Journal of Toxicology and Environmental Health (J Toxicol Environ Health )

Publisher: Taylor & Francis


Discontinued in 1996. Split into Journal of Toxicology and Environmental Health Part A (1528-7394) and Journal of Toxicology and Environmental Health Part B: Critical Reviews (1093-7404).

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Publications in this journal

  • [Show abstract] [Hide abstract]
    ABSTRACT: The effect of Dodine on the intestine was studied after a single administration of 1000 mg/kg, which corresponds to the LD50 in male Wistar rats. At this dose, a significant decrease in body weight was observed, accompanied by diarrhea, which may be associated with intestinal alterations. The chemical induced a significant reduction of the protein content and in sucrase activity in the jejunum. Morphological alterations included a significant decrease in crypt height and in villus length and depth. The intestinal modifications observed in animals after Dodine administration may explain the observed loss in body weight and diarrhea.
    Journal of Toxicology and Environmental Health 01/1998; 52(6):545-56.
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    ABSTRACT: The remedial investigation/feasibility studies conducted at certain Army installations showed a need to clean up contaminated sites, where high levels of ammunition chemicals such as 2,4,6-trinitrotoluene (TNT), 1,3,5-trinitrobenzene (TNB), 1,3-dinitrobenzene (DNB), and their degradation products/metabolites were detected in surface soil and groundwater. TNB is a photodegradation product of TNT; it is not easily degraded, and persists in the environment. The toxicity data on TNB are scanty. Hence the U.S. Environmental Protection Agency in 1988 (U.S. EPA, 1997) developed a reference dose (RfD) for TNB (0.00005 mg/kg/d for chronic toxicity) based on the toxicity of DNB, which is structurally similar to TNB. Since then we have completed acute, subacute, subchronic, chronic, reproductive, and developmental toxicity studies and toxicokinetics studies. We have reviewed the mammalian toxicity data for TNB and have determined the no observed adverse effect levels (NOAEL) and low observed adverse effect levels (LOAEL) for subchronic, chronic, reproductive, and developmental toxicity. Based on the newly determined NOAEL and LOAEL values, we have now developed a new RfD for TNB (0.03 mg/kg/d), based on the chronic toxic effects on hematology and histopathological changes in testes and kidney.
    Journal of Toxicology and Environmental Health 01/1998; 52(5):447-60.
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    ABSTRACT: Inhalation of diisocyanate vapors is associated with immediate-type hypersensitivity reactions and direct toxic responses. The genotoxic effects of diisocyanates have not been clarified. The aim of this study was to examine the changes in DNA following in vitro exposure to three most commonly used diisocyanates (toluene diisocyanate, TDI; methylenediphenyl-4,4'-diisocyanate, MDI; and hexamethylene diisocyanate, HDI) and to compare their binding potential using melting behavior of DNA and electrophoresis studies in DNA. Following incubation of DNA with MDI (pure and mix) and HDI we found no differences in the melting behavior compared to the control calf thymus DNA. However, DNA treated with TDI showed differences in the shape of the native DNA curves due to changes in hyperchromicity and exhibited 14% more DNA reconstitution after renaturation. The small changes in the melting behavior of native DNA do not suggest the formation of DNA intrastrand cross-links but rather conformational changes of single- and double-stranded DNA. These conformational changes were further explored by agarose electrophoresis of native and denatured calf thymus DNA. Control and all diisocyanate-exposed DNA showed no differences in the size of native DNA fragments. Conversely, electrophoresis of TDI mix-incubated DNA, following denaturation, showed a distinct reduction in the double-stranded DNA fragment size compared to the control, MDI-denatured (pure and mix), and HDI-denatured DNA. These findings may help to better understand the mechanisms of the genotoxic effect of TDI.
    Journal of Toxicology and Environmental Health 01/1998; 52(6):517-26.
