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R Sim

Publications and source records attributed to R Sim.

At least 37 records · Page 2Linked to original sources
PubMed1995

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 Crohn's 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 Crohn's 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.

Animals↗
PubMed1995

The potent bone-resorbing mediator of Actinobacillus actinomycetemcomitans is homologous to the molecular chaperone GroEL.

Actinobacillus actinomycetemcomitans is a Gram-negative bacterium implicated in the pathology of localized juvenile periodontitis, a condition involving rapid destruction of alveolar bone. We have established that gentle extraction of this bacterium in saline releases a proteinaceous fraction (which we have termed surface-associated material [SAM] which has potent osteolytic activity in the murine calvarial bone resorption assay. Fractionation of the SAM has now revealed that activity is associated with a 62-kD protein. This bone-resorbing activity can be blocked by a monoclonal antibody (raised to the whole bacterium) that is claimed to recognize a protein homologous to the Escherichia coli molecular chaperone GroEL. Purification of this bone-resorbing protein to homogeneity has been achieved by a combination of anion exchange, gel filtration, and ATP-affinity chromatography and the NH2-terminal sequence shows > 95% homology to E. coli GroEL. This GroEL homologue is found in the SAM of A. actinomycetemcomitans but is not found in the osteolytically active SAM from other Gram-negative or Gram-positive bacteria. The GroEL protein from E. coli, but not from Mycobacterium tuberculosis and Mycobacterium leprae, also showed activity in the bone resorption assay. We believe this to be the first observation that a molecular chaperone has the capacity to stimulate the breakdown of connective tissue.

Aggregatibacter actinomycetemcomitans↗
PubMed1995

Lectin-carbohydrate interactions in disease. T-cell recognition of IgA and IgD; mannose binding protein recognition of IgG0.

Two disease associated lectin-carbohydrate interactions have been studied. (1) A T-cell surface lectin which binds IgA1 and IgD is expressed on CD4+ and CD8+ T-lymphocytes in a number of diseases including systemic lupus erythematosus, rheumatoid arthritis (RA), Behcet's disease and IgA nephropathy. We have demonstrated that calcium independent binding to this receptor is mediated by the O-linked disaccharide Gal beta 3GalNAc which is associated with the hinge regions of both IgA1 and IgD. (2) In rheumatoid arthritis the proportion of IgG0 glycoform populations lacking terminal galactose increases. We have shown that terminal GlcNAc residues on oligosaccharides in the Fc region of IgG0 can bind to the C-type lectin, serum mannose binding protein, and thus activate the classical complement pathway. This provides a mechanism of activation of the complement system not available to the other classes of IgG glycoforms.

Carbohydrate Metabolism↗
PubMed1994

A vascular hypersensitivity model of acute multifocal gastrointestinal infarction.

We have investigated the hypothesis that submucosal vasculitis may account for the patchy transmural inflammation observed in Crohn's disease. Test ferrets (N = 11) were sensitized to human albumin. Five days after the last sensitization injection, human albumin microspheres (15-150 microns diameter) were injected intraarterially into the mesenteric circulation of a defined loop of mid-gut. Six control ferrets showed no histological abnormality at either 48 hr or two weeks after intraarterial injection. At 48 hr, five of six presensitized ferrets demonstrated submucosal vasculitis with fibrinoid necrosis. In two cases there was transmural inflammation and mucosal ulceration. A further five presensitized ferrets received weekly subcutaneous human albumin injections following the mesenteric intraarterial injection of albumin microspheres: after two weeks one animal demonstrated mild perivascular inflammatory changes and another demonstrated vasculitis. One of the two animals with transmural inflammation and mucosal ulceration at 48 hr, and the animal with vasculitis at two weeks, had precipitating antibodies to human serum albumin. This model demonstrates that an immune-mediated submucosal vasculitis can sometimes result in discontinuous transmural inflammation of the intestinal wall.

Animals↗
PubMed1994

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. METHODS: Gastric epithelial cell proliferation was assessed in 22 H. pylori-positive duodenal ulcer patients before and 6 weeks after 'triple therapy' with bismuth, tetracycline and metronidazole. Cell proliferation was studied either by immunostaining for the proliferating cell nuclear antigen (PCNA) or by a microdissection technique. RESULTS: Eradication was successful in 10 of the 22 H. pylori-positive patients. Treatment with 'triple therapy' resulted in a significant fall in the rate of gastric epithelial cell proliferation; this effect was seen in both the gastric body and antrum. There was a significant correlation between the number of PCNA-labelled cells and the histological grade of activity (neutrophil inflammation) (r = 0.49, P = 0.02); the same correlation was found for the number of mitoses per gland (r = 0.5, P = 0.02). There was no significant difference in the treatment effect for eradicated or non-eradicated patients or either the body or antrum. Six patients, who had at least one antral biopsy that showed evidence of focal intestinal metaplasia, had a higher rate of cell proliferation. CONCLUSIONS: The reduction in epithelial cell proliferation in the body and antrum after triple therapy is independent of successful eradication of H. pylori, and it may be due to an anti-inflammatory effect of triple therapy.

