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. 2011 Sep 1;7(9):e1002224. doi: 10.1371/journal.ppat.1002224

Figure 1. The membrane of freshly formed detached cells is intact and retains phosphatidylserine asymmetry.

Figure 1

HepG2 cells were infected with fluorescent P. berghei parasites and detached cells were collected at either 65 or >75 hours of infection. They were then stained with the nuclear dye Hoechst 33342 (blue) and several additional live stains to characterize the nature of the surrounding membrane. The existence of a membrane in general was shown by staining with Vybrant DiO (green) in cells infected with P. berghei-mCherry (red, top panel). The presence of phosphatidylserine in the outer membrane leaflet, an indicator for ongoing cell death, was tested using pSIVA (green) in cells infected with P. berghei-mCherry (red, middle panel). Propidium iodide (red) is a membrane-impermeable nuclear stain and served to check the integrity of the membrane of P. berghei-GFP (green)-infected detached cells (lower panel). Quantification of the phenotypes (mean + SEM of three independent experiments) clearly shows that the membrane of freshly formed detached cells was intact and phosphatidylserine-negative while the membrane of older detached cells slowly lost phosphatidylserine asymmetry and integrity. Total n for 65hpi - Vybrant DiO: 712, pSIVA: 1483, PI: 1291. Total n for 75hpi - Vybrant DiO: 899, pSIVA: 874, PI: 1564. Bars  = 10 µm; WF (wide-field).