Absorption and retention of selenium from intrinsically labeled egg and selenite as determined by stable isotope studies in humans

A study was carried out with four healthy young adult men, consuming a self-selected diet, to investigate quantitative aspects of the gastrointestinal absorption, urinary excretion, and body retention of egg selenium in comparison with selenite. The approach involved simultaneous consumption of egg biologically labeled (intrinsic) with the stable isotope 74Se and a dose of selenite labeled with 76Se (extrinsic label). Four labeled test diets, given on days 6, 16, 26, and 36 of the study were employed, each differing in their protein source: test diet I, 74Se-labeled egg white; diet II, 74Se-labeled egg yolk (high labeling dose) plus balanced L-amino acid mixture; diet III, 74Se-labeled egg yolk (low labeling dose) plus balanced amino acid mixture; and diet IV, balanced amino acid mixture extrinsically labeled with both 74SeO32- and 76SeO32-. The latter diet was included to assess the magnitude of any cross-isotope methodological bias. Fractional absorption (means +/- SEM) for Diet IV was 0.771 +/- 0.010 for the 74SeO32- and 0.656 +/- 0.021 for the 76SeO32- (ratio: 0.851 +/- 0.020); reflecting a small overall cross-isotope bias. Accepting the measurements made with 74SeO32- as the more accurate, experimentally determined values of absorption for the extrinsic tag were adjusted accordingly. The corrected absorption for these diets (% of dose) was (mean +/- SEM; first value for intrinsic label, second value for extrinsic label): diet I, 54.1 +/- 0.7 and 55.4 +/- 2.2; diet II, 76.7 +/- 0.8 and 83.0 +/- 1.8; diet III, 79.0 +/- 1.5 and 85.2 +/- 4.0.(ABSTRACT TRUNCATED AT 250 WORDS)     

Chitosan improves insulin sensitivity as determined by the euglycemic-hyperinsulinemic clamp technique in obese subjects

In accordance with obesity is associated with insulin resistance and dyslipidemia and chitosan decrease weight and lipids, but its effect on insulin sensitivity is unknown. Our hypothesis for the research was that chitosan improves insulin sensitivity estimated with the euglycemic-hyperinsulinemic clamp technique in obesity. We undertook this study with the objective to determine the effect of chitosan on insulin sensitivity using the euglycemic-hyperinsulinemic clamp technique in obese patients during a 3-month period. A randomized, double-blind clinical trial was carried out in 12 obese adults without diabetes mellitus. During a 3-month period, 6 patients received chitosan (750 mg, 3 times per day) 30 minutes before meals, and the other 6 subjects received placebo. Serum glucose, total cholesterol, high-density lipoprotein cholesterol, and triglycerides (TG) were measured. Insulin sensitivity was estimated with the euglycemic-hyperinsulinemic clamp technique before and after the intervention. Insulin sensitivity increased significantly with the administration of chitosan (2.4 ± 1.4 vs 3.6 ± 1.4 mg kg⁻¹ min⁻¹; P = .043). In addition, there was a decrease in weight (90.7 ± 14.2 vs 84.7 ± 13.7 kg; P = .027), body mass index (34.3 ± 2.7 vs 31.6 ± 2.2 kg/m²; P = .028), waist circumference (106 ± 12 vs 99 ± 9 cm; P = .028) and TG (2.4 ± 0.9 vs 1.6 ± 0.9 mmol/L; P = .028) in the chitosan group. In conclusion, 3-month administration of chitosan increased insulin sensitivity in obese patients and demonstrated a decrease in weight, body mass index, waist circumference, and TG.     

Variation of concentration of heavy metals, calcium and magnesium with sex as determined by atomic absorption spectrophotometry

The concentrations of ten elements: Pb, Cd, Cr, Mn, Fe, Ni, Cu, Zn, Ca and Mg in hair, fingernails and toenails of girl and boy students between 20-24 years of age, living in nonindustrialized areas of Rajasthan state in India were analysed by Atomic Absorption Spectrophotometer. Adequate quality assurance was ensured by inter-laboratory exerciese, the results of which overall showed good consistency. With the exception of Cu, all metals were found to be significant in fingernails and toenails of boys as compared to boys hair while in case of girl students all metals except zinc in toenails were found to be significant in hair. Using Pearson's Correlation Coefficient we obtained information about high positive and negative correlations among metals in hair, finger nails and toenails of boy and girl students.     

