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  1. AU="Shafer, Timothy J"
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  1. Artikel: Application of Microelectrode Array Approaches to Neurotoxicity Testing and Screening.

    Shafer, Timothy J

    Advances in neurobiology

    2019  Band 22, Seite(n) 275–297

    Abstract: Neurotoxicity can be defined by the ability of a drug or chemical to alter the physiology, biochemistry, or structure of the nervous system in a manner that may negatively impact the health or function of the individual. Electrophysiological approaches ... ...

    Abstract Neurotoxicity can be defined by the ability of a drug or chemical to alter the physiology, biochemistry, or structure of the nervous system in a manner that may negatively impact the health or function of the individual. Electrophysiological approaches have been utilized to study the mechanisms underlying neurotoxic actions of drugs and chemicals for over 50 years, and in more recent decades, high-throughput patch-clamp approaches have been utilized by the pharmaceutical industry for drug development. The use of microelectrode array recordings to study neural network electrophysiology is a relatively newer approach, with commercially available systems becoming available only in the early 2000s. However, MEAs have been rapidly adopted as a useful approach for neurotoxicity testing. In this chapter, I will review the use of MEA approaches as they have been applied to the field of neurotoxicity testing, especially as they have been applied to the need to screen large numbers of chemicals for neurotoxicity and developmental neurotoxicity. In addition, I will also identify challenges for the field that when addressed will improve the utility of MEA approaches for toxicity testing.
    Mesh-Begriff(e) Electrophysiology/instrumentation ; Electrophysiology/methods ; Humans ; Microelectrodes ; Neurotoxicity Syndromes/diagnosis ; Neurotoxicity Syndromes/physiopathology ; Toxicity Tests/instrumentation ; Toxicity Tests/methods
    Sprache Englisch
    Erscheinungsdatum 2019-05-09
    Erscheinungsland United States
    Dokumenttyp Journal Article ; Review
    ISSN 2190-5215
    ISSN 2190-5215
    DOI 10.1007/978-3-030-11135-9_12
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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  2. Artikel ; Online: Identification of neurotoxicology (NT)/developmental neurotoxicology (DNT) adverse outcome pathways and key event linkages with in vitro DNT screening assays.

    Pitzer, Emily M / Shafer, Timothy J / Herr, David W

    Neurotoxicology

    2023  Band 99, Seite(n) 184–194

    Abstract: There is a need to assess compounds reliably and quickly for neurotoxicity (NT) and developmental neurotoxicity (DNT). Adverse outcome pathways (AOPs) enable the mapping of molecular events to an apical endpoint in a chemical agnostic manner and have ... ...

    Abstract There is a need to assess compounds reliably and quickly for neurotoxicity (NT) and developmental neurotoxicity (DNT). Adverse outcome pathways (AOPs) enable the mapping of molecular events to an apical endpoint in a chemical agnostic manner and have begun to be applied in NT and DNT testing frameworks. We assessed the status of NT/DNT AOPs in the AOP-Wiki (ca. 2/1/23; https://aopwiki.org/), to characterize the state of AOP development, identify strengths and knowledge gaps, elucidate areas for improvement, and describe areas for future focus. AOPs in the Wiki database were assessed for inclusion of NT/DNT molecular events and endpoints, AOP development and endorsement, as well as the linkages of key neurodevelopmental processes with in vitro new approach methods (NAMs). This review found that 41 AOPs have been proposed detailing NT/DNT, of which eight were endorsed by working parties in OECD. Further, this review determined that learning and memory is included as an adverse outcome in eight NT/DNT AOPS, often without distinction regarding the varying forms of learning and memory, regional specification, temporal dynamics, or acquisition mechanisms involved. There is also an overlap with key events (KEs) and in vitro NAMs, which synaptogenesis appeared as a common process. Overall, progress on NT/DNT AOPs could be expanded, adding in modes of action that are missing, improvement in defining apical endpoints, as well as utilizing NAMs further to develop AOPs and identify gaps in current knowledge.
    Mesh-Begriff(e) Humans ; Adverse Outcome Pathways ; Risk Assessment ; Toxicity Tests/methods ; Neurotoxicity Syndromes/diagnosis ; Neurotoxicity Syndromes/etiology ; Neurotoxicity Syndromes/metabolism ; Learning
    Sprache Englisch
    Erscheinungsdatum 2023-10-20
    Erscheinungsland Netherlands
    Dokumenttyp Review ; Journal Article
    ZDB-ID 800820-6
    ISSN 1872-9711 ; 0161-813X
    ISSN (online) 1872-9711
    ISSN 0161-813X
    DOI 10.1016/j.neuro.2023.10.007
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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  3. Artikel: Toward a Better Testing Paradigm for Developmental Neurotoxicity: OECD Efforts and Regulatory Considerations

