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Biomedical subjects

G Vantrappen

Publications and source records attributed to G Vantrappen.

At least 109 records · Page 6Linked to original sources
PubMed1990

Comparison of SVD methods to extract the foetal electrocardiogram from cutaneous electrode signals.

The paper presents and compares three methods making use of the singular value decomposition (SVD) of a matrix to extract the foetal electrocardiogram (FECG) from cutaneously recorded electrode signals. The first method constructs a set of orthogonal foetal signals (the so-called principal foetal signals) from the recordings, but needs electrode positions far from the foetal heart, in addition to the abdominal electrodes that pick up a mixture of maternal and foetal electrocardiogram. An online adaptive algorithm has been developed such that a real-time implementation becomes feasible. The second method is a new online approach to a technique presented by van Oosterom. Although this method has some important drawbacks and is suboptimal as far as foetal signal-to-noise ratio is concerned, it is still very useful when only a foetal trigger is required, as the signal obtained is not a complete FECG. Finally, a third method is proposed, based on the generalised SVD and interpreted with the new concept of oriented signal-to-signal ratio. An online version is also presented for this method and some results are shown.

Electrocardiography↗
PubMed1990

Predictability of the postoperative course of Crohn's disease.

Eighty-nine patients who had been treated by ileal resection for Crohn's disease between 1979 and 1984 were included in a prospective cohort follow up to study the natural course of early postoperative lesions. Recurrent lesions were observed endoscopically in the neoterminal ileum within 1 year of surgery in 73% of the patients, although only 20% of the patients had symptoms. Three years after surgery, the endoscopic recurrence rate had increased to 85% and symptomatic recurrence occurred in 34%. The ultimate course of the disease was best predicted by the severity of the early postoperative lesions, as observed at ileoscopy. Clinical parameters that influenced outcome were preoperative disease activity, the indication for surgery, and the number of surgical resections. When patients were stratified for preoperative disease activity, the severity of lesions found at endoscopy remained a strong predictive factor for symptomatic recurrence. In 22 other patients submitted to "curative" ileal resection and ileocolonic anastomosis, the segment to be used as neoterminal ileum was carefully examined during surgery, and two large biopsies were taken before making the anastomosis. An ileoscopy was performed 6 months after surgery. Although all patients had a macroscopically normal neoterminal ileum and 19 had entirely normal biopsies at the time of surgery, 21 patients were found at ileoscopy to have developed ileitis involving a 15-cm segment (range, 4-30 cm), and 20 had unequivocal microscopic lesions on biopsies. These studies suggest that early lesions in the neoterminal ileum after Crohn's resection do not originate from microscopic inflammation present in this bowel segment at the time of surgery. The early postoperative lesions in the neoterminal ileum seem to be a suitable model to study the pathogenesis of Crohn's disease and also to evaluate new therapeutic modalities, either to prevent development of these early lesions or to treat progressive recurrence.

Actuarial Analysis↗
PubMed1990

Development of motilin receptors and of motilin- and erythromycin-induced contractility in rabbits.

The development of the motilin receptor was studied through contraction and binding studies of groups of three rabbits aged between 2 and 289 days. The contractility of small intestinal smooth muscle strips was measured isotonically. The aborally decreasing gradient in response to motilin, known to exist in adult rabbits, was already present at day 8 (maximum contractile responses expressed as a percent of the maximal response to acetylcholine were 77% +/- 9%, 34% +/- 10%, and 25% +/- 8% for duodenal, jejunal, and ileal strips, respectively). Throughout the observation period, the doses of motilin and its agonist erythromycin that were required to induce 50% of the response remained constant and were not significantly different from doses required for adults (their negative logarithms were 8.55 +/- 0.35 and 5.70 +/- 0.25, respectively). The correlation between the maximum contractile response toward motilin and erythromycin was almost perfect (r2 = 0.82). Binding studies with iodinated norleucine13-porcine motilin were performed using antral smooth muscle tissue homogenates. The maximum number of binding sites increased rapidly after 8 days (3.3 +/- 0.4 fmol/mg protein) and reached a peak at 21 days (20.7 +/- 1.4 fmol/mg protein), but decreased at that point toward the adult value (40 days, 10.6 +/- 1.3; 289 days, 9.8 +/- 1.1 fmol/mg protein). The dissociation constant, however, remained unchanged. The peak value of receptor density occurred at about the time that the rate of increase of the length of the intestine and of the weight of the antrum were at maximum levels (at 18 and 27 days, respectively). Motilin receptors are expressed early postnatally, and the regional gradient in sensitivity towards motilin is also established soon after birth. If applicable to humans, an early response to erythromycin may have therapeutic value.