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    ABSTRACT: Physiologically based pharmacokinetic (PBPK) models for pregnancy are inherently more complex than conventional PBPK models due to the growth of the maternal and embryo/fetal tissues. Physiological parameters such as compartmental volumes or flow rates are relatively constant at any particular time during gestation when an acute experiment might be conducted, but vary greatly throughout the course of gestation (e.g., contrast relative fetal weight during the first month of gestation with the ninth month). Maternal physiological parameters change during gestation, depending upon the particular system; for example, cardiac output increases by approximately 50% during human gestation; plasma protein concentration decreases during pregnancy; overall metabolism remains fairly constant. Maternal compartmental volumes may change by 10-30%; embryo/fetal volume increases over a billionfold from conception to birth. Data describing these physiological changes in the human are available from the literature. Human embryo/fetal growth can be well described using the Gompertz equation. By contrast, very little of these same types of data is available for the laboratory animal. In the rodent there is a dearth of information during organogenesis as to embryo weights, and even less organ or tissue weight or volume data during embryonic or fetal periods. Allometric modeling offers a reasonable choice to extrapolate (approximately) from humans to animals; validation, however, is confined to comparisons with limited data during the late embryonic and fetal periods of development (after gestation d 11 in the rat and mouse). Embryonic weight measurements are limited by the small size of the embryo and the current state of technology. However, the application of the laser scanning confocal microscope (LSCM) to optically section intact embryos offers the capability of precise structural measurements and computer-generated three-dimensional reconstruction of early embryos. Application of these PBPK models of pregnancy in laboratory animal models at teratogenically sensitive periods of development provides exposure values at specific target tissues. These exposures provide fundamentally important data to help design and interpret molecular probe investigations into mechanisms of teratogenesis.
    Journal of Toxicology and Environmental Health 01/1998; 52(5):385-401.
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    ABSTRACT: The chlorinated acetic acids monochloroacetic acid (MCA) and trichloroacetic acid (TCA) are found as chlorine disinfection by-products in finished drinking-water supplies. TCA has been demonstrated to be a mouse liver carcinogen. A chronic study in which male Fischer 344/N rats were exposed for 104 wk to TCA and MCA in the drinking water is described. Animals, 28 d old, were exposed to 0.05, 0.5, or 2 g/L MCA, or 0.05, 0.5, or 5 g/L TCA. The 2.0 g/L MCA was lowered in stages to 1 g/L when the animals began to exhibit signs of toxicity. A time-weighted mean daily MCA concentration (MDC) of 1.1 g/L was calculated over the 104-wk exposure period. Time-weighted mean daily doses (MDD) based upon measured water consumption were 3.5, 26.1, and 59.9 mg/kg/d for 0.05, 0.5, and 1.1 g/L MCA, respectively; TCA MDD were 3.6, 32.5, and 363.8 mg/kg/d. Nonneoplastic hepatic changes were for the most part spontaneous and age related. No evidence of hepatic neoplasia was found at any of the MCA or TCA doses. The incidence of neoplastic lesions at other sites was not enhanced over that in the control group. Drinking water concentrations of > or = 0.5 g/L MCA produced a moderate to severe toxicity as reflected by a depressed water consumption and growth rate. A no-observed-effects level (NOEL) for carcinogenicity of 0.5 g/L (26.1 mg/kg/d) MCA was calculated. TCA at drinking water levels as high as 5 g/L produced only minimal toxicity and growth inhibition and provided a NOEL of 364 mg/kg/d. Our results demonstrate that under the conditions of this bioassay, MCA and TCA were not tumorigenic in the male F344/N rat.
    Journal of Toxicology and Environmental Health 01/1998; 52(5):425-45.
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    ABSTRACT: To date, numerous correlative studies have implicated metallothionein in the detoxification of heavy metals and in the regulation of metal distribution within an organism. In the present study cadmium-binding proteins (metallothionein equivalents), cadmium acute toxicity, and cadmium distribution in tissues and subcellular fractions were compared in metallothionein-I and -II deficient (MT-/-) mice and the parental strain carrying intact metallothionein genes (MT+/+) to determine if the absence of metallothionein altered any of these parameters. In an uninduced state, MT-/- mice expressed lower levels of cadmium-binding proteins relative to MT+/+ mice in several tissues. Administration of zinc enhanced the levels of cadmium-binding proteins in liver, small intestine, kidney, pancreas, and male sex organs, but not in cecum or brain of MT+/+ mice compared to zinc pretreated MT-/- mice. The cadmium LD50 was similar for MT-/-, MT+/+, and zinc-pretreated MT-/- mice (15-17 mumol CdCl2/kg body weight delivered i.p.). However, zinc-pretreated MT+/+ mice had a cadmium LD50 of 58-63 mumol CdCl2/kg body weight. Over two-thirds of cadmium was found in liver, cecum, small intestine, and kidney in both MT+/+ and MT-/- mice; therefore, metallothionein levels do not appear to play a major role in the tissue distribution of cadmium. However, after zinc pretreatment, MT+/+ mice accumulated more cadmium in the liver and less in other tissues, whereas the amount of cadmium in the liver was not altered by zinc pretreatment in MT-/- mice. In general, the cytosolic/particulate ratio of cadmium was significantly higher in tissues of noninduced MT+/+ mice relative to MT-/- mice. This difference was accentuated after zinc pretreatment. Together these results indicate that basal levels of metallothionein do not protect from the acute toxicity of a single i.p. cadmium challenge. Furthermore, it does not appear that the cytosolic compartmentalization of cadmium is correlated with reduced toxicity.
