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Biomedical subjects

J Janssens

Publications and source records attributed to J Janssens.

At least 163 records · Page 9Linked to original sources
PubMed1989

Effects of sodium ascorbate (vitamin C) and 2-methyl-1,4-naphthoquinone (vitamin K3) treatment on human tumor cell growth in vitro. I. Synergism of combined vitamin C and K3 action.

The effects of sodium ascorbate (vitamin C) and 2-methyl-1,4-naphthoquinone (vitamin K3) administered separately or in combination on the in vitro cultured human neoplastic cell lines MCF-7 (breast carcinoma), KB (oral epidermoid carcinoma), and AN3-CA (endometrial adenocarcinoma) have been examined. When given separately, vitamin C or K3 had a growth inhibiting action only at high concentrations (5.10(3) mumol/1 and 10(5) nmol/l, respectively). Combined administration of both vitamins demonstrated a synergistic inhibition of cell growth at 10 to 50 times lower concentrations. At this level separately given vitamins are not toxic. The sensitivity to this treatment was somewhat different in the three cell lines, being slightly higher for KB line. This tumor cell growth inhibitory effect was completely suppressed by the addition of catalase to the culture medium containing vitamins C and K3, suggesting an excessive production of hydrogen peroxide as being implied in mechanisms responsible for the above-mentioned effects.

Adenocarcinoma↗
PubMed1989

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↗
PubMed1989

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↗
PubMed1989

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↗
PubMed1989

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↗
PubMed1989

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↗
PubMed1989

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↗
PubMed1989

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↗
PubMed1989

Effect of rioprostil, 600 micrograms, on the interdigestive myoelectrical activity of the humans small intestine.

The effect of rioprostil, a PGE1 analogue, on the interdigestive motility of the upper human small intestine was investigated in 8 normal volunteers in a double-blind, placebo-controlled study. Rioprostil was administered intraduodenally in a dose of 600 micrograms. The myoelectrical activity was recorded simultaneously at 8 different levels of the jejunum, at 10 cm intervals. Rioprostil, 600 micrograms, does not disrupt the migrating motor complex (MMC) and does not change the characteristics of phase 3 of the MMC, except for an increased propagation velocity. The main effect of rioprostil, 600 micrograms, is a marked inhibition of phase 2 contractions without induction of propulsive motility patterns during phase 2. This may explain why rioprostil in a dose of 600 micrograms is not markedly diarrheogenic in man.

Adult↗
PubMed1989

Gastro-oesophageal reflux disease, an important cause of angina-like chest pain.

Angina-like chest pain in patients with coronary arteriography raises difficult diagnostic problems. The pain may be due to microvascular angina (or syndrome X). It is postulated that during the typical angina of these patients, the ST segment shifts on exercise electrocardiogram and the abnormal electrophysiologic tests on cardiac catheterisation are due to a decreased coronary flow reserve related to microvascular abnormalities. Angina-like chest pain may also be of oesophageal origin. Gastro-oesophageal reflux and oesophageal motility disorders are the two commonest oesophageal abnormalities held responsible for the pain. Recent observations suggest that sensitivity of the oesophagus to several stimuli may be another important cause of chest pain of oesophageal origin. This condition is called irritable oesophagus. Twenty-four hour pH- and pressure-recording is at present the best way to reach a specific diagnosis about the nature of the oesophageal abnormality.

Angina Pectoris↗
PubMed1989

Sequential dacarbazine chemotherapy followed by recombinant interleukin-2 in metastatic melanoma. A pilot multicentre phase I-II study.

