Experimental formation of cleft palate in mice with polychlorinated biphenyls (PCB)

The teratological effect of polychlorinated biphenyls (PCB) was examined using the ddY strain of mouse. PCB in 0.05 ml ethanol was injected daily, subcutaneously into the back of pregnant mice, for 10 days from day 6 of gestation. Cleft palates were found in fetuses at the 18th gestation, with a significant dose response between 10 mg and 50 mg as total body dose of PCB per pregnant mouse. Comparison of these results with simultaneous observations of body weight of dam or fetus, and number of resorbed and dead fetuses, indicated that cleft palate formation was due mainly to the specific effect of PCB and not to its general toxicity. Cleft lip, brachydactyly, and syndactyly were also found. In the control mice receiving no PCB and no treatment, no external malformations were found in 1765 live fetuses. These results demonstrate a teratogenic effect of PCB in the ddY strain of mouse after subcutaneous injection.     

Age-specific reference ranges for polychlorinated biphenyls (PCB) based on the NHANES 2001-2002 survey

The Centers for Disease Control and Prevention (CDC) conducted analyses for 34 polychlorinated biphenyl (PCB) congeners in blood samples collected from a statistically representative sample of the U.S. population during the National Health and Nutrition Examination Survey (NHANES) and reported overall population percentiles. Because the serum concentrations of many persistent organochlorine compounds are strongly age dependent, data were analyzed from the NHANES 2001-2002 sampling cycle to identify age-specific reference ranges for the measured congeners on a lipid-adjusted serum basis. In addition, reference ranges were estimated for the sum of the 34 measured PCB congeners. Because many congeners were frequently nondetectable, estimates for summed PCB levels are dependent upon the assumption used to replace nondetectable concentrations in the calculation. The effect of nondetects on the summed congeners totals is particularly strong for younger ages. The NHANES 2001-2002 PCB serum data demonstrate strong age-related trends, with older individuals displaying higher concentrations of most congeners and of summed PCB congeners. These age-specific reference ranges for PCB concentrations are critical for accurate interpretation of measured serum concentrations of PCB congeners in individuals.     

Testing of residues of vegetable drugs, organochlorine herbicides and polychlorinated biphenyls (PCB)

According to the establishment of methods for the determination of PSM residues in vegetable drugs the authors tried to detect organo-chlorinated compounds, which are used in agriculture and industry thus becoming of interest for the quality control of vegetable drugs. In most of the cases the determination was carried out by liquid/liquid partition between acetonitrile/n-hexane in combination with the CC using florisil for sample purification and capillary GC with a methyl silicone rubber column. Some of the results required a confirmation using a Megabore D-608 column (J&W Scientific).     

Studies of foetal death and foetal weight in guinea pigs fed polychlorinated biphenyls (PCB)

Pregnant guinea pigs were fed a total dose of 100 mg of the commercial PCB preparation Clophen A50 during days 16 to 60 of gestation. This treatment caused severe foetal, but no maternal, death. Contrarily, a total dose of 25 mg or 100 mg of 2,2',4,4',5,5'-hexachlorobiphenyl (HCB) did not cause foetal death in the guinea pig. The prenatal growth rate was increased by a total dose of 25 mg, but not by 100 mg, of HCB.     

Genotoxic effects of polychlorinated biphenyls (PCB 153, 138, 101, 118) in a fish cell line (RTG-2)

Polychlorinated biphenyls (PCBs) are persistent pollutants in aquatic environments, often causing the decline or disappearance of wild populations. The primary aim of this study was to investigate the genotoxic effects of some PCBs (PCB153 (2,2′,4,4′,5,5′-hexachlorobiphenyl) and 138 (2,2′,3,4,4′,5′-hexachloro-biphenyl), both non-dioxin-like compounds, and the pentachlorobiphenyls PCB118 (2,3′,4,4′,5-) and 101 (2,2′,4′,5,5′-), the former an ortho-substituted, low-affinity dioxin-like compound and the latter a non-coplanar congener classified as non-dioxin-like) in fish cells (RTG-2). These congeners are mostly present in surface waters and in edible aquatic organisms and the loss of DNA integrity in vitro serves as a sensitive biomarker of cytogenetic alterations and is considered as an initial step for the identification of genotoxic effects.The alkaline comet assay and the micronucleus test show clear genotoxic damage after short and longer exposure (2 and 24 h) to maximum soluble, non-cytotoxic doses, evident sooner with PCBs 101 and 118. Oxidative stress situations involving ROS release, reduction in total GSH, lipid peroxidation and alteration to superoxide dismutase, seen after exposure with all the congeners, though with different kinetics, seem the most likely explanation for the genotoxic damage. This appears to be confirmed by the modified comet assay (pH 10) for detection of oxidized bases using endonuclease III. The increased generation of intracellular ROS might explain the apoptosis seen after treatment with the single PCBs and evaluated on the basis of the rise in 3-7 caspase activity. Therefore both the non-coplanar, non-dioxin-like PCBs (153, 138, 101) and the low-affinity dioxin-like compound PCB118 cause evident genotoxic damage, probably as a consequence of oxidative stress.     

