端粒长度及变化规律

端粒是位于染色体末段的一种特殊结构,具有维持染色体稳定的功能。不同的细胞,同一细胞的不同染色体具有不同的端粒长度;端粒长度是由基因控制的,并受到各种外界因素的影响;端粒长度随细胞的增殖与分化而缩短或者延长,细胞内在的端粒长度调控机制控制着端粒长度在一定的范围内变化。本文还分析了在端粒长度研究方面存在的问题。     

亚硒酸钠对肝细胞L-02端粒酶活性和端粒长度的作用

通过研究硒对端粒酶活性和端粒长度的作用 ,探讨硒抗衰老的生物学机制。实验以人肝细胞株L 0 2为研究对象 ,分别补充 0 .5和 2 .5 μmol L亚硒酸钠 ,采用端粒重复序列扩增 焦磷酸根酶联发光法、逆转录聚合酶链式反应法及流式荧光原位杂交法 ,分别检测细胞的端粒酶活性、人端粒酶逆转录酶催化亚基基因 (hTERT)的表达及端粒长度的变化。结果表明 :常规培养的肝细胞株L 0 2的端粒酶活性和hTERT基因表达水平均较低。补充 0 .5和2 .5 μmol L亚硒酸钠三周后细胞生长状况良好、端粒酶活性和hTERT基因表达水平显著性增高 ,且呈一定的剂量 效应关系。细胞补充亚硒酸钠四周后端粒长度显著增长。说明营养浓度的亚硒酸钠可通过提高端粒酶活性和增长端粒长度来减缓L 0 2肝细胞衰老、延长细胞寿命。     

端粒酶(Telomerase)PCR ELISA——用于检测端粒酶活性的快速方法

宝灵曼公司最近推出了一种端粒酶PCR ELISA,它能对培养细胞或其他生物样品的细胞提取物中的端粒酶活性作高度灵敏的定性检测。 端粒是真核细胞染色体末端的特殊DNA-蛋白质结构,端粒DNA的特点是含有大量串连重复并富含G的重复序列,这些序列在进化中是高度保守的。端粒被认为可以阻止基因组DNA被降解或发生有害的重组,如:末端融合、重排、染色体易位和染色体缺失。由于DNA聚合酶不能复制线性DNA的最末端,所以在普通的体细胞中,端粒的末端会随周期性的复制被逐渐的缩短;这种现象在体内、体外均已被证实,并看来与高等真核生物中正常体细胞的增生受到限制相关,亦似乎在细胞衰老的过程中扮演一定的角色(“mitotic clock”;参看Greider and Blackburn,     

端锚聚合酶(Tankyrase)和端粒

端粒是真核细胞染色体末端的一个特殊结构 ,由一段具有特定重复序列的ＤＮＡ和端粒结合蛋白组成 ,是维持染色体结构稳定的重要因素。端粒ＤＮＡ的复制不是由ＤＮＡ聚合酶完成的 ,而是由端粒酶 (ｔｅｌｏｍｅｒａｓｅ)催化合成后添加到染色体的末端。正常细胞随着细胞分裂活动的进行 ,端粒ＤＮＡ逐渐缩短 ,当缩短到一定程度时 ,染色体结构被破坏 ,细胞进入衰老期并以死亡而告终。但当细胞发生癌变时 ,由于端粒酶的重新激活 ,这种端粒ＤＮＡ随分裂活动发生渐进性缩短的趋势受到阻遏 ,使正常细胞转化成具有无限分裂能力的永生化恶性细胞。研究…     

