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K M Tytgat

Publications and source records attributed to K M Tytgat.

At least 19 recordsLinked to original sources
PubMed2000

H pylori colocalises with MUC5AC in the human stomach.

BACKGROUND: The bacterium Helicobacter pylori is able to adhere to and to colonise the human gastric epithelium, yet the primary gene product responsible as a receptor for its adherence has not been identified. AIMS: To investigate the expression of the gastric mucins MUC5AC and MUC6 in the gastric epithelium in relation to H pylori colonisation in order to examine their possible roles in the binding of H pylori. PATIENTS: Seventy two consecutive patients suspected of having H pylori infection. METHODS: MUC5AC, MUC6, and H pylori were detected in single sections of antral biopsy specimens using immunohistochemical triple staining. RESULTS: MUC5AC was expressed in the superficial epithelium and the upper part of the gastric pits. MUC6 expression was detected in the lower part of the gastric pits. The expression of both mucins in the epithelium was complementary. In each patient, there was a sharply delineated transition between MUC5AC and MUC6 producing cell populations. In all H pylori positive patients there was a striking colocalization of H pylori and MUC5AC; more than 99% of the bacteria were associated with either extracellular MUC5AC or the apical domain of MUC5AC producing cells. CONCLUSIONS: H pylori is very closely associated with extracellular MUC5AC and epithelial cells that produce MUC5AC. This indicates that MUC5AC, but not MUC6, plays a role in the adhesion of H pylori to the gastric mucosa.

Bacterial Adhesion↗
PubMed1999

Gastrointestinal expression and partial cDNA cloning of murine Muc2.

To help us investigate the role of mucin in the protection of the colonic epithelium in the mouse, we aimed to identify the murine colonic mucin (MCM) and its encoding gene. We isolated MCM, raised an anti-MCM antiserum, and studied the biosynthesis of MCM in the gastrointestinal tract. Isolated MCM resembled other mucins in physicochemical properties. Anti-MCM recognized MCM as well as rat and human MUC2 on Western blots, interacting primarily with peptide epitopes, indicating that MCM was identical to murine Muc2. Using anti-MCM and previously characterized anti-human and anti-rat MUC2 antibodies, we identified a murine Muc2 precursor in the colon of approximately 600 kDa, which appeared similar in size to rat and human MUC2 precursors. Western blotting, immunoprecipitation of metabolically labeled mucins, and immunohistochemistry showed that murine Muc2 was expressed in the colon and the small intestine but was absent in the stomach. To independently identify murine Muc2, we cloned a cDNA fragment from murine colonic mRNA, encoding the 302 NH2-terminal amino acids of murine Muc2. The NH2 terminus of murine Muc2 showed 86 and 75% identity to the corresponding rat and human MUC2 peptide sequences, respectively. Northern blotting with a murine Muc2 cDNA probe showed hybridization to a very large mRNA, which was expressed highly in the colon and to some extend in the small intestine but was absent in the stomach. In situ hybridization showed that the murine Muc2 mRNA was confined to intestinal goblet cells. In conclusion, by two independent sets of experiments we identified murine Muc2, which appears homologous to rat and human MUC2. Because Muc2 is prominently expressed in the colon, it is most likely to be the predominant mucin in the colonic mucus layer.

Amino Acid Sequence↗
PubMed1997

Be aware of abdominal tuberculosis.

Abdominal tuberculosis is often diagnosed in a late stage because symptoms are aspecific. Two patients with intestinal tuberculosis and tuberculous peritonitis respectively, both from endemic countries presented with long-standing fever, abdominal pain and weight loss. Acid fast bacilli were present in aspirate and biopsy specimens obtained by colonoscopy and laparoscopy respectively; PCR was positive for M. tuberculosis complex and later M. tuberculosis was cultured. Both patients responded to antituberculous therapy. In one patient AIDS was diagnosed.

Adult↗
PubMed1996

Quantitative analysis of MUC2 synthesis in ulcerative colitis.

