It is assumed that oxidative stress due to reactive oxygen species (ROS) such as superoxide anion (·O2-), hydrogen peroxide (H2O2) and hydroxyl radical (·OH) may result in oxidative damage to lipids and DNA. On the other hand, chromium(VI) compounds, potent carcinogens, are known to induce lipid peroxidation. However, it is not clear how Cr(VI) induces lipid peroxidation and DNA damage. In this article, in order to clarify the mechanism by which Cr(VI) enhances lipid peroxidation, the lipid-peroxidizing activity of Cr(IV) and Cr(V), Cr intermediates possibly produced in the reductive metabolism of Cr(VI), were compared with that of Cr(VI) and Cr(III), and the inhibitory effects of ROS scavengers on lipid peroxidation induced by Cr(IV) and Cr(V) were examined by incubating mouse liver homogenate with Cr and scavenger compounds. Cr(IV), Cr(V) and Cr(VI) compounds effectively enhanced lipid peroxidation of homogenate in this order. The lipid-peroxidizing effect of Cr(IV) was suppressed more remarkably by superoxide dismutase, catalase and formate, specific scavengers of ·O2-, H2O2 and ·OH, respectively, than that of Cr(V), which is indicative of the involvement of ·O2-, H2O2 and ·OH in lipid peroxidation stimulated by these Cr species. These results suggest the possible participation of Cr(IV), Cr(V), ·O2-, H2O2 and ·OH in Cr(VI)-enhanced lipid peroxidation.
A convenient analytical procedure based on one-step, phase-transfer-catalyzed derivatization has been established for the simultaneous determination of azide, cyanide and thiocyanate in aqueous samples by gas chromatography - mass spectrometry (GC-MS). In order to obtain cleaner extracts, a polymer-bound phosphonium salt was employed as the catalyst, and pentafluorobenzyl bromide (PFB-Br) as a derivatization reagent. The extraction and derivatization of these analytes, as well as the concentration of the resultant derivatives into the organic phase were simultaneously achieved during a 30-min phase-transfer-catalyzed process at 38°C. Rapid and reliable GC-MS determination could be readily performed for these analytes, not only in various beverages but also in diluted, large-volume aqueous samples such as food washings. In addition to electron impact ionization MS (EI-MS), negative-ion chemical ionization MS (NICI-MS) was also employed to detect trace-level analytes, as well as to accomplish incontrovertible identification. The detection limits in various beverages were typically 0.1-0.5μg/ml by EI-MS and 25-100ng/ml by NICI-MS, both in the full-scan mode.
Hexachlorobenzene (HCB) and pentachlorobenzene (PECB) were used to clarify how the rate at which lipophilic environmental pollutants are metabolized will affect their transfer to pups. In this study, the ratio of PECB/HCB transference to fetuses and suckling pups was investigated in rats fed a diet containing HCB (35.1nmol/100g diet) and PECB (351nmol/100g diet). The amounts of HCB and PECB transferred to fetuses were 0.44% and 0.15% of the amounts consumed by their dams, respectively, and the PECB/HCB concentration ratio in fetuses was 3.4. In pregnant rats on the day before parturition, the PECB concentrations in organs and fat tissue were 3 to 4 times higher than those of HCB. After parturition, PECB rapidly disappeared from the body of nursing rats during the lactation period, especially when compared with HCB. On day 2 after birth, HCB and PECB concentrations in the stomach contents of suckling pups were highest, and the PECB concentration was 3.5 times higher than that of HCB. HCB in the stomach contents decreased gradually (T1/2=5.7 d) and PECB decreased rapidly (T1/2=2.8 d) during the 15 d after birth. These findings indicate that the PECB/HCB transferred to fetuses and suckling pups was the same ratio found in the blood of their dams.
Recently, the calcined powder of oyster shells has been found to possess antibacterial activity, and has been considered for use as a bactericidal agent. In this study, calcined shell preparations were made from oysters, scallops, clams and roll shells, and their antibacterial activities were compared using total aerobic counts and E. coli. It was found that the calcined shell calcium from surf clams had the highest activity. Further comparison of activity was made between the calcined surf oyster preparation which was known to have antibacterial activity and the calcined surf clam preparation, and calcined surf clam calcium was found to have higher antibacterial activities against pathogenic Escherichia coli O157 : H7, Pseudomonas aeruginosa and Staphylococcus aureus. The antibacterial activity was due to the strong alkalinity of aqueous solutions of this calcined calcium preparation
Indoor exposure to chlorpyrifos and 2, 3, 3, 3, 2', 3', 3', 3'-octachlorodipropylether (OCDPE, a synergist, commercial name S-421 in Japan) of residents living in two houses (B and F) treated for termite control, was investigated by examining the residual levels in ambient air and in polished rice stock in houses through five years after their application. Chlorpyrifos and OCDPE levels detected in the air of the dining room of house B ranged from 0.007 to 0.11μg/m3 and from 0.12 to 0.79μg/m3, respectively. Chlorpyrifos and OCDPE levels detected in the air of a Japanese-style room in house F ranged from 0.07 to 0.41μg/m3 and from 0.008 to 0.046μg/m3, respectively. The estimated combined daily intake of chlorpyrifos from air and rice, was around 3μg in house B and 4μg in house F, below the recommended reference dose (RfD) of 3μg/kg/d from all sources. The estimated combined daily intake of OCDPE from air and rice was approximately 48μg in house B and 0.5μg in house F. Termiticide concentration in both air and rice depended on the season, being high in summer and lower in winter. Chlorpyrifos and OCDPE levels in the indoor air in the breathing zone did not decrease during the five years after their application for termite control.
