N-Nitrosodiethylamine (NDEA), a well-studied N-nitrosamine, was tested in rats to compare the dose-response relationship of three genotoxicity endpoints. Mutant / mutation frequencies were determined ...using the transgenic rodent (TGR) gene mutation assay and error corrected next generation sequencing (ecNGS) (i.e., duplex sequencing (DS)), and genetic damage was detected by the alkaline comet assay. Big Blue® (cII Locus) animals (n = 6 per dose group) were administered doses of 0.001, 0.01, 0.1, 1, 3 mg/kg/day NDEA by oral gavage. Samples were collected for cII mutation and DS analyses following 28-days of exposure and 3 days recovery. In a separate study, male Sprague-Dawley (SD) rats (n = 6 per dose group) were administered the same doses by oral gavage for two consecutive days and then samples collected for the alkaline comet assay. A dose-related increase in mutant / mutation frequencies of the liver but not duodenum was observed using the TGR assay and DS with DS resulting in a slightly more sensitive response, with a lower benchmark dose (BMD). In addition, a dose-related increase in percent tail DNA was observed in the liver using the alkaline comet assay. Therefore, DS and comet assays showed good utility for hazard identification and dose-response analysis of a representative N-nitrosamine comparable to the TGR gene mutation assay.
Display omitted
•TGR and DS detected NDEA dose-responsive increase in liver mutant / mutation frequencies.•DS was slightly more sensitive than TGR (i.e., lower BMD).•NDEA DS substitution primarily T > C.•Acute alkaline comet assay detected dose-responsive NDEA genotoxicity.
Dozens of millions of people are exposed to gadolinium-based contrast agents annually for enhanced magnetic resonance imaging. Gadolinium-based contrast agents are known nephrotoxins and can trigger ...the potentially fatal condition of systemic fibrosis. Risk factors are practically entirely undefined. We examined the role of NADPH oxidase 4 (Nox4) in gadolinium-induced systemic disease. Age- and weight-matched mice were randomized to experimental diabetes (streptozotocin) and control groups followed by systemic gadolinium-based contrast agent treatment. Nox4-deficient mice were randomized to experimental diabetes and gadolinium-based contrast agent treatment. Skin fibrosis and cellular infiltration were apparent in both gadolinium-based contrast agent-treated and experimental diabetes groups. Similarly, both groups demonstrated renal pathologies with evidence of reactive oxygen species generation. Deletion of Nox4 abrogated both skin and renal pathology, whether from diabetes or gadolinium-based contrast agent treatment. These discoveries demonstrate the importance of Nox4 in gadolinium-based contrast agent- and diabetes-induced fibrosis.
A mouse model of gadolinium-based contrast agent- and diabetes-induced fibrosis was used to demonstrate the role of NADPH oxidase 4 (Nox4) in gadolinium-induced systemic disease. Using these models, we established the role of Nox4 as a mediator of reactive oxygen species generation and subsequent skin and kidney fibrosis. These novel findings have defined Nox-4-mediated mechanisms by which gadolinium-based contrast agents induce systemic diseases.
A study was conducted on BALB/c mice infected with Leishmania (Leishmania) amazonensis to analyse the effects of 0.5% miltefosine (MTF) hydrogel treatment on cutaneous leishmaniasis (CL) lesions. The ...mice were treated for 25 days topically, and lesion sizes, parasite loads, histopathology, ultrastructure, cytokines including interleukin 4 (IL-4), tumour necrosis factor alfa (TNFα), interferon gamma (IFNγ), IL-10, and vascular endothelial growth factor (VEGF) profiles were evaluated on days 0, 12, 25, and 85. After 12 days of treatment, the lesion sizes and parasite numbers decreased. By day 60 post treatment, there were no lesions and only a few parasites. At day 25, there was a temporary papillomatosis reaction, an increase in mast cells, a few giant cells, and granulomas, and a decrease in diffuse inflammatory infiltrate and parasites. Transmission electron microscopy (TEM) examination showed early ultrastructural changes, including macrophages without parasites and vacuoles containing electrodense material. At the different evaluated times, the cytokine regulation indexes (ICRs) decreased for IL-4, TNFα, and VEGF. According to the study, the 0.5% MTF hydrogel was effective and showed positive results from the early stages of usage. The MTF directly targeted parasites, downregulated the release of IL-4, TNFα, and VEGF, increased mast cell production, and induced granuloma reaction during evaluation periods.
•Identification of factors to be considered when evaluating Ames test data.•The relative strengths and weaknesses of currently used evaluation criteria.•The use of a combination of criteria when ...evaluating test data.•The need for repeat testing using the same or modified experimental conditions.•The implementation and use of solvent and positive control charts.
