Cytogenetic analysis of buccal cells from shoeworkers and pathology and anatomy laboratory workers exposed to n-hexane,toluene, methyl ethyl ketone and formaldehyde

People employed in the shoe manufacture and repair industry are at an increased risk for cancer, the strongest evidence being for nasal cancer and leukaemia. A possible causal role for formaldehyde is likely for cancer of the buccal cavity and nasopharynx. Exfoliated buccal cells are good source of tissue for monitoring human exposure to inhaled and ingested occupational and environmental genotoxicants. To assess the cytogenetic damage related to occupational exposure to airborne chemicals during shoe-making and the processes in pathology and anatomy laboratories, the micronuclei (MN) count per 3000 cells was measured in buccal smears from shoe-workers (group I, n = 22) exposed to mainly n-hexane, toluene and methyl ethyl ketone (MEK) and from anatomy and pathology staff (group II, n = 28) exposed to formaldehyde (FA). Eighteen male university staff were used as controls. The mean time-weighted average (TWA) concentrations of n-hexane, toluene and MEK in 10 small shoe workshops were 58.07 p.p.m., 26.62 p.p.m. and 11.39 p.p.m., respectively. The measured air concentrations of FA in the breathing zone of the anatomy and pathology laboratory workers were between 2 and 4 p.p.m. Levels of 2,5-hexadione (2,5-HD) and hippuric acid (HA), metabolic markers of n-hexane and toluene exposure, respectively, were significantly higher in the urine of workers in group I than in control subjects (p < 0.001 and p < 0.01, respectively). The mean (±SD) MN frequencies in buccal mucosa cells from workers in group I, group II and controls were 0.62±0.45%, 0.71±0.56% and 0.33±0.30%, respectively (p < 0.05 and p < 0.05 compared with controls for group I and group II, respectively). The effects of smoking, age and duration of exposure on the frequency of micronucleated buccal cells from workers in all three groups studied were also evaluated. Overall, the results suggest that occupational exposure to organic solvents, mainly n-hexane, toluene, MEK and FA, may cause cytogenetic damage in buccal cells and that use of exfoliated buccal cells seems to be appropriate to measure exposure to organic solvents.     

Determination of 2,5-hexanedione,a metabolite of n-hexane,in urine: evaluation and application of three analytical methods

Three methods for the determination of 2,5-hexanedione (2,5-HD) in urine were compared in order to assess their applicability for toxicokinetic studies and biological monitoring of occupational exposure to n-hexane. Two of them were based on derivatization, followed by gas chromatography and electron-capture detection. of these two, one is a modification of the other, already published, method. The third one involves direct extraction of 2,5-HD followed by gas chromatography and flame-ionization detection. To determine 2,5-HD in urine of workers occupationally exposed to n-hexane, the most straightforward method, direct extraction of 2,5-HD from urine, has been proven to be the most suitable. However, in case of very low concentrations of 2,5-HD in urine, or analysis of small samples of blood, e.g. in kinetic studies, it is necessary to use a more sensitive procedure. The sensitivity of the methods based on the derivation of 2,5-HD followed by electron-capture detection, was, as expected, much higher in terms of analytical reliability. By using these methods, however, precautions are necessary to avoid a matrix effect.     

Evaluation of 2,5-hexanedione in urine of workers exposed to n-hexane in Brazilian shoe factories

Urinary 2,5-hexanedione (2,5-HD) is used as a biomarker for biological monitoring of workers exposed to n-hexane. The purpose of this study was to compare two types of treatment of urine samples during clean-up (with and without acidic hydrolysis) and to study the exposure situation of workers exposed to n-hexane during shoe manufacturing. There, various glues containing n-hexane are used. Quantification of 2,5-HD was carried out by gas chromatography and flame ionization detection (GC-FID). Fifty-two urine samples taken from workers of seven shoe factories were analyzed. Thirty-four persons from the administrative staff of the same factories served as controls. They were not known to be exposed to n-hexane. The samples treated with acidic hydrolysis showed levels (average 0.94 mg/l) approximately 10 times higher than samples without acidic hydrolysis (0.09 mg/l). The difference is predominantly caused by the conversion of other metabolites of n-hexane (e.g. 4,5-dihydroxy-2-hexanone) to 2,5-HD in the presence of acids. Our results also show, that exposure to n-hexane is different between various industries. Levels of 2,5-HD in urine are predominantly dependent on the type of operation (how the glue is applied on the leather during shoe manufacturing). Simple measures, e.g. using a glue handgun instead of a paintbrush significantly decreased exposure to n-hexane.     

