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排序方式: 共有96条查询结果,搜索用时 15 毫秒
31.
32.
P. CIAIS M. WATTENBACH N. VUICHARD P. SMITH S. L. PIAO A. DON S. LUYSSAERT I. A. JANSSENS A. BONDEAU R. DECHOW A. LEIP PC. SMITH C. BEER G. R. VAN DER WERF S. GERVOIS K. VAN OOST E. TOMELLERI A. FREIBAUER E. D. SCHULZE CARBOEUROPE SYNTHESIS TEAM 《Global Change Biology》2010,16(5):1409-1428
We estimated the long‐term carbon balance [net biome production (NBP)] of European (EU‐25) croplands and its component fluxes, over the last two decades. Net primary production (NPP) estimates, from different data sources ranged between 490 and 846 gC m?2 yr?1, and mostly reflect uncertainties in allocation, and in cropland area when using yield statistics. Inventories of soil C change over arable lands may be the most reliable source of information on NBP, but inventories lack full and harmonized coverage of EU‐25. From a compilation of inventories we infer a mean loss of soil C amounting to 17 g m?2 yr?1. In addition, three process‐based models, driven by historical climate and evolving agricultural technology, estimate a small sink of 15 g C m?2 yr?1 or a small source of 7.6 g C m?2 yr?1. Neither the soil C inventory data, nor the process model results support the previous European‐scale NBP estimate by Janssens and colleagues of a large soil C loss of 90 ± 50 gC m?2 yr?1. Discrepancy between measured and modeled NBP is caused by erosion which is not inventoried, and the burning of harvest residues which is not modeled. When correcting the inventory NBP for the erosion flux, and the modeled NBP for agricultural fire losses, the discrepancy is reduced, and cropland NBP ranges between ?8.3 ± 13 and ?13 ± 33 g C m?2 yr?1 from the mean of the models and inventories, respectively. The mean nitrous oxide (N2O) flux estimates ranges between 32 and 37 g C Eq m?2 yr?1, which nearly doubles the CO2 losses. European croplands act as small CH4 sink of 3.3 g C Eq m?2 yr?1. Considering ecosystem CO2, N2O and CH4 fluxes provides for the net greenhouse gas balance a net source of 42–47 g C Eq m?2 yr?1. Intensifying agriculture in Eastern Europe to the same level Western Europe amounts is expected to result in a near doubling of the N2O emissions in Eastern Europe. N2O emissions will then become the main source of concern for the impact of European agriculture on climate. 相似文献
33.
Haiyan Xia Yun Cao Xiaoman Dai Zvonimir Marelja Di Zhou Ran Mo Sahar Al-Mahdawi Mark A. Pook Silke Leimkühler Tracey A. Rouault Kuanyu Li 《PloS one》2012,7(10)
Friedreich ataxia (FRDA) is an inherited neurodegenerative disease caused by frataxin (FXN) deficiency. The nervous system and heart are the most severely affected tissues. However, highly mitochondria-dependent tissues, such as kidney and liver, are not obviously affected, although the abundance of FXN is normally high in these tissues. In this study we have revealed two novel FXN isoforms (II and III), which are specifically expressed in affected cerebellum and heart tissues, respectively, and are functional in vitro and in vivo. Increasing the abundance of the heart-specific isoform III significantly increased the mitochondrial aconitase activity, while over-expression of the cerebellum-specific isoform II protected against oxidative damage of Fe-S cluster-containing aconitase. Further, we observed that the protein level of isoform III decreased in FRDA patient heart, while the mRNA level of isoform II decreased more in FRDA patient cerebellum compared to total FXN mRNA. Our novel findings are highly relevant to understanding the mechanism of tissue-specific pathology in FRDA. 相似文献
34.
35.
Axel Barlow Catharine E. Pook Robert A. Harrison Wolfgang Wüster 《Proceedings. Biological sciences / The Royal Society》2009,276(1666):2443-2449
The processes that drive the evolution of snake venom variability, particularly the role of diet, have been a topic of intense recent research interest. Here, we test whether extensive variation in venom composition in the medically important viper genus Echis is associated with shifts in diet. Examination of stomach and hindgut contents revealed extreme variation between the major clades of Echis in the proportion of arthropod prey consumed. The toxicity (median lethal dose, LD50) of representative Echis venoms to a natural scorpion prey species was found to be strongly associated with the degree of arthropod feeding. Mapping the results onto a novel Echis phylogeny generated from nuclear and mitochondrial sequence data revealed two independent instances of coevolution of venom toxicity and diet. Unlike venom LD50, the speed with which venoms incapacitated and killed scorpions was not associated with the degree of arthropod feeding. The prey-specific venom toxicity of arthropod-feeding Echis may thus be adaptive primarily by reducing venom expenditure. Overall, our results provide strong evidence that variation in snake venom composition results from adaptive evolution driven by natural selection for different diets, and underscores the need for a multi-faceted, integrative approach to the study of the causes of venom evolution. 相似文献
36.
