Lechniak D, Switoński M, Sosnowski M
Agricultural University of Poznań, Department of Genetics and Animal Breeding, Poznań, Poland.
Theriogenology. 1996 Jul 15;46(2):267-77. doi: 10.1016/0093-691x(96)00183-5.
The present work describes a cytogenetic study of in vitro matured bovine oocytes to determine the proportion of unreduced oocytes carrying the diploid number of chromosomes. Studied oocytes were derived either from a pool of oocytes collected from several different donors, or from oocytes collected separately from individual donors. In vitro maturation was performed by culturing immature oocytes for 24 h in TCM199-medium supplemented with estrous cow serum and hormones at 39 degrees C in 5% CO2. Chromosomal complement of in vitro matured oocytes was studied by Giemsa-staining and produced analyzable results in approximately 60% of the cases. The results revealed that approximately 75% of oocytes had matured to the MII stage in both groups of oocytes studied. Of these MII oocytes, 11 and 12.4% (from the oocyte pool or from individual cows, respectively) contained the diploid set of chromosomes. The occurrence of diploid MII oocytes was not quite uniform among donors: 40.5% of all cows produced one, 18.9% produced two and 2.7% (one cow) produced three diploid MII oocytes. However, a positive relationship between the number of MII oocytes in general and diploid MII oocytes among individual donors was not found. The possible factors that may lead to the formation of diploid MII oocytes observed under IVM procedures are discussed. The results of this study showed a higher incidence of diploid oocytes in cattle than previously reported.
本研究描述了对体外成熟的牛卵母细胞进行的细胞遗传学研究，以确定携带二倍体染色体数目的未减数卵母细胞的比例。所研究的卵母细胞要么来自从几个不同供体收集的卵母细胞库，要么来自分别从个体供体收集的卵母细胞。体外成熟是通过将未成熟卵母细胞在补充有发情母牛血清和激素的TCM199培养基中于39℃、5%二氧化碳条件下培养24小时来进行的。通过吉姆萨染色研究体外成熟卵母细胞的染色体组成，约60%的情况产生了可分析的结果。结果显示，在所研究的两组卵母细胞中，约75%的卵母细胞已成熟至MII期。在这些MII期卵母细胞中，分别有11%和12.4%（来自卵母细胞库或个体母牛）含有二倍体染色体组。二倍体MII期卵母细胞在供体中的出现并不完全一致：所有母牛中40.5%产生1个，18.9%产生2个，2.7%（1头母牛）产生3个二倍体MII期卵母细胞。然而，未发现个体供体中MII期卵母细胞总数与二倍体MII期卵母细胞之间存在正相关关系。讨论了在体外成熟程序下观察到的可能导致二倍体MII期卵母细胞形成的因素。本研究结果表明，牛中二倍体卵母细胞的发生率高于先前报道。
