Urinary and serum metabolites of di-n-pentyl phthalate in rats

Di-n-pentyl phthalate (DPP) is used mainly as a plasticizer in nitrocellulose. At high doses, DPP acts as a potent testicular toxicant in rats. We administered a single oral dose of 500 mg kg⁻¹ bw of DPP to adult female Sprague-Dawley rats (N = 9) and collected 24-h urine samples 1 d before and 24- and 48-h after DPP was administered to tentatively identify DPP metabolites that could be used as exposure biomarkers. At necropsy, 48 h after dosing, we also collected serum. The metabolites were extracted from urine or serum, resolved with high performance liquid chromatography, and detected by mass spectrometry. Two DPP metabolites, phthalic acid (PA) and mono(3-carboxypropyl) phthalate (MCPP), were identified by using authentic standards, whereas mono-n-pentyl phthalate (MPP), mono(4-oxopentyl) phthalate (MOPP), mono(4-hydroxypentyl) phthalate (MHPP), mono(4-carboxybutyl) phthalate (MCBP), mono(2-carboxyethyl) phthalate (MCEP), and mono-n-pentenyl phthalate (MPeP) were identified based on their full scan mass spectrometric fragmentation pattern. The ω − 1 oxidation product, MHPP, was the predominant urinary metabolite of DPP. The median urinary concentrations (μg mL⁻¹) of the metabolites in the first 24 h urine collection after DPP administration were 993 (MHPP), 168 (MCBP), 0.2 (MCEP), 222 (MPP), 47 (MOPP), 26 (PA), 16 (MPeP), and 9 (MCPP); the concentrations of metabolites in the second 24 h urine collection after DPP administration were significantly lower than in the first collection. We identified some urinary metabolic products in the serum, but at much lower levels than in urine. Because of the similarities in metabolism of phthalates between rats and humans, based on our results and the fact that MHPP can only be formed from the metabolism of DPP, MHPP would be the most adequate DPP exposure biomarker for human exposure assessment. Nonetheless, based on the urinary levels of MHPP, our preliminary data suggest that human exposure to DPP in the United States is rather limited.     

Metabolic responses of weeping willows to selenate and selenite

Goal, Scope and Background Selenium (Se) is one of the most widely distributed elements of the earth’s crust at low concentrations. The extensive use of Se-containing chemicals due to anthropogenic activities has increased the ecological risk to environmental compartments. Plants, under unfavorable environmental conditions, often increase the formation of reactive oxygen species (ROS), and consequently plant antioxidant enzymatic systems have been proposed to be important in plant stress tolerance. The goal of this study was to find out the metabolic responses of plants to Se, to provide quantitative information whether exogenous Se has a beneficial role in plants, and to investigate the potential of vegetation management of Se for potential phytoremediation. Material and Methods Pre-rooted plants of weeping willows (Salix babylonica L.) were grown hydroponically in growth chambers and treated with Na₂SeO₄ or Na₂SeO₃ at 24.0 ± 1°C for 168 h. Five different treatment concentrations were used, ranging from 0.44 to 8.72 mg Se/L for the treatments exposed to SeO₄²⁻ and from 0.50 to 10.0 mg Se/L for the treatments exposed to SeO₃²⁻, respectively. Transpiration rates, soluble protein contents and antioxidative enzyme activities of the plants were monitored to evaluate toxicity from exogenous Se exposure. At the end of the study, total Se in the hydroponic solution was analyzed by hydride generation-atomic fluorescence spectrometry (HG-AFS). Results Both chemical forms of Se at low concentrations showed growth-promoting effects on plants. A significant decrease of transpiration rates and of soluble protein contents of plants was observed at higher Se concentrations after 168 h of exposure. Measurable change of superoxide dismutases (SOD) activity in leaves was only detected under high Se treatments. Catalase (CAT) activity was significantly affected by the Se application. Slight change of peroxidase (POD) activity was measured in all treatments, whereas significant inhibition of POD activity was detected for the plants exposed to SeO₃²⁻ of 10.0 mg Se/L. Se-induced stress appeared in all treatments, thus resulting in measurable increase of glutathione peroxidase (GSH-Px) activity of the plants. Although both chemical forms of Se were taken up by weeping willows efficiently, their uptake rates were different. Discussion Of all measured parameters, POD and CAT activities in leaves were noted the most sensitive indicator for the plants exposed to SeO₄²⁻ and SeO₃²⁻, respectively. Deleterious effects on plant physiological functions due to Se application were not observed over 168 h of exposure. This is largely due to the fact that well-established antioxidant enzymatic systems in plants and higher activities of GSH-Px largely reduced the negative effects on plants; SeO₃²⁻ caused much more severe stress to plants than SeO₄²⁻ at higher Se application rates. The uptake mechanisms between the two chemical species were quite different. Conclusions Neither visible toxic symptoms nor metabolic lesions were observed at low concentrations of Se, probably due to the effective established enzymatic systems in weeping willows. All selected parameters for toxicity determination were significantly correlated to Se application, but metabolic responses of plants to SeO₄²⁻ and SeO₃²⁻ were quite different. GSH-Px in leaves was probably the principle enzyme responsible for stress reduction from Se exposure. Due to their different chemical properties, weeping willows showed a faster uptake rate for SeO₄²⁻ than for SeO₃²⁻. Recommendations Exogenous Se has a beneficial role in plants and vegetation management of Se is a potential remediation strategy in cleaning up Se-contaminated sites. Further investigation on the biochemical mechanism of Se metabolism will provide insight to the specific interactions between Se and plants on the molecular level. Perspectives Weeping willow has a sound potential for phytoremediation of Se-contaminated sediment and groundwater because the tree is not only tolerant to Se but also uptakes chemical species from the environment.     

