No disturbance of myelination in the central nervous system by selective 3H beta-irradiation.

The effect of a selective irradiation of myelin by 3H beta-particles was studied by light and electron microscopic methods in guinea pig spinal cord. The animals were injected with [3H]leucine shortly after birth when the rate of myelin biosynthesis is high and sacrificed 130 days later. In spinal cord the radioactivity was mainly preserved in myelin because the half life of myelin proteins is much higher than that of most other CNS proteins. As a consequence the irradiation dose in the white matter was much higher than in the gray matter. In myelin internally irradiated by 3H beta-particles within 130 days at a dose of 10 Gy no alterations could be detected either by morphological or by morphometric methods.