三种抗癫痫药对癫痫患者脑电图的背景影响比较研究

目的：研究对比三种抗癫痫药（苯妥因钠、丙戊酸钠、卡马西平）对癫痫患者脑电图的背景影响。方法：选取我院于2009年3月至2011年2月收治的60例癫痫患者,随机分为苯妥因钠（PHT）、卡马西平（CBZ）和丙戊酸钠（SVP）组各20例,动态观察各组患者于治疗期间痫样波放电的频度和EEG背景的变化。结果：EEG痫样波放电的抑制率以SVP最为明显,而CBZ在EEG背景活动影响方面均比其他两组显著。结论：三种药物对癫痫波放电的抑制顺序是SVP〉PHT〉CBZ,SVP组明显优于其他两组。     

A widespread plant-fungal-bacterial symbiosis promotes plant biodiversity,plant nutrition and seedling recruitment

Highly diverse microbial assemblages colonize plant roots. It is still poorly understood whether different members of this root microbiome act synergistically by supplying different services (for example, different limiting nutrients) to plants and plant communities. In order to test this, we manipulated the presence of two widespread plant root symbionts, arbuscular mycorrhizal fungi and nitrogen-fixing rhizobia bacteria in model grassland communities established in axenic microcosms. Here, we demonstrate that both symbionts complement each other resulting in increased plant diversity, enhanced seedling recruitment and improved nutrient acquisition compared with a single symbiont situation. Legume seedlings obtained up to 15-fold higher productivity if they formed an association with both symbionts, opposed to productivity they reached with only one symbiont. Our results reveal the importance of functional diversity of symbionts and demonstrate that different members of the root microbiome can complement each other in acquiring different limiting nutrients and in driving important ecosystem functions.     

Atrial natriuretic peptides in essential hypertension: basal plasma levels and relationship to sodium balance.

The identification of the atrial natriuretic peptides (ANP) as a new hormonal system has provided a new perspective on the mechanisms controlling renal sodium excretion and abnormalities in sodium homeostasis. The present article focuses on the potential importance of ANP (ANF 99-126) in essential hypertension with particular reference to circulating ANP levels and the relationship between the ANP and the renin-angiotensin system in the control of sodium balance and blood pressure. There is now considerable evidence demonstrating that a substantial proportion of patients with essential hypertension have raised circulating ANP levels. Given the known biological actions of ANP, these raised levels point to important compensatory mechanisms. This is further supported by studies during alterations in dietary sodium intake, as sodium restriction high-lighted important relationships between ANP and the renin angiotensin system. The potential importance of ANP in essential hypertension is strengthened by recent demonstration of natriuretic and antihypertensive actions associated with small increases in circulating ANP as induced by administration of exogenous ANP. Furthermore, the recent development of orally active inhibitors of ANP metabolism now provides a basis to determine the therapeutic importance of specific manipulation of endogenous ANP levels in patients with essential hypertension.     

Uncertainty in ensemble forecasting of species distribution

Species distribution modelling has been widely applied in order to assess the potential impacts of climate change on biodiversity. Many methodological decisions, taken during the modelling process and forecasts, may, however, lead to a large variability in the assessment of future impacts. Using measures of species range change and turnover, the potential impacts of climate change on French stream fish species and assemblages were evaluated. Our main focus was to quantify the uncertainty in the projections of these impacts arising from four sources of uncertainty: initial datasets (Data), statistical methods [species distribution models (SDM)], general circulation models (GCM), and gas emission scenarios (GES). Several modalities of the aforementioned uncertainty sources were combined in an ensemble forecasting framework resulting in 8400 different projections. The variance explained by each source was then extracted from this whole ensemble of projections. Overall, SDM contributed to the largest variation in projections, followed by GCM, whose contribution increased over time equalling almost the proportion of variance explained by SDM in 2080. Data and GES had little influence on the variability in projections. Future projections of range change were more consistent for species with a large geographical extent (i.e., distribution along latitudinal or stream gradients) or with restricted environmental requirements (i.e., small thermal or elevation ranges). Variability in projections of turnover was spatially structured at the scale of France, indicating that certain particular geographical areas should be considered with care when projecting the potential impacts of climate change. The results of this study, therefore, emphasized that particular attention should be paid to the use of predictions ensembles resulting from the application of several statistical methods and climate models. Moreover, forecasted impacts of climate change should always be provided with an assessment of their uncertainty, so that management and conservation decisions can be taken in the full knowledge of their reliability.     

Molecular coevolution among cryptically simple expansion segments of eukaryotic 26S/28S rRNAs

The set of "expansion segments" of any eukaryotic 26S/28S ribosomal RNA (rRNA) gene is responsible for the bulk of the difference in length between the prokaryotic 23S rRNA gene and the eukaryotic 26S/28S rRNA gene. The expansion segments are also responsible for interspecific fluctuations in length during eukaryotic evolution. They show a consistent bias in base composition in any species; for example, they are AT rich in Drosophila melanogaster and GC rich in vertebrate species. Dot-matrix comparisons of sets of expansion segments reveal high similarities between members of a set within any 28S rRNA gene of a species, in contrast to the little or spurious similarity that exists between sets of expansion segments from distantly related species. Similarities among members of a set of expansion segments within any 28S rRNA gene cannot be accounted for by their base-compositional bias alone. In contrast, no significant similarity exists within a set of "core" segments (regions between expansion segments) of any 28S rRNA gene, although core segments are conserved between species. The set of expansion segments of a 26S/28S gene is coevolving as a unit in each species, at the same time as the family of 28S rRNA genes, as a whole, is undergoing continual homogenization, making all sets of expansion segments from all ribosomal DNA (rDNA) arrays in a species similar in sequence. Analysis of DNA simplicity of 26S/28S rRNA genes shows a direct correlation between significantly high relative simplicity factors (RSFs) and sequence similarity among a set of expansion segments. A similar correlation exists between RSF values, overall rDNA lengths, and the lengths of individual expansion segments. Such correlations suggest that most length fluctuations reflect the gain and loss of simple sequence motifs by slippage-like mechanisms. We discuss the molecular coevolution of expansion segments, which takes place against a background of slippage-like and unequal crossing-over mechanisms of turnover that are responsible for the accumulation of interspecific differences in rDNA sequences.      

Plasma immunoreactive atrial natriuretic peptide and changes in dietary sodium intake in man

Plasma levels of immunoreactive atrial natriuretic peptides (IrANP) have been measured in 8 normotensive subjects during alterations in dietary sodium intake. Subjects were studied on their normal sodium intake (2 days) then on a low sodium intake (7 days, 10 mmols Na+/day) and subsequently on a high sodium intake (14 days, 350 mmols Na+/day with the diets being given in a fixed order. Plasma levels (mean +/- S.E.M.) of IrANP on a normal sodium diet were 7.3 +/- 0.9 pg/ml; 4.5 +/- 0.8 on the 7th day of a low sodium intake and 10.8 +/- 1.3; 16.6 +/- 3.3; 15.5 +/- 4.2; 15.6 +/- 2.3 pg/ml respectively or the 1st, 3rd, 10th and 14th day on the high sodium intake. Changes in plasma IrANP were closely associated with changes in urinary sodium excretion. These results suggest that in normal subjects the atrial natriuretic peptides may play an important role in the adaptation to increases in dietary sodium intake both on a short and on a longer term basis.