Expression of inducible nitric oxide synthase activity in human colon epithelial cells: modulation by T lymphocyte derived cytokines

Background—Nitricoxide (NO) synthesis and inducible nitric oxide synthase (iNOS)expression are increased in colonic biopsy specimens from patients withulcerative colitis, but the cellular source of NO production is not known.
Aims—To examine thedistribution of iNOS in human colonic mucosa and to explore the abilityof T lymphocyte derived cytokines to regulate iNOS expression andactivity in human colonic epithelial cells.
Methods—iNOSexpression was examined using immunohistochemistry in colonic biopsysamples from 12 patients with ulcerative colitis and three withinfectious colitis and compared with 10normal controls. In vitro iNOSexpression and activity were determined in HT-29 cell cultures; nitritelevels were measured using a fluorescent substrate, iNOS mRNAexpression by northern blot analysis, and iNOS protein expression bywestern blot analysis.
Results—No iNOSexpression was detected (10 of 10) in non-inflamed mucosa derived fromnormal controls. In 11 of 12 cases of newly diagnosed ulcerativecolitis, iNOS protein was expressed in the epithelial cells, while noother positive cells were found in the lamina propria. Similar iNOSlabelling was found in colonic biopsy samples from patients withinfectious colitis in the acute phase, but when re-examined in samplesfrom patients in total remission, no iNOS staining was observed. Bothinterleukin (IL)-13 and IL-4, but not IL-10, are potent inhibitors ofiNOS expression and activity induced by an optimal combination ofcytokines, namely IL-1α, tumour necrosis factor α and interferonγ.
Conclusions—The datasuggest that the epithelium is the major source of iNOS activity inulcerative colitis and that IL-13 and IL-4 may act as intrinsicregulators of NO generation in intestinal inflammation.

Keywords:interleukin 13; nitric oxide; inducible nitric oxidesynthase; colonic epithelial cells; ulcerative colitis

     

HIV enteropathy: comparative morphometry of the jejunal mucosa of HIV infected patients resident in the United Kingdom and Uganda

Aims—To compare jejunal mucosalmorphometry in HIV infected patients resident in London and Uganda.
Patients—Twenty HIV positivepatients from London and 16 from Uganda were studied, and compared withHIV negative control subjects from both sites.
Methods—Stools and biopsy specimenswere examined for enteropathogens. Surface area to volume (S:V) ratiowas estimated morphometrically, mean crypt length of jejunal biopsyspecimens was measured, and HIV infected cells detectedimmunohistochemically were quantified.
Results—Enteric pathogens weredetected in none of the London patients, and in three Ugandan patients.S:V ratio was lower, and mean crypt length higher, in the specimens ofLondon patients than in normal subjects, but there was no difference inS:V ratio or mean crypt length between Ugandan patients and controls. A negative correlation was present between S:V ratio and mean crypt length in all biopsy specimens analysed. HIV infected cells were detected only in lamina propria.
Conclusion—Infection of cells inthe lamina propria of the jejunum with HIV stimulates crypt cellproliferation, and a fall in villous surface area. The mucosal responseto HIV is masked by other pathogens in the African environment.

Keywords:HIV; jejunum; AIDS; enteropathy

     

Rectal cell proliferation and colon cancer risk in patients with hypergastrinaemia

Background—The influence of gastrin on the colonicmucosa is still uncertain. Some authors have suggested a stimulatingeffect on the growth of normal and malignant colonic epithelium, while others have shown no association between gastrin and neoplastic development.
Aims—To evaluate the effect of gastrin oncolorectal cell proliferation, patients with chronic endogenoushypergastrinaemia underwent proctoscopy. Biopsy specimens were taken inorder to study rectal cell kinetics.
Patients and controls—Ten patients with chronicautoimmune gastritis (CAG), six patients with Zollinger-Ellisonsyndrome (ZES), and 16 hospital controls took part in this study.Patients with CAG and ZES had basal serum gastrin concentrationssignificantly higher than controls (p<0.001).
Methods—Immunohistochemistry was performed on 3 µm sections of rectal biopsy specimens incubated with5'-bromodeoxyuridine.
Results—The percentage of proliferating cells inthe entire crypts (overall labelling index) was similar in all thegroups. However, the labelling frequency in the upper two fifths of the glands (ϕh value) was significantly higher in patients with CAG orZES compared with controls (p<0.01 in both patient groups versus controls).
Conclusions—Endogenous hypergastrinaemia isassociated with rectal cell proliferation defects, similar to thoseobserved in conditions at high risk for colon cancer. The effect of theincreased serum concentrations of gastrin on the colorectal mucosaafter treatment with drugs inhibiting gastric acid secretion should be investigated.

