169,720 research outputs found
IDENTIFICATION AND FULL CHARACTERIZATION OF A NEW METABOLITE OF METOCLOPRAMIDE
No full textThe metabolism of metoclopramide 1 has been reinvestigated by HPLC
coupled with mass spectrometry. The urine of healthy volunteers showed
the presence of a new metabolite 2 derived from the enzymatic oxidation
of the primary aromatic amino group of 1 to the hydroxylamino moiety.
The structure of the new metabolite was ascertained by its fragmentation
pattern in the mass spectrometer and unambiguously secured by an
independent synthesis. In addition, the tertiary amine group of 1 was
selectively oxidized to the corresponding N-oxide. This compound and its
ring oxidation metabolites were not detected in the urine of the tested
volunteers
Anti-clastogenic activity of two structurally related pterocarpans purified from Bituminaria bituminosa in cultured human lymphocytes
No full textPlant-derived isoflavones are currently receiving much attention because of their phyto-estrogenic, antioxidant, anti- mutagenic, and anti-tumor activities. In this study we have evaluated the clastogenic and anti-clastogenic activities in human lymphocytes of two structurally related pterocarpans, iso-flavonoid derivatives, termed erybraedin C and bitucarpin A, recently purified from Bituminaria bituminosa and chemically characterized. Mitomycin C (MMC) and the radio-mimetic bleomycin (BL) were used as reference clastogens. The end point studied was micronucleus formation. The results obtained in this study indicate that erybraedin C and bitucarpin A, when assayed alone, do not affect either the mitotic index or the cell-proliferation index of human lymphocytes. Interestingly, both compounds appear to be non-clastogenic in the range of concentrations used. In contrast, both substances seem to affect significantly the clastogenic effects induced by BL and MMC. A 1-h pre-exposition of the cell culture to erybraedin C was necessary to display its anti-clastogenic potential against BL, whereas bitucarpin A was inactive in this respect, with a structure-activity relationship. In contrast, the clastogenic activity of MMC was significantly reduced by both erybraedin C and bitucarpin A, using either a pre-incubation schedule or simultaneous treatment. These results suggest that the protective effects displayed by the two anti-clastogenic compounds against MMC could be due to the induction or inhibition of cellular reductive metabolic enzymes
SYNTHESIS OF A METABOLITE OF METOCLOPRAMIDE AND ITS DETECTION IN HUMAN URINE
No full textThe synthesis of 2-(4-amino-5-chloro-2-methoxybenzamido) acetic acid 2,
a metabolite of metoclopramide 1, has been accomplished through the
coupling of 4-amino-5-chloro-2-methoxybenzoic acid 4 with glycine benzyl
ester followed by a catalytic hydrogenation. Such a metabolite could not
be detected directly in the human urines but only after its
transformation into the corresponding methyl ester 6. Compound 6 was
prepared both by condensing acid 4 with glycine methyl ester and by
reacting acid 2 with diazomethane. HPLC analyses of biological samples
were therefore performed after treatment with diazomethane. In five
healthy volunteers, the percentage of 6 spanned the range 0.6-1.2\%
SYNTHESIS AND PHARMACOLOGICAL INVESTIGATION OF NEW CHIRAL MUSCARINIC ANTAGONISTS
No full textThe two pairs of enantiomers of isoxazolidin-3-ones 3 and 4 were
synthesized by means of Lipase PS-catalyzed hydrolyses of suitable
racemic butyrates. The same butyrates were also employed as key
intermediates in the preparation of racemic 3 and 4. The antimuscarinic
potency of the new compounds was assayed in two in vitro functional
tests. The eutomers (-)-3 and (-)-4 share the same stereochemistry (5R)
of the most potent enantiomer of `'azamuscarone'' 2, a structurally
related muscarinic agonist. Such a spatial arrangement around the chiral
center of 2-4, coupled with the low values of eudismic ratio, represents
an anomaly among the chiral muscarinic ligands. This anomaly was
accounted for by the absence of a chiral center at C-2, a positon whose
configuration is crucial in determining the high enantioselectivity of
muscarinic agonists and antagonists
New strategies to quantify aluminum hydroxide in powder coatings by thermogravimetric analysis and ATR-FT-MIR spectroscopy coupled with chemometrics
No full textPowder coatings industry is a growing trade sector in our days and the process control phase is a critical step with the increasing necessity for rapid methods. In this research, we evaluated the possibility of aluminum hydroxide quantification in powder coatings using thermogravimetric analysis and ATR-FT-MIR spectroscopy. Spiked powder coatings sample standards were realized with a known amount of aluminum hydroxide from 0 to 22% in weight. The thermogravimetric analysis (TGA) was optimized, and the aluminum hydroxide content was determined with a stoichiometric formula based on the delta at the inflection point (DTG curve were derived) in TGA results. The spectroscopic data were acquired, and multivariate regression (Partial Least Squares Regression) was used to model the aluminum hydroxide content with respect to the spectral signal. Models were validated with an external set of real powder coating samples. In this article, a step-by-step model development procedure is illustrated as well as the issues addressed. In addition, models showed the possibility of identifying some additives and resins using only the spectroscopic information
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Mitomycin C in highly myopic eyes - Author reply
No full textOphthalmology. 2005 Feb;112(2):208-18; discussion 219.
