Parshall B. Bush

Tissue residues of dietary cadmium in wood ducks

One-week-old wood ducks were fed cadmium in diets containing 18 or 30% protein for a period of three months. Seven drakes from each group were sacrificed, and blood, brain, muscle, kidney, liver, and wing feather tissues were collected and analyzed for cadmium. Highest cadmium concentrations were found in the kidney, liver, and feather tissues; blood, muscle, and brain cadmium residue levels were undetectable. Except in the kidney tissue, protein level of the diet did not affect cadmium residue levels. For birds that were changed to a cadmium-free, high-protein ration at 13 weeks of age, regression analysis indicated a significant decrease in cadmium residue levels for the kidney tissue only. Growth, as measured by body weight at 13 weeks of age, was not affected by the various cadmium treatment levels. Histopathological examination revealed lesions in the kidney tissues of the 100 ppm cadmium treatment groups, which were more severe in those birds receiving the 18% protein diet. Vacuolation of the pancreatic acinar cells was observed in all groups, but tended to occur more frequently in the higher cadmium level groups.

Sublethal concentrations of mercury in river otters: Monitoring environmental contamination

Hair, muscle, and liver mercury concentrations were determined in river otter (Lutra canadensis) carcasses collected from the lower coastal plain and piedmont of Georgia. Mean muscle and hair mercury concentrations were greater (P<0.001) in otters from the lower coastal plain (4.42 and 24.25 mg/kg wet wt, respectively) compared to otters from the piedmont (1.48 and 15.24 mg/kg, respectively). Liver tissue from lower coastal plain otters averaged 7.53 mg/kg mercury. Mean fetus brain and muscle mercury concentrations were 1.03 and 1.58 mg/kg wet wt, respectively, and fetal muscle mercury concentrations were correlated (r=0.92) with maternal muscle mercury concentrations. Comparison of mercury concentrations found in Georgia otters to those associated with adverse effects in otter and mink (Mustela vison), indicate sublethal contamination with concentrations in some individuals approaching that observed in experimentally dosed individuals that developed clinical signs of mercurialism. Mercury concentrations in fish from the lower coastal plain approached or exceeded concentrations demonstrated to be toxic to experimentally dosed otters.

Bioaccumulation and Metabolic Effects of the Endocrine Disruptor Methoprene in the Lobster, Homarus americanus

Abstract Methoprene is a pesticide that acts as a juvenile hormone agonist. Although developed initially against insects, it has since been shown to have toxic effects on larval and adult crustaceans. Methoprene was one of several pesticides applied to the Western Long Island Sound (WLIS) watershed area during the summer of 1999; the other pesticides were malathion, resmethrin, and sumethrin. These pesticides were applied as part of a county-by-county effort to control the mosquito vector of West Nile Virus. Subsequently, the seasonal lobster catches from the WLIS have decreased dramatically. The lethality of the pesticides to lobsters had been unknown. We studied the effects of methoprene while other investigators studied effects of the other pesticides. We questioned whether methoprene, through its effects on larvae, adults or both, could have contributed to this decline. We found that low levels of methoprene had adverse effects on lobster larvae. It was toxic to stage II larvae at 1 ppb. Stage IV larvae were more resistant, but did exhibit significant increases in molt frequency beginning at exposures of 5 ppb. Juvenile lobsters exhibited variations in tissue susceptibility to methoprene: hepatopancreas appeared to be the most vulnerable, reflected by environmental concentrations of methoprene inhibiting almost all protein synthesis in this organ. Our results indicated that methoprene concentrates in the hepatopancreas, nervous tissue and epidermal cells of the adult lobster. Methoprene altered the synthesis and incorporation of chitoproteins (cuticle proteins) into adult postmolt lobster explant shells. SDS PAGE analyses of adult post–molt shell extracts revealed changes in the synthesis of chitoproteins in the methoprene-treated specimens, suggesting that methoprene affects the normal pathway of lobster cuticle synthesis and the quality of the post-molt shell. Although it is likely that a combination of factors led to the reduced lobster population in WLIS, methoprene may have contributed both by direct toxic effects and by disrupting homeostatic events under endocrine control.

