bluuebunny/crossref_metadata_2025 huggingface dataset:
HIV-1 Vpr Oligomerization but Not That of Gag Directs the Interaction between Vpr and Gag
Authors: Fritz Joëlle V. , Dujardin Denis , Godet Julien , Didier Pascal , De Mey Jan , Darlix Jean-Luc , Mély Yves , de Rocquigny Hugues
Published: November 2009

During HIV-1 assembly, the viral protein R (Vpr) is incorporated into newly made viral particles
via
an interaction with the C-terminal domain of the Gag polyprotein precursor Pr55
Gag
. Vpr has been implicated in the nuclear import of newly made viral DNA and subsequently in its transcription. In addition, Vpr can affect the cell physiology by causing G
2
/M cell cycle arrest and apoptosis. Vpr can form oligomers, but their roles have not yet been investigated. We have developed fluorescence lifetime imaging microscopy-fluorescence resonance energy transfer-based assays to monitor the interaction between Pr55
Gag
and Vpr in HeLa cells. To that end, we used enhanced green fluorescent protein-Vpr that can be incorporated into the virus and tetracysteine (TC)-tagged Pr55
Gag
-TC. This TC motif is tethered to the C terminus of Pr55
Gag
and does not interfere with Pr55
Gag
trafficking and the assembly of virus-like particles (VLPs). Results show that the Pr55
Gag
-Vpr complexes accumulated mainly at the plasma membrane. In addition, results with Pr55
Gag
-TC mutants confirm that the
41
LXXLF domain of Gag-p6 is essential for Pr55
Gag
-Vpr interaction. We also report that Vpr oligomerization is crucial for Pr55
Gag
recognition and its accumulation at the plasma membrane. On the other hand, Pr55
Gag
-Vpr complexes are still formed when Pr55
Gag
carries mutations impairing its multimerization. These findings suggest that Pr55
Gag
-Vpr recognition and complex formation occur early during Pr55
Gag
assembly.
The Major Determinant for Addition of Tegument Protein pUL48 (VP16) to Capsids in Herpes Simplex Virus Type 1 Is the Presence of the Major Tegument Protein pUL36 (VP1/2)
Authors: Ko Debbie H. , Cunningham Anthony L. , Diefenbach Russell J.
Published: November 2009

In this study a number of herpes simplex virus type 1 (HSV-1) proteins were screened, using a yeast-two-hybrid assay, for interaction with the tegument protein pUL48 (VP16). This approach identified interactions between pUL48 and the capsid proteins pUL19 (VP5), pUL38 (VP19C), and pUL35 (VP26). In addition, the previously identified interaction of pUL48 with the major tegument protein pUL36 (VP1/2) was confirmed. All of these interactions, except that of pUL35 and pUL48, could be confirmed using an
in vitro
pulldown assay. A subsequent pulldown assay with intact
in vitro
-assembled capsids, consisting of pUL19, pUL38, and pUL18 (VP23) with or without pUL35, showed no binding of pUL48, suggesting that the capsid/pUL48 interactions initially identified were more then likely not biologically relevant. This was confirmed by using a series of HSV-1 mutants lacking the gene encoding either pUL35, pUL36, or pUL37. For each HSV-1 mutant, analysis of purified deenveloped C capsids indicated that only in the absence of pUL36 was there a complete loss of capsid-bound pUL48, as well as pUL37. Collectively, this study shows for the first time that pUL36 is a major factor for addition of both pUL48 and pUL37, likely through a direct interaction of both with nonoverlapping sites in pUL36, to unenveloped C capsids during assembly of HSV-1.
The U24 Protein from Human Herpesvirus 6 and 7 Affects Endocytic Recycling
Authors: Sullivan Brian M. , Coscoy Laurent
Published: November 2009

