Reevaluation of hydropathy profiles of voltage-gated ionic channels

A reevaluation of the secondary structure of Na, Ca and K channel proteins led to the following results. Only three segments (S1, S5 and S6) of each repeat are sufficiently hydrophobic to be predicted as transmembrane helices, if a window of 19 amino acids is used. Some of the S2 and S3 segments show higher hydrophobic values when calculated with the window of 9 amino acids and can be predicted as short helices. S4 segments are strongly hydrophilic and cannot be predicted as transmembrane helices. Some of the S2, S3 and S4 segments have an amphipathic character; however, these helices do not span a membrane. A model is proposed where 12 hydrophobic transmembrane helices surround 12 shorter helices, forming a hydrophilic pore. In addition, a unique pattern for S4 segments of voltage-gated channel proteins is defined.     

Reevaluation of hydropathy profiles of voltage-gated ionic channels

A reevaluation of the secondary structure of Na, Ca and K channel proteins led to the following results. Only three segments (S1, S5 and S6) of each repeat are sufficiently hydrophobic to be predicted as transmembrane helices, if a window of 19 amino acids is used. Some of the S2 and S3 segments show higher hydrophobic values when calculated with the window of 9 amino acids and can be predicted as short helices. S4 segments are strongly hydrophilic and cannot be predicted as transmembrane helices. Some of the S2, S3 and S4 segments have an amphipathic character; however, these helices do not span a membrane. A model is proposed where 12 hydrophobic transmembrane helices surround 12 shorter helices, forming a hydrophilic pore. In addition, a unique pattern for S4 segments of voltage-gated channel proteins is defined.     

Sphingosine 1-phosphate induces differentiation of adipose tissue-derived mesenchymal stem cells towards smooth muscle cells

Sphingosine 1-phosphate (S1P) is a bioactive sphingolipid which regulates multiple biological parameters in a number of cell types, including stem cells. Here we report, for the first time, that S1P dose-dependently stimulates differentiation of adipose tissue-derived mesenchymal stem cells (ASMC) towards smooth muscle cells. Indeed, S1P not only induced the expression of smooth muscle cell-specific proteins such as α-smooth muscle actin (αSMA) and transgelin, but also profoundly affected ASMC morphology by enhancing cytoskeletal F-actin assembly, which incorporated αSMA. More importantly, S1P challenge was responsible for the functional appearance of Ca²⁺ currents, characteristic of differentiated excitable cells such as smooth muscle cells. By employing various agonists and antagonists to inhibit S1P receptor subtypes, S1P₂ turned out to be critical for the pro-differentiating effect of S1P, while S1P₃ appeared to play a secondary role. This study individuates an important role of S1P in AMSC which can be exploited to favour vascular regeneration. Received 06 March 2009; accepted 17 March 2009     

Ubiquitin-proteasome system

The 26S proteasome is the multi-protein protease that recognizes and degrades ubiquitinylated substrates targeted for destruction by the ubiquitin pathway. In addition to the well-documented subunit organization of the 26S holoenzyme, it is clear that a number of other proteins transiently associate with the 26S complex. These transiently associated proteins confer a number of different roles such as substrate presentation, cleavage of the multi-ubiquitin chain from the protein substrate and turnover of misfolded proteins. Such activities are essential for the 26S proteasome to efficiently fulfill its intracellular function in protein degradation.     

Developmental regulation of p70 S6 kinase by a G protein-coupled receptor dynamically modelized in primary cells

The mechanisms whereby G protein-coupled receptors (GPCR) activate signalling pathways involved in mRNA translation are ill-defined, in contrast to tyrosine kinase receptors (TKR). We compared a GPCR and a TKR, both endogenously expressed, for their ability to mediate phosphorylation of 70-kDa ribosomal S6 kinase p70S6K in primary rat Sertoli cells at two developmental stages. In proliferating cells stimulated with follicle-stimulating hormone (FSH), active p70S6K was phosphorylated on T389 and T421/S424, through cAMP-dependent kinase (PKA) and phosphatidyl-inositide-3 kinase (PI3K) antagonizing actions. In FSH-stimulated differentiating cells, active p70S6K was phosphorylated solely on T389, PKA and PI3K independently enhancing its activity. At both developmental stages, insulin-induced p70S6K regulation was consistent with reported data. Therefore, TKR and GPCR trigger distinct p70S6K active conformations. p70S6K developmental regulation was formalized in a dynamic mathematical model fitting the data, which led to experimentally inaccessible predictions on p70S6K phosphorylation rate.     