HeLa细胞端粒酶最适反应条件及活性重建

端粒是真核细胞染色体末端的重复ＤＮＡ序列 ,其生物学功能是防止染色体ＤＮＡ降解、末端融合、非正常重组和染色体的缺失[1] .由于存在“末端复制问题” ,随着老化人体细胞端粒重复序列长度不断缩短 ,但在生殖细胞中由于端粒酶的存在 ,端粒序列并不缩短 .端粒酶是由蛋白质和ＲＮＡ构成的核蛋白 ,是依赖ＲＮＡ的ＤＮＡ聚合酶 ,在ＤＮＡ3’端合成端粒重复序列[2 ] .研究表明 ,在 85 %～ 95 %的人肿瘤细胞中可以检测到端粒酶的活性[3 ,4 ] ,而在正常体细胞中除生殖细胞和造血干细胞等极少数细胞中存在端粒酶活性外 ,均检测不到端粒酶活性 ,这…     

端粒位置效应与人类衰老

端粒随细胞分裂进行性缩短不但防止了人类肿瘤的发展,而且与人类的衰老密切相关。另外,端粒中存在一种特殊的现象：端粒位置效应,它首先在酵母中发现,表现为靠近端粒序列附近的基因表达因端粒的位置效应而沉默。在人类细胞中也存在端粒位置效应,并且有多种因子参与此效应,它可能对细胞生长停止、肿瘤以及衰老发生时等许多随端粒缩短密切相关基因的程序性表达产生重要作用。     

端粒DNA与细胞的衰老,死亡

端粒ＤＮＡ与细胞的衰老、死亡白丽荣（河北衡水师专生物系,０５３０００）端粒ＤＮＡ是真核生物染色体的天然末端,它的生物学功能是保持染色体稳定。近年来研究发现,端粒ＤＮＡ决定了细胞寿命,并与细胞的自然凋亡及癌化有关。端粒（Ｔｅｌｏｍｅｒｅ）是指真核细胞线...     

端粒植入胃癌7901细胞对细胞生长、端粒和端粒酶的影响

研究外源端粒片段植入胃癌7901细胞后对细胞生长、端粒长度和端粒酶活性的影响.采用lipofectTM2000介导的转染方式,将含有端粒片段质粒pSXneo-1.6-T2AG3转染胃癌细胞SGC7901,PCR在基因水平上鉴定外源性端粒片段的植入后,采用TRAP法检测转染细胞端粒酶活性变化,TRF法检测转染细胞端粒长度变化,MTT法检测细胞生长曲线,RT-PCR测定转染细胞hTERT表达变化.染色体核型分析细胞染色体变化.结果显示端粒片段成功导入SGC7901细胞后获得稳定的细胞株,端粒片段植入后细胞生长变慢,端粒长度延长不明显,端粒酶活性明显降低,hTERT mRNA表达水平下降,核型分析显示转染前后细胞染色体数目无明显变化.实验成功将携带了1600 bp端粒TTAGGG重复序列的真核表达载体pSX-T2AG3-neo稳定转染至人胃癌7901细胞中,端粒植入降低细胞端粒酶的活性和下调端粒酶活性亚单位hTERT的表达,但对端粒长度无明显影响.     

端粒-端粒酶系统与糖尿病和胰岛β细胞

端粒和端粒酶共同构成端粒-端粒酶系统,参与细胞衰老、增殖和凋亡的调控,在多种增龄性疾病中发挥重要作用。研究表明,端粒-端粒酶系统异常与糖尿病和胰岛β细胞功能异常有关,改变端粒酶的活性有希望作为糖尿病细胞治疗的措施之一。本文就端粒-端粒酶系统在糖尿病胰岛β细胞中的研究进展做一综述。     

The potential mechanism for the different expressions of gelatinases induced by all-trans retinoic acid in different cells