Modulation of T-cell receptor expression and signaling is essential to the survival of many viruses. The U24 protein expressed by human herpesvirus 6A, a ubiquitous human pathogen, has been previously shown to downregulate the T-cell receptor. Here, we show that U24 also mediates cell surface downregulation of a canonical early endosomal recycling receptor, the transferrin receptor, indicating that this viral protein acts by blocking early endosomal recycling. We present evidence that U24 is a C-tail-anchored protein that is dependent for its function on TRC40/Asna-1, a component of a posttranslational membrane insertion pathway. Finally, we find that U24 proteins from other roseoloviruses have a similar genetic organization and a conserved function that is dependent on a proline-rich motif. Inhibition of a basic cellular process by U24 has interesting implications not only for the pathogenicity of roseoloviruses but also for our understanding of the biology of endosomal transport.
Newcastle Disease Virus-Vectored Vaccines Expressing the Hemagglutinin or Neuraminidase Protein of H5N1 Highly Pathogenic Avian Influenza Virus Protect against Virus Challenge in Monkeys
Authors: DiNapoli Joshua M. , Nayak Baibaswata , Yang Lijuan , Finneyfrock Brad W. , Cook Anthony , Andersen Hanne , Torres-Velez Fernando , Murphy Brian R. , Samal Siba K. , Collins Peter L. , Bukreyev Alexander
Published: November 2009

H5N1 highly pathogenic avian influenza virus (HPAIV) causes periodic outbreaks in humans, resulting in severe infections with a high (60%) incidence of mortality. The circulating strains have low human-to-human transmissibility; however, widespread concerns exist that enhanced transmission due to mutations could lead to a global pandemic. We previously engineered Newcastle disease virus (NDV), an avian paramyxovirus, as a vector to express the HPAIV hemagglutinin (HA) protein, and we showed that this vaccine (NDV/HA) induced a high level of HPAIV-specific mucosal and serum antibodies in primates when administered through the respiratory tract. Here we developed additional NDV-vectored vaccines expressing either HPAIV HA in which the polybasic cleavage site was replaced with that from a low-pathogenicity strain of influenza virus [HA(RV)], in order to address concerns of enhanced vector replication or genetic exchange, or HPAIV neuraminidase (NA). The three vaccine viruses [NDV/HA, NDV/HA(RV), and NDV/NA] were administered separately to groups of African green monkeys by the intranasal/intratracheal route. An additional group of animals received NDV/HA by aerosol administration. Each of the vaccine constructs was highly restricted for replication, with only low levels of virus shedding detected in respiratory secretions. All groups developed high levels of neutralizing antibodies against homologous and heterologous strains of HPAIV and were protected against challenge with 2 × 107PFU of homologous HPAIV. Thus, needle-free, highly attenuated NDV-vectored vaccines expressing either HPAIV HA, HA(RV), or NA have been developed and demonstrated to be individually immunogenic and protective in a primate model of HPAIV infection. The finding that HA(RV) was protective indicates that it would be preferred for inclusion in a vaccine. The study also identified NA as an independent protective HPAIV antigen in primates. Furthermore, we demonstrated the feasibility of aerosol delivery of NDV-vectored vaccines.
Mutations in Classical Swine Fever Virus NS4B Affect Virulence in Swine
Authors: Fernandez-Sainz I. , Gladue D. P. , Holinka L. G. , O'Donnell V. , Gudmundsdottir I. , Prarat M. V. , Patch J. R. , Golde W. T. , Lu Z. , Zhu J. , Carrillo C. , Risatti G. R. , Borca M. V.
Published: November 2009

