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  • 2000-2004  (4)
  • 2004  (2)
  • 2002  (2)
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  • 2000-2004  (4)
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  • 1
    Electronic Resource
    Electronic Resource
    Optimization of plasma grid material in cesium-seeded volume negative-ion sources : Papers from the Ninth International Conference on Ion Sources (2002)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 964-966 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In cesium-seeded hydrogen negative-ion sources, surface production on the plasma grid plays an important role in negative ion production. To enhance the surface, it is required to use material that would give a lower work function when Cs is absorbed on the surface. In a semicylindrical and cesium-seeded volume negative-ion source, eight materials (W, Cu, Mo, V, Cr, Ni, Ag, and Au) were tested as candidates for the plasma grid material. To avoid deposition of the cathode material on these materials, a filament-free plasma source was used, to fire the microwave (2.45 GHz) discharge in the Kamaboko source. The material surface was examined by measuring the photoelectron current by laser irradiation. It was observed that the discharge enhanced the photoelectron current when the material was biased negatively to the plasma potential during discharge. In the present experiment, Ni, Au, and Ag surfaces with a Cs layer showed a higher photoelectron current than the others. This was 1.5 times larger than that of Cu and W used as a plasma grid and filament in conventional high current negative ion sources. It is expected that higher negative-ion production efficiency would be obtained by using Ni, Ag, and Au as the plasma grid material, if deposition of filament materials is avoided on the surface. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1428419
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Urinary 3-bromotyrosine and 3-chlorotyrosine concentrations in asthmatic patients: lack of increase in 3-bromotyrosine concentration in urine and plasma proteins in aspirin-induced asthma after intravenous aspirin challenge (2004)
    Oxford, UK : Blackwell Science Ltd
    Clinical & experimental allergy 34 (2004), S. 0 
    Details
    ISSN: 1365-2222
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background Eosinophil peroxidase and myeloperoxidase halogenate tyrosine residues in plasma proteins and generate 3-bromotyrosine (BY) and 3-chlorotyrosine (CY), respectively.Objectives (1) To estimate urinary concentrations of BY and CY in asthmatic patients. (2) To investigate BY concentration in relation to urinary leukotriene E4 (LTE4) concentration in order to evaluate the activation of eosinophils in patients with aspirin-induced asthma (AIA).Methods BY and CY were quantified with a gas chromatograph-mass spectrometer using 13C-labelled compounds as internal standards.Results (1) Activation of eosinophils and neutrophils by immobilized IgG1 induced preferential formation of BY and CY, respectively. (2) A significantly higher concentration of BY was observed in the urine from asthmatic patients than in that from healthy control subjects (45±21.7 vs. 22.6±10.8 ng/mg-creatinine, P〈0.01). CY concentration was also elevated in the urine from asthmatic patients (4.4±3.2 vs. 1.5±1.0 ng/mg-creatinine, P〈0.01). (3) After intravenous aspirin challenge of aspirin-induced asthmatic patients, the concentration of BY in urine did not significantly change. No significant change was also observed in the ratio of BY concentration to total tyrosine concentration in plasma proteins. In contrast, the concentration of urinary LTE4 significantly increased after the intravenous aspirin challenge.Conclusion Determination of BY and CY concentrations may be useful for monitoring the activation of eosinophils and neutrophils in asthmatic patients, respectively. After aspirin challenge of AIA patients, the increased concentration of urinary LTE4 did not accompany changes in BY concentration in both urine and plasma proteins. These results may preclude the activation of eosinophils after aspirin challenge in patients with AIA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2222.2004.01968.x
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  • 3
    Electronic Resource
    Electronic Resource
    Increase in urinary leukotriene B4 glucuronide concentration in patients with aspirin-intolerant asthma after intravenous aspirin challenge (2004)
    Oxford, UK : Blackwell Science Ltd
    Clinical & experimental allergy 34 (2004), S. 0 
    Details
    ISSN: 1365-2222
