• Journal of fish pathology
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• v.36 no.2
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• pp.287-292
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• 2023

This study investigated the genetic determinants of plasmid-mediated antibiotic resistance (PMAR) to quinolones and tetracycline in 106 Aeromonas strains isolated from eel (Anguilla japonica, 70 strains) and ornamental fish (36 strains) in Korea. Quinolones and tetracycline resistance phenotypes were found to be widely distributed throughout the both fish groups. However, the prevalence of qnr and tet genes was higher in ornamental fish strains than in eel strains (42.9% vs. 86.1% for qnr and 51.4% vs. 69.4% for tet). In addition, the profiling of the present genetic determinants revealed the dominance of qnrS, tetA, tetE and tetE+qnrS genes for eel strains but of tetA+qnrS qnrS and tetE+qnrS genes for ornamental fish strains. These results indicate that aquaculture and related industries could be a major threat to public health due to the possible spread of PMAR.

• Development and Reproduction
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• v.12 no.3
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• pp.261-266
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• 2008

In the present study, we investigated in vivo effects of Manchurian trout recombinant gonadotrophin hormone (mt-rGTH) on the induction of maturation in female eel, Anguilla japonica. The brood stock, female eel (450$\pm$50 g) were weekly injected intramuscularly with different doses of 0.1, 1, 10 ${\mu}g\m{\ell}$/fish (mt-rFSH or mt-rLH) for 10 week. The effects of r-mtGTH were analyzed by gonadosomatic index (GSI), ovarian follicle diameter and sex steroid levels. All groups did not exhibit significant differences in the GSI values. Whereas plasma testosterone (T) and estradiol-17$\beta$ (E2) levels did not change significantly in control group, plasma levels of T and E2 by injection of the r-mtFSH or r-mtLH were increased at 2 or 4 week after injection. In addition, injection of the mt-rFSH (1, 10 ${\mu}g/m{\ell}$/fish) or mt-rLH (0.1, 1, 10 ${\mu}g/m{\ell}$/fish) significantly increased follicle diameters comparing to the control group. These results demonstrate that the recombinant hormone may affect early ovary development and maturation in female eel. Taken together, these results suggest that the recombinant Manchurian trout FSH and LH are effective for reproductive activities in female eel.

• Journal of Life Science
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• v.23 no.10
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• pp.1288-1294
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• 2013

Knowledge of morphological changes in eel larvae is very important for artificial rearing of eel larvae. In this study, we investigated the morphological structure of the head region and histological changes of the eye retina in artificially reared larvae at various stages and in glass eel just after metamorphosis. Structural changes were observed in the upper jaw (maxilla) and the lower jaw (mandible) after 100 dah (day after hatchery) and after metamorphosis. Teeth had degenerated by the time of completion of metamorphosis. Major histological changes observed in the eye retina were the formation of the outer plexiform layer and the outer nuclear layer from 100 dah larva and a change in the rod cell layer after metamorphosis. The cornea was not observed at 10 dah in the eel larva. More information is needed on the early developmental stages of eel larvae to enable mass production of glass eels. The results obtained in the present research will be useful when developing novel rearing programs for eel larvae.

• Korean Journal of Veterinary Research
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• v.44 no.4
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• pp.643-648
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• 2004

Efficacy of ciprofloxacin was evaluated in laboratory and field studies for control of streptococcal infection in flounder and eel. In disc diffussion test, all streptococcal strains showed high sensitivity to the ciprofloxacin. Minimum inhibitory concentrations of ciprofloxacin against all streptococcal strains used in this study were less than $0.195{\mu}g/ml/$. In laboratory studies where fishes were challanged with Streptococcus iniae, significant reductions in mortality were observed among fish receiving ciprofloxacin (in fed) at 100 mg/kg/body weight or more daily for 3 d when compared with mortality of non-medicated controls. Similar results were achieved when 100 mg/kg/body weight of ciprofloxacin was used in field trials.

• Journal of fish pathology
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• v.20 no.3
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• pp.291-297
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• 2007

The effect of aspirin on the recovery of nitrite-induced methemoglobinemia in cultured eels (Anguilla japonica) was studied. Methemoglobinemia was induced by exposing eels to nitrite (120 ㎎ NO2-N/ℓ) for 24 hr. The nitrite exposed eels were bathed in 20 ppm aspirin solution (Aspirin), 0.8 % NaCl solution (NaCl), 20 ppm aspirin plus 0.8% NaCl solution (NaCl + Aspirin) and 50% nitrite free water(control) for 24 hr to recover from nitrite toxicity. Peripheral blood was taken from the arterious bulb from all groups to analyse hematocrit value, hemoglobin concentration, and nitrite concentration of the blood. Histopathological features of gill were also observed. Aspirin and control groups were more effective than NaCl and NaCl + Aspirin groups in recovery of hematocrit value and hemoglobin concentration, methemoglobin rate and nitrite concentration. The histopathological features on the gill of aspirin group were similar to those of normal eels, but other groups showed focal hyperemia in the lamellar carpillaries, epithelial hyperplasia. These results suggested that aspirin was very effective to recover from methemoglobinemia in nitrite-induced cultured eels.

