铁转运机制与相关基因的研究进展

铁素营养分子生物学方面的研究有了很大进展。人们利用各种特异突变株和差异筛选已克隆到部分与铁转运有关的基因。本文主要在分子生物学水平概括了酵母铁吸收转运机制和植物缺铁胁迫相关基因及其基因表达的研究进展。     

植物铁吸收、转运和调控的分子机制研究进展

铁是植物正常生命活动所必需的微量矿质元素, 铁离子的吸收、转运和利用是一个复杂的过程, 很多基因参与了这一过程。本文对近10年来发现和分离的参与植物铁吸收、转运及调控的基因研究进展进行了综述。根据最近的研究结果, 提出了植物控制铁吸收的分子调控模式(机理I)。     

植物铁吸收、转运和调控的分子机制研究进展

铁是植物正常生命活动所必需的微量矿质元素,铁离子的吸收、转运和利用是一个复杂的过程,很多基因参与了这一过程。本文对近10年来发现和分离的参与植物铁吸收、转运及调控的基因研究进展进行了综述。根据最近的研究结果,提出了植物控制铁吸收的分子调控模式(机理I)。     

耐辐射奇球菌铁结合蛋白DRA0258的抗氧化功能

【目的】通过对极端环境耐受的耐辐射奇球菌Deinococcus radiodurans R1全基因组进行序列比对分析,获得具有铁储备蛋白Ferritin类似功能基序的未知功能蛋白DRA0258,采用分子生物学技术对该蛋白的功能和性质进行了验证和分析。【方法】首先对DRA0258进行克隆表达和纯化,并经络合物显色法测定蛋白上铁结合含量;通过三段连接敲除法构建dra0258突变株,检测突变株在双氧水协迫下的生存率、总抗氧化活性及过氧化氢酶活性;利用实时定量PCR检测突变株内抗氧化酶类及铁转运相关性调控蛋白的基因转录水平。【结果】经体内外蛋白铁含量检测证实DRA0258具有一定的铁结合能力;双氧水生存率实验表明dra0258的缺失导致细胞的抗氧化能力显著下降;过氧化氢酶活性、总抗氧化活性检测及抗氧化酶类的基因转录水平检测证实dra0258基因的缺失导致细胞内一些抗氧化基因转录水平下调,细胞的抗氧化应激系统受到损伤,并影响了一些铁调控网络蛋白的基因转录水平。【结论】本研究证实DRA0258是一种铁结合蛋白,该编码基因的缺失影响胞内铁转运系统并使细胞抗氧化能力下调。     

乳铁蛋白对铁代谢的影响及其在神经退行性疾病中的应用

乳铁蛋白是一种具有多种生理功能的铁结合性糖蛋白,是铁在机体内代谢及转运关键载体。目前,有关乳铁蛋白对神经退行性疾病的防治作用及应用研究已成为该领域的新热点。本文主要介绍了铁在机体内的代谢;铁转运蛋白-乳铁蛋白转运系统：铁转运主要是由转铁蛋白受体和乳铁蛋白受体介导的,铁转运入脑的途径主要是转铁蛋白-转铁蛋白受体途径,还有乳铁蛋白-乳铁蛋白受体途径及其他途径;铁对脑损伤的作用机制,其中铁参与的氧化应激反应以及铁代谢和铁转运相关基因的突变或缺失可能都是引起脑损伤的原因;最后简述乳铁蛋白在防治神经退行性疾病中最新的进展,乳铁蛋白修饰的纳米粒子可能是目前最有效治疗神经退行性疾病的方法之一。     

鼠伤寒沙门菌感染巨噬细胞铁稳态相关基因mRNA表达谱

用荧光定量PCR法检测鼠RAW264.7巨噬细胞感染与未感染鼠伤寒沙门菌后18种铁穗态相关基因的表达,评估宿主与病原体相互作用中铁稳态效应。研究显示,活的鼠伤寒沙门菌感染巨噬细胞1 h后可以诱导转铁蛋白受体表达,引起细胞内动态铁池相关基因的mRNA水平上长。基因表达分析显示,沙门菌通过诱导铁氧还原酶(Steap3)、铁膜转运蛋白(Dmt1)、铁调节因子Tfr2/Hfe以及铁调节蛋白(Irp1和Irp2)的表达主动吸收铁,而经铁转运蛋白(Fpn1)的铁外流并无明显改变。沙门菌在感染后1h积极地驱动了转铁蛋白介导的铁吸收程序。     

