The β subunit gate loop is required for RNA polymerase modification by RfaH and NusG

In all organisms, RNA polymerase (RNAP) relies on accessory factors to complete synthesis of long RNAs. These factors increase RNAP processivity by reducing pausing and termination, but their molecular mechanisms remain incompletely understood. We identify the β gate loop as an RNAP element required for antipausing activity of a bacterial virulence factor RfaH, a member of the universally conserved NusG family. Interactions with the gate loop are necessary for suppression of pausing and termination by RfaH, but are dispensable for RfaH binding to RNAP mediated by the β' clamp helices. We hypothesize that upon binding to the clamp helices and the gate loop RfaH bridges the gap across the DNA channel, stabilizing RNAP contacts with nucleic acid and disfavoring isomerization into a paused state. We show that contacts with the gate loop are also required for antipausing by NusG and propose that most NusG homologs use similar mechanisms to increase RNAP processivity.     

Ryanodine does not produce negative chronotropic effect on action potential generation in heart pacemaker cells of young frogs Rana temporaria

The goal of the present work consisted in studying role of Ca²⁺ released via ryanodine-sensitive receptors of the sarcoplasmic reticulum in modulation of frequency of action potential (AP) generation of cells of the pacemaker type of the young and adult frog heart. Ryanodine (3 μM) decreased the AP generation frequency in adult frogs by 43%, while produced no effect in young animals. Duration of the diastolic depolarization decreased more than twice as compared with control. Ryanodine (20 μM) inhibited completely the AP generation spontaneous activity in adult frogs, whereas in young animals the negative chronotropic effect was observed, on average, by 14%. The rate of diastolic depolarization did not change. Based on analysis of our obtained data and the literature data, we have concluded that in young frogs there takes place the spatial-temporal uncoupling of the sarcoplasmic reticulum and the sarcolemmal membrane. Original Russian Text ? V. F. Golovko, 2006, published in Zhurnal Evolyutsionnoi Biokhimii i Fiziologii, 2006, Vol. 42, No. 4, pp. 335–339.     

Effects of GABA antagonist-induced seizures on 3H-muscimol and 3H-diazepam binding in the rat striatum]

The binding of 3H-muscimol and 3H-diazepam to rat striatum membranes after picrotoxin- and bicuculline-induced seizures was characterized. No alteration in the maximal binding capacity (Bmax) of 3H-muscimol was observed. However, bicuculline produced a 27% decrease in Kd. Both picrotoxin and bicuculline increased the binding capacity of 3H-diazepam. Bicuculline produced a 86% increase in Kd. These results suggest that the GABA antagonists-induced seizures may modulate 3H-muscimol and 3H-diazepam binding in rat striatum.     

3H-tert-butylbicyclo-ortho-benzoate--a new ligand for chloride ion channel of GABA-A receptor]

The study was made of the binding of 35S-t-butylbicyclophosphorothionate and 3H-t-butylbicycloorthobenzoate (TBOB) which label a GABAA receptor-regulated chloride ionophores to glass fiber filters GF/B and GF/C. The rate of 3H-TBOB binding was higher. GABA displayed a biphasic effect on 3H-TBOB binding to rat brain synaptic membrane; enhancement at low concentrations of the agent and inhibition at higher ones. The results suggest that GABA may modulate the 3H-TBOB binding.     

Sampling for global epidemic models and the topology of an international airport network

Mathematical models that describe the global spread of infectious diseases such as influenza, severe acute respiratory syndrome (SARS), and tuberculosis (TB) often consider a sample of international airports as a network supporting disease spread. However, there is no consensus on how many cities should be selected or on how to select those cities. Using airport flight data that commercial airlines reported to the Official Airline Guide (OAG) in 2000, we have examined the network characteristics of network samples obtained under different selection rules. In addition, we have examined different size samples based on largest flight volume and largest metropolitan populations. We have shown that although the bias in network characteristics increases with the reduction of the sample size, a relatively small number of areas that includes the largest airports, the largest cities, the most-connected cities, and the most central cities is enough to describe the dynamics of the global spread of influenza. The analysis suggests that a relatively small number of cities (around 200 or 300 out of almost 3000) can capture enough network information to adequately describe the global spread of a disease such as influenza. Weak traffic flows between small airports can contribute to noise and mask other means of spread such as the ground transportation.     

