Comprehensive In Vitro Toxicity Testing of a Panel of Representative Oxide Nanomaterials: First Steps towards an Intelligent Testing Strategy

Nanomaterials (NMs) display many unique and useful physico-chemical properties. However, reliable approaches are needed for risk assessment of NMs. The present study was performed in the FP7-MARINA project, with the objective to identify and evaluate in vitro test methods for toxicity assessment in order to facilitate the development of an intelligent testing strategy (ITS). Six representative oxide NMs provided by the EC-JRC Nanomaterials Repository were tested in nine laboratories. The in vitro toxicity of NMs was evaluated in 12 cellular models representing 6 different target organs/systems (immune system, respiratory system, gastrointestinal system, reproductive organs, kidney and embryonic tissues). The toxicity assessment was conducted using 10 different assays for cytotoxicity, embryotoxicity, epithelial integrity, cytokine secretion and oxidative stress. Thorough physico-chemical characterization was performed for all tested NMs. Commercially relevant NMs with different physico-chemical properties were selected: two TiO2 NMs with different surface chemistry – hydrophilic (NM-103) and hydrophobic (NM-104), two forms of ZnO – uncoated (NM-110) and coated with triethoxycapryl silane (NM-111) and two SiO2 NMs produced by two different manufacturing techniques – precipitated (NM-200) and pyrogenic (NM-203). Cell specific toxicity effects of all NMs were observed; macrophages were the most sensitive cell type after short-term exposures (24-72h) (ZnO>SiO2>TiO2). Longer term exposure (7 to 21 days) significantly affected the cell barrier integrity in the presence of ZnO, but not TiO2 and SiO2, while the embryonic stem cell test (EST) classified the TiO2 NMs as potentially ‘weak-embryotoxic’ and ZnO and SiO2 NMs as ‘non-embryotoxic’. A hazard ranking could be established for the representative NMs tested (ZnO NM-110 > ZnO NM-111 > SiO2 NM-203 > SiO2 NM-200 > TiO2 NM-104 > TiO2 NM-103). This ranking was different in the case of embryonic tissues, for which TiO2 displayed higher toxicity compared with ZnO and SiO2. Importantly, the in vitro methodology applied could identify cell- and NM-specific responses, with a low variability observed between different test assays. Overall, this testing approach, based on a battery of cellular systems and test assays, complemented by an exhaustive physico-chemical characterization of NMs, could be deployed for the development of an ITS suitable for risk assessment of NMs. This study also provides a rich source of data for modeling of NM effects

Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

Analysis of reactive oxygen species generating systems in rat epididymal spermatozoa.

International audienceEpididymal sperm maturation culminates in the acquisition of functional competence by testicular spermatozoa. The expression of this functional state is dependent upon a redox-regulated, cAMP-mediated signal transduction cascade that controls the tyrosine phosphorylation status of the spermatozoa during capacitation. Analysis of superoxide anion (O2(-.)) generation by rat epididymal spermatozoa has revealed a two-component process involving electron leakage from the sperm mitochondria at complexes I and II and a plasma membrane NAD(P)H oxidoreductase. Following incubation in a glucose-, lactate-, and pyruvate-free medium (-GLP), O2(-.) generation was suppressed by 86% and 96% in caput and cauda spermatozoa, respectively. The addition of lactate, malate, or succinate to spermatozoa incubated in medium -GLP stimulated O2(-.) generation. This increase could be blocked by rotenone and oligomycin (R/O) in the presence of malate or lactate but not succinate. Stimulation with all three substrates, as well as spontaneous O2(-.) production in +GLP medium, was blocked by the flavoprotein inhibitor, diphenylene iodonium. Diphenylene iodonium, but not R/O, suppressed NAD(P)H-induced lucigenin-dependent chemiluminescence. This NAD(P)H-dependent enzyme resided in the sperm plasma membrane and its activity was regulated by zinc and uncharacterized cytosolic factors. Reverse transcription-polymerase chain reaction analysis indicated that the sperm NAD(P)H oxidoreductase complex is quite distinct from the equivalent leukocyte system

