Regulatory Mechanisms in Gastrointestinal Function includes a collection of contemporary topics in gastrointestinal research. The control of gastroduodenal electrolyte transport and the influence of drugs on bicarbonate secretion are reviewed in detail. The importance of the interactions between calcium and cyclic-AMP in intestinal secretion is emphasized in a comprehensive chapter that systematically addresses each link in the mechanisms that regulate chloride secretion. Other important topics included in the book are neural reflex modulation of intestinal epithelial transport, the influence of the microcirculation on intestinal secretion, and nitric oxide as a mediator of physiologic and pathophysiologic secretion. The expertise of the authors has resulted in a breadth of important contemporary topics covered in depth.
Three distinct types of contractions perform colonic motility functions. Rhythmic phasic contractions (RPCs) cause slow net distal propulsion with extensive mixing/turning over. Infrequently occurring giant migrating contractions (GMCs) produce mass movements. Tonic contractions aid RPCs in their motor function. The spatiotemporal patterns of these contractions differ markedly. The amplitude and distance of propagation of a GMC are several-fold larger than those of an RPC. The enteric neurons and smooth muscle cells are the core regulators of all three types of contractions. The regulation of contractions by these mechanisms is modifiable by extrinsic factors: CNS, autonomic neurons, hormones, inflammatory mediators, and stress mediators. Only the GMCs produce descending inhibition, which accommodates the large bolus being propelled without increasing muscle tone. The strong compression of the colon wall generates afferent signals that are below nociceptive threshold in healthy subjects. However, these signals become nociceptive; if the amplitudes of GMCs increase, afferent nerves become hypersensitive, or descending inhibition is impaired. The GMCs also provide the force for rapid propulsion of feces and descending inhibition to relax the internal anal sphincter during defecation. The dysregulation of GMCs is a major factor in colonic motility disorders: irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), and diverticular disease (DD). Frequent mass movements by GMCs cause diarrhea in diarrhea predominant IBS, IBD, and DD, while a decrease in the frequency of GMCs causes constipation. The GMCs generate the afferent signals for intermittent short-lived episodes of abdominal cramping in these disorders. Epigenetic dysregulation due to adverse events in early life is one of the major factors in generating the symptoms of IBS in adulthood.
The Gastrointestinal Section of the International Union of Pharmacology (IUPHAR) was established in 1994 in Montreal, Canada. The establishment of the GI Section recognizes the international progress of gastrointestinal pharmacology, including basic and human studies. The Gastrointestinal Section of IUPHAR organized the first symposium, Biochemical Pharmacology as an Approach to Gastrointestinal Diseases: from Basic Science to Clinical Perspectives, on 10-12 October, 1995, in Pécs, Hungary. The main topics were: Gastrointestinal secretory and excretory fuctions Gastrointestinal motility Biochemical-pharmacological mechanisms in neural and hormonal actions involved in GI functions Main normal and pathological biochemical mechanisms in GI functions GI mucosal injury and protection Molecular mechanisms of premalignant and malignant diseases in GI tract Use of isolated cells and cell cultures in bioochemical-pharmacological studies to approach GI diseases. The presented papers are published in this book.
The mammalian gastrointestinal mucosa is a rapidly self-renewing tissue in the body, and its homeostasis is preserved through the strict regulation of epithelial cell proliferation, growth arrest, and apoptosis. The control of the growth of gastrointestinal mucosa is unique and, compared with most other tissue in the body, complex. Mucosal growth is regulated by the same hormones that alter metabolism in other tissues, but the gastrointestinal mucosa also responds to host events triggered by the ingestion and presence of food within the digestive tract. These gut hormones and peptides regulate the growth of the exocrine pancreas, gallbladder epithelium, and the mucosa of the oxyntic gland region of the stomach and the small and large intestines. Luminal factors, including nutrients or other dietary factors, secretions, and microbes that occur within the lumen and distribute over a proximal-to-distal gradient, are also crucial for maintenance of normal gut mucosal regeneration and could explain the villous-height-crypt-depth gradient and variety of adaptation, since these factors are diluted, absorbed, and destroyed as they pass down the digestive tract. Recently, intestinal stem cells, cellular polyamines, and noncoding RNAs are shown to play an important role in the regulation of gastrointestinal mucosal growth under physiological and various pathological conditions. In this book, we highlight key issues and factors that control gastrointestinal mucosal growth and homeostasis, with special emphasis on the mechanisms through which epithelial renewal and apoptosis are regulated at the cellular and molecular levels.
