Selenium Transfer Research Articles

Selenium status in cattle

Selenium may affect a wider range of metabolic functions than only those associated with nutritional myodegeneration, but there is controversy regarding the type of problems that may be associated with suboptimal selenium status in cattle. An animal's nutritional requirement for selenium and vitamin E depends on age, physiological stage and species. In cattle, low selenium status becomes critical near calving when cows are more susceptible to intramammary infections, retained placenta, or infections in the neonate. Analysis of serum samples (n=204) submitted to the Iowa State University Veterinary Diagnostic Laboratory between January 2000 and July 2001, showed a mean (ñSD) serum selenium value of 68.4ñ17 ppb for adult Holstein cows in the Iowa and Wisconsin areas. Because cattle receiving higher levels of selenium and vitamin E than typically recommended may show improved immunocompetence, the levels found in this survey can be considered adequate for reproductive performance, but marginal for optimal resistance to mastitis pathogens or for adequate transfer of selenium to the suckling calf. This report also contradicts previous claims that selenium deficiency contributes to stillborn/weakborn calves. Studies relating selenium concentrations in blood and serum to common clinical conditions of cattle attributed to poor selenium status are reviewed; methods of supplementation are also addressed.

The Selenium Content of the Flora and Plant and Animal Foodstuffs in Germany

The objective of the ten years' study was to track the transfer of selenium in the food chains of animals and humans. The selenium content of the flora varies significantly with the geological origin of the soil, its pH, plant species, plant age, and the protein content of the plant parts eaten. In Central Europe, the flora on the usually neutral loess soils is seleniumrich, whereas the acidic soils formed by the weathering of gneiss, slate, granite, phyllite and Bunter as well as diluvial sands, bear a selenium-poor vegetation. The bioavailability of soil selenium increases significantly with pH. From 1988 until the end of the millenium, the selenium content of vegetable foods was studied systematically in 75 food types and 1035 samples. It was found that, with few exceptions, vegetable foods are generally poor in selenium. This applies in particular to all foods rich in starch and sugar. Protein-rich leguminosae, cruciferes rich in glucosinolate (mustard, caraway, cabbages) and especially such vegetable...

Role of oceans as biogenic sources of selenium

The pathways leading to the volatilisation and atmospheric transfer of selenium from oceanic environments are poorly understood. They may however affect the global distribution of selenium and its impact on marine and terrestrial ecosystems. In this paper we describe the results of experiments which provide a reasonable estimate of the global selenium budget. Gaseous selenium compounds were determined in the North Atlantic Ocean during a Spring bloom of phytoplankton species which are known to be a large source of atmospheric sulphur. The results demonstrate that significant concentrations of gaseous selenium species occur in surface ocean waters, and their production is closely linked to the gaseous sulphur species turnover. Selective uptake and biotransformation of dissolved selenium in seawater by phytoplankton is a major pathway for the production of gaseous selenium compounds in marine environments and their emission to the atmosphere. It is therefore suggested that such a major selenium source supplies the terrestrial environment with selenium that can be used as an essential nutrient for animal and human life.

Partitioning of arsenic, selenium, and cadmium during the combustion of Pittsburgh and Illinois #6 coals in a self-sustained combustor

An important environmental issue is the emission of semi-volatile toxic metals, such as arsenic, selenium, and cadmium, from the combustion of coal. These materials may vaporize in the hot portions of the combustor then return to the solid phase in cooler zones of the process downstream. Understanding the mechanisms by which toxic metals partition between the vapor and solid phases is an important step for predicting and mitigating the effect of these metals upon the environment. Particulate ash samples were withdrawn from a 17-kW pilot-scale downflow combustor in which pulverized coal was burned under self-sustaining conditions. The samples were size segregated in a Berner low pressure impactor, and then analyzed using neutron activation. This research approach has suggested mechanisms, which govern the partitioning of arsenic, selenium, and cadmium in practical pulverized coal combustion processes. The results suggest that volatilization and subsequent transfer of selenium to submicron particle surfaces appears to be an important post-combustion phase mechanism for Illinois #6 coal but not for Pittsburgh seam coal. Most of the selenium in the Pittsburgh submicron fly ash, cadmium in Illinois #6 submicron fly ash, and arsenic in both Pittsburgh and Illinois #6 submicron fly ash enters the post-combustion zone in the solid phase. The dominant heterogeneous partitioning mechanism for transformation to large, supermicron particles is the reaction of metal vapor on the surface or within the pores of an ash particle. The results also suggest that the rate of transformation is dominated either by an exterior surface reaction-controlled regime or a pore diffusion-controlled regime. A relationship between the concentration of solid phase arsenic, selenium, and cadmium to calcium in supermicron particles was also observed, suggesting the formation of As–Ca, Se–Ca, and Cd–Ca reaction products.

