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PubMedDate not supplied

Apparent selenium toxicity in emus (Dromaius novaehollandiae).

A commercial emu breeder experienced high embryonic mortality during the 1992-93 breeding season, apparently associated with high levels of selenium. The feed was a mixture of catfish food supplemented with a vitamin E and selenium premix. The mixture contained an average of 1.4 ppm selenium. Selenium analysis was conducted on eggs from several hens laid during the period of vitamin and selenium supplementation and after the supplementation was withdrawn. Initial egg selenium levels ranged from 1.2 to 7.1 ppm, with a mean value of 4.2 +/- 0.7 ppm (n = 9). Eggs collected over a 2-month period post-withdrawal contained 2.1 +/- 0.2 ppm selenium (n = 6). Eggs sampled between 2 and 3 months post-withdrawal contained 1.1 +/- 0.1 ppm selenium (n = 4). Egg selenium levels decreased significantly over the 3-month period (P < 0.05) for each individual sample.

Animal Feed↗
PubMed1996

Selenium and fertility in animals and man--a review.

To evaluate the information on selenium with relation to fertility in animals and man the available literature was reviewed. Selenium is incorporated in the sperm mitochondria capsule and may thus affect the behavior and function of the spermazoon. Se seems to be essential for normal spermatozoa development in both experimental animals and in livestock and probably also in humans. Regarding selenium and female fertility only sparse information exists. In experimental animals a low selenium level affects fertility in males, but little attention has been devoted to female reproductive performance, and the data are insufficient for conclusion. In livestock numerous investigations have been performed and the effects of selenium supplementation often in combination with other antioxidants have been evaluated, but no valid conclusion can be drawn. In general adequate nutritional supply will secure optimal reproduction in both males and females, while additional supplementation seems to have a negative effect. In humans contradictive information is found. Both low and high sperm selenium concentrations are reported to have a negative influence on the number of spermatozoa and on the motility. The optimal sperm selenium concentration waits to be defined. Some evidence indicates that a metabolic defect in a selenium incorporation into sperm cells may be associated with human infertility. No human data relating selenium to female infertility were found.

Animals↗
PubMedDate not supplied

Metabolism of subtoxic levels of selenium in animals and humans.

Since high levels of selenium are used as cancer chemopreventive agents in animals and humans, a better understanding of the metabolism of subtoxic levels is desirable. Absorption from rat small intestine using in situ double perfusion, ligated intestinal segments, and brush border membrane vesicles (BBMV) was used to study selenium absorption. A level of 1.2 mM intraluminal selenite was required to inhibit 50 percent of the transepithelial transport of 3-0-methylglucose, indicating a high tolerance of the intestinal tract to selenium. The relative efficiency patterns for uptake of different selenocompounds during in vitro perfusion and in vivo ligated segments were identical with selenomethionine (SeMet) > selenate > selenite. In contrast, selenite was taken up most rapidly by BBMV, followed by SeMet and selenate in decreasing order. Ligated segments, double perfusion experiments, and uptake by BBMV indicated that selenium as selenodiglutathione or selenodicysteine was taken up faster than when present as selenite. Selenate and SeMet appeared in the vascular effluent largely unchanged, but selenite was metabolized extensively during absorption. Most of the selenium in plasma from subjects living in a high selenium area of China was associated with albumin, which is likely a result of high dietary intake of SeMet. Cracked fingernails and extensive hair loss were the symptoms of selenium toxicity in these individuals. Low adverse effect level of dietary (mean LOAEL) selenium was calculated to be about 1540 +/- 653 micrograms per day (or 28 micrograms/kg body weight) and the maximum safe dietary (mean NOAEL) selenium was calculated to be 819 +/- 126 micrograms per day (or 15 micrograms/kg body weight).

Animals↗
PubMedDate not supplied

Utilization of selenium from different chemical entities for selenoprotein biosynthesis by mammalian cell lines.

