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Following the oral administration of 75Se-selenofolate in two normal healthy volunteers, retention was measured by whole body counting, and distribution throughout the body was determined with a hybrid scanner. Approximately 65% of the dose was absorbed from the GI tract. The metabolic data obtained from this study was used to calculate the integrated radiation dose to the liver, and the effective dose equivalent.
Bentonites in feeds cause error in the analysis for Se by the AOAC (3.097-3.101) fluorometric method for Se in plants. The error apparently results from the binding of the piazselenol by insoluble residue from the bentonite. This effect is avoided by diluting digests to volume after reduction with HCl, centrifuging or allowing to stand, and analyzing a portion of the clear supernatant liquid. Insoluble residues present after digestion of plant materials do not appear to cause a similar error.
To investigate the effect of selenium in relation to different environmental conditions a study on the kinetics of the element in mice has been carried out on 54 female mice. 75Se (selenite) was administered as a single dose or continuously through drinking water. Different dosage levels were used ranging from "tracer dose" to subtoxic doses. Wholebody counts revealed a biphasic elimination. The first rapid phase was strongly dose-dependent, while the slower second phase of elimination appeared independent of dose as well as mode of administration with a biological half-life of 14.4 +/- 3.2 days. Liver, blood, kidney and lungs were found to contain most of the selenium, here also a two-phased elimination was observed. The biological half-lives for elimination calculated during the second phase gave a mean of 10.7 days with a range of 8.7 to 12.5 days. With continuous administration through drinking water a steady state was obtained after 300 to 400 hours of administration according to concentration. A linearity between amount retained at steady state and log concentration in drinking water is indicated. The results on biological half-lives are discussed in relation to previous publications.
Selenium-75 selenite and technetium-99m sulphur colloid scans were performed on 38 South African Blacks with intrahepatic space-occupying lesions. Uptake of selenite was demonstrated in the 'cold area' on the sulphur colloid scan in 17 out of 19 patients with hepatocellular carcinoma, but in 16 patients with amoebic liver abscess there was no uptake of selenite in the 'cold area'. In 3 patients with secondary involvement in the liver, 2 had positive uptake of selenite in the affected region. 75Se selenite was found to be useful in the differential diagnosis of intrahepatic lesions.
The formation of the nicotinamide adenine dinucleotide phosphate-dependent formate dehydrogenase in Clostridium thermoaceticum is stimulated by the presence of molybdate and selenite in the growth medium. The highest formate dehydrogenase activity was obtained with 2.5 x 10(-4) M Na(2)MoO(4) and 5 x 10(-5) Na(2)SeO(3). Tungstate but not vanadate could replace molybdate and stimulate the formation of formate dehydrogenase. Tungstate stimulated activity more than molybdate, and in combination with molybdate the stimulation of formation of formate dehydrogenase was additive. Formate dehydrogenase was isolated from cells grown in the presence of Na(2) (75)SeO(2), and a correlation was observed between bound (75)Se and enzyme activity.
During investigations on athyreotic patients given large test doses of 131I, whole-body counting has shown the presence of 75Se contamination in some patients. The investigations were carried out to measure the small long-term component of 131I retention in such patients. In an earlier paper (Smith and Edmonds, 1977), we concluded that the effects of 75Se contamination were negligible in the patients described. Subsequent studies on a further small group of similar patients, however, have indicated that the levels of contamination are variable, and this report is intended as a warning of the possibility of measurement error due to this contamination in metabolic studies similar to those to be described. The effects of 75Se contamination observed in two out of five patients studied have been assessed.
After incubation for 1 hr with (75)Se-selenate, excised roots of Astragalus crotalariae, a selenium-accumulating species, and A. lentiginosus, a nonaccumulator, had absorbed radioactivity to levels well over the external concentration. About 98% of the radioactivity was ethanol-soluble, and when analyzed by column and paper chromatography and by electrophoresis proved to be selenate. This and previous evidence shows an active transport for selenate. Considerably less radioactivity was absorbed when (75)Se-selenite was supplied to the excised roots, and levels of the ethanol-soluble radioactivity did not exceed the external concentration. A good deal of the radioactivity was ethanol-insoluble. Analysis of the soluble radioactivity from both species showed appreciable conversion of selenite to other forms.
SeHCAT, a synthetic homologue of thaurocolic acid, may be used to examine the dynamics of enterohepatic circulation. A greater retention of SeHCAT may be attributed to a defective hepatic clearance and to a partial redistribution of the biliary acid pool outside the enterohepatic circle. This method has been applied to 20 patients affected with chronic hepatic disorders. The percentage of retention of SeHCAT in normal subjects was 19-20 on average. The hepatopathic patient has an average SeHCAT retention of 54%. After treatment with polyunsaturated phosphatidylcholine (EPL) plus vitamin B complex i.v., the percentage of SeHCAT retention was significantly less than 31% (P less than 0.001). It can be hypothesized that the drug determines an improvement of the enterohepatic circle (acting on the hepatic clearance) in patients with chronic hepatic disorders as shown by the reduction of the percentage of SeHCAT retention noticed.
