The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
E. Stroben - One of the best experts on this subject based on the ideXlab platform.
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Marisa cornuarietis (Gastropoda, prosobranchia): a potential TBT bioindicator for freshwater environments
Ecotoxicology, 1995Co-Authors: U. Schulte-oehlmann, C. Bettin, P. Fioroni, J. Oehlmann, E. StrobenAbstract:The ramshorn snail Marisa cornuarietis (L., 1767) exhibits imposex (occurrence of male parts in addition to the female genital duct) under the influence of TBT (tributyltin) in laboratory experiments and accumulates this biocide in a time-and concentration-dependent manner. A comparison of BCF (bioconcentration factors) demonstrates that this limnic species accumulates more TBT than marine species. Evidence is given that TBT causes hormonal disorders which are responsible for imposex development. The testosterone/oestradiol quotient reflects the imposex development which can be described by a classification scheme differentiating four stages in Marisa cornuarietis . In the background of the constantly increasing organotin concentration in the limnic environment Marisa cornuarietis could be a well-suited bioindicator for TBT pollution. No other limnic species with a lower threshold concentration for measurable TBT effects is reported within the literature.
U. Schulte-oehlmann - One of the best experts on this subject based on the ideXlab platform.
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Marisa cornuarietis (Gastropoda, prosobranchia): a potential TBT bioindicator for freshwater environments
Ecotoxicology, 1995Co-Authors: U. Schulte-oehlmann, C. Bettin, P. Fioroni, J. Oehlmann, E. StrobenAbstract:The ramshorn snail Marisa cornuarietis (L., 1767) exhibits imposex (occurrence of male parts in addition to the female genital duct) under the influence of TBT (tributyltin) in laboratory experiments and accumulates this biocide in a time-and concentration-dependent manner. A comparison of BCF (bioconcentration factors) demonstrates that this limnic species accumulates more TBT than marine species. Evidence is given that TBT causes hormonal disorders which are responsible for imposex development. The testosterone/oestradiol quotient reflects the imposex development which can be described by a classification scheme differentiating four stages in Marisa cornuarietis . In the background of the constantly increasing organotin concentration in the limnic environment Marisa cornuarietis could be a well-suited bioindicator for TBT pollution. No other limnic species with a lower threshold concentration for measurable TBT effects is reported within the literature.
Tatsuya Oda - One of the best experts on this subject based on the ideXlab platform.
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possible factors responsible for the fish killing mechanisms of the red tide phytoplankton chattonella marina and cochlodinium polykrikoides
Coastal Environmental and Ecosystem Issues of the East China Sea, 2010Co-Authors: Daekyung Kim, Tatsuya OdaAbstract:Generation of reactive oxygen species (ROS) such as superoxide (O2 –) and hydroxyl radical (·OH) by Chattonella marina could be confirmed by ESR spin trapping method. Several lines of evidence suggested that cell surface structure of C. marina, glycocalyx, has NADPH-dependent O2 – generation system. Immunohistochemical analysis of gill lamellae from yellowtail exposed to C. marina using antiserum against crude glycocalyx demonstrated that there were the antigns recognaised by the antiserum on the surface of gill lamellae. The results suggest that continuous accumulation of discharged glycocalyx on the gill surface occurs during C. marina exposure, which may be responsible for the ROSmediated severe gill tissue damage leading to fish death. As compare to C. marina, the levels of O2 – and H2O2 detected in Cochlodinium polykrikoides were trace levels. Furthermore, no significant increase in O2 – generation by C. polykrikoides was observed in the presence of lectins or fish mucus prepared from skin and gill of yellowtail, whereas C. marina generated increased level of O2 – responding to these stimuli. The cell-free aqueous extract prepared from C. polykrikoides showed toxic effect on HeLa cells, but the extract of C. marina had almost no effect. Furthermore, gradual accumulation of polysaccharides in the medium was observed during the culture of C. polykrikoides, and the medium gradually became viscous, but no such change was observed in the medium of C. marina. These results suggest that ichthyotoxic mechanisms of C. marina and C. polykrikoides are different. ROS may play a significant role in the fish-killing activity of C. marina, whereas in the case of C. polykrikoides, certain toxic substances or polysaccharides are mainly responsible for the toxicity rather than ROS.