Four different cell lines (Hep G2, THP-1, EL 4 6.1, and ECV 304) were grown in a selenium-deficient standard medium (5% fetal calf serum in RPMI 1640 resulting in 5.5 nM selenium of unknown bioavailability) and supplemented with increasing concentration of selenium in the form of sodium selenite, selenomethionine and serum-bound selenium. The activities of two types of glutathione peroxidases (cGPx and PHGPx) were measured to estimate the availability of selenium for selenoprotein synthesis. Only sodium selenite between 1 and 100 nM was found to consistently induce GPx activity in all cell lines, whereas selenomethionine in equal concentrations was practically ineffective. Only THP-1 cells were able to utilize selenium from serum as efficiently as sodium selenite. PHGPx activity similarly responded to selenium supplementation, but was not increased in EL 4 6.1 cells. Our data demonstrate that conventional tissue culture media require selenium supplementation to guarantee adequate selenoprotein biosynthesis in cultured cells. The chemical nature of the selenium compound used for such supplement is as critical for in vitro cultivated cells as for dietary intake.

Animals↗
PubMed1996

[Status and selenium intake as related to the thyroid gland in the population of Znojmo].

In a group of 360 people aged 6-65 years of both sexes from the Znojmo area the author investigated the selenium status and intake by serum analyses (246 cases), urine analyses (356 cases) and hair analyses (28 analyses in middle-aged men). By correlation analysis the author investigated the relationship of selenium and metabolic and peripheral thyroid parameters. From the low selenium concentration in all investigated materials (42 micrograms Se/l serum, 8.2 micrograms Se/urine, 7.2 micrograms Se/g creatinine in urine and 0.23 microgram Se/g hair) the author concludes that there is selenium deficiency in the investigated population, the primary cause being a low dietary selenium intake (average adult intake 17 to 25 micrograms Se/day). From significant, though loose correlations between selenium concentrations and thyroid parameters (size, texture, number of nodes), serum concentrations of thyroid hormones (and their ratios resp.), as well peripheral parameters of hormone actions (Achilles tendon reflex, pulse rate or anthropometric variables) the conclusion is drawn that the selenium deficiency is so marked that it interferes in the investigated population with the regulation of the organism by thyroid hormones. This effect may be caused by changes of hormone formation in the thyroid gland due to the concentration of Se-dependent peroxidase, but in particular changes of their metabolism in the circulation and periphery, as selenium participates in the active centre of deiodase I in the formation of metabolically active triiodothyronine, and selenium deficiency has an impact also on deiodase II activity in some specialized tissues.

Adolescent↗
PubMed1997

[Selenium content in wheat and rye flow from Russia, cis nations and Baltic countries].

Selenium concentrations in wheat and rhy flour of Russia and CSC vary from 46 to 577 mg/kg and from 6 to 87 mg/kg correspondingly. The highest wheat flour selenium--300-600 mg/kg--is typical to wheat, imported from USA and Canada. Low values of selenium wheat flour (34-64 mg/kg) and of selenium rhy flour (5-20 mg/kg) from Kaliningrad, Novgorod, Pskov, Leningrad regions, Altay, Byelorussia and Baltic countries show the possibility of low selenium consumption by the population of these regions. Low selenium is demonstrated for wheat flour imported to Kirghizia - 81 +/- 31 mg/kg and produced in north-western part of Ukrain: Volinsk, Sumi, Kiev regions--64-78 mg Se/kg. Sakhalin and selenium-deficient Buryatia utilize predominently imported wheat flour with high selenium content - 250-260 mg/kg. Native grain with relatively high selenium is found in Kurgan, Orenburg, Lipetsk, Tambov regions, Tataria and Uzbekistan - 160-185 mg/kg.

Baltic States↗
PubMed1998

Comparison of 3 methods of selenium assessment in cattle.

Three tests are routinely done to assess blood status of selenium in cattle: serum selenium, whole blood selenium, and glutathione peroxidase. The objective of this study was to compare the various analytical methods for determining blood selenium status in groups of mature cows and beef calves. Twenty to 30 blood samples per herd were collected from 8 beef herds in central Alberta and 1 dairy in Alberta herd twice a year from the spring of 1992 through the fall of 1995, and once from 185 spring calves in 2 beef herds in Saskatchewan. Serum and whole blood samples were submitted to 1 laboratory and whole blood samples were submitted to a 2nd laboratory. Samples for glutathione peroxidase determinations were submitted to a 3rd laboratory. Pearson's correlation coefficients and Cohen's kappa were calculated for each possible comparison among the different measures. The best agreement was observed between serum and whole blood analysis within Laboratory A. The remaining comparisons reflected poor agreement. Comparison of herd-level assessment resulted in better agreement than comparison of individual sample results among laboratories and procedures for all combinations tested. Serum selenium analysis was the only laboratory procedure for which external reference material was utilized. Serum selenium, whole blood selenium, and glutathione peroxidase measure different compartments of the blood selenium pool. The time frame of interest, supplementation practices, and the stability of recent dietary intake determine the optimum assessment method for individual animals or herds. Determination of the serum status or of blood selenium is more consistently measured at the herd-level than for individual samples.