Cytogenetic analysis of buccal cells from shoe-workers and pathology and anatomy laboratory workers exposed to n-hexane, toluene, methyl ethyl ketone and formaldehyde.

People employed in the shoe manufacture and repair industry are at an increased risk for cancer, the strongest evidence being for nasal cancer and leukaemia. A possible causal role for formaldehyde is likely for cancer of the buccal cavity and nasopharynx. Exfoliated buccal cells are good source of tissue for monitoring human exposure to inhaled and ingested occupational and environmental genotoxicants. To assess the cytogenetic damage related to occupational exposure to airborne chemicals during shoe-making and the processes in pathology and anatomy laboratories, the micronuclei (MN) count per 3000 cells was measured in buccal smears from shoe-workers (group I, n = 22) exposed to mainly n-hexane, toluene and methyl ethyl ketone (MEK) and from anatomy and pathology staff (group II, n = 28) exposed to formaldehyde (FA). Eighteen male university staff were used as controls. The mean time-weighted average (TWA) concentrations of n-hexane, toluene and MEK in 10 small shoe workshops were 58.07 p.p.m., 26.62 p.p.m. and 11.39 p.p.m., respectively. The measured air concentrations of FA in the breathing zone of the anatomy and pathology laboratory workers were between 2 and 4 p.p.m. Levels of 2,5-hexadione (2,5-HD) and hippuric acid (HA), metabolic markers of n-hexane and toluene exposure, respectively, were significantly higher in the urine of workers in group I than in control subjects (p < 0.001 and p < 0.01, respectively). The mean (+/- SD) MN (0/00) [corrected] frequencies in buccal mucosa cells from workers in group I, group II and controls were 0.62 +/- 0.45%, 0.71 +/- 0.56% and 0.33 +/- 0.30%, respectively (p < 0.05 and p < 0.05 compared with controls for group I and group II, respectively). The effects of smoking, age and duration of exposure on the frequency of micronucleated buccal cells from workers in all three groups studied were also evaluated. Overall, the results suggest that occupational exposure to organic solvents, mainly n-hexane, toluene, MEK and FA, may cause cytogenetic damage in buccal cells and that use of exfoliated buccal cells seems to be appropriate to measure exposure to organic solvents.     

A note on urinary trans,trans-muconic acid level among Thai press workers

Benzene is a common toxic volatile substance associated with many industrial processes. Benzene exposure is of particular concern because recent research indicates that it can result in chronic toxicity and thousands of workers in industrial plants experience ongoing exposure. Therefore, the determination and control of benzene exposure among at-risk workers is very important. Urinary trans,trans-muconic acid (ttMA) determination is a helpful test for monitoring groups of at-risk workers for exposure to benzene. In this study, 103 urine samples were obtained from 60 controls and 43 occupational exposed press workers in a press factory in Bangkok. All samples were analysed for ttMA using a previously reported method. The average urinary ttMA levels for the control and exposed groups were 0.08±0.03 mg g^?1 creatinine and 0.56±0.65 mg g^?1 creatinine, respectively. Significantly higher urinary ttMA levels were observed among the press workers (p=0.03). The introduction of public health policies concerning the prevention of exposure to benzene among at-risk workers is recommended, and more widespread use of biological monitoring for the assessment and control of occupational exposure to industrial chemicals is encouraged.     

Biological monitoring of exposure to sevoflurane in operating room personnel by the measurement of hexafluoroisopropanol and fluoride in urine

