


Vol 11, No 2 (2017)
- Year: 2017
- Articles: 8
- URL: https://journal-vniispk.ru/1990-7478/issue/view/13267
Reviews
Mitochondrial cytopathies: Their causes and correction pathways
Abstract
Mitochondrial cytopathies are a heterogeneous group of systemic disorders caused by mutations in mitochondrial or nuclear genome. The review presents some data on pathogenic mutations in mitochondrial DNA leading to the imbalance in the oxidation phosphorylation processes and energy metabolism in the cells and eventually to the development of mitochondrial cytopathy. The pathways of medicated correction are examined, which are aimed at obtaining optimal energy efficiency of mitochondria with impaired functions, increase of the efficiency of energy metabolism in the tissues, as well as prevention of mitochondrial membrane damage by free radicals using antioxidants and membrane protectors. A conclusion is drawn on the inefficiency of currently used therapeutic strategies and the necessity of new approaches, which can be gene therapy of mitochondrial diseases. Some modern methods for gene defects correction, capable of restoring or removing the damaged gene, expressing full gene product, or blocking the mutant or strange genes work are analyzed. It is shown that the described approaches to the gene therapy of human mitochondrial diseases demand the introduction of foreign sequences into nuclear or mitochondrial genome of a living person, which completely excludes their practical application because of the uncertainty of the outcome. A perspective approach in solving this problem may be a creation of a system allowing the correction of defect genes without introducing synthetic nucleotides into the human genome. Phenotypic selection combined with a capacity of homologous recombination, artificially imparted to mitochondria of yeast Yarrowia lipolytica, allows for replication of intact human mitochondrial DNA in yeast mitochondria, supporting a full-size native human mitochondrial DNA in the yeast cells and eliminating pathogenic mutations by means of standard sitedirected PCR mutagenesis. After the correction in the Y. lipolytica cells, copies of mitochondrial DNA of an individual patient may be returned to him using the transfection of mesenchymal stromal cells followed by selection of transfectants grown in minimal culture media, in which the cells with higher respiratory mitochondrial activity will gain the advantage.



Modern views on the mechanisms of sodium ion transport from the external environment in freshwater hydrobionts
Abstract
On the basis of kinetic characteristics of the ion exchange between freshwater aquatic organisms and external medium, the existing concepts on the action mechanisms of the ion carriers located in cell membranes of skin ionocytes of embryos and in the gill epithelium of fishes are analyzed. It is shown that the main mechanism compensating for the Na+ loss by the organism of freshwater hydrobionts into the external environment is the Na+-Cl– cotransporter and, to a certain degree, the Na+-K+-2Cl– cotransporter. A supplementary role in the Na+ transport from the water under extreme conditions may play the Na+/H+ and Na+/NH4+ exchangers.



Articles
Impact of external influences on characteristics of domains in biological membranes
Abstract
Living systems continually interact with the environment. External influences evoke complex processes in the entire system. In this work, the impact of external influences on the behavior of the domains in biological membranes is considered both in general and on special examples. A general approach of nonequilibrium statistical thermodynamics proposed by L.A. Stratonovich along with the same approach adapted to stochastic storage processes are applied. Both the Stratonovich theory and the storage models allow characterizing specific features of the stationary non-equilibrium states as well as the behavior of the highly non-equilibrium processes in open systems, such as live organisms.



Activation of the contact pathway of blood coagulation on the circulating microparticles may explain blood plasma coagulation induced by dilution
Abstract
Recent studies have shown that the contact activation of blood coagulation can be initiated on the surface of circulating microparticles–particles formed as a result of the activation or apoptosis of blood cells or endothelial cells. In the present work, by means of a mathematical model, we investigated the mechanism of the activation of contact pathway of blood plasma coagulation. The model describes membrane-dependent reactions of the activation of factors XII and XI with account of the presence of blood plasma inhibitors. All reactions were described by ordinary differential equations integrated by an implicit multistep method. The current mathematical model is based on our previous model of factor XII activation on the platelet surface. The initial model is modified by the addition of factor XI, kallikrein, and blood plasma inhibitors. We show that the amidolytic activity of the contact pathway factors associated with the microparticles is proportional to the concentration of microparticles. In previous studies, an increase in the overall solution amidolytic activity after the dilution of plasma was observed. Computational analysis of the contact pathway activation in the diluted plasma shows that the increase in the activation appears from the dilution of blood plasma inhibitors. Thus, a well-known experimental phenomenon of the hypercoagulability of plasma after dilution can be explained by an increased activation of the blood plasma coagulation through the contact pathway on the circulating microparticles. In addition, the computational analysis reveals that a rapid stop of the contact pathway activation on the microparticles observed in the experiments could be explained by the rapid depletion of the free activation surface.