Adult↗
PubMed1994

Ulceration, fibrosis and diaphragm-like lesions in the caecum of rats treated with indomethacin.

BACKGROUND: Patients on nonsteroidal anti-inflammatory drugs can develop curious intestinal fibrotic diaphragms. METHODS: Groups of rats received indomethacin mixed into a powdered diet at 3 mg.kg/day for 6 and 12 weeks and 6 mg.kg/day for up to 6 weeks. In an attempt to reproduce a human dosing regimen, another group of rats, for a total of 30 weeks, received consecutive periods of indomethacin at 3 mg.kg/day for 12 weeks, 4.5 mg.kg/day for 1 week, 6 mg.kg/day for 1 week, control diet for 6 weeks, 4.5 mg.kg/day for 2 weeks and finally, a control diet for a healing period of 8 weeks. Control rats received powdered diet alone. At termination, the small and large intestines were examined macroscopically and histologically. RESULTS: Indomethacin caused microcytic anaemia, hypoalbuminaemia, small intestinal ulceration, caecal ulceration and inconspicuous raised mucosal lesions in the caecum that histologically showed submucosal fibrosis with disruption and thickening of the apical muscularis mucosae. No control rats showed any abnormality. CONCLUSION: These fibrotic lesions of the rat caecum resemble human diaphragms and may arise from healed caecal ulcers.

Administration, Oral↗
PubMed1994

Dexamethasone promotes ulcer plugging in experimental enteritis.

AIM: We investigated the effect of dexamethasone on indomethacin-induced ulceration in the rat. METHODS: Groups of four rats received oral indomethacin (15 mg/kg) and the jejunal mucosa was examined 24 h later for mucosal ulceration. Three of the groups received oral dexamethasone (1, 3 and 6 mg/kg) 0.5 h prior to indomethacin, while the fourth received vehicle. Haematological evaluation was performed and ulcers were assessed both histologically and immunohistochemically. RESULTS: Indomethacin caused multifocal jejunal ulceration that was reduced only by the highest dose of dexamethasone (6 mg/kg). Indomethacin caused a significant fall in the blood haemoglobin concentration that was prevented by dexamethasone at all doses. The ulcers induced by indomethacin alone were deep, punched-out and haemorrhagic while the ulcers arising in rats pre-treated with dexamethasone (all doses) were 'plugged' by a white fibrino-purulent exudate. Histologically, the dexamethasone ulcer exudate was composed of bacteria, fibrin, mucus and a significant increase in the numbers of neutrophils. Dexamethasone alone had no significant pathological effect on the small intestine. CONCLUSIONS: We report the observation that dexamethasone at high doses inhibits indomethacin-induced jejunal ulceration in the rat while at low doses it promotes 'plugging' of ulcers with bacteria, fibrin, mucus and neutrophils that probably reduces haemorrhage from the ulcer base.

Animals↗
PubMed1993

Evidence of persistent measles virus infection in Crohn's disease.

Transmission electron microscopy was used to examine the microvasculature of perfusion-fixed tissues from Crohn's disease and control patients. Paramyxovirus-like particles, and inclusions consisting of condensations of nucleocapsid, in giant cells and endothelium at foci of vascular injury were identified in all 9 Crohn's disease patients. Tissues from patients with Crohn's disease were also examined by either in situ hybridisation (n = 10) or immunohistochemistry (n = 15), and compared to inflammatory and noninflammatory controls (n = 22). Hybridisation for measles virus N-protein genomic RNA was positive in all cases of Crohn's disease localising to foci of granulomatous vasculitis and lymphoid follicles. Positive immunohistochemical staining for measles virus nucleocapsid protein was positive in 13 of 15 patients with Crohn's disease, localising to foci of granulomatous inflammation. Hybridisation for measles virus RNA was positive in a minority of control intestinal tissues; viral inclusions were not seen ultrastructurally. Immunostaining was negative in control cases of intestinal tuberculosis. These observations suggest that measles virus is capable of causing persistent infection of the intestine and that Crohn's disease may be caused by a granulomatous vasculitis in response to this virus.

