Final Report: FRIENDS Children's Environmental Health Center

EPA Grant Number: R829390
Center: CECEHDPR - University of Illinois FRIENDS Children’s Environmental Health Center
Center Director: Schantz, Susan L.
Title: FRIENDS Children's Environmental Health Center
Investigators: Schantz, Susan L.
Institution: University of Illinois at Urbana
EPA Project Officer: Louie, Nica
Project Period: November 1, 2001 through October 31, 2006 (Extended to October 31, 2008)
Project Amount: $5,568,992
RFA: Centers for Children's Environmental Health and Disease Prevention Research (2001) RFA Text |  Recipients Lists
Research Category: Children's Health , Health Effects , Human Health , Health

Objective:

The FRIENDS Children’s Environmental Health Center was funded in 2001 with the goal to develop and implement a highly integrated program of mechanistic research aimed at understanding the developmental neurotoxicity of exposure to polychlorinated biphenyls (PCBs) and methyl mercury (MeHg) at the molecular, cellular, whole animal and human health levels. These were the first comprehensive studies specifically designed to assess the combined effects of these two widespread neurotoxic contaminants. The studies were designed so that findings from mechanistic studies at the molecular and cellular level would inform and guide in vivo animal studies and, similarly, findings from in vivo animal studies would inform and guide epidemiological research in exposed humans. This type of multi-level, integrated approach is only possible with a Center or Program Project funding mechanism that allows investigators with very different training and expertise to conduct parallel and highly integrated research projects. The Center included an Administrative Core (Project 1), three inter-related research projects (Projects 2,3 and 4) and an Analytical Toxicology Core (Project 5) which prepared and characterized the experimental PCB mixture used in the laboratory studies and provided PCB and MeHg analysis for all three research projects.

A unique aspect of the research was the care that was taken to model exposure in the human population as closely as possible in laboratory animal studies. This included using fish contaminant data from the Wisconsin Department of Natural Resources to create an experimental PCB mixture that modeled the PCB congener profile in fish consumed by the human population under study in Project 2 as closely as possible (Fox River PCB mix). Before undertaking the neurochemical and neurobehavioral studies in Projects 3 and 4, the mixture was characterized for its aryl hydrocarbon receptor (AhR) activity, ryanodine receptor (RyR) activity and developmental toxicity (Kostyniak et al., 2005). The research approach also included using PCB/MeHg exposure ratios that were similar to those found in the fish consumed by the human population as well as an extended exposure period beginning prior to conception and continuing throughout gestation and lactation. Although time-consuming and labor intensive this chronic oral exposure more accurately modeled exposure as it occurs in the human population.

Summary/Accomplishments (Outputs/Outcomes):

Research conducted in each of the research projects is summarized below and all publications resulting from the research are listed at the end of this report.

Project 2: Perinatal PCBs and Neuropsychological/Auditory Function (Sweeney, PI)

The primary goals of Project 2 were to evaluate the impact of PCB and MeHg exposure on women’s reproductive health and child development in Hmong refugees consuming contaminated fish from the Fox River and other local waters in northeastern Wisconsin, and to develop effective educational strategies to reduce exposure in this group of recent immigrants with limited education and poor English literacy.

Specific Aim 1: Establish a cohort of Hmong couples of childbearing age who have a high probability of consuming fish from the Fox River and other polluted waters in northeastern Wisconsin.

The Hmong are a semi-migratory ethnic group from the mountainous regions of Laos. Primarily agriculturists, they lived in large clans that acted as both social and economic units. When the Vietnam War spread into Laos, the United States (US) enlisted Hmong tribesmen to aid in covert operations there. After the war, retaliation by the Communist Pathet Lao forced the Hmong to flee to refugee camps in Thailand and most eventually resettled in other countries, primarily the US. Wisconsin is surpassed only by Minnesota and California as the states with the highest number of Hmong residents (US Census Bureau, 2000). According to recent census figures, approximately 33,791 Hmong currently reside in Wisconsin and 2,957 live in the Green Bay, Wisconsin metropolitan area (report by the University of Wisconsin, Madison, because they were considered to be at high risk for PCB and MeHg exposure due to their propensity to engage in subsistence fishing in highly polluted local waterways.

The basic demographic and reproductive characteristics of the reproductive age men and women recruited to our study are described in Kornosky et al. (2008). Women in the sample ranged in age from 16-46 years (mean 31.2) and men ranged from 19-60 (mean 35.4). However, only about half of the men and women were certain of their exact age. More than half of the men (50.4%) and women (59.6%) had no formal education. However, even though educational attainment was low, 82.3% of the men and 76.6% of the women were employed at the time of enrollment into our study. Total yearly income was less than $40,000 for 67.9% of the study population, and family size was large, with an average of 6-7 people (5.2 children) per household. In contrast, the average US family has 3-4 people and a mean household income of $56,000 (US Census Bureau, 2000). Consumption of alcohol, smoking and use of illicit drugs was very low, especially among the women. Only 3 women classified themselves as current drinkers and none reported smoking cigarettes.

Specific Aim 2: Describe the fish consumption practices, serum PCB levels and reproductive experiences of this population.

The exposure characteristics of the population are described in two manuscripts. Schantz et al. (submitted) reports PCB, DDE and MeHg exposures and their relation to local fish consumption and other predictors. Serum samples from 142 people were analyzed for PCBs and p,p’-DDE by capillary column gas chromatography with electron capture detection (ECD). Whole blood was analyzed for total mercury by cold vapor atomic absorption spectrometry and atomic fluorescence spectroscopy. Lipid-adjusted total PCB concentrations ranged from 8.7-3,091 ng/g, with a geometric mean of 183.6 ng/g. DDE ranged from 0.3-7,083 with a geometric mean of 449.8 ng/g. Men had higher PCB and DDE concentrations than women. Only 21 of the 142 people who provided a blood sample were not sport-caught fish consumers, but fish eaters had much higher total serum PCB concentrations (arithmetic mean of 347.6 ng/g lipid) than non-fish eaters (arithmetic mean of 87.8 ng/g lipid). Not surprisingly, serum PCB concentrations were significantly correlated with fish consumption (r=0.43, p<0.0001). The p,p’-DDE concentrations in this sample of Hmong refugees from northeastern Wisconsin were quite high in comparison with other fish eating populations and unexpectedly, the DDE concentrations were not related to fish consumption (r=0.09, p=0.29). Instead serum DDE was strongly associated with the number of years spent in a Thai refugee camp before immigrating to the US (r=0.60; p<0.0001). This likely reflects the use of DDT for malaria control in the refugee camps. PCB congeners 138, 153, 118 and 180 accounted for a smaller percentage of the total PCBs than has been reported in other fish eating populations, and several lightly chlorinated congeners were present in relatively large amounts. This somewhat unique pattern of exposure may reflect the heavy use of Aroclor 1242, a lightly chlorinated mixture of PCBs, in the paper industry in northeastern Wisconsin. Mercury exposure was low in this population. Only five of the 142 individuals sampled (3.5%) had blood Hg concentrations above 5.8 μg/L, the concentration upon which the EPA’s RfD of 0.1 μg/Kg/day was based.

