成体干细胞的可塑性

传统观念认为,成体干细胞只能分化成其自身来源组织的细胞类型。但近年大量的研究表明,成体干细胞可跨系甚至跨胚层分化成在发育上与之无关的其他组织的细胞类型,即具有可塑性。文章对成体干细胞可塑性的研究结果、分化机制、应用前景及需解决的问题等进行了综述。     

Intestinal stem cell replacement follows a pattern of neutral drift

With the capacity for rapid self-renewal and regeneration, the intestinal epithelium is stereotypical of stem cell-supported tissues. Yet the pattern of stem cell turnover remains in question. Applying analytical methods from population dynamics and statistical physics to an inducible genetic labeling system, we showed that clone size distributions conform to a distinctive scaling behavior at short times. This result demonstrates that intestinal stem cells form an equipotent population in which the loss of a stem cell is compensated by the multiplication of a neighbor, leading to neutral drift dynamics in which clones expand and contract at random until they either take over the crypt or they are lost. Combined with long-term clonal fate data, we show that the rate of stem cell replacement is comparable to the cell division rate, implying that neutral drift and symmetrical cell divisions are central to stem cell homeostasis.     

Human endothelial cell growth factor: cloning, nucleotide sequence, and chromosome localization

Several of the endothelial cell polypeptide mitogens that have been described probably play a role in blood vessel homeostasis. Two overlapping complementary DNA clones encoding human endothelial cell growth factor (ECGF) were isolated from a human brain stem complementary DNA library. Southern blot analysis suggested that there is a single copy of the ECGF gene and that it maps to human chromosome 5 at bands 5q31.3 to 33.2 A 4.8-kilobase messenger RNA was present in human brain stem messenger RNA. The complete amino acid sequence of human ECGF was deduced from the nucleic acid sequence of these clones; it encompasses all the well-characterized acidic endothelial cell polypeptide mitogens described by several laboratories. The ECGF-encoding open reading frame is flanked by translation stop codons and provides no signal peptide or internal hydrophobic domain for the secretion of ECGF. This property is shared by human interleukin-1, which is approximately 30 percent homologous to ECGF.     

杉木不同无性系间生长性状差异性研究

通过对12年生杉木无性系试验林生长性状进行比较分析,探讨不同无性系生长性状表现的差异性。研究结果表明,除了第1组的树高和第3组的胸径外,其余的无性系间的树高、胸径和材积有显著或极显著的差异。广义遗传力变化范围：树高为0.389～0.771,胸径为0.169～0.703,材积为0.377～0.674,试验中无性系的胸径、树高和材积3个性状多具中等以上的广义遗传力,其变异主要受遗传控制。按选择强度估算,优良无性系累积的材积平均遗传增益达到了40%以上,最优无性系累积的材积平均遗传增益达到55%以上。无性系年轮宽度自髓心向外总体上呈逐年波动下降的趋势,但不同无性系的变化趋势还是有较大的差异。     

FKBP38条件性基因敲除胚胎干细胞株的建立

[目的]通过电转的方法,建立FKBP38细胞株.[方法]对自制的MEF细胞进行MMC处理,从而得到Feeder细胞,并在Feeder细胞上培养ES细胞.[结果]通过电转的方法,将FKBP38载体转入ES细胞中,经G418,Ganc筛选克隆和PCR检测,得到FKBP38阳性克隆.[结论] FKBP38 CKO胚胎干细胞株构建完成.     

