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991.
哺乳动物是一类最进化并在地球上占主导地位的动物类群,重建其系统发育关系一直是分子系统学的研究热点。随着越来越多物种全基因组测序的完成,在基因组水平上探讨该类动物的系统发育关系与进化成为研究的热点。本文从全基因组序列,稀有基因组变异及染色体涂染等几个方面简要介绍了当前系统发育基因组学在现生哺乳动物分子系统学中的应用,综合已有的研究归纳整理了胎盘亚纲的总目及目间的系统发育关系,给出了胎盘动物19 个目的系统发育树。本文还分析了哺乳动物系统发育基因组学目前所面临的主要问题及未来的发展前景。 相似文献
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993.
Battles John J. Armesto Juan J. Vann David R. Zarin Daniel J. Aravena Juan Carlos Pérez Cecilia Johnson Arthur H. 《Plant Ecology》2002,158(1):5-19
Research in pristine forests provides a necessary reference of energy and nutrient cycling in absence of anthropogenic influence. Therefore two unpolluted watersheds in the Cordillera de Piuchué of southern Chile (42 °30 S) were chosen for detailed ecosystem analysis. The goals of this study were to quantify the distribution of the living biomass in the research watershed and to document topographic gradients in the vegetation. Across a small spatial gradient from ravine bottom to ridgetop (approximately 60 m in elevation and < 300 m in length) in the Cordillera de Piuchué watersheds, there were significant shifts in vegetation composition, structure, and biomass. Based on sampling in 18, 100 m2 plots, we identified three distinct community associations: a Fitzroya forest at the bottom of the watershed, a mid-slope Pilgerodendron-Tepualia transition zone, and a ridgetop moorland community. The Fitzroya forest was dominated by a cohort of approximately 400 year-old Fitzroya cupressoides trees. Both tree basal area (138 m2/ha) and total live biomass (656 Mg ha–1) reached a maximum in this vegetation type. The Pilgerodendron-Tepualia forest consisted of smaller, shorter, and younger trees with dominance shared by Pilgerodendron uviferum, Tepualia stipularis, and to a lesser extent, F. cupressoides. Basal area and biomass were half that of the Fitzroya forest (69.5 m2 ha–1; 350 Mg ha–1) but tree density was 65% greater. The moorland can best be described as an open community of mosses and cushion plants that included low stature individuals of P. uviferum, F. cupressoides, and T. stipularis. The size and age structure of F. cupressoides in the bottomland forest suggest that the current cohort of adult trees was established following a catastrophic disturbance and that F. cupressoides is unable to regenerate under its own canopy. In contrast, the size structure of the tree populations in the Pilgerodendron-Tepualia zone indicates that all the constituent tree species, except F. cupressoides, are able to reproduce at least at some microsites in the understory. The watershed-level means for live biomass were 306 Mg ha–1 of aboveground tree biomass, 25 Mg ha–1 of large root biomass (diameter ge 1 cm), and 46 Mg ha–1 of small root biomass (diameter < 1 cm). 相似文献
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995.
Xiao-hong Cao Si-si Zhao Dong-yue Liu Zhuo Wang Li-li Niu Li-hua Hou Chun-ling Wang 《Chemico-biological interactions》2011,(1):16
The surfactin can inhibit proliferation and induce apoptosis in cancer cells. Moreover, surfactin can induce cell death in human breast cancer MCF-7 cells through mitochondrial pathway. However, the molecular mechanism involved in this pathway remains to be elucidated. Here, the reactive oxygen species (ROS) and Ca2+ on mitochondria permeability transition pore (MPTP) activity, and MCF-7 cell apoptosis which induced by surfactin were investigated. It is found that surfactin evoked mitochondrial ROS generation, and the surfactin-induced cell death was prevented by N-acetylcysteine (NAC, an inhibitor of ROS). An increasing cytoplasmic Ca2+ concentration was detected in surfactin-induced MCF-7 apoptosis, which was inhibited by 1,2-bis (2-aminophenoxy) ethane-N,N,N′,N′-tetraacetic acid (BAPTA-AM, a chelator of calcium). In addition, the relationship between ROS generation and the increase of cytoplasm Ca2+ was determined. The results showed that surfactin initially induced the ROS formation, leading to the MPTP opening accompanied with the collapse of mitochondrial membrane potential (ΔΨm). Then the cytoplasmic Ca2+ concentration increased in virtue of the changes of mitochondrial permeability, which was prevented by BAPTA-AM. Besides, cytochrome c (cyt c) was released from mitochondria to cytoplasm through the MPTP and activated caspase-9, eventually induced apoptosis. In summary, surfactin has notable anti-tumor effect on MCF-7 cells, however, there was no obvious cytotoxicity on normal cells. 相似文献
996.
