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Bolon B. Toxicologic Pathology Forum Opinion: Rational Approaches to Expanded Neurohistopathology Evaluation for Nonclinical General Toxicity Studies and Juvenile Animal Studies. Toxicol Pathol 2023; 51:363-374. [PMID: 38288942 DOI: 10.1177/01926233231225239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2024]
Abstract
Existing nervous system sampling and processing "best practices" for nonclinical general toxicity studies (GTS) were designed to assess test articles with unknown, no known, or well-known neurotoxic potential. Similar practices are applicable to juvenile animal studies (JAS). In GTS and JAS, the recommended baseline sampling for all species includes brain (7 sections), spinal cord (cervical and lumbar divisions [cross and longitudinal sections for each]), and 1 nerve (sciatic or tibial [cross and longitudinal sections]) in hematoxylin and eosin-stained sections. Extra sampling and processing (ie, an "expanded neurohistopathology evaluation" [ENHP]) are used for agents with anticipated neuroactivity (toxic ± therapeutic) of incompletely characterized location and degree. Expanded sampling incorporates additional brain (usually 8-15 sections total), spinal cord (thoracic ± sacral divisions), ganglia (somatic ± autonomic, often 2-8 total), and/or nerves (2-6 total) depending on the species and study objectives. Expanded processing typically adds special neurohistological procedures (usually 1-4 for selected samples) to characterize glial reactions, myelin integrity, and/or neuroaxonal damage. In my view, GTS and JAS designs should sample neural tissues at necropsy as if ENHP will be needed eventually, and when warranted ENHP may incorporate expanded sampling and/or expanded processing depending on the study objective(s).
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2
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Moser VC, Morris-Schaffer K, Richardson JR, Li AA. Glyphosate and neurological outcomes: A systematic literature review of animal studies. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART B, CRITICAL REVIEWS 2022; 25:162-209. [PMID: 35676826 DOI: 10.1080/10937404.2022.2083739] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Studies of nervous system effects of glyphosate, a widely used herbicide, have not been critically examined. The aim of this paper was to systematically review glyphosate-induced neurotoxicity literature to determine its usefulness in regulatory decision-making. The review was restricted to mammalian studies of behavior, neuropathology, and neuropharmacology; in vitro and other biochemical studies were considered supplementary information. Glyphosate formulation studies were also considered, despite uncertainties regarding toxicities of the formulated products; no studies used a formulation vehicle as the control. Inclusion criteria were developed a priori to ensure consistent evaluation of studies, and in vivo investigations were also ranked using ToxRTool software to determine reliability. There were 27 in vivo studies (open literature and available regulatory reports), but 11 studies were considered unreliable (mostly due to critical methodological deficiencies). There were only seven acceptable investigations on glyphosate alone. Studies differed in terms of dosing scenarios, experimental designs, test species, and commercial product. Limitations included using only one dose and/or one test time, small sample sizes, limited data presentation, and/or overtly toxic doses. While motor activity was the most consistently affected endpoint (10 of 12 studies), there were considerable differences in outcomes. In six investigations, there were no marked neuropathological changes in the central or peripheral nervous system. Other neurological effects were less consistent, and some outcomes were less convincing due to influences including high variability and small effect sizes. Taken together, these studies do not demonstrate a consistent impact of glyphosate on the structure or function of the mammalian nervous system.
