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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 119 (1971), S. 208-226 
    ISSN: 1432-0878
    Keywords: Median eminence ; Hypophysial portal vessels ; Pars distalis ; Ultrastructure ; Development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Nerve fibres containing granular vesicles first appear in the median eminence of the rat on the 16th foetal day while secretory granules in the cells of the adenohypophysis are not present till the 17th foetal day. These observations suggest that the differentiation and early activity of pars distalis cells may depend on substances elaborated at nerve terminals in the median eminence. Although the loops of the primary plexus of portal vessels do not develop until the 4th postnatal day, substances released by nerve fibres in the neurohypophysis could reach the pars distalis through vessels already present at the 15th foetal day in the mesenchyme between the diencephalon and the adenohypophysis. This view is supported by the fact that the earliest cells to exhibit ultrastructural evidence of secretory activity are in the rostral pole of the pars distalis, the first region of the gland to become vascularized. The earliest granules to appear in the cells of the pars distalis correspond to those which are considered to contain mucoprotein hormones; somatotrophin type granules were seen only in postnatal tissues. The finding that, in the median eminence, the development of granular vesicles precedes that of agranular vesicles is discussed with reference to the times at which neurosecretory materials and monoamines become detectable in the region.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 152 (1974), S. 493-512 
    ISSN: 1432-0878
    Keywords: Median eminence ; 6-Hydroxydopamine ; Fluorescence ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The extent of degeneration and regeneration of catecholamine-containing nerve fibres in the external layer of the median eminence of the rat has been assessed following treatment with 6-OHDA. Ultrastructural and fluorescence histochemical evidence suggests that nerve terminal degeneration occurs in the external layer of the caudal regions of the median eminence, including the anatomical stem, following intravenous injection of 6-OHDA in a dose of 100 mg/kg. No degeneration in the external layer of the median eminence was observed when the drug was given as sequential intracisternal injections to adult rats or neonatal rats by subcutaneous injections. The fluorescence histochemical studies suggest that regeneration of catecholamine-containing neurons is substantially complete within three weeks of treatment with intravenous 6-OHDA.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 104 (1970), S. 541-556 
    ISSN: 1432-0878
    Keywords: Median eminence ; Rat ; Monoamine fluorescence ; Output of pars distalis hormones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The distribution of monoamines in the median eminence of foetal, neonatal and adult rats has been studied with the Falck-Hillarp fluorescence histochemical technique in preparations in which the hypothalamus and pituitary gland were in continuity. In adult rats monoamine fluorescence is present throughout the median eminence, including the anatomical stem. In foetal rats a few sagittally-directed varicose fluorescent fibres are seen in the median eminence. In neonatal rats palisade layer fluorescence in appreciable amounts is first seen on the fourth day in the region of the anatomical stem. By the eighth day it has spread throughout the palisade layer of the entire median eminence, and by the end of the third week it has attained adult intensity. The appearance of monoamines in the median eminence, the development of a functional hypophysial portal system, and a changing pattern of development of function in both the hypothalamo-pituitary-adrenal and hypothalamo-pituitary-thyroid axes thus all appear to be contemporaneous events. It is suggested that the monoamines of the median eminence represent part of a neural system influencing the output of pars distalis hormones, in particular of ACTH and TSH secretion.
    Type of Medium: Electronic Resource
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