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nitric oxide synthase like enzyme mediated nitric oxide generation by harmful red tide phytoplankton chattonella marina
Journal of Plankton Research, 2006Co-Authors: Daekyung Kim, Kenichi Yamaguchi, Tatsuya OdaAbstract:The unicellular marine phytoplankton Chattonella marina is known to exhibit potent fish-killing activity. Previous studies have demonstrated that C. marina produces reactive oxygen species (ROS), and ROS-mediated ichthyotoxic mechanism has been postulated. However, the exact toxic mechanism is still controversial. In this study, we obtained evidence that C. marina produces nitric oxide (NO) under normal growth conditions. We utilized chemiluminescence (CL) reaction between NO and luminol-H 2 O 2 to detect NO in C. marina cell suspensions. In this assay, significant CL was observed in C. marina in a cell-number-dependent manner, and this was diminished by the addition of 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (carboxy-PTIO), a specific NO scavenger. The NO generation by C. marina was also confirmed by a spectrophotometric assay based on the measurement of the diazo-reaction-positive substances (NO x ) and by fluorometric assay using highly specific fluorescent indicator of NO. The NO level in C. marina was significantly decreased by N G -nitro-L-arginine methyl ester (L-NAME), a specific NO synthase (NOS) inhibitor. The addition of L-arginine resulted in the increased NO level, whereas NaNO 2 had no effect. These results suggest that a NOS-like enzyme is mainly responsible for NO generation in C. marina.
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Deleterious effect of Chattonella marina on short-necked clam (Ruditapes philippinarum); possible involvement of reactive oxygen species
Journal of Plankton Research, 2004Co-Authors: Daekyung Kim, Osamu Kumamoto, Kyoung-seon Lee, Aiko Kuroda, Akihiko Fujii, Atsushi Ishimatus, Tatsuya OdaAbstract:In laboratory exposure experiments, Chattonella marina showed a deleterious effect on short-necked clams (Ruditapes philippinarum). Accumulated C. marina cells were observed in gill tissues of the clams exposed to C. marina. Immunohistochemical analysis using antiserum against the crude glycocalyx of C. marina suggested that the glycocalyx was present on the gill surface. Mucus substances prepared from gill tissue of the clams stimulated C. marina to generate increased amounts of O - 2 in a concentration-dependent manner. These results suggest that reactive oxygen species (ROS)-mediated gill tissue damage is one of the causative factors responsible for the harmful effect of C. marina on shellfish.
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mechanism of superoxide anion generation in the toxic red tide phytoplankton chattonella marina possible involvement of nad p h oxidase
Biochimica et Biophysica Acta, 2000Co-Authors: Daekyung Kim, Tatsuya Oda, Atsushi Ishimatsu, Atsushi Nakamura, Tarou Okamoto, Nobukazu Komatsu, Takaji Iida, Tsuyoshi MuramatsuAbstract:Red tide phytoplankton Chattonella marina is known to produce reactive oxygen species (ROS), such as superoxide anion (O2−), hydrogen peroxide (H2O2) and hydroxyl radical (OH), under normal physiological conditions. Although several lines of evidence suggest that ROS are involved in the mortality of fish exposed to C. marina, the mechanism of ROS generation in C. marina remains to be clarified. In this study, we found that the cell-free supernatant prepared from C. marina cells showed NAD(P)H-dependent O2− generation, and this response was inhibited by diphenyleneiodonium, an inhibitor of mammalian NADPH oxidase. When the cell-free supernatant of C. marina was analyzed by immunoblotting using antibody raised against the human neutrophil cytochrome b558 large subunit (gp91phox), a main band of approximately 110 kDa was detected. The cell surface localization of the epitope recognized with this antibody was also demonstrated in C. marina by indirect immunofluorescence. Furthermore, Southern blot analysis performed on genomic DNA of C. marina with a probe covering the C-terminal region of gp91phox suggested the presence of a single-copy gene coding for gp91phox homologous protein in C. marina. These results provide evidence for the involvement of an enzymatic system analogous to the neutrophil NADPH oxidase as a source of O2− production in C. marina.
