Trace elemental content of biological materials

The advantages and disadvantages of neutron activation analysis (NAA) and inductively coupled plasma-source mass spectrometry (ICP-MS) for the analysis of biological materials is reviewed. Comparison is made between NAA (instrumental) and ICP-MS (conventional pneumatic solution nebulization and laser ablation) analysis of the biological reference material National Bureau of Standards (NBS) SRM 1577 Bovine Liver. Relatively good agreement is achieved between the results for the 18 elements analyzed by both techniques and those either certified or reported in the literature. Elemental concentrations for Li, Mg, Al, Ca, Cr, Mn, Fe, Cu, Zn, Br, Rb, and Cs are also reported for IAEA Mixed Human Diet (H9), NBS SRM 909 Human Serum, and NBS SRM 1577a Bovine Liver, analyzed by solution nebulization ICP-MS.     

Trends in trace element determinations in blood,serum, and urine of the dutch population,and the role of neutron activation analysis

A critical review on the quality of literature data on trace elements in human blood, serum, and urine of inhabitants in the Netherlands has shown that many of the currently available data have been established 15–20 years ago. Only in a few publications are quality indicators mentioned, which should be considered typical—and minimal —for studies resulting at reference values. The use of neutron activation analysis for determination of trace elements in human body fluids was restricted to a few studies in the 1970s. However, although it is frequently assumed that the sensitivity of NAA might be insufficient, it is demonstrated that modern, large, well-type Ge detectors may serve well for the determination of trace elements in human body fluids via radiochemical NAA, for example.     

The application of preirradiation combustion and neutron activation analysis technique for the determination of iodine in food and environmental reference materials

The pre-irradiation combustion (PC) of samples to liberate iodine, followed by trapping the iodine on charcoal and quantifying the element by neutron activation analysis (NAA), has been used at the National Institute of Standards and Technology for the determination of iodine in biological materials. The applicability of this technique to numerous environmental and dietary matrices is illustrated by analysis of a range of certified reference materials (CRMs) and a powdered grass material that was prepared as an in-house reference material (RM). Because of the combustion step involved, samples with low or no fat content (e.g., cereal products, selected botanical specimens, and nonfat milk powder) and inorganic materials (e.g., coal fly ash and dried sediments) are more suited for analysis by this method. In general, the results for several types of samples obtained by this method agreed with those obtained by a second radiochemical (R) NAA, as well as by a third method using inductively coupled plasma mass spectrometry (ICP-MS). PC-NAA is a useful technique for determining iodine in biological and environmental samples, especially for verification of iodine results obtained from other methods.     

Simultaneous analysis for multiple heavy metals in contaminated biological samples

In the present study, the conditions of analysis by inductively coupled plasma-atomic emission spectrometry (ICP-AES) were investigated. Twenty-six elements (Mg: 25 ppm; Sc: 10 ppm; Ti: 50 ppm; others: 100 ppm) were used as the elements interfering with selected 24 wavelengths. Consequently, the background values in 19 elements were subjected to some influences. However, all of these effects disappeared at low concentrations—less than 1 ppm of interfering elements. Next, the values from the ordinary calibration method were compared with those from the standard addition method using several biological samples. There was a discrepancy in the results obtained from both methods because of the sample, and three patterns were observed. However, no discrepancy was observed in the values for the standard reference materials using both methods. There was no significant difference between the certified values of the standard reference materials and the obtained ones by ICP. Therefore, the analytical wavelengths and the methods in the present study were suggested to be useful for ICP-AES analysis for environmental and/or biological samples.     

