Electron microscopic observation of the primary cilium in the pancreatic islets.

Abstract

Summary.A primary cilium often projected from the Golgi region of pancreatic A, B and D cells.The proximal portion of the cilium was found surrounded by a tubular invagination of the plasmalemma, and then the cilium extended into the intercellular canaliculus. The most proximal portion of the ciliary membrane exhibited periodical densities which might correspond to the ciliary necklace.The axoneme of the cilium was basically of the 9+0 pattern, i.e., nine peripheral doublets and no central singlet, though it was modified along the length of the cilium.Although a few appendages were projected from each doublet, it was difficult to identify dynein arms and nexin links.At the most proximal portion of the cilium, a "champagne-glass" structure connected each doublet with the ciliary membrane.The distal and proximal centrioles of the diplosome were connected to each other by a striated band.The proximal centriole, which served as a basal body, had accessory structures, such as alar sheets, basal feet and rootlets.Frequent projections of the primary cilium and its elaborate structure suggest that the cilium is not an aberrant structure but rather one which plays a certain role in the islet cell function.

Restricted expression of somatostatin receptor 3 to primary cilia in the pancreatic islets and adenohypophysis of mice

“…Bars 20 μm lation or via intercellular spaces to act upon other islet cells in a paracrine manner. Some morphologists have recognized the development of a special intercellular canalicular system apart from the perivascular spaces within pancreatic islets (7,39). As shown by the present SEM observation, the primary cilia were usually located in these intercellular canalicules, i.e., microvillous channels among islet cells, but did not face the perivascular spaces.…”

“…Therefore, an interesting inquiry to be addressed in future studies is whether BBS patients and BBS protein-knockout mice normally express SSTR3 on the primary cilia of insulin cells. Cells of pancreatic ducts and islets possess the primary cilia, but acinar cells of the exocrine pancreas apparently lack them (1,5,22,39). An electron microscopic study by Yamamoto and Kataoka (39) has reported in detail the ultrastructure of primary cilia on islet cells of some animal species.…”

“…In most regions, somatostatin functions as a local hormone which is conveyed by local circulation or diffusion through an intercellular space to regulate neighboring cells. Many electron microscopic observations have demonstrated the solitary cilium in endocrine cells such as pancreatic islet cells (39), pituitary endocrine cells (2), and adrenal endocrine cells (37,38). However, it remains unknown whether the primary cilia in these endocrine cells express SSTR3 and other signal molecules for sensing.…”

Immunohistochemical demonstration of dopamine receptor D2R in the primary cilia of the mouse pituitary gland

“…Endocrine cells also possess primary cilia in the adenohypophysis, pancreatic islets, and adrenal gland. Electron microscopic studies of these endocrine cells have demonstrated the existence of single cilia which display a structural organization unlike that of the motile cilia (5,45,49). Our recent immunohistochemical study revealed an abundance of SSTR3-expressing solitary cilia in growth hormone (GH)-secreting cells and insulin-secreting β-cells of the mouse (24).…”

Ultrastructural studies of cilia formation during thyroid gland differentiation in grass snake embryos

“…In addition, the structural relationship between the primary cilium and the Golgi complex and the presence of the small secretory vesicles near the membrane of the ciliary pocket of the differentiating cilia might also indicate the participation of these structures in secretory processes during the early stages of thyroid development. Similarly, primary cilia have frequently been found in the endocrine cells of the pancreas (Yamamoto and Kataoka, 1986;Bertelli and Regoli, 1994;Aughsteen, 2001) and some authors have suggested that they are probably involved in secretory processes (Aughsteen, 2001). The involvement of cilia in secretory processes was also demonstrated in a study that described the anatomical interrelationship between the primary cilium, the Golgi apparatus of chondrocytes and smooth muscle cells (Poole et al, 1997).…”