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Biomedical subjects

I Bjarnason

Publications and source records attributed to I Bjarnason.

At least 73 records · Page 4Linked to original sources
PubMed1997

A randomized, double-blind, crossover comparative endoscopy study on the gastroduodenal tolerability of a highly specific cyclooxygenase-2 inhibitor, flosulide, and naproxen.

BACKGROUND: Inhibition of constitutively expressed cyclooxygenase (Cox-1) is thought to play an important role in the gastrointestinal toxicity of nonsteroidal anti-inflammatory drugs (NSAID), while their therapeutic action may be due to inhibition of the enzyme Cox-2, which is specifically expressed at sites of inflammation. NSAIDs with high affinity and specifity for Cox-2 hold the promise of maintaining efficacy without the gastrointestinal side effects of conventional NSAIDs. METHODS: We assessed the gastrointestinal tolerability of flosulide (20 mg twice a day), a highly selective Cox-2 inhibitor with that of naproxen (500 mg twice a day), which has equal affinity for Cox-1 and -2 in 19 patients with osteoarthrosis in a randomized, double blind, crossover endoscopy study. Subjects were treated for 2 weeks with a 2-week washout period. Gastroduodenal damage was primarily assessed as by Lanza (grades 0-4). RESULTS: No stomach damage was seen in 13 (68%) patients after flosulide and in 5 (37%) after naproxen (P < 0.001). Lanza scores were significantly lower after flosulide (0.58) than after naproxen (1.47) (P < 0.001; odds ratio, 84.4; 95% confidence interval, 1.45-4908). Flosulide was significantly better tolerated (P < 0.005) than naproxen. CONCLUSION: These results endorse the idea that highly selective Cox-2 inhibitors may be associated with lesser gastrointestinal side effects than conventional NSAIDs.

Adult↗
PubMed1996

Nonsteroidal antiinflammatory drugs and uncoupling of mitochondrial oxidative phosphorylation.

OBJECTIVE: There is a lack of correlation between cyclooxygenase (COX) inhibition and nonsteroidal anti-inflammatory drug (NSAID)-induced gastrointestinal (GI) damage; it has been suggested that mucosal damage may be initiated by a "topical" action of NSAIDs involving mitochondrial injury. We evaluated the effect of a range of NSAIDs and related compounds on mitochondrial function and assessed the differences between them in relation to their physicochemical properties. METHODS: Stimulation of respiration, as an indicator of mitochondrial uncoupling, was measured in isolated coupled rat liver mitochondrial preparations, using an oxygen electrode. RESULTS: Conventional NSAIDs and acidic prodrugs all had stimulatory effects on mitochondrial respiration at micromolar concentrations (0.02-2.7 microM); higher concentrations were inhibitory. The uncoupling potency was inversely correlated with drug pKa (r = -0.87, P < 0.001; n = 12). Drugs known to have good GI tolerability, including modified flurbiprofen (dimero-flurbiprofen and nitrobutyl-flurbiprofen), nabumetone (a non-acidic prodrug), and non-acidic highly selective COX-2 inhibitors, did not cause uncoupling. CONCLUSION: The ability to uncouple mitochondrial oxidative phosphorylation is a common characteristic of antiinflammatory agents with an ionizable group. Modification or absence of an ionizable moiety reduces the effect on mitochondria and could lead to improved NSAID GI safety.

Animals↗
PubMed1996

Influence of anti-rheumatic drugs on gut permeability and on the gut associated lymphoid tissue.

There is great interest in the association between intestinal inflammation and the various arthropathies. However, most studies assessing intestinal function in these diseases are confounded by the fact that non-steroidal anti-inflammatory drugs (NSAIDs) have profound effects on the small intestine. Hence NSAIDs cause quite distinct and severe biochemical damage during drug absorption (uncoupling of mitochondrial oxidative phosphorylation proving to be most important) which results in increased intestinal permeability. All commonly used NSAIDs, apart from aspirin and nabumetone, are associated with increased intestinal permeability in man. Whilst reversible in the short term, it may take months to improve following prolonged NSAID use. Increased intestinal permeability appears to be the central mechanism of converting the biochemical damage to an inflammatory tissue reaction (NSAID enteropathy). The inflammatory enteropathy is not, however, unique to NSAIDs but similar changes are found with other permeability breakers. In intestinal infections and in diseases associated with reduced mucosal defence, suggesting that the small intestinal inflammation represents a common final pathway for a number of intestinal injuries. Spondylarthropathies are associated with a high prevalence of terminal ileitis, but as most patients have been receiving NSAIDs it has been difficult to dissociate the effects of NSAIDs on intestinal function from that of the ileitis itself. Nevertheless, two studies suggest that increased intestinal permeability in spondylarthropathies occur independently of NSAID ingestion. Whilst these findings may have implications for the development of arthritis, the permeability changes in spondylarthropathy do not differ quantitatively or qualitatively from that of NSAIDs or other permeability breakers. NSAID enteropathy can be differentiated from spondylarthropathic enteropathy by differences in location of disease and lack of predilection of certain HLA types. However, as the two may coexist both enteroscopy and ileocolonoscopy may be necessary for this distinction.

