Adjustment of the myelin sheath to axonal atrophy in the rat spinal root by the formation of infolded myelin loops.

Atrophy of the L4 dorsal and ventral spinal roots was experimentally induced by unilateral sciatic neurectomy in groups of young (2 and 4 months) and older (12 months) albino rats. During the 4 months following neurectomy, the occurrence of infolded myelin loops (IMLs) was quantitatively examined in transverse sections prepared using perfusion fixation with glutaraldehyde and embedding in epoxy resin. The number of IMLs was higher on the operated side and increased with the time of survival and the age of the animals.

The role of Schmidt-Lanterman incisures in Wallerian degeneration.

The number of the Schmidt-Lanterman incisures and their intrasegmental distribution were studied at 36 h after transection of the rat sciatic nerve. Examination of teased, proximo-distally oriented, myelinated nerve fibers revealed no difference between the distal and the proximal stump. The results indicate that no proliferation of the incisures is required for the fiber fragmentation: numerous incisures are normally available in the midinternodal area where the degeneration begins.

The incidence of naturally-occurring primary brain tumours in the laboratory rat.

Histological analysis of 90 spontaneous primary tumours of the brain observed among 8960 ageing rats (Sprague-Dawley-derived) revealed 55 granular-cell meningiomas, 19 neoplastic reticuloses, 11 neuroglial tumours, 4 pineal tumours, and one pleomorphic, meningeal sarcoma. Although all these tumour types can occur in man and other animal species, the high incidence of granular-cell tumours, and the low degree of differentiation of some neuroglial and pineal tumours, appear to be characteristic attributes of the rat.

Changes in cellular noradrenaline fluorescence in the denervated rat superior cervical ganglion.

The microfluorimetrical investigation showed that in the principal perikarya of the rat superior cervical ganglion, after inhibition of noradrenaline-synthesis and unilateral preganglionic axotomy, the fluorescence of newly synthesized noradrenaline was most intense at the periphery of the perikarya of the intact side.