H L Waldum

St. Olavs Hospital, Nidaros, Sør-Trøndelag, Norway

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Publications (320)1327.63 Total impact

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    H L Waldum · Ø Hauso · R Fossmark ·

    Alimentary Pharmacology & Therapeutics 08/2015; 42(3):389. DOI:10.1111/apt.13282 · 5.73 Impact Factor
  • Helge L Waldum · Øystein F Sørdal ·

    Applied immunohistochemistry & molecular morphology: AIMM / official publication of the Society for Applied Immunohistochemistry 06/2015; DOI:10.1097/PAI.0000000000000190 · 2.01 Impact Factor
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    ABSTRACT: Hypergastrinemia causes carcinoids or carcinomas in the gastric corpus in animal models. Helicobacter pylori (HP) infection in patients causes atrophy, hypergastrinemia and promotes gastric carcinogenesis. Many patients with gastric cancer have hypergastrinemia and it has therefore been hypothesized that hypergastrinemia promotes carcinogenesis. We have examined the associations between serum gastrin, the anatomical localization of gastric cancer, histological classification and patient survival. Patients with non-cardia gastric adenocarcinomas were included prospectively (n = 80). Tumour localization, histological classification according to Laurén and disease stage were recorded. Preoperative fasting serum gastrin was analysed by radioimmunoassay and HP serology by ELISA. Patient survival was determined after a median postoperative follow-up of 16.5 years. Hypergastrinemic patients had carcinomas located in the gastric corpus more often compared to normogastrinemic patients (81.8 vs 36.2%, p = 0.002). Patients with disease stage 2-4 and hypergastrinemia had shorter survival than normogastrinemic patients [5.0 (1.1-8.9) vs 10.0 (6.4-13.6) months (p = 0.04)]. There was no significant difference in serum gastrin or survival between patients with intestinal and diffuse type carcinomas. Hypergastrinemia was associated with adenocarcinomas in the gastric corpus and shorter survival. The findings support the hypothesis that hypergastrinemia promotes carcinogenesis and affects biological behaviour. © 2015 APMIS. Published by John Wiley & Sons Ltd.
    Apmis 05/2015; 123(6). DOI:10.1111/apm.12380 · 2.04 Impact Factor
  • Helge L Waldum · Per M Kleveland · Reidar Fossmark ·
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    ABSTRACT: Nordic research on physiology and pathophysiology of the upper gastrointestinal tract has flourished during the last 50 years. Swedish surgeons and physiologists were in the frontline of research on the regulation of gastric acid secretion. This research finally led to the development of omeprazole, the first proton pump inhibitor. When Swedish physiologists developed methods allowing the assessment of acid secretion in isolated oxyntic glands and isolated parietal cells, the understanding of mechanisms by which gastric acid secretion is regulated took a great step forward. Similarly, in Trondheim, Norway, the acid producing isolated rat stomach model combined with a sensitive and specific method for determination of histamine made it possible to evaluate this regulation qualitatively as well as quantitatively. In Lund, Sweden, the identification of the enterochromaffin-like cell as the cell taking part in the regulation of acid secretion by producing and releasing histamine was of fundamental importance both physiologically and clinically. Jorpes and Mutt established a center at Karolinska Institutet in Stockholm for the purification of gastrointestinal hormones in the 1960s, and Danes followed up this work by excelling in the field of determination and assessment of biological role of gastrointestinal hormones. A Finnish group was for a long period in the forefront of research on gastritis, and the authors' own studies on the classification of gastric cancer and the role of gastrin in the development of gastric neoplasia are of importance. It can, accordingly, be concluded that Nordic researchers have been central in the research on area of the upper gastrointestinal physiology and diseases.
    Scandinavian Journal of Gastroenterology 04/2015; 50(6):1-8. DOI:10.3109/00365521.2015.1009157 · 2.36 Impact Factor
  • Øyvind Hauso · Tom Christian Martinsen · Helge Waldum ·
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    ABSTRACT: Objective: The etiology of the inflammatory bowel diseases is unknown, although genetic factors play a role, and tobacco smoking has opposite effect on the two entities. Inflammation is central in the pathogenesis, and treatment is aiming to suppress it. The active part of salazopyrin, the oldest drug in use in the treatment of ulcerative colitis, is 5-aminosalicylic acid (5-ASA). In the present paper, we wanted to discuss the etiology and pathogenesis of ulcerative colitis in relation to the beneficial effects of 5-ASA and particularly whether this compound has a specific effect on ulcerative colitis. Methods/results: 5-ASA seems to have a selective positive effect on ulcerative colitis in inducing remission, preventing relapse and possibly reducing the risk of cancer. In contrast to other agents used in the treatment of ulcerative colitis, 5-ASA does not have any known anti-inflammatory effect on other organs or other colonic inflammatory diseases like diverticulitis. Moreover, the effect on experimental colitis in rodents is not convincing. Conclusion: 5-ASA seems to have a specific effect on the inflammation in ulcerative colitis. Research on the mechanism of its action may give information on the etiology of ulcerative colitis. 5-ASA is a first-line treatment that should be given once daily in high doses and for long term to reduce the possibility of recurrence and risk of colonic cancer. Side effects with 5-ASA are rare, and every patient with ulcerative colitis who tolerate this drug, should be treated with 5-ASA.
    Scandinavian Journal of Gastroenterology 03/2015; 50(8):1-9. DOI:10.3109/00365521.2015.1018937 · 2.36 Impact Factor
  • Helge L Waldum · Oyvind Hauso · Oystein F Sørdal · Reidar Fossmark ·