Hematological effects of chlorine dioxide (ClO2) and its metabolites were investigated. In vitro exposure of mouse, rat and human blood cells to ClO2 and the reduction by-product, chlorite (ClO2-) resulted in the formation of methemoglobin, a decrease in the activities of glucose-6-phosphate dehydrogenase (G-6-PD) and glutathione peroxidase (GPX) and in the content of reduced glutathione (GSH), and an increase in hydrogen peroxide (H2O2) formation and hemolysis. The H2O2 formation and hemolysis induced by ClO2 and ClO2- in mouse blood cells were the highest among cells tested, and human blood cells were more resistant to the oxidative stress than rat and mouse blood cells. Both compounds also showed more toxic responses to E. coli mutants lacking production of catalase DSH19 (katEG), superoxide dismutase DSH56 (sodAB) and both of them DSH67 (katEG sodAB) than the wild strain DSH7 by Kat-sod assay, as a biological detection method for reactive oxygen species, suggesting the production of H2O2 and superioxide anion. For subchronic study of ClO2, mice received drinking water containing 100, 1000, 1500 or 2000mg/l ClO2 in the presence of the stabilizer, 1200mg/l of sodium bicarbonate ad libitum for 30, 60 or 90days. Statistically significant hematological changes were observed in animals exposed to more than 1000mg/l ClO2, which showed augmented G-6-PD activity in erythrocytes and increased resistance to hemolysis in hypotonic solution. The results of this study therefore indicate that ClO2 acutely causes hematotoxicity toward mice by producing reactive oxygen species and by weakening the protection systems to oxidative stress in erythrocytes, although the latter may be induced by long term exposure, while humans appear to be more resistant to this hematotoxicity.
We attempted to purify and identify the active antioxidants in human-placenta extracts (PLx). Purification was performed successively by 40% methanol precipitation, Sephadex G-50 gel chromatography, and high-performance liquid chromatography (HPLC). The supernatant of PLx after 40% methanol precipitation possessed 85% of the original antioxidant activity. Elution of the antioxidants from gel chromatography gave mainly three peaks with approximately 98% recovery of the antioxidant activity. The antioxidant activity was then fractionated by HPLC with a recovery of approximately 90% of the activity. Three components were obtained, and based on HPLC retention times, UV, NMR, and FAB-MASS, they were identified as uracil, tyrosine, and phenylalanine.
Human-placenta extract (PLx) possesses various physiologically important activities, such as antioxidant activity and anti-inflammatory activity. Our previous study elucidated that uracil, tyrosine, and phenylalanine function as the main antioxidative substances in PLx. In order to confirm whether these compounds have similar function as PLx, we examined the effects of the administration on ethanol-induced liver injury in mice. As a result, PLx suppressed ethanol-induced decrease in hepatic glutathione level, increase in thiobarbituric acid reaction substance (TBARS), increase in the activities of glutamate pyruvate transaminase, glutamate oxaloacetate transaminase, and superoxide dismutase, and decrease in the activity of catalase. A mixture of uracil, tyrosine, and phenylalanine showed similar antioxidant activity to PLx, except for failure to suppress the increase in TBARS. Although these results suggest that PLx has some other unknown components to alleviate acute alcoholic liver injury, the mixture of uracil, tyrosine, and phenylalanine appeared to have almost the same ability to suppress acute ethanol-induced liver injury in mice as that of PLx.
