溴的生物必需性(二)

根据微量元素必需性的经典定义,从溴的生态地球化学、溴的生物学功能及溴的人体健康效应方面论述了溴是生命必需微量元素的16项理由.分3期刊出.本期发表第二部分.     

溴的生物必需性(上)

根据微量元素必需性的经典定义,从溴的生态地球化学、溴的生物学功能及溴的人体健康效应方面论述了溴是生命必需微量元素的16项理由.分3期刊出.本期发表第一部分.     

必需微量元素与人体健康

人的躯体与各内脏都是由多种化学元素组成的，人体现已检出81种元素，其中有14种是人体必需微量元素。微量元素与人体健康密切相关。本文阐述了必需微量元素在人体内的生理功能，同时简述了必需微量元素的来源、微量元素间的相互作用以及必需微量元素缺乏或过量对人体产生的影响。     

微量元素与中草药

中草药在我国流传应用已有几千年的历史,为中华民族的生存发展与繁衍做出巨大的贡献,人体14种必需微量元素在中草药中都可以找到。必需微量元素不同种类的中草药对必需微量元素的富集也不同,在矿物药中的必需微量元素就更为丰富,随着近代医学的飞速发展及中草药药理学研究的不断深入,人们认识到必需微量元素对人体的正常发育和生命活动是十分重要的,对疾病的治疗、预防也起着十分重要的作用。随着无机化合物的广泛研究和元素医学的兴起,中草药必需微量元素的研究逐渐成为新的课题。     

必需微量元素的发现简史及锗的必需性问题

概述了必需微量元素的发现简史和锗在生物微量元素周期表中的特殊地位，列出了锗可能也是必需微量元素的某些证据。     

微量元素与小儿厌食

人体必需微量元素的不足或缺乏,主要是缺乏时即会引起机体生物功能及生化代谢的紊乱或异常,尤其是小儿。小儿由于生长发育快,对各种必需微量元素需求量相对增加,因而特别容易引起必需微量元素和宏量元素的不足或缺乏。     

浅论必需微量元素过量时在人体中的毒性

除简要介绍了必需微量元素作用外，还着重讨论了必需微量元素过量时，对人体的毒性问题。     

必需微量元素与皮肤病

必需微量元素是人体必不可少的微量元素,在人体防治各类疾病中占有重要地位,不足或缺乏都可能引起身体不适或疾病,皮肤的疾患与必需微量元素也同样有着密切的联系。     

人体微量元素平衡关键在于饮食的平衡

人体所需的微量元素,特别是必需微量元素,是不能在体内合成的,必需通过日常生活的饮食给予提供平衡。也就是说,人体的饮食平衡不了,体内的必需微量元素就绝对平衡不了,人体微量元素关键在于饮食的平衡。日本营养专家提出正常人每日要吃40种以上食品,否则难免身体免患病,     

卷心菜与微量元素

蔬菜是人们日常生活中必不可少的食物,是人体必需微量元素和宏量元素的主要来源,人体中必需微量元素和宏量元素的多与少,会直接引起人体生理机能的亢进或衰退,必需微量元素和宏量元素与人体健康是密切相关和必不可少的。社会的发展,人民的进步,随着人们对日常生活中食品营养及安全的日益重视,对蔬菜中微量元素特别是必需微量元素和宏量元素及有害元素的含量,以及对所种植蔬菜的土壤中是否存在有害元素污染的了解是非常必要和十分重要的。     

Certification of a second-generation biological reference material (freeze-dried human serum) for trace element determinations

The certification of a second-generation biological reference material (freeze-dried human serum) for trace element determinations is described. The material was prepared under rigorously controlled conditions to avoid extraneous additions. Analytical data were obtained by the authors as well as by numerous other intra- and extra-mural investigators, solicited on the basis of established experience in determining selected elements. For 14 trace elements (aluminium, chromium, manganese, iron, cobalt, copper, zinc, arsenic, selenium, bromine, rubidium, molybdenum, cadmium and caesium) certified values (in ng g^?1 or μg g^?1 dry weight) are listed; for an additional element (nickel) a best estimate (in ng g^? dry weight) is added. Trace element concentrations in the material, which is available to the scientific community, closely approximate those in normal, lyophilized blood plasma or serum samples. The material thus provides the means to check the accuracy and precision of analytical procedures for quantifying low-level trace elements in the best possible conditions and to detect errors that can easily be overlooked when reference materials with higher levels of trace elements are used. In addition, and in contrast to already existing biological reference materials with high levels of trace elements, it offers the possibility of identifying unsuspected errors at the sample preparation stage.     

Determination of trace element impurities in aspirin tablets by neutron activation analysis

Twenty five trace and minor elements (aluminium, arsenic, barium, bromine, cerium, chlorine, cobalt, chromium, cesium, europium, iron, hafnium, potassium, magnesium, manganese, sodium, rubidium, antimony, scandium, selenium, strontium, thorium, titanium, vanadium and zinc) in five different Egyptian aspirin brands (Aspo, Askin, Aspocid, Aspeol and Rivo) have been determined by instrumental neutron activation analysis. It has been concluded that the concentration of arsenic, barium, bromine, cobalt, chromium, iron (except in Aspocid), magnesium, manganese, rubidium, selenium, strontium and zinc in the Egyptian brands is below or within the concentration range reported for these elements in 16 American aspirin and aspirin-like brands.     