     

Urokinase and the intestinal mucosa: evidence for a role in epithelial cell turnover

Background—The functions of urokinase inintestinal epithelia are unknown.
Aims—To determine the relation of urokinaseexpressed by intestinal epithelial cells to their position in thecrypt-villus/surface axis and of mucosal urokinase activity toepithelial proliferative kinetics in the distal colon.
Methods—Urokinase expression was examinedimmunohistochemically in human intestinal mucosa. Urokinase activitywas measured colorimetrically in epithelial cells isolated sequentiallyfrom the crypt-villus axis of the rat small intestine. In separate experiments, urokinase activity and epithelial kinetics (measured stathmokinetically) were measured in homogenates of distal colonic mucosa of 14 groups of eight rats fed diets known to alter epithelial turnover.
Results—From the crypt base, an ascendinggradient of expression and activity of urokinase was associated withthe epithelial cells. Median mucosal urokinase activities in each ofthe dietary groups of rats correlated positively with autologous mediannumber of metaphase arrests per crypt (r=0.68; p<0.005)and per 100 crypt cells (r=0.75; p<0.001), but not withcrypt column height.
Conclusions—Localisation of an enzyme capable ofleading to digestion of cell substratum in the region where cells areloosely attached to their basement membrane, and the association of its activity with indexes of cell turnover, suggest a role for urokinase infacilitating epithelial cell loss in the intestine.

Keywords:urokinase; intestinal epithelium; colon; epithelialproliferation

     

Effect of cereal fibre source and processing on rectal epithelial cell proliferation

Background—Low fat and wheat bran interventionssignificantly reduced the growth of small to large adenomas andmodestly suppressed rectal epithelial cell proliferation in theAustralian Polyp Prevention Project.
Aim—To study the effect of unprocessed wheat bran,unprocessed oat bran and processed wheat bran (Kellogg's All Bran) onrectal epithelial cell proliferation.
Patients—Twenty subjects with recent adenomas anda high fat background diet were recruited.
Methods—Rectal biopsy specimens were taken atentry and at the end of three six-week periods of oat bran (64 g/day),wheat bran (25 g/day) and All Bran (38 g/day), all in associationwith a diet <25% energy as fat, in a randomised cross-over trial.Each of the bran supplements had a total of 11 g dietary fibre. The biopsy specimens were fixed in methacarn and stainedimmunohistochemically for presence of the proliferating cell nuclearantigen (PCNA). The kinetics used to measure proliferation werelabelling index, whole distribution of labelled cells, and labelledcells in the top two-fifths of crypts using analysis of variance.
Results—There were no significant differences inmean labelling indexes between the four diets or in the percentage oflabelled cells in the top two-fifths (p=0.59), but activity in the top two-fifths of crypts was lowest with wheat bran. The mean (SD) labelling indexes were 2.23 (0.11)% for control, 2.13 (0.08)% forwheat bran, 2.19 (0.09)% for oat bran, and 2.12 (0.08)% for All Bran.The proportion in the top two-fifths of the crypts was 2.6 (0.6)% forcontrol, 2.15 (0.5)% for wheat bran, 3.3 (0.9)% for oat bran, and 3.1 (0.9)% for All Bran. On analysis of whole distribution, there was nosignificant overall effect of diets but there was a difference betweensubjects. Analysis including total fibre intake also did not identifyeffects on proliferation.
Conclusion—In this study of high risk subjectswith initial high fat diets, dietary fibre in association with a lowfat diet had no effect on rectal epithelial cell proliferation,although wheat bran had the greatest effect on percentage of labelledcells in the top two-fifths of crypts.