Applicability of TOF-SIMS for the assessment of lipid composition of cell membrane structures
Abstract
Langmuir–Blodgett lipid films and plasma membranes of glioma cells were analyzed using timeof-flight secondary ion mass spectrometry (TOF-SIMS). Bi3+ primary ion beam was determined to be most efficient in various experimental setups. TOF-SIMS was shown to be applicable for a quantitative analysis of model lipid structures, as well as plasma membranes of glioma cells U87MG in vitro. A combination of atomic-force microscopy and scanning electron microscopy yielded the depth resolution of ~10–20 nm for cell surface scanning by primary ion beam.



Mathematical model of action potential in higher plants with account for the involvement of vacuole in the electrical signal generation
Abstract
Electrical signals, including action potential (AP), play an important role in plant adaptation to the changing environmental conditions. Experimental and theoretical investigations of the mechanisms of AP generation are required to understand the relationships between environmental factors and electrical activity of plants. In this work we have elaborated a mathematical model of AP generation, which takes into account the participation of vacuole in the generation of electrical response. The model describes the transporters of the plasma membrane (Ca2+, Cl–, and K+ channels, H+- and Ca2+-ATPases, H+/K+ antiporter, and 2H+/Cl– symporter) and the tonoplast (Ca2+, Cl–, and K+ channels; H+- and Ca2+-ATPases; H+/K+, 2H+/Cl–, and 3H+/Ca2+ antiporters), with due consideration of their regulation by second messengers (Ca2+ and IP3). The apoplastic, cytoplasmic and vacuolar buffers are also described. The properties of the simulated AP are in good agreement with experimental data. The AP model describes the attenuation of electrical signal with an increase in the vacuole area and volume; this effect is related to a decrease in the Ca2+ spike magnitude. The electrical signal was weakly influenced by the K+ and Cl– content in the vacuole. It was also shown that the contribution of vacuolar IP3-dependent Ca2+ channels into the generation of calcium spike during AP was insignificant with the given parameters of the model. The results provide theoretical evidence for the significance of the vacuolar area and volume in plant cell excitability.



PIP1 aquaporins, sterols, and osmotic water permeability of plasma membranes from etiolated pea seedlings
Abstract
Plasma membrane isolated from microsomal membranes of pea seedling root and shoot cells by means of aqueous two-phase polymer system was separated by flotation in discontinuous OptiPrep gradient into “light” (≤1.146 g/cm3) and “heavy” (≥1.146 g/cm3) fractions. Osmotic water permeability of plasma membrane and its two fractions was investigated by inducing transmembrane osmotic gradient on the vesicle membrane and recording the kinetics of vesicle osmotic shrinkage by the stopped-flow method. Rate constants of osmotic shrinkage and coefficients of osmotic water permeability of the membranes were estimated on the basis of the kinetic curve approximation by exponential dependencies and using electron microscope data on vesicles sizes. In plasma membrane and its fractions the content of sterols and PIP1 aquaporins was determined. It was found that in “light” PM fractions from both roots and shoots the content of PIP1 aquaporins and sterols was higher and the osmotic water permeability coefficient was lower than in “heavy” fractions of plasma membrane. The results indicate that plasma membrane of roots and shoots is heterogeneous in osmotic water permeability. This heterogeneity may be related with the presence of microdomains with different content of aquaporins and sterols in the membrane.



Analysis of exo- and endocytosis in the mouse nerve ending in experimental diabetes mellitus
Abstract
Diabetes mellitus (DM) is a systemic disease characterized by changes in many organs and tissues, including the motor system. The processes of exo- and endocytosis in the motor nerve ending of the mouse diaphragm muscle during high-frequency activity in experimental alloxan model of DM were studied. Endplate potentials (EPPs) were recorded using intracellular microelectrodes during single and high-frequency (50 Hz, 1 min) stimulation. In mice with the experimental DM, the amplitude-time parameters of EPPs did not differ from those of the control; however, an increase in EPPs depression and a slower recovery were observed during high-frequency stimulation. Using an endocytosis marker FM 1-43, it was shown that in animals with experimental DM fluorescence intensity of the nerve terminals loaded with the dye by high-frequency stimulation increased that was prevented by 1-azakenpaullone (2 μM), an inhibitor of slow dynamin-1-mediated endocytosis. In addition, in the model animals, the destaining of the pre-loaded nerve terminals during high-frequency (50 Hz) stimulation slowed down. The obtained data indicate that in the experimental first type DM recycling of synaptic vesicles via long path becomes more pronounced and the mechanisms of the vesicular transport are impaired, which was confirmed by methods of mathematical modeling.


