Biomedical subjects

E H Jansen

Publications and source records attributed to E H Jansen.

At least 19 recordsLinked to original sources

PubMed1998

Hypergastrinaemia during long-term omeprazole therapy: influences of vagal nerve function, gastric emptying and Helicobacter pylori infection.

AIM: elucidate the mechanisms that lead to severe hypergastrinaemia during long-term omeprazole therapy for gastro-oesophageal reflux disease (GERD). PATIENTS AND METHODS: A total of 26 GERD patients were studied during omeprazole maintenance therapy. Twelve patients with severe hypergastrinaemia (gastrin > 400 ng/L) were compared with 14 control patients (gastrin < 300 ng/L). Helicobacter pylori serology and a laboratory screen were obtained in all patients. Gastric emptying was scored by the evidence of food remnants upon endoscopy 12 h after a standardized meal. Gastric antrum and corpus biopsies were analysed for histological parameters, as well as somatostatin and gastrin concentrations. All patients underwent a meal-stimulated gastrin test and the hypergastrinaemia patients also underwent a vagal nerve integrity assessment by pancreatic polypeptide testing (PPT). RESULTS: Severe hypergastrinaemia patients had a longer duration of treatment (80 vs. 55 months; P = 0.047) and were characterized by a higher prevalence of H. pylori infection (9/12 vs. 2/14, P = 0.004), corpus mucosal inflammation and atrophic gastritis (P < 0.04). This was reflected in lower serum pepsinogen A concentrations (mean +/- S.E.M. 53.6 +/- 17.9 vs. 137 +/- 16.0 mg/L, P = 0.03), pepsinogen A/C ratio (1.8 +/- 0.3 vs. 4.1 +/- 0.6, P = 0.005) and mucosal somatostatin concentrations (2.75 +/- 0.60 vs. 4.48 +/- 1.08 mg/g protein, P = 0.038). Two patients in the hypergastrinaemia group had signs of delayed gastric emptying, but none in the normogastrinaemia group did (P = N.S.). In addition, both groups had a normal meal-stimulated gastrin response. CONCLUSION: Severe hypergastrinaemia during omeprazole maintenance therapy for GERD is associated with the duration of therapy and H. pylori infection, but not with abnormalities of gastric emptying or vagal nerve integrity.

Aged↗

PubMed1997

Omeprazole as a diagnostic tool in gastroesophageal reflux disease.

OBJECTIVE: To determine the diagnostic value of empirical treatment with omeprazole in the diagnosis of gastroesophageal reflux disease (GERD). METHODS: Patients with symptoms suggestive of GERD underwent upper gastrointestinal endoscopy and 24-h esophageal pH monitoring. Patients with reflux esophagitis grade 0 or 1 were included in the study and were randomized to double-blind treatment with either 40 mg omeprazole or placebo o.m. The effect of treatment was evaluated after 1 and 2 wk with a symptom questionnaire with a four-grade Likert scale, and symptomatic response outcome was compared with the results of 24-h pH-metry. RESULTS: Ninety-eight patients were included; however, 13 were excluded from the final analysis because of protocol violation. Of the remaining 85 patients, 54 had no signs of esophagitis at endoscopy, and 31 had esophagitis grade 1. The pH registration showed pathological gastroesophageal reflux in 47 patients (55%). Forty-one patients were randomized to treatment with omeprazole and 44 to placebo. There was a significant correlation between the pH registration result and response to omeprazole (p = 0.04, chi2), but not to placebo (p = 0.16). With pH-metry as the gold standard, the omeprazole test had positive and negative predictive values of 68% and 63%, respectively, for the diagnosis of GERD. When the omeprazole test was used as the gold standard, the positive and negative predictive values of pH monitoring were 68 % and 63 %, respectively. Similar sensitivity was found when the pH-metry was compared with presence of esophagitis. CONCLUSION: Determination of the symptomatic response to 40 mg of omeprazole for 14 days is a simple and inexpensive tool for the diagnosis of GERD, with a sensitivity and specificity comparable to 24-h pH monitoring.

