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991.
Grassland restoration has become a key tool in addressing the drastic losses of seminatural grassland since the mid‐twentieth century. This study examined the restoration by green hay transfer of upland hay meadows, a particularly scarce and vulnerable habitat, over an 11‐year chronosequence. The community composition of 18 restoration meadows was compared with that of donor reference sites in two study areas in the Pennine region of northern England. The study investigated: differences in community composition between donor and restoration meadows; transfer of upland hay meadow target species; and the effect of time and isolation from neighboring meadows on the community composition of the restoration meadows. Results showed that restoration meadows differed from donor meadows in that some target species were easily transferred whilst others were not found in the restoration meadows, or were at low levels of cover. Time had a significant effect on the community composition of the restoration meadows, but the similarity between restoration sites and donor sites did not increase with time, and the effect of isolation was not significant. The study showed that the green hay transfer method increases botanical diversity and is an important first step in meadow restoration. However, further restoration activity, such as seed addition, is likely to be required if restoration sites are to resemble closely the reference donor sites. 相似文献
992.
Tak Fung Ryan A. Chisholm Kristina Anderson‐Teixeira Norm Bourg Warren Y. Brockelman Sarayudh Bunyavejchewin Chia‐Hao Chang‐Yang Rutuja Chitra‐Tarak George Chuyong Richard Condit Handanakere S. Dattaraja Stuart J. Davies Corneille E. N. Ewango Gary Fewless Christine Fletcher C. V. Savitri Gunatilleke I. A. U. Nimal Gunatilleke Zhanqing Hao J. Aaron Hogan Robert Howe Chang‐Fu Hsieh David Kenfack YiChing Lin Keping Ma Jean‐Remy Makana Sean McMahon William J. McShea Xiangcheng Mi Anuttara Nathalang Perry S. Ong Geoffrey Parker E‐Ping Rau Jessica Shue Sheng‐Hsin Su Raman Sukumar I‐Fang Sun Hebbalalu S. Suresh Sylvester Tan Duncan Thomas Jill Thompson Renato Valencia Martha I. Vallejo Xugao Wang Yunquan Wang Pushpa Wijekoon Amy Wolf Sandra Yap Jess Zimmerman 《Ecology letters》2020,23(1):160-171
Among the local processes that determine species diversity in ecological communities, fluctuation‐dependent mechanisms that are mediated by temporal variability in the abundances of species populations have received significant attention. Higher temporal variability in the abundances of species populations can increase the strength of temporal niche partitioning but can also increase the risk of species extinctions, such that the net effect on species coexistence is not clear. We quantified this temporal population variability for tree species in 21 large forest plots and found much greater variability for higher latitude plots with fewer tree species. A fitted mechanistic model showed that among the forest plots, the net effect of temporal population variability on tree species coexistence was usually negative, but sometimes positive or negligible. Therefore, our results suggest that temporal variability in the abundances of species populations has no clear negative or positive contribution to the latitudinal gradient in tree species richness. 相似文献
993.
Kip D. Zimmerman Theodore G. Schurr Wei-Min Chen Uma Nayak Josyf C. Mychaleckyj Queen Quet Lee H. Moultrie Jasmin Divers Keith L. Keene Diane L. Kamen Gary S. Gilkeson Kelly J. Hunt Ida J. Spruill Jyotika K. Fernandes Melinda C. Aldrich David Reich W. Timothy Garvey Carl D. Langefeld Michèle M. Sale Paula S. Ramos 《American journal of physical anthropology》2021,175(4):905-919
994.
Krista L. McGuire Sara G. Payne Matthew I. Palmer Caitlyn M. Gillikin Dominique Keefe Su Jin Kim Seren M. Gedallovich Julia Discenza Ramya Rangamannar Jennifer A. Koshner Audrey L. Massmann Giulia Orazi Adam Essene Jonathan W. Leff Noah Fierer 《PloS one》2013,8(3)
In urban environments, green roofs provide a number of benefits, including decreased urban heat island effects and reduced energy costs for buildings. However, little research has been done on the non-plant biota associated with green roofs, which likely affect their functionality. For the current study, we evaluated whether or not green roofs planted with two native plant communities in New York City functioned as habitats for soil fungal communities, and compared fungal communities in green roof growing media to soil microbial composition in five city parks, including Central Park and the High Line. Ten replicate roofs were sampled one year after planting; three of these roofs were more intensively sampled and compared to nearby city parks. Using Illumina sequencing of the fungal ITS region we found that green roofs supported a diverse fungal community, with numerous taxa belonging to fungal groups capable of surviving in disturbed and polluted habitats. Across roofs, there was significant biogeographical clustering of fungal communities, indicating that community assembly of roof microbes across the greater New York City area is locally variable. Green roof fungal communities were compositionally distinct from city parks and only 54% of the green roof taxa were also found in the park soils. Phospholipid fatty acid analysis revealed that park soils had greater microbial biomass and higher bacterial to fungal ratios than green roof substrates. City park soils were also more enriched with heavy metals, had lower pH, and lower quantities of total bases (Ca, K, and Mg) compared to green roof substrates. While fungal communities were compositionally distinct across green roofs, they did not differentiate by plant community. Together, these results suggest that fungi living in the growing medium of green roofs may be an underestimated component of these biotic systems functioning to support some of the valued ecological services of green roofs. 相似文献
995.
