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Biomedical subjects

P Sandra

Publications and source records attributed to P Sandra.

At least 55 records · Page 3Linked to original sources
PubMed1997

HPLC fractions of human uremic plasma inhibit the RBC membrane calcium pump.

We have reported that uremic plasma filtrates (UF) inhibit the red blood cell (RBC) membrane calcium pump. The inhibitor was dialyzable, smaller than 3,000 molecular weight, heat-stable, and protease-resistant. In the present study, we used reverse-phase preparative HPLC, analytical HPLC, and Sephadex G-25 elution to identify inhibitory fractions. Inhibition was confirmed in three different bioassays: (1) Sr2+ efflux in intact RBC, the primary bio-assay; (2) 45Ca efflux in intact RBC; and (3) calcium ATPase activity in isolated RBC membranes. Active fractions were analyzed by mass spectrometry, capillary electrophoresis, enzymatic analysis, gas chromatography-mass spectrometry, and nuclear magnetic resonance spectroscopy. These demonstrated a number of compounds, including: sugars, polyols, osmolytes like betaine and myoinositol, amino acids, and other metabolites, such as 3-D-hydroxybutyrate, dimethylglycine, trimethylamine-N-oxide, guanidinoacetic acid and glycine. Many individual compounds were then tested for an effect on the calcium pump. Thus, HPLC was able to separate a substantial number of compounds in inhibitory fractions. Efforts are under way for precise identification of the inhibitor, to advance our understanding of uremic toxicity and/or hypertension in CRF.

Adult↗
PubMed1997

[Determination of phycotoxins in aquatic medium by capillary electrophoresis].

Marine phycotoxins present a major public health problem due to their ability to contaminate seafoods. Toxic phytoplankton is not limited, however, to the coastal areas in Europe. There are more and more problems in freshwater reservoirs, in lakes, and in ponds from which grazing animals get their water. Okadaic acid (OA), a polyether toxin from the marine dinoflagellate, Prorocentrum lima, and microcystins (MCYSTs), a potent hepatotoxic cyclic heptapeptides produced by many strains of cyanobacteria have been shown to be a powerful tumor promotor. Thus, considerable effort has been undertaken to find sensitive and easy detection techniques for the determination of phycotoxins from various matrices (microalgae, freshwater, mussels, fish, ...). Different biological and chemical methods have been developed to identify these toxins in shellfish and fish. The mouse bioassay method has been widely used for the detection of toxins such as maitotoxin and ciguatoxin, which are not easily identified by chemical procedures. In this report we describe a capillary electrophoretic method that enables us to detect okadaic acid, microcystins (MCYST-YR, MCYST-LR, MCYST-RR) and maitotoxin in picogram range.

Animals↗
PubMed1996

Detection of cyanobacterial toxins (microcystins) in cell extracts by micellar electrokinetic chromatography.

A micellar electrokinetic chromatography (MEKC) method with UV detection is described for the rapid and efficient separation of three microcystins: microcystin-YR (MCYST-YR), microcystin-LR (MCYST-LR) and microcystin-RR (MCYST-RR). A detection limit of 7.5 pg for each toxin was achieved. The UV intensities of these toxins measured at 200 nm showed good linearity in the range 7.5-150 pg. The production of MCYST-LR in three cultured strains of cyanobacteria, namely Microcystis aeruginosa strain IP7806, Microcystis aeruginosa strain IP7813 and Oscillatoria agardhii strain IP7805, was evaluated.

Bacterial Toxins↗
PubMed1995

Chemotaxonomic characterization of yeast cells.

Yeast species are analyzed on the basis of their lipid composition to evaluate if chemotaxonomic classification of different species is feasible. The cell walls of samples of Baker's and Brewer's yeast are disrupted by smashing the cells with glass beads at low temperatures. The liberated lipids are extracted with chloroform-methanol. Fractionation of the extract into simple lipids and complex lipids (phospholipids) is performed by column chromatography on silica gel. Elution with methanol produces the simple lipids fraction, whereas elution with methanol-chloroform-ammonium hydroxide produces the phospholipid fraction. The latter fraction is analyzed by high-performance liquid chromatography with light-scattering detection. High-temperature capillary gas chromatography of the simple lipids fraction permits the separation of waxes, sterols, squalene, sterol esters, free fatty acids, monoglycerides, diglycerides, and triglycerides.

