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  • arsenobetaine  (2)
  • Key words C-peptide functional test  (1)
  • arsenosugars  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Discriminative capacity of fasting C-peptide levels in a functional test according to different criteria of response to a stimulus (1997)
    Springer
    Acta diabetologica 34 (1997), S. 42-45 
    Details
    ISSN: 1432-5233
    Keywords: Key words C-peptide functional test ; Insulin-dependent diabetes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In order to study the discriminative capacity of the C-peptide basal values (BV) in a functional test, we analysed the C-peptide response curve after a mixed meal in 26 insulin-dependent patients. The five criteria of response used were: (1) any increment after the stimulus; (2) percentual increment above 21%; (3) absolute in-crement above 0.35 ng/ml; (4) incremental area above 42.76 ng ⋅ min ⋅ml–1, and (5) peak value above 2.16 ng/ml. Considering the first two criteria, many patients showed positive responses, in the diabetic group as a whole and when we analysed patients with BV ≥ 0.74 ng/ml and 〈0.74 ng/ml separately. When we applied only the last three criteria the number of positive responses was considerably smaller. Moreover, the majority of patients with BV 〈 0.74 ng/ml could not increase their levels over the ones established above. In patients with BV ≥ 0.74 ng/ml, the number of positive and negative responses were similar. The comparison between the subgroups achieves statistical significance only for incremental area (χ 2 = 3.55, P = 0.03). We conclude that the functional test was important mainly for patients with BV ≥ 0.74 ng/ml, and could have been omitted for patients with BV 〈 0.74 ng/ml. The best criteria of response were those based on the mean minus two standard deviations of each parameter in a non-diabetic group (the last three criteria), especially the incremental area.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005920050064
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  • 2
    Electronic Resource
    Electronic Resource
    Evidence of the Presence of Dimethylated, Trimethylated and "Refractory' Arsenic Compounds in Estuarine Salt-marsh Halophytes (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 11 (1997), S. 439-450 
    Details
    ISSN: 0268-2605
    Keywords: halophytes ; arsenobetaine ; arsenocholine ; tetramethylarsonium ; arsenosugars ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Five species of halophytes were sampled in the salt marshes of the Tagus estuary, dried, ground and digested. They were further extracted with ethanol and the extracts passed through weak and strong cationic ion-exchange resins, purified through TLC and submitted to pyrolysis mass spectrometry and HPLC-ICP/MS. Arsenic content and hydride-forming arsenic species were verified, in each step, by GF-AA and HG-QFAA. A high content of arsenic was found in the samples of halophytes studied, both di- and tri-methylated arsenic compounds being present. A considerable fraction of this arsenic content seems to be refractory to hydride generation. Moreover, the arsenic fraction found seems to have the same ion-exchange behaviour as the refractory fractions formerly studied in estuarine water.A partial characterization of these structures by pyrolysis-GC-MS suggests the presence of arsenobetaine and arsenocholine compounds. Furthermore, HPLC-ICP/MS data seem to confirm the presence of these compounds. In addition, the latter hyphenated technique strongly suggests the presence of a number of other organoarsenicals including tetramethylarsonium (TMAs), trimethylarsine oxide (TMAO), cacodylate (DMA) and possibly an arsenosugar-type compound. © 1997 by John Wiley & Sons, Ltd.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    Refractory methylated arsenic compounds in estuarine waters: Tracing back elusive species (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 8 (1994), S. 43-56 
    Details
    ISSN: 0268-2605
    Keywords: Arsenic ; identification ; DCI MS/MS ; hydride generation ; arsenobetaine ; arsenocholine ; methylarsenic ; chlorine ; fluorine ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Water from the Tagus estuary, Portugal, was concentrated and purified through evaporation, solvent extraction, ion exchange and HPLC, and peaks of refractory arsenicals were detected by difference between total arsenic (GF AA) and hydride-forming arsenic species (HG QF AA). DCI mass spectra of these fractions presented peaks at m/z 139, 157 and 159; the proportion of m/z 157 and 159 peaks, approx. 3:1, suggested a chlorinated moiety. DCI MS/MS daughter-ion fragmentation of these peaks seems compatible with dimethylarsenic (cacodylic) acid and structures of the type Me2As(O)Cl or Me3As(OH)F. The refractory character of these fractions, however, cannot be explained by these structures. Further work with mixtures of halogen and arsenic species injected in the HPLC system showed that fluoride and iodide can shift DMA (dimethylarsenic) and TMAO (trimethylarsine oxide) to shorter retention times but not to Rf values similar to refractory arsenicals. These latter are attained by mixtures of sodium chloride + arsenobetaine, and sodium fluoride and chloride + arsenocholine. We suggest that peaks at m/z 139 and 157 correspond to fragments of a heavier refractory molecule mainly formed by halogenated betaines including chloroarsenobetaine and chloro- and fluoro-arsenocholine.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aoc.590080109
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