Influence of genetic polymorphism on t,t-MA/S-PMA ratio in 301 benzene exposed subjects.

This study investigated the effect of polymorphic genes GSTT1, GSTM1, GSTA1, EHPX1, NQO1, CYP2E1, CYP1A and MPO on the urinary concentrations and ratio (R) of the benzene metabolites trans,trans-muconic acid (t,t-MA) and S-phenyl mercapturic acid (S-PMA) in 301 oil refinery workers. The metabolites' concentrations are lower and R is higher (100.66) in non-smokers (n=184) than in smokers (n=117, R=36.54). Non-smokers have lower S-PMA and a higher R in GSTT1 null genotypes than in positive, and a higher S-PMA and a lower R in GSTA1 wild type genotypes. In smokers the GSTT1 null genotype effect on both S-PMA and R is confirmed, and is also shown in GSTM1 null, but not in GSTA1 wild type genotypes. GSTT1 null polymorphism reduces the conjugation rate of benzene epoxide with GSH, and to a lesser extent also GSTTA1 mutant, GSTM1 null and NQO1 mutant genotypes. The activity of one GST is compensated by another in GSTM1 and GSTA1 defective subjects, but not in GSTT1 null genotypes, whose average S-PMA excretion is about 50% with respect to the positive ones, for the same benzene exposure. R showed to be a more sensitive marker for these effects than the metabolite levels.

Treatment of osteoid osteoma with CT-guided percutaneous radiofrequency thermoablation.

Osteoid osteoma is a benign bone tumor with a male predominance occurring mainly in children and young adults. The most common symptom is intermittent pain that worsens at night and is at least partially relieved by nonsteroidal anti-inflammatory drugs. The purpose of this study was to assess the long-term effectiveness of computed tomography-guided percutaneous radiofrequency thermoablation in patients with a minimum follow-up of 2 years. Twenty patients with osteoid osteoma (15 men and 5 women) with a mean age of 20.7 years (range, 4-61 years; 12 patients aged 20 years or younger) underwent computed tomography-guided percutaneous radiofrequency thermoablation. Lesion sites were the femur (n=9), tibia (n=7), pelvis (n=1), talus (n=1), cuneiform bone (n=1), and humerus (n=1). Mean follow-up was 44 months (range, 3-106 months). Pain relief was significant in 95% of patients; it disappeared within 24 hours in 14 patients, within 3 days in 4, and within 7 days in 1. The patient with persistent symptoms underwent another percutaneous radiofrequency thermoablation procedure that was successful. The difference between pre- and postoperative pain was significant (P ≤ .01). No recurrences occurred. Computed tomography-guided percutaneous radiofrequency thermoablation is a safe, minimally invasive, and economical procedure with high technical and clinical success rates, and it effectively and durably enhances quality of life.

Correlation between environmental and biological monitoring of exposure to benzene in petrochemical industry operators.

The present work was aimed to study in petrochemical industry operators the correlation, if any, between environmental exposure to low levels of benzene and two biological exposure indexes in end-shift urine, i.e. trans, trans-muconic acid (t,t-MA) and S-phenylmercapturic acid (SPMA). Exposure to benzene was assessed in 133 male subjects employed in outdoor operations in a petrochemical plant, using personal passive-diffusive air samplers worn at the breathing zone; adsorbed benzene was determined by GC-FID analysis. S-PMA was determined by a new HPLCMS/MS method, after (quantitative) acidic hydrolysis of the cysteine conjugate precursor. t,t-MA was measured by an HPLC-UV method. Smoking habits were assessed by means of a self-administered questionnaire. Both environmental and biological monitoring data showed that benzene exposure of petrochemical industry operators was low (mean values were 0.014ppm, 101mug/g creat, and 2.8mug/g creat, for benzene, t,t-MA, and S-PMA, respectively) if compared with the ACGIH limits. Cigarette smoking was confirmed to be a strong confounding factor for the urinary excretion of both metabolites: statistically significant increases of t,t-MA and S-PMA levels were recorded in smokers when compared to non-smokers (p<0.0001). The best correlation found was that between exposure to benzene and S-PMA levels, particularly in non-smokers. This was partly due to the hydrolysis of the S-PMA precursor N-acetyl-S-(1,2-dihydro-2-hydroxyphenyl)-l-cysteine, a crucial step of the new analytical method used, which indeed reduced the variability of the results by means of an improved standardization of this critical preanalytical factor. A weaker correlation was found between exposure to benzene and t,t-MA, possibly explained by the fact that the latter is also a metabolite of sorbic acid, a common diet component. In summary, even at such low levels of exposure, urinary metabolites proved to be a useful tool for assessing individual occupational exposure to benzene, S-PMA appearing to be a more specific biomarker than t,t-MA, particularly in non-smokers.