Low Selenium Concentrations Research Articles

Effects of dietary beta-carotene and selenium on initiation and promotion of pancreatic carcinogenesis in azaserine-treated rats.

In the present study the effects of 0.1 or 1.0 g beta-carotene/kg diet (L beta C or H beta C) and 1.0 mg or 2.5 mg selenium/kg diet (LSel or HSel), as well as combinations of the respective low and high concentrations of beta-carotene and selenium (LMix or HMix) on the initiation/early promotion phase or on the late promotion phase of pancreatic carcinogenesis in azaserine-treated rats, were investigated using cell proliferation and volumetric data of atypical acinar cell foci (AACF) as parameters. The present results indicate chemopreventive effects of dietary selenium, dietary beta-carotene and of their combination on the development of acinar pancreatic lesions induced in rats by azaserine. The inhibitory effect was most pronounced when beta-carotene and/or selenium were added to the diets during the late promotion phase of the carcinogenic process, although inhibition was also observed with these compounds when they were added to the diets during the first 5 weeks of the study only (initiation/early promotion phase). Neither in the initiation/early promotion phase nor in the late promotion phase was a dose-related trend observed. The multiplicities of AACF with a diameter over 1.0 mm and of carcinomas in situ (CIS), as well as the incidence of CIS were not significantly different among the groups. However, in the late promotion experiment a dose-related decline in multiplicity could be observed in the selenium supplemented groups and in the groups receiving combinations of beta-carotene and selenium. Cell proliferation in azaserine-induced AACF, as estimated by the bromodeoxyuridine (BrdU) labeling index, was significantly higher in H beta C, HSel, LMix and HMix groups (initiation/early promotion phase) as well as in H beta C, LSel, HSel, LMix and HMix groups (late promotion phase) than in high fat controls. From the present results it can be concluded that: (i) beta-carotene and selenium have inhibitory effects on pancreatic carcinogenesis induced in rats by azaserine; (ii) the most clear effects were observed when selenium was given as such, or in combination with beta-carotene during the late promotion phase; and (iii) beta-carotene and selenium stimulate cell proliferation in AACF.

Stoichiometry of Cd(S,Se) nanocrystals by anomalous small-angle x-ray scattering

In Cd(S,Se)-doped glasses the optical properties are strongly dependent on the size of the nanocrystals, but can be also largely modified by changes in the crystal stoichiometry; however, the information on both stoichiometry and size is difficult to obtain in crystals smaller than 10 nm. The intensity scattered at small angles is classically used to get information about nanoparticles sizes. Moreover the variation of amplitude of this intensity with the energy of the x ray—‘‘the anomalous effect’’—near the selenium edge is related to stoichiometry. Anomalous small-angle x-ray scattering has been used as a tentative method to get information about stoichiometry in nanocrystals with size lower than 10 nm. Experiments have been performed on samples treated for 2 days at temperatures in the range 540–650 °C. The samples treated at temperatures above 580 °C contain crystals with size larger than 4 nm. For all these samples the anomalous effect has nearly the same amplitude, and we found the stoichiometry x=0.4 for the CdSxSe1−x nanocrystals. This agrees with the previous results obtained by scanning electron microscopy and Raman spectroscopy. The results are also confirmed by measurements of the position of the optical absorption edge and by wide-angle x-ray scattering experiments. For the sample treated at 560 °C, the nanocrystal size is 3 nm and the stoichiometry x=0.6 is deduced from the anomalous effect. For samples treated at lower temperatures the anomalous effect is not observable, indicating an even lower selenium content in the nanocrystals (x≳0.7). We observed differences in the Se content of nanocrystals for different heat treatments of the same initial glass. These results may be very helpful to interpret the change in the optical properties when the temperature of the treatments decreases in the range 560–590 °C. In this temperature range, compositional effects seem to be of the same order of magnitude as the effects of the quantum confinement.

Age dependency of selenium and cadmium content in human liver, kidney, and thyroid.

