蠕動是一種能夠幫助食物通過胃腸道以及促進胃腸道產生能動性的類似波浪的收縮運動。它由一種叫做Cajal (ICC)間質細胞的起搏器細胞產生的慢波所控制。ICCs亦幫助由腸神經系統(ENS)到平滑肌的信息傳導。嚙齒動物和人類實驗表明，老化所導致的ICC細胞數量下降和腸神經退化與排便睏難和便秘有關。通過研究ICC和ENS在正常老化情況下和加速膽碱能神經元喪失的阿爾茲海默症(AD)老鼠模型(Tg2576)中的變化，我們對治療神經退化性疾病也許會有新的認識。本課題的目的在于，研究老化情況下正常老鼠模型及澱粉樣前體蛋白質(APP)過量表達下的AD老鼠模型的胃腸道在形態及功能上的變化。 / 六個月大的Tg2576和同齡野生型對照的全樣載片免疫組化實驗顯示， 十二指腸 (P < 0.05)和迴腸 (P < 0.01)中的腸神經細胞顯著降低，迴腸 (P < 0.001)中的GFAP陽性的腸神經膠質細胞也顯著消失。S100陽性的腸神經膠質細胞在胃竇（胃部中的起搏區域）(P < 0.05), 迴腸 (P < 0.05)和結腸 (P < 0.05)中顯著喪失。這些結果表明，在早期的AD階段，ENS已經出現變質。ICC細胞數量在六個月大的Tg2576和同齡野生型對照的所有腸胃部分並沒有顯著性差異 (P > 0.05)。同時，早期AD階段的基本蠕動節奏也並沒有發生改變。除此之外，結腸和十二指腸的GFAP/S100陽性的腸神經膠質細胞比例並沒有顯著增加，表明在早期AD階段，可能出現了炎症。 / 利用石蠟切片進行β澱粉樣蛋白免疫組化，天狼猩紅溶液化驗和硫代黃素T溶液化驗可以測試不溶的澱粉樣斑塊是否存在。結果指出在六個月大的Tg2576所有腸胃部分都觀察到澱粉樣斑塊聚集而在不同的腸胃部分聚集的程度都有所分別。除了結腸外，六個月大的野生型對照所有腸胃部分都觀察不到澱粉樣斑塊聚集。澱粉樣斑塊形成的增長可能和早期AD階段出現的腸神經細胞和腸神經膠質細胞喪失互相關聯。 / 應用電泳轉移酶標免疫印斑技術，測試六個月大的Tg2576和同齡野生型對照的迴腸和結腸中，膽碱乙酰轉移酶 (ChAT，出自興奮神經元)， 神經元型一氧化氮合酶(nNOS，出自抑制神經元)， 膠質細胞源性神經營養因子 (GDNF， 出自腸神經膠質細胞)和可溶解的β澱粉樣蛋白寡聚體的表達是否改變。和野生型對照相比，Tg2576的nNOS的表達在迴腸 (P < 0.05) 而不是結腸 (P > 0.05) 中顯著增加。而ChAT，GDNF和各β澱粉樣蛋白寡聚體 (十二聚物，九聚物和六聚物)在六個月大的Tg2576和同齡野生型對照之間並沒有顯著改變 (P > 0.05)。綜上結果表明，在早期AD階段，腸胃道中的抑制信號有所增加，但是β澱粉樣蛋白寡聚體可能不是引致腸胃道中的腸神經細胞和腸神經膠質細胞喪失的原因。 / 在腸胃道的組織學和生化實驗之後，我們利用了微電極陣列 (MEA) 系統來量度出自胃竇和迴腸的慢波信號。量度出來的主導頻率(DF)和功率分佈可以成為測量在老化的ICR老鼠和早期AD階段下腸胃道的功能有沒有變化的參數。在硝苯地平存在下，尼古丁顯著地刺激三個月大 (P < 0.05) 和 六個月大 (P < 0.05) 的ICR老鼠中胃竇和迴腸的慢波活動但未能引起十二個月大 (P > 0.05) 的ICR老鼠中的慢波活動，說明神經退化可能在十二個月的年齡開始。附加了河豚毒素的情況下，尼古丁不能再刺激三個年齡組中胃竇和迴腸的慢波活動 (P > 0.05)，由此證明了尼古丁是對腸神經細胞起作用再去激發ICC的活動。六個月大的Tg2576和同齡野生型對照之間的胃竇和迴腸的基准讀數沒有顯著分別 (P > 0.05)。然而，尼古丁顯著地增加野生型對照中胃竇和迴腸的DF和胃電過速範圍 (P < 0.05) 但是不能刺激Tg2576中胃竇和迴腸的電流活動 (P > 0.05)，示意在早期AD階段腸胃道中已經出現了腸神經細胞和/或腸神經膠質細胞喪失。 / 綜上所言，研究結果提出AD老鼠模型有形態學，生物化學和功能上的轉變。本課題提供了在研究神經退化疾病上的基礎，也支持ENS是中樞神經系統早期病變前的關口這個假設。 / Peristalsis is the wave-like contraction that moves food along the gastrointestinal (GI) tract and generates GI motility. Peristalsis is modulated by slow waves that originate from pacemaker cells called interstitial cell of Cajal (ICC). ICCs also modulate and transduce inputs from the enteric nervous system (ENS) to the smooth muscle. Recent studies in rodents and humans demonstrated that a decrease in ICC number and enteric neurodegeneration during ageing is associated with difficult bowel movements and constipation. By studying ICC and the ENS during normal aging and in a mouse model (Tg2576) of Alzheimer’s disease (AD) where cholinergic loss may be exaggerated, we may gain new perspectives on the treatment of degenerative diseases. The aim of the present study therefore, was to investigate the morphological and functional changes of the GI tract of mice during ageing and in an AD mouse model over-expressing amyloid precursor protein (APP) using an isolated tissue approach. / Whole mount immunohistochemistry of 6-month-old Tg2576 mice and their age-matched wild type (WT) controls revealed that there were significant losses of enteric neurons in the duodenum (P < 0.05) and ileum (P < 0.001), and of GFAP-positive enteric glial cells in the ileum (P < 0.001). There was also a loss of S100-positive glial cells in the antrum (pacemaker region in the stomach) (P < 0.05), ileum (P < 0.05) and colon (P < 0.05). These results indicated the alteration of the ENS