Inhibition of in vitro enteric neuronal development by endothelin-3: mediation by endothelin B receptors.
The terminal colon is aganglionic in mice lacking endothelin-3 or its receptor, endothelin B. To analyze the effects of endothelin-3/endothelin B on the differentiation of enteric neurons, E11-13 mouse gut was dissociated, and positive and negative immunoselection with antibodies to p75(NTR )were used to isolate neural crest- and non-crest-derived cells. mRNA encoding endothelin B was present in both the crest-and non-crest-derived cells, but that encoding preproendothelin-3 was detected only in the non-crest-derived population. The crest- and non-crest-derived cells were exposed in vitro to endothelin-3, IRL 1620 (an endothelin B agonist), and/or BQ 788 (an endothelin B antagonist). Neurons and glia developed only in cultures of crest-derived cells, and did so even when endothelin-3 was absent and BQ 788 was present. Endothelin-3 inhibited neuronal development, an effect that was mimicked by IRL 1620 and blocked by BQ 788. Endothelin-3 failed to stimulate the incorporation of [3H]thymidine or bromodeoxyuridine. Smooth muscle development in non-crest-derived cell cultures was promoted by endothelin-3 and inhibited by BQ 788. In contrast, transcription of laminin alpha1, a smooth muscle-derived promoter of neuronal development, was inhibited by endothelin-3, but promoted by BQ 788. Neurons did not develop in explants of the terminal bowel of E12 ls/ls (endothelin-3-deficient) mice, but could be induced to do so by endothelin-3 if a source of neural precursors was present. We suggest that endothelin-3/endothelin B normally prevents the premature differentiation of crest-derived precursors migrating to and within the fetal bowel, enabling the precursor population to persist long enough to finish colonizing the bowel. (+info)
Expression of nitric oxide synthase in inflammatory bowel disease is not affected by corticosteroid treatment.
AIM: To examine the effect of corticosteroid treatment on the expression of inducible nitric oxide synthase (iNOS) in the colon of patients with inflammatory bowel disease. METHODS: Four groups of patients were studied: (1) ulcerative colitis treated with high dose corticosteroids (six patients, 10 blocks); (2) ulcerative colitis patients who had never received corticosteroids (10 patients, 16 blocks); (3) Crohn's disease treated with high dose corticosteroids (12 patients, 24 blocks); (4) Non-inflammatory, non-neoplastic controls (four patients, six blocks). Full thickness paraffin sections of colons removed at surgery were immunostained with an antibody raised against the C terminal end of iNOS. Sections were assessed semiquantitatively for the presence and degree of inflammation and immunoreactivity for nitric oxide synthase. RESULTS: Cases of ulcerative colitis and Crohn's disease with active inflammation showed strong staining for nitric oxide synthase. The staining was diffuse in ulcerative colitis and patchy in Crohn's disease, in accordance with the distribution of active inflammation. Staining was seen in epithelial cells and was most intense near areas of inflammation such as crypt abscesses. Non-inflamed epithelium showed no immunoreactivity. Treatment with corticosteroids made no difference to the amount of nitric oxide synthase. CONCLUSIONS: Expression of nitric oxide synthase is increased in both ulcerative colitis and Crohn's disease and appears to be unaffected by treatment with corticosteroids. Disease severity necessitated surgery in all the cases included in this study, regardless of whether or not the patients had received long term corticosteroid treatment. It seems therefore that a high level of iNOS expression and, presumably, production of nitric oxide characterise cases which are refractory to clinical treatment; this suggests that specific inhibition of the enzyme may be a useful therapeutic adjunct. (+info)
Colon and rectal anastomoses do not require routine drainage: a systematic review and meta-analysis.
