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dc.contributor.advisorBenson, Bryanten_US
dc.contributor.authorHAUSER, URSULA ESTHER.
dc.creatorHAUSER, URSULA ESTHER.en_US
dc.date.accessioned2011-10-31T16:51:59Z
dc.date.available2011-10-31T16:51:59Z
dc.date.issued1986en_US
dc.identifier.urihttp://hdl.handle.net/10150/183862
dc.description.abstractFemale golden Syrian hamsters are seasonally breeding animals, capable of maintaining continuous estrous cycles when the daylength is 12.5 hrs. or longer. In shorter photoperiod (SP) the ovaries of anovulatory animals are characterized by few small growing follicles, an absence of corpora lutea and extensive hypertrophied interstitium. Steroid-histochemical studies revealed that enzymes related to steroidogenesis show intense activity in the interstitial tissue of SP-exposed animals. The major objectives of these studies were to examine SP-induced hormonal and ovarian changes which occur prior to onset of the acyclic condition in inbred LSH/SsLak hamsters. Other experiments explored hormonal changes in the absence of ovarian hormones and the interaction of SP and steroids. Initial results revealed that the LSH/SsLak hamster ceased estrous cyclicity between 14 and 31 days of SP exposure, a response far more uniform than generally seen in outbred hamsters. Experiments carried out in SP-exposed cyclic animals indicated that the secondary FSH surge and follicular recruitment were not affected by SP treatment, follicular recruitment were not affected by SP treatment, and that no major changes in gonadotropin levels and ovarian steroids were present on individual days of the estrous cycle. Once the animals were anestrous, daily gonadotropin surges were present and pituitary gonadotropin contents increases. Serum PRL levels showed a slight, yet significant, decrease in SP cycling animals followed by a further reduction in pituitary and serum levels after animals ceased cycling. Medial basal hypothalamic LHRH contents did change in SP, yet there was a significant increase in the preoptic area, and LHRH became significantly elevated in both areas after the animals became anestrous. Ovarian histology revealed fewer corpora lutea and a slight shift from healthy to atretic antral follicles. Experiments carried out in ovariectomized SP-treated animals showed that serum gonadotropin levels were significantly reduced, and that estrogen treatment was either equally or less effective in reducing levels in SP animals. In contrast, PRL levels did not change and responded in a dose dependent way to estrogen treatment. Although the studies yielded no definite proof, the result suggest that SP impairs the maintenance of follicular growth leading eventually to the acyclic state.
dc.language.isoenen_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.subjectHamsters -- Fertility.en_US
dc.subjectPhotoperiodism.en_US
dc.subjectLight -- Physiological effect.en_US
dc.titlePHOTOPERIODIC REGULATION OF THE FEMALE REPRODUCTIVE SYSTEM IN THE SYRIAN HAMSTER (OVARY, PINEAL, HORMONES, PITUITARY).en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.identifier.oclc697650128en_US
thesis.degree.grantorUniversity of Arizonaen_US
thesis.degree.leveldoctoralen_US
dc.contributor.committeememberKrutzsch, Philip H.en_US
dc.contributor.committeememberBlask, David E.en_US
dc.contributor.committeememberLeadem, Christopher A.en_US
dc.identifier.proquest8623851en_US
thesis.degree.disciplineAnatomyen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.namePh.D.en_US
refterms.dateFOA2018-06-23T02:06:22Z
html.description.abstractFemale golden Syrian hamsters are seasonally breeding animals, capable of maintaining continuous estrous cycles when the daylength is 12.5 hrs. or longer. In shorter photoperiod (SP) the ovaries of anovulatory animals are characterized by few small growing follicles, an absence of corpora lutea and extensive hypertrophied interstitium. Steroid-histochemical studies revealed that enzymes related to steroidogenesis show intense activity in the interstitial tissue of SP-exposed animals. The major objectives of these studies were to examine SP-induced hormonal and ovarian changes which occur prior to onset of the acyclic condition in inbred LSH/SsLak hamsters. Other experiments explored hormonal changes in the absence of ovarian hormones and the interaction of SP and steroids. Initial results revealed that the LSH/SsLak hamster ceased estrous cyclicity between 14 and 31 days of SP exposure, a response far more uniform than generally seen in outbred hamsters. Experiments carried out in SP-exposed cyclic animals indicated that the secondary FSH surge and follicular recruitment were not affected by SP treatment, follicular recruitment were not affected by SP treatment, and that no major changes in gonadotropin levels and ovarian steroids were present on individual days of the estrous cycle. Once the animals were anestrous, daily gonadotropin surges were present and pituitary gonadotropin contents increases. Serum PRL levels showed a slight, yet significant, decrease in SP cycling animals followed by a further reduction in pituitary and serum levels after animals ceased cycling. Medial basal hypothalamic LHRH contents did change in SP, yet there was a significant increase in the preoptic area, and LHRH became significantly elevated in both areas after the animals became anestrous. Ovarian histology revealed fewer corpora lutea and a slight shift from healthy to atretic antral follicles. Experiments carried out in ovariectomized SP-treated animals showed that serum gonadotropin levels were significantly reduced, and that estrogen treatment was either equally or less effective in reducing levels in SP animals. In contrast, PRL levels did not change and responded in a dose dependent way to estrogen treatment. Although the studies yielded no definite proof, the result suggest that SP impairs the maintenance of follicular growth leading eventually to the acyclic state.


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