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Biomedical subjects

G Vantrappen

Publications and source records attributed to G Vantrappen.

At least 127 records · Page 7Linked to original sources

Primary malignant fibrous histiocytoma of the esophagus.

A 59-year-old man was admitted to the hospital for dysphagia and fever. Esophagogram and upper gastrointestinal endoscopy revealed a polypoid mass in the midesophagus. Subtotal esophagectomy, cervical esophagogastrostomy, and lymph node dissection were performed. The histological diagnosis of the tumor was malignant fibrous histiocytoma. An area of severe epithelial dysplasia was found in the esophageal mucosa 3 cm under the tumor.

Esophageal Neoplasms↗

The role of intracellular calcium stores in motilin induced contractions of the longitudinal muscle of the rabbit duodenum.

The contraction of longitudinal muscle strips of the rabbit duodenum in response to motilin and acetylcholine was investigated in normal and high K+-solutions in the presence and absence of external calcium, in order to demonstrate the existence of pharmaco-mechanical coupling for motilin and to examine whether the peptide mobilizes calcium from an intracellular store. In depolarized smooth muscle (140 mM K+), motilin (3.2 x 10(-9)-1 x 10(-7) M) and acetylcholine (1 x 10(-5) M) were still capable of causing a considerable, transient, concentration-dependent contraction in the presence of Ca2+. The 'extra'-contraction to motilin was not blocked by tetrodotoxin (1 microgram/ml) nor by atropine (10(-7) M), but acetylcholine (10(-5) M) was blocked by atropine. Verapamil (10(-7) M) could selectively block the K+ contraction without affecting the extra agonist contraction. Nitroprusside was ineffective up to 10(-4) M in high K+-solutions, but in normal Hepes-buffer it caused a concentration-dependent rightward shift of the concentration-response curve of motilin and acetylcholine contractions. In a calcium-depleted medium, high K+-depolarized muscle strips were still responsive to motilin and acetylcholine, but higher concentrations (10(-6) M) were needed than in the presence of calcium and the contractions reached only 57 +/- 11% and 74 +/- 9% respectively of the maximal contraction in 1.2 mM Ca2+ containing solutions. The response to motilin (10(-6) M) was not only smaller than that to acetylcholine (10(-5) M), it also faded more rapidly with time.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗

Interdigestive myoelectric complex in germ-free rats.

The effect of intestinal bacteria on the interdigestive myoelectric complex (IDMEC) was studied by recordings of the electrical activity of the proximal and distal small bowel in fasting germ-free (n = 6), gnotobiotic (n = 7), and conventional (n = 6) rats in vivo. Germ-free and gnotobiotic rats were operated and studied in germ-free or gnotobiotic conditions. The IDMEC period (mean +/- SD) in the proximal and distal small bowel was significantly longer in germ-free rats (20 +/- 2 min and 102 +/- 14 min) as compared to conventional rats (13 +/- 1 min and 58 +/- 5 min). Association of germ-free rats with a limited flora (gnotobiotic rats) decreased the IDMEC period significantly (15 +/- 1.5 min and 75 +/- 14 min). The migration velocity of the IDMEC was inversely related to the IDMEC period. These observations confirm previous data suggesting that the interdigestive motor complex has a role in the homeostasis of the bacterial content of the small bowel.

Animals↗

Risk factors which determine the long term outcome of Neodymium-YAG laser palliation of colorectal carcinoma.

We have analysed the long term results of YAG laser palliation for incurable colorectal carcinoma in 88 patients. Although initial palliation was achieved in 82%, good palliation could only be maintained in 51% and 41% of patients surviving 6 months and 12 months respectively. The relative inefficacy of YAG laser therapy for palliation of rectal cancer is due to the failure to control extraluminal tumour growth, complications of YAG laser therapy and the poor general condition of these elderly patients. Factors influencing the efficacy of palliation, besides life expectancy, included T classification, and length of the neoplastic stricture. Treatment-related mortality due to perforation was 2.3%. YAG laser therapy, applied as the sole therapeutic modality, is effective for short term palliation of incurable colorectal carcinoma, but is not adequate for long term palliation in most patients. Trials should be conducted to study the effect of combined treatment (e.g. laser + radiotherapy) on palliation.