Cell Wall↗
PubMed1994

On the possibility of performing chiral wall-coated open-tubular electrochromatography in 50 micron internal diameter capillaries.

Recent results have demonstrated acceptable enantiomer separations in open, 50 microns internal diameter capillaries, coated with a chiral stationary phase, a technique known as electrochromatography. According to existing literature, smaller column diameters, 10 microns or less, are generally preferred for this mode of operation. The conditions under which the wider columns can be used are discussed.

Chromatography↗
PubMed1994

Application of micellar electrokinetic chromatography to the quality control of pharmaceutical formulations: the analysis of xanthine derivatives.

Micellar electrokinetic chromatography (MEKC) has been applied to the analysis of three different drugs. Although belonging to different therapeutic classes, all these drugs contain xanthine derivatives as active substances. Pentoxifylline was separated from eight related xanthines. Quantitative MEKC was applied to determine impurities (caffeine and xanthine) in the purified drug at the 0.05-0.1% level and also for the determination of the active substance in Agapurin tablets. Ethofylline and theophylline were separated from ephedrine and mebrophenhydramine and determined in Xantedrylettae tablets while caffeine was separated from mephenhydramine and determined in Kinedryl tablets. In all cases, simple borate buffers with sodium dodecyl sulfate as the surfactant were satisfactory and little separation optimization was required. The relative standard deviation (RSD) of the migration times was better than 1% while the RSD of the observed areas was better than 2%. This demonstrates that MEKC is a valuable alternative for the traditional high-performance liquid chromatography analysis of drugs and drug formulations.

Chemistry, Pharmaceutical↗
PubMed1994

The determination of non-steroidal antiinflammatory drugs in pharmaceuticals by capillary zone electrophoresis and micellar electrokinetic capillary chromatography.

Ibuprofen, indomethacin, ketoprofen, piroxicam and diclofenac have been quantified in dragees, suspension, suppositories, capsules, injection solutions and tablets by capillary zone electrophoresis (CZE) and micellar electrokinetic capillary chromatography (MEKC). The experiments were performed without specific sample pretreatment. The reproducibility of the method was investigated. Good quantitation was obtained in short analysis times. CE and MEKC are found to offer a good alternative to conventional HPLC methods.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1994

Sub- and supercritical fluid chromatography on packed columns: a versatile tool for the enantioselective separation of basic and acidic drugs.

Various chiral stationary phases were investigated in sub- and supercritical fluid chromatography for the separation, without derivatization, of basic (beta-blockers, benzodiazepines) and acidic (nonsteroidal anti-inflammatory drugs, beta-agonists) pharmaca. For all racemates, baseline separation was achieved within short analysis times. For several solutes, the high resolution obtained allowed injection of milligram amounts and semipreparative collection of the enantiomers. The parameters affecting enantioselectivity (column efficiency, influence of modifiers and basic or acidic additives, and temperature) have been studied. Enantiomerization of 3-OH-benzodiazepines could be suppressed by working at low temperatures or by using acetonitrile as a comodifier. Serial coupling of different chiral stationary phase columns resulted in a column triplet (Chiralpak AD, an amylose derivative; Chiralcel OD, a cellulose derivative; and Chirex 3022, a Brush-type with pi-donor characteristics) on which all solutes investigated could be baseline separated.

Adrenergic beta-Agonists↗
PubMed1993

Quantitation of organic acids in sugar refinery juices with capillary zone electrophoresis and indirect UV detection.

During sugar refinement, monitoring of organic acids such as formate, tartrate, succinate, malate, glycolate and acetate in the process "juices" is important for process control. Matrix effects can lead to problems in conventional chromatographic ion analysis of these solutions. Capillary zone electrophoresis, with indirect UV detection, has been shown to be a good alternative, requiring almost no sample preparation, other than dilution, and with fast analysis time (less than 7 min). A co-elution problem for the formate-tartrate pair could be solved by adding small amounts of bivalent metal ions to the electrophoresis buffer. Quantitative analyses of the organic acids in the juices from beet sugar production and from the processing of a hydrolysed chicory root extract (Cichorium intybus) are reported.

Acids↗
PubMed1993

Gas chromatographic determination of alkyl lysophospholipids after solid-phase extraction from cell culture media.

