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PubMed2003

No-carrier-added synthesis of aliphatic and aromatic radioselenoethers via selenocyanates.

Various aliphatic and aromatic [(75)Se]selenoethers were prepared at the no-carrier-added (n.c.a.) level using a new radiosynthetic pathway, based on the formation of alkyl[(75)Se]selenocyanates as intermediates. Using one-pot model reactions of elemental (75)Se, sodium cyanide and various alkylbromides in ethanol, the preparation of alkyl[(75)Se]selenocyanates was examined and optimized. Purification of these (75)Se-labeled intermediates and subsequent conversion with alkyl and aryl lithium or Grignard compounds in anhydrous diethyl ether yielded radioselenoethers with radiochemical yields of up to 55% (related to (75)Se(0)) within an overall reaction time of 20 min. This is the first method described to obtain n.c.a. arylselenoethers.

Cyanates↗
PubMedDate not supplied

Synergism of methylmercury and selenium producing enhanced antibody formation in mice.

Mice fed 1, 5, and 10 ppm methylmercury plus 6 ppm selenium for 10 wk had a significant increase in antibody synthesis. Since methylmercury singly depresses antibody synthesis and the response was greater than that produced by selenium alone, synergism between methylmercury and selenium occurred. In this case, the synergism is considered to be advantageous to a host, while exposure by other combinations of environmental contaminants may be detrimental. Mercury concentrations in the kidney were markedly elevated when methylmercury and selenium were administered simultaneously compared to when methylmercury was given without selenium supplement. These results indicate that data collected from individual pollutants may not be of value in predicting responses to multiple exposure.

Animals↗
PubMed1994

Distribution and chemical form of selenium in mice after administration of selenocystine.

To elucidate the relationship between chemical forms of selenium in tissues and subacute liver damage induced by selenocystine (T. Hasegawa et al., Arch. Toxicol., 68, 91 (1994)), the distribution and chemical form of selenium were investigated in ICR male mice treated with the chemical orally (50 mg/kg) and intravenously (5 mg/kg). The time-distribution of selenium in plasma, erythrocytes and liver after separate administration varied. However, Sephadex G-150 chromatograms of plasma, and stroma-free hemolysate from mice treated orally or intravenously with selenocystine, revealed that selenium exists mainly in the albumin and hemoglobin fractions, respectively, and is neither route- or time-dependent. Sephadex G-150 chromatograms of liver cytosol of the animals 1 h after oral administration or 1 and 6 h after intravenous administration showed two selenium-containing fractions, void volume and a low-molecular fraction (Kav = 0.85); 6 h after oral treatment, however, animals had an additional high-molecular fraction (Kav = 0.45). Levels of acid-volatile selenium and dialyzable selenium in the fraction with a Kav value of 0.45 were similar, being 31.2% and 30.3%, respectively. No acid-volatile selenium was recognized in the non-dialyzable high-molecular fraction. The present study demonstrated that when selenocystine is administered orally to mice, the selenium which produces acid-volatile selenium by acidification may bind to protein sulfhydryl groups in the liver cytosol; this was not seen in the case of intravenous administration.

Administration, Oral↗
PubMed1991

The protection of invertebrates, fish, and vascular plants against inorganic mercury poisoning by sulfur and selenium derivatives.

Protection of organisms against mercury (Hg) poisoning is most commonly associated with the antagonistic effects of selenium (Se)-compounds against mercury alkyls in higher animals. This study shows that there is no consistent difference among Periodic Group VIA derivatives including S(IV), S(II) organic, Se (IV), Se (II) organic, possibly Se VI, as well and Te (IV) in their ability to protect against mercury poisoning. The organisms used in assays were: Coleus explants (leaf abscission); turnip (germination); pea (growth inhibition and Hg uptake); a planarian (regeneration); the brineshrimp (excystment, phototaxy); the mealworm larva Tenebrio (metamorphosis) and the fish "tilapia" (survival, Hg uptake). Thiamine was the most effective of the Group VIA derivatives against the widest spectrum of organisms and test systems. In planarian regeneration, it was active where S and Se compounds failed. The most unexpected observation was the hastening of insect metamorphosis by HgCl2 and the enhancement of that effect by thiamine.