Aged↗

Observation of the propagation direction of human electrogastric activity from cutaneous recordings.

Electrogastric signals have been successfully measured both intraluminally and cutaneously. Although it has been claimed by several researchers that the propagation direction of the electrogastric activities cannot be observed from cutaneous recordings, it is the aim of the paper to show that it is feasible. The reason why the propagation direction has never been observed from cutaneous recordings is that the reported methods for the abdominal measurements are not adequate. In the paper it is pointed out that the stomach should be localised before the measurement and the electrodes should be attached along the longitudinal axis of the stomach.

Diabetes Mellitus↗

Algorithm for data reduction and automatic analysis of intestinal motility tracings and other smooth biological signals.

An algorithm is presented for the processing of smooth biological signals with an important implicit data reduction. It is a solid basis for an automatic analysis of these signals. The algorithm is based on the approximation of the signals with a linear combination of cubic B-splines. Depending on the parameters, a data reduction of between 8:1 and 12:1 can be achieved. The most important differences from conventional biological signal processing methods are the representation of the signal by the coefficients of the linear combination instead of a series of samples and the analysis by calculations of the time of the appearance of patterns instead of iterative searching. The approximation and analysis of long-lasting multichannel signals can be performed online with a modern microprocessor. Approximating the signal with a linear combination of cubic B-splines with equally spaced knots, according to the linear least-squares criterion gives the desired data reduction and an elegant way to perform an automatic analysis. A window calculation scheme makes it possible to handle very long signals online.

Algorithms↗

Adaptive method for cancellation of respiratory artefact in electrogastric measurements.

Electrogastric measurements are useful for medical research and in clinical diagnosis. The measurements, however, contain very heavy respiratory artefact. Existing conventional frequency-domain filters cannot be used because of the possible overlap of the frequencies of the gastric signals and respiratory artefact. In the paper, the methods of measuring cutaneous and intraluminal gastric signals and reference respiratory signals are described. An adaptive cancellation technique is developed, which is simple and easy to implement for online processing. It is proved by experiments to be very efficient, i.e. the respiratory artefact can be completely cancelled, while the gastric signal component is not affected. Other possible applications in biomedical signal analysis are also discussed.

Electricity↗

Experimental studies of injection therapy for severe nonvariceal bleeding in dogs.

Efficacy and tissue effects of injection therapy for nonvariceal upper gastrointestinal bleeding were studied in 16 mongrel dogs. The results were compared with those obtained by neodymium-yttrium-aluminum-garnet laser, bipolar electrocoagulation, and heater probe. Epinephrine (1:10,000), absolute ethanol, and 1% polidocanol were used as injection solutions. In acute, severely bleeding experimental ulcers as well as in transected submucosal arteries, injection methods were not as effective as thermal methods in achieving complete hemostasis, although injection therapy, especially with large volumes of epinephrine (1:10,000), very quickly decreased the rate of bleeding. Chronic experiments showed that epinephrine (1:10,000) caused almost no tissue injury, but also did not induce vessel thrombosis. In contrast, absolute ethanol and 1% polidocanol caused tissue necrosis, ulceration, and vessel thrombosis, the former by acute dehydration and fixation of the tissue, the latter by acute edema and subsequent inflammation and sclerosis. These data suggest that although epinephrine injection may slow or temporarily stop bleeding, this modality is not as efficacious as injection with 1% polidocanol or absolute ethanol in inducing definitive vessel thrombosis. In the present experimental conditions sclerotherapy was not as effective as thermal methods in achieving hemostasis. These data also show that injection therapy with 1% polidocanol and absolute ethanol is by no means safer than thermal methods.