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    ABSTRACT: Gastric cancer occurs almost exclusively in patients with gastritis. Since Helicobacter pylori (Hp) was proved to cause gastritis, Hp was also expected to play a role in gastric carcinogenesis. Despite extensive studies, the mechanisms by which Hp cause gastric cancer are still poorly understood. However, there is evidence that the anatomical site of Hp infection is of major importance. Infection confined to the antral mucosa protects against gastric cancer but predisposes to duodenal ulcer, whereas Hp infection of the oxyntic mucosa increases the risk of gastric cancer. Hp infection does not predispose to cancers in the gastric cardia. In patients with atrophic gastritis of the oxyntic mucosa, the intragastric pH is elevated and the concentration of microorganisms in the stomach is increased. This does not lead to increased risk of gastric cancer at all anatomical sites. The site specificity of Hp infection in relation to cancer risk indicates that neither Hp nor the changes in gastric microflora due to gastric hypoacidity are carcinogenic per se. However, reduced gastric acidity also leads to hypergastrinemia, which stimulates the function and proliferation of enterochromaffin-like (ECL) cells located in the oxyntic mucosa. The ECL cell may be more important in human gastric carcinogenesis than previously realized, as every condition causing long-term hypergastrinemia in animals results in the development of neoplasia in the oxyntic mucosa. Patients with hypergastrinemia will far more often develop carcinomas in the gastric corpus. In conclusion, hypergastrinemia may explain the carcinogenic effect of Hp.
    Digestive Diseases and Sciences 12/2014; 60(6). DOI:10.1007/s10620-014-3468-9 · 2.61 Impact Factor
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    ABSTRACT: Objective: Vagotomy causes inhibition of basal and post-prandial acid secretion in humans, but the knowledge about the trophic effect of the vagal nerves is limited. Vagotomy is known to induce hypergastrinemia and we aimed to study the long-term effects of proximal gastric vagotomy (PGV) on the oxyntic mucosa and the enterochromaffin-like (ECL) cell density in particular. Material and methods: Eleven patients operated with PGV because of duodenal ulcer and age- and sex-matched controls were examined 26 to 29 years postoperatively by gastroscopy with biopsies from the antrum and oxyntic mucosa. Neuroendocrine cell volume densities were calculated after immunohistochemical labeling of gastrin, the general neuroendocrine cell marker chromogranin A (CgA) and the ECL cell marker vesicular monoamine transporter 2 (VMAT2). Gastritis was graded and Helicobacter pylori (H. pylori) status was determined by polymerase chain reaction of gastric biopsies. Fasting serum gastrin and CgA were measured. Results: Serum gastrin was higher in the PGV group compared to controls (median 21.0 [interquartile range (IQR) = 22.0] pmol/L vs 13.0 [IQR = 4.0] pmol/L, p = 0.04). However, there was neither a significant difference in serum CgA or in CgA (neuroendocrine) nor VMAT2 (ECL cell) immunoreactive cell volume density in the oxyntic mucosa. There was significantly more inflammation and atrophy in H. pylori-positive patients, but PGV did not influence the grade of gastritis. Conclusion: Despite higher serum gastrin concentrations, patients operated with PGV did not have higher ECL cell mass or serum CgA. Vagotomy may prevent the development of ECL cell hyperplasia caused by a moderate hypergastrinemia.
    Scandinavian Journal of Gastroenterology 08/2014; 49(10):1-8. DOI:10.3109/00365521.2014.950979 · 2.36 Impact Factor
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    Hang Yang · Haili Qi · Jingli Ren · Jing Cui · Zhenfeng Li · Helge L Waldum · Guanglin Cui ·
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    ABSTRACT: Nuclear factor-kappaB (NF-κB)/interleukin (IL-6) pathway links chronic inflammation to colitis associated cancer (CAC). In this study, we examined the dynamic temporal changes of the NF-κB/IL-6 pathway during the procession of experimental CAC mouse model. Mice were sacrificed after induction for 14, 16, 18, and 22 weeks for the examination of tumor burden, inflammation degree, and protein level of NF-κB and IL-6 in bowel tissues. The results showed that tumor burden and inflammation severity in the bowels were gradually increased over the observed time-points. The expressions of IL-6 and NF-κB proteins were gradually increased after induction of dysplastic lesions over times. These data provide new information on the dynamic temporal changes of NF-κB/IL-6 pathway in relation to CAC development that may be relevant in the design of future investigations of therapeutic interventions to effectively target CAC processes.
    06/2014; 2014:130981. DOI:10.1155/2014/130981
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    ABSTRACT: Purpose To assess the exocrine and neuroendocrine properties of tumour cells in diffuse gastric cancer with signet ring cell differentiation. Material and methods Mucin mRNA and protein expressions (MUC1, 2, 3, 4, 5 AC, 6 and MUC13) were assessed by immunohistochemistry and in situ hybridization. The neuroendocrine properties were evaluated by protein and mRNA expression of the general neuroendocrine markers chromogranin A and synaptophysin. Results No MUC expression was observed in signet ring tumour cells including the amorphous substance in any of the nine cases. All cases showed immunoreactivity to synaptophysin, and seven out of nine cases immunoreactivity to chromogranin A in signet ring and non-signet ring tumour cells. Chromogranin A mRNA expression was observed in tumour cells in all samples with retained mRNA. Conclusions The lack of MUC protein and mRNA in signet ring tumour cells suggests the amorphous substance is not mucin. The lack of MUC mRNA expression in non-signet ring tumour cells questions exocrine differentiation in this tumour group. The abundant protein expression of the general neuroendocrine markers CgA and synaptophysin, and mRNA expression in tumour cells strengthens the hypothesis that this tumour group may be of neuroendocrine origin.
    Experimental and Molecular Pathology 06/2014; 96(3). DOI:10.1016/j.yexmp.2014.02.008 · 2.71 Impact Factor
  • Reidar Fossmark · Liv Sagatun · Arne K. Sandvik · Helge Waldum ·