• Journal of fish pathology
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• v.15 no.2
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• pp.49-56
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• 2002

Effects of Temperature on the Pharmacokinetics of norfloxecin (NFX) were studied in the cultured carp,Cyprinus carpio, and cel, Anguilla japonica, using high performance liquid chromatography (HPLC) originally developed for quinolone determination in livesrocks. Pharmacokinetics of NFX was apparently affected by ambiem water temperature. In a two-compaament model for carp after oral dosage of 20 mg/K01 at $13^{\circ}C$ and $23^{\circ}C$ and 5.20/hr, respectively. In carp the $K_{\iota\nu}$, $T_{max}$and $C_{max}$ for carp at $13^{\circ}C$ were 13.30/hr, 17.44 ${\mu}g$/$m\ell$ and 7.00 ${\mu}g$/$m\ell$, respectively. The" correspoeding values at $23^{\circ}C$ were 3.93/hr, 15.40 ${\mu}g$/$m\ell$ and 9.44 ${\mu}g$/$m\ell$, respectively. The AUC and T were 355.66 ${\mu}g$ hr/$m\ell$, and 12.70 hr at $13^{\circ}C$ and 417,24 ${\mu}g$ hr/$m\ell$ and 13.86 hrs at $23^{\circ}C$, respectively. Similar trends were revealed in the NFX pharmacokinetics of eel kept under the two water temperature regimes aftee oral NFX dosage of 20 mg/kg. These pharmacokinetkal results have some implication in the optimal usage of recently introduced antibacterials in farmed fish, which were originally adapted for poultry and mammalian species.

• Journal of fish pathology
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• v.33 no.2
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• pp.153-161
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• 2020

Cytochrome P450(CYP) gene is involved in the biotransformation of drugs and environmental pollutants. In this study, we analyzed the nucleotide sequence of the Anguilla japonica CYP1(AjCYP1) family gene and examined the relative expression of AjCYP1A, AjCYP1B and AjCYP1C1 in response to the exposure to environmental pollutants. After exposure to B[a]P 20mg/kg bw, the expression of AjCYP1 family gene increased over time. Among four tissues examined (liver, spleen, gill and kidney), AjCYP1 family gene was expressed significantly in the kidney. Compared with the control group, AjCYP1A was expressed about 5-fold at 48 hr, AjCYP1B about 6-fold at 24 hr, and AjCYP1C1 about 4-fold at 24 hr. However, after exposure to B[a]P 200mg/kg bw, AjCYP1A did not change in all tissues. On the other hand, AjCYP1B was expressed at about 4-fold at 24 hr in the spleen and 4-fold at 48 hr in the gill. Finally AjCYP1C1 was expressed 3.7-fold and 4.3-fold in the spleen and kidneys at 48 hr, respectively. Taken together, our results suggest that the expression of AjCYP1 gene in eel tissues might be used as a useful tool to assess the exposure to environmental pollutants in aquaculture system.

• Proceedings of the Korean Aquaculture Society Conference
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• 2005.05a
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• pp.117-117
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• 2005

• Proceedings of the Korean Aquaculture Society Conference
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• 2004.05a
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• pp.360-361
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• 2004

• Journal of fish pathology
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• v.14 no.1
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• pp.31-36
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• 2001

A novel clonidine binding sites were characterized in the intestinal membrane isolated from seawater eels, Anguilla japonica. The specific clonidine binding sites consisted of at least two classes, high affinity ($K_d=1.4{\pm}0.3$ nM n = 5) and low affinity ($K_d=175{\pm}34$ nM n = 5) sites. The specific binding of 2 nM [$^3H$]clonidine was most enhanced at $20^{\circ}C$ and pH 7.5, and reversed by unlabelled clonidine. Such binding was hardly inhibited by adrenaline, yohimbine or rauwolscine, indicating that most binding sites are distinct from $\alpha_2$-adrenoceptor. The specific clonidine binding sites was inhibited by various imidazoline/guanidinium drugs, indicating existence of imidazoline/guanidinium receptive sites (IGRS) or imidazoline receptors in the eel intestine. Competition experiments revealed that rank order to displace 2 nM [$^3H$]clonidine from their binding sites was as follows : guanabenz > cirazoline = naphazoline = UK14,304 = ST587 $\geq$ clonidine $\geq$ idazoxan = RX821002 = tolazoline > ST93 = oxymetazoline = amiloride = ST91 > yohimbine = efaroxan = rauwolscine $\geq$ adrenaline = ST567 = histamine = agmatine. Although physiological role of IGRS is not clear yet even in mammalian cell/tissues, eel intestine may be a good model to elucidate how the IGRS act in the cell and to decide what is the endogenous ligand for the IGRS.