Determination of mandelic acid and phenylglyoxylic acid in urine by reagent-free ion chromatography / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To develop a method for determination of mandelic acid (MA) and phenylglyoxylic acid (PGA) in urine by reagent-free ion chromatography.</p><p><b>METHODS</b>Ion chromatography was performed on an AS19 column with a gradient elution solution containing 10-35 mmoL/L KOH at a flow rate of 1.00 ml/min, and MA and PGA were detected at ultraviolet wavelengths of 225 nm and 254 nm, respectively. The samples were diluted 10 times with purified water, then purified on a silver column to remove high concentrations of chloride ion, and injected after being filtered through a 0.2-µm m filter membrane.</p><p><b>RESULTS</b>The recoveries of standard addition of MA and PGA were 96.5% and 99.3%, respectively, with both relative standard deviations less than 5.0%. Good linear relationships were noted in the range of 1.0-100.0 mg/L for both MA and PGA (r >0.9995). The detection limits of MA and PGA were 0.02 mg/L and 0.05 mg/L, respectively; the minimum detectable concentrations of MA and PGA were 0.2 mg/L and 0.5 mg/L (when the sampling amount was 5.0 ml and diluted to 50.0 ml with water, and the injection volume was 300 µL).</p><p><b>CONCLUSIONS</b>This method is fast, convenient, and highly sensitive and selective. It can be used for the analysis of MA and PGA in the urine of styrene-exposed workers.</p>

Influence of genetic polymorphisms of epoxide hydrolase 1 on metabolism of styrene in body / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To investigate the role of genetic polymorphisms of epoxide hydrolase 1 (EPHX1) in the metabolism of styrene in vivo.</p><p><b>METHODS</b>Fifty-six styrene-exposed workers, who worked in the painting workshop of an enterprise for manufacturing glass fiber-reinforced plastic yachts in Shandong Province, China for over one year and were protected in approximately the same way, were selected as study subjects. The 8-hour time-weighted average concentration (8 h-TWA) of styrene and the concentrations of mandelic acid (MA) and phenyl glyoxylic acid (PGA) as urinary metabolites were measured. The genetic polymorphisms of EPHX1 were detected by polymerase chain reaction-restriction fragment length polymorphism analysis.</p><p><b>RESULTS</b>The urinary concentrations of MA and PGA were 177.25±82.36 mg/g Cr and 145.91±69.73 mg/g Cr, respectively, and the 8 h-TWA of styrene was 133.28±95.81 mg/m3. Urinary concentrations of MA and PGA were positively correlated with 8 h-TWA of styrene (R=0.861, P < 0.05; R=0.868, P < 0.05). The subjects were divided into high-exposure group (8 h-TWA >50 mg/m(3)) and low-exposure group (8 h-TWA ≤ 50 mg/m(3), and in the two groups, the urinary concentrations of MA and PGA were significantly higher in the individuals carrying high-activity genotypes of EPHX1 than in those carrying low-activity genotypes of EPHX1 (P < 0.05).</p><p><b>CONCLUSION</b>Genetic polymorphisms of EPHX1 play an important role in the metabolic process of styrene in vivo.</p>

Acute oxalate nephropathy caused by ethylene glycol poisoning

Ethylene glycol (EG) is a sweet-tasting, odorless organic solvent found in many agents, such as anti-freeze. EG is composed of four organic acids: glycoaldehyde, glycolic acid, glyoxylic acid and oxalic acid in vivo. These metabolites are cellular toxins that can cause cardio-pulmonary failure, life-threatening metabolic acidosis, central nervous system depression, and kidney injury. Oxalic acid is the end product of EG, which can precipitate to crystals of calcium oxalate monohydrate in the tubular lumen and has been linked to acute kidney injury. We report a case of EG-induced oxalate nephropathy, with the diagnosis confirmed by kidney biopsy, which showed acute tubular injury of the kidneys with extensive intracellular and intraluminal calcium oxalate monohydrate crystal depositions.

