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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 153 (1978), S. 23-36 
    ISSN: 1432-0568
    Keywords: Electron microscopy ; Quail embryo ; Rathke's pouch
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Adenohypophyseal region of quail embryo has been examined by electron microscopy from stage 12 to stage 21 of Zacchei (1961). The Seessel's pouch develops prior to the early stages of adenohypophysis formation, then regresses while Rathke's pouch proliferates and differentiates. From Rathke's pouch formation by stage 12 (48 h of incubation) until appearance of the first secretory granules by stage 21 (6 days of incubation), there are no major ultrastructural modifications in adenohypophyseal cells. Mitochondria, Golgi vesicles, polysomic ribosomes, pinocytotic vesicles, and mitotic figures become more numerous while nucleocytoplasmic ratio and the number of ribosomes and lipid droplets decreases. The major change is the appearance of secretory granules by day 6 of incubation. This phenomenon occurs at the same time as in chick embryo, despite an incubation period shorter for quail than for chick. Mitotic figures are mainly distributed near the pouch lumen, while secretory granules are first located in the peripheral cells of the cephalic part ofpars distalis primordium. The hypothetical role of mesenchyme and vascularization is discussed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0568
    Keywords: Adenohypophyseal rudiment ; Follicular cells ; Ultrastructure ; Culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The epithelial rudiment of 4 day-old quail embryo adenohypophysis, cultivated in vitro under conditions allowing glandular differentiation, displays peripheral cells that progressively acquire follicular cell features. They elongate, develop numerous microvilli, junctional complexes, interlocking membranes and bundles of microfilaments. These follicular-like cells derive from peripheral epithelial cells that, in situ, become glandular. These results show that follicular cells can develop from undifferentiated cells. They undergo this pathway of development, in all likelihood, as a result of perturbations in their microenvironment.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0568
    Keywords: Adenohypophyseal rudiment ; Self-differentiation ; Ultrastructure ; Quail
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Isolated epithelial rudiments of 3–4 days quail embryo adenohypophysis were cultivated in vitro. Differentiation of glandular cells occured when culture conditions allowed the formation of explants characterized by the presence of a fibroblastic sheet and of an epithelial roof surrounding a central cavity. Differentiation did not occur when culture conditions did not allow the fibroblastic sheet to be established or resulted in the absence of a cavity. The importance of the explant structure in differentiation is also indicated by the location of glandular cells. In vitro they differentiate near the cavity derived from Rathke's pouch lumen while in situ they first appear at the periphery of the rudiment, near the basement membrane. The results of this study show that the adenohypophyseal primordium can differentiate without any mesenchymal influence. The observed differentiation seems to be correlated with fibroblast-secreted material, and this hypo-thesis is discussed.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Epithelial rudiments of adenohypohysis were removed from chick and quail embryos between days 3 and 5 of development. Chick rudiments were grafted for 11-13 days onto the chorioallantoic membrane of decapitated chick embryo hosts. Quail rudiments were cultivated in vitro for 6 days. Both grafted and cultivated Rathke's pouches differentiated into adenohypophyseal tissue. The adenohypophyseal tissue cultured on chorio-allantoic membrane exhibited cells reacting with the following immune sera: anti-β-(1-24)ACTH, anti-α-(17-39)-ACTH, anti-α-endorphin, anti-β-endorphin and anti-β-LPH, which also gave a positive reaction when applied to adenohypophysis of corresponding age which had differentiated in situ. In situ, corticotrophs were located exclusively in the cephalic lobe of adenohypophysis. Therefore, the differentiation of corticotrophs in the whole graft, i.e., from both cephalic and caudal lobes of Rathke's pouch, showed that the cells of the caudal lobe, or at least some of them, were uncommitted when the rudiment was removed. In vitro, tissue derived from Rathke's pouch contained cells reacting with antibodies to β-(1-24)-ACTH, α-(17-39)-ACTH, and β-LPH, as did adenohypophysis from quail embryos of corresponding age (9-10 days), differentiated in situ. The differentiation of quail Rathke's pouch in vitro corroborates that differentiation can occur without influence from hypothalamus and, moreover, shows that at least some kinds of cells can differentiate without influence exerted by any other encephalic factors, and in the absence of mesenchyme. The question arises whether fibroblastic cells derived from Rathke's pouch cells act as feeder-cells and/or secrete some factors promoting differentiation.
    Additional Material: 25 Ill.
    Type of Medium: Electronic Resource
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