Search

The motor nerve conduction velocity (NCV) was studied in the ulnar and sciatic-tibial nerves of dogs of various ages. The adult values are reached between six months and one year of age. The NCV remains on a plateau range of approximately 60 ± 10 m/sec from one to seven years of age. After seven years there is a gradual decline in NCV so that by 10 years the velocity is reduced by 10–15 per cent. In addition to the reduction of velocity there is also an increased dispersion of the evoked muscle action potential.

Muscles from 50 dogs were examined at various times after denervation. Electromyography (EMG) studies were made and motor nerve conduction velocities (NCV) measured. In partial denervation a reduced interference pattern was demonstrated in certain cases. In one case, which resembled spinal muscular atrophy in humans, giant motor unit potentials were present. Iii normal relaxed muscle, spontaneous activity was only recorded from the end plate zone. This ‘end plate noise’ was abolished by muscle relaxants. In denervated muscle, fibrillations and positive sharp waves were present in increasing numbers 5-7 days after denervation. After a total nerve lesion the NCV in the distal segment remained normal for 5-7 days when conduction ceased. The evoked muscle action potential decreased in amplitude during this period. These findings and their physiological origins arc discussed.

Two cases in dogs of spinal cord infarction due to intervertebral disc emboli were investigated. One case showed evidence of disc protrusions and emboli were found in a peridiscal artery. The emboli appeared to have originated from the annulus fibrosis and were identified by their staining properties. In the second case, the source of the emboli was presumptive and based solely on their histochemistry.

Neurofilament-enriched fractions were prepared from defined regions of the central nervous system and the sciatic nerve of a dog which had been diagnosed to have giant axonal neuropathy. These fractions were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis together with a neurofilament fraction from normal dogs. The three neurofilament polypeptides with molecular weights of 230,000, 145,000, and 68,000 daltons found in normal dogs were also present in the diseased animal, and in the same relative amounts, indicating that the protein composition of neurofilaments which accumulate in this disorder has not been altered.