by Chiu Pui Yu. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 86-118). / Abstracts in English and Chinese. / Title Page --- p.i / Abstract --- p.ii-iv / Acknowledgement --- p.v / Table of Contents --- p.vi-viii / List of Tables --- p.ix / List of Figures --- p.x-xii / List of Abbreviations --- p.xiii / Chapter Section I: --- Introduction / Chapter Chapter 1: --- Overview --- p.1-2 / Chapter Chapter 2: --- Teratogenic Effects of Hyperglycemia / Chapter 2.1 --- What is Hyperglycemia --- p.3 / Chapter 2.2 --- Teratogenic Effects of Hyperglycemia --- p.4-6 / Chapter 2.2.1 --- Human Studies / Chapter 2.2.2 --- Animal Studies / Chapter 2.3 --- Timetables for Embryogenesis: Rats versus Humans --- p.7 / Chapter 2.4 --- Mechanisms of Hyperglycemia Induced Teratogenesis --- p.8-12 / Chapter 2.4.1 --- What are Free Radicals? / Chapter 2.4.2 --- Major Free Radical Species Involvedin Hyperglycemic Teratogenesis / Chapter 2.4.3 --- Molecular Damage Induced by Reactive Oxygen Species / Chapter 2.4.4 --- Supporting Evidence of Reactive Oxygen Species Causing Anomalies / Chapter 2.4.5. --- Hyperglycemia and Formation of Free Radicals / Chapter Chapter 3: --- Caffeine as Teratogen and Antioxidant / Chapter 3.1 --- Popularity of Caffeine --- p.13 / Chapter 3.2 --- Basic Metabolism of Caffeine --- p.14 / Chapter 3.3 --- Biological Actions of Caffeine --- p.15 / Chapter 3.4 --- Teratogenicity of Caffeine --- p.16-20 / Chapter 3.4.1 --- Animal Studies / Chapter 3.4.1.1 --- Teratogenic Effects of Caffeine in Animals / Chapter 3.4.1.2 --- Teratogenic Dose of Caffeine / Chapter 3.4.1.3 --- Interspecies Sensitivity / Chapter 3.4.2 --- Human Studies / Chapter 3.5 --- Possible Mechanisms for the Teratogenic Actions of Caffeine --- p.21 / Chapter 3.6 --- Caffeine as an Antioxidant --- p.22 / Chapter 3.7 --- Combined Effects of Caffeine with Other Substances --- p.23 / Chapter Chapter 4: --- Combined Effects of Hyperglycemia and Caffeine on Early Embryogenesis- A Question to be Answered / Chapter 4.1 --- Possible Links between Hyperglycemia and Caffeine --- p.24 / Chapter 4.2 --- Objectives of the Present Study --- p.25 / Chapter 4.3 --- Hypothesis --- p.26 / Chapter Section II: --- Research Designs and Methods / Chapter Chapter 5: --- Materials and Methods / Chapter 5.1 --- Licenses --- p.27 / Chapter 5.2 --- Overall Study Design --- p.28-40 / Chapter 5.2.1 --- Whole Embryo Culture Model / Chapter 5.2.1.1 --- Animals / Chapter 5.2.1.2 --- Explantation of Embryos and Serum Collection / Chapter 5.2.1.3 --- Preparation of Serum / Chapter 5.2.1.4 --- Culture Media / Chapter 5.2.1.5 --- Embryo Culture / Chapter 5.2.2 --- Experimental Groups / Chapter 5.2.3 --- Morphological Assessment / Chapter 5.2.4 --- Quantitation of Oxidative Stress / Chapter 5.2.5 --- Protein Assay / Chapter 5.3 --- Statistical Evaluation --- p.41 / Chapter Chapter 6: --- Laboratory Considerations / Chapter 6.1 --- Whole Embryo Culture Model --- p.42-43 / Chapter 6.1.1 --- Subjects / Chapter 6.1.2 --- Time Mating / Chapter 6.1.3 --- Culture Medium / Chapter 6.1.4 --- Gas Phase and Rotating Bottle Culture Method / Chapter 6.2 --- Quantification of Oxidative Stress --- p.47-49 / Chapter 6.2.1 --- 8-Isoprostaglandins F2a as a Marker / Chapter 6.2.2 --- Assay for 8-Isoprostaglandins F2a / Chapter 6.2.2.1 --- Enzyme Immunoassay versus Gas Chromatography/ Mass Spectrometry / Chapter Section III: --- Results / Chapter Chapter 7: --- Results / Chapter 7.1 --- Justifications of Methods of Statistical Analysis --- p.50 / Chapter 7.2 --- Effects of Hyperglycemia on Early Embryogenesis --- p.51-56 / Chapter 7.2.1 --- Effects of Hyperglycemia on Morphological Development / Chapter 7.2.2 --- Effects of Hyperglycemia on Production of 8-isoprostaglandins F2a / Chapter 7.2.3 --- Effects of Hyperglycemia on Total Protein Content / Chapter 7.3 --- Effects of Caffeine on Early Embryogenesis --- p.57-61 / Chapter 7.3.1 --- Effects of Caffeine on Morphological Development / Chapter 7.3.2 --- Effects of Caffeine on Total Protein Content / Chapter 7.4 --- Combined Effects of Hyperglycemia and Caffeine on Early Embryogenesis --- p.62-66 / Chapter 7.4.1 --- Combined Effects of Hyperglycemia and Caffeine on Morphological Development / Chapter 7.4.2 --- Combined Effects of Hyperglycemia and Caffeine on Production of 8-isoprostaglandins F2a / Chapter 7.4.3 --- Combined Effects of Hyperglycemia and Caffeine on Total Protein Content / Chapter Section IV: --- Discussion and Conclusions / Chapter Chapter 8: --- Discussion --- p.67-83 / Chapter Chapter 9: --- Conclusions and Future Directions --- p.84 / Appendices --- p.85 / References --- p.86-118

Mode of access: World Wide Web. / Thesis (Ph. D.)--University of Hawaii at Manoa, 2005. / Includes bibliographical references (leaves 116-154). / Electronic reproduction. / Also available by subscription via World Wide Web / xvii, 157 leaves, bound ill. 29 cm

Previous studies have focused on gastric dysmotility and delayed emptying in diabetes mellitus. There is little information about the effects of hyperglycemia on colonic motility and secretion. 5-HT was reported to mediate contractile activity by activating receptors on both enteric neurons and smooth muscle cells. The aim of this study was to investigate and compare the effects of 5-HT on circular contractile activity coordinated with secretion in streptozocin-induced diabetic and non-diabetic rats. Sonomicrometry and voltage clamping techniques were used to measure motility and secretion simultaneously in isolated whole thickness colonic sheets. Male Sprague Dawley rats were injected with streptozocin (65 mg/kg body weight) in 0.1 M sodium citrate buffer, into the tail veins. Glucose levels of 300-400 mg/dl and above were achieved. The control rats were injected with the same volumes of vehicle (0.1 M sodium citrate buffer). Animals were sacrificed 10-12 days following the induction of hyperglycemia. Flat sheets of colon were mounted serosal side up in Ussing chambers. 1 mm piezocrystals were glued to the serosal surface 4-5 mm apart to measure circular contractions as decrease in inter-crystal distances (ICD). Voltage-clamping the tissues at 0 mV was used ix to measure short circuit current (Isc), indicative of chloride secretion. In diabetic rats 50 gM 5-HT caused mean amplitude of contractions of 174 ± 26 gm (n=4), which was significantly reduced as compared to the response in non-diabetic rats of 970 + 243 gm (n=4; p<0.05). The secretory response in diabetic rats paralleled the reduction in ICD (diabetic: 23 +1 gA/cm2, controls: 57 + 18 gA/cm2). Neural blockade with 0.1 gM TTX revealed a decreased myogenic contractile activity in diabetic rats. The mean amplitude of contractions after TTX in diabetic rats was 162 ± 45 gm verses controls of 612 ± 86 gm. These results suggest that the reduction of the 5-HT contractile response in diabetic rats may be a composite of direct effects on the smooth muscle as well as indirect effects on the neurons. / Department of Physiology and Health Science