Leaching and persistence of herbicides for kudzu (Pueraria montana) control on pine regeneration sites

Abstract Clopyralid, picloram, triclopyr, metsulfuron, and tebuthiuron were applied to control kudzu on four loblolly pine forest regeneration sites during July 1997. Spot treatments were applied to recovering kudzu in June 1998 and June 1999. Soil leachate was monitored for these five herbicides from July 1997 to December 2000. All herbicides were detected in shallow (51–58 cm deep) and deep lysimeters (84–109 cm deep). Clopyralid was not persistent and limited leaching occurred, with residue levels of 0.4 to 2.8 μg L−1 in 12 of 102 deep lysimeter samples. Picloram was mobile and persisted at 0.6 to 2.5 μg L−1 in shallow and deep lysimeters for at least 10 mo after the initial application. Triclopyr residues were not persistent in shallow lysimeters and remained < 6 μg L−1 during the study. Metsulfuron persisted at < 0.1 μg L−1 for 182 to 353 d in shallow lysimeters and at < 0.07 μg L−1 for 182 to 300 d in the deep lysimeters in various plots. Tebuthiuron peaks in the deep lysimeters ranged from 69 to 73...

Impact of hexazinone on invertebrates after application to forested watersheds

The impact of the herbicide, hexazinone, was assessed on aquatic macrophytes, aquatic and terrestrial invertebrate communities within forested watersheds in the Piedmont region of Georgia. Four replicate watersheds received hexazinone on April 23, 1979, and were subsequently monitored for eight months. Residue levels in terrestrial invertebrates were a maximum of two orders of magnitude greater than comparable levels (0.01 to 0.18 ppm) found in forest floor material. Aquatic organisms in a second order perennial stream were exposed to intermittent concentrations of hexazinone (6 to 44 ppb). Hexazinone and its metabolites were generally not detected (<0.1 ppm) in aquatic invertebrates and macrophytes. No major alterations in species composition or diversity were detected in the aquatic macroinvertebrate community. Terrestrial microarthropod samples collected near the end of the study period revealed no major community changes.

Modulation of immune responses in mice by d-limonene.

The immunotoxicologic effects of d-limonene were determined. This naturally occurring substance is widely used in food flavorings and is a common additive in cosmetics. In the present study, BALB/c mice were treated with d-limonene for 9 wk. Effects on T- and B-cell responses were determined after 4 and 8 wk of treatment. Concanavalin-A responses at 8 wk, but not 4 wk, were suppressed in treated mice. A similar trend was observed for phytohemagglutinin and lipopolysaccharide responses. Evidence was presented that d-limonene had polyclonal activator action. Mice primed with keyhole limpet hemocyanin (KLH) prior to initiation of d-limonene treatment had suppressed primary and secondary anti-KLH responses. Mice treated with d-limonene prior to KLH priming produced significant increased antibody responses. Additional evidence for polyclonal stimulation was obtained by histopathologic examination of secondary lymphoreticular tissue. Significant secondary follicle development and prominent lymphoid nodules and aggregates were found in the pancreas and intestinal mucosa, particularly apparent in mice receiving the highest d-limonene dosage. A subchronic LD50 study was conducted wherein BALB/c mice received 16 daily doses of d-limonene. An LD50 of approximately 0.0850 mg d-limonene/kg (corrected for 82% purity) was determined.

Variations in Density and Chemical Composition of White-Tailed Deer Antlers

Eighteen sets of cast antlers were collected from seven male white-tailed deer, Odocoileus virginianus , maintained on a high nutritional plane. Density and chemical compositional differences were found to occur among deer and as a result of age and portion of antler analyzed. Antler density varied among deer, tended to decrease with age, and was lower along the length of the main beam than along the tines or at the antler tips. Chemical composition also varied among deer. Various elements were affected in differing ways by increases in age. Possible physiological and morphological reasons for these differences are discussed and a hypothesis regarding their behavioral significance is proposed.