Peck et al (in press) reports phthalate exposure in a subset of the men and women recruited into the study. The reproducibility of urinary phthalate metabolite concentrations has not been well characterized in nonpregnant women of reproductive age. Therefore, our objectives were to describe the distribution of urinary phthalate metabolites concentrations among this population of Hmong women of reproductive age, and to evaluate intra- and inter-individual variability of phthalate metabolite concentrations. Ten phthalate metabolites were measured in first morning urine samples collected from 45 women and 20 of their spouses who were members of the larger cohort. Repeated first morning urine samples were collected and analyzed from 25 women who provided up to three samples over approximately one month. Measurement variability was assessed using intraclass correlations (ICCs) and surrogate category analysis. Linear mixed models were used to evaluate the associations between participant characteristics and phthalate metabolite concentrations. Nine of the 10 phthalate metabolites were detected in > 80% of all samples analyzed, of which seven were detected in all samples. As a measure of reliability, ICCs were strongest for monobenzyl phthalate (0.64) and weakest for the metabolites of di(2-ethylhexyl)phthalate (DEHP) (ranging from 0.13 to 0.22). Similarly, surrogate category analysis suggested that a single urine sample characterized average one-month exposure with reasonable accuracy across low, medium and high tertiles for all metabolites except the DEHP metabolites. Geometric mean concentrations of monoethyl phthalate increased with age, but patterns by education, income, body mass index, environmental tobacco smoke or season were not observed when measures were adjusted for urinary dilution. Our results suggest that the participant characteristics assessed in this study have limited influence on inter-individual variability of phthalate metabolite concentrations. With regard to intra-individual variability, our results suggest that urinary concentrations of some phthalate metabolites are more reproducible over time and less subject to exposure misclassification than others (e.g., metabolites of DEHP).

Kornosky et al. (2008) includes a detailed analysis of the reproductive characteristics of the population, before and after immigration to the US. The women differed from the general US population in several important ways. Contraceptive use was reported in just 28% of the women, whereas approximately 73% of married women of childbearing age in the general US population report current contraceptive use. The mean age at menarche was 13.5 years, slightly older than the 12.6 reported in the US population at large. However, interpretation of this finding is difficult, given the uncertainty of many Hmong women regarding their true age. Couples had an average of 5.2 children, a much higher birth rate than in the US population at large. Infertility, defined as the inability to conceive for at least 12 months was reported in 5.7% of the women, lower than the 10.2% reported for women of childbearing age in the US. Prenatal care increased and breast feeding decreased after immigration to the US. In total, only 44% of the live births among these women had prenatal care during the first trimester. When this was restricted to just births that occurred in the US, 60% initiated prenatal care in the first trimester. This is still much lower than the 81% that has been reported in the general US population. Over 90% of infants born in Laos or Thailand were breast fed, whereas only about 11% of US-born infants were breast fed. Interestingly, the sex ratio differed by the country of origin. Births in the refugee camps had the lowest ratio: 83.8 male births per 100 females. Just the opposite was true in Laos where there were 147.6 male births per 100 female. The ratio for births in the US was similar to the ratio reported in the population at large (100.9 males per 100 females vs. 104.6 to 100 in the general population). These figures must be interpreted with caution due to the small sample size, but the lower sex ratio in the refugee camps is consistent with lower sex ratios that have been reported in other populations subjected to political, social or environmental stressors. Interestingly, decreases in male births have also been reported in offspring of men exposed to DDT. As outlined above, serum DDE concentrations in this population are significantly elevated and the concentrations are highly correlated with the number of years spent in a refugee camp.

Specific Aim 3: Examine the relationship between PCB and MeHg exposure, serum thyroid hormone concentrations during pregnancy and cognitive, motor and auditory function in infancy.

Several issues related to working with this population of recent Hmong immigrants with low levels of educational attainment, poor English literacy and a general distrust for western medicine significantly impacted our ability to successfully complete this aim within the time frame of the funding. Issues that impeded our progress included finding individuals to recruit, interview and test study participants who had sufficient education and were also fluent in the Hmong language, training new employees with little or no prior research experience to serve in these roles, gaining the trust of the community, and adapting typical research protocols to be sensitive to traditional cultural practices of the Hmong, some of which are significantly outside the mainstream of American culture. We were successful in overcoming these obstacles, and we did implement protocols to identify when study participants became pregnant, follow their pregnancies to collect health data and blood samples at appropriate intervals, and collect cord blood and auditory and neuropsychological data from their infants at birth. This process involved establishing collaborations with four local hospitals. However, the study was in the early stages of recruitment of the birth cohort when it was learned that the competitive renewal would not be funded. At that time, 14 women were pregnant or had given birth, approximately 20 others were enrolled and were being followed to identify pregnancy and active recruitment of additional women who were planning to become pregnant was underway. The decision was made to halt further recruitment at that time because we could not justify recruiting women whom we quite likely would not have sufficient funds to follow to term.

Although it was extremely disappointing to discontinue a study of this magnitude just as it was getting underway, the research team learned a tremendous amount that could be extremely valuable to others planning to conduct health-related research in recent immigrants from non-western cultures. In addition, as outlined below, the research team was able to develop and distribute a number of useful educational materials within the community. Furthermore, this research program spawned a successful spin off project funded by ATSDR which is still underway. The goals of the ATSDR-funded research were to assess neuropsychological function in adolescents and adults from the same population. These studies, because they did not involve pregnancy and child birth, were somewhat easier to implement successfully. At this time, the collection of neuropsychological data from Hmong adults is completed and data analysis is underway. Recently, a competitive renewal of the grant allowed the data collection in adolescents to be expanded to include children from other ethnic backgrounds and to include analysis of additional contaminants including PBDEs.

Specific Aim 4: Develop education and intervention programs that will be effective in reducing PCB and MeHg exposure in recent immigrants with poor English literacy.

Several educational strategies were developed and implemented in collaboration with community advisors and the local Hmong Association in Green Bay, Wisconsin. These included a fish consumption advisory that was based on the fish consumption advice in the Wisconsin Fishing Advisory, but focused on the 5 fishing areas that were the most popular fishing sites for the local Hmong population. The advisory used pictures to identify the different fish species and included a minimum of written information. The advisory was translated into both Hmong and Laotian by local interpreters. This fishing advisories were distributed to the local community in a number of different forums including at the Hmong Association, at yearly open houses held in the community by the research group in collaboration with the Hmong Association, at local Hmong New Years celebrations and at other local Hmong events such as a large soccer tournament/community fair held every May. Copies of the fishing advisory were also distributed to all study participates every March prior to the start of the fishing season. The fishing advisory was shared with both the Wisconsin and Minnesota departments of public health and is also available to other researchers, organizations and the public through the FRIENDS Center website at http://friendscenter.illinois.edu/pdf/Green_Bay_Area_Fishing_Advisory.

An educational video was also developed and distributed within the community. The video used well-known and respected local community members as actors and narrators and is available in either Hmong or Laotian with English subtitles. The approximately 20 minute video provides basic information about the contaminants in the fish, illustrates how to use the fishing advisory to determine which fish are safe to catch and eat, and demonstrates how to filet the fish to remove the parts (skin and fat) that are highest in PCB content. The video also discusses the best ways to cook fish (steaming, broiling or grilling) to further reduce PCB exposure and provides an example of how to prepare fish using a traditional Hmong recipe. In the example, a local Hmong family first removes the skin and fat and then steams the fish with traditional spices and vegetables. The video was distributed to study participants, local organizations and the Wisconsin and Minnesota departments of health. Additional copies are available to researchers, organizations or members of the public by request. In addition, clips from the video are available at the FRIENDS Center website at http://friendscenter.illinois.edu/video.html.

An educational newsletter was developed and distributed periodically to study participants, local community leaders and local organizations that serve the Hmong population. The newsletter provided updates on the progress of the study, informed the community about upcoming events such as the yearly open house sponsored by the center, provided answers for frequently asked questions and included news stories on topics relevant to the research focus of the Center. Back copies of the newsletters are available on the FRIENDS Center website at http://friendscenter.illinois.edu/newsletter.html.

Finally, several educational games were developed for children to teach safe fishing practices. These included an educational bingo game and a wheel of fortune game. These were used at the open houses and other community events to teach children about safe fishing practices. Information about these games has been shared with various researchers and organizations and is available by contacting Susan Schantz (schantz@illinois.edu).

