Development of the endocrine pancreas during larval phases of Rana temporaria

Abstract

The pancreatic endocrine component was studied at different stages of development in the tadpoles of Rana temporaria. The material was embedded in Epon, and serial semithin and thin sections were made in order to correlate ultrastructural features and tinctorial traits of the endocrine cells. Serial semithin sections were also stained with the peroxidase-antiperoxidase immunocytochemical method and with silver impregnations for argyrophilia and argentaffinity. In early larvae (legless tadpoles). A and B cells are present. Both can be found within ducts and exocrine tissue or, more frequently, in cellular clusters among the ducts and acini. These primitive islets are solid structures, surrounded but not penetrated by capillaries. Mitoses were observed in A and B cells. In the following phase (tadpoles with hindlegs), D and pancreatic polypeptide-immunoreactive cells are also present, as well as numerous endocrine cells scattered among exocrine tissue. There is also a change in the vascular-insular pattern: capillaries not only surround but also penetrate the endocrine group. The structure of the endocrine pancreas in older tadpoles is similar. Tinctorial traits and ultrastructural features of endocrine cells are described, and the origin of primitive islets is discussed.

Fine structure and immunocytochemistry of cells within the endocrine pancreas of the gar (Lepisosteus osseus)

“…The presence of large numbers of nerve terminals in the gar is consistent with what is observed in mammalian (Orci et al 1976) and amphibian (Ortiz de Zarate et al 1991) islets. Nerve fibres have also been reported in the islets of lampreys and teleosts (Carrillo et al 1986;Agulleiro et al 1993;Jönsson 1993).…”

“…The average size of B-cell granules (110 nm) in gars was less than in most other vertebrates, which ranged from an average of 165 to 622 nm (Brinn 1975;Kobayashi et al 1976;Ortiz de Zarate et al 1991;Agulleiro et al 1993), although it appears that the gar has one of the greatest ranges of granule sizes (60-470 nm). The gar had the same average size of B-cell granules as the lamprey (110 nm), but lamprey granules had a size range of only 140-200 nm .…”

“…The granules in dumbbell-shaped or oblong profile measured 330 nm along the long axis in tadpoles (Ortiz de Zarate et al 1991), whereas the oblong profiles of granules of the gar D cells averaged 200 nm in length. D cells in gilthead sea bream and sea bass contained only round secretory granules (Abad et al 1992;Agulleiro et al 1993).…”

Atividades enzimáticasde girinos de rã-touro submetidos a rações com níveis de proteína

“…Os resultados obtidos no presente estudo são basicamente semelhantes com as alterações encontradas no sistema digestório das espécies Xenopus laevis e Rana temporária (Leone et al, 1976, Ortiz De Zarete et al, 1991.…”

Intercalated Duct Cells in the Moorhen (Gallinula chloropus) Pancreatic Islet

“…There have been many reports on the relationship between the exocrine and endocrine pancreas, both ontogenetically and phylogenically. They have described islet cells within exocrine pancreatic ducts, and sometimes having a common lumen with tubules in the early development in anuran (Ortiz et al , 1991), avian (Ono, 1967), rats (Fujii, 1979), bovine (Sanchez, 1987), and human embryos (Like and Orci, 1972). Intercalated ducts and centroacinar cells have been reported to be mingled with islet cells in some cases of inflammation, cancer, or hyperactivation of the pancreas (Yang and Hunter, 1959), Wang et al (1995) have described proliferation and differentiation of exocrine duct cells as representing the major mechanism of endocrine beta-cell neogenesis in the rat after pancreatic duct ligation.…”