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Ultracentrifugal analysis of ribosomes has revealed that ribosomes extracted from guinea pig liver were dissociated through two intermediate components with 50 S and 60 S to a final stage, in which the large (47 S) and the small (32 S) subunit exist in a weight ratio of 2:1, similar to the E. coli ribosomes. From the molecular weight determination, it was suggested that, in the intermediate stage, the small subunit probably exists as a dimer, thus overlapping the sedimentation peak of the large subunit. Sedimentation analysis either by ultracentrifugation or by sucrose density gradient centrifugation has shown that the 50 S and the 60 S components are both composed of the large and the small subunit. It was found that the small subunit is released from the 50 S and 60 S component in the solution containing less than 1 - 2.5 x 10-5 M Mg ion, while in the solution containing more Mg ion, no such release was observed. The small and the large subunit were isolated in the presence of Mg and the association between the same and the different kind of ribosomal subunit was examined. These components, which were isolated by the sucrose density centrifugation, were observed by an electronmicroscope using shadow casting method. All the particles were spherical except the small subunit which appeared as a flattened disc. The observed diameters of these particles were clearly larger than those for the unhydrated spherical molecules calculated from their molecular weights but were smaller than those of hydrodynamically equivalent spheres calculated from the molecular weight and sedimentation coefficient.

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.

The light scattering studies were performed on microsomal particles isolated from rabbit brains. It was demonstrated that the measurement of dissymmetry coefficient as well as of angular scattering patterns afforded a means to estimate, at least semiquantitatively, changes in volume of microsomal vesicles. In hypertonic sucrose or salt media, Boyl-van't Hoff's relation was found to be applicable to the osmotic behaviour of brain microsomes. ATP and ADP caused contraction of microsomes in the presence of a monovalent cation. Participation of Na-K-dependent ATPase in such a microsomal contraction could not be proved, though some enzymic process is highly probably involved. The preliminary results strongly suggest that the antimeycin-insensitive electron transport system in brain microsomes described previously is closely related to volume changes of microsomes. (Author)

In view of the fact that little attention has been paid to electron transfer system of brain microsomes, some studies have been made on microsomal cytochrome b5 and related oxidative activities and their relation to cation incorporation of brain microsomes. The results obtained strongly suggest the presence in neuronal elements of these cyanide- and antimycin-insensitive oxidative activities and a tentative formulation of electron transfer pathways in brain microsomes was presented. Some preliminary evidences for the view that cation incorporation in the brain microsomes is linked with the above-stated electron transfer system were obtained, but not yet conclusive. Using the light-scattering technique, it was demonstrated that the brain microsomes are capable of changing their shape or volume in vitro either passively by changes in the osmotic pressure of suspension medium or actively by ATP and Na or K ion. The questions as to whether Na and K dependent ATP-ase participates in such an active contraction of brain microsomes and whether electron transport through the cyanide-insensitive oxidative pathways is obligatory for microsomal contraction are now under investigations. (Author)