NS4B is one of the nonstructural proteins of classical swine fever virus (CSFV), the etiological agent of a severe, highly lethal disease of swine. Protein domain analysis of the predicted amino acid sequence of the NS4B protein of highly pathogenic CSFV strain Brescia (BICv) identified a putative Toll/interleukin-1 receptor (TIR)-like domain. This TIR-like motif harbors two conserved domains, box 1 and box 2, also observed in other members of the TIR superfamily, including Toll-like receptors (TLRs). Mutations within the BICv NS4B box 2 domain (V2566A, G2567A, I2568A) produced recombinant virus NS4B.VGIv, with an altered phenotype displaying enhanced transcriptional activation of TLR-7-induced genes in swine macrophages, including a significant sustained accumulation of interleukin-6 (IL-6) mRNA. Transfection of swine macrophages with the wild-type NS4B gene partially blocked the TLR-7-activating effect of imiquimod (R837), while transfection with the NS4B gene harboring mutations in either of the putative boxes displayed decreased blocking activity. NS4B.VGIv showed an attenuated phenotype in swine, displaying reduced replication in the oronasal cavity and limited spread from the inoculation site to secondary target organs. Furthermore, the level and duration of IL-6 production in the tonsils of pigs intranasally inoculated with NS4B.VGIv were significantly higher than those for animals infected with BICv. The peak of IL-6 production in infected animals paralleled the ability of animals infected with NS4B.VGIv to resist challenge with virulent BICv. Interestingly, treatment of peripheral blood mononuclear cell cultures with recombinant porcine IL-6 results in a significant decrease in BICv replication.
The Effect of Gypenosides on Cardiac Function and Expression of Cytoskeletal Genes of Myocardium in Diabetic Cardiomyopathy Rats
Authors: Ge Min , Ma Shanfeng , Tao Liang , Guan Sudong
Published: November 2009

The relationship between changes of cardiac function and the gene expressions of two major myocardial skeleton proteins, titin and nebulin, and the effect of gypenosides on these gene expressions in diabetic cardiomyopathy rat were explored in the present study. Forty Sprague-Dawley rats were randomly divided into three groups: control group, diabetic cardiomyopathy group and gypenosides-treated diabetic cardiomyopathy group. The diabetic cardiomyopathy was induced in rats by injecting streptozotocin (STZ, 55 mg/kg) intraperitoneally. Seven weeks after the rats suffered from diabetes, the rats were treated with gypenosides 100 mg/kg per day orally for six weeks in gypenosides-treated group. In the meanwhile, the pure water was given to diabetic cardiomyopathy and the control groups. Subsequently, the cardiac functions, including left ventricular systolic pressure (LVSP), left ventricular end diastolic pressure (LVEDP), ± dP/dtmaxand t–dP/dmaxt, as well as the mRNA content and proteins of titin and nebulin in myocardium were determined. The results indicated that (1) the diabetic cardiomyopathy rats had decreased LVSP and ± dP/dtmax, increased LVEDP, and prolonged t–dP/dtmaxthan normal rats; (2) LVSP and ± dP/dtmaxin diabetic cardiomyopathy rats treated with gypenosides were significantly higher and LVEDP and t–dP/dtmaxwere significantly lower than those without giving gypenosides; (3) the mRNA contents and proteins of titin and nebulin in diabetic cardiomyopathy rats were remarkably lower than those in the control rats and gypenosides had no effect on mRNA and protein expression levels of titin and nebulin in diabetic cardiomyopathy rats. We conclude that (1) the cardiac function as well as the mRNA expressions of titin and nebulin decreased in diabetic cardiomyopathy rats; (2) gypenosides secure cardiac muscles and their function from diabetic impairment and these beneficial effects of gypenosides are not by changing the expressions of titin and nebulin.
Effect of Triterpene Acids of Eriobotrya japonica (Thunb.) Lindl. Leaf and MAPK Signal Transduction Pathway on Inducible Nitric Oxide Synthase Expression in Alveolar Macrophage of Chronic Bronchitis Rats
Authors: Huang Y. , Li J. , Meng X. M. , Jiang G. L. , Li H. , Cao Q. , Yu S. C. , Lv X. W. , Cheng W. M.
Published: November 2009

