David J. Hoffman

Hood College, Maryland, United States

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Publications (132)283.47 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Despite extensive studies of methylmercury (MeHg) toxicity in birds, molecular effects on birds are poorly characterized. To improve our understanding of toxicity pathways and identify novel indicators of avian exposure to Hg, the authors investigated genomic changes, glutathione status, and oxidative status indicators in liver from laughing gull (Larus atricilla) hatchlings that were exposed in ovo to MeHg (0.05-1.6 µg/g). Genes involved in the transsulfuration pathway, iron transport and storage, thyroid-hormone related processes, and cellular respiration were identified by suppression subtractive hybridization as differentially expressed. Quantitative polymerase chain reaction (qPCR) identified statistically significant effects of Hg on cytochrome C oxidase subunits I and II, transferrin, and methionine adenosyltransferase RNA expression. Glutathione-S-transferase activity and protein-bound sulfhydryl levels decreased, whereas glucose-6-phosphate dehydrogenase activity increased dose-dependently. Total sulfhydryl concentrations were significantly lower at 0.4 µg/g Hg than in controls. Together, these endpoints provided some evidence of compensatory effects, but little indication of oxidative damage at the tested doses, and suggest that sequestration of Hg through various pathways may be important for minimizing toxicity in laughing gulls. This is the first study to describe the genomic response of an avian species to Hg. Laughing gulls are among the less sensitive avian species with regard to Hg toxicity, and their ability to prevent hepatic oxidative stress may be important for surviving levels of MeHg exposures at which other species succumb. Environ. Toxicol. Chem. 2012; 31: 2588-2596. © 2012 SETAC.
    Environmental Toxicology and Chemistry 08/2012; 31(11):2588-96. · 2.83 Impact Factor
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    ABSTRACT: Methylmercury chloride and seleno-L-methionine were injected separately or in combinations into mallard eggs (Anas platyrhynchos), and embryo mortality and teratogenic effects (deformities) were modeled using a logistic regression model. Methylmercury was injected at doses that resulted in concentrations of 0, 0.2, 0.4, 0.8, and 1.6 µg/g Hg in the egg on a wet weight basis and selenomethionine at doses that resulted in concentrations of 0, 0.1, 0.2, 0.4, and 0.6 µg/g Se in the egg, also on a wet weight basis. When selenomethionine and methylmercury were injected separately, hatching probability decreased in both cases. However, when methylmercury was injected at 1.6 µg/g in combination with selenomethionine at 0.2 µg/g, the presence of the methylmercury resulted in less embryo mortality than had been seen with 0.2 µg/g Se by itself, but it increased the number of deformed embryos and hatchlings. Selenomethionine appeared to be more embryotoxic than equivalent doses of methylmercury when injected into eggs, and both injected methylmercury and selenomethionine were more toxic to mallard embryos than when deposited naturally in the egg by the mother. The underlying mechanisms behind the interactions between methylmercury and selenomethionine and why methylmercury appeared to improve hatching probability of Se-dosed eggs yet increased deformities when the two compounds were combined are unclear. These findings warrant further studies to understand these mechanisms in both laboratory and field settings.
    Environmental Toxicology and Chemistry 12/2011; 31(3):579-84. · 2.83 Impact Factor
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    ABSTRACT: Methylmercury chloride and seleno-L-methionine were injected separately or in combinations into the fertile eggs of mallards (Anas platyrhynchos), chickens (Gallus gallus), and double-crested cormorants (Phalacrocorax auritus), and the incidence and types of teratogenic effects were recorded. For all three species, selenomethionine alone caused more deformities than did methylmercury alone. When mallard eggs were injected with the lowest dose of selenium (Se) alone (0.1 μg/g), 28 of 44 embryos and hatchlings were deformed, whereas when eggs were injected with the lowest dose of mercury (Hg) alone (0.2 μg/g), only 1 of 56 embryos or hatchlings was deformed. Mallard embryos seemed to be more sensitive to the teratogenic effects of Se than chicken embryos: 0 of 15 chicken embryos or hatchlings from eggs injected with 0.1 μg/g Se exhibited deformities. Sample sizes were small with double-crested cormorant eggs, but they also seemed to be less sensitive to the teratogenic effects of Se than mallard eggs. There were no obvious differences among species regarding Hg-induced deformities. Overall, few interactions were apparent between methylmercury and selenomethionine with respect to the types of deformities observed. However, the deformities spina bifida and craniorachischisis were observed only when Hg and Se were injected in combination. One paradoxical finding was that some doses of methylmercury seemed to counteract the negative effect selenomethionine had on hatching of eggs while at the same time enhancing the negative effect selenomethionine had on creating deformities. When either methylmercury or selenomethionine is injected into avian eggs, deformities start to occur at much lower concentrations than when the Hg or Se is deposited naturally in the egg by the mother.