Keywords:cereal fibre; rectal epithelial proliferation; PCNA; fibre solubility

     

Severe upper gastrointestinal polyposis associated with sparse colonic polyposis in a familial adenomatous polyposis family with an APC mutation at codon 1520

Background—Familial adenomatouspolyposis usually results in colonic polyposis with hundredsto thousands of polyps, congenital hypertrophy of the retinal pigmentepithelium (CHRPE), and variable extracolonic features. Recent reportsindicate that patients with distal mutations between codons 1445 and1578 do not express CHRPE and have a high incidence of desmoid tumours.
Patients—The family studied has an unusualphenotype of sparse colonic polyposis but profuse uppergastrointestinal polyposis. Affected subjects do not have CHRPE.
Methods—The protein truncation testfollowed by sequencing identified a 2 base pair deletion at codon 1520 in the APC gene. This results in a frameshift creating a stop codon 13 codons downstream.
Results—This family demonstrates that sparsecolonic polyposis but severe upper tract polyposis may be associatedwith mutations between codons 1445 and 1578.
Conclusions—Study of duodenal and colonic polypsin further cases with mutations in this region is warranted. Suchmutations may preferentially cause duodenal adenomas and desmoidtumours as somatic mutations in these tumours also occur in thisregion, unlike colorectal tumours where somatic mutations occur moreproximally. This study emphasises the importance of screening the uppergastrointestinal tract even when the colonic disease is mild.

Keywords:familial adenomatous polyposis; duodenal polyps; APCmutations; colorectal polyps

     

The Bacteroides fragilis pathogenicity island links virulence and strain competition

The mature microbiome is a stable ecosystem that resists perturbation despite constant host exposure to exogenous microbes. However, the microbial mechanisms determining microbiome development and composition are poorly understood. We recently demonstrated that a non-toxigenic B. fragilis (NTBF) strain restricts enteric colonization by an enterotoxigenic (ETBF) strain dependent on a type VI secretion system (T6SS). We show here that a second enterotoxigenic strain is competent to colonize, dependent on the Bacteroides fragilis pathogenicity island (BFPAI). Additional data showing complex environmental regulation of the Bacteroides fragilis toxin (BFT) suggest that virulence factors may be adapted to modify the colonic niche to provide a strain-specific colonization advantage. We conclude that more complex models of host-microbe-microbiome interactions are needed to investigate this hypothesis.     

Bacteroides fragilis enterotoxin cleaves the zonula adherens protein, E-cadherin

Strains of Bacteroides fragilis associated with diarrheal disease (enterotoxigenic B. fragilis) produce a 20-kDa zinc-dependent metalloprotease toxin (B. fragilis enterotoxin; BFT) that reversibly stimulates chloride secretion and alters tight junctional function in polarized intestinal epithelial cells. BFT alters cellular morphology and physiology most potently and rapidly when placed on the basolateral membrane of epithelial cells, suggesting that the cellular substrate for BFT may be present on this membrane. Herein, we demonstrate that BFT specifically cleaves within 1 min the extracellular domain of the zonula adherens protein, E-cadherin. Cleavage of E-cadherin by BFT is ATP-independent and essential to the morphologic and physiologic activity of BFT. However, the morphologic changes occurring in response to BFT are dependent on target-cell ATP. E-cadherin is shown here to be a cellular substrate for a bacterial toxin and represents the identification of a mechanism of action, cell-surface proteolytic activity, for a bacterial toxin.     

Spontaneous secretion of interferon γ and interleukin 4 by human intraepithelial and lamina propria gut lymphocytes

