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PubMed2001

A multiwire proportional counter for XAS fluorescence experiments.

A multiwire proportional counter was used in fluorescence X ray absorption measurements and a comparison to a Si(Li) and NaI(Tl) detectors was done. The main features of the multiwire proportional counter are its high counting rate capability (10(7)) counts x s(-1)) and large active area (6 x 6 cm2). It was shown that the MWPC is suitable for fluorescence absorption. Although the maximum capability was not reached in the present experiments, it was found that as the counting rate increase the MWPC performance became better than Si(Li) detectors and shows a similar response to the scintillator counter at medium counting rates (up to 10(5) counts x s(-1)).

Journal Article↗
PubMed1976

Uptake and retention of 133Ba and 140Ba-140La in mouse tissues.

The distribution of barium in the mouse has been determined qualitatively by whole-body autoradiography after i.v. administration of 133BaCl2 solution. The quantitative distribution of 104Ba and 140La has been analyzed after i.p. injections of the two nuclides in equilibrium by measuring the activity in excised organs in a two-channel scintillation counter. Approximate doses to the eyes and different parts of the skeleton have been calculated.

Animals↗
PubMed1987

[A new evaporation procedure for monitoring of iodine-125 in liquid waste].

A simplified monitoring method of 125I in liquid waste was devised. The waste water of 200 cm3 was taken on a Saran (polyvinylidene chloride) film covering a stainless steel vat. A stable iodine (20 mg) and sodium hydroxide (1 mmol) was added. The water was evaporated using an infra-red lamp. After heating to dryness, the Saran film was folded and transferred into a polyethylene tube. The radioactivity of 125I was counted with a well type NaI(Tl) scintillation counter. When a multi-channel analyzer was available for counting, an absolute decay rate of 125I was calculated with single and sum photo-peak counts. The radioactivity of 125I counted by a single-channel counter must be corrected with the counting efficiency of about 55%, with a special emphasis of a self absorption of photons. The recovery of 125I for concentrations below the permissible level was more than 98%.

Iodine Radioisotopes↗
PubMed1981

A simple method for measuring total calcium in small tissue samples.

A simple and accurate method for determining total calcium in small tissue samples using aequorin is described. The method involves measuring the calcium-induced luminescence of aequorin with the tritium channel of a liquid scintillation counter. The sensitivity of the method and specificity of the method for calcium have been determined and, theoretically, this method could determine calcium in tissue samples weighing 3 mg or as little as 2 nmol of calcium could be measured.

Aequorin↗
PubMed1979

Evaluation of 99mTc-albumin dilution curve with simultaneous injection of 99mTc- and 131I-albumins.

A critical comparison of radiocardiograms with 99mTc- and 131I-albumins was made to determine whether or not 99mTc-albumin can be used as a tracer for measuring blood volume (BV) and cardiac output (CO). Simultaneous injection of both isotopes was given to twenty-two patients to obtain radiocardiograms for each by means of a single scintillation counter with two pulse height analyzers. Such method allows for the determination of the energy levels for both 99mTc and 131I. The radiocardiographic pattern was somewhat different between 99mTc- and 131I-radiocardiograms: The ratio of left to right peak height was 16% on the average lower in the 99mTc-radiocardiogram in the 131I-one. The reason for the lower ratio is explained by greater absorption of 99mTc-radioactivity within the soft tissue interposing between the scintillation probe and heart. The values for 99mtc-derived blood volume were 7.4% on the average larger than those for 131I-derived blood volume (p less than 0.01), although the correlation was excellent (r = 0.98, p less than 0.01). There was no systemic difference between cardiac output determined by 99mTc- and 131I-albumins since the overstimation of blood volume can compensate for the understimation of CO/BV by 99mTc-study. In view of its rapid extravasation, 99mTc-albumin is not so appropriate tracer for accurate measurements of BV and CO/BV, although it may be used for measurement of cardiac output.

Adolescent↗
PubMed2000

Endogenous fatty acid synthesis in squamous cell carcinomas of the oral cavity.

We measured the synthesis of endogenous fatty acids in oral squamous cell carcinoma, its adjacent tissue, and normal oral tissues that were collected fresh from surgical specimens. The tissues were minced in Roswell Park Memorial Institute Medium 1640 (RPMI 1640) and incubated in [1(2)-(14)C] acetic acid, sodium salt ((14)CH(3)(14)CO(2)Na). Total lipids were then extracted and(14)C was measured by scintillation counter. We found that incorporation of(14)C in the total lipids of squamous cell carcinoma was significantly higher than in the other tissues.

Carbon Radioisotopes↗
PubMed1990

A combustion method for the simultaneous determination of 3H, 14C, and 35S in triply labeled organic samples by liquid scintillation counting.

