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Biomedical subjects

W Ritter

Publications and source records attributed to W Ritter.

At least 145 records · Page 8Linked to original sources
PubMed1980

[Pharmacodynamic and pharmacokinetic studies of muzolimine in patients with hepatogeneous ascites (author's transl)].

A clinical pharmacological study was carried out with 11 patients suffering from hepatogeneous ascites. After pretreatment with spironolactone (twice daily 100 mg), 80 mg of a new loop diuretic, muzolimine, were administered orally in addition to 100 mg of spironolactone. The diuretic effect started rapidly, reached its maximum about 6 h after administration and declined slowly until 24 h. The electrolyte profile showed a pronounced excretion of sodium and chloride, whereas potassium excretion was distinctly lower. Sodium/potassium ratio was 5.9 during the first 8 hours, and the mean ratio was 5.2 during 24 hours. Urinary volume and sodium excretion were significantly correlated with plasma levels of muzolimine. Mean plasma half-life of muzolimine in these patients with liver cirrhosis was 7.9 h and was thus longer than in healthy volunteers.

Ascites↗
PubMed1979

A brain event related to the making of a sensory discrimination.

Event-related potentials associated with detected targets in a vigilance task were analyzed in two ways: (i) by sorting the potentials in terms of sequential reaction time bins of 50 milliseconds and (ii) by examining the single trial waveforms. A negative component (N2) covaried in latency with reaction time. These results support the hypothesis that N2 reflects a decision process which controls behavioral responses in sensory discrimination tasks.

Behavior↗
PubMed1978

Efficacy of propranolol in the control of exercise-induced or augmented ventricular ectopic activity.

The effect of propranolol on exercise-induced or augmented ventricular ectopy was studied in sixteen male patients, six of whom had documented coronary artery disease. Fifteen patients were exercised after two weeks of oral therapy, fourteen after single oral therapy and eight patients after intravenous therapy. Propranolol dosage was titrated to produce maximal beta-adrenergic blockade. Effective reduction of exercise-induced ventricular ectopy occurred in ten of fifteen patients (P less than 0.001), and in five of six patients with coronary disease (P less than 0.02). Propranolol therapy abolished ventricular couplets in eight of twelve patients and ventricular tachycardia in four of the patients. Single oral and intravenous therapy had similar or greater effects. Plasma propranolol levels following different routes of administration did not correlate with exercise-induced maximal heart rates or percent reduction in ventricular ectopy. When compared to exercise in eleven patients, ambulatory monitoring underestimated the severity, particularly the highest grades, of ventricular ectopy.

Adult↗
PubMed1977

Comparison of the pharmacodynamic effects of furosemide and BAY g 2821 and correlation of the pharmacodynamics and pharmacokinetics of BAY g 2821 (muzolimine).

In a biometrically planned, double-blind study on 12 Oedema-free male patients the saluretic effect of muzolimine 30 mg was compared with furosemide 40 mg. The plasma level of muzolimine was determined and correlated with its pharmacodynamics. In terms of excretion during the 12-hour observation period muzolimine 30 mg had as great a cumulative effect as furosemide 40 mg. There was a significant difference in the time-response curve. During the first gwo hours furosemide 40 mg had more saluretic effect than muzolimine 30 mg. Between two and four hours there was no significant difference between the two substances. Between four and six hours, however, muzolimine was somewhat more effective than furosemide, although the difference did not reach the level of significance. After 6 h there was no longer any difference between the two compounds. The half-life of the fall in concentration of muzolimine in plasma was 3.7 up to 10 h after its administration. The time-response curve of the increased urine excretion correlated well with the time course of the concentration of muzolimine in plasma.

Adult↗
PubMed1977

Thin-layer densitometric determination of muzolimine (BAY g 2821), a structurally new diuretic drug, at the nanogram level in biological fluids.

