228 leaves : ill. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis -- University of Adelaide, Dept. of Psychology, 1968

Thesis -- University of Adelaide, Dept. of Psychology, 1968.

Thesis (M.S.)--Wisconsin. / Includes bibliographical references (leaves 109-116).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1981. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 164-177).

Daily determinations on the nitrogen exoretion in thyroid-treated goldfish and subsequent death by anoxia showed that thyroxin immersion caused a high initial rise in the nitrogen excretion. This is presumably due to metabolism of available protein. This rise was followed by a sharp drop, during which carbohydrates and fats are probably utilized. A second lower peak in nitrogen excretion was registered later, probably due to general tissue breakdown, similar to starvation symptoms. The relative height of the peaks varied with the dose of hormone given. While lower doses and high temperature elevated the nitrogen excretion, higher doses tended to depress it. Desiccated thyroid feeding also had a rather depressive action. The anoxia experiments showed that the higher the dose of the hormone, the longer were the fish able to survive over untreated controls. It was concluded that thyroid treatment increases metabolism in goldfish, which is not accompanied by a raised oxygen consumption as in mammals but by an adaptation to lower oxygen tensions, anaerobic metabolism and respiration. This adaptation seems to increase in efficiency with increasing dose of thyroid hormone. / Science, Faculty of / Zoology, Department of / Graduate

A technique was developed for studying the effect of anoxia in the newborn rat with particular reference to persistence of electrical activity in the heart. In contrast to previous investigations in this field, no drastic surgical procedures were used, and the animals were held in a relatively undisturbed state in a closed temperature regulated chamber which could be filled with a gas mixture of any desired composition. Eleven newborn rats could be placed in the chamber at the same time under the same conditions, and electrocardiographic recordings could be obtained simultaneously from four animals at a time. Anoxia was produced by flushing and filling the chamber with tank nitrogen (99.9% N₂), and the period of persistence of electrocardiographic activity was determined taking as endpoint the last recorded electrical potential from the heart. Two hundred and thirty-two rats were used, ranging in age from three hours to eight days postnatal. The results obtained agree substantially with those reported by other workers using cruder methods. The "survival time" of electrocardiographic activity in the four day old group was only half that observed in newborn rats less than twelve hours postnatal, the difference being highly significant. However, there was no further significant change in "survival time" during the period from four to eight days. The technique developed should prove useful in studying many problems of neonatal physiology. / Medicine, Faculty of / Cellular and Physiological Sciences, Department of / Graduate

by Yu Kei-li. / Bibliography: leaves 171-210 / Thesis (M.Ph.)--Chinese University of Hong Kong, 1984

In periodontitis, local oxygen supply and consumption in gingival tissues may be significantly altered due to the inflammatory process. The etiology agent of periodontal disease i.e. anaerobic bacterial biofilm is known to confer a low oxygen tension in the vicinity of periodontitis lesion. The oxygen shortage will lead to the stabilization of HIF-1α, the regulatory subunit of hypoxia-inducible factor (HIF)-1, which through controlling specific downstream genes transcription may modulate multiple cellular functions and hence shape the process of periodontitis. Lipopolysaccharide (LPS), a cell wall component of anaerobic bacteria, has been considered to be involved in the pathogenesis of periodontitis. Its interaction with host peptides including LPS-binding protein (LBP), CD14, MD-2 and Toll-like receptor (TLR) 4 may trigger the production of inflammatory cytokines. In this project we hypothesize that hypoxia and bacterial components may induce HIF-1α activity, which in turn impacts upon on the pathological process of periodontitis. This project aimed to detect in vivo expression of HIF-1α and TLR4 in human gingivae; to examine whether LPS could induce HIF-1α activity through pattern recognition receptor like TLR4 on human primary gingival fibroblasts (HGF); and to investigate the combined effect of hypoxia and LPS on type I collagen metabolism in HGF. Human gingival biopsies were collected from advanced periodontitis or clinically healthy sites. By immunohistochemistry, both HIF-1α and TLR4 peptides appeared to express in gingival epithelium. In periodontal pockets, there appeared a marked increase in HIF-1α and TLR4 expression in fibroblast-like and leukocyte-like cells. Human primary gingival keratinocytes (HGK) and fibroblasts (HGF) were cultured. Transcripts of TLR4, MD-2 and CD14 were identified in HGK, HGF and periodontal tissue using RT-PCR. Their protein products were identified in both cell types in vitro using immunoblotting. LBP transcript was only found in gingival biopsies but not in HGK and HGF culture. HGF treated by Escherichia coli LPS ranging from 0.2 μg/mL to 200 μg/mL showed nuclear accumulation of HIF-1α peptide, detectable by immunocytofluorescence and immunoblotting. This accumulation could be attenuated by treatment with TLR4-neutralizing antibody. Under hypoxia, LPS further increased HIF-1α accumulation. Using quantitative real-time PCR (qPCR), hypoxia and/or LPS appeared to enhance the transcription of certain enzymes or enzyme subunits that are related to collagen assembly and crosslink, including prolyl 4-hydroxylases, lysyl hydroxylases, lysyl oxidase and lysyl oxidase-like enzymes. These increased transcription could be downregulated by pretreatment with TLR4-neutralizing antibody or an HIF-α inhibitor, 3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole (YC-1). Finally, preliminary experiments showed KN-93 [Ca2+/Calmodulin-dependent protein kinase (CaMK) II inhibitor] or cyclosporine-A (calcineurin inhibitor) appeared able to attenuate the LPS-induced HIF-1α accumulation, indicating a possible role for intracellular calcium signal in regulating HIF-1α. In conclusions, human periodontitis is associated with increased expression of TLR4 and HIF-1α in gingivae; hypoxia causes and LPS/TLR4 signal associate with HIF-1α accumulation and activity in human gingival fibroblasts, and subsequently modulate in a certain extend collagen metabolism through upregulating the transcript expression of several collagen-related proteins. All these implicate possibility of an adaptive physiological or pathological response of human gingival fibroblasts towards gram-negative bacterial biofilm challenge in human periodontium. / published_or_final_version / Dentistry / Doctoral / Doctor of Philosophy

