Spike-induced cytoarchitectonic changes in epileptic human cortex are reduced via MAP2K inhibition.

Interictal spikes are electroencephalographic discharges that occur at or near brain regions that produce epileptic seizures. While their role in generating seizures is not well understood, spikes have profound effects on cognition and behaviour, depending on where and when they occur. We previously demonstrated that spiking areas of human neocortex show sustained MAPK activation in superficial cortical Layers I-III and are associated with microlesions in deeper cortical areas characterized by reduced neuronal nuclear protein staining and increased microglial infiltration. Based on these findings, we chose to investigate additional neuronal populations within microlesions, specifically inhibitory interneurons. Additionally, we hypothesized that spiking would be sufficient to induce similar cytoarchitectonic changes within the rat cortex and that inhibition of MAPK signalling, using a MAP2K inhibitor, would not only inhibit spike formation but also reduce these cytoarchitectonic changes and improve behavioural outcomes. To test these hypotheses, we analysed tissue samples from 16 patients with intractable epilepsy who required cortical resections. We also utilized a tetanus toxin-induced animal model of interictal spiking, designed to produce spikes without seizures in male Sprague-Dawley rats. Rats were fitted with epidural electrodes, to permit EEG recording for the duration of the study, and automated algorithms were implemented to quantify spikes. After 6 months, animals were sacrificed to assess the effects of chronic spiking on cortical cytoarchitecture. Here, we show that microlesions may promote excitability due to a significant reduction of inhibitory neurons that could be responsible for promoting interictal spikes in superficial layers. Similarly, we found that the induction of epileptic spikes in the rat model produced analogous changes, including reduced neuronal nuclear protein, calbindin and parvalbumin-positive neurons and increased microglia, suggesting that spikes are sufficient for inducing these cytoarchitectonic changes in humans. Finally, we implicated MAPK signalling as a driving force producing these pathological changes. Using CI-1040 to inhibit MAP2K, both acutely and after spikes developed, resulting in fewer interictal spikes, reduced microglial activation and less inhibitory neuron loss. Treated animals had significantly fewer high-amplitude, short-duration spikes, which correlated with improved spatial memory performance on the Barnes maze. Together, our results provide evidence for a cytoarchitectonic pathogenesis underlying epileptic cortex, which can be ameliorated through both early and delayed MAP2K inhibition. These findings highlight the potential role for CI-1040 as a pharmacological treatment that could prevent the development of epileptic activity and reduce cognitive impairment in both patients with epilepsy and those with non-epileptic spike-associated neurobehavioural disorders.

Pesticides in the Great Barrier Reef catchment area: Plausible risks to fish populations.

Waterways that drain the Great Barrier Reef catchment area (GBRCA) transport pollutants to marine habitats, provide a critical corridor between freshwater and marine habitats for migratory fish species, and are of high socioecological value. Some of these waterways contain concentrations of pesticide active ingredients (PAIs) that exceed Australian ecotoxicity threshold values (ETVs) for ecosystem protection. In this article, we use a "pathway to harm" model with five key criteria to assess whether the available information supports the hypothesis that PAIs are or could have harmful effects on fish and arthropod populations. Strong evidence of the first three criteria and circumstantial weaker evidence of the fourth and fifth criteria are presented. Specifically, we demonstrate that exceedances of Australian and New Zealand ETVs for ecosystem protection are widespread in the GBRCA, that the PAI contaminated water occurs (spatially and temporally) in important habitats for fisheries, and that there are clear direct and indirect mechanisms by which PAIs could cause harmful effects. The evidence of individuals and populations of fish and arthropods being adversely affected species is more circumstantial but consistent with PAIs causing harmful effects in the freshwater ecosystems of Great Barrier Reef waterways. We advocate strengthening the links between PAI concentrations and fish health because of the cultural values placed on the freshwater ecosystems by relevant stakeholders and Traditional Owners, with the aim that stronger links between elevated PAI concentrations and changes in recreationally and culturally important fish species will inspire improvements in water quality. Integr Environ Assess Manag 2024;00:1-24. © 2023 Commonwealth of Australia and The Commonwealth Scientific and Industrial Research Organisation. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Dispersal of the pesticide diuron in the Great Barrier Reef.

