ISSN:0267-1379    

出版商:OVID    

年代:2000

数据来源: OVID

ISSN:0267-1379    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Increased awareness of the high prevalence of celiac disease and the degree of underdiagnosis has led to calls for routine screening in certain groups. The potential consequences of underdiagnosis have been the subject of several studies. Where there is a delay in diagnosis, there may be an increased risk of associated autoimmune diseases. Alternatively, there may be marked neurological complications, or fetal growth retardation where pregnancy preceeds diagnosis. Once a diagnosis is obtained, treatment may become easier with further evidence that oats are well tolerated by most people with celiac disease. Screening will be facilitated by the development of highly sensitive and specific enzyme-linked immunosorbent assays for tissue transglutaminase. Further insights into the genetics of the condition have been gained with the discovery of a new human leukocyte antigen susceptibility type, plus a possible non-human-leukocyte antigen susceptibility gene. Curr Opin Gastroenterol 2000, 16:102–106 © 2000 Lippincott William & Wilkins, Inc.

ISSN:0267-1379    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The gastrointestinal tract is the most common site for extranodal lymphomas. The most common, and consequently the most studied, gastrointestinal lymphoma is gastric mucosa-associated lymphoid tissue lymphoma, which is a paradigm for all gastrointestinal lymphomas. Recent advances in oncogenesis, genetics, and immunology have all yielded important discoveries that enhance our understanding of this lymphoma. The implications of these new advances are beginning to translate into changes in therapeutic approach.

ISSN:0267-1379    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Alone among organs of the body, the gut is able to mediate reflexes in the absence of input from the brain or spinal cord. This ability appears to be caused by the secretion of serotonin (5-HT) by enterochromaffin (EC) cells of the mucosal epithelium. This 5-HT is secreted into the wall of the gut, where it stimulates the mucosal processes of intrinsic and extrinsic primary afferent neurons. The intrinsic primary afferents, which are activated by 5-HT1P/4receptors, initiate peristaltic and secretory reflexes. The extrinsic primary afferent neurons send distress and other signals to the central nervous system. Extrinsic nerves are activated by 5-HT3receptors. The 5-HT that is involved in mucosal signaling is inactivated by uptake into mucosal epithelial cells, which are mediated by an integral membrane protein called the serotonin reuptake transporter (SERT). The epithelial SERT is the same molecule as that which transports 5-HT in the central and enteric nervous systems. Increasing evidence suggests that abnormal enteric release or inactivation of 5-HT is involved in the pathogenesis of irritable bowel syndrome (IBS). Spread of 5-HT to inappropriate sites in IBS may activate 5-HT3receptors on extrinsic afferent fibers and motor neurons, giving rise to visceral hypersensitivity and abnormal motility, respectively. A potent 5-HT3antagonist, such as alosetron, can prevent both of these effects and is therefore useful in treating IBS. 5-HT also appears to function as a growth factor in the development of enteric neurons. The developmental effects of 5-HT are mediated by the 5-HT2Breceptor, which is developmentally regulated. The importance of serotonergic mechanisms in enteric physiology probably accounts for the gastrointestinal “side effects” of compounds that inhibit SERT. The newly discovered role of 5-HT in enteric neuronal development suggests that drugs that interfere with the action or inactivation of 5-HT should be used in pregnancy only with extreme caution, if at all.

ISSN:0267-1379    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

It is now more than 25 years since small bowel enteroscopy (SBE) was first described. For several reasons, this technique developed more slowly than other more usual forms of endoscopy. First, small bowel disease is relatively rare in comparison with other gastrointestinal diseases. Also, there was lack of initial design agreement, and three different types of enteroscopes were developed within a short time of each other, two of which (push-type and sonde) are now available commercially. Finally, commercial interests of the manufacturers of endoscopes were mainly focused on the more conventional, large volume markets.In the last few years, specifically designed modern small bowel enteroscopes have become available and, in centers that have access to them, they have superseded attempts at SBE using adult or pediatric colonoscopes. There are now clear indications for SBE, such as: the investigation of obscure causes of bleeding and anemia; malabsorption; clarification of x-ray abnormalities; and, increasingly, the application of therapeutic endoscopy to lesions within the small bowel. Problem areas remain, but with advancing technology and more professional interest in this area, these will be addressed during the next few years.

