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At least 595 records · Page 33Linked to original sources
PubMed1998

Measurement of 222Rn concentration in Kenyan groundwater.

Groundwater samples from different parts of Kenya have been analyzed for their 222Rn concentrations. Samples were drawn from municipal supplies, springs, wells and bore holes in different geological terrains. In the analysis, conventional liquid scintillation counting, using the Packard protocol for measuring radon in water, was employed. This is the first time these water sources are being tested for radioactivity. The preliminary results are presented, and they showed that 222Rn is the main contributor to the radioactivity in most portable waters in Kenya. 222Rn activity concentrations range from 0.8 +/- 0.5 to 371.7 +/- 33.5 Bq L(-1).

Fresh Water↗
PubMed1999

17 beta-estradiol: behavior during waste water analyses.

The distribution between the aqueous and solid phase of 17 beta-estradiol in the ng-range in waste water was investigated by spiking experiments with a radio-labeled hormone. The distribution was measured by liquid scintillation counting. The major part of 17 beta-estradiol remained in the aqueous phase and did not adsorb to the solids. The fraction in the aqueous phase could be enriched by a conventional solid phase extraction with a recovery rate of up to 100%. Losses were negligible and the compound did not adsorb to the surfaces of glass bottles.

Adsorption↗
PubMed1999

Radiochemical assay for determination of dihydropyrimidinase activity using reversed-phase high-performance liquid chromatography.

A radiochemical assay was developed to measure the activity of dihydropyrimidinase (DHP) in human liver homogenates. The method is based on the separation of radiolabeled dihydrouracil from N-carbamyl-beta-alanine by HPLC with on-line detection of radioactivity combined with detection of 14CO2 by liquid scintillation counting. The assay was linear with time and protein concentration. The minimum amount of radiolabeled products which could be determined proved to be 12 pmol using a purified stock solution of [2-(14)C]-5,6-dihydrouracil. This highly sensitive assay is especially suitable to identify patients with a dihydropyrimidinase deficiency.

Amidohydrolases↗
PubMed1989

Bacterial growth kinetics: modelling and evaluation of two-compartment radioassay.

Quantitative measurements of bacterial growth may be made using a radioassay technique. This method measures, by scintillation counting, the 14CO2 derived from the bacterial metabolism of a 14C-labeled substrate. Mathematical growth models may serve as reliable tools for estimation of the generation rate constant (or slope of the growth curve) and provide a basis for evaluating assay performance. Two models, i.e., exponential and logistic, are proposed. Both models yielded an accurate fit to the data from radioactive measurement of bacterial growth. The exponential model yielded high precision values of the generation rate constant, with an average relative standard deviation of 1.2%. Under most conditions the assay demonstrated no changes in the slopes of growth curves when the number of bacteria per inoculation was changed. However, the radiometric assay by scintillation method had a growth-inhibiting effect on a few strains of bacteria. The source of this problem was thought to be hypersensitivity to trace amounts of toluene remaining on the detector.

Bacteria↗
PubMedDate not supplied

High efficiency photolabeling of human serum albumin and human gamma-globulin with [14C]methyl 4-azido-2,3,5,6-tetrafluorobenzoate.

The efficiency of photolabeling of HSA and IgG with [14C]methyl 4-azido-2,3,5,6-tetrafluorobenzoate has been studied using size exclusion chromatography in conjunction with liquid scintillation counting. Labeling efficiencies of 78% for HSA and 82% for IgG have been determined. The extent of bond insertion into proteins exceeds the C-H insertion efficiency in cyclohexane with less wastage into anilinium and azo side products. These results suggest that the photoprobe accesses hydrophobic regions of both proteins prior to photolysis.

Affinity Labels↗
PubMed1984

Methods of plasma catecholamine measurement including radioimmunoassay.