    Archives of Environmental Contamination and Toxicology 11/2011; 62(3):519-28. · 2.01 Impact Factor
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    ABSTRACT: In a previous study, the embryotoxicity of methylmercury dissolved in corn oil was compared among 26 species of birds. Corn oil is not soluble in the water-based matrix that constitutes the albumen of an egg. To determine whether the use of corn oil limited the usefulness of this earlier study, a comparison was made of the embryotoxicity of methylmercury dissolved in corn oil versus water. Mallard (Anas platyrhynchos) and chicken (Gallus gallus) eggs were injected with methylmercury chloride dissolved in corn oil or water to achieve concentrations of 0, 0.2, 0.4, 0.8, and 1.6 µg/g mercury in the egg on a wet weight basis. Hatching success at each dose of mercury was compared between the two solvents. For mallards, 16.4% of the eggs injected with 1.6 µg/g mercury dissolved in water hatched, which was statistically lower than the 37.6% hatch rate of eggs injected with 1.6 µg/g mercury dissolved in corn oil, but no differences in hatching success were observed between corn oil and water at any of the other doses. With chicken eggs, no significant differences occurred in percentage hatch of eggs between corn oil and water at any of the mercury doses. Methylmercury dissolved in corn oil seems to have a toxicity to avian embryos similar to that of does methylmercury dissolved in water. Consequently, the results from the earlier study that described the toxicity of methylmercury dissolved in corn oil to avian embryos were probably not compromised by the use of corn oil as a solvent.
    Environmental Toxicology and Chemistry 06/2011; 30(9):2103-6. · 2.83 Impact Factor
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    ABSTRACT: We injected mallard (Anas platyrhynchos) eggs with methylmercury chloride at doses of 0, 0.05, 0.1, 0.2, 0.4, 0.8, 1.6, 3.2, and 6.4 μg mercury/g egg contents on a wet-weight basis. A case of hormesis seemed to occur because hatching success of eggs injected with 0.05 μg/g mercury (the lowest dose) was significantly greater (93.3%) than that of controls (72.6%), whereas hatching success decreased at progressively greater doses of mercury. Our finding of hormesis when a low dose of methylmercury was injected into eggs agrees with a similar observation in a study in which a group of female mallards was fed a low dietary concentration of methylmercury and hatching of their eggs was significantly better than that of controls. If methylmercury has a hormetic effect at low concentrations in avian eggs, these low concentrations may be important in a regulatory sense in that they may represent a no-observed adverse effect level (NOAEL).
    Archives of Environmental Contamination and Toxicology 05/2011; 62(1):141-4. · 2.01 Impact Factor
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    ABSTRACT: Previous studies have found widespread Pb poisoning of waterfowl in the Coeur d'Alene River Basin in northern Idaho, USA, which has been contaminated by mining and smelting activities. We studied the exposure of ground-feeding songbirds to Pb, sampling 204 American robins (Turdus migratorius), song sparrows (Melospiza melodia), and Swainson's thrushes (Catharus ustulatus) throughout the basin. These songbirds had mean blood Pb concentrations (mg/kg, dry weight) of less than 0.19 at a reference area (25 mg Pb/kg soil), 1.09 at moderately contaminated sites (170 to 1300 mg Pb/kg soil), and 2.06 at highly contaminated sites (2000 to 5000 mg Pb/kg soil). Based on guidelines for evaluating blood Pb in birds, 6% of robins from the highly contaminated sites had background concentrations, 24% were subclinically poisoned, 52% were clinically poisoned, and 18% were severely clinically poisoned with Pb. Blood Pb concentrations were lower in song sparrows than in robins and lowest in Swainson's thrushes. More than half of the robins and song sparrows from all contaminated sites and more than half of the Swainson's thrushes from highly contaminated sites showed at least 50% inhibition of the activity of the enzyme δ-aminolevulinic acid dehydratase (ALAD), commonly used as a measure of exposure to Pb. The highest hepatic Pb concentration of 61 mg/kg (dry weight) was detected in a song sparrow. Using Al as a marker for soil in songbird ingesta, we estimated average soil ingestion rates as 20% in robins, 17% in song sparrows, and 0.7% in Swainson's thrushes. Soil Pb in ingesta accounted for almost all of the songbirds' exposure to Pb. Based on these results, it is recommended that ecological risk assessments of ground-feeding songbirds at contaminated sites include soil ingestion as a pathway of exposure to Pb.
