Biophysics最新文献

A plant-derived polyphenol, genistein, has a high level of biological activity, which stimulates the study of its applicability for the prevention and treatment of tumor, cardiovascular and neurodegenerative diseases. Taking into account the ability of genistein to bind to DNA the interaction of genistein with nucleosomes and nucleosome complexes with poly(ADP-ribose) polymerase 1 (PARP1) has been studied in this work. It was found that genistein did not affect the structure of nucleosomal DNA in a wide range of concentrations, while at high concentrations it caused a change in the structure of linker DNA, bringing the DNA helices closer together. In chromatosomes, genistein did not cause dissociation of the linker histone and conformation changes in the linker DNA region. At high concentrations, genistein hindered the formation of nucleosome complexes with PARP1.

Data are presented that indicate that when the vegetation conditions of plants change, the expression levels of genes encoding chloroplast carbonic anhydrases, as well as the carbonic anhydrase activity of chloroplast compartments, change. The results of experiments with mutants in the genes of chloroplast carbonic anhydrases indicate that the activity of chloroplast carbonic anhydrases determines the nature of changes in photosynthesis reactions in response to changes in environmental conditions. Possible mechanisms of carbonic anhydrase participation in the light-dependent processes in the chloroplast are proposed. Based on the results we obtained, a hypothesis has been proposed about the interrelated functioning of carbonic anhydrases in chloroplasts.

The biological activity of 2-ethyl-6-methyl-3-hydroxypyridine carnitinate was studied. The drug showed high antiradical and antioxidant activity; this could indicate anti-stress properties, which were studied on a model of acute hypobaric hypoxia. Acute hypobaric hypoxia activated lipid peroxidation by 2.3 times, which resulted in changes in the content of C18 and C20 fatty acids in mitochondrial membranes; the index of double bonds of C18 fatty acids decreased by 18.2%, the content of 20:3ω3 by 13%, 20:2ω6 by 80% and 20:1ω9 by 33%. These changes were accompanied by changes in the bioenergetic characteristics of mitochondria. The maximum oxidation rates of NAD-dependent substrates decreased by 28–35%. The administration of 10^–6 mol/kg of 2-ethyl-6-methyl-3-hydroxypyridine carnitinate to animals for 5 days inhibited lipid peroxidation, prevented changes in the composition of fatty acids of mitochondrial membranes, and, consequently, changes in the bioenergetic characteristics of mitochondria; this probably determined the anti-stress properties of the drug, as indicated by an increase in life expectancy by 3.5–4.0 times and an increase in the survival rate of mice by 12–40% under conditions of various types of hypoxia. In addition, the drug stimulated the germination and growth of wheat seedlings.

Nitric oxide is a signaling molecule of plants under stressful conditions; this molecule can also have a toxic effect. A study of the dose-dependent effect of the nitric oxide donor sodium-μ2-dithiosulphate-tetranitrosyl diferrate tetrahydrate on the structural state of mitochondrial membranes of epicotyles of pea seedlings has been carried out. Upon treating mitochondria with this drug at a concentration of 10^–8 M, thermally induced structural transitions were observed at temperatures from 15°C to 21°C and from 30°C to 36°C in lipid regions, and at temperatures from 12°C to 15°C and from 27°C to 33°C in the protein regions of the membranes. The drug showed antioxidant properties in the lipid regions of the membranes, leading to the accumulation of long unsaturated fatty acids. Treatment of mitochondria with sodium-μ2-dithiosulphate-tetranitrosyl diferrate tetrahydrate at a dose of 10^–4 M caused a significant increase in the level of lipid peroxidation and the fluidity of the lipid phase of membranes.

