Preferential deletion of exons in Duchenne and Becker muscular dystrophies

Duchenne and Becker muscular dystrophy (DMD and BMD) genes are located in Xp21 on the short arm of the X chromosome. DMD patients display a much more severe clinical course than BMD patients, and yet about 10% of cases of each have been reported to have deletions for parts of the gene. Using a complementary DNA subclone of the DMD gene we have screened 66 DMD and BMD patients who had not previously shown deletions with the probes then available. Fifteen patients have a deletion of this part of the gene, indicating a higher deletion frequency in this region (22%). Exons were deleted in five severely affected DMD patients and in ten BMD patients. Significantly, most of these deletions begin in the same region of the cDNA, which implies that there is a common mechanism for the generation of many of these mutations. An apparently identical deletion in one family gave classical BMD in two brothers (presenting in their teens) and only very mild muscle weakness in their 86-year-old great-great-uncle. Taking these data together with data using the probes previously published, we are able to detect deletions directly in 40% of our families requiring antenatal diagnosis or carrier detection.     

Deletion of brain dystroglycan recapitulates aspects of congenital muscular dystrophy

Fukuyama congenital muscular dystrophy (FCMD), muscle-eye-brain disease (MEB), and Walker-Warburg syndrome are congenital muscular dystrophies (CMDs) with associated developmental brain defects. Mutations reported in genes of FCMD and MEB patients suggest that the genes may be involved in protein glycosylation. Dystroglycan is a highly glycosylated component of the muscle dystrophin-glycoprotein complex that is also expressed in brain, where its function is unknown. Here we show that brain-selective deletion of dystroglycan in mice is sufficient to cause CMD-like brain malformations, including disarray of cerebral cortical layering, fusion of cerebral hemispheres and cerebellar folia, and aberrant migration of granule cells. Dystroglycan-null brain loses its high-affinity binding to the extracellular matrix protein laminin, and shows discontinuities in the pial surface basal lamina (glia limitans) that probably underlie the neuronal migration errors. Furthermore, mutant mice have severely blunted hippocampal long-term potentiation with electrophysiologic characterization indicating that dystroglycan might have a postsynaptic role in learning and memory. Our data strongly support the hypothesis that defects in dystroglycan are central to the pathogenesis of structural and functional brain abnormalities seen in CMD.     

An agrin minigene rescues dystrophic symptoms in a mouse model for congenital muscular dystrophy

Congenital muscular dystrophy is a heterogeneous and severe, progressive muscle-wasting disease that frequently leads to death in early childhood. Most cases of congenital muscular dystrophy are caused by mutations in LAMA2, the gene encoding the alpha2 chain of the main laminin isoforms expressed by muscle fibres. Muscle fibre deterioration in this disease is thought to be caused by the failure to form the primary laminin scaffold, which is necessary for basement membrane structure, and the missing interaction between muscle basement membrane and the dystrophin-glycoprotein complex (DGC) or the integrins. With the aim to restore muscle function in a mouse model for this disease, we have designed a minigene of agrin, a protein known for its role in the formation of the neuromuscular junction. Here we show that this mini-agrin-which binds to basement membrane and to alpha-dystroglycan, a member of the DGC-amends muscle pathology by a mechanism that includes agrin-mediated stabilization of alpha-dystroglycan and the laminin alpha5 chain. Our data provides in vivo evidence that a non-homologous protein in combination with rational protein design can be used to devise therapeutic tools that may restore muscle function in human muscular dystrophies.     

钨在等离子体破裂时的表面损伤

在托卡马克类型的聚变装置中,面向等离子体材料在等离子体破裂过程中要承受剧烈的热负荷,这会使得面向等离子体材料表面受到严重的损伤。实验中将纯钨样品放入HT-7托卡马克的刮削层中,以研究等离子体与纯钨表面的作用。实验后发现样品表面产生了等离子体冲击痕和熔化斑痕。     

Defective membrane repair in dysferlin-deficient muscular dystrophy

Muscular dystrophy includes a diverse group of inherited muscle diseases characterized by wasting and weakness of skeletal muscle. Mutations in dysferlin are linked to two clinically distinct muscle diseases, limb-girdle muscular dystrophy type 2B and Miyoshi myopathy, but the mechanism that leads to muscle degeneration is unknown. Dysferlin is a homologue of the Caenorhabditis elegans fer-1 gene, which mediates vesicle fusion to the plasma membrane in spermatids. Here we show that dysferlin-null mice maintain a functional dystrophin-glycoprotein complex but nevertheless develop a progressive muscular dystrophy. In normal muscle, membrane patches enriched in dysferlin can be detected in response to sarcolemma injuries. In contrast, there are sub-sarcolemmal accumulations of vesicles in dysferlin-null muscle. Membrane repair assays with a two-photon laser-scanning microscope demonstrated that wild-type muscle fibres efficiently reseal their sarcolemma in the presence of Ca2+. Interestingly, dysferlin-deficient muscle fibres are defective in Ca2+-dependent sarcolemma resealing. Membrane repair is therefore an active process in skeletal muscle fibres, and dysferlin has an essential role in this process. Our findings show that disruption of the muscle membrane repair machinery is responsible for dysferlin-deficient muscle degeneration, and highlight the importance of this basic cellular mechanism of membrane resealing in human disease.     