Background—Cytokines secreted by intestinal Tlymphocytes probably play a critical role in regulation of the gutassociated immune responses.
Aims—To quantify interferon γ (IFN-γ) andinterleukin 4 (IL-4) secreting cells (SC) among human intraepithelial(IEL) and lamina propria (LPL) lymphocytes from the duodenum and rightcolon in non-pathological situations and in the absence of in vitro stimulation.
Patients—Duodenal and right colonic biopsyspecimens were obtained from patients with no inflammation of theintestinal mucosa.
Methods—Intraepithelial and lamina propria cellsuspensions were assayed for numbers of cells spontaneously secretingIFN-γ and IL-4 by a two site reverse enzyme linked immunospottechnique (ELISPOT).
Results—The relatively high proportion ofduodenal lymphocytes spontaneously secreting IFN-γ (IEL 3.6%; LPL1.9%) and IL-4 (IEL 1.3%; LPL 0.7%) contrasted with the very lownumbers of spontaneously IFN-γ SC and the absence of spontaneouslyIL-4 SC among peripheral blood mononuclear cells. In the basal state,both IFN-γ and IL-4 were mainly produced by CD4⁺ cells.Within the colon, only 0.2% of IEL and LPL secreted IFN-γ in thebasal state, and 0.1% secreted IL-4.
Conclusions—Compared with peripheral lymphocytessubstantial proportions of intestinal epithelial and lamina proprialymphocytes spontaneously secrete IFN-γ and/or IL-4. These cytokinesare probably involved in the normal homoeostasis of the humanintestinal mucosa. Disturbances in their secretion could play a role inthe pathogenesis of gastrointestinal diseases.

     

Expression of cell membrane complement regulatory glycoproteins along the normal and diseased human gastrointestinal tract

Background/Aims—Uncontrolled complementactivation may be of immunopathological importance in inflammatorydiseases of the gastrointestinal tract. Expression of membrane boundfactors that regulate complement activation was therefore studied in situ.
Methods—Frozen tissue specimens were obtained frompatients with Helicobacter pylori gastritis, coeliacdisease, Crohn's disease, or ulcerative colitis, and fromhistologically normal controls. Sections were examined byimmunofluorescence with monoclonal antibodies to protectin (CD59),decay accelerating factor (DAF), and membrane cofactor protein (MCP).
Results—Protectin and MCP were widely expressed innormal and diseased mucosae. MCP was generally observed basolaterallyon all epithelial cells, whereas apical protectin expression was moreintense on the epithelium of normal colonic mucosa than in the normalduodenum (p = 0.001). Epithelial DAF and to some extent protectin wereupregulated in gastritis, coeliac disease, and inflammatory boweldisease. Areas of the stomach with intestinal metaplasia expressed DAF,unlike the adjacent gastric epithelium. Parietal cells of the gastricbody expressed neither protectin nor DAF.
Conclusion—Epithelial complement inhibitorymolecules were expressed differently at various normal gastrointestinalsites and also in association with mucosal disease, suggesting variable protective potential. Such molecules could play a role in the development of gastric atrophy by protecting areas of intestinal metaplasia. Conversely, parietal cells appeared to be potentially vulnerable targets for complement attack.

Keywords:Helicobacter pylori; coeliac disease; Crohn's disease; ulcerative colitis; immunofluorescence; complementregulatory proteins

     

Increased state of activation of CD4 positive T cells and elevated interferon γ production in pouchitis

Background—Immunoregulatory abnormalities of Tcells might be of importance in the pathogenesis of pouchitis afterileoanal pouch anastomosis (IAP).
Aims—To characterise T cell subsets, their stateof activation, and production of cytokines in inflamed and non-inflamedpouches in patients with ulcerative colitis (UC) and familialadenomatous polyposis (FAP). The influence of T cell activation onmucosal transformation was also studied.
Patients—Mucosal biopsy specimens were taken from42 patients with IAP (33 with UC and nine with FAP).
Methods—Mononuclear cells were isolated bystandard techniques and characterised by three colour flow cytometry.Interferon γ (IFN-γ) production was studied using the ELISPOT technique.
Results—In patients with UC with pouchitis therewas a significant increase in the CD4:CD8 ratio, expression ofactivation markers on CD3+ cells, and number of IFNγ producingmononuclear cells compared with patients with UC without pouchitis(CD4:CD8 ratio 1.3 (range 0.7-2.7) versus 0.6 (0.1-1.0), p=0.012). Inaddition, a positive correlation between increased crypt depth and thenumber of CD4+ cells (r=0.57) was shown.
Conclusion—The observed increase in activatedmucosal CD4+ T cells and IFN-γ production might lead to mucosaldestruction and crypt hyperplasia as seen in pouchitis.

