PHYSICO-CHEMICAL STUDIES ON THE MICROSOMAL RIBONUCLEOPROTEIN PARTICLES

By ESR spectra and magnetic susceptibility measurement, the ferromagnetic behavior of liver ribosome, ribosomal RNA and thymus DNA was studied. The results obtained strongly suggested that RNA and DNA of high molecular weight are ferromagnetic in themselves and hence they would be so even in the ribosomes or nuclei. Some studies on the brain microsomes were made. Using the method of isolating liver ribosome, it was found that brain ribosomes were also composed of 110s, 80s and 60s component. Electron microscopically, they appeared very similar to liver microsomes. Using ultracentrifugation in the density gradient of sucrose, subfractionation of brain homogenate was carried out. The mitochondrial as well as the microsome particles were found to contain some physiologically active substances such as ACh, SP, Nor and 5HT. Elec tronmicroscopical observations strongly suggested that these substances, which were assumed as a candidate of central transmitter hitherto, were normally present in the particles similar to the isolated nerve ending described by de Robertis school. The activity of these substances recovered in the microsomal fraction seems to be attributed to the microvesicles (i.e., synaptic vesicles) originated from the disrupted endings. According to their stainability with OsO4, these ending-like elements seem to be classified into two categories; cholinergic ones containing ACh and SP and non-cholinergic ones containing Nor and 5HT. The former is lighter and lightly stained with OsO4.