Animals↗
PubMed1996

Intestinal inflammation, ileal structure and function in HIV.

OBJECTIVES: This study examines small intestinal absorption-permeability, intestinal inflammation and ileal structure and function in HIV-positive male homosexuals. METHODS: Thirty HIV-seropositive male homosexuals at various stages of disease underwent intestinal absorption permeability and 111indium leukocyte studies (for quantification of intestinal inflammation). Twenty-six men with AIDS had a dual radioisotopic ileal function test (whole body retention of tauro 23-[75Se]-selena 25-homocholic acid and 58cobalt-labelled cyanocobalamine), and 17 underwent ileocolonoscopy with terminal ileal biopsy. RESULTS: Well, HIV-infected, subjects had normal intestinal absorption-permeability, but both functions were impaired upon the development of AIDS. The median faecal excretion of 111indium in well patients (0.66%) did not differ significantly (P > 0.5) from controls (0.46%), but subjects with AIDS who were well or who had diarrhoea had significant (P < 0.005) intestinal inflammation (1.33% and 2.18%, respectively). The median 7-day retention of tauro 23-[75Se]-selena 25-homocholic acid in well patients with AIDS (38.9%) did not differ significantly (P > 0.2) from controls (39.3%), whereas the absorption of 58cobalt-labelled cyanocobalamine was significantly (P < 0.05) lower than controls (32.1% and 59.4%). Patients with AIDS-diarrhoea had significant (P < 0.001) malabsorption of both the bile acid (7.7%) and vitamin B12 (8.9%) which was more severe than in Crohn's ileitis (14.2% and 30.3%, respectively). Morphometric analyses of ileal biopsies were unremarkable in AIDS. CONCLUSIONS: These studies demonstrate a low-grade enteropathy in patients with AIDS, severe ileal malabsorption in patients with AIDS diarrhoea and relatively minor ileal morphologic changes. Malabsorption of bile acids may play a pathogenic role in patients with AIDS and diarrhoea.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Mucosal antibodies in inflammatory bowel disease are directed against intestinal bacteria.

In contrast with normal subjects where IgA is the main immunoglobulin in the intestine, patients with active inflammatory bowel disease (IBD) produce high concentrations of IgG from intestinal lymphocytes, but the antigens at which these antibodies are directed are unknown. To investigate the specificities of these antibodies mucosal immunoglobulins were isolated from washings taken at endoscopy from 21 control patients with irritable bowel syndrome, 10 control patients with intestinal inflammation due to infection or ischaemia, and 51 patients with IBD: 24 Crohn's disease (CD, 15 active, nine quiescent), 27 ulcerative colitis (UC, 20 active, seven inactive). Total mucosal IgG was much higher (p < 0.001) in active UC (median 512 micrograms/ml) and active CD (256 micrograms/ml) than in irritable bowel syndrome controls (1.43 micrograms/ml), but not significantly different from controls with non-IBD intestinal inflammation (224 micrograms/ml). Mucosal IgG bound to proteins of a range of non-pathogenic commensal faecal bacteria in active CD; this was higher than in UC (p < 0.01); and both were significantly greater than controls with non-IBD intestinal inflammation (CD p < 0.001, UC p < 0.01) or IBS (p < 0.001 CD and UC). This mucosal IgG binding was shown on western blots and by enzyme linked immunosorbent assay (ELISA) to be principally directed against the bacterial cytoplasmic rather than the membrane proteins. Total mucosal IgA concentrations did not differ between IBD and controls, but the IgA titres against faecal bacteria were lower in UC than controls (p < 0.01). These experiments show that there is an exaggerated mucosal immune response particularly in active CD but also in UC directed against cytoplasmic proteins of bacteria within the intestinal lumen; this implies that in relapse of IBD there is a breakdown of tolerance to the normal commensal flora of the gut.

