共查询到20条相似文献,搜索用时 125 毫秒
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1992年3月至5月,作用在陕西省考察,获得陆生贝类一批,经鉴定发现2新种,即双片喇叭螺Boysidia dilamellaris sp.nov.和凤县喇叭螺Boysidia fengxianensis sp.nov.,隶于肺螺亚纲、柄眼目、虹蛹螺科、喇叭螺属。文内对2新种形态特征、栖息环境进行地描述,并对其相似种进行了讨论。 相似文献
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Replacement of two to four guanines by adenines in the human telomere DNA repeat dG3(TTAG3)3 did not hinder the formation of quadruplexes if the substitutions took place in the terminal tetrad bridged by the diagonal loop of the intramolecular antiparallel three‐tetrad scaffold, as proved by CD and PAGE in both Na+ and K+ solutions. Thermodynamic data showed that, in Na+ solution, the dG3(TTAG3)3 quadruplex was destabilized, the least by the two G:A:G:A tetrads, the most by the G:G:A:A tetrad in which the adenosines replaced syn‐guanosines. In physiological K+ solution, the highest destabilization was caused by the 4A tetrad. In K+, only the unmodified dG3(TTAG3)3 quadruplex rearranged into a K+‐dependent quadruplex form, none of the multiple adenine‐modified structures did so. This may imply biological consequences for nonrepaired A‐for‐G mutations. © 2010 Wiley Periodicals, Inc. Biopolymers 93: 880–886, 2010. 相似文献
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Julia D. Harrison 《American anthropologist》2000,102(1):159-160
Oka: Behind the Barricades. 1998. 312 minutes. For more information contact the National Film Board of Canada, 3155 Côte de Lisse Rd., St. Laurent, Quebec H4N 2N4. Series of four videos:
Kanehsatake: 270 Years of Resistance. 1993. 120 minutes. Directed by Alanis Obomsawin .
Spudwrench: Kahnawake Man. 1997. 58 minutes. Directed by Alanis Obomsawin .
My Name is Kahentiiosta. 1995. 30 minutes. Directed by Alanis Obomsawin .
Acts of Defiance. 1992. 104 minutes. Directed by Alec MacLeod . 相似文献
Kanehsatake: 270 Years of Resistance. 1993. 120 minutes. Directed by Alanis Obomsawin .
Spudwrench: Kahnawake Man. 1997. 58 minutes. Directed by Alanis Obomsawin .
My Name is Kahentiiosta. 1995. 30 minutes. Directed by Alanis Obomsawin .
Acts of Defiance. 1992. 104 minutes. Directed by Alec MacLeod . 相似文献
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Using CD and NMR, we determined the structure of an RNA oligomer, r(GGAGGUUUUGGAGG) (R14), comprising two GGAGG segments joined by a UUUU segment. A modified quadruplex structure was observed for r(GGAGGUUUUGGAGG) in solution even in the absence of K(+). An unusually stable dimeric RNA quadruplex architecture formed from two strands of r(GGAGGUUUUGGAGG) at low K(+) concentration is reported here. In each strand of r(GGAGGUUUUGGAGG), two sets of successive turns in the GGAGG segments and turns at both ends of the UUUU loops drive four G-G steps to align in a parallel manner, a core with two stacked G-tetrads being formed. Two adenine bases bind to two edges of one G:G:G:G tetrad through the sheared G:A mismatch augmenting the tetrad into a G:G(:A):G:G(:A) hexad. Thus, one molecule of r(GGAGGUUUUGGAGG) folds into a modified quadruplex comprising a G:G:G:G tetrad, a UUUU double-chain reversal loop and a G:G(:A):G:G(:A) hexad. Two such molecules further associate by stacking through the dimeric hexad-hexad interface with a rotational symmetry. The ribose rings of most nucleotides take S (close to C2'-endo) puckering, which is unusual for an RNA. K(+) can increase the stability of this quadruplex structure; the number of bound K(+) was estimated from the results of the titration experiment. Besides G:G and G:A mismatches, a network of hydrogen bonds including O4'-NH(2) and C-H..O hydrogen bonds, and the extensive base stacking contribute to the high thermodynamic stability of R14. Our results could provide the stereochemical and thermodynamic basis for elucidating the biological role of the GGAGG-containing RNA segments abundantly existing in various RNAs. Relevance to quadruplex-mediated mRNA-FMRP binding and HIV-1 genome RNA dimerization is discussed. 相似文献
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Webba da Silva M 《Biochemistry》2005,44(10):3754-3764
A template-based approach was used to design unprecedented architectural motifs into a known DNA framework. The structure formed by the sequence d(GCGGTTGGAT) in 0.1 M Na(+) solution has been determined using molecular dynamics simulations constrained by distance and dihedral restraints derived from NMR experiments. The molecular topology has been previously observed for the sequence d(GCGGTGGAT) (Webba da Silva, M. (2003) Biochemistry 42, 14356-65). Insertion of a single thymine into the double chain reversal formed by the segment GGTGG results in the unprecedented experimental demonstration of a T:(G:G:G:G):T hexad. The bi-stranded hexad results from the pairing alignment of two G(T-G) triads. Each triad results from recognition of the sheared edge of a guanine by the Watson-Crick edge of a thymine of the segment GGTTGG. The alignment is stabilized by base-stacking of the thymine to the sugar pucker of the preceding thymine. The latter is involved in formation of the T:A:A:T tetrad alignment by forming a hydrogen bond with the free amino proton of a Watson-Crick aligned A:A mispair. We have thus established that residues in double chain reversal loops linking juxtaposed tetrads of a quadruplex stem may facilitate formation of yet unknown hydrogen bond alignments. By employing a systematic approach analysis of sequence motifs appearing in double chain reversals, bridging tetrad layers should allow for the prediction of topologies and architectural motifs appearing in biologically relevant genomic regions. 相似文献