    Sachana, Magdalini / Shafer, Timothy J / Terron, Andrea

    Biology. 2021 Jan. 23, v. 10, no. 2

    2021  

    Abstract: Characterization of potential chemical-induced developmental neurotoxicity (DNT) hazard is considered for risk assessment purposes by many regulatory sectors. However, due to test complexity, difficulty in interpreting results and need of substantial ... ...

    Abstract Characterization of potential chemical-induced developmental neurotoxicity (DNT) hazard is considered for risk assessment purposes by many regulatory sectors. However, due to test complexity, difficulty in interpreting results and need of substantial resources, the use of the in vivo DNT test guidelines has been limited and animal data on DNT are scarce. To address challenging endpoints such as DNT, the Organisation for Economic Co-Operation and Development (OECD) chemical safety program has been working lately toward the development of integrated approaches for testing and assessment (IATA) that rely on a combination of multiple layers of data (e.g., in vitro, in silico and non-mammalian in vivo models) that are supported by mechanistic knowledge organized according to the adverse outcome pathway (AOP) framework. In 2017, the OECD convened a dedicated OECD expert group to develop a guidance document on the application and interpretation of data derived from a DNT testing battery that relies on key neurodevelopmental processes and is complemented by zebrafish assays. This review will provide a brief overview of the OECD DNT project and summarize various achievements of relevance to the project. The review also presents an opportunity to describe considerations for uptake of the DNT in an in vitro battery in a regulatory context.
    Schlagwörter Danio rerio ; adverse outcome pathways ; animals ; batteries ; chemical safety ; computer simulation ; neurotoxicity
    Sprache Englisch
    Erscheinungsverlauf 2021-0123
    Erscheinungsort Multidisciplinary Digital Publishing Institute
    Dokumenttyp Artikel
    Anmerkung NAL-AP-2-clean
    ZDB-ID 2661517-4
    ISSN 2079-7737
    ISSN 2079-7737
    DOI 10.3390/biology10020086
    Datenquelle NAL Katalog (AGRICOLA)

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  4. Artikel: Toward a Better Testing Paradigm for Developmental Neurotoxicity: OECD Efforts and Regulatory Considerations.

    Sachana, Magdalini / Shafer, Timothy J / Terron, Andrea

    Biology

    2021  Band 10, Heft 2

    Abstract: Characterization of potential chemical-induced developmental neurotoxicity (DNT) hazard is considered for risk assessment purposes by many regulatory sectors. However, due to test complexity, difficulty in interpreting results and need of substantial ... ...

    Abstract Characterization of potential chemical-induced developmental neurotoxicity (DNT) hazard is considered for risk assessment purposes by many regulatory sectors. However, due to test complexity, difficulty in interpreting results and need of substantial resources, the use of the in vivo DNT test guidelines has been limited and animal data on DNT are scarce. To address challenging endpoints such as DNT, the Organisation for Economic Co-Operation and Development (OECD) chemical safety program has been working lately toward the development of integrated approaches for testing and assessment (IATA) that rely on a combination of multiple layers of data (e.g., in vitro, in silico and non-mammalian in vivo models) that are supported by mechanistic knowledge organized according to the adverse outcome pathway (AOP) framework. In 2017, the OECD convened a dedicated OECD expert group to develop a guidance document on the application and interpretation of data derived from a DNT testing battery that relies on key neurodevelopmental processes and is complemented by zebrafish assays. This review will provide a brief overview of the OECD DNT project and summarize various achievements of relevance to the project. The review also presents an opportunity to describe considerations for uptake of the DNT in an in vitro battery in a regulatory context.
    Sprache Englisch
    Erscheinungsdatum 2021-01-23
    Erscheinungsland Switzerland
    Dokumenttyp Journal Article ; Review
    ZDB-ID 2661517-4
    ISSN 2079-7737
    ISSN 2079-7737
    DOI 10.3390/biology10020086
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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  5. Artikel ; Online: Assaying Spontaneous Network Activity and Cellular Viability Using Multi-Well Microelectrode Arrays.