应用稀土调控藏红花胚性愈伤组织的生长与分化

为提高藏红花（Crocus sativus）胚性愈伤组织的繁殖系数与出芽率,以建立藏红花离体快繁体系,解决其资源短缺问题,采用两步法,用稀土调控其胚性愈伤组织的生长与分化。结果表明,在添加了0.25mg·L-1NAA、3mg·L-16-BA和400mg·L-1CH的B5固体培养基中,0.04mmol·L-1La3＋促进胚性愈伤组织生长的效果最佳,繁殖系数为12,是不添加稀土处理组的1.48倍;在添加了0.25mg·L-1NAA、3mg·L-16-BA和400mg·L-1CH的1/2B5固体培养基中,0.06mmol·L-1Ce3＋促进胚性愈伤组织分化出芽的效果最佳,出芽率高达84.5%,是不添加稀土处理组的1.81倍,且高于国外报道的出芽率（40%）。初步解决了藏红花胚性愈伤组织生长慢和出芽率低等问题,为建立高效稳定的藏红花离体快繁体系奠定了基础。     

Comparison of SR-excited X-ray fluorescence analysis with neutron activation analysis for hair and fiber

Human scalp hair and some kinds of vegetable and animal fibers were analyzed by means of the SR excited X-ray fluorescence method (SRXFA) and the neutron activation method (NAA). Human hair samples collected from five males and five females were washed by the IAEA method prior to analysis. In the SRXFA analysis, samples were excited by monochromated X-rays. Fluorescence X-rays were measured by an Si(Li) detector. The elements detected in all hair samples were S, Ca, Cu, Fe, Zn, Br, and Sr. The elements K, Ti, Cr, Mn, Ni, Se, Hg, and Pb were also detected in several samples. After SRXFA analysis these same samples were analyzed by the NAA method. Elements such as Cu, Zn, and Br were detected by both methods, and their relative concentrations show a good agreement of variation between individuals. However, Pb was only detected by SRXFA, and Na, Au, and Sb were only detected by NAA. Therefore, these two methods are complementary to each other for trace element analysis.     

Interlaboratory analysis of IRM NSC-21 Compost Vitahum

The preparation of internal reference material, NSC-21 Compost Vitahum, including its stabilization, homogeneity testing, and evaluation of an interlaboratory comparison in which 19 laboratories took part using several analytical methods is described. From the results of the intercomparison, consensus values were derived for the contents of Cd, Cu, Ni, Pb, and Zn, whereas for As, Co, Cr, Fe, Hg and Mn, information values were derived. Bimodal distribution of the As and Cr results was obtained, presumably because of incomplete dissolution of the elements from the matrix if insufficiently aggressive decomposition procedures were employed. Some problems encountered were elucidated by application of neutron activation analysis (NAA) in its nondestructive and destructive (radiochemical) modes.     

Camouflage that is spot on! Optimization of spot size in prey-background matching

Camouflage is a key predation prevention mechanism. The most intuitive camouflage strategy is background matching, where a prey resembles the colour and pattern of its background. Spots (e.g. geometric ‘elements’ that constitute a pattern) are a common feature on the body of prey, but the effect of their size in relation to elements in the background is rarely examined in camouflage studies. Here, we test the survivorship of computer generated prey possessing patterns of elements grouped into eight size classes on backgrounds composed of elements of the same eight size classes. All 64 possible combinations were presented to human volunteers (n = 10) acting as ‘predators’ in a computer simulation. As hypothesised, prey survivorship was high when the prey-background element size difference was low. We found significant asymmetry, however, in survivorship pattern: prey morphs with elements larger than those of the backgrounds were harder to detect than morphs with elements smaller than those of the backgrounds. When testing for potential trade-offs we determined that, in a habitat consisting of an equal proportion of two backgrounds with a large element size difference between them, net survivorship of specialist prey morphs (same element size as one of the backgrounds) was similar to that of generalist morphs (intermediate element size). When the two backgrounds were less distinctive, i.e. reduced element size difference between the backgrounds, generalist prey morphs achieved significantly better net survivorship than specialists.     