Animals↗
PubMed1998

The synergistic effects of vitamin E and selenium in iron-overloaded mouse hearts.

OBJECTIVES: To determine whether supplementation with vitamin E and selenium can improve myocardial antioxidant defenses in iron-overloaded mouse hearts. INTERVENTIONS: Iron-overload state was created in B6D2F1 mice (n = 20) by daily injection of iron dextran (5 mg intraperitoneally/mouse) for four weeks. The mice were also simultaneously randomly assigned to receive vitamin E (alpha-tocopherol acetate, 40 mg intraperitoneally, n = 5), selenium (sodium selenite, 1 part/million orally, n = 5), both (vitamin E + selenium, n = 5) or iron-only treatment (n = 5). The hearts were harvested for determination of selenium concentration and glutathione peroxidase activity. In a subsequent study, 15 B6D2F1 mice were randomly assigned to receive daily injections of iron (n = 5) or iron and combined antioxidant treatment (vitamin E + selenium, n = 5), or to serve as controls (n = 5) for four weeks. The hearts were harvested for determination of total iron concentrations. MAIN RESULTS: Significantly greater concentrations of heart selenium and glutathione peroxidase activity were observed in groups supplemented with both agents, as opposed to iron-only treated or single supplemented mice. Significantly lower concentrations of iron were found in controls and in those receiving combined iron and antioxidant treatment (vitamin E + selenium) than in iron-only treated mice. CONCLUSIONS: Vitamin E and selenium function synergistically in the myocardium to provide important antioxidant defenses in iron-overload states, including increased concentrations of selenium, increased glutathione peroxidase activity and decreased concentrations of iron.

Animals↗
PubMed1996

Selenium-regulated translation control of heterologous gene expression: normal function of selenocysteine-substituted gene products.

In eukaryotes, the synthesis of selenoproteins depends on an exogenous supply of selenium, required for synthesis of the novel amino acid, selenocysteine, and on the presence of a "selenium translation element" in the 3' untranslated region of mRNA. The selenium translation element is required to re-interpret the stop codon, UGA, as coding for selenocysteine incorporation and chain elongation. Messenger RNA lacking the selenium translation element and/or an inadequate selenium supply lead to chain termination at the UGA codon. We exploited these properties to provide direct translational control of protein(s) encoded by transfected cDNAs. Selenium-dependent translation of mRNA transcribed from target cDNA was conferred by mutation of an in-frame UGU, coding for cysteine, to UGA, coding for either selenocysteine or termination, then fusing the mutated coding region to a 3' untranslated region containing the selenium translation element of the human cellular glutathione peroxidase gene. In this study, the biological consequences of placing this novel amino acid in the polypeptide chain was examined with two proteins of known function: the rat growth hormone receptor and human thyroid hormone receptor beta 1. UGA (opal) mutant-STE fusion constructs of the cDNAs encoding these two polypeptides showed selenium-dependent expression and their selenoprotein products maintained normal ligand binding and signal transduction. Thus, integration of selenocysteine had little or no consequence on the functional activity of the opal mutants; however, opal mutants were expressed at lower levels than their wild-type counterparts in transient expression assays. The ability to integrate this novel amino acid at predetermined positions in a polypeptide chain provides selenium-dependent translational control to the expression of a wide variety of target genes, allows facile 75Se radioisotopic labeling of the heterologous proteins, and permits site-specific heavy atom substitution.

Animals↗
PubMed1998

Effect of organic forms of selenium on delta-aminolevulinate dehydratase from liver, kidney, and brain of adult rats.

