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排序方式: 共有298条查询结果,搜索用时 203 毫秒
1.
Jennifer D. Watts Mary Farina John S. Kimball Luke D. Schiferl Zhihua Liu Kyle A. Arndt Donatella Zona Ashley Ballantyne Eugénie S. Euskirchen Frans-Jan W. Parmentier Manuel Helbig Oliver Sonnentag Torbern Tagesson Janne Rinne Hiroki Ikawa Masahito Ueyama Hideki Kobayashi Torsten Sachs Daniel F. Nadeau John Kochendorfer Marcin Jackowicz-Korczynski Anna Virkkala Mika Aurela Roisin Commane Brendan Byrne Leah Birch Matthew S. Johnson Nima Madani Brendan Rogers Jinyang Du Arthur Endsley Kathleen Savage Ben Poulter Zhen Zhang Lori M. Bruhwiler Charles E. Miller Scott Goetz Walter C. Oechel 《Global Change Biology》2023,29(7):1870-1889
Arctic-boreal landscapes are experiencing profound warming, along with changes in ecosystem moisture status and disturbance from fire. This region is of global importance in terms of carbon feedbacks to climate, yet the sign (sink or source) and magnitude of the Arctic-boreal carbon budget within recent years remains highly uncertain. Here, we provide new estimates of recent (2003–2015) vegetation gross primary productivity (GPP), ecosystem respiration (Reco), net ecosystem CO2 exchange (NEE; Reco − GPP), and terrestrial methane (CH4) emissions for the Arctic-boreal zone using a satellite data-driven process-model for northern ecosystems (TCFM-Arctic), calibrated and evaluated using measurements from >60 tower eddy covariance (EC) sites. We used TCFM-Arctic to obtain daily 1-km2 flux estimates and annual carbon budgets for the pan-Arctic-boreal region. Across the domain, the model indicated an overall average NEE sink of −850 Tg CO2-C year−1. Eurasian boreal zones, especially those in Siberia, contributed to a majority of the net sink. In contrast, the tundra biome was relatively carbon neutral (ranging from small sink to source). Regional CH4 emissions from tundra and boreal wetlands (not accounting for aquatic CH4) were estimated at 35 Tg CH4-C year−1. Accounting for additional emissions from open water aquatic bodies and from fire, using available estimates from the literature, reduced the total regional NEE sink by 21% and shifted many far northern tundra landscapes, and some boreal forests, to a net carbon source. This assessment, based on in situ observations and models, improves our understanding of the high-latitude carbon status and also indicates a continued need for integrated site-to-regional assessments to monitor the vulnerability of these ecosystems to climate change. 相似文献
2.
A Duperray C Madani E M Chambaz 《Biochemical and biophysical research communications》1981,103(4):1294-1301
Difluoromethylornithine (DFMO), a selective inhibitor of ornithine decarboxylase, was used to probe the possible role of polyamines in the regulation of proliferation and steroidogenic activities of bovine adrenocortical cells in primary culture. The presence of DFMO in the culture medium not only suppressed the polyamine increase observed in proliferating control cells but resulted in a rapid depletion of the putrescine and spermidine cellular content, while spermine remained at a basal level. The proliferation of DFMO-treated cells was rapidly blocked and resumed at a normal rate upon addition of putrescine to the medium. DFMO-treated cells showed an impaired steroidogenic response to ACTH while adenylate cyclase stimulation was not altered. Thus, while ornithine decarboxylase and polyamines may be required for adrenocortical cell replication, deprivation of these compounds did not facilitate the expression of differentiated cell functions, as observed with granulosa cells. 相似文献
3.