S100A6 protein: functional roles

S100A6 protein belongs to the A group of the S100 protein family of Ca²⁺-binding proteins. It is expressed in a limited number of cell types in adult normal tissues and in several tumor cell types. As an intracellular protein, S100A6 has been implicated in the regulation of several cellular functions, such as proliferation, apoptosis, the cytoskeleton dynamics, and the cellular response to different stress factors. S100A6 can be secreted/released by certain cell types which points to extracellular effects of the protein. RAGE (receptor for advanced glycation endproducts) and integrin β1 transduce some extracellular S100A6’s effects. Dosage of serum S100A6 might aid in diagnosis in oncology.     

国际科技合作中知识转移风险的研究

随着科技全球化的发展和深入,国际科技合作成为各国政府和科研机构提升自身科研水平和核心竞争力的有力途径。然而,在国际科技合作中进行知识的转移与交流时,不可避免的面临着各种各样的风险,如何识别扣防范这些风险成为目前亟待解决的议题。有鉴于此,本文从知识、合作成员和环境三个维度,系统的对国际科技合作中的知识转移风险因素进行了分析,并据此进一步构建出相应的风险防范机制模型,力图为降低国际科技中的知识转移风险提供科学的理论依据。     

Electrophoretic analysis of lactate NAD oxidoreductase in interspecific hybrids between three species of the genus Sphaeroma: S. monodi, S. Rugicauda and S. hookeri]

The electrophoretic analysis of lactate NAD oxydoreductase in interspecific hybrids between three species of genus Sphaeroma (S. monodi, S. rugicauda and S. hookeri hookeri) leads, for each category of hybrids, to a distribution between the two parental enzymatic patterns and, consequently, shows the absence of an isozyme appropriate to these hybrids.     

Joining S100 proteins and migration: for better or for worse,in sickness and in health

The vast diversity of S100 proteins has demonstrated a multitude of biological correlations with cell growth, cell differentiation and cell survival in numerous physiological and pathological conditions in all cells of the body. This review summarises some of the reported regulatory functions of S100 proteins (namely S100A1, S100A2, S100A4, S100A6, S100A7, S100A8/S100A9, S100A10, S100A11, S100A12, S100B and S100P) on cellular migration and invasion, established in both culture and animal model systems and the possible mechanisms that have been proposed to be responsible. These mechanisms involve intracellular events and components of the cytoskeletal organisation (actin/myosin filaments, intermediate filaments and microtubules) as well as extracellular signalling at different cell surface receptors (RAGE and integrins). Finally, we shall attempt to demonstrate how aberrant expression of the S100 proteins may lead to pathological events and human disorders and furthermore provide a rationale to possibly explain why the expression of some of the S100 proteins (mainly S100A4 and S100P) has led to conflicting results on motility, depending on the cells used.     

Ubiquitin-proteasome system

20S proteasomes constitute the proteolytic core of large protease complexes found in all branches of life. Among these, the eukaryotic 26S proteasome ubiquitously poses as a vital final entity in regulated degradation of intracellular proteins. The composition of 20S core particles has been disclosed in detail, facilitated by groundbreaking studies on ancestral prokaryotic 20S proteasomes of low complexity and culminated in the crystal structure determination of the much more complex eukaryotic particles. This article first summarizes insights into the structural organization of the 20S core followed by characterization of its proteolytic activities, which are confined to the central cavity of the particle. In eukaryotes they reside in three different subunit types differing in their preference for cleavage sites in substrates as well as in their importance for the proteasome's cellular function. The second part reviews current knowledge on the biogenesis pathways of 20S core particles, which have to ensure not only the fixed subunit arrangement but also activation of proteolytic subunits in a late assembly state.     