The gas chromatographic determination of 1-O-octadecyl-2-O-methyl-DL-glycero-3-phosphorylcholine (Et-18-OMe), an anti-invasive alkyl lysophospholipid, in cell culture media is described. Sample clean-up was performed by solid-phase extraction on a weak cation-exchange column of the CBA type (carboxylic acid). For quantitation, the structural analogue Et-16-OMe as the internal standard was used after derivatization with trimethylsilyl bromide. The described method was free of interferences in cell culture media. The overall precision for twenty determinations was 14.99%.

Cells, Cultured↗
PubMed1993

Capillary zone electrophoresis and micellar electrokinetic capillary chromatography of some non-steroidal antiinflammatory drugs (NSAIDs).

The possibilities of capillary electrophoresis (CE) and micellar electrokinetic capillary chromatography (MEKC) were investigated for the qualitative analysis of some non-steroidal antiinflammatory drugs. In CE the influence of the pH of the buffer and its ionic strength were investigated for a test mixture of six compounds. Also the influence of organic modifiers was studied. The best conditions were applied to the separation of 15 drugs. In MEKC the influence of the concentration of SDS in buffers with pH ranges of 8.0-9.0 was investigated. The influence of an organic modifier, namely acetonitrile was discussed, whereby an interesting phenomenon of change in retention behaviour was noted. A combination of CE and MEKC allows the separation of the 15 above-mentioned compounds and forms an interesting alternative to HPLC.

Acetonitriles↗
PubMed1993

Chemical and physicochemical characterization of petrolatums used in eye ointment formulations.

Petrolatums from different manufacturers were characterized by viscosity measurements, oil number and ratio of low to high mol. wt components (capillary gas chromatography). Viscosity measurements and oil numbers of original materials did not correlate with the viscosity of the processed material in eye ointments. The ratio of high carbon number components to the low carbon number components was a reliable predictor for the viscosity of the formulation.

Chemical Phenomena↗
PubMed1993

Lipid composition of leprosy-derived corynebacteria, a distinct group of corynebacteria, and of a reference Corynebacterium.

Leprosy-derived corynebacteria (LDC) are diphtheroid organisms isolated from leprosy patients and previously characterized by DNA and cell wall analysis. Three groups of LDC components of taxonomic value, glycolipids, and phospholipids and cell-wall-bound lipids were analyzed in comparison with those of a reference strain C. hoffmannii (CH). The main CH glycolipid, "cord factor" (trehalose dimycolate), was missing from LDC. Among phospholipids, phosphatidylinositol and phosphatidylglycerol had lowered proportions in LDC, as compared to CH, whereas phosphatidylethanolamine and cardiolipin were absent from both microorganisms. Bound lipids in acidic extracts of delipidated LDC yielded arabinose corynomycolate in lesser quantity with respect to CH. Alkaline hydrolysis of whole cells released fatty acids and mycolic acids, which were analyzed by gas chromatography/mass spectrometry. Reference CH, grown in the absence of serum, yielded C16:0 and C18:1 (major) and C18:0 (minor) fatty acids, as well as C32, C34, and C36 corynomycolic acids. All these components, particularly mycolates, had lowered proportions when this organism was grown in the presence of serum. Dominant LDC components were, in addition to C16:0, C18:0, and CI8:u fatty acids, cholesterol from serum. Very low concentrations of corynomycolic acids with a high degree of unsaturation were found in these organisms, suggesting a dependence of lipid metabolism on growth conditions. The presence in LDC of tuberculostearic acid (C19r:0), a mycobacterial component found in some pathogenic corynebacteria, was carefully explored: Traces of C19r:0 were found in LDC 19 grown in the presence of delipidated serum, but not in LDC 15 nor in C. hoffmannii. Present data, in conjunction with previous studies on DNA and mycolic acids, disclose basic differences in the composition of LDC and conventional corynebacteria.

Cell Wall↗
PubMed1992

Fractionation by SFE and microcolumn analysis of the essential oil and the bitter principles of hops.

Supercritical fluid extraction (SFE) is evaluated and optimized for the enrichment and fractionation of the essential oil and the bitter principles of hops (Humulus lupulus), both of which contribute to the flavor of beer. Profiles of the essential oil of different hop varieties are compared. The bitter principles, the humulones and lupulones, are analyzed by miniaturized liquid chromatography (micro-LC) and by micellar electrokinetic chromatography (MEKC).