Pesticides from urban and agricultural runoff have been detected at concentrations above current water quality guidelines in the Great Barrier Reef (GBR) marine environment. We quantify the load of the pesticide diuron entering GBR waters using the GBR-Dynamic SedNet catchment model. After comparison of simulated distributions with observations at 11 monitoring sites we determined a half-life of diuron in GBR marine waters of 40 days. We followed diuron dispersal in the GBR (2016-2018) using the 1 km resolution eReefs marine model. The highest diuron concentrations in GBR waters occurred in the Mackay-Whitsunday region with a spike in January and March 2017, associated with 126 and 118 kg d-1 diuron loads from Plane Creek and the O'Connell River respectively. We quantify areas of GBR waters exposed to potentially ecotoxic concentrations of diuron. Between 2016 and 2018, 400 km2 and 1400 km2 of the GBR were exposed to concentrations exceeding ecosystem threshold values of 0.43 and 0.075 µg L-1 respectively. Using observed mapped coral and seagrass habitat, 175 km2 of seagrass beds and 50 km2 of coral habitats had peak diuron concentrations above 0.075 µg L-1 during this period. While the highest concentrations are localised to river plumes and inshore environments, non-zero diuron concentrations extend along the Queensland coast. These simulations provide new knowledge for the understanding of pesticide dispersal and management-use in GBR catchments and the design of in-water monitoring systems.

Individual and combined effects of diuron and light reduction on marine microalgae.

Coastal ecosystems such as those in the Great Barrier Reef (GBR) lagoon, are exposed to stressors in flood plumes including low light (caused by increased turbidity) and agricultural pesticides. Photosystem II (PSII)-inhibiting herbicides are the most frequently detected pesticides in the GBR lagoon, but it is not clear how their toxicity to phototrophic species depends on light availability. This study investigated the individual and combined effects of PSII-inhibiting herbicide, diuron, and reduced light intensity (as a proxy for increased turbidity) on the marine diatom, Phaeodactylum tricornutum. Effective quantum yield (EQY) and cell density were measured to calculate responses relative to the controls over 72-h, in tests with varying stressor intensities. Individually, diuron concentrations (0.1-3 µg l-1) were not high enough to significantly reduce growth (cell density), but led to decreased EQY; while, low light generally led to increased EQY, but only reduced growth at the lowest tested light intensity (5 µmol photons m-2 s-1) after 48-hours. P. tricornutum was less affected by diuron when combined with low light scenarios, with increased EQY (up to 163% of the controls) that was likely due to increased electron transport per photon, despite lesser available photons at this low light intensity. In contrast, growth was completely inhibited relative to the controls when algae were simultaneously exposed to the highest stressor levels (3 µg l-1 diuron and 5 µmol photons m-2 s-1). This study highlights the importance of measuring more than one biological response variable to capture the combined effects of multiple stressors. Management of water quality stressors should consider combined impacts rather than just the impacts of individual stressors alone. Reducing suspended sediment and diuron concentrations in marine waters can decrease harmful effects and bring synergistic benefits to water quality.

Interactions among multiple stressors vary with exposure duration and biological response.

Coastal ecosystems are exposed to multiple anthropogenic stressors. Effective management actions would be better informed from generalized predictions of the individual, combined and interactive effects of multiple stressors; however, few generalities are shared across different meta-analyses. Using an experimental study, we present an approach for analysing regression-based designs with generalized additive models that allowed us to capture nonlinear effects of exposure duration and stressor intensity and access interactions among stressors. We tested the approach on a globally distributed marine diatom, using 72 h photosynthesis and growth assays to quantify the individual and combined effects of three common water quality stressors; photosystem II-inhibiting herbicide exposure, dissolved inorganic nitrogen (DIN) enrichment and reduced light (due to excess suspended sediment). Exposure to DIN and reduced light generally resulted in additivity, while exposure to diuron and reduced light resulted in additive, antagonistic or synergistic interactions, depending on the stressor intensity, exposure period and biological response. We thus find the context of experimental studies to be a primary driver of interactions. The experimental and modelling approaches used here bridge the gap between two-way designs and regression-based studies, which provides a way forward to identify generalities in multiple stressor interactions.

Modulation of locomotor behaviors by location-specific epileptic spiking and seizures.

