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71.
Masson Stephane; Angeli Nadine; Guillard Jean; Pinel-Alloul Bernadette 《Journal of plankton research》2001,23(10):1041-1060
Understanding the spatial dynamics of predators and their preyis one of the most important goals in aquatic ecology. We studiedspatial and temporal onshoreoffshore distribution patternsin young of the year (YOY) Eurasian perch (Perca fluviatilis)and crustacean zooplankton (Daphnia hyalina, Cyclops prealpinus)along a transect in Lake Annecy (France). Our study representsa first attempt at coupling hydroacoustic fish survey and highfrequency zooplankton recording to assess simultaneously thelarge-scale distribution patterns of YOY fish and their zooplanktonprey over a diel cycle (day, dusk and night sampling). We hypothesizedthat the spatial distribution of zooplankton could be shapedby both anti-predator behaviour (horizontal and vertical migrations)and predation losses. Fish biomass, size structure and dietwere assessed from split-beam echosounding and net trawlingsamples, whereas crustacean abundances were estimated with asmall modified LonghurstHardy continuous plankton recorder.We evaluated the diel changes in the spatial distribution patternsof fish and zooplankton and determined the overlap between theirdistributions. Fish biomass was dominated by YOY perch in upperwarmer layers and salmonids (Coregonus lavaretus and Salvelinusalpinus) in the colder and oxygenated deep layers. YOY perchwere aggregated in dense schools in the epilimnion during theday and dispersed at night. Fish biomass was distributed alonga strong increasing onshoreoffshore gradient at night,whereas crustacean prey showed a decreasing gradient. This onshoreoffshorenegative gradient in crustacean distribution, expressed on ashorter scale during the day, shifted toward the surface watersat night. A distinct kinetic of diel vertical migration (DVM)patterns was exhibited by daphnid and cyclopoid populationsand resulted in distinct vulnerability to perch predation. Spatio-temporaldistribution of crustaceans in Lake Annecy during the diel cyclestudy was probably shaped both by predation loss to YOY perchand by anti-predator behaviour (DVM, DHM) by zooplankton. Theimplications for fine-scale studies of fish-zooplankton interactionsare discussed. 相似文献
72.
A short peptide at the amino terminus of the Sendai virus C protein acts as an independent element that induces STAT1 instability 下载免费PDF全文
The Sendai virus C protein acts to dismantle the interferon-induced cellular antiviral state in an MG132-sensitive manner, in part by inducing STAT1 instability. This activity of C maps to the first 23 amino acids (C(1-23)) of the 204-amino-acid (aa)-long protein (C(1-204)). C(1-23) was found to act as an independent viral element that induces STAT1 instability, since this peptide fused to green fluorescent protein (C(1-23)/GFP) is at least as active as C(1-204) in this respect. This peptide also induces the degradation of C(1-23)/GFP and other proteins to which it is fused. Most of C(1-204), and particularly its amino-terminal half, is predicted to be structurally disordered. C(1-23) as a peptide was found to be disordered by circular dichroism, and the first 11 aa have a strong potential to form an amphipathic alpha-helix in low concentrations of trifluoroethanol, which is thought to mimic protein-protein interaction. The critical degradation-determining sequence of C(1-23) was mapped by mutation to eight residues near its N terminus: (4)FLKKILKL(11). All the large hydrophobic residues of (4)FLKKILKL(11), plus its ability to form an amphipathic alpha-helix, were found to be critical for STAT1 degradation. In contrast, C(1-23)/GFP self-degradation did not require (8)ILKL(11), nor the ability to form an alpha-helix throughout this region. Remarkably, C(1-23)/GFP also stimulated C(1-204) degradation, and this degradation in trans required the same peptide determinants as for STAT1. Our results suggest that C(1-204) coordinates its dual activities of regulating viral RNA synthesis and counteracting the host innate antiviral response by sensing both its own intracellular concentration and that of STAT1. 相似文献
73.