A sensitive and specific thin-layer densitometric method was developed for the determination of muzolimine (BAY g 2821), a structurally new diuretic drug of the pyrazolinone type. For detection of the drug on thin-layer chromatographic plates, a colour reaction with 4-dimethylaminocinnamaldehyde is carried out. The detection limit was 50 pg per spot on commercially available silica gel 60 plates. A nearly linear relationship between integrated peak area and amount per spot was obtained in the range from 100 pg to 1 mug per spot. For quantitative determination in biological fluids, a recovery of about 100% is achieved by a single extraction with dichloromethane, and the extract is spotted directly on to the plate. The detection limit of muzolimine in plasma and urine was 1 ng/ml, and inaccuracy in the nanogram range was found to be 5-8%. The assay was applied to pharmacokinetic studies and can be recommended for monitoring plasma levels of muzolimine in patients.

Chromatography, Thin Layer↗
PubMed1977

The scalp topography of potentials in auditory and visual discrimination tasks.

Averaged event-related cortical potentials (ERPs) were obtained from an array of scalp electrodes overlying the left hemicranium in response to regularly presented visual or auditory stimuli (non-signals)and to infrequent random replacements by different stimuli (signals) in the same modality. A motor response was required to the signals. Non-signal ERPs were subtracted from signal ERPs and the topographic distributions of the negative (N2 delta) and positive (P3 delta) components were plotted as isopotential maps. N2 delta distributions differed for the auditory and visual modalities, whereas P3delta was modality unspecific. These topographic data were compared to those from the previous study of missing stimulus potentials (Simson et al. 1976) using maps representing the contributions from unilateral cerebral sources. The N2 delta and negative missing stimulus potential distributions ascribed to cortical activity within the secondary auditory and visual regions, whereas the late positive component (positive missing stimulus potential or P3 delta) were considered to derive principally from inferior parietal association cortex.

Adult↗
PubMed1977

Pharmacokinetics of Bay g 2821 in the dog and in man.

The pharmacokinetics of Bay g 2821, a new diuretic agent, were studied in dogs, healthy volunteers and in patients with renal insufficiency. The drug was rapidly absorbed after oral administration, peak plasma levels (approx. 0.4 microgram/ml) occurring within 1 hour. Elimination of the unchanged drug from plasma was biphasic - an initial rapid decline with a half-life of about 3 hours, followed by a longer second phase with a half-life of 13 to 17 hours. Results were similar in healthy volunteers and in patients with renal insufficiency. It is assumed that the drug is mainly eliminated in bile, probably after biotransformation, and elimination in the urine is a minor pathway.

Animals↗
PubMed1976

The scalp topography of potentials associated with missing visual or auditory stimuli.

Averaged potentials time-locked to regularly presented visual and auditory stimuli and to the occasional random deletion of a stimulus were recorded from a scalp electrode array overlying the left hemicranium. The major components of visual and auditory evoked potentials and of the potentials associated with missing stimuli (MSP) were measured and their amplitude distributions depicted in the form of isopotential maps. The N1 components of the VEP and AEP had distributions compatible with sources in and near the respective primary cortical projection areas. The P2 components were more widely distributed and could be attributed in part to generators within modality specific association areas. The MSP comprised two main components, an initial negativity (NMSP) and a later positive wave (PMSP). The NMSP distributions were different in the visual and auditory modalities, and were similar to the respective EP topographies. The NMSP appeared to reflect a more powerful contribution of association areas than did the evoked responses. The PMSP topography was modality unspecific with distributions which were maximal over the parietal region. The possible functional significance of the NMSP and PMSP was considered in the light of their timing and topography.

Adult↗
PubMed1975

On the independence of the CNV and the P300 components of the human averaged evoked potential.

