No abstract

Fast transport of intra-axonal organelles was studied in motor nerve from amyotrophic lateral sclerosis (ALS) patients. Organelle traffic in ALS nerves demonstrated a significant increase in anterograde mean speed, while retrograde mean speed was decreased compared with that of controls. Retrograde traffic density (organelles per unit time) was also significantly decreased in the ALS specimens. Anterograde transport machinery is therefore intact and may be responding to the increased physiologic demand of larger motor units. Diminished retrograde speed and organelle traffic density are consistent with a defect in retrograde transport and could impair communication between axon terminals and perikarya.

No abstract

No abstract

Moving intra-axonal organelles demonstrate frequent variations in speed when viewed over several seconds. To evaluate these and other motion variations, a long-term analysis of organelle motion in isolated axoplasm of Myxicola infundibulum was carried out using differential interference contrast optics and analog and digital image enhancement techniques. Motion characteristics of individual organelles were analyzed for periods of up to 58 minutes. Three principle observations on organelle motion were made: 1) Classes of organelles of the same size demonstrated a 5- to 25-fold variation of speed, with the slowest speeds occurring most frequently; 2) organelle speeds over individual translocations (motion without stopping) are inversely proportional to their size, but the speeds calculated for the long-term analysis of organelle motion (total distance travelled/total observation time, including pauses) did not reflect this observation; and 3) organelles displayed variable trip lengths, durations, mean speeds, and pause durations, and the relationships between these variations showed no repetitive patterns. In contrast to reported observations of uniform velocities of organelles moving on isolated microtubule preparations, these observations suggest that a variety of factors must play a role in organelle translocation in Myxicola axoplasm.