Reactions of benzo]pa]pyrene diol-epoxides with DNA and nucleosomes in aqueous solutions

The rate of solvolysis of benzo[$\text{a}$]pyrene diol-epoxide in aqueous solutions can be followed by fluorescence spectroscopy. When DNA was present the rat of breakdown of benzo[$\text{a}$]pyrene diol-epoxide was substantially enhanced, while at the same time fluorescence intensity was decreased. This decrease, however, was due to noncovalently bound tetraols and does not seem to be a function of the covalent adducts formed. Nucleosomal core particles, reacted under identical conditions, showed very little quenching of the pyrene-like chromophore. When increasing amounts of cysteine were present the covalent binding could be prevented in both free DNA and nucleosomal DNA. Analysis of the distribution of the carcinogen to nucleosomal DNA showed that the covalently bound carcinogen was located at or within 10 bases of the 5′-OH region of the nucleosomal DNA.     

Effects of caffeine on sister-chromatid exchanges (SCE) in vivo.

Chinese hamsters were twice treated with caffeine via stomach tube. The single doses were either 20, 100, 200 or 400 mg per kg body weight. A dose-dependent increase was observed in the frequencies of SCE induced in vivo in bone-marrow cells. Two intraperitoneal injections of the chemical mutagens, cyclophosphamide or benzo[a]pyrene, led to a pronounced increase of the frequency of SCE. Simultaneous applications of the chemical mutagens and caffeine decreased the rate of SCE. The effect of caffeine per se to induce SCE, and the mechanisms by which caffeine reduces the level of SCE induced by chemical mutagens are discussed.     

A novel bioreactor for the biodegradation of inhibitory aromatic solvents: Experimental results and mathematical analysis

A novel bioreactor for the biodegradation of toxic aromatic solvents, such as benzene, toluene, and xylenes in liquid effluent stream, was developed. Silicon tubing was immersed in the completely mixed and aerated bioreactor, and liquid toluene as a model solvent was circulated within the tubing. Toluene diffused out of the tube wall and was transferred at high rate into the culture broth, where biodegradation occurred. The effect of operating parameters on the toluene transfer rate was investigated. During continuous operation, the biodegradation rate was considerably higher than those obtained using conventional methods. A mathematical model was established for continuous biodegradation, and simulation results coincided with the experimental results. The performance and operational criteria of the bioreactor were analyzed on the basis of both the experimental and simulation results. (c) 1992 John Wiley & Sons, Inc.     

Air pollution by carcinogenic PAHs and plasma levels of p53 and p21(WAF1) proteins

We analyzed the effect of exposure to carcinogenic polycyclic aromatic hydrocarbons (c-PAHs) in ambient air on the plasma levels of p53 and p21^WAF1 proteins among city policemen, bus drivers and controls in three European cities: Prague (Czech Republic), Kosice (Slovakia) and Sofia (Bulgaria). p53 and p21^WAF1 proteins are key regulators of the cell cycle and are accepted as universal markers of genotoxic stress and DNA damage. In total 204 exposed subjects (100 smokers, 104 nonsmokers) and 152 controls (54 smokers, 98 nonsmokers) were analyzed. Personal exposure to c-PAHs was evaluated using personal samplers during the working shift. The levels of p53 and p21^WAF1 proteins were assessed by ELISA assay. There were no differences between the levels of either protein between exposed and controls, or smokers and nonsmokers, in any city. However, we observed significant differences in p53 plasma levels in all subjects regardless of the exposure status between the individual cities (median values: 5, 31, 234 pg/ml, p < 0.001, for Prague, Kosice and Sofia, respectively). The levels correspond to the differences in exposure levels to c-PAHs and benzo[a]pyrene (B[a]P) in the individual cities. A multiple linear regression analysis confirmed that c-PAHs exposure is a variable significantly affecting levels of both proteins in all locations. When all subjects were divided into the group exposed to below-median levels of c-PAHs and the group exposed to above-median levels of c-PAHs we found significantly higher p53, as well as p21^WAF1 levels in the above-median exposure group (p53, 167 pg/ml versus 25 pg/ml, p < 0.001; p21^WAF1, 2690 pg/ml versus 2600 pg/ml, p < 0.05). Among all subjects p53 plasma levels were positively correlated with p21^WAF1 levels, exposure to B[a]P, c-PAHs and levels of total DNA adducts; for p21^WAF1 levels we observed the positive correlation with cotinine, c-PAHs exposure, total and B[a]P-like DNA adduct levels. In conclusion our results suggest that p53 and p21^WAF1 proteins plasma levels may be useful biomarkers of c-PAHs environmental exposure.     

