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Biomedical subjects

M Eckert

Publications and source records attributed to M Eckert.

At least 73 records · Page 4Linked to original sources
PubMed1988

Single and multiple dose pharmacokinetics of tenoxicam in the elderly.

Fourteen elderly subjects (10 women, 4 men) with a mean age of 81 (SD 6.7) years and in need of anti-inflammatory drug treatment were given a single dose of 20 mg tenoxicam. After a drug-free interval of 5 weeks, multiple dose treatment with 20 mg tenoxicam once daily for 56 days was initiated. The single and multiple dose kinetics of tenoxicam were investigated after HPLC determination of tenoxicam in the plasma. The elimination half-life of tenoxicam ranged from 44 to 132 h (mean 71.9 h) with no significant difference between the single and multiple dosage regimens. Tenoxicam reached maximum plasma concentrations after 1.4 and 1.1 h, with values of 3.6 and 15.5 micrograms.ml-1, for the single and multiple dosage regimen respectively. The corresponding trough values (24-h values) were 1.8 and 11.7 micrograms.ml-1. A mean accumulation ratio of 5.1 was calculated. The mean increase in the area under the plasma concentration time curves at steady-state was 21% more than predicted from the initial single dose. This deviation from linearity was considered to be of minor clinical significance. The kinetics of tenoxicam in elderly were similar to that published for young healthy volunteers.

Aged↗
PubMed1988

The influence of early odour experience on the neural response of the olfactory bulb in laboratory mice.

In mice (strain NMRI) the influence of olfactory rearing conditions on the ontogenetic development of the bulbar electroencephalogram (EEG) was investigated. The cages of control animals were perfused continually with filtered air, whereas in the three experimental groups geraniol was added to the atmosphere at different times (group G0-13, from birth till day 13; group G0-6, from birth till day 6; group G6-12, from day 6 till day 12). At various ages the EEG of the bulbus olfactorius was studied by means of permanently implanted tungsten electrodes, and the neural response to nest odour and geraniol (10(-2) vol. %) was recorded. No differences were found between the groups regarding the overall development of the bulbar EEG, nor did the raising conditions affect the neural response to nest odour. However, in groups G0-13 and G6-12 a marked response to the odour of geraniol was recorded, while in the controls and the individuals that had experienced geraniol only during their first week of life, the bulbar response to this odourant did not differ from that obtained following stimulation with clean air. In the animals of group G0-13, which were investigated as adults (day 70), the prominent geraniol response was still recordable 2 months after the last contact with the odour. These results indicate that odours experienced during a sensitive period in the nest evoke neuronal alterations in the olfactory system of the mouse that facilitate processing of a known odourant.

Aging↗
PubMed1988

Simultaneous localization of a classical neurotransmitter (GABA) and a peptide transmitter candidate (proctolin) in the nervous system of the cockroach, Periplaneta americana.

The distribution of the neurotransmitter gamma-aminobutyric acid (GABA) in the 6th abdominal ganglion of the cockroach Periplaneta americana was investigated using an antiserum against GABA. The high number of GABA immunoreactive neurons refer to the important function of this transmitter substance. The relation between the GABAergic system and the proctolinergic system in the 6th abdominal ganglion was examined by means of an immunohistochemical double staining technique. The results show that probably GABA and proctolin do not coexist within one neuron.

Animals↗
PubMed1987

A comparative study of the immunohistochemical localization of a presumptive proctolin-like peptide, thyrotropin-releasing hormone and 5-hydroxytryptamine in the rat central nervous system.

