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Biochemical changes in mouse brain myelin during experimental primary amoebic meningo-encephalitis
Abstract:
Myelin membranes were purified from normal as well as experimental primary amoebic meningo-encephalitis-afflicted mouse brains. Infected myelin fractions were observed to form a floating fraction in 0.32 M sucrose. Total proteins, total lipids, phospholipids, cholesterol and galactolipids decreased markedly due to amoebic infection. Phosphatidyl choline, phosphatidyl ethanolamine plus phosphatidyl serine and sphingomyelin were decreased with a concomitant increase in lysophosphatidyl choline, lysophosphatidyl ethanolamine plus lysophosphatidyl serine and phosphatidic acid. SDS-polyacrylamide gel electrophoresis of myelin proteins exhibited six major protein fractions. Marked depletion in proteolipid protein was observed; 5'-nucleotidase activity increased while Na,K-ATPase and Mg-ATPase activities decreased. Infected myelin Na,K-ATPase had lower Vmax and higher Km values than normal. Arrhenius plots of normal myelin Na,K-ATPase exhibited transition temperature at 22 degrees C while no transition temperature could be observed in case of infected myelin Na,K-ATPase.
Insights
Primary amoebic meningoencephalitis significantly alters mouse brain myelin composition and function. Key lipids and proteins decrease, while enzyme activities and membrane fluidity are disrupted.
Area of Science:
- Neuroscience
- Biochemistry
- Pathology
Background:
- Primary amoebic meningoencephalitis (PAM) is a rare but devastating central nervous system infection.
- Myelin, the protective sheath around nerve fibers, is crucial for proper neurological function.
- Understanding myelin alterations in PAM is vital for developing therapeutic strategies.
Purpose of the Study:
- To investigate the biochemical and functional changes in myelin during experimental primary amoebic meningoencephalitis.
- To characterize the alterations in myelin protein and lipid composition.
- To assess the impact of infection on myelin-associated enzyme activities and membrane properties.
Main Methods:
- Purification of myelin membranes from normal and experimentally infected mouse brains.
- Biochemical analysis of total proteins, lipids, phospholipids, cholesterol, and galactolipids.
- SDS-polyacrylamide gel electrophoresis for protein fraction analysis.
- Enzyme activity assays (5'-nucleotidase, Na,K-ATPase, Mg-ATPase).
- Kinetic analysis of Na,K-ATPase (Vmax, Km) and Arrhenius plot analysis.
Main Results:
- Infected myelin showed altered buoyant density and significant decreases in total proteins, lipids, phospholipids, cholesterol, and galactolipids.
- Specific phospholipid changes included decreased phosphatidyl choline, phosphatidyl ethanolamine, phosphatidyl serine, and sphingomyelin, with increased lysophosphatidyl derivatives and phosphatidic acid.
- SDS-PAGE revealed marked depletion of proteolipid protein.
- 5'-nucleotidase activity increased, while Na,K-ATPase and Mg-ATPase activities decreased in infected myelin.
- Infected myelin Na,K-ATPase exhibited reduced Vmax and increased Km, and lost its characteristic transition temperature observed in normal myelin.
Conclusions:
- Primary amoebic meningoencephalitis causes profound biochemical alterations in mouse brain myelin.
- These changes include significant depletion of structural proteins and lipids, and dysregulation of key enzymatic activities.
- The loss of membrane transition temperature in infected myelin suggests altered lipid packing and membrane fluidity, contributing to neurological dysfunction in PAM.