Enantiomeric Enrichment of 2,2′,3,3′,6,6′-Hexachlorobiphenyl (PCB 136) in Mice After Induction of CYP Enzymes

Several PCB congeners, present in commercial PCB formulations, are chiral. These PCBs can undergo enantiomeric enrichment in many animal species and in humans due to currently uncharacterized enantioselective biotransformation processes. To investigate if certain cytochrome P-450 enzymes (CYPs), such as CYP2B’s, are responsible for this enantiomeric enrichment, we investigated the enantioselective disposition of (±)-PCB 136 in female mice after induction of different CYP enzymes by pretreatment with corn oil alone, β-naphthoflavone (CYP1A’s), phenobarbital (CYP2B’s), or dexamethasone (2B’s and 3A’s), followed by oral PCB administration. PCB 136 levels were significantly lower in phenobarbital- and, to a lesser extent, in dexamethasone-pretreated animals, presumably due to the induction of PCB 136 metabolizing enzymes. Although (+)-PCB 136 was enriched in all tissues, none of the pretreatments altered the enantioselective disposition of PCB 136 in a manner that suggests a particular CYP subfamily as the cause of the enrichment of (+)-PCB 136. Fecal PCB levels and enantiomeric fraction values changed over time in a manner consistent with slower digestive motility in the mice pretreated with phenobarbital and dexamethasone. Overall, this study does not support the hypothesis that metabolism by CYP2B enzymes is responsible for the enrichment of (+)-PCB 136 in mice.     

Toxicity of 3,4,5,3′,4′,5′-hexachlorobiphenyl to mink

Diets supplemented with 0.01 or 0.05 ppm (mg/kg) of 3,4,5,3,4,5-hexachlorobiphenyl (345-HCB) were fed to mink to investigate the toxicological manifestations of this toxic polychlorinated biphenyl congener in a sensitive species. Dietary exposure of mink to 0.05 ppm 3,4,5,3,4,5-hexachlorobiphenyl for 135 days resulted in 50% mortality while no deaths occurred on 0.01 ppm 345-HCB. Clinical signs of toxicity included anorexia, bloody stools, disrupted molting patterns, and thickened, elongated and deformed nails. Ascites and gastric ulcers were present in animals that died. Statistically significant increases in liver, kidney, and adrenal gland weights were found in the 345-HCB-treated mink. Decreases in total and free triiodothyronine concentrations were observed in mink fed the 345-HCB-treated diets and total thyroxine was decreased in the mink fed 0.05 ppm 345-HCB. No consistent histopathologic lesions were found in the thyroid or adrenal glands of the 345-HCB-treated mink, nor were there any statistically significant differences between the 345-HCB-treated and the control mink in serum epidermal growth factor levels, plasma 17-estradiol and progesterone concentrations, hepatic aminopyrine N-demethylase, and benzo()pyrene hydroxylase activities, hypothalamic norepinephrine, dopamine, and serotonin concentrations or in the incorporation of (³H) thymidine by concanavalin-A-stimulated lymphocytes.Published with the approval of the Michigan Agricultural Experiment Station as Journal Article Number11963.     

Tissue Distribution of Methylsulfonyl Metabolites Derived from 2,2′,4,5,5′-Penta- and 2,2′,3,4′,5′,6-Hexachlorobiphenyls in Rats

The time courses of fecal excretion and tissue distribution of metabolites derived from 2,2′,4,5,5′-pentachlorobiphenyl (CB101) and 2,2′,3,4′,5′,6-hexachlorobiphenyl (CB149) were investigated in male Wistar rats. The metabolism of both congeners involved primarily hydroxylation at the 3-position, and methylthiolation at the 4-position. Metabolites distributed in tissue were dominated by different ratios of 3- and 4-methylsulfonyl (MeSO₂) metabolites. The 3-/4-MeSO₂ metabolite ratios in liver and adipose tissue for both congeners were 0.41–0.61 at day 4, and then increased to 0.85–1.00 for up to day 42. In contrast, the ratios in lung were 0.03–0.04, and then decreased to 0.01. Compared to the unchanged PCBs at day 42, the distribution ratios of 3-MeSO₂ metabolites were greater in the order of liver (0.46 for CB101 and 0.21 for CB149) > kidney > blood > lung > adipose tissue, whereas those of 4-MeSO₂ metabolites were in the order of lung (9.50 for CB101 and 4.00 for CB149) > kidney > blood > liver > adipose tissue, indicating the different binding affinity of 3-MeSO₂ metabolites in liver from that of 4-MeSO₂ metabolites in lungs of rats. Furthermore, the structure-tissue affinity relationship for 3-MeSO₂ metabolites was investigated, following the administration of 11 3-MeSO₂-PCB congeners to rats. The results indicated that the retention potential of 3-MeSO₂ metabolites in the liver largely depends on the ortho-chlorine substitution in the biphenyl ring rather than the degree of chlorination. Received: 17 July 1998/Accepted: 11 January 1999     

