Graduation date: 1993

Bibliography: leaves 148-166. / xi, 166 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The chicken embryo's ability to match the perfusion of its chorioallantoic membrane to regional differences in shell conductance was investigated. / Thesis (Ph.D.)--Adelaide University, Dept. of Environmental Biology, 2001

Cardiac, metabolic and growth response of early-stage chicken embryos to perturbations in yolk environment was investigated. Also, effects of parental hypoxia exposure on hypoxia resistance, thermal tolerance and body length of zebrafish larvae were investigated. In the first study, thyroxine, triiodothyronine and testosterone produced differential effects on heart rate and development rate of chicken embryos during the first 4 days of development. Triiodothyronine caused a dose-dependent increase in heart rate when applied at 40 or 70 hours of age, while thyroxine caused a dose-dependent increase in heart rate when applied at 40 hours only. Testosterone and propyl-thiouracil (deiodinase antagonist) did not have an effect on heart rate. Development rate was not changed by thyroxine, triiodothyronine, testosterone or propyl-thiouracil, which suggested that heart rate changes did not result from changes in embryo maturity. In the second study, chicken embryos exposed to yolks of different bird species during early-stage embryonic development showed changes in heart rate, mass-specific oxygen consumption and body mass that scaled with the egg mass, incubation period length, and yolk triiodothyronine and testosterone levels of the species from which yolk was derived. In the third study, this phenomenon was investigated between layer and broiler chickens. Heart rate, oxygen consumption and body mass of broiler and layer embryos were significantly changed by a breed-specific change in yolk environment. Yolk triiodothyronine and testosterone concentrations of broiler and layer eggs did not suggest that these hormones were responsible for physiological and morphological changes observed. The final study demonstrated that hypoxia resistance and body lengths, but not thermal tolerance of zebrafish larvae was increased by parental hypoxia exposure.

Austrofundulus limnaeus is a species of annual killifish which inhabits ephemeral ponds in South America. The species is able to survive seasonally desiccating ponds due to their ability to produce robust embryos. The embryos of this species are capable of entering a developmental arrest, termed diapause II, which precedes the onset of drought. While in this arrested state embryos exhibit the greatest tolerance to anoxia of any characterized vertebrate at 25ºC. Furthermore, when raised at 30ºC, embryos escape the entrance to diapause II and go on to develop directly. Currently, little is known about the molecular mechanisms which induce and maintain this developmentally arrested state. In this study I have developed methods to analyze changes in histone modifications in the context of diapause II. Histone modifications were chosen due to their extreme conservation and well characterized role as modulators of gene expression in other systems. Results utilizing adapted immunobased assays show significant changes in the global amount of H3S10P, H3K27me and H3K4me, as the embryos progress from early embryogenesis through the exit of diapause. Additionally, it is revealed that there exists a degree of phenotypic plasticity with regards to the entrance into diapause II which is modulated by the environment (severe hypoxia 0.1% O2). This work builds a foundation for future histone modification studies and contributes the development of several tools to the field. This study contributes to a greater molecular understanding of the cue(s) which influence the remarkable phenomenon of obligate developmental arrest in a vertebrate embryo.

Chan Oi Chi. / "May 2004." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (p. 259-310) / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

The chicken ductus arteriosi (DA) are two embryonic blood vessels that shunt blood away from the non-ventilated lungs and towards the body and chorioallantoic membrane. I show that prostaglandins have a diminished role in maintaining chicken DA patency and nitric oxide inhibits oxygen induced contraction of the day 19 proximal DA in a time dependent manner. The pathways governing oxygen induced contraction in the chicken DA are similar to those found in mammals and include contributions from ROS, Kv channels, L-type Ca2+ channels, and the Rho kinase pathway. Longer exposure to high oxygen generates increased oxygen induced constriction of the day 19 DA that may be mediated through the Rho kinase pathway.

Bone morphogenetic proteins (BMPs) are diffusible molecules involved in a variety of cellular interactions during development. In particular, Bmp4 expression accompanies the development of the ear sensory organs during patterning and specification of sensory cell fates, and it has been shown to play a role in inner ear development and morphogenesis. However, there is no understanding of the cellular effects of BMP4 in prosensory progenitors, and about its role in the process of sensory fate specification. The present thesis project was aimed at exploring the effects of BMP-signaling on the development of hair-cells, using the chick inner ear as a model.The specific aims proposed were:1- Analyze the cellular effects caused by addition of BMP4 in a model of isolated chick otic vesicles in culture, measuring parameters of cell proliferation, cell death and sensory cell fate specification.2- Analyze the cellular effects caused by inhibition of BMP4 signaling in a model of isolated chick otic vesicles in culture, measuring parameters of cell proliferation, cell death and sensory cell fate specification.3- Analyze the expression in the innear ear of downstream targets of BMP signalling, in particular, analyse the members of Id gene family.4- Analyze the regulation of Id genes by BMP signalling in the inner ear.5- Analyze the expression of genes involved in the process of terminal differentiation, in particular, Btg1 and Btg2 genes6- Analyze the regulation of Btg1 and Btg2 gene by BMP signalling in the inner ear