Determination of nickel, calcium and magnesium in xylem sap by flame atomic absorption spectrometry using a microsampling technique.

INTRODUCTION: Knowledge of xylem sap chemical composition is important to the understanding of translocation, detoxification and tolerance mechanisms. However, the small amount of sample available often hampers its characterisation. Hence, low volume consumption techniques are needed for xylem sap analysis. OBJECTIVE: To develop a microsampling technique for the determination of elements in xylem sap from different plants by flame atomic absorption spectrometry (FAAS). METHODOLOGY: The microsampling device was optimised in terms of sample volume and integration time. The analytical characteristics of the microsampling technique (micro-FAAS) were established and compared with those of FAAS with traditional continuous nebulisation. The method was validated by means of an independent technique. RESULTS: Ca, Mg and Ni were determined in a 50 microL aliquot of xylem sap solution/element that was introduced directly into the flame via the microsampling accessory. Good precision was obtained with relative standard deviations of 1.1, 0.6 and 2.3% for Ca, Mg and Ni, respectively. Matrix effects resulting from the physical characteristics of the samples and possible chemical interferences caused by phosphate and/or sulphate were ruled out. CONCLUSION: A simple, rapid and reproducible microsampling technique coupled to FAAS was developed and successfully applied in the determination of Ca, Mg and Ni in xylem sap.

Effects of dietary magnesium excess in White Leghorn hens.

The effects of excess dietary magnesium on White Leghorn laying hens were investigated in two experiments and a third experiment looked at the effect of dietary phosphorus on excess magnesium in the diet. In Experiment 1, magnesium levels of 0.15, 0.8, and 1.2% were fed in a diet containing 2.5% calcium to hens 30 wk of age for 5 wk. A control diet with 3.5% calcium and 0.15% magnesium was also fed. In Experiment 2, hens 65 wk of age fed 3.5% calcium were fed dietary magnesium levels of 0.15, 0.36, 0.53, 0.76, and 0.91% for 4 wk. In these two experiments, excess magnesium reduced egg production, decreased feed consumption, decreased body weight, decreased percentage eggshell, reduced plasma calcium, and increased plasma magnesium and tibia magnesium but changes seen in tibia weight, percentage ash, and tibia calcium and phosphorus were variable. More changes from feeding excess magnesium were seen in the young, high producing hens in Experiment 1. In Experiment 3, hens 50 wk of age were fed a marginal calcium level (2.5%) with an excess of magnesium (0.8%) and a control level of available phosphorus (0.45%) and this was compared to a low (0.25%) and a high level (0.9%) of available phosphorus for a 4-wk experimental period. At the end of the experimental period, hens fed low phosphorus had lower egg production and lower feed consumption than the hens fed higher levels of phosphorus. Body weight was lower in the hens fed the two lower levels of phosphorus. Percentage eggshell was lower than the controls when fed low phosphorus and higher when fed high phosphorus. These results suggest that high phosphorus diets are better than low phosphorus diets when excess magnesium is fed to laying hens. Further study is needed to investigate the role of phosphorus when excess magnesium is fed.

Evaluation of multiple micronutrient supplementation in the management of oral submucous fibrosis in Karachi, Pakistan.

Oral submucous fibrosis (OSF) is an oral precancerous condition characterized by symptoms such as intolerance to spicy food, altered salivation, progressive difficulty in opening the mouth, and signs like vesiculation, ulceration, blanching, rigidity, and stiffening of the oral mucosa and depapillation and altered mobility of the tongue. It is seen mostly among people of Indian subcontinent origin. The major structural change is extensive fibroelastic scarring of the lamina propria and deeper connective tissues. A combination of micronutrients (vitamins A, B complex, C, D, and E) and minerals (iron, calcium, copper, zinc, magnesium, and others) was evaluated for its efficacy in controlling the symptoms and signs of OSF in 117 compliant subjects in Karachi, Pakistan, in a single-arm preliminary study. The subjects received supplementation for one to three years. Significant improvement in symptoms, notably intolerance to spicy food, burning sensation, and mouth opening, was observed at exit. The interincisor distance deteriorated in 11 subjects (10%) at exit; it was stable in 56 subjects (49%) and improved in 48 (41%). The mean interincisor distance was 19.1 +/- 10.8 (SD) mm at exit compared with 16.2 +/- 7.5 mm at baseline. A significant proportion of concomitant lesions like leukoplakia also regressed at exit. The major outcome from this study was a beneficial clinical response in subjects with OSF to multiple micronutrient intervention, which justifies its further evaluation in well-designed randomized controlled trials in other settings in South Asia.

Micronutrients (magnesium, zinc, and copper): are mineral supplements needed for athletes?

Mineral elements, including magnesium, zinc, and copper, are required by the body in modest amounts for the maintenance of health and for the development of optimal physiological function. For athletes, adequate amounts of these minerals are required for physical training and performance. Studies of athletes during training, as compared to nontraining control subjects, indicate the potential for increased losses of minerals in sweat and urine. Some studies report suboptimal intakes of minerals, particularly among athletes who are actively attempting to lose weight to meet standards for competition. However, most athletes consume diets that provide adequate amounts of minerals to meet population standards. Athletes should be counseled to consume foods with high nutrient density rather than to rely on mineral supplements. General use of mineral supplements can alter physiological function and impair health.

[Nutritive value of daily food rations prepared in different regions of the country. III. The levels of calcium, phosphorus, magnesium, iron and potassium]. / Wartosc odzywcza calodziennych racji pokarmowych odtwarzanych w kilku regionach kraju. Cz. III. Zawartosc wapnia, fosforu, magnezu, zelaza i potasu.

Studies on the content of macrominerals in daily diets reconstructed in 1988 on the basis of the analysis of family budgets in 1986 carried out by the Central Statistical Bureau were carried on. Two social groups i.e. manual and mental workers with medium income were considered. The diets were prepared for 5 regions (Warszawa, Lublin, Olsztyn, Poznan, Wroclaw). According to the studies the requirements for calcium and magnesium were met in about 70% and those for iron in about 84%. The content of potassium in the diets was in the range of recommended allowances while the phosphorus exceeded the allowances by about 20-30%. The comparison of the presently studied diets with the ones from 1973, 1980, 1981 showed a lower degree of realization of the recommended intake of calcium and magnesium in 1986. The content of studied minerals in the diets was usually similar in all five regions.

Calcium, phosphorus, and magnesium: how much is too much for infant formulas?

Despite the use of metabolic balance studies and measurements of bone mineral content, it is difficult to assess the requirements of Ca and P in growing infants. From observations made forty years ago with cow's milk formulas it is obvious what is too much calcium and phosphorus in infant formulas. These observations were utilized in the development of "humanized cow's milk formulas" in the 1950s. Though the total concentrations of Ca and P have been greatly reduced in these formulas, the Ca/P ratio imbalance, compared to human milk, persists. Infants fed these formulas still receive a relative phosphorus load, and cases of neonatal tetany are still occasionally reported. Thus, formula-fed infants have higher serum P and lower serum Ca concentrations than do human milk-fed infants. Unlike Ca and P, the magnesium concentration of infant formulas is similar to that of human milk, and Mg toxicity from formulas has not been reported. Like Ca and P, however, it is difficult to determine the growing infant's requirement for magnesium. The available information does not favor either increasing or decreasing the present concentrations of Ca, P or Mg in infant formulas. The upper limit for these minerals should remain at the present concentrations: 45-50 mg/dl (65-75 mg/100 kcal) for Ca, 30-40 mg/dl (48-58 mg/100 kcal) for P and 12 mg/dl (18 mg/100 kcal) for Mg.