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31.
Aditya S. Khanna Sarah T. Roberts Susan Cassels Roger Ying Grace John-Stewart Steven M. Goodreau Jared M. Baeten Pamela M. Murnane Connie Celum Ruanne V. Barnabas 《PloS one》2015,10(8)
Introduction
Prevention of mother-to-child HIV transmission (PMTCT) strategies include combined short-course antiretrovirals during pregnancy (Option A), triple-drug antiretroviral treament (ART) during pregnancy and breastfeeding (Option B), or lifelong ART (Option B+). The WHO also recommends ART for HIV treatment and prevention of sexual transmission of HIV. The impact of PMTCT strategies on prevention of sexual HIV transmission of HIV is not known. We estimated the population-level impact of PMTCT interventions on heterosexual HIV transmission in southwestern Uganda and KwaZulu-Natal, South Africa, two regions with different HIV prevalence and fertility rates.Materials and Methods
We constructed and validated dynamic, stochastic, network-based HIV transmission models for each region. PMTCT Options A, B, and B+ were simulated over ten years under three scenarios: 1) current ART and PMTCT coverage, 2) current ART and high PMTCT coverage, and 3) high ART and PMTCT coverage. We compared adult HIV incidence after ten years of each intervention to Option A (and current ART) at current coverage.Results
At current coverage, Options B and B+ reduced heterosexual HIV incidence by about 5% and 15%, respectively, in both countries. With current ART and high PMTCT coverage, Option B+ reduced HIV incidence by 35% in Uganda and 19% in South Africa, while Option B had smaller, but meaningful, reductions. The greatest reductions in HIV incidence were achieved with high ART and PMTCT coverage. In this scenario, all PMTCT strategies yielded similar results.Discussion
Implementation of Options B/B+ reduces adult HIV incidence, with greater effect (relative to Option A at current levels) in Uganda than South Africa. These results are likely driven by Uganda’s higher fertility rates. 相似文献32.
Comparative epigenomic analysis of murine and human adipogenesis 总被引:2,自引:0,他引:2
33.
This article deals with the order of verbal suffixes in Adyghe, a polysynthetic language of the Caucasus. Traditionally the
structure of the Adyghe word form and the order of its affixes were described in terms of template morphology. However, we
present new data demanding another, substantially different approach. We demonstrate that for the most part suffix ordering
within the Adyghe verb follows strictly compositional rules. This feature is a manifestation of the polysynthetic nature of
the language. 相似文献
34.
Lander Baeten Margot Vanhellemont Pieter De Frenne An De Schrijver Martin Hermy Kris Verheyen 《Oecologia》2010,163(4):1021-1032
The differential ability of forest herbs to colonize secondary forests on former agricultural land is generally attributed
to different rates of dispersal. After propagule arrival, however, establishing individuals still have to cope with abiotic
soil legacies from former agricultural land use. We focused on the plastic responses of forest herbs to increased phosphorus
availability, as phosphorus is commonly found to be persistently bioavailable in post-agricultural forest soils. In a pot
experiment performed under field conditions, we applied three P levels to four forest herbs with contrasting colonization
capacities: Anemone nemorosa, Primula elatior, Circaea lutetiana and Geum urbanum. To test interactions with light availability, half of the replicas were covered with shade cloths. After two growing seasons,
we measured aboveground P uptake as well as vegetative and regenerative performance. We hypothesized that fast-colonizing
species respond the most opportunistically to increased P availability, and that a low light availability can mask the effects
of P on performance. All species showed a significant increase in P uptake in the aboveground biomass. The addition of P had
a positive effect on the vegetative performances of two of the species, although this was unrelated to their colonization
capacities. The regenerative performance was affected by light availability (not by P addition) and was related to the species’
phenology. Forest herbs can obviously benefit from the increased availability of P in post-agricultural forests, but not all
species respond in the same way. Such differential patterns of plasticity may be important in community dynamics, as they
affect the interactions among species. 相似文献
35.
Morpheus unbound: reimagining the morphogen gradient 总被引:9,自引:0,他引:9
The theory that the spatial organization of cell fate is orchestrated by gradients of diffusing molecules was a major contribution to 20th century developmental biology. Although the existence of morphogens is no longer in doubt, studies on the formation and function of their gradients have yielded far more puzzles than answers. On close inspection, every morphogen gradient seems to use a rich array of regulatory mechanisms, suggesting that the tasks carried out by such systems are far more extensive than previously thought. 相似文献
36.
37.
