Scanning electron microscopy (SEM) of the chick embryo primitive streak

Area of Science:

• Developmental Biology
• Cell Biology
• Embryology

Background:

• The primitive streak is a transient structure in early embryonic development.
• Understanding cell differentiation and migration during gastrulation is crucial for developmental biology.

Purpose of the Study:

• To investigate the ultrastructure of primitive streak cells using Scanning Electron Microscopy (SEM).
• To determine if primitive streak cells exhibit distinct morphologies based on their future differentiation pathways (ectoderm, mesoderm, endoderm).

Main Methods:

• Scanning Electron Microscopy (SEM) was used to examine primitive streak cells in early chick embryos (Hamburger and Hamilton stages 2-5).
• Embryos were prepared by endoderm stripping and fracturing to visualize the primitive streak structure.
• Comparative analysis of cell morphology between primitive streak cells and surrounding ectodermal, endodermal, and mesodermal cells.

Main Results:

• Primitive streak cells displayed a unique morphology distinct from surrounding ectodermal, endodermal, and mesodermal cells.
• Streak cells were closely packed with long axes oriented from ectoderm to endoderm and possessed flat, leaf-like processes.
• SEM analysis did not reveal morphological differences among streak cells that could predict their specific future cell fate.

Conclusions:

• All cells migrating through the primitive streak during gastrulation share a common cellular structure.
• The observed cell morphology may be adapted for the migratory movements characteristic of invagination.
• This suggests a uniform migratory behavior for cells traversing the primitive streak, irrespective of their final destination.