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Changes of H+ gradient at various energy states of mitochondria were studied. There was a close relation between the extent of H+ gradient and the level of ATP formation; the former decreased as a result of ATP synthesis but was not completely abolished. A partial depression of H+ gradient was also observed in the presence of uncouplers of oxidative phosphorylation. The H+ gradient seemed to be more closely related to the ion translocation than ATP formation. In the presence of Ca++ the energy of H+ gradient was utilized in translocating Ca++ rather than synthesizing ATP. These findings further substantiate the chemiosmotic theory of MITCHELL on mitochondrial electron and energy transfer.

Circular DNA isolated from human kidney mitochondria was studied by electron microscopy. I. Mean contour length of monomers of the mitochondrial DNA was 4.96 ± SE 0.28 /μ 2. The complex molecules (oligomers) of mitochondrial DNA were observed in frequency of 6.2 per cent. Among them circular dimers accounted for two per cent of all circular DNA molecules. 3. Circular DNA fibers with an intermediate perimeter between the　monomer and dimer, and with a contour length shorter than 3 μ were occasionally observed. 4. Some discussions were made on the emergence of the circular dimer.

The in vitro effects of phenol and p-halogenated phenols on mitochondrial energy transfer reactions were examined using isolated rat liver mitochondria. The relationship between physiochemical properties of phenolic compounds and their effects on mitochondria were studied. Phenol and p-halogenated phenols induced the release of K+ ions from mitochondria, suggesting a change in permeability to K+ ions. A decrease in the respiratory control index, an increase in K+ release and stimulation of latent ATPase activity were observed with these compounds in the descending order of p-iodophenol, p-bromophenol, p-chlorophenol, p-fluorophenol and phenol. The concentrations of the phenolic compounds resulting in fifty percent inhibition of the respiratory control index and those resulting in fifty percent release of K+ ions significantly correlated with Hammett's substituent constant (sigma) and the hydrophobic binding constant (pi) of the compounds.

Oxidative stress, including the reactive oxygen or nitrogen species generated in the enzymatical oxidationor auto-oxidation of an excess amount of dopamine, is thought to play an important role in dopaminergic neurotoxicity. Dopamine and its metabolites containing 2 hydroxyl residues exert cytotoxicityin dopaminergic neuronal cells, primarily due to the generation of highly reactive dopamine and DOPA quinones. Dopamine and DOPA quinones may irreversibly alter protein function through the formation of 5-cysteinyl-catechols on the proteins. Furthermore, the quinone formation is closely linked to other representative hypotheses such as mitochondrial dysfunction, inflammation, oxidative stress, and dysfunction of the ubiquitin-proteasome system, in the pathogenesis of neurodegenerative diseases. Therefore, pathogenic effects of the dopamine quinone have recently focused on dopaminergicneuron-specific oxidative stress. In this article, we primarily review recent studies on the pathogenicity of quinone formation, in addition to several neuroprotective approaches against dopaminequinone-induced dysfunction of dopaminergic neurons.

Formation of 5'-AMP, 5'-GMP, 5'-CMP and 5'UMP was confirmed in isolated rat liver mitochondria incubated with alpha-ketoglutarate, inorganic phosphate, purine nucleoside and pyrimidine nucleoside. Increased incorporation of 32Pi into ATP, GTP and UTP was observed by adding purine- and pyrimidine nucleosides. The phosphorylation of nucleosides was inhibited severely by arsenite and affected slightly by the addition of nuclear or post-mitochondrial fraction.

The intracellular localization of the avian myeloblastosis virus (AMV) genome was studied. Nuclear and mitochondrial DNAs from myeloblasts were examined by hybridization with 32P labeled AMV-RNA of high molecular weight for the presence of virus specific DNA sequences. Nuclear DNA (nDNA) from myeloblasts specifically hybridized with viral RNA, whereas purified closed circular mitochondrial DNA (mtDNA) did not hybridize with viral RNA. It was therefore concluded that viral genome was present in nuclear DNA and not in mitochondrial DNA. Likewise, in normal chick cells, nDNA but not mtDNA hybridized with viral RNA.

Mitochondrial RNA (mtRNA) was synthesized from purine and pyrimidine nucleosides in coupling with oxidative phosphorylation using isolated mitochondria. The in vivo synthesized mtRNA was adenine-uracil rich and sedimented at about 20 S by sucrose density gradient centrifugation. A major part of the newly synthesized mtRNA was shown to be poly (A)-containing RNA by the resistance to the digestion with pancreatic RNase and RNase T1 and the affinity to poly (U)-Sepharose columns or Millipore filters.