Adult↗

PubMed1996

Advances in sample preparation, electrophoretic separation and detection methods for rat cytochrome P450 enzymes.

A limited overview is given of the separation and detection of specific cytochrome P450 enzymes of the rat. Separation methods include group-specific chromatographic separation and electrophoretic separation in and elution from polyacrylamide gels. Detection methods that are considered include enzymatic analysis with and without chromatographic step using liquid chromatography and immunochemical methods following separation of the cytochrome P450 enzymes by polyacrylamide gel electrophoresis (Western blotting). The advantages and limitations of the various methods have been compared and discussed.

Animals↗

PubMed1995

A new physiological biomarker for nitrate exposure in humans.

After toxicological studies with nitrate/nitrite in rats it was observed with nuclear magnetic resonance that N-methylnicotinamide (NMN), a metabolite of tryptophan was increased. The use of NMN as a biomarker for nitrate/nitrite exposure was investigated further in additional experiments with rats and in a human study with volunteers. Rats have been exposed to 36 mmol KCl, KNO2 or KNO3 per 1 tap water for 13 weeks. In general, the animals receiving KNO2 showed a statistically significant (P < 0.01) 2-fold increase in NMN compared with the KCl group. This increase was observed after a relatively high exposure (about 800 mg/kg body wt./day). It was also noticed that the initial increase in urinary NMN concentrations decreased after prolonged exposure for 12 weeks. To investigate the induction of urinary NMN in humans, an experiment has been performed in which 8 volunteers received a single oral dose of sodium nitrate, corresponding with 10 mg NaNO3/kg body wt./day (2 times the acceptable daily intake for nitrate). A rapid increase of urinary NMN (up to 6-fold) was observed in 4 volunteers. In the other 4 volunteers the urinary NMN concentration did hardly react. When the experiment was repeated with the same volunteers, it was remarkable to see that in this experiment all volunteers showed the same individual response on urinary NMN as in the first experiment. It is concluded that NMN can possibly be a good biomarker for the internal nitrite exposure of humans, but further studies are necessary to assess its value.

Animals↗

PubMed1995

Proteinuria, lipoproteins and renal apolipoprotein deposits in uninephrectomized female analbuminemic rats.

To elucidate the pathogenetic role of hyperlipidemia per se in the development of glomerulosclerosis, severely hyperlipidemic female analbuminemic rats (NAR) and mildly hyperlipidemic male NAR were studied for a period of 37 weeks after uninephrectomy (UNX). Plasma cholesterol increased from 6.3 +/- 0.4 (week 4) to 11.9 +/- 0.6 mmol/liter (week 37) in the female NAR, and from 4.3 +/- 0.1 to 6.4 +/- 0.5 mmol/liter in the male NAR in the same period. Plasma protein concentration was also consistently higher in female NAR (60 +/- 1 g/liter) as compared to male NAR (52 +/- 1 g/liter). Plasma viscosity was higher in female NAR than in male NAR, but there were no differences in blood viscosity. Proteinuria increased progressively in the UNX female NAR from 25 weeks after surgery, reaching a final value of 141 +/- 37 mg/day. No proteinuria occurred in the UNX male NAR (final value 15 +/- 2 mg/day). Glomerular capillary pressure, measured prior to the onset of proteinuria, was not significantly different in UNX female NAR and UNX male NAR. At the end of the study glomerulosclerosis and lipid deposition was only found in the UNX female NAR. Throughout the study hyperfiltration and hyperperfusion, relative to the one-kidney clearances of the sham-operated (2K) animals, were not different in UNX male and female NAR. No differences were observed in blood pressure. Hypertrophy, evaluated by glomerular diameters, was less pronounced in UNX female NAR (174 +/- 3 microns) than in UNX male NAR (190 +/- 7 microns). Glomerular diameters in 2K female and male NAR were similar (respectively 158 +/- 2 and 157 +/- 4 microns). Plasma apo B levels were similar (2K female NAR: 204 +/- 8 U; 2K male NAR 204 +/- 13 U), but cholesterol and triglyceride content of apo B-containing lipoproteins, namely VLDL, IDL and LDL, was increased twofold in the female NAR as compared to the male NAR, implying a larger particle size in the female NAR. Deposition of apo B and apo E was observed in the glomerular mesangium of UNX female NAR, particularly in sclerotic lesions. Glomerular apo A-I deposits were localized primarily in visceral epithelial cells and were not associated with sclerotic lesions. The development of proteinuria and glomerulosclerosis after UNX in female NAR but not in male NAR may depend upon differences in plasma lipoprotein composition, but is apparently not related to differences in whole kidney hyperfiltration and hyperperfusion, glomerular capillary pressure, or blood viscosity.