The inhibitory effect of various forms of organic selenium compounds and of diphenyl ditelluride (PhTe)2 on delta-aminolevulinate dehydratase (delta-ALA-D) from liver, kidney, and brain of rats was investigated because it has been reported that organocalcogens catalyze the oxidation of thiols. Diphenyl diselenide (PhSe)2, rho-chloro-diphenyl diselenide (rho ClPhSe)2, propyl-2-2-diphenyl diselenide, and propyl-2-methoxy-2-phenyl selenide inhibited delta-ALA-D and the IC50 ranged from 2 to 32 microM depending on the selenium compound and whether it was preincubated with the enzyme. (rho ClPhSe)2 was the most potent inhibitor of delta-ALA-D, and preincubation increased the inhibitory potency of all the tested compounds. Inorganic selenium compounds (sodium selenite, Na2SeO3 and selenium dioxide, SeO2) inhibited delta-ALA-D, and the potency of SeO2 was greater than that of (rho ClPhSe)2. Diphenyl ditelluride (PhTe)2 also inhibited delta-ALA-D but with relatively lower potency than that of organic and inorganic selenium compounds. The inhibitory effect of propyl-2-2-diphenyl diselenide and propyl-2-methoxy-2-phenyl selenide seems to be mediated by (PhSe)2 since the compounds decomposed rapidly to (PhSe)2 in aqueous medium. The inhibitory action of selenium forms on delta-ALA-D from liver, kidney, and brain was antagonized by sulfhydryl protecting agents (dithiotreitol and reduced glutathione). The effects of organic selenium compounds on delta-ALA-D were related to the stability of the Se-Se (or Se-C) bond because the compound methyl-diphenyl diselenide (which possesses the most stable Se-C-Se bond) did not inhibit the enzyme. The inhibitory action of (PhSe)2 was not related to the formation of oxyradicals in the medium since superoxide dismutase and catalase did not affect the inhibition of delta-ALA-D by (PhSe)2. delta-ALA-D from cucumber leaves was not inhibited by selenium or tellurium compounds which suggests that these compounds act directly on the B or beta-site of the animal enzyme. These results suggest that delta-ALA-D from liver, kidney, and brain is a potential molecular target for the toxic effect of organic forms of selenium and tellurium.

Animals↗
PubMed1997

[Selenium administration in severe inflammatory surgical diseases and burns in childhood].

PATIENTS AND METHOD: Substitution of selenium was performed in the University Clinic of Paediatric Surgery in Dresden in the time from 1994 to 1996 in 34 children aged 1 to 16 years with severe inflammatory surgical diseases as well a s widespread burns. Seven further patients have been examined within this time who have not received substitution of selenium as preliminary comparison group. All these patients fulfilled the criteria of "Systemic Inflammatory Response Syndrome" (SIRS). The following paraclinical parameters were examined: white cell count, interleukin 6, C-reactive protein, fibrinogen, malondialdehyde, activity of glutathione peroxidase in plasma and level of selenium in plasma and whole blood. RESULTS: Patients with initially low level of selenium who received substitution of selenium reached normal ranges more quickly than patients without substitution. Originally partly elevated values of malondialdehyde as sign of increased peroxidation of lipids were normalized under substitution of selenium. Initially low activity of selenium level in plasma showed a clear increase under substitution of selenium as sign of increased protection of the cell membrane. CONCLUSION: The substitution of selenium in children with SIRS is a supportive therapy.

Adolescent↗
PubMed1997

[Effect of selenium administration on various laboratory parameters in patients with acute pancreatitis].

BACKGROUND: Recent studies presented evidence that activation of oxygen derived free radicals occurs in patients with acute pancreatitis. The purpose of this study was to evaluate the effect of sodium selenite as a possible antioxidant therapy in acute pancreatitis. PATIENTS AND METHOD: 16 patients with moderate form of acute pancreatitis received a high dose of sodium selenite. Selenium in serum and whole blood, zinc, copper, manganese, superoxid dismutase (SOD), glutathione peroxidase (Gpx) and malondialdehyde (MDA) were determined (before selenium substitution, 3 days later, 8 days later, before demission). No selenium deficiency could be detected before selenium substitution. RESULT: The selenium therapy caused a significant increase in selenium, a moderate increase in activity of Gpx, a significant decrease in activity of MDA, whereas SOD remained unchanged. CONCLUSION: Concerning the particular point of view of "deficiency management", there is no need of selenium substitution in patients with a moderate form of acute pancreatitis in our region. The highly normal selenium concentration we established by our therapy is possibly connected with a decrease of the oxidative stress in acute pancreatitis. More clinical follow-up studies with more patients, who have different grades of severity of the acute pancreatitis, and besides that a control group of patients without selenium substitution, are necessary for evaluating the clinical relevance of our results.

