Magnification imaging in inflammatory bowel disease: a useful aid for the prediction of disease relapse?
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Biomarkers↗
Biomedical subjects
R Bisschops
Publications and source records attributed to R Bisschops.
CRF-induced calcium signaling in guinea pig small intestine myenteric neurons involves CRF-1 receptors and activation of voltage-sensitive calcium channels.
Corticotropin-releasing factor (CRF) is a 41-amino acid peptide with distinct effects on gastrointestinal motility involving both CRF-1 and CRF-2 receptor-mediated mechanisms that are generally claimed to be centrally mediated. Evidence for a direct peripheral effect is rather limited. Electrophysiological studies showed a cAMP-dependent prolonged depolarization of guinea pig myenteric neurons on application of CRF. The current study aimed to test the direct effect of CRF on myenteric neurons and to identify the receptor subtype and the possible mechanisms involved. Longitudinal muscle myenteric plexus preparations and myenteric neuron cultures of guinea pig small intestine were incubated with the calcium indicator Fluo-4. Confocal Ca(2+) imaging was used to visualize activation of neurons on application of CRF. All in situ experiments were performed in the presence of nicardipine 10(-6) M to reduce tissue movement. Images were analyzed using Scion image and a specifically developed macro to correct for residual minimal movements. A 75 mM K(+)-Krebs solution identified 1,076 neurons in 46 myenteric ganglia (16 animals). Administration of CRF 10(-6) M and CRF 10(-7) M during 30 s induced a Ca(2+) response in 22.4% of the myenteric neurons (n = 303). Responses were completely abolished in the presence of the nonselective CRF antagonist astressin (n = 55). The selective CRF-1 receptor antagonist CP 154,526 (n = 187) reduced the response significantly to 2.1%. Stresscopin, a CRF-2 receptor agonist, could not activate neurons at 10(-7) M, and its effect at 10(-6) M (15.3%, n = 59) was completely blocked by CP 154,526. TTX 10(-6) M (n = 70) could not block the CRF-induced Ca(2+) transients but reduced the amplitude of the signals significantly. Removal of extracellular Ca(2+) blocked all responses to CRF (n = 47). L-type channels did not contribute to the CRF-induced Ca(2+) transients. Blocking N- or P/Q-type Ca(2+) channels did not reduce the responses significantly. Combined L- and R-type Ca(2+) channel blocking (SNX-482 10(-8) M, n = 64) abolished nearly all responses in situ. Combined L-, N-, and P/Q-type channel blocking also significantly reduced the response to 8.6%. Immunohistochemical staining for CRF-1 receptors clearly labeled individual cell bodies in the ganglia, whereas the CRF-2 receptor staining was barely above background. CRF induces Ca(2+) transients in myenteric neurons via a CRF-1 receptor-dependent mechanism. These Ca(2+) transients highly depend on somatic calcium influx through voltage-operated Ca(2+) channels, in particular R-type channels. Action potential firing through voltage-sensitive sodium channels increases the amplitude of the Ca(2+) signals. Besides centrally mediated effects, CRF is likely to modulate gastrointestinal motility on the myenteric neuronal level.
Animals↗
Influence of ghrelin on gastric emptying and meal-related symptoms in idiopathic gastroparesis.
BACKGROUND: Ghrelin, the endogenous ligand of the growth hormone secretagogue receptor, is released from the stomach. Animal studies suggest that ghrelin stimulates gastrointestinal motor activity. AIM: To investigate the influence of ghrelin on gastric emptying rate and meal-related symptoms in idiopathic gastroparesis. METHODS: In six patients with idiopathic gastroparesis, a breath test was used to measure gastric emptying rates (t(1/2)) for solids and liquids after administration of saline or ghrelin 40 microg/30 min in a double-blind, randomized fashion. At each breath sampling, the patient was asked to grade the intensity of six different symptoms (epigastric pain, bloating, postprandial fullness, nausea, belching and epigastric burning) and these were added to obtain meal-related symptom severity score. RESULTS: Ghrelin significantly enhanced liquid emptying (t(1/2): 86 +/- 7 vs. 53 +/- 6 min, P = 0.02) and tended to enhance solid emptying (144 +/- 45 vs. 98 +/- 15 min, P = 0.06). Ghrelin pre-treatment significantly decreased cumulative meal-related symptom score (196 +/- 30 vs. 136 +/- 23, P = 0.04) and individual scores for fullness (55 +/- 8 vs. 39 +/- 8, P = 0.02), and for pain (40 +/- 8 vs. 16 +/- 5, P < 0.05). CONCLUSIONS: In idiopathic gastroparesis, administration of ghrelin enhances gastric emptying and improves meal-related symptoms. These observations suggest a potential for ghrelin receptor agonists in the treatment of gastroparesis.
Breath Tests↗
Influence of ghrelin on interdigestive gastrointestinal motility in humans.
