Studies on bioavailability of some bulk and trace elements in mexican tortilla using an in vitro model

An in vitro gut model was used to investigate the bioavailability of calcium, magnesium, cadmium, chromium, iron, manganese, and lead in the Mexican (maize) tortilla. The samples (4 g) were digested in quartz tubes using concentrated nitric acid (12 mL) at 65‡C (2 h) and then at 120‡C (4 h). Total element concentration was determined by atomic absorption spectrometry. Enzymatic hydrolysis was carried out in two steps: first, with pepsin in a hydrochloric acid medium (pH 1.8) and then after neutralization with sodium bicarbonate (pH 6.0), with the mixture of pancreatine, amylase, and bile salts extract. Elements under study were determined in the supernatant by atomic absorption spectrometry. The bioavailable fraction of each element in tortilla was evaluated as the percentage of total element content found in the solution after enzymolysis. The obtained results showed relatively low bioavailability of the selected elements (from 2% to 32%), which possibly may be ascribed to the presence of dietary fiber in tortilla.     

On-line deproteinization by adsorption of proteins on a polyethylene powder pre-column for the determination of Na,K, Mg and Ca in human serum by high-performance liquid chromatography

Deproteinization of human serum was carried out on-line using a polyethylene powder cartridge as pre-column. The serum sample, after dilution, was injected into the chromatograph, and when passing through the cartridge the proteins were adsorbed by the polyethylene. A protein-free eluate was carried to the analytical column while the pre-column was washed with methanol and water to elute the adsorbed proteins by changing the pump channels. After washing, the pre-column was conditioned with the eluent to receive the next sample. Deproteinization was evaluated off- and on-line using pooled serum, and testing the protein residue after passing through a polyethylene cartridge with the Comassie Brilliant Blue reaction. Parameters such as serum volume, eluent and washing solution were investigated. Sodium, potassium, magnesium and calcium determinations were performed by high-performance liquid chromatography with conductimetric detection. The proposed method is suitable for the determination of these cations in serum samples without further treatments. The total analysis time was about 20 min and a linear range from 0.3 to 1.2 mg/l for sodium, potassium, magnesium and calcium was observed. The method was characterized by a precision of about 95% and recoveries from spiked samples were between 96 and 102%. The results for serum samples analysed by the proposed method were compared with photometry and atomic absorption spectrometry.     

Effect of isoproterenol (ISO) on rat heart,liver, kidney,and muscle tissue levels of zinc,copper, and magnesium

X-ray fluorescence and atomic absorption spectrometry were used to measure the concentrations of zinc, copper, and magnesium in the heart, liver, skeletal muscle, and kidney following isoproterenol-induced myocardial necrosis in male albino rats. Serum activities of lactic dehydrogenase (LDH), creatine phosphokinase (CPK), and glutamic oxaloacetic transaminase (SGOT) were also measured. There was depletion of myocardial zinc, copper, and magnesium on d 1, followed by an uptake of all these elements on d 2. The liver showed a significant uptake of magnesium, along with depletion of copper. There was no change in the kidney and skeletal muscle concentrations of these elements. Possible explanations for the observed changes and their therapeutic significance are presented.     

Reference Values for Serum Magnesium Levels in Young Adult Iranian Subjects

This study aims at determining the reference values for serum magnesium (Mg) concentrations in Iranian adults. Serum Mg level was measured using flame atomic absorption spectrometry in 491 subjects (233 men and 258 women), aged 20-50 years, randomly selected from a population-based study. The International Federation of Clinical Chemistry guidelines and the robust method were used for determining the reference values. The 95% reference values for serum Mg concentration were 1.83-2.49, 1.79-2.48, and 1.83-2.55 mg/dL in men, women, and total population, respectively. The prevalences of hypo- and hypermagnesemia, according to the reference values obtained in the current study, were 2.5% and 4.0%, respectively. In conclusion, this study reports serum Mg reference values based on current standards in a large healthy population of young Iranian adults.     

