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At least 883 records · Page 49Linked to original sources
PubMed1994

Standardization of a micro-cytotoxicity assay for human natural killer cell lytic activity.

Cytotoxicity assays are widely used to evaluate the functional activity of NK and T cells against tumour target cells and the release of radioactive sodium chromate from labelled target cells is still the most commonly used marker of target lysis in culture supernatants. We describe here the standardization of a micro-cytotoxicity test in which the number of cytolytic effector and tumour target cells have been decreased by a factor of 10. The release obtained by 500 tumour target cells was compared with the release obtained by 5000 target cells in the standard cytotoxicity assay for target:effector cell ratios from 1:1 to 1:100. Both gamma and beta emissions of the 51Cr isotope were evaluated to determine the assay release. The results obtained by the micro-cytotoxicity assay (500 target cells) were comparable to those of the standard assay (5000 target cells) and 51Cr release evaluation using the gamma counter was the most sensitive method of determining lytic activity using 500 tumour target cells. beta counter evaluation using solid phase scintillation was found to be a reproducible alternative method, even if the lytic curves cannot be compared with those obtained using the traditional method.

Chromium↗
PubMed2005

A study of the extraction behavior of thallium with tribenzylamine as the extractant.

A simple solvent extraction study for thallium has been conducted based on the extraction of thallium as a chlorocomplex (tetrachlorothallate (III) anion) with tribenzylamine. Radiolabelled Tl (III) was used to study the extraction behavior of thallium. The beta activity of the extracted ion-association complex has been monitored using liquid scintillation counting and Geiger Muller counter. The effect of various diluents such as toluene, chloroform and isobutylmethylketone (MIBK) were studied. The extraction efficiency was 95% when chloroform and MIBK were used as diluents for tribenzylamine at an overall concentration of 0.25 mol dm(-3) NaCl and 0.5 mol dm(-3) H(2)SO(4). The phenomenon of severe chemical quenching was observed with chloroform as the diluent. The recovery of thallium was found to be 95% at varying concentrations ranging from 5 to 20 microg ml(-1) Tl (III) with a relative standard deviation of 2.5%.

Benzylamines↗
PubMedDate not supplied

Software coincidence counting.

A system designed for absolute activity measurement is described using a digital method. The system is based on data recording from a coincidence measurement and subsequent software processing of the data records. The data acquisition device collects amplitudes of individual pulses from analogue-to-digital converters and supplies them with time information. Software processing of data records from this system offers many benefits in comparison to conventional coincidence counting, for example it enables to perform time and pulse height analysis and setting of coincidence parameters by using a wide variety of evaluation methods to one data record. The digital system was tested with a 4pi beta-gamma coincidence detectors arrangement consisting of a proportional counter and two NaI(Tl) scintillation detectors. The results obtained with a 60Co source are presented.

Journal Article↗
PubMed1984

Kinetic differences between fed and starved Chinese hamster ovary cells.

When Chinese hamster (CHO-K1) cells are grown as monolayer cultures, they eventually reach a population-density plateau after which no net increase in cell numbers occurs. The kinetics of aged cells in nutritionally deprived (starved) or density-inhibited (fed) late plateau-phase cultures were studied by four methods: (i) Reproductive integrity and cell viability were monitored daily by clonogenic-cell assay and erythrosin-b dye-exclusion techniques. (ii) Mitotic frequencies of cells from 18 day old cultures were determined during regrowth by analysing time-lapse video microscope records of dividing cells. (iii) Tritiated-thymidine ([3H]TdR) autoradiography was used to determine the fractions of DNA-synthesizing cells in cultures entering plateau phase and during regrowth after harvest. (iv) The rate of labelled nucleoside uptake and incorporation into DNA was measured using liquid scintillation or sodium iodide crystal counters after labelling with [3H]TdR or [125I]UdR. Non-cycling cells in starved cultures accumulate primarily as G1 phase cells. Most cells not in G1 phase had stopped in G2 phase. Very few cells (less than 2%) were found in S phase. In contrast, about half of the cells in periodically fed cultures were found to be in DNA-synthetic phase, and the percentage of these S phase cells fluctuated in a manner reflecting the frequency of medium replacement. Populations of both types of plateau-phase cultures demonstrate extremely coherent cyclic patterns of DNA synthesis upon harvest and reculturing. They retain this high degree of synchrony for more than three generations after the resumption of growth. From these data it is concluded that nutritionally deprived (starved) late plateau-phase cells generally stop in either G1 or G2 phase, whereas periodically fed late plateau-phase cultures contain a very large fraction of cycling cells. Populations of cells from these two types of non-expanding cultures are kinetically dissimilar, and should not be expected to respond to extracellular stimuli in the same manner.

