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Results for “Green analytical method”

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At least 217 records · Page 12Linked to original sources

PubMed1996

Surgical resection of hepatocellular carcinoma in cirrhotic patients: prognostic value of preoperative portal pressure.

BACKGROUND & AIMS: Although resection of hepatocellular carcinoma complicating cirrhosis is restricted to patients with preserved liver function, postoperative hepatic decompensation develops in some patients. The aim of this study was to determine the value of increased portal pressure in the development of postoperative hepatic decompensation. METHODS: Twenty-nine cirrhotic patients with Child-Pugh's class A disease and hepatocellular carcinoma (all except one < 5 cm) scheduled to undergo resection were evaluated by conventional criteria and by a systemic and hepatic hemodynamic study. Predictors of decompensation were assessed among a series of 44 clinical, analytical, tumoral, and hemodynamic parameters. RESULTS: Eleven patients had unresolved decompensation 3 months after surgery. Bilirubin and blood ureic nitrogen levels, platelet count, wedged hepatic venous pressure, hepatic venous pressure gradient, and indocyanine green intrinsic clearance were significantly associated with unresolved decompensation, but only hepatic venous pressure gradient was significant, in the multivariate analysis (P = 0.0001; odds ratio, 1.90; 95% confidence interval, 1.12-3.22). The preoperative gradient of patients with unresolved decompensation was higher than that of patients without it (13.9 +/- 2.4 and 7.4 +/- 3.5 mm Hg, respectively; P < 0.001). CONCLUSIONS: Cirrhotics with increased portal pressure are at high risk of hepatic decompensation after resection of hepatocellular carcinoma. Surgical resection should therefore be restricted to patients without portal hypertension.

Aged↗

PubMed1989

Serum albumin. Differences in assay specificity.

Serum albumin is one of the most common parameters used in evaluating nutritional status. Three of the popular methods available for measuring serum albumin are serum protein electrophoresis and the two dye binding methods: BCG and BCP. BCG is currently the most popular method because of its simplicity, rapidity, and cost. Although electrophoretic methods are considered more accurate, BCP has shown to correlate well with electrophoresis in most cases. BCG often overestimates serum albumin levels, although its specificity can be improved by minimizing contact time with the serum sample. The average difference between BCG methods and other methods is usually 0.5-0.6 g/dL. From a quantitative standpoint, some might consider the difference in specificity of BCG versus the other two methods to be insignificant; however, from a qualitative standpoint, the difference could easily alter the interpretation of nutritional assessment parameters. Because of differences in analytical methods, serum albumin measurements should be interpreted in the context of the assay being used and the accepted normal range for that laboratory. Likewise, published studies, especially those that stratify degrees of malnutrition and/or risk of complications based on specific serum albumin levels, should specify the assay methodology utilized.

Blood Protein Electrophoresis↗

PubMed2005

Characterization of membrane vesicles in plant extracts.

During the preparation of plant extracts by a press-slit technique, membranes of cell walls and cell organelles of the plant material form vesicles, which are colloidally dispersed. It was assumed that chlorophyll-containing green extracts enclose lipoidic structures. Vesicles in aqueous mistletoe extracts (extracts of Viscum album L.) were analyzed by cryo-transmission electron microscopy (cryo-TEM) without fixation. For the first time, it was possible to analyze unfixed vesicles in the mistletoe extract. Micrographs of cryo-TEM showed predominantly unilamellar vesicles of different sizes. The quantification of vesicles was established through the analysis of phospholipids, which are major components of membranes. The method was validated mainly according to ICH guidelines for the validation of analytical methods (Q2A and Q2B). For further characterization of the vesicle size, a method was developed which is based on the separation of the vesicles from low molecular weight substances by size exclusion chromatography. Fractions were collected and average sizes were determined by multi-angle laser light scattering (MALLS). Furthermore, the UV-vis absorbance and phospholipid concentration were analyzed. Phospholipid quantification was in agreement with photometrical data. Sizes determined by cryo-TEM and by light scattering showed consistent results.

Cell Fractionation↗

PubMed2003

The measurement of adenosine and estrogen receptor expression in rat brains following ovariectomy using quantitative PCR analysis.

