The toxicity of fluoranthene to Hyalella azteca in sediment and water-only exposures under varying light spectra

In the US Environmental Protection Agency methods for sediment toxicity testing, the light regimen is specified as a 16:8 light dark cycle with 500-1000 lx. The potential for photoinduced toxic effects from this requirement is evaluated. Hyalella azteca were exposed to fluoranthene in both water only and sediment to examine the impact of light spectra on the toxicity of fluoranthene. The light sources included gold fluorescent light (lambda > 500 nm), cool white fluorescent light, and UV-enhanced fluorescent light. Toxicity was determined as mortality after 10 days of exposure. The extent of mortality was determined both as LC(50) and LR(50) (median lethal body residue). In water-only exposures, the toxicity of fluoranthene was greatest under the UV-enhanced spectra, followed by fluorescent light, and least toxic under the gold light. Both the LC(50) and LR(50) values exhibited the same pattern. The toxicity under gold light gave an LR(50) of 0.81 mmol kg(-1) (0.82-0.79, 95% CI) similar to values expected for the acute toxicity of nonpolar narcotic (anesthetic) compounds. The LR(50) values under the other two light sources were substantially lower, 4 and 58 times lower for the fluorescent and UV-enhanced exposures, respectively. In sediment, toxicity was not significantly affected by the light source. Toxicity occurred only when the body residue concentration approached that of the LR(50) under gold light from the water-only exposures. Thus, H. azteca were significantly protected from the light by burrowing into the sediment.     

Toxicity of uranium, molybdenum, nickel, and arsenic to Hyalella azteca and Chironomus dilutus in water-only and spiked-sediment toxicity tests

A series of laboratory spiked-sediment toxicity tests with the amphipod Hyalella azteca and the midge Chironomus dilutus were undertaken to determine acute and chronic toxicity thresholds for uranium (U), molybdenum (Mo), nickel (Ni), and arsenic (As) based on both whole-sediment (total) and pore water exposure concentrations. Water-only toxicity data were also generated from separate experiments to determine the toxicities of these metals/metalloids under our test conditions and to help evaluate the hypothesis that pore water metal concentrations are better correlated with sediment toxicity to benthic organisms than whole-sediment metal concentrations. The relative toxicity of the four elements tested differed depending on which test species was used and whether whole-sediment or pore water metal concentrations were correlated with effects. Based on measured whole-sediment concentrations, Ni and As were the two most acutely toxic elements to H. azteca with 10-d LC50s of 521 and 532 mg/kg d.w., respectively. Measured pore water concentrations indicated that U and Ni were the two most acutely toxic elements, with 10-d LC50s to H. azteca of 2.15 and 2.05 mg/L, respectively. Based on pore water metal concentrations, the no-observed-effect concentrations (NOECs) for growth were (H. azteca and C. dilutus, respectively) 0.67 and 0.21 mg/L for U, <0.37 and 0.60 mg/L for Ni, and 16.43 and <0.42 mg/L for As. Pore-water lowest-observed-effect concentrations (LOECs) for growth were (H. azteca and C. dilutus, respectively) 2.99 and 0.48 mg/L for U, 0.37 and 2.33 mg/L for Ni, and 58.99 and 0.42 mg/L for As. For U and Ni, results from 96-h water-only acute toxicity tests correlated well with pore water metal concentrations in acutely toxic metal-spiked sediment. This was not true for As where metalloid concentrations in overlying water (diffusion from sediment) may have contributed to toxicity. The lowest whole-sediment LOEC reported here for As was 6.6- and 4-fold higher than the Canadian Council of Ministers of the Environment interim sediment quality guideline and the Canadian Nuclear Safety Commission (CNSC) lowest effect level (LEL), respectively. The lowest whole-sediment LOECs reported here for Ni, U and Mo were 4-, 17.5-, and >260-fold higher, respectively, than the CNSC LELs for these metals/metalloids. Data on pore water metal concentrations in toxic sediment would be a useful addition to future Guidelines documents.     

