• Journal of Aquaculture
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• v.19 no.3
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• pp.197-204
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• 2006

The pathogenicity and infection route of the Scuticociliate, Philasterdies dicentrarchi, were investigated with the 3 and 5 cm-group of juvenile flounders, Paralichthys olivaceus. The infection rates of 3 cm-group were 40% four days post infection (D.P.I.) and increased to be 90.1% 24 D.P.I., whereas those of 5 cm-group were 20% 8 D.P.I., 42% 16 D.P.I., and 81% 24 D.P.I. The results showed there were several infection routes to internal organs Olive flounder. The first route was started with the infection at the soft part of caudal fin and later reached at fin ray and muscle tissue; the second one was started from lips and mouth tissue of upper jaw and later the pathogen could be observed at either muscle tissue or eyeball and brain; the third one was begun at caudal fin and later the pathogen reached at brain tissu'e through spiral cord; the fourth one was started with the infections at abdominal cavity and anus. P. dicentrarchi infected to brain tissue was first observed 14 D.P.I in 3 cm-group and 20 D.P.I. in 5 cm-group of the juvenile flounder. This indicated that the brain infection of P. dicentrarchi might occur faster in small-sized flounder than large-sized one.

• Journal of Aquaculture
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• v.16 no.3
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• pp.151-158
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• 2003

This study was conducted to estimate the effects of residual chlorine dioxide ($CIO_2$) in chlorinated seawater on survival and physiological responses (hematocrit: Ht, hemoglobin: Hb, serum electrolyte and glucose levels, and osmolality) of olive flounder, Paralichthys olivaceus. All the flounders were exposed for 10 min to different concentrations of residual $CIO_2$ just after chlorination for 1 min in each experimental aquarium (EA). ClO$_2$-free seawater was continuously supplied to each EA after 10 min exposure to $CIO_2$. By means of probit analysis, the median lethal times (LT$_{50}$, min) of flounder exposed to 0.43 and 0.51 ppm $CIO_2$, were at 103 and 32 min, respectively. In the range from 0.34 to 0.51 ppm $CIO_2$, the values of Ht, Hb, electrolytes and osmolality of fish exposed to $CIO_2$ were significantly elevated as elapsed time and residual concentrations of $CIO_2$ increased after chlorination. The levels of Ht, Hb, electrolytes and osmolality in flounder exposed to 0.27 ppm $CIO_2$ were not significantly different compared to control fish, which were maintained in $CIO_2$-free seawater; however, the levels of serum glucose were significantly increased with elapse times.

• Korean Journal of Ichthyology
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• v.20 no.4
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• pp.248-254
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• 2008

Olive flounder (Paralichthys olivaceus) is one of the most popular farmed fish in Korea. Genetic variability of the fish was investigated by means of microsatellite DNA markers. All of the 8 microsatellite loci were analyzed in this study. For the confirmation of genetic variation during a shift in generation, microsatellite variability was compared within the same hatchery strains but produced in different spawning years. When genetic variability of farmed flounders produced in 2006 and 2007 was compared with that of 2003, a marked reduction of genetic variability was observed in the 2006 and 2007 populations. Mean number of alleles per locus and expected mean heterozygosity decreased from 9.75 and 0.796 (in 2003 population) to 7.78 and 0.785 (in 2006 population), respectively. Moreover, we have observed the distortion of allele frequency. These results show that reduced genetic variability of farmed olive flounder in processed generation has lower numbers of alleles and genetic variability than these of wild fish. Our results suggest that to have a sustainable aquaculture of this species, there is need for scientific broodstock management based on genetic variation and more intensive breeding practices to improve genetic diversity and to avoid detrimental inbreeding effects.

