著者

Masahiro Hirota Shogo Higaki Takumi Higaki Seiichiro Hasezawa

出版者

日本放射線安全管理学会

雑誌

Radiation Safety Management (ISSN:13471511)

巻号頁・発行日

vol.12, no.2, pp.43-47, 2013 (Released:2013-12-19)

参考文献数

10

被引用文献数

2

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The contamination of spinach collected immediately following the Fukushima Daiichi nuclear disaster was investigated. The radionuclides deposited in the spinach were 132Te, 131I, 132I, 134Cs, 136Cs and 137Cs. Only 40% of these radionuclides were removed when the spinach was washed with water or detergent. The two outside leaves of each spinach stump were contaminated with the radionuclides, but the three inside leaves were nearly uncontaminated. The most significant contamination was observed on the concavities, creases, veins and leaf or stem injuries of the spinach. Most of the radionuclides deposited on the surface, leading to a radioactivity concentration of the epidermal tissue 9 times that of the mesophyll tissue.

著者

Yuuki Sakai Takumi Higaki Kimitsune Ishizaki Ryuichi Nishihama Takayuki Kohchi Seiichiro Hasezawa

出版者

Japanese Society for Plant Biotechnology

雑誌

Plant Biotechnology (ISSN:13424580)

巻号頁・発行日

vol.39, no.1, pp.5-12, 2022-03-25 (Released:2022-03-25)

参考文献数

32

被引用文献数

1 2

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The development of the plant body starts with spore germination in bryophytes. In many cases, the first division of the spore occurs after germination and cell elongation of the spore. In Marchantia polymorpha, asymmetric division occurs upon spore germination to generate two daughter cells: the larger one retains the ability to divide and develops into the thallus via sporeling or protonema, while the smaller one maintains tip growth and differentiates into the first rhizoid, providing a scaffold for initial development. Although spore germination of M. polymorpha was described in the 19th century, the intracellular processes of the first asymmetric division of the spore have not been well characterized. In this study, we used live-cell imaging analyses to elucidate microtubule dynamics during the first asymmetric division concomitantly with germination. In particular, we demonstrated that the preprophase band was not formed in the spore and that the bipolar prospindle, which is a microtubule structure surrounding the nucleus during prophase, migrated from the center to the periphery in the spore, suggesting that it was the earliest visible sign of cell polarity. We also showed that the occurrence of asymmetric division depended on actin filaments. Our findings regarding the first division of the spore in M. polymorpha will lead to a better model for cell-autonomous asymmetric division in plants.

著者

Yumi Hirakawa Seiichiro Hasezawa Takumi Higaki

出版者

Japan Mendel Society, International Society of Cytology

雑誌

CYTOLOGIA (ISSN:00114545)

巻号頁・発行日

vol.83, no.3, pp.289-293, 2018-09-25 (Released:2018-10-12)

参考文献数

29

被引用文献数

1

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We previously established an experimental system for efficient pathogenic signal induced-cell death using tobacco BY-2 cells and culture filtrate of a plant pathogenic bacterium, Erwinia carotovora. Using this experimental system, cytoskeletal and vacuolar changes during the process of filtrate-induced cell death were characterized in detail. However, the initial events induced by the filtrate were largely unknown. In this study, reactive oxygen species (ROS) production and endocytosis stimulation were examined in BY-2 cells treated with the filtrate of E. carotovora. Transient ROS production within 2 min was observed after the filtrate treatment. Treatment with the Ca2+ chelator BAPTA or the protein kinase inhibitor K252a significantly inhibited ROS production in a dose-dependent manner, suggesting that ROS production depends on Ca2+ influx or protein phosphorylation. In addition, internalization of the endocytic marker FM4-64 was promoted by filtrate treatment within 30 min, suggesting that the filtrate treatment stimulated endocytosis. These results showed that ROS production and subsequent endocytosis stimulation are the initial events induced by culture filtrate of E. carotovora in BY-2 cells.

著者

Junko Hasegawa Takumi Higaki Yuki Hamamura Daisuke Kurihara Natsumaro Kutsuna Tetsuya Higashiyama Seiichiro Hasezawa Sachihiro Matsunaga

出版者

日本メンデル協会、国際細胞学会

雑誌

CYTOLOGIA (ISSN:00114545)

巻号頁・発行日

vol.79, no.4, pp.467-474, 2014-12-25 (Released:2015-01-16)

参考文献数

31

被引用文献数

1 7

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Vacuoles occupy 80–90% of a mature plant cell and mainly contribute to all types of cell expansion. Zeocin, an inducer of DNA double-strand breaks, causes cell expansion with endoreduplication. The vacuolar structure after zeocin treatment was examined in tobacco (Nicotiana tabacum) cultured cells expressing GFP fused to a vacuole membrane protein. We found that the genotoxic stress induced the cell expansion with subdivision of the vacuolar lumen by cytoplasmic strands. When a femtosecond laser was used to cut off the cytoplasmic strand, mitochondrial transport along the strand stopped. This suggested that in the elongated cells under the genotoxic stress, the transport of subcellular materials was activated for DNA repair within the damaged cell nucleus by the construction of a network of cytoplasmic strands in the vacuolar lumen.

著者

Takumi Higaki Aya Kato Fumiyoshi Myouga Natsumaro Kutsuna Seiichiro Hasezawa Noriko Nagata

出版者

日本バイオイメージング学会

雑誌

bioimages (ISSN:09192719)

巻号頁・発行日

vol.22, pp.1-7, 2014 (Released:2015-06-30)

参考文献数

12

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Recent advances in bioimaging equipment have allowed for the significant and rapid acquisition of biological images. Consequently, new methods are energetically being developed to quantitatively and objectively evaluate the biological features of many bioimages. Recently, we described the application of the CARTA (Clustering-Aided Rapid Training Agent) image classification framework, which can be used to obtain highly accurate classifications of a wide variety of biomedical images. However, the efficacy of this technology in association with transmission electron microscopy (TEM) images has not been evaluated. We herein report the automatic classification of chloroplast TEM images of chloroplasts of wild-type Arabidopsis thaliana and four kinds of mutants impaired in chloroplast-targeted proteins. CARTA successfully classified the TEM images based on their genetic backgrounds. As previously reported with fluorescent microscopic and magnetic resonance images, CARTA reduced the annotation cost while maintaining accuracy. Furthermore, using images obtained with different accelerating voltages resulted in biologically meaningless classifications, suggesting that TEM settings are critical for chloroplast morphological classification. CARTA is expected to be useful for future computational inspections of the ultrastructure visualized with TEM.