Animals↗

Starch digestion in normal subjects and patients with pancreatic disease, using a 13CO2 breath test.

A 13CO2 starch breath test was developed to study starch digestion in 13 healthy volunteers and 16 patients with pancreatic disease. As starch is hydrolyzed to glucose that is subsequently oxidized to CO2, the excretion of 13CO2 after starch intake, compared with the excretion of 13CO2 after glucose intake, should be a measure of starch hydrolysis. In normal subjects both the hourly 13CO2 excretion rate and the cumulative percentage of 13CO2 excretion after starch ingestion were significantly different from those after glucose ingestion. Comparable differences were found with the patient group. In addition, the 13CO2 excretion after starch intake in normal subjects was markedly different from that of patients with pancreatic disease. Even after correction for endocrine pancreatic insufficiency by calculating the ratio of 13CO2 excretion after starch intake over 13CO2 excretion after glucose intake, the difference between the control group and the patient group was statistically significant. This study indicates that starch hydrolysis is the rate-limiting step in starch digestion. It also confirms recent findings suggesting that starch digestion is impaired in some patients with pancreatic disease. The 13CO2 starch breath test may prove to be useful in evaluating the digestibility of various starch preparations in physiologic and pathological conditions.

Adult↗

Stress-induced changes in gastric emptying, postprandial motility, and plasma gut hormone levels in dogs.

The influence of acoustic stress on postprandial gastrointestinal motility, gastric emptying, and plasma gastrin, pancreatic polypeptide, motilin, and somatostatin was evaluated in conscious dogs. Six dogs were equipped with strain-gauge transducers and were exposed from 1-3 h after the meal to prerecorded music (80-90 dB broad frequency noise), which produced a significant (p less than or equal to 0.05) lengthening of the gastric (31.2%) and jejunal (37.0%) postprandial pattern. In 4 other dogs with gastric cannula, a 2-h session of acoustic stress beginning just after eating a radiolabeled standard meal induced a slowing of gastric emptying of both liquid (45.7%) and solid (47.1%) phases of the test meal when measured 0.5 h after feeding. In contrast, when measured 2 h after feeding, similar values of gastric emptying of liquids and solids were observed in stressed and control animals. Compared with controls, the postprandial increases of plasma gastrin and pancreatic polypeptide levels were significantly enhanced in stressed animals and occurred early (15 min after the meal). Although postprandial decrease in plasma motilin was unchanged by acoustic stress, the rise in plasma somatostatin level was significantly (p less than or equal to 0.05) prolonged in stressed dogs. These results indicate that acoustic stress affects gastric and intestinal postprandial motility in dogs, delaying the recovery of the migrating motor complex pattern, inducing a transient slowing of gastric emptying, and enhancing the feeding-induced release of gastrin, pancreatic polypeptide, and somatostatin. Such hormonal changes might be due to a direct effect of stress rather than being the consequence of acoustic stress-induced slowing of gastric emptying.

Animals↗

Description of a real-time system to extract the fetal electrocardiogram.

An overview is given of the FEMME-project (Fetal Electrocardiogram Measuring Method and Equipment). The project started in 1981 and is, at the moment, close to producing a prototype personal computer-based system. This records simultaneously a number of cutaneous potential signals and derives from this set one or more maternal electrocardiogram-free fetal heart signals, by combining linearly the recorded signals. An on-line adaptive algorithm based on the Singular Value Decomposition (SVD) has been designed to compute the coefficients in these linear combinations. This algorithm will be implemented on a DSP board that can be plugged into the real-time recording system. The system will be very useful in studies of the fetal electrocardiogram during pregnancy, but also in all other studies such as fetal heart rate variability, fetal movements, etc., where a precise trigger of the electrical signal from the fetal heart is required.

Computer Systems↗

Erythromycin is a motilin receptor agonist.

