Java medaka (Oryzias javanicus), which is distributed in estuarine waters of East to Southeast Asia, is proposed here for consideration as a new marine test fish. Semi‐static acute toxicity tests were conducted at 26°C for 1 week, 2 weeks, and 1 month old Java‐medaka exposed to 4‐chlorophenol and zinc, and 2 weeks olds exposed to potassium dichromate (hexavalent chromium) and sodium hypochlorite (residue chlorine). Ninety‐six hours LC50s of 4‐chlorophenol, zinc, hexavalent chromium, and residue chlorine were from 3.0 to 4.1, from 12.4 to 14.7, 7.4, and 0.05 mg/L, respectively. There were no large differences in sensitivity for 4‐chlorophenol and zinc among the three growth stages. Compared with other fish species, these LC50s were relatively low suggesting that Java medaka has relatively high sensitivity to chemicals. This fish is quite easy to keep in the laboratory, with low mortalities at early stages and it takes about 3 months to mature from hatching, suggesting that this fish can be used not only for short‐term toxicity tests but also for early life stage toxicity tests. From these results, Java‐medaka is highly recommended as a marine test fish for ecotoxicity tests. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2008.

To assess possible adverse effects of residual chlorines from hypochlorite-treated seawater to non-target marine organisms, bioassays were carried out on marine amphipod Hyale barbicornis and estuarine fish Oryzias javanicus. Acute toxicity tests were first conducted using various concentrations of sodium hypochlorite (NaOCl) followed by a long-term exposure to residual chlorines from a test water treated with 1 mg L−1 NaOCl. Results showed that NaOCl was acutely toxic to both organisms. However, long-term exposure to residual chlorines from NaOCl-treated waters caused no major adverse effects to both organisms under laboratory conditions since free chlorines in the treated water was reduced to about 10% by 23-h holding and 1-h aeration. No H. barbicornis died but residual chlorine-exposed juveniles had significantly shorter body lengths at the end of exposure. Residual chlorine-exposed O. javanicus also showed no significant differences to that of the control in all measured endpoints except for hatching time. The results suggest that using 1 mg L−1 NaOCl for disinfection of ballast waters will produce residual chlorines that is far below the LC50 and EC50 of H. barbicornis and O. javanicus even on a long-term basis.

Estrone is a natural estrogen detected in sewage treatment works effluents and in estuarine waters. However, there is little information on the effects of estrone on marine fish. This study investigated the effects of estrone on reproduction of the estuarine fish, Java medaka ( Oryzias javanicus ). Java medaka were exposed to concentrations of 39, 198, 484, 1,188, and 3,701 ng/L of estrone from embryonic stages up to adult stages for 239 d after hatching. The fertility and egg numbers of Java medaka exposed to 1,188 and 3,701 ng/L were significantly lower than that of control. The hepatic vitellogenin concentrations in male Java medaka exposed to estrone greater than 484 ng/L were significantly higher than that of control. Oocytes in testis (testis‐ova) were not detected in the males in any of the exposure groups. The lowest‐observed‐effect concentration and no‐observed‐effect concentration for Java medaka were 484 and 198 ng/L of estrone. These results suggest that in relatively low estrone concentrations, 39 and 198 ng/L, Java medaka will not be affected by exposure to estrone.

Estrogens (17 B-estradiol and estrone) concentrations in river and estuarine waters around Kuala Lumpur, Malaysia were determined by enzyme-linked immunosorbent assay while estrogenic potential of the waters were ascertained by three in vitro bioassays, namely E-screen, Ishikawa cell-alkaline phosphatase and yeast estrogen screen. Moreover, hepatic vitellogenin, a precursor of yolk protein that is specific to females, were examined in male and female Java-medaka collected in the same area. 17B-estradiol and estrone concentrations were less than 6.1 ng/L and 127 ng/L, respectively. The highest 17B-estradiol equivalent activity, 284 ng/L, was detected by in vitro assay in Sungai Kuyoh, which was adjacent to a sewage plant. 17B-estradiol and estrone concentrations were not equal to their estrogenic potentials determined by in vitro assay implying the presence of other estrogenic chemicals in these waters. Hepatic vitellogenin concentrations of both male and female java-medaka were the same to laboratory-cultured individuals. Although relatively high estrogen concentrations were detected in some waters of Malaysia, these were not high enough to induce hepatic vitellogenin in male fishes. Further research, however, is necessary to cover more number of sampling sites.

17β-estradiol (E2) is a female hormone which is known to be one of the strongest estrogenic chemicals in the environment. The present study investigated the effects of E2 on the reproduction of the estuarine fish, Java-medaka (Oryzias javanicus). Starting from the embryonic stages, Java-medaka was exposed for 6 months to 9.5, 16, 68, 159 and 243ng/l of E2. The fecundity of Java-medaka exposed to E2 levels >16ng/l was significantly lower than that of the control. The appearance of secondary sexual characteristics seemed to be inhibited by exposure to 159 and 243ng/l E2. Vitellogenin concentrations in the liver of male fish exposed to 68, 159 and 243ng/l were significantly higher than that of the control. Thirty-three and sixty percent of male fishes exposed to 159 and 243ng/l, respectively, had testis-ova. These results suggest that reproduction in the Java-medaka, especially the male fish, could be affected by exposure to E2 concentrations greater than 16ng/l.

