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191.
Assaf Sukenik Ruth N. Kaplan‐Levy Yehudit Viner‐Mozzini Antonio Quesada Ora Hadas 《Journal of phycology》2013,49(3):580-587
Akinetes are spore‐like nonmotile cells that differentiate from vegetative cells of filamentous cyanobacteria from the order Nostocales. They play a key role in the survival and distribution of these species and contribute to their perennial blooms. Various environmental factors were reported to trigger the differentiation of akinetes including light intensity and quality, temperature, and nutrient deficiency. Here, we report that deprivation of potassium ion (K+) triggers akinete development in the cyanobacterium Aphanizomenon ovalisporum. Akinetes formation is initiated 3 d–7 d after an induction by K+ depletion, followed by 2–3 weeks of a maturation process. Akinete formation occurs within a restricted matrix of environmental conditions such as temperature, light intensity or photon flux. Phosphate is essential for akinete maturation and P‐limitation restricts the number of mature akinetes. DNA replication is essential for akinete maturation and akinete development is limited in the presence of Nalidixic acid. While our results unequivocally demonstrated the effect of K+ deficiency on akinete formation in laboratory cultures of A. ovalisporum, this trigger did not cause Cylindrospermopsis raciborskii to produce akinetes. Anabaena crassa however, produced akinetes upon potassium deficiency, but the highest akinete concentration was achieved at conditions that supported vegetative growth. It is speculated that an unknown internal signal is associated with the cellular response to K+ deficiency to induce the differentiation of a certain vegetative cell in a trichome into an akinete. A universal stress protein that functions as mediator in K+ deficiency signal transduction cascade, may communicate between the lack of K+ and akinete induction. 相似文献
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194.
T. Mitchell Aide Matthew L. Clark H. Ricardo Grau David López‐Carr Marc A. Levy Daniel Redo Martha Bonilla‐Moheno George Riner María J. Andrade‐Núñez María Muñiz 《Biotropica》2013,45(2):262-271
Forest cover change directly affects biodiversity, the global carbon budget, and ecosystem function. Within Latin American and the Caribbean region (LAC), many studies have documented extensive deforestation, but there are also many local studies reporting forest recovery. These contrasting dynamics have been largely attributed to demographic and socio‐economic change. For example, local population change due to migration can stimulate forest recovery, while the increasing global demand for food can drive agriculture expansion. However, as no analysis has simultaneously evaluated deforestation and reforestation from the municipal to continental scale, we lack a comprehensive assessment of the spatial distribution of these processes. We overcame this limitation by producing wall‐to‐wall, annual maps of change in woody vegetation and other land‐cover classes between 2001 and 2010 for each of the 16,050 municipalities in LAC, and we used nonparametric Random Forest regression analyses to determine which environmental or population variables best explained the variation in woody vegetation change. Woody vegetation change was dominated by deforestation (?541,835 km2), particularly in the moist forest, dry forest, and savannas/shrublands biomes in South America. Extensive areas also recovered woody vegetation (+362,430 km2), particularly in regions too dry or too steep for modern agriculture. Deforestation in moist forests tended to occur in lowland areas with low population density, but woody cover change was not related to municipality‐scale population change. These results emphasize the importance of quantitating deforestation and reforestation at multiple spatial scales and linking these changes with global drivers such as the global demand for food. 相似文献
195.
