Zur Aktualität der Organisationstheorie von Luxemburg und Gramsci: zwischen emanzipatorischer Theoriebildung und ahistorischer Bezugnahme

Big parts of the left refer to Rosa Luxemburg and Antonio Gramsci as two main theorists of organization theory. In this article, we present their thinking towards problems of class consciousness, the activity of the masses, bureaucracy, political parties, parliament and hegemony. We argue that in main regards they complement each other. Finally we figure out how one can use this theoretical approach under today’s different conditions and which problems might appear if we don’t bear in mind such differences

Evaluation of new alternative strategies to predict neurotoxicity with human based test systems

Animal experiments are still the ‘gold standard’ in safety evaluation defined by the OECD (Organisation for Economic Co-operation and Development) or the US EPA (Environmental Protection Agency). Millions of animals are used each year to assess the risk of chemical toxicities for human health. But animal experiments are expensive, time-consuming and have a restricted prediction capacity regarding human toxicity. Hence the demand for validated alternative strategies is high. Validated differentiation protocols of embryonic stem cells or immortalized human organ specific cell lines provide the possibility to recapitulate human development and to study organ specific toxicity of different developmental stages (immature to mature) in vitro. In the framework of this doctoral thesis, we provide insights into the development and evaluation of test systems established specifically to assess neurodevelopmental toxicity as well as neurotoxicity in vitro.In a first step we evaluated an assay based on neurite outgrowth assessment to detect putative developmentally neurotoxic chemicals. This assay was based on a human mesencephalic neuronal precursor cell line, called LUHMES. In the study, the model has been challenged for its reliability and consistency using more than 50 compounds and combinations of them. We proved the applicability of the assay for screening, and suggest that the test has the potential to be used for identification and potency-ranking of putative developmental toxicants with regard to effects on neurite growth.In a second step we used different human stem cell-based test systems to mimic several stages of the early human neurodevelopment in vitro. We analysed the transcriptome changes of these test systems after exposure to two developmental toxicants, valproic acid and methylmercury. Both toxicants induced test system and compound specific transcriptome changes. A common toxicant specific signature of transcription factor binding sites was identified for the different test systems, which we suggest as classifier for compound grouping in future experiments.In a last step we used a well described model compound 1-methyl-4-phenylpyridinium (MPP+) to analyse the suitability of Omics combinations to monitor the MPP+ induced changes on LUHMES. We found early large adaptive metabolome and transcriptome changes which taken together lead to the identification of novel pathways involved in early MPP+ toxicity. The findings of this thesis contribute to alternative test-strategy development in neurotoxicity and disclose important considerations when developing in vitro test systems

Assessment of Chemical-Induced Impairment of Human Neurite Outgrowth by Multiparametric Live Cell Imaging in High-Density Cultures

Chemicals that specifically alter human neurite outgrowth pose a hazard for the development of the nervous system. The identification of such compounds remains a major challenge, especially in a human test system. To address this issue, we developed an imaging-based procedure in LUHMES human neuronal precursor cells to quantify neurite growth of unfixed cultures. Live imaging allowed the simultaneous evaluation of cell viability and neurite outgrowth within one culture dish. The procedure was used to test the hypothesis that inhibitors of specific pathways can impair neurite outgrowth without affecting cell viability. Although the cells were grown at high density to allow extensive networking, overall neurite growth in this complex culture was quantified with a signal-to-noise ratio of > 50. Compounds such as U0126 slowed the extension of neuronal processes at concentrations > 4 times lower than those causing cell death. High numbers of individual viable cells without neurites were identified under such conditions, and neurite outgrowth recovered after washout of the chemical. Also an extensionpromoting compound, Y-27632, was identified by this unique multiparametric imaging approach. Finally, the actions of unspecific cytotoxicants such as menadione, cadmium chloride, and sodium dodecyl sulfate were tested to evaluate the specificity of the new assay. We always found a ratio of EC50 (cell death)/EC50 (neurites) < 4 for such chemicals. The described novel test system may thus be useful both for high-throughput screens to identify neuritotoxic agents and for their closer characterization concerning mode of action, compound interactions, or the reversibility of their effects

Automated image processing to quantify neurite growth in Luhmes human neuronal precursor cells

Chemicals that specifically inhibit human neurite outgrowth pose a hazard to the developing nervous system. Identifying such chemicals remains a major challenge in biological research. In response to the need for more efficient methods to identify potential developmental neurotoxicants, an image processing framework is presented that allows to automatically quantify neurite growth in LUHMES human neuronal precursor cells. For this purpose, a H-33342 staining is used in order to identify the outline of the nucleus of each neuronal cell. Based on this outline, a region growing approach is performed that expands the soma until an intensity threshold is reached, which allows to quantify the number of cells with neurites. The results demonstrate that our image processing framework can rapidly quantify chemical effects on neurite outgrowth. Concentration-response data for neurite outgrowth allows for the determination of the specificity of chemical effects on developing neuronal cells. Further studies will examine the utility of the approach for other cell-based assays of neurite outgrowth