Model of Active Transport of Ions in Archaea Cells

A mathematical model of the active transport of main ions in cells of archaebacteria has been constructed. A set of equations has been developed and solved for ion fluxes through the bacterium membrane. The model is based on the principle “one ion—one transport system.” Considering experimental data, the major transport mechanism was determined for each ion and the balance equation was written on the basis of this mechanism in the stationary state. This allowed calculating values of the membrane potential and intracellular concentrations of the ions independently. The calculated values of the intracellular concentrations and resting potential are in qualitative agreement with the corresponding experimental values for cells of extremely halophilic archaea.     

Requirements on Models and Models of Active Transport of Ions in Biomembranes

Requirements on models of the active transport of ions in biomembranes have been formulated. The basic requirements include an explicit dependence of the resting potential and intracellular concentrations of ions on the difference of ATP-ADP chemical potentials, a consideration of the reversibility of the ionic pump operation, a correlation between theoretical and experimental data on the resting potential and intracellular concentrations of ions for different types of cells, the pump efficiency approaching 100%, and a tendency of the resting potential to the Donnan potential if the active transport is blocked. A model satisfying the aforementioned requirements has been proposed by the authors as an example.     

Energetic aspects of CO oxidation in desulfovibrio desulfuricans

In cell suspension of Desulfovibrio desulfuricans B-1388, oxidation of CO as the only energy source is associated with reduction of SO42-. After a 2-h incubation of cells in 8% CO, 81% of the gas is converted. Oxidation of 1 mole CO results in formation of 0.23 mole H2S. Intracellular ATP content increases from 2.5 (control) to 8.3 nmoles/mg (during CO conversion). Dinitrophenol inhibits sulfate reduction and CO oxidation. CO dehydrogenase was detected in cytoplasmic and membrane cell fractions (59 and 34%, respectively).     

Early Stages of the Evolution of Life: a Cybernetic Approach

Early stages of the evolution of life are considered in terms of control theory. A model is proposed for the transport of substances in a protocell possessing the property of robustness with regard to changes in the environmental concentration of a substance.     

Feedback equilibrium control during human standing

Equilibrium maintenance during standing in humans was investigated with a 3-joint (ankle, knee and hip) sagittal model of body movement. The experimental paradigm consisted of sudden perturbations of humans in quiet stance by backward displacements of the support platform. Data analysis was performed using eigenvectors of motion equation. The results supported three conclusions. First, independent feedback control of movements along eigenvectors (eigenmovements) can adequately describe human postural responses to stance perturbations. This conclusion is consistent with previous observations (Alexandrov et al., 2001b) that these same eigenmovements are also independently controlled in a feed-forward manner during voluntary upper-trunk bending. Second, independent feedback control of each eigenmovement is sufficient to provide its stability. Third, the feedback loop in each eigenmovement can be modeled as a linear visco-elastic spring with delay. Visco-elastic parameters and time-delay values result from the combined contribution of passive visco-elastic mechanisms and sensory systems of different modalities     

Nonequilibrium Statistical Model of Active Transport of Ions and ATP Production in Mitochondria

A model of the active transport of ions through internal membranes of mitochondria is proposed. If concentrations of ions in a cell are known, this model allows calculating concentrations of all main ions (H⁺, Ca⁺², K⁺, Mg²⁺, Na⁺, Cl⁻) in the mitochondrion matrix and the resting potential across the membrane. The theoretical values satisfactorily agree with available experimental data on the concentrations and the potentials, including different operating regimes of the adenosine triphosphate (ATP) synthetase (the main regime, short circuiting or ATP synthetase blocking). The active transport of Mg²⁺ ions in exchange for protons was assumed. In accordance with the model, the ATP synthetase operation is possible only if the stoichiometric coefficient of protons is 3.     

Spatiotemporal patterns of macrophage migration inhibitory factor (Mif) expression in the mouse placenta

Background  

Macrophage migration inhibitory factor (MIF) has special pro-inflammatory roles, affecting the functions of macrophages and lymphocytes and counter-regulating the effects of glucocorticoids on the immune response. The conspicuous expression of MIF during human implantation and early embryonic development also suggests this factor acts in reproductive functions. The overall goal of this study was to evaluate Mif expression by trophoblast and embryo placental cells during mouse pregnancy.     

Biological complexity,quantum coherent states and the problem of efficient transmission of information inside a cell

The intracellular channel of information transmission was analyzed from the point of view of complexity. The most important steps in the transfer of information within a cell are the folding, transport and recognition of proteins. It was shown that the large number of conformational degrees of freedom that proteins possess can paradoxically lead to an information channel with an exponentially small capacity. To resolve this paradox, a model, which assumes a quantum collective behavior of biologically important molecules, was proposed. Experiments to test the quantum nature of the intracellular transfer of information were also proposed.