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21.
LINE-1 (L1) is the most represented sequence of the human genome (17% of the total genomic mass). Moreover, it has been proposed for many years and demonstrated more recently that L1 has contributed to the mobilization of pseudogenes, small non-coding RNAs, such as tRNAs or snRNAs, and SINEs. In fact, it is estimated that L1 is responsible for at least 30% of our genome. The mobilization of non-L1 RNAs can occur in different ways and at different steps of the retrotransposition cycle. Here, by looking at U6 snRNA sequences mobilized by L1, we have observed an ancient repeat sequence derived from U6, present in all primate genomes. We were able to trace its origin in Euarchota genomes, most likely during the divergence of the four orders; Scandentia, Dermoptera, Plesiadapiform (extinct) and Primates. 相似文献
22.
Direct and Indirect Relationships Between Specific Leaf Area, Leaf Nitrogen and Leaf Gas Exchange. Effects of Irradiance and Nutrient Supply 总被引:6,自引:0,他引:6
We present a series of competing path models relating interspecificpatterns between specific leaf area, leaf nitrogen content,net photosynthesis and stomatal conductance and test these againstdata from 22 species of herbaceous plants grown under controlledconditions with contrasting irradiance and nutrient supply rates.We then compare these results with two previous data sets, onebased on field measures and one based on glasshouse measures,to determine the robustness of the results. Only one model wasable to account for the patterns of direct and indirect effectsbetween the four variables to all data sets. In this model specificleaf area is the forcing variable that directly affects bothleaf nitrogen levels and net photosynthetic rates. Leaf nitrogenthen directly affects net photosynthetic rates which in turnthen affect stomatal conductance to water. Copyright 2001 Annalsof Botany Company Comparative ecology, modelling, path analysis, photosynthesis, plant strategies, SLA, specific leaf area, stomatal conductance 相似文献
23.
Lehtinen SK Hance N El Meziane A Juhola MK Juhola KM Karhu R Spelbrink JN Holt IJ Jacobs HT 《Genetics》2000,154(1):363-380
The mitochondrial genotype of heteroplasmic human cell lines containing the pathological np 3243 mtDNA mutation, plus or minus its suppressor at np 12300, has been followed over long periods in culture. Cell lines containing various different proportions of mutant mtDNA remained generally at a consistent, average heteroplasmy value over at least 30 wk of culture in nonselective media and exhibited minimal mitotic segregation, with a segregation number comparable with mtDNA copy number (>/=1000). Growth in selective medium of cells at 99% np 3243 mutant mtDNA did, however, allow the isolation of clones with lower levels of the mutation, against a background of massive cell death. As a rare event, cell lines exhibited a sudden and dramatic diversification of heteroplasmy levels, accompanied by a shift in the average heteroplasmy level over a short period (<8 wk), indicating selection. One such episode was associated with a gain of chromosome 9. Analysis of respiratory phenotype and mitochondrial genotype of cell clones from such cultures revealed that stable heteroplasmy values were generally reestablished within a few weeks, in a reproducible but clone-specific fashion. This occurred independently of any straightforward phenotypic selection at the individual cell-clone level. Our findings are consistent with several alternate views of mtDNA organization in mammalian cells. One model that is supported by our data is that mtDNA is found in nucleoids containing many copies of the genome, which can themselves be heteroplasmic, and which are faithfully replicated. We interpret diversification and shifts of heteroplasmy level as resulting from a reorganization of such nucleoids, under nuclear genetic control. Abrupt remodeling of nucleoids in vivo would have major implications for understanding the developmental consequences of heteroplasmy, including mitochondrial disease phenotype and progression. 相似文献
24.
