Molecular determinants of voltage-dependent slow inactivation of the Ca2+ channel.

Ba(2+) current through the L-type Ca(2+) channel inactivates essentially by voltage-dependent mechanisms with fast and slow kinetics. Here we found that slow inactivation is mediated by an annular determinant composed of hydrophobic amino acids located near the cytoplasmic ends of transmembrane segments S6 of each repeat of the alpha(1C) subunit. We have determined the molecular requirements that completely obstruct slow inactivation. Critical interventions include simultaneous substitution of A752T in IIS6, V1165T in IIIS6, and I1475T in IVS6, each preventing in additive manner a considerable fraction of Ba(2+) current from inactivation. In addition, it requires the S405I mutation in segment IS6. The fractional inhibition of slow inactivation in tested mutants caused an acceleration of fast inactivation, suggesting that fast and slow inactivation mechanisms are linked. The channel lacking slow inactivation showed approximately 45% of the sustained Ba(2+) or Ca(2+) current with no indication of decay. The remaining fraction of the current was inactivated with a single-exponential decay (pi(f) approximately 10 ms), completely recovered from inactivation within 100 ms and did not exhibit Ca(2+)-dependent inactivation properties. No voltage-dependent characteristics were significantly changed, consistent with the C-type inactivation model suggesting constriction of the pore as the main mechanism possibly targeted by Ca(2+) sensors of inactivation.     

Epidemiological problems of ozena and the means for controlling this infection

Clinical, bacteriological, serological and epidemiological studies of ozena morbidity among the population of Minsk were carried out in 1970-1980. On January 1, 1981, the ozena morbidity rate among the inhabitants of Minsk was 26.72%. Ozena was found to affect mainly children and women. A wide spread of the family foci of this disease (31.68%) was revealed. The results of this study indicate that the source of K. ozaenae is a sick person who begins to excrete the bacteria in the prodromal period of the disease and may continue to excrete them for many years. The transfer of K. ozaenae occurs probably by droplet or contact infection. The droplet infection is less active in the absence of symptoms (coughing, sneezing) facilitating excretion of the infective agent into the air and in cases of the low susceptibility of persons to ozena. The main measures for controlling ozena are the timely detection and sanitation of the sources of ozena, as well as the current disinfection of the infection foci in apartments.     

Plasmid content in Yersinia pestis strains of different origin

Plasmid content in 242 Yersinia pestis strains from various natural plague foci of the U.S.S.R. and other countries was studied. Of these strains, 172 (71%) were shown to carry three plasmids described previously of about 6, 45-50 and 60 MDa, respectively. Twenty strains (8%) from different foci harboured additional cryptic plasmids, most often of about 20 mDa in size. Plasmid pPst displayed considerable constancy of its molecular mass. On the contrary, size variations of pCad (45-49 MDa) and, especially, pFra (60-190 MDa) were found. Molecular mass of these plasmids correlated with the host strain origin.     

Application of three-dimensional molecular hydrophobicity potential to the analysis of spatial organization of membrane domains in proteins: I. Hydrophobic properties of transmembrane segments of Na+, K+-ATPase

A new computer-aided molecular modeling approach based on the concept of three-dimensional (3D) molecular hydrophobicity potential has been developed to calculate the spatial organization of intramembrane domains in proteins. The method has been tested by calculating the arrangement of membrane-spanning segments in the photoreaction center ofRhodopseudomonas viridis and comparing the results obtained with those derived from the X-ray data. We have applied this computational procedure to the analysis of interhelical packing in membrane moiety of Na⁺, K⁺-ATPase. The work consists of three parts. In Part I, 3D distributions of electrostatic and molecular hydrophobicity potentials on the surfaces of transmembrane helical peptides were computed and visualized. The hydrophobic and electrostatic properties of helices are discussed from the point of view of their possible arrangement within the protein molecule. Interlocation of helical segments connected with short extramembrane loops found by means of optimization of their hydrophobic/hydrophilic contacts is considered in Part II. The most probable 3D model of packing of helical peptides in the membrane domain of Na⁺, K⁺-ATPase is discussed in the final part of the work.     

Effects of prodigiozan on post-radiation recovery of hemopoietic precursor cells and colony-stimulating factor level in long-term cultures of mouse bone marrow

Prodigiozan injected to long-term cultures of mouse bone marrow 24 h before irradiation increased CFUs and CFU-GM number and colony-stimulating factor (CSF) level by the time of delivery of ionizing radiation. As early as 60 min following irradiation of bone marrow structures with a dose of 2 Gy the number of CFUs and CFU-GM decreased considerably, and from day 3 on after irradiation the indices under study were gradually restored. By day 14 the cultures preinjected with prodigiozan exhibited higher recovery levels. The decrease in the number of precursor cells 60 min after irradiation was accompanied by a drastic increase in the CSF content of cultures; the CSF release in cultures protected with prodigiozan was more moderate than in the irradiated controls.     

Complementary addressed modification of nucleic acids with the alkylating derivatives of oligothymidylate ethyl phosphotriesters. Effect of the phosphotriester fragments' configuration

The alkylating derivatives of four individual diastereomers of the oligonucleotide [dTp(Et)]3dTpU and two individual diastereomers of oligonucleotide [dTp(Et)dTp]4 have been synthesized. The reagents with the phosphorus atoms in the enantiomeric p" configuration are shown to be more efficient in reacting with poly(dA) and with nucleic acids in Krebs-2 ascites carcinoma cells compared to those with the phosphorus atoms in the p' configuration.     

Tracing eye movements in various types of stroboscopic stimulation

Relationship between eye ability to perceive smooth motion under stroboscopic stimulation on forward motion (from which stationary positions of the object) in the plane perpendicular to the look line was found. For diagnostics and occupational selection it is suggested to carry out stimulation in several directions thus obtaining additional information about the visual system of the person under test.     

Increased number of nucleoli in the salivary gland cells of Drosophila melanogaster under conditions of rDNA dose compensation

A considerable increase in the number of nucleoli non-associted with the nucleolar organizer (NO) was shown in the salivary gland cells of Drosophila melanogaster mutants, heterozygous for a deficiency of NO. The frequency of formation of additional nucleoli increased with the raising of the chromosome polyteny level. By means of in situ hybridization we showed that in the mutant and the wildtype polytene cells the ribosomal DNA (rDNA) of these unlawful nucleoli included ribosomal gene repeats (18S+28S) with two types of insertions: ivs-I and ivs-II Such additional nucleoli can be attached to varying sites of the polytene chromosomes containing type I insertion sequences.     

Evaluation of quantitative parameters of the interaction of antibody-bearing liposomes with target antigens

The model system for the analysis of targeted liposomes is proposed--the layer of protein antigen adsorbed on polystyrene wells. Antibodies were treated with palmitoyl chloride and liposomes were produced by the cholate dialysis method in the presence of the modified protein (7 X 10(-4) mol protein/mol lipid). Affinity of antibody-bearing liposomes to the antigen on the surface of Multiwell plates was studied, and apparent dissociation constant value was estimated: KD was in the range 1.5 to 5 X 10(-9) M liposomes. Sequential transfers of liposomes in antigen-coated plates revealed that the high-affinity fraction of liposomes is adsorbed first. The bound fraction has 1.7-times-higher protein content. For effective in vivo targeting it would be necessary to have high-affinity liposomes and a high concentration of the target antigen.