Search PubMed⌕ Search

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.

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

At least 91 records · Page 5Linked to original sources
PubMed1992

A rapid, sensitive and economic method for the detection, quantification and confirmation of aflatoxins.

A rapid, sensitive and economic method for the detection, quantification and confirmation of aflatoxins is described. Aflatoxins B1, B2, G1, and G2, are extracted by methanol/water (85 + 15) and partitioned into methylene dichloride. The methylene dichloride solution is cleaned up on a polypropylene column, filled with 0.5 g silica gel 60. The aflatoxins are eluted with chloroform-acetone (90:10) and are detected using bidirectional thin-layer chromatography (TLC) with aluminium silica gel foil. The mean recovery of aflatoxins B1, B2, G1, and G2 in corn samples was 73, 78, 80, and 64%, respectively; the limit of detection was 0.5 micrograms/kg. The results can also be confirmed by derivative formation using trifluoroacetic acid on the TLC plate. The method has been applied to a wide range of foods with good results.

Aflatoxins↗
PubMed1992

Quantification of N-acetyl-L-aspartic acid in urine by isotope dilution gas chromatography-mass spectrometry.

A method for quantification of N-acetyl-L-aspartic acid by isotope dilution gas chromatography-mass spectrometry using 15N-[2H3]acetyl-L-aspartic acid is described. The method is sufficiently sensitive to be used with solvent extraction techniques commonly employed for urinary organic acid analysis. The mean concentration of N-acetyl-L-aspartic acid in 80 normal and abnormal control urine specimens was 19.7 +/- 10.8 mg/g creatinine (12.7 +/- 7.8 mmol/mol creatinine). Seven patients, ages 9 months to 7 years, with Canavan-van Bogaert syndrome had urinary N-acetyl-L-aspartic acid levels from 606 to 4760 mg/g creatinine. The method can also be used with cerebrospinal fluid, in which the concentration of N-acetyl-L-aspartic acid is about one-tenth of that in urine.

Aspartic Acid↗
PubMed1992

Tc-99m-HMDP bone uptake quantification and plasma osteocalcin levels in hemodialysis patients--a preliminary study.

In this preliminary study plasma osteocalcin levels and Tc-99m-HMDP (Technetium 99m hydroxymetylene diphosphonate) bone uptake (BU) were measured in 10 chronic end-stage renal failure patients who were on maintenance hemodialysis. The aim of this study was to determine the correlation between bone uptake and osteocalcin-a sensitive and specific marker of osteoblastic activity. There was a statistically significant increase in both 20 and 180 minute uptake in the patient group (36 +/- 2.7 and 39 +/- 3.6) when compared to the normal volunteers (32 +/- 3.1 and 19 +/- 2.7). Plasma osteocalcin levels were also significantly high (24.5 +/- 5.6 ng/ml) when compared with normal values (6.5 +/- 2.3 ng/ml). The correlations between osteocalcin and 20 and 180 min BU were high (r = 0.62 and 0.72 respectively). In conclusion, our preliminary study suggests that, in hemodialysis patients, Tc-99m-HMDP bone uptake quantification is a sensitive and non-invasive method for showing increased osteoblastic activity.

Adolescent↗
PubMed1978

Early quantification of experimental myocardial infarction with technetium-99m glucoheptonate: scintigraphic and anatomic studies.

Recent advances in understanding of the pathophysiology of myocardial necrosis indicate the need for a noninvasive method that will allow detection and quantification of infarcts in the first few hours after the onset of infarction. Myocardial infarct scintigraphy using technetium-99m glucoheptonate is capable of detecting infarction in dogs and man within 4 to 6 hours of onset. Studies were performed in 45 dogs with acute myocardial infarction: 28 with with an anterior infarct, 5 with an inferior infarct, 6 with an anterior infarct studied after infusion of mannitol and 6 with ligation of the left anterior descending coronary coronary artery and reperfusion of the ischemic area. The dogs were given 20 m Ci of technetium-99m glucoheptonate 1 hour after coronary occlusion, subjected to imaging 5 to 9 hours later and then killed. The experiments revealed that (1) scintigraphic infarct size correlated with infarct weight for anterior (r = 0.85) and inferior (r = 0.88) infarcts; (2) technetium-99m glucoheptonate also concentrated in a rim of myocardium around the infarct that probably represented the ischemic zone; and (3) technetium-99m glucoheptonate uptake by infarcted myocardium could be greatly increased with mannitol and reperfusion.

Animals↗
PubMed1992

Automated, on-line quantification of left ventricular dimensions and function by echocardiography with backscatter imaging and lateral gain compensation.