    Integrated Environmental Assessment and Management 04/2011; 7(4):587-95.
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    ABSTRACT: Controlled laboratory studies with game farm mallards (Anas platyrhynchos) and chickens (Gallus gallus) have demonstrated that methylmercury can cause teratogenic effects in birds, but studies with wild species of birds are lacking. To address this need, doses of methylmercury chloride were injected into the eggs of 25 species of birds, and the dead embryos and hatched chicks were examined for external deformities. When data for controls were summed across all 25 species tested and across all types of deformities, 24 individuals out of a total of 1,533 (a rate of 1.57%) exhibited at least one deformity. In contrast, when data for all of the mercury treatments and all 25 species were summed, 188 deformed individuals out of a total of 2,292 (8.20%) were found. Some deformities, such as lordosis and scoliosis (twisting of the spine), misshapen heads, shortening or twisting of the neck, and deformities of the wings, were seldom observed in controls but occurred in much greater frequency in Hg-treated individuals. Only 0.59% of individual control dead embryos and hatchlings exhibited multiple deformities versus 3.18% for Hg-dosed dead embryos and hatchlings. Methylmercury seems to have a widespread teratogenic potential across many species of birds.
    Environmental Toxicology and Chemistry 03/2011; 30(7):1593-8. · 2.83 Impact Factor
  • J Christian Franson, David J Hoffman, Paul L Flint
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    ABSTRACT: The relationships of selenium (Se) concentrations in whole blood with plasma activities of total glutathione peroxidase, Se-dependent glutathione peroxidase, and glutathione reductase were studied in long-tailed ducks (Clangula hyemalis) and common eiders (Somateria mollissima) sampled along the Beaufort Sea coast of Alaska, USA. Blood Se concentrations were >8 µg/g wet weight in both species. Linear regression revealed that the activities of total and Se-dependent glutathione peroxidase were significantly related to Se concentrations only in long-tailed ducks, raising the possibility that these birds were experiencing early oxidative stress.
    Environmental Toxicology and Chemistry 03/2011; 30(6):1479-81. · 2.83 Impact Factor
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    ABSTRACT: Bioindicators of oxidative stress were examined in prebreeding and breeding adult and chick Forster's terns (Sterna forsteri) and in prebreeding adult Caspian terns (Hydroprogne caspia) in San Francisco Bay, California. Highest total mercury (THg) concentrations (mean ± standard error; µg/g dry wt) in liver (17.7 ± 1.7), kidney (20.5 ± 1.9), and brain (3.0 ± 0.3) occurred in breeding adult Forster's terns. The THg concentrations in liver were significantly correlated with hepatic depletion of reduced glutathione (GSH), increased oxidized glutathione (GSSG):GSH ratio, and decreased hepatic gamma-glutamyl transferase (GGT) activity in adults of both tern species. Prefledging Forster's tern chicks with one-fourth the hepatic THg concentration of breeding adults exhibited effects similar to adults. Total mercury-related renal GSSG increased in adults and chicks. In brains of prebreeding adults, THg was correlated with a small increase in glucose-6-phosphate dehydrogenase (G-6-PDH) activity, suggestive of a compensatory response. Brain THg concentrations were highest in breeding adult Forster's terns and brain tissue exhibited increased lipid peroxidation as thiobarbituric acid-reactive substances, loss of protein bound thiols (PBSH), and decreased activity of antioxidant enzymes, GSSG reductase (GSSGrd), and G-6-PDH. In brains of Forster's tern chicks there was a decrease in total reduced thiols and PBSH. Multiple indicator responses also pointed to greater oxidative stress in breeding Forster's terns relative to prebreeding terns, attributable to the physiological stress of reproduction. Some biondicators also were related to age and species, including thiol concentrations. Enzymes GGT, G-6-PDH, and GSSGred activities were related to species. Our results indicate that THg concentrations induced oxidative stress in terns, and suggest that histopathological, immunological, and behavioral effects may occur in terns as reported in other species.