Scale-dependence in polychlorinated biphenyl (PCB) exposure effects on waterbird habitat occupancy

Spatial scale is rarely considered in population-level assessments of contaminant impacts on wild animals; as a result misinterpretation of the relationship between contaminant exposure and population status may occur. We assessed the strength of expression of polychlorinated biphenyl (PCB) exposure effects at local vs. regional spatial scales on population status in five species of waterbirds, “bioaccumulators” often promoted as indicators of contaminant effects in aquatic ecosystems. Our focus was the upper Hudson River where PCBs occur at levels reported to have adverse impacts on wild birds. At the local scale, waterbird habitat occupancy was estimated from 220 repeat surveys made between 2001 and 2010 along the same survey route divided into 25 contiguous river segments with markedly different PCB concentrations. At the regional scale, waterbird habitat occupancy in relation to proximity to the upper Hudson River was estimated across 1248 Breeding Bird Atlas survey blocks while controlling for region-wide variation in habitat availability. At the local scale, many associations of habitat and sampling covariates with species detection probabilities were evident but none, including PCB concentration, with habitat occupancy, extinction or colonization of a given river segment. At the regional scale, survey effort and habitat factors not related to PCB exposure were the most important drivers of waterbird occurrence although two species were more likely to occur farther from the contaminated river segment. Spatial scale clearly mediates expression of contaminant impacts on wild bird populations; large-scale, expert-generated databases provide an underused opportunity for better delineating the spatial scales at which population impacts occur and risk assessments should be performed.     

Biological monitoring of indoor-exposure to dioxin-like and non-dioxin-like polychlorinated biphenyls (PCB) in a public building

The release of PCBs from sealant material in public buildings and the resulting indoor air levels have raised growing concerns about possible human health effects connected with this exposure. Ambient monitoring of PCBs in a public building has revealed a contamination with the more volatile lower chlorinated PCB 28, PCB 52 and PCB 101. This gave reason for a large biological monitoring study in order to examine the internal exposure to PCBs in persons working in that building. Blood samples from 209 persons employed in the PCB-contaminated building were drawn. 98 persons matched for age and gender working in non-contaminated buildings served as control group. Plasma samples were analysed for the six indicator PCBs (PCB 28, 52, 101, 138, 153, 180) and 12 dioxin-like PCBs using GC/MS (LOD: 0.01 μg/L). Significant differences between both collectives were only found for the plasma levels of the lower chlorinated PCB 28, PCB 52 and PCB 101 and for the dioxin-like congeners PCB 105 and PCB 118, which are due to inhalative exposure to these congeners via indoor air. Median plasma levels of PCB 28, PCB 52 and PCB 101 in the employees of the contaminated building were 0.087 μg/L, 0.024 μg/L and 0.012 μg/L, respectively. The concentrations of the higher chlorinated PCBs and all other dioxin-like congeners investigated were within the normal range of the general population. There was no relationship between indoor air measurements and internal exposure of the employees in the corresponding office, but estimated lifetime exposure of the employees turned out to be a significant factor for plasma levels of PCB 28. Our biomonitoring results served as a basis for individual risk communication and successful risk management.     

Rat liver changes after subchronic exposition to polychlorinated biphenyls (PCB)of low chlorine content