To provide on-line quantification of left ventricular cavity dimensions and function by echocardiography 60 control subjects and 10 patients with cardiac dysfunction were studied. A novel, ultrasound imaging system was used which was developed to detect and track, in real time, ventricular endocardial blood boundaries based on quantitative assessment of acoustic properties of tissue. In addition, lateral gain compensation, a robust and novel image enhancement procedure, was used to provide instantaneous measurement and display of cavity areas and functional indexes on a beat-by-beat basis within regions of interest drawn around the blood pool cavity. In control subjects, short-axis end-diastolic area averaged 13.1 +/- 3.7 cm2 (SD), end-systolic area 5.9 +/- 2.7 cm2, and fractional area change 55.6 +/- 11.2%. Apical views yielded corresponding values of 23.8 +/- 4.5 cm2, 15.5 +/- 3.4 cm2 and 34.7 +/- 7.8%. Instantaneous peak rate of cavity area change approximated 50 cm2/s in systole and 60 cm2/s in diastole in each view. Serial measurements of area and functional index were reproducible over intervals of 2 to 3 weeks. Patients with dilated ventricles exhibited average apical view area values of 49.1 +/- 6.1 cm2 and 43.1 +/- 4.9 cm2 in diastole and systole with a fractional area change of 12.2 +/- 3.0%. Thus, results with on-line echocardiographic backscatter imaging-assisted automated edge detection are reproducible and capable of delineating cardiac dysfunction conveniently, promptly and serially at the bedside.

Adult↗
PubMed1992

Quantitative ultrasonic imaging: tissue characterization and instantaneous quantification of cardiac function.

Quantitative myocardial tissue characterization is being developed to complement and expand conventional echocardiography by delineating the physical state of myocardium under diverse pathophysiologic conditions. Real-time quantitative integrated backscatter imaging has already been applied to patients with ischemic heart disease, hypertrophic cardiomyopathy, and cardiac allograft rejection in clinical investigations performed in the United States, Europe, and Japan. A recently introduced modification of imaging processing algorithms employed for characterization of tissue facilitates automatic detection of endocardial-blood interfaces and on-line quantification of ventricular size and function. Further progress and anticipated developments in quantitative ultrasonic imaging will undoubtedly augment the clinical applications of tissue characterizations based on myocardial integrated backscatter for improved diagnosis, elucidation of pathophysiology, and assessment of cardiac function.

Animals↗
PubMed1977

Quantification of fetal heart rate variability by magnetocardiography and direct electrocardiography.

A computer method for quantification of fetal heart rate (FHR) variability from fetal magnetocardiography during pregnancy and from direct fetal electrocardiography during labor is presented. It is based on statistical analysis of the QRS interval sequences. Beat-to-beat variation is characterized by a differential index (DI) and long-term variation by an interval index (II). The effect of the sample time on the DI is minimal, and hence the DI can be calculated from rather short samples. The II is more sensitive to FHR trends and should be calculated from longer samples, but between the periodic changes, accelerations, and decelerations. Variable amounts of detection pulses are lost in both methods. The DI is sensitive to the missing intervals; no analysis result should be accepted if the number of lost intervals exceeds 10 per cent. The II is less sensitive to the number of missing intervals. The means and standard deviations of the variability indices for eight fetuses during pregnancy and for five fetuses during labor are presented.

Computers↗
PubMed1992

A transfer membrane method for in situ detection and quantification of trehalase.

A method for the detection and quantification of trehalase activity (EC 3.2.1.28) by immobilization to a membrane support has been developed. Protein samples partly enriched for porcine and Galleria mellonella wax moth larvae trehalase activities were fractionated by polyacrylamide gel electrophoresis, followed by electrophoretic transfer to PVDF membranes, and incubated in a solution containing trehalose (20 mg/ml), glucose oxidase (40 U/ml), phenazine methosulfate (0.06 mg/ml), and nitro blue tetrazolium (0.24 mg/ml) in 20 mM sodium phosphate buffer, pH 6.5. The intensity of the red-colored bands, developed directly on the membrane, was quantified using a computing, laser densitometer and shown to be linearly proportional to the original enzyme activity in extracts determined by liquid assay. The temperature inactivation profile of wax moth trehalase was measured. Alteration of the electrophoresis sample buffer composition further revealed the presence of putative trehalase isoforms in wax moth larval extracts whose relative levels of activity were altered during the course of starvation and infection with Tipula iridescent virus.

Animals↗
PubMed1992

Quantification of peptide aldehyde ligands immobilized for the affinity chromatography of endopeptidases.

