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991.
Tibor Erős Lise Comte Ana Filipa Filipe Albert Ruhi Pablo A. Tedesco Ulrich Brose Marie-Josée Fortin Xingli Giam Katie Irving Claire Jacquet Stefano Larsen Sapna Sharma Julian D. Olden 《Ecography》2020,43(8):1156-1166
Despite the increasing ubiquity of biological invasions worldwide, little is known about the scale-dependent effects of nonnative species on real-world ecological dynamics. Here, using an extensive time series dataset of riverine fish communities across different biogeographic regions of the world, we assessed the effects of nonnative species on the temporal variability and synchrony in abundance at different organizational levels (population, metapopulation, community and metacommunity) and spatial scales (stream reach and river basin). At the reach scale, we found that populations of nonnative species were more variable over time than native species, and that this effect scaled up to the community level – significantly destabilizing the dynamics of riverine fish communities. Nonnative species not only contributed to reduced community stability, but also increased variability of native populations. By contrast, we found no effect of nonnative species dominance on local interspecific synchrony among native species. At the basin scale, nonnative metapopulations were again more variable than the native ones. However, neither native metapopulations nor metacommunities showed differences in temporal variability or synchrony as nonnative species dominance increased basin-wide. This suggests a ‘dilution effect’ where the contribution to regional stability of local native populations from sites displaying low levels of invasion reduced the destabilizing effects of nonnative species. Overall, our results indicate that accounting for the destabilizing effect of nonnative species is critical to understanding native species persistence and community stability. 相似文献
992.
Marine food webs are highly compartmentalized, and characterizing the trophic niches among consumers is important for predicting how impact from human activities affects the structuring and functioning of marine food webs. Biomarkers such as bulk stable isotopes have proven to be powerful tools to elucidate trophic niches, but they may lack in resolution, particularly when spatiotemporal variability in a system is high. To close this gap, we investigated whether carbon isotope (δ13C) patterns of essential amino acids (EAAs), also termed δ13CAA fingerprints, can characterize niche differentiation in a highly dynamic marine system. Specifically, we tested the ability of δ13CAA fingerprints to differentiate trophic niches among six functional groups and ten individual species in the Baltic Sea. We also tested whether fingerprints of the common zooplanktivorous fishes, herring and sprat, differ among four Baltic Sea regions with different biochemical conditions and phytoplankton assemblages. Additionally, we investigated how these results compared to bulk C and N isotope data for the same sample set. We found significantly different δ13CAA fingerprints among all six functional groups. Species differentiation was in comparison less distinct, due to partial convergence of the species' fingerprints within functional groups. Herring and sprat displayed region‐specific δ13CAA fingerprints indicating that this approach could be used as a migratory marker. Niche metrics analyses showed that bulk isotope data had a lower power to differentiate between trophic niches than δ13CAA fingerprinting. We conclude that δ13CAA fingerprinting has a strong potential to advance our understanding of ecological niches, and trophic linkages from producers to higher trophic levels in dynamic marine systems. Given how management practices of marine resources and habitats are reshaping the structure and function of marine food webs, implementing new and powerful tracer methods are urgently needed to improve the knowledge base for policy makers. 相似文献
993.
Stecyk JA Larsen BC Nilsson GE 《American journal of physiology. Regulatory, integrative and comparative physiology》2011,301(4):R1132-R1142
The crucian carp (Carassius carassius) seems unique among vertebrates in its ability to maintain cardiac performance during prolonged anoxia. We investigated whether this phenomenon arises in part from a myocardium tolerant to severe acidosis or because the anoxic crucian carp heart may not experience a severe extracellular acidosis due to the fish's ability to convert lactate to ethanol. Spontaneously contracting heart preparations from cold-acclimated (6-8°C) carp were exposed (at 6.5°C) to graded or ungraded levels of acidosis under normoxic or anoxic conditions and intrinsic contractile performance was assessed. Our results clearly show that the carp heart is tolerant of acidosis as long as oxygen is available. However, heart rate and contraction kinetics of anoxic hearts were severely impaired when extracellular pH was decreased below 7.4. Nevertheless, the crucian carp heart was capable of recovering intrinsic contractile performance upon reoxygenation regardless of the severity of the anoxic + acidotic insult. Finally, we show that increased adrenergic stimulation can ameliorate, to a degree, the negative effects of severe acidosis on the intrinsic contractile properties of the anoxic crucian carp heart. Combined, these findings indicate an avoidance of severe extracellular acidosis and adrenergic stimulation are two important factors protecting the intrinsic contractile properties of the crucian carp heart during prolonged anoxia, and thus likely facilitate the ability of the anoxic crucian carp to maintain cardiac pumping. 相似文献
994.