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Inhibitory effect of the iron chelator Desferrioxamine (Desferal) on the generation of activated oxygen species by Chattonella marina
Marine Biology, 1996Co-Authors: Ienobu Kawano, Tatsuya Oda, Atsushi Ishimatsu, Tsuyoshi MuramatsuAbstract:Recent studies demonstrated that the toxic red tide phytoplankton Chattonella spp. produce activated oxygen species such as superoxide anion (O2-), hydrogen peroxide (H2O2), and hydroxyl radicals (·OH), which may be responsible for the toxicity of this flagellate. However, the mechanism behind the production of these oxygen radicals and H2O2 by Chattonella spp. is largely unknown, and the physiological significance of activated oxygen species for Chattonella spp. is also unclear. In the present study, we investigated the involvement of iron in the generation of O2-and H2O2 by C. marina. The generation of O2-by C. marina was related to the growth phase; the highest rate of O2-production was observed during the exponential growth phase. However, no such increase during the exponential growth phase was observed in C. marina growing in an iron-deficient medium, even though the growth of C. marina was not significantly affected by iron-deficiency during the first 4 d. In addition, the iron chelator desferrioxamine (Desferal) strongly inhibited the generation of both O2-and H2O2 by C. marina in a concentration-dependent manner. The growth of C. marina was also inhibited by Desferal. Furthermore, in the presence of 500 μM Desferal, C. marina-induced growth inhibition of the marine bacteria Vibrio alginolyticus was almost completely abolished. These results suggest that iron is required for the generation of activated oxygen species by C. marina, as well as for its own growth.
C. Bettin - One of the best experts on this subject based on the ideXlab platform.
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Marisa cornuarietis (Gastropoda, prosobranchia): a potential TBT bioindicator for freshwater environments
Ecotoxicology, 1995Co-Authors: U. Schulte-oehlmann, C. Bettin, P. Fioroni, J. Oehlmann, E. StrobenAbstract:The ramshorn snail Marisa cornuarietis (L., 1767) exhibits imposex (occurrence of male parts in addition to the female genital duct) under the influence of TBT (tributyltin) in laboratory experiments and accumulates this biocide in a time-and concentration-dependent manner. A comparison of BCF (bioconcentration factors) demonstrates that this limnic species accumulates more TBT than marine species. Evidence is given that TBT causes hormonal disorders which are responsible for imposex development. The testosterone/oestradiol quotient reflects the imposex development which can be described by a classification scheme differentiating four stages in Marisa cornuarietis . In the background of the constantly increasing organotin concentration in the limnic environment Marisa cornuarietis could be a well-suited bioindicator for TBT pollution. No other limnic species with a lower threshold concentration for measurable TBT effects is reported within the literature.
P. Fioroni - One of the best experts on this subject based on the ideXlab platform.
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Marisa cornuarietis (Gastropoda, prosobranchia): a potential TBT bioindicator for freshwater environments
Ecotoxicology, 1995Co-Authors: U. Schulte-oehlmann, C. Bettin, P. Fioroni, J. Oehlmann, E. StrobenAbstract:The ramshorn snail Marisa cornuarietis (L., 1767) exhibits imposex (occurrence of male parts in addition to the female genital duct) under the influence of TBT (tributyltin) in laboratory experiments and accumulates this biocide in a time-and concentration-dependent manner. A comparison of BCF (bioconcentration factors) demonstrates that this limnic species accumulates more TBT than marine species. Evidence is given that TBT causes hormonal disorders which are responsible for imposex development. The testosterone/oestradiol quotient reflects the imposex development which can be described by a classification scheme differentiating four stages in Marisa cornuarietis . In the background of the constantly increasing organotin concentration in the limnic environment Marisa cornuarietis could be a well-suited bioindicator for TBT pollution. No other limnic species with a lower threshold concentration for measurable TBT effects is reported within the literature.