The interaction between nesprins and sun proteins at the nuclear envelope is critical for force transmission between the nucleus and cytoskeleton

Maintaining physical connections between the nucleus and the cytoskeleton is important for many cellular processes that require coordinated movement and positioning of the nucleus. Nucleo-cytoskeletal coupling is also necessary to transmit extracellular mechanical stimuli across the cytoskeleton to the nucleus, where they may initiate mechanotransduction events. The LINC (Linker of Nucleoskeleton and Cytoskeleton) complex, formed by the interaction of nesprins and SUN proteins at the nuclear envelope, can bind to nuclear and cytoskeletal elements; however, its functional importance in transmitting intracellular forces has never been directly tested. This question is particularly relevant since recent findings have linked nesprin mutations to muscular dystrophy and dilated cardiomyopathy. Using biophysical assays to assess intracellular force transmission and associated cellular functions, we identified the LINC complex as a critical component for nucleo-cytoskeletal force transmission. Disruption of the LINC complex caused impaired propagation of intracellular forces and disturbed organization of the perinuclear actin and intermediate filament networks. Although mechanically induced activation of mechanosensitive genes was normal (suggesting that nuclear deformation is not required for mechanotransduction signaling) cells exhibited other severe functional defects after LINC complex disruption; nuclear positioning and cell polarization were impaired in migrating cells and in cells plated on micropatterned substrates, and cell migration speed and persistence time were significantly reduced. Taken together, our findings suggest that the LINC complex is critical for nucleo-cytoskeletal force transmission and that LINC complex disruption can result in defects in cellular structure and function that may contribute to the development of muscular dystrophies and cardiomyopathies.     

The role of cutaneous feedback for anticipatory grip force adjustments during object movements and externally imposed variation of the direction of gravity

Grip force adjustments to changes of object loading induced by external changes of the direction of gravity during discrete arm movements with a grasped object were analyzed during normal and anesthetized finger sensibility. Two subjects were seated upright in a rotatable chair and rotated backwards into a horizontal position during discrete movements with a hand-held instrumented object. The movement direction varied from vertical to horizontal inducing corresponding changes in the direction of gravity, but the orientation of the movement in relation to the body remained unaffected. During discrete vertical movements a maximum of load force occurs early in upward and late in downward movements; during horizontal movements two load force peaks result from both acceleratory and deceleratory phases of the movement. During performance with normal finger sensibility grip force was modulated in parallel with fluctuations of load force during vertical and horizontal movements. The grip force profile adopted to the varying load force profile during the transition from the vertical to the horizontal position. The maximum grip force occurred at the same time of maximum load force irrespective of the movement plane. During both subjects' first experience of digital anesthesia the object slipped from the grasp during rotation to the horizontal plane. During the following trials with anesthetized fingers subjects substantially increased their grip forces, resulting in elevated force ratios between maximum grip and load force. However, grip force was still modulated with the movement-induced load fluctuations and maximum grip force coincided with maximum load force during vertical and horizontal movements. This implies that the elevated force ratio between maximum grip and load force does not alter the feedforward system of grip force control. Cutaneous afferent information from the grasping digits seems to be important for the economic scaling of the grip force magnitude according to the actual loading conditions and for reactive grip force adjustments in response to load perturbations. However, it plays a subordinate role for the precise anticipatory temporal coupling between grip and load forces during voluntary object manipulation.     

Open resource metagenomics: a model for sharing metagenomic libraries

Both sequence-based and activity-based exploitation of environmental DNA have provided unprecedented access to the genomic content of cultivated and uncultivated microorganisms. Although researchers deposit microbial strains in culture collections and DNA sequences in databases, activity-based metagenomic studies typically only publish sequences from the hits retrieved from specific screens. Physical metagenomic libraries, conceptually similar to entire sequence datasets, are usually not straightforward to obtain by interested parties subsequent to publication. In order to facilitate unrestricted distribution of metagenomic libraries, we propose the adoption of open resource metagenomics, in line with the trend towards open access publishing, and similar to culture- and mutant-strain collections that have been the backbone of traditional microbiology and microbial genetics. The concept of open resource metagenomics includes preparation of physical DNA libraries, preferably in versatile vectors that facilitate screening in a diversity of host organisms, and pooling of clones so that single aliquots containing complete libraries can be easily distributed upon request. Database deposition of associated metadata and sequence data for each library provides researchers with information to select the most appropriate libraries for further research projects. As a starting point, we have established the Canadian MetaMicroBiome Library (CM²BL [1]). The CM²BL is a publicly accessible collection of cosmid libraries containing environmental DNA from soils collected from across Canada, spanning multiple biomes. The libraries were constructed such that the cloned DNA can be easily transferred to Gateway® compliant vectors, facilitating functional screening in virtually any surrogate microbial host for which there are available plasmid vectors. The libraries, which we are placing in the public domain, will be distributed upon request without restriction to members of both the academic research community and industry. This article invites the scientific community to adopt this philosophy of open resource metagenomics to extend the utility of functional metagenomics beyond initial publication, circumventing the need to start from scratch with each new research project.     

