Luminescent enzyme-linked receptor assay for estrogenic compounds

The analytics of endocrine-disrupting compounds has become a major issue during recent years. Several test systems have been developed for endocrine-disrupting chemicals. Yeast reporter gene assays and MCF-7 cell-based proliferation assays (E-screen) are particularly popular. A correlation of an enzyme-linked receptor assay (ELRA) with a yeast reporter gene assay is shown. In addition, the development of an ultra-sensitive luminescent ELRA with a detection limit of 20 ng/L for 17-estradiol in the sample is reported. Data for real sample analysis are shown in this paper. ELRA characteristics are compared with cell-based assays, and the issue of detection limits is addressed. In this context, the detection limits of the cell-based assays have been claimed to be below the ELRA detection limits. However, it is clarified that the given detection limits for the yeast estrogen screen and the E-screen are usually based on concentrations of 17-estradiol in the well, not in the sample, whereas ELRA detection limits are concentrations in the sample.     

Combined biological and chemical assessment of estrogenic activities in wastewater treatment plant effluents

Five wastewater treatment plant effluents were analyzed for known endocrine disrupters and estrogenicity. Estrogenicity was determined by using the yeast estrogen screen (YES) and by measuring the blood plasma vitellogenin (VTG) concentrations in exposed male rainbow trout (Oncorhynchus mykiss). While all wastewater treatment plant effluents contained measurable concentrations of estrogens and gave a positive response with the YES, only at two sites did the male fish have significantly increased VTG blood plasma concentrations after the exposure, compared to pre-exposure concentrations. Estrone (E1) concentrations ranged up to 51 ng L^–1, estradiol (E2) up to 6 ng L^–1, and ethinylestradiol (EE2) up to 2 ng L^–1 in the 90 samples analyzed. Alkylphenols, alkylphenolmonoethoxylates and alkylphenoldiethoxylates, even though found at µg L^–1 concentrations in effluents from wastewater treatment plants with a significant industrial content, did not contribute much to the overall estrogenicity of the samples taken due to their low relative potency. Expected estrogenicities were calculated from the chemical data for each sample by using the principle of concentration additivity and relative potencies of the various chemicals as determined with the yeast estrogen screen. Measured and calculated estradiol equivalents gave the same order of magnitude and correlated rather well (R ²=0.6).An erratum to this article can be found at     

需求中断下具零售商激励的双渠道供应链价格与生产决策

研究了由一个制造商和一个零售商所组成的两周期双渠道供应链.在第一周期需求实现之前,建立了生产量;在第二周期,基于第一周期的生产量和需求的实现确定了最优销售价格,进而确定了最优的生产量,实现了生产量的优化.通过需求中断下制造商和零售商的垂直整合,讨论了中断情形下价格和生产量对利润的影响.实证结果证实,集中式供应链的最优价格决策受零售渠道顾客偏好和市场规模变化的影响较为显著.     

Kinetic study of cell disruption by ionic polymers with varied charge density

The effect of charge density and hydrophobicity of the polymeric cations on cell disruption is studied thermodynamically and kinetically by using the budding yeast protoplast. It is found that cationic polymers drastically disrupt the cells above a certain concentration while nonionic and anionic ones do not. Reduced charge density of copolymers of cationic and nonionic monomers resulted in decreased cell disruption. However, it is further experimentally proved that the disruption of the cells occurs only when the polycation has a certain hydrophobicity. The stronger the hydrophobicity of the cationic polymer, the more cooperatively the cells are disrupted. Received: 29 May 2000 Accepted: 1 September 2000     

