Cytoplasmic K/Na balance in heart muscle cells of young and old rats under oxygen and substrate deficiency

Age-related changes in the content of the major cellular cations of potassium and sodium in heart muscle cells of Wistar rats have been studied. The cytoplasmic concentration of potassium and sodium was determined by the electron probe microanalysis. The results revealed differences in both the concentration of the elements in young and old control animals and the responses of a cardiomyocyte to the state of acute hypoxic deenergization modelled on a perfused heart. The data are consistent with the hypothesis about the presence of genetically-related age changes in the conductance of potassium channels, which in old animals are realized against the background of deficient supply of tissues with oxygen and substrate.     

Accelerating membrane insertion of peripheral proteins with a novel membrane mimetic model

Characterizing atomic details of membrane binding of peripheral membrane proteins by molecular dynamics (MD) has been significantly hindered by the slow dynamics of membrane reorganization associated with the phenomena. To expedite lateral diffusion of lipid molecules without sacrificing the atomic details of such interactions, we have developed a novel membrane representation, to our knowledge, termed the highly mobile membrane-mimetic (HMMM) model to study binding and insertion of various molecular species into the membrane. The HMMM model takes advantage of an organic solvent layer to represent the hydrophobic core of the membrane and short-tailed phospholipids for the headgroup region. We demonstrate that using these components, bilayer structures are formed spontaneously and rapidly, regardless of the initial position and orientation of the lipids. In the HMMM membrane, lipid molecules exhibit one to two orders of magnitude enhancement in lateral diffusion. At the same time, the membrane atomic density profile of the headgroup region produced by the HMMM model is essentially identical to those obtained for full-membrane models, indicating the faithful representation of the membrane surface by the model. We demonstrate the efficiency of the model in capturing spontaneous binding and insertion of peripheral proteins by using the membrane anchor (γ-carboxyglutamic-acid-rich domain; GLA domain) of human coagulation factor VII as a test model. Achieving full insertion of the GLA domain consistently in 10 independent unbiased simulations within short simulation times clearly indicates the robustness of the HMMM model in capturing membrane association of peripheral proteins very efficiently and reproducibly. The HMMM model will provide significant improvements to the current all-atom models by accelerating lipid dynamics to examine protein-membrane interactions more efficiently.     

Electron probe microanalysis of rubidium retention in myocell of rat heart during acute ischemia

In the given investigation contents of potassium and its physiological analog, rubidium, are determined in cardiomyocyte. Applying Electron Probe Microanalysis (EPMA), cytoplasmic concentrations of elements (K, Rb) are measured. The data obtained exhibit that for initial acute ischemia phase the active transport is involved in the uptake of rubidium which competes with potassium entry in cardiac myocell. Then, deep deenergization leads to the intracellular potassium depletion and rubidium retention. This suggests that Rb⁺ is physiologically not complete analog for K⁺. Results of combined perfusion with and without rubidium allow us to hypothesize the appearance of cascade of ionic transports to compensate acute ischemic disturbances following the oxygen and substrate deficiency.     

3-D reconstruction of early preimplantation mouse embryo

Method of 3-D reconstruction approaches for early mouse embryo in preimplantation stages was modified. The developed technique is based on application of light microscopy of serial thin sections and well known soft operating. The designed method enabled us 1) to get serial sections of a single mouse embryo; 2) to create an orthogonal system independent on the sample for orientation of virtual sections. The adequacy of 3-DR protocol was checked on reconstruction of air bubbles embedded in epoxy resin as a model of sphere.     

Three-dimensional (3-D) structures formed by immortalized human fibroblast cells in simulated microgravity

3-D structures were obtained at rotatory cultivation of CH immortalyzed human fibroblasts attached to glass microcarrier beads. The morphology of cells from these cultures was studied by scanning electron microscopy. A number of structural alterations in fibrillar filopodia of CH cells were revealed as compared with cells grown in stationary monolayer cultures, namely, smaller length, uneven caliber, the presence of curvatures, and disturbed branching pattern. Filopodia displayed unusual formations: protuberance-like and "mammoth's tusk"-like off-shoots, foamy spreadings in distal segments, and spiral windings of filopodia. The susceptibility of CH cells morphology to mechanical environment makes them a promising model for gravitational biology studies.     

The Use of ToF-SIMS for Analysis of Bioorganic Samples

The technique for the preparation of biological tissue sections developed for Electron Probe Microanalysis has been adapted for ToF-SIMS analysis of mouse GV stage oocytes. GV-oocyte sample preparation involves the following steps: plunge freezing, freeze drying, impregnation in an embedding medium, and section cutting. Molecule-specific images of the distribution of molecules in a single oocyte have been obtained with the described technique and ToF-SIMS analysis. The ToF-SIMS analysis data show that the efficient lateral image resolution is approximately 1 μm. Hence, ToF-SIMS enables us to study the distribution of chemical substances in relation to the morphological data obtained by scanning electron microscopy or conventional light microscopy.     

Circulation of excitation waves in a model medium containing unexcitable obstacles

The 3D structure of the heart tissue of Wistar rats from different age groups has been reconstructed by light microscopy of consecutive series of semithin sections. At the histological resolution level, connective tissue segments in the myocardium of aged (18 months) animals were found, while in the myocardium of young (2 months) animals no connective tissue segments were observed. A mathematical model and the results of the 3D reconstruction were used to simulate the formation of excitation wave circulation in the myocardium. The values of conductivity and the excitability threshold, and the pulse frequency rates were found at which the disturbances of the heart rhythm resulting from the excitation wave circulation are predicted by the mathematical modeling.