Marine gradients of halogens in moss studies by epithermal neutron activation analysis

INAA is known to be a powerful technique for the simultaneous determination of chlorine, bromine and iodine. In this paper INAA using epithermal neutrons is shown to be particularly useful to elucidate marine gradients of these elements. Examples are from a transect study in northern Norway where samples of the feather moss Hylocomium splendens were collected at distances of 0-300 km from the coastline. All three elements decrease exponentially as a function of distance from the ocean in the moss samples, strongly indicating that the atmospheric supply from the marine environment is the predominant source of these elements to the terrestrial ecosystem. It is suggested that environmental studies of halogens in general and iodine in particular is a promising future area of application for INAA, when employing epithermal neutrons. This revised version was published online in July 2006 with corrections to the Cover Date.     

Evaluation of membrane filters for instrumental neutron activation analysis of airborne particulates

Four types of membrane filter have been studied with respect to trace element contamination and resistance to damage during irradiation with neutrons. Filters consisting of a teflon membrane and a polyolefin ring were low in all trace elements except zinc but failed mechanically during irradiation. Teflon filters backed with polyethylene or polypropylene were low in contamination and possessed excellent resistance to irradiation damage. Polycarbonate filters proved high in bromine and copper and became brittle during irradiation.     

Comparative study of activation analyses for the determination of trace halogens in geological and cosmochemical samples.

Halogens (fluorine, chlorine, bromine and iodine) were determined by activation analyses (neutron activation analysis (NAA), photon activation analysis (PAA) and prompt gamma-ray analysis (PGA)) for geological and cosmochemical solid samples. We studied how each analytical method was for the determination of trace amounts of halogens in rock samples. Radiochemical NAA (RNAA) showed the highest analytical reliability for three halogens (chlorine, bromine and iodine), whereas a set of four halogens (fluorine, chlorine, bromine and iodine) could be determined in principle by radiochemical PAA (RPAA) from a single specimen. Although it is a non-destructive method, PGA showed an analytical sensitivity for chlorine comparable to those of RNAA and RPAA.     

From a rock to a hard place: Journeys of a radiochemist through inner and outer space

A brief chronicle is presented of one radiochemist's meanders through the fields of meteoritics, lunar studies, and geochemistry to current studies of possible relationships of trace element imbalances to diseases affecting the brain and spinal cord. This range of studies is used to underscore the broad applications of radiochemistry and the need to maintain educational programs and research in radiochemistry. Our recent studies of tissues from subjects with Alzheimer's disease (AD) and amyotrophic lateral sclerosis (ALS), have shown that imbalances exist for concentrations of many trace elements, compared to corresponding concentrations in control subjects. Among the elements most frequently found imbalanced are aluminum, bromine, cadmium, copper, iron, mercury, rubidium, and zinc. Several of these elements may be involved in processes leading to free-radical-induced oxidative damage in Alzheimer's disease. Our multi-technique analytical approach to these studies is briefly reviewed.     

Determination of arsenic,chromium, mercury,selenium and zinc in tropical marine fish by neutron activation

Determination of arsenic, chromium, mercury, selenium and zinc in several commonly consumed tropical marine fishes have been carried out by neutron activation followed by radiochemical separation to remove the interfering activities of sodium, potassium, bromine, and phosphorus, etc., in order to establish the baseline data and to measure the levels of contamination, if any. The results of this study positively indicate that the marine fishes of Bangladesh have concentrations much below the permissible levels for these toxic elements. A radiochemical scheme for the separation of seven trace elements in biological material is also presented in this paper.     

Minor and trace element contents in pituitary gland of “normal” humans: an evaluation of analytical data

In the study of trace elements in the different human brain areas, a critical evaluation of the values available in the literature is of great importance in attempting to establish reliable baseline levels, i.e., Reference Values (RVs) for toxicological assessment studies.This paper reviews the published values of minor and trace elements in the pituitary gland (hypophysis) of “normal” humans.Eighteen published papers are taken into account, 15 of which refer to the entire gland, whereas in three of them, only the adenohypophysis is considered.It turns out that essential elements such as Cu, Fe, Se and Zn were more frequently determined, whereas As, Br, Ca, Co, Cr, Cs, K, Mg, Mn, Ni and Rb were seldom investigated.Mercury was determined by several authors because of the concern caused by Hg release from dental amalgam fillings.Most values were obtained by Neutron Activation Analysis (NAA), which appears to have played a pioneer role in this field.Literature data on trace element levels in pituitary gland are at present insufficient to establish RVs; rather, they can be considered only as indicative values.Future investigations based on large populations of control subjects, with standardization of the preanalytical factors and the use of fit-for-purpose Standard or Certified Reference Materials (SRMs, CRMs) should therefore be envisaged.