Determination of urinary arsenic, mercury, and selenium in steel production workers

The fumes and dust of trace elements and their compounds are very toxic and have been related to an increase in the incidence of diseases. Occupational exposure to toxic metals and metalloids can be determined by means of workplace air measurements and biological monitoring. The aim of our investigation was to determine the concentrations of As, Hg, and Se in urine samples under routine clinical laboratory conditions. To assess the reliability of these methods, critical factors such as detection limit(s), calibration range(s), cost, accuracy, and precision were studied. The method was employed for the quantitative determination of arsenic, mercury, and selenium in urine samples from steel production and quality control workers and healthy unexposed controls. After pretreatment with acids, the samples were digested by means of a microwave oven. Arsenic was determined by hydride atomic absorption spectrometry and mercury was determined by cold vapor atomic absorption spectrometry, whereas selenium was determined by a graphite furnace atomic absorption spectrometry. The results indicate those urinary arsenic, mercury, and selenium levels of the exposed workers are significantly higher than those of the controls. The possibility that these elements are involved in the etiology of diseases is discussed and recommendations are made to improve workplace ventilation and industrial hygiene practices.     

Magnesium,zinc, and manganese in atherosclerosis of the aorta

Atomic absorption spectrometry was used in a quantitative study of zinc, magnesium, and manganese on 71 postmortal human aortas. Samples were obtained from accident victims 35-65 years of age. Fibrous plaques had higher levels of all three elements when compared to normal aortic tissue. The difference was significant for zinc (p less than 0.001) and magnesium (p less than 0.01). The high elemental levels may be both a cause and effect of atherosclerosis or the result of another unknown parameter.     

Magnesium,calcium, copper,and zinc in meals

Meals of 12 diets were prepared from conventional foods with precautions against contamination by metallic elements because of epidemiologic associations between ischemic heart disease and the metabolism of magnesium, calcium, copper, and zinc. Magnesium, calcium, copper, and zinc were measured by atomic absorption spectrometry with satisfactory accuracy and precision. The mean daily amount of copper in the diets was less than the apparent adult requirement. Mean amounts of magnesium and zinc were close to apparent requirements; however, adults consuming amounts less than one standard deviation below these means may be depleting body stores and be at risk of pathology. Magnesium and copper were highly correlated (r=0.849,P=0.0001) in meals. This and other significant correlations probably will prevent the relationships of these elements to ischemic heart disease from being elucidated by epidemiology. Metabolic experiments will be necessary to differentiate among several hypotheses.     

Chromium, Zinc and Magnesium Concentrations in the Pubic Hair of Obese and Overweight Women

The study addressed chromium, zinc and magnesium concentrations in the pubic hair of obese and overweight women. It was carried out on hair collected from 85 women at the age of 16-80 living in the Podkarpackie Voivodeship (southern Poland). The experimental and control groups consisted of 39 and 46 females, respectively. The pubic hair was prepared under a procedure established by the International Atomic Energy Agency, followed by wet digestion in a microwave oven. The concentration of the metals in the pubic hair and reference material was assayed with the flame (Mg, Zn) and flameless (Cr) atomic absorption spectrometry. The pubic hair of overweight and obese women from the experimental group revealed significantly higher chromium and magnesium concentrations and significantly lower concentrations of zinc than in the control group. An increase in BMI brought about an increase in chromium and magnesium concentrations while zinc concentration decreased with increasing BMI. The disturbances in the mineral balance of overweight and obese women were also demonstrated by significantly different ratios of the elements compared with the control group.     

Assessment of some elements in human permanent healthy teeth,their dependence on number of metallic amalgam fillings,and interelements relationships

In this study, 60 human permanent healthy teeth (without filling) were collected postmortem and analyzed using flame atomic absorption spectrometry (FAAS), cold vapor atomic absorption spectrometry (CVAAS), hydride generation atomic absorption spectrometry (HGAAS), and electrothermal atomic absorption spectrometry (ETAAS) for the determination of Ca, Hg, Se, Cu, and Ag. The concentration of these elements was assessed in carious and noncarious teeth, different tooth groups, with age and with number of amalgam fillings. A negative correlation was found between Ca and the number of amalgam fillings, and significant negative correlations were found between Ca and three other metals (Hg, Ag, and Cu) that indicate the possibility of substitutions of Ca by three other metals. Significant positive correlations were found among the number of amalgam fillings and Hg, Ag, Cu and Se showed metal concentration in permanent healthy teeth were affected by the presence of the number of amalgam filling. In addition, significant positive correlations between Hg and Ag, Hg and Cu, and Ag and Cu proved the suspicion that the Hg content in permanent healthy teeth was mainly found because of the influence of amalgam filling, not from other sources. Moreover, the significant positive correlation between Hg−Se and Ag−Se showed the formation of mercuric selenide and silver selenide complexes as part of a natural mechanism of detoxification. Consequently, the permanent healthy teeth would be considered as a bioindicator for the accumulation of long-term exposure of Hg and Ag.     