Prophylaxis and therapeutic effects of raspberry (Rubus idaeus) on renal stone formation in Balb/c mice

PURPOSE: To evaluate the prophylactic potential of herbal decoction from Rubus idaeus, a medicinal plant widely used in the Middle East to treat kidney stones, by assessing the effect of administration in experimentally induced calcium oxalate (CaOx) nephrolithiasis in mice. MATERIALS AND METHODS: This study was based on administration of glyoxylate and/or herbal treatments simultaneously for 12 days, followed by histological and biochemical tests. Group I was used as a negative control. Group II was only given daily intra-abdominal injection of glyoxylate (80 mg/Kg). Group III and IV were given 100 mg/kg/day and 200 mg/kg/day of aqueous extract of R. idaeus by gavage, respectively in addition to glyoxylate injection. To examine the effect of anti-oxidants on hyperoxaluria-induced changes in kidney, the enzymatic and non-enzymatic anti-oxidant levels were assessed. RESULTS: Significant reductions were obtained in the urinary oxalate, calcium and phosphorus values in the herbal-treated groups relative to untreated animals while creatinine excretion increased. Serum oxalate, calcium and creatinine were significantly reduced, while phosphorus was not significantly changed. Kidney content of calcium was higher in the untreated group. Mice in treated groups at 12 days had significantly more superoxide dismutase, catalase, glutathione reductase (GSH) and G6PD activities than the untreated group. Hyperoxaluria-induced generation of malondialdehyde (MDA) and protein carbonyls was significantly prevented in the treated groups. R. idaeus had a significantly high content of vitamin E in the herbal treated groups. The histology showed more CaOx deposition in the kidneys of untreated animals. CONCLUSION: Rubus idaeus has an impressive prophylactic effect on CaOx stones in nephrolithic mice. There is a possible role of lipid peroxidation in CaOx stone formation which may has a relationship with the major risk factors in urine including oxalate, calcium, phosphorus and MDA. Further experimental studies are required to elucidate the chemical constituents of the active ingredients of this interesting plant.

A Case of Primary Hyperoxaluria with Renal Allograft Dysfunction / 대한신장학회지

Primary hyperoxaluria is a rare disorder of glyoxylate metabolism in which hepatic enzyme deficiencies result in overproduction of oxalate. The resulting elevation of urinary oxalate excretion leads to recurrent urolithiasis and progressive nephrocalcinosis. End-stage renal disease frequently occurs and is accompanied by systemic oxalate deposition along with its harmful effects. With the rarity and various clinical heterogeneity of the disease, the high proportion of patients in whom diagnosis is made after advanced renal failure have developed it. On account of its high rate of graft loss associated with primary hyperoxaluria, isolated kidney transplantation has been replaced by combined liver/kidney transplantation. In this report, we describe a case of primary hyperoxaluria with kidney graft failure who had a history of recurrent renal stones.

External Quality Assessment Scheme for Biological Monitoring of Occupational Exposure to Toxic Chemicals

OBJECTIVES: In this study, we summarized the External Quality Assessment Scheme (EQAS) for the biological monitoring of occupational exposure to toxic chemicals which started in 1995 and continued until a 31st round robin in the spring of 2010. The program was performed twice per year until 2009, and this was changed to once a year since 2010. The objective of the program is to ensure the reliability of the data related to biological monitoring from analytical laboratories. METHODS: One hundred and eighteen laboratories participated in the 31st round robin. The program offers 5 items for inorganic analysis: lead in blood, cadmium in blood, manganese in blood, cadmium in urine, and mercury in urine. It also offers 10 items for organic analysis, including hippuric acid, methylhippuric acid, mandelic acid, phenylglyoxylic acid, N-methylformamide, N-methylacetamide, trichloroacetic acid, total trichloro-compounds, trans,trans-muconic acid, and 2,5-hexanedione in urine. Target values were determined by statistical analysis using consensus values. All the data, such as chromatograms and calibration curves, were reviewed by the committee. RESULTS: The proficiency rate was below 70% prior to the first round robin and improved to over 90% for common items, such as PbB and HA, while those for other items still remained in the range of 60-90% and need to be improved up to 90%. CONCLUSION: The EQAS has taken a primary role in improving the reliability of analytical data. A total quality assurance scheme is suggested, including the validation of technical documentation for the whole analytical procedure.

The Effects of Long-Term, Low-Level Exposure to Monocyclic Aromatic Hydrocarbons on Worker's Insulin Resistance

OBJECTIVES: This study was designed to investigate whether long-term, low-level exposure to monocyclic aromatic hydrocarbons (MAHs) induced insulin resistance. METHODS: The subjects were 110 male workers who were occupationally exposed to styrene, toluene, and xylene. One hundred and ten age-matched male workers who had never been occupationally exposed to organic solvents were selected as a control group. Cytokines, which have played a key role in the pathogenesis of insulin resistance, and oxidative stress indices were measured. Assessment of exposure to MAHs was performed by measuring their ambient levels and their urinary metabolites in exposed workers, and the resulting parameters between the exposed group and non-exposed control groups were compared. RESULTS: There was no significant difference in general characteristics and anthropometric parameters between the two groups; however, total cholesterol, fasting glucose, fasting insulin, and homeostasis model assessment of insulin resistance levels were significantly higher in the exposed group. Phenylglyoxylic acid levels showed significant association with tumor necrosis factor-alpha, total oxidative status, and oxidative stress index via multiple linear regression analysis. Further, there was a negative correlation between methylhippuric acid levels and total anti-oxidative capacity, and there was a significant relationship between MAHs exposure and fasting glucose levels, as found by multiple logistic regression analysis (odds ratio = 3.95, 95% confidence interval = 1.074-14.530). CONCLUSION: This study indicated that MAHs increase fasting glucose level and insulin resistance. Furthermore, these results suggested that absorbing the organic solvent itself and active metabolic intermediates can increase oxidative stress and cytokine levels, resulting in the changes in glucose metabolism and the induction of insulin resistance.

