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J Mráz

Publications and source records attributed to J Mráz.

At least 19 recordsLinked to original sources
PubMed2005

N-Methylcarbamoyl-lysine adduct in globin: a new metabolic product and potential biomarker of N, N-dimethylformamide in humans.

Metabolism of the solvents N,N-dimethylformamide (DMF) and N-methylformamide (MF) results in the formation of N-methylcarbamoyl adducts at the N-terminal valine and lysine in blood protein globin, of which the lysine adduct has so far only been reported in rats given high doses of both solvents [Mráz, J., Simek, P., Chvalová, D., Nohová, H., Smigolová, P., 2004. Studies on the methyl isocyanate adducts in globin. Chem. Biol. Interact. 148, 1-10]. Here we examined whether the lysine adduct is produced, and accessible to analysis, in humans occupationally or experimentally exposed to DMF. Globin from exposed subjects (n=35) and unexposed controls (n=5) was analyzed by two methods. Edman degradation was used as a sensitive reference method to measure the valine adduct by converting it to 3-methyl-5-isopropylhydantoin (MVH). The MVH levels in globin of the exposed subjects were in the range of 1-441 nmol/g, in controls <1 nmol/g. The principal method of globin analysis consisted of enzymatic hydrolysis with pronase to release free N(epsilon)-(N-methylcarbamoyl)lysine (MLU) and N-methylcarbamoylvaline (MVU), which were determined by HPLC/MS/MS, with no clean-up or preconcentration steps needed. For MLU, the parent and product ions were m/z 204-->173, and the limit of detection was approximately 5 nmol/g globin. MLU was found in most globins from the exposed subjects but not in the controls. A close correlation between the MLU and MVH levels (nmol/g) was observed: MLU=7+0.48 MVH (R(2)=0.84, n=32). In conclusion, MLU can be easily measured in globin of workers exposed to DMF. The findings also indicate a long-term persistence of MLU in the human body, and consequently, its potential as a biomarker of chronic exposure to DMF.

Biomarkers↗
PubMed2004

Analysis of metabolites of N,N-dimethylformamide in urine samples.

AIM: To assess the suitability of different methods for biological monitoring of internal dose to N,N-dimethylformamide (DMF) in occupational settings. METHODS: The determination of urinary metabolites of DMF, N-hydroxymethyl- N-methylformamide (HMMF), N-methylformamide (NMF) and N-acetyl- S-(N-methylcarbamoyl) cysteine (AMCC) was carried out by four selected analytical procedures. Two methods solely measured total NMF (HMMF and NMF). The other two methods measured both total NMF and AMCC in one analytical run. All four methods were tested on 34 urine samples from workers exposed to DMF. RESULTS: Comparison of the four methods for determination of total NMF in urine showed that results were similar for three methods, while the remaining one provided NMF levels significantly lower (by 22%) than the other methods. Thus, all but one of the tested methods for the determination of total NMF can be considered to be suitable for biological monitoring of internal dose to DMF. The two tested methods for the determination of AMCC afforded results that showed high correlation but differed significantly (by 10%). CONCLUSION: The choice of the biomonitoring method depends mainly on the purpose for which the measurement is conducted. For evaluation of acute exposures or to assess safety measures in the working area, an updated version of the traditional method of Kimmerle and Eben (1975a, b) for the determination of total NMF in urine is sufficient. For risk assessment after exposure to DMF, the determination of AMCC should be carried out, since AMCC, but not total NMF, is supposed to be related to the toxicity of DMF. However, there is still a need to develop an easier, more sensitive and more selective method for the determination of AMCC in urine until AMCC can be considered for regulatory purposes in occupational settings.

Acetylcysteine↗
PubMed2004

Studies on the methyl isocyanate adducts with globin.

