No description available.

A radioimmunoassay was developed, specific for the gastrointestinal polypeptide, motilin. Antisera were raised in guinea pigs and rabbits. The immunogen was porcine motilin, conjugated to bovine serum albumin by the carbodiimide condensation reaction. The routine antiserum behaved identically towards endogenously- released motilin and the pure standard preparation. A radioactive tracer of high 125 specific activity was obtained after incorporation of - iodine into the motilin molecule by the chloramine-T method. The optimum conditions for all other assay variables were established to produce the most sensitive displacement Cstandard) curve. Motilin antiserum, coupled directly to an agarose matrix, retained full antibody activity and sensitivity. It is a feasible technique for use in both the radioimmunoassay and in the extraction of motilin from both serum and tissue extracts. The fasting serum levels of IR- motilin was 190 - 131 pg/ml in men and 294 -'.44 pg/ml in dogs (mean - SD) . The increase in motor activity in the extrinsically denervated fundic pouch of the dog after duodenal alkalinization was associated with a concomitant elevation in serum IR- motilin levels. This increase in serum IR- motilin was in the same range as that achieved by the exogenous administration of the porcine polypeptide which produced the same motor response. Duodenal acidification produced an apparent increase in serum IR-motilin with no associated increase in gastric motor activity. Only one peak of motilin immunoreactivity was detected when serum containing alkali-stimulated motilin or a partially purified duodenal extract were subjected to gel filtration on Sephadex G-50. The distribution of motilin throughout the hog gastrointestinal tract, determined by radioimmunoassay on partially purified extracts, agreed with the immunocytochemical findings that motilin was predominantly located in the duodeninn and jejunum, with traces.in the upper ileum. Virtually the intact molecule was required for the expression of full biological potency. The individual amino acids were important inasmuch as they contributed to the charge distribution and conformation of the molecule. The physiological release and function of motilin have yet to be determined. Elevated levels of circulating IR- motilin have not been associated with any gastro-intestinal function, although they appear to be depressed by feeding. Motilin has been implicated in the control of the interdigestive phase of gastric motor activity. It may be acting in a local or paracrine manner. Motilin has not been implicated in any .•cU'in±cal.rst"ait"eC&s sjffetfce i The hormonal status of gastric inhibitory polypeptide (GIP) has been studied with the existing radioimmunoassay, modified to improve the label specific activity (by ion exchange chromatography). Direct coupling of GIP antisera to agarose beads was unsatisfactory, antibody activity and sensitivity being greatly reduced by the close proximity of the solid matrix. The postulated role of GIP as the enterogastrone1 of Kosaka and Lim, suggested by studies with exogenously-administered polypeptide, was confirmed by experiments in the dog. Pentagastrin-stimulated gastric acid secretion was inhibited by intra-duodenal infusion with glucose or fat; this inhibition being associated with a significant elevation in the circulating serum IR- GIP levels, within the range produced by ingestion of a mixed meal. GIP does not appear to be involved in the inhibition of gastric acid secretion produced by duodenal acidification. Endogenous;GIP.stimulated by either fat or glucose exhibited at least 3 Immunoreactive components after column chromatography. The IR- GIP eluting in the void volume appeared to represent a non-specific complex between GIP and a serum protein and is possibly biologically inactive. A second IR-GIP component with a molecular weight of 7500-8000 (ProGIP), eluted ahead of the established form of GIP (molecular weight = 5105). ProGIP has been found to be relatively unstable. ProGIP and GIP^QQQ have also been detected in extracts of hog duodenal mucosa. The established insulinotropic effect of GIP correlates best with that percentage of the total IR- GIP composed of ProGIP and GIP500(). The relative proportions of IR- GIP500Q and IR- ProGIP in serum samples taken at different times after ingestion of either fat or glucose, suggest that ProGIP is either a precursor of GIP or that the ProGIP-producing cells occupy a more distal region of the duodenal and jejunal mucosa than the GIP- producing cells. Exogenous administration of synthetic somatostatin in dogs and man will inhibit both.GIP release by either fat or glucose and the insulino-tropic action of GIP at the level of the 8/-cell. Naturally-occurring intestinal or pancreatic somatostatin may contribute to the control of GIP release and serve to modulate the GIP- mediated response of the gastric parietal or pancreatic β-cell. / Medicine, Faculty of / Cellular and Physiological Sciences, Department of / Graduate

