共查询到20条相似文献，搜索用时 15 毫秒
1.
AG Schepers HJ Snippert DE Stange M van den Born JH van Es M van de Wetering H Clevers 《Science (New York, N.Y.)》2012,337(6095):730-735
The concept that tumors are maintained by dedicated stem cells, the so-called cancer stem cell hypothesis, has attracted great interest but remains controversial. Studying mouse models, we provide direct, functional evidence for the presence of stem cell activity within primary intestinal adenomas, a precursor to intestinal cancer. By "lineage retracing" using the multicolor Cre-reporter R26R-Confetti, we demonstrate that the crypt stem cell marker Lgr5 (leucine-rich repeat-containing heterotrimeric guanine nucleotide-binding protein-coupled receptor 5) also marks a subpopulation of adenoma cells that fuel the growth of established intestinal adenomas. These Lgr5(+) cells, which represent about 5 to 10% of the cells in the adenomas, generate additional Lgr5(+) cells as well as all other adenoma cell types. The Lgr5(+) cells are intermingled with Paneth cells near the adenoma base, a pattern reminiscent of the architecture of the normal crypt niche. 相似文献
2.
Cloning of a factor required for activity of the Ah (dioxin) receptor. 总被引：56，自引：0，他引：56
E C Hoffman H Reyes F F Chu F Sander L H Conley B A Brooks O Hankinson 《Science (New York, N.Y.)》1991,252(5008):954-958
The aryl hydrocarbon (Ah) receptor binds various environmental pollutants, such as polycyclic aromatic hydrocarbons, heterocyclic amines, and polychlorinated aromatic compounds (dioxins, dibenzofurans, and biphenyls), and mediates the carcinogenic effects of these agents. The complementary DNA and part of the gene for an 87-kilodalton human protein that is necessary for Ah receptor function have been cloned. The protein is not the ligand-binding subunit of the receptor but is a factor that is required for the ligand-binding subunit to translocate from the cytosol to the nucleus after binding ligand. The requirement for this factor distinguishes the Ah receptor from the glucocorticoid receptor, to which the Ah receptor has been presumed to be similar. Two portions of the 87-kilodalton protein share sequence similarities with two Drosophila proteins, Per and Sim. Another segment of the protein shows conformity to the consensus sequence for the basic helix-loop-helix motif found in proteins that bind DNA as homodimers or heterodimers. 相似文献
3.
目的分析两种入路显微手术治疗垂体瘤的临床疗效，以探讨合理有效的手术方式．方法将分别采用经鼻、蝶窦入路和经颅人路手术的92例垂体瘤患者分为两组，对其疗效进行对比分析，并观察两组患者治疗后3～12个月的临床疗效．结果手术结果和随访显示：经鼻、蝶窦手术组患者的症状、视力、激素水平恢复情况均明显优于经颅手术组，肿瘤全切率及术后并发症情况亦较优，两组比较差异具有统计学意义（P〈0．05）．结论经鼻、蝶窦入路显微手术治疗垂体瘤是一种安全、有效的手术方法，且并发症少，有进一步临床应用价值． 相似文献
4.
Wirgin I Roy NK Loftus M Chambers RC Franks DG Hahn ME 《Science (New York, N.Y.)》2011,331(6022):1322-1325
The mechanistic basis of resistance of vertebrate populations to contaminants, including Atlantic tomcod from the Hudson River (HR) to polychlorinated biphenyls (PCBs), is unknown. HR tomcod exhibited variants in the aryl hydrocarbon receptor 2 (AHR2) that were nearly absent elsewhere. In ligand-binding assays, AHR2-1 protein (common in the HR) was impaired as compared to widespread AHR2-2 in binding TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) and in driving expression in reporter gene assays in AHR-deficient cells treated with TCDD or PCB126. We identified a six-base deletion in AHR2 as the basis of resistance and suggest that the HR population has undergone rapid evolution, probably due to contaminant exposure. This mechanistic basis of resistance in a vertebrate population provides evidence of evolutionary change due to selective pressure at a single locus. 相似文献
5.
