Thiobarbituric Acid Test Research Articles

Antioxidant activity of Cinnamomum cassia.

The antioxidant activities of hot water extracts (HWECC) and ethanol extracts (EECC) from the dry bark of Cinnamomum cassia Presl were evaluated in this study. Results showed that at 1.0 mg/mL, the ethanol extracts of C. cassia (96.30%) exhibited a greater inhibition than the alpha-tocopherol (93.74%) on FeCl(2)-ascorbic acid induced lipid peroxidation of rat liver homogenate in vitro. From 0.05 to 1.0 mg/mL, the EECC demonstrated the highest superoxide anions scavenging activity and the strongest anti-superoxide formation activity (p < 0.05). The same extract also showed an excellent antioxidant activity in enzymatic and nonenzymatic liver tissue oxidative systems. EECC revealed the strongest antioxidant activity followed by alpha-tocopherol and HWECC. Compared to alpha-tocopherol, the IC(50) values of EECC were found to be lower in thiobarbituric acid test (IC(50) = 0.24 mg/mL vs 0.37 mg/mL), in cytochrome c test (IC(50) = 0.16 mg/mL vs 0.27 mg/mL) and in xanthine oxidase inhibition test (IC(50) = 0.09 mg/mL vs 0.19 mg/mL). The present study concludes that EECC could be used as a good source of antioxidant in the dietary supplement.

Comparison of methods for determining malondialdehyde in dry sausage by HPLC and the classic TBA test

A reproducible and sensitive HPLC assay with fluorometric detection for measuring malondialdehyde as an index of lipid peroxidation in dry sausage (salami) has been developed. Following the homogenisation of dry sausage in water, a solution of 5% ice-cooled trichloroacetic acid led to the precipitation of the proteins. The addition of thiobarbituric acid (TBA) (0.02 M) to the filtered mixture and its corresponding incubation (35 min, 100 °C) completed the method. High correlation coefficients (r>0.977), with regard to the distillative TBA test, were obtained. Ratios between the HPLC and the distillation method of 2.23 were found. Also, the effect of the antioxidant BHT and an examination of the distillative classic TBA test have been done. Results indicate that this HPLC method, on account of its simplicity, sensitivity and specificity, may be preferred over the classic TBA test for estimating the rancidity of dry sausage.

Inhibitory effects of peptide-bound polysaccharides on lipid oxidation in emulsions

The inhibitory effects of polysaccharides on lipid oxidation in emulsions were investigated. Methyl linoleate was emulsified by β-casein or surfactants to prepare emulsions, and the oxidation was induced by an azo-compound or FeSO 4 addition. The initial oxidation was followed by measuring the oxygen consumption in the emulsions for 30 min, and the extent of the lipid oxidation over a long time (∼48 h) was evaluated by the determination of the unoxidized lipid by gas chromatography and the thiobarbituric acid test. Peptide-bound polysaccharides, such as gum arabic and soluble soybean polysaccharides (SSPS), showed an ability to inhibit lipid oxidation, whereas maltodextrin and pullulan exhibited no inhibitory effects. Especially, SSPS almost perfectly suppressed the lipid oxidation from the initial to the late stages, irrespective of the emulsifiers and oxidation-inducing reagents. The mechanism whereby the peptide-bound polysaccharides inhibited the lipid oxidation in the emulsions is considered in terms of the chemical composition and other properties of the polysaccharides.

Antioxidative activity and total phenolic compounds of leaf, root and petiole of four accessions of Centella asiatica (L.) Urban

Antioxidative activity and total phenolic compounds of root, leaf and petiole of four accessions of Centella asiatica (L.) Urban, namely CA 01, CA 05, CA 08 and CA 11, were evaluated. Antioxidative activity of the extracts was measured using the ferric thiocyanate (FTC) method and thiobarbituric acid (TBA) test. The antioxidative activities were then compared with that of α-tocopherol (natural antioxidant) and butylated hydroxytoulene or BHT (synthetic antioxidant). The results showed that CA 01 and CA 05 had the highest antioxidative activities among the accessions tested. Results also showed that both leaf and root of C. asiatica had high antioxidative activity, which was as good as that of α-tocopherol. The total phenolic content, determined according to the Folin–Ciocalteu method, varied from 3.23 to 11.7 g/100 g dry sample, and showed strong association ( r 2=0.90) with antioxidative activity. The results suggest that phenolic compounds are the major contributors to the antioxidative activities of C. asiatica.