We report an experiment designed to assess the interactions between the CNV and the P300 components of human event-related potential. Eight subjects were each presented with series of experimental trials on all of which either a 1200 c/sec or an 800 c/sec tone was presented. There were three independent variables: (a) The presence or absence of a warning flash 1000 msec prior to the tone. (b) The task assigned to the subject--that is subjects were either to make a discriminative response to the tone or, on half the series, to predict prior to the tiral which of the two tones would be presented. (c) The predictability of the tone frequency. On half the series high and low tones alternated from trial to trial. On the other series, tones were chosen randomly on each trial. The data show that the amplitude of the P300 component is not affected by the presence or absence of a warning stimulus. Furthermore, the distributions of P300 and the CNV over the scalp are quite different. These conclusions are supported by a principal component and a discriminant analysis of the data. We conclude that the CNV and the P300 reflect the activity of functionally distinct cortical mechanisms.

Analysis of Variance↗
PubMed1975

Cortical evoked potentials elicited by real speech words and human sounds.

Averaged evoked potentials were recorded from PZ and left and right temporo-parietal electodes to real speech words and human sounds in 8 right-handed subjects. Stimuli were presented in a "no task" condition where the subject was instructed to listen attentively, and a vigilance condition where the subject responded to a particular word or sound during a run of such stimuli. The vigilance condition produced two classes of stimuli:signals and non-signals. Evoked potentials to physically identical words or sounds were examined when they were "no task", non-signal and signal stimuli. P300 amplitude increased significantly as a function of increasing task demands going from "no task" to non-signal to signal. When a strict statistical criterion for multiple comparisons (Bonferroni test) was applied in looking for asymmetries between hemispheres, only 2 isolated left greater than right differences turned out to be significant. Review of the literature concerning evoked potential correlates of differential hemispheric processing pointed up flaws in design, statistical technique, and inconsistencies in reported findings which suggested that while evoked potentials may sometimes reflect differences in hemispheric functioning, this effect is marginal at best.

Adult↗
PubMed1975

The late positive component (P300) and information processing in sentences.

Averaged visual evoked potentials to sequentially flashed words comprising a sentence were recorded from vertex and left and right temporoparietal electrodes in 8 right-handed subjects. In condition 1 the sentence took the form: The -eel is on the shoe, in which the first grapheme was omitted from the second word, so that the subject did not know the meaning of the second word until he viewed the last word. In condition 2, the sentence took the form: The heel is on the shoe, in which the second word was given and the last word provided no further information. P300 latency to words which delivered information (last word of condition 1, second word of condition 2) were significantly longer than P300 latency to any of the other words in the sentence, as well as to the same position word in the other condition. Comparisons of P300 latencies to redundant words (the, is, on) within and between conditions showed no significant differences. P300 amplitude to the last word was significantly larger than P300 amplitude to any of the other words within the sentence, even in condition 2 where the second word delivered information. The major effect of information delivery was on P300 latency, while "syntactic closure" had its major effect on P300 amplitude. The fact that evoked potentials to all words had P300 components was attributed to the engagement of the P300 system whenever task-related language stimuli are used.

Adolescent↗
PubMed1975

Antagonism of fenoterol against beta-blocking drugs bunitrolol and practolol in asthmatics.

In 4 X 10 young white male histamine-sensitive asthmatics without bronchitis or emphysema, the antagonism of fenoterol (40 mug) to bunitrolol (2.5 and 5 mg) or practolol (20 and 30 mg) was tested in an open comparative trial. Pulse frequency and several physiological parameters were determined before and after histamine challenge test, after injection of beta-blocking drug and after injection of fenotrolol. All groups were found to be equally sensitive to histamine. Bunitrolol and practolol were found to have no influence on histamine effect. It was also found that bunitrolol in the dosages tested is a much more potent beta-blocking drug in the bronchi compared to practolol in the dosages tested were equivalent. beta-Blockade of practolol (20 or 30 mg) could completely be antagonized by 40 mug fenoterol; this dosage was not sufficient to antagonize 2.5 or 5 mg bunitrolol.

Adolescent↗