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Biomedical subjects

R Widmer

Publications and source records attributed to R Widmer.

At least 19 recordsLinked to original sources
PubMed1999

Dysmotility of the small intestine in achalasia.

During recent years there has been increasing evidence for extraoesophageal dysfunction in achalasia. The aim was to investigate whether motility of the small intestine is abnormal in achalasia. Thirteen patients (eight men, five women) aged 52 (33-85) years were studied. They had all previously undergone treatment with pneumatic balloon dilatation and were free of dysphagia when examined. Ambulatory 24-h motility was recorded in the upper jejunum under standardized caloric intake with a digital datalogger and catheter-mounted pressure transducers located beyond the ligament of Treitz. Visual analysis was performed by two observers and data underwent quantitative analysis of phasic contractile events using a computer program. Normal values were obtained from 50 healthy controls. In the fasting state, a complete loss of cyclic MMC activity (n = 2), an abnormally prolonged phase II (n = 2) and disturbances in the aboral migration of phase III (n = 5) were observed. Postprandial motor response was absent (n = 2) or frequently showed a contraction frequency below the normal range (n = 5). Further abnormalities consisted in hypomotility during phase II (n = 3) and in a reduced frequency of migrating clustered contractions in the fasting (n = 2) or postprandial state (n = 2). In addition, motor events not present in any healthy subject, giant migrating contractions (n = 5), retrograde clustered contractions (n = 6) and repetitive retrograde contractions (n = 3) were identified. Each patient exhibited findings out of the range of normal. Dysmotility of the proximal small intestine is present in achalasia.

Adult↗
PubMed1998

Position-independent expression of a human nerve growth factor-luciferase reporter gene cloned on a yeast artificial chromosome vector.

Two yeast artificial chromosomes containing the entire human nerve growth factor gene were isolated and mapped. By homologous recombination a luciferase gene was precisely engineered into the coding portion of the NGF gene and a neomycin selection marker was placed adjacent to one of the YAC telomeres. Expression of the YAC-based NGF reporter gene and a plasmid-based NGF reporter gene were compared with the regulation of endogenous mouse NGF protein in mouse L929 fibroblasts. In contrast to the plasmid-based reporter gene, expression and regulation of the YAC-based reporter gene was independent of the site of integration of the transgene. Basic fibroblast growth factor and okadaic acid stimulated expression of the YAC transgene, whereas transforming growth factor-beta and dexamethasone inhibited it. Although cyclic AMP strongly stimulated production of the endogenous mouse NGF, no effect was seen on the human NGF reporter genes. Downregulation of the secretion of endogenous mouse NGF already occurred at an EC50 of 1-2 nM dexamethasone, but downregulation of the expression of NGF reporter genes occurred only at EC50 of 10 nM. This higher concentration was also required for upregulation of luciferase genes driven by the dexamethasone-inducible promoter of the mouse mammary tumor virus in L929 fibroblasts.

Animals↗
PubMed1998

Discrimination of irritable bowel syndrome by non-linear analysis of 24-h jejunal motility.

Conventional analysis of ambulatory longterm manometry of the small intestine has revealed abnormalities in patients with the irritable bowel syndrome (IBS). The aim was to use methods from non-linear dynamics, in particular the concepts of symbolic dynamics and entropy, in order to discriminate motility in IBS from healthy subjects. 24-h jejunal motility was recorded in 30 IBS patients and 30 healthy subjects. Computerized analysis of contraction amplitudes and intercontractile intervals was performed. Both time series were analysed by symbolic dynamics and entropy to quantify the degree of randomness inherent in the signal. During phase II IBS patients exhibited significantly increased entropies for the intercontractile intervals (IBS: 0.978 +/- 0.016, C: 0.965 +/- 0.020, P = 0.004) and for the contraction amplitudes (IBS: 0.978 +/- 0.008, C: 0.970 +/- 0.026, P = 0.05) compared with healthy subjects. In addition, a significantly increased mean contraction amplitude (mmHg) was found in patients (IBS: 25.2 +/- 4.8, C: 22.2 +/- 3.1, P = 0.003). Considering a combination of both parameters, a diagnostic accuracy of 82% was achieved. We conclude that phase II motility of the small intestine is more random in IBS than in health. Symbolic dynamics seems to be a promising new concept for the analysis of long-term gastrointestinal motility recordings.