Acute Disease↗
PubMed1990

Effect of selenium deficiency on tissue taurine concentration and urinary taurine excretion in the rat.

The purpose of this study was to determine the effect of selenium deficiency on tissue taurine levels and urinary taurine excretion. Weanling male Sprague-Dawley rats were fed selenium-deficient or selenium-adequate diets for 20 weeks. As selenium deficiency developed, urinary taurine excretion increased in selenium-deficient rats compared to controls. At 12 weeks, the selenium-deficient rats excreted 1.7-fold more taurine than control rats. At the same time plasma glutathione peroxidase was 1.2% of control and plasma glutathione was 226% of control. At 20 weeks, renal taurine was decreased but renal glutathione was increased in selenium-deficient rats compared to controls. Feeding the experimental diet for 6 weeks without methionine supplementation caused a fall in urinary taurine excretion. However, there was no difference between selenium-deficient and control rats. These results indicate that selenium deficiency affects renal handling of taurine in the rat when dietary sulfur amino acids are not restricted.

Journal Article↗
PubMed2000

Effects of selenium deficiency on the formation and detoxification of endogenous electrophiles in rats.

Selenium deficiency could be expected to lead to enhanced lipid peroxidation through loss of selenium-dependent glutathione peroxidase activity. Such a relation has, however, been difficult to verify. In the present study, the influence of selenium deficiency in rats on in vivo doses of some endogenously occurring low-molecular mass aldehydes and epoxides was determined. In vivo doses were measured by mass-spectrometric analysis according the N-alkyl Edman method of reaction products (adducts) with N-terminal valines in hemoglobin. Despite variations between experiments, the adduct levels of acetaldehyde and malonaldehyde were shown to be significantly higher in rats fed a selenium-deficient diet than in controls fed a selenium-adequate diet. No significant effect was found for the other aldehydes measured. In contrast, the in vivo doses of endogenous ethylene oxide and propylene oxide were lowered in selenium-deficient rats, indicating a 1.7-times faster detoxification rate. This was verified by the lower adduct levels in selenium-deficient rats following intraperitoneal administration of these epoxides at moderate doses. In conclusion, the results seem to reflect the complex changes of induced and reduced enzyme activities in response to selenium deficiency. Measurement of reactive compounds through their adducts to hemoglobin has shown its ability to elucidate the effects of selenium deficiency per se.

Journal Article↗
PubMed2000

beta-Carotene and selenium supplementation enhances immune response in aged humans.

Background: Nutritional research has focused on the effects of specific nutrients' ability to cause or prevent cancer. While beta-carotene and selenium (both important for antioxidant systems) have cancer prevention capabilities, their antineoplastic mechanism(s) remains to be elucidated. Methods: In a prospective, randomized study design we evaluated immunological changes in free-living, healthy aged humans (57-84 years of age) given a placebo, beta-carotene (45 mg/day), and/or selenium (400 µg/day) supplement for 6 months and after 2 months of discontinuation. Peripheral blood lymphocytes were evaluated and subtyped using flowcytometry. Natural killer (NK) cell cytotoxicity was determined by a fluorescent method. Plasma diene conjugates were assessed to evaluate changes in oxidative stress. Results: Selenium and selenium plus beta-carotene supplementation caused an increase in total T cells by 27% and 31%, respectively (p <.05). The only group that was different (in T lymphocytes) from the controls (placebo group) after 6 months of supplementation (p <.05) was the selenium-supplemented group (+65%). Much of this increase was the result of an increase in CD4(+) T-cell subsets. Selenium or beta-carotene supplementation for 3 months increased NK cell cytotoxicity over pretreatment levels by 58% and 34%, respectively; however, these levels returned to +12% and -6% of pretreatment levels after 6 months supplementation. Selenium plus beta-carotene supplementation caused an increase in the percentage of NK cell by 121% and 161% at 3 and 6 months, respectively. However, the increased numbers of NK cells were not correlated with NK cell activity. Conclusions: We found that selenium enhanced immune function (NK cell cytotoxicity) and phenotypic expression of T-cell subsets, whereas beta-carotene affected only immune function. Increased NK cell cytotoxicity may last for only a short period of supplementation and was not sustained throughout the 6 months of supplementation. Supplemental selenium and beta-carotene seemed to affect immune function in aged subjects by different mechanisms.

