| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1988: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1987: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
In the first year (1987), the fertilization and cleavage of bovine oocytes matured by intra- or extra-follicular methods were invesigated. Cocytes were fertilized in vitro or in the rabbit oviduct and cleavage was assessed after in vitro and in vivo (rabbit oviducts) culture of in vitro fertilized and xenogenously fertilized oocytes, respectively. The intra-follicular method did not increase the nuclear maturation rate as compared with the extra-follicular method (57.9 and 52.7%). However, the proportions of in vivo fertilized eggs (49.3%) and of cleaved eggs (34.6%) in the rabbit oviduct were higher (p<0.025) in the intra-follicular oocytes than those of the extra-follicular oocytes. These results demonstrated that the intra-follicular method of bovine oocytes provided a physiological environment for cytoplasmic maturation leading to higher fertilizability and cleavage than the conventional culture of extra-follicular oocytes.
In the second year (1988), a co-culture system for oocyte maturation was established using granulosa cells in media (TCM 199 + 10% estrous cow serum). In vitro fertilization rate was improved by the use of swim-up and heparin treatment in frozen-thawed bovine spermatozoa (50 -60%). Presently, I have obtained rates of in vitro maturation (60 -70%), fertilization (50 -60%), cleavage (50%) and development into blastocysts (10 -20%) . For development of in vitro fertilized eggs, bovine oviduct epithelial cells were sucssesfully employed in media. One of three heifers received thransfer of in votro developed blastocysts was pregnant, and has been expecting the calving in march 23th, 1989 at the Obihiro University Farm.
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