Selenium and cadmium concentrations were investigated in 60 autopsy tissue samples obtained from fetal life up to adulthood (defined in this study as 25-87 y of age) in Styria, a moderately industrialized region in Austria that has a low selenium supply. During the first 2 y after birth, median liver selenium concentrations were slightly lower (i.e., 1.5 nmol/g wet weight) than concentrations found in fetal life (i.e., 2.9 nmol/g) and adulthood (2.1 nmol/g). Whereas in the fetal period median selenium content in the kidney cortex (2.1 nmol/g) and the thyroid gland (1.6 nmol/g) was lower than that found in the liver, the reverse was true for adults (i.e., kidney, 5.5 nmol/g; thyroid, 4.3 nmol/g). Tissue cadmium concentrations approached 0 during gestation. Accumulation in the kidney and liver commenced immediately after birth. In the thyroid gland of adults, significantly higher concentrations of cadmium were found. Median concentrations in adults showed no statistical significant age dependency (i.e., liver, 7.6 nmol/g; kidney, 59.8 nmol/g; thyroid, 11.2 nmol/g). In summary, the data revealed very low tissue selenium concentrations and low cadmium burdens for the Styrian population that was not exposed occupationally.

SELENIUM STATUS OF WHITE-TAILED DEER IN SOUTHERN FLORIDA

Samples of serum, liver, kidney, and heart were collected for selenium analysis from 174 white-tailed deer (Odocoileus virginianus) in southern Florida (USA), 1984 to 1988, to determine the selenium status of these animals. Deer were obtained from eight sites and classified by five age-class groups. For serum and the three tissues analyzed, selenium concentrations varied significantly (P < 0.001) among sites. Differences between years (P < 0.0004) were found for heart and kidney, age-class (P < 0.004) for kidney and season (P < 0.02) for liver. Low selenium concentrations were evident, in that 75% of all serum samples analyzed contained less than the critical concentration (< 0.06 ppm) by livestock standards, with 50% of serum samples less than 0.03 ppm, evidence of a severe deficiency. Likewise, tissue selenium concentrations (dry basis) were below critical livestock concentrations in 13% of the liver samples (< 0.25 ppm), 36% in kidney (< 3.0 ppm) and 19% in heart (< 0.15 ppm). Based on serum and tissue data, selenium dietary intake was low and may have been deficient for white-tailed deer in southern Florida.

Selenium concentrations in the razorback sucker (Xyrauchen texanus): Substitution of non-lethal muscle plugs for muscle tissue in contaminant assessment

A single muscle plug was collected from each of 25 live razorback suckers inhabiting the Colorado River basin and analyzed for selenium by instrumental neutron activation. Eight fish from Ashley Creek and three from Razorback Bar exhibited selenium concentrations exceeding 8 μg/g, a level associated with reproductive failure in fish. Concentrations of selenium in eggs and milt were significantly correlated with selenium concentrations in muscle plugs and together indicate a possible explanation for the decline of this species in the Colorado River basin. Muscle plugs (<50mg) and muscle tissue (20 g) were collected from dorsal, anterior, and posterior areas of common carp, flannelmouth sucker, and an archived razorback sucker and analyzed for selenium. Concentrations of selenium in muscle plugs were significantly correlated with selenium concentrations in muscle tissue from the same location and fish (r=0.97). Coefficients of variation for selenium concentrations in each fish were <6.5% for muscle tissue, but ranged from 1.5 to 32.4% for muscle plugs. Increased variation in muscle plugs was attributed to lower selenium concentrations found in the anterior muscle plugs of flannelmouth suckers. Mean selenium concentrations in muscle plugs and tissue from dorsal and posterior areas and muscle tissue from the anterior area were not significantly different. The non-lethal collection of a muscle plug from dorsal and posterior areas of the razorback sucker and other fish species may provide an accurate assessment of selenium concentrations that exist in adjacent muscle tissue.

