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排序方式: 共有240条查询结果,搜索用时 15 毫秒
31.
To investigate the occurrences of polychlorinated biphenyls (PCBs) in suburban vegetable soils of Changchun area, Northeast China, 106 urban vegetable soil samples were collected from Changchun City, Nongan County, Dehui City, Yushu City, Jiutai City, Shuangyang District. We analyzed the concentrations, compositions and sources of 7 PCBs in top soils of Changchun area, and evaluated the non-carcinogenic and carcinogenic risk of PCBs pollution to exposed population. The total concentrations of 7 PCBs ranged from 1.31 to 148 ng/g dry weight (dw) with a mean value of 42.0 ng/g and dominated by Hepta-CBs and Penta-CBs. Principal component analysis (PCA) revealed that PCB pollution in soils of Changchun area mainly related to transportation, vehicle emissions, paints and other industries. Human health risk assessment showed that the cumulative non-carcinogenic and the cumulative carcinogenic risk in children and adults in the industrial land and residential land were acceptable, considering only 7 PCBs homologues were analyzed in this study, the actual risk could be higher. 相似文献
32.
John A. Craft Fiona E. Robertson Mary E. McPhail Elaine Brown Ronald M. Stagg 《Comparative biochemistry and physiology. Toxicology & pharmacology : CBP》2001,129(2):115-127
Induction of cytochrome P4501A (CYP1A) in fish is an important biomarker in marine monitoring programmes but a number of factors complicate interpretation of data based on catalytic activity. To provide additional analytical tools, we have cloned and sequenced entire (dab) and partial cDNAs (flounder, turbot, sand eel) from several fish species. A detailed analysis comparing the new sequences to those on the database (13 sequences) is presented and identifies an invariant, teleost-specific sequence (195-IVVSVANVICGMCFGRRYDH-214) which might be the basis for production of a species cross-reactive antibody. Northern and slot blots of fish RNA (sand eel, plaice, turbot, flounder and dab) showed extensive cross-species hybridisation with each of the cDNAs (sand eel, plaice, turbot, flounder and dab). The exception was turbot RNA, which only gave adequate hybridisation when the turbot probe was used. Attempts to normalise the hybridisation data to GAPDH mRNA were not satisfactory since there were significant species differences in expression of this gene and expression was suppressed (20–40%) by β-naphthoflavone treatment. The CYP1A probes indicated induction levels relative to untreated dab of: plaice (five-fold); turbot (12-fold); flounder (12-fold); and dab (10-fold). The study demonstrates the relative ease with which species-specific molecular probes can be generated and used. 相似文献
33.
Ashraf A Khan Rong-Fu Wang Mohamed S Nawaz Carl E Cerniglia 《FEMS microbiology letters》1997,154(2):317-324
The nucleotide sequence of the bphB gene of Pseudomonas putida strain OU83 was determined. The bphB gene, which encodes cis-biphenyl dihydrodiol dehydrogenase (BDDH), was composed of 834 base pairs with an ATG initiation codon and a TGA termination codon. It can encode a polypeptide of 28.91 kDa, containing 277 amino acids. Promoter-like and ribosome-binding sequences were identified upstream of the bphB gene. The bphB nucleotide sequence was used to produce His-tagged BDDH, in Escherichia coli. The His-tagged BDDH construction, carrying a single 6×His tail on the N-terminal portion, was active. The molecular mass of the native enzyme was 128 kDa and on SDS-PAGE analysis the molecular mass was 31 kDa. This enzyme requires NAD+ for its activity and its optimum pH is 8.5. Nucleotide and the deduced amino acid sequence analyses revealed a high degree of homology between the bphB gene from Pseudomonas putida OU83 and the bphB genes from P. cepacia LB400 and P. pseudoalcaligenes KF707. 相似文献
34.
Qiao JX Cheney DL Alexander RS Smallwood AM King SR He K Rendina AR Luettgen JM Knabb RM Wexler RR Lam PY 《Bioorganic & medicinal chemistry letters》2008,18(14):4118-4123
Ortho-substituted biphenyl moieties are widely used in drug design. We herein report a successful use of the perpendicular conformation of the alpha-substituted phenylcyclopropyl groups to mimic the aplanar, biologically active conformation of the ortho-substituted biphenyl moieties to achieve structural diversity. This is exemplified by the design and synthesis of a series of highly potent pyrazole bicyclic-based Factor Xa (FXa) inhibitors bearing alpha-substituted phenylcyclopropyl P4 moieties. The designed perpendicular conformation was confirmed by the X-ray structure of FXa-bound compound 2r. The potential structural basis for the high FXa potency in the phenylcyclopropyl P4 analogs and their improved FXa inhibitory activities compared with the biphenyl P4 counterparts are discussed. 相似文献
35.
