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1.
Our objective was to evaluate the usefulness of the germination vs. the X-ray test in determining the initial viability of seeds of five wild species (Moringa peregrina, Abrus precatorius, Arthrocnemum macrostachyum, Acacia ehrenbergiana and Acacia tortilis) from Saudi Arabia. Usually several days were required to determine the viability of all five species via germination tests. However, X-ray test will give immediate results on filled/viable seeds. Seeds of all species, except Acacia ehrenbergiana and Acacia tortilis showed high viability in both germination (96–72% at 25/15 °C, 94–70% at 35/25 °C) and X-ray (100–80%) test. Furthermore, there was a general agreement between the germination (19%, 14% at 25/15 °C and 17% and 12% at 35/25 °C) and X-ray (8%, 4%) tests in which seed viability of Acacia ehrenbergiana and Acacia tortilis was very low due to insect damaged embryo as shown in X-ray analysis. Seeds of Abruspreca torius have physical dormancy, which was broken by scarification in concentrated sulfuric acid (10 min), and they exhibited high viability in both the germination (83% at 25/15 °C and 81% at 35/25 °C) and X-ray (96%) tests. Most of the nongerminated seeds of the five species except those of Acacia ehrenbergiana and Acacia tortilis, were alive as judged by the tetrazolium test (TZ). Thus, for the five species examined, the X-ray test was proved to be a good and rapid predictor of seed viability.  相似文献   
2.
Identifying which introduced species have the greatest potential for establishment, spread and impact is critical for prioritizing pre‐ and post‐border control. Using species distribution modelling and existing species locations we assessed the establishment risk based on the climatic suitability areas of 25 plant species listed as eradication targets under South African regulations. To improve confidence, three bioclimatic models were used to predict the potential distribution of each species. This information was combined with the number of localities and the “eradication feasibility syndromes” in a scoring‐categorical system to rank the species. Three management groups were identified. Group “A” includes species with medium‐high establishment risk and higher likelihood to be eradicated, these species should be a priority for eradication. Group “B” includes species with a medium‐low establishment risk but given the low number of known population and the species characteristics, eradication is likely to be feasible. Finally species in group “C” scored a medium‐high establishment risk but the eradication would be difficult due to the high number of known localities. This ranking provides a rapid method to prioritize the management towards the eradication of new potential invasive plant species in the country combining the establishment risk, known number of localities and the inferred eradication success.  相似文献   
3.
Herbivory is a fundamental process that controls primary producer abundance and regulates energy and nutrient flows to higher trophic levels. Despite the recent proliferation of small‐scale studies on herbivore effects on aquatic plants, there remains limited understanding of the factors that control consumer regulation of vascular plants in aquatic ecosystems. Our current knowledge of the regulation of primary producers has hindered efforts to understand the structure and functioning of aquatic ecosystems, and to manage such ecosystems effectively. We conducted a global meta‐analysis of the outcomes of plant–herbivore interactions using a data set comprised of 326 values from 163 studies, in order to test two mechanistic hypotheses: first, that greater negative changes in plant abundance would be associated with higher herbivore biomass densities; second, that the magnitude of changes in plant abundance would vary with herbivore taxonomic identity. We found evidence that plant abundance declined with increased herbivore density, with plants eliminated at high densities. Significant between‐taxa differences in impact were detected, with insects associated with smaller reductions in plant abundance than all other taxa. Similarly, birds caused smaller reductions in plant abundance than echinoderms, fish, or molluscs. Furthermore, larger reductions in plant abundance were detected for fish relative to crustaceans. We found a positive relationship between herbivore species richness and change in plant abundance, with the strongest reductions in plant abundance reported for low herbivore species richness, suggesting that greater herbivore diversity may protect against large reductions in plant abundance. Finally, we found that herbivore–plant nativeness was a key factor affecting the magnitude of herbivore impacts on plant abundance across a wide range of species assemblages. Assemblages comprised of invasive herbivores and native plant assemblages were associated with greater reductions in plant abundance compared with invasive herbivores and invasive plants, native herbivores and invasive plants, native herbivores and mixed‐nativeness plants, and native herbivores and native plants. By contrast, assemblages comprised of native herbivores and invasive plants were associated with lower reductions in plant abundance compared with both mixed‐nativeness herbivores and native plants, and native herbivores and native plants. However, the effects of herbivore–plant nativeness on changes in plant abundance were reduced at high herbivore densities. Our mean reductions in aquatic plant abundance are greater than those reported in the literature for terrestrial plants, but lower than aquatic algae. Our findings highlight the need for a substantial shift in how biologists incorporate plant–herbivore interactions into theories of aquatic ecosystem structure and functioning. Currently, the failure to incorporate top‐down effects continues to hinder our capacity to understand and manage the ecological dynamics of habitats that contain aquatic plants.  相似文献   
4.
