Bayesian statistical concepts with examples from rodent toxicology studies.

The theory and practice of statistics comprises two main schools of thought: frequentist statistics and Bayesian statistics. Frequentist methods are most commonly used to analyze animal-based laboratory data, while Bayesian statistical methods have been implemented less widely and may be relatively unfamiliar to practitioners in experimental science. This paper provides a high-level overview of Bayesian statistics and how they compare with frequentist methods.

Inter-Rater and Intra-Rater Agreement in Scoring Severity of Rodent Cardiomyopathy and Relation to Artificial Intelligence-Based Scoring.

We previously developed a computer-assisted image analysis algorithm to detect and quantify the microscopic features of rodent progressive cardiomyopathy (PCM) in rat heart histologic sections and validated the results with a panel of five veterinary toxicologic pathologists using a multinomial logistic model. In this study, we assessed both the inter-rater and intra-rater agreement of the pathologists and compared pathologists' ratings to the artificial intelligence (AI)-predicted scores. Pathologists and the AI algorithm were presented with 500 slides of rodent heart.

Immunotoxicity of N-butylbenzenesulfonamide: impacts on immune function in adult mice and developmentally exposed rats.

N-butylbenzenesulfonamide (NBBS) is a high-production volume plasticizer that is an emerging contaminant of concern for environmental and human health. To understand the risks and health effects of exposure to NBBS, studies were conducted in adult-exposed mice and developmentally exposed rats to evaluate the potential for NBBS to modulate the immune system. Beginning between 8 and 9 weeks of age, dosed feed containing NBBS at concentrations of 0, 313, 625, 1250, 2500, and 5000 ppm was continuously provided to B6C3F1/N female mice for 28 days.

Evaluation of immunotoxicity of sodium metavanadate following drinking water exposure in female B6C3F1/N mice in a 28-day study.

Sodium metavanadate (NaVO ) is a pentavalent vanadium compound used in the metal industry and dietary supplements; human exposure occurs through inhalation of fumes and dust and ingestion of NaVO -containing products. The objective of this study was to assess the potential immunotoxicity of NaVO . Female B6C3F1/N mice were exposed to 0-500 ppm NaVO in drinking water for 28 days and evaluated for effects on immune cell populations and innate, cellular-mediated, and humoral-mediated immunity.

Short-term toxicity studies of thallium (I) sulfate administered in drinking water to Sprague Dawley rats and B6C3F1/N mice.

Thallium is a heavy metal that is known to induce a broad spectrum of adverse health effects in humans including alopecia, neurotoxicity, and mortality following high dose acute poisoning events. Widespread human exposure to thallium may occur via consumption of contaminated drinking water; limited toxicity data are available to evaluate the corresponding public health risk. To address this data gap, the Division of Translational Toxicology conducted short-term toxicity studies of a monovalent thallium salt, thallium (I) sulfate.

Chronic Inhalation Exposure to Antimony Trioxide Exacerbates the MAPK Signaling in Alveolar Bronchiolar Carcinomas in B6C3F1/N Mice.

Antimony trioxide (AT) is used as a flame retardant in fabrics and plastics. Occupational exposure in miners and smelters is mainly through inhalation and dermal contact. Chronic inhalation exposure to AT particulates in B6C3F1/N mice and Wistar Han rats resulted in increased incidences and tumor multiplicities of alveolar/bronchiolar carcinomas (ABCs).

Evaluation of the herbicide glyphosate, (aminomethyl)phosphonic acid, and glyphosate-based formulations for genotoxic activity using in vitro assays.

Glyphosate, the most heavily used herbicide world-wide, is applied to plants in complex formulations that promote absorption. The National Toxicology Program reported in 1992 that glyphosate, administered to rats and mice at doses up to 50,000 ppm in feed for 13 weeks, showed little evidence of toxicity, and no induction of micronuclei was observed in the mice in this study. Subsequently, mechanistic studies of glyphosate and glyphosate-based formulations (GBFs) that have focused on DNA damage and oxidative stress suggest that glyphosate may have genotoxic potential.

Gene expression profiling after exposure to a chemical carcinogen, Pentabrominated Diphenyl Ether, at different life stages.

Exposure to environmental hazards occurs at different stages of our lifetime-infant, child, adult. This study integrates recently published toxicogenomics data to examine how exposure to a known rat chemical carcinogen (pentabrominated diphenyl ether (PBDE)) upregulated liver transcriptomic changes at different life cycle stages (PND 4, PND 22, adult). We found that at all three life cycle stages PBDE exposure induced hepatocellular transcriptomic changes in disease pathways including cancer, metabolic, membrane function, and Nrf2 antioxidant pathways, pathways all characteristics of chemical carcinogens.

