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1.
Novel synthetic mimics of antimicrobial peptides have been developed to exhibit structural properties and antimicrobial activity similar to those of natural antimicrobial peptides (AMPs) of the innate immune system. These molecules have a number of potential advantages over conventional antibiotics, including reduced bacterial resistance, cost-effective preparation, and customizable designs. In this study, we investigate a family of nylon-3 polymer-based antimicrobials. By combining vesicle dye leakage, bacterial permeation, and bactericidal assays with small-angle X-ray scattering (SAXS), we find that these polymers are capable of two interdependent mechanisms of action: permeation of bacterial membranes and binding to intracellular targets such as DNA, with the latter necessarily dependent on the former. We systemically examine polymer-induced membrane deformation modes across a range of lipid compositions that mimic both bacteria and mammalian cell membranes. The results show that the polymers' ability to generate negative Gaussian curvature (NGC), a topological requirement for membrane permeation and cellular entry, in model Escherichia coli membranes correlates with their ability to permeate membranes without complete membrane disruption and kill E. coli cells. Our findings suggest that these polymers operate with a concentration-dependent mechanism of action: at low concentrations permeation and DNA binding occur without membrane disruption, while at high concentrations complete disruption of the membrane occurs. This article is part of a Special Issue entitled: Interfacially Active Peptides and Proteins. Guest Editors: William C. Wimley and Kalina Hristova.  相似文献   
2.
Temperature and nutrient availability play key roles in controlling the pathways and rates at which energy and materials move through ecosystems. These factors have also changed dramatically on Earth over the past century as human activities have intensified. Although significant effort has been devoted to understanding the role of temperature and nutrients in isolation, less is known about how these two factors interact to influence ecological processes. Recent advances in ecological stoichiometry and metabolic ecology provide a useful framework for making progress in this area, but conceptual synthesis and review are needed to help catalyze additional research. Here, we examine known and potential interactions between temperature and nutrients from a variety of physiological, community, and ecosystem perspectives. We first review patterns at the level of the individual, focusing on four traits – growth, respiration, body size, and elemental content – that should theoretically govern how temperature and nutrients interact to influence higher levels of biological organization. We next explore the interactive effects of temperature and nutrients on populations, communities, and food webs by synthesizing information related to community size spectra, biomass distributions, and elemental composition. We use metabolic theory to make predictions about how population‐level secondary production should respond to interactions between temperature and resource supply, setting up qualitative predictions about the flows of energy and materials through metazoan food webs. Last, we examine how temperature–nutrient interactions influence processes at the whole‐ecosystem level, focusing on apparent vs. intrinsic activation energies of ecosystem processes, how to represent temperature–nutrient interactions in ecosystem models, and patterns with respect to nutrient uptake and organic matter decomposition. We conclude that a better understanding of interactions between temperature and nutrients will be critical for developing realistic predictions about ecological responses to multiple, simultaneous drivers of global change, including climate warming and elevated nutrient supply.  相似文献   
3.
Persistent quadriceps strength deficits in individuals with anterior cruciate ligament reconstruction (ACLr) have been attributed to arthrogenic muscle inhibition (AMI). The purpose of the present study was to investigate the effect of vibration-induced hamstrings fatigue on AMI in patients with ACLr. Eight participants with unilateral ACLr (post-surgery time: M = 46.5, SD = 23.5 months; age: M = 21.4, SD = 1.4 years) and eight individuals with no previous history of knee injury (age: M = 22.5, SD = 2.5 years) were recruited. A fatigue protocol, consisting of 10 min of prolonged local hamstrings vibration, was applied to both the ACLr and control groups. The central activation ratio (CAR) of the quadriceps was measured with a superimposed burst of electrical stimulation, and hamstrings/quadriceps coactivation was assessed using electromyography (EMG) during isometric knee extension exercises, both before and after prolonged local vibration. For the ACLr group, the hamstrings strength, measured by a load cell on a purpose-built chair, was significantly (P = 0.016) reduced about 14.5%, indicating fatigue was actually induced in the hamstrings. At baseline, the ACLr group showed a trend (P = 0.051) toward a lower quadriceps CAR (M = 93.2%, SD = 6.2% versus M = 98.1%, SD = 1.1%) and significantly (P = 0.001) higher hamstrings/quadriceps coactivation (M = 15.1%, SD = 6.2% versus M = 7.5%, SD = 4.0%) during knee extension compared to the control group. The fatigue protocol significantly (P = 0.001) increased quadriceps CAR (from M = 93.2%, SD = 6.2% to M = 97.9%, SD = 2.8%) and significantly (P = 0.006) decreased hamstrings/quadriceps coactivation during knee extension (from M = 15.1%, SD = 6.2% to M = 9.5%, SD = 4.5%) in the ACLr group. In conclusion, vibration-induced hamstrings fatigue can alleviate AMI of the quadriceps in patients with ACLr. This finding has clinical implications in the management of recovery for ACLr patients with quadriceps strength deficits and dysfunction.  相似文献   
4.
