Showing papers on "Selenium published in 1979"

Selenium, vitamin E and the response to swimming stress in the rat.

Abstract: Experiments were conducted to determine the effects of exercise on rat glutathione peroxidase system enzymes and lipid peroxidation among animals supplemented and unsupplemented with selenium (Se) and vitamin E (E). Liver, muscle and blood were taken before, immediately after and 24 hours after exercising to exhaustion by swimming. No effect of exercise was found on muscle or liver enzymes, although exercise resulted in depressed glutathione reductase (GR) and glucose-6-phosphate dehydrogenase (G6PD) activities in erythrocytes immediately after exercise. Dietary Se supplementation did result in increased hepatic muscle and erythrocyte glutathione peroxidase activity, and decreased hepatic GR, G6PD and "malic enzyme" activities. Thiobarbituric acid reactive substances, and indicator of lipid peroxidation, increased in liver and muscle subsequent to exercise. This increase was reduced in liver, but not eliminated, by dietary E supplementation. The increase was not affected by dietary E in muscle, nor by dietary Se in either tissue.

Serum levels of selenium, calcium, copper magnesium, manganese and zinc in various human diseases.

Abstract: Serum selenium as well as serum zinc, copper, magnesium, calcium and manganese were investigated in a control group of adult males and in 11 groups of patients in various disease states Not only the change of each trace element but also the possible association between elements was studied in the various groups All patients were fasting when sampled and studied only after the acute phase of the disease was corrected Trace metal determinations were performed by atomic absorption spectrophometry (Mg, Ca, Cu, Zn) and by neutron activation analysis (Se, Mn) All patients showed low serum zinc when compared to controls Cirrhotic patients had a low serum selenium level as well as low calcium, magnesium and zinc Emphysemia and cancer patients had an elevated serum copper concentration while copper and manganese levels were elevated in congestive heart failure, infection and pschoses To our knowledge this is the first time low serum selenium values have been demonstrated to be associated with the low serum zinc, calcium and magnesium levels found in cirrhotic patients

Influence of vitamin E and selenium on immune response mechanisms.

Abstract: Vitamin E and selenium have both been shown to have immunostimulatory effects in a variety of species when administered in quantities in excess of established deitary requirements. Responses to each nutrient appeared to be independent of the nutrition of the other. Deficiencies of vitamin E and selenium conversely caused suppression of the immune response system, particularly, cell mediated mechanisms. Suppression was shown to be associated with serum factors coating lymphocytes from dogs deficient in vitamin E and selenium. Oral supplementation with vitamin E transformed or removed the suppressive factors, dietary selenium had no effect. In vitro peripheral lymphocyte blast transformation tests corroborated observations of in vivo studies. Reducing agents and synthetic anti-oxidants eliminated suppressive effects in vitro. Suppression was most marked in dogs fed diets highest in polyunsaturated fatty acid (PUFA) content, providing conditions most conductive to lipid peroxidation in vivo. The essential fatty acids linoleic and arachidonic have been shown to similarly influence immunoregulatory mechanisms in vivo. The effect may be a direct one since plasma membrane fluidity of lymphoid cells increases the probability of modification of cell--antigen interactions by PUFA. However, their effect may also be an indirect one. PUFA are known precursor substances of E anf F type prostaglandins which have been shown to affect immediate and delayed hypersensitivity by stimulating synthesis of cyclic AMP. More definitive studies are needed to resolve this question.

Separation of Toxic Heavy Metals by Sulfide Precipitation

Abstract: Sulfide precipitation with Na2S is found to be highly effective to obtain a high degree of separation of heavy metal cations (Cd, Zn, Cu, and Pb) and of the oxyanions of arsenic and selenium from complex wastewaters. The metal separation characteristics are evaluated with a dilute synthetic mixture and with an actual copper smelting plant wastewater. The overall separation of arsenic and other heavy metals and precipitate settling rates are optimum at sulfide dosages about 60% of the theoretical values and at a final pH greater than 8.0. The removals of Cd, Zn, and Cu from the actual wastewaters are greater than 99%, and As and Se removals are 98 and >92%, respectively. Cd, Cu, and Zn concentrations in the range of 0.05 to 0.1 mg/1 can be achieved with sulfide precipitation. The metal separations and settling rates obtained with conventional hydroxide precipitation (lime) are considerably lower than those obtained with sulfide precipitation.

Selenium content and glutathione peroxidase activity in the plasma and erythrocytes of non-pregnant and pregnant women.

Abstract: Decreases in the glutathione peroxidase activity and in the selenium content were found in the plasma of pregnant women as compared with a control group. In the erythrocytes, both parameters remained unchanged. In both groups a fraction of about 0.90 of the glutathione peroxidase in the blood, was contained in the erythrocytes, whereas the selenium was nearly evenly distributed between plasma and red blood cells. A positive correlation existed between the total amount of selenium in the erythrocytes and that in the plasma.

Distribution of glutathione peroxidase activity and selenium in the blood of dairy cows.

Abstract: The distribution of glutathione peroxidase (GSH-Px) activity and selenium concentrations among several components in the blood of dairy cows was examined. Approximately 98% of the GSH-Px activity in peripheral blood was associated with the erythrocytes when enzyme activity was expressed as units per milliliter of blood. The GSH-Px activity expressed per cell was approximately fourfold greater for peripheral leukocytes than for erythrocytes. The cellular component contained a greater proportion (approx 73%) of whole blood selenium than did the plasma. A positive linear relationship (r = 0.958) between blood GSH-Px activity and blood selenium concentrations was found in dairy cattle under practical field conditions.

