Further immunocytochemical analysis of the neuroblasts with SRIF-like immunoreactivity (ir) was carried out on the chick embryo medulla and pons. 5 or 100 microns rombencephalon sections were obtained from 60 White Leghorn chick embryos at stages (E = Embryonic days) ranging from E4 1/2 to E18 and incubated with rabbit polyclonal antibodies against synthetic cyclic Somatostatin-14, according to PAP-DAB technique. In the medulla and pons the ir appeared as from E12. From E12 to E13 1/2-E14 the ir distribution gradually changed. From E14 to E18 numbers and spatial arrangement of the positive neuroblast groups did not show substantial changes; in these respects the ir distributional pattern proved to be markedly different from the one observed by the Authors in adult animals. Moreover, from E13 to E15 the positive neuroblast density appeared to be higher than that of positive neurons in adults. These results are consistent with a possible SRIF local regulative role.
"To date, most studies have focussed on changes at the peripheral level – plasma hormone concentrations or in vitro deiodinase activities (Thommes & Hylka 1977, Hylka et al. 1986, Galton & Hiebert 1987, Darras et al. 1992). Data on the ontogenetic appearance of hypothalamic factors in the chicken brain are, however, restricted to immunocytochemical studies (corticotropin-releasing hormone (CRH): Josza et al. 1986; TRH: Thommes et al. 1985; SRIH: Ambrosi et al. 1992). Accordingly, this paper describes the ontogenetic profile of hypothalamic TRH and SRIH concentrations during chick embryo development and posthatch growth. "
[Show abstract][Hide abstract] ABSTRACT: Thyrotropin-releasing hormone (TRH) and somatostatin (SRIH) concentrations were determined by RIA during both embryonic development and posthatch growth of the chicken. Both TRH and SRIH were already detectable in hypothalami of 14-day-old embryos (E14). Towards the end of incubation, hypothalamic TRH levels increased progressively, followed by a further increase in newly hatched fowl. SRIH concentrations remained stable from E14 to E17 and doubled between E17 and E18 to a concentration which was observed up to hatching. Plasma GH levels remained low during embryonic development, ending in a steep increase at hatching. Plasma TSH levels on the other hand decreased during the last week of the incubation. During growth, TRH concentrations further increased, whereas SRIH concentrations fell progressively towards those of adult animals. Plasma TSH levels increased threefold up to adulthood; the rise in plasma GH levels during growth was followed by a drop in adults. In conclusion, the present report shows that important changes occur in the hypothalamic TRH and SRIH concentration during both embryonic development and posthatch growth of the chicken. Since TRH and SRIH control GH and TSH release in the chicken, the hypothalamic data are compared with plasma GH and TSH fluctuations.
Journal of Endocrinology 12/1998; 159(2):219-25. · 3.72 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The development of somatostatin-immunoreactive neurons and fibres was studied, using immunocytochemistry, in the brain of the brown trout. Somatostatinergic perikarya were found in many regions including several telencephalic areas, the preoptic nucleus, anterior tuberal and lateral tuberal nuclei, the lateral recess nucleus, dorsal tuberal nucleus, the pre- and pseudoglomerular nuclei, central thalamic nucleus, optic tectum, interpeduncular nucleus, several isthmal and reticular nuclei and the solitary fascicle nucleus. The ventrolateral area of the telencephalon and the nucleus lateralis tuberis are the first immunoreactive nuclei to appear in ontogeny, and cells of some telencephalic areas and of the lateral optic recess nucleus, the latest. Somatostatin-immunoreactive fibre tracts innervate the hypophysis and different regions of the brain. The most richly innervated areas in adults are the dorsolateral telencephalic area and the organon vasculosum laminae terminalis. Two patterns of production of somatostatinergic cells were observed: that of populations in which cell numbers increase over the lifetime of the fish, and that of populations whose cell number is established early in development or even diminishes in adulthood. These results provide interesting contrasts to those previously reported in birds and mammals.
Anatomy and Embryology 03/1995; 191(2):119-37. DOI:10.1007/BF00186784 · 1.39 Impact Factor
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