N-Linked glycosylation of a baculovirus-expressed recombinant glycoprotein in insect larvae and tissue culture cells 总被引:2,自引:3,他引:2
The potential of insect cell cultures and larvae infected with recombinant
baculoviruses to produce authentic recombinant glycoproteins cloned from
mammalian sources was investigated. A comparison was made of the N-linked
glycans attached to secreted alkaline phosphatase (SEAP) produced in four
species of insect larvae and their derived cell lines plus one additional
insect cell line and larvae of one additional species. These data survey
N-linked oligosaccharides produced in four families and six genera of the
order Lepidoptera. Recombinant SEAP expressed by recombinant isolates of
Autographa californica and Bombyx mori nucleopolyhedroviruses was purified
from cell culture medium, larval hemolymph or larval homogenates by
phosphate affinity chromatography. The N-linked oligosaccharides were
released with PNGase-F, labeled with 8- aminonaphthalene-1-3-6-trisulfonic
acid, fractionated by polyacrylamide gel electrophoresis, and analyzed by
fluorescence imaging. The oligosaccharide structures were confirmed with
exoglycosidase digestions. Recombinant SEAP produced in cell lines of
Lymantria dispar (IPLB-LdEIta), Heliothis virescens (IPLB-HvT1), and Bombyx
mori (BmN) and larvae of Spodoptera frugiperda, Trichoplusia ni ,
H.virescens , B.mori , and Danaus plexippus contained oligosaccharides that
were structurally identical to the 10 oligosaccharides attached to SEAP
produced in T.ni cell lines. The oligosaccharide structures were all
mannose-terminated. Structures containing two or three mannose residues,
with and without core fucosylation, constituted more than 75% of the
oligosaccharides from the cell culture and larval samples.
相似文献
37.
38.
Nicholas PC Horrocks 《Ostrich》2016,87(1):95-97
I report an instance of usurpation of a Crowned Lapwing Vanellus coronatus nest by a pair of African Wattled Lapwings Vanellus senegalensis. The nest, which originally contained a single Crowned Lapwing egg, eventually contained an additional three Wattled Lapwing eggs, before it was predated. Although parents of both species were observed in the vicinity of the nest, video monitoring showed that the Wattled Lapwings incubated all four eggs. Detection of embryonic heart rate suggested that all the eggs were probably viable up until the nest was destroyed. Nest usurpation in shorebirds is rare, and given the easily accommodated nest requirements and minimal costs of nest construction in these species, is difficult to explain. I speculate that the occurrence described here may represent a case of mistaken identity by the female Wattled Lapwing when choosing a nest scrape, since there seems to have been little benefit to the usurping species of taking over an already occupied nest. 相似文献
39.
Determinants of participation restriction among community dwelling stroke survivors: A path analysis
Background
Apart from promoting physical recovery and assisting in activities of daily living, a major challenge in stroke rehabilitation is to minimize psychosocial morbidity and to promote the reintegration of stroke survivors into their family and community. The identification of key factors influencing long-term outcome are essential in developing more effective rehabilitation measures for reducing stroke-related morbidity. The aim of this study was to test a theoretical model of predictors of participation restriction which included the direct and indirect effects between psychosocial outcomes, physical outcome, and socio-demographic variables at 12 months after stroke. 相似文献40.
Anita Malhotra Simon Creer Catharine E. Pook Roger S. Thorpe 《Molecular phylogenetics and evolution》2010,54(1):172-178
Despite much effort towards resolving the molecular phylogenetic tree for pitvipers, some aspects remain unresolved. In particular, the sister group of the diverse New World radiation has remained impossible to identify with any certainty. In this study, which for the first time includes nuclear intron data from all major groups of Asian pitvipers as well as representatives of the New World radiation, Bayesian inference allows Gloydius to be identified as the most likely sister group to the New World radiation and sheds light on other ambiguous relationships among the Old World pitvipers. The sister group relationship of “Ovophis” okinavensis and “Trimeresurus” gracilis is confirmed by the addition of nuclear genes, and we hypothesise that they form a sister group to the Gloydius + New World clade, best supported when the phylogenetic signal from gaps is included in the form of a simple-coded matrix. 相似文献