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At least 271 records · Page 15Linked to original sources
PubMed1985

Liquid scintillation counting of 55Fe applied to air-filter samples.

A simple and rapid method has been improved for determination of low specific activity of 55Fe with a liquid scintillation counter. High counting efficiency was obtained for a sample containing up to 150 mg of iron using mixture of a colorless solution of phosphate iron complex and an emulsifier liquid scintillator. The detection limit was 0.31 Bq (8.4 pCi) per gram iron assuming the counting for 1000 minutes and 95% confidence level. This counting method was applied to determination of 55Fe in air-filter samples.

Air Pollutants↗
PubMed2000

Development of a 5-hydroxytryptamine(2A) receptor binding assay for high throughput screening using 96-well microfilter plates.

A high throughput screening method for the analysis of 5-hydroxytryptamine(2A) (5-HT(2A)) receptor binding parameters has been developed, using 96-well filter plates of the Millipore MultiScreen system in combination with a MicroBeta PLUS microplate scintillation counter. MAFB filter plates (GF/B filter over a Durapore membrane) were used because of the lower nonspecific binding of the radioligand to GF/B filter material than to GF/C filters. Comparing different scintillation cocktails, highest counting efficiency and shortest equilibration time were detected with Betaplatescint, after drying the plates at 50 degrees C for 2 h. Measuring the plates without the plastic underdrain increased the counting efficiency by about 39% as compared with counting the plate with the underdrain intact. Presoaking the wells with 0.5% polyethyleneimine for 2 h reduced the nonspecific binding to the filter material by about 50%. A linear relationship of protein concentration and radioligand binding was established up to a protein concentration of 165 microg of protein/well. In the assays, 70 microg of protein/well was generally used, which has turned out to be favorable with respect to the number of counts obtained. When a higher concentration of protein was used, the period of time needed to aspirate the plate was too long because of obstruction of the filter material. Receptor-radioligand equilibration was reached after about 20 min at concentrations less than 0.05 nM [(3)H]ketanserin-HCl; at higher concentrations it was reached after about 10 min. Saturation analysis of [(3)H]ketanserin-HCl resulted in a mean B(max) of 393 fmol/mg protein and a K(D) of 2.0 nM using rat frontal cortex as a receptor source. Competition experiments with known 5-HT(2A) receptor ligands-DOB-HCl (K(i) = 59 nM), DOET-HCl (K(i) = 137 nM), DOM-HCl (K(i) = 533 nM), DMT (K(i) = 1,985 nM), and TMA-HCl (K(i) = 22,340 nM)-were in accordance with literature values.

Animals↗
PubMedDate not supplied

[Dependence of the 14C label determination efficiency in proteins under certain experimental conditions].

A simple, economical, highly productive and easily reproducible method is suggested for making 14C-labelled preparations of denaturated proteins to determine their radioactivity by the liquid scintillation counter. The advantages of the methods are as follows: it is possible for a short period of time to make a large number of preparations; the counted vessels are not contaminated during the work; scintillation liquid consumption is considerably reduced.

Carbon Radioisotopes↗
PubMed1983

The neutron sensitivity of a Geiger-Müller counter between 0.5 and 8 MeV.

Geiger-Müller counters are often used in mixed-field dosimetry to determine the photon dose fraction. For accurate dose specification, their neutron sensitivities must be known. The pulsed beam time-of-flight method was used to determine the neutron sensitivities of an energy-compensated type ZP1320/PTFE Geiger-Müller counter in the 0.5-8-MeV region. The flux of monoenergetic neutrons from the T(p,n)3He and D(d,n)3He reactions, which were used in these measurements, was determined from time-of-flight spectra with an NE213 scintillation counter of known efficiency.

Calibration↗
PubMed1994

Towards automatic detection of point mutations: use of scintillating microplates in solid-phase minisequencing.

