[Histological and ultrastructural study of degeneration of the lumbar intervertebral disc in the rabbit following nucleotomy, with special reference to the topographical distribution pattern of the degeneration].

The degenerative and repair processes of rabbit lumbar disc after nucleotomy were topographically followed by light and electron microscopy. Light microscopic studies showed a proliferation of cells with large pericellular matrices in the inner annulus. Electron microscopic changes of the inner annular cells showed an increase in the number of micropinocytotic vesicles in the first 8 weeks following nucleotomy, early appearance of lysosomes, and a reduction in the amount of rough endoplasmic reticula from 6 weeks after operation. 'Islet areas' consisting of small ruthenium red positive materials increased in number in the pericellular matrices. These changes were topographically similar to each of them. Activation of remnant notochordal cells was evident morphologically and autoradiographically. It seemed most likely that cells of the inner annulus were activated for a initial certain period following nucleotomy, while they degenerated rapidly after surgery. Light microscopy showed these changes of annular tissue following nucleotomy to be just like those after disc incision.