Body and organ weight data in 28-day toxicological studies in two mouse strains.

Toxicological studies were performed in an AAALAC (American Association for Laboratory Animal Care)-approved laboratory at BASF SE, Ludwigshafen, Germany, in accordance with the German Animal Welfare Act and the effective European Council Directive 2010/63/EU. Data were recorded in the BASF SE pathology data capture system. Historical control data (2008-2013) were compiled for a) Twelve 28-day studies performed according to OECD 407 with mice from Janvier C57BL/j Rj (J) and Charles River CD-1 (CRL), in total 73 control females and 73 control males, 5-8 weeks old at the beginning of the studies. Data collected: terminal body weight, organ weights of adrenal glands, brain, epididymides, heart, kidneys, liver, ovaries, prostate, seminal vesicles (with coagulating glands), spleen, testes, thymus, uterus. b) Eight immunotoxicity studies (duration of 28 days) performed according to EPA Health Effects Test Guidelines OPPTS 870.7800 with mice from Janvier C57BL/j Rj (J). 48 control females and 16 control males 5-7 weeks old at the beginning of the studies. Data collected: terminal body weight, mean absolute and relative weights of spleen and thymus. This data helps interpreting effects caused by treatment in toxicology studies in the mouse. Coefficients of variation were calculated and discussed in the accompanying research paper: "Variance of body and organ weights in 28-day studies in mice" (Marxfeld et al. 2019).

Variance of body and organ weights in 28-day studies in mice.

The OECD guideline 407 outlines the conduct of 28-day studies in rodents to detect systemic toxicity with focus on endocrine and immunotoxic effects. It was validated with the rat as preferred model species. Justification is required for other rodent species, as an increased variability is expected compared to the rat. We investigated the variability of organ weights in the mouse and compared this to data published for the rat in the validation report of test guideline 407. Furthermore, the influence of the immunotoxic model substance cyclophosphamide on spleen and thymus weights in the mouse in immunotoxicity studies (duration 28 days) is reported and discussed, an immunotoxic model substance was not included in the validation report. Historical control data were compiled for mouse studies performed according to OECD 407 and for immunotoxicity studies between 2008 and 2013 at BASF SE. For absolute weights, the coefficient of variation was determined for each study group and compared with the rat. Adrenal glands, ovaries and to lesser degree testes and prostate showed higher coefficients of variation in the mouse (most pronounced in adrenal glands in male animals: rat 5%-17%, CD1 mouse 20%-51%). Effects of cyclophosphamide were best detected measuring the thymus weight.

Differences in the toxicity of cerium dioxide nanomaterials after inhalation can be explained by lung deposition, animal species and nanoforms.

Considerable differences in pulmonary responses have been observed in animals exposed to cerium dioxide nanoparticles via inhalation. These differences in pulmonary toxicity might be explained by differences in lung deposition, species susceptibility or physicochemical characteristics of the tested cerium dioxide nanoforms (i.e. same chemical substance, different size, shape, surface area or surface chemistry). In order to distinguish the relative importance of these different influencing factors, we performed a detailed analysis of the data from several inhalation studies with different exposure durations, species and nanoforms, namely published data on NM211 and NM212 (JRC repository), NanoAmor (commercially available) and our published and unpublished data on PROM (industry provided). Data were analyzed by comparing the observed pulmonary responses at similar external and internal dose levels. Our analyses confirm that rats are more sensitive to developing pulmonary inflammation compared to mice. The observed differences in responses do not result purely from differences in the delivered and retained doses (expressed in particle mass as well as surface area). In addition, the different nanoforms assessed showed differences in toxic potency likely due to differences in their physicochemical parameters. Primary particle and aggregate/agglomerate size distributions have a substantial impact on the deposited dose and consequently on the pulmonary response. However, in our evaluation size could not fully explain the difference observed in the analyzed studies indicating that the pulmonary response also depends on other physicochemical characteristics of the particles. It remains to be determined to what extent these findings can be generalized to other poorly soluble nanomaterials.

