猪肝微粒体体外代谢2,2’,4,4’-四溴联苯醚

多溴联苯醚(PBDEs)是一类在环境中普遍存在的持久性有机污染物,研究PBDEs的体外代谢行为对理解其在体内的富集和转化具有重要意义。文章以猪肝微粒体作为研究对象,以体外代谢形式研究其对2,2’,4,4’-四溴联苯醚(BDE-47)的代谢能力,优化了代谢条件,并研究了0.01、0.05、0.1、0.5、1、5、10 mg/L的BDE-47对细胞色素P450酶系中7-乙氧基香豆素-O-脱乙基酶(ECOD)、7-乙氧基异吩唑酮-O-脱乙基酶(EROD)和苯胺4-羟基化酶(ANH)活性的影响。结果表明,孵育0.1 mg/L的BDE-47时,猪肝微粒体对BDE-47的代谢率可达到28.6%。实验所设各浓度BDE-47均能够保护微粒体的ECOD活性,但较高浓度的BDE-47(0.5、1、5 mg/L)对微粒体的EROD活性有显著抑制作用,而各浓度BDE-47对ANH活性没有显著影响。     

Research needs identified at the second PCB workshop in Brno,Czech Republic,May 7–11, 2002

More than 150 scientists from the Americas, Europe, and Asia met in Brno, Czech Republic, in May 2002 at the Second PCB Workshop, entitled “Recent Advances in the Environmental Toxicology and Health Effects of PCBs”. NIEHS/EPA-Superfund Basic Research Program, the Graduate Center for Toxicology at the University of Kentucky, and the Research Centre for Atmospheric and Environmental Chemistry and Ecotoxicology of Masaryk University, Brno, sponsored the Workshop. At six separate sessions (including posters) the origins, human residues and exposures, actions, biomarkers, risk and remediation issues relating to PCBs were discussed.     

Studies on the origin of the methylsulfonyl‐containing metabolites from propachlor

Abstract

Metabolites in which the chlorine from propachlor has been replaced by a cysteine group or a methylsulfonyl group [‐S(O₂) CH₃] are present in the urine of rats dosed orally with propachlor. In the present study, urine from rats given single oral doses of ³⁵S‐labeled cysteine conjugate of propachlor contained metabolites having the methylsulfonyl groups labeled with S. No metabolites containing ¹⁴C‐labeled methylsulfonyl groups were isolated from urine of rats given single oral doses of the cysteine conjugate of propachlor in which the cysteine group was uniformly labeled with ¹⁴C. These findings show that the cysteine conjugate of propachlor is the source of sulfur in the methylsulfonyl‐containing metabolites. Therefore, we suggest that a C‐S lyase present in the animal cleaves the cysteine conjugate of propachlor and thus allows further metabolism of the sulfur to a methylsulfonyl moiety.     

6:2氟调羧酸在蚯蚓体内的毒理效应及代谢转化

以赤子爱胜蚓(Eisenia fetida)为受试生物,通过活体与离体实验,研究6:2氟调羧酸(6:2FTCA)在蚯蚓体内的毒理效应和代谢转化机制.结果表明,6:2FTCA对蚯蚓体内丙二醛(MDA)含量和过氧化物酶(POD)活性无显著影响,但能够使过氧化氢酶(CAT)活性提高,使超氧化物歧化酶(SOD)和谷胱甘肽转移酶(GST)活性显著升高,说明6:2FTCA对蚯蚓产生了氧化胁迫效应.6:2FTCA在蚯蚓细胞色素P450(CYP450)和GST酶提取液中的降解动力学均符合一级动力学模型,在CYP450(0.014/h)酶液中的降解速率明显高于GST (0.006/h),其终端全氟羧酸(PFCAs)代谢产物为全氟己酸(PFHxA)、全氟戊酸(PFPeA)和全氟丁酸(PFBA),说明CYP450和GST参与了6:2FTCA在蚯蚓体内的代谢转化,且CYP450贡献大于GST.蚯蚓肠道好氧微生物对6:2FTCA具有显著的降解效果,终端PFCAs降解产物为PFHxA和PFPeA,而肠道厌氧微生物对6:2FTCA无降解作用.     