Amplification of toluene dioxygenase genes in a hybrid Pseudomonas strain to enhance the biodegradation of benzene, toluene, and p-xylene mixture

A hybrid metabolic pathway through which benzene, toluene, and p-xylene (BTX) mixture could be simultaneously mineralized was previously constructed in Pseudomonas putida TB101 (Lee, Roh, Kim, Biotechnol. Bioeng 43: 1146-1152, 1994). In this work, we improved the performance of the hybrid pathway by cloning the todC1C2BA genes in the broad-host-range multicopy vector RSF1010 and by introducing the resulting plasmid pTOL037 into P. putida mt-2 which harbors the archetypal TOL plasmid. As a result, a new hybrid strain, P. putida TB103, possessing the enhanced activity of toluene dioxygenase in the hybrid pathway was constructed. The degradation rates of benzene, toluene, and p-xylene by P. putida TB103 were increased by about 9.3-, 3.7-, and 1.4-fold, respectively, compared with those by previously constructed P. putida TB101. Apparently, this improved capability of P. putida TB103 for the degradation of BTX mixture resulted from the amplification of the todC1C2BA genes. Furthermore, a relatively long lag period for benzene degradation observed when P. putida TB101 was used for the degradation of BTX mixture at low dissolved oxygen (DO) tension disappeared when P. putida TB103 was employed. (c) 1995 John Wiley & Sons, Inc.     

栉孔扇贝在BaP 胁迫下生物标志物筛选的研究

研究采用染毒→清除→二次染毒实验, 研究了BaP 对栉孔扇贝组织解毒代谢酶活力和DNA 损伤的影响, 筛选了栉孔扇贝在BaP 胁迫下的生物标志物。结果表明: BaP 对栉孔扇贝鳃丝、消化盲囊芳烃羟化酶(AHH)、谷胱甘肽硫转移酶(GST)活力和还原型谷胱甘肽含量(GSH)及DNA 损伤影响显著(PaP 处理组鳃丝AHH 活力与对照组无明显差异外, 其他处理组组织AHH 活力均被显著诱导, 于15d 时达到最大值, GST 活力和GSH 含量则呈逐渐下降趋势, 5d 时达到最小值, 之后趋于稳定; 而组织DNA 链断裂(F 值)基本呈下降趋势, DNA-蛋白质交联(DPC 值)呈逐渐升高, 至15d 时分别达到最小值和最大值。在清除(15—45d)阶段, 各处理组组织AHH 活力逐渐下降,GST 活力和GSH 含量则逐渐升高, 在25—40d 时均恢复至对照组水平; 各处理组组织F 值和低浓度处理组(0.05、0.5 μg/L)DPC 值分别呈逐渐升高和下降趋势, 于35—40d 时恢复至对照组水平, 而高浓度处理组(5、10 μg/L)DPC 值仍显著高于对照组水平。在二次染毒(45—60d)期间, 除鳃丝AHH 活力在50d 时达到最大值外, 其他指标变化趋势与一次染毒基本一致。由此可见, 栉孔扇贝在BaP 胁迫下组织解毒代谢酶活力和DNA 损伤表现出明显的时间剂量效应性和稳定性, 依据相关性分析, 提出以鳃丝AHH 活力和消化盲囊GST活力为防御型生物标志物, 鳃丝、消化盲囊DPC 值为损伤型生物标志物, 并将AHH、GST 活力和DPC 值整合作为BaP 毒性评定的组合型生物标志物, 全面评价PAHs 的污染毒性。       