The findings from Project 2 illustrate that some sport-caught fish consumers in the US remain at risk of PCB exposure at concentrations that may put the fetus at risk for neurodevelopmental delays or deficits. Recent immigrants from Southeast Asia may be particularly likely to have elevated PCB exposure because they are more likely to engage in subsistence fishing. They also have a relatively high birth rate compared to the US population as a whole. This study evaluated exposures in Hmong refugees, but Laotian and Vietnamese immigrants are also heavy fish consumers and could also be at increased risk. These data also highlight the fact that recent immigrants to the U.S., particularly those from parts of the world where DDT has been used extensively for malaria control, may have elevated body burdens of DDE irrespective of their fish eating status. It will be important to define the potential long term health risks from this exposure.

The findings of this study also provide evidence that environmental phthalate exposures are prevalent among women of reproductive age in underserved populations. The study demonstrated that phthalate metabolites concentrations are reproducible over a one month sampling interval for most metabolites, but caution should be exercised when using single samples to estimate exposure to DEHP. Given the limited number of studies in reproductive-aged women, future investigations are required to determine if adverse reproductive outcomes are associated with phthalate exposures at levels that have been commonly observed in the population.

Project 3: Neurobehavioral Effects of PCBs and Methylmercury in Rats (Schantz, PI)

The primary goal of Project 3 was to use a rodent model to characterize the effects of PCBs alone, MeHg alone or PCBs and MeHg in combination on cognitive and auditory function. As outlined below, an experimental PCB mixture was formulated that closely modeled the PCB congener profile in fish consumed by the human population under study in Project 2. In addition, groups exposed to both PCBs and MeHg received the two contaminants in a ratio that modeled the PCB to MeHg ratio present in the fish. Pharmacological challenges were used to investigate the role of changes in dopamine function in mediating specific PCB- and MeHg-related behavioral impairments, and the results of the these studies were used to design cognitive and auditory testing protocols for children exposed to these chemicals via consumption of contaminated fish in northeastern Wisconsin.

Specific Aim 1: Model human exposure to PCBs and MeHg from Fox River fish in the laboratory rat.

Data on the PCB congener profile in walleye from the Fox River in northeastern Wisconsin were obtained from the Wisconsin Department of Natural Resources. This information was used to create an experimental mixture that approximated the congener profile in Fox River fish (Kostyniak et al., 2005). The mixture consists of 35% Aroclor 1242, 35% Aroclor 1248, 15% Aroclor 1254 and 15% Aroclor 1260. As shown in the figure (see below), the congener distribution is very similar to that in the fish. The dioxin-like activity of the mixture was estimated using a cell-based reporter gene assay that assesses aryl hydrocarbon receptor-responsive luciferase activity, and was found to be very low (approximately 25 pg dioxin toxic equivalents/mg PCB). In contrast the ryanodine receptor activity in terms of potency and efficacy as determined in 3H-ryanodine binding studies was relatively high with an EC50 of 1.8μM and aBmax of 5.1 pmol/mg protein. Interestingly, the slope of the dose response obtained with the Fox River PCB Mixture was steeper than the slopes observed for any of the individual commercial Aroclor mixtures, suggesting a higher proportion of congeners active at the ryanodine receptor. Primarily coplanar PCB congeners are active at the aryl hydrocarbon receptor, while primarily non-coplanar PCB congeners are active at the ryanodine receptor.

Comparison of the Fox River PCB Mixture to the PCB Congener Profile in Fish from the River

Before initiating behavioral studies, the developmental toxicity of the Fox River PCB Mix was evaluated in vivo (Kostyniak et al., 2005). Female Long Evans rats were exposed to 0, 1, 3, or 6 mg/kg/day beginning 4 weeks prior to breeding and continuing until litters were weaned on Postnatal Day 21. There were few signs of developmental toxicity at these doses. Gestational weight gain, litter size, percent live births and litter size were unaffected. Pups in all 3 exposure groups were slightly smaller at birth and remained smaller at weaning, but these deficits were relatively small. Liver-to-body-weight ratios increased, particularly in the 6 mg/kg group, most likely due to liver enzyme induction that typically follows PCB exposure. The mixture markedly reduced circulating T4 concentrations at weaning. In contrast, T3 was only slightly reduced. This pattern, a marked reduction in T4 with a smaller reduction in T3, is consistent with that reported previously for Aroclor 1254.

Specific Aim 2: Characterize the cognitive and auditory effects of perinatal exposure to the Fox River PCB Mixture alone, MeHg alone or the PCB mixture and MeHg combined.

Cognitive Function

An important goal of the cognitive studies was to assess the effects of the Fox River PCB Mix on various aspects of executive function. Male and female Long Evans rats were exposed to the Fox River PCB Mix and tested on a series of cognitive tasks assessing cognitive flexibility, working memory and response inhibition. The most striking finding was that PCB-exposed rats showed evidence of deficits in response inhibition (Sable et al., 2006; Sable et al., 2009). Long-Evans rats were exposed to corn oil (control), the Fox River PCB Mixture alone (1 or 3 mg/kg), MeHg alone (1.5 or 4.5 ppm), the low combination (1 mg/kg PCBs + 1.5 ppm MeHg), or the high combination (3 mg/kg PCBs + 4.5 ppm MeHg) throughout gestation and lactation. Male and female offspring were trained to asymptotic performance on a differential reinforcement of low rates (DRL) operant task as adults. In this task, the rat was required to wait 15 seconds between lever presses in order to obtain food reinforcers. Presses occurring before 15 seconds reset the timer to zero and delayed the reinforcer. PCB-exposed groups had a significantly lower ratio of reinforced to non-reinforced responses than controls. Groups exposed to MeHg alone were not impaired and the deficits observed in PCB-exposed groups were not seen when PCBs were co-administered with MeHg. Overall, the findings suggest that developmental exposure to PCBs can decrease DRL performance. Unexpectedly, co-exposure to MeHg seemed to mitigate the detrimental effects of PCBs on response inhibition.

Ratio of Reinforced to Non-reinforced Responses on the DRL Task

Auditory Function

Rats developmentally exposed to PCBs and MeHg, alone or in combination, were also assessed to determine the impact of these contaminants on auditory function (Powers et al., 2006; Powers et al., 2009). In an initial study, female Long-Evans rats were exposed to 0, 1, 3 or 6 mg/kg of the Fox River PCB Mix beginning 28 days prior to breeding, throughout gestation until weaning at PND 21 (Powers et al., 2006). Hearing was assessed when the animals were young adults using two complimentary approaches: distortion product otoacoustic emissions (DPOAEs) were used to assess the functional integrity of the cochlea, and auditory brain stem responses (ABRs) were used to assess the integrity of the auditory pathway from the auditory nerve to the cortex.

It is believed that PCBs affect hearing by damaging the outer hair cells of the cochlea. Thus, we hypothesized that DPOAEs would be a particularly sensitive method for measuring PCB-induced hearing loss. This was confirmed in our research. All three doses of PCBs reduced the amplitude of the cochlear response and increased the threshold for a cochlear response across a range of frequencies (see figure below). The high dose resulted in a 40% reduction in the amplitude of the distortion product. There were also reductions in the threshold of the ABR response, in the absence of any significant changes in the amplitude or latency of the ABR wave forms. This is also suggestive of cochlear damage.

In a follow-up study females were exposed to 1 mg/kg PCB, 3 mg/kg PCB, 1.5 ppm MeHg, 4.5 ppm MeHg, 1 mg/kg PCB + 1.5 ppm MeHg, or 3 mg/kg PCB + 4.5 ppm MeHg for the same exposure period (Powers et al., 2009). As in the previous study, auditory function of the offspring was assessed in adulthood by measuring distortion production otoacoustic emissions (DPOAEs) and auditory brainstem responses (ABRs). Groups exposed to PCBs alone had attenuated DPOAEs, elevated DPOAE thresholds, and elevated ABR thresholds in comparison to controls, replicating our earlier findings. Groups exposed to MeHg alone did not differ from controls. Intriguingly, the effects of PCB exposure on auditory function appeared to be attenuated by co-exposure to MeHg, paralleling the finding we observed on response inhibition in the DRL task (Sable et al., 2009; see above).

