Fig. 6. De novo synthesis of phospholipids by T. gondii. The indicated ¹⁴C-labeled phosphatidylcholine precursors were introduced to either untreated, purified extracellular parasites (EC) or intracellular (IC) parasites. Labeling was performed at either 2°C (2C) or 37°C (37C) before parasites were harvested for analysis by thin layer chromatography using the solvent system chloroform/methanol/acetic acid/water (25:15:4:2), and lipids detected by autoradiography after visualizing standards. The plates were exposed to X-ray film for identical time periods. The migration of standards (stds.) is indicated: PA, phosphatidic acid; PC, phosphatidylcholine; acet. acid, acetic acid. Asterisks indicate three clearly resolved phosphatidylcholine spots. O, origin.