Constitutive and inducible expression of cytochromes P4501A (CYP1A1 and CYP1A2) in normal prostate and prostate cancer cells

Constitutive and benzo[a]pyrene (B[a]P) inducible expression of CYP1A1 and CYP1A2 in prostate cancer and normal prostate epithelial cells were examined by immunoblotting. Androgen independent prostate cancer cell lines DU145 and PC3 have constitutive expression of CYP1A and CYP1A1 and CYP1A2, respectively. Four micromolar B[a]P did not appear to induce CYP1A1 or CYP1A2 expression in DU145 or PC3 cells. The androgen dependent prostate cancer cell line, LnCap, also has constitutive expression of CYP1A1 and CYP1A2. However, both CYP1A1 and CYP1A2 are induced by treatment of LnCap cells with 4 microM B[a]P. Untreated normal prostate and primary prostate tumor cells have no detectable CYP1A1 expression. Treatment with 4 microM B[a]P induced CYP1A1 expression in both normal and primary tumor prostate cells. Constitutive CYP1A2 expression was detected in normal prostate cells with little or no induction by exposure to 4 microM B[a]P. Primary prostate tumor cells did not show constitutive expression of CYP1A2. However, CYP1A2 was induced by 4 microM B[a]P in primary prostate tumor cells. These observations indicate that hormonal and cancer specific factors affect the expression and induction of the phase I metabolic enzymes, CYP1A1 and CYP1A2 in prostate cells. These observations may be related to the potential smoking-linked higher risk of prostate cancer development and morbidity of prostate cancer patients who smoke.     

Benzo[a]pyrene-induced cell cycle progression is through ERKs/cyclin D1 pathway and requires the activation of JNKs and p38 mapk in human diploid lung fibroblasts

Treatment of cells with carcinogen Benzo[a]pyrene (B[a]P) allows cells to evade G1 arrest and induces cells abnormal proliferation. However, the mechanisms of its action at cellular level are not well understood. To address this question, normal human embryo lung diploid fibroblasts (HELF) were selected in the present study. We found that exposure of cells with 2.5 μM of B[a]P for 24 h resulted in a decrease of G1 population by 11.9% (P < 0.05) and a increase of S population by 17.2% (P < 0.05). Treatment of cells with B[a]P also caused dose-related activation of MAPK and induction of cyclin D1 protein expression, whereas the CDK4 protein levels were not significantly affected by B[a]P. Overexpression of cyclin D1 protein stimulated by B[a]P was significantly inhibited by 50 μM AG126 (an inhibitor of ERK1/2), but not by 25 μM SP600125 (an inhibitor of JNK1/2) or 5 μM SB203580 (an inhibitor of p38 mapk), suggesting that B[a]P-induced cyclin D1 expression was only regulated by ERK1/2 pathway. However, AG126, SP600125 or SB203580 led to cell cycle significantly arrested in G1 phase, indicating that ERK1/2, JNK1/2 and p38 mapk pathways are all required for B[a]P-induced G1/S transition. In addition, HELF cells transfecting with antisense cyclin D1 cDNA or antisense CDK4 cDNA showed significantly G1 arrest after B[a]P stimulation. These results suggested that B[a]P exposure accelerated the G1→S transition by activation of MAPK signaling pathways. Cyclin D1 and CDK4 are rate-limiting regulators of the G1→S transition and expression of cyclin D1 is predominantly regulated by ERK1/2 pathway in HELF cells.     