A proctolin (PROC)-like peptide was studied immunohistochemically in the hypothalamus, lower brainstem and spinal cord of the rat using an antiserum against PROC conjugated to thyroglobulin. Neuronal cell bodies containing PROC-like immunoreactivity (PROC-LI) were observed in the dorsomedial, paraventricular and supraoptic nuclei of the hypothalamus and in the nucleus raphe magnus, nucleus raphe pallidus, nucleus raphe obscurus and nucleus interfascicularis nervi hypoglossi in the medulla oblongata. Fibers containing PROC-LI were seen in the median eminence and in other hypothalamic nuclei, and in the lower brainstem in cranial motor nuclei including the dorsal motor nucleus of the vagus nerve, the motor trigeminal nucleus, the facial nucleus and nucleus ambiguous, and in lower numbers in the nucleus of the solitary tract and locus coeruleus. Fibers containing PROC-LI were also located in the spinal cord, in the intermediolateral cell column at thoracic levels and in the ventral horns at all levels of the spinal cord. After transection of the spinal cord, all PROC-immunoreactive fibers below the lesion disappeared. Following injection of Fast blue into the thoracic spinal cord, retrogradely labeled cells in the nuclei raphe pallidus, obscurus and magnus and nucleus interfasciculari nervi hypoglossi were seen to contain PROC-LI. PROC-LI had a similar distribution as thyrotropin-releasing hormone (TRH)-LI in the above-mentioned areas and coexistence of TRH-LI and PROC-LI was shown in cell bodies in the hypothalamus and medulla oblongata. PROC-LI could also be shown to coexist with 5-hydroxytryptamine (5-HT)-LI in neuronal cell bodies in the lower brainstem. The results demonstrate the occurrence of a PROC-like peptide in the mammalian nervous system, and these neurons seem to be at least largely identical to previously described TRH systems. A possible involvement of the PROC-like peptide in spinal motor control is discussed in relation to the well-established role of PROC in control of motor behavior in insects and invertebrates.

Animals↗
PubMed1986

Comparative pharmacokinetics and cardiovascular effects of tiapamil in healthy volunteers and patients with hepatic cirrhosis.

Tiapamil 70 mg was administered i.v. to 8 healthy male volunteers and 8 patients (7 males, 1 female) with biopsy proven hepatic cirrhosis. Two of the patients also received 600 mg p.o. Serial plasma and urine samples were collected and the parent drug in plasma and urine and desmethyl-tiapamil in urine were assayed by a specific HPLC method. The plasma and urine data for the parent drug after i.v. and p.o. dosing were simultaneously fitted to linear p.o. and i.v. two compartment models with exit from and input into the central compartment. Absorption was assumed to be a first order process. In the volunteers the mean pharmacokinetic parameters were: 101 l for the steady-state volume of distribution 750 ml X min-1 for nonrenal clearance, 195 ml X min-1 for renal clearance and 1.7 h for the half-life of the terminal disposition phase. The urinary recoveries of the parent drug and desmethyltiapamil averaged 21.4 and 0.8% of the dose, respectively. In the patients the steady-state volume of distribution, the amount of unchanged drug in urine and the half-life of the terminal disposition phase were significantly increased (171 l, 29.0% of the dose, 3.5 h, respectively). Decreased plasma protein binding in the patients accounted for the larger steady-state volume of distribution. The nonrenal clearance of 519 ml X min-1, tended to be smaller in the patients than in the volunteers. Together with the increased urinary recovery of tiapamil in the patients this indicates a moderately impaired elimination capacity in the cirrhotics.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1986

Proctolin immunoreactive neurons in the human brain stem.

Using the peroxidase-antiperoxidase (PAP) technique it could be established that a variety of nerve cells of human Pons and Medulla oblongata contain proctolin-like material. These neurons belong to the Nuc. olivaris caudalis, Nuc. originis n. hypoglossi, Nuc. raphes dorsalis and the Nuc. ambiguus. Furthermore, proctolin immunoreactive peptide was found to be contained in certain fiber systems (Lemniscus medialis and fiber tracts near the Raphe).

Aging↗
PubMed1985

The influence of permanent odor stimuli on the postnatal development of neural activity in the olfactory bulbs of laboratory mice.