Luca Testi Francisco Orgaz Francisco Villalobos 《Environmental and Experimental Botany》2008,63(1-3):168-177
We measured eddy covariance fluxes of CO2 and H2O over a flat irrigated olive orchard during growth, in different periods from Leaf Area Index (LAI) of 0.3–1.9; measurements of soil respiration were also collected. The daily net ecosystem exchange flux (FNEE) was practically zero at LAI around 0.4 or when the orchard intercepted 11% of the incoming daily radiation; at the end of the experiment, with LAI of 1.9 (and the fraction of intercepted daily radiation close to 0.5), FNEE was around 10 g CO2 m−2 day−1. The night-time ecosystem respiration (Reco), calculated from eddy fluxes in well-mixed night conditions, show a clear but non-linear dependence with LAI; it ranged from 0.05 to 0.15 mg CO2 m−2 s−1 (in average), being the lower limit ideally close to the heterotrophic soil respiration at the site. The gross primary production flux (FGPP) was linearly related to LAI within the LAI range of this experiment (with 11 g CO2 m−2 day−1 increments per unit of LAI) and to the fraction of intercepted radiation. The maximum rates of FGPP (0.75 mg CO2 m−2 s−1) were obtained in the summer mornings of 2002, at LAI close to 1.9. FGPP was strongly modulated by vapour pressure deficit (VPD) through the canopy conductance, even in absence of water stress. Hence, especially in the summer, the maximum rates of carbon assimilation are reached always before noon. The daily course of FGPP shows a two-phase pattern, first related to irradiance and then to canopy conductance. The water use efficiency (WUE) was, in average, 3.8, 6.3 and 7 g CO2 L−1 in 1999, 2001 and 2002, respectively, with maxima always in the early morning. Hourly WUE was strongly related to VPD (WUE = −10.25 + 22.52 × VPD−0.34). Our results suggest that drip irrigated orchards in general, and olive in particular, deserve specific carbon exchange and carbon budget studies and cannot be easily included in other biomes. 相似文献
997.
Introduced exotic species cause environmental changes and threat public health in target sites. Illegal trade has enhanced this problem. To first report these risks in Brazil, exotic snakes found in São Paulo City (SPC) (23°32 S, 46°38 W), southeastern Brazil, and sent to Instituto Butantan between 1995 and 2000, were listed and characterized by their biological attributes. Seventy-six individuals of sixteen alien species were collected. Euriecians snakes, mainly booids, were predominant. Using multivariate techniques, their ecological niches were compared to those of 26 native species, as a way to point out the resource's availability. To evaluate the potential of successful implantation, two species absent in SPC and considered as problem snakes are included in these analyses: the brown treesnake Boiga irregularis and the habu Trimeresurus flavoviridis. There were niche similarities between these pest snakes, exotic booids and native viperids largely due to the similarities in the chosen prey (mammals), diel activity (nocturnal), color pattern (variegated) and body size (medium to large). To avoid predictable undesirable effects of implanted pest snakes, traffic control and punishment should be improved, as well as parallel environmental education programs. 相似文献
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999.
1000.
Abstract 1 Since the late 1970s, the western flower thrips has spread from its original distribution in western North America to become a major worldwide crop pest. 2 A wide range of data sources have been used to map the original distribution in the U.S.A. and Canada, and the progress of the spread in the U.S.A., Canada, Europe, northern Africa and Australia. 3 The possible reasons for the start of the spread are discussed. The most likely reason is that intensive insecticide use in horticulture in the 1970s and 1980s selected an insecticide resistant strain or strains. These then established in glasshouses across North America and spread from there to Europe, Asia, Africa and Australia. 4 The international spread of the western flower thrips occurred predominantly by the movement of horticultural material, such as cuttings, seedlings and potted plants. Within Europe, an outward spread from the original outbreak in the Netherlands is discernible. The speed of spread was 229 ± 20 km/year. 5 The spread has not been restricted to glasshouses. The western flower thrips has established outdoors in areas with milder winters; for example, across the southern U.S.A., southern Europe and Australia. It also overwinters in some regions with colder winters. 6 Polyphagous phytophagous thrips have many factors predisposing them to become worldwide crop pests, particularly in glasshouses. Some other species that might spread in a similar way to the western flower thrips are listed. 相似文献