Mourad Aribi Warda Meziane Salim Habi Yasser Boulatika Hélène Marchandin Jean-Luc Aymeric 《PloS one》2015,10(9)
Background
Dietary selenium is of fundamental importance to maintain optimal immune function and enhance immunity during infection. To this end, we examined the effect of selenium on macrophage bactericidal activities against Staphylococcus aureus.Methods
Assays were performed in golden Syrian hamsters and peritoneal macrophages cultured with S. aureus and different concentrations of selenium.Results
Infected and selenium-supplemented animals have significantly decreased levels of serum nitric oxide (NO) production when compared with infected but non-selenium-supplemented animals at day 7 post-infection (p < 0.05). A low dose of 5 ng/mL selenium induced a significant decrease in macrophage NO production, but significant increase in hydrogen peroxide (H2O2) levels (respectively, p = 0.009, p < 0.001). The NO production and H2O2 levels were significantly increased with increasing concentrations of selenium; the optimal macrophage activity levels were reached at 20 ng/mL. The concentration of 5 ng/mL of selenium induced a significant decrease in the bacterial arginase activity but a significant increase in the macrophage arginase activity. The dose of 20 ng/mL selenium induced a significant decrease of bacterial growth (p < 0.0001) and a significant increase in macrophage phagocytic activity, NO production/arginase balance and S. aureus killing (for all comparisons, p < 0.001).Conclusions
Selenium acts in a dose-dependent manner on macrophage activation, phagocytosis and bacterial killing suggesting that inadequate doses may cause a loss of macrophage bactericidal activities and that selenium supplementation could enhance the in vivo control of immune response to S. aureus. 相似文献25.
Hadj Boumediene Meziane Clara Moisello Bernardo Perfetti Svetlana Kvint Ioannis Ugo Isaias Angelo Quartarone Alessandro Di Rocco Maria Felice Ghilardi 《PloS one》2015,10(1)
In previous studies of young subjects performing a reaction-time reaching task, we found that faster reaction times are associated with increased suppression of beta power over primary sensorimotor areas just before target presentation. Here we ascertain whether such beta decrease similarly occurs in normally aging subjects and also in patients with Parkinson’s disease (PD), where deficits in movement execution and abnormalities of beta power are usually present. We found that in both groups, beta power decreased during the motor task in the electrodes over the two primary sensorimotor areas. However, before target presentation, beta decreases in PD were significantly smaller over the right than over the left areas, while they were symmetrical in controls. In both groups, functional connectivity between the two regions, measured with imaginary coherence, increased before the target appearance; however, in PD, it decreased immediately after, while in controls, it remained elevated throughout motor planning. As in previous studies with young subjects, the degree of beta power before target appearance correlated with reaction time. The values of coherence during motor planning, instead, correlated with movement time, peak velocity and acceleration. We conclude that planning of prompt and fast movements partially depends on coordinated beta activity of both sensorimotor areas, already at the time of target presentation. The delayed onset of beta decreases over the right region observed in PD is possibly related to a decreased functional connectivity between the two areas, and this might account for deficits in force programming, movement duration and velocity modulation. 相似文献
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27.
Cédric Hubas Bruno Jesus Mickael Ruivo Tarik Meziane Najet Thiney Dominique Davoult Nicolas Spilmont David M. Paterson Christian Jeanthon 《PloS one》2013,8(12)
There is a relative absence of studies dealing with mats of purple sulphur bacteria in the intertidal zone. These bacteria display an array of metabolic pathways that allow them to disperse and develop under a wide variety of conditions, making these mats important in terms of ecosystem processes and functions. Mass blooms of purple sulphur bacteria develop during summer on sediments in the intertidal zone especially on macroalgal deposits. The microbial composition of different types of mats differentially affected by the development of purple sulphur bacteria was examined, at low tide, using a set of biochemical markers (fatty acids, pigments) and composition was assessed against their influence on ecosystem functions (sediment cohesiveness, CO2 fixation). We demonstrated that proliferation of purple sulphur bacteria has a major impact on intertidal mats diversity and functions. Indeed, assemblages dominated by purple sulphur bacteria (Chromatiaceae) were efficient exopolymer producers and their biostabilisation potential was significant. In addition, the massive growth of purple sulphur bacteria resulted in a net CO2 degassing whereas diatom dominated biofilms represented a net CO2 sink. 相似文献
28.
