Packard scintillation counter

PMT assays were performed as described by Vannier et al. [3] by adding an equal volume of an enzyme preparation to a 0.1 M Tris-HCl buffer containing 3.36 pM of [ C]SAM (1.8 GBq mmol, 740 kBq ml", NEN), 1% (WA ) BSA and 12% sucrose, with or without 0.2% pectic acceptor. The incubation was run at 28°C for 12 h. After precipitation of the reaction product in 70% ethanol, the methylated polymers were selectively extracted with 0.5% ammonium oxalate and radioactivity was measured in a Tricarb 2250 CA Packard scintillation counter. 

Fig. 32 (179). Chemiluminescence assay of bovine erythrocuprein and different Cu2+-amino acid complexes at pJi 7.8. None Cu(Lys)2 50 nM Cu(His)a, 100 nM Cu-Tyr, 145 nM bovine erythrocuprein, 8 nM. The assay components were pipetted in a disposable scintillation vial at room temperature. The total volume was 2.22 ml. The assay mixture was composed of HEPES buffer, 50 mM xanthine, 0.33 mM catalase, 800 i.U. luminol, 1 mM The reaction was started with 0.08 units xanthine oxidase (definition as given by J. Cooper, P. A. Srere, M. Tabachnick and E. Rocker, Arch. Biochem. Biophys. 74 (1958) 306). The first reading was taken after 10 sec. During the counting the coincidence of the Packard scintillation counter was turned on. The background was 4 1 cpm...

Erythrocuprein inhibited the luminol-enhanced chemiluminescence caused by singlet oxygen produced in a xanthine-xanthine oxidase system as measured in a Packard scintillation counter (Weser and Paschen 1972). 

Uniformly labeled C-8-D with a specific activity of 2.99 juc/mg was administered orally to pregnant females at 2 /xg/kg/day from 6-15 days of gestation. Three females were sacrificed on alternate days during days 6-20 of pregnancy. Triplicate samples of fetus, placenta, blood, brain, abdominal fat, and sartorius muscle were procured from each female. The samples were dissolved in 1 ml of Soluene (Packard Instruments) to which 15 ml of Aquasol were added. Each sample vial was counted for 30 min in a Nuclear Chicago Mark I liquid scintillation counter. 

Radioactivity measurement The radioactivities of lead isotopes and their decay products were measured with TRICARB 3380 liquid scintillation counter (Packard Inc.). The radioisotopes concerned, and their decay charateristies are shown in Figure 2. In the case of the direct method, the absolute radioactivity can be obtained by the integral... 

Capsules were equilibrated with a tracer solution overnight. A capsule pellet (0.2-0.5 ml) was then placed in 5 ml test buffer (PBS or RPMI-1640 medium, Gib-co/BRL, New York, NY) on a shaker and a 0.2-ml aliquot was immediately sampled by a screen-protected pipette with further samples being taken over the next 700 s. The tracer quantity was assayed using the methods described below. A final sample was taken after the capsules has been in contact with the buffer for several hours (equilibrated tracer quantity) and the increment to the tracer concentration at each time was calculated. From the progress of tracer to equilibrium on a semilog plot a slope denoted as the zero -order rate flux constant was obtained and has been used as a measure of capsule permeability. [3H] -Glucose (580 daltons),insulin (6.2 kDa), and ovalbumin (45 kDa) have been used as tracers. Radioactivity was measured by means of a Packard 2000CA Liquid Scintillation Counter (Packard Instruments,... 

After exposures to radioactive compounds in water, fish and plants were burned in a Packard 306 oxidizer and HC-carbon dioxide was measured with a Beckmen LS-7500 liquid scintillation counter using PCS (Amersham) xylene (2 1) as counting solution with C toluene (Amersham) as standard. 

