Effects of neurotoxic insecticides on heat-shock proteins and cytokine transcription in Chinook salmon (Oncorhynchus tshawytscha).

This study investigated sublethal, molecular effects of two current-use insecticides, chlorpyrifos (CP) and esfenvalerate (EV) in juvenile Chinook salmon. Heat-shock protein (hsp60, hsp70, hsp90) expression was quantified by Western blotting in muscle, liver and gill, and transcription of four cytokines (TGF-beta, IL-1beta, IGF-1, Mx-protein) was measured by real-time TaqMan PCR in anterior kidney and spleen. Expression of hsp was increased in muscle and liver at 1.2 and 7.2 microg/L CP, and at 0.01 and 0.1 microg/L EV, respectively. Transcription of IL-1beta and TGF-beta was elevated in kidney at 1.2 microg/L CP, while EV had no effect. No changes in cytokine transcription were observed in the spleen. Our results show that these insecticides cause cellular effects at environmental concentrations, and that hsps are sensitive indicators of sublethal exposure to CP and EV. In addition, CP may exert immunotoxic effects by altering the transcription of important mediators of the fish immune system.

Impaired serial visual search in children with developmental dyslexia.

In order to test the hypothesis of attentional deficits in dyslexia, we investigated the performance of children with developmental dyslexia on a number of visual search tasks. When tested with conjunction tasks for orientation and form using complex, letter-like material, dyslexic children showed an increased number of errors accompanied by faster reaction times in comparison to control children matched to the dyslexics on age, gender, and intelligence. On conjunction tasks for orientation and color, dyslexic children were also less accurate, but showed slower reaction times than the age-matched control children. These differences between the two groups decreased with increasing age. In contrast to these differences, the performance of dyslexic children in feature search tasks was similar to that of control children. These results suggest that children with developmental dyslexia present selective deficits in complex serial visual search tasks, implying impairment in goal-directed, sustained visual attention.

Expression of immune-regulatory genes in juvenile Chinook salmon following exposure to pesticides and infectious hematopoietic necrosis virus (IHNV).

Impairment of fish immune function as a consequence of polluted aquatic environments can result in changes in susceptibility to disease. In this study, we investigated the effects of two widely used insecticides, chlorpyrifos (CP) and esfenvalerate (EV), and a pathogen, infectious hematopoietic necrosis virus (IHNV), singly and in combination, on survival and cytokine (Mx protein, IL-1beta, TGF-beta and IGF-1) expression in juvenile Chinook salmon. Fish were exposed for 96 h to sublethal concentrations of CP (3.7 microg L(-1)) or EV (0.08 microg L(-1)), allowed to recover in clean water for seven days, then exposed to IHNV (6.4x10(5)TCID(50)mL(-1)) for 1.5h. Mortality was recorded daily, and spleen and anterior kidney samples were collected on day 4 (after CP or EV treatment), day 20 and day 60 (after CP or EV treatment and subsequent IHNV exposure) of the experiment. Significant mortality after 60 days was observed following exposure to EV (17%) or IHNV (20%), and prior insecticide exposure did not synergize the acute effects of pathogen treatment. By day 4, exposure to CP as well as EV led to a significant decrease of Mx protein and IL-1beta expression; by day 20, EV-exposed fish significantly overexpressed IL-1beta. Mx protein transcription was up-regulated in spleen and kidney of all IHNV-exposed fish groups by day 20. All but one treatment (EV) led to significantly decreased IGF-1 transcription in spleen on days 20 and 60, whereas a short-term increase was seen after CP exposure (day 4). In kidney, decreases of IGF-1 transcription were less pronounced. TGF-beta transcription was up-regulated in CP/IHNV and EV/IHNV exposure groups. Our results indicate that CP and EV alter the expression of cytokines, but this did not negatively affect the ability of fish to survive a subsequent exposure to IHNV. Induced TGF-beta transcription indicated that the combined stressors affected fish in a synergistic manner, but the consequences are unknown. Increased transcription of Mx protein was a reliable indicator of virus exposure.

Pesticide and pathogen: heat shock protein expression and acetylcholinesterase inhibition in juvenile Chinook salmon in response to multiple stressors.

