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Biomedical subjects

J Vlcek

Publications and source records attributed to J Vlcek.

At least 37 records · Page 2Linked to original sources
PubMed1994

Pharmacokinetics of sodium humate in chickens.

Free or liposome-encapsulated sodium humate was administered to chickens intracardially, orally or subcutaneously and the following principal pharmacokinetic parameters were determined using the MW Pharm software for two-compartment models: elimination half-life (t1/2 el), steady state distribution volume (Vdss), blood clearance (Cl), maximal drug concentration (Cmax), time required for appearance of Cmax (tmax), area under the curve (AUC) and bioavailability (F). Blood clearance of liposome-encapsulated sodium humate was higher than that of free sodium humate regardless of the way of administration. On the other hand, the elimination half-life was longer after the extravascular than after the intracardial administration. Cmax values indicate that the penetration of sodium humate from the injection site into blood circulation is very slow. Biological availability of sodium humate also depended on the way of administration and dosage form. Aside from the intracardial administration, the highest bioavailability was found after subcutaneous administration of free sodium humate.

Animals↗
PubMed1994

[The effect of sodium huminate on cadmium deposition in the organs of chickens].

In the chickens with an experimental load of cadmium chloride (CdCl2 x 2.5 H2O) at a rate of 0.3 mg per bird and day the effect was investigated of various forms of sodium humate administration in free and/or liposomal form as exerted on cadmium concentrations in liver, kidneys and muscle. The values of the field below the curve (AUC) showing average cadmium concentrations in the investigated tissues of chickens (liver, kidneys, muscle) in the given time interval of 1-14 days were higher in all cases in the tissues of chickens which received cadmium, that means in the groups K2, P1, P2, P3 and P4 in comparison with the negative control (K1). Statistical significance of differences was demonstrated in liver and kidneys. No statistically significant changes were observed in the muscle. Simultaneous administration of cadmium and HuNa (P1), and also other methods of HuNa administration (P2, P3, P4) reduced cadmium concentrations in liver, kidneys and muscle statistically significantly only in P1 group in liver and kidneys. Cadmium concentrations on days 1, 3, 8 and 14 after termination of experimental treatments were lowest in the liver of the 1st control group (negative control), which received HuNa only (Tab. I). Five-day administration of 0.3 mg cadmium (positive control) influenced its values statistically highly significantly in the liver of all experimental groups in all the investigated time intervals (Tab. I). The first experimental group, which received cadmium simultaneously with HuNa had the statistically significantly lower values on days 3, 8 and 14 in comparison with the positive control. Simultaneous administration of cadmium and HuNa reduces cadmium availability and so its absorption and deposition in liver are lower. Cadmium concentrations on days 1, 3, 8 and 14 after termination of experimental treatments were lowest in the kidneys of chickens of the 1st control group (negative control), which received HuNa only (Tab. II). Five-day cadmium administration (positive control) influenced its values in the kidneys of all experimental groups highly statistically significantly in all the investigated time intervals (Tab. II). The first experimental group which received cadmium simultaneously with HuNa had the statistically significantly lower values on days 3, 8 and 14 in comparison with the positive control. Simultaneous administration of cadmium and HuNa reduced cadmium availability and so its absorption and deposition in liver are lower. Cadmium concentrations in the muscle on days 1, 3, 8 and 14 after termination of experimental treatments were lowest in the 1st control group (negative control), which received HuNa only (Tab. III).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Hyperparathyroidism after kidney transplantation: a retrospective case controlled study.

We studied retrospectively patients with hyperparathyroidism after successful renal allotransplantation. Since 1972, 1119 transplantations have been performed in our department, and 534 patients survive with functioning grafts. Hyperparathyroidism requiring parathyroidectomy developed in 32 (5.9%). The frequency of interventions increased markedly after introduction of cyclosporine A treatment in our unit. The time between transplantation and parathyroidectomy was 22.5 months (SD 16.5, range 1-82 months). The age of the patients was 49.0 years (SD 10.5, range 17-63 years); the group consisted of 16 female and 16 male patients. All patients but two (no measurement performed) repeatedly exhibited high serum parathormone and calcium levels and therefore underwent surgery. In comparison to a control group, matched for time of transplantation, age, sex, and cause of renal failure, the patients with hyperparathyroidism had longer dialysis treatment (54.2 months, range 9-132 vs 26.9 months, range 1-72) and exhibited lower phosphate concentrations in the early posttransplantation period. Before surgery, serum chemistry was different for hyperparathyroid and control subjects: serum calcium 2.80 +/- 0.23 mmol/l vs 2.48 +/- 0.13 mmol/l and alkaline phosphatase 157.4 +/- 92.0 U/l vs 85.2 +/- 51.5, respectively. We did not see any influence of oral phosphate binders, calcium supplementation, or vitamin D treatment on the development of parathyroid gland hyperactivity during dialysis treatment. Serum creatinine concentration did not change after parathyroidectomy. In four patients, long-term calcium supplementation after surgery was necessary.

Adult↗
PubMed1991

Netilmicin in the neonate: population pharmacokinetic analysis and dosing recommendations.

