Improved Ultrastructural Detail in Tissues Fixed with Potassium Permanganate

An improved method has been developed for fixation with potassium permanganate. Although this is one of the methods widely used to preserve the dense cores of adrenergic storage vesicles, fixation of other tissue components is usually poor. The main differences from previously reported methods using potassium permanganate are the use of a physiological saline as the vehicle for all solutions, and, following this, very rapid dehydration before infiltration with plastic. Cellular and intercellular details of tissue ultrastructure may, in general, be evaluated as satisfactorily as with conventional fixatives, with the exception of certain protein elements associated with ribosome, microtubule, and myofilament organization. Nerve endings with agranular or clear vesicles may be distinguished from adrenergic endings since the dense cores of the vesicles of the latter are preserved by this method.     

Inhibition of gliding movement by calcium in doublet microtubules on Tetrahymena ciliary dyneins in vitro

We examined the effects of Ca ions on the gliding movement of Tetrahymena ciliary doublet microtubules induced by 14S or 22S dyneins in an in vitro motility assay system. The doublet microtubule appeared as circular-arc in solution, about 5 to 6 μm in length [1]. The doublet microtubules glided distal-end first on a 14S or 22S dynein-coated glass surface either clockwise or counterclockwise following the addition of ATP. The diameter of the circular path changed according to Ca concentration in the solution. Gliding velocity was from 1 to 5 μm/s. The addition of 0.1% Nonidet P-4O was necessary to induce the gliding movement on 22S dynein. This movement on 22S dynein was strongly inhibited above 0.5 mM ATP in the presence of 10⁻⁹ M Ca, and at 0.05 to 1 mM ATP in the presence of 10⁻³ M Ca. Many studies have indicated that Ca ions regulate ciliary movement [2–8] in which dyneins and doublet microtubule in the axoneme may play an essential role. The inhibition of the gliding movement of doublet microtubule on dyneins at appropriate concentrations of Ca and ATP as observed in this study may be the key for understanding Ca regulation of ciliary motility.     

Arginase as an inhibitory principle in liver plasma membranes arresting the growth of various mammalian cells in vitro

Plasma membranes prepared from rat livers inhibited the in vitro growth of various mammalian cells including hepatoma cells in a concentration-dependent manner, showing an almost complete arrest of cell growth at 0.1 mg protein/ml. Some of these cells tested, i.e., leukemia (L1210 and P388) and myeloma (P₃-NS-1/1-Ag4-1) cells, were labile in the presence of plasma membranes (losing the viability), and CHO (Chinese hamster ovary) cells became round without detaching from the substratum. The culture medium preincubated with liver plasma membranes no longer supported the growth of hepatoma cells (AH13 and AH66F). However, the ‘conditioned’ medium supplemented with l-arginine, supported the growth of the cells. Moreover, the addition of l-ornithine to the cultures containing plasma membranes markedly reduced the inhibitory effect of plasma membranes. The plasma membrane preparations were found to possess considerable arginase activity. These results seem to indicate the possible involvement of arginase in the inhibition of cell growth by liver plasma membranes.     

Ultrastructural and biochemical identification of con A receptors in the desmosome

Correlated ultrastructural and biochemical methods were used to identify and localize Concanavalin A (Con A) receptors in the desmosomes of bovine epidermis. Specific carbohydrate residues were labeled with ferritin-Con A in thin sections of tissue embedded in a hydrophilic resin. Quantitative mapping of ferritin distribution in labeled desmosomes revealed that Con A receptors are localized in the intercellular zone and concentrated along the desmosomal midline or central dense stratum. Labeling was almost entirely absent when sections were treated with ferritin-Con A in the presence of 0.1 M α-methyl mannoside, a hapten-inhibitor of Con A. “Whole” desmosomes and desmosomal intercellular regions (desmosomal “cores”) were purified from bovine muzzle epidermis. Sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis reveals a limited number of major desmosomal protein constituents. Certain of these are glycoproteins and are greatly enriched in the core fraction. Almost all the desmosomal glycoproteins are intensely labeled when electrophoretic gels of whole desmosome or core fractions are exposed to fluorescent Concanavalin A.     

