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Scanning electron microscopy of the development of the mesoderm layer in chick embryos
Abstract:
The distribution of mesoderm, the structure of mesoderm cells and relationship between mesoderm and ectoderm were examined by SEM in embryos at stages 3 to 5. The mesoderm was displayed by removal of the endoderm and by fracturing the embryos through mesoderm containing regions. Within the mesoderm layer four zones could be distinguished by their cell shape and arrangement--the primitive streak, a multilayered compact area around the margins of the area pellucida, multilayered and loosely arranged cells near the primitive streak and a flattened monolayer of cells around the advancing lateral and anterior edges of the mesoderm sheet. Secretion of basement membrane by the ectoderm was seen to precede the arrival of mesoderm cells. This suggests that ectoderm alone can synthesize basement membrane without mesodermal contribution.
Insights
Scanning early embryos using scanning electron microscopy (SEM), this study reveals distinct mesoderm zones and their arrangement. Ectoderm synthesizes basement membrane before mesoderm arrival, suggesting independent ectodermal capability.
Area of Science:
- Developmental Biology
- Embryology
- Cell Biology
Background:
- Understanding early embryonic development is crucial for developmental biology.
- The formation and differentiation of germ layers, particularly mesoderm, are key events.
- The interaction between ectoderm and mesoderm during gastrulation is complex.
Purpose of the Study:
- To investigate the spatial distribution and cellular structure of mesoderm in early embryos.
- To elucidate the relationship between mesoderm and ectoderm during embryonic development.
- To determine the origin of basement membrane synthesis in relation to mesoderm migration.
Main Methods:
- Scanning Electron Microscopy (SEM) was employed to visualize embryonic structures.
- Embryos at stages 3 to 5 were analyzed.
- Endoderm removal and embryo fracturing techniques were used to expose mesodermal layers.
Main Results:
- Four distinct zones within the mesoderm layer were identified based on cell morphology and arrangement: primitive streak, marginal zone, peri-primitive streak zone, and leading edge.
- The primitive streak showed a multilayered compact structure.
- The leading edge of the mesoderm sheet consisted of a flattened monolayer of cells.
Conclusions:
- Ectoderm secretes basement membrane prior to mesoderm cell arrival.
- This suggests that ectoderm possesses the intrinsic ability to synthesize basement membrane independently of mesodermal contribution.
- The findings provide insights into the early patterning and cell interactions during embryonic development.