Osmotic fragility curves of IRBCs obtained from synchronized

P falciparum cultures. The IRBCs contained either young (A) or mature (B) parasite forms. The osmotic fragility measurements were performed as described for Figure3, using mostly uninfected cohort cells as controls. Synchronization was performed as described in “Materials and methods.” Micrographs of representative fields from Giemsa-stained smears of the synchronized, concentrated cultures used for the osmotic fragility measurements are shown on the right of the corresponding figures (original magnification, × 1000). (A) A single experiment with culture containing rings and young trophozoite stage parasites. Top fraction (●): 91% parasitemia, all rings and young trophozoites. Bottom fraction (○; cohorts): 94% uninfected cells, 6% rings. (B) Shown is 1 of 2 identical experiments with similar results. The culture contained mature stage trophozoites and 1.2% ring-stage parasites before final gelatin flotation. Top fraction (●, ○): 86% parasitemia, 33% mature trophozoites, and 53% schizonts and segmentors. Bottom fraction (▾, ▿): 97% uninfected cohorts and 3% rings.