    Gastroenterology 05/2014; 146(5):S-317-S-318. DOI:10.1016/S0016-5085(14)61142-2 · 16.72 Impact Factor
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    ABSTRACT: Objective: E-cadherin plays a crucial role in the adhesion between epithelial cells and thus epithelial integrity. Moreover, germline mutations in the E-cadherin gene (CDH1) causing loss of E-cadherin function (adhesion) leads to hereditary gastric cancer of the diffuse type, according to Laurén. Even sporadic gastric carcinomas of the diffuse type often lose E-cadherin expression due to mutations. Lack of E-cadherin has been recorded at an early phase in such carcinomas. For 25 years, we have provided evidence for neuroendocrine (NE) cell origin of gastric carcinomas of diffuse type. The present study was, therefore, done to examine whether normal NE cells in the gastrointestinal tract express E-cadherin or not. Methods: During upper gastrointestinal endoscopy, biopsies were taken from normal oxyntic mucosa, gastric carcinoids, gastric carcinomas, and from normal duodenal mucosa. Tissues were examined by immunohistochemistry (IHC) using antibodies toward chromogranin A, synaptophysin, and E-cadherin. Isolated mucosal cells were prepared from biopsies of normal mucosa and examined by antibodies against the same markers by immunofluorescence. Results: Normal gastrointestinal NE cells did not express E-cadherin as assessed by IHC or immunocytochemistry. No expression of E-cadherin was found on tumor cells from gastric carcinoids or cancer of diffuse type examined by IHC. Conclusion: Our findings, which are in contrast to some previous studies, may explain why there is a discrepancy between lack of atypia and malignant biological behavior of such tumors. Since they normally lack the adhesion molecule E-cadherin, reflected in their spread occurrence, only minor changes may result in malignant behavior.
    Scandinavian Journal of Gastroenterology 04/2014; 49(8). DOI:10.3109/00365521.2014.909275 · 2.36 Impact Factor
  • Fatemeh Zeinali · Oyvind Hauso · Rune Wiseth · Marcel Moufack · Helge L Waldum ·
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    ABSTRACT: Objectives: Serotonin (5-HT) most likely plays an important role in the pathogenesis of pulmonary arterial hypertension (PAH). We aimed to test if venous plasma 5-HT is a potential biomarker of PAH. We also measured venous blood β-thromboglobulin (β-TG) in all participants to ensure that any increase in serotonin levels measured is due to platelet release. Design: Blood samples from patients (n = 9) with pulmonary arterial hypertension (Group 1 of the World Health Organization classification of pulmonary hypertension) as well as healthy volunteers (n = 9) were analyzed. We used enzyme-linked immunosorbent assay (ELISA) to measure venous platelet-poor plasma 5-HT and β-TG in patients with pulmonary arterial hypertension (PAH) and in age-matched normal controls. Results: Venous platelet-free plasma 5-HT and β-TG were almost similar in patients with PAH and healthy controls with only a slight trend toward increased 5-HT levels in patients with PAH. No correlation was found between venous platelet-poor plasma 5-HT and disease severity. There was no association between venous plasma 5-HT and the mean pulmonary artery pressure. Conclusions: Our data suggest that 5-HT is not significantly elevated in venous platelet-free plasma in patients with PAH and may accordingly not be a useful biomarker in this condition.
    Scandinavian cardiovascular journal: SCJ 01/2014; 48(2). DOI:10.3109/14017431.2014.886335 · 1.03 Impact Factor
  • O. Hauso · H. Nordbo · E. Ringnes · O. Sordal · I Nordrum · H. Waldum ·

