Liquid Scintillation Measurements Research Articles

Chemical interaction of disulfiram with nitrosodimethylamine after in vitro enzymatic activation.

The in vitro reaction between disulfiram (DSF) and N-nitroso[14C]dimethylamine [( 14C]NDMA) was studied. Incubations of DSF with [14C]NDMA were carried out in the presence of rat liver microsomes, control 9000 g (S9) supernatant fraction and phenobarbital-induced S9 fraction. H.p.l.c. analysis and liquid scintillation measurement provided evidence for the formation of methyldiethyldithiocarbamate (MeDDTC) as a product of the reaction between diethyldithiocarbamate (DDTC), the main active metabolite of DSF and the 'methyl-cation' released by NDMA after enzymatic activation. The amount of MeDDTC found here was consistent with the rate of oxidation of NDMA to formaldehyde. Scintillation counting confirmed that other radioactive peaks, not due to MeDDTC, were unrelated to the methylation of L-cysteine by [14C]NDMA.

Double ratio technique for determining the type of quenching in liquid scintillation measurement

A new double ratio technique which enables the detection of whether prepared samples for liquid scintillation measurement are predominantly colour- or chemical-quenched has been proposed. This technique makes it possible to determine the quenching correction curve to be employed in finding the activities of samples, resulting in reduction in the error which may arise from the difference between colour and chemical quenchings. This technique has been applied to the cases of 3H and 14C radioassays, and found to be practicable.

Arachidonic acid metabolism in reproductive tissues of pregnant guinea pig under in vivo circumstances

Uptake and metabolism of tritium labelled arachidonic acid have been studied under in vivo circumstances in placenta, uterus and fetal membranes of pregnant guinea pigs on days 40 and 60 of pregnancy. Distribution of radioactivity within the lipid fractions of the selected tissues showed a characteristic pattern depending on the gestational ages. Composition of labelled lipids was determined by radio thin layer chromatography and quantitated with liquid scintillation measurements. The main site of arachidonic acid incorporation was the 2-position of phosphatidylcholine. Near term, a considerable PGF 2α-synthesis from exogenously administered 3-H-arachidonic acid could be demonstrated for the first time “in vivo”.

Selective bidirectional transport of [ 3H] d-aspartate in the pigeon retino-tectal pathway

Selective uptake and bidirectional axonal migration of tritiated D-aspartate ([ 3H] d-asp) within a sub-population of retino-tectal neurons was shown by radioautography in the pigeon visual system. Six hours after either pulse injection or prolonged topical application of [ 3H] d-asp to the optic tectum, light microscope radioautographs exhibited an intense and preferential labeling of incoming optic fibers, within tectal layer 1. These axons could be traced back to their perikarya in the ganglion cell layer of the contralateral retina. Conversely, 6–48 h after intra-vitreous injection of [ 3H] d-asp, anterogradely-labeled axons could be followed from the fiber layer of the retina to layer 1–7 of the contralateral optic tectum. In addition, several mesodiencephalic primary visual relay nuclei showed some degree of radioautographic labeling. Labeled retinofugal axons originated from a restricted contingent of small intensely reactive ganglion cells which were heterogeneously distributed throughout the retina. These cells were particularly numerous in the postero-superior quadrant which is known to project to the ventro-caudal aspect of the tectum. Indeed, both radioautography and liquid scintillation measurements showed that the bulk of anterogradely transported radioactivity (more than 80% as free asp) was accumulated in this tectal region. In contrast, when [ 14C] l-leucine was injected together with [ 3H] d-asp, anterogradely transported 14 c-labeled proteins were evenly distributed throughout the tectum. Finally, part of the radioactivity present in tectum 48 h after intraocular [ 3H] d-asp could be released ‘in vitro’ by 47 mm K + stimulation, in a Ca 2+ dependent manner. These results strongly suggest that the pigeon retinal ganglion cells which are here reported selectively to take up, transport and release [ 3H] d-asp may well utilize l-aspartate, l-glutamate or a closely related substance as a neurotransmitter.

Conversion of a cellulose support sample to a homogeneously dispersed system for liquid scintillation measurement

A new sample preparation technique which allows a cellulose support sample to homogeneously disperse into a liquid scintillator has been proposed. The support sample was treated with concentrated suplphuric acid and hydrogen peroxide to form a homogeneously dispersed system. This technique makes it possible to find the activity of the support sample, which has been so far unable to be determined.

Liquid scintillation counting of inorganic radiochemicals in high-efficiency scintillators

Methods of incorporating inorganic radiochemicals into liquid and solgel scintillators that exhibit high scintillation yield are described. Liquid-scintillation measurements have been made at the National Bureau of Standards on 31 different radionuclides for a variety of application in radionuclide metrology. Sample preparation techniques are described for a number of radionuclides that differ markedly in their chemical behavior as well as in their nuclear-decay characteristics. Particular emphasis is given to radionuclides such as 55 Fe and 241 Pu which decay by emission of low-energy radiations.

