A-B. Scanning electron microscopy with sputter coating demonstrates that mHSEC visualized at (A) 3500X or (B) 30,000X have numerous fenestrae (arrows). C-D. Scanning electron microscopy demonstrates that BAEC, visualized at (C) 3500X or (D) 30,000X, lack fenestrae. E-H. Scanning electron microscopy demonstrates that TSEC maintain a limited number of fenestrae between 100 to 150 nm, organized in sieve plates (arrows). Panels represent: (E) sputter coating at 3500X, (F) sputter coating at 30,000X, (G) carbon coating at 20,000X, and (H) carbon coating at 50,000X.