Synthesis of New Azulene Derivatives and Study of Their Effect on Lipid Peroxidation and Lipoxygenase Activity.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Characterisation of antioxidative activities of various extracts of Centella asiatica (L) Urban

Antioxidative activity of various extracts from different parts of Centella asiatica, including leaves, petioles (stolons) and roots, using three types of solvents (ethanol, water and light petroleum), were evaluated using a linoleic acid model system and the thiobarbituric acid test. Results showed that the ethanol extract of all parts of C. asiatica exhibited significantly ( P<0.05) higher antioxidative activity than the water extract, while the light petroleum ether showed negligible activity. Increasing the concentration of the extract (1000–3000 ppm) resulted in increase in antioxidative activity of both the ethanol and the water extract. From 3000 ppm upward, antioxidative activity of the ethanol extract was not significantly different ( P<0.05) from that of α-tocopherol. Roots showed the highest activity of the parts tested. The antioxidative activities of the ethanol extracts were found to be stable up to 50 °C and exhibited optimum activity at neutral pH.

Antioxidative activity of extracts from Mengkudu ( Morinda citrifolia L.) root, fruit and leaf

This study was conducted to evaluate the antioxidative activity of extracts from different parts of Mengkudu ( Morinda citrifolia L.), including leaf, fruit and root. Methanol and ethyl acetate were used as solvents and antioxidative effects measured by a ferric thiocyanate method (FTC) and thiobarbituric acid test (TBA). The methanol extract of Mengkudu root exhibited high antioxidative activity that was not significantly ( P<0.05) different from α-tocopherol or butylated hydroxyl toluene (BHT), while the methanol extracts of fruit and leaf showed negligible activities. On the other hand, the ethyl acetate extract of all parts of Mengkudu exhibited significant antioxidative activity, which is comparable to that of both α-tocopherol and BHT. Similar trends of antioxidant activity were observed using either the FTC or TBA methods. Roots showed the highest activity of the parts tested. The results suggest that several compounds contribute to antioxidative activity of different parts of Mengkudu. Activity in the roots may be due to both polar and non-polar compounds but, in the leaf and fruit, only to non-polar compounds.

Synthesis of new azulene derivatives and study of their effect on lipid peroxidation and lipoxygenase activity.

The relationship between free radicals and acute or chronic inflammation has been well established. We have previously reported the significant antioxidant activity of the natural azulene derivatives chamazulene and guaiazulene. Furthermore, some synthetic azulene analogues have been found to possess anti-inflammatory activity. In this investigation we report the synthesis of five 3-alkyl or 3-(hydroxy)alkylazulene-1-carboxylic acids and esters, from tropolone, via the corresponding furanone. The synthesised compounds were tested for their effect on the peroxidation of rat hepatic microsomal membrane lipids, applying the 2-thiobarbituric acid test. Their anti-inflammatory activity was evaluated in vitro by the offered inhibition of soybean lipoxygenase. All the tested molecules were found to inhibit lipid peroxidation by 100% at 1 mM. They were also found to considerably inhibit lipoxygenase activity. The above results are discussed in relation to the structure and physicochemical properties of the examined azulene derivatives.