The total RNA was isolated from pokeweed (Phytolacca americana ) leaves using the method of guanidine isothiocyanite and used as a template to amplify the deleted mutant pokeweed antiviral protein (PAP) gene by RT-PCR and then the gene was cloned into the pGEMR-T vector. The sequencing results showed that the PAP gene consisted of 711nt, which was 99.6% identical to the PAP gene reported by Lin et al (1991). The IPTG-inducible expression vector containing the PAP gene was constructed and transferred into the E. coli strain BL21 (DE3)-plysS. A specific protein was produced after induction with 0.4m mol/L IPTG and its molecular weight was 26ku. The results of the double diffusion on the agar plate and the western blotting test showed that the protein produced in E. coli was highly identical with the PAP extracted by a Frenchman from French pokeweed leaves. These revealed that PAP gene was actually achieved and exactly expressed in E . coli. 相似文献
6.
[目的]克隆猪生长激素启动子,确定其启动子核心序列和主要的顺式作用元件。[方法]根据NCBI上公布的序列设计引物,PCR扩增了猪生长激素5’端-1 821～+61 bp的序列,并通过移步缺失的方法,获得9段长短不一的启动子序列,将其分别构建到双荧光素酶表达载体pGL3-basic上。通过重组质粒瞬时转染大鼠垂体瘤细胞(GH3)、猪髋动脉血管内皮细胞(PIEC)和猪肾细胞(PK15)和转染后细胞荧光素酶活性的测定,检测这些5’末端缺失质粒在垂体及非垂体细胞中的相对转录活性。[结果]成功扩增了猪GH基因5’上游启动区1 882 bp的片段,并构建了9个pGL3-mGH promoter报告基因载体;双荧光素酶报告基因检测系统证实插入报告基因载体中的启动子具有非常强的细胞特异性。[结论]猪生长激素特异性在垂体细胞中表达,其最小启动子位于-110 bp以内,启动子区-218～-110 bp和-429～-218 bp间存在正向调控元件。 相似文献
7.
[目的]克隆猪生长激素启动子,确定其启动子核心序列和主要的顺式作用元件。[方法]根据NCBI上公布的序列设计引物,PCR扩增了猪生长激素5’端-1821~+61bp的序列,并通过移步缺失的方法,获得9段长短不一的启动子序列,将其分别构建到双荧光素酶表达载体pGL3-basic上。通过重组质粒瞬时转染大鼠垂体瘤细胞(GH3)、猪髋动脉血管内皮细胞(PIEC)和猪肾细胞(PK15)和转染后细胞荧光素酶活性的测定,检测这些5’末端缺失质粒在垂体及非垂体细胞中的相对转录活性。[结果]成功扩增了猪GH基因5’上游启动区1882bp的片段并构建了9个pGL3-mGHpromoter报告基因载体;双荧光素酶报告基因检测系统证实插入报告基因载体中的启动子具有非常强的细胞特异性。[结论]猪生长激素特异性在垂体细胞中表达,其最小启动子位于-110bp以内,启动子区-218~-110bp和-429~-218bp间存在正向调控元件。 相似文献
8.
大肠息肉癌变的内镜诊断及病理分析 总被引：6，自引：1，他引：5
目的：分析大肠息肉癌变的分布、大小、形态、病理特征及寻求息肉癌变的早期诊断、防治的方法。方法：回顾性分析经内镜诊断的68例（71个）大肠息内癌变的内镜、病理与临床资料。结果：1660例（2540个）大肠息肉中有68例（71个）癌变，癌变率为4．10％，左半结肠息肉癌变69个，占息肉癌变总数的97.18%。绒毛状腺瘤、混合腺瘤癌变率较高（分别为56．76％、14．71％），管状腺瘤癌变率较低（为4．17％）。息肉直径＞2.0cm者癌变率为37.40%，息肉直径1.0-2.0cm者癌变率为4.64%，息肉直径＜1cm者癌变率为0.43%，息肉直径＞2.0cm者癌变率明显高于2.0cm以下者。广基息肉癌变率10.08%。结论：左半结肠息肉、宽基息肉、直径＞2.0cm息肉、绒毛状腺瘤容易癌变。大肠息肉不论大小应尽可能予以切除，全瘤送检。内镜切除大肠息肉可预防息肉癌变。 相似文献
9.
许多研究已表明PRLR基因是影响山羊繁殖力的一个候选基因。课题以内蒙古阿尔巴斯绒山羊为研究对象,利用RT-PCR技术检测PRLR基因在内蒙古绒山羊生殖轴的表达。结果表明,PRLR基因在内蒙古绒山羊下丘脑、垂体、卵巢中均有表达,说明下丘脑、垂体、卵巢是催乳素作用的靶器官,同时也阐明催乳素对内蒙古绒山羊的繁殖力的影响是通过与靶器官受体基因结合来发挥其功能的,为进一步探讨催乳素对内蒙古绒山羊繁殖影响的作用途径及调控机理奠定基础。 相似文献
10.
