Abstract
Myelin is formed by a satellite cell which wraps around the axon to form a continuous spiral of membrane. This membrane has a distinctive lipid and protein composition when compared with other membran ous structures. The myelin components may be synthesized at the level of the forming membrane, or transported into the membrane following synthesis by some other intracellular organelle.
The synthesis of sulfatide, a membrane lipid, by 95 and 17-day-old rats was determined after a single intraperitoneal injection of 35S-sulfate into the sulfatide of whole brain, myelin, non-myelin organelles, and 105,000 × g supernatant of brain was followed. At times when there was no further de novo synthesis of lipid, the amount of labelled sulfatide in myelin continued to increase while that of non-myelin membranes decreased. The transfer of sulfatide from non-myelin structures to myelin appeared to be mediated by soluble lipoproteins which were isolated from supernatant, characterized, and found to contain labelled sulfatide.
In vitro studies, indicated that isolated myelin contained galactocerebroside sulfokinase, the enzyme involved in the synthesis of sulfatides. Thus, isolated myelin contains some membranous components capable of synthesizing myelin lipids.
These studies suggest that a lipid component of myelin is both transported into the forming membrane by a carrier lipprotein and synthesized by the myelin membrane. The relationship between these two mechanisms of formation of myelin components during development will be discussed. (SPR)
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Herschkowitz, N., McKhann, G. 92 Mechanism of Myelin Formation During Development. Pediatr Res 1, 223–224 (1967). https://doi.org/10.1203/00006450-196705000-00098
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DOI: https://doi.org/10.1203/00006450-196705000-00098