Factors affecting bovine ovarian responsiveness to stimulation by pregnant mare's serum gonadotropin (PMSG) were studied. Initially, the effects of plasma progesterone concentration on the response were considered using a progesterone-releasing intravaginal device (PRID) to provide an artificial source of the hormone. Due to inherent biological variation in vivo, in vitro methods were developed in which cAMP and progesterone production by granulosa cells were measured. Regardless of the size of the follicles from which the cells originated, PMSG stimulated significant cAMP accumulation. Cyclic AMP production was similar between aspirated granulosa cells and those scraped from the follicle wall, between ovaries with and without a corpus luteum from the same animal, and between follicles from animals early ( 10 days) in their estrous cycles. The PMSG failed to stimulate bovine granulosa cells to synthesize significantly more progesterone than untreated cells. Unlike porcine granulosa cells, bovine cells from antral follicles of any size appeared to luteinize spontaneously in culture. / Hormonal changes in the preovulatory follicle were measured using the PMSG/hCG-treated prepubertal gilt as a model. After hCG administration, follicular fluid levels of cAMP peaked at 4 hr followed 24 hr later by a rise in prostaglandins F and E (PGF, PGE) concentrations which peaked near the expected time of ovulation. Indomethacin injection blocked ovulation and the prostaglandin rise, although the inhibition could be reversed by the administration of PGF(,2)(alpha). Temporal changes in estrone, estradiol-17(beta), progesterone, androstenedione, testosterone and 5 (alpha)-dihydrotestosterone were also measured. / In an effort to decrease endogenous levels of inhibin, thereby increasing endogenous FSH and thence follicular development, heifers, ewes and does were actively immunized against porcine follicular fluid or proteinaceous fractions of bovine seminal plasma. In some animals, plasma FSH concentrations were elevated although ovulation rates and estrous cycle lengths were not altered. / A culdoscopy technique was developed for repeated monitoring of ovarian morphological changes in cows.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.68557 |
| Date | January 1981 |
| Creators | Downey, Bruce R. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Animal Science) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 000594734, proquestno: AAINK51936, Theses scanned by UMI/ProQuest. |
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