The objectives of this study were to evaluate the value of urinary hexafluoroisopropanol (HFIP) and fluoride (F^-) measurement for the biological monitoring of operating room personnel exposed to sevoflurane. Fifty members of operating room staffs from eight different hospitals took part in the study. To assess external exposure to sevoflurane, air samples were collected during the whole anaesthesia period by a passive sampling device (3M 3500 organic vapour monitor) attached close to the breathing zone of each subject. Urine was collected before (BA) and at the end of anaesthesia (EA) for the determination of HFIP, fluoride and creatinine. Average airborne concentration of sevoflurane was 19.0 ppm (range: ND-139.9 ppm) with a mean duration of anaesthesia of 221 min (range: 60-435 min). There was a better correlation between external and internal exposure as estimated by EA urinary HFIP (r = 0.78; p &lt;0.0001) compared with EA urinary F^- (r = 0.41; p = 0.0031). Furthermore determination of urinary HFIP seemed more suited than that of F^- for the assessment of sevoflurane exposure because of lower background in BA samples (86 % of BA HFIP values were under the limit of detection). Based on these results, values of 9.6 and 4.3 mg HFIP g^-1 creatinine correspond to airborne concentrations of 50 and 20 ppm of sevoflurane, respectively. Among the confounding parameters investigated (body mass index (BMI), sex, cytochrome P450 polymorphism) only BMI showed statistically significant influence on sevoflurane metabolism at these low levels of exposure. The measurement of HFIP in urine at the end of the surgical procedure constitutes a good index to assess occupational exposure to sevoflurane. Further studies will be necessary to propose an health-based limit value which remains to be determined from the relationship between effects and internal dose as can be assessed by HFIP measurement in urine.     

Urinary 2,5 hexanedione as a biomarker of n-hexane exposure

n-Hexane is a saturated aliphatic hydrocarbon widely used in industry. In most cases it is used as a mixture with hexane isomers and various others solvents in the form of commercial hexane. n-Hexane is metabolized oxidatively to a number of compounds, including 2,5-hexanedione (2,5-HD), which is eliminated through the urine and is implicated in the neurotoxic effect of this solvent. The main objective of this study was to evaluate urinary 2,5-HD as a biomarker of n-hexane exposure. The study was carried out in seven industrial units. Post-shift urine samples from 111 workers who handled commercial hexane were collected and analysed for 2,5-HD by capillary gas chromatography. Air sampling was performed in the breathing zones of the workers, and the air samples were analysed using validated methods. Monitoring individual exposures showed that n-hexane exposure varied from 5 to 70 p.p.m. (mean ±SD = 15.24 ±2.98 p.p.m.). Significant correlation was observed between exposure to n-hexane and urinary 2,5-HD levels, with high correlation coefficients ( ρ= 0.81, p = 0.000), suggesting that urinary 2,5-HD is a good biomarker of occupational exposure to n-hexane. Urinary 2,5-HD is recommended as a better tool than air monitoring in the assessment of health risk, namely the early detection of n-hexane neurotoxicity.     

Biological monitoring among benzene-exposed workers in Bangalore city,India

Abstract

Environmental and biological monitoring was carried out in the winter season of 2004 for 30 gasoline station workers (study subjects) and 30 office workers (controls) of Bangalore city, India. Personal air sampling was carried out in the breathing zone of workers using an Anasorb CSC sorbent tube (SKC 226-01) fitted to the low-flow personal samplers (PCXR4 and pocket pump Model No. 210-1002) at a flow rate of 200 ml min^?1 during the shift work of 8 h. The benzene content adsorbed in the sorbent tube (SKC 226-01) was desorbed with 1 ml of benzene-free carbon disulfide on a developing vibrator and later analysed by Trace GC fitted with MXT-624 column and flame ionization detector. The mean time weighted average benzene concentration found among study and controls was 1.10±1.08 and 0.070±0.035 mg m^?3, respectively. Biological monitoring for benzene exposure was performed by measuring trans,trans muconic acid (t,t-MA) in the end shift urine samples using HPLC-UV technique. End-shift urine samples (1 ml) were adjusted to pH 7–9 with phosphate buffer pH 7.4 passed through the preconditioned Q-SAX anion-exchange cartridge and the (t,t-MA) is extracted with 10% acetic acid and later analysed by HPLC-UV detection The mean t,t-MA found among study and controls were 563.16±281.81 and 266.88±110.65 µg g^?1 creatinine. About 50% of the study subjects (15) have higher t,t-MA values than the biological exposure index of the American Conference of Government Industrial Hygienist (ACGIH). Correlation is significant at 5% level (p<0.05) between personal air benzene concentration and urinary t,t-MA in the study group. Based on these findings, the t,t-MA can be used as a biomarker for benzene exposure.     