Temperature-dependent elimination of 2,4,6,2′, 4′-pentachloro[U-14C]biphenyl inNereis virens (Polychaeta)

Four groups of 22 to 24 sandworms,Nereis virens, were maintained in closed aquarium systems with continuous charcoal filtration and 45 L capacity at 20% salinity and 4, 8, 12, and 16°C. The worms of 2.0 to 5.4 g initial wet weight inhabiting glass tubes were given 10 oral doses of 0.3g 2,4,6,2,4-pentachloro[U-¹⁴C]biphenyl (PCB) during 10 consecutive days and were subsequently allowed to eliminate the compound for up to 45 weeks. Consumption and accumulation averaged 80.9, 78.3, 73.5, and 68.4% at the four temperatures. The elimination may be described with an exponential function and was fastest at 12°C. For instance, the times of initial 30% decrease t_e30 were 18.7, 16.8, 5.3, and 8.0 weeks at 4, 8, 12, and 16°C. Forty to 45% of the eliminated PCB were recovered from the feces, and the amounts from the feces confirmed the optimum PCB elimination at 12°C. The elimination optimum at submaximum temperatures suggests that PCB elimination byNereis virens, at least in part, is an active process. By comparison with earlier work, a dependence of the elimination times t_e30 or t_e50 on initial concentration was found thus favoring a multicompartment elimination model. Unequal PCB contents of anterior and posterior worm parts were governed by unequal lipid contents.     

The Effects of 3,3′,4,4′,5-Pentachlorobiphenyl (PCB 126) on Mink (<Emphasis Type="Italic">Mustela vison</Emphasis>) Reproduction and Kit Survivability and Growth

This study was conducted to determine if dietary exposure to 3,3′4,4′,5-pentachlorobiphenyl (PCB 126) would have an adverse effect on the reproductive performance of female mink (Mustela vison) and survivability and growth of their kits. Standard dark, female mink were fed diets containing PCB 126 at concentrations of 0, 0.24, 2.4, and 24 μg PCB 126/kg feed (0, 24, 240 and 2,400 ng 2,3,7,8-tetrachlorodibenzo-p-dioxin [TCDD] toxic equivalents [TEQs]/kg, respectively) from 21 days prior to breeding until weaning of their kits at six weeks of age. There were no significant differences in the number of females that whelped or the average litter size between the control group and the 0.24 μg PCB 126/kg feed group. In addition, kit body weights at birth and at three, six and 28 weeks of age as well as kit survivability through weaning were similar between the two groups. In contrast, female mink fed diets containing 2.4 and 24 μg PCB 126/kg feed that had confirmed matings, failed to whelp. Histological examination of their uterine horns verified fetal implantation sites or placental scars, which indicated partial fetal development. Based on the impaired reproductive performance reported in this study, a no observable adverse effect level (NOAEL) of 0.24 μg PCB 126/kg feed (24 ng TEQs/kg) and a lowest observable adverse effect level (LOAEL) of 2.4 μg PCB 126/kg feed (240 ng TEQs /kg) were determined.     

Occurrence of Selected Polybrominated Diphenyl Ethers and 2,2′,4,4′,5,5′-Hexabromobiphenyl (BB-153) in Sewage Sludge and Effluent Samples of a Wastewater-Treatment Plant in Cape Town,South Africa