BACKGROUND: Recent studies in animals have shown that ghrelin stimulates upper gastrointestinal motility through the vagus and enteric nervous system. The aim of the present study therefore was to simultaneously investigate the effect of administration of ghrelin on upper gastrointestinal motility and to elucidate its mode of action by measuring plasma levels of gastrointestinal hormones in humans. MATERIALS AND METHODS: Nine healthy volunteers (four males; aged 22-35 years) underwent combined antroduodenal manometry and proximal stomach barostat study on two separate occasions at least one week apart. Twenty minutes after the occurrence of phase III of the migrating motor complex (MMC), saline or ghrelin 40 mug was administered intravenously over 30 minutes in a double blind, randomised, crossover fashion. Ghrelin, motilin, pancreatic polypeptide, glucagon, and somatostatin were measured by radioimmunoassay in blood samples obtained at 15-30 minute intervals. The influence of ghrelin or saline on MMC phases, hormone levels, and intraballoon volume was compared using paired t test, ANOVA, and chi(2) testing. RESULTS: Spontaneous phase III occurred in all subjects, with a gastric origin in four. Administration of ghrelin induced a premature phase III (12 (3) minutes, p<0.001; gastric origin in nine, p<0.05), compared with saline (95 (13) minutes, gastric origin in two). Intraballoon volumes before infusion were similar (135 (13) v 119 (13) ml; NS) but ghrelin induced a longlasting decrease in intraballoon volume (184 (31) v 126 (21) ml in the first 60 minutes; p<0.05). Administration of ghrelin increased plasma levels of pancreatic polypeptide and ghrelin but motilin, somatostatin, and glucagon levels were not altered. CONCLUSIONS: In humans, administration of ghrelin induces a premature gastric phase III of the MMC, which is not mediated through release of motilin. This is accompanied by prolonged increased tone of the proximal stomach.
Adult↗
Electrical stimulation reveals complex neuronal input and activation patterns in single myenteric guinea pig ganglia.
The myenteric plexus plays a key role in the control of gastrointestinal motility. We used confocal calcium imaging to study responses to electrical train stimulation (ETS) of interganglionic fiber tracts in entire myenteric ganglia of the guinea pig small intestine. ETS induced calcium transients in a subset of neurons: 52.2% responded to oral ETS, 65.4% to aboral ETS, and 71.7% to simultaneous oral and aboral ETS. A total of 41.3% of the neurons displayed convergence of oral and aboral ETS-induced responses. Responses could be reversibly blocked with TTX (10(-)6 M), demonstrating involvement of neuronal conduction, and by removal of extracellular calcium. omega-Conotoxin (5 x 10(-7) M) blocked the majority of responses and reduced the amplitude of residual responses by 45%, indicating the involvement of N-type calcium channels. Staining for calbindin and calretinin did not reveal different response patterns in these immunohistochemically identified neurons. We conclude that, at least for ETS close to a ganglion, confocal calcium imaging reveals complex oral and aboral input to individual myenteric neurons rather than a polarization in spread of activity.
Animals↗
A survey on gastroenterology training in Europe.
BACKGROUND: Specialist training in gastroenterology and hepatology is not standardised in different European countries. AIM: The aim of this survey was to assess the different teaching and socioeconomic aspects of training programmes in Europe. METHODS: Seventy questionnaires were distributed to last year trainees or newly graduated gastroenterologists. Forty two respondents (60%) from 34 major training centres in 10 different European countries replied. RESULTS: Overall, the data revealed major diversity for all aspects analysed, between and within the different European countries. Both the duration of training (range 4-10.4 years) and workload (range 48.5-89.2 hours per week) differed markedly between countries. The average number of endoscopic procedures (gastroscopies, range 300-2600; colonoscopies, range 73-550; endoscopic retrograde cholangiopancreatographies, range 1-385) differed also. One third of last year trainees reported that they felt uncertain in some endoscopic procedure. The European trainee was on call for 5-6 nights a month on average (range 1-8). Monthly wages differed considerably between countries, ranging from 767 to 2180 Euro. CONCLUSION: We found major differences in the professional aspects and socioeconomic conditions of gastroenterologist/hepatologist training in 10 different European countries, probably leading to differences in quality of training. In several countries or centres the average number of procedures was below the threshold issued by the European Board of Gastroenterology or the American Gastroenterological Association. Issuing a European diploma for gastroenterology is a valuable effort towards meeting this problem. Further studies are needed to re-evaluate the training programmes in Europe and to define threshold numbers and technical end points for assessment of endoscopic skills.
Adult↗
Causes and treatment of functional dyspepsia.
Functional dyspepsia is a clinical syndrome defined by upper abdominal symptoms without identifiable cause by conventional diagnostic means. Recent studies have established that functional dyspepsia is a heterogeneous disorder in which different pathophysiologic disturbances underlie different symptom profiles. Delayed gastric emptying is associated with postprandial fullness, nausea, and vomiting; impaired accommodation is associated with early satiety and weight loss; and hypersensitivity to gastric distention is associated with epigastric pain, belching, and weight loss. The pathogenesis of functional dyspepsia is unknown but may be postinfectious in a subgroup of patients. The role of psychological disturbances and of duodenal hypersensitivity requires further study. Treatment of the underlying pathophysiologic abnormality seems logical, but options for pharmacotherapy are limited to acid suppression, prokinetic drugs, and antidepressants. Psychotherapy can be considered for refractory patients. Several novel drug therapies are under evaluation.
Dyspepsia↗
Imaging of neuronal activity in the gut.
Over the past few years, several groups have used voltage-sensitive dyes or calcium-indicator dyes to optically monitor the activity of several enteric neurons simultaneously. Some of the initial practical problems have been solved and these studies have successfully shown the spread of electrical activation within the enteric neuronal circuitry in cultures and in ex vivo specimens. The basic mechanisms underlying voltage-sensitive dye or calcium-indicator signals and their relation to changes in membrane potential need further investigation. Application of these techniques will provide more insight into neuronal interaction and spread of activation. The ability to simultaneously record activity in other cells in the same focal plane offers the potential to investigate how the integrated neuronal circuits are linked to effector cells in their close neighbourhood. Progress in optical imaging of enteric neuronal activity should ultimately lead to a better knowledge of gastrointestinal physiology and pathophysiology.
Animals↗