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Papers by Ichiro Imai

Research paper thumbnail of Virus-like particles in an apochlorotic flagellate in Hiroshima Bay, Japan

Marine Ecology Progress Series, 1993

Research paper thumbnail of Phylogenetic analysis of intracellular bacteria of a harmful marine microalga, Heterocapsa circularisquama (Dinophyceae)

Aquatic Microbial Ecology, 2004

Research paper thumbnail of Algicidal Marine Bacteria Isolated from Northern Hiroshima Bay, Japan

Research paper thumbnail of Growth of Red Tide Phytoplankton

Research paper thumbnail of Relationships between intracellular bacteria and the bivalve killer dinoflagellate Heterocapsa circularisquama (Dinophyceae)

Fisheries Science, Oct 1, 2001

Research paper thumbnail of Selenium Requirement for Growth of a Novel Red Tide Flagellate <i>Chattonella verruculosa</i> (Raphidophyceae) in Culture

Research paper thumbnail of Different Nutrient Availabilities of Surface and Bottom Water under Nutrient-depleted Conditions during Bloom Formation of the Toxic Dinoflagellate Alexandrium tamarense in Osaka Bay, Japan

Research paper thumbnail of Harmful algal blooms and environmentally friendly control strategies in Japan

Fisheries Science, Jun 30, 2021

Research paper thumbnail of Gran (Bacillariophyce ae) in culture

Research paper thumbnail of Pathogens of Harmful Microalgae

Research paper thumbnail of First record of two warm-water HAB species Chattonella marina (Raphidophyceae) and Cochlodinium polykrikoides (Dinophyceae) on the west coast of Hokkaido, northern Japan in summer 2014

Regional Studies in Marine Science, 2016

Research paper thumbnail of Cyst morphology of a chain-forming unarmored dinoflagellate Gyrodinium impudicum Fraga et Bravo

Phycological Research, 2001

ABSTRACT Cysts of a chain-forming dinoflagellate Gyrodinium impudicum Fraga et Bravo (Gymnodinial... more ABSTRACT Cysts of a chain-forming dinoflagellate Gyrodinium impudicum Fraga et Bravo (Gymnodiniales) were found in surface sediments of Harima-Nada and Nakaumi, western Japan. The detailed morphology of living and empty cysts is described. The living cysts are roundish to ellipsoidal in polar view, and hemispherical in lateral view. Among three empty cysts obtained, two different archeopyles were observed; either a long slit with an operculum, or a hole with irregular zigzag outline. The living cysts of Gyro. impudicum are morphologically similar to those of the genus Chattonella antiqua (Hada) Ono and Chattonella marina (Subrahmanyan) Y. Hara et Chihara (Raphidophyceae), except cyst color and contents. The living cysts of Gyro. impudicum were rarely encountered, and their density was always less than 1 cell in 1 cm−3 in the present samples.

Research paper thumbnail of Seasonal distribution of species of the toxic dinoflagellate genus Dinophysis in Maizuru Bay (Japan), with comments on their autofluorescence and attachment of picophytoplankton

Research paper thumbnail of Polymerase chain reaction primers for highly selective detection of algicidal Proteobacteria

Research paper thumbnail of The Effect of Salinity on the Size of Initial Cells During Vegetative Cell Enlargement Ofcoscinodiscus Wailesii(Bacillariophyceae) in Culture

Diatom Research, 1999

ABSTRACT

Research paper thumbnail of Ecophysiology, life cycle, and bloom dynamics of Chattonella in the Seto Inland Sea, Japan

NATO ASI SERIES G …, 1998

Research paper thumbnail of Occurrence of Chattonella Red Tide and Cyst Dynamics in Sediments in Northern Hiroshima Bay, the Seto Inland Sea, Japan

Nippon Suisan Gakkaishi, 1993

Research paper thumbnail of 63(1)今井Hc

Research paper thumbnail of Esterification of xanthophylls by human intestinal Caco-2 cells

