Fig. 6. Drug washout experiments demonstrate that treatment with 0.5 µM oryzalin is fully reversible, but treatment with 2.5 µM oryzalin causes irreparable damage. Quantification of 48-hour oryzalin treatment followed by a 48-hour recovery in the absence of the drug demonstrates that Toxoplasma nuclear division and segregation occur in 0.5 µM oryzalin (left panel). The blue columns enumerate the numbers of normal and abnormal parasitophorous vacuoles that were present at the time of drug treatment (primary vacuoles). The green columns quantify the numbers of secondary vacuoles that were made by parasites that lysed from primary vacuoles and invaded new host cells during the washout and recovery phase. Parasites treated with 0.5 µM oryzalin can recover and go on to make invasive parasites that are capable of replication after drug removal. However, in 2.5 µM oryzalin (right panel), the continued replication of DNA is uncoupled from spindle microtubule-mediated chromosome segregation and produces both aberrant primary vacuoles and second generation parasites that have unbalanced nuclei or lack nuclei and are incapable of continued growth.

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