Liver changes were studied after subchronic feeding a diet containing 2000 ppm PCB [chlorine content 42% corresponding to trichlorobiphenyls (triCB)]. The products differed in their content of highly chlorinated biphenyls (Cl₅-biphenyl; 5%=triCB-5, 2%=triCB-2 and 0.4%=triCB-0.4). The most striking difference was observed in respect to their porphyrinogenic actions. TriCB-0.4 and triCB-2 caused an increase of porphyrins about 10-fold, whereas the liver porphyrin content of triCB-5 treated rats was 175-fold higher than normal. In all cases of porphyria the porphyrins consisted mainly of uro- and heptacarboxyporphyrin. In contrast to their different porphyrinogenic effects all triCB products caused an equal induction of -aminolaevulinate synthetase, but no increase of -aminolaevulinate dehydratase activity.TriCB-5 was also a stronger inducer than triCB-0.4 and triCB-2 regarding microsomal monoxygenases and UDP-glucuronyltransferase. The quantitative differences of the effect can be correlated to PCB residues in the liver. In triCB-5 fed rats a much higher accumulation of highly chlorinated components could be determined.The histological examination by light and electron microscopy showed no significant differences in the effects caused by all three triCB products. In livers of all rats cell hypertrophy could be observed due to a considerable hyperproliferation of tubular and vesicular SER. SER membranes were tightly packed and sometimes disrupted. Membrane arrays of various size were found in most hepatocytes. The mitochondria were dislocated by these formations and were sometimes swollen. There was neither centrilobular or periportal necrosis nor fibrosis nor fatty degeneration.It may be concluded that PCB of low chlorine content (42%) are much less toxic than highly chlorinated PCB. However, the small amount of highly chlorinated components, present as contaminants in commercial products containing 42% chlorine, may accumulate and exert toxic effects.

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Zusammenfassung Es wird über Leberveränderungen an Ratten nach subchronischer Fütterung mit 2000 ppm PCB berichtet. Dabei wurden drei Chargen eines technischen Trichlorbiphenyls eingesetzt, die einen unterschiedlichen Gehalt (%) an hochchlorierten Komponenten (d. h.5 Cl) hatten, und zwar: 5% =triCB-5; 2% = triCB-2 und 0,4% = triCB-04. Der auffälligste Wirkungsunterschied der Präparate bestand in den porphyrinogenen Eigenschaften. Während triCB-0,4 und triCB-2 einen Anstieg des Porphyringehaltes der Leber um den Faktor 17 bzw. 7 verursachten, stieg der Gehalt nach triCB-5 175fach höher als normal an. Die Porphyrine bestanden hauptsächlich aus Uroporphyrin und Heptacarboxyporphyrin. Im Gegensatz zu den unterschiedlichen porphyrinogenen Wirkungen bewirkten alle drei triCB-Präparate eine gleich hohe Induktion der -Aminolaevulinatsynthetase. Die -Aminolaevulinatdehydratase erfuhr keine Veränderung ihrer Aktivität.Die mikrosomalen Monoxygenasen und die UDP-Glucuronyltransferase wurden durch alle drei triCB induziert. Die höchsten Werte wurden wieder durch triCB-5 erzielt. Sie korrelieren damit zu den PCB-Rückständen in der Leber, denn nach Fütterung mit triCB-5 kam es zu einer wesentlich höheren Akkumulation der hochchlorierten Komponenten.Bei licht- und elektronenmikroskopischer Untersuchung konnten keine signifikant unterschiedlichen Wirkungen der triCB-Präparate festgestellt werden. Die Lebern aller Tiere zeigten eine erhebliche Zellhypertrophie, die durch die Hyperproliferation des tubulären und vesikulären glatten endoplasmatischen Retikulums hervorgerufen wurde. Die Membranen des Retikulums waren dicht gepackt und manchmal zerrissen. In den meisten Zellen konnten außerdem unterschiedlich große membrane arrays gesehen werden, die zu einer Verdrängung von Mitochondrien führte. Einige Mitochondrien waren geschwollen. Zentrolobuläre oder periportale Nekrosen, Fibrosen oder fettige Degenerationen konnten nicht beobachtet werden.Aus den Untersuchungen kann gefolgert werden, daß PCB-Produkte mit niedrigem Chlorgehalt (42%) wesentlich weniger toxisch sind als solche mit hohem Gehalt. Toxische Effekte können aber dadurch auftreten, daß die in den Handelspräparaten als Verunreinigung enthaltenen hochchlorierten Komponenten akkumulieren.

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Abbreviations ALA-D -aminolaevulinate dehydratase - ALA-S -aminolaevulinate synthetase - BSP sulfobromophthalein - cyt. cytochrome - diCB commercial PCB mixture (Aroclor^® 1232, Monsanto) of preferably dichlorobiphenyls - hexaCB commercial PCB mixture (Aroclor^® 1260) of preferably hexachlorobiphenyls - tetraCB commercial PCB mixture (Aroclor^® 1248) of preferably tetrachlorobiphenyls - triCB-5, triCB-2, triCB-0.4 PCB mixtures of preferably trichlorobiphenyls containing 5% (2%, 0.4%) highly chlorinated biphenyls ( pentachlorobiphenyls) Some of these results have been reported at the Spring Meeting of the Deutsche Pharmakologische Gesellschaft, Mainz, 1975 (Grote et al., 1975c)This work was carried out within the coordinated research program Polychlorinated Biphenyls in the Environment which was supported by a grant of the German Federal Ministry for Research and Technology     

