Cultivation of the erythrocytic stages of Plasmodium berghei in Leydig cell tumor cultures.

Twelve different established cell-lines were used in attempts to cultivate the erythrocytic stages of Plasmodium berghei, P. vinckei vinckei, P. coatneyi or P. knowlesi. Intracellular parasites were seen in only mouse Leydig cell testicular tumor (LCT) cultures inoculated with red cells infected with P. berghei. Intracellular parasites were present at 15 to 96 h after inoculation, being most numerous at 36 h. Most intracellular stages were rings, trophozoites, schizonts and merozoites; gametocytes were few in number and present only at 36 and 48 h. Intracellular parasites were normal in general morphology and staining characteristics at 15 to 48 h, but were abnormal after 72 h. Infected host cells exhibited progressive nuclear and cytoplasmic degenerative changes, which ultimately resulted in death of the cell. Uninfected cells appeared normal. The ability of parasites in LCT cultures to produce infections upon injection into mice was similar to that obtained with control cultures without LCT cells.

Cultivation of the erythrocytic stages of Plasmodium berghei in primary bone marrow cells.

Cultures of primary bone marrow cells, obtained from the tibiae and femora of hamsters (HBM), mice (MBM), or rats (RBM) were inoculated with red cells infected with Plasmodium berghei, P. vinckei vinckei, or P. knowlesi. Merozoites, rings, trophozoites, schizonts and a few gametocytes were seen in HBM and MBM cells inoculated with P. berghe-infected red cells. At 1 to 2 or 3 days after inoculation in HBM and MBM, the number of intracellular asexual stages decreased slightly or remained the same, whereas at 3 to 7 or 8 days a 4 to 7-fold increase occurred. Parasites then decreased in number from days 8 to 11 and no parasites were seen on day 12. Intracellular parasites were most numerous at 7 and 8 days in MBM and HBM cultures, respectively. Mice injected with supernatant or cells from control cultures (without cultured cells) or primary cultures inoculated 1 and 2 days earlier with P. berghei- or P. vinckei vinckei-infected red cells always became infected. Mice injected with material from 3-day-old control and experimental cultures usually became infected, and those injected with 4- to 12-day-old cultures never became infected.