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J Janssens

Publications and source records attributed to J Janssens.

At least 73 records · Page 4Linked to original sources
PubMed2000

Receptor-induced Ca(2+) signaling in cultured myenteric neurons.

We studied the effect of excitatory neurotransmitters (10(-5) M) on the intracellular Ca(2+) concentration ([Ca(2+)](i)) of cultured myenteric neurons. ACh evoked a response in 48.6% of the neurons. This response consisted of a fast and a slow component, respectively mediated by nicotinic and muscarinic receptors, as revealed by specific agonists and antagonists. Substance P evoked a [Ca(2+)](i) rise in 68.2% of the neurons, which was highly dependent on Ca(2+) release from intracellular stores, since after thapsigargin (5 microM) pretreatment only 8% responded. The responses to serotonin, present in 90.7%, were completely blocked by ondansetron (10(-5) M), a 5-HT(3) receptor antagonist. Specific agonists of other serotonin receptors were not able to induce a [Ca(2+)](i) rise. Removing extracellular Ca(2+) abolished all serotonin and fast ACh responses, whereas substance P and slow ACh responses were more persistent. We conclude that ACh-induced signaling involves both nicotinic and muscarinic receptors responsible for a fast and a more delayed component, respectively. Substance P-induced signaling requires functional intracellular Ca(2+) stores, and the 5-HT(3) receptor mediates the serotonin-induced Ca(2+) signaling in cultured myenteric neurons.

Acetylcholine↗
PubMed2000

Differential Ca(2+) signaling characteristics of inhibitory and excitatory myenteric motor neurons in culture.

Physiological studies on functionally identified myenteric neurons are scarce because of technical limitations. We combined retrograde labeling, cell culturing, and fluorescent intracellular Ca(2+) concentration ([Ca(2+)](i)) signaling to study excitatory neurotransmitter responsiveness of myenteric motor neurons. 1, 1-Didodecyl-3,3,3',3'-tetramethyl indocarbocyanine (DiI) was used to label circular muscle motor neurons of the guinea pig ileum. DiI-labeled neurons were easily detectable in cultures prepared from these segments. The excitatory neurotransmitters (10(-5) M) acetylcholine, substance P, and serotonin induced a transient rise in [Ca(2+)](i) in subsets of DiI-labeled neurons (66.7, 56.5, and 84. 3%, respectively). DiI-labeled motor neurons were either inhibitory (23.8%) or excitatory (76.2%) as assessed by staining for nitric oxide synthase or choline acetyltransferase. Compared with excitatory motor neurons, significantly fewer inhibitory neurons in culture responded to acetylcholine (0 vs. 69%) and substance P (12.5 vs. 69.2%). We conclude that combining retrograde labeling and Ca(2+) imaging allows identification of differential receptor expression in functionally identified neurons in culture.

Acetylcholine↗
PubMed2000

A new method for fast haptoglobin phenotyping and hemoglobin binding capacity calculation based on capillary zone electrophoresis.

A capillary zone electrophoresis method was developed for haptoglobin (Hp) phenotyping in hemoglobin (Hb) supplemented serum. The method allows a complete resolution of the major haptoglobin phenotypes Hp 1-1, Hp 2-1, and Hp 2-2 based on the difference in charge-to-mass ratio of their Hb-Hp complexes. Identification of these phenotypes was achieved by their significant differences in migration times and their marked difference in electrophoretic pattern. Our method showed full agreement with starch gel electrophoresis. Furthermore, following neuraminidase treatment of the serum, the Hp subtypes Hp1-1FF, FS and SS could be resolved, based on the same criteria as the phenotyping. The new electrophoretic method allowed typing of the rare phenotypes Hp 2-1 modified (Hp 2-1M) and Hp Johnson. The calculated hemoglobin binding capacity of serum correlates well with the nephelometrically determined haptoglobin concentration. The new method for typing haptoglobin gives prospectives for fast haptoglobin typing and Hp 1-1 subtyping.

Electrophoresis, Capillary↗
PubMed1999

Eradication of Helicobacter pylori in functional dyspepsia: randomised double blind placebo controlled trial with 12 months' follow up. The Optimal Regimen Cures Helicobacter Induced Dyspepsia (ORCHID) Study Group.

