Figure 4. Undulating membranes of the TZ.

A. Within about 50 µm deeper than Fig. 2F, the membranes take on their characteristic undulating patterns, both low amplitude (arrowhead) and high amplitude (arrows). The cells are irregular in shape and are at the early stages of compaction with average cell thicknesses about 1 µm. Note the uniform dense staining of the cytoplasm. Also note that many circular profiles have irregular shapes because their membranes are also taking on the undulating morphology. B. At higher magnification the paired membranes of a region of high amplitude undulations can be seen individually. Based on previous studies, the segments that are convex toward the cytoplasm contain a high density of aquaporin0 (arrowheads) and the apposing concave segments are limited in protein or are pure bilayers (arrows). The membrane thickness is about 7 nm.