Hypoxic responses in quail development differ depending upon stage, duration and level of oxygen partial pressure of embryo. Incubation was switched to/from 110mmHg partial pressure (hypoxia), to/from 150mmHg (normoxia) during different stages in development, and control was incubated in normoxia throughout. Hatchability and embryo survival resulted in no hatchlings in continuous hypoxia. Responses to various hypoxic exposures throughout development resulted in recovery/repair of hypoxic damage by hatch. Heart and body mass, beak and toe length, hemoglobin, and hematocrit were measured to determine embryo responses to hypoxia during development at days 10, 15, and hatch. Hypoxia seemed to have the most deleterious effects on eggs in continuous hypoxia. Collectively, data indicate critical developmental windows for hypoxia susceptibility, especially during mid-embryonic development.

Hypoxia, a state of low oxygen, is a feature of most solid tumours as a consequence of poor tumour vascularisation. The mechanisms, which allow cancer cells to survive and continue to grow in hypoxia, are coordinated by the transcription factor HIF. The tumour suppressor gene van Hippel-Lindau (vHL) that targets HIF for degradation is mutated in the vast majority of renal cell carcinomas (RCCs), highlighting the importance of hypoxia to tumour biology. There is, therefore, an important need to understand the adaptive changes mediated by hypoxia and to target this clinically. One class of genes regulated by HIF are microRNAs (miRNAs). MiRNAs are short, single stranded RNA that primarily inhibit protein expression from target m RNA. The first aim of this project was to identify novel hypoxia regulated miRNAs in bladder cancer and assess their functional significance. It was found that a number of miRNAs were induced in hypoxic conditions. The hypoxic induction of miR-210 was conserved in all cell lines tested. MiR-145 was found to be highly induced by hypoxia in RT4, a cell line derived from a low- grade, non-muscle invasive tumour. We showed that miR-145 was a novel, HIF target gene with two hypoxia response elements identified within the promoter. Functionally we found that miR-145 induces apoptosis in RT4 cells. MiR-100 was downregulated in hypoxia, but this downregulation did not involve HIF. Regulation of miR-100 was of interest, as it is known to target FGFR3, a gene commonly overexpressed or mutated in bladder cancer. Concomitant with a decrease in miR-100, both the mRNA and protein level of FGFR3 were found to increase in hypoxia in RT4 and RT112 cells. Increased FGFR3 expression in hypoxia was involved in sustaining activation of the downstream signaling targets phospho-PKB and phospho-ERK. In addition, we demonstrate a role for FGFR3 in regulating both 2D and 3D growth and of miR-100 in regulating 3D growth of RT4 cells. We also showed that miR-100 decreased the protein levels of mammalian target of rapamycin (mTOR). However, transfection of miR-l00 into RT4 cells did not affect the sensitivity of this cell line to rapamycin. The genetic and biochemical changes that occur in (hypoxic) tumours may alter their responsiveness to chemotherapeutic agents such as rapamycin. The second aim of this project was to investigate the responsiveness of RCCs to clinically approved chemotherapeutic agents, with the goal of correlating any differences in response to alterations in expression of specific genes. Although hypoxia regulated miR-100 did not affect sensitivity to rapamycin, we extended these studies and investigated the role of vHL status on response of renal cancer cell lines to sorafenib, sunitinib, rapamycin and metformin. We found that the presence of vHL increased resistance to rapamycin. Sensitivity to these drugs was also tested in 10 primary cell lines. There was varying sensitivity to these drugs across the cell lines representing the heterogeneity of renal cancer. We analysed the expression of a number of genes in the m TOR and hypoxic pathways in these tumours, we found the expression of a known hypoxic gene REDDl correlated with sensitivity to rapamycin. REDDl expression levels were also higher in tumour tissue when compared to normal renal parenchymal tissue and was associated with other prognostic markers such as CA9, miR-210 and vascular invasion suggesting a role as a diagnostic or prognostic marker and in patient selection for treatment with rapamycin.

No description available.

"December 2003" / Includes bibliographical references (leaves 183-224) / xvii, 236 leaves : ill. (chiefly col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Obstetrics and Gynaecology, 2004

Thesis (M. Phil.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Thesis (Ph.D.)--Ohio University, August, 2009. / Release of full electronic text on OhioLINK has been delayed until September 1, 2012. Includes bibliographical references (leaves 89-107)

Thesis (Ph.D.)--Ohio University, August, 2009. / Title from PDF t.p. Release of full electronic text on OhioLINK has been delayed until September 1, 2012. Includes bibliographical references (leaves 89-107)

This thesis is concerned with the chemical control of breathing during exercise in humans. Chapter 1 reviews some of the relevant studies in animals and humans. Chapter 2 describes the experimental apparatus and the technique of dynamic end-tidal forcing performed using a computer-controlled gas-mixing system. Chapter 3 describes a study of the effects of sustained hypoxia on ventilation during steady exercise. The acute ventilatory response to hypoxia (AHR) was increased during exercise as compared with rest, but the magnitude of the subsequent decline in ventilation (HVD), expressed as a fraction of the AHR, was reduced. A simple model of the hypoxic peripheral chemoreflex is proposed, in which the mechanisms underlying AHR and HVD are functionally separate and can be independently modulated by external factors. Chapter 4 assesses changes in peripheral chemoreflex sensitivity to hypoxia in terms of the degree of decline in AHR measured in the resting periods shortly after prior conditioning periods of hypoxia and/or exercise. At rest, a second AHR measured 6 min after a period of sustained hypoxia had declined by 30% as compared with the initial AHR. In contrast, the AHR measured in the resting period after a period of sustained hypoxic exercise was only 11% smaller in magnitude than the AHR measured after a period of euoxic exercise. The results suggest that the degree to which hypoxic sensitivity declines during sustained hypoxia is genuinely attenuated, rather than masked, by exercise. Chapter 5 describes the changes in respiration during prolonged exercise breathing air with and without added CO₂. During prolonged poikilocapnic exercise, ventilation remained constant, but metabolic CO₂ production, respiratory quotient and end-tidal P_CO2 declined; a result which suggests that in man, ventilation can be dissociated from the CO₂ flux. During hypercapnic exercise, ventilation progressively increased; this was interpreted as being due to a correction by end-tidal forcing of the natural tendency for end-tidal CO₂ to decline, together with an independent effect of CO₂ per se on the ventilation. Chapter 6. Electrical muscle stimulation was used as means of inducing non-volitional exercise. Electrically-induced exercise increased the AHR as compared with rest, and with voluntary exercise at matched external work rate. The AHRs during electrical stimulation and voluntary exercise matched to the internal work rate were similar. Chapter 7. Electrical muscle stimulation was used in paraplegic subjects in whom there would be no neural control of exercise. Electrically-induced exercise increased the AHR as compared with rest. When compared with the data from Chapter 6, the results suggest that the observed increase in AHR during normal voluntary exercise can be wholly accounted for by the increase in metabolic CO₂ production, or closely related factors. Chapter 8 presents a brief summary of the findings in this thesis.

published_or_final_version / abstract / toc / Molecular Biology / Master / Master of Philosophy

published_or_final_version / abstract / toc / Physiology / Master / Master of Philosophy