Unique species of ceramide (Cer) with very-long-chain polyunsaturated fatty acid (VLCPUFA), mainly 28–32 carbon atoms, 4–5 double bonds, in nonhydroxy and 2-hydroxy forms (n-V Cer and h-V Cer, respectively), are generated in rat spermatozoa from the corresponding sphingomyelins during the acrosomal reaction. The aim of this study was to determine the properties of these sperm-distinctive ceramides in Langmuir monolayers. Individual Cer species were isolated by HPLC and subjected to analysis of surface pressure, surface potential, and Brewster angle microscopy (BAM) as a function of molecular packing. In comparison with known species of Cer, n-V Cer and h-V Cer species showed much larger mean molecular areas and increased molecular dipole moments in liquid expanded phases, which suggest bending and partial hydration of the double bonded portion of the VLCPUFA. The presence of the 2-hydoxyl group induced a closer molecular packing in h-V Cer than in their chain-matched n-V Cer. In addition, all these Cer species showed liquid-expanded to liquid-condensed transitions at room temperature. Existence of domain segregation was confirmed by BAM. Additionally, thermodynamic analysis suggests a phase transition close to the physiological temperature for VLCPUFA-Cers if organized as bulk dispersions.  相似文献   
5.
Sticholysin I (St I) is a pore-forming toxin (PFT) produced by the Caribbean Sea anemone Stichodactyla helianthus belonging to the actinoporin protein family, a unique class of eukaryotic PFT exclusively found in sea anemones. As for actinoporins, it has been proposed that the presence of sphingomyelin (SM) and the coexistence of lipid phases increase binding to the target membrane. However, little is known about the role of membrane structure and dynamics (phase state, fluidity, presence of lipid domains) on actinoporins' activity or which regions of the membrane are the most favorable platforms for protein insertion. To gain insight into the role of SM on the interaction of St I to lipid membranes we studied their binding to monolayers of phosphatidylcholine (PC) and SM in different proportions. Additionally, the effect of acyl chain length and unsaturation, two features related to membrane fluidity, was evaluated on St I binding to monolayers. This study revealed that St I binds and penetrates preferentially and with a faster kinetic to liquid-expanded films with high lateral mobility and moderately enriched in SM. A high content of SM induces a lower lateral diffusion and/or liquid-condensed phases, which hinder St I binding and penetration to the lipid monolayer. Furthermore, the presence of lipid domain borders does not appear as an important factor for St I binding to the lipid monolayer.  相似文献   
6.
