Assessment of intestinal absorption of trace metals in humans by means of stable isotopes

This study is aimed to demonstrate the feasibility of stable isotopes for the assessment of reliable data on fractional intestinal absorption of trace metals in healthy humans. Among the various methods available, the double isotope technique, i.e. one isotope given orally together with the test substance to be investigated and another isotope injected intravenously to correct for retention and endogenous excretion of the particular trace metal, provides quantitative figures of intestinal absorption at reasonable expenses with regard to costs for materials and number of samples to be evaluated. The trace metals exemplarily included in this study, i.e. iron, cobalt and molybdenum show diverging relations between absorbed fractions and amounts administered which are indicative for different regulatory mechanisms of their body content. Food ligands influence the fractional absorption significantly so that the uptake from a composite meal cannot be derived from results on uptake from particular foodstuffs. Therefore, validated data on the behaviour of intestinal absorption will significantly contribute to a better understanding of human trace metal metabolism.     

Comparative Investigations on Intestinal Calcium Absorption from Two Therapeutic Preparations in Postmenopausal Women

Abstract

Intestinal calcium absorption from two different therapeutic preparations was compared intraindividually in 12 postmenopausal women. An amount of 800 mg of calcium as lactogluconate/carbonate or citrate was given in random order respectively. Each test dose was labelled with stable ⁴⁴Ca. At the same time a tracer dose of ⁴²Ca was injected intravenously. The amount of calcium absorbed was derived from the ratio of the stable tracers in blood serum and urine 24 hours after administration. Mean bioavailability of the calcium citrate preparation was higher (30%) than from the calcium lactogluconate/carbonate preparation (25%).     

Effect of oxalate test dose size on absolute and percent oxalate absorption

The purpose of this pilot study was to establish the dependence or independence of oxalate absorption on the quantity of the test dose of sodium oxalate over a range of test doses corresponding to physiological dietary oxalate intake values. Gastrointestinal oxalate absorption was measured with the [13C2]oxalate absorption test. Six healthy volunteers were always tested under standardized dietary conditions with 63 mg dietary oxalate and 800 mg dietary calcium per day. The volunteers were tested thrice each with sodium oxalate test doses of 25, 50, 200, and 600 mg. Additionally, 1000 mg sodium oxalate was applied once to three of these volunteers. The oxalate absorption of the six volunteers tested under the standardized conditions with 50 mg sodium [13C2]oxalate was 7.2 +/- 2.62 % (mean +/- SD), similar to the 120 volunteers tested previously: 8.0 +/- 4.4 % (mean +/- SD). The tests with sodium [13C2]oxalate doses in the range 25-1000 mg revealed similar percent oxalate absorption values. In conclusion, in healthy volunteers, the amount of oxalate absorbed in the gastrointestinal tract increased proportionally with the higher test doses of oxalate. However, percent oxalate absorption remained unchanged with test doses in the dose range of physiological dietary oxalate intakes.     

微波消解-火焰原子吸收光谱法测定彝药毒清药中微量元素

建立火焰原子吸收光谱法测定＂毒清药＂中钙、镁、铁、锌、铜、锰元素含量的方法。用浓硝酸微波消解样品,采用校准曲线法测定。结果显示毒清药中含有Ca9.07mg/g,Mg3.56mg/g,Fe2.11mg/g,Zn0.070mg/g,Cu0.022mg/g,Mn0.61mg/g。RSD为3.1%—9.6%,回收率为94%—105%。此方法简单、准确,结果令人满意。     

Determination of Macro- and Microelements in Cow,Goat, and Human Milk Using Inductively Coupled Plasma Optical Emission Spectrometry

The contents of macro- and microelements in cow, goat, and human milk from Croatia were measured and compared for the first time. The highest concentrations of element were measured in milk cow: calcium 1.4 g/kg, sodium 0.6 g/kg, zinc 4.0 mg/kg, strontium 0.4 mg/kg; goat: magnesium 0.2 g/kg, potassium 2.2 g/kg, iron 0.8 mg/kg, manganese 71 µg/kg, selenium 35 µg/kg, molybdenum 20 µg/kg, chromium 72 µg/kg, lithium 14 µg/kg; and human: copper 193 µg/kg. Equal content of molybdenum (20 µg/kg) was determined in cow and goat milk. Significant differences in element levels between the three species were determined. Concentrations of magnesium, manganese, selenium, chromium, and lithium in goat milk were significantly higher than in cow milk. Significantly lower levels of calcium, potassium, sodium, magnesium, zinc, selenium, and strontium were determined in human milk than in cow and goat milk. Chromium content was significantly higher in goat than in human milk. Copper content in human milk was significantly higher than in cow milk. Correlations, mostly moderate and positive, were found between elements in cow and goat milk.     

