Chromosomal distribution of interstitial telomeric sequences as signs of evolution through chromosome fusion in six species of the giant water bugs (Hemiptera,Belostoma)

Tandem arrays of TTAGG repeats show a highly conserved location at the telomeres across the phylogenetic tree of arthropods. In giant water bugs Belostoma, the chromosome number changed during speciation by fragmentation of the single ancestral X chromosome, resulting in a multiple sex chromosome system. Several autosome–autosome fusions and a fusion between the sex chromosome pair and an autosome pair resulted in the reduced number in several species. We mapped the distribution of telomeric sequences and interstitial telomeric sequences (ITSs) in Belostoma candidulum (2n = 12 + XY/XX; male/female), B. dentatum (2n = 26 + X₁X₂Y/X₁X₁X₂X₂), B. elegans (2n = 26 + X₁X₂Y/X₁X₁X₂X₂), B. elongatum (2n = 26 + X₁X₂Y/X₁X₁X₂X₂), B. micantulum (2n = 14 + XY/XX), and B. oxyurum (2n = 6 + XY/XX) by FISH with the (TTAGG)_n probes. Hybridization signals confirmed the presence of TTAGG repeats in the telomeres of all species examined. The three species with reduced chromosome numbers showed additional hybridization signals in interstitial positions, indicating the occurrence of ITS. From the comparison of all species here analyzed, we observed inverse relationships between chromosome number and chromosome size, and between presence/absence of ITS and chromosome number. The ITS distribution between these closely related species supports the hypothesis that several telomere–telomere fusions of the chromosomes from an ancestral diploid chromosome number 2n = 26 + XY/XX played a major role in the karyotype evolution of Belostoma. Consequently, our study provide valuable features that can be used to understand the karyotype evolution, may contribute to a better understanding of taxonomic relationships, and also elucidate the high plasticity of nuclear genomes at the chromosomal level during the speciation processes.     

E. coli chromosomal DNA in a transgene locus created by microprojectile bombardment in tobacco

Transgenic Research -     

喉癌STK15基因表达和染色体不稳定的研究

为研究喉鳞状细胞癌中STK15基因表达及其与染色体不稳定的相关性,提取50例喉鳞状细胞癌及配对癌旁正常组织和喉鳞状细胞癌Hep-2细胞系的RNA,反转录合成cDNA,以β-actin为内对照进行PCR扩增,用软件分析电泳结果,研究喉癌中STK15基因表达的水平;以Hep-2细胞系为代表应用常规和高分辨G显带方法进行核型分析。在50例喉癌中,癌组织STK15表达高于配对癌旁正常组织的有34例,占68％,经统计学分析,肿瘤组与对照组差异显著,Hep-2细胞系中STK15基因表达高于内对照β-actin;Hep-2细胞系中存在显著的染色体不稳定,染色体数目变化于43－84条之间,众数为69－74条,结构畸变主要表现为13条标记染色体,本研究首次发现STK15基因在喉癌中表达增高,它可能通过中心体异常而引起染色体不稳定,在喉癌的发生,发展中发挥一定作用。     

Evidence for Chromosomal Macronuclear Substructures in Tetrahymena*†

SYNOPSIS.
Under the growth conditions employed, the G₁ macronucleus of Tetrahymena pyriformis HSM contains 7.4 × 10^-12 g DNA, the G₂ micronucleus 0.42 × 10^-12 g. DNA content from the Tetrahymena thermophila macronucleus did not significantly differ from that of HSM, but the micronucleus contained about twice as much DNA as the micronucleus of the HSM cells. The T. thermophila macronucleus contained on average enough DNA for ˜ 35 haploid micronuclear copies. A new spreading technic allowed separation of macronuclear substructures from cells of late G₂ to early G₁. Photometric determination of DNA content of 345 individual structures suggested the existence of 5 different-sized macronuclear structures with a DNA content corresponding to 2, 4, 8, and 16 × the basic values. Comparison of the DNA content of these structures with (a) mitotic micronuclear chromosomes and (b) meiotic micronuclear chromosomes of T. thermophila cells suggests that the 5 basic values of macronuclear structures derive from structures of micronuclear chromosomes. The micronuclear chromosomes of T. pyriformis may be oligotenic. It is suggested that these results further our understanding of macronuclear organization.     

Niacin deficiency modulates genes involved in cancer: Are smokers at higher risk?

The role of niacin’s metabolite, nicotinamide adenine dinucleotide (NAD), in DNA repair via base-excision repair pathway is well documented. We evaluated if niacin deficiency results in genetic instability in normal human fetal lung fibroblasts (MRC-5), and further, does it leads to enhanced accumulation of cigarette smoke–induced genetic damage? MRC-5 cells were grown discretely in niacin-proficient/deficient media, and exposed to nicotine-derived nitrosamine ketone (NNK, a cigarette smoke carcinogen). Niacin deficiency abated the NAD polymerization, augmented the spontaneous induction of micronuclei (MN) and chromosomal aberrations (CA) and raised the expression of 10 genes and suppressed 12 genes involved in different biological functions. NNK exposure resulted in genetic damage as measured by the induction of MN and CA in cells grown in niacin-proficient medium, but the damage became practically marked when niacin-deficient cells were exposed to NNK. NNK exposure raised the expression of 16 genes and suppressed the expression of 56 genes in cells grown in niacin-proficient medium. NNK exposure to niacin-deficient cells raised the expression of eight genes including genes crucial in promoting cancer such as FGFR3 and DUSP1 and suppressed the expression of 33 genes, including genes crucial in preventing the onset and progression of cancer like RASSF2, JUP, and IL24, in comparison with the cells grown in niacin-proficient medium. Overall, niacin deficiency interferes with the DNA damage repair process induced by chemical carcinogens like NNK, and niacin-deficient population are at the higher risk of genetic instability caused by cigarette smoke carcinogen NNK.     

