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91.
Passianoto Caio C. Ahrens Toby Feigl Brigitte J. Steudler Paul A. Melillo Jerry M. do Carmo Janaina B. 《Plant and Soil》2004,258(1):21-29
We have investigated a subset of restoration practices applied to a degraded pasture at Fazenda Nova Vida, a 22000 ha cattle ranch in Rond^onia, Brazil. Nitric oxide (NO) and carbon dioxide (CO2) emissions from soils were measured in conventional tillage and current pasture sites to assess N and C losses. Mean daily NO emissions from tilled plots were at least twice those from the pasture. Nitric oxide emissions from the tilled sites showed a strong diurnal pattern, while those from the pasture sites did not. Mean daytime NO emissions from the tilled sites were 9.7 g NO-N m–2 h–1, while mean nighttime emissions were 29.7 g NO-N m–2 h–1. In the pasture sites, NO emissions were 7.6 g NO-N m–2 h–1 during the day, and 7.7 g NO-N m–2 h–1 at night. Surface soil temperature was a good inverse predictor (r
2=0.75) of NO emissions from the tilled sites. Carbon dioxide emissions from the tilled sites were generally larger than CO2 emissions from the pasture sites. The mean CO2 emission rate from the tilled sites was 179 mg C m–2 h–1, while it was 123 mg C m–2 h–1 from the pasture sites. There was no distinct diurnal pattern for CO2 emissions. We found that the very high temperatures measured at the soil surface in the tillage plots, in the range of 40–45°C, reduced the rate of NO emission. The reduction in NO emissions may be because of the sensitivity of autotrophic nitrifiers to high temperatures. This study provides insights on how land-use change may alter regional NO fluxes by exposing certain microbial communities to extreme environmental conditions. Future studies of NO emissions in tropical agricultural systems where soils are bare for extend periods need to make diurnal measurements or the daily fluxes will be substantially underestimated. 相似文献
92.
Becca Asquith Angelina J Mosley Adrian Heaps Yuetsu Tanaka Graham P Taylor Angela R McLean Charles RM Bangham 《Retrovirology》2005,2(1):1-9
Background
Cellular infection with human immunodeficiency virus (HIV) both in vitro and in vivo requires a member of the chemokine receptor family to act as a co-receptor for viral entry. However, it is presently unclear to what extent the interaction of HIV proteins with chemokine receptors generates intracellular signals that are important for productive infection.Results
In this study we have used a recently described family of chemokine inhibitors, termed BSCIs, which specifically block chemokine-induced chemotaxis without affecting chemokine ligands binding to their receptors. The BSCI termed Peptide 3 strongly inhibited CCR5 mediated HIV infection of THP-1 cells (83 ± 7% inhibition assayed by immunofluoresence staining), but had no effect on gp120 binding to CCR5. Peptide 3 did not affect CXCR4-dependent infection of Jurkat T cells.Conclusion
These observations suggest that, in some cases, intracellular signals generated by the chemokine coreceptor may be required for a productive HIV infection. 相似文献93.
Jianwei Li Gangsheng Wang Melanie A. Mayes Steven D. Allison Serita D. Frey Zheng Shi Xiao‐Ming Hu Yiqi Luo Jerry M. Melillo 《Global Change Biology》2019,25(3):900-910
Global soil carbon (C) stocks are expected to decline with warming, and changes in microbial processes are key to this projection. However, warming responses of critical microbial parameters such as carbon use efficiency (CUE) and biomass turnover (rB) are not well understood. Here, we determine these parameters using a probabilistic inversion approach that integrates a microbial‐enzyme model with 22 years of carbon cycling measurements at Harvard Forest. We find that increasing temperature reduces CUE but increases rB, and that two decades of soil warming increases the temperature sensitivities of CUE and rB. These temperature sensitivities, which are derived from decades‐long field observations, contrast with values obtained from short‐term laboratory experiments. We also show that long‐term soil C flux and pool changes in response to warming are more dependent on the temperature sensitivity of CUE than that of rB. Using the inversion‐derived parameters, we project that chronic soil warming at Harvard Forest over six decades will result in soil C gain of <1.0% on average (1st and 3rd quartiles: 3.0% loss and 10.5% gain) in the surface mineral horizon. Our results demonstrate that estimates of temperature sensitivity of microbial CUE and rB can be obtained and evaluated rigorously by integrating multidecadal datasets. This approach can potentially be applied in broader spatiotemporal scales to improve long‐term projections of soil C feedbacks to climate warming. 相似文献
94.