    Choo, Seline S / Keever, Jackson Y / Brown, Jasmine / Strickland, Jenna D / Shafer, Timothy J

    Methods in molecular biology (Clifton, N.J.)

    2023  Band 2644, Seite(n) 133–154

    Abstract: Microelectrode array (MEA) technology is a neurophysiological method that allows for the measurement of spontaneous or evoked neural activity to determine chemical effects thereon. Following assessment of compound effects on multiple endpoints that ... ...

    Abstract Microelectrode array (MEA) technology is a neurophysiological method that allows for the measurement of spontaneous or evoked neural activity to determine chemical effects thereon. Following assessment of compound effects on multiple endpoints that evaluate network function, a cell viability endpoint in the same well is determined using a multiplexed approach. Recently, it has become possible to measure electrical impedance of cells attached to the electrodes, where greater impedance indicates greater number of cells attached. This would allow rapid and repeated assessments of cell health as the neural network develops in longer exposure assays without impacting cell health. Typically, the lactate dehydrogenase (LDH) assay for cytotoxity and CellTiter-Blue® (CTB) assay for cell viability are only performed at the end of the chemical exposure period because these assays involve lysing of the cells. Procedures describing the multiplexed methods in acute and network formation screening are included in this chapter.
    Mesh-Begriff(e) Microelectrodes ; Cell Survival ; L-Lactate Dehydrogenase ; Neurons ; Nerve Net
    Chemische Substanzen L-Lactate Dehydrogenase (EC 1.1.1.27)
    Sprache Englisch
    Erscheinungsdatum 2023-05-04
    Erscheinungsland United States
    Dokumenttyp Journal Article ; Research Support, U.S. Gov't, Non-P.H.S.
    ISSN 1940-6029
    ISSN (online) 1940-6029
    DOI 10.1007/978-1-0716-3052-5_9
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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  6. Artikel ; Online: Translational neurotoxicology - The 17th biennial meeting of the International Neurotoxicology Association.

    Westerink, Remco H S / Shafer, Timothy J / Fritsche, Ellen / van Thriel, Christoph

    Neurotoxicology

    2022  Band 90, Seite(n) 79–80

    Mesh-Begriff(e) Humans ; Neurotoxicity Syndromes ; Societies, Scientific
    Sprache Englisch
    Erscheinungsdatum 2022-02-28
    Erscheinungsland Netherlands
    Dokumenttyp Congress ; Editorial
    ZDB-ID 800820-6
    ISSN 1872-9711 ; 0161-813X
    ISSN (online) 1872-9711
    ISSN 0161-813X
    DOI 10.1016/j.neuro.2022.02.010
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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  7. Artikel: Pervasive environmental chemicals impair oligodendrocyte development.

    Cohn, Erin F / Clayton, Benjamin L L / Madhavan, Mayur / Yacoub, Sara / Federov, Yuriy / Paul-Friedman, Katie / Shafer, Timothy J / Tesar, Paul J

    bioRxiv : the preprint server for biology

    2023  

    Abstract: Exposure to environmental chemicals can impair ... ...

    Abstract Exposure to environmental chemicals can impair neurodevelopment
    Sprache Englisch
    Erscheinungsdatum 2023-02-12
    Erscheinungsland United States
    Dokumenttyp Preprint
    DOI 10.1101/2023.02.10.528042
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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  8. Artikel ; Online: Pervasive environmental chemicals impair oligodendrocyte development.