IN VIVO ASSESSMENT OF FREE RADICAL ACTIVITY DURING SHOCK WAVE LITHOTRIPSY USING A MICRODIALYSIS SYSTEM: THE RENOPROTECTIVE ACTION OF ALLOPURINOL

Shock wave lithotripsy is believed to cause renal damage directly through cellular injury from high energy shock waves and indirectly through vascular injury and resultant ischemia, which gives rise to oxygen free radical compounds. The transient and volatile nature of free radicals and derived products makes their detection difficult. Moreover, certain medications may provide a protective effect against shock wave lithotripsy induced renal parenchymal injury. We introduced an innovative microdialysis system for in vivo sampling of interstitial fluids that can be analyzed for free radical mediated lipid peroxidation products after shock wave lithotripsy treatment in the swine model. In addition, this system was used to test the antioxidant or renoprotective action of allopurinol. Ten juvenile swine were assigned to a nonmedicated control group that underwent shock wave lithotripsy or to a group that was premedicated with allopurinol before shock wave lithotripsy. Each group of animals underwent shock wave lithotripsy to the lower pole of the right kidney and received a total of 10,000 shock waves. Dialysate fluid was collected at 1,000-shock wave increments via probes surgically implanted into the lower pole of the right and left kidneys before lithotripsy. Samples were immediately preserved in liquid nitrogen and subsequently analyzed for the presence and concentration of conjugated diene levels, a measure of lipid peroxidation. Five additional juvenile swine were assigned to a sham treated group that did not undergo shock wave lithotripsy. Dialysate fluid was collected from the lower pole of the right and left kidneys to establish baseline or pre-lithotripsy levels of conjugated dienes. After shock wave lithotripsy conjugated diene levels increased almost 100-fold over that in the right kidneys of the nonmedicated control group. The difference was statistically significant compared to levels in the contralateral untreated kidneys (p <0.01). Right kidneys in the group premedicated with allopurinol did not demonstrate an increase in conjugated diene levels during shock wave lithotripsy. The results of this study confirm shock wave lithotripsy induced free radical activity as well the antioxidant and protective nature of allopurinol. The newly described microdialysis system enables real-time sampling of interstitial fluids during shock wave lithotripsy. It represents a unique method for assessing free radical formation and evaluating the protective effects of additional antioxidant medications.

The effect of netilmicin and vancomycin on lipid peroxidation processes in cerebrospinal fluid in children with hydrocephalus.

In biological systems, it is difficult to determine free radicals because of their reactivity and their very short time of existence. On the basis of markers, which come into being as a result of radical processes, one might believe that there exist reactive oxygen species. One of the determinants of free radical activity of oxygen is the presence of malondialdehyde (MDA), a final product of lipid peroxidation. This study aimed at finding the answer to the question whether the concentration of netylmicin and vancomycin influences the amount of substances reacting with thiobarbituric acid (TBA) in cerebrospinal fluid (CSF) in children with hydrocephalus. Applying the TBA test for examinations with antibiotics added both in vivo and in vitro, we could demonstrate that increased concentration of the examined antibiotics in cerebrospinal fluid reduces the amount of MDA. The results obtained demonstrate that products of lipid peroxidation are present in the CSF samples analyzed. In this study, we found that the concentration of vancomycin and netilmicin influenced the lipid peroxidation process in cerebrospinal fluid in children with hydrocephalus, thus confirming anti-inflammatory properties of the antibiotics applied.

Determination of Malondialdehyde as Dithiobarbituric Acid Adduct in Biological Samples by HPLC with Fluorescence Detection: Comparison with Ultraviolet-Visible Spectrophotometry

Living cells are constantly exposed to reactive oxygen species, some of which are capable of initiating lipid peroxidation by abstraction of an allylic proton from a polyunsaturated fatty acid. This process, by multiple stages leading to the formation of lipid hydroperoxides, is a known contributor to the development of atherosclerosis (1). The thiobarbituric acid (TBA) test is an easy and quick assay for the assessment of lipid peroxidation in which malondialdehyde (MDA) is derivatized. The rationale and methodology have been discussed in detail elsewhere (2)(3) and have rightfully been criticized for low specificity and artifact formation because only a fraction of the MDA measured was generated in vivo (1)(3). Furthermore, the TBA derivatization procedure itself leads to the formation of several MDA-unrelated ultraviolet (UV)-absorbing and fluorescent species, the latter as shown in Fig. 1⇓ , A–C. Despite this fact, the method remains one of the most useful and commonly used measurements of oxidative damage because of its simplicity. In recent years, several HPLC-based TBA assays have evolved with increased specificity (4)(5)(6)(7), but nevertheless the spectrophotometric methods remain commonly used. In the present report, MDA was quantified in plasma, erythrocytes, and liver homogenates from 3-month-old guinea pigs by either our “modern” TBA test based on HPLC with fluorescence detection, which quantifies only the genuine MDA(TBA)2 adduct, or by the original less specific and less sensitive spectrophotometric method, which measures the total absorbance of several species. The purpose was to evaluate the use of the original TBA test by today’s standards by assessing the overestimation and sensitivity in the various applications that are routinely performed in several laboratories. All compounds were of the highest quality available. Specifically, butylated hydroxytoluene (BHT), tetramethoxypropane, TBA, and phosphotungstic acid were from Fluka. Sample …