MUC2 is the predominant mucin in the human colon responsible for the protective mucus layer. We developed methods to quantify MUC2 biosynthesis, which were used to study the regulation of MUC2 expression in the colon of normal individuals and of patients with ulcerative colitis. Colonic biopsies were metabolically labeled, and biosynthesis of MUC2 precursor was quantified using SDS-PAGE. Total MUC2 and MUC2 mRNA were quantified using blotting techniques. MUC2 precursor biosynthesis and total MUC2 levels were significantly decreased in ulcerative colitis patients with active inflammation compared to controls. In contrast, both these parameters returned to control values during remission of the inflammation, demonstrating that colonic biosynthesis and total amounts of MUC2 vary according to the activity of the disease. However, MUC2 mRNA levels were similar in all patients and independent of disease activity, indicating that these variations in MUC2 synthesis are post-transcriptionally regulated.

Biomarkers, Tumor↗
PubMed1996

MUC2 is the prominent colonic mucin expressed in ulcerative colitis.

BACKGROUND: It has been shown that MUC2 is the prominent mucin synthesised in healthy colon. AIM: To identify the predominant mucins in ulcerative colitis (UC) and to study their biosynthesis. METHODS AND RESULTS: Mucin was purified from UC resection specimens. This mucin on sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE) presented as one, high molecular weight, periodic acid/Schiff's reagent (PAS) stainable band. Amino acid composition showed a close resemblance to that of MUC2. Immunoprecipitation with a specific anti-MUC2 antiserum confirmed that this mucin was MUC2. In addition, on the mRNA level MUC2 was also the most prominent mucin expressed in UC. Polyclonal antiserum was elicited, mainly recognising mucin peptide epitopes of UC and normal colonic mucin. Biosynthetic studies with [35S]amino acids showed that the MUC2-precursor in UC displayed a molecular mass on SDS-PAGE of approximately 600 kDa. This precursor was converted into a mature MUC2 with anomalous mobility on SDS-PAGE of 550 kDa and was secreted. Only this 550 kDa band could be labelled with [35S]sulphate and stained by PAS. CONCLUSIONS: This study shows that in parallel with the mucin expression in healthy controls, MUC2 is the major mucin expressed in UC. Qualitatively, MUC2 biosynthesis seems unchanged in UC.

Amino Acids↗
PubMed1995

Biosynthesis of rat MUC2 in colon and its analogy with human MUC2.

In order to identify the mucins synthesized and secreted in the rat colon, we studied their biochemical characteristics and biosynthesis and evaluated their analogy to human colonic mucins. Purified mucin from both species appeared similar with respect to composition, buoyant density and mobility on SDS/PAGE. Isolated rat colonic mucin (RCM) was used to elicit a polyclonal antiserum, which was used in metabolic labelling studies to identify mucins and mucin precursors. RCM is synthesized as a 600 kDa precursor protein, which oligomerizes before O-glycosylation. The mature, high-molecular mass mucin is secreted and displays an anomalous molecular mass on SDS/PAGE of approximately 650 kDa. Polymorphism in precursor size was found among different rats, suggesting genetic heterogeneity. Molecular mass, biosynthesis and secretion of RCM appeared similar to human MUC2. Moreover, RCM precursor could be immunoprecipitated using specific anti-(human MUC2) antisera, indicating that the RCM can be designated rat MUC2. This study describes the biosynthesis of two homologous mucins in two different species. The high degree of similarity suggests functional analogy.

Amino Acids↗
PubMed1995

Preparation of anti-mucin polypeptide antisera to study mucin biosynthesis.

Mucins are very heavily O-glycosylated glycoproteins. For in depth studies on the cell biological aspects of mucins, anti-polypeptide antibodies are essential. We therefore developed a method for the preparation and screening of polyclonal antisera against mucin peptide epitopes. Mucins from five different tissues were isolated using CsCl/guanidinium.HCl density gradient centrifugation, and polyclonal antisera were prepared. Specificity for mucin peptide epitopes was determined by Western blotting, immunohistochemistry, and immunoprecipitation. The versatility of each anti-mucin antiserum for the study of mucin biosynthesis was tested in metabolic labeling experiments on tissue explants. All polyclonal antisera were directed primarily against peptide epitopes of mucin precursors as well as of fully glycosylated mucins. Each of the polyclonal antisera enabled us to study the mucin biosynthesis in the organ where the mucin was isolated from originally. Our mucin isolation method yields very pure mucins with sufficiently intact polypeptides to reproducibly elicit polyclonal anti-polypeptide antisera. As the sera recognized the polypeptides, primarily independent of the state of O-glycosylation, the intermediate steps in the biosynthesis of the mucins could be identified.