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Affiliation(s)
| | - Keith Morris-Schaffer
- Exponent Inc, Center for Chemical Regulation and Food Safety, Sacramento, California
| | - Jason R Richardson
- Department of Environmental Health Sciences, Robert Stempel School of Public Health and Social Work, Florida International University, Miami, FL, United States
| | - Abby A Li
- Exponent Inc, Center for Health Sciences, Oakland, CA, United States
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3
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Kolinko Y, Malečková A, Kochová P, Grajciarová M, Blassová T, Kural T, Trailin A, Červenková L, Havránková J, Vištejnová L, Tonarová P, Moulisová V, Jiřík M, Zavaďáková A, Tichánek F, Liška V, Králíčková M, Witter K, Tonar Z. Using virtual microscopy for the development of sampling strategies in quantitative histology and design-based stereology. Anat Histol Embryol 2021; 51:3-22. [PMID: 34806204 DOI: 10.1111/ahe.12765] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Accepted: 10/31/2021] [Indexed: 02/03/2023]
Abstract
Only a fraction of specimens under study are usually selected for quantification in histology. Multilevel sampling or tissue probes, slides and fields of view (FOVs) in the regions of interest (ROIs) are required. In general, all parts of the organs under study should be given the same probability to be taken into account; that is, the sampling should be unbiased on all levels. The objective of our study was to provide an overview of the use of virtual microscopy in the context of developing sampling strategies of FOVs for stereological quantification. We elaborated this idea on 18 examples from multiple fields of histology, including quantification of extracellular matrix and muscle tissue, quantification of organ and tumour microvessels and tumour-infiltrating lymphocytes, assessing osseointegration of bone implants, healing of intestine anastomoses and osteochondral defects, counting brain neurons, counting nuclei in vitro cell cultures and others. We provided practical implications for the most common situations, such as exhaustive sampling of ROIs, sampling ROIs of different sizes, sampling the same ROIs for multiple histological methods, sampling more ROIs with variable intensities or using various objectives, multistage sampling and virtual sampling. Recommendations were provided for pilot studies on systematic uniform random sampling of FOVs as a part of optimizing the efficiency of histological quantification to prevent over- or undersampling. We critically discussed the pros and cons of using virtual sections for sampling FOVs from whole scanned sections. Our review demonstrated that whole slide scans of histological sections facilitate the design of sampling strategies for quantitative histology.
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Affiliation(s)
- Yaroslav Kolinko
- Department of Histology and Embryology, Faculty of Medicine in Pilsen, Charles University, Pilsen, Czech Republic.,Faculty of Medicine in Pilsen, Biomedical Center, Charles University, Pilsen, Czech Republic
| | - Anna Malečková
- Faculty of Applied Sciences, European Centre of Excellence NTIS, University of West Bohemia, Pilsen, Czech Republic
| | - Petra Kochová
- Faculty of Applied Sciences, European Centre of Excellence NTIS, University of West Bohemia, Pilsen, Czech Republic
| | - Martina Grajciarová
- Department of Histology and Embryology, Faculty of Medicine in Pilsen, Charles University, Pilsen, Czech Republic.,Faculty of Medicine in Pilsen, Biomedical Center, Charles University, Pilsen, Czech Republic
| | - Tereza Blassová
- Department of Histology and Embryology, Faculty of Medicine in Pilsen, Charles University, Pilsen, Czech Republic.,Faculty of Medicine in Pilsen, Biomedical Center, Charles University, Pilsen, Czech Republic
| | - Tomáš Kural
- Department of Histology and Embryology, Faculty of Medicine in Pilsen, Charles University, Pilsen, Czech Republic
| | - Andriy Trailin
- Faculty of Medicine in Pilsen, Biomedical Center, Charles University, Pilsen, Czech Republic
| | - Lenka Červenková
- Faculty of Medicine in Pilsen, Biomedical Center, Charles University, Pilsen, Czech Republic.,Department of Pathology, Third Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Jiřina Havránková
- Department of Histology and Embryology, Faculty of Medicine in Pilsen, Charles University, Pilsen, Czech Republic.,Faculty of Medicine in Pilsen, Biomedical Center, Charles University, Pilsen, Czech Republic
| | - Lucie Vištejnová
- Department of Histology and Embryology, Faculty of Medicine in Pilsen, Charles University, Pilsen, Czech Republic.,Faculty of Medicine in Pilsen, Biomedical Center, Charles University, Pilsen, Czech Republic
| | - Pavla Tonarová
- Faculty of Medicine in Pilsen, Biomedical Center, Charles University, Pilsen, Czech Republic
| | - Vladimíra Moulisová
- Faculty of Medicine in Pilsen, Biomedical Center, Charles University, Pilsen, Czech Republic
| | - Miroslav Jiřík
