Selenium

About: Selenium is a research topic. Over the lifetime, 21192 publications have been published within this topic receiving 429715 citations. The topic is also known as: Se & selen.

Transformations of selenium as affected by sediment oxidation-reduction potential and pH.

Abstract: Etude en laboratoire de l'influence du potentiel redox et du pH des sediments sur la solubilite, la speciation et la volatilisation du selenium

Biochemistry of selenium.

Abstract: 1. Forms of Selenium.- 1.1 Low Molecular-Weight Compounds.- 1.1.1 Selenocysteine.- 1.1.2 Selenocystine.- 1.1.3 Selenohomocystine.- 1.1.4 Se-methylselenocysteine.- 1.1.5 Selenocystathionine.- 1.1.6 Selenomethionine.- 1.1.7 Se-methylselenomethionine.- 1.1.8 Dimethyl Selenide.- 1.1.9 Dimethyl Diselenide.- 1.1.10 Trimethyl Selenonium.- 1.1.11 Elemental Selenium.- 1.1.12 Selenotaurine.- 1.1.13 Selenocoenzyme A.- 1.1.14 Other Compounds.- 1.2 Macromolecular Forms of Selenium.- 1.2.1 Formate Dehydrogenase.- 1.2.2 Glycine Reductase.- 1.2.3 Nicotinic Acid Hydroxylase.- 1.2.4 Xanthine Hydrogenase.- 1.2.5 Thiolase.- 1.2.6 Glutathione Peroxidase.- 1.2.7 Miscellaneous Selenoproteins.- 1.2.8 Seleno-tRNA's.- 11.11 References.- 2. Selenium Deficiency Diseases in Animals.- 2.1 Introduction.- 2.2 Dietary Liver Necrosis and Factor 3.- 2.2.1 Discovery.- 2.2.2 Pathology.- 2.2.3 Biochemical Defect.- 2.2.4 Hepatosis Dietetica.- 2.3 Nutritional Muscular Dystrophy.- 2.3.1 Pathology.- 2.3.2 Prevention of NMD.- 2.4 Exudative Diathesis.- 2.5 Pancreatic Degeneration.- 2.6 Mulberry Heart Disease.- 2.7 Reproductive Problems.- 2.8 Myopathy of the Gizzard.- 2.9 Growth.- 2.10 Selenium-Responsive Unthriftiness of Sheep and Cattle.- 2.11 Periodontal Disease of Ewes.- 2.12 Encephalomalacia.- 11.11 References.- 3. Metabolism of Selenium.- 3.1 Absorption.- 3.2 Placental Transfer.- 3.3 Mechanism of the Antioxidant Action of Selenium.- 3.4 Effect of Paraquat.- 3.5 Effect on Cytochrome P-450.- 3.6 Selenium and Hepatic Heme Metabolism.- 11.11 References.- 4. Comparative Metabolism and Biochemistry of Selenium and Sulphur.- 4.1 Introduction.- 4.2 Comparative Metabolism of Selenium and Sulphur.- 4.2.1 Microorganisms.- 4.2.2 Plants.- 4.2.3 Animals.- 4.3 Comparative Biochemistry of Selenium and Sulphur.- 4.3.1 Selenopersulfide as an Electron Transfer Catalyst.- 4.3.2 Iron-Sulphur Proteins.- 4.3.3 Sulphur Salts and Selenium Toxicity in Animals.- 4.3.4 Other Selenium-Sulphur Interactions.- 11.11 References.- 5. Biological Interactions of Selenium with Other Substances.- 5.1 Cadmium.- 5.1.1 Pathological Effects.- 5.1.2 Cadmium-Zinc Interactions.- 5.1.3 Cadmium-Selenium Interactions.- 5.1.4 Effect on Drug Response.- 5.2 Arsenic.- 5.3 Copper.- 5.4 Silver.- 5.5 Cobalt.- 5.6 Manganese.- 5.7 Lead.- 5.8 Mercury.- 5.8.1 Inorganic and Organic Mercury.- 5.8.2 Tissue Distribution.- 5.8.3 Properties of the Mercury-Selenium Complex.- 5.8.4 Teratogenicity.- 5.9 Thallium.- 5.10 Tellurium.- 5.11 Vanadium.- 5.12 Bismuth.- 5.13 Other Substances.- 11.11 References.- 6. Environmental Occurrence of Selenium.- 6.1 Geochemistry of Selenium.- 6.2 Soil Selenium.- 6.3 Uptake and Concentration of Trace Elements in the Roots, Stems, and Leaves of Plants.- 6.4 Forage Selenium.- 6.5 Selenium in Water.- 6.6 Selenium in Food.- 6.7 Intakes and Recommended Daily Allowance in Humans.- 6.8 Regulations in Regard to Animal Diets.- 11.11 References.- 7. Toxicity of Selenium.- 7.1 Introduction.- 7.1.1 Acute Toxicity.- 7.1.2 Blind Staggers.- 7.1.3 Alkalai Disease.- 7.1.4 Toxicity in Rabbits.- 7.1.5 Toxicity in Hamsters.- 7.1.6 Toxicity in Sheep.- 7.1.7 Toxicity in Rats.- 7.1.8 Effect of Diet on Toxicity.- 7.1.9 Biochemical Lesions.- 7.1.10 LD50 of Various Selenium Compounds.- 7.2 Industrial Medical Aspects.- 7.2.1 Occupational Hazards.- 7.2.2 Permissible Limits for Selenium Exposure.- 7.2.3 Toxicity in Humans.- 11.11 References.- 8. Selenium in Health and Disease.- 8.1 Selenium and Cancer.- 8.1.1 Skin Cancer.- 8.1.2 Liver Cancer.- 8.1.3 Colon Cancer.- 8.1.4 Breast Cancer.- 8.1.5 Tracheal Cancer.- 8.1.6 Chemotherapeutic Effect of Selenium.- 8.1.7 Epidemiological Relationship.- 8.1.8 Selenium Blood Levels in Cancer Patients.- 8.1.9 Selenium as a Carcinogen.- 8.2 Selenium and Mutagenesis.- 8.2.1 Antimutagenicity.- 8.2.2 Mutagenicity.- 8.3 Selenium and Immunity.- 8.3.1 Effect of Selenium on Humoral Immunity.- 8.3.2 Cell-Mediated Immunity.- 8.3.3 Nonspecific Immune Effects of Selenium.- 8.4 Selenium and Dental Caries.- 8.5 The Anti-Inflammatory Properties of Selenium.- 8.6 Selenium and Heart Disease.- 8.6.1 Animals.- 8.6.2 Humans.- 8.7 Selenium and Aging.- 8.8 Cystic Fibrosis.- 8.9 Multiple Sclerosis.- 8.10 Cataracts.- 8.11 Other Diseases.- 8.12 Radioselenium as a Diagnostic Agent.- 11.11 References.- 9. Synthetic Forms of Selenium and Their Chemotherapeutic Uses.- 9.1 Anti-Infective Agents.- 9.1.1 Antibacterial.- 9.1.2 Antiviral.- 9.2 Antifungal Agents.- 9.3 Antiparasitic Agents.- 9.4 Compounds Affecting the Central Nervous System.- 9.4.1 Hypnotics.- 9.4.2 Analgesics and Local Anesthetics.- 9.4.3 Tranquilizing Drugs.- 9.5 Compounds that Affect the Autonomic Nervous System.- 9.6 Compounds that Affect the Circulatory System.- 9.7 Anti-Inflammatory Compounds.- 9.8 Antihistamines.- 9.9 Anticancer Agents.- 9.10 Antiradiation Agents.- 9.11 Steroids.- 9.12 Selenocoenzyme A.- 9.13 Selenium-Containing Carbohydrates.- 9.14 Seleno-Amino Acids.- 11.11 References.- 10. Analytical Methods of Selenium Determination.- 10.1 Introduction.- 10.2 Sample Preparation and Storage.- 10.3 Destructive Analysis.- 10.3.1 Ashing.- 10.3.2 Closed-System Combustion.- 10.3.3 Wet Digestion.- 10.3.4 Measurement of Selenium.- 10.4 Nondestructive Analysis.- 10.4.1 Neutron Activation Analysis.- 10.4.2 X-Ray Fluorescence Analysis.- 10.4.3 Proton-Induced X-Ray Emission.- References.