The reuse of treated effluent from wastewater treatment plants (WWTPs) as alternative water source for sport-field or landscape irrigation, agricultural, and other industrial purposes is growing significantly. Similarly, the application of treated sludge (biosolid) to agricultural soils is now being considered globally as the most economic means of sludge disposal. However, the presence of emerging organic contaminants in these matrices, including polybrominated diphenyl ethers (PBDEs), which are potential endocrine disruptors, portends a high health risk to humans and the environment in general. In this study, effluent and sewage sludge samples collected from a WWTP were analysed for some selected PBDE congeners (BDE congeners 28, 47, 99 100 153 154 183, and 209) as well as BB-153 using a high-capillary gas chromatograph equipped with an electron capture detector. The sum of the eight PBDE congeners ranged from 369 to 4370, 19.2 to 2640, and 90.4 to 15,100 ng/l for raw water, secondary effluent, and final effluent, respectively. A similar result was observed for sewage sludge samples, which ranged between 13.1 and 652 ng/g dry weight (dw). The results obtained for BB-153 were generally lower compared with those found for most PBDE congeners. These ranged from ND to 18.4 ng/l and ND to 9.97 ng/g dw for effluents and sewage sludge, respectively. In both matrices, BDE 47 and 209 congeners were found to contribute significantly to the overall sum of PBDEs. The reuse of the treated effluent, particularly for agricultural purposes, could enhance the possibility of these contaminants entering into the food chain, thus causing undesirable health problems in exposed subjects.     

Embryotoxicity of 3,3′,4,4′-tetrachloroazobenzene and 3,3′,4,4′-tetrachioroazoxybenzene in the chick embryo

The toxicity of 3,3,4,4-tetrachloroazobenzene (TCAB) and 3,3,4,4-tetrachloroazoxybenzene (TCAOB) to chick embryos was examined. TCAB or TCAOB was dissolved in corn oil and injected into the air cell of fertile chicken eggs. The time of injection had a major effect on embryo mortality as eggs injected with TCAB or TCAOB on the fourth day of incubation had a higher incidence of embryo mortality than eggs injected on days 11–13. Both TCAB and TCAOB were more toxic than all other chemicals that have been tested in the chick embryo with the exception of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Comparing the potency of the two compounds, TCAOB was more potent than TCAB in the chick embryo with an estimated LD₅₀ of 12 ng and 44 ng respectively. Rump edema was the major abnormality observed in embryos treated with either TCAB or TCAOB. Other malformations included altered feather pattern and lack of down, hemorrhage, external viscera, reduced body size, failure to withdraw the yolk sac, beak malformation, dilation of blood vessels, and monomicropthalmia. The results of this investigation suggest that both TCAB and TCAOB are teratogenic in the chick embryo.This work was presented in part at the Annual Meeting of the Society of Toxicology, San Diego, CA, March 1–5, 1981.     

Response of xenobiotic metabolizing enzymes of rainbow trout (Oncorhynchus mykiss) to the mono-ortho substituted polychlorinated PCB congener 2,3′,4,4′,5-pentachlorobiphenyl,PCB-118, detected by enzyme activities and immunochemical methods

The rnono-ortho-substituted polychlorinated PCB congener 2,3,4,4,5-pentachlorobiphenyl (PCB-118) was administered i.p. (30 mg/kg body weight) to gonadally immature rainbow trout (Oncorhynchus mykiss), of both sexes. In liver microsomes prepared from fish killed 4 days after administration, the cytochrome P450-dependent monooxygenase activities of 7-ethoxyresorufin O-deethylase (EROD), aryl hydrocarbon hydroxylase (AHH), and aldrin epoxidase (AE) were measured. In addition, NADPH-cytochrome c reductase (NCCR) was analyzed, and the content of a specific cytochrome P450 isozyme was determined with Western blotting and an enzyme-linked immunosorbent assay (ELISA) using rabbit anticod P450IA1 IgG. The monooxygenase parameters EROD and AHH were significantly induced to 558 and 268%, respectively, of the corresponding control values, while NCCR and AE activities were not affected. The antibodies to cod P450IA1 recognized a single protein band (M_r = 58 000 D) in the rainbow trout liver microsomes. The ELISA absorbance of this protein in the PCB-118 treated fish was 401% of the corresponding value in the controls. These results demonstrate that PCB-118 is an effective inducer of the subfamily cytochrome P450IA1 in rainbow trout liver microsomes.     

