In vitro effects of bethanechol on specimens of intestinal smooth muscle obtained from the duodenum and jejunum of healthy dairy cows

OBJECTIVE: To describe the in vitro effects of bethanechol on contractility of smooth muscle preparations from the small intestines of healthy cows and define the muscarinic receptor subtypes involved in mediating contraction. SAMPLE POPULATION: Tissue samples from the duodenum and jejunum collected immediately after slaughter of 40 healthy cows. PROCEDURES: Cumulative concentration-response curves were determined for the muscarinic receptor agonist bethanechol with or without prior incubation with subtype-specific receptor antagonists in an organ bath. Effects of bethanechol and antagonists and the influence of intestinal location on basal tone, maximal amplitude (A(max)), and area under the curve (AUC) were evaluated. RESULTS: Bethanechol induced a significant, concentration-dependent increase in all preparations and variables. The effect of bethanechol was more pronounced in jejunal than in duodenal samples and in circular than in longitudinal preparations. Significant inhibition of the effects of bethanechol was observed after prior incubation with muscarinic receptor subtype M(3) antagonists (more commonly for basal tone than for A(max) and AUC). The M(2) receptor antagonists partly inhibited the response to bethanechol, especially for basal tone. The M(3) receptor antagonists were generally more potent than the M(2) receptor antagonists. In a protection experiment, an M(3) receptor antagonist was less potent than when used in combination with an M(2) receptor antagonist. Receptor antagonists for M(1) and M(4) did not affect contractility variables. CONCLUSIONS AND CLINICAL RELEVANCE: Bethanechol acting on muscarinic receptor sub-types M(2) and M(3) may be of clinical use as a prokinetic drug for motility disorders of the duodenum and jejunum in dairy cows.

Prospective study on bright lumen magnetic resonance colonography in comparison with conventional colonoscopy

The aim of this prospective trial was to evaluate sensitivity and specificity of bright lumen magnetic resonance colonography (MRC) in comparison with conventional colonoscopy (CC). A total of 120 consecutive patients with clinical indications for CC were prospectively examined using MRC (1.5 Tesla) which was then followed by CC. Prior to MRC, the cleansed colon was filled with a gadolinium-water solution. A 3D GRE sequence was performed with the patient in the prone and supine position, each acquired during one breathhold period. After division of the colon into five segments, interactive data analysis was carried out using three-dimensional post-processing, including a virtual intraluminal view. The results of CC served as a reference standard. In all patients MRC was performed successfully and no complications occurred. Image quality was diagnostic in 92% (574/620 colonic segments). On a per-patient basis, the results of MRC were as follows: sensitivity 84% (95% CI 71.7-92.3%), specificity 97% (95% CI 89.0-99.6%). Five flat adenomas and 6/16 small polyps (< or =5 mm) were not identified by MRC. MRC offers high sensitivity and excellent specificity rates in patients with clinical indications for CC. Improved MRC techniques are needed to detect small polyps and flat adenomas.

Contribution of mucosal maltase-glucoamylase activities to mouse small intestinal starch alpha-glucogenesis