Time course of lung retention and toxicity of inhaled particles: short-term exposure to nano-Ceria.

Two Ceria nanomaterials (NM-211 and NM-212) were tested for inhalation toxicity and organ burdens in order to design a chronic and carcinogenicity inhalation study (OECD TG No. 453). Rats inhaled aerosol concentrations of 0.5, 5, and 25 mg/m(3) by whole-body exposure for 6 h/day on 5 consecutive days for 1 or 4 weeks with a post-exposure period of 24 or 129 days, respectively. Lungs were examined by bronchoalveolar lavage and histopathology. Inhaled Ceria is deposited in the lung and cleared with a half-time of 40 days; at aerosol concentrations higher than 0.5 mg/m(3), this clearance was impaired resulting in a half-time above 200 days (25 mg/m(3)). After 5 days, Ceria (>0.5 mg/m(3)) induced an early inflammatory reaction by increases of neutrophils in the lung which decreased with time, with sustained exposure, and also after the exposure was terminated (during the post-exposure period). The neutrophil number observed in bronchoalveolar lavage fluid (BALF) was decreasing and supplemented by mononuclear cells, especially macrophages which were visible in histopathology but not in BALF. Further progression to granulomatous inflammation was observed 4 weeks post-exposure. The surface area of the particles provided a dose metrics with the best correlation of the two Ceria's inflammatory responses; hence, the inflammation appears to be directed by the particle surface rather than mass or volume in the lung. Observing the time course of lung burden and inflammation, it appears that the dose rate of particle deposition drove an initial inflammatory reaction by neutrophils. The later phase (after 4 weeks) was dominated by mononuclear cells, especially macrophages. The progression toward the subsequent granulomatous reaction was driven by the duration and amount of the particles in the lung. The further progression of the biological response will be determined in the ongoing long-term study.

Comparative inhalation toxicity of multi-wall carbon nanotubes, graphene, graphite nanoplatelets and low surface carbon black.

BACKGROUND: Carbon nanotubes, graphene, graphite nanoplatelets and carbon black are seemingly chemically identical carbon-based nano-materials with broad technological applications. Carbon nanotubes and carbon black possess different inhalation toxicities, whereas little is known about graphene and graphite nanoplatelets. METHODS: In order to compare the inhalation toxicity of the mentioned carbon-based nanomaterials, male Wistar rats were exposed head-nose to atmospheres of the respective materials for 6 hours per day on 5 consecutive days. Target concentrations were 0.1, 0.5, or 2.5 mg/m3 for multi-wall carbon nanotubes and 0.5, 2.5, or 10 mg/m3 for graphene, graphite nanoplatelets and low-surface carbon black. Toxicity was determined after end of exposure and after three-week recovery using broncho-alveolar lavage fluid and microscopic examinations of the entire respiratory tract. RESULTS: No adverse effects were observed after inhalation exposure to 10 mg/m3 graphite nanoplatelets or relatively low specific surface area carbon black. Increases of lavage markers indicative for inflammatory processes started at exposure concentration of 0.5 mg/m3 for multi-wall carbon nanotubes and 10 mg/m3 for graphene. Consistent with the changes in lavage fluid, microgranulomas were observed at 2.5 mg/m3 multi-wall carbon nanotubes and 10 mg/m3 graphene. In order to evaluate volumetric loading of the lung as the key parameter driving the toxicity, deposited particle volume was calculated, taking into account different methods to determine the agglomerate density. However, the calculated volumetric load did not correlate to the toxicity, nor did the particle surface burden of the lung. CONCLUSIONS: The inhalation toxicity of the investigated carbon-based materials is likely to be a complex interaction of several parameters. Until the properties which govern the toxicity are identified, testing by short-term inhalation is the best option to identify hazardous properties in order to avoid unsafe applications or select safer alternatives for a given application.

