Biomedical subjects
V Mornstein
Publications and source records attributed to V Mornstein.
Effect of ultrasound on DNA synthesis in tumor cells.
The objective of this study was to consider the influence of continuous-wave (CW) ultrasound (800 kHz) on DNA synthesis in Ehrlich ascitic tumor cells in vitro. The 10-min irradiation was carried out in rotating polyethylene tubes (5 rpm). Incorporation of 3H-thymidine was employed to detect DNA synthesis. Replication and unscheduled (repair) DNA synthesis were distinguished by means of hydroxyurea treatment before insonation. It was established that the use of 0.5 W/cm2 and 1.0 W/cm2 (ISA) CW ultrasound interfered with DNA synthesis showing up as inhibition. The inhibition became most noticeable when starting insonation in a sample cooled to 5 degrees C. During insonation, the sample temperature was allowed to increase to the ambient (water bath) temperature of 37 degrees C. However, at an ultrasound intensity (SA) of 0.1 W/cm2 such inhibition was not proven, but a moderate stimulation of DNA synthesis was demonstrated. Changes in DNA synthesis after insonation were found to be transient because of a lack of stimulatory and/or inhibitory ultrasound effects after 1-h incubation at 37 degrees C. In our experimental conditions no effects on DNA synthesis due to the effects of the insonated medium on the cells were discernible. No statistically significant changes in unscheduled DNA synthesis were observed. Possible action mechanisms are discussed.
Electrochemical behaviour of proteins at graphite electrodes. I. Electrooxidation of proteins as a new probe of protein structure and reactions.
Electrochemical oxidation of proteins at a paraffin-wax-impregnated spectroscopic graphite electrode was studied by means of linear sweep and differential pulse voltametric techniques. It was found that proteins at the graphite electrode yield an oxidation current in the vicinity of potentials of 0.7-0.8 V in the range of neutral pH values. This current has the characteristics of adsorption currents. It was shown that irreversible electrooxidation of tyrosine or tryptophan residues is responsible for the occurrence of these protein currents. This previously undescribed electrochemical activity of proteins was exploited for the demonstration of the influence of urea on the accessibility of both tyrosine and tryptophan residues in protein molecules for interaction with their environment. It was also demonstrated that voltammetry at graphite electrodes permits an electrochemical analysis of proteins that do not contain cystine or cysteine residues.