ISSN:0730-7268    

DOI:10.1002/etc.5620100601

出版商:Wiley Periodicals, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThese studies were carried out to determine if oils obtained from wild fish populations were contaminated with polychlorinated‐p‐dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) and, if they were contaminated, would they result in embryo toxicity as measured by the Japanese medaka(Oryzias latipes)embryo larval bioassay (ELA). Three fish oils [Baltic herring oil (HO 1); Baltic herring oil spiked with 44 parts per trillion (pptr) of 1,2,3,7,8,9‐HxCDD, 120 pptr OCDD and 130 pptr 2,3,7,8‐TCDF (HO 2*); and a commercially available cod liver oil (CL)] and a corn oil sample were tested for embryo toxicity in a static renewal protocol. The ELA assay was selected due to its sensitivity to biological effects following dioxin and dibenzofuran exposure. Two of the fish oils (HO 1 and HO 2*) were from Baltic herring collected from the Gulf of Bothnia, Sweden, and the third was a commercially available Icelandic cod liver oil. The Baltic herring oil contained higher levels of both PCDDs and PCDFs than the cod liver oil: 2,3,7,8‐TCDD, 5X; 1,2,3,7,8‐PeCDD, 5X; 1,2,3,6,7,8‐HxCDD, 6X; 2,3,7,8‐TCDF, 3X; 1,2,3,7,8,‐PeCDF, 3X; 2,3,4,7,8‐PeCDF, 4X; 1,2,3,4,7,8/1,2,3,4,7,9‐HxCDF, 3X; 1,2,3,6,7,8‐HxCDF, 4X; and 1,2,3,4,6,7,8‐HpCDF, 2X. The HO 1 sample resulted in 30 to 90% death, whereas the HO 2* sample caused 100% death. The major lesions were hemorrhage, cardiac effects and tissue necrosis. The time to lesion occurrence and the types of lesions were similar to those observed in studies using pure 2,3,7,8‐TCDD. The rearing solution control, corn oil control and cod liver oil samples caused no mortality or lesions. The lethality and lesions caused by these oils in the ELA system were similar to those reported inSalmo Salterwith the M74‐syndrome from Sweden. The use of contaminated fish oils, therefore, may be one cause of poor viability in hatchery salmon reared in Sweden, and care should be taken when using naturally occurring fish or

ISSN:0730-7268    

DOI:10.1002/etc.5620100602

出版商:Wiley Periodicals, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractStudies of the carcinogenic activity of commercial polychlorinated biphenyl (PCB) and polybrominated biphenyl (PBB) formulations in rodents have shown that (a) when given at appropriate doses and for extended periods of time, PCB and PBB mixtures cause preneoplastic lesions and carcinomas; (b) cancerous lesions are confined principally to the liver; (c) there is a marked trend from enzyme‐altered foci to neoplastic nodules to hepatocellular carcinoma with time; and (d) PCB mixtures with high chlorine content are more potent in causing hepatocellular carcinoma than mixtures with low chlorine content. Practically no data are available on the activity of individual PCBs or PBBs as carcinogens; however, considerable data exist on the activity of congeneric PCBs and PBBs as promoters/initiators of two‐stage hepatocarcinogenesis in the rat. The compounds studied were either acutely toxic (coplanar) biphenyl congeners, nonacutely toxic congeners or halogenated biphenyls with intermediate acute toxicity. Acutely toxic PCBs/PBBs as well as those without acute toxicity and those with intermediate toxicity may all promote hepatocarcinogenesis in the rat, but probably by different mechanisms. The ability of congeneric PCBs and PBBs to stimulate cellular growth and division (mitogenic effects) on the one hand and/or hepatotoxic effects on the other most likely contributes to the carcinogenic effects seen. We assert that the assessment of risk for PCB/PBB exposure must take into account the potential long‐term toxic effects of exposure to all three groups of polyhalogenated biph

