Fig. 4. The T. gondii lipid body. Parasites were grown in host cells exposed to the fluorescent probe NBD-cholesterol throughout the course of infection. Following host cell lysis, the purified, labeled parasites were allowed to infect fresh coverslip-grown host cells. After a 1 hour infection, coverslips were fixed, photoactivated in the presence of diaminobenzidine, and processed for electron microscopic analysis. An intracellular parasite is shown in low magnification in the top-left panel, and its prominent lipid body demarcated with electron-dense reaction product is shown in high magnification in the top-right panel. Two additional profiles of typical lipid bodies are depicted in the lower panels. The arrow in the top-left panel denotes an intravacuolar liposome. Bars, 500 nm (low magnification); 100 nm (high magnification).