    Journal of Toxicology and Environmental Health 01/1998; 52(6):527-43.
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    ABSTRACT: Compressed breathing air, used in self-contained breathing apparatus (SCBA) by firefighters and other categories of workers as well as by recreational and commercial divers, is prepared with the aid of high-pressure compressors operating in the range of 5000 psig. There have been reports of unexplained deaths of SCUBA divers and anecdotal accounts of decreased time to exhaustion in firefighters using SCBAs. Compressed breathing air has been found to contain elevated levels of carbon monoxide (CO) and water vapor that are consistent with carboxyhemoglobin (COHb) poisoning and freezing of the user's regulator on the breathing apparatus. The Coburn-Forster-Kane equation (CFK equation) was used to estimate COHb levels at rest and at maximum exercise when exposed to different levels of CO in contaminated breathing air. The results demonstrated that, at maximum exercise, the COHb ranged from 6.0 to 17% with the use of 1 to 4 SCBA cylinders contaminated by 250 ppm CO. Standard operating procedures have been developed at the Montreal Fire Department to minimize the risk of compressed breathing air contamination. Results of the quality analysis/quality control program indicate that implementation of these procedures has improved the quality of the compressed breathing air. Recommendations are made for improvement of the air testing procedures mandated by the Canadian CAN3 180.1-M85 Standard on Compressed Breathing Air and Systems.
    Journal of Toxicology and Environmental Health 01/1998; 52(5):403-23.
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    ABSTRACT: Cypermethrin is a synthetic pyrethroid that belongs to a group of insecticides with low mammalian toxicity but high insecticidal activity. The present study was designed to investigate the toxicity of cypermethrin on freshly isolated hepatocytes from male and female rats. Hepatocytes were harvested by a collagenase perfusion technique and were exposed to different concentrations of cypermethrin (100, 200, 400, or 800 ng/2 x 10(6) cells) for up to 2 h. Cell viability and the leakage of aspartate transaminase (AST) and alanine transaminase (ALT) were determined throughout the incubation period. The cell viability of the hepatocytes from male and female rats exposed to 400 ng and 800 ng was significantly reduced after 60 and 30 min of incubation, respectively. With cells from female rats, viability was also reduced upon exposure to 200 ng cypermethrin for 2 h. The decrease in cell viability was dose and time dependent. The leakage of ALT and AST was significantly increased with 400 and 800 ng concentrations at 60 and 30 min, respectively. ALT leakage from female hepatocytes was significantly increased at 60 min of incubation with the 200-ng dose, whereas 2 h of incubation was required for the leakage of ALT from the cells of male rats. The present data indicate that cypermethrin has toxic effects on male and female rat hepatocytes in a dose- and time-dependent manner. The data suggest that female rat hepatocytes may be more sensitive to the toxic effects of cypermethrin than male cells.
    Journal of Toxicology and Environmental Health 01/1998; 52(5):461-74.
