Fig 4.

SAL- and GA-treated tissue cysts are defective for reactivation. After cysts were generated for 7 days, the alkaline stress medium was removed and replaced with normal medium containing the indicated concentrations of SAL or GA for an additional 3 days. Alkaline medium (pH 8.1) was retained in some samples as a positive control to prevent reactivation. Following the incubation in normal medium without SAL or GA for another 7 days, the extent of reactivation of tachyzoite infection was assessed by determining the degree of host cell lysis relative to that for the alkaline control using an Alpha Innotech imager. (A) The diagram shows a time line of the experimental setup. (B) The histogram shows the results from two experiments, each performed in triplicate. Error bars indicate standard deviations, and asterisks indicate a statistically significant difference relative to results for the alkaline control (P < 0.05, two-tailed unpaired t test).