Influence of a downstream narrowing on the flow profile in a tube

The distance over which the upstream flow conditions in a tube are disturbed by a stenosis downstream, i.e. the outlet length, was investigated for Reynolds numbers in the range 210-2900. Two methods were used, the Navier-Stokes equations were solved with a computer and a physical model was constructed and maximal velocities were measured with an ultrasound Doppler system. The computer model showed that Re number does not influence the outlet length, varying the stenosis area from 25% to 90% has an effect. However, the outlet length remained small, below 70% of the diameter of the tube. The physical model confirmed for a 75% stenosis that the outlet length is small, this method set the limit at not more than 1.2 times the tube diameter.     

Genetic diversity and differentiation in natural and reintroduced populations of Bencomia exstipulata and comparisons with B. caudata (Rosaceae) in the Canary Islands: an analysis using microsatellites

Variation at five polymorphic microsatellite loci was used to investigate genetic diversity and differentiation of two tetraploid Canarian endemics, Bencomia exstipulata and B. caudata. Data were analysed and are discussed in terms of tetrasomic (autotetraploid) and disomic (allotetraploid) inheritance. In both cases, genetic diversity values were similar to those described in other tetraploid plant species. High genetic differentiation between the only two described natural populations of B. exstipulata was detected (F_ST = 0.411). Bayesian cluster analysis revealed a geographical structure with distinct genetic groups from each island. High genetic differentiation and low genetic diversity of the B. exstipulata population from Tenerife suggest a recent population bottleneck, perhaps caused by the most recent major volcanic eruption, for this natural locality. This may be heightened by possible inbreeding depression and the monoecy of these species. Polymorphic microsatellite loci were also tested across all species in the Bencomia alliance. These reliably amplified the target sequence, suggesting a high degree of conservation of the sequences flanking the microsatellites. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 160 , 429–441.     

汉滩病毒M、S基因不同拼接方式在昆虫细胞中融合表达效果比较

将汉滩病毒囊膜糖蛋白G1与核蛋白(NP)部分片段以不同方式拼 接,构建G1S0.7或S0.7G1嵌合基因,分别插入杆状病毒表达载体pFBD,转化DH10Bac致敏菌, 获得含有嵌合基因的重组穿梭质粒Bacmid,用其转染Sf9细胞,快速筛选出含有G1S0.7或S0.7 G1嵌合 基因的重组杆状病毒,在昆虫细胞中表达外源融合蛋白.利用间接免疫荧光、ELISA和免疫 印迹对表达产物进行检测.结果表明,含G1S0.7嵌合基因之重组杆状病毒可在昆虫细胞中表 达出融合蛋白,该蛋白可被抗汉滩病毒核蛋白及糖蛋白G1特异性单抗所识别,其分子量约97 kD;含S0.7G1嵌合基因之重组杆状病毒在昆虫细胞中表达的融合蛋白,只能被抗汉滩病毒核 蛋白特异性单抗所识别,其分子量约43kD.上述结果提示,G1S0.7嵌合基因可能在昆虫细胞 中表达出完整的具有生物学活性的融合蛋白,S0.7G1嵌和基因的昆虫细胞表达产物不完整 ,且生物学活性不如G1S0.7嵌合基因的表达产物.     

Search for haplotype interactions that influence susceptibility to type 1 diabetes, through use of unphased genotype data

Type 1 diabetes is a T-cell-mediated chronic disease characterized by the autoimmune destruction of pancreatic insulin-producing beta cells and complete insulin deficiency. It is the result of a complex interrelation of genetic and environmental factors, most of which have yet to be identified. Simultaneous identification of these genetic factors, through use of unphased genotype data, has received increasing attention in the past few years. Several approaches have been described, such as the modified transmission/disequilibrium test procedure, the conditional extended transmission/disequilibrium test, and the stepwise logistic-regression procedure. These approaches are limited either by being restricted to family data or by ignoring so-called "haplotype interactions" between alleles. To overcome this limit, the present study provides a general method to identify, on the basis of unphased genotype data, the haplotype blocks that interact to define the risk for a complex disease. The principle underpinning the proposal is minimal entropy. The performance of our procedure is illustrated for both simulated and real data. In particular, for a set of Dutch type 1 diabetes data, our procedure suggests some novel evidence of the interactions between and within haplotype blocks that are across chromosomes 1, 2, 3, 4, 5, 6, 7, 8, 11, 12, 15, 16, 17, 19, and 21. The results demonstrate that, by considering interactions between potential disease haplotype blocks, we may succeed in identifying disease-predisposing genetic variants that might otherwise have remained undetected.     

