• Fisheries and Aquatic Sciences
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• 제5권3호
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• pp.191-199
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• 2002

Pacific oysters Crassostrea gigas (Thunberg) were collected on April, 1999 and March­September, 2000 from Goseung Bay along the southern coast of Korea. The oysters tested cp;;ected from a depth of 0.5-2 m in which they cultured by a long line hanging method. The oxygen consumption rates (OCR) of oysters held under constant temperature and darkness (CC), were determined using an automatic intermittent-flow-respirometer (AIFR). Depending on holding periods after oyster collection, the experiments were divided into two groups: Group 7-d (held to ambient temperature for ca. 7 days) and Group 2l-d (held to ambient temperature for ca. 21 days). The OCR for Group 7-d single oyster displayed two peaks every day under CC, while Group 2l-d single oyster showed one peak every day. It is likely that the rhythmic patterns 02.6-12.8 hours) of the OCR in the Group 7-d single oyster may have been influenced by tidal currents at the sampling site. The rhythmic patterns (24.3-24.7 hours) in the Group 2l-d single oyster may have been shifted from two peaks to one peak each day under CC. The present study concludes that the OCR rhythm of wild oysters in nature is governed by two lunar-day clocks (24.8 hours); one driving one peak and the other driving the second peak. When oysters are subjected to the long-term CC conditions, one of the two-clock systems is depressed or only intermittently becomes active. Jpwever. the OCR rhythms by two to three oysters occurred arrhythmic patterns during the experiments and exhibited some evidence of weak rhythmicity of compared to those of a single oyster. It could be partly due to differences group effects.

• Fisheries and Aquatic Sciences
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• 제24권4호
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• pp.171-179
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• 2021

To better understand the ecological functioning of the coastal ecosystem in Gamak Bay on the southern coast of Korea, seasonal changes in the density, biomass, and secondary production of the copepod community were investigated. Environmental measurements (temperature, salinity, and chlorophyll a) and copepod sampling were performed seasonally from January to December 2006. The mean density of copepods (excluding nauplii) varied from 949 to 5,999 ind · m^-3; copepod density was at its highest from March to July. The copepod community comprised 32 taxa, including Calanoida, Cyclopoida, and Harpacticoida. The predominant species were Paracalanus parvus s. l., Acartia omorii, Eurytemora pacifica, Oithona similis, A. erythraea, Centropages abdominalis, Pseudodiaptomus marinus, and Calanus sinicus. There were significant spatial and seasonal variations in copepod total biomass, which ranged from 0.33 to 43.10 mg C m^-3. Mean secondary production of the copepods in Gamak Bay, estimated as 2.05 ± 1.63 mg C m^-3 d^-1 using the Huntley and Lopez growth model, was over 2 times higher than the value given by application of the Hirst and Bunker model (1.09 ± 0.85 mg C m^-3 d^-1). The daily production rate to biomass (P/B) ratio varied between 0.08 and 0.86 d^-1 (Huntley and Lopez model), and 0.18 and 0.33 d^-1 (Hirst and Bunker model). Our results emphasize the ecological significance of using models to estimate the secondary production of copepods and provides the first report of copepod production in Gamak Bay.

• Bulletin of the Korean Chemical Society
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• 제32권5호
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• pp.1645-1649
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• 2011

[ ${\beta}$ ]Ketoacyl acyl carrier protein synthase I (KAS I) is involved in the elongation of unsaturated fatty acids in bacterial fatty acid synthesis and a therapeutic target of designing novel antibiotics. In this study, we performed receptor-oriented pharmacophore-based in silico screening of E. coli KAS I (ecKAS I) with the aim of identifying novel inhibitors. We determined one pharmacophore map and selected 8 compounds as candidates ecKAS I inhibitors. We discovered one antimicrobial compound, YKAe1008, N-(3-pyridinyl) hexanamide, displaying minimal inhibitory concentration (MIC) values in the range of 128-256 ${\mu}g/mL$ against MRSA and VREF. YKAe1008 was subsequently assessed for binding to ecKAS I using saturation-transfer difference NMR spectroscopy. Further optimization of this compound will be carried out to improve its antimicrobial activity and membrane permeability against bacterial cell membrane.