Influence of a niosomal formulation on the oral bioavailability of acyclovir in rabbits

The purpose of this research was to prepare acyclovir niosomes in a trial to improve its poor and variable oral bioavailability. The nonionic surfactant vesicles were prepared by the conventional thin film hydration method. The lipid mixture consisted of cholesterol, span 60, and dicetyl phosphate in the molar ratio of 65:60:5, respectively. The percentage entrapment was approximately 11% of acyclovir used in the hydration process. The vesicles have an average size of 0.95 microm, a most probable size of 0.8 microm, and a size range of 0.4 to 2.2 microm. Most of the niosomes have unilamellar spherical shape. In vitro drug release profile was found to follow Higuchi's equation for free and niosomal drug. The niosomal formulation exhibited significantly retarded release compared with free drug. The in vivo study revealed that the niosomal dispersion significantly improved the oral bioavailability of acyclovir in rabbits after a single oral dose of 40 mg kg(-1). The average relative bioavailability of the drug from the niosomal dispersion in relation to the free solution was 2.55 indicating more than 2-fold increase in drug bioavailability. The niosomal dispersion showed significant increase in the mean residence time (MRT) of acyclovir reflecting sustained release characteristics. In conclusion, the niosomal formulation could be a promising delivery system for acyclovir with improved oral bioavailability and prolonged drug release profiles.     

State and federal cleanup levels for petroleum hydrocarbons in soil: State of the states and implications for the future

The Association for Environmental Health and Sciences Foundation has been collecting information on state-by-state petroleum cleanup levels (CULs) for soil since 1990, with the most recent survey in 2012. These data form the basis for this analysis, including a comparison of the CULs to U.S. Environmental Protection Agency (USEPA) regulatory values. The results illustrate the evolving complexity of state regulatory approaches to petroleum mixtures; benzene, toluene, ethylbenzene, and xylenes; and carcinogenic polycyclic aromatic hydrocarbons, as well as the use of multiple exposure scenarios and pathways to regulate petroleum in soil. Different fractionation approaches in use by various states and the USEPA are discussed, their strengths and limitations are reviewed, and their implications for site CULs are evaluated. Because of an increasing array of scenarios and pathways, CUL ranges have widened over time. As the regulatory environment for petroleum releases becomes more complex, it is increasingly important to develop a conceptual site model for fate, transport, land use assumptions, and exposure pathways at petroleum-contaminated sites to enable selection of the most appropriate CULs available.     

苯并[a]芘对小鼠肝脏和肾脏中丙二醛和过氧化氢酶的影响

目的探讨苯并[a]芘（B（a）P）对小鼠肝脏和肾脏脂质过氧化及抗氧化能力的影响。方法采用B（a）P口腔灌胃连续染毒3 d后,取肝、肾组织作匀浆,采用TBA比色法测定鼠肝脏和肾脏内的丙二醛（MDA）的含量,钼酸铵比色法测定鼠肝脏和肾脏内的过氧化氢酶（CAT）的含量。结果肝中各剂量染毒组的MDA含量增加,其中5 mg/kg、10 mg/kg剂量组与油剂对照组比较差异有显著性（P〈0.05）。肾脏中各剂量染毒组的MDA含量均有所增加,其中10 mg/kg剂量组与对照组比较差异有显著性（P〈0.05）。肝脏中各剂量染毒组的CAT的含量低剂量增加高剂量减少,肾脏中各剂量染毒组的CAT的含量增加。结论B（a）P可引起MDA含量增加诱导小鼠肝肾的脂质过氧化损伤。     

两种典型土壤胶体对镉的生物有效性的影响

采用黑麦草盆栽试验,研究了人工Cd污染(10.91mg·kg-1)黄棕壤和红壤(简称原土)及其胶体组分(简称胶体)和去胶后组分(简称去胶)Cd的生物有效性,并研究了EDTA对Cd解吸和生物有效性的影响.结果表明:(1)各处理黑麦草株高、地上部干重、根干重、总生物量都表现为胶体＞原土＞去胶,胶体上总生物量分别是原土和去胶处理的(1.31±0.02)倍和(1.82±0 21)倍.(2)黑麦草体内Cd浓度、及其对Cd的富集系数都表现为胶体＜原土＜去胶,表明胶体中Cd的生物有效性＜原土＜去胶.(3)黄棕壤各组分Cd的解吸率分别表现为胶体和原土约为0,去胶组分为(10.5±3.5)%,红壤各组分平均为(20.8±1 9)%,但加入EDTA则明显增加了Cd的解吸,导致黑麦草体内Cd浓度显著增加,黑麦草地上部干重、根干重、总生物量降低.EDTA对Cd的活化作用表现为去胶＞原土＞胶体,黄棕壤＞红壤,EDTA对各处理植株Cd总量的影响与此吻合.这说明,土壤镉的生物有效性受土壤胶体及其pH等的强烈影响.     

