Treatment of L. major-infected macrophages with Pentostam and NCI compounds. Macrophages were obtained, infected with L. major promastigotes, and treated with NCI compound 83633, 351520, or 13512 or Pentostam, as described in the text. The numbers of intracellular amastigotes per 100 macrophages (A) and the numbers of macrophages infected with at least one amastigote (B) were determined by visual examination of fixed, mounted specimens. The concentrations of each compound are indicated. The values represent the averages of three separate determinations (except for Pentostam at 50 μg/ml, which had one determination [and, therefore, a P value could not be determined]), with the error bars indicating the range of values. *, values significantly different (P < 0.05) from those for the controls with DMSO only, as determined by Student's t test.