    Environmental Toxicology and Chemistry 12/2010; 30(4):920-9. · 2.83 Impact Factor
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    ABSTRACT: When waterfowl feed from the bottom of bodies of water, they sometimes ingest sediments along with their food, and this sediment can be a major source of contaminants. Learning how much sediment waterfowl can consume in their diet and still maintain their health would be helpful in assessing potential threats from contaminants in sediment. In a controlled laboratory study the maximum tolerated percentage of sediment in the diet of mallards (Anas platyrhynchos) was measured. When fed a well-balanced commercial avian diet, 50, 60, or 70% sediment in the diet on a dry-weight basis did not cause weight loss over a two-week period. Ducks fed this same commercial diet, but containing 80 or 90% sediment, lost 8.6 and 15.6% of their body weight, respectively, in the first week on those diets. After factoring in the ability of the mallards to sieve out some of the sediment from their diet before swallowing it, we concluded that the mallards could maintain their health even when approximately half of what they swallowed, on a dry-weight basis, was sediment.
    Environmental Toxicology and Chemistry 07/2010; 29(7):1621-4. · 2.83 Impact Factor
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    ABSTRACT: Environmental contaminants are transported over great distances to Arctic ecosystems, where they can accumulate in wildlife. Whether contaminant concentrations in wildlife are sufficient to produce adverse effects remains poorly understood. Exposure to contaminants elevates oxidative stress with possible fitness consequences. The glaucous gull (Larus hyperboreus), an Arctic top predator, was used as a bioindicator for investigating relationships between contaminant levels (organochlorines and polychlorinated biphenyls [OC/PCB], mercury [Hg], and selenium [Se]) and measures of oxidative stress (glutathione [GSH] metabolism and lipid peroxidation) in Canadian Arctic ecosystems. Contaminant levels were low and associations between contaminant exposure and oxidative stress were weak. Nevertheless, glutathione peroxidase activity rose with increasing hepatic Se concentrations, levels of thiols declined as Hg and OC/PCB levels rose, and at one of the two study sites levels of lipid peroxidation were elevated with increasing levels of hepatic Hg. These results suggest the possibility of a deleterious effect of exposure to contaminants on gull physiology even at low contaminant exposures.
    Journal of Toxicology and Environmental Health Part A 06/2010; 73(15):1058-73. · 1.83 Impact Factor
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    ABSTRACT: The ideal study of the effects of methylmercury on the reproductive success of a species of bird would be one in which eggs contained mercury concentrations ranging from controls to very heavily contaminated, all at the same site. Such a study cannot be realized at a Hg-contaminated area or under laboratory conditions but could be achieved by introducing methylmercury into breeding females and allowing them to deposit Hg in their eggs. Female mallards (Anas platyrhynchos) were intraperitoneally injected with solutions of methylmercury chloride dissolved in corn oil, propylene glycol, dimethyl sulfoxide, mineral oil, Olestra, Crisco, lard, hard paraffin, and a combination of hard and soft paraffin. In some cases, egg laying was delayed, as a result of either the solvent itself (in the case of Olestra, Crisco, and lard) or the highest concentration of methylmercury chloride (500 microg/g) in some of the solvents. Mercury in eggs ranged from a control level (<0.1 microg/g) to approximately 14 microg/g on a wet weight basis, which more than covers the range of concentrations reported in wild bird eggs. Mercury concentrations in a series of eggs from the same female declined mostly as a result of excretion of Hg in prior eggs and not because of the length of time since the injection. Intraperitoneal injections hold promise in field studies in which one would like to study the reproductive effects of a wide range of methylmercury levels in the eggs of a wild bird and under the natural conditions that exist in the field.
