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971.
In this study, we used a random approach to determine which amino acid pairs in human coagulation factor IX precursor are more sensitive to its 99 variants. The results show that the randomly unpredictable amino acid pairs are more sensitive to variants. 相似文献
972.
Lian C Oishi R Miyashita N Nara K Nakaya H Wu B Zhou Z Hogetsu T 《Molecular ecology》2003,12(3):609-618
The early stage of volcanic desert succession is underway on the southeastern slope of Mount Fuji. We used markers of nuclear microsatellites (simple sequence repeats; SSR) and chloroplast microsatellites (cpSSR) to investigate the population genetic structure and reproduction dynamics of Salix reinii, one of the dominant pioneer shrubs in this area. The number of S. reinii genets in a patch and the area of the largest genet within the patch increased with patch area, suggesting that both clonal growth and seedling recruitment are involved in the reproduction dynamics of S. reinii. Five polymorphic cpSSR markers were developed for S. reinii by sequencing the noncoding regions between universal sequences in the chloroplast genome. Nineteen different cpSSR haplotypes were identified, indicating that S. reinii pioneer genets were created by the long-distance dispersal of seeds originating from different mother genets around the study site, where all vegetation was destroyed during the last eruption. Furthermore, the clustered distributions of different haplotypes within each patch or plot suggested that newly colonized genets tended to be generated from seeds dispersed near the initially established mother genets. These results revealed that the establishment of the S. reinii population on the southeastern slope of Mount Fuji involved two sequential modes of seed dispersal: long-distance dispersal followed by short-distance dispersal. 相似文献
973.
Induction of cytochrome P450 1A is required for circulation failure and edema by 2,3,7,8-tetrachlorodibenzo-p-dioxin in zebrafish 总被引:1,自引:0,他引:1
Teraoka H Dong W Tsujimoto Y Iwasa H Endoh D Ueno N Stegeman JJ Peterson RE Hiraga T 《Biochemical and biophysical research communications》2003,304(2):223-228
The mechanism of toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is thought to result from changes in gene expression via the aryl hydrocarbon receptor (AHR). The induction of cytochrome P450 1A (CYP1A) in various organs is a cardinal effect of TCDD. However, whether CYP1A is involved in endpoints of TCDD toxicity is controversial. We investigated the role of CYP1A in TCDD-induced developmental toxicities using gene knock-down with morpholino antisense oligos. Exposure of zebrafish embryos to TCDD, at concentrations eliciting the hallmark endpoints of developmental toxicity, induced CYP1A in the heart and vascular endothelium throughout the body. This induction by TCDD was markedly inhibited by morpholinos to zebrafish arylhydrocarbon receptor 2 (zfAHR2-MO) and to zebrafish CYP1A (zfCYP1A-MO). The zfAHR2-MO but not the zfCYP1A-MO inhibited zfCYP1A mRNA expression, indicating the specificities of these morpholinos. Injection of either zfAHR2-MO or zfCYP1A-MO blocked the representative signs of TCDD developmental toxicity in zebrafish, pericardial edema and trunk circulation failure. The morpholinos appeared do not affect normal development in TCDD-untreated embryos. These results suggest a mediatory role of zfCYP1A induction through zfAHR2 activation in causing circulation failure by TCDD in zebrafish. This is the first molecular evidence demonstrating an essential requirement for CYP1A induction in TCDD-evoked developmental toxicities in any vertebrate species. 相似文献
974.
975.
976.
A pair of stereoisomeric covalent adducts to guanine in double-stranded DNA, derived from the reaction of mutagenic and tumorigenic metabolites of benzo[a]pyrene, have been well characterized structurally and thermodynamically. Both high-resolution NMR solution structures and an array of thermodynamic data are available for these 10S (+)- and 10R (-)-trans-anti -[BP]-N(2)-dG adducts in double-stranded deoxyoligonucleotides. The availability of experimentally well-characterized duplexes containing these two stereoisomeric guanine adducts provides an opportunity for evaluating the molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) method for computing thermodynamic properties from molecular dynamics ensembles. We have carried out 3-ns molecular dynamics simulations, using NMR solution structures as the starting models for the 10S (+)- and 10R (-)-trans-anti-dG adducts in a DNA duplex 11-mer using AMBER 6.0. We employed the MM-PBSA method to compute the free energies, enthalpies, and entropies of the two adducts. Our complete thermodynamic analysis agrees quite well with the full experimental thermodynamic characterization of these adducts, showing essentially equal stabilities of the two adducts. We also calculated the nuclear Overhauser effect (NOE) distances from the molecular dynamics trajectories, and compared them against the experimental NMR-derived NOE distances. Our results showed that the simulated structures are in good agreement with the NMR experimental NOE data. Furthermore, the molecular dynamics simulations provided new structural and biological insights. Specifically, the puzzling observation that the BP aromatic ring system in the 10S (+)-trans-anti-dG adduct is more exposed to the aqueous solvent than the 10R (-)-trans-anti-dG adduct, is rationalized in terms of the adduct structures. The structural and thermodynamic features of these stereoisomeric adducts are also discussed in relation to their reported low susceptibilities to nucleotide excision repair. 相似文献
977.
