SEARCH · Search PubMed

Results for “quantification”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 235 records · Page 13Linked to original sources

PubMed1988

Improved high-performance liquid chromatographic assay for the quantification of 5-bromo-2'-deoxyuridine and 5-bromouracil in plasma.

A sensitive and specific procedure using high-performance liquid chromatography (HPLC) was developed for the quantification of 5-bromo-2'-deoxyuridine (BUdR) and 5-bromouracil (BU) in plasma. BUdR and BU were first extracted with a mixture of ethyl acetate and 2-propanol from plasma presaturated with solid ammonium sulfate. Following evaporation of the organic extract, the remaining residue was reconstituted in saturated ammonium sulfate solution, washed with a mixture of n-pentane-methylene chloride and re-extracted with the original solvent mixture. The organic extract was evaporated, reconstituted in mobile phase and chromatographed on a regular-bore ODS HPLC column using ultraviolet absorbance detection. The BUdR and BU quantification limits were both 0.1 microM, the mean intra-assay coefficients of variation were 5.0 and 5.6%, respectively, and the mean inter-assay coefficients of variation were 5.4 and 10.7%, respectively. This method was used to determine steady-state femoral arterial and hepatic venous plasma concentrations of BUdR and BU in a patient receiving a continuous intravenous infusion of BUdR (20 mg/kg per day).

Aged↗

PubMed1986

Plasma quantification of quazepam and its 2-oxo and N-desmethyl metabolites by capillary gas chromatography.

The authors have developed a gas chromatographic method for the simultaneous quantification of quazepam in plasma and its two main metabolites, 2-oxoquazepam and N-desmethylquazepam. This method involves an extraction from plasma using butyl acetate, and an analysis by electron-capture detection on a CP-Sil 5 WSCOT capillary column. Intra- and inter-day precision and accuracy were better than 10% for each of these three compounds, even near their detection limit estimated at 0.2 ng/ml. Linearity proved satisfactory between 0.2 and 60-70 ng/ml. For endogenous plasma components, adequate specificity was achieved. Despite some inconveniences, a long analysis time, a progressive saturation of the column owing to a low oven temperature, and a relatively short life-span of the CP-Sil 5 columns, this method was the only one available in the literature for the quantification of quazepam and its metabolites from the same plasma sample. It was successfully applied to phase I studies in healthy volunteers.

Anti-Anxiety Agents↗

PubMed1988

Sensitive quantification of pseudoephedrine in human plasma and urine by high-performance liquid chromatography.

An assay for the selective quantification of pseudoephedrine in human plasma and urine was developed using high-performance liquid chromatography with UV detection at 205 nm. Analyte and internal standard were extracted from alkaline plasma or urine into a mixture of n-hexane and diethyl ether, and the organic phase was back-extracted into dilute acid. The chromatographic system comprises microparticulate cyanopropyl-silica as stationary phase and a ternary solvent mixture with ion-pair reagents as mobile phase. Using 0.25 ml plasma, the lower limit of quantification was 25 ng/ml with excellent linearity up to 1000 ng/ml. In urine, the calibration ranged from 2.5 to 100 micrograms/ml. The selectivity of the method was demonstrated for several pharmaceuticals with similar structures. The validated method was applied to a pharmacokinetic study with a single oral dose of 100 mg of pseudoephedrine in two galenic formulations. Precision and accuracy data of the assay and calculated pharmacokinetic parameters are presented.

Adolescent↗

PubMed1989

Capillary gas chromatographic-mass spectrometric method for the identification and quantification of some benzodiazepines and their unconjugated metabolites in plasma.

A gas chromatographic-mass spectrometric method for the identification and/or quantification of diazepam, clobazam, flunitrazepam, triazolam, midazolam, oxazepam and lorazepam and some of their desmethylated and hydroxylated metabolites in plasma is described. Benzodiazepines were extracted from plasma with butyl acetate at pH 9; the hydroxylated compounds were then silylated with N,O-bis (trimethylsilyltrifluoroacetamide). Analysis was performed using a compact mass-selective detector operating in the electron-impact mode. Depending on the concentration, identification was performed either by direct comparison of the observed mass spectra with reference spectra or by the relative intensities of the most intense and characteristic ions in the selected-ion monitoring (SIM) mode. Quantification was performed in the SIM mode using the most intense ion. The intra-assay precision and accuracy were better than 5-6%; linearity was satisfactory up to 1-2 micrograms/ml. The detection limit was 1-5 ng/ml for most of the benzodiazepines. This method can be easily used in clinical situations when a safe and rapid response is essential for patient treatment.

