Hajime Suzuki

Nagoya University, Nagoya, Aichi, Japan

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Publications (6)11.65 Total impact

  • Riho Gojo · Hajime Suzuki · Takafumi Tezuka
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    ABSTRACT: The growth (cell division) of Chlorella cells cultured under photosynthetically active radiation (PAR) without near-UV radiation was inferior to that under PAR with near-UV radiation. To elucidate this phenomenon, the relationship between near-UV radiation and ethylene production in Chlorella cells was examined. The suppression of ethylene production by UV radiation suggests that this phenomenon is associated with the production of ethylene. Chlorella (a eukaryotic protista) was found to produce ethylene from methionine via S-adenosyl-methionine (SAM) and 1-aminocyclo-propane-1-carboxylate (ACC) as in higher plants, and the activity of ACC oxidase, a limiting factor of ethylene production, appears to be associated with the growth of Chlorella. A possible mechanism for the action of near-UV radiation on ethylene biosynthesis and growth suppression by ethylene is discussed.
    No preview · Article · Feb 2004 · Environmental sciences: an international journal of environmental physiology and toxicology
  • Riho Gojo · Hajime Suzuki · Takafumi Tezuka
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    ABSTRACT: The wavelength of natural sunlight reaching the Earth's surface was detected to be above 300 nm using a multichannel spectrodetector and the ratio of UV to photosynthetically active radiation (PAR) of sunlight in Japan (137 degrees E/35 degrees 11' N, altitude; 50 m) in early summer was estimated to be 0.07:1 (i.e., 7%). On the basis of this UV/PAR ratio, Chlorella ellipsoidea (IAM-27) cells were cultured in flasks under various conditions of UV irradiation in growth chambers. The growth (cell division) of these cells without near-UV radiation was inferior to that with near-UV radiation. Growth at a UV/PAR ratio of 7% (natural conditions), determined tentatively using our detector in the present study, was maximal similar to those at 14% and 28%; whereas that at 0.7% was somewhat less and that at 70% was considerably less. Growth was linked with the activities of stress enzymes. NAD(P)H-dependent oxidase [NAD(P)-DH] and xanthine oxidase (XOD), extracted from Chlorella exposed to near-UV radiation demonstrated lower activities than those from Chlorella not exposed to near-UV radiation. On the other hand, superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APOD) extracted from Chlorella exposed to near-UV radiation have higher activities than those from unexposed Chlorella. Near-UV radiation clearly acted as an important factor for growth (cell division), at least at UV/PAR ratios of up to 0.28:1.
    No preview · Article · Feb 2004 · Environmental sciences: an international journal of environmental physiology and toxicology
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    ABSTRACT: Five enzymes involved in the generation and scavenging of reactive oxygen species, i.e., NADH/NADPH oxidase, xanthine oxidase (XOD), superoxide dismutase (SOD), ascorbate peroxidase, and catalase were assayed in various tissues of the Japanese monkey. Their activities were largely different between tissues. Generally, small intestine, kidney, and cerebellum contained larger amounts of these enzymes than other tissues. Multiplicities of these enzymes were analyzed by staining of their enzymatic activities after electrophoresis. The number of isozymes was 2 in the case of NADPH oxidase and catalase, and 3 in the case of XOD, SOD, and ascorbate peroxidase. The expression of these isozymes differed between tissues, suggesting the occurrence of tissue-specific systems to generate and scavenge reactive oxygen species in the Japanese monkey.
    Preview · Article · Mar 2001 · ZOOLOGICAL SCIENCE
  • Hajime Suzuki · Akiko Tsuruhara · Takafumi Tezuka
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    ABSTRACT: The mechanism of self incompatibility in pistils of Lilium longiflorum Thunb. cv. Hinomoto, which is overcome by heat treatment, was analyzed. Immersing detached pistils in a distilled water bath held at 45°C for 5 min suppressed levels of ethylene and activities of 1-aminocyclopropane-1-carboxylate (ACC) oxidase at 6 h after self- and cross-incompatible pollination. However, the levels and activities showed no significant difference 48 h after pollination. Levels of ACC and activities of ACC synthase at 6 h after self-incompatible pollination were lower in pistils with heat treatment. Moreover, the heat treatment suppressed the activity of superoxide dismutase and enhanced the activity of catalase, ascorbate peroxidase, dehydroascorbate reductase, and glutathione reductase. In addition, the amount of hydrogen peroxide (H2O2) was reduced by heat treatment. In summary, heat treatment suppressed the ethylene-forming system and also enhanced the hydrogen peroxide-scavenging system in self-pollinated pistils associated with self incompatibility. A possible correlation between self incompatibility and stress in pistils after self-incompatible pollination is discussed based on the results obtained using heated pistils.
    No preview · Article · Feb 2001 · Sexual Plant Reproduction
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    Akiko Tsuruhara · Hajime Suzuki · Takafumi Tezuka
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    ABSTRACT: The effects of exogenous cAMP on the activities of the stress enzymes were studied using the extracts from stigmas and styles of Lilium longiflorum cv. Hinomoto without pollination in relation to self-incompatibility. The activity of NADH- and NADPH-dependent oxidases (O2/--forming enzymes) was inhibited by cAMP. This inhibition was noncompetitive with NAD(P)H.
    Preview · Article · Jan 1999 · Plant and Cell Physiology
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    ABSTRACT: An attempt was made to examine the possible connection between self-incompatibility in Lilium longiflorum and the stress response using pistils after self-incompatible pollination. The growth of pollen tubes in the pistil after self-incompatible pollination was promoted by treatment with germanium compounds [(GeCH2CH2COOH)2O3 and GeO2], which are scavengers of active oxygen species, such as O2− and H2O2. The promotion by germanium compounds of the growth of pollen tubes after self-incompatible pollination was reflected by the detection of elevated levels of activity of superoxide-forming NADPH-dependent oxidase, xanthine oxidase, superoxide dismutase, catalase and ascorbate peroxidase, all of which are associated with stress responses, in pistils upon self-incompatible pollination as compared to the activities of these enzymes after cross-compatible pollination. A possible connection between self-incompatibility and stress in pistils upon self-incompatible pollination is discussed on the basis of these results.
    Preview · Article · Feb 1997 · Plant and Cell Physiology