Differences in myelination between spinal cord and corticular tissue transplanted intraocularly in rats.

This paper compares the myelination in rat cortex and spinal cord transplanted on the embryonic day (E) 12, 14, 16, 18, 20 and right after birth (P0) into the anterior eye chamber of adult rats. Myelinated fibers were not observed in either cortical or spinal cord transplants of E12. When transplanted on E14, abundant myelinated fibers developed in the spinal cord and gathered at the periphery of the transplants as a "white matter". In the grafted cortex myelinated fibers were found when transplantation occurred on E16 or later. The myelinated fibers, however, remained scarce or formed only narrow bundles. The number and distribution of myelinated fibers did not depend on the donor's age between E16 and P0: even in the latter case transplanted cortex were found without myelination. The differences could be attributed to the different development of the cortical and spinal cord oligodendrocytes and to the different intrinsic organization of the grafted samples.