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Size and surface charge properties of myelin vesicles from normal and diseased (multiple sclerosis) brain
Abstract:
Differences have been observed between myelin vesicles prepared from normal human central nervous system and from white matter of patients who died with multiple sclerosis (MS). The mean cross-sectional area of the vesicles was 5.69 +/- 0.17 micron 2 from normal myelin and 3.71 +/- 0.28 micron 2 for diseased myelin. Vesicle size was reduced to 4.08 +/- 0.21 micron 2 when normal myelin vesicles were prepared in the presence of 0.1 mM EDTA. The presence of Ca2+ during the preparation of the vesicles had no effect on the mean cross-sectional area. In the case of MS myelin vesicles, 0.1 mM EDTA had no effect on vesicle size, whereas the presence of Ca2+ increased the vesicle size from 3.71 +/- 0.28 to 5.40 +/- 0.31 micron 2. Electrokinetic analysis revealed that the electrophoretic mobility of normal myelin vesicles was -5.169 +/- 0.193 X 10(-8) compared with -6.093 +/- 0.202 X 10(-8) m2 s-1 V-1 for the MS myelin vesicles. The presence of 0.1 mM EDTA increased the electrophoretic mobility of the normal vesicles to -6.483 +/- 0.151 X 10(-8) m2 s-1 V-1 but did not significantly affect that of the MS vesicles. Addition of 0.1 mM Ca2+ decreased the electrophoretic mobility of both normal and MS vesicles to similar mobilities. From these data, the surface charge densities were calculated for both normal and MS myelin vesicles and found to be -2.93 and -5.39 mV m-1, respectively. The phase transition temperature determined by wide-angle x-ray diffraction studies was 63 degrees C for normal myelin vesicles and 43 degrees C for MS myelin vesicles.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Multiple sclerosis (MS) alters myelin vesicle size and surface charge. MS myelin vesicles are smaller and have higher surface charge density than normal myelin, with altered responses to EDTA and calcium ions.
Area of Science:
- Neuroscience
- Biochemistry
- Materials Science
Background:
- Multiple sclerosis (MS) is a demyelinating disease affecting the central nervous system.
- Myelin vesicles are crucial components of the myelin sheath, involved in its structure and function.
- Understanding biophysical differences in myelin from MS patients is vital for disease research.
Purpose of the Study:
- To investigate the biophysical properties of myelin vesicles from normal and multiple sclerosis (MS) human central nervous system.
- To compare the size, surface charge, and thermal properties of myelin vesicles in normal and MS white matter.
Main Methods:
- Preparation and characterization of myelin vesicles from normal and MS human brain tissue.
- Measurement of vesicle cross-sectional area and electrophoretic mobility.
- Analysis of surface charge density and phase transition temperature using wide-angle X-ray diffraction.
Main Results:
- MS myelin vesicles exhibited a smaller mean cross-sectional area (3.71 µm²) compared to normal myelin vesicles (5.69 µm²).
- EDTA reduced normal myelin vesicle size, while Ca²+ increased MS myelin vesicle size, indicating differential ion sensitivity.
- Electrophoretic mobility and calculated surface charge density were significantly different between normal (-2.93 mV m⁻¹) and MS (-5.39 mV m⁻¹) myelin vesicles.
- Phase transition temperature was lower in MS myelin vesicles (43°C) than in normal myelin vesicles (63°C).
Conclusions:
- Myelin vesicles in multiple sclerosis display distinct biophysical characteristics compared to normal myelin.
- These differences in size, surface charge, and thermal properties may contribute to the pathology of multiple sclerosis.
- The findings provide insights into the structural and functional alterations of myelin in MS.