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  • 1995-1999  (40)
  • 1955-1959  (1)
  • 1
    Electronic Resource
    Electronic Resource
    2-Phenyl-4-hydroxyphthalazin-1-one: A Benzoannelated Derivative of Maleic Hydrazide (1998)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 671-676 
    Details
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The monoclinic crystals (space group P21/a, Z = 8) of 2-phenyl-4-hydroxyphthalazin-1-one, C14H10N2O2, have two independent molecules (A and B) in the asymmetric unit. Both occur as the lactim–lactam (hydroxy–one) structure, which is also found in the parent molecule maleic hydrazide (both triclinic and monoclinic polymorphs), dichloromaleic hydrazide and luminol (3-aminophthalhydrazide). The molecular arrangement is based on strings of alternating A and B molecules linked by hydroxyl...carbonyl hydrogen bonds, with only van der Waals interactions between adjacent strings. Comparison is made of the measured bond lengths for (monoclinic) maleic hydrazide and values from high-level ab initio calculations, and reasonably good agreement is obtained, with indications of improvements when allowance is made for electron correlation and hydrogen bonding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108768197015760
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  • 2
    Electronic Resource
    Electronic Resource
    Diagnostic and therapeutic applications of azulenyl nitrone spin traps (1999)
    Springer
    Cellular and molecular life sciences 56 (1999), S. 626-633 
    Details
    ISSN: 1420-9071
    Keywords: Key words. Azulenyl nitrones; azulenes; nitrones AZN; PBN; S-PBN; free radicals; spin traps; antioxidants; neuroprotection; oxidative stress; assay; amyotrophic lateral sclerosis; FALS; superoxide dismutase; transgenic mice; stroke; ischemia/reperfusion; Parkinson’s disease; MPTP; axotomy; neurodegeneration.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Azulenyl nitrones have been recently demonstrated to constitute a new class of nitrone-based spin traps with the unprecedented capacity to tag free radicals by yielding characteristically colored and highly visible diamagnetic (and paramagnetic) spin adducts. In addition, a comparison of the oxidation potentials of azulenyl nitrones such as 1 and congeners to those of conventional nitrone spin traps previously investigated as potential antioxidant therapeutics such as N-tert-butyl-α-phenylnitrone and its related ortho-sodium sulfonate reveals that the azulene-derived spin traps are far more readily oxidized. These special features render azulenyl nitrones of interest with regard to both their distinct ability to engender the convenient use of colorimetric detection to monitor free radical-mediated oxidative stress in biological systems, and to their potentially enhanced efficacy as neuroprotective antioxidants vs. those conventional nitrone spin traps earlier examined as such. Herein is reported an overview of recent developments pertaining to the use of azulenyl nitrones in the detection of oxidative stress in animal models of amyotrophic lateral sclerosis and stroke, and to their neuroprotective activity in animal models of Parkinson’s disease, stroke and neurodegeneration within the retina.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000180050457
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  • 3
    Electronic Resource
    Electronic Resource
    Inward rectifier potassium channels in plants differ from their animal counterparts in response to voltage and channel modulators (1995)
    Springer
    European biophysics journal 24 (1995), S. 107-115 
    Details
    ISSN: 1432-1017
    Keywords: Potassium channel ; KAT1 ; Voltage dependence ; Cesium block ; pH dependence ; Kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract We have investigated the electrophysiological basis of potassium inward rectification of the KAT1 gene product from Arabidopsis thaliana expressed in Xenopus oocytes and of functionally related K+ channels in the plasma membrane of guard and root cells from Vicia faba and Zea mays. The whole-cell currents passed by these channels activate, following steps to membrane potentials more negative than −100 mV, with half activation times of tens of milliseconds. This voltage dependence was unaffected by the removal of cytoplasmic magnesium. Consequently, unlike inward rectifier channels of animals, inward rectification of plant potassium channels is an intrinsic property of the channel protein itself. We also found that the activation kinetics of KAT1 were modulated by external pH. Decreasing the pH in the range 8.5 to 4.5 hastened activation and shifted the steady state activation curve by 19 mV per pH unit. This indicates that the activity of these K+ channels and the activity of the plasma membrane H+-ATPase may not only be coordinated by membrane potential but also by pH. The instantaneous current-voltage relationship, on the other hand, did not depend on pH, indicating that H+ do not block the channel. In addition to sensitivity towards protons, the channels showed a high affinity voltage dependent block in the presence of cesium, but were less sensitive to barium. Recordings from membrane patches of KAT1 injected oocytes in symmetric, Mg2+-free, 100 mM-K+, solutions allowed measurements of the current-voltage relation of single open KAT1 channels with a unitary conductance of 5 pS. We conclude that the inward rectification of the currents mediated by the KAT1 gene product, or the related endogenous channels of plant cells, results from voltage-modulated structural changes within the channel proteins. The voltage-sensing or the gating-structures appear to interact with a titratable acidic residue exposed to the extracellular medium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00211406
