Radioassay of Low Specific Activity Tritiated Water by Improved Liquid Scintillation Techniques

1957 ◽  
Vol 29 (12) ◽  
pp. 1774-1776 ◽  
Author(s):  
C. A. Ziegler ◽  
D. J. Chleck ◽  
J. Brinkerhoff
Keyword(s):  
Liquid Scintillation ◽  
Specific Activity ◽  
Tritiated Water

STEROID FORMATION IN PORCINE OVARIAN TISSUE IN VITRO

1970 ◽  
Vol 63 (3) ◽  
pp. 441-453 ◽  
Author(s):  
Asbjørn Aakvaag
Keyword(s):  
Liquid Scintillation ◽  
Specific Activity ◽  
Ovarian Tissue ◽  
Gas Liquid Chromatography ◽  
Similar Concentration ◽  
Endogenous Substrates ◽  
Exogenous Progesterone ◽  
Relative Utilization ◽  
Radioactive Substrate

ABSTRACT Slices of non-luteinized porcine ovaries have been incubated in the presence or absence of human chorionic gonadotrophin (HCG) and exogenous radioactive substrates. Progesterone, 17α-hydroxyprogesterone and androstenedione were isolated in a radiochemically pure form. The chemical mass and the specific activity were determined by gas liquid chromatography and liquid scintillation spectrometry. HCG stimulated the rate of formation of androstenedione in the absence of exogenous substrates with a factor of 4–8. In the presence of pregnenolone or progesterone at a concentration of about 2 × 10−6 mol/l the stimulatory effect of HCG was either abolished or markedly reduced. The conversion of exogenous progesterone to androstenedione was reduced in response to HCG indicating that the capacity of the tissue to convert progesterone to androstenedione was limited, and that the limit was reached at this rather low substrate concentration. These findings furthermore suggest that the endogenous rather than the exogenous radioactive substrate will be »preferred« by the tissue. The observations demonstrate the necessity of measuring both the radioactivity and the chemical mass of the products in investigations of this type using radioactive substrates. The formation of progesterone from endogenous substrates was also stimulated by HCG. [1-14C] acetate and [7α-3H]cholesterol were not utilized by the tissue for steroid formation. Exogenous [4-14C] pregnenolone and [7α-3H] progesterone in similar concentration were both utilized for production of 17α-hydroxyprogesterone and androstenedione. HCG had no effect on the relative utilization of the radioactive substrates.

Estimation of water content by tritium dilution of animals subjected to rapid live-weight changes

1969 ◽  
Vol 72 (1) ◽  
pp. 31-40 ◽  
Author(s):  
W. R. McManus ◽  
R. K. Prichard ◽  
Carolyn Baker ◽  
M. V. Petruchenia
Keyword(s):  
Body Weight ◽  
Water Content ◽  
Total Body Water ◽  
Compensatory Growth ◽  
Specific Activity ◽  
Tritiated Water ◽  
Body Water ◽  
Under Nutrition ◽  
The Mean ◽  
Total Body

SUMMARYThe use of tritiated water to estimate total body-water content of animals experiencing recovery from under-nutrition was studied.The time for equilibration of tritiated water (TOH), given intraperitoneally, with total body water (TBW) was determined in rabbits and in rats. As judged by the specific activity of blood water, equilibration had occurred by 76–125 min in the rabbit and did not appear to be affected by the plane of nutrition. However, between slaughter groups the specific activity of water obtained from the liver 180 min after injection of TOH was significantly different from the specific activity of water simultaneously obtained from the blood plasma. It is concluded that the liver is not a suitable tissue to use for testing achievement of equilibration.As judged by the specific activity of blood water compared to that of water from the whole body macerate, equilibration in mature rats either in stable body condition or undergoing rapid compensatory growth occurred in less than 60 min.A trial comparing TOH-space (corrected by 3% body weight) and actual TBW (by desiccation) was conducted on thirty rabbits which experienced under-nutrition followed by compensatory growth.Prior to under-nutrition the agreement between actual and estimated TBW was satisfactory and within 2·3%. During compensatory growth the agreement was poor— the TOH values over-estimating actual TBW by about 12%.A trial with mature rats confirmed the findings with rabbits. For rats in stable body weight the mean estimated TOH-space for fourteen animals was within 1·2% of the actual TBW. For fourteen rats undergoing compensatory growth the mean estimated TOH-space (corrected by 3% body weight) overestimated actual TBW by 6·2%.