杉木种子园管理和建园无性系筛选的研究

本文综合分析了45个无性系单株产量、早期败育率、中期败育率、后期败育率、中期后期总败育率、优良粒率、发芽率、活力等指标的差异,并用单指标和多指标综合评分法,从原有一代种子园淘汰15个劣质无性系来改善种子园的产量和质量;另从中选出速生、丰产、结实量高、质量好的15个无性系,结合子代测定,作为营建二代种子园材料。为现有一代种子园经营管理和二代种子园营建提供科学依据。     

美丽异木棉花形态结构特征和观赏类型划分

通过嫁接繁殖栽培试验,对美丽异木棉的花期和花形态结构特征进行调查,结果表明:美丽异木棉的花期、花型、花瓣大小和颜色等形态特征在产地和无性系间存在较大差异,花期8月中旬至翌年3月上旬,花期延续时间可达190d,盛花期为10月中旬至11月上旬;花型分为直伸和反卷两种类型,直伸花型占82.47％;花瓣基部颜色分为白色、黄白色、浅黄色和黄色,黄色占54.55％;花瓣先端颜色分为白色(浅灰色)、浅红色、红色、深红色、紫红色,红色占59.09％;花平均长10.51 cm、宽11.91 cm;根据花瓣的长宽比,花瓣形状可分为长匙形(条形)、匙形和宽匙形,匙形占46.75％.聚类分析揭示美丽异木棉可分为直干早花大花宽瓣花型、直干迟花较大花型和大腹迟花较小花型等7个类型,其中直干早花大花宽瓣花型共25个无性系是较优良的观赏类型,是选育的重点.     

Genetic Variation and Yield Performance of Jerusalem Artichoke Germplasm Collected in China

Jerusalem artichoke (Helianthus tuberosus L.) is a perennial tuberous plant rich in inulin and is a potential energy crop.This study was conducted in a semiarid region of the Loess Plateau to investigate variations in morphological and agronomic characteristics and yield performance of 59 Jerusalem artichoke clones collected from 24 provinces in China.The germplasm we collected exhibited variations either in qualitative or in quantitative traits. Substantial genetic variations (genotype coefficient of variation ＞20%) in the main stem diameter, main stem number per plant, branch number per main stem, tuber number per plant, tuber size, tuber yield, and top yield (i.e., aboveground biomass) were found as well. Seven clones had a tuber yield ranging between 9.1-10.6 t ha-1, 7 clones had a top yield ranging between 18.1-31.3 t ha-1, and 15clones had a total biomass yield (i.e., tuber and top weight) between 25.0-35.0 t ha-1 on an oven-dried weight basis under the drought soil and climatic condition in the semiarid region. The 59 Jerusalem artichoke clones were clustered into 8groups based on 17 quantitative traits, and indicated that the most prevalent clones planted by farmers exhibited relatively low variation. Correlation analysis was conducted on the morphology and agronomy of the clones. This investigation suggests possible genetic improvement of Jerusalem artichoke for a higher tuber yield or a top biomass yield, and as a promising application for inulin or bioenergy in semiarid regions.     

Research on Isolation and Clone of Embryonic Stem Cell-Like in Bovine

Bovine embryonic stem cell would be invaluable for researching the aspect of animal cloning, production transgenic animal and discussion of gene function in vitro. With the object of establishing an effective culture system for isolation and clone of bovine pluripotent stem cell, we cultured bovine embryos and mouse embryos including morula blastula and hatached blastula and obtained animal ICM on Primary marine embryonic fibroblast (Primary murine embryonic fibroblast, PMEF) feeder layer with tissue medium(DMEM supplemented with 15ml/100ml NBS ,0.1μmol/L Na2SeO3, 0. 1mmol/L β-mercaptoethanol, 1 000ng/ml LIF,10 ng/ml IGF, 1mmol/L necessary amino acid and 1mmol/L L-glutamine), then, we obtained mouse ICM and bovine ICM. Moreover, we isolated and cloned the 6 passage bovine ES like cells(12 cell lines) and 9 passage marine ES like cells (52 cell lines) deriving from bovine ICM and murine ICM respectively on the feeder layer of PMEF by disaggregating ICM and ES cell clones of bovine and murine into smaller clumps through digesting with 0. 125g/100ml trypsin and 0.02g/100ml EDTA and scattering with a glass needle. The pluripotency of both murine and bovine ES like cells was identified with morphological character, histochemistry identification, karyotype analysis and differentiation of ES cells in vitro or in vivo. This result showed that bovine embryonic stem cell and murine embryonic stem cell had developmental pluripotency.     

