Vol 62, No 2 (2017)

The formation of ice microparticles in 0.2-mm thin layers of aqueous solutions of cryoprotective agents cooled to temperatures reaching–196°C was studied. The shape and size of ice microparticles were determined by cryomicroscopy. At temperatures below 0°C, the formation of solid ice masses was observed; further cooling caused ice fracturing induced by emerging thermomechanical stresses and the formation of microparticles. The shape and size of the particles depended on the composition of the frozen solution and on the rate of cooling. The components of cryoprotective solutions (cryoprotectants, egg yolk, sugars, and lipids) significantly changed the shape and size of the ice microparticles.

A comparative study of pH values in recrystallized aqueous solutions of manganese, copper, and iron sulfates and the calculated values for the pH levels of similar solutions obtained directly from solid salts has been performed for the first time. The trend for the positive deviation of the pH_rec values from the pH_calc values has been established. The positive deviation was the strongest in the case of iron sulfate solutions. The sample of the recrystallized aqueous solution (recrystallized water) consisted of water obtained by melting of the initial aqueous solution after freezing of 60% of the solution (by volume). Four hypotheses were proposed to explain the positive deviation of pH_rec from pH_calc: (1) low СО₂ concentration; (2) more efficient adsorption of anions on the freezing front compared to that of cations; (3) mechanochemical and radiation chemical processes that occur upon the melting of ice; and (4) Fe²⁺-catalyzed decomposition of hydrogen peroxide formed in the recrystallized solution. Analysis of the putative causes showed that the fourth hypothesis provided the most adequate explanation of the difference between pH_rec and pH_calc. The formation of hydrogen peroxide in recrystallized water is proposed to occur due to the recombination of OH radicals formed during the radiation chemical processes.

The protein refractive index was observed to increase by 8 · 10^–6 during proteolysis of bovine serum albumin (BSA, 4 mg/mL) with pepsin (2.2 mg/mL). It was believed earlier that the refractive index of a protein solution depends only on the protein concentration and amino-acid composition and remains unchanged during protein hydrolysis. An increase in the refractive index during proteolysis in solution was detected using an original laser interferometer with an improved sensitivity. The interferometer makes it possible to measure the difference in refractive index between solutions in two cells to an accuracy of approximately 6 · 10^–7.

The photodissociation process of the nitrosyl hematoporphyrin complex has been studied using quantum-chemical methods. Photolysis of hematoporphyrin complexes is of high biological usefulness and is widely employed in laser-therapy methods. However, the mechanism of photodissociation of these complexes is not entirely clear. Based on the computations, we propose a detailed mechanism for the photolysis of the nitrosyl hematoporphyrin complex. A transition “dissociative” excited state has been described, which has an energy barrier value of only 0.4 eV for NO dissociation.

A individual approach to the treatment of cancer patients, which takes the genetic features of the patient’s metabolism into account, allows one to choose an appropriate drug and its dose, that increases the efficiency of therapy and prevents the development of side toxic effects. For this purpose, we developed a biological microarray-based method for studying the primary structure of patient DNA and identifying polymorphisms in the UGT1A1, DPYD, GSTP1, and ABCB1 genes associated with alterations in xenobiotic metabolism. Genotyping of samples from 89 cancer patients and 15 healthy donors was carried out using the developed microarray. The results of determination of the primary structure of DNA samples coincided completely with the control sequencing. To increase the specificity of determination of polymorphic variants of the UGT1A1 gene, we used hybridization probes containing LNA nucleotides. The frequencies of polymorphic allelic variants of the UGT1A1*28, DPYD*2A, GSTP1 (I105V), and ABCB1 (C3435T) genes in the studied sample were 0.39, 0, 0.33, and 0.57, respectively.