Adolescent↗
PubMed1996

Assessing the site of increased intestinal permeability in coeliac and inflammatory bowel disease.

BACKGROUND: The precise site of intestinal permeability changes in patients with coeliac and inflammatory bowel disease is unknown. AIMS: To design a non-invasive technique for the localisation of altered gastrointestinal permeability to 51chromium labelled EDTA (51CrEDTA). The method depends on comparing and defining concentration/time profiles in serum of a series of simultaneously ingested indicators with a well defined absorption site (3-0-methyl-D-glucose (jejunal indicator), 57cobalt labelled vitamin B12 (ileal indicator), and sulphasalazine (caecal-colonic indicator)) in relation to simultaneously ingested 51CrEDTA. SUBJECTS: Five normal controls, six patients with untreated coeliac disease, five with Crohn's ileitis, and five with pan-ulcerative colitis underwent study, which entailed the simultaneous ingestion of the above four test substances followed, during the next 24 hours, by timed serial collection of urine and serum for marker analysis. RESULTS: Urinary excretion of 51CrEDTA was significantly increased in all patient groups. Analysis of serum appearances and profiles of the markers suggested that the increased intestinal permeation of 51CrEDTA took place in the diseased jejunum in patients with coeliac disease, predominantly in the ileum in Crohn's disease and in the colon in the patients with pan-ulcerative colitis. CONCLUSION: A new non-invasive technique has been assessed that permits the localisation of the site of permeability changes with the gastrointestinal tract.

Adult↗
PubMed1996

Evaluation of differential disaccharide excretion in urine for non-invasive investigation of altered intestinal disaccharidase activity caused by alpha-glucosidase inhibition, primary hypolactasia, and coeliac disease.

BACKGROUND/AIM: The reliability of a quantitative method for the non-invasive assessment of intestinal disaccharide hydrolysis was assessed. METHODS: Differential excretion of intact disaccharide, expressed as ratios of lactulose to appropriate hydrolysable disaccharides in urine collected following combined ingestion, has been investigated in healthy volunteers with drug induced alpha-glucosidase inhibition, in subjects with primary hypolactasia, and patients with coeliac disease. RESULTS: Oral administration of the alpha-glucosidase inhibitor 'Acarbose' (BAY g 5421, 200 mg) together with sucrose and lactulose increased the urinary sucrose/lactulose excretion ratios (% dose/10 h) fivefold. The effect was quantitatively reproducible, a higher dose of 'Acarbose' (500 mg) increasing the excretion ratio to about 1.0 indicating complete inhibition of intestinal sucrase activity. The suitability of the method for measuring differences in dose/response and duration of action was assessed by comparing three different alpha-glucosidase inhibitors (BAY g 5421, BAY m 1099, and BAY o 1248) and found to be satisfactory. Subjects with primary adult hypolactasia had urine lactose/lactulose excretion ratios raised to values indicating reduced rather than complete absence of lactase activity whereas sucrose/lactulose ratios were not significantly affected. 'Whole' intestinal disaccharidase activity assessed by this method demonstrated impairment of lactase, sucrase, and isomaltase in eight, one, and seven, respectively, of 20 patients with coeliac disease. By contrast in vitro assay of jejunal biopsy tissue indicated pan-disaccharidase deficiency in all but five of these patients. This shows the importance of distinguishing between 'local' and 'whole' intestinal performance. CONCLUSIONS: Differential urinary excretion of ingested disaccharides provides a reliable, quantitative, and non-invasive technique for assessing profiles of intestinal disaccharidase activity.

Acarbose↗
PubMed1996

Early pathogenic events in NSAID-induced gastrointestinal damage.

A number of studies show that the idea that inhibition of cyclooxygenase is the sole mechanism of NSAID-induced gastrointestinal damage is no longer tenable. We re-examined various aspects of the mechanism of small intestinal damage due to NSAIDs in rat. Subcellular organelle marker enzyme studies show selective alterations in mitochondrial and brush border marker enzymes. Electron microscopy shows changes compatible with uncoupling of mitochondrial oxidative phosphorylation. In vitro, all common acidic-NSAIDs (n = 15) were found to uncouple oxidative phosphorylation at concentrations (microM) easily achievable within intestinal epithelium. Experiments in bile duct ligated animals show that intact indomethacin within the gastrointestinal lumen is required for uncoupling. Relative importance and pathophysiological consequences of uncoupling and inhibition of cyclooxygenase were assessed following administration of R and S flurbiprofen: the former selectively uncouples whilst the latter is also an effective cyclooxygenase inhibitor. R flurbiprofen uncoupled in vitro and in vivo, increased intestinal permeability and caused mild intestinal inflammation, but had not significant effect on prostanoid levels and produced no ulcers. S flurbiprofen uncoupled and increased intestinal permeability equally but was associated with significant decreases in intestinal prostanoid levels, more inflammation and numerous ulcers. Collectively these studies suggest that uncoupling may underlie the "topical" phase of NSAID damage which leads to increased intestinal permeability and inflammation, but concomitant inhibition of cyclooxygenase is essential to drive the inflammation to ulcers.

