Reports

This Adverse Outcome Pathway (AOP) describes the linkage between Deiodinase 1 inhibition and increased mortality via reduced anterior swim bladder inflation. The swim bladder is a gas-filled organ found in many bony fish species and typically consists of two gas-filled chambers. The posterior chamber inflates during early development (embryo), while the anterior chamber inflates during late development (larva). Both chambers are important for fish to control buoyancy and the anterior chamber has an additional role in hearing. This AOP is part of a network of 5 AOPs describing how disruption of the thyroid hormone system can affect developmental processes involved in swim bladder inflation. The network includes three molecular initiating events representing the inhibition of enzymes that are important for thyroid hormone synthesis and activation. It describes how inhibition of thyroperoxidase and/or deiodinase, leads to reduced swim bladder inflation, resulting in reduced swimming performance, increased mortality and ultimately, decreased population trajectory in fish. This AOP network is currently mainly based on experimental evidence from studies on fish species with a two-chambered swim bladder. This AOP is referred to as AOP 158 in the Collaborative Adverse Outcome Pathway Wiki (AOP-Wiki).

This Adverse Outcome Pathway (AOP) describes the linkage between binding to proteins involved in protection against oxidative stress and impairment in learning and memory. Production, binding and degradation of Reactive Oxygen Radicals are tightly regulated in the body, and an imbalance between production and protection may cause oxidative stress, which is common to many toxicity pathways. Oxidative stress may lead to an imbalance in glutamate neurotransmission, which is involved in learning and memory. Oxidative stress may also cause cellular injury and death. During brain development and in particular during the establishment of neuronal connections and networks, such perturbations may lead to functional impairment in learning and memory. The weight-of-evidence supporting the relationship between the key events described in this AOP is based mainly on developmental effects observed after an exposure to mercury, a heavy metal known for its strong affinity to many proteins having anti-oxidant properties. This AOP is referred to as AOP 17 in the Collaborative Adverse Outcome Pathway Wiki (AOP-Wiki).

This Adverse Outcome Pathway (AOP) describes the linkage between Thyroperoxidase inhibition and increased mortality via reduced anterior swim bladder inflation. The swim bladder is a gas-filled organ found in many bony fish species and typically consists of two gas-filled chambers. The posterior chamber inflates during early development (embryo), while the anterior chamber inflates during late development (larva). Both chambers are important for fish to control buoyancy and the anterior chamber has an additional role in hearing. This AOP is part of a network of 5 AOPs describing how disruption of the thyroid hormone system can affect developmental processes involved in swim bladder inflation. The network includes three molecular initiating events representing the inhibition of enzymes that are important for thyroid hormone synthesis and activation. It describes how inhibition of thyroperoxidase and/or deiodinase, leads to reduced swim bladder inflation, resulting in reduced swimming performance, increased mortality and ultimately, decreased population trajectory in fish. This AOP network is currently mainly based on experimental evidence from studies on fish species with a two-chambered swim bladder. This AOP is referred to as AOP 159 in the Collaborative Adverse Outcome Pathway Wiki (AOP-Wiki).

This Adverse Outcome Pathway (AOP) describes the linkage between Chitin synthase 1 inhibition and mortality in arthropods. In order to grow and develop, arthropods need to shed their exoskeleton (or cuticle) periodically and replace it with a new one in a process called molting. Successful molting, and therefore a successful development necessitates stability and integrity of the cuticle to support muscular contractions involved in the shedding of the old cuticle. Arthropods heavily rely on chitin synthesis as chitin is one of the main constituents of the cuticle. The cuticular chitin synthase (CHS-1) is the key enzyme in the biosynthetic pathway and arthropods are therefore especially dependent on its proper function. The present AOP describes the effects of CHS-1 chemical inhibition on the molting process leading to increased mortality in arthropods. Knowledge gaps still exist in the process and this AOP may help guiding assay development for further experimental studies, addressing these gaps. This AOP is referred to as AOP 360 in the Collaborative Adverse Outcome Pathway Wiki (AOP-Wiki).