Antibodies, Viral↗
PubMed1993

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 Crohn's disease were studied prospectively from relapse (Crohn's 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 Crohn's 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 Crohn's disease. The plasma factor XIIIA concentration may prove a useful laboratory marker of disease activity.

Adolescent↗
PubMed1993

Early mucosal changes in Crohn's disease.

Aphthoid ulceration has been regarded as an early macroscopic feature of Crohn's disease, yet the cause of this mucosal lesion is unknown. Examination of areas of apparently normal and non-inflamed bowel in Crohn's disease has allowed the identification of mucosal changes which occur before macroscopic and microscopic ulceration. Thirty five resection specimens from patients with Crohn's 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 Crohn's 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.

Capillaries↗
PubMed1993

Immunohistochemical study of tissue factor expression in normal intestine and idiopathic inflammatory bowel disease.

AIMS: To investigate the localisation of tissue factor expression in normal and inflamed intestine. METHODS: Serial cryostat sections of tissue taken from patients with Crohn's disease (n = 8), ulcerative colitis (n = 5), and from controls (n = 5) were stained with haematoxylin and eosin and immunostained for tissue factor, collagen type IV, fibrinogen and platelet glycoprotein IIIa. RESULTS: In control tissues tissue factor was present as a continuous layer along the epithelial basal lamina: sections from controls did not immunostain for fibrinogen or platelets. In non-ulcerated inflamed mucosa, tissue factor staining intensified in cases of Crohn's disease and was associated with fibrin deposition. Staining for tissue factor was either patchy or absent in cases of ulcerative colitis and there was no fibrin deposition. This change accompanied the early destruction of the epithelial basal lamina in ulcerative colitis that was not seen in Crohn's disease. In both diseases tissue factor expression in severely inflamed and ulcerated mucosa was present on lamina propria macrophages and vascular endothelium and was associated with fibrin or platelet thrombi. In three of eight cases of Crohn's disease tissue factor expression and thrombi were evident in areas of submucosal vasculitis. These were not seen in adjacent normal vessels. CONCLUSIONS: These observations are consistent with a tissue factor haemostatic barrier in the intestine: this barrier seems to be incomplete or defective in ulcerative colitis. Tissue factor expression by macrophages and endothelial cells may be important, particularly in the microvascular thrombosis and induration which are characteristic of Crohn's disease.

Adult↗
PubMed1993

Autologous marrow injection in the treatment of delayed and non-union in long bones.

A retrospective study of the use of autologous bone marrow injection for the treatment of delayed and non-union of long bones in an Orthopaedic Department, Singapore General Hospital from 1990-1991 is presented. There were 10 patients with 11 fractures (8 tibia and one each of humerus, femur and radius-ulna) available for study. Percutaneous injection of autologous marrow alone was used to stimulate healing of delayed and non-unions treated initially by plating, external fixation and in one case, by plaster cast. Marrow injection stimulated a callus formation sufficient to unite 9 of the fractures. The median time to clinical union was 10 weeks (range 4-23 weeks) and radiological union 17 weeks (range 9-29 weeks). Most patients had discomfort at the donor and injected sites for one to two days. There was one case of infection but none of the significant donor site morbidity was associated with standard open autologous grafting. Bone marrow injection was effective in stimulating bony union, with numerous advantages and considerably lower morbidity compared with standard open autologous grafting. Shorter inpatient stay was a significant feature.

Adult↗
PubMed1992

Neuroendocrine changes in rat stomach during experimental diabetes mellitus.

The effects of 48 days of streptozotocin-induced diabetes mellitus in rats on plasma concentrations of gastrin, somatostatin, pancreatic glucagon, and enteroglucagon have been assessed. In addition, neuroendocrine changes in sections of gastric mucosa were quantified using a computer-assisted morphometric system following immunohistochemical staining with polyclonal antibodies directed against gastrin, PGP 9.5 (a neural protein), and somatostatin. Diabetes resulted in significantly increased fasting plasma concentrations of somatostatin, and entero- and pancreatic glucagon. In contrast, lower plasma gastrin concentrations and decreased antral G-cell density were noted in diabetic rats. Gastric somatostatin and neuronal PGP 9.5 stain densities were unaltered by diabetes. Stomachs of diabetic rats weighed less, but both the jejunum and ileum showed evidence of mucosal hyperplasia. The gastric neuroendocrine atrophy observed in diabetes may be a consequence of elevated plasma somatostatin derived from nongastric sources. The enhanced growth of the intestinal mucosa may be related, directly or indirectly, to raised intraluminal glucose concentration in diabetes.