A thesis submitted to the Faculty of Medicine, University of the Witwatersrand, Johannesburg, for the degree of Doctor of Medicine. / An attempt was made to document iron losses from the body as a whole, as well as from individual excretory routes using a combination of radioisotopic and chemical techniques. The purpose of this work was to gain a better understanding of external body exchange, and to resolve some of the existing controversies regarding the magnitude of daily iron losses. The basis for this controversy is extensively reviewed in the thesis / IT2018

The gastrointestinal tract has a large functional reserve. This is particularly true of the small intestine, and early studies by Flint in 1912, showed that dogs could withstand 50%-70% small intestinal resection, returning to normal health after an initial period of weight loss and malabsorption. No doubt, this reserve is in part due to the very high rate of epithelial proliferation in small bowel mucosa. Intestinal adaptation is the result of morphological and functional changes, and while these parameters can be accurately appreciated, the mechanisms by which these changes take place, are still under active investigation. This section summarises the changes, both structural and functional, in the adaptive process, and this is followed by a review of the background work done on the possible mechanism of adaptation. The normal anatomy of intestinal mucosa is however, considered first. Most of the work done to date in the field of intestinal adaptation, involves the small bowel, and this part of the gut will be discussed predominantly, but data available on colonic growth will be mentioned.

No description available.