The goal of this study was to investigate the possible therapy mechanism of triterpene acids of Eriobotrya japonica (Thunb.) Lindl. Leaf (TAL) in alveolar macrophage (AM) of chronic bronchitis (CB) rats. CB model was established by injection of bacillus calmette guein (BCG) plus lipopolisacharide (LPS) in rats. TAL significantly inhibited the increased NO concentration, iNOS expression and phosphorylation of p38 MAPK in alveolar macrophages (AMs) of CB rats. Using in vivo test, we found that SB203580, a p38 MAPK inhibitor, (10 μM) significantly inhibited inducible nitric oxide synthase (iNOS) mRNA expression in AM. This data indicate that TAL highly decreases excessive iNOS expression and NO induction, and p38 MAPK signal transduction participates in iNOS expression and NO induction in AM of CB rats. The effect of TAL on iNOS expression in AM may be related to its inhibition of p38 MAPK signal transduction.
Proliferative Effects of Chishao on Schwann Cells are FGF-uPA, and ERK- and JNK-Dependent
Authors: Huang Kun Shan , Lu Min-Jin , Chen Yueh-Sheng , Tsai Fuu-Jen , Kuo Wei-Wen , Cheng Yi-Chang , Lin Chien-Chung , Tsai Chang-Hai , Huang Chih-Yang , Lin Jaung-Geng , Ou Hsiu-Chung
Published: November 2009

This study evaluated the proliferative effects of chishao on RSC96, Schwann cells. A dose-dependent proliferative effect of chishao was obtained by methylthiazol tetrazolium (MTT), proliferating cell nuclear antigen (PCNA) Western blotting, and wound healing assays in Schwann cells administered with chishao (0–500 mg/ml), except at 500 mg/ml concentration. The chishao-treated cells also showed a dose-dependent activated fibroblast growth factor-2 (FGF-2) signaling with increased urokinase plasminogen activator (uPA) and decreased plasminogen activator inhibitor-1 (PAI-1), enhanced proliferative proteins, extracellular signal regulated kinase (ERK) and c-Jun N-terminal kinase (JNK)-signaling. Using mitogen-actvated protein kinase (MAPK)-signaling chemical inhibitors, U0126, SB203580, and SP600125, the proliferative effects of chishao on RSC cells were identified to be ERK- and JNK- signaling dependent. Based on the results, applying appropriate doses of chishao to Schwann cells would be a potential approach for enhancing neuron regeneration.
Intradermal Acupuncture on Shen-Men and Nei-Kuan Acupoints Improves Insomnia in Stroke Patients by Reducing the Sympathetic Nervous Activity: A Randomized Clinical Trial
Authors: Lee Seung Yeop , Baek Yong Hyeon , Park Seong Uk , Moon Sang Kwan , Park Jung Mi , Kim Young Suk , Jung Woo Sang
Published: November 2009

This study is a double-blind randomized controlled trial on the effect of intradermal acupuncture on insomnia after stroke. Hospitalized stroke patients with insomnia were enrolled in the study and were randomly assigned to either a real intradermal acupuncture group (RA group) or a sham acupuncture group (SA group). The RA group received intradermal acupuncture on Shen-Men (He-7) and Nei-Kuan (EH-6) for three days, and the SA group received sham acupuncture on the same points. The effect of acupuncture on insomnia was measured using Insomnia Severity Index (ISI) and Athens Insomnia Scale (AIS) at baseline and three days after treatment. To assess the effect of acupuncture on the autonomic nervous function, the subjects' blood pressure and heart rate variability were monitored. Fifty-two subjects (27 in the RA group and 25 in the SA group) were included in the final analysis. The insomnia-related scales ISI and AIS showed greater improvement of insomnia in the RA group than in the SA group. Moreover, there is a greater reduction of the number of non-dippers and a greater decrease of the LF/HF ratio (heart rate variability) in the RA group than in the SA group. These results indicate that sympathetic hyperactivities were stabilized in the RA group. It can thus be concluded that intradermal acupuncture on Shen-Men and Nei-Kuan is a useful therapeutic method for post stroke-onset insomnia as it reduces sympathetic hyperactivities.
The Knowledge-Inducing Culture — An Integrative Framework of Cultural Enablers of Knowledge Management
Authors: Zheng Wei
Published: November 2009

