van't Hoff enthalpies without baselines

Analysis of thermal melting curves represents one important approach for evaluating protein stability and the consequences of amino acid substitution on protein structure. By use of the van't Hoff relationship, the differential melting curve can be robustly fit to only three parameters, two of which are the underlying physical constants of melting temperature (Tm) and van't Hoff enthalpy (deltaHvH). Calculated Tm and deltaHvH values are insensitive to the choice of pre- and post-transition baselines. Consequently, the method accurately computes Tm and deltaHvH for extremely truncated data sets, in the complete absence of baseline information, and for proteins with low melting temperatures, where the traditional direct approach routinely fails. Moreover, agreement between deltaHvH values obtained using points derived from pre- vs. post-transition data provide an independent method for detecting some classes of non-two-state transitions. Finally, fitting of the differential denaturation curve should prove useful for analysis of abbreviated data sets obtained from high throughput array analysis of protein stability.     

Flax (Linum usitatissimum L.) depends on arbuscular mycorrhizal fungi for growth and P uptake at intermediate but not high soil P levels in the field

The contribution of indigenous arbuscular mycorrhizal fungi (AMF) to growth and phosphorus (P) uptake by oilseed flax (Linum usitatissimum L.) was examined in two field experiments covering soil P levels from 20–86 mg kg-1 NaHCO3-extractable P. The fumigant dazomet was applied to the soil in half of the plots to obtain control plants with reduced mycorrhiza formation. An extensive AMF colonization of up to 48% of the root length was established in untreated soil of both experiments, although P fertilization reduced colonization to 28–39% at the latest harvests. Fumigation markedly decreased or totally prevented AMF colonization throughout the experiments. Root growth responded to fumigation by increased total and specific root length. Shoot P uptake was decreased by fumigation at soil P levels lower than ca. 50 mg kg-1 whereas shoot growth was reduced by fumigation at soil P levels lower than ca. 40 mg kg-1. The effects of fumigation were ascribed to the suppression of mycorrhiza formation. The effect of the AMF increased with decreasing soil P levels. Phosphorus inflow through roots (based on shoot P uptake) was reduced more strongly by fumigation than total P uptake. The P inflow through fungal tissue in roots was estimated to 4 × 10-14 mol P cm-1 s-1. We conclude that AMF are essential to flax growth at soil P levels below ca. 40 mg P kg-1, which is representative of the conditions under which most flax is grown.     

Effects of grazing on plant species composition and spatial distribution in rangelands of the Sahel

The effects of grazing by livestock on plant species composition and spatial distribution have been studied at Sadoré, Niger. Herbaceous species were recorded in plots of increasing size from 1/64 to 1024 m² in ten fallow plots subjected to five different grazing treatments over the previous three years. Treatments consisted of three intensities of grazing, and of protection from grazing for either 3 or 14 years. For all treatments, the number of species fitted a normal distribution with the log (ln) of the area inventoried. However, the fit improved slightly when the model included two successive log-normal distributions respectively considered as species distribution within a patch and at the patch mosaic scale. Across treatments, the optimal sampling areas averaged 3.8 ± 1.1 m² for the within-patch and 725 ± 113 m² for the mosaic scale distributions. It is argued that similarity between treatments in the overall log-normal distribution resulted from compensations between the divergent trends that affected species distribution within and across patches depending on the grazing status. Long-term protection resulted in a regular spatial arrangement of highly contrasted, but internally homogeneous patches. Heavy grazing ensued the dominance of a few species in contagious patches but also left niches for scattered individuals of other species. Tests of the relative frequency of each plant species, together with the average area needed to record that species, were used to characterize specific response to grazing. A majority of species encountered in old Sahelian fallows were either fostered by grazing, indifferent or tolerant to grazing. However, more than a third of the species appeared sensitive to heavy grazing, and no relationships were found between species response to grazing and palatability.     

