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  • 1
    ISSN: 1520-5010
    Source: ACS Legacy Archives
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Neurofibroma type 1 tissue was investigated for the presence of growth-promoting activity on human neuroblastoma cells. The activity was isolated by gel filtration and reversed-phase column chromatographs from neurofibroma type 1 extracts. An adenosine-containing dinucleotide (adenylyl(3′-5′)cytidine-3′-phosphate) was identified as one of the major components of the activities by its enzymatic fragmentation and liquid chromatography/mass spectrometry. Synthetic adenosine-containing dinucleotide derivatives such as cytidyl(3′-5′)adenosine, cytidyl(2′-5′)adenosine, adenylyl(3′-5′)cytidine, and adenylyl(2′-5′)cytidine showed a similar action. Cytidyl(3′-5′)adenosine, cytidyl(2′-5′)adenosine, and adenylyl(2′-5′)cytidine, which are able to release a free adenosine through enzymatic hydrolysis, in particular elicited a strong activity corresponding to that of adenosine with the highest action. These results suggest that neuroblastoma cells are able to use adenosine-containing dinucleotides as well as mononucleotides for their survival and proliferation.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Melbourne, Australia : Blackwell Science Asia Pty. Ltd.
    Clinical and experimental pharmacology and physiology 29 (2002), S. 0 
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. In the present study, we have examined the effects of the quinolones norfloxacin (NFLX), enoxacin (ENX), ofloxacin (OFLX), tosufloxacin (TFLX), lomefloxacin (LFLX), sparfloxacin (SPFX) and grepafloxacin (GPFX) on the efflux of doxorubicin from mouse leukaemia P388/ADR cells expressing P-glycoprotein. The relationship between their partition coefficients (hydrophobicity) and effluxing potencies was also elucidated.2. Both TFLX and SPFX strongly increased the intracellular accumulation of doxorubicin (5 μmol/L) in P388/ADR cells, but had no effect on P388/S cells not expressing P-glycoprotein. The rank of order of the potency of the quinolones (TFLX 〉 SPFX 〉 GPFX 〉 NFLX) was not related directly to their hydrophobicity. These results suggest that some quinolones can reverse anticancer drug resistance.3. Because GPFX is more highly excreted into the bile than other known quinolones, the effects of doxorubicin (10 mg/kg) or the well-known inhibitors of P-glycoprotein, namely cyclosporine A (10 mg/kg) and erythromycin (100 mg/kg), on the biliary excretion of GPFX at steady state was studied in rats.4. Doxorubicin, cyclosporine A and erythromycin significantly decreased the biliary clearance of GPFX. Cyclosporine A and erythromycin had a much stronger inhibitory effect on the biliary excretion of GPFX than doxorubicin. These results suggest the possibility that GPFX is, at least in part, excreted into the bile by a P-glycoprotein-mediated transport mechanism.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A fundamental study was performed to establish a method of quantitative analysis using mass chromatography by the direct inlet system. The samples were aspirin, phenacetin and caffeine, which are often used as cold medicines, and barbital, allobarbital, phenobarbital and phenytoin which are difficult to analyse by gas chromatography in their intact states. N-acetylsulfamine and ethyl p-aminobenzoate were used as internal standards. Direct inlet mass chromatography was performed by an on-line system of the Shimadzu LKB-9000 and the GC-MSPAC 300. The ratio of the cumulative ions of certain peaks of sample and the internal standard was studied. It was found that, whether the sample is a pure reagent or a mixture, the ratio of cumulative ions of a peak specific to the sample and of a selected peak of the internal standard is proportional to the sample size, the error being less than ±3.5% for aspirin, phenacetin and caffeine, and less than ±2.7% for barbital, allobarbital and phenobarbital. The same relationship was observed for the phenobarbital and phenytoin mixed in rat plasma, the error being less than ±2.0%. It can be concluded that this method is applicable to the quantiative determination of medicines in urine, body fluids and other biological samples.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 2 (1969), S. 195-207 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectra of several compounds obtained during the process of Stork's isoxazole synthesis9 as well as the related isoxazoles have been investigated. The fragmentations of simple alkyl isoxazoles are nicely formulated via azirine intermediates. A striking difference between the spectra of isoxazoles and those of methylfurans as to the relative abundance of [M  -  l] peaks is noteworthy. The very low abundance of these peaks in the former reflects the unique character of isoxazole nucleus due to the preferential cleavage of N—O linkage rather than a benzylic C—H bond rupture. If an alkyl substituent is present at 4-position in 3,5-dimethylisoxazoles, strong peaks at m/e 110, 68 and 43 are common in their spectra. The analyses of metastable transitions and high resolution measurements have demonstrated that the formation of these ions can be interpreted by a mechanism involving the cleavage of N—O linkage.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 1 (1968), S. 199-204 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three isomeric compounds, I, II and III, were prepared and their mass spectra recorded. Comparisons of the spectra showed that the fragmentation of I proceeds only by way of II, and that II itself is transformed in part to III upon electron impact. It is suggested that selective ionization of each one of the two isolated functional groups in II may afford two isomeric radical ions, IIa and IIb. A possible interrelation to the photochemistry of these compounds is also discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Feasibility for the structural characterization of modified nucleosides in transfer RNA at low microgram levels has been investigated by using continuous-flow frit-fast atom bombardment liquid chromatography/mass spectrometry (frit-FAB LC/MS). Sample of tRNAPhe from brewer's yeast (Saccharomyces cerevisiae) was used as a main model, and enzymatically hydrolysed by nuclease P1 and alkaline phosphatase. The resulting nucleoside mixture was separated by using a microbore reversed-phase LC column (150 mm × 0.5 mm i.d.) with an aqueous ammonium acetate-methanol gradient, and the mass spectra were acquired on both positive and negative ionization modes. The modified nucleosides were characterized by comparison of the relative LC elution times with authentic nucleosides, and further confirmed by the structural information from the frit-FAB mass spectra where both molecular and base ions were in general observed as intense peaks in both ionization modes. Tyically, 0.06-0.2 A260 units (3-10 μg) of isoaccepting tRNA was enough to obtain full-scan mass spectra of modified nucleosides, often occurring at a frequency of one per tRNA molecule using positive ion detection. The LC/MS system was used to screen modified nucleosides in tRNA of the extremely thermophilic microorganism Pyrodictium occultum.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The determination of drug metabolites is very important in the biochemical field. However, the procedure for doing this has been very complicated in many cases. The major reason is because of the need for fairly large amounts of the samples. We have been studying procedures for the determination and identification by use of mass spectrometry, which usually gives a lot of information rapidly from very small amounts of the samples (below μg). In this paper, the metabolites excreted in urine and bile following oral administration of 2-(diethyamino)ethyl tetrahydro-α-(1-naphthylmethyl)-2-furanpropionate oxalate (1) in rats, were investigated by means of mass spectrometry and other techniques. The drug was not excreted unchanged in urine. Of the eight metabolites suspected to be present in urine and bile, the structures of three metabolites were elucidated to be tetrahydro-α-(1-naphthylmethyl)-2-furanpropionic acid (3) and α-(1-naphthylmethyl)-2-perhydro-5-oxofuranpropionic acid (4) in urine, and diethylaminoethanol (2) in bile. These metabolites might also be present as their structural isomers or conjugates.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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