The round profiles within the tubular networks are not vesicles, but varicose tubules. The round profiles within the tubular networks are not vesicles, but varicose tubules. Cells from cricket fat bodies were infected with P. grylli and fixed and prepared for EM tomography (A-D), routine EM (F-J) or for EM by high pressure freezing and cryosubstitution (E). (A-D) 200-nm-thick sections of a meront as extracted virtual sections of part of a TN (with three perpendicular views of the same single voxel indicated by yellow crosses). Enlargements of the white boxes are indicated by white arrows. Thick arrows indicate connections between round profiles and other structures. (E-J) Samples were pretreated without (E) and with NEM for 15 minutes (F,G) or AlF4 for 20 minutes (H-J). Thin arrows in F,G indicate TNs, thick arrows in G indicate microsporidia plasmalemma. Asterisks in G,H,J indicate the vesiculated Golgi of the host cell. Normal TNs are seen in microsporidia treated with both NEM (F,G) and AlF4 (I,J). Bar, 120 nm (A-D, original sections); 35 nm (A-D, enlargements); 150 nm (E,F,H,I); 500 nm (G,J). Galina V. Beznoussenko et al. J Cell Sci 2007;120:1288-1298 © The Company of Biologists Limited 2007