The activity of electroneutral ion transport in response to the effect of the gasotransmitters carbon monoxide and hydrogen sulfide was investigated. It was shown that phenylephrine, an activator of receptorregulated calcium uptake, enhanced the relaxing action of carbon monoxide and hydrogen sulfide. In contrast, inhibition of the membrane potassium conductance, especially its voltage-dependent component, decreased the myogenic effects of carbon monoxide in the smooth muscles. The effects of hydrogen sulfide depended on its concentration and the means of activation of the cell transport systems. Furthermore, sodium-dependent components of the membrane conductivity are also involved in the effects of this gasotransmitter on ion transport systems in addition to the calcium and potassium conductance. This expands the range of the potential gasotransmitter-affected targets of signaling pathways, which may result in either activation or inhibition of cell functions. The consequences of such impacts on the functionally significant responses of cells, organs, and systems should be taken into account in various physiological and pathological states.

We demonstrated that the level of phospholipids in the liver mitochondrial fraction is increased by 60% during the winter hibernation season in the Yakut ground squirrel S. undulatus; the phospholipid composition in sleeping animals is characterized by an increase in phosphatidylethanolamine compared with summer animals. A sharp increase in the level of cholesterol, as well as fatty acid, monoglycerides, and diglycerides was found in the mitochondrial fraction of hibernating ground squirrels in relation to summer ground squirrels. Functional changes during hibernation concern the level of phosphatidylserine (the growth in sleeping animals compared with active animals). Seasonal modification of the lipid composition of the liver mitochondria (particularly, an increase in the level of cholesterol) can play a role in the resistance of mitochondria to the seasonal increase in the level of fatty acids in the liver. Lipids of the liver mitochondrial fraction are involved in the ground squirrel adaptation to the hibernation season.

Using electron paramagnetic resonance, the dose-dependence effect of dopamine on methemoglobin formation in erythrocytes of patients with Parkinson’s disease under the activation of oxidative stress induced by acrolein and the possibilities for the correction of this pathological process using carnosine in vitro experiments have been examined. It was shown that incubation of erythrocytes with 1.5 mM dopamine did not change the methemoglobin content, while incubation with 15 mM dopamine caused a two fold increase in the methemoglobin content compared to its initial level; 10 μM acrolein increased methemoglobin formation threefold. Administration of 15 mM dopamine and, after 1 h, 10 μM acrolein to the incubation system increased methemoglobin formation tenfold compared to its initial level. Preincubation of erythrocytes with 5 mM carnosine followed by acrolein addition prevented the increase in the methemoglobin content, while carnosine had no effect on methemoglobin formation induced by dopamine.

The type of mechanical stresses that arise in erythrocyte membranes on exposure to catecholamines and steroid hormones is considered. Tensors of mechanical stresses and displacements were obtained for a membrane interacting with hormones. A possible mechanism of membrane rupture under mechanical stresses is discussed. Catecholamines and androgens increase the microviscosity of membranes, and alternating kink and stretching sites occur in the lipid membrane bilayer to produce a checker-wise pattern. The membrane becomes thinner in a stretching site (smectic A → smectic C transition). When tensile stresses increase further and exceed a certain critical value the membrane may rupture. It is possible that a gel phase L_β• → liquid crystalline phase L_α transition takes place in the stretching site of the lipid bilayer prior to disruption. The density of the lipid bilayer decreases in the process, pores form, and then cracks occur.

Isolation of luminophores from the mycelium of a luminous fungus Neonothopanus nambi is reported. In addition to the emission peak with a maximum at 520–530 nm (the wavelength of visible green light) that corresponded to the maximum of light emission by the fungus in vivo, the fluorescence spectra of the raw extracts contained a peak with a maximum in the visible blue-light range. The luminophore that emitted the blue light was an individual compound with a molecular weight of 894 Da. Calculations that took the isotope composition of chemical elements into account pointed at C₅₂H₆₅N₂O₁₁, C₅₁H₆₅N₄O₁₀, C₅₃H₆₁N₆O₇, C₄₇H₆₅N₄O₁₃, and C₄₆H₆₅N₆O₁₂ as the putative chemical formulae of the luminophore. A sample that contained substances of a yellow color was obtained; these substances emitted fluorescence at the wavelengths of green visible light. The luminophores in this sample probably included riboflavin or derivatives thereof (flavin mononucleotide or flavin adenine dinucleotide).