Fluorometric and radioenzymatic assays are presently the most widely used techniques for the estimation of plasma, urine, and tissue catecholamines. The fluorometric assay lacks specificity and sensitivity. The radioenzymatic assay is significantly more sensitive and specific but is technically very complex, time consuming, and expensive. A newer methodology has been developed by modification of a 125I radioimmunoassay for metanephrine. The assay utilizes an antibody that specifically binds metanephrine. Plasma and urinary epinephrine and norepinephrine are detected by conversion to metanephrine with the enzymes catechol-O-methyl-transferase (COMT) and phenylethanolamine-N-methyltransferase (PNMT). The major advantages of the radioimmunoassay are the savings in cost and time. The radioenzymatic assay utilizes an expensive tritium-labeled compound, S-adenosylmethionine, and requires multiple organic solvent-extraction steps, thin-layer chromatography, and liquid scintillation counting. The radioimmunoassay requires only one extraction with alumina to aid in specificity and to concentrate the catecholamines. Sample detection is by gamma counting. The radioenzymatic assay is presently the reference method for catecholamines and is best suited for small numbers of samples where sample volume is limited and exquisite sensitivity is required. The radioimmunoassay is rapid, has sufficient sensitivity, specificity, and precision for most applications and is best applied to the analysis of large numbers of samples.

Catechol O-Methyltransferase↗
PubMed1977

[Problems in the use of radioactively labelled bacteria in experiments. 2. Quantitative method for the evaluation of pathogens in the calf lung by means of labelled bacteria after aerosol or intratracheal administration].

By means of two aerosol apparatures radioactive labelled Pasteurella-multocida-germs were given to calves via a respiratory mask. Labelling of Pasteurellae was done internal by using special nutritive media with Fe-59 or P-32. In a period of 10-25 minutes 5 X 10(9)-10(10) labelled bacteria were given to the animals for inhalation. Another animal group was injected intratrachealy with the same quantity of labelled germs. Immediately after termination of germ application the animals were killed and dissected. After solution or homogenization, respectively of the total lung tissue radioactivity was determined by liquid-scintillation-counting (Fe-59) or Cerenkov-measurement (P-32), respectively. The activities recovered from lung homogenates rendered is possible to calculate the received amount of bacteria. 40-80% of germs would be recovered in the lung after application by intratracheal injection while only 1-7% could be recovered after individual aerosol application lasting for 15-25 minutes.

Aerosols↗
PubMed1993

[3H-leucine incorporation into the secretory cells of the murine mammary gland under the action of adrenomimetics].

Although there is some evidence suggesting the involvement of the sympathoadrenal system in the mammary gland function, the precise mechanism by which adrenergic agents may influence galactopoietic processes is largely unknown. The aim of this study was to investigate whether the reported decrease in milk and organic substance content after catecholamine administration might be due to the inhibition of protein synthesis. For that purpose, the incorporation of 3H-leucine into the secretory cells of the mammary gland of lactating mice under the influence of the alpha-adrenoceptor agonist phenylephrine and the beta-adrenoceptor agonist isoproterenol, respectively, was studied by light microscopic autoradiography. Tissue radioactivity as a whole was measured by liquid scintillation counting. It was shown that neither the alpha- nor the beta-agonist simultaneously given with the labeled amino acid were able to change the amount of radioactivity taken up by the mammary gland. From this result it is concluded that a transitory increase in catecholamine concentration in the blood has no effect on mammary gland protein synthesis.

Animals↗
PubMed1998

Gel electrophoretic quantitation of protein carbonyls derivatized with tritiated sodium borohydride.

A method for the quantitation of protein carbonyls, which have been widely employed as markers of protein oxidative damage, is described. Protein carbonyls were derivatized with tritiated sodium borohydride and the tritiated proteins were separated on SDS-PAGE. Protein bands, visualized by Coomassie blue staining, were then excised and incubated in 30% H2O2 at 60 degrees C for 48 h. Tritium, incorporated into the proteins, was quantitated by liquid scintillation counting after gel solubilization by H2O2. This method can be applied to the measurement of carbonylation of specific proteins as it employs SDS-PAGE and has the advantage that unreacted NaB3H4 in the labeling reaction mixture need not be removed. The present method, when combined with immunochemical detection of protein carbonyls, should be very useful in the quantitation of oxidative damage to individual proteins.