Association between metabolic gene polymorphisms and susceptibility to peripheral nerve damage in workers exposed to n-hexane: A preliminary study

Abstract

Chronic exposure to n-hexane may result in peripheral neuropathy. 2,5-Hexanedione (2,5-HD) has been identified as a toxic metabolite of n-hexane. The CYP2E1, CYP1A1 and GST genes are involved in the formation of 2,5-hexanedione from n-hexane as well as the elimination of 2,5-HD-formed electrophile, and these genes are highly polymorphic in the general population. A nested case-control study in an industrial cohort was conducted to evaluate the associations between polymorphisms in these metabolic genes and n-hexane-induced peripheral nerve damage. The study subjects included 22 cases, who worked in a printing factory with symptoms of peripheral nerve damage, and 163 controls, who came from the same factory of cases. DNA was extracted from blood samples and genotyping was conducted for CYP2E1 Pst, CYP2E1 Dra, CYP2E1 Ins96, CYP1A1 Msp, GSTT1 null, GSTM1 null and GSTP1 105V. Unconditional logistic regression was applied to estimate the odds ratio and 95% confidence intervals. There were no significant differences between the two groups regarding age, sex, smoking and alcohol status. A significant association between Dra polymorphism and peripheral nerve damage was found. The frequency of CYP2E1 Dra homozygous mutation in the case group (18.2%) was higher than that in the control group (3.7%, p=0.015). Individuals with homozygote genotype (CC) of CYP2E1 Dra had a significantly higher risk of peripheral nerve damage compared with those with DD genotype (adjusted OR?=?5.58, 95% CI?=?1.32–23.65) after n-hexane exposure duration, sex, age, smoking and alcohol status were adjusted. No significant association was found that CYP2E1 Pst, CYP2E1 Ins96, CYP1A1 Msp, GSTT1, GSTM1, GSTP gene polymorphisms associated with the susceptibility of peripheral nerve damage. These findings suggested that CYP2E1 gene might increase the susceptibility to n-hexane-induced peripheral damage.     

Assessment of occupational exposure to PAHs in an Estonian coke oven plant- correlation of total external exposure to internal dose measured as 1-hydroxypyrene concentration

The exposure of cokery workers to polynuclear aromatic hydrocarbons at an Estonian oil shale processing plant was assessed by using occupational hygiene and biomonitoring measurements which were carried out twice, in midwinter and in the autumn. To assess the external dose of polynuclear aromatic hydrocarbons, pyrene and benzo[a]pyrene concentrations were measured from the breathing zone of workers during a workshift. Skin contamination with pyrene and benzo[a]pyrene was assessed by skin wipe sampling before and after the workshift. As a biomarker of overall exposure to polynuclear aromatic hydrocarbons, and as an integral of all absorption routes of pyrene, 1-hydroxypyrene concentration was measured from post shift urine samples. Of the personal air samples, 18% exceeded the Finnish threshold limit value of benzo[a]pyrene (10 μg m^-3). Mean value (two separate measurements together) for benzo[a]pyrene was 5.7 μg m^-3 and for pyrene, 8.1 μg m^-3. Based on skin wipe sample analyses, the skin contamination was also obvious. The mean value of benzo[a]pyrene in the samples collected after the shift was 1.2 ng cm^-2. Benzo[a]pyrene was not found in control samples. The mean value of urinary 1-hydroxypyrene concentration was 6.0 μmol mol^-1 creatinine for the exposed workers and 0.5 μmol mol^-1 creatinine for the controls. This study undoubtedly shows the usefulness of 1-hydroxypyrene as an indicator of internal dose of polynuclear aromatic hydrocarbons. It can be concluded that the cokery workers at the Kohtla-Järve plant are exposed to high concentrations of polynuclear aromatic compounds, and the exposure level is considerably higher during the winter measurements.     

Urinary 2,5 hexanedione as a biomarker of n-hexane exposure

n-Hexane is a saturated aliphatic hydrocarbon widely used in industry. In most cases it is used as a mixture with hexane isomers and various others solvents in the form of commercial hexane. n-Hexane is metabolized oxidatively to a number of compounds, including 2,5-hexanedione (2,5-HD), which is eliminated through the urine and is implicated in the neurotoxic effect of this solvent. The main objective of this study was to evaluate urinary 2,5-HD as a biomarker of n-hexane exposure. The study was carried out in seven industrial units. Post-shift urine samples from 111 workers who handled commercial hexane were collected and analysed for 2,5-HD by capillary gas chromatography. Air sampling was performed in the breathing zones of the workers, and the air samples were analysed using validated methods. Monitoring individual exposures showed that n-hexane exposure varied from 5 to 70 p.p.m. (mean±SD = 15.24±2.98 p.p.m.). Significant correlation was observed between exposure to n-hexane and urinary 2,5-HD levels, with high correlation coefficients (ρ= 0.81, p = 0.000), suggesting that urinary 2,5-HD is a good biomarker of occupational exposure to n-hexane. Urinary 2,5-HD is recommended as a better tool than air monitoring in the assessment of health risk, namely the early detection of n-hexane neurotoxicity.     

