Fig. 7. Histograms of DNA content showing cell-cycle progression in extracellular parasites. Parasites were harvested and analyzed by flow cytometry according to three different protocols: (1) by mechanically inducing escape from host cells, washing to remove debris, staining with Hoechst 33342, followed by flow cytometry analysis (1 hr, red); (2) with a 12 hour delay after induced exit from host cells before washing, staining, and analysis (12 hr, green); and (3) harvested, washed, Hoechst stained and analyzed approximately 24 hours after spontaneous lysis of an entire culture dish of host cells (24 hr, blue). The graph shows superimposed histograms of fluorescence intensity (proportional to DNA content) of approximately 1x10⁵ single cells from each of the three preparations, in arbitrary units on a logarithmic scale.