TY - JOUR A1 - Trent, Davis A1 - Thielemann, Christiane A1 - Monici, Monica T1 - How are cell and tissue structure and function influenced by gravity and what are the gravity perception mechanisms? JF - npj Microgravity N2 - Progress in mechanobiology allowed us to better understand the important role of mechanical forces in the regulation of biological processes. Space research in the field of life sciences clearly showed that gravity plays a crucial role in biological processes. The space environment offers the unique opportunity to carry out experiments without gravity, helping us not only to understand the effects of gravitational alterations on biological systems but also the mechanisms underlying mechanoperception and cell/tissue response to mechanical and gravitational stresses. Despite the progress made so far, for future space exploration programs it is necessary to increase our knowledge on the mechanotransduction processes as well as on the molecular mechanisms underlying microgravity-induced cell and tissue alterations. This white paper reports the suggestions and recommendations of the SciSpacE Science Community for the elaboration of the section of the European Space Agency roadmap “Biology in Space and Analogue Environments” focusing on “How are cells and tissues influenced by gravity and what are the gravity perception mechanisms?” The knowledge gaps that prevent the Science Community from fully answering this question and the activities proposed to fill them are discussed. KW - Zellkultur KW - Schwere KW - Raumfahrtbiologie Y1 - 0024 UR - https://rdcu.be/dyCjL U6 - https://doi.org/10.1038/s41526-024-00357-9 VL - 2014 IS - 10 / 16 SP - 1 EP - 7 ER - TY - CHAP A1 - Nick, Christoph A1 - Thielemann, Christiane A1 - Joshi, Ravi A1 - Schneider, Jörg T1 - Niedrigtemperatur-Transfer von vertikal ausgerichteten Kohlenstoff Nanoröhren auf Mikrostrukturen T2 - Mikro-Nano-Integration - 3. GMM-Workshop, Stuttgart, Deutschland, 2011 N2 - Vertikal angeordnete Kohlenstoff Nanoröhren (engl. vertically aligned carbon nanotubes; VA-CNT) können seit einigen Jahren mit hoher Reproduzierbarkeit durch CVD-Verfahren bei 600 °C - 800 °C auf Katalysatorschichten aus Aluminium und Eisen hergestellt werden. Sie zeigen sehr gute Eigenschaften im Bereich der Feldemission, aber auch in sub-µm Vias. Allerdings sind die relativ hohen Temperaturen oft nicht prozesskompatibel und müssen vermieden werden um keine Degradation darunterliegender Strukturen in Kauf zu nehmen. Da die Reduzierung der CVD-Temperaturen beim Wachstum der VA-CNTs unter 600 °C zu hohen Defektraten führt, schlagen wir ein neues Verfahren zum Transfer der VA-CNTs bei niedrigen Temperaturen vor. In einer Kombination aus Flip-Chip- und Stempel-Technik werden hoch geordnete, mikrostrukturierte VA-CNTs auf temperaturempfindliche Substrate aus Kalk-Natron-Glas, Gold oder Kupfer bei Temperaturen von 100 °C transferiert. Die vertikale Struktur der Nanoröhren bleibt dabei erhalten. Eine leitende Verbindung kann durch ein leitfähiges, bio-kompatibles Polymer gewährleistet werden, was eine Erweiterung des Einsatzbereichs auf Life-Science Applikationen erlauben würde. KW - Kohlenstoff-Nanoröhre Y1 - 2011 ER - TY - CHAP A1 - Yilmazoglu, Oktay A1 - Al-Daffaie, Shihab A1 - Hartnagel, Hans A1 - Joshi, Ravi A1 - Yadav, Sandeep A1 - Schneider, Jörg A1 - Nick, Christoph A1 - Thielemann, Christiane T1 - CNT photocathodes based on GaAs high-frequency photoswitches T2 - 25th International Vacuum Nanoelectronics Conference, 9 - 13 July 2012, Jeju, South Korea N2 - A high-frequency photocathode based on carbon nanotube (CNT) blocks on semiisolating GaAs or low-temperature grown GaAs was fabricated and used for electron emission in a diode configuration. The CNT blocks can achieve high currents and current densities of I=0.5 mA and J=28 mA/cm 2 at E=2.1 V/μm, respectively. The photomodulation was achieved with a GaAs photoswitch electrically connected to the bottom of the CNT block emitter. This photocathode can find applications in high frequency tubes and optically driven X-ray sources. KW - Kohlenstoff-Nanoröhre Y1 - 2012 