The response of Alaskan arctic tundra to experimental warming: differences between short- and long-term responses

Global climate models predict continued rapid warming for most of the Arctic throughout the next century. To further understand the response of arctic tundra to climate warming, four sites in northern Alaska were warmed for five to seven consecutive growing seasons using open‐top chambers. Sites were located in dry heath and wet meadow communities near Barrow (71°18′N, 156°40′W) and Atqasuk (70°29′N, 157°25′W). Change in plant community composition was measured using a point frame method. During the period of observation, species richness declined in control plots by up to 2.7 species plot^?1. Responses to warming varied by site but similar trends included increased canopy height (?0.1 to 2.3 cm) and relative cover of standing dead plant matter (1.5–6.0%) and graminoids (1.8–5.8%) and decreased species diversity (0.1–1.7 species plot^?1) and relative cover of lichens (0.2–9.1%) and bryophytes (1.4–4.6%) (parentheses enclose the range of average values for the sites). The response to warming was separated into an initial short‐term response assessed after two growing seasons of warming and a secondary longer‐term response assessed after an additional three to five growing seasons of warming. The initial responses to warming were similar in the four sites, while the secondary responses varied by site. The response to warming was greater at Barrow than Atqasuk because of a greater initial response at Barrow. However, the long‐term response to warming was projected to be greater at Atqasuk because of a greater secondary response at Atqasuk. These findings show that predictions of vegetation change due to climate warming based on manipulative experiments will differ depending on both the duration and plant community on which the study focuses.     

Plant growth promoting rhizobacteria accelerate nodulation and increase nitrogen fixation activity by field grown soybean [Glycine max (L.) Merr.] under short season conditions

A 3 × 2 × 2 factorial field experiment, organized in a randomized complete block split-plot with four replications, was conducted in 1994 to evaluate the effect of two plant growth-promoting rhizobacteria (PGPR) strains (Serratia liquefaciens 2-68 or Serratia proteamaculans 1-102) on nodulation, nitrogen fixation, and total nitrogen yield by two soybean cultivars in a short season area. The experiments were conducted at the Emile A. Lods Research Centre, McGill University, Macdonald Campus, Montreal, Canada, and performed at two adjacent sites. One site was fumigated with methyl bromide (50 g m^-2). Another site was kept unfumigated. Co-inoculation of soybean with B. japonicum and PGPR increased soybean nodulation and hastened the onset of nitrogen fixation, when the soils were still cool. Total fixed N, fixed N as a percentage of total plant N, and protein and N yield were also increased by PGPR inoculation. AC Bravor tended to be more responsive to both PGPR treatments for total fixed N and N yields than Maple Glen, suggesting that inoculation with PGPR was more effective for cultivars with higher yield potentials.     

A complete set of overlapping cosmid clones of M-ABA virus derived from nasopharyngeal carcinoma and its similarity to other Epstein-Barr virus isolates

DNA of the transforming, nondefective Epstein-Barr virus (EBV) strain M-ABA, which is derived from nasopharyngeal carcinoma cells, was cloned as large overlapping pieces into the cosmid pHC79. The termini were cloned from closed circular virus DNA molecules out of M-ABA cell DNA in phage λL47. The large overlapping clones were used to prepare a library of subclones with inserts of 1–15 kb. A detailed restriction enzyme map of M-ABA virus DNA reveals the close similarity to isolates from other sources. The high number of tandem repeats in EBV DNA stresses the importance of using cloning vectors that can be propagated in recA^?Escherichia coli hosts.     

Neuronal Ras activation inhibits adult hippocampal progenitor cell division and impairs spatial short‐term memory

A large number of endogenous and exogenous factors have been identified to upregulate and downregulate proliferation, differentiation and/or survival of newborn cells in the adult hippocampus. For studying neuronal mechanisms mediating the impact of those factors, we used a transgenic synRas mouse model expressing constitutively activated Valin12‐Harvey Ras selectively in differentiated neurons. BrdU injections showed significantly reduced proliferation of new cells within the adult hippocampus of transgenic animals compared with their wild‐type siblings. In contrast, the relative survival of newborn cells was increased in synRas mice, although this effect did not fully compensate for diminished proliferation. Inhibition of progenitor cell proliferation and enhancement of cellular survival were more pronounced in males compared with females. Double labelling and doublecortin immunostaining verified that specifically newborn neurons were decreased in synRas mice. Reduced cell generation was observed already 2 h after BrdU pulse injections, identifying an early precursor cell population as target of the inhibitory transgene effect. Differences in proliferation remained stable after 24 h and were specific for the subgranular zone of the dentate gyrus, as subventricular cell generation was not affected supporting a non‐cell autonomous effect on neural hippocampal progenitors. Transgene expression only starts with synaptic differentiation and therefore reduced proliferation must represent an indirect secondary consequence of synRas activity in differentiated neurons. This was associated with impaired spatial short‐term memory capacities as observed in a radial maze paradigm. Our data suggest that constantly high Ras activity in differentiated neurons downregulates hippocampal precursor cell generation in the neuronal lineage, but is modulated by sex‐dependent factors.     