Chemical availability and sediment toxicity of pyrethroid insecticides to Hyalella azteca: application to field sediment with unexpectedly low toxicity

Tenax extraction is a simple, inexpensive approach to estimate the bioavailability of hydrophobic organic contaminants from sediment. In the present study, a single-point Tenax extraction was evaluated regarding its correlation with the acute toxicity to Hyalella azteca using field-collected sediments in California, USA. Pyrethroids were believed to be the primary contributor to the observed toxicity, and a significant correlation existed between the expected toxicity (given pyrethroid concentrations) and the mortality at most sampling sites. A small subset of sites, however, showed unexpectedly low toxicity to H. azteca despite high concentrations of pyrethroids. These samples were evaluated by Tenax extraction with the expectation that this procedure, which qualifies bioavailable instead of total pyrethroid concentration in sediment, would better explain the anomalously low toxicity. The term bioavailable toxic unit was proposed to link sediment toxicity with chemical availability, and the toxicity in the 17 selected sediments was better explained using Tenax extraction. The r2 value of the regression between sediment toxicity and toxic unit for the 17 sediments increased from 0.24 to 0.60 when the Tenax-extractable concentration was used in place of the total concentration. Results also showed that adsorption to sand particles might play a controlling role in pyrethroid bioavailability and, in turn, sediment toxicity to benthic invertebrates.     

Validation of a chronic dietary cadmium bioaccumulation and toxicity model for Hyalella azteca exposed to field-contaminated periphyton and lake water

A model previously developed in the laboratory to predict chronic bioaccumulation and toxicity of cadmium to Hyalella azteca from a diet of periphyton was validated by comparing predictions with measurements of Cd in two exposure scenarios: laboratory-cultured H. azteca exposed for 28?d to field-contaminated water and periphyton, and Cd measured in field-collected H. azteca. In both exposure scenarios, model predictions of bioaccumulation were shown to be robust; however, effects on Cd bioaccumulation from complexation with dissolved organic carbon (DOC) and inhibition of Cd bioaccumulation by Ca2? must be incorporated into the model to permit its wider application. The model predicted that 80 to 84% of Cd in H. azteca came from periphyton when H. azteca were chronically exposed to dissolved Cd in lake water at 2.63 to 3.01?nmol/L and periphyton at 1,880 to 2,630 nmol/g ash-free dry mass. Dietary Cd contributed markedly to the model-predicted decrease in 28-d survival to 74% at environmental Cd concentrations in food and water. In reality, survival decreased to 10%. The lower than predicted survival likely was due to the higher nutritional quality of periphyton used to develop the model in the laboratory compared with the field-collected periphyton. Overall, this research demonstrated that Cd in a periphyton diet at environmental concentrations can contribute to chronic toxicity in H. azteca.     

Enrichment of elements in detritus from a constructed wetland and consequent toxicity to Hyalella azteca

In a pilot constructed wetland treatment system specifically designed to treat constituents of flue gas desulfurization wastewater, detritus adsorbs significantly high concentrations of Hg, Se, and As. Results of this research indicate that Hg, Se, and As were enriched in detritus from Schoenoplectus californicus and Typha angustifolia collected from the constructed wetland by factors up to 4600, 26,300, and 15,600, respectively. As an important food source for many organisms, element enrichment makes the detritus an even greater source of contaminants to the food web. Results demonstrate that the natural decomposition of plants in this constructed wetland treatment system produces detritus enriched with Hg, Se, and As at levels potentially hazardous to aquatic organisms. To completely assess ecological risks associated with the use of constructed wetland treatment systems, contaminant enrichment, bioavailability, and toxicity in detritus must be considered.     

