| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1997: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 1996: ¥1,100,000 (Direct Cost: ¥1,100,000)
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| Research Abstract |
In mammalian oocytes, fertilization-associated calcium [Ca2+]i oscillations are responsible for the activation of development. It has been proposed that the sperm may interact with receptors in the oocyte's plasma membrane and engage intracellular signaling pathways that result in Ca2+ release. A different line of investigation suggests that upon sperm-oocyte fusion, a sperm cytosolic factor is released into the oocyte which interacts with unknown cytosolic targets, and generates [Ca2+]i oscillations. In this study, we demonstrated that injections of xeno-sperm crude extracts (SF) into other mammalian oocytes couses activation and in vitro parthenogenetic development. A hypothesis we supported in the mechanism of signal transduction at fertilization proposes that a factor from the sperm (SF) is released into the egg and, by interacting with unknown cytosolic targets, generates activation of oocytes. Injection of various sperm into hamster, mouse, rabbit, pig and bovine oocytes (this me
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ans that gametes' membrane fusion was by-passed) activated oocytes similar to those observed during fertilization, in our study. To further test the physiological relevance of SF,SF is obtained from porcine sperm were injected into hamster oocytes. It was caused pronuclear formation but formation is delayd compared to that of normal hamster fertilization. Probably it was due to fertilized hamster oocytes oscillate with higher frequency than porcine oocytes. Thus, if SF contains a physiological initiator of [Ca2+]i oscillations, injection of SF from one species into oocytes of a different species should be able to induce Ca2+ responses in these oocytes and it should respect the pattern characteristic of each species. Long lasting oscillations are characteristic of mammalian fertilization and they are critical for the activation of embryonic development. It may triggered by sperm cytosolic factors. For example, stimulation of this pathway may be used for parthenogenetic activation in embryo cloning and its inhibition may offer insights in contraception. Less
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