The test material (solid or liquid) is applied uniformly and topically to a three-dimensional human skin model, comprising at least a reconstructed epidermis with a functional stratum corneum. Two tissue replicates are used for each treatment (exposure time), and for controls. Corrosive materials are identified by their ability to produce a decrease in cell viability below defined threshold levels at specified exposure periods. The principle of the human skin model assay is based on the hypothesis that corrosive chemicals are able to penetrate the stratum corneum by diffusion or erosion, and are cytotoxic to the underlying cell layers.
The test method utilizes an artificial membrane designed to respond to corrosive substances in a manner similar to animal skin in situ. The in vitro membrane barrier test method may be used to test solids, liquids (aqueous substances with a pH in the range of 4.5 to 8.5 often do not qualify for testing) and emulsions. The test described in this Test Guideline allows the identification of corrosive chemical substances and mixtures and allows the subcategorisation of corrosive substances as permitted in the GHS. This classification is based on the substance penetration time through the membrane barrier. The test system is composed of two components, a synthetic macromolecular bio-barrier and a Chemical Detection System (which one detect the test substance). An appropriate number of replicates is prepared for each test substance and its corresponding controls. The times of applying the test substance to the membrane barrier are recorded and staggered. The time (in minutes) elapsed between application of the test substance to the membrane barrier and barrier penetration is used to predict the corrosivity of the test substance.
The test material (150 μL for liquids or solid with 150 μL of deionised water added on the top) is applied for up to 24 hours to the epidermal surfaces of skin discs (three skin discs are used for each test and control substance) in a two-compartment test system in which the skin discs function as the separation between the compartments. The skin discs are taken from humanely killed rats aged 28-30 days. Corrosive materials are identified by their ability to produce a loss of normal stratum corneum integrity and barrier function, which is measured as a reduction in the TER below a threshold level (5kΩ for rat). A dye-binding step incorporated into the test procedure permits to determine if the increase in ionic permeability is due to physical destruction of the stratum corneum.
The test material (solid or liquid) is applied uniformly and topically to a three-dimensional human skin model, comprising at least a reconstructed epidermis with a functional stratum corneum. Two tissue replicates are used for each treatment (exposure time), and for controls. Corrosive materials are identified by their ability to produce a decrease in cell viability below defined threshold levels at specified exposure periods. Coloured chemicals can also be tested by used of an HPLC procedure. The principle of the human skin model assay is based on the hypothesis that corrosive chemicals are able to penetrate the stratum corneum by diffusion or erosion, and are cytotoxic to the underlying cell layers.
This Test Guideline is intended primarily for use with rats and mice, and for oral administration. Both sexes should be used. Each dose group and concurrent control group should contain at least 50 animals of each sex. At least three dose levels and a concurrent control should be used. Animals are dosed with the test substance daily (oral, dermal or inhalation administration) and the mode of exposure should be adjusted according to the toxicokinetic profile of the test substance. The duration of the study will normally be 24 months for rodents. For specific strains of mice, duration of 18 months may be more appropriate. Termination of the study should be considered when the number of survivors in the lower dose groups or the control group falls below 25 per cent. The results of these studies include: measurements (weighing, food consumption), and, at least, daily and detailed observations, as well as gross necropsy and histopathology.
This Test Guideline is designed for use with the rat. It specifically addresses the daily oral administration, by gavage, (in the diet, in drinking water or by capsules) of the test substance. When the study is conducted as a separate study, at least 20 animals (10 females and 10 males) should be used in each dose. At least three dose groups and a control group should generally be used. Dose levels should be selected by taking into account any previously observed toxicity and kinetic data available for the test compound or related materials. The dosing regimen may be 28 days, subchronic (90 days) or chronic (1 year or longer). The procedures set out in this Test Guideline may also be used for an acute neurotoxicity study. The limit test corresponds to one dose level of at least 1000 mg/kg body weight. The results of this study include measurements (weighing, food /water consumption), functional tests, and, at least, daily detailed observations (Ophthalmology, haematology, clinical biochemistry and histopathology). At least five males and five females, selected from test group, should be perfused in situ and used for detailed neurohistopathology at the end of the study. The findings of the study should be evaluated in terms of the incidence, severity and correlation of neurobehavioural and neuropathological effects (neurochemical or electrophysiological effects as well if supplementary examinations are included) and any other adverse effects observed.
The in vitro chromosome aberration test may employ cultures of established cell lines, cell strains or primary cell cultures. Cell cultures are exposed to the test substance (liquid or solid) both with and without metabolic activation during about 1.5 normal cell cycle lengths. At least three analysable concentrations of the test substance should be used. At each concentration duplicate cultures should normally be used. At predetermined intervals after exposure of cell cultures to the test substance, the cells are treated with a metaphase-arresting substance, harvested, stained. Metaphase cells are analysed microscopically for the presence of chromosome aberrations.
Emerging Field of Synthetic Biology” was held in July 2009 in Washington, DC
under the auspices of the United States National Academies, the Organisation
for Economic Co-operation and Development and the Royal Society.
The document looks at the state of science and technology in the OECD across four broad dimensions:
• Section A: Innovation and R&D.
• Section B: Human Resources in Science and Technology (HRST).
• Section C: Patents.
• Section D: Other areas (ICT, globalisation, industrial structure).
This new publication is a product of the OECD-Eurostat Entrepreneurship Indicators Programme, which is a long-term programme of internationally-comparable policy-relevant entrepreneurship statistics. The work involves developing standard definitions and concepts and engaging countries and international Agencies in the collection of data. An international group of statisticians and analysts provides guidance to the Programme that benefits from sponsorship by the Ewing Marion Kauffman Foundation in the United States.
This report offers policy insights and stimulates new research to complement and further develop the recent OECD Teaching and Learning International Survey (TALIS) and the upcoming PISA 2012 assessment, which will again focus on mathematics. In addition, this report may be of interest to teachers, educators and officials within national and local educational authorities responsible for the professional development of teachers or for programme development, as well as members of school boards and parent advisory bodies.
The OECD’s 2nd World Forum on Statistics, Knowledge and Policy 'Measuring and Fostering the Progress of Societies' held in Istanbul in June 2007 brought together a diverse group of leaders from more than 130 countries to debate these issues. These proceedings contain 40 papers presented at the Forum.