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Titolo:
EFFECT OF THYROIDECTOMY ON MAINTENANCE OF SEASONAL REPRODUCTIVE SUPPRESSION IN THE EWE
Autore:
THRUN LA; DAHL GE; EVANS NP; KARSCH FJ;
Indirizzi:
UNIV MICHIGAN,REPROD SCI PROGRAM,DEPT BIOL,300 N INGALLS BLDG,RM 1101SW ANN ARBOR MI 48109 UNIV MICHIGAN,REPROD SCI PROGRAM,DEPT BIOL ANN ARBOR MI 48109 UNIV MICHIGAN,DEPT PHYSIOL,REPROD SCI PROGRAM ANN ARBOR MI 48109
Titolo Testata:
Biology of reproduction
fascicolo: 4, volume: 56, anno: 1997,
pagine: 1035 - 1040
SICI:
0006-3363(1997)56:4<1035:EOTOMO>2.0.ZU;2-L
Fonte:
ISI
Lingua:
ENG
Soggetto:
GONADOTROPIN-RELEASING-HORMONE; NEGATIVE FEEDBACK ACTION; LUTEINIZING-HORMONE; BREEDING-SEASON; TIMING ONSET; SECRETION; SHEEP; RHYTHM; GLAND; PHOTOREFRACTORINESS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
35
Recensione:
Indirizzi per estratti:
Citazione:
L.A. Thrun et al., "EFFECT OF THYROIDECTOMY ON MAINTENANCE OF SEASONAL REPRODUCTIVE SUPPRESSION IN THE EWE", Biology of reproduction, 56(4), 1997, pp. 1035-1040

Abstract

Thyroid hormones are essential to end the breeding season in sheep; however, it is not clear whether thyroid hormone action is limited to initiation of seasonal reproductive suppression in the ewe, The purposeof this study was to determine the influence of thyroid hormones on maintenance of anestrus and onset of the subsequent breeding season in the ewe. In both experiments, ewes were thyroidectomized (THX) either soon after they had completed the transition from the breeding season to anestrus or just before the transition into the breeding season (late anestrus), All ewes were ovariectomized and received constant-release silicone elastomer implants of estradiol, Circulating levels of LH were monitored as an index of seasonal changes in reproductive neuroendocrine activity, After thyroidectomy early in anestrus, timing of thesubsequent LH rise, indicative of the next neuroendocrine breeding season, was the same among THX and thyroid-intact ewes, As observed previously, LH remained elevated in ewes THX late in anestrus beyond the time associated with development of anestrus, We conclude therefore that thyroid hormones are not needed to maintain suppression of the reproductive neuroendocrine axis once anestrus has been established, nor dothey influence the onset of the subsequent breeding season in the ewe, Rather, thyroid hormone action on seasonal alterations of the reproductive neuroendocrine axis in the ewe is restricted to the changes that cause development of anestrus.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 02/12/20 alle ore 07:52:12