Lam Ching-wan. / "May 2000." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (p. 91-101). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

G6Pase-alpha and G6Pase-beta share kinetic properties and active site structures, which lie on the luminal side of the endoplasmic reticulum (ER). For hydrolysis of G6P to glucose, G6Pase-alpha or G6Pase-beta must couple with an ubiquitously expressed ER-transmembrane protein, the G6P transporter (G6PT) that translocates G6P from the cytoplasm into the lumen of the ER. The primary role of the G6Pase/G6PT complex is therefore to provide endogenous glucose to the ER lumen. The essential role of the G6Pase-alpha/G6PT complex in glucose homeostasis has been well established, and the deficiencies in G6Pase-alpha and G6PT cause glycogen storage disease type Ia (GSD-Ia) and GSD-Ib, respectively. Both patients manifest the same metabolic phenotype of disturbed glucose homeostasis. While the metabolic abnormalities of GSD-Ia and GSD-Ib are almost identical, GSD-Ib patients exhibit neutropenia and myeloid dysfunctions which are not observed in GSD-Ia patients. Since G6Pase-beta and G6PT share an ubiquitous expression pattern, we hypothesized that the G6Pase-beta/G6PT complex might be functional in neutrophils and that the myeloid defects in GSD-Ib are due to the loss of activity of that complex. To test this hypothesis, we generated G6Pase-beta-deficient (G6pc3 --/--) mouse strains and showed that G6pc3--/-- mice manifest neutropenia; defects in neutrophil respiratory burst, chemotaxis, and calcium flux; and increased susceptibility to bacterial infection mimicking GSD-Ib patients. Consistent with this, G6pc3--/-- neutrophils exhibit enhanced ER stress and apoptosis. Taken together, the results demonstrate that endogenous glucose production in the ER via G6P translocation and metabolism are critical for normal neutrophil functions and that an ER stress-mediated neutrophil apoptosis is one mechanism underlying myeloid dysfunctions in the G6pc3--/-- mice. / Macrophages are the abundant leukocytes in the decidua throughout pregnancy and were thought to play a vital role in decidual homeostasis, placental development, and maintenance of a successful pregnancy. We hypothesized that endogenous glucose production in the ER might also be critical for normal macrophage function and G6pc3--/-- females manifesting neutropenia, neutrophil and macrophage dysfunctions might suffer from pregnancy-associated complications. Here we show that G6pc3--/-- macrophages exhibited impaired respiratory burst activity and repressed trafficking in vivo during an inflammatory response. The litter size and pregnancy frequency were markedly reduced in female G6pc3--/-- matings as compared to female G6pc3+/--/G6pc3+/+ matings, indicative of reduced fertility. The pregnancy-associated mortality risk was greatly increased in G6pc3--/--. Pathological analyses revealed that the sick or dying G6pc3--/-- mothers were emaciated and suffered from dental dysplasia and otitis media. Consistent with this, parental male and female G6pc3--/-- mice were more neutropenic than their age-matched virgin G6pc3 --/-- mice. Taken together, our results show that macrophage dysfunction, defective macrophage trafficking, neutrophil dysfunction, and enhanced neutropenia underlie the reduced fertility and increased mortality of G6pc3--/-- mothers. / Cheung, Yuk Yin. / Advisers: Janice Chou; Kam Bo Wong. / Source: Dissertation Abstracts International, Volume: 73-03, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 92-107). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

For the development of a G6PD-deficient mouse model, we introduced the mutant Gpdxa-m1Neu allele (a severe ENU-induced mutation that results in 13-15% G6PD activities of wild type littermates) into the C57L/J background (a strain that constitutively exhibits low G6PD activity) through a breeding program. Of significance is that 78% of the F2 generation had G6PD activities <2 U/g Hb, levels similar to those of severe G6PD deficiency in human. The efficacy of this model was preliminary verified by the known haemolytic agent, naphthalene, as demonstrated by the decrease of GSH/GSSG ratio by 24.6% (P=0.032) and increase of methaemoglobin by 4.5 fold (P=0.8) when compared with the respective control without treatment. / Genetic analysis of 14 