Inhibition of benzo[a]pyrene-induced cytotoxicity and cytochrome P450 1A activity by dietary flavonoids in human liver cell model: structure-activity relationship

Inhibition of benzo[a]pyrene (B[a]P)-induced cytotoxicity and cytochrome p450 1A (CYP 1A) activity by flavonoids (1–100 M) was examined in terms of the structure-activity relationship in the human liver-derived cell model (HepG2). Two hydroxyl groups in the 5- and 7-position of flavonoids were essential to inhibit B[a]P-induced cytotoxicity. Generally, flavones (IC₅₀; 5.0–17.2 M) were more potent than the corresponding flavonols (IC₅₀; 42.7–131.8 M), and flavonoids such as apigenin (IC₅₀; 7.2 M) were more active than the corresponding isoflavonoids, genistein (IC₅₀; 61.7 M). The planar structure of flavone proved to be important in inhibiting B[a]P-induced toxicity and CYP 1A activity. The inhibitory effect of flavonoids on B[a]P-induced CYP 1A activity was correlated well with the inhibition of B[a]P-induced cytotoxicity (r=0.635, p<;0.01).     

Benzo[a]pyrene-7,8-quinone-3'-mononucleotide adduct standards for 32P postlabeling analyses: detection of benzo[a]pyrene-7,8-quinone-calf thymus DNA adducts

Benzo[a]pyrene-7,8-quinone (BPQ) is one of the reactive metabolites of the widely distributed archetypal polycyclic aromatic hydrocarbon, benzo[a]pyrene (B[a]P). The formation of BPQ from B[a]P through trans-7,8-dihydroxy-7,8-dihydroB[a]P by the mediation of aldo-keto reductases and its role in the genotoxicity and carcinogenesis of B[a]P currently are under extensive investigation. Toxicity pathways related to BPQ are believed to include both stable and unstable (depurinating) DNA adduct formation as well as reactive oxygen species. We previously reported the complete characterization of four novel stable BPQ-deoxyguanosine (dG) and two BPQ-deoxyadenosine (dA) adducts (Balu et al., Chem. Res. Toxicol. 17 (2004) 827-838). However, the identification of BPQ-DNA adducts by 32P postlabeling methods from in vitro and in vivo exposures required 3'-monophosphate derivatives of BPQ-dG, BPQ-dA, and BPQ-deoxycytidine (dC) as standards. Therefore, in the current study, BPQ adducts of dGMP(3'), dAMP(3'), and dCMP(3') were prepared. The syntheses of the BPQ-3'-mononucleotide standards were carried out in a manner similar to that reported previously for the nucleoside analogs. Reaction products were characterized by UV, LC/MS analyses, and one- and two-dimensional NMR techniques. The spectral studies indicated that all adducts existed as diastereomeric mixtures. Furthermore, the structural identities of the novel BPQ-dGMP, BPQ-dAMP, and BPQ-dCMP adducts were confirmed by acid phosphatase dephosphorylation of the BPQ-nucleotide adducts to the corresponding known BPQ-nucleoside adduct standards. The BPQ-dGMP, BPQ-dAMP, and BPQ-dCMP adduct standards were used in 32P postlabeling studies to identify BPQ adducts formed in vitro with calf thymus DNA and DNA homopolymers. 32P postlabeling analysis revealed the formation of 8 major and at least 10 minor calf thymus DNA adducts. Of these BPQ-DNA adducts, the following were identified: 1 BPQ-dGMP adduct, 2 BPQ-dAMP adducts, and 3 BPQ-dCMP adducts. This study represents the first reported example of the characterization of stable BPQ-DNA adducts in isolated mammalian DNA and is expected to contribute significantly to the future BPQ-DNA adduct studies in vivo and thereby to the contribution of BPQ in B[a]P carcinogenesis.     