Cartilage is an essential skeletal connective tissue in vertebrates. It comprises extracellular matrix components, especially for collagens and proteoglycans. Once the cartilage is damaged, it has limited self-repair capacity. Thus, by understanding the dynamic cellular process of chondrogenesis and chondrocyte differentiation would be necessary in developing therapeutic approaches for cartilage repair. Currently, there is a great interest in the development of cell therapy to repair damaged tissues. In particularly, human mesenchymal stem cells (hMSCs) are attractive candidates for the treatment of skeletal system disorders because they can be greatly expanded ex vivo and they readily differentiate into chondrocytes upon stimulation. Studies have demonstrated low environmental oxygen tension could affect the chondrogenic differentiation of hMSCs. The three basic helix-loop-helix (bHLH) motif-containing hypoxia inducible factor α (HIF-α) subunits (i.e. HIF-1α, HIF-2α and HIF-3α) are the major oxygen-sensitive transcription factors regulating physiological responses under hypoxia. Of significance, HIF-1α has been reported to induce a hyaline chondrocyte-like phenotype in human articular chondrocytes. The aim of this study was to investigate the roles of all three human HIF-α paralogues in chondrogenesis, particularly for the transcriptional regulation of chondrocyte-specific genes, including type II collagen (COL2A1) and aggrecan (AGC1). The effect of all three human HIF-α paralogues on the chondrogenic differentiation of hMSCs could then be investigated. Self-inactivating lentivirus vector (SIN-LV) shuttle plasmids coding for murine SOX9, wild-type and oxygen-insensitive versions of human HIF-1α and HIF-2α or wild-type HIF-3α were generated. These plasmids were used in luciferase-based promoter assays and to generate SIN-LV particles for overexpression studies. Our data revealed that SOX9, a key transactivator of chondrogenesis, strongly activates the transcription of COL2A1 and AGC1. Ectopic expression of HIF-2α could also induce the transcription of COL2A1 and AGC1. Strikingly, a cooperative transcriptional up-regulation of COL2A1 and AGC1 via the overexpression of HIF-1α and SOX9 was observed. Furthermore, HIF-3α was shown to inhibit the SOX9–dependent transcriptional up-regulation of COL2A1 and AGC1. Here, the multipotency of hMSCs cultured under hypoxia (1% O2 tension) was also illustrated. A pilot study for overexpressing exogenous gene in chondrogenic stimulated hMSC pellets via SIN-LV particles is described. Eventually, a rationale is provided for manipulating HIF-α expression in chondrogenic stimulated hMSC pellet via SIN-LVs encoding HIF-α subunits to study the contribution of HIF-α paralogues on promoting the chondrogenic differentiation of hMSCs. / published_or_final_version / Orthopaedics and Traumatology / Doctoral / Doctor of Philosophy

Exercise-induced hypoxemia [EIAH, arterial PO2 < 90 mmHg and/or alveolar-arterial oxygen partial pressure gradient (A-a DO2) ≥ 25 mmHg] occurs during strenuous exercise in some healthy women. There is conflicting opinion if performing successive bouts of strenuous exercise reduces the severity of EIAH. The aim was to (a) test the hypothesis that the severity of EIAH would be reduced with three successive bouts of strenuous exercise, (b) to determine if repeated bouts of exercise increases hyperventilation thus improving arterial PO2. Seven fit female subjects with EIAH [arterial PO2 or PaO2= 88 +/- 2 mmHg, A-a DO 2 = 25 +/- 3 mmHg and 7 fit female control subjects (PaO2 = 100 +/- 5 mmHg, A-a DO2 = 16 +/- 5 mmHg) performed three bouts of intense exercise on a cycle ergometer at 236 +/- 27 watts [oxygen consumption at end of each set = 48 +/- 6 mL/kg/min, or 96 +/- 5% of maximum] for 5 min each with 10 min of rest between sets. Arterial PO 2 increased [EIAH Delta = +4 +/- 5 mmHg. 95% CI = 0.6 to 7.8; Control Delta = +2 +/- 2 mmHg. 95% CI = 0.4 to 3.6] and arterial PCO 2 or PaCO2 decreased [EIAH Delta = -5 +/- 4 mm Hg, 95% CI = -7.4 to -2.2; Control Delta = -4 +/- 2 mmHg, 95% CI = -5.8 to -2.4] between set 1 and set 3 (P< 0.05). Also, 34% of the variance in the change in PaO2, was explained by the variance in the change of PaCO2 (P < 0.05). In conclusion, repeat exercise improves PaO2, which is related to improved hyperventilation.