Deltosides from Allium nutans L

Steroid glicoside which structure was elucidated by using mass-spectroscopic and NMR techniques, has been isolated using column chromatography on reverse-phase silicagel (C-18) from underground parts of Allium nutans. This compounds for the first time was isolated from the plants of genus Allium.     

Photosynthetic Pigments in Native Plants of the Taiga Zone at the European Northeast Russia

Russian Journal of Plant Physiology - The content and composition of photosynthetic pigments in 160 plant species representing the native flora of the taiga zone in European Northeast Russia were...     

Thermocline deepening boosts ecosystem metabolism: evidence from a large‐scale lake enclosure experiment simulating a summer storm

Extreme weather events can pervasively influence ecosystems. Observations in lakes indicate that severe storms in particular can have pronounced ecosystem‐scale consequences, but the underlying mechanisms have not been rigorously assessed in experiments. One major effect of storms on lakes is the redistribution of mineral resources and plankton communities as a result of abrupt thermocline deepening. We aimed at elucidating the importance of this effect by mimicking in replicated large enclosures (each 9 m in diameter, ca. 20 m deep, ca. 1300 m³ in volume) a mixing event caused by a severe natural storm that was previously observed in a deep clear‐water lake. Metabolic rates were derived from diel changes in vertical profiles of dissolved oxygen concentrations using a Bayesian modelling approach, based on high‐frequency measurements. Experimental thermocline deepening stimulated daily gross primary production (GPP) in surface waters by an average of 63% for >4 weeks even though thermal stratification re‐established within 5 days. Ecosystem respiration (ER) was tightly coupled to GPP, exceeding that in control enclosures by 53% over the same period. As GPP responded more strongly than ER, net ecosystem productivity (NEP) of the entire water column was also increased. These protracted increases in ecosystem metabolism and autotrophy were driven by a proliferation of inedible filamentous cyanobacteria released from light and nutrient limitation after they were entrained from below the thermocline into the surface water. Thus, thermocline deepening by a single severe storm can induce prolonged responses of lake ecosystem metabolism independent of other storm‐induced effects, such as inputs of terrestrial materials by increased catchment run‐off. This highlights that future shifts in frequency, severity or timing of storms are an important component of climate change, whose impacts on lake thermal structure will superimpose upon climate trends to influence algal dynamics and organic matter cycling in clear‐water lakes.     

Activities of respiratory pathways and the pool of nonstructural carbohydrates in greening leaves of spring wheat seedlings

Seedlings of spring wheat (Triticum aestivum L.) were used to study the dynamics of leaf respiration, the respiratory pathway ratio, and relation of activities of these pathways to the content of soluble carbohydrates in the leaf during greening of seedlings for 48 h under continuous photosynthetically active light (190 μmol/(m² s)). Changes in leaf respiration during de-etiolation were closely related to modulation of the alternative respiratory pathway (AP) activity. The rate of cytochrome respiratory pathway (CP) depended directly on the carbohydrate content and growth rate. These relations suggest that the substrate regulation of CP activity during greening is mediated by the energy needs for growth and is effectively regulated by the mechanism of respiratory control. The highest rates of AP were observed after a 6-h exposure of seedlings to light. The proportion of CP/AP at this stage was close to unity. The temporal pattern of AP activity during de-etiolation was independent on the content of soluble carbohydrates. Hence, in addition to substrate regulation of AP, there are other intricate mechanisms of AP involvement. Our results are in accordance to the state that the alternative respiratory pathway participates in maintaining homeostasis in phototrophic cells during development of the photosynthetic function.