Cell number and incidence of chromosomal anomalies in bovine blastocysts fertilized in vitro followed by culture in vitro or in vivo in rabbit oviducts.
The total number of cells and the incidence of chromosomal anomalies in bovine blastocysts cultured in vitro or in vivo in rabbit oviducts were investigated from the four-cell stage after in-vitro fertilization of in-vitro matured follicular oocytes. The total number of cells (80 vs 179) in the oviduct-cultured blastocysts was nearly double that (43 vs 80) of blastocysts cultured in vitro at early and expanded blastocyst stages. In both culture systems, the total number of cells increased with the stage of development. Mitotic index (number of metaphase plates/total number of cells) of blastocysts decreased with development from early (11.5 vs 13.8%) to hatched blastocyst stages (4.8 vs 2.8%) in in-vitro and in-vivo culture systems, respectively. Overall, chromosomal anomalies were observed in 37.5% (27 27 ) of embryos cultured in vitro and in 28.0% (7 24 ) cultured in vivo, respectively. Incidence of chromosomal anomalies did not depend on such factors as culture system or stage of development. Most chromosomal anomalies were polyploid and mixoploid cells.
Iwasaki
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NODAI Research Institute, Tokyo University of Agriculture Setagaya-ku, Tokyo 156, Japan.
Nakahara
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T