Perspectives on quantifying and influencing household metabolism

Household metabolism is a concept that is concerned with the analysis of stocks and flows of energy, matter, and information at the household scale. This paper starts by providing a brief overview of the concept of household metabolism. Rather than attempting an in-depth review and analysis of this field, the article subsequently maps the contributions and perspectives of a broad variety of research traditions that have an interface with the concept of household metabolism. Next, this paper highlights a number of controversial issues connected to household metabolism, and studies at the interface of household metabolism. Finally, this paper argues that the concept of household metabolism can provide valuable help in diagnosing misalignments between enacted system dynamics and expressed societal goals, and can help to design research that facilitates their alignment.     

能量代谢动力学模型对污水处理参数优化

从本质上说,微生物的降解的过程就是微生物能量代谢的过程,从能量守恒原理出发,通过简化,导出了能量代谢动力学模型,从而从微观领域建立了能量参数与系统参数之间的联系,同时通过模型实验求解出其中的参数,找出微生物比增殖速率和基于ATP的能量比利用速率之间的关系,进而可以根据实际进水水质对系统参数进行计算,优化处理过程,用以确定和校正一些凭经验设计的关键参数。因此,能量代谢方程在理论上和实践上都具有重要的意义。     

Rethinking urban political ecology from the outside in: greenbelts and boundaries in the post-suburban city

This paper engages the existing literature on Urban Political Ecology (UPE) from the perspective of regulating urban expansion through greenbelts. The paper makes a contribution to a better understanding of suburbanisation and postsuburbanisation which have so far not been at the centre of the concerns of UPE. In an era of global suburbanisation greenbelts differ from similar boundary setting exercises in the past and are as varied as the suburbanisation processes and their governance themselves. While conscious of those varieties, we focus here on the Greater Golden Horseshoe (GGH) greenbelt in Ontario that was created by provincial legislation in 2005. With the 2005 legislation, the Ontario government declared 720,000 hectares off limits for conventional urban development. The Greenbelt Act created an expansive area under protection from the Niagara Peninsula in the south to the Bruce Peninsula in the north, the Niagara Escarpment in the west to a series of moraines in the east. We will argue that the GGH greenbelt has become a prime negotiation space for the overall re-regulation of urban political ecologies in Southern Ontario. Largely surrounding the booming Toronto region, the GGH greenbelt is expansion space and projection screen of a suburbanizing region in search of redefinition.     

Metabolism of the14C-labeled herbicide clodinafop-propargyl in plant cell cultures of wheat and tobacco

The metabolism of ¹⁴C-clodinafop-propargyl (CfP) was examined in cell cultures of wheat (Triticum aestivum L. cv. ‘Heines Koga II’) and tobacco (Nicotiana tabacum L.). Besides the non-transgenic tobacco culture, cultures transformed separately with cDNA of human cytochrome P450-monooxygenases (P450s) CYP1A1, CYP1A2, CYP3A4, CYP2B6 and CYP2C19 were examined. Experiments with wheat were executed in the presence and absence of safener cloquintocet-mexyl (CqM). After 48 h of incubation, only about 10% of applied ¹⁴C was found in media (both tobacco and wheat). Non-extractable residues of ¹⁴C-CfP in wheat cells were 16.54% (without CqM) and 30.87% (with CqM). In all tobacco cultures, 82.41–92.46% of applied radioactivity was recovered in cell extracts. In contrast to wheat, non-extractable residues amounted only to 1.50–2.82%. As determined by radio-thin layer chromatography (TLC) and -high-performance liquid chromatography (HPLC), the parent CfP was not found in the cell extracts of wheat; in tobacco cell extracts, only traces of CfP were detected. After a hydrolysis of assumed carbohydrate conjugates of CfP derived polar ¹⁴C-labeled compounds, TLC and HPLC analysis showed that in wheat, a more complex pattern of metabolites of CfP were observed as compared to all tobacco cultures. In hydrolysates resulting from wheat, the identity of three primary products was confirmed by means of GC-EI-MS: free acid clodinafop (Cf), hydroxy-Cf hydroxylated at the pyridinyl moiety, and 4-(5-chloro-3-fluoropyridin-2-yloxy)phenol. In hydrolysates derived from all tobacco cultures, main metabolite was Cf besides only traces of further unidentified products. Differences among the different tobacco cultures (non-transgenic, transgenic) did not emerge. According to kinetics of disappearance of primary metabolite Cf as well as formation of polar soluble products and non-extractable residues, metabolization of CfP proceeded at a noticeably higher rate in wheat cells treated with safener CqM than in cells without CqM treatment. Thus, these results indicated a stimulation of CfP's metabolism by CqM, although metabolic profiles observed in CqM treated and non-treated cells (after hydrolysis) were qualitatively similar. The findings obtained from all tobacco cultures suggested that with the exception of ester cleavage to Cf, CfP cannot be metabolized by tobacco itself or by the human P450s examined.     