Two G protein oncogenes in human endocrine tumors 总被引：55，自引：0，他引：55
J Lyons C A Landis G Harsh L Vallar K Grünewald H Feichtinger Q Y Duh O H Clark E Kawasaki H R Bourne 《Science (New York, N.Y.)》1990,249(4969):655-659
Somatic mutations in a subset of growth hormone (GH)-secreting pituitary tumors convert the gene for the alpha polypeptide chain (alpha s) of Gs into a putative oncogene, termed gsp. These mutations, which activate alpha s by inhibiting its guanosine triphosphatase (GTPase) activity, are found in codons for either of two amino acids, each of which is completely conserved in all known G protein alpha chains. The likelihood that similar mutations would activate other G proteins prompted a survey of human tumors for mutations that replace either of these two amino acids in other G protein alpha chain genes. The first gene so far tested, which encodes the alpha chain of Gi2, showed mutations that replaced arginine-179 with either cysteine or histidine in 3 of 11 tumors of the adrenal cortex and 3 of 10 endocrine tumors of the ovary. The mutant alpha i2 gene is a putative oncogene, referred to as gip2. In addition, gsp mutations were found in 18 of 42 GH-secreting pituitary tumors and in an autonomously functioning thyroid adenoma. These findings suggest that human tumors may harbor oncogenic mutations in various G protein alpha chain genes. 相似文献
11.
Aryl hydrocarbon hydroxylase induction in human leukocytes 总被引：6，自引：0，他引：6
A method for determining aryl hydrocarbon hydroxylase induction in human leukocytes is described. Leukocytes from healthy volunteers were cultured in the presence of phytohemagglutinin, a mitogen. Addition of 3-methylcholanthrene to 72-hour cultures induced a fourfold increase in aryl hydroxylase activity. In the absence of a mitogenic agent, 3-methylcholanthrene stimulation of increased enzymatic activity did not occur. 相似文献
12.
Natural aryl hydrocarbon receptor ligands control organogenesis of intestinal lymphoid follicles 总被引：1，自引：0，他引：1
Kiss EA Vonarbourg C Kopfmann S Hobeika E Finke D Esser C Diefenbach A 《Science (New York, N.Y.)》2011,334(6062):1561-1565
13.
Cui H Cruz-Correa M Giardiello FM Hutcheon DF Kafonek DR Brandenburg S Wu Y He X Powe NR Feinberg AP 《Science (New York, N.Y.)》2003,299(5613):1753-1755
Loss of imprinting (LOI), an epigenetic alteration affecting the insulin-like growth factor II gene (IGF2), is found in normal colonic mucosa of about 30% of colorectal cancer (CRC) patients, but it is found in only 10% of healthy individuals. In a pilot study to investigate the utility of LOI as a marker of CRC risk, we evaluated 172 patients at a colonoscopy clinic. The adjusted odds ratio for LOI in lymphocytes was 5.15 for patients with a positive family history [95% confidence interval (95% CI), 1.70 to 16.96; probability P = 0.002], 3.46 for patients with adenomas (95% CI, 1.14 to 11.37; P = 0.026), and 21.7 for patients with CRC (95% CI, 3.48 to 153.6; P = 0.0005). LOI can be assayed with a DNA-based blood test, and it may be a valuable predictive marker of an individual's risk for CRC. 相似文献
14.
Control of cytochrome P1-450 gene expression by dioxin 总被引：34，自引：0，他引：34
15.
Identification of a thyroid hormone receptor that is pituitary-specific 总被引：45，自引：0，他引：45
R A Hodin M A Lazar B I Wintman D S Darling R J Koenig P R Larsen D D Moore W W Chin 《Science (New York, N.Y.)》1989,244(4900):76-79
Three cellular homologs of the v-erbA oncogene were previously identified in the rat; two of them encode high affinity receptors for the thyroid hormone triiodothyronine (T3). A rat complementary DNA clone encoding a T3 receptor form of the ErbA protein, called r-ErbA beta-2, was isolated. The r-ErbA beta-2 protein differs at its amino terminus from the previously described rat protein encoded by c-erbA beta and referred to as r-ErbA beta-1. Unlike the other members of the c-erbA proto-oncogene family, which have a wide tissue distribution, r-erbA beta-2 appears to be expressed only in the anterior pituitary gland. In addition, thyroid hormone downregulates r-erbA beta-2 messenger RNA but not r-erbA beta-1 messenger RNA in a pituitary tumor-derived cell line. The presence of a pituitary-specific form of the thyroid hormone receptor that may be selectively regulated by thyroid hormone could be important for the differential regulation of gene expression by T3 in the pituitary gland. 相似文献
16.
