A large-scale in vitro production system for Plasmodium falciparum.

near their center so that the anterior and posterior ends were juxtaposed (Fig. 1). Folded sporozoites were most numerous 32 HAI but were present up to 43 HAI. At 32 HAI, many small round meronts were seen near the basement membrane of the crypt enterocytes, below or beside the host cell nucleus. Several nuclei were scattered ramdomly throughout the developing meront and an eosinophilic refractile body was present (Fig. 2). The meronts increased in size during 32 to 40 HAI, the nuclei became peripherally arranged and the refractile body persisted. As the merozoites developed, they appeared to bud in a whorled pattern from a central residuum. Nuclei of the merozoites were arranged side by side (Fig. 3). Mature meronts were first seen 40 HAI. Twenty-five meronts were 16-27 X 12.8-19 gtm (mean 20.8 X 15.6 tm) and in cross section contained about 22 merozoites that were arranged randomly in the parasitophorous vacuole (Fig. 4). The first generation merozoites were approximately 7.6 X 1.3 Atm and had centrally located nuclei. Mature meronts were most numerous 43 HAI but were still present in sections from animals killed 51 HAI. The first generation meront differs from the second generation meront in the time of maturation and in the size of the meront and merozoites. The mature second generation meronts were 19.8 X 12.6 ,m (mean) and contained about 39 merozoites that were 17.4 X 2 ,im (mean). The third generation meront was smaller (mean 13.1 X 11.2 ,um) then the first generation meront and did not mature until 120 HAI. Merozoites of the first generation meronts appeared to bud from a central residual body. This is similar to that reported for the third generation meront (Todd and Lepp, 1971, loc. cit.).