| Budget Amount *help |
¥3,890,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥390,000)
Fiscal Year 2007: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000)
Fiscal Year 2006: ¥2,200,000 (Direct Cost: ¥2,200,000)
|
|---|
| Research Abstract |
To elucidate mechanisms of oocyte cytoplasmic maturation (such as a hydration, liquid coalescence and clearing of the ooplasm) during oocyte maturation and to develop techniques for in vitro production of good quality eggs, the present study examined the following studies in the Japanese eel spawn buoyant eggs.
1. The present study shows the process of oocyte cytoplasmic maturation during de novo oocyte maturation in the Japanese eel. Moreover, we also developed the incubation techniques for mimic the cytoplasmic maturation occurred in vivo. Using the techniques we developed, we found that cytoplasmic maturation was induced by the maturation-inducing steroid that was synthesized in the ovarian follicles by the stimulation of gonadotropin. Cytoplasmic maturation induced by maturation-inducing steroid may be mediated by protein synthesis in the oocyte. IGF-I, but not GAP junction may be involved in the cytoplasmic maturation of eel oocytes.
2. The present study also indicates that oocyte h
… More
ydration is mediated by yolk proteolysis which creates the osmotic driving force and aquaporin possibly facilitates water uptake into oocytes. Moreover, the study indicates that the ovarian follicles in the Japanese eel may play an essential role in oocyte hydration, although the precise role must be identified in the further research.
3. The present study also examined the Japanese eel for the presence and cellular distribution of eel AQP-1o in the ovarian follicles during oocyte growth, oocyte maturation and ovulation by the immunocytochemistry. Anti-AQP-1o antibody was raised in a rabbit against a synthetic peptide corresponding to a part of the C-terminal region of eel AQP-1o. Immunoreactivity was first observed in the cytoplasm around the yolk globules which were located in the peripheral region of the oocytes during the primary yolk globule stage; thereafter, the immunoreactivity was observed throughout the cytoplasm of the oocyte as vitellogenesis progressed. The immunoreactivity became localized around the large membrane-limited yolk masses which were formed by the fusion of yolk globules. It also localized below the oocyte plasma membrane in the migratory nucleus stage oocytes, mature oocytes and ovulated eggs. These results are different from those observed in the oocytes of gilthead sea bream and suggest the existence of a distinct and characteristic mechanism of oocyte hydration in the eel.
4. We tried to develop the techniques for in vitro production of good quality eggs in the Japanese eel. Although we found the oocyte maturation and ovulation occurred at 12 and 18 hours after incubation with maturation-inducing steroid respectively, we could not obtained fertilized eggs. Further studies are necessary to develop the techniques for obtaining good quality eggs in vitro. Less
|