Reproductive and developmental toxicity following exposure to organophosphate ester flame retardants and plasticizers, triphenyl phosphate and isopropylated phenyl phosphate, in Sprague Dawley rats.

Two organophosphate esters used as flame retardants and plasticizers, triphenyl phosphate (TPHP) and isopropylated phenyl phosphate (IPP), have been detected in environmental samples around the world. Human exposure primarily occurs via oral ingestion with reported higher concentrations in children. Currently, there are no data to evaluate potential risk from exposure to either TPHP or IPP during fetal development.

Analysis of incidence data in developmental toxicity studies: Statistical tests to account for litter effects in fetal defect data.

Background: When analyzing fetal defect incidence in laboratory animal studies, correlation in responses within litters (i.e., litter effects) can lead to increased false-positive rates if litter effects are not incorporated into the analysis.

A cross-sectional clinical study in women to investigate possible genotoxicity and hematological abnormalities related to the use of black cohosh botanical dietary supplements.

Black cohosh (BC; Actaea racemosa L.), a top-selling botanical dietary supplement, is marketed to women primarily to ameliorate a variety of gynecological symptoms. Due to widespread usage, limited safety information, and sporadic reports of hepatotoxicity, the Division of the National Toxicology Program (DNTP) initially evaluated BC extract in female rats and mice.

Single nucleotide polymorphism patterns associated with a cancer resistant phenotype.

Background And Aims: In this study ten mouse strains representing ~90% of genetic diversity in laboratory mice (B6C3F1/J, C57BL/6J, C3H/HeJ, A/J, NOD.B1oSnH2/J, NZO/HILtJ, 129S1/SvImJ, WSB/EiJ, PWK/PhJ, CAST/EiJ) were examined to identify the mouse strain with the lowest incidence of cancer. The unique single polymorphisms (SNPs) associated with this low cancer incidence are reported.

Inter-pathologist agreement on diagnosis, classification and grading of canine glioma.

Histopathological evaluation of tumours is a subjective process, but studies of inter-pathologist agreement are uncommon in veterinary medicine. The Comparative Brain Tumour Consortium (CBTC) recently published diagnostic criteria for canine gliomas. Our objective was to assess the degree of inter-pathologist agreement on intracranial canine gliomas, utilising the CBTC diagnostic criteria in a cohort of eighty-five samples from dogs with an archival diagnosis of intracranial glioma.

Statistical Analysis of Rodent Body Weight Data is Robust to Departures from Normality in Historical National Toxicology Program Studies Dated 1980-2013.

Parametric statistical tests used to assess body weight changes in rodent experiments assume a normal distribution, and the actual distribution of the rodent body weights is often assumed to be approximately normal. In order for statistical tests to be deemed appropriate without routinely confirming the normal distribution for rodent body weight data, the tests must be powerful enough to detect meaningful changes even when a population deviates from a normal distribution. Here, we present a novel analysis to assess the normality of rodent body weight data for control animals in 1,386 National Toxicology Program (NTP) studies and determined how robust a set of procedures are to detect departures from normality.

Cobalt-induced oxidative stress contributes to alveolar/bronchiolar carcinogenesis in B6C3F1/N mice.

Rodent alveolar/bronchiolar carcinomas (ABC) that arise either spontaneously or due to chemical exposure are similar to a subtype of lung adenocarcinomas in humans. B6C3F1/N mice and F344/NTac rats exposed to cobalt metal dust (CMD) by inhalation developed ABCs in a dose dependent manner. In CMD-exposed mice, the incidence of Kras mutations in ABCs was 67% with 80% of those being G to T transversions on codon 12 suggesting a role of oxidative stress in the pathogenesis.

Evaluation of skin sensitization induced by four ionic liquids.

Ionic liquids (ILs) are synthetic solvents used as replacements for volatile organic solvents. Human exposure occurs through dermal or oral routes. In rodents, several ILs were reported to induce dermal toxicity, irritation, and sensitization.

Immunotoxicity studies of sulfolane following developmental exposure in Hsd:Sprague Dawley SD rats and adult exposure in B6C3F1/N mice.

