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Abstract
The folliculostellate cells of the mammalian pituitary are non-endocrine cells that are implicated in long-distance communication and paracrine signaling, but to date, these cells have yet to be characterized in teleosts. We found that the stellate cells of the teleost pituitary share many common attributes with mammalian folliculostellate cells. By labeling of stellate cells in live preparations of tilapia pituitaries we investigated their distribution, association with other endocrine cells and their anatomical and functional coupling. In the pars intermedia, stellate cells were arranged around neuronal bundles and their processes extended into the pars distalis. Within the pars distalis, stellate cells formed close associations with FSH cells and, to a lesser degree, with GH and LH cells, suggesting differential paracrine regulation of the two gonadotrope populations. The production of follistatin by stellate cells further corroborates the notion of a paracrine role on FSH release. We also found stellate cells to form gap junctions that enabled dye transfer to neighboring stellate cells, implicating that these cells form a large-scale network that connects distant parts of the pituitary. Our findings represent the first wide-scale study of stellate cells in teleosts and provide valuable information regarding their functional roles in pituitary function.
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Abstract
MicroRNAs (miRNAs) are transcriptional and posttranscriptional regulators involved in nearly all known biological processes in distant eukaryotic clades. Their discovery and functional characterization have broadened our understanding of biological regulatory mechanisms in animals and plants. They show both evolutionary conserved and unique features across Metazoa. Here, we present the current status of the knowledge about the role of miRNA in development, growth, and physiology of teleost fishes, in comparison to other vertebrates. Infraclass Teleostei is the most abundant group among vertebrate lineage. Fish are an important component of aquatic ecosystems and human life, being the prolific source of animal proteins worldwide and a vertebrate model for biomedical research. We review miRNA biogenesis, regulation, modifications, and mechanisms of action. Specific sections are devoted to the role of miRNA in teleost development, organogenesis, tissue differentiation, growth, regeneration, reproduction, endocrine system, and responses to environmental stimuli. Each section discusses gaps in the current knowledge and pinpoints the future directions of research on miRNA in teleosts.
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Affiliation(s)
| | - Igor Babiak
- Faculty of Aquaculture and Biosciences, University of Nordland, Bodø, Norway
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Chiba A, Oka S, Honma Y, Ishiyama M. Ultrastructure of the agranular cells in the adenohypophysis of the South American lungfish, Lepidosiren paradoxa. J Morphol 1991; 207:73-79. [PMID: 29865500 DOI: 10.1002/jmor.1052070109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Light and electron microscopic examination demonstrated two types of non-endocrine agranular cells, cavity boundary cells and stellate cells, in the adenohypophysis of the South American lungfish, Lepidosiren paradoxa. The cavity boundary cells line the hypophyseal cleft and diverticulum and display few microvilli, occasional cilia, prominent junctional complexes, and many cytoplasmic microfilaments. The stellate cells are scattered in the glandular parenchyma and are devoid of microvilli and cilia. When adjacent, they are connected to one another by desmosomes. Pinocytotic vesicles or caveolae are frequently seen along the plasma membrane of the agranular cells adjoining the endocrine cells or abutting on the basement membrane. Possible roles of the agranular cells, physically and metabolically supportive functions, are discussed on the basis of their ultrastractural features.
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Affiliation(s)
- Akira Chiba
- Department of Biology, School of Dentistry at Niigata, Nippon Dental University, Niigata 951, Japan
| | - Shunya Oka
- Department of Biology, School of Dentistry at Niigata, Nippon Dental University, Niigata 951, Japan
| | - Yoshiharu Honma
- Sado Marine Biological Station, Faculty of Science, Niigata University, Niigata 952-21, Japan
| | - Mikio Ishiyama
- Department of Oral Histology, School of Dentistry at Niigata, Nippon Dental University, Niigata 951, Japan
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Harrisson F. Facts and hypotheses concerning the function of non-granulated cells in the adenohypophysis of vertebrates. Bioessays 1988; 8:168-71. [PMID: 3044359 DOI: 10.1002/bies.950080511] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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Young G, Ball JN. Ultrastructural changes in the adenohypophysis during the ovarian cycle of the viviparous teleost Poecilia latipinna. III. The growth hormone, adrenocorticotrophic, and prolactin cells and the pars intermedia. Gen Comp Endocrinol 1983; 52:86-101. [PMID: 6313471 DOI: 10.1016/0016-6480(83)90161-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
During the monthly cycle of vitellogenesis, intraovarian gestation, and parturition, the pituitary growth hormone (GH) cells show ultrastructural changes indicative of an increase in secretory activity related to vitellogenesis. In contrast, the pituitary adrenocorticotrophic (ACTH) cells are relatively inactive during vitellogenesis, but become active during late pregnancy in the few days before parturition. The prolactin cells and the two cell types of the pars intermedia do not appear to change their secretory activity during the cycle. In discussing these findings it is suggested that GH may play a metabolic role related to vitellogenesis, and that corticosteroids, secreted in response to elevated output of ACTH, may facilitate follicular rupture and/or the expulsion of the brood at the end of pregnancy.