The goal of this study was to find genes that encode cytoskeletal proteins that are potential candidates for the role of triggers in cell mechanosensitivity in the fruit fly. Centrifugation was used to simulate the hypergravity effects (2g group); the constantly changing orientation of the larvae in the gravity field was performed in order to simulate the effects of microgravity (0g group) for 1.5, 6, 12 and 24 h. mRNA levels of different genes that encode the components of both tubulin and actin cytoskeleton were assessed by qRT-PCR. In the 0g group the mRNA levels of beta-tubulin and Msps were reduced after 1.5 h of the exposure and remained unchanged until 12 h, while they exceeded the control level after 24 h. The mRNA level of chaperonin containing T-complex 1 polypeptide subunits recovered earlier: after 6 and 12 h of the microgravity exposure. At the same time, the hypergravity effect led to more significant changes in the mRNA level of TCP1 complex components compared with those of tubulin and Msps. The mRNA level of beta-actin isoforms under micro- and hypergravity was decreased up to 12 h of the exposure, however, it remained reduced under microgravity conditions, while it recovered (Act87E) and even exceeded (Act57B) the reference level under hypergravity conditions. The mRNA level of supervillin was almost unchanged. Under microgravity conditions the mRNA level of fimbrin was decreased (it recovered by the 24 h time point), while the mRNA level of alpha-actinin was significantly increased by the 12 h time point of the exposure and after 24 h it was reduced to the control level. In contrast, under hypergravity conditions the mRNA level of fimbrin initially increased, and after 24 h it dropped below the control, while the mRNA level of alpha-actinin was significantly reduced, and after 24 h it was higher than the reference level. Similar results were obtained earlier in the experiments in rodents, but similar dynamics were observed for alpha-actinin isoforms 1 and 4, although no changes were observed for fimbrin. Since Drosophila melanogaster has no alpha-actinin isoform 4, it is hypothesized that its role in the cell is played by fimbrin.

The system of hemostasis includes coagulation of blood plasma and formation of platelet aggregate. Plasma clotting is a cascade of proteolytic reactions, triggered by the contact of blood plasma with any tissue except the normal vessel endothelium. During the contact an enzymatic complex is formed of the soluble blood plasma protein, factor VIIa, and a membrane-anchored protein, tissue factor. This complex is called extrinsic tenase; it is the key initiator of blood coagulation. The main substrates of extrinsic tenase are blood plasma factors X and IX. During the reaction they undergo proteolytic cleavage and become active serine proteases, factors Xa and IXa, respectively. Factor Xa in complex with its cofactor factor Va catalyzes formation of the key coagulation enzyme, thrombin, which leads to fibrin polymerization and plasma gelation. Although all of the proteins that participate in this process have been known for a long time, several questions remain unanswered. As an example, what is the role of the reaction surface on which the complex is formed, what is the role of membrane-bound multimeres of factor X (Xa), and in what way does the activation of the factor VII proceed? Here, we review recent theoretical and experimental works focused on the biophysical mechanisms of extrinsic tenase functioning and discuss some of these problems.

Three-dimensional spiral waves of electrical excitation in the myocardium are sources of dangerous cardiac arrhythmias. In this work, the dynamics of spiral waves of electrical excitation were studied in a symmetric anatomical model of the human heart left ventricle and a realistic ionic cell model of the human ventricular myocardium. Three factors that affect the drift waves in the heart were compared for the first time: the geometry of the heart wall, myocardial anisotropy, and wave chirality. Cardiac anisotropy was identified as a main factor in determining the drift of spiral waves. In the isotropic case, the dynamics were determined by the wall thickness, but did not depend on the wave chirality. In the anisotropic case, chirality was found to play a crucial role.

Experiments with white rats were carried out to study the effects of original antithrombin DNA aptamers on the renal function and animal survival in rhabdomyolisis caused by intramuscular injection of a hyperosmolar glycerol solution. The DNA aptamers were demonstrated to exert a nephroprotective effect, reducing a retention azotemia and proteinuria, and improving the renal excretory function and overall survival of animals.