Effects of pod infection by Mycosphaerella pinodes on yield components of pea (Pisum sativum)

Yield reduction of pea (Pisum sativum) due to various types of infections by Mycosphaerella pinodes on pods was assessed. A range of disease severities was created on pods of pea plants grown in the glasshouse, by painting the pods with different concentrations of spore suspensions, at three different pod development stages: lag phase, the beginning of seed filling (BSF) and mid-filling of the seeds. Seed number at harvest was reduced only if the pods were infected before BSF, as shown previously for whole plant infections. Pod infections led to individual seed weight (ISW) losses from zero (for late infections, at mid-filling) to 20% (for earlier infections and severe disease). Infection during the lag phase affected ISW by reducing seed growth rate, whereas infection at BSF tended to reduce the duration of seed filling. There was a linear relationship between the area under the disease progress curve and the percentage decrease in ISW. This model should be complemented by the effect of leaves and stem infections, in order to predict ISW losses in diseased crop conditions, in which epidemics occur on all aerial parts of the pea plant.     

抗衰老药物对线虫生存曲线影响的荟萃分析

随着世界人口老龄化步伐的加快,衰老机制及抗衰老药物的研究日益成为生物医学领域的热点前沿之一.国内外已有大量研究报道抗衰老药物能够延长多种模式生物包括线虫、果蝇、小鼠、大鼠及灵长类等的寿命,然而,这些药物延缓衰老方式的差异仍缺乏系统研究.因此,本研究以衰老研究的热点模式生物线虫为对象,搜集1990年以来国内外刊物上正式发表的有关抗衰老药物寿命试验的研究文献及其涉及的生存曲线,利用荟萃分析比较了不同抗衰老药物与生存曲线变化类型间的关系,并结合药物的药理作用探讨其延寿机制.生存曲线特征聚类结果与药物生物学分类交叉分析结果表明,药理作用类型与增益类型具有很强相关性,提示这2种分类方法的结果是匹配的.抗氧化剂类药物和控制血糖类药物对生存曲线的改善总体增益虽然不是最高,但相对于正常组生存曲线其增益部分呈平移形,表明该类药物可以通过改善年龄结构对整个群体产生显著增益,且其衰老曲线的特征与自然衰老相似.抗癫痫药物及胃肠道菌群相关药物总体增益较大,其曲线增益形状呈梯形,提示该类药物(尤其是胃肠道菌群相关药物)尽管显著延长了少数个体的最大寿命,但是从整个群体来看,大多数个体寿命延长程度并不明显,受益的少数个体可能需要较长的外界资源支持方能保持较长时间的存活状态,这种模式既不大众化也不经济.综上所述,清除自由基和控制血糖类药物对健康老年有着更为积极合理的作用与效应.     

Lipoic acid entrains the hepatic circadian clock and lipid metabolic proteins that have been desynchronized with advanced age

It is well established that lipid metabolism is controlled, in part, by circadian clocks. However, circadian clocks lose temporal precision with age and correlates with elevated incidence in dyslipidemia and metabolic syndrome in older adults. Because our lab has shown that lipoic acid (LA) improves lipid homeostasis in aged animals, we hypothesized that LA affects the circadian clock to achieve these results. We fed 24 month old male F344 rats a diet supplemented with 0.2% (w/w) LA for 2 weeks prior to sacrifice and quantified hepatic circadian clock protein levels and clock-controlled lipid metabolic enzymes. LA treatment caused a significant phase-shift in the expression patterns of the circadian clock proteins Period (Per) 2, Brain and Muscle Arnt-Like1 (BMAL1), and Reverse Erythroblastosis virus (Rev-erb) β without altering the amplitude of protein levels during the light phase of the day. LA also significantly altered the oscillatory patterns of clock-controlled proteins associated with lipid metabolism. The level of peroxisome proliferator-activated receptor (PPAR) α was significantly increased and acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS) were both significantly reduced, suggesting that the LA-supplemented aged animals are in a catabolic state. We conclude that LA remediates some of the dyslipidemic processes associated with advanced age, and this mechanism may be at least partially through entrainment of circadian clocks.     

