Induction of glutathione-S-transferase in the Northern quahog Mercenaria mercenaria after exposure to the polychlorinated biphenyl (PCB) mixture Aroclor 1248

The glutathione-S-transferases (GSTs) from the Northern quahog (Mercenaria mercenaria) were examined after an injection of a polychlorinated biphenyl (PCB) mixture, Aroclor 1248, to a concentration of ~50 ppm. Enzymatic analysis indicated a fourfold increase in the GST activity of quahogs injected with PCBs compared with that of the control. An electrophoretic analysis of the GST from the PCB-exposed quahogs showed a 1.5-fold increase in the concentration over that of the control. Purification of the GST on a glutathione affinity column yielded a glutathione binding protein, in addition to the GSTs. However, the amount of the glutathione binding protein in the PCB-injected quahogs was found to decrease by ~50% in comparison to the glutathione binding protein in the control quahogs.     

Novel maltotriose esters enhance biodegradation of Aroclor 1242 by Burkholderia cepacia LB400

The objective of this research was to evaluate the effect of enzymatically synthesized maltotriose fatty acid monoesters (Ferrer, M., et al. 2000 Tetrahedron 56, 4053–4061) on Aroclor 1242 solubilization and biodegradation. Three forms of the surfactant, laurate, palmitate and stearate monoester, were tested. Potential enhancement of solubilization of hydrophobic substances mediated by these non-ionic surfactants was exploited in this study. A polychlorinated biphenyl (PCB) degrading organism, Burkholderia cepacia LB400, was also selected. It was found that all surfactants were effective in solubilizing Aroclor 1242 but the rate of Aroclor 1242 biodegradation proceeded rapidly only in the presence of 6-O-palmitoylmaltotriose. For example, the addition of 48 mg 6-O-palmitoylmaltotriose/l increased the apparent solubility from 140 to 305 g/l. As a result, only 8% of the Aroclor remained at the end of 24 h incubation. In contrast, 49.2% of the Aroclor 1242 remained in the absence of surfactant. It appears that maltotriose fatty acid monoesters can significantly increase the bioavailability, and thereby accelerate the biodegradation of highly chlorinated PCBs, particularly Aroclor 1242, by Burkholderia cepacia LB400. The possibility of obtaining these biodegradable surfactants with high yield, easy recovery and high purity by using a new enzymatic methodology, makes maltotriose esters available for bioremediation purposes.     

Glycosylphosphatidylinositol (GPI) hydrolysis by Transforming Growth Factor-β1 (TGF-β1) as a potential early step in the inhibition of epithelial cell proliferation

Glycosylphosphatidylinositol (GPI) was previously identified in rabbit articular chondrocytes as being a precursor of inositolphosphate glycan (IPG), released upon (Transforming Growth Factor-) (TGF-) exposure, and capable of mimicking the proliferative effects of the growth factor. Here, using mink lung epithelial cells (CCL 64), which are known to be growth-inhibited by TGF-, we studied the potential role of GPI-derived molecules in the antiproliferative effect of TGF-1. We first identified an endogenous pool of GPI material and three different anionic forms of IPG in epithelial cells pre-labeled with [3H] glucosamine. Shortly (8 min) after TGF-1 addition, the cells responded by a rapid and transient hydrolysis of GPI, accompanied by the release of the most anionic form of IPG. This TGF--released IPG, after partial purification, was shown to decrease the proliferation of CCL 64 cells. Moreover, anti-IPG antibodies reduced the effects of TGF- and blocked the effects of partially purified IPG. These data strongly suggest that GPI hydrolysis may be an early step of the TGF- signalling pathway involved in growth inhibition of epithelial cells.     

The effects of prenatal PCBs on adult female paced mating reproductive behaviors in rats

Polychlorinated biphenyls (PCBs) are a family of toxicants that persist in measurable quantities in human and wildlife tissues, despite their ban in production in 1977. Some PCB mixtures can act as endocrine disrupting chemicals (EDCs) by mimicking or antagonizing the actions of hormones in the brain and periphery. When exposure to hormonally active substances such as PCBs occurs during vulnerable developmental periods, particularly prenatally or in early postnatal life, they can disrupt sex-specific patterning of the brain, inducing permanent changes that can later be manifested as improper sexual behaviors. Here, we investigated the effects of prenatal exposure to the PCB mixture Aroclor (A) 1221 on adult female reproductive behaviors in a dose-response model in the Sprague-Dawley rat. Using a paced mating paradigm that permits the female to set the timing of mating and control contact with the male during copulation, we were able to uncover significant differences in female-typical sexual activities in A1221-exposed females. Specifically, A1221 causes significant effects on mating trial pacing, vocalizations, ambulation and the female's likelihood to mate. The results further demonstrate that the intermediate treatment group has the greatest number of disrupted endpoints, suggestive of non-linear dose responses to A1221. These data demonstrate that the behavioral phenotype in adulthood is disrupted by low, ecologically relevant exposures to PCBs, and the results have implications for reproductive success and health in wildlife and women.     

Cellular and molecular mechanisms mediating the effects of polychlorinated biphenyls on oocyte developmental competence in cattle.

