Biology subjects

Miyamoto, N.

Publications and source records attributed to Miyamoto, N..

4 recordsLinked to original sources

bioRxiv2025

Field potential Imaging in human iPSC- derived Cardiomyocytes using UHD-CMOS-MEA

Evaluation using beat propagation analysis of human iPS cardiomyocytes is an effective approach for assessing human cardiac safety in drug development. However, current applications are primarily focused on detecting QT prolongation and arrhythmia risk, while its ability to comprehensively detect cardiotoxicity remains insufficient. Additionally, predicting the mechanism of action, which is crucial in drug development, remains challenging. In this study, we employed field potential imaging (FPI) using an ultra-high-density (UHD) CMOS microelectrode array (MEA) comprising 236,880 electrodes with high spatiotemporal resolution, capable of recording the activity of a monolayer of cardiomyocytes with tens of electrodes per cell. This method enabled the establishment of novel electrophysiological endpoints, including the number of excitation origins, fluctuations in origin positions, conduction velocity, and propagation area. Pharmacological characterization revealed drug-specific effects: isoproterenol increased excitation origins, mexiletine reduced conduction velocity, and E-4031 decreased propagation area while inducing early afterdepolarizations. Multivariate analysis of 13 compounds across 17 electrophysiological endpoints distinguished conduction velocity and propagation patterns based on their mechanisms of action. Additionally, 0.1 M doxorubicin exposure for 24 hours significantly reduced conduction velocity and propagation area, allowing early detection of chronic cardiotoxicity. These findings suggest that UHD-CMOS-MEA-based FPI enhances cardiotoxicity detection at low concentrations and precisely characterizes ion channel activity across different drug concentrations. The integration of novel electrophysiological endpoints derived from UHD-CMOS-MEA-based FPI, including excitation origin analysis, conduction velocity, and propagation area, along with multivariate analysis, is anticipated to establish a next-generation in vitro platform for comprehensive cardiotoxicity risk assessment and mechanism-based prediction of drug candidates.

pharmacology and toxicology↗

bioRxiv2024

Circatidal control of gene expression in the deep-sea hot vent shrimp Shinkaicaris leurokolos

Biological clocks are a ubiquitous feature of all life, enabling the use of natural environmental cycles to track time. Although studies on circadian rhythms have contributed greatly to the knowledge of chronobiology, biological rhythms in dark biospheres such as the deep sea remain poorly understood. Here, based on a laboratory free-running experiment, we reveal potentially endogenous rhythms in gene expression of the deep-sea hydrothermal vent shrimp Rimicaris leurokolos. Oscillations with [~]12-hour periods, likely reflecting tidal influence, greatly prevail over others in the temporal transcriptome, indicating R. leurokolos likely depends on a circatidal clock consisting of at least some components independent of the circadian clocks. The tidal transcripts exhibit an antiphased expression pattern divided into two internally synchronized clusters, correlated with wide-ranging biological processes that occur in the nucleus and cytoplasm, respectively. In addition, comparing the tidal transcripts with the [~]12-hour ultradian rhythms genes in fruit flies and mice shows large similarity, indicating the likely scenario of broad impact of the tide on the [~]12-hour oscillations across the metazoan. These findings not only provide new insights into the temporal adaptations in deep-sea organisms but also highlight deep-sea hydrothermal vent organisms as intriguing models for chronobiological, particularly 12-hour ultradian rhythms, studies.

ecology↗

bioRxiv2023

Observation of electromyogram and electrocardiogram changes with deqi for the development of an objective evaluation index of the occurrence of deqi

A unique sensation called "deqi" occurs in acupuncture, which is considered an essential variable in the study of the mechanisms and effects of acupuncture. However, an objective method for evaluating deqi is yet to be established. Therefore, we aimed to create an objective evaluation index for deqi using electromyogram (EMG) and electrocardiogram (ECG), which are expected to present characteristic changes based on the findings of previous studies. This study included 16 healthy adult male subjects. ST36 stimulation was performed three times after a one-week washout (N=48). EMG was used to calculate myopotentials, and ECG was used to calculate the heart rate (HR) immediately after stimulation. The subjects declared whether Deqi occurred, and the characteristic reactions of deqi in EMG and ECG were evaluated. In 48 trials, Deqi occurred 42 times and did not occur 6 times. Myopotentials were significantly higher when deqi occurred than when it did not. Furthermore, a positive correlation was identified between subjective sensation and the rate of change in myopotential. Deqi significantly increased the myopotential levels, indicating that it induced involuntary muscle activity. This involuntary muscle activity may be related to the stretch reflexes and nerve stimulation. For the HR immediately after stimulation, no change with deqi was identified, although a significant decrease in HR was found in cases without deqi. Deqi could induce a transient stress response and inhibit the decrease in the HR caused by acupuncture. The results of this study indicate two characteristics of deqi obtained from EMG and ECG: an increase in myopotential and an inhibition of the decrease in HR expected with acupuncture. These characteristics could provide objective evidence for the occurrence of deqi. Future studies with larger sample sizes are required toto further strengthen the objective assessment of deqi.

neuroscience↗

bioRxiv2023

Millisecond-scale behaviours of plankton quantified in situ and in vitro using the Event-based Vision Sensor (EVS)

The Event-based Vision Sensor (EVS) is a bio-inspired sensor that captures detailed motions of objects, developed with the applicability to become the eyes of machines and especially self-driving cars. Compared to conventional frame-based image sensors as employed in video cameras, EVS has an extremely fast motion capture equivalent to 10,000-fps even with standard optical settings and additionally has high dynamic ranges for brightness and also lower consumption of memory and energy. These features make the EVS an ideal method to tackle questions in biology, such as the fine-scale behavioural ecology. Here, we developed 22 characteristic features for analysing the motions of aquatic particles from the raw data of the EVS, and deployed the EVS system in both natural environments and laboratory aquariums to test its applicability to filming and analysing plankton behaviour. Our EVS monitoring in turbid water at the bottom of Lake Biwa, Japan identified several particles exhibiting distinct cumulative trajectory with periodicities in their motion (up to 16 Hz), suggesting that they were living organisms with rhythmic behaviour. We also carried out EVS monitoring in the deep sea aided by infrared lighting to minimise influence on behaviour, and observed particles with active motion and periodicities over 40 Hz. Furthermore, we used the EVS to observe laboratory cultures of six species of zooplankton and phytoplankton, confirming that they have species-specific motion periodicities of up to 41 Hz. We applied machine learning to automatically classify particles into five categories (four categories of zooplankton plus passive particles), which achieved an accuracy up to 86%. Our attempts to use the EVS for biological observations, especially focusing on its millisecond-scale temporal resolution and wide dynamic range provide a new avenue to investigate rapid and periodical motion and behaviour in small organisms. Given its compact size with low consumption of battery and memory, the EVS will likely be applicable in the near future for the automated monitoring of the behaviour of plankton by edge computing on autonomous floats, as well as quantifying rapid cellular-level activities under microscopy.

animal behavior and cognition↗