蛹虫草金属硫蛋白分离纯化及性质研究

研究探讨锌离子胁迫下蛹虫草Cordyceps militaris金属硫蛋白的产生及性质。蛹虫草菌丝体以15g/L Zn2+在10L发酵罐中诱导培养56h后收集,产率为每升发酵液收集12.021g菌丝体（干重）,细胞破碎取上清液通过两次凝胶柱层析,冷冻干燥得到蛹虫草金属硫蛋白纯品。利用Bradford法进行蛋白质含量测定,用银饱和分析法结合原子吸收光谱（AAS）测定MT含量,发酵终点处金属硫蛋白含量为12.876mg/g菌丝体（湿重）。用电喷雾质谱法测得金属硫蛋白的分子量为7 390Da,用Ellman’s方法和火焰原子吸收法分别测得每分子蛋白质含有14个巯基、结合5个Zn原子。氨基酸组成分析结果显示,每分子蛋白质共含57个氨基酸,其中含有13个半胱氨酸,疏水氨基酸占29.8%,且含有组氨酸。以上表明,研究中的蛹虫草金属硫蛋白与哺乳动物金属硫蛋白结构差异较大,但与酵母菌金属硫蛋白结构组成类似。     

Evaluation of total contents of Al,As, Ca,Cd, Fe,K, Mg,Ni, Pb,Zn and their fractions leached to the infusions of different tea samples. A multivariate study

ABSTRACT

Total aluminum, arsenic, calcium, cadmium, iron, lead, potassium, magnesium, nickel and zinc were determined in black tea by electro thermal atomic absorption spectrometry after ultrasonic assisted pseudo-digestion with mixture of acid and oxidant. All the metals were also determined in the tea infusions in order to know the percentage of each element leached into the liquor. A conventional acid digestion on electric hot plate was used to obtain total metals under study for comparative purpose. Analytical results for Al, As, Ca, Cd, Fe, K, Mg, Ni, Pb and Zn obtained by ultrasound assisted pseudodigestion, and conventional wet digestion methods showed a good agreement, thus indicating the possibility of using ultrasonic assisted digestion sample preparation instead of intensive treatments inherent with the acid digestion methods on electric hot plate. The validity and accuracy of both procedures were checked by using certified sample of NIES No. 7 (Tea Leaves). Non significant differences were observed for P>0.05 when comparing the values obtained by both methods (paired t-test).

Principal component analysis (PCA) was applied in order to determine the different amount of metals as main sources of variability in the data sets and to establish the relation between samples (branded and nonbranded tea samples) and micronutrient, trace and toxic metals (variables). Hierarchical cluster analysis (HCA) was used to explore the different branded and nonbranded tea samples grouping according to the essential and toxic metals as additional information to the out put obtained by PCA.     

Lead, copper, zinc, and magnesium content in hair of children and young people with some neurological diseases

The lead, copper, zinc, and magnesium levels of scalp hair taken from 153 children aged 1–15 yr and young people (16–18 yr) with selected neurological disorders (hyperexcibility, loss of consciousness, and epileptiform convulsions of an unknown origin, etc.), were measured using the atomic absorption spectrometry method and then compared with a control group of healthy children (n=108). The research indicated significantly reduced mean levels of magnesium in the hair of children suffering from selected neurological diseases (in children aged 11–15 yr of age, above 30%; up to 5 yr of age, nearly 30%; the differences were statistically significant at p<0.05) and slightly decreased mean levels of copper (differences statistically significant at p<0.05, particularly in the 11 to 15-yr category). Differences in zinc levels in hair were inconsiderable (not statistically significant in any age groups). The lead level in the hair of the above-mentioned group of children was exceeded in relation to the control group (a statistically significant difference at p<0.05 for the total group). A more than twofold decrease in the mean value of the Mg/Pb ratio (and a nearly 30% decrease in the value of the Mg/Zn ratio) in the hair of children suffering from neurological diseases suggests that the high toxicity of lead accompanying, among other things, magnesium deficiencies might be a cause of the observed disorders in children.     