Peripheral blood mononuclear cell (PBMNC) is one of powerful tools for therapeutic angiogenesis in hindlimb ischemia. However, traditional approaches with transplanted PBMNCs show poor therapeutic effects in severe ischemia patients. In this study, we used autograft models to determine whether hypoxic pretreatment effectively enhances the cellular functions of PBMNCs and improves hindlimb ischemia. Rabbit PBMNCs were cultured in the hypoxic condition. After pretreatment, cell adhesion, stress resistance, and expression of angiogenic factor were evaluated in vitro. To examine in vivo effects, we autografted preconditioned PBMNCs into a rabbit hindlimb ischemia model on postoperative day (POD) 7. Preconditioned PBMNCs displayed significantly enhanced functional capacities in resistance to oxidative stress, cell viability, and production of vascular endothelial growth factor. In addition, autologous transplantation of preconditioned PBMNCs significantly induced new vessels and improved limb blood flow. Importantly, preconditioned PBMNCs can accelerate vessel formation despite transplantation on POD 7, whereas untreated PBMNCs showed poor vascularization. Our study demonstrated that hypoxic preconditioning of PBMNCs is a feasible approach for increasing the retention of transplanted cells and enhancing therapeutic angiogenesis in ischemic tissue.  相似文献   
7.
目的:检测Myc和TP53在食管癌组织和远端无癌组织的表达情况,并分析其与临床病理因素之间的关系,初步探讨Myc和TP53在新疆食管癌发生发展中可能存在的特点。方法:经Trizol一步法提取88例新疆地区食管癌组织及其远端无癌组织标本总RNA,m RNA逆转录为c DNA,经聚合酶链式反应生成产物,运用光密度值即半定量RT-PCR技术检测88例新疆地区食管癌组织、远端无癌组织中Myc和TP53的m RNA表达情况及二者阳性表达率,并分析Myc和TP53的表达与临床病理因素之间的相关性。结果:1 Myc的m RNA相对表达量在食管癌组织中高于远端无癌组织,差异有显著性(P0.01);TP53的m RNA相对表达量在远端无癌组织中高于癌组织(P0.05);2 Myc的阳性表达率在88例食管癌组织中高于远端无癌组织(P0.05);TP53的阳性表达率在远端无癌组织中高于癌组织(P0.05);3Myc的表达与分化程度(P0.01)、TNM分期(P0.01)、淋巴结转移(P0.05)、侵犯深度(P0.05)和族别(P0.05)有关,与性别无关;TP53的表达与侵犯程度(P0.01)有关,与性别、分化程度、TNM分期、淋巴结转移和族别均无关;4 88例食管癌组织中,Myc和TP53的表达呈现负相关(r=-0.501,P0.0 1)。结论:Myc在新疆地区食管癌组织中表达上调,TP53则表达减弱。说明Myc参与食管癌的发生和发展,而TP53则可能保护正常组织不发生癌变。  相似文献   
8.
A better understanding of how ecological novelty influences interactions in new combinations of species is key for predicting interaction outcomes, and can help focus conservation and management efforts on preventing the introduction of novel organisms or species (including invasive species, GMOs, synthetic organisms, resurrected species and emerging pathogens) that seem particularly ‘risky’ for resident species. Here, we consider the implications of different degrees of eco‐evolutionary experience of interacting resident and non‐resident species, define four qualitative risk categories for estimating the probability of successful establishment and impact of novel species and discuss how the effects of novelty change over time. Focusing then on novel predator–prey interactions, we argue that novelty entails density‐dependent advantages for non‐resident species, with their largest effects often being at low prey densities. This is illustrated by a comparison of predator functional responses and prey predation risk curves between novel species and ecologically similar resident species, and raises important issues for the conservation of endangered resident prey species.  相似文献   
9.
Biodiversity‐ecosystem functioning experiments have established that species richness and composition are both important determinants of ecosystem function in an experimental context. Determining whether this result holds for real‐world ecosystem services has remained elusive, however, largely due to the lack of analytical methods appropriate for large‐scale, associational data. Here, we use a novel analytical approach, the Price equation, to partition the contribution to ecosystem services made by species richness, composition and abundance in four large‐scale data sets on crop pollination by native bees. We found that abundance fluctuations of dominant species drove ecosystem service delivery, whereas richness changes were relatively unimportant because they primarily involved rare species that contributed little to function. Thus, the mechanism behind our results was the skewed species‐abundance distribution. Our finding that a few common species, not species richness, drive ecosystem service delivery could have broad generality given the ubiquity of skewed species‐abundance distributions in nature.  相似文献   
10.
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