Presence of polycyclic aromatic hydrocarbons in some South Indian food components.

South Indian food dishes, comprising several deep fried items have been proved to be mutagenic. Polycyclic aromatic hydrocarbons (PAHs) such as, benzo(a)pyrene, chrysene and dibenzanthracene, which are potent and proven carcinogens have been identified and quantified in several of the commonly consumed South Indian food dishes and food components. Most of the pyrolysed items contained PAHs in appreciable quantities. PAHs were detected in significant levels in salted, sundried and oil fried vegetables and fishes. Some of the raw and uncooked food components also revealed the presence of PAHs.     

Comparison of in vivo and in vitro binding of polycyclic hydrocarbons to DNA

The in vivo binding of [³H]benzo(a)pyrene (BP) and 3-[³H]methylcholanthrene (3MC) to liver and lung DNA was studied in A/J mice. Only in liver was there any reduction in total DNA-bound radioactivity between 4 h and 24 h after administration of the hydrocarbon. DNA was fractionated on Sephadex LH-20 after enzymatic digestion. A single deoxyribonucleoside-BP adduct was detected whereas two major 3MC-adducts were observed. With both BP and 3MC, three additional peaks of radioactivity eluted rapidly in the lung DNA experiments while a fourth was noted with liver DNA. The nucleoside-bound adducts from lung represented a much larger proportion of the total radioactivity than with liver. In vitro analysis of 3MC binding to DNA showed the nucleoside-bound adducts to be predominantly deoxyguanosine-dependent but that the early peaks were independent of base suggesting binding to another part of the DNA molecule, perhaps phosphate, i.e., phosphotriesters.     

Effect of some polycyclic aromatic hydrocarbons on protein synthesis in vitro

1. The effect of the strongly carcinogenic polycyclic aromatic hydrocarbons benzo[a]pyrene, 3-methylcholanthrene and dibenz[a,h]anthracene and of the non-carcinogenic anthracene, pyrene and phenanthrene on protein synthesis was studied in vitro with subcellular systems from rat liver. 2. Both types of hydrocarbons affect amino acid activation and inhibit transfer of labelled amino acids from transfer RNA to ribosomes. 3. Only the carcinogenic compounds stimulate the incorporation of labelled algal-protein hydrolysate and of some individual amino acids into transfer RNA. The most active dose was 10mmug. under the conditions used. This effect is abolished by preincubation of pH5 enzymes with the carcinogens before the addition of radioactive amino acids. 4. The carcinogens stimulate the incorporation of some amino acids into ribosomal protein whereas the non-carcinogenic compounds have no such effects. 5. Polynucleotide-dependent stimulation of protein synthesis is greatly enhanced in the presence of the carcinogenic hydrocarbons when either free amino acids or transfer RNA charged with labelled amino acids are used. The non-carcinogenic compounds induce a partial inhibition of this process. 6. It is concluded, in agreement with other authors, that carcinogens may increase the number of active incorporation sites on both transfer and ribosomal RNA. Possible mechanisms of such an effect are discussed.     

Mutagenicity of polycyclic hydrocarbons. II. Monitoring genetical hazards of chrysene in vitro and vivo.

Mutagenicity tests were performed with chrysene in the Salmonella/microsome test, NMRI-mice oocytes, bone-marrow cells and spermatogonia of Chinese hamsters. Only in mice oocytes was a weak but significant increase of structural chromosome aberrations observed. Correlations were found between weak carcinogenic and observed weak mutagenic activities of chrysene in vitro and in vivo.     

Binding of polycyclic aromatic hydrocarbons (PAHs) to teleost aryl hydrocarbon receptors (AHRs)

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous, environmental contaminants that pose a potential risk to fish populations. Both field and laboratory studies suggest that exposure of the early life stages of fish to PAH can mimic the embryotoxic effects of the planar halogenated hydrocarbons (PHHs), the most potent of which is 2,3,7,8-tetrachlorodibenzo-p-dioxin. PHH toxicity is mediated by the aryl hydrocarbon receptor (AHR) and PHH potency is predicted by its AHR-binding affinity and CYP1A induction potency. However, the role of the AHR, if any, in mediating the developmental effects of PAH to fish remains unknown. In this study we looked at the AHR binding affinity of a test set of PAH that had been previously ranked for their potency for inducing teleost CYP1A. PAH that induced CYP1A inhibited [3H]TCDD binding to in vitro-expressed AHRs from rainbow trout and the AHR expressed in PLHC-1 fish hepatoma cells. Generally, the relative rank order for AHR binding affinity predicted the rank order of these same PAH for inducing CYP1A reported in other studies. There was a strong, positive relationship between binding to the PLHC-1 AHR (stimulus) and the EC50s for CYP1A induction (response) in whole juvenile trout and in RTL-W1 cells, but EC50s were much higher than expected for a 1:1 stimulus/response relationship. These data show that the ability of PAH to bind to teleost AHR predicts PAH potency for CYP1A induction. If PAH toxicity is receptor-mediated and predicted by induction potencies, we will have a powerful mechanistic-based tool for rapidly assessing the risk of toxicity to fish of PAH from any source.     