In our laboratory we have developed a quantitative-polymerase chain reaction (Q-PCR) strategy to examine the differential expression of adenosine receptor (ADOR), A(1), A(2A), A(2B) and A(3), and estrogen receptors (ER) alpha and beta. Brain and uterine mRNA were first used to optimise specific amplification conditions prior to SYBR Green I real time analysis of receptor subtype expression. SYBR Green I provided a convenient and sensitive means of examining specific PCR amplification product in real time, and allowed the generation of standard curves from which relative receptor abundance could be determined. Real time Q-PCR analysis was then performed, to examine changes in receptor expression levels in brains of adult female Wistar rats 3-month post ovariectomy. Comparison with sham-operated age-matched control rats demonstrated both comparative and absolute-copy number changes in receptor levels. Evaluation of both analytical methods investigated 18S rRNA as an internal reference for comparative gene expression analysis in the brain. The results of this study revealed preferential repression of ADORA(2A) (>4-fold down) and consistent (>2-fold) down-regulation of ADORA(1), ADORA(3), and ER-beta, following ovariectomy. No change was found in ADORA(2B) or ER-alpha. Analysis of absolute copy number in this study revealed a correlation between receptor expression in response to ovariectomy, and relative receptor subtype abundance in the brain.

Animals↗

PubMed2007

Decolorization of ionic liquids for spectroscopy.

It has been widely recognized that although ionic liquids should be colorless, they are frequently not. Colored samples appear to be pure by most analytical techniques (e.g., NMR spectroscopy, mass spectrometry, HPLC, and ion chromatography), and there have been many attempts to identify the source of color in our own laboratories and others-after 20 years the best that can be said is that the impurities are at a very low level (probably parts per billion) with very high molar extinction coefficients. In this paper, we do not identify these impurities but describe a practical method for removing them for spectrochemical applications. We clearly note that the method is not "green", but we anticipate that it will only be applied to the small volumes of ionic liquids required for fundamental spectroscopic studies in academia but not in industrial processes.

Journal Article↗

PubMed2007

Line FRAP with the confocal laser scanning microscope for diffusion measurements in small regions of 3-D samples.

We present a truly quantitative fluorescence recovery after photobleaching (FRAP) model for use with the confocal laser scanning microscope based on the photobleaching of a long line segment. The line FRAP method is developed to complement the disk FRAP method reported before. Although being more subject to the influence of noise, the line FRAP model has the advantage of a smaller bleach region, thus allowing for faster and more localized measurements of the diffusion coefficient and mobile fraction. The line FRAP model is also very well suited to examine directly the influence of the bleaching power on the effective bleaching resolution. We present the outline of the mathematical derivation, leading to a final analytical expression to calculate the fluorescence recovery. We examine the influence of the confocal aperture and the bleaching power on the measured diffusion coefficient to find the optimal experimental conditions for the line FRAP method. This will be done for R-phycoerythrin and FITC-dextrans of various molecular weights. The ability of the line FRAP method to measure correctly absolute diffusion coefficients in three-dimensional samples will be evaluated as well. Finally we show the application of the method to the simultaneous measurement of free green fluorescent protein diffusion in the cytoplasm and nucleus of living A549 cells.

Algorithms↗

PubMed2002

Quantitative monitoring of the mRNA expression pattern of the TGF-beta-isoforms (beta 1, beta 2, beta 3) during transdifferentiation of hepatic stellate cells using a newly developed real-time SYBR Green PCR.

Current methods to determine the mRNA of the TGF-beta-isoforms, beta 1, beta 2, and beta 3, are not sensitive enough to detect small alterations in the expression levels. Therefore, we established a SYBR Green I-based real-time quantitative PCR procedure with fragment-specific standards. The advantage of gene-specific quantification is the possibility to be abstain from the need to compare results with a house-keeping gene having a different sequence and PCR efficiency. Reproducibility of the results and analytical variances of the real-time PCR assays were tested. In transdifferentiating rat hepatic stellate cells (HSC) the TGF-beta 1-mRNA was found to be the predominant isoform expressed followed by TGF-beta 3 and low amounts of TGF-beta 2-mRNA. An alteration of the TGF-beta 1,-beta 2, and -beta 3 ratio during HSC transdifferentiation could not be detected. Furthermore, the GAPDH mRNA expression varied during HSC activation, and thus is not recommended as a standard in real-time PCR quantifications.