U6 - https://doi.org/10.1109/IVNC.2012.6316840 ER - TY - JOUR A1 - Emmerich, Florian A1 - Thielemann, Christiane T1 - Optimizing dimensions of unipolar Teflon-FEP piezoelectrets with micro-system-technology JF - Journal of Physics: Conference Series N2 - In this work we present a new micro-system-technology based production process for unipolar ferroelectrets. Theoretical analysis of the influence of the air-gap size on the electric field distribution as well as on the induced charge on the electrodes shows superior performance of unipolar piezoelectrets with small air-gaps. For the production of these small air-gaps we developed a new design using a photoresist thermoforming master, an integrated micro-heater and shadow masks for metallization. Unipolar piezoelectrets produced with this technology exhibit increased d33-coefficients compared to designs in previous publications. These piezoelectrets are highly preferable for energy-harvesting applications, as they promise high electric power output. KW - Mikrosystemtechnik Y1 - 2017 VL - 2018 IS - 1052 SP - 1 EP - 4 ER - TY - CHAP A1 - Mayer, Margot A1 - Arrizabalaga, Onetsine A1 - Ritter, Sylvia A1 - Thielemann, Christiane T1 - Human Embryonic Stem Cell Derived Neurospheres - A Novel Three Dimensional Model For Neurotoxicological Studies T2 - Frontiers N2 - At present, most neurotoxicological studies in the field of microelectrode array (MEA) technology are based on in vivo or in vitro animal models, particularly in mice or rats. These models contributed much to our knowledge about molecular and cellular mechanisms of neurotoxins affecting the central nervous system. Yet, animal models are not necessarily capable to forecasting the effectiveness of treatment in clinical trials. Therefore the development and characterization of suitable neuronal cell models derived from human cells is emerging in the field of toxicity testing. In this study, we present neurospheres (NS) as a new three dimensional (3D) neuronal cell model based on human embryonic stem cells (hESC), coupled onto microelectrode arrays (MEA). This cell-based assay serves as platform to investigate effects of neuroactive substances on network communication. In order to characterize the neurospheres’ reaction, the well-known GABA receptor antagonist bicuculline and the sodium channel blocker carbamazepine are applied. Preliminary results reveal anticipated and physiologically reasonable alterations in network activity. Thus, we have the first evidence that hESC derived NS are a promising 3D cell model for neurotoxicity testing. In further studies, this model will be used to investigate effects of ionizing radiation on network signaling. KW - human embryonic stem cells KW - neurospheres KW - MEA chips KW - 3D KW - Mikroelektrode KW - Array KW - Embryonale Stammzelle Y1 - 2016 U6 - https://doi.org/10.3389/conf.fnins.2016.93.00081 VL - 2016 IS - MEA Meeting 2016 ER - TY - JOUR A1 - Nick, Christoph A1 - Schlaak, Helmut A1 - Thielemann, Christiane T1 - Simulation and Measurement of Neuroelectrodes' Characteristics with Integrated High Aspect Ratio Nano Structures JF - AIMS Journal N2 - Improving the interface between electrodes and neurons has been the focus of research for the last decade. Neuroelectrodes should show small geometrical surface area and low impedance for measuring and high charge injection capacities for stimulation. Increasing the electrochemically active surface area by using nanoporous electrode material or by integrating nanostructures onto planar electrodes is a common approach to improve this interface. In this paper a simulation approach for neuro electrodes' characteristics with integrated high aspect ratio nano structures based on a point-contact-model is presented. The results are compared with experimental findings conducted with real nanostructured microelectrodes. In particular, effects of carbon nanotubes and gold nanowires integrated onto microelectrodes are described. Simulated and measured impedance properties are presented and its effects onto the transfer function between the neural membrane potential and the amplifier