Shelterin复合体在恶性血液病中的研究进展

<正>端粒是指位于线性染色体末端的含有成千上万个DNA短串联重复序列的特殊结构,广泛存在于真核生物中。端粒由两条长短不同的DNA链组成:一条富含G(鸟嘌呤碱基),另一条富含C(胞嘧啶碱基),在人体中6个碱基的序列(TTAGGG)位于端粒头部、CCCTAA位于尾部。主要包括2个结构功能域:端粒双链结构域和端粒单链结构域。富含G的DNA 3'端突出为单链,形成3'端悬垂链,     

老年高血压患者端粒长度和端粒酶活性的影响因素

<正>端粒是重复的TTAGGG碱基序列的染色体末端结构,主要作用是维持细胞染色体稳定性和DNA完整复制。端粒酶是由DNA和蛋白质组成,为依赖RNA的一种特殊DNA聚合酶,端粒的生物合成有赖于端粒酶[1]。高血压是老年人常见的一种慢性病,发病率高,是多种心脑血管病的重要危险因素,但其发病机制,目前仍不明确。年龄依赖的端粒功能失调可能参与其发病过程。     

端粒重复序列结合因子2小干扰核糖核酸逆转胃癌细胞多药耐药性的研究

阿霉素(Adriamycin,ADR)和依托泊苷是临床常用的肿瘤化学治疗药物,主要作用机制为抑制DNA拓扑异构酶,导致DNA双链断裂(double-strand DNA breaks, DSB) [1].肿瘤细胞发生耐药与多种机制有关,其中对DNA损伤修复的影响是其中重要的一环[2].端粒重复序列结合因子2(telomeric repeat binding factor 2, TRF2)能够通过维持端粒末端的T环结构,防止端粒被DNA损伤修复机制检测为DSB,维持端粒的正常结构和功能[3-4].     

正常衰老期间和三体性21患者中淋巴细胞的端粒DNA丢失

端粒是含有高度保守性重复序列的特殊核酸蛋白质复合结构,位于染色体末端。细胞衰老的端粒假说指出,在复制衰老期间,人类染色体上端粒DNA的(TTAGGG)n序列丢失可能最终导致细胞周期出口。由于已知淋巴细胞的复制能力有限,且在体内研究发现衰老期间血细胞中的端粒DNA会丢失,如果免疫系统的衰老是某些老年个体以及由三体性21引起的Down综合征(DS)患者的病态诱因,而且在细胞衰老期间端粒序列缩短能起作用,那么就可期望在这些个体的淋巴细胞中存在已缩短的端粒     

不同端粒片段通过沉默信息调节因子1/抑癌基因P53促进血管平滑肌细胞凋亡

目的:研究不同端粒寡核苷酸序列对大鼠胸大动脉平滑肌细胞(A7R5)凋亡的影响,及沉默信息调节因子1(SIRT1)/抑癌基因P53(P53)信号通路是否参与调控端粒寡核苷酸序列诱导A7R5的凋亡。方法:将三种端粒重复序列端粒寡核苷酸序列的二聚体、四聚体、六聚体[TE-12(TTAGGG)2、TE-24(TTAGGG)4、TE-36(TTAGGG)6]转染至A7R5,分别作为TE-12组、TE-24组、TE-36组,另设A7R5空白为阴性对照组。应用流式细胞仪检测各端粒寡核苷酸序列转染后A7R5的凋亡情况。采用逆转录多聚酶联反应(RT-PCR)及蛋白免疫印迹(Western-blot)检测TE-12组、TE-24组、TE-36组及阴性对照组SIRT1、P53基因及蛋白水平。结果:将TE-12、TE-24、TE-36成功转染进A7R5,各组转染率差异无统计学意义。TE-12组A7R5凋亡率明显高于TE-36组、TE-24组和阴性对照组,TE-24组细胞凋亡率最低,但亦明显高于阴性对照组,差异均有统计学意义(P均0.05)。TE-12组A7R5SIRT1m RNA及蛋白水平明显高于TE-36组、TE-24组和阴性对照组,差异均有统计学意义(P均0.05)。TE-24组A7R5P53m RNA及蛋白水平明显低于TE-36组、TE-12组和阴性对照组,差异均有统计学意义(P均0.05)。结论:端粒寡核苷酸序列促进A7R5的凋亡。不同结构的端粒寡核苷酸序列引起A7R5凋亡程度不同,在选取的三种结构中,端粒单链序列TE-12引起A7R5凋亡最明显。端粒寡核苷酸序列对A7R5凋亡的作用可能与SIRT1/P53信号通路有关。     