地表UV-B辐射增强对土壤-冬小麦系统N2O排放的影响机理研究

为了解UV-B增强条件下农田N₂O响应规律,采用室外盆栽实验,研究了地表UV-B辐射增强20%对土壤-冬小麦系统N₂O排放的影响及其影响机理.结果表明,在小麦返青期,UV-B辐射增强处理对该系统N₂O的排放影响不显著;在小麦的拔节期,UV-B辐射增强处理显著降低了土壤-小麦系统N₂O的排放,并减少了该系统的呼吸速率.UV-B辐射增强对N₂O的影响机理主要表现在对小麦植株N代谢过程的影响,如显著增加     

Storage and metabolism of radioactively labeled pyrrolizidine alkaloids by butterflies and larvae of Mechanitis polymnia (Lepidoptera: Nymphalidae,Ithomiinae)

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     

Enantioselective effects of imazethapyr residues on Arabidopsis thaliana metabolic profile and phyllosphere microbial communities

Imazethapyr (IM) is a widely used acetolactate synthase-inhibiting chiral herbicide. It has long-term residuals that may be absorbed by the human body through the edible parts of plants, such as vegetable leaves or fruits. Here, we selected a model plant, Arabidopsis thaliana, to determine the effects of R-IM and S-IM on its leaf structure, photosynthetic efficiency, and metabolites, as well as the structures of microorganisms in the phyllosphere, after 7 days of exposure. Our results indicated enantiomeric differences in plant growth between R-IM and S-IM; 133 µg/kg R-IM showed heavier inhibition of photosynthetic efficiency and greater changes to subcellular structure than S-IM. R-IM and S-IM also had different effects on metabolism and leaf microorganisms. S-IM mainly increased lipid compounds and decreased amino acids, while R-IM increased sugar accumulation. The relative abundance of Moraxellaceae human pathogenic bacteria was increased by R-IM treatment, indicating that R-IM treatment may increase leaf surface pathogenic bacteria. Our research provides a new perspective for evaluating the harmfulness of pesticide residues in soil, phyllosphere microbiome changes via the regulation of plant metabolism, and induced pathogenic bacterial accumulation risks.     

侧流污泥返送到缺氧池对A2/O系统效能影响研究

为了探究侧流化学磷回收后生物污泥返送对主流系统的影响,连续85d对A²/O系统厌氧池混合液中的磷进行侧流化学回收,并将侧流生物污泥回流到缺氧池,考察了系统整体的磷、氮、有机物的去除,及生物除磷途径与污泥性能的变化.结果表明,刚开始系统除磷效果有所提高,出水PO₄^3-浓度为（0.07±0.04） mg/L;20d后污泥沉降性能开始变差,除磷性能恶化,但对氮和有机物去除一直无显著影响;厌氧释磷速率和好氧吸磷速率下降,但缺氧吸磷速率却增加,缺氧反硝化聚磷和好氧聚磷的除磷比例由43.20%上升为53.38%,反硝化聚磷除磷得到了加强;污泥微生物胞内PHA和糖原的代谢模式无变化,但厌氧段合成的PHA量逐步下降;侧流磷最大回收量占进水磷量的24.75%,能够实现可观的磷回收效果;系统发生崩溃后,停止侧流化学磷回收,系统各功能就会逐渐得到恢复,可实现系统连续运行.     

酚类及羟基化合物对BaP代谢影响的研究

经叔-丁基-羟基-苯甲醚(BHA)对照、HPLC分析结果表明,天然化合物如从甜瓜蒂(Cucumis melo L. cucurbitaceae)提取的葫芦素B、从徐长卿根(Pycnostelma paniculatum(Bge)K.Shum)提取的牡丹酚、人工合成的对乙氧基苯酚及维生素E中间体2,3,5-三甲基氢醌对BaP在大鼠肝微粒体体外代谢均有不同程度的抑制作用。当其浓度为25μM时,对BaP9,10-二醇及9-OHBaP的生成抑制较对BaP7,8-二醇及BaP4,5-二醇的更强。