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 739 records · Page 41Linked to original sources
PubMed1993

Reverse transcription and polymerase chain reaction technique for quantification of mRNA in primary astrocyte cultures.

The reverse transcription and polymerase chain reaction technique (RT-PCR) was assessed for the quantification of changes in mRNA levels from primary astrocyte cultures. The effects of dibutyryl cyclic AMP (dBcAMP) on glial fibrillary acidic protein (GFAP) mRNA and the effects of tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), and lipopolysaccharide (LPS) on interleukin-6 (IL-6) mRNA were examined. Two quantitative PCR methods were used: one involved carrying out the reaction in the exponential phase and the other involved the coamplification of a competitive target sequence. Increased GFAP mRNA in response to chronic dBcAMP treatment and increased IL-6 mRNA in response to TNF-alpha/IL-1 beta were readily detected. Both RT-PCR techniques were found to be suitable for the detection of large as well as smaller (twofold) changes in mRNA levels. The advantages and limitations of RT-PCR for mRNA quantification are discussed.

Animals↗
PubMed2006

Analytical techniques for quantification of amorphous/crystalline phases in pharmaceutical solids.

The existence of different solid-state forms such as polymorphs, solvates, hydrates, and amorphous form in pharmaceutical drug substances and excipients, along with their downstream consequences in drug products and biological systems, is well documented. Out of these solid states, amorphous systems have attracted considerable attention of formulation scientists for their specific advantages, and their presence, either by accident or design is known to incorporate distinct properties in the drug product. Identification of different solid-state forms is crucial to anticipate changes in the performance of the material upon storage and/or handling. Quantitative analysis of physical state is imperative from the viewpoint of both the manufacturing and the regulatory control aimed at assuring safety and efficacy of drug products. Numerous analytical techniques have been reported for the quantification of amorphous/crystalline phase, and implicit in all quantitative options are issues of accuracy, precision, and suitability. These quantitative techniques mainly vary in the properties evaluated, thus yielding divergent values of crystallinity for a given sample. The present review provides a compilation of the theoretical and practical aspects of existing techniques, thereby facilitating the selection of an appropriate technique to accomplish various objectives of quantification of amorphous systems.

Calorimetry↗
PubMed1977

Quantification of lidocaine and several metabolites utilizing chemical-ionization mass spectrometry and stable isotope labeling.

Quantification of the suspected metabolites of lidocaine in humans was carried out using the direct insertion probe and chemicalionization mass spectrometry. Deuterated analogs of the metabolites of lidocaine were added to serial human plasma and urine samples and were used as internal standards following oral administration of 250 mg of lidocaine hydrochloride monohydrate to two male subjects and 202 mg of lidocaine free base to one male subject. The average results after analysis of the 0-24 hr urine samples, before beta-glucuronidase-sulfatase treatment, indicated the presence of seven of the possible metabolites in the following amounts (percent of administered dose based on the free base): lidocaine, 1.95; omega-ethylamino-2,6-dimethylacetanilide, 4.90; omega-amino-2,6-dimethylacetanilide, 0.88; m- and/or p-hydroxylidocaine, 0.73; m- and/or p-hydroxy-omega-ethylamino-2,6-dimethylacetanilide, 0.56; 2,6-dimethylaniline, 0.97; and 4-hydroxy-2,6-dimethylaniline, 63.5. Both N-ethyl- and N,N-diethylglycine were detected in human and Rhesus monkey urine, although quantification was not achieved.

Acetanilides↗
PubMed1994

A rapid HPLC method for the quantification of tyrothricin, menthol, and benzocaine in pharmaceutical formulations.

A rapid, sensitive, and accurate reversed-phase HPLC method has been developed for the analysis and quantification of pharmaceutical formulations containing tyrothricin (1), an antibiotic used in antiseptic buccal compressed tablets for local application. The assay has been carried out under isocratic conditions, using a stationary phase of alumina particles coated with polybutadiene and an alkaline mobile phase (pH = 8.2). No HPLC method was reported for the analysis of 1. So, this new technique is an alternative to the slow and tedious microbiological methods. On the other hand, it allows the simultaneous quantification of 1, benzocaine (2), and menthol (3), an aromatic compound not currently analyzed by liquid chromatography.