Influence of ethylbenzene on the levels of mandelic acid and phenylglyoxylic acid in urine, ultrastructure and the expressions of Mitochondrial apoptotic-related proteins in the rat nephridial tissues / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To investigate the influence of ethylbenzene on the levels of mandelic acid (MA) and phenylglyoxylic acid (PGA) in urine, the ultrastructure and the expressions of mitochondrial apoptotic-related genes in the rat nephridial tissues.</p><p><b>METHODS</b>Four groups of 10 males of Sprague-Dawley rats were allocated randomly into four groups: control (C) group, low (L) group, moderate (M) group and high (H) group, and inhaled daily with different doses of ethylbenzene: 0, 433.5 mg/m(3), 4335 mg/m(3), and 6500 mg/m(3) 6 h per day, 5 days per week for 13 weeks. The mandelic acid and phenylglyoxylic acid in the urine was assayed by high performance liquid chromatography. The ultrastructure of nephridial tissue was observed via electron microscope. The protein expression levels of Bax, Bcl-2, cytochrome C, Caspase-9 and Caspase-3 in nephridial tissues were measured by Western blot, respectively.</p><p><b>RESULTS</b>The levels of MA [(0.303 +/- 0.148) mg/L, (0.404 +/- 0.154) mg/L] and PGA [(0.168 +/- 0.104) mg/L, (0.174 +/- 0.092) mg/L] in the urine of M and H groups were significantly higher than that in the control and L group [(0.084 +/- 0.070) mg/L, (0.041 +/- 0.029) mg/L] (P < 0.05, respectively). It has been shown a dose-effect relationship between the contents of MA, PGA and MA + PGA and inhaled ethylbenzene, respectively. The mitochondria of rat nephridial tissue of H group became a compact and vacuolar structure with disorder and loss of cristae. The expression levels of Bax in mitochondria of nephridial tissues of M and H groups were significantly lower than that in the control group (P < 0.05). Caspase-3 expression level in H group was remarkably higher than that in the control group (P < 0.05). Compared with the control group, the expression levels of cytochrome C and Caspase-9 were enhanced, while the expression levels of Bcl-2 were restrained in all ethylbenzene-treated groups (P < 0.05, P < 0.05, respectively). The expression levels of Caspase-3 in M and H groups were significantly higher than that in the control group and L group (P < 0.05).</p><p><b>CONCLUSION</b>Ethylbenzene can induce apoptosis in the cells of nephridial tissues. The apoptotic mechanism might be involved with up-regulation of Bax, cytochrome C, Caspase-9 and Caspase-3, as well as restraint of Bcl-2. The level of MA and PGA in the rat urine could be a parameter of biological dose in vivo after ethylbenzene inhalation.</p>

Determination of cotinine, phenylglyoxylic acid and mandelic acid in human urine by GC/MS / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To establish a GC/MS method for analysis of cotinine (COT), phenylglyoxylic acid (PA) and mandelic acid (MA) in human urine.</p><p><b>METHODS</b>Human urine samples were extracted by CCl(3) and derivatized with MSTFA after dried completely. The contents of COT, PA and MA were measured by GC/MS method with DB-5MS capillary column and EI ion-source.</p><p><b>RESULT</b>The calibration curves for COT in urine samples were linear over the concentration ranges of 0.0002 approximately 3.5 microg ml(-1), while PA and MA were both of 1.25 approximately 160 microg ml(-1). The limits of quantification were 0.0002 microg ml(-1), 1.25 microg ml(-1) and 1.25 microg ml(-1) for COT, PA and MA, respectively. The assay recoveries for COT, PA and MA ranged from 89.53% approximately 102.4%, 84.88% approximately 91.46% and 83.46% approximately 13.6%, respectively.</p><p><b>CONCLUSION</b>The established method can detect cotinine, phenylglyoxylic acid and mandelic acid simultaneously, which would be used in routine assessment and monitoring of the internal exposure to nicotine and styrene in human body.</p>

Exploring QSAR of peripheral benzodiazepine receptor binding affinity of N,N-dialkyl-2-phenylindol-3-yl-glyoxylamides using physico-chemical descriptors.