Dimethyldioxirane epoxidation of polycyclic fluoranthene hydrocarbons.

Direct epoxidation of polycyclic fluoranthenes with dimethyldioxirane provides several new mono- and di-oxide derivatives.     

Characteristics of DNA during binding with polycyclic aromatic hydrocarbons in vitro]

Polycyclic aromatic hydrocarbons (PAH) were covalently bound to DNA by means of various activating systems. The following systems were used: the microsomal fraction of the rat liver, the system with I2, the system with ascorbic acid and FeSO4. Breaks in DNA due to the activating systems action appeared in all of these systems. Plateau of the PAH binding system curve in the microsomal system cannot be attributed either to the fall of the PAH metabolism rate to zero, or to the PAH binding sites in DNA. This plateau is the result of equalization of the rates of the two contrary-directed processes: the binding of metabolites and their removal due to DNA degradation. Because of the breaks in DNA caused by the activating systems, the authors failed to discover the changes in sedimentation data of DNA due to the covalently bound PAH.     

Inhibition of meiotic divisions of rat spermatocytes in vitro by polycyclic aromatic hydrocarbons

The toxic effects of polycyclic aromatic hydrocarbons (PAH) on spermatogenic cells undergoing meiotic division were investigated in vitro. Toxicity was assayed as alterations in cell nucleus morphology and cell survival and by DNA flow cytometry. Benzo[a]pyrene (BP) and 7,12-dimethylbenz[a]anthracene (DMBA) inhibited the progression of spermatocytes through meiotic division and were highly cytotoxic at concentrations higher than 1 microM. These results were obtained upon addition of a drug-metabolizing system, indicating that the seminiferous tubules lack the enzymes required for the initiation of PAH metabolism. The spindle poisons, e.g., vincristine and Colcemid, a group of direct-acting agents, affected spermatogenesis during meiotic division in a manner similar to that observed with PAH. In contrast, adriamycin did not inhibit meiotic division, although it did induce the formation of meiotic micronuclei as a result of chromosome breakage. It is concluded that low concentrations, i.e., 0.1 microM of PAH, strongly inhibit meiotic division, presumably after metabolic activation to reactive molecules functionally resembling direct-acting alkylating agents. High concentrations of PAH are cytotoxic.     

Binding of polycyclic aromatic hydrocarbons to DNA of cells in culture: a rapid method for its analysis using hydroxylapatite column chromatography.

A rapid procedure to study the interaction of carcinogens with DNA in cultured cells has been developed. The cells, which are labeled with 7,12-[3H]dimethylbenz[a] anthracene ([3H]DMBA), are lysed with 0.24 M phosphate buffer (pH 6.8), 1% sodium dodecyl sulfate (SDS), 8 M urea and 0.01 M ethylenediamine-tetraacetate (EDTA) and sonicated. The cell lysates are fractionated on columns of hydroxylapatite. Proteins and RNA are removed with 8 M urea in 0.24 M phosphate buffer (pH 6.8). DMBA-bound DNA is eluted with 0.4 M phosphate buffer (pH 6.8). DMBA-DNA isolated by this procedure is virtually free from proteins and RNA. Thermal stability, ultraviolet spectra and the density of DNA is not altered by DMBA binding. The uptake of DMBA by mouse epidermal cells is rapid and the binding of DMBA to DNA is linear for the first 8 h of exposure. DMBA binds to DNA in all phases of the cell cycle. However, the highest binding occurs immediately following maximum DNA synthesis.     

Biodegradation of polycyclic hydrocarbons by Phanerochaete chrysosporium.

The ability of the white rot fungus Phanerochaete chrysosporium to degrade polycyclic aromatic hydrocarbons (PAHs) that are present in anthracene oil (a distillation product obtained from coal tar) was demonstrated. Analysis by capillary gas chromatography and high-performance liquid chromatography showed that at least 22 PAHs, including all of the most abundant PAH components present in anthracene oil, underwent 70 to 100% disappearance during 27 days of incubation with nutrient nitrogen-limited cultures of this fungus. Because phenanthrene is the most abundant PAH present in anthracene oil, this PAH was selected for further study. In experiments in which [14C]phenanthrene was incubated with cultures of P. chrysosporium containing anthracene oil for 27 days, it was shown that 7.7% of the recovered radiolabeled carbon originally present in [14C]phenanthrene was metabolized to 14CO2 and 25.2% was recovered from the aqueous fraction, while 56.1 and 11.0% were recovered from the methylene chloride and particulate fractions, respectively. High-performance liquid chromatography of the 14C-labeled material present in the methylene chloride fraction revealed that most (91.9%) of this material was composed of polar metabolites of [14C]phenanthrene. These results suggest that this microorganism may be useful for the decontamination of sites in the environment contaminated with PAHs.     