Keywords:pouchitis; T cell activation; mucosaltransformation

     

Expression of a marker for colonic crypt base cells is correlated with poor prognosis in human colorectal cancer

Background—There is a need for markers in colorectal cancer which will allow subclassification of stage groups into subgroups with high versus low risk of recurrent disease.
Aims—To develop monoclonal antibodies that recognise antigens on immature crypt base cells, on the assumption that in a neoplasm undifferentiated but not the terminally differentiated cells will be responsible for tumour progression.
Methods—Colon crypt cells which were isolated from human colonic mucosa by EDTA/EGTA incubation were studied. By stepwise harvesting, crypt base cell enriched fractions were obtained, and after incubation with antibodies against dominant antigens, used as immunogens.
Results—Of one crypt base cell specific antibody (5E9), the reactive epitope appeared to be a non-terminal carbohydrate in the mucin O-glycans of the colon. The epitope did not seem to be colon specific, but was expressed in a variety of other tissues. In colorectal carcinomas, 5E9 immunoreactivity identified a subgroup of patients with a tendency for worse prognosis.
Conclusion—A mucin associated maturation epitope was identified in colonic crypt base cells, the expression of which in Dukes'' stage B3 colorectal carcinoma may be associated with poor prognosis.

     

Poor diagnostic value of colonic CD44v6 expression and serum concentrations of its soluble form in the differentiation of ulcerative colitis from Crohn's disease

Background—Increased expression ofCD44v6 on colonic crypt epithelial cells in ulcerative colitis has beensuggested as a diagnostic tool to distinguish ulcerative colitis fromcolonic Crohn's disease.
Aims—To investigate colonicCD44v6 expression and serum concentrations of soluble CD44v6 (sCD44v6)in patients with ulcerative colitis and Crohn's disease.
Methods—Colonic biopsy samples wereobtained from 16 patients with ulcerative colitis, 13 with ileocolonicCrohn's disease, and 10 undergoing polypectomy. Serum samples wereobtained from 15 patients with active ulcerative colitis, 20 withactive Crohn's disease, and 20 healthy donors. Colonic CD44v6expression was evaluated immunohistochemically by monoclonal antibody2F10 and the higher affinity monoclonal antibody VFF18. Serum sCD44v6concentrations were measured by ELISA.
Results—2F10 stained colonicepithelium of inflamed ulcerative colitis and Crohn's disease samplesin 80% and 40% of cases, respectively, and VFF18 in 95% and 87%,respectively. Both monoclonal antibodies displayed a sensitivity andspecificity of 60% and 87% to differentiate ulcerative colitis fromcolonic Crohn's disease. Serum concentrations of sCD44v6 were lower inpatients with ulcerative colitis (median 153 ng/ml; interquartile range(IQR) 122-211) compared with Crohn's disease (219; IQR 180-243) andhealthy donors (221; IQR 197-241 (p=0.002)). Its sensitivity andspecificity to discriminate ulcerative colitis from Crohn's diseasewas 75% and 71%, respectively.
Conclusion—Colonic CD44v6 and serumsCD44v6 concentrations do not facilitate reliable differentialdiagnosis between ulcerative colitis and Crohn's disease.

Keywords:CD44 variant 6; differential diagnosis; immunohistochemistry; soluble CD44v6

     

Gut barrier function in malnourished patients

Background—The integrity of the gastrointestinalmucosa is a key element in preventing systemic absorption of enterictoxins and bacteria. In the critically ill, breakdown of gut barrier function may fuel sepsis. Malnourished patients have an increased riskof postoperative sepsis; however, the effects of malnutrition onintestinal barrier function in man are unknown.
Aims—To quantify intestinal barrier function,endotoxin exposure, and the acute phase cytokine response inmalnourished patients.
Patients—Malnourished and well nourishedhospitalised patients.
Methods—Gastrointestinal permeability wasmeasured in malnourished patients and well nourished controls using thelactulose:mannitol test. Endoscopic biopsy specimens werestained and morphological and immunohistochemical featuresgraded. The polymerase chain reaction was used to determinemucosal cytokine expression. The immunoglobulin G antibody response toendotoxin and serum interleukin 6 were measured by enzyme linkedimmunosorbent assay.
Results—There was a significant increase inintestinal permeability in the malnourished patients in associationwith phenotypic and molecular evidence of activation of lamina propriamononuclear cells and enterocytes, and a heightened acute phase response.
Conclusions—Intestinal barrier function issignificantly compromised in malnourished patients, but the clinicalsignificance is unclear.

