[Ultrastructure of erythrocytic stage of Plasmodium vivax in humans]

After the merozoite entered the erythrocyte, the membrane debris in the parasitophorous vacuoles of early ring form was passed out through a narrow external aperture in erythrocyte to the exterior. The trophozoite was oval or irregular in shape. Ingestion of host cell cytoplasm occurred cystostomally. The asexual parasite possessed cristate mitochondria and was surrounded by a single-membraned pellicle. The gametocyte possessed cristate mitochondria and was surrounded by two unit membranes. The cytoplasm of mature macrogametocytes contained many ribosomes, mitochondria and osmiophilic bodies and a small nucleus while microgametocytes contained fewer ribosomes, osmiophilic bodies and mitochondria and a large nucleus. Three characteristic morphological alterations were observed within the host cells, that is, small vesicles, cytoplasmic cleft and caveola-vesicle complex. The clefts within the cytoplasm of the host erythrocytes were present in all human malarial parasites. The small vesicles distributed all over the cytoplasm were surrounded by a unit membrane. The caveola-vesicle complex consisted of caveolae was surrounded by small vesicles and probably corresponds to a Schüffner's dot. (Figs. 1-13).