The 35 kd pulmonary surfactant-associated protein is encoded on chromosome 10

Summary The genomic components identified by each of two closely related cDNA clones for the major 35 kilodalton non-serum surfactant-associated proteins (PSP-A) were shown to derive from human chromosome 10 by Southern blot analysis of DNAs from human-rodent somatic cell hybrids. By in situ hybridization to human metaphase chromosomes, the cDNA probes were localized to the region 10q21-q24.     

Resilience and restoration of tropical and subtropical grasslands,savannas, and grassy woodlands

Despite growing recognition of the conservation values of grassy biomes, our understanding of how to maintain and restore biodiverse tropical grasslands (including savannas and open‐canopy grassy woodlands) remains limited. To incorporate grasslands into large‐scale restoration efforts, we synthesised existing ecological knowledge of tropical grassland resilience and approaches to plant community restoration. Tropical grassland plant communities are resilient to, and often dependent on, the endogenous disturbances with which they evolved – frequent fires and native megafaunal herbivory. In stark contrast, tropical grasslands are extremely vulnerable to human‐caused exogenous disturbances, particularly those that alter soils and destroy belowground biomass (e.g. tillage agriculture, surface mining); tropical grassland restoration after severe soil disturbances is expensive and rarely achieves management targets. Where grasslands have been degraded by altered disturbance regimes (e.g. fire exclusion), exotic plant invasions, or afforestation, restoration efforts can recreate vegetation structure (i.e. historical tree density and herbaceous ground cover), but species‐diverse plant communities, including endemic species, are slow to recover. Complicating plant‐community restoration efforts, many tropical grassland species, particularly those that invest in underground storage organs, are difficult to propagate and re‐establish. To guide restoration decisions, we draw on the old‐growth grassland concept, the novel ecosystem concept, and theory regarding tree cover along resource gradients in savannas to propose a conceptual framework that classifies tropical grasslands into three broad ecosystem states. These states are: (1) old‐growth grasslands (i.e. ancient, biodiverse grassy ecosystems), where management should focus on the maintenance of disturbance regimes; (2) hybrid grasslands, where restoration should emphasise a return towards the old‐growth state; and (3) novel ecosystems, where the magnitude of environmental change (i.e. a shift to an alternative ecosystem state) or the socioecological context preclude a return to historical conditions.     

甲亢甲低患者肝纤维化指标检测的临床意义分析

目的：探讨甲状腺功能亢进（甲亢）、甲状腺功能减低（甲低）与肝纤维化指标的关系及其可能的机制。方法：采用放射免疫分析法（R1A）检测57例甲亢患者、43例甲低患者、39例甲亢治疗后甲状腺激素正常者和50例健康成人的血清Ⅳ型胶原（1V-C）、Ⅲ型前胶原（PCⅢ）、透明质酸（HA）、层粘连蛋白（LN）、T3、T4、FT3、FT4、TSH、TGA、TMA含量。结果：甲亢患者组血清中1V-C、PCⅢ含量比正常对照组及甲低患者组显著性增高（P〈0.05）;治疗后甲状腺激素下降,1V-C、PCⅢ含量也随之下降（与治疗前比较P〈0.01）;HA、LN在四组中无显著性差异（P〉0.05）,在甲亢治疗前后无显著性差异（P〉0.05）。各项肝纤维化指标与TGA、TMA的阳性率无关。结论：甲亢患者可有不同程度的肝功能损害,血清中甲状腺激素水平增高时,1V-C、PCⅢ水平也增高,在用1V-C、PCⅢ判断肝纤维化时应注意有无甲状腺疾病特别是甲亢。未发现HA、LN含量与甲状腺激素水平的关系。     

Gene expression analysis of zebrafish retinal ganglion cells during optic nerve regeneration identifies KLF6a and KLF7a as important regulators of axon regeneration

Unlike mammals, teleost fish are able to mount an efficient and robust regenerative response following optic nerve injury. Although it is clear that changes in gene expression accompany axonal regeneration, the extent of this genomic response is not known. To identify genes involved in successful nerve regeneration, we analyzed gene expression in zebrafish retinal ganglion cells (RGCs) regenerating their axons following optic nerve injury. Microarray analysis of RNA isolated by laser capture microdissection from uninjured and 3-day post-optic nerve injured RGCs identified 347 up-regulated and 29 down-regulated genes. Quantitative RT-PCR and in situ hybridization were used to verify the change in expression of 19 genes in this set. Gene ontological analysis of the data set suggests regenerating neurons up-regulate genes associated with RGC development. However, not all regeneration-associated genes are expressed in differentiating RGCs indicating the regeneration is not simply a recapitulation of development. Knockdown of six highly induced regeneration-associated genes identified two, KLF6a and KLF7a, that together were necessary for robust RGC axon re-growth. These results implicate KLF6a and KLF7a as important mediators of optic nerve regeneration and suggest that not all induced genes are essential to mount a regenerative response.