Ca-controlled, reversible structural transition in myelin

When excised goldfish spinal cord is kept in physiological saline at room temperature, the myelin multilayers swell. As studied by X-ray diffraction, the original repeating distance of 150 A (AS myelin) swells to 177 A (AL myelin); no intermediate distances are seen. At least 70% of the myelin can u...

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Bibliographic Details
Published in:Neurochemical research 1986-08, Vol.11 (8), p.1103-1129
Main Authors: BLAUROCK, A. E, YALE, J. L, ROOTS, B. I
Format: Article
Language:English
Subjects:
Analytical, structural and metabolic biochemistry
Animals
Biological and medical sciences
Calcimycin - pharmacology
Calcium - physiology
Carassius auratus
Colchicine - pharmacology
Deoxyglucose - physiology
Electron Probe Microanalysis
Fundamental and applied biological sciences. Psychology
Glucose - pharmacology
Goldfish
Humans
In Vitro Techniques
Kinetics
Lipoproteins, myelin
Myelin Proteins - metabolism
Nerve Fibers, Myelinated - drug effects
Nerve Fibers, Myelinated - metabolism
Peripheral Nerves - metabolism
Proteins
Sodium Cyanide - pharmacology
Spinal Cord - metabolism
Temperature
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Summary:When excised goldfish spinal cord is kept in physiological saline at room temperature, the myelin multilayers swell. As studied by X-ray diffraction, the original repeating distance of 150 A (AS myelin) swells to 177 A (AL myelin); no intermediate distances are seen. At least 70% of the myelin can undergo this gradual conversion. Omitting glucose from the saline, or substituting 2-deoxy-D-glucose for the glucose, or adding NaCN to the saline all promote conversion. Cooling retards the rate but does not prevent conversion. Omitting Ca does prevent conversion, however, and substituting Mg, Sr, or Ba for Ca also does so. Moreover, agents that increase the rate of conversion in Ca-containing saline by up to 5 fold (NaCN, colchicine, A23187) fail to convert myelin in Ca-free saline. We then converted AL myelin back to AS by withdrawing Ca. After converting in NaCN-containing saline, up to 3/4 of the AL myelin recompacts in Ca-free saline; however, none of the myelin recompacts if NaCN is present in the Ca-free saline. Little or no recompaction occurs after conversion in saline without NaCN. Based on our results, we suggest that the oligodendrocytes may maintain AS myelin in vivo by pumping Ca out of the myelin sheath. The myelin in a human PNS nerve has been induced to undergo a similar cycle of swelling and recompaction.
ISSN:0364-3190
1573-6903
DOI:10.1007/BF00965941