OBJECTIVE: Many surgeons continue to place a prophylactic drain in the pelvis after completion of a colorectal anastomosis, despite considerable evidence that this practice may not be useful. The authors conducted a systematic review and meta-analysis of randomized controlled trials to determine if placement of a drain after a colonic or rectal anastomosis can reduce the rate of complications. METHODS: A search of the Medline database of English-language articles published from 1987 to 1997 was conducted using the terms "colon," "rectum," "postoperative complications," "surgical anastomosis," and "drainage." A manual search was also conducted. Four randomized controlled trials, including a total of 414 patients, were identified that compared the routine use of drainage of colonic and/or rectal anastomoses to no drainage. Two reviewers assessed the trials independently. Trial quality was critically appraised using a previously published scale, and data on mortality, clinical and radiologic anastomotic leakage rate, wound infection rate, and major complication rate were extracted. RESULTS: The overall quality of the studies was poor. Use of a drain did not significantly affect the rate of any of the outcomes examined, although the power of this analysis to exclude any difference was low. Comparison of pooled results revealed an odds ratio for clinical leak of 1.5 favoring the control (no drain) group. Of the 20 observed leaks among all four studies that occurred in a patient with a drain in place, in only one case (5%) did pus or enteric content actually appear in the effluent of the existing drain. CONCLUSIONS: Any significant benefit of routine drainage of colon and rectal anastomoses in reducing the rate of anastomotic leakage or other surgical complications can be excluded with more confidence based on pooled data than by the individual trials alone. Additional well-designed randomized controlled trials would further reinforce this conclusion. (+info)
Segmental colonic transit after oral 67Ga-citrate in healthy subjects and those with chronic idiopathic constipation.
Measurement of segmental colonic transit is important in the assessment of patients with severe constipation. 111In-diethylenetriamine pentaacetic acid (DTPA) has been established as the tracer of choice for these studies, but it is expensive and not readily available. 67Ga-citrate is an inexpensive tracer and when given orally is not absorbed from the bowel. It was compared with 111In-DTPA in colonic transit studies in nonconstipated control subjects and then in patients with idiopathic constipation. METHODS: Studies were performed after oral administration of 3 MBq (81 microCi) 67Ga-citrate or 4 MBq (108 microCi) 111In-DTPA in solution. Serial abdominal images were performed up to 96 h postinjection, and computer data were generated from geometric mean images of segmental retention of tracer, mean activity profiles and a colonic tracer half-clearance time. RESULTS: There were no differences in segmental retention of either tracer or in mean activity profiles between control subjects and constipated patients. Results in constipated subjects were significantly different from those in controls. The mean half-clearance times of tracer for control subjects were 28.8 h for 67Ga-citrate and 29.9 h for 111In-DTPA in control subjects and 75.0 h for 67Ga-citrate and 70.8 h for 111In-DTPA in constipated patients. CONCLUSION: Oral 67Ga-citrate can be used as a safe alternative to 111In-DTPA for accurate measurement of segmental colonic transit. (+info)
Modulation of distal colonic epithelial barrier function by dietary fibre in normal rats.
BACKGROUND: Dietary fibre influences the turnover and differentiation of the colonic epithelium, but its effects on barrier function are unknown. AIMS: To determine whether altering the type and amount of fibre in the diet affects paracellular permeability of intestinal epithelium, and to identify the mechanisms of action. METHODS: Rats were fed isoenergetic low fibre diets with or without supplements of wheat bran (10%) or methylcellulose (10%), for four weeks. Paracellular permeability was determined by measurement of conductance and 51Cr-EDTA flux across tissue mounted in Ussing chambers. Faecal short chain fatty acid (SCFA) concentrations were assessed by gas chromatography, epithelial kinetics stathmokinetically, and mucosal brush border hydrolase activities spectrophotometrically. RESULTS: Body weight was similar across the dietary groups. Conductance and 51Cr-EDTA flux were approximately 25% higher in animals fed no fibre, compared with those fed wheat bran or methylcellulose in the distal colon, but not in the caecum or jejunum. Histologically, there was no evidence of epithelial injury or erosion associated with any diet. The fibres exerted different spectra of effects on luminal SCFA concentrations and pH, and on mucosal indexes, but both bulked the faeces, were trophic to the epithelium, and stimulated expression of a marker of epithelial differentiation. CONCLUSIONS: Both a fermentable and a non-fermentable fibre reduce paracellular permeability specifically in the distal colon, possibly by promoting epithelial cell differentiation. The mechanisms by which the two fibres exert their effects are likely to be different. (+info)
The role of psychological and biological factors in postinfective gut dysfunction.