Post-translational insertion of a fragment of the glucose transporter into microsomes requires phosphoanhydride bond cleavage

Most eukaryotic secretory and membrane proteins insert co-translationally into the membrane of the rough endoplasmic reticulum (RER), and are targeted there by one or more NH2-terminal or internal signal sequences. However, little is known about the actual translocation and membrane integration processes. In particular, any energy requirements for targeting and integration have remained obscure because of the inability to uncouple the processes from concomitant protein synthesis. We recently showed that the human glucose transporter (GT), an integral membrane glycoprotein, can insert post-translationally into dog pancreatic microsomes with low but demonstrable efficiency in vitro, and that a fragment corresponding to the NH2-terminal 340 amino acids and 8 of the 12 membrane-spanning alpha-helixes of GT (GT-N) can insert with significantly greater efficiency. We report here that post-translational insertion of GT-N into pancreatic microsomes requires energy in the form of a phosphodiester bond, and suggest that co-translational insertion of proteins into the RER may also require energy independent of that used for polypeptide synthesis.     

需求突变情况下的双渠道供应链协调

研究了在直销和通过零售商的传统销售渠道共存的物流服务模式下,一个生产商和一个零售商的协调关系.以最大化供应商的总利润为目标,在假定需求是价格的线性函数的前提下,研究传统供应链需求突变对整个供应链的影响,以及如何通过改变直销链的价格策略来影响供应链的需求,从而实现整个供应网络的供需协调,并为生产商提供了需求突变下的解决方案.最后对契约模型进行了数值仿真分析,给出了契约的选择及参数的求解方法.研究结果表明,在突变程度和成本满足一定的关系时,生产商可以利用直销链来应对零售商需求订单的突变,反之,生产商会选择与零售商改变契约,来共同应对需求突变.     

Efficient disruption of small asteroids by Earth's atmosphere

Accurate modelling of the interaction between the atmosphere and an incoming bolide is a complex task, but crucial to determining the fraction of small asteroids that actually hit the Earth's surface. Most semi-analytical approaches have simplified the problem by considering the impactor as a strengthless liquid-like object ('pancake' models), but recently a more realistic model has been developed that calculates motion, aerodynamic loading and ablation for each separate particle or fragment in a disrupted impactor. Here we report the results of a large number of simulations in which we use both models to develop a statistical picture of atmosphere-bolide interaction for iron and stony objects with initial diameters up to approximately 1 km. We show that the separated-fragments model predicts the total atmospheric disruption of much larger stony bodies than previously thought. In addition, our data set of >1,000 simulated impacts, combined with the known pre-atmospheric flux of asteroids with diameters less than 1 km, elucidates the flux of small bolides at the Earth's surface. We estimate that bodies >220 m in diameter will impact every 170,000 years.     

基于需求数量突变的供应链协调

研究由一个制造商和一个销售商组成的二级供应链在需求数量突变时的协调.分析了常规运作下、需求数量突变下集成供应链的收益和分散供应链各企业的收益.应用Shapley值法进行需求数量突变时收益的再分配,有效地解决了个体理性和集体理性的冲突,达到了供应链协调的目的.     

Leigh综合征肌肉超微结构观察

目的：研究Leigh综合征肌肉的超微结构。方法：取1例Leigh综合征患儿腓肠肌组织,经常规样品制备后进行电镜观察。结果：部分肌纤维出现下列超微结构改变：(1)局灶性肌原纤维、线粒体和肌浆网消失。(2)肌膜下柱状同心圆板层体聚集。(3)细胞核两端线粒体聚集,线粒体内晶格状包涵体常见。结论：本病例出现的形态学改变提示Leigh综合征不仅是一种中枢神经系统疾病,而且是一种线粒体肌病。     

Cortex-restricted disruption of NMDAR1 impairs neuronal patterns in the barrel cortex

In the rodent primary somatosensory cortex, the configuration of whiskers and sinus hairs on the snout and of receptor-dense zones on the paws is topographically represented as discrete modules of layer IV granule cells (barrels) and thalamocortical afferent terminals. The role of neural activity, particularly activity mediated by NMDARs (N-methyl-D-aspartate receptors), in patterning of the somatosensory cortex has been a subject of debate. We have generated mice in which deletion of the NMDAR1 (NR1) gene is restricted to excitatory cortical neurons, and here we show that sensory periphery-related patterns develop normally in the brainstem and thalamic somatosensory relay stations of these mice. In the somatosensory cortex, thalamocortical afferents corresponding to large whiskers form patterns and display critical period plasticity, but their patterning is not as distinct as that seen in the cortex of normal mice. Other thalamocortical patterns corresponding to sinus hairs and digits are mostly absent. The cellular aggregates known as barrels and barrel boundaries do not develop even at sites where thalamocortical afferents cluster. Our findings indicate that cortical NMDARs are essential for the aggregation of layer IV cells into barrels and for development of the full complement of thalamocortical patterns.     

热预处理对细胞分裂效率的影响

以发酵酵母为研究对象,采用超声波空蚀和高压均质方法对细胞进行机械细胞分裂,研究了热预处理对微生物细胞分裂效率的作用。结果表明：酵母悬浮液的温度经热预处理从室温（22±1）℃上升到40-50℃时,达到相同程度的细胞分裂效率所需的能量降低了;当酵母悬浮液的温度经热预处理上升到50℃时,蛋白质浓度达到最大值,蛋白质发生变质的热预处理温度≥52℃。