Bioconcentration, biotransformation, and elimination of polycyclic aromatic hydrocarbons in sheepshead minnows (Cyprinodon variegatus) exposed to contaminated seawater

Sheepshead minnows (Cyprinodon variegatus) were continuously exposed to two concentrations of polycyclic aromatic hydrocarbons (PAHs) dissolved in seawater (sigma PAH = 7.57 and 72.31 microg/L) for 36 d, followed by 8 d of depuration. The PAHs studied were naphthalene (NPH or C0-NPH), phenanthrene (PHE or C0-PHE), pyrene (PYR), 2-methylnaphthalene (C1-NPH), 1,3-dimethylnaphthalene (C2-NPH), 2-isopropylnaphthalene (C3-NPH), 9-methylphenanthrene (C1-PHE), and 9-ethylphenanthrene (C2-PHE). Uptake rate constants (k1) for NPHs increased with increasing degree of alkylation and log value of the octanol/water partition coefficient (Kow), whereas k1 values for three- and four-ring PAHs were lower despite their high log Kow values. Elimination rate constants (k2) for the homologue series of NPHs and PHEs generally increased with decreasing degree of alkylation and log Kow values. However, the depuration time did not directly correlate with the molecular size for nonalkylated PAHs. Bioconcentration factors (BCFs) were estimated from the ratio of k1 to k2 and also directly from PAH concentrations in fish tissue and water samples, and the factors generated by the two methods were very similar. A significant positive correlation was determined between log BCFs and log Kow values for the series of C0- through C3-NPH at both low (r2 = 0.985, p = 0.0077) and high (r2 = 0.956, p = 0.022) exposures, although this correlation was not determined for all the PAHs studied. As a result of increased metabolism and/ or reduced bioavailability with increasing lipophilic character, the estimated BCFs for C0- through C2-PHE and PYR were generally lower than those for C0- through C3-NPH. The two exposure levels revealed minor variations in k1 and k2 values for parent PAHs and in the temporal pattern of PAH metabolite concentrations in bile. The present results indicate that the presence and nature of alkyl groups have a significant influence on the kinetics and metabolism of PAHs in fish.     

Role of the mycelium in the elimination of aflatoxin B1 from contaminated substrates]

When the aflatoxin-producing strain of Aspergillus flavus, nr 14409 developed in mixed cultures with non toxigenic strains, in solid or liquid media, it produced less aflatoxin than in pure culture. Investigations in view to elucidate the process promoting the toxin disappearance showed that the mycelium could immobilize a large amount of aflatoxin by adsorption on its walls.     

Bioconcentration ratio of diazinon by freshwater fish and snail

Summary The bioconcentration ratios of diazinon from water by freshwater fishes were generally larger than that of crayfish and snails. Among fishes, the bioconcentration ratio of diazinon by topmouth gudgeon was the highest value, 152 being average. However, elimination of diazinon from fish body was linearly rapid. The influence of test concentration on the bioconcentration ratio was not so much considerable. The bioconcentration ratio of diazinon in whole body of topmouth gudgeon was increased proportional to the body weight.     

Bioconcentration and Depuration of Chlorpyrifos in the Marine Mollusc Mytilus edulis

The bioconcentration and depuration of chlorpyrifos [O,O-diethyl-O-(3,5,6-trichloro-2-pyridil) phosphorothioate] for the marine mollusc Mytilus edulis was investigated under laboratory conditions in experimental aquaria. Renewal tests at concentrations of 1 and 3.2 mg/L followed by depuration tests were conducted. Organisms were exposed to pesticide concentrations for 38 days and then were maintained in clean sea water until the chlorpyrifos were eliminated. Two different methods to estimate toxicokinetic rate constants of chlorpyrifos were compared. Toxicokinetic rate constants appeared to be dependent upon the level of exposure, probably due to the toxic stress produced by the high exposure level assayed. Lipid based Bioconcentration Factor (BCF) calculated by first order kinetic fit was found to be 482 ± 86. The depuration of chlorpyrifos by mussels maintained in clean sea water was fitted to first order one-compartment model, and the depuration rate constant estimated was similar to that calculated in the bioconcentration phase. The BCF obtained was lower than expected for K _ow of chlorpyrifos, suggesting metabolic biotransformation of the parent pesticide. Received: 18 July 1996/Accepted: 5 January 1997     