mutation hotpots was performed on 98 hemi-/homozygous and 17 heterozygous G6PD-deficient human subjects. We developed a novel Multiplex Primer Extension Reaction (MPER) assay and detected seven specific mutations in 97 subjects: c.1376G>T (33.7%), c.1388G>A (29.6%), c.871G>A + c.1311C>T (12.3%), c.95A>G (9.2%), c.392G>T (7.1%), c.1024C>T (6.2%) and c.1360C>T (1.0%). For the genotyping of 15 heterozygous female, all mutations were identified as follows: c.1376G>T/Normal (33.3%), c.1388G>A/Normal (26.7%), c.871G>A/Normal + c.1311C>T/Normal (20.0%), c.95A>G/Normal (13.3%) and c.392G>T./Normal (6.7%). The c.871G>A and 'silent' mutation c.1311 C>T was newly found to coexist in a high proportion of genotype in our population. / Glucose-6-phosphate dehydrogenase (G6PD)-deficient subjects are vulnerable to chemical-induced haemolysis if exposed to oxidative agents. Little is known, however, of the haemolytic effects of Chinese herbal medicine on G6PD-deficient subjects. Only one case study has reported that a G6PD-deficient newborn developed severe haemolysis after ingestion of Rhizoma Coptidis. Besides, recent studies reported that green tea and its constituents exerted pro-oxidative effects on cellular systems in culture. / Glucose-6-phosphate dehydrogenase deficiency is a genetic disorder inherited in the X-linked manner. The condition is prevalent in the Mediterranean region, Africa and Southeast Asia. In Hong Kong, the frequency of G6PD deficiency is around 4.5% in males and 0.3% in females. Over 140 specific mutations of the X-linked gene for G6PD have been characterized in various geographic regions. However, the local mutation pattern has not been clearly determined. / In conclusion, some Chinese herbal medicine, tea and tea polyphenols significantly altered the oxidative status of G6PD-deficient erythrocytes in vitro. Their in vivo effects on G6PD-deficient individuals would be further investigated by the novel G6PD-dificient mouse model. / In this study, we aim (1) to investigate effects of (a) a panel of Chinese Herbal Medicine (CHM), (b) tea and its constituents, on the oxidative status of human G6PD-deficient erythrocytes in vitro ; (2) to characterize the genotype of G6PD-deficiency in the Chinese population and their specific response to oxidative stress; (3) to develop a novel strain of mice as a model for study of chemicals agents on G6PD-deficient red cell in vivo. / Our results showed that six of eighteen CHM significantly reduced GSH levels in the G6PD-deficient erythrocytes (p<0.05, n=10). After exposure to 1 mg/mL of Rhizoma Coptidis, GSH levels in G6PD-deficient erythrocytes was decreased by 48.9 +/- 5.4% (P<0.001, n=10). At 5 mg/mL of Cortex Moutan, Radix Rehmanniae, Radix Bupleuri, Rhizoma Polygoni Cuspidati and Flos Chimonanthi, GSH levels were decreased significantly (P=0.001 to 0.004) by 51.8 +/- 7.6%, 25.9 +/- 6.7%, 21.0 +/- 6.9%, 17.5 $ 6.7% and 8.7 +/- 6.8% respectively. There were noticeable increases in levels of methaemoglobin by 2.8 fold (5 mg/mL, P=0.012) and 3.4 fold (10 mg/mL, P=0.016) in the presence of Rhizoma Coptidis and Cortex Moutan, respectively, in G6PD-deficient erythrocytes. / We also investigated the pro-oxidative effect of tea and its polyphenolic components on G6PD erythrocytes from G6PD-deficient (n=8) and normal adult (n=8) subjects. The tea extracts significantly reduced GSH and increased GSSG levels in G6PD-deficient erythrocytes in a dose-dependent manner (0.5-10 mg/mL), but not in normal erythrocytes. Similar dose-dependent responses to (-)-Epigallocatechin (EGC) and (-)-Epigallocatechin-3gallate (EGCG), but not to the other polyphenols, were observed. In G6PD-deficient cells, GSH was reduced by 43.3% (EGC at 0.05 mg/mL) and 33.3% (EGCG at 0.5 mg/mL), compared with pre-challenged levels. The concentration of methaemoglobin was increased significantly when these cells were challenged with tea extracts, and EGC. Plasma haemoglobin levels were higher in G6PD-deficient samples after exposure to tea extracts, EGCG, EGC and gallic acid, compared with those in normal blood. / Ko Chun Kay. / "August 2006." / Advisers: Tai Fai Fok; Kwai Har Karen Li. / Source: Dissertation Abstracts International, Volume: 68-03, Section: B, page: 1577. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. xxii-xliii). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.