猪L-Myc基因的分子克隆及在细胞重编程中的应用

【目的】克隆猪L-Myc基因,并在蛋白水平表达的情况下探索其在细胞重编程中的作用,为深入研究猪L-Myc基因替代c-Myc诱导多能干细胞（induced pluripotent stem cell,iPSC）奠定基础。【方法】先通过NCBI序列比对,采用RT-PCR克隆猪L-Myc基因cDNA,生物信息学分析猪L-Myc基因与人和小鼠的同源性,构建融合表达载体pEGFP/L-Myc-C1,通过载体转染和免疫印记检测猪L-Myc基因cDNA的蛋白水平表达;再将L-Myc基因装入逆转录病毒载体中,分别使用不同的转录因子诱导猪胎儿成纤维细胞（porcine embryo fibroblast,PEF）,通过形态变化和碱性磷酸酶（AP）染色验证猪L-Myc基因在细胞重编程中的作用。【结果】①获得了1 113 bp的猪L-Myc基因cDNA,编码364个氨基酸,理论分子质量为40 kD;②生物信息学分析显示猪L-Myc基因与人和小鼠高度同源;③免疫印记检测结果说明猪L-Myc基因cDNA能够在蛋白水平表达;④细胞诱导试验和AP染色结果显示转录因子Oct4、Sox2、Klf4和L-Myc（OSKL）组合诱导的细胞阳性克隆率明显高于Oct4、Sox2和Klf4（OSK）组合的阳性克隆率。【结论】获得了猪L-Myc基因,并且该基因在蛋白水平表达且在细胞重编程过程中起到了重要的作用。     

Site-specific gene expression in vivo by direct gene transfer into the arterial wall

A recombinant beta-galactosidase gene has been expressed in a specific arterial segment in vivo by direct infection with a murine amphotropic retroviral vector or by DNA transfection with the use of liposomes. Several cell types in the vessel wall were transduced, including endothelial and vascular smooth muscle cells. After retroviral infection, a recombinant reporter gene was expressed for at least 5 months, and no helper virus was detected. Recombinant gene expression achieved by direct retroviral infection or liposome-mediated DNA transfection was limited to the site of infection and was absent from liver, lung, kidney, and spleen. These results demonstrate that site-specific gene expression can be achieved by direct gene transfer in vivo and could be applied to the treatment of such human diseases as atherosclerosis or cancer.     

杉木无性系测定及速生优良无性系选择

在福建省洋口国有林场,对14年生的杉木无性系测定林进行调查和分析测定,从参试的60个无性系中选择出2594等10个速生优良无性系,14年生时的树高、胸径、材积平均值分别达15.10 m、21.47 cm和0.302 57 m3,与第2代种子园混合种后代相比,材积的现实增益达24.25%,生长性状表现十分突出,具有广阔的推广应用前景.     

楸树无性系苗期年生长参数的分析

对楸树30个无性系苗期苗高和地径的年生长动态进行了调查,并用Logistic方程对苗高和地径的生长动态进行拟合,分析了年生长动态规律及生长参数。研究结果表明:楸树无性系苗期年生长高度符合"S"型生长曲线。分别以苗高和地径划分苗木的年生长阶段,其苗高和地径的速生期持续时间分别为93~136 d和57~120 d,苗高、地径拟合值与苗高、地径实测值呈极显著的相关关系,相关系数分别为0.746 3和0.816 8。无性系的苗高与速生期始期、速生期结束期与速生点、地径与速生期始期呈显著的相关关系。     

Retroviral vector-mediated gene transfer into human hematopoietic progenitor cells

The transfer of the human gene for hypoxanthine phosphoribosyltransferase (HPRT) into human bone marrow cells was accomplished by use of a retroviral vector. The cells were infected in vitro with a replication-incompetent murine retroviral vector that carried and expressed a mutant HPRT complementary DNA. The infected cells were superinfected with a helper virus and maintained in long-term culture. The production of progeny HPRT virus by the bone marrow cells was demonstrated with a colony formation assay on cultured HPRT-deficient, ouabain-resistant murine fibroblasts. Hematopoietic progenitor cells able to form colonies of granulocytes or macrophages (or both) in semisolid medium in the presence of colony stimulating factor were present in the nonadherent cell population. Colony forming units cloned in agar and subsequently cultured in liquid medium produced progeny HPRT virus, indicating infection of this class of hematopoietic progenitor cell.     