Sedigheh Zakeri Ahmad Raeisi Mandana Afsharpad Qutbuddin Kakar Faezeh Ghasemi Hoda Atta Ghasem Zamani Muhammad Suleiman Memon Masoud Salehi Navid Dinparast Djadid 《Parasitology international》2010,59(1):15-21
In this study, the diversity of Plasmodium vivax populations circulating in Pakistan and Iran has been investigated by using circumsporozoite protein (csp) and merozoite surface proteins 1 and 3α (msp-1 and msp-3α) genes as genetic markers. Infected P. vivax blood samples were collected from Pakistan (n = 187) and Iran (n = 150) during April to October 2008, and were analyzed using nested-PCR/RFLP and sequencing methods. Genotyping pvmsp-1 (variable block 5) revealed the presence of type 1, type 2 and recombinant type 3 allelic variants, with type 1 predominant, in both study areas. The sequence analysis of 33 P. vivax isolates from Pakistan and 30 from Iran identified 16 distinct alleles each, with one allele (R-8) from Iran which was not reported previously. Genotyping pvcsp gene also showed that VK210 type is predominant in both countries. Moreover, based on the size of amplified fragment of pvmsp-3α, three major types: type A (1800 bp), type B (1500 bp) and type C (1200 bp), were distinguished among the examined isolates that type A was predominant among Pakistani (72.7%) and Iranian (77.3%) parasites. PCR/RFLP products of pvmsp-3α with HhaI and AluI have detected 40 and 39 distinct variants among Pakistani and Iranian examined isolates, respectively. Based on these three studied genes, the rate of combined multiple genotypes were 30% and 24.6% for Pakistani and Iranian P. vivax isolates, respectively. These results indicate an extensive diversity in the P. vivax populations in both studies. 相似文献
4.
Rahbar Mohammad Reza Zarei Mahboubeh Jahangiri Abolfazl Khalili Saeed Nezafat Navid Negahdaripour Manica Fattahian Yaser Ghasemi Younes 《International journal of peptide research and therapeutics》2020,26(3):1269-1282
International Journal of Peptide Research and Therapeutics - Acinetobacter baumannii is an important pathogen responsible for nosocomial infections worldwide. Trimeric autotransporters, the... 相似文献
5.
Zhihua Liu John S. Kimball Nicholas C. Parazoo Ashley P. Ballantyne Wen J. Wang Nima Madani Caleb G. Pan Jennifer D. Watts Rolf H. Reichle Oliver Sonnentag Philip Marsh Miriam Hurkuck Manuel Helbig William L. Quinton Donatella Zona Masahito Ueyama Hideki Kobayashi Eugnie S. Euskirchen 《Global Change Biology》2020,26(2):682-696
Arctic and boreal ecosystems play an important role in the global carbon (C) budget, and whether they act as a future net C sink or source depends on climate and environmental change. Here, we used complementary in situ measurements, model simulations, and satellite observations to investigate the net carbon dioxide (CO2) seasonal cycle and its climatic and environmental controls across Alaska and northwestern Canada during the anomalously warm winter to spring conditions of 2015 and 2016 (relative to 2010–2014). In the warm spring, we found that photosynthesis was enhanced more than respiration, leading to greater CO2 uptake. However, photosynthetic enhancement from spring warming was partially offset by greater ecosystem respiration during the preceding anomalously warm winter, resulting in nearly neutral effects on the annual net CO2 balance. Eddy covariance CO2 flux measurements showed that air temperature has a primary influence on net CO2 exchange in winter and spring, while soil moisture has a primary control on net CO2 exchange in the fall. The net CO2 exchange was generally more moisture limited in the boreal region than in the Arctic tundra. Our analysis indicates complex seasonal interactions of underlying C cycle processes in response to changing climate and hydrology that may not manifest in changes in net annual CO2 exchange. Therefore, a better understanding of the seasonal response of C cycle processes may provide important insights for predicting future carbon–climate feedbacks and their consequences on atmospheric CO2 dynamics in the northern high latitudes. 相似文献
6.
Kashif Bilal Samee U. Khan Sajjad A. Madani Khizar Hayat Majid I. Khan Nasro Min-Allah Joanna Kolodziej Lizhe Wang Sherali Zeadally Dan Chen 《Cluster computing》2013,16(3):575-589
The Information and Communication Technology sector is considered to be a major consumer of energy and has become an active participant in Green House Gas emissions. Lots of efforts have been devoted to make network infrastructure and network protocols power-aware and green. Among these efforts, Adaptive Link Rate (ALR) is one of the most widely discussed approaches. This survey highlights the most recent ALR approaches with a brief taxonomy and the state of the art. 相似文献
7.