Organisational cultural factors are key to knowledge management effectiveness. Existing research on cultural factors that facilitate knowledge management has been fragmented. This paper proposes a theoretical framework that integrates existing research on cultural factors that influence knowledge management. This framework incorporates three cultural categories: cultural factors related to the orientation to knowledge, cultural factors related to the orientation to people and cultural factors related to the orientation to work. Each category influences knowledge management in a different way, related to the effectiveness, efficiency and sustainability of knowledge management. This framework has significant implications for practice and research.
Impact of Technological Innovation Capabilities on the Market Value of Firms
Authors: Annavarjula Madan , Mohan Ramesh
Published: November 2009

In the era of globalisation and with the advent of knowledge economies, organisational innovation has assumed a critical role in enhancing economic performance of firms. Proponents of the Resource Based View of the firm and its more recent extensions such as the Knowledge Based View and Dynamic Capabilities Theory have suggested that generation, diffusion and application of organisational knowledge could be the source of sustained competitive advantage and superior performance of firms. While there is near unanimity in accepting the vital role of innovation in a firm's performance, consensus on what constitutes organisational innovation and how to measure it has proven to be elusive so far. Most previous research in this area has conceptualised innovation through one or more dimensions of a firm's innovative capability using R&D of a firm only. The measurement of the construct has thus reflected this narrow conceptualisation with a single measure of R&D expenditure being the most often used proxy. This study utilises a broader definition of organisational innovation capabilities that includes the generation, dissemination and strength of innovative activity in a firm. The unique features of this study is that it uses multiple indicators of a firm's innovation profile along with lagged measures of market value using fixed effects panel data analysis.
Knowledge Management in a Business-to-Business Context: An Indian Exemplar?
Authors: Rod Michel R. M. , Saunders Sarena E. , Beal Tim
Published: November 2009

A conceptual framework originating within the Operations Research literature is presented as a means of informing researchers about how they might better understand and exploit knowledge management/sharing/transfer in business-to-business knowledge networks. Preliminary analysis of a recent Indian case study supports the utility of this framework through the identification of facilitators (information systems, mediators) and barriers (distance, organisational) to successful knowledge flow between organisations both domestically and internationally. The ongoing challenge is to increase our understanding of how firms can better balance knowledge protection and sharing such that managers involved in these inter-organisational exchanges can maximise the benefits to both sides of the dyad; especially in emerging markets such as India with different market characteristics, institutional development and business customer behaviours.
DOES REGULATIONS ALWAYS CONTRIBUTE POSITIVELY TOWARDS TECHNOLOGY EVOLUTIONS IN THE EUROPEAN MOBILE INDUSTRY
Authors: BHUTTO ARABELLA , MOIN-UDDIN ABRO QAZI
Published: November 2009

This paper demonstrates how the regulatory framework causes mobile industry operators to evolve towards advancing Location Based Services (LBS) by integrating several technological resources: but at the same time how the same regulatory framework slows down the pace of technology evolution by not providing precise enough regulations related to the accuracy of technological alternatives for the adoption of these resources. Based on the facts derived from the literature of technology evolution, and the industrial practices of mobile operators in Europe, this paper argues that the delay in the acceptance of mobile based LBS has occurred partly due to the low available precision of the regulatory framework given by the European Commission (EC). The findings indicate that a regulatory framework which is clear enough for the introduction of new LBS in the market is less precise in terms of defining accuracy for these applications. Furthermore by not making these accuracy issues clear, a regulatory framework may cause hindrance in the technology evolution for the acceptance of LBS, as although customers' demand emerge, but due to lesser quality, consumers do not see these services sufficiently striking.
CALCULATING THE CARBON FOOTPRINT OF A CHEMICAL PLANT: A CASE STUDY OF AKZONOBEL
Authors: STEIN MICHAEL , KHARE ANSHUMAN
Published: November 2009