Benzodiazepines↗

PubMed1984

Noninvasive quantification of stenotic semilunar valve areas by Doppler echocardiography.

Fourteen patients, aged 1 month to 13 years, with congenital semilunar valve stenosis (11 pulmonary and 3 aortic) were studied for orifice area quantification calculated from a Doppler echocardiographic equation: Area = SV/0.88 X V2 X VET, where SV = stroke volume, V2 = maximal velocity and VET = ventricular ejection time. Results from individual measurements used in this formula and derived area were compared with individual results from cardiac catheterization and valve area derived from the Gorlin formula. Ventricular ejection time by cardiac catheterization ranged from 0.17 to 0.44 second (mean +/- standard deviation [SD] 0.27 +/- 0.09), and by Doppler study from 0.20 to 0.41 second (mean +/- SD 0.29 +/- 0.06) (r = 0.65, standard error of the estimate [SEE] = 0.03, y = 0.149 + 0.528x). Pressure gradient by catheterization ranged from 30 to 125 mm Hg (mean +/- SD 56.6 +/- 33.1), and by Doppler study from 17.6 to 100 mm Hg (mean +/- SD 46.8 +/- 27.9) (r = 0.91, SEE = 8.8, y = 1.23 + 0.904x). Stroke volume was measured by Doppler study simultaneously with cardiac catheterization in nine patients; results at cardiac catheterization with thermodilution measurements (cardiac output/heart rate) ranged from 5.5 to 53.4 cc (mean +/- SD 24.7 +/- 20), and by Doppler study from 5.8 to 46.9 cc (mean +/- SD 23 +/- 18) (r = 0.96, SEE = 3.5). Area quantification was performed in two ways. In Group 1, heart rate-matched stroke volumes from cardiac catheterization were used in the derived equation for Doppler study (all patients). In Group 2, the stroke volume used was that obtained by Doppler study, which was performed simultaneously with cardiac catheterization (nine patients).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1987

Quantification of 5- and 15-HPETE's by direct chemical ionization mass spectrometry.

This report describes the application of direct chemical ionization mass spectrometry (DCIMS) to the identification and quantification of 5- and 15-HPETEs. A unique feature of the method is use of a polyimide-coated fused silica fiber that allows vaporization of the hydroperoxides, with very low excess energy, into the plume of the chemical ionization reagent gas plasma. Mass spectra are obtained that allow identification of the nonreduced and nonderivatized free acid forms of 5- and 15-HPETE as well as their quantification from 1 microgram to 100 picograms.

Animals↗

PubMed1995

Type II collagen quantification in experimental chondrogenesis.

Type II collagen is an excellent indicator of the cartilage phenotype. Accurate quantification with existing methods requires about 100 micrograms of collagen. We have developed a method which allows for accurate quantification of type II collagen in samples as small as 1 microgram (and sample volumes as little as 1 microliters). Types I and II collagen were pepsin purified, cleaved with cyanogen bromide, and dissolved in sample buffer at concentrations of 0.125-200 micrograms/microliters. Volumes of 1 microliter were analyzed by electrophoresis on microgels. The gels were scanned on a laser densitometer and the ratios of the alpha 1 (II)CB10 to the alpha 1(I)CB7,8 plus alpha 1(II)CB11 determined. The cyanogen bromide-derived (CNBr) peptides could be resolved at concentrations as low as 0.25 microgram/microliter. The ideal working concentration for purified collagens was 1-8 micrograms/microliters. Standard mixtures of both purified and non-purified types I and II collagen were analyzed. At a concentration of 1 microgram/microliter the ratio of the bands referred to above was closely related to the relative proportion of type II collagen, in a polynomial fashion. At 8 micrograms/microliters there was an almost perfect linear relationship. The presence of 15-30% type III collagen had < 5% effect on the measurements of type II collagen. The method is simple, reliable, fast and automated. It should have good potential for application in cartilage research as it permits quantitation of type II collagen in extremely small samples of tissue.

Cartilage, Articular↗

PubMed1995

Isolation and quantification of cholesterol oxides in dairy products by selected ion monitoring mass spectrometry.