Erythromycin A (EMA) is a potent stimulator of gastrointestinal motor activity. In vitro studies suggest that it mimics motilin, a peptide that stimulates motor activity in human and in rabbit via smooth muscle receptors. We have compared the in vitro contractile effect of EMA and two derivatives, 8,9-anhydro-EMA-6,9-hemiketal (EM201) and EMA N-oxide, on rabbit duodenal smooth-muscle strips with their ability to displace iodinated motilin bound to crude smooth-muscle membrane fractions. The concentrations required to induce 50% of the maximum contractile response to a supramaximal dose of acetylcholine were 5.0 x 10(-8), 2.0 x 10(-6), and 1.0 x 10(-4) M for, respectively, EM201, EMA, and EMA N-oxide. The concentrations required to displace 50% of the labeled motilin were, in the same order, 1.0 x 10(-8), 1.3 x 10(-7), and 4.0 x 10(-6) M. Both parameters were well correlated. The dose-response curve of the EMA was parallel to that of motilin and the effects of motilin and EMA were additive. Contractions induced by EMA were insensitive to pretreatment with tetrodotoxin or atropine. EMA had no effect on muscle strips of rat or dog duodenum but did induce contractions in human strips. EMA was totally ineffective on ileal preparations, which are also unresponsive to motilin and in which motilin binding is absent. EMA has therefore the same regional and species specificity as motilin. We conclude that EMA is a motilin receptor agonist.

Animals↗

Pathophysiology of reflux esophagitis.

Prolonged (24 h) intra-esophageal pH measurements have shown that short-lasting reflux episodes regularly occur in normal subjects, especially in the postprandial period. This phenomenon has been called physiological reflux. When the reflux episodes become more frequent and last longer, symptoms and esophagitis ensue. The mechanism of symptom production (pyrosis and/or chest pain) is incompletely understood. Chemoreceptors are involved but manometric disturbances and irritability of the esophagus may play an important role. The pathogenesis of pathological reflux is multifactorial: 1. An ineffective anti-reflux barrier at the level of the gastroesophageal junction is the most important factor in the pathogenesis of reflux. 2. Once reflux has occurred, an appropriate clearing of the refluxed material is necessary to minimize the contact time of the noxious agent with the esophageal mucosa. This clearing function is a two-step operation. In the refluxed material the concentration of H+ is the most irritant factor although pepsine increases its noxious character. Bile acid reflux decreases the epithelial resistance. The mucosal resistance to noxious agents is determined by the mucous layer, the cytoprotective properties of the epithelium, the regeneration capacity of the cells and by a number of post-epithelial factors.

Esophagitis, Peptic↗

Efficacy and safety of rioprostil, 300 micrograms b.d., in the treatment of gastric ulcer: a comparison vs. ranitidine, 150 mg b.d., in a randomized multicentre study.

The aim of this study is a double-blind evaluation of the efficacy and safety of rioprostil, 300 micrograms, compared with ranitidine, 150 mg, when given twice a day for 4 or 8 weeks in patients with active, uncomplicated gastric ulcer disease. A total of 194 patients are entered into the study, of which 182 are statistically evaluated for efficacy. Eighty-seven receive rioprostil and 95 receive ranitidine. All patients receive two oral doses of study medication daily. After 4 weeks' treatment, 47.1% of the patients receiving rioprostil are endoscopically healed compared with 53.7% of those receiving ranitidine. After 8 weeks' treatment, the cumulative cure rates are 76.2% and 80.9% respectively. Side effects occur in 26% of the patients receiving rioprostil and in 15% of the patients receiving ranitidine. Gastrointestinal side effects are most common. Changes in stool consistency (i.e. soft stools or mild diarrhoea) are the most reported symptoms in patients receiving rioprostil. These effects are generally self-limiting. Three patients on rioprostil and one patient on ranitidine discontinue treatment due to side effects. No clinically significant changes in biochemical variables occur in either group throughout the treatment period. Rioprostil, 300 micrograms b.d., is a safe and effective treatment for gastric ulcer disease. Healing rates and alleviation of pain are comparable for both treatment groups. The change in stool consistency with rioprostil is of only minor clinical importance, that is, it occurs on about 2% of treatment days.

