Glycogen content of preimplantation mouse embryos

Abstract

Abstract Preimplantation mouse embryos of various stages of development, from single‐cell zygotes to late blastocysts, were fixed on microscope slides and were stained using the periodic acid‐Schiff method. Half of the slides were treated with diastase before staining to determine whether the positive material was glycogen. Glycogen was found in all of the stages studied, regardless of whether development had occurred in vivo or in vitro . Single‐cell zygotes were not as heavily stained as the two‐cell embryos, but this could be due to the decrease in volume which occurs between these two stages. Large amounts of positive material were found in the cleavage stages, from two‐cell to morula, but a decrease occurred during the growth of the blastocyst. By the late blastocyst stage, glycogen is no longer found in the trophoblast cells and is present only in small amounts in the inner cell mass. The decrease in PAS‐positive diastase‐removable material during the blastocyst stages suggests that glycogen may serve as an energy source during the fifth day of development, when the blastocyst is undergoing expansion and hatching. Culture experiments and enzyme analyses have provided evidence that the cleaving embryo undergoes some basic changes in the pattern of energy metabolism, and it is possible that additional changes might occur in the blastocyst stage.