Toxic effects of PCB126 and TCDD on shortnose sturgeon and Atlantic sturgeon

Exposure to chemical contaminants is often invoked to explain recruitment failures to populations of sturgeon worldwide, but there is little empirical evidence to support the idea that young sturgeon are sensitive at environmentally relevant concentrations. The authors used shortnose sturgeon (Acipenser brevirostum) and Atlantic sturgeon (Acipenser oxyrinchus) as models to investigate the sensitivities of sturgeon to early-life-stage toxicities from embryonic exposures to graded doses of polychlorinated biphenyl 126 (PCB126) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Survival to hatching of shortnose sturgeon decreased with increasing dose, although the duration of the embryonic period was not significantly altered by exposure in either species. Morphometric features of larvae of both species were affected by dose, including shortening of the body, reduction in head size, reduction in quantity of yolk reserves, and reduction in eye size. Eye development in both species was delayed with increasing dose for both chemicals. The persistence of larvae in a food-free environment decreased inversely with dose in both species, with sharp declines occurring at PCB126 and TCDD doses of ≥1 ppb and ≥0.1 ppb, respectively. Dose-responsive early-life-stage toxicities reported here are among the more sensitive found in fish and occurred at burdens similar to those found in situ in a sympatric bottom-dwelling bony fish in the Hudson River Estuary. The present study is among the first demonstrating the sensitivity of any sturgeon to the hallmark early-life-stage toxicities induced by aryl hydrocarbon receptor agonists. Environ. Toxicol. Chem. 2012; 31: 2324-2337. ? 2012 SETAC.     

Bioconcentration of inorganic and organic thallium by freshwater phytoplankton

Uptake of inorganic Tl(I) and dimethylthallium, (CH3)2Tl+, by Chlorella spp. (Chlorophyta) and the diatom Stephanodiscus hantzschii (Heterokontophyta) were measured using radio-tracer techniques in water from Lakes Erie and Superior (North America). Uptake of both Tl(I) and dimethylthallium was bioactive. Uptake of [204Tl]-Tl(I) was greater in Lake Superior water than in Lake Erie water due to the greater K content in Lake Erie that inhibits Tl(I) uptake by phytoplankton but not that of [204Tl]-dimethylthallium. Volume-based bioconcentration factors for Tl(I) after 72 h of exposure were 5 x 10(4) and 1.1 x 10(4) for Chlorella sp. and S. hantzschii; for dimethylthallium they were 7.8 x 10(2) and 8.3 x 10(3). Both Tl(I) and Tl(III) were concentrated similarly by Chlorella spp. These results suggest that chlorophytes, but not diatoms, accumulate Tl(I) to a greater extent than dimethylthallium. Greater bioaccumulation factors of inorganic Tl are possible in waters containing low amounts of K+; water quality guidelines seeking to protect biota from deleterious effects of Tl should consider the role of K.     

Bioconcentration of methylmercury in microzooplankton in a temperate river

To understand the bioconcentration of methylmercury (MeHg) at the base of the riverine food chain, we determined levels of dissolved organic carbon, microseston, Hg, and MeHg in surface water in relation to the microzooplankton MeHg from Yeongsan River. The spatial distribution of unfiltered Hg (0.29-3.1 ng/L) and dissolved Hg (0.15-0.74 ng/L) closely followed the microseston distribution. The spatial distribution of unfiltered MeHg (0.0078-0.077 ng/L) and dissolved MeHg (0.0069-0.018 ng/L) increased with increasing distance from the river mouth and appeared to arise from the shallow wetlands surrounding the upper riverbanks and then to be transported downstream. The logarithm of the MeHg bioconcentration factor for microzooplankton ranged from 5.3 to 6.0 (5.7 ± 0.18), and for microseston ranged from 4.0 to 5.4 (4.9 ± 0.35). Linear correlation statistics comparing microzooplankton MeHg and river water characteristics revealed that microzooplankton MeHg concentration was most significantly correlated with unfiltered MeHg (r = 0.83) and particulate MeHg (r = 0.80) levels. This result suggests that MeHg in unfiltered river water, which is relatively easy to determine, can be used as a surrogate for MeHg in microzooplankton that may influence MeHg levels in higher-trophic-level organisms.     

