Study of the dynamics of the electrode plasma in a high-current magnetically insulated transmission line

A series of experiments was carried out in the S-300 facility (3 MA, 0.15 Θ, 100 ns) to study the behavior of a section of a magnetically insulated transmission line (MITL) at current densities of up to 500 MA/cm² and linear current densities of up to 6 MA/cm (i.e., at parameters close to those expected in a fast Z-pinch fusion reactor projected in Sandia National Laboratories). The surface explosion of the ohmically heated MITL electrode is accompanied by the formation of a plasma layer on its surface. This can deteriorate of the transmission properties of the line because the vacuum gap is short-circuited by the plasma produced. The parameters of the electrode plasma and its effect on the MITL transmission properties were investigated experimentally. Possible consequences of the above effects are evaluated, and MHD simulations of the electrode explosion and the subsequent spread of the plasma layer are performed. It is shown that the time during which an MITL segment preserves its transmission properties conforms to the requirements of the conceptual fusion reactor.     

Identification of histone demethylases in Saccharomyces cerevisiae

Based on the prediction that histone lysine demethylases may contain the JmjC domain, we examined the methylation patterns of five knock-out strains (ecm5Delta, gis1Delta, rph1Delta, jhd1Delta, and jhd2Delta (yjr119cDelta)) of Saccharomyces cerevisiae. Mass spectrometry (MS) analyses of histone H3 showed increased modifications in all mutants except ecm5Delta. High-resolution MS was used to unequivocally differentiate trimethylation from acetylation in various tryptic fragments. The relative abundance of specific fragments indicated that histones K36me3 and K4me3 accumulate in rph1Delta and jhd2Delta strains, respectively, whereas both histone K36me2 and K36me accumulate in gis1Delta and jhd1Delta strains. Analyses performed with strains overexpressing the JmjC proteins yielded changes in methylation patterns that were the reverse of those obtained in the complementary knock-out strains. In vitro enzymatic assays confirmed that the JmjC domain of Rph1 specifically demethylates K36me3 primarily and K36me2 secondarily. Overexpression of RPH1 generated a growth defect in response to UV irradiation. The demethylase activity of Rph1 is responsible for the phenotype. Collectively, in addition to Jhd1, our results identified three novel JmjC domain-containing histone demethylases and their sites of action in budding yeast S. cerevisiae. Furthermore, the methodology described here will be useful for identifying histone demethylases and their target sites in other organisms.     

Differences between cellular mechanisms of ATP-and noradrenaline-induced inhibition of visceral smooth muscles under conditions of selective and combined activation of M<Subscript>2</Subscript> or M<Subscript>3</Subscript> cholinoreceptors

Our studies of the role of phospholipase C in inhibitory synaptic action upon visceral smooth muscles demonstrated that, under conditions of carbachol (CCh)-induced pre-activation of cholinoreceptors, ATP-or noradrenaline (NA)-evoked relaxation of these muscles is mediated by the phospholipase C-independent pathway, while the phospholipase C-dependent pathway does not manifest itself as a mechanism that determines the inhibitory effect of the above transmitters. Under conditions of pre-activation of muscarinic cholinoreceptors, ATP-and NA-induced relaxation is continued due to activation of inositol trisphosphate (InsP₃)-sensitive receptors despite the fact that the pathway of inhibition is phospholipase C-independent. This is confirmed by complete depression of the inhibitory effects of ATP and NA against the background of CCh-induced contraction after pre-incubation of the studied preparations together with 100 μM 2-APB, a blocker of InsP₃ receptors. Selective blockings of either M₂ or M₃ cholinoreceptors are accompanied by a complete loss of the ability of the above blocker of InsP₃ receptors (2-APB) to suppress ATP-and NA-induced contraction of smooth muscles in the state of CCh-induced contraction. It can be hypothesized that, under conditions of selective pre-activation of M₂ or M₃ cholinoreceptors, the mechanisms of intracellular signalling mediating the inhibition events are modified. The InsP₃-dependent pathway that determines both adrenergic and purinergic inhibition of smooth muscles is switched off, and the inhibitory action of neurotransmitters is realized under such conditions through the InsP₃-independent pathway. Therefore, in our study we first found differences between cellular mechanisms underlying ATP-and NA-induced inhibition of smooth muscles under conditions of selective activation of either M₂ or M₃ cholinoreceptors and the mechanisms underlying the relaxing action of inhibitory neurotransmitters under conditions of combined synergistic activation of cholinoreceptors of both the above-mentioned subtypes. Neirofiziologiya/Neurophysiology, Vol. 39, No. 1, pp. 22–31, January–February, 2007.     