Archives of Biochemistry and Biophysics, 2009

We recently found that peridinin, which is uniquely present in dinoflagellates, reduced cell viab... more We recently found that peridinin, which is uniquely present in dinoflagellates, reduced cell viability by inducing apoptosis in human colon cancer cells. Peridinin is also found in edible clams and oysters because the major food sources of those shellfish are phytoplanktons such as dinoflagellates. Little is known, however, about the fate of dietary peridinin and its biological activities in mammals. The aim of the present study was to investigate the enzymatic esterification of xanthophylls, especially peridinin which is uniquely present in dinoflagellates, using differentiated cultures of Caco-2 human intestinal cells. We found that peridinin is converted to peridininol and its fatty acid esters in differentiated Caco-2 cells treated with 5mumol/L peridinin solubilized with mixed micelles. The cell homogenate was also able to deacetylate peridinin and to esterify peridininol. Other xanthophylls, such as fucoxanthin, astaxanthin and zeaxanthin, were also esterified, but at relatively lower rates than peridinin. In this study, we found the enzymatic esterification of xanthophylls in mammalian intestinal cells for the first time. Our results suggest that the esterification of xanthophylls in intestinal cells is dependent on their polarity.

Research paper thumbnail of Life Cycle Strategies of the Centric Diatoms in a Shallow Embayment Revealed by the Plankton Emergence Trap/Chamber (PET Chamber) Experiments

Frontiers in Marine Science

In situ emergence of the centric diatoms from the surface sediment, along with the occurrence of ... more In situ emergence of the centric diatoms from the surface sediment, along with the occurrence of the vegetative cells in the water column, were monitored monthly in a shallow embayment, Ago Bay, of central Japan, where light penetrated to the seafloor. The in situ emergence flux (cells m-2 day-1) was measured by experiments using a ‘plankton emergence trap/chamber (PET chamber)’. During the study period from July 2006 to May 2008, germinating and rejuvenating cells of centric diatoms were successfully collected by the PET chamber. Furthermore, vegetative cells forming long-chain colonies, including the species which have not been known to form resting stage cells, were also found, indicating that these cells already inhabited the surface sediment prior to the start of the PET chamber experiments. The vegetative cells could be cells that grew after germination/rejuvenation and/or cells deposited from the upper layer in the water column. When comparing emergence flux in the PET chambe...

Research paper thumbnail of Virus-like particles in an apochlorotic flagellate in Hiroshima Bay, Japan

Marine Ecology Progress Series, 1993

Research paper thumbnail of Phylogenetic analysis of intracellular bacteria of a harmful marine microalga, Heterocapsa circularisquama (Dinophyceae)

Aquatic Microbial Ecology, 2004

Research paper thumbnail of Algicidal Marine Bacteria Isolated from Northern Hiroshima Bay, Japan

Research paper thumbnail of Growth of Red Tide Phytoplankton

Research paper thumbnail of Relationships between intracellular bacteria and the bivalve killer dinoflagellate Heterocapsa circularisquama (Dinophyceae)

Fisheries Science, Oct 1, 2001

Research paper thumbnail of Selenium Requirement for Growth of a Novel Red Tide Flagellate <i>Chattonella verruculosa</i> (Raphidophyceae) in Culture

Research paper thumbnail of Different Nutrient Availabilities of Surface and Bottom Water under Nutrient-depleted Conditions during Bloom Formation of the Toxic Dinoflagellate Alexandrium tamarense in Osaka Bay, Japan

Research paper thumbnail of Harmful algal blooms and environmentally friendly control strategies in Japan

Fisheries Science, Jun 30, 2021

Research paper thumbnail of Gran (Bacillariophyce ae) in culture

Research paper thumbnail of Pathogens of Harmful Microalgae

Research paper thumbnail of First record of two warm-water HAB species Chattonella marina (Raphidophyceae) and Cochlodinium polykrikoides (Dinophyceae) on the west coast of Hokkaido, northern Japan in summer 2014

Regional Studies in Marine Science, 2016

Research paper thumbnail of Cyst morphology of a chain-forming unarmored dinoflagellate Gyrodinium impudicum Fraga et Bravo