A method for isolation, detection and quantification of cholesterol oxidation products based on solid phase extraction in combination with preparative HPLC and gas chromatography-mass spectrometry selected ion monitoring has been developed for dairy products. The isolation procedure had a high recovery and artifact formation was minimal, as shown by isotope labelling. The limits of detection ranged from 0.3 to 35 pg/microliters of the isomeric forms of 7-hydroxycholesterol, 20 alpha-hydroxycholesterol, the isomeric forms of cholesterol-5,6-epoxides, cholestanetriol, 25-hydroxycholesterol and 7-ketocholesterol corresponding to a limit of quantification of 2-6 ng oxysterol/g lipid in the dairy product, depending on the nature of the cholesterol oxidation product.

Cholestanols↗

PubMed2026

From Peaks to Power: Systematic Evaluation of Chromatographic Sampling Reveals Determinants of Quantification and Biological Discovery in DIA Proteomics.

Modern DIA proteomics increasingly emphasizes throughput and depth for large-cohort studies, but methods are often optimized using proxy metrics that can mask losses in quantifiable signal and statistical power. Here, we evaluate how data points per peak and other chromatographic features jointly contribute to quantification and downstream biological discovery. Using a matrix-matched calibration curve dataset, we checked how the number of data points per peak (DPPP) affects the limits of detection and quantification (LOD/LOQ). Reduced DPPP minimally affected LOD but substantially degraded LOQ. Feature modeling and nonparametric association analyses identified precursor peak area as the strongest feature-level predictor of LOQ, whereas DPPP showed weaker and context-dependent effects. Simulations of chromatographic peak integration recapitulated these trends, showing that increased sampling primarily improves integration precision, while quantitative accuracy is strongly governed by peak height and peak shape. Finally, when comparing 20 cancer vs 20 control plasma samples processed with Seer Proteograph, the decrease in DPPP led to a loss of statistical significance for proteins with low-abundance precursors. These findings argue that DIA optimization should prioritize LOQ and statistical power metrics─not identifications alone─by balancing sampling density with chromatographic peak height and quality to maximize useful biological signal.

Proteomics↗

PubMed1978

Quantification of three-dimensional structures.

A mathematical model, based on additive subcomponents of grouping, subitizing and adding, was derived to account for quantification latencies of three-dimensional block arrangements. Subitizing is the process that people use to directly quantify a small number of objects without counting. It was found that most people consistently subitized up to four blocks. With more than four blocks, people resorted to grouping and adding, and the model was able to account for these data. The structural variables of compactness, symmetry, linearity, and planarity were shown to have small effects on quantification latencies relative to the large effect of number of blocks. Of these structural variables, compactness had the largest effect, and in terms of the model, it is suggested that visual structure had its effect on the perceptual grouping subcomponent.

Adolescent↗

PubMed1993

Immunohistochemical distribution and quantification of crystal matrix protein.

The aim of this study was to determine the immunohistochemical distribution and quantification of crystal matrix protein (CMP). CMP, a 31 kDa glycoprotein, is the principal macromolecule found in calcium oxalate crystals generated in human urine, and is a potent inhibitor of crystal aggregation. A polyclonal rabbit anti-human CMP antibody was used to examine renal tissue by immunohistochemical techniques and light microscopy (N = 45). Twenty-five other human organs were similarly assessed. Quantification was performed using a visual analogue scale. CMP was visible as cytoplasmic staining in the epithelial cells of the TALH and the distal convoluted tubule including the macula densa in a subgroup of nephrons. CMP was not identified elsewhere in the urinary tract or in the extrarenal organs examined. Despite a trend indicating that the kidneys of normal men had more CMP than those of normal women, the difference failed to reach significance (P = 0.11). There was, however, more CMP in the stone formers group compared with either normal men (P < 0.01) or normal women (P < 0.01). This protein may be an important determinant of calcium oxalate kidney stone disease.

Aged↗

PubMed1993

Spectrofluorimetric method for the quantification of 7-hydroxycoumarin in urine and plasma using both extracted and unextracted samples.