Metabolism of Hydrogen Selenide and Methylated Selenides

Abstract: Inorganic forms of selenium are readily metabolized to a variety of or-ganoselenium compounds in microorganisms, plants, and animals. The metabolism of selenium may either enhance or reduce the biological activity of this element. Nutritionally active inorganic selenium compounds, such as sodium selenite or sodium selenate, can be converted to physiologically active forms of selenium such as the selenoenzyme, GSH (glutathione) peroxidase. Toxic levels of selenite or selenate can be detoxified by the formation of methylated selenides that are readily excreted and usually less toxic.

Catalytic action of L-methionine gamma-lyase on selenomethionine and selenols.

Abstract: We examined the catalytic action of L-methionine gamma-lyase (EC 4.4.1.11) on selenomethionine (2-amino-4-(methylseleno)butyric acid), methaneselenol, l-hexaneselenol, and benzeneselenol. The enzyme catalyzes alpha, gamma-elimination of selenomethionine to yield alpha-letobutyrate, ammonia, and methaneselenol, and also its gamma-replacement reaction with various thiols to produce S-substituted homocysteines. Selenomethionine is an even better substrate than methionine in alpha, gamma-elimination but is less effective in gamma-replacement. In addition, L-methionine gamma-lyase catalyzes gamma-replacement reaction of methionine and its derivatives with selenols to form the corresponding Se-substituted selenohomocysteines, although selenols are less efficient substituent donors than thiols. This is the first proven mechanism for the incorporation of selenium atom into amino acids.

Mutagenic activity of selenium compounds.

Abstract: The mutagenicities of selenate (SeO 4 2− ) and selenite (SeO 3 2− ) were determined by two bacterial assay systems: Kada's rec -assay and Ames's Salmonella test. In both assays, these compounds were found to be weak mutagens. In the Salmonella test, selenate (0.05 revertants/nmole) and selenite (0.2 revertants/nmole) gave rise to base-pair substitution.

Determination of germanium, arsenic, selenium, tin and antimony in complex samples by hydride generation-microwave-induced plasma atomic-emission spectrometry

Abstract: This paper describes the utilisation of a semi-automatic hydride generation device coupled to a microwave-induced argon-helium plasma that is used with a 0.5-m monochromator for the analysis of germanium, arsenic, selenium, tin and antimony in several complex samples. Incorporated in the system are a condensation tube and a Chromosorb 102 column that are used to separate the analyte species from hydrogen evolved during the course of the generation reaction, and to separate the analytes from condensed contaminants that cause spectral background interferences.Results reported are standard recoveries and relative precision for germanium, arsenic, selenium, tin and antimony in whole blood and in enriched flour. Also reported are arsenic and antimony values for NBS orchard leaves. Results obtained on complex samples are compared with the precision obtained for aqueous standards.

Neonatal erythrocyte glutathione peroxidase deficiency as a consequence of selenium imbalance during pregnancy.

Abstract: Summary. The red blood cell (RBC) glutathione peroxidase (GSH-Px) activity and routine haematological parameters were measured in 38 healthy north Italian full-term pregnant women and in their newborn infants. In 31 pairs the serum selenium concentration was also measured. Data were compared with those of 20 normal adult controls (10 males and 10 females). Newborn infants exhibited significantly lower RBC GSH-Px activity and serum selenium concentrations than adult controls. Pregnant women had serum selenium values intermediate between those of adult female controls and their newborn infants. In both the pregnant women and newborns the RBC GSH-Px activity correlated with the level of selenium in serum which suggests that the neonatal RBC GSH-Px deficiency may be partially due to insufficient availability of selenium during pregnancy. Factors other than selenium concentration, e.g. hormonal and genetic, might also affect the RBC GSH-Px activity as suggested by sex differences and mother/child concordances in enzyme activity found in our cases.

The biological selenium status of livestock in Britain as indicated by sheep erythrocyte glutathione peroxidase activity

Abstract: The reliability of erythrocyte glutathione peroxidase activity as an indicator of selenium status in livestock is discussed. Based on this measurement, a survey is described of the biological selenium status of sheep on each of 329 farms in Britain. Results showed that 47 per cent of these farms were probably unable to provide grazing livestock with sufficient selenium to maintain blood levels greater than 0.075 microgram per ml. Increased selenium deficiency from the increasing use of home grown feeds as a major constituent of livestock rations may be causally related to the increase of white muscle disease and other selenium responsive diseases in Britain.

A hydrometallurgical process for recovering precious metals from anode slime

Abstract: A hydrometallurgical process for recovering precious metals, such as gold, silver, selenium, and tellurium etc. from anode slime has been developed and tested successfully. The process comprises three major unit operations: leaching, liquid-liquid extraction, and reduction. The decopperized anode slime is first leached with nitric acid at an elevated temperature to obtain a leach solution containing at least about 95% by weight of the silver content, 96% by weight of the selenium content and 76% by weight of the tellurium content of the decopperized anode slime. Silver in the nitric acid leach solution is recovered in the form of silver chloride. Subsequent to the recovery of silver chloride, the selenium, tellurium, copper and other impurities-containing solution is denitrated and chlorinated by a liquid-liquid extraction technique. This selenium, tellurium, copper and other impurities-containing chloride solution is treated to separate tellurium from selenium, copper and other impurities by a liquid-liquid extraction technique. Selenium and tellurium are then recovered individually by passing sulfur dioxide through the selenium-containing and tellurium-containing solutions. The nitric acid leach residue is treated with aqua regia to leach gold and other impurities at an elevated temperature for a period of about 1 to 4 hours. The gold-containing solution is sent to separate gold from other impurities by a liquid-liquid extraction technique. Gold with a purity of greater than 99.9% is recovered by introducing a reducing agent to the gold-loaded organic extractant at an elevated temperature for a period of about 2 to 4 hours. This newly developed process is pollution-free, energy-saving, and economic to compare with conventional pyrometallurgical processes.