Animals↗
PubMed1992

A ferret model of acute multifocal gastrointestinal infarction.

Based on the demonstration of mural granulomatous vasculitis in Crohn's disease, it was hypothesized that this vasculitis may account for the discontinuous pattern of lesions in this condition. Accordingly, the present study investigated the histological changes produced by interruption of the submucosal and mucosal microcirculation in the ferret midgut. Two techniques were used. First, up to 30 adjacent vasa recta were ligated using microsurgical techniques; this produced no evidence of ischemic damage. Second, interruption of the submucosal collateral plexus by the intra-arterial injection of styrene microspheres (27-, 50-, or 90-microns diameter) produced acute intestinal mucosal damage. A combination of 27- and 90-microns spheres resulted in focal mucosal inflammation, necrosis, and ulceration. "Summit" lesions with normal adjacent mucosa were observed 48 hours after embolization, with evidence of regeneration of the mucosa overlying the occluded vessels at 72 hours. This model shows that focal gastrointestinal infarction with normal adjacent mucosa can be produced by acute occlusion of submucosal and mucosal arteries.

Acute Disease↗
PubMed1992

Mucosal capillary thrombi in rectal biopsies.

We studied the initial rectal biopsy from 46 patients in whom subsequent follow-up established the diagnosis of either self-limited colitis or inflammatory bowel disease. An additional 12 non-inflamed rectal biopsies were also studied. There was between 2 and 8 years of follow-up in each of these cases. Staining for fibrin (MSB, fibrinogen), platelets (factor XIIIA, Y2/51), and capillary basement membrane (reticulin, collagen 4) was performed to identify thrombotic material within capillaries. Mucosal capillary thrombi were best identified by staining for factor XIIIA; thrombi were observed in 8/13 cases of ulcerative colitis, 4/10 cases of Crohn's disease, 1/3 cases of unspecified inflammatory bowel disease and 5/20 cases of self-limited colitis. The presence of capillary thrombi was not related to the severity of inflammation, but none of the control biopsies showed capillary thrombi. Their presence seems of little diagnostic value in distinguishing inflammatory bowel disease from self-limited colitis. The pathogenetic significance of these mucosal capillary thrombi is uncertain.

Adult↗
PubMed1992

Kielland's forceps delivery: is it a dying art?

A retrospective study in the use of Kielland's Forceps for rotation of the foetal head and mid-cavity delivery in Kandang Kerbau Hospital, Singapore from 1987-1990 is presented. Out of a total of 53,889 singleton births during this period, Kielland's Forceps was used for delivery in 137 (0.25%) patients with an incidence of 0.65% in the primiparae and 0.07% in the multiparae. Primiparity, induction of labour and epidural analgesia were associated with a significantly higher incidence of rotational delivery by Kielland's forceps. The success rate of Kielland's forceps delivery was 93.4% (128 of 137). There was no maternal or perinatal mortality. About one-third of the mothers experienced postpartum morbidity, commonest being retention of urine, postpartum haemorrhage and vaginal lacerations. Traumatic injuries were present in about one-quarter of the babies and were minor. Out of a total of 306 mid-cavity deliveries for occipito-transverse malposition, Kielland's forceps accounted for 38.2% (117), vacuum extraction 30.7% (94), manual rotation followed by Neville-Barnes forceps 11.1% (34) and Caesarean section 20.0% (61). The junior specialists tended to use vacuum extraction for rotational delivery more than the senior specialists.

Birth Injuries↗
PubMed1991

Granulomatous vasculitis in Crohn's disease.

This study investigated a possible vascular origin for granulomas in Crohn's disease. Twenty-four consecutive resected specimens of small and large intestinal Crohn's disease were preserved by arterial perfusion-fixation with 10% formol saline, at mean arterial pressure (100 mm Hg). Fifteen specimens contained granulomas on routine examination of H&E-stained sections. These 15 specimens were examined in detail using a range of immunohistochemical staining techniques to identify vascular structures and granulomas. A total of 485 granulomas were found, 85% of which were identified as being directly involved in vascular injury. The majority (77%) of granulomas were deep to the mucosa; they were found most frequently in the submucosa (42%). The techniques used in this study enhanced the recognition of granulomatous vasculitis. The results suggest that the majority of granulomas in Crohn's disease form within walls of blood vessels. Vascular localization of granulomatous inflammation suggests that the intestinal microvasculature contains an early element in the pathogenesis of Crohn's disease.

Crohn Disease↗