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991.
Tony Gamble Anthony J. Geneva Richard E. Glor David Zarkower 《Evolution; international journal of organic evolution》2014,68(4):1027-1041
To explain the frequency and distribution of heteromorphic sex chromosomes in the lizard genus Anolis, we compared the relative roles of sex chromosome conservation versus turnover of sex‐determining mechanisms. We used model‐based comparative methods to reconstruct karyotype evolution and the presence of heteromorphic sex chromosomes onto a newly generated Anolis phylogeny. We found that heteromorphic sex chromosomes evolved multiple times in the genus. Fluorescent in situ hybridization (FISH) of repetitive DNA showed variable rates of Y chromosome degeneration among Anolis species and identified previously undetected, homomorphic sex chromosomes in two species. We confirmed homology of sex chromosomes in the genus by performing FISH of an X‐linked bacterial artificial chromosome (BAC) and quantitative PCR of X‐linked genes in multiple Anolis species sampled across the phylogeny. Taken together, these results are consistent with long‐term conservation of sex chromosomes in the group. Our results pave the way to address additional questions related to Anolis sex chromosome evolution and describe a conceptual framework that can be used to evaluate the origins and evolution of heteromorphic sex chromosomes in other clades. 相似文献
992.
Michael R. Connor Anthony F. Cann James C. Liao 《Applied microbiology and biotechnology》2010,86(4):1155-1164
Interest in producing biofuels from renewable sources has escalated due to energy and environmental concerns. Recently, the
production of higher chain alcohols from 2-keto acid pathways has shown significant progress. In this paper, we demonstrate
a mutagenesis approach in developing a strain of Escherichia coli for the production of 3-methyl-1-butanol by leveraging selective pressure toward l-leucine biosynthesis and screening for increased alcohol production. Random mutagenesis and selection with 4-aza-d,l-leucine, a structural analogue to l-leucine, resulted in the development of a new strain of E. coli able to produce 4.4 g/L of 3-methyl-1-butanol. Investigation of the host’s sensitivity to 3-methyl-1-butanol directed development
of a two-phase fermentation process in which titers reached 9.5 g/L of 3-methyl-1-butanol with a yield of 0.11 g/g glucose
after 60 h. 相似文献
993.
Alexandra Magro Christine Ducamp Felipe Ramon-Portugal Emilie Lecompte Brigitte Crouau-Roy Anthony Frederick George Dixon Jean-Louis Hemptinne 《Evolutionary ecology》2010,24(1):251-271
Faced with an ephemeral prey, aphidophagous ladybirds rely on the hydrocarbons present in the tracks of their larvae to choose
an unoccupied patch for egg laying. Although both conspecific and heterospecific larval tracks might deter females from oviposition,
the response to the later is often less striking. Several explanations have been suggested to account for this. In this paper
we tested the phylogeny hypothesis, which predicts that the chemical composition of the tracks of closely related species
of ladybirds will be more similar to one another than to those of more distantly related species. Qualitative and quantitative
information on the chemical nature of the larval tracks and a molecular phylogeny of seven species belonging to three different
genera are provided, and the congruence between these two sets of results assessed. The results confirm the phylogeny hypothesis
and infer a gradual mode of evolution of these infochemicals. 相似文献
994.
995.
Vessela D. Kancheva Luciano Saso Petya V. Boranova Abdullah Khan Manju K. Saroj Mukesh K. Pandey Shashwat Malhotra Jordan Z. Nechev Sunil K. Sharma Ashok K. Prasad Maya B. Georgieva Carleta Joseph Anthony L. DePass Ramesh C. Rastogi Virinder S. Parmar 《Biochimie》2010
The chain-breaking antioxidant activities of eight coumarins [7-hydroxy-4-methylcoumarin (1), 5,7-dihydroxy-4-methylcoumarin (2), 6,7-dihydroxy-4-methylcoumarin (3), 6,7-dihydroxycoumarin (4), 7,8-dihydroxy-4-methylcoumarin (5), ethyl 2-(7,8-dihydroxy-4-methylcoumar-3-yl)-acetate (6), 7,8-diacetoxy-4-methylcoumarin (7) and ethyl 2-(7,8-diacetoxy-4-methylcoumar-3-yl)-acetate (8)] during bulk lipid autoxidation at 37 °C and 80 °C in concentrations of 0.01–1.0 mM and their radical scavenging activities at 25 °C using TLC–DPPH test have been studied and compared. It has been found that the o-dihydroxycoumarins 3–6 demonstrated excellent activity as antioxidants and radical scavengers, much better than the m-dihydroxy analogue 2 and the monohydroxycoumarin 1. The substitution at the C-3 position did not have any effect either on the chain-breaking antioxidant activity or on the radical scavenging activity of the 7,8-dihydroxy- and 7,8-diacetoxy-4-methylcoumarins 6 and 8. The comparison with DL-α-tocopherol (TOH), caffeic acid (CA) and p-coumaric acid (p-CumA) showed that antioxidant efficiency decreases in the following sequence: 相似文献
996.
