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 811 records · Page 45Linked to original sources
PubMed1982

A radioimmunoassay method for quantification of alpha-tropomyosin in heart homogenates.

A new, extremely sensitive, solid phase radioimmunoassay has been developed to quantify tropomyosin levels in heart tissue homogenates. Specific antibody was coupled to Sepharose 4B and saturation levels of [125I]tropomyosin bound. Release of radiolabel into the supernatant portion occurred when heart homogenates, authentic tropomyosin or tropomyosin in the presence of homogenate were added to these immunobeads. Quantification of the amount of tropomyosin was based on the level of release effected by standard tropomyosin with and without homogenate. The assay was determined to be highly specific and sensitive for tropomyosin. Picomolar quantities of the protein were readily detectable. Linearity extended well over the range of 5-200 ng tropomyosin in the homogenate. The method can be applied to other proteins for quantification during embryonic development.

Amino Acids↗
PubMed1996

Detection and quantification of protein-losing enteropathy with indium-111 transferrin.

Localisation and quantification of protein loss in protein-losing enteropathy (PLE) is useful in the clinical management of hypoalbuminaemia. Indium-111 transferrin offers the opportunity of combining localisation and quantification using a single agent. Twenty-five studies were performed in 23 patients with suspected PLE: 111In-transferrin was prepared by incubating autologous cell-free plasma with 111In chloride in vitro for 15 min. Protein loss was quantified by comparing whole-body counts recorded with an uncollimated gamma camera at 3 h and 5 or 6 days after injection of 111In-transferrin. Gamma camera imaging performed at 3 and 24 h after injection demonstrated a site of protein loss in 15 studies. Whole-body 111In excretion was abnormally elevated in 13 of these, ranging from 16% to 34% (normal <10%), was not assessed in one and was less than 10% in a patient with carcinoid syndrome. In the ten studies that were negative on imaging, whole-body 111In excretion was normal in nine and elevated at 22% in a further patient with carcinoid syndrome. Overall, the mean whole-body 111In excretion in studies with positive imaging was 21.4% (SD 6.1%) (n=14), significantly higher (P<0.01) than in studies with negative imaging, in which it was 7.5% (SD 6.7%) (n=10). This technique should be useful for the combined approach of localising and quantifying protein loss in PLE.

Adult↗
PubMed1992

A visual field quantification system for the Goldmann Perimeter.

We have developed a visual field quantification system that can accurately quantify the measurement results by the Goldmann Perimeter (GP). This system calculates the plural indexes introduced in published papers. In recent years, several isopter quantification methods have been proposed. In these methods, the isopters are digitized and the data are input into a computer, after which a computer program evaluates the changes in the isopters quantitatively. However, each program is only able to evaluate private indexes. We have developed a system that quantifies data using multiple methods. This system used five methods that have been introduced in published papers. With this system, a physician can analyze GP data with multiple methods and can diagnose diseases accurately. We have already input about 2500 GP recording papers into the computer by this system. We then calculated the plural indexes, and visualized the temporal changes in the perimetry.

Humans↗
PubMed1977

Cytofluorometric quantification of the activity and reaction kinetics of acid phosphatase.

This paper describes how fluorogenic substrates derived from naphthol AS can be used for the microscopic demonstration and cytofluorometric quantification of the activity and reaction kinetics of acid phosphatase in single living cells. A special study has been made of acid naphthol AS-BI phosphatase. However, the method can be extended to other hydrolytic enzymes. The method is sensitive and accurate because: quantification of very low enzyme activity is possible; the reaction kinetics can be evaluated with a good degree of precision inasmuch as the initial reaction velocity is derived over short times; there is an absence of distributional error; and the errors due to extra-cellular diffusion of the hydrolysed substrate, to photodecomposition, and to autofluorescence can be contained within very narrow limits. The procedures for determining enzyme activity and reaction kinetics, and the instrumental characteristics and devices required for carrying out these measurements, are described. Some possible applications are indicated.

Acid Phosphatase↗
PubMed1987

NMR spectrometry. A new method for total stool fat quantification in chronic pancreatitis.

In the present investigation, suitability of nuclear magnetic resonance (NMR) spectrometry for total stool fat quantification in patients with normal or impaired exocrine pancreatic function (chronic pancreatitis) has been analyzed in comparison with a conventional chloroform-methanol extraction technique. Basic temperature-dependence studies of NMR spectrometry (90 degrees/180 degrees radiofrequency pulse sequence) on 21 chloroform-methanol extracted pure total stool lipid standards (weight range: 0.05-1.6 g) revealed significantly (P less than 0.05) improving correlations between NMR signal amplitudes and corresponding weights at increasing temperatures (r = 0.952/40 degrees C, r = 0.965/60 degrees C, r = 0.988/80 degrees C), thus indicating 80 degrees C as optimal temperature for NMR spectrometric total stool fat quantification. In subsequent comparative measurements of lyophilized stool samples, NMR spectrometry (at 80 degrees C) and conventional chloroform-methanol extraction provided significantly (P less than 0.001) correlated results with respect to total fecal fat contents/day of quantitatively collected and homogenized stools in 93 patients with known exocrine pancreatic function (secretin-pancreozymin test), irrespective of whether correlations were determined for all 93 patients (r = 0.983) or separately for patients with normal (N = 45; r = 0.867), moderately reduced (N = 31; r = 0.946), or highly reduced (N = 17; r = 0.992) exocrine pancreatic function and correspondingly increased total fecal fat excretions.

