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Biomedical subjects

H Poppe

Publications and source records attributed to H Poppe.

At least 37 records · Page 2Linked to original sources
PubMed1996

Effects of AWD 23-111, a new antiarrhythmic substance, on cardiac conduction and refractoriness.

In isolated spontaneously beating guinea pig hearts, the effects of AWD 23-111 (N-(dicyclohexylcarbamoylmethyl)-N-(3-diethylamino-propyl)-4-nit robenzamid -hydrochloride), a new synthetic class III antiarrhythmic agent with sodium antagonistic properties, were investigated on cardiac electrophysiological parameters, that is, conduction and refractoriness. Concentration-dependent prolongation of the atrioventricular, intraventricular, and His bundle conduction times and of sinus node cycle length were present. At 0.3 microM the repolarization period was prolonged significantly. No reverse use-dependent effect on the repolarization period was observed. During rapid pacing (pacing cycle length = 120 ms for the ventricle and 180 ms for the atrium) the rate-dependent intraventricular (QRS) or atrioventricular conduction time (AVCT) prolongation follows an exponential function of the beat number and is characterized by a drug-specific time constant. The time constant for the intraventricular conduction time prolongation in the presence of 0.1 microM AWD 23-111 was very long at 150 +/- 29 beats (mean +/- SEM; n = 6), indicating a slow binding kinetic to the sodium channel. At 0.1 microM AWD 23-111, a significant increase in the ventricular effective refractory period was reached when the interstimulus interval (S1-S1) was 120 ms and the number of conditioning stimuli (S1) was higher than the time constant. The time constant for the rate-dependent AVCT prolongation in the presence of 0.3 microM AWD 23-111 was 34 +/- 6 beats (n = 6). The effective refractory period of the atrioventricular conduction significantly increased with the number of conditioning stimuli (S1), until the number was comparable with the time constant. In conclusion, AWD 23-111 exerts a wide variety of actions on the cardiac conduction system. Its combined effects on the potassium and sodium channels seem to be responsible for the marked rate-dependent effect on ventricular refractoriness and for the lack of a reverse use-dependency on JT prolongation.

Animals↗
PubMed1996

Rate-dependent effects of detajmium and propafenone on ventricular conduction and refractoriness in isolated guinea pig hearts.

Detajmium (4--3'-diethylamino-2'-hydroxypropyl--ajmalin) is an Na(+)-channel-blocking drug with an extremely long recovery from use-dependent sodium channel block. The aim of the present study was to investigate the rate-dependent effects of detajmium on the intraventricular conduction of isolated, spontaneously beating, guinea pig hearts in comparison with the effects of propafenone. Detajmium (0.3 microM) and propafenone (0.3 microM) caused comparable prolongations of the intraventricular conduction time during sinus rhythm. The time to steady state of the rate-dependent QRS prolongation during rapid ventricular pacing follows an exponential function of the beat number after an abrupt change of frequency and is characterized by a drug-specific time constant. This time constant was significantly longer for detajmium (tau = 265 +/- 165 beats; mean +/- SEM; n = 6) than for propafenone (tau = 31 +/- 4 beats; n = 11; p < 0.01). In the presence of propafenone, QRS duration peaked initially before decreasing to a steady state. Detajmium, in contrast, progressively broadened the QRS complex. Both substances caused the greatest increase in the ventricular effective refractory period (V-ERP) when the number of conditioning stimuli (interstimulus interval, 120 ms) was in the range of the time constant. However, when the number of conditioning stimuli was further increased, the V-ERP for propafenone diminished progressively. In conclusion, propafenone displayed, in comparison with detajmium, only a transient rate-dependent effect on intraventricular conduction and V-ERP.

Ajmaline↗
PubMed1995

Capillary electrophoresis of peptides using rectangular and cylindrical geometries: a comparative study.

A study on the use of rectangular columns in capillary zone electrophoresis (CZE) is presented. The equations controlling the hydrodynamic flow and the plate height in rectangular capillaries are deduced. Several experiments were carried out in order to test the validity of these equations. Also, the possibilities of these columns in terms of thermal dissipation, efficiency, analysis speed and sample capacity were studied and compared with those for cylindrical tubing. The results from both rectangular and cylindrical columns are compared to each other, employing the parameters mentioned above, and also with those predicted by theory. The advantages, i.e. better heat dissipation, higher speed and larger sample capacity, and drawbacks, i.e. high fragility and incompatibility with some capillary electrophoresis instruments, of employing rectangular geometries in CZE are discussed.

Electric Conductivity↗
PubMed1995

Effect of pH and ionic strength of running buffer on peptide behavior in capillary electrophoresis: theoretical calculation and experimental evaluation.

The effect of pH and ionic strength of running buffer on peptide behavior in capillary electrophoresis (CE) is studied. A system for predictions of peptide migration in CE (SPPMCE) developed in our laboratory has been tested in a wide range of pH and buffer concentrations. The SPPMCE consists of a computer program for calculating peptide pKa values, an equation which relates peptide structures to their electrophoretic mobilities and a coupled computer program for the prediction of electropherograms. More than 25 different buffers have been employed, covering a pH range of 2-11 and a concentration range of 5-100 mM. Results from experiments are compared with the theoretical predictions. Good agreement is observed, which confirms the utility of the SPPMCE and allows fast and easy optimization of peptide separations in CE, with nothing more than the amino acid sequence of the linear peptide as the input.