- Faculty of Medicine in Pilsen, Biomedical Center, Charles University, Pilsen, Czech Republic.,Faculty of Applied Sciences, European Centre of Excellence NTIS, University of West Bohemia, Pilsen, Czech Republic
| | - Anna Zavaďáková
- Faculty of Medicine in Pilsen, Biomedical Center, Charles University, Pilsen, Czech Republic
| | - Filip Tichánek
- Faculty of Medicine in Pilsen, Biomedical Center, Charles University, Pilsen, Czech Republic.,Department of Pathological Physiology, Faculty of Medicine in Pilsen, Charles University, Pilsen, Czech Republic
| | - Václav Liška
- Faculty of Medicine in Pilsen, Biomedical Center, Charles University, Pilsen, Czech Republic.,Department of Surgery and Biomedical Center, Faculty of Medicine in Pilsen, Charles University, Pilsen, Czech Republic
| | - Milena Králíčková
- Department of Histology and Embryology, Faculty of Medicine in Pilsen, Charles University, Pilsen, Czech Republic.,Faculty of Medicine in Pilsen, Biomedical Center, Charles University, Pilsen, Czech Republic
| | - Kirsti Witter
- Institute of Morphology, Department of Pathobiology, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Zbyněk Tonar
- Department of Histology and Embryology, Faculty of Medicine in Pilsen, Charles University, Pilsen, Czech Republic.,Faculty of Medicine in Pilsen, Biomedical Center, Charles University, Pilsen, Czech Republic
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4
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Bolon B, Dostal LA, Garman RH. Neuropathology Evaluation in Juvenile Toxicity Studies in Rodents: Comparison of Developmental Neurotoxicity Studies for Chemicals With Juvenile Animal Studies for Pediatric Pharmaceuticals. Toxicol Pathol 2021; 49:1405-1415. [PMID: 34620000 DOI: 10.1177/01926233211045321] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The developmental neuropathology examination in juvenile toxicity studies depends on the nature of the product candidate, its intended use, and the exposure scenario (eg, dose, duration, and route). Expectations for sampling, processing, and evaluating neural tissues differ for developmental neurotoxicity studies (DNTS) for chemicals and juvenile animal studies (JAS) for pediatric pharmaceuticals. Juvenile toxicity studies typically include macroscopic observations, brain weights, and light microscopic evaluation of routine hematoxylin and eosin (H&E)-stained sections from major neural tissues (brain, spinal cord, and sciatic nerve) as neuropathology endpoints. The DNTS is a focused evaluation of the nervous system, so the study design incorporates perfusion fixation, plastic embedding of at least one nerve, quantitative analysis of selected brain regions, and sometimes special neurohistological stains. In contrast, the JAS examines multiple systems, so neural tissues undergo conventional tissue processing (eg, immersion fixation, paraffin embedding, H&E staining only). An "expanded neurohistopathology" (or "expanded neuropathology") approach may be performed for JAS if warranted, typically by light microscopic evaluation of more neural tissues (usually additional sections of brain, ganglia, and/or more nerves) or/and special neurohistological stains, to investigate specific questions (eg, a more detailed exploration of a potential neuroactive effect) or to fulfill regulatory requests.
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5
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Pardo ID, Rao DB, Morrison JP, Huddleston C, Bradley AE, Bolon B, Garman RH. Nervous System Sampling for General Toxicity and Neurotoxicity Studies in Rabbits. Toxicol Pathol 2020; 48:810-826. [PMID: 33094688 DOI: 10.1177/0192623320957637] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Although manuscripts for multiple species recommending nervous system sampling for histopathology evaluation in safety assessment have been published in the past 15 years, none have addressed the laboratory rabbit. Here, we describe 2 trimming schemes for evaluating the rabbit brain in nonclinical toxicity studies. In both schemes, the intact brain is cut in the coronal plane to permit bilateral assessment. The first scheme is recommended for general toxicity studies (tier 1) in screening agents where there is no anticipated neurotoxic potential; this 6-section approach is consistent with the Society of Toxicologic Pathology (STP) "best practice" recommendations for brain sampling in nonrodents (Toxicol Pathol 41: 1028-1048, 20131). The second trimming scheme is intended for dedicated neurotoxicity studies (tier 2) to characterize known or suspected neurotoxicants where the nervous system is a key target organ. This tier 2 strategy relies on coronal trimming of the whole brain into 3-mm-thick slices and then evaluating 12 sections. Collection of spinal cord, ganglia, and nerve specimens for rabbits during nonclinical studies should follow published STP "best practice" recommendations for sampling the central nervous system1 and peripheral nervous system (Toxicol Pathol 46: 372-402, 20182).
