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981.
982.
Yan Xiao Junbing Tang Hua Qing Changfang Zhou Weijing Kong Shuqing An 《Hydrobiologia》2011,658(1):353-363
The purpose of this article was to study the trade-offs among vegetative growth, clonal, and sexual reproduction in an aquatic
invasive weed Spartina alterniflora that experienced different inundation depths and clonal integration. Here, the rhizome connections between mother and daughter
ramets were either severed or left intact. Subsequently, these clones were flooded with water levels of 0, 9, and 18 cm above
the soil surface. Severing rhizomes decreased growth and clonal reproduction of daughter ramets, and increased those of mother
ramets grown in shallow and deep water. The daughter ramets disconnected from mother ramets did not flower, while sexual reproduction
of mother ramets was not affected by severing. Clonal integration only benefited the total rhizome length, rhizome biomass,
and number of rhizomes of the whole clones in non-inundation conditions. Furthermore, growth and clonal reproduction of mother,
daughter ramets, and the whole clone decreased with inundation depth, whereas sexual reproduction of mother ramets and the
whole clones increased. We concluded that the trade-offs among growth, clonal, and sexual reproduction of S. alterniflora would be affected by inundation depth, but not by clonal integration. 相似文献
983.
Dirong Gong Xiaoyu Jia Baolin Wang Feng Wang Chunyu Zhang Liansheng Jiang 《Inorganica chimica acta》2011,373(1):47-53
A series of 2,6-bis(imino)pyridyl iron(III) complexes of the general formula [2,6-(ArNCMe)2C5H3N]FeCl3 (Ar = -C6H5, 3a; 2-MeC6H4, 3b; 2-EtC6H4, 3c; 2-iPrC6H4, 3d; cyclohexyl, 3e; 4-MeC6H4, 3f; 4-iPrC6H4, 3g; 4-FC6H4, 3h and 4-CF3C6H4, 3i), activated by alkylaluminum, MAO or MMAO, have been investigated in 1,3-butadiene polymerization. Iron(III) complex (3a), with the least steric hindrance around the metal center, gives polymer up to 99% in yield in 4 h (butadiene to iron ratio = 1000), and trans-1,4 selectivity about 94.7% at room temperature in toluene, while those (3b-3d) bearing alkyl substituents at the 2-position of each N-aryl ring exhibit much lower catalytic activity and tunable trans-1,4 selectivity. Introduction of an alkyl group at the 4-position (para-position, 3f and 3g) exerts a slightly beneficial effect on the trans-1,4 selectivity, while electronegative groups at the same position (3h and 3i) affect negatively on the activity. The effects of temperature, types of cocatalyst and Al/Fe molar ratio on the polymerization behavior are investigated. More importantly, a mechanism for forming trans-1,4 structure is also proposed. 相似文献
984.
Xu S Schlüter PM Scopece G Breitkopf H Gross K Cozzolino S Schiestl FP 《Evolution; international journal of organic evolution》2011,65(9):2606-2620
Floral isolation is an important component of pollinator-driven speciation. However, up to now, only a few studies have quantified its strength and relative contribution to total reproductive isolation. In this study, we quantified floral isolation among three closely related, sympatric orchid species of the genus Ophrys by directly tracking pollen flow. Ophrys orchids mimic their pollinators' mating signals, and are pollinated by male insects during mating attempts. This pollination system, called sexual deception, is usually highly specific. However, whether pollinator specialization also conveys floral isolation is currently under debate. In this study, we found strong floral isolation: among 46 tracked pollen transfers in two flowering seasons, all occurred within species. Accounting for observation error rate, we estimated a floral isolation index ≥0.98 among each pair of species. Hand pollination experiments suggested that postpollination barriers were effectively absent among our study species. Genetic analysis based on AFLP markers showed a clear species clustering and very few F(1) hybrids in natural populations, providing independent evidence that strong floral isolation prevents significant interspecies gene flow. Our results provide the first direct evidence that floral isolation acts as the main reproductive barrier among closely related plant species with specialized pollination. 相似文献
985.
986.
Dan Wang Jing Mao Bin Zhou Xiao-Fu Liao Shi-Qiang Gong Yan Liu Jing-Tao Zhang 《Biotechnology letters》2011,33(1):191-197
Purpose of work
Our study provides a promising alternative of biomimetic coating which functionalizes the dental implant with adhesion peptides and may be useful for enhancing the bone remodeling around Ti implants. 相似文献987.
In Pseudomonas aeruginosa, quorum sensing (QS) regulates dozens of genes and proteins, many of which contribute to the virulence of this pathogen.
QS inhibitory (QSI) compounds have been proposed as potential agents for treatment of bacterial infections. To search for
Ps. aeruginosa QS inhibitors, we constructed an effective screening system, QSIS-lasI selector, based on the PlasI-sacB reporter, in which QS could be induced with 20 nM 3-oxo-N-[(3S)-tetrahydro-2-oxo-3-furanyl]-dodecanamide (3-oxo-C12-HSL). During screening of the crude extracts from 65 marine fungi, an isolate of Penicillium atramentosum was found to have QSI activity. Thin-layer chromatography assay of the fungal extracts for bioautographic identification
of QSIS-lasI indicated that this fungus produced several QSI compounds, including QS inhibitors other than penicillic acid or patulin. 相似文献
988.
Evidence is accumulating that estradiol (E2) may play a dual role in carcinogenic and anticarcinogenic effects by different metabolic pathways. It has been shown that some metabolites of E2 exert proliferative and others anti-proliferative properties on human cancer cells. In the present study, the effects of E2 and its four primary metabolites including 2-hydroxyestradiol (2OHE2), 4-hydroxyestradiol (4OHE2), 2-methoxyestradiol (2ME), and 4-methoxyestradiol (4ME) on proliferation and cell cycle in RL95-2 human endometrial cells were investigated. Our results indicate that 2ME and 2OHE2, but not E2, 4ME, and 4OHE2, exhibit the inhibitory effect through cell cycle arrest at G2/M. 2ME and 2OHE2-induced G2/M cell cycle arrest associated with activation of p53 (Ser15), upregulation of p21(WAF1/Cip1) (p21) and GADD45, inactivation of Cdc2 (Tyr15), as well as downregulation of Cyclin B1. 2ME and 2OHE2-mediated cell cycle arrest at G2/M was also related to activation of protein kinase Chk1 which is associated with p53 (Ser20) activation and downstream responses. 相似文献
989.
990.
Min Fei Na Li Yuguan Ze Jie Liu Xiaolan Gong Yanmei Duan Xiaoyang Zhao Han Wang Fashui Hong 《Biological trace element research》2011,139(1):72-80
In order to study the mechanisms underlying the effects of lanthanoid (Ln) on the liver, ICR mice were injected with LaCl3, CeCl3, and NdCl3 at a dose of 20 mg/kg BW into the abdominal cavity daily for 14 days. We then examined oxidative stress-mediated responses
in the liver. The increase of lipid peroxide in the liver produced by Ln suggested an oxidative attack that was activated
by a reduction of antioxidative defense mechanisms as measured by analyzing the activities of superoxide dismutase, catalase,
and ascorbate peroxidase, as well as antioxidant levels such as glutathione and ascorbic acid, which were greatest in Ce3+ treatment, medium in Nd3+, and least in La3+. Our results also implied that the oxidative stress in the liver caused by Ln likely is Ce3+ > Nd3+ >La3+, but the mechanisms need to be further studied in future. 相似文献