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Wright GM. Ultrastructure of the adenohypophysis in the larval anadromous sea lamprey, Petromyzon marinus L. J Morphol 1983; 176:325-39. [PMID: 6887260 DOI: 10.1002/jmor.1051760306] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The ultrastructure of the adenohypophysis (AH) in the larval anadromous sea lamprey, Petromyzon marinus L., was examined. The AH is subdivided into three regions, the pro-, meso-, and meta-AH. Cells of the nasopharyngeal stalk extend directly beneath the pro- and meso-AH to form the ventral surface of the gland. Some cells in the pro- and meso-AH are arranged into small follicles. Each region of the AH is characterized by a single granulated (secretory) cell type. Granulated cells constitute 80-90% of the pro-AH and contain secretory granules that range from 800 to 2400 A in diameter. Only 10-20% of the cells in the meso-AH are granulated and they contain much smaller secretory granules (400 to 1250 A diameter) than those in the pro-AH. Granulated cells constitute 80-90% of the meta-AH and contain only a few secretory granules, ranging from 1000 to 2500 A in diameter, and many vesicles containing either a loose flocculent or dense granular material. Non-granulated (stellate) cells are found in all regions. They are characterized by their long cell processes, abundant cytoplasmic filaments, and variable electron density. The appearance of organelles in these cells suggests they are nonsecretory. They may play a role in maintaining the structural integrity of the gland and the regulation of granule release in the pro-AH. Two types of nongranulated cells make up 80-90% of the meso-AH. Type I are stellate cells, type II may be undifferentiated cells. The functional significance of the secretory cells in the larval AH is discussed.
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Dubourg P, Chambolle P, Kah O, Maïza S, Olivereau M. [Ultrastructure of prolactin cells and survival of Gambusia sp. (teleost fish) in deionized water enriched in calcium or sodium]. Gen Comp Endocrinol 1983; 50:432-44. [PMID: 6688404 DOI: 10.1016/0016-6480(83)90264-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The ultrastructure of the prolactin (PRL) cells of Gambusia was studied in animals kept in deionized water (EDes) and in EDes supplemented either with Ca2+ (10,2 and 15,3 mM) or with Na+ (10,2 and 15,3 mM). In environments supplemented with CaCl2 the maximal survival was 40 days. The stimulation of PRL cells was similar to that described in EDes. On the contrary, in environments supplemented with NaCl, 50% of the animals are still alive after 45 days. PRL cells are slightly stimulated and their ultrastructural aspect is similar to that observed in controls kept in freshwater. The significance of these results is discussed in relation with our present knowledge of the pituitary control of osmoregulation in teleost fish.
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Leatherland JF, Renfree MB. Ultrastructure of the nongranulated cells and morphology of the extracellular spaces in the pars distalis of adult and pouch-young tammar wallabies (Macropus eugenii). Cell Tissue Res 1982; 227:439-50. [PMID: 7151130 DOI: 10.1007/bf00210898] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Differentiated nongranulated (folliculo-stellate) cells were observed in the centre and periphery of the cords of cells in the pars distalis of the adult tammar wallaby (Macropus eugenii). The nongranulated cells formed follicles containing a small lumen: the cell apices were joined by junctional complexes including zonulae adhaerentes and maculae adhaerentes (desmosomes). Follicles of granulated cells were also occasionally found. Follicles were rarely observed in the adult, but were numerous and generally larger in pouch-young wallabies. Moreover, whereas the involvement of granulated cells in the follicles of the adult was infrequent, they were common components of follicular structures in the pouch-young. The marginal cells at the periphery of the pars distalis in contact with the hypophysial cleft had many of the cytological characteristics of the nongranulated cells in the central pars distalis. In both adult and pouch-young wallabies, nongranulated cells at the periphery of the cell cords were juxtaposed such that they formed "sinusoid-like" spaces or lacunae, presumably as part of the extravascular channel system. The observations are discussed in light of the proposed phagocytotic, metabolite and/or hormone transport and "stem cell" roles attributed to these cells.
