Biofizika最新文献

The propagation of excitation wave in the inhomogeneous anisotropic finite element model of cardiac muscle is investigated. In this model, the inhomogeneity stands for the rotation of anisotropy axes through the wall thickness and results from a fibrous-laminar structure of the cardiac muscle tissue. Conductivity of the cardiac muscle is described using a monodomain model and the Aliev-Panfilov equations are used as the relationships between the transmembrane current and transmembrane potential. Numerical simulation is performed by applying the splitting algorithm, in which the partial differential solution to the nonlinear boundary value problem is reduced to a sequence of simple ordinary differential equations and linear partial differential equations. The simulation is carried out for a rectangular block of the cardiac tissue, the minimal size of which is considered to be the thickness of the heart wall. Two types of distribution of the fiber orientation angle are discussed. The first case corresponds 'to the left ventricle of a dog. The endocardium and epicardium fibers are generally oriented in the meridional direction. The angle of fiber orientation varies smoothly through the wall thickness making a half-turn. A circular layer, in which the fibers are oriented in the circumferential direction locates deep in the cardiac wall. The results of calculations show that for this case the wave form strongly depends on a place of initial excitation. For the endocardial and epicardial initial excitation one can see the earlier wave front propagation in the endocardium and epicardium, respectively. At the intramural initial excitation the simultaneous wave front propagation in the endocardium and epicardium occurs, but there is a wave front lag in the middle of the wall. The second case refers to the right ventricle of a swine, in which the endocardium and epicardium fibers are typically oriented in the circumferential direction, whereas the subepicardium fibers undergo an abrupt change in the angle of orientation. For this case the dependence of the wave front on the location of initial excitation is weak. One can see the earlier wave front propagation in the middle of the wall. However, the wave front formation rate is different: with highest velocity for intramural initial excitation and with lowest one during excitation on the endocardial surface.

The paper deals with an approach to the description of the age and temporal dynamics of cancer, based on the model describing the dynamics of the age of cancer as a second order phase transition. This approach is widely used for studying physical systems. This model of cancer development as second order phase transitions is in a good agreement with medical statistics. The cancer incidence dynamics is described only with two free parameters, easily verified according to statistics and well interpreted. The applicability of the second order phase transition model for description of a non-physical system defines the universal nature of the processes occurring during phase transitions.

The article is devoted to a modern understanding of locomotor activity of olfactory cilia as a form of chemotaxis. It includes an analysis of published data and also the results of experimental research performed by the authors.

It has been shown that dinitrosyl iron complexes with thiol-containing ligands, bound with modified bovine serum albumin with high amount of thiol groups, appeared in baker yeast or in animal tissues in the presence of exogenous or endogenous nitric oxide, respectively, are represented predominantly by EPR-silent binuclear form. This form can be transformed into EPR-active mononuclear form of dinitrosyl iron complexes with an increase in pH to basic values, into EPR-active form of mononuclear iron nitrosyl complexes in case of bielectronic recovery of the binuclear form of dinitrosyl iron complexes or under the action of dithiocarbamate derivatives. The latter induced the transformation of dinitrosyl iron complexes into EPR-active mononitrosyl iron complexes with dithiocarbamates. A significant amount of binuclear dinitrosyl iron complexes with thiol-containing ligands in living systems and identical biological activity of these complexes and endogenous nitric oxide systems allow of considering endogenous binuclear dinitrosyl iron complexes as a "working form" of endogenous nitric oxide recognized now as a universal regulator of biological processes.

In this research the changes in the supramolecular structure of distilled water during germination of the seed in this water were studied. We used three methods: gravimetry, precision thermal analysis, electron work function measurements. In the first stage of seed germination--seed swelling--the seed extracts coherent domains in the water, herewith due to the transition of coherent domains adsorbed in nanofields into a stable state the flow of electromagnetic energy appears. In the second stage of the experiment--germ growing--the flow of biophotons occurs. This is evidenced by the increased water electron work function. A hypothetical model of the process of zucchini seed germination is suggested.