Animals↗
PubMed1996

Gastroduodenal tolerability of highly specific cyclo-oxygenase-2 inhibitor.

Inhibition of constitutively expressed cyclo-oxygenase (COX-1) by NSAIDs is thought to play an important role is the gastrointestinal toxicity of NSAIDs. To minimise the intestinal toxicity of NSAIDS, highly selective COX-2 (induced at inflammatory sites) inhibitors have been developed. One such is flosulide. We assessed the gastroduodenal tolerability of flosulide (20 mg twice a day) in man and compared it with that of naproxen (500 mg twice a day) in a randomised, double blind crossover fashion in 19 patients with osteoarthrosis. Treatment period was 2 weeks with a 2-week washout period with endoscopy before and after each treatment. Gastroduodenal damage was assessed as by Lanza (Grades 0-4) and by the Gastroscopic Rating Scale (Grades 0-9). Flosulide was significantly better tolerated (p < 0.005, analyses of deviance) than naproxen. No stomach damage was seen in 13 (68%) patients following flosulide and 5 (37%) following naproxen (p < 0.001). Lanza scores following flosulide (0.58) were significantly better than that of naproxen (1.47) (p < 0.001). The duodenal damage was mild with both treatments. The selective COX-2 inhibitor, flosulide, is significantly better tolerated and causes less gastric mucosal damage than naproxen when given for two weeks.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1995

Mitochondrial gene expression in small intestinal epithelial cells.

Most mitochondrial genes are transcribed as a single large transcript from the heavy strand of mitochondrial DNA, and are subsequently processed into the proximal mitochondrial (mt) 12 S and 16 S rRNAs, and the more distal tRNAs and mRNAs. We have shown that in intestinal epithelial biopsies the steady-state levels of mt 12 S and 16 S rRNA are an order of magnitude greater than those of mt mRNAs. Fractionation of rat small intestinal epithelial cells on the basis of their maturity has shown that the greatest ratios of 12 S mt rRNA/cytochrome b mt mRNA or 12 S mt rRNA/cytochrome oxidase I mt mRNA are found in the surface mature enterocytes, with a progressive decrease towards the crypt immature enteroblasts. Cytochrome b and cytochrome oxidase I mt mRNA levels are relatively uniform along the crypt-villus axis, but fractionation experiments showed increased levels in the crypt base. The levels of human mitochondrial transcription factor A are also greater in immature crypt enteroblasts compared with mature villus enterocytes. These results show that the relative levels of mt rRNA and mRNA are distinctly regulated in intestinal epithelial cells according to the crypt-villus position and differentiation status of the cells, and that there are higher mt mRNA and mt TFA levels in the crypts, consistent with increased transcriptional activity during mitochondrial biogenesis in the immature enteroblasts.

Adult↗
PubMed1995

Intestinal permeability: an overview.

The noninvasive assessment of intestinal permeability in humans has a 20-year history. Because the tests are increasingly used in clinical practice and research and because there is much controversy, we reviewed the literature and outlined the potential and possible shortcomings of these procedures. Data was obtained from personal files and from a systemic search through MEDLINE and EMBASE. The principle of the differential urinary excretion of orally administered test markers is explained with reference to the desired physicochemical properties of the markers and how the principle can be exploited to allow assessment of various other gastrointestinal functions. The use of intestinal permeability tests for diagnostic screen for small bowel disease and assessment of responses to treatment, the pathogenesis of disease, normal intestinal physiology, and the effect of drugs and toxins on the intestine is described and reviewed. The controversy surrounding the anatomic location of the permeation pathways that the markers use is highlighted. Noninvasive tests of intestinal permeability have fulfilled early promises of usefulness in clinical practice and research. There is now a need for integrated research into the basic mechanisms of regulatory control of the intestinal barrier function.