Netilmicin pharmacokinetics were studied in neonates of 27 to 42 weeks' gestational age and 0.8 to 5.0 kg body weight in their first 2 weeks of life by the population pharmacokinetic approach. The data were best described by a two-compartment model. Clearance depends on body weight, gestational age, and postnatal age. Volume of distribution of the central and peripheral compartments was also related to body weight. Including these patient characteristics in the population pharmacokinetic regression model resulted in a marked reduction of the unexplained interindividual variability. This enabled us to derive dosage recommendations that result in peak and average concentrations within the desired range for 95% of the neonates with gestational age above 31 weeks, thus avoiding the need for individual drug-level monitoring in a well-defined large group of patients. Only for infants with gestational age less than 31 weeks who are less than 6 days old is individual dose adjustment based on serum concentration measurements required.

Body Weight↗
PubMed1990

[Serum levels and urinary excretion of amino acids during high intensity physical exertion in healthy men].

The authors investigated the effect of a physical load on a bicycle ergometer on serum concentrations and urinary excretion of 19 amino acids. The initial load of 1 W/kg was increased after 5-minute intervals by 10-20 W to achieve the maximum after 50 minutes exercise. During the last 2-3 minutes of the maximal load a spiroergometric examination was made. The serum alanine concentration increased under these conditions significantly from 474 +/- 133 to 739 +/- 171 mumol/l (p less than 0.001), while the serum threonine concentration declined significantly from 155 +/- 39 to 143 +/- 37 mumol/l (p less than 0.05). Urinary excretion and renal clearance of amino acids declined significantly (p less than 0.05-0.001). The authors found a significant correlation between the drop of the urinary excretion and the rise of serum concentration of alanine (p less than 0.05). The drop of the urinary alanine excretion can contribute to its elevated serum concentration. The fractional amino acid excretions did not decline and the decline of amino acid and creatinine clearances was more or less proportional. The authors conclude that the decline of amino acid excretion is directly associated with a drop of glomerular filtration. The revealed, correlations between the drop of gin, lys, pala, thr and Na excretion suggest that the sodium transport through the nephron can influence the transport of these amino acids.

Amino Acids↗
PubMed1990

Nonlinear kinetics of propafenone metabolites in healthy man.

The pharmacokinetics of oral and i.v. propafenone and its major metabolites have been investigated in 8 healthy subjects. The total body clearance of propafenone was 963 ml/min, the terminal half-life 198 min and its absolute bioavailability was 15.5%. The two active metabolites (5-hydroxypropafenone and N-depropylpropafenone) showed non-linear kinetics in that both the dose-corrected area under the serum concentration-time curve and the amount excreted in the urine were larger after oral dosing. This resulted in considerably higher serum concentrations of the metabolites despite comparable serum concentrations of the parent compound. Thus, the concentration-effect relationship in the same patient may differ after oral and intravenous doses if concentrations of the active metabolite(s) are not taken into consideration. Although the mechanism of the nonlinearity is not clear, the data indicate that it may be due to saturable biliary excretion of the metabolites.

Biotransformation↗
PubMed1982

Some remarks on 99Mo-99mTc generator kinetics.

Attention is drawn to some erroneous and incomplete pieces of information on 99Mo-99mTc generator kinetics published in the literature. The assumption that 99mTc is eluted completely from the generator leads to the incorrect 99TmTc activity-time curve plotted in some papers. It is shown that the time at which 99mTc activity in the generator reaches the maximum value depends on the efficiency of 99mTc separation. The expression derived on by authors allows the prediction of 99mTc activity available in the second separation performed several hours after the previous separation.

Kinetics↗
PubMed1982

Renal function in brain dead patients with respect to transplantation.

We examined the renal function in 18 brain dead patients 2-0 h before removing the kidneys and 72 h after their transplantation to the recipient. The kidneys were preserved by simple hypothermia. In brain dead patients we found no demonstrable relationships between PCr and CCr or between Purea and CCr. At this time the Purea and PCr values are not a sufficiently accurate indicator of renal function. We also examined the plasma and urinary concentrations of Na, K, urea and osmotically active substances and calculated their excretion fractions. We found that, prior to removal, the kidneys were in a state of combined osmotic and water diuresis. The osmotic diuresis was chiefly of a non-sodium type and was produced by a mannitol load. Water diuresis was evidently caused by inhibition of ADH output consequent to brain hypoxia. We also investigated the relationship between the CCr values before nephrectomy and in the early posttransplantation phase. We found that there was a relationship between the recipient's CCr values in the early posttransplantation period and donor's CCr/total ischaemic time index. Calculation of this index can be valuable, especially in high risk transplantations.

Adolescent↗
PubMed1979

Results of regular study on radionuclidic purity of 99mTc obtained from 99Mo--99mTc generators.

A total of 39 99mTc eluates obtained from 9 99Mo--99mTc generators delivered by The Radiochemical Centre Amersham during one year was studied with regard to their radionuclide purity. Using a Ge(Li) spectrometer the contaminants 60Co, 103Ru, 131I, 134Cs, 140Ba, 140La and 188Re were found in 99mTc-eluates with average levels ranging from 2.9 X 10(-3) to 2.8 X 10(-1) per cent of 99mTc activity. The additional total body absorbed dose caused by these contaminants, as calculated from their average content in 99mTc eluates, was less than 1% of the dose due to 99mTc pertechnetate.

Radiation Dosage↗