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PubMed1967

Determination of 14C-labelled ketone bodies by liquid-scintillation counting.

1. A method of assaying (14)C in ketone bodies present in blood by using liquid-scintillation counting is described. 2. d(-)-beta-Hydroxy[(14)C]butyrate is converted quantitatively into [(14)C]acetoacetate by means of a coupled oxidoreduction reaction involving NAD(+), d(-)-beta-hydroxybutyrate dehydrogenase and malic dehydrogenase in the presence of a high concentration of oxaloacetate. 3. [(14)C]Acetoacetate is decarboxylated to acetone and carbon dioxide which are trapped separately in a double-well flask and counted subsequently. 4. The method permits the determination of (14)C activity in the individual ketone bodies and allows the activity in the carboxyl carbon atoms of acetoacetate or of d(-)-beta-hydroxybutyrate to be assayed separately from the activity in the remainder of the molecule. 5. Recoveries of (14)C-labelled ketone bodies added to blood approach 100% with good reproducibility in replicate analyses.

Acetoacetates↗
PubMed1984

A procedure to measure the specific activities of dopamine and its metabolites in rat striatum, based on HPLC, electrochemical detection and liquid scintillation counting.

A procedure to determine the specific activities (s.a.) of the putative neurotransmitter dopamine (DA) and its metabolites in rat striatum is described. For this purpose 200 mu Ci L-[3,5-3H]tyrosine was injected via a jugular vein cannula into freely moving rats. Contents and radioactivity of striatal tyrosine, DA, 3,4-dihydroxyphenylacetic acid (DOPAC), 3-methoxytyramine (3-MT) and homovanillic acid (HVA) were determined by means of HPLC, electrochemical detection (ECD) and liquid scintillation counting. In the phase system applied DA, DOPAC, 3-MT and HVA can be separated in a single run after direct injection of striatal supernatants. The selectivity of the phase system was sufficient to analyse the supernatant of two rat striata over a 150 X 4.6 mm column, even when DA turnover was strongly stimulated. Tyrosine levels and radioactivity were measured by re-analysis of the front peak with divergent mobile phase parameters. In order to demonstrate the applicability of the present procedure, the s.a. of DA and its metabolites, as found 20 min after [3H]tyrosine administration, and the effect of haloperidol thereupon, are presented.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1991

Determining the 222Rn exhalation rate of building materials using liquid scintillation counting.

A new method for determining the free 222Rn exhalation rate from building materials is described. The sample is enclosed in a container from which the exhaled Rn is continuously purged by nitrogen gas. After 2-3 h, when the Rn level in the container has reached a steady-state concentration, the outflowing Rn is trapped on silica gel at about -190 degrees C. About 16 h after sampling, the silica gel is analyzed by liquid scintillation counting to determine the area exhalation rate. The method described has a good repeatability and reproducibility with coefficients of variation of 7.8% and 8.3%, respectively, at 5 Bq m-2 h-1. The low limit of detection of 11 mBq 222Rn offers the opportunity to quantify the exhalation rate of almost all kinds of building materials. It was found that the air humidity strongly influences the exhalation rates of building material and, therefore, should be controlled. Two typical building materials were investigated. For gypsum, an increase in the exhalation rate with increasing water vapor pressure was found, whereas for concrete, a linear decrease with increasing water vapor pressure was observed. The 222Rn area exhalation rates of 20 Dutch building materials, including some experimental ones, were determined at 50% RH, 20 degrees C, showing a range of less than 0.02-15.8 Bq m-2 h-1. The lowest values were found for natural gypsum board, the highest for phosphogypsum blocks. Building materials containing fly ash gave area exhalation rates comparable to those of similar materials without fly ash.

Air Pollutants, Radioactive↗
PubMed1985

Effects of instability of samples during liquid scintillation counting on the results of ligand-binding studies by equilibrium dialysis.

In binding studies using equilibrium dialysis, mixing of the aqueous samples with scintillation cocktails designed to accommodate aqueous samples produced grossly erroneous binding data. The amount of [1,5-14C]citrate apparently bound to rabbit muscle phosphofructokinase was a linear function of the citrate concentration, with no tendency to approach saturation, and highly variable. This problem was caused by very slow precipitation of citrate in the scintillation cocktail. Addition of a solubilizer stabilized the count rate during scintillation counting and resulted in acceptable binding curves.

Animals↗
PubMedDate not supplied

[The liquid scintillation counting of the 14C natural level in ethanol: a comparison of different standardisation methods (author's transl)].