    Environmental Toxicology and Chemistry 05/2010; 29(5):1079-83. · 2.83 Impact Factor
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    ABSTRACT: The purpose of this experiment was to use mallards (Anas platyrhynchos) tested under controlled conditions to determine how much harm to reproduction resulted from various concentrations of mercury in eggs. Breeding pairs of mallards were fed a control diet or diets containing 1, 2, 4, or 8 microg/g mercury, as methylmercury chloride. Mean concentrations of mercury in eggs laid by parents fed 0, 1, 2, 4, or 8 microg/g mercury were 0.0, 1.6, 3.7, 5.9, and 14 microg/g mercury on a wet-weight basis. There were no signs of mercury poisoning in the adults, and fertility and hatching success of eggs were not affected by mercury. Survival of ducklings and the number of ducklings produced per female were reduced by the 4 and 8-microg/g dietary mercury treatments (that resulted in 5.9 and 14 microg/g mercury in their eggs, respectively). Ducklings from parents fed the various mercury diets were just as heavy as controls at hatching, but by 6 days of age ducklings whose parents had been fed 4 or 8 microg/g mercury weighed less than controls. Because we do not know if absorption of mercury from our diets would be the same as absorption from natural foods, the mercury concentrations we report in eggs may be more useful in extrapolating to possible harmful effects in nature than are the dietary levels we fed. We conclude that mallard reproduction does not appear to be particularly sensitive to methylmercury.
    Ecotoxicology 03/2010; 19(5):977-82. · 2.50 Impact Factor
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    ABSTRACT: Breeding pairs of mallards (Anas platyrhynchos) were fed a control diet or a diet containing 0.5 microg/g mercury (Hg) in the form of methylmercury chloride. There were no effects of Hg on adult weights and no overt signs of Hg poisoning in adults. The Hg-containing diet had no effect on fertility of eggs, but hatching success of eggs was significantly higher for females fed 0.5 microg/g Hg (71.8%) than for controls (57.5%). Survival of ducklings through 6 d of age was the same (97.8%) for controls and mallards fed 0.5 microg/g mercury. However, the mean number of ducklings produced per female was significantly higher for the pairs fed 0.5 microg/g Hg (21.4) than for controls (16.8). Although mercury in the parents' diet had no effect on mean duckling weights at hatching, ducklings from parents fed 0.5 microg/g Hg weighed significantly more (mean = 87.2 g) at 6 d of age than did control ducklings (81.0 g). The mean concentration of Hg in eggs laid by parents fed 0.5 microg/g mercury was 0.81 microg/g on a wet-weight basis. At this time, one cannot rule out the possibility that low concentrations of Hg in eggs may be beneficial, and this possibility should be considered when setting regulatory thresholds for methylmercury.
    Environmental Toxicology and Chemistry 03/2010; 29(3):650-3. · 2.83 Impact Factor
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    ABSTRACT: Measurements of Hg concentrations in avian eggs can be used to predict possible harm to reproduction, but it is not always possible to sample eggs. When eggs cannot be sampled, some substitute tissue, such as female blood, the diet of the breeding female, or down feathers of hatchlings, must be used. When female mallards (Anas platyrhynchos) were fed diets containing methylmercury chloride, the concentration of Hg in a sample of their blood was closely correlated with the concentration of Hg in the egg they laid the day they were bled (r2 = 0.88; p < 0.001). Even when the blood sample was taken more than two weeks after an egg was laid, there was a strong correlation between Hg concentrations in female blood and eggs (r2 = 0.67; p < 0.0002). When we plotted the dietary concentrations of Hg we fed to the egg-laying females against the concentrations of Hg in their eggs, the r2 value was 0.96 (p < 0.0001). When the concentrations of Hg in the down feathers of newly hatched ducklings were plotted against Hg in the whole ducklings, the r2 value was 0.99 (p < 0.0003). Although measuring Hg in eggs may be the most direct way of predicting possible embryotoxicity, our findings demonstrate that measuring Hg in the diet of breeding birds, in the blood of egg-laying females, or in down feathers of hatchlings all can be used to estimate what concentration of Hg may have been in the egg.