糖尿病是一种呈现流行趋势的代谢紊乱综合症，现如今，全球大约有3.46亿糖尿病患者， 这庞大的数字给各国的公共健康安全支出带来了严重的财政负担。 其中，二型糖尿病（T2DM）占90%。其特点是周围组织的胰岛素抵抗以及后期损伤的胰岛β细胞的功能。在饮食后，小肠会分泌两种肠促胰岛素，葡萄糖依赖性促胰岛素多肽（GIP）和胰高血糖素样肽-1（GLP-1）。两种多肽的主要功能是促进餐后胰岛细胞中胰岛素的分泌，另外他们还可以通过其自身的G蛋白偶联受体，GIPR和GLP-1R发挥其他作用，如葡萄糖依赖性的刺激胰岛素的生成，刺激胰岛β细胞的增殖，抑制细胞的凋亡等。这些功能也使肠促胰岛素成为糖尿病治疗的一种手段，比如Exendin-4和DPP4抑制剂。 然而，除了在胰岛中的作用，肠促胰岛还可能和脂质代谢相关，其中GIP和脂质代谢的报导研究的更加深入。在肥胖的状态下，血液中GIP含量高于正常水平；GIPR基因敲除老鼠和GIPR的抑制剂喂养的小鼠可以抵抗高脂饮食诱导的肥胖和2型糖尿病；GIP还可以直接调节脂肪细胞的脂肪生成和脂解。这些数据表明GIP在肥胖和糖尿病的发生过程中可能存在促进作用,这使得GIP治疗药物的开发需要谨慎的对待。 / 为了进一步研究GIP在脂肪细胞中发挥的生物学效应，在本研究中，我们利用腺病毒介导技术通过在脂肪细胞中过表达GIPR来增加GIP的活性，然后检查GIP在脂肪细胞中所起的作用。实验结果表明,GIP可以通过cAMP-PKA信号通路迅速并且长期的刺激脂肪细胞的炎症反应，增强IKKβ-NFκB信号通路和增加炎症基因的表达。更深入的机制研究表明，JNK 信号通路也参与GIP诱导的炎症反应，抑制JNK通路可以大部分恢复GIP增加的炎症因子的表达和IKKβ的磷酸化水平。由于长期的炎症反应，脂肪细胞的胰岛素信号通路受到GIP的损伤，在GIPR过表达的脂肪细胞中，胰岛素刺激的AKT磷酸化水平和葡萄糖吸收能力都被GIP降低，葡萄糖转运蛋白4（Glut-4）的表达水平也同时减少。因此，本研究结果表明GIP可能在肥胖的发展过程中，通过诱导脂肪细胞的炎症反应来损伤胰岛素敏感性而最终导致2型糖尿病的发生。 / Diabetes mellitus is a type of metabolic syndrome that has prevailed all over the world with the development of economic and over-nutrient lifestyle. It is estimated to 346 million diabetes patients in the worldwide most recently. The huge population put a major burden on the cost of public health care to all the countries. Among the types of diabetes, type 2 diabetes (T2DM) makes up 90% of recorded cases. The characteristics of T2DM are insulin resistance of peripheral tissues and impaired pancreatic cell function and mass. Two major incretins GIP (glucose-dependent insulinotropic peptide) and GLP-1 (glucagon-like peptide 1) are secreted from gut in response to food ingestion. The prominent role of GIP and GLP-1 is to stimulate glucose-dependent insulin release in pancreatic β cell. In addition, they both exert multiple biological effects via their relative G-protein coupled receptors, GIPR and GLP-1R, including glucose-stimulated insulin production, cell proliferation and anti-apoptosis in pancreatic β cells. The beneficent effects of incretins potentiate them as targets for the treatment of diabetes. GLP-1 analog, exendin-4 and DDP4 (dipeptidyl peptidase-4) inhibitors (to prevent GIP and GLP-1 from degradation) have been already used in clinical research. However, in addition to their effects on pancreatic β cell, both peptides are also related to lipid metabolism. The role of GIP has been studied more extensively. In obese state, the circulating level of GIP is elevated. GIPR knockout (KO) mice are resistant to high fat diet (HFD) induced obesity, a similar phenotype is found in GIPR antagonist administrated HFD-mice. Moreover, GIP also directly promotes lipogenesis and lipolysis in adipocytes. The rising evidence suggests a potential role of GIP in adipocyte biology and lipid metabolism, which diminishes the enthusiasm of GIP as a candidate therapeutic reagent for T2DM. / In order to further understand the biological effects of GIP in adipocytes, here, we over-expressed GIPR in 3T3-L1 CAR adipocytes via adenovirus-mediated gene transfer technology to enhance the activity of GIP. The results demonstrate that GIP impairs the physiological functions of adipocytes as a consequence of increasing the production of inflammatory cytokines, chemokines, and phosphorylation of IkB kinase (IKK) β through activation of the cyclic AMP-protein kinase A (cAMP-PKA) pathway. Activation of Jun N-terminal Kinase (JNK) pathway is also observed in GIP-induced inflammatory responses in adipocytes. An inhibitor of JNK blocks GIP-stimulated secretion of inflammatory cytokines and chemokines, as well as phosphorylation of IKKβ. The chronic inflammatory response eventually impairs insulin signaling in adipocytes, as demonstrated by reduction of protein kinase B (PKB/AKT) phosphorylation. The subsequently physiological analysis also indicates that GIP inhibits insulin-stimulated glucose uptake, and gene expression analysis reveals a decrease of glucose transporter 4 (Glut-4) in the meanwhile. The results suggest that GIP may be one of stimuli attributable to obesity induced insulin resistance via induction of adipocyte inflammation. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Nie, Yaohui. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 95-111). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Abstract --- p.i / 摘要 --- p.iii / Acknowledgements --- p.v / INTRODUCTION --- p.1 / Chapter Part 1 --- Obesity and Type 2 diabetes --- p.1 / Chapter 1.1 --- Introduction to diabetes --- p.1 / Chapter 1.1.2 --- Physiology of adipocyte --- p.4 / Chapter 1.1.3 --- Mechanism of obesity induced diabetes --- p.10 / Chapter Part 2 --- Incretins and T2DM --- p.12 / Chapter 2.1 --- History of incretins --- p.12 / Chapter 2.2 --- Physiological actions of incretins --- p.14 / Chapter 2.3 --- Molecular mechanism of incretin actions in pancreas --- p.16 / Chapter 2.4 --- Incretins and T2DM --- p.19 / Chapter Part 3 --- Incretins and lipid metabolism --- p.23 / Objective --- p.26 / Methods and materials --- p.28 / Chapter 1 --- Cell culture --- p.28 / Chapter 1.1 --- 3T3-L1 culture and differentiation --- p.28 / Chapter 1.2 --- 3T3-L1 CAR culture and differentiation --- p.29 / Chapter 2 --- Cloning and recombinant adenovirus construction --- p.30 / Chapter 2.1 --- Plasmid construct --- p.30 / Chapter 2.2 --- Construct of recombinant adenoviruses --- p.30 / Chapter 2.3 --- Generation and infection of the adenoviruses --- p.31 / Chapter 3 --- Physiological and morphological assays --- p.32 / Chapter 3.1 --- Lipolysis assay --- p.32 / Chapter 3.2 --- TUNEL assay --- p.32 / Chapter 3.3 --- Glucose uptake --- p.33 / Chapter 3.4 --- Glut-4 localization --- p.33 / Chapter 4 --- Gene expression analysis --- p.35 / Chapter 4.1 --- Quantitative real-time PCR --- p.35 / Chapter 4.2 --- Immunoblot analysis --- p.35 / Chapter 4.3 --- ELISA assay --- p.36 / Chapter 5 --- Isolation of primary adipocytes --- p.37 / Results --- p.38 / Chapter Part 1 --- Role of GIP in 3T3-L1 cells --- p.38 / Chapter 1.1 --- Differentiation of 3T3-L1 adipocytes --- p.38 / Chapter 1.2 --- GIP slightly stimulates phosphorylation of p-CREB and lipolysis in 3T3-L1 cells. --- p.40 / Chapter 1.3 --- Analysis of gene expression in GIP-treated adipocytes --- p.42 / Chapter 1.4 --- Discussion --- p.44 / Chapter Part 2 --- Role of GIP in GIPR over-expressing 3T3-L1 CAR adipocytes --- p.46 / Chapter 2.1 --- Differentiation of 3T3-L1 CAR adipocytes --- p.46 / Chapter 2.2 --- Functional tests in GIPR over-expressing 3T3-L1 CAR adipocytes. --- p.48 / Chapter 2.3 --- Effect of GIP on cell viability --- p.50 / Chapter 2.4 --- Analysis of gene expression in GIP-treated adipocytes --- p.52 / Chapter 2.5 --- GIP activates inflammatory responses in GIPR over-expressing adipocytes --- p.54 / Chapter 2.6 --- Inhibition of IKKb pathway restores GIP-induced inflammatory responses --- p.56 / Chapter 2.7 --- Effects of GIP on adipocytes are partially dependent on the cAMP-PKA pathway --- p.58 / Chapter 2.8 --- Activation of cAMP-PKA pathway induces adipocyte inflammation. --- p.60 / Chapter 2.9 --- cAMP-Epac pathway is not involved in GIP-induced inflammation --- p.62 / Chapter 2.10 --- GIP stimulates cell stress activated kinases --- p.64 / Chapter 2.11 --- JNK partially mediates GIP-induced adipocyte inflammation --- p.65 / Chapter 2.12 --- Inhibition of JNK pathway partially restores GIP-induced inflammatory responses --- p.67 / Chapter 2.13 --- GIP impairs insulin signaling in GIPR over-expressing 3T3-L1 CAR adipocytes via inducing inflammatory response --- p.69 / Chapter 2.14 --- GIP enhances basal glucose uptake but impairs insulin stimulated glucose uptake in 3T3-L1 CAR GIPR over-expressing adipocytes --- p.71 / Chapter 2.15 --- Discussion --- p.73 / Chapter Part 3 --- Role of GIP in primary adipocytes --- p.78 / Chapter 3.1 --- GIPR expression level in primary adipocytes --- p.78 / Chapter 3.2 --- Analysis of gene expression in primary adipocytes after GIP treatment --- p.80 / Chapter 3.3 --- Discussion --- p.81 / SUMMARY --- p.82 / Chapter Future investigation --- p.83 / Chapter Appendix 1: --- Abbreviations --- p.86 / Chapter Appendix 2: --- Protocols --- p.90 / Preparation of competent cells --- p.90 / Outlines of recombinant adenovirus preparation --- p.91 / Virus titering (TCID50) --- p.92 / Primers for real-time PCR --- p.93 / Chapter Publications and Scientfic activities --- p.94 / Thesis related publication: --- p.94 / Other pubiliations: --- p.94 / Scientific activities: --- p.94 / References --- p.95

