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Scintillation solutions containing surface active substances, soluble in Toluene, could be used for efficient counting of 125I. The use of Triton X-114 in the proportion 30% v/v with a Toluene-2,5-Diphenyloxazole basic scintillation solution, provides a method for the measurement of liquid and solid samples with 50% efficiency and aqueous sample capacity up to 25%.
Liquid scintillation counting solutions for radioimmunoassay of hepatitis associated antigen (HBsAg) are evaluated and discussed. Data is also presented which indicates that liquid scintillation counting could be carried out by placing cut-off Ausria-125 test tubes in counting vials containing 10 ml of either Brays, Unogel, or Instagel solutions. The data suggest that Brays was the least effective and Unogel and Instagel were the most effective liquid scintillation counting solutions. This is a fundamental consideration if a laboratory is contemplating an initial investiment in counting equipment. The acquisition of a liquid scintillation counter provides additional capabilities for the clinical laboratory interested in radioisotope measurements. In addition, if a laboratory already has a liquid scintillation counter (Beta counter), the director of the clinical laboratory may elect not to purchase additional counting equipment (gamma counter) since he already has the added advantage of measuring iodine-125 with the Beta counter. The authors propose liquid scintillation (RIA) as an alternative counting system for HBsAg detection in hospital patients and donors.
Following a 10 min pulse labeling with 3H-TdR, flasks of asynchronous monolayer cultures of Chinese hamster ovary cells were subjected to mitotic selection at 2 hr intervals. The mitotic index of the selected populations was always greater than 90%. Counts per min per cell obtained by liquid scintillation counting were plotted versus time after the pulse label. Comparisons were made between cycle times obtained by the mitotic-scintillation counting method and by the standard per cent labeled mitosis technique. The resulting curves were used for calculations of the cell cycle times and the lengths of G1, S, G2 and M phases of the cell cycle. There was less than 2% difference in the cell cycle times obtained using the scintillation method as compared to times calculated from autoradiographic data obtained from individual petri dishes. The mitotic-scintillation counting technique is simple, accurate and rapid and allows the calculation of the cell kinetics parameters within 1 hr of the end of the experiment.
A major expense of radioimmunoassay involving tritiated tracers is that of liquid scintillation counting. We present a micro-scale method that markedly reduces the cost of liquid scintillation counting. The radioimmunoassay is done in 10 X 50 mm tubes. The antibody-bound tracer is precipitated with a second antibody, the precipitate is resuspended in 0.1 ml of water, and 0.3 ml of dioxane is added. One milliliter of a toluene-based scintillation cocktail is added, and the tube is capped and placed in an adapter for liquid scintilation counting. When this method was applied to a double-antibody testosterone radioimmunoassay, it performed comparably to assays counted by the usual method.
Detection of gamma emitting isotopes is achieved conventionally by using a gamma spectrometer, or in some cases by liquid scintillation counting. We applied these two methods to the detection of 51 Chromium released in a lymphocyte-mediated cytotoxic reaction. Detection in liquid scintillation appeared more efficient than conventional gamma detection: 16.74% vs 1,11%. It is therefore possible to reduce by a factor of 10 the number of target cells in the cytotoxic assay if liquid scintillation counting is used. Either method gave the same results when applied on the same samples. Liquid scintillation counting is to be preferred when high sensitivity is needed. In addition it offers the advantage of using the same apparatus for detection of gamma or beta emitting isotopes.
During the course of a kinetic enzyme study of bisphosphoglyceromutase (EC 2.7.5.4.) a chemiluminescent effect was encountered in the liquid scintillation counting of the beta-emission from 32Pi. A method is described for overcoming the effect, thereby permitting the accurate determination of the radioactive compounds. It is important to check for chemiluminescent effects early in the development of new procedures that involve liquid scintillation counting.