METABOLIC EFFECTS OF ACUTE EXPOSURE TO METHOPRENE IN THE AMERICAN LOBSTER, HOMARUS AMERICANUS

Abstract Methoprene was a constituent of the pesticide cocktail applied to the Western Long Island Sound (WLIS) watershed area during the summer of 1999. Subsequently, the seasonal lobster catches from the WLIS have decreased dramatically. We have been engaged in ongoing studies of the effects of methoprene on larval, juvenile and adult lobsters. Most recently, we found that Stage IV larvae exposed to 50 ppb methoprene experience >90% mortality rate after 3 days. Bioaccumulation studies on adult lobsters showed that methoprene concentrated against the gradient of the surrounding seawater (50 ppb) in hepatopancreas (1.55 ppm), gonad (5.18 ppm), epithelial tissue (6.17 ppm) and, most significantly, the eyestalks (28.83 ppm). Exposure to methoprene altered the expression of the stress proteins and the pattern of ubiquitinylation of cytosolic proteins by Day 1 Stage I larvae and by epithelial tissue of postmolt juvenile lobsters. Postmolt juvenile animals also demonstrated an altered pattern of protein phosphorylation in their epithelial tissues following methoprene exposure, indicating that it may interfere with cell signaling pathways. Increasing concentrations of methoprene were associated with increasing chitoproteins in the microsomal fractions of Day 1 Stage I larvae, suggesting that methoprene may compromise the exocytosis of shell matrix precursors from the epithelial cells. Methoprene did not, however, alter the activity of chitin synthase in these larvae. Although it is likely that a combination of harmful events and exposures led to the reduced lobster population in WLIS, methoprene may have contributed to the decline both by direct toxic effects and by disrupting homeostatic processes.

Effects of the insecticides carbofuran and fenvalerate on adenylate parameters in bluegill sunfish (Lepomis macrochirus)

Bluegills (Lepomis macrochirus) were exposed to two sublethal concentrations of carbofuran, a carbamate insecticide, and fenvalerate, a synthetic pyrethroid insecticide, in continuous flow bioassay systems for 30 days. Adenylate parameters (ATP concentration, total adenylates concentration, and adenylate energy charge) were monitored in gill, liver, muscle, and stomach tissues. There were significant decreases in adenylate energy charge of gill and stomach tissue relative to initial values after 10 days of exposure to 30 μg/L carbofuran. There was also a significant decline in adenylate energy charge in gills of fish exposed to 0.2 μg/L fenvalerate relative to initial values. These values returned to normal by the end of the experiment. The biological significance of these changes is uncertain. Adenylate parameters may not be sufficiently sensitive to reflect sublethal effects of pesticides which affect the nervous system of fishes.

Pesticide induced alterations in gene expression in the lobster, Homarus americanus.

Using subtractive hybridization, we have identified 17 genes that are either up- or down-regulated in the hepatopancreas (Hp) of the lobster, Homarus americanus, by acute exposure to the juvenile hormone analog methoprene. The expression of some of the genes obtained from the subtraction libraries was confirmed by real time Q-PCR experiments. These genes encode several different classes of proteins including: structural, enzymatic and regulatory polypeptides. Enzymes represent the predominant genes up-regulated by methoprene. Included in this group are betaine-homocysteine S-methyltransferase (BHMT) and two other enzymes of the methionine cycle. Increased expression of a translation factor (eIF2), as well as of cytosolic (aldose reductase), structural (beta-tubulin, L5A) and plasma membrane (CD42d) proteins was observed. In addition, a major feature of altered gene expression in methoprene treated Hp was increased levels of enzymes associated with protein turnover, including trypsin, ubiquitin conjugating enzyme and ubiquitin carboxyl terminal hydrolase. Down-regulation of the members of the hemocyanin family was observed. Assays confirmed elevated levels of trypsin in the Hp of lobsters after 24 h exposure to methoprene. Our findings suggest a wide variety of cellular targets are altered by methoprene.