Fifty years after the publication of The Principles of Humane Experimental Technique by W.M.S. Russell and R.L. Burch there is a heightened interest in the development and application of in vitro methods. The reasons behind this interest in new toxicological methods are numerous. Some are grounded in legislative bans on animal testing, such as the European Union's 7th Amendment to the Cosmetics Directive which prohibits the use of animals to assess the safety of cosmetics and their ingredients. Others are due to the need for a pragmatic approach to large legislated testing programs such as the EU's Registration, Evaluation, Authorization and Restriction of Chemicals (REACH) program. Without the use of in vitro methods it is unlikely that all the proposed toxicity testing could be completed. Other reasons behind the new interest are due to ethical concerns - either by consumers who wish to purchase products they feel support their moral views about the use of animals, or by toxicologists themselves who feel strongly that non-animal methods should be used whenever possible. One of the strongest drivers for the use of in vitro methods is science itself. The need to understand the detailed mechanisms of toxicity have caused many researchers to adopt in vitro methods. Advances in molecular and cellular biology in recent years have led to an unprecedented development of useful computational and cellular toxicology testing methods. These activities have recently been dramatically highlighted by a report from the US National Academy of Sciences' (NAS) report: Toxicity Testing in the 21st Century: A Vision and a Strategy. The report clearly calls for a new toxicity testing strategy - one that relies on cell based methods which model toxicological pathways. The publication of this report has stirred interest in new toxicological approaches not only in the United States but throughout the world. It has helped to energize numerous organizations and societies working in the area.…
In silico assessment of skin sensitization is increasingly needed owing to the problems concerning animal welfare, as well as excessive time consumed and cost involved in the development and testing of new chemicals. Skin sensitization positive/negative prediction models with discriminant function were generated and parameter analysis was discussed on the basis of QSAR technology. Samples used in this research were selected from the list of "Maximale Arbeitsplatz-Konzentration" (MAK) and "Biologischer Arbeitsstoff-Toleranz-Wert" (BAT) values 2008, Deutschen Forschungsgemeinschaft (DFG) for positive samples (skin sensitizers) and from the classification results of the Japanese Globally Harmonized System of Classification and Labeling of Chemicals (GHS) Inter-ministerial Committee of the National Institute for Technology and Evaluation for negative skin sensitizers (controls). A total of 291 compounds (122 positive sensitizers and 169 negative sensitizers) were used in this study. Parameters were generated from 2-D and 3-D structures of compounds. All of the approximately 800 parameters generated were reduced to 47 parameter sets and 32 parameter sets by feature selection. Various linear and non-linear discriminant analysis methods were applied using 2 parameter sets. All data analyses were performed using ADMEWORKS/ModelBuilder software. Perfect classification ratios (100%) were achieved using Support Vector Machine and AdaBoost for 32 parameters. The highest prediction ratio of 81.44% by Leave-Ten-Out Cross-Validation was achieved with Neutral Network for 47 parameter sets. Log P was not found to be important. This is the first QSAR model for skin sensitization from Japan. Future studies of this QSAR model are needed to improve its efficacy.
The embryonic stem cell test (EST) is a well-known in vitro embryotoxicty test protocol. We therefore investigated the embryotoxicity of four plasticizers by the EST protocol. Three parameters (ID50, IC50ES and IC503T3) obtained by the results were substituted for the prediction model for classification. Each embryotoxicity level of DBP, BBP and DEHA was classified into the category of "weak embryotoxicity". Only DEHP was classified as "no embryotoxicity". As we carried out these experiments, we were able to identify new weak points in the EST protocol; that is, using the high concentration solution of the four plasticizers, it is difficult to make an embryoid body (EB) from the hanging drop culture of the EST protocol. A surface-active agent should be considered when such a phenomenon occurs. When using special chemical substances, improvement of the EST method from the viewpoint of physical properties is also desired.
The cardiac toxicity of arsenic trioxide (ATO) was studied in chick embryos. Fertilized eggs of White Leghorns were incubated and investigated. The chick embryonic heart has been often used in pharmacologic and toxicologic experiments. After ATO at 0.25, 0.5 or 1.0 mg/egg was injected into fertilized eggs, heart rates (HRs) were measured by electrocardiogram. After low dosing of ATO, the heart rate was not different compared with control. However, HRs significantly decreased in a dose- and time-dependent manner (p<0.05). In addition, arrhythmia was produced by high dosing of ATO. These findings indicate that ATO has a marked influence on the heart rate dose- and time-dependently in chick embryos.