Animals↗

PubMed2000

Comparative analysis of tea catechins and theaflavins by high-performance liquid chromatography and capillary electrophoresis.

This paper describes the simultaneous determination of catechins and theaflavins in green and black teas, using reversed-phase high-performance liquid chromatography (HPLC) and capillary electrophoresis (CE). The tea polyphenols analyzed included (+)-catechin, catechin gallate, (-)-epicatechin, epicatechin-3-gallate, epigallocatechin, epigallocatechin-3-gallate, theaflavin, theaflavin-3-monogallate, theaflavin-3'-monogallate and theaflavin-3,3'-gallate. These polyphenols together with six other tea ingredients such as caffeine, adenine, theophylline, quercetin, gallic acid and caffeic acid were separated within 27 min by HPLC and in less than 10 min by CE. The optimal analytical conditions of both chromatographic methods were investigated for the convenience and reliability for routine analysis. Both HPLC and CE were found to be reliable and compatible. The reproducibility of the within-day assay using both methods was generally >90%. The day-to-day variation of retention time was <5% for HPLC, while the variation of migration time for CE was <2%. The analysis time of CE was three-times faster, however it is five-times less sensitive than HPLC, which has detection limits of 0.05 microg/ml and 0.5 microg/ml for catechins and theaflavins, respectively.

Biflavonoids↗

PubMed1998

Direct measurement of SR release flux by tracking 'Ca2+ spikes' in rat cardiac myocytes.

1. Ca2+ release flux across the sarcoplasmic reticulum (SR) during cardiac excitation-contraction coupling was investigated using a novel fluorescence method. Under whole-cell voltage-clamp conditions, rat ventricular myocytes were dialysed with a high concentration of EGTA (4.0 mM, 150 nM free Ca2+), to minimize the residence time of released Ca2+ in the cytoplasm, and a low-affinity, fast Ca2+ indicator, Oregon Green 488 BAPTA-5N (OG-5N; 1.0 mM, Kd approximately 31 microM), to optimize the detection of localized high [Ca2+] in release site microdomains. Confocal microscopy was employed to resolve intracellular [Ca2+] at high spatial and temporal resolution. 2. Analytical and numerical analyses indicated that, under conditions of high EGTA concentration, the free [Ca2+] change is the sum of two terms: one major term proportional to the SR release flux/Ca2+ influx, and the other reflecting the running integral of the released Ca2+. 3. Indeed, the OG-5N transients in EGTA-containing cells consisted of a prominent spike followed by a small pedestal. The OG-5N spike closely resembled the first derivative (d[Ca2+]/dt) of the conventional Ca2+ transient (with no EGTA), and mimicked the model-derived SR Ca2+ release function reported previously. In SR Ca2+-depleted cells, the OG-5N transient also closely followed the waveform of L-type Ca2+ current (ICa). Using ICa as a known source of Ca2+ influx, SR flux can be calibrated in vivo by a linear extrapolation of the ICa-elicited OG-5N signal. 4. The OG-5N image signal was localized to discrete release sites at the Z-line level of sarcomeres, indicating that the local OG-5N spike arises from 'Ca2+ spikes' at transverse (T) tubule-SR junctions (due to the imbalance between calcium ions entering the cytosol and the buffer molecules). 5. Both peak SR release flux and total amount of released Ca2+ exhibited a bell-shaped voltage dependence. The temporal pattern of SR release also varied with membrane voltage: Ca2+ release was most synchronized and produced maximal peak release flux (4.2 mM s-1) at 0 mV; in contrast, maximal total release occurred at -20 mV (71 versus 61 microM at 0 mV), but the localized release signals were partially asynchronous. Since the maximal conventional [Ca2+] transient and contraction were elicited at 0 mV, it appears that not only the amount of Ca2+ released, but also the synchronization among release sites affects the whole-cell Ca2+ transient and the Ca2+-myofilament interaction.