Reaction conditions affecting the relationship between thiobarbituric acid reactivity and lipid peroxidesin human plasma

The thiobarbituric acid (TBA) reactivity of human plasma was studied to evaluate its adequacy in quantifying lipid peroxidation as an index of systemic oxidative stress. Two spectrophotometric TBA tests based on the use of either phosphoric acid (pH 2.0, method A) or trichloroacetic plus hydrochloric acid (pH 0.9, method B) were employed with and without sodium sulfate (SS) to inhibit sialic acid (SA) reactivity with TBA. To correct for background absorption, the absorbance values at 572 nm were subtracted from those at 532 nm, which represent the absorption maximum of the TBA:MDA adduct. Method B gave values of TBA-reactive substances (TBARS) 2-fold higher than those detected with method A. SS lowered TBARS by about 50% with both methods, indicating a significant involvement of SA in plasma TBA reactivity. Standard SA, at a physiologically relevant concentration of 1.5 mM, reacted with TBA, creating interference problems, which were substantially eliminated by SS plus correction for background absorbance. When method B was carried out in the lipid and protein fraction of plasma, SS inhibited by 65% TBARS formation only in the latter. Protein TBARS may be largely ascribed to SA-containing glycoproteins and, to a minor extent, protein-bound MDA. Indeed, EDTA did not affect protein TBARS assessed in the presence of SS. TBA reactivity of whole plasma and of its lipid fraction was instead inhibited by EDTA, suggesting that lipoperoxides (and possibly monofunctional lipoperoxidation aldehydes) are involved as MDA precursors in the TBA test. Pretreatment of plasma with KI, a specific reductant of hydroperoxides, decreased TBARS by about 27%. Moreover, aspirin administration to humans to inhibit prostaglandin endoperoxide generation reduced plasma TBARS by 40%. In conclusion, reaction conditions affect the relationship between TBA reactivity and lipid peroxidation in human plasma. After correction for the interfering effects of SA in the TBA test, 40% of plasma TBARS appears related to in vivo generated prostaglandin endoperoxides and only about 60% to lipoperoxidation products. Thus, the TBA test is not totally specific to oxidant-driven lipid peroxidation in human plasma.

Performance of a lipase-catalyzed transesterified palm kernel olein and palm stearin blend in frying banana chips

Abstract The frying performance of an enzymatically transesterified palm stearin and palm kernel olein (1:1 by weight) blend was compared with its control (physical mixture or no enzyme added) and a commercial plastic frying shortening (CS). The samples were used as deep-fat frying media at 180°C for banana chips for seven consecutive days. The samples were then analysed for iodine value (IV), free fatty acid (FFA) content, peroxide value (PV), thiobarbituric acid (TBA) value, p-anisidine value (AV), total polar compounds (TPC), fatty acid composition, specific extinction, E1%1cm at 233 and 269 nm, polymer contents, viscosity and colour indices. The fried banana chips were analysed for acceptability by sensory evaluations. Storage properties of the banana chips were also evaluated by trained sensory panellists and a modified TBA test. The transesterified blend was found to have significantly (P 0.05; for all the attributes tested) between the acceptability of the banana chips fried by the transesterified and control blends. However, the banana chips fried in CS had significantly (P