Animals↗

PubMed1993

Plasma lipoproteins and renal apolipoproteins in rats with chronic adriamycin nephrosis.

The relation between plasma lipoprotein composition and renal apolipoprotein deposition was studied in nephrotic rats in which stable renal function had been monitored for 7 months after a single low dose of adriamycin (ADR, 3 mg/kg). Proteinuria was observed 3 weeks after ADR and increased progressively up to about 0.5 g/day (versus 0.07 g/day in controls; P < 0.001), while the creatinine clearance remained stable at about 80% of control values. Hypercholesterolaemia was observed 6 weeks after ADR, and increased progressively up to 7.0 +/- 1.0 mmol/l (versus 2.3 +/- 0.1 mmol/l in controls; P < 0.001). Cholesterol was primarily located in LDL2 and HDL2 lipoproteins. Plasma apolipoprotein (apo) A-I increased by more than 400% in the nephrotic rats (P < 0.001). Apo B and apo E increased by about 60% (P < 0.01), whereas apo A-IV remained unchanged. Focal sclerotic lesions in glomeruli had an incidence of 50 +/- 10% in ADR rats versus 2 +/- 1% in controls (P < 0.001). Immunohistochemistry revealed apo A-I and apo A-IV in the visceral epithelium. Apo E immunoreactivity and lipid deposits were observed in focal glomerular sclerotic lesions of ADR rats. Neither apolipoproteins nor lipids were detected in glomeruli of controls. Proximal tubular localization of apolipoproteins was extensive for apo A-I, apo A-IV and apo E, but no differences were observed in tubular deposition of apolipoproteins between ADR and control rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Liquid chromatographic purification and detection of anabolic compounds.

The role of liquid chromatography within methods of analysis for steroids, related compounds and beta-agonists in biological samples is discussed. Special attention is given to the application of liquid chromatography in sample preparation and extract clean-up. Different forms of liquid chromatography, including immunoaffinity chromatography, are compared and evaluated. Methods for confirmation based on gas chromatography-mass spectrometry and cryotrapping Fourier transform infrared spectrometry are discussed.

Adrenergic beta-Antagonists↗

PubMed1992

High-performance liquid chromatographic separation and detection methods for anabolic compounds.

The role of high-performance liquid chromatography (HPLC) in methods of analysis for anabolic compounds in biological samples is reviewed. Special attention is given to both the separation and detection of anabolic compounds. A distinction is made between on-line detection systems, such as ultraviolet detection and diode-array detection, and off-line detection methods with special emphasis on immunochemical detection methods using non-isotopic labels. A number of applications are given to elucidate the possibilities of HPLC in the analysis of anabolic compounds.

Anabolic Agents↗

PubMed1992

Detection of the enzymatic activity of cytochrome P-450 enzymes by high-performance liquid chromatography.

The reactions catalysed by the various cytochrome P-450 enzymes are reviewed with respect to the analysis of products by high-performance liquid chromatography (HPLC). Especially biotransformation reactions of purified cytochrome P-450 enzymes in a reconstituted system and in microsomes mainly of rat liver origin are considered. Emphasis is put on the specificity of product formation due to the individual isozymes of cytochrome P-450. It is shown that the presence of eight cytochrome P-450 isozymes can be monitored and determined by specific product formation after HPLC analysis, which is an important parameter in toxicological studies.

