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.

Studies on the colon not only serve medical interest or clinical purposes, but are also a highly interesting subject of comparative physiology, from which we can learn much about the basic principles in physiology. Presented here are examples of research on colonic ion transport of each vertebrate group, including the classical models of epithelia, rat and rabbit, and also on the special and unique features in fish, amphibians, reptiles, birds, and selected mammals such as the guinea pig. Physiology and pathophysiology of ion transport in the human large intestine are as well covered as the use of colonic cell cultures as model systems for crypt cell properties.

The functional and organic alterations of the colon constitute one of the leading reasons why patients consult gastroenterologists. The irritable colon is one of the most com mon causes of discomfort in human beings. The organic pathology of the large bowel (malignancy and chronic inflammatory disease) contributes, particularly among Occi dental peoples, to discouragingly high levels of morbidity and mortality. One realizes the importance of having a thorough physiologic knowledge of the colon in order to scientifically plan the functional treatment of organic colonic dis eases. If we consider the large amount of material published on the physiology of the esophagus, stomach, small bowel, pancreas, and liver, we realize that the colon has been relatively neglected. The chapters in this book have been written by people who have done their utmost to alter this imbalance. I want to thank all the contributors for their generous collaboration that allows me to present in one volume virtually all the information known about the structure and function of the colon, and to record my deep graditude to Dr. Howard Spiro for his willingness to include this volume in his series. I would also like to express my sincere appreciation to Plenum Publishing Corporation for making this book possible. A spe cial thanks goes to Dr.

Oral Drug Absorption, Second Edition thoroughly examines the special equipment and methods used to test whether drugs are released adequately when administered orally. The contributors discuss methods for accurately establishing and validating in vitro/in vivo correlations for both MR and IR formulations, as well as alternative approaches for MR an

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.