A committee was constituted within the International Workshop on Genetic Toxicology Testing (IWGT) to evaluate the current criteria for a valid Ames test and to provide recommendations for interpretation of test results. Currently, determination of a positive vs. a negative result is made by applying various data evaluation procedures for comparing dosed plates with the concurrent solvent control plates. These evaluation procedures include a requirement for a specific fold increase (2- or 3-fold, specific to the bacterial strain), formal statistical procedures, or subjective (expert judgment) evaluation. After extensive discussion, the workgroup was not able to reach consensus recommendations in favor of any of these procedures. There was a consensus that combining additional evaluation criteria to the comparison between dosed plates and the concurrent solvent control plates improves test interpretation. The workgroup recommended using these additional criteria because the induction of mutations is a continuum of responses and there is no biological relevance to a strict dividing line between a positive (mutagenic) and not-positive (nonmutagenic) response. The most useful additional criteria identified were a concentration-response relationship and consideration of a possible increase above the concurrent control in the context of the laboratory’s historical solvent control values for the particular tester strain. The workgroup also emphasized the need for additional testing to resolve weak or inconclusive responses, usually with altered experimental conditions chosen based on the initial results. Use of these multiple criteria allowed the workgroup to reach consensus on definitions of “clear positive” and “clear negative” responses which would not require a repeat test for clarification. The workgroup also reached consensus on recommendations to compare the responses of concurrent positive and negative controls to historical control distributions for assay acceptability, and the use of control charts to determine the validity of the individual test.
Summary
To identify forces shaping the Escherichia coli intraspecies ecological structure, we have characterized in terms of phylogenetic group (A, B1, D and B2) belonging, presence/absence of ...extraintestinal virulence genes (pap, sfa, hly and aer) and intra‐host phylotype diversity a collection of 1898 commensal isolates originating from 387 animals (birds and mammals) sampled in the 1980s and the 2000s. These data have been compared with 760 human commensal isolates, sampled from 152 healthy subjects in the 2000s, and analysed with the same approach. The prevalence of the E. coli phylogenetic groups in birds, non‐human mammals and humans is clearly different with a predominance of D/B1, A/B1 and A/B2 strains respectively. A major force shaping the ecological structure is the environment with a strong effect of domestication and the year of sampling followed by the climate. Host characteristics, as the diet and body mass, also influence the ecological structure. Human microbiota are characterized by a higher prevalence of virulence genes and a lower intra‐host diversity than the non‐human mammal ones. This work identifies for the first time a group of strains specific to the animals, the B1 phylogenetic group strains exhibiting the hly gene. In conclusion, a complex network of factors seems to shape the ecological structure of commensal E. coli, with anthropogenic factors playing a major role and perturbing natural niche equilibrium.
The leitmotifs of magnetic resonance imaging (MRI) contrast agent-induced complications range from acute kidney injury, symptoms associated with gadolinium exposure (SAGE)/gadolinium deposition ...disease, potentially fatal gadolinium encephalopathy, and irreversible systemic fibrosis. Gadolinium is the active ingredient of these contrast agents, a non-physiologic lanthanide metal. The mechanisms of MRI contrast agent-induced diseases are unknown. Mice were treated with a MRI contrast agent. Human kidney tissues from contrast-naïve and MRI contrast agent-treated patients were obtained and analyzed. Kidneys (human and mouse) were assessed with transmission electron microscopy and scanning transmission electron microscopy with X-ray energy-dispersive spectroscopy. MRI contrast agent treatment resulted in unilamellar vesicles and mitochondriopathy in renal epithelium. Electron-dense intracellular precipitates and the outer rim of lipid droplets were rich in gadolinium and phosphorus. We conclude that MRI contrast agents are not physiologically inert. The long-term safety of these synthetic metal-ligand complexes, especially with repeated use, should be studied further.
Under ICH M7, impurities are assessed using the bacterial reverse mutation assay (i.e., Ames test) when predicted positive using in silico methodologies followed by expert review. N-Nitrosamines ...(NAs) have been of recent concern as impurities in pharmaceuticals, mainly because of their potential to be highly potent mutagenic carcinogens in rodent bioassays. The purpose of this analysis was to determine the sensitivity of the Ames assay to predict the carcinogenic outcome with curated proprietary Vitic (n = 131) and Leadscope (n = 70) databases. NAs were selected if they had corresponding rodent carcinogenicity assays. Overall, the sensitivity/specificity of the Ames assay was 93–97% and 55–86%, respectively. The sensitivity of the Ames assay was not significantly impacted by plate incorporation (84–89%) versus preincubation (82–89%). Sensitivity was not significantly different between use of rat and hamster liver induced S9 (80–93% versus 77–96%). The sensitivity of the Ames is high when using DMSO as a solvent (87–88%). Based on the analysis of these databases, the Ames assay conducted under OECD 471 guidelines is highly sensitive for detecting the carcinogenic hazards of NAs.
•Sensitivity analysis of the Ames assay to predict carcinogenicity of N-nitrosamines was performed on proprietary databases.•Sensitivity of the Ames assay conducted under OECD 471 guidelines was found to be high.•Plate incorporation vs preincubation, DMSO as solvent, and rat vs hamster liver induced S9 did not impact sensitivity.
The role of trabeculae carneae in modulating left ventricular (LV) diastolic compliance remains unclear. The objective of this study was to determine the contribution of trabeculae carneae to the LV ...diastolic compliance. LV pressure-volume compliance curves were measured in six human heart explants from patients with LV hypertrophy at baseline and following trabecular cutting. The effect of trabecular cutting was also analyzed with finite-element model (FEM) simulations. Our results demonstrated that LV compliance improved after trabecular cutting (p < 0.001). Finite-element simulations further demonstrated that stiffer trabeculae reduce LV compliance further, and that the presence of trabeculae reduced the wall stress in the apex. In conclusion, we demonstrate that integrity of the LV and trabeculae is important to maintain LV stiffness and loss in trabeculae leads to more LV compliance.
PDF
