Thesis (M.S.)--Oregon State University, 1976. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

No description available.

Growth experiments were conducted with bluegill, Lepomis macrochirus, for 102 days under three different photoperiods at 26 C. One daily photoperiod increased from 15.5 to 19.8 hours, another decreased from 15.5 to 12.3 hours, and a third was held constant at 15.5 hours. Growth, food consumption (mealworms, Tenebrio molitor), and food conversion efficiency were evaluated for bluegill under each set of conditions.Under the conditions used in this experiment there was no apparent effect of photoperiod on the growth of bluegill. This was true for all measurements of growth, food consumption, and food conversion efficiency. It was also true when males and females were compared for each of these measurements.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1956. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 48-49).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1956. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 69-74).

The physiological effects of the pineal gland on the prolactin cells of the adenohypophysis were examined in short photoperiod-exposed male hamsters, as well as in blinded male and female hamsters. Pituitary storage of prolactin was assessed by monitoring radioimmunoassayable prolactin levels in the pituitaries in vivo and the total amount of immunoreactive prolactin in vitro. The effects of the pineal on prolactin secretion were estimated by measuring immunoassayable prolactin titers in the serum. Prolactin synthesis was measured by the ability of anterior pituitaries to incorporate ³H-leucine into prolactin in vitro. Finally, the effects of blinding and the activated pineal on hypothalamic hypophysiotrophic activity was assessed by incubating pituitaries in the presence of neutralized, acidic extracts of the stalk-medium eminence (SME) region of the mediobasal hypothalamus. In the male hamster, the pineal gland inhibits PRL cell function which encompasses reductions in the synthesis, storage and release of prolactin. The depressions in prolactin release and in pituitary storage are evident as early as three weeks after males are deprived of light. However, the inhibitory influence of the pineal on prolactin synthesis may be only partially apparent by eight to nine weeks after male hamsters are deprived of light, and is not fully evident until 12 weeks of light restriction. In the blinded female hamster, the synthesis, storage and release of prolactin are also markedly suppressed. However, all aspects of prolactin cell inhibition in the female may not be pineal-mediated. Furthermore, it appears that there may be some direct hypothalamic mechanism by which orbital enucleation inhibits prolactin cell function that is independent of the pineal gland. Based on the data presented in this dissertation, it is concluded that the SME region of the female hamster contains inhibitory activity which may be specifically responsible for the inhibition of prolactin synthesis. Furthermore, blinding and the pineal gland may independently exert rather specific influences upon hypophysiotrophic activity within the SME region of the female hamster.

published_or_final_version / Zoology / Master / Master of Science

Three hundred and thirty lines of guar (Cyamopsis tetragonoloba (L.) taub.) were planted in five locations throughout central and southwestern United States to find diverse photoperiod response types for closer physiological and genetic study. Dates of planting studies were done in 1982 and 1983 in hopes that the photoperiod responses would be obvious in field conditions but they were not. The 1982 dates of planting studies in Arizona, Kansas, and Texas indicated that the date of planting was more important than the selection of cultivar in expectations of high yield even though cultivar selection was very important. The 1983 dates of planting experiment in Tucson, Arizona showed suggestions that photoperiod existed in guar but it took controlled, greenhouse conditions to characterize photoperiodism in guar and to be able to conduct genetic analysis. In greenhouse studies, guar was found to be a quantitative short-day plant, the initiation of buds and floral development were accelerated under short-day conditions. Six guar lines were characterized for the critical photoperiod in days from first true leaf to the first floral bud and from first floral bud to the first flower. No effect of photoperiod on the growth and development from emergence to the first true leaf was observed. The critical photoperiod for days from first true leaf to first bud for the lines are as follows: PI217925-1-1, Mesa, and Mills are between 14 and 15 hours, Kinman and SEAH-90 are between 13 and 14 hours, and PI217925-2 is between 12 and 13 hours. The critical photoperiod for days from first floral bud to first flower for the lines are: PI217925-1-1, Mesa, Kinman, and PI217925-2 are between 12 and 13 hours, SEAH-90 is between 13 and 14 hours, and Mills is day-neutral. Different photoperiodic responses occur for days from first true leaf to first floral bud and days from first floral bud to first flower. This follows a proposed genetic system of photoperiodic actions that has genes for photoperiod sensitivity, short-day versus long-day reaction, critical photoperiod, and genes for the amount of time delay for each developmental stage. The segregations of the guar crosses were explained by the model.

No description available.

Seasonal physiology has evolved as an adaptive strategy to changing environments with daylength (photoperiod) used as the predominant environmental cue to suit breeding and other functions to the external season. However, seasonal physiological state is determined not only by the photoperiod that is currently in effect but also by the animal's history, allowing changes in physiology in anticipation to the seasons. Many mammals and birds show internally timed, long-term (circannual) changes in seasonal physiology, synchronised to the seasons by changing photoperiods. The importance of history-dependent photoperiodic programming applies also to puberty attainment in juvenile animals, timed by the photoperiod received by the mother during gestation. In this project I investigated the effects of both types of history-dependent timing on the neuroendocrine pathways for photoperiodic regulation of seasonal physiology. In mammals, photoperiod is transmitted via the pineal hormone melatonin, which acts on the pars tuberalis (PT) to regulate thyrotropin (TSH) expression and in turn controls seasonal physiology via effects on the hypothalamic synthesis of type 2 and 3 thyroid hormone deiodinases (Dio2 and Dio3), and thus the local regulation of thyroid hormone metabolism, and downstream changes in hypothalamic neuropeptidergic signalling. Using two circannual species, the Soay sheep (Ovis aries) –a short-day breeder – and the European hamster (Cricetus cricetus) – a long-day breeder – exposed to constant photoperiodic conditions, my findings reveal that in both models, in the absence of seasonal cues, internal circannual timing is initiated at the PT control of TSH and transmitted to the regulation of hypothalamic T3 regulation and neuropeptides. Siberian hamsters (Phodopus sungorus) were placed under different photoperiods during gestation and transferred to a photoperiod of intermediate duration at weaning. Reproductive activation under these conditions was dependent upon early life exposure and this effect controls history-dependent changes in hypothalamic deiodinases. Interestingly, the gestational experience was reflected in PT TSH expression and Dio2 expression as early as birth time. The same prenatal effects were observed in a strain of seasonal mice, (Mus musculus molossinus). Overall my dissertation has established that: i) both the circannual and the melatonin signals converge on TSH expression to synchronise seasonal biological activity; ii) the photoperiodic pituitary-hypothalamic network is programmed by prenatal experience; and iii) this pathway is already functional before birth. Overall, my results highlight the PT as a conserved central site in mammals for the integration of multiple seasonal cues which via differential control of thyroid hormone levels in the hypothalamus dictates the timing in seasonal physiology.