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Membrane particles on fracture faces of frozen myelin
Abstract:
Freeze-fracture electron microscopy reveals constant and widespread presence of membrane particles on the fracture faces of frozen myelin. In unfixed myelin frozen shortly after dissection the distribution of the particles is uniform. In glutaraldehyde-fixed and/or glycerol-impregnated myelin the particles frequently occupy a network interspersed with circumscribed particle-free areas of variable dimension. In these membranes the network of particles is propagated radially across many lamellae. Particle-rich areas are closely apposed and contrast with frequent delamination of adjacent particle-free regions. We propose that, as in other plasma membranes, the particles of myelin represent protein-containing structures intercalated across the hydrophobic matrix of a membrane with bilayer organization. Our results indicate that these structures contain sites which mutually interact at the surface of apposed membranes and may be important in maintaining the organizational integrity of myelin.
Insights
Freeze-fracture electron microscopy shows membrane particles in myelin. These particles may interact, maintaining myelin
Area of Science:
- Neuroscience
- Cell Biology
- Biophysics
Background:
- Myelin is a crucial insulating sheath in the nervous system.
- Its structural integrity is vital for proper nerve function.
- The molecular organization of myelin membranes remains incompletely understood.
Purpose of the Study:
- To investigate the distribution and nature of particles within myelin membranes.
- To understand the role of these particles in myelin structure and stability.
Main Methods:
- Freeze-fracture electron microscopy was employed.
- Myelin samples were examined in both unfixed and fixed/impregnated states.
Main Results:
- Constant and widespread membrane particles were observed on myelin fracture faces.
- Unfixed myelin showed uniform particle distribution.
- Fixed/impregnated myelin exhibited a network of particles, often organized radially across lamellae, with particle-free regions.
- Particle-rich areas were closely apposed, contrasting with particle-free regions.
Conclusions:
- Myelin particles likely represent protein structures within the lipid bilayer.
- These protein structures may possess interaction sites crucial for maintaining myelin's organizational integrity.