Sulfolane is a solvent used in the petrochemical industry and a groundwater contaminant in areas near refineries. The current studies were conducted to assess the impact of oral exposure to sulfolane on the immune system using two models: (1) a perinatal drinking water exposure to 0, 30, 100, 300, or 1000 mg/L from gestation day (GD) 6 until ∼13 weeks-of-age in Harlan Sprague Dawley rats; and, (2) a 90-day gavage exposure of adult female B6C3F1/N mice to 0, 1, 10, 30, 100, or 300 mg/kg/day. Immune parameters evaluated included measurement of antibody production against sheep red blood cells (SRBC) and keyhole limpet hemocyanin (KLH), measurements of natural killer (NK) cell activity, cytotoxic T-cell (CTL) activity, and T-cell proliferation, as well as measures of splenic immune cell populations, hematological parameters, and histopathology of immune tissues.

Immunohistochemical evaluation of immune cell infiltration in canine gliomas.

Evasion of the immune response is an integral part of the pathogenesis of glioma. In humans, important mechanisms of immune evasion include recruitment of regulatory T cells (Tregs) and polarization of macrophages toward an M2 phenotype. Canine glioma has a robust immune cell infiltrate that has not been extensively characterized.

Qualitative and Quantitative Neuropathology Approaches Using Magnetic Resonance Microscopy (Diffusion Tensor Imaging) and Stereology in a Hexachlorophene Model of Myelinopathy in Sprague-Dawley Rats.

It is well established that hexachlorophene, which is used as an antibacterial agent, causes intramyelinic edema in humans and animal models. The hexachlorophene myelinopathy model, in which male Sprague-Dawley rats received 25 to 30 mg/kg hexachlorophene by gavage for up to 5 days, provided an opportunity to compare traditional neuropathology evaluations with magnetic resonance microscopy (MRM) findings. In addition, stereology assessments of 3 neuroanatomical sites were compared to quantitative measurements of similar structures by MRM.

Using Artificial Intelligence to Detect, Classify, and Objectively Score Severity of Rodent Cardiomyopathy.

Rodent progressive cardiomyopathy (PCM) encompasses a constellation of microscopic findings commonly seen as a spontaneous background change in rat and mouse hearts. Primary histologic features of PCM include varying degrees of cardiomyocyte degeneration/necrosis, mononuclear cell infiltration, and fibrosis. Mineralization can also occur.

Transcriptomic data from the rat liver after five days of exposure to legacy or emerging brominated flame retardants.

Large-scale gene expression analysis of legacy* and emerging** brominated flame retardants were conducted in the male Harlan Sprague Dawley rat [1]. Each animal was dosed for 5 days with the chemical at concentrations of 0.1 - 1000 μmol/kg body weight per day.

Comparative toxicity and liver transcriptomics of legacy and emerging brominated flame retardants following 5-day exposure in the rat.

The relative toxicity of three legacy and six emerging brominated flame retardants* was studied in the male Harlan Sprague Dawley rat. The hepatocellular and thyroid toxicity of each flame retardant was evaluated following five-day exposure to each of the nine flame retardants (oral gavage in corn oil) at 0.1-1000 μmol/kg body weight per day.

Postnatal Effects of Gestational and Lactational Gavage Exposure to Boric Acid in the Developing Sprague Dawley Rat.

Human exposure to boron occurs primarily through diet and drinking water sources. Animal studies have found that reduced fetal weight following gestational exposure to boron (as boric acid) is the most sensitive toxicological effect. However, recent studies suggest that newborns in areas with elevated boron in drinking water may receive levels of exposure that exceed the U.

Evaluation of 2-methoxy-4-nitroaniline (MNA) in hypersensitivity, 14-day subacute, reproductive, and genotoxicity studies.

2-Methoxy-4-nitroaniline (MNA), an intermediate in the synthesis of azo dyes used in textiles and paints, is structurally similar to carcinogenic anilines. Human exposure occurs primarily in the occupational setting through handling of dye dust, and through use and disposal of MNA-containing products. MNA has been reported to induce contact hypersensitivity in a human, myocardial necrosis in rats, and bacterial mutagenicity.

Unique microRNA alterations in hepatocellular carcinomas arising either spontaneously or due to chronic exposure to Ginkgo biloba extract (GBE) in B6C3F1/N mice.

Ginkgo biloba extract (GBE) is used in traditional Chinese medicine as a herbal supplement for improving memory. Exposure of B6C3F1/N mice to GBE in a 2-year National Toxicology Program (NTP) bioassay resulted in a dose-dependent increase in hepatocellular carcinomas (HCC). To identify key microRNAs that modulate GBE-induced hepatocarcinogenesis, we compared the global miRNA expression profiles in GBE-exposed HCC (GBE-HCC) and spontaneous HCC (SPNT-HCC) with age-matched vehicle control normal livers (CNTL) from B6C3F1/N mice.