Lisa Kolden Midtb? Mohammad Madani Ibrahim Lene Secher Myrmel Ulrike Liisberg Aune Anita R?yneberg Alvheim Nina S. Liland Bente E. Torstensen Grethe Rosenlund Bj?rn Liaset Trond Brattelid Karsten Kristiansen Lise Madsen 《PloS one》2013,8(1)
Background
To ensure sustainable aquaculture, fish derived raw materials are replaced by vegetable ingredients. Fatty acid composition and contaminant status of farmed Atlantic salmon (Salmo salar L.) are affected by the use of plant ingredients and a spillover effect on consumers is thus expected. Here we aimed to compare the effects of intake of Atlantic salmon fed fish oil (FO) with intake of Atlantic salmon fed a high proportion of vegetable oils (VOs) on development of insulin resistance and obesity in mice.Methodology/principal findings
Atlantic salmon were fed diets where FO was partly (80%) replaced with three different VOs; rapeseed oil (RO), olive oil (OO) or soy bean oil (SO). Fillets from Atlantic salmon were subsequently used to prepare Western diets (WD) for a mouse feeding trial. Partial replacement of FO with VOs reduced the levels of polychlorinated biphenyls (PCB) and dichloro-diphenyl-tricloroethanes (DDT) with more than 50% in salmon fillets, in WDs containing the fillets, and in white adipose tissue from mice consuming the WDs. Replacement with VOs, SO in particular, lowered the n−3 polyunsaturated fatty acid (PUFA) content and increased n−6 PUFA levels in the salmon fillets, in the prepared WDs, and in red blood cells collected from mice consuming the WDs. Replacing FO with VO did not influence obesity development in the mice, but replacement of FO with RO improved glucose tolerance. Compared with WD-FO fed mice, feeding mice WD-SO containing lower PCB and DDT levels but high levels of linoleic acid (LA), exaggerated insulin resistance and increased accumulation of fat in the liver.Conclusion/Significance
Replacement of FO with VOs in aqua feed for farmed salmon had markedly different spillover effects on metabolism in mice. Our results suggest that the content of LA in VOs may be a matter of concern that warrants further investigation. 相似文献8.
Mohammad Foad Abazari Fatemeh Soleimanifar Seyed Ehsan Enderami Navid Nasiri Fatemeh Nejati Seyed Ahmad Mousavi Masoud Soleimani Jafar Kiani Pegah Ghoraeian Mousa Kehtari 《Journal of cellular biochemistry》2020,121(2):1169-1181
Human-induced pluripotent stem cells-derived hepatocyte-like cells (hiPSCs-HLCs) holds considerable promise for future clinical personalized therapy of liver disease. However, the low engraftment of these cells in the damaged liver microenvironment is still an obstacle for potential application. In this study, we explored the effectiveness of decellularized amniotic membrane (dAM) matrices for culturing of iPSCs and promoting their differentiation into HLCs. The DNA content assay and histological evaluation indicated that cellular and nuclear residues were efficiently eliminated and the AM extracellular matrix component was maintained during decelluarization. DAM matrices were developed as three-dimensional scaffolds and hiPSCs were seeded into these scaffolds in defined induction media. In dAM scaffolds, hiPSCs-HLCs gradually took a typical shape of hepatocytes (polygonal morphology). HiPSCs-HLCs that were cultured into dAM scaffolds showed a higher level of hepatic markers than those cultured in tissue culture plates (TCPs). Moreover, functional activities in term of albumin and urea synthesis and CYP3A activity were significantly higher in dAM scaffolds than TCPs over the same differentiation period. Thus, based on our results, dAM scaffold might have a considerable potential in liver tissue engineering, because it can improve hepatic differentiation of hiPSCs which exhibited higher level of the hepatic marker and more stable metabolic functions. 相似文献
9.
10.
Farhani Ibrahim Nezafat Navid Mahmoodi Shirin 《International journal of peptide research and therapeutics》2019,25(2):541-553
International Journal of Peptide Research and Therapeutics - Shigella spp. causes severe diarrhea and dysenteric disease, which known as shigellosis. Until now, no licensed vaccine is available for... 相似文献