SOME PROPERTIES OF ISOLATED NEURONAL CELL FRACTIONS

Abstract

Abstract— 1. Histochemical evidence was presented illustrative of the composition of neuronal and neuropil (‘glial’) fractions isolated according to a previously published procedure. The neuropil refers to all cortical tissue other than neuronal perikarya.2. On the basis of cell counts and of DNA content, an average cell mass of 100‐110 pg was calculated for cells in the neuronal fraction. Eight per cent of the total DNA was recovered in the neuronal fraction.3. Both fractions synthesized ATP in vitro. Concentrations after 60 min incubation with glucose were: neuropil, 7–36 μmoles/mg protein; neuronal, 12–31 μmoles/mg protein.4. Osmotic shock or homogenization resulted in changes in turbidity of the cell fractions which were interpreted as indicative of loss of cell structure. The free pool amino acids glutamate, glutamine, GABA, aspartate and alanine were retained in the precipitable material through several washes with isotonic solutions. Homogenization released 72 per cent of the neuronal and 68 per cent of the neuropil amino acids into the supernatant, but only 37 per cent and 19 per cent respectively of the protein.5. By contrast with earlier reports, K+ accumulation has now been demonstrated in both neuronal and neuropil fractions. After incubation with glucose, K+ level were calculated as being 80 per cent of slice in the neuronal, and 65 per cent in the neuropil fraction. These results, and those of the osmotic shock experiments, were taken as indicative of the retention of some cell structure.6. By comparison, cell fractions prepared by other procedures, using acetone‐glycerol‐water or tetraphenylboron for tissue disaggregation, produced preparations with limited metabolic capabilities; oxygen uptake, CO2 and lactate production were all lowered substantially.