Digestion of starch requires activities provided by 6 interactive small intestinal enzymes. Two of these are luminal endo-glucosidases named alpha-amylases. Four are exo-glucosidases bound to the luminal surface of enterocytes. These mucosal activities were identified as 4 different maltases. Two maltase activities were associated with sucrase-isomaltase. Two remaining maltases, lacking other identifying activities, were named maltase-glucoamylase. These 4 activities are better described as alpha-glucosidases because they digest all linear starch oligosaccharides to glucose. Because confusion persists about the relative roles of these 6 enzymes, we ablated maltase-glucoamylase gene expression by homologous recombination in Sv/129 mice. We assayed the alpha-glucogenic activities of the jejunal mucosa with and without added recombinant pancreatic alpha-amylase, using a range of food starch substrates. Compared with wild-type mucosa, null mucosa or alpha-amylase alone had little alpha-glucogenic activity. alpha-Amylase amplified wild-type and null mucosal alpha-glucogenesis. alpha-Amylase amplification was most potent against amylose and model resistant starches but was inactive against its final product limit-dextrin and its constituent glucosides. Both sucrase-isomaltase and maltase-glucoamylase were active with limit-dextrin substrate. These mucosal assays were corroborated by a 13C-limit-dextrin breath test. In conclusion, the global effect of maltase-glucoamylase ablation was a slowing of rates of mucosal alpha-glucogenesis. Maltase-glucoamylase determined rates of digestion of starch in normal mice and alpha-amylase served as an amplifier for mucosal starch digestion. Acarbose inhibition was most potent against maltase-glucoamylase activities of the wild-type mouse. The consortium of 6 interactive enzymes appears to be a mechanism for adaptation of alpha-glucogenesis to a wide range of food starches.

Evidence of native starch degradation with human small intestinal maltase-glucoamylase (recombinant)

Action of human small intestinal brush border carbohydrate digesting enzymes is thought to involve only final hydrolysis reactions of oligosaccharides to monosaccharides. In vitro starch digestibility assays use fungal amyloglucosidase to provide this function. In this study, recombinant N-terminal subunit enzyme of human small intestinal maltase-glucoamylase (rhMGAM-N) was used to explore digestion of native starches from different botanical sources. The susceptibilities to enzyme hydrolysis varied among the starches. The rate and extent of hydrolysis of amylomaize-5 and amylomaize-7 into glucose were greater than for other starches. Such was not observed with fungal amyloglucosidase or pancreatic alpha-amylase. The degradation of native starch granules showed a surface furrowed pattern in random, radial, or tree-like arrangements that differed substantially from the erosion patterns of amyloglucosidase or alpha-amylase. The evidence of raw starch granule degradation with rhMGAM-N indicates that pancreatic alpha-amylase hydrolysis is not a requirement for native starch digestion in the human small intestine.

TREM-1--expressing intestinal macrophages crucially amplify chronic inflammation in experimental colitis and inflammatory bowel diseases

Triggering receptor expressed on myeloid cells-1 (TREM-1) potently amplifies acute inflammatory responses by enhancing degranulation and secretion of proinflammatory mediators. Here we demonstrate that TREM-1 is also crucially involved in chronic inflammatory bowel diseases (IBD). Myeloid cells of the normal intestine generally lack TREM-1 expression. In experimental mouse models of colitis and in patients with IBD, however, TREM-1 expression in the intestine was upregulated and correlated with disease activity. TREM-1 significantly enhanced the secretion of relevant proinflammatory mediators in intestinal macrophages from IBD patients. Blocking TREM-1 by the administration of an antagonistic peptide substantially attenuated clinical course and histopathological alterations in experimental mouse models of colitis. This effect was also seen when the antagonistic peptide was administered only after the first appearance of clinical signs of colitis. Hence, TREM-1-mediated amplification of inflammation contributes not only to the exacerbation of acute inflammatory disorders but also to the perpetuation of chronic inflammatory disorders. Furthermore, interfering with TREM-1 engagement leads to the simultaneous reduction of production and secretion of a variety of pro-inflammatory mediators such as TNF, IL-6, IL-8 (CXCL8), MCP-1 (CCL2), and IL-1beta. Therefore, TREM-1 may also represent an attractive target for the treatment of chronic inflammatory disorders.

[Intestinal stomas--indications, stoma types, surgical technique]

The formation of an intestinal stoma is one of the most frequent operations in visceral surgery. Despite new operative techniques and a more restrictive use of the stoma, the stoma formation remains an often necessary surgical procedure, which results to a dramatic change in the patients' life. The stoma formation and its later closure are associated with a high morbidity. Many complications, such as stoma necrosis, stoma retraction or stoma prolapse, are related to surgical mistakes made during stoma formation. These complications are therefore largely avoidable. The stoma formation needs careful planning together with a professional stoma nursing team. Moreover, it is mandatory that the stoma formation is made with great care and that it meticulously follows the well established surgical principles. A perfectly placed, technically correctly fashioned and easy to care for stoma is essential for a good patients'quality of life.

