Ultrastructure alterations of BMS cells expressing P1 from the inducible ERE promoter. (A) BMS cell prior to induction. (B-F) Cells 4 days after the addition of estradiol. Cells containing green fluorescent bodies (GFB) were selected using a micro-manipulator under the fluorescence microscope. The white arrows indicate electron-dense structures uniquely associated with the presence of the GFBs. CW indicates the cell wall.