Na(+)-K(+)-ATPase isoforms in different areas of calf brain.

The isoform composition and type of Na(+)-K+ ATPase functional complexes in a number of calf brain membranes were determined. Functionally active enzymes were obtained from microsomes from calf cerebral cortex grey matter, brain stem, and stem axolemma by two different methods involving (1) the selective removal of contaminating proteins according to Jorgensen (1974) and (2) the selective solubilization of the enzyme with subsequent reformation of the membrane structure according to Esmann (1988). The protein components of the isolated preparations were separated by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate, transferred to an immobilon membrane [poly(vinylidene difluoride) membrane] by electroblotting, and subjected to structural analysis. The N-terminal amino acid sequences of the alpha- and beta-subunits (alpha 1, alpha 2, alpha 3, beta 1, beta 2) and the isoform composition and type of alpha n beta m functional complexes present in the different microsome preparations were determined. Brain grey matter Na(+)-K+ ATPase was characterized by biphasic kinetics with respect to ouabain inhibition (Ki approximately 10(-6) M and -1.5 x 10(-8) M) and comprised a set of isozymes with subunit compositions of alpha 1 beta 1, alpha 2 beta m, and alpha 3 beta m (where m = 1 and/or 2), with the alpha 1 beta 1 form clearly predominating. Na(+)-K+ ATPase from brain stem and axolemma consisted mainly of a mixture of the isozymes alpha 2 beta 1 and alpha 3 beta 1, which had identical ouabain inhibition constants (Ki approximately 10(-7) M), but in the axolemma there was a large quantity of the alpha 3 beta 1 isozyme. The catalytic subunit alpha 3 within the untreated enzyme complex had increased sensitivity towards endogenous proteolysis. It was therefore possible to isolate enzyme containing the alpha 3 catalytic subunit only in the presence of the protease inhibitor diisopropyl fluorophosphate (DIPF). In the absence of this inhibitor there was a specific fragmentation of the polypeptide chain, resulting in the formation of an extremely stable N-terminal fragment of molecular mass 55 kDa.

[Cytological characteristics of carminomycin-resistant P-388 lymphoid leukosis]. / Tsitologicheskaia kharakteristika limfoleikoza P-388, rezistentnogo k karminomitsinu.

The carminomycin-resistant strain (P-388/c) of P-388 lymphoid leukemia is obtained. Resistance development is accompanied by higher sensitivity to cytostatics, rise of hyperploidy, replacement of the stem line, presence of definite markers in leukemic cells as well as by the appearance of a clone of cells with higher dry mass. At the level of CFUs after the carminomycin administration more remote terms of cell restoration than in case of P-388/c lymphoid leukemia are determined. The P-388/c lymphoid leukemia cells lost their sensitivity to carminomycin at the stage of the DNA synthesis. Accumulation of cells is observed in phase G2 of the mitotic cycle.

[Chromosomes and drug resistance of tumors]. / Khromosomy i lekarstvennaia rezistentnost' opukholei.

Since most cancers eventually become refractory to chemotherapy, the development of drug resistance within tumour populations remains a major concern in the cancer treatment. The development of drug resistance is often correlated with specific chromosomal modifications. Though chromosomal aberrations are generally much more frequent in cancer than in normal cells, there are no qualitative differences between the aberrations in cancer and in normal cells. At present the genetic basis of drug resistance may be induced by gene amplification, which can be alternatively associated with chromosomal homogeneously stained regions or with double microchromosomes. The both phenomena are essentially the same: they reflect the mechanism for the amplification of genes stimulating tumour viability under unfavourable conditions.

[Formalin-induced chemiluminescence in model protein-lipid systems]. / Khemiliuminestsentsiia v model'nykh sistemakh belok-lipid pod vozdeistviem formalina

Mechanisms of formalin--induced luminescence of protein-lipid complexes have been studied. Free radical reactions of lipid oxidation were shown to be necessary for generating luminescence quanta. The luminescence intensity was mostly promoted by fluorescing products formed in the reoxidized system protein-lipid. Formalin-induced flash of luminescence in these systems may evidently serve as an express-method for analysing protein sample contamination with unsaturated lipids.

[Effect of dimethylbenzanthracene on lymphocytes of the peripheral blood in man]. / Deistvie dimetilbenzantratsena na limfotsity perifericheskoi krovi cheloveka

Human peripheral blood lymphocytes were subjected to the action--at first of phitohemagglutinin (PHA) and then of 9, 10-dimethyl-1,2-benzanthracene (DMBA) in various concentrations. Lymphocytes subjected to the action of PHA and then of the DMBA (in a dose of 0.5 gamma/ml) continued to divide during the whole observation period (14 days). The action of DMBA on the intact lymphocytes not only failed to induce their division, but also eliminated their sensitivity to the subsequent action of PHA at least for several days. The results obtained are discussed from the aspect of general oncogenesis theory put forward earlier.