A surprising result of these studies was that co-exposure to MeHg appeared to attenuate PCB-induced deficits in both cognitive and auditory function. Interactive effects of co-exposure to PCBs and MeHg have also been observed in vitro. In rat brain tissue, exposure to either PCBs or MeHg caused increased intracellular calcium release. Co-exposure resulted in an increase that was greater than the additive effects of the two chemicals individually, but co-exposure at higher concentrations or for longer durations produced antagonistic effects (Bemis & Seegal Neurotoxicology. 21(6):1123-1134; 2000). It is clear that PCBs and MeHg can interact in complex ways to cause functional changes, but the nature of this interaction remains unresolved and will require further study.

Specific Aim 3: Investigate the role of changes in specific neurotransmitter systems in mediating behavioral effects of PCBs and MeHg.

To evaluate the role of catecholamines in mediating the effects of the Fox River PCB Mixture on response inhibition, drug challenges with amphetamine were conducted as a continuation of the DRL 15 study (Sable et al., 2009). Each rat was trained to asymptotic performance on the DRL 15 task. Then doses of 0, 0.5, and 1.0 mg/kg amphetamine were given IP 10 min prior to DRL testing twice weekly via a counterbalanced Latin square design. The percent change in the ratio of reinforced:nonreinforced trials was analyzed, with a positive change indicating improved performance and a negative change indicating impaired performance (see figure below).

In all groups, amphetamine impaired performance in a dose-dependant manner, as is expected with higher degrees of dopamine receptor stimulation. However, especially in the male rats (see a, above), amphetamine did not impair performance in PCB- and MeHg-treated rats to the same extent that it did in controls. AMPH was less disruptive to responding in males receiving PCBs alone, MeHg alone, and 1.0 mg/kg PCB + 1.5 ppm MeHg. This is consistent with a state of dopamine hypofunctionality. That is, increased dopamine release resulting from amphetamine is presumed to be less disruptive in PCB- or MeHg-exposed rats where basal dopamine activity is lower. This contrasts with control rats, whose basal dopamine levels are in the normal range, where amphetamine results in excessive dopamine release and greater impairments in performance. Paradoxically, the disruption in responding by AMPH in males given 3.0 mg/kg PCB + 4.5 ppm MeHg did not differ from controls.

Specific Aim 4: Use results from animal experiments to guide the selection of behavioral tasks for use in children exposed to PCBs and MeHg via consumption of Fox River fish.

Although neurological assessments of infants could not be initiated because the birth cohort study was terminated early, the findings from the cognitive and auditory studies in laboratory rats were used to develop a test battery for assessing neuropsychological and auditory function in a parallel project funded by ATSDR (TS000072). In that study, 14-18 year-old children in northeastern Wisconsin whose families are sport fish consumers are being assessed to evaluate their exposure to fish-borne contaminants and the relationship between this exposure and neurological outcomes. Because the animal studies suggested that PCB exposure is associated with deficits in executive functions and with problems with inhibitory control, in particular, the battery focuses on assessing executive functions including working memory, planning, cognitive flexibility, attention and inhibitory control. Similarly, the findings from auditory testing in laboratory rats were used to develop a protocol for assessing auditory function in the children. Because the animal studies point to the cochlea as the primary site of action for PCBs on auditory function, the protocol for testing children focuses on assessing cochlear function through the measurement of distortion product otoacoustic emissions. This research is currently in progress and approximately 40 of a planned 250 children have been assessed as of 12/31/2008.

Significance of the Findings from Project 3

The findings emerging from the research in project 2 have been instrumental in shaping the course of our research program for the future in several important ways. First, the finding that rats exposed to the Fox River PCB mixture exhibited a striking dose-dependent deficit in auditory function that persisted into adulthood was the basis for two currently funded lines of research. The first, funded by an R01 from NIEHS (ES015687), is aimed at understanding the underlying mechanisms through which PCBs alter cochlear function and induce hearing loss. The potential for early PCB exposure to exacerbate later noise-induced hearing loss is also being evaluated. The second line of research, funded by ATSDR (TS000072) and by a grant from the University of Illinois Research Board, uses methods that closely parallel those used to assess cochlear function in the rodent studies to assess whether PCB exposure from contaminated fish has any impact on cochlear function/hearing in adolescent children.

In addition, the complementary neurochemical studies (Project 4) and neurobehavioral studies (Project 3) conducted with FRIENDS Center funding have revealed that the pattern of neurochemical and cognitive deficits following developmental PCB exposure closely parallels the pattern of deficits seen in children with attention deficit hyperactivity disorder (ADHD). That is, PCB-induced hypofunctionality of brain dopamine systems appears to cause animals to have difficulty performing various cognitive tasks that require inhibitory control for their successful execution (Bemis and Seegal, 2004; Sable and Schantz, 2006; Sable et al., 2006, Sable et al., 2009). An important aim of our current laboratory studies funded by NIEHS (ES015687) is to further understand the mechanisms through which PCBs and also the polybrominated diphenyl ethers (PBDEs), which are structurally similar to PCBs, alter brain dopamine function, as well as how these changes in brain dopamine impact key aspects of cognitive function (i.e. attention and inhibitory control) that are affected in ADHD children. A current postdoc in the lab, Dr. Paul Eubig has a K08 grant pending that would expand these studies to include a detailed assessment of the particular aspects of inhibitory control that are impacted by PCB exposure and the role of dopaminergic and noradrenergic activity in particular brain regions in mediating these effects. Because of the parallels with ADHD, our research has the potential to contribute significantly to the understanding of this common childhood disorder.

Furthermore, because PCBs alter dopamine function and cause deficits in inhibitory control, we have also hypothesized that early PCB exposure could change the organism’s sensitivity to psychostimulant drugs such as amphetamine and cocaine and thus increase the risk of drug abuse in adolescence and/or adulthood. A recent postdoc in the lab, Dr. Helen Sable, obtained a Pathway to Independence Grant (K99 ES015428) to pursue this line of research. Dr. Sable recently moved to a tenure track faculty position in the Department of Psychology at the University of Memphis, where she is continuing to carry out these studies.

Project 4: Developmental Effects of PCBs and Methylmercury (Seegal, PI)

We have previously demonstrated that co-exposure to polychlorinated biphenyls (PCBs) and methyl mercury (MeHg)—two of the major neurotoxicants found in contaminated fish from the Fox River—synergistically increased the release of dopamine (DA) in striatal tissue from adult animals and altered intracellular calcium concentrations in cells in culture (Bemis and Seegal, Environ Health Perspect., 107, 879-885, 1999; Bemis and Seegal, Neurotoxicology, 21, 1123-1134, 2000). Here, we extend this work to include tissue derived from early postnatal animals where we characterize the effects PCBs on the dopamine transporter and DA uptake. We also examined the consequences of PCB and MeHg on the vesicular monoamine transporter, ROS formation and mitochondrial function. Finally, we examined the developmental consequences of exposure to PCB and MeHg using organotypic co-cultures of striatum and substantia nigra from embryonic brains. These findings, high-lighted below, are organized by the Specific Aims delineated in the funded application. The figures presented below, many from the publications included on the list of publications that resulted from this grant, indicate that we have accomplished the majority of the goals of the project.

Specific Aim 1: Do PCBs and methylmercury alter release and synthesis of DA and intracellular calcium concentrations in vitro?

PCBs and Methylmercury Reduce Synaptosomal DA Concentrations: Greatest Reductions in the Young

Striatal synaptosomes from postnatal day (PND) 7, 14, 21, or 70 rats were exposed ex vivo to either Fox River PCB Mix (10, 20 or 40 μM) or methylmercury (1, 1, 2.5, 5, or 10 μM) for 30 min. Both PCBs and MeHg reduced synaptosomal DA concentrations in a dose-dependent manner, although MeHg resulted in greater changes than did PCBs. Most importantly, the greatest changes were seen in tissue from PND7 animals (Dreiem et al., NeuroToxicology, submitted).

