Thesis (Ph. D.)--Oregon State University, 1968. / Typescript. Includes bibliographical references (leaves 113-116). Also available on the World Wide Web.

Thesis (M.S.)--Texas State University--San Marcos, 2008. / Vita. Includes bibliographical references (leaves 47-51). Also available on microfilm.

Thesis (Honors)--College of Wiliam and Mary, 2008. / Includes bibliographical references (leaves 47-49). Also available via the World Wide Web.

Thesis (Honors)--College of William and Mary, 2009. / Includes bibliographical references (leaves 42-43). Also available via the World Wide Web.

No description available.

Female 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.

Discrete changes in the amplitude, frequency, and cellular localisation of calcium ion (Ca2+) transients encode information about numerous stimuli and function to mediate stimulus-specific responses. Cytoplasmic Ca2+ (Ca2+cyt) undergoes circadian oscillations in concentration that appear to be under the control of the same endogenous oscillator that regulates expression of genes in the photoperiodic-flowering pathway. It is currently not known whether these circadian [Ca2+cyt] oscillations are biochemical artefacts or are decoded and function to transduce clock dependent responses. Calmodulin (CaM) is a primary node in Ca2+ signalling in plants and as such is a promising target for investigating the role of Ca2+ in clock-controlled processes. In this study, Arabidopsis thaliana were treated with experimentally validated concentrations of pharmacological CaM inhibitors. Under inductive photoperiods (16 h light : 8 h dark), CaM inhibition was found to increase developmental flowering time, whilst under non-inductive photoperiods no such changes were evident. Inhibition of CaM led to changes in expression of the key clock gene TIMING OF CAB EXPRESSION 1 and flowering time genes, CONSTANS and FLOWERING LOCUS T and removed repression of flowering in darkness. These observations are consistent with CaM modulating the activity of the putative clock component GIGANTEA and the proteasomal targeting protein SUPPRESSOR OF PHYA-105. Due to the unwanted side effects often generated by chemical CaM inhibitors, a peptide inhibitor of CaM comprising a green fluorescent protein / calspermin fusion and labelled smGN was developed. Surface plasmon resonance analysis and affinity chromatography showed smGN to have extremely high selectivity for, and affinity to, CaM and to function as a powerful inhibitor of CaM in vitro. Further work on the methodology used to deploy smGN as a recombinant alternative to chemical CaM inhibitors in planta is also described.

The Atlantic salmon (Salmo salar) has two developmental processes which are clearly seasonal; smoltification is restricted to the spring and maturation to late autumn. In the farming industry the seasonality of juvenile production is primarily responsible for the seasonal production in market-sized fish. Both smoltification and maturation appear to be controlled by mechanisms timed by photoperiod. This thesis investigates the effects of photoperiod on smoltification and maturation. The performance of both out-of-season eggs and particularly smolts are closely examined and the possible application of photoperiod techniques in the industry discussed. Both potential SI and S2 parr were subjected to natural photoperiods or a range of artificial photoperiods under constant and ambient temperature conditions. S I and S2 smolts reared under natural photoperiods were transferred to sea water during April and May. A 2-3 month period of short days followed by a period of long days was observed to advance smoltification; 0+ and 1+ smolts were transferred to sea during December (4 month advance) and October (6 month advance), respectively. A 12 month seasonal photocycle delayed by 3 months delayed smoltification by 2 months. Out-of-season smolts were produced in January, March, April, May, June, July, October, November and December. All groups of out-of-season smolts exhibited the same growth potential as natural smolts. The different transfer date of out-of-season smolts therefore resulted in different harvest periods compared to natural smolts. The age at maturity of out-of-season smolts was positively related to the length of the seawater growing period prior to the completion of maturation. Out-of-season smolts exhibited increased maturation in association with an increased size (compared to natural smolts) for a particular time of year. These large maturing fish were generally harvested as superior salmon prior to flesh deterioration. Mortality during the first month in sea water was significantly higher in a number of out-of-season smolt groups compared to natural smolts. This was considered to be related to site-specfic environmental conditions rather than the smoltification process. Smoltification was also examined under constant photoperiods and a 4 week period of short daylengths. Dissociation and suppression of certain aspects of smoltification were observed. The different aspects of smoltification: the development of bimodality, hypoosmoregulatory ability, decrease in condition and smolt coloration appeared to be controlled by different independent mechanisms. The development of bimodality, hypoosmoregulatory ability and possibly coloration appeared to be controlled by independent endogenous rhythms. The decrease in condition factor, associated with the parr-smolt transformation required a period of short day length greater than 2 months followed by a period of long daylength. Smoltification and maturation were examined in salmon retained in constant 1DOC borehole water. Smolts held in fresh water grew steadily and matured producing eggs and sperm both in- and out-of-season. There was, however, a period of increased mortality after smoltification and egg quality was reduced especially in fish subjected to photoperiod manipulation. The salmon responded to photoperiodic manipulation. Abrupt changes in photoperiod advanced spawning by 12 weeks and a reciprocal seasonal photoperiod (6 month out of phase with a natural photoperiod) advanced spawning by 22 weeks. The maturation process in the Atlantic salmon would appear to be controlled by similar mechanisms to those described for the rainbow trout. Freshwater holding conditions appeared to decrease the age at maturity and reduce egg quality. The progeny of freshwater broodstock (FI generation) successfully completed smoltification and seawater transfer. Photoperiodic manipulation can be used to produce out-of-season smolts and eggs. Through the use of photoperiod, farms could increase and target production. This could remove the seasonality from the production cycle and help stabilise the pricing structure for market salmon.

No description available.

Thesis (M.S.)--University of Wisconsin--Madison, 1965. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 45-50.