Radioimmunoassays for methotrexate are described, involving use of a rabbit antiserum to a conjugate of the drug and bovine serum albumin and the drug labeled with tritium, selenium-75, or iodine-125. Of the two gamma emitters, the 75Se-labeled drug was prepared by the Radiochemical Centre, Amersham, England and the 125I-labeled drug in the laboratory, by the Chloramine T iodination technique. The stability of labels with both methods allows use of the faster, cheaper, and simpler gamma-counting techniques, with results available after 3 h. All three methods have acceptable sensitivity, accuracy, precision, and reproducibility, and are specific for methotrexate, with no significant interference from naturally occurring folates or leucovorin. The assays in which the gamma emitters are used have significant practical advantages over the beta emitter and are much better suited to automation and clinical application. The main advantage of 75Se=labeled methotrexate is its longer half-life, 121 days, as compared with 60 days for 125I.
After intramuscular injections of 500 muCi 75Se, semen was collected periodically over a 63-day period from a selenium-deficient and a selenium-injected ram which were then killed for collection of the reproductive organs for the gel filtration studies. Testes, accessory glands and semen were also obtained from a bull injected intravenously with 75Se. Gel filtration (Sephadex G 150) of ram testis cytosol resulted in 4 75Se peaks (Ve/Vo ratios of 1 X 1, 1 X 5, 2 X 3, 2 X 9). In the selenium-injected ram the glutathione peroxidase (GSH-Px) peak (Ve/Vo 1 X 5) predominated, but in the selenium-deficient ram, radioactivity of the GSH-Px peak was less than that of the higher molecular weight peak (Ve/Vo 1 X 1). Gel filtration chromatograms of bull testis cytosol yielded 5 75Se peaks (Ve/Vo 1 X 1, 1 X 5, 1 X 9, 2 X 4, 2 X 8). In chromatograms of ram seminal plasma on Sephacryl S-200 there were 2 major (Ve/Vo 1 X 4, 1 X 1) and 2 minor peaks (Ve/Vo 1 X 7, 2 X 4). 75Se increased with time up to 49 days after injection in all peaks. 75Se-labelled bull seminal plasma yielded 2 75Se peaks (Ve/Vo 1 X 1, 1 X 4) which corresponded to the major peaks of ram seminal plasma. Bull and ram seminal plasma GSH-Px activities per mg protein were comparable (28 and 29 nmol NADPHox/min, respectively), but when expressed per ml seminal plasma, activity of the bull was more than 7 times the highest activity of ram seminal plasma (2908 and 385 nmol NADPHox/min, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)
Twenty-two mineral elements are known to be essential for animal life. These are calcium, phosphorus, sulphur, potassium, sodium, chlorine, magnesium, iron, iodine, copper, manganese, zinc, cobalt, molybdenum, selenium, chromium, tin, vanadium, fluorine, silicon, nickel and arsenic. Naturally occurring and man-made dietary imbalances of many of these elements and their interactions with other minerals are described and their functions and requirements by farm animals are outlined. The nature and importance of metabolic interactions among the mineral elements are discussed and the important concept stressed that there is no single minimum requirement or safe tolerance of a particular mineral, but a series of such minimum requirements and safe tolerances depending on the extent to which other minerals with which it interacts is present or absent from the diet. Radioactive tracer elements are shown to be of great value in the determination of mineral nutrient availability to the animal and for following mineral metabolic movements in the body. They are also shown to have considerable potential for the diagnosis of mineral imbalances. Various in vivo and in vitro techniques, involving both radioactive and stable tracers developed for the early diagnosis of mineral deficiencies are described and the strengths and weaknesses of such techniques in comparison with standard biochemical tests, are discussed. The need for further critical studies with isotopic tracers in the detection and diagnosis of mineral imbalances is emphasized. The main types of biochemical criteria used in the diagnosis of mineral deficiencies and excesses are given, with appropriate examples of their use.
With the introduction of a selenium bile acid SeHCAT (tauro-23-75Se-Selena-25 homocholic acid) a new and clinically valuable test for the functioning of the terminal ileum has been made available. Previous studies have shown that the test detects patients with bile acid malabsorption due to ileal disease. In this study SeHCAT retention was evaluated in nine patients with Crohn's disease and in seven healthy controls after intravenous administration of 0.15 MBq (4 muCi). A simple way of expressing the results is proposed. By using the calculated time required to eliminate 50% of the SeHCAT (WBR50), information is obtained as to the degree of terminal ileum malfunction regarding bile acid absorption. Accurate values seem to be achieved within 48 hours. As the SeHCAT is a gamma-ray emitter the dose retained could be measured by external counting. We suggest a practical design for the test using a simple scintillation spectro-photometer with a single detector in a low-background room. In patients and healthy controls the SeHCAT retention as calculated by WBR50 was 63 hrs (15-163) and 120 hrs (range 99-141), respectively. There was no overall relation between SeHCAT elimination and the intestinal transit time, although in the patient group a significant correlation was demonstrated, probably secondary to the impairment of the terminal ileum. A significant correlation was shown between the outcome of the test and the faecal excretion of total bile acids.
