Massey Documents by Type

Permanent URI for this communityhttps://mro.massey.ac.nz/handle/10179/294

Browse

Filters

1984 - 198912000 - 20021

Settings

Has files: YesSubject: search.filters.subject.Gonadotropin

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Investigation in female rats of the effects of androgen treatment, during the pre- and postnatal periods, on growth and reproductive function : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University
    (Massey University, 1984) Sommerville, Elizabeth Mary
    In experiments investigating the perinatal period of sensitivity to androgen of hypothalamic functions, testosterone propionate (TP) was administered to female rats at different ages before and after birth and for varying time intervals. Administration of TP was by subcutaneous injection in oil, or by subcutaneous polydimethylsiloxane (PDS) capsules. Plasma testosterone concentrations were measured by radioimmunoassay in adult female rats after insertion and removal 72h later, of 3 sizes of TP-filled capsule (5, 10 and 20mm crystal length); in 3 day old female neonates after insertion and removal 4h later of a TP-filled capsule (2.5mm crystal length), or after injection of TP (90μg in oil); and in growing female rats after neonatal implantation with a TP-filled capsule (2.5mm crystal length) which was not removed (chronic implantation). The plasma half-life of testosterone estimated after implantation with TP capsules was much shorter in adults (1h) than in neonates (8.6h). After TP injection to 3 day old rats the half-life was 48h and after chronic implantation of TP capsules was 69h. Exposure of foetal rats to exogenous androgen, achieved by subcutaneous implantation of pregnant rats with TP capsules (3 sizes) for 24h or 72h at varying stages during gestation, did not alter ovarian function, feminine sexual behaviour or growth, despite abnormal development of the external vaginal opening in rats exposed to TP during the last 6 days of gestation. Female rats aged 2, 3 or 5 days given brief periods of TP treatment by subcutaneous 2.5mm PDS TP-filled capsules, removed after 4, 8 or 24h, were compared with rats given 90μg TP by injection at the same ages. Control of gonadotrophin secretion, as indicated by ovarian morphology and cyclic changes in the vaginal epithelium, was sensitive to alteration by brief periods of exposure to TP. Treatment on days 2 or 3 with 4h implants produced anovulatory sterility at 90 days in at least 50% of animals. Feminine sexual behaviour, assessed by lordosis quotient, was depressed only by treatment longer than 24h at any of the 3 ages. Injection with TP prevented ovulation and depressed the lordosis quotient regardless of day of treatment. Although analysis of variance demonstrated an increased body weight from 14 weeks in rats injected with TP on days 2 or 5, regression analysis did not confirm an increased growth rate. The external vaginal orifice was altered by 4h TP implants given on days 2 or 3, but was unaffected by TP treatment of any duration given on day 5. Testosterone propionate-filled capsules (2.5mm), implanted in female rats on days 2, 3 or 5 and not removed, prevented ovulation and abolished feminine sexual behaviour. Adult body weight was severely retarded by treatment commencing on day 2, but not altered by treatment beginning on days 3 or 5. It can be concluded from this investigation that the hypothalamic control of gonadotrophin secretion in the female rat is insensitive to androgen prenatally, and is very sensitive 2 or 3 days after birth, when even brief (estimate of 28h exposure) periods of treatment are able to prevent ovulation. The control of feminine sexual behaviour is insensitive to prenatal TP. Depression of behaviour appears to require a longer neonatal period of exposure to TP (estimate of 48h minimum exposure) than that required to modify gonadotrophin secretion. Stimulation of growth appears to be a variable feature of the androgenized rat.
  • Thumbnail Image
    Item
    Hormonal stimulation of ovarian development, ovulation and oviposition in Japanese quail : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Physiology at Massey University, Palmerston North, New Zealand
    (Massey University, 2002) Bennett, Ellen Joan
    Stimulation of ovarian development and ovulation leading to production of fertile offspring using exogenous hormones has been successful in mammals, but until recently this was not the case for avian species. These techniques would be useful for increasing the reproductive output of endangered birds such as the kakapo. Pregnant mare serum gonadotropin (PMSG) was used to stimulate ovarian development in Japanese quail as it is readily available, easy to use, and equally effective as avian gonadotropins. The research examined the best method for administering PMSG, and the doses, duration and frequency of treatment required to stimulate follicular growth. Treatment with PMSG can stimulate ovarian development, ovulation and oviposition in Japanese quail held under a short day photoperiod. However, there was considerable variation in ovarian response to PMSG between birds receiving the same treatment. In birds in which large yellow follicles developed, many follicles were similar in size and were not arranged in a hierarchy. Doses of 20-80 IU PMSG were the most appropriate for stimulating ovarian development in Japanese quail. Doses lower than 20 IU PMSG stimulated little or no ovarian development in most birds, and doses higher than 80 IU PMSG led to overstimulation of follicular development in most birds. Continuous delivery of PMSG by osmotic pumps and daily treatment using injections were equally effective in stimulating ovarian development in Japanese quail. The use of daily injections is a more practical method of delivering PMSG to birds, as it does not involve surgery and allows more control over dosage and timing of treatment. Treating birds with injections of PMSG every two days rather than daily led to a rate of ovarian growth similar to that of long day birds. Treatment every four days was not sufficient to stimulate ovarian development in quail. Restricting the feed intake of quail did not have any affect on the ovarian response to PMSG treatment. Although PMSG can stimulate ovarian development and ovulation in Japanese quail, further work is required to increase the number of birds that respond to treatment, increase the number of eggs produced by an individual, and improve egg quality.