output signal are studied based on the point-contact-model. Simulations show, in good agreement with experimental results, that electrode impedances can be dramatically reduced by the integration of high aspect ratio nanostructures such as gold nanowires and carbon nanotubes. This lowers thermal noise and improves the signal-to-noise ratio for measuring electrodes. It also may increase the adhesion of cells to the substrate and thus increase measurable signal amplitudes. KW - Neuronales Netz KW - Mikroelektrode Y1 - 2015 U6 - https://doi.org/10.3934/matersci.2015.3.189 VL - 2015 IS - 2 SP - 189 EP - 202 ER - TY - JOUR A1 - Alves, Caroline L. A1 - Wissel, Lennart A1 - Capetian, Philipp A1 - Thielemann, Christiane T1 - Functional connectivity and convolutional neural networks for automatic classification of EEG data JF - Clinical Neurophysiology KW - Elektroencephalographie KW - Neuronales Netz Y1 - 2022 U6 - https://doi.org/https://doi.org/10.1016/j.clinph.2022.01.086 VL - 2022 IS - 137 SP - e37 EP - e47 ER - TY - JOUR A1 - Bouillet, Thomas A1 - Ciba, Manuel A1 - Alves, Caroline L. A1 - Rodrigues, Francisco A. A1 - Thielemann, Christiane A1 - Colin, Morvane A1 - Buée, Luc A1 - Halliez, Sophie T1 - Revisiting the involvement of tau in complex neural network remodeling: analysis of the extracellular neuronal activity in organotypic brain slice co-cultures JF - Journal of Neural Engineering N2 - Objective: Tau ablation has a protective effect in epilepsy due to inhibition of the hyperexcitability/hypersynchrony. Protection may also occur in transgenic models of Alzheimer's disease by reducing the epileptic activity and normalizing the excitation/inhibition imbalance. However, it is difficult to determine the exact functions of tau, because tau knockout (tauKO) brain networks exhibit elusive phenotypes. In this study, we aimed to further explore the physiological role of tau using brain network remodeling. Approach: The effect of tau ablation was investigated in hippocampal-entorhinal slice co-cultures during network remodeling. We recorded the spontaneous extracellular neuronal activity over two weeks in single-slice cultures and co-cultures from control and tauKO mice. We compared the burst parameters and applied concepts and analytical tools intended for the analysis of the network synchrony and connectivity. Main results: Comparison of the control and tauKO co-cultures revealed that tau ablation had an anti-synchrony effect on the hippocampal-entorhinal two-slice networks at late stages of culture, in line with the literature. Differences were also found between the single-slice and co-culture conditions, which indicated that tau ablation had differential effects at the sub-network scale. For instance, tau ablation was found to have an anti-synchrony effect on the co-cultured hippocampal slices throughout the culture, possibly due to a reduction in the excitation/inhibition ratio. Conversely, tau ablation led to increased synchrony in the entorhinal slices at early stages of the co-culture, possibly due to homogenization of the connectivity distribution. Significance: The new methodology presented here proved useful for investigating the role of tau in the remodeling of complex brain-derived neural networks. The results confirm previous findings and hypotheses concerning the effects of tau ablation on neural networks. Moreover, the results suggest, for the first time, that tau has multifaceted roles that vary in different brain sub-networks. KW - Neuronales Netz KW - Alzheimerkrankheit KW - Gehirn KW - Schnittpräparat Y1 - 2022 U6 - https://doi.org/DOI 10.1088/1741-2552/aca261 VL - 2022 IS - November SP - 1 EP - 2 ER - TY - JOUR A1 - Ciba, Manuel A1 - Bestel, Robert A1 - Nick, Christoph A1 - Ferraz de Arruda, Guilherme A1 - Peron, Thomas A1 - Henrique, Comin César A1 - da Fontoura Costa, Luciano A1 - Aparecido Rodrigues, Francisco A1 - Thielemann, Christiane T1 - Comparison of Different Spike Train Synchrony Measures Regarding Their Robustness to Erroneous Data from Bicuculline-Induced Epileptiform Activity JF - Neural Computation N2 - As synchronized