Determinations of subnanomole elemental levels by NAA and their possible impact on human health related issues

Neutron activation analysis (NAA) is an appropriate tool for the determination of trace elements in biological systems. The virtually blank-free NAA procedures fittingly complement precautions employed in sampling and sample preparation of biological matrices. Results from instrumental NAA procedures used to establish baseline values and time trends for elements in human tissues demonstrate the advantages as well as the limits of these procedures for nanomole and, in a considerable number of instances, subnanomole elemental levels. In addition, subnanomole mass fractions have been determined with extremely low limits of detection by employing NAA with radiochemical separations isolating very low levels of radioactivity from the matrix background. The elements reviewed in this article include Cr, Se, Pt, and others that have been determined by NAA at subnanomole levels in human tissues and body fluids and in biological macromolecules.     

芨芨草愈伤组织器官发生及植株再生

芨芨草(Achnatherum splendens (Trin.) Nevski)种子消毒并在MS培养基上萌发获得无菌苗, 以幼苗的叶鞘和胚轴为外植体诱导愈伤组织, 经继代后进一步诱导不定芽及生根。研究结果表明, 诱导愈伤组织最适合的培养基为B5+1.5 mg.L-12,4-D+0.5 mg.L-1 NAA; 诱导芽分化较适合的培养基为B5+0.5 mg.L-1 6-BA +0.2 mg.L-1 NAA; 1/4 B5+1.0 mg.L-1 NAA+0.2 mg.L-1 IBA +1.0 g.L-1活性炭培养基则有利于芨芨草试管苗的生根。本实验建立了完整的芨芨草植株再生体系, 移栽成活率高。     

Determination of trace elements in normal and diabetic whole blood by neutron activation analysis

Biological Trace Element Research - The concentration of 10 trace elements in samples of normal and diabetic whole blood were investigated by neutron activation analysis (NAA). Instrumental NAA...     

应用稀土调控藏红花胚性愈伤组织的生长与分化

为提高藏红花(Crocus sativus)胚性愈伤组织的繁殖系数与出芽率, 以建立藏红花离体快繁体系, 解决其资源短缺问题, 采用两步法, 用稀土调控其胚性愈伤组织的生长与分化。结果表明, 在添加了0.25 mg·L^–1 NAA、3 mg·L^–1 6-BA和400 mg·L^–1 CH的B₅固体培养基中, 0.04 mmol·L^–1 La³⁺促进胚性愈伤组织生长的效果最佳, 繁殖系数为12, 是不添加稀土处理组的1.48倍; 在添加了0.25 mg·L^–1 NAA、3 mg·L^–1 6-BA和400 mg·L^–1 CH的1/2 B₅固体培养基中, 0.06 mmol·L^–1 Ce³⁺促进胚性愈伤组织分化出芽的效果最佳, 出芽率高达84.5%, 是不添加稀土处理组的1.81倍, 且高于国外报道的出芽率(40%)。初步解决了藏红花胚性愈伤组织生长慢和出芽率低等问题, 为建立高效稳定的藏红花离体快繁体系奠定了基础。     

Intraneuronal N-acetylaspartate supplies acetyl groups for myelin lipid synthesis: evidence for myelin-associated aspartoacylase

Despite its growing use as a radiological indicator of neuronal viability, the biological function of N-acetylaspartate (NAA) has remained elusive. This is due in part to its unusual metabolic compartmentalization wherein the synthetic enzyme occurs in neuronal mitochondria whereas the principal metabolizing enzyme, N-acetyl-L-aspartate amidohydrolase (aspartoacylase), is located primarily in white matter elements. This study demonstrates that within white matter, aspartoacylase is an integral component of the myelin sheath where it is ideally situated to produce acetyl groups for synthesis of myelin lipids. That it functions in this manner is suggested by the fact that myelin lipids of the rat optic system are well labeled following intraocular injection of [14C-acetyl]NAA. This is attributed to uptake of radiolabeled NAA by retinal ganglion cells followed by axonal transport and transaxonal transfer of NAA into myelin, a membrane previously shown to contain many lipid synthesizing enzymes. This study identifies a group of myelin lipids that are so labeled by neuronal [14C]NAA, and demonstrates a different labeling pattern from that produced by neuronal [14C]acetate. High performance liquid chromatographic analysis of the deproteinated soluble materials from the optic system following intraocular injection of [14C]NAA revealed only the latter substance and no radiolabeled acetate, suggesting little or no hydrolysis of NAA within mature neurons of the optic system. These results suggest a rationale for the unusual compartmentalization of NAA metabolism and point to NAA as a neuronal constituent that is essential for the formation and/or maintenance of myelin. The relevance of these findings to Canavan disease is discussed.     