The organic samples triply labeled with 3H, 14C, and 35S were combusted in a flow-type combustion flask under a continuous oxygen flow. The oxygen gas containing the combustion products, which were mainly 3H2O, 14CO2, and 35SO2, was introduced into successive 0.5 M H2O2 and Oxisorb (2-methoxyethylamine). The 35SO2 and 3H2O that had been partially adsorbed onto the inner wall of the combustion flask were recovered by rinsing the wall with an H2O2 solution. 3H and 35S were quantitatively recovered from the H2O2 solutions. 14C was not found in the H2O2 solutions and was recovered from Oxisorb quantitatively. The amounts of 3H, 35S, and 14C were determined by measuring the radioactivity of the H2O2 solutions and of Oxisorb with a liquid scintillation counter. Thus the separate determination of 14C and 35S in a sample was achieved. Through this combustion method, the materials including fresh animal tissues up to ca. 300 mg were conveniently combusted with quantitative recovery of 3H, 14C, and 35S.

Carbon Dioxide↗
PubMed1999

An ultrahigh-throughput screening assay for estrogen receptor ligands.

Members of the steroid and thyroid hormone receptor superfamily (nuclear receptors) play diverse roles in mammalian physiology, in both normal and pathological states. For this reason, and because nuclear receptors are natural receptors for lipophilic small molecules, they are important therapeutic targets for the pharmaceutical industry. Here we describe a method for screening for ligands for one of these receptors, the estrogen receptor. The method is rapid, robust, and reliable, and has been used in an ultrahigh-throughput robotic screen. The receptor is crosslinked to a scintillant-containing solid support (FlashPlate) via a receptor-specific antibody. Test compounds are assayed for competition with a radiolabeled estrogen for binding to the immobilized receptor. Receptor-ligand complexes are allowed to form and receptor-bound radioactivity is detected in a scintillation counter. The assay has been designed for both isoforms of the estrogen receptor, alpha and beta, using separate antibodies for each. Given a radioactive tracer and an appropriate antibody, many of which are now commercially available, the assay could be established for any nuclear receptor.

Ligands↗
PubMedDate not supplied

Low-level measurements of tritium in water.

Using a liquid scintillation counter, an experimental procedure for measuring low-level activity concentrations of tritium in environmental water has been developed by our laboratory, using the electrolytic tritium enrichment. Additionally, some quality tests were applied in order to assure the goodness of the method. Well-known water samples collected in the Tagus River (West of Spain) and the Danube River (Bulgaria), both affected by nuclear plant releases, were analysed and results were compared to previous data. The analytical procedure was applied to drinking water samples from the public water supply of Seville and mineral waters from different springs in Spain in order to characterize its origin. Due to the very low levels of tritium in the analysed samples, some results were reported as lower than the minimum detectable activity concentration (MDA). However, the count rate of these measurements was over the background count rate of LS counter in all the cases. For that reason, an exhaustive discussion about the meaning of the MDA, using an experimental essay, was made in order to establish a rigorous criterion that leads to a reliable value in the case of low-level measurements.

Industrial Waste↗
PubMed1998

Multiwell 14CO2-capture assay for evaluation of substrate oxidation rates of cells in culture.

14CO2 capture is commonly used to evaluate the cellular oxidation rate of respiratory substrates. A modification of the established 14CO2-capture method was developed that enables the use of cells in adherent culture and easy analysis of multiple samples under different culture conditions. The use of commercially available culture and filter plates designed for use in a multiplate scintillation spectrophotometer enabled substrate oxidation rates to be evaluated for cells in a 24-well plate format without the need to dislodge the cells from the culture substrate as is required in traditional methods. Evaluation of radioactivity captured in potassium hydroxide-saturated filters was accomplished by adding scintillation fluid to the filter plate wells and counting. Alternatively, filters could be removed and placed in vials for evaluation in a conventional scintillation counter. This method was applied to the oxidation of 14C-glutamine by human breast cell lines and demonstrated concentration-dependent linear accumulation of captured counts.

Breast Neoplasms↗
PubMed1993

New instruments for high throughput receptor binding assays.

The TopCount Microplate Scintillation Counter and the Matrix 9600 Direct Beta Counter are microplate compatible instruments developed to meet the needs of investigators using radioisotope assays adapted for very high throughput. This paper describes these instruments and their application to receptor binding assays. When combined with the appropriate sample handling equipment and filter media, use of these multi-detector instruments improves sample handling efficiency and shortens overall counting time. The assay protocols including filtration through glass fiber mats and membrane filters have been investigated. Results obtained from these new instruments are compared to standard techniques using conventional liquid scintillation and gamma counting.

