Acta biochimica et biophysica Hungarica最新文献

The effect of 2.45 GHz frequency and 10 mW/cm2 power density microwave irradiation on the in vitro cultured human peripheral lymphocytes blast transformation was examined. In the number of the blast cells we did not find significant difference at cultures irradiated for 1 x 5 hours and 3 x 1 hours as compared to the controls. The number of the blast cells was found to increase when Phytohemagglutinin-stimulated lymphocyte cultures were exposed to repeated irradiation for 6 days (1 hour a day). The microwave irradiation did not influence the degree of the spontaneous blast transformation in any groups.

Plasma membrane vesicles were purified from the roots of sunflower (Helianthus annuus L. cv. Topflor) by aqueous polymer two-phase partitioning. The optimal conditions for separation were determined by systematic variation of the polymer concentration and salt composition. The phase system containing 6% (w/w) dextran T-500, 6% (w/w) polyethylene glycol 3350, 250 mM sucrose, 5 mM potassium phosphate, pH 7.8, without added salts proved to be the best. The ATPase activity had a pH optimum at 6.5 and it was stimulated by Mg2+, but not by Ca2+. The plasma membrane MgATPase activity was inhibited by vanadate but not by nitrate, an inhibitor of tonoplast ATPase. Only 10% of the microsomal protein was responsible for 36% of the total MgATPase activity. Moreover IDPase activity, a Golgi marker, appeared to be very low indicating the high purity of the preparation.

MgATPase activity of plasma membrane from sunflower roots purified by phase partitioning was tested using different permeabilizing agents. MgATPase activity showed similar dependence on Triton X-100, digitonin and Zwittergent 3-14 concentration, the curves resulted from the stimulatory and inhibitory reactions. The latency calculated at their optima was only 52%. In case of n-octyl glucoside the latency was 77%, while the highest latency (82%) was measured in the presence of lysophosphatidylcholine, and it was the only surfactant which did not inhibit the PM ATPase even at 10 times the concentration giving maximum release of latent activity. Therefore, for the further characterization of the PM ATPase lysophosphatidylcholine is suggested to be used as detergent.

We examined the effect of cadmium, zinc, copper and mercury ions on the rate of total RNA synthesis and on the accumulation of ribosomal RNAs in Synechococcus sp. PCC 6301, an obligate photoautotrophic cyanobacterium. It was found that treatment of cells with growth-inhibitory concentrations of cadmium and zinc ions severely decreased the rate of total RNA synthesis both under light (growing) and dark (non-growing) conditions, while copper and mercury ions had different inhibitory effects under these conditions. Moreover, cadmium and zinc ions substantially inhibited the "normal" processing of high-molecular-mass rRNAs and the in vivo postmaturational cleavage of 23S rRNA in the light and interfered with the accumulation of dark-specific RNAs of 0.33 x 10(6), 0.24 x 10(6) and 0.16 x 10(6) daltons in the dark. On the other hand, copper and mercury ions had a similar effect in the light, but did not abolish the accumulation of dark-specific, rRNA-derived, RNAs in the dark.

The determination of isoeffect curves (sometimes within given contours) from data given in an n x m matrix is a general scientific problem. The algorithm to be described is useful e.g. for pen plotters not only in the case of brachytherapy but in teletherapy too. It takes into consideration the effect of the body contour (isodose curves are not plotted outside the contour). The points with the desired dose value are rearranged into continuous line segments. The segments are characterized by the serial number of their start point and that of their extremity and by a variable the value of which can be 0 or 1 depending on whether the segment is closed or not. The number of the unconnected segments is the fourth variable characterizing the isodose line. The sorting algorithm ensures the less motion of the pen and the less tests during the plotting process. The algorithm has been implemented on IBM compatible PC's.