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Studies of human myelin proteins during old age
Abstract:
The electrophoretic protein patterns of myelin isolated from frontal and callosal white matter were studied in adult man up to the age of 90 years. The proportions of the four major myelin proteins remained virtually unchanged as did the total protein content of white matter and of purified myelin. The total mass of purified myelin that could be recovered from white matter gradually decreased with age, suggesting an age-related loss of myelin sheath and probably neurons as well, without detectable alterations of the regular protein composition of myelin. In most cases basic protein of myelin was preceded by one or two minor protein components on electrophoresis. One of them is tentatively identified as "prebasic" protein similar to the one previously observed in other species, because of its close electrophoretic apposition to the main basic protein. The second component was found less frequently and was thought to arise from specific types of proteolysis of myelin proteins. Prolonged time intervals between death and autopsy had little, if any, effect on the proportions of basic protein and proteolipid protein. Similar results were obtained when bovine brain was incubated under conditions designed to simulate post-mortem autolysis. It was there fore concluded that meaningful data on proteins of human central myelin may be obtained even though an autopsy was not performed within a few hours of death.
Insights
Human myelin protein composition remains stable with age, despite a decrease in myelin mass. This indicates an age-related loss of myelin sheath and neurons without altering protein structure, allowing reliable study even post-mortem.
Area of Science:
- Neuroscience
- Biochemistry
- Aging Research
Background:
- Myelin, the protective sheath around nerve fibers, is crucial for efficient neural signal transmission.
- Understanding age-related changes in myelin composition is vital for comprehending neurological health decline.
Purpose of the Study:
- To investigate age-related alterations in the electrophoretic protein patterns of human myelin.
- To assess the impact of post-mortem intervals on myelin protein integrity.
Main Methods:
- Electrophoretic analysis of myelin proteins isolated from human frontal and callosal white matter (up to 90 years).
- Comparison of protein profiles and content in relation to age.
- Incubation of bovine brain tissue to simulate post-mortem autolysis.
Main Results:
- Proportions of major myelin proteins and total protein content remained consistent with age.
- A gradual decrease in the total mass of purified myelin was observed with aging.
- Minor protein components, potentially 'prebasic' protein and proteolysis products, were identified.
- Extended post-mortem intervals had minimal impact on key myelin protein proportions.
Conclusions:
- Human central myelin protein composition is remarkably stable throughout adulthood.
- Age-related myelin loss occurs without significant changes in its fundamental protein makeup.
- Reliable analysis of human central myelin proteins is feasible even with delayed autopsy procedures.