A sensitive spectrofluorimetric assay has been developed for the determination of 7-hydroxycoumarin (7-OHC) in urine and plasma. Assay systems for urine and plasma were developed and compared with regard to linearity, accuracy, precision, limit of quantification, percentage recovery and assay time. The amount of 7-OHC conjugated to glucuronide and excreted in the urine, was determined following treatment with beta-glucuronidase (5000 U ml(-1);1 U = 16.67 nkat) for 30 min at 37 degrees C. This allows the urinary concentration of free, total and conjugated 7-OHC to be determined. Samples were extracted with diethyl ether and a suitable aliquot of reconstituted extract diluted in 0.1 mol 1(-1) phosphate buffered saline (PBS), pH 10.0 and transferred to a 96 well microtitre plate. The 7-OHC concentration was also determined without prior solvent extraction. Aliquots (20 microl) of urine and plasma samples were transferred to a 96 well microtitre plate and dilutes to 200 microl with PBS, pH 10.0. The fluorescence intensity was determined at excitation and remission wavelengths of 370 and 450 nm, respectively, for both extracted and unextracted samples. Linear ranges of 7-OHC in urine and plasma, using either method, were found to be 0.5-10 and 10-100 micrograms ml(-1). Inter- and intra-day precision studies, using both methods, demonstrated relative standard deviations of below 10% across the linear range. The limit of quantification of 7-OHC in urine and plasma was 0.5 micrograms ml(-1) using both methods. Both methods have been used successfully to determine the concentration of 7-OHC excreted in the urine of patients. The percentage of the dose recovered as 7-OHC over a 24 h period was 92-98%, using unextracted and extracted samples, respectively, with 98% of this recovered as the glucuronide conjugate. The two methods are a significant improvement on a previously described method and provide an alternative to high-performance liquid chromatography.

Buffers↗

PubMed1986

Complete quantification of the total concentration of rat skeletal-muscle Na+ + K+-dependent ATPase by measurements of [3H]ouabain binding.

In the standard [3H]ouabain-binding assay for quantification of the Na,K-ATPase (Na+ + K+-dependent ATPase) concentration in rat skeletal muscles, samples are incubated for 2 X 60 min in 1 microM-[3H]ouabain at 37 degrees C followed by a wash-out for 4 X 30 min at 0 degree C. To obtain accurate determinations, values determined by this standard assay should be corrected for non-specific uptake and retention of [3H]ouabain (11% overestimation), loss of specifically bound [3H]ouabain during wash-out (21% underestimation), evaporation from muscle samples during weighing (4% overestimation), impurity of [3H]ouabain (5% underestimation) and incomplete saturation of [3H]ouabain binding sites (6% underestimation). Thus corrected the standard [3H]ouabain-binding assay determines the total Na,K-ATPase concentration. Hence, in the soleus muscle of 12-week-old rats the total [3H]ouabain-binding-site concentration is 278 +/- 20 pmol/g wet wt. This is at variance with the evaluation of the Na,K-ATPase concentration from Na,K-ATPase activity measurements in muscle membrane fractions, where the recovery of Na,K-ATPase is only 2-18%. Quantification of the total Na,K-ATPase concentration is of particular importance since it is a prerequisite for the discussion of quantitative aspects of the Na,K-ATPase.

Animals↗

PubMed1992

Quantification of apolipoprotein B-48 and B-100 in rat liver endoplasmic reticulum and Golgi fractions.

We have developed a method for measurement of apolipoprotein (apo) B-48 and apo B-100 in blood and subcellular fractions of rat liver based on SDS/PAGE followed by quantitative immunoblotting using 125I-Protein A. Standard curves were prepared in each assay using apo B prepared from total rat lipoproteins by extraction with tetramethylurea. Subcellular fractions (rough and smooth endoplasmic reticulum and Golgi fractions) were prepared from rat liver and separated into membrane and cisternal-content fractions. For quantification, membrane fractions were solubilized in Triton X-100, and the apo B was immunoprecipitated before separation by SDS/PAGE and immunoblotting. Content fractions were concentrated by ultrafiltration and separated by SDS/PAGE without immunoprecipitation. Quantification of apo B in subcellular fractions and detection of apo B by immunoblotting yielded consistent results. In all fractions apo B-48 was the major form, accounting for approximately three-quarters of the total apo B. By using marker enzymes as internal standards, it was calculated that all of the apo B was recovered in the endoplasmic reticulum and Golgi fractions, with approximately 80% of each form of apo B in the endoplasmic reticulum. More than 90% of the apo B of the rough- and smooth-endoplasmic-reticulum fractions was membrane-bound, whereas approx. 33 and 15% of the apo B of the cis-enriched Golgi fractions and trans-enriched Golgi fractions respectively were membrane-bound.