Bibliography: leaves 112-140. / xi, 141, [39] leaves, [8] leaves of plates : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The aims of this thesis are to determine the initial cleavage sites of purified pepsin in long-R3-IGF-I and assess whether the resulting cleavages affect biological activity, to design and produce analogues of long-R3-IGF-I which contain amino acid substitutions, to characterise the resulting analogues for pepsin resistance and retention of biological activity and to assess the stability of the long-R3-IGF-I analogues under in vivo conditions using luminal stomach flushings. / Thesis (Ph.D.)--University of Adelaide, Dept. of Biochemistry, 1996

Thesis (Ph. D.)--Columbia University, 1929. / Vita. Bibliography: p. 82-87.

(A) Gastric Secretion The present study was performed to investigate the canine post-pancreatic duct ligation GIP secretion in response to fat ingestion using a meat meal mixed with unhydrolyzed or hydrolyzed whipping cream, and to determine whether GIP plays a role in the production of hyperacid secretion in the pancreatic duct ligated dogs. Four mongrel female dogs were prepared with Heidenhain pouch (HP) and gastric fistula (GF), and daily acid secretion from the HP was measured before and after pancreatic duct ligation (PDL). HP acid output, serum immunoreactive gastrin (IR-Ga) and serum immunoreactive gastric inhibitory polypeptide (IR-GIP) concentrations during five hours following oral ingestion of a meat meal alone, a meat meal mixed with 125g of unhydrolyzed cream and meat meal mixed with 125g of hydrolyzed cream were measured before and after PDL. Twenty four hour HP acid outputs increased significantly in each of the four dogs after PDL. Five hour HP acid outputs in response to a meat meal alone and a meat meal plus unhydrolyzed cream were modestly increased, while those in response to a meat meal plus hydrolyzed cream were rather reduced after PDL. Serum IR-Ga responses to all stimulants were lowered after PDL and those to meat meal plus hydrolyzed cream lowered most markedly. Serum IR-GIP responses to a meat meal alone were significantly increased, while those to a meat meal plus unhydrolyzed and hydrolyzed cream were reduced. The results of the present study demonstrate serum IR-GIP in response to a meat meal is increased by PDL in dogs, suggesting augmented acid juice passing into the intestinal lumen is responsible for the increased GIP response. It is indicated that hypo-secretion of GIP is not the cause of hypersecretion of gastric acid in the PDL dogs. (B) Glucose Metabolism. Functional alteration in glucose homeostasis especially concerning the early onset of diabetes after PDL was studied in dogs. Intravenous (i.v.) and intragastric glucose tolerance tests were performed at two to ten weeks and two weeks after PDL respectively. Serum glucose, IRI, and IR-GIP in response to a meat meal with and without unhydrolyzed or hydrolyzed fat were estimated at six weeks after PDL. Significantly impaired glucose tolerance and early phase IRI secretion after i.v. glucose were shown at two to ten weeks after PDL. Intragastric glucose load revealed delayed pattern of serum glucose and IRI (no evidence of glucose intolerance or diminished IRI secretion), indicating decreased gastric motility after PDL. Serum IR-GIP response to intragastric glucose load was not attenuated by the operation but showed a similar pattern to IRI response. Serum IRI responses to meat meals with and without unhydrolyzed or hydrolyzed cream were impaired after PDL. It is indicated that dogs after PDL show early onset (two to ten weeks) of diabetes, i.e. blunted early phase insulin secretion, 2 the mechanism of GIP secretion as an insulinotropic enterohormone remains intact after PDL if sufficient stimulants are given. / Surgery, Department of / Medicine, Faculty of / Graduate

Diss. (sammanfattning) Göteborg : Göteborgs universitet, 2009. / Härtill 7 uppsatser.