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  • 1
    ISSN: 1432-0878
    Keywords: Pituitary ; Teleost ; GTH-cells ; Innervation ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In the male black molly, Poecilia latipinna, morphological and functional aspects of the gonadotropic (GTH-)cells have been studied at the ultrastructural level. The cells exclusively occupy the ventral and lateral areas of the meso-adenohypophysis. In the black molly there is evidence of the presence of only one type of gonadotropic cell. In the GTH-cells of most specimens, the rough endoplasmic reticulum is weakly developed. The secretory vesicles are characterized by cores with varying diameters; this variation was not observed in the secretory vesicles of the other types of pituitary cells, except in the TSH-cells. After applying a histochemical method for the demonstration of polysaccharides, small black deposits appear in the core of the secretory vesicles of the GTH and TSH-cells only; this indicates the glycoproteinaceous nature of the hormones produced in these cells. Male black mollies treated with methyl-testosterone have significantly smaller GTH-cells and a lesser number of secretory vesicles and mitochondria in these cells. GTH-cell activity in Poeciliinae may be thus influenced by androgens by means of a negative feed-back mechanism. The GTH-cells are innervated by both type A and type B neurosecretory fibres. There are indications that the type A fibres may originate from the pars lateralis cells of the nucleus lateralis tuberis; the origin of the type B fibres is uncertain.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0878
    Keywords: Pituitary salmonids ; GTH-cells ; Ultrastructure ; Ovariectomy ; Radioimmunoassay
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Among the cells of the pituitary generally believed to produce glycoprotein gonadotropin (GTH) five forms were distinguished, based on the amount and the diameter of granules and globules and the appearance of the rough endoplasmic reticulum. In sham-operated trout so-called “globular” cells predominated, whereas after ovariectomy these were replaced by so-called “cisternal” cells, suggesting that both belong to one GTH-cell type. In addition, ovariectomy caused a strong increase in plasma GTH-levels. This indicates that the transition from globular to cisternal cells is accompanied by extrusion of GTH, and thus points to a storage of GTH in the granules and globules. It is argued that one of the five forms has the morphological characteristics of thyrotropic cells and may not produce glycoprotein GTH.
    Type of Medium: Electronic Resource
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