Animals↗
PubMed1983

Total body potassium determination using a whole-body counter.

A scanning bed whole-body counter with two NaI(Tl) scintillation detectors was used for total body potassium determination with 40K for clinical application. For the calibration an in vivo dilution technique with 42K was used. The present counting method effectively minimised effects of redistribution and body build. For routine use the (W/H)1/2 calibration curve is suggested instead of the more complicated individual 42K calibration.

Body Composition↗
PubMed1978

A thin 4 pi beta-counter operating by negative high voltage for the 4 pi beta-gamma coincidence measurement. --Operating characteristics.

A thin 4 pi beta-counter with five anode wires was operated by supplying negative high voltage to the inner wall and showed good plateau characteristics in the case of using only the center anode to take out signals in the previous experiments. This counter, as the 4 pi beta-counter and both 2 pi beta-counters, showed good plateau characteristics in these detailed experiments and no dependency on the disintegration rates examined up to 6000 dps. Then a 4 pi beta-gamma coincidence equipment was set up using this 4 pi beta-counter and one NaI(T1) scintillation detector with size of 76 mmphi x 76 mm. The radioactivities that were measured for beta-gamma and electron capture-gamma decay nuclides by this coincidence equipment were coincided with those measured by the other one. The improvement of the gamma-ray detection efficiency to aim was achieved by that the efficiency obtained by this system was the same as one by the other system having two NaI(T1) detectors with the same size.

Gamma Rays↗
PubMed1999

In-vivo measurement of low energy photon emitters: room-temperature semiconductor diodes vs. large scintillators and germanium crystals.

The in-vivo monitoring of low energy x- and gamma-ray emitters gained importance with the increasing use of these radionuclides in nuclear medicine and nuclear energy production. The main problems encountered are the lack of accuracy in the measurement and the high detection limits obtained with the classical techniques [proportional counters, thin NaI(TI) or phoswich scintillators]. The best technique available today is the array of planar germanium detectors. The purpose of this paper is to analyze specific problems in the assessment of low energy photon emitters in the body and to describe applications of room-temperature diodes (silicon and CdZnTe) using a new technique involving a portable jacket. In certain cases, the device can be used outside a shielded room, making possible an immediate long counting, reducing the psychological stress, and optimizing the medical treatment and the intervention. By considering the attenuation effect, this work shows that an optimized volume of the diodes reduces the detection limits of the counting. The developed methodology offers new possibilities in the assessment of radioactive deposition in the body and in the long term follow-up of the metabolism of radionuclides in small quantities.

Germanium↗
PubMed2004

Neutron field produced by 25 MeV deuteron on thick beryllium for radiobiological study; energy spectrum.

Biological data is necessary for estimation of protection from neutrons, but there is a lack of data on biological effects of neutrons for radiation protection. Radiological study on fast neutrons has been done at the National Institute of Radiological Sciences. An intense neutron source has been produced by 25 MeV deuterons on a thick beryllium target. The neutron energy spectrum, which is essential for neutron energy deposition calculation, was measured from thermal to maximum energy range by using an organic liquid scintillator and multi-sphere moderated 3He proportional counters. The spectrum of the gamma rays accompanying the neutron beam was measured simultaneously with the neutron spectrum using the organic liquid scintillator. The transmission by the shield of the spurious neutrons originating from the target was measured to be less than 1% by using the organic liquid scintillator placed behind the collimator. The measured neutron energy spectrum is useful in dose calculations for radiobiology studies.