Gelatinases include matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9). The increased expressions of gelatinases are implicated in the pathogenesis of cell injury and cell death. All-trans retinoic acid (ATRA) is an import biological agent which can regulate the expressions of gelatinases and take part in cell injury and cell death. ATRA exerts its biological effect by the high-affinity binding to retinoic acid receptors (RARs). The RARs consist of three isoforms: RAR-α, RAR-β and RAR-γ. However, it is interesting that the effect of ATRA on the expressions of gelatinases is different in different cells. There is no report to explore the possible mechanism for it at present. In this context, we review the published reports and draw a hypothesis that: (i) The distributions of RARs isoforms are different in different cells; (ii) ATRA activates the different RARs isoforms in different cells; (iii) The roles of different RARs isoforms for regulating the expression of MMP-2 or MMP-9 are different in different cells. So, ATRA takes a different function on the expressions of MMP-2 and MMP-9 in different cells. Once the potential strategy can be successfully confirmed, it would be prone to comprehend why the ATRA regulates the different expressions of gelatinases in different cells.     

Species richness and cover along a 60-year chronosequence in old-fields of southeastern Spain

We analyse changes in plant cover and species richness along a 60-year chronosequence in semi-arid Mediterranean old-fields of southeastern Spain. The objectives were: (i) to study patterns of species richness along the abandonment gradient in semi-arid conditions (e.g., to test the “humped-back model” in our system); (ii) to test whether different broad life forms (annuals, forbs, grasses and woody species) showed different patterns along the abandonment gradient, and (iii) to examine to what extent plants with different dispersal strategies dominate at different stages of succession. The explained variance of the regression relating species richness to years since abandonment is improved when considering different life forms. The results suggest that cover and richness of different functional groups show a non-linear unimodal (often positive-skewed) pattern along the gradient (age since abandonment). Maximum total richness is found at young stages of abandonment (<20 years), when most life forms and dispersal strategies coexist. Annuals and perennial forbs reached their maximum richness during the first 10 years of abandonment. About 45% of total woody species richness is reached at this time as a consequence of early colonization of zoochorous shrubs. While the results showed a tendency towards a life-form replacement sequence, the pattern is not so clear when looking at the different dispersal strategies. The results complement previous results in Mediterranean conditions and emphasise the importance of considering different functional types when studying successional patterns. This revised version was published online in June 2006 with corrections to the Cover Date.     

Why the term “larva” is ambiguous,or what makes a larva?

The term “larva” is used for many different metazoans. Although this implies a uniform meaning, the term has in fact been used to address immatures with very different characteristics. For providing more precise reference how the term larva is applied in a specific context, I outline here different criteria that have been used to identify an immature as a larva. These include larvae that (a) differ morphologically from their adult (morpho-larva s. l.); (b) differ morphologically from their adult and additionally possess structures that become reduced during ontogeny (morpho-larva s. str.); (c) have a different ecological niche than their adult (eco-larva s. l.); (d) have a different ecological niche than their adult and additionally fulfil a dispersal function (eco-larva s. str.); (e) transform by a metamorphosis to the non-larval immature or adult (metamorph-larva); (f) differ from the adult by having evolved new structures in the early stages (apo-larva); (g) differ from the adult as the adult has evolved new structures (plesio-larva). The differentiation of these criteria will provide a more precise reference reducing possible misunderstanding and allowing a more precise communication.     

Mechanisms of heat inactivation in Salmonella serotype Typhimurium as affected by low water activity at different temperatures

AIMS: To determine the effect of reduced water activity (a(w)) on thermal inactivation of Salmonella serotype Typhimurium at different temperatures and its mechanism. METHODS AND RESULTS: D-value determinations at a range of different temperatures showed that heating at reduced a(w) (0.94, produced by addition of glucose or sodium chloride to nutrient broth) was protective at temperatures above 53-55 degrees C but sensitizing below this temperature. Using selective enumeration media to determine injury, it was shown that at lower heating temperatures cells survived at high a(w) with cytoplasmic injury whereas at low a(w) these cells were killed. At higher temperatures ribosome degradation was a more important cause of death and was inhibited by low a(w) heating media thereby providing greater heat resistance. CONCLUSIONS: The observed change in behaviour reflects the different reactions responsible for thermal death at different temperatures and their different response to reduced a(w). SIGNIFICANCE AND IMPACT OF THE STUDY: This work qualifies the previous assumption that reduced a(w) is protective and suggests that the efficacy of low temperature pasteurization regimes may be increased by reduced a(w).     