Cell cycle-dependent regulation of extra-adrenal glucocorticoid synthesis in murine intestinal epithelial cells

Glucocorticoids are anti-inflammatory steroids with important applications in the treatment of inflammatory diseases. Endogenous glucocorticoids are mainly produced by the adrenal glands, although there is increasing evidence for extra-adrenal sources. Recent findings show that intestinal crypt cells produce glucocorticoids, which contribute to the maintenance of intestinal immune homeostasis. Intestinal glucocorticoid synthesis is critically regulated by the transcription factor liver receptor homologue-1 (LRH-1). As expression of steroidogenic enzymes and LRH-1 is restricted to the proliferating cells of the crypts, we aimed to investigate the role of the cell cycle in the regulation of LRH-1 activity and intestinal glucocorticoid synthesis. We here show that either pharmacological or molecular modulation of cell cycle progression significantly inhibited expression of steroidogenic enzymes and synthesis of glucocorticoids in intestinal epithelial cells. Synchronization of intestinal epithelial cells in the cell cycle revealed that expression of steroidogenic enzymes is preferentially induced at the G(1)/S stage. Differentiation of immature intestinal epithelial cells to mature nonproliferating cells also resulted in reduced expression of steroidogenic enzymes. This cell cycle-related effect on intestinal steroidogenesis was found to be mediated through the regulation of LRH-1 transcriptional activity. This mechanism may restrict intestinal glucocorticoid synthesis to the proliferating cells of the crypts.

Treatment of intestinal and hepatic mucormycosis in an immunocompromized child

During ALL chemotherapy, a 4-year-old patient presented with febrile neutropenia and abdominal pain. Ultrasound examinations were repeatedly normal. Computerized tomography on day 7 demonstrated appendicitis and multiple hepatic foci identified as mucormycosis (Absidia corymbifera). Successful outcome was achieved by aggressive re-surgery, long-term antifungal therapy with serum level-monitored posaconazole, and recovery of neutrophil counts. Considering the interference of posaconazole with CYP3A4, vincristine was administered during 72 hr posaconazole windows. Pediatric intestinal mucormycosis, still associated with a >70% case-fatality rate, calls for early imaging and surgery to establish the diagnosis, reduce the fungal mass, and provide a rationale for using posaconazole.

Human intestinal maltase-glucoamylase: crystal structure of the N-terminal catalytic subunit and basis of inhibition and substrate specificity

Human maltase-glucoamylase (MGAM) is one of the two enzymes responsible for catalyzing the last glucose-releasing step in starch digestion. MGAM is anchored to the small-intestinal brush-border epithelial cells and contains two homologous glycosyl hydrolase family 31 catalytic subunits: an N-terminal subunit (NtMGAM) found near the membrane-bound end and a C-terminal luminal subunit (CtMGAM). In this study, we report the crystal structure of the human NtMGAM subunit in its apo form (to 2.0 A) and in complex with acarbose (to 1.9 A). Structural analysis of the NtMGAM-acarbose complex reveals that acarbose is bound to the NtMGAM active site primarily through side-chain interactions with its acarvosine unit, and almost no interactions are made with its glycone rings. These observations, along with results from kinetic studies, suggest that the NtMGAM active site contains two primary sugar subsites and that NtMGAM and CtMGAM differ in their substrate specificities despite their structural relationship. Additional sequence analysis of the CtMGAM subunit suggests several features that could explain the higher affinity of the CtMGAM subunit for longer maltose oligosaccharides. The results provide a structural basis for the complementary roles of these glycosyl hydrolase family 31 subunits in the bioprocessing of complex starch structures into glucose.