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  • Springer  (70)
  • 1995-1999  (62)
  • 1965-1969  (6)
  • 1945-1949  (2)
  • 1
    ISSN: 1432-1017
    Keywords: Iron superoxide dismutase ; SOD ; X-ray absorption ; XAS ; Extended X-ray absorption fine structure ; EXAFS ; P. shermanii ; E. coli ; Metalloproteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The local structure of the iron site in ferric superoxide dismutase from P. shermanii was analyzed by X-ray absorption spectroscopy. The metal-ligand cluster of the enzyme is found to be similar to the crystallographically investigated ferric superoxide dismutase from E. coli. At pH 6.4 the enzyme is five-fold coordinated with three histidines, an aspartate and a water molecule. The average bond lengths between the metal and the histidines are about 2.10 Å, between metal and aspartate they are about 1.86 Å and between metal and water 1.96 Å. With an increase in pH a change in the coordination number from five to six is observed both in pre-edge peak and EXAFS spectra analysis. However, the bond lengths of the ligands do not change dramatically, they are conserved for the aspartate and increase slightly to 2.13 Å for the average metal - histidine distance at pH 9.3. The observation of the increase in coordination number is correlated with a decrease in enzymatic activity which occurs in the high pH range. The zinc EXAFS spectra of P. shermanii superoxide dismutase have shown that zinc can be incorporated in the active center instead of the iron.
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  • 2
    ISSN: 1432-0983
    Keywords: Key words Petite mutation ; Error-prone repair ; Paraquat ; Psoralen photo-induced DNA-damage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The original pso3-1 mutant isolate of the yeast Saccharomyces cerevisiae exhibits a pleiotropic mutagen-sensitivity phenotype that includes sensitivity to UVA-activated 3-carbethoxypsoralen, to UVC-light, to mono- and bi-functional nitrogen mustard, to paraquat, and to cadmium; on the other hand, it shows hyper-resistance (HYR) to nitrosoguanidine when compared to established wild-type strains. Also, the original pso3-1 mutant exhibits a low UVC-induced mutability and mitotic gene conversion and a high rate of spontaneous and UVC-induced petite mutations. Since the HYR to the nitrosoguanidine (MNNG) phenotype resembles that of low glutathione-containing yeast cells, the original pso3-1 mutant was crossed to a gsh1 knock-out mutant that lacks the enzyme for the first step in glutathione biosynthesis and the resulting diploid was tested for complementation. While there was none for HYR to nitrosoguanidine, and other low glutathione-related phenotypes, some other phenotypic characteristics of pso3-1, e.g. UVC sensitivity and UVC-induced mutability were restored to a wild-type level. Tetrad analysis of a diploid derived from a cross of the original haploid pso3-1 isolate with a repair-proficient, normal glutathione-containing, PSO3 GSH1 wild-type led to the separation of a leaky gsh1 mutation phenotype from that of the repair-deficient pso3-1 phenotype. Linkage studies by tetrad and random spore analyses indicated no linkage of the two genes. This shows that the low glutathione content in the original pso3-1 isolate is due to a second, additional, mutation in the GSH1 locus and is unrelated to the pso3-1 mutation. Thus, the original pso3-1 isolate is a pso3-1 gsh1 double mutant with most of the particular characteristics of the pleiotropic sensitivity phenotype contributed by either the pso3-1 or the gsh1-leaky mutant allele. The expression of a few phenotypic characteristics of pso3, however, were most pronounced in pso3-1 mutants with a low glutathione pool.
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  • 3
    ISSN: 1090-6509
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The x-ray spectra of a plasma generated by heating CO2 and Ar clusters with high-intensity femtosecond laser pulses with q las≃1018 W/cm2 are investigated. Spatially resolved x-ray spectra of a cluster plasma are obtained for the first time. Photoionization absorption is observed to influence the spectral line profiles. The recorded features of the x-ray emission spectra definitely indicate the existence of a large relative number of excited ions (≃10−2–10−3) with energies of 0.1–1 MeV in such a plasma. Possible mechanisms underlying the acceleration of ions to high energies are discussed. It is shown that the experimental results can be attributed to the influence of ponderomotive forces in standing waves generated by the reflection of laser radiation from the clusters.
