M. Sanz Alaejos

Selenium and cancer: some nutritional aspects

The level of selenium in cancer patients is lower than that in control subjects. However, low selenium levels in body fluids can be due to the malnutrition observed in these patients. There is evidence from epidemiologic studies that high dietary selenium intakes and high selenium status in people are associated with lower cancer mortality. However, contradictory information has been found in some prospective studies. The presence of other nutrients in selenium-rich foods can influence the role of the selenium in cancer etiology. Therefore, there are selenium antagonistic elements that inhibit the anticarcinogenic effects of selenium and other antioxidant micronutrients such as ascorbic acid, retinol, beta-carotene, alpha-tocopherol, and some other elements have a synergistic effect on the prevention of cancer.

Concentrations of iron, copper and zinc in human milk and powdered infant formula

Concentrations of iron, copper and zinc were determined in 56 samples of mature human milk from Canarian women and 5 samples of powdered infant formula. According to the literature our data fall within the normal limits in each kind of milk. The mean concentration of Fe, Cu and Zn of powdered infant formula was significantly higher than those concentrations found in the human milks. Significant differences among the concentrations of the studied metals for the milks of considered mothers were observed. The Fe, Cu and Zn intakes of infants fed with human milk are lower than the requirements recommended by the Food and Nutrition Board (1989). However, the infants fed with powdered infant formula had consumed an adequate intake of Fe and Cu. A progressive decrease of the metal concentrations with the lactation stage was observed. The human milk obtained in spring presented Fe and Zn concentrations lower than in autumn, which could be due to changes in nutritional habits of the mothers. Age of mother and number of previous children seem to influence the Zn and Cu concentrations of human milk.Concentrations of iron, copper and zinc were determined in 56 samples of mature human milk from Canarian women and 5 samples of powdered infant formula. According to the literature our data fall within the normal limits in each kind of milk. The mean concentration of Fe, Cu and Zn of powdered infant formula was significantly higher than those concentrations found in the human milks. Significant differences among the concentrations of the studied metals for the milks of considered mothers were observed. The Fe, Cu and Zn intakes of infants fed with human milk are lower than the requirements recommended by the Food and Nutrition Board (1989). However, the infants fed with powdered infant formula had consumed an adequate intake of Fe and Cu. A progressive decrease of the metal concentrations with the lactation stage was observed. The human milk obtained in spring presented Fe and Zn concentrations lower than in autumn, which could be due to changes in nutritional habits of the mothers. Age of mother and number of previous children seem to influence the Zn and Cu concentrations of human milk.

Enhancement of the fluorescence intensity of Se-2,3-diaminonaphthalene complex in aqueous solution by adding organic solvents

Fluorescence of the Se-2,3-diaminonaphthalene (DAN) complex has been studied in aqueous solutions with several organic solvents. With all organic solvents, the wavelength of the emission maxima in water was shifted to shorter wavelengths. However, the wavelength of the excitation maxima did not change. Fluorescence intensity (IF) of the Se-DAN complex observed with most organic media, increased with respect to the IF observed in water. However, the precision was poorer using the organic solvents than the precision found in water. Tetrahydrofuran (90%) and 1,4-dioxane (90%) exhibit the highest increases of IF. Higher enhancements of IF of the Se-DAN complex were observed when the concentration of organic solvent increased. So, the equations In IF = a + b · (% organic solvent)23 and 1/IF = a + b · (% organic solvent)12 could be established. Maximum IF of the Se-DAN complex in the studied organic media was obtained at a pH between 2.5 and 3.5. Tetrahydrofuran and acetonitrile showed the highest stability in the presence and absence of sunlight. Tetrahydrofuran (90%) and acetonitrile (60%) presented the best detection limits 1.96 and 3.00 μg Se l−1, respectively, showing a 23- and 15-fold improvement of the detection limit in aqueous medium. Acetonitrile (60%) was satisfactorily compared with hydride generation-atomic absorption spectrometry.

Urinary selenium concentrations in heroin abusers.