Effects of 3,3′,4,4′-tetrachloroazoxybenzene on selected immune parameters of the mouse

The effects of 3,3,4,4-tetrachloroazoxy-benzene (TCAOB) on the immune system of mice was examined and compared with cyclophosphamide (CY). This chemical can be produced as a result of microbial degradation of commonly used chloroaniline herbicides. Herbicides of the acylan-iline class generally have a low mammalian toxicity while remaining relatively inexpensive. Therefore, TCAOB could be formed anywhere in the environment where choroaniline pesticides are used. TCAOB treatment caused thymic atrophy and a decrease in white blood cell (WBC) count after sheep red blood cell (SRBC) immunization. A decline in the number of Lyt-1⁺ cells (T-helper lymphocytes) was seen in all TCAOB animals, with unimmunized mice also showing a decreased number of Lyt-2.2⁺ cells (T-suppressor lymphocytes). No change was found in the ratio of these two cell types. TCAOB did, however, result in a severe reduction in the number of plaque-forming-cells (PFCs) and in serum antibody concentration. CY caused a decrease in thymus weight, WBC count, the number of cells recovered per spleen, and the relative percentages of Lyt-l⁺ and Lyt-2.2⁺ cells recovered. The mice exhibited a lower lymphocyte blastogenic response to lipopolysaccharide (LPS) than control animals, but no change in Concanavalin A (Con-A) responsiveness. CY also resulted in a severe drop in the number of PFCs and the quantity of antibody produced following SRBC immunization.     

Short-Term Distribution, Metabolism, and Excretion of 2,2′,5-Tri-, 2,2′,4,4′-Tetra-, and 3,3′,4,4′-Tetrachlorobiphenyls in Prepubertal Rats

The excretion and tissue retention of three ¹⁴C-labeled lower chlorinated biphenyls were examined in prepubertal male and female Sprague-Dawley rats following IV administration. Urine and feces were collected individually at different time intervals up to 72 h for pharmacokinetic analyses. After 72 h, different organs were removed and extracted in acetone:hexane (1:1, v/v) to determine radioactivity. Within the first 10 h after dosing, 2,2′,5-trichlorobiphenyl (PCB 18) was rapidly excreted in urine (8–18% of the administered dose), whereas only 0.6–0.8% of 2,2′,4,4′-tetrachlorobiphenyl (PCB 47) and 0.3–0.8% 3,3′,4,4′-tetrachlorobiphenyl (PCB 77) were found in urine during this time period. The half-life of elimination was shortest for PCB 18 (37.5 to 49.2 h). The half-lives for PCB 47 and PCB 77 were 351 to 672 h and 152 to 186 h, respectively. The cumulative total excretion (urinary + fecal) of PCB 18 within 72 h was 51–62%, of PCB 77 was 22–25%, and of PCB 47 was 7–10%. No parent PCBs were detected in urine. PCB 47 accumulated preferentially in adipose tissues (subcutaneous fat > mesenteric fat); relatively high levels of PCB 47 were also found in adrenals, ovaries, lungs, liver, and skin. The highest concentration of PCB 77 was found in serum, followed by adipose tissues. Very low concentrations of PCB 18 were found in most tissues; the highest being found in serum, followed by ovaries and adrenal glands. This study suggests that prepubertal rats retain higher short-term serum levels and have lower excretion rates than adult rats. Received: 3 February 1998/Accepted: 16 August 1998     

Toxicities of 2,2′,4,4′- and 3,3′,4,4′-tetrachlorobiphenyls to house flies at different ages and enzyme levels

Two tetrachlorobiphenyls (2,2,4,4-tetraCB and 3,3,4,4-tetraCB) had different effects on the longevity of adult female house flies (Musca domestica), depending on enzyme levels at dosing. Twenty-four-hour acute toxicities of the two tetrachlorobiphenyls were also compared with one trichlorobiphenyl (2,2,5-triCB) at different enzyme levels. 2,2,4,4-tetraCB killed more than 90% of the flies within 12 h at the highest dose (1,667 ppm, g/g); however, the toxicity of the moderate dose (1,250 ppm) was age-dependent and greater in 1- and 15-day-old flies and lower in 5-day-old flies. Daily mortality patterns of the lower doses (390 and 833 ppm) were similar to the control. LT₅₀s (time for 50% death) were also different in different age groups at the moderate dose. The toxicity of 3,3,4,4-tetraCB was similar to the control in all age groups, with a slight increase in the early mortalities and a decrease in the LT₅₀s at the highest (1,200 ppm) dose.The twenty-four-hour lethality of 2,2,4,4-tetraCB was very high, even at the lower doses in 1- and 15-day-old flies. Lower doses were least toxic at day 5, when the levels of cytochrome P₄₅₀ enzymes were at the highest. On the other hand, the acute toxicity of 2,2,5-triCB increased from 5 and 15% in 1- and 15-day-old flies, respectively, to about 50% in 5-day-old flies, suggesting bioactivation of 2,2,5-triCB. The acute toxicity of 3,3,4,4-tetraCB was negligible in all ages of house flies.     

