Biofizika最新文献

The influence of transcranial electromagnetic stimulation on the development of an active avoidance reflex with painful reinforcement in laboratory rats is investigated. It is shown, that an exposure of the rats' brain to electromagnetic radiation in the millimeter range ((λ = 5,6 and 7,1 mm), modulated as a series of low-frequency pulses, leads to a suppression of the development of the conditioned avoidance reflex occurred in 50% of cases. In other 25% of cases irradiation leads to inhibition of reflex development. Transcranial electromagnetic stimulation after intraperitoneal injection of the blocking agent of serotonergic receptors (kitryl) has no influence on reflex development. Electromagnetic brain stimulation does not influence reflex retention in the case when it has been acquired. Based on the data obtained it is assumed that transcranial electromagnetic stimulation promotes the development of serotonin, exerting an inhibiting effect on the formation of temporal bindings of the studied conditioned reflex.

Expression patterns of segmentation genes are formed under the influence of maternal transcription factor gradients, which initiate spatially localized expression in the cascade of segmentation genes. Bcd is one of these activators. We have studied one model of regulation in the gap gene network by varying the concentration of this protein. We have shown that the known gap gene network topology is not sufficient to explain experimental data on the shifts exhibited by the hb anterior expression domain by change in Bcd concentration in the embryo. As the result of modeling with these experimental data taken into account, a new topology is obtained that determines the correct shifts of the hb expression domain. These results suggest that interactions among the three hb, Kr and gt genes are key regulatory factors for the valid behaviour of the hb expression pattern with Bcd concentration changes. This study made it possible to specify the limits of validity for phenomenological models of gene networks.

Gene networks contain a recurring motif, called the feed-forward loop, in which a transcription factor regulates target expression directly and indirectly via the second regulator. Here we present the results of mathematical modeling of feed-forward loops with either the transcription factor or miRNA as a repressor in the indirect pathway. We showed that the substitution of the transcription factor with miRNA changes the dynamic behavior of the feed-forward loop and lends new properties critical for biological system functioning.

The optical activity of DNA liquid-crystalline dispersions is being investigated based on a theory for absorption of electromagnetic waves by large molecular aggregates. The impact on the dispersions-optical properties, exerted by the interaction between the complexes of nucleic acid molecules and nanoparticles, is being considered.

The dynamics of oxidative metabolism in healthy people's blood (n = 30) under the influence of gaseous nitric oxide and dinitrosyl iron complexes is explored. In all blood samples we studied lipid peroxidation intensity and malonic dialdehyde in plasma and erythrocytes, plasma antioxidant potential and activity of superoxide dismutase. During our investigations it was possible for the first time to identify the peculiarities in the responses of pro- and antioxidant blood systems in vitro to the treatment with nitrogen monoxide as the free. radical and its storage form (as a component of dinitrosyl iron complexes). So, a pronounced prooxidant effect for the gas flow from the "Plazon" apparatus moderately decreases when a tenfold dilution of a NO-containing mixture is made. Gas flow from the experimental NO-generator causes minimal prooxidant action, and injection of water solution of dinitrosyl iron complexes in blood specimens leads to an antioxidant action, as limitation of lipoperoxidation processes in plasma and stimulation of superoxide dismutase in erythrocytes.

Since exudate diagnostic procedures require the attention of an expert ophthalmologist as well as regular monitoring of the disease, the workload of expert ophthalmologists will eventually exceed the current screening capabilities. Retinal imaging technology is a current practice screening capability providing a great potential solution. In this paper, a fast and robust automatic detection of exudates based on moving average histogram models of the fuzzy image was applied, and then the better histogram was derived. After segmentation of the exudate candidates, the true exudates were pruned based on Sobel edge detector and automatic Otsu's thresholding algorithm that resulted in the accurate location of the exudates in digital retinal images. To compare the performance of exudate detection methods we have constructed a large database of digital retinal images. The method was trained on a set of 200 retinal images, and tested on a completely independent set of 1220 retinal images. Results show that the exudate detection method performs overall best sensitivity, specificity, and accuracy of 90.42%, 94.60%, and 93.69%, respectively.

Four experiments on long-term monitoring of pulse rate and blood biochemical parameters in four healthy volunteers (women) were conducted. The duration of each experiment was 90 minutes, electrocardiography was performed continuously, taking blood sampling every two minutes. In venous blood the current concentrations of triiodothyronine, cortisol, glucose, stable metabolites of nitrogen oxides (NO(x)) were determined. Synchronicity in oscillations of cortisol and free triiodothyronine levels in the blood of all four volunteers was detected, as well as the presence of the periods of 7-8 min and 15-17 min in the spectra of these biochemical parameters was observed. The periods in the spectra of NO(x) are equal to 7 min, 13 min and 25-30 min. It is shown that the, dynamics of variations in the heart rate is determined mostly by the rhythms of fluctuations in the level of NO(x) in the blood, and the periods in wavelet spectra of these physiological parameters in all four volunteers are close to the periods of their spectra synchronous variations of a. geomagnetic field vector in the frequency range of 0.5-3 mHz. The results obtained in this study indicate that. the presence of nitric oxide and its metabolites in the blood is a biochemical factor, with high probability of its participation in the developmental process of the fine "tuning" of the body to the variations of the geomagnetic field providing synchronization of variations in heart rate and geomagnetic fluctuations in the geomagnetic quiet conditions.

The application of Brownian dynamics for simulation of transient protein-protein interactions is reviewed. The review focuses on theoretical basics of Brownian dynamics method, its particular implementations, advantages and drawbacks of the method. The outlook for future development of Brownian dynamics-based simulation techniques is discussed. Special attention is given to analysis of Brownian dynamics trajectories. The second part of the review is dedicated to the role of Brownian dynamics simulations in studying photosynthetic electron transport. Interactions of mobile electron carriers (plastocyanin, cytochrome c6, and ferredoxin) with their reaction partners (cytochrome b6f complex, photosystem I, ferredoxin:NADP-reductase, and hydrogenase) are considered.

In order to evaluate the toxic effect of silver (AgNP) and titanium dioxide (TiO2) nanoparticles their influence on the expression of genes of biomarkers of inflammatory responses and apoptosis in human lymphocytes was studied. An increase in the IL-6, IL-8, TNF-α and p53 genes expression in the concentration range of silver and titanium dioxide nanoparticles of 10-40 μk g/ml was found. Increased expression of IL-6, IL-8, TNF-α and p53 genes under the nanoparticles action indicates the stimulation of the immune system and of apoptosis, respectively.

In this review we have focused on the advances madein observing the photo-induced response in bacteriorhodopsin and understanding the mechanisms of retinal-protein interactions which are still obscure. We discuss our recent data obtained on the wild type of bacteriorhodopsin and model compounds. This paper presents our new spectroscopic data on amino acids obtained using FT-IR emission spectroscopy. Based on the characteristics of the structure and optical properties of glycine and L-lysine that simulate a photo-induced behaviour of an opsin under natural conditions we tried to find an answer to one of the most important questions concerning the role of protein in the primary processes in bacteriorhodopsin.