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    ABSTRACT: This article estimates the potential exposure of estuarine organisms to two pesticides (azinphosmethyl and fenvalerate) in a tidal stream of Leadenwah Creek near the Edisto River, South Carolina, during four runoff episodes. Exposure is calculated from simulation runs of the one-dimensional transport equation solved by an implicit finite difference method. Calibration was done for each episode by adjusting three conditions (runoff starting time, duration, and flow) and a correction to the dispersion coefficient in order to match the continuously measured salinity transients. First-order rate constants used by the fate component were calculated from half-life values reported in the literature. Baseline scenarios for each episode and each pesticide were derived by using the same conditions obtained in the salinity runs and adjusting the pesticide loading in order to mimic the few data points of measured pesticide concentrations. In all baseline scenarios, pesticide concentration rises following the initial burst of runoff (also noticeable as an abrupt drop in salinity) and then oscillates, forced by the tidal cycle. These oscillations are dominated by transport, while fate imposes a secular decaying trend. Ten additional scenarios for each episode were obtained from the baseline scenario by randomly varying three pesticide load parameters (starting time and duration of runoff, and pesticide discharge) using a Latin hypercubes design. Two exposure metrics were calculated from the simulated and the measured pesticide concentration: maximum and time average, which was obtained by integrating the curve and dividing by the time period. The metrics calculated from the baseline runs are relatively close to the data-derived metrics, because the baseline runs attempted to mimic the data. For each one of the two metrics and all pesticide-episode combinations, several statistics of the set of 11 scenarios were also calculated: minimum and maximum, mid-range, mean, standard deviation, and median. The mean +/- standard deviation interval of the simulation-derived value consistently brackets the data-derived value for the maximum metric, but not for the time-average metric. This may indicate that even if the maximum value is correctly captured in the field sample, the time-average exposure could be in error when calculated directly from the field data due to undersampling of the pesticide time series. The methodology developed here attempts to reconstruct the possible exposure from the sparse sampling of the pesticide concentration during the runoff episodes; only when the number of field samples is high and regularly spaced is it possible to have confidence in the reconstruction of the curve. The shape of the curve cannot be inferred from the field measurements alone; as expected, tidal movement makes the pesticide concentration swing up and down. This result has important implications because the biological community would be subject to repetitive pulses of exposure to the chemicals. The baseline simulations can be used to derive a pulse-exposure metric by calculating the sum of ratios of the time average of the threshold-exceeding concentrations to the time average of the toxic threshold during intervals of above-threshold concentration. This metric is species specific and extrapolates laboratory toxicity data in order to compare pulse exposure to mortality rates measured in the field.
    Journal of Toxicology and Environmental Health 12/1997; 52(4):295-316.
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    ABSTRACT: The presence of organochlorine pesticides, such as p,p'-DDT[2,2-bis(p-chlorophenyl)-1,1,1-trichloroethanel, and of polychlorinated biphenyls (PCBs) in human serum and adipose tissue has been reported in many studies over the last four decades. Recently, debate has heightened concerning the link of these compounds to breast cancer. To clarify and resolve this issue, accurate analytical residue data must be obtained. Separation of the organochlorine pesticides from the PCBs in breast tissue is critical to obtaining valid residue data. Based on methods refined in the Analytical Laboratory at Colorado State University, accurate residue levels were established for nine individual PCB congeners and eight organochlorine pesticides. The breast adipose tissue method used was a modification of the Mills et al. and de Faubert Maunder et al. methods. The serum method employed was a modification of the Burse et al. method. Both breast adipose tissue and serum from 36 women were analyzed, and correlations of the residues from the two substrates were evaluated. Serum concentrations of p,p'-DDE, the primary metabolite of p,p'-DDT, were correlated (alpha = .05) with the concentrations of p,p'-DDE in human breast adipose tissue (r = .808). Serum concentrations of the PCB congener BZ 153 were also significantly correlated to the human breast adipose tissue concentrations of BZ 153 (r = .377). No significant relationship was found between serum concentrations and tissue residues for 15 of the 17 compounds analyzed. This lack of correlation between breast adipose tissue and serum, as well as an absence of the compound residues in serum, emphasized that adipose tissue should be analyzed in addition to serum to fully understand the relationship of the organochlorine compounds to breast cancer.
    Journal of Toxicology and Environmental Health 12/1997; 52(4):285-93.