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  • 4
    ISSN: 1090-6487
    Keywords: 52.50.Jm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The x-ray spectra of a plasma produced by heating CO2 clusters with intense femtosecond laser pulses with λ=0.8 μm and λ=0.4 μm are investigated. Spatially resolved x-ray spectra of the cluster plasma are obtained. The observed characteristic features of the x-ray emission spectra show unequivocally that such a plasma contains quite a large relative number of ions (≃10−2–10−3) with energies of 0.1–1 MeV. The contour of the OVIII Lyα line is found to have characteristic features that are especially conspicuous when the clusters are heated with second-harmonic pulses. These features cannot be explained by any mechanisms known to the authors.
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  • 5
    ISSN: 1435-0653
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Glycine max (L.) Merr.] root infection by [Fusarium solani (Mart.) Sacc. F. sp. glycine (Burk.)] (Rfs1), sudden death syndrome (SDS), and soybean cyst nematode (SCN; Heterodera glycines Ichinohe; Rhg4 and rhg1) were previously identified in 'Essex' × 'Forrest'. This study tests the effectiveness of those markers in selecting for disease resistance among recombinant inbred lines from 'Flyer' × 'Hartwig'. A total of 535 among 739 lines were scored by two markers, providing four genotypes. A stratified random sample of 50 lines was evaluated for SDS by F. solani root infection severity at two locations and SCN race 3 index of parasitism in the greenhouse. Selection with BLT65 identified 281 among 671 lines with the genomic region that underlies Rhg4-derived SCN resistance. Selection with Satt038 identified 230 among 613 lines containing the genomic region that underlies resistance to SDS (rfs1) and rfg1-derived SCN resistance. A total of 93 out of 535 lines had genomic regions that underlie resistance to both SDS and SCN in Essex × Forrest. Segregation of both markers was not random (P ≤ 0.05). Infection severity means for genotypes with the Hartwig allele at Satt038 (28-29%) were lower (P = 0.0001, R2 = 28%) than with the Flyer allele (31-42%); irrespective of maturity group. BLT65 was not associated with infection severity. Mean SCN index of parasitism was lower (P ≤ 0.05) only for genotypes carrying the Hartwig allele at both Satt038 and BLT65. Therefore, alleles conferring resistance to SDS and SCN in Essex × Forrest are transferable to other populations.
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  • 6
    ISSN: 1434-601X
    Keywords: PACS:29.25.Dz Neutron sources – 25.40.Ve Other reactions above meson production thresholds – 13.75.Cs Nucleon-nucleon interactions (including antinucleons, deuterons etc.)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstact: The kinetic energy spectrum and the polarization of the PSI neutron beam produced in the reaction 12C(p,n)X at 0° with 590 MeV polarized protons were investigated. A strong energy dependence of the neutron beam polarization is observed which was not expected at the time the neutron beam was built.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 178 (1996), S. 579-604 
    ISSN: 1432-1351
    Keywords: Crustacean ; Chemoreception ; Mechanoreception ; Deutocerebrum ; Motoneurons ; Projection neurons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Neurons in the brain of the spiny lobster that respond to chemical and mechanical stimulation of the antennule (antenna I) were recorded and stained intracellularly. Described here are neurons that do not arborize in the olfactory and accessory lobes of the deutocerebrum, but rather primarily target the lateral and/or the median antennular neuropils of the deutocerebrum. Some of the neurons also extend into the antennal and tegumentary neuropils of the tritocerebrum and the neuropils of the median protocerebrum. Included are antennular sensory afferents, antennular motoneurons, projection neurons descending from the central brain, projection neurons ascending from the central brain and projection neurons descending from the eyestalk ganglia. Collectively, these neurons consitutute a novel antennular sensory pathway that is parallel to and independent of the antennular olfactory pathway. The novel pathway integrates mechanosensory and non-olfactory chemosensory information in the lateral and/or the median antennular neuropils, which also serve as lower motor centers of the antennule. Division of the arthropod deutocerebrum into two, functionally distinct chemosensory pathways may reflect differences in how chemosensory information is processed that is fundamental to understanding the origin of the sense of smell.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 178 (1996), S. 605-628 
    ISSN: 1432-1351
    Keywords: Crustacean ; Olfaction ; Mechanoreception ; Local interneurons ; Projection neurons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Neurons in the olfactory deutocerebrum of the spiny lobster, Panulirus argus, were recorded intracellularly and filled with biocytin. Recorded neurons arborized in the olfactory lobe (OL), a glomerular neuropil innervated by olfactory and some presumptive mechanosensory antennular afferents. The neurons responded to chemosensory input from the lateral antennular flagellum bearing the olfactory sensilla but not the medial flagellum bearing many non-olfactory chemosensory sensilla. Many neurons received additional mechanosensory input. Thus the OL integrates specifically olfactory with mechanosensory input. OL neurons had multiglomerular arborizations restricted to one or two of the three horizontal layers of the columnar glomeruli. OL local interneurons comprised “core” neurons with tree-like neurites and terminals in the base of the glomeruli and “rim” neurons with neurites surrounding the OL and terminals in the cap/subcap. The somata of OL local interneurons lay in the medial soma cluster (100000 somata). OL projection neurons arborized in the base of the glomeruli and ascended via the olfactory glomerular tract to the lateral protocerebrum. A parallel projection pathway is constituted by projection neurons of the accessory lobe, a glomerular neuropil without afferent innervation but intimate links to the OL. The projection neuron somata constituted the lateral soma cluster (200000 somata).