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96.
R Quintero‐Torres HA Castillo‐Matadamas Jeff F Young RM Bermúdez Cruz 《Luminescence》2014,29(5):440-444
Relaxation dynamics is universal in science and engineering; its study serves to parameterize a system's response and to help identify a microscopic model of the processes involved. When measured data for a phenomenon cannot be fitted using one exponential, the choice of an alternative function to describe the decay becomes nontrivial. Here, we contrast two different, but fundamentally related approaches to fitting nontrivial decay curves; exponential decomposition and the gamma probability density function. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
97.
Woody materials decayed more rapidly in a first order stream than in larger streams in eastern Quebec, Canada. The rate of annual mass loss (k) was highest (k=1.20) for alder wood chips in a first order stream and lowest (k=0.04) for black spruce wood chips in a ninth order stream. Decay rates for woody materials in a first order stream were inversely related to their initial lignin to nitrogen ratios. In larger streams, decay rates of woody materials were inversely related to their initial lignin concentrations. A number of quantifiable relationships were found to exist between the initial lignin and nitrogen contents of woody materials and the nitrogen dynamics of decaying wood. 相似文献
98.
Iavarone C Acunzo M Carlomagno F Catania A Melillo RM Carlomagno SM Santoro M Chiariello M 《The Journal of biological chemistry》2006,281(15):10567-10576
Mitogen-activated protein (MAP) kinases have a central role in several biological functions, including cell adhesion and spreading, chemotaxis, cell cycle progression, differentiation, and apoptosis. Extracellular signal-regulated kinase 8 (Erk8) is a large MAP kinase whose activity is controlled by serum and the c-Src non-receptor tyrosine kinase. Here, we show that RET/PTC3, an activated form of the RET proto-oncogene, was able to activate Erk8, and we demonstrate that such MAP kinase participated in RET/PTC3-dependent stimulation of the c-jun promoter. By using RET/PTC3 molecules mutated in specific tyrosine autophosphorylation sites, we characterized Tyr(981), a known binding site for c-Src, as a major determinant of RET/PTC3-induced Erk8 activation, although, surprisingly, the underlying mechanism did not strictly depend on the activity of Src. In contrast, we present evidence that RET/PTC3 acts on Erk8 through Tyr(981)-mediated activation of c-Abl. Furthermore, we localized the region responsible for the modulation of Erk8 activity by the RET/PTC3 and Abl oncogenes in the Erk8 C-terminal domain. Altogether, these results support a role for Erk8 as a novel effector of RET/PTC3 and, therefore, RET biological functions. 相似文献
99.
Sonia Harmand David DeGusta Ludovic Slimak Jason Lewis Stephanie Melillo Ilsa Dohmen Mohamed Omar 《Comptes Rendus Palevol》2009,8(5):481-492
New sites from the Lower Paleolithic of the Republic of Djibouti: Initial results from a recent survey of the Gobaad Basin, Central Afar. Previous research in the Republic of Djibouti resulted in two notable Paleolithic findings: the Oldowan elephant butchery site of Barogali, excavated by J. Chavaillon and A. Berthelet, and a Homo erectus/sapiens maxilla described by L. de Bonis et al. These discoveries were made in the 1980s, and no paleoanthropological surveys have been conducted in Djibouti in the following decades. In 2007, the Mission archéologique et paléontologique Afar Djibouti (MAPAD) carried out a new survey of the Gobaad Basin and discovered several new archaeological and paleontological sites attributed to the Lower Paleolithic. Three sites in particular contain rich concentrations of lithic artifacts on the surface that, based on field examination, can be attributed to the Oldowan. Of these, the site of Chekheyti Issie 3 (CKI-3) is the largest, comprising a surface of well over 100 m2 of abundant Oldowan lithics in spatial association with fossil hippopotamus remains. The presence of lithic refits, identified in an ad hoc fashion in the field, suggests that the site was minimally disturbed. Further excavation and analysis of CKI-3 should provide insight into carcass acquisition and processing by early hominids. More generally, the newly discovered sites in the Gobaad Basin will allow for the testing of a range of hypotheses regarding both local and regional variation in hominid technology, behavior, and subsistence strategies in the Lower Pleistocene. 相似文献
100.
Narayan P Subramaniyam Outi RM Väisänen Katrina E Wendel Jaakko AV Malmivuo 《Nonlinear biomedical physics》2010,4(Z1):S4