A novel endonuclease of 55-kDa was found in rat liver mitochondria by a zymographic assay, in addition to the 29 kDa enzyme that is well-known as endonuclease G (Endo G). Subcellular localization of these enzymes in rat liver cells was examined by biochemical fractionation. Endo G was located in both nuclei and mitochondria as has been previously reported, while the 55-kDa enzyme was only detected in the mitochondrial fraction. The levels of the endonucleases in the mitochondria varied greatly among the rat organs, and the activity in the heart was about 30 times higher than that in the liver. The 55-kDa enzyme and Endo G were extracted from bovine heart mitochondria with 0.4 M NaCl. During purification the 55-kDa enzyme and Endo G were copurified because of their similar chromatographic behavior, so they were separated by gel filtration or electrophoresis in the presence of SDS and the proteins were then renatured. The nucleolytic properties of the 55-kDa enzyme resembled those of Endo G and other known mitochondrial nucleases. The enzyme degraded single-stranded DNA more rapidly than duplex DNA at a weak alkaline pH, requiring Mg²⁺ or Mn²⁺ but not Ca²⁺ or Zn²⁺. Nicks generated by the enzyme had 5′-P and 3′-OH ends. The 55-kDa enzyme, like Endo G, displayed an unusually strong preference to nick within a (dG)_n · (dC)_n tract.

Fas antigen (ag) is a cell surface protein known to trigger apoptosis in a variety of cells upon specific antibody binding. On the other hand, Bcl-2 protein, an oncogene product located at the mitochondrial inner surface, prolongs cell survival by blocking apoptosis. In this study we examined the expression of Fas ag and bcl-2 protein in 17 cases of hepatocellular carcinoma (HCC) to determine their role on HCC. By flow cytometric analysis, mean (SD) value of the expression of Fas ag on hepatocytes derived from normal liver, diseased liver (chronic hepatitis or liver cirrhosis) and HCC was 5.8 (4.7)%, 10.3 (6.9)%, and 24.0 (18.2)%, respectively. Fas ag expression on hepatoma cells was significantly greater than normal and diseased liver cells. The expression of Bcl-2 protein in normal liver, diseased liver and HCC was 4.3 (8.5)%, 0.8 (2.5)% and 2.1 (3.4)%, respectively, and the difference was not significant. These results suggest that induction of apoptosis may be a possible therapy against HCC.

1) The fate and rate of degradation of I131 labelled rabbit γ-globulin, which retained its native antigenicity and antibody specificity was studied in the guinea-pigs. 2) Blood elimination rate of heterologous γ-globulin is higher than that of homologous γ-globulin. 3) Denatured and digested γ-globulin departs from the blood more rapidly than the native one, and urinary excretion rates of denaturated and digested γ-globulin are higher than that of the native one. It is inferred, therefore, that the denatured and digested γ-globnlin is more liable to be resolved and decomposed in the reticulo-endothelial organs than the native one. And the value obtained from the urinary excretion reflects the rate of protein break down in some cellular compartments. 4) Following the plasmaphresis the increase in antigen elimination was lessened and delayed as compared with control animals. 5) The organ distribution of heterologous I131-γ-globulin is to the lymphnode> the spleen> the liver> the lung> the kidney> the intestine in descending order. Heterologous I 131 -γ- globulin is deposited in greater quantity in the reticulo-enclotherial organ than other single organ. 6) Following the intravenous injection of I131 labelled antigens, the ratio of the specific activity of mitochondria and microsom to that of whole liver homogenate was determined over a period from 15 minutes to 3 hours in guinea-pigs, and following results were obtained. a) Organ and intracellular distribution of Il3l labelled homologous γ-globulin shows no great difference compared to that of heterologous one. b) The intracellular distribution of heterologous γ-globulin is in mitochondrial> microsomal> nuclear fraction in descending order. c) The heterologous γ-globulin quantity of mitochondrial fraction or microsomal fraction in the spleen is higher than that of the liver. 7) The antibody distribution of intracellular glanules measured in terms of radioactivity with a Geiger-Muller counter, after the reaction of I131 labelled antigen. The quantity of distribution of intracellular glanules decreases in mitochondrial fraction> microsomal fraction> nuclear fraction in descending order.