Chromatography↗
PubMed1991

Subfractions in uremic plasma ultrafiltrate inhibit calcitriol metabolism.

Previous study from our laboratory has demonstrated that uremic plasma ultrafiltrate suppresses both the production rate (PR) and metabolic clearance rate (MCR) of calcitriol in normal rats. To characterize the the substances responsible for the suppression of the synthesis and degradation of calcitriol, we fractionated 20 ml uremic plasma ultrafiltrates into 13 fractions using high-performance liquid chromatography (HPLC) and studied the effect of each fraction on calcitriol metabolism. We measured the MCR and PR of calcitriol in normal rats after they were infused for 20 hours with each fraction dissolved in 20 ml normal saline. Using a UV absorption and fluorescence emission technique, several known uremic compounds were identified as individual peaks corresponding to the fractions. We found that fractions 4, and 6 to 13 markedly reduced the MCR of calcitriol. The patterns of the MCR suppression by the HPLC fractions suggest that there were at least two groups of chemically distinguishable compounds. Infusion of a solution containing all 13 fractions of the uremic ultrafiltrate also inhibited the calcitriol synthesis. One of the 13 fractions (fraction 4, containing uric acid, xanthine, and hypoxanthine) was further fractionated into eight subfractions. Infusion of subfractions 4 to 7 markedly reduced both the PR and MCR of calcitriol. We conclude that uremic plasma ultrafiltrate contains factors that inhibit calcitriol synthesis and degradation. These substances have molecular weight less than 2,000 Daltons.

Animals↗
PubMed1990

Gas-liquid chromatographic profiling of plasma lipids using high-temperature-polarizable capillary columns.

We have examined the potential usefulness in plasma lipid profiling of capillary columns coated with a high-temperature-polarizable phenylmethyl silicone liquid phase, previously employed for gas-liquid chromatography (GLC) of natural triacylglycerols. The column yielded an excellent resolution for plasma triacylglycerols, cholesteryl esters and the trimethylsilyl (TMS) and tert-butyldimethylsilyl (t-BDMS) ethers of free cholesterol, as well as of the TMS and t-BDMS ethers of the diacylglycerols and ceramides released from plasma phospholipids by phospholipase C digestion. The various lipid classes were resolved into molecular species according to chain length and number of double bonds. The different molecular species were recovered in variable proportions as indicated by comparisons of peak area percentages obtained on the polar columns with those recorded on non-polar columns, which have been previously shown to give correct quantitative proportions. The cholesteryl esters are thermally degraded at high temperatures and must be eluted at as low a temperature as possible. Under the selected experimental conditions, the cholesteryl esters were found to partly interdigitate with the triacylglycerol species of carbon numbers 46-48. The TMS and t-BDMS ethers of diacylglycerols and ceramides emerged clearly ahead of the leading triacylglycerol of the 42 acyl carbon series. However, the diacylglycerol and ceramide species overlapped and interdigitated extensively with each other. Due to low polarity below 280 degrees C, the polarizable-liquid phase was not suitable for the resolution of the molecular species of monoacylglycerols and free fatty acids, which were separated on the basis of carbon number only. Nevertheless, capillary GLC on the polarizable liquid phases provides a novel and informative profiling of plasma lipids, the application of which to the assay of plasma lipid abnormalities deserves further examination.

Ceramides↗
PubMed1988

Identification of the more complex triacylglycerols in bovine milk fat by gas chromatography-mass spectrometry using polar capillary columns.

The fourth most volatile 2.5% molecular distillate of butteroil obtained by redistillation of the most volatile 10% cut was examined by gas chromatography on a polar capillary column (RSL-300) with electron impact and chemical ionization mass spectrometry. For this purpose the distillate was first freed from the acetyldiacylglycerols by thin-layer chromatography on plain silica gel and the remainder resolved into long and short chain length saturates, cis- and trans-monoenes, dienes and trienes by thin-layer chromatography on silver nitrate-silica gel. The order of gas chromatographic elution was established for more than 100 major and minor species making up the bulk of the molecular distillate. The results were used to derive the quantitative composition of the triacylglycerol species making up the various peaks obtained by polar capillary column gas chromatography of the total molecular distillate, which closely resembles the lower half of the molecular mass distribution of whole bovine milk fat.

Animals↗