Cold sensitivity of thermophilic and mesophilic RNA polymerases

RNA polymerase from mesophilic Deinococcus radiodurans displays the same cold sensitivity of promoter opening as RNA polymerase from the closely related thermophilic Thermus aquaticus. This suggests that, contrary to the accepted view, cold sensitivity of promoter opening by thermophilic RNA polymerases may not be a consequence of their thermostability.     

Active transport of organic acids in the proximal tubules of the surviving rat kidney normally and under various influences. II. The effect of exogenous cyclic 3',5'-AMP and of substances that alter its intracellular concentration]

Exogenous cyclic 3',5'-AMP (cAMP) and substances known to increase the intracellular concentration of this nucleotide (isoproterenol, theophylline, noradrenaline, lactate) were shown to inhibit the transport of fluorescein (a weak organic acid) into the rat renal proximal tubules at 20 degrees C. Carbacholine decreasing intracellular cAMP concentration stimulated the transport. Propranolol, a beta-adrenergic blockator, diminished significantly the inhibitory effect of noradrenaline on the transport. Lactate and carbacholine when added simultaneously, neutralize their action. The inhibitory action of intracellular cAMP on the transport is supposed to be a result of the diminition of a pool of endogenous weak organic acids which may take part in the exchange of diffusion with the marker anion across basal plasma membrane.     

Anti-rabies immunoglobulin preparation based on F(ab')2 fragments

Technology of manufacturing of new anti-rabies immunoglobulin preparation based on F(ab')2 fragments has been developed. This preparation is characterized by low reactogenicity, increased virus-neutralizing activity and stability.     

Monoclonal antibodies inhibiting RNA polymerase from Escherichia coli

Monoclonal hybridoma antibodies directed against RNA polymerase from E. coli have been obtained. Only a few have been found to inhibit the enzyme activity. Antibodies produced by two clones, PYN-1 and PYN-2, inhibit RNA polymerase at the stage of RNA chain elongation. The PYN-1 antibodies react with the beta'-subunit of the enzyme. The PYN-2 antibodies react with the beta-subunit and with its 130 kDa amber fragment.     

Transport of monovalent thallium across the membrane of oocyte of the lamprey <Emphasis Type="Italic">Lampetra fluviatilis</Emphasis>

Mechanisms of transport of monovalent thallium across the membrane of oocyte of the lamprey Lampetra fluviatilis were studied by using ²⁰⁴Tl. The Tl⁺ transport in lamprey oocytes has been shown to be realized by at least two pathways: through Na/K-pump and by mechanisms of Na,K,Cl-cotransport. In the standard Ringer solution (mM): 4 KCl, 140 NaCl, 0.5 CaCl₂, 5 glucose, 10 Tris-HCl-in the presence of ouabain, the coefficient of the ²⁰⁴Tl stationary distribution (cell/medium) was within the range of 2.3–2.5, while the time necessary to reach its 50% value amounted to 40–45 min at 20°C. In potassium-free media, transport of ²⁰⁴Tl via Na/K-pump was described by simple kinetics with saturation and was characterized by the value V _max = 520 pmol/(cell h) and K _M = 0.3 mM. In the presence of 4 mM K⁺ and 0.1 mM/1 Tl⁺, the ouabain-sensitive Tl⁺ flux decreased to 75 pmol/(cell h). At activation of the mechanism of Na,K,Cl-cotransport by the outer Na⁺ (in Na-NMDG media of different composition) the total influx of Tl⁺ reached 193 ± 20 pmol/(cell h), while the bumetanide-sensitive component—119 ± 12 pmol/(cell h) with K _M for Na⁺ about 20 mM. In the incubation media with variable concentration of chloride ions (replacement of Cl⁻ by NO₃) the total Tl⁺ flux reached 220 ± 21, while via the mechanisms of Na,K,Cl-cotransport—87 ± 8 pmol/(cell h). Under our experimental conditions, mechanisms of active transport and Na,K,Cl-cotransport accounted for 94% of the Tl⁺ influx. The potassium channels that usually are permeable also to monovalent thallium ions were not revealed.     

Intercontinental spread of promiscuous mercury-resistance transposons in environmental bacteria

We demonstrate that horizontal spread of mer operons similar to worldwide spread of antibiotic-resistance genes in medically important bacteria occurred in bacteria found in ores, soils and waters. The spread was mediated by different transposons and plasmids. Some of the spreading transposons were damaged in different ways but this did not prevent their further spread. Certain transposons are mosaics composed of segments belonging to distinct sequence types. These mosaics arose as a result of homologous and site-specific recombination. Our data suggest that the mercury-resistance operons of Gram-negative environmental bacteria can be considered as a worldwide population composed of a relatively small number of distinct recombining clones shared, at least partially, by environmental and clinical bacteria.