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1.
Abere Shiferaw Alemu Russell R. Kempker Admasu Tenna Christopher Smitson Nega Berhe Daniel Fekade Henry M. Blumberg Abraham Aseffa 《PloS one》2013,8(3)
Background
Cryptococcal disease is estimated to be responsible for significant mortality in Sub-Saharan Africa; however, only scarce epidemiology data exists. We sought to evaluate the prevalence of and risk factors for cryptococcal antigenemia in Ethiopia.Methods
Consecutive adult HIV-infected patients from two public HIV clinics in Addis Ababa, Ethiopia were enrolled into the study. A CD4 count ≤200 cells/μl was required for study participation. Patients receiving anti-retroviral therapy (ART) were not excluded. A cryptococcal antigen test was performed for all patients along with an interview, physical exam, and medical chart abstraction. Logistic regression analysis was used to assess risk factors for cryptococcal antigenemia.Results
369 HIV-infected patients were enrolled; mean CD4 123 cells/μl and 74% receiving ART. The overall prevalence of cryptococcal antigenemia was 8.4%; 11% in patients with a CD4 count <100 cells/μl, 8.9% with CD4 100 to 150 cells/μl and 5.7% with CD4150-200 cell/μl. 84% of patients with cryptococcal antigenemia were receiving ART. In multivariable analysis, increasing age, self reported fever, CD4 count <100 cells/μl, and site of screening were associated with an increased risk of cryptococcal antigenemia. No individual or combination of clinical symptoms had optimal sensitivity or specificity for cryptococcal antigenemia.Conclusion
Cryptococcal antigenemia is high in Ethiopia and rapid scale up of screening programs is needed. Screening should be implemented for HIV-infected patients with low CD4 counts regardless of symptoms or receipt of ART. Further study into the effect of location and environment on cryptococcal disease is warranted. 相似文献2.
Tenna Toftegaard Diana Posledovich Jos A. Navarro‐Cano Christer Wiklund Karl Gotthard Johan Ehrln 《Oikos》2019,128(4):493-502
Variation in the degree of synchrony among host plants and herbivores can disrupt or intensify species interactions, alter the strength of natural selection on traits associated with phenological timing, and drive novel host plant associations. We used field observations from three regions during four seasons to examine how timing of the butterfly herbivore Anthocharis cardamines relative to six host plant species (Arabis hirsuta, Cardamine pratensis, Arabis glabra, Arabidopsis thaliana, Thlaspi caerulescens and Capsella bursa‐pastoris) influenced host species use and the choice of host plant individuals within populations. Butterflies laid a larger fraction of their eggs on species that were closer to the butterfly's preferred stage of development than on other host species. Within host plant populations, butterflies showed a stronger preference for individuals with a late phenology when plants within the population were on average more developed at the time of butterfly flight. Our results suggest that changes in synchrony between herbivores and their host plants are associated with changes in both host species use and the choice of host plant individuals differing in phenology within populations. This is likely to be an important mechanism generating variation in interaction intensities and trait selection in the wild, and therefore also relevant for understanding how anthropogenic induced changes, such as global warming, will influence natural communities. 相似文献
3.
Jes Jessen Rasmussen Annette Baattrup-Pedersen Tenna Riis Nikolai Friberg 《Aquatic Ecology》2011,45(2):231-242
We surveyed macrophyte community structure and measured community metabolism and nutrient uptake along a temperature gradient
(9.7–17.4°C) in four Icelandic streams influenced by geothermal heating. The study streams are part of the geothermal area
in Hengill that is uniquely characterised by streams with comparable water chemistry despite the geothermal influence. Stream
metabolism was studied applying the diurnal upstream–downstream dissolved oxygen change technique. Nutrient uptake was studied
by adding solutions of nitrogen and phosphorus together with a conservative tracer. Rates of primary production (GPP) and
uptake of nitrate–N and phosphate-P increased with increasing stream temperature. GPP was 20 times higher (up to 12.99 g O2 m−2 day−1) and rates of nutrient uptake were up to 30-times higher (up to 22.99, 13.31 and 7.94 mg m−2 h−1 for ammonium, nitrate and phosphate, respectively) in the warmest streams compared with the coldest. Furthermore, macrophytes,
when present, were strongly controlling ecosystem processes. Our study implies that temperature may affect stream ecosystem
processes both directly (i.e. physiologically) and indirectly (i.e. by changing other structural parameters). 相似文献
4.