• Korean Journal of Microbiology
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• v.42 no.3
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• pp.199-204
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• 2006

Streptococcosis of olive flounder(Paralichthys olivaceus) is an important bacterial disease in Jeju island. In this study, we investigated monthly infection pattern of this disease in different size of the flounder fish. Even though the disease occurred throughout the year, the infection ratio was relatively higher in the months with warm water season. The infection was more prevalent in adult flounder over 30 cm total length compare to these of small size fish. Two infectious species of streptococcosis pathogens were detected by multiplex PCR assay. Detection ratios of Streptococcus iniae and S. parauberis reached up to 46% and 54%, respectively, from June 2003 to May 2005 in Jeju island. S. iniae occurred intensively from September to October, whereas S. parauberis reported from March to May. S. iniae and S. parauberis infections of cultured flounder share some common features, but clinical findings showed considerable differences between two diseases. Distended abdomen, protruded anus and ascitic fluid in the peritoneal cavity are evident lesions detected in S. iniae infection, whereas, flounders infected by S. parauberis showed prominent lesions such as darkened surface and haemorrhaging in the non-ocular side. Both streptococcosis pathogens were sensitive to antibiotics, such as ampicillin and amoxicillin. However, S. iniae strains were more sensitive to doxycycline, erythromycin and oxytetracycline than S. parauberis strains.

• Microbiology and Biotechnology Letters
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• v.50 no.3
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• pp.347-353
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• 2022

In this study, the effect of a synbiotic mixture of probiotics and 3% inulin on the growth, non-specific immune response, and mortality due to disease resistance of Paralichthys olivaceus was investigated. The results revealed that an 8-week diet of synbiotic-added feed, had no significant effect on the growth of P. olivaceus, Analysis of the hematological parameters revealed that there was a significant difference in the content of AST, total protein, and cholesterol among the groups, whereas there was no significant difference in the ALT and glucose contents. Further, there was no significant difference in the lysozyme activity of the synbiotic and control group after 8 weeks' feeding. In addition, when the symbiotic mixture was used rather than probiotics alone, the NBT activity of the synbiotic group increased compared to that of the control group. Moreover, when only probiotics were used, the cytokine expression in the spleen of the samples was significantly lower than that in the control group, whereas the expression was significantly higher in the spleen of the synbiotics group. However, there was no significant difference in the cytokine expression in the liver, intestine, and kidney of the three groups. Lastly, after injection for 2 weeks, the mortality rates of the control group towards Edwardsiella tarda, Streptococcus parauberis, and Streptococcus iniae were 95, 85 and 85%, respectively; those of the probiotics group were 85, 80, and 80%, respectively; and those of the synbiotics group were 80, 80, and 85%, respectively.

• Journal of fish pathology
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• v.36 no.2
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• pp.337-348
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• 2023

This study was undertaken to evaluate the effect of amprolium hydrochloride on detoxification process of olive flounder Paralichthys olivaceus. A series of two experiment was performed based on the LD₅₀ value obtained for amprolium. First, thirty flounder (average weight 230.27 g; average length 27.99 cm) was randomly allocated into five groups. Treatment was carried out using intra-muscular injection of amprolium at the dose levels of 4, 8, 16, and 32 mg/kg body weight. At 8, 24 and 48 h post injection, liver and kidney were collected for expression assay of drug metabolizing enzymes and pro-inflammatory cytokine genes. We found that the interleukin-1β (IL-1β) mRNA level were induced at 32 mg/kg and CYP1A genes showed the opposite pattern, while UDP-glucuronosyl-transferase (UGT1A7) and GST were significantly reduced in the liver. Moreover, the suppression of drug metabolizing enzymes and cytokine gene in the kidney was observed after treatment. Another treatment was carried out using intramuscular injection with 4, 8, 16, and 32 mg/kg and 60, 80, 100, 120 mg/kg body weight. At 6 days post injection, liver was collected. The IL-1β expression was markedly induced in the experimental group treated with 4 mg/kg. In addition, glutathione S-transferase (GST) mRNA level was higher in the group with 4 mg/kg. In conclusion, our data suggests that amprolium seem to cause direct or indirect physical, or biological toxicity of flounders, although this drug is considered one of the safest synthetic anticoccidial drugs of the livestock industry.