Dependence of lipid peroxidation on pigmentation of the porcine iris

Melanin has been shown to act as antioxidant in lipid peroxidation studies. We have now investigated lipid peroxidation in dependence on stromal pigmentation in isolated porcine irises. The same number of lightly pigmented and heavily pigmented porcine irises (visual selection) were homogenized in buffer (50 mmol/l Na2HPO4, 50 mmol/l NaH2PO4 and 4 mmol/l sodium azide; 1:20 w/v). 500 microliters homogenate were incubated at 37 degrees C for 5, 10, 20 and 40 min in absence and presence of Fe2+ as inducer of lipid peroxidation. Lipid peroxidation was assayed by the thiobarbituric acid (TBA) test. Results are expressed as nmol of TBA reactive material produced (TBAR) per mg protein. Fe2+ concentration of the supernatant was determined spectrophotometrically with phenanthroline. 70 mumol/l, 180 mumol/l and 360 mumol/l Fe2+ induced lipid peroxidation. A plateau region was reached after 20 min. Lipid peroxidation differed in dependence on stromal pigmentation in porcine irises by a factor of 2.8. 180 mumol/l Fe2+ induced 1.373 +/- 0.138 nmol TBAR/mg protein in lightly pigmented irises compared to 0.491 +/- 0.125 nmol TBAR/mg protein in heavily pigmented irises after 10 min incubation (p < 0.0001, n = 4). On the other hand, the content of Fe2+ in the supernatant was the same within error. There was a stronger induction of lipid peroxidation in lightly pigmented porcine irises compared to heavily pigmented porcine irises. This effect may be related to the difference in stromal melanin content and its antioxidant activity.

Suitability of chemical parameters in setting quality standards for deep-fried snacks

A study was carried out to examine the suitability of chemical parameters in setting quality standards for deep-fried snacks. Three types of the most commonly consumed deep-fried snacks in India, viz., muruku (an extruded noodle-like product made out of a mixture of rice flour and black gram dhal flour), chekodi (made out of refined wheat flour) and potato chips were analysed for chemical parameters such as peroxide value, acid value, Kreis test, p-anisidine value and thiobarbituric acid tests along with organoleptic evaluation at different time interval points (0,15,30 and 90 days) of storage, at room temperature (27±3°C). The peroxide value for fried snacks viz., muruku and chekodi, both in control and experiment increased gradually up to 30 days. However, such change was not observed with other chemical parameters. Thus, among the chemical parameters, only peroxide value appears to be suitable in setting realistic standards for deep-fried snacks up to a storage period of 30 days. The organoleptic evaluation of all the three fried snacks revealed that there is no consistent pattern for the three parameters viz., odor, taste and overall acceptability, except for chekodi.

A simple, highly sensitive and improved method for the measurement of bleomycin-detectable iron: the ‘catalytic iron index’ and its value in the assessment of iron status in haemochromatosis

In the presence of ferrous ions (Fe(2+)), the anti-tumour agent bleomycin will induce DNA degradation. Degradation of DNA into substances detectable by the thiobarbituric acid test has been used previously for the detection of iron in a form that is capable of catalysing the formation of the potentially harmful hydroxyl free radical. In the present paper, we describe the application of the ethidium-binding assay of DNA damage to the measurement of bleomycin-detectable iron, comparing its performance with the conventional method in the assessment of iron standard solutions and plasma samples from haemochromatosis patients. The ethidium-binding assay proved to be more responsive than the thiobarbituric acid test in the detection of DNA damage induced by very low concentrations of iron, but became saturated at higher iron concentrations. Agreement between the two versions of the assay in the identification of plasma samples containing bleomycin-detectable iron was good, but agreement on the actual concentrations of such iron in the positive samples was poor. This discrepancy is believed to be due to interference with the thiobarbituric acid assay by plasma. Consequently, it was not possible to obtain reliable estimates of free iron concentrations in plasma when using the conventional version of the bleomycin assay. We have devised a parameter of iron status called the catalytic iron index. For healthy, non-haemochromatotic individuals, the mean value of this parameter was found to be 0.81 (range 0.78-0.84; n=20). Elevated values were observed in some plasma samples from haemochromatosis patients, but these showed no correlation with serum ferritin levels. In contrast, correlations were seen with both serum iron and transferrin saturation levels, but only when these were above the normal range.