Mitomycin C modulation of corneal wound healing after photorefractive keratectomy in highly myopic eyes.
Gambato C, Ghirlando A, Moretto E, Busato F, Midena E.
SourceRefractive Surgery Service and Antimetabolite Therapy Research Unit, Department of Ophthalmology, University of Padova, Padova, Italy.
Abstract
PURPOSE: To evaluate the role of topical mitomycin C in corneal wound healing (CWH) after photorefractive keratectomy (PRK) in highly myopic eyes.
DESIGN: Prospective, double-masked, randomized clinical trial.
PARTICIPANTS: Seventy-two eyes of 36 patients affected by high (>7 diopters) myopia.
METHODS: In each patient, one eye was randomly assigned to PRK with intraoperative topical 0.02% mitomycin C application, and the fellow eye was treated with a placebo. Postoperatively, mitomycin C-treated eyes received artificial tears (3 times daily, tapered in 3 months), whereas the fellow eye was treated with fluorometholone sodium 2% and artificial tears (3 times daily, tapered in 3 months).
MAIN OUTCOME MEASURES: Uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA), contrast sensitivity, manifest refraction, and biomicroscopy. Contrast sensitivity was determined using the Pelli-Robson chart. Corneal confocal microscopy documented CWH.
RESULTS: Mean follow-up was 18 months (range, 12-36). No side effects or toxic effects were documented. At 12-month follow-up examination, UCVAs (logarithm of the minimum angle of resolution) were 0.4+/-0.48 and 0.5+/-0.53 (P = .03) in mitomycin C-treated eyes and corticosteroid-treated eyes, respectively. At 1 year, corneal haze developed in 20% of corticosteroid-treated eyes, versus 0% of mitomycin C-treated eyes. At 12, 24, and 36 months, corneal confocal microscopy showed activated keratocytes and extracellular matrix significantly more evident in untreated eyes (Ps = 0.004, 0.024, and 0.046, respectively).
CONCLUSION: Topical intraoperative application of 0.02% mitomycin C can reduce haze formation in highly myopic eyes undergoing PRK.
Comment in
Ophthalmology. 2006 Feb;113(2):357; author reply 357-8
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Synchrotron radiation Ca K-edge 2D-XANES spectroscopy for studying the stratigraphic distribution of calcium-based consolidants applied in limestones
No full textIn Heritage Science, the evaluation of stone consolidation treatments by investigating the nature of in situ newly formed products and their penetration depth within the consolidated matrix is a grand challenge. A number of analytical methods have been proposed, but, currently, most of them are not able to supply a full overview of the spatial, structural and compositional information of the newly formed crystalline and amorphous phases with a submicrometric lateral resolution. Here, we examined, the capabilities of synchrotron radiation (SR)-based two-dimensional X-ray absorption near-edge structure (2D-XANES) spectroscopy at Ca K-edge for determining the structural and compositional properties of the compounds formed after the application of a calcium acetoacetate-based consolidant on a porous carbonatic stone (limestone) and for investigating their stratigraphic distribution at the submicrometric scale length. We evaluated advantages and drawbacks of three Ca K-edge 2D-XANES-based approaches: (i) transmission mode full-field-XANES (FF-XANES) imaging; (ii) micro-X-ray fluorescence (μ-XRF) mapping above the Ca K-edge combined with the acquisition of XRF mode μ-XANES spectra at a limited number of spots; (iii) full-spectral μ-XANES (FS μ-XANES) mapping in XRF mode and its variant called selectively induced X-ray emission spectroscopy (SIXES) mapping. Overall, Ca K-edge 2D-XANES spectroscopy provided accurate qualitative and semi-quantitative information on the newly formed calcium carbonates (i.e., amorphous calcium carbonate, vaterite and calcite) and their stratigraphic distribution at the submicrometric scale, thus opening a new scenario to study the carbonatation process of calcium-based consolidants in limestones
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