The catalytic subunit of yeast telomerase, Est2p, is a telomere associated throughout most of the cell cycle, while the Est1p subunit binds only in late S/G2 phase, the time of telomerase action. Est2p binding in G1/early S phase requires a specific interaction between telomerase RNA (TLC1) and Ku80p. Here, we show that in four telomerase-deficient strains (cdc13-2, est1Ä, tlc1-SD, and tlc1-BD), Est2p telomere binding was normal in G1/early S phase but reduced to about 40–50% of wild type levels in late S/G2 phase. Est1p telomere association was low in all four strains. Wild type levels of Est2p telomere binding in late S/G2 phase was Est1p-dependent and required that Est1p be both telomere-bound and associated with a stem-bulge region in TLC1 RNA. In three telomerase-deficient strains in which Est1p is not Est2p-associated (tlc1-SD, tlc1-BD, and est2Ä), Est1p was present at normal levels but its telomere binding was very low. When the G1/early S phase and the late S/G2 phase telomerase recruitment pathways were both disrupted, neither Est2p nor Est1p was telomere-associated. We conclude that reduced levels of Est2p and low Est1p telomere binding in late S/G2 phase correlated with an est phenotype, while a WT level of Est2p binding in G1 was not sufficient to maintain telomeres. In addition, even though Cdc13p and Est1p interact by two hybrid, biochemical and genetic criteria, this interaction did not occur unless Est1p was Est2p-associated, suggesting that Est1p comes to the telomere only as part of the holoenzyme. Finally, the G1 and late S/G2 phase pathways for telomerase recruitment are distinct and are likely the only ones that bring telomerase to telomeres in wild-type cells. 相似文献
74.
Gosset G Satre M Blaive B Clément JL Martin JB Culcasi M Pietri S 《Analytical biochemistry》2008,380(2):184-194
The 31P nuclear magnetic resonance (NMR) characteristics, toxicity, and cellular penetration of five linear or cyclic α-aminophosphonate highly sensitive pH probes were investigated in Dictyostelium discoideum cells and isolated rat hearts and were compared with three phosphonic acid derivatives. The line width broadening at pH pKa, which was satisfactorily modelized for all compounds, was significantly limited in biological milieu for the new markers, affording a four- to sixfold better accuracy in pH determination. Cellular uptake or washout of nontoxic concentrations (<15 mM) of α-aminophosphonates occurred by rapid passive permeation, whereas standard probes required a much slower fluid-phase pinocytosis and transport processes that could ultimately lead to trapping. Using mild concentrations (<4 mM) three α-aminophosphonates having 6 < pKa < 7 allowed an easy and simultaneous 31P NMR determination of cytosolic, acidic, and extracellular compartments in anoxic–reoxygenated or starving D. discoideum. 相似文献
75.
Nathalie Droin Jean-Baptiste Hendra Patrick Ducoroy Eric Solary 《Journal of Proteomics》2009,72(6):918
Human defensins, which are small cationic peptides produced by neutrophils and epithelial cells, form two genetically distinct alpha and beta subfamilies. They are involved in innate immunity through killing microbial pathogens or neutralizing bacterial toxins and in adaptive immunity by serving as chemoattractants and activators of immune cells. α-defensins are mainly packaged in neutrophil granules (HNP1, HNP2, HNP3) or secreted by intestinal Paneth cells (HD5, HD6), while β-defensins are expressed in mucosa and epithelial cells. Using surface enhanced laser desorption/ionisation time-of-flight (SELDI-TOF) mass spectrometry (MS), α-defensins were found to be expressed in a variety of human tumours, either in tumour cells or at their surface. HNP1–3 peptides are also secreted and their accumulation in biological fluids was proposed as a tumour biomarker. Conversely, β-defensin-1 (HBD-1) is down-regulated in some tumour types in which it could behave as a tumour suppressor protein. Alpha-defensins promote tumour cell growth or, at higher concentration, provoke cell death. These peptides also inhibit angiogenesis, which, in addition to immunomodulation, indicates a complex role in tumour development. This review summarizes current knowledge of defensins to discuss their role in tumour growth, tumour monitoring and cancer treatment. 相似文献
76.
This is the first detailed report of social factors affecting fish-eating in Japanese macaques under natural circumstances. We video-recorded a complete event of fish eating, involving a new fish food species for the monkeys on Koshima island. Following the discovery of a large beached sea bass by a peripheral male, we observed a total of 16 individuals feeding on the fish in turns, and interacting around it. The rank order of access to the fish was mainly explained by the spatial position of group members, whereas dominance determined how long the fish was monopolized. Although limited, the tolerated presence of close-bystanders while feeding was affected by kinship and affiliation. Genealogic data suggested that fish-eating behavior was well maintained in terms of maternal lineages. This report should contribute to a better understanding of how social features may constrain the long-term diffusion of feeding innovations in free-ranging primate groups. 相似文献
77.
