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181.
Mark A. McPeek Laurel B. Symes Denise M. Zong Curtis L. McPeek 《Evolution; international journal of organic evolution》2011,65(2):419-428
The selection pressures imposed by mate choice for species identity should impose strong stabilizing selection on traits that confer species identity to mates. Thus, we expect that such traits should show nonoverlapping distributions among closely related species, but show little to no variance among populations within a species. We tested these predictions by comparing levels of population differentiation in the sizes and shapes of male cerci (i.e., the clasper structures used for species identity during mating) of six Enallagma damselfly species. Cerci shapes were nonoverlapping among Enallagma species, and five of six Enallagma species showed no population variation across their entire species ranges. In contrast, cerci sizes overlapped among species and varied substantially among populations within species. These results, taken with previous studies, suggest that cerci shape is a primary feature used in species recognition used to discriminate conspecific from heterospecifics during mating. 相似文献
182.
Dwarf apple MbDREB1 enhances plant tolerance to low temperature, drought, and salt stress via both ABA-dependent and ABA-independent pathways 总被引:3,自引:0,他引:3
183.
A new species of Orchidaceae, Calanthe yaoshanensis Z. X. Ren & H. Wang from northeastern Yunnan, China, is described and illustrated. It is morphologically similar to C. brevicornu Lindley, from which it differs by having a glabrous column and an elliptical middle lobe with three triangular lamellae. The morphological differences between C. yaoshanensis and related species are discussed. The habitat was investigated and its conservation status was assessed as a ‘Critically Endangered’ (CR). 相似文献
184.
Liu C Sage JC Miller MR Verhaak RG Hippenmeyer S Vogel H Foreman O Bronson RT Nishiyama A Luo L Zong H 《Cell》2011,146(2):209-221
185.
186.
茄子microRNAs与其靶基因的生物信息学预测 总被引:2,自引:0,他引:2
microRNAs(miRNAs)是一类在真核生物中发现的长度为21 nt左右、非编码、内源性的单链小分子RNA,通过与靶基因的互补发挥转录后水平的负调控作用。目前,已在许多物种中报道了miRNAs的存在,然而还未见关于茄子miRNAs的报道。根据miRNAs在植物中的高度保守性及其前体的二级结构特征,文章通过同源预测的方法,将已知植物的miRNAs与茄子EST数据库比对,经过一系列的筛选,最终预测到12个家族的16条茄子miRNAs,其中包括3个miRNA家族的正义/反义miRNAs,而miR390和miR399家族的正义/反义miRNAs属于第一次发现。文章还通过在线软件psRNATarget预测到15条茄子miRNAs的71个靶基因,这些靶基因主要编码与茄子生长发育、新陈代谢以及胁迫响应等过程相关的蛋白。 相似文献
187.
Toosendanin, a triterpenoid from Melia toosendan Sieb et Zucc, has been found before to be an effective anti-botulism agent, with a bi-phasic effect at both motor nerve endings and central
synapse: an initial facilitation followed by prolonged depression. Initial facilitation may be due to activation of voltage-dependent
calcium channels plus inhibition of potassium channels, but the depression is not fully understood. Toosendanin has no effect
on intracellular calcium or secretion in the non-excitable pancreatic acinar cells, ruling out general toosendanin inhibition
of exocytosis. In this study, toosendanin effects on sensory neurons isolated from rat nodose ganglia were investigated. It
was found that toosendanin stimulated increases in cytosolic calcium and neuronal exocytosis dose dependently. Experiments
with membrane potential indicator bis-(1,3-dibutylbarbituric acid)trimethine oxonol found that toosendanin hyperpolarized
capsaicin-insensitive but depolarized capsaicin-sensitive neurons; high potassium-induced calcium increase was much smaller
in hyperpolarizing neurons than in depolarizing neurons, whereas no difference was found for potassium-induced depolarization
in these two types of neurons. In neurons showing spontaneous calcium oscillations, toosendanin increased the oscillatory
amplitude but not frequency. Toosendanin-induced calcium increase was decreased in calcium-free buffer, by nifedipine, and
by transient receptor potential vanilloid 1 (TRPV1) antagonist capsazepine. Simultaneous measurements of cytosolic and endoplasmic
reticulum (ER) calcium showed an increase in cytosolic but a decrease in ER calcium, indicating that toosendanin triggered
ER calcium release. These data together indicate that toosendanin modulates sensory neurons, but had opposite effects on membrane
potential depending on the presence or absence of capsaicin receptor/TRPV 1 channel. 相似文献
188.
Sean J. Wu Christopher B. Eiben John H. Carra Ivan Huang David Zong Peixian Liu Cindy T. Wu Jeff Nivala Josef Dunbar Tomas Huber Jeffrey Senft Rowena Schokman Matthew D. Smith Jeremy H. Mills Arthur M. Friedlander David Baker Justin B. Siegel 《The Journal of biological chemistry》2011,286(37):32586-32592
Past anthrax attacks in the United States have highlighted the need for improved measures against bioweapons. The virulence of anthrax stems from the shielding properties of the Bacillus anthracis poly-γ-d-glutamic acid capsule. In the presence of excess CapD, a B. anthracis γ-glutamyl transpeptidase, the protective capsule is degraded, and the immune system can successfully combat infection. Although CapD shows promise as a next generation protein therapeutic against anthrax, improvements in production, stability, and therapeutic formulation are needed. In this study, we addressed several of these problems through computational protein engineering techniques. We show that circular permutation of CapD improved production properties and dramatically increased kinetic thermostability. At 45 °C, CapD was completely inactive after 5 min, but circularly permuted CapD remained almost entirely active after 30 min. In addition, we identify an amino acid substitution that dramatically decreased transpeptidation activity but not hydrolysis. Subsequently, we show that this mutant had a diminished capsule degradation activity, suggesting that CapD catalyzes capsule degradation through a transpeptidation reaction with endogenous amino acids and peptides in serum rather than hydrolysis. 相似文献
189.
A polysaccharide isolated from Cordyceps sinensis,a traditional Chinese medicine,protects PC12 cells against hydrogen peroxide-induced injury 总被引:12,自引:0,他引:12
Li SP Zhao KJ Ji ZN Song ZH Dong TT Lo CK Cheung JK Zhu SQ Tsim KW 《Life sciences》2003,73(19):2503-2513
Cordyceps sinensis, a well-known traditional Chinese medicine, possesses activities in anti-tumour, anti-oxidation and stimulating the immune system; however, the identity of active component(s) is not determined. By using anti-oxidation activity-guided fractionation, a polysaccharide of molecular weight approximately 210 kDa was isolated from cultured Cordyceps mycelia by ion-exchange and sizing chromatography. The isolated polysaccharide, having strong anti-oxidation activity, contains glucose, mannose and galactose in a ratio of 1 : 0.6 : 0.75. The pre-treatment of isolated polysaccharide on the cultured rat pheochromocytoma PC12 cells shows strong protective effect against hydrogen peroxide (H(2)O(2))-induced insult. Treatment of the cells with the isolated polysaccharide at 100 microg/ml prior to H(2)O(2) exposure significantly elevated the survival of PC12 cells in culture by over 60%. In parallel, the H(2)O(2)-induced production of malondialdehyde in cultured cells was markedly reduced by the polysaccharide treatment. Moreover, the pre-treatment of the isolated polysaccharide significantly attenuated the changes of glutathione peroxidase and superoxide dismutase activities in H(2)O(2)-treated cells in a dose-dependent manner. This is the first report in identifying a polysaccharide from Cordyceps, which protects against the free radical-induced neuronal cell toxicity. 相似文献
190.