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| Kiyota, Maki; Numayama, Naoko; Goto, Ken. |
| Plant defenses against photo-oxidative stress have been studied almost exclusively with respect to stress responses, and little is known about how non-enzymic antioxidants change under constant conditions without a time cue or an environmental stress. Here, we show that, in both the flagellated alga Euglena gracilis Z and the angiosperm Spinacia oleracea L., the potent antioxidant L-ascorbic acid (Asc) displays a circadian rhythm with a maximum at subjective midday, a physiological state reflecting that attained at noon under daily light/dark cycles. Thus, photosynthetic organisms can maximize antioxidant levels in anticipation of midday, when photo-oxidative stress is most severe. These results may partly explain the in-phase circadian UV-C resistance... |
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Palavras-chave: Antioxidant; L-ascorbic acid; Circadian; Euglena gracilis; Midday; Photooxidation; Spinach. |
| Ano: 2006 |
URL: http://ir.obihiro.ac.jp/dspace/handle/10322/716 |
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| Chang,L.; Liu,Y.Y.; Zhu,B.; Li,Y.; Hua,H.; Wang,Y.H.; Zhang,J.; Jiang,Z.; Wang,Z.R.. |
| Period2 is a core circadian gene, which not only maintains the circadian rhythm of cells but also regulates some organic functions. We investigated the effects of mPeriod2 (mPer2) expression on radiosensitivity in normal mouse cells exposed to 60Co-γ-rays. NIH 3T3 cells were treated with 12-O-tetradecanoylphorbol-13-acetate (TPA) to induce endogenous mPer2 expression or transfected with pcDNA3.1(+)-mPer2 and irradiated with 60Co-γ-rays, and then analyzed by several methods such as flow cytometry, colony formation assay, RT-PCR, and immunohistochemistry. Flow cytometry and colony formation assay revealed that irradiated NIH 3T3 cells expressing high levels of mPer2 showed a lower death rate (TPA: 24 h 4.3% vs 12 h 6.8% and control 9.4%; transfection:... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Circadian; MPer2; Radiation; Cell death; Proliferation; DNA repair. |
| Ano: 2009 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-879X2009001000003 |
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| Bolige, Aoen; Goto, Ken. |
| Little is known about the photoreceptors involved in the photoperiodism of unicellular organisms, which we elucidated by deriving their action spectra. The flagellated alga Euglena gracilis exhibits photoperiodism, with a long-day response in cell reproduction. The underlying clock is a circadian rhythm with photoinductive capability, peaking at subjective dusk and occurring at the 26th hour in continuous darkness (DD) when transferred from continuous light (LL); it regulates photoinduction, a high-irradiance response (HIR), of a dark-capability of progressing through cell division. We derived the action spectra by irradiating E. gracilis with monochromatic light for 3 h at around the 26th hour; the action maxima occurred at 380, 450–460, 480, 610, 640,... |
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Palavras-chave: Cell division cycle; Complementary chromatic adaptation; Circadian; Euglena; End-of-day; Photoperiodism; Phytochrome; Shade avoidance. |
| Ano: 2007 |
URL: http://ir.obihiro.ac.jp/dspace/handle/10322/719 |
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