Applications of isotope differentiation for metabolic studies with di‐(2‐ethylhexyl) phthalate

Abstract

The pervasiveness of the plasticizer di‐(2‐ethylhexyl) phthalate (DEHP) in the environment and especially in the laboratory results in a background that may cause severe interference with analytical studies. Animal‐to‐animal variability in the distribution of DEHP metabolites in excreta normally makes it necessary to use large groups of animals when different treatments are compared. Finally, radioactive tracers are usually considered undesirable for metabolic studies involving human subjects. All of these problems can be overcome through the use of muliple isotopic labels, especially ¹²C/¹³C/¹⁴C. Examples are given involving rats and monkeys, and applicability to humans is discussed. The principles involved are not limited to any particular class of test compounds. In rats, the competing pathways for metabolism of phthalate esters produce a different distribution of metabolites from a small intravenous dose of DEHP than from a large oral dose.     

Fate and residues of 14C‐chloramphenicol in laying chickens 1

Abstract

Studies were conducted to determine the metabolic fate of chloramphenicol (CAP) in White Leghorn using the ^l4C‐labelled compound. In one experiment birds were administered orally via intra‐crop, a single dose of 100 mg (equivalent to 66 mg kg^‐1 body weight) of CAP containing 14 μCi ¹⁴C‐CAP, and its absorption, elimination and distribution in plasma were recorded. Orally dosed ¹⁴C‐compound was rapidly absorbed, efficiently distributed in plasma and eliminated in excreta (>70% in 5 hr). After 5 h, CAP equivalent residues in tissues were lower than 15 μg g^‐1 for this treatment. In a second experiment birds were given intra‐crop dose of either 0.5 or 5 mg of CAP (each dose contained 2.5 μCi ¹⁴C‐CAP) daily for five consecutive days followed by a seven day withdrawal period and elimination of ¹⁴C in excreta and eggs was monitored. More than 95% of the administered ¹⁴C was eliminated within the first 24 h after dosing. Radiocarbon (¹⁴C) was deposited preferentially in yolks compared to albumen or other tissues. Residues declined when feeding was stopped. Various metabolites were isolated and identified by a combination of TLC, LC, and LC‐MS. The main metabolic route of CAP in laying hens appears to be the glucuronidation. Cleavage of the dichloroacetate moiety was only a minor route.     

Research Articles

The metabolism of phenanthrene was studied both in cell suspension cultures of wheat (Triticum aestivum) and soybean (Glycine max), and in intact plants of the water mossFontinalis antipyretica. Metabolism in cell suspension cultures strongly differed between the monocotyle and the dicotyle plant. Only small amounts oftrans-phenanthrene-9,10-dihydrodiole and phenanthrene-9,10-dione were detectable in the wheat culture. Soybean cultures, in contrast demonstrated a strong turnover resulting in a 75% reduction of the initial phenanthrene concentration. Metabolites were phenanthrene-9,10-dione, not further characterized polar metabolites and bound residues. Intact plants ofFontinalis antipyretica metabolized only small amounts of phenanthrene. Data obtained from cell cultures did not provide information for the metabolic potential in intact plants. Therefore standardized tests with model systems like suspension cultures lead to inadequate assessment of the ecological risk of certain xenobiotics.     

北京市地下水中高危害污染物筛选

地下水污染物对用水安全和人民健康造成了巨大的威胁.为开展地下水中高危害污染物筛选,改进了传统的危害评价方法,构建了涵盖毒理学优先指数法（Tox Pi）,吸收、分布、代谢、排泄（ADME）性质评估法和二模网络分析法的污染物危害评估-筛选-表征综合体系,针对北京市地下水中非靶检测到的234种疏水性有机污染物（HOCs）开展危害评估和毒害污染物筛选.利用Tox Pi方法筛选出危害潜力排名前20的污染物,在此基础上耦合其ADME性质进一步识别出17种高优先级HOCs,并通过二模网络分析,系统表征了这17种高优先级HOCs作用的基因分子靶点,通过关联性和加权平均度分析最终得到10种高危害的HOCs,并揭示其毒作用类型多集中于内分泌干扰效应、致癌效应以及遗传毒性.研究结果可为我国区域地下水污染物的防治提供技术支撑.