Leishmania amazonensis promastigotes

Fig. 1. Inhibition of Leishmania mexicana amazonensis promastigote proliferation by inhibitors of ADP-ribosyl transferase. Promastigotes of strain LV78 ware grown at 27°C in LIT medium (21) with 10% fetal calf serum in the presence of a range of concentrations of inhibitors. Cell densities were determined after 48 hrs incubation and growth rates were calculated for control and experimental cultures. The growth rate at each concentration of inhibitor was expressed as a percentage of the growth rate in control cultures. The starting ceU density was 1.3 x 10 promastigotes/ml. The mean and standard error (except where encompassed by the symbol) of four cultures are shown for each concentration of inhibitor.

Binding studies of I-labeled human transferrin to membrane preparations revealed the presence of a high affinity saturable binding site K = 2.2 x 10 m), similar to that of human transferrin receptor. Purified amastigotes of L. infantum and L. mexicana amazonensis also bind I-labeled transferrin similarly to promastigote membrane preparations. It is thus likely that transferrin mediates iron transport in both life stages of Leishmania parasites. 

Fig. 2. Effect of 3-methoxybenzamide on the differentiation of Leishmania mexicana amazonensis amastigotes. Infected J774 cell cultures were homogenized and the amastigotes released were puified using PercoU (14). The amastigotes were washed with LIT m um (21) and resuspended in LIT medium with 10% fet calf serum. Cultures were pre-incubated at 34°C for 4 hrs at 9.5 x lO cells/ml in the presence of 2.5 mM 3-methoxybenzamide and in untreated control cultures. Differentiation was then induced by transferring the cultures to 27°C. Differentiation was monitored microscopically and the concentrations of promastigotes (Fig. 2a) and amastigotes (Fig. 2b) were determined. (4) Cultures containing 2.5 mM 3-methoxybenzamide. ( ) Controls. Mean and standard errors (unless encompassed by the symbols) of at least four cultures are shown for each time point.

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