| Budget Amount *help |
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 1999: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1998: ¥2,800,000 (Direct Cost: ¥2,800,000)
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| Research Abstract |
Parthenogenetic activation of oocytes is a key component of the current mammalian cloning regimen. This study was designed to examine the cellular alterations of the bovine and porcine oocytes at different ages following different activation stimulations. In Experiments 1 and 2, bovine oocytes of 22,30 and 40 h after in vitro maturation was activated by an electrical pulse (100Vmm, 50μsec), Ca ionophore, and combined with cycloheximide or 6-dimethylaminopurine. It is suggested that older bovine oocytes are more readily activated and that the age-dependent surface ultrastructural alterations correlate very well with the age dependent activation of oocytes. It was also shown that surface characteristics of the bovine oocyte were more profoundly changed by a combination of parthenogenetic stimulation, and that the ultrastructural effects were reversible. In Experiments 3 and 4, porcine oocytes were matured in vitro to examine morphodynamics of the cumulus-oocyte association during oocyte
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maturation. It was concluded that the cumulus-oocyte transzonal projections became disconnected between MI and MII stage as a result of cumulus expansion. However, the cumulus-cumulus communications remained intact at these stages. In Experiments 5 and 6, the activation rate, developmental pattern and changes in microtubule and microfilament assembly of the porcine oocytes activated electrically or chemically were evaluated in relation to the oocyte aging. The present results suggest that a higher activation rate was obtained in the porcine oocytes after two electrical pulses that in those after Ca ionophore or ethanol treatments and that the disorganization of microtubule and the alteration of microfilament distribution observed in the aged oocyte may result in higher incidences of diploid parthenotes and fragmentation, respectively. It is also suggested that increased development to blastocysts after the combined treatment of electrical pulses and CD may due to higher incidence of diploid parthenotes derived from CD treatment. Less
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