ABSTRACT
This chapter reviews the cell proliferation-promoting activities residing in unfertilized eggs. The culture cell system is one of the most available methods which help to analyze biological phenomena in vitro involving so many complex factors. It is obvious that hen egg substances possess cell growth-promoting activities for various cell lines. In early experiments, extracts of 10- and 16-day-embryos, in which cell proliferation occurs vigorously, had been used but unfertilized eggs were recognized as a more convenient substitute. Egg yolk was shown to have the effect of supporting mammal embryogenesis. Equine embryos grew normally with high ratios in the presence of 20-60 % of relatively high content yolk, although it was ineffective for those of the murine and bovine embryos. The optimal concentration of yolk lipoproteins for the cell growth-promoting effect was found to be approximately 100-500 μg/ml by several independent studies using different types of cell lines.