Genomic Analysis Reveals Chromosomal Variation in Natural Populations of the Uncultured Psychrophilic Archaeon Cenarchaeum symbiosum 总被引:3,自引:0,他引:3 下载免费PDF全文
Christa Schleper Edward F. DeLong Christina M. Preston Robert A. Feldman Ke-Ying Wu Ronald V. Swanson 《Journal of bacteriology》1998,180(19):5003-5009
Molecular phylogenetic surveys have recently revealed an ecologically widespread crenarchaeal group that inhabits cold and temperate terrestrial and marine environments. To date these organisms have resisted isolation in pure culture, and so their phenotypic and genotypic characteristics remain largely unknown. To characterize these archaea, and to extend methodological approaches for characterizing uncultivated microorganisms, we initiated genomic analyses of the nonthermophilic crenarchaeote Cenarchaeum symbiosum found living in association with a marine sponge, Axinella mexicana. Complex DNA libraries derived from the host-symbiont population yielded several large clones containing the ribosomal operon from C. symbiosum. Unexpectedly, cloning and sequence analysis revealed the presence of two closely related variants that were consistently found in the majority of host individuals analyzed. Homologous regions from the two variants were sequenced and compared in detail. The variants exhibit >99.2% sequence identity in both small- and large-subunit rRNA genes and they contain homologous protein-encoding genes in identical order and orientation over a 28-kbp overlapping region. Our study not only indicates the potential for characterizing uncultivated prokaryotes by genome sequencing but also identifies the primary complication inherent in the approach: the widespread genomic microheterogeneity in naturally occurring prokaryotic populations. 相似文献
978.
胆固醇逆向转运的分子机制 总被引:9,自引:0,他引:9
胆固醇逆向转运是周围细胞胆固醇转运至肝脏转化、清除的重要生理过程,它在维持机体胆固醇代谢平衡和对抗动脉粥样硬化发生及发展中起重要作用。研究证实胆固醇逆向转运直是高密度脂蛋白在多种生物活性分子参与下,由新生前β-HDL到成熟α-HDL递变的胆固醇转运及代谢过程。 相似文献
979.
杀灭土壤中线虫对小麦生长和吸收N,P的影响 总被引:8,自引:2,他引:8
盆栽条件下研究了施用杀线剂(克线磷,67mg·kg-1干土)和干热(105℃,2h)两种杀线措施对小麦生长和N、P养分吸收的影响.杀线剂对土壤中线虫的平均杀灭率约为80%,干热处理的杀灭率为100%.在杀线剂处理中,苗期至抽穗期小麦生物量、拔节期至成熟期植株含N量、全生育期植株吸N量以及抽穗和成熟期吸P量均显著低于对照.土壤干热处理后抽穗和成熟期小麦的生物量、含N量及N、P吸收量也比对照显著降低.两种杀线处理植株地上部生物量和N、P吸收量与相应处理全株变化趋势基本一致.但杀灭线虫对植株含P量影响较小.分析杀线虫后小麦生长和养分吸收受抑主要与土壤有机氮的矿化作用减弱、微生物活动产生的植物生长促进物质降低有关 相似文献
980.
大鼠催乳素基因真核细胞可表达性质粒的构建及应用研究 总被引:4,自引:0,他引:4
735bp的PRLcDNA片段从质粒PRL-SP65#1中回收后,用粘性末端连接法将其重组到真核表达载体pcDNA3上,筛选出正向连接重组体pcDNA3-PRLS和反向连接重组体pcDNA3-PRLAS。将重组体pcDNA3-PRLs和空载体pcDNA3分别转入NIH3T3细胞系,用G418筛选出阳性细胞后与未转染的NIH3T3细胞在加E2和不加E2的情况下,用原位杂交的方法,分别用PRLcDNA探针和原癌基因c-H-rascDNA探针进行检测,未转染的NIH3T3细胞在加E2和不加E2时都几乎无催乳素基因的表达,同样,转入空载体的NIH3T3细胞也无PRL的表达,而转入重组体pcDNA3-PRLS的NIH3T3细胞则有大量的PRL基因的表达,与对照组相比有显著差异(P<0.01)。正常和转入空载体的NIH3T3细胞有一定程度的原癌基因c-H-ras的表达,当分别加入E2和转入重组体pcDNA3-PRLS后,NIH3T3细胞中的c-H-ras基因表达水平都显著升高(P<0.05)。 相似文献