海洋底栖硅藻细胞中矿物元素含量分析

采用火焰原子吸收分光光度法对八种海洋底栖硅藻细胞中Mg,Fe,K,Ca,Mn,Zn,Cu,Ni,Pb,Cr,Cd共11种矿物元素的含量进行了测定。方法的相对标准偏差<6.85%,相关系数为0.998 9～0.9999,回收率95%～103%。结果表明,所筛选的八种海洋底栖硅藻中含有较丰富的常量元素和微量元素,常量元素Mg,Fe,K,Ca的含量为10-1～102 mg·g-1数量级,微量元素Mn,Zn,Cu,Ni的含量为10-3～10-1 mg·g-1数量级。其含量依次为Mg>Fe>Ca>K>Mn>Zn,Cu和Ni的含量极少,有害重金属元素Pb,Cr和Cd含量极微。Mg, K和Mn含量最高的是半裸舟形藻,分别为(17.224 0±0.030 2)mg·g-1 SD,(1.788 5±0.093 9)mg·g-1 SD和(0.225 3±0.001 1)mg·g-1SD。Fe(4.231 4±0.030 9)mg·g-1 SD), Zn(0.116 7±0.002 9)mg·g-1 SD), Cu(0.022 7±0.000 7)mg·g-1 SD)和Ni(0.014 7±0.000 5)mg·g-1 SD)含量最高的是双尖菱板藻细头变种,而菱形藻细胞中Ca(6.353 7±0.041 2)mg·g-1 SD含量最高。     

The effect of oral administration of calcium and magnesium on intestinal oxalate absorption in humans

Calcium oxalate (CaOx) urolithiasis is the most common urinary stone disease (70-75 % of all stones consist of CaOx in countries with western diet). Oxalate is the most lithogenic substance in CaOx crystallisation in urine. Oxalate is either synthesized within the body or absorbed from food. As oxalate is not metabolized in the human body, it appears unchanged in urine. Conventional analysis methods cannot distinguish between endogenous and exogenous oxalate. Our [13C2]oxalate absorption test enabled measurement of intestinal oxalate absorption and quantification of the influence of Ca- and Mg-supplementation on it. The effects of the oral administration of these supplements were compared in order to obtain valid data for recommendations for CaOx urolithiasis patients. A 10 mmol supplement of both ions decreased the oxalate absorption significantly, calcium being more than twice as effective.     

微波消解-火焰原子吸收光谱法测定川牛膝中的6种微量元素

建立火焰原子吸收光谱法测定凉山牛膝中Ca、Mg、Fe、Zn、Cu、Mn元素含量的方法。用浓硝酸微波消解样品,采用校准曲线法测定。凉山牛膝中含有Ca 7.67mg/g,Mg 1.07mg/g,Fe 0.243mg/g,Zn 0.0425mg/g,Cu 0.00549mg/g,Mn 0.0826mg/g。RSD为1.8%—4.8%,回收率为96%—107%。方法简单、准确,结果令人满意。     

珍珠明目滴眼液中微量钙的共沉淀分离原子吸收光谱分析

采用硝酸锶-碳酸钾共沉淀分离富集珍珠明目滴眼液中的微量钙,用原子吸收分光光度法测定其含量。进样溶液钙浓度在0.0～20.0μg·mL-1范围内与其422.7 nm处的吸光度成良好线性关系,检出限为0.06 μg·mL-1。该法用于珍珠明目滴眼液中钙的测定,具有灵敏、简便、快速、准确、重复性好,平均回收率为97.0%～98.3%,相对标准偏差RSD为0.4%。     

原子吸收光谱法测定中成药中微量元素

利用原子吸收光谱法测定了老年咳喘片、复方半夏片、胃痛宁片、拳参片、参芪降糖胶囊、夏桑菊颗粒和美国洋参含片7种中成药中Ca,Mg,Fe,Zn,K,Na,Mn,Cu,Cr,Co,Sr,Ni,Cd和Pb元素的含量。详细研究了消化液(混酸)种类、混酸中HNO₃和HClO₄比例、消化液体积及消化时间对测定结果的影响。结果表明：所选7种药物中Ca,Mg,Fe,K和Na的含量普遍比较丰富;治疗糖尿病的药物参芪降糖胶囊中Mn的含量较为丰富,而胃痛宁片中有较丰富的Sr,Mn和Cu元素。     

负吸光度法测定牛奶中的钙

研究了钙离子与酸性铬蓝K的反应条件,建立了一种负吸光度法测定钙离子的新方法,钙量在0.0-2.4μg/mL范围内与负吸光度呈线性关系,检出限为2.3×10<'-5>g/L,方法应用于牛奶中钙离子的测定,结果满意.     