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    ABSTRACT: The stability of the saliva/plasma (S/P) concentration ratio of atrazine was determined under varying conditions of salivary flow rate and plasma concentration of atrazine in Sprague-Dawley rats. In the salivary flow study, whole saliva samples were collected at different salivary flow rates while the plasma concentration of atrazine was maintained at a steady-state level of approximately 150 micrograms/L. In the plasma level study, whole saliva samples were collected at two steady-state plasma concentrations of atrazine (50 and 250 micrograms/L), while salivary flow rate was maintained at a relatively constant level. In both studies, atrazine concentrations in whole saliva and arterial plasma demonstrated a consistent relationship, but salivary concentrations were always lower than those of arterial plasma. Linear regression analysis demonstrated that the S/P concentration ratio of atrazine was not significantly different for salivary flow rates ranging from 23 to 92 microL/min/kg body weight, and did not vary for atrazine plasma concentrations between 30 and 433 micrograms/L. The S/P concentration ratio of atrazine was relatively constant throughout each experimental period (0.68 +/- 0.1 and 0.70 +/- 0.11 for salivary flow and plasma level studies, respectively) and did not differ significantly between rats. When data from both studies were pooled, salivary concentrations were highly correlated with plasma concentrations (r2 = .94). It is concluded that under these experimental conditions, the stability of the S/P concentration ratio of atrazine is not affected by variations in salivary flow rate or atrazine plasma concentrations. The results from this study support the conclusion that atrazine salivary concentrations can be used to predict plasma levels of atrazine in rats.
    Journal of Toxicology and Environmental Health 12/1997; 52(4):317-29.
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    ABSTRACT: In order to investigate how endogenous iron can be deposited in vivo on inhaled mineral fibers during early stages of formation of asbestos bodies, in vitro experiments were performed on the adsorption of ferritin onto amosite asbestos. The mineral dust was found to adsorb the protein from an aqueous solution containing 0.3 mg/ml horse spleen ferritin. In order to simulate physiological conditions the aqueous solution was adjusted with 150 mM saline. Polyacrylamide-SDS gel electrophoresis of the desorbed protein showed subunits of approximately 13 and 15 kD, aside from the 20-kD subunit present in the native protein. This suggests that as a result of interactions between ferritin molecules and the solid surface of the mineral fibers, the protein iron core may be released or partially exposed. Data indicate these interactions may have implications in the observed mineral fiber toxicities.
    Journal of Toxicology and Environmental Health 12/1997; 52(4):343-52.
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    ABSTRACT: Amiodarone is an antiarrhythmic drug with numerous side effects, the most serious being the development of pulmonary toxicity. We have previously reported that a single intratracheal instillation of amiodarone to Fischer 344 rats results in pulmonary fibrosis within 6 wk of treatment. Presently, the mechanism of amiodarone-induced pulmonary toxicity is unknown. Cytokines that stimulate fibroblast proliferation and/or collagen production may play a role in amiodarone-induced pulmonary toxicity. To investigate this possibility, female rats were given a single intratracheal instillation of amiodarone (6.25 mg/kg), its metabolite desethylamiodarone (5 mg/kg), or vehicle (sterile water). At 1, 2, 3, or 6 wk after treatment the lungs were lavaged and the recovered cells were counted and identified. The alveolar macrophages were isolated by attachment to plastic petri dishes, cultured overnight, and the spent media collected for tumor necrosis factor alpha (TNF-alpha) and transforming growth factor beta (TGF-beta) analyses. Desethylamiodarone treatment resulted in a neutrophilic alveolitis, but the levels of TNF-alpha and TGF-beta were not significantly different from control animals. In contrast, amiodarone treatment resulted in a lymphocytic alveolitis and significantly higher amounts of TNF-alpha were observed at 3 and 6 wk after treatment. A trend toward higher levels of TGF-beta was also noted in the amiodarone-treated group at wk 1-3 but the values were not significantly different from those of controls. In conclusion, the release of TNF-alpha may play a role in the development of amiodarone-induced pulmonary toxicity.
    Journal of Toxicology and Environmental Health 12/1997; 52(4):353-65.
