Innate immunity and protective effects of orally administered betaine against viral and bacterial diseases in the olive flounder Paralichthys olivaceus (Temminck & Schlegel).

Sustainable methods that increase farmed fish yield while controlling infections are required to prevent economic losses in aquaculture farms. In this study, we evaluated the effects of betaine-supplemented (0%, 0.1%, 0.5%, and 1.0%) feed on the growth and immunity of the olive flounder Paralichthys olivaceus. Feed conversion ratios, post-infection cumulative mortality rates and innate immune responses were monitored. Weight gain was significantly higher with 0.5% and 1.0% than with 0% and 0.1% betaine-supplemented feed. Lysozyme activity was highest with 1.0% betaine. Respiratory burst activity was highest with 0.5% and 1.0% betaine. Serum bactericidal activity against Edwardsiella tarda was highest with 1.0% betaine (40% increase in survival rates compared with those in the control). Furthermore, serum virucidal activity against the viral haemorrhagic septicaemia virus (VHSV) was higher with 1.0% betaine than with other concentrations. With 0.5% and 1.0% betaine, the survival rates against VHSV were higher than those in the control until day 11, after which they declined. Our study suggests that betaine is a promising agent for promoting the growth of and enhancing immunity against E. tarda in olive flounders. Our findings may further contribute to developing necessary alternatives to conventional antibiotics in fish farming.

Effect of TBT and PAHs on CYP1A, AhR and Vitellogenin Gene Expression in the Japanese Eel, Anguilla japonica.

Gene expressions of cytochrome P4501A (CYP1A), aryl hydrocarbon receptor (AhR) and vitellogenin (Vg) by endocrine disruptors, benzo[α]pyrene (B[a]P) and tributyltin (TBT) were examined in cultured eel hepatocytes which were isolated from eels treated previously with B[a]P (10 mg/kg) or estradiol-17ß (20 mg/kg) in vivo, and the relationship between CYP1A, AhR and Vg genes were studied. When the cultured eel hepatocytes were treated with B[a]P (10(-6)-10(-5) M) the gene expressions of CYP1A and AhR were enhanced in a concentration-dependent manner. However, when treated with TBT (10(-9)-10(-5) M) the gene expressions of CYP1A and AhR were suppressed at high concentrations (10(-6)-10(-5) M), while having no effects at low concentrations (10(-9)-10(-7) M). Gene expression of Vg was also suppressed by TBT in a concentration-dependent manner in cultured eel hepatocytes which was previously treated in vivo with estradiol-17ß.

Androgen action on hepatic vitellogenin synthesis in the eel, Anguilla japonica is suppressed by an androgen receptor antagonist.

Involvement of additional hormones other than estrogen in the control of vitellogenin (Vg) synthesis has been suggested in fish. However, no satisfactory explanation on the mechanism of the action of these hormones has been reported. In this study, we have exploited the possibility of androgen receptor mediation during the androgen action on the pathway of Vg synthesis. Hepatocytes were prepared from sexually immature Japanese eel Anguilla japonica and treated with estradiol-17beta (E2), 17alpha-methyltestosterone (MT), growth hormone, tamoxifen or flutamide, or in combination of these. Spent culture media were analysed by SDS-PAGE for Vg detection. Results from the chemical treatments demonstrated the necessity of E2 as the primary factor for Vg synthesis and requirement of additional hormones for the full expression of Vg. The effects of E2 and MT were effectively blocked by tamoxifen, an estrogen receptor antagonist and flutamide, an androgen receptor antagonist, respectively, indicating ER-mediated estrogen action and AR-mediated androgen action on Vg synthesis in this species.

Characterization of lipopolysaccharide responsive proteins that binds to the 5'-flanking regions of mouse Rantes.

When macrophage (like the RAW264.7 cell line) was stimulated with lipopolysaccharide (LPS), factors that bind specifically to the LPS responsive element (LRE) of murine Rantes gene appeared in the nucleus. An electrophoretic mobility shift assay (EMSA) detected 2 specific bands, designated as S (slow) and M (middle). The S band appeared within 15 min of LPS stimulation, and reached its highest intensity within 2 h. The M band was present in unstimulated cells, but after stimulation its intensity increased and reached its highest intensity also in about 2 h. Significantly, in LPS hyporesponsive 10-9 macrophage like cells, the S band was absent. The M band was present in equal amounts in stimulated and unstimulated cells. The results suggest that the S band was induced by LPS stimulation. In the nuclear extract, the native molecular weight of the S band-forming factor was approximately 270 kDa, and that of the M bands-forming factor was approximately 140 kDa. U.V. cross linking studies consistently showed at least 2 different polypeptides of approximate molecular mass of 70 kDa, both in the S band-forming factor (complex) and the M band-forming factor (complex). In the nuclear extracts of both the LPS stimulated and unstimulated cells, we detected a factor with approximate molecular mass of 120 kDa that could convert the S band-forming complex to the M band-forming complex. This factor, designated as a converting factor, is a protein phosphatase since its activity was blocked by okadaic acid, an inhibitor of Ser/Thr protein phosphatase. Also, purified protein phosphatase type 1 (PP-1) could convert the S band-forming complex to the M band-forming complex.