Keywords:protein-energy malnutrition; intestinalpermeability; endotoxin; cytokine

     

Gastrointestinal transit and prolonged ambulatory colonic motility in health and faecal incontinence

Background—Colonic motor function has not beenstudied in the ambulatory setting over a prolonged period in theunprepared state. Furthermore, the disturbance of this function inpatients with faecal incontinence is unknown.
Aim—To study colonic function over two to threedays in the ambulatory, unprepared state in health and in patientswith idiopathic faecal incontinence.
Methods—Six healthy women and six women withfaecal incontinence and a structurally intact anal sphincter ingested adual radioisotope meal, and had a six sensor, solid state manometric probe colonoscopically inserted into the left colon. Scanning wasperformed until radioisotope left the gut and pressure was recorded fora median of 44hours.
Results—Three of six patients showed abnormalgastric emptying. Patients showed no disturbance of colonicradioisotope transit. Controls had a median of 12, whereas patients hada median of 16, high amplitude propagated waves per 24 hours. In threepatients urge incontinence was associated with high amplitude (up to500 cm water) propagated waves which often reached the rectum. These high pressure waves were identical to those occuring in healthy subjects, the only difference being the lack of adequate sphincter response. Passive incontinence was not associated with colonic motor activity. Defaecation in all subjects was associated with identical propagated waves, and distal movement of 13%(median) of right colonic content and excretion of 32% from the leftcolon and rectum. The urge to defaecate was associated with eitherpropagated waves (45%) or non-propagated contractions (55%). Rectalmotor complexes were recorded in both groups of subjects, but similar rhythmic activity was also recorded in the sigmoid and descending colon.
Conclusions—Normal colonic function consists offrequent high pressure propagated waves. Rhythmic activity occurs bothproximal to and in the rectum. Defaecation is characterised by highpressure propagated waves associated with coordinated anal sphincterrelaxation. Patients with faecal incontinence may have a widespreaddisturbance of gut function. Urge incontinence, an urge to defaecate,and defaecation can all be associated with identical high amplitude propagated pressure waves.

Keywords:colonic motility; gastric emptying; faecalincontinence

     

Peutz-Jeghers polyps, dysplasia, and K-ras codon 12 mutations

Background—Peutz-Jeghers syndrome (PJS) is a rare,autosomal dominant, polyposis syndrome, associated with an increasedrisk of gastrointestinal and extragastrointestinal malignancy.Occasionally dysplasia occurs in PJS polyps.
Aims—In colorectal carcinomas, mutations in codon12 of the K-ras oncogene are common and are found atsimilar frequency in precursor adenomas. Therefore, K-rascodon 12 point mutations in PJS polyps were evaluated.
Materials and methods—Fifty two PJS polyps,including four with dysplasia, collected from 19 patients with PJS,were analysed for mutations in the K-ras codon 12 by amutant enriched polymerase chain reaction procedure, followed by allelespecific oligodeoxynucleotide hybridisation.
Results—A K-ras codon 12 mutation wasidentified in one colonic polyp with dysplasia. The mutation was foundin the non-neoplastic epithelial cells and not in the dysplasticcomponent of the polyp.
Conclusions—K-ras codon 12 pointmutations are very rare in PJS polyps, by contrast with colorectaladenomas. The findings support previous evidence that there seems to beno intrinsic relation between K-ras codon 12 mutation and dysplasia.

Keywords:Peutz-Jeghers syndrome; polyps; dysplasia; K-ras codon 12 mutations

     

Increased expression of an inducible isoform of nitric oxide synthase and the formation of peroxynitrite in colonic mucosa of patients with active ulcerative colitis