Lipid peroxidation in porcine irises: Dependence on pigmentation

Purpose. Pigmentation of the iris is caused by varying amounts of melanin pigment granula in a constant number of melanocytes in the superficial stroma. Melanin has been shown to act as antioxidant. We have now investigated lipid peroxidation in dependence on stromal pigmentation in isolated porcine irises. Methods. The same number of lightly and heavily pigmented porcine irises (visual selection) were homogenized (1:20w/v) in buffer (50mmol/l phosphate buffer and 4mmol/l sodium azide). 500µl homogenate were incubated at 37°C in duplicate for 5, 10, 20 and 40 min in absence and presence of Fe 2+ as inducer of lipid peroxidation. The amount of lipid peroxidation was assayed by the thiobarbituric acid (TBA) test. The results are expressed as nmol of TBA reactive material (TBAR) produced/mg protein. Fe 2+ concentration of the supernatant was determined spectrophotometrically with 1,10 orthophenanthroline. Concentrations of D -glucose and D -fructose in iris tissue homogenates were determined spectrophotometrically by enzymatic bioanalysis. Results. 70, 180 and 360 µmol/l Fe 2+ induced lipid peroxidation. A plateau region was reached after 20 min. The amount of lipid peroxidation differed in dependence on stromal pigmentation in porcine irises. The effect was most significant at 180 µmol/l Fe 2+, which induced 1.373 ± 0.138 nmol TBAR/mg protein in lightly compared to 0.491 ± 0.125 nmol TBAR/mg protein in heavily pigmented irises after 10 min incubation (p < 0.0001, n = 4). Similar effects (factor 2–3) were also measured after 20 and 40 min incubation. On the other hand, the content of Fe 2+ in the supernatant was the same within error. Sugar concentrations (D -glucose and D -fructose) did not differ significantly for the two differently pigmented iris tissues. Conclusions. There is a stronger induction of lipid peroxidation in lightly compared to heavily pigmented porcine irises. This effect may be related to the difference in stromal melanin content and its antioxidant activity.

Total Plasma Malondialdehyde Levels in 16 Taiwanese College Students Determined by Various Thiobarbituric Acid Tests and an Improved High-Performance Liquid Chromatography-based Method

Objectives: In determining the plasma malondialdehyde MDA levels in some Taiwanese college students, we found rather different results by using different thiobarbituric acid TBA tests, even by the high-performance liquid chromatography HPLC-based methods. Here, we re-evaluated four commonly used TBA tests and improved the HPLC-based test. Design and Methods: We used the blood plasma of 16 college volunteers to determine plasma MDA by using four methods: a spectrophotometric measurement of thiobarbituric acid-reactive substances (TBARS) in the TCA-supernatant of plasma (Method A); a fluorescence measurement of plasma lipid peroxides (Method B); and two different HPLC-based measurements of MDA with either 532-nm measurement (Method C, HPLC/532 nm) or fluorescence measurement (Method D, HPLC/fluor.). Results: The levels of MDA or TBA reactive substances obtained from the four methods differed substantially (0.39 ± 0.15; 2.14 ± 0.73; 0.75 ± 0.22; and 0.38 ± 0.15 μM for Methods A, B, C, and D, respectively). The results were positively correlated between Methods A and B ( r = 0.740, p < 0.02) and between Methods C and D ( r = 0.516, p < 0.05). However, results were negatively correlated between Methods B and D ( r = −0.548, p < 0.05). Because most plasma MDA is bound to proteins, we modified the HPLC-based methods (C and D) by adding an alkaline hydrolysis step, and the plasma TBA-MDA adduct detected by HPLC/532 nm was referred to as total MDA. Results show that alkaline hydrolysis was a critical step for measurement of total MDA in plasma because this treatment led to release of MDA from plasma proteins. We also adapted the potassium iodide (KI) treatment of plasma from Method D to reduce lipid hydroperoxides. Our modified method gave a total MDA level in the 16 volunteers of ∼1.5 μM, which was equal to protein-bound MDA plus free MDA. This total MDA level was positively ( p < 0.05) correlated with the level of TBA reactive substances obtained from Methods C ( r = 0.63, p < 0.05) and D ( r = 0.48, p < 0.07), but was not correlated with those from Methods A and B. The recovery (84∼105%), precision (within-assay coefficient of variation: 2.4%, between-assay coefficient of variation: 4∼8%) and sensitivity of the modified procedure were comparable to other HPLC-based methods. Conclusion: By using a validated modification of HPLC-based TBA method, the total plasma MDA in 16 Taiwanese college students was found to be 1.54 μM, which was relatively high compared to those obtained by other HPLC-based method, primarily due to the release of protein-bound MDA by alkaline hydrolysis. This level equaled the sum of protein-bound MDA and free MDA in plasma, confirming that this level represents total plasma MDA.

