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A wavelike pattern of retrograde axonal transport of lead was demonstrated in rat sciatic nerve after injection of 203Pb into the triceps surae muscle. The transport rate was about 10 mm per day, and the lead reached the spinal cord by 9 days after injection. The distribution of lead within the spinal cord indicated the possibility of retrograde axonal transport in the upper and lower motor neurons, which might explain how lead enters the central nervous system and could be related to the postulated role of lead in causing amyotrophic lateral sclerosis. Lead may be useful in investigating retrograde transport experimentally.

• Evidence is accumulating that a number of previously unexplained human diseases may arise from a deficiency of DNA repair enzymes. Studies on the motoneurons of patients with amyotrophic lateral sclerosis (ALS), and those of an animal model of motoneuronal degeneration, the wobbler mouse, indicate the presence of major abnormalities of RNA metabolism. We advance the hypothesis that the primary abnormality in ALS is the accumulation of abnormal DNA, which is unable to undertake normal transcription, in motoneurons. This abnormal DNA may arise from a deficiency of an isozyme of one of the DNA repair enzymes.

Evidence is cited from the literature and from personal experience with the "inflammatory" form of facioscapulohumeral syndrome that the creatine phosphokinase reduction occurring during pharmacologic treatment of various neuromuscular diseases does not necessarily imply therapeutic benefit.

Female carriers of the gene for Duchenne muscular dystrophy have been reported to have a decreased total body potassium concentration and a reduced biological half-life of rubidium chloride Rb 86. We have studied these factors in four "definite" carriers, five normal women, and two normal men. There was no significant difference between the mean values of either factor for the first two groups. The biological half-life of Rb 86 was significantly shorter than in normal women in one carrier, who also has a raised serum creatine phosphokinase activity. These results indicate that neither measurement is likely to be of great value in the detection of carriers of Duchenne muscular dystrophy.