Isocyanates such as methylisocyanate (MIC), an intermediate in the synthesis of carbamate pesticides, or diisocyanates, used in the production of plastics, are highly reactive toxic compounds that spontaneously bind to biological macromolecules. In vivo formation of stable adducts with blood protein globin offers possibilities for biomonitoring of internal exposure to various reactive species. Thus, biomonitoring of the isocyanates through determination of their specific adducts with globin is a challenge. In this study, we characterized the adducts formed in human globin upon treatment with 100-fold molar excess of MIC. The globin was subject to enzymatic hydrolysis with pronase, and the hydrolysate was analysed by high performance liquid chromatography with positive atmospheric pressure chemical ionization mass spectrometric detection (HPLC/APCI-MS). The two major MIC adducts were those with N-terminal Val and side-chain of Lys, as confirmed by comparison with the synthetic standards. About 20 other adducts were observed, and several of them were tentatively identified using their MS and MS/MS spectra. Whereas detection of the adducts with Tyr and His was expected, the adducts with Trp and Phe, and a Lys adduct containing two MIC moieties, were probably analytical artifacts resulting from the transcarbamoylation during globin hydrolysis rather than products of direct carbamoylation. The other detected products were MIC-Val-His, derived from the N-terminal dipeptide of globin beta-chain, and dipeptides consisting of MIC-Lys attached to Gly, Val, Leu, Thr, and Glu. Failure to detect the corresponding non-modified dipeptides suggests that the pronase action may be hampered by the amino acid modification. MIC is known as a metabolic intermediate of the industrial solvents N,N-dimethylformamide (DMF) and N-methylformamide (MF) in humans and rats. The HPLC/APCI-MS analysis of globin from rats injected with DMF or MF, 1000 mg/kg, revealed the presence of the MIC adducts with both Val and Lys. The level of the Val adduct in globin from the DMF-dosed rats, determined using Edman degradation and GC/MS, was ca. 40 nmol/g, which is a level common in workers occupationally exposed to DMF. This suggests that also the Lys adduct in such human globin samples can be feasible to analysis and is therefore considered for further studies as a potential biomarker of exposure to DMF.

Animals↗
PubMed2002

Effect of alanyl-glutamine on leucine and protein metabolism in irradiated rats.

The mechanism by which glutamine produces a favorable effect in the treatment of sepsis, injury, burns and abdominal irradiation is not completely understood. The main aim of this study was to evaluate the effect of alanyl-glutamine (AlaGln) administration on the metabolism of proteins in irradiated rats. The rats were exposed to whole-body irradiation (8Gy) and then fed intragastrically with a mixture of glucose and amino acids either with AlaGln or without AlaGln. At 48 hours after irradiation, parameters of whole-body protein metabolism and DNA synthesis in intestinal mucosa were investigated using a primed, continuous infusion of [1-14C]leucine and [3H]thymidine. In addition, we evaluated the effect of irradiation and AlaGln on gut morphology, blood count and amino acid concentrations in blood plasma and skeletal muscle. Control rats were not irradiated but were given identical treatment. An increase in whole-body leucine oxidation, and insignificant changes in whole-body proteolysis and in protein synthesis were observed after irradiation. In irradiated rats we observed a decrease in muscle glutamine concentration, a decrease in protein synthesis in jejunum, colon and heart, and an increase in synthesis of proteins of blood plasma and spleen. Morphological examination and measurement of DNA synthesis failed to demonstrate any favorable effect of AlaGln supplementation on irradiated gut. However, administration of AlaGln resulted in a decrease in whole-body proteolysis and leucine oxidation which caused an increase in the fraction of leucine incorporated into the pool of body proteins. We conclude that the data obtained demonstrate that irradiation induces metabolic derangement associated with increased oxidation of essential branched-chain amino acids (valine, leucine and isoleucine) and that these disturbances can be ameliorated by administration of AlaGln.

Amino Acids↗
PubMed2000

[Effect of Stopangin mouth spray on blood alcohol levels measured by the Alcotest 7410 analyser made by Drager].

During a check-up of a driver by a police patrol in the Czech Republic by means of a breath analyzer of Dräger Co. an alcohol blood level of 0.50 g/kg was assessed. Later the driver reported that before the test he used at 30- and 5-minute intervals the drug Stopangin spray. In the Institute of Forensic Medicine the authors made an experiment which revealed that 22 minutes after administration of the drug the apparatus gave a negative result. Agreement with these conclusions was expressed also by a representative of Dräger Co. and the results were published as an expert opinion with a recommended procedure for the police of the Czech Republic in the South Moravian region.