OBJECTIVES: To determine whether eradication of Helicobacter pylori relieves the symptoms of functional dyspepsia. DESIGN: Multicentre randomised double blind placebo controlled trial. SUBJECTS: 278 patients infected with H pylori who had functional dyspepsia. SETTING: Predominantly secondary care centres in Australia, New Zealand, and Europe. INTERVENTION: Patients randomised to receive omeprazole 20 mg twice daily, amoxicillin 1000 mg twice daily, and clarithromycin 500 mg twice daily or placebo for 7 days. Patients were followed up for 12 months. MAIN OUTCOME MEASURES: Symptom status (assessed by diary cards) and presence of H pylori (assessed by gastric biopsies and 13C-urea breath testing using urea labelled with carbon-13). RESULTS: H pylori was eradicated in 113 patients (85%) in the treatment group and 6 patients (4%) in the placebo group. At 12 months follow up there was no significant difference between the proportion of patients treated successfully by intention to treat in the eradication arm (24%, 95% confidence interval 17% to 32%) and the proportion of patients treated successfully by intention to treat in the placebo group (22%, 15% to 30%). Changes in symptom scores and quality of life did not significantly differ between the treatment and placebo groups. When the groups were combined, there was a significant association between treatment success and chronic gastritis score at 12 months; 41/127 (32%) patients with no or mild gastritis were successfully treated compared with 21/123 (17%) patients with persistent gastritis (P=0. 008). CONCLUSION: No convincing evidence was found that eradication of H pylori relieves the symptoms of functional dyspepsia 12 months after treatment.

Adult↗
PubMed1999

Neurochemical coding of myenteric neurons in the guinea-pig antrum.

Electrophysiological studies of myenteric neurons in the guinea-pig antrum suggest that different neuroactive compounds are involved in synaptic transmission. It is not known what neurotransmitters and neuropeptides are present and to what extent they colocalize. Immunohistochemical stainings were performed on whole-mount preparations of the guinea-pig antrum. Immunoreactivity for neuron-specific enolase was used as a general marker and was set at 100%. There was no overlap between cholinergic and nitrergic neurons, resulting in two separate subpopulations. The presence of choline acetyltransferase immunoreactivity was used to identify the cholinergic subset, which accounted for 56% of the cells. Immunoreactivity for nitric oxide synthase, on the other hand, was displayed in 40.7% of the neurons. Substance-P immunoreactivity was present in 37.4% of the cells and vasoactive intestinal peptide and neuropeptide Y in 21.7% and 28.6%, respectively. Small subsets of neurons had immunoreactivity for serotonin (3.9%), calretinin (6.8%) and calbindin (0.5%). Colocalization studies revealed several subgroups of neurons, containing one or more of the screened markers. Though some similarity is found in the chemical coding of the antrum compared to that of the small intestine and the corpus, remarkable differences can be seen in the occurrence of some subpopulations. Cholinergic neurons are not as predominant as in other parts of the gut, serotonin presence is doubled and some vasointestinal-peptide-positive neurons express substance P. These differences might reflect the highly specialized function of the antrum; however, the exact role of these classes remains to be established.

Animals↗
PubMed1999

Effect of sumatriptan, a 5HT1 agonist, on the frequency of transient lower esophageal sphincter relaxations and gastroesophageal reflux in healthy subjects.

OBJECTIVE: Meals increase the rate of transient lower esophageal sphincter (LES) relaxations, in part by gastric distension. The 5HT1 agonist sumatriptan reduces fasting fundic tone, prolongs the meal-induced fundic relaxation, and delays gastric emptying. We therefore hypothesized that sumatriptan might have a significant effect on the rate of postprandial transient LES relaxations and gastroesophageal reflux. We aimed to study the effect of sumatriptan on postprandial transient LES relaxations and reflux in healthy subjects. METHODS: Esophageal manometry and pH monitoring were performed in 13 healthy volunteers for 30 min before and 90 min after a semiliquid meal (790 kcal). Sumatriptan 6 mg subcutaneous (s.c.) or s.c. placebo were administered on separate days 30 min after the meal. RESULTS: Sumatriptan significantly increased postprandial LES pressure from 11.0 +/- 1.2 mm Hg to 17.6 +/- 1.2 mm Hg (p < 0.05). However, reflux events were not diminished. In the contrary, reflux was more frequent after sumatriptan than after placebo (3 [1.5-4.5]/30 min vs 2 [0-3]/30 min, p < 0.05). Transient LES relaxations were more frequent after sumatriptan, particularly in the second 30-min period after drug administration (3 [2.5-5]/30 min vs 2 [1.5-2]/30 min, p < 0.05). CONCLUSIONS: Sumatriptan prevents the natural decay in rate of transient LES relaxations that occurs after a meal and favors the occurrence of gastroesophageal reflux despite increasing LES pressure. The sustained postprandial high rate of transient LES relaxations after sumatriptan may be a consequence of a prolonged fundus relaxation and retention of meal in the proximal stomach.

