A.P. Dhillon

Early mucosal changes in Crohn's disease.

Aphthoid ulceration has been regarded as an early macroscopic feature of Crohns disease, yet the cause of this mucosal lesion is unknown. Examination of areas of apparently normal and non-inflamed bowel in Crohns disease has allowed the identification of mucosal changes which occur before macroscopic and microscopic ulceration. Thirty five resection specimens from patients with Crohns disease were compared with 12 specimens from patients with ulcerative colitis and 13 controls. Specimens were fixed either by immersion in formalin in the routine way or by perfusion fixation with formalin at mean arterial pressure. Immunostaining for macrophages, vessel wall, and blood constituents allowed identification of small mucosal capillaries which were not apparent otherwise. In Crohns disease damage and rupture of these small capillaries occurred before infiltration of the lamina propria by inflammatory cells. Loss of the overlying epithelium seemed to follow this vascular damage.

Effect of eradication of Helicobacter pylori on gastric epithelial cell proliferation

Background: Helicobacter pylori is associated with B‐type gastritis, duodenal ulcer disease, and possibly gastric carcinoma. The object of this study was to assess the effect of eradication of H. pylori infection on gastric epithelial cell proliferation.

EARLY HISTOLOGICAL FEATURES OF SMALL INTESTINAL INJURY INDUCED BY INDOMETHACIN

The early histological features of indomethacin‐induced jejunal injury in the rat are described in tissues preserved by perfusion‐fixation with 10% formolsaline. After an oral dose of indomethacin (15 mg/kg, known to cause severe multifocal ulceration of the rat jejunum), groups of rats were anaesthetized with subsequent perfusion‐fixation of the gastrointestinal tract at 1, 2, 3, 6 and 48 h after dosing. Using routine light microscopic techniques, we have observed a sequence of four distinct stages, in time, of small intestinal injury. The earliest histological features were shortening of the villi, epithelial stratification, basal lamina degeneration, eosinophil degranulation and infiltration of the epithelium prior to infiltration of the mucosa by neutrophils. We consider that these earliest changes, seen at 1, 2 and 3 h, represent a distinct histological entity termed Type 1 change or villous ‘tufting’. Type 2 change includes all of the features of Type 1 change plus the subsequent infiltration of the mucosa by neutrophils at 2, 3 and 6 h. Type 3 change includes necrosis of the upper‐third of the villi and was mainly seen at 3 and 6 h. Type 4 change describes extreme injury to more than one‐third of the mucosa with severe, acute inflammation and perforation of the bowel wall by 48 h. Although a small number of neutrophils had appeared to infiltrate the mucosa as early as 2 h after dosing, they were only significantly increased at 3, 6 and 48 h. Possible pathogenic mechanisms involved in shortening of villi as a result of smooth muscle contraction and the role of mucosal eosinophils in NSAID‐induced jejunal injury in the rat are discussed.

Smoking, the oral contraceptive pill, and Crohn's disease

Both cigarette smoking and the oral contraceptive pill have been implicated as aggravating factors in Crohns disease. Based upon the recent demonstration of multifocal gastrointestinal infarction in Crohns disease, a possible pathogenic mechanism for this condition, we propose how smoking and the oral contraceptive pill may potentiate a tendency for focal thrombosis and hence exacerbate the activity of Crohns disease.Both cigarette smoking and the oral contraceptive pill have been implicated as aggravating factors in Crohns disease. Based upon the recent demonstration of multifocal gastrointestinal infarction in Crohns disease, a possible pathogenic mechanism for this condition, we propose how smoking and the oral contraceptive pill may potentiate a tendency for focal thrombosis and hence exacerbate the activity of Crohns disease.

Vascular anatomy defines sites of indomethacin induced jejunal ulceration along the mesenteric margin

Background—Indomethacin induces ulceration in the rat jejunum with sparing of the ileum. The ulcers localise between vasa recta along the mesenteric margin of the bowel, observations that have not been fully explained. Aim—To examine the relationship between the localisation of experimental ulcers and the vascular anatomy of the rat small intestine. Methods—The normal vascular anatomy of the rat jejunum and ileum was studied and compared using arterial carbon ink perfusion. The anatomical localisation of early and advanced lesions induced by indomethacin was examined with particular reference to the vasculature. Mucosal injury induced by feeding vessel ligation for 24 hours or brief ischaemia-reperfusion injury was examined. The existence of anatomically sensitive sites to indomethacin was tested in a two dose study. Results—In the rat jejunum, poorly vascularised sites along the mesenteric margin were highly susceptible to indomethacin induced injury, such sites being absent from the ileum. Villous contraction was a feature of both early indomethacin injury and ischaemia-reperfusion injury in the rat jejunum. Twenty four hour ligation of jejunal vasa brevia selectively induced ischaemic injury along the mesenteric margin. Two doses of indomethacin to rats did not induce greater injury than a single dose. Conclusions—Results support the hypothesis that the rat jejunum possesses vascularly compromised sites along the mesenteric margin that are susceptible to indomethacin induced injury. Indomethacin may cause ischaemia-reperfusion injury selectively at these sites.

Congestive gastropathy and Helicobacter pylori: an endoscopic and morphometric study.