Accumulation and effects of polychlorinated biphenyls (PCBs) in avian species were evaluated at a Superfund site located at Crab Orchard National Wildlife Refuge, Illinois, and seven criteria were used to assess whether there was a causal relationship between PCB exposure and observed reproductive effects. European starlings (Sturnus vulgaris) were monitored at nest boxes constructed at each of two exposed and two reference sites. During the breeding season, starling productivity (number of chicks produced per nest) and adult nest attentiveness behavior (provisioning behavior) were monitored. At 15 days post-hatch, chicks were collected for contaminant and biomarker analyses. Chicks were necropsied, ethoxyresorufin-O-deethylase (EROD) activity measured in liver tissue, and PCB (Aroclor 1254) and 34 chlorinated biphenyl (CB) congener concentrations measured in carcasses using gas chromatography. PCB and CB concentrations also were measured in eggs that failed to hatch. Mean Aroclor 1254 and quantified CB concentrations were greater (P<0.001) in eggs that failed to hatch and 15-day-old chicks collected from PCB sites compared to those collected from reference sites. EROD activity was greater (P=0.005) in 15-day-old chicks collected from PCB sites and was correlated with carcass PCB concentrations. Reduced adult nest attentiveness behavior and decreased chick survival were observed at PCB sites. Six of the seven causal criteria evaluated provided evidence that observed reproductive effects resulted from exposure to PCBs. Using this weight-of-evidence approach provided a means for establishing the likely cause of effects and thus provided managers with information needed in decision-making processes. 相似文献
36.
Hellmuth Lilienthal Leo van der Ven Alfons Hack Astrid Roth-Härer Aldert Piersma Joseph Vos 《人类与生态风险评估》2009,15(1):76-86
The widespread use of brominated flame retardants (BFRs) has led to increasing concentrations in environmental samples. Previous reports suggested endocrine activity of these compounds. Because thyroid hormones and sex steroids are known to regulate the development of the nervous system, we examined neurobehavioral and endocrine effects of gestational exposure to 2,2′4,4′,5-pentabrominated diphenyl ether (PBDE99) and lifetime exposure to tetrabromobisphenol A (TBBPA) or hexabromocyclododecane (HBCD) in rats. Treatment with PBDE99 (0, 1, or 10 mg/kg bw) reduced serum testosterone and estradiol in male offspring and affected sexual development in both sexes. Exposed males exhibited increased sweet preference, indicating feminization of this sexually dimorphic behavior. In TBBPA and HBCD experiments, a benchmark design was used with dose ranges of 0-3000 mg/kg bw/day and 0–100 mg/kg bw/day, respectively. Because thyroid hormones are critical for auditory development, brainstem auditory evoked potentials (BAEPs) were recorded in young adult offspring. TBBPA exposure elevated BAEP thresholds in females and prolonged latencies in both sexes. Benchmark doses were comparable for auditory effects and decreased plasma T4. HBCD increased BAEP thresholds and delayed BAEP waves only in males, but the relation to thyroid hormones remains to be determined. HBCD also reduced latencies in haloperidol-induced catalepsy, suggesting effects on the dopaminergic system. 相似文献
37.
Irina F. Sevrioukova 《Journal of molecular biology》2009,390(5):924-11096
Apoptosis-inducing factor (AIF) is a bifunctional mitochondrial flavoprotein critical for energy metabolism and induction of caspase-independent apoptosis, whose exact role in normal mitochondria remains unknown. Upon reduction with NADH, AIF undergoes dimerization and forms tight, long-lived FADH2-NAD charge-transfer complexes (CTC) that are proposed to be functionally important. To obtain a deeper insight into structure/function relations and redox mechanism of this vitally important protein, we determined the X-ray structures of oxidized and NADH-reduced forms of naturally folded recombinant murine AIF. Our structures reveal that CTC with the pyridine nucleotide is stabilized by (i) π-stacking interactions between coplanar nicotinamide, isoalloxazine, and Phe309 rings; (ii) rearrangement of multiple aromatic residues in the C-terminal domain, likely serving as an electron delocalization site; and (iii) an extensive hydrogen-bonding network involving His453, a key residue that undergoes a conformational switch to directly interact with and optimally orient the nicotinamide for charge transfer. Via the His453-containing peptide, redox changes in the active site are transmitted to the surface, promoting AIF dimerization and restricting access to a primary nuclear localization signal through which the apoptogenic form is transported to the nucleus. Structural findings agree with biochemical data and support the hypothesis that both normal and apoptogenic functions of AIF are controlled by NADH. 相似文献
38.