• Fisheries and Aquatic Sciences
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• 제12권3호
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• pp.194-202
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• 2009

Sulfated fucans are known to have both anti-thrombotic and anti-coagulant activities. In this study, the variation in platelet aggregation and anti-coagulant activities was investigated in vitro with regard to administered dose, molecular weight distribution, sulfate content, and sugar composition in two algal fucoidans from Eisenia bicyclis and Undaria pinnatifida sporophylls (Mekabu). The anti-coagulant activity largely correlated with sulfate content and with molecular weight distribution in a dose-dependent manner. However, both fucoidans demonstrated inhibitory responses to ADP-induced platelet aggregation in dose- and structure-dependent manners that contrasted with the anti-coagulant activity. Neither molecular weight distribution nor sulfate content greatly affected platelet-aggregation inhibition (PA-inhibition) by the fucoidan fractions, whereas anti-coagulant activity was sensitive to these structural factors. Interestingly, an E. bicyclis fucoidan fraction exhibited almost complete PA-inhibition at a treatment dose of 500 mg/mL while retaining weak anti-coagulant activity. In conclusion, these observations suggest that fucoidan may be a useful anti-thrombotic or anti-platelet agent in various arterial thrombotic disorders, including post-vascular intervention with controlled bleeding complications, due to its anti-coagulant modulating activity.

• Fisheries and Aquatic Sciences
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• 제5권3호
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• pp.156-164
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• 2002

Enteromorpha prolifera of the isomorphic diploid sporophyte and the haploid gametophyte generations inhabit rocks, tidal flats and tidal pools in the middle parts of intertidal zones. In this experiment, their thalli were observed by bare eyes from October and experienced $74\pm16.5cm$ maximum growth the following March and April. The rate of occurrence of the thalli per month was highest in March, while their biomass peaked at $1,464\pm41.5 g/m^2$ in Jangheung in April. Genetic similarity was investigated samples of E. prolifera collected from Muan, Wando, Jangheung, Yosu and Jinhae, at the south coast of Korea. Random amplified polymorphic DNA (RAPD) markers were used. For the RAPD analysis, 3 ng of the DNA extracted from the thalli using he phenol/chloroform method was amplified by PCR with a 25 {\mu}L$ reaction solution, arbitrary primers and 36 cycles. Among the 60 primers used, 31 yielded products, most of which showed diverse electrophoresis patterns. Similarities among the groups compared ranged from 0.37 to 0.58. We conclude that the use of RAPD analysis is appropriate to characterize the genetic variability of this commercial species along its geographical distribution.

• Fisheries and Aquatic Sciences
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• 제6권4호
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• pp.172-179
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• 2003

The safety of pufferfish (Lagocephalus gloveri) liver oil and the contents of some nutritional components were examined to obtain important information on their use as high valued functional foods. Pufferfish liver oil was extracted by the hot-water method using $1\%$ NaOH solution to remove toxic compounds, and then purified using a general purifying method of fish oil. Any extraordinary clinical symptoms were not observed from all groups administrated with pufferfish liver oil throughout the test period. None of the rats died when administrated the highest concentration of 10 mL/kg of the pufferfish liver oil. Vitamin A content was 114.2 ppm, as a retinal equivalent in the oil extracted using hot-water, but the content was higher (169.3 ppm) in oil extracted using n-hexane. Vitamin D and E were not detected in ppm in oil extracted using hot-water. Vitamin D in the pufferfish liver oil extracted using n-hexane was also undetected, but vitamin E was at 32.5 ppm. Among the 18 minerals detected, the sodium content was the highest at 253.5 ppm, followed by 13.9 ppm ofpotassium, 1.5 ppm of calcium, 0.2 ppm of magnesium, and other trace minerals. The contents of EPA and DHA were $0.8\%\;and\;14.8\%$, respectively, in the pufferfish liver oil extracted using hot-water. Considering these results, there is potential that pufferfish liver oil could be used as a functional food.