Aerosols↗
PubMed1999

2,4-toluenediisocyanate and hexamethylene-diisocyanate adducts with blood proteins: assessment of reactivity of amino acid residues in vitro.

Diisocyanates, reactive compounds used in plastics industry and potent occupational allergens, readily bind to proteins both in vitro and in vivo, however, the pattern of adducts with individual amino acids has not been investigated systematically. In this study, potential of the proteinogenic amino acid residues for carbamoylation with 2,4-toluenediisocyanate (2,4-TDI) and hexamethylenediisocyanate (HDI) was evaluated. The diisocyanates were incubated in an in vitro system (buffer pH 7.4/dioxane 50:50) with: (a) a series of Nalpha-benzyloxycarbonyl amino acids (Z-amino acids) and N-acetylcysteine (Ac-Cys), model compounds for non-N-terminal amino acids of the protein chain; (b) dipeptides Val-Phe and Asp-Phe, model compounds for N-termini of globin and albumin, respectively. Reactivity of the compounds tested, evaluated from their depletion during incubation with the diisocyanates (measured by HPLC), was in the order: Ac-Cys = Asp-Phe > Val-Phe = Nalpha-Z-Lys >> Nalpha-Z-His for 2,4-TDI, and Ac-Cys > Asp-Phe > Val-Phe = Nalpha-Z-Lys > Nalpha-Z-His > N-Z-Tyr for HDI, however, the adducts with Ac-Cys were unstable. Reactions of other amino acid residues (e.g. Ser, Thr, Met, Trp, Arg, Asn, Gln) with 2,4-TDI and HDI were not observed. Thus, N-terminal amino acids and Lys residues are likely to produce most abundant adducts with diisocyanates in proteins. Further, three amino compounds with increasing pKa values (Val-Phe, Val and Nalpha-Z-Lys) were incubated with 2,4-TDI and N-acetyl-S-[4-(2-amino)tolylcarbamoyl]cysteine, a 2,4-TDI-derived thiocarbamate with carbamoylating activity, in media with 10% and no dioxane, respectively. Here, reactivity of the amino compounds was decreasing in the order: Val-Phe > Val > Nalpha-Z-Lys, which reflects the mechanism of the amine-isocyanate reaction. The experiments also demonstrate the effect of a solvent (organic phase content) on the yield of the carbamoylation reactions.

Albumins↗
PubMed1999

Plasma amino acid levels after carbon tetrachloride induced acute liver damage. A dose-response and time-response study in rats.

The aims of the present study were to assess the changes of individual plasma amino acid levels in relation (1) to the severity of liver damage and (2) to the process of liver recovery. Acute liver injury was induced by an intragastric administration of CCl4 diluted in olive oil in doses of 2, 4 and/or 6 g of CCl4 per kg b.w. The control rats received olive oil only. Animals were sacrificed at 16, 24, 48 and 96 hours after treatment. The severity of liver injury was assessed by histological examination, by changes in ALT and AST in the blood plasma and by changes in liver weight. Statistical analysis was carried by ANOVA, p < 0.05 was considered significant. The Spearman rank correlation coefficient was used as a measure of the degree of linear relationship between variable and dose. In the period of the development of acute liver damage, i.e. at 16 and 24 hours after treatment, an increase in blood plasma amino acid levels and positive correlations with the dose of CCl4 were observed for most individual amino acids. The only exception was arginine which decreased in a dose dependent manner. At a phase of liver recovery, i.e. at 48 and 96 hours after CCl4 treatment, the concentrations of some individual amino acids decreased below the control values. The negative correlation with the dose of CCl4 occurred for taurine and isoleucine (at 48 hours) and taurine, threonine, valine, methionine, isoleucine and leucine (at 96 hours).

Acute Disease↗
PubMed1999

Metabolism of benzene in human liver microsomes: individual variations in relation to CYP2E1 expression.