人端粒保护蛋白1的结构与功能

人类端粒DNA由富含G的短片段重复序列(TTAGGG)串联组成,包括双链和3’端突出的单链两部分,不能编码蛋白质〔1-2〕。通常认为端粒酶是调控端粒DNA长度最重要的因素,端粒酶活性的降低将导致端粒长度的下降,细胞分裂停滞。端粒酶活性通常由其催化亚单位(端粒酶逆转录酶)所决定〔3-4〕,但奇怪的是,端粒双链DNA结合蛋白TRF1与TRF2,也能调控端粒酶活性,但它们并无直接联系。最近的研究显示人端粒保护蛋白1     

端粒酶反义寡聚脱氧核苷酸对肝癌细胞影响的研究

细胞凋亡(Apoptosis)是由基因控制的细胞主动死亡方式.应用药物选择性诱导肿瘤细胞凋亡能改善肿瘤的预后[1].染色体端粒(Telomere)是位于细胞染色体末端的一种特殊结构,在人体细胞中,端粒由串联的短片段重复序列(TTAGGG)n及一些结合蛋白组成,在染色体的定位、复制、保护和控制细胞生长寿命等方面起重要作用,并与细胞凋亡密切相关[2].端粒酶 (Telomerase)是一种核糖核蛋白,它通过不断合成端粒重复序列添加至染色体末端,维持染色体稳定.Bcl-2(B-cell lymphoma/leukemia-2)基因是一种癌基因,可抑制多种因素引起的细胞凋亡,Bcl-2蛋白高表达是端粒酶激活的途径之一[3].我们旨在探讨端粒酶反义寡聚脱氧核苷酸(ASDDN-t)诱导肝癌细胞凋亡[4],抑制端粒酶活性,从而抑制肝癌细胞的生长,为肝癌基因治疗提供依据.     

端粒酶与肺癌诊断

1　端粒　　端粒是真核生物染色体末端的一段特殊结构 ,由ＤＮＡ序列及相关蛋白质组成 ,该序列富含鸟嘌呤碱基Ｇ ,具有种属特异性[1] 。人的端粒包括重复的 5’ -ＴＴＡＧＧＧ - 3’序列 ,在体外形成发夹折叠的二级结构 ,为染色体末端提供了一个保护性的“帽子” ,防止染色体的异常重组、端 -端融合及保护ＤＮＡ不被核酸酶及连接酶所破坏等作用[2 ] 。通常细胞每分裂 1次 ,端粒丢失约 5 0～ 2 0 0个碱基对 ,这是由于ＤＮＡ聚合酶不能完全复制线性ＤＮＡ末端所致 ,端粒酶的存在和活化解决了这一末端复制的问题[3 ] 。随着染色体端粒的不断丢…     

健脾理气方药物血清对肝癌细胞端粒酶活性及凋亡的影响

目的 观察健脾理气方药物血清对肝癌细胞SMMC-7721端粒酶活性的影响以及诱导肿瘤细胞凋亡的作用,探讨其抗肿瘤治疗的作用机制.方法 采用端粒重复序列扩增(TRAP)结合非变性聚丙烯酰胺凝胶电泳银染法,利用健脾理气方中药灌服新西兰兔后制备含药血清,观察健脾理气方药物血清对体外培养的人肝癌细胞株SMMC-7721端粒酶活性的影响,同时利用流式细胞仪检测和荧光显微镜观察对细胞凋亡的影响.结果 健脾理气药物血清在d 4开始对肿瘤细胞的端粒酶活性有抑制作用,电泳条带光密度明显降低;并能诱导肿瘤细胞的凋亡,凋亡的比例随作用时间的延长而升高,流式细胞术检测d2,d4,d 6的凋亡比例分别为0.81%,5.16%,8.45%.结论 对肿瘤细胞端粒酶活性的抑制和诱导肿瘤细胞凋亡是健脾理气中药抗肿瘤治疗作用机制的一部分.     