Levels of metals in hair of young children as an indicator of environmental pollution

In 1982 the levels of lead (Pb), cadmium (Cd), vanadium (V), copper (Cu), and selenium (Se) were determined in hair of 231 four- to five-year-old children. The objective was to explore the feasibility of using metal-in-hair levels in groups of children as an indicator of environmental pollution. The study was carried out in four areas, which were assumed to differ in ambient pollution by metals. A questionnaire on personal data, socioeconomic status, intake of beverages, and life-style was completed by the parents. The metal-in-hair levels covered a large range. The variables pertaining to location together with sex, presence of a garden, and drinking of coffee and/or tea explained 32% of the variance of Pb, 24% of the variance of Cd, and 21% of the variance of V. The total variance explained by all measured questionnaire items was at best 38%. The location was the most important factor. Cu and Se levels did not differ between the locations.     

Total sulfur amino acid requirement of healthy school-age children as determined by indicator amino acid oxidation technique

BACKGROUND: Current total sulfur amino acid (TSAA) requirements of children are based on a factorial estimate that involves several assumptions. OBJECTIVE: The objective was to determine the TSAA requirement (methionine alone) of healthy school-age children by measuring the appearance of 13CO2 (F13CO2) in breath after the oxidation of l-[1-13C]phenylalanine in response to graded methionine intakes. DESIGN: Six healthy school-age children randomly received each of 6 methionine intakes (0, 5, 10, 15, 25, and 35 mg.kg(-1).d(-1)) along with an amino acid mixture to give a final protein intake of 1.5 g.kg(-1).d(-1) and an energy intake of 1.7 x resting energy expenditure. The diet was devoid of cysteine. The mean TSAA requirement was determined by applying a biphase linear regression crossover analysis on F13CO2 data, which identified a breakpoint at minimal F13CO2 in response to graded methionine intakes. RESULTS: The mean and population-safe (upper 95% CI) intakes of TSAA (as methionine) were determined to be 12.9 and 17.2 mg.kg(-1).d(-1), respectively. CONCLUSIONS: The current study suggests that children of this age group have a mean TSAA requirement similar to that of adults (12.6 mg.kg(-1).d(-1)). Therefore, it is valid to use a factorial approach, which assumes that maintenance requirements in childhood are similar to adult requirements, to estimate TSAA requirements in school-age children.     

Levels of methyleugenol in a subset of adults in the general U.S. population as determined by high resolution mass spectrometry

We developed a sensitive and accurate analytical method for quantifying methyleugenol (ME) in human serum. Our method uses a simple solid-phase extraction followed by a highly specific analysis using isotope dilution gas chromatography-high resolution mass spectrometry. Our method is very accurate; its limit of detection is 3.1 pg/g and its average coefficient of variation is 14% over a 200-pg/g range. We applied this method to measure serum ME concentrations in adults in the general U.S. population. ME was detected in 98% of our samples, with a mean ME concentration of 24 pg/g (range < 3.1-390 pg/g). Lipid adjustment of the data did not alter the distribution. Bivariate and multivariate analyses using selected demographic variables showed only marginal relationships between race/ethnicity and sex/fasting status with serum ME concentrations. Although no demographic variable was a good predictor of ME exposure or dose, our data indicate prevalent exposure of U.S. adults to ME. Detailed pharmacokinetic studies are required to determine the relationship between ME intake and human serum ME concentrations.     

