Targeting FoxO1 with AS1842856 Suppresses Adipogenesis

Hyperplasia (i.e., increased adipogenesis) contributes to excess adiposity, the hallmark of obesity that can trigger metabolic complications. As FoxO1 has been implicated in adipogenic regulation, we investigated the kinetics of FoxO1 activation during adipocyte differentiation, and tested the effects of FoxO1 antagonist (AS1842856) on adipogenesis. We found for the first time that the kinetics of FoxO1 activation follows a series of sigmoid curves, and reveals the phases relevant to clonal expansion, cell cycle arrest, and the regulation of PPARγ, adiponectin, and mitochondrial proteins (complexes I and III). In addition, multiple activation-inactivation transitions exist in the stage of terminal differentiation. Importantly, persistent inhibition of FoxO1 with AS1842856 almost completely suppressed adipocyte differentiation, while selective inhibition in specific stages had differential effects on adipogenesis. Our data present a new view of FoxO1 in adipogenic regulation, and suggest AS1842856 can be an anti-obesity agent that warrants further investigation.     

Agricultural intensification and farmland birds: new insights from a central European country

The relationship between agricultural intensification and a decline in farmland bird populations is well documented in Europe, but the results are mostly based on data from the western part of the continent. In the former socialist eastern and central European countries, political changes around 1990 resulted in a steep decline in the intensity of agriculture. Therefore, one would expect populations of farmland birds to have recovered under these conditions of lower agricultural intensity. We explored population trends of 19 farmland bird species in the Czech Republic between 1982 and 2003 using data from a large‐scale monitoring scheme, and, additionally, we looked for relationships between such population changes and a number of variables describing the temporal development of Czech agriculture. Most farmland species declined during the focal period, and this decline was steepest in farmland specialists (Northern Lapwing Vanellus vanellus, Skylark Alauda arvensis, Linnet Carduelis cannabina and Yellowhammer Emberiza citrinella). Although the intensity of agriculture was lower after than before 1990, the overall decline continued in most farmland bird species, albeit at a slower rate. The correlations between agricultural intensity and farmland bird decline showed opposite patterns to that found in other European studies, because bird populations were highest in years with the most intensive agriculture. We speculate that this pattern could have resulted from the impact of different driving forces causing farmland bird decline in different periods. The high intensity of agriculture could have caused the decline of the originally abundant populations before 1990. After 1990, the decreasing area of arable land could be the most important factor resulting in the continued decline of farmland bird populations. Our results demonstrate that the drivers of farmland bird population changes could differ across Europe, and thus investigations into the effect of farmland management in different parts of the continent are urgently required.     

Reovirus variants selected for resistance to ammonium chloride have mutations in viral outer-capsid protein sigma3

Mammalian reoviruses are internalized into cells by receptor-mediated endocytosis. Within the endocytic compartment, the viral outer capsid undergoes acid-dependent proteolysis resulting in removal of the sigma3 protein and proteolytic cleavage of the mu1/mu1C protein. Ammonium chloride (AC) is a weak base that blocks disassembly of reovirus virions by inhibiting acidification of intracellular vacuoles. To identify domains in reovirus proteins that influence pH-sensitive steps in viral disassembly, we adapted strain type 3 Dearing (T3D) to growth in murine L929 cells treated with AC. In comparison to wild-type (wt) T3D, AC-adapted (ACA-D) variant viruses exhibited increased yields in AC-treated cells. AC resistance of reassortant viruses generated from a cross of wt type 1 Lang and ACA-D variant ACA-D1 segregated with the sigma3-encoding S4 gene. The deduced sigma3 amino acid sequences of six independently derived ACA-D variants contain one or two mutations each, affecting a total of six residues. Four of these mutations, I180T, A246G, I347S, and Y354H, cluster in the virion-distal lobe of sigma3. Linkage of these mutations to AC resistance was confirmed in experiments using reovirus disassembly intermediates recoated with wt or mutant sigma3 proteins. In comparison to wt virions, ACA-D viruses displayed enhanced susceptibility to proteolysis by endocytic protease cathepsin L. Image reconstructions of cryoelectron micrographs of three ACA-D viruses that each contain a single mutation in the virion-distal lobe of sigma3 demonstrated native capsid protein organization and minimal alterations in sigma3 structure. These results suggest that mutations in sigma3 that confer resistance to inhibitors of vacuolar acidification identify a specific domain that regulates proteolytic disassembly.     