The imbalance between dynamic and stable microtubules underlies neurodegeneration induced by 2,5-hexanedione

Exposure to environmental toxins, including hydrocarbon solvents, increases the risk of developing Parkinson's disease. An emergent hypothesis considers microtubule dysfunction as one of the crucial events in triggering neuronal degeneration in Parkinson's disease. Here, we used 2,5-hexanedione (2,5-HD), the toxic metabolite of n-hexane, to analyse the early effects of toxin-induced neurodegeneration on the cytoskeleton in multiple model systems. In PC12 cells differentiated with nerve growth factor for 5 days, we found that 2,5-HD treatment affected all the cytoskeletal components. Moreover, we observed alterations in microtubule distribution and stability, in addition to the imbalance of post-translational modifications of α-tubulin. Similar defects were also found in vivo in 2,5-HD-intoxicated mice. Interestingly, we also found that 2,5-HD exposure induced significant changes in microtubule stability in human skin fibroblasts obtained from Parkinson's disease patients harbouring mutations in PRKN gene, whereas it was ineffective in healthy donor fibroblasts, suggesting that the genetic background may really make the difference in microtubule susceptibility to this environmental Parkinson's disease-related toxin. In conclusion, by showing the imbalance between dynamic and stable microtubules in hydrocarbon-induced parkinsonism, our data support the crucial role of microtubule defects in triggering neurodegeneration.     

Evaluation of increased proportion of cells with unusually high sister chromatid exchange counts as a cytogenetic biomarker for lead exposure

Sister chromatid exchange (SCE) frequency and high-frequency cells (HFCs) were analyzed in 50 storage battery plant workers with mean blood lead level (BLL) of 40.14±9.99 μg/dL. The mean BLL in the control group (n=30) was 9.77±1.67 μg/dL. This difference in mean BLLs between control and exposed group was statistically significant (p<0.05) and reflects clearly the lead exposure in the workers. Urinary aminolevulinic acid (U-ALA) was also determined in both control (3.37±0.89 mg ALA/g creatinine) and exposed groups (12.39±6.18 mg ALA/g creatinine) and U-ALA excretion was statistically higher (p<0.05) in lead-exposed workers. The relationship between biomarkers of lead exposure/effect and HFC percentage was higher than the relationship between biomarkers of lead exposure/effect and SCE frequency. Accordingly, HFC analysis seemed to be more sensitive than the SCE analysis as a cytogenetic biomarker for lead exposure. Additionally, the statistically significant correlation (r ²=0.880, p<0.01) between U-ALA excretion and HFC percentage in lead-exposed workers supported the probability of ALA mediated indirect mechanism for lead genotoxicity.     

Analysis and evaluation of trans,trans-muconic acid as a biomarker for benzene exposure

Benzene is an important industrial chemical and, due to its occurrence in mineral oil and its formation in many combustion processes, a widespread environmental pollutant. Since benzene is hematoxic and has been classified as a human carcinogen, monitoring and control of benzene exposure is of importance. Although trans,trans-muconic acid (ttMA) was identified as a urinary metabolite of benzene at the beginning of this century, only recently has its application as a biomarker for occupational and environmental benzene exposure been investigated. The range of metabolic conversion of benzene to ttMA is about 2–25% and dependent on the benzene exposure level, simultaneous exposure to toluene, and probably also to genetic factors. For the quantitation of ttMA in urine, HPLC methods using UV and diode array detection as well as GC methods combined with MS or FID detection have been described. Sample pretreatment for both HPLC and GC analysis comprises centrifugation and enrichment by solid-phase extraction on anion-exchange sorbents. Described derivatization procedures prior to GC analysis include reaction with N,O-bis(trimethysilyl)acetamide, N,O-bis(trimethylsilyl)trifluoroacetamide, pentafluorobenzyl bromide and borontrifluoride–methanol. Reported limits of detection for HPLC methods range from 0.1 to 0.003 mg l⁻¹, whereas those reported for GC methods are 0.03–0.01 mg l⁻¹. Due to its higher specificity, GC methods appear to be more suitable for determination of low urinary ttMA levels caused by environmental exposure to benzene. In studies with occupational exposure to benzene (>0.1 ppm), good correlations between urinary ttMA excretion and benzene levels in breathing air are observed. From the reported regressions for these variables, mean excretion rates of ttMA of 1.9 mg g⁻¹ creatinine or 2.5 mg l⁻¹ at an exposure dose of 1 ppm over 8 h can be calculated. The smoking-related increase in urinary ttMA excretion reported in twelve studies ranged from 0.022 to 0.2 mg g⁻¹ creatinine. Only a few studies have investigated the effect of exposure to environmental levels of benzene (<0.01 ppm) on urinary ttMA excretion. A trend for slightly increased ttMA levels in subjects living in areas with high automobile traffic density was observed, whereas exposure to environmental tobacco smoke did not significantly increase the urinary ttMA excretion. It is concluded that urinary ttMA is a suitable biomarker for benzene exposure at occupational levels as low as 0.1 ppm. Biomonitoring of exposure to environmental benzene levels (<0.01 ppm) using urinary ttMA appears to be possible only if the ingestion of dietary sorbic acid, another precursor to urinary ttMA, is taken into account.     