Effect of straw amendment and plant growth on selenium transfer in a laboratory soil-plant system

Knowledge of the transfers of selenium (Se) in the soil-plant-atmosphere environmental compartments is fundamental in assessing Se cycling through the environment. The purpose of this study was to determine the effects of straw amendments and barley (Hordeum vulgare L.) on Se cycling in soils from Kesterson Reservoir, Merced County, CA (0.68 mg soluble Se kg−1, 6.15 mg total Se kg−1), and to evaluate the feasibility of these agricultural practices as bioremediation strategies. Four treatments were evaluated: soil only, soil + straw, soil + plant, and soil + straw + plant. Straw amendments greatly reduced Se from soil solution (92–97% of initial soluble Se). Selenate [Se(VI)] was the predominant species in soil solution. Phosphate-extractable Se did not account for the decline in soluble Se. Selenium volatilized by microbes represented only 4–5% of the soluble Se removed. Highest Se removal from soil solution and highest Se volatilization rates occurred when both microbial activity and growth were maximal. Selenate microbial reduction to more insoluble Se forms is indicated as being responsible for this removal. Plants did not account for as much Se removal from soil solution as did straw amendments. Total shoot Se corresponded to 1–9% of soluble Se removal. At the end of the experiment, Se in plants represented 0.1–0.7% of total Se in the system, and the Se volatilized accounted for 0.2 to 0.5% of total Se inventory. The results obtained in this study suggest the use of straw amendments as a remediation technique for managing Se contamination at Kesterson Reservoir. Key words: Barley, selenium, soil solution, straw, volatilization

ChemInform Abstract: First Example of Selenium Transfer Reaction of Primary Selenoamides and Selenourea. Novel Synthesis of Dialkyl Diselenides from Alkyl Halides.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Effect of Selenium Supplementation of Cows on Maternal Transfer of Selenium to Fetal and Newborn Calves

A trial was conducted to determine the effect of maternal supplementation of Se on transfer of Se to the fetus during late gestation. Holstein cows were randomly assigned at dry-off to receive no Se or 3mg/d of supplemental Se as selenite delivered via an intraruminal bolus. Supplementation significantly increased concentrations of Se in blood of dams at parturition. Similarly. calves of cows that were supplemented with Se had higher Se in blood and liver. Colostral concentrations of Se were increased by maternal Se supplementation; Se increased in the casein fraction. The Se concentrations in blood, plasma, and liver of calves were positively correlated with the Se concentrations in plasma of the dam at parturition. Concentrations of Se in colostrum and in calf liver also were closely correlated. Concentrations of Se in calf liver at d 42 were closely correlated with concentrations of Se in liver at birth. Maternal supplementation of Se increased Se reserves in the liver of the newborn and in colostrum. Carryover effects of Se supplementation of dams were evident in calves at 42 d of age.

ChemInform Abstract: Group Transfer Addition Reactions of Selenomalononitriles to Chiral Enol Ethers. Asymmetric Radical Addition and Selenium Transfer Reactions.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

First example of selenium transfer reaction of primary selenoamides and selenourea. Novel synthesis of dialkyl diselenides from alkyl halides

As selenium transfer reagents, arylselenoamides react with a variety of alkyl halides in ethanol under mild conditions to give dialkyl diselenides in excellent yields. Similarly, alkyl halides treated with selenourea form dialkyl diselenides. The possible mechanism is discussed.

Copper-promoted intramolecular selenium transfer from a PSe group to a P–CH2–P methylene carbon producing an unusual methaneselone ligand

The bis(diphenylphosphino)methane selenides CH2(Ph2P)Ph2PSe and CH2(Ph2PSe)2, react with copper(II) chloride giving an unidentified copper(I) complex; exposure to the air affords the new bifunctional, tridentate iigand bis(diphenylphosphoryl)methaneselone SeC(Ph2PO)2 linking copper(I) and copper(II) in the trinuclear complex [CuII{CuICl2[µ-SeC(Ph2PO)2]}2].