Method for the Determination of Selenium in Low-Selenium Grain and the Effect of Liming on the Uptake of Selenium by Barley and Oats

Abstract Selenium was determined in grain of barley and oats grown at locations distributed all over Sweden with the objective of studying the influence of liming on the selenium uptake at natural levels in the soil. The samples were taken from on-going field experiments, limed to different levels. An analytical procedure, carried out in a single test tube, was developed to cope with the low selenium concentrations in the grain. It involves combined wet/dry ashing of the organic matter, reduction to selenite by hydrochloric acid, complexation to obtain a brominated piazselenol, extraction of the complex into toluene, and finally determination by capillary gas chromatography with electron capture detection. The concentrations of selenium in the grains investigated were low, ranging from 1.5 to 16 ng g−1 dry weight. The limit of detection for a 0.1 g sample is 0.4 ng g−1, as estimated by three times the standard deviation of the blank determination (n = 34) and the absolute limit of detection for pure solutions is below 20 fg (0.5 μl injection on the column). The procedure was validated by determinations on reference materials, testing an alternate digestion procedure, and by determination using hydride generation atomic absorption spectrometry. Liming of the soil was found to have a small, but significant negative effect on plant uptake of selenium.

Factors affecting the selenium intake of people in Transbaikalian Russia.

The selenium concentration in foods grown and consumed and in plasma, red blood cells, and toenails of people living in the district of Chita in the transbaikalian part of Russia were studied in August 1991. Preliminary results from the area have suggested low selenium intakes and the possible occurrence of cardiomyopathy (Keshan disease) in the population. A low selenium concentration in foods grown locally was found: mean selenium concentration in wheat grains was 1, 5, and 28 micrograms/kg, respectively, in three villages studied, that of oats was between 3-6 micrograms/kg, and of cow's milk 10-27 micrograms/kg dry matter. The selenium concentration of bread was considerably higher, between 87-337 micrograms/kg dry wt, presumably because wheat imported from the US had been used for baking. Occasional samples of pork, beef, and mutton contained between 32-218 micrograms selenium/kg dry wt. Low selenium concentrations were observed in samples of soil and river water. The mean plasma selenium concentration of 52 persons was 1.02 mumol/L, including 33 children and 19 adult subjects. The selenium concentrations in red blood cells and toenails were 1.95 mumol/L and 0.61 mg/kg, respectively. No symptoms of heart disease caused by selenium deficiency were observed. It is concluded that the selenium status of people was fairly good thanks to the contribution to dietary intake of imported wheat with a high selenium content. As the selenium concentration was very low in foods grown in the area, the selenium intake of the population will be reduced to a very low level if only locally produced foods are consumed.

Cathodic stripping voltammetry of HgSe

The problem with the presence of several cathodic stripping peaks for HgSe in acidic Se(IV) solutions has been addressed using linear sweep, cyclic, square-wave and differential pulse stripping voltammetry at a hanging-mercury-drop electrode (HMDE). When very small amounts of selenium are accumulated, the selenium is dissolved in the HMDE and a single cathodic stripping peak is obtained. The solubility of selenium in mercury was estimated to 1–2 nmol cm −3 . The deposition of larger amounts of selenium gives rise to up to three film stripping peaks, most probably because of the reduction of thin two-dimensional and thicker three-dimensional HgSe islands formed simultaneously on the mercury surface. In the presence of Cl −, a single narrow HgSe film stripping peak is observed after deposition at a potential close to the positive potential limit of the electrode. The different voltammetric stripping techniques have been evaluated with respect to sensitivity and applicability. At low selenium concentrations, when the selenium is dissolved in the mercury electrode, square-wave or differential pulse stripping voltammetry is the method of choice. At higher concentrations, when most of the material is present as HgSe, linear sweep voltammetry is the most reliable technique.

The impact of selenium fertilisation on the distribution of selenium in rivers in Finland