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  • 4
    Electronic Resource
    Electronic Resource
    Efficient transformation of scutellar tissue of immature maize embryos (1997)
    Springer
    Theoretical and applied genetics 94 (1997), S. 737-748 
    Details
    ISSN: 1432-2242
    Keywords: Key words Biolistic transformation ; Maize ; Cereals ; Somatic embryogenesis ; Immature embryos
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract   An efficient transformation system for maize was established by improving transformation conditions for the particle bombardment of the scutellar tissue of immature embryos. Particle bombardment was carried out using constructs containing the pat gene as the selection marker and a PDS 1000/He gun (Biorad). Transformation parameters, such as the amount of gold particles used per bombardment, particle velocity, preculture time of the scutellum prior to bombardment and osmotic treatment of the target tissue before and after bombardment, were analysed. Fertile transgenic regenerants of the maize inbred lines H99, A188 and Pa91 and the crosses A188×H99 and Pa91×H99 were selected on Basta-containing medium. The transformation frequency was between 2% and 4%. A total of 29 transgenic plant lines was obtained and verified with Southern blot analysis. All of the transgenic plants were fertile and set seeds. The R1 progeny of single plants was analysed. A Mendelian segregation of the transgenes was observed for all of the transformants tested. For 1 candidate, stable inheritance and stable expression of the transgenes were followed up to the R4 generation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220050473
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  • 5
    Electronic Resource
    Electronic Resource
    Very accurate, simultaneous determination of trace amounts of Co and Ni in biological materials by radiochemical neutron activation analysis (1996)
    Springer
    Journal of radioanalytical and nuclear chemistry 207 (1996), S. 401-412 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A very accurate and sensitive method for the simultaneous determination of trace amounts of Co and Ni in biological materials has been elaborated. The method is based on radiochemical neutron activation. Irradiation of samples in Cd-shielded channel of a nuclear reactor assures balanced activity ratio of58Co and60Co isotopes and favourable detection limits for both nickel and cobalt. Column chromatography (ion exchange and extraction) has been used for the quantitative and selective isolation of the determined radionuclides. High accuracy of the method has been demonstrated by the analysis of several certified reference materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02071245
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  • 6
    Electronic Resource
    Electronic Resource
    Nitrogen distribution measurements by neutron induced autoradiography (1998)
    Springer
    Journal of radioanalytical and nuclear chemistry 234 (1998), S. 59-63 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A method utilizing plastic track detectors was developed to determine the nitrogen distribution and concentration in the presence of boron in metals. Experiments were performed at the UVAR (cadmium ratio ≈25) and the NIST Reactor (cadmium ratio ≈3000). The minimum detectable concentration of nitrogen at a given concentration of boron has been estimated using the detector’s response to10B(n,α)7 Li reaction products in terms of track size distribution. The capability of the technique to detect nitrogen in the presence of boron has been demonstrated using 316L stainless steel with a nitrogen concentration of ≈560 ppm and a boron concentration of ≈0.86 ppm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02389748
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  • 7
    Electronic Resource
    Electronic Resource
    Characterization and use of the new NIST rapid pneumatic tube irradiation facility (1998)
    Springer