Benzocaine↗
PubMed2005

Quantification of angiogenesis induced in rabbit cornea by breast carcinoma of women treated with tamoxifen.

BACKGROUND: The aim of this study was to evaluate the effect of tamoxifen on angiogenesis induced in rabbit cornea by breast carcinoma from post-menopausal women. METHODS: Thirteen post-menopausal women with operable, estrogen receptor-positive breast carcinomas, treated with 20 mg of tamoxifen daily for 30 days prior to undergoing definitive surgery, participated in this study. Twenty-six virgin female New Zealand white rabbits, 3-4 months old, weighing approximately 2.5 kg each, were divided into two groups of 13 animals and received corneal implants of tumor either pre- or post-tamoxifen treatment. After 10 days, the animals were sacrificed, the region of the cornea between the tumor implant and the limbus was removed and quantification of angiogenesis was carried out by evaluating the entire hematoxylin-eosin stained slide, using a 10x objective lens (100x magnification). Student t-test was used in the statistical analysis of the data and statistical significance was established at P < 0.05. RESULTS: Mean microvessel count was 106.8 +/- 5.9 pre-tamoxifen treatment and 54 +/- 5.6 post-treatment. According to Student t-test, there was a significant reduction in mean microvessel density following treatment with tamoxifen (P < 0.001). CONCLUSIONS: Rabbit cornea proved to be an interesting experimental model for the quantification of angiogenesis. Tamoxifen, when administered for 30 days to post-menopausal women with breast cancer, significantly inhibited angiogenesis induced by tumor fragments in rabbit cornea.

Animals↗
PubMed2006

Microwave- and ultrasound-assisted extraction of vanillin and its quantification by high-performance liquid chromatography in Vanilla planifolia.

Microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE) and conventional extraction of vanillin and its quantification by HPLC in pods of Vanilla planifolia is described. A range of nonpolar to polar solvents were used for the extraction of vanillin employing MAE, UAE and conventional methods. Various extraction parameters such as nature of the solvent, solvent volume, time of irradiation, microwave and ultrasound energy inputs were optimized. HPLC was performed on RP ODS column (4.6 mm ID x 250 mm, 5 microm, Waters), a photodiode array detector (Waters 2996) using gradient solvent system of ACN and ortho-phosphoric acid in water (0.001:99.999 v/v) at 25 degrees C. Regression equation revealed a linear relationship (r2 > 0.9998) between the mass of vanillin injected and the peak areas. The detection limit (S/N = 3) and limit of quantification (S/N = 10) were 0.65 and 1.2 microg/g, respectively. Recovery was achieved in the range 98.5-99.6% for vanillin. Maximum yield of vanilla extract (29.81, 29.068 and 14.31% by conventional extraction, MAE and UAE, respectively) was found in a mixture of ethanol/water (40:60 v/v). Dehydrated ethanolic extract showed the highest amount of vanillin (1.8, 1.25 and 0.99% by MAE, conventional extraction and UAE, respectively).

Antimutagenic Agents↗
PubMed2006

Separation and quantification of terpenoids of Boswellia serrata Roxb. extract by planar chromatography techniques (TLC and AMD).

An high-performance TLC (HPTLC) method for the separation of boswellic acids, the active constituents in Boswellia serrata extract, has been developed and TLC of these compounds on silica by automated multiple development (AMD) using solvent gradients was performed. Enhancement of the separation of boswellic acids on HPTLC plates was carried out by AMD chromatography. Densitometric analysis of the developed plate was carried out to quantify the four boswellic acids. 11-Keto-beta-boswellic acid (KBA) and acetyl-11-keto-beta-boswellic acid (AKBA) were quantified by densitometric scanning of the developed plate at 254 nm. beta-Boswellic acid (BA) and acetyl-beta-boswellic acid (ABA) were quantified after derivatization with anisaldehyde sulfuric acid reagent at 560 nm. The AMD system provided a clean separation according to polarity for each of the four groups studied and good results were obtained. The proposed HPTLC method for the simultaneous quantification of the major boswellic acids BA, ABA, KBA, and AKBA was found to be simple, precise, specific, sensitive, and accurate and can be used for routine quality control and for the quantification of these compounds in plant materials. The study of market products revealed significant variations in the content of these pharmacologically active compounds in commercial samples.

