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  • 1995-1999  (10)
  • 1975-1979  (5)
  • Analytical Chemistry and Spectroscopy  (8)
  • Biochemistry and Biotechnology  (2)
  • Canine  (2)
  • Computational Chemistry and Molecular Modeling
  • United States
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Years
Year
  • 1
    ISSN: 1432-1912
    Keywords: Dispersion ; Refractoriness ; ATP-sensitive potassium channel ; Canine ; Programmed electrical stimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The proarrhythmic effects of the ATP-sensitive potassium channel modulators cromakalim (n = 10; 0.01 to 0.3 mg/kg i.v.), glibenclamide (n = 10; 0.3 to 10 mg/kg i.v.) or volume equivalents of vehicle (n = 10) were evaluated in post-infarcted anaesthetised dogs. Dogs were anaesthetised, subjected to an anterior-apical myocardial infarction, and allowed to recover. At 7.4 ± 0.7 days post infarction, animals were anaesthetised again, electrophysiologic measurements (effective refractory periods, QT-intervals and ventricular fibrillation thresholds) were taken, and animals were tested for arrhythmias using a programmed electrical stimulation protocol. Only animals that did not have programmed electrical stimulation-inducible arrhythmias were used. Ventricular fibrillation thresholds were determined twice, once before the first dose then after the last dose of drug. At the end of the experiment, animals were subjected to ligation of the left circumflex coronary artery and survival was measured over the next two hours. Cromakalim significantly increased heart rate and decreased blood pressure. Although cromakalim significantly reduced effective refractory periods, it neither increased electrical dispersion, as determined by the standard deviation or coefficient of variance of the effective refractory period, nor did it enhance inducibility (0 out of 10 in both vehicle and cromakalim treated animals), change ventricular fibrillation thresholds, or reduce sudden death survival relative to vehicle. Glibenclamide did not increase electrical dispersion, but slightly increased the incidence of programmed electrical stimulation-induced arrhythmias (3 out of 10), and lowered ventricular fibrillation thresholds values. However, these changes were not statistically significant. Glibenclamide did not significantly affect survival relative to vehicle. Infarct sizes of the left ventricle were not statistically different among groups. In conclusion, cromakalim and glibenclamide did not affect dispersion of refractoriness. Glibenclamide did demonstrate a propensity towards proarrhythmic activity. However, the doses needed to observe proarrhythmic activity with glibenclamide were significantly higher than those needed for clinical treatment of hyperglycemia.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1912
    Keywords: Key words Dispersion ; Refractoriness ; ATP-sensitive potassium channel ; Canine ; Programmed electrical stimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The proarrhythmic effects of the ATP-sensitive potassium channel modulators cromakalim (n=10; 0.01 to 0.3 mg/kg i.v.), glibenclamide (n=10; 0.3 to 10 mg/kg i.v.) or volume equivalents of vehicle (n=10) were evaluated in post-infarcted anaesthetised dogs. Dogs were anaesthetised, subjected to an anterior-apical myocardial infarction, and allowed to recover. At 7.4±0.7 days post infarction, animals were anaesthetised again, electrophysiologic measurements (effective refractory periods, QT-intervals and ventricular fibrillation thresholds) were taken, and animals were tested for arrhythmias using a programmed electrical stimulation protocol. Only animals that did not have programmed electrical stimulation-inducible arrhythmias were used. Ventricular fibrillation thresholds were determined twice, once before the first dose then after the last dose of drug. At the end of the experiment, animals were subjected to ligation of the left circumflex coronary artery and survival was measured over the next two hours. Cromakalim significantly increased heart rate and decreased blood pressure. Although cromakalim significantly reduced effective refractory periods, it neither increased electrical dispersion, as determined by the standard deviation or coefficient of variance of the effective refractory period, nor did it enhance inducibility (0 out of 10 in both vehicle and cromakalim treated animals), change ventricular fibrillation thresholds, or reduce sudden death survival relative to vehicle. Glibenclamide did not increase electrical dispersion, but slightly increased the incidence of programmed electrical stimulation-induced arrhythmias (3 out of 10), and lowered ventricular fibrillation thresholds values. However, these changes were not statistically significant. Glibenclamide did not significantly affect survival relative to vehicle. Infarct sizes of the left ventricle were not statistically different among groups. In conclusion, cromakalim and glibenclamide did not affect dispersion of refractoriness. Glibenclamide did demonstrate a propensity towards proarrhythmic activity. However, the doses needed to observe proarrhythmic activity with glibenclamide were significantly higher than those needed for clinical treatment of hyperglycemia.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-7225
    Keywords: Colon cancer ; diet ; family history ; United States ; women
