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Electron-microscopic identification of Gomori-positive rings in normal spinal cord white matter
Abstract:
Longitudinal vibratome slices from glutaraldehyde-fixed adult guinea pig lateral funiculus white matter were incubated in a Gomori medium, stained with ammonium sulfide, osmicated and section-embedded in vestopal. Following light-microscopic localization of ring-shaped deposits of reaction product series of thin sections were cut from these areas. In the electron microscope ring-shaped deposits of reaction product were consistently found to surround lamellated myelinoid bodies within glial cells. By following the series some of these cells could be identified as microglia. Sparse aggregates of reaction product were occasionally seen outside myelinoid bodies in typical astrocytes. Precipitates were not related to myelinoid bodies associated with typical oligodendrocytes. The findings suggest that microglia and possibly astroglia participate in the breakdown of spontaneously formed myelin fragments in normal adult white matter.
Insights
Microglia and astrocytes in adult guinea pig white matter break down myelin fragments. This study identifies glial cells involved in myelin debris clearance in the central nervous system.
Area of Science:
- Neuroscience
- Cell Biology
- Histology
Background:
- The central nervous system (CNS) contains myelin, a lipid-rich sheath essential for nerve impulse conduction.
- Myelin turnover and debris clearance are crucial for maintaining CNS homeostasis and function.
- The specific glial cells responsible for clearing spontaneously formed myelin fragments in normal adult white matter remain incompletely understood.
Purpose of the Study:
- To investigate the cellular mechanisms involved in the breakdown of myelin fragments in adult guinea pig lateral funiculus white matter.
- To identify the types of glial cells that phagocytose and process myelin debris.
- To elucidate the role of microglia and astrocytes in myelin maintenance and turnover.
Main Methods:
- Preparation of longitudinal vibratome slices from adult guinea pig lateral funiculus white matter.
- Incubation in Gomori medium, staining with ammonium sulfide, and osmication for ultrastructural visualization.
- Embedding in vestopal and examination using light and electron microscopy to identify reaction product deposits and cellular structures.
Main Results:
- Ring-shaped deposits of reaction product were consistently observed surrounding lamellated myelinoid bodies within glial cells.
- Electron microscopy identified some of these glial cells as microglia, actively involved in myelin breakdown.
- Sparse reaction product aggregates were also found associated with astrocytes, suggesting their participation, while oligodendrocytes showed no related precipitates.
Conclusions:
- Microglia are key players in the breakdown of spontaneously formed myelin fragments in normal adult white matter.
- Astrocytes may also contribute to the clearance of myelin debris, although to a lesser extent than microglia.
- These findings highlight the dynamic nature of myelin maintenance and the active role of glial cells in clearing myelin debris in the healthy adult CNS.