Broadley K Larsen L Herst PM Smith RA Berridge MV McConnell MJ 《Journal of cellular biochemistry》2011,112(7):1869-1879
The switch from oxidative phosphorylation to glycolytic metabolism results in cells that generate fewer reactive oxygen species (ROS) and are resistant to the intrinsic induction of apoptosis. As a consequence, glycolytic cancer cells are resistant to radiation and chemotherapeutic agents that rely on production of ROS or intrinsic apoptosis. Further, the level of glycolysis correlates with tumor invasion, making glycolytic cancer cells an important target for new therapy development. We have synthesized a novel redox-active quinone phloroglucinol derivative, PMT7. Toxicity of PMT7 was in part due to loss of mitochondrial membrane potential in treated cells with subsequent loss of mitochondrial metabolic activity. Mitochondrial gene knockout ρ0 cells, a model of highly glycolytic cancers, were only half as sensitive as the corresponding wild-type cells and metabolic pathways downstream of MET were unaffected in ρ0 cells. However, PMT7 toxicity was also due to a block in autophagy. Both wild-type and ρ0 cells were susceptible to autophagy blockade, and the resistance of ρ0 cells to PMT7 could be overcome by serum deprivation, a situation where autophagy becomes necessary for survival. The stress response class III deacetylase SIRT1 was not significantly involved in PMT7 toxicity, suggesting that unlike other chemotherapeutic drugs, SIRT1-mediated stress and survival responses were not induced by PMT7. The dependence on autophagy or other scavenging pathways makes glycolytic cancer cells vulnerable. This can be exploited by induction of energetic stress to specifically sensitize glycolytic cells to other stresses such as nutrient deprivation or potentially chemotherapy. 相似文献
995.
Gitte Petersen Lone Aagesen Ole Seberg Ida Hartvig Larsen 《Cladistics : the international journal of the Willi Hennig Society》2011,27(4):428-446
Direct optimization was used to reconstruct the phylogeny of the 26 diploid taxa included in the genus Hordeum. The total data set was composed of 16 nucleotide sequence regions from the nuclear as well as the plastid genome. The nine nuclear regions were from single‐copy, protein coding genes located on six of the seven chromosome pairs in the diploid H. vulgare genome. The seven plastid regions comprise protein coding genes as well as intergenic regions. Studies of character congruence between data partitions showed no correlation between chromosomal location and congruence among the nuclear sequences and a level of congruence among the plastid sequences comparable with the level among the nuclear sequences. Combined analysis of all data resolved the phylogeny completely with most clades being robust and well supported. However, due to incongruence among data partitions some relationships are still and likely to remain ambiguously inferred. Rather than adding still more genes to the phylogenetic analyses, patterns of incongruence may be better explored by adding data from multiple specimens per taxon. For some species relationships the plastid data appear positively misleading, emphasizing the need for caution if plastid data are the only or dominant type of data used for phylogenetic reconstruction and subsequent re‐classification.© The Willi Hennig Society 2011. 相似文献
996.
The mobile fauna associated with two sympatric kelp species with different holdfast morphology (Saccorhiza polyschides and Laminaria hyperborea) was compared to test for differences in the assemblage structure of holdfast-associated mobile epifauna. A total of 24,140
epifaunal individuals were counted from 30 holdfasts of each kelp species. Overall epifaunal abundances exceeded faunal abundances
previously reported from holdfasts of other kelps. Three taxonomic groups, Amphipoda, Mollusca, and Polychaeta, accounted
for ca. 85% of all individuals. Total abundances increased with the amount of habitat available, quantified either as the
volume or the area provided by the holdfasts. The multivariate structure of the epifaunal assemblage did not differ between
holdfasts of the two kelp species. However, epifaunal assemblages responded differentially to the habitat attributes provided
by each type of kelp holdfast: multivariate variation in the assemblage structure of epifauna was mostly explained by holdfast
area and volume for L. hyperborea, and by the surface-to-volume ratio for S. polyschides holdfasts. Therefore, the physical attributes of biogenic habitats, here kelp holdfasts that better predict patterns in the
assemblage structure of associated fauna can differ according to their different physical morphology, even though the overall
assemblage structure of associated fauna was similar. 相似文献
997.