A method is described for quantification of aldehyde and aldehyde semicarbazone groups attached to an insoluble matrix. Semicarbazones are converted to aldehydes, and the aldehydes are coupled with 4-phenylazoaniline. The excess reagent is washed off, and the remainder then displaced with salicylaldehyde. The quantity of the phenylazoaniline/salicylaldehyde adduct is determined spectrophotometrically, allowing the calculation of the amount of aldehyde or semicarbazone per unit volume of the matrix. Analyses by the new method show that four matrices offered commercially for this type of immobilization differ greatly in coupling capacity and stability of the conjugate under conditions of affinity chromatography.

Aldehydes↗
PubMed1992

Quantification of gene expression over a wide range by the polymerase chain reaction.

We investigated the usefulness of the polymerase chain reaction (PCR) method for the relative quantification of gene expression using a simultaneously amplified sequence of beta-actin mRNA as an internal control for the target sequence of tax/rex mRNA of human T-cell leukemia virus type I. The PCR product of the internal control was reduced by delaying the addition of the primers for its sequence. The photostimulated luminescence of the bands was measured with a laser image analyzer, and the values were plotted against the cycle number. The cycle differences between the logarithmic phase of the curves for the target sequence and for beta-actin (delta cycle) showed a linear correlation with the initial concentration of the sample. This method is highly sensitive for evaluating gene expression over a wide range.

Actins↗
PubMed1992

Characterization and quantification of diadenosine hexaphosphate in chromaffin cells: granular storage and secretagogue-induced release.

The presence of diadenosine hexaphosphate (Ap6A) in chromaffin cells is described. The characterization of Ap6A has been accomplished by HPLC techniques, using three different elution conditions, rechromatography, and coelution with standards. Treatment with phosphodiesterase from Crotalus durissus produced AMP and adenosine pentaphosphate. The HPLC techniques described allowed the quantification of Ap6A in the picomole range. Chromaffin granules store Ap6A in a quantity of 48.5 +/- 9.7 nmol/mg protein, with a molar ratio ATP/Ap6A of 27. In chromaffin cells the Ap6A value was 1.46 +/- 0.32 nmol/10(6) cells. Diadenosine hexaphosphate was released from chromaffin cells by the action of carbachol and a value of 64 +/- 15 pmol/10(6) cells was obtained, which represents 4-5% of the total cellular content.

Adrenal Medulla↗
PubMed1992

Quantification of cysteine sulfinic acid decarboxylase in male and female rats: effect of adrenalectomy and methionine.

Hepatic cysteine sulfinic acid decarboxylase (EC 4.1.1.29) activity has been reported to decrease in response to both L-methionine (Met) feeding and adrenalectomy in rats. A series of experiments was conducted to (a) determine if CSAD depression was evident in female rats fed a methionine-supplemented diet; and (b) determine if adrenal hormones mediated the response of CSAD to dietary methionine. Cysteine sulfinic acid decarboxylase (CSAD) activity was measured in livers of male and female rats fed a methionine-supplemented diet. In female rat liver, CSAD activity was only 25% of the activity measured in livers of male rats. Hepatic enzyme activity in male rats fed a casein-based basal diet containing 0.6% L-methionine was 2.5-fold higher than activity in male rats fed a methionine-supplemented diet containing 1.35% L-methionine (+Met). Similarly, enzyme activity in livers of female rats fed the basal diet was 1.7-fold higher than in female rats fed a methionine-supplemented diet. CSAD activity in adrenalectomized (ADX) male rats fed the basal diet was depressed (990 +/- 120 nmol/min.g liver) compared to activity in intact controls (2347 +/- 89) and sham controls (2040 +/- 143) fed the basal diet. CSAD activity was further depressed in ADX, intact controls, and sham controls fed +Met. Immunochemical detection and quantification of CSAD protein in rat liver demonstrated that changes in CSAD protein were consistent with the observed decreased enzyme activity in female rats, ADX rats, and rats fed +Met. S-Adenosylmethionine and S-adenosylhomocysteine concentrations tended to increase in livers of rats fed +Met. ADX rats fed +Met had the greatest increase in S-adenosylmethionine and S-adenosylhomocysteine concentrations. The depression in hepatic CSAD observed after feeding +Met to rats does not appear to involve adrenal function.

Adrenalectomy↗
PubMed1975

A column radioassay for the quantification of vitamin B-12.

A rapid and convenient column radioassay for the quantification of vitamin B-12 in clinical specimens has been developed. A mixture of the specimen and radiolabeled B-12 was applied to a column containing immobilized intrinsic factor and allowed to incubate for two hours. A buffer wash then separated bound and free B-12. The average intra- and inter-assay coefficients of variation over the range of interest was about 30 pg/ml in the sample and recovery and parallelism studies gave satisfactory results. The values obtained for clinical specimens by the column procedure correlated well with those obtained by reference method.

Binding Sites↗
PubMed1976

Automatic recognition and quantification of interictal epileptic activity in the human scalp EEG.