The influence on liquid scintillation counting efficiency of internal standards toluene-14C, hexadecane-14C and ethanol-14C has been studied for low level-14C measuring of ethanol samples. Many biological and synthetic samples of ethanol have been counted: the best results are obtained with external standardisation on quenching calibration curve made with ethanol-14C. External standardisation on quenching calibration curve made with toluene-14C is preferable to internal standardisation with ethanol-14C. Hesadecane-14C as internal standard gives activities rather higher than true values.

Carbon Radioisotopes↗
PubMed1984

In-vitro uptake and metabolism of [3H]-5-hydroxytryptamine in the pineal glands of the rabbit, rat and hamster. A comparative study with the use of autoradiography, chromatography and liquid-scintillation counting.

Pineal glands of rat, rabbit and hamster were incubated during day or night in Merlis' fluid containing [3H]-5-hydroxytryptamine (=[3H]-HT) by the use of a 20-min pulse with or without postincubation in "cold" medium for 15, 30, 45 or 60 min. (1) Selective autoradiographic labeling was observed in sympathetic nerve terminals; this reaction was missing after bilateral surgical removal of the superior cervical ganglia. In contrast, a scarce and diffuse labeling was found in pinealocytes (Pi) and interstitial cells (IC) of both untreated and ganglionectomized animals. (2) With the use of thin-layer chromatography, it could be shown in the rat that the well-known indoles of the pineal gland are formed from [3H]-HT. (3) During preparation for electron microscopy (EM), the total loss of indoles from pineal glands was studied by means of liquid-scintillation counting; approximately 57% of the radioactivity of the pineal glands was released into EM-processing solutions, mainly into the glutaraldehyde fixative. In summary, our results show that in this type of experiment with pineal glands of mammals, the routinely used EM-procedures are inadequate to visualize the uptake and metabolism of exogenous indoles in Pi and IC. Furthermore, the data differ considerably from those obtained with the pineal organs of several reptilian and avian species when a similar cytological procedure is used. It appears that protein(s) located in the densely packed vesicles of the pineal cells of sauropsids, homologous to mammalian pinealocytes, may play a crucial role in indole binding (specific indole-binding proteins); this may help to interpret the diverging results obtained in different amniotes.

Animals↗
PubMedDate not supplied

Development of MCTS technique for 3-PM liquid scintillation counting.

We have developed a multi-channel time scaling method that is suitable for activity measurement of beta emitting nuclides by means of 3-PM Liquid Scintillation Counting, using non-extending dead times and linear amplifiers. Since it enables to obtain the accidental coincidences directly, the true values for both double and triple coincidences are determined by simply taking into account the correction due to dead times. The advantages of the method are demonstrated by studying the activity of 204Tl and 14C. The measured results were compared with those derived by using the mathematical formulae.

Journal Article↗
PubMed1985

Quantitation of hepatitis B virus DNA (HBV DNA) in serum using the spot hybridization technique and scintillation counting.

The simple spot hybridization technique to detect HBV DNA in serum was modified to concentrate Dane particles by pelleting. This minimised interference by serum components and allowed larger volumes of sera (up to 500 microliters) to be used in serial dilution on borderline positive samples and increased the efficiency of filtering through a "Hybri.Dot' system. Quantification of HBV DNA by 32P-scintillation Cerenkov counting based on serial standards of cloned HBV DNA processed through the "Hybri.dot' was easy to perform and the assay had good sensitivity (detection limit 2 pg, mode 6.25 pg), precision and accuracy. The pellet-simple spot quantitative assay proved more sensitive than those involving lengthier extraction procedures or direct application of serum to hybridization filters. Scintillation counting curves were linear over a wider range (0-800 pg HBV DNA) than optical densitometry measurements (0-50 pg) of autoradiographs. There was an excellent correlation with DNA polymerase activity (r = 0.948; P less than 0.001) but the assay proved more sensitive since HBV DNA (greater than 45 pg cloned equivalents) was detected in 4 out of 14 DNA polymerase negative sera and in 7 of 7 borderline (DNA polymerase cpm range 116-303) samples. This sensitive, quantitative HBV DNA assay should be of considerable value in studies on infectivity and effectiveness of antiviral therapies.

DNA, Viral↗
PubMed2000

Application of alpha/beta discrimination in liquid scintillation counting for the purity control of 99mTc medical solutions.