during the early stages of AD. There were no differences in ICC arears of all GI regions between 6-month-old Tg2576 mice and their age-matched WT controls (P > 0.05), and there was no alteration of basal peristaltic rhythm during the early stages of AD. The non-significant increase of GFAP to S100 enteric glial cell ratio in the duodenum and colon might indicate an ongoing inflammatory process in these two GI regions during the early stages of AD. / The presence of insoluble amyloid plaques was studied using Aβ immunohistochemistry, Sirius red assay and Thioflavin-T assay on paraffin wax sections. The aggregation of amyloid plaques was observed in all the GI regions of 6-month-old Tg2576 mice and the levels of amyloid plaque varied in different regions. No amyloid plaques were found in the GI tract of 6-month-old WT animals excepting the colon. The increase in formation of amyloid plaques might be correlated to the losses of enteric neurons and enteric glial cells during the early stages of AD. / Western blot analysis was performed on frozen sections of tissues from the ileum and colon to investigate whether there were changes in choline acetyltransferase (ChAT, from excitatory neurons), neuronal nitric oxide synthase (nNOS, from inhibitory neurons), glial cell line-derived neurotrophic factor (GDNF, from enteric glia) and soluble Aβ oligomers between 6-month-old Tg2576 mice and WT controls. nNOS expression significantly increased in the ileum (P < 0.05) but not in the colon (P > 0.05) of Tg2576 mice compared with WT controls. There were no differences in the expressions of ChAT, GDNF and Aβ oligomers (docecamer, nonamer and hexamer) in the ileum and colon between Tg2576 mice and WT controls (P > 0.05). These results imply that there is an increase in the inhibitory signal in the GI tract during the early stages of AD but soluble Aβ oligomers might not be the cause of neuronal and glial losses in the GI tract. / Following histological and biochemical studies of different GI regions, slow wave signals from the antrum and ileum were measured using a microelectrode array (MEA) system. The dominant frequencies (DFs) and power distributions were measured and these served as parameters for measuring functional changes in the GI tract during ageing in ICR mice and the early stages of AD. In the presence of nifedipine, nicotine significantly stimulated the slow wave activities in the antrum and ileum of 3-month-old (P < 0.05) and 6-month-old (P < 0.05) ICR mice but failed to trigger the slow wave activities in 12-month-old (P > 0.05) ICR mice, suggesting the neurodegeneration might begin with the age between 6 and 12 months. With the addition of tetrodotoxin, nicotine failed to stimulate the slow wave activities in the antrum and ileum of three age groups (P > 0.05) and it showed that nicotine only acted on enteric neurons to trigger the ICC activities. There were no differences in the antral and ileal baseline recordings between 6-month-old Tg2576 mice and their age-matched WT controls (P > 0.05). However, nicotine significantly increased DFs and tachygastria ranges of the antrum and ileum in WT controls (P < 0.05) but failed to increase electrical activitiy of the antrum and ileum in Tg2576 mice (P > 0.05), thus suggesting a loss of neuronal and/or glial cells in the GI tract during the early stages of AD. / In conclusions, these findings suggest the mouse model for AD has morphological, biochemical and functional changes in the GI tract. The present studies provide a foundation for the investigation of degenerative diseases and support the hypothesis that the ENS may be the gateway for the early pathological changes in the central nervous system. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Hui, Chin Wai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 180-200). / Abstracts also in Chinese. / PUBLICATIONS RELATED TO THE WORK IN THIS THESIS --- p.i / ABSTRACT --- p.ii / 摘要 --- p.iv / ACKNOWLEDGEMENTS --- p.vi / LIST OF ABBREVIATIONS --- p.vii / Chapter CHAPTER 1 --- Introduction --- p.1 / Chapter 1.1 --- General introduction --- p.1 / Chapter 1.2 --- Interstitial cells of Cajal (ICCs) as electrical pacemaker cells in GI tract --- p.1 / Chapter 1.2.1 --- ICC subtypes in GI tract --- p.2 / Chapter 1.3 --- Hypotheses of slow wave generation --- p.4 / Chapter 1.3.1 --- Mechanisms of the NSCC pacemaking hypothesis --- p.5 / Chapter 1.3.2 --- Mechanisms of the alternative hypothesis --- p.6 / Chapter 1.4 --- Involvement of ion channels in slow wave generation of ICC --- p.6 / Chapter 1.4.1 --- Calcium channels --- p.6 / Chapter 1.4.2 --- Sodium channels --- p.7 / Chapter 1.4.3 --- Potassium channels --- p.7 / Chapter 1.4.4 --- Chloride channels --- p.8 / Chapter 1.4.5 --- Non-selective cation channels --- p.8 / Chapter 1.5 --- Distribution of several types of receptors in ICC --- p.11 / Chapter 1.5.1 --- Purinergic receptors --- p.11 / Chapter 1.5.2 --- Muscarinic receptors --- p.11 / Chapter 1.5.3 --- Tachykinin receptors --- p.12 / Chapter 1.5.4 --- Vasoactive intestinal peptide receptors --- p.12 / Chapter 1.5.5 --- Serotonin receptors --- p.13 / Chapter 1.6 --- Introductions and functions of enteric nervous system --- p.15 / Chapter 1.6.1 --- Interaction amongst the central, peripheral and enteric nervous system: brain-gut axis --- p.15 / Chapter 1.6.2 --- Enteric neuronal subtypes in the GI tract --- p.15 / Chapter 1.6.2.1 --- Motor neurons --- p.16 / Chapter 1.6.2.2 --- Interneurons --- p.16 / Chapter 1.6.2.3 --- Intrinsic primary afferent neurons --- p.18 / Chapter 1.6.3 --- Enteric glial cells --- p.18 / Chapter 1.6.3.1 --- Enteric glial subtypes in the GI tract --- p.18 / Chapter 1.6.3.2 --- Communication between enteric neurons and glial cells --- p.19 / Chapter 1.6.3.3 --- Possible functions of enteric glial cells in the GI tract --- p.19 / Chapter 1.6.3.3.1 --- Secretion of neurotrophic factors --- p.20 / Chapter 1.6.3.3.2 --- Secretion of reduced glutathione --- p.20 / Chapter 1.6.3.3.3 --- Secretion of transforming growth factor-beta 1 --- p.21 / Chapter 1.7 --- Interactions amongst ICC, enteric neurons and enteric glial cells --- p.21 / Chapter 1.8 --- Gastrointestinal disorders --- p.22 / Chapter 1.8.1 --- Mechanisms for cell depletion --- p.22 / Chapter 1.8.1.1 --- Autoimmune attack --- p.22 / Chapter 1.8.1.2 --- Hyperglycaemia and diabetes mellitus --- p.24 / Chapter 1.8.1.3 --- Oxidative stress --- p.25 / Chapter 