Finland is a country covered by thin layers of glacial deposits, mainly till, on top of Precambrian igneous and metamorphic rocks. The environment is characterised by low selenium (Se) concentrations. To improve the Se intake of the population, Se-supplemented fertilisers have been used nationwide since 1985. This raises the possibility of undesirable environmental effects of the operation. The present study, the first one dealing with Se concentration of stream waters and stream sediments in Finland, throws light on the mobilisation of Se in the environment. The median Se concentrations (range) in stream waters and stream sediments were 67.5 ng 1 −1 (32–180 ng 1 −1) and 258 μg kg −1 (29–3940 μg kg −1), respectively. There was a highly significant correlation between the Se concentration of stream waters and sediments ( r=0.313, P<0.001, n=204). The rainfall-related seasonal variations of the Se concentrations in stream water exceeded 100%. The stream water Se concentrations decreased from 1991 to 1992, possibly as the result of a reduction in the amount of Se added to fertilisers since 1991. The stream water Se concentrations correlated with those in well water and with cultivated field area per community. About 8.5% of the Se in stream waters was in particulate form. The fractions of the total Se in humic substances (36%) and selenate (35.7%) dominated the Se species of stream waters, while selenite comprised only 9.6% of the total Se. Cultivation and the use of Se-supplemented fertilisers may have temporarily increased the Se concentrations in headwater stream and river waters in Finland.

Lipid peroxidation as a measure of oxygen free radical damage in the very low birthweight infant.

(ABSTRACTOxygen free radical mediated tissue injury is implicated as a major factor in the pathogenesis of the long term complications seen in the premature infant, and direct evidence of their role in the development of these long term problems is lacking. A prospective observational study of 78% of very low birthweight infants admitted to a level III neonatal intensive care unit in 1992 was undertaken to determine the relationship between lipid peroxidation products, antioxidant activity, and outcome. Lipid peroxidation (malondialdehyde-thiobarbituric acid, MDA-TBA) and antioxidant activity (vitamin E and glutathione peroxidase activity) were measured in 22 very low birthweight infants in the cord blood and the infant's blood at 24 hours, 48 hours, and 1 week of age and correlated with outcome measures. The normal range for these measures was established in the cord blood samples of 48 consecutive healthy full term infants. The concentration of MDA-TBA at 1 week correlated with the number of days of oxygen treatment and number of days of positive pressure ventilatory support. Controlling for gestational age and antenatal complications simultaneously the MDA-TBA concentration remained significantly associated with the number of days of oxygen treatment and the number of days of positive pressure ventilatory support. Glutathione peroxidase was low in the premature and full term infants consistent with the low concentrations of selenium known to be present in southern New Zealand. There was evidence of a quadratic relationship between vitamin E at 1 week and the total number of days of supplementary oxygen requirement, with both high and low values associated with increased oxygen requirement. This association, however, did not remain after controlling for gestational age and antenatal complications. These results support the role of oxygen free radicals in mediating tissue damage associated with the development of chronic lung disease in the premature infant.

Low platelet glutathione peroxidase activity and serum selenium concentration in patients with chronic renal failure: relations to dialysis treatments, diet and cardiovascular complications.

1. Selenium status was investigated in patients with chronic renal failure, with special regard to its relations to the dialysis treatments, dietary habits and clinical signs of atherosclerosis. 2. Serum selenium concentration and platelet glutathione peroxidase activity were measured in 45 patients with chronic renal failure subdivided into three groups according to the type of treatment: 15 non-dialysed, 15 on haemodialysis, 15 on continuous ambulatory peritoneal dialysis. A 7-day diet history was carried out in all patients. Seventeen of the patients with chronic renal failure had clinically overt cardiovascular disease. Forty-five age-matched healthy subjects were considered as controls. 3. Both serum selenium concentration and platelet glutathione peroxidase were significantly reduced in all patients with chronic renal failure compared with control subjects; a direct and significant correlation was found between the two parameters. No differences in selenium status were observed among the non-dialysed, haemodialysis and continuous ambulatory peritoneal dialysis groups. No correlation between total calorie or protein intakes and selenium indices were observed. The chronic renal failure patients with cardiovascular complications showed a further significant reduction in both serum selenium concentration and platelet glutathione peroxidase activity as compared with the patients without cardiovascular complications; these two groups were similar with respect to the other well-known cardiovascular risk factors (age, smoking, plasma lipids, hypertension, body mass index). 4. It is concluded that a low selenium concentration is present in chronic renal failure, which is independent of dialysis and is accompanied by biological repercussion in terms of reduced platelet glutathione peroxidase activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of various flavonoids and simple phenolics on development of exudative diathesis in the chick

