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Molecular Composition of Myelin Synthesized Subsequent to Irradiation

Ole A. Schjeide, Robert I-San Lin and Jean De Vellis
Radiation Research
Vol. 33, No. 1 (Jan., 1968), pp. 107-128
DOI: 10.2307/3572246
Stable URL: http://www.jstor.org/stable/3572246
Page Count: 22
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Molecular Composition of Myelin Synthesized Subsequent to Irradiation
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Abstract

Myelin has been isolated from brain stems of control rats and their head-irradiated littermates (700 rads at 2 days of age). Rats were sacrificed at 20, 30, 40, and 180 days of age. Much less myelin was found to be deposited in brain stems of head-irradiated rats as compared to controls. However, within experimental error, no differences were ascertained, as functions of either age or irradiation, in major building blocks of myelin. These include total protein, total sterol, phosphatidyl serine, sphingomyelin, phosphatidyl choline + lyso-phosphatidyl choline, phosphatidyl ethanolamine + phosphatidal ethanolamine, and cerebroside + cerebroside sulfate. However, the proportions of all normal unsaturated fatty acids in myelin from irradiated rats were lower with respect to their saturated counterparts than in control myelin. Markedly lower ratios of both monounsaturated C24 acid and monounsaturated C26 fatty acid to their saturated counterparts were noted, and the proportion of total C26 to total C24 fatty acids was less. In fact, longer-chain-length fatty acids were generally present in smaller amounts in irradiated myelin. Similar differences in proportions of myelin fatty acids occur normally among varying age groups. Myelin from more mature animals contains higher proportions of unsaturated fatty acids and higher proportions of the longer-chain-length fatty acids than myelin from younger animals. These observations are consistent with the view that X-irrdiation given to the head at an early age prevents the normal biochemical differentiation of the glial cells giving rise to myelin.

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