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Objective: The purpose was to investigate whether dietary associations with risk of colon cancer in women differ by family history of the disease. Methods: Data were analyzed from a prospective cohort study of 35,216 Iowa (United States) women aged 55 to 69 years at baseline. Through 31 December 1995, 241 colon cancers were identified through record linkage with the State Health Registry. The cohort was stratified on family history of colon cancer in first-degree relatives; nutrient intakes were divided into tertiles. Results: Analyses using Cox regression revealed that the association of most dietary components with colon cancer incidence were similar for individuals with and without a family history. However, total calcium intake was associated inversely with colon cancer among women with a negative family history (relative risk [RR]=0.50 for upper cf lower tertile, P 〈 0.001), but was unrelated to incidence for women with a positive family history (RR=1.1 for upper cf lower tertile, P=0.69). Similarly, total vitamin E intake was associated with lower risk among women with a negative family history (RR=0.67 for upper cf lower tertile, P=0.04), but not among women with a positive family history (RR=0.87 for upper cf lower tertile, P=0.67). High intakes of fiber, fruits, and vegetables were each weakly inversely associated with risk among family-history negative women, but not among family-history positive women. Conclusions: These data, if corroborated, suggest that dietary factors typically associated with lower risk may be less effective risk-reduction interventions against colon cancer for individuals with a family history of colon cancer.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-7225
    Keywords: Breast cancer ; body mass index ; females ; United States ; weight gain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: We examined whether associations of adult weight gain with the risk of postmenopausal breast cancer vary by stature, waist-hip ratio (WHR), and early adult size in a cohort of 37,105 Iowa (United States) women. Both low body mass index (kg/m2) (BMI) at age 18 and high subsequent weight-gain were associated independently with increased risk of incident postmenopausal breast cancer. After stratifying on BMI at age 18, high weight gain was associated with increased risk irrespective of whether early BMI was low (relative risk [RR]=1.92, 95 percent confidence interval [CI]=1.45–2.53) or high (RR=1.59, Ci=1.19–2.12). Women with lower BMI at 18 were at a higher risk at all levels of weight change, but having low BMI at age 18 and low subsequent weight gain conferred no significantly excess risk over those with high BMI at 18 and low gain. An inconsistent increase in risk was associated with taller stature; there was no additional risk associated with high WHR. Part of the observed risk from lower early size may reflect greater weight gain by lighter women. Limiting adult weight gain thus may be a feasible method to avoid increasing an individual's risk of breast cancer. Reasons for different effects of early cf late weight gain are not established, but benefits of a greater size at age 18 are likely to be offset by increased risks of other weight-related diseases at older ages.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The products from base-specific, dideoxy-nucleotide chain-termination DNA sequencing reactions catalyzed by the modified T7 DNA polymerase have been analyzed by using the technique of matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry. Preliminary experiments were performed to determine detection limits for a synthetic mixture of mixed-base single-stranded DNA which contained a 14-mer, a 21-mer, and a 41-mer; acceptable spectra, showing peaks for each component, were obtainable for samples that contained as little as 5 fmol per component. Initial sequencing reactions were therefore carried out on 2-pmol amounts of a short synthetic template that was 45 nucleotides in length, employing 2 pmol of 12-mer as the primer strand. This provided readable sequence information out to the 19th base past the primer. Using a 21-mer primer, nearly the entire sequence of the template could be read.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1076-5174
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In a study designed to examine the nature of short-lived, electrophilic intermediates liberated during decomposition of N,N′-bis(2-chloroethyl)-N-nitrosourea (BCNU) in vitro and also on administration of BCNU (140 μmol i.p.) to rats in vivo, both on-line and off-line LC/MS/MS techniques were employed to detect and characterize the corresponding glutathione (GSH) adducts present in incubation media and excreted into bile, respectively. In vitro, four GSH conjugates were formed and these were identified, on the basis of their product ion spectra, as products of S-and N-carbamoylation and alkylation reactions. Although the relative proportions of these in vitro adducts were found to depend on the molar ratios of GSH and BCNU, the major adduct under all conditions studied proved to be S-(2-chloroethylcarbamoyl)glutathione (SCG). Analysis of untreated bile samples by means of on-line LC/MS/MS with constant neutral loss (129 u) and precursor ion (m/z 179) scanning techniques again led to the detection of four GSH conjugates, although only one of these (SCG) was common to the group of adducts identified in vitro. All of the GSH conjugates detected in bile represented products of S-carbamoylation, indicating that the alkylating moiety released from BCNU undergoes reactions in vivo with nucleophiles other than GSH.