Rapid expression of heat shock protein (hsp) families in response to a variety of stressors has been demonstrated in many organisms, including fish. The present 60-d challenge study was designed to compare hsp induction in juvenile Chinook salmon following exposure to individual pesticides, virus, and both stressors combined. Heat shock protein expression patterns over time were monitored and related to the extent of virus infection and mortality. Acetylcholinesterase (AChE) inhibition and recovery in response to applied stressors were measured in brain. High enzyme inhibition levels have been correlated with imminent mortality, and other sublethal physiological effects have been observed in fish concurrent with depressed AChE activity. Mortality was elevated considerably in fish exposed to 0.08 microg/L of the pyrethroid esfenvalerate (EV). Mortality due to infectious hematopoietic necrosis virus (IHNV) was lower in groups previously treated with pesticides; however, these fish died sooner than individuals exposed to virus only. Both pesticides, EV and the organophosphate (OP) chlorpyrifos (CP), as well as virus exposure, induced hsp expression, but highest hsp levels were observed after the combined treatments, suggesting an additive effect between virus and pesticides. Highest virus titers were accompanied by strongest hsp induction, indicating a connection between virus concentration and hsp expression. In conclusion, the measurement of hsp expression appears to be a very sensitive, integrative indicator of stress. Esfenvalerate and IHNV did not affect AChE activity, and exposure to 3.7 microg/L CP led to significantly inhibited AChE for at least 20 d. The time required for complete recovery of AChE activity raises concern about deleterious behavioral effects.

Synergistic effects of esfenvalerate and infectious hematopoietic necrosis virus on juvenile chinook salmon mortality.

Sublethal concentrations of pollutants may compromise fish, resulting in increased susceptibility to endemic pathogens. To test this hypothesis, juvenile chinook salmon (Oncorhynchus tshawytscha) were exposed to sublethal levels of esfenvalerate or chlorpyrifos either alone or concurrently with infectious hematopoietic necrosis virus (IHNV). Three trials were performed with fish exposed to concentrations of IHNV between 0.8 x 10(2) and 2.7 x 10(6) plaque-forming units/ml and to 5.0 microg/L of chlorpyrifos or 0.1 microg/L of esfenvalerate. The presence and concentration of IHNV in dead fish were assayed by virus isolation and plaque assay techniques, respectively. Among groups exposed to both esfenvalerate and IHNV, 83% experienced highly significant (p < 0.001) mortality, ranging from 20 to 90% at 3 d post-virus exposure, and cumulatively died from 2.4 to 7.7 d sooner than fish exposed to IHNV alone. This trend was not seen in any other treatment group. Virus assays of dead fish indicate a lethal synergism of esfenvalerate and IHNV. Chlorpyrifos had no observed effect on total mortality or IHNV susceptibility. The present results suggest that accepted levels of pollutants may be seemingly nonlethal to fish but, in fact, be acting synergistically with endemic pathogens to compromise survivorship of wild fish populations through immunologic or physiologic disruption.

Toxicity of storm-water runoff after dormant spray application in a french prune orchard, Glenn County, California, USA: temporal patterns and the effect of ground covers.

Organophosphorous (OP) insecticides, especially diazinon, have been detected routinely in surface waters of the Sacramento and San Joaquin River watersheds, coincident with rainfall events following their application to dormant orchards during the winter months. Preventive best management practices (BMP) aim at reducing off-site movement of pesticides into surface waters. Two proposed BMPs are: The use of more hydrophobic pyrethroid insecticides believed to adsorb strongly to organic matter and soil and the use of various types of ground cover vegetation to increase the soil's capacity for water infiltration. To measure the effectiveness of these BMPs, storm water runoff was collected in a California prune orchard (Glenn County, CA, USA) during several rainstorms in the winter of 2001, after the organophosphate diazinon and the pyrethroid esfenvalerate were applied to different orchard sections. We tested and compared acute toxicity of orchard runoff from diazinon- and esfenvalerate-sprayed sections to two species of fish (Pimephales promelas, Onchorhynchus mykiss) and three aquatic invertebrates (Ceriodaphnia dubia, Simocephalus vetelus, Chironomus riparius), and determined the mitigating effect of three ground cover crops on toxicity and insecticide loading in diazinon-sprayed orchard rows. Runoff from the esfenvalerate-sprayed orchard section was less toxic to waterflea than runoff from the diazinon-sprayed section. However, runoff from the orchard section sprayed with esfenvalerate was highly toxic to fish larvae. Samples collected from both sections one month later were not toxic to fish, but remained highly toxic to invertebrates. The ground cover crops reduced total pesticide loading in runoff by approximately 50%. No differences were found between the types of vegetation used as ground covers.

Isomer selectivity in aquatic toxicity and biodegradation of cypermethrin.