Phycological Research, 2001

ABSTRACT Cysts of a chain-forming dinoflagellate Gyrodinium impudicum Fraga et Bravo (Gymnodinial... more ABSTRACT Cysts of a chain-forming dinoflagellate Gyrodinium impudicum Fraga et Bravo (Gymnodiniales) were found in surface sediments of Harima-Nada and Nakaumi, western Japan. The detailed morphology of living and empty cysts is described. The living cysts are roundish to ellipsoidal in polar view, and hemispherical in lateral view. Among three empty cysts obtained, two different archeopyles were observed; either a long slit with an operculum, or a hole with irregular zigzag outline. The living cysts of Gyro. impudicum are morphologically similar to those of the genus Chattonella antiqua (Hada) Ono and Chattonella marina (Subrahmanyan) Y. Hara et Chihara (Raphidophyceae), except cyst color and contents. The living cysts of Gyro. impudicum were rarely encountered, and their density was always less than 1 cell in 1 cm−3 in the present samples.

Research paper thumbnail of Seasonal distribution of species of the toxic dinoflagellate genus Dinophysis in Maizuru Bay (Japan), with comments on their autofluorescence and attachment of picophytoplankton

Research paper thumbnail of Polymerase chain reaction primers for highly selective detection of algicidal Proteobacteria

Research paper thumbnail of The Effect of Salinity on the Size of Initial Cells During Vegetative Cell Enlargement Ofcoscinodiscus Wailesii(Bacillariophyceae) in Culture

Diatom Research, 1999

ABSTRACT

Research paper thumbnail of Ecophysiology, life cycle, and bloom dynamics of Chattonella in the Seto Inland Sea, Japan

NATO ASI SERIES G …, 1998

Research paper thumbnail of Occurrence of Chattonella Red Tide and Cyst Dynamics in Sediments in Northern Hiroshima Bay, the Seto Inland Sea, Japan

Nippon Suisan Gakkaishi, 1993

Research paper thumbnail of 63(1)今井Hc

Research paper thumbnail of Esterification of xanthophylls by human intestinal Caco-2 cells

Archives of Biochemistry and Biophysics, 2009

We recently found that peridinin, which is uniquely present in dinoflagellates, reduced cell viab... more We recently found that peridinin, which is uniquely present in dinoflagellates, reduced cell viability by inducing apoptosis in human colon cancer cells. Peridinin is also found in edible clams and oysters because the major food sources of those shellfish are phytoplanktons such as dinoflagellates. Little is known, however, about the fate of dietary peridinin and its biological activities in mammals. The aim of the present study was to investigate the enzymatic esterification of xanthophylls, especially peridinin which is uniquely present in dinoflagellates, using differentiated cultures of Caco-2 human intestinal cells. We found that peridinin is converted to peridininol and its fatty acid esters in differentiated Caco-2 cells treated with 5mumol/L peridinin solubilized with mixed micelles. The cell homogenate was also able to deacetylate peridinin and to esterify peridininol. Other xanthophylls, such as fucoxanthin, astaxanthin and zeaxanthin, were also esterified, but at relatively lower rates than peridinin. In this study, we found the enzymatic esterification of xanthophylls in mammalian intestinal cells for the first time. Our results suggest that the esterification of xanthophylls in intestinal cells is dependent on their polarity.

Research paper thumbnail of Life Cycle Strategies of the Centric Diatoms in a Shallow Embayment Revealed by the Plankton Emergence Trap/Chamber (PET Chamber) Experiments

Frontiers in Marine Science

In situ emergence of the centric diatoms from the surface sediment, along with the occurrence of ... more In situ emergence of the centric diatoms from the surface sediment, along with the occurrence of the vegetative cells in the water column, were monitored monthly in a shallow embayment, Ago Bay, of central Japan, where light penetrated to the seafloor. The in situ emergence flux (cells m-2 day-1) was measured by experiments using a ‘plankton emergence trap/chamber (PET chamber)’. During the study period from July 2006 to May 2008, germinating and rejuvenating cells of centric diatoms were successfully collected by the PET chamber. Furthermore, vegetative cells forming long-chain colonies, including the species which have not been known to form resting stage cells, were also found, indicating that these cells already inhabited the surface sediment prior to the start of the PET chamber experiments. The vegetative cells could be cells that grew after germination/rejuvenation and/or cells deposited from the upper layer in the water column. When comparing emergence flux in the PET chambe...

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