The use of cytoenzymological changes in some parasitic protozoa for screening the carcinogenicity of chemicals

Changes in the Golgi bodies and in hydrolytic enzymes were observed in parasitic ciliates (Nyctotheroides puytoraci) and flagellates (Opalina sudafricana and Protoopalina sp.) after the administration of a single dose of 0.5 mg beta-naphthylamine (BNA) to their host, Bufo regularis. The experiment was carried out during the host's pre-breeding season, from November to February (when only trophozoites are available); the trophozoites were examined 21 days after the injection of BNA. Use of the silver impregnation technique showed an increase in the size of the granular argentophilic Golgi bodies in all three trophozoites after administering BNA to their host. In addition, a larger number of acid phosphatase and nonspecific esterase granules was found in the endoplasm of the three parasites after the injection. The localization of acid phosphatase and nonspecific esterase was found to be similar to the distribution of the Golgi bodies in both the control and the treated preparations. The results could be useful, in that some protozoans could be employed for the quick detection of chemical carcinogenicity if changes in their hydrolytic enzyme content are used as a diagnostic feature.     

Cluster analysis in predicting the carcinogenicity of chemicals using short-term assays

Cluster analysis can be a useful tool for exploratory data analysis to uncover natural groupings in data, and initiate new ideas and hypotheses about such groupings. When applied to short-term assay results, it provides and improves estimates for the sensitivity and specificity of assays, provides indications of association between assays and, in turn, which assays can be substituted for one another in a battery, and allows a data base containing test results on chemicals of unknown carcinogenicity to be linked to a data base for which animal carcinogenicity data are available. Cluster analysis was applied to the Gene-Tox data base (which contains short-term test results on chemicals of both known and unknown carcinogenicity). The results on chemicals of known carcinogenicity were different from those obtained when the entire data base was analyzed. This suggests that the associations (and possibly the sensitivities and specificities) which are based on chemicals of known carcinogenicity may not be representative of the true measures. Cluster analysis applied to the total data base should be useful in improving these estimates. Many of the associations between the assays which were found through the use of cluster analysis could be 'validated' based on previous knowledge of the mechanistic basis of the various tests, but some of the associations were unsuspected. These associations may be a reflection of a non-ideal data base. As additional data becomes available and new clustering techniques for handling non-ideal data bases are developed, results from such analyses could play an increasing role in strengthening prediction schemes which utilize short-term tests results to screen chemicals for carcinogenicity, such as the carcinogenicity and battery selection (CPBS) method (Chankong et al., 1985).     

The use of Caenorhabditis elegans in parasitic nematode research

There is increasing interest in the use of the free-living nematode Caenorhabditis elegans as a tool for parasitic nematode research and there are now a number of compelling examples of its successful application. C. elegans has the potential to become a standard tool for molecular helminthology researchers, just as yeast is routinely used by molecular biologists to study vertebrate biology. However, in order to exploit C. elegans in a meaningful manner, we need a detailed understanding of the extent to which different aspects of C. elegans biology have been conserved with particular groups of parasitic nematodes. This review first considers the current state of knowledge regarding the conservation of genome organisation across the nematode phylum and then discusses some recent evolutionary development studies in free-living nematodes. The aim is to provide some important concepts that are relevant to the extrapolation of information from C. elegans to parasitic nematodes and also to the interpretation of experiments that use C. elegans as a surrogate expression system. In general, examples have been specifically chosen because they highlight the importance of careful experimentation and interpretation of data. Consequently, the focus is on the differences that have been found between nematode species rather than the similarities. Finally, there is a detailed discussion of the current status of C. elegans as a heterologous expression system to study parasite gene function and regulation using successful examples from the literature.     

On the use of historical control data for trend test in carcinogenicity studies

Historical control data are often available in carcinogenicity studies and are included for testing dose effects in current studies. A new method is developed for incorporating the historical control information into a dose effect test. The method generalizes the test procedures proposed by Tarone (1982, Biometrics 38, 215-220) and Ibrahim and Ryan (1996, Biometrics 52, 1478-1485) by taking into account the variation resulting from parameter estimation based on historical data. Two examples are discussed for illustrating the proposed method.     

The carcinoGENOMICS project: critical selection of model compounds for the development of omics-based in vitro carcinogenicity screening assays

Recent changes in the European legislation of chemical-related substances have forced the scientific community to speed up the search for alternative methods that could partly or fully replace animal experimentation. The Sixth Framework Program project carcinoGENOMICS was specifically raised to develop omics-based in vitro screens for testing the carcinogenic potential of chemical compounds in a pan-European context. This paper provides an in-depth analysis of the complexity of choosing suitable reference compounds used for creating and fine-tuning the in vitro carcinogenicity assays. First, a number of solid criteria for the selection of the model compounds are defined. Secondly, the strategy followed, including resources consulted, is described and the selected compounds are briefly illustrated. Finally, limitations and problems encountered during the selection procedure are discussed. Since selecting an appropriate set of chemicals is a frequent impediment in the early stages of similar research projects, the information provided in this paper might be extremely valuable.     