甘油-3磷酸转酰酶氨基酸与植物抗冷性关系初探

甘油 - 3磷酸转酰酶 (GPAT)与植物抗冷性密切相关。南瓜 (Cucurbitamoschata)与黑子南瓜 (Cucurbitaficifolia)同属不同种 ,亲缘关系较近 ,但却存在显著的抗冷性差异。南瓜及黑子南瓜GPAT基因的克隆 ,可以使我们从二者推导的有限氨基酸的差异中对GPAT氨基酸组成及其与植物抗冷性作一定的探讨。发现在南瓜与黑子南瓜 13个不同的氨基酸残基中有 3个与抗冷性植物拟南芥菜 (Arabidopsisthaliana)、豌豆 (Pisumsativum)、红花 (Carthamustincto rius)和菠菜 (Spinaciaoleracea)等相同 ,可能与黑子南瓜比南瓜更具抗冷性的原因有关。比较南瓜、黑子南瓜、豌豆、红花、拟南芥菜和菠菜等植物中GPAT基因推导的氨基酸序列发现 ,在比较抗冷的拟南芥菜、红花、豌豆和菠菜等植物中 ,虽然它们之间的亲缘关系都比较远 ,但某些位点上的氨基酸残基却完全相同 ,而与南瓜等抗冷性较差的植物不同 ,这些位点的氨基酸残基可能也与GPAT对底物酰基的选择性有关。     

Conformational analysis of melittin in solution phase: vibrational circular dichroism study

The vibrational absorption and vibrational circular dichroism (VCD) spectra of melittin in D(2)O solutions at different pH values, different salt concentrations, or different 2,2,2-trifluoroethanol (TFE) concentrations are recorded in the amide I' (1850-1600 cm(-1)) region. Two models are used to simulate this peptide in different conditions, and a coupled oscillator program is used to obtain the calculated absorption and VCD spectra. This study indicates that melittin adopts a mixed structure in D(2)O solution at low pH, low salt concentration, or low TFE concentration. With an increase in pH, salt concentration, or TFE concentration, the structure changes to alpha-helix and further increases lead to aggregation. These results demonstrate the versatility of VCD in probing the conformations of peptides under different environmental perturbations.     

Flow cytometry and live confocal analysis for the evaluation of the uptake and intracellular distribution of FITC-ODN into HaCaT cells

In this study, the mechanism of the internalization and the cellular distribution of 59 fluorescein conjugated PS-ODN (FITC-ODN) after transfection with different mixed lipidic vesicles/oligo complexes (lipoplexes) have been investigated. Mixed lipidic vesicles were prepared with one of the most used cationic lipid (DOTAP) and different amounts of a cholic acid (UDCA) to release the oligo into HaCaT cells. Using flow cytometry, the cellular uptake of the oligo was studied with and without different inhibitors able to block selectively the different pathways involved in the internalization mechanism. The intracellular distribution of the oligo was analyzed by confocal laser scanning microscopy (CLSM), treating the cells with the lipoplexes and directly observing without any fixing procedure. To better carry out the colocalization studies, fluorescent-labeled markers, specific for the different cellular compartments, were coincubated with 59 fluorescein-conjugated 29-mer phosphorotioate oligonucleotide (FITC-ODN). The different lipidic vesicles affect the internalization mechanism of FITC-ODN. After using the inhibitors, the uptake of complexes involved a different internalization mechanism. The live CLSM analysis demonstrated that, after 1 hour from the complex incubation, the oligo was transferred into cells and localized into the endosomes; after 24 hours, the oligo was intracellularly localized close to the nuclear structure in a punctuate pattern. However, the results from fusion experiments showed also a binding of a quite low amount of oligo with the cell membranes.     