In human liver microsomes the oxidations of benzene, chlorzoxazone, aniline, dimethylformamide, and 4-nitrophenol were significantly correlated with each other and with the level of cytochrome P450 (CYP) 2E1 estimated by immunoblotting. Moreover, benzene oxidation to water-soluble metabolites was suppressed by 0.1 mM diethyldithiocarbamate, supposedly a specific inhibitor of CYP2E1 at this level. None of these metabolic rates correlated with immunochemically determined levels of CYP1A2, 2C9, and 3A4 nor oxidation of 7-ethoxyresorufin, tolbutamide, and nifedipine. Benzene oxidation to water-soluble metabolites was characterized by typical Michaelis-Menten kinetics. The different benzene K(m) values seen in individual human microsomal samples were not correlated with the level or activity of CYP1A2, 2C9, 2E1, and 3A4 but could be due to CYP2E1 microheterogeneity. The lowest K(m) for benzene oxidation could be related to C/D and/or c1/c2 polymorphism of CYP2E1 gene. Covalent binding of benzene reactive metabolites to microsomal proteins was also correlated with the CYP2E1 metabolic rates and immunochemical levels. At high concentrations of benzene covalent binding was inversely related to benzene concentrations (as well as to formation of water-soluble metabolites) in agreement with the view that secondary metabolites, mainly benzoquinone, are responsible for the covalent binding.

Benzene↗
PubMed1999

Effect of ethanol on the urinary excretion of cyclohexanol and cyclohexanediols, biomarkers of the exposure to cyclohexanone, cyclohexane and cyclohexanol in humans.

OBJECTIVES: This study explored the acute effect of ethanol (EtOH) on the urinary excretion of cyclohexanol (CH-ol), 1,2- and 1,4-cyclohexanediol (CH-diol), biomarkers of exposure to important solvents, and chemical intermediates cyclohexanone (CH-one), cyclohexane (CH) and cyclohexanol. METHODS: Volunteers (5-8 in each group) were exposed for 8 hours either to CH-one, CH or CH-ol vapor at concentrations of about 200, 1000, and 200 mg/m3, respectively, with concomitant ingestion of EtOH (4 14-g doses taken during the exposure). Urine was collected for 72 hours and analyzed for CH-ol and CH-diols using a procedure involving acidic hydrolysis and gas chromatographic determination. RESULTS: The metabolic yields of CH-ol, 1,2-, and 1,4-CH-diol, respectively, in the exposures with EtOH were as follows: 11.3%, 36%, 23% after the exposure to CH-one, 3.1%, 15%, 8% after the exposure to CH, and 6.6%, 24%, 18% after the exposure to CH-ol. [The corresponding values obtained previously in matching experiments without EtOH were as follows: 1.0%, 39%, 18% (CH-one); 0.5%, 23%, 11% (CH); and 1.1%, 19%, 8% (CH-ol).] The excretion curves of the metabolites in the exposures with EtOH were not delayed when compared with the corresponding curves of a comparison group. CONCLUSIONS: The urinary excretion of CH-diols is much less sensitive to EtOH than that of CH-ol. It is recommended to employ CH-diols as useful and more reliable biomarkers of exposure to CH-one, CH and CH-ol in field examinations.

Adult↗
PubMed1998

1,2- and 1,4-Cyclohexanediol: major urinary metabolites and biomarkers of exposure to cyclohexane, cyclohexanone, and cyclohexanol in humans.

The metabolism and toxicokinetics of cyclohexane (CH) and cyclohexanol (CH-ol), important solvents and chemical intermediates, were studied in volunteers after 8-h periods of inhalation exposure at concentrations of 1010 and 236 mg m(-3), respectively (occupational exposure limits: CH, 1050 mg m(-3); CH-ol, 200 mg m(-3)). Of the dose of absorbed parent compounds, the yields of urinary CH-ol and 1,2- and 1,4-cyclohexanediol (CH-diol) were 0.5%, 23.4%, and 11.3%, respectively, after exposure to CH and 1.1%, 19.1%, and 8.4%, respectively, after exposure to CH-ol as determined by a gas chromatography method involving hydrolysis of glucuronide conjugates. The metabolic patterns of CH and CH-ol were very similar to that of cyclohexanone (CH-one) studied in the laboratory previously. For all three compounds, peak excretion of CH-ol occurred at the end of the exposure period, after which it decayed rapidly. Excretion curves of 1,2- and 1,4-CH-diol reached maximal values within 0-6 h postexposure, with subsequent elimination half-lives being 14-18 h. The rate-limiting step in the elimination of CH compounds from the organism is renal clearance of CH-diols. Determination of CH-diols in end-of-shift urine samples is recommended as a useful new method of biomonitoring of CH, CH-ol, and CH-one at the workplace. However, due to accumulation of CH-diols in the body during repeated exposure, quantitative relationships between the exposure and the level of CH-diols have to be adjusted according to the day of sampling during the working week.

