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At least 325 records · Page 18Linked to original sources
PubMed1998

Improved ternary matrices for the analysis of ferri-pyoverdins by fast atom bombardment mass spectrometry.

The use of explosives as matrices, a principle used previously in plasma desorption mass spectrometry, was applied to fast atom bombardment mass spectrometry (FABMS). Ternary matrices were prepared by the addition of picric acid and related compounds to the binary matrix routinely used for the analysis of peptides, viz. thioglycerol-dithiodiethanol. With the new matrices, the spectra of three ferri-pyoverdins (iron-siderophore complexes which are often difficult to analyse by FABMS with standard matrices) showed a significant increase in both intensity and duration of the ion current. They present a valuable tool for the analysis of problematic analytes and for collision-induced dissociation MS/MS experiments.

Indicators and Reagents↗
PubMed1999

Free radical scavengers from Mutisia friesiana (Asteraceae) and Sanicula graveolens (Apiaceae).

The water-soluble extract of Sanicula graveolens (Apiaceae) and Mutisia friesiana (Asteraceae) showed radical scavenging activity in the DPPH decoloration assay. Bioassay-guided isolation led to caffeic acid derivatives and flavonoids as the main active compounds of both species. After hydrolysis, caffeic acid and quercetin proved to be the bioactive principles of both plants.

Antioxidants↗
PubMed2000

Antioxidant activity of Nigella sativa essential oil.

The essential oil of black cumin seeds, Nigella sativa L., was tested for a possible antioxidant activity. A rapid evaluation for antioxidants, using two TLC screening methods, showed that thymoquinone and the components carvacrol, t-anethole and 4-terpineol demonstrated respectable radical scavenging property. These four constituents and the essential oil possessed variable antioxidant activity when tested in the diphenylpicrylhydracyl assay for non-specific hydrogen atom or electron donating activity. They were also effective.OH radical scavenging agents in the assay for non-enzymatic lipid peroxidation in liposomes and the deoxyribose degradation assay. GC-MS analysis of the essential oil obtained from six different samples of Nigella sativa seeds and from a commercial fixed oil showed that the qualitative composition of the volatile compounds was almost identical. Differences were mainly restricted to the quantitative composition.

Animals↗
PubMed2000

Oxidation of HMG-CoA reductase inhibitors by tert-butoxyl and 1, 1-diphenyl-2-picrylhydrazyl radicals: model reactions for predicting oxidatively sensitive compounds during preformulation.

Hydrogen atom abstraction rate constants for the reaction of tert-butoxyl and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical with the HMG-CoA reductase inhibitors lovastatin, simvastatin, and statins I-IV were measured. This series of diene-containing drugs is known to be prone to oxidation. The tert-butoxyl radical was generated by the thermolysis of di-tert-butylperoxyoxalate at 40 degrees C. A competitive kinetic method was used to determine the relative rate of hydrogen atom abstraction by tert-butoxyl radical to beta-scission. The absolute rate constants were calculated using the experimentally determined product ratios of t-butanol to acetone and the known rate of beta-scission of tert-butoxyl radical. The rate constants for the reaction with DPPH radical were measured spectrophotometrically by monitoring the loss of DPPH radical as a function of substrate concentration. The rate constants correlate well with the structure of the molecules studied. These kinetic techniques allow for oxidatively sensitive compounds to be identified early in the drug development cycle. The tert-butoxyl radical, a strong hydrogen atom abstractor, is representative of the hydroxyl (. OH) and alkoxyl (. OR) radicals; in contrast the DPPH radical, a much weaker radical, is a good kinetic model for hydroperoxyl (. OOH) and peroxyl (. OOR) radicals. These kinetic methods can be used to quantitatively assess the lability of drug candidates towards reaction with oxygen-centered radicals at an early stage of development and facilitate the design of inhibiting strategies.

Bepridil↗
PubMed1975

The effects of various fixative-buffer combinations on lung fine structure.