Reduction of greenhouse gas emissions is one of the key requirements for sustainable production and consumption, but while the Canadian chemical industry has been very successful in reducing emissions to water and air, and while non- CO2 greenhouse gas emissions have been minimised as well, reduction of CO2 emissions has been less successful. The industry itself forecasts that further reduction of CO2 emissions will be minimal. On the other hand concerns about global warming are increasing, while at the same time the chemical industry increases its commitment to sustainability. Determining the carbon footprint of a chemical plant and of its products will help to identify more emissions reduction possibilities and is a necessary step for the further reduction of the chemical industry's environmental impact.

Carbon footprint determination is a corporate goal for AkzoNobel, an international coatings and specialty chemicals company, but the carbon footprint is not yet established for many products, and the information available from the chemical industry is scarce. This paper presents a case study of AkzoNobel's Saskatoon Plant and its attempt to calculate and analyse the carbon footprint of the plant and its main products which are used in the potash industry.
AN EVALUATION OF TOOLS FOR AN ASSESSMENT OF CUMULATIVE EFFECTS IN SOCIOECONOMIC IMPACT STUDIES
Authors: CROOKES DOUGLAS J. , DE WIT MARTIN P.
Published: November 2009

Cumulative effects assessments have been defined as environmental assessments done well. However, socioeconomic studies within the EIA process seldom adequately address cumulative effects. One of the reasons for this is that the socioeconomic tools used in the EIA process have not been evaluated and, where necessary, updated to address cumulative effects. This article evaluates current and potential tools, from a variety of paradigms, including economic, industrial ecology and systems theory. An unexpected result was that traditional economic appraisal techniques such as CBA performed quite well against identified criteria. In addition, a number of other newer techniques were also found to be suitable. The article concludes with recommendations on how to practically address cumulative effects in socioeconomic studies.
EUCLIDEAN MINIMA AND CENTRAL DIVISION ALGEBRAS
Authors: BAYER-FLUCKIGER EVA , CERRI JEAN-PAUL , CHAUBERT JÉRÔME
Published: November 2009

The notion of Euclidean minimum of a number field is a classical one. In this paper, we generalize it to central division algebras and establish some general results in this new context.
LOCAL RIEMANN HYPOTHESIS FOR COMPLEX NUMBERS
Authors: OLOFSSON RIKARD
Published: November 2009

In this paper, a special class of local ζ-functions is studied. The main theorem states that the functions have all zeros on the line ℜ(s) = 1/2. This is a natural generalization of the result of Bump and Ng stating that the zeros of the Mellin transform of Hermite functions have ℜ(s) = 1/2.
A NEW COMBINATORIAL STUDY OF THE ROGERS–FINE IDENTITY AND A RELATED PARTIAL THETA SERIES
Authors: ALLADI KRISHNASWAMI
Published: November 2009

We provide a transparent combinatorial derivation of a variant of the Rogers–Fine identity and a new combinatorial proof of a related partial theta series.
The c-MYCNHE III1: Function and Regulation
Authors: González Verónica , Hurley Laurence H.
Published: November 2009

c-MYC is an important regulator of a wide array of cellular processes necessary for normal cell growth and differentiation, and its dysregulation is one of the hallmarks of many cancers. Consequently, understanding c-MYC transcriptional activation is critical for understanding developmental and cancer biology, as well as for the development of new anticancer drugs. The nuclease hypersensitive element (NHE) III1region of the c-MYC promoter has been shown to be particularly important in regulating c-MYC expression. Specifically, the formation of a G-quadruplex structure appears to promote repression of c-MYC transcription. This review focuses on what is known about the formation of a G-quadruplex in the NHE III1region of the c-MYC promoter, as well as on those factors that are known to modulate its formation. Last, we discuss the development of small molecules that stabilize or induce the formation of G-quadruplex structures and could potentially be used as anticancer agents.
Identification of a novel phosphorylation site on TBC1D4 regulated by AMP-activated protein kinase in skeletal muscle
Authors: Treebak Jonas T. , Taylor Eric B. , Witczak Carol A. , An Ding , Toyoda Taro , Koh Ho-Jin , Xie Jianxin , Feener Edward P. , Wojtaszewski Jørgen F. P. , Hirshman Michael F. , Goodyear Laurie J.
Published: November 2009