The Sushi peptides: structural characterization and mode of action against Gram-negative bacteria

The compositional difference in microbial and human cell membranes allows antimicrobial peptides to preferentially bind microbes. Peptides which specifically target lipopolysaccharide (LPS) and palmitoyl-oleoyl-phosphatidylglycerol (POPG) are efficient antibiotics. From the core LPS-binding region of Factor C, two 34-mer Sushi peptides, S1 and S3, were derived. S1 functions as a monomer, while S3 is active as a dimer. Both S1 and S3 display detergent-like properties in disrupting LPS aggregates, with specificity for POPG resulting from electrostatic and hydrophobic forces between the peptides and the bacterial lipids. During interaction with POPG, the S1 transitioned from a random coil to an α-helix, while S3 resumed a mixture of α-helix and β-sheet structures. The unsaturated nature of POPG confers fluidity and enhances insertion of the peptides into the lipid bilayer, causing maximal disruption of the bacterial membrane. These parameters should be considered in designing and developing new generations of peptide antibiotics with LPS-neutralizing capability. Received 2 October 2007; received after revision 2 November 2007; accepted 4 December 2007 J. L. Ding, B. Ho: Co-senior authors.     

Mutagenic effect of UV-light and X-rays onStreptomyces nigrifaciens and yield of the antifungal substance

Résumé Changement de capacité de production antibiotique chez mutants nouveaux deStreptomyces nigrifaciens.

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Thanks are due to PrincipalS. Sinha of Agra College, Agra, for providing all facilities and to C.S.I.R., New Delhi, for award of research followship to S.G.     

3S技术在江汉平原湿地监测中的应用

文章以江汉平原湿地监测为例，就3S技术在湿地监测中的应用做了说明。文章在简述江汉平原自然地理概况、江汉平原湿地3S技术监测意义的基础上，分析了进行湿地3S监测的技术方法与流程路线，建立了相应的湿地类型解译标志，并就湿地监测过程中的一些技术问题进行了讨论。     

Photoreceptor properties of an ectopic eye in the fleshfly,Sarcophaga bullata

Summary Ectopic eyes were produced on the fleshfly,Sarcophaga bullata by transplantation of imaginal eye discs. Electrophysiological and histological observations of these supernumerary eyes indicate the absence of synaptic connections between retinular cells and higher order neurons.Supported by an University of New Brunswick research grant to P.S. and NSF grant BNS-76-11921 and NIH grant 1-R01-EY-02487-01A1 to W.S.S.We would like to thank Dr I.A. Meinertzhagen for suggestions and Mary Johnson for technical assistance.     

Development of visual sensitivity in the fly,Sarcophaga bullata

Summary Ontogeny of light response in the compound eyes of the fly,Sarcophaga bullata was investigated. Even though the eyes are structurally differentiated before eclosion they become electrophysiologically functional only after eclosion.Supported by grants from University of New Brunswick and NSERC to P.S. and NIH grant DHHS-1-RO1-EY 03408-03 to W.S.S. We would like to thank Mark Biagi and Roger Smith for technical assistance.     