ISSN:0730-7268    

DOI:10.1002/etc.5620100603

出版商:Wiley Periodicals, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractIn 1979, rice oil contaminated with polychlorinated dibenzofurans (PCDFs) was ingested in a widespread poisoning episode in Taiwan. The PCDFs are structural analogs of 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD). TCDD and the PCDFs are thought to share the same mechanism of action that involves binding to the Ah receptor. In our studies, we compared the effects of TCDD on rat liver to effects in placentas of women exposed to PCDF‐contaminated rice oil. TCDD is a hepatocarcinogen in female rats. Measured parameters included concentrations of human placental PCDF congeners or rat liver TCDD and induction of cytochrome P‐450 isozymes, epidermal growth factor receptor (EGFR) and glucocorticoid receptor (GCR). Placentas from PCDF‐exposed women contained two PCDFs: 2,3,4,7,8‐penta CDF (100 ppt) and 1,2,3,4,7,8‐hexa CDF (400 ppt). The 2,3,4,7,8‐penta CDF binds the Ah receptor 60% as well as TCDD, and the 1,2,4,7,8‐hexa CDF binds 9% as well as TCDD. Cytochrome P1‐450 was induced approximately 100‐fold in exposed placentas. This induction was considered maximal. Placental PCDF concentrations associated with this induction were compared to the amount of hepatic TCDD required to maximally induce the rat liver homolog of P1‐450. These comparisons, accounting for differences in Ah receptor binding, suggested that humans are more sensitive than rats to the P1‐450 inductive actions of the toxic halogenated aromatics. Several assumptions are made, and their validity is discussed. As with the P1‐450, humans are more sensitive to the effects of the halogenated aromatics on EGFR (EGF‐stimulated autophosphorylation) and GCR (binding capacity) than are rats. Although the relationship of these biochemical changes to the carcinogenic effects of TCDD and its analogs is not clear, our data suggest that it is prudent to retain a conservative risk assessment for

ISSN:0730-7268    

DOI:10.1002/etc.5620100604

出版商:Wiley Periodicals, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractOur previous studies have found that early exposure to polychlorinated biphenyls (PCBs) through milk of the dam can affect fertility when male offspring reach adulthood. A significant proportion of ovulated eggs in normal females mated to PCB‐exposed males do not implant. This effect does not appear to be related to reduced weight gain of pups during PCB exposure. In this study, dams with litters were given peanut oil or a PCB mixture (Aroclor 1254) in oil at doses of 8, 16, 32 and 64 μg/g (PCBI, II, III, IV) on days 1,3,5,7 and 9 of lactation. At 120 d of age the male offspring were mated to normal females. Oviducts/uteri of sperm‐positive females were flushed and eggs examined at the expected pronuclear, two‐ to four‐cell and blastocyst stages of development. We observed either a significant decrease or a decline in number and percent of normal fertilized eggs and eggs at the two‐ to four‐cell and blastocyst stages in females mated to male offspring of PCBII, III and IV. Neither reduced ventral prostate weights nor an increased incidence of a right kidney abnormality were correlated with reduced fertility. Caudal sperm reserves, sperm production, epididymal sperm morphology and FSH levels were not affected; testosterone levels were not reduced as compared to those of controls. With one exception, epididymal sperm motility parameters were not significantly different. It appears that early postnatal exposure to PCBs affects ability of sperm to fertilize eggs but not production, morphology or motility of epid

ISSN:0730-7268    

DOI:10.1002/etc.5620100605

出版商:Wiley Periodicals, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractIn recent years, there has been growing concern about the potential long‐term neurobe‐havioral effects of perinatal polychlorinated biphenyl (PCB) exposure. We have addressed this issue in a series of studies at the Harlow Primate Laboratory. Offspring of rhesus monkeys (Macaca mulatto) exposed to commercial PCB mixtures (Aroclor 1016 or Aroclor 1248) were tested on two‐choice discrimination‐reversal learning at 1.5 years of age and on delayed spatial alternation, a spatial learning and memory task, at four to six years of age. Deficits in performance were observed on both tasks. The deficit observed on delayed spatial alternation in Aroclor 1248‐exposed monkeys was quite dramatic. The monkeys were tested for 80 test sessions, but were never able to achieve control levels of performance. This effect was observed when the monkeys were four to six years of age (young adulthood), even though they had not been exposed to PCBs since they were weaned at four months of age. The pattern of effects on both discrimination‐reversal learning and delayed spatial alternation was suggestive of damage to the prefro

ISSN:0730-7268    

DOI:10.1002/etc.5620100606

出版商:Wiley Periodicals, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe polyhalogenated aromatic hydrocarbons (PHHs), consisting of the chlorinated and brominated biphenyls, dibenzo‐p‐dioxins and dibenzofurans, are important environmental contaminants affecting both wildlife and humans. Although the biological effects due to acute or chronic exposure to these compounds have been extensively investigated with animal models, relatively little is known concerning the long‐term ramifications of such exposure due to the persistent body burdens of some PHH congeners. This review examines the persistent effects of these contaminants for two biological end points: tumor formation and induction of cytochrome P‐450‐associated mixed function oxygenases in target tissues. Literature and data are presented that indicate that retained PHH congeners continue for many months to exert biological effects that contribute to tumor development in rodent livers and lungs. Effects of specific congeners, retention profiles of these congeners in target tissues and the long‐term induction of cytochrome P‐450 IA1‐associated enzyme activity are all consistent with activation of the Ah receptor's being an integral part of the tumor pro

