Effect of DNase on DNA-like fibrils in chloroplasts and mitochondria

For the purpose to confirm the localization of DNA in chloroplasts and mitochondria, the cells of Spinacia oleracea fixed with glutaraldehyde-Os04 were observed by electron microscope with or without DNase treatment. &#34;DNA fibril complexes&#34; have always been found in the electron-transparent regions of the chloroplasts and mitochondria of the cells receiving no DNase treatment. By treating with DNase, the DNA fibril complexes of these organellae are reduced considerably in their density, leaving only faintly visible ghostlike structure or having completely disappeared. These observations confirm that the DNA fibril complexes in chloroplasts and mitochondria as demonstrated by glutaraldehyde-OsO4 fixation are the DNAcontaining structures similar to those found by formalin or buffered OsO4 fixation, and suggest that it will have only a small amount of the material other than DNA distinct from the case of DNA in the nucleus.</p

Malignant cell transformation by the SV-40 DNA and phagocytic activity related to alteration of cell membranes

In vitro cell transformation of human embryo cells could be induced by the DNA purified from SV 40. The result shows clearly that cell transforms a part of viral DNA into the genome. In addition, for the purpose of clarifying th~ biological differences between the normal and transformants the alteration of cell membraneous structures of transformants (hamster and mouse fibroblasts) were observed from mechanism of phagocytosis. The iron colloid particles are taken up by normal diploid fibroblasts but not by the human and hamster transformants. This fact suggests a differ~nce in the molecular arrangement of the cell membranes between the normal and transformants. In the presence of histones, however, the transformants phagocytize the colloid particles very actively. The results show that cell membranes of transformants are altered in the molecular structure r~sponsible for the surface charge. In addition, there is no remarkable quantative differences of sialic acids on the cell surfaces of non-malignant and malignant transformants so that phagocytic activity might be correlated to the alteration of molecular composition of cell membrane itself rather than of cell surfaces, i. e, sialic acids.</p

Studies on the mechanism of phagocytosis. I. Effect of metabolic inhibitors on the phagocytosis of iron colloid particles by ascites macrophages

For the purpose to clarify the mechanism of phagocytosis or pinocytosis, the observations on the tumor ascites, including the macrophages as well as the tumor cells, were carried out by incubating with the iron colloid with or without pretreatment by several inhibibitors of glycolysis, oxidative phosphorylation and respiration, or under hypotonic or cold environments. The results have demonstrated that there are three steps in the phagocytosis. The first step is the adhesion of the substance to the cell surface, which is not an energy-requiring process. The second step is the engulfing which proceeds by using the energy supplied by glycolysis. The third is the accumulation of the substance into the vesicles through the canaliculi connecting the cell surface with the vesicles. The discussion was made on the existence of the active site on the cell surface to which the substance can be adhered, and the accumulation mechanism of the material into the phagocytic vesicles by the membrane flow, the flowing movement of the outer lipid layer of a unit membrane through the canaliculi which connect the cell surface to the phagocytic vesicles.</p

Malignant transformation of human cell in vitro by the SV 40 DNA and related alteration in biological activity of cell membranes

In vitro cell transformation of human embryonic cells could be induced by DNA extracted from virions of SV 40 purified by density gradient centrifugation. The result shows clearly that cell transformation is in· duced by incorporation ofa part of viral DNA into the genome. In addition, for the purpose of clarifing the biological differences between the normal and transformant, the alteration of the cell membrane structures of transformants was observed from the mechanism of phagocytosis. The iron colloid particles are taken up by normal diploid fibroblasts but not by the human and hamster transformants. This fact suggests a difference in the molecular arrangement of the cell membranes between the normal and transformants. In the presence of histones, however, the transformants phagocytize the colloid particles very actively. The results show cell membranes of transformants are altered in the molecular structure responsible for the surface charge.</p

Loosening of the cytomembrane of Ehrlich ascites tumor cell by unsaturated fatty acid

Ehrlich ascites tumor cells affected by oleic and linoleic acids lose their cytomembrane followed by the leak out of ribosomes. Some cells survived through this treatment when they were transplanted into mouse peritoneal cavity, but they changed their characteristics showing wider and less basophilic cytoplasm and smaller nuclei with dense nuclear chromatin and ambiguous nucleoli. In spite of many attempts, no qualitative changes have been found between normal and cancer cells. Recently, Ishikawa found the specific antigenicity of cancer cell membrane which was common to several strains of canccr cells. Grobstein and coworkers have clarified that pancreatic cells can differentiate in association with neighboring mesenchymal cells, probably getting some information. Their works suggest that the cell differentiation will be induced by mutual association of cells by which the cell will receive some substance acting as the information for differentiation. Taking the works of Ishikawa and his collabolators into consideration, it seems that cancer cells may be unable to differentiate by their defective or incomplete cell membrane through which they cannot associate with neighboring cells and fail to get the information. Almost all of the biological characteristics of cancer cells, immaturity, autonomic growth, invasive and metastatic properties independent from the neighboring cell groups, are well explained or consistent with this view. Recently, we found that the cell membrane can be loosened by some unsaturated fatty acids resulting in the leak-out of ribosomes. In this paper it is demonstrated how the Ehrlich ascites tumor cell affected by fatty acids lose their cytomembrane and the ribosomes and how the cells survived through this treatment show different characteristics from the original ones, taking the appearance more matured cells.</p