Glucuronidation of hydroxylated polychlorinated biphenyls (PCBs)

Polychlorinated biphenyls (PCBs) may be metabolized to hydroxylated compounds. While many of these metabolites are further converted to either the glucuronic acid or the sulfate conjugates by phase II enzymes, which facilitates their excretion, some hydroxylated PCBs persist in the body. This may reflect their inability to be conjugated. A possible role of uridine diphosphate glucuronosyl transferase (UGT) in the elimination of hydroxylated metabolites of PCBs was therefore investigated. Glucuronidation studies of PCB metabolites included ones which are eliminated with relative ease and also ones which are reported to be retained in blood. Liver microsomes, prepared from male Wistar rats treated by intraperitoneal injections of phenobarbital for 3 days (400 micromol/kg/day), were used as the source of UGT. Enzyme kinetics (V(max) and K(m)) were determined for each of the metabolites. The efficiency of glucuronidation (V(max)/K(m)) was found to vary from <3 to 116 microL/min/mg and was dependent on the structure of the metabolites. Substitution of chlorine atoms on the nonhydroxylated ring greatly lowered the V(max) of the enzyme, with substitution in the meta and para positions being least favorable for enzyme activity. Steric hindrance around the hydroxyl group by chlorines on adjacent carbon atoms did not play a major role. A weak relationship between the calculated dihedral angle (planarity), pK(a), log D, and enzyme activity was determined (r(2) < 0.5). However, a stronger relationship for the surface area and surface volume of the molecule was observed (r(2) >or= 0.5). This study explains in part why some PCB metabolites persist in the body.     

Effect of polychlorinated biphenyls and polychlorinated quaterphenyls in Cynomolgus monkey (Macaca fascicularis)

Female Cynomolgus monkeys (Macaca fascicularis) with P-KC-400, Y-PCB, PY-PCB or polychlorinated quaterphenyls (PCQ) received a daily dose of 5 mg for 20 weeks, and some monkeys received a daily dose of 10 mg of Y-PCB or 0.5 mg of PCQ. The chemical compositions of the polychlorobiphenyls (PCB) used for the oral administration were as follows: P-KC-400, PCB from which polychlorodibenzofurans (PCDF) have been removed from Kanecklor 400, largely contains tri- and tetrachlorobiphenyls and no PCDF. Whereas, Y-PCB and PY-PCB, PCB with constituents similar to PCB ingested by yusho patients, largely contain penta- and hexachlorobiphenyls, in addition, PCDF of 400 ppm was present only in Y-PCB, but not in PY-PCB. There were immunosuppression, enlargement and histopathological changes of the liver (such as interstitial inflammation, and proliferation of epithelial cells of biliary duct, etc.) in the groups fed P-KC-400 and PY-PCB (free of PCDF). In the group fed Y-PCB (with PCDF), there were more apparent decreases in body weight, immunosuppression, fatty liver and histopathological changes than in the groups P-KC-400 and PY-PCB. In addition, there were hair loss, acneform eruptions, edema of the eyelid, congestion and abscess of the Meibomian gland, and cornifications of the skin, characteristic dermatological findings of yusho disease.     

Chiral effects in the induction of drug-metabolizing enzymes using synthetic atropisomers of polychlorinated biphenyls (PCBs)

Atropisomers of the polychlorinated biphenyls 2,2',3,4,4',6-hexachlorobiphenyl (II) and 2,2',3,3',4,4',6,6'-octachlorobiphenyl (III), stable to racemization under physiological conditions, were administered to immature male Sprague-Dawley rats. The racemic hexachlorobiphenyl (II) was found to be a potent (phenobarbital-type) inducer, whereas (+)-II and (-)-II, administered at 100 mumol/kg, showed clearly differing potencies as inducers with (+)-II enhancing aminopyrine N-demethylase, aldrin epoxidase and cytochrome P-450 content more potently than (-)-II. In contrast, the racemic octachlorobiphenyl (III) and its individual enantiomers were only weak phenobarbital-type inducers of cytochrome P-450, and the enantiomers of III were equally (weakly) potent. Separate studies conducted to investigate pharmacokinetic influences on the differential potency of the enantiomers of II showed that after 5 days the concentration of (+)-II in the liver was twice as high as that of its antipode. Therefore, enantioselectivity in disposition as well as in recognition may be responsible for the differential potency seen.     

