Regulation of spirocyst discharge in the model sea anemone, Nematostella vectensis

Test probes were touched to tentacles to investigate whether discharge of spirocysts likely is regulated by hair bundle mechanoreceptors. Significantly more spirocysts discharge onto test probes in the presence of vibrations at 11–15 Hz as compared to 0 Hz. Adding N-acetylneuraminic acid, NANA, shifts maximal discharge of spirocysts upwards to 36–40 Hz, and possibly to 21–25 Hz. In contrast, NANA shifts maximal discharge of basitrichous isorhiza nematocysts downwards to 1–20 Hz. Thus, discharge of cnidae (‘stinging capsules’) is differentially regulated according to the type of cnida. Furthermore, it appears that chemodetection of N-acetylated sugars is not a prerequisite to capturing prey because, in seawater alone, maximal discharge of cnidae occurs at frequencies overlapping movements of calmly swimming prey. Nevertheless, chemodetection of N-acetylated sugars broadens the range of frequencies stimulating maximal discharge of cnidae and, therefore, likely enhances prey capture.     

定性与定量评估4种重金属及2种农药混合物对费氏弧菌的毒性相互作用

重金属与农药共同暴露产生的联合毒性作用可以对实际环境产生潜在的风险。为了研究重金属与农药混合物在不同浓度比毒性相互作用(协同、拮抗与加和)及其定量评估相互作用大小,根据单个物质无观测浓度(NOEC)、5%效应浓度(EC5)、10%效应浓度(EC10)和50%效应浓度(EC50),设计3组混合物体系(即农药-农药、重金属-重金属和农药-重金属)分别按NOEC、EC5、EC10和EC50浓度比的12条混合物射线,测试单个化合物及混合物对以费氏弧菌的发光抑制急性毒性,利用浓度加和(CA)、独立作用(IA)、模型偏差比(MDR)及其观测值置信区间定性和定量评估12条混合物射线的毒性相互作用。结果表明,农药-农药二元混合物体系和农药-重金属六元混合物体系均产生明显的协同作用,其中农药-农药混合物体系中,混合物射线EE-NOEC在50%效应下协同作用大小达到30.6(MDRCA和MDRIA数值);混合物射线EE5、EE10的协同作用大小接近于混合物射线EE-NOEC,混合物射线EE50的效应大于15%时CA和IA计算的MDR值均在置信区间上限的上方,即混合物发生协同作用;农药-重金属混合物体系的4条混合物射线EE-NOEC、EE5、EE10和EE50在所有测试浓度水平的MDR值均在置信区间上限的上方,呈现出明显的协同作用;在50%效应下,混合物射线EE-NOEC、EE5、EE10和EE50的MDRCA和MDRIA值分别为4.05和4.91、6.12和7.98、3.70和4.60、2.62和2.59。重金属-重金属四元混合物体系除了EC50浓度比混合物表现出拮抗作用,其余混合物在所有测试浓度范围的MDR值均在置信区间范围内,均为加和作用。因此,混合物的毒性相互作用大小随着组分浓度比变化而发生变化。     

五元氨基甲酸酯类农药混合物体系对青海弧菌的毒性特点

以5种氨基甲酸酯类农药涕灭威(ALD)、残杀威(BAY)、呋喃丹(CAR)、灭多威(MET)和抗蚜威(PIR)为研究对象,应用均匀设计射线法设计五元混合物体系共6条射线(U1,U2,…,U6),应用基于发光菌青海弧菌Q67的微板毒性分析法(MTA)系统地考察了5种农药及其混合物的毒性,以浓度加和(CA)为参考模型分析混合物毒性相互作用(协同或拮抗作用)。结果表明,Logti和Weibull函数能较好地拟合5种氨基甲酸酯农药及其混合物对发光菌Q67的浓度-效应数据(R20.99,RMSE0.032);以EC50的负对数值pEC50为毒性指标,5种农药的毒性顺序为BAY(pEC50=2.87)CAR(pEC50=2.67)ALD(pEC50=2.00)MET(pEC50=1.99)PIR(pEC50=1.79);依据CA,五元氨基甲酸酯类农药的6条混合物射线中,有2条呈加和作用,4条呈拮抗作用,其中U2和U4在整条浓度-效应曲线上呈现了明显的拮抗作用,而U3和U6的弱拮抗作用分别发生在混合物浓度的中高浓度区和中低浓度区;五元氨基甲酸酯类农药混合物的毒性与组分灭多威(MET)的浓度比呈良好的负相关关系(r=-0.9238),且线性模型对混合物毒性具有良好的预测能力。     

Comparing model averaging with other model selection strategies for benchmark dose estimation

Model averaging (MA) has been proposed as a method of accommodating model uncertainty when estimating risk. Although the use of MA is inherently appealing, little is known about its performance using general modeling conditions. We investigate the use of MA for estimating excess risk using a Monte Carlo simulation. Dichotomous response data are simulated under various assumed underlying dose–response curves, and nine dose–response models (from the USEPA Benchmark dose model suite) are fit to obtain both model specific and MA risk estimates. The benchmark dose estimates (BMDs) from the MA method, as well as estimates from other commonly selected models, e.g., best fitting model or the model resulting in the smallest BMD, are compared to the true benchmark dose value to better understand both bias and coverage behavior in the estimation procedure. The MA method has a small bias when estimating the BMD that is similar to the bias of BMD estimates derived from the assumed model. Further, when a broader range of models are included in the family of models considered in the MA process, the lower bound estimate provided coverage close to the nominal level, which is superior to the other strategies considered. This approach provides an alternative method for risk managers to estimate risk while incorporating model uncertainty.