Boswellia↗
PubMed2004

Quantification of focal dystonia in pianists using scale analysis.

Focal dystonia in pianists is a task-specific movement disorder that causes loss of pianistic skills and provokes irregularities in playing. So far, no method has been available for objective quantification of the disorder. Eight professional pianists with focal dystonia and eight healthy professional pianists matched by age, gender, and handedness were examined, using a newly developed MIDI-based Scale Analysis as well as the Arm Dystonia Disability Scale (ADDS). Key velocities and timing parameters were analyzed. In 5 pianists with dystonia, follow-up examinations were carried out after treatment with botulinum toxin-A. In affected hands, significantly higher mean standard deviations of timing parameters were seen compared with healthy reference hands. After treatment with botulinum toxin-A, significant improvements in performance parameters were monitored by Scale Analysis. Mean standard deviations of inter-onset intervals correlated with ADDS scores. We conclude that Scale Analysis is an effective and precise tool for quantification of focal dystonia in pianists and provides fine resolution. It is independent of rating methods and allows reliable follow-up examinations during treatment.

Adult↗
PubMed1997

Validity of long-term electromyography in the quantification of tremor.

We previously developed a method of tremor quantification using long-term electromyography registration of antagonistic forearm muscles that is reliable, sensitive, and specific for pathologic tremors. The present study demonstrates that tremor occurrence as measured by this method correlates well with clinical parameters of tremor in idiopathic Parkinson's disease (PD) and essential tremor (ET) (subscores of the Unified Parkinson's Disease Rating Scale for PD, tremor rating according to Bain et al. for ET). We conclude that the method is a valid and objective means of tremor quantification in PD and ET.

Activities of Daily Living↗
PubMed2002

Quantification of myocardial blood flow and blood flow reserve in the presence of arterial dispersion: a simulation study.

Myocardial blood flow (MBF) can be quantified using dynamic T1-weighted MRI of diffusible tracers and a mathematical model of underlying vasculature. Quantification of MBF by means of T1- weighted MRI requires knowledge of the arterial input function (AIF). The AIF can be estimated from the left ventricular (LV) cavity. However, dispersion may occur between the LV and the tissue of interest because of the laminar blood flow profiles, branching of venules, and because of stenosis. To evaluate the influence of dispersion on the results of MBF quantification, a simulation study was performed. The dispersion was described as a convolution of the AIF with an exponential residue function. Synthetic tissue and AIF curves were analyzed and the derived parameters fit to the simulated parameters. The results show that an unaccounted dispersion may result in a systematic underestimation of MBF up to approximately 50%. Underestimation increases with increasing dispersion and with increasing MBF. Assuming equal dispersion at rest and during hyperemia, myocardial perfusion reserve (MPR) estimates are also susceptible to underestimation of approximately 20%. An unaccounted dispersion therefore can lead to systematic underestimation of both blood flow and perfusion reserve.

Computer Simulation↗
PubMed2001

Improved perfusion quantification in FAIR imaging by offset correction.

Perfusion quantification using pulsed arterial spin labeling has been shown to be sensitive to the RF pulse slice profiles. Therefore, in Flow-sensitive Alternating-Inversion Recovery (FAIR) imaging the slice selective (ss) inversion slab is usually three to four times thicker than the imaging slice. However, this reduces perfusion sensitivity due to the increased transit delay of the incoming blood with unperturbed spins. In the present article, the dependence of the magnetization on the RF pulse slice profiles is inspected both theoretically and experimentally. A perfusion quantification model is presented that allows the use of thinner ss inversion slabs by taking into account the offset of RF slice profiles between ss and nonselective inversion slabs. This model was tested in both phantom and human studies. Magn Reson Med 46:193-197, 2001.