The aim of current research was to find negative effects caused by eliminating power line interference in ECG signal with narrow-band recursive notch filter and to search for a filtering method that will solve a problem of signal distortion. During the study the method of ECG filtering with narrow-band recursive filter was described. The main negative attribute of this filter is a transient noise, also called "ringing" effect, as the reaction to a single impulse visible as R spikes on the ECG signals. It was discovered, that "ringing" effect appears after the impulse during forward filtering and before the impulse during backward filtering. Based on this effect we proposed a method the main idea of which was to build the finite signal with regions without transients.

Continuous generation of hydrogen peroxide catalyzed by low concentrations of 1,1-dimethylhydrazine (heptyl)--a rocket fuel component--in air saturated water was shown by the method of enhanced chemiluminescence in the system of luminol-p-iodophenol-peroxidase. The concentration dependence and the influence of heat and light on the formation of hydrogen peroxide in the water under the influence of dimethylhydrazine at concentrations considerably lower than maximum allowable concentrations were studied, and the physical-chemical mechanism of this process was considered. It is supposed that dimethylhydrazine at ultra-low concentrations is associated with air nanobubbles and represents a long-lived complex performing catalysis of hydrogen peroxide formation under the influence of heat and light. We put forward the new concept of.toxicity of dimethylhydrazine at very low concentrations due to violation of homeostasis of reactive oxygen species formation in aqueous solutions entering the body of humans and animals.

Coherent sources of electromagnetic waves in the terahertz frequency range are very promising for various applications, including biology and medicine. In this paper we propose a scheme of a compact terahertz source, in which terahertz radiation is generated due to effective interaction of electrons in a quantum well with an electromagnetic wave of a corrugated waveguide. We have shown that the generation of electromagnetic waves with a frequency of 1012 sec(-1) and an output power of up to 25. mW is possible in the proposed scheme.

A comparative study of antioxidant (radical-interceptor) properties of tryptanthrin (quinazoline alkaloid shows a high anti-inflammatory activity and it is found in many types of different families of higher plants and microorganisms, including the human microbiome) in the systems of 2,2'-azo-bis(2-methylpropionamidin)dihydrochloride-luminol and hemoglobin-hydrogen peroxide-luminol has been conducted and the influence on the permeability of planar bilayer lipid membranes is evaluated. Trolox was used as a reference antioxidant, and ascorbic acid and dihydroquercetin were taken as standards. Tryptanthrin exhibits very weak antioxidant activity, being markedly inferior to the reference standard and antioxidants while testing antioxidant activity in both studied systems. By the efficacy of antioxidative action the substrates in the systems studied can be arranged in the following order: dihydroquercetin > trolox > ascorbic acid > tryptanthrin. Antioxidant potential of tryptanthrin is approximately 1000 and 3000 times lower than that of trolox and bioflavonoid dihydroquercetine, respectively. Tryptanthrin causes no significant changes in the permeability of planar bilayer membranes in a dose range of 0.5 to. 10 μg/ml. Our data show that tryptanthrin displays no significant radical-interceptor and membranotropic activities. It can be assumed that the observed high anti-inflammatory activity of tryptanthrin is not related to the neutralizing effect against reactive oxygen species and the influence on the permeability of cell membranes. The anticipated mechanisms of biological activity of tryptanthrin are discussed.

The effect of in vivo laser irradiation by optical radiation on blood from different patients is studied. The objects of research were three series of blood samples from patients whose treatment course included extracorporeal UV blood irradiation, intravenous laser blood irradiation and supra-venous blood laser irradiation. Before and after irradiation the results on optic oximetry and gas content of venous blood were compared. The results of positive and negative influence of blood irradiation on characteristics of an oxygen exchange in separate patients and on the maintenance of some products of metabolism are represented. It is shown that at the same power dose, their changes depend on individual, initial values of hemoglobin oxygen saturation of venous blood and its photoinduced changes which objectively reflect individual sensitivity of patients to the action of optical radiation on blood and can be used for assessment of the efficiency of phototherapy.