Muscarinic receptor (mAChR). Membrane preparations adjusted to 500 pg protein in a final volume of 500 pL buffer were incubated with [3H]-quinuclidinyl benzilate (QNB) (52.3 Ci/mmol Dupont NEN) for 1 h at 20° in the absence and presence of alkaloids, employing 20 pM atropine as a positive control substance. The incubation was stopped with 3 mL ice-cold 0.9% NaCI-solution and filtered (by suction) through Whatman GF/C glass fiber filters. The filters were washed three times with 3 ml 0.9% NaCI, placed in vials, and dried for 30 min at 60°C. Their radioactivity was measured in a liquid scintillation counter (RackBeta, Pharmacia) using Ultima-Gold" (Packard) as the scintillation cocktail. 

Tritium as a low energy beta-emitter is most conveniently measured by liquid scintillation counting. In general, the tritium measurement is the most complicated of all the radionuclide labels. The difficulties are related to the character of the sample which is tritium labeled. Tritium labeling is not suitable in all cases ir. which the system yields high chemiluminiscence the samples are coloured or turbid. Recently, however, new types of liquid scintillation counters appeared which make it possible to count tritium even under such complicated conditions (Beckman, Packard, Kontron, Berthold). 

Figure 3-21. Plastic adapters for use of mini vials in a standard scintillation counter. (Courtesy of Packard Instrument Co., Inc.)...

Determination of Radioactivity. All samples were counted in a Nuclear Chicago Isocap 300 liquid scintillation counter equipped with a Teletype computerized for direct calculation of disintegrations per minute. Fifty microliters of blood were directly counted for radioactivity after solubilization (1 mL of 1 N NaOH). After incubation at room temperature for 15 min the sample was decolorized by adding 200 fxL of hydrogen peroxide and incubating at 80°C for 30 min. The processed samples were mixed with 100 fxL of 80% acetic acid and 15 mL of Insta-gel (Packard), and were counted. Approximately 60-100 mg of tissue were solubilized following the same method as for blood. From the collected urine an aliquot (2 mL) was counted directly with 15 mL Insta-gel. The feces were dried overnight at room temperature, and a 60-100-mg aliquot was combusted (12) and counted for radioactivity. 

The °Y was assayed using either a Nal(Tl) solid scintillation counter to measure the bremsstrahlung or a Tri-Carb 2100TR liquid scintillation counter (Packard Instrument Co., USA). All radioactive measurements were made using a Nal(Tl) counter. 

Conventional scintillation counters such as the Microbeta (Wallac/Perkin Elmer, Turku, Finland) or the TopCount (Packard, Meriden, USA) use photomultiplier detection systems that count 8 or 12 wells at a time, resulting in a readout time of 40 minutes per 384-well microplate. Bialkali photocathodes (Sb-Rb-Cs or Sb-K-Cs) used in standard photomultipliers have a maximum spectral response at about 420 nm, with a quantum efficiency for detection of up to 30%. Thus, the aforementioned instruments are ideally suited for filtration assays and SPA assays with the blue-emitting YSi and PVT beads. 

The radioactivity in urine, bile, plasma, HPLC fractions, and extracts is determined by mixing aliquots of the samples with a scintillation cocktail (e.g., Ecolite cocktail) (5 or 15 mL) and counting with LSC (e.g., Packard 2250CA Tri-Carb Liquid Scintillation counter, Packard Instrument Company, Meriden, CT) for 5-10 min. Radioactivity in feces, blood, and tissues is usually determined by combustion of aliquots by an oxidizer followed by LSC. Another method to determine total radioactivity is to digest the aliquots of feces,... 

Uses Primary fluor used as scintillation counters or in wavelength shifters Manuf./Distrib. Aldrich http //www.sigma-aldrich.com] DuPont http //www.dupont.com] Fluka http //www.sigma-aldrich.com] Packard BioScience BV Penta Mfg. http //WWW. pentamfg. com Sigma Spectrum Quality Prods. http //www.spectrumchemical. com... 

Analytical grade p-xylene is mixed with 2.5 diphenyl-oxazole (PPO) and p-bis-(o-methylstyrl)-benzene to a final concentration of 21 g/1 and 4.5 g/1, respectively. Various volumes of dehydrated alcohol (0.5% water) were added to the xylene scintillator. In all cases, 25 ml of the xylene-alcohol mixture was counted. All measurements were made in plastic vials (American Searle Corporation, Chicago, IL) in a Packard Tri-Carb Counter Model 3380 or a Beckman LS-200 Liquid Scintillation Counter. 

