Impaired Myelinogenesis and Early Maturation of Oligodendrocytes in Black Tremor Hamster with Central Nervous System Myelin Deficiency

Abstract

Oligodendrocytes and myelin in the corpus callosum of black tremor and normal hamsters aged 3, 7, and 14 weeks were ultrastructurally examined to determine myelination index (ratio of myelin thickness/diameter of axon), percentage of naked axons, and proportions of oligodendroglial subtypes (light, medium and dark). The mutant hamsters were remarkably hypomyelinated, with a low myelination index and a high proportion of naked axons, but the proportions of the three subtypes in the mutants were comparable with those of normal hamsters at 3 weeks of age, suggesting the low myelinogenetic activity of oligodendrocytes in the mutant. Furthermore, oligodendrocytes of the mutant hamsters appeared to mature earlier than those of age-matched controls, since the proportions of dark inactive oligodendrocytes at 7 and 14 weeks of ages were higher than those of the control hamsters.