Ultrastructure and morphometric analysis of preimplantation mouse embryos

Abstract

During cleavage, both qualitative and quantitative morphologic characters of mouse ova change. Up to the 8-cell stage, the volume density of mitochondria remains nearly the same although it increases during early and late blastocyst stages. While a rise of the volume fraction of granular endoplasmic reticulum is noticed during cleavage, the volume density of agranular endoplasmic reticulum diminishes gradually from the 1-cell stage onwards. An increase in the volume fraction of autophagic vacuoles is found, the maximum being reached in early blastocysts. The volume fraction of crystalloid inclusions slightly increases after the 4-cell stage, but this increase is statistically insignificant. The volume density of filamentous material (plaques) conspicuously decreases in all studied embryos from the beginning of cleavage. Starting with the 2-cell stage, the volume fraction of lipid droplets remains practically unchanged. No differences in volume densities of the Golgi apparatus, multivesicular and residual bodies, and large cytoplasmic vesicles with medium electron-dense content are found between the respective cleavage stages.

Lysosome Dispersion in Osteoblasts Accommodates Enhanced Collagen Production during Differentiation

“…The relative abundance of organelles can vary from cell to cell as required for cell specializations. For instance, changes in the amount and morphology of the endoplasmic reticulum and mitochondria occur during development, suggesting that the amount and structure of these organelles are both temporally and spatially regulated (9). In certain circumstances, organelle positioning and abundance can change within the same cell in response to receptor signaling events.…”

Following the course of pre-implantation embryo patterning by non-linear microscopy

“…Studies using electro-microscopy analysis show that mitochondria represent the major intracellular structures until the stage of 8-cell embryos (Cech and Sedlackova, 1983). Since mitochondria are the major ATP-generating organelles of the cell (Wilding et al, 2009), they can fairly enough be considered to embody the energetic status of the cell.…”

Pre-Implantation Development

“…The outline of the cell mass becomes more even and barely suggests the existence of separate cells. This change is called 'compaction'; it has been recognized in all species investigated for its occurrence and is evidently an essential step towards the next new feature, the development of a fluidfilled cavity among the blastomeres, leading to the formation of the blastocyst (the series of events is well illustrated in Figure 2.3, from Kaufman, 1983; ultrastructural changes during the corresponding stages of development in the mouse egg have been described by Cech and Sedlackova, 1983).…”