Antioxidant Status of Rat Liver Mitochondria under Conditions of Moderate Hypothermia of Different Duration.

For evaluation of the contribution of the antioxidant system of mitochondria into the dynamics of changes in the prooxidant status, the content and activity of some of its components were studied under conditions of moderate hypothermia of varying duration. It was found that short-term hypothermia significantly increased superoxide dismutase activity and decreased the levels of low-molecular-weight antioxidants. Increasing the duration of hypothermia to 1 h led to suppression of activities of superoxide dismutase, glutathione reductase, and glutathione peroxidase and a decrease in glutathione content. Further prolongation of hypothermia (to 3 h) was associated with a significant increase in superoxide dismutase and glutathione peroxidase activities and normalization of the rate of glutathione reductase catalysis; the concentration of glutathione increased significantly.

Respiratory Characteristics of Rat Liver Mitochondria Depend on the Duration of Moderate Hypothermia.

The development of pathological or compensatory-and-adaptive reactions in homoeothermic animals during various periods of hypothermia can be caused by shifts in the respiratory functions of the mitochondria. Short-term hypothermia promoted an increase in the rates of the glutamate- and succinate-dependent respiration of mitochondria. Phosphorylation rate increased as well, while oxidative phosphorylation coefficient (P/O), respiratory control, and 2,4-DNP sensitivity depended. Changes in respiratory characteristics in the dynamics of prolonged hypothermia depends on the type of substrate. Prolongation of hypothermia to 1 h was associated with further intensification of succinate-dependent respiration, decrease in P/O and respiratory control, while prolongation of hypothermia to 3 h led to their normalization. The majority of respiratory characteristics of glutamate-dependent respiration did not change under these conditions and their levels were the same as during short-term hypothermia.

Thermostability of Lactate Dehydrogenase in Rat Brain under Conditions of Short-Term Moderate Hypothermia.

Thermostability of rat brain lactate dehydrogenase (LDH) was studied in intact animals and animals subjected to moderate short-term hypothermia. Two exponential stages, rapid and slow, were distinguished in the thermodenaturation kinetics. The contribution of the rapid phase to the lactate dehydrogenase denaturation kinetics was more significant: the energy of activation for this phase was 2.33 times lower than that for the slow phase. Moderate shortterm hypothermia led to a significant decrease of lactate dehydrogenase thermostability: thermodenaturation rate constants for the rapid (k1) and slow (k2) phases increased. Significant changes in parameters a and b reflecting the initial proportion of the two native forms of the enzyme developed only at 40°C. As hypothermia caused no appreciable changes in the energy of activation of lactate dehydrogenase denaturation, a significant contribution of the entropic factor to the decrease of free energy of enzyme denaturation was hypothesized. The data indicated significant labilization of lactate dehydrogenase structure under conditions of moderate hypothermia.

Effect of Hypothermia on Kinetic Characteristics of Lactate Dehydrogenase in Rat Brain under Conditions of Global Ischemia and Reperfusion.

We studied activity and kinetic characteristics of lactate dehydrogenase (LDH) in rat brain under conditions of incomplete global ischemia followed by reperfusion against the background of mild hypothermia. It was found that hypothermia leads to a decrease in LDH activity in the ischemic brain; the maximum velocity of the enzyme-catalyzed activity decreased and Michaelis constant increased, due to which the efficiency of catalysis decreased to the level observed in control rats. Ischemia against the background of hypothermia was accompanied by a decrease in the inhibition constant and narrowing of effective pyruvate concentration range. Blood flow resumption in the ischemic brain against the background of mild hypothermia led to an increase in LDH activity, the maximum reaction velocity increased, and Michaelis constant decreased, which lead to a significant increase in the efficiency of catalysis. This was accompanied by an increase in enzyme inhibition constant and a shift of the optimum on the concentration curve towards lower pyruvate concentrations.

[Accumulation of magnetic nanoparticles in plants grown on soils of Apsheron peninsula].

The disclosure of magnetic nanoparticles in five plant species growing in Apsheron peninsula have been detected by the EPR method. The EPR spectra of these nanoparticles proved to be similar to those of synthesized magnetic nanoparticles. The result demonstrated that plants are capable of absorbing magnetic nanoparticles from the soil. The accumulation of nanoparticles in plants is confirmed by the presence of a broad EPR signal whose maximum position of the low-field component changes from g = 2.38 and halfwidth of the signal of 32 mT at room temperature to g = 2.71 and 50-55 mT at 80 K. The intensity of the broad EPR signal for plants grown in radioactively contaminated areas (170-220 mkR per h) was substantially lower compared with plants grown on clean soil. The parameters of the broad EPR signal and its dependence on the temperature of recording were identical with those for synthetic magnetic nanoparticles. The photosynthetic activity and changes in the genome of irradiated plants by the analysis of PCR products were studied.

[Practical value of certain prognostic scales in wound dystrophy].

The authors gave comparative characteristics of the data available in literature and the scales of evaluation of the severity and prognosis of wound dystrophy used by them.

Role of dendrimers in advanced drug delivery and biomedical applications: a review.

AIM: Dendrimers dendritic structural design holds vast promises, predominantly for drug delivery, owing to their unique properties. Dendritic architecture is widespread topology found in nature and offers development of specific properties of chemical substances. Dendrimers are an ideal delivery vehicle candidate for open study of the effects of polymer size, charge, and composition on biologically relevant properties such as lipid bilayer interactions, cytotoxicity, bio-distribution, internalization, blood plasma retention time, and filtration. This article reviews role of dendrimers in advanced drug delivery and biomedical applications.

Two types of kinetics of membrane potential of water plant leaves illuminated by ultraviolet light.

The effects of ultraviolet-B (UV-B) radiation on plasma membrane of water plant (Elodea canadensis, Vallisneria spiralis) cells were investigated by using microelectrode methods. A fast and reversible depolarization of membrane potential occurs initially during exposure of leaf cells to UV on a white light background, after which a slow phase of depolarization sets in. On action series, UV is pulsed for 15 s, with dark interval of 3 min, no monotonous response of systems on the UV excitation is observed. The action spectrum of the fast UV response lies in the interval of 300-330 nm and that of the slow phase-in the interval of 280-300 nm. The input impedance of membranes remains unchanged during the period of exposure. It is concluded that the H(+)-extruding complex of plant cell plasma membranes really consists of two types of interrelated electronic H(+)-pumps: an H(+)-pump of redox-active nature and the H(+)-pump of the H(+)-ATPase enzyme complex. Clearly, during the exposure of leaf cells to UV light, initially, the H(+)-pump of redox-active nature and then H(+)-ATPase are inhibited. It is proposed that the initial chromophore of UV-B light on plasma membrane can be one of the components of H(+)-pump of redox-active nature. It is probably the molecular of quinone.

[Light-dependent paramagnetic center in photosystem 2 of higher plants]. / Svetozavisimyi paramagnitnyi tsentr v fotosisteme 2 vysshikh rastenii.

In subchloroplast fragments of photosystem II from Vicia faba, free from P700 contamination, a free-radical ESR signal (singlet of 9 G peak-to-peak line-width, g approximately 2,0025) appears under illumination in presence of silicomolybdate as electron acceptor. Using ESR-active electron donors and acceptors as well as conventional redox reagents Hill activity of preparations has been evaluated under different conditions. Evidences are presented that the light-induced dark-reversible silicomolybdate-dependent ESR signal is of the same origin as photobleaching centered at 680 nm which has been earlier interpreted as a result of P680 center of photosystem II oxydation. The relaxation properties of this paramagnetic center as measured by microwave power saturation are different from that of P700+-center in photosystem I.

[Structural organization of rimorphin and its synthetic analogs]. / Strukturnaia organizatsiia rimorfina i ego sinteticheskikh analogov.

The spatial structure and conformations of rimorphin were investigated using theoretical conformational analysis. The spatial organization of the peptide can be described by a set of 11 low-energy conformations of the backbone. By solving the reverse conformational problem, a number of modified amino acid sequences ([Ala2], [Ala3], [MePhe9], [MeLys10], [MeVal11], and [MeVal12]-analogs of rimorphin) were determined that have spatial structures corresponding to the set of low-energy conformations and should, therefore, possess physiological activity.

[Effect of hypothermia on Na(+)-K(+)-ATPase activity and hemoglobin binding in the rat erythrocyte membranes]. / Vliianie gipotermii na aktivnost' Na(+)-K(+)-ATFazy i sviazyvanie gemoglobina v membranakh éritrotsitov krys.

The activity of Na+/K(+)-ATPase and hemoglobin binding in membranes of rat erythrocytes during hypothermia (20 degrees C) was studied. Hypothermia causes an increase in hemoglobin binding and a decrease in Na+/K(+)-ATPase activity. It was found in in vitro experiments that the addition of hemoglobin to the membranes does not affect the Na+/K(+)-ATPase activity in control animals and decreases the activity of the enzyme in hypothermia.

[Reduction paths of reaction centers of photosystem I of photosynthesis]. / O putiakh vosstanovleniia reaktsionnykh tsentrov fotosistemy I fotosinteza

The behaviour of ESR signal I in blue-green algae and chloroplasts is considered under various illumination and with various previous treatment. It is shown that the main process determining the kinetics of P700 plus reduction is the reaction with reduced components of the electron transfer chain between the two photosystems. If the accumulation of the products is inhibited by any way, then the reduction rate depends on the reactions with reducing agents in the incubation medium accumulated under irradiation before experiment. These exogenic reducing agents may be removed from the chloroplasts with repeated washings, and from algae-by means of the dark incubation for a long time. The relation of cyclic and noncyclic electron transfer is considered with and without artificial cyclic flow mediator.

[Molar extinction of pigment in the reaction center of photosystem II chloroplasts]. / Moliarnaia ékstinktsiia pigmenta v reaktsionnom tsentre fotosistemy II khloroplastov.

The absolute spin number in the Photosystem I chloroplast fragments from Vicia faba plant photooxidized in the presence of silicomolybdate has been carefully measured by means of camparison of ESR signals of P680-centers and of nitroxyl free radical aqueous solution. The data obtained together with simultaneous measurement of light-induced bleaching centered at 680 nm have been used to determine the molar extinction of reduced P680-center epsilon680 = 0.66 . 10(5) M-1 cm-1.

[The effect of hypothermia on kinetic characteristics of the rat brain synaptic membrane Na,K-ATPase].

The effect of profound hypothermia (acute or prolonged) on Km for ATP, Vm and strophanthine K affinity to Na,K-ATPase in the rat brain synaptosomal membranes was investigated. The temperature dependence of Na,K-ATPase activity in temperature range 5-40 degrees C was also studied. Hypothermia decreases Km and Vm, and increases affinity of strophanthine K to the enzyme. There are two linear sections in Arrhenius plots ofNa,K-ATPase activity. Hypothermia does not change position of the break point in Arrhenius plots. The mechanisms and biological significance of the changes revealed are discussed.