Three-day-old broiler chicks were fed a diet containing low concentrations of selenium and vitamin E for 21 days to produce exudative diathesis. Dietary supplements (1000 mg/kg) of various flavonoids and simple phenolics were tested for their protectiveness against the disorder. Two of the flavonoids, rutin and silymarin, markedly reduced the incidence and severity of exudative diathesis, while three other flavonoids (catechin, quercetin, and morin) and with of the simple phenolics tested (p-coumaric and ferulic acid) provided no protection

Determination of trace quantities of selenium and arsenic in canned tuna fish by using electroanalytical techniques

Fifteen brands and types of tuna fish were analyzed for selenium by using differential-pulse cathodic-stripping voltammetry. The cans with high and low concentrations of selenium were analyzed for arsenic by using differential-pulse polarography. Three samples with different levels of added As and a blank were analyzed for each can of tuna fish. Four sample-digestion methods with several variations of each were tested to determine the most reliable technique. An acid-digestion procedure using HNO 3 and Mg(NO 3) 2, 6H 2O with an 18-h predigestion step gave the best results, with an average recovery of 98.2%. The selenium concentration of the cans analyzed ranged from 0·034 to 1·20 μg g −1, with an average concentration of 0·68 ± 0·27 μg g −1. The arsenic concentrations of the two cans analyzed were 1·62 μg g −1 and 2·41 μg g −1 in the low- and high-selenium cans, respectively. The selenium concentrations found in the tuna fish are not excessively high and do not seem to pose a problem. The arsenic concentration of 2·41 μg g −1 does, however, approach the maximum allowable level set by the FDA at 2·6 ppm.

Heavy metal and selenium levels in young cattle egrets from nesting colonies in the northeastern United States, Puerto Rico, and Egypt.

Colonially-nesting species of herons and egrets breed mainly in coastal areas, along rivers or near other large bodies of water. Such areas are also preferred for human development, exposing nesting birds to various pollutants. From 1989-1991, the concentrations of heavy metals and selenium were studied in the feathers of fledgling cattle egrets Bubulcus ibis, a terrestrially-feeding insectivore, from New York and Delaware in the northeastern United States, from Puerto Rico, and from Egypt. There were geographic differences in the concentrations of lead, mercury, cadmium, manganese, selenium, and chromium in the feathers of these egrets. Lead levels were 41 times higher in the feathers of cattle egrets from Cairo compared to the other sites. This difference was attributed to the continuing use of leaded gasoline and the dense automobile traffic in Cairo. However, other differences remain unexplained. Similarly, levels of chromium and manganese were also higher in Cairo than at any other sites. Cadmium levels were similar at all places except for higher levels in eastern Puerto Rico. Mercury concentrations were twelve times higher in the feathers of cattle egrets at Aswan compared to Cairo. In Puerto Rico, we also compared levels in adult cattle egrets with young and found higher concentrations of mercury and manganese, but lower concentrations of selenium in the adults. Using feathers from young cattle egrets is a potentially sensitive tool for biomonitoring for metals, especially lead, since they reflect the local area surrounding the breeding colony.

The nature of malnutrition in children with end-stage liver disease awaiting orthotopic liver transplantation

To evaluate malnutrition in chronic liver disease, and its relationship to nutrient deficiencies and hepatic dysfunction, 27 children with end-stage liver disease were studied. Mean protein-energy intakes were 70% of recommended daily intakes. The patients were underweight and stunted with reduced mean triceps and subscapular skinfold thicknesses and midupper arm circumference. Mean total body potassium was only 63 +/- 18% of that expected for age and sex. Deficiency of essential fatty acids (32%), and low concentrations of fat-soluble vitamins (A, 92%; E, 32%), iron (32%), zinc (42%), and selenium (13%) were common. Serum ammonia concentrations were raised in all patients, and increased methionine, tyrosine, and glutamic acid, and reduced glutamine concentrations were noted. There was no correlation between the degree of malnutrition and the degree of liver synthetic function, the degree of cholestasis, or the degree of liver injury. We suggest that potentially correctable factors in addition to liver failure (eg, inadequate absorbed intake) were important determinants of malnutrition in these patients.

