On the crests, the most common feature of the epithelial cells is MG132 purchase the varied granular content, from electron dense to completely electron lucent. These cells have a reduced content of melanosomes and most of them are partially melanized (Figure 4(e)). Due to their location on the crests, the other vesicles containing granular or finer material may correspond to those containing a phycobilin-like pigment (Figure 4(e)), as previously observed by fluorescence microscopy [29].Figure 4Transmission electron microphotographs of the side (a�Cf) and sole (g�Ci) foot epithelia. (a) General view showing secretory cells (types (a) and (b)) and pigmented epithelial cells with a prominent microvillus border (mv), a small group …The sole epithelial cells show differences in morphology and pigmentation relative to the side foot epithelium.

The most noteworthy features of the sole epithelial cells are the lack of pigmented cells and the profusion of cilia on their apical domain (Figures 4(g) and 4(h)). A mucus layer forming a blanket over the top of the ciliated cells can also be observed (Figure 4(g)).3.3.2. Secretory Cell Types Along the side foot, epithelial secretory cells are scattered among epithelial cells. They are similar in shape and appearance to goblet cells, and characterized by an apical surface swollen with secretory granules and a narrow basal region with the nucleus (Figure 1(a)). By TEM, four different types of secretory cells (A, B, C, and D) are found, which are mostly distinguished by the appearance and electron density of secretory granules.

The secretory granules of the cells identify here as type ��A�� are completely electron-lucent, very tightly packed and occupy the entire cytoplasm (Figures 4(a), 5(a), and 5(d)). The type ��B�� secretory cell has electron-lucent granules with finely granular material and a small nucleus located basolaterally (Figure 4(a)). The type ��C�� contains secretory granules with an unequal distribution of electron-dense and electron-lucent material (Figure 5(a)). Their nuclei are small and appear compressed in the basal part of the cell, where bodies with tightly packed membrane can be observed (Figure 5(b)). Moreover, a prominent rough endoplasmic reticulum is found close to the nucleus (Figure 5(c)). Extrusion of secretory material from the cell is often observed, and, occasionally, a number of granules remain apparent outside (Figure 5(a)). The cell type ��D�� possesses atypical secretory granules consisting of highly abundant tightly packed and swirled membranes, which may correspond to residual material (Figure 5(d)).Figure 5Transmission electron microphotographs of different types of side secretory cells (a�Cd) and subepithelial Dacomitinib glands (e�Cg).