Acetylcholine↗
PubMed1990

Gastrin, motilin and pancreatic polypeptide levels after two different parenteral regimens in infants.

We studied the effect of 2 different parenteral regimens upon gastrin, motilin and pancreatic polypeptide (PP) levels in infants. In 15 children, aged 1-25 months, plasma peptide levels were measured by radioimmunoassay in the fasting state and after a 2-h infusion of either a mixture of amino acids, glucose and lipids (A) or a mixture of amino acids and glucose (B) only. Wide interindividual fluctuations were noted, especially for motilin and PP, but, except for PP, intraindividual fluctuations were low. Indeed, a good correlation was found, not only between the 2 pre-infusion levels, but also between pre- and postinfusion levels in both experiments. In fact for all 3 peptides, pre- and postinfusion levels differed only slightly and non-significantly. We conclude that during parenteral feeding levels of motilin, PP and gastrin remain practically unchanged and are not influenced by the addition of lipids. In addition, during the observation period basal levels did not change, indicating that the mechanisms regulating basal secretion were not affected.

Amino Acids↗
PubMed1990

Multichannel adaptive enhancement of the electrogastrogram.

The electrogastric signal can be measured cutaneously on the abdomen. This is attractive because it is harmless to patients or volunteers. However, the poor quality of the cutaneous measurements necessitates signal enhancements. Hence, in this paper, an adaptive multichannel signal enhancing system is proposed. The mu-vector least mean square (LMS) algorithm is applied to adjust the weights of the adaptive filters in the system. The detailed description and the performance analysis of the system is given in the paper. Applying the proposed system, the respiratory artifact, the electrode-skin noise, some of motion artifacts, and the electrocardiography (ECG) can be efficiently reduced while the characteristics of the relevant gastric signal is less affected.

Adaptation, Physiological↗
PubMed1990

13CO2 breath test to measure the hydrolysis of various starch formulations in healthy subjects.

13CO2 starch breath test was used to study the effect of physicochemical characteristics of starch digestion. As starch is hydrolysed to glucose, which is subsequently oxidised to CO2, differences in 13CO2 excretion after ingestion of different starch products must be caused by differences in hydrolysis rate. To study the effect of the degree of chain branching, waxy starch, containing 98% amylopectin, was compared with high amylose starch, containing 30% amylopectin, and normal crystalline starch, containing 74% amylopectin. The effect of the extent of gelatinisation was studied by comparing extruded starch and crystalline starch. Finally, the possible inhibitory effect of adding wheat fibre to extruded starch on the hydrolysis rate was studied. The 13CO2 excretion from two to four hours after intake of crystalline starch was significantly lower than that of extruded starch. Waxy starch was hydrolysed much faster than high amylose starch, but there was no significant difference between waxy starch and normal crystalline starch. Addition of wheat fibre did not influence the hydrolysis rate. The 13CO2 starch breath test is an attractive test for the study of factors affecting carbohydrate assimilation.

Adult↗
PubMed1990

Ambulatory 24 hour intraoesophageal pH and pressure recordings v provocation tests in the diagnosis of chest pain of oesophageal origin.

Fifty patients with non-cardiac chest pain underwent 24 hour intraoesophageal pH and pressure recording and provocation tests to determine the relative value of both techniques in establishing the oesophageal origin of the chest pain. Twenty six patients (52%) had at least one positive provocation test: the acid perfusion test was positive related in 18 patients (36%), the edrophonium test in 16 patients (32%), the vasopressin test in five patients (10%), and the balloon distension test (performed in only 20 patients) in one (5%). The 24 hour pH and pressure recording correlated spontaneous chest pain attacks with abnormal motility or gastro-oesophageal reflux in 19 patients (38%). Fourteen of these patients also had at least one positive provocation test. Therefore, 24 hour pH and pressure recordings are only slightly better than a set of provocation tests in identifying the oesophagus as the cause of chest pain (10% diagnostic gain). In the case of oesophageal chest pain, however, 24 hour recording appeared to be the only way to identify the nature of the underlying oesophageal abnormality that caused the spontaneous pain attacks--for example, gastro-oesophageal reflux, motility disorders, or irritability of the oesophagus.