INTRODUCTION: Epilepsy is a debilitating neurological condition characterized by spontaneous seizures as well as significant comorbid behavioral abnormalities. In addition to seizures, epileptic patients exhibit interictal spikes far more frequently than seizures, often, but not always observed in the same brain areas. The exact relationship between spiking and seizures as well as their respective effects on behavior are not well understood. In fact, spiking without overt seizures is seen in various psychiatric conditions including attention-deficit hyperactivity disorder. METHODS: In order to study the effects of spiking and seizures on behavior in an epileptic animal model, we used long-term video-electroencephalography recordings at six cortical recording sites together with behavioral activity monitoring. Animals received unilateral injections of tetanus toxin into either the somatosensory or motor cortex. RESULTS: Somatosensory cortex-injected animals developed progressive spiking ipsilateral to the injection site, while those receiving the injection into the motor cortex developed mostly contralateral spiking and spontaneous seizures. Animals with spiking but no seizures displayed a hyperactive phenotype, while animals with both spiking and seizures displayed a hypoactive phenotype. Not all spikes were equivalent as spike location strongly correlated with distinct locomotor behaviors including ambulatory distance, vertical movements, and rotatory movement. CONCLUSIONS: Together, our results demonstrate relationships between brain region-specific spiking, seizures, and behaviors in rodents that could translate into a better understanding for patients with epileptic behavioral comorbidities and other neuropsychiatric disorders.

Adjusting Tropical Marine Water Quality Guideline Values for Elevated Ocean Temperatures.

Increased frequency of summer heatwaves and poor water quality are two of the most prevalent and severe pressures faced by coral reefs. While these pressures often co-occur, their potential risks to tropical marine species are usually considered independently. Here, we extended the application of multisubstance-Potentially Affected Fraction (ms-PAF) to a nonchemical stressor, elevated sea surface temperature. We then applied this method to calculate climate-adjusted water quality guideline values (GVs) for two reference toxicants, copper and the herbicide diuron, for tropical marine species. First, we developed a species sensitivity distribution (SSD) for thermal stress based on published experimental data for 41 tropical benthic marine species using methods adapted from water quality GV derivation. This enabled quantitative predictions of community effects as temperatures exceeded acclimation values. The resulting protective temperature values (PTx) were similar to temperatures known to initiate coral bleaching and are therefore relevant for application in multistressor risk assessments. The extended ms-PAF method enabled the adjustment of current water quality GVs to account for thermal stress events. This approach could be applied to other ecosystems and other non-contaminant stressors (e.g., sediment, low salinity, anoxia, and ocean acidification), offering an alternative approach for deriving environmental GVs, reporting and assessing the risk posed by multiple stressors.

α-Synuclein interacts directly but reversibly with psychosine: implications for α-synucleinopathies.

Aggregation of α-synuclein, the hallmark of α-synucleinopathies such as Parkinson's disease, occurs in various glycosphingolipidoses. Although α-synuclein aggregation correlates with deficiencies in the lysosomal degradation of glycosphingolipids (GSL), the mechanism(s) involved in this aggregation remains unclear. We previously described the aggregation of α-synuclein in Krabbe's disease (KD), a neurodegenerative glycosphingolipidosis caused by lysosomal deficiency of galactosyl-ceramidase (GALC) and the accumulation of the GSL psychosine. Here, we used a multi-pronged approach including genetic, biophysical and biochemical techniques to determine the pathogenic contribution, reversibility, and molecular mechanism of aggregation of α-synuclein in KD. While genetic knock-out of α-synuclein reduces, but does not completely prevent, neurological signs in a mouse model of KD, genetic correction of GALC deficiency completely prevents α-synuclein aggregation. We show that psychosine forms hydrophilic clusters and binds the C-terminus of α-synuclein through its amino group and sugar moiety, suggesting that psychosine promotes an open/aggregation-prone conformation of α-synuclein. Dopamine and carbidopa reverse the structural changes of psychosine by mediating a closed/aggregation-resistant conformation of α-synuclein. Our results underscore the therapeutic potential of lysosomal correction and small molecules to reduce neuronal burden in α-synucleinopathies, and provide a mechanistic understanding of α-synuclein aggregation in glycosphingolipidoses.

Transcriptomic, lipid, and histological profiles suggest changes in health in fish from a pesticide hot spot.

