Eiji Okimasu

Immunostimulatory effects of fermented vegetable product on the non-specific immunity of Japanese flounder Paralichthys olivaceus

The stimulatory effect of fermented vegetable product (FVP) upon the phagocytic and superoxide generation of leukocytes was studied in the Japanese flounder Paralichthys olivaceus. The phagocytic activity of casein-induced, intraperitoneal leukocytes was investigated and quantified, that is the activity significantly increased (P<0.05 or <0.01) by the addition of FVP beyond 3 mg/kg body weight. Further analysis investigated the effect of FVP on superoxide generation in leukocytes. Established in vitro cytochrome c reduction assay was used to measure superoxide generation; reduced levels of FVP in assay samples had a profound effect on superoxide generation. FVP was also incorporated in commercial diets and fed to Japanese flounder for 4 weeks. The phagocytic activities and superoxide generation of peritoneal induced leukocytes were significantly higher (P<0.05, <0.01) in fish fed the FVP supplemented diet than fish fed the control diet. FVP feeding in fish had a significantly higher (P<0.05) activity of lysozyme than in the control fish.

The dietary effects of a fermented vegetable product on glutathione peroxidase activity and lipid peroxidation of Japanese flounder Paralichthys olivaceus

To study the dietary effects of fermented vegetable product (FVP) on the protection against lipid peroxidation of various tissues in Japanese flounder, Paralichthys olivaceus. The fish were fed on experimental diets with or without FVP for 4 weeks. The glutathione concentrations in serum or liver had a tendency to increase on FVP-feeding fish. The FVP-feeding fish showed higher glutathione peroxidase (GPx) activity of liver than the control fish, and the GPx activity was increased by the administration of 6 mg/kg body weight/day FVP (P<0.05). Conversely, fish fed on FVP containing diets exhibited significantly (P<0.05) lower lipid peroxidants of serum and liver than the control fish. The FVP is suggested to suppress lipid peroxidation in the administrated fish, which led to enhancement of antioxidant effect against cultured fish.

Isolation of a microalga, Synechocystis sp. SY-4, potentially useful as a rotifer feed

An algal strain, SY-4, that grows between 25°C and 35°C was isolated from coastal seawater by enrichment culture, and identified as a blue-green alga (cyanobacterium) of the Synechocystis species. This microorganism was found to be a potentially useful feed for rotifer culture.

Effect of a dietary fermented vegetable product on the heat shock response of Japanese flounder Paralichthys olivaceus

Stress is considered a major problem in fish culture, because fish are farmed under such conditions as poor water conditions, the presence of chemical components, and with handling stress. These conditions can be a cause of growth reduction, fish diseases, and poor survival [1, 2]. Fish will respond to a stressors by inducing a generalized physical stress response, which is characterized by an increase in stress hormones and other substances. The responses are similar to those of other vertebrates and help maintain normal conditions or homeostatic state [3, 4]. Recently, protection from fish diseases and reduction of several stresses have become major interests in fish culture. To overcome these problems, vitamins and other substance have been tried in cultured fish. The use of natural compounds as supplements is safer for the cultured fish and more effective means of reducing stress response in aquatic organisms. Manda is a fermented vegetable product (FVP) made by natural fermentation of fruits, vegetables, plant roots, marine algae, and kokuto, a kind of non-centrifugal cane sugar. These raw materials are crushed and fermented for more than three years and three months by lactobacillus, bacillus, and yeast generated spontaneously from the raw materials at room temperature. The products have been known as natural health foods in Japan for a number of years. The FVP is a sweet, black–brown, paste containing 32.9% water, 2.2% protein, 0.1% fat, 60.3% carbohydrate, and 1.9% ash, vitamins, and minerals [5]. Kawai and Matsuura reported that FVP inhibited emotional stressinduced stomach ulcers in rat [6]. The substance caused a reduction in lipid peroxidant formation [7], and activation of glutathione peroxidase [8] and the non-specific immune system in fish [9]. The heat shock protein (hsp) group belong to a family of proteins which are expressed in response to the several stressors. In the hsp family, hsp70 has been most widely studied and is involved in multiple cellular processes such as protein transcription, protein folding, and regulation of the stress response [10]. Dietz and Somero reported that hsp70 was induced in several tissues of marine teleost fishes by raising the temperature [11]. In this study, we investigated the effect of FVP on changes of stress protein (hsp70) and the concentration of serum cortisol and glucose. Japanese flounder, Paralichthys olivaceus, which had been hatched and reared in our laboratory, were kept in 200-l tanks with a continuous supply of air (3.6 l/min) and sea water (3.0 l/min). Fish weighing 233 ± 27 g (mean ± SD) were randomly distributed into four groups of tanks. Water temperature varied from 20–24 C during the experiment. One group fed on Super Ex diet (Nihonnosanko) served as control, and the others were fed on diet containing 3 or 15 mg/kg body weight/day of FVP. Each diet was fed to fish using a regime of 12 g/kg body weight of fish per day for 6 days a week. After 2 weeks, fish were transferred to high-water-temperature tanks (31 C) for 2 h, and then, were returned breeding tanks (21 C). Gills T. Ashida (&) M. Takagaki Y. Matsuura Manda Fermentation Co. Ltd, 5800-95 Shigei, Onomichi-Innoshima, Hiroshima 722-2192, Japan e-mail: takayuki_ashida@manda-kohso.co.jp