Molecular mechanisms involved in the toxic effects of polychlorinated biphenyls (PCBs) and brominated flame retardants (BFRs)

Exposure to polychlorinated biphenyls (PCBs) and brominated flame-retardants (BFRs) in human, primates, and rodents is accompanied by neurobehavioral changes. These involve adverse effects on both memory and learning and motor activity. There are also adverse effects observed on the endocrine and immune system. This review is restricted to our laboratory's recent findings of effects of these compounds on the nervous system and some molecular effects on the immune system. In the nervous system, data showed that PCBs and BFRs produce an effect on neurotransmitter transport mechanisms, in particular the neurotransmitter dopamine. It was demonstrated that this might explain the loss of dopamine in the brain seen after exposure to PCB. Further, it may explain the behavior of dopamine in preparations in vitro from brain tissue after exposure to PCB. Recently it was also reported that PCB and some BFRs induce formation of reactive oxygen species (ROS) in neurons. ROS act as messengers in the nervous system and may also be involved in cell death. In the case of PCB exposure, a correlation between ROS formation and death of neurons was found. In the immune system it was shown that PCBs and some of the BFRs induce formation of ROS in neutrophils (granulocytes). This takes place primarily through phosphorylation and subsequent activation of the NADPH oxidase. This production of ROS may have an adverse effect on the immune system.     

Lack of effects of polychlorinated biphenyls on testosterone synthesis in mice

Male mice were exposed to two different preparations of PCBs. The pure congener 2,2',4,4',5,5'-hexachlorobiphenyl (6-CB) was given at daily doses of 4, 20, and 40 mg/kg b.wt. during the perinatal or pubertal period. A technical mixture of PCB (Clophen A50) was administered during puberty at daily doses of 8, 40, 80, 120, and 160 mg/kg b.wt. Treatments were, in the different experiments, carried out every second or third day for three to five weeks. Treatment during puberty was started when the mice were 5 weeks old. The perinatal exposure was started on day 13 of gestation and ended on day 24 post partum. There were no significant differences in the plasma levels of testosterone between the treated mice and the controls after any of the treatments, but there was an increase in the relative testes weights for the animals treated perinatally. No influence on the biosynthesis of testosterone in the testicular interstitial cells in vitro could be demonstrated.     

Apoptosis-mediated immunotoxicity of polychlorinated biphenyls (PCBs) murine splenocytes

Polychlorinated biphenyls (PCBs) exhibited immunotoxicity on antibody forming response to T-dependent antigen of sheep red blood cells, primary activation of T cells by mixed lymphocyte response, and lymphocyte proliferation induced by various mitogens. These immunosuppressions were related with the loss of lymphocyte viability which was determined by the propidium iodide method, and this death was proven to be linked with apoptosis which showed DNA fragmentation detected by the diphenylamine method and agarose gel electrophoresis. The degree of DNA fragmentation was increased in a dose- and time-dependent manner in PCB-treated splenocytes. In conclusion, it was assumed that apoptosis was attributable to the immunotoxicity of PCBs in murine splenocytes.     

Comparison of polychlorinated biphenyl (PCB) induced effects on innate immune functions in harbour and grey seals

Polychlorinated biphenyls (PCBs) are known to have detrimental effects on the innate immune system of several mammalian species. Top predators such as marine mammals may be badly affected as PCBs can bioaccumulate in their blubber to high concentrations and previous studies have suggested that harbour seals may be particularly vulnerable to the immunotoxic effects of such contaminants. To investigate the effects of PCBs on innate immune functions in phocid seals, blood samples were collected from harbour and grey seals and exposed in vitro to a mixture of Aroclors. Separated mononuclear (PBMCs) and polymorphonuclear (PMNCs) leukocytes from each species were incubated with Aroclors (at 3 and 30 ngml(-1)) for 3 and 24 h incubation periods, after which phagocytosis, respiratory burst and cytotoxic activity were measured. The phagocytic activity of harbour seal PMNCs was decreased at both incubation times and at both Aroclor concentrations tested, but there was no effect on the grey seals. Similarly, the respiratory burst activity of harbour seals was decreased at both incubation times, but only at the higher concentration used. There were no differences in the cytotoxic activity of the PBMCs with respect to incubation times or concentrations in either species. However, differences were observed in the level of cytotoxic activity against YAC-1 target cells, with the grey seal PBMCs showing higher levels of activity. The observed differences in phagocytosis, respiratory burst and cytotoxic activity of the leukocytes following incubation with PCBs may have implications for the previously recorded differences in disease susceptibility between grey and harbour seals.