Effect of selenium and molybdenum on methylbenzylnitrosamine-induced esophageal lesions and tissue trace metals in the rat

Thirty-six weanling male Sprague-Dawley rats were randomly assigned to one of four treatment groups: SE rats received 4.0 ppm selenium as sodium selenite in drinking water containing 1% sucrose; 15MO rats received 15 ppm molybdenum as sodium molybdate in the drinking water; 45MO rats received 45 ppm molybdenum in their water; and CON rats received distilled-deionized water containing only 1% sucrose. The esophageal carcinogen methylbenzylnitrosamine (MBN) was administered intragastrically in 10% ethanol twice per week for 5 wk at a dose of 2.5 mg/kg. MBN dosing was followed by a 12-wk period for tumor promotion. After this, heart, lungs, liver, spleen, kidneys, testes, tibia, muscle, brain and esophagus were excised. The esophagus was examined for MBN-induced lesions using dissecting and light microscopes and a portion was analyzed for Se. All other tissues were analyzed for Cu, Zn, Fe and Mn; some were also analyzed for Se and Mo. Most rats had precancerous lesions, and all rats had papillomas. There were no significant differences among the four treatment groups in the incidence and number per rat of precancerous lesions or gross papillomas. The SE group had significantly fewer carcinomas per rat than the other groups. The SE rats exhibited a number of significant differences in tissue trace element concentrations; in particular, they had higher Fe concentrations in heart, kidney and spleen than the other rats. The SE rats also had significantly greater urinary excretion of Mn and Fe, and excretion of the latter elements was significantly correlated with that of selenium.(ABSTRACT TRUNCATED AT 250 WORDS)     

Stages of the Baltic Sea evolution in the geochemical record and radiocarbon dating of sediment cores from the Arkona Basin

Four sediment cores from the southern part of the Arkona Basin were analyzed in terms of their geochemical composition, age and stratigraphy. The main stages of the Baltic Sea: the Baltic Ice Lake, the Ancylus Lake and the Littorina Sea were identified in all the analyzed cores. The data confirmed the high water fluctuation and significant environmental changes during the Baltic Sea evolution in the Late-Glacial and the Holocene. The signs of the second regression of the Baltic Ice Lake, dated at around 11 000 cal BP, were identified at a depth of 24 m b.s.l. Regression of the Ancylus Lake, dated at 9300 cal BP, was identified at a depth of 23 m b.s.l. The most pronounced period was the transition stage between the Ancylus Lake and the Littorina Sea. The record of the Littorina Sea onset in the sediments of the Arkona Basin is marked as a sudden increase in loss on ignition, biogenic silica, magnesium, calcium, iron and strontium. The age of the Littorina Sea in the Arkona Basin was estimated as younger than 8200 cal BP.     

Micro-spatial variations of heavy metals in the teeth of walrus as determined by laser ablation ICP-MS: The potential for reconstructing a history of metal exposure

This study explored the possibility of using laser ablation inductively-coupled plasma-mass spectroscopy to measure trace metals and other elements within the annual growth layers of the teeth of walrus harvested from the Canadian Arctic. Using sample ablation footprints of 125 m diameter on transects across the exposed cross-sections of teeth, this technique detected Pb, Cu, Zn and Sr, but not Cd, in tooth cementum. The micro-spatial patterns of elements were consistent among different transects on the same tooth, and revealed subtle differences between animals of different ages. The youngest walrus in the sample (4 yr) contained higher concentrations of Pb and Cu than older animals in the growth layer deposited during the first year of life, while the oldest animal (33 yr) exhibited higher Pb and Zn than younger animals in the outer layer corresponding to the year 1988. The differences between animals and across annual layers may reflect both life history and metal exposure phenomena, including high amounts of metals transferred from mothers to pups in maternal milk. The ability to detect metals in a repeatable fashion within annual growth layers suggests that metal exposure histories accurate to within a year might be re-constructed for the lifetimes of long-lived animals, and that a series of such individual studies would allow exposure histories covering centuries to be quickly assembled. These data may suggest the most likely explanation for the currently high levels of some metals observed in certain Arctic marine mammals, i.e., natural phenomenon or anthropogenic contamination.     

Distribution of selenium, molybdenum and uranium in sediment cores from the Colorado River delta, Baja California, Mexico

The distribution of selenium, molybdenum and uranium was studied in ~1.5 m sediment cores from the Colorado River delta, at the Colorado (CR) and Hardy (HR) riverbeds. Core HR2 showed highest Se, Mo and U concentrations at its bottom (2.3, 0.95 and 1.8 μg g⁻¹) within a sandy-silt layer deposited prior to dam construction. In CR5 the highest concentrations of these elements (0.9, 1.4 and 1.7 μg g⁻¹ respectively) were located at the top of the core within a surface layer enriched in organic carbon. A few samples from HR2 had Se above the probable toxic effect level guidelines.     

