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Results for “Absolute quantification”

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At least 91 records · Page 5Linked to original sources

PubMed1991

[Quantification of T-lymphocyte subpopulations. Immunological marker in human immunodeficiency virus infections].

The absolute number of CD4+ and CD8+ T cells was counted directly in the blood of 75 healthy controls and 223 individuals infected with human immunodeficiency virus (HIV). The HIV-seropositive individuals were also classified clinically according to the system recommended by the Centers for Disease Control. We observed a pattern of changes in the T cell subset counts of the patient group. This pattern could be defined by five T cell stages ranging from normal T cell subset values to values representing severe T cell immunodeficiency. A close correlation was observed between the immunological and clinical classification of the patients. Quantification of T cell subsets may provide useful information in the follow-up of individuals infected with HIV, particularly in assessing the indications for antiviral therapy, and its effects.

HIV Infections↗

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↗

PubMed1987

[The effect of terguride on the dynamics and mean level of vigilance. A controlled electroencephalographic study with elderly subjects].

The influence of a 3-week medication period with terguride (trans-dihydro-lisuride) in a dosage of 2 X 0.2 mg/d per os upon the 10-min resting EEG of elderly, clinically normal volunteers (mean age 70 years was investigated. Eight subjects received placebo and 7 subjects received terguride under double-blind conditions. The EEG data were analysed, inter alia, by a newly-developed method of quantification which uses information on topographical relationships of the absolute alpha-powers provided by two anterior and two posterior leads. Under terguride, but not under placebo, a significant increase of subvigilant patterns was found. If one were to disregard the baseline situation, which was characterized in the present sample by a distinct restriction of the physiological dynamics of vigilance at a reduced level (dynamic rigidity), this finding would have to be interpreted as sedation. A non-physiological pre-drug situation was indicated by marked and sustained anteriorization of alpha-activity. Taking into account our additional finding that terguride, but not placebo, eliminates this non-physiological alpha-anteriorization, we interpret the increase of subvigilant patterns in the course of the recording period as a resolution of the preexisting dynamic rigidity and, consequently, as a therapeutically desirable effect.

Aged↗

PubMed1992

High pressure liquid chromatographic analysis of the serum concentration of cefuroxime after an intravenous bolus injection of cefuroxime in patients with a coronary artery bypass grafting.

A simple reversed-phase high pressure liquid chromatographic method was developed for the determination of cefuroxime in the serum of patients undergoing coronary artery bypass grafting. The serum was cleaned up with a 3.3% solution of perchloric acid in water. Cefalexine was used as an internal standard. Detection was made by a UV multi-wavelength detector. The optimum wavelength for cefuroxime is 275 nm. The absolute recovery of this method was 90.9%; the limit of quantification was 0.7 mg/l. This analytical method was used in a study to investigate the cefuroxime serum concentration--time curves in 26 patients undergoing coronary artery bypass grafting. It was found that one single dose is sufficient to obtain effective serum concentrations.

Adult↗

PubMed1986

Quantification of cell surface roughness; a method for studying cell mechanical and adhesive properties.

The presence on the surface of nucleated cells of a variety of asperities of different size and shape plays a prominent role in cell-cell and cell-substrate interaction. Also, the organization of these asperities is directly related to cellular cytoskeletal elements. In the present report, we describe a simple and objective method of studying electron micrographs to quantify the roughness of cell contours. Constant-length segments of cell boundaries are compared to reference circular segments with common extremities and enclosing the same area. This procedure was performed with a digitizer connected to a microcomputer, and it was used to analyse model contours or electron micrographs of (i) target tumour cells bound by cytotoxic T lymphocytes and (ii) thymocytes sticking to concanavalin A-coated surfaces. It is shown that this method allows precise quantification of cell deformation in adhesive zones, which may allow absolute evaluation of adhesive stimuli.

Animals↗

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↗

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↗

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↗

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↗

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↗

PubMed1995

Absolute phasic blood flow measurement in the brain using digital subtraction angiography.