Animals↗
PubMed1994

Determination of selenium in biological matrices using a kinetic catalytic method.

A simple and sensitive catalytic spectrophotometric method was developed for the determination of selenium in biological matrices. The method is based on the catalytic effect of selenium on the reaction of Methylene Blue (MB) with sodium sulfide. For a given reaction between MB and sodium sulfide, the change in the MB absorbance with time was monitored, then the time (t) required for completion of the reaction was determined, and t-1 was calculated. A plot of t-1 versus selenium concentration constituted the calibration graph, which was linear in the range 2.5-30 ng ml-1 selenium. In this study, experimental parameters and the effect of interferences on determinations of selenium were examined. Tetramethylammonium hydroxide digestion was applied to blood, hair and urine samples; it was found to give the best results for urine. Then the catalytic method was applied to urine samples (84.9% recovery).

Catalysis↗
PubMed2005

Anti-thyroid drugs and thyroid hormone synthesis: effect of methimazole derivatives on peroxidase-catalyzed reactions.

Syntheses and characterization of the selenium analogue (MSeI) of anti-thyroid drug methimazole and a series of organoselenium compounds bearing N-methylimidazole pharmacophore are described. In contrast to the sulfur compound that exists predominantly in its thione form, the selenium analogue exists in a selenol form, which spontaneously oxidizes in air to produce the corresponding diselenide. The reduction of the diselenide by GSH or NaBH(4) affords the biologically active selenol, which effectively inhibits the lactoperoxidase (LPO) activity in vitro. The monoselenides having N-methylimidazole moiety are found to be much less active than the selenol, suggesting that the presence of a selenol moiety is important for the LPO inhibition. The kinetic and mechanistic studies reveal that MSeI inhibits the LPO activity by reducing the H(2)O(2), providing a novel method to reversibly inhibit the enzyme. Although MSeI strongly inhibits LPO, the enzyme's activity can be completely recovered by increasing the H(2)O(2) concentration. On the other hand, the inhibition by methimazole (MMI), the sulfur analogue, cannot be reversed by increasing the H(2)O(2) concentration, leading to a complete inactivation of the enzyme. The reversible inhibition of LPO by some of the selenium derivatives is correlated with their glutathione peroxidase (GPx) activity, and the high GPx activity of the selenium compounds as compared with their sulfur analogues suggests that the selenium derivatives may protect the thyroid gland from oxidative damage.

Antithyroid Agents↗
PubMed2005

Proposed criteria for assessing the efficacy of cancer reduction by plant foods enriched in carotenoids, glucosinolates, polyphenols and selenocompounds.

BACKGROUND AND AIMS: The cancer-protective properties of vegetable consumption are most likely mediated through 'bioactive compounds' that induce a variety of physiologic functions including acting as direct or indirect antioxidants, regulating enzymes and controlling apoptosis and the cell cycle. The 'functional food' industry has produced and marketed foods enriched with bioactive compounds, but there are no universally accepted criteria for judging efficacy of the compounds or enriched foods. SCOPE: Carotenoids, glucosinolates, polyphenols and selenocompounds are families of bioactive compounds common to vegetables. Although numerous studies have investigated the agricultural and human health implications of enriching foods with one or more of these compounds, inadequate chemical identification of compounds, lack of relevant endpoints and inconsistencies in mechanistic hypotheses and experimental methodologies leave many critical gaps in our understanding of the benefits of such compounds. This review proposes a decision-making process for determining whether there is reasonable evidence of efficacy for the both the compound and the enriched food. These criteria have been used to judge the evidence of efficacy for cancer prevention by carotenoids, polyphenols, glucosinolates and selenocompounds. CONCLUSIONS: The evidence of efficacy is weak for carotenoids and polyphenols; the evidence is stronger for glucosinolates and lycopene, but production of enriched foods still is premature. Additionally there is unacceptable variability in the amount and chemical form of these compounds in plants. The evidence of efficacy for selenocompounds is strong, but the clinical study that is potentially the most convincing is still in progress; also the variability in amount and chemical form of Se in plants is a problem. These gaps in understanding bioactive compounds and their health benefits should not serve to reduce research interest but should, instead, encourage plant and nutritional scientists to work together to develop strategies for improvement of health through food.