Young laboratory mice were kept from birth in a surrounding with one dominating synthetical odor substance (geraniol, C10H18O; experimentals); the controls were bred under normal conditions. Between postnatal days 10 and 35 the development of the neural activity in the olfactory bulb and the response to the synthetical (geraniol) and a natural odor (nest material) were tested at 6 different stages of age. By means of a computer the total energy and the frequency composition (power spectra) of the electrophysiologically leaded potentials were analyzed at the time of stimulation and without stimulation. The developmental increment of neural activity was retarded at the experimentals, but the typical high-frequency waves (oscillations) appeared about 5-6 days earlier than in the controls. Both odor substances induced neural responses measured by energy and frequency changes in the power spectra. In controls none of the odors leads to noticeable changes in the composition of frequencies at days 10 and 14. Beginning at postnatal day 18 the odor substances of nest material evoked increasing neural reactions; at all stages of age geraniol induced only slight alterations in the power spectra. In the experimentals responses could be measured first at day 14. The changes in power spectra rapidly increased in the following 3 weeks and the responses to geraniol reached several times more intense levels than in the controls. The influence of permanent olfactory stimuli on the ontogenetic development of the olfactory bulb and the extreme plasticity of this system are discussed.

Acyclic Monoterpenes↗
PubMed1984

Proctolin-related material in the mouse brain as revealed by immunohistochemistry.

By use of a specific antiserum against the insect peptide proctolin we were able to identify proctolin-immunoreactive neurons in the mouse brain. These nerve cells belong to the nuc. mesencephalicus n. trigemini. Furthermore, the antiserum stained very few nerve fibers with varicosities in the immediate neighborhood of the roof of the third ventricle. The chemical identity of the immunoreactive material with genuine proctolin remains to be elucidated.

Animals↗
PubMed1984

Pharmacokinetics and hemodynamic effects of tiapamil: exercise performance, thallium stress scintigraphy, and radionuclide ventriculography.

The pharmacokinetic behavior and hemodynamic effects of tiapamil, a calcium antagonist, were studied in 16 cardiac patients during an eight-day treatment course, giving oral doses of 600 mg daily. The hemodynamic effects were investigated using exercise performance tests, thallium stress scintigraphy, and radionuclide ventriculography. The areas under the plasma concentration-time curve after the final dose were greater than after the first dose for both tiapamil (+53 per cent) and its metabolite (+24 per cent). One possible explanation is that tiapamil undergoes saturable intestinal wall metabolism. Alternatively, like verapamil, it may undergo a saturable hepatic elimination process. The hemodynamic test series showed that, despite increasing the exercise tolerance, tiapamil significantly reduced the rate-pressure product, an index of myocardial oxygen requirement. Regional myocardial perfusion clearly improved. Ventriculography showed a significant increase in ejection fraction (+18 per cent), cardiac index (+12 per cent), and stroke volume index (+19 per cent). At the same time, the measured mean arterial pressure decreased significantly by about 10 per cent and the calculated peripheral vascular resistance, by about 19 per cent.

Anti-Arrhythmia Agents↗
PubMed1983

[Management of pregnant women with thalassemia minor].

Owing to the fact that Germany has become the domicile of a great number of aliens from Mediterranean countries, an increasing number of thalassaemia cases have been reported and given cause for a thorough investigation. Since thalassaemia minor is a hereditary disease, a special prophylaxis has to take place in case of pregnancy: 1. examination of child's generator, 2. genetic counselling, 3. embryoscopy and extraction of embryonic blood, 4. if thalassaemia is diagnosed, an abortion should be taken into consideration.

Adult↗
PubMed1983

Pharmacokinetic and clinical considerations in the choice of a hypnotic.

Not only has insomnia become much more frequent in the last hundred years but its causes have also changed considerably. In the treatment of insomnia, benzodiazepines--because of their additional anxiolytic effect--offer substantial advantages over other sleep-inducing agents. The residual fraction--the quotient of plasma concentration at 12 h after drug intake to maximum plasma concentration--makes it possible to differentiate between the benzodiazepines according to their suitability as anxiolytics or hypnotics. Midazolam has the lowest residual fraction of all known benzodiazepines and thus, administered in the appropriate dosage, also has the shortest duration of activity.

Anti-Anxiety Agents↗
PubMed1983

Pharmacokinetics and bioavailability of midazolam in man.

