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Molecular and cellular aspects of facultative delayed implantation in the mouse
Abstract:
Various aspects of RNA, DNA and protein synthesis, as well as cellular fine structure, were examined in mouse embryos during the developmental diapause associated with delayed implantation, and during the reactivation of the embryo either by hormonal administration or by culture in vitro. The findings from these studies demonstrate that a cessation of DNA synthesis and mitosis, and a marked decline in the level of protein synthesis, but not of RNA synthesis, accompany diapause. Reactivation of the blastocyst results in the resumption of DNA synthesis and cell division, as well as in quantitative and qualitative changes in protein synthesis. At the fine-structural level diapause is indicated by the accumulation of lipid-like vacuoles, microfilaments, a basal lamina coating trophectodermal cells and the disassembly of polysomes into ribosomes. Significantly, nucleolar morphology remains unaltered during diapause and cisternae of the rough-surfaced endoplasmic reticulum persist at least for the first five days of delay. Reactivation of diapausing blastocysts is associated with the reassembly of polysomes and the accumulation of large quantities of an amorphous material within the cisternae of the rough-surfaced endoplasmic reticulum. Studies of blastocyst growth and development in vitro suggest experimental approaches to the question of the regulation delayed implantation. Finally, the role of ionic balances and concentrations in the control of the onset, maintenance and termination of delayed implantation in the mouse is discussed.
Insights
Mouse embryo diapause, a state of developmental arrest during delayed implantation, involves suppressed DNA synthesis and protein production. Reactivation restores these processes, offering insights into developmental regulation.
Area of Science:
- Developmental Biology
- Reproductive Biology
- Cellular Biology
Background:
- Delayed implantation in mice involves a period of developmental arrest known as diapause.
- Understanding the molecular and cellular changes during diapause and reactivation is crucial for reproductive biology.
Purpose of the Study:
- To investigate RNA, DNA, and protein synthesis during mouse embryo diapause and reactivation.
- To examine fine-structural changes in mouse embryos during delayed implantation and subsequent development.
- To explore the role of in vitro culture and ionic balances in regulating delayed implantation.
Main Methods:
- Analysis of RNA, DNA, and protein synthesis in mouse embryos.
- Electron microscopy to study cellular fine structure.
- In vitro culture of blastocysts.
- Discussion of ionic balances in implantation regulation.
Main Results:
- Diapause is characterized by cessation of DNA synthesis and mitosis, and reduced protein synthesis, while RNA synthesis is maintained.
- Reactivation involves resumption of DNA synthesis, cell division, and altered protein synthesis.
- Ultrastructural changes include lipid vacuole accumulation, microfilament presence, basal lamina formation, and polysome disassembly during diapause; reactivation shows polysome reassembly and endoplasmic reticulum changes.
Conclusions:
- Mouse embryo diapause involves specific molecular and ultrastructural modifications.
- Reactivation triggers significant cellular and synthetic recovery.
- In vitro studies and ionic balance are key areas for further research into delayed implantation regulation.