A liquid scintillation counting method for simultaneous determination of three radioactive nuclides (3H, 14C, and 22Na) of biological interest was studied. By comparing the beta spectra of the three nuclides, their counting energy ranges, A, B, and C, were determined. 22NA was set high enough to avoid any spillover counts from lower-energy nuclides. Region A for 3H was set to maximize the counting efficiency. A good correlation between the counting efficiency for 22Na in region C and the counting efficiency of other nuclides in all regions was obtained. Prior to 3H and 14C dpm calculations, the 22Na counts spilled down in regions A and B were subtracted from the total counts in regions A and B. A simple linear equation was then used to compute 3H and 14C dpm. Findings show that the method presented is adaptable for highly quenched samples up to quenching indices of tSIE = 100. The method is useful for studying the biological transport coupled to Na+.
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An insert vial situated at the center of the counting medium and containing a standard count has been used for quench correction in the liquid scintillation counting of gels containing suspensions of silicic acid scrapings from thin layer chromatoplates. The method has provided a simple and direct means of routine count correction for a range of 14-C-labeled lipid classes following separation on thin layer chromatoplates. The use of insert vial provides several advantages over other methods for the count correction of these suspensions.
A new quantitative assay for migration inhibitory factor (MIF) employs 3H-labelled cultured mouse or human lymphoid cells migrating from capillary tubes. Capillaries filled with labelled cells are placed in liquid scintillation counting vials, along with the MIF-containing sample and are removed at the end of a five-hour incubation period. The residual, labelled cells which have migrated out of the tubes are solubilized and counted in a liquid scintillation counter. While cultured lymphoblast cells are routinely used in the assay, the method was checked against mouse and guinea pig peritoneal exudate cells in both the labelled cell technique and the conventional chamber assay. The assay is technically simple to perform and a useful tool for laboratory research purposes because of the short span of time needed to obtain the results. These advantages indicate a potential for automation and use of this assay in a clinical immunology laboratory. Statistical analysis of data from both assays demonstrated that the relative variation among replicates is lower in the labelled cell assay. The new assay also measured a significant difference between controls and MIF-containing samples when the migration index (MI) was greater than 80%. Criteria for significant inhibition of migration are discussed in regard to the use of analysis of variance (ANOVA) and other statistical procedures, and the inadequacy of a single measure, such as the MI, is discussed.
Fast atom bombardment mass spectrometry and liquid scintillation counting have been used to study the biodegradation of a novel cationic surfactant in live sludge. The rates of primary biodegradation and the extent of complete mineralization were determined. Furthermore, an intermediate degradation product was identified and its rates of formation and subsequent removal have been established. These data find utility in assessing the environmental safety of the surfactant and the accuracy of various environmental fate models.
Liquid scintillation counting of trichloracetic acid extracts of [3H] TdR-labelled lymphocytes has been studied by a direct suspension method without previous solubilization. In this new method, mixing of the labelled powder in water suspension with Scintillator Emulsifying Mixture (SEM) results in a firm gel whose mechanical properties provide an heterogeneous sample ready for counting. Counting efficiency and stability of such samples are related to the amount of labelled cells. Comparative studies with standard hyamine procedure have shown that this simple and rapid method gives reliable results.
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Spontaneous and PHA induced RNA and DNA synthesis was measured qualitatively by autoradiography and quantitatively by scintillation counting in blood lymphoic cells of newborn infants, older infants, and adults. Spontaneous RNA synthesis was found in transitional cells, large phagocytic lymphoid cells and lymphocytes. Transitional cells and phagocytic lymphoid cells also synthesized DNA spontaneously. Quantitatively, spontaneous RNA synthesis was active in both newborn infants and in adults, but significantly less so in older infants. PHA stimulation for 18 h increased RNA synthesis significantly in blood lymphoid cells of newborn infants and adults, and to a much lesser but still significant degree in older infants. Spontaneous DNA synthesis was significantly greater in newborn infants than in older infants and adults. PHA stimulation for 18 h had no effect on thymidine incorporation in any of the groups studied.
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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.
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