推动消除乙型肝炎 注重经济学评估

WHO制定和发布了全球消除乙型肝炎（乙肝）规划,并在各国推广实施。继续开展乙肝免疫预防,推行基于社区慢性乙肝抗病毒治疗,是消除乙肝最重要的策略。据WHO消除乙肝所需费用测算,后者将消耗巨量资金。中国乙肝免疫预防成效显著,但人群中慢性乙肝数量庞大,消除乙肝需要大量公共卫生资源,对决策构成挑战。乙肝防治经济学研究可为我国消除乙肝提供决策依据和技术支持,由本期"乙肝防治经济学评价"栏目的论文可见,其方法和技术进展令人振奋。     

阿维菌素原药对昆明小鼠免疫功能的影响

目的探讨阿维菌素原药对昆明小鼠细胞免疫功能、体液免疫功能和非特异性免疫功能的影响。方法阿维菌素设3个剂量组20、10、5mg/kg和阴性对照组,连续给昆明小鼠染毒28d;T淋巴细胞增殖和迟发型变态反应（DTH）检测细胞免疫功能;抗体生成细胞数（PFC）和半数溶血值（HC50）测定检测体液免疫功能;腹腔巨噬细胞吞噬鸡红细胞、碳粒廓清试验和NK细胞活性测定检测非特异性免疫功能。结果 20mg/kg组小鼠T淋巴细胞增殖能力为0.76（阴性对照为0.86）,HC50为128.45（阴性对照为140.96）,PFC为89.21×106（阴性对照为113.33×106）;20和10mg/kg组碳廓清吞噬指数分别为5.59、5.61（阴性对照为7.96）,鸡红细胞吞噬指数分别为0.86、0.90（阴性对照为1.05）,以上结果均比阴性对照组明显降低,且差异有统计学意义﹙P〈0.01﹚。结论阿维菌素原药对昆明小鼠在细胞免疫功能、体液免疫功能和非特异性免疫功能方面均有抑制作用。     

The Concentrations and Bioconcentration Factors of Copper and Zinc in Edible Mushrooms

Copper and zinc contents have been determined in up to 28 species of edible mushrooms from different sites in the province of Lugo (NW Spain). Two hundred thirty-eight collected samples were analyzed by an anodic stripping voltammetric technique using a drop mercury as the working electrode. The results showed that the element concentrations were species-dependent, and the highest metal levels corresponded to the following species: Calvatia utriformis (235.5 mg Cu/kg), Macrolepiota procera (217.8 mg Cu/kg), and Agaricus macrosporus (217.7 mg Cu/kg) and Calvatia utriformis (265.8 mg Zn/kg), Lactarius delicious (231.0 mg Zn/kg), and Agaricus macrosporus (221.3 mg Zn/kg) for Cu and Zn, respectively. All mushroom species bioaccumulated copper and zinc. Nevertheless, some individual samples of the species, such as Hydnum repandum, Cantharellus cibarius, and Coprinus comatus, were bioexclusors (BCF < 1). The hymenophore in mushrooms showed higher mean metal levels than the rest of the fruit bodies, with statistically significant differences. The copper and zinc concentrations were compared to literature data and levels set by legislation. It can be concluded that the consumption of these mushrooms cannot be considered a toxicological risk, and they provide an important nutritional requirement to the diet. Received: 9 April 2002/Accepted: 6 August 2002     

Bioconcentration of chlorinated hydrocarbons from sediment by oligochaetes

Previously published data on the accumulation of 15 chlorinated hydrocarbons from sediment by oligochaetes have been interpreted on the basis of bioconcentration from interstitial water. Calculation of the interstitial water concentration allowed determination of uptake and clearance rate constants together with bioconcentration factors (KB) for these compounds. These three factors each exhibited a systematic relationship to the octanol/water partition coefficient (KOW). The log KB versus log KOW relationship was roughly linear over the log KOW range from 4.4 to 6.4 and displayed an increasing nonlinear deviation for log KOW values greater than 6.4. These relationships are qualitatively similar to those established for other aquatic organisms where bioconcentration from water was the mechanism involved. This suggests that interstitial water may be the phase from which lipophilic compounds in sediment are bioconcentrated by oligochaetes. An expression relating the bioconcentration factor to the biotic concentration and various sediment characteristics has also been developed.