Effects of Calcium, Magnesium, and Sodium on Alleviating Cadmium Toxicity to Hyalella azteca

Received: 14 July 1999/Accepted: 16 November 1999     

Acute and chronic toxicity of nickel to a cladoceran (Ceriodaphnia dubia) and an amphipod (Hyalella azteca)

This study evaluated acute and chronic nickel (Ni) toxicity to Ceriodaphnia dubia and Hyalella azteca with the objective of generating information for the development of a biotic ligand model for Ni. Testing with C. dubia was used to evaluate the effect of ambient hardness on Ni toxicity, whereas the larger H. azteca was used to derive lethal body burden information for Ni toxicity. As was expected, acute C. dubia median lethal concentrations (LC50s) for Ni increased with increasing water hardness. The 48-h LC50s were 81, 148, 261, and 400 microg/L at hardnesses of 50, 113, 161, and 253 mg/L (as CaCO3), respectively. Ceriodaphnia dubia was found to be significantly more sensitive in chronic exposures than other species tested (including other daphnids such as Daphnia magna); chronic toxicity was less dependent on hardness than was acute toxicity. Chronic 20% effective concentrations (EC20s) were estimated at <3.8, 4.7, 4.0, and 6.9 microg/L at hardnesses of 50, 113, 161, and 253 mg/L, respectively. Testing with H. azteca resulted in a 96-h LC50 of 3,045 microg/L and a 14-d EC20 of 61 microg/L at a hardness of 98 mg/L (as CaCO3). Survival was more sensitive than was growth in the chronic study with H. azteca. The 20% lethal accumulation effect level based on measured Ni body burdens was 247 nmol/g wet weight.     

核函数logistic回归模型在全基因组关联研究中的应用

[导读]探讨基于基因水平的核函数logistic回归模型及其在全基因组关联研究中的应用.以全基因组关联研究模拟数据为例,介绍核函数logistic回归模型在基因水平检测遗传变异与复杂性疾病之间关联的分析策略.模拟结果表明,在所有已知基因检验结果中致病位点所在基因假设检验的P值最小.结果提示基于基因水平的核函数logistic回归模型能够充分提取和综合基因中多个遗传突变位点信息,降低统计学检验的自由度,同时还能够控制多种协变量因素和交互作用,在检测致病基因与疾病关联时具有一定的效能.     

广义估计方程与多水平logistic回归模型在临床纵向数据分析中的应用及比较

目的探讨广义估计方程和多水平模型的应用与临床纵向研究以解决个体重复观测数据内部的相关性问题。方法根据临床纵向实例数据的特点,拟合因变量为二分类的广义估计方程和多水平模型,并与一般logistic模型比较。结果广义估计方程和多水平模型的分析结果与一般logistic模型不同。由于未能考虑个体内重复观测数据的相关性,一般logistic模型错误显示临床分期与近期疗效相关,而广义估计方程和多水平模型分析结果则显示相关无统计学意义。经分层分析也未发现临床分期与近期疗效的关联。结论广义估计方程和多水平模型都能有效地考虑重复观测数据内部相关性并能处理有缺失值的资料。与多水平模型相比,广义估计方程的参数估计较为稳定,可有效的估计各解释变量的效应。     

Evaluation of Cox's model and logistic regression for matched case-control data with time-dependent covariates: a simulation study

Case-control studies are typically analysed using the conventional logistic model, which does not directly account for changes in the covariate values over time. Yet, many exposures may vary over time. The most natural alternative to handle such exposures would be to use the Cox model with time-dependent covariates. However, its application to case-control data opens the question of how to manipulate the risk sets. Through a simulation study, we investigate how the accuracy of the estimates of Cox's model depends on the operational definition of risk sets and/or on some aspects of the time-varying exposure. We also assess the estimates obtained from conventional logistic regression. The lifetime experience of a hypothetical population is first generated, and a matched case-control study is then simulated from this population. We control the frequency, the age at initiation, and the total duration of exposure, as well as the strengths of their effects. All models considered include a fixed-in-time covariate and one or two time-dependent covariate(s): the indicator of current exposure and/or the exposure duration. Simulation results show that none of the models always performs well. The discrepancies between the odds ratios yielded by logistic regression and the 'true' hazard ratio depend on both the type of the covariate and the strength of its effect. In addition, it seems that logistic regression has difficulty separating the effects of inter-correlated time-dependent covariates. By contrast, each of the two versions of Cox's model systematically induces either a serious under-estimation or a moderate over-estimation bias. The magnitude of the latter bias is proportional to the true effect, suggesting that an improved manipulation of the risk sets may eliminate, or at least reduce, the bias.     