基于投影寻踪分类法的甘蔗种质综合评价

基于投影寻踪分类法对40份从法国和菲律宾引进的甘蔗种质进行综合评价。方差分析结果表明,各种质间茎径、单茎质量、蔗糖分等主要工农艺性状均存在显著差异(P0.01),变异系数介于5.68%～51.55%,变异广泛。对各种质的株高、茎径、有效茎、单茎质量、锤度、甘蔗蔗糖分、蔗汁蔗糖分、简纯度和纤维分等9个主要工农艺性状指标进行投影方向和投影值大小分析,结果表明:投影方向以甘蔗蔗糖分的最高,其后依次为锤度、蔗汁蔗糖分、简纯度、单茎质量和茎径等,株高和有效茎的较低;40份种质投影值大小各异,根据投影值大小,结合聚类分析将40份种质划分为5个类群,各类群投影值介于0.00～2.50,其中,第Ⅳ类群的5份种质资源(FR97–127、FR97–53、VMC95–29、VMC96–169和VMC97–30)综合性状表现优良,可供甘蔗杂交利用。综合来看,投影寻踪分类法可作为大量甘蔗种质资源评价的有效途径。     

尾叶桉无性系苗期光合作用特性研究

[目的]探索尾叶桉无性系苗期光合作用指标与生长指标间的关系。[方法]以20个尾叶桉无性系为材料,测定了扦插90d苗木的第3、4片叶的光合作用生理指标,3年后调查了无性系的树高、胸径、冠幅、干形和分枝性状。[结果]尾叶按无性系的净光合速率与光强呈显著的二次曲线关系,光饱和点为1967．7μmol／（m2·s）;不同无性系的光合生理指标存在显著差异,No．23无性系的净光合速率最高（17．178p,moL／（m2·s））,为总体平均值的119．50％;净光合速率、气孔导度的日变化进程具有一定的相似性,8：00～16：00期间相对稳定,18：00突降至最低点;胞间CO2浓度的日变化趋势与净光合速率相反;光合作用特性指标与生长指标存在一定程度的正相关关系。[结论]该研究为尾叶桉无性系的早期选择提供了依据。     

杨树大径级工业用材林适生品种选择

为选择适宜培育杨树大径级工业用材林的优良品种,以生产中广泛应用和新选育的52个黑杨派杨树无性系为材料,进行多点、多年造林试验,对生长量、形质指标、木材材性、性状遗传、抗虫性、抗逆性等性状,采用单性状评价、多性状综合选择.结果表明,优良无性系的材积生长量超过对照I--69杨13.8%~82.0%,各无性系间在生长、干形、冠形、木材材性、抗病虫性、抗逆性等方面存在广泛的遗传变异,且性状受强度或中等遗传控制;20世纪90年代广泛应用的品种以50号、卡帕茨、中林46最好,其次为中林14I、--69、中林28、中林23,以I--214、露易莎、西玛杨较差;20世纪90年代中后期新选育的杨树品种以L35I、--107、L323、L324最好,其次为T26、T66I、--102、中菏1号.     

Distinctive termini characterize two families of human endogenous retroviral sequences

Human DNA contains many copies of endogenous retroviral sequences. Characterization of molecular clones of these structures reveals the existence of two related families. One family consists of full-length (8.8 kilobases) proviral structures, with typical long terminal repeates (LTR's). The other family consists of structures, which contain only 4.1 kilobases of gag-pol sequences, bounded by a tandem array of imperfect repeats 72 to 76 base pairs in length. Typical LTR sequences that exist as solitary elements in the genome were cloned and characterized.