (MDR) mouse SEWA tumor cells and sensitive Chinese Hamster CHO cells, the resistant hybrid cells were completely without recognizable mouse chromosomes. Instead, numerous chromatin bodies (CB) were found that contained copies of a high molecular weight P-glycoprotein gene (PGY1) associated with the MDR condition. The present paper reports on the CB under long-term selective and nonselective growth. The CB were of a stability intermediate between that of double minutes (DM) and homogeneously staining regions (HSR). The stability of the CB was different in the two hybrid lines studied.