苋菜IRT1基因克隆、序列及表达分析

通过对镉超积累苋菜品种天星米铁转运蛋白基因( IRT1)的克隆、序列及表达分析,旨在为植物修复镉污染土壤奠定基础.依据同源克隆原理,通过RACE技术克隆苋菜IRT1基因及生物信息学方法分析基因序列结构和功能,Northern杂交研究基因表达.苋菜IRT1基因cDNA全长1135 bp,包含完整的阅读框,编码322个氨基酸.苋菜IRT1蛋白与已知铁转运蛋白相似性在53.70％-63.04％,具有铁转运蛋白典型的功能结构特征,即N端含有1个信号肽、氨基酸序列上具有完整的ZIP家族功能结构域( Pfam:Zip)和7个跨膜结构域(TMs).苋菜IRT1蛋白还具有1个COG0428超级家族(转运二价金属离子功能)、2个蛋白激酶C磷酸化位点和2个酪蛋白Ⅱ磷酸化位点.低铁胁迫时苋菜根中IRT1基因表达量增加,加镉处理没有改变IRT1基因表达量.因此,推断苋菜IRT1基因是ZIP家族的一员,具有转运二价金属离子功能,将基因在GenBank中注册,序列号为:GU363501,命名为AmIRT1.     

膜铁转运蛋白1，铁调素的靶分子？

膜铁转运蛋白1是重要的跨膜铁输出分子,主要分布于十二指肠和单核巨噬系统的细胞膜上,参与机体的肠铁吸收和巨噬细胞对铁的再循环等过程。铁调素是调节机体铁代谢平衡的激素,机体通过肝脏分泌的铁调素对铁转运相关蛋白的表达进行调控,从而实现机体自身的铁稳态。最新研究显示,铁调素的靶分子可能是膜铁转运蛋白1,它通过直接的作用引起膜铁转运蛋白1的内化(internalization)、降解,从而调节其在细胞膜上的表达量,进而控制肠铁吸收和巨噬细胞对铁的再循环过程,以维持机体的铁稳态。     

高山离子芥铁转运蛋白基因编码序列的克隆及其抗逆性表达的实时定量分析

铁转运蛋白 (iron transport protein,IRT)是具有跨膜运输离子功能的特殊蛋白质,属于金属离子转运家族的成员．本研究运用RACE方法从高山离子芥（Chorispora bungeana）中克隆得到完整的铁转运蛋白cDNA,命名为CbIRT（基因登录号为EU330924）．该基因全长1 290 bp,包含1个1 035 bp的开放阅读框（ORF）,编码344个氨基酸的蛋白．系统进化树分析显示,该基因与拟南芥AtIRT1和遏蓝菜TcIRT-G的亲缘关系最近,同源性分别达到了87.4%和86.5%,而在氨基酸序列水平与拟南芥AtIRT1的同源性达到了89%,表明克隆得到的CbIRT属于金属离子转运体家族成员．实时荧光定量方法对高山离子芥CbIRT基因在不同温度和铁营养水平条件下的表达情况进行分析表明,CbIRT对零下低温和零上低温的表达水平呈截然不同的反应;正常铁营养状态下,CbIRT是微量表达的,而缺铁及低温处理都可以大幅度地促进该基因的表达,富铁可以抑制该基因的表达．显示了该蛋白在转运Fe离子方面的重要作用．     

