Nuclear Chicago scintillation counter

They also carried out end group analysis by means of a Chicago Nuclear liquid scintillation counter to count C14-labeled end groups. 

The results of the count rate linearity are shown in Table 1. The activity of 1-125 varied from 623 CPM to 95,447 CPM (Nuclear Chicago gamma counter). There was a corresponding increase in the 1-125 activity measured in the liquid scintillation counter using the Gamma Vials. The mean of the ratios of the activity of 1-125 as measured by the liquid scintillation counter to the camma counter was. 77 (SD. 014, range. 75 to. 79). 

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 Analysis. Samples of urine, feces, and tissues were combusted to COo and analyzed for radioactivity (5). By using this method the recovery of radioactivity from samples spiked with C was 95 dt 5%. To determine the radioactivity expired as CO2, 5-ml aliquots of the solution used to trap the CO2 were added to 15 ml of a scintillation counting solution containing 4 grams 2,5-diphenyloxazole (PPO) and 0.1 grams l,4-bis-2(5-phenyloxazolyl)-benzene (POPOP) per liter of 1 1 toluene 2-methoxyethanol. Samples were counted for radioactivity in a Nuclear Chicago Mark II liquid scintillation counter. Counting eflSciency was corrected by the internal standard technique. 

Radioisotope Procedures. Radioactive volatile acids separated by Wiseman-Irvin chromatography were collected in 1 ml of 0.5N KOH. The aqueous fraction containing the acid was transferred to a scintillation vial and evaporated to dryness in a vacuum oven at 20 psi and 50 °C. The residue was redissolved in 0.1 ml distilled H2O before adding 4 ml of absolute ethanol and 15 ml of scintillation fluid 2,5-diphenyloxazole (PPO) and 0.01% 1,4-bis[2-(5-phenyloxazolyl)]benzene (POPOP) in toluene. Samples were counted in a liquid scintillation counter (Nuclear Chicago Corp.). 

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. 

CT-polymerase B (DNA-dependent RNA-polymerase) was obtained from calf-thymus tissues and assayed as reported earlier (71). Activity measurements were performed in a toluen1e system, using a Liquid Scintillation Counter Mark I (Nuclear Chicago). 

The specific radioactivity of the various bases, after purification, was checked on a Nuclear Chicago Delta Scintillation Counter. 

The percentage recovery of added DMNA was determined by using C--labelled DMNA. The radioactivity of samples was determined with a liquid scintillation counter (Nuclear Chicago Co.). About 10 counts of C-DMNA were added to 250 ml of culture medium corresponding to about 2 yg. 

All radioactive measurements were made in a Nuclear Chicago Unicap 300 scintillation counter. However, there are three distinct... 

Analytical chromatography was carried out with Me0H NH 0H H20 (7 1 2) on Whatman No. 1 paper, radioactivities of tritiated and iodinated materials were measured with Beckman LS-233 liquid scintillation and Nuclear-Chicago 1185 gamma counters, respectively, and SDS polyacrylamide gel electrophoreses were performed employing the procedures of Weber and Osborn (10). 

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