Adult↗
PubMed1997

The evidence for conjugated mandelic and phenylglyoxylic acids in the urine of rats dosed with styrene.

Male Wistar rats were dosed intraperitoneally with styrene (400 mg/kg). Urine samples were collected over phosphate buffer, pH 6.5 for 24 h. Excretion of mandelic (MA) and phenylglyoxylic acid (PGA) amounted to 1.66 +/- 0.62 and 5.21 +/- 2.44% of dose, respectively, as determined by ion-pair HPLC. After acidic hydrolysis, the amount of MA and PGA found in urine increased to 2.10 +/- 0.84 and 6.81 +/- 3.20% (mean +/- S.D.; n = 7), respectively. A similar increase was observed after alkaline hydrolysis of urine samples. Differences between hydrolysed and non-hydrolysed samples were significant in the paired t-test (P < 0.05). Further, urine samples were fractionated by HPLC. Fractions were subjected to acidic hydrolysis and analysed by HPLC and GC/MS. Both MA and PGA were detected in the fraction which did not contain any of these metabolites before hydrolytic treatment. Thus, MA and PGA, which are used as biomarkers of exposure to styrene, form hydrolysable conjugates in the rat. At least a minor part of the total urinary MA and PGA is bound in these conjugates.

Animals↗
PubMed1996

Oxidative phenotype polymorphism (P450 2D6) and metabolism of toluene.

Oxidative phenotype P-450 2D6 was examined using sparteine test in 3 groups of persons to determine if there is a coincidence in the defect of the oxidative biotransformation of sparteine and impaired oxidation of toluene, which could explain interindividual differences in the amounts of hippuric acid in the urine in exposed persons. The following groups of persons were examined: 30 rotogravure printers exposed to toluene vapors at concentrations of 8-307 ppm; 20 workers, 2 months after the cessation of the long-term exposure to toluene at concentrations of 104-1,170 ppm; 48 healthy volunteers with no exposure to toluene. Among the 98 persons 5 poor metabolizers (PMs) of sparteine were found, none in the group of printers exposed to toluene. In the experimental exposure chamber 5 PMs and 6 extensive metabolizers (EMs) were exposed to toluene concentration of 245 ppm for 5 hours. Hippuric acid and o-cresol in the urine, and toluene both in blood and in alveolar air were measured. However, no significant differences were found in either of these parameters between the PM and EM groups. Thus, the sparteine test does not appear to be applicable in the identification of persons with higher risk arising from toluene exposure.

Adult↗
PubMed1995

[Effectiveness of dilatation of distal urethral stenosis in girls].

Dilatation of distal urethral stenoses is one of the relatively frequent minor operations in child urology. The authors present a group of 830 female patients age 2-16 years treated by dilatation of the urethra in 1988-1994. According to the predominating finding they divide the cases into three groups--vesicoureteral reflux (VUR), infection of the urinary pathways (IUP), enuresis--and in these they evaluate the effectiveness of the operation, which was greatest in the group of patients with IUP (37%). Finally they discuss both possibilities of treatment of stenoses--dilatation and urethrotomy.

Adolescent↗
PubMed1994

Uptake, metabolism and elimination of cyclohexanone in humans.

The metabolism and toxicokinetics of cyclohexanone (CH-one), an important solvent and chemical intermediate, have been studied in volunteers during and after 8-h exposures to CH-one vapour at a concentration of 101, 207 and 406 mg.m-3. The pulmonary ventilation in these experiments was typically 11 l.min-1 and retention in the respiratory tract was 58%. After exposure to CH-one, 207 mg.m-3, the metabolic yields of cyclohexanol (CH-ol), 1,2- and 1,4-cyclohexanediol (CH-diol) as determined in urine by a gas chromatographic method involving hydrolysis of glucuronide conjugate were 1.0% +/- 0.3%, 39% +/- 5% and 18% +/- 2% (n = 8), respectively. Peak excretion of CH-ol was achieved at the end of the exposure period, after which it decayed rapidly. Elimination of 1,2- and 1,4-CH-diol reached maximum values a few hours following exposure, with subsequent elimination half-times of 16 +/- 2 and 18 +/- 4 h, respectively. Repeated exposure to CH-one vapour (around 200 mg.m-3) for five consecutive days (8 h/day) resulted in cumulative excretion of CH-diols. The permeation rate of CH-one liquid through the skin was 0.037-0.069 mg.cm-2.h-1 (n = 3), indicating that the contribution of percutaneous absorption to total CH-one occupational intake is of minor importance. CH-diols are recommended as biomarkers of exposure to CH-one.