All data are expressed as a percent of the vehicle control. *p<0.05, **p<0.01, ***p<0.001 indicate the significance of post hoc t-tests comparing individual doses with their respective control.

In addition we have shown that co-exposure of PND7 striatal synaptosomes to PCBs and MeHg antagonized the reductions in synaptosomal DA seen following exposure to PCBs only. – i.e., the effects on synaptosomal DA were less than predicted from the addition of the effects of the two contaminants presented singly. These results stand in sharp contrast to the synergism seen in adult synaptosomes following exposure to PCBs and MeHg (Bemis and Seegal, Environ. Health Perspect., 107, 879-885, 1999).

PCBs Increase Media Dopamine Concentrations in Striatal Tissue—Evidence of Dopamine Transporter (DAT) Inhibition

Striatal synaptosomes prepared from adult rat brain were exposed ex vivo to either Aroclor 1254 or one of four individual PCB congeners (see legend on figure). PCBs significantly increased media DA concentrations in a dose-dependent manner demonstrating that the dopamine transporter was inhibited by PCBs. All data are expressed as a percent of the vehicle control. N=9-10 observations per exposure condition; *p≤0.05, **p≤0.01, ***p≤0.001 indicate the significance of post hoc t-tests comparing individual doses with their respective control (Bemis and Seegal, Toxicol. Sci., 80, 288-885, 2004).

PCBs Reduce Dopamine Uptake into Striatal Synaptosomes in an Age-Dependent Manner

Congener #95 (2,3,6,2’,5’ PCB) inhibited [3H]-DA uptake to a greater extent in striatal synaptosomes from postnatal day (PND) 7 and 14 animals than in synaptosomes from adult rats. These results, demonstrating greater inhibition of the dopamine transporter in tissue from young animals, provide a mechanistic basis for the larger decreases in DA concentrations seen in the immature brain.

Specific Aim 2: What are the consequences of PCB and MeHg induced ‘Free’ DA and Intracellular Calcium?

PCB-Induced Elevations in Total DOPAC Correlate with Reductions in Synaptosomal Dopamine—Evidence of Vesicular Monoamine Transporter Inhibition

Synaptosomes, prepared from the striata of adult male rats, were exposed ex vivo to various PCBs (40 μM for 30 min). Total 3,4,-di-hydroxyphenylacetic acid (DOPAC) concentrations, a widely accepted measure of metabolized cytosolic (non-vesicularly stored) DA, increased and were significantly correlated with decreased synaptosomal DA concentrations (p≤0.001). These findings suggest that elevations in cytosolic DA due to PCB-induced VMAT2 inhibition (seen here as DOPAC) play a key role in regulating synaptosomal DA content (Bemis and Seegal, Toxicol. Sci., 80, 288-885, 2004).

MeHg induces greater ROS formation in striatal synaptosomes from younger rats

Striatal synaptosomes were loaded with DCFH-DA and exposed to MeHg for 30 min before ROS formation was assessed by measuring increase in DCF fluorescence. The results are given as percentage of age-matched vehicle controls (controls are set to 100%). Each value is the mean of 16 to 22 wells in three to four independent experiments ± SE. *Significantly different from age-matched controls (p≤0.05, ANOVA, Dunnett’s test) (Dreiem, Gertz and Seegal, Toxicol. Sci., 87, 156-162, 2005).

Methylmercury Reduces Mitochondrial Function in an ROS Independent Fashion

We have assessed the consequences of MeHg induced ROS formation in synaptosomes from adult rats on mitochondrial membrane potential (ΔΨm) and mitochondrial metabolic function (assessed by reduction of methylthiazoletetrazolium (MTT)). MeHg reduced mitochondrial membrane potential and mitochondrial metabolic function (see table below) although these reductions were not prevented by co-incubation with Trolox—a potent anti-oxidant. Therefore, we conclude that ROS is not the cause of mitochondrial dysfunction and loss of mitochondrial membrane potential after MeHg exposure—rather, that mitochondrial membrane dysfunction is an early event in MeHg toxicity and that ROS formation may be an effect of that damage (Dreiem and Seegal, NeuroToxicology, 28, 720-726, 2007).

1 MeHg concentration was 5 μM in the 2 methylthiazoletetrazolium (MTT) assay and 0.5 μM MeHg for 3 mitochondrial membrane potential (Δ Ψm ) measurements.

a Significantly different from control (p≤0.001). b Not significantly different from MeHg alone.

MeHg Exposure Increases Cytosolic Calcium Levels in Rat Striatal Synaptosomes

MeHg was added to synaptosomes (arrow) preloaded with Fura-2, and the levels of cytosolic calcium were assessed by monitoring of the 340 nm/380 nm fluorescence ratio of fura-2. When the experiments were repeated in calcium-free HEPES buffer with 20 μM EGTA, the MeHg-induced increases in cytosolic calcium levels appeared to be slightly smaller, however, the reductions were not significant (data not shown). The figure shows the means of three independent experiments after subtraction of starting levels (Dreiem and Seegal, NeuroToxicology, 28, 720-726, 2007).

MeHg exposure increases mitochondrial calcium levels in rat striatal Synaptosomes

MeHg was added to synaptosomes (arrow) preloaded with rhod-2, and the levels of mitochondrial calcium were assessed by monitoring of the 580 nm fluorescence of rhod-2. Higher concentrations (< 5 μM Mehg) did not lead to a further increase in mitochondrial calcium levels (data not shown).The figure shows the means of five independent experiments after subtraction of starting levels (Dreiem and Seegal, NeuroToxicology, 28, 720-726, 2007).

Specific Aim 3: What are the developmental neurological consequences of exposure to PCBs and MeHg?

PCBs and MeHg Decrease Striatal Dopamine, in Organotypic Co-Cultures of Striatum and SN

We have examined the biochemical consequences of PCB or MeHg exposure using an organotypic co-culture model which allows two distinct regions of brain tissue to be cultured over an extended period of time. Here, embryonic day 21 (E21) rat striatum and E14 rat substantia nigra (SN) are co-cultured to model the developing nigro-neostriatal DA system. In co-culture, DA neurons of the SN project to and innervate the striatal tissue in a manner similar to that observed in vivo. We have now demonstrated that exposure to low micromolar concentrations of the Fox River PCB Mix reduces striatal (A) and ventral mesencephalon (VM, B) DA concentrations (Lyng, Snyder-Keller and Seegal, Toxicol. Sci., 97, 128-139, 2007). Additionally, we have demonstrated that sub-micromolar doses of MeHg results in a dose dependent decrease in striatal DA concentrations (not shown).

In further studies we used the organotypic co-culture system to determine whether alterations in the vesicular storage of DA, resulting from PCB exposure and consequent induction of oxidative stress, leads to GABA and DA neuronal dysfunction. 24h exposure to an environmentally relevant mixture of PCBs reduced tissue DA and GABA concentrations, increased medium levels of DA and measures of oxidative stress in both the striatum and VM. Alterations in neurochemistry and increases in measures of oxidative stress were blocked in the presence of the anti-oxidant n-acetylcysteine (NAC). To determine whether alterations in the vesicular storage of DA were responsible for PCB induced oxidative stress and consequent reductions in GABA levels, we depleted DA from the co-cultures using α-methyl-p-tyrosine (AMPT). AMPT reduced striatal and VM DA levels by 90% and 70%, respectively and yet subsequent PCB exposure neither increased levels of oxidative stress nor resulted in GABA depletion. These results suggest that PCB-induced alterations in the vesicular storage of DA, resulting in increased levels of unsequestered DA, leads to increased oxidative stress, depletion of tissue glutathione, and consequent reductions in tissue GABA concentrations.