Adult↗
PubMed1996

Interpretation of flow encoding and quantification in MRI: time domain versus frequency domain.

The traditional approach to flow effects in MRI is based on the gradient moment expansion. Recently, we have presented an alternative description by using linear response theory: the distortions of the velocity waveform induced by the gradient waveforms were analyzed in the frequency domain on the basis of the transfer function. In the present paper, we perform an analysis of flow encoding and quantification in the time domain, on the basis of the impulse response. The analysis shows that flow encoding should be interpreted as a weighted averaging process. Instantaneous flow encoding is determined by the centroid of the impulse response, but care should be taken regarding the physical meaning of the instant of encoding. The relationship of this approach to the frequency domain and gradient moment expansion approaches is clarified. By way of example, some interesting applications are investigated: asymmetrical phase encoding gradients to minimize misregistration and oscillating read-out gradients for flow quantification. A variety of new applications are expected to derive from the combination of both the time and frequency domains.

Magnetic Resonance Imaging↗
PubMed2004

Semiautomatic segmentation and stenosis quantification of 3D contrast-enhanced MR angiograms of the internal carotid artery.

A technique is presented for the segmentation and quantification of stenosed internal carotid arteries (ICAs) in 3D contrast-enhanced MR angiography (CE-MRA). Segmentation with sub-pixel accuracy of the ICA is achieved via level-set techniques in which the central axis serves as the initialization. The central axis is determined between two user-defined points, and minimal user interaction is required. For quantification, the cross-sectional area is measured in the stenosis and at a reference segment in planes perpendicular to the central axis. The technique was applied to 20 ICAs. The variation in measurements obtained by this method in comparison with manual observations was 8.7%, which is smaller than the interobserver variability among three experts (11.0%).

Algorithms↗
PubMed2005

Quantification of renal perfusion and function on a voxel-by-voxel basis: a feasibility study.

The feasibility of a voxel-by-voxel deconvolution analysis of T(1)-weighted DCE data in the human kidney and its potential for obtaining quantification of perfusion and filtration was investigated. Measurements were performed on 14 normal humans and 1 transplant at 1.5 T using a Turboflash sequence. Signal time-courses were converted to tracer concentrations and deconvolved with an aorta AIF. Parametric maps of relative renal blood flow (rRBF), relative renal volume of distribution (rRVD), relative mean transit time (rMTT), and whole cortex extraction fraction (E) were obtained from the impulse response functions. For the normals average cortical rRBF, rRVD, rMTT, and E were 1.6 mL/min/mL (SD 0.8), 0.4 mL/mL (SD 0.1), 17s (SD 7), and 22.6% (SD 6.1), respectively. A gradual voxelwise rRBF increase is found from the center of two infarction zones toward the edges. Voxel IRFs showed more detail on the nefron substructure than ROI IRFs. In conclusion, quantitative voxelwise perfusion mapping based on deconvolved T(1)-DCE renal data is feasible, but absolute quantification requires inflow correction. rRBF maps and quantitative values are sufficiently sensitive to detect perfusion abnormality in pathologic areas, but further research is necessary to separate perfusion from extraction and to characterize the different compartments of the nephron on the (sub)voxel level.

Algorithms↗
PubMed2006

Quantification of vitamin C in the rat brain in vivo using short echo-time 1H MRS.

Both ultrashort echo-time STEAM and MEGA-PRESS-edited spectroscopy were used to validate noninvasive quantification of vitamin C (ascorbate) in the developing rat brain, where changes in ascorbate concentration have been reported. Despite strong overlap with resonances from glutamine, glutamate, glutathione, and macromolecules, reliable quantification of ascorbate (Cramer-Rao lower bounds<0.2 micromol/g) by LCModel analysis of STEAM (TE=2 ms) spectra was possible at 9.4 T. Ascorbate concentrations quantified from the STEAM spectra were in very good agreement with concentrations calculated from fully resolved ascorbate resonances in MEGA-PRESS-edited spectra measured from identical volumes of interest. Ascorbate concentrations measured using STEAM decreased with increasing postnatal rat age, in agreement with published brain ascorbate concentrations measured in vitro using high-performance liquid chromatography (HPLC).

