Fig. 7. rDNA ultrastructures after specific staining, showing the variation in thickness of rDNA fibers (A). Note the `arrow-like structures' along the thicker parts of the rDNA fiber (B,C,E). The maximum length of the arrow-like structures is 200 nm, whereas the fibers extending from these structures measure about 6 nm in diameter (E, arrows). D represents the transverse section of the arrow-like structure. Bar, 0.5 µm (A), 0.3 µm (B) and 30 nm (C-E). Asterisks indicate FCs.