Johann B?hm Frédéric Chevessier André?Maues De?Paula Catherine Koch Shahram Attarian Claire Feger Daniel Hanta? Pascal Laforêt Karima Ghorab Jean-Michel Vallat Michel Fardeau Dominique Figarella-Branger Jean Pouget Norma?B. Romero Marc Koch Claudine Ebel Nicolas Levy Martin Krahn Bruno Eymard Marc Bartoli Jocelyn Laporte 《American journal of human genetics》2013,92(2):271-278
Tubular aggregates are regular arrays of membrane tubules accumulating in muscle with age. They are found as secondary features in several muscle disorders, including alcohol- and drug-induced myopathies, exercise-induced cramps, and inherited myasthenia, but also exist as a pure genetic form characterized by slowly progressive muscle weakness. We identified dominant STIM1 mutations as a genetic cause of tubular-aggregate myopathy (TAM). Stromal interaction molecule 1 (STIM1) is the main Ca2+ sensor in the endoplasmic reticulum, and all mutations were found in the highly conserved intraluminal Ca2+-binding EF hands. Ca2+ stores are refilled through a process called store-operated Ca2+ entry (SOCE). Upon Ca2+-store depletion, wild-type STIM1 oligomerizes and thereby triggers extracellular Ca2+ entry. In contrast, the missense mutations found in our four TAM-affected families induced constitutive STIM1 clustering, indicating that Ca2+ sensing was impaired. By monitoring the calcium response of TAM myoblasts to SOCE, we found a significantly higher basal Ca2+ level in TAM cells and a dysregulation of intracellular Ca2+ homeostasis. Because recessive STIM1 loss-of-function mutations were associated with immunodeficiency, we conclude that the tissue-specific impact of STIM1 loss or constitutive activation is different and that a tight regulation of STIM1-dependent SOCE is fundamental for normal skeletal-muscle structure and function. 相似文献
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197.
Bjarne Brudeli Kjetil Wessel Andressen Lise Román Moltzau Nils Olav Nilsen Finn Olav Levy Jo Klaveness 《Bioorganic & medicinal chemistry》2013,21(22):7134-7145
Serotonin (5-hydroxytryptamine, 5-HT) is an important signaling molecule in the central nervous system (CNS) and in non-neuronal tissues and organs. Serotonin mediates a positive chronotropic and inotropic response through 5-HT4 receptors in the atrium and ventricle of the heart. Recent investigations have revealed increased expression of the 5-HT4(b) isoform in cardiomyocytes of chronic arrhythmic and failing hearts, and that the use of 5-HT4 receptor antagonists may be beneficial for treating these conditions. The 5-HT4 receptor possesses a transmembrane (TM) binding site important for ligand affinity and recognition, as well as a capacity to accommodate bulky ligands. A new series of peripherally-acting 5-HT4 receptor antagonists were prepared by combining the acidic biphenyl group from the class of angiotensin II receptor blockers (ARBs) with the SB207266 (piboserod) scaffold. The new compounds were pharmacologically evaluated and carboxylic acid 21 was identified as a potent and promising 5-HT4 receptor antagonist with moderate affinity for the AT1 receptor. The permeability of carboxylic acid 21 in a Caco-2 assay was low and the corresponding prodrug esters 23a–f were therefore prepared. The pharmacokinetics of methyl ester 20 and n-butyl ester 23c were evaluated in a rat model, revealing incomplete metabolism to carboxylic acid 21. However, methyl ester 20 is a potent 5-HT4 receptor antagonist with binding affinities in the low picomolar range. Methyl ester 20 has promising oral bioavailability and pharmacokinetics and may target 5-HT4 receptors in both CNS and peripheral organs. 相似文献
198.
Light brown apple moth, Epiphyas postvittana (Walker), is a newly invasive pest in California. Habrobracon gelechiae Ashmead is an indigenous North American ectoparasitoid of lepidopterans. Using E. postvittana as the host, we determined H. gelechiae host stage preference for oviposition and suitability for larval growth: the parasitoid attacked second to fifth instars, but preferred older (third to fifth) host larvae for oviposition, laying more eggs per clutch on the largest (fifth instar). Offspring survival was better on larger (third to fifth instars) hosts. Adult survival and fecundity and immature temperature development were studied at three key temperatures. At 12°C, H. gelechiae failed to oviposit. At 22 and 30°C, H. gelechiae had, respectively, egg to adult developmental times of 15.4 and 8.7 days, adult female survival of 54.8 and 27.2 days, lifetime parasitism of 39.9 and 21.8 hosts and 181 and 151 eggs per female, an intrinsic rate of increase of 0.107 and 0.165, and mean generation time 30.7 and 18.9 days. We studied intraguild interactions with the endoparasitoid Meteorus ictericus Nees, and found that H. gelechiae did not discriminate against hosts that were parasitised by M. ictericus. Neither the paralysing venom injected by H. gelechiae or the presence of the ectoparasitoid's eggs or larvae arrested M. ictericus development. We also conducted a field release of H. gelechiae on two plant species commonly infested by E. postvittana and showed that H. gelechiae was able to locate and attack moth larvae on both hosts. 相似文献
199.
Hsi-Min Hsiao Ramil E. Sapinoro Thomas H. Thatcher Amanda Croasdell Elizabeth P. Levy Robert A. Fulton Keith C. Olsen Stephen J. Pollock Charles N. Serhan Richard P. Phipps Patricia J. Sime 《PloS one》2013,8(3)
Introduction
Cigarette smoke is a profound pro-inflammatory stimulus that contributes to acute lung injuries and to chronic lung disease including COPD (emphysema and chronic bronchitis). Until recently, it was assumed that resolution of inflammation was a passive process that occurred once the inflammatory stimulus was removed. It is now recognized that resolution of inflammation is a bioactive process, mediated by specialized lipid mediators, and that normal homeostasis is maintained by a balance between pro-inflammatory and pro-resolving pathways. These novel small lipid mediators, including the resolvins, protectins and maresins, are bioactive products mainly derived from dietary omega-3 and omega-6 polyunsaturated fatty acids (PUFA). We hypothesize that resolvin D1 (RvD1) has potent anti-inflammatory and pro-resolving effects in a model of cigarette smoke-induced lung inflammation.Methods
Primary human lung fibroblasts, small airway epithelial cells and blood monocytes were treated with IL-1β or cigarette smoke extract in combination with RvD1 in vitro, production of pro-inflammatory mediators was measured. Mice were exposed to dilute mainstream cigarette smoke and treated with RvD1 either concurrently with smoke or after smoking cessation. The effects on lung inflammation and lung macrophage populations were assessed.Results
RvD1 suppressed production of pro-inflammatory mediators by primary human cells in a dose-dependent manner. Treatment of mice with RvD1 concurrently with cigarette smoke exposure significantly reduced neutrophilic lung inflammation and production of pro-inflammatory cytokines, while upregulating the anti-inflammatory cytokine IL-10. RvD1 promoted differentiation of alternatively activated (M2) macrophages and neutrophil efferocytosis. RvD1 also accelerated the resolution of lung inflammation when given after the final smoke exposure.Conclusions
RvD1 has potent anti-inflammatory and pro-resolving effects in cells and mice exposed to cigarette smoke. Resolvins have strong potential as a novel therapeutic approach to resolve lung injury caused by smoke and pulmonary toxicants. 相似文献200.
Task switch costs often show an asymmetry, with switch costs being larger when switching from a difficult task to an easier task. This asymmetry has been explained by difficult tasks being represented more strongly and consequently requiring more inhibition prior to switching to the easier task. The present study shows that switch cost asymmetries observed in arithmetic tasks (addition vs. subtraction) do not depend on task difficulty: Switch costs of similar magnitudes were obtained when participants were presented with unsolvable pseudo-equations that did not differ in task difficulty. Further experiments showed that neither task switch costs nor switch cost asymmetries were due to perceptual factors (e.g., perceptual priming effects). These findings suggest that asymmetrical switch costs can be brought about by the association of some tasks with greater difficulty than others. Moreover, the finding that asymmetrical switch costs were observed (1) in the absence of a task switch proper and (2) without differences in task difficulty, suggests that present theories of task switch costs and switch cost asymmetries are in important ways incomplete and need to be modified. 相似文献