1.8.1.4 --- Ageing --- p.26 / Chapter 1.9 --- Alzheimer’s disease --- p.28 / Chapter 1.9.1 --- Genetics and pathogenesis of Alzheimer’s disease --- p.28 / Chapter 1.9.1.1 --- Aggregation of amyloid beta protein --- p.29 / Chapter 1.9.1.2 --- Genetic factors of AD --- p.29 / Chapter 1.9.1.3 --- Tau hyperphosphorylation and neurofibrillary tangles --- p.31 / Chapter 1.9.2 --- Current treatment for Alzheimer’s disease --- p.33 / Chapter 1.9.2.1 --- Symptomatic treatment --- p.33 / Chapter 1.9.2.2 --- Disease-modifying treatment --- p.34 / Chapter 1.9.2.3 --- Other potential drugs for AD treatment --- p.35 / Chapter 1.9.3 --- Possible animal models for AD investigation --- p.36 / Chapter 1.9.4 --- Possible correlations between Alzheimer’s disease and the enteric nervous system --- p.36 / Chapter 1.10 --- Aim of study --- p.37 / Chapter CHAPTER 2 --- Investigation into the morphologies of enteric nervous system and interstitial cell of Cajal in Tg2576 mice --- p.38 / Chapter 2.1 --- Introduction --- p.38 / Chapter 2.1.1 --- Molecular markers for ICC, ENC, and EGC --- p.38 / Chapter 2.1.2 --- Aims and objectives --- p.39 / Chapter 2.2 --- Materials and methods --- p.41 / Chapter 2.2.1 --- Animals --- p.41 / Chapter 2.2.2 --- Tissue preparation --- p.41 / Chapter 2.2.3 --- Immunohistochemistry --- p.42 / Chapter 2.2.4 --- Image acquisition and analysis --- p.43 / Chapter 2.3 --- Results --- p.44 / Chapter 2.3.1 --- General observations --- p.44 / Chapter 2.3.2 --- Area and pattern of ICCs and the ENS in the stomach --- p.46 / Chapter 2.3.3 --- Area and pattern of ICCs and the ENS in the duodenum --- p.52 / Chapter 2.3.4 --- Area and pattern of ICCs and the ENS in the jejunum --- p.56 / Chapter 2.3.5 --- Area and pattern of ICCs and the ENS in the ileum --- p.60 / Chapter 2.3.6 --- Area and pattern of ICCs and the ENS in the colon --- p.66 / Chapter 2.4 --- Discussion --- p.70 / Chapter 2.4.1 --- Major findings --- p.70 / Chapter 2.4.2 --- Possible alterations of the ENS during AD --- p.70 / Chapter 2.4.3 --- Morphological changes of the ENS in relation to genotype --- p.71 / Chapter 2.4.4 --- Morphological changes of ICCs in relation to genotype --- p.72 / Chapter 2.4.5 --- Morphological changes of the ENS and ICCs in relation to GI regions --- p.72 / Chapter 2.4.6 --- Inflammatory conditions in different GI regions --- p.73 / Chapter 2.5 --- Conclusion --- p.74 / Chapter CHAPTER 3 --- Formation of amyloid plaques in the brain and the GI tract of Tg2576 mice --- p.75 / Chapter 3.1 --- Introduction --- p.75 / Chapter 3.1.1 --- The absence of amyloid plaques in rodents --- p.75 / Chapter 3.1.2 --- Overexpression of human APP in transgenic mice --- p.76 / Chapter 3.1.3 --- Distribution of human APP and Aβ deposition in human and transgenic mice --- p.77 / Chapter 3.1.4 --- Transgene and promoter in Tg2576 mouse --- p.77 / Chapter 3.1.5 --- Methods for Aβ plaque detection --- p.78 / Chapter 3.1.6 --- Aim and objectives --- p.78 / Chapter 3.2 --- Materials and methods --- p.80 / Chapter 3.2.1 --- Animals --- p.80 / Chapter 3.2.2 --- Tissue processing --- p.80 / Chapter 3.2.3 --- Preparation of paraffin wax blocks and slide sections --- p.81 / Chapter 3.2.4 --- Aβ immunohistochemistry --- p.82 / Chapter 3.2.5 --- Sirius red assay --- p.83 / Chapter 3.2.6 --- Thioflavin-T assay --- p.84 / Chapter 3.2.7 --- Image acquisition --- p.84 / Chapter 3.3 --- Results --- p.85 / Chapter 3.3.1 --- Aβ immunohistochemistry --- p.85 / Chapter 3.3.1.1 --- The absence of positive immunoreactivity in the brain --- p.85 / Chapter 3.3.1.2 --- The presence of positive immunoreactivity in the GI tract of Tg2576 mice --- p.85 / Chapter 3.3.2 --- Sirius red assay --- p.92 / Chapter 3.3.2.1 --- The presence of positive immunoreactivity in the brain of Tg2576 mice --- p.92 / Chapter 3.3.2.2 --- Characteristics of Sirius red staining in the GI tract --- p.92 / Chapter 3.3.2.3 --- The presence of positive immunoreactivity in the GI tract of Tg2576 mice --- p.92 / Chapter 3.3.3 --- Thioflavin-T assay --- p.98 / Chapter 3.3.3.1 --- The presence of positive immunoreactivity in the brain of Tg2576 mice --- p.98 / Chapter 3.3.3.2 --- The presence of positive immunoreactivity in the GI tract of Tg2576 mice --- p.98 / Chapter 3.4 --- Discussion --- p.104 / Chapter 3.4.1 --- The presence of a small amount of amyloid plaques in the brain of young Tg2576 mice --- p.104 / Chapter 3.4.2 --- The presence of amyloid plaques in the GI tract --- p.104 / Chapter 3.4.3 --- Plaque formation in relation to genotype --- p.105 / Chapter 3.4.4 --- Possible effects of amyloid plaques in the brain and GI tract --- p.106 / Chapter 3.5 --- Conclusion --- p.108 / Chapter CHAPTER 4 --- Expression of Aβ oligomers, ChAT, nNOS and GDNF in the GI tract of Tg2576 mice --- p.109 / Chapter 4.1 --- Introduction --- p.109 / Chapter 4.1.1 --- Common and peripheral types of ChAT --- p.109 / Chapter 4.1.2 --- Three subtypes of NOS --- p.111 / Chapter 4.1.3 --- Functions of glial cell line-derived neurotrophic factor in the ENS --- p.112 / Chapter 4.1.4 --- Neurotoxicity of soluble Aβ peptides --- p.113 / Chapter 4.1.5 --- Aims and objectives --- p.113 / Chapter 4.2 --- Materials and methods --- p.115 / Chapter 4.2.1 --- Animals --- p.115 / Chapter 4.2.2 --- Preparation of materials --- p.115 / Chapter 4.2.3 --- Sample preparation --- p.117 / Chapter 4.2.4 --- Separating and stacking gels preparation --- p.118 / Chapter 4.2.5 --- Western blot --- p.119 / Chapter 4.2.6 --- Image acquisition and analysis --- p.120 / Chapter 4.3 --- Results --- p.122 / Chapter 4.3.1 --- Increase in nNOS expression in the ileum of Tg2576 mice --- p.122 / Chapter 4.3.2 --- No changes in the expressions of Aβ oligomers, ChAT, nNOS and GDNF in the colon of Tg2576 mice --- p.122 / Chapter 4.4 --- Discussion --- p.127 / Chapter 4.4.1 --- The absence of “cholinergic hypothesis of AD in the GI tract of Tg2576 mice --- p.127 / Chapter 4.4.2 --- Increased expression of nNOS in the ileum of Tg2576 mice --- p.128 / Chapter 4.4.3 --- Neuronal and glial losses may be related to the reduced GDNF expression --- p.129 / Chapter 4.4.4 --- No relationship between the Aβ oligomers and neuronal damages in the GI tract --- p.129 / Chapter 4.5 --- Conclusion --- p.129 / Chapter CHAPTER 5 --- Microelectrode array (MEA) study on slow wave activity in the GI tract --- p.131 / Chapter 5.1 --- Introduction --- p.131 / Chapter 5.1.1 --- Components in