人基因多态性与肝纤维化的发生

基因多态性(genetic polymorphisms)普遍存在,如单个碱基的缺失和插入、短串联重复序列、单核苷酸多态性(single nucleotide polymorphism,SNP)等.其中SNP是最常见的基因多态性,指一个碱基的替换.人类全基因组中约有一千万个SNP,其等位基因频率不低于1%.     

Three layer functional model and energy exchange concept of aging process

Relying on a certain degree of abstraction, we can propose that no particular distinction exists between animate or living matter and inanimate matter. While focusing attention on some specifics, the dividing line between the two can be drawn. The most apparent distinction is in the level of structural and functional organization with the dissimilar streams of ‘energy flow’ between the observed entity and the surrounding environment. In essence, living matter is created from inanimate matter which is organized to contain internal intense energy processes and maintain lower intensity energy exchange processes with the environment. Taking internal and external energy processes into account, we contend in this paper that living matter can be referred to as matter of dissipative structure, with this structure assumed to be a common quality of all living creatures and living matter in general. Interruption of internal energy conversion processes and terminating the controlled energy exchange with the environment leads to degeneration of dissipative structure and reduction of the same to inanimate matter, (gas, liquid and/or solid inanimate substances), and ultimately what can be called ‘death.’ This concept of what we call dissipative nature can be extended from living organisms to social groups of animals, to mankind. An analogy based on the organization of matter provides a basis for a functional model of living entities. The models relies on the parallels among the three central structures of any cell (nucleus, cytoplasm and outer membrane) and the human body (central organs, body fluids along with the connective tissues, and external skin integument). This three-part structural organization may be observed almost universally in nature. It can be observed from the atomic structure to the planetary and intergalactic organizations. This similarity is corroborated by the membrane theory applied to living organisms. According to the energy nature of living matter and the proposed functional model, the decreased integrity of a human body's external envelope membrane is a first cause of the structural degradation and aging of the entire organism. The aging process than progresses externally to internally, as in single cell organisms, suggesting that much of the efforts towards the restoration and maintenance of the mechanisms responsible for structural development should be focused accordingly, on the membrane, i.e., the skin. Numerous reports indicate that all parts of the human body, like: bones, blood with blood vessels, muscles, skin, and so on, have some ability for restoration. Therefore, actual revival of not only aging tissue of the human body's membrane, but the entire human body enclosed within, with all internal organs, might be expected. We assess several aging theories within the context of our model and provide suggestions on how to activate the body's own anti-aging mechanisms and increase longevity. This paper presents some analogies and some distinctions that exist between the living dissipative structure matter and inanimate matter, discusses the aging process and proposes certain aging reversal solutions.     

Unusual responses of nocturnal pineal melatonin synthesis and secretion to swimming: Attempts to define mechanisms