Beta-normal distribution in dose–response modeling and risk assessment for quantitative responses

To establish allowable daily intakes for humans from animal bioassay experiments, benchmark doses corresponding to low levels of risk have been proposed to replace the no-observed-adverse-effect level for non-cancer endpoints. When the experimental outcomes are quantal, each animal can be classified with or without the disease. The proportion of affected animals is observed as a function of dose and calculation of the benchmark dose is relatively simple. For quantitative responses, on the other hand, one method is to convert the continuous data to quantal data and proceed with benchmark dose estimation. Another method which has found more popularity (Crump, Risk Anal 15:79–89; 1995) is to fit an appropriate dose–response model to the continuous data, and directly estimate the risk and benchmark doses. The normal distribution has often been used in the past as a dose–response model. However, for non-symmetric data, the normal distribution can lead to erroneous results. Here, we propose the use of the class of beta-normal distribution and demonstrate its application in risk assessment for quantitative responses. The most important feature of this class of distributions is its generality, encompassing a wide range of distributional shapes including the normal distribution as a special case. The properties of the model are briefly discussed and risk estimates are derived based on the asymptotic properties of the maximum likelihood estimates. An example is used for illustration.

3种氨基糖苷类抗生素对水生生物的时间依赖联合毒性作用比较

以3种氨基糖苷类(AG)抗生素:硫酸安普霉素(APR)、双氢链霉素(DIH)和硫酸链霉素(STS)为研究对象,以生态系统中2类重要的水生生物分解者如青海弧菌(Vibrio qinghaiensis sp.-Q67,Q67)和生产者蛋白核小球藻(Chlorella pyrenoidosa,CP)为受试生物,运用均匀设计射线法设计抗生素三元混合物体系,共5条具有不同浓度配比的射线,应用已建立的分别基于Q67和CP的时间毒性微板分析法系统测试抗生素及其三元混合物射线对Q67和CP在不同暴露时间的毒性。对于Q67和CP,暴露时间分别为0.25、2、4、8、12 h和12、24、48、72、96 h。应用浓度加和(CA)模型分析混合物在不同暴露时间的毒性相互作用。结果表明:APR、DIH和STS及其5条混合物射线对2种指示生物的毒性均具有明显的时间依赖性,且Q67对AG抗生素及其混合物射线的响应比CP的灵敏;以半数效应浓度的负对数p EC50值为毒性大小指标,3种抗生素对2种指示生物的毒性大小顺序随暴露时间的变化而变化,3种AG抗生素对Q67和CP分别在12 h和96 h的毒性大小顺序均为STSDIHAPR;5条具有不同浓度配比的混合物射线对Q67在不同暴露时间的毒性均呈加和作用,但对CP的毒性既有加和作用也有拮抗作用,且拮抗作用随暴露时间和组分浓度配比的变化而变化,表明AG抗生素毒性的联合毒性作用与暴露生物、暴露时间以及混合物组分的浓度配比等有关。     

Distribution-free two-sample comparisons in the case of heterogeneous variances

Behavioral ecologists are often faced with a situation where they need to compare the central tendencies of two samples. The standard tools of the t test and Mann–Whitney U test (equivalent to the Wilcoxon rank-sum test) are unreliable when the variances of the groups are different. The problem is particularly severe when sample sizes are different between groups. The unequal-variance t test (Welch test) may not be suitable for nonnormal data. Here, we propose the use of Brunner and Munzel’s generalized Wilcoxon test followed by randomization to allow for small sample sizes. This tests whether the probability of an individual from one population being bigger than an individual from the other deviates from random expectation. This probability may sometimes be a more clear and informative measure of difference between the groups than a difference in more commonly used measures of central tendency (such as the mean). We provide a recipe for carrying out a statistical test of the null hypothesis that this probability is 50% and demonstrate the effectiveness of this technique for sample sizes typical in behavioral ecology. Although the test is not available in any commercial software package, it is relatively straightforward to implement for anyone with some programming ability. Furthermore, implementations in R and SAS are freely available on the internet.     

Immobilising of Cd,Pb, and Zn contaminated arable soils close to a former Pb/Zn smelter: a field study in Austria over 5 years

Numerous smelter sites are surrounded by rural land. The entrance of non-essential metals such as lead or cadmium into the food chain is very likely as well as phytotoxicity effects of zinc. Finding a realistic solution for these large-scale contaminations was one aim of this study. Previous results from pot experiments showed a high potential for the reduction of metals entering the food chain via crops grown on smelter-contaminated soils from Arnoldstein, Austria, by the use of amendments for immobilisation. A further aim was to optimise a field experiment for overcoming the gap between pot and field experiments and to look for long-term efficiency of the treatments [lime (CA), red mud (RM), gravel sludge + red mud (GS + RM)]. Field experiment results were obtained for 5 years. Besides soil and soil pore water samples, the following harvests were yielded: spring barley (Hordeum distichon ssp. L.) (2004–2005), narrowleaf plantain (Plantago lanceolata L.) (2006–2007) and velvet grass (Holcus lanatus L.) (2007–2008). The long-term efficiency of GS + RM led us to conclude that their application seems to be a realistic and practical measure for extensively contaminated land, best in combination with metal excluding cultivars.