Between April 1988 and August 1989, 30 melanoma patients were entered in a multicentre Phase II study of dacarbazine (DTIC) 850 mg/m2 i.v. bolus on day 1, and recombinant interleukin-2 (rIL-2) (Cetus) 18 x 10(6) IU/m2/day i.v. continuous infusion on days 4-9. Six treatment cycles were given: the first two at an interval of 13 days, and further cycles at intervals of 20 days. Twenty patients are currently evaluable for toxicity and 18 for response. Two of these patients presented with metastatic intraocular melanoma. Median age was 48 years (range 18-83), and median Karnofsky index was 100 (range 80-100). Four patients had received prior radiotherapy and one had received prior immunotherapy. Seventeen patients received two cycles of treatment and nine patients received three or more cycles. Four patients responded (22%): two complete remissions and two partial remissions. Stable disease was seen in six patients (33%). Responses occurred in the lung, skin, spleen and lymph nodes. Seventy-five percent of the patients received the full dose of rIL-2 during cycle 1, whilst only 2 out of 9 (22%) received the planned dose on the third cycle. Rebound lymphocytosis of 5.3 x 10(3)/L (range 1.2-18.1) occurred 24-48 h after rIL-2, but was not predictive for response. Currently, there is no evidence that pretreatment with DTIC impacts negatively on the rIL-2-stimulated lymphocyte proliferation. The toxicity profile of this treatment regimen did not differ significantly from that already described for similar regimens of rIL-2. However, in this interim analysis, there was a trend for a higher percentage of patients (25%) to experience severe weight gain (greater than 10%). This study shows that this treatment regimen is active in metastatic melanoma, with acceptable toxicity. Further research will focus on using other chemotherapeutic agents and/or other biological response modifiers (e.g. interferons, tumour necrosis factor) in combination with rIL-2.

Adolescent↗
PubMed1988

Termination of early pregnancy by the 3 beta-hydroxysteroid dehydrogenase inhibitor epostane.

Progesterone is essential to sustain pregnancy in the first eight weeks. Its synthesis requires the enzyme 3 beta-hydroxysteroid dehydrogenase (3-HSD). We tested the efficacy of an orally administered 3-HSD inhibitor, epostane, in terminating unwanted early pregnancy. Fifty women in the fifth through eight weeks of pregnancy took epostane (200 mg orally every six hours) for seven days. By day 14, pregnancy had been terminated in 42 of the 50 patients (84 percent). Eight women (16 percent) did not abort and underwent dilation and curettage. Vaginal blood loss occurred on average on the third day of epostane treatment, and abortion on the fifth day. Two patients had incomplete abortions; one required a transfusion because of blood loss. Nausea was frequent (in 86 percent), but 76 percent of the participants concluded that epostane was preferable to dilation and curettage. The mean (+/- SD) pretreatment progesterone level (76 +/- 16 nmol per liter) decreased by day 7 (to 16 +/- 11 nmol per liter) and day 14 (to 10 +/- 9 nmol per liter) in those who aborted; levels of human chorionic gonadotropin also decreased from the mean at base line (73 +/- 72 kIU per liter) to 18 +/- 7 kIU per liter on day 7 and 9 +/- 5 kIU per liter on day 14. In those who did not abort after epostane treatment, progesterone levels decreased only slightly by day 7 (to 52 +/- 21 nmol per liter) and rose again (to 81 +/- 18 nmol per liter) by day 14. Among women who responded to epostane, normal menstrual periods had resumed by day 42 after the beginning of treatment in 72 percent. We conclude that epostane taken orally is an effective and safe method for the noninvasive termination of undesired early pregnancy.

3-Hydroxysteroid Dehydrogenases↗
PubMed1988

Cisapride stimulates propulsive motility patterns in human jejunum.

The effects of cisapride on upper gut motility were studied in seven healthy volunteers by means of a novel intraluminal electromyographic technique in a placebo-controlled study. In the interdigestive state, cisapride (10 mg intravenous bolus injection) markedly increased the number of spike bursts. The most obvious effect was observed during the first 5-min period when a nonmigrating phase-3-like activity (stationary phase 3) occurred, which lasted for 2.6 +/- 0.4 min. This initial pattern was followed by an intense phase 2 activity, characterized by a 10-fold increase in the number of groups of repetitive spike bursts and a sixfold increase in the number of ultrarapid single propagated spike bursts (ultrarapid peristaltic rushes). Cisapride induces in the human upper gut a remarkable pattern of aborally propagated (peristaltic) contractions, which are very likely responsible for the active propulsion of intestinal contents in the interdigestive state.

Adult↗