Amino Acid Sequence↗
PubMed1994

Simultaneous determination of urinary creatinine, calcium and other inorganic cations by capillary zone electrophoresis with indirect ultraviolet detection.

A method for the rapid analysis of calcium and creatinine in urine has been developed using capillary zone electrophoresis without sample pretreatment other than dilution. Cations of NH3, K, Na, Mg, Ca, Li, Ba and creatinine in human urine samples could be separated within 7 min. Background electrolyte (BGE) was composed of 5 mmol/l pyridine (chromophore), 3.6 mmol/l tartaric acid and 2 mmol/l 18-crown-6, having a pH of 4.05. An indirect UV detection mode was employed at 255 nm. Efforts were made to eliminate the interaction between cations and proteins and to minimize the electromigrative dispersion (EMD) for the analytes of interest by selecting a suitable BGE and sample dilution solution. Quantitative analyses were performed for calcium and creatinine. The calibration plots showed good linearity over the concentration range of interest to clinical analysis. Data on recoveries and reproducibilities are also reported. Results for urine samples (previously collected and frozen) from a variety of healthy and pathological individuals were in good agreement with those obtained by the Technicon SMA II calcium and creatinine methods.

Ammonia↗
PubMed1994

Simulation and optimization of peptide separation by capillary electrophoresis.

The different mobility equations that have appeared in the literature for predicting peptide mobility were compared. A modified equation that relates the mobility of individual proteolytic species of a peptide to its composition has been obtained: mu = 1758 log(1 + 0.297q)/M0.411, where mu is the electrophoretic mobility in 10(-9) m2/s.V, q is the integral value of the charge of the species and M its molecular mass. Also, a rough estimation of the set of pKa values for a peptide was developed. The usefulness of this equation together with a computer program for predicting separations of compounds by capillary zone electrophoresis is demonstrated, employing real electropherograms of peptides from the literature or from experiments.

Amino Acid Sequence↗
PubMed1993

Determination of enantiomers of bupivacaine in serum using an on-line coupled three column liquid chromatographic system.

An on-line coupled HPLC system is described for the determination of the enantiomers of bupivacaine in serum. The method involves three steps: (i) pre-concentration and clean-up; (ii) the determination of the racemates on a reversed-phase column; and (iii) the separation of the racemates, heart-cut from the reversed-phase column, on an alpha-glycoprotein column. The method is suitable to determine the enantiomers in serum down to 0.1 micrograms ml-1 and can be fully automated. The bupivacaine time course of patients will be shown.

Bupivacaine↗
PubMed1992

In vivo targeting of OV-TL 3 immunoliposomes to ascitic ovarian carcinoma cells (OVCAR-3) in athymic nude mice.

Specific binding of immunoliposomes to target tumor cells was investigated in a xenograft model (athymic nude mice) of i.p. growing human ovarian carcinoma (OVCAR-3). For the first time, quantitative evidence is presented that attachment of a tumor-specific antibody (OV-TL 3) dramatically enhances the association of liposomes with i.p. growing OVCAR-3 cells. The OV-TL 3-mediated binding of liposomes to the OVCAR-3 cells was rapid; 30 min after i.p. injection approximately 70% of the injected dose of OV-TL 3 immunoliposomes was associated with the OVCAR-3 cells while for unconjugated liposomes a value of only approximately 3% was obtained. At 2 h after injection, a maximal binding level of 84% was achieved in case of the OV-TL 3 immunoliposomes whereas the binding level of unconjugated liposomes was still about 3%. Twenty-four h after injection about 83% of the injected dose OV-TL 3 immunoliposomes still was associated with the OVCAR-3 cells, compared to about 10% of the injected dose of unconjugated liposomes. Accordingly, unconjugated liposomes disappeared from the peritoneal cavity much faster than the OV-TL 3 immunoliposomes. By comparison with immunoliposomes bearing irrelevant antibody, the specificity of the binding of the OV-TL 3 immunoliposomes to the OVCAR-3 cells was demonstrated. In addition, it was observed that the sustained high OV-TL 3 immunoliposome levels found in the peritoneal cavity are the result of both reduced particle clearance from the peritoneal cavity and the tenacious binding of the immunoliposomes to the tumor cells. Finally, data are presented showing that the degree of binding of OV-TL 3 immunoliposomes to OVCAR-3 cells in vitro and in vivo correlates positively with the antibody (Fab') density on the liposomes.

Animals↗
PubMed1991

Method for the characterization of stationary phases for the separation of proteins by high-performance liquid chromatography.

A conformational change of lysozyme and myoglobin can be visualized with transition curves in a high-performance liquid chromatographic (HPLC) system using a diode-array detector and UV difference spectrometry. Transition temperatures calculated from the curves are affected by the mobile phase composition and the column packing material. Flow-rates as used in HPLC do not have a measurable influence.