The microcirculation of the gastrointestinal tract is under the control of both myogenic and metabolic regulatory systems. The myogenic mechanism contributes to basal vascular tone and the regulation of transmural pressure, while the metabolic mechanism is responsible for maintaining an appropriate balance between O2 demand and O2 delivery. In the postprandial state, hydrolytic products of food digestion elicit a hyperemia, which serves to meet the increased O2 demand of nutrient assimilation. Metabolically linked factors (e.g., tissue pO2, adenosine) are primarily responsible for this functional hyperemia. The fenestrated capillaries of the gastrointestinal mucosa are relatively permeable to small hydrolytic products of food digestion (e.g., glucose), yet restrict the transcapillary movement of larger molecules (e.g., albumin). This allows for the absorption of hydrolytic products of food digestion without compromising the oncotic pressure gradient governing transcapillary fluid movement and edema formation. The gastrointestinal microcirculation is also an important component of the mucosal defense system whose function is to prevent (and rapidly repair) inadvertent epithelial injury by potentially noxious constituents of chyme. Two pathological conditions in which the gastrointestinal circulation plays an important role are ischemia/reperfusion and chronic portal hypertension. Ischemia/reperfusion results in mucosal edema and disruption of the epithelium due, in part, to an inflammatory response (e.g., increase in capillary permeability to macromolecules and neutrophil infiltration). Chronic portal hypertension results in an increase in gastrointestinal blood flow due to an imbalance in vasodilator and vasoconstrictor influences on the microcirculation. Table of Contents: Introduction / Anatomy / Regulation of Vascular Tone and Oxygenation / Extrinsic Vasoregulation: Neural and Humoral / Postprandial Hyperemia / Transcapillary Solute Exchange / Transcapillary Fluid Exchange / Interaction of Capillary and Interstitial Forces / Gastrointestinal Circulation and Mucosal Defense / Gastrointestinal Circulation and Mucosal Pathology I: Ischemia/Reperfusion / Gastrointestinal Circulation and Mucosal Pathology II: Chronic Portal Hypertension / Summary and Conclusions / References / Author Biography
Now in paperback, the second edition of the Oxford Textbook of Critical Care is a comprehensive multi-disciplinary text covering all aspects of adult intensive care management. Uniquely this text takes a problem-orientated approach providing a key resource for daily clinical issues in the intensive care unit. The text is organized into short topics allowing readers to rapidly access authoritative information on specific clinical problems. Each topic refers to basic physiological principles and provides up-to-date treatment advice supported by references to the most vital literature. Where international differences exist in clinical practice, authors cover alternative views. Key messages summarise each topic in order to aid quick review and decision making. Edited and written by an international group of recognized experts from many disciplines, the second edition of the Oxford Textbook of Critical Careprovides an up-to-date reference that is relevant for intensive care units and emergency departments globally. This volume is the definitive text for all health care providers, including physicians, nurses, respiratory therapists, and other allied health professionals who take care of critically ill patients.
On July 9-10, 2014, the Institute of Medicine's Food Forum hosted a public workshop to explore emerging and rapidly developing research on relationships among the brain, the digestive system, and eating behavior. Drawing on expertise from the fields of nutrition and food science, animal and human physiology and behavior, and psychology and psychiatry as well as related fields, the purpose of the workshop was to (1) review current knowledge on the relationship between the brain and eating behavior, explore the interaction between the brain and the digestive system, and consider what is known about the brain's role in eating patterns and consumer choice; (2) evaluate current methods used to determine the impact of food on brain activity and eating behavior; and (3) identify gaps in knowledge and articulate a theoretical framework for future research. Relationships among the Brain, the Digestive System, and Eating Behavior summarizes the presentations and discussion of the workshop.
The secretions of the exocrine pancreas provide for digestion of a meal into components that are then available for processing and absorption by the intestinal epithelium. Without the exocrine pancreas, malabsorption and malnutrition result. This chapter describes the cellular participants responsible for the secretion of digestive enzymes and fluid that in combination provide a pancreatic secretion that accomplishes the digestive functions of the gland. Key cellular participants, the acinar cell and the duct cell, are responsible for digestive enzyme and fluid secretion, respectively, of the exocrine pancreas. This chapter describes the neurohumoral pathways that mediate the pancreatic response to a meal as well as details of the cellular mechanisms that are necessary for the organ responses, including protein synthesis and transport and ion transports, and the regulation of these responses by intracellular signaling systems. Examples of pancreatic diseases resulting from dysfunction in cellular mechanisms provide emphasis of the importance of the normal physiologic mechanisms.
As aging trends in the United States and Europe in particular are strongly suggestive of increasingly older society, it would be prudent for health care providers to better prepare for such changes. By including physiology, disease, nutrition, pharmacology, pathology, radiology and other relevant associated topics, Geriatric Gastroenterology fills the void in the literature for a volume devoted specifically to gastrointestinal illness in the elderly. This unique volume includes provision of training for current and future generations of physicians to deal with the health problems of older adults. It will also serve as a comprehensive guide to practicing physicians for ease of reference. Relevant to the geriatric age group, the volume covers epidemiology, physiology of aging, gastrointestinal physiology, pharmacology, radiology, pathology, motility disorders, luminal disorders, hepato-biliary disease, systemic manifestations, neoplastic disorders, gastrointestinal bleeding, cancer and medication related interactions and adverse events, all extremely common in older adults; these are often hard to evaluate and judge, especially considering the complex aging physiology. All have become important components of modern medicine. Special emphasis is be given to nutrition and related disorders. Capsule endoscopy and its utility in the geriatric population is also covered. Presented in simple, easy to read style, the volume includes numerous tables, figures and key points enabling ease of understanding. Chapters on imaging and pathology are profusely illustrated. All chapters are written by specialists and include up to date scientific information. Geriatric Gastroenterology is of great utility to residents in internal medicine, fellows in gastroenterology and geriatric medicine as well as gastroenterologists, geriatricians and practicing physicians including primary care physicians caring for older adults.