    11th Annual ENETS Conference for the Diagnosis and Treatment of; 01/2014
  • Helge L Waldum · Oyvind Hauso · Reidar Fossmark ·
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    ABSTRACT: The purpose of this review, based upon 40 years of research, is to clear old controversies. The gastric juice is a strong acid with active enzymes (pepsin and lipase); ideal for killing swallowed microorganisms. Totally isolated rat stomach and histamine determination. Human gastric carcinomas were examined for ECL cell differentiation since tumours found in rodents after dosing with inhibitors of acid secretion were reclassified to be of ECL cell origin. The gastrin receptor is localized to the ECL cell only, where gastrin stimulates the function and growth. Drug induced hypoacidity induces hypergastrinemia and ECL cell hyperplasia responsible for rebound acid hypersecretion. Every condition with long-term hypergastrinemia disposes to ECL cell neoplasia. In man both atrophic gastritis and gastrinoma lead to ECL cell carcinoids. Proton pump inhibitors induce hypergastrinemia with ECL cell hyperplasia and ECL cell carcinoids that disappear when stopping treatment. The gastrin antagonist netazepide induces regression of ECL cell carcinoids due to atrophic gastritis. Human gastric carcinomas of diffuse type, particularly the signet ring subtype, show ECL cell differentiation, suggesting involvement of gastrin in the carcinogenesis. Helicobacter pylori (Hp) causes gastritis and peptic ulcer and when infecting the antrum only, gives a slight hypergastrinemia with acid hypersecretion predisposing to duodenal ulcer, but protecting from gastric cancer. When Hp infection spreads to oxyntic mucosa, it induces atrophy, reduced acid secretion, marked hypergastrinemia and cancer. It is remarkable that the interaction between Hp and gastrin may explain the pathogenesis of most diseases in the upper gastrointestinal tract. This article is protected by copyright. All rights reserved.
    Acta Physiologica 11/2013; 210(2). DOI:10.1111/apha.12208 · 4.38 Impact Factor
  • Reidar Fossmark · Helge Waldum ·

