In experiments on isolated kidney and liver mitochondria, it is shown that oleate hydroperoxide induces a much smaller increase in the controlled respiration rate and DeltaPsi decrease than the same concentrations of oleate. Palmitate appears to be less efficient than oleate but more efficient than oleate hydroperoxide. In all cases, GDP and CAtr cause some recoupling, CAtr being more effective. Addition of 0.2 mM GDP before CAtr does not prevent further DeltaPsi increase by subsequent CAtr addition. On the other hand, GDP added after CAtr is without any effect. GDP partially prevents the DeltaPsi lowering by ADP at the State 4--State 3 transition if small amounts of CAtr are present. The data are consistent with the suggestion of F. Goglia and V.P. Skulachev (FASEB J. 17, 1585-1591, 2003) that fatty acid anions are translocated by mitochondrial anion carriers much better than their hydroperoxides. As to GDP recoupling, it cannot be regarded as a specific probe for uncoupling by UCPs since it can be mediated by the ATP/ADP antiporter.
Tetrahymena pyriformis is used in diverse studies as a non-mammalian alternative due to their resemblance in many main metabolic cycles. However, such basic features of mitochondrial energetics as Delta psi (electrical potential difference across the inner mitochondrial membrane) or maximal stimulation of respiration by uncouplers with different mechanisms of uncoupling, such as DNP (2,4-dinitrophenol) and FCCP (p-trifluoromethoxycarbonylcyanide phenylhydrazone), have not been studied in living ciliates. Tetrahymena pyriformis GL cells during stationary growth phase after incubation under selected conditions were used in this study. Maximal stimulation of cellular respiration by FCCP was about six-fold, thus the proton motive force was high. The DNP uncoupling effect was significantly lower. This suggests low activity of the ATP/ADP-antiporter, which performs not only exchange of intramitochondrial ATP to extramitochondrial ADP, but also helps in the uncoupling process. It participates by a similar mechanism in electrophoretic transport from matrix to cytosol of ATP(4-) and DNP anion, but not FCCP anion. Thus, in contrast with mammalian mitochondria, T. pyriformis mitochondria cannot rapidly supply the cytosol with ATP; possibly the cells need high intramitochondrial ATP. The difference between DNP and FCCP is hypothetically explained by low Delta psi value and/or an increase in concentration of long-chain acyl-CoAs, inhibitors of the ATP/ADP-antiporter. The first suggestion is confirmed by absence of mitochondria with bright fluorescence in T. pyriformis stained with the Delta psi-sensitive probe MitoTracker Red. These data suggest that T. pyriformis cells are useful as a model for study of mitochondrial role in adaptation at the intracellular level.
The aim of the work was to clad Ti-Ta-Nb coating on a substrate of pure titanium. Cladding was carried out by non-vacuum electron-beam treatment. As a result a good quality coating thickness of about 2 mm was obtained. Microstructural and microhardness tests were conducted. Dendritic structure and the borders of the former grains of β-phase were revealed. At the microlevel, the coating has a martensitic structure. The average hardness of coating is about 4000 MPa.
Multilayer materials produced by explosive welding of low carbon steel were investigated. Non-uniform structure of interlayer boundary was characterized using visible light microscopy, SEM and TEM. It was shown that 4 zones with different structure and mechanical properties present in the welded seams. To estimate fatigue properties of the multilayer materials kinetic diagram of fatigue failure were used. It was revealed that larger boundary waves give more significant contribution to fatigue crack resistance. In experiments carried out in the current research number of cycles to failure of multilayer materials was higher than those for bulk materials.
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