Animals↗
PubMed1994

Stability of sulphadimidine during raw fermented sausage preparation.

The transformation of sulphadimidine (SDM) during raw fermented sausage preparation was studied to elucidate the SDM decrease found in an earlier study. The raw fermented sausages were prepared from batters containing 1 and 10 mg [14C]-SCM kg-1. The sausages and the brines were analysed using methods based on solid-phase extraction followed by HPLC combined with liquid scintillation counting. It can be concluded that the decrease in SDM level is mainly caused by (i) leaching into the brine (approx. 25%), (ii) transformation of SDM, possibly by reactions with components in the sausage or the brine, as the presence of five reaction products from SDM could be demonstrated, and (iii) formation of bound residues (approx. 20%).

Animals↗
PubMed2006

Standardization of 222Rn by LSC and comparison with alpha- and gamma-spectrometry.

Liquid scintillation counting (LSC) was used for the measurement of 222Rn in equilibrium with its daughters, with detection efficiency close to 5. The appropriate corrections were considered, including one related to the probability that the 165-micros half-life 214Po decays during the dead time of the counter initiated by the disintegration of his parent nuclide, 214Bi. The dead-time determination of a commercial LS counter is also presented using a 222Rn standard source. The LSC 222Rn sources were prepared by transfer of 222Rn produced by a solid 226Ra source into LSC cocktail frozen at 77K, flame-sealed afterwards. They were measured using the LNHB triple coincidence counter with adjustable extending-type dead-time unit, between 8 and 100 micros; two different procedures were used to calculate an effective dead time and then to deduce the counting rate extrapolated to zero dead-time value. The LSC results were compared with those obtained by cryogenic alpha-particle spectrometry (LNHB system) and by gamma-ray spectrometry for the same radon source in the LSC vial; the geometry transfer coefficient was calculated using the ETNA software. Measurement results and uncertainties are discussed.

Algorithms↗
PubMed1988

Detection of pentachlorophenol and its glucuronide and sulfate conjugates in fish bile and exposure water.

The glucuronide and sulfate conjugates of pentachlorophenol (PCP) that were present in the bile and exposure water of goldfish (Carassius auratus) were used to develop methodology to quantify PCP and its metabolites. Reverse phase HPLC with radioactivity detection separated PCP and its metabolites, and was used to verify a method of quantification that used differential extraction and scintillation counting. Extractions of aqueous phase at pH 2 or 8, with butanol, ethyl acetate, or ether indicated that ether at pH 8 best separated PCP from its metabolites. The sulfate conjugate of PCP was the major metabolite produced when goldfish were exposed to 125 micrograms 14C-PCP/l. It was present primarily in the exposure water, but also appeared in the bile.

Animals↗
PubMed1993

Rapid and accurate microfractionation of the contents of small centrifuge tubes: application in the measurement of molecular weight of proteins via sedimentation equilibrium.

The contents of small centrifuge tubes containing solutions of radiolabeled proteins that had been centrifuged to sedimentation equilibrium were fractionated using a new device based upon the mechanical design of Attri and Minton (Anal. Biochem. 152, 319-328, 1986). Individual fractions, corresponding to laminae of 0.15 mm column height within the tube, were collected using one of two methods: (a) automatic mixing with scintillation fluid and delivery to vials mounted in a fraction collector, or (b) collection of undiluted fractions on scintillation vial caps impregnated with solid scintillator. Gradients of protein concentration were obtained via scintillation counting of sequential fractions. Molecular weights of proteins ranging from 4 x 10(4) to 3.5 x 10(5) were calculated by fitting the theoretical expression for sedimentation equilibrium of an ideal homogeneous solute to the experimental gradients. The values so obtained agree well with values obtained by optical scanning of the unfractionated centrifuge tube, and with values obtained from the literature.

Animals↗
PubMed1991

A method for quantifying radioactivity associated with protein in silver-stained polyacrylamide gels.