Barramundi (Lates calcarifer) were collected at the beginning (1st sampling) and end (2nd sampling) of the wet season from Sandy Creek, an agriculturally impacted catchment in the Mackay Whitsundays region of the Great Barrier Reef catchment area, and from Repulse Creek, located approximately 100 km north in Conway National Park, to assess the impacts of pesticide exposure. Gill and liver histology, lipid class composition in muscle, and the hepatic transcriptome were examined. The first sample of Repulse Creek fish showed little tissue damage and low transcript levels of xenobiotic metabolism enzymes. Sandy Creek fish showed altered transcriptomic patterns, including those that regulate lipid metabolism, xenobiotic metabolism, and immune response; gross histological alterations including lipidosis; and differences in some lipid classes. The second sampling of Repulse Creek fish showed similar alterations in hepatic transcriptome and tissue structure as fish from Sandy Creek. These changes may indicate a decrease in health of pesticide exposed fish.

Ecotoxicity thresholds for ametryn, diuron, hexazinone and simazine in fresh and marine waters.

Triazine and urea herbicides are two groups of photosystem II inhibiting herbicides frequently detected in surface, ground and marine waters. Yet, there are few water quality guidelines for herbicides. Ecotoxicity thresholds (ETs) for ametryn, hexazinone and simazine (triazine herbicides) and diuron (a urea herbicide) were calculated using the Australian and New Zealand method for deriving guideline values to protect fresh and marine ecosystems. Four ETs were derived for each chemical and ecosystem that should theoretically protect 99, 95, 90 and 80% of species (i.e. PC99, PC95, PC90 and PC80, respectively). For all four herbicides, the phototrophic species were significantly more sensitive than non-phototrophic species, and therefore, only the former data were used to calculate the ETs. Comparison of the ET values to measured concentrations in 2606 samples from 15 waterways that discharge to the Great Barrier Reef (2011-2015) found three exceedances of the simazine PC99, regular exceedances (up to 30%) of the PC99 in a limited number of rivers for ametryn and hexazinone and frequent (> 40%) exceedances of the PC99 and PC95 ETs in at least four waterways for diuron. There were no exceedances of the marine ETs in inshore reef areas. Further, ecotoxicity data are required for ametryn and hexazinone to fresh and marine phototrophic species, for simazine to marine phototrophic species, for tropical phototrophic species, repeated pulse exposures and long-term (2 to 12 months) exposures to environmentally relevant concentrations.

Hepatic transcriptomic profiles from barramundi, Lates calcarifer, as a means of assessing organism health and identifying stressors in rivers in northern Queensland.

Resource managers need to differentiate between sites with and without contaminants and those where contaminants cause impacts. Potentially, transcriptomes could be used to evaluate sites where contaminant-induced effects may occur, to identify causative stressors of effects and potential adverse outcomes. To test this hypothesis, the hepatic transcriptomes in Barramundi, a perciforme teleost fish, (Lates calcarifer) from two reference sites, two agriculturally impacted sites sampled during the dry season, and an impacted site sampled during the wet season were compared. The hepatic transcriptome was profiled using RNA-Seq. Multivariate analysis showed that transcriptomes were clustered based on site and by inference water quality, but not sampling time. The largest differences in transcriptomic profile were between reference sites and a site sampled during high run-off, showing that impacted sites can be identified via RNA-Seq. Transcripts with altered abundance were linked to xenobiotic metabolism, peroxisome proliferation and stress responses, indicating putative stressors with the potential for adverse outcomes in barramundi.

An improved method for calculating toxicity-based pollutant loads: Part 1. Method development.

Pollutant loads are a means for assessing regulatory compliance and setting targets to reduce pollution entering receiving waterbodies. However, a pollutant load is often comprised of multiple chemicals, which may exert joint toxicity on biota. When the ultimate goal for assessing pollutant loads is to protect ecosystems from adverse effects of toxicants, then the total pollutant load needs to be calculated based on the principles of mixture toxicology. In this article, an improved method is proposed to convert a pollutant load to a toxicity-based load (toxic load) using a modified toxic equivalency factor (TEF) derivation method. The method uses the relative potencies (RePs) of multiple species to represent the response of the ecological community. The TEF is calculated from a percentile of a cumulative distribution function (CDF) fitted to the RePs. The improvements permit the determination of which percentile of the CDF generates the most environmentally relevant and robust toxic loads. That is, environmental relevance ensures that a reduction in the toxic load is likely to result in a corresponding improvement in ecosystem health and robustness ensures that the calculation of the toxic loads is not biased by the reference chemical used. The improved methodology will therefore ensure that correct management decisions will be made and ultimately, a reduction in the toxic load will lead to a commensurate improvement in water quality. Integr Environ Assess Manag 2017;13:746-753. © 2016 SETAC.

