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  • 1
    Online Resource
    Online Resource
    Influence of Pinealectomy and Pineal Stalk Deflection on Circadian Gastrointestinal Tract Melatonin Rhythms in Zebra Finches ( Taeniopygia guttata )
    SAGE Publications ; 1999
    In:  Journal of Biological Rhythms Vol. 14, No. 3 ( 1999-06), p. 185-189
    Details
    In: Journal of Biological Rhythms, SAGE Publications, Vol. 14, No. 3 ( 1999-06), p. 185-189
    Abstract: The authors examined levels of melatonin in the plasma and various tissues in intact, pinealectomized, and pineal stalk–deflected zebra finches kept under 12:12 LD to determine if the melatonin found in the gastrointestinal tract is secreted in a circadian manner. In intact and pineal stalk-deflected birds, there is a clear day-night rhythm in melatonin content of the plasma, pineal gland, eyes, proventriculus, crop, duodenum, jejunum/ileum, colon, heart, and liver. In contrast, pinealectomy abolished the day-night rhythm. These results indicate that most of the melatonin present in the gastrointestinal tract of zebra finches is of pineal origin. However, some melatonin remained. This suggests that this melatonin may be locally synthesized and has paracrine and/or autocrine functions. Nonetheless, the results do not lend support to the contention that this putative melatonin secretion by the gastrointestinal tract is circadian.
    Type of Medium: Online Resource
    ISSN: 0748-7304 , 1552-4531
    URL: Article
    DOI: 10.1177/074873099129000588
    Language: English
    Publisher: SAGE Publications
    Publication Date: 1999
    detail.hit.zdb_id: 2018064-0
    SSG: 12
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  • 2
    Online Resource
    Online Resource
    Seasonal neuroplasticity in the songbird telencephalon: A role for melatonin
    Proceedings of the National Academy of Sciences ; 1999
    In:  Proceedings of the National Academy of Sciences Vol. 96, No. 8 ( 1999-04-13), p. 4674-4679
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 96, No. 8 ( 1999-04-13), p. 4674-4679
    Abstract: Neuroplasticity in the vocal control system of songbirds is strongly influenced by seasonal fluctuations in circulating testosterone. These seasonally plastic telencephalic structures are implicated in the learning and production of song in songbirds. The role of the indoleamine melatonin in seasonal adaptations in birds has remained unclear. In this experiment, European starlings were castrated to remove the neuromodulating activity of gonadal steroids and were exposed to different photoperiods to induce reproductive states characteristic of different seasonal conditions. Long days increased the volume of the song-control nucleus high vocal center compared with its volume on short days. Exogenous melatonin attenuated the long-day-induced volumetric increase in high vocal center and also decreased the volume of another song-control nucleus, area X. This effect was observed regardless of reproductive state. To our knowledge, this is the first direct evidence of a role for melatonin in functional plasticity within the central nervous system of vertebrates.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.96.8.4674
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1999
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 3
    Online Resource
    Online Resource
    〉A Highly Rudimentary Circadian Melatonin Profile in a Nocturnal Bird, the Barn Owl (Tyto alba)
    Springer Science and Business Media LLC ; 1998
    In:  The Science of Nature Vol. 85, No. 8 ( 1998-8), p. 402-404
    Details
    In: The Science of Nature, Springer Science and Business Media LLC, Vol. 85, No. 8 ( 1998-8), p. 402-404
    Type of Medium: Online Resource
    ISSN: 0028-1042 , 1432-1904
    URL: Article
    DOI: 10.1007/s001140050523
    RVK:
    TA 1000
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 1998
    detail.hit.zdb_id: 1462930-6
    detail.hit.zdb_id: 2075363-9
    detail.hit.zdb_id: 123257-5
    SSG: 11
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  • 4
    Online Resource
    Online Resource
    Seasonal and Daily Variations in Plasma Melatonin in the High-Arctic Svalbard Ptarmigan ( Lagopus mutus hyperboreus )
    SAGE Publications ; 1999
    In:  Journal of Biological Rhythms Vol. 14, No. 4 ( 1999-08), p. 314-319
    Details
    In: Journal of Biological Rhythms, SAGE Publications, Vol. 14, No. 4 ( 1999-08), p. 314-319
    Abstract: This study presents the daily rhythm of melatonin secretion throughout one year in a bird from the northern hemisphere, the Svalbard ptarmigan ( Lagopus mutus hyperboreus), which lives naturally at 76-80°N. Eight Svalbard ptarmigan were caged outdoors at 70°N and blood sampled throughout one day each month for 13 months. At this latitude, daylight is continuous between May and August, but there is a short period of civil twilight around noon from late November to mid January. There was no daily rhythm in plasma melatonin in May-July. Plasma melatonin levels varied significantly throughout the day in all other months of the year, with the nighttime increase reflecting the duration of darkness. The highest mean plasma concentration occurred at midnight in March (110.1 ± 16.5 pg/ml) and represented the annual peak in estimated daily production. Around the winter solstice, melatonin levels were significantly reduced at noon and elevated during the nearly 18 h of consecutive darkness, and the estimated mean daily production of melatonin was significantly reduced. Thus, at the times of the year characterized by light-dark cycles, melatonin may convey information concerning the length of the day and, therefore, progression of season. The nearly undetectable low melatonin secretion in summer and the reduced amplitude and production in midwinter indicate a flexible circadian system that may reflect an important adaptation to life in the Arctic.
    Type of Medium: Online Resource
    ISSN: 0748-7304 , 1552-4531
    URL: Article
    DOI: 10.1177/074873099129000731
    Language: English
    Publisher: SAGE Publications
    Publication Date: 1999
    detail.hit.zdb_id: 2018064-0
    SSG: 12
    Location Call Number Limitation Availability
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