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321.
322.
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. 相似文献
323.
Ann-Katrin Luks Christiaan Wijntjes Burkhard Schmidt 《Journal of environmental science and health. Part. B》2016,51(2):71-80
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. 相似文献
324.
Phillip W. Albro J. Ronald Hass Carl C. Peck Sandra T. Jordan Jean T. Corbett Joanna Schroeder 《Journal of environmental science and health. Part. B》2013,48(6):701-714
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. 相似文献
325.
M. Humayoun Akhtar Khaled Abo ElSooud Atef M. Shehata Anwar ‐ul‐Haq 《Journal of environmental science and health. Part. B》2013,48(5):1061-1084
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. 相似文献
326.
Christiane Schrenk Christian E. W. Steinberg 《Environmental science and pollution research international》1998,5(2):83-88
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. 相似文献
327.
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. 相似文献
328.
微塑料(MPs)作为新型污染物对水体的污染影响已成为研究热点.为探究淡水环境中MPs丰度与氮代谢功能之间的响应关系,以乌梁素海为研究对象,借助蔡司显微镜检测水体中MPs丰度,并利用宏基因测序分析水体中氮代谢功能菌群及功能基因的分布特征,使用相关性分析法对MPs丰度与氮代谢功能微生物和氮代谢功能基因之间的作用关系进行探讨分析.结果表明,淡水环境中MPs对优势菌门中蓝细菌门和厚壁菌门的影响更高,MPs的存在会促进其富集和生长;优势菌属中对分枝杆菌属的促进和对Candidatus_Planktophila的抑制更明显,进一步说明在淡水环境中MPs会通过影响微生物群落而影响氮正常代谢,并且碳氮固定和反硝化等途径是MPs影响氮代谢的重要途径.从氮代谢功能基因角度分析,发现MPs丰度对硝化(pmoA-amoA、pmoB-amoB、pmoC-amoC)、反硝化(nirK、napA)和异化硝酸盐还原(nrfA)过程中部分功能基因存在显著影响(P < 0.05),并且MPs丰度对氮代谢相同途径不同功能基因的影响存在差异性,因此MPs在水环境中的影响非常复杂,对水环境的危害不容忽视. 相似文献
329.
330.
Summary. Tracer feeding studies with radioactively labeled pyrrolizidine alkaloids (PAs) were performed to attain experimental information
about the specificity and mechanisms of uptake, metabolism and storage of PAs in the alkaloid sequestering ithomiine butterfly
Mechanitis polymnia. Adult butterflies easily ingest the tracers offered dissolved in a saturated sugar solution. Feeding of [14C]rinderine (free base) confirmed that M. polymnia is well adapted to sequester and maintain PAs of the lycopsamine type. Approximately 80% of the ingested radioactivity can
be recovered in methanol extracts of the butterflies over a period of at least 6 hours. Labeled rinderine is efficiently N-oxidized and transformed into a metabolite of still unknown structure. These two metabolites are formed in almost equal amounts
and account for more than 90% of total radioactivity. After four hours the toxic free base is only detectable in traces. Radioactively
labeled senecioylretronecine (free base), a PA that often accompanies PAs of the lycopsamine type in plants, is metabolized
in a different manner. The toxic free base disappeared as fast as the tertiary rinderine, but the final products which accumulated
in a stable ratio after 12 hours were mainly two polar metabolites of unknown structure; senecioylretronecine N-oxide accounts for less than 10% of total PAs. Labeled senecionine a macrocyclic PA, which never has been found in wild caught
M. polymnia is only slowly N-oxidized. In females ca 50% of the ingested senecionine is still present as free base after 24 hours, whereas under the same
conditions in males this percentage is only ca 20%. This difference in N-oxidation was the only significant sex-specific difference observed in various experiments. Larvae of M. polymnia which feed on Solanum tabacifolium, a plant that does not contain PAs, are able to sequester and partly N-oxidize labeled senecioylretronecine and senecionine. However, the storage is not very efficient; with the two tracers less
than 5% of radioactivity remained in the bodies after 24 hours.
Received 19 October 1999; accepted 24 November 1999 相似文献