Self-radiation induced exchange between tritiated water and organic compounds. The labelling of L-chiro-inositol, myo-inositol and Hexa-O-methyl-L-chiro-inositol

1975 ◽  
Vol 28 (9) ◽  
pp. 1981 ◽  
Author(s):  
DHT Fong ◽  
CL Bodkin ◽  
MA Long ◽  
JL Garnett
Keyword(s):  
Organic Compounds ◽  
Radiochemical Purity ◽  
Specific Activity ◽  
Tritiated Water ◽  
High Specific Activity ◽  
Methyl Derivative ◽  
Radiation Induced ◽  
By Products ◽  
Gas Exposure

The stereochemistry of the tritiation of L-chiro-inositol, myo-inositol and hexa-O-methyl-L-chiro-inositol by self-radiation induced exchange with tritiated water of high specific activity has been investigated. Predominance of configurational retention was found to accompany tritium labelling in the two inositols, while substantial configurational inversion occurred in the hexa-O-methyl derivative. Tritiation occurred predominantly at C 1 in L-chiro-inositol, with slight inversion at this position alone accompanying the labelling. Comparison with Wilzbach T2 gas exposure results indicates the HTO method yields less by-products, myo-inositol having a radiochemical purity of 97%.

DEFINITIVE IDENTIFICATION OF MICROQUANTITIES OF RADIOACTIVE STEROIDS BY RECRYSTALLIZATION TO CONSTANT SPECIFIC ACTIVITY

1965 ◽  
Vol 49 (2_Suppl) ◽  
pp. S7-S77 ◽  
Author(s):  
Leonard R. Axelrod ◽  
Charles Matthijssen ◽  
Joseph W. Goldzieher ◽  
Jean E. Pulliam
Keyword(s):  
Liquid Scintillation ◽  
Specific Activity ◽  
Inorganic Materials ◽  
Dual Isotope ◽  
Advantages And Disadvantages ◽  
Yield Values ◽  
Solvent Systems ◽  
Identification Techniques ◽  
Constant Specific Activity

ABSTRACT Studies of steroid metabolism using isotopically-labeled compounds at physiological levels present unique problems in the identification of the metabolites and in the demonstration of their radiochemical purity. The submicrogram quantities of material available preclude the use of classical identification techniques. The character of the evidence obtained, the advantages and disadvantages of chromatographic and countercurrent distribution methods are discussed. Crystallization to constant specific activity is a recognized method for demonstrating that a substance is not radiochemically impure. Its parameters have never been accurately defined. Its true power is achieved only when it is preceded by extensive purification of the material to be characterized. In this way, the unknown material is first categorized by its migration rate in various solvent systems, and then by its crystalline identity with the carrier compound. The likelihood of two dissimilar steroids being both isopolar and isomorphic is held to be remote. Liquid scintillation spectrometry and gravimetry are the techniques used for the determination of constant specific activity. This method for measurement of radioactivity is extremely flexible, sensitive, and lends itself to dual-isotope experiments. Gravimetry under standardized conditions is suitably precise and much more generally applicable than spectroscopic quantitation. The parameters of the technique of rapid, forced microcrystallization are analyzed. In particular, the problem of contamination of crystals is analyzed in detail, and it is pointed out that classical concepts of purification by crystallization, developed chiefly in connection with ionic inorganic materials, must be modified when applied to nonionic steroid compounds. A mathematical analysis of the errors inherent in this technique indicates that 3 successive crystallizations of a pure radioactive compound should yield values for the specific activity which are within ± 5 % of the average of the 3 values.