    International Journal of Cancer 11/2013; 133(9). DOI:10.1002/ijc.28227 · 5.09 Impact Factor
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    ABSTRACT: Long-term Helicobacter pylori infection causes gastritis leading to hypergastrinemia and predisposes to gastric cancer. Our aim was to assess the role of gastrin in oxyntic mucosal inflammation in H. pylori-infected Mongolian gerbils by means of the gastrin receptor antagonist netazepide (YF476). We studied 60 gerbils for 18 months and left five animals uninfected (control group), inoculated 55 with H. pylori, and treated 28 of the infected animals with netazepide (Hp+YF476 group). Twenty-seven infected animals were given no treatment (Hp group). We measured plasma gastrin and intraluminal pH. H. pylori detection and histologic evaluations of the stomach were carried out. All 55 inoculated animals were H. pylori positive at termination. Eighteen animals in the Hp group had gastritis. There was a threefold increase in mucosal thickness in the Hp group compared to the Hp+YF476 group, and a threefold increase in oxyntic neuroendocrine cells in the Hp group compared to the Hp+YF476 group (p < .05). All animals in the Hp+YF476 group had macro- and microscopically normal findings in the stomach. Plasma gastrin was higher in the Hp group than in the control group (172 ± 16 pmol/L vs 124 ± 5 pmol/L, p < .05) and highest in the Hp+YF476 group (530 ± 36 pmol/L). Intraluminal pH was higher in the Hp group than in the Hp+YF476 group (2.51 vs 2.30, p < .05). The gastrin antagonist netazepide prevents H. pylori-induced gastritis in Mongolian gerbils. Thus, gastrin has a key role in the inflammatory reaction of the gastric mucosa to H. pylori infection in this species.
    Helicobacter 07/2013; 18(6). DOI:10.1111/hel.12066 · 4.11 Impact Factor
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    ABSTRACT: Antimicrobial peptides may influence the pathogenesis and course of inflammatory bowel disease (IBD). We sought to clarify the role of the antimicrobial glycoprotein lipocalin 2 (LCN2) in the colon by determining its localization and regulation in IBD. Following a microarray gene expression study of colonic biopsies from a large IBD population (n=133), LCN2 was localized using immunohistochemistry and in situ hybridization. Moreover, we examined the regulation of LCN2 in HT-29 cells with a panel of Pattern Recognition Receptors (PRRs) and sought evidence by immunohistochemistry that the most relevant PRR, the Toll-like receptor TLR3, was indeed expressed in colonic epithelium in IBD.LCN2 was among the ten most upregulated genes in both active ulcerative colitis (UCa) and active Crohn`s disease (CDa) vs healthy controls. LCN2 protein was found in both epithelial cells and infiltrating neutrophils, while mRNA synthesis was located solely to epithelial cells indicating that de novo synthesis and thus regulation of LCN2 as measured in the gene expression analysis takes place in the mucosal epithelial cells. LCN2 is a putative biomarker in feces for intestinal inflammation, different from calprotectin due to its epithelial site of synthesis. LCN2 release from the colonic epithelial cell line HT-29 was enhanced by both IL-1β and the TLR3 ligand poly(I:C), and TLR3 was shown to be constitutively expressed in colonic epithelial cells and markedly increased during inflammation.
    Clinical & Experimental Immunology 05/2013; 173(3). DOI:10.1111/cei.12136 · 3.04 Impact Factor
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    ABSTRACT: The stomach is innervated by the vagal nerve. Several studies have demonstrated that the vagal nerve has a trophic effect on the rat oxyntic mucosa and that the trophic effect of hypergastrinemia is dependent on intact vagal innervation. The effect of vagal denervation on gastric carcinogenesis has been examined in Mastomys natalensis and hypergastrinemic transgenic INS-GAS mice, with no effect of unilateral vagotomy in Mastomys but an anti-carcinogenic effect in INS-GAS mice. A proportion of female Japanese cotton rats develop spontaneous hypergastrinemia and ECL cell derived gastric carcinomas. In the current study we have examined the effects of unilateral anterior subdiaphragmatic vagotomy on gastric carcinogenesis. Female Japanese cotton rats were operated with unilateral anterior vagotomy or sham-operation at age 2months and were terminated at age 10months. Ten of fifteen animals operated by anterior vagotomy and 11 of 16 sham-operated developed hypergastrinemia. Vagotomy did not affect intragastric pH or serum gastrin. When comparing the anterior and posterior side of the stomachs, vagotomy did not affect the occurrence of dysplasia or carcinoma development in the oxyntic mucosa. However, vagotomy resulted in lower stomach weight and reduced oxyntic mucosal thickness on the anterior side. Vagotomy also resulted in a reduction in volume density of chromogranin A positive cells in the oxyntic mucosa. In conclusion, vagotomy reduced the trophic effects of hypergastrinemia on the ECL cell and oxyntic mucosa, but did not prevent gastric carcinogenesis in female Japanese cotton rats. The effects of vagotomy gastric carcinogenesis in animal models are conflicting and further studies in patients should be done to clarify the clinically significant effects of vagotomy.
