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| Bolige, Aoen; Hagiwara, Shin-ya; Zhang, Yulan; Goto, Ken; 後藤, 健. |
| Cell population growth is gated to occur in particular circadian phases, which has been known for over four decades in various organisms including cyanobacteria and human. However, little is known as to which cell cycle phases from G(1) to M are primarily regulated by the circadian rhythm or when in a circadian cycle this primary regulation takes place. We report here that in the flagellate alga Euglena gracilis grown photoautotrophically, the circadian rhythm primarily prevented developmentally matured G(2) cells from progressing to mitosis, such that cell population growth occurred only during subjective night. In addition, we found that the circadian rhythm also arrests G(1)-to-S and S-to-G(2) transitions at particular circadian phases. |
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Palavras-chave: Cell cycle; Circadian rhythms; Englena gracilis; G2-arrest; Mitosis. |
| Ano: 2005 |
URL: http://ir.obihiro.ac.jp/dspace/handle/10322/717 |
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| Bolige, Aoen; Kiyota, Maki; Goto, Ken; 後藤, 健. |
| Radiation-induced stress, either from visible or UV light, is strongest at midday. We found that, in the absence of stress or time cues, Euglena gracilis Z was the most resistant to UV-C and UV-B at subjective midday, whether judged from immediate or reproductive survival. The circadian UV-resistance rhythms were free-running in stationary cultures under 1-h light/1-h dark cycles or continuous darkness, indicating that cell-cycle dependent DNA susceptibility to UV was not involved. We moreover examined what was the primary cause of the circadian U-V resistance, estimated as the immediate cell survival. The half-maximal lethal dose (LD50) of UV-C at subjective midday (the most resistant phase) was 156 J/m(2), which is similar to 3-fold that at subjective... |
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Palavras-chave: Antioxidant; L-ascorbic acid; Circadian rhythms; Dimethylsulfoxide; Euglena gracilis; Photo-oxidation; UV-sensitivity. |
| Ano: 2005 |
URL: http://ir.obihiro.ac.jp/dspace/handle/10322/718 |
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