Antioxidative stress response in workers exposed to carbon disulfide.

To study the effects of carbon disulfide (CS2) on antioxidative stress systems of exposed workers. Enzyme-linked immunosorbent assay (ELISA) and thiobarbituric acid test (BAT) were conducted on 67 exposed workers and 88 controlled ones in a viscose rayon factory to determine their serum cuprozinc-superoxide dismutase (CuZnSOD) and malonyldialdehyde (MDA) levels. The average levels of CuZnSOD in workers exposed to CS2 both above and below 10 mg/m3 were higher than those in the control group (P < 0.0001), showing some dose-effect and dose-response relationships. SOD levels increased when the exposure index (EI) was less than 300, and remained at a high level at the range of 300 to 900. When EI was higher than 900, SOD tended to decrease. Meanwhile, the serum MDA levels increased. Both CS2 concentrations and exposure time contribute to the MDA levels. CS2 exposure could influence the stress response of the oxidative-antioxidative system of workers. Increased SOD levels could be considered as the stress response of antioxidative system to CS2 exposure in the early stages, and the influence of CS2 on SOD might be bi-directional. SOD and MDA might become objective indices in workers' health surveillance. The role of these two indices in the intoxication mechanism still needs to be clarified.

The role of reactive oxygen species in testicular dysfunction associated with varicocele.

To determine the level of malondialdehyde (MDA), an indirect indicator of lipid peroxidation-induced injury by reactive oxygen species, in testicular biopsy specimens from infertile patients with and without varicocele. Levels of MDA were measured in the testicular biopsy specimens from 25 infertile men (15 with varicocele, mean age 30.0 years, SD 5.7, range 23-45, and 10 without, mean age 28.7 years, SD 4.2, range 21-34). All patients were evaluated by a detailed history, physical examination, semen analysis (at least twice), serum follicle-stimulating hormone and free testosterone levels, testicular biopsy and contact imprint. Scrotal colour Doppler ultrasonography was used to confirm suspected varicocele. The level of MDA in testicular biopsy specimens was measured using the thiobarbituric acid test and the results expressed per unit tissue weight. As a causal factor for infertility, varicocele was identified in 15 men (60%), testicular failure in four (16%), idiopathic infertility in four (16%) and obstruction in two (8%). Of the 15 patients with varicocele, eight had bilateral varicocele and it was subclinical in three; the varicocele was grade I in four, grade II in six and grade III in two. The mean (SD) MDA level in the men with a subclinical varicocele was 15.7 (3.1) pmol/mg tissue, while in those with grade I-III varicocele it was 32.9 (12.25), 37.1 (12.25) and 86.9 (2.89) pmol/mg tissue, respectively. The levels in patients with grade III varicocele were significantly greater than in the other groups (P < 0.05). The mean MDA level in patients with or without varicocele was 38.3 (22.92) and 33.5 (18.93) pmol/mg tissue, respectively (P > 0.05). These results suggest that increasing levels of MDA are associated with higher grades of varicocele and support a possible rationale for controlled trials in infertile men with varicocele.