    Environmental Toxicology and Chemistry 02/2010; 29(2):389-92. · 2.83 Impact Factor
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    ABSTRACT: Blood collected from song sparrows (Melospiza melodia) and American robins (Turdus migratorius) captured with mist nets in a lead-contaminated (assessment) area and nearby uncontaminated (reference) areas within the Coeur d'Alene Basin in northern Idaho was analyzed for δ-aminolevulinic acid dehydratase activity (ALAD) and hematocrit levels, and livers were analyzed for lead. Mean ALAD inhibition in the assessment area was 51% in song sparrows and 75% in American robins. The proportion of the sampled population with ALAD inhibition >50% was calculated to be 43% for song sparrows and 83% for American robins. Assessment area hematocrit values for song sparrows (x = 39.9) and American robins (x = 39.5) were lower than in reference areas (x = 42.4 for song sparrows and 40.2 for American robins); however, differences were not statistically significant (p > 0.05). Significantly higher levels of lead (wet weight) were found in livers from song sparrows captured on the assessment area (x = 1.93 ppm) than on reference areas (x = 0.10 ppm) (p = 0.0079). Study results indicate that 43% (95% confidence interval [CI] = 12.9-77.5%) of the song sparrows and 83% (95% CI = 41.8-99.2%) of the American robins inhabiting the floodplain along the Coeur d'Alene River in the assessment area are being exposed to lead at levels sufficient to inhibit ALAD by > 50%. Variability in lead exposure indicators was attributed to high variability in environmental lead concentrations in the Coeur d'Alene River Basin.
    Environmental Toxicology and Chemistry 11/2009; 18(6):1190 - 1194. · 2.83 Impact Factor
  • David J. Hoffman, Gary H. Heinz
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    ABSTRACT: Earlier studies have reported on the toxicity and related oxidative stress of different forms of Se, including seleno- D,L-methionine, in mallards (Anas platyrhynchos). This study compares the effects of Se (seleno-D,L-methionine) and Hg (methylmercury chloride) separately and in combination. Mallard drakes received one of the following diets: untreated feed (controls), or feed containing 10 ppm Se, 10 ppm Hg, or 10 ppm Se in combination with 10 ppm Hg. After 10 weeks, blood, liver, and brain samples were collected for biochemical assays. The following clinical and biochemical alterations occurred in response to Hg exposure: hematocrit and hemoglobin concentrations decreased; activities of the enzymes glutathione (GSH) peroxidase (plasma and liver), glutathione-S-transferase (liver), and glucose-6-phosphate dehydrogenase (G-6-PDH) (liver and brain) decreased; hepatic oxidized glutathione (GSSG) concentration increased relative to reduced glutathione (GSH); and lipid peroxidation in the brain was detected by increased thiobarbituric reactive substances (TBARS). Effects of Se alone included increased hepatic GSSG reductase activity and brain TBARS concentration. Selenium in combination with Hg partially or totally alleviated effects of Hg on GSH peroxidase, G-6-PDH, and GSSG. These findings are compared in relation to field observations for diving ducks and other aquatic birds. It is concluded that since both Hg and excess Se can affect thiol status, measurement of associated enzymes in conjunction with thiol status may be a useful bioindicator to discriminate between Hg and Se effects. The ability of Se to restore the activities of G-6-PDH, GSH peroxidase, and glutathione status involved in antioxidative defense mechanisms may be crucial to biological protection from the toxic effects of methylmercury.
    Environmental Toxicology and Chemistry 10/2009; 17(2):161 - 166. · 2.83 Impact Factor
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    ABSTRACT: Morphological and biochemical indexes of contaminant exposure were examined in hatching common terns (Sterna hirundo) and black-crowned night herons (Nycticorax nycticorax) from industrialized and nonindustrialized locations in the Great Lakes. In 1984, naturally incubated, pipping common tern and black-crowned night heron embryos collected from industrialized locations exhibited smaller femur-length-to-body-weight ratios, elevated hepatic microsomal aryl hydrocarbon hydroxylase (AHH) activities, and lower hepatic DNA concentrations (P < 0.05). In addition, a high incidence of subcutaneous edema was noted in pipping herons (P < 0.01). In 1985, reduced hatching success was observed for laboratory-incubated common tern eggs collected from the industrialized sites, compared to nonindustrialized sites (P < 0.01). Day-old hatchlings exhibited reduced femur-length-to-body-weight ratio, developmental anomalies, and elevated hepatic AHH activity (P < 0.05). For hatching common terns studied in 1984 and 1985, femur-length-to-body-weight ratio was inversely related to AHH activity (r = −0.67, P < 0.05) and inversely related to log-transformed PCB concentrations (r = −0.70, P ≤ 0.05) of unincubated eggs from the same colony. The activity of AHH in hatching terns was also directly related (r = 0.71, P ≤ 0.05) to log-transformed PCB concentrations in unincubated eggs. Other examined contaminants, including DDE, other organochlorine pesticides, and mercury, were not directly related to these effects.