Algorithms↗

PubMed2001

Development of a Monte Carlo track structure code for low-energy protons in water.

PURPOSE: The development of a new generation of Monte Carlo track structure code is described, which simulates full slowing down of low-energy proton history tracks (lephist) in the range 1 keV-1 MeV in water. MATERIAL AND METHODS: All primary protons are followed down to 1 keV and all electrons to 1 eV. All primary interactions, including elastic scattering, ionization, excitation and charge exchange processes by protons and neutral hydrogen were taken into account. Cross-sections for proton and hydrogen impact were obtained from experimental data for water. Where data were lacking, the existing experimental data were fitted and extrapolated. The tracks of secondary electrons were generated using the electron track code kurbuc. The cross-sections and the energy transfer data were individually evaluated for the principal interactions induced by protons and hydrogen atoms in water. The analysis starts with the published cross-section data for water using a semi-empirical model including contributions from the neutral hydrogen atoms. For excitation cross-sections, the original Miller-Green analytical formula was used. For ionization by neutral hydrogen atoms, the same energy spectrum was assumed for secondary electrons as for protons. The total cross-sections were taken from the experiment of Blorizadeh and Rudd (1986b, c). For the stripping of charge by neutral hydrogen the data of Toburen et al. (1968) were used. RESULTS: Data are presented on total and differential elastic cross-sections as a function of energy and scattering angle respectively; single and double differential cross-sections for secondary electrons ejected by various energy proton impact; total cross-sections due to proton and hydrogen impact on water; stopping power cross-sections; and fraction of stopping power for water for protons as a functions of proton energy. CONCLUSIONS: Tracks were analysed to provide confirmation on the reliability of the code and information on physical quantities, such as range, W, restricted stopping power, radial dose profiles and some microdosimetric parameters. Model calculations show good agreement with the experimental and calculated data.

Algorithms↗

PubMed2004

[Construction of AFLP molecular markers linkage map and localization of green cocoon gene in silkworm (Bombyx mori)].

Based on an improved method of AFLP, AFLP markers were employed for construction of a linkage map and localization of Gc gene used a set of 44 backcross lines( BC1) of silkworm ( Bombyx mori) as a mapping population. In this work, all together 3 956 bands were obtained by 28 pairs of primers and 141.3 bands each primer pair on average. Among them 2 836 bands were in good agreement with the segregation pattern. A total of 1 018 (25.7%) polymorphic AFLP markers were detected. The 693 (68.1%) of polymorphic markers with 1:1 segregation ratio ( P < or = 0.05) were obtained. Furthermore,The analytical model was based on the backcross type and the parameters were set as following: LOD = 3.0, maximum recombination value of 0. 20 and use the command ' group', 'compare', 'try', 'map' and 'ripple' to construct the linkage maps. 407 of the 693 loci were chi2 tested in agreement with 1:1 segregation were divided into 33 linkages by Mapmaker/Exp(Version 3.0), with a total map distance of 3 676.7 cM and a mean distance of 9.1 cM between markers. The morphological gene Gc was located between L-P4T6-107 and L-PT6T4-84 on linkage group 22. In addition, 286 markers were not included in the linkage groups. The efficiency of loci mapping was 58.7%. Among the 33 linkage groups, the morphological marker Gc classically localized on linkage group 15 was relocated on linkage group 22 on the map, suggesting that this molecular linkage group corresponds to linkage group 15 on the linkage map based on morphological characters. All these have laid an important base for the marker assisted breeding of the silkworm.

Animals↗

PubMed2006

Chemical ecology in wheat plant-pest interactions. how the use of modern techniques and a multidisciplinary approach can throw new light on a well-known phenomenon: allelopathy.