原子吸收光谱法测定冬凌草中的矿物元素

用原子吸收光谱法测定冬凌草中影响人体健康的8种矿物元素Cu、Zn、Fe、Mn、Ca、Mg、Se和Pb的含量。样品经硝酸-高氯酸消解后,采用偏振塞曼效应扣除背景吸收,用火焰原子吸收光谱法检测积分吸收测定冬凌草中Cu、Zn、Fe、Mn、Ca和Mg的含量,用石墨炉程序升温原子吸收光谱法检测峰值吸收测定Se和Pb含量。测定结果显示:该方法的精密度RSD为1.22%—5.64%;加标回收率为95.0%—110.5%;8种矿物元素的检出限(P=95%,α=0.5)分别为Cu0.034、Zn0.0028、Fe0.031、Mn0.110、Ca0.367、Mg0.132mg·mL-1,Pb1.40μg.L-1和Se1.86μg.L-1。该方法简便快速、灵敏、准确,适用于中药冬凌草中矿物元素含量的测定。     

吸湿性均匀混合气溶胶粒子等效吸收系数计算分析

以两种典型的吸湿性气溶胶组分(氯化钠和硫酸铵)为例,采用米氏散射程序,计算了粒子的吸收效率因子等光学参量,并分析了吸湿性气溶胶粒子加热的等效吸收系数随时间的变化规律,着重分析了忽略粒子自身吸收对等效吸收系数的影响,常规计算值与等效吸收系数在1μs时相对误差可达到234.7%和255.2%。同时,就不同相对湿度、不同波长对等效吸收系数含时变化规律的影响进行了对比分析,并讨论了采用均匀混合模型计算结果的相对误差,在1μs时实际值与计算值相对误差最大,分别小于3.62%和7.07%。     

Secretion of 13C-labelled oligosaccharides into human milk and infant's urine after an oral [13C]galactose load

Human milk oligosaccharides seem to play an important role in the infant's defense against bacterial and viral infections of the gastrointestinal and the urogenital tract. In this study, we investigated the influence of dietary carbohydrates on the biosynthesis of lactose and oligosaccharides in the human mammary gland and their renal excretion by the human milk-fed infant. For this purpose, a lactating woman was given 27 g galactose (Gal) containing 2 g [13C] Gal (1-13C/99%) immediately after breakfast. In the following 36 h, milk (5-10 ml) was collected before each nursing. Infant's urine was collected over a period of 24 h. 13C-enrichment was measured in total milk, milk fat and protein, in the carbohydrate fraction as well as in urine by isotope ratio mass spectrometry (IRMS). Milk carbohydrates and deproteinized urine samples were fractionated by Sephadex G25 gel filtration and further analyzed by IRMS, high performance thin layer chromatography and and high pH anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD). IRMS revealed that in milk a maximal delta 13CPDB was reached within 8 h after Gal intake which then rapidly declined in the following 8 h. The cumulative 13C-elimination over this first peak was 6.9% of the oral 13C-dose. The highest 13C-enrichment was detectable in the carbohydrate fraction, mainly in lactose and neutral oligosaccharides. Compared to the enrichment of human milk, the delta 13CPDB of infant's urine was delayed. In urine, the highest amount of 13C was found in the Sephadex G25 fractions which mainly contained lactose, fucosyl-lactose, lacto-N-tetraose (LNT), fucosyl-LNT and difucosyl-LNT. For further characterization, individual components were separated by HPAEC-PAD and subsequently analyzed by fast atom bombardment mass spectrometry and IRMS. The data show, that orally applied Gal is incorporated in milk, especially in lactose and neutral oligosaccharides. Obviously, some of these components were absorbed by the infant and then excreted with urine. There, oligosaccharides may serve as analogous receptors for bacterial or viral adhesion molecules, and, hence, may prevent urogenital infections in breastfed infants.     

