| Budget Amount *help |
¥2,300,000 (Direct Cost: ¥2,300,000)
Fiscal Year 1996: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1995: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Research Abstract |
1995 : We developed the effective method of induction of ovarian maturation and ovulation of the cultured tiger puffer Takifugu rubripes by hormonal treatments in order to supply the fertilized eggs for aquaculture. The LHRH-a cholesterol pellet (LHRH-a 400 mg/kg) implantation successully induced overian maturation for three-year-old cultured tiger puffer which had yolk accumulated ovaries. Thereafter single injection of HCG (500IU/kg) combined with chum salmon pituitary (SP) homogenate (7 mg/kg) was applied to the fish to sinchronize ovulation among fish. In Experiment I (fish with oocytes *900 mm in diameter), fertilized eggs were obtained from 5 of 7 fish used. In Experiment II (fish with oocytes between 800 and 900 mm in diameter), fertilized eggs were obtained from 8 of 10 fish tereated. On the contrary, in Experiment III as a conventional method (repeated injection of HCG+SP at 5 days interval without LHRH-a treatment), fertilized eggs were obtained from two of 5 fish. Mean ferti
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lization rates in the three experiments were 55.1,53.6, and 11.0%, respectively. In Exp. I and II,ovulation was mainly occurred between 96 and 120 hours after HCG+SP injection. Thus, a thchnique for obtaining eggs of high quality from the cultured tiger puffer was developed.
1996 : The study was designed to obtain derect evidence for the authentic maturation-inducing hormone (MIH) of tiger puffer, Takifugu ruberipes. To this end, we used yolk free follicle cells at four different stages of oocyte development. The yolk free follicle cells were incubated with the ^<14>C-labeled 17a-hydroxyprogesterone for 2hr, followed by chromatographic separation of the radioactive steroids. The radioactive metabolites produced were identified and tested for their ability to induce germinal vesicle breakdown (GVBD) in oocytes in vitro. Furthermore, in vivo production of candidates for MIH was investigated by monitoring the serum steroid levels during final oocyte maturation. The results obtained in this study provide evidence that 20b-S is the naturally occurring MIH in tiger puffer. Less
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