Changes in DA (A) and GABA (B) concentrations in the striatum, VM, and medium of organotypic co-cultures following a 24-h exposure to vehicle control, 8 μM FR PCBs, or 10 μM H2O2, each in the presence or absence of 1 mM n-acetylcysteine (NAC). Samples underwent HPLC-ECD for determination of DA and GABA content, and each value represents the mean ± S.E.M. of 7–12 samples. Within a region, those bars labeled with different letters denote values significantly different from one another (p≤0.05). (Lyng and Seegal, NeuroToxicology, 29, 301-308, 2008). Changes in the total GSH content of the VM and striatum of organotypic co-cultures following a 24-h exposure to vehicle control, 8 μM FR PCBs, or 10 μM H2O2, each in the presence or absence of 1 mM NAC. Each value represents the mean ± S.E.M. of 8–10 samples. Within a region, those bars labeled with different lettedenote values significantly different from one another (p≤0.05 Lyng and Seegal, NeuroToxicology, 29, 301-308, 2008).

Significance of the Findings from Project 4

In summary, in Project 4 we have demonstrated that both PCBs and MeHg reduce DA function in a number of different preparations of neuronal tissue from developing animals; that tissue from early preweaning animals is uniquely sensitive to these exposures and that this sensitivity may be due to higher contaminant induced oxidative stress because of limited anti-oxidant potential of developing central nervous system tissue. The above findings provide a better understanding of the mechanisms of actions of these two contaminants during development which, in turn, provide needed information for risk assessment and intervention. In addition, we have demonstrated co-exposure to these fish-borne contaminants leads to significant neurochemical interactions, reinforcing the need to revise fish consumption guidelines that are currently based on exposure to single contaminants.

Project 5: Analytical Toxicology Core Facility

The objective of the Analytical Toxicology Core Facility (ATCF) was to provide analytical support to both the epidemiological and animal research projects of the FRIENDS Children’s Environmental Health Center. The ATCF support involved the development of new analytical techniques, analyses of samples and analyses of data. All procedures were controlled by a strict QC/QA program. This laboratory has extensive experience determining specific congeners of PCBs and pesticides and heavy metals at ppb levels in biological samples, and has participated in nationwide proficiency programs for PCBs, pesticides and mercury. The ATCF also performed a reporter gene bioassay for the quantification of total dioxin (TCDD) toxic equivalents (TEQs) in Hepa 1c1c7, mouse hepatoma cells, which are stably transfected with the reporter plasmid p2Dluc containing 2 copies of the DRED consensus sequence. Primary accomplishments of the ATCF are summarized below.

Preparation of Congener Specific Dosing Solutions:

Considerable effort early in the grant was devoted to the preparation of the appropriate PCB congener mix to be used for the animal studies throughout the tenure of the Center Grant. PCB congener profiles were obtained for 15 subjects consuming Fox River fish. There was considerable variation in absolute levels of total PCBs but a similar congener profile. Women with an extensive history of breast feeding tended to have lower PCB levels particularly of the higher chlorinated congeners which tend to bioaccumulate. PCB congener profiles for human subjects and PCB congener profiles Fox River walleye and white bass, were compared. As might be expected, fish PCB congener profiles did not correspond directly with that found in the subjects. Fish tended to have a congener profile with a more concentrated Arochlor 1242 like pattern in which there was a more predominant emphasis on lower chlorinated congeners than in the human subjects. It was decided that for animal studies, which are intended to mimic human exposures, we would prepare an animal dosing mixture, which mimicked Fox River fish PCB profiles. We constructed various theoretical mixtures of PCBs from published congener contents of various Aroclors. The Aroclor mix, which predicted a profile most similar to that found in the Fox River fish was a mixture containing 35% Aroclor1242, 35% Aroclor 1248, 15 % Aroclor 1254 and 15% Aroclor 1260. The mixture was prepared and underwent confirmation analysis by GC/ECD, to verify its similarity with the congener profiles in Fox River Fish (Kostyniak, et al., 2005). PCB congener profiles of the final dosing solution were compared to the theoretical Aroclor construct and the Fox River fish profiles. As seen in the figure below, there was good agreement in the congener profiles of the three groups. This mixture was used for the animal studies performed under this grant.

Fish v Theoretical v Actual Dosing Solution Mix of Aroclors 1242/1248/1254/1260

Assessment of Potential Vectors other than Fox River Fish for PCB Exposure:

In an attempt to assess other potential vectors of PCB exposure in the study population, imported foodstuffs primarily from Thailand were obtained. These foods are obtained from specialty food stores in Green Bay and are used on a regular basis by the study population. The foodstuffs for PCB analysis include seven of the most popular brands of fish sauce, ten varieties of pickled and canned fish, four varieties of crab and shrimp paste, and shrimp crackers. Methods of extraction were modified for each of these sample matrices to enable PCB congener and pesticide determination. PCB and pesticide levels in the foodstuffs tested were considerably lower than found in Fox River fish. Seven of the most popular brands of fish sauce, which is eaten on a daily basis, had levels of individual PCB congeners well below 1 ng/g. Thus the fish sauces are not a significant vector for PCB and pesticide exposure. It was concluded that it is unlikely that there was appreciable contribution to current body burdens of PCBs due to exposure from foodstuffs purchased from local Asian markets.

Assessment of total dioxin like activity in dosing solutions and foodstuffs by the reporter gene assay:

The reporter gene bioassay was developed as an economical, rapid bioassay that can screen environmental and biological specimens for complex mixtures of compounds that elicit dioxin-like activity. Dioxin-like compounds include polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) with chlorine on at least the 2,3,7,8 positions and the coplanar (non-ortho) and mono-ortho substituted PCBs that have biological and toxicological activities similar to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The reporter gene bioassay system was developed based on the premise that dioxin-like compounds initially bind to the AhR and subsequently that the ligand-activated AhR binds to dioxin response elements on DNA. A murine hepatoma cell line (hepa 1c 1c7) was stably transfected with the p2Dluc plasmid containing two DREs upstream from the firefly luciferase gene. A 96-well cell culture plate format has been optimized for this cell-based reporter gene bioassay system to assess AhR-responsive luciferase activity of dioxin-like chemicals, individually and in complex, real world mixtures. The reporter gene bioassay is exceptionally sensitive, detecting levels of TCDD as low as 1 pM (0.06 pg/200 μl/well). Results are expressed as ppt (part per trillion) of dioxin TEQs in the dosing solution or foodstuff on a wet weight and lipid weight basis. Dosing solutions were found to contain dioxin toxic equivalents (TEQs) of at least 60 ppb in the corn oil from the dosing solution which contained 31.4 mg PCBs/g corn oil. Foodstuffs from the Asian markets having the highest PCB and pesticide concentrations were analyzed for total dioxin equivalents in the reporter gene assay. All food samples were at or very near the limits of detection for the method.

Advances in Analytical Methods:

PCBs and Pesticides: Existing methods for analysis of PCB congeners in serum and milk were modified and extended to other sample matrices including foodstuffs. A major modification in the method of solvent extraction and column cleanup was accomplished by incorporating an automated extraction process using the Dionex ASE 300 system, allowing for rapid extraction and cleanup using elevated pressure and temperature. The introduction of this technology resulted in an improvement in lower blanks, lower limits of detection and higher recoveries of individual PCB congeners in the assay. The mean recovery for 23 individual PCB congeners and pesticides from 4 g samples of serum was 103.8 + 6.6%. The method has also been applied to the analysis of fish and fish products from the Asian markets. The method avoids an acid treatment step for removal of lipids, which is common to many methods, and results in high recoveries. The mean recovery of 12 individual PCB congeners and pesticides from 5 g samples of fish was 98.4 + 7.7%. Chromatograms indicated no breakdown products for any of the congeners of interest.