Preparation of 14C- and 3H-Labeled Aflatoxins

1971 ◽  
Vol 54 (5) ◽  
pp. 1027-1031
Author(s):  
J L Ayres ◽  
D J Lee ◽  
R O Sinnhuber
Keyword(s):  
Thin Layer ◽  
Aspergillus Flavus ◽  
Column Chromatography ◽  
Aflatoxin B1 ◽  
Sodium Acetate ◽  
Specific Activity ◽  
Tritiated Water ◽  
New Method ◽  
Extraction And Purification ◽  
Constant Specific Activity

Abstract A new method for the preparation of 14C- and 3H-labeled aflatoxins was devised, using rice as a supporting mold media. Labeled precursors were added to sterile rice and the mixture was inoculated with Aspergillus flavus spores. After a 7 day incubation at 25°C, the toxins were extracted with chloroform and purified by column chromatography and subsequent recrystallization. Aflatoxins B1 and G1 were recovered with 70% efficiency from the culture. Incorporation of radioactivity was examined with glucose-U-14C, sodium acetate-1-14C, and sodium acetate-2-14C. The latter gave the most efficient incorporation of 14C at 0.1% for aflatoxin B1 and 0.05% for aflatoxin G1. Conversion of 3H from tritiated water was 0.006% for aflatoxin B1 and 0.003% for aflatoxin G1. Extensive tests of radiopurity were performed on the labeled toxin which included: recrystallization to constant specific activity, thin layer and column chromatography, and hydrogenation of aflatoxin B1 to tetrahydrodeoxoaflatoxin B1. The rice-culturing technique gave good toxin yields of 1 mg aflatoxin B1/g rice. The purification was simplified by the absence of highly radioactive impurities and no appreciable degradation of labeled toxins was noted throughout extraction and purification.

scholarly journals Direct Absorption Method and Liquid Scintillation Counting for Radiocarbon Measurements in Organic Carbon from Sediments

Radiocarbon ◽  
2010 ◽  
Vol 52 (2) ◽  
pp. 794-799 ◽  
Author(s):  
Ionut Faurescu ◽  
Carmen Varlam ◽  
Ioan Stefanescu ◽  
Stela Cuna ◽  
Irina Vagner ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Liquid Scintillation ◽  
Specific Activity ◽  
Potassium Dichromate ◽  
Isotopic Fractionation ◽  
Raw Material ◽  
Total Carbon ◽  
Wet Oxidation ◽  
Direct Absorption ◽  
Absorption Method

In this paper, we investigate a procedure for radiocarbon determination in forest soil and slurry from lake sediments. The total carbon in these samples can be both inorganic and organic. Inorganic carbon can be analyzed in a straightforward manner using the direct absorption method by sample acidification and CO2 capture. For organic carbon, we investigate a hybrid method using the wet-oxidation of organic carbon followed by direct absorption. To evaluate the wet-oxidation processes with potassium dichromate (K2Cr2O7) and potassium permanganate (KMnO4), we performed several experiments using different quantities of soil and sediments in order to establish the quantity of CO2 for each type of sample. The 2 methods offer comparable results for 14C-specific activity (about 0.234 ± 0.024 Bq/g C), values that are expected for these kinds of samples. We also investigated the possibility of isotopic fractionation occurring during CO2 production from raw material by measuring δ13C levels from samples and obtained CO2.

Use of Dissolved Acetylene in Liquid Scintillation Counters for the Measurement of Carbon-14 of Low Specific Activity

Nature ◽  
1954 ◽  
Vol 173 (4412) ◽  
pp. 992-993 ◽  
Author(s):  
B. N. AUDRIC ◽  
J. V. P. LONG
Keyword(s):  
Liquid Scintillation ◽  
Specific Activity ◽  
Carbon 14
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