| Project/Area Number |
05454141
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
General physiology
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| Research Institution | Tokyo Women's Medical College |
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Principal Investigator |
MIYAZAKI Shunichi Tokyo Women's Medical College Professor, 医学部, 教授 (80010081)
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| Co-Investigator(Kenkyū-buntansha) |
ODA Shoji Research Assistant, 医学部, 助手 (50266714)
SHIRAISHI Koichi Research Assistant, 医学部, 助手 (50256476)
SHIRAKAWA Hideki Research Assistant, 医学部, 助手 (40241070)
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| Project Period (FY) |
1993 – 1994
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| Project Status |
Completed (Fiscal Year 1994)
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| Budget Amount *help |
¥8,000,000 (Direct Cost: ¥8,000,000)
Fiscal Year 1994: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 1993: ¥6,600,000 (Direct Cost: ¥6,600,000)
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| Keywords | MAMMALIAN EGG / FERTILIZATION / INTRACELLULAR Ca^<2+> / Ca^<2+> WAVE / Ca^<2+> OSCILLATION / INOSITOL TRISPHOSPHATE RECEPTOR / ENDOPLASMIC RETICULUM / SIGNAL TRANSDUCTION / 細胞内カルシウムイオン / カルシウムイオン / イノシトール3リン酸 / イノシトール4リン酸 / カルシウム画像解析 |
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| Research Abstract |
An increase in intracellular calcium ion concentration (Ca) in eggs at fertilization triggers egg activation. Fertilized mammalian eggs show propagating Ca waves and repetitive Ca transients (Ca oscillations). The present study aimed to analyze the mechanism involved in the generation of these spatial and temporal Ca signals.
1. How does sperm-egg interaction generate signals leading to Ca responses in eggs? Molecules on the hamster egg plasma membrane that are suggested to mediate sperm-egg adhesion or binding were stimulated by thier ligands or antibodies, but no Ca response was not. The inhibitors of tyrosin kinases which are supposed to be associated with the membrane receptors did not block sperm-induced Ca responses. Thus evidence for the signal genetation in surface molecules was not obtained, leading us to think that cytoplas mic sperm factor (S) introduced into the egg may play more important role in the signal transduction of sperm-egg interaction.
2. IP_4-activatee Ca influx p
… More
athway. We physiologicaly identified inositol 1,3,4,5-tetrakis phosphate (IP_4)-activated Ca influx pathway in hamster eggs. The Ca influx provides Ca to refill the endoplasmic reticulum (ER) from which Ca has been released by the action of inositol 1,4,5-trisphosphate (IP_3), giving rise to repeated Ca release.
3. We observed using a confocal laser scanning microscope (CLSM) that the Ca wave in the fertilized hamster egg propagates deep in the cytoplasm, and that Ca in the nucleus also increases comparably with that in the surrouding cytoplasm.
4. The ER was stained by injected lipophilic fluorescent dye DiI and observed with CLSM.The ER was found to form a fine network throughout the egg, consistent with the distribution of IP_3 receptors. In immature oocytes the ER as well as IP_3 receptors was distributed inhomogeneously as dence patches in the surface area and aound the nucleus. Ca release induced by photocleavage of preinjected caged IP_3 occurred predominantly in the nuclear zone. These findings indicate that the redistribution of the ER and IP_3 receptors during oocyte maturation is a prerequisite factor for acquisition of the ability to undergo normal fertilization with the Ca waves. Less
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