    Environmental Toxicology and Chemistry 10/2009; 12(6):1095 - 1103. · 2.83 Impact Factor
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    ABSTRACT: High concentrations of boron and arsenic have been associated with irrigation drain water and aquatic plants consumed by waterfowl. Both compounds affect the central nervous system and cause generalized physiological distress in mammals and waterfowl. We examined sublethal effects of boron and arsenic on the behavior of developing mallard ducklings (Anas platyrhynchos). Day-old ducklings received an untreated diet (control) or a diet containing 100, 400, or 1,600 ppm boron, added as boric acid, or 30, 100, or 300 ppm arsenic, added as sodium arsenate. Activity schedules and behavior durations were analyzed for effects at the various treatment levels. Both boron and arsenic at the highest levels had significant effects on the activity schedules of developing ducklings, including increased time at rest and under the provided heat lamp. We also observed decreases in the amount of time treated ducklings spent in alert behaviors and in the water in comparison to control ducklings. High levels of boron (1,600 ppm) increased feeding time overall but did not increase the amount of food consumed. Arsenic had no effect on feeding behavior. There were no differences found in the durations of behaviors as a result of treatment. These findings, in combination with reported effects on the growth and physiology of ducklings under identical treatments, suggest that reported concentrations of these compounds in aquatic plants in the Central Valley of California could adversely affect normal duckling development and survival.
    Environmental Toxicology and Chemistry 10/2009; 10(7):911 - 916. · 2.83 Impact Factor
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    ABSTRACT: Arsenic (As) has been found at elevated concentrations in irrigation drainwater and in aquatic plants utilized by waterfowl. Mallard (Anas platyrhynchos) ducklings received an untreated diet (controls) or diets containing 30, 100 or 300 ppm As added as sodium arsenate. After 10 weeks blood and tissue samples were collected for biochemical and histological examination. Arsenic accumulated significantly in brain and liver of ducklings fed 100 or 300 ppm but did not result in histopathological lesions. The 300-ppm dietary As concentration decreased overall growth (weight gain) in males, whereas all concentrations of As decreased overall growth and rate of growth in females. Food consumption was less during the first three weeks in the 300-ppm group and during the second week for the 100-ppm group compared to controls. Plasma sorbitol dehydrogenase activity and plasma glucose concentration were higher in the 300-ppm group compared to controls. Plasma triglyceride concentration increased in all As-treated groups. Brain ATP was lower in the 300-ppm group and sodium/potassium-dependent ATPase activity was higher in the 30- and 100-ppm groups. Hepatic glutathione peroxidase activity was lower in the 300-ppm group and malondialdehyde lower in all treatment groups. All treatment levels caused elevation in hepatic glutathione and ATP concentrations. These findings, in combination with altered duckling behavior (increased resting time), suggest that concentrations of As that have been found in aquatic plants (up to 430 ppm dry weight) could adversely affect normal duckling development.
    Environmental Toxicology and Chemistry 10/2009; 9(6):785 - 795. · 2.83 Impact Factor

Publication Stats

3k Citations
283.47 Total Impact Points


  • 2012
    • Hood College
      Maryland, United States
  • 2000–2011
    • United States Geological Survey
      • Patuxent Wildlife Research Center
      Wellsboro, PA, United States
  • 2010
    • Environment Canada
      Montréal, Quebec, Canada
  • 2009
    • University of California, Davis
      • Department of Wildlife, Fish and Conservation Biology
      Davis, CA, United States
  • 2001–2005
    • Frostburg State University
      • Biology
      Frostburg, MD, United States
  • 2003
    • Autonomous University of Barcelona
      • Facultat de Veterinària
      Cerdanyola del Vallès, Catalonia, Spain
  • 2002
    • Texas Tech University
      Lubbock, Texas, United States
  • 1984–1993
    • U.S. Fish and Wildlife Service
      • Division of Ecological Services
      Washington, Washington, D.C., United States