Ultrastructural cytochemistry using potassium iodide (KI) for detection of sarcoplasmic reticulum (SR). (A) SR profiles from uninfected SkMC displaying positive reaction products for KI around the nucleus (N) (arrow) and in the cytoplasm (arrowhead). (B) SkMC infected for 4 h with T. gondii shows the presence of SR profiles containing the reaction product for KI in the cytoplasm (asterisk) surround the nucleus (N) and the PV (arrow). Demarcation in the complex internal membrane of the parasite could also be observed (arrowhead). (C) Profiles of SR revealed by KI (small arrow) are observed near and in fusion processes with PV (asterisk) and also inside the PV (arrowhead). Association of several lipid droplets (LD) darkened - revealed by imidazole technique can be seen with the PVM (thick arrow). (D) After 24 h of T. gondii-SkMC interaction several parasites were observed within the PV containing vesicles of different morphologies and sizes labeled with KI (arrows) and around the nucleus (N). Bars: A = 50 μm; B and C = 0.5 μm; D = 1 μm.