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  • 1
    Electronic Resource
    Electronic Resource
    Changes in Basal Hypothalamic Chicken Gonadotropin-Releasing Hormone-I and Vasoactive Intestinal Polypeptide Associated with a Photo-Induced Cycle in Gonadal Maturation and Prolactin Secretion in Intact and Thyroidectomized Starlings (Sturnus vulgaris) (2002)
    Oxford, UK : Blackwell Science, Ltd
    Journal of neuroendocrinology 14 (2002), S. 0 
    Details
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Chicken gonadotropin-releasing hormone-I (GnRH-I) and the avian prolactin-releasing hormone, vasoactive intestinal polypeptide (VIP), were measured in the basal hypothalamus in male starlings during photo-induced gonadal growth and the subsequent development and maintenance of reproductive photorefractoriness. Comparisons were made with thyroidectomized birds, which maintain breeding condition irrespective of changes in photoperiod. In intact birds, basal hypothalamic GnRH-I increased four-fold after photostimulation and then decreased 115-fold over 12 weeks to values characteristic of long-term photorefractoriness. Pituitary and plasma prolactin increased after photostimulation, reaching peak values when the testes were regressing, and returned to low values in long-term photorefractory birds. Basal hypothalamic VIP did not change after photostimulation in intact birds. In photostimulated thyroidectomized birds, values for basal hypothalamic GnRH-I and VIP, and for pituitary and plasma prolactin, remained no different to those of nonphotostimulated intact birds. These observations confirm that reproductive photorefractoriness is related to a decrease in hypothalamic GnRH-I. However, photorefractoriness in terms of prolactin secretion is not similarly related to a decrease in basal hypothalamic VIP. The mechanisms responsible for the decrease in prolactin in long-term photorefractory birds and for the total lack of photoperiodic responses in thyroidectomized birds remain unresolved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2826.2002.00807.x
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  • 2
    Electronic Resource
    Electronic Resource
    Photoperiodic Control of the Concentration of Luteinizing Hormone, Prolactin and Testosterone in the Male Emu (Dromaius novaehollandiae), a Bird that Breeds on Short Days (2001)
    Oxford, UK : Blackwell Science, Ltd
    Journal of neuroendocrinology 13 (2001), S. 0 
    Details
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The objective of this study was to establish, for a short-day breeding bird, the male emu, whether the breeding season is principally controlled by changes in photoperiod, and to investigate the endocrine mechanisms involved. Two groups of adult males were subjected to three alternating periods of 150–185 days of 14 h light/day (LD) and 10 h light/day (SD) terminating in a 360-day period of LD or SD. Transfer from LD to SD led to increases in plasma concentrations of luteinizing hormone (LH) and testosterone, after 82 ± 8 and 73 ± 3 (SEM) days, and an increase in prolactin concentrations after 115 ± 12 days. Concentrations of LH and testosterone began to decrease before transfer back to LD, at a time when prolactin concentrations were approaching peak values. Transfer from LD to 360 days of SD resulted in increases in LH and testosterone concentrations, and these terminated after an increase in prolactin concentrations. After transfer from SD to 360 days of LD, plasma concentrations of LH and testosterone began to increase, after delays of 222 ± 24 and 225 ± 13 days, and were high at the end of the study, while prolactin values remained depressed throughout. These observations clearly show that seasonal breeding in the emu is directly controlled by changes in photoperiod. The dynamics of the hormonal responses to change of photoperiod suggest that, despite being short-day breeders, the photoregulation of breeding in emus involves mechanisms that are currently accepted for birds, rather than mechanisms that have been proposed for short-day breeding mammals. The initiation of breeding in emus is due to dissipation of photorefractoriness by short days which leads to an increase in the secretion of gonadotrophins to levels that are sufficient to support full reproductive condition. The termination of breeding, while days are still short, is due to the antigonadotrophic action of prolactin which, unusually for birds, increases while the days are still short. In conclusion, breeding activity in male emus is strongly controlled by photoperiod. Emus are short-day breeders, but the central mechanisms that regulate the secretion of reproductive hormones seem to be similar to those previously proposed for long-day breeding birds. The pattern of prolactin secretion in emus suggests an important role for this hormone in the termination of the breeding cycle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2826.2001.00722.x
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  • 3
    Electronic Resource
    Electronic Resource
    Distribution and Regulation by Oestrogen of Fully Processed and Variant Transcripts of Gonadotropin Releasing Hormone I and Gonadotropin Releasing Hormone Receptor mRNAs in the Male Chicken (2001)
    Oxford, UK : Blackwell Science, Ltd
    Journal of neuroendocrinology 13 (2001), S. 0 
    Details