Evaluation of Apex Large volume injector: A large volume injector which will allow for higher sample volume of extracts to be injected into the Gas Chromatograph was evaluated and standardized. It allows for increased size of the sample extract being analyzed (10 – 20 uL vs. 1 uL), resulting in lower detection limits for samples. This is particularly important for rat brain tissue samples, where sample weights are only in the mg range. This also reduces sample preparation time, by decreasing the amount of solvent evaporation necessary for final sample extracts. The injector is effective in increasing the sensitivity by allowing larger volume samples to be injected and the response is linear.

PBDE Analysis:

The GC-MS was upgraded to enable positive/negative chemical ionization. GC-MS chromatographic conditions were developed to analyze for 7 of the most predominate PBDE’s using negative ion chemical ionization (NCI). These are:

2,4,4’-tribromodiphenyl ether (PBDE -28)

2,2’,4,4’-tetrabromodiphenyl ether (PBDE-47)

2,2’4,4’,5-pentabromodiphenyl ether (PBDE-99)

2,2’,4,4’,6-pentabromodiphenyl ether (PBDE-100)

2,2’,4,4’,5,5’-hexabromodiphenyl ether (PBDE-153)

2,2’,4,4’,5,6’-hexabromodiphenyl ether (PBDE-155)

2,2’,3,4,4’,5’,6-heptabromodiphenyl ether (PBDE-183)

ChemStation Software for Data Acquisition and Processing: ChemStation software was installed on a new computer system which allows for complete control of instrumental parameters for the HP6890 Gas Chromatograph, data acquisition, calibration, and processing of chromatographic data. In addition, we are evaluating the use of Retention Time Locking (RTL) software, which allows for automated adjustments in the column head pressure to maintain constant retention times. This is critical in the analysis of PCB congeners, where the retention times are used for identification, and any shifts require recalibration. It is common for retention times to shift over time, and with routine maintenance of the system.

Lipids: Methods for the determination of total serum lipids were improved by modifying manual methods to automated standard enzymatic procedures. Total serum lipids are calculated by summation of the individual lipid components from the measurement of total cholesterol, free cholesterol, triglycerides, and phospholipids.

Analysis of Center Samples:

A total of 6,000 analyses were performed during the grant period for analytes of interest including specific PCB congeners, pesticides, cholesterol, free cholesterol, triglycerides, phospholipids and mercury. This includes actual samples (human serum, rat brain and serum, dosing solutions, fish tissues, and foodstuffs) received from Center projects, as well as samples for the development of new methods, evaluation of new sample matrices and new equipment, and quality control/calibration samples.

Participation in the Artic Monitoring and Assessment Programme (AMAP) Ring Test for Persistent Organic Pollutants in Human Serum:

The laboratory participated in a proficiency program for PCB congeners, selected pesticides (DDE, HCB and Mirex) and lipids in human serum. The program is administered by the Centre de Toxicologie du Quebec. There are three rounds of proficiency samples/year. The lab has consistently obtained the highest possible rating of excellent. A low bias in one round in 2007 was rectified in the following round in 2008. Typical proficiency data for both PCBs and Lipids are provided in the figures below:


Journal Articles: 21 Displayed | Download in RIS Format

Other center views: All 38 publications 22 publications in selected types All 21 journal articles
Type Citation Sub Project Document Sources
Journal Article Bemis JC, Seegal RF. Polychlorinated biphenyls and methylmercury act synergistically to reduce rat brain dopamine content in vitro. Environmental Health Perspectives 1999;107(11):879-885. R829390 (2005)
R829390 (Final)
R825812 (1999)
  • Full-text from PubMed
  • Abstract from PubMed
  • Associated PubMed link
  • Abstract: ResearchGate-Abstract
    Exit
  • Journal Article Bemis JC, Seegal RF. Polychlorinated biphenyls and methylmercury alter intracellular calcium concentrations in rat cerebellar granule cells. NeuroToxicology 2000;21(6):1123-1134. R829390 (2005)
    R829390 (Final)
    R825812 (1999)
  • Abstract from PubMed
  • Abstract: ResearchGate-Abstract
    Exit
  • Journal Article Bemis JC, Seegal RF. PCB-induced inhibition of the vesicular monoamine transporter predicts reductions in synaptosomal dopamine content. Toxicological Sciences 2004;80(2):288-295. R829390 (2005)
    R829390 (Final)
    R829390C004 (2004)
    R825812 (1999)
  • Abstract from PubMed
  • Full-text: OUP-Full Text HTML
    Exit
  • Abstract: OUP-Abstract
    Exit
  • Other: OUP-Full Text PDF
    Exit
  • Journal Article Dietrich KN, Eskenazi B, Schantz S, Yolton K, Rauh VA, Johnson CB, Alkon A, Canfield RL, Pessah IN, Berman RF. Principles and practices of neurodevelopmental assessment in children: lessons learned from the Centers for Children's Environmental Health and Disease Prevention Research. Environmental Health Perspectives 2005;113(10):1437-1446. R829390 (2005)
    R829390 (Final)
    R829390C002 (2005)
    R827027 (2002)
    R829388 (2006)
    R829388 (Final)
    R829388C006 (2005)
    R829389 (2005)
    R829389 (Final)
    R831710 (2005)
    R831710 (Final)
    R831711 (2005)
    R832141 (2006)
    R832141 (2007)
    R832141 (Final)
  • Full-text from PubMed
  • Abstract from PubMed
  • Associated PubMed link
  • Full-text: CCCEH-Full Text PDF
    Exit
  • Journal Article Dreiem A, Gertz CC, Seegal RF. The effects of methylmercury on mitochondrial function and reactive oxygen species formation in rat striatal synaptosomes are age-dependent. Toxicological Sciences 2005;87(1):156-162. R829390 (2005)
    R829390 (Final)
    R829390C004 (2005)
  • Abstract from PubMed
  • Full-text: OUP-Full Text-HTML
    Exit
  • Abstract: OUP-Abstract
    Exit
  • Other: OUP-Full Text-PDF
    Exit
  • Journal Article Dreiem A, Seegal RF. Methylmercury-induced changes in mitochondrial function in striatal synaptosomes are calcium-dependent and ROS-independent. NeuroToxicology 2007;28(4):720-726. R829390 (2005)
    R829390 (Final)
  • Full-text from PubMed
  • Abstract from PubMed
  • Associated PubMed link
  • Full-text: ScienceDirect-Full Text-HTML
    Exit
  • Abstract: ScienceDirect-Abstract
    Exit
  • Other: ScienceDirect-Full Text-PDF
    Exit
  • Journal Article Eskenazi B, Gladstone EA, Berkowitz GS, Drew CH, Faustman EM, Holland NT, Lanphear B, Meisel SJ, Perera FP, Rauh VA, Sweeney A, Whyatt RM, Yolton K. Methodologic and logistic issues in conducting longitudinal birth cohort studies: lessons learned from the Centers for Children's Environmental Health and Disease Prevention Research. Environmental Health Perspectives 2005;113(10):1419-1429. R829390 (2005)
    R829390 (Final)
    R829390C002 (2005)
    R827027 (2002)
    R829389 (2003)
    R829389 (2004)
    R829389 (2005)
    R829389 (Final)
    R831709 (2005)
    R831709C001 (2004)
    R831710 (2005)
    R831710 (Final)
    R831710C001 (2006)
    R831710C002 (2006)
    R831711 (2005)
    R831711 (2006)
    R831711 (2007)
    R831711 (Final)
    R831711C001 (2006)
    R831711C002 (2004)
    R831711C002 (2006)
    R831711C003 (2006)
    R832141 (2005)
    R832141 (2007)
    R832141 (Final)
  • Full-text from PubMed
  • Abstract from PubMed
  • Associated PubMed link
  • Full-text: CCCEH-Full Text PDF
    Exit
  • Journal Article Kornosky JL, Peck JD, Sweeney AM, Adelson PL, Schantz SL. Reproductive characteristics of Southeast Asian immigrants before and after migration. Journal of Immigrant and Minority Health 2008;10(2):135-143. R829390 (2005)
    R829390 (Final)
  • Abstract from PubMed
  • Abstract: Springer-Abstract
    Exit
  • Journal Article Kostyniak PJ, Hansen LG, Widholm JJ, Fitzpatrick RD, Olson JR, Helferich JL, Kim KH, Sable HJ, Seegal RF, Pessah IN, Schantz SL. Formulation and characterization of an experimental PCB mixture designed to mimic human exposure from contaminated fish. Toxicological Sciences 2005;88(2):400-411. R829390 (2005)
    R829390 (Final)
    R829388 (2006)
    R829388 (Final)
    R829388C006 (2005)
  • Abstract from PubMed
  • Full-text: OUP-Full Text-HTML
    Exit
  • Abstract: OUP-Abstract
    Exit
  • Other: SilverChair-Full Text-PDF
    Exit
  • Journal Article Lyng GD, Synder-Keller A, Seegal RF. Dopaminergic development of prenatal ventral mesencephalon and striatum in organotypic co-cultures. Brain Research 2007;1133(1):1-9. R829390 (2005)
    R829390 (Final)
  • Full-text from PubMed
  • Abstract from PubMed
  • Associated PubMed link
  • Full-text: ScienceDirect-Full Text-HTML
    Exit
  • Abstract: ScienceDirect-Abstract
    Exit
  • Other: ScienceDirect-Full Text-PDF
    Exit
  • Journal Article Lyng GD, Synder-Keller A, Seegal RF. Polychlorinated biphenyl-induced neurotoxicity in organotypic co-cultures of developing rat ventral mesencephalon and striatum. Toxicological Sciences 2007;97(1):128-139. R829390 (2005)
    R829390 (Final)
  • Abstract from PubMed
  • Full-text: OUP-Full Text-HTML
    Exit
  • Abstract: OUP-Abstract
    Exit
  • Other: OUP-Full Text-PDF
    Exit
  • Journal Article Lyng GD, Seegal RF. Polychlorinated biphenyl-induced oxidative stress in organotypic co-cultures: experimental dopamine depletion prevents reductions in GABA. NeuroToxicology 2008;29(2):301-308. R829390 (2005)
    R829390 (Final)
  • Full-text from PubMed
  • Abstract from PubMed
  • Associated PubMed link
  • Full-text: ScienceDirect-Full Text-HTML
    Exit
  • Abstract: ScienceDirect-Abstract
    Exit
  • Other: ScienceDirect-Full Text-PDF
    Exit
  • Journal Article Powers BE, Widholm JJ, Lasky RE, Schantz SL. Auditory deficits in rats exposed to an environmental PCB mixture during development. Toxicological Sciences 2006;89(2):415-422. R829390 (2005)
    R829390 (Final)
  • Abstract from PubMed
  • Full-text: OUP-Full Text-HTML
    Exit
  • Abstract: Toxicological Sciences-Abstract
    Exit
  • Other: SilverChair-Full Text-PDF
    Exit
  • Journal Article Roegge CS, Wang VC, Powers BE, Klintsova AY, Villareal S, Greenough WT, Schantz SL. Motor impairment in rats exposed to PCBs and methylmercury during early development. Toxicological Sciences 2004;77(2):315-324. R829390 (2005)
    R829390 (Final)
    R829390C001 (2004)
  • Abstract from PubMed
  • Full-text: OUP-Full Text HTML
    Exit
  • Other: SilverChair-Fulll Text PDF
    Exit
  • Journal Article Roegge CS, Morris JR, Villareal S, Wang VC, Powers BE, Klintsova AY, Greenough WT, Pessah IN, Schantz SL. Purkinje cell and cerebellar effects following developmental exposure to PCBs and/or MeHg. Neurotoxicology and Teratology 2006;28(1):74-85. R829390 (2005)
    R829390 (Final)
    R829390C001 (2005)
    R829388 (2006)
    R829388 (Final)
    R829388C006 (2005)
  • Abstract from PubMed
  • Full-text: Science Direct-Full Text HTML
    Exit
  • Abstract: Science Direct-Abstract
    Exit
  • Other: Science Direct-Full Text-PDF
    Exit
  • Journal Article Roegge CS, Schantz SL. Motor function following developmental exposure to PCBS and/or MEHG. Neurotoxicology and Teratology 2006;28(2):260-277. R829390 (2005)
    R829390 (Final)
    R829390C001 (2005)
  • Abstract from PubMed
  • Full-text: ScienceDirect-Full Text-HTML
    Exit
  • Abstract: ScienceDirect-Abstract
    Exit
  • Other: ScienceDirect-Full Text-PDF
    Exit
  • Journal Article Roegge CS, Wang VC, Powers BE, Klintsova A, Villareal S, Greenough WT, Schantz SL. Motor functions in rats exposed to PCBs and methylmercury during early development. Neurotoxicology and Teratology 2002;24(3):424-425. R829390C001 (2002)
    R829390C001 (2003)
    not available
    Journal Article Sable HJK, Powers BE, Wang VC, Widholm JJ, Schantz SL. Alterations in DRH and DRL performance in rats developmentally exposed to an environmental PCB mixture. Neurotoxicology and Teratology 2006;28(5):548-556. R829390 (2005)
    R829390 (Final)
  • Abstract from PubMed
  • Full-text: ScienceDirect-Full Text-HTML
    Exit
  • Abstract: ScienceDirect-Abstract
    Exit
  • Other: ScienceDirect-Full Text-PDF
    Exit
  • Journal Article Seegal RF, Brosch KO, Okoniewski RJ. Coplanar PCB congeners increase uterine weight and frontal cortical dopamine in the developing rat: implications for developmental neurotoxicity. Toxicological Sciences 2005;86(1):125-131. R829390 (2005)
    R829390 (Final)
    R829390C004 (2005)
  • Abstract from PubMed
  • Full-text: OUP-Full Text-HTML
    Exit
  • Abstract: OUP-Abstract
    Exit
  • Other: SilverChair-Full Text-PDF
    Exit
  • Journal Article Sweeney AM, Peck JD, Gasior DM, Gardiner J, Schantz SL. Perinatal PCBs and mercury exposure and neurodevelopmental effects. Epidemiology 2004;15(4):S147-S148. R829390 (Final)
    R829390C002 (2004)
  • Abstract: LWW-Abstract
    Exit
  • Journal Article Widholm JJ, Villareal S, Seegal RF, Schantz SL. Spatial alternation deficits following developmental exposure to Aroclor 1254 and/or methylmercury in rats. Toxicological Sciences 2004;82(2):577-589. R829390 (2002)
    R829390 (2005)
    R829390 (Final)
    R829390C001 (2004)
  • Abstract from PubMed
  • Full-text: OUP-Full Text-HTML
    Exit
  • Abstract: OUP-Abstract
    Exit
  • Other: SilverChair-Full Text-PDF
    Exit
  • Supplemental Keywords:

    RFA, Health, Scientific Discipline, Geographic Area, Midwest, Toxicology, Health Risk Assessment, Chemistry, Risk Assessments, Susceptibility/Sensitive Population/Genetic Susceptibility, Disease & Cumulative Effects, Children's Health, genetic susceptability, Ecological Risk Assessment, Molecular Biology/Genetics, human data, neurotoxic, Fox River, behavioral assessment, PCBs, pesticides, motor development, children, neurotoxicity, cognitive development, behavioral deficits, methylmercury, PCB, Wisconsin (WI), animal studies, reproductive health, biomedical research, exposure assessment

    Progress and Final Reports:

    Original Abstract
  • 2002 Progress Report
  • 2003 Progress Report
  • 2004 Progress Report
  • 2005 Progress Report
  • 2006
  • 2007
  • Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R829390C001 Neurobehavioral Effects of PCBs and Methylmercury in Rats
    R829390C002 Perinatal PCB Exposure and Neuropsychological/Auditory Function
    R829390C003 FRIENDS Analytical Toxicology Core Facility
    R829390C004 Developmental Effects of PCBs and Methylmercury