Instrumental neutron activation analysis of rib bone samples and of bone reference materials

The instrumental neutron activation analysis method was used for the determination of trace elements in rib bone samples taken from autopsies of accident victims. The elements Br, Ca, Cl, Cr, Fe, Mg, Mn, Na, P, Sr, Rb, and Zn were determined in cortical tissues by using short and long irradiations with thermal neutron flux of the IEA-R1m nuclear reactor. The reference materials NIST SRM 1400 Bone Ash and NIST SRM 1486 Bone Meal were also analyzed in order to evaluate the precision and the accuracy of the results. It was verified that lyophilization is the most convenient process for drying bone samples because it does not cause any element losses. Comparisons were made between the results obtained for rib samples and the literature values as well as between the results obtained for different ribs from a single individual and for bones from different individuals.     

Comparison of the relative and k0 methods for the standardization of NAA with stable low-flux reactors

Thek ₀ standardization method was Actapted for NAA with stable low-flux reactors where flux monitors are not needed. The modifiedk ₀ method offers the convenience of the use of libraries of sensitivity constants. It was compared to the relative method for 52 elements using a SLOWPOKE reactor and 6 counting geometries. The sensitivity constants determined fromk ₀ values were found to be as accurate or more accurate than those measured with standards. NAA with this modifiedk ₀ method should be accurate to 3% for light elements and 5% for heavy elements.     

IAEA internet database of natural matrix reference materials

The International Atomic Energy Agency maintains a database on internationally available certified reference materials of natural origin. The database was updated in 1998 and prepared for an Internet implementation. A user-friendly structure was created, providing two main pathways for browsing, either according to the matrix classification or the producer’s name. The database presently contains over 20,000 values for 480 measurands and 1085 reference materials from 43 different producers. Most of the materials entered contain values for trace and minor elements (66%).     

Considerations in the determination of boron at low concentrations

Experimental evidence now supports the nutritional essentiality of boron (B) in some biological systems, and accordingly, the need for reliable analytical B data is increasing. However, the accurate determination of B in biological materials is a formidable challenge at low concentrations (<1 mg B/kg). Recent studies still show significant analytical discrepancies in the analysis of animal tissues and fluids, despite the development of instrumental techniques such as TIMS, ICP-MS, ICP-ES, ICAP, SIMS, NA-MS, PGAA, NRA, and so forth, which have demonstrated detection limits approaching or exceeding (μgB/kg concentrations. Since boric acid is both volatile and ubiquitous in nature, the chemical and physical pathways for B contamination and its loss are manifold, especially during sample preparation. An added obstacle is the inadequacy of biological reference materials certified for B below mg B/kg. With an emphasis toward sample preparation and ICP-MS analysis, examples are provided in this article to help the analyst avoid common problems associated with the analysis of B from biological sources. Topics that are discussed include contamination from Teflon vessels during microwave digestion, losses owing to freeze-drying, B isotopic variations, standards preparation, reagent backgrounds, and instrumental interferences.     