Resveratrol improves mitochondrial function and protects against metabolic disease by activating SIRT1 and PGC-1alpha 总被引:30,自引:0,他引:30
Lagouge M Argmann C Gerhart-Hines Z Meziane H Lerin C Daussin F Messadeq N Milne J Lambert P Elliott P Geny B Laakso M Puigserver P Auwerx J 《Cell》2006,127(6):1109-1122
Diminished mitochondrial oxidative phosphorylation and aerobic capacity are associated with reduced longevity. We tested whether resveratrol (RSV), which is known to extend lifespan, impacts mitochondrial function and metabolic homeostasis. Treatment of mice with RSV significantly increased their aerobic capacity, as evidenced by their increased running time and consumption of oxygen in muscle fibers. RSV's effects were associated with an induction of genes for oxidative phosphorylation and mitochondrial biogenesis and were largely explained by an RSV-mediated decrease in PGC-1alpha acetylation and an increase in PGC-1alpha activity. This mechanism is consistent with RSV being a known activator of the protein deacetylase, SIRT1, and by the lack of effect of RSV in SIRT1(-/-) MEFs. Importantly, RSV treatment protected mice against diet-induced-obesity and insulin resistance. These pharmacological effects of RSV combined with the association of three Sirt1 SNPs and energy homeostasis in Finnish subjects implicates SIRT1 as a key regulator of energy and metabolic homeostasis. 相似文献
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The oxygen and nutrient dynamics of the zooxanthellate, upside down jellyfish (Cassiopea sp.), were determined both in situ and during laboratory incubations under controlled light conditions. In the laboratory,
Cassiopea exhibited a typical Photosynthesis–Irradiance (P–I) curve with photosynthesis increasing linearly with irradiance, until
saturation was reached at an irradiance of ~400 μE m−2 s−1, with photosynthetic compensation (photosynthesis = respiration) being achieved at an irradiance of ~50 μE m−2 s−1. Under saturating irradiation, gross photosynthesis attained a rate of almost 3.5 mmol O2 kg WW−1 h−1, whereas the dark respiration rate averaged 0.6 mmol O2 kg WW−1 h−1. Based upon a period of saturating irradiance of 9 h, the ratio of daily gross photosynthesis to daily respiration was 2.04.
Thus, photosynthetic carbon fixation was not only sufficient to meet the carbon demand of respiration, but also to potentially
support a growth rate of ~3% per day. During dark incubations Cassiopea was a relatively minor source of inorganic N and P, with the high proportion of NO
X
(nitrate + nitrite) produced indicating that the jellyfish were colonised by nitrifying bacteria. Whereas, under saturating
irradiance the jellyfish assimilated ammonium, NO
X
and phosphate from the bathing water. However, the quantities of inorganic nitrogen assimilated were small by comparison
to carbon fixation rates and the jellyfish would need to exploit other sources of nitrogen, such as ingested zooplankton,
in order to maintain balanced growth. During in situ incubations the presence of Cassiopea had major effects on benthic oxygen and nutrient dynamics, with jellyfish occupied patches of sediment having 3.6-fold higher
oxygen consumption and 4.5-fold higher ammonium regeneration rates than adjacent patches of bare sediment under dark conditions.
In contrast at saturating irradiance, jellyfish enhanced benthic photosynthetic oxygen production almost 100-fold compared
to the sediment alone and created a small sink for inorganic nutrients, whereas unoccupied sediment patches were sources of
inorganic nutrients to the water column. Overall, Cassiopea greatly enhanced the spatial and temporal heterogeneity of benthic fluxes and processes by creating “hotspots” of high activities
which switched between being sources or sinks for oxygen and nutrients over diurnal irradiance cycles, as the metabolism of
the jellyfish swapped between heterotrophy and net autotrophy. 相似文献