Macrophyte communities in unimpacted European streams: variability in assemblage patterns, abundance and diversity 总被引:5,自引:5,他引:0
Annette Baattrup-Pedersen Krzysztof Szoszkiewicz Rebi Nijboer Mattie O’Hare Teresa Ferreira 《Hydrobiologia》2006,566(1):179-196
Macrophytes are an important component of aquatic ecosystems and are used widely within the Water Framework Directive (WFD)
to establish ecological quality. In the present paper we investigated macrophyte community structure, i.e., composition, richness
and diversity measures in 60 unimpacted stream and river sites throughout Europe. The objectives were to describe assemblage
patterns in different types of streams and to assess the variability in various structural and ecological metrics within these
types to provide a basis for an evaluation of their suitability in ecological quality assessment. Macrophyte assemblage patterns
varied considerably among the main stream types. Moving from small-sized, shallow mountain streams to medium-sized, lowland
streams there was a clear transition in species richness, diversity and community structure. There was especially a shift
from a predominance of species-poor mosses and communities dominated by liverwort in the small-sized, shallow mountain streams
to more species-rich communities dominated by vascular plants in the medium-sized, lowland streams. The macrophyte communities
responded to most of the features underlying the typological framework defined in WFD. The present interpretation of the WFD
typology may not, however, be adequate for an evaluation of stream quality based on macrophytes. First and most important,
by using this typology we may overlook an important community type, which is characteristic of small-sized, relatively steep-gradient
streams that are an intermediate type between the small-sized, shallow mountain streams and the medium-sized, lowland streams.
Second, the variability in most of the calculated metrics was slightly higher when using the pre-defined typology. The consistency
of these results should be investigated by analysing a larger number of sites. Particularly the need of re-defining the typology
to improve the ability to detect impacts on streams and rivers from macrophyte assemblage patterns should be investigated.
Electronic supplementary material Electronic supplementary material is available for this article at
and accessible for authorised users. 相似文献
5.
Mattie T. O’Hare Annette Baattrup-Pedersen Rebi Nijboer Krzysztof Szoszkiewicz Teresa Ferreira 《Hydrobiologia》2006,566(1):197-210
The impact of altering hydro-morphology on three macrophyte community types was investigated at 107 European stream sites.
Sites were surveyed using standard macrophyte and habitat survey techniques (Mean Trophic Rank Methodology and River Habitat
Survey respectively). Principal Components Analysis shows the macrophyte community of upland streams live in a more structurally
diverse physical habitat than lowland communities. Variables representing the homogeneity and diversity of the physical environment
were used to successfully separate un-impacted from impacted sites, e.g. homogeneity of depth and substrate increased with
decreasing quality class for lowland sites (ANOVA p < 0.05). Macrophyte attribute groups and structural metrics such as species richness were successfully linked to hydro-morphological
variables indicative of impact. Most links were specific to each macrophyte community type, e.g., the attribute group liverworts,
mosses and lichens decreased in abundance with increasing homogeneity of depth and decreasing substrate size at lowland sites
but not at upland sites. Elodea canadensis, Sparganium emersum and Potamogeton crispus were indicative of impacted lowland sites. Many of the indicator species are also known to be tolerant to other forms of
impact. The potential for a macrophyte tool indicative of hydro-morphological impact is discussed. It is concluded one could
be constructed by combining indicator species and metrics such as species richness and evenness. 相似文献
6.
Aveta A Tenna S Cagli B Segreto F Lombardo GA Persichetti P 《Plastic and reconstructive surgery》2012,129(6):1004e-1005e; author reply 1005e-1006e
7.
