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Results for “Absolute quantification”

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At least 181 records · Page 10Linked to original sources

PubMed1996

On-line laser-photometric monitoring of aerosol deposition in ventilated rabbit lungs.

A photometric technique was developed for on-line measurement of aerosol deposition in isolated, ventilated, and perfused rabbit lungs. A jet nebulizer was used for aerosolization of saline (hygroscopic particles) and di(2-ethylhexyl) sebacate (nonhygroscopic particles). Aerosol concentration (laser photometer, constructed for measurements in rabbit lungs) and flow rate (commercial pneumotachograph) were continuously monitored at the inlet of the tracheal cannula. Computer-assisted data processing allowed the breath-by-breath calculation of inhaled and exhaled aerosol mass, thus providing the deposition fraction. With the use of hygroscopic particles, however, this approach was hampered by the humidity-induced particle growth in the airways, leading to an overestimation of the aerosol concentration in exhaled air. This effect was corrected by an algorithm using a "particle growth factor" derived breath by breath from the photometer signal. To test the reliability of this approach, saline particles carrying technetium-99m label were aerosolized into rabbit lungs with the use of various ventilator settings, and the aerosol deposition was assessed in parallel by photometry and by radioactivity detection over the lung and over a trap in the exhaled-air circuit. Superimposable curves of cumulative aerosol deposition, with changes in kinetics dependent on the ventilator mode, were obtained. For a given ventilator setting, absolute values of the deposition fraction were 0.32 +/- 0.04 (radiotracer quantification) and 0.36 +/- 0.04 (photometry; means +/- SD; n = 4). We conclude that the presented laser-photometric technique allows reliable on-line monitoring of the deposition of both nonhygroscopic and hygroscopic aerosol particles in ventilated lungs.

Aerosols↗

PubMed1978

Vectorcardiographic quantification of infarct size in baboons.

A vectorcardiographic method has been developed for determining the absolute size of myocardial infarcts in baboons resulting from coronary artery ligation. Spatial area (mvolt . msec) and voltage (mvolt) difference-vectors were obtained for 8 animals by measuring the voltage loss and temporal deviation from pre- to post-ligation McFee scalar leads. The difference vectors were then correlated with the absolute infarct volumes, which were derived by histological assessment 10 days after ligation. Absolute lesion sizes ranged from approximately 2 cc to 14 cc, involving 10-30% of ventricular muscle mass. The correlation coefficient, r, for the area deviation index was 0.98 (SEE = +/- 0.24 cc); and for the voltage deviation index, r was 0.92 (SEE = +/- 0.51 cc). These results demonstrate that the severity of infarction can be accurately determined if prepathological vectorcardiograms are available.

Animals↗

PubMed1999

Effects of cadmium on metallothionein-I and metallothionein-II mRNA expression in rat ventral, lateral, and dorsal prostatic lobes: quantification by competitive RT-PCR.

Highly sensitive, sequence-specific competitive reverse transcriptase-polymerase chain reaction (RT-PCR) protocols were established for the detection and quantification of metallothionein (MT)-I and MT-II messages, in absolute values, in rat tissues. Detection limits for these protocols were in the range of 5 to 10 amol per microgram total RNA. Levels of MT-I and MT-II transcripts in the three major prostatic lobes, kidney, and testis were measured in untreated and cadmium (Cd)-treated rats. The dorsal prostate (DP), lateral prostate (LP), kidney, and testis expressed substantial levels of MT-I and MT-II mRNA while the ventral prostate (VP) had extremely low levels of the transcripts. Cd treatment induced higher levels of MT-I and/or MT-II mRNA expression in all tissues studied with the exception of LP. In the LP, Cd treatment caused reductions of MT-I and MT-II mRNA levels. The Cd-induced levels attained in the VP following Cd exposure were still markedly lower than those found in the kidney, testis, LP, and DP of untreated animals. These findings contradict previous claims that the MT genes in rat VP are unresponsive to Cd activation. The susceptibility of VP to Cd toxicity/carcinogenicity may therefore be explained by low levels of Cd-induced expression rather than lack of induction of MTs.

Animals↗

PubMed1994

Determination of plasma fatty acid composition in neonates by gas chromatography.

Total fatty acids in plasma of neonates have been analysed as their methyl esters by gas chromatography. They were separated on a capillary column coated with a SP-2380 stationary phase. As little as 100 microliters of plasma is used for the analysis. The extraction procedure was performed with dichloromethane-methanol (2:1) and fatty acids were methylated with boron trifluoride-methanol. The quantification of fatty acids is based on an internal standard method. Absolute values (micrograms fatty acid per 100 microliters plasma) are given together with relative values (%). At a signal-to-noise ratio of 3, the detection limits for flame ionisation detection are between 0.08 to 0.51 ng. The high sensitivity and precision permits the effective determination of the fatty acids in neonate plasma.