Quantitative Analysis of Carbon-14 Labelled Polychlorinated Biphenyls and Hexachlorobenzene in Biological Samples Using an Oxidative Combustion Method

Abstract Carbon-14 labelled glucose, polychlorinated biphenyls, and hexachlorobenzene at concentrations of 0.01-1200 nanograms were oxidized in a combustion chamber at 900C. The 14CO2 emitted was trapped in an organic base. and its radioactivity measured. Recovery rates of 95-104% were obtained from samples oxidized with mannitol, while recoveries of samples oxidized with dried fish ranged from 93—101%. This method provides an alternate technique of sample preparation for materials that may yield a highly quenched solution following conventional sample preparation procedures for liquid scintillation measurements.

Determination of the half-life 137Cs by a new method

For the purpose of demonstrating the capability of a new specific-activity method for the determination of long half-lives, the half-life of 137Cs has been determined once again. In this particular case, quantities of 137Cs of the order of 0.1 μg were accurately measured and collected in a polycrystalline matrix of aluminium by means of a process called quantitative ion implantation. The activity of each quantity of 137Cs so collected was determined by liquid scintillation measurement on a solution of the quantity. A half-life value of (29.86±0.27)y was arrived at.

Human vascular endothelial cells in culture. Growth and DNA synthesis.

Human endothelial cells, obtained by collagenase treatment of term umbilical cord veins, were cultured using Medium 199 supplemented with 20% fetal calf serum. Small clusters of cells initially spread on plastic or glass, coalesced and grew to form confluent monolayers of polygonal cells by 7 days. Cells in primary and subcultures were identified as endothelium by the presence of Weibel-Palade bodies by electron microscopy. A morphologically distinct subpopulation of cells contaminating some primary endothelial cultures was selectively subcultured, and identified by ultrastructural criteria as vascular smooth muscle. Autoradiography of endothelial cells after exposure to [(3)H]thymidine showed progressive increases in labeling in growing cultures beginning at 24 h. In recently confluent cultures, labeling indices were 2.4% in central closely packed regions, and 53.2% in peripheral growing regions. 3 days after confluence, labeling was uniform, being 3.5 and 3.9% in central and peripheral areas, respectively. When small areas of confluent cultures were experimentally "denuded," there were localized increases in [(3)H]thymidine labeling and eventual reconstitution of the monolayer. Liquid scintillation measurements of [(3)H]thymidine incorporation in primary and secondary endothelial cultures in microwell trays showed a similar correlation of DNA synthesis with cell density. These data indicate that endothelial cell cultures may provide a useful in vitro model for studying pathophysiologic factors in endothelial regeneration.

Liquid scintillation measurement for β-ray emitters followed by γ-rays

The β-ray emitters which are followed by γ-rays have been measured utilizing a liquid scintillation counter. This instrument enables the nuclides to be accurately measured without any absorption and scattering of radiations under the condition of 4π geometry. The radioactivities of 46Sc, 59Fe, 60C and 86Rb were determined with the aid of a channel ratio method and an external standard method. The results obtained agree considerably well with the values found by γ-ray spectrometry.

Growth regulatory interactions between stationary human glia-like cells and normal and neoplastic cells in culture: I. Normal cells

Density-dependent growth control of fetal and adult human cells from glia, meninges, skin, and lung has been examined in vitro. Autochthonous growth control was assessed by a crowding index at terminal cell density, which is an indirect indicator of the number of population doublings that pass between confluence and plateau level of the growth curve. The index varied from 1.4 (adult glia-like cells) to 6.3 (fetal lung fibroblasts). Stationary glia-like cells were used as bottom layers to assess the growth capacity of superinoculated test cells. Four independent methods were employed. 1. 1. Determination of the increase in cell number of combined cultures of bottom cells and superinoculated cells. 2. 2. A new double label autoradiographical assay by which the proliferation of the superinoculated test cells could distinguished from that of the bottom layer. 3. 3. A colony assay by which the fraction of single cells capable of growth on stationary glialike cells was computed. 4. 4. Liquid scintillation measurement of the incorporation of tritiated thymidine of test cells seeded on glia-like cells whose DNA synthesis had been eliminated by mitomycin C. It was found that, regardless of method employed, stationary glia-like cells inhibited the proliferation of fetal and adult glia-like cells, fetal and adult meningocytes and fetal and adult skin fibroblasts. The multiplication of fetal and adult lung fibroblasts was only partially inhibited. The results are discussed particularly with regard to their implication in the interpretation of experiments in which defective growth control of neoplastic cells is assessed by their ability to grow on stationary normal cells.

Direct liquid scintillation measurement of the natural carbon radioactivity of glycerols for the determination of their biological origin

AbstractGlycerol of recent biological origin can be differentiated from that produced from archaic sources of carbon, e.g. mineral oil or coal products, by measuring the 14C content by liquid scintillation counting.In the case of synthetic glycerol derived from archaic carbon the count rate, i.e. background, was independent of the amount of sample added, while with natural glycerol the count rate increases linearly with the amount of sample. It is possible to detect 15% of natural glycerol in admixture with synthetic glycerol with a confidence of 99%.

Immunoblast formation by recirculating and non-recirculating rat lymphocytes cultured in diffusion chambers.

