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Journal ArticleDOI

Thyrotrophin in the pars tuberalis triggers photoperiodic response

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TLDR
Two waves of gene expression are identified in the quail MBH associated with the initiation of photoinduced secretion of luteinizing hormone and increased TSH in the pars tuberalis seems to trigger long-day photoinduced seasonal breeding.
Abstract
Molecular mechanisms regulating animal seasonal breeding in response to changing photoperiod are not well understood. Rapid induction of gene expression of thyroid-hormone-activating enzyme (type 2 deiodinase, DIO2) in the mediobasal hypothalamus (MBH) of the Japanese quail (Coturnix japonica) is the earliest event yet recorded in the photoperiodic signal transduction pathway. Here we show cascades of gene expression in the quail MBH associated with the initiation of photoinduced secretion of luteinizing hormone. We identified two waves of gene expression. The first was initiated about 14 h after dawn of the first long day and included increased thyrotrophin (TSH) beta-subunit expression in the pars tuberalis; the second occurred approximately 4 h later and included increased expression of DIO2. Intracerebroventricular (ICV) administration of TSH to short-day quail stimulated gonadal growth and expression of DIO2 which was shown to be mediated through a TSH receptor-cyclic AMP (cAMP) signalling pathway. Increased TSH in the pars tuberalis therefore seems to trigger long-day photoinduced seasonal breeding.

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Citations
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Journal ArticleDOI

Photoperiodic induction without light-mediated circadian entrainment in a High Arctic resident bird

TL;DR: Data show that the Svalbard ptarmigan does not require circadian entrainment to develop a photoperiodic response involving conserved molecular elements found in temperate species, and is likely to maintain seasonal synchrony in polar regions.
Journal ArticleDOI

Multisensory Non-photoperiodic Cue Advances the Onset of Seasonal Breeding in Island Canaries (Serinus canaria)

TL;DR: It is found that direct exposure of the birds to fresh green vegetation represented the strongest stimulus and advanced breeding by up to 2 months compared to controls, and single non-photoperiodic sensory cues are insufficient to affect the timing of seasonal breeding.
Book ChapterDOI

Arcuate nucleus, median eminence, and hypophysial pars tuberalis.

TL;DR: The arcuate nucleus (ARC) is located in the mediobasal hypothalamus and forms a morphological and functional entity with the median eminence (ME), the ARC-ME as discussed by the authors.
Journal ArticleDOI

Alternation between short- and long photoperiod reveals hypothalamic gene regulation linked to seasonal body weight changes in Djungarian hamsters (Phodopus sungorus)

TL;DR: The data suggest that body weight regulation appears to be tightly linked to a co‐ordinated regulation of several genes in the hypothalamus, including those involved in thyroid hormone metabolism.
Journal ArticleDOI

Opportunism, photoperiodism, and puberty: Different mechanisms or variations on a theme?

TL;DR: Understanding the mechanisms regulating avian puberty and seasonal breeding might in some cases provide greater insight into the mechanistic control of puberty in nonrodent mammals.
References
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Journal ArticleDOI

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Journal ArticleDOI

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Journal ArticleDOI

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Journal ArticleDOI

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