Arachidonic Acid↗

PubMed1998

Pharmacokinetics of clenbuterol in the ostrich.

The aim of this study was to investigate the pharmacokinetics of clenbuterol in the ostrich as no such data is available. Clenbuterol (2 mg) was given as a single oral dose to nine ostriches. Blood samples were collected over a period of 96 h after administration and urine for a period of 5 d. Plasma and urine samples were frozen at -20 degrees C pending analysis. Clenbuterol was quantified using a gas chromatograph-mass selective detector. The method for quantification of clenbuterol in plasma was validated by analysing spiked quality control samples at different concentrations. The limit of quantification was determined to be 0.75 ng ml-1 with an absolute recovery of more than 80%. The geometric mean maximum plasma clenbuterol concentration was 4.40 ng ml-1 with 3.0 h as the median time for maximum concentration. The plasma elimination half-life was 19.7 h. The clenbuterol concentration was above 0.75 ng ml-1 in plasma for 48 h and above 1.0 ng ml-1 in urine for 5 d. These data can be useful in residue analysis for clenbuterol in ostriches.

Adrenergic beta-Agonists↗

PubMed1998

Quantifying the radiation dosage to individual skeletal lesions treated with samarium-153-EDTMP.

UNLABELLED: Samarium-153ethylenediaminetetramethylenephosphonate (EDTMP) is used in the treatment of painful skeletal lesions. This study attempted to quantify the radiation dosage to individual lesions on both the macroscopic and microscopic level. METHODS: A gamma camera-based quantification technique was adapted and refined for 153Sm. The accuracy of the technique was determined by using a realistic phantom. The activity and volume of lesions as well as normal bone were determined and used to estimate the radiation dosages to these regions. Two patients died of unrelated causes shortly after receiving 153Sm-EDTMP. This made it possible to compare the gamma camera results with direct measurements. It also allowed for autoradiographic examination of the lesions. Finally, the microscopic radiation dosages were estimated. RESULTS: The phantom study indicated that the quantification technique was off, on average, by 4.1% (s.d. = 8.1%). The absolute activity concentration of trabecular bone was found to be approximately 0.22 MBq/g, and that of cortical bone was found to be approximately 0.1 MBq/g, regardless of the dosage administered. The corresponding concentrations for lesions were between 3 and 7 times higher than that of normal bone, with no apparent ceiling. From these results, the macroscopic radiation dosage could be estimated. The dosage to normal bone varied between 0.9 and 3.9 cGy x kg/MBq, and that of the lesions varied between 5.2 and 27.1 cGy x kg/MBq. The autopsy results confirmed that the gamma camera technique was accurate. The autoradiography showed clearly that the activity was associated with the surface of the bone. From these findings, the microscopic radiation dosage distribution was estimated for cortical and trabecular bone as well as osteoblastic lesions. The variation in the microscopic dosage compared to the macroscopic dosage was quite large. Microscopic dosages, when compared to the macroscopic dosages, were as high as 965% and as low as 14.9%. CONCLUSION: The techniques used have been proven to be accurate. The activity in normal bone may be at a ceiling value for all the administered doses, which could explain the small variation. This is not true for the lesions. The large variation in dosages on a microscopic scale, combined with the ceiling in normal bone, may explain the lower than expected toxicity and relatively quick relapse of the patients.

Autoradiography↗

PubMed1994

Cytochrome P-450 levels of immature rat ovaries during early follicular development: quantification, cellular and subcellular distribution, enzymatic activity and response to FSH in vivo and in vitro.