Drivers of temporal changes in temperate forest plant diversity vary across spatial scales 下载免费PDF全文
Markus Bernhardt‐Römermann Lander Baeten Dylan Craven Pieter De Frenne Radim Hédl Jonathan Lenoir Didier Bert Jörg Brunet Markéta Chudomelová Guillaume Decocq Hartmut Dierschke Thomas Dirnböck Inken Dörfler Thilo Heinken Martin Hermy Patrick Hommel Bogdan Jaroszewicz Andrzej Keczyński Daniel L. Kelly Keith J. Kirby Martin Kopecký Martin Macek František Máliš Michael Mirtl Fraser J.G. Mitchell Tobias Naaf Miles Newman George Peterken Petr Petřík Wolfgang Schmidt Tibor Standovár Zoltán Tóth Hans Van Calster Gorik Verstraeten Jozef Vladovič Ondřej Vild Monika Wulf Kris Verheyen 《Global Change Biology》2015,21(10):3726-3737
Global biodiversity is affected by numerous environmental drivers. Yet, the extent to which global environmental changes contribute to changes in local diversity is poorly understood. We investigated biodiversity changes in a meta‐analysis of 39 resurvey studies in European temperate forests (3988 vegetation records in total, 17–75 years between the two surveys) by assessing the importance of (i) coarse‐resolution (i.e., among sites) vs. fine‐resolution (i.e., within sites) environmental differences and (ii) changing environmental conditions between surveys. Our results clarify the mechanisms underlying the direction and magnitude of local‐scale biodiversity changes. While not detecting any net local diversity loss, we observed considerable among‐site variation, partly explained by temporal changes in light availability (a local driver) and density of large herbivores (a regional driver). Furthermore, strong evidence was found that presurvey levels of nitrogen deposition determined subsequent diversity changes. We conclude that models forecasting future biodiversity changes should consider coarse‐resolution environmental changes, account for differences in baseline environmental conditions and for local changes in fine‐resolution environmental conditions. 相似文献
38.
Gokoffski KK Wu HH Beites CL Kim J Kim EJ Matzuk MM Johnson JE Lander AD Calof AL 《Development (Cambridge, England)》2011,138(19):4131-4142
Studies of the olfactory epithelium model system have demonstrated that production of neurons is regulated by negative feedback. Previously, we showed that a locally produced signal, the TGFβ superfamily ligand GDF11, regulates the genesis of olfactory receptor neurons by inhibiting proliferation of the immediate neuronal precursors (INPs) that give rise to them. GDF11 is antagonized by follistatin (FST), which is also produced locally. Here, we show that Fst(-/-) mice exhibit dramatically decreased neurogenesis, a phenotype that can only be partially explained by increased GDF11 activity. Instead, a second FST-binding factor, activin βB (ACTβB), inhibits neurogenesis by a distinct mechanism: whereas GDF11 inhibits expansion of INPs, ACTβB inhibits expansion of stem and early progenitor cells. We present data supporting the concept that these latter cells, previously considered two distinct types, constitute a dynamic stem/progenitor population in which individual cells alternate expression of Sox2 and/or Ascl1. In addition, we demonstrate that interplay between ACTβB and GDF11 determines whether stem/progenitor cells adopt a glial versus neuronal fate. Altogether, the data indicate that the transition between stem cells and committed progenitors is neither sharp nor irreversible and that GDF11, ACTβB and FST are crucial components of a circuit that controls both total cell number and the ratio of neuronal versus glial cells in this system. Thus, our findings demonstrate a close connection between the signals involved in the control of tissue size and those that regulate the proportions of different cell types. 相似文献
39.
Range expansion and contraction has occurred in the history of most species and can seriously impact patterns of genetic diversity. Historical data about range change are rare and generally appropriate for studies at large scales, whereas the individual pollen and seed dispersal events that form the basis of geneflow and colonization generally occur at a local scale. In this study, we investigated range change in Fagus sylvatica on Mont Ventoux, France, using historical data from 1838 to the present and approximate Bayesian computation (ABC) analyses of genetic data. From the historical data, we identified a population minimum in 1845 and located remnant populations at least 200 years old. The ABC analysis selected a demographic scenario with three populations, corresponding to two remnant populations and one area of recent expansion. It also identified expansion from a smaller ancestral population but did not find that this expansion followed a population bottleneck, as suggested by the historical data. Despite a strong support to the selected scenario for our data set, the ABC approach showed a low power to discriminate among scenarios on average and a low ability to accurately estimate effective population sizes and divergence dates, probably due to the temporal scale of the study. This study provides an unusual opportunity to test ABC analysis in a system with a well-documented demographic history and identify discrepancies between the results of historical, classical population genetic and ABC analyses. The results also provide valuable insights into genetic processes at work at a fine spatial and temporal scale in range change and colonization. 相似文献
40.
Lander Baeten Gorik Verstraeten Pieter De Frenne Margot Vanhellemont Karen Wuyts Martin Hermy Kris Verheyen 《Plant Ecology》2011,212(5):901-909
The colonization rates of understorey plants into forests growing on former agricultural land differ remarkably among species.
Different dispersal and recruitment largely account for the contrasting colonization rates, but different effects of the soil
legacies of former agricultural land use on plant performance may also play a role. Seven herbaceous forest species were sampled
in paired post-agricultural and ancient forest stands to study whether land-use history has an effect on the aboveground nutrient
concentrations (N, P and N:P ratios) and biomass of forest herbs and, if so, whether slow and fast colonizing species respond
differently. Results showed that P concentrations were significantly affected by former land use with higher concentrations
in the post-agricultural stands. N concentrations were unaffected and N:P ratios were significantly higher in the ancient
stands. Nutrient concentrations varied considerably among species, but the variation was unrelated to their colonization capacity.
Six out of the seven species had higher biomass in the post-agricultural stands relative to the ancient stands, and the degree
to which the species increased biomass was positively related to their colonization capacity, i.e., the fast colonizing species
showed the strongest increase. Such differential responses to past land use may contribute to the contrasting colonization
capacity of forest plants. Land-use history thus affected both the nutrient concentrations and biomass of forest herbs, and
only the biomass response was related to colonization capacity. 相似文献