Animals↗
PubMed1980

Effect of selenium and dimethyl dioctadecyl ammonium bromide on the vaccine-induced immunity of Swiss-Webster mice against malaria (Plasmodium berghei).

The results of the study described in this paper demonstrate that selenium, administered in drinking water, potentiates the protective effect of a killed Plasmodium berghei vaccine for Swiss-Webster mice. We also report that a vaccine consisting of P. berghei antigen combined with the adjuvant dimethyl dioctadecyl ammonium bromide conferred a significantly high level of protective immunity. An additive effect was shown in that the greatest degree of protection was afforded to the group of mice maintained on selenium and vaccinated with antigen-dimethyl dioctadecyl ammonium bromide. Almost all of the animals treated in this manner survived the challenging infection, the course of which was typically of a transitory parasitemia not exceeding 10% at the peak.

Animals↗
PubMed2005

Investigation of selenium-containing root exudates of Brassica juncea using HPLC-ICP-MS and ESI-qTOF-MS.

Selenium-containing root exudates were investigated in a known selenium accumulator model plant. Indian mustard (Brassica juncea) plants were grown hydroponically and supplemented with selenite (SeO(3)(2-)) in a 25% Hoagland's nutrient solution. Additive concentrations were 0, 1, 5 and 20 microg mL(-1) Se with five replicate plants per treatment level. Plants were exposed to the respective Se solutions for two weeks, then placed in deionized water for two more weeks. The hydroponic solutions were collected for analysis after the first two weeks of selenium supplementation (day 14) and twice during the deionized water period (days 21 and 28). Separation by ion-pairing high performance liquid chromatography was followed by inductively coupled plasma-mass spectrometry (ICP-MS) for selenium specific detection. Chromatographic peaks unable to be identified by retention-time matching were collected for analysis by electrospray ionization mass spectrometry (ESI-MS). Additional chemical experiments were performed for structural elucidation. Several selenium-containing compounds were identified in the exudate-containing solution and two were identified as selenocystine and the selenosulfate (SSeO(3)(2-)) ion. The presence of dimethylselenide (CH(3)SeCH(3)) is also observed but cannot be attributed exclusively to plant exudation because plants were not grown in sterile conditions. Further, the incorporation of fortified selenoamino acids into peptide structures was found to occur under neutral pH conditions, suggesting that exuded enzymes might facilitate such a reaction. Finally, physiological differences resulting from selenium supplementations were noted and discussed.

Chromatography, High Pressure Liquid↗
PubMed1978

Modification of methylmercury toxicity and metabolism by selenium and vitamin E: possible mechanisms.

Selenium and vitamin E exert powerful effects in reducing acute or chronic methylmercury toxicity. Levels of selenium normally found in foods (below 1 ppm) delay the onset of toxic signs caused by much higher levels of methylmercury. Tissue levels of mercury in selenium-supplemented animals equal or exceed those found in animals given methylmercury alone. Selenium does not appear to act by simply modifying intake, absorption, excretion, or distribution of methylmercury, and direct effects of both selenium and vitamin E have been observed in vitro when methylmercury was added to cultured nervous tissue cells. The only established functions for selenium and vitamin E in animals are related to the prevention of oxidative damage in tissues. To encompass the protective effects of selenium and vitamin E and to explain other toxicological aspects of methylmercury and other alkylmetals, a new hypothesis is proposed: The toxicity of the alkylmetals is not caused soley by the intact molecule, but also involves free radicals formed by homolytic fission of the carbon-metal bond.

Animals↗
PubMed1981

Phagocytosis, cellular distribution, and carcinogenic activity of particulate nickel compounds in tissue culture.