Background—Increased production of reactivemetabolites of oxygen and nitrogen has been implicated in chronicinflammation of the gut. The object of this study was to examine themagnitude and location of nitric oxide synthase (NOS) activity andperoxynitrite formation in the colonic mucosa of patients withulcerative colitis in relation to the degree of inflammation.
Subjects—Thirty three patients with activeulcerative colitis (17 with mild or moderate inflammation, 16 withsevere inflammation).
Methods—Inducible NOS activity was determined inthe colonic mucosa by measuring the conversion ofL-arginine to citrulline in the absence of calcium. Thelocalisation of NOS and nitrotyrosine immunoreactivity was assessedimmunohistochemically using the labelled streptavidin biotin method.
Results—Inducible NOS activity increased inparallell with the degree of inflammation of the mucosa. Expression ofinducible NOS was found not only in the lamina propria, but also in the surface of the epithelium. Peroxynitrite formation as assessed bynitrotyrosine staining was frequently observed in the lamina propria ofactively inflamed mucosa.
Conclusions—Nitric oxide and peroxynitriteformation may play an important role in causing irreversible cellularinjury to the colonic mucosa in patients with active ulcerative colitis.

Keywords:nitric oxide; peroxynitrite; nitricoxide synthase; ulcerative colitis; colonic mucosa

     

The distal colon provides reserve storage capacity during colonic fluid overload

Background—In addition to its absorptive functionthe capacity of the colon to retain fluid might be relevant incompensating for increased fluid loads and prevention of diarrhoea. Thedistal colon is considered to be mainly a conduit without extensivestorage function.
Aims—To evaluate colonic volume capacity in amodel of pure osmotic diarrhoea.
Methods—A non-absorbable, iso-osmotic solution(OS) containing polyethylene glycol (500 ml) was infused into thecaecum of nine healthy volunteers; the control group (n=5) received anequal amount of an easily absorbable electrolyte solution (ES). Fluids were radiolabelled with technetium-99m and gamma camera images wereobtained for 48 hours. Counts in the proximal and distal colon weremeasured and regional and overall colonic transit and stool output were quantified.
Results—After OS, in contrast to ES, faecal outputwas increased significantly (p<0.05), but colonic transit after OS was not different from transit after ES (p>0.05). This indicates storage of OS in the colon: after OS infusion, counts in the proximal colondecreased linearly while the distal colon stored approximately 30% ofradioactivity for the whole 48 hour study period. After OS, stooloutput correlated with distal (p<0.01), but not with proximal(p>0.05), colonic transit. In constrast, after ES, stool output wasdetermined by proximal colonic transit (p<0.05) but not by transitthrough the distal colon (p>0.05).
Conclusion—The distal colon retainsnon-absorbable fluid volumes extensively. In our model transit throughthe distal colon—but not the proximal colon—determined the time atwhich diarrhoea occurred.

Keywords:osmotic diarrhoea; colonic transit; storagecapacity; colonic scintigraphy

     

Intestinal metaplasia at the squamocolumnar junction in patients attending for diagnostic gastroscopy

Background—The incidence of adenocarcinoma of theoesophagus and gastric cardia is increasing rapidly. Barrett'soesophagus is the major risk factor. Intestinal metaplasia at thesquamocolumnar junction in the absence of Barrett's oesophagus iscommon but its relation to adenocarcinoma and gastro-oesophageal refluxdisease is unclear.
Aims—To study the prevalence and clinical,endoscopic, and histological associations of intestinal metaplasia atthe squamocolumnar junction.
Methods—Biopsy specimens were taken from 120 randomly selected patients undergoing routine diagnostic endoscopy.Eight biopsy specimens, taken from above and below the squamocolumnarjunction, gastric fundus, and gastric antrum, were stained withhaematoxylin/eosin, alcian blue/periodic acid-Schiff, and Gimenez, andgraded independently by one pathologist.
Results—Intestinal metaplasia at thesquamocolumnar junction was found in 21 patients (18%). Metaplasia wasassociated with increasing age (p<0.01) and antral intestinalmetaplasia (p=0.04). Logistic regression analysis revealed that age wasthe only independent predictor (p<0.01). There was no association withsymptomatic, endoscopic, or histological markers of gastro-oesophagealreflux disease.
Conclusions—Intestinal metaplasia at thesquamocolumnar junction is a common finding. It is associated withincreasing age but not gastro-oesophageal reflux disease.

Keywords:intestinal metaplasia; Barrett's oesophagus; gastro-oesophageal reflux disease; oesophagus; gastric cardia; adenocarcinoma