Adult↗
PubMed1997

Normal platelets and megakaryocytes are produced in vivo in the absence of thrombopoietin.

Thrombopoietin (TPO) has been established as the major regulator of megakaryocyte and platelet production. In vitro and in vivo studies have demonstrated that TPO affects both megakaryocyte proliferation and maturation. In vitro, TPO has been reported to be essential for full development of megakaryocytes and platelets. These studies are in contrast to results observed in vivo in mice deficient in the TPO or c-mpl gene (TPO-/- and c-mpl-/-). Both TPO-/- and c-mpl-/- mice exhibit a 90% reduction in megakaryocyte and platelet levels. But even with this small number of circulating platelets, these mice do not have any excessive bleeding. Ultrastructural analysis indicates that platelets and megakaryocytes present in the knockout mice are morphologically normal. Characterization of platelet function shows that platelets from knockout mice are functionally identical to the wild-type platelets as measured by upregulation of 125I-fibrinogen binding to platelets in response to adenosine diphosphate (ADP) stimulation and by platelet attachment to the immobilized extracellular matrix proteins, collagen and von Willebrand factor (vWF). These results demonstrate that in vivo, TPO is required for the control of megakaryocyte and platelet number but not for their maturation. Other factors with megakaryocytopoietic activity may be able to compensate for the maturational role of TPO and lead to the formation of normal megakaryocytes and platelets in TPO-/- and c-mpl-/- mice.

Animals↗
PubMed1997

Metabolism of thrombopoietin (TPO) in vivo: determination of the binding dynamics for TPO in mice.

Previous in vivo studies have established that plasma thrombopoietin (TPO) levels are regulated by binding to c-Mpl on platelets and that, in vitro, platelets bind and degrade TPO. To determine if the in vivo metabolism of TPO was specific and saturable, we injected normal CD-1 mice IV with trace amounts of 125I-rmTPO with or without a saturating concentration of rmTPO. The amount of radioactivity present in the spleen, blood cell fraction, platelet fraction, tibia/fibula, and femur was significantly greater in the mice receiving 125I-rmTPO alone. Conversely, the amount of radioactivity present in the plasma was significantly greater in the mice receiving both 125I-rmTPO and rmTPO, thus suggesting the uptake of rmTPO by the spleen, platelets, and bone marrow in vivo was saturable. Platelet and spleen homogenates from animals receiving 125I-rmTPO alone showed a degradation pattern of 125I-rmTPO similar to that observed in vitro using mouse platelet rich plasma. To determine the in vivo binding dynamics for rmTPO, mice were injected with 125I-rmTPO alone or with increasing concentrations of rmTPO; spleen and blood cell-associated radioactivity was determined at 2 hours postinjection. A 4-parameter curve fit of the data indicated that the "in vivo binding affinity" for rmTPO was approximately 6.4 microg/kg. These data indicate that after a dose of approximately 6.4 microg/kg, 50% of all c-Mpl receptors will be saturated with rmTPO. Electron microscopy indicated that radioactivity was present bound to and within megakaryocytes and platelets in both sternum and spleen and platelets in circulation. Together these data demonstrate that in vivo, 125I-rmTPO is mainly metabolized by platelets and to a small extent by cells of the megakaryocyte lineage, via a specific and saturable mechanism.

Animals↗
PubMed1997

Human platelets as a model for the binding and degradation of thrombopoietin.

Recent studies have shown that plasma thrombopoietin (TPO) levels appear to be directly regulated by platelet mass and that removal of plasma TPO by platelets via binding to the c-Mpl receptor is involved in the clearance of TPO in rodents. To help elucidate the role of platelets in the clearance of TPO in humans, we studied the in vitro specific binding of recombinant human TPO (rhTPO) to human platelet-rich plasma (PRP), washed platelets (WP), and cloned c-Mpl. Using a four-parameter fit and/or Scatchard analysis, the approximate affinity of rhTPO for its receptor, which was calculated from multiple experiments using different PRP preparations, was between 128 and 846 pmol/L, with approximately 25 to 224 receptors per platelet. WP preparations gave an affinity of 260 to 540 pmol/L, with approximately 25 to 35 receptors per platelet, and erythropoietin failed to compete with 125I-rhTPO for binding to WP. Binding and dissociation studies conducted with a BiaCore apparatus yielded an affinity of 350 pmol/L for rhTPO binding to cloned c-Mpl receptors. The ability of PRP to bind and degrade 125I-rhTPO was both time- and temperature-dependent and was blocked by the addition of excess cold rhTPO. Analysis of platelet pellets by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that 125I-rhTPO was degraded into a major fragment of approximately 45 to 50 kD. When 125I-rhTPO was incubated with a platelet homogenate at pH = 7.4, a degradation pattern similar to intact platelets was observed. Together, these data show that human platelets specifically bind rhTPO with high affinity, internalize, and then degrade the rhTPO.

