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111.
Ancient asymmetries in the evolution of flowers 总被引:1,自引:0,他引:1
Dorsoventral asymmetry in flowers is thought to have evolved many times independently as a specialized adaptation to animal pollinators. To understand how such a complex trait could have arisen repeatedly, we have compared the expression of a gene controlling dorsoventral asymmetry in Antirrhinum with its counterpart in Arabidopsis, a distantly related species with radially symmetrical flowers. We found that the Arabidopsis gene is expressed asymmetrically in floral meristems, even though they are destined to form symmetrical flowers. This suggests that, although the flowers of the common ancestor were probably radially symmetrical, they may have had an incipient asymmetry, evident at the level of early gene activity, which could have been recruited many times during evolution to generate asymmetric flowers. 相似文献
112.
P Zapater I Gómez-Hurtado G Peiró JM González-Navajas I García P Giménez A Moratalla J Such R Francés 《PloS one》2012,7(8):e43371
Background
Bacterial translocation is a frequent event in cirrhosis leading to an increased inflammatory response. Splanchnic adrenergic system hyperactivation has been related with increased bacterial translocation. We aim at evaluating the interacting mechanism between hepatic norepinephrine and inflammation during liver damage in the presence of bacterial-DNA.Animals and Methods
Forty-six mice were included in a 16-week protocol of CCl4-induced cirrhosis. Laparotomies were performed at weeks 6, 10, 13 and 16. A second set of forty mice injected with a single intraperitoneal dose of CCl4 was treated with saline, 6-hydroxidopamine, Nebivolol or Butoxamine. After 5 days, mice received E. coli-DNA intraperitoneally. Laparotomies were performed 24 hours later. Liver bacterial-DNA, norepinephrine, TNF-alpha, IL-6 and beta-adrenergic receptor levels were measured.Results
Bacterial-DNA translocation was more frequent in CCl4-treated animals compared with controls, and increased as fibrosis progressed. Liver norepinephrine and pro-inflammatory cytokines were significantly higher in mice with vs without bacterial-DNA (319.7±120.6 vs 120.7±68.6 pg/g for norepinephrine, 38.4±6.1 vs 29.7±4.2 pg/g for TNF-alpha, 41.8±7.4 vs 28.7±4.3 pg/g for IL-6). Only beta-adrenergic receptor-1 was significantly increased in treated vs control animals (34.6±7.3 vs 12.5±5.3, p = 0.01) and correlated with TNF-alpha, IL-6 and norepinephrine hepatic levels in animals with bacterial-DNA. In the second set of mice, cytokine levels were increased in 6-hydroxidopamine and Nebivolol (beta-adrenergic receptor-1 antagonist) treated mice compared with saline. Butoxamine (beta-adrenergic receptor-2 antagonist) didn’t inhibit liver norepinephrine modulation of pro-inflammatory cytokines.Conclusions
Beta-adrenergic receptor-1 mediates liver norepinephrine modulation of the pro-inflammatory response in CCl4-treated mice with bacterial-DNA. 相似文献113.
114.
K?Zouaoui?BoudjeltiaEmail author Ph?Cauchie Cl?Remacle M?Guillaume D?Brohée JL?Hubert M?Vanhaeverbeek 《BMC biotechnology》2002,2(1):8
Background
Determination of clot lysis times on whole blood, diluted whole blood, plasma or plasma fraction has been used for many years to assess the overall activity of the fibrinolytic system. We designed a completely computerised semi-automatic 8-channel device for measurement and determination of fibrin clot lysis. The lysis time is evaluated by a mathematical analysis of the lysis curve and the results are expressed in minute (range: 5 to 9999). We have used this new device for Euglobulin Clot Lysis Time (ECLT) determination, which is the most common test used in laboratories to estimate plasma fibrinolytic capacity. 相似文献115.
Cross-hybridizing snake satellite, Drosophila, and mouse DNA sequences may have arisen independently 总被引:2,自引:0,他引:2
Previous reports have interpreted hybridization between snake satellite DNA
and DNA clones from a variety of distant taxonomic groups as evidence for
evolutionary conservation, which implies common ancestry (homology) and/or
convergence (analogy) to produce the cross- hybridizing sequences. We have
isolated 11 clones from a genomic library of Drosophila melanogaster, using
a cloned 2.5-kb snake satellite probe of known nucleotide sequence. We have
also analysed published sequence data from snakes, mice, and Drosophila.
These data show that (1) all of the cross-hybridization between the snake,
fly, and mouse clones can be accounted for by the presence of either of two
tandem repeats, [GATA]n and [GACA]n and (2) these tandem repeats are
organized differently among the different species. We find no evidence that
these sequences are homologous apart from the existence of the simple
repeat itself, although their divergence from a common ancestral sequence
cannot be ruled out. The sequences contain a variety of homogeneous
clusters of tandem repeats of CATA, GA, TA, and CA, as well as GATA and
GACA. We suggest that these motifs may have arisen by a self-accelerating
process involving slipped-strand mispairing of DNA. Homogeneity of the
clusters might simply be the result of a rate of accumulation of tandem
repeats that exceeds that of other mutations.
相似文献
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119.
Asensio JL; Canada FJ; Bruix M; Gonzalez C; Khiar N; Rodriguez-Romero A; Jimenez-Barbero J 《Glycobiology》1998,8(6):569-577
The specific interaction of hevein with GlcNAc-containing oligosaccharides
has been analyzed by1H-NMR spectroscopy. The association constants for the
binding of hevein to a variety of ligands have been estimated from1H-NMR
titration experiments. The association constants increase in the order
GlcNAc-alpha(1-->6)-Man < GlcNAc < benzyl-beta-GlcNAc <
p-nitrophenyl-beta-GlcNAc < chitobiose < p-
nitrophenyl-beta-chitobioside < methyl-beta-chitobioside <
chitotriose. Entropy and enthalpy of binding for different complexes have
been obtained from van't Hoff analysis. The driving force for the binding
process is provided by a negative DeltaH0which is partially compensated by
negative DeltaS0. These negative signs indicate that hydrogen bonding and
van der Waals forces are the major interactions stabilizing the complex.
NOESY NMR experiments in water solution provided 475 accurate protein
proton-proton distance constraints after employing the MARDIGRAS program.
In addition, 15 unambiguous protein/carbohydrate NOEs were detected. All
the experimental constraints were used in a refinement protocol including
restrained molecular dynamics in order to determine the highly refined
solution conformation of this protein- carbohydrate complex. With regard to
the NMR structure of the free protein, no important changes in the protein
nOe's were observed, indicating that carbohydrate-induced conformational
changes are small. The average backbone rmsd of the 20 refined structures
was 0.055 nm, while the heavy atom rmsd was 0.116 nm. It can be deduced
that both hydrogen bonds and van der Waals contacts confer stability to the
complex. A comparison of the three-dimensional structure of hevein in
solution to those reported for wheat germ agglutinin (WGA) and hevein
itself in the solid state has also been performed. The polypeptide
conformation has also been compared to the NMR-derived structure of a
smaller antifungical peptide, Ac-AMP2.
相似文献
120.