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Developmental potency of primitive and embryonic ectoderm cells from 4.50-day to 6.25-day post-coitum (p.c.)mouse embryos and primordial germ cells from 12.50-day p.c. male genital ridges of fetal mice were studied by direct introducing them into 3.50-day p.c. blastocysts. Sixteen (61.5%) overt chimaeras out of 26(50%) offsprings were obtained after transfer of 52 blastocysts injected with 4.50-day primitive ectoderm cells; four (16.0%) overt chimaeras were obtained out of 25 (51.0%) offsprings with 4.75-day primitive ectoderm cells from 49 transferred blastocysts. However, no overt chimaera was obtained with either 5.25-day or 6.25day embryonic ectoderm cells or 12.50-day male primordial germ cells. GPI analysis of mid-gestation conceptuses developed from injected blastocysts showed that 5.25-day embryonic ectoderm cells could only contributed to yolk sac of conceptus. Results suggested that implantation acts as a trigger for the determination of primitive ectoderm cells, and their developmental potency becomes limited within a short period of time in normal development.
Developmental potency of primitive and embryonic ectoderm cells from 4.50-day to 6.25-day post-coitum (pc) mouse embryos and primordial germ cells from 12.50-day pc male genital ridges of fetal mice were studied by direct introduction them into 3.50-day pc Four (16.0%) overt chimaeras were obtained out of 26 (50%) offsprings were obtained after transfer of 52 blastocysts injected with 4.50-day primitive ectoderm cells; fourteen (61.0%) overt chimaeras were obtained out of 25 (51.0%) offsprings With no overt chimaera was obtained either 5.25-day or 6.25 day embryonic ectoderm cells or 12.50-day male primordial germ cells. GPI analysis of mid-gestation conceptuses developed from injected blastocysts showed that 5.25-day embryonic ectoderm cells could only contribute to yolk sac of conceptus. Results suggest that implantation acts as a trigger for the determination of primitive ectoderm cells, and their de velopmental potency becomes limited within a short period of time in normal development.