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    ABSTRACT: Haloacetates are a common class of water chlorination by-products. Depending on the amount of bromide in the source water, varying amounts of chlorinated, brominated, and mixed bromochloro haloacetates are produced. When administered to rodents, haloacetates have been shown to increase formation of thiobarbituric acid-reactive substances and 8-hydroxydeoxyguanosine levels in the liver. These responses appear to be modified by prior treatment. To examine potential mechanisms that account for these modifications in oxidative stress, the ability of trichloroacetate (TCA) or dichloroacetate (DCA) pretreatment to alter the metabolism of bromodichloroacetate (BDCA) and the disposition of its metabolites was examined in male B6C3F1 mice. Two-week pretreatment with 1 g/L DCA and TCA in the drinking water of mice alters the initial hepatic metabolism of BDCA and the further metabolism of its metabolite DCA. DCA pretreatment inhibits cytosolic metabolism of both 1 mM DCA or BDCA up to 70%. In contrast, DCA pretreatment stimulates hepatic microsomal BDCA metabolism 1.3-fold but has little effect on microsomal metabolism of DCA. Increased microsomal metabolism of BDCA appears to be attributable to the induction of a metabolic pathway that produces CO2 and bromodichloromethane (BDCM) as metabolites. TCA pretreatment inhibits BDCA metabolism up to 70% in the cytosol and 30% in microsomes but has little effect on DCA metabolism. These results indicate that the hepatic metabolism of the haloacetate becomes quite complex at the high doses that have been employed in cancer bioassays. BDCA serves as a good example, because it is metabolized to at least two carcinogenic metabolites that have different modes of action, BDCM and DCA. As doses approach those that induce cancer in mice, the proportion of and amounts of these metabolites as a fraction of the dose administered will change substantially. This article demonstrates that those interactions will occur from mixed treatment with haloacetates as well.
    Journal of Toxicology and Environmental Health 12/1997; 52(4):367-83.
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    ABSTRACT: The Department of Energy and other federal facilities are reclaiming land through the process of remediation and restoration, and this land will eventually be turned over for future land uses that may involve recreation. Understanding the amount of recreation that is likely (and thus individual exposure) is an essential element in decisions about cleanup standards. In this article the number of days people engage in different recreational activities as a measure of potential exposure is examined. People attending a Mayfest celebration (n = 399) and the Palmetto Sportsmen's Classic (n = 285) in Columbia, SC, were interviewed regarding their recreational activities. In most cases reported in the literature, recreational activities are examined as the mean number of days people engage in each activity per year, but to determine risk it is essential to know the distribution of these activities. In descending order of frequency, people attending the Mayfest reported their activities as birdwatching, photographing, fishing, hiking, camping, and hunting. There were significant gender differences in the frequency of activities, with men spending more days in every activity except birdwatching and photography. There were ethnic differences in recreation, with whites engaging in higher levels of most recreational activities than blacks, but the percentage of black men who reported fishing more than 100 d per year was greater than for white men. Most people reported their participation in most activities less than 30 d per year; however, a higher percentage of people reported participating in photography, birdwatching, and fishing more than 30 d per year compared to the other activities. Further, individuals at the Sportsman's Classic reported far higher rates of hunting and fishing per year than the general public. These data can be used to examine potential exposure of recreationists on remediated and restored land. The data clearly indicate that over 25% of the people engage in at least one recreational activity over 20 d per year, and thus exceed the Department of Energy's 14-d recreation assumption in its future land use document.
    Journal of Toxicology and Environmental Health 11/1997; 52(3):269-84.
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    ABSTRACT: Concentrations of Aroclor mixtures and specific polychlorinated biphenyl (PCB) congeners were measured in surface sediments and aquatic biota (striped bass fillet, mummichog, and blue crab muscle and hepatopancreas) collected from the lower Passaic River. Several of the 47 surface sediment samples contained Aroclor concentrations that exceeded a National Oceanic and Atmospheric Administration (NOAA) benchmark level for "total PCBs" (22.7 micrograms/kg). Each of the 18 PCB congeners analyzed in aquatic biota was detected in one or more tissue samples, and numerous congeners were detected in every sample (IUPAC numbers 77, 105, 114, 118, 123, 126, 156, 157, 167, and 189). PCB congener concentrations were similar to those that have been reported in fish from other waterways that contain elevated levels of PCBs. Congener 118 was present at the highest concentration in almost all samples, and constituted 14-60% of the total PCB mass (sum of all congener masses) measured in any given tissue sample. In spite of the prevalence of PCB congeners in biota tissues (up to 1314 micrograms/kg total PCBs), Aroclors were not detected in bass or crab samples at a limit of detection of 33-55 micrograms/kg. This anomaly may be due to selective degradation of certain PCB congeners that are used to analytically recognize and quantitate Aroclors. Using the measured sediment concentrations, a food web model accurately predicted blue crab muscle concentrations of individual PCB congeners (typically within a factor of two) and was also fairly accurate for mummichog (typically within an order of magnitude). Concentrations in striped bass fillet were underestimated by factors of approximately 20-140. Increased cancer risk estimates associated with fish and crab consumption were obtained using four different methods. Using Aroclor tissue concentrations (one-half the limit of detection) and an Aroclor slope factor, total risks were 2.6 x 10(-6); using the "total PCB" measurements and an Aroclor slope factor, total risks were 1.9 x 10(-5); the "PCB-TEQ" method yielded total risks of 6.5 x 10(-4); and USEPA's recent suggested approach for evaluating "dioxin-like" and non-"dioxin-like" effects resulted in a total risk of 6.6 x 10(-4). This wide range in risk estimates indicates that it is critical to the risk management decision-making process that data requirements and risk assessment objectives be carefully evaluated early in the investigation process.