Adult↗
PubMed1997

Ambulatory long-term jejunal manometry in diabetic patients with cardiac autonomic neuropathy.

Concerning alteration of small bowel motility in diabetic patients with autonomic neuropathy controversial data were obtained with stationary manometry and over a limited period of time. The aim of our study was to examine ambulatory 24 h jejunal motility in 15 diabetic patients with cardiac autonomic neuropathy compared with data obtained in 50 healthy controls. Twenty-four hour motility was recorded in the proximal jejunum with a portable datalogger and tube-mounted miniature pressure sensors. Diurnal and nocturnal fasting motility and the motor response to a standardized evening meal of 600 kcal were evaluated by visual and computer-aided analysis. The following abnormalities were found during fasting motility (n = number of patients): absence of phase III over 24 h (n = 2), retrograde migration or simultaneous occurrence of phase III (n = 5). During postprandial motility irregular bursts with tonic baseline elevation (n = 3) and contraction frequencies below the range of controls (n = 8) occurred. Furthermore patients exhibited an inversion of the normal relationship between phase I and phase II during nocturnal MMC-cycles, and discrete clustered contractions were diminished (P < 0.01) in the fasting and digestive state. All patients showed at least one abnormal manometric finding. We conclude that small bowel motility in diabetic autonomic neuropathy is characterized by disturbances in the generation and aboral migration of phase III, an altered circadian variability of the MMC cycle and by postprandial hypomotility.

Adult↗
PubMed1996

Effect of intestinal resection on human small bowel motility.

BACKGROUND: Few data are available on adaptive changes of human small bowel motility after intestinal resection. AIM: To characterise jejunal motility after extensive and limited distal intestinal resection. METHODS: Seven patients with a short bowel syndrome after total ileal and partial jejunal resection (residual jejunal segments between 60 and 100 cm) and six patients with limited distal ileal resection (resected segment between 30 and 70 cm) underwent ambulatory 24 hour jejunal manometry 15 (6-24) months after the operation. Normal values were obtained from 50 healthy subjects. Fasting motility and the motor response to a 600 kcal solid meal were analysed visually and by a computer program. RESULTS: Limited ileal resection did not result in changed jejunal motility. After extensive distal resection, patients had a significantly shorter migrating motor complex (MMC) cycle and a significantly shorter duration of the postprandial motor response compared with controls (p < 0.005). Intestinal resection had no influence on jejunal contraction frequency and amplitude and did not lead to any abnormal motor pattern. CONCLUSION: Extensive distal resection of the small intestine produces distinct abnormalities of fasting and postprandial motility in the intestinal remnant. The shortening of digestive motility and the increased frequency of MMC cycling could contribute to malabsorption and diarrhoea in the short bowel syndrome.

Adult↗
PubMed1996

Ambulatory 24-hour jejunal motility in diarrhea-predominant irritable bowel syndrome.