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Affiliation(s)
- Ingrid D Pardo
- 390190Pfizer, Inc, Global Pathology and Investigative Toxicology, Groton, CT, USA
| | - Deepa B Rao
- ToxPath Specialists, LLC (a StageBio Company), Frederick, MD, USA
| | | | - Colleen Huddleston
- 390190Pfizer, Inc, Global Pathology and Investigative Toxicology, Groton, CT, USA
| | - Alys E Bradley
- 57146Charles River Laboratories Edinburgh Ltd, Tranent, East Lothian, Scotland, United Kingdom
| | | | - Robert H Garman
- Consultants in Veterinary Pathology, Inc, Murrysville, Pennsylvania, PA, USA
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6
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Fisher JE, Ravindran A, Elayan I. CDER Experience With Juvenile Animal Studies for CNS Drugs. Int J Toxicol 2019; 38:88-95. [DOI: 10.1177/1091581818824313] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
A survey was undertaken to evaluate juvenile animal studies conducted for drug applications reviewed by the Center for Drug Evaluation and Research between 2009 and 2014. Some conclusions about the nonclinical pediatric safety assessment based on studies performed in support of central nervous system–active compounds are presented here. A total of 44 completed studies from 32 New Drug Applications submitted to the Divisions of Psychiatry and Neurology Products were evaluated. Data on animal species and age range used, endpoints evaluated, and outcomes included in labeling were analyzed. Of the drugs evaluated, all but one had studies conducted in rats. In some cases, a second study in a nonrodent species (dog) was also conducted. Indices of growth and development and standard general toxicity parameters were included in all of the studies. Expanded neurohistopathology evaluations, bone mineral density measurements, and reproductive and neurobehavioral functional assessments were also generally carried out. A variety of neurological and neurobehavioral tests were employed. In the majority of rat studies, the potential for long-term cognitive impairment was evaluated using a complex water maze. Juvenile animal studies provided safety information considered relevant to drug use in children and that was included in labeling for 78% of the applications surveyed. The most commonly reported findings in labeling were for neurobehavioral effects, including changes in locomotor activity, auditory startle habituation, and learning and memory. Of the studies described in labeling with neurobehavioral effects, 54% found these effects to be persistent and to provide evidence of developmental neurotoxicity.