Replicative bypass repair of ultraviolet damage to DNA of mammalian cells: Caffeine sensitive and caffeine resistant mechanisms

Replicative bypass repair of UV damage to DNA was studied in wide variety of human, mouse and hamster cells in culture. Survival curve analysis revealed that in established cell lines (mouse L, Chinese hamster V79, HeLa S3 and SV40-transformed xeroderma pigmentosum (XP)), post-UV caffeine treatment potentiated cell killing by reducing the extrapolation number and mean lethal UV fluence (Do). In the Do reduction as the result of random inactivation by caffeine of sensitive repair there were marked clonal differences among such cell lines, V79 being most sensitive to caffeine potentiation. However, other diploid cell lines (normal human, excision-defective XP and Syrian hamster) exhibited no obvious reduction in Do by caffeine. In parallel, alkaline sucrose sedimentation results showed that the conversion of initially smaller segments of DNA synthetized after irradiation with 10 J/m² to high-molecular-weight DNA was inhibited by caffeine in transformed XP cells, but not in the diploid human cell lines. Exceptionall, diploid XP variants had a retarded ability of bypass repair which was drastically prevented by caffeine, so that caffeine enhanced the lethal effect of UV. Neutral CsCl study on the bypass repair mechanism by use of bromodeoxyuridine for DNA synthesis on damaged template suggests that the pyrimidine dimer acts as a block to replication and subsequently it is circumvented presumably by a new process involving replicative bypassing following strand displacement, rather than by gap-filling de novo. This mechanism worked similarly in normal and XP cells, whether or not caffeine was present, indicating that excision of dimer is not always necessary. However, replicative became defective in XP variant and transformed XP cells when caffeine was present. It appears, therefore, that the replicative bypass repair process is either caffeine resistant or sensitive, depending on the cell type used, but not necessarily on the excision repair capability.     

Detection of SO2 at the ppm Level with Localized Surface Plasmon Resonance (LSPR) Sensing

Plasmonics - Detection and monitoring of SO2 is important because it is a representative toxic gas in the atmospheric environment that is emitted from industrial and natural processes. Localized...     

MicroRNA-30c attenuates fibrosis progression and vascular dysfunction in systemic sclerosis model mice

Molecular Biology Reports - Systemic sclerosis (SSc) is characterized by peripheral circulatory disturbance and fibrosis in skin and visceral organs. We recently demonstrated that...     

Copper-dependent DNA damage induced by hydrazobenzene,an azobenzene metabolite

Hydrazobenzene is carcinogenic to rats and mice and azobenzene is carcinogenic to rats. Hydrazobenzene is a metabolic intermediate of azobenzene. To clarify the mechanism of carcinogenesis by azobenzene and hydrazobenzene, we investigated DNA damage induced by hydrazobenzene, using ³²P-5′-end-labeled DNA fragments obtained from the c-Ha-ras-1 proto-oncogene and the p53 tumor suppressor gene. Hydrazobenzene caused DNA damage in the presence of Cu(II). Piperidine treatment enhanced the DNA damage greatly, suggesting that hydrazobenzene caused base modification and liberation. However, azobenzene did not cause DNA damage even in the presence of Cu(II). Hydrazobenzene plus Cu(II) caused DNA damage frequently at thymine residues. Catalase and a Cu(I)-specific chelator inhibited Cu(II)-mediated DNA damage by hydrazobenzene. Typical ^·OH scavengers did not inhibit the DNA damage. The main active species is probably a metal oxygen complex, such as Cu(I)-OOH. Formation of 8-oxo-7, 8-dihydro-2′-deoxyguanosine was increased by hydrazobenzene in the presence of Cu(II). Oxygen consumption and UV-Visible spectroscopic measurements have shown that hydrazobenzene is autoxidized to azobenzene with H₂O₂ formation. It is considered that the metal-mediated DNA damage by hydrazobenzene through H₂O₂ generation may be relevant for the expression of carcinogenicity of azobenzene and hydrazobenzene.