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271.
The objective of this work was to evaluate potential interactions between 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and polychlorinated biphenyls congeners (PCBs) in rats. Groups of five adult female rats were given 0, 2.5, 25, 250, or 1000?ng TCDD/kg body weight/day or TCDD in combination with a mixture of PCB congeners at a concentration of 2 or 20?µg?kg?1 body weight/day by gavage for 28 days. After the 28-day treatment period, the rats were killed for the analysis of biochemical, liver enzyme activities, and hematological and pathological end points. Growth suppression, increased absolute and relative liver weights, and decreased thymic weight were observed in the 1000?ng TCDD group alone, or the groups receiving a mixture of 1000?ng TCDD and 2 and 20?µg PCBs. TCDD-increased liver and thymic weights were not altered by PCBs; however, growth suppression was more pronounced in animals receiving 1000?ng TCDD and 2?µg PCBs. Increased hepatic microsomal methoxy resorufin-O-demethylase and ethoxy resorufin-O-deethylase activities occurred in 250 and 1000?ng?kg?1 TCDD-treated animals, which were antagonized by PCBs. Effects of 250?ng TCDD on serum cholesterol and liver uridine diphosphate glucuronosyl transferase activity were reduced by 20?µg PCBs. Treatment with 1000?ng TCDD increased serum albumin, decreased liver vitamin A, increased kidney vitamin A, and liver microsomal glutathione-S-transferase activity, which were not affected by PCBs. Decreased hemoglobin, platelet, packet cell volume, and red cell indices were observed in TCDD-treated rats, but no interactive effects were seen. Histopathological evaluation revealed that liver, thyroid, and thymus were the target organs, but the effects of co-exposure to PCBs and TCDD were variable. These results indicate that the mixture effects of PCBs and TCDD may be additive, synergistic, or antagonistic depending on the dose level and end points measured. 相似文献
272.
Thirty diet samples from three different social groups were collected both in summer and in winter seasons using duplicate portion technique with three collection days. Toxic element concentrations, including Pb, Cd, as well as some essential elements were determined by atomic absorption spectrometry (AAS). The average dietary intakes of Taiwanese were estimated as follows (means ± S.D., n = 30): Mg, 175 ± 77 mg/day; Zn, 9.5 ± 11.4 mg/day; Mn, 2.8 ± 1.3 mg/day; Cu, 1.6±1.7mg/day; Ni, 0.13 ± 0.14 mg/day; Cd, 58 ± 62 μg/day, and Pb, 31 ±26 μg/day. The obtained elemental concentrations were scattered due to different dietary habits and cooking methods. In addition, a strong correlation arose between the trace element concentrations in agricultural products and in the diet of regional areas of Taiwan. Analysis results indicated that average intakes are consistently below current US Recommended Daily Allowances (RDAs) for Mg and Zn, within the recommended safe and adequate RDA for Mn, and below the FAO/WHO Provisional Tolerable Daily Intakes (PTDIs) for Pb. The average daily intakes of Cd by regional area of Taiwan markedly exceeded those of other countries and the PTI value during the summer. 相似文献
273.
含雄黄的中成药中砷的生物可给性及其初步风险评价 总被引:1,自引:0,他引:1
为研究含雄黄中成药中砷的含量状况,探明其中砷对人体的健康风险,选取含雄黄的中成药为研究对象,分析其中砷含量;通过人工胃肠体外模拟系统研究中成药中砷的生物可给性,并在此基础上进行初步的人体健康风险评价。结果显示,含雄黄中成药样品中砷全量为9.9×102~8.8×104mg·kg-1。中成药砷的生物可给性在胃阶段为0.20%~2.17%,小肠阶段为0.26%~2.43%。以WHO每日允许摄入量(ADI)为标准的健康风险评价结果表明,若以砷全量衡量,所有含雄黄中成药均对人体健康具有巨大风险;若以小肠阶段可给砷含量评价,砷日摄入量与ADI比值范围为1.48%~879.68%,约70%含雄黄的中成药的可给砷含量仍足以威胁人体健康。 相似文献
274.
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276.
Characterization and coagulation of a polyaluminum chloride (PAC) coagulant with high Al13 content 总被引:1,自引:0,他引:1
A polyaluminum chloride (PAC) coagulant was prepared from AlCl3 x 6H2O and Na2CO3. The Al13 species in PAC was separated and purified by the SO4(2-)/Ba2+ deposition-replacement method, and characterized by 27Al-NMR and XRD. From 27Al-NMR spectroscopy, it was found that PAC obtained after separation and purification contained more Al13 (PAC-Al13, for short) than original PAC before separation and purification. In XRD spectra, a strong Al13 signal appeared in the range of 2theta from 5 to 25 degrees. Jar tests were performed to test the coagulation efficiency of AlCl3, PAC and PAC-Al13 in treating synthetic or actual water samples. Compared with PAC and AlCl3, PAC-Al13 gives the best results for turbidity, humic acid and color removal, and achieves the highest charge-neutralizing ability. Under the study conditions, PAC-Al13 gave about 90% humic acid removal and almost 100% reactive blue dye removal when its dosages were 4.0 and 15 mg/L as Al, respectively. The Al13 species has a higher positive charge and is the most effective polymeric Al species in water and wastewater treatment. 相似文献
277.
278.
The geocycles of N, Fe and S in the ocean are tightly coupled and together exert strong influence on biogeochemistry of the earth system. We investigate this interaction by inserting macro-micronutrient cycling into a high resolution ocean model that realistically represents the general circulation. Simulated chlorophyll distributions reproduce many features of satellite-based measurements of ocean color. Meridional sections through model results and seasonally averaged SeaWiFS data agree reasonably well, both in the oligotrophic gyres and along fronts. Discrepancies are associated in many cases with shelf, ridge or island effects. Dimethyl sulfide peaks and their chlorophyll correlations are similar to those obtained on major oceanographic expeditions. Lack of strong regional relationships between the sulfide and phytoplankton may be partly explained by correspondence between time constants for production and for the traversal of mesoscale transport features. In general the eddies and filaments of tropical instability waves are well represented, including the onset of the 1997-1998 El Ni?o. North-south shifts of the transition zone chlorophyll front appear prominently in the results. 相似文献
279.
Bacteria resistant to Cu2+, Ni2+ or Zn2+ were isolated from the rhizosphere of water hyacinth (Eichhornia crassipes (Mart.)) and their metal ion removal capacities (RCs) were determined. The Ni2+ and Zn2+ RCs of the respective metal ion-resistant bacteria were less than 4.1 mg g(-1), while one of the Cu2+-resistant bacteria (Strain CU-1) showed a significant high Cu2+ RC of 10.6 mg g(-1). The effect of inoculating water hyacinth with Strain CU-1 on its Cu2+ RC was further studied. Water hyacinths were treated with an antibiotic, oxytetracycline (OTC), to remove most rhizospheric bacteria of plant roots. Inoculation of Strain CU-1 increased the Cu2+ RC of the plant root by 1.91 (OTC-treated) and 1.56 (OTC-untreated) folds respectively when compared with the control. Results also showed that Strain CU-1 colonized onto the plant root and led to the increase of Cu2+ RC of the roots of water hyacinth. 相似文献
280.