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The aim of this study was to increase understanding of the occurrence and regulation of chicken gonadotropin releasing hormone I (cGnRH I) and chicken gonadotropin releasing hormone receptor (cGnRH-R) mRNA variants in the hypothalamic-pituitary-testicular axis (HPTA). The study was carried out in the cockerel. Fully processed cGnRH I mRNA (cGnRH Ia) and a variant transcript (cGnRH Ib) with a retained intron 1 were observed in the preoptic/anterior hypothalamus (POA), the basal hypothalamus, anterior pituitary gland, and testes. Fully processed cGnRH-R mRNA (cGnRH-Ra) and a variant transcript (cGnRH-Rb) with a deletion were detected in the same tissues. In juvenile cockerels, concentrations of cGnRH Ia and b in the POA increased after castration, and this was prevented by oestrogen treatment. In the anterior pituitary gland, the concentration of cGnRH-Ra increased after castration and this was reversed by oestrogen treatment. In intact adult cockerels, oestrogen treatment depressed plasma luteinizing hormone but did not affect concentrations of cGnRH I and cGnRH-R mRNAs in the POA, basal hypothalamus, and anterior pituitary gland, suggesting that locally produced oestrogen, by aromatization, may exert maximal suppression on cGnRH I and GnRH-R mRNAs. In intact adult cockerels, the concentrations of cGnRH Ia and b in the testis, but not cGnRH-Ra and b, were depressed by oestrogen treatment. It was concluded that fully processed and variant cGnRH I and cGnRH-R mRNAs occur in all components of the HPTA. Oestrogen appears to play a role in the regulation of cGnRH Ia and b in the POA and testes, and of cGnRH-Ra in the POA and anterior pituitary gland.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2826.2001.00587.x
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  • 4
    Electronic Resource
    Electronic Resource
    Identification of hypothalamic nuclei involved in osmoregulation using fos immunocytochemistry in the domestic hen (Gallus domesticus), Ring dove (Streptopelia risoria), Japanese quail (Coturnix japonica) and Zebra finch (Taenopygia guttata) (1995)
    Springer
    Cell & tissue research 282 (1995), S. 351-361 
    Details
    ISSN: 1432-0878
    Keywords: Osmoregulation ; fos immunocytochemistry ; Hypothalamus ; Vasotocin ; Domestic hen Gallus domesticus ; Japanese quail Coturnix japonica ; Ring dove Streptopelia risoria ; Zebra finch, Taenopygia guttata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Domestic hens were injected intraperitoneally with hypertonic or isotonic saline and killed 0.5, 1, 2, 6, 12 and 24 h later. Japanese quail, Ring doves and Zebra finches were treated in the same way and killed 2 h later. Using fos immunocytochemistry, fos-positive cells were visualized in the preoptic-anterior hypothalamus. In all species, two hours after treatment with hypertonic but not with isotonic saline, a prominent cluster of fos-positive cells was seen close to the mid-line, dorsal to the anterior part of the third ventricle, in and around the nucleus commissurae pallii. The cell cluster was associated with the dorsal region of the organum vasculosum laminae terminalis and passed caudo-dorsally above the anterior commissure into the area of the subfornical organ, spreading diffusely into the nucleus septalis medialis and the nucleus dorsomedialis anterior thalami. The maximal expression of c-fos was seen 2 h after treatment with hypertonic saline: weak fos immunoreactive product was seen at 0.5, 1 h and 6 h but not after 12 and 24 h. In all birds, 2 h after treatment with hypertonic but not with isotonic saline, fos-positive cells were also seen in the nucleus paraventricularis and nucleus supraopticus. Double immunocytochemistry in the domestic hen with an antibody to vasotocin showed that these fos-positive cells were classical magnocellular vasotocinergic neurones. This study extends earlier studies in birds using lesioning and electrophysiological techniques to identify the precise cellular localization of the avian “osmoreceptive complex” projected onto a stereotaxic atlas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00319125
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  • 5
    Electronic Resource
    Electronic Resource
    Identification of hypothalamic nuclei involved in osmoregulation using fos immunocytochemistry in the domestic hen (Gallus domesticus), Ring dove (Streptopelia risoria), Japanese quail (Coturnix japonica) and Zebra finch (Taenopygia guttata) (1995)
    Springer
    Cell & tissue research 282 (1995), S. 351-361 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Osmoregulation ; fos immunocytochemistry ; Hypothalamus ; Vasotocin ; Domestic hen Gallus domesticus ; Japanese quail Coturnix japonica ; Ring dove Streptopelia risoria ; Zebra finch ; Taenopygia guttata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Domestic hens were injected intraperitoneally with hypertonic or isotonic saline and killed 0.5, 1, 2, 6, 12 and 24 h later. Japanese quail, Ring doves and Zebra finches were treated in the same way and killed 2 h later. Using fos immunocytochemistry, fos-positive cells were visualized in the preoptic-anterior hypothalamus. In all species, two hours after treatment with hypertonic but not with isotonic saline, a prominent cluster of fos-positive cells was seen close to the mid-line, dorsal to the anterior part of the third ventricle, in and around the nucleus commissurae pallii. The cell cluster was associated with the dorsal region of the organum vasculosum laminae terminalis and passed caudo-dorsally above the anterior commissure into the area of the subfornical organ, spreading diffusely into the nucleus septalis medialis and the nucleus dorsomedialis anterior thalami. The maximal expression of c-fos was seen 2 h after treatment with hypertonic saline: weak fos immunoreactive product was seen at 0.5, 1 h and 6 h but not after 12 and 24 h. In all birds, 2 h after treatment with hypertonic but not with isotonic saline, fos-positive cells were also seen in the nucleus paraventricularis and nucleus supraopticus. Double immunocytochemistry in the domestic hen with an antibody to vasotocin showed that these fos-positive cells were classical magnocellular vasotocinergic neurones. This study extends earlier studies in birds using lesioning and electrophysiological techniques to identify the precise cellular localization of the avian ”osmoreceptive complex” projected onto a stereotaxic atlas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410050486
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    Paper (German National Licenses)
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