Simultaneous determination of urinary 1- and 2-naphthols, 3- and 9-phenanthrols,and 1-pyrenol in coke oven workers

A method was developed for simultaneous quantification of urinary 1- and 2-naphthols, 3- and 9-phenanthrols and 1-pyrenol using gas chromatography with mass spectrometry (GC-MS). This method was applied to urine samples from coke oven workers (n =28) and controls (n =22) from Northern China. Geometric mean levels of urinary 1-naphthol (58.8 μg l^?1), 2-naphthol (34.1 μg l^?1), 3-phenanthrol (7.35 μg l^?1), 9-phenanthrol (1.28 μg l^?1) and 1-pyrenol (25.4 μg l^?1) were significantly higher among coke oven workers than controls. All the substances tested were highest among top-of-oven workers, who had 15-fold higher 1-naphthol, eight-fold higher 2-naphthol and 20-fold higher 1-pyrenol levels compared with controls. Using multiple linear regression models, 72.5% of the variation in 1- and 2-naphthol and 82.8% of the variation in 1-pyrenol were explained by the concentration of naphthalene or pyrene in the urine, the work category and the smoking intensity. Cigarette consumption significantly contributed to levels of urinary 1-pyrenol and naphthols, particularly 2-naphthol. A negative relationship between work category and the ratio of naphthols/1-pyrenol was observed among smokers. Our results suggest that urinary naphthols and phenanthrols reflect polycyclic aromatic hydrocarbon (PAH) exposure as well as the widely used 1-pyrenol, and that interactions between cigarette smoking and PAH exposure result in different patterns of metabolism for individual PAHs.     

Association between urinary indicators of renal dysfunction and metal concentrations in workers chronically co-exposed to cadmium,zinc and lead

The study was carried out in 31 workers co-exposed to cadmium, lead and zinc fumes and dusts in a zinc ore refinery. Urinary cadmium, lead, zinc, β₂-M levels and NAG activities were determined to evaluate the possible dose-effect relationship between these parameters. A correlation was found between urinary cadmium, lead and zinc concentrations, and urinary β₂-M levels and NAG activities of the exposed group. A statistically significant increase was also observed for urinary NAG activity in exposed workers who had urinary cadmium concentrations > 2 μg g^?1 creatinine. However, in the same exposed group, the increment of β₂-M was not statistically significant. In conclusion, the present study thus confirms the earlier observations and may suggest the notion that the urinary NAG seems to be a more sensitive indicator than urinary β₂-M level in early stages of renal injury of moderately cadmium co-exposure with lead and zinc even at urinary cadmium concentration as low as 2 μg g^?1 creatinine. When the earlier studies on the irreversibility of cadmium-induced tubular dysfunction and the present results were taken into consideration, the present health-based biological limit proposed by the WHO (5 μg g^?1 creatinine) seems to be high for the occupational exposure to cadmium.     

