Fine Structure of Human Malaria In Vitro*†

SYNOPSIS. The erythrocytic cycle of the human malaria parasite, Plasmodium falciparum, was examined by electron microscopy. Three strains of parasites maintained in continuous culture in human erythrocytes were compared with in vivo infections in Aotus monkeys. The ultrastructure of P. falciparum is not altered by continuous cultivation in vitro. mitochondria contain DNA-like filaments and some cristae at all stages of the erythrocytic life cycle. The Golgi apparatus is prominent at the schizont stage and may be involved in the formation of rhoptries. In culture, knob-like protrusions first appear on the surface of trophozoite-infected erythrocytes. The time of appearance of knobs on cells in vitro correlates with the life cycle stage of parasites which are sequestered from the peripheral circulation in vivo. Knob material of older parasites coalesces and forms extensions from the erythrocyte surface. Some of this material is sloughed from the host cell surface. The parasitophorous vacuole membrane breaks down in erythrocytes containing mature merozoites both in vitro and in vivo. Merozoite structure is similar to that of P. knowlesi. The immature gametocytes in culture have no knobs.     

Venation Pattern and Fruit Development in Lomatium dasycarpum (Umbelliferae)

Venation patterns of flower and fruit, and their relationshipto fruit development, are described for Lomatium dasycarpum(T. and G.) Coult. and Rose, a member of the tribe Peucedaneae(Umbelliferae). Comparisons of these observations are made withreports of fruit anatomy for other Peucedaneae, such as Angelica,Peucedanum, and Heracleum. These comparisons indicate that thereare distinctly different patterns of development leading toa mature fruit with a similar dorsal flattening. The possiblesignificance of such observations, with regard to our understandingof generic relationships in the tribe, is discussed.     

Why Kinetoplasts?*

SYNOPSIS. The history and present status of our knowledge of trypanosomated kinetoplasts are reviewed and the practical and general theoretical benefits which can result from the continued study and improved understanding of these unique organelles are discussed.