tokens: After 5 days in culture with a saturating concentration ( 3.6 X 10 ( -8 ) M ) of hormone , the cells reached a saturation density of about 9.0 X 10 ( 6 ) viable cells/ml ( about 4.0 X 10 ( 6 ) viable cells/ml in the controls ) , while the modal volume of the resulting cell population was approximately 60 % , as compared to the volume of untreated cells .