FIGURE 2. Engberg plot of Fe and Cr in a Packard Tri-Carb 3320 liquid scintillation counter. Window settings 50-1000 divisions. 

Radiolabeling Procedure. [ C]-Formaldehyde labeling of siuface A was performed in a self-fabricated metal sample holder with four wells (diameter = 7 mm). Acetonitrile (50 fiL) containing 10.0 mM NaBHsCN and 2.0 mM [ C]-formaldehyde was iiyected into each well. After incubation for 4 h at 20 °C, the excess radioactive solution was removed and the exposed surface washed with CH3CN 10 times and water 10 times. The demounted samples were extensively washed again with water and then dried with N2. The same procedure was also applied to the control surfaces of Ti and acetylated A The radioactivity of each sample was measured by scintillation counting in 5 mL of scintillation fluid (1080 mL of toluene, 920 mL of Triton X-100, 5.4 g of 2,5-diphenyloxazole, 0.2 g of l,4-bis-2-(5-phenyloxazolyl) benzene, and 40 mL of acetic acid) on a Tri-Carb 2300TR liquid scintillation counter (Packard Instrument Co., USA). 

An aliquot of the corresponding fraction of the samples was counted in a Packard Tricarb Scintillation counter. Other aliquots were esterified. The distribution of the radioactivity between the fatty acids was determined by gas liquid radiochromatography (Alaniz et al, 1976). The labeled methyl esters were identified by equivalent chain length determination and comparison with authentic standards. The fatty acid composition of serum, HTC cells and lipid fractions of culture cells was analyzed by gas liquid chromatography. The specific radioactivities for linoleic and arachidonic acids were calculated with those data after measuring the radioactivity in an aliquot in which the mass distribution of the fatty acids had previously been determined by gas liquid chromatography in the presence of an internal standard of eicosaenoic acid. 

The remaining mixture was incubated at 37°C and further samples were taken at 15, 30 and 45 minutes. The paper discs were immediately washed twice in 10 mPI ammoniumformiate,then in aqua dest. and finally in 96 % ethanol. After drying, the remaining radioactivity was estimated in a liquid scintillation counter (Packard) using POPOP (0,3 g/l) and PPO (7,0 g/l) in toluol. 

Place the sample plates separated by clear spacer plates (and a stop plate see manufacturer s instructions) in the scintillation counter. Several laboratories (J. Hall, S. Kay, P. Hardin, R. Stanewsky, A. Sehgal) use a Packard TopCount bioluminescence/scintilla-tion counter. 

Boemsen, K. O. (2000). Using the TopCount microplate scintillation and luminescence counter and deep-well lumaplate microplates in combination with micro-separation techniques for metabolic studies, in Application note, AN004-TC. Packard Instrument Co. Available at http //www.perkinelmer.com. 

To quantify luciferase reporter gene expression in cell lysates, transfer 50 pi cell lysate from each well into a 96-well black flat-bottom microplate. Add 100 pi luciferase buffer per well, and optionally mix with a pipette. Measure the chemiluminescence intensity (count time 0.20 min with background correction) using a luminometer, e.g., a Microplate Scintillation Luminescence Counter (Canberra Packard) or a Wallac Victor 2 Multi-label Counter (PerkinElmer). 

Acid extracts were combusted for 2 min in a Packard, Tricarb Model 306 sample oxidizer. Three 0.5-ml aliquots of each of the cooled sulfuric acid extracts were transferred into combustion cones containing a paper absorbent. About 0.1 g of Combust Aid was added immediately prior to placement in the combustion basket of the oxidizer. Labeled C02 was trapped in Carbo-Sorb (approx. 7 ml) and scintillation cocktail containing Permafluor V (about 13 ml). Radioactivity was measured by liquid scintillation analysis in a Beckman LS 6800 counter and corrected for efficiency and recovery. Data collected as dpm s were converted to mg based on the amount of paraquat ion in the original spray solution. 

Count radioactivity bound to SPA beads in a Topcount microplate scintillation and luminescence counter (Packard). 

---