Celiac Disease↗
PubMed2001

Quantification of Constitutive Endothelial and Inducible Nitric Oxide Synthase mRNA by Competitive Reverse Transcription-polymerase Chain Reaction.

Nitric oxide (NO) participates in the general homeostatic control of the vasculature, and it is involved in the process of vascular remodelling. NO in particular inhibits the proliferation of vascular smooth muscle cells and has been shown to possess antiatherogenic properties. Two important molecules control NO synthesis, namely constitutive endothelial (ecNOS) and inducible (iNOS) nitric oxide synthase. To investigate the regulation of the ecNOS and iNOS mRNA expression in various tissues, we describe the design and validation of a reliable and efficient competitive RT-PCR approach for quantification of ecNOS and iNOS mRNA in rat tissue. Prior to reverse transcription, the total RNA was supplemented with internal standard RNA-competitors, which were constructed by a modified site-directed mutagenesis followed by in vitro transcription using T7-polymerase. This technique allows the easy and fast (within a single day) construction of an internal, recombinant RNA-fragment without the use of cloning techniques. Only two additional "linker" primers containing the sequence of T7-promoter, the primers used for the wild type of ecNOS and iNOS mRNA and the primers of a spacer gene are needed. In addition, all steps of the procedure can be streamlined by convenient commercially available kits. We conclude that the described technique is a valid and reliable method for the absolute quantification of small amounts of specific mRNA. </hea

Journal Article↗
PubMed1998

Radiometric quantification of Mycobacterium avium complex.

The purpose of this study was to establish a system that would allow rapid and reliable quantification of Mycobacterium avium complex infection with a method that was as sensitive as counting of colony-forming units but less time-consuming and safer in the laboratory. The radiometric system for quantification of mycobacteria (Bactec, Becton Dickinson, USA) which calculates growth curves, was found to be faster, safer, and as sensitive as the established method of counting colony-forming units, with a low intra-assay variation and a wide assay range. Furthermore, the calculated growth curves provided important additional information about replication characteristics of the mycobacteria.

Carbon Dioxide↗
PubMed1995

Quantification of Coxiella burnetii by polymerase chain reaction (PCR) and a colorimetric microtiter plate hybridization assay (CMHA).

A colorimetric microtiter plate hybridization assay (CMHA) for the quantitative determination of Coxiella burnetii DNA after amplification by externally controlled polymerase chain reaction (PCR) is described. The quantification assay is based on an enzyme linked immunosorbent assay (ELISA) format. Cloned DNA, representing a sequence complementary to an internal part of the diagnostic amplicon, was noncovalently attached to the wells of a microtiter plate. Biotinylated PCR product was hybridized to the immobilized capture probe. Bound product was detected via streptavidin horse-radish peroxidase. The devised nonisotopic technique allows specific, rapid, and convenient quantification of C. burnetii DNA. Additionally, it is compatible with standard laboratory ELISA equipment, making this assay amenable to automation and permitting processing of large sample numbers.

Bacterial Proteins↗
PubMedDate not supplied

Multicenter evaluation of a novel quantification method for rubella and toxoplasmosis antibodies.

Antibody quantification by EIA is possible without a standard curve. Following the so-called alpha method only one test dilution is used, the resulting absorbance is corrected and the IU/ml will be calculated by means of a mathematical formula. This new kind of a single point measurement was evaluated in seven independent laboratories by comparison with commercial EIAs using a standard curve or a titer calibration line. For the quantification of IgG against rubella virus this study comprised 1,480 individual samples and three comparison EIAs. For IgG against Toxoplasma gondii a total of 743 samples was evaluated in two comparison tests. The results obtained by the alpha method show a precision and accuracy more than sufficient for routine testings. Also the technical expenses and reagent costs were reduced. Prerequisites and limitations are discussed against the background of the problem of immune status definition.

Animals↗
PubMed1993

Non-radioactive PCR method for quantification of HIV-infected peripheral blood mononuclear cells in HIV-positive subjects.