Production of styrene oxide from styrene by a recombinant Escherichia coli with enhanced AcrAB-TolC efflux pump level in an aqueous-organic solvent two-phase system

ABSTRACT

The AcrAB-TolC efflux pump is involved in the organic solvent tolerance of Escherichia coli. Most E. coli strains are highly sensitive to organic solvents such as n-hexane and cyclohexane. Here, a recombinant E. coli transformed with an expression plasmid containing acrAB and tolC became tolerant to n-hexane and cyclohexane. The levels of AcrA, AcrB, and TolC in the recombinant increased by 3- to 5-fold compared to those in the control strain without the plasmid for acrAB or tolC. To investigate the usability of the recombinant as a biocatalyst in an aqueous-organic solvent two-phase system, we further introduced xylMA xylene monooxygenase genes from Pseudomonas putida mt-2 into the recombinant and examined the production of styrene oxide from styrene. The resulting recombinant produced 1.8 mg and 1.0 mg styrene oxide mL^?1 of medium in a medium overlaid with a 25% volume of n-hexane and cyclohexane containing 10% (wt vol^?1) styrene, respectively.     

Efficient method for the quantitation of urinary leukotriene E4: extraction using an Empore C18 disk cartridge

We describe here an efficient procedure for the precise quantitation of leukotriene E₄ (LTE₄) in a small volume of urine, which was achieved mainly by the use of an Empore extraction disk cartridge. After addition of [³H]LTE₄ to 2 ml of urine, an Empore C₁₈ cartridge was used for initial extraction of the urine, which resulted in the extraction of LTE₄ in a small volume of solvent. The eluate could then be injected onto a high-performance liquid chromatography column without further concentration. After separation by high-performance liquid chromatography, LTE₄ was extracted from the effluent using an Empore C₁₈ cartridge. The concentration of LTE₄ was subsequently quantified by enzyme immunoassay. LTE₄ can be recovered from urine with sufficient efficiency (69.9±4.7%, mean±S.D., n = 101). The coefficient of variation of the assay procedure was less than 10%. When urine was spiked with different amounts of LTE₄, the recovery of LTE₄ added to the urine specimen was less than 120%. The concentration of LTE₄ in urine from normal healthy subjects was 48.0±15.3 pg/mg creatinine (n = 15).     

Redox status of the testes and sperm of rats following exposure to 2,5-hexanedione

Objectives: Exposure to 2,5-hexanedione (2,5-HD) is well known to be associated with reproductive dysfunctions in both humans and animals. However, the role of oxidative stress in 2,5-HD-induced toxicity in testes and sperm has not yet been studied.

Methodology: The present study investigated the influence of 2,5-HD on antioxidant systems in the testes and epididymal sperm of rats following exposure to 0, 0.25, 0.5, and 1% 2,5-HD in drinking water for 21 consecutive days.

Results: Administration of 0.5% 2,5-HD significantly (P?<?0.05) decreased epididymis weight, whereas 1% 2,5-HD-treated rats showed significantly decreased body weight, testis, and epididymis weights compared with the control group. Exposure to 2,5-HD caused a significant dose-dependent increase in the activities of superoxide dismutase, catalase, and glutathione peroxidase in both testes and sperm compared with the control group. Moreover, 2,5-HD-exposed rats showed significant decrease in glutathione-S-transferase activity and glutathione level with concomitant significant elevation in the levels of hydrogen peroxide and malondialdehyde in both testes and sperm. Testicular and epididymal atrophy with significant, dose-dependent, decrease in epididymal sperm number, sperm motility, and viability were observed in 2,5-HD-treated rats.

Conclusion: 2,5-HD exposure impaired testicular function and sperm characteristics by disruption of the antioxidant systems and consequently, increased oxidative stress in the treated rats.     

Different Administration Schedules of the Same Dose of 2,5-Hexanedione Influence the Development of Neuropathy and the Toxicokinetics

The same total dose (1.2 g/kg/week) of 2,5-hexanedione (2,5-HD) was administered subcutaneously at 100 mg/kg/12 hr, 200 mg/kg/24 hr, and 400 mg/kg/48 hr to three groups of Donryu rats. The peripheral neuropathy induced by 2,5-HD was confirmed by clinical observation every day, and neurophysiological measurements every 4 weeks. During the 15th week of this experiment, 2,5-HD concentrations in plasma 0.5 to 24 hours after injection were determined. It was found that the greater the dose of 2,5-HD per treatment injected, the earlier peripheral neuropathy developed. Toxicokinetic analysis showed that both the values of the area under the plasma concentration versus time curve and the half life of 2,5-HD were increased, but the excretion parameters (Ke) were decreased, in animals treated with 200 mg/kg/24 hr and 400 mg/kg/48 hr 2,5-HD.