Ultrastructure of Plasmodium falciparum "in vitro". I. Base-line for drug effects evaluation.

A chloroquine-sensitive and a chloroquine-resistant strain of Plasmodium falciparum were examined in drug-free culture. Apart from the presence of knobs on the erythrocytes infected with sensitive parasites, no major differences between the two strains were observed. Nevertheless, the parasites of each strain show a variety of morphological features, some of which are quite similar to drug-induced alterations concerning cytoplasmic organelles, feeding process, and host-parasite interactions.