Audio feedback: richer language but no measurable impact on student performance

Audio feedback has been shown to be popular and well received by students. However, there is little published work to indicate how effective audio feedback is in improving student performance. Sixty students from a first year science degree agreed to take part in the study; thirty were randomly assigned to receive written feedback on coursework, thirty students received their feedback via audio files. Mean marks awarded for the coursework for each group were not significantly different. The end of module test included questions that specifically assessed topics from the coursework. Overall test results were not significantly different for the two groups, nor were marks for the coursework-specific questions. Samples of the tutor feedback were analysed and the language categorised. The mean word counts for audio feedback were significantly higher than word counts for written feedback. Analysis of the language used in feedback (measured by word count) indicated significantly higher word counts for audio feedback in the following categories, ‘explaining misunderstandings’ and ‘demonstration of good practice’. Since word counts for audio feedback might be expected to include a number of ‘filler’ words, the number of comments made under different categories was also compared for audio and written feedback. Significantly more comments were made using audio feedback in the categories ‘giving praise’, ‘explaining misunderstandings’, ‘demonstration of good practice’ and ‘justifying marks’. Under the heading ‘suggesting approaches to future work’ more comments were made using written feedback than audio, although the mean number of comments in both forms of feedback in this category was very low. Whilst marks may not be improved for those students receiving audio rather than written feedback, the feedback given is much richer

Non-immortalized human neural stem (NS) cells as a scalable platform for cellular assays

The utilization of neural stem cells and their progeny in applications such as disease modelling, drug screening or safety assessment will require the development of robust methods for consistent, high quality uniform cell production. Previously, we described the generation of adherent, homogeneous, non-immortalized mouse and human neural stem cells derived from both brain tissue and pluripotent embryonic stem cells (Conti et al., 2005; Sun et al., 2008). In this study, we report the isolation or derivation of stable neurogenic human NS (hNS) lines from different regions of the 8-9 gestational week fetal human central nervous system (CNS) using new serum-free media formulations including animal component-free conditions. We generated more than 20 adherent hNS lines from whole brain, cortex, lobe, midbrain, hindbrain and spinal cord. We also compared the adherent hNS to some aspects of the human CNS-stem cells grown as neurospheres (hCNS-SCns), which were derived from prospectively isolated CD133(+)CD24(-/lo) cells from 16 to 20 gestational week fetal brain. We found, by RT-PCR and Taqman low-density array, that some of the regionally isolated lines maintained their regional identity along the anteroposterior axis. These NS cells exhibit the signature marker profile of neurogenic radial glia and maintain neurogenic and multipotential differentiation ability after extensive long-term expansion. Similarly, hCNS-SC can be expanded either as neurospheres or in extended adherent monolayer with a morphology and marker expression profile consistent with radial glia NS cells. We demonstrate that these lines can be efficiently genetically modified with standard nucleofection protocols for both protein overexpression and siRNA knockdown of exogenously expressed and endogenous genes exemplified with GFP and Nestin. To investigate the functional maturation of neuronal progeny derived from hNS we (a) performed Agilent whole genome microarray gene expression analysis from cultures undergoing neuronal differentiation for up to 32 days and found increased expression over time for a number of drugable target genes including neurotransmitter receptors and ion channels and (b) conducted a neuropharmacology study utilizing Fura-2 Ca(2+) imaging which revealed a clear shift from an initial glial reaction to carbachol to mature neuron-specific responses to glutamate and potassium after prolonged neuronal differentiation. Fully automated culture and scale-up of select hNS was achieved; cells supplied by the robot maintained the molecular profile of multipotent NS cells and performed faithfully in neuronal differentiation experiments. Here, we present validation and utility of a human neural lineage-restricted stem cell-based assay platform, including scale-up and automation, genetic engineering and functional characterization of differentiated progeny

Conserved and divergent patterns of expression of DAZL, VASA and OCT4 in the germ cells of the human fetal ovary and testis-2

<p><b>Copyright information:</b></p><p>Taken from "Conserved and divergent patterns of expression of DAZL, VASA and OCT4 in the germ cells of the human fetal ovary and testis"</p><p>http://www.biomedcentral.com/1471-213X/7/136</p><p>BMC Developmental Biology 2007;7():136-136.</p><p>Published online 18 Dec 2007</p><p>PMCID:PMC2211489.</p><p></p>64 d; d, 16 wk). DAZL positive germ cells were rare in the 1st trimester (e, ovary 61 d; g, testis 64 d) but groups of cells ('nests', labelled N) with cytoplasmic staining were present in the 2nd trimester ovaries (f, 20 wk). During the 2nd trimester VASA protein was detected in the cytoplasm of female germ cells (i, 14 wk; j, 18 wk) throughout the ovary with the exception of the sub-epithelial layer. In the testes (k, 15 wk; l, 16 wk) VASA-positive germ cells were found in all cords