Velocity measurements of particulate neuroplasmic flow in organized mammalian CNS tissue cultures.

The movements of spherical particles in the range of 0.3 to 0.8 mum diameter within neurities of cultured embryonic mouse spinal cord fragments were observed and recorded by means of Nomarski optics and time-lapse photocinematography at high power. Particulate movements were measured by projecting the motion pictures onto a calibrated screen and recording the distances moved with time of linearly moving particles and making note of the direction (toward or away from the neuron soma) of movement. In all, 128 particles were measured in six cultures. These measurements were taken away from the neuron soma near the periphery of the neurites. Eight-three particles were noted to be moving toward the neuron at a mean velocity of 1.03 +/- 0.38 (SD) mum/sec while 45 anterograde moving particles were noted to move at 1.07 +/- 0.62 (SD) mum/sec. Statistical analysis of these veolcities revealed no significant difference between them. Particles which were elongated and probably represented mitochondria moved more sluggishly and could not be measured accurately by the techniques employed. It appeared the spherical particles moving in a retrograde direction originated at the neurite tip apparently by pinocytosis. There was a suggestion that anterograde flow and retrograde flow may have been affected unequally by factors which develop in the observation chamber over a period of 2 hr or more. The most likely factor responsible was probably hypoxia.