Neuronal dynamics and axonal flow. 3. Cellulifugal transport of labeled neuroplasm in isolated nerve preparations.

Abstract

The localized labeling by tritiated leucine of ganglionic protein in excised isolated mouse nerve preparations is feasible. There is initial time-limited seepage of incorporated label through endoneurial channels, which was recorded quantitatively (up to several millimeters per day). Intraneuronal protein transport through axonal flow from ganglion to peripheral nerve continues in isolated preparations after subcutaneous transplantation and explantation in vitro. Daily translocation of intra-neuronal protein from ganglion to nerve is between 6 and 11%. On the tenuous assumptions that protein concentration in axons is roughly 4%, that most nonproteinaceous compounds also come from the perikaryon, and that most axonal water is structurally bound this would indicate a daily movement down the axon of between 1 1/2 to 3 times the volume of ganglionic mass. For a nerve cell of 40 [mu] diameter with an axon of 6 [mu] diameter, this would amount to an advance of axonal flow of the order of 1 mm per day, which agrees with previous determinations. Some indications of proximodistal movement within the nerve portion itself were also obtained. Besided providing confirmation and better quantification for the phenomenon of neuroplasmic flow, the method seems uniquely suited for short-term mass experiments.