Phenylsulfinylselenyl chloride (PhSO2SeCl): a new reagent for the formation of C–Se and N–Se bonds. Generation and in situ Diels–Alder trapping of selenonitrosoarene intermediates (Ar–NSe)

The novel electrophilic selenium transfer reagent phenylsulfinylselenyl chloride, PhSO2SeCl, 3 has been prepared and reacted with enolisable carbonyl compounds to yield α-selenoketones and diselenides; reaction of reagent 3 with arylamines in the presence of triethylamine and dimethylbutadiene affords 1,2-selenazine derivatives, providing the first evidence for Diels–Alder trapping of selenonitroso intermediates, Ar–NSe.

The placental transfer and toxicity of selenite relative to cadmium in the human term perfused placenta

Selenite and cadmium both cause reproductive effects in animals. Cadmium is an acute placental toxicant, with apparent limited transfer to the fetus. This study examines the placental transfer of selenite, and the hypothesis that similar to cadmium, selenite may also be a direct placental toxicant. Using dual perfusion of the human term placental lobule, both non-protein bound (< 776 Da) selenite and cadmium equilibrated across the placenta within 4 h. The transfer of selenium, added as selenite, was not limited at concentrations from 2-40 nmol/ml. At initial maternal concentrations of 20 nmol/ml, selenium attained higher concentrations in the fetal perfusate compared with cadmium concentrations. Protein binding of cadmium in perfusates (45 per cent at 30 min) and placental cytosol (approx. 87 per cent) was greater than selenium (perfusate, 7 per cent at 30 min, cytosol, 50-60 per cent), which may partially account for the differences in placental transfer. Cadmium (20 nmol/ml) produced adverse effects on the production and release of human chorionic gonadotropin (hCG) in 4 h. No adverse effects were noted during 4 h exposures to selenite at initial concentrations of up to 40 nmol/ml. Thus, unlike cadmium, in which placental accumulation and direct placental toxicity contributed to acute reproductive effects, selenite at concentrations up to 40 nmol/ml was not a direct toxicant under these perfusion conditions.

Accumulation of selenium in a model freshwater microbial food web

The transfer of selenium between bacteria and the ciliated protozoan, Paramecium putrinum, was examined in laboratory cultures. The population growth of the ciliate was not inhibited in the presence of the highest concentrations of dissolved selenite or selenate tested (10(3) micrograms liter-1). Experiments with radioactive 75selenite or 75selenate indicated that accumulation of selenium by ciliates through time was low when feeding and metabolism were reduced by incubating at 0 degrees C. However, selenium accumulated in ciliate biomass during incubation with dissolved 75Se and bacteria at 24 degrees C and also when bacteria prelabeled with 75Se were offered as food in the absence of dissolved selenium. When 75Se-labeled bacterial food was diluted by the addition of nonradioactive bacteria, the amount of selenite and selenate in ciliates decreased over time, indicating depuration by the ciliates. In longer-term (> 5-day) fed-batch incubations with 75selenite-labeled bacteria, the selenium concentration in ciliates equilibrated at approximately 1.4 micrograms of Se g (dry weight)-1. The selenium content of ciliates was similar to that of their bacterial food on a dry-weight basis. These data indicate that selenium uptake by this ciliate occurred primarily during feeding and that biomagnification of selenium did not occur in this simple food chain.

Group transfer addition reactions of selenomalononitriles to chiral enol ethers. Asymmetric radical addition and selenium transfer reactions

Group transfer addition reactions of alkyl phenylselenomalononitriles to enol ethers derived from trans-2-phenylcyclohexanol and 8-phenylmenthol occur cleanly, and moderate to excellent stereoselection is observed in both the radical addition and phenylselenium transfer steps.