BACKGROUND: Whether small-bowel motility is abnormal in the irritable bowel syndrome (IBS) is a controversy at present. The aim of our study was to compare ambulatory long-term jejunal motility in 35 IBS patients with predominant diarrhea to normal values obtained in 50 healthy controls. METHODS: Twenty-four-hour motility was recorded in the proximal jejunum with a portable datalogger and tube-mounted miniature pressure sensors. Fasting motility in the waking (W) and sleeping (S) state and the motor response to a standardized evening meal of 600 kcal underwent visual and computer-aided analysis. RESULTS: Fasting motility in patients showed migrating motor complex (MMC) cycles of normal length and composition. Uninterrupted runs of discrete clustered contractions during phase II (W) occurred in 57% of patients and 52% of controls but had a significantly longer duration in patients (33 +/- 5 versus 19 +/- 7 min; p < 0.005). During phase II (W) IBS patients had an increase in aborally propagated contractions (41 +/- 2% versus 35 +/- 2%; p < 0.01) and higher contraction amplitudes (26.3 +/- 0.8 versus 23.0 +/- 0.5 mm Hg; p < 0.01). Similar differences were obtained during postprandial motility (47 +/- 3% versus 39 +/- 3%; p < 0.01, and 25.9 +/- 0.9 versus 23.8 +/- 0.05 mm Hg; p < 0.02). In three patients (8.6%) disturbed aboral migration of phase III and irregular burst activity, manometric features of chronic idiopathic intestinal pseudo-obstruction, were identified. Whereas 57% of patients had an entirely normal 24-h manometry, 43% had at least one finding not present in any healthy control. CONCLUSION: Small-intestinal motility is frequently but not universally abnormal in diarrhea-predominant IBS. The abnormal manometric findings are heterogeneous and range from subtle quantitative changes to severe qualitative abnormalities resembling chronic idiopathic intestinal pseudo-obstruction in a small subset of patients.

Adult↗
PubMed1996

Distribution of DNA and alginate in purulent cystic fibrosis sputum: implications to pulmonary targeting strategies.

Cystic fibrosis (CF) patients frequently experience recurring airway infections characterized by thick, viscous sputum. The consistency and nature of these purulent secretions may produce a significant barrier to the successful delivery of drugs and gene therapy vectors designed to treat CF. We have carried out a series of in vitro studies to determine the distribution of two macromolecular components typically present in purulent sputum, bacterial alginate and neutrophil-derived DNA. Sputum samples were obtained from hospitalized CF patients. DNA and alginate were disrupted, respectively, by the in vitro additions of human recombinant deoxyribonuclease I (rhDNase) or alginate lyase prepared from a mucoid strain of Pseudomonas aeruginosa. N-acetyl-L-cysteine (acetylcysteine) was similarly used to collapse the mucin matrix of these samples for comparison. Using a centrifugation-based rheological method known as the compaction assay, a greater maximal response was observed for rhDNase compared to alginate lyase treatment. A simultaneous addition of these enzymes to purulent sputum produced an additive compaction response. Electron microscopy was used to identify alginate and DNA components within the mucin matrix of sputa and to evaluate changes following treatment with high concentrations of alginate lyase or rhDNase. DNA was more widely distributed throughout purulent samples than alginate. Differences in the distribution of DNA and alginate may explain, at least in part, the larger compaction response to rhDNase versus alginate lyase treatment. An improved understanding of DNA and alginate distribution within purulent CF sputum may lead to improvements in drug and vector delivery to airway epithelial cells.

Alginates↗
PubMed1995

Use of the Escherichia coli chromosomal DHFR gene as selection marker in mammalian cells.

The folA gene, the chromosomal dhfr gene of Escherichia coli, was engineered for expression in mammalian cells. In contrast to plasmid-derived bacterial dhfr genes previously used as selection markers in mammalian cells, the folA gene product is inhibitable by methotrexate (MTX) and trimethoprim (TMP). Therefore, this dhfr may present an alternative to mammalian dhfr species currently used as amplifiable selection markers. Transfected E. coli folA dhfr could complement the lack of endogenous DHFR in Chinese hamster ovary (CHO) cells lacking a functional dhfr gene. Both MTX and TMP inhibited growth of E. coli folA dhfr-transfected CHO cells. Expression of E. coli folA DHFR could be visualized by incubating the transfected cells with a fluorescent methotrexate derivative (F-MTX). Binding of F-MTX to E. coli folA DHFR was inhibitable as by both MTX and TMP, whereas MTX but not TMP blocked binding of F-MTX to recombinant mouse DHFR.

Animals↗
PubMed1995

Production of the chimerical plasminogen activator K2tu-PA in CHO cells.