1. Six adult Friesian cows were given 75Se as either 75SeO32- or 75SeO42- intravenously. Five of the cows had cannulas in an hepatic vein, the portal vein and one carotid artery to enable the uptake of 75Se by the liver to be measured. Radioactive balance studies were carried out on two of the cows given 75SeO32- and two given 75SeO42-. A seventh cow was given an oral dose of 75Se-labelled barley and the excretion of 75Se in faeces, urine and milk was measured for 14 d. 2. After the injection of 75SeO32- plasma 75Se concentration decreased during the first 30 min with a mean half-life (t 1/2) of 15.6 min. From 30 to 60 min after dosing the concentration of radioactivity increased to reach approximately 50% of the level present 2 min after dosing. Following the injection of 75SeO42- the 75Se was cleared with a mean t 1/2 of 28.5 min during the first 30 min and plasma radioactivity increased only slightly during the next 30 min. 3. during the phase of rapid clearance of 75Se after the injection of 75SeO32- the hepatic venous 75Se concentration was approximately 5% lower than portal venous 75Se concentration. During the period when plasma 75Se activity was increasing the activity in hepatic venous plasma was 3% greater than portal activity. Of the 75Se cleared from plasma after injecting 75SeO32- 40% was calculated to be removed by the liver. 4. After intravenous dosing with 75SeO32- or 75SeO42- approximately 9.5 and 17.0% respectively of the dose injected was excreted in faeces and 10% in urine within 14 d. Almost three times as much 75Se was excreted in urine and 3.5 times as much in faeces during the first 24 h after dosing with 75SeO42- as after 75SeO32-.
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It is unclear whether bile acid absorption is affected by ileoanal pouch construction. Bile acid absorption was measured in the abdomen of 16 patients with pouches (nine with good and seven with poor pouch function based on a clinical score) and in six patients with an end ileostomy using a radiolabelled synthetic bile acid (75SeHCAT) enema and dynamic scintigraphy. The median (interquartile range) 75SeHCAT absorption was 81 (79-87) per cent in patients with ileostomy, 46 (43-53) per cent in patients having well functioning pouches, and 24 (18-38) per cent in the group with poor pouch function (P < 0.01). Log transformation of the absorption curves revealed a two-component uptake (fast component t1/2 = 1.4-7.2 min; slow component t1/2 = 16-144 min) in all patients with ileostomy, in eight of nine patients with pouches with good function, and in one of seven patients with a poorly functioning pouch (P < 0.05); in the other six patients with poorly functioning pouches, only the slow component of absorption was present. This test showed significantly reduced bile acid absorption in patients with an ileoanal pouch and gave an objective discrimination between well and poorly functioning pouches.
Horizontal two-dimensional polyacrylamide gel electrophoresis with immobilised pH gradients in the first dimension has been applied to the analysis of human skin fibroblast and muscle myoblast total cell proteins. Excellent two-dimensional separations of skin fibroblast proteins were obtained using pH 4-10 immobilised pH gradient gels with a long interelectrode distance (16 cm), but resolution was degraded, particularly of the more acidic proteins, by the use of shorter (10 cm) gels. Improved resolution of acidic and basic proteins was obtained using separate pH 4-7 and pH 7-10 immobilised pH gradient gels respectively in the first dimension. Two-dimensional protein maps of skin fibroblast proteins were visualised both by silver staining and by autoradiography of samples labelled synthetically with [35S]methionine. Horizontal two-dimensional electrophoresis, using pH 4-7 and pH 7-10 immobilised pH gradient gels in the first dimension, was applied to the analysis of protein samples from skin fibroblasts and muscle myoblasts dual-labelled synthetically with [35S]methionine and [75Se]selenomethionine in an attempt to identify sets of proteins specific to each cell type. In addition, two-dimensional maps or protein samples derived from normal individuals and patients with Duchenne muscular dystrophy were compared to search for protein changes associated with the disease state. Although sets of qualitative protein spot differences were observed by visual inspection of the two-dimensional gels, more rigorous qualitative and quantitative analysis of the patterns using a computerised analysis system will be required to obtain the maximum amount of information from these data.
By in vivo labeling with [75Se]selenite and separation of the proteins in the tissue homogenates by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), several selenium-containing proteins or protein subunits were detected in rat tissues (liver, lung, spleen and prostate). Their distribution among the cell components was investigated after fractionation by means of differential centrifugation. The selenium-containing proteins in the 16 kDa range were found to be mainly membrane-bound. By two-dimensional electrophoresis they were resolved into three labeled spots, two with the same relative molecular mass and pI values of about 4.8 and 5.0 and the third with a slightly lower molecular mass and a pI of 4.8. For further investigation they were concentrated and separated from the other labeled compounds by SDS-PAGE using preparative flow-through electrophoresis.