施氏假单胞菌A1501铁吸收调节蛋白Fur的表达特性与功能鉴定

铁是细胞生理代谢的重要金属元素,是多种氧化还原酶类、过氧化物酶类的重要组成部分。革兰氏阴性菌中,胞内铁转运、储存和利用主要由铁吸收调节蛋白Fur（ferric uptake regulator）调控。水稻根际联合固氮菌——施氏假单胞菌（Pseudomonas stutzeri）A1501基因组中含有一个fur同源基因,但其具体功能尚不清楚。比较了A1501中fur基因及其编码蛋白的序列特征,并通过实时荧光定量PCR（real-time quantitative,qRT-PCR）和Western blotting杂交方法测定了fur基因和Fur蛋白的表达特性,结果发现fur基因表达水平与环境中铁浓度呈负相关,在铁限制条件下高表达,铁过量条件下表达受抑制。构建了fur基因突变株和功能回补株,表型测定发现fur突变影响了A1501的碳源代谢谱,并导致A1501对过氧化氢胁迫敏感。胞内铁含量测定表明,fur突变株内的铁含量为野生型的1.3倍,进一步qRT-PCR测定表明fur突变影响了铁离子转运系统及过氧化物酶编码基因的表达。研究结果为解析根际微生物胞内铁平衡调节及根际环境适应机制奠定了理论基础。     

人类活动影响下新疆生态环境的一些变化

人类活动引起的新疆生态环境变化主要有以下几方面:1.河流流程缩短,河水矿化度和泥沙含量增加;2.湖泊水位下降,湖面缩小或变干,湖水矿化度升高;3.森林破坏,面积缩小;4.草场的产草量降低,牧草质量下降; 5.土壤次生盐渍化、沼泽化和肥力下降;6.土地沙漠化不断扩大。     

Imaging erythrocytes under physiological conditions by atomic force microscopy

Since its invention in the mid 1980s atomic force microscopy has revolutionised the way in which surfaces can be imaged. Close to atomic resolution has been achieved for some materials and numerous images of molecules on surfaces have been recorded. Atomic force microscopy has also been of benefit to biology where protein molecules on surfaces have been studied and even whole cells have been investigated. Here we report a study of red blood cells which have been imaged in a physiological medium. At high resolution, the underlying cytoskeleton of the blood cell has been resolved and flaws in the cytoskeleton structure may be observed. Comparison of the normal 'doughnut' shaped cells with swollen cells has been undertaken. Differences in both the global properties of the cells and in the local features in cytoskeleton structure have been observed.     

THE ACCUMULATION OF ELECTROLYTES : VII. ORGANIC ELECTROLYTES PART 2

Analyses have been made of the inorganic constituents of the juices expressed from the leaves of Rheum, Rumex, and Oxalis. It has been shown that in all cases there is a large excess of inorganic cations over anions in the sap, the average ratio of cations to anions being 3.8 (Part 1, p. 239). The ash analyses of plant tissues (chiefly leaves) reported in the literature have been examined critically, and it has been shown that the preponderance of inorganic cations over inorganic anions in the ash and in the sap is general. It has been concluded that the excess of inorganic cations is consistent with the view that cations pass into the protoplasm chiefly in the form of hydroxides, and are accumulated either in the form of organic salts (such as the oxalates) or in non-polar linkage. It has been concluded that practically all the potassium and sodium found in plant ash must have been present originally in the form of soluble ionogenic compounds, but that a considerable part of the calcium and magnesium may have been present originally in the form of insoluble salts or as components of non-polar compounds. The methods whereby the cations, particularly potassium, may have been accumulated have been discussed, and it has been concluded that as it does not seem very probable that they enter chiefly as nitrates or bicarbonates we may suppose that they go in to a large extent as hydrates: this is highly probable in the case which has been most carefully investigated (Valonia).     

Photomyoclonic seizures in the baboon, Papio papio.

The inborn seizure response of Papio papio to intermittent light stimulation has been reviewed as a model of human epilepsy. The electrographic and clinical features have been described and useful methodology has been outlined. A diurnal cyclicity in seizure responsiveness has been described with greatest seizure severity at 8 AM in parallel with a rise in urinary output of cortisol. Hormonal influences on the seizure response have been described for ethinyl estradiol, thyroxin, and triiodothyronine. Evidence regarding neurotransmitter involvement has been reviewed. Data regarding use of the animal for anticonvulsant testing in single and chronic doses has been discussed. Particular advantages of the model for study of age-related drug effects and the assessment of the effects of chronically administered anticonvulsant agents on learning and memory have been described.     