Chromatography, High Pressure Liquid↗
PubMed1990

Gene technology in medical diagnostics and criminal procedure and liability for malpractice in Germany.

The increasing employment of gene technological procedures in medical diagnostics and criminal procedure has forced both the medical and the legal professions to focus their attention on the complex question of liability of physicians, lab technicians, and other personnel involved in applying these measures. This article gives an outline, by citing practical cases, of the major aspects of liability for malpractice that are relevant under German law. Bearing in mind that this article will be read predominantly by members of the Anglo-American common-law legal system, the legal aspects - even though they are German legal aspects - are viewed in the light of the common law. The article examines three major issues: (a) liability for diagnoses employing gene technological procedures: (b) liability for wrong testimony based on 'genetic finger-printing': and (c) the donor's rights concerning his or her DNA-probe.

DNA Fingerprinting↗
PubMed1989

Performance of carbohydrate-modified fused-silica capillaries for the separation of proteins by zone electrophoresis.

The walls of fused-silica capillaries were chemically modified with small carbohydrate moieties in order to diminish the wall adsorption of proteins in capillary zone electrophoresis. A diol-type coating, prepared by bonding of gamma-glycidoxy propyltrimethoxysilane to the wall followed by acidic hydrolysis, shows for proteins a similar electrophoretic behaviour as various pH values to a polyethylene glycol (PEG) coating tested previously. Although good peak shapes were obtained for proteins in the pH range 3-5, the efficiency on the diol coating is worse than that on the PEG coating. At higher pH values the peaks are deformed and the efficiency is lost. A maltose coating appears to shield the silica surface well for proteins up to pH 7. The peak shapes of proteins are acceptable, but the efficiency of the maltose coating is smaller than that on the diol coating. The diol coating is stable in the indicated pH range. However, with the maltose coating good stability is obtained only on adding an antimicrobial agent to the buffers.

Carbohydrates↗
PubMed1989

Weather influence on the prevalence of carbon monoxide intoxications.

In a retrospective study over 7 years, data from patients admitted to the Emergency Department with CO intoxication, together with meteorological data were analysed. A statistically significant difference in weather conditions was noticed between CO-intoxication days and reference days. Different weather conditions were found to be present, according to the source of CO, i.e. gas boiler or coal stove. If these data are confirmed, a major role in the prevention of CO intoxication or its sequellae can be played by the media through weather broadcasting. Warning can raise the index of suspicion of physicians and warn the population for vague, collectively appearing sensations of ill feeling.

Adolescent↗
PubMed1989

[Synthesis of 3-cyano-6-methyl-4-pyridyl-2(1H)-pyridinethiones as well as 2-substituted 6-methyl-4-pyridyl-pyridine-3-carbonitriles and 3-carbonic acid amides, respectively, and testing their cardiovascular activity].

By the base catalyzed reaction of our previously described 3-cyano-6-methyl-4-pyridyl-2(1H)-pyridinethiones 1 and 2, respectively, with branched and unbranched, respectively, alkyl, aralkyl-, alkinyl-, hydroxyalkyl-, ethoxycarbonyl- and carbamoylalkylhalides the new in 2-position substituted 6-methyl-4-pyridyl-pyridine-3-carbonitriles 15-30 were formed. By means of oxidation of the 2-methylthio-substituted pyridine-3-carbonitriles 3 and 4 with potassium periodate and potassium permanganate in diluted acetic acid, respectively, the sulfinyl compounds 5 and 6, respectively, and the sulfonyl compounds 7 and 8, respectively, were prepared. By heating of 3 and 4, respectively, with concentrated sulphuric acid the 2-methylthio-pyridine-3-carboxamides 9 and 10 were obtained. The oxidation of these compounds with potassium periodate and potassium permanganate, respectively, had yield the pyridines 11 and 12, respectively, as well as 13 and 14, respectively.

Amides↗
PubMed1988

[Synthesis of 3-substituted 6-methyl-4-pyridyl-2 (1H) pyridones and testing of their cardiovascular action].

Reaction of our previously described and in 4- and 6-, respectively, position with 3- and 4-, respectively, substituted 3-cyan-2(1H)-pyridones 4 and 5 with concentrated sulphuric acid had yielded the 3-carbamoyl-pyridones 8 and 9. Hofmann reaction was followed and the 3-amino substituted pyridones 10 and 11 were formed. As by-products the 5-bromo substituted 3-amino-pyridones 12 and 13 were obtained. 4 and 5 were refluxed in the presence of diluted sulphuric acid to yield the decarboxylated pyridones 14 and 15. Cardiotonic Activity of the compounds 4-9 compared to amrinone (Cordemcura) was investigated.

Animals↗
PubMed1987

Influence of the day of the week and the weather on people using a telephone support system.

The calls to a telephone counselling service at Louvain, during a 21-month period, from one telephone zone were analysed. Data were studied in relation to the type of weather, which was recorded every day. Calls made by women about health and interpersonal problems showed a relationship to the weather, while calls apparently motivated by masturbation intentions from male callers increased when the weather improved.

Belgium↗