Binding of beryllium to nuclear acidic proteins.

In vitro beryllium (Be) binding to rat liver nuclei has been reassessed (KAss = 2.0 X 10(6) M: n = 17 nmol Be/mg protein). Be also binds to rat liver nucleoli (KAss approx. 4 X 10(6) M: n = 10 nmol Be/mg protein). Examination of rat liver chromatin fractionated on a hydroxyapatite column shows that Be does not bind to histone or to the non-histone protein eluted by 0.05 M sodium phosphate. Be is strongly bound to the non-histone proteins eluted by 0.2 M sodium phosphate (KAss = 1.1 X 10(6) M: n = 55 nmol Be/mg protein) and also to the same extent to the fraction containing DNA which is subsequently eluted from the column. Evidence is provided that the latter binding is not due to DNA. The fractions containing the Be-binding proteins also contain the proteins which are phosphorylated to the greater extent.     

Biodegradation of polycyclic aromatic hydrocarbons

The intent of this review is to provide an outline of the microbial degradation of polycyclic aromatic hydrocarbons. A catabolically diverse microbial community, consisting of bacteria, fungi and algae, metabolizes aromatic compounds. Molecular oxygen is essential for the initial hydroxylation of polycyclic aromatic hydrocarbons by microorganisms. In contrast to bacteria, filamentous fungi use hydroxylation as a prelude to detoxification rather than to catabolism and assimilation. The biochemical principles underlying the degradation of polycyclic aromatic hydrocarbons are examined in some detail. The pathways of polycyclic aromatic hydrocarbon catabolism are discussed. Studies are presented on the relationship between the chemical structure of the polycyclic aromatic hydrocarbon and the rate of polycyclic aromatic hydrocarbon biodegradation in aquatic and terrestrial ecosystems.     

污染土壤中多环芳烃生物降解的调控研究

选用温度、湿度、表面活性剂ＴＷ８０和ＣＮＰ比４个因素为调控因子,采用正交法进行周期为１５０天的实验研究．结果表明,３０天后,土壤中ＰＡＨｓ的降解率可达４４．５～７４．６％,６０天后,达７０．４～９３．７％,降解率的不同与调控条件显著相关．在此期间,降解最佳条件为４０℃,湿度２５％,ＣＮＰ比为１２０１０１,ＴＷ８０分别为２００～５００ｍｇ·ｋｇ－１．实验结束时,土壤中ＰＡＨｓ的降解率达９１．２～９９．８％．降解的最佳条件是４０℃,湿度１５％．经Ｒ值判别表明,不同时期各因子对ＰＡＨｓ降解影响有所不同．温度对ＰＡＨｓ降解影响较大,表面活性剂对土壤中ＰＡＨｓ的生物降解有调控作用．     

Binding of polycyclic aromatic hydrocarbons to mutants of odorant-binding protein: a first step towards biosensors for environmental monitoring

Polycyclic aromatic hydrocarbons are among the most threatening pollutants widely present in the environment. Simple and economic methods of continuous monitoring of these compounds in real time are not yet available, although becoming increasingly needed. Odorant-binding proteins (OBPs) present unique characteristics of thermal and chemical stability for building robust, reliable, and inexpensive biosensors for such molecules. To investigate this possibility, we have engineered the pig OBP, whose three-dimensional structure has been resolved, introducing a tryptophan residue in the core of the binding pocket, as a fluorescence reporter for the presence of bound ligands. Binding affinities of several polyaromatic hydrocarbons to mutagenically modified OBPs were measured in competitive binding assays. Moreover, the presence of aromatic ligands was also successfully monitored in the modified OBPs by recording the quenching of intrinsic fluorescence of the protein. These data indicate that OBPs bind several aromatic polycyclic compounds with good affinities, that the specificity of these proteins can be easily modified by changing specific amino acid residues and that the introduction of a tryptophan residue in the binding site allows monitoring of aromatic ligands using direct fluorescence measurements.     

Biomarkers of carcinogenesis in humans exposed to polycyclic aromatic hydrocarbons

The frequencies of micronuclei (MN) in cytokinesis-blocked lymphocytes of 91 steel foundry workers were analysed. On the basis of ambient PAH levels at the work stands and 1-hydroxypyrene concentrations in the urine, the coke-oven workers were the most exposed as compared to the rollers reference group. The difference in results for the two groups studied was not statistically significant, although MN were slightly higher for coke-oven workers. The frequency of MN did not increase with exposure: after some increase in 1-10 years, a decreasing tendency was observed.