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Biomedical subjects

T R Swift

Publications and source records attributed to T R Swift.

59 records · Page 4Linked to original sources
PubMedDate not supplied

Acute effects of phenytoin on peripheral nerve function in the rat.

The acute effect of intraperitoneal injection of phenytoin on rat peripheral nerve was studied. Conduction velocities in the ventral caudal nerve were measured hourly and phenytoin blood levels were obtained 4 to 5 hours after injection. Conduction velocity decreased by 23% in the 25 phenytoin-treated animals from a control value of 30.0 plus or minus 1.3m/sec (mean plus or minus SEM) to a 4-hour value of 23.0 plus or minus 1.3 m/sec (P less than 0.001). The phenytoin blood level 4 hours after injection was 45.0 plus or minus 1.3 micrograms/ml. Amplitudes of evoked muscle action potentials in the treated group decreased by 37% from control values. High levels of phenytoin induce prompt slowing of nerve conduction velocity within hours, which may be mediated by mechanisms similar to those responsible for toxic central effects.

Action Potentials↗
PubMedDate not supplied

Disorders of neuromuscular transmission other than myasthenia gravis.

Disorders of neuromuscular transmission in humans are caused by a wide variety of agents including systemic diseases, drugs, environmental toxins, animal envenomation, cations, and hormones. Some are genetically determined. Many are of known etiology. All such disorders interfere with one or more events in the sequence whereby a nerve impulse excites a muscle action potential. In many disorders of neuromuscular transmission, abnormal fatigue occurs, and some cases respond dramatically to treatment. Investigation of the microphysiology, microanatomy, and pharmacology of both normal and diseased neuromuscular junctions has increased our knowledge of these disorders.

Action Potentials↗
PubMedDate not supplied

Nerve conduction velocity varies inversely with height.

Even when all known factors affecting the determination of nerve conduction velocity are controlled, large individual variations persist. In 40 normal controls, we found that peroneal and sural conduction velocities varied inversely with body height (P less than 0.001). This height effect is not due to temperature differences, and it explains almost 50% of the intersubject variability in conduction velocity. We hypothesize that the height influence reflects abrupt, rather than gradual, tapering of axons distally. This mode of tapering may help explain the decrements in conduction velocity from proximal to distal nerve segments and from upper to lower extremities, which have long been observed in clinical electromyography. Clinical recognition of this height effect is important lest one label as abnormal an individual with mildly slowed peripheral nerve conduction velocity solely related to large stature.

Adolescent↗