Figure 6
PS externalisation in pRBC exposed heat stress. (a) Fluorescence histograms and (b) bar graphs of pRBC showed an increase in PS externalisation by mixed-stage cultures immediately after exposure to 40 °C for 24 h (i) and was still apparent at 48 h (ii), although the latter difference was not statistically significant. No increase was noted in synchronised ring-stage pRBC immediately after exposure to 41 °C for 2 h (iii), with an apparent decrease noted at 48 h; however, it should be noted that the 37 °C control parasites used for comparison had developed to late stages, which typically have higher PS externalisation, even without stress. When comparing the heat-stressed culture at both time points (iii and iv), no change was apparent. Although PS externalisation was not seen in late-stage pRBC exposed to 41 °C for 2 h immediately after heat stress (v), an increase was observed a day later (vi). Representative histograms are merged data sets of at least two samples. Parasite stages are shown on the left as either mixed-stage cultures (Mixed) or synchronised (Sync) early- or late-stage cultures. Heat stress conditions are shown on the right. Gates on individual histograms indicate the percentage of infected erythrocytes that are PS positive. Comparisons between control and heat-stressed parasites have P-values that are significant at <0.05 (*), <0.001 (***) or not significant (ns)