Kinetics of competitive inhibition and cometabolism in the biodegradation of benzene, toluene, and p-xylene by two Pseudomonas isolates

Two Pseudomonas species (designated strains B1 and X1) were isolated from an aerobic pilot-scale fluidized bed reactor treating groundwater containing benzene, toluene, and p-xylene (BTX). Strain B1 grew with benzene and toluene as the sole sources of carbon and energy, and it cometabolized p-xylene in the presence of toluene. Strain X1 grew on toluene and p-xylene, but not benzene. In single substrate experiments, the appearance of biomass lagged the consumption of growth substrates, suggesting that substrate uptake may not be growth-rate limiting for these substrates. Batch tests using paired substrates (BT, TX, or BX) revealed competitive inhibition and cometabolic degradation patterns. Competitive inhibition was modeled by adding a competitive inhibition term to the Monod expression. Cometabolic transformation of nongrowth substrate (p-xylene) by strain B1 was quantified by coupling xylene transformation to consumption of growth substrate (toluene) during growth and to loss of biomass during the decay phase. Coupling was achieved by defining two transformation capacity terms for the cometabolizing culture: one that relates consumption of growth substrate to the consumption of nongrowth substrate, and second that relates consumption of biomass to the consumption of nongrowth substrate. Cometabolism increased decay rates, and the observed yield for strain B1 decreased in the presence of p-xylene. (c) 1993 Wiley & Sons, Inc.     

On the tropical soils; The influence of organic matter (OM) on phosphate bioavailability

Application of organic manure (OM) and crop residues in agricultural soils can potentially influence positively or negatively the availability of soil phosphorus (P) through soil mineralization, sorption, or desorption of soil-bound P. Traditionally, the addition of OM can reduce the capacity of the soil colloids to adsorb P, thus increasing the release of P in soil solution, but also added OM can increase the adsorption site and increase the fixation or sorption of P to soil colloids, thus reducing the availability of P in soil solution and loss to the environment. The highly weathered tropical soils (HWTS) are susceptible to P insufficiency because HWTS have high P adsorption and fixation; this is mainly due to high concentration of P adsorbent. The main P adsorbents in HWTS include Al, Fe, Ca, and clay minerals, which are principally the same binding or adsorbent for OM compounds, but in excess, are toxic (Al and Fe) to crops. Thus, the presence of OM in HWTS can compromise the adsorption and availability of P in agricultural soils following phosphatic fertilizer applications. In this study, the influence of OM on P adsorption and availability was characterized to have a clear understanding of how OM influences P availability in agricultural soils, especially in highly weathered tropical soil. It is clearly outlined that the application of OM and crop residues can positively or negatively influence the availability of P in agricultural soils for plant uptake and dictate the P that is available for loss to the environment. Thus, the addition of organic matter as a strategy to increase P bioavailability for plant uptake must be treated with care because their contribution is not strait forward to be positive in many agricultural soils.     

气候变化对作物矿质元素利用率影响研究进展

作物矿质元素利用率对气候变化的响应是目前全球变化研究中既重要、又复杂,且认知最少的科学领域。这个科学问题的研究关系到解密或预测陆地植物及农作物矿质胁迫对全球气候变化响应的机理,为将来农业投入提供理论依据,是应对气候变化的当务之急。目前只有少数研究,通过模拟试验,探索性地开展了CO_2浓度或温度升高的环境条件下,矿质元素在土壤-植物系统迁移、分布和储存特征的研究。从相关的文献报道来看,CO_2浓度升高环境条件下,小麦和水稻作物籽粒中大量和痕量元素的富集水平一般呈下降趋势。但温度升高情况下,作物各器官对对矿质元素的吸收情况则更为复杂。正由于气候因素与植物矿质元素利用率之间关系的复杂性,在气候变化背景下,解密作物矿质胁迫对全球气候变化响应的科学问题,尚需改进试验方法、手段,从土壤性质、作物生态生理,以及农业生态系统中矿质元素在土壤-作物系统中迁移转化的过程,全面考察作物矿质元素利用率对气候变化的响应机理。