Fatty acid composition of the amphipod Dikerogammarus villosus: feeding strategies and trophic links
Maazouzi C Masson G Izquierdo MS Pihan JC 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2007,147(4):868-875
Fatty acid (FA) compositions were determined for the invader amphipod Dikerogammarus villosus collected from July to September 2002, in an overheated, high-conductivity dammed reservoir in north-eastern France. Predominant fatty acids were the polyunsaturated fatty acids (PUFA): eicosapentaenoic acid (EPA), linoleic acid (LA), arachidonic acid (ARA), linolenic acid (LNA) together with the monounsaturated fatty acid 18:1omega9 and the saturated fatty acid 16:0. FA markers indicated that available food was constituted of incompletely degraded phytodetritus and terrestrial inputs, as well as animal remains. PUFA contents depended on the diet and the capacity of animals to desaturate and elongate LNA and LA in long chain PUFA as EPA and ARA respectively. Based on their FA compositions, we showed that gammarids represent naturally-occurring freshwater sources of essential PUFA, and could play a fundamental role in pelagic-benthic coupling and energy recycling in the ecosystem. The complexity of the feeding strategies of D. villosus--detritivorous, omnivorous, carnivorous--makes this species efficient at exploiting different components of the available food and may be a key factor in its high invasive success. 相似文献
78.
Marina Giuliano Mauro Andreotti Giuseppe Liotta Haswell Jere Jean-Baptiste Sagno Martin Maulidi Sandro Mancinelli Ersilia Buonomo Paola Scarcella Maria F. Pirillo Roberta Amici Susanna Ceffa Stefano Vella Leonardo Palombi Maria Cristina Marazzi 《PloS one》2013,8(7)
Background
Optimized preventive strategies are needed to reach the objective of eliminating pediatric AIDS. This study aimed to define the determinants of residual HIV transmission in the context of maternal antiretroviral therapy (ART) administration to pregnant women, to assess infant safety of this strategy, and to evaluate its impact on maternal disease.Methodology/Principal Findings
A total of 311 HIV-infected pregnant women were enrolled in Malawi in an observational study and received a nevirapine-based regimen from week 25 of gestation until 6 months after delivery (end of breastfeeding period) if their CD4+ count was > 350/mm3 at baseline (n = 147), or indefinitely if they met the criteria for treatment (n. 164). Mother/child pairs were followed until 2 years after delivery. The Kaplan-Meier method was used to estimate HIV transmission, maternal disease progression, and survival at 24 months. The rate of HIV infant infection was 3.2% [95% confidence intervals (CI) 1.0-5.4]. Six of the 8 transmissions occurred among mothers with baseline CD4+ count > 350/mm3. HIV-free survival of children was 85.8% (95% CI 81.4-90.1). Children born to mothers with baseline CD4+ count < 350/mm3 were at increased risk of death (hazard ratio 2.6, 95% CI 1.1-6.1). Among women who had stopped treatment the risk of progression to CD4+ count < 350/mm3 was 20.6% (95% CI 9.2-31.9) by 18 months of drug discontinuation.Conclusions
HIV transmission in this cohort was rare however, it occurred in a significative proportion among women with high CD4+ counts. Strategies to improve treatment adherence should be implemented to further reduce HIV transmission. Mortality in the uninfected exposed children was the major determinant of HIV-free survival and was associated to maternal disease stage. Given the considerable proportion of women reaching the criteria for treatment within 18 months of drug discontinuation, life-long ART administration to HIV-infected women should be considered. 相似文献79.
The transcriptional histone acetyltransferase cofactor TRRAP associates with the MRN repair complex and plays a role in DNA double-strand break repair 下载免费PDF全文
Robert F Hardy S Nagy Z Baldeyron C Murr R Déry U Masson JY Papadopoulo D Herceg Z Tora L 《Molecular and cellular biology》2006,26(2):402-412
80.
Laurine M Gilles Thomas Widiez Laurine M Gilles Abdelsabour Khaled Jean-Baptiste Laffaire Sandrine Chaignon Ghislaine Gendrot Jérôme Laplaige Hélène Bergès Genséric Beydon Vincent Bayle Pierre Barret Jordi Comadran Jean-Pierre Martinant Peter M Rogowsky Thomas Widiez 《The EMBO journal》2017,36(6):707-717
Gynogenesis is an asexual mode of reproduction common to animals and plants, in which stimuli from the sperm cell trigger the development of the unfertilized egg cell into a haploid embryo. Fine mapping restricted a major maize QTL (quantitative trait locus) responsible for the aptitude of inducer lines to trigger gynogenesis to a zone containing a single gene NOT LIKE DAD (NLD) coding for a patatin-like phospholipase A. In all surveyed inducer lines, NLD carries a 4-bp insertion leading to a predicted truncated protein. This frameshift mutation is responsible for haploid induction because complementation with wild-type NLD abolishes the haploid induction capacity. Activity of the NLD promoter is restricted to mature pollen and pollen tube. The translational NLD::citrine fusion protein likely localizes to the sperm cell plasma membrane. In Arabidopsis roots, the truncated protein is no longer localized to the plasma membrane, contrary to the wild-type NLD protein. In conclusion, an intact pollen-specific phospholipase is required for successful sexual reproduction and its targeted disruption may allow establishing powerful haploid breeding tools in numerous crops. 相似文献