An improved method for calculating toxicity-based pollutant loads: Part 2. Application to contaminants discharged to the Great Barrier Reef, Queensland, Australia.

Pollutant loads are widely used to set pollution reduction targets and assess regulatory compliance for the protection of receiving waterbodies. However, when a pollutant load consists of a mixture of chemicals, reducing the overall load (mass) will not necessarily reduce the toxicity by a similar amount. This can be overcome by setting targets based on toxicity-based loads (toxic loads, TLs), where the load is modified according to the relative toxicity (expressed as toxic equivalency factors [TEFs]) of each toxicant. Here, we present the second article of a 2-part series in which a case study is used to demonstrate the application of the toxic load method proposed in Part 1. The toxic load method converts a pollutant load, comprised of multiple chemicals, to a toxic load, using a modified TEF approach. The modified approach uses a cumulative distribution of relative potency (ReP) estimates of multiple species to determine a TEF. It further improves upon previously published methods by including two tests to select the optimal percentile of the ReP distribution to determine the TEF. The first test is a test for environmental relevance that compares results against an independent mixture method, identifying the percentile that produces the most environmentally relevant TEFs and TLs. The second is a test for robustness which ensures the results are independent of the ReP of the selected reference chemical. Here, the TL method is applied to mixtures of pesticides that are discharged from agricultural land to the Great Barrier Reef (GBR) to test its utility. In this case study, the most environmentally relevant and robust TLs were generated using the 75th percentile of the ReP cumulative distribution. The results demonstrate that it is essential to develop pollution reduction targets based on toxic loads and making progress to meeting them will lead to a commensurate reduction in toxic effects caused by toxicants in waters of the GBR. Integr Environ Assess Manag 2017;13:754-764. © 2016 SETAC.

Randomized Controlled Trial of Mind Reading and In Vivo Rehearsal for High-Functioning Children with ASD.

This randomized controlled trial evaluated the efficacy of a computer software (i.e., Mind Reading) and in vivo rehearsal treatment on the emotion decoding and encoding skills, autism symptoms, and social skills of 43 children, ages 7-12 years with high-functioning autism spectrum disorder (HFASD). Children in treatment (n = 22) received the manualized protocol over 12 weeks. Primary analyses indicated significantly better posttest performance for the treatment group (compared to controls) on 3 of the 4 measures of emotion decoding and encoding and these were maintained at 5-week follow-up. Analyses of secondary measures favored the treatment group for 1 of the 2 measures; specifically, ASD symptoms were significantly lower at posttest and follow-up.

Comparison of Adaptive Behavior Measures for Children with HFASDs.

Adaptive behavior rating scales are frequently used to gather information on the adaptive functioning of children with high-functioning autism spectrum disorders (HFASDs), yet little is known about the extent to which these measures yield comparable results. This study was conducted to (a) document the parent-rated VABS-II, BASC-2, and ABAS-II adaptive behavior profiles of 6- to 11-year-olds with HFASDs (including relative strengths and weaknesses); (b) examine the extent to which these measures yielded similar scores on comparable scales; and (c) assess potential discrepancies between cognitive ability and adaptive behavior across the measures. All three adaptive measures revealed significant deficits overall for the sample, with the VABS-II and ABAS-II indicating relative weaknesses in social skills and strengths in academic-related skills. Cross-measure comparisons indicated significant differences in the absolute magnitude of scores. In general, the VABS-II yielded significantly higher scores than the BASC-2 and ABAS-II. However, the VABS-II and ABAS-II yielded scores that did not significantly differ for adaptive social skills which is a critical area to assess for children with HFASDs. Results also indicated significant discrepancies between the children's average IQ score and their scores on the adaptive domains and composites of the three adaptive measures.