A variety of fixatives, buffers and fixation procedures were compared in rat and squirrel monkey lung in an attempt to preserve optimally both the cytologic details of pulmonary parenchyma as well as the acellular avelolar lining layer. In initial experiments utilizing the fixative of Ito and Karnovsky ('68), an electron-dense deposit was observed on the alveolar surface. Experiments were carried out in an attempt to determine what component of this fixative was responsible for the reaction product observed. In addition,immersion fixation of tissue blocks was compared to the whole lung fixation method of Kikkawa ('70). Kikkawa ('70) achieved excellent preservation of the acellular alveolar lining layer by such a fixation technique. In all lungs examined, whenever a phosphate buffer was utilized with primary aldehyde fixation, an electron-dense precipitate was observed on the luminal surfaces of the type I and II pulmonary epithelial cells. Additional sites of reaction product were pinocytotic vesicles of the type I cells and membranous arrays within the alveolar lumen. Such deposits were never observed when a sodium cacodylate buffer was used. No such granules were observed in areas of lung where the acellular alveolar lining layer had been preserved. The implications of these findings with regard to lung histochemical procedures and the possible relationship of these phosphate buffer-dependent granules to the surfactant system are discussed.

Animals↗
PubMed1991

Layered collagen fabric of cerebral aneurysms quantitatively assessed by the universal stage and polarized light microscopy.

We evaluated the effectiveness of the Universal stage, an instrument for measuring three-dimensional orientation of birefringent materials, for studying the collagen fabric in the wall of brain aneurysms. Vessels from autopsy were fixed at normal arterial distending pressure with 10% formalin, and prepared for polarized light microscopy, with paraffin embedding and staining with picrosirius red for birefringent enhancement. Quantitative data were obtained from tangential and oblique sections (7 microns thickness) of an intact 8 mm aneurysm, a 1.5 mm aneurysm, and a tangential section (3 microns thickness) of a cerebral artery. Sections of full-size aneurysms seen through the microscope, adjusted either for plane or circularly polarized light, revealed distinctive layers of collagen across the aneurysmal wall, which at higher magnification were further subdivided. Three-dimensional measurements, numbering 1,082, were made by use of the Universal stage attachment to the polarizing microscope. They were plotted by computer-controlled graphics on Lambert projections and analyzed by circular statistics. When assessed layer by layer, the collagen spanned a full range of orientations relative to the tangential plane. The circular standard deviation, a measure of the spread of alignment about the mean, was as low as 10 degrees for coherently organized collagen and as high as 40 degrees for the least coherently organized collagen, values characteristic of either the organized tunica media, or the least organized tunica adventitia of cerebral arteries. Although there was a marked thinning of the wall of one aneurysm, there was no evidence of structural weakness based only on the directional organization assessed by our measurements.

Autopsy↗
PubMedDate not supplied

Screening of chemiluminescence constituents of cereals and DPPH radical scavenging activity of gamma-oryzanol.

The chemiluminescence (CL) constituents of cereals were detected by CL using the H(2)O(2)-acetaldehyde system. The cereals tested, such as rice, millet and sorghum, exhibited various levels of CL activity. The gamma-oryzanol fraction was extracted from brown rice and separated into four constituents by HPLC. The four constituents were identified as cycloartenyl ferulate, 24-methylenecycroartanyl ferulate, campesteryl ferulate and beta-sitosteryl ferulate. Free radical scavenging activities with 1,1-diphenyl-2-picrylhydrazyl (DPPH) and CL intensities of four constituents (gamma-oryzanol components) were measured and compared with that of gallic acid, which is a typical free radical scavenger. Four constituents scavenged DPPH radicals and scavenging activities were proportional to CL intensities. Concentrations of four CL constituents required to quench 50% (IC(50)) of the free radicals ranged from 0.9 to 1.1 mmol/L. We demonstrated that measurement of CL intensities was a rapid and convenient method for screening DPPH radical scavenging activities of rice.

Bepridil↗