Influence of age on the relative sensitivity of Hyalella azteca to diazinon,alkylphenol ethoxylates,copper, cadmium,and zinc

Laboratories testing Hyalella azteca use a wide range of ages (or sizes) of the amphipod in their studies. The objective of this study was to investigate age-specific differences in sensitivity of the amphipod to contaminants with varying toxic modes of action. Hyalella azteca, ranging in age from <1 to 26 d, were tested in 96-h water-only exposures with the organophosphate pesticide diazinon, a mixture of alkylphenol ethoxylates (nonionic surfactants), copper sulfate, cadmium chloride, and zinc sulfate. Overall age-specific differences in sensitivity to the five test chemicals were relatively small; 96-h LC50 values typically varied by 50% or less among the various age classes of H. azteca. When differences in sensitivity were observed, trends were apparently related to the contaminant tested rather than to the age of the amphipods, i.e., no particular age class consistently was the most sensitive to the toxicants.     

Photoinduced lethal and sublethal toxicity of retene, a polycyclic aromatic hydrocarbon derived from resin acid, to coregonid larvae

A comparative investigation on the acute phototoxicity of retene to vendace (Coregonus albula) and whitefish (C. lavaretus), both having pelagial larvae in spring, was conducted. To test the concept of early warning of sublethal biomarkers in relation to lethality to posthatch stages, we examined the effects of ultraviolet-B (UV-B) and retene on the levels of cytochrome P4501A (CYP1A) and heat shock protein 70 (HSP70) by exposing the animals to elevated levels of these factors for 48 and 72 h, respectively. Whereas UV-B and retene on their own were not lethal, simultaneous retene and UV-B exposure caused very high mortality to both species. The median lethal concentration (LC50; i.e., the concentration at which half of the larvae died) of retene as a precursor was 41 g/L for vendace and 15 to 16 microg/L, depending on the UV-B dose, for whitefish. Retene evoked substantial induction of CYP1A in larvae of both species, and UV-B induced CYP1A in whitefish. In vendace, no effect on HSP70 levels by any factor was observed. In whitefish, however, UV-B radiation and water retene alone upregulated HSP70, but no additive response was detected. The CYPIA is a biomarker of exposure to retene in both species. The HSP70 is an early warning signal of UV-B exposure in whitefish. As a species, vendace appears to be more resistant than whitefish to the phototoxicity of retene, as indicated by the higher tolerance.     

基于决策树模型与logistic回归模型的HBV宫内传播影响因素分析

目的:结合logistic回归与 χ 2自动交互检测法（CHAID）决策树模型探讨乙型肝炎病毒（HBV）宫内传播的影响因素及其相互关系。 方法:选取2007-2013年在太原市第三人民医院产科分娩的689对HBsAg阳性母亲及其新生儿,通过问卷调查和病历查阅获得母亲及其新生儿的一般人...     

Adjusting for unmeasured confounding due to either of two crossed factors with a logistic regression model

