Homeostatic regulation of NCAM polysialylation is critical for correct synaptic targeting

During development, axonal projections have a remarkable ability to innervate correct dendritic subcompartments of their target neurons and to form regular neuronal circuits. Altered axonal targeting with formation of synapses on inappropriate neurons may result in neurodevelopmental sequelae, leading to psychiatric disorders. Here we show that altering the expression level of the polysialic acid moiety, which is a developmentally regulated, posttranslational modification of the neural cell adhesion molecule NCAM, critically affects correct circuit formation. Using a chemically modified sialic acid precursor (N-propyl-D: -mannosamine), we inhibited the polysialyltransferase ST8SiaII, the principal enzyme involved in polysialylation during development, at selected developmental time-points. This treatment altered NCAM polysialylation while NCAM expression was not affected. Altered polysialylation resulted in an aberrant mossy fiber projection that formed glutamatergic terminals on pyramidal neurons of the CA1 region in organotypic slice cultures and in vivo. Electrophysiological recordings revealed that the ectopic terminals on CA1 pyramids were functional and displayed characteristics of mossy fiber synapses. Moreover, ultrastructural examination indicated a "mossy fiber synapse"-like morphology. We thus conclude that homeostatic regulation of the amount of synthesized polysialic acid at specific developmental stages is essential for correct synaptic targeting and circuit formation during hippocampal development.     

MSCs定向诱导移植修复关节软骨的实验研究

目的 用组织工程方法修复软骨损伤.方法 兔骨髓间充质干细胞体外扩增诱导分化后,移植于兔关节损伤区,术后进行大体及x线观察.结果 实验组移植8周后,软骨损伤区由透明软骨样组织填充,软骨修复良好.结论 自体间充质干细胞移植可修复关节软骨损伤.     

用于视频传输的自适应分级正交幅度调制不等保护方法

针对已有用于无线视频传输不等保护的分级正交幅度调制(HQAM)不能适应无线信道时变特性和频率选择性的问题,提出一种自适应HQAM不等保护方法(A-HQAM).首先将视频码流按其对恢复视频质量的重要性划分出不同的优先级,然后根据优先级不同数据允许的误码率上限和子载波信道质量,自适应确定对应的HQAM调制参数,最后将视频数据调制到各子载波上实现不等保护传输.与已有同类方法相比,A-HQAM方法可减小无线信道时变特性和频率选择性的影响,改善恢复视频质量.仿真结果表明,相比基于HQAM的不等保护方法,A-HQAM方法可使恢复视频质量平均提高1dB.     

柠康酸培养体系对A. pascens DMDC12的胁迫作用与其SOD活性的提高

研究报道了野生型高度耐盐节杆菌Arthrobacter pascens DMDC12）经柠康酸体系培养后,导致胞内超氧化物歧化酶（SOD）大量表达．该菌的无细胞粗酶液SDS—PAGE表明,随着培养过程中碳源柠康酸的利用,亚基相对分子质量约为25000处的蛋白产生了显著诱导．经N-末端测序表明该蛋白为SOD,无细胞粗酶液酶活可达787U／g湿菌体．4种不同培养体系对该菌SOD活性影响表明,常规的葡萄糖、酵母膏或柠檬酸作为碳源或能源时,菌体的SOD处于较低水平,发酵液pH呈碱性可对该菌SOD有一定促进作用．在柠康酸培养体系中,无细胞粗酶液SOD的比活为常规培养基培养后的2．3—4．3倍,表明除pH外尚存在其他因素比如某种中间代谢物对菌体产生的胁迫压力显著促进了SOD的表达．本研究首次报道微生物生长环境胁迫作用对菌体SOD活力的影响,相关结论对利用微生物生存胁迫手段促进菌体大量产生SOD具有重要的指导作用．     

不同泥龄下溶解性微生物产物对膜污染的影响

采用4套平行运行的小试膜生物反应器(membrane bioreactors,MBR)对不同泥龄下膜生物反应器中溶解性微生物产物(soluble microbial products,SMP)的膜污染行为进行研究.结果显示,SMP的膜污染潜势和积累程度均随着泥龄的缩短而增大;MBR中与出水中SMP的相对分子质量分布相似;SMP的相对分子质量分布呈明显的双峰特征,泥龄长时高分子含量升高;SMP中的碳水化合物较蛋白质更容易在MBR中积累,泥龄短时尤为显著.因此,SMP组分按照不同形式划分,其膜污染潜势推测为碳水化合物>蛋白质,小分子组分>大分子组分.     

Estimating the young evolutionary age of marbled crayfish from museum samples

ABSTRACT

The obligately parthenogenetic, all-female marbled crayfish, Procambarus virginalis, is a triploid descendant of the similarly looking, sexually reproducing slough crayfish, Procambarus fallax, native to Florida and southern Georgia. We have earlier hypothesised that marbled crayfish may have originated from P. fallax only some 25 years ago, perhaps in captivity. In order to investigate the young evolutionary age hypothesis in more detail, I searched the P. fallax collection of the Smithsonian Institution Museum of Natural History (USNM, Washington, D.C.) for evidence of marbled crayfish before its detection in the German aquarium trade in 1995. In particular, I analysed the sex ratio of P. fallax and the frequency of pure female samples throughout its entire distribution range to detect potentially misidentified marbled crayfish among the P. fallax. If marbled crayfish had originated from P. fallax long ago, spread throughout Florida and Georgia and erroneously been sampled as P. fallax, then the sex ratio of the P. fallax in the collection should be significantly biased towards females and pure female samples should be much more frequent than in related Procambarus species. Comparison of P. fallax (n = 2299) with its closest relatives P. seminolae (n = 801) and P. leonensis (n = 150) revealed female proportions of 55.33%, 53.93% and 54.67%, respectively, which are not significantly different from each other. The average female proportion of the 14 Procambarus species investigated (8641 specimens) was 52.54 ± 7.54% (mean ± standard deviation). Moreover, pure female samples consisting of more than 3 specimens that could represent hidden marbled crayfish were not conspicuously more common in P. fallax (2.33%) than in all Procambarus species investigated (1.24 ± 1.79%). These data suggest that the P. fallax collection of the USNM consists of real, sexually reproducing P. fallax and does most likely not include hidden marbled crayfish, supporting the young evolutionary age hypothesis for marbled crayfish.     

P/HZSM-5分子筛催化乙醇脱水制备乙烯

采用浸渍法制备一系列P/HZSM-5分子筛催化剂,考察P含量对乙醇脱水制备乙烯的影响,并以X线衍射（XRD）、N₂吸附脱附（BET）、²⁷AL核磁共振(²⁷AL MAS NMR)等表征手段研究了P物种对HZSM-5分子筛结构和酸性质的影响。结果表明:H₃PO₄的添加会在某种程度上促进骨架四面体Al原子的脱离,从而有效地降低催化剂酸强度,进而减弱了催化剂的活性,但有利于延长使用寿命。结合NH₃-TPD表征结果,P的添加量控制在2.0%比较合适。