Absolute values of cytochrome P-450 (cyt. P-450) content were determined by dual beam spectrophotometry in mitochondrial and microsomal fractions of granulosa cells and stroma (theca and interstitial cells) obtained from ovaries of immature rats treated with diethylstilbestrol (DES) or with DES and FSH. Cholesterol side-chain cleavage activity and aromatase activity were also measured in relevant cell fractions. The cyt. P-450 content in the granulosa cell mitochondria was significantly increased in FSH-treated animals (cyt.P-450 in nmols/mg protein, mean +/- SE: DES-treated 0.027 +/- 0.00213, N = 9; DES/FSH-treated 0.0668 +/- 0.0120, N = 13, P = 0.014). The increased cyt. P-450 content was associated with an increase in cholesterol side-chain cleavage activity confirming the functional relevance of the spectrophotometric measurements. The increase in cyt. P-450 content in stroma after FSH treatment was not statistically significant but there was a significant increase in cholesterol side-chain cleavage activity. The cholesterol side-chain cleavage activity of intact granulosa cells from secondary follicles of DES-treated rats was significantly stimulated by in vitro exposure to FSH during 2 hr assay incubations. A significant cyt. P-450 content was detected in the microsomal fraction of granulosa cells from DES-treated rats which was not associated with aromatase activity. Granulosa cell microsomal cyt. P-450 content was not significantly altered by in vivo FSH treatment despite a dramatic increase in aromatase activity of such microsomal preparations.

Animals↗

PubMed1993

Normal-phase high-performance liquid chromatographic determination of epristeride, a prostatic steroid 5 alpha-reductase enzyme inhibitor, in human plasma.

An highly sensitive and selective high-performance liquid chromatographic method was developed for the determination of epristeride [17 beta-(N-tert.-butyl carboxamido)-androst-3,5-diene-3-carboxylic acid, SK&F 105657], a potent inhibitor of the prostatic steroid 5 alpha-reductase enzyme, in human plasma samples. Epristeride is currently in development for the treatment of benign prostatic hyperplasia. The analytical method involves isolation of epristeride and the internal standard [17 beta-(N,N-diisopropyl carboxamido) estra-1,3,5 (10)-triene-3-carboxylic acid, SK&F 105419] from plasma by solid-phase extraction prior to chromatographic separation on an aminopropyl silica column, using hexane-methylene chloride-2-propanol-acetic acid as the mobile phase, with subsequent ultraviolet absorption detection. The absolute recovery of epristeride from plasma was 90.2 +/- 2.96. The limit of quantification for epristeride was 2.5 ng/ml. Linear response was observed for concentrations of epristeride ranging from 1 to 500 ng/ml plasma. The assay was sufficiently sensitive, accurate and precise to support pharmacokinetic studies in human subjects.

5-alpha Reductase Inhibitors↗

PubMed1989

Automatic shape quantification of freely suspended red blood cells by isodensity contour tracing and tangent counting.

In several blood diseases, the resting red blood cells show deviations from the normal discoidal shape. This is of great diagnostic importance. Similar shape changes occur if cells are subjected to various physical and chemical treatments. An automatic on-line method is introduced which can quantify the mean shape of such cells, freely suspended and unaltered by the method. With the cells inside a special flow chamber, pictures are taken in the form of optical sections using a CCD camera. The image processing includes digitization, cumulation of regions of interest (ROI), contour determination by two-dimensional histogram and isodensity contour tracing, chain coding and tangent counting. The method determines the mean of the absolute number of tangents per section Ts, a quantitative unique shape factor, which allows quantification of pathological red blood cell shapes and follow-up shape changes in experiments, and makes different experiments quantitatively comparable.

Erythrocyte Count↗

PubMed1996

A comparison of glottal voice source quantification parameters in breathy, normal and pressed phonation of female and male speakers.

This study concerns a comparison of different quantification techniques that have been developed to parameterize a voice source that has been estimated using inverse filtering that applies no flow mask (i.e. absolute flow values are not obtained). The speech material consisted of voices of three different phonation types produced by 5 female and 5 male subjects. Quantification of the voice source was computed using three time-based quotients that were extracted from the glottal flow waveforms, two time-based parameters that were extracted from the flow and its first derivative, one amplitude-domain quotient that was defined using both the flow and its derivative, and one frequency domain parameter that was computed from the flow signal. The results showed that phonation types could be separated from each other most effectively when quantification was based on parameters that were extracted between the instant of the maximal glottal opening and the minimum peak of the flow derivative.

Female↗

PubMed1992

Valid estimation of IL2 secretion by PHA-stimulated T-cell clones absolutely requires the use of anti-CD25 monoclonal antibody to prevent IL2 consumption.

