Regulation ofL-valine absorption by opioids interacting withμ-receptors in rabbit ileum

In intact tissue, [d-Ala²,MePhe⁴, Gly-ol⁵] enkephalin (10^–5 M;-ligand), diminsihed short-circuit current (I_sc) and increased water, Na⁺ and Cl^– net fluxes in vitro under open circuit conditions; it also inhibitedL-valine absorption andL-valine-dependent variations of short-circuit current (I_{sc, val}). Naloxone (10^–6 M) antagonized these effects. In the absence of the muscularis and myenteric plexus this enkephalin or morphine (-ligand) reduced I_sc and I_{sc, val}. These enkephalin effects occurred at different times. Different concentrations of enkephalin were tested for their effects on I_{sc, val}. [d-Ala²,d-Leu⁵] enkephalin (mainly a -ligand) significantly decreased I_sc but not I_{sc, val}. The reduction ofL-valine absorption does not depend on the effects on basal ion transport. Interaction of opioids with-receptors located in the submucosal plexus and/or in the epithelial cell accounts for this reduction. This enkephalin effect seems to be at least partially under the control of the myenteric plexus.     

Purification et cristallisation de 1'α-amylase de bactérie

Summary The purification and crystallization of bacterial -amylase are described. It is not identical with pancreas -amylase, but its action on starch is the same.     

Post-mating clutch piracy in an amphibian

Female multiple mating and alternative mating systems can decrease the opportunity for sexual selection. Sperm competition is often the outcome of females mating with multiple males and has been observed in many animals, and alternative reproductive systems are widespread among species with external fertilization and parental care. Multiple paternity without associated complex behaviour related to mating or parental care is also seen in simultaneously spawning amphibians and fishes that release gametes into water. Here we report 'clutch piracy' in a montane population of the common frog Rana temporaria, a reproductive behaviour previously unknown in vertebrates with external fertilization. Males of this species clasp the females and the pair deposits one spherical clutch of eggs. No parental care is provided. 'Pirate' males search for freshly laid clutches, clasp them as they would do a female and fertilize the eggs that were left unfertilized by the 'parental' male. This behaviour does not seem to be size-dependent, and some males mate with a female and perform clutch piracy in the same season. Piracy affected 84% of the clutches and in some cases increased the proportion of eggs fertilized, providing direct fitness benefits both for the pirate males and the females. Sexual selection--probably caused by a strong male-biased sex ratio--occurs in this population, as indicated by size-assortative mating; however, clutch piracy may reduce its impact. This provides a good model to explore how alternative mating strategies can affect the intensity of sexual selection.     

Reconfigurable self-assembly through chiral control of interfacial tension

From determining the optical properties of simple molecular crystals to establishing the preferred handedness in highly complex vertebrates, molecular chirality profoundly influences the structural, mechanical and optical properties of both synthetic and biological matter on macroscopic length scales. In soft materials such as amphiphilic lipids and liquid crystals, the competition between local chiral interactions and global constraints imposed by the geometry of the self-assembled structures leads to frustration and the assembly of unique materials. An example of particular interest is smectic liquid crystals, where the two-dimensional layered geometry cannot support twist and chirality is consequently expelled to the edges in a manner analogous to the expulsion of a magnetic field from superconductors. Here we demonstrate a consequence of this geometric frustration that leads to a new design principle for the assembly of chiral molecules. Using a model system of colloidal membranes, we show that molecular chirality can control the interfacial tension, an important property of multi-component mixtures. This suggests an analogy between chiral twist, which is expelled to the edges of two-dimensional membranes, and amphiphilic surfactants, which are expelled to oil-water interfaces. As with surfactants, chiral control of interfacial tension drives the formation of many polymorphic assemblages such as twisted ribbons with linear and circular topologies, starfish membranes, and double and triple helices. Tuning molecular chirality in situ allows dynamical control of line tension, which powers polymorphic transitions between various chiral structures. These findings outline a general strategy for the assembly of reconfigurable chiral materials that can easily be moved, stretched, attached to one another and transformed between multiple conformational states, thus allowing precise assembly and nanosculpting of highly dynamical and designable materials with complex topologies.     

Poincaré对偶代数，Macaulay对偶系及Steenrod运算

Poincaré对偶代数起源于拓扑学家关于闭流形的上同调的工作，Macaulay对偶系则产生于多项式代数中不可约理想的研究。这两种思想借助于基本交换代数（特别是Gorenstein代数）的工具而紧密结合起来。Steenrod运算也来自代数拓扑学，但最好将它看作破解隐藏在特征P≠o的Frobenius映射下的信息的手段。[第一段]     

Frequent mutation of histone-modifying genes in non-Hodgkin lymphoma

Follicular lymphoma (FL) and diffuse large B-cell lymphoma (DLBCL) are the two most common non-Hodgkin lymphomas (NHLs). Here we sequenced tumour and matched normal DNA from 13 DLBCL cases and one FL case to identify genes with mutations in B-cell NHL. We analysed RNA-seq data from these and another 113 NHLs to identify genes with candidate mutations, and then re-sequenced tumour and matched normal DNA from these cases to confirm 109 genes with multiple somatic mutations. Genes with roles in histone modification were frequent targets of somatic mutation. For example, 32% of DLBCL and 89% of FL cases had somatic mutations in MLL2, which encodes a histone methyltransferase, and 11.4% and 13.4% of DLBCL and FL cases, respectively, had mutations in MEF2B, a calcium-regulated gene that cooperates with CREBBP and EP300 in acetylating histones. Our analysis suggests a previously unappreciated disruption of chromatin biology in lymphomagenesis.     

基于C164微控制器的电动自行车变频控制研究

介绍了基于西门子C164微控制器的电动自行车变频控制研究，主要从变频原理、微机控制、系统整体三方面给出了详细的说明，系统设计简单，控制效率高，有很好的发展前途。