Ying Teng Xianghui Sun Lingjia Zhu Peter Christie Yongming Luo 《International journal of phytoremediation》2017,19(8):732-738
The accumulation, chemical speciation and distribution of polychlorinated biphenyls (PCBs) were investigated in various parts of alfalfa. Moreover, the adsorption characteristics for PCB 28 by alfalfa and the influencing factors of the adsorption characteristics were studied. There were different degrees of PCB accumulation in alfalfa roots, root nodules and shoots. The decreasing order of the accumulation of PCBs in plant tissues was root nodules > roots > shoots, and the decreasing order of the total PCB contents was roots > shoots > root nodules, indicating that the roots were the main sink for PCB accumulation. There were three modes of PCB speciation in alfalfa roots and root nodules, comprising strong sorption (78%) and weak sorption (19%) on tissue surfaces and absorption within tissues (2%). The adsorption isotherms of PCB 28 indicate that the adsorption capacities of root nodules and shoots were both significantly higher than that of the roots. Both lipids and carbohydrates, and especially lipids, affected the PCB adsorption capacities of the tissues. These results may help in the elucidation of the mechanisms of sorption and accumulation of PCBs in the plants and their main influencing factors and thus contribute to the development of phytoremediation technologies for PCB-contaminated soils. 相似文献
39.
Reddy NR Krishnamurthy S Chourasia TK Kumar A Joy KP 《Neurochemistry international》2011,59(5):582-590
Because estrogen plays important neurotrophic and neuroprotective roles in the brain by activating estrogen receptors (ERs), disruption of normal estrogen signaling can leave neurons vulnerable to a variety of insults, including β-amyloid peptide (Aβ). Aroclor1254 (A1254) belongs to the endocrine-disrupting chemical (EDC) polychlorinated biphenyls and has anti-estrogenic properties. In the present study, we evaluated the effect of A1254 on the protective activity of estrogen against Aβ toxicity in differentiated cholinergic SN56 cells. Aged Aβ25-35 causes apoptotic cell death in differentiated SN56 cells, and the cytotoxic evidences are effectively rescued by estrogen. We found that A1254 abolishes the neuroprotective activity of estrogen against Aβ toxicity, and attenuates the suppressive effect of estrogen on Aβ-induced tau phosphorylation and JNK activation. The effects of A1254 on the neuroprotective effects of estrogen in Aβ toxicity are very similar to the effects of the estrogen receptor antagonist ICI182,780. Thus, exposure to EDCs that have anti-estrogenic activity might interfere with normal estrogen-activated neuroprotective signaling events and leave neurons more vulnerable to dangerous stimuli. Our present results provide new understanding of the mechanisms contributing to the harmful effects of EDCs on the function and viability of neurons, and the possible relevance of EDCs in the pathogenesis of neurodegenerative diseases such as Alzheimer’s disease. 相似文献
40.
Kumar P Mohammadi M Viger JF Barriault D Gomez-Gil L Eltis LD Bolin JT Sylvestre M 《Journal of molecular biology》2011,405(2):531-44
The biphenyl dioxygenase of Burkholderia xenovorans LB400 is a multicomponent Rieske-type oxygenase that catalyzes the dihydroxylation of biphenyl and many polychlorinated biphenyls (PCBs). The structural bases for the substrate specificity of the enzyme's oxygenase component (BphAELB400) are largely unknown. BphAEp4, a variant previously obtained through directed evolution, transforms several chlorobiphenyls, including 2,6-dichlorobiphenyl, more efficiently than BphAELB400, yet differs from the parent oxygenase at only two positions: T335A/F336M. Here, we compare the structures of BphAELB400 and BphAEp4 and examine the biochemical properties of two BphAELB400 variants with single substitutions, T335A or F336M. Our data show that residue 336 contacts the biphenyl and influences the regiospecificity of the reaction, but does not enhance the enzyme's reactivity toward 2,6-dichlorobiphenyl. By contrast, residue 335 does not contact biphenyl but contributes significantly to expansion of the enzyme's substrate range. Crystal structures indicate that Thr335 imposes constraints through hydrogen bonds and nonbonded contacts to the segment from Val320 to Gln322. These contacts are lost when Thr is replaced by Ala, relieving intramolecular constraints and allowing for significant movement of this segment during binding of 2,6-dichlorobiphenyl, which increases the space available to accommodate the doubly ortho-chlorinated congener 2,6-dichlorobiphenyl. This study provides important insight about how Rieske-type oxygenases can expand substrate range through mutations that increase the plasticity and/or mobility of protein segments lining the catalytic cavity. 相似文献