Electron microscopic observations on alterations in cultured Plasmodium falciparum and infected erythrocytes after treatment with cyclic AMP in vitro.

The fine structure of Plasmodium falciparum treated with cyclic AMP in vitro was studied. Cyclic AMP stimulated the appearance of membranous structures in P. falciparum-infected erythrocytes. Two types of membranous structures originating from the host cell were observed: multilaminate membranous structures and multistranded layer-like membranous structures. The multilaminate structures may play a role in gametocytogenesis and the maturation of the gametocyte. The multilaminate structures were either free in the cytoplasm of infected erythrocytes or present in association with the parasitophorous vacuole membrane surrounding immature gametocytes. These structures may originate from the erythrocyte plasma membrane and the parasitophorous vacuole membrane. Other notable findings in P. falciparum treated with cyclic AMP included the presence of loop-like membrane structures protruding from the plasma membrane of the parasite and termination of some plasma membranes of the parasite in dense granular structures.