目的:探讨来曲唑联合妈富隆治疗多囊卵巢综合征患者的临床疗效。方法:选择2015年12月至2017年12月我院接诊的90例多囊卵巢综合征患者,通过随机数表法分为观察组(n=46)和对照组(n=44)。对照组给予妈富隆治疗,观察组联合来曲唑治疗。比较两组治疗前后血清卵泡刺激素(FSH)、黄体生成素(LH)、睾酮(T)、血清血管内皮生长因子(VEGF)、内皮抑素(ES)、肝细胞生长因子(HGF)、单核细胞趋化蛋白-1(MCP-1)水平的变化和治疗后的临床疗效,并随访半年,记录排卵率和妊娠率。结果:治疗后,两组血清FSH、LH、T、VEGF、ES、HGF、MCP-1水平均较治疗前明显降低(P0.05),且观察组以上指标均明显低于对照组(P0.05);观察组临床总有效率[91.30%vs. 75.00%]、排卵率[78.26%vs. 36.96%]、妊娠率[59.09%vs. 5.91%]均明显高于对照组(P0.05)。结论:来曲唑联合妈富隆治疗多囊卵巢综合征的临床效果显著优于妈富隆单药治疗,其可有效改善患者内分泌,提高妊娠率,可能与降低血清VEGF、ES、HGF、MCP-1的表达相关。  相似文献   
5.
目的:探讨血清降钙素原(PCT)、C反应蛋白(CRP)、淀粉样蛋白(SAA)、外周血白细胞计数(WBC)及中性粒细胞比例(N)在新生儿感染中的临床应用价值。方法:随机选取2015年10月~2017年6月在我院治疗并确诊感染的出生三日内的新生儿106人,以及未感染新生儿57人,将其分为未感染组、一般感染组及败血症组,比较其血清PCT、CRP、SAA、WBC及中性粒细胞比例。结果:败血症组的N、PCT均高于未感染组(P0.05),而败血症组的WBC高于或者低于未感染组(P0.05);一般感染组的N、PCT均高于未感染组(P0.05);败血症组PCT高于感染组(P0.05)。WBC、N、PCT用于鉴别诊断一般感染和败血症的ROC曲线的曲线下面积依次为0.551、0.580、0.815,当PCT的值设为6.785 ng/mL时,其鉴别诊断一般感染和败血症的灵敏度50.0%,特异度为97.7%。结论:PCT对于诊断败血症有较高的诊断价值,能有效鉴别一般感染和败血症,中性粒细胞比例和白细胞在诊断细菌感染方面是PCT的补充,三者联合诊断可以提高新生儿细菌感染的诊断准确性。  相似文献   
6.
7.
《植物生态学报》2017,41(1):115
Aims Shrub species have evolved specific strategies to regulate biomass allocation among various organs or between above- and belowground biomass and shrub biomass model is an important approach to estimate biomass allocation among different shrub species. This study was designed to establish the optimal estimation models for each organ (leaf, stem, and root), aboveground and total biomass of 14 common shrub species in Mountain Luya, Shanxi Province, China. Furthermore, we explored biomass allocation characteristics of these shrub species by using the index of leaf biomass fraction (leaf to total biomass), stem biomass fraction (stem to total biomass), root biomass fraction (root to total biomass), and root to shoot mass ratio (R/S) (belowground to aboveground biomass).
Methods We used plant height, basal diameter, canopy diameter and their combination as variables to establish the optimal biomass estimation models for each shrub species. In addition, we used the ratios of leaf, stem, root to total biomass, and belowground to aboveground biomass to explore the difference of biomass allocation patterns of 14 shrub species.
Important findings Most of biomass estimation models could be well expressed by the exponential and linear functions. Biomass for shorter shrub species with more stems could be better estimated by canopy area; biomass for taller shrub species with less stems could be better estimated by the sum of the square of total base diameter multiply stem height; and biomass for the rest shrub species could be better estimated by canopy volume. The averaged value for these shrub species was 0.61, 0.17, 0.48, and 0.35 for R/S, leaf biomass fraction, stem biomass fraction, and root biomass fraction, respectively. Except for leaf biomass fraction, R/S, stem biomass fraction, and root biomass fraction for shrubs with thorn was significantly greater than that for shrubs without thorn.  相似文献   
8.
