Isolation and characteristics of endonuclease tightly bound to alpha-polymerase from the rat liver

Three major polypeptides are found in purified DNA polymerase alpha from rat liver: 160, 77 and 58 kDa. The electrophoretic analysis has identified polypeptide 160 kDa as the catalytically active subunit of DNA polymerase alpha. The other two polypeptides showed no DNA polymerase activity. Individual polypeptide p77 kDa purified by sodium dodecyl sulfate polyacrylamide gel electrophoresis was used to produce antibodies in rabbits. Immunoblot analysis indicated that the complex DNA polymerase alpha-3'-5'-exonuclease contained polypeptide p77 kDa. To elucidate the function of the p77 kDa protein we have prepared an immunoabsorbent column with antibodies against the p77 kDa polypeptide. The antibody column purified p77 kDa protein was homogeneous according to sodium dodecyl sulfate gel electrophoresis. The activity of alpha-polymerase was increased approximately 10-fold as a result of purification of DNA polymerase alpha from the p77 kDa protein. The in vitro experiments showed the identity of the p77 kDa polypeptide to endonuclease. It cleaved both single-stranded and double-stranded DNA. The function of endonuclease p77 kDA in complex with DNA polymerase alpha remains obscure.     

Electron microscopic study of the interaction of Yersinia pseudotuberculosis with macrophages and HeLa cells

The comparative electron-microscopic study of early stages of the interaction of Y. pseudotuberculosis virulent strain (No. 282) with "professional" (macrophages) and "nonprofessional" (HeLa cells) phagocytes has been carried out. The character of the intimate mechanism of this interaction has been found to be essentially different. The common feature for both systems is the adsorption of bacteria and their penetration into cells due to phagocytosis. But the subsequent fate of Y. pseudotuberculosis is different. In HeLa cells they are isolated from the cytoplasm by multilayer membrane structures, thus remaining morphologically intact. In macrophages the destruction of the microbe in phagolysosomes occurs.     

Formation of an internal transport barrier and magnetohydrodynamic activity in experiments with the controlled density of rational magnetic surfaces in the T-10 Tokamak

Results are presented from experiments on the formation of an internal electron transport barrier near the q = 1.5 rational surface in the T-10 tokamak. The experiments were carried out in the regime with off-axis electron cyclotron resonance (ECR) heating followed by a fast plasma current ramp-up. After suppressing sawtooth oscillations by off-axis ECR heating, an internal transport barrier began to form near the q = 1.5 rational surface. In the phase of the current ramp-up, the quality of the transport barrier improved; as a result, the plasma energy confinement time increased 2–2.5 times. The intentionally produced flattening of the profile of the safety factor q(r) insignificantly affected magnetohydrodynamic activity in the plasma column in spite of the theoretical possibility of formation of substantial m/n = 3/2 and 2/1 magnetic islands. Conditions are discussed under which the flattening of the profile of the safety factor q near low-order rational surfaces leads to the formation of either an internal transport barrier or the development of an island magnetic structure induced by tearing modes.     

Mechanisms governing radial heat fluxes in tokamak plasma

A method for analyzing the characteristics of turbulence responsible for radial heat transport is proposed. The method is based on the previously proposed hypotheses (to a great extent, confirmed experimentally) concerning the consistency of normalized pressure profiles in tokamak plasmas and the mechanism of internal transport barrier formation. Using the proposed approach, it is shown that, under an external action on the plasma, when the plasma heat flux onto the wall grows, the spectrum of turbulent modes broadens due to the excitation of modes with lower poloidal numbers m. Thus, in contrast to the conventional diffusion approach, the transport coefficient depends on the flux intensity. A mechanism of formation of internal transport barriers is proposed.