An attempt was made at using a small computer to recognize and quantify interictal epileptic activity (spikes and sharp waves) in the human scalp EEG. To perform the automatic recognition, the EEG of each channel is broken down into half-waves. A half-wave is characterized by its duration and its amplitude relative to the background activity. A wave is characterized by the durations and amplitudes of its two component half-waves, by the second derivative at its apex measured relative to the background activity, and by the duration and amplitude of the following half-wave. Particular combinations of these parameters were found to characterize spikes and sharp waves and are used for their recognition and quantification. Specific methods are used for the rejection of spike-like or sharp wave-like wave forms such as eye blinks, muscle potentials and sharp alpha activity and were found to perform with a high level of reliability. Interchannel relationships are thoroughly examined to determine areas of maximal epileptogenicity. Sixteen channels can be analyzed in real time. Results are presented in a simple picture containing localizing and quantitative information. Specific questions regarding the time relationships of spikes in different channels can be asked interactively by the user. The system is of potential use in clinical electroencephalography.

Alpha Rhythm↗
PubMed1979

Electroencephalographic quantification by time domain analysis in normal 7--15-year-old children.

Automatic EEG analysis was performed on 239 apparently healthy school age children. The children were classed in 3 age groups: (1) average age of 7; (2) average age of 11; (3) average age of 15. A time analysis method, comparable to classical visual analysis, permitted quantification of the records. The mean amplitude, frequency and percentage time for alpha and theta rhythms were determined for each subject for fronto-central and centro-occipital derivations bilaterally. Records were performed during periods of rest with eyes open and eyes closed. During hyperventilation, records were taken with eyes closed. The normal ranges of parameters were determined by calculating their means and standard deviations, for each age group under each recording condition. Delta and beta rhythm values were not calculated, because of their rarity in this apparently normal sample. The precision obtained by automatic analysis could not have been obtained by means of classical visual analysis. The present findings suggest that the statistical analysis of well-defined groups of normal and pathological children could be of significant value.

Adolescent↗
PubMed1979

Microprocessor-based EEG spike detection and quantification.

A microprocessor-based system for the detection and quantification of sharp EEG waveforms is described. The hierarchical approach utilises initial transient detection based on computation of a second-derivative measure of curvature, followed by pattern-recognition and artifact-rejection routines based on consideration of specific waveform parameters. Initials results demonstrate an ability to approximate human-analysis results, while providing precise measures of amplitude, duration, and sharpness. The decreasing cost of microprocessors makes multichannel configurations economically feasible.

Analog-Digital Conversion↗
PubMed1992

Production of monoclonal antibodies against the human anaphylatoxin C5a des Arg and their application in the neoepitope-specific sandwich-ELISA for the quantification of C5a des Arg in plasma.

A panel of ten murine monoclonal antibodies (MAbs) was raised against the human anaphylatoxin C5a des Arg. The MAbs were shown to abrogate or significantly inhibit the chemotactic activity in zymosan activated serum. MAb 4A2E10E2 and MAb 3G3C4 were used as capture and detecting antibody, respectively, in a sandwich enzyme-linked immunosorbent assay (ELISA) for the quantification of C5a des Arg. This ELISA was shown to be very sensitive (detection limit 20 pg/ml) and could be applied directly to plasma/serum samples. The lack of interference by plasma components, in particular C5, suggested specificity for an epitope on C5a (des Arg) which is concealed in native C5 and exposed on the activation fragment only, i.e., a 'neoepitope'. The mean C5a des Arg level in EDTA-plasma from 25 healthy individuals assessed at a 1/20 dilution was 11.2 ng/ml (SD 3.4; range 6.4-16.8 ng/ml). The applicability of the assay was investigated in patients treated with haemodialysis using different membranes. Markedly elevated plasma levels of C5a des Arg were found in blood returning from the dialyzer following contact with cuprophane membranes.

Animals↗
PubMed1992

An enzyme-linked immunosorbent assay for the quantification of solubilized CD14 in biological fluids.

A simple and robust two site-binding ELISA for the quantification of solubilized CD14 in human and animal body fluids is described. The principle of the assay depends on the specific binding of sCD14 to two monoclonal antibodies (MEM-18, RoMo-1) recognizing different epitopes of this glycoprotein. The detection limit for sCD14 was 1 ng/ml. The method was used to quantify sCD14 in different biological fluids, giving an intra-assay coefficient of variation and an interassay coefficient of variation of about 9%. The assay was used to measure sCD14 in human serum and plasma and other body fluids in health and disease, and in cell culture supernatants. With the exception of monkeys there was no reactivity with 29 other species screened. In healthy volunteers the sCD14 serum level had a mean value of 3.98 +/- 0.3 micrograms/ml (mean SEM, n = 102).

Antibodies, Monoclonal↗