A major problem encountered for quantification of IL2 production by stimulated T cells is its simultaneous consumption by these activated cells. In the present study, 40 T-cell clones (TCC) derived from normal peripheral blood, hyperplastic lymph nodes (LN) or lymph nodes involved by malignant lymphomas, were studied for their ability to produce IL2. When supernatants were generated in the presence of 20% fetal calf serum (FCS), no IL2 could be detected for 22 of the 40 TCC, whereas very low levels were found for the 18 other TCC (mean value 31 pg/ml; range from 10 pg/ml to 114 pg/ml); in contrast, when conditioned media were produced with reduced amounts of FCS (final concentration, 1%) as well as in the presence of an anti-CD25 monoclonal antibody (final concentration, 50 micrograms/ml), all TCC were found to release IL2, and very high quantities of this lymphokine were measured (mean value: 11,387 pg/ml; range, from 250 pg/ml to 37,000 pg/ml). Consequently, inhibition of IL2 consumption by PHA-stimulated TCC seems to be an absolute requirement for estimating the true capacity of T cells to produce this lymphokine.

Animals↗

PubMedDate not supplied

Quantitation of metabolites in NMR spectra from isolated tissues, using 14N spectroscopy and nitrate to determine tissue volume.

Quantification of metabolites is a goal of many biomedical NMR studies. To obtain absolute measurements of metabolite concentrations is often both difficult and time-consuming. In this paper a method for determining metabolite concentrations directly is described and validated. It is applicable to studies of amphibian muscles, and with suitable precautions, to other isolated organs and tissues. The method is based upon using 14N NMR and nitrate-containing solutions to determine what fraction (F) of the sensitive volume of the RF coil is occupied by tissue. As the concentration of nitrate is known it can be used to calibrate other 14N metabolites in the tissue. Moreover, once F is determined, it can be used to calibrate metabolites in spectra from other nuclei e.g., 31P or 31C. All that is required is that a spectrum from a standard for that nucleus is obtained. Thus this method does not require any 'internal' (intrinsic to the tissue) standard, and is extremely quick and simple to use.

Adenosine Triphosphate↗

PubMed1991

Comments on radiation dosimetry and linear energy transfer.

The quantification of the physical effects of ionizing radiation in human tissue is the basis of risk assessment. This quantification results from determination of kerma or absorbed dose. The procedure for the absolute determination of absorbed dose with an ionization chamber is discussed. The biological effects of ionizing radiation are dependent, not only on the absorbed dose but also on a second physical parameter, the linear energy transfer.

Energy Transfer↗

PubMed1992

High-performance liquid chromatographic determination of usnic acid in plasma.

A high-performance liquid chromatographic method for the determination of usnic acid in human plasma using diclofenac sodium as internal standard is described. Plasma proteins were precipitated with methanol. A 250 mm x 4 mm I.D. Nucleosil. C18 (5 microns) column with a mobile phase consisting of methanol-phosphate buffer (pH 7.4) (70:30, v/v) was used. Chromatography was performed at ambient temperature with flow-rate of 1 ml min-1 and ultraviolet detection at 280 nm. Each analysis required no longer than 7 min. Quantification was achieved by measurement of the peak-height ratio and the absolute recovery varied from 93.8 to 97.3%. The limit of quantitation of usnic acid in plasma was 0.25 micrograms ml-1. The intra-day relative standard deviation (R.S.D.) ranged from 1.24 to 4.53% and the inter-day R.S.D. from 2.23 to 8.25% at three different concentrations. The method was applied to the determination of plasma levels of usnic acid after intravenous and oral administration to study its disposition in a healthy male rabbit.

Administration, Oral↗

PubMed1989

Acetylation phenotyping of isoniazid using a simple and accurate high-performance liquid chromatography.

A simple, specific, accurate and reproducible method for the analysis of isoniazid and its major metabolite, N-acetylisoniazid in urine using high-performance liquid chromatography (HPLC) is described. The assay is performed after extraction of isoniazid, N-acetylisoniazid and 5-(4-methylphenyl)-5-phenylhydantoin (internal standard) from urine using a mixture of chloroform:isopropanol (70:30, v/v) and eluted from a 5 microns C-18 reversed phase column at ambient temperature with a mobile phase consisting of 10 mM sodium acetate:methanol:acetonitrile (40:40:20, v/v) containing 10 mM dioctylsulphosuccinate sodium and adjusted to pH 2.9 with sulphuric acid (less than 1 ml), at a flow rate of 1 ml/min with u.v. detection at 266 nm. Quantification was achieved by the measurement of the peak height ratio, and the absolute recoveries ranged from 94 to 99%. Within-day coefficients of variation ranged from 2.81 to 4.54% for isoniazid and from 2.37 to 3.75% for N-acetylisoniazid. Between-day CVs varied from 3.27 to 5.62% and from 2.5 to 4.91% for isoniazid and N-acetylisoniazid, respectively. Preliminary stability tests using a urine sample from a subject showed an increase in mean isoniazid concentration of about 25% after 1 month storage at -20 degrees C. The method was used for acetylation phenotyping of five individuals.