Filtration↗
PubMed1952

Scintigrams of the thyroid gland; the diagnosis of morphologic abnormalities with I131.

Functioning thyroid tissue containing sufficient radioiodine can be visualized by scanning the gland with a directional scintillation counter.(4) This visual representation of the gland is called a "scintigram." Scintigrams have been invaluable in the detection and study of both "toxic" and non-functioning nodules, diffuse enlargement in hyperthyroidism and the subsequent reduction in gland size after treatment, carcinoma, and aberrant thyroid tissue.

Humans↗
PubMedDate not supplied

[Cost-benefit of the Schilling test using cobalt-57].

Our purpose in the present publication is to determine the cost-benefit relation of the Schilling test used to measure the intestinal absorption of radioactive vitamin B12. The 60Co-B12 urinary excretion Schilling test was first reported in 1953, and five years later it was being performed at the National Institute of Nutrition (INNSZ) in Mexico City. It was performed in its original version until 1969 and from 1970 to 1980, the direct absorption was measured with a whole-body counter. For the last nine years we have used the Schilling test with 57Co labeled cyanocobalamin. From January 1981 through March 1990, 240 of these tests were carried out in 120 patients. The results were tabulated and compared with their clinical diagnosis. We analyzed our laboratory and labor costs. An oral dose of 0.5 micrograms of vitamin B12 labelled with 18.5 Bq of 57Co is taken by the fasting patients and two hours later one mg of standard B12 vitamin is injected. Urine is collected for 48 hours and the radioactivity is measured in a scintillation counter. Three days later the test is repeated with an additional oral dose of intrinsic factor (IF). The total expense is calculated using the following factors: the cost of the imported radioactive vitamin, IF capsules, parenteral B12 vitamin, syringes, equipment use and its depreciation, laboratory material, and salaries for the professional and administrative personnel.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1981

[Measurement of 222Rn in air using liquid scintillation techniques (author's transl)].

A simple method for the measurement of 222Rn in air was established. At first step radon daughters in air were eliminated from air by suction using glass fiber filter, after that the air were introduced directly to the scrubbing bottle filled with scintillator based on toluene and bubbled until the concentration of 222Rn in the liquid scintillator reached equilibrium state. Then 120ml of the bubbled liquid scintillator were sealed in the teflon vial for the measurement of radioactivity. After the radioactive equilibrium between 222Rn and its daughters were reached, the radioactivity were measured by the low background liquid scintillation counter. The detection limit of 222Rn in air by this method was 3 x 10(-3) Bq/l air (8 x 10(-14)Ci/l air). Though alpha spectrometry by multi-channel analyzer was also achieved, the integral counting method was used more effectively. This method was effectively applied to determine the relatively high concentration of 222Rn in air.

Air↗
PubMed1977

[Radiochemical purity of 123I for medical use (author's transl)].

123I for use in clinical diagnostic procedures has been produced by bombarding antimony with 40 MeV 3He particles. The purity of 123I was measured with a Ge(Li)spectrometer and a low energy Ge(Li) detector. The 123I-product was followed for 1.5 months with a well-type NaI scintillation counter to establish the half-life and confirm the identity of the nuclides. In order to minimize the yield of 121I the optimum cooling time and chemical procedures are presented. After 20 h cooling, the 121I, 124I and 125I contaminants were about 1.8, 4.3 and 0.04% respectively. These values were in agreement with those calculated from the thick-target yield curves. The calculated absorbed dose to the thyroid by the 123I and by-product nuclides were only 4.3 and 7.3% of 131I. 123I could be measured at the window of 99mTc of a NaI scintillation camera and a curie-meter with an error of 10%.

Half-Life↗
PubMed2001

96-well plate-based method for total collagen analysis of cell cultures.

Total collagen assays are often laborious and use large quantities of consumables. We have developed a new method of assaying total 3H-proline-labeled collagen from cultured cells. Cells and media are harvested from 96-well plates directly onto fiberglass filtermats and counted in the Wallac 1205 flat-bed scintillation counter (BetaPlate). The assay was validated by comparison with a traditional total collagen assay. The resulting assay provides a rapid one-step method for quantifying collagen synthesis, which, unlike many collagen assays, does not require extensive dialysis or precipitation of proteins.

Carbon Radioisotopes↗
PubMed1962

Iodine-125 as a protein label in immunology.

Iodine-125 has the relatively long half-life of 60 days, and emits 27.3- to 35.5-kev photon radiation, permitting counting in an ordinary well crystal scintillation counter with 30 to 40 percent efficiency. The emission of low-energy electrons having the same general energy range as tritium beta radiation electrons allows high-resolution autoradiography. These properties, together with the other advantages of radioactive iodine, make this nuclide a particularly satisfactory label for immunologically active proteins.

Electrons↗