Motivated by an investigation of the effect of surface water temperature on the presence of Vibrio cholerae in water samples collected from different fixed surface water monitoring sites in Haiti in different months, we investigated methods to adjust for unmeasured confounding due to either of the two crossed factors site and month. In the process, we extended previous methods that adjust for unmeasured confounding due to one nesting factor (such as site, which nests the water samples from different months) to the case of two crossed factors. First, we developed a conditional pseudolikelihood estimator that eliminates fixed effects for the levels of each of the crossed factors from the estimating equation. Using the theory of U‐Statistics for independent but non‐identically distributed vectors, we show that our estimator is consistent and asymptotically normal, but that its variance depends on the nuisance parameters and thus cannot be easily estimated. Consequently, we apply our estimator in conjunction with a permutation test, and we investigate use of the pigeonhole bootstrap and the jackknife for constructing confidence intervals. We also incorporate our estimator into a diagnostic test for a logistic mixed model with crossed random effects and no unmeasured confounding. For comparison, we investigate between‐within models extended to two crossed factors. These generalized linear mixed models include covariate means for each level of each factor in order to adjust for the unmeasured confounding. We conduct simulation studies, and we apply the methods to the Haitian data. Copyright © 2016 John Wiley & Sons, Ltd.     

Application of a generalized random effects regression model for cluster-correlated longitudinal data to a school-based smoking prevention trial

In cluster-randomized trials, groups of subjects (clusters) are assigned to treatments, whereas observations are taken on the individual subjects. Since observations on subjects in the same cluster are typically more similar than observations from different clusters, analyses of such data must take intracluster correlation into account rather than assuming independence among all observations. Random effects models are useful for this purpose. The problem becomes more complicated if, in addition, repeated observations are taken on subjects over time. This introduces intraindividual correlation, which is typical for longitudinal studies. The Waterloo Smoking Prevention Project, study 3 (WSPP3), 1989-1996, is a study giving rise to cluster-correlated longitudinal data, where schools were randomized to either a smoking intervention program or to a control condition. Smoking status was assessed on grade 6 students in these schools, with annual follow-up observations throughout elementary and high school years. The authors illustrate the use of a generalized random effects model for analyzing this type of data. This model obtains appropriate estimates and standard errors for both individual-level covariates and those at the level of the cluster.     

基于正则化回归的变量选择方法在高维数据中的应用

变量筛选和模型估计一直是高维数据的研究热点,而高维数据的维度灾难问题日渐突出,传统的统计分析方法因模型不稳定不再适用,本文对高维数据中基于正则化回归的变量选择方法的原理、适用的数据类型及优缺点、调整参数的选择进行综述。     

基于随机森林算法和多因素logistic回归分析模型的孕期抑郁影响因素

目的  分析孕期抑郁检出率探讨可能的影响因素,识别高危人群为预防抑郁症提供科学依据。方法  对云南省某县2022年5月处于孕期的女性人群采用爱丁堡产后抑郁症量表(Edinburgh Postnatal Depression Scale,EPDS)进行抑郁筛查,利用随机森林算法对影响因素进行重要性排序,用滑动窗口序贯向前选择法降维,将重要性评分最高且平均袋外估算误差率最小的影响因素纳入多因素logistic回归分析模型,估计影响因素的作用方向及效应值。结果  732名孕妇接受问卷筛查,孕期抑郁检出率为13.8%(101/732)。随机森林算法分析显示,变量数为7时平均袋外估算误差率最小。将重要性排名前7的影响因素纳入多因素logistic回归分析模型,结果显示：孕期焦虑、既往不良情绪史、生孩子的经济担忧、家人对孩子有性别期盼是孕期抑郁的危险因素,第2次怀孕、高社会支持水平是孕期抑郁的保护因素,孕妇自评健康状况不满意与孕期抑郁无关。结论  孕期有焦虑的女性很可能伴有抑郁,对生育费用、孩子性别的担忧和既往的不良情绪史会增加孕期抑郁的风险,足够的社会支持和既往的孕育史可以减少孕期抑郁发生的风险。建议加强孕期抑郁筛查,早期识别孕期抑郁症的高危人群。     

Application of logistic regression to the analysis of diagnostic data: exact modeling of a probability tree of multiple binary variables.