99mTc is a widely used nuclide in nuclear medicine for diagnosis. 99mTc solutions are eluted from 99Mo/99mTc generators as sodium chloride solutions. As the 99Mo source is a fission product extracted from the reprocessing of nuclear fuel, one might expect the presence of radioactive impurities. One point of special concern described in the 1997 European Pharmacopoeia (1996) is the possible contamination in alpha-impurities (U, Pu, Am, Cm, ...) which must be very low. In order to check this impurity concentration, we used liquid scintillation counting (LSC) with alpha/beta discrimination and a commercial extractive scintillator, Alphaex. We first made measurements using synthetic mixtures of alpha and beta-emitters and then using the real effluent. This paper describes the measurement procedure used with the optimum chemical conditions for a correct extraction of the alpha-emitting nuclides. The sensitivity of the method is also described from the measurements made using the real effluent with an addition of a quantitative amount of alpha particle contamination.

Biological Science Disciplines↗
PubMed1982

The estimation of low levels of 14C in biological samples by alkaline extraction and liquid scintillation counting.

A liquid extraction method capable of accurately estimating low levels of 14C in blood and faecal samples is described. The lower limit of detection is about 4 pCi of 14C per g wet wt of ovine faeces and the lowest level of quantitative determination is 33 pCi per g. Extraction of soluble material is efficient and 14C present in the extract as n-[1-14C]hexadecane, D-[U-14C]glucose, [1-14C]stearic acid, [1-14C]methionine, or Na2 14CO3 is estimated without loss. The aqueous extraction medium used contains 2.5% (v/v) Synperonic NP9 (a non-ionic emulsifier) and 3.5% NaOH and samples are decolorised using hydrogen peroxide. The extract is counted without neutralisation in an inexpensive scintillation mixture based on an emulsifiable oil rather than on an aromatic solvent. It consists of White Spirit 100 (53.8% v/v), Synperonic NP9 (30.8% v/v), octan-2-ol (10.8% v/v), benzyl alcohol (4.6% v/v) and 2,5-diphenyl oxazole (3 g/l). Ethanediol added with the aqueous alkaline extract acts as a third cosurfactant. The advantage of this mixture over one based on an aromatic solvent is that it has a much larger capacity for the concentrated blood and faecal extracts.

Animals↗
PubMed2000

An external-sample liquid scintillation counting for 75Se and its application to selenoprotein detection.

An external-sample liquid scintillation (LS) counting for the gamma emitter 75Se has been developed. An expressly designed well-type LS vial and a 2,5-diphenyoxazole-1,4-bis(5-phenyl-2-oxazoyl)-benzene-xylene solution containing 35% tertrabutylzinn allow 75Se to be counted in a standard LS counter with counting efficiency up to 43.2%, much higher than that of conventional LS counting method. This external sample LS has a good count rate linearity and exhibits low background count rates. After in vivo labeling with [75Se]selenite, 75Se distributions and the Se-containing proteins present in tissues of male rat were investigated by means of sodium dodecyl sulfate-polyacrylamide gel electrophoresis, external-sample LS and gamma-detector. Eight Se-containing proteins or protein subunits were detected to be Se-containing proteins or protein subunits in arterial wall, and their apparent molecular masses (Mr) were 76.4, 67.0, 57.4, 30.3, 25.4, 22.7, 21.7, and 15.1 kDa, respectively. In addition, eight 75Se-labeled proteins (Mr: 66.8, 57.0, 43.1, 30.0, 24.8, 19.8, 18.0, and 14.8 kDa) were found in brain homogenates, and nine 75Se-labeled proteins (Mr: 117.0, 78.0, 66.6, 57.2, 43.0, 38.1, 25.0, 20.1, and 18.0 kDa) were detected in testis homogenates. Some of them should be new biologically important selenoproteins that have not been identified so far.

Animals↗
PubMed2002

Determination of 36Cl in biological shield concrete using pyrohydrolysis and liquid scintillation counting.

A method for the determination of 36Cl in biological shield concrete of nuclear reactors was developed. Cl in the concrete sample was extracted quantitatively by pyrohydrolysis at 900 degrees C and recovered in Na2CO3 solution for subsequent measurement of 36Cl by liquid scintillation counting. WO3 was used as an accelerator in the pyrohydrolysis. The Cl extraction procedure was optimized by investigating experimental conditions with the use of ion chromatography and its recovery was evaluated by the analysis of the geochemical reference samples. The detection limit of 36Cl was 0.02 Bq g(-1) for a sample weight of 2 g. The relative standard deviation was 3-7% for the samples containing 0.5 Bq g(-1) levels of 36Cl. The method was applied to determine 36Cl in biological shield concrete of the Japan Power Demonstration Reactor.

Journal Article↗