Thermal stability of electron transport in PS II membranes and particles from the thermophilic cyanobacteria

Thermal stability of the ferricyanide (FC) and dichlorophenolindophenol (DCIP) reducing reactions was investigated in isolated membrane preparations and PS II particles with active water splitting system from the cyanobacterium Synechococcus elongatus. In a hypotonic medium, the thermostability was seen to be much higher for the DCIP than for the FC reduction reaction. After the addition of high concentrations of polyethylene glycol (Mwt = 4000) or sodium citrate to the medium, the FC reduction reaction appeared to be more temperature resistant. Data on the effects of temperature, DCMU and detergents on the electron transfer rate in PS II provide evidence suggesting that the different thermal stabilities of the two reactions are due to different physico-chemical properties of the electron donor sites to FC and DCIP. The data suggest that regions of contact between individual macromolecular complexes of the electron transport chain are the most labile sites of the photosynthetic apparatus. The role of the composition and properties of the intracellular medium on thermostability are emphasized.     

Electrophysical analysis of Escherichia coli cell damage caused by silver ions]

The influence of Ag+ (0.5-10 microM) on Escherichia coli K-12 cells was studied by electrophoresis and electro-orientation spectroscopy methods. It was shown that the pH-dependency of the cell electrokinetic potential (phosphate-citrate buffer with ion strength 0.02) practically didn't changed after Ag+ treatment, but in low-conductive media electrophoretical mobility of intact and inactivated by heat (70 degrees, 15 min) cells gradually decreased as the Ag+ concentration increased. It was due to the Ag+ adsorption on the cell surface and could not be used for the definite characterization of the cell damage. The high-frequency decrease in the cell electro-orientation spectrum shifted to the region of lower frequencies, K+ was excreted by cells, slight raise of the medium pH occurred and significant changes of cell osmotic properties were observed as a result of Ag+ action. All these changes showed the disturbance of barrier properties of the cytoplasmic membrane. Besides the damaging action of Ag+ on cell membranes increased with the decrease of pH and decreased after the addition of Mg2+, Ca2+ and Sr2+ in low concentrations.     

Stereological analysis of ultrastructural changes in cardiomyocytes during adriblastina-induced cardiomyopathy

Both single and graded administration of an anthracycline antibiotic adriablastine at a dose of 20 mg/kg to white rats have resulted in cardiomyocyte volume decrease, dystrophia and lysis of myofibrils, and reduction of mitochondrial surface density volume. Accumulations of myelin bodies of different configuration and diffuse myolysis were observed. Myelin bodies and diffuse myolysis of cardiomyocytes in adriablastine-induced cardiomyopathy are believed to be a morphological sign of lipid peroxidation.