Turnover of proliferative cells in the spinal cord after X irradiation and its relation to time-dependent repair of radiation damage.

The changes in labelling index of neuroglial cells of the rat cervical cord following 20 Gy X rays are compared with the timing and pattern of the repair of radiation damage in the spinal cord. The start of time-dependent repair coincides with the release of the proliferative neuroglia from a block at the G1/S border. The evidence suggests that the time-dependent repair reflects the normal unstimulated proliferation of the surviving neuroglial cells and that homeostatically stimulated recruitment to the proliferative neuroglia does not occur until the period just before the development of paralysis. A normal cell-cycle time of about one month for the spinal cord neuroglia is indicated from the observed pattern of labelling.