A method is described in which individual proteins labeled with weak beta-emitting radionuclides, separated by polyacrylamide gel electrophoresis, and stained with silver are released from the gel by the use of the periodate soluble cross-linking agent N,N'-dialyltartardiamide. The radioactivity can then be quantitated using liquid scintillation counting. The method is shown to be insensitive to reasonable variations in the intensity of staining as well as the gel volume over a practical range of gel slices. Recovery from the gel is extremely good with 93% of the counts associated with 14C-labeled proteins of known radioactive concentration being recovered. Analysis of a complex mixture of 3H-labeled proteins indicates resolution similar to that obtainable by autoradiography without the problems associated with quenching of autoradiographic signal by the staining procedure. The method is used to determine the amount of fucose and mannose incorporated into a putative cell adhesion protein during development of the cellular slime mold Dictyostelium purpureum.

Autoradiography↗
PubMed1985

Scintillometric determination of unscheduled DNA synthesis in primary cultures of rat-liver cells. A hydroxylapatite batch assay.

A new procedure has been examined for measuring unscheduled DNA synthesis (UDS) in hepatocyte primary cultures by liquid-scintillation counting. DNA of the hepatocyte lysates was eluted with K-phosphate buffers after absorption on hydroxylapatite in order to reduce the background produced by cytoplasmic radioactivity. To inhibit hepatocyte replicative synthesis, hydroxyurea (10 mM) and cytosine arabinoside (80 microM) were added to the cultures. This procedure was found capable of detecting UDS elicited by 0.3 - 10 mM N-nitrosodimethylamine.

Animals↗
PubMed1988

Enhancement of polyacrylamide gel slice dissolution in hydrogen peroxide by cupric sulfate.

An improved method is described for quantitation of radio-labelled protein by scintillation counting after polyacrylamide gel electrophoresis. The method is based upon copper catalyzed dissolution of gel slices in hydrogen peroxide under ambient conditions. Complete dissolution of gel sections was accomplished by incubation at 25 degrees C in 30% H2O2 that contained 0.9 mM CuSO4. Recovery of tritiated protein was greater than 90% under these conditions while in the absence of CuSO4 recovery was less than 50%.

Acrylic Resins↗
PubMed1991

Inter-laboratory ring trial of in vitro DNA repair tests using rat hepatocytes: further testing and conclusive remarks.

The results of the extension of a collaborative study for the detection of chemical-induced DNA damage in rat hepatocytes in vitro are presented in this report. Three coded compounds, i.e. 1,4-butanediol dimethanesulphonate, hydrazine sulphate and sodium dichromate, were tested for DNA repair synthesis by seven different laboratories, either using autoradiographic procedures or the liquid scintillation counting technique. Inter-laboratory standardization was intentionally not requested in order to investigate the validity of each study design under routine conditions. 1,4-Butanediol dimethanesulphonate was clearly positive in most laboratories; sodium dichromate was generally positive, while the results on hydrazine sulphate were contradictory.

Animals↗
PubMed1983

Radioenzymatic assay for direct measurement of plasma pyridoxal 5'-phosphate.

A radioenzymatic assay for measurement of pyridoxal 5'-phosphate (PLP) is described, based on the incubation of L-[3H]tyrosine (10(6) cpm, spec. acty. 1.88 Ci/mol) in the presence of the apoenzyme tyrosine decarboxylase (EC 4.1.1.25) from Streptococcus faecalis and PLP in phosphate buffer (0.1 mol/L, pH 5.5) at 37 degrees C for 60 min. The decarboxylated metabolite formed, [3H]tyramine, was selectively extracted into ethyl acetate, and the tritium radioactivity in the sample was determined by liquid scintillation counting. As little as 0.5 nmol of PLP can be detected per liter. The assay is specific, no cross reactivity having been noted for several compounds closely related to PLP. With this we could directly measure the concentrations of PLP in plasma without prior deproteinization and ether washing of the samples. Using the assay to determine plasma concentrations of PLP in healthy adult populations, we found results that were comparable with previously reported data.

Apoenzymes↗