A new holistic approach on research into allelopathy was launched in the FATEALLCHEM project. The project was financed by the European Commission in the 5th Framework Programme and involved agronomists, biologists, analytical chemists, organic chemists, environmental chemists, ecotoxicologists, and modelers. Benzoxazinones from wheat (Triticum aestivum L.) were the main group of compounds studied in the project. The project showed that future assessments of an extensive use of allelopathic crops must include the development of validated analytical methods, considerations of relevant concentrations, studies on soil transformation, ecotoxicological studies on individual compounds and mixtures, evaluation on human and mammal toxicity, and joint effect studies on weeds, insects, and pathogens. The project results clearly showed the relevance of optimizing the exploitation of cereal benzoxazinones. Crop rotation is a very traditional practice, which was given less importance for decades but is now regaining its importance in agricultural practice as a means of controlling weed seed banks and soilborne diseases and pests. When using cereals as catch crops and green manure, the allelopathic properties of the cereals could now be much more extensively exploited, choosing varieties with optimal production of benzoxazinones and optimizing the time of sowing in relation to the formation of bioactive metabolites.

Ecology↗

PubMed1999

Health sector reform and the interpretation of policy context.

Health sector reform is on the policy agenda of national governments and international agencies. This paper focuses on the policy process of health sector reform and, more specifically, the policy context. The importance of understanding policy context is emphasised and the elements of policy context are discussed. These are: demographic and epidemiological change; processes of social and economic change; economic and financial policy; politics and the political regime; ideology, public policy and the public sector. The paper then discusses the means for, and methods of, interpretation of the policy context. Particular emphasis is placed on linking policy context with an overall understanding of the policy process, the 'messiness' of policy-making, the interrelationship between the contextual factors, the contextual factors interpreted by policy actors, the use of analytical categories in the policy analysis. The paper concludes on the importance of strengthening policy analysis for effective health sector reform.

Developing Countries↗

PubMed2002

Capillary electrophoretic assay and purification of cylindrospermopsin, a cyanobacterial toxin from Aphanizomenon ovalisporum, by plant test (blue-green Sinapis test).

Toxic cyanobacteria are known to produce cyanotoxins, toxic secondary metabolites. In recent years the cylindrospermopsin (tricyclic guanidinyl hydroxymethyluracil)-producing organisms Aphanizomenon ovalisporum, Cylindrospermopsis raciborskii, and Umezakia natans have been inhabiting polluted fresh waters. Cylindrospermopsin, a potent hepatotoxic cyanotoxin, has been implicated in cases of human poisoning as well. This study describes the isolation and purification of cylindrospermopsin from A. ovalisporum with the help of a slightly modified Blue-Green Sinapis Test, a plant test suitable for determining the cyanotoxin content of chromatographic fractions besides plankton samples. The recent modification, using microtiter plates for the assay, improves the method and reduces the amount of sample needed for the assay. This approach proved that plant growth and metabolism, at least in the case of etiolated Sinapis alba seedlings, are inhibited by cylindrospermopsin. The establishment of capillary electrophoresis of cylindrospermopsin and consideration of the results reported here lead us to the expectation that capillary electrophoresis of cylindrospermopsin may be a powerful and useful analytical method for investigating cyanobacterial blooms for potential cylindrospermopsin content and toxicity. Confirmation of chemical identity of the purified compound is performed by UV spectrophotometry, NMR, and MALDI-TOF.

Alkaloids↗

PubMed2003

New contributions to the field of bead-injection spectroscopy-flow-injection analysis: determination of cobalt.

A bead-injection spectroscopy-flow-injection analysis (BIS-FIA) system with spectrophotometric detection has been developed for the determination of cobalt. A homogeneous bead suspension of Dowex 50 W resin (600 microL) previously loaded with the chromogenic reagent 1-(2-pyridylazo)-2-naphthol (PAN) was injected to fill the flow-cell. Co is injected into the carrier (pyrophosphate, pH 5) and reacts with the immobilized chromogenic reagent to form a green chelate. The analytical signal corresponds to the formation of the Co-PAN complex on the solid surface. At the end of the analysis, the beads are discarded by reversing the flow and instantaneously transported out of the system. The sensor shows both excellent selectivity, which could also be increased with a simple on-line modification to avoid interferences from Ni(II), Zn(II) and Cu(II), and good sensitivity; the detection limit was 19 ng mL(-1), the linear range 50-2000 ng mL(-1) and the RSD (%) 4.16. The method was satisfactorily applied to the determination of Co in waters, pharmaceuticals and alloy steels.