Simplification of molecular genetic techniques is one of the main features of large-scale clinical applications of mutation analysis. The solid-phase minisequencing method, which is based on single-nucleotide primer extension by a DNA polymerase on a solid support, is an easy way of detecting point mutations of previously known locations. Here the procedure was further simplified by the use of microplates made of scintillating plastics, a microplate format scintillation counter and an automatic microplate washer. DNA samples from patients with either a hereditary aspartylglucosaminidase (AGA) gene point mutation or an acquired N-ras gene mutation were analyzed by three different minisequencing detection procedures utilizing tritiated nucleotides. The new counting method with scintillating plates was compared to traditional liquid scintillation counting in scintillation vials or to another microplate format procedure, which requires addition of scintillation liquid. In all three methods, normal individuals, heterozygous carriers of the AGA mutation and homozygous patients could be unequivocally discriminated. The N-ras mutation in leukemic blasts could also be detected with high resolution. The coefficients of variation and reproducibility of the scintillating microplate method were almost identical to those of the traditional liquid scintillation assay, which was used as a reference method. The technical innovations adopted here for performing minisequencing assays reduce significantly the labor required without affecting the quality of the results.

Aspartylglucosylaminase↗
PubMed1991

Histidine decarboxylase measurement in brain by 14CO2 trapping.

A method for measuring histidine decarboxylase (HDC) in crude rat brain homogenates was developed by modification of existing 14CO2-trapping methods. The addition of EDTA to tissue homogenates and assay buffer reduced non-enzymatic decarboxylation, and improved assay sensitivity and reliability. Addition of polyethylene glycol (molecular weight 300, PEG300) to the homogenizing buffer increased enzyme stability, permitting storage of crude homogenates. Studies of time course, tissue dilution and blanks showed that up to 8 mg of tissue could be assayed successfully with a 3.5-hr incubation. S-alpha-Fluoromethylhistidine (FMH) and alpha-hydrazinohistidine, specific inhibitors of HDC, induced concentration-dependent reductions of enzyme activity by up to 90%, whereas inhibitors of other decarboxylases had little or no effect. Kinetic studies of the enzyme in crude homogenates yielded Km and Vmax values similar to those found previously with other HDC methods, although a poor fit was found to a single enzyme model. When determined by the new method, the distribution of HDC in seven regions of the rat brain agreed well with previous results. The method is rapid, simple to perform, and requires no specialized equipment other than a scintillation counter.

Animals↗
PubMed1999

Imaging systems in assay screening.

High-throughput screening laboratories continuously seek higher throughput, lower cost and compound conservation. In an attempt to approach these goals, improvements in traditional detection instruments (e.g. scintillation counters, fluorescence plate readers, luminometers) are being made. A more radical alternative is the use of image-based detection methods, which have the advantage that large numbers of wells can be quantified in a single detection procedure (favouring miniaturization) and that faint luminescence or scintillation assays can be accomplished very rapidly. However, image-based screening is a very new technology and must prove itself before being broadly accepted. In this review, the technology of a commercial instrument for image-based screening (the LEADseeker from Amersham Pharmacia Biotech, Amersham, UK) is described, and its performance summarized with scintillation, luminescence, fluorescence and absorbance signals.

Journal Article↗
PubMed2002

Characterisation of an ultra-miniature counter for microdosimetric measurements in a therapeutic 400 MeV/A carbon beam.

Single event spectra of a clinical carbon beam have been measured by an ultra-miniature tissue-equivalent proportional counter (UMC). In order to cover the energy range of the Bragg peak, the incident energy of the carbon beam was degraded by aluminium plates. Single event spectra for carbon-events incident to the UMC were analysed and selected at several carbon energies using thin scintillation counters. It was found that the dose weighted lineal energy distributions have a doublet peak structure due to incident carbon beam and fragment contributions.

Calibration↗
PubMed1984

Quantification of P-32 removed during leukapheresis by bremsstrahlung counting.