Diagnosis of Helicobacter pylori

The different invasive and noninvasive diagnostic tests for Helicobacter pylori have been applied mainly in emerging countries. Molecular methods have been developed, especially a test for detection of H. pylori and its clarithromycin resistance directly from stools. The long-term effects of eradication on histologic lesions have been studied in a meta-analysis and the prognostic value of post-treatment in gastric mucosa-associated lymphoid tissue lymphoma has been assessed. An operating link for gastritis assessment (the OLGA staging) has also been published. Attempts to simplify the urea breath test protocol have been made, and new stool antigen tests have been proposed and compared to those previously available.     

Intermediate filament structure.

In the past year, several new developments concerning the structure of intermediate filament proteins and their assembly into intact intermediate filaments have been made: the coiled-coil structure of a rod domain has been elucidated; the basis of the chain interaction and its role in intermediate filament assembly has been specified; the organization of nearest-neighbour molecules in keratin intermediate filaments has been determined; and the glycine loop structures of the terminal domains of epidermal keratin chains have been defined. In addition, mutations in intermediate filament chains that promote pathology have been reported for the first time.     

Synthesis, resolution and charge-donor properties of six tryptophan analogues.

In order to investigate the special function of tryptophan in peptide hormones, six tryptophan analogues have been synthesized, in which structural resemblance has been grossly retained and potentially essential properties have only partially been varied. The L-enantiomers have been isolated after enzymatic digestion of racemic dipeptide derivatives, and charge-transfer properties of the compounds have been studied.     

Postoperative hypoparathyroidism: risk of complications]

For assessing the risk of adverse complications of surgery the group of 130 patients with post-operational hypoparathyroidism was analysed. Surgical hypoparathyroidism has been diagnosed in 51% of operated on thyroid gland patients. Laryngeal nerves have been damaged in 46.6% of patients. The injury to laryngeal nerves has been irreversible in 2/3 of patients, and reversible in the remaining 1/3. Cataract, nephrolithiasis and vitamin D3 intoxication have been observed in some cases before surgery. Their incidence increased in severe surgical hypoparathyroidism. Osteoporosis of the spine has been diagnosed in 49% of patients including some with vertebral fractures. No correlation between the degree of spine osteoporosis and diagnosis before surgery, number of operations on thyroid gland, and type of therapy has been noted. The symptoms of hypercalcemia have been diagnosed in 5 patients out of which hypercalcemia has been transient in 2 patients, and lasted for 1-5 months in the remaining 3 patients. The results of 7,873 analyses of mineral metabolism have been assessed. Hypocalcemia has been found in 38.4%, hypercalcemia in 1.6%, hypomagnesemia in 25.7%, hyperphosphatemia in 41.5%, decreased alkaline phosphatase serum activity in 28.7%, and hypercalciuria in 22.4% of cases. Surgical hypoparathyroidism is frequently accompanied by surgical hypothyroidism and injury to the recurrent laryngeal nerves.     

Evaluation of phenol and formaldehyde concentrations in air of certain newly built houses on the terrain of Bia?ystok]

Phenol and formaldehyde concentrations have been assayed in the air of 125 apartments in newly constructed houses in Bia?ystok. Xylamide and Solfotox have been used as constmetion materials preservatives in these buildings. Control group consisted of 125 apartments built traditionally. Phenol concentration in the air of the control apartments has not exceeded acceptable values whereas it has been over acceptable values in 80% of the apartments, in which above mentioned preservatives have been used. Formaldehyde concentration in the air of control apartments and 101 apartments of tested group has been within the range of acceptable values. It was much higher in 6 apartments. No apartment exposed to chemicals has been free from formaldehyde.     

Cultivation of the gonococcus in nutrient broths

The dynamics of the multiplication of gonococci and the parameters of their growth have been studied in the process of batch cultivation in liquid culture media with different content of bovine blood serum. The protective and stimulating action of the serum on the growth of gonococci has been shown. The optimization of the process of cultivation has been carried out; as a result, the growth of test strains in a culture medium containing no serum has been achieved. Phasic changes in the ultrastructure of gonococci in the process of their cultivation in liquid media have been followed. 9- to 12-hour cultures of gonococci grown in liquid culture media have been found the most valuable and physiologically active.