Vol 74, No 3 (2019)

The stability of chromatosome when introducing posttranslational modifications and mutations observed in the case of oncological diseases into the structure of the linker histone was studied using bioinformatics analysis. The chromatosome is formed under the interaction of the nucleosome with the linker histone. This interaction can be characterized by the binding free energy. We hypothesized that oncomutations and posttranslational modifications of the linker histone are associated with a change in its free energy of binding to the nucleosome, and it probably leads to a change in chromatin compaction, thus affecting gene expression. Calculations of the binding free energy were performed using algorithms of the FoldX program. Screening of positions of posttranslational modifications in the linker histone for the presence of steric constraints was also performed. The analysis of the obtained data allowed for the identification of oncomutations and posttranslational modifications that significantly change the binding free energy of the linker histone with the nucleosome, thereby probably affecting the structure of the entire chromatin.

The embryonic and larval stages of amphibian development are promising model objects for developmental biology, experimental biology, and medicine. However, the existing methods of laboratory research do not take into account the biological features of model amphibian species. In addition, not enough attention is paid to standardizing the experimental conditions and minimizing the experimenter’s influence on their results. The fact that the experimental research methodology developed for one amphibian species cannot be used for similar research on another species without significant modification with consideration of the biology of this object is also not accounted for. The article summarizes the results of many years of research devoted to the study of factors that influence the results of laboratory experiments on the embryonic developmental stages of the common toad Bufo bufo. By the example of this species, new methodological approaches to laboratory research have been developed, allowing consideration for the species’ particular biological features, minimization in the heterogeneity of the effects from previously uncontrolled factors, and standardizing the conditions for conducting experiments. Maintaining the temperature at 15–17°C throughout the experiment, taking regular measurements at regular intervals (8 h), and conducting each test at two values of the initial egg density (recommended 30 and 120 eggs in a single string per standard aquarium) is recommend. When setting up experiments, one should take into account the influence of not only “bulk” but also “surface” and “linear” densities. It is also shown that any additional effects of the experimenter on the embryos associated with the removal of dead individuals performed during the experiments can have a significant impact on the result; therefore, such effects should be minimized.

Damage to the plasma membrane (PM) of cells in pea leaf epidermis determined by its permeability to propidium iodide (PI), which binds to DNA of cell nuclei, and programmed cell death (PCD) detected by the destruction of cell nuclei were investigated. PM of the epidermal cells in the isolated epidermis was permeable to PI (it stained their nuclei). PM of the guard cells did not allow PI to pass through. KCN, an inducer of PCD, caused the destruction of both epidermal and guard cell nuclei. KCN-induced destruction of guard cell nuclei was accompanied by the penetration of PI into the cells. The polycation chitosan at a concentration of 0.1 mg/mL caused the destruction of the epidermal cell nuclei, but the permeability of the guard cell PM for PI staining their nuclei was induced at a concentration of 1 mg/mL. Other polycations (cytochrome c, polylysine, polyethylenimine, and protamine) also caused staining of the guard cell nuclei by PI. Polyanions (polyacrylic acid, dextran, and heparin) initiated the destruction of cell nuclei, which was accompanied by the penetration of PI into cells. Detergents Triton X-100 and lauryldimethylamine-N-oxide produced the permeability of the guard cell PM for PI and prevented the destruction of the nuclei that was induced by KCN. Treatment of the epidermis with Triton X-100 (for 2 h with its subsequent washing) increased the destruction of the guard cell nuclei that was caused by KCN. Polycations polyethyleneimine and protamine were prevented, while chitosan, cytochrome c, and polylysine, on the contrary, enhanced KCN-induced destruction of the guard cell nuclei. The obtained data shows that the destruction of cell nuclei upon induction of cell death with KCN or polyanions is accompanied by damage to PM (producing its permeability for PI). Damage to PM caused by detergents or polycations prior to cell treatment by KCN can prevent or, on the contrary, intensify the destruction of cell nuclei.

Poly(ADP-ribose)polymerase 1 (PARP1) is involved in the processes of DNA repair, replication, transcription, cell cycle regulation, and apoptosis. Participation of PARP1 in DNA repair is determined by the ability of the enzyme to interact with various damages and noncanonical structures of DNA with consequent polyADP-ribosylation of neighboring proteins. Earlier, for mononucleosomes containing a DNA end recapitulating double-strand DNA break near the nucleosome, it was found that PARP1 induces nucleosome structural changes in the absence of NAD⁺. In the present work, it is reported that PARP1 induces similar structural changes in nucleosomes containing either DNA ends extending from the core by 20 bp or containing hairpins at the DNA ends. In all the cases, PARP1 caused changes in DNA wrapping on the surface of the histone octamer that are accompanied by an increase in the distance between adjacent DNA gyres. These PARP1-mediated changes in the nucleosome structure presumably contribute to chromatin decondensation and facilitate access of repair enzymes to damaged DNA.

Bioelectrical properties of various developing fragments of the heart undergo significant changes during pre- and postnatal ontogeny. However, the general pattern of the heart’s structure and the bioelectrical features of various parts of the “mature” heart are specifically determined in the early stages of embryogenesis. Specifically, the presence of myocardium with a phenotype, which is similar to a pacemaker, was revealed in the interatrial septum (IAS) of the mammalian heart using histological methods. However, the electrical activity in this structure remains understudied. The aim of the present study was to examine the capability of the IAS to generate action potentials spontaneously and the effects of adrenergic stimulation on the bioelectrical activity of the IAS. For this purpose, we recorded the resting and action potentials in the multicellular isolated perfused preparations of the IAS and left atrium from the rat heart at the end of day 1 and at day 60 of postnatal life using the standard microelectrode technique. We found that α₁-adrenomimetic phenylephrine (PE) modified the patterns of action potentials in the samples of IAS and the atrial myocardium from the animals of both ages. In the resting samples without any electrical stimulation, PE induced the generation of action potential in the IAS but not in the atrium because of oscillations in the level of cytoplasmic calcium. Application of the inhibitor of hyperpolarization activated current (I_f) ZD 7288 led to a decrease in the rate of slow diastolic depolarization of action potential in the IAS pacemaker cells, a decrease in the frequency, and the appearance of train activity. Thus, in newborn and adult rats, the IAS myocardium generates spontaneous electrical activity. A necessary condition for the occurrence of pacemaker activity is adrenergic stimulation. The capability to generate spontaneous activity is probably associated with the presence of pacemaker current I_f in the IAS cardiomyocytes.

18 Healthy volunteers were involved and the effect of functional neuromuscular electrical stimulation, which causes flexion of the hand on the corticospinal excitability during motor imaging and resting state, was investigated in this study. It was shown that the combined action of functional electrical stimulation and the kinesthetic motor imagery leads to an increase of the amplitude of motor evoked potentials, caused by a single-pulse transcranial magnetic stimulation. At the same time, in the state of motor rest, this effect was not obtained. Since a change in corticospinal excitability at the cortical level may affect the processes of plastic reorganization necessary for the restoration of motor functions after strokes and other neurotraumas, the results of this work have a direct practical potential. In particular, the possibility of creating effective training complexes for the motor recovery based on motor imagery brain-computer interfaces with functional neuromuscular stimulation as a sensorimotor feedback is discussed. Rehabilitation with the use of such training complexes will help to elucidate the mechanisms of motor recovery, which are based on the phenomena of neuroplasticity due to changes in the excitability of neurons of the sensorimotor cortex.