Selenium-dependent enzymes.

Abstract: Selenium, molecular weight 78.96, resembles sulfur in many of its chemical properties and occurs in inorganic forms as H2Se, H2Se2O3, H2SeO3, and H2SeO4 which are the analogues of hydrogen sulfide, thiosulfate, sulfite, and sulfate, respectively. The commonly available radionuclide, 75Se, is a gamma emitter (half-life 122 days) that is used extensively as a tracer in biochemical studies and as a radiopharmaceutical agent for diagnostic purposes. Organoselenium compounds, in general, are less stable and more reactive than the corresponding sulfur analogues and these properties may account for the toxicity of selenium when it is incorporated indiscriminately in place of sulfur in cellular constituents. On the other hand living systems may have exploited the greater reactivity of certain types of organoselenium compounds in those instances where selenium is specifically required as a component of an enzyme or other macromolecule. Several enzymic processes that do not distinguish selenium from sulfur and therefore may be important in selenium toxicity were discussed in some detail in two earlier reviews on selenium biochemistry (1, 2) and this aspect of the problem is not treated here. Rather, the information currently available on the properties and catalytic functions of the four known selenium-dependent enzymes is summarized. These enzymes are formate dehydrogenases of Escherichia coli and several anaerobic bacteria, clostridial glycine reductase, mammalian and avian glutathione peroxidase, and nicotinic acid hydroxylase of Clostridium barkeri. Additional selenoproteins whose catalytic activities are as yet unidentified are mentioned.

Current Knowledge on the Importance of Selenium in Food for Living Organisms: A Review

Abstract: Selenium is one of the elements classified within the group of micronutrients which are necessary in trace amounts for the proper functioning of organisms. Selenium participates in the protection of cells against excess H2O2, in heavy metal detoxification, and regulation of the immune and reproductive systems as well. It also ensures the proper functioning of the thyroid gland. Selenium induces the occurrence of the selenoprotein synthesis process involved in the antioxidant defense mechanism of the organism. Recent years have brought much success in the studies on selenium. Anticarcinogenic properties of selenium against some cancers have been reported. Supplementation is increasingly becoming a solution to this problem. A large number of different supplementation methods are promoting studies in this area. Slight differences in the selenium content can result in excess or deficiency, therefore supplementation has to be done carefully and cautiously.