Administration, Cutaneous↗
PubMed1994

[Use of heterotopic substitutes in the urinary bladder in children and adults].

Intestinal replacements of the urinary bladder are a solution of severe congenital damage of the lower urinary pathways also in young patients. The children tolerate the operation very well. Already at the age of four years they are able to cope with the catheterization of the stoma of the urinary reservoir. The continence of the lower urinary pathways contributes also considerably to improvement of the mental development of the child.

Adolescent↗
PubMed1994

Effects of essential phospholipids on the amino acid metabolism in whole body irradiated rats.

Ionizing radiation induces injury to cell membranes resulting in an increase of plasma amino acids concentration and catabolic response of the body. Essential phospholipids (EPL) administered before radiation protect the cell structures and can be used for their renewal. For this reason EPL are expected to have some effect on amino acid metabolism in radiation sickness. The adult male Wistar rats were injected with EPL in a dose of 125 mg EPL/kg b.w. (Essentiale) or saline solution. Three h later whole-body gamma irradiation with a single dose of 10 Gy was performed. Untreated pair-fed rats served as control. The rats were sacrificed 2 days after irradiation. In irradiated rats a decrease in body weight, increased concentrations of plasma amino acids, higher oxidation of branched chain keto acids in liver mitochondria, higher incorporation of leucine into liver proteins and decreased leucine incorporation into proteins of small intestine were observed. In EPL pretreated rats a longer survival time, a higher body weight, lower levels of plasma amino acids and higher protein synthesis in small intestine and in liver when compared with irradiated, saline treated rats were found. No significant changes were observed in branched chain amino acid oxidation measured by means of labeled ketoisocaproate in liver mitochondria.

Amino Acids↗
PubMed1993

Bronchial arteries in experimental pulmonary infarction: angiographic and morphometric study.

OBJECTIVES: The aim was to investigate (1) whether collateral bronchopulmonary circulation developing due to chronic pulmonary embolism could prevent the evolution of pulmonary infarction after induction of pulmonary venous outflow impairment; and (2) how collateral bronchopulmonary circulation developed after acute embolisation of the lung with impaired pulmonary venous outflow. METHODS: Fifty two mongrel dogs were studied. Thirty six dogs were experimental animals and 16 were in a control group. Unilateral impairment of pulmonary venous outflow was induced by constriction of the left pulmonary veins in two groups of experimental dogs: (1) three months after and (2) one hour before bilateral embolisation of the pulmonary artery. All animals were killed 12 days after constriction. The size of the bronchial arteries was evaluated from angiograms. The diameter and the wall thickness of the arteries were measured during histology. RESULTS: In all experimental dogs, haemorrhagic infarctions developed distally to emboli in the left lung regardless of whether the bronchial arteries were dilated before induction of pulmonary venous constriction or whether collateral circulation started to develop after pulmonary venous constriction. Constriction of the pulmonary veins was an essential factor for pulmonary infarction to develop as no infarction developed in the embolised regions of the right lungs with intact pulmonary venous outflow. Pulmonary venous constriction alone did not cause dilatation or hypertrophy of the bronchial arteries. After pulmonary artery embolisation, the same enlargement and hypertrophy of the bronchial arteries occurred both in the left lung with previously impaired venous outflow and in the right lung with intact pulmonary veins. CONCLUSIONS: Expanded bronchopulmonary circulation did not prevent the development of infarction in the embolised region of the lung with impaired pulmonary venous outflow. Development of collateral bronchopulmonary circulation was not influenced by previously impaired pulmonary venous outflow.

Animals↗