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Affiliation(s)
- J. Edward Fisher
- Division of Neurology Products, Center for Drug Evaluation and Research (CDER), Office of New Drugs (OND), US Food and Drug Administration (FDA), Silver Spring, MD, USA
| | - Arippa Ravindran
- Division of Psychiatry Products, Center for Drug Evaluation and Research (CDER), Office of New Drugs (OND), US Food and Drug Administration (FDA), Silver Spring, MD, USA
| | - Ikram Elayan
- Division of Psychiatry Products, Center for Drug Evaluation and Research (CDER), Office of New Drugs (OND), US Food and Drug Administration (FDA), Silver Spring, MD, USA
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7
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Li AA, Sheets LP, Raffaele K, Moser V, Hofstra A, Hoberman A, Makris SL, Garman R, Bolon B, Kaufmann W, Auer R, Lau E, Vidmar T, Bowers WJ. Recommendations for harmonization of data collection and analysis of developmental neurotoxicity endpoints in regulatory guideline studies: Proceedings of workshops presented at Society of Toxicology and joint Teratology Society and Neurobehavioral Teratology Society meetings. Neurotoxicol Teratol 2017; 63:24-45. [PMID: 28757310 PMCID: PMC6634984 DOI: 10.1016/j.ntt.2017.07.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 07/24/2017] [Accepted: 07/26/2017] [Indexed: 11/20/2022]
Abstract
The potential for developmental neurotoxicity (DNT) of environmental chemicals may be evaluated using specific test guidelines from the US Environmental Protection Agency or the Organisation for Economic Cooperation and Development (OECD). These guidelines generate neurobehavioral, neuropathological, and morphometric data that are evaluated by regulatory agencies globally. Data from these DNT guideline studies, or the more recent OECD extended one-generation reproductive toxicity guideline, play a pivotal role in children's health risk assessment in different world areas. Data from the same study may be interpreted differently by regulatory authorities in different countries resulting in inconsistent evaluations that may lead to inconsistencies in risk assessment decisions internationally, resulting in regional differences in public health protection or in commercial trade barriers. These issues of data interpretation and reporting are also relevant to juvenile and pre-postnatal studies conducted more routinely for pharmaceuticals and veterinary medicines. There is a need for development of recommendations geared toward the operational needs of the regulatory scientific reviewers who apply these studies in risk assessments, as well as the scientists who generate DNT data sets. The workshops summarized here draw upon the experience of the authors representing government, industry, contract research organizations, and academia to discuss the scientific issues that have emerged from diverse regulatory evaluations. Although various regulatory bodies have different risk management decisions and labeling requirements that are difficult to harmonize, the workshops provided an opportunity to work toward more harmonized scientific approaches for evaluating DNT data within the context of different regulatory frameworks. Five speakers and their coauthors with neurotoxicology, neuropathology, and regulatory toxicology expertise discussed issues of variability, data reporting and analysis, and expectations in DNT data that are encountered by regulatory authorities. In addition, principles for harmonized evaluation of data were suggested using guideline DNT data as case studies.
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Affiliation(s)
| | | | | | - Virginia Moser
- US EPA National Health and Environmental Effects Research Laboratory, Office of Research and Development (NHEERL, ORD), USA
| | | | - Alan Hoberman
- Charles River Laboratories, Global Developmental, Reproductive and Juvenile Toxicology, USA.
| | - Susan L Makris
- US EPA National Center for Environmental Assessment, Office of Research and Development (NCEA ORD), USA.
| | | | | | | | - Roland Auer
- University of Saskatchewan, Department of Pathology, Canada.
| | | | | | - Wayne J Bowers
- Department of Neuroscience, Carleton University, Ontario, Canada
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8
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Sharma AK, Morrison JP, Rao DB, Pardo ID, Garman RH, Bolon B. Toxicologic Pathology Analysis for Translational Neuroscience. Int J Toxicol 2016; 35:410-9. [DOI: 10.1177/1091581816636372] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
A half-day American College of Toxicology continuing education course presented key issues often confronted by translational neuroscientists when predicting human risk from animal-derived toxicologic pathology data. Two talks correlated discrete structures with major functions in brains of rodents and nonrodents. The third lecture provided practical advice to obtain highly homologous rodent brain sections for quantitative morphometry in developmental neurotoxicity testing. The last presentation discussed demographic influences (eg, species, strain, sex, age), physiological attributes (eg, body composition, brain vascularity, pharmacokinetic/pharmacodynamic patterns, etc), and husbandry parameters (eg, group housing) recognized to impact the actions of neuroactive chemicals. Speakers described common cases of real-world challenges to animal data interpretation encountered when designing studies or extrapolating biological responses across species. The efficiency of translational neuroscience efforts will likely be enhanced as new methods (eg, high-resolution non-invasive imaging) improve our capability to cross-connect subtle anatomic and/or biochemical lesions with functional changes over time.