ISSN:0267-1379    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The development of small bowel transplantation has long been hindered by the immunological and infectious barriers peculiar to the small bowel. Gradual progress has been achieved during the past decade with the use of tacrolimus and the availability of better anti-infection prophylaxis. The current status of small bowel transplantation as a life-saving option for patients failing on total parenteral nutrition and those who have developed irreversible liver failure is undisputed. Small bowel transplantation can be performed as either an intestine-only graft or as part of a composite graft with the liver and, on occasion, other organs. The various techniques of donor and recipient operations are relatively standardized. Despite the progress made, the most common causes of death and graft loss continue to be sepsis, rejection, and lymphomas. Further progress can be achieved by development of more effective immunosuppressive and immunomodulatory strategies. The role of inducing chimerism by adjuvant donor-specific bone marrow transfusions to promote graft tolerance is uncertain. Until the mortality and graft losses are further reduced, the role of small bowel transplantation will be limited to a salvage procedure for failure of total parenteral nutrition rather than a primary treatment of intestinal failure.

ISSN:0267-1379    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The noninvasive assessment of small intestinal permeability in humans is now within the capability of any routine biochemistry laboratory. There remain however, many pitfalls for the unwary when performing these tests. Importantly, it has now been shown that normal intestinal permeability relates to geographical location rather than race. Recent studies show that it may be possible to simplify the procedure even further. The main recent focus of interest in measuring intestinal permeability relates to patients with AIDS and inflammatory bowel disease, the effects of nonsteroidal anti-inflammatory drugs on the small bowel, and the use of these tests in the pediatric population and critically ill. Some groups have now started to focus their attention on the possible systemic consequences of increased intestinal permeability, whereas others have shown that increased small bowel permeability results in small intestinal inflammation that may in turn be associated with blood and protein loss.

ISSN:0267-1379    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

During the period of review, work has been ongoing to refine existing techniques and to better define normal patterns of small intestinal motility. Researchers continue to learn more about the established neurohumoral control mechanisms of motility, as well as the effects and potential importance of newly discovered neuropeptides and receptors. There has also been continued interest in alterations in motility in various disease states and in the effects on motility of a number of pharmacologic agents.

ISSN:0267-1379    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Some key advances occurred last year in understanding mechanisms involved in nutrient absorption. A novel “prechylomicron transport vesicle” was identified; its movement to the Golgi is the rate-limiting step for triacylglycerol absorption. A scavenger receptor (type BI) in the brush border membrane appears to facilitate cholesterol uptake. Several studies define mechanisms for gastrointestinal peptide hormone stimulation of glucose uptake. An oligopeptide transporter, PepT1, is transcriptionally upregulated by certain dietary amino acids and dipeptides. Surprisingly, both insulin and fasting double the maximum velocity for dipeptide uptake (via PepT1), but they act by different mechanisms. Three transporters, SMVT (sodium-dependent multivitamin transporter for biotin and pantothenate), SVCT (for vitamin C), and CaT1 (for Ca uptake from the lumen) have been cloned and are active when expressed in various cells. Additional studies provide insights on Ca absorption and vitamin D action in aging, estrogen deficiency, and adaptation to a low Ca diet. Nramp2, also called DMT1 (divalent metal ion transporter), seems to be a major regulator of transferrin-independent, nonheme iron uptake. Finally, the protein HFE associates with the transferrin receptor and is part of an iron-sensing mechanism that regulates iron absorption. It is defective in hereditary hemochromatosis. HFE and Nramp2 (DMT1) genes are reciprocally regulated.

ISSN:0267-1379    

出版商:OVID    

年代:2000

数据来源: OVID