THE ACTIVITY OF 5'-NUCLEOTIDASE DETERMINED HISTOCHEMICALLY IN THE DEVELOPING RAT BRAIN

The enzyme 5'-nucleotidase is found to occur in the nerve fibres of the rat brain, probably in the myelin sheath. The enzyme develops rapidly during the period associated with myelination. Its rate of development is at first rapid, but later proceeds at a reduced pace until the animal reaches maturity. Biochemical levels during maturation, and the levels of enzyme activity left after histochemical processing, have been compared and found to be of a similar order. A series of illustrations show the increasing intensity of enzyme activity during maturation. The biochemical findings for the corresponding ages are graphically represented. Microscopically, the changes occurring in the first 10 days, and after the 80th day, cannot be differentiated: the very young animals show no activity and the mature animals show an uniformly high activity. Some special areas show a relatively low enzyme activity. A freeze-drying method is described which appears suitable for preparing nervous tissues for the microscopic study of 5'-nucleotidase activity. It is suggested that this enzyme may prove of value in the study of demyelinating disorders.