Angela I. Bordin Jan S. Suchodolski Melissa E. Markel Kaytee B. Weaver J?rg M. Steiner Scot E. Dowd Suresh Pillai Noah D. Cohen 《PloS one》2013,8(6)
Background
Rhodococcus equi is an important pathogen of foals. Enteral administration of live, virulent R. equi during early life has been documented to protect against subsequent intrabronchial challenge with R. equi, indicating that enteral mucosal immunization may be protective. Evidence exists that mucosal immune responses develop against both live and inactivated micro-organisms. The extent to which live or inactivated R. equi might alter the intestinal microbiome of foals is unknown. This is an important question because the intestinal microbiome of neonates of other species is known to change over time and to influence host development. To our knowledge, changes in the intestinal microbiome of foals during early life have not been reported. Thus, the purpose of this study was to determine whether age (during the first month of life) or administration of either live virulent R. equi (at a dose reported to protect foals against subsequent intrabronchial challenge, viz., 1×1010 colony forming units [CFU]) or inactivated virulent R. equi (at higher doses, viz., 2×1010 and 1×1011 [CFU]) altered the fecal microbiome of foals.Methodology/Principal Findings
Fecal swab samples from 42 healthy foals after vaccination with low-dose inactivated R. equi (n = 9), high-dose inactivated R. equi (n = 10), live R. equi (n = 6), control with cholera toxin B (CTB, n = 9), and control without CTB (n = 8) were evaluated by 454-pyrosequencing of the 16S rRNA gene and by qPCR. No impact of treatment was observed among vaccinated foals; however, marked and significant differences in microbial communities and diversity were observed between foals at 30 days of age relative to 2 days of age.Conclusions
The results suggest age-related changes in the fecal microbial population of healthy foals do occur, however, mucosal vaccination does not result in major changes of the fecal microbiome in foals. 相似文献996.
Eric R. Lafontaine Shawn M. Zimmerman Teresa L. Shaffer Frank Michel Xiudan Gao Robert J. Hogan 《PloS one》2013,8(10)
Burkholderia pseudomallei, the etiologic agent of melioidosis, is a saprophytic bacterium readily isolated from wet soils of countries bordering the equator. Burkholderia mallei is a host-adapted clone of B. pseudomallei that does not persist outside of its equine reservoir and causes the zoonosis glanders, which is endemic in Asia, Africa, the Middle East and South America. Infection by these organisms typically occurs via percutaneous inoculation or inhalation of aerosols, and the most common manifestation is severe pneumonia leading to fatal bacteremia. Glanders and melioidosis are difficult to diagnose and require prolonged antibiotic therapy with low success rates. There are no vaccines available to protect against either Burkholderia species, and there is concern regarding their use as biological warfare agents given that B. mallei has previously been utilized in this manner. Hence, experiments were performed to establish a mouse model of aerosol infection to study the organisms and develop countermeasures. Using a hand-held aerosolizer, BALB/c mice were inoculated intratracheally with strains B. pseudomallei 1026b and B. mallei ATCC23344 and growth of the agents in the lungs, as well as dissemination to the spleen, were examined. Mice infected with 102, 103 and 104 organisms were unable to control growth of B. mallei in the lungs and bacteria rapidly disseminated to the spleen. Though similar results were observed in mice inoculated with 103 and 104
B. pseudomallei cells, animals infected with 102 organisms controlled bacterial replication in the lungs, dissemination to the spleen, and the extent of bacteremia. Analysis of sera from mice surviving acute infection revealed that animals produced antibodies against antigens known to be targets of the immune response in humans. Taken together, these data show that small volume aerosol inoculation of mice results in acute disease, dose-dependent chronic infection, and immune responses that correlate with those seen in human infections. 相似文献
997.