Animals↗
PubMed1995

Antibodies to colonic epithelial cells from the serum and colonic mucosal washings in ulcerative colitis.

It has been suggested that antibodies to a colonocyte protein of 40 kD (an intestinal isoform of tropomyosin) are specifically found in the serum and mucosa of patients with ulcerative colitis, which has important pathogenic implications. This study isolated and purified tropomyosin from the colonic mucosa, but no specific binding to this protein has been detected in serum samples or immunoglobulins isolated from mucosal washings of 20 ulcerative colitis (UC) patients by enzyme linked immunosorbent assay (ELISA) compared with 21 controls or 17 Crohn's disease (CD) patients. Samples from a further 12 patients with UC and primary sclerosing cholangitis (it is proposed that cross reactivity against the intestinal tropomyosin isoform accounts for the extraintestinal disease) also did not show binding to tropomyosin, whereas monoclonal antitropomyosin antisera bound both ELISAs and western blots. This study also examined the proteins in the normal colonic biopsy specimens on western blots that are bound by both serum samples and mucosal immunoglobulin preparations from these patients groups; there was no specific IgG or IgA binding to patients with UC or UC/primary sclerosing cholangitis, whereas binding to mitochondrial proteins of 70,000 and 45,000 was seen in samples from 12 primary biliary cirrhosis positive controls. This work does not support the hypothesis that autoimmune activity against the intestinal isoform or tropomyosin is important in the pathogenesis of ulcerative colitis.

Adolescent↗
PubMed1995

Effect of longterm misoprostol coadministration with non-steroidal anti-inflammatory drugs: a histological study.

Prostaglandins are widely used in the prevention and healing of non-steroidal anti-inflammatory drug (NSAID) induced gastric and duodenal ulcers, but their longterm effect on the human gastric mucosa is unknown. This study assessed the effect of coadministration of prostaglandins with NSAIDs on the histology of the gastroduodenal mucosa. Histological appearances (using the Sydney system) of gastric biopsy specimens from 180 patients receiving longterm NSAID treatment of whom 90 had been receiving misoprostol (400-800 micrograms/day) for one to two years were studied. Both groups of patients were comparable with regard to clinical and demographic details. There was no significant difference (p > 0.1) in the prevalence of chronic gastritis (total, corpus or antrum only) between patients receiving (36 of 90 (40%)) or not receiving misoprostol (35 of 90 (39%)). Chronic gastritis was equally associated with the presence of Helicobacter pylori, 86% and 73% (p > 0.1), respectively, in the two groups. Significantly fewer patients receiving misoprostol had reactive gastritis than those receiving only NSAIDs (8 (9%) versus 27 (30%), p < 0.01). Reactive gastritis was not associated with H pylori. Thirty nine (43%) of the misoprostol treated patients had normal histology compared with 16 (18%) receiving only NSAIDs (p < 0.01). These results show two different patterns of gastric damage in patients receiving NSAIDs, namely chronic and reactive gastritis. Misoprostol treatment was associated with a significantly reduced prevalence of reactive gastritis and it is suggested that this, along with its antisecretory action, may explain the reduced prevalence of gastroduodenal lesions when coadministered with NSAIDs.

Adult↗
PubMed1995

Intestinal absorptive capacity, intestinal permeability and jejunal histology in HIV and their relation to diarrhoea.

Intestinal function is poorly defined in patients with HIV infection. Absorptive capacity and intestinal permeability were assessed using 3-O-methyl-D-glucose, D-xylose, L-rhamnose, and lactulose in 88 HIV infected patients and the findings were correlated with the degree of immunosuppression (CD4 counts), diarrhoea, wasting, intestinal pathogen status, and histomorphometric analysis of jejunal biopsy samples. Malabsorption of 3-O-methyl-D-glucose and D-xylose was prevalent in all groups of patients with AIDS but not in asymptomatic, well patients with HIV. Malabsorption correlated significantly (r = 0.34-0.56, p < 0.005) with the degree of immune suppression and with body mass index. Increased intestinal permeability was found in all subgroups of patients. The changes in absorption-permeability were of comparable severity to those found in patients with untreated coeliac disease. Jejunal histology, however, showed only mild changes in the villus height/crypt depth ratio as compared with subtotal villus atrophy in coeliac disease. Malabsorption and increased intestinal permeability are common in AIDS patients. Malabsorption, which has nutritional implications, relates more to immune suppression than jejunal morphological changes.

Adult↗