    Regulatory Peptides 03/2013; 184. DOI:10.1016/j.regpep.2013.03.006 · 1.83 Impact Factor
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    ABSTRACT: Primary (AL) amyloidosis of the gastrointestinal tract is relatively rare, and symptomatic amyloidosis of the stomach is even more seldom. We present the case of a patient who was referred to upper endoscopy because of weight loss, nausea, and vomiting. Large areas of intramucosal hemorrhages were seen, and biopsies resulted in profuse bleeding stopped with endoscopic clips. The biopsies showed amyloid depositions and further workup revealed that the patient also had cardiac and neuropathic involvements. The patient started treatment with dexamethasone, melphalan and bortezomib. After treatment was started the nausea and epigastric discomfort improved, and a reduction in the biochemical markers troponin T, NT-proBNP, and M-component was observed. Gastric amyloidosis is rarely seen at upper endoscopy in patients without a previously established diagnosis, but the unusual endoscopic findings and bleeding tendency after biopsy should be kept in mind by gastroenterologists.
    02/2013; 2013(8):525439. DOI:10.1155/2013/525439
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    ABSTRACT: In inflammatory bowel disease (IBD), genetic susceptibility together with environmental factors disturbs gut homeostasis producing chronic inflammation. The two main IBD subtypes are Ulcerative colitis (UC) and Crohn's disease (CD). We present the to-date largest microarray gene expression study on IBD encompassing both inflamed and un-inflamed colonic tissue. A meta-analysis including all available, comparable data was used to explore important aspects of IBD inflammation, thereby validating consistent gene expression patterns. Colon pinch biopsies from IBD patients were analysed using Illumina whole genome gene expression technology. Differential expression (DE) was identified using LIMMA linear model in the R statistical computing environment. Results were enriched for gene ontology (GO) categories. Sets of genes encoding antimicrobial proteins (AMP) and proteins involved in T helper (Th) cell differentiation were used in the interpretation of the results. All available data sets were analysed using the same methods, and results were compared on a global and focused level as t-scores. Gene expression in inflamed mucosa from UC and CD are remarkably similar. The meta-analysis confirmed this. The patterns of AMP and Th cell-related gene expression were also very similar, except for which was consistently higher expressed in UC than in CD. Un-inflamed tissue from patients demonstrated minimal differences from healthy controls. There is no difference in the Th subgroup involvement between UC and CD. Th1/Th17 related expression, with little Th2 differentiation, dominated both diseases. The different expression between UC and CD suggests an IBD subtype specific role. AMPs, previously little studied, are strongly overexpressed in IBD. The presented meta-analysis provides a sound background for further research on IBD pathobiology.
    PLoS ONE 02/2013; 8(2):e56818. DOI:10.1371/journal.pone.0056818 · 3.23 Impact Factor

Publication Stats

5k Citations
1,327.63 Total Impact Points


  • 2004-2015
    • St. Olavs Hospital
      • • Department of Gastroenterology
      • • Department of Medicine
      Nidaros, Sør-Trøndelag, Norway
  • 1997-2014
    • Norwegian University of Science and Technology
      • • Department of Cancer Research and Molecular Medicine
      • • Department of Circulation and Medical Imaging
      • • Faculty of Medicine
      Nidaros, Sør-Trøndelag, Norway
  • 2001-2012
    • NTNU Samfunnsforskning
      Nidaros, Sør-Trøndelag, Norway
  • 2009
    • The University of Chicago Medical Center
      Chicago, Illinois, United States
  • 2007
    • Universitetet i Tromsø
      • Department of Clinical Medicine (IKM)
      Tromsø, Troms Fylke, Norway
  • 1985-2007
    • University Hospital of North Norway
      Tromsø, Troms, Norway
  • 2003
    • Uppsala University
      Uppsala, Uppsala, Sweden
  • 1995-1996
    • University of Bergen
      • Surgical Research Laboratory
      Bergen, Hordaland, Norway
  • 1992-1994
    • University of California, San Diego
      San Diego, California, United States