Adolescent↗
PubMed1999

Functional esophageal disorders.

The functional esophageal disorders include globus, rumination syndrome, and symptoms that typify esophageal diseases (chest pain, heartburn, and dysphagia). Factors responsible for symptom production are poorly understood. The criteria for diagnosis rest not only on compatible symptoms but also on exclusion of structural and metabolic disorders that might mimic the functional disorders. Additionally, a functional diagnosis is precluded by the presence of a pathology-based motor disorder or pathological reflux, defined by evidence of reflux esophagitis or abnormal acid exposure time during ambulatory esophageal pH monitoring. Management is largely empirical, although efficacy of psychopharmacological agents and psychological or behavioral approaches has been established for several of the functional esophageal disorders. As gastroesophageal reflux disease overlaps in presentation with most of these disorders and because symptoms are at least partially provoked by acid reflux events in many patients, antireflux therapy also plays an important role both in diagnosis and management. Further understanding of the fundamental mechanisms responsible for symptoms is a priority for future research efforts, as is the consideration of treatment outcome in a broader sense than reduction in esophageal symptoms alone. Likewise, the value of inclusive rather than restrictive diagnostic criteria that encompass other gastrointestinal and non-gastrointestinal symptoms should be examined to improve the accuracy of symptom-based criteria and reduce the dependence on objective testing.

Esophageal Motility Disorders↗
PubMed1999

Role of nitric oxide in fasting gastric fundus tone and in 5-HT1 receptor-mediated relaxation of gastric fundus.

Fasting gastric fundus tone is maintained by continuous cholinergic input. 5-Hydroxytryptamine-1 (5-HT1) receptor activation decreases gastric fundus tone in humans. Whether this fundus-relaxing effect is mediated via inhibition of cholinergic input or via activation of a nitrergic pathway is unknown. The aim of the present study was to determine the effect of nitrergic inhibition on feline gastric fundus tone and on 5-HT1 receptor-mediated relaxation of the fundus. Administration of Nomega-nitro-L-arginine methyl ester (L-NAME) alone caused a significant decrease of the mean baseline volume (P < 0.005), which was restored completely by addition of L-arginine. Sumatriptan caused a dose-dependent relaxation of the gastric fundus (P < 0.0005). This relaxation was inhibited by L-NAME (P < 0.02) and was restored by prior administration of L-arginine. Buspirone did not cause any change in mean baseline volume, whereas the sumatriptan-induced relaxation was not affected by prior administration of NAN-190. Our data indicate that fasting fundus tone relies not only on continuous cholinergic input but also on continuous nitrergic input, implying that fasting fundus tone is maintained by the balance of a cholinergic and nitrergic drive. Furthermore, fundus relaxation via 5-HT1 receptor activation is mediated through activation of a nitrergic pathway.

Animals↗
PubMed1999

Capillary zone electrophoresis: an additional technique for the identification of hemoglobin variants.

Two capillary zone electrophoresis kits (Hb A2 and Hb A1c) were tested for confirmation and identification of hemoglobin variants. The capillary zone electrophoresis experiments were performed at pH 4.7 (Hb A1c kit) and 8.7 (Hb A2 kit) in a 24 cm uncoated fused silica capillary tube (25 microm I.D.). Normal hemoglobins and common hemoglobin variants, including Hbs S, D-Punjab, C, E, O-Arab, and G-Philadelphia, were successfully separated by both methods within a few minutes. Both systems provided completely different elution profiles of normal and abnormal hemoglobin fractions tested and were complementary. The inter-assay coefficient of variations of the migration times of hemoglobin variants were less than 1.0 and 1.3% by the Hb A2 and Hb A1c, respectively. This permits a higher resolution of some hemoglobin variants in low concentrations, like Hb S in newborns, compared with conventional electrophoresis methods. The present capillary zone electrophoresis methods are sensitive, rapid, not labor intensive, and highly selective for the separation of hemoglobin variants. Combination of both methods with some conventional methods, such as isoelectrofocusing, allows identification of Hbs C, E, O-Arab, S, and D-Punjab, as well as their quantification. We have demonstrated that the conventional electrophoresis methods (electrophoresis at pH 6.5 in citrate agar gel and electrophoresis at pH 8.6 on cellulose acetate) can be advantageously replaced by the present capillary zone electrophoresis methods in a clinical laboratory practice for the detection and quantification of hemoglobin variants.