The activity of P-32 removed during leukapheresis of a patient previously administered P-32 for therapy of chronic myelogenous leukemia (CML) was determined. The bremsstrahlung produced by P-32 beta rays in the pheresis bags allowed the quantitation of radioactivity by well counting in a sodium iodide detector and by a gamma camera. Bremsstrahlung counting demonstrated that leukapheresis removes such a small amount of radioactivity that the therapeutic effect of a previously administered P-32 dose was still valid. Bremsstrahlung counting offers advantages to a Nuclear Medicine Department over the conventional use of a liquid scintillation counter to detect P-32 beta rays in that it is simpler and more readily available.

Humans↗
PubMed1987

Lymphocyte proliferation and cytotoxic assays using flat-bed scintillation counting.

Lymphocyte 51Cr release and [3H]thymidine uptake assays were evaluated with respect to measurement of sample radioactivity using the flat-bed scintillation counter. 51Cr lysates were spotted onto a glass fibre filter sheet while [3H]thymidine-labelled cells were filtered onto a similar sheet using a cell harvester. The 96 samples were rapidly processed for counting, without removal of individual sample areas. Either form of preparation showed good linearity of count rate with the quantity of material on the filter. Reproducibility was good; the coefficient of variation for 96 samples being within 5%. The low background and high efficiency of this counter results in increased assay sensitivity and allows considerable economies in materials to be made. A commercial version of the counter has six counting heads permitting a high rate of sample throughput.

Beta Particles↗
PubMed1978

[The influence of gravity on the distribution of fat embolism in the eye (author's transl)].

In human fat embolism we often find different grades of changes in both eyes of a patient. This was experimentally verified in rabbits. The anesthetized animals were held in lateral position so that one eye was continuously higher than the other. Labelled fat was injected intravenously, and then the activity in each eye was measured by a scintillation-counter. By this method a significantly higher rate of fat embolism was found in the upper eye.

Animals↗
PubMed1990

Quantitative autoradiographic imaging using gas-counter technology.

Gas counters based on the multiwire proportional counter (MWPC) and multistep avalanche (MSA) technologies can combine the functions of imaging and quantitation (or assay) of radioactively labelled electrophoretograms and blots. Submillimeter spatial resolutions combined with good quantitation have been achieved for the most common beta-emitting radio labels. The current state of development of this technology is reviewed and assessments of the performance of these devices relative to the more traditional systems (X-ray film and the scintillation counter) presented. Particular attention is paid to the potential of these devices to enhance the productivity of the scanning of blots and the performance of assays.

Animals↗
PubMed1995

Scintillating microtitration plates as platform for determination of [3H]estradiol binding constants for hER-HBD.

A novel approach to direct determination of ligand binding constants for the human estrogen receptor hormone binding domain was developed. Recombinantly produced human receptor in yeast extracts was attached to scintillating microtitration plates. Radioligand binding to receptors was determined in a multi-detector scintillation counter designed for the microtitration plate format. The method was employed in equilibrium binding experiments, in binding competition tests and in determination of kinetic rate constants. The results obtained show that the methodology is valid in comparison to previously published data regarding hormone binding characteristics of estrogen receptors. Furthermore, the methodology offers several advantages over previous binding assays because the scintillating microtitration plates constitute both the binding reaction vial and the scintillant for the detection of bound radioactivity.

Binding Sites↗
PubMed1999

A sub-boiling distillation method for the preparation of low carbon content water from urine samples for tritium measurement by liquid scintillation counting.

A new preparation method was developed for obtaining low carbon content water from urine samples for the measurement of tritium by a liquid scintillation counter. The method uses a simple and convenient subboiling distillation bottle. Many urine samples have been purified by this method and the change of tritium level in a tritium-handling radiation-worker was observed.

Carbon↗
PubMed1986

[Measurement of the 125I and 14C radioactivity in double-labeled blood samples].

A method for detection of 14C and 125I radioactivity in labeled samples with variable quenching using only liquid scintillation counter is described. Precision, sensitivity and reproduction of this method are comparable with those of the previously used ones, but this method is more suitable and adequate for computerisation.

Animals↗