Calibration↗

PubMed2004

Determination of fifteen priority phenolic compounds in environmental samples from Andalusia (Spain) by liquid chromatography-mass spectrometry.

This work describes the optimisation of a method to determinate fifteen phenolic compounds in waters, sediments and biota (green marine algae) by liquid chromatography coupled to mass spectrometry (LC-MS) with atmospheric pressure chemical ionisation (APCI) in the negative mode. The LC separations of the studied compounds and their MS parameters were optimised in order to improve selectivity and sensitivity. Separation was carried out with a C(18) column using methanol and 0.005% acid acetic as mobile phase in gradient mode. The molecular ion was selected for the quantitation in selective ion monitoring (SIM) mode. A solid-phase extraction (SPE) method was applied in order to preconcentrate the target analytes from water samples. However, extraction of the compounds from sediment and biota samples was carried out by liquid-solid extraction with methanol/water after studying the influence of other organic solvents. In addition, a clean-up step by SPE with HLB Oasis cartridges was necessary for sediments and biota. The proposed analytical methodology was validated in the target environmental matrices by the analysis of spiked blank matrix samples. Detection limits were 10-50 ng L(-1) for water, 1-5 microg kg(-1) for sediments and 2.5-5 microg kg(-1) for biota samples. Good recoveries and precision values were obtained for all matrices. This methodology has been successfully applied to the analysis of incurred water, sediment and biota samples from Andalusia (Spain).

Biodiversity↗

PubMed1992

Techniques for obtaining analytical solutions to the multicylinder somatic shunt cable model for passive neurones.

The somatic shunt cable model for neurones is extended to the case in which several equivalent cylinders, not necessarily of the same electrotonic length, emanate from the cell soma. The cable equation is assumed to hold in each cylinder and is solved with sealed end conditions and a lumped soma boundary condition at a common origin. A Green's function (G) is defined, corresponding to the voltage response to an instantaneous current pulse at an arbitrary point along one of the cylinders. An eigenfunction expansion for G is obtained where the coefficients are determined using the calculus of residues and compared with an alternative method of derivation using a modified orthogonality condition. This expansion converges quickly for large time, but, for small time, a more convenient alternative expansion is obtained by Laplace transforms. The voltage response to arbitrary currents injected at arbitrary sites in the dendritic tree (including the soma) may then be expressed as a convolution integral involving G. Illustrative examples are presented for a point charge input.

Animals↗

PubMed2003

Assessing the feasibility of using neural precursor cells and peripheral blood mononuclear cells for detection of bioactive Sindbis virus.

Viruses form a significant class of bio-threat agents. Currently, the only method to determine the bioactivity of viruses in vitro is to measure viral and cellular responses after co-incubation of cells with virus. Our goal is to find biomarkers for classification of agents, establishment of bioactivity, and/or prediction of disease outcomes. To begin development of a cell-based biosensor for detection of bioactive Sindbis virus (SV), our model analyte, we surveyed the outcomes of SV interaction with primary rat neural precursor cells (NPC) and human peripheral blood mononuclear cells (PBMC). Confocal fluorescence analysis of NPC treated with recombinant SV carrying green-fluorescent-protein (SV-GFP) showed that most cells were GFP positive by day 1 post inoculation. 4',6-Diamidino-2-phenylindole dihydrochloride (DAPI) staining of the nucleus showed nuclear condensation and fragmentation, and the percentage of TUNEL positive cells were higher in virus-treated cells than in mock-treated control. Also, there were less BrdU positive cells in virus-treated cells compared to control. Thus, SV infects NPC, decreases cellular proliferation, and induces cell death via apoptosis. PBMC were treated with SV- or UV-inactivated SV. By day 5 post infection, there were fewer adherent cells in SV-treated PBMC compared to UV-inactivated SV treated PBMC. However, the percentage of viable cells remained the same, and virus growth curves showed only clearance of virus. Thus, SV induces detachment of a subpopulation of PBMC while not killing most of the cells. Together, these results indicate that NPC and PBMC respond to bioactive SV inoculation, suggesting potential use as detectors of SV in cell-based biosensor paradigm. These studies also provide the rationale, time-scale, and phenotypic correlates for further studies with gene expression arrays.

Animals↗