This Test Guideline, covering nanomaterials spanning from 1 nm to 1000 nm, is intended for particle size and particle size distribution measurements of nanomaterials. The TG includes the following methods: Atomic Force Microscopy (AFM), Centrifugal Liquid Sedimentation (CLS)/Analytical Ultracentrifugation (AUC), Dynamic Light Scattering (DLS), Differential Mobility Analysis System (DMAS), (Nano)Particle Tracking Analysis (PTA/NTA), Small Angle X-Ray Scattering (SAXS), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM). For measuring the diameter and length of fibres, analysing images captured with electron microscopy is currently the only method available.

This Test Guideline describes an in vivo erythrocyte Pig-a gene mutation assay (hereafter called the Pig-a assay) which uses an endogenous mammalian gene, the phosphatidylinositol glycan class A gene (Pig-a), as a reporter of somatic-cell gene mutation. In vivo gene mutation tests, such as the Pig-a assay, are especially relevant for assessing mutagenicity because physiological factors, such as absorption of the test chemical from the site of exposure, distribution of the test chemical throughout the test system via systemic circulation, and in vivo metabolism and DNA repair processes, all contribute to the mutagenic responses. The Pig-a assay can be performed with commonly used strains of rats or mice and the test can be conducted without euthanizing the animals. These properties facilitate integration of the Pig-a assay into many in vivo rodent testing protocols.

This Test Guideline (TG) describes a harmonised procedure to determine the Volume Specific Surface Area (VSSA) of powdered solid manufactured nanomaterials (MNs). The VSSA (in m2/cm3) of a material is calculated by multiplying its mass specific surface area (in m2/g) with its skeletal density (in g/cm3). The determination of the external and internal (mass) specific surface area (SSA) of powdered solid MNs is done by the Brunauer, Emmett and Teller (BET) method. This TG also provides instructions on how to determine the skeletal density (ρ) of the MN by gas pycnometry.

This Test Guideline describes a standardised method to examine the transformation of chemicals in pig and cattle liquid manure under anaerobic conditions. The experiments are performed to determine the rate of transformation of the test chemical, the identity and rates of formation and decline of transformation products and residues). Such studies are relevant for chemicals that are administered to housed animals and are subsequently excreted (e.g. veterinary medicinal products or feed additives) or for chemicals that are applied in buildings for livestock and may also enter the manure collected from these animal housings (e.g. biocides). Pesticides may also be introduced into manure via contaminated animal feed.

This Test Guideline proposes defined approaches (DA) combining data generated in vitro methods, with information sources such as physicochemical properties. The prediction from a DA may be used alone to determine eye hazard potential according to the hazard classes of the UN GHS (Categories 1, 2, or not classified). A DA consists of a fixed data interpretation procedure (DIP) (i.e. a mathematical model, a rule-based approach) applied to data (e.g in silico predictions, in chemico, in vitro data) generated with a defined set of information sources to derive a prediction without the need for expert judgment. The DAs use method combinations intended to overcome some of the limitations of the individual, stand-alone methods in order to provide increased confidence in the overall obtained result.

This Test Guideline describes an in vitro procedure the identification on its own of chemicals (substances and mixtures) not requiring classification (No Cat), requiring classification for eye irritation (Cat 2) and requiring classification for serious eye damage (Cat 1) according to the UN GHS ocular hazard categories. It makes use of reconstructed human cornea-like epithelium (RhCE) which closely mimics the histological, morphological, biochemical and physiological properties of the human corneal epithelium. The test evaluates the ability of a test chemical to induce cytotoxicity in a RhCE tissue construct, as measured by the MTT assay. RhCE tissue viability following exposure to a test chemical is measured by enzymatic conversion of the vital dye MTT by the viable cells of the tissue into a blue MTT formazan salt that is quantitatively measured after extraction from tissues. Cytotoxicity is measured at different time points of exposure; this is one of the methodological differences with the original TG 492.