Electrophoresis, Capillary↗
PubMed1999

Acute axonal polyneuropathy in chronic alcoholism and malnutrition.

In contrast to the classic, slowly progressive polyneuropathy in alcoholic patients, acute forms, clinically mimicking Guillain-Barré syndrome, are rare. We present a patient who developed motor weakness and sensory loss in all four limbs within four days. Laboratory data were consistent with long-term alcohol abuse and documented thiamine deficiency. Repeated cerebrospinal fluid examinations were normal. Electrophysiological studies showed an acute sensorimotor polyneuropathy with predominantly axonal involvement. We conclude that acute alcoholic neuropathy has to be distinguished from Guillain-Barré syndrome and other forms of acute polyneuropathy by using clinical, laboratory, and electrophysiological data. Both ethanol toxicity and vitamin deficiency could play a role in the pathogenesis.

Adult↗
PubMed1999

Evaluation of a capillary electrophoresis method for routine determination of hemoglobins A2 and F.

Hemoglobin A2 (Hb A2) and hemoglobin F (Hb F) are important analytes in the diagnosis and follow up of Hb diseases. We evaluated a new capillary zone electrophoresis (CZE) kit for Hb A2 and Hb F measurements. The imprecision ranged from 3% to 6% for Hb A2 and Hb F at physiological and pathological concentrations. The method compared well with cation-exchange HPLC for Hb A2 and Hb F and with anion-exchange chromatography in microcolumns (MAEC), for Hb A2. Nevertheless, higher results were obtained [Hb A2 CZE (%) = 1.233 Hb A2 HPLC - 0.2; Hb A2 CZE (%) = 1.190 Hb A2 MAEC + 0.1; Hb FCZE (%) = 1.118 Hb FHPLC + 0.4], and new reference values had to be determined (Hb A2 2.7-3.8%; Hb F <1.2%). Quantification of Hb A2 was not influenced by Hb S. Measurement of Hb F was accurate and precise except at low concentrations in Hb AS patients. This new CZE kit is rapid, precise, and reliable, and seems appropriate for use in clinical laboratories.

Electrophoresis, Capillary↗
PubMed1998

Role of impaired gastric accommodation to a meal in functional dyspepsia.

BACKGROUND & AIMS: Impaired accommodation of the proximal stomach to a meal has been reported in functional dyspepsia, but its relevance to symptoms is unclear. The aim of this study was to test the hypothesis that impaired gastric accommodation causes early satiety. METHODS: A gastric barostat was used to study postprandial fundus relaxation in 35 healthy subjects and 40 patients with functional dyspepsia. Gastric emptying, Helicobacter pylori status, sensitivity to gastric distention, and a dyspepsia symptom score were obtained from all patients. In addition, the effect of sumatriptan, a fundus-relaxing 5-hydroxytryptamine1 agonist, on gastric accommodation and on early satiety in dyspeptic patients was studied. RESULTS: Impaired gastric accommodation to a meal was found in 40% of the patients. In univariate analysis, this was associated with early satiety and weight loss but not with hypersensitivity to gastric distention, presence of H. pylori, or delayed gastric emptying. In a multivariate analysis, only early satiety was associated with impaired gastric accommodation. Sumatriptan restored gastric accommodation, thereby significantly improving meal-induced satiety. CONCLUSIONS: Impaired relaxation of the proximal stomach to a meal is present in a high proportion of patients with functional dyspepsia. It is associated with symptoms of early satiety. Restoring gastric accommodation with a fundus-relaxing drug improves early satiety.

Adult↗
PubMed1998

The influence of cisapride on gastric tone and the perception of gastric distension.

