Axoplasmic transport of mitochondria in cultured dorsal root ganglion cells.

The movements of individual mitochondria in cultured mouse dorsal root ganglion cells were directly observed by using fluorescent staining with rhodamine 123 in combination with video microscopic techniques. This gives greater spatial and temporal resolution and much higher specificity than possible by conventional methods. The instantaneous velocities were 0.55 +/- 0.11 microns/s anterograde and 0.60 +/- 0.10 microns/s retrograde. Movement of the mitochondria was in fits and starts, and some reversed direction. The number of mitochondria moving retrogradely was 1.5-1.9 times greater than the number moving anterogradely. The average length of mitochondria moving retrogradely was 2.8 microns and of mitochondria moving anterogradely was 4.1 microns. These results suggest that mitochondria increase their numbers by division in the nerve fiber terminal.