A defect in the cell cycle of neuroglia in the myelin deficient jimpy mouse.

One h after receiving a single pulse of [3H]thymidine, spinal cords from jimpy and control animals were examined for labeled cells and for cells in mitosis. Although the number of labeled cells was significantly higher in jimpy spinal cords at 14 and 20 days postnatal, the number of mitotic cells was not. In normal animals, the ratio of the number of labeled cells to the number of mitotic cells (L:M) was close to 4:1 regardless of the age of the animal or the labeling index. In jimpy animals, the L:M ratio was always close to 8:1. Previous ultrastructural studies have shown that the great majority of [3H]thymidine-labeled cells in jimpy central nervous system (CNS) at these ages are oligodendrocytes. Therefore, the unusually high L:M ratio indicates that there is an abnormality in some aspect of the jimpy oligodendroglial cell cycle.