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Zaccone, G., Lauweryns, J . M., Fasulo, S., Tagliafierro, G., Ainis. L. & Licala, A . 1992. Immunocytochemical localization of serotonin and neuropeptides in the neuroendocrine paraneurons of teleost and lungfish gills.-Acta Zoologica (Stockholm) 73: 177-183.Neuroendocrine (NE) cells in the gills of six fish species were identified by serotonin and peptide immunohistochemistry. They occur either as single cells or as cell clusters within the filamental epithelium. Two populations of NE cells were identified that exhibit an immunoreactivity either for serotonin alone or for met-enkephalin and leu-enkephalin co-distributed in the same cells. We demonstrate for the first time the occurrence of open-type endocrine cells in the fish gill epithelium and confirm the presence of only serotonin-immunopositive cells of the closed type. The NE cells of the species studied do not react positively to other neuroendocrine markers occurring in the mammalian lung. Great differences probably exist in the expression of these epitopes on antigenic structures among various animal species.Although the physiological role of neuropeptides and serotonin in the fish gill NE cells is unknown, the presence of these molecular markers is of interest not only from an evolutionary aspect, but also in terms of a potential animal model to study the supposed functions of the airway neuroendocrine system in the vertebrates.

This chapter describes the distributional patterns of the neuroendocrine cells in the respiratory surfaces of fishes and their bioactive secretions which are compared with similar elements in higher vertebrates. The neuroendocrine cells in the airways of fishes differentiate as solitary and clustered cells, but the clusters are not converted into neuroepithelial bodies which are reported in terrestrial vertebrates. The dipnoan fish Protopterus has innervated neuroendocrine cells in the pneumatic duct region. In Polypterus and Amia the lungs have neuroendocrine cells that are apparently not innervated. Two types of neuroendocrine cells are found in the gill of teleost fishes. These cells are very different by their location, structure and immunohistochemistry. Advanced studies on functional morphology of neuroendocrine cells in fish airways are still necessary to increase our understanding of their multifunctional role in the gill area. Microsc. Res. Tech. 37:4–12, 1997. © 1997 Wiley‐Liss, Inc.

Abstract:The oocytes of the abyssal Teleost, Hoplostethus mediterraneus were studied. Four stages of growth were observed and the oocytes of all the stages were surrounded by follicular cells and had several nucleoli in the nucleus. In the oocytes of the II° stage, vacuoles without contents, in oocytes of the III° stage several vacuoles with a basophilic contents and small yolk globules were identified. General and basic proteins, ribonucleoproteins, acid proteoglycans with -COOH groups were recognized in the cytoplasm, in the nucleoli of oocytes in the II° stage and in the vacuolar contents of oocytes in the III° stage. In the follicular cells, in the pellucid zone, in the yolk globules, from their beginning, glycoproteins were present. Positivity, for all lectins used, was revealed in the follicular cells and in the four stages of oocytes growth. α-D-glucose and α-D-mannose binding sites were in the pellucid zone and in the initial yolk globules. In the lather galactose and β-N-acetyl glucosamine were present too. nNOS and VIP immunopositivity revealed at the periphery of the cytoplasm and at network of nerve fibres between oocytes, suggests NO is involved in a mechanism of regulation of the gametogenesis and of the spawning.

SummaryThe presence of calbindin D28K in fish (Heteropneustes fossilis) gill was studied by use of specific antibodies raised against chick duodenal 28 kD a calbindin in immunoperoxidase and electron-microscopic labelling experiments. Immunoreactivity for calbindin D28K, which has been observed in the intestine of a number of avian and mammalian species, is reported for the first time in the gill. It was primarily located in neuroendocrine (NE) cells. Some immunoreactivity was also located in the glycocalyx of the non-endocrine cells, i.e., the pavement cells, which have ultrastructural characteristics quite different from those of endocrine cells.The calbindin-immunopositive NE cells were ascertained in both gill filamental and lamellar epithelium. All the NE cells contained secretory granules as the most distinc tive feature of these cells. Ultrastructurally, two types of NE cells were distinguished according to the morphology of their secretory granules.The calbindin immunoreactivity in the NE cells was stimulated when the calcium concentration of the ambient water was rcduccd. The present findings suggest that NE