Extraction of aquatic plants based on continuous removal method and analysis of its temporal and spatial changes—A case study of Guanting Reservoir

光谱特征变量的筛选作为水生植物识别的重要手段之一, 在水生植物种类识别研究中应用广泛。该研究将实测光谱特征提取与多时相Landsat 8 OLI影像数据分析相结合, 找到一种有效识别不同种类水生植物的特征变量。在水生植物反射光谱特征分析中引入矿质分析中普遍使用的连续统去除法, 对光谱重采样结果作连续统去除处理后提取光谱吸收深度特征。采用单因素方差分析法对比7个光谱重采样波段和3个连续统去除吸收深度敏感波段, 发现经连续统去除处理的短波红外1波段(SWIR1CR)对于不同类型的水生植物区分效果最佳。将连续统去除法应用到遥感影像处理上, 发现SWIR1CR波段能较好区分沉水植物和挺水植物; 结合影像归一化植被指数和SWIR1CR波段可较好区分三类水生植物。结合特征波段筛选结果采用支持向量机分类方法, 得到水生植物的分类结果精度为86.33%, 对比全生长期12期影像提取的水生植物分布图, 发现水生植物主要分布于官厅水库库区南北岸浅水区, 水生植物面积最大时约占库区总面积的35.13%; 其中沉水植物年内生长分布变化幅度较大, 6月上旬开始迅速生长; 10月份水生植物开始衰减; 11月份水生植物占库区面积的20%, 沉水、浮水植物大幅衰减消失。     

Modelling catheter–vein biomechanical interactions during an intravenous procedure

A reliable intravenous (IV) access into the upper extremity veins requires the insertion of a temporary short peripheral catheter (SPC). This so common procedure is, however, associated with a risk of developing short peripheral catheter thrombophlebitis (SPCT) which causes distress and potentially prolongs patient hospitalization. We have developed and studied a biomechanical SPC–vein computational model during an IV procedure, and explored the biomechanical effects of repeated IV episodes on onset and reoccurrences of SPCT. The model was used to determine the effects of different insertion techniques as well as inter-patient biological variability on the catheter–vein wall contact pressures and wall deformations. We found that the maximal pressure exerted upon the vein wall was inhomogeneously distributed, and that the bending region was exposed to significantly greater pressures and deformations. The maximal exerted contact pressure on the inner vein's wall was 2938 Pa. The maximal extent of the SPC penetration into the vein wall reached 3.6 μm, which corresponds to approximately 100% of the average height of the inner layer, suggesting local squashing of endothelial cells at the contact site. The modelling describes a potential biomechanical damage pathway that can explain the reoccurrence of SPCT.     

Circadian Characteristics of Plasma Cortisol in Children with Standard and Short Stature

Cortisol (CT) concentrations (in mUg/dl) were determined by radioimmunoassay in plasma obtained at about 3-hr intervals during a 24-hr sampling span from 42 boys and 13 girls of short stature (2–4 standard deviations below their peer group mean), and from a reference group of 11 boys and 10 girls with standard stature, before any treatment were administered to the former. Subjects were 11.20 0.37 years of age at the time of study, and were living on a diurnal waking (～07:30 to ～22:30), nocturnal resting routine during sampling, consuming the usual hospital diet. Circadian rhythm parameters were computed separately for each group by the single and population-mean cosinor Tits of a 24-hr cosine curve. A comparison of circadian parameters indicates a statistically significant difference in acrophase (>P =0.033) between short and standard children, as well as added differences in rhythm-adjusted mean (M; P=0.011) and (P =0.035) between boys and girls of short stature. These differences, as well as any other added information from relevant marker rhythms, should be taken into account for the time-specification of therapy before treatment starts in children of short stature.     

CRISPR/Cas9‐mediated whole genomic wide knockout screening identifies mitochondrial ribosomal proteins involving in oxygen‐glucose deprivation/reperfusion resistance

Recanalization therapy by intravenous thrombolysis or endovascular therapy is critical for the treatment of cerebral infarction. However, the recanalization treatment will also exacerbate acute brain injury and even severely threatens human life due to the reperfusion injury. So far, the underlying mechanisms for cerebral ischaemia‐reperfusion injury are poorly understood and effective therapeutic interventions are yet to be discovered. Therefore, in the research, we subjected SK‐N‐BE(2) cells to oxygen‐glucose deprivation/reperfusion (OGDR) insult and performed a pooled genome‐wide CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 (CRISPR‐associated protein 9) knockout screen to discover new potential therapeutic targets for cerebral ischaemia‐reperfusion injury. We used Metascape to identify candidate genes which might involve in OGDR resistance. We found that the genes contributed to OGDR resistance were primarily involved in neutrophil degranulation, mitochondrial translation, and regulation of cysteine‐type endopeptidase activity involved in apoptotic process and response to oxidative stress. We then knocked down some of the identified candidate genes individually. We demonstrated that MRPL19, MRPL32, MRPL52 and MRPL51 inhibition increased cell viability and attenuated OGDR‐induced apoptosis. We also demonstrated that OGDR down‐regulated the expression of MRPL19 and MRPL51 protein. Taken together, our data suggest that genome‐scale screening with Cas9 is a reliable tool to analyse the cellular systems that respond to OGDR injury. MRPL19 and MRPL51 contribute to OGDR resistance and are supposed to be promising targets for the treatment of cerebral ischaemia‐reperfusion damage.