Biofizika最新文献

In order to study the effects caused by silver nitrate (AgNO3) on model lipid membranes, we studied multibilayer membranes based on L-α-dipalmitoylphosphatidylcholine (DPPC) and AgNO3 aqueous soluitions in a wide concentration range (up to 30 wt%) by means of differential scanning calorimetry. It has been shown that the presence of AgNO3 leads both to an increase in the main phase transition temperature (T(m)) and appearance of an additional phase transition peak (T(m)), suggesting increasing of both density and heterogeneity of the lipid membrane. The effect of nitrate ions (NO ) was shown to be of the opposite nature (bilayer fluidizing), so the integral densifying effect of AgNO3 can be referred solely to the action of silver ions (Ag(+)). With increasing AgNO3 concentration, the tendency was observed to opposite changes in T(m) and T'(m) peaks intensity, thereby at about 26. wt% of AgNO3 the initial peak (T(m)) disappeared. In the range of Ag+ therapeutic concentrations (up to 2 wt%) no significant changes in the DPPC membrane were revealed. This can be one of the reasons of the absence of a damaging effect of silver drugs on a host organism with simultaneous pronounced bactericidal effect.

This contribution presents the results of analysis of the dynamics of the bioluminescence of luminous bacteria Photobacterium phosphoreum IMV B-7071 under optimal conditions of their growth. A quasi-harmonic nature of the bacterial bioluminescence dynamics was detected. The observed periods of these changes have similar values compared with those in the earlier defined periods of changes in physicochemical properties of water. The relationship between biorhythms and a quasi-harmonic nature of changes in physicochemical properties of water is discussed.

Antitumor activity of the novel for oncology compound, such as polysuccinimide, against some of experimental tumor models (Lewis lung carcinoma, Acatol adenocarcinoma, Ca-755 adenocarcinoma) has been established. This drug induced 60-80% tumor growth inhibition of these murine solid tumor strains. Polysuccinimide is also effective (60%) against development of metastatic process in lung (Lewis lung carcinoma). Polysuccinimide causes no changes in pH level in tumor tissue (P-388 leukemia, Acatol adenocarcinoma). This agent may be recommended for further profound preclinical study.

Quantitative evaluation of the accuracy of the rapid equilibrium assumption in the steady-state enzyme kinetics was obtained for an arbitrary mechanism of an enzyme-catalyzed reaction. This evaluation depends only on the structure and properties of the equilibrium segment, but doesn't depend on the structure and properties of the rest (stationary part) of the kinetic scheme. The smaller the values of the edges leaving equilibrium segment in relation to values of the edges within the equilibrium segment, the higher the accuracy of determination of intermediate concentrations and reaction velocity in a case of the rapid equilibrium assumption.

Computer simulation of the electrical activity in sinoatrial node cells interacting via gap junctions with fibroblasts revealed that interaction with fibroblasts results in greater oscillation frequency of sinoatrial node cells. We have found out that fibroblasts also decrease the oscillation amplitude of the intrinsic central cells or completely suppress their spontaneous activity, while weakly affect the oscillation amplitude of peripheral cells.

The technique for recording of chlorophyll a fluorescence induction kinetics has been used for assessment of the physiological state of leaves of tillet (Tilia cordata), pendent white birch (Betula pendula), American arborvitae (Thuja occidentalis) in urban environments. Different sensitivity of plants to adverse growing conditions was observed. The most sensitive JIP test parameters such as PI(ABS), F(V)/F(0), F(V)/F(M), R(fd) are determined to be used as indicators of the physiological state of urban phytocenosis. Recommendations for the application of this technique in monitoring studies are given.

We consider the propagation of autowaves in the moving liquid excitable medium. The shapes of the autowave fronts in cases of the Poiseuille and Couette flows are determined in flat capillaries within a kinematic approach. We show the existence of a critical velocity for the flows above which the autowave fronts should break off. The possibility of a diode effect--the one-way capillary conductivity--is studied. The results of computer simulations are in good agreement with the theoretical predictions.

The decomposition pathways of hemoglobin UV absorption spectrum into the absorption spectra of the protein and non-protein components are proposed and substantiated by means of an additive model. We have established that the heme component has an absorption band with a maximum at λ(max) = 269.2 nm (ε = 97163) and the apoprotein component has an absorption band with a maximum at λ(max) = 278.4 nm (ε = 48669) for the wavelength range from 240.0 to 320.0 nm. An integral relative proportion of absorption for the heme fraction (78.8%) and apoprotein (21.2%) in the investigating wavelength range is defined.

A mathematical model of the formation of distal arterial pulse wave signal in the blood vessels of the upper limbs was considered. The formation of distal arterial pulse wave is represented as a composition of forward and reverse pulse waves propagating along the human arterial system. The system of formal analogy between pulse waves propagation along the human arterial system and the propagation of electrical oscillations in electrical transmission lines with distributed parameters was proposed. Dependencies of pulse wave propagation along the human arterial system were obtained by solving the one-dimensional Navier-Stokes equations for a few special cases.

Effective accumulation of binuclear dinitrosyl iron complexes with glutathione was shown after a subcutaneous para lymphatic injection of an aqueous solution of a dinitrosyl-iron complex into animal lung tissue at a single-dose of 2 micromoles per kilogram two times a day with a 2-h interval. Two hours later after the administration was repeated the concentration of these complexes was 16 micromoles per kilogram of tissue dropping down for the last two hours to 7 micromoles per kilogram of tissue. At one dose injection of binuclear dinitrosyl iron complexes with glutathione their concentration in 2 and 4 hours was two times lower than in the previous experiments. Presumably at the obtained concentration of dinitrosyl iron complexes a bactericidal effect in lungs can be observed against mycobacterium tuberculosis and rapidly proliferating lung tumors.