The pharmacokinetic behaviour and the bioavailability of midazolam were investigated in six volunteers after intravenous (0.15 mg/kg) and oral administration (10, 20 and 40 mg). Following rapid intravenous injection of midazolam, the plasma concentration of the substance decreased to approximately 10% within 2 h owing to a rapid rate of distribution. A two compartment model adequately described the kinetics of midazolam in plasma. The following average values were found: elimination half-life, 2.3 h; total clearance, 323 ml/min, and apparent volume of distribution at steady-state (VSS), 50.21. After oral administration, the drug is rapidly absorbed. Maximum plasma levels are reached within 30 min and the drug is rapidly eliminated from plasma with practically the same half-life as determined after i.v. administration. The bioavailability after the ingestion of 10, 20 and 40 mg midazolam in the form of tablets ranged from 31 to 72%, due to the high liver extraction quota of midazolam.

Administration, Oral↗
PubMed1983

Relationship between plasma concentration and effect of midazolam after oral and intravenous administration.

In a double-blind, cross-over study in six healthy volunteers, the effects of different oral doses of midazolam (10, 20 and 40 mg), or 0.15 mg kg-1 midazolam administered intravenously and of placebo were investigated. Plasma concentrations of midazolam and of its active alpha-hydroxy metabolite were measured at the same time. The effect was assessed using objective and subjective methods (reaction time, tracing test, subjects' self-assessment and investigator's subjective assessment). The respective time courses of the plasma concentration and of the effect (reaction time, number of errors in the tracing test) were almost identical. Peak plasma levels and maximum effects were attained within 30 min. In general, the effect after intravenous injection of 0.15 mg kg-1 and after an oral dose of 10 mg midazolam lasted for 2 h following administration and its duration was doubled (i.e. to 4 h) after the 20 mg oral dose. Between the logarithm of the plasma concentration and the effect, there is a sigmoidal relationship that is virtually time independent. Particularly in the first few hours after oral administration the effect is intensified by the alpha-hydroxy metabolite of midazolam which is formed by first-pass metabolism. At identical plasma concentrations of midazolam, the oral dose produced more marked effects than did the intravenous administration. Correlation of the measured effects with the total (midazolam + alpha-hydroxy midazolam) plasma concentration reveals a closer sigmoidal relationship.

Administration, Oral↗
PubMed1983

Comparison of the effects of intravenously administered midazolam, triazolam and their hydroxy metabolites.

The aim of the study was to compare the pharmacological activity and clinical effect after i.v. administration of midazolam, triazolam and their hydroxy metabolites, and, secondly, to compare the clinical effects of midazolam and triazolam in doses yielding the same duration of action (15 mg and 0.25 mg, respectively). In a randomized, cross-over procedure, six healthy volunteers received one of the following in the morning at approximately weekly intervals: 15 mg midazolam; 9 mg alpha-hydroxy midazolam; 1 mg triazolam; 1 mg alpha-hydroxy triazolam; 1 mg 4-hydroxy triazolam. Tests of drug effect (investigator's assessment, psychometric testing, and self-rating by subjects) were carried out at different times in the 24-h period following administration. Triazolam 0.25 mg was also studied in four of these six subjects to supplement the findings in the cross-over study. Triazolam 1 mg was shown to have the strongest, most long-lasting effect. Midazolam 15 mg had almost the same intensity of effect but this was shorter lasting, i.e. 5 h as against 10 h for 1 mg triazolam. The alpha-hydroxy metabolites had a duration of action about half that of the parent compounds and a less potent effect, and 4-hydroxy triazolam was virtually devoid of effect. The lower 0.25-mg dose of triazolam had about the same duration of action as 15 mg midazolam but did not achieve the same degree of maximum effect as measured by psychometric tests and self-assessment by subjects. The findings of this study indicate that midazolam would be suitable for use in situations in which a brief but intense hypnotic sedative effect is desired.

Adult↗
PubMed1982

[A method for the ultrastructural, immunocytochemical detection of ecdysone].

The investigations were carried out with prothoracic glands of Galleria mellonella. The influence of various fixation media on the preservation of the ultrastructure and on the immunocytochemical staining of the steroid ecdysone was studied. An immunocytochemical staining technique for ecdysone is described allowing the ultrastructural localization of ecdysone in different cellular compartments.

Animals↗