Regulation of N-acetylaspartate and N-acetylaspartylglutamate biosynthesis by protein kinase activators

The neuronal dipeptide N-acetylaspartylglutamate (NAAG) is thought to be synthesized enzymatically from N-acetylaspartate (NAA) and glutamate. We used radiolabeled precursors to examine NAA and NAAG biosynthesis in SH-SY5Y human neuroblastoma cells stimulated with activators of protein kinase A (dbcAMP; N6,2'-O-dibutyryl cAMP) and protein kinase C (PMA; phorbol-12-myristate-13-acetate). Differentiation over the course of several days with dbcAMP resulted in increased endogenous NAA levels and NAAG synthesis from l-[(3)H]glutamine, whereas PMA-induced differentiation reduced both. Exogenously applied NAA caused dose dependent increases in intracellular NAA levels, and NAAG biosynthesis from l-[(3)H]glutamine, suggesting precursor-product and mass-action relationships between NAA and NAAG. Incorporation of l-[(3)H]aspartate into NAA and NAAG occurred sequentially, appearing in NAA by 1 h, but not in NAAG until between 6 and 24 h. Synthesis of NAAG from l-[(3)H]aspartate was increased by dbcAMP and decreased by PMA at 24 h. The effects of PMA on l-[(3)H]aspartate incorporation into NAA were temporally biphasic. Using short incubation times (1 and 6 h), PMA increased l-[(3)H]aspartate incorporation into NAA, but with longer incubation (24 h), incorporation was significantly reduced. These results suggest that, while the neuronal production of NAA and NAAG are biochemically related, significant differences exist in the regulatory mechanisms controlling their biosynthesis.     

N-acetylaspartate in the vertebrate brain: metabolism and function

N-Acetyl-l-aspartate (NAA) is an amino acid that is present in the vertebrate brain. Its concentration is one of the highest of all free amino acids and, although NAA is synthesized and stored primarily in neurons, it cannot be hydrolyzed in these cells. Furthermore, neuronal NAA is dynamic and turns over more than once each day by virtue of its continuous efflux, in a regulated intercompartmental cycling via extracellular fluids, between neurons and a second compartment in oligodendrocytes. The metabolism of NAA, between its anabolic compartment in neurons and its catabolic compartment in oligodendrocytes, and its possible physiological role in the brain has been the subject of much speculation. There are two human inborn errors in metabolism of NAA. One is Canavan disease (CD), in which there is a buildup of NAA (hyperacetylaspartia) and associated spongiform leukodystrophy, caused by a lack of aspartoacylase activity. The other is a singular human case of lack of NAA (hypoacetylaspartia), where the enzyme that synthesizes NAA is apparently absent. There are two animal models currently available for studies of CD. One is a rat with a natural deletion of the catabolic enzyme, and the other a gene knockout mouse. In addition to the presence of NAA in neurons, its prominence in ¹H nuclear magnetic resonance spectroscopic studies has led to its wide use in diagnostic human medicine as both an indicator of brain pathology and of disease progression in a variety of CNS diseases. In this review, various hypotheses regarding the metabolism of NAA and its possible role in the CNS are evaluated. Based on this analysis, it is concluded that although NAA may have several functions in the CNS, an important role of the NAA intercompartmental system is osmoregulatory, and in this role it may be the primary mechanism for the removal of intracellular water, against a water gradient, from myelinated neurons.     

南极菲尔德斯半岛水生植物的生物地球化学特征研究

利用中子活化分析技术,得到南极西湖沉积岩芯中水生植物（镰刀藓）的22种化学元素含量,发现南极水生植物的地球化学元素含量范围变化较大,而且在沉积层次上,各个元素的变异系数也较大,水生植物吸收和累积元素的特征为：稀土元素,U,As极容易为植物吸收同化,Ca,Co,Sc为水生植物容易吸收的元素,Th,Hf,Na为水生植物难以同化的元素。同时,研究发现水生植物的直接营养物源为湖水中的可溶性离子;对水生植物的22种化学元素进行聚类分析,发现稀土元素,Ca,Zn,U之间,As,Fe,Co之间共生关系密切,对水生植物具有相似的生理作用。