Christopher S. Bland Eric T. Wang Anthony Vu Marjorie P. David John C. Castle Jason M. Johnson Christopher B. Burge Thomas A. Cooper 《Nucleic acids research》2010,38(21):7651-7664
Recent genome-wide analyses have elucidated the extent of alternative splicing (AS) in mammals, often focusing on comparisons of splice isoforms between differentiated tissues. However, regulated splicing changes are likely to be important in biological transitions such as cellular differentiation, or response to environmental stimuli. To assess the extent and significance of AS in myogenesis, we used splicing-sensitive microarray analysis of differentiating C2C12 myoblasts. We identified 95 AS events that undergo robust splicing transitions during C2C12 differentiation. More than half of the splicing transitions are conserved during differentiation of avian myoblasts, suggesting the products and timing of transitions are functionally significant. The majority of splicing transitions during C2C12 differentiation fall into four temporal patterns and were dependent on the myogenic program, suggesting that they are integral components of myogenic differentiation. Computational analyses revealed enrichment of many sequence motifs within the upstream and downstream intronic regions near the alternatively spliced regions corresponding to binding sites of splicing regulators. Western analyses demonstrated that several splicing regulators undergo dynamic changes in nuclear abundance during differentiation. These findings show that within a developmental context, AS is a highly regulated and conserved process, suggesting a major role for AS regulation in myogenic differentiation. 相似文献
997.
Antonio Placido Fran?ois Sieber Anthony Gobert Raffaele Gallerani Philippe Giegé Laurence Maréchal-Drouard 《Nucleic acids research》2010,38(21):7711-7717
All tRNAHis possess an essential extra G–1 guanosine residue at their 5′ end. In eukaryotes after standard processing by RNase P, G–1 is added by a tRNAHis guanylyl transferase. In prokaryotes, G–1 is genome-encoded and retained during maturation. In plant mitochondria, although trnH genes possess a G–1 we find here that both maturation pathways can be used. Indeed, tRNAHis with or without a G–1 are found in a plant mitochondrial tRNA fraction. Furthermore, a recombinant Arabidopsis mitochondrial RNase P can cleave tRNAHis precursors at both positions G+1 and G–1. The G–1 is essential for recognition by plant mitochondrial histidyl-tRNA synthetase. Whether, as shown in prokaryotes and eukaryotes, the presence of uncharged tRNAHis without G–1 has a function or not in plant mitochondrial gene regulation is an open question. We find that when a mutated version of a plant mitochondrial trnH gene containing no encoded extra G is introduced and expressed into isolated potato mitochondria, mature tRNAHis with a G–1 are recovered. This shows that a previously unreported tRNAHis guanylyltransferase activity is present in plant mitochondria. 相似文献
998.
Song Y Zong H Trivedi ER Vesper BJ Waters EA Barrett AG Radosevich JA Hoffman BM Meade TJ 《Bioconjugate chemistry》2010,21(12):2267-2275
Magnetic resonance imaging (MRI) has long been used clinically and experimentally as a diagnostic tool to obtain three-dimensional, high-resolution images of deep tissues. These images are enhanced by the administration of contrast agents such as paramagnetic Gd(III) complexes. Herein, we describe the preparation of a series of multimodal imaging agents in which paramagnetic Gd(III) complexes are conjugated to a fluorescent tetrapyrrole, namely, a porphyrazine (pz). Zinc metalated pzs conjugated to one, four, or eight paramagnetic Gd(III) complexes are reported. Among these conjugates, Zn-Pz-8Gd(III) exhibits an ionic relaxivity four times that of the monomeric Gd(III) agent, presumably because of increased molecular weight and a molecular relaxivity that is approximately thirty times larger, while retaining the intense electronic absorption and emission of the unmodified pz. Unlike current clinical MR agents, Zn-Pz-1Gd(III) is taken up by cells. This probe demonstrates intracellular fluorescence by confocal microscopy and provides significant contrast enhancement in MR images, as well as marked phototoxicity in assays of cellular viability. These results suggest that pz agents possess a new potential for use in cancer imaging by both MRI and near-infrared (NIR) fluorescence, while acting as a platform for photodynamic therapy. 相似文献
999.
The immune system normally responds to influenza virus by making neutralizing antibodies to regions of the viral spike, the hemagglutinin, that vary year to year. This natural response protects against circulating subtypes but necessitates production of new vaccines annually. Newer vaccine approaches have succeeded in eliciting broadly neutralizing antibodies to highly conserved yet vulnerable regions of the hemagglutinin and suggest potential pathways for the development of universal influenza vaccines. 相似文献
1000.
Lang AE 《Nature medicine》2010,16(11):1223-1226
Neurodegenerative diseases such as Parkinson's disease and Alzheimer's disease represent a crucial and exponentially increasing challenge to health care systems throughout the world. There is an urgent need for effective treatments that will both delay their onset and slow their inexorable progression. Many obstacles stand in the way of realizing these goals. It is expected that future advances will have a major impact on how and when the diagnosis will be made. It is hoped that these will eventually make it possible to initiate effective disease-modifying therapies long before the neurodegenerative process becomes established and symptomatic. 相似文献