Possibility to study cell membrane topography using tritium planigraphy

The method of tritium planigraphy was adopted for the investigation of intact cells. Conditions for the incorporation of thermally activated tritium atoms in the erythrocytes are described. The accessibility of erythrocytes hemoglobin for tritium was compared to that of free hemoglobin. By comparing specific radioactivities of amino acids it was shown that the incorporation of the label into free hemoglobin was over 100 times higher than into that in erythrocytes. The cell membrane was highly tritiated. Thus the plasma membrane protects the cell inner regions from penetration of the hot tritium atoms. Tritium planigraphy can be used for studying the cell surface topography.     

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).     

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     

Determination of the accessible surface of lysozyme and human serum albumin molecules by the total tritium labeling method

Amino acids composing an accessible surface of lysozyme and human serum albumin (HSA) globules were determined by the total tritium labelling method. A good correlation between our data on the distribution of the tritium label for the lysozyme molecule and X-ray data on the tertiary structure for this macromolecule was received. Lysozyme was used as a standard for determining the accessible surface of the globule albumin. It was shown that the accessible surface of the albumin globule is substantially more hydrophobic (average accessible surface area of hydrophobic amino acids is 130 A2 in HSA and 20 A2 in lysozyme) than in lysozyme. The HSA molecule is characterized by high values of: the accessible surface area, the ratio of extended area to the folded one, and the surface roughness index. These data indicate that the HSA molecule is less compactly packed than lysozyme.     

The use of thermally activated tritium atoms for structural-biological investigations: the topography of the TMV protein-accessible surface of the virus

Thermally activated tritium atoms were used for studying the topography of the TMV protein-accessible surface of the virus. The accessibility profile of amino acid residues in a protein polypeptide chain was determined from data on the intramolecular distribution of a tritium label in the TMV protein. It was shown that tryptic peptides T3, T4, T12, the N-terminal region of peptide T1 and the proximal tryptic peptide T8 (located 20 to 25 A (1 A = 0.1 nm) from the viral axis) are accessible to tritium labelling. The fact of tritiation of the viral RNA was detected as well. This evidence was compared with the high-resolution X-ray analysis data for the TMV. A model is suggested to explain the exposure of the buried sites of the virus to thermally activated tritium atoms. The possibilities and limitations of this method in studying the surface topography of proteins in supramolecular systems as well as for location of protein antigenic regions are discussed.     

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.     

Antiviral potential of Bulgarian medicinal plants

Medicinal plants have been widely used to treat a variety of infectious and non-infectious diseases. Bulgarian flora includes 4,300 plant species, over 500 of which are rare or endemic to the country or the Balkan region. The aim of the present work is to summarize comprehensively the investigations on the antiviral activity of Bulgarian medicinal plants from the past three decades. The effect of different extracts derived from in vitro propagated plants has been examined as well. The phytochemical composition and its influence on specific steps of the viral life cycle have been discussed in this paper. The review includes the following families: Amaryllidaceae, Fabaceae, Geraniaceae, Lamiaceae, Onagraceae, Ranunculaceae, Rosaceae, Scrophulariaceae and Rhodophyta. Special attention has been paid to viruses as important human pathogens.