Isolated Erythrocytic Forms of Plasmodium Berghei

An Electron-Microscopical Study

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  • Department of Zoology, University of Illinois, Urbana, Illinois 61801
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The fine structure of Plasmodium berghei was studied after its release from rat erythrocytes by one of four methods—cell disintegration by French press, or lysis by saponin, antiserum, or distilled water. Cell disintegration by French press released the largest proportion of structurally intact parasites generally lacking closely associated arrays of erythrocyte membranes. However, the total number of parasites harvested by this method was comparatively few. On the other hand, the saponin-freed parasite material contained a large number of parasites, most of which appeared intact, but several parallel arrays of host membranes were also present. Lysis by antiserum freed some apparently intact parasites, but there were also several damaged forms and unbroken cells. Lysis by distilled water yielded very few healthy parasites; most freed forms contained vacuolar inclusions or were broken into smaller pieces. A double-unit membrane limiting the parasite cytoplasm, at least at intervals, was evident in several of the electron micrographs of isolated P. berghei and of P. berghei found outside the host cell in infected whole blood. Alterations in the nucleoplasm and varied forms of a double-membraned vacuole were frequently observed in the freed parasites. Food vacuoles and cytostomes, when present, appeared normal in the isolated parasites.

Author Notes

Present address: Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, Connecticut 06510.