A low plasma selenium is a risk factor for peripartum cardiomyopathy. A comparative study in Sahelian Africa

A specific selenium deficiency is a risk factor for Keshan disease, an endemic cardiomyopathy observed in China. In a Sahelian area of Niger, plasma selenium concentration was measured by neutronic activation and particle induced X-ray emission in 35 black African women with peripartum cardiomyopathy and 36 breast-feeding women without cardiac failure as controls. The plasma selenium concentration in patients was lower (48 ± 25 ng/ml, mean ± standard deviation) than in controls (77 ± 16 ng/ml) ( P < 0.0001). Moreover, 40% ( 14 35 ) patients with peripartum cardiomyopathy had very low plasma selenium concentrations, below 45 ng/ml, versus none in controls. A low plasma selenium concentration is a risk factor for the Sahelian peripartum cardiomyopathy.

Characteristics of selenium in australian marine biota

AbstractThe occurrence, distribution and speciation of selenium in Australian marine biota is discussed. Biochemical pathways for the accumulation of selenium by marine organisms are also postulated. Comparison of the levels of selenium in macroalgae, fish, crustaceans and molluscs indicates that preferential accumulation of selenium by particular taxa does not occur. Phaeophyta have significantly lower selenium concentrations than Rhodophyta and Chlorophyta. Fish have lower selenium contents in muscle tissues than molluscs and crustaceans. Marine animals with different dietary intake (planktonic vs herbivorous vs carnivorous) are not observed to have significantly different levels of selenium (P&gt;0.05). Selenium in all the organisms studied was predominantly associated with free amino‐acids or protein residues and was not present as characterizable inorganic selenium species (SeO32−, SeO42−). These results indicate that selenium is probably only incorporated into biota for specific biochemical purposes with any exces selenium being excreted or eliminated.

Electrochemical synthesis of semiconducting CdSe thin films

Semiconducting CdSe thin films were synthesized by cathodic electrodeposition from an aqueous acid solution. Alloy formation occurs when the growth rate is limited by selenium ion mass transport and when the cadmium is underpotentially deposited. The composition and the physical properties of the asgrown layers are very sensitive to the selenium concentration of the solution and to the applied potential. CdSe films always have a zinc blende structure (instead of the normal wurtzite structure) with a strong (111) preferred orientation. It is shown that the best characteristics (stoichiometry, crystallinity, band gap width, etc.) are obtained with low selenium concentrations and in a narrow potential range. By using these appropriate preparation conditions, it will be possible to reduce the chemical and physical post-treatments generally applied to these kinds of semiconducting thin films in order to increase their solar energy conversion performances in solid or liquid junction cells.

Low selenium status and cot deaths

Selenium is a naturally occurring trace element essential to the health of many mammal and avian species. Low levels of selenium are evidenced by a variety of symptoms, mainly in the cardiac and musculo-skeletal systems. Tasmania and South Island, New Zealand, both have low soil levels of selenium and high rates of cot death. Evidence is presented to suggest that these may be related via a pathway involving maternal selenium status during gestation or low selenium content in mothers' milk.

Flow Injection Analysis with On-Line Preconcentration of Trace Selenium

A flow injection analysis system has been developed for the determination of very low concentrations (<1 ng/ml) of selenium(IV). The system involves a micro column packed with a resin loaded with Bismuthiol-II sulfonate (Bis-II S) for the on-line preconcentration of trace selenium(IV) and a manifold for the quantification of selenium based on the Se-catalyzed reduction of 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H tetrazolium bromide (MTT). Selenium was selectively collected as selenotrisulfide (-S-Se-S-) on the resin by reaction with Bis-II S, and eluted with a small volume of penicillamine solution which withdraws the selenium from the resin. Selenium thus eluted as penicillamine selenotrisulfide was introduced to the flow injection analyzer, where penicillamine selenotrisulfide catalyzes the reduction of MTT to formazan by dithiothreitol. The interference from copper ion was eliminated by the adsorption of Cu on the resin as a bathocuproine disulfonate chelate. Reliability of the present method was confirmed from the determination of selenium contents in a biological standard sample.