Effects of clofibric acid (p-chlorophenoxyisobutyric acid) on carbon tetrachloride (CCl4)-induced hepatocellular necrosis and fatty liver were investigated. Male Wistar rats were fed a diet containing 0.5% (w/w) clofibric acid for 7 days before the administration of CCl4 (1ml/kg, p.o.) and the treatment with clofibric acid continued throughout the time course of the study. In rats given only CCl4, the serum activity of alanine aminotransferase (ALT) increased rapidly and reached a maximum level at 24h after the administration of CCl4. The rats pretreated with clofibric acid exhibited a significantly lower serum level of ALT compared with the rats treated with CCl4 alone until 24h following CCl4 dosing. However, the maximum level that was observed at 48h after the administration of CCl4 to the rats pretreated with clofibric acid was similar to the highest level observed in the CCl4 alone group at 24h after CCl4 dosing. The hepatic glycogen level steeply decreased at 3h after the administration of CCl4 and reached the lowest level at 12h preceding the definite appearance of necrosis, with gradual recovery noted by 96h. An evident decrease in glycogen level was also noted in the group given clofibric acid throughout the time course. In rats treated with both CCl4 and clofibric acid (clofibric acid + CCl4), hepatic glycogen was exhausted from 3h and the depletion lasted until 96h after dosing of CCl4. The serum level of glucose was not increased, but rather decreased markedly after the administration of CCl4 in both the rats receiving CCl4 alone and in the rats treated with clofibric acid + CCl4. The hepatic content of triglyceride increased rapidly and reached a level about 5-fold greater than the control at 12h after the administration, then the elevated level lasted until 96h of the time course. The increase in the hepatic content of triglyceride induced by CCl4 was significantly suppressed by pretreatment with clofibric acid and returned to the basal level by 96h after dosing of CCl4. The results of histopathological examination of liver sections stained by hematoxylin and eosin, and oil red O, were very consistent with the biochemical changes mentioned above. These results indicate that dietary pretreatment with clofibric acid suppressed the necrosis of hepatocytes in the initial stage, but not in the late stage ; rather, the recovery of liver from necrosis was delayed. Also this drug significantly suppressed fatty liver caused by CCl4.
The inducibility by organomercury of the broad-spectrum mer operon on pMRA17 cloned from Pseudomonas K-62 plasmid pMR26 was assessed in the absence of a functional merB gene. The mer polypeptides encoded by the mer genes on pMRA17 were almost identified in maxicell induced not only by Hg2+ but also by C6H5Hg+ or CH3Hg+. Maxicell with pMRD103, a merB-deletion plasmid constructed from pMRA17, also produced the corresponding mer polypeptides when maxicell was induced by Hg2+, whereas no mer polypeptides were detected in the maxicell induced by C6H5Hg+ or CH3Hg+. These results suggest that merB is needed for induction of the pMRA17 mer operon expression by organomercurials. Next, to test the inducibility of pMRA17 mer operon expression from its own promoter, a promoterless lacZ was fused with the mer operon, where merB was deleted in plasmid pB43merlacZ. Only Hg2+, but not C6H5Hg+ or CH3Hg+, can activate β-galactosidase expression in bacteria with pB43merlacZ. These results not only imply that the pMRA17 MerR is a narrow-spectrum regulator that did not recognize organomercury as a direct inducer, but also confirms that merB is required for induction of the pMRA17 mer operon expression by organomercurials.
The quantity of acetaldehyde was determined using an apparatus containing a reactor with immobilized aldehyde dehydrogenase in a flow line. NADH formed by an enzymatic reaction was fluorometrically detected. The optimal concentration of NAD+ in the carrier was determined. Various buffer types were examined as a carrier medium. When the pH of the carrier was 7.8, great peak areas due to NADH were observed for buffers of phosphate, pyrophosphate, HEPES, PIPES-(piperazine-N, N'-bis(2-ethanesulfonic acid)) and triethanolamine, compared with that for Tris buffer. In the pH range from 7.0 to 8.0, the peak area due to NADH increased with the increase of pH in the case of phosphate buffer, in contrast to the case of Tris buffer in which peak area decreased with the increase of pH. When the carrier composed of phosphate buffer (0.1M, pH7.8) was used, the calibration curve for acetaldehyde was linear in the range of 0.2-10μM (r=0.9994). Detection limit (S/N=3) was 0.1μM.Relative standard deviation of peak area at 2μM was 2.6% (n=7). The sampling rate was 40 samples h-1. This method was applied to the analysis of aldehyde in several liquors, and aldehyde content determined by the method agreed with that determined by a commercially available test-kit method.
To investigate the role of metallothionein (MT) on the accumulation and toxicity of orally administered cadmium (Cd), metallothionein null and 129/Sv mice were fed a Cd-containing diet (50ppm) for four months. Cd concentrations in the liver and kidney of MT null mice did not exceed 10μg/g throughout the exposure period, while a time-dependent increase in tissue Cd concentrations was observed in the control mice. However, no apparent nephrotoxicity was observed in MT null mice, as is contrary to previous observations in which repeated subcutaneous injections of Cd caused renal dysfunction in MT null mice, though the renal Cd concentrations did not exceed 10μg/g. The results of this study suggest that the route of Cd administration plays an important role in the manifestation of Cd nephrotoxicity, even in the absence of MT.
We studied the influence of powdered green tea (PGT) and its caffeine content on the adipose conversion of 3T3-L1 cells by insulin and lipolysis of well-differentiated 3T3-L1 cells. In the 11 days of culture with insulin, the fat cells exhibited more numerous and larger intracytoplasmic lipid droplets, and the activities of glycerophosphate dehydrogenase (GPDH), a marker of adipose conversion, were increased. When PGT and insulin were added simultaneously, the accumulation of lipid droplets and the increase of GPDH were significantly inhibited (p < 0.01). But the caffeine, which has the same concentration as PGT, accelerated adipose conversion. When PGT or caffeine was exposed to mature adipocytes, smaller-sized intracytoplasmic lipid droplets selectively disappeared. These data suggest that PGT inhibited lipogenesis and stimulated lipolysis.
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