Nucleoside H-phosphonates. 14. Synthesis of nucleoside phosphoroselenoates and phosphorothioselenoates via stereospecific selenization of the corresponding H-phosphonate and H-phosphonothioate diesters with the aid of new selenium-transfer reagent, 3H-1,2-benzothiaselenol-3-one

An efficient conversion of nucleoside H-phosphonate and nucleoside H-phosphonothioate diesters into the corresponding phosphoroselenoates and phosphorothioselenoates was achieved with a new selenium-transferring regent, 3H-1,2-benzothiaselenol-3-one (BTSe, 1). The regent is soluble in common organic solvents and shows an enhanced rate of selenium transfer compared to elemental selenium or potassium selenocyanate. The reaction was found to be stereospecific and occurs with retention of configuration at the phosphorus center. BTSe also proved to be effective in the conversion of phosphite triesters into the corresponding phosphoroselenoates under reactions conditions which are compatible with both solution- and solid-phase synthesis of oligonucleotides

3 H-1,2-benzothiaselenol-3-one. A new selenizing reagent for nucleoside H-phosphonate and H-phosphonothioate diesters

A new selenium-transferring reagent, 3 H-1,2-benzothiaselenol-3-one ( 1), has been developed for the conversion of nucleoside H-phosphonate and nucleoside H-phosphonothioate diesters into the corresponding seleno analogues. The reagent is soluble in common organic solvents and shows an enhanced rate of selenium transfer compared to elemental selenium or potassium selenocyanate. Selenization with the reagent 1 is stereospecific and most likely occurs with retention of configuration at the phosphorus centre.

ChemInform Abstract: The First Selenium Transfer Reagent: Preparation and Mechanism of Formation.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The first selenium transfer reagent: preparation and mechanism of formation

The reaction of bis allylselenide 7 with N-chlorobenzotriazole affords the first selenium transfer reagent 5 as an analog to SeX 2. The formation of this product followed by 77Se NMR gives strong evidence for the intermediacy of the first recorded alkyl selenurane 9 as well as a selenonium ion 10.

Synthesis and NMR spectroscopy of the five-coordinate platinum(II) complexes [Pt(pp 2-P,P′,P″)(dppmE-P,E)](O 3SCF 3) 2 [pp2 = PhP(CH 2CH 2PPh 2) 2, dppme = Ph 2PCH 2P(E)Ph 2, E = S, Se

The title compounds were generated by the reaction between [Ptpp 2Cl 2, dppmE] and TlO 3SCF 3. On the basis of solution 31P, 77Se and 195Pt NMR spectroscopic data, a square-pyramidal structure is proposed with the chalcogen atom in the apical position. In contrast, [Pt(pp 2-P,P′,P″)(dppmO-P)](O 3SCF 3) 2 is four-coordinate. The reaction between Ptpp 2Cl 2 and dppmSe 2 involves a selenium transfer yielding the cis and trans isomers of [PtPhP(CH 2CH 2PPh 2)(CH 2CH 2P(Se)Ph 2-P,P′)(dppmSe-P,Se)](O 3SCF 3) 2, which are also accessible from [Pt(pp 2-P,P′,P″)(dppmSe-P,Se)](O 3SCF 3) 2 and elemental selenium.

Comparative embryotoxicity of selenite and selenate: uptake in murine embryonal and fetal tissues and effects on blastocysts and embryonic cells in vitro

The placental transfer and distribution pattern of selenium (Se) in embryonic and fetal tissues after intravenous injection of Na 2 75SeO 3 (Se 4+) or Na 2 75SeO 4 (Se 6+) has been investigated in mice in early, mid, and late pregnancy by use of whole-body autoradiography combined with gamma-counting. The given doses correspond to 45 μg Se/kg. In order to compare the direct toxicity in early embryonic stages, the two valence forms were studied by using in vitro systems with (1) mouse blastocysts and (2) chick embryo fibrobaasts, differentiating into chondrocytes. The embryonic and fetal uptake after administration of Se 4+ and Se 6+ was almost identical. The placental transfer of Se was restricted but, nevertheless, increased with time after dosing and with progression from embryonic through fetal stages thereby suggesting active placental transfer. The highest uptake in the embryo was observed in the neuro-epithelium while the eye, liver and skeleton dominated the distribution pattern in the fetal period. Selenite (Se 4+) was more toxic than selenate (Se 6+) in the vn vitro system, in which embryonic mesenchymal limb bud cells differentiated into chondrocytes as well as in the blastocyst culture system. The results may suggest a direct effect of Se in the embryo as explanation to reported malformations in experimental studies.