activity is associated with basic brain functions and pathological states, spike train synchrony has become an important measure to analyze experimental neuronal data. Many measures of spike train synchrony have been proposed, but there is no gold standard allowing for comparison of results from different experiments. This work aims to provide guidance on which synchrony measure is best suited to quantify the effect of epileptiform-inducing substances (e.g., bicuculline, BIC) in in vitro neuronal spike train data. Spike train data from recordings are likely to suffer from erroneous spike detection, such as missed spikes (false negative) or noise (false positive). Therefore, different timescale-dependent (cross-correlation, mutual information, spike time tiling coefficient) and timescale-independent (Spike-contrast, phase synchronization (PS), A-SPIKE-synchronization, A-ISI-distance, ARI-SPIKE-distance) synchrony measures were compared in terms of their robustness to erroneous spike trains. For this purpose, erroneous spike trains were generated by randomly adding (false positive) or deleting (false negative) spikes (in silico manipulated data) from experimental data. In addition, experimental data were analyzed using different spike detection threshold factors in order to confirm the robustness of the synchrony measures. All experimental data were recorded from cortical neuronal networks on microelectrode array chips, which show epileptiform activity induced by the substance BIC. As a result of the in silico manipulated data, Spike-contrast was the only measure that was robust to false-negative as well as false-positive spikes. Analyzing the experimental data set revealed that all measures were able to capture the effect of BIC in a statistically significant way, with Spike-contrast showing the highest statistical significance even at low spike detection thresholds. In summary, we suggest using Spike contrast to complement established synchrony measures because it is timescale independent and robust to erroneous spike trains. KW - Neuronales Netz Y1 - 2020 U6 - https://doi.org/10.1162/neco_a_01277 VL - 32 IS - 3 SP - 1 EP - 25 ER - TY - JOUR A1 - Oster, Stefan A1 - Daus, Andreas A1 - Erbes, Christian A1 - Goldhammer, Michael A1 - Bochtler, Ulrich A1 - Thielemann, Christiane T1 - Long‐term electromagnetic exposure of developing neuronal networks: A flexible experimental setup JF - Bioelectromagnetics N2 - Neuronal networks in vitro are considered one of the most promising targets of research to assess potential electromagnetic field induced effects on neuronal functionality. A few exposure studies revealed there is currently no evidence of any adverse health effects caused by weak electromagnetic fields. Nevertheless, some published results are inconsistent. Particularly, doubts have been raised regarding possible athermal biological effects in the young brain during neuronal development. Therefore, we developed and characterized a flexible experimental setup based on a transverse electromagnetic waveguide, allowing controlled, reproducible exposure of developing neuronal networks in vitro. Measurement of S‐parameters confirmed very good performance of the Stripline in the band of 800–1000 MHz. Simulations suggested a flexible positioning of cell culture dishes throughout a large exposure area, as specific absorption rate values were quite independent of their position (361.7 ± 11.4 mW/kg) at 1 W, 900 MHz. During exposure, thermal drift inside cellular medium did not exceed 0.1 K. Embryonic rat cortical neurons were cultivated on microelectrode array chips to non‐invasively assess electrophysiological properties of electrogenic networks. Measurements were taken for several weeks, which attest to the experimental setup being a reliable system for long‐term studies on developing neuronal tissue. KW - RF exposure setup KW - mobile communication frequencies KW - SAR dosimetry KW - microelectrode array KW - electrophysiology KW - Neuronales Netz KW - Mikroelektrode KW - Array Y1 - 2016 U6 - https://doi.org/10.1002/bem.21974 VL - 2016 IS - 37 SP - 264 EP - 278 ER -