Th17/Treg细胞失衡与子宫颈癌

Th17细胞是近年发现的一种新型CD4^＋效应性T细胞,以其特异性的分泌IL-17而命名。介导免疫耐受的Treg细胞和介导炎症反应的Th17细胞间功能和分化过程相互对抗,在正常状态下,两者保持平衡,但机体发生功能异常时常表现出Treg/Th17失衡,引起炎性反应、自身免疫性疾病、移植物抗宿主病等的发生和发展,并决定疾病的转归和预后,在肿瘤免疫中亦发挥了重要作用。该文就Treg/Th17失衡在肿瘤,尤其是子宫颈癌发生发展中的作用进行综述。     

太湖生态系统能量闭合特征及其影响因素

地表能量不闭合不仅限制了涡度相关观测数据在陆面模型发展和验证等应用性研究中的价值,还给生态系统CO2源汇特征辨析带来不确定性。基于太湖避风港站2012年涡度相关通量、辐射、气象和水温梯度观测数据,分析了太湖能量闭合的多尺度(小时、日和月)时间变化特征,阐述了大气稳定度、摩擦风速和湖风对太湖能量闭合状况的影响。结果表明:太湖小时尺度的能量闭合度为0.59,且昼夜差异较小;日尺度的能量闭合度为0.73,在内陆水体观测结果中处于中等水平;月平均能量闭合度呈现冬季高、夏季低的季节变化特征;年平均时太湖仍有27%的能量不闭合。因摩擦风速减小,太湖能量闭合度在大气极不稳定条件下要比弱不稳定条件下结果低0.3;对于太湖这类大型浅水湖泊,其能量闭合度全天都受动力湍流交换强度制约,能量闭合度随摩擦风速增大而显著提高;虽然湖风发生使太湖小时尺度的能量闭合度降低了0.1,但其影响在日尺度上并不明显。     

绝经前后细菌性阴道病厌氧菌群及耐药性分析

目的了解绝经前后细菌性阴道病患者标本中优势厌氧菌群,检测厌氧菌分离株对5-硝基咪唑类和林可霉素类抗生素的耐药性。方法采集165例未绝经和125例绝经阴道病患者以及84例未绝经和68例绝经正常妇女的阴道分泌物,测定其pH。采用选择性厌氧培养基分离类杆菌、梭杆菌、乳杆菌、优杆菌、消化链球菌和消化球菌,将分离的厌氧菌株鉴定至种。同时采用二倍平皿稀释法,测定塞克硝唑、替硝唑、甲硝唑、林可霉素和克林霉素对760株厌氧菌的最低抑菌浓度。结果100%细菌性阴道病患者、97.6%未绝经和98.5%绝经正常妇女的阴道分泌物中分离出厌氧菌。阴道炎患者标本中,类杆菌属、普氏菌属和紫质单胞菌属厌氧菌分离率高于相应对照组(P<0.05;P<0.01),其中以多毛类杆菌、腐败类杆菌、脆弱类杆菌、产黑普氏菌、不解糖紫质单胞菌为优势菌群;梭杆菌属、优杆菌属、消化球菌属和消化链球菌属厌氧菌分离率与相应对照组比较差异无显著性(P>0.05);乳杆菌属分离率明显低于相应对照组(P<0.01)。未绝经正常妇女和患者及绝经正常妇女和患者阴道分泌物pH分别为4.5±0.2、5.5±0.8、6.5±0.3和6.5±1.0。塞克硝唑、替硝唑和甲硝唑对355株革兰阴性厌氧菌M IC90值为1~8μg/m l,林可霉素和克林霉素则为4~16μg/m l;塞克硝唑、替硝唑和甲硝唑对405株革兰阳性厌氧菌M IC90值为8~32μg/m l,林可霉素和克林霉素则为4~16μg/m l。     

供氮水平对落叶松幼苗光合作用的影响

为探讨落叶松光合作用对外界供氮环境变化的响应规律,采用砂培方法在温室内设置了4种供氮浓度(1、4、8mmol/L和16mmol/L),对生长在不同供氮水平下落叶松(Larixgmelinii)1年生幼苗的气体交换参数、叶绿素荧光参数以及一些生化指标进行了测定。结果显示,随供氮水平的提高,落叶松幼苗针叶氮含量、叶绿素含量、类胡罗卜素含量、可溶性蛋白(TSP)含量和光饱和净光合速率(Pmax)均显著增加,同时伴随着叶磷含量和胞间与外界CO2浓度之比(Ci/Ca)的降低。然而,当供氮水平超过8mmol/L增至16mmol/L时,TSP含量及Pmax不再增加,反而略有下降。供氮不足显著降低了幼苗针叶光系统最大光能转换效率(Fv/Fm)、光系统量子效率(ΦPS)和光化学猝灭系数(qP),却增加了非光化学猝灭系数(NPQ)。而增加供氮可使Fv/Fm和ΦPS回升,同时qP升高,NPQ下降,但当供氮水平超过8mmol/L后,各叶绿素荧光参数变化幅度较小。结果表明,增加供氮可显著提高落叶松幼苗的光合能力,增加光系统天线色素捕获的光能用于光化学电子传递的份额,减缓光抑制。然而,16mmol/L已经超过落叶松幼苗最适的供氮水平,过量供氮引起的负面效应可能主要与过低的叶磷含量导致的营养失衡有关。