Animals↗

PubMed1995

Quantification of signalling components and amplification in the beta-adrenergic-receptor-adenylate cyclase pathway in isolated adult rat ventricular myocytes.

We have investigated the stoichiometric relationship of proteins involved in beta-adrenergic-receptor-mediated signal transduction in isolated rat cardiac myocytes. These cells contain about 2.1 x 10(5) beta-adrenergic receptors per cell, as determined by radio-ligand-binding assays. We have assessed the amount of Gs alpha present in myocyte membranes by immunoblotting using a purified glutathione S-transferase-Gs alpha fusion protein as a standard for quantification. By this method, we determined that cardiac myocytes contain about 35 x 10(6) and 12 x 10(6) molecules per cell of the 45 and 52 kDa forms of Gs alpha, respectively. [3H]Forskolin binding assays were used to assess the formation of high-affinity forskolin binding sites representing Gs alpha-adenylate cyclase complexes occurring in response to Gs alpha activation. Quantification of the adenylate cyclase complexes was facilitated by the permeabilization of cells with saponin. The addition of isoprenaline (isoproterenol) and guanosine 5'-[gamma-thio]trisphosphate to saponin-permeabilized myocytes results in the formation of 6 x 10(5) Gs alpha-adenylate cyclase complexes. Taken together, the data presented here demonstrate that, in a physiologically relevant setting, G-protein is present in large stoichiometric excess relative to both receptor and effector. In addition, we show that, overall, only modest signal amplification occurs between receptor and adenylate cyclase. Thus adenylate cyclase (rather than Gs) is the component distal to receptor that limits agonist-mediated increases in cyclic AMP production. Although limited data are as yet available for other G-protein-regulated effectors, we hypothesize that the stoichiometry of signalling components and the extent of signal amplification described for the beta-adrenergic response pathway will be applicable to other G-protein-coupled hormone receptor systems.

Adenylyl Cyclases↗

PubMed1977

[Quantification and statistical analysis of ordinal scale type data in psychiatry (author's transl)].

Observational data from psychiatric patients are usually of the ordinal scale type. Therefore, in the traditional one-rating-per-symptom-and-patient-situation, the resulting score values can be analysed only by applying nonparametric statistical methods. These methods are rather inefficient when--as is usual--there are only four-point-scales for evaluating the symptoms. Moreover, non-parametric methods are not available as of yet to take into consideration the often complex structure of data from psychiatric studies. This leads to the conclusion that the quantification of ordinal scale type data would be very desirable in order that parametric statistical methods could be applied. Such a method of quantification is proposed on the basis of the audiovisual psychiatric rating technique. It is shown that the data resulting from the many-ratings-per-symptom-and-patient-situation can be subjected to parametric statistical methods. In applying the proposed method, therefore, much better use could be made of and a maximum of information could be extracted from the data in psychiatric studies.

Humans↗

PubMed1979

[A new method of pericardiocentesis and quantification of pericardial effusions by echocardiography (author's transl)].

With a new method for safe and complete evacuation of pericardial effusions it was possible to check the quantification of pericardial fluid is was possible to check the quantification of pericardial fluid by echocardiography. Using a formula based on the assumption that in systole the pericardial fluid is distributed equally around the contracting heart (like a coat enveloping a sphere), it was demonstrated that pericardial effusions ranging from 250 to 600 ml could be fairly accurately measured. Smaller effusions were not so readily determined. Effusions over 600 ml could be only roughly measured, usually being underestimated.

Echocardiography↗

PubMed1991

[Value of supine thoracic radiography in the diagnosis and quantification of pleural effusions: comparison with sonography].

The purpose of this prospective study was to verify the value of the supine chest radiograph with regard to the recognition and quantification of pleural effusions. The findings of supine chest radiographs were compared to those of chest sonography in a total of 320 pleural cavities. The correct identification and quantification of a pleural effusion was possible by supine chest radiograph alone in only 55% of cases (176/320). In 20% (64/320) supine chest x-ray was falsely negative and in 15% (48/320) falsely positive. In 10% an existing effusion was in fact recognised on supine chest x-ray; however the amount of effusion was wrongly estimated.

Adolescent↗