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Density functional theory is tested on a large ensemble of model compounds containing a wide variety of functional groups to understand better its ability to reproduce experimental molecular geometries, relative conformational energies, and dipole moments. We find that gradient-corrected density functional methods with triple-ζ plus polarization basis sets reproduce geometries well. Most bonds tend to be approximately 0.015 Å longer than the experimental results. Bond angles are very well reproduced and most often fall within a degree of experiment. Torsions are, on average, within 4 degrees of the experimental values. For relative conformational energies, comparisons with Hartree-Fock calculations and correlated conventional ab initio methods indicate that gradient-corrected density functionals easily surpass the Hartree-Fock approximation and give results which are nearly as accurate as MP2 calculations. For the 35 comparisons of conformational energies for which experimental data was available, the root mean square (rms) deviation for gradient-corrected functionals was approximately 0.5 kcal mol-1. Without gradient corrections, the rms deviation is 0.8 kcal mol-1, which is even less accurate than the Hartree-Fock calculations. Calculations with extended basis sets and with gradient corrections incorporated into the self-consistent procedure generate dipole moments with an rms deviation of 5%. Dipole moments from local density functional calculations, with more modest basis sets, can be scaled down to achieve roughly the same accuracy. In this study, all density functional geometries were generated by local density functional self-consistent calculations with gradient corrections added in a perturbative fashion. Such an approach generates results that are almost identical to the self-consistent gradient-corrected calculations, which require significantly more computer time. Timings on scalar and vector architectures indicate that, for moderately sized systems, our density functional implementation requires only slightly less computer resources than established Hartree-Fock programs. However, our density functional calculations scale much better and are significantly faster than their MP2 counterparts, whose results they approach. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Tab.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A highly sensitive and specific assay is described for the bronchodilator drug terbutaline in human plasma and urine, based on single ion monitoring gas chromatography mass spectrometry and employing a homologue of the drug as internal standard. Recovery of terbutaline and internal standard into ethyl acetate is effected at pH 9.8, while back-extraction into dilute acid serves to purify the initial extract. Following preparation of O-TMS, N-TFA derivatives, the drug and its homologue are detected by selected ion monitoring of their common base ion at m/e 355. The limit of detection of terbutaline by this procedure is 0.3 ng ml-1 from a 4 ml sample of plasma.
    Additional Material: 5 Ill.
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  • 9
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Gas chromatography mass spectrometry has been used to study the reaction between a range of aromatic, alicyclic and aliphatic sulphate esters and three perfluoroacylating reagents, viz. trifluoroacetic, pentafluoropropionic and heptafluorobutyric anhydride. Aromatic sulphates were found to react readily, when treated with a 1:1 mixture of a perfluoroacid anhydride and dry ethyl acetate, to form the perfluoroester derivative of the parent phenol in quantitative yield. Non-aromatic sulphates, on the other hand, gave a variety of products. A mechanism is proposed for the one-step derivatization of aromatic sulphates and the potential of the procedure for the analysis of sulphate conjugates by mass spectrometry is discussed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 8 (1976), S. 489-499 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Finite perturbation calculations using CNDO/2 wave functions are presented for the determination of 31P—13C and 31P—1H couplings. The calculations were carried out on 46 molecules and a comparison with experimental values is given. The groups of compounds considered were phosphonium cations, phosphine oxides, alkylidenephosphoranes, phosphine sulfides, phosphoranes and phosphines. With the exception of phosphines, the finite perturbation approach reproduces the experimental couplings with fair accuracy. It is found that there is a good correlation with the calculated 1J(P, C) and the phosphorus 3s-carbon 2s bond orders for tetra- and pentavalent phosphorus compounds. This lends support to the growing body of evidence for the direct relationship of the magnitude of 1J(P, C) and percent s character in the hybrid orbital on the carbon comprising the P—C bond. The finite perturbation technique was also used to explore the effects of geometrical changes on P—C and P—H couplings. Finally, the effect of deleting d orbitals on phosphorus is discussed briefly.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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