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Shikata T.,Prefectural University of Kumamoto | Shikata T.,Japan National Research Institute of Fisheries And Environment of Inland Sea | Sakurada K.,Kumamoto Prefectural Fisheries Research Center | Jomoto Y.,Prefectural University of Kumamoto | And 6 more authors.
Nippon Suisan Gakkaishi (Japanese Edition) | Year: 2011

In the Yatsushiro Sea, from June to October 2008, growth dynamics of Chattonella antiqua were investigated by weekly and monthly samplings in relation to nutrients. To test how well the water in the samples supported the growth of C. antiqua, bioassays of growth of a cultured strain of C. antiqua were also conducted. In closed-off sections of the sea, DIN and DIP concentrations increased and then C. antiqua bloomed at the end of August. In the bioassays, C. antiqua growth decreased with the lack of N-, P- or Fe-sources in comparison with the growth in the complete media. However, the addition of N-source promoted the growth although the addition of P- or Fe-sources had almost no effect, in comparison with basic seawater. The present study indicates that C. antiqua growth is limited primarily by N-source, and secondarily by P- and Fe-sources in the Yatsushiro Sea.

Shikata T.,Prefectural University of Kumamoto | Shikata T.,Graduate University for Advanced Studies | Sakurada K.,Kumamoto prefectural Fisheries Research Center | Jomoto Y.,Prefectural University of Kumamoto | And 4 more authors.
Nippon Suisan Gakkaishi (Japanese Edition) | Year: 2010

In the Yatsushiro Sea, we investigated the population dynamics of phytoplankton and some environmental factors, such as water temperature, salinity and underwater visibility. The field investigations at 8 offshorestations and Himedo were conducted monthly from April 2008 to March 2009 and weekly from June to October 2008, respectively. Moreover, we examined the growth of main phytoplankton species under different conditions of temperature, salinity and light intensity in the laboratory. Diatoms such as Skeletonerna costa turn, Chaetoceros spp., Thalassiosira spp. and Asterionellopsis gracialis dominated throughout the investigation periods, except for a Chattonella antiqua bloom in August 2008 in the sea. However, the dominant species of diatom fluctuated over time. Laboratory studies indicated that the growth characteristics of main phytoplankton species under different condi tions of water temperature and salinity vary among species, where as the growth characteristics under different light intensities are similar to each other; the growth of most phytoplankton species tested saturated at a light intensity of 80 mo-2 ms-1 . From statistical analyses with laboratory data, we found that the seasonal and temporal dynamics of dominant phytoplankton species are closely related to water temperature and salinity and underwater light intensity, respectively, in the Yatsushiro Sea.

Egoshi K.,Kurume Shin Ai Womens College | Oka T.,Kurume Shin Ai Womens College
Nippon Shokuhin Kagaku Kogaku Kaishi | Year: 2012

A determination method ofmelatonin in boiled rice using precolumn derivatization was developed. The extraction method was as follows. Boiled rice (20 g), 10 g of distilled water and 0.1 g a-amylase were weighed into a mortar, the boiled rice was liquefied by homogenization at 40? for 10 min, and stirred for 20 min on a magnetic stirrer. Then, 2.5 g of Na2 CO3 was added to the mixture, the mixture was homogenized by a glass homogenizer, and stirred for 60 min at room temperature. The melatonin in the mixture was extracted with dichloromethane and adsorbed to Sep-Pak Silica cartridge. The adsorbed melatonin was eluted by dichloromethane/ methanol (1:1), and the eluant was evaporated to dryness. For the derivatization ofmelatonin, 150 μL ofaqueous 2 mol/L Na2 CO3, 100 μL of100 mmol/L H2 O2, 50 μL of1 mmol/L CuSO4 and 700 μL ofwater were added to the residue, and the mixture was heated in a water bath (94-96?) for 6 min. The synthesized melatonin derivative was extracted with ethyl acetate, evaporated to dryness, dissolved in 15% (v/v) aqueous CH3 CN, and subjected to HPLC analysis. When standard melatonin was added to the liquefied boiled rice, the recovery rate was 99.6±6.9% (mean±S.D; n=6) for milled rice and 76.7 ±5.6% (n=4) for brown rice. Melatonin content in boiled rice was determined to be 71.6 and 86.2 pg/g for two cultivars of milled rice 107.0 and 130.2 pg/g for two cultivars of brown rice, and 36. 2, 36. 6 and 50. 5 pg/g for three brands of commercial packaged boiled rice. These results suggest that the present method is suitable for the determination of melatonin in boiled rice.

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