The effect of chlorination degree and substitution pattern on the interactions of polychlorinated biphenyls with model bacterial membranes

Polychlorinated biphenyls (PCB) are persistent organic pollutants that due to their chemical resistivity and inflammability found multiple applications. In spite of the global ban for PCB production, due to their long half-lives periods, PCB accumulate in the soils, so effective bioremediation of the polluted lands is of crucial importance. Some of the 209 PCB congeners exhibit increased toxicity to soil bacteria and their presence impoverish the soil decomposer community and slows down the degradation of environmental pollutants in the soils. The exact mechanism of PCB antimicrobial activity is unknown, but it is strictly related with the membrane activity of PCB. Therefore, to shed light on these interactions we applied Langmuir monolayers formed by selected phospholipids as model bacterial membranes. In our studies we tested 5 PCB congeners differing in the degree of chlorination and the distribution of the chlorine substituents around the biphenyl frame. Special attention was paid to tetra-substituted PCB because of their increased presence in the environment and disubstituted PCB being their degradation products. To characterize the model membranes as Langmuir monolayers, we used surface pressure measurements, Brewster angle microscopy and Grazing Incidence X-ray Diffraction. It turned out that among the tetra-substituted PCB the ortho-substituted non-dioxin like compound was much more membrane destructive than the flat dioxin-like congener. On the contrary, among the di-substituted PCB the flat para-substituted 2,2′-dichlorobiphenyl turned out to exhibit high membrane activity.     

Variation in polychlorinated biphenyl levels in common carp from a primarily agricultural drainage

Concentrations of polychlorinated biphenyls (PCBs) in common carp, Cyprinus carpio, from the Des Moines River, Iowa, were assessed for variability related to sampling location, sampling period, fish age, and fat content. Concentrations were highest at a location near the City of Des Moines; they were substantially lower in 1981 than in 1980. Age and fat content had little influence on PCB concentrations in carp. Overall concentrations were some of the lowest recorded in the United States and Canada in recent times.The Unit is jointly supported by Iowa State University, the Iowa State Conservation Commission, and the U.S. Fish and Wildlife Service.Journal Paper No. 10754 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 2465. Financed by a grant from the U.S. Department of Defense Army Corps of Engineers and made available through the Engineering Research Institute, Iowa State University.     

Transglutaminase activity during the differentiation of macrophages

For the examination of the participation of the microsomal electron transport system in mutagenic activation by 4-dimethylaminoazobenzene (DAB), 4-methylaminoazobenzene (MAB) and their 3′-methyl-derivatives (3′-methyl-DAB and 3′-methyl-MAB), monospecific antibodies to NADPH-cytochrome P-450 reductase, 3-methylcholanthrene-inducible major P-450 (MC-P-448) and phenobarbital-inducible major P-450 (PB-P-450) were used. In Ames' assay system, the antibody to NADPH-cytochrome P-450 reductase inhibited the mutagenicities of DAB, MAB, 3′-methyl-DAB and 3′-methyl-MAB by 94, 94, 90 and 87%, respectively. The antibody to MC-P-448 inhibited their mutagenicities by more than 90%, while the antibody to PB-P-450 inhibited the mutagenicities less than 20%. These results indicate that the microsomal electron transport system, especially MC-P-448, is involved in activation of these dyes.     

On the inhibition of microsomal drug metabolism by polychlorinated biphenyls (PCB) and related phenolic compounds.

The in vitro metabolism of p-nitroanisole, aminopyrine, and aniline by rat liver microsomal monoxygenases were studied in the presence of different polychlorinated biphenyl (PCB) mixtures and some related hydroxybiphenyls. The tested PCB mixtures contained preferably dichloro- (di-CB), tetrachloro- (tetra-CB), or hexachlorobiphenyls (hexa-CB). All PCB were competitive inhibitors of only aminopyrine demethylation by normal microsomes (Ki 22-39 micron). In microsomes of PCB-pretreated rats the aminopyrine demethylation was inhibited noncompetitively by di-CB and hexa-CB whereas tetra-CB remained a competitive inhibitor (Ki 12 micron). Moreover, after PCB pretreatment all PCB were competitive inhibitors of p-nitroanisole demethylation. 2-OH-biphenyl and 4-OH-biphenyl caused competitive inhibition of aminopyrine demethylation and aniline hydroxylation but failed to inhibit p-nitroanisole metabolism by normal microsomes. Chlorinated 4-hydroxybiphenyls inhibited competitively the metabolism of both type I and type II substrates. However, after PCB pretreatment all phenolic compounds caused uncompetitive inhibition of aniline hydroxylation.     

