| Project/Area Number |
11660185
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
General fisheries
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| Research Institution | Tokyo University of Fisheries |
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Principal Investigator |
OSHIRO Takashi Tokyo University of Fisheries, Department of Aquatic Biosciences, Associate Professor, 水産学部, 助教授 (10201401)
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| Co-Investigator(Kenkyū-buntansha) |
TAKEYAMA Haruko Tokyo University of Agriculture & Technology, Department of Biotechnology, Associate Professor, 工学部, 助教授 (60262234)
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| Project Period (FY) |
1999 – 2000
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| Project Status |
Completed (Fiscal Year 2000)
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| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 2000: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1999: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Keywords | Lymnaea stagnalis / hermaphrodite snail / caudo-dorsal cell hormone (CDCH) / albumen gland / meiosis-regulating factor / osmotic pressure / haemolymph / ecdysone / 産卵ホルモン / 卵白腺 / 卵爽膜腺 / セロトニン / エクゾソン |
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| Research Abstract |
(1) Snails could be stimulated to oviposit egg-mass within 3h by their transfer from polluted stagnant water into clean aerated one. MALDI-MS analysis revealed that caudo-dorsal cell hormone (CDCH) were released from cerebral commissure(COM) into haemolymph (HL) within 30 min after transfer. The crude extracts of COM with dorsal bodies (DB) could induce in vitro gamete-release(oocytes and sperm) from the dissected ovotesis-digestive gland complex.
(2) Ovulated oocytes soon appeared, moved and fertilized in the distal part of spermoviduct (DSO). Meiosis and cleavage could be induced by immersing DSO oocytes in snail saline, HL and distilled water, while they were strictly inhibited in vivo till spawning. Isolated oocytes just spawned with capsule (egg membrane + perivitelline fluid) could show polar body formation and cleavage in hypotonic solution of mannitol but in hypertonic ones they could not. Immersion test showed that most osmolytes with low molecular weight immediately penetrate the capsule, which always keep perivitelline fluid hypertonic than HL by inner colloid osmotic pressure. This seems to be the major reason why oocyte meiosis can never be allowed before spawning.
(3) Immersion of spawning snails in 10^<-3>〜10^<-1>M solution of β-ecdysone slightly increased the whole volume of egg capsule. Formation of perivitelline fluid may be stimulated by this steroid.
(4) Complementary DNA of ecdysone receptor was not obtained by RT-PCR from the extract of the reproductive tract of mature snails.
(5) HPLC-EIA demonstrated that β-ecdysone level in HL reached the peak at the early phase of oocyte-packaging (at the secretion of albumen gland) and rapidly decreased. Alpha-ecdysone level gradually increased and showed the peak around spawning time. Then β-ecdysone may play an important role in preventing meiosis through the formation of perivitelline fluid.
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