Journal Article↗
PubMed1998

The effect of injectable barium selenate on the selenium status of horses on pasture.

AIM: To examine the effect of intramuscular barium selenate on the blood selenium concentration of horses with marginal selenium status. METHODS: Eighteen mares were assigned to one of six groups. The mares in groups 1-4 received barium selenate at 0.5, 0.75, 1.0 and 1.5 mg Se/kg, respectively, injected into the right pectoral muscle mass. The mares in group 5 received sodium selenate at 0.05 mg Se/kg orally at 8-week intervals. The mares in group 6 were left untreated. Blood samples were collected at 0, 1, 2, 5, 10, 30, 60, 90, 120, 180, 240, 300 and 360 days after the initial treatment for assay of whole blood and plasma selenium. Injection site reactions were recorded on each sampling date. RESULTS: Treatment with barium selenate at each dose rate significantly increased whole blood, plasma and blood cell selenium concentrations when compared to no treatment or oral treatment with sodium selenate, and maintained group mean whole blood selenium concentrations in the adequate range (>1600 nmol/l) until the end of the experimental period of 1 year. The severity of injection site reactions increased with dose rate but was considered acceptable alt the lower dose rates used. CONCLUSION: The injection of barium selenate placed aseptically at a deep intramuscular site was efficacious in correcting the selenium status of mares grazing pasture with a selenium content of 0.01-0.07 mg/kg DM. However, some swelling and fibrosis at the injection site was apparent at all dose rates used. CLINICAL RELEVANCE: There is currently no long-acting selenium supplementation product licensed in New Zealand for use in horses. Barium selenate promises to provide a useful method for selenium supplementation for horses, with an effective duration of at least 1 year following a single injection.

Journal Article↗
PubMed2006

Absorption of selenium by Lactuca sativa as affected by carboxymethylcellulose.

Several organic compounds of high molecular weight present in soil interact with selenium and may act as active binding agents affecting its availability in soil, and, consequently, selenium uptake by plants. This study is aimed at investigating the effects of polysaccharides on selenium speciation in soil and on selenium absorption by Lactuca sativa L. plants. Three-week-old seedlings were transplanted into pots filled with soil, and sodium selenite at rates of 1.5 and 5mgSekg(-1) of soil, or sodium selenate at a rate of 1.5mgSekg(-1) of soil were applied. Carboxymethylcellulose (CMC) was added to the soil at rates of 0, 3 and 30mgkg(-1) of soil. After 48 and 110d from transplanting plants were harvested, separated into root and shoot, and fresh and dry matter weights were recorded. Total selenium was determined in both soil and plant samples. A sequential extraction was used to investigate the different Se oxidation states and assess the availability of Se in soil after the final harvesting. Both selenite and selenate were absorbed by roots, but plants amended with Se(VI+) showed higher selenium concentration than plants amended with Se(IV+). Selenite appears to be less mobile than selenate both in soil and plants. The addition of carboxymethylcellulose to soil decreased the amount of selenium absorbed by plants. CMC interacted with Se, making it less mobile as evidenced by the increase in the insoluble fractions. The insoluble Se forms in soil may represent environmental Se sinks potentially available for plants if the substrate is re-used for subsequent growth cycles and selenium species are mobilized as a result of biological and chemical processes.

Carboxymethylcellulose Sodium↗
PubMed2003

Plants, selenium and human health.

Selenium is an essential nutrient for animals, microorganisms and some other eukaryotes. Although selenium has not been demonstrated to be essential in vascular plants, the ability of some plants to accumulate and transform selenium into bioactive compounds has important implications for human nutrition and health, and for the environment. Selenium-accumulating plants provide unique tools to help us understand selenium metabolism. They are also a source of genetic material that can be used to alter selenium metabolism and tolerance to help develop food crops that have enhanced levels of anticarcinogenic selenium compounds, as well as plants that are ideally suited for the phytoremediation of selenium-contaminated soils.

Adaptation, Physiological↗