Agnes N. Kiragga Barbara Castelnuovo Rachel Musomba Jonathan Levin Andrew Kambugu Yukari C. Manabe Constantin T. Yiannoutsos Noah Kiwanuka 《PloS one》2013,8(12)
Background
In sub-Saharan Africa, a large proportion of HIV positive patients on antiretroviral therapy (ART) are lost to follow-up, some of whom are dead. The objective of this study was to validate methods used to correct mortality estimates for loss-to-follow-up using a cohort with complete death ascertainment.Methods
Routinely collected data from HIV patients initiating first line antiretroviral therapy (ART) at the Infectious Diseases Institute (IDI) (Routine Cohort) was used. Three methods to estimate mortality after initiation were: 1) standard Kaplan-Meier estimation (uncorrected method) that uses passively observed data; 2) double-sampling methods by Frangakis and Rubin (F&R) where deaths obtained from patient tracing studies are given a higher weight than those passively ascertained; 3) Nomogram proposed by Egger et al. Corrected mortality estimates in the Routine Cohort, were compared with the estimates from the IDI research observational cohort (Research Cohort), which was used as the “gold-standard”.Results
We included 5,633 patients from the Routine Cohort and 559 from the Research Cohort. Uncorrected mortality estimates (95% confidence interval [1]) in the Routine Cohort at 1, 2 and 3 years were 5.5% (4.9%–6.3%), 6.6% (5.9%–7.5%) and 7.4% (6.5%–8.5%), respectively. The F&R corrected estimates at 1, 2 and 3 years were 11.2% (5.8%–21.2%), 15.8% (9.9%–24.8%) and 18.5% (12.3% –27.2%) respectively. The estimates obtained from the Research Cohort were 15.6% (12.8%–18.9%), 17.5% (14.6%–21.0%) and 19.0% (15.3%–21.9%) at 1, 2 and 3 years respectively. Using the nomogram method in the Routine Cohort, the corrected programme-level mortality estimate in year 1 was 11.9% (8.0%–15.7%).Conclusion
Mortality adjustments provided by the F&R and nomogram methods are adequate and should be employed to correct mortality for loss-to-follow-up in large HIV care centres in Sub-Saharan Africa. 相似文献998.
Jill E. Schneider Justina D. Wise Noah A. Benton Jeremy M. Brozek Erin Keen-Rhinehart 《Hormones and behavior》2013
The neuroendocrinology of ingestive behavior is a topic central to human health, particularly in light of the prevalence of obesity, eating disorders, and diabetes. The study of food intake in laboratory rats and mice has yielded some useful hypotheses, but there are still many gaps in our knowledge. Ingestive behavior is more complex than the consummatory act of eating, and decisions about when and how much to eat usually take place in the context of potential mating partners, competitors, predators, and environmental fluctuations that are not present in the laboratory. We emphasize appetitive behaviors, actions that bring animals in contact with a goal object, precede consummatory behaviors, and provide a window into motivation. Appetitive ingestive behaviors are under the control of neural circuits and neuropeptide systems that control appetitive sex behaviors and differ from those that control consummatory ingestive behaviors. Decreases in the availability of oxidizable metabolic fuels enhance the stimulatory effects of peripheral hormones on appetitive ingestive behavior and the inhibitory effects on appetitive sex behavior, putting a new twist on the notion of leptin, insulin, and ghrelin “resistance.” The ratio of hormone concentrations to the availability of oxidizable metabolic fuels may generate a critical signal that schedules conflicting behaviors, e.g., mate searching vs. foraging, food hoarding vs. courtship, and fat accumulation vs. parental care. In species representing every vertebrate taxa and even in some invertebrates, many putative “satiety” or “hunger” hormones function to schedule ingestive behavior in order to optimize reproductive success in environments where energy availability fluctuates. 相似文献
999.
Sarah?R. Leonard Ashley?R. Cormier Xiaodong Pang Maxwell?I. Zimmerman Huan-Xiang Zhou Anant?K. Paravastu 《Biophysical journal》2013,105(1):222-230
MAX8, a designer peptide known to undergo self-assembly following changes in temperature, pH, and ionic strength, has demonstrated usefulness for tissue engineering and drug delivery. It is hypothesized that the self-assembled MAX8 nanofiber structure consists of closed β-hairpins aligned into antiparallel β-sheets. Here, we report evidence from solid-state NMR spectroscopy that supports the presence of the hypothesized β-hairpin conformation within the nanofiber structure. Specifically, our 13C-13C two-dimensional exchange data indicate spatial proximity between V3 and K17, and 13C-13C dipolar coupling measurements reveal proximity between the V3 and V18 backbone carbonyls. Moreover, isotopic dilution of labeled MAX8 nanofibers did not result in a loss of the 13C-13C dipolar couplings, showing that these couplings are primarily intramolecular. NMR spectra also indicate the existence of a minor conformation, which is discussed in terms of previously hypothesized nanofiber physical cross-linking and possible nanofiber polymorphism. 相似文献
1000.
Amit Choubey Rajiv?K. Kalia Noah Malmstadt Aiichiro Nakano Priya Vashishta 《Biophysical journal》2013,104(11):2429-2436
Cholesterol (CHOL) molecules play a key role in modulating the rigidity of cell membranes and controlling intracellular transport and signal transduction. Using an all-atom molecular dynamics approach, we study the process of CHOL interleaflet transport (flip-flop) in a dipalmitoylphosphatidycholine (DPPC)-CHOL bilayer over a time period of 15 μs. We investigate the effect of the flip-flop process on mechanical stress across the bilayer and the role of CHOL in inducing molecular order in bilayer leaflets. The simulations are carried out at physiologically relevant CHOL concentration (30%), temperature (323 K), and pressure (1 bar). CHOL flip-flop events are observed with a rate constant of 3 × 104 s−1. Once a flip-flop event is triggered, a CHOL molecule takes an average of 73 nanoseconds to migrate from one bilayer leaflet to the other. 相似文献