Beryllium↗
PubMed2001

Factor of merit and minimum detectable activity for 90Sr determinations by gas-flow proportional counting or Cherenkov counting.

The determination of 90Sr in environmental samples can be done by using a gas-flow proportional counter (beta-counting) or a liquid-scintillation spectrometer (Cherenkov counting). In this work, we present the factor of merit (FOM) and the minimum detectable activity (MDA) for both the counters. Quantitative relationships are proposed for FOM and MDA determination.

Journal Article↗
PubMed1993

A rapid method for monitoring of uranium and radium in drinking water.

A time-saving and fairly accurate method for monitoring U and 226Ra in drinking water has been devised, using low-background liquid scintillation spectrometry and pulse-shape analysis. The samples are prepared for counting by evaporating water in a liquid scintillation vial. The residue is dissolved in 1 ml of 0.5 N HCl, and a scintillation cocktail is added. Counting is carried out twice: a few days and a month after the sample preparation using the Quantulus, a liquid scintillation spectrometer equipped with a guard counter and pulse-shape analyser. The counter produces separate alpha and beta spectra which enable calculation of the approximate U and 226Ra contents. These correlate well with the results obtained by radiochemical methods. The measured spectra give valuable information on the nuclide content, e.g. increased U, 226Ra, 210Pb and 210Po activities, and on the 234U: 238U activity ratio in the water. This kind of information is very valuable in deciding on the necessity for time-consuming radiochemical analyses for radiation protection purposes or exploration for U ore deposits. In many cases the results from the Quantulus are sufficient to determine the U and 226Ra levels in drinking water. The lower limits of detection for U and 226Ra are 0.02 and 0.01 Bq/l, respectively, when the counting time is 180 min and the sample volume 38 ml.

Environmental Monitoring↗
PubMed1979

Radionuclide computerized ventilation studies.

Studies of regional lung function have developed rapidly in the last few years. Xenon -133 is the most frequently used isotope because of its physiocochemical and biologic properties. Fixed counters are being replaced by the scintillation camera interfaced to a computer allowing easy acquisition and interpretation of results and numerical data. The use of isotopes other than 133Xe, such as 81mKr, is less widespread. In this article, a method is described for studying regional ventilation in which the isotope used is 133Xe, the radioactivity is recorded by a scintillation camera, interfaced to a computer andsix (or 12) regions for both lungs are selected and investigated. The regional ventilation is expressed as an absolute value in ml/min/ml of ventilated volume as well as the relative contribution in percent of each zone to the total ventilation and volume. To illustrate this method, the results are reported for healthy subjects and for patients with chronic bronchitis and emphysema. Scintigraphs of individual cases are presented. Certain theoretic problems related to calculation of regional ventilation are discussed.

Bronchitis↗
PubMed2002

Validated accuracy of a novel urea breath test for rapid Helicobacter pylori detection and in-office analysis.

BACKGROUND: A novel 14C-urea breath test (UBT) was developed to detect the presence of Helicobacter pylori by bench analysis in office, enabling the practitioner to readily reveal H. pylori infection. AIM: To validate the novel UBT (Heliprobe) versus conventional UBT. METHODS: Pretreatment (n = 203) and post-treatment (n = 147) detection of H. pylori. Additional tests with encapsulated 14C-urea (n = 37) were validated. After intake of liquid or encapsulated 14C-urea, exhaled 14CO2 in breath was trapped in benzethoniumhydroxide/ethanol, or adsorbed to LiOH-soaked pads on a dry cover surface (Heliprobe BreathCard). The amount of adsorbed 14C was detected using a beta-scintillator or two Geiger-Müller counters operating in parallel (Heliprobe Analyzer). RESULTS: For pretreatment detection, we found full concordance between the UBTs, with 100% sensitivity and specificity (CI 95-100% and 97-100%, respectively) and strong agreement (r = 0.80, CI 0.75-0.85; kappa = 1, CI 0.86-1.14; P < 0.0001). Similarly, for post-treatment follow-up detection, sensitivity and specificity were 100% (CI 85-100% and 97-100%, respectively) with significant agreement (r = 0.48, CI 0.34-0.59; kappa = 1, CI 0.84-1.16; P < 0.0001). The use of encapsulated 14C-urea did not change agreement between the tests. Sensitivity and specificity were 100% (CI 72-100% and 87-100%, respectively) with strong agreement between the tests (r = 0.71, CI 0.50-0.84; kappa = 1, CI 0.68-1.32; P < 0.0001). CONCLUSION: The novel Heliprobe UBT, with either liquid or encapsulated 14C-urea, seems equi-efficacious to conventional UBT in fulfilling its role as the non-invasive gold standard for detection of H. pylori.