Sclerodermus pupariae Yang et Yao (Hymenoptera: Bethylidae) is used as a potential biocontrol agent for several buprestid and cerambycid larvae. This study aimed to enhance the efficiency of mass‐rearing of this parasitoid by investigating the fitness gain of this bethylid wasp, including the proportion of successful parasitism and development, brood size, sex ratio, proportion of winged female offspring, body size and longevity of female offspring, under eight different maternal parasitoid density treatments using Thyestilla gebleri Faldermann as host in the laboratory. The results indicated that the foundress densities did not affect the parasitism or emergence rate of this parasitoid. Brood size of the parasitoids increased significantly when the number of maternal wasps ranged from one to four. However, further increases in foundress number did not affect the parasitoid brood size. The sex ratios of S. pupariae were always female‐biased. The proportions of male in the progeny colonies were <10% throughout all experimental treatments. The percentage of winged female progeny was not significantly influenced by the density of adult maternal parasitoids. Body sizes of parasitoids significantly declined with increasing maternal parasitoid densities. Although the parasitoid body size reduced when maternal wasp number was higher, it could be compromised by the relatively higher number of female offspring produced. Further, more than 70% of the parasitoids remained alive when they were stored at 12°C for four months throughout the experiments. These findings suggest that exposure of four female wasps to a single host larva would result in the highest fitness of S. pupariae. Our findings might provide a new approach to enhance the efficiency of mass‐rearing of this bethylid wasp.  相似文献   
9.
Complete and nearly complete mtDNA genome sequences were used to resolve differences between two palaeontology‐based hypotheses on timing of the origin of the Baikal endemic sponge family Lubomirskiidae (Haplosclerida, Demospongiae). Bayesian ratio test, when coupled with estimates of substitution rates based on known palaeontological findings, provided strong evidence for the Miocene origin over the Late Oligocene one. The common ancestor of the present day sponges in Lake Baikal diverged about 2,3 million years ago (Ma), while Lubomirskia baicalensis, Rezinkovia echinata, Baikalospongia intermedia profundalis and B. bacillifera split in the Pleistocene about 0,7 Ma. A phylogenetic analysis within the family suggested that speciation may have coincided with the occurrence of cold climatic conditions. We argue that the cause of speciation may be niche splitting due to temperature, depth and possibly feeding preferences.  相似文献   
10.
The parapagurid hermit crabs Sympagurus dimorphus (Studer, 1883) and Parapagurus bouvieri (Stebbing, 1910) form dominant components of South African deeper-water benthic invertebrate communities and, as adults, forego the use of “traditional” gastropod shells in favour of symbiotically associated Epizoanthus carcinoecia. A total of 1,122 adult S. dimorphus and 549 adult P. bouvieri derived from demersal research trawl surveys were examined to investigate parameters of population structure, carcinoecia association and morphology. S. dimorphus had a female-biased sex ratio of 1:1.5, and P. bouvieri an equal sex ratio of 1:1. The proportion of males of both species increased with cephalothoracic shield length (CL). The lengths of the major right chelipeds of both S. dimorphus males and females, and P. bouvieri males were positively allometric, and negatively allometric in P. bouvieri females. All P. bouvieri inhabited carcinoecia, while 3.39% (n = 38) of S. dimorphus specimens occupied gastropod shells. There was a positive relationship between S. dimorphus CL and rate of gastropod shell occupation (r2 = 0.96). In S. dimorphus, number of zoanthid polyps forming the carcinoecia pseudoshell increased with both total shell volume (R2 = 0.73) and colony height (R2 = 0.61), but no such relationships were found for P. bouvieri. Euspira napus was the most common original shell around which carcinoecia developed in both S. dimorphus (45.45%) and P. bouvieri (39.00%). We speculate that these hermit species exist along an evolutionary continuum of carcinoecia use. Sympagurus dimorphus retains the ability to occupy both gastropod shells and pseudoshells and, like most other hermit crabs, continue to use shells/carcinoecia as shelters to protect the entire body. In contrast, adult P. bouvieri appear to be totally reliant on carcinoecia, which they use more as a brood pouch covering only the abdomen, rather than as a shelter into which they can fully retract to escape predation.  相似文献   
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