Biophysics

A chronic respiratory load was produced in Wistar rats by tracheal binding to produce a twofold increase of pleural pressure oscillation amplitude during respiration. Eight weeks after the surgery, a higher proportion of type-I muscle fibers (MFI) in the costal diaphragm along with a greater MFI cross-section area and a higher succinate dehydrogenase activity in MFII in the lumbar diaphragm were observed. During recording the mechanical activity of ring preparations of diaphragm arteries under isometric conditions, an increase in endothelium-dependent relaxation was found, whereas endothelium-independent relaxation and arterial reactivity to noradrenaline did not change. Tracheal binding did not produce any changes of MF in the gastrocnemius muscle, but endothelium-dependent relaxation of gastrocnemius feed arteries was reduced. We conclude that chronic respiratory load affects the endothelial function in diaphragm arteries in a manner favorable for blood flow control in the diaphragm. Functional alterations in gastrocnemius arteries may be associated with the reduced locomotor activity of operated rats.

The formation of dinitrosyl iron complexes with thiol-containing ligands in plant tissues (parsley and apple leaves) in the presence of nitric monoxide was demonstrated using electron paramagnetic resonance. In two types of tissues dinitrosyl iron complexes are predominantly represented by the binuclear diamagnetic form. This diamagnetic form can be transformed in EPR-detectable mononitrosyl iron complexes with diethyldithiocarbamate due to the ability of diethyldithiocarbamate to accept the iron-mononitrosyl groups from iron-dinitrosyl fragments of binuclear complexes. A similar transformation was observed under the effect of diethyldithiocarbamate on a mononuclear paramagnetic form of dinitrosyl iron complexes. The significant amount of binuclear dinitrosyl iron complexes found in plant tissues suggests that these complexes can be considered as a “working form” of nitric monoxide, which is recognized now as a universal regulator of metabolic processes in plants as well as in other organisms.

Sensitive methods of differential UV spectrophotometry and differential scanning microcalorimetry were used to study the interaction of small and large quantities of the natural antitumor antibiotic actinomycin D with clusters of native and fragmented calf thymus DNA during thermal melting. At micromolar (physiological) concentrations, actinomycin is incorporated in untwisted sites of DNA rather than in the double helix. Actinomycin stabilizes these sites and therefore slightly increases the overall melting temperature of DNA. The antibiotic effectively interacts with the nucleotides of native DNA at a ratio of 1: 868, especially strongly with the clusters of satellite fractions and DNA fragments. At low concentrations, it stabilizes the «loose» bilizes the double helix and causes DNA aggregation.

In this study, we have determined the power of the cilium on the foot sole of a medium-sized pond snail, Lymnaea stagnalis, gliding upward in anaerobic water. As has been shown, the foot sole houses approximately 1.3 · 109 cilia, displaying a total power of 1.47 · 10−6 W, the power of one cilium being 1.1 · 10−15 W and of a single ciliary beat being 1.1 · 10−16 W.

Abstract—In addition to troponin and tropomyosin, cardiac myosin-binding protein C (cMyBP-C), which has an effect on the function of myosin and thin filament activation, is involved in regulation of the actin–myosin interaction in the myocardium. The β-isoform of myosin heavy chain expressed in slow skeletal muscles is identical to that in the myocardium; however, myosin isoforms in slow skeletal muscles and in cardiac muscle differ in the composition of the myosin light chain isoforms. We investigated the effect of cMyBP-C on the calcium regulation of the interaction of the myosin of slow skeletal muscle (m. soleus) with actin, using an in vitro motility assay and an optical trap. It was found that the physiological concentration of cMyBP-C resulted in increased calcium sensitivity of the sliding velocity of regulated thin filaments over myosin extracted from the slow soleus muscle and increased the velocity of thin filaments, as opposed to cardiac myosin. In the optical trap, cMyBP-C did not affect the step size of myosin but reduced the duration of a single actin–myosin interaction, thus explaining the increase in the velocity of filaments in the in vitro motility assay. Thus, the regulatory properties of cMyBP-C are exhibited in different ways depending on the composition of myosin light chain isoforms.

The results of research on the consequences of cryopreservation of fungi testifying to stability of their morphology are reviewed, and a number of facts indicating changes in the properties of fungi and the mutagenicity of cryopreservation are presented. The investigations of the last decade confirm Rozanov’s hypothesis that cryopreservation must increase the resource of hereditary variation in the organisms.

The values of the parameters of serum-free media (concentration of Na+, amino acids, and carbohydrates, as well as the pH values) have been determined at which the rate of the differentiation of neuroblastoma cells is minimal, and the rate of proliferation is maximal. It was shown that media inducing the differentiation of 70% of cells during the cell cycle provide the maximal time of survival of differentiated cells.

Reconstruction of the spatial structure of inulinase (EC 3.2.1.7) from Kluyveromyces marxianus (an enzyme that hydrolyzes inulin and other fructose-based polymers to fructose) was carried out by highthroughput computational modeling. A structural model of a closely related homologous protein, viz., invertase from yeast Saccharomyces cerevisiae (PDB-ID: 4EQV), was used as a template. The reconstructed model can be used for computer calculations for optimizing the biotechnological feasibility of inulinase.

Exposure of intact rats and human erythrocytes to low-intensity pulsed magnetic field leads to similar biphasic changes in the electrophoretic mobility of erythrocytes; this is accompanied by modification of their membrane and cytoskeletal protein spectrum.