Determination of polychlorinated biphenyls in human blood by solid-phase extraction including on-column lipid decomposition

A method for the isolation of polychlorinated biphenyls (PCBs) from human blood using solid-phase extraction (SPE) has been developed. The procedure incorporates decomposition of lipids by concentrated sulphuric acid directly on the SPE column. Conditions for transferring PCBs onto the SPE column and washing the decomposed blood components from the SPE column were optimised. After clean-up the extracts were analysed using gas chromatography with electron capture detection. An average recovery of PCBs from spiked blood samples was about 78±8% and an average precision was about 109±7%. Quantitation has been done using four internal standards and calibration curves based on five concentration levels. Low procedural blanks made it possible to determine PCBs in blood quantitatively at a level down to 2–10 pg g⁻¹. The integrated method for blood is fast, less laborious than methods using liquid–liquid extraction and has a low consumption of organic solvents.     

CAPACITY AND MODE OF PCB METABOLISM IN SMALL CETACEANS1

Based on a comparative approach using PCB isomer and congener compositions in higher animals and their food organisms, the capacity and mode of PCB metabolism in small cetaceans were studied and the following conclusions were drawn: (1) Small cetaceans can metabolize some of the lower chlorinated biphenyls and this capacity seems to be the same in all species of these animals. (2) The values of MI, an index to evaluate the capacity of PCB metabolism, showed that the metabolic capacity of small cetaceans was extremely low as compared to those of birds and terrestrial mammals. (3) The structural requirements for PCB metabolism were different in animal species, in that small cetaceans have no capacity to metabolize a group of PCBs with adjacent non-chlorinated meta and para carbons in biphenyl rings. (4) No development of PB (phenobarbital)-type enzymes, and a lower activity of MC (3-methylcholanthrene)-type enzymes were suggested in small cetaceans, which implies long-term accumulation and possible reproductive toxicity of persistent organochlorines in these animals. The present approach should provide an important insight into the physiological responses of small cetaceans to persistent toxic chemicals.     

Effects of orally administered insecticides and polychlorinated biphenyls on the parasite fauna of two species of piscivorous birds

A study was initiated to determine the effects of various levels of ingested DDT and its metabolites and polychlorinated biphenyls on young double-crested cormorants, Phalacrocorax a. auritus, and white pelicans, Pelencanus erythrorhynchos. One phase of this research was concerned with the effects of ingested insecticides and polychlorinated biphenyls on the parasite fauna of these birds. Statistical analysis indicated a decrease in the numbers of ectoparasites on the feathers of cormorants as dosage of insecticides and as residue levels on the feathers increased. Similar results were noted with ectoparasites and gular lice of white pelicans receiving a daily dosage of either polychlorinated biphenyls or a mixture of DDT, DDD, and DDE. There were no significant differences in the numbers of endoparasites between the control and treated birds in either the cormorants or pelicans.     

An Integrated Surfactant Solubilization and PCB Bioremediation Process for Soils

Two decades after the manufacture and use of polychlorinated biphenyls (PCBs) were banned, PCB contamination remains widespread in the environment. Technologies available for PCB remediation are limited and often impractical for soils with dispersed PCB contamination. In this study, two remediation processes have been integrated for use on PCB-contaminated soils. This remediation strategy links in situ surfactant washing of PCBs from soil with aerobic biodegradation of the resulting surfactant-PCB solution by two field application vectors (F A Vs), Pseudomonas putida IFL5::TnPCB and Ralstonia eutropha B30F4::TnPCB, which utilize surfac-tants as growth substrates and cometabolize PCBs. A bench-scale demonstration of this process was performed using PCB-contaminated soils from an electric power substation site. In a 2-day recycling wash using a 1% (wt/vol) surfactant solution, greater than 70% of the PCBs were removed from the soil. In the biodegradation phase, greater than 90% of the surfactant and 35% of the PCBs were biodegraded in 12 days. The residual PCBs were partitioned onto a solid carrier resulting in greater than 90% removal of PCBs from the bioreactor effluent and a 50-fold reduction in the amount of PCB-contaminated material.