Cytochemical demonstration of nucleoside phosphatase activity in myelinated nerve fibers of the rat

Summary The histochemical and cytochemical localization of end product from the Wachstein-Meisel reaction was examined in transverse frozen sections of rat ischiatic nerve and spinal nerve roots. A variety of fixatives, substrates, and inhibitors were used at varying pH. Following glutaraldehyde fixation, nucleoside phosphatase activity was noted in the axon-Schwann cell interface of both unmyelinated and myelinated nerve fibers. The presence of this enzymatic activity at this strategic location in the nerve fiber complex attests to the importance of this space as a metabolically active site.Additional deposits of end product occurred on neurofilaments of myelinated and unmyelinated axons and were observed as diffuse axonal stains by light microscopy. These precipitates had a predilection for tissue fixed in formalin or hydroxyadipaldehyde and were relatively more prominent following acidic incubations. The resemblance between these deposits and spurious axonal acid phosphatase precipitates was discussed.This study was supported by Grant NB 04161 of the National Institute of Neurological Disease and Blindness.