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Chronic Pulmonary Aspergillosis (CPA) is a destructive pulmonary disease caused by a fungal infection, affecting mainly individuals with prior or concurrent pulmonary conditions. It has a global prevalence of 42 per 100,000 population, but in the US and Europe, prevalence is less than 1 per 100,000. The clinical definition of CPA is based on various factors accounting for comorbidities, clinical presentation, and duration. It may be categorized into five subtypes that the disease may evolve between over time. Based on global consensus covering the spectrum of low-resource to high-resource settings, diagnosis is a multi-factorial process that involves a combination of clinical presentation persisting over 3 months, radiological findings, positive culture growth, and serological tests. CPA remains underdiagnosed due to a lack of awareness and is often misdiagnosed due to the comorbidities present. Treatment options are limited due to a lack of research. Furthermore, associated comorbidities and drug interactions further complicate treatment plans. Follow-up throughout treatment should be based on understanding the predictors of mortality. Identification of potential relapse or resistance to antifungal therapy is crucial to limit the low long-term survival rate. Awareness surrounding this devastating disease needs to be raised further to enable earlier identification, improve understanding of patient factors associated with prognosis, and the future potential for targeted therapies. This review aims to raise awareness of this rare condition among practitioners, by providing an overview of common risk factors influencing the prevalence and incidence of the disease. We further discuss current approaches and recent advancements in CPA diagnosis and treatment. 相似文献
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The putative pea PINOID homolog, PsPK2, is expressed in all growing plant parts and is positively regulated by auxin, gibberellin, and cytokinin. Here, we studied hormonal regulation of PsPK2::GUS expression compared with DR5::GUS and PID::GUS in Arabidopsis. PsPK2::GUS, DR5::GUS, and PID::GUS expression in Arabidopsis shoots is mainly localized in the stipules, hydathodes, veins, developing leaves, and cotyledons. Unlike DR5::GUS, PsPK2::GUS, and PID::GUS are weakly expressed in root tips. Both DR5::GUS and PsPK2::GUS are induced by different auxins and are more sensitive to methyl indole acetic acid, 4-chloro-indole acetic acid, and α-naphthalene acetic acid than others. GA(3) has no significant effect on GUS activity in DR5::GUS-transformed seedlings compared to the control, but induction by auxin and gibberellin in combination is synergistic. Cytokinin increases auxin transport in Arabidopsis seedlings. Auxin, gibberellin, and cytokinin all increase GUS activity in shoots of PsPK2::GUS transformed plants compared to the control. However, only auxin and gibberellin increase GUS activity in PID::GUS shoots. In conclusion, auxin, gibberellin, and cytokinin positively regulate PsPK2 expression in shoots, but not in roots. Auxin and gibberellin also upregulate AtPIN1 and LEAFY expression, which is similar to PsPIN1 and Uni in pea. With minor exceptions, the orthologous genes from both species are regulated similarly. 相似文献
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Jay S. Ghurye Victoria Cepeda-Espinoza Mihai Pop 《The Yale journal of biology and medicine》2016,89(3):353-362
Advances in sequencing technologies have led to the increased use of high throughput sequencing in characterizing the microbial communities associated with our bodies and our environment. Critical to the analysis of the resulting data are sequence assembly algorithms able to reconstruct genes and organisms from complex mixtures. Metagenomic assembly involves new computational challenges due to the specific characteristics of the metagenomic data. In this survey, we focus on major algorithmic approaches for genome and metagenome assembly, and discuss the new challenges and opportunities afforded by this new field. We also review several applications of metagenome assembly in addressing interesting biological problems. 相似文献
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Gastric cancer is still one of the most prevalent and deadliest cancers in the world. Although our knowledge about the disease has progressed extraordinarily, this has not been accompanied by our capacity to effectively treat the disease. In the last years, immunotherapy made its way into the cancer field and was responsible for major changes in the treatment success rates for several cancer types. Although gastric cancer was not among the first successful targets of this type of therapy, the relationship between this type of cancer, immunosurveillance and immunotherapy is now being actively researched. In this article, we review the literature of the past year regarding the relationship between gastric cancer, its immune microenvironment and response to immunotherapy. Published data indicate that the immune microenvironment influences the clinical behaviour of gastric cancer, and is correlated with its histologic and molecular subtypes with an emphasis on the microsatellite‐ and EBV‐positive tumour subgroups. Although the literature regarding response to immunotherapy is scarce, there is good evidence that patient stratification for immunotherapy is going to become a reality in gastric cancer. 相似文献
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By definition, a vitamin is a substance that must be obtained regularly from the diet. Vitamin A must be acquired from the diet, but unlike most vitamins, it can also be stored within the body in relatively high levels. For humans living in developed nations or animals living in present-day vivariums, stored vitamin A concentrations can become relatively high, reaching levels that can protect against the adverse effects of insufficient vitamin A dietary intake for six months, or even much longer. The ability to accumulate vitamin A stores lessens the need for routinely consuming vitamin A in the diet, and this provides a selective advantage to the organism. The molecular processes that underlie this selective advantage include efficient mechanisms to acquire vitamin A from the diet, efficient and overlapping mechanisms for the transport of vitamin A in the circulation, a specific mechanism allowing for vitamin A storage, and a mechanism for mobilizing vitamin A from these stores in response to tissue needs. These processes are considered in this review. 相似文献