Adult↗
PubMed1990

Effects of substance P on [Ca2+]i and force in intact guinea pig ileal smooth muscle.

In intact sheets of the guinea pig ileal longitudinal muscle, loaded with fura-2, both substance P (SP)- and K(+)-induced contractile responses are preceded by cytoplasmic free Ca2+ ([Ca2+]i) variations. In response to SP (10(-10)-10(-7) M), [Ca2+]i and force increased concentration dependently. From 10(-9) M on, the response was biphasic: an initial Ca2+ spike and force transient were followed by a tonic component. The [Ca2+]i and force vs. log [SP] curves were sigmoidal for the initial phasic component, while a homologous receptor desensitization caused a reduced tonic component of the [Ca2+]i and contractile response at higher concentrations of SP. Both intracellular Ca2+ release and Ca2+ influx play a role in the effect of the peptide. In depolarizing solutions (140 mM K+) and in Ca2(+)-free medium (2 mM EGTA), SP induced a transient increase in [Ca2+]i and force. The Ca2+ stores used by SP and acetylcholine (ACh) overlap. [Ca2+]i and force fell to base-line levels when the extracellular Ca2+ was reduced from 1.2 to 0.2 mM during stimulation with SP. Verapamil reduced the tonic response. We also studied the relation between [Ca2+]i and force for the peak and steady-state values after stimulation with increasing concentrations of SP and K+. The phasic force response was linearly related to log [Ca2+]i. During the sustained response to K+, the Ca2+ sensitivity of the contractile/regulatory proteins was decreased, whereas no changes were observed during prolonged stimulation with the peptide.

Animals↗
PubMed1990

Visualization and characterization of gastric contractions using a radionuclide technique.

With the use of the radionuclide gastric-emptying test and a new data processing method, the contraction characteristics of the stomach were analyzed. After ingestion of a radiolabeled test meal, dynamic images of the stomach were acquired and analyzed to determine the frequency, amplitude, and rate of gastric contractions in healthy subjects. The frequency of antral contractions was found to be inversely related with food retention in the stomach; in contrast, the amplitude of the contractions decreased progressively during the course of gastric emptying. The peaks of both antral contraction and filling rate and the time of their occurrence remained constant throughout gastric emptying. The observed patterns of phase distribution and sequential phase changes of the food in the stomach confirmed noninvasively what was already known from invasive technique, i.e., that the proximal stomach does not undergo phasic contractions and that, in the distal stomach, smooth muscle contraction originates in midcorpus and propagates aborally to the pylorus. The scintigraphic test can be used to noninvasively and quantitatively characterize gastric motor function and to delineate the spatial sequence of gastric contractions. This technique can be applied to study the pathophysiology of gastric emptying in various motor disorders.

Adult↗
PubMed1990

Recent studies of the pathophysiology and diagnosis of esophageal symptoms.

The three main symptoms of esophageal disease or disorder are dysphagia, chest pain, and heartburn. Dysphagia in achalasia is mainly due to a non-relaxing lower esophageal sphincter (LES). The mechanism of dysphagia in diffuse esophageal spasm and related motor disorders is related to a combination of several factors including incomplete LES relaxation, failed or weak peristalsis (pressure less than 30 mmHg in the distal esophagus, and orad positive pressure gradient). Meal manometry and balloon distention may prove to be useful provocation tests. Chest pain of esophageal origin may be due to gastroesophageal reflux and esophageal motility disorders; it may also be a manifestation of an irritable esophagus, in which the esophagus is hypersensitive to various stimuli (chemical, mechanical, ischemic). Esophageal provocation tests may suggest the esophageal origin of the pain but do not give information on the nature of the esophageal disorder. Twenty-four-hour pH and pressure measurements may, however, yield this information. Heartburn and acid regurgitations are the most typical symptoms of gastroesophageal reflux. Transient relaxations of the LES are considered to be an important contributory mechanism of reflux. Absent basal LES pressure is another mechanism, which accounts for about one-fourth of the reflux episodes in patients with severe reflux esophagitis. During long-lasting inappropriate relaxations, swallows often produce deglutitive contraction waves that die out in the upper esophagus, suggesting that reflux often occurs during periods of inhibition of both LES tone and peristaltic esophageal activity.