Animals↗

PubMed1991

Comparison of high-performance liquid chromatographic detection methods for thyronine and tyrosine residues in toxicological studies of the thyroid.

Four high-performance liquid chromatographic methods for the detection of thyroid hormones (iodinated thyronines) and precursors (iodinated tyrosines) have been developed and evaluated. Two methods consist of direct determination of the parent compounds with detection at ultraviolet wavelength (230 nm) and with electrochemical detection. The two other methods consist of a pre-column derivatization (with fluorenylmethyl chloroformate and dabsyl chloride) prior to high-performance liquid chromatographic analysis. The various methods were evaluated based on their practical use and sensitivity. The method with direct ultraviolet detection turned out to be the most practical method. With this method analyses of thyroid homogenates have been performed from rats from a toxicological experiment.

Animals↗

PubMed1991

Measurement of enzyme activities of cytochrome P-450 isoenzymes by high-performance liquid chromatographic analysis of products.

A method is described for the qualitative and quantitative determination of the isoenzymes of cytochrome P-450 from rat liver microsomes. Microsomes are incubated with the endogenous steroid 17 beta-testosterone, which results in the formation of a number of stereo-specific hydroxylation products of testosterone. The hydroxylated products were identified using standards or by comparison with data from the literature. The products can be analysed by reversed-phase gradient high-performance liquid chromatography. The assay has been optimised for pH, linearity and time of incubation. An evaluation of the assay was performed for different kinds of microsomes, microsomal dilution and specificity for particular cytochrome P-450 isoenzymes.

Animals↗

PubMed1991

High-performance liquid chromatographic investigation of product formation in the horseradish peroxidase-enhanced chemiluminescence of luminol with different enhancers.

A reversed-phase high-performance liquid chromatographic method for the investigation of the chemiluminescence-producing oxidation of luminol by the enzyme horseradish peroxidase is presented. Both the kinetics and the mechanism of product formation can be monitored. Special attention is paid to the mechanism of enhancement of the chemiluminescence by phenolic compounds, such as p-iodophenol, p-hydroxycinnamic acid and 6-hydroxybenzothiazole. The function of the enhancers was elucidated partially by the observation of a higher degradation rate of luminol. In addition, it was concluded that the mechanism of enhancement is probably different for the various enhancers, based on the product formation.

Chromatography, High Pressure Liquid↗

PubMed1991

Determination of proteolytic hydrolysis of thyroglobulin.

A method for the determination of the free thyronine- and tyrosine-like amino acids in the thyroidal protein thyroglobulin is presented. The compounds of interest are monoiodotyrosine, diiodotyrosine, thyronine, diiodothyronine, triiodothyronine and tetraiodothyronine. The extent of proteolysis was followed by high-performance liquid chromatographic monitoring of both the remaining peptides and the formation of the free thyroidal amino acids. Total hydrolysis was achieved by a combination of proteolytic enzymes. A number of enzymes were tested, such as trypsin, chymotrypsin, pronase, aminopeptidase-M, carboxypeptidase-A, carboxypeptidase-P and carboxypeptidase-Y. The best combination turned out to be pronase followed by aminopeptidase-M. The relative amounts of the enzymes, with respect to the substrate thyroglobulin, and the time of incubation were optimized to achieve total proteolysis in 4 h. The method was applied successfully to samples from a toxicological experiment with sodium bromide.

Animals↗

PubMed1991

Development of a competitive enzyme immunoassay for 17 alpha-19-nortestosterone.