Population changes in Czech passerines are predicted by their life‐history and ecological traits

A species’ susceptibility to environmental change might be predicted by its ecological and life‐history traits. However, the effects of such traits on long‐term bird population trends have not yet been assessed using a comprehensive set of explanatory variables. Moreover, the extent to which phylogeny affects patterns in the interspecific variability of population changes is unclear. Our study focuses on the interspecific variability in long‐term population trends and annual population fluctuations of 68 passerine species in the Czech Republic, assessing the effects of eight life‐history and five ecological traits. Ordination of life‐history traits of 68 species revealed a life‐history gradient, from ‘r‐selected’ (e.g. small body mass, short lifespan, high fecundity, large clutch size) to ‘K‐selected’ species. r‐selected species had more negative population trends than K‐selected species, and seed‐eaters declined compared with insectivores. We suggest that the r‐selected species probably suffer from widespread environmental changes, and the seed‐eaters from current changes in agriculture and land use. Populations of residents fluctuated more than populations of short‐distance migrants, probably due to the effect of winter climatic variability. Variance partitioning at three taxonomic levels showed that whereas population trends, population fluctuations and habitat specialization expressed the highest variability at the species level, most life‐history traits were more variable at higher taxonomic levels. These results explain the loss of statistical power in the relationship between life histories and population trends after controlling for phylogeny. However, we argue that a lack of significance after controlling for phylogeny should not reduce the value of such results for conservation purposes.     

Interaction of chemotactic factors with human macrophages: induction of transmembrane potential changes

The electrophysiology of chemotactic factor interaction with cultured human macrophages was investigated with standard intracellular recording techniques. In initial studies, E. coli endotoxin-activated serum, added to cell cultures during intracellular recordings, caused membrane hyperpolarizations which were greater than 30 s in duration, 10-50 mV in amplitude, and associated with decreased membrane resistance. Control serum produced smaller hyperpolarizations lasting 10-20 s and 5-30 m V in amplitude. Endotoxin-activated human serum deficient in the third complement component (C3) did not produce hyperpolarizations unless the serum was reconstituted with C3 before activation. Fractionation of normal activated serum by molecular seive chromatography (G-75 Sephadex) indicated that only fractions that eluted with an estimated molecular weight of 12,500 produced membrane potential changes. The active material that was chemotactic for the macrophages was identified as the small molecular weight cleavage product of C5, C5a, by heat stability (30 min at 56 degrees C) and inactivation by goat antisera to human C5 but not C3. 17 percent of macrophages stimulated with C5a exhibited a biphasic response characterized by a small (2-6 mV), brief (1-10 s) depolarization associated with a decreased membrane resistance preceding the larger and prolonged hyperpolarizations. Magnesium-ethylene glycol bis[β-aminoethyl ether]N,N'-tetraacetic acid (Mg [2.5 mM]-EGTA [5.0 mM]) blocked the C5a-evoked potential changes, whereas colchine (10(- 6)M) and cytochalasin B (3.0 μg/ml did not. Hydrocortisone sodium succinate (0.5 mg/ml) decreased the percentage of cells responding to C5a. In related studies, synthetic N-formyl methionyl peptide (f-met-leu-phe), which had chemotactic activity for cultured macrophages, produced similar membrane potential changes. Repeated exposure of macrophages to C5a or f- met-leu-phe resulted in desensitization to the same stimulus. Simultaneous photomicroscope and intracellular recording studies during macrophage stimulation with chemotactic factor demonstrated that the membrane potential changes preceded membrane spreading, ruffling, and pseudopod formation. These observations demonstrate that ion fluxes associated with membrane potential changes are early events in macrophage activation by chemotactic factors     

Morphological Constraints of Shoot Demography of a Clonal Plant: Extra- and Intravaginal Tillers of Festuca rubra

Abstract Festuca rubra forms tillers in two different ways: extravaginally and intravaginally. Demography of these two tiller types was observed in seventeen selected tussocks of Festuca rubra s.s. over four growing seasons. Extravaginal tillers were bigger at birth and on the average produced twice as many daughter tillers per tiller. In general, the natality and mortality of extravaginal tillers were less regular than that of intravaginal tillers. Overall tillering rate per tiller was correlated with the density of the surrounding vegetation; mortality, natality and tiller life span were not. High density of the surrounding vegetation did not result in increased formation of extravaginal tillers. The proportion of the extravaginal tillers was not correlated with the density of the F. rubra tussocks. There is no evidence for foraging by extravaginal tillers, but they do act as founders of small clusters of tillers.