Chest Pain↗
PubMed1990

Recurrence of Crohn's lesions in the neoterminal ileum after ileal resection and ileocolonic anastomosis.

The recurrence rate after "curative" resection for Crohn's disease is variously reported to be between 17% and 81%. Endoscopic-histological studies in over 200 patients allowed us to demonstrate that 71% of the patients have endoscopic evidence of recurrence within the first year of surgery. The early lesions consist of small aphtoid ulcers. Later these lesions become confluent and result in large, often longitudinal ulcerations, separated by a thickened nodular mucosa with inflammatory cell infiltration. Eventually stenosis develops. These lesions are in 90% of the cases confined to the neoterminal ileum and around the anastomosis. Pre- and postoperative studies indicated that these ulcers do not develop from preexisting lesions left behind at surgery. However, the segment to be used as neoterminal ileum contains an increased number of HLA-DR+, ATPase + dendritic cells in the lamina propria. These findings suggest that immunological processes play a role in the development of recurrent lesions. We further showed that the severity of the early recurrence allows to predict the future course of the disease.

Adolescent↗
PubMed1990

[The ototoxicity of cisplatin: a clinical study].

The ototoxic side effects of cisplatin are evaluated in 23 patients by a conventional and high-frequency audiogram. The ototoxicity of cisplatin consists of a high frequency loss which was found to be dose and frequency related. The hearing loss started predominantly in the higher frequencies (12-16 kHz) and the ototoxicity increased with increasing dose of cisplatin. The ototoxicity of cisplatin appears to be inversely related with the patient's age, although it is difficult to draw definite conclusions because age and dose are closely related to each other in our study.

Adult↗
PubMed1990

[Interrelations between the presence or lack of bile and bile acids in the small-intestinal lumen, release of motilin and pancreatic polypeptide and migrating myoelectric complex in dogs].

5 male and 1 female dogs weighing 15-20 kg were used in the study. Animals underwent the functional cholecystectomy, bidirectional cannulation of the common bile duct and the implantation of 9 bipolar electrodes located in the stomach and small intestine. In 13 experiments performed on 4 dogs the interdigestive myoelectric activity was recorded and plasma motilin and PP levels were determined by radioimmunoassay during: 1) the control period where the spontaneous bile circulation was preserved, 2) bile depletion with or without intravenous motilin (56 pmol.kg-1.hr-1) infusion, 3) intraduodenal infusion of 50 mM Na-taurocholate with or without intravenous infusion of PP (400 pmol.kg-1.hr-1). During 88 additional experiments performed on all operated animals, which comprised the control studies, bile deprivation experiments and bile or bile acid infusions, the interdigestive myoelectric activity was recorded along with the estimation of sites of phase III origin. Motilin infusion at the lack of bile and bile acids in the intestine elicited the premature phase III in the duodenum, markedly increased the percentage of phases III originating from the stomach, inhibited the arrival of phase I of the myoelectric cycle and lowered plasma PP level. Infusion of PP despite the presence of bile acids in the small intestinal lumen caused the phase III originated from the proximal or mild jejunum and lowered plasma motilin level. Thus, unlike bile or bile acids, both motilin and PP are directly responsible for the appearance of phase III in the stomach and proximal small bowel of the dog. The luminal bile appears only to play a mediatory role influencing the release of the hormonal peptides examined here.

Animals↗
PubMed1990

[Inhibition of the interdigestive myoelectric cycles in dogs by a single administration of bile acids into the branch of the cranial mesenteric artery].