Hydrological and environmental variables outperform spatial factors in structuring species,trait composition,and beta diversity of pelagic algae 下载免费PDF全文
Naicheng Wu Yueming Qu Björn Guse Kristė Makarevičiūtė Szewing To Tenna Riis Nicola Fohrer 《Ecology and evolution》2018,8(5):2947-2961
There has been increasing interest in algae‐based bioassessment, particularly, trait‐based approaches are increasingly suggested. However, the main drivers, especially the contribution of hydrological variables, of species composition, trait composition, and beta diversity of algae communities are less studied. To link species and trait composition to multiple factors (i.e., hydrological variables, local environmental variables, and spatial factors) that potentially control species occurrence/abundance and to determine their relative roles in shaping species composition, trait composition, and beta diversities of pelagic algae communities, samples were collected from a German lowland catchment, where a well‐proven ecohydrological modeling enabled to predict long‐term discharges at each sampling site. Both trait and species composition showed significant correlations with hydrological, environmental, and spatial variables, and variation partitioning revealed that the hydrological and local environmental variables outperformed spatial variables. A higher variation of trait composition (57.0%) than species composition (37.5%) could be explained by abiotic factors. Mantel tests showed that both species and trait‐based beta diversities were mostly related to hydrological and environmental heterogeneity with hydrological contributing more than environmental variables, while purely spatial impact was less important. Our findings revealed the relative importance of hydrological variables in shaping pelagic algae community and their spatial patterns of beta diversities, emphasizing the need to include hydrological variables in long‐term biomonitoring campaigns and biodiversity conservation or restoration. A key implication for biodiversity conservation was that maintaining the instream flow regime and keeping various habitats among rivers are of vital importance. However, further investigations at multispatial and temporal scales are greatly needed. 相似文献
8.
9.
Aquatic mosses are important primary producers in High-Arctic lakes, but little information is available on their contribution to the overall production in these lakes. In order to predict effects of climate change on whole-lake ecosystem characteristics, more knowledge is needed on the role of moss in primary production, the extent of nutrient limitation of moss primary production and whether moss serves as food resource for secondary producers. In this study, we conducted an in situ growth experiment of an aquatic moss in a High-Arctic lake in NE Greenland and used these data to determine annual net production of this moss in the whole lake. We also measured tissue-N and tissue-P in order to assess nutrient limitation of moss production, measured in situ decomposition rates by litter bag experiments over 1 year and assessed the role of moss as food source by analysing stable isotope 15N and 13C of relevant organism groups in the lake. Net primary production of moss was 1.3 gC m?2 year?1 and constituted 23 % of the total benthic primary production and 18 % of the total lake primary production. Stoichiometric assessments suggested N and P limitation of moss growth. On average, 15 % of the standing biomass was decomposed per year. Our results also indicate that moss is not directly used as food resource by herbivores, but the most abundant herbivore, Lepidurus arcticus, is feeding on the epiphytic biofilm on the moss. Moss biomass is instead incorporated into the microbial decomposer pathway. All together, the study shows that moss plays an important ecological role as primary producer in High-Arctic lakes and functions as substrate for periphytic biofilm that serves as food resource for important herbivore invertebrates. 相似文献
10.
Diana Posledovich Tenna Toftegaard Jose A. Navarro‐Cano Christer Wiklund Johan Ehrlén Karl Gotthard 《Biological journal of the Linnean Society. Linnean Society of London》2014,113(4):981-991
Latitudinal clines in thermal reaction norms of development are a common phenomenon in temperate insects. Populations from higher latitudes often develop faster throughout the range of relevant temperatures (i.e countergradient variation) because they must be able to complete their life cycle within a shorter seasonal time window compared to populations at lower latitudes. In the present study, we experimentally demonstrate that two species of butterflies Anthocharis cardamines (L.) and Pieris napi (L.) instead show a cogradient variation in thermal reaction norms of post‐winter pupal development so that lower latitude populations develop faster than higher latitude populations. The two species share host plants but differ in the degree of phenological specialization, as well as in the patterns of voltinism. We suggest that the pattern in A. cardamines, a univoltine phenological specialist feeding exclusively on flowers and seedpods, is the result of selection for matching to the phenological pattern of its local host plants. The other species, P. napi, is a phenological generalist feeding on the leaves of the hosts and it shows a latitudinal cline in voltinism. Because the latitudinal pattern in P. napi was an effect of slow development in a fraction of the pupae from the most northern population, we hypothesize that this population may include both bivoltine and univoltine genotypes. Consequently, although the two species both showed cogradient patterns in thermal reaction norms, it appears likely that this was for different reasons. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 981–991. 相似文献