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Nunez EA, Gershon MD. Phasic secretion by follicular cells of the bat adenohypophysis during the prearousal period of their annual life cycle. THE AMERICAN JOURNAL OF ANATOMY 1982; 165:111-20. [PMID: 7148727 DOI: 10.1002/aja.1001650203] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The fine structure of the follicular (nongranulated) cells of the adenohypophysis of the bat was examined at different periods of the annual life cycle. Follicular cells were found in all regions of the pars distalis of both active and hibernating bats. Throughout the active phase of the life cycle and during most of the hibernating period, the structure of follicular cells is unchanged. Toward the end of hibernation, however, striking ultrastructural changes occur. The most obvious of these alterations is the appearance in follicles of dense rod-shaped bodies within the follicular luminal space. Just prior to arousal, the rodlike bodies become much wider and appear more as paracrystalline aggregates of dense material. Images indicate that the dense rod-shaped bodies are packaged in vesicles in the cytoplasm of the follicular cells. The fusion of the membrane of filled vesicles with the plasma membrane of the follicular cell results in the release of their dense rod-shaped bodies into the follicular lumen by exocytosis. These cyclic ultrastructural changes indicate that follicular cells have a phasic secretory activity.
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Betchaku T, Douglas WW. Cellular composition of the rostral pars distalis of the anterior pituitary gland of the alewife, Alosa pseudoharengus, during the spawning run. Anat Rec (Hoboken) 1981; 199:403-21. [PMID: 6266281 DOI: 10.1002/ar.1091990309] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The rostral pars distalis of the anterior pituitary gland of the marine alewife, Alosa pseudoharengus, during its annual spawning run to fresh water was examined histologically. The rostral pars distalis is composed of many interconnecting follicles of various sizes. Contrary to earlier reports, the follicular epithelium contains not only prolactin (PRL) cells but corticotropic (ACTH) cell and thyrotropic (TSH) cells (in addition to two nonendocrine cell types). Basally all three endocrine cell types make direct contact with the basement membrane which separates the follicles from the neurohypophysial processes. Apically, however, only the prolactin cells, the largest of the three, protrude into the follicular lumen by means of the small ciliated apical protruberance. All other cellular elements are sealed from the follicular lumen by a layer of covering cells which have properties of transitional epithelial cells. In the follicular epithelium, the slender TSH cells are intercalated between the large conspicuous prolactin cells. The ACTH cells, the smallest of the three endocrine cells, lie in deep invaginations in the basal regions of the individual PRL cells in such a way that on cursory examination they can be mistaken for the nuclei of the latter. Only a small portion of the cellular surface of the ACTH cell escapes the enveloping prolactin cell to make contact with the basement membrane of the follicle. In teleosts, prolactin, ACTH, and TSH have all been implicated in the regulation of hydromineral metabolism and reproductive development. The intimate spatial relation between the three endocrine cells in the alewife rostral pars distalis thus raises the possibility of some functional interactions at the adenohypophysial level, perhaps as an adaptation of this anadromous teleost whose reproductive development and behavior is associated with large changes in ambient salinity. The functional significance of the follicular lumen is discussed together with possible sensory functions of the PRL cells.
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Girod C, Lhéritier M. [Ultrastructure of folliculo-stellar cells in the hypophyseal pars distalis of the rock squirrel (Citellus variegatus Erxleben), the dormouse (Graphiurus murinus Desmaret), and the hedgehog (Erinaceus europaeus Linnaeus)]. Gen Comp Endocrinol 1981; 43:105-22. [PMID: 6260566 DOI: 10.1016/0016-6480(81)90037-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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12
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Dubourg P, Chambolle P, Olivereau M, Kah O. [Ultrastructure of prolactin cells of Gambusia (teleost fish) in fresh water, deionized water and hypersaline medium]. Gen Comp Endocrinol 1980; 41:554-62. [PMID: 6893313 DOI: 10.1016/0016-6480(80)90061-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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Rawdon BB. Ultrastructure of the Non-granulated Hypophysial Cells in the TeleostPseudocrenilabrus philander (Hemihaplochromis philander), with Particular Reference to Cytological Changes in Culture. ACTA ZOOL-STOCKHOLM 1978. [DOI: 10.1111/j.1463-6395.1978.tb00108.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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