ISSN:0730-7268    

DOI:10.1002/etc.5620100607

出版商:Wiley Periodicals, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractInduction of liver microsomal cytochrome P450 by 3,3′,4,4′‐tetrachlorobiphenyl (TCB) was evaluated in winter flounder from two different sites, one offshore (Georges Bank) and one coastal (Narrow River, Narraganseti, Rhode Island). Immunoblot analysis of liver microsomes with monoclonal antibody 1–12–3 to scup P450E (P450IA1) revealed P450IA protein content of 0.01 nmol/mg in Georges Bank fish that were not treated with TCB. By comparison, untreated Narrow River fish had an 80‐fold greater content of immunodetected P450IA protein, indicating a strong environmental induction in these fish. In Georges Bank fish the total (spectrophotometrically measured) microsomal P450 content and the content of P450IA protein were induced progressively by intraperitoneal doses of TCB ranging from 0.1 to 10.0 mg/kg. Ethoxyresorufin‐O‐deethylase (EROD) specific activity (activity per mg protein) was also progressively induced, but the catalytic efficiency or turnover number (i.e., activity/nmol P450IA) was less in fish given the greater doses of TCB. In Narrow River fish TCB treatment resulted in no significant change (atP≤ 0.05) in total microsomal P450 content or in P450IA protein content, although they tended to be less (total P450) or greater (P450IA) in fish given the greater doses. The EROD activity per mg protein was less in Narrow River fish given greater TCB doses than it was in control fish. EROD activities per nmol of P4501A protein in control Narrow River fish were less than those in any treatment group of Georges Bank fish and tended to diminish even further with TCB treatment. The results show that 3,3′,4,4′‐TCB induces P450IA in winter flounder and that TCB acts in vivo to inhibit the activity of P450IA enzyme by mechanisms not yet known. The lower catalytic efficiency of P450IA enzyme in Narrow River fish than in Georges Bank fish indicates that P450IA inhibition, whether caused by TCB or some other agent, does occur in the environment. The data also indicate that prior condition, including existing environmental induction, can strongly influence the responses of P450IA protein to additional

ISSN:0730-7268    

DOI:10.1002/etc.5620100608

出版商:Wiley Periodicals, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe mineralization of [14C]acetate or [14C]glucose was studied in aseptic subsoil samples at 10°C. At 1 μg/L and 100 μg/L, the mineralization showed first‐order kinetics preceded by a short lag phase. For the sandy subsurface soils, the half‐lives of acetate or glucose varied from 0.5 until 21 d, whereas a peat subsoil and a sandy surface soil produced half‐lives of 11 and 1.6 h, respectively.The EC50 is the toxicant concentration that causes 50% reduction of the percentage substrate mineralized at a certain incubation time and increases with time. The time‐independent toxicant concentration IC50 gives 50% inhibition of the mineralization rate and is equal to the EC50 at short incubation times. The IC50 of pentachlorophenol varied between 0.1 and 880 mg/kg subsoil. The aerobic mineralization of acetate in surface sand showed an IC50 of 28 mg pentachlorophenol/kg. Hydrochloric acid showed IC50 values ranging from pH 6.2 to pH 2.8. For chlorite and cadmium, the IC50 values were 34 and 59 mg/kg, respectively.When soils were incubated with 100 mg acetate/L, exponential growth kinetics were observed. Under these conditions the inhibitory effect of pentachlorophenol was relatively small because the resistant part of the acetate‐mineralizing microflora could grow and replace the inhibited part. The kinetics show why toxicity tests using high substrate concentrations are less sensitive than tests using more natural low substrate concentrations. The model predicts that slow‐growing microorganisms, which are vital to the functioning of the ecosystem, would recover only very slowly from the toxic effects of environme

ISSN:0730-7268    

DOI:10.1002/etc.5620100609

出版商:Wiley Periodicals, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractBioconcentration factors, uptake rate constants and elimination rate constants of a series of organophosphorous pesticides were determined in the guppy(Poecilia reticulata).The results of these three toxicokinetic parameters were related to measured octanol/water partition coefficients (Kow). A simple one‐compartment model fitted the uptake and elimination characteristics of the chemicals. A biphasic relationship was observed between logk1(uptake rate constant) and logKow, whereas elimination rate constants were inversely related toKow. For some of the test compounds substantially higher elimination rates were found, compared to isolipophilic chlorobenzenes, which resulted in lower bioconcentration factors. This divergent behavior is discussed in view of possible biotransformation reactions for these compound

ISSN:0730-7268    

DOI:10.1002/etc.5620100610

出版商:Wiley Periodicals, Inc.    

年代:1991

数据来源: WILEY