Osmotic regulation of the sodium pump in rat brain synaptosomes]

Effect of medium osmolarity on 3H-ouabain binding and the rate of ouabain-sensitive 86Rb+ transport in the rat brain synaptosomes was studied. A decrease in tonicity to 230 mOsm increases both parameters indicating the activation of the sodium pump upon synaptosome swelling. The effect is retained in the absence of inside-oriented Na+ gradient, i. e. a rise in Na(in) is not responsible for hypoosmotic activation. Colchicine (5mM) decreased and cytochalasin B (40 microM) increased the ouabain binding. In the presence of cytochalasin B the inhibition of binding observed under hypotonic conditions was shifted to higher osmolarity values. It is suggested that volume regulation of the sodium pump is controlled by the cytoskeleton elements.     

Structural-membrane regulation of intercellular contacts of low-molecular weight peptides]

It has been shown by microelectrode techniques and microcytofluorometry that fragments of the substance P and L-vasopressin--low molecular physiologically active peptides of wide regulatory action--bind to the receptors on the surface of plasma membranes outside the region of high permeable gap contact in unimolar concentrations and cause an increase in the rate of intracellular diffusion exchange of inorganic ions and fluorescein molecules in the salivary gland cells of Drosophila larva. The growth of intracellular contact permeability induced by low peptide concentrations is blocked by carbodiimide--a reagent cross-linking the membrane proteins. On the basis of the previous data it is suggested that the functions of intracellular contacts are regulated by the distant action mechanism involving the generalized structural rearrangements of plasma membranes.     

Sites responsible for stimulation of brain Na,K-ATPase by serotonin

Serotonin (10(-6)-10(-3) M) stimulates Na,K-ATPase in the rat brain cortex homogenate with a maximal effect at 10(-4) M. Deseril (10(-5) M), antagonist of serotonin receptors, removes the stimulating effect. Deseril has no influence on noradrenaline-induced ATPase activation; the alpha-adrenergic blocker phentolamine does not affect serotonin activation. The effects of the two transmitters are additive. It is assumed that the mediators interact with different membrane sites, serotonin activation being initiated via the serotonin receptors.     

Simulation of the distribution of spinocerebellar ataxia type 1 in Yakut populations: Model parameters and results of simulation

Demographic and clinical genetic parameters used for simulation modeling of the prevalence of spinocerebellar ataxia type 1 (SCA1) in Yakut populations are described. Demographic parameters of simulated populations and the clinical genetic characteristics of carriers of the SCA1 mutant allele in them have been compared with actual data on Abyisky and Ust-Aldansky uluses of the Republic of Sakha (Yakutia). The results of a series of simulation experiments (without migration or spontaneous mutagenesis) agree with the conclusion that the high prevalence of rate of spinocerebellar ataxia type 1 in Yakut populations may be maintained because of their specific demographic structure. Prediction of the disease prevalence has shown that it will take about 1290 years for natural selection to eliminate the mutation from the population. If medical genetic counseling (MGC) is offered to 1% of the carriers of the mutation, this period will be reduced to 200 years.     

Protein damage after treatment with ozone of protoplasts and isolated E. coli membranes

The features of ozone-induced damage of E. coli plasma membrane proteins are investigated. A conclusion is made that protein fluorescence quenching is connected with modification of amino acid residues in the vicinity of tryptophane residues. Such modification may be a consequence of reaction with either ozone itself or products of its interaction with membrane lipids and/or proteins. The suggestion of Goldstein and McDonagh that ozone has a predilection for more hydrophilical membrane domains is confirmed. The data obtained are in agreement with a supposition about the leading role of proteins in deleterious action of ozone on cells.     

Effect of the general anesthetic ketamine on the potassium permeability of plasma membranes of brain synaptosomes

General anesthetic ketamine (1 mM) decreases relative sodium permeability (PNa+/PK+) of synaptosomes measured by transmembrane potential--external potassium concentration curves. Since tetrodotoxin (10(-7) M) does not affect the value PNa+/PK+ it is concluded that potassium permeability of the membrane increases in the presence of ketamine.     

Results of the long laboratory storage of Streptoverticillium hachijoense (Jamaguchi) Baldacci, the producer of trichomycin]

Viability, morphologo-cultural features and antibiotic properties of Sv. hachijoense, strain LIA-0052 stored for 10 years in a dry state and in the state of a resting culture were studied. Spores and mycelium of 2-week strains most stable to some chemical and physical factors were used for drying. It was found that viability of strain LIA-0052 was maintained for a longer period of time after lyophilization, in garden soil and agar culture under a layer of mineral oil. By the end of the observation period the viability of the soil culture decreased and the morphologo-cultural properties were stabilized. When the strain was cultivated on media with sucrose, the level of its antibiotic activity increased.