Anti-Ulcer Agents↗

Efficacy and safety of rioprostil, 300 micrograms b.d., in the treatment of duodenal ulcer: a double-blind, controlled multicentre clinical study vs. ranitidine.

This study is undertaken to evaluate the efficacy and safety of rioprostil, 300 micrograms, compared with ranitidine, 150 mg, when given twice daily for 4-6 weeks to patients with active, uncomplicated duodenal ulcer. The effects of each drug on ulcer healing are evaluated by endoscopy. Of a total of 355 patients who have entered this study, 319 are statistically evaluated for efficacy; 162 receive rioprostil and 157 receive ranitidine. After 4 weeks of treatment, 63% of the patients receiving rioprostil are endoscopically healed, compared with 72% of those receiving ranitidine. After 6 weeks of treatment, the cumulative healing rates are 86% and 93.5% respectively; this difference is statistically significant. Diarrhoea is the main adverse event, but is generally mild and self-limiting. These results indicate that rioprostil, 300 micrograms b.d., is a safe and effective treatment for duodenal ulcer, but is slightly less effective than ranitidine, 150 mg b.d.

Adult↗

Pathophysiology and treatment of gastro-oesophageal reflux disease.

Gastro-oesophageal reflux occurs when the pressure barrier of the lower oesophageal sphincter (LOS) fails due to a low basal pressure (less than or equal to 6 mm Hg), sphincteric relaxations or a noncompensated increase in intragastric pressure. This reflux becomes pathological when it leads to symptoms severe enough for the patient to seek medical help or results in reflux oesophagitis or its complications. Damage to the oesophageal mucosa develops when the balance between aggressive and defensive factors is no longer in equilibrium. The main aggressive factor is acid-pepsin or alkaline bile secretion. Defence against this aggression is based on rapid removal of the refluxate from the oesophagus (oesophageal clearance) and on poorly understood mucosal resistance. The length of time acid is in contact with the oesophageal mucosa is shortened by adoption of an upright position, by swallow-induced oesophageal peristalsis and saliva. Treatment of pathological reflux aims (1) to decrease acid aggression by means of H2-receptor antagonists or proton pump inhibitors; (2) to strengthen the anti-reflux barrier and improve oesophageal clearance by prokinetic drugs that increase the LOS pressure and enhance peristaltic contractions; and (3) to boost mucosal resistance by sucralfate or prostaglandin analogues. Initial treatment of gastro-oesophageal reflux disease may be symptomatic provided that there are no alarming symptoms, such as dysphagia, anaemia or weight loss. Usually either H2-receptor blockers or prokinetic drugs are used. Endoscopy is indicated whenever alarming symptoms are present and when there is insufficient symptomatic improvement after a 4-6-week therapeutic trial. Moderate oesophagitis may be treated in the same way.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Ulcer Agents↗

Endoscopy in inflammatory bowel disease.

Ileocolonoscopy is a very useful diagnostic examination for the assessment of inflammatory bowel disease. Specific indications justify the procedure only when they are likely to influence therapeutic management. Colonoscopy of the entire colon and the terminal ileum can be necessary to establish a differential diagnosis, to determine the extent of inflammatory activity, preoperatively to guide the surgeon, and to examine the bowel proximal to stomas. Early endoscopic examination of the ileocolonic anastomosis after resection of the terminal ileum and part of the colon enables evaluation of the severity of recurrence, predicting clinical outcome. Routine postoperative colonoscopy is, however, not warranted, as we do not have a medical treatment influencing evolution of the disease. Total colonoscopy is also indicated for prevention of cancer in long-standing ulcerative colitis. The best screening strategy has still to be identified.

Colitis, Ulcerative↗