Changes in the form and ultrastructure of the smooth-muscle cells in the human aorta in prenatal ontogeny]

The shape of smooth muscle cells (SMC) was analysed using the phase contrast microscopy of cell suspensions obtained by alcohol-alkali dissociation, as well as the semithin sections prepared in perpendicular planes. The phenotype of SMC was analysed using transmission electron microscopy. The shape of SMC changes from preferentially round to preferentially spindle-like and stellate one during development. The differentiation of SMC is accompanied with the increase in the contractile apparatus content and in the decrease in the content of synthetic organelles.     

Rational antimicrobial pharmacotherapy of secondary infections in patients with pulmonary tuberculosis]

The results of 3-year (2002-2004) local microbiological monitoring of secondary infections due to opportunistic microflora that complicated the treatment of the main disease in patients of a regional (Moscow) tuberculosis hospital are presented. The monitoring revealed the leading microorganisms, the etiological agents of the secondary lower respiratory tract infection in the patients with pulmonary tuberculosis. The level of their resistance to the up-to-date antimicrobials was determined. Recommendations for optimization of antibacterial therapy of patients with pulmonary tuberculosis complicated by secondary lower respiratory tract infection due to opportunistic microorganisms were developed and validated.     

An essential step of kinetochore formation controlled by the SNARE protein Snap29

The kinetochore is an essential structure that mediates accurate chromosome segregation in mitosis and meiosis. While many of the kinetochore components have been identified, the mechanisms of kinetochore assembly remain elusive. Here, we identify a novel role for Snap29, an unconventional SNARE, in promoting kinetochore assembly during mitosis in Drosophila and human cells. Snap29 localizes to the outer kinetochore and prevents chromosome mis‐segregation and the formation of cells with fragmented nuclei. Snap29 promotes accurate chromosome segregation by mediating the recruitment of Knl1 at the kinetochore and ensuring stable microtubule attachments. Correct Knl1 localization to kinetochore requires human or Drosophila Snap29, and is prevented by a Snap29 point mutant that blocks Snap29 release from SNARE fusion complexes. Such mutant causes ectopic Knl1 recruitment to trafficking compartments. We propose that part of the outer kinetochore is functionally similar to membrane fusion interfaces.     

Study of the interaction between cytochrome c and cytochrome oxidase by tritium planigraphy

Treatment of molecular crystals of the bovine cytochrome oxidase and the cytochrome oxidase-cytochrome c complex with thermally activated tritium leads to highly labelled cytochrome oxidase preparations. HPLC separation of its subunits and measurements of radioactivity of each polypeptide allow to determine the shielding of cytochrome oxidase surface sites by cytochrome c in the complex.     

Channels produced by spider venoms in bilayer lipid membrane: mechanisms of ion transport and toxic action

The selectivity of ion channels produced by latrotoxin obtained from a black widow spider venom and by venom from the spider Steatoda paykulliana in bilayer phospholipid membrane was studied. Experimental current-voltage curves of these channels were used for the estimation of parameters of a two barrier model of their energy profiles. Selectivities of both types of channels are similar. Alkaline earth cations are permeable, the permeability increasing in the order Mg2+ less than Ca2+ less than Sr2+ less than Ba2+. In contrast transition metal cations block the channel, their efficiency decreases in the order: Cd2+ greater than or equal to Ni2+ greater than Zn2+ greater than Co2+ greater than Mn2+ (Steatoda paykulliana spider venom) and Cd2+ greater than Co2+ greater than Ni2+ greater than Zn2+ greater than Mn2+ (latrotoxin). Amplitudes of current carried by corresponding ions are mainly determined by the depth of the potential well for this ion, i.e., by its affinity to the cation binding site in the channel. The channels are also permeable to monovalent cations but they do not bind them. Selectivity for monovalent cations depends on Ca2+ concentration at the cis-side of membrane in the micromolar range. However, the addition of Ca2+ to the trans-side up to 10 mM does not affect currents carried by monovalent ions. It is suggested that venom-induced calcium channels have two conformational states with different selectivities which interconvert upon binding one calcium ion. Possible general schemes for the organisation of calcium channels in excitable membranes are also discussed. Finally, using a mathematical model of synaptic transmission, possible mechanisms of toxic action of spider venoms are considered.     

Protein from beef heart mitochondria inducing the potassium channel conductivity of bilayer lipid membrane

Protein (M. m. 60 000) inducing selective potassium conductance of bilayer lipid membranes (BLM) was isolated from mitochondria and homogenate of the beef heart. This protein was obtained by means of alcohol (ethanol) extraction and was purified by gel-filtration on Sephadex G-15 and G-50 followed by electrophoresis in the 10% polyacrylamide gel. 6-10 g/ml of the protein produced the conductivity channels on BLM with amplitude divisible of 24 +/- 4 pmho. The channels of 175 +/- 7 pmho were the most typical ones. The modification of BLM by K+-transport in protein under the conditions of potassium gradient resulted in the appearance of the membrane potential close to the theoretical Nernst potential.     

Mapping DNA by stochastic relaxation: schedule for optimal annealing.

The analysis of the various cooling schedules for the simulated annealing algorithm is made towards the restriction map construction. Algorithm behaviour under control of three different cost functions is considered and the discrete cost function is found to handle successfully experimental data with realistic error sizes. A program using this function has been derived from the algorithm to construct linear and circular DNA maps.     

Influence of caffeine on processes of regulation of the intracellular Ca2+ concentration in isolated neurons of the edible snail

Changes in the intracellular concentration of Ca²⁺ ([Ca²⁺]_in) that occur during prolonged depolarization of the plasma membrane were studied in isolated neurons of the edible snailHelix pomatia, using the calcium-sensitive probe Fura-2. The dependence of the amplitude of the calcium response on the value of the depolarization in the presence of 5 mM caffeine, in contrast to that observed in a normal solution, practically disappeared. This fact indicates that caffeine promotes calcium-dependent release of Ca²⁺ from the intracellular depots, which is the determining factor in the increase in [Ca²⁺]_in during depolarization. Processes of reduction of [Ca²⁺]_in to the steady-state levels were described by one exponential function, and in the presence of caffeine they occurred twice as rapidly as in the normal solution. Such an acceleration of the kinetics of the relaxation of [Ca²⁺]_in is evidently associated with an increase in the efficiency of the work of the calcium pump of the intracellular calcium depots, which might lead to a decrease in the steady-state of level of [Ca²⁺]_in even below the level observed for the normal extracellular solution.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 23, No. 1, pp. 66–73, January–February, 1991.     

Method of selecting mutations for the plasmid genes of streptomycin resistance in Escherichia coli K-12 cells

Evidence is presented that streptomycin-dependent mutants of Escherichia coli K-12 are incompatible with the functional activity of streptomycin-resistance genes coding for aminoglycoside adenilyl transferase. On the basis of this phenomenon, a method for selection of streptomycin-sensitive mutations in these genes is proposed, and the possibility of the direct selection of hybrid DNA molecules carrying inserts inactivating streptomycin-resistance genes is discussed. The effectiveness of the method for isolation of streptomycin-sensitive R100.1 plasmid derivatives was demonstrated.