TBC1D4 (also known as AS160) regulates glucose transporter 4 (GLUT4) translocation and glucose uptake in adipocytes and skeletal muscle. Its mode of action involves phosphorylation of serine (S)/threonine (T) residues by upstream kinases resulting in inactivation of Rab-GTPase-activating protein (Rab-GAP) activity leading to GLUT4 mobilization. The majority of known phosphorylation sites on TBC1D4 lie within the Akt consensus motif and are phosphorylated by insulin stimulation. However, the 5′-AMP-activated protein kinase (AMPK) and other kinases may also phosphorylate TBC1D4, and therefore we hypothesized the presence of additional phosphorylation sites. Mouse skeletal muscles were contracted or stimulated with 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside (AICAR), and muscle lysates were subjected to mass spectrometry analyses resulting in identification of novel putative phosphorylation sites on TBC1D4. The surrounding amino acid sequence predicted that S711 would be recognized by AMPK. Using a phosphospecific antibody against S711, we found that AICAR and contraction increased S711 phosphorylation in mouse skeletal muscle, and this increase was abolished in muscle-specific AMPKα2 kinase-dead transgenic mice. Exercise in human vastus lateralis muscle also increased TBC1D4 S711 phosphorylation. Recombinant AMPK, but not Akt1, Akt2, or PKCζ, phosphorylated purified muscle TBC1D4 on S711 in vitro. Interestingly, S711 was also phosphorylated in response to insulin in an Akt2- and rapamycin-independent, but a wortmannin-sensitive, manner, suggesting this site is regulated by one or more additional upstream kinases. Despite increased S711 phosphorylation with AICAR, contraction, and insulin, mutation of S711 to alanine did not alter glucose uptake in response to these stimuli. S711 is a novel TBC1D4 phosphorylation site regulated by AMPK in skeletal muscle.
A mathematical model of rat ascending Henle limb. II. Epithelial function
Authors: Weinstein Alan M. , Krahn Thomas A.
Published: November 2009

A mathematical model of ascending Henle limb (AHL) epithelium has been fashioned using kinetic representations of Na+-K+-2Cl−cotransporter (NKCC2), KCC4, and type 3 Na+/H+exchanger (NHE3), with transporter densities selected to yield the reabsorptive Na+flux expected for rat tubules in vivo. Of necessity, this model predicts fluxes that are higher than those measured in vitro. The kinetics of the NKCC and KCC are such that Na+reabsorption by the model tubule is responsive to variation in luminal NaCl concentration over the range of 30 to 130 mM, with only minor changes in cell volume. Peritubular KCC accounts for about half the reabsorptive Cl−flux, with the remainder via peritubular Cl−channels. Transcellular Na+flux is turned off by increasing peritubular KCl, which produces increased cytosolic Cl−and thus inhibits NKCC2 transport. In the presence of physiological concentrations of ammonia, there is a large acid challenge to the cell, due primarily to NH4+entry via NKCC2, with diffusive NH3exit to both lumen and peritubular solutions. When NHE3 density is adjusted to compensate this acid challenge, the model predicts luminal membrane proton secretion that is greater than the HCO3−-reabsorptive fluxes measured in vitro. The model also predicts luminal membrane ammonia cycling, with uptake via NKCC2 or K+channel, and secretion either as NH4+by NHE3 or as diffusive NH3flux in parallel with a secreted proton. If such luminal ