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41.
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Jonathan A. Myers Jonathan M. Chase Iván Jiménez Peter M. Jørgensen Alejandro Araujo‐Murakami Narel Paniagua‐Zambrana Renate Seidel 《Ecology letters》2013,16(2):151-157
Site‐to‐site variation in species composition (β‐diversity) generally increases from low‐ to high‐diversity regions. Although biogeographical differences in community assembly mechanisms may explain this pattern, random sampling effects can create this pattern through differences in regional species pools. Here, we compared assembly mechanisms between spatially extensive networks of temperate and tropical forest plots with highly divergent species pools (46 vs. 607 species). After controlling for sampling effects, β‐diversity of woody plants was similar and higher than expected by chance in both forests, reflecting strong intraspecific aggregation. However, different mechanisms appeared to explain aggregation in the two forests. In the temperate forest, aggregation reflected stronger environmental correlations, suggesting an important role for species‐sorting (e.g. environmental filtering) processes, whereas in the tropics, aggregation reflected stronger spatial correlations, more likely reflecting dispersal limitation. We suggest that biogeographical differences in the relative importance of different community assembly mechanisms contribute to these striking gradients in global biodiversity. 相似文献
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Regina Coeli Elio H. Baba Neusa Araujo Paulo M. Z. Coelho Guilherme Oliveira 《PLoS neglected tropical diseases》2013,7(12)
Background
Schistosomiasis has a considerable impact on public health in many tropical and subtropical areas. In the new world, schistosomiasis is caused by the digenetic trematode Schistosoma mansoni. Chemotherapy is the main measure for controlling schistosomiasis, and the current drug of choice for treatment is praziquantel (PZQ). Although PZQ is efficient and safe, its repetitive large-scale use in endemic areas may lead to the selection of resistant strains. Isolates less susceptible to PZQ have been found in the field and selected for in the laboratory. The impact of selecting strains with a decreased susceptibility phenotype on disease dynamics and parasite population genetics is not fully understood. This study addresses the impact of PZQ pressure on the genetics of a laboratory population by analyzing frequency variations of polymorphic genetic markers.Methodology
Infected mice were treated with increasing PZQ doses until the highest dose of 3×300 mg/Kg was reached. The effect of PZQ treatment on the parasite population was assessed using five polymorphic microsatellite markers. Parasitological and genetic data were compared with those of the untreated control. After six parasite generations submitted to treatment, it was possible to obtain a S. mansoni population with decreased susceptibility to PZQ. In our experiments we also observed that female worms were more susceptible to PZQ than male worms.Conclusions
The selective pressure exerted by PZQ led to decreased genetic variability in S. mansoni and increased endogamy. The understanding of how S. mansoni populations respond to successive drug pressure has important implications on the appearance and maintenance of a PZQ resistance phenotype in endemic regions. 相似文献46.
Fabio E. Leal Lishomwa C. Ndhlovu Aaron M. Hasenkrug Fernanda R. Bruno Karina I. Carvalho Harry Wynn-Williams Walter K. Neto Sabri S. Sanabani Aluisio C. Segurado Douglas F. Nixon Esper G. Kallas 《PLoS neglected tropical diseases》2013,7(2)
HTLV-1 infection is associated with several inflammatory disorders, including the neurodegenerative condition HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). It is unclear why a minority of infected subjects develops HAM/TSP. CD4+ T cells are the main target of infection and play a pivotal role in regulating immunity to HTLV and are hypothesized to participate in the pathogenesis of HAM/TSP. The CD39 ectonucleotidase receptor is expressed on CD4+ T cells and based on co-expression with CD25, marks T cells with distinct regulatory (CD39+CD25+) and effector (CD39+CD25−) function. Here, we investigated the expression of CD39 on CD4+ T cells from a cohort of HAM/TSP patients, HTLV-1 asymptomatic carriers (AC), and matched uninfected controls. The frequency of CD39+ CD4+ T cells was increased in HTLV-1 infected patients, regardless of clinical status. More importantly, the proportion of the immunostimulatory CD39+CD25− CD4+ T-cell subset was significantly elevated in HAM/TSP patients as compared to AC and phenotypically had lower levels of the immunoinhibitory receptor, PD-1. We saw no difference in the frequency of CD39+CD25+ regulatory (Treg) cells between AC and HAM/TSP patients. However, these cells transition from being anergic to displaying a polyfunctional cytokine response following HTLV-1 infection. CD39−CD25+ T cell subsets predominantly secreted the inflammatory cytokine IL-17. We found that HAM/TSP patients had significantly fewer numbers of IL-17 secreting CD4+ T cells compared to uninfected controls. Taken together, we show that the expression of CD39 is upregulated on CD4+ T cells HAM/TSP patients. This upregulation may play a role in the development of the proinflammatory milieu through pathways both distinct and separate among the different CD39 T cell subsets. CD39 upregulation may therefore serve as a surrogate diagnostic marker of progression and could potentially be a target for interventions to reduce the development of HAM/TSP. 相似文献
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Severo Juliana Soares Morais Jennifer Beatriz Silva Beserra Jessica Batista dos Santos Loanne Rocha de Sousa Melo Stéfany Rodrigues de Sousa Gustavo Santos de Matos Neto Emídio Marques Henriques Gilberto Simeone do Nascimento Marreiro Dilina 《Biological trace element research》2020,193(1):81-88
Biological Trace Element Research - Excessive adipose tissue promotes the manifestation of endocrine disorders such as reduction of the secretion of zinc-α2-glycoprotein (ZAG), an adipokine... 相似文献
49.
de Araujo Junior Raimundo Fernandes Eich Christina Jorquera Carla Schomann Timo Baldazzi Fabio Chan Alan B. Cruz Luis J. 《Molecular and cellular biochemistry》2020,468(1-2):153-168
Molecular and Cellular Biochemistry - Accumulating evidence indicates that ceramide (Cer) and palmitic acid (PA) possess the ability to modulate switching of macrophage phenotypes and possess... 相似文献
50.
Francielle C. Mosele Rafael Bissi Ricci Phablo Abreu José C. Rosa Neto 《Journal of cellular physiology》2020,235(9):6183-6193
Activation, proliferation, and differentiation of satellite cells can be influenced by extracellular factors, such as adiponectin. This adipokine has been proposed as a regulator of in vitro myogenesis, but its action on in vivo regeneration is not still elucidated. We used C57BL/6 (wild-type [WT]) and adiponectin knockout (AdKO) mice injured with barium chloride at periods of 3, 7, and 14 days after injury. The AdKO presented a higher number of centralized nuclei after 7 days, and a reduction in myogenic genes was observed after 3 days. Moreover, these mice presented an increase in anti-inflammatory cytokines after 3 and 7 days, and an increase in the M2 gene marker and proinflammatory cytokines after 7 days. The WT demonstrated an increase in adiponectin messenger RNA after 7 days. These results demonstrate that adiponectin is important in tissue remodeling during regeneration and that its deficiency does not compromise the maturation of muscle fibers, due to an increase in anti-inflammatory response; however, there is a possible impairment in proinflammatory response and an increase in centralized myonuclei. 相似文献