Abstract Urinary selenium (Se) concentrations (μg Se/l and μg Se/g creatinine) have been determined in heroin abusers and in healthy controls. Heroin abusers showed significantly ( P ) lower urinary Se concentrations (μg Se/l and μg Se/g creatinine) than healthy controls. The decrease of the urinary Se concentration (μg Se/g creatinine) observed with the increase in age of heroin abusers may be due to the higher exposure to heroin with increased age. No significant differences ( P > 0.100 ) of urinary Se concentrations (both as μg Se/l and μg Se/g creatinine) are observed between heroin abusers during methadone treatment and heroin abusers who have stopped taking the drug, with respect to healthy controls.

Fluorimetric Determination of Selenium in Biological Samples

ABSTRACT Most authors have used the fluorescence of Se-DAN complex for the fluorimetric determination of Se in biological samples. A considerable variation of the analytical conditions of this fluorimetric determination has been observed. All the original Se-compounds in the sample must be converted to selenite. Therefore, a previous step of mineralization of samples and reduction to selenite is required for the fluorimetric determination. The conditions for the digestion of samples may be chosen as a function of the sample to be analyzed. Heating with HCl for a variable time is usually used in the reduction step. For the complete formation of Se-DAN complex and to obtain the maximum fluorescent signal, the pH must be adjusted to values between 1-3 and then heated for a variable time depending on the temperature chosen. Application of organic solvents, surfactants and cyclodextrins has been studied to increase the fluorescent intensity and improve the sensitivity of the fluorimetric determination in aqueo...

On the determination of the free concentration of ligands

Working with a sufficient excess of any of the protonated forms of a ligand is shown to guarantee the validity of the determination of its free concentration when calculated by disregarding complexing effect. This result significantly extends the possibilities of studying the stability constants of co-ordination systems.

Concentrations of selenium in human milk

Abstract Selenium (Se) concentrations in 58 samples of mature human milk from Canarian women were determined by spectrofluorimetry. According to the literature the Se concentrations found fall within the normal limits. The concentration of Se in human milk was compared with that in powdered infant formula and presented significantly lower concentrations in the latter. Babies fed with human milk had an adequate intake of Se. However, babies fed with powdered infant formula consumed only 56% of the requirements recommended by The National Research Council. No changes in Se concentration were observed between lactation stages. Human milk produced in springtime was found to be richer in Se than that produced in the autumn, which could be due to changes in the nutritional habits of the mothers. The mothers age, weight, height and number of previous children were not found to influence the Se levels in the milk.

Polarographic analysis of the mixed-ligand system Cu(II)-glycine—glycinate

The polarographic method has been applied to the study of the mixed-ligand system Cu(II)-glycine-glycinate, in aqueous medium, at I = 1.0M (NaClO(4)) and 25 -/+ 0.1 degrees . The stabilization of the mixed complex [CuG(G(-))](+) has been made clear and its stability constant (beta(11) = 1 x 10(9)) has been determined. The stability constants of the complexes [CuG]I(2+) (beta(10) = 17), [CuG(2)](2+) (beta(20) = 230), [Cu(G(-))](+) (beta(01) = 2.1 x 10(8)) and [Cu(G(-))(2)] (beta(02) = 1.7 x 10(15)) have also been calculated.

NIVELES DE SELENIO EN AGUAS POTABLES DE CANARIAS SELENIUM LEVELS IN DRINKING WATER OF CANARY ISLANDS (SPAIN) NIVEIS DE SELENIO EN AUGAS POTABLES DE CANARIAS

Abstract Selenium (IV) and total Se concentrations have been determined in drinking waters from different places of Tenerife and Gran Canaria islands. Fluorimetric methods applied have been previously optimized deducing that those are precise (C.V. = 4.1 and 2.2% for Se(IV) and total Se, respectively) and presented determination limits and recoveries of 0.01 and 0.08 mg/1 and 89.1 and 99.2% for Se(IV) and total Se respectively. Neither sample have exceeded the maximum concentration (10 mg/l) established by Spanish directorate and the majority (69.4%) showed Se(IV) concentrations lower than 0.9 mg/l. The contribution to the Se daily intake due to the consumption of water in Canary Island is low. Mean concentration of Se(IV) in the detected samples (71.4%) was 0.96±0.43 mg/l and mean concentration of Se total in analyzed samples (30.6%) was 1.80±0.61 mg/l. The Se concentrations levels were higher than the most reported data from Europe. Selenium (IV) specie have constituted a 66.6% of total Se.