Congestive gastropathy is a frequent cause of upper gastrointestinal haemorrhage in patients with portal hypertension. The pathogenesis is thought to involve venous congestion with gastric mucosal capillary dilatation. We studied the relation between gastric mucosal capillary dilatation, measured morphometrically, and endoscopic appearances in 74 patients with portal hypertension and 20 control subjects. We also investigated the frequency of gastric colonisation with Helicobacter pylori. Mucosal capillaries in patients were significantly dilated compared with control subjects (p less than 0.001) but the degree of dilatation was not related to the severity of the endoscopic appearances. H pylori was identified in 19 of 74 (26%) patients but was not related to the severity of the endoscopic appearances. These results suggest that other factors in addition to mucosal venous and capillary congestion are important in the pathogenesis of endoscopic congestive gastropathy and that gastric colonisation with H pylori is unlikely to be one of these factors.

Persistent measles virus infection of the intestine: confirmation by immunogold electron microscopy.

This study sought to investigate persistent measles virus infection of the intestine: a novel protocol for immunogold electron microscopy was developed using a polyclonal anti-measles nucleoprotein antibody on reprocessed, formalin fixed paraffin wax embedded tissue sections. Antibody binding was detected using both immunoperoxidase and light microscopy on tissue sections, and 10 nm gold conjugated secondary antibody and electron microscopy on ultrathin sections. The techniques were validated using both measles infected vero cells and human tissues with established measles infection: these included brain affected by subacute sclerosing panencephalitis and acute measles appendicitis. The technique was applied subsequently to six untreated cases of granulomatous Crohns disease, and two cases of ileocaecal tuberculosis, a granulomatous control. Mumps primary antibody--applied to both mumps infected vero cells, and measles infected vero cells and tissues studied by immunoperoxidase, and measles antibody on mumps infected cells studied by immunoperoxidase and immunogold--were used as specificity controls: the primary antibodies identified their respective target antigen and there was no antibody cross reactivity. Measles virus nucleocapsids labelled with gold conjugated antibody in both infected cells and tissues, including foci of granulomatous inflammation in five of six cases of Crohns disease: in the fifth case, the granuloma could not be identified in ultrathin section. In one of the tuberculosis cases, a low level of signal was noted while the second case was negative. Labelling adopted a characteristic pattern in all infected tissues, strengthening the specificity of these findings. This study provides the first direct confirmation of persistent measles virus infection of the intestine.

Focal nodular hyperplasia‐like areas in cirrhosis

Aims:  Focal nodular hyperplasia‐like lesions have rarely been described in cirrhotic livers. We describe five cases of such lesions.

Factor XIIIA subunit and Crohn's disease.

Factor XIIIA is the active subunit of plasma factor XIII that is responsible for cross linking fibrin into a stable clot. Sixteen patients with Crohns disease were studied prospectively from relapse (Crohns disease activity index > 150) into remission. Plasma factor XIIIA concentrations were significantly lower in active disease (median 63 (95% CI 46-72) U/dl) than remission (median 90 (95% CI 60-112) U/dl; p = 0.002). Plasma factor XIIIA concentrations correlated positively with the activity index (p = 0.005) and platelet count (p = 0.003), and negatively with serum albumin (p = 0.006). In five patients with persistent aggressive disease, the factor XIIIA concentration remained below the lower range of normal despite apparent clinical improvement in response to medical treatment. Tissues from three patients who underwent surgical resection during the study were immunostained for factor XIIIA. Gut mucosal and submucosal macrophages stained strongly for factor XIIIA. In one patient, capillary thrombi near superficial mucosal erosions immunostained for factor XIIIA in macroscopically normal mucosa. Similar changes were identified in more severely inflamed sections of intestine from the other two patients. The demonstration of significantly low plasma factor XIIIA concentrations in active Crohns disease, and the immunostaining of factor XIIIA in capillary thrombi in the bowel wall, suggest that activation of coagulation may be involved in the pathogenesis of Crohns disease. The plasma factor XIIIA concentration may prove a useful laboratory marker of disease activity.

Focal reduction of villous blood flow in early indomethacin enteropathy: a dynamic vascular study in the rat

Background—Oral indomethacin causes villous shortening, microvascular damage, and distortion, which might induce mucosal ischaemia and necrosis. Aims—In order to determine the early events in indomethacin induced jejunal injury we examined the temporal relations between morphological damage and changes in villous blood flow following indomethacin. Methods—In anaesthetised rats, mid jejunal villi were exteriorised in a chamber and observed by fluorescence microscopy. Blood flow in surface capillaries was calculated from velocities and diameters. Indomethacin was applied by both luminal and intravenous routes for 90 minutes, after which the animal was perfusion fixed and the villi were processed for histological examination. Control animals received intravenous or luminal bicarbonate (1.25%). Results—Blood flow slowed in individual villi at 20 minutes, and progressed to complete stasis (in another group) by 45 minutes. Histological examination at 20 minutes revealed microvascular distortion, but no villous shortening: crypt depth:villous height ratios were 0.356 (0.02) in test and 0.386 (0.01) in surrounding villi (p>0.5). At stasis, the villi under study showed epithelial clumping and were shortened: crypt depth:villous height ratios were 0.92 (0.2) in test and 0.42 (0.06) in surrounding villi (p<0.02). Vehicle alone had no effect on either blood flow or histology. Conclusions—Focal slowing of villous blood flow and microvascular distortion precede villus shortening and epithelial disruption, and indicate that damage to surface microvasculature is an early event in indomethacin induced mucosal injury in this model.