MAIN OUTCOME MEASURES: Preparation of fibroblast feeder layer;growth of embryonic stem cells;results of alkaline phosphatase staining;cell differentiation tendency.

• 主要观察指标：成纤维细胞饲养层的制备情况，胚胎干细胞的生长状态、碱性磷酸酶染色结果及分化趋势。