Proliferative and nonproliferative lesions of the rat and mouse mammary, Zymbal's, preputial, and clitoral glands.

The mammary gland of laboratory rodents is an important organ for the evaluation of effects of xenobiotics, especially those that perturb hormonal homeostasis or are potentially carcinogenic. Mammary gland cancer is a leading cause of human mortality and morbidity worldwide and is a subject of major research efforts utilizing rodent models. Zymbal's, preputial, and clitoral glands are standard tissues that are evaluated in animal models that enable human risk assessment of xenobiotics. A widely accepted and utilized international harmonization of nomenclature for mammary, Zymbal's, preputial, and clitoral gland lesions in laboratory animals will improve diagnostic alignment among regulatory and scientific research organizations and enrich international exchanges of information among toxicologists and pathologists.

Proliferative and nonproliferative lesions of the rat and mouse hepatobiliary system.

The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP) and North America (STP) to develop an internationally-accepted nomenclature for proliferative and non-proliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature and differential diagnosis for classifying microscopic lesions observed in the hepatobiliary system of laboratory rats and mice, with color microphotographs illustrating examples of some lesions. The standardized nomenclature presented in this document is also available for society members electronically on the internet (http://goreni.org). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous and aging lesions as well as lesions induced by exposure to test materials. A widely accepted and utilized international harmonization of nomenclature for lesions of the hepatobiliary system in laboratory animals will decrease confusion among regulatory and scientific research organizations in different countries and provide a common language to increase and enrich international exchanges of information among toxicologists and pathologists.

Octyl methoxycinnamate: two generation reproduction toxicity in Wistar rats by dietary administration.

Wistar rats continuously received octyl methoxycinnamate (OMC) in the diet through two successive generations at nominal doses of 0, 150, 450 or 1000 mg/kg bw/day. OMC had no adverse effects on estrous cycles, mating behavior, conception, parturition, lactation and weaning, sperm and follicle parameters, macropathology and histopathology of the sexual organs. 1000 mg/kg bw/day reduced parental food consumption and body weight (-14% to -16% in males, -4% to -5% females), increased liver weight, produced hepatic cytoplasmic eosinophilia and erosion/ulceration of glandular stomach mucosa. and led to a slightly decreased implantation rate in the top dose F0 and F1 dams. The high dose F1 and F2 pups had reduced lactation weight gain and organ weights and delayed sexual maturation landmarks. There was no evidence of a selective influence of the test compound on pups' sexual landmarks. The NOAEL (no observed adverse effect level) is 450 mg/kg bw/day for fertility and reproductive performance, for systemic parental and developmental toxicity.

Prevalidation of a rat liver foci bioassay (RLFB) based on results from 1600 rats: a study report.

A rat liver foci bioassay (RLFB) based on an initiation-promotion protocol employing preneoplastic foci of altered hepatocytes (FAH) as an endpoint, was prevalidated in 5 different laboratories. FAH were identified by immunohistochemical demonstration of glutathione-S-transferase (placental form, GSTP) and by staining with hematoxilin/eosin (H&E), and their area fraction was quantified morphometrically. The four model hepatocarcinogens N-nitrosomorpholine, 2-acetylaminofluoren, phenobarbital, and clofibrate were selected according to characteristic differences in their presumed mode of action, and tested in a total of 1,600 male and female rats at 2 different dose levels. The chemicals were found to differ characteristically in their potency and dose-response relationship to induce FAH when given alone or when administered following initiation with diethylnitrosamine. The interlaboratory variation was small for results obtained with the GSTP-stain and somewhat larger with respect to H&E. The assessment of the carcinogenic potential of the four chemicals by the different laboratories was in the same range and the nature of their dose-response relationships did not differ essentially between laboratories. Our results suggest that this RLFB is a sensitive bioassay, providing potentially valuable information for risk assessment including the classification of carcinogenic chemicals according to their mode of action.