Related Experiment Videos
Production and formation of the basement membrane in embryonic tissues of the mouse. An electron-microscopic study
Abstract:
Mouse embryos (strain NMRI) of days 9 + 2h, 9 + 12h, 10 + 2h, 10 + 12h, 11 + 2h, 12 + 2h, 13 + 2h, and 14 + 2h were fixed (i) in 3% glutaraldehyde + 3% paraformaldehyde, (ii) in 1% glutaraldehyde + 1% tannic acid, or (iii) in 1% glutaraldehyde + 1.5% ruthenium red. The electronmicroscopic picture of the basement membrane (BM) changed depending on the fixative used. Addition of tannic acid led to a higher staining intensity of glycoproteins, whereas after ruthenium red proteoglycans were more heavily stained. The BM around the neural tube and around the epithelial tubules in the lung anlage were investigated electron microscopically. After fusion, the BM in the dorsal regions of the neural tube is missing; on days 9-10 it is, however, reformed. Between days 11 and 13 wide gaps in the BM of the lung anlage occur at the growth buds of the epithelial tubes, which are bridged on late day 13. In the basal parts of these two epithelial types membrane-bordered granules of different density occur singly or in groups. It is postulated that these structures contain BM-material and represent secretion granules. After secretion, BM-material is first bound to the cell membrane. This process is important for the initiation of the formation of the BM. Further growth, however, proceeds via lateral aggregation (self-assembly). Thus, intercellular gaps are bridged independent of the cell membrane. The process of lateral aggregation may also explain deviations from the normal course of the BM.
Insights
The basement membrane (BM) formation in mouse embryos is influenced by fixatives and involves secretion granules. This process, crucial for embryonic development, occurs via cell membrane binding and lateral aggregation.
Area of Science:
- Developmental Biology
- Cell Biology
- Electron Microscopy
Background:
- The basement membrane (BM) is a critical extracellular matrix structure essential for tissue organization and development.
- Understanding BM formation is key to comprehending embryonic development and potential developmental abnormalities.
Purpose of the Study:
- To investigate the ultrastructural changes in the basement membrane during mouse embryonic development.
- To analyze the impact of different fixatives on basement membrane visualization.
- To elucidate the mechanism of basement membrane formation and repair.
Main Methods:
- Mouse embryos (NMRI strain) at various developmental stages (days 9-14) were examined.
- Fixation was performed using three different glutaraldehyde-based solutions.
- Electron microscopy was employed to visualize basement membrane ultrastructure.
Main Results:
- Fixatives significantly altered the electron microscopic appearance of the basement membrane, affecting the staining of glycoproteins and proteoglycans.
- The basement membrane around the neural tube showed transient absence and reformation.
- Gaps in the lung anlage basement membrane were observed and bridged by day 13, with evidence of secretion granules involved in BM formation.
Conclusions:
- Basement membrane formation involves initial binding to the cell membrane followed by lateral aggregation (self-assembly).
- Secretion granules likely contribute BM material for formation and repair.
- This self-assembly mechanism may explain variations in basement membrane development.