Aging↗
PubMed2007

Effect of signal-to-noise ratio and spectral linewidth on metabolite quantification at 4 T.

The accuracy and precision of measurements of metabolite concentrations from short echo-time spectra has previously been characterized at l.5 T as a function of signal-to-noise ratio (SNR) and peak linewidth. The purpose of this study was to characterize the systematic error in quantification of metabolite concentrations associated with linewidth and SNR for the major metabolites of interest in the short echo-time 1H-MR spectrum at 4 T. Simulated 4 T LASER localized spectra (TE = 46 ms) were generated with full width at half maximum (FWHM) over the range 4-14 Hz, and SNR over the range 5-500 by adding 100 Gaussian-distributed noise realizations at each combination of SNR and linewidth. Linewidth and SNR were treated as independent parameters, and therefore an increase in linewidth at a constant SNR resulted in increased metabolite areas. All spectra were fitted in the time domain using identical prior-knowledge and relative parameter starting values. Six metabolites (N-acetylaspartate, glutamate, creatine, myo-inositol, glycerophosphocholine, phosphocholine) were quantified with >90% accuracy and <10% standard deviation at SNR = 10 for linewidths ranging from 8 to 14 Hz FWHM. These simulations did not consider additional sources of variation, including eddy current artifacts, incomplete macromolecule baseline removal, and incomplete water suppression. Regardless, the results show that metabolite quantification from 4 T short echo-time 1H-MRS is sensitive to SNR and linewidth.

Aspartic Acid↗
PubMed1991

Quantification of glutamate, glutamine, and other metabolites in in vivo proton NMR spectroscopy.

A reliable quantification of in vivo 1H MRS spectra is hampered by extensive line overlap, by intensity distortions due to the water suppressing pulse sequence and complex modulation patterns of J-coupled spins, and by deviations between the experimental and model lineshapes in computer fitting programs. By correcting the experimental lineshape, using a suitable pulse sequence, and incorporating prior knowledge about the spin systems and the intensity distortions, a sufficient quantification is possible. If reliable T2 values are available absolute concentrations can be determined.

Animals↗
PubMedDate not supplied

Absolute quantification and NMR visibility of glycogen in the isolated, perfused rat heart using 13C NMR spectroscopy.

NMR spectroscopy, possibly, does not detect 100% of large molecules such as glycogen (mol.wt = 10(7)-10(9)). Using both NMR and chemical quantification methods, we have, therefore, determined the NMR visibility of cardiac glycogen (defined as the ratio of the NMR value to the chemical value, expressed as a percentage) in the isolated, perfused heart. Rats (n = 7) were pretreated for 60 min with 0.2 mg/kg isoproterenol (s.c.) to deplete their endogenous myocardial glycogen stores (mainly 12C). The hearts were then aerobically perfused (65 cm H2O, at 37 degrees C) in a double-walled chamber (the annulus contained a standard), for 70 min with Krebs buffer plus 3.5 mM [13C]1-glucose and 5 mM sodium acetate (natural abundance). From 70 to 175 min the sole substrate was natural abundance acetate (5 mM). 13C NMR spectra for glycogen quantification were acquired in two different ways; by applying 896, 90 degree pulses at 0.33 s intervals with 1H decoupling ('fast', practical spectra) and by applying 896, 90 degree pulses at 5 s intervals ('slow', impractical spectra). Hearts were then removed from the magnet, freeze-clamped (-196 degrees C) and analysed chemically. Cardiac glycogen, quantified from the 'fast' spectra (using conversion factors) and the 'slow' spectra was 16.8 +/- 1.1 and 16.1 +/- 1.8 (mean +/- SEM) mumol glucosyl units/heart, respectively. After correction of the chemical value for the residual [12C]glycogen (determined from 1H NMR spectra of the extracted glycogen after hydrolysis), the NMR-visibilities were calculated to be 101 +/- 6 and 109 +/- 7%, for the 'fast' and 'slow' spectra, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