Polychlorinated biphenyls (PCBs) can interfere with normal reproductive functions acting as endocrine disruptors. Aroclor-1254 (A-1254), is a pool of more than 60 congeners used for in vitro studies because its composition is representative of PCBs environmental pollution. We previously demonstrated that the exposure of bovine oocytes to A-1254 during in vitro maturation (IVM) was detrimental not only to the maturation process but also induced a significant increase of polyspermy and a reduction of developmental competence. Therefore, we investigated whether A-1254 acts on two processes that occur during IVM and may be related with its negative effects: maternal mRNA polyadenylation and cortical granules (CGs) migration and exocytosis. Bovine cumulus-oocyte complexes (COCs) were exposed to 0.1 microg/ml of A-1254 during IVM, a level of exposure known to affect oocyte maturation, fertilization, and developmental competence. Oocyte exposure to A-1254 altered the poly(A) tail length of 5 out of 10 genes examined. PCBs effect on mRNA polyadenylation was different depending on the gene considered and resulted either in a shorter or in a longer poly(A) tail. At the end of maturation, Aroclor treated oocytes presented clustered CG in a significantly higher percentage than the control group. In addition, CG exocytosis after 8 hr of fertilization occurred at significantly lower extent in zygotes derived from the exposed group compared to control. Our results indicated that the lower developmental competence of oocytes exposed to PCBs during IVM can be related to the interaction of these contaminants with mechanisms regulating maternal mRNA storage in the ooplasm and normal CGs function.     

Glutamate antagonism fails to reverse mitochondrial dysfunction in late phase of experimental neonatal asphyxia in rats

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.     

The nature of the cellulose-binding domain effects the activities of a bacterial endoglucanase on different forms of cellulose

Abstract The hybrid Pseudomonas cepacia strain JHR22 was tested for its ability to degrade Aroclor 1221 in soil. The influence of supplements—mineral salts and trace elements—on the degradation was investigated. Disapperance of Aroclor 1221 congeners, occurence of metabolites, and release of chloride were measured under different conditions. After 45 days the hybrid organism, strain JHR22, was still present at high numbers in soil, independently of whether the soil had been sterilized prior to inoculation or not. There was only a minor difference in degradation efficiency between sterilized and untreated soil with about 70% release of chloride when 10⁷ cells/g soil were inoculated. The whole hybrid pathway, originating from three different strains, was found to be stable under the conditions tested. Mineral salts did not significantly affect the degradation rate or survival of the hybrid strain.     

Degradation of Aroclor 1221 and survival of strains in soil microcosms

Three bacterial strains able to use different aromatic compounds as the sole carbon and energy source were tested for their potential to degrade Aroclor 1221 in soil microcosms when present in mixed culture. Disappearance of polychlorinated biphenyls (PCBs), occurrence of metabolites, release of chloride, and survival of the laboratory-selected strains were investigated under different conditions. In principle, complete mineralization of various congeners of Aroclor 1221, a technical mixture of PCBs, by the mixed culture was possible. The autochthonous microflora negatively affected the degradation due to formation of a toxic compound from 4-chlorobenzoate. 4-Chlorobenzoate was produced by one of the added strains, Pseudomonas sp. JHK, during degradation of 4-chlorobiphenyl. The unknown metabolite of 4-chlorobenzoate led to a rapid decrease in viable counts of the laboratory-selected strains in the soil microcosm.Correspondence to: J. Havel     

Metabolic study of 7-methylbenzo[a]pyrene with rat liver microsomes: Separation by reversed-phase and normal-phase high performance liquid chromatography and characterization of metabolites

The 7-methylbenzo[a]pyrene (7-MBaP) was incubated with liver microsomes of rats pretreated with polychlorinated biphenyls (Aroclor 1254) (PCBs). Metabolites of 7-MBaP were isolated by both reversed-phase and normal-phase high performance liquid chromatography (HPLC) and were characterized by nuclear magnetic resonance, UV-visible and mass spectral analyses. The predominant metabolite of 7-MBaP was found to be 3-hydroxy-7-methylbenzo[a]pyrene (3-hydroxy-7-MBaP). Other identified metabolites include 7-MBaP 4,5-, 7,8-, and 9,10-trans-dihydrodiols, 7-hydroxymethyl-BaP, 7-hydroxymethyl-BaP trans-9,10-dihydrodiol, 9-hydroxy-7-MBaP, 3-hydroxy-7-hydroxymethyl-BaP, 7-MBaP 1,6- and 3,6- quinones, and a hydroquinone which is also formed by further metabolism of the 3-hydroxy-7-MBaP. Comparative metabolic studies of 7-MBaP and BaP indicated that, relative to that of BaP, the methyl substituent of 7-MBaP slightly increases the formation of 3-hydroxy-7-MBaP and decreases the metabolism at other regions of the 7-MBaP molecule. The finding that a 7,8-dihydrodiol is a metabolite indicates that, like BaP, 7-MBaP may also be activated to the potentially reactive 7,8-dihydrodiol 9,10-epoxides although their formations are significantly reduced.