微波消解- 火焰原子吸收光谱法测定蜂胶中金属元素含量

目的:测定一种原产地为加拿大的蜂胶中金属元素的含量,为进一步研究蜂胶营养价值提供数据,同时改进测量方法。方法:用微波消解法处理样品,用硝酸和过氧化氢的混合物作为消解剂进行微波消解,并优化消解条件,然后用火焰原子吸收光谱法测定蜂胶制品中钙、铁、镁、锌、钠、钾、铜的含量。结果:七种元素相对标准偏差为0.85%~2.33%(n=7),回收率在96.5%~104.7%之间。试验结果表明该蜂胶中含有丰富的金属元素,且与河南产蜂胶相比,加拿大产蜂胶中多种金属元素含量远低于河南产蜂胶。结论:使用本文方法测定蜂胶中的金属元素含量,结果准确,方法可靠。为进一步探讨蜂胶制品金属元素与其保健功能的关系提供了有用数据。     

Cardiac copper,magnesium, and zinc in recent and old myocardial infarction

X-ray fluorescence spectrometry and atomic absorption spectrometry were used in a quantitative study of zinc, copper, and magnesium in 71 postmortal human hearts. Samples were obtained from individuals who had demonstrated no previous clinical or subsequent pathological findings of myocardial infarction and from victims of a recent or an old infarction. A significant difference (p<0.001) in the elemental levels was observed between the noninfarct and the recent infarct groups. The noninfarct group had higher cardiac levels of all three elements. However, the difference in elemental concentrations between the noninfarct and the old-infarct groups was not significant. Cardiac levels of zinc (p<0.001) and copper (p<0.01) were significantly greater in the old-infarct group than in the recent-infarct group. Magnesium levels were higher in the recent-and-old-infarct group than in the recent infarct group (p<0.01). It is possible that the elements are redistributed during myocardial infarction, and that uptake of these elements (from the serum pool) by the heart may be important in maintaining myocardial integrity and function.     

The preparation and characterization of chitosan rods modified with Fe by a chelation mechanism

Chitosan composite rods (CS–Fe³⁺) were prepared via an in situ precipitation method. The relationships among the preparation, structures, and properties of the CS–Fe³⁺ composite rods have been investigated. The results of Fourier-transform infrared spectroscopy (FTIR) and core electron X-ray photoelectron spectroscopy (XPS) indicate that the CS and Fe³⁺ are coordinated via a chelation mechanism. The content of Fe³⁺ in the complex was determined by atomic absorption spectrometry (AAS) and elemental analysis (EA), the results of which suggested that the content of Fe³⁺ in the complex can be controlled by the concentration of the ferric salts during coordination. The changes in thermal stability and crystallization properties were measured by thermogravimetric analysis (TGA) and X-ray diffraction (XRD) patterns, respectively. Scanning electron microscopy (SEM) was used to observe the morphological change of the CS–Fe³⁺ complex rod. After coordination with Fe³⁺, the CS rod had a denser, layered structure. However, the layered structure cannot remain intact when the ratios of –NH₂/Fe³⁺ are 100/15 and 100/20. Moreover, its thermal stability decreased, and its bending strength was improved significantly (from 86 MPa to more than 210 MPa), despite the remarkable decrease in the degree of crystallinity.     