A fluorescent screening platform for the rapid evaluation of chemicals in cellular reprogramming

Current strategies to monitor reprogramming into induced pluripotent stem cells (iPSCs) are limited in that they rely on the recognition of advanced stage biomarkers or they involve the transduction of genetically-modified cells. These limitations are particularly problematic in high-throughput screenings where cell availability, low cost and a rapid experimental protocol are critical issues. Herein we report the application of a pluripotent stem cell fluorescent probe (i.e. CDy1) as a reporter for the rapid screening of chemicals in reprogramming iPSCs. CDy1 stains early-stage iPSCs at 7dpi as well as matured iPSCs; hence it can partially overcome the slow kinetics of the reprogramming process. As a proof of concept, we employed a CDy1-based screening in 384 well-plates to examine the effect of newly synthesized hydroxamic acid derivatives in reprogramming mouse fibroblasts transduced with Oct4, Sox2 and Klf-4 without c-Myc. One compound (1-26) was identified as a reprogramming enhancer by 2.5-fold and we confirmed that 1-26 behaves as a histone deacetylase (HDAC) inhibitor. The successful identification of novel small molecules enhancing the generation of iPSCs by means of a rapid and simple protocol demonstrates the suitability of this CDy1-based screening platform for the large scale and high-throughput evaluation of iPSC modulators.     

The use of tritiated cellulose in screening for cellulolytic microorganisms

Summary Phosphoric acid swollen cellulose has been reduced with³H-KBH₄ and the resulting radioactive amorphous cellulose is broken down by a number of cellulolytic bacteria and fungi with accumulation of radioactive label in the culture filtrate. This is detected by scintillation counting. Non-cellulolytic microorganisms do not behave in a similar manner.     

凹唇壁蜂寄生螨安全防治药剂的筛选

本研究在实验室条件下对凹唇壁蜂Osmia excavata Alfken寄生螨的安全防治药剂进行筛选。通过玻片浸渍法和浸虫法分别室内测定了12种常用杀螨剂和4种常用试剂对凹唇壁蜂蜂茧、成蜂及其寄生螨Tortonia sp.的急性毒力。结果显示,常用药剂中的双甲脒、乳酸、次氯酸钠、冰乙酸杀螨效果较好而对壁蜂和蜂茧的杀伤力低,其对蜂螨的LC50分别为81.81 mg/L,0.06 mg/L,0.14 mg/L,0.34 mg/L;对壁蜂成蜂的LC50分别为170.05 mg/L,0.64 mg/L,0.31 mg/L,0.47 mg/L;对蜂茧的LC50分别为5653.30 mg/L,0.47 mg/L,1.2 mg/L,0.59 mg/L。常用药剂哒螨灵杀螨效果较好,对蜂茧安全性高,对蜂茧的LC50为7441.91 mg/L,但对壁蜂成蜂不安全(LC50=648.58 mg/L)。阿维菌素对壁蜂成蜂、蜂茧和蜂螨毒力均较高,LC50分别为0.77 mg/L,122.66 mg/L,126.54 mg/L。因此,推荐使用对蜂螨药效好、对壁蜂和蜂茧安全的药剂双甲脒、乳酸、次氯酸钠和冰乙酸。建议哒螨灵、三氯杀螨醇在出蜂期间禁止使用,可以在茧期使用。常用药剂中唑螨酯、甲维盐及常用试剂中的甲酸等对蜂螨的效果相对较差而对蜂茧的影响较高,因而不建议使用。阿维菌素可用于预先处理蜂巢和蜂管。     

Industrial microbial enzymes: their discovery by screening and use in large-scale production of useful chemicals in Japan

The application of microbial enzymes to large-scale organic synthesis is currently attracting much attention, and has been uniquely developed especially in Japan. The discovery of new microbial enzymes through extensive and persistent screening has brought about many new and simple routes for synthetic processes. The application of these enzymes in so-called 'hybrid processes' of enzymatic and chemical reactions, provide one possible way to solve environmental problems.     

The use of cortisone-treated mice in the screening of soil for pathogenic fungi

Summary Fifty-seven samples of desert soils were screened for pathogenic fungi by injection into cortisone-treated and non-treated mice. Four samples yielded pathogenic fungi in the cortisone-treated mice only.Nocardia asteroides was isolated from the cortisone-treated mice and from the controls. All of the cortisone-treated and the control mice injected with soil from the root zone of a dead century plant became critically ill very shortly after injection and cultures from all of the animals showed a variety of fungi. Seven species were isolated from the cortisone-treated animals and 5 species from the controls.The yeast,Torulopsis glabrata, was found in 69 of the 225 control mice and in 115 of the 213 cortisone-treated animals that came to autopsy. This organism was not considered to have been derived from the soil.The results appear to justify the conclusion that this method of soil screening deserves further consideration and study.     

The challenge of testing chemicals for potential carcinogenicity using multiple short-term assays: an analysis of a proposed test battery for hair dyes

Recent reports of the association of hair dyes usage with increased bladder cancer risk in women with the slow NAT-2 acetylator phenotype have resulted both in attempts to identify the putative carcinogen as well as in devising batteries of tests that could be used to screen for such putative carcinogens in hair dye formulations, their intermediates and final products. Analytical studies have reported the presence of traces ( approximately 0.5 ppm) of the carcinogen 4-aminobiphenyl in some hair dye preparations. In parallel, SCCNFP (Scientific Committee on Cosmetic and Non-Food Products Intended for Consumers) has suggested the deployment of a battery of six in vitro assays followed by an in vivo assay. The practicality of deploying and interpreting such a battery is analyzed herein as it is expected to result in 64 and 128 possible test results and SCCNFP does not provide detailed guidance of how the test results are to be interpreted. In this study we have applied a previously described Bayesian approach which takes advantage of the known predictive performances of individual assays, to analyze the possible outcomes of the 6-7 test batteries. While the SCCNFP battery is clearly risk-averse, it is shown that performing all of the assays is not always necessary and moreover it does not necessarily improve predictive performance. Finally, based upon the reported mutagenicity of 4-aminobiphenyl, it is doubtful that this "impurity" would be detected by the test battery.