peristalsis-controlling unit --- p.131 / Chapter 5.1.2 --- Techniques in evaluating slow wave activity --- p.131 / Chapter 5.1.2.1 --- Patch clamp --- p.132 / Chapter 5.1.2.2 --- Calcium imaging --- p.132 / Chapter 5.1.3 --- Application of microelectrode array in evaluating slow wave activity --- p.134 / Chapter 5.1.4 --- Aims and objectives --- p.136 / Chapter 5.2 --- Methods and materials --- p.137 / Chapter 5.2.1 --- Animals --- p.137 / Chapter 5.2.2 --- Tissue preparation --- p.137 / Chapter 5.2.3 --- Electrical recordings --- p.138 / Chapter 5.2.4 --- Analysis and Statistics --- p.139 / Chapter 5.3 --- Results --- p.142 / Chapter 5.3.1 --- Experiments on ICR mice --- p.142 / Chapter 5.3.1.1 --- Nicotine stimulates the slow wave activity in the antrum in the presence of NIF but not in the presence of NIF and 500 nM TTX --- p.142 / Chapter 5.3.1.2 --- Nicotine stimulates the slow wave activity in the ileum in the presence of NIF but only partially stimulates activity in the presence of NIF and 500 nM TTX --- p.152 / Chapter 5.3.1.3 --- The use of 1 μM TTX completely blocked the nicotine stimulation in the ileum --- p.160 / Chapter 5.3.1.4 --- The dominant frequency of baseline increased in the ileum of 12-month-old ICR but not in the antrum in the presence of NIF --- p.162 / Chapter 5.3.2 --- Experiments on Tg2576 mice and their wild type controls --- p.164 / Chapter 5.3.2.1 --- No differences in both antral and ileal baseline DFs between 6- month-old non-transgenic and Tg2576 mice --- p.164 / Chapter 5.3.2.2 --- Nicotine stimulates slow wave activity in the antrum of 6-month-old wild type controls but not of Tg2576 mice --- p.164 / Chapter 5.3.2.3 --- Nicotine stimulates slow wave activity in the ileum of 6-month-old wild type controls but not of Tg2576 mice --- p.167 / Chapter 5.4 --- Discussion --- p.171 / Chapter 5.4.1 --- Pharmacological effects of nicotine in the GI tract --- p.171 / Chapter 5.4.2 --- Excitatory effects of nicotine in the slow wave activities of the stomach and ileum --- p.172 / Chapter 5.4.3 --- Changes of ICC functions and neuronal activities during ageing --- p.174 / Chapter 5.4.4 --- Enteric neurodegeneration leads to alteration in the ENS function in Tg2576 mice --- p.175 / Chapter 5.4.5 --- Conclusion --- p.176 / Chapter CHAPTER 6 --- Concluding discussion --- p.177 / REFERENCES --- p.180

No description available.

Hippocampal mineralocorticoid receptor mRNA expression was increased in male hamsters exposed to 18 days of short photoperiod relative to animals maintained under long day illumination (p < 0.05). Short day hamsters were also characterized by increased weight gain, and heavier adrenal glands (p < 0.05). The larger adrenals showed selective increases in the widths of the zonae reticularis and glomerulosa (p < 0.001). Incidences of torpor and reduced body temperature were observed in the short day animals. No changes were found in reproductive organ weights, systolic blood pressure, open-field behavior, or stress levels of plasma corticosteroids. We conclude that the hamster brain-adrenal axis responds rapidly to changes in photoperiod, raising the possibility that this axis is a primary mediator of shortened photoperiod responses.