Abstract: The effect of swimming at night on rat pineal melatonin synthesis was compared with that of light exposure at night. Rats were forced to swim at 0030 hr (lights out at 2000 hr) and sacrificed by decapitation 15 and 30 min later, immediately after swimming. Other groups of animals were exposed to white light (650μW/cm²) for 15 and 30 min at same time. Swimming caused a rapid and highly significant drop in the melatonin content in the pineal gland; however, the activity of N-acetyltransferase (NAT), the supposed rate limiting enzyme in the melatonin production, was not changed. Despite the drop in pineal melatonin levels, serum concentrations of the indole remained elevated in the rats that swam. In contrast, melatonin levels in the pineal and serum of light exposed rats fell precipitously, accompanied by a significant suppression of NAT activity. Since we anticipated that the strenuous exercise associated with swimming may induce release of artrial natriuretic peptide (ANP) from the heart, which in turn could cause the release of pineal melatonin, in a second study we injected physiological saline intravenously to stretch the cardiac muscle and release ANP. Three milliliters of normal saline was injected during the day into the jugular vein of anesthetized rats that were pretreated with isoproterenol to stimulate pineal melatonin production. Animals were killed 15 min after the saline injection, and pineal NAT activity and pineal melatonin levels were measured. The saline injections caused no alteration in the elevated levels of either NAT or melatonin. These data suggest that the disparity in pineal NAT activity (which was high) and pineal melatonin (which was low), in animals swum at night, may not be caused by ANP which is released during strenuous exercise such as swimming.     

Melatonin and photoperiodic time measurement: Seasonal breeding in the sheep

Abstract: Well-established circadian physiology supports the view that photoperiodic time measurement utilizes the coincidence between the presence of light and a photosensitive phase of a 'biological clock' to alter reproductive status—the so-called external coincidence model of seasonal breeding. In this review, we examine the mechanism whereby photoperiod interacts with presumed suprachiasmatic nuclei activity to allow endogenous melatonin to normally synchronize reproductive activity to the optimal time of year. The Romney Marsh sheep is particularly explored as an experimental model. It is suggested that the on/off activity of seasonal reproduction may be a robust mechanism able to be predictably manipulated by the judicious use of the light/dark cycle and exogenous melatonin, but firmly based on circadian principles.     

Serological survey of HIV and syphilis in pregnant women in Madagascar

Objectives Peripartal transmission of human immunodeficiency virus (HIV) and Treponema pallidum, the causative agent of syphilis, leads to severe consequences for newborns. Preventive measures require awareness of the maternal infection. Although HIV and syphilis testing in Madagascar could be theoretically carried out within the framework of the national pregnancy follow‐up scheme, the required test kits are rarely available at peripheral health centres. In this study, we screened blood samples of pregnant Madagascan women for HIV and syphilis seroprevalence to estimate the demand for systemic screening in pregnancy. Methods Retrospective anonymous serological analysis for HIV and syphilis was performed in plasma samples from 1232 pregnant women that were taken between May and July 2010 in Ambositra, Ifanadiana, Manakara, Mananjary, Moramanga and Tsiroanomandidy (Madagascar) during pregnancy follow‐up. Screening was based on Treponema pallidum haemagglutination tests for syphilis and rapid tests for HIV, with confirmation of positive screening results on line assays. Results Out of 1232 pregnant women, none were seropositive for HIV and 37 (3%) were seropositive for Treponema pallidum. Conclusions Our findings are in line with previous studies that describe considerable syphilis prevalence in the rural Madagascan population. The results suggest a need for screening to prevent peripartal Treponema pallidum transmission, while HIV is still rare. If they are known, Treponema pallidum infections can be easily, safely and inexpensively treated even in pregnancy to reduce the risk of transmission.     

Variabilité des concentrations plasmatiques de l’angiotensinogène et risque d’hypertension artérielle chez le rat transgénique

Aim

Genetic polymorphisms of the human angiotensinogen gene are frequent and may induce up to 30% increase of plasma angiotensinogen concentrations with a blood pressure increase of up to 5 mmHg. Their role for the pathogenesis of human arterial hypertension remains unclear. High plasma angiotensinogen levels could increase the sensitivity to other blood pressure stressors.

Methods

Male transgenic rats with a 9-fold increase of plasma angiotensinogen concentrations and male non-transgenic rats aged 10 weeks were treated or not with NG-Nitro-L-arginine-methyl ester for 3 weeks in their drinking water (n = 3/group). Systolic blood pressure and body weight were measured at baseline and at the end of the study when left ventricular weight and ventricular expression of angiotensin I-converting enzyme and procollagen Iα1 were determined (polymerase chain reaction).

