SEDIMENTATION ANALYSIS OF RIBONUCLEIC ACID EXTRACTED FROM ISOLATED MAUTHNER NERVE FIBRE COMPONENTS

Segments of spinal cords from goldfish or from carp were incubated in vitro in the presence of RNA precursors for varying periods of time to isolate Mauthner nerve fibres from the fresh unfixed tissue or from the fixed spinal cord.

Abstract

Abstract— Segments of spinal cords from goldfish or from carp were incubated in vitro in the presence of RNA precursors for varying periods of time. Mauthner nerve fibres were isolated from the fresh unfixed tissue, or, for the separate analyses of axon and myelin sheath, from the fixed spinal cord. The myelinated Mauthner fibre isolated from the incubated spinal cord showed RNA synthesis. A considerable part of the material sedimented at 4 S , but part of the nucleic acid was recovered at higher sedimentation values, up to 30 S. Newly synthesized RNA was extracted from the isolated myelin sheath as well as from the axon. Isolated myelinated Mauthner fibres were also incubated in vitro with RNA precursors. In this case incorporation occurred exclusively in material sedimenting at 4 S or lower. The turnover rate for RNA from the fibre was of a higher order than that of the bulk of RNA from the spinal cord. The findings of RNA synthesis in these tissue components lacking nuclei could possibly be explained as owing to mitochondria. Studies by electron microscopy demonstrated the extent of purity of the isolated components and it was found that contamination was so small as to make it unlikely that the RNA investigated originated in contaminating tissue.