A nested PCR method for quantification of HIV-infected peripheral blood mononuclear cells (PBMC) which does not use radioactivity nor plasmids is described. Quantification was achieved by means of limiting dilutions and an ACH2 cell standard. The method was used to study 23 HIV-infected patients. A significant correlation was seen between the stage of HIV disease, as classified by CDC criteria, and the number of infected PBMC. Although the CD4+ cell count also correlated well with the stage of HIV disease, there was only weak correlation between the result obtained by the PCR method and the CD4+ cell count.

Base Sequence↗
PubMed1989

Full threshold versus quantification of defects for visual field testing in glaucoma.

Nineteen glaucoma patients, 17 ocular hypertensives, and 16 normal subjects underwent visual field testing on the Humphrey Field Analyzer using two programs: full threshold (thresholding of all test points with double-crossing technique) and quantification of defects (thresholding only points that deviated more than 6 dB from a presumed normal retinal contour). The purpose of the study was to compare the diagnostic value of information gained by the latter, less time-consuming test with that of the full threshold procedure. The average time requirement per eye was 13 min 11 s for full thresholding and 4 min 22 s for quantification of defects. Of the 104 sets of fields, the diagnosis was at variance in 18. The differences were most often due to shallow defects in otherwise normal fields or shallow defects surrounding deeper scotomas that had been detected by both programs. The shallow defects placed the fields in more advanced diagnostic categories and were all detected with the full threshold technique.

Diagnosis, Computer-Assisted↗
PubMedDate not supplied

NMRES: an artificial intelligence expert system for quantification of cardiac metabolites from 31phosphorus nuclear magnetic resonance spectroscopy.

The application of high-resolution 31Phosphorus Nuclear Magnetic Resonance (31P NMR) Spectroscopy in biology and medicine has provided new insights into biochemical processes and also a unique assessment of metabolites. However, accurate quantification of biological NMR spectra is frequently complicated by: (a) non-Lorentzian form of peak lineshapes, (b) contamination of peak signals by neighboring peaks, (c) presence of broad resonances, (d) low signal-to-noise ratios, and (e) poorly defined sloping baselines. Our objectives were to develop an expert system that captures and formalizes 31P NMR spectroscopists' expert knowledge, and to provide a reliable, efficient, and automated system for the interpretation of biological spectra. The NMR Expert System (NMRES) was written in the C and OPS5 programming languages and implemented on a Unix-based (Ultrix) mainframe system with XWindows bit-map graphics display. Expert knowledge was acquired from NMR spectroscopists and represented as production rules in the knowledge base. A heuristic weights method was employed to determine the confidence levels of potential peaks. Statistical and numerical methods were used to facilitate processing decisions. NMR spectra obtained from studies of ischemic neonatal and immature hearts were used to assess the performance of the expert system. The expert system performed signal extraction, noise treatment, resonance assignment, intracellular pH determination, and metabolite intensity quantitation in about 10 s per 4 KB (kilobyte) spectrum. The peak identification success rate was 98.2%. Peak areas and pH estimated by the expert system compared favorably with those determined by human experts. We conclude that the expert system has provided a framework for reliable and efficient quantification of complex biological 31P NMR spectra.

Artificial Intelligence↗
PubMed1997

Quantification of the presence and activity of specific microorganisms in nature.

Traditional techniques for assessment of microbial numbers and activity generally lack the specificity required for risk assessment following environmental release of genetically engineered microbial inocula. Immunological and molecular-based techniques, such as DNA probing and genetic tagging, were initially used to determine the presence or absence of microorganisms in environmental samples. Increasingly they are being developed for quantification of populations of specific organisms, either indigenous or introduced, in the environment. In addition, they are being used to quantify the activity of particular organisms or groups of organisms, greatly extending the range of techniques available to the microbial ecologist. This article reviews the use of traditional techniques for the quantification of microbial population size and activity and the application of molecular techniques, including DNA probing, genetic marking, use of fluorescent probes, and quantitative PCR, in combination with advanced cell detection techniques such as confocal laser scanning microscopy and flow cytometry.

Bacteria↗
PubMed1990

Preliminary study of quantification of regurgitant volume in mitral regurgitation by color Doppler echocardiography.

A method for quantification of regurgitant volume in mitral regurgitation (MR) was studied. 31 cases of MR were investigated with color Doppler. The reliability of measuring velocity by Doppler and the influence of pressure gradient on MR were assessed and confirmed by experimental device. The results suggested that the best method in quantification of the regurgitant volume was "calibrating method" (r = 0.99; P less than 0.01), the next to the best was "volume method" (r = 0.74; P less than 0.01), whereas the regurgitant volume evaluated by multiplication of area, velocity and time was far from the actual regurgitant volume (r = 0.47; P greater than 0.05). The velocity of blood flow measured by Doppler is closely correlated to results obtained from experiments (r = 0.69; P less than 0.05). We believe that the ratio of back flow area and average area of left atrium calculated by Helmcke's method reflects the severity of the disease to a certain degree, bu there are many problems unsolved, e.g. the determination of the velocity of blood flow by color Doppler is dependent on the degree of brightness of coloration; the brighter the color, the quicker the speed it represents, whereas the darker coloration speaks for slower speed.