Results

At baseline, transgenic rats had +18 mmHg higher bood pressure and –8% lower body weight compared to non-transgenic rats (P < 0.05) without significant changes for the vehicle groups throughout the study (P > 0.05). NG-Nitro-L-arginine-methyl ester increased blood pressure, left ventricular weight and left ventricular weight indexed for body weight by +41%, +17.6% and +18.6% (P < 0.05) in transgenic and +25%, +5.3% and +6.7% (P > 0.05) in non-transgenic rats compared to untreated animals, respectively. Cardiac gene expression showed no differences between groups (P > 0.05).

Conclusion

Increased plasma angiotensinogen levels may sensitize to additional blood pressure stressors. Our preliminary results point towards an independent role of angiotensinogen in the pathogenesis of human hypertension and associated end-organ damage.     

Morphological and immunocytochemical heterogeneity of cultured pinealocytes from one-week-and two-month-old rats: Planimetric and densitometric investigations

Abstract: In vitro preparations of rat pinealocytes are widely used for biochemical analyses of signal transduction processes. This paper deals with morphological and immunocytochemical features of such preparations. Special attention was paid to the problems of whether pinealocytes represent a heterogeneous cell population and how such heterogeneity may develop during ontogeny. The investigations were performed with cells which were obtained from the pineal organ of one-week-and two-month-old rats, attached to synthetic peptide-coated coverslips or tissue culture chamber slides, and maintained under in vitro conditions overnight. The attached cells were then fixed with paraformaldehyde. These preparations yielded monolayers of spherical cells of different sizes; most cells were isolated, but some of them were aggregated and formed small clusters. On the average, the cells from the one-week-old animals were smaller than the cells from the two-month-old animals. Immunocytochemical demonstration of S-antigen, a pinealocyte-specific marker, showed that the majority of the cells from two-month-old animals were intensely or moderately labelled. Pinealocytes from one-week-old animals were less S-antigen immunoreactive. Only very few cells (less than 1% displayed glial fibrillary acidic protein (GFAP)-immunoreactivity. Planimetric investigations of the cell size and semiquantitative densitometric investigations of the intensity of the S-antigen immunoreaction revealed that (i) pinealocytes kept in vitro form a heterogeneous cell population, and that (ii) this heterogeneity increases during postnatal development from one-week-old to two-month-old animals. Two groups of pinealocytes can be distinguished based on their developmental fate: pinealocytes of one group grow dramatically, but show only a moderate increase in S-antigen immunoreactivity, and pinealocytes of the other group retain their size, but display a distinct increment in S-antigen immunoreacti vitv.     

Effects of pinealectomy and melatonin administration on certain indices of ovarian hyperplasia and/or hypertrophy in rats with both ovaries intact or after unilateral ovariectomy

Abstract: In earlier studies from other laboratories it was shown that melatonin decreased ovarian weight in rats and inhibited compensatory hypertrophy of the remaining ovary after unilateral ovariectomy. This study was designed to examine the influence of melatonin on certain indices of ovarian hyperplasia and/or hypertrophy in adult female rats with both ovaries preserved and with either an intact pineal gland or with the pineal gland removed (pinealectomy, PX) or, finally, in sham-PX animals. Similar studies were conducted on rats after unilateral ovariectomy, referring the examined parameters to the remaining intact ovary. The studies included mitotic activity of granulosa layer cells and corpus luteum cells, ovarian weight, ovarian cross-sectional area, cross-sectional area of the granulosa layer of all the Graafian follicles and the cross-sectional areas of the corpora lutea, visible on the ovarian cross-section. On the basis of results, we conclude that: 1) the effect of PX on the processes of ovarian hyperplasia and hypertrophy may vary; analogously, exogenous melatonin administration may influence ovarian hyperplasia and hypertrophy in different ways; 2) PX and exogenous melatonin may, under certain conditions, exert similar biological effects, even synergistic effects; 3) melatonin inhibits ovarian growth processes, while the effects of PX are variable; 4) the results indicate that in experiments performed on rats, with the use of two control groups, i.e., intact and sham-PX, melatonin effects on these two groups may differ.