| A series of experiments were conducted to investigate the effects of vitamin C and live attenuated Vibrio anguillarum, on the whole-body-composition, growth, selected specific and non-specific immune parameters (immunoglobulin, specific antibody production, Alternative complement pathway activity, cortisol, lysozyme activity, respiratory burst) of flounder, Paralichthys olivaceus. Four experiments: In experiment I, The effects of the levels of dietary vitamin C (100 mg AA/kg; 130 mg AA/kg; 180 mg AA/kg) on growth, whole-body-composition and some non-specific immune parameters of flounder (Paralichthys olivaceus) in different salinities (16‰, 3 l‰, 40‰). hi experiment II, To examine the mechanism by which vitamin C alter leucocytes function, a series of in vitro manipulations were conducted with cells isolated from the blood, head kidney and spleen of the flounder fed a diet supplemented with minimum requirement levels of vitamin C (25mg AA/kg) for 4 weeks. In experiment III, In vitro manipulations of vitamin C concentrations alter intracellular O2 production of leucocytes isolated from gut-associated lymphoid tissue of the flounder (Paralichthys olivaceus), in order to test the effect vitamin C on the gut-associated lymphoid tissue of flounder .In experiment IV, The efficacy of attenuated live bacterin of Vibrio anguillarum in flounder (Paralichthys olivaceus), to supply for the application of the attenuated live bacterin with the preliminary information.The results were as follows:(1) The growth of flounder was affected by the levels of dietary vitamin C and the culturing water salinities significantly. In brackish water (O2), of which the salinity was moderate, flounder grew fastest among the experimental groups. Moreover, it is beneficial for the accumulation of vitamin C in the liver.(2) The crude protein and moisture in the flounder were not affected by the salinity of the culturing water, the crude lipid content decreased with the salinity increased significantly (P<0.05). On the contrary, there was a increasing trend of ashescontent with the salinities increased.(3) The whole-body-composition was not affected by dietary vitamin C.(4) Under the experimental conditions, alternative complement pathway activity (ACHso units/ ml) was not affected by dietary vitamin C and water salinity.(5) High water salinity (‰) induced higher serum cortisol levels when compared with those subjected to seawater and brackish. Diets supplemented moderate (130mg AA/kg) levels of vitamin C could reduce cortisol levels.(6) The lysozyme activity of sera increased with increasing levels of vitamin C supplementation, but it was not affected by the salinity.(7) There were some effects of vitamin C concentration on intracellular O2 production of leucocytes isolated from blood and head kidney. When vitamin C was supplied at l0umol/L levels to the medium, the intracellular O2 production reached the highest values.(8) There were no effects of vitamin C on intracellular O2 production of leucocytes isolated from spleen.(9) Based on above data, media containing l0umol/L will be beneficial for the maintaining natural function of head kidney and blood leucocytes.(10) The intracellular O2 production of flounder cells isolated from gut-associated lymphoid tissue was significantly affected by attenuated live bacterin intraperitoneally injected.(ll)The intracellular O2 production of flounder blood leucocytes was affected byattenuated live bacterin intraperitoneally injected. (12) Alternative complement pathway activity of flounder sera was stimulated byattenuated live bacterin intraperitoneally injected. (13)The relative percentage survival (RPS) of immunized flounder challenged withvirulent V. anguillarum after 3-month post- intraperitoneally injection withattenuated live bacterin exceeded 70%. (14) After intraperitoneal vaccination, the attenuated live bacterin induced a betterantibody response.(15) No bac... |
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