A novel method of cultivating cardiac myocytes in agarose microchamber chips for studying cell synchronization

We have developed a new method that enables agar microstructures to be used to cultivate cardiac myocyte cells in a manner that allows their connection patterns to be controlled. Non-contact three-dimensional photo-thermal etching with a 1064-nm infrared focused laser beam was used to form the shapes of agar microstructures. This wavelength was selected as it is not absorbed by water or agar. Identical rat cardiac myocytes were cultured in adjacent microstructures connected by microchannels and the interactions of asynchronous beating cardiac myocyte cells observed. Two isolated and independently beating cardiac myocytes were shown to form contacts through the narrow microchannels and by 90 minutes had synchronized their oscillations. This occurred by one of the two cells stopping their oscillation and following the pattern of the other cell. In contrast, when two sets of synchronized beating cells came into contact, those two sets synchronized without any observable interruptions to their rhythms. The results indicate that the synchronization process of cardiac myocytes may be dependent on the community size and network pattern of these cells

On-chip constructive cell-Network study (I): Contribution of cardiac fibroblasts to cardiomyocyte beating synchronization and community effect

<p>Abstract</p> <p>Backgrounds</p> <p>To clarify the role of cardiac fibroblasts in beating synchronization, we have made simple lined-up cardiomyocyte-fibroblast network model in an on-chip single-cell-based cultivation system.</p> <p>Results</p> <p>The synchronization phenomenon of two cardiomyocyte networks connected by fibroblasts showed (1) propagation velocity of electrophysiological signals decreased a magnitude depending on the increasing number of fibroblasts, not the lengths of fibroblasts; (2) fluctuation of interbeat intervals of the synchronized two cardiomyocyte network connected by fibroblasts did not always decreased, and was opposite from homogeneous cardiomyocyte networks; and (3) the synchronized cardiomyocytes connected by fibroblasts sometimes loses their synchronized condition and recovered to synchronized condition, in which the length of asynchronized period was shorter less than 30 beats and was independent to their cultivation time, whereas the length of synchronized period increased according to cultivation time.</p> <p>Conclusions</p> <p>The results indicated that fibroblasts can connect cardiomyocytes electrically but do not significantly enhance and contribute to beating interval stability and synchronization. This might also mean that an increase in the number of fibroblasts in heart tissue reduces the cardiomyocyte 'community effect', which enhances synchronization and stability of their beating rhythms.</p

Stability of beating frequency in cardiac myocytes by their community effect measured by agarose microchamber chip

To understand the contribution of community effect on the stability of beating frequency in cardiac myocyte cell groups, the stepwise network formation of cells as the reconstructive approach using the on-chip agarose microchamber cell microcultivation system with photo-thermal etching method was applied. In the system, the shapes of agarose microstructures were changed step by step with photo-thermal etching of agarose-layer of the chip using a 1064-nm infrared focused laser beam to increase the interaction of cardiac myocyte cells during cultivation. First, individual rat cardiac myocyte in each microstructure were cultivated under isolated condition, and then connected them one by one through newly-created microchannels by photo-thermal etching to compare the contribution of community size for the magnitude of beating stability of the cell groups. Though the isolated individual cells have 50% fluctuation of beating frequency, their stability increased as the number of connected cells increased. And finally when the number reached to eight cells, they stabilized around the 10% fluctuation, which was the same magnitude of the tissue model cultivated on the dish. The result indicates the importance of the community size of cells to stabilize their performance for making cell-network model for using cells for monitoring their functions like the tissue model

On-chip constructive cell-network study (II): on-chip quasi-in vivo cardiac toxicity assay for ventricular tachycardia/fibrillation measurement using ring-shaped closed circuit microelectrode with lined-up cardiomyocyte cell network

<p>Abstract</p> <p>Backgrounds</p> <p>Conventional <it>in vitro </it>approach using human ether-a-go-go related gene (hERG) assay has been considered worldwide as the first screening assay for cardiac repolarization safety. However, it does not always oredict the potential QT prolongation risk or pro-arrhythmic risk correctly. For adaptable preclinical strategiesto evaluate global cardiac safety, an on-chip quasi-<it>in vivo </it>cardiac toxicity assay for lethal arrhythmia (ventricular tachyarrhythmia) measurement using ring-shaped closed circuit microelectrode chip has been developed.</p> <p>Results</p> <p>The ventricular electrocardiogram (ECG)-like field potential data, which includes both the repolarization and the conductance abnormality, was acquired from the self-convolutied extracellular field potentials (FPs) of a lined-up cardiomyocyte network on a circle-shaped microelectrode in an agarose microchamber. When Astemisol applied to the closed-loop cardiomyocyte network, self-convoluted FP profile of normal beating changed into an early afterdepolarization (EAD) like waveform, and then showed ventricular tachyarrhythmias and ventricular fibrilations (VT/Vf). QT-prolongation-like self-convoluted FP duration prolongation and its fluctuation increase was also observed according to the increase of Astemizole concentration.</p> <p>Conclusions</p> <p>The results indicate that the convoluted FPs of the quasi<it>-in vivo </it>cell network assay includes both of the repolarization data and the conductance abnormality of cardiomyocyte networks has the strong potential to prediction lethal arrhythmia.</p

ARTICLE EDUCATIONAL AND PSYCHOLOGICAL MEASUREMENT YASUDA ET AL. ASSESSMENT OF INTRAINDIVIDUAL VARIABILITY IN POSITIVE AND NEGATIVE AFFECT USING LATENT STATE-TRAIT MODEL ANALYSES

Intraindividual variability in positive and negative affect was assessed by the positive affect (Contentment, Joy, Vigor, Love, and Excitement) and negative affect (Depression, Hostility, Anxiety, Agitation, and Social Anxiety) subscales of the state version of the Comprehensive Personality and Affect Scales (COPAS) during a 3-week period. Using the latent state-trait model analysis, which takes both intraindividual variability and interindividual difference into account by controlling measurement error, it was shown that the variability could be measured reliably by the scores of the COPAS. In particular, a total of 56.9% to 63.5% and 48.2% to 60.6% of the reliable interindividual difference in positive and negative affect, respectively, was attributed to the intraindividual variability

Quantum reservoir computing with repeated measurements on superconducting devices

Reservoir computing is a machine learning framework that uses artificial or physical dissipative dynamics to predict time-series data using nonlinearity and memory properties of dynamical systems. Quantum systems are considered as promising reservoirs, but the conventional quantum reservoir computing (QRC) models have problems in the execution time. In this paper, we develop a quantum reservoir (QR) system that exploits repeated measurement to generate a time-series, which can effectively reduce the execution time. We experimentally implement the proposed QRC on the IBM's quantum superconducting device and show that it achieves higher accuracy as well as shorter execution time than the conventional QRC method. Furthermore, we study the temporal information processing capacity to quantify the computational capability of the proposed QRC; in particular, we use this quantity to identify the measurement strength that best tradeoffs the amount of available information and the strength of dissipation. An experimental demonstration with soft robot is also provided, where the repeated measurement over 1000 timesteps was effectively applied. Finally, a preliminary result with 120 qubits device is discussed