17.
【目的】利用EMS对水稻（Oryza sativa L.）保持系品种宜香1B进行诱变,筛选出3份长护颖突变体。通过基因定位和克隆,探明控制该性状的遗传基础以及分子机理,并在不同器官进行表达分析,了解该基因表达特点。【方法】以3份水稻长护颖突变体Oslg-1、Oslg-2和Oslg-3为材料,进行表型分析、等位性鉴定、基因定位、生物信息学分析,以及qRT-PCR定量表达分析。【结果】Oslg-1突变体小穗在幼穗发育早期与野生型无明显差异,但在成熟期其护颖的远轴表皮细胞凸起且粗糙,形成的结节轴向对齐排列,且毛状物较多,形成垂直相间的横纵沟,与外稃表皮细胞结构相似。遗传分析表明,该类突变表型受1对隐性基因控制,OsLG定位于第7染色体短臂SSR标记RM5344和RM20934之间,遗传距离分别为1.11和0.82 cM,物理距离为246.3 kb。对该区域候选基因分析和测序,发现LOC_Os07g04670基因在编码区第182位碱基（T→A）改变,导致其编码氨基酸第61位（Leu→His）的改变。等位性分析表明,Oslg-2、Oslg-3与Oslg-1属等位变异,进而对突变体Oslg-2和Oslg-3的OsLG测序,突变分别发生在第316位（T→A）和119位（T→C）碱基,导致其编码的氨基酸第106位（Trp→Arg）和第40位（Leu→Pro）突变。对该基因进行同源进化分析和序列比对,表明该基因可能调控水稻护颖伸长。对本突变材料的候选基因和另一控制护颖性状的PAP2进行实时荧光定量PCR（qRT-PCR）分析,结果表明,OsLG在水稻的叶片、穗、叶鞘和根中均有表达,且在穗部表达最高,而PAP2在除穗部以外的其他部位几乎不表达,表明2个控制护颖性状的基因均具有组织特异性,且PAP2的特异性更强;在长护颖突变体中,2个基因表达量均下调,表明其具有协同表达特点。【结论】3份水稻长护颖突变体OsLG与已报道的G1为同一基因,其功能结构域内氨基酸的突变导致长护颖发育;OsLG和PAP2在穗部具有协同表达的特点。 相似文献
18.
Human dioxin-inducible cytochrome P1-450: complementary DNA and amino acid sequence 总被引：23，自引：0，他引：23
Induction of cytochrome P1-450 has been linked to susceptibility to certain chemically induced cancers in mouse and man. Treatment of the human cell line MCF-7 with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) results in high levels of aryl hydrocarbon (benzo[a]pyrene) hydroxylase (P1-450) activity. This cell line was used to isolate a human P1-450 full-length complementary DNA (cDNA) clone. The cDNA is 2566 nucleotides in length, encodes a polyadenylated messenger RNA (2.8 kilobases in length), and has a continuous reading frame producing a protein with 512 residues (molecular weight, 58,151). The human P1-450 cDNA and protein are 63 percent and 80 percent similar to mouse P1-450 cDNA and protein, respectively. Whereas the mouse TCDD-inducible P-450 gene subfamily has two members (P1-450 and P3-450), the human TCDD-inducible gene subfamily appears to have only one gene (P1-450). 相似文献
19.
20.
将IL15和PAP基因通过一甘氨酸接头(Gly4Ser)3连接在一起,构建原核和植物表达载体,以期表达具有导向杀伤活性的融合蛋白.在引物设计中,通过引物在IL15基因下游引入(Gly4Ser)3的编码序列和BamHI位点,然后采取分步克隆及PCR、酶切、连接等一系列分子克隆方法,将IL15和PAP基因融合在一起,构建融合蛋白的原核与植物表达载体.经PCR和NcoI/SalI双酶切鉴定及测序,证实原核表达载体pET32a-IL15/PAP及植物表达载体pB-I P中均插入了正确的融合基因序列. 相似文献