黄土丘陵区不同功能群植物碳氮磷生态化学计量特征及其对微地形的响应

研究黄土丘陵区植物碳氮磷生态化学计量特征及其对微地形变化的响应,对于深入理解植物对丘陵山地环境的适应策略具有重要的意义。以黄土丘陵区森林草原带不同微地形环境(坡向、坡位)下的不同功能群植物为研究对象,对不同功能群植物叶片和细根的C、N、P含量及其化学计量特征进行了研究。结果表明:(1)叶氮含量(LN)、叶磷含量(LP)、根氮含量(RN)、根碳含量(RC)、叶碳/叶氮(LC/LN)、叶碳/叶磷(LC/LP)、叶氮/叶磷(LN/LP)、根碳/根氮(RC/RN)和根氮/根磷(RN/RP)在科属间差异显著(P0.05),而叶碳含量(LC)、根磷含量(RP)和根碳/根磷(RC/RP)在科属间差异不显著(P0.05)。(2)不同科属植物生态化学计量特征对微地形变化的响应不同,禾本科细根C/N在阴坡、阳坡差异性显著,豆科植物根N含量在不同坡位间差异显著(P0.05);菊科植物叶N含量、叶C含量、根N含量、叶片C/N和细根C/N在不同坡位间差异显著(P0.05)。(3)禾本科植物在中坡位受N、P元素共同影响,在其它坡位主要受N元素限制;豆科植物在中坡位和上坡位主要受P元素限制,在下坡位和峁顶受N、P元素共同影响;菊科植物上坡位受N、P元素共同影响,在其他坡位主要受N元素限制。研究表明,不同科属植物在不同微地形条件下受限的营养元素不同,对丘陵多变环境也存在不同的适应策略。     

What are we measuring? Novices agree amongst themselves (but not always with experts) in their assessment of dog behaviour

Humans differ in how they perceive, assess, and measure animal behaviour. This is problematic because strong observer bias can reduce statistical power, accuracy of scientific inference, and in the worst cases, lead to spurious results. Unfortunately, reports and studies of measurement reliability in animal behaviour studies are rare. Here, we investigated two aspects of measurement reliability in working dogs: inter‐observer agreement and criterion validity (comparing novice ratings with those given by experts). Here, we extend for the first time a powerful framework used in human psychological studies to investigate three potential aspects of (dis)agreement in nonhuman animal behaviour research: (a) that some behaviours are easier to observe than others; (b) that some subjects are easier to observe than others; and (c) that observers with different levels of experience with the subject animal give the same or different ratings. We found that novice observers with the same level of experience agreed upon measures of a wide range of behaviours. We found no evidence that age of the dogs affected agreement between these same novice observers. However, when observers with different levels of experience (i.e., novices vs. a working dog expert) assessed the same dogs, agreement appeared to be strongly affected by the measurement instrument used to assess behaviour. Given that animal behaviour research often utilizes different observers with different levels of experience, our results suggest that further tests of how different observers may measure behaviour in different ways are needed across a wider variety of organisms and measurement instruments.     

呼伦贝尔草原黄羊体况的初步评价

对呼伦贝尔草原地区黄羊肾脏重量和肾脏中心脂肪指数的变化进行了研究。初步评价了不同年龄－性别组黄羊以及不同季节黄羊体况的差异。发现：黄羊左肾重量大于右肾,不同年龄－性别组黄羊间肾重存在极显的差异（P＜0．01）,并且肾重与体重呈显的正相关性（P＜0．01）;黄羊肾重存在季节性差异,春季肾重大于秋、冬二季;KMFI值在不同的年龄－性别组间也呈明显的差异性（P＜0．01）,KMFI值亦与体重吴正相关性（P＜0．01）;不同的季节,黄羊KMFI值差异明显（P＜0．01）。黄羊秋季体况最好,而冬末春初则较差。