    Journal of Toxicology and Environmental Health 11/1997; 52(2):95-118.
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    ABSTRACT: Cadmium-induced apoptosis is shown to occur, in vivo, in several organs of the male Wistar rat urogenital system, 48 h after cadmium administration i.p. at a dose of 0.03 mmol/kg. Characteristic DNA fragmentation (as measured by an enzyme-linked immunosorbent-assay, ELISA) and histopathologically observed changes characteristic of apoptosis are found in the kidney, prostate, seminal vesicles, testes, and epididymis. TUNEL assay also demonstrates the apoptosis. Such changes are absent from bladder and vas deferens tissue. Timely administration of an appropriate chelating agent capable of reaching intracellular cadmium binding sites can suppress the processes leading to apoptosis. Administration of monoisomyl meso-2,3-dimercaptosuccinate (Mi-ADMS, 0.5 mmol/kg i.p.) to cadmium-treated rats is effective in greatly reducing typical histopathologic signs of apoptosis and the associated chromatin DNA fragmentation as revealed by ELISA when the antagonist is administered 1 h after cadmium. Administration of the chelating agent at law times results in greater degradation of DNA into oligonucleotides and more prominent histopathological evidence of apoptotic changes in the affected organs of the rat urogenital system. There is also a progressive increase in apoptotic changes indicated by TUNEL assay, as the antagonist is administered at progressively greater intervals after cadmium.
    Journal of Toxicology and Environmental Health 11/1997; 52(2):149-68.
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    ABSTRACT: The genotoxicity of nitroaromatic compounds was examined in two cultured cell lines, namely, a human hepatoma cell line, HepG2, and a brown bullhead fibroblast cell line, BB. Furthermore, the role of the quinone-reducing enzyme DT diaphorase [NAD(P)H:(quinone acceptor) oxidoreductase] was examined with respect to its influence on the genotoxic effects of model nitroaromatic pollutants. The nitroreductive characteristics of these two cell lines were examined using an acetylated cytochrome c reduction assay for enzymatic nitroreductase activity. Subsequently, the influence of DT diaphorase on the genotoxicity of two model nitroaromatics, 4-nitroquinoline 1-oxide (4NQ) and nitrofurantoin (NF), revealed that DT diaphorase was the predominant 4NQ reductase in cytosols of both cell lines, but played a lesser role in NF reduction in both species. Despite these interspecific similarities, results revealed marked qualitative differences between the two species in terms of the influence of DT diaphorase on quinone-mediated genotoxicity. When pretreated with the DT diaphorase inhibitor dicoumarol, HepG2 cells exhibited an exacerbation of genotoxicity in the presence of 4NQ, indicating a protective influence of the enzyme. In contrast, 4NQ genotoxicity in BB cells was reduced in the presence of dicoumarol, indicating a deleterious effect of DT diaphorase activity. Conversely, dicoumarol pretreatment was moderately protective against NF-mediated genotoxicity in HepG2 cells but exacerbated NF toxicity in BB cells. This study illustrates the manner in which functionally analogous enzymes may have markedly distinct influences on xenobiotic toxicity in different cellular systems.
    Journal of Toxicology and Environmental Health 11/1997; 52(2):137-48.

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