Rat lymphocytes of two types were obtained and their reactions to antigens studied in an in vivo situation. Lymphocytes which recirculate between blood and lymph (RL) were collected from a thoracic duct catheter, and non‐recirculating lymphocytes (NRL) were separated from the blood of rats that had been depleted of thoracic duct lymph for up to six days. The cells were suspended in diluted mouse plasma and cultured for three or five days in diffusion chambers. The cell‐impermeable chambers were implanted into the peritoneal cavities of rats, mice, or irradiated mice. The proliferation, differentiation and death of the cells were quantified by total and differential cell counting and by liquid scintillation measurement and radioautographic evaluation of 3H‐thymidine incorporating cells.Lymphoid cell populations contained immunoblast precursor cells in numbers roughly proportional to the content of RL. Even after prolonged lymph drainage, however, some blast cells were still detected among cultured blood leucocytes. The presence of macrophages did not appear to influence the formation of blast cells. A slight morphological difference between typical RL and NRL has been observed, the latter cells having some monocyte features.

Metabolism and distribution of yolk DNA in embryos of Ophryotrocha labronica La Greca and Bacci.

Exposure of the polychaeteOphryotrocha labronica to3H-thymidine during vitellogenesis leads to substantial incorporation of label in the ooplasm, especially in yolk granule DNA. In embryos from oocytes labelled in this way it was possible to follow the amount and localization of the labelled material (DNA) throughout early development by means of light microscopical and electron microscopical autoradiography; liquid scintillation measurements also were carried out.

Mesure absolue directe de l'activité des emetteurs β purs par scintillation liquide

ABSOLUTE DIRECT MEASUREMENT OF THE ACTIVITY OF PURE β EMITTERS FOR LIQUID SCINTILLATION This paper describes a method by which liquid scintillation measurement of the activity of pure β emitters can be corrected for the error due to zero probability. It makes use of the fact that when the activity of a source is measured by two phototubes, three equations are obtained: measurement in each of the channels and coincidence or sommation measurement, with three unknowns-activity of the source and conversion factor of each of the detectors. It is thus possible to arrive at the absolute activity of the sample. Part one explains the theory and describes the experimental apparatus. Application of the method to the direct absolute measurement of Tritium by liquid scintillation will be dealt with in a second publication.

A methods for the determination of sulphur in some biological materials.

A rapid and versatile method for the determination of sulphur in biological materials based on the stoicheiometric combination of mercury(II) and sulphur(II) with an acetone-dithizone indicator is described. Although slightly less sensitive than some other micro methods it has a wide range and is less subject to interference.Precautions are suggested for total sulphur determination of samples with a high sulphate-sulphur concentration. Convenient procedures for the determination of total sulphur, total sulphate-sulphur, ester sulphate-sulphur, neutral sulphur and inorganic sulphate-sulphur are outlined, and also the possibility of combining liquid scintillation measurements of sulphur-35 with the same determinations.

Sensitivity enhancement for low level activities by complete syntheses of liquid scintillation solvents

Abstract In order to take full advantage of liquid scintillation measurements for low level radioactivity, a large part of the solvent should be synthesized from the material of the sample to be counted. This procedure has been applied to three natural radioactivity dating a large part of the solvent should be synthesized from the material of the sample to be counted. This procedure has been applied to three natural radioactivity dating methods. For carbon-14, the most sensitive and practical of the various liquids investigated is benzene. The compound, in addition to being a good liquid scintillation solvent, contains 92% carbon. The work on the synthesis of benzene for carbon-14 dating is now complete with yields approaching 100% and less than eight hours total chemical preparation time. Furthermore, the isotope effect for carbon has been proven to be small and reproducible to better than 1/2%. A synthesis of benzene for low level tritium measurements has also been developed. Benzene contains 8 % hydrog...

Tritiated thymidine: effect of decomposition by self-radiolysis on specificity as a tracer for DNA synthesis.

Tritiated thymidine undergoes decomposition by self-radiolysis. As shown by beta liquid-scintillation measurement and by autoradiography, the resultant breakdown products did not label DNA, but entered macromolecules, other than nucleic acid, contained in the cytoplasm. Caution should be exercised in using aged tritiated thymidine solutions.

A simplified technique for the liquid scintillation measurement of radioactivity on paper chromatograms containing toluene-insoluble C 14- and H 3-labeled compounds

A convenient and relatively efficient technique was developed for the routine measurement of radioactivity distribution on one-dimensional paper chromatograms containing low amounts of H 3- and C 14-labeled compounds which are insoluble in the scintillation solvent toluene. A pilot strip, 2 cm wide, was cut out from the chromatogram and divided into 3 4 cm bands along the length of the chromatostrip. Each band was placed in a standard 20-ml screw-top glass vial. Methanol (0.2 ml) was added and the contents were shaken occasionally for 2 or 3 min. Both the methanol and filter paper band were flooded with 10 ml scintillation fluid and the contents were counted. This technique was found to be more satisfactory in terms of efficiency and reproducibility than several other methods tested.

Preparation of samples of biological material for liquid scintillation measurement of low-energy β-emitters

Preparation of samples of biological material for liquid scintillation measurement of low-energy β-emitters