Because 17 beta-19-nortestosterone and its esters are frequently used anabolic steroids in cattle in Europe, there is a need for an assay that can also detect certain metabolites. The enzyme immunoassay described here involves the detection and quantitation of the major metabolite 17 alpha-19-nortestosterone in urine. The assay is based on the coating of an antibody raised in a rabbit against 17 alpha-19-nortestosterone-3-carboxy-methyloxime-bovine serum albumin (17 alpha-19-NT-3-CMO-BSA), the competitive incubation of 17 alpha-19-NT and the 17 alpha-19-nortestosterone-3-CMO-horseradish peroxidase label, followed by the detection of the blue colour developed by the action of the enzyme on tetramethylbenzidine. The 3-CMO conjugate of 17 alpha-19-nortestosterone was used to produce an antibody with selective affinity for the 17 alpha-epimer. For the optimization of the assay, different coatings and incubation conditions were tested. The standard curve ranged between 0.98 and 4000 pg per well, with a B/B0 50% of +/- 65 pg per well. Colour was measured with a microtitre plate reader. The method was validated by means of certified blank and spiked cattle urine samples.

Animals↗

PubMed1991

Hyperlipoproteinemia in Nagase analbuminemic rats: effects of pravastatin on plasma (apo)lipoproteins and lecithin:cholesterol acyltransferase activity.

The present study demonstrates very high levels of plasma lipids and high density lipoprotein (HDL) apolipoproteins (apoA-I and apoE) in female Nagase analbuminemic rats (NAR) fed a semi-synthetic diet in order to further increase the hyperlipidemia present in this strain. Plasma apoB-containing lipoproteins (very low, intermediate, and low density lipoproteins) were also elevated in NAR. Plasma cholesterol was mainly present in lipoprotein particles with a density between 1.02 and 1.12 g/ml. Separation of lipoprotein classes by gel filtration showed that the major cholesterol-carrying lipoprotein fractions in NAR plasma are apoE-rich HDL and apoA-I-rich HDL. The high HDL levels in NAR are explained, at least partly, by the two- to threefold elevated activity of plasma lecithin:cholesterol acyltransferase (LCAT). The lysophosphatidylcholine generated in the LCAT reaction, as well as plasma free fatty acids, are bound to lipoproteins in NAR plasma. A study was carried out to determine whether the elevated LDL and aopoE-rich HDL levels could be corrected by administration of the HMG-CoA reductase inhibitor pravastatin (at a dose of 1 mg/kg per day). Pravastatin treatment results in a 43% decrease in plasma triglycerides in NAR, but not in Sprague-Dawley (SDR) rats, and had no significant effect on plasma total cholesterol, phospholipids apolipoproteins A-I, A-IV, B, or E, as well as on plasma LCAT activity levels in NAR or SDR.

Animals↗

PubMed1990

Serum proteins of rats exposed to organic solvents examined by horizontal two-dimensional electrophoresis with an immobilized pH gradient in the first dimension.

Serum proteins of rats, exposed to methoxyethylacetate and a combination of methoxyethylacetate and isobutylacetate, were analyzed by horizontal high resolution two-dimensional gel electrophoresis with immobilized pH gradients in the first dimension. A total of 410 polypeptides were detected with either increasing or decreasing spot intensities after rat exposure to the organic solvents.

Acetates↗

PubMed1989

Application of optimization procedures for the separation of anabolic compounds by high-performance liquid chromatography.

A simple systematic approach is presented for optimizing high-performance liquid chromatographic separations of anabolics with multi-component isocratic mobile phases. A computer program was obtained and adjusted for use with an IBM-compatible XT personal computer. The program requires experimental retention data with three quaternary solvent mixtures to calculate the optimum solvent composition using a geometric model of a prism. For each possible composition of the mobile phase the set of retention data can be calculated. Applications are shown for mixtures of anabolic compounds using a mobile phase composed of methanol, tetrahydrofuran and acetonitrile. The predicted retention data agreed very well with the experimental data.

Anabolic Agents↗

PubMed1989

Quantitative analysis of anabolics on thin-layer chromatographic plates using image analysis techniques.

A new detection system is introduced for the quantitative analysis of thin-layer chromatographic plates, which is based on a relatively simple, cheap but advanced image analysis system. Both one- and two-dimensional plates can be analysed. Recording and analysis can also be performed from photographs or even slides. Applications are shown for a number of samples containing anabolic compounds.

Anabolic Agents↗