Experiments were performed on 10 fasted dogs equipped with perfused catheter which was placed into the branch of the cranial mesenteric artery supplying the short duodenal or jejunal segment. In addition, 9 bipolar electrodes for electromyographic examinations were implanted into the stomach and small bowel including the perfused intestinal segment. Na-taurocholate, Na-taurodeoxycholate (TD) and Na-taurochenodeoxycholate were infused for 2 hr in 2 different doses (reaching in blood, which supplies the intestine, the concentration about 7.5 and about 50 mumol.l-1) or injected for 0.5 min (reaching the concentration about 200 mumol.l-1 in the blood) close intraarterially to the animals. The lower dose of bile acid infused caused no significant changes in myoelectric activity. The higher dose of bile acid infused significantly inhibited the occurrence of action potentials (prolongation of phase I of the migrating myoelectric complex) for the period much longer than the bile acid infusion itself. Both stimulatory (the phase III-like myoelectric activity, vomiting) and inhibitory effects of action potentials as well as changes in frequency and amplitude of resting potentials were triggered by bile acid injection. Alterations induced by TD administration were the strongest. The immediate appearance of the inhibitory effect suggests the mediatory role of the nervous system in this response. In normal conditions the bile acids appear to regulate the motor function of the digestive tract solely when they enter the intestinal lumen. Their raised level in plasma, as observed in many liver and biliary tract diseases must give, as a consequence, an unfavourable effects which may be a cause for the arrival of gastrointestinal manifestations (the motor component) during a course of above affections.

Animals↗
PubMed1990

Intravenous erythromycin dramatically accelerates gastric emptying in gastroparesis diabeticorum and normals and abolishes the emptying discrimination between solids and liquids.

Erythromycin, a macrolide antibiotic, has recently been shown to have a motilin like effect on gastrointestinal muscle strips. In this study, we have evaluated the effect of erythromycin on patients with delayed gastric emptying and healthy subjects using the dual radionuclide technique. Twelve patients with gastroparesis diabeticorum and ten healthy age- and sex-matched controls were studied. Gastric emptying of solids and liquids was determined using 99mTc-SC scrambled egg and 111In-DTPA in water. Following a baseline study and on a separate day, each patient and control received a 15-min i.v. perfusion of erythromycin starting at meal ingestion. Eleven out of the 12 patients were restudied after a 3-wk oral administration. In patients and controls, i.v. erythromycin dramatically accelerated gastric emptying of both solids and liquids which were emptied at the same rate. After chronic oral administration, solid and liquid emptying remained significantly accelerated. Erythromycin appears to be a very powerful gastrokinetic drug. Derived compounds with the gastrokinetic effect and without the antibiotic activity could be useful in dyspeptic patients with delayed gastric emptying.

Diabetes Complications↗
PubMed1989

Comparison of endoscopic polidocanol injection and YAG laser therapy for bleeding peptic ulcers.

392 patients were examined by endoscopy for acute upper gastrointestinal bleeding; 140 had ulcers containing an actively bleeding visible vessel or a non-bleeding visible vessel and were enrolled in a randomised trial of three endoscopic methods of haemostasis--adrenaline (1/10(4] alone, adrenaline plus polidocanol 1%, and adrenaline followed by yttrium-aluminium-garnet (YAG) laser photocoagulation. For patients with non-bleeding visible vessels sham treatment was significantly less effective in achieving haemostasis (8 of 20 patients) than were adrenaline plus polidocanol (18 of 20; p = 0.002) and adrenaline plus laser (16 of 20; p = 0.012). All three treatments significantly reduced total transfusion needs compared with sham treatment. For the whole group of patients, adrenaline plus polidocanol was significantly more effective than adrenaline alone in achieving permanent haemostasis; adrenaline plus laser was also more effective than adrenaline alone, but not significantly so. The efficacy of the three treatments was enhanced by repeated application on recurrence of bleeding. Since injection therapy with adrenaline and polidocanol was at least as effective as adrenaline plus laser therapy, it should be preferred over laser therapy because it is cheaper, easier to use, and perhaps also safer.

Acute Disease↗
PubMed1989

Porous-layer open-tubular gas chromatography in combination with an ion trap detector to assess volatile metabolites in human breath.

A method is described for the quantification of major volatile substances in human breath without preconcentration. Methanol, ethanol, acetaldehyde and acetone are well separated by porous-layer open-tubular column gas chromatography. Low-level detection was possible by means of an ion trap detector. Halothane has been used as internal standard.

Acetaldehyde↗