The uptake, toxicity, and morphological transformation efficacy of various water-insoluble nickel compounds were examined in tissue culture. Particles (2.2 to 4.8 micrometers) of crystalline Ni3S2, crystalline NiS, and crystalline Ni3Se2 were actively phagocytized by cultured cells as determined by light and electron microscopy. However, particles of similar size consisting of amorphous NiS and metallic nickel were not significantly phagocytized despite long exposure periods to high concentrations. X-ray fluorescence spectrometry measurements of metal levels in subcellular fractions isolated from cells treated with crystalline Ni3S2, crystalline NiS, or amorphous NiS confirmed that amorphous NiS did not significantly enter the cells, either as a phagocytized particle or in a solubilized form, while the other two crystalline nickel compounds were actively taken up. Cells treated with amorphous NiS contained nickel levels generally less than 10% of the nickel levels in whole cells and in cytoplasmic fractions, or nuclear fractions of cells treated with either crystalline NiS or crystalline Ni3S2. The phagocytized nickel particles were always observed in the cytoplasm with light and electron microscopy, but substantial nickel levels were measured in the nuclear fraction. These and other results suggest that the nickel particles were broken down in the cytoplasm to a size range no longer detectable with the electron microscope and then subsequently entered the nucleus. Control experiments suggest that at least 20% of the nickel measured in the nucleus isolated from cells treated with Ni3S2 is no longer part of a sedimentable particle with the same particle size and/or solubility properties of the parent compound. A substantial portion of the nickel associated with the nuclear fraction coprecipitated with trichloroacetic acid-insoluble material, suggesting that nickel binds strongly to cellular macromolecules. The phagocytized particulate nickel compounds were more cytotoxic as determined by reduction of cell-plating efficiency and induced more morphological transformations in the Syrian hamster embryo cell transformation assay than did the particulate nickel compounds which were not phagocytized. Manganese dust inhibited the morphological transformation induced by Ni3S2 and also reduced the phagocytosis of Ni3S2 particles.

Animals↗
PubMed1992

Transamination of some sulphur- or selenium-containing amino acids by bovine liver glutamine transaminase.

S-(3-aminopropyl)cysteine and Se-(3-aminopropyl)selenocysteine are deaminated by bovine liver glutamine transaminase. The corresponding alpha-keto acids, S-(3-aminopropyl)-thiopyruvic acid and Se-(3-aminopropyl)selenopyruvic acid, are produced which spontaneously cyclize to ketimine derivatives. They have been identified by comparing their UV absorption spectra and some chemical or chromatographic properties with chemically synthesized authentic samples. Also S-(2-aminoethyl)homocysteine is the substrate for the enzyme. Kinetic parameters determined in comparison to thialysine and selenalysine show that neither the presence of a sulphur or a selenium atom nor the relative position of the atom in the carbon chain appreciably affects the substrate specificity of the enzyme. However, the length of the carbon chain has some influence on it.

Amino Acids↗
PubMed2005

Chemical forms of selenium for cancer prevention.

Cancer is becoming an increasingly significant disease worldwide. Currently, more than 7 million people die each year from cancer. With the existing knowledge, at least one-third of worldwide cancer cases could be prevented. Searching for naturally occurring agents in routinely consumed foods that may inhibit cancer development, although challenging, constitutes a valuable and plausible approach to the control and prevention of cancer. To date, the use of the micronutrient selenium (Se) in human clinical trials is limited, but the outcome indicates that Se is among the most promising agents. Although it is convenient to describe the effects of Se in terms of the element, it must always be kept in mind that the chemical form of Se and the dose are determinants of its biological activities. Hyphenated techniques based on coupling chromatographic separation with inductively coupled plasma mass spectrometric (ICP-MS) detection are now established as the most realistic and potent analytical tools available for real-life speciation analysis. These speciation investigations provide evidence that the Se compounds, which can generate monomethylated Se (e.g., Se-methylselenocysteine and methylseleninic acid), are more efficacious than other Se compounds because of their chemoprevention activity.

Anticarcinogenic Agents↗
PubMedDate not supplied

Studies regarding the effects of an antioxidant compound in top athletes.

The authors performed a controlled trial in 15 top junior athletes (road cyclists) in order to make evident some antioxidant effects of a new compound, containing selenium, vitamin E, glutathion and cysteine, prepared as tablets. Nonproteic -SH and lipid peroxides (MDA) in blood have been recorded initially on basal conditions and 3 weeks later--during the time the athletes received daily, before training session, 2 h cycling on road about 70km--2 tablets of the antioxidant product (respectively placebo). Then, after one week we applied the cross over method. 3 weeks of antioxidant treatment induced significant increase of the nonproteic -SH and significant decrease of the lipid peroxides (MDA), especially in comparison with placebo treatment. These results support the idea of some antioxidant effects of this compound which might be useful in the biological preparation of endurance athletes.