The transfer of calcium ions through the cell membrane of a cardiomyocyte is associated with overcoming a high energy barrier and can be impaired by vibration. Since drugs of the calcium channel blocker group are able to reduce damage to mitochondria and cell membranes, the effect of the calcium channel blocker nifedipine (adalat) at a dose of 7.5 mg/kg on the energy metabolism of cardiomyocytes in a vibration-mediated (56 sessions of vibration with a frequency of 44 Hz and an amplitude of 0.5 mm) model of cellular hypoxia was evaluated. The functional states of mitochondria in the composition of 30% homogenate of the myocardial tissue of the left ventricle of the rabbit heart were studied using the polarographic method with a closed galvanic oxygen sensor in a thermostatically controlled 1 mL cuvette with a protein content of 2.4 ± 0.5 mg, measured by a modified microbiuretic assay. In animals subjected to vibration in the presence of calcium channel blockers, the rate of endogenous respiration (V_e) remained at the level of intact animals and was 16.4 ± 4.1 [ng-atom O] min^–1 mg^–1 protein; sensitivity to amytal increased by 39% and sensitivity to malonate decreased by 40% compared with the indicators in animals subjected to vibration without pharmacological protection. The indicators of the ratio of the activity of mitochondrial enzyme complexes I and II and the processes of regulation in different metabolic states of mitochondria confirmed the restoration of the activity of mitochondrial enzyme complex I suppressed by vibration and the regulatory restriction of mitochondrial enzyme complex II. The revealed energy-protective effect of calcium channel blockers increased the vibration resistance of the tissue, preventing the development of necrotic changes in it.

Using spectrophotometry, the effect of viral lysis on light absorption in a virus-infected culture of microalgae Tetraselmis viridis was studied compared with the growth of a control uninfected culture. Some methodological issues of conducting multi-day experiments have been worked out, considering the natural titers of algal viruses, equal volumes of composite microbiota (algal viruses, nutrient medium, and microalgae cultures), conditions (temperature and illumination) in the experiment and control with the prevention of the possibility of viral contamination of microalgae in the control. It was found in the dynamics of experiments that during destruction (lysis) of hosts (microalgae cells) by viruses there was an increase in the amount of dissolved organic matter.

Despite the obvious importance of temperature for brain functioning, it remains one of the least studied parameters of the brain. The temperature is determined by the balance between the release of heat during metabolism and its removal by the bloodstream, which is regulated by neurovascular coupling. Using the method of laser speckle contrast imaging and micro-diamond thermometry, we performed a long-term simultaneous recording of blood flow velocity and temperature in the brain of anesthetized animals in vivo for the first time. To study the coupling between temperature and blood flow two approaches were used: enhancing the general blood flow by intraperitoneal injection of adrenaline and enhancing neuronal activity by applying KCl solution to the brain surface. The data we obtained indicated that the temperature of the nerve tissue had a more complex dynamics compared to blood flow, which was apparently associated with direct or indirect activation of both individual neurons and neural ensembles. Studies of temperature dynamics can make a significant contribution to understanding the nature of neurovascular coupling.

Recent studies using priming, the effect of precedence, in the restoration of impaired functions and cognitive rehabilitation of neurological clinic patients have been analyzed. Various types of priming were considered, including transcranial magnetic and electrical stimulation, as well as the preliminary presentation of acoustic and visual stimuli. The presented data show that the range of conditions and specific types of successful application of priming in the clinic is quite wide, and the number of studies increases annually. It is believed that the activation of neuroplasticity mechanisms underlies the positive effects of priming in the treatment of many neurological and psychogenic disorders. Using the example of the author’s own research, the advantages of visual priming in the form of resonance scanning and LED photostimulation with a gradually increasing frequency within the basic rhythms of the electroencephalogram are emphasized.

A review of image visualization methods and other biophysical approaches that demonstrate the validity of using higher invertebrates from the crustacean subtype Daphnia magna as a test model for biomedical and ecotoxicological studies is presented. The main characteristics of animals are described, such as a transparent body, small size, filter type of nutrition, and the presence of well-formed organs, as well as a short life cycle, high fertility and sensitivity to toxicants, which allow the use of this test organism in in vivo experiments as a model alternative to warm-blooded animals. The publications are reviewed in which D. magna was used as a model for visualizing the accumulation and distribution of nanomaterials in the body, as well as for analyzing the mechanisms of cytotoxicity. The methods of fluorescence imaging, interference microscopy and spectrophotometry are described.