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Affiliation(s)
| | | | - Deepa B. Rao
- Center for Drug Evaluation and Research (CDER), US Food and Drug Administration, Silver Spring, MD, USA
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9
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Sheets LP, Li AA, Minnema DJ, Collier RH, Creek MR, Peffer RC. A critical review of neonicotinoid insecticides for developmental neurotoxicity. Crit Rev Toxicol 2016; 46:153-90. [PMID: 26513508 PMCID: PMC4732412 DOI: 10.3109/10408444.2015.1090948] [Citation(s) in RCA: 79] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Revised: 09/01/2015] [Accepted: 09/02/2015] [Indexed: 01/21/2023]
Abstract
A comprehensive review of published and previously unpublished studies was performed to evaluate the neonicotinoid insecticides for evidence of developmental neurotoxicity (DNT). These insecticides have favorable safety profiles, due to their preferential affinity for nicotinic receptor (nAChR) subtypes in insects, poor penetration of the mammalian blood-brain barrier, and low application rates. Nevertheless, examination of this issue is warranted, due to their insecticidal mode of action and potential exposure with agricultural and residential uses. This review identified in vitro, in vivo, and epidemiology studies in the literature and studies performed in rats in accordance with GLP standards and EPA guidelines with imidacloprid, acetamiprid, thiacloprid, clothianidin, thiamethoxam, and dinotefuran, which are all the neonicotinoids currently registered in major markets. For the guideline-based studies, treatment was administered via the diet or gavage to primiparous female rats at three dose levels, plus a vehicle control (≥20/dose level), from gestation day 0 or 6 to lactation day 21. F1 males and females were evaluated using measures of motor activity, acoustic startle response, cognition, brain morphometry, and neuropathology. The principal effects in F1 animals were associated with decreased body weight (delayed sexual maturation, decreased brain weight, and morphometric measurements) and acute toxicity (decreased activity during exposure) at high doses, without neuropathology or impaired cognition. No common effects were identified among the neonicotinoids that were consistent with DNT or the neurodevelopmental effects associated with nicotine. Findings at high doses were associated with evidence of systemic toxicity, which indicates that these insecticides do not selectively affect the developing nervous system.
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Affiliation(s)
| | - Abby A. Li
- Exponent Health Sciences,
San Francisco,
CA,
USA
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10
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Garman RH, Li AA, Kaufmann W, Auer RN, Bolon B. Recommended Methods for Brain Processing and Quantitative Analysis in Rodent Developmental Neurotoxicity Studies. Toxicol Pathol 2015; 44:14-42. [PMID: 26296631 DOI: 10.1177/0192623315596858] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Neuropathology methods in rodent developmental neurotoxicity (DNT) studies have evolved with experience and changing regulatory guidance. This article emphasizes principles and methods to promote more standardized DNT neuropathology evaluation, particularly procurement of highly homologous brain sections and collection of the most reproducible morphometric measurements. To minimize bias, brains from all animals at all dose levels should be processed from brain weighing through paraffin embedding at one time using a counterbalanced design. Morphometric measurements should be anchored by distinct neuroanatomic landmarks that can be identified reliably on the faced block or in unstained sections and which address the region-specific circuitry of the measured area. Common test article-related qualitative changes in the developing brain include abnormal cell numbers (yielding altered regional size), displaced cells (ectopia and heterotopia), and/or aberrant differentiation (indicated by defective myelination or synaptogenesis), but rarely glial or inflammatory reactions. Inclusion of digital images in the DNT pathology raw data provides confidence that the quantitative analysis was done on anatomically matched (i.e., highly homologous) sections. Interpreting DNT neuropathology data and their presumptive correlation with neurobehavioral data requires an integrative weight-of-evidence approach including consideration of maternal toxicity, body weight, brain weight, and the pattern of findings across brain regions, doses, sexes, and ages.
