Table 4.

Spontaneous reversion of drug resistance of aneuploid Chinese hamster cell lines propagated for 30 generations without selective drugs

Cell line	Number of colonies* without drugs	Number of colonies* with drugs	Relative resistance, percent
B 644-Col02‡	15	4	27
B 644-A5 + Col01‡	107	1	<1
B 644-A5 + P5 + Col01‡	400	34	12
D 3-MTX5‡	100†	40†	40
D 313-P5 + Col01‡	40	42	>100
D 313-P5 + Col02‡	204	184	90

^*Aliquots of 5,000 and 50,000 cells were plated per 10-cm Petri dish and an area of 560 mm² was counted. In the presence of drugs, colonies were typically smaller and included more granulated cells, than in the absence. 

^† Percent confluence. 

^‡ Col02 is resistant to 0.2 μg and Col01 to 0.1 μg colcemid per 10-cm dish, A5 is resistant to 5 μg araC, P5 is resistant to 5 μg puromycin, and MTX5 is resistant to 5 μg methotrexate.