Figure 4.

Stereological analysis of umbrella cells and determination of vesicle/membrane continuity. (A) Mounted bladder tissue was fixed in the presence of 0.01% (wt/vol) ruthenium red and processed for TEM. Arrows point to discoidal vesicles that are in proximity, but not continuous with the apical membrane. (B–F) Serial sections of an umbrella cell reveal the discontinuity of vesicles with each other and the plasma membrane. Arrowheads depict individual discoidal vesicles as they appear and disappear within the sections. The dashed box surrounds an area of clustered discoidal vesicles that remain distinct from one another in all sections. A large plasma membrane-associated vesicle is marked with an asterisk. Uroepithelium was incubated in chambers for 20 min with stretch (░⃞) or without (▪) (G) or for 5 h with stretch (░⃞) or without stretch (▪) (H). The apical, basolateral, and vesicle surface areas were determined as described in MATERIALS AND METHODS. Shown is mean ± SEM (n = 50). Values that are significantly different (p < 0.05) from matched control values are marked with an asterisk.