• Bulletin of the Korean Chemical Society
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• 제32권9호
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• pp.3219-3222
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• 2011

Three types of ${\beta}$-ketoacyl acyl carrier protein synthase (KAS) are important for overcoming the bacterial resistance problem. Recently, we reported the discovery of a antimicrobial flavonoid, YKAF01 (3,6-dihydroxyflavone), which exhibits antibacterial activity against Gram-positive bacteria through inhibition of ${\beta}$-ketoacyl acyl carrier protein synthase III (KAS III). In this report, we suggested that YKAF01 can be an inhibitor ${\beta}$-ketoacyl acyl carrier protein synthase I (KAS I) with dual inhibitory activity for KAS I as well as KAS III. KAS I is related to the elongation of unsaturated fatty acids in bacterial fatty acid synthesis and can be a good therapeutic target of designing novel antibiotics. We performed docking study of Escherichia coli KAS I (ecKAS I) and YKAF01, and determined their binding model. YKAF01 binds to KAS I with high binding affinity ($2.12{\times}10^6$) and exhibited an antimicrobial activity against the multidrug-resistant E. coli with minimal inhibitory concentration (MIC) value of 512 ${\mu}g$/mL. Further optimization of this compound will be carried out to improve its antimicrobial activity and membrane permeability against bacterial cell membrane.

• Fisheries and Aquatic Sciences
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• 제6권3호
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• pp.130-134
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• 2003

Proinflammatory effects of bacterial lipopolysaccharide (LPS) have been assessed by analysing the induction of two inflammatory genes, $interleukin-1\beta$ $(IL-1\beta)$ and cyclooxygenase-2 (COX-2), in rainbow trout (Oncorhynchus mykiss) macrophage cells. Production of a metabolite of arachidonic acid by COX-2, prostaglandin $E_2\;(PGE_2)$, was also analysed in macrophage cells after LPS stimulation. Northern blot analysis revealed that LPS $(5{\mu}g/mL)$ significantly upregulated $IL-1\beta$ (54 times) and COX-2 (40.7 times) gene expression in macrophage cells after 4 h stimulation. According to RT-PCR (Reverse Transcription Polymerase Chain Reaction) analysis, $IL-1\beta$ gene induction in LPS stimulated macrophage cells was started within 1h and significantly increased thereafter until 4h. Meanwhile, COX-2 gene induction by LPS was delayed in comparison with $IL-1\beta$ gene induction as a faint band was observed after 4h stimulation in head kidney macrophage cells. LPS also significantly increased $PGE_2$ production in head kidney leucocytes, presumably via activating COX-2 expression that metabolites arachidonic acid to $PGE_2$. In conclusion, it was demonstrated that LPS could induce two main inflammatory and immune related genes, $IL-1\beta$ and COX-2, and increase $PGE_2$ production in trout head kidney macrophage cells, representing a strong inflammatory activity.

• Fisheries and Aquatic Sciences
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• 제14권4호
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• pp.251-256
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• 2011

We screened for antibacterial substances against methicillin-resistant Staphylococcus aureus (MRSA). Methanolic extract of Eisenia bicyclis exhibited anti-MRSA activity according to a disk diffusion assay. To identify the active compound(s), the methanolic extract was further fractionated using hexane, dichloromethane, ethyl acetate, and n-butanol. The ethyl acetate-soluble fraction showed both the greatest anti-MRSA activity and the highest polyphenol content. The minimum inhibitory concentrations of the ethyl acetate fraction ranged from 32 to 64 ${\mu}g$ per mL against methicillin-susceptible S. aureus and MRSA strains. High-performance liquid chromatography analysis revealed that both the methanolic extract and the ethyl acetate soluble fraction contained sizeable quantities of dieckol, which is a known anti-MRSA compound. Thus, these data strongly suggest that the anti-MRSA activity of E. bicyclis may be mediated by phlorotannins such as dieckol.

• Fisheries and Aquatic Sciences
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• 제13권3호
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• pp.244-253
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• 2010

The quality of marine sediments from the industrialized coastal areas of Korea (Ulsan Bay, Masan Bay, and artificial Lake Shihwa) was investigated using a bacterial bioluminescence toxicity test. Sediment toxicity results were compared with the levels of chemical contamination (trace metals, organic wastewater markers, acid volatile sulfides, total organic carbon). Effective concentration 50% (EC50) of sediments ranged from 0.014 to 1.126 mg/mL, which is comparable to or lower than values in contaminated lakes, rivers, and marine sediments of other countries. Sediment reference index (SRI) ranged from 13 to 1044, based on the EC50 of the negative control sample. Mean average SRI values in Masan Bay and Lake Shihwa were approximately 8 and 9 times as high as that in Ulsan Bay, indicating higher sediment toxicity and greater contamination in the two former regions. Sediment toxicity were strongly associated with the concentrations of some chemicals, suggesting that this test may be useful for determining potential chemical contamination in sediments.