考虑疫情风险与双重时效性的生鲜品供应中断库存控制策略研究

为解决重大疫情引发的供应中断导致生鲜品库存水平振荡,在市场需求随机变化的情形下,建立一个由供应商、配送中心和零售商组成的三级生鲜供应链库存系统,考虑由疫情引起的三种风险情景,引入系统动力学模型对零售商动态库存系统运营进行仿真分析。研究发现：受疫情风险传导系数和变质率两个序参量影响,供应链库存呈现振荡趋势;通过确定不同供应中断时长下的疫情风险情景提出优化保鲜投入策略、安全库存策略、以及共享库存联合提前转运策略有效降低零售端库存水平振荡并使其呈现渐稳趋势,实现产品在交付过程中的双重时效性,达到供需匹配,缓解疫情风险带来的影响,为相关零售企业提供决策支持。     

Removal of endocrine‐disrupting compounds from water using macroporous molecularly imprinted cryogels in a moving‐bed reactor

Highly efficient removal of endocrine‐disrupting compounds (EDCs) such as 17β‐estradiol (E2), 4‐nonylphenol (NP) and atrazine from water was achieved using a novel macroporous adsorption medium. The medium consisted of a macroporous poly(vinyl alcohol) (PVA) cryogel with molecularly imprinted polymer (MIP) particles embedded in it. The MIP was prepared using E2, NP and atrazine as templates. The macroporous composite molecularly imprinted cryogels were formed inside the open‐ended protective shells, known as Kaldnes carriers. These adsorbents (defined as Macroporous Gel Particles, MGPs) were evaluated on the removal of E2, NP and atrazine from water using different column configurations, namely column filled with the MGPs (packed‐bed column) and in moving‐bed reactors (defined here as moving‐bed MGPs reactor). Complete binding (> 99%) of E2 from a spiked aqueous solution (1 mg/L) was achieved using E2‐MIP/MGPs in a moving‐bed MGPs reactor at the retention time in the reactor of 4 min, while only 77% was bound to the nonimprinted medium (NIP/MGPs). Similar results were also obtained for the adsorption medium imprinted with atrazine. All contaminants studied (E2, atrazine and NP) were effectively removed from water at low (environmentally relevant) concentrations by the respective adsorption medium.     

Analytical approach for monitoring endocrine-disrupting compounds in urban waste water treatment plants

The presence of endocrine-disrupting compounds in influent and effluent water samples from four waste water treatment plants located in Italy was studied. The estrogen-like activity of the water samples was measured using a chemiluminescent recombinant yeast assay which is based on genetically engineered yeast cells that express the human estrogen receptor. This receptor, once activated, elicits the expression of the reporter gene lac-Z and, consequently, the production of β-galactosidase, which is then measured by chemiluminescence. To control and minimize sample matrix effects, an external control based on a modified yeast strain stably expressing β-galactosidase was developed and also used in the assay. Rapid and sensitive chemiluminescent enzyme immunoassays were also developed and validated for the quantification of 17β-estradiol, estrone, and estriol in waste water samples. Results from both methods were compared with a reference high-performance liquid chromatography and electrospray ionization tandem mass spectrometry (HPLC ESI-MS-MS) method developed for the quantification of natural estrogens. The recombinant yeast assay revealed a significant estrogenic activity in the influent samples, ranging from 80 to 400 pmol/L 17β-estradiol equivalents (EEQ), which was reduced by 70–95 % in the effluent samples. The yeast assay also showed a systematic 20–30 % overestimation of estrogenic activity relative to the HPLC ESI-MS-MS method, suggesting the presence of other compounds in the samples with estrogenic activity. The chemiluminescent enzyme immunoassays showed the presence of estrogens in the influent samples (mean concentrations: 350–450 pmol/L for estrone, 5–100 pmol/L for 17β-estradiol, 25–300 pmol/L for estriol), with significantly lower concentrations detected in the respective effluent samples. The waste water treatment was able to reduce natural estrogen concentrations by 40–95 %, although a high variability was observed. The enzyme immunoassay data correlated well with data obtained by the HPLC ESI-MS-MS method. Although the recombinant yeast assay represents a useful tool for a first-level screening of estrogenic activity due to its simplicity and high analytical throughput, sample matrix effects observed in waste water of industrial origin were found to strongly affect the yeast cells response, even when properly corrected for using the external control, thereby limiting its use to urban waste water. Its integration with chemiluminescent enzyme immunoassays would improve its performance by reducing false negative results, thereby enabling its use in extensive studies monitoring for the presence of endocrine-disrupting compounds in urban treatment plant effluents.     