Breath Tests↗
PubMed1983

Kinetics of trace element chromium(III) in the human body.

Chromium(III) has been reported to be an essential trace element involved in the control of glucose metabolism by insulin. We have studied the distribution and kinetics of intravenous [51Cr]chromium(III) in six human subjects using a whole-body scintillation scanner, a whole-body counter, and plasma counting. Principal concentrations were found in the liver, spleen, soft tissue, and bone. The data were fit to a model consisting of a plasma pool in equilibrium with fast (T1/2 = 0.5-12 h), medium (1-14 days), and slow (3-12 mo) compartments, and transfer rates were calculated for exchanges between compartments. Each of the imaged organs appeared to contain varying proportions of each compartment. Two patients with hemochromatosis, in which iron overload is postulated to exclude chromium transport, were found to have altered rate constants. The results should be useful in assessing the metabolism and nutritional requirement of chromium(III) in humans and its importance in disease processes such as diabetes.

Autoradiography↗
PubMed1978

Studies of whole-body retention and clearance of inhaled noble gases.

The in vivo measurements of 127Xe and 79Kr clearance from the whole body indicate five components, with biologic half-times ranging from 13 sec to 17.04 h. The slowest component correlated highly with percent total-body fat, the half-time varying between 7.59 and 17.04 for xenon and between 4.20 and 9.62 h for krypton. The long-term retention was localized to regions of high fat content as determined by the coincidence mode of the whole-body counter and images obtained with the scintillation camera. The estimated dose based on the retention data of this study would indicate increased doses to body fat and gonads as compared with those previously calculated. These increased doses are due to the longer retention of noble gases in fat. After 10-min inhalations of a mixture of 127Xe and air and 79Kr and air, approximately one third of the total 127Xe and one fifth of the total 79Kr were transferred to the body tissues, extrapolated back to the start of gas washout. Of this amount, approximately 13% of the 127Xe and approximately 9% of the 79Kr were associated with the slowest component.

Adipose Tissue↗
PubMed2001

Differential dosimetry in a neutron-proton mixed field with low-pressure proportional counters.

For a mixed radiation field of neutrons and protons, radiation events were discriminated between photons, neutrons, and protons using a thin plastic scintillator. Distributions of lineal energy were measured with low-pressure proportional counters (LPPCs). To estimate the distribution of lineal energy for ICRU muscle, measurements were carried out using A-150-walled, graphite-walled, ZrO2-walled, and Zr-walled counters. Data were corrected for different atomic compositions between the A-150 plastic and ICRU muscle.

Energy Transfer↗
PubMed2005

The 12B counter: an active dosemeter for high-energy neutrons.

High-energy accelerators can produce strong time-structured radiation fields. Such dose shots are generated at linear machines with low duty cycles as well as at circular machines when complete fills are instantaneously lost. The main dose component behind thick shielding is due to high-energy neutrons occurring at that time structure. Dosemeters based on Geiger-Mueller tubes or proportional counters fail here completely. The 12B counter, a novel dosemeter made of a plastic scintillator using carbon activation for event-like exposure, has been introduced. High-energy neutrons activate the carbon nuclei by three inelastic reactions. The decay patterns with half-lives between 20 ms and 20 min can be exploited depending on the time structure of the radiation field. The response of the 12B counter was measured along with some other dosemeters, both active and passive, in the radiation field behind the lateral concrete shielding of a 7.5 GeV proton transfer line.

Boron↗