In the analysis and presentation of diagnostic relationships by means of conventional multiple logistic regression, the following limitations occur: 1) the model starts not from the prior disease odds but from the posterior disease odds for all test variables having a zero value; 2) apart from the odds ratio, other test characteristics cannot be read from the model; 3) the sequence of entering of terms is guided by pure statistical criteria and not primarily by the criterion gain in certainty; 4) interactions are not very comprehensibly represented and are difficult to interpret. A method dealing with these limitations with respect to the analysis of data on the relationships between binary tests and disease outcome is described. Essential is the transformation of any test variable x to (x - x0), where x0 is that specific (virtual) value of x so that: posterior disease odds = prior disease odds, and consequently LRx0 = 1. Moreover, a simple branching structure is introduced while the terms are entered in order of decreasing gain in certainty. Examples are given for one-, two-, and three-test situations with and without dependency and interaction of tests, and general formulas are presented. For situations with the same prior probability, and the same overall discrimination of the separate test variables, all equations clearly have a common basis. Inclusion of new variables does not affect coefficients previously included in the model, and terms without a significant contribution can be skipped without affecting other coefficients. Standard errors and confidence intervals of test characteristics can be computed using the BMDP LR program. Further study needs to be done on the inclusion of continuous variables and cost-benefit aspects, and comparison with the performance of the CART program.     

基于logistic回归和随机森林的急性缺血性卒中3个月预后预测模型的构建

目的 基于logistic回归和随机森林构建急性缺血性卒中（acute ischemic stroke,AIS）3个月预后预测模型,并比较预测效果。方法 使用中国国家卒中登记Ⅱ（China National Stoke Registry Ⅱ,CNSRⅡ）数据库中的AIS数据,备选预测因子包括人口学特征、既往病史、用药史、临床检测指标、入院情况、院内情况、出院情况等不同时间点的变量。将数据按照8∶2随机分为训练集和测试集,在训练集中分别使用logistic回归和随机森林构建AIS患者3个月预后预测模型,在测试集中使用受试者工作特征曲线下面积（area under curve, AUC）评价区分度,使用Homser - Lemeshow检验和校准图来评价校准度。结果 最终纳入数据分析共9 847例AIS患者,其中61～80岁6 093例,男性6 477例,预后不良1 515例。在测试集中,logistic回归与随机森林的AUC差异无统计学意义（0.821,95%CI:0.815～0.827vs 0.825,95%CI:0.821～0.829,P = 0.268）,且两类模型的校准度均较好（χ2 = 5.67,P = 0.684 vs χ2 = 8.52,P = 0.385）。结论 基于logistic回归和随机森林建立的AIS患者3个月预后预测模型的区分度和校准度均较好。     

基于决策树法和Logistic回归预测神经外科老年住院患者医院感染风险的研究

目的应用决策树卡方自动交互检测(CHAID)算法和二分类Logistic回归分析法分别构建神经外科老年住院患者医院感染风险预测模型,并对模型的预测结果做对比分析。方法回顾性分析2018年1月-2019年6月海南省人民医院神经外科≥60岁老年住院患者,应用CHAID算法和Logistic回归分析法分别建立风险预测模型,通过受试者工作特征曲线(ROC)的曲线下面积(AUC)对两种模型的预测效果进行对比评价。结果共收集患者1 111人,其中医院感染131人,感染发病率11.79%;CHAID法和Logistic回归分析法均显示住院天数≥31 d、使用呼吸机、泌尿道插管是医院感染发生的重要影响因素;决策树模型风险预测的正确率为88.2%,模型拟合效果较好,Logistic回归模型Hosmer-Lemeshow拟合优度检验显示模型拟合较好(χ~2=9.690,P>0.05);决策树模型AUC为0.881(95%CI:0.861～0.899),Logistic回归模型AUC为0.880(95%CI:0.860～0.899),两模型预测价值均为中等,其存在的差异无统计学意义(Z=0.188,P>0.05)。结论将两模型相结合可以从不同层面发现医院感染的影响因素,能更充分地了解各因素间的相互关系。医院感染风险模型的建立可以为加强院感防控措施提供参考依据,更有效地指导医院感染防控工作。