    Cohn, Erin F / Clayton, Benjamin L L / Madhavan, Mayur / Lee, Kristin A / Yacoub, Sara / Fedorov, Yuriy / Scavuzzo, Marissa A / Paul Friedman, Katie / Shafer, Timothy J / Tesar, Paul J

    Nature neuroscience

    2024  Band 27, Heft 5, Seite(n) 836–845

    Abstract: Exposure to environmental chemicals can impair neurodevelopment, and oligodendrocytes may be particularly vulnerable, as their development extends from gestation into adulthood. However, few environmental chemicals have been assessed for potential risks ... ...

    Abstract Exposure to environmental chemicals can impair neurodevelopment, and oligodendrocytes may be particularly vulnerable, as their development extends from gestation into adulthood. However, few environmental chemicals have been assessed for potential risks to oligodendrocytes. Here, using a high-throughput developmental screen in cultured cells, we identified environmental chemicals in two classes that disrupt oligodendrocyte development through distinct mechanisms. Quaternary compounds, ubiquitous in disinfecting agents and personal care products, were potently and selectively cytotoxic to developing oligodendrocytes, whereas organophosphate flame retardants, commonly found in household items such as furniture and electronics, prematurely arrested oligodendrocyte maturation. Chemicals from each class impaired oligodendrocyte development postnatally in mice and in a human 3D organoid model of prenatal cortical development. Analysis of epidemiological data showed that adverse neurodevelopmental outcomes were associated with childhood exposure to the top organophosphate flame retardant identified by our screen. This work identifies toxicological vulnerabilities for oligodendrocyte development and highlights the need for deeper scrutiny of these compounds' impacts on human health.
    Mesh-Begriff(e) Oligodendroglia/drug effects ; Animals ; Mice ; Humans ; Flame Retardants/toxicity ; Female ; Cells, Cultured ; Cell Differentiation/drug effects ; Mice, Inbred C57BL ; Environmental Pollutants/toxicity
    Chemische Substanzen Flame Retardants ; Environmental Pollutants
    Sprache Englisch
    Erscheinungsdatum 2024-03-25
    Erscheinungsland United States
    Dokumenttyp Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't
    ZDB-ID 1420596-8
    ISSN 1546-1726 ; 1097-6256
    ISSN (online) 1546-1726
    ISSN 1097-6256
    DOI 10.1038/s41593-024-01599-2
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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  9. Artikel ; Online: Integrating Data From In Vitro New Approach Methodologies for Developmental Neurotoxicity.

    Carstens, Kelly E / Carpenter, Amy F / Martin, Melissa M / Harrill, Joshua A / Shafer, Timothy J / Paul Friedman, Katie

    Toxicological sciences : an official journal of the Society of Toxicology

    2022  Band 187, Heft 1, Seite(n) 62–79

    Abstract: In vivo developmental neurotoxicity (DNT) testing is resource intensive and lacks information on cellular processes affected by chemicals. To address this, DNT new approach methodologies (NAMs) are being evaluated, including: the microelectrode array ... ...

    Abstract In vivo developmental neurotoxicity (DNT) testing is resource intensive and lacks information on cellular processes affected by chemicals. To address this, DNT new approach methodologies (NAMs) are being evaluated, including: the microelectrode array neuronal network formation assay; and high-content imaging to evaluate proliferation, apoptosis, neurite outgrowth, and synaptogenesis. This work addresses 3 hypotheses: (1) a broad screening battery provides a sensitive marker of DNT bioactivity; (2) selective bioactivity (occurring at noncytotoxic concentrations) may indicate functional processes disrupted; and, (3) a subset of endpoints may optimally classify chemicals with in vivo evidence for DNT. The dataset was comprised of 92 chemicals screened in all 57 assay endpoints sourced from publicly available data, including a set of DNT NAM evaluation chemicals with putative positives (53) and negatives (13). The DNT NAM battery provides a sensitive marker of DNT bioactivity, particularly in cytotoxicity and network connectivity parameters. Hierarchical clustering suggested potency (including cytotoxicity) was important for classifying positive chemicals with high sensitivity (93%) but failed to distinguish patterns of disrupted functional processes. In contrast, clustering of selective values revealed informative patterns of differential activity but demonstrated lower sensitivity (74%). The false negatives were associated with several limitations, such as the maximal concentration tested or gaps in the biology captured by the current battery. This work demonstrates that this multi-dimensional assay suite provides a sensitive biomarker for DNT bioactivity, with selective activity providing possible insight into specific functional processes affected by chemical exposure and a basis for further research.
    Mesh-Begriff(e) Humans ; Neurogenesis ; Neuronal Outgrowth ; Neurons ; Neurotoxicity Syndromes/etiology ; Toxicity Tests/methods
    Sprache Englisch
    Erscheinungsdatum 2022-02-24
    Erscheinungsland United States
    Dokumenttyp Journal Article ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S.
    ZDB-ID 1420885-4
    ISSN 1096-0929 ; 1096-6080
    ISSN (online) 1096-0929
    ISSN 1096-6080
    DOI 10.1093/toxsci/kfac018
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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  10. Artikel ; Online: Integrated Omic Analyses Identify Pathways and Transcriptomic Regulators Associated With Chemical Alterations of In Vitro Neural Network Formation.

    Marable, Carmen A / Frank, Christopher L / Seim, Roland F / Hester, Susan / Henderson, W Matthew / Chorley, Brian / Shafer, Timothy J

    Toxicological sciences : an official journal of the Society of Toxicology

    2022  Band 186, Heft 1, Seite(n) 118–133

    Abstract: Development of in vitro new approach methodologies has been driven by the need for developmental neurotoxicity (DNT) hazard data on thousands of chemicals. The network formation assay characterizes DNT hazard based on changes in network formation but ... ...

    Abstract Development of in vitro new approach methodologies has been driven by the need for developmental neurotoxicity (DNT) hazard data on thousands of chemicals. The network formation assay characterizes DNT hazard based on changes in network formation but provides no mechanistic information. This study investigated nervous system signaling pathways and upstream physiological regulators underlying chemically induced neural network dysfunction. Rat primary cortical neural networks grown on microelectrode arrays were exposed for 12 days in vitro to cytosine arabinoside, 5-fluorouracil, domoic acid, cypermethrin, deltamethrin, or haloperidol as these exposures altered network formation in previous studies. RNA-seq from cells and gas chromatography/mass spectrometry analysis of media extracts collected on days in vitro 12 provided gene expression and metabolomic identification, respectively. The integration of differentially expressed genes and metabolites for each neurotoxicant was analyzed using ingenuity pathway analysis. All 6 compounds altered gene expression that linked to developmental disorders and neurological diseases. Other enriched canonical pathways overlapped among compounds of the same class; eg, genes and metabolites altered by both cytosine arabinoside and 5-fluorouracil exposures are enriched in axonal guidance pathways. Integrated analysis of upstream regulators was heterogeneous across compounds, but identified several transcriptomic regulators including CREB1, SOX2, NOTCH1, and PRODH. These results demonstrate that changes in network formation are accompanied by transcriptomic and metabolomic changes and that different classes of compounds produce differing responses. This approach can enhance information obtained from new approach methodologies and contribute to the identification and development of adverse outcome pathways associated with DNT.
    Mesh-Begriff(e) Adverse Outcome Pathways ; Animals ; Microelectrodes ; Neural Networks, Computer ; Neurotoxicity Syndromes/genetics ; Neurotoxicity Syndromes/metabolism ; Rats ; Transcriptome
    Sprache Englisch
    Erscheinungsdatum 2022-01-04
    Erscheinungsland United States
    Dokumenttyp Journal Article
    ZDB-ID 1420885-4
    ISSN 1096-0929 ; 1096-6080
    ISSN (online) 1096-0929
    ISSN 1096-6080
    DOI 10.1093/toxsci/kfab151
    Datenquelle MEDical Literature Analysis and Retrieval System OnLINE

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