产妇和新生儿体内重金属水平及其影响因素分析

目的了解某地区产妇及新生儿血砷、汞和铅的水平,分析其相关影响因素。方法在某地区随机抽取A、B两所医院,选择2012年4—5月间住院分娩的产妇共226名,采集产妇静脉血和新生儿脐带血,采用电感耦合等离子体质谱法测定全血中砷、汞和铅的浓度,并对产妇进行问卷调查。结果 226对产妇和新生儿血铅浓度范围分别为2.65~67.00μg/L和4.05~70.89μg/L,均低于100μg/L的限值;A医院产妇和新生儿血砷平均浓度分别为1.20μg/L和1.23μg/L,均高于B医院(0.62μg/L和0.71μg/L),差异具有统计学意义(P0.05),血汞和血铅浓度差异均无统计学意义(P0.05);新生儿脐带血中砷、汞和铅浓度与产妇静脉血中同种元素浓度呈显著正相关(P0.01),相关系数分别为0.925、0.832和0.765;多重线性回归分析结果显示,家庭年收入越高,产妇及其新生儿血砷浓度越高(P0.05);产妇文化程度则对血铅水平有显著影响,文化程度越高,产妇及其新生儿血铅浓度越低(P0.05)。结论该地区产妇和新生儿体内砷、汞、铅暴露水平较低,但胎盘对重金属缺乏有效屏障作用,仍应采取有效措施减少产妇和新生儿重金属暴露。     

Levels of 226Ra, 210Pb and total U in fish near a Saskatchewan uranium mine and mill

Radionuclide levels in fish from the Beaverlodge Lake area, Saskatchewan, Canada, varied significantly among lakes, species and tissues, but did not vary with fish sex or age. Fish from lakes affected by an operating uranium mine and mill had radionuclide levels one to two orders of magnitude above levels in fish from an uncontaminated control lake. Concentrations were greatest in white suckers, intermediate in lake whitefish, and low in lake trout. Skin and bone contained the highest radionuclide levels; levels in flesh were much lower. The mean ash-weight concentration of 226Ra in non-control, eviscerated, whole fish was 9.3, 1.8 and 0.8 pCi X g-1 in white suckers, lake whitefish and lake trout respectively. Mean 210Pb levels for those species were 4.0, 1.4 and 0.5 pCi X g-1, while U content was 96.8, 28.2 and 5.8 micrograms X g-1, respectively. Radium-226 content in forage fish ranged from 9.7-70 pCi X g-1. Lead-210 levels ranged from 3.9-55.0 pCi X g-1, while U levels ranged from 15-119 micrograms X g-1. Bioconcentration factors varied among sites, species and tissues. The primary radionuclide transfer pathway appears to be via sediments, either through direct contact or through food organisms. Bottom-feeding species had the highest radionuclide levels while piscivorous fish had the lowest levels. The internal dose rate to non-control fish are comparatively low; any effects are likely to occur at the genetic level.     

Acid volatile sulfide and simultaneously extracted metals in the sediment cores of the Pearl River Estuary, South China

The acid-volatile sulfide (AVS), simultaneously extracted metals (SEM), total metals, and chemical partitioning in the sediment cores of the Pearl River Estuary (PRE) were studied. The concentrations of total metals, AVS, and SEM in the sediment cores were generally low in the river outlet area, increased along the seaward direction, and decreased again at the seaward boundary of the estuary. The amounts of AVS were generally greater in deeper sediments than in surface sediments. SEM/AVS was >1 in the surface sediments and in the river outlet cores. The ratio was <1 in the sediments down the profiles, suggesting that AVS might play a major role in binding heavy metals in the deep sediments of the PRE. The SEM may contain different chemical forms of trace metals in the sediments, depending on the metal reaction with 1M cold HCl in the AVS procedure compared with the results of the sequential chemical extraction. The SEM/AVS ratio prediction may overestimate trace metal availability even in the sediments with high AVS concentrations.