• Journal of fish pathology
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• v.10 no.2
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• pp.97-111
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• 1997

In the winter of 1995, mass mortality occurred in cultured flounder, Paralichthys olivaceus in Gurongpo, Kyoungbuk, Korea. From the observations of moribund and dead fish, parasitic ciliates, which were shown as white spots to the naked eye, were considered to be involved in the mass mortality. From heavily infected flounders, histopathological, morphological and biological characterization of these ciliates were carried out. In the histological observation, many ciliates were found under the epithelia of gill filaments and skin, and caused hyperplasia of epithelial and mucus cells at the infected areas. The ciliates found on the body surface, fins and gills were very similar to Cryptocaryon irritans. However the ciliates showed two different patterns of reproductian, i.e., typical form(palintomy)and atypical form(budding plus multiple fission) at $16^{\circ}C$ of water temperature. The occurrence ratio between typical and atypical form was about 3:2. Tomitogenesis takes 8-14 days in the typical and 13-15 days in the atypical form. In the viability test at different temperatures and salinities, the typical form died below 30‰ at $12^{\circ}C$, below 20‰ at $16^{\circ}C$, below 15‰ at $20^{\circ}C$, and below 25‰ at $24^{\circ}C$, respectively. On the other hand, the atypical form died below 20‰ at $12^{\circ}C$, below 15‰ at 16-$20^{\circ}C$, and below 25‰ at $24^{\circ}C$, respectively. The results suggested that the atypical has better viability at low salinity than that of the typical at low temperatures. In the excystment time and success rates of excystment according to temperatures, the typical form showed 8 days, 30% at $12^{\circ}C$ : 6.5 days, 50%, at $16^{\circ}C$ : 5.5 days, 75% at $20^{\circ}C$ : and 7 days, 10% at $24^{\circ}C$, respectively. On the other hand, the atypical form showed 15.5 days at $12^{\circ}C$ : 14 days, 76.6% at $16^{\circ}C$ : 12 days, 72.2% at $20^{\circ}C$ : 10 days 31.6% at $24^{\circ}C$, respectively. The results suggested that the atypical form had longer excystment time than that of the typical form at any temperature and showed better stability at low temperatures.

• Journal of Life Science
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• v.27 no.11
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• pp.1369-1375
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• 2017

The purpose of this study was to investigate the cellular characterization of phospholipase C-${\delta}1$ in olive flounders (Paralichthys olivaceus). In general, phospholipase C signaling pathways are distributed in nuclei at plasma membranes and in cytoplasms, although the pathways' nuclear localization mechanisms are unclear. P. olivaceus duplicates type-A PoPLC-${\delta}1$ (PoPLC-${\delta}1A$), which has a high similarity to the human isoform PLC-${\delta}$; type-B PoPLC-${\delta}1$ (PoPLC-${\delta}1B$ [Sf]), which has a low similarity to the human isoform PLC-${\delta}$ and the alternative splice variant PoPLC-${\delta}1B$ (Lf), which has a nuclear localization signal (NLS) and a nuclear export signal (NES) for nuclear imports and exports, respectively. This study confirmed the effects of the cellular localization and translocation of GFP-tagged PoPLC-${\delta}1A$, PoPLC-${\delta}1B$ (Sf) and PoPLC-${\delta}1B$ (Lf). It administered treatments of $Ca^{2+}$ ionophore ionomycin and endoplasmic reticulum (ER)-$Ca^{2+}$ pump inhibitor thapsigargin to hirame natural-embryo (HINAE) cells. A laser-scanning confocal microscope was used. GFP-tagged PoPLC-${\delta}1A$ was distributed to the cellular organelles, rather than to the cytoplasms and cytomembranes, when PoPLC-${\delta}1B$ (Lf) and PoPLC-${\delta}1B$ (Sf) were localized at the plasma membranes. The treatments of ionomycin and thapsigargin showed the accumulation of PoPLC-${\delta}1A$ in the nuclei when PoPLC-${\delta}1B$ (Lf) nucleocytoplasmic shuttling and PoPLC-${\delta}1B$ (Sf) nucleocytoplasmic shuttling were not observed. The results were the first evidence that PoPLC-${\delta}1A$, which contains functional, intact NES sequences, has a main role in nucleocytoplasmic shuttling and translocation in fish.