Acetylation↗

PubMed1990

High-performance liquid chromatographic analysis of indomethacin in serum.

A rapid high-performance liquid chromatographic (HPLC) method for quantitative determination of indomethacin in serum is described. The assay was performed after single extraction of indomethacin and itraconazole (internal standard) from serum using diethyl ether and eluted from a 4 micron C-18 reversed-phase column at ambient temperature. The mobile phase consisted of ethanol:water:glacial acetic acid (65:34:1, v/v) pumped isocratically at a flow rate of 1.3 ml/min. The effluent was monitored at 254 nm. Quantification was achieved by the measurement of the peak area ratio, and the absolute recoveries ranged from 94 to 97%. Within-day coefficients of variation (CV) ranged from 2.72 to 5.70% and between-day CV varied from 3.61 to 6.1%. Stability testing indicated that indomethacin is stable for at least 30 days in serum at -20 degrees C. The method was used to study indomethacin pharmacokinetics in rabbits.

Animals↗

PubMed1997

Subnanogram-concentration measurement of buprenorphine in human plasma by electron-capture capillary gas chromatography: application to pharmacokinetics of sublingual buprenorphine.

We describe a sensitive and specific method for the measurement of buprenorphine in human plasma. The method involves a structural analog as an internal calibrator, careful control of pH during sample extraction to maximize drug recovery, and back-extraction into acid followed by reextraction to eliminate endogenous interferences. After evaporation, sample residues are derivatized with heptafluorobutyric anhydride and analyzed by separation on a fused-silica polymethylsiloxane capillary column and electron-capture detection. Calibration curves were linear in the ranges 0.1-2.0 micrograms/L and 2.0-20 micrograms/L, with within-run CVs of 9.7% at 0.1 microgram/L to 5.0% at 20 micrograms/L, and total CVs of 15.9% at 0.1 microgram/L to 6.5% at 10 micrograms/L. The limit of quantification was 0.1 microgram/L. The method was utilized in studies to determine the absolute bioavailability of sublingual doses of 2 mg of buprenorphine in 1 mL of 300 mL/L ethanol and the bioequivalence of sublingual 8-mg tablet and 300 mL/L ethanol solution formulations.

Administration, Sublingual↗

PubMed1992

[Quantification of regional cerebral blood flow using 99mTc-HMPAO SPECT and intravenous 133Xe injection method].

We converted an absolute value of 133Xe-CBF (initial slope index, ISI) to the three dimensional CBF-SPECT using the intravenous 133Xe injection technique and 99mTc-HMPAO SPECT according to the microsphere model (method A), and the three compartment model described by Lassen et al. (method B): [formula: see text] [formula: see text] where f = flow in the region of interest (ROI), fr = flow in the reference region, C = count density of 99mTc-HMPAO SPECT in the ROI, Cr = count density of 99mTc-HMPAO SPECT in the reference region, and alpha = conversion to clearance ratio of HMPAO. We used alpha value of 1.5, and the whole cerebrum as a reference region. Four asymptomatic subjects and 15 patients with ischemic cerebrovascular disease were entered the study. In method A, excellent correlation was seen between ISI and SPECT-CBF in both of the cerebral hemisphere (r = 0.993; p < 0.001, n = 38) and the cerebellar hemisphere (r = 0.901; p < 0.001, n = 38). When back diffusion of HMPAO was corrected by method B, correlation coefficient of SPECT-CBF with ISI was equivalent to that in method A in the cerebrum (r = 0.978; p < 0.001, n = 38), while the correlation coefficient ih the cerebellum was lowered (r = 0.726; p < 0.001, n = 38) although high flow to low flow ratio was increased. Reproducibility of rCBF assessed 1 week apart from the first CBF-SPECT was highly reproducible in all of the brain regions; correlation coefficient ranged from 0.757 to 0.910 with a mean correlation coefficient of 0.834 (n = 11). The slope and intercept of the linear regression line between 2nd rCBF versus 1st CBF were 0.889 (range, 0.791-1.141) and 5.5 (range, -9.1-13.4), respectively. Regional CBF measured by method B was approximately 20% increase from that measured by method A. However, there was no significant difference in the reproducibility of rCBF between the two methods. Our results indicate that rCBF can be simply and noninvasively quantified using 99mTc-HMPAO SPECT and absolute unit of CBF measured by 133Xe injection technique. SPECT-CBF offers high resolution images and may be applicable for various cerebrovascular disorders in routine clinical use.

Adult↗