Fig. 5.

Toxicity does not preclude the use of BrdU as a short-term labelling agent in P. falciparum. a ELISA on +TK parasites, plated at 1 × 10⁶ parasites/well, after 48 h exposure to the three lowest concentrations of BrdU used in the MSF assay shown in Fig. 3b. Background signal, obtained from the sample incubated without BrdU, has been subtracted from all readings. Error bars show standard deviation of triplicate readings. A parallel MSF-type assay on the same parasites shows that DNA content is similar in all samples, confirming that within 48 h, severe growth inhibition has not occurred at these sub-IC50 exposures. b ELISA on +TK parasites (1 × 10⁶ parasites/well), after pulses of BrdU from 15 min to 4 h, applied at the trophozoite stage. The background signal, obtained from parallel samples incubated without BrdU, has been subtracted from each set of readings. Error bars show standard deviation of triplicate readings. c MSF assay on +TK parasites after 1 or 2 h pulses of BrdU (5 mM to 2.3 nM) at trophozoite stage, followed by washing and growth in fresh medium for 48 h. Parasites were also kept in BrdU for the full 48 h, as in Fig. 3b, for comparison. Error bars show standard deviation of triplicate readings. IC50 values were calculated with GraphPad Prism software, 95 % confidence intervals are given in parentheses