BACKGROUND: Delayed gastric emptying, impaired gastric accommodation to a meal and hypersensitivity to gastric distension have been implied in the pathophysiology of functional dyspepsia. Dyspeptic patients are often treated with the prokinetic drug cisapride. AIM: To assess the effects of cisapride on perception of gastric distension and gastric accommodation to a meal. METHODS: Eighteen healthy volunteers underwent a gastric barostat study on two occasions, after pretreatment with placebo or cisapride 10 mg q.d.s. Graded isobaric and isovolumetric distensions were performed until the subjects reported discomfort. Volume and pressure changes were recorded and perception was scored by a questionnaire. In 10 volunteers, the amplitude of the gastric accommodation to a mixed liquid meal was also measured. RESULTS: Pre-treatment with cisapride significantly lowered thresholds for perception and for discomfort, both during isobaric (4.3 +/- 0.7 vs. 3.2 +/- 0.7 and 12.2 +/- 1.2 vs. 9.2 +/- 0.9 mmHg above minimal distending pressure (MDP), respectively, P < 0.05) and isovolumetric (256 +/- 46 vs. 200 +/- 35 and 644 +/- 36 vs. 511 +/- 40 mL, respectively, P < 0.05) distensions. Cisapride significantly enhanced the size of the meal-induced fundus relaxation (143 +/- 37 vs. 270 +/- 50 mL, P < 0.05). CONCLUSIONS: Cisapride enhances both the perception of gastric distension and the gastric accommodation to a meal. These data suggest that cisapride may provide benefit to patients with impaired postprandial relaxation of the fundus.

Adult↗
PubMed1998

Actions of the 5-hydroxytryptamine 1 receptor agonist sumatriptan on interdigestive gastrointestinal motility in man.

BACKGROUND: Pharmacological studies of the enteric nervous system have shown the presence of several subtypes of 5-hydroxytryptamine (5HT) receptor, which might be involved in control of the migrating motor complex. AIMS: To study the effect of sumatriptan, an agonist of enteric neuronal 5HT1p receptors, on interdigestive motility in man. SUBJECTS AND METHODS: In 12 healthy subjects, interdigestive motility was recorded manometrically in the upper gastrointestinal tract. In seven subjects blood samples were drawn every 15 minutes for radioimmunoassay of motilin and somatostatin. After two phase 3s of the migrating motor complex, 6 mg of sumatriptan was administered subcutaneously. Recording continued until two more phase 3s had occurred. RESULTS: Sumatriptan induced a premature phase 3 in the jejunum after a median of 10 (8) minutes. The duration of the migrating motor complex cycle was shortened at the expense of phase 2. After sumatriptan, plasma somatostatin concentrations were reduced and gastric phase 3s were suppressed, although median motilin concentrations and the occurrence of plasma motilin peaks were not affected. Phase 3s of the migrating motor complex preceding sumatriptan were associated with motilin peaks, while phase 3s after sumatriptan were not. Furthermore, pretreatment with sumatriptan prevented the induction of a gastric phase 3 by the motilin agonist erythromycin. CONCLUSIONS: Administration of the 5HT1P receptor agonist sumatriptan induces a premature intestinal phase 3, suppresses gastric phase 3s, prevents induction of a gastric phase 3 by erythromycin, and reduces plasma somatostatin concentrations.

Adult↗
PubMed1998

Ambulatory gastrojejunal manometry in severe motility-like dyspepsia: lack of correlation between dysmotility, symptoms, and gastric emptying.

BACKGROUND: Previous studies have failed to identify manometric patterns of gastrointestinal motor activity that can distinguish dyspepsia from health. AIMS: To test the hypothesis that the combined use of prolonged, ambulatory, antrojejunal manometry and computer aided analysis in patients selected for the severity of their symptoms could reveal new insights into gastrointestinal motor activity in patients with severe motility-like dyspesia. METHODS: Twenty four hour antrojejunal ambulatory manometry was performed in 14 patients and 10 healthy volunteers. Parameters characterising digestive and fasted motility were obtained by a validated computer program and visual analysis. Scoring systems quantified the degree of dysmotility as well as the severity of symptoms. Gastric emptying times were measured in each patient. RESULTS: There was a high prevalence of antral and jejunal dysmotility both during the interdigestive period (71% of patients) and in the postprandial period (78%). During the interdigestive period there was a reduced incidence of antral and jejunal phases, a larger contribution of phase 2 during migrating motor complex cycles, and aberrant configuration of jejunal phase 3 in 29% of patients. Postprandially, the most frequent finding was antral (29% of patients) or jejunal (29%) hypomotility or hypermotility. Minute rhythm was present both during the postprandial (29% of patients) and the interdigestive period (21%). There was no positive correlation between symptom scores, gastric half emptying times, or motility scores. CONCLUSION: Even with the use of prolonged recordings and advanced computer aided analysis, it is not possible to identify a specific motor pattern which can discriminate patients with severe motility-like dyspepsia from those with other diseases or even healthy individuals. Clinical symptoms or gastric half emptying times are poor predictors of gastrointestinal dysmotility in patients with functional dyspepsia.

Adolescent↗