Ultrastructural and Molecular Changes in the Developing Small Intestine of the Toad Bufo regularis

Figure 1

Electron micrographs of the anterior portion of the small intestine of the larval stage 42 ((a)–(d)) and the premetamorphic stage 50 ((e)–(h)) showing the following. (a) and (b): epithelial cells contact to the basal lamina (arrow head). (c): an immature fibroblast-like cell (Fim) with large nuclei and poorly developed cell organelles. (d): a mitotic cell (Mt) in the connective tissue. (e): a fibroblast with well-developed rough endoplasmic reticulum (rER). (f): connective tissue (Ct) contains a fibroblast (F) with well-developed rER. (g): a goblet cell (GC) containing mucous granules (MG) in the apical surface of the larval epithelium. (h): supranuclear cytoplasm of two adjacent columnar cells with uniform microvilli (MV), numerous mitochondria (Mi), and vesiculated rough endoplasmic reticulum (rER) beneath a well-developed terminal web (TW). The lateral junctional complex joining neighboring cells is visible. Scale bar = 1 μm.