    Journal of radioanalytical and nuclear chemistry 233 (1998), S. 155-160 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Recently a new rapid pneumatic tube facility was inserted into a long unused location in the NIST 20 MW nuclear reactor. This facility was designed and constructed specifically for rapid INAA using short lived activation products. Included is a computer controlled console which uses fast sensors to accurately measure the irradiation capsule flight time, and a loss-free counting system connected to a 32% efficient PHGe detector with a transistor reset preamplifier. Measurement of travel, times from end-of-irradiation to detector were 473±8 ms. Measurement of the thermal neutron fluence rate was 5.0·1013 n·cm−2·s−1. The other three pneumatic tubes in the NIST reactor have transfer times of 3 to 15 seconds, and no timing capability more accurate than human response. This new facility substantially improves our ability to accurately determine activation products with half-lives from 1 to 100 seconds. Characterization information reported on this new irradiation facility includes absolute fluence measurements, fluence rate variations within the capsule and variations with time, and determination of analytical sensitivities for fluorine-20 selenium-77m, and silver-110g.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02389664
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  • 8
    Electronic Resource
    Electronic Resource
    The application of instrumental neutron activation analysis for the certification of the new NIST Fly Ash SRM (1995)
    Springer
    Journal of radioanalytical and nuclear chemistry 193 (1995), S. 7-14 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The National Institute of Standards and Technology (NIST) recently released the second renewal of its “Trace Elements in Coal Fly Ash” Standard Reference Material (SRM 1633b). This new material is currently certified for 23 major, minor and trace elements, and concentrations of an additional 24 elements are provided for “information only” purposes. Current plans are to certify the concentrations of a number of rare earths upon completion of additional analytical work now in progress. Instrumental neutron activation analysis (INAA) has played a major role in the certification of this new material in view of its potential for accuracy, multielemental capability, ability to assess homogeneity, high sensitivity for many elements, and essentially blank-free nature. For an element to be certified in a NIST SRM its concentration is usually determined by at least two independent analytical techniques. INAA has provided analytical information for 15 of the 23 elements certified, as well as for 22 of the 24 elements listed for “information only”. In addition, INAA has provided much of the homogeneity information for this SRM. This paper will describe these analytical procedures, and highlight those designed to optimize and assess the accuracy of the INAA measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02041911
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  • 9
    Electronic Resource
    Electronic Resource
    The NIST rapid irradiation and counting system (1997)
    Springer
    Journal of radioanalytical and nuclear chemistry 215 (1997), S. 47-50 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Apparatus is being developed for short irradiation and rapid counting at the NIST Reactor, optimized for accurate neutron activation analysis via activation products ranging in half-life from about 500 ms to 500 s. This facility is designed to irradiate a sample either in a well-thermalized neutron flux at 3·1013 n·cm−2·s−1, or in a higher flux with a larger fast and epithermal component. The design transfer time for a 1-ml rabbit is 500 ms, measured to 10 ms precision. Timing information for both irradiation and counting will be transferred automatically to the activation analysis workstation computer. The γ-ray spectrometer system is selected and tuned for accurate measurement at high and varying counting rates, using loss-free counting (LFC) technology. A detailed calibration and characterization of this system has been performed. Accurate measurement requires that attention be paid to the systematic and random errors to which LFC is subject, but this requirement is minor compared to the advantages of undistorted spectral shape, the ability to solve the decay equations exactly, and the wider useful range of counting rates in the spectrometer system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02109876
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  • 10
    Electronic Resource
    Electronic Resource
    Szilard-Chalmers reaction in praseodymium compounds (1999)
    Springer
    Journal of radioanalytical and nuclear chemistry 240 (1999), S. 637-641 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The β-emitting isotope142gPr (T 1/2=19.13 h, E(β)max=2.16 MeV) is a suitable radionuclide for internal radiotherapy with tumor-seeking biomolecules.142gPr can be prepared from natural141Pr by irradiation with thermal neutrons. We investigated the Szilard-Chalmers reaction in well-defined complexes with various ligands and a salt in order to measure the enrichment factors and extracted yields to find a route for the production142gPr of high specific radioactivity, ionic142gPr3+ was separated from the complex by cation exchange and high performance liquid chromatography (HPLC).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02349425
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