Differential stimulation of signaling pathways initiated by Edg-2 in response to lysophosphatidic acid or sphingosine-1-phosphate

Lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) are produced during cell activation and have multiple effects on cells. A family of seven transmembrane-spanning domain G-protein-coupled receptors, named Edg, mediate these effects of LPA and S1P. In this study, transient overexpression of Edg-2 sensitized MG63 human osteosarcoma cells to both LPA- and S1P-mediated stimulation of fibronectin matrix deposition and actin stress fiber formation. Both lipids were active in the 1-20 nM concentration range on cells transfected with Edg-2 as compared to the 10-200 nM range on mock-transfected cells. The signaling pathway for matrix deposition by Edg-2-transfected cells was Rho dependent. Overexpression of Edg-2 also caused a tenfold decrease in the concentration of either LPA or S1P that activated MAPKinase (Erkl/2) in MG63 cells. LPA- or S1P-stimulated activation of Erkl/2 was Gi dependent. These results indicate that, in MG63 cells, Edg-2 mediates actin stress fiber formation, fibronectin matrix assembly, and MAPKinase activation in response to either LPA or S1P.     

Phytosterols from pressmud residue obtained after methanogenic fermentation

Summary Pressmud, a sugar factory waste, was fermented with methanogenic bacteria in an anaerobic fermenter for 40 days at 31±2°C. The pressmud residue obtained after fermentation was used as a source for the extraction of phytosterols. The anaerobic digestion degraded the organic matter and resulted in enrichment of phytosterols from 0.33% in the pressmud to 3.05% in the residue. Refluxing of 100 g of residue with benzene, petroleum ether, and ethanolic KOH (1051) yielded 8 g of soft cake, which on further fractionation with methylcyanide and isopropanol gave three fractions: 1) a crude mixture of phytosterols, 2) resin, and 3) undigested organic matter. The crude mixture of phytosterols after purification on neutral alumina followed by GLC analysis resulted in the separation of 68.7% of -sitosterol, 18.4% of stigmasterol and 12.9% of campesterol and brassicasterol together. Phytosterols were extracted more easily from fermented than from unfermented samples, because of biodegration of lipophilic compounds by the methanogenic bacteria.Acknowledgments. S.K.S. and J.C.S. are thankful to the authorities of the U.G.C., New Delhi, for the award of Teacher-fellowships. R.C.S., R.A.K.S. and D.K.M. are thankful to the authorities of the C.S.I.R., New Delhi, for providing R.A., S.R.F., and J.R.F., respectively. Reprint request to S.N.M.     

从近年科技投入变化看美国科技政策的变化

美国能够成为世界头号科技大国，其科技政策功不可没。近年来，美国不断调整其科技政策以保证站在世界的最前列，这可以从美国在科技中投入的不断变化看出来。本文基于冷战结束至今美国在科技中投入的变化，分析了美国科技政策十几年来的变化特点。     

Nucleolar localization and circadian regulation of Per2S,a novel splicing variant of the Period 2 gene

In this work, we show for the first time that a second splicing variant of the core clock gene Period 2 (Per2), Per2S, is expressed at both the mRNA and protein levels in human keratinocytes and that it localizes in the nucleoli. Moreover, we show that a reversible perturbation of the nucleolar structure acts as a resetting stimulus for the cellular clock. Per2S expression and periodic oscillation upon dexamethasone treatment were assessed by qRT-PCR using specific primers. Western blot (WB) analysis using an antibody against the recombinant human PER2 (abRc) displayed an intense band at a molecular weight of ~55 kDa, close to the predicted size of Per2S, and a weaker band at the expected size of Per2 (~140 kDa). The antibody raised against PER2 pS662 (abS662), an epitope absent in PER2S, detected only the higher band. Immunolocalization studies with abRc revealed a peculiar nucleolar signal colocalizing with the nucleolar marker nucleophosmin, whereas with abS662 the signal was predominantly diffuse all over the nucleus and partially colocalized with abRc in the nucleolus. The analysis of cell fractions by WB confirmed the enrichment of PER2S and the presence of PER2 in the nucleolar compartment. Finally, a pulse (1 h) of actinomycin D (0.01 μg/ml) induced reversible nucleolar disruption, PER2S de-localization and circadian synchronization of clock and Per2S genes. Our work represents the first evidence that the Per2S splicing isoform is a clock component expressed in human cells localizing in the nucleolus. These results suggest a critical role for the nucleolus in the process of circadian synchronization in human keratinocytes.