农作物种质资源调查数据标准制定与共享

系统提取并分析了农作物种质资源普查数据、调查数据、评价数据和保存数据等数据信息,采用基于数据元技术方法制定了农作物种质资源调查数据标准和数据元目录;定义了种质资源调查数据集以及对象和属性的映射关系;给出了基于XML数据标准存储及交换策略。标准的制定使农作物种质资源调查在"数据层"上达到统一,规范了数据库构建,促进了农作物种质资源调查数据的整合和共享。     

青海门源赭红尾鸲鸣唱方言的时间稳定性

鸟类的鸣唱方言是研究非人类文化进化及其与种群遗传分化相互作用的理想素材。该研究通过比较跨度8年的2001年和2009年青海门源赭红尾鸲(Phoenicurus ochruros rufiventris)鸣唱,研究结果显示,青海门源赭红尾鸲的种特异性音节、经典唱段中的部分音节、典型唱段结构和鸣唱方言的基本形式都具有较高的时间稳定性。2009年赭红尾鸲唱段曲目多于2001年,共享唱段出现了一定的分化,唱段的共享程度和鸣唱的相似性与个体领域间的距离相关,相邻个体的鸣唱相似性程度高于较远距离的个体。     

人卵巢癌细胞微观形态的AFM观察

目的:探讨原子力显微镜(AFM)在人卵巢癌细胞微观形貌表征方面的应用。方法:应用原子力显微镜分别观察培养的高低转移的人卵巢癌细胞及其周围纤连蛋白原纤维和经过紫杉醇药物处理后的细胞的微观形态,进一步对正常的卵巢癌细胞组织和经过紫杉醇药物处理后的卵巢癌细胞组织经过超声波处理后组织的微观结构进行AFM成像观察。结果:高转移特性的卵巢癌细胞周围的纤维少而短;而低转移特性的卵巢癌细胞周围的纤维多且长。经过紫杉醇药物处理后的细胞的形态发生了变化,结构呈现不规则状,且与基底没有纤维连接。结论:不同类型的卵巢癌细胞受其生物功能的影响在基底上的形态不同。药物处理后的癌细胞微观组织发生了变化,与其核溶,核碎和核解的生理变化过程相符。正常的卵巢癌细胞组织结构之间的黏附力较小,故超声波处理后呈现分散的分布。经过紫杉醇药物处理后的卵巢癌细胞组织结构之间的黏附力较大,超声波处理后分布在基底上的结构较紧凑。     

Characterisation of Structures in Salivary Secretion Film Formation. An Experimental Study with Atomic Force Microscopy

The purpose of the present study was to characterise the structure dynamics of pure salivary secretions retained on controlled surfaces with different surface energies in the early stage of salivary film formation. Germanium prisms prepared to have either low surface energy or medium surface energy were incubated in fresh secretions of either human parotid saliva (HPS) or human submandibular/sublingual saliva (HSMSLS) for 15, 90, and 180 min. After controlled rinsing with distilled water, the surfaces were air dried and thereafter imaged with atomic force microscopy (AFM). The amount of adsorbed material and the size of the structures detected increased with increased saliva exposure time. The film thicknesses varied from 10 to 150 nm, and both HPS and HSMSLS films contained structures with diameters varying from 40 nm to 2 μm. Some of these were clustered into special formations. The HPS films exhibited a more granular morphology than the HSMSLS films. Furthermore, branched lines were detected on the low surface energy germanium prisms incubated in saliva. The results indicate that exposure time, surface energy, and type of salivary secretion all are factors affecting the adsorption characteristics of salivary films.     

A Genetic Crossword

Simple models clarify lung and thorax structure and function for 14-19-year-olds     

GENETIC SIMILARITY BETWEEN PARENTS PREDICTS HATCHING FAILURE: NONINCESTUOUS INBREEDING IN THE GREAT REED WARBLER?

The DNA-fingerprinting technique was used to find the true pedigrees and to detect the overall genetic similarity between mates of great reed warblers (Acrocephalus arundinaceus) at an isolated breeding site in Sweden. The study covered 4 yr preceded by 3 yr when almost all adults and nestlings in the study area had been banded. DNA fingerprinting revealed that the putative father had sired 97% of the young (N = 455). The mate's genetic similarity, revealed as the proportion of bands shared in restriction fragment length polymorphism (RFLP) patterns, was high compared with other species of wild birds. Also, band sharing was higher between mates native to the area than between pairs in which the female was experimentally introduced from a distant breeding site. Hatching success of eggs was negatively correlated with the degree of genetic similarity between the mates, whereas pedigree data, up to the level of great-grandparents, clearly demonstrated an absence of close inbreeding. These are the first data showing a significant fitness cost associated with the choice of a mate that has high genetic similarity, even if it is not a close kin. This cost might be caused by generalized negative consequences of genomewide inbreeding in the present study, possibly accentuated by recent population bottlenecks.