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 182 (1998), S. 677-686 
    ISSN: 1432-1351
    Keywords: Key words Electrophysiology ; Brain ; Insect ; Histamine ; GABA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Whole-cell patch-clamp recordings were obtained from 116 freshly dissociated neuronal somata from the optic lobe of adult locusts (Schistocerca gregaria). Prerequisites were a papain treatment and the directed transfer of somata to the recording chamber by dabbing. Of the recorded somata, 65 were from lamina and 51 from other optic lobe neurons. All somata supported voltage-activated outward currents and some (24% of optic lobe, 3% of lamina neurons) also fast inward currents. Most lamina neurons supported an outward current that activated (V 1/2=−8.5 mV) and inactivated rapidly and a sustained outward current. Some lamina and most optic lobe neurons expressed only a sustained outward current (V 1/2=−9.4 mV). GABA and histamine elicited inward currents at negative holding potentials. Most optic lobe (95%) but only 18% of lamina neurons showed a γ-aminobutyric acid (GABA) current, whereas a similar percentage of optic lobe (50%) and lamina neurons (67%) expressed a histamine current. Both currents reversed near the chloride equilibrium potential, were reversibly reduced by picrotoxin, and did not show rundown. Thus, they likely represent chloride currents mediated by ionotropic receptors. Our data indicate that the lamina neurons recorded mainly represent monopolar cells postsynaptic to histaminergic photoreceptors. The optic lobe neurons, on which GABA and histamine apparently act as inhibitory neurotransmitters, are more heterogeneous.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Contributions to mineralogy and petrology 130 (1998), S. 162-175 
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The fluid-absent reaction 12 zoisite = 3 lawsonite + 7 grossular + 8 kyanite + 1 coesite was experimentally reversed in the model system CaO-Al2O3-SiO2-H2O (CASH) using a multi-anvil apparatus. The upper pressure stability limit for zoisite was found to extend to 5.0 GPa at 700 °C and to 6.6 GPa at 950 °C. Additional experiments both in the H2O-SiO2-saturated and in the H2O-Al2O3-saturated portions of CASH provide further constraints on high pressure phase relationships of lawsonite, zoisite, grossular, kyanite, coesite, and an aqueous fluid. Consistency of the present experiments with the H2O-saturated breakdown of lawsonite is demonstrated by thermodynamic analysis using linear programming techniques. Two sets of data consistent with databases of Berman (1988) and Holland and Powell (1990) were retrieved combining experimental phase relationships, calorimetric constraints, and recently measured elastic properties of solid phases. The best fits result in G f ,1,298 ∘,zoisite=−6,499,400 J and S 1,298 ∘,zoisite=302 J/K, and G f ,1,298 ∘,lawsonite=−4,514,600 J and S 1,298 ∘,lawsonite=220 J/K for the dataset of Holland and Powell, and G f ,1,298 ∘,zoisite=−6,492,120 J and S 1,298 ∘,zoisite=304 J/K, and G f ,1,298 ∘,lawsonite=−4,513,000 J and S 1,298 ∘,lawsonite= 218 J/K for the dataset of Berman. Examples of the usage of zoisite as a geohygrometer and as a geobarometer in rocks metamorphosed at eclogite facies conditions are worked, profiting from the thermodynamic properties retrieved here.
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