Floyd TL Koehn BH Kitchens WH Robertson JM Cheeseman JA Stempora L Larsen CP Ford ML 《Journal of immunology (Baltimore, Md. : 1950)》2011,186(4):2033-2041
Donor-reactive memory T cells (Tmem) can play an important role in mediating graft rejection after transplantation. Transplant recipients acquire donor-reactive Tmem not only through prior sensitization with alloantigens but also through previous exposure to environmental pathogens that are cross-reactive with allogeneic peptide-MHC complexes. Current dogma suggests that most, if not all, Tmem responses are independent of the requirement for CD28 and/or CD154/CD40-mediated costimulation to mount a recall response. However, heterogeneity among Tmem is increasingly being appreciated, and one important factor known to impact the function and phenotype of Ag-specific T cell responses is the amount/duration of Ag exposure. Importantly, the impact of Ag exposure on development of costimulation independence is currently unknown. In this study, we interrogated the effect of decreased Ag amount/duration during priming on the ability of donor-reactive Tmem to mediate costimulation blockade-resistant rejection during a recall response after transplantation in a murine model. Recipients possessing donor-reactive Tmem responses that were generated under conditions of reduced Ag exposure exhibited similar frequencies of Ag-specific T cells at day 30 postinfection, but, strikingly, failed to mediate costimulation blockade-resistant rejection after challenge with an OVA-expressing skin graft. Thus, these data demonstrate the amount/duration of Ag exposure is a critical factor in determining Tmem's relative requirement for costimulation during the recall response after transplantation. 相似文献
998.
Jørgensen S Eskildsen M Fugger K Hansen L Larsen MS Kousholt AN Syljuåsen RG Trelle MB Jensen ON Helin K Sørensen CS 《The Journal of cell biology》2011,192(1):43-54
The eukaryotic cell cycle is regulated by multiple ubiquitin-mediated events, such as the timely destruction of cyclins and replication licensing factors. The histone H4 methyltransferase SET8 (Pr-Set7) is required for chromosome compaction in mitosis and for maintenance of genome integrity. In this study, we show that SET8 is targeted for degradation during S phase by the CRL4(CDT2) ubiquitin ligase in a proliferating cell nuclear antigen (PCNA)-dependent manner. SET8 degradation requires a conserved degron responsible for its interaction with PCNA and recruitment to chromatin where ubiquitylation occurs. Efficient degradation of SET8 at the onset of S phase is required for the regulation of chromatin compaction status and cell cycle progression. Moreover, the turnover of SET8 is accelerated after ultraviolet irradiation dependent on the CRL4(CDT2) ubiquitin ligase and PCNA. Removal of SET8 supports the modulation of chromatin structure after DNA damage. These results demonstrate a novel regulatory mechanism, linking for the first time the ubiquitin-proteasome system with rapid degradation of a histone methyltransferase to control cell proliferation. 相似文献
999.
Bendsen NT Stender S Szecsi PB Pedersen SB Basu S Hellgren LI Newman JW Larsen TM Haugaard SB Astrup A 《Journal of lipid research》2011,52(10):1821-1828
Consumption of industrially produced trans fatty acids (IP-TFA) has been positively associated with systemic markers of low-grade inflammation and endothelial dysfunction in cross-sectional studies, but results from intervention studies are inconclusive. Therefore, we conducted a 16 week double-blind parallel intervention study with the objective to examine the effect of IP-TFA intake on biomarkers of inflammation, oxidative stress, and endothelial dysfunction. Fifty-two healthy overweight postmenopausal women (49 completers) were randomly assigned to receive either partially hydrogenated soybean oil (15.7 g/day IP-TFA) or control oil without IP-TFA. After 16 weeks, IP-TFA intake increased baseline-adjusted serum tumor necrosis factor (TNF) α by 12% [95% confidence interval (CI): 5-20; P = 0.002] more in the IP-TFA group compared with controls. Plasma soluble TNF receptors 1 and 2 were also increased by IP-TFA [155 pg/ml (CI: 63-247); P < 0.001 and 480 pg/ml (CI: 72-887); P = 0.02, respectively]. Serum C-reactive protein, interleukin (IL) 6 and adiponectin and subcutaneous abdominal adipose tissue mRNA expression of IL6, IL8, TNFα, and adiponectin as well as ceramide content were not affected by IP-TFA, nor was urinary 8-iso-prostaglandin-F(2α). In conclusion, this dietary trial indicates that the mechanisms linking dietary IP-TFA to cardiovascular disease may involve activation of the TNFα system. 相似文献
1000.