考虑应急设施中断风险与防御的可靠性选址模型研究

为提高应急设施运行的可靠性和抵御中断风险的能力, 研究中断情境下的应急设施选址-分配决策问题。扩展传统无容量限制的固定费用选址模型, 从抵御设施中断的视角和提高服务质量的视角建立选址布局网络的双目标优化模型, 以应急设施的建立成本和抵御设施中断的加固成本最小为目标, 以最大化覆盖服务质量水平为目标, 在加固预算有限及最大最小容量限制约束下, 构建中断情境下应急设施的可靠性选址决策优化模型。针对所构建模型的特性利用非支配排序多目标遗传算法(NSGA-Ⅱ)求解该模型, 得到多目标的Pareto前沿解集。以不同的算例分析和验证模型和算法的可行性。在获得Pareto前沿的同时对不同中断概率进行灵敏度分析, 给出Pareto最优解集的分布及应急设施选址布局网络的拓扑结构。     

Determination of octylphenol and nonylphenol in aqueous sample using simultaneous derivatization and dispersive liquid–liquid microextraction followed by gas chromatography–mass spectrometry

A simple and fast sample preparation method for the determination of nonylphenol (NP) and octylphenol (OP) in aqueous samples by simultaneous derivatization and dispersive liquid–liquid microextraction (DLLME) was investigated using gas chromatography–mass spectrometry (GC/MS). In this method, a combined dispersant/derivatization catalyst (methanol/pyridine mixture) was firstly added to an aqueous sample, following which a derivatization reagent/extraction solvent (methyl chloroformate/chloroform) was rapidly injected to combine in situ derivatization and extraction in a single step. After centrifuging, the sedimented phase containing the analytes was injected into the GC port by autosampler for analysis. Several parameters, such as extraction solvent, dispersant solvent, amount of derivatization reagent, derivatization and extraction time, pH, and ionic strength were optimized to obtain higher sensitivity for the detection of NP and OP. Under the optimized conditions, good linearity was observed in the range of 0.1–1000 μg L⁻¹ and 0.01–100 μg L⁻¹ with the limits of detection (LOD) of 0.03 μg L⁻¹ and 0.002 μg L⁻¹ for NP and OP, respectively. Water samples collected from the Pearl River were analyzed with the proposed method, the concentrations of NP and OP were found to be 2.40 ± 0.16 μg L⁻¹ and 0.037 ± 0.001 μg L⁻¹, respectively. The relative recoveries of the water samples spiked with different concentrations of NP and OP were in the range of 88.3–106.7%. Compared with SPME and SPE, the proposed method can be successfully applied to the rapid and convenient determination of NP and OP in aqueous samples.     

Microwave-assisted phase-transfer catalysis for the rapid one-pot methylation and gas chromatographic determination of phenolics

Microwave-assisted phase-transfer catalysis (PTC) is reported for the first time, for the one-step extraction–derivatization–preconcentration and gas chromatographic determination of twenty phenols and ten phenolic acids. The well established phase-transfer catalytic methylation is largely accelerated when heating is replaced with the “greener” microwave irradiation. The overall procedure was thoroughly optimized and the analytes were determined by GC/MS. The method presented adequate analytical characteristics being more sensitive in analyzing phenols than phenolic acids. The limits of detection without any additional preconcentration steps (e.g. solvent evaporation) were adequate and ranged from 0.4 to 15.8 ng/mL while limits of quantitation were between 1.2 and 33.3 ng/mL. The method was applied to the determination of phenols, in spiked environmental samples and phenolic acids in aqueous infusions of commercially available pharmaceutical dry plants. The recoveries of fortified composite lake water samples and Mentha spicata aqueous infusions ranged from 89.3% to 117.3% for phenols and 93.3% to 115.2% for phenolic acids.