Fig. 9. Electron micrographs of isolated shark choroid plexus (CP) subjected in vitro to heat stress or zinc exposure in complete culture medium (L-15E). (A–E) Scanning electron micrographs of dogfish shark IVth CP ventricular surface (CSF-side); (F–J) transmission electron micrographs of shark IVth CP. (A,F) Freshly harvested tissue immediately processed for fixation. (B,G) Tissues held at 13.5°C for 7.5 h in L-15E. (C,H) Tissues incubated at 18.5°C for 6 h followed by incubation at 13.5°C for 1.5 h. (D,I) Tissues incubated initially at 13.5°C for 5 h, then at 23.5°C for 1 h followed by 13.5°C for 1.5 h. (E,J) Tissues incubated with 50 µmol l^–1 ZnSO₄ at 13.5°C for 6 h followed by recovery in zinc-free medium at 13.5°C for 1.5 h. mv, microvilli; v, ventricular or cerebrospinal fluid-side; g, fat globule. Scale bars, 5 µm.