New data on the taxonomy,distribution, and ecology of the weevil genus <Emphasis Type="Italic">Otiorhynchus</Emphasis> germar (Coleoptera,Curculionidae)

The subgenus Pocusogetus Rtt. of the genus Otiorhynchus Germ. is revised. The subgenus includes O. rosti Strl., O. shapovalovi Davidian et Yunakov, O. obsulcatus Strl., O. fischtensis Rtt., and O. gusakovi sp. n. closely related to O. fischtensis (both from Mt. Fisht, the Western Caucasus). O. fischtensis is transferred from the subgenus Vicoranius Rtt., its lectotype is designated. A key to species of Pocusogetus is given. The systematic position of the subgenera Pocusogetus and Vicoranius in the genus Otiorhynchus is discussed. New data on the geographical distribution and ecology of the little-known species of the subgenera Obvoderus Rtt., Pseudoprovadilus Magnano, and Clypeorhynchus Yunakov et Arzanov are given. Some features of ecological differentiation between Otiorhynchus species in the alpine and subalpine zones of the Caucasus are discussed.     

Characterization of novel microsatellite loci in rare minnow (<Emphasis Type="Italic">Gobiocypris rarus</Emphasis>) and amplification in closely related species in Gobioninae

Rare minnow (Gobiocypris rarus) is an endangered small fish endemic to upper reach of the Yangtze River. From a (GT)n enriched genomic library, 32 microsatellites were isolated and characterized. Nineteen of these loci were polymorphic in a test population with alleles ranging from 2–7, and observed and expected heterozygosities from zero to 0.8438, and 0.2679 to 0.8264, respectively. In the cross-species amplifications, 13 out of 19 polymorphic loci were found to be also polymorphic in at least one of the 7 closely related species of the subfamily Gobioninae. These polymorphic microsatellite loci should provide sufficient level of genetic diversity to evaluate the fine-scale population structure in rare minnow and its closely related species for the conservation purpose.     

An NMR study of the conformational mobility of steroid estrogen 7α-methyl-8α analogues

All the signals in the ¹H and ¹³C NMR spectra of some analogues of 7α-methyl-8α-and 6-oxa-8α-steroid estrogens were completely assigned. Considering the values of nuclear Overhauser effect and vicinal coupling constants, these steroids were shown to exhibit a fast, on the NMR time scale, conformational equilibrium arising due to the inversion of ring B. The conformer populations were obtained from a comparison of the experimental and theoretical values of the dihedral angles and the interproton distances. This conformational equilibrium was shown to depend on the nature of atom in position 6: for the 7α-methyl-6-oxa-8α analogues of the steroid estrogens, the population of the conformer with the pseudoaxial orientation of the 7α-methyl group was observed to be decreased compared with the 7α-methyl-8α analogue.     

The DNA-dependent protein kinase catalytic subunit is phosphorylated in vivo on threonine 3950, a highly conserved amino acid in the protein kinase domain

The protein kinase activity of the DNA-dependent protein kinase (DNA-PK) is required for the repair of DNA double-strand breaks (DSBs) via the process of nonhomologous end joining (NHEJ). However, to date, the only target shown to be functionally relevant for the enzymatic role of DNA-PK in NHEJ is the large catalytic subunit DNA-PKcs itself. In vitro, autophosphorylation of DNA-PKcs induces kinase inactivation and dissociation of DNA-PKcs from the DNA end-binding component Ku70/Ku80. Phosphorylation within the two previously identified clusters of phosphorylation sites does not mediate inactivation of the assembled complex and only partially regulates kinase disassembly, suggesting that additional autophosphorylation sites may be important for DNA-PK function. Here, we show that DNA-PKcs contains a highly conserved amino acid (threonine 3950) in a region similar to the activation loop or t-loop found in the protein kinase domain of members of the typical eukaryotic protein kinase family. We demonstrate that threonine 3950 is an in vitro autophosphorylation site and that this residue, as well as other previously identified sites in the ABCDE cluster, is phosphorylated in vivo in irradiated cells. Moreover, we show that mutation of threonine 3950 to the phosphomimic aspartic acid abrogates V(D)J recombination and leads to radiation sensitivity. Together, these data suggest that threonine 3950 is a functionally important, DNA damage-inducible phosphorylation site and that phosphorylation of this site regulates the activity of DNA-PKcs.