Electron Microscope Study of the Exoerythrocytic Form of Plasmodium gallinaceum in Thin Sections of Infected Tissue Cultures*

Abstract

SYNOPSIS. The exoerythrocytic forms of Plasmodium gallinaceum in thin sections of infected tissue cultures have been examined with the electron microscope. It was seen that important changes occur in the fine structure of the parasite during the various phases of the cycle. The cytoplasm of the merozoites at the beginning and at the end of each cycle shows a great electron density due to a fine granulation. Larger granules are found at one pole of the parasite. The merozoites have a large nucleus in the center, and an oval body of great electron density at one pole, the significance of which is unknown. Short canaliculi can also be seen in the cytoplasm, but no mitochondria have been found. The cytoplasm of the schizonts shows a low electron density. It contains small particles scattered irregularly throughout its whole mass. The nuclei are not well defined; the oval body observed in the merozoites apparently has disappeared. Short canaliculi are present everywhere; however, mitochondria could not be identified with certainty. In the final phase of the cycle, in the rosette formations, the cytoplasm assumes again the fine granular structure. The future merozoites are grouped around a cytoplasmic core, with which they are directly connected. The whole segmenter is situated in a vacuole formation. In cross sections of the merozoites an opening in the central pole has been observed.

Electron Microscope Studies of Reproducing and Interkinetic Toxoplasma

“…The presence of multinucleated cells, containing several, preformed organanisms in a rosette arrangement, corresponds to a type of propagation usually designated as schizogony. Furthermore, electron microscope observations on the segmenter phase in the schizogonic cycle of other protozoa, Plasmodium gallinaceum (13) and Plasmodium lophurae ( 16), closely accord with those obtained from the Toxoplasma rosettes. The residual cytoplasmic material connected by strands with the filial organisms appears to correspond to the residual body observed in the malarial parasites.…”

Pinocytotic Uptake and the Digestion of Hemoglobin in Malaria Parasites*†

“…I t is encased in a double membrane (Figs. 1-3, 7-9, [16][17][18]21). To the outer membrane ribonucleoprotein particles are attached.…”

“…Droplets of host cytoplasm are trapped into these invaginations with the subsequent formation of food vacuoles. This assumption is strengthened by two facts: 1) Malaria parasites in their exoerythrocytic stage, and therefore in a different type of host cell, have not been observed to feed by pinocytosis (21); 2) However, Babesia, an unrelated parasite which also lives intracellularly in erythrocytes, feeds on the host cell in exactly the same way as malarial parasites in their intraerythrocytic stage (38). Both facts indicate that there is a close relationship between the surrounding medium and the manner of feeding in these parasites.…”

In Vitro Development of Exoerythrocytic Forms of Plasmodium Gallinaceum Sporozoites In Avian Macrophages

“…In vitro cultures of EEF of avian malaria have been successfully obtained with tissue explants from birds or embryos previously infected with sporozoites or blood parasites [5,6,8,10,15,16,19,201. However, Dubin et al [l], reported negative results by several groups in their attempts to obtain EEF directly from sporozoites in vitro.…”