• Journal of fish pathology
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• v.31 no.1
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• pp.23-34
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• 2018

The pharmacokinetic properties of cefadroxil (CDX) were studied after oral administration for 7 days to cultured olive flounders (average 660 g), Paralichthys olivaceus. For examination of pharmaco-kinetic profiles, CDX of 45 to 225 mg/kg body weight was administered at two different water temperatures, $13{\pm}3^{\circ}C$ or $22{\pm}3^{\circ}C$. CDX concentrations were determined in muscle, plasma, gastrointestinal tract, hematopoietic organs and liver by HPLC-MS/MS. Muscle samples were taken at 0.25, 0.5, 1, 3, 7, 14 and 28 days post dose, whereas plasma, gastrointestinal tract, hematopoietic organs and liver concentrations were measured at 1, 3, 7, 14 and 28 days post-dosing. The kinetic profiles of $C_{max}$, $T_{max}$, $T_{1/2}$ of CDX were analyzed by fitting to a non-compartmental model with PKSolver program. The following pharmacokinetic parameters were obtained with oral administration of 45 and 225 mg/kg at 13 and $22^{\circ}C$ in muscle, plasma, gastrointestinal tract, hematopoietic organs and liver, respectively: $C_{max}$ (maximum tissue concentration)=$985.98-5,032.86{\mu}g/kg$, $5,670.99-38,922.23{\mu}g/l$, $2,457.27-10,192.78{\mu}g/kg$, $886.04-3,070.87{\mu}g/kg$ and $1,188.15-3,814.33{\mu}g/kg$; $T_{max}$ (time for maximum concentration)= every 1 day; $MRT_{0-{\infty}}$ (mean residence time)= 1.51-4.74, 2.12-3.06, 4.25-13.18, 1.37-18.66 and 1.78-29.76 days; $T_{1/2}$ (half-life)= 1.08-3.47, 1.14-5.42, 3.56-10.99, 1.17-14.93 and 1.25-28.55 days.

• Microbiology and Biotechnology Letters
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• v.47 no.1
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• pp.132-138
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• 2019

Among several marine-derived microorganisms isolated from the coast of Jeju Island that had antimicrobial activity against fish disease pathogens, Bacillus subtilis MD-02 was tested for its dietary effect on the innate immune response and disease resistance of olive flounder. Strain MD-02 was fed to the olive flounder at a concentration of $1.2{\times}10^4$, $1.2{\times}10^6$, or $1.2{\times}10^8CFU/100g$, respectively. Consequently, the hematocrit was higher in these three groups than that in the control group at 4 weeks, and the aspartate aminotransferase and alanine aminotransferase levels were decreased in the $1.2{\times}10^8$ and $1.2{\times}10^4CFU/100$ groups compared with the control group levels. The amylase activity and total protein were significantly increased in the $1.2{\times}10^4CFU/100g$ group at 3 weeks. The innate immune response, determined from the lysozyme and macrophage activities, was higher in the $1.2{\times}10^8CFU/100g$ group than in the control group. In addition, treatment of the olive flounders with Streptococcus parauberis at $1.2{\times}10^6CFU/ml$ confirmed the mortality rate, which was 100% in the control group and 40-60% in the groups fed B. subtilis MD-02, indicating that the fish had resistance to fish disease pathogens. Therefore, it was confirmed that when fed MD-02, olive flounder builds an innate immune response and acquires resistance to fish disease pathogens, indicating that B. subtilis MD-02 can be developed as a beneficial feed additive.