The Development of New Concepts for Assessing Reproductive Toxicity Applicable to Large Scale Toxicological Programmes

Large scale toxicological testing programmes which are currently ongoing such as the new European chemical legislation REACH require the development of new integrated testing strategies rather than applying traditional testing schemes to thousands of chemicals. The current practice of requiring in vivo testing for every possible adverse effect endanger the success of these programmes due (i) to limited testing facilities and sufficient capacity of scientific/technical knowledge for reproductive toxicity; (ii) an unacceptable number of laboratory animals involved (iii) an intolerable number of chemicals classified as false positive. A key aspect of the implementation of new testing strategies is the determination of prevalence of reproductive toxicity in the universe of industrial chemicals. Prevalences are relevant in order to be aware on the expected rate of false classification during the toxicological testing and to implement appropriate measures for their avoidance. Furthermore, a detailed understanding on the subendpoints affected by reproductive toxicants and the underlying mechanisms will lead to more science based testing strategies integrating alternative methods without compromising the protection of consumers

Bulk Damage Effects in Irradiated Silicon Detectors due to Clustered Divacancies

High resistivity silicon particle detectors will be used extensively in experiments at the future CERN Large Hadron Collider where the enormous particle fluences give rise to significant atomic displacement damage. A model has been developed to estimate the evolution of defect concentrations during irradiation and their electrical behaviour according to Shockley-Read-Hall (SRH) semiconductor statistics. The observed increases in leakage current and doping concentration changes can be described well after gamma irradiation but less well after fast neutron irradiation. A possible non-SRH mechanism is considered, based on the hypothesis of charge transfer between clustered divacancy defects in neutron damaged silicon detectors. This leads to a large enhancement over the SRH prediction for V2 acceptor state occupancy and carrier generation rate which may resolve the discrepancy

The Development of New Concepts for Assessing Reproductive Toxicity Applicable to Large Scale Toxicological Programmes

Large scale toxicological testing programmes which are currently ongoing such as the new European chemical legislation REACH require the development of new integrated testing strategies rather than applying traditional testing schemes to thousands of chemicals. The current practice of requiring in vivo testing for every possible adverse effect endanger the success of these programmes due (i) to limited testing facilities and sufficient capacity of scientific/technical knowledge for reproductive toxicity; (ii) an unacceptable number of laboratory animals involved (iii) an intolerable number of chemicals classified as false positive. A key aspect of the implementation of new testing strategies is the determination of prevalence of reproductive toxicity in the universe of industrial chemicals. Prevalences are relevant in order to be aware on the expected rate of false classification during the toxicological testing and to implement appropriate measures for their avoidance. Furthermore, a detailed understanding on the subendpoints affected by reproductive toxicants and the underlying mechanisms will lead to more science based testing strategies integrating alternative methods without compromising the protection of consumers

Characterization of CmaA, an Adenylation-Thiolation Didomain Enzyme Involved in the Biosynthesis of Coronatine

Several pathovars of Pseudomonas syringae produce the phytotoxin coronatine (COR), which contains an unusual amino acid, the 1-amino-2-ethylcyclopropane carboxylic acid called coronamic acid (CMA), which is covalently linked to a polyketide-derived carboxylic acid, coronafacic acid, by an amide bond. The region of the COR biosynthetic gene cluster proposed to be responsible for CMA biosynthesis was resequenced, and errors in previously deposited cmaA sequences were corrected. These efforts allowed overproduction of P. syringae pv. glycinea PG4180 CmaA in P. syringae pv. syringae FF5 as a FLAG-tagged protein and overproduction of P. syringae pv. tomato CmaA in Escherichia coli as a His-tagged protein; both proteins were in an enzymatically active form. Sequence analysis of CmaA indicated that there were two domains, an adenylation domain (A domain) and a thiolation domain (T domain). ATP-(32)PP(i) exchange assays showed that the A domain of CmaA catalyzes the conversion of branched-chain l-amino acids and ATP into the corresponding aminoacyl-AMP derivatives, with a kinetic preference for l-allo-isoleucine. Additional experiments demonstrated that the T domain of CmaA, which is posttranslationally modified with a 4′-phosphopantetheinyl group, reacts with the AMP derivative of l-allo-isoleucine to produce an aminoacyl thiolester intermediate. This covalent species was detected by incubating CmaA with ATP and l-[G-(3)H]allo-isoleucine, followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. It is postulated that the l-allo-isoleucine covalently tethered to CmaA serves as the substrate for additional enzymes in the CMA biosynthetic pathway that catalyze cyclopropane ring formation, which is followed by thiolester hydrolysis, yielding free CMA. The availability of catalytically active CmaA should facilitate elucidation of the details of the subsequent steps in the formation of this novel cyclopropyl amino acid

Workshop on the validation and regulatory acceptance of innovative 3R approaches in regulatory toxicology - Evolution versus revolution.

At a joint workshop organized by RIVM and BfR, international experts from governmental institutes, regulatory agencies, industry, academia and animal welfare organizations discussed and provided recommendations for the development, validation and implementation of innovative 3R approaches in regulatory toxicology. In particular, an evolutionary improvement of our current approach of test method validation in the context of defined approaches or integrated testing strategies was discussed together with a revolutionary approach based on a comprehensive description of the physiological responses of the human body to chemical exposure and the subsequent definition of relevant and predictive in vitro, in chemico or in silico methods. A more comprehensive evaluation of biological relevance, scientific validity and regulatory purpose of new test methods and assessment strategies together with case studies that provide practical experience with new approaches were discussed as essential steps to build up the necessary confidence to facilitate regulatory acceptance

Desorption-diffusion model and lost gas quantity estimation of coalbed methane from coal core under drilling fluid medium

The differences of coalbed methane (CBM) desorption-diffusion from coal drilling-core under various drilling fluid medium are not considered in the present calculating methods of lost CBM quantity, which leads possibly to the inaccuracy of CBM quantity in coal seam. Here we took the desorption of CBM from coal core under drilling fluid medium as a pressure-swing process, and based on the Langmuir equation and Fick-first law, established the desorption-diffusion model and numerical modeling method of lost gas (including free CBM) calculation in coal core under various drilling fluid mediums through physical simulation test and by considering comprehensively primary factors. The results showed that the physical simulated t-Qt curves can be rightly fitted by the numerical modeling data, which indicated the ultimate desorption quantity from the numerical modeling was adjacent to that from the physical simulation as a whole. It was found that the lost CBM quantity from the modeling method was generally higher than that from the direct method when lost time was relatively long. Thus, we suggest that it is necessary to emend the active China national standard through further investigation, since the lost CBM quantity from coal drilling-core was generally underestimated using the method in the current standard. © 2010 Science China Press and Springer-Verlag Berlin Heidelberg