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Pulse-chase profiles of radiolabeled protein in frog lumbar motor neuron cell bodies. Following a 2h labeling period with 3H-leucine at 17 ° C, hemicords from one side of six frogs were exposed to frog Ringer solution containing 5mM unlabeled leucine for up to 180 min, followed by cell body isolation. Hemicords from the opposite side were taken immediately after the pulse period and their cell bodies were used to determine the initial time point (0 min) for the chase period. This peculiar and intriguing oscillation in the cpm/cell body is unexplained and may or may not involve export of newly synthesized protein from the motor neuron cell body.