Lead,copper, zinc,and magnesium levels in hair of children and young people with some disorders of the osteomuscular articular system

The lead, copper, zinc, and magnesium contents of scalp hair taken from 173 children aged 1–15 yr and young people (16–18 yr) with certain disorders of the osteomuscular articular system (osteomuscular pains of unknown origin, once described as “growing pains”) were measured, using the flame atomic absorption spectrometry method, and then compared with those of 108 normal, healthy children. The research showed increased average levels of lead (a statistically significant p<0.05 in both the overall group of children, and in those over 11 yr old), and zinc (increased in the total group, in a statistically significant way at p<0.10 only in adolescents over 15 yr old) and decreased levels of copper (although not significantly) in the hair of children suffering from “rheumatic” diseases, as compared with controls. The magnesium levels for the total group of ill children were admittedly enhanced, but in the youngest children, the levels were reduced. The values of the Mg/Pb and Mg/Zn ratios were lower (in the youngest children, 70% decrease of the Mg/Pb ratio) and Zn/Cu were higher in the group of children suffering from rheumatic diseases than in the healthy children. The difference of Mg/Pb ratio between the total controls and rheumatic subjects was statistically significant at p<0.05 and the Zn/Cu at p<0.10. The Mg/Zn ratio was not statistically significant.     

湿式消解-石墨炉原子吸收光谱法测定金线莲铅、铜、镉含量

采用湿式消解法对金线莲药材进行处理,石墨炉原子吸收光谱法测定其铅(Pb)、铜(Cu)、镉(Cd)等重金属元素含量。结果表明,Pb、Cu、Cd 三种元素的原子化温度分别是2100、2200和1800 ℃,灰化温度分别是400、800和250 ℃。Pb、Cu、Cd三种元素的检出限分别为0.47、0.50、0.62 μg·L-1,其加标回收率在92.7%～94.0%之间,平均相对标准偏差为1.71%,说明仪器精密度良好,湿式消解-石墨炉原子吸收光谱法能有效测定金线莲药材中Pb、Cu、Cd含量。     

微波消解－火焰原子吸收光谱法测定蜂胶中金属元素含量

目的：测定一种原产地为加拿大的蜂胶中金属元素的含量,为进一步研究蜂胶营养价值提供数据,同时改进测量方法。方法：用微波消解法处理样品,用硝酸和过氧化氢的混合物作为消解剂进行微波消解,并优化消解条件,然后用火焰原子吸收光谱法测定蜂胶制品中钙、铁、镁、锌、钠、钾、铜的含量。结果：七种元素相对标准偏差为O．85％～2．33％（n=7）,回收率在96．5％～104．7％之间。试验结果表明该蜂胶中含有丰富的金属元素,且与河南产蜂胶相比,加拿大产蜂胶中多种金属元素含量远低于河南产蜂胶。结论：使用本文方法测定蜂胶中的金属元素含量,结果准确,方法可靠。为进一步探讨蜂胶制品金属元素与其保健功能的关系提供了有用数据。     

固定化镍离子亲和层析胶的制备及其性能鉴定

以Sepharose 6B为原料,在强碱性条件下用环氧氯丙烷活化,再与亚氨基二乙酸（IDA）的钠盐溶液反应,在活化好的胶颗粒表面接上很多手臂IDA;最后与硫酸镍溶液反应,使手臂IDA与Ni²⁺发生螯合反应,即得到固定化Ni²⁺亲和层析胶（Ni²⁺-IDA）.采用原子吸收法及从大肠杆菌表达产物中纯化重组人B淋巴细胞刺激因子（hBLyS）等方法检测制备胶的理化指标和纯化蛋白质的性能.结果表明用此法制得的亲和胶与相应商品胶的性能完全一致,而成本却不到商品胶的十分之一.     

Effect of cold-restraint stress on the distribution of trace elements in rat tissues

The aim of this study was to assess the effects of cold-restraint stress on blood and the other tissue levels of trace elements. The experiment was performed on male Swiss albino rats. The animals were divided to two groups: control and stressed groups. In the stressed group, the rats were subjected to immobilization for 4 h at 4°C. At the end of the experimental period, blood and tissue samples were collected from all of the animals. The levels of zinc, copper, magnesium, and manganese were measured using flame and graphite furnace atomic absorption spectrometry. In rats subjected to stress, the zinc levels of serum were increased, whereas in the duodenum and brain, zinc was found to decrease when compared to the control. The magnesium content of both the stomach and duodenum were reduced, but the manganese levels of the liver, kidneys, and brain significantly increased because of stress. In conclusion, cold-restraint stress may affect the metabolic process by changing the distributions of zinc, magnesium, and manganese in tissues.