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background Aspirin challenge of aspirin-intolerant asthma (AIA) patients causes a significant increase in leukotriene E4 (LTE4) concentration in urine. However, knowledge on leukotriene B4 (LTB4) generation in patients with AIA is insufficient. Recent research has demonstrated that exogenously administered LTB4 is excreted as glucuronide into the urine in human healthy subjects.Objective The purpose of this study is to estimate urinary LTB4 glucuronide (LTBG) concentration in the clinically stable condition in healthy subjects and asthmatic patients and to investigate changes in urinary LTBG concentration in patients with AIA after aspirin challenge.Methods A provocation test was performed by intravenous aspirin challenge. After urine was hydrolysed by β-glucuronidase, the fraction containing LTB4 was purified by high-performance liquid chromatography and LTB4 concentration was quantified by enzyme immunoassay. Urinary LTBG concentration was calculated as the difference between the concentration obtained with hydrolysis and that without hydrolysis.Results (1) After hydrolysis, the presence of urinary LTB4 was verified by gas chromatography-mass spectrometry-selected ion monitoring. (2) The urinary LTBG concentration was significantly higher in the asthmatic patients than in the healthy subjects (median, 5.37 pg/mg creatinine [range 1.2–13] vs. 3.32 pg/mg creatinine [range, 0.14–10.5], P=0.0159). (3) The patients with AIA (n=7), but not those with aspirin-tolerant asthma (n=6), showed significant increases in LTBG and LTE4 excretions after aspirin challenge. (4) When the concentrations after aspirin challenge were analysed simultaneously, a significant linear correlation was observed between urinary LTBG concentration and urinary LTE4 concentration in patients with AIA (Spearman's rank correlation test, r=0.817, P=0.0003).Conclusion LTBG is present in human urine, albeit at a concentration lower than urinary LTE4. In addition to a marked increase in cysteinyl-leukotriene production, aspirin challenge induced LTB4 production in AIA patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2222.2004.02034.x
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  • 4
    Electronic Resource
    Electronic Resource
    A comparative study of eicosanoid concentrations in sputum and urine in patients with aspirin-intolerant asthma (2002)
    Oxford, UK : Blackwell Science, Ltd
    Clinical & experimental allergy 32 (2002), S. 0 
    Details
    ISSN: 1365-2222
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background Although many studies have assumed that the overproduction of cysteinyl- leukotrienes (cys-LTs) and an imbalance of arachidonic acid metabolism may be plausible causes for the pathogenesis of aspirin-intolerant asthma (AIA), there has been little experimental evidence to substantiate this notion in lower airways of patients with AIA.Objectives The purpose of this study was to compare the eicosanoid concentrations in sputum and urine from patients with AIA.Methods The concentrations of sputum cys-LTs, prostaglandin E2 (PGE2), PGF2α, PGD2 and thromboxane B2 were measured to assess local concentrations of eicosanoids in patients with AIA and in those with aspirin-tolerant asthma (ATA). The concentrations of two urinary metabolites, leukotriene E4 (LTE4) and 9α11βPGF2, were also measured to corroborate the relationship between the eicosanoid biosynthesis in the whole body and that in lower airways.Results The concentration of PGD2 in sputum was significantly higher in patients with AIA than in those with ATA (median, 5.3 pg/mL vs. 3.1 pg/mL, P 〈 0.05), but there was no significant difference in the concentration of the corresponding metabolite, 9α11βPGF2, between the two groups. No differences were noted in the concentrations of other prostanoids in sputum between the two groups. The sputum cys-LT concentrations showed no differences between the two groups, in spite of the observation that the concentration of urinary LTE4 was significantly higher in patients with AIA than in those with ATA (median, 195.2 pg/mg-cre vs. 122.1 pg/mg-cre, P 〈 0.05). There was a significant correlation among the concentration of cys-LTs, the number of eosinophils and the concentration of eosinophil-derived neurotoxin (EDN) in sputum.Conclusion The urinary concentration of LTE4 does not necessary reflect cys-LT biosynthesis in lower airways. A significantly higher concentration of PGD2 in sputum from patients with AIA suggests the possible ongoing mast cell activation in lower airways.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2745.2002.01507.x
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