Animals↗
PubMed1994

Biosynthesis of human colonic mucin: Muc2 is the prominent secretory mucin.

BACKGROUND/AIMS: Human colonic epithelium produces large amounts of mucin. The aim of this study was to examine mucin biosynthesis in the human colon. METHODS: Human colonic mucin was isolated using CsCl density gradients, and polyclonal antiserum was raised. Biosynthesis of colonic mucins was studied by labeling colonic explants with 35S-labeled amino acids or [35S]sulfate and subsequent immunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). RESULTS: The polyclonal antiserum specifically recognized colonic mucin, primarily reacting with peptide epitopes. Biosynthetic pulse/chase experiments showed a 35S-amino acid-labeled mucin precursor of about 600 kilodaltons, which was converted into a mature, glycosylated, and sulfated mucin and subsequently secreted into the medium. This mature mucin comigrated with isolated colonic mucin with an apparent molecular weight of 550 kilodaltons on SDS-PAGE, whereas gel filtration indicated that the molecular weight is actually much larger. Independent immunoprecipitation with an anti-Muc2 antiserum showed cross-reactivity with the 600-kilodalton precursor. CONCLUSIONS: These results show the biosynthesis of a secretory colonic mucin for the first time. This mucin is synthesized as a precursor protein of approximately 600 kilodaltons, which, after glycosylation, is secreted as a glycoprotein with an apparent molecular weight of 550 kilodaltons on SDS-PAGE. It is very likely that this mucin is Muc2.

Colon↗
PubMed1993

Can severity of symptoms be used as an outcome measure in trials of non-ulcer dyspepsia and Helicobacter pylori associated gastritis?

Most trials of non-ulcer dyspepsia (NUD) and Helicobacter pylori associated gastritis (HPAG) have not used validated methods of measuring symptoms. Three attributes are necessary for use of symptom severity scoring systems as outcome measures in clinical trials: reproducibility, responsiveness to change and validity compared to corroborating measures. The objective of this study was to establish that selected gastrointestinal symptoms recorded as a series of 5-point Likert Scales meet the 3 criteria for use as outcome measures in clinical trials. Patients with NUD (Helicobacter pylori-negative) and HPAG were studied. A preliminary assessment of 24 patients was used to select the 8 most frequently occurring and most severe symptoms. These symptoms were then scored in a further 55 patients to assess their utility as outcome measures. Observations were made at 3 time points, enrollment (T1), after 1 week with no intervention (T2) and after 4 weeks of therapy for either disease (T3). The study took place in a university hospital outpatient gastroenterology service. Symptom scores were reproducible before treatment (symptom scores at T1 and T2 were correlated), responsive (symptom scores changed after treatment between T2 and T3) and valid (symptom score changes corresponded to changes in general health status). Scoring of gastrointestinal symptom severity using 5-point Likert Scales satisfies the 3 criteria for use as outcome measures in clinical trials of NUD and HPAG.

Clinical Trials as Topic↗
PubMed1990

[The course of benign stomach ulcer; results of a follow-up study].

A follow-up investigation was conducted in 112 patients in whom a benign gastric ulcer had been found endoscopically between 1978 and 1984. Nine patients had been operated upon, mainly in the earlier years. Out of 65 patients ultimately selected for the study 38 underwent gastroscopy and 35 could be evaluated. Of these 21 (60%) had complaints and another 60% used intermittent or continuous medication because of complaints referred to the stomach. In 15 patients erosions (4) or benign gastric ulcers (11) were found. In all patients in whom it was looked for Campylobacter pylori was found in the gastric mucosa. The benign gastric ulcer is a chronic, recurrent affection. We did not find a large proportion of asymptomatic recurrent ulcers. Many patients continue to use drugs. The complaints in patients with mucosal lesions are often atypical.

Adult↗
PubMed1990

Liver tumors.

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Carcinoma, Hepatocellular↗
PubMed1990

Crohn's disease.

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Crohn Disease↗