Synthetic pyrethroids (SPs) are widely used in both agricultural and urban regions for insect control. Unlike many other pesticides, SPs are chiral compounds consisting of stereoisomers. However, occurrence of isomer selectivity in environmental processes is poorly understood for SPs. We evaluated isomer selectivity in toxicity of cypermethrin (CP) to Ceriodaphnia dubia and in its biodegradation by microbial isolates and in sediment. Among the eight enantiomers, two enantiomers (1R-cis-alphaS and 1R-trans-alphaS) were found to be toxic to C. dubia. Bacteria strains isolated from sediment selectively degraded CP diastereomers and enantiomers. The trans diastereomers were preferentially degraded over the cis diastereomers. Of the two active enantiomers, 1R-cis-alphaS was degraded slower, whereas 1R-trans-alphaS was degraded faster than the other stereoisomers. Similar isomer selectivity was observed during CP degradation in whole sediment. Since ecotoxicity is likely caused only by the biologically active enantiomers, knowledge on isomer selectivity may improve our understanding of the ecological risks of CP and analogous SPs.

Biomarker responses in Macoma nasuta (Bivalvia) exposed to sediments from northern San Francisco Bay.

Our study investigates biomarker responses and survival of Macoma nasuta exposed to sediments collected from six locations in northern San Francisco Bay. Biomarkers analyzed were stress proteins (hsp70) in gill, mantle and digestive gland, lysosomal membrane damage and histopathologic lesions. Sediments and clam tissues were analyzed for a comprehensive suite of heavy metals and trace organic pollutants. Sediment grain size and organic carbon content were determined. Clams accumulated metals, polyaromatic hydrocarbons (PAHs) and organochlorine pesticides (aldrin and p,p(')-DDT and its metabolites p,p(')-DDD and p,p(')-DDE). Pearson and Spearman correlation analysis revealed that mortality, hsp70 in gill and histopathologic lesion scores in gonads, and lysosomal membrane damage were significantly correlated with tissue concentrations of DDT and/or its metabolites. Tissue concentrations of metals, in particular nickel, chromium, and copper, were associated with macrophage aggregates in digestive gland and germ cell necrosis. Cadmium was linked to mortality and lysosomal membrane damage.

The influence of salinity on the heat-shock protein response of Potamocorbula amurensis (Bivalvia).

For biomarkers to be useful in assessing anthropogenic impacts in field studies involving aquatic organisms, they should not be affected by naturally occurring changes in environmental parameters such as salinity. This is especially important in estuarine environments and for relatively unspecific biomarkers like heat-shock proteins (hsps, stress proteins). In this study, the heat-shock protein response was measured in the euryhaline clam, Potamocorbula amurensis, after exposure to a range of salinities reflecting normal and extreme environmental conditions in Northern San Francisco Bay, California. The ability to raise cellular hsp70 levels in response to heat-shock was significantly impaired in P. amurensis collected from a low (0.5 ppt) salinity field site, and after 14 day exposure to low salinity in the laboratory.

Molecular and cellular biomarker responses to pesticide exposure in juvenile chinook salmon (Oncorhynchus tshawytscha).

We determined the effects of two pesticides, chlorpyrifos and esfenvalerate in juvenile Chinook salmon. Four to five month old salmon were exposed to a range of pesticide concentrations, and tissue samples of surviving fish were analyzed for stress protein expression, cytokine transcription, and acetylcholinesterase (AChE) activity. At the highest concentrations, both pesticides led to complete mortality, whereas medium and low concentrations resulted in high survival rates. Significant differences in stress protein expression, cytokine transcription and AChE activity were found between control and surviving chlorpyrifos-exposed fish. Elevated stress protein expression was the only detectable response to esfenvalerate.

Effects of dietary exposure to the pyrethroid pesticide esfenvalerate on medaka (Oryzias latipes).

The pyrethroid insecticide esfenvalerate is widely used on orchard crops throughout California. In the aquatic environment, this compound is likely to accumulate in sediments, food particles and benthic organisms due to its lipophilicity and environmental persistence. This pilot project tested the hypothesis that esfenvalerate is toxic to medaka (Oryzias latipes) when taken up with the diet. For 7 days fish were fed diets, which contained esfenvalerate in three different concentrations (4, 21, 148 mg/kg, measured). Endpoints measured were mortality, fecundity, fertilization and hatching success of embryos, viability of larvae and cellular stress protein (hsp60, hsp70, hsp90) levels. The toxicity of aqueous exposure of medaka to esfenvalerate was also determined. Whereas the 96-h LC50 in the aqueous exposure was <9.4 microg/l, the dietary exposure did not cause mortality. Possible effects of dietary esfenvalerate were seen on fertilization and hatching success and the number of non-viable larvae. Expression of hsp60 and hsp90 showed a dose-dependent response pattern.