[Development of the fragments of embryonal spinal cord in a damaged peripheral nerve of a mature animal].

By means of morphological methods dynamics of the spinal cord development in 14-day-old rat embryos implanted into the sciatic nerve of mature rats have been studied. The implants preserve their viability during 5 months after the operation and their cells continue to differentiate beginning from neuroepithelial cells and neuroblasts up to young and mature neurons with histotypical signs of motoneurons. In 6 h and 1 day after transplantation the neuroepithelial cells continue their mitotic division. In 3 days, however, their mitotic activity decreases essentially and differentiation of neuroblasts begins. In 7 days the implants consist mainly of differentiated neuroblasts and glial cells. As demonstrates electron microscopy, in 30 days after the operation in the implants there is a well developed neuropil, where mature neurons, myelinated axons are situated and synaptic contacts are present.