Background/Aims: During hepatic fibrosis:, hepatic stellate cells (HSCs) transform into myofibroblastic cells and lose their intracellular droplets of retinyl esters, the storage form of vitamin A. Recently, we have demonstrated that 9,13-di-cis-retinoic;acid (RA), a geometric isomer identified as. a stable and major metabolite of vitamin A in circulation, stimulates the synthesis of plasminogen activator (PA) and induces PA/plasmin-dependent latent transforming growth factor (TGF)-beta activation in HSC cultures, probably via induction and activation of RA receptor (RAR) a, The aim of the present study was to address a potential link between the loss of retinyl esters to increased formation of RA(s), which might play a role in facilitating TGF-beta-mediated liver fibrogenesis in vivo,Methods: We examined the effect of 9,13-di-cis-RA on transactivating activity of RARa in HeLa cells as well as its effect on PA- and TGF-beta-dependent collagen synthesis in rat and human HSC cultures, We measured the changes in 9,13-di-cis-RA levels both during activation of rat HSCs in vitro and during porcine serum-induced rat hepatic fibrosis in vivo and correlated this with RAR alpha/beta, PA, TGF-beta and type I procollagen mRNA expression in the fibrotic liver.Results: B,13-di-cis-RA transactivated RARa, and provoked PA/plasmin and TGF-beta-dependent procollagen synthesis in HSCs. 9,13-di-cis-RA levels were increased both in activated HSCs in vitro and in fibrotic liver accompanying the enhanced expression of RAR alpha/beta, PA, TGF-beta and procollagen in vivo.Conclusions: These findings suggest a potential link between 9,13-di-cis RA formation and hepatic fibrosis via formation of TGF-beta in vivo and thus provide further insight into the biologic role of retinoids during hepatic fibrogenesis.

We examined the effect of dietary oils with different fatty acid compositions on the growth of visceral adipose tissue in rats. Rats were fed for 4 mo starting at weaning a basal diet containing (12 g/100 g diet) perilla oil rich in (n-3) polyunsaturated fatty acids (PUFA), safflower oil rich in (n-6) PUFA, olive oil rich in monounsaturated fatty acid, or beef tallow rich in saturated fatty acids. The amount of food consumed and body weight gain did not differ among the four dietary groups. The weight of the epididymal fat pad and the serum triglyceride concentration in perilla oil-fed rats were significantly lower (P < 0.05) than those of olive oil- and beef tallow-fed groups. The product of [(volume of individual adipocytes) x (number of adipocytes in epididymal fat pad)], which presumably represents total adipocyte volume in the fat pad, was significantly lower (P < 0.05) in perilla oil-fed rats than in beef tallow- and olive oil-fed groups. Expression of the late genes of adipocyte differentiation, peroxisome proliferator-activated receptor alpha, adipocyte P2 and adipsin, was significantly (P < 0. 05) down-regulated in epididymal fat tissue of rats that had been fed perilla oil rather than beef tallow or olive oil, whereas expression of the early gene, lipoprotein lipase, was not significantly affected. Greater levels (P < 0.05) of (n-3) PUFA in the membrane phospholipid fraction of the fat tissue were observed in perilla oil-fed rats than in the other dietary groups. These results suggest that perilla oil or (n-3) PUFA prevents excessive growth of adipose tissue in rats at least in part by suppressing the late phase of adipocyte differentiation.

We studied the mechanism by which 9,13-di-cis-retinoic acid (9,13dcRA), a novel and endogenous stereoisomer of all-trans-RA, induces TGF-beta formation in a human liver stellate cell line, LI90. 9,13dcRA induced the expression of RAR alpha and RARbeta, enhanced the production of tissue-type plasminogen activator (tPA), thereby, surface plasmin levels, and induced the activation of latent TGF-beta. Similar effects were obtained with RAR alpha-selective retinoid, but not with RARbeta- or RARgamma-selective retinoid, and the induction was inhibited by RAR alpha-selective antagonist. These results suggest that 9,13dcRA up-regulates tPA expression, resulting in the formation of TGF-beta by LI90 cells, at least in part, via induction and activation of RAR alpha.

We studied a cell-cell interaction via transforming growth factor-beta (TGF-beta ) between liver stellate cells (SCs) and parenchymal cells (PCs) using co-cultures of rat primary SCs and PCs. Both TGF-beta added exogenously to the culture medium, and TGF-beta produced endogenously from SCs after stimulation with retinoic acid (RA), suppressed the production and secretion of albumin from PCs. This effect occurred at the translational level, but not at the transcriptional level; TGF-beta, as well as SC culture medium conditioned by RA, did not affect the albumin mRNA levels, but decreased the biosynthesis of [35-S]methionine-labeled albumin without altering its post-translational degradation rate. These results suggest that TGF-beta generated from SCs facilitates the development of liver cirrhosis not only by inducing the production of fibrotic components from SCs, but also by impairing the function of the surrounding PCs.