BACKGROUND: Both psychological and physiological disturbances have been implicated in the aetiopathogenesis of irritable bowel syndrome (IBS). AIMS: To investigate how the psychological factors act, and the involvement of infective and physiological factors. METHODS: Consecutive patients hospitalised for gastroenteritis reported life events for the previous 12 months, and past illness experiences on standardised questionnaires. They also completed psychometric questionnaires for anxiety, neuroticism, somatisation, and hypochondriasis. In some patients, rectal biopsy specimens were obtained during the acute illness and at three months postinfection. RESULTS: Ninety four patients completed all questionnaires: 22 patients were diagnosed with IBS after their gastroenteritis (IBS+), and 72 patients returned to normal bowel habits (IBS-). IBS+ patients reported more life events and had higher hypochondriasis scores than IBS- patients. The predictive value of the life event and hypochondriasis measures was highly significant and independent of anxiety, neuroticism, and somatisation scores, which were also elevated in IBS+ patients. Rectal biopsy specimens from 29 patients showed a chronic inflammatory response in both IBS+ and IBS- patients. Three months later, specimens from IBS+ patients continued to show increased chronic inflammatory cell counts but those from IBS- patients had returned to normal levels. IBS+ and IBS- patients exhibited rectal hypersensitivity and hyper-reactivity and rapid colonic transit compared with normal controls, but there were no significant differences between IBS+ and IBS- patients for these physiological measurements. CONCLUSION: Psychological factors most clearly predict the development of IBS symptoms after gastroenteritis but biological mechanisms also contribute towards the expression of symptoms. (+info)
Is early post-operative treatment with 5-fluorouracil possible without affecting anastomotic strength in the intestine?
Early post-operative local or systemic administration of 5-fluorouracil (5-FU) is under investigation as a means to improve outcome after resection of intestinal malignancies. It is therefore quite important to delineate accurately its potentially negative effects on anastomotic repair. Five groups (n = 24) of rats underwent resection and anastomosis of both ileum and colon: a control group and four experimental groups receiving daily 5-FU, starting immediately after operation or after 1, 2 or 3 days. Within each group, the drug (or saline) was delivered either intraperitoneally (n = 12) or intravenously (n = 12). Animals were killed 7 days after operation and healing was assessed by measurement of anastomotic bursting pressure, breaking strength and hydroxyproline content. In all cases, 5-FU treatment from the day of operation or from day 1 significantly (P<0.025) and severely suppressed wound strength; concomitantly, the anastomotic hydroxyproline content was reduced. Depending on the location of the anastomosis and the route of 5-FU administration, even a period of 3 days between operation and first dosage seemed insufficient to prevent weakening of the anastomosis. The effects of intravenous administration, though qualitatively similar, were quantitatively less dramatic than those observed after intraperitoneal delivery. Post-operative treatment with 5-FU, if started within the first 3 days after operation, is detrimental to anastomotic strength and may compromise anastomotic integrity. (+info)
Low tumour cell proliferation at the invasive margin is associated with a poor prognosis in Dukes' stage B colorectal cancers.
The conflicting results about the prognostic impact of tumour cell proliferation in colorectal cancer might be explained by the heterogeneity observed within these tumours. We have investigated whether a systematic spatial heterogeneity exists between different compartments, and whether the presence of such a systematic heterogeneity has any impact on survival. Fifty-six Dukes' stage B colorectal cancers were carefully morphometrically quantified with respect to the immunohistochemical expression of the proliferative marker Ki-67 at both the luminal border and the invasive margin. The proliferative activity was significantly higher at the luminal border compared with the invasive margin (P<0.001), although the two compartments were also significantly correlated with each other. Tumours with low proliferation at the invasive margin had a significantly poorer prognosis both in univariate (P = 0.014) and in multivariate survival analyses (P = 0.042). We conclude that Dukes' B colorectal cancers exhibit a systematic spatial heterogeneity with respect to proliferation, and tumours with low proliferation at the invasive margin had a poor prognosis. The present data independently confirm recent results from the authors, and provide new insights into the understanding of tumour cell proliferation in colorectal cancer. (+info)