Fig. 6. (A, B) Phase-contrast images of mhc^- cells 1 minute after exchange of the medium to buffer without (A) or with (B) 2 mM quinine. Bar, 10 µm. (C) Sequential fluorescence images of an mhc^- cell showing expulsion of a contractile vacuole. The cell had been stained with RH-795 10 minutes before quinine application. A patch of fluorescence stayed on the cell membrane at the site of expulsion of one of the contractile vacuoles. Intervals between successive frames are 13.7 seconds in the upper panel. The intervals in the lower panel are 0.55 seconds to show the moment of discharge at shorter time intervals. Bar, 5 µm.