KOPLS-DA在掺杂牛奶判别中的应用

运用核隐变量正交投影(kernel orthogonal projection to latent structure, KOPLS)方法,建立掺杂牛奶与纯牛奶的判别模型。分别配置含有三聚氰胺牛奶(0.01～3 g·L-1)和尿素牛奶(1～20 g·L-1)样品各40个,采集纯牛奶及掺杂牛奶样品的近红外光谱。选择4 200～4 800 cm-1为建模区间,采用KOPLS分别建立掺杂三聚氰胺、掺杂尿素、两种掺杂牛奶与纯牛奶的判别模型,并利用这些模型对未知样品进行判别。研究结果表明：与偏最小二乘判别(partial least squares discriminant analysis, PLS-DA)和隐变量正交投影判别(orthogonal projections to latent structures discriminant analysis, OPLS-DA)建模方法相比,KOPLS-DA具有更强的掺杂判别能力,对掺杂三聚氰胺、掺杂尿素牛奶和两种掺杂牛奶的判别正确率分别为95%,100%和97.5%。     

Light-Induced Absorption in Bismuth Titanium Oxide Crystals Illuminated with Narrow-Band Light

Results of investigations into the dynamics of light-induced absorption in bismuth titanium oxide crystals doped with calcium (Bi₁₂TiO₂₀:Ca) illuminated with quasimonochromatic light of semiconductor light-emitting diodes at two wavelengths from the set = 870, 660, and 525 nm are presented. Based on an analysis of the experimental data, a model of charge transfer by defect centers describing the observed phenomena is suggested.     

Interaction of electromagnetic waves with a magnetized nonuniform plasma slab

The absorption, reflection, and transmission of electromagnetic waves by a nonuniform plasma slab immersed in an ambient uniform magnetic field of various strengths are studied in this paper. The effects of the plasma parameters and magnetic field strength on the absorbed, reflected, and transmitted power are discussed. The magnetized nonuniform plasma slab is modeled by a series of magnetized uniform plasma subslabs. The calculation results show that the effects of the magnetic field strength and density gradient on the absorbed power, as well as the frequency band of resonant absorption, are significant. A complete analysis utilizing the scattering matrix method is also used to compare the above calculation results which neglect multiple reflections between subslab interfaces. Broadband absorption of electromagnetic waves can be achieved by changing the magnetic field strength and plasma density. More than 90% of the electromagnetic wave power can be absorbed in a magnetized nonuniform plasma slab with width of 12 cm and the absorption bandwidth can range from 1 to 20 GHz with different plasma parameters and external magnetic field strengths.     

Effect of oxalate test dose size on absolute and percent oxalate absorption

The purpose of this pilot study was to establish the dependence or independence of oxalate absorption on the quantity of the test dose of sodium oxalate over a range of test doses corresponding to physiological dietary oxalate intake values. Gastrointestinal oxalate absorption was measured with the [¹³C₂]oxalate absorption test. Six healthy volunteers were always tested under standardized dietary conditions with 63 mg dietary oxalate and 800 mg dietary calcium per day. The volunteers were tested thrice each with sodium oxalate test doses of 25, 50, 200, and 600 mg. Additionally, 1000 mg sodium oxalate was applied once to three of these volunteers. The oxalate absorption of the six volunteers tested under the standardized conditions with 50 mg sodium [¹³C₂]oxalate was 7.2 ± 2.62 % (mean ± SD), similar to the 120 volunteers tested previously: 8.0 ± 4.4 % (mean ± SD). The tests with sodium [¹³C₂]oxalate doses in the range 25–1000 mg revealed similar percent oxalate absorption values. In conclusion, in healthy volunteers, the amount of oxalate absorbed in the gastrointestinal tract increased proportionally with the higher test doses of oxalate. However, percent oxalate absorption remained unchanged with test doses in the dose range of physiological dietary oxalate intakes.     

牛奶水溶液的偏振三维荧光光谱研究

测得由伊利、蒙牛公司生产的纯牛奶、高钙奶、高钙低脂奶的偏振三维荧光光谱,发现在激发偏振片和发射偏振片取向平行时,偏振荧光强度高于取向垂直时的值。通过一个简单的模型估算了各种牛奶样品等效荧光团的激发偶极子和发射偶极子之间的夹角,均小于40°,且高钙低脂奶对应荧光团激发偶极子和发射偶极子之间的夹角略小于纯牛奶和高钙奶。实验还发现,在激发偏振片和发射偏振片取向平行时,高钙低脂奶的偏振荧光强度明显高于纯牛奶和高钙奶,与理论计算相符。     

原子吸收光谱法测定婴幼儿奶粉中铁含量不确定度的评定

建立了原子吸收光谱法测定婴幼儿奶粉中铁含量不确定度评定的数学模型,分析了检测过程中不确定度来源并计算了各不确定度分量,得出合成标准不确定度和扩展不确定度。在婴幼儿奶粉中铁含量的测定中,测量值为8.156mg/100g,其扩展不确定度为0.11mg/100g,k=2。影响铁含量测量结果不确定度的最大因素是校准曲线拟合引入的不确定度。