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Isolation of myelinoid Marchi-positive bodies from normal rabbit spinal cord
Abstract:
Normal rabbit spinal cord was homogenized in sucrose and fractionated by centrifugation in a sucrose density gradient system slightly modified after the Norton-Poduslo method for the isolation of myelin. The following fractions were recovered: the fraction floating on 0.32 M sucrose, the myelin fraction at the 0.32 M/0.85 M interface and the pellet. After fixation in glutaraldehyde the fractions were subjected to Marchi staining, a histochemical method used for the demonstration of degenerating myelin. The floating fraction was enriched in Marchi-positive bodies as compared to the homogenate while the myelin fraction and the pellet contained low amounts. No esterified cholesterol was found in the floating fraction. Since histochemical and electron microscopical studies have shown that Marchi-positive myelinoid bodies in the normal CNS are associated with node-paranode regions our results indicate a possibility to isolate and biochemically characterize a presumably closely myelin-related fraction of known anatomical origin. The absence of esterified cholesterol in the floating fraction shows that biochemical or biophysical properties other than a content of esterified cholesterol may give rise to a positive Marchi reaction.
Insights
Researchers isolated a novel fraction from rabbit spinal cord, distinct from myelin, that stains positively for degenerating myelin. This fraction lacks esterified cholesterol, suggesting alternative properties contribute to myelin staining.
Area of Science:
- Neuroscience
- Biochemistry
- Histology
Background:
- Myelin isolation is crucial for understanding central nervous system (CNS) disorders.
- The Marchi stain is a histochemical method for detecting degenerating myelin.
- Previous studies link Marchi-positive bodies to node-paranode regions.
Purpose of the Study:
- To isolate and biochemically characterize a fraction closely related to myelin from normal rabbit spinal cord.
- To investigate the composition of a Marchi-positive fraction.
- To explore the properties of myelin-related structures.
Main Methods:
- Sucrose density gradient centrifugation modified from the Norton-Poduslo method.
- Fractionation of homogenized rabbit spinal cord.
- Glutaraldehyde fixation and Marchi staining of isolated fractions.
Main Results:
- A fraction floating on 0.32 M sucrose was enriched in Marchi-positive bodies.
- The isolated myelin fraction and pellet showed low amounts of Marchi-positive bodies.
- The floating fraction was devoid of esterified cholesterol.
Conclusions:
- A biochemically distinct, myelin-related fraction can be isolated from normal CNS tissue.
- The presence of esterified cholesterol is not essential for a positive Marchi reaction.
- This isolated fraction offers a potential avenue for studying myelin-related structures and their biochemical properties.