Development of a CHO cell-based production system for the hybrid plasminogen activator K2tu-PA is described. Using the major immediate-early promoter of mouse cytomegalovirus (MCMV) transient and stable expression levels were 3-10-fold higher than those obtained with several other strong promoters. Splicing and polyadenylation signals from the rabbit beta-globin gene were used downstream of the DNA segment coding for K2tu-PA. The strong enhancer moiety of the MCMV promoter also stimulated strongly the promoter of the dihydrofolate reductase (DHFR) gene, placed adjacently for selection/gene amplification purposes. One construct with opposing K2tu-PA and DHFR RNA transcripts yielded the highest expression level with a single copy of the plasmid, but K2tu-PA expression was consistently lost after amplification of such genes, possibly as a result of the formation of antisense RNA. With other constructs, K2tu-PA production leveled off at 6.5 micrograms per million cells per day despite a high gene copy number. This was due to a combination of inefficient mRNA translation and mRNA instability, caused by elements from the untranslated portions of tissue-type and urokinase-type plasminogen activator cDNA which were included in the expression vector. After elimination of these inhibitory DNA segments, 4-5-times higher expression levels were reached.

Animals↗
PubMed1994

Effect of the quaternary ammonium compound trospium chloride on 24 hour jejunal motility in healthy subjects.

This study aimed to record 24 hour jejunal motility in healthy ambulant subjects and to analyse changes in motility caused by the oral administration of an anticholinergic agent, the quaternary ammonium compound, trospium chloride. In a placebo-controlled, double blind crossover trial, 24 hour jejunal motility was recorded in 12 healthy volunteers, aged 25 (21-30) years, using a digital data logger connected to two strain-gauge transducers mounted 20 cm apart in a flexible nasojejunal catheter. A computer program was developed to determine contraction parameters. Trospium chloride (15 mg orally thrice daily) prolonged the duration of irregular contractile activity after meals (p < 0.02) and reduced its contraction frequency and amplitude (p < 0.001). In the fasting state, the cycle length of the migrating motor complex was prolonged (p < 0.01) by an extended phase I (p < 0.025). Phase III was shortened (p < 0.005) and showed a slower aboral migration velocity (p < 0.005). Clustered contractions were less frequent during postprandial and fasting periods (p < 0.01). Runs of clustered contractions were completely absent with trospium chloride. Digital manometry was useful for long term recordings of jejunal motility and enabled the motor effects of an anticholinergic agent to be characterised in ambulant subjects.

Adult↗
PubMed1994

Computerized analysis of ambulatory long-term small-bowel manometry.

BACKGROUND: Ambulatory long-term manometry is increasingly being used to study small-bowel motility. This study aimed to develop computer-aided data analysis including the elimination of artefacts, identification of individual phasic contractions, and analysis of aboral propagation. METHODS: Data processing included low-pass filtering, base-line adaptation, cross-comparison of channels, and application of threshold values for contraction parameters. Automated analysis was validated by a visual reference standard. RESULTS: Artefacts were related to cardiovascular and respiratory activity, changes in body posture, and contractions of the abdominal wall. Automated recognition of contractions reached a sensitivity of 92% and a positive predictive value of 88% compared with the visual standard. Mean contraction amplitude and duration of computer analysis were 96% and 93%, respectively, of the visually obtained values. Propagation analysis under ambulatory conditions showed good agreement with previous results by stationary recordings. CONCLUSIONS: Computerized analysis provided valid and reproducible data on small-bowel phasic contractile events and propagative activity by digital long-term manometry.

Adult↗
PubMed1987

Adjuvant intravesical chemotherapy of superficial bladder cancer with monthly doxorubicin or intensive mitomycin. A comparison of two consecutive series.

120 patients with the first occurrence of TNM stage Ta or T1 bladder carcinoma were given adjuvant intravesical treatment in 2 consecutive series. The first 60 received doxorubicin monthly for 6 months, then on the 9th and 12th month following surgery. The second series was given mitomycin weekly for 2 months, then monthly to the end of the first year. Median follow-up is 48 months in the first series and 15 in the second. In the doxorubicin group, 28 patients had recurrences. The recurrence rate is 1.86/100 patient-months. Seventeen of these first relapses occurred within the first year. In the 'intensive' mitomycin series, where 36 patients were observed for 12 months or more, 3 relapsed. The recurrence rate to date is 0.35. The relapse-free survival probability at 12 months is 75% in the first series and 93% in the second. Treatment was stopped due to toxicity in 4 patients in the doxorubicin group and in 10 of the mitomycin group.

Administration, Intravesical↗