THE NISSL SUBSTANCE OF LIVING AND FIXED SPINAL GANGLION CELLS

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Abstract
Living chick spinal ganglion neurons grown for 19-25 days in vitro were photographed with a color translating UV microscope (UV-91) at 265 287, and 310 m[mu]. This instrument is unique in permitting rapid accumulation of UV information with minimal damage to the cell; the color translating faculty was not utilized. In the photographs taken at 265 m[mu] of the living neurons, discrete UV-absorbing cyto-plasmic masses were observed which were found to be virtually unchanged in appearance after formalin fixation. These were identical with the Nissl bodies of the same cells seen after staining with basic dyes. The correlation of UV absorption, ribonuclease extraction and staining experiments with acid and basic dyes confirmed the ribonucleo-protein nature of these Nissl bodies in the living and fixed cells. No change in distribution or concentration of UV-absorbing substance was seen in the first 12 UV photographs of a neuron, and it is concluded that the cells had not been subjected to significant UV damage during the period of photography. On the basis of these observations, as well as previous findings with phase-contrast microscopy, it is concluded 125[ 1958] NERVOUS SYSTEM 1432-1442 that Nissl bodies pre-exist in the living neuron as discrete aggregates containing high concentrations of nucleoprotein.