Validity and reliability of the Chinese (Singapore) version of the Parkinson’s Disease Questionnaire (PDQ-39)

Objective: The purpose of the study was to validate the Chinese (Singapore) version of the Parkinson’s Disease Questionnaire (PDQ-39CSV) and its briefer version (PDQ-8CSV). Methods: A convenience sample of Chinese-speaking Singaporeans with Parkinson’s disease (PD) (n=63) completed a questionnaire containing the PDQ-39CSV and the Chinese (Singapore) EQ-5D. A subgroup also participated in a retest and/or a focus group discussion. A priori hypotheses were tested by examining correlations between PDQ-39CSV, PDQ-8CSV and EQ-5D scores and using principal component factor analysis. Reliability was assessed using Cronbach’s α and intra-class correlation coefficients (ICC). Results: Thirty-two PDQ-39CSV items correlated satisfactorily with their hypothesized dimensions (Spearman’s ρ ≥ 0.4). Factor analysis yielded a component on which all 8 PDQ-39CSV dimensions were substantially loaded (loading range: 0.53–0.89). As hypothesized, the PDQ-39CSV and PDQ-8CSV summary indices were highly correlated (Pearson’s r:0.95, ICC:0.94); correlations between related PDQ and EQ-5D scores were generally strong (Spearman’s ρ: 0.38–0.76, p<0.001 for all). Cronbach’s α values ranged from 0.64 to 0.90 and ICC values from 0.66 to 0.86. Conclusion: This study provides preliminary evidence supporting validity and reliability of both the PDQ-39CSV and its briefer version.     

The alcohol-preferring (P) and high-alcohol-drinking (HAD) rats – Animal models of alcoholism

The objective of this article is to review the literature on the utility of using the selectively bred alcohol-preferring (P) and high-alcohol-drinking (HAD) lines of rats in studies examining high alcohol drinking in adults and adolescents, craving-like behavior, and the co-abuse of alcohol with other drugs. The P line of rats meets all of the originally proposed criteria for a suitable animal model of alcoholism. In addition, the P rat exhibits high alcohol-seeking behavior, demonstrates an alcohol deprivation effect (ADE) under relapse drinking conditions, consumes amounts of ethanol during adolescence equivalent to those consumed in adulthood, and co-abuses ethanol and nicotine. The P line also exhibits excessive binge-like alcohol drinking, attaining blood alcohol concentrations (BACs) of 200 mg% on a daily basis. The HAD replicate lines of rats have not been as extensively studied as the P rats. The HAD1,2 rats satisfy several of the criteria for an animal model of alcoholism, e.g., these rats will voluntarily consume ethanol in a free-choice situation to produce BACs between 50 and 200 mg%. The HAD1,2 rats also exhibit an ADE under repeated relapse conditions, and will demonstrate similar levels of ethanol intake during adolescence as seen in adults. Overall, the P and HAD1,2 rats have characteristics attributed to an early onset alcoholic, and can be used to study various aspects of alcohol use disorders.     

Effect of fipronil on brain and muscle ultrastructure of Nilaparvata lugens (Stål) (Homoptera: Delphacidae)

The ultrastructure of Nilaparvata lugens brain cells was damaged by treatment at different fipronil concentrations. The cell showed swollen mitochondria and vacuolization, but no mitochondrial cristae. Rough endoplasmic reticulum (RER) fragmentation and degranulation were seen. The dilatation of endoplasmic reticulum cisterns was very prominent, and the predominant lamellar RERs were arranged chaotically. The Golgi apparatus demonstrated obvious changes in configuration, as dilated with closed cisternae and atypical vesicles. The mitochondria mainly showed large vacuolization in muscles. Nuclear degeneration and condensation and increased numbers of large hydropic vacuoles and lysosomes were observed. It was concluded that the effect on cellular components was fipronil-specific. Changes in cellular ultrastructure seem to be an appropriate ecotoxicological indicator of the insecticide's efficacy.