The present QSAR study has attempted to explore the structural and physicochemical requirements of ligands N,N-dialkyl-2-phenylindol-3-yl-glyoxylamides for binding with peripheral benzodiazepine receptor (PBR). The calculated partition coefficient values show parabolic relations with the PBR binding affinity, suggesting that the binding affinity increases with increase in the partition coefficient of the compounds until it reaches the critical value after which the affinity decreases. The critical value of logP is within range of 6.052-6.410. Furthermore, positive Wang-Ford.charge values of carbonyl oxygens of the glyoxamide moiety and negative Wang-Ford charge value of the glyoxamide nitrogen are conducive for the binding affinity. Again, the indole moiety should have favorable charge distribution. Higher values of the parameters dipole moment (Dipole) and moment of inertia (I_z) of the ligands are conducive for the binding affinity. The presence of hydrogen atom at R2 and cyclic moiety at R1 and R2 positions are detrimental to the binding affinity.

Glyoxylate cycle is required for the overproduction of glutamate but is not essential for Corynebacterium glutamicum growth on glucose / 生物工程学报

The glyoxylate cycle was hypothesed to be indispensable for glutamate overproduction in coryneform bacteria, for it was thought to fulfill anaplerotic functions and to supply energy during the growth phase. During glutamate overproduction phase, however, it has been noted that the high level of the cycle is detrimental to the glutamate production. In order to clarify the relationship between the glutamate production and the glyoxylate cycle, a chromosomal aceA-disrupted mutant of wild-type C. glutamicum ATCC 13032 was constructed. The isocitrate lyase (ICL) activity of the parental strain was 0.011 u/mg of protein and reached 1.980 u/mg of protein after acetate induction; the mutant strain WTdeltaA, however, had no detectable ICL activity and was no longer able to grow on minimal medium with acetate as the sole carbon source. Compared with the wild-type C. glutamicum WT, the mutant strain WTdeltaA, exhibited the same growth rate with glucose as the sole carbon source, indicating glyoxylate cycle is not required for its growth on glucose. On the contrary, the glutamate production in WTdeltaA was severely impaired and more residual glucose was found in the fermentation broth at the end of fermentation with the mutant strain than with the wild-type strain. Further investigations into the relationship between the glutamate production and the glyoxylate cycle are under the way, which may help to elucidate the mechanism of glutamate overproduction.

A study on biomarkers of styrene / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To study the biomarkers of styrene and to provide theoretical basis for bio-monitoring of styrene.</p><p><b>METHODS</b>Urinary mandalic acid (MA), phenylglyoxalic acid (PGA) and mercapturic acid (MUA) of styrene were examined by high performance liquid chromatography (HPLC).</p><p><b>RESULTS</b>The correlation regression equations between exposure dose and MA, PGA and MUA level in morning urinary samples were: ŷ = 2.58x + 70.82; ŷ = 1.66x + 37.42; ŷ = 0.05x + 0.55 respectively. The correlation regression equations between exposure dose and MA, PGA and MUA level in post-shift urinary samples were: ŷ = 1.85x + 89.02; ŷ = 1.33x + 4.32; ŷ = 0.04x + 0.68 respectively. All showed close dose-response relationship.</p><p><b>CONCLUSIONS</b>The level of MA, PGA and MUA in morning or post-shift urinary samples may be used as bio-monitoring indexes of styrene.</p>

A study on the adduct characteristics of styrene and DNA / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To explore the adduct characteristics of styrene and DNA.</p><p><b>METHODS</b>The adduct reactions between styrene, urinary mandalic acid(MA), phenylglyoxalic acid(PGA), mercapturic acid of styrene (UMA) and DNA were studied by ultraviolet spectral analysis. The SO-DNA adducts by 32P-post labeled method, the chemical structures of SO-DNA adducts by GC-MS and NMR were also studied.</p><p><b>RESULTS</b>SO combined with DNA at O6, N2 positions of dGMP to form six adducts, but styrene, urinary mandalic acid, phenylglyoxalic acid and mercapturic acid of styrene did not react with DNA to form adduct.</p><p><b>CONCLUSIONS</b>Styrene formed adduct with DNA through its active center metabolite--SO after entering the body. SO combined with DNA at O6, N2 positions of dGMP to form adducts. If these DNA adducts are not repaired or are mis-repaired before cell duplication, the gene mutation and chemical damage would happen. No adduct reactions are seen among other metabolites of styrene.</p>