A plasma global metabolic profiling approach applied to an exercise study monitoring the effects of glucose, galactose and fructose drinks during post-exercise recovery

A global metabolic profiling methodology based on gas chromatography coupled to time-of-flight mass spectrometry (GC-TOFMS) for human plasma was applied to a human exercise study focused on the effects of beverages containing glucose, galactose, or fructose taken after exercise and throughout a recovery period of 6 h and 45 min. One group of 10 well trained male cyclists performed 3 experimental sessions on separate days (randomized, single center). After performing a standardized depletion protocol on a bicycle, subjects consumed one of three different beverages: maltodextrin (MD)+glucose (2:1 ratio), MD+galactose (2:1), and MD+fructose (2:1), consumed at an average of ～1.25 g of carbohydrate (CHO) ingested per minute. Blood was taken straight after exercise and every 45 min within the recovery phase. With the resulting blood plasma, insulin, free fatty acid (FFA) profile, glucose, and GC-TOFMS global metabolic profiling measurements were performed. The resulting profiling data was able to match the results obtained from the other clinical measurements with the addition of being able to follow many different metabolites throughout the recovery period. The data quality was assessed, with all the labelled internal standards yielding values of <15% CV for all samples (n=335), apart from the labelled sucrose which gave a value of 15.19%. Differences between recovery treatments including the appearance of galactonic acid from the galactose based beverage were also highlighted.     

千岛湖姥山马尾松种群结构和分布格局研究

为研究千岛湖马尾松(Pinus massoniana)种群动态变化,在姥山岛上设置面积为5.76 hm2的固定样地,进行群落学调查。根据野外调查的数据,对马尾松种群的结构和分布格局进行分析。结果表明:马尾松种群1、2级个体数极少,仅占样地中马尾松个体数的0.06%和1.01%,幼苗、幼树储备严重不足,5级个体的比例最高,达到28.28%,马尾松种群径级结构为纺锤型;马尾松种群的存活曲线为凸型。这些均表明马尾松种群的年龄结构趋向衰退型。但马尾松种群中树个体很多,在较长的时期内马尾松还不会退出群落。马尾松种群静态生命表也可看出中一些小型径级的死亡率为负值,也说明马尾松种群幼苗严重缺乏,种群呈衰退趋势。马尾松种群各径级和总体的分布格局均呈聚集分布,从小树→中树→大树聚集指数逐渐减小,种群呈扩散趋势。     

Just how strapping was KNM-WT 15000?

For over twenty years, the young, male Homo erectus specimen KNM-WT 15000 has been the focus of studies on growth and development, locomotion, size, sexual dimorphism, skeletal morphology, and encephalization, often serving as the standard for his species. Prior research on KNM-WT 15000 operates under the assumption that H. erectus experienced a modern human life history, including an adolescent growth spurt. However, recent fossil discoveries, improvements in research methods, and new insights into modern human ontogeny suggest that this may not have been the case. In this study, we examine alternative life history trajectories in H. erectus to re-evaluate adult stature estimates for KNM-WT 15000. We constructed a series of hypothetical growth curves by modifying known human and chimpanzee curves, calculating intermediate growth velocities, and shifting the age of onset and completion of growth in stature. We recalculated adult stature for KNM-WT 15000 by increasing stature at death by the percentage of growth remaining in each curve. The curve that most closely matches the life history events experienced by KNM-WT 15000 prior to death indicates that growth in this specimen would have been completed by 12.3 years of age. These results suggest that KNM-WT 15000 would have experienced a growth spurt that had a lower peak velocity and shorter duration than the adolescent growth spurt in modern humans. As a result, it is likely that KNM-WT 15000 would have only attained an adult stature of 163 cm (∼5′4″), not 185 cm (∼6′1″) as previously reported. KNM-WT 15000's smaller stature has important implications for evolutionary scenarios involving early genus Homo.     

Circulating muscle-specific microRNA, miR-206, as a potential diagnostic marker for rhabdomyosarcoma

Presently there is no serum biomarker of rhabdomyosarcoma (RMS). Several studies have shown that profiles of microRNA (miRNA) expression differ among tumor types. Here we evaluated the feasibility of using muscle-specific miRNAs (miR-1, -133a, -133b and -206) as biomarkers of RMS. Expression of muscle-specific miRNAs, especially miR-206, was significantly higher in RMS cell lines than in other tumor cell lines, as well as in RMS tumor specimens. Further, serum levels of muscle-specific miRNAs were significantly higher in patients with RMS tumors than in patients with non-RMS tumors. Normalized serum miR-206 expression level could be used to differentiate between RMS and non-RMS tumors, with sensitivity of 1.0 and specificity of 0.913. These results raise the possibility of using circulating muscle-specific miRNAs, especially miR-206, as landmark biomarkers for RMS.