Echocardiography, Doppler↗
PubMedDate not supplied

Application of polyacrylamide gel electrophoresis/neutron activation analysis for protein quantification.

A combination of two methods, polyacrylamide gel electrophoresis (PAGE) and neutron activation analysis (NAA), has been applied to solutions containing phosphoproteins for the purpose of protein quantification. The proteins were separated by molecular weight using PAGE, and then the whole gel was activated by neutron bombardment. Densitometric measurements of the developed bands from 32P, taken from autoradiographs of the activated gels, resulted in quantification of the phosphorus, and then the related protein. This PAGE/NAA method was applied to several phosphoprotein-containing materials, including commercial milk products and reference materials, i.e., IAEA A-11, milk powder, and SRM 1845, Cholesterol in Egg Powder.

Caseins↗
PubMedDate not supplied

Science, art, and artifacts: how important is quantification for the practicing physician interpreting myocardial perfusion studies?

Although considerable efforts have been directed toward improving imaging agents and imaging equipment, relatively little attention has been given to factors that optimize image interpretation. Stress myocardial perfusion images are often interpreted by visual inspection alone. This may introduce considerable inter- and intraobserver variability. Importantly, clinical usefulness of myocardial perfusion imaging may not be consistently reproduced in many laboratories using visual analysis. Relative myocardial distribution of imaging agents on either planar or single-photon emission computed tomographic images can be readily quantified and compared with normal data files by computer processing. Quantification of myocardial perfusion images provides a reproducible measure of the extent of perfusion abnormalities and defect reversibility. The extent of perfusion abnormalities has been shown to have prognostic significance. Computer quantification of myocardial perfusion images improves not only the overall diagnostic yield but also enhances reliability, accuracy, confidence, and reproducibility of interpretation.

Coronary Circulation↗
PubMed1997

A method for the quantification of benzodiazepine receptors by using 123I-iomazenil and SPECT with one scan and one blood sampling.

Iodine-123-iomazenil (Iomazenil) is a ligand of central type benzodiazepine receptors for single photon emission computed tomography (SPECT). Previously we reported a simple, table look-up method for quantification of its binding potential (BP) by using two SPECT scans and calibrated standard input function with one blood sampling. This method is based on a two-compartment model (K1: influx rate constant; k2: efflux rate constant; Vd (= K1/k2): the total distribution volume corresponding BP), and requires two SPECT scans for calculating both K1 and Vd values. If the K1 value in the two-compartment model can be assumed to be constant, the radioactivity of one SPECT scan at 180 min after injection can be considered to tabulate as a function of Vd for a given K1 value and a given input function, and a table look-up procedure provides the corresponding Vd value. The purpose of this study was to develop a simple, autoradiographic method for quantification of BP by using one SPECT scan and calibrated standard input function with one blood sampling. SPECT studies were performed on 14 patients. A dynamic SPECT scan was initiated following an intravenous bolus injection of Iomazenil. A static SPECT scan was performed at 180 min after the injection. Frequent blood sampling from the brachial artery was performed on all subjects to determine the arterial input function. Simulation studies revealed that errors in calculated Vd values were around +/-10-15% for varied K1 values. A good correlation was observed between total distribution volume values calculated by three-compartment model analysis and those calculated by the present method (r = 0.90), supporting the validity of this method. The present method is simple and applicable for clinical use, and will be able to provide images of BP.

Adult↗
PubMed1998

Application of a beta microprobe for quantification of regional cerebral blood flow with (15)O-water and PET in rhesus monkeys.

A beta microprobe was successfully applied to monitor arterial input function for quantification of regional cerebral blood flow (rCBF) in the monkey brain with (15)O-water and positron emission tomography (PET). The sensitivity of the probe was approximately 0.83 to 1.67 cps/kBq/ml depending on the studies. A preliminary study was performed to find a suitable use and to evaluate the performance of the system and data analysis procedure. The results showed that dispersion correction of measured input function was unnecessary if microprobes were connected directly to the arterial catheter. Then multiple CBF measurements were done in three monkeys under anesthesia. Identical regions of interest were placed with the aid of magnetic resonance imaging (MRI) of each monkey and rCBF values were estimated. Estimated rCBFs were reproducible for several measurements. The mean CBF value for a pentobarbital anesthetized monkey was 46.0 ml/min/100 g (PaCO2 = 46.3 mmHg). This shows that the use of the beta microprobe for quantification of rCBF with PET was validated. The lack of a need for dispersion correction of observed input function is an advantage with the beta microprobe system because the probes are small enough to be placed near the arterial sampling site.

Animals↗