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Dive into the research topics where Akari Mizuno is active.

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Featured researches published by Akari Mizuno.


Biochemical and Biophysical Research Communications | 2012

Microscopic heat pulses induce contraction of cardiomyocytes without calcium transients

Kotaro Oyama; Akari Mizuno; Seine A. Shintani; Hideki Itoh; Takahiro Serizawa; Norio Fukuda; Madoka Suzuki; Shin'ichi Ishiwata

It was recently demonstrated that laser irradiation can control the beating of cardiomyocytes and hearts, however, the precise mechanism remains to be clarified. Among the effects induced by laser irradiation on biological tissues, temperature change is one possible effect which can alter physiological functions. Therefore, we investigated the mechanism by which heat pulses, produced by infra-red laser light under an optical microscope, induce contractions of cardiomyocytes. Here we show that microscopic heat pulses induce contraction of rat adult cardiomyocytes. The temperature increase, ΔT, required for inducing contraction of cardiomyocytes was dependent upon the ambient temperature; that is, ΔT at physiological temperature was lower than that at room temperature. Ca(2+) transients, which are usually coupled to contraction, were not detected. We confirmed that the contractions of skinned cardiomyocytes were induced by the heat pulses even in free Ca(2+) solution. This heat pulse-induced Ca(2+)-decoupled contraction technique has the potential to stimulate heart and skeletal muscles in a manner different from the conventional electrical stimulations.


American Journal of Physiology-cell Physiology | 2011

Real-time measurement of the length of a single sarcomere in rat ventricular myocytes: a novel analysis with quantum dots

Takahiro Serizawa; Takako Terui; Tatsuya Kagemoto; Akari Mizuno; Togo Shimozawa; Fuyu Kobirumaki; Shin'ichi Ishiwata; Satoshi Kurihara; Norio Fukuda

As the dynamic properties of cardiac sarcomeres are markedly changed in response to a length change of even ∼0.1 μm, it is imperative to quantitatively measure sarcomere length (SL). Here we show a novel system using quantum dots (QDs) that enables a real-time measurement of the length of a single sarcomere in cardiomyocytes. First, QDs were conjugated with anti-α-actinin antibody and applied to the sarcomeric Z disks in isolated skinned cardiomyocytes of the rat. At partial activation, spontaneous sarcomeric oscillations (SPOC) occurred, and QDs provided a quantitative measurement of the length of a single sarcomere over the broad range (i.e., from ∼1.7 to ∼2.3 μm). It was found that the SPOC amplitude was inversely related to SL, but the period showed no correlation with SL. We then treated intact cardiomyocytes with the mixture of the antibody-QDs and FuGENE HD, and visualized the movement of the Z lines/T tubules. At a low frequency of 1 Hz, the cycle of the motion of a single sarcomere consisted of fast shortening followed by slow relengthening. However, an increase in stimulation frequency to 3-5 Hz caused a phase shift of shortening and relengthening due to acceleration of relengthening, and the waveform became similar to that observed during SPOC. Finally, the anti-α-actinin antibody-QDs were transfected from the surface of the beating heart in vivo. The striated patterns with ∼1.96-μm intervals were observed after perfusion under fluorescence microscopy, and an electron microscopic observation confirmed the presence of QDs in and around the T tubules and Z disks, but primarily in the T tubules, within the first layer of cardiomyocytes of the left ventricular wall. Therefore, QDs are a useful tool to quantitatively analyze the movement of single sarcomeres in cardiomyocytes, under various experimental settings.


The Journal of General Physiology | 2016

Nano-imaging of the beating mouse heart in vivo: Importance of sarcomere dynamics, as opposed to sarcomere length per se, in the regulation of cardiac function.

Fuyu Kobirumaki-Shimozawa; Kotaro Oyama; Togo Shimozawa; Akari Mizuno; Takashi Ohki; Takako Terui; Susumu Minamisawa; Shin'ichi Ishiwata; Norio Fukuda

¡Vive la différence! In cardiac contraction, the reduction in sarcomere length—rather than length itself—determines contractile force.


BioMed Research International | 2012

Sarcomere Imaging by Quantum Dots for the Study of Cardiac Muscle Physiology

Fuyu Kobirumaki-Shimozawa; Kotaro Oyama; Takahiro Serizawa; Akari Mizuno; Tatsuya Kagemoto; Togo Shimozawa; Shin'ichi Ishiwata; Satoshi Kurihara; Norio Fukuda

We here review the use of quantum dots (QDs) for the imaging of sarcomeric movements in cardiac muscle. QDs are fluorescence substances (CdSe) that absorb photons and reemit photons at a different wavelength (depending on the size of the particle); they are efficient in generating long-lasting, narrow symmetric emission profiles, and hence useful in various types of imaging studies. Recently, we developed a novel system in which the length of a particular, single sarcomere in cardiomyocytes can be measured at ~30 nm precision. Moreover, our system enables accurate measurement of sarcomere length in the isolated heart. We propose that QDs are the ideal tool for the study of sarcomere dynamics during excitation-contraction coupling in healthy and diseased cardiac muscle.


Biophysical Journal | 2014

Real-Time Imaging of Sarcomere Dynamics in the Mouse Heart In Vivo

Fuyu Kobirumaki-Shimozawa; Kotaro Oyama; Akari Mizuno; Takako Terui; Togo Shimozawa; Takashi Ohki; Shin'ichi Ishiwata; Norio Fukuda


Biophysical Journal | 2013

Microscopic Heat Pulses Induce Ca2+-Independent Contraction of Cardiomyocytes

Kotaro Oyama; Akari Mizuno; Seine A. Shintani; Hideki Itoh; Takahiro Serizawa; Norio Fukuda; Madoka Suzuki; Shin'ichi Ishiwata


生物物理 | 2012

1PS009 In vivoマウス心臓におけるサルコメア長のリアルタイム計測(日本生物物理学会第50回年会(2012年度))

Akari Mizuno; Fuyu Kobirumaki-Shimozawa; Kotaro Oyama; Takako Terui; Erisa Hirokawa; Togo Simozawa; Shin'ichi Ishiwata; Norio Fukuda


生物物理 | 2012

2H1510 Ca^ に依存しない熱パルスによる心筋細胞のOn-Off制御(筋肉,口頭発表,日本生物物理学会第50回年会(2012年度))

Kotaro Oyama; Akari Mizuno; Seine A. Shintani; Hideki Itoh; Takahiro Serizawa; Norio Fukuda; Madoka Suzuki; Shin'ichi Ishiwata


Seibutsu Butsuri | 2012

1PS009 Real-time measurement of sarcomere length in the mouse heart in vivo by using a-actinin-GFP(The 50th Annual Meeting of the Biophysical Society of Japan)

Akari Mizuno; Fuyu Kobirumaki-Shimozawa; Kotaro Oyama; Takako Terui; Erisa Hirokawa; Togo Simozawa; Shin'ichi Ishiwata; Norio Fukuda


Seibutsu Butsuri | 2012

2H1510 Ca^ -independent on-off regulation of a cardiomyocyte by microscopic heat pulses(Muscle,Oral Presentation,The 50th Annual Meeting of the Biophysical Society of Japan)

Kotaro Oyama; Akari Mizuno; Seine A. Shintani; Hideki Itoh; Takahiro Serizawa; Norio Fukuda; Madoka Suzuki; Shin'ichi Ishiwata

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Norio Fukuda

Jikei University School of Medicine

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Takako Terui

Jikei University School of Medicine

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Fuyu Kobirumaki-Shimozawa

Jikei University School of Medicine

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Satoshi Kurihara

Jikei University School of Medicine

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Hideki Itoh

Shiga University of Medical Science

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