Antioxidants↗
PubMed1992

An acute mercuric mercury poisoning: chemical speciation of hair mercury shows a peak of inorganic mercury value.

A woman ingested a dose of sublimate (approximately 0.9 g) in an attempted suicide. She survived and recovered in response to a combination of therapies including chelate (BAL) therapy, plasma exchange, haemodialysis and peritoneal dialysis. Serum inorganic mercury concentration, urinary inorganic mercury excretion and hair inorganic and organic mercury and selenium concentrations, along the length from the scalp to the distal part, were measured. Longitudinal analysis of hair, revealed a peak in inorganic mercury corresponding to the time of mercury ingestion. Organic mercury and selenium in the hair had different patterns of longitudinal variation from that of inorganic mercury. The biological half-life (23.5 d) of serum inorganic mercury levels was in good agreement with values previously reported in the literature.

Adult↗
PubMedDate not supplied

Hydrogen selenide poisoning: an illustrative case with review of the literature.

Hydrogen selenide is a non-metallic compound currently receiving attention in both medicine and electronics. Toxicity results in multiple symptoms, the most characteristic of which is a garlicky odor of the breath. A young woman exposed repeatedly to hydrogen selenide gas developed gastrointestinal complaints, dental caries, conjunctivitis, nail deformities, and garlicky breath. Other reported cases are discussed along with various proposed treatments.

Abdomen↗
PubMed1983

The effect of methylmercury on the distribution and excretion of selenium by the guinea pig.

The influence of methylmercury (MeHg) on the tissue and subcellular binding of selenium was determined. Adult female guinea pigs received either 75Se (as sodium selenite) or MeHg (as chloride) followed 5 h later by an equimolar dose of 75Se. Animals were sacrificed 1, 3, 7, and 13 days after administration. Pretreatment with MeHg significantly altered the organ distribution of 75Se, particularly during the first week of the study. 75Se concentrations were markedly reduced in most organs of animals receiving both 75Se and MeHg except the liver, which contained markedly elevated 75Se levels. The subcellular distribution of 75Se was also altered by MeHg. Within liver, kidney and brain, 75Se was primarily bound to nuclear and mitochondrial fractions in both treatment groups, but nuclear binding was higher in animals receiving both compounds. Within nuclear fractions, most 75Se was bound to insoluble-nonhistone proteins. In the presence of MeHg, total nuclear binding of 75Se increased, but total binding to insoluble-nonhistone proteins decreased. MeHg also reduced the total 75Se binding to high molecular weight proteins of the soluble fraction. Alterations in tissue and subcellular binding of MeHg and Se may contribute to the lower degree of toxicity observed in animals receiving both compounds.

Animals↗
PubMed2002

Characterization of selenium species in Brazil nuts by HPLC-ICP-MS and ES-MS.

Brazil nuts have been classified as the foodstuffs that contain the highest level of unadulterated selenium, an essential trace element that appears to prevent cancer. To date, characterization of the selenium species in brazil nuts has not yet been investigated. In this work, various sample preparation approaches, including microwave extractions and enzymatic treatments, are examined with the goal of species preservation and subsequent selenium speciation; of these approaches, an enzymatic treatment with Proteinase K proved most effective. High-performance liquid chromatography (HPLC) separation strategies and inductively coupled plasma mass spectrometry (ICP-MS) detection schemes will also be presented. Extracts are evaluated against available standards for the commercially obtainable seleno-amino acids, selenomethionine (SeMet), selenoethionine (SeEt), and selenocystine (SeCys); selenomethionine was demonstrated to be the most abundant of these seleno-amino acids. Further characterization of unidentified selenium-containing peaks is attempted by the employment of several procedures, including electrospray-mass spectrometry (ES-MS). A peptide structure was identified; however, this was considered a tentative proposal due to the large background produced by the extremely complicated brazil nut matrix.

Chromatography, High Pressure Liquid↗