RATIONALE AND OBJECTIVES: In this study, an angiographic method using first-pass distribution analysis was used for quantification of phasic volumetric blood flow. Studies were conducted in an angiographic perfusion phantom and in an animal model (rabbit) after intraarterial injection of contrast material. METHODS: Digital subtraction angiography and first-pass distribution algorithm were used to assess the absolute volumetric flow rates. The method, based on the conservation of contrast material in successive angiographic images, uses the videodensitometric information in the arterial bed. Measurements were made by summing the pixel values in the region of interest, covering the whole perfusion bed. A contrast pass curve was generated for a sequence of images to obtain instantaneous volumetric flow rates. RESULTS: Instantaneous and mean absolute volumetric flow measurements made in the angiographic perfusion phantom and the common carotid artery of the animal models correlated well with validation measurements made using ultrasound flowprobes. The measured (M) and known (K) flow rates in the carotid artery were related by M = 0.87 K + 2.50 mL/minute (r = 0.96, standard error of the estimate = 3.79 mL/minute, n = 25) and M = 0.92 K - 1.00 mL/minute (r = 0.98, standard error of the estimate = 4.04 mL/minute, n = 38) using the videodensitometric and entrance vessel calibration techniques, respectively. Conclusion. Results demonstrate the potential use of the first-pass distribution method in conjunction with digital subtraction angiography for measuring phasic arterial blood flow in vivo.

Algorithms↗

PubMed1992

The effect of averaging cardiac Doppler spectrograms on the reduction of their amplitude variability.

The effect of averaging cardiac Doppler spectrograms on the reduction of their amplitude variability was investigated in 30 patients. Beat-to-beat variations in the amplitude of Doppler spectrograms were also analysed. The quantification of amplitude variability was based on the computation of the area under the absolute value of the derivative function of each spectrum composing mean spectrograms. Fast Fourier transform using a Hanning window was used to compute Doppler spectra. Results obtained over systolic and diastolic periods showed that the reduction of amplitude variability followed an exponentially decreasing curve characterised by the equation f (r) = 100 e-beta(r-1), where r is the number of cardiac cycles, beta the exponentially decreasing rate, and 100 the normalised variability for r = 1. In systole, the decreasing rate beta was 0.165, whereas in diastole it was 0.225. Reductions of the variability in systole for a number of cardiac cycles of 5, 10, 15, and 20 were 48, 77, 90 and 96 per cent, respectively. In diastole, reductions of the variability for the same numbers of cardiac cycles were 59, 87, 96 and 99 per cent, respectively. Based on these results, it can be concluded that no significant improvement in the reduction of amplitude variability may be obtained by averaging more than 20 cardiac cycles.

Echocardiography, Doppler↗

PubMed1985

Cytofluorometric quantification of cell-surface antigens by indirect immunofluorescence using monoclonal antibodies.

A method has been developed to determine the absolute number of binding sites on lymphoid cells by flow cytometric analysis of indirect immunofluorescence data after saturation the related monoclonal antibodies (mAbs). First, the cell lines RPMI 8402, MOLT-4, CEM and HSB-2 were studied to determine the number of p67, T cell-associated antigen molecules expressed on their membrane, as judged by the binding of radiolabeled T101 (CD5) mAb. Then saturating doses of unlabeled T101 followed by fluorescent anti-mouse reagent were applied to these cell lines in each new experiment in order to build a standard curve relating the mean fluorescence intensity of these known cell populations to the mean number of cell-bound T101 mAb molecules. This internal standard curve was a straight line, and it was used to assess the absolute number of mAb molecules bound to other lymphoid cells. The technique was shown to be applicable to other mAb of IgG class even if used in unpurified form. These biological standards can be routinely used as internal references to establish the quantitative phenotype of lymphoid cells. The present method is referred to as quantitative indirect immunofluorescence assay (QIIF). It can be used with any flow cytometer equipped with a microcomputer.

Antibodies, Monoclonal↗