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Affiliation(s)
- Robert H Garman
- Consultants in Veterinary Pathology, Inc., Murrysville, Pennsylvania, USA
| | - Abby A Li
- Exponent Inc., San Francisco, California, USA
| | | | - Roland N Auer
- Hôpital Ste-Justine, Département de Pathologie, Université de Montréal, Québec, Canada
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11
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Developmental Neurotoxicology: History and Outline of Developmental Neurotoxicity Study Guidelines. Food Saf (Tokyo) 2015. [DOI: 10.14252/foodsafetyfscj.2015012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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12
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Morrison JP, Sharma AK, Rao D, Pardo ID, Garman RH, Kaufmann W, Bolon B. Fundamentals of translational neuroscience in toxicologic pathology: optimizing the value of animal data for human risk assessment. Toxicol Pathol 2014; 43:132-9. [PMID: 25398755 DOI: 10.1177/0192623314558306] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
A half-day Society of Toxicologic Pathology continuing education course on "Fundamentals of Translational Neuroscience in Toxicologic Pathology" presented some current major issues faced when extrapolating animal data regarding potential neurological consequences to assess potential human outcomes. Two talks reviewed functional-structural correlates in rodent and nonrodent mammalian brains needed to predict behavioral consequences of morphologic changes in discrete neural cell populations. The third lecture described practical steps for ensuring that specimens from rodent developmental neurotoxicity tests will be processed correctly to produce highly homologous sections. The fourth talk detailed demographic factors (e.g., species, strain, sex, and age); physiological traits (body composition, brain circulation, pharmacokinetic/pharmacodynamic patterns, etc.); and husbandry influences (e.g., group housing) known to alter the effects of neuroactive agents. The last presentation discussed the appearance, unknown functional effects, and potential relevance to humans of polyethylene glycol (PEG)-associated vacuoles within the choroid plexus epithelium of animals. Speakers provided real-world examples of challenges with data extrapolation among species or with study design considerations that may impact the interpretability of results. Translational neuroscience will be bolstered in the future as less invasive and/or more quantitative techniques are devised for linking overt functional deficits to subtle anatomic and chemical lesions.
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Affiliation(s)
| | | | - Deepa Rao
- National Toxicology Program, National Institute of Environmental Health Sciences and Integrated Laboratory Systems, Research Triangle Park, North Carolina, USA
| | | | - Robert H Garman
- Consultants in Veterinary Pathology, Inc., Murrysville, Pennsylvania, USA
| | | | - Brad Bolon
- The Ohio State University, College of Veterinary Medicine, Columbus, Ohio, USA
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13
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Neal-Kluever A, Aungst J, Gu Y, Hatwell K, Muldoon-Jacobs K, Liem A, Ogungbesan A, Shackelford M. Infant toxicology: State of the science and considerations in evaluation of safety. Food Chem Toxicol 2014; 70:68-83. [DOI: 10.1016/j.fct.2014.05.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Revised: 05/02/2014] [Accepted: 05/03/2014] [Indexed: 11/26/2022]
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14
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Webster JD, Dunstan RW. Whole-slide imaging and automated image analysis: considerations and opportunities in the practice of pathology. Vet Pathol 2013; 51:211-23. [PMID: 24091812 DOI: 10.1177/0300985813503570] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Digital pathology, the practice of pathology using digitized images of pathologic specimens, has been transformed in recent years by the development of whole-slide imaging systems, which allow for the evaluation and interpretation of digital images of entire histologic sections. Applications of whole-slide imaging include rapid transmission of pathologic data for consultations and collaborations, standardization and distribution of pathologic materials for education, tissue specimen archiving, and image analysis of histologic specimens. Histologic image analysis allows for the acquisition of objective measurements of histomorphologic, histochemical, and immunohistochemical properties of tissue sections, increasing both the quantity and quality of data obtained from histologic assessments. Currently, numerous histologic image analysis software solutions are commercially available. Choosing the appropriate solution is dependent on considerations of the investigative question, computer programming and image analysis expertise, and cost. However, all studies using histologic image analysis require careful consideration of preanalytical variables, such as tissue collection, fixation, and processing, and experimental design, including sample selection, controls, reference standards, and the variables being measured. The fields of digital pathology and histologic image analysis are continuing to evolve, and their potential impact on pathology is still growing. These methodologies will increasingly transform the practice of pathology, allowing it to mature toward a quantitative science. However, this maturation requires pathologists to be at the forefront of the process, ensuring their appropriate application and the validity of their results. Therefore, histologic image analysis and the field of pathology should co-evolve, creating a symbiotic relationship that results in high-quality reproducible, objective data.
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Affiliation(s)
- J D Webster
- Department of Pathology, Genentech, 1 DNA Way, South San Francisco, CA 94080, USA.
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Bolon B, Garman RH, Pardo ID, Jensen K, Sills RC, Roulois A, Radovsky A, Bradley A, Andrews-Jones L, Butt M, Gumprecht L. STP position paper: Recommended practices for sampling and processing the nervous system (brain, spinal cord, nerve, and eye) during nonclinical general toxicity studies. Toxicol Pathol 2013; 41:1028-48. [PMID: 23475559 DOI: 10.1177/0192623312474865] [Citation(s) in RCA: 122] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The Society of Toxicologic Pathology charged a Nervous System Sampling Working Group with devising recommended practices to routinely screen the central nervous system (CNS) and peripheral nervous system (PNS) in Good Laboratory Practice-type nonclinical general toxicity studies. Brains should be weighed and trimmed similarly for all animals in a study. Certain structures should be sampled regularly: caudate/putamen, cerebellum, cerebral cortex, choroid plexus, eye (with optic nerve), hippocampus, hypothalamus, medulla oblongata, midbrain, nerve, olfactory bulb (rodents only), pons, spinal cord, and thalamus. Brain regions may be sampled bilaterally in rodents using 6 to 7 coronal sections, and unilaterally in nonrodents with 6 to 7 coronal hemisections. Spinal cord and nerves should be examined in transverse and longitudinal (or oblique) orientations. Most Working Group members considered immersion fixation in formalin (for CNS or PNS) or a solution containing acetic acid (for eye), paraffin embedding, and initial evaluation limited to hematoxylin and eosin (H&E)-stained sections to be acceptable for routine microscopic evaluation during general toxicity studies; other neurohistological methods may be undertaken if needed to better characterize H&E findings. Initial microscopic analyses should be qualitative and done with foreknowledge of treatments and doses (i.e., "unblinded"). The pathology report should clearly communicate structures that were assessed and methodological details. Since neuropathologic assessment is only one aspect of general toxicity studies, institutions should retain flexibility in customizing their sampling, processing, analytical, and reporting procedures as long as major neural targets are evaluated systematically.
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Affiliation(s)
- Brad Bolon
- 1The Ohio State University, Columbus, Ohio, USA
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Tsuji R, Crofton KM. Developmental neurotoxicity guideline study: issues with methodology, evaluation and regulation. Congenit Anom (Kyoto) 2012; 52:122-8. [PMID: 22925212 DOI: 10.1111/j.1741-4520.2012.00374.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Recently social concerns have been increasing about the effects of environmental factors on children's health, especially on their nervous systems. The U.S. Environmental Protection Agency (EPA) and the Organisation for Economic Co-operation and Development (OECD) have published testing guidelines for developmental neurotoxicity (DNT). Approximately 110 guideline studies have been conducted to date. Importantly, information from these studies has provided data critical for regulatory decisions for a number of chemicals. However, the DNT guidelines do not always satisfy all stakeholders because of some uncertainties in their methodology, evaluation, and regulation. Methodological issues include incomplete harmonization between EPA and OECD guidelines, criticisms of the methodology for learning and memory testing, and unspecified positive control substances. Potential artifacts in morphometric neuropathological measures, criteria for observation measures, uncertainty of postnatal offspring exposure, especially in feeding studies, and extrapolation of data from rats to humans are major evaluation issues. In addition, there is some uncertainty in the use of an additional safety factor for susceptibility of infants and children. Moreover, the DNT guidelines have extensive time and cost requirements, use large numbers of animals, and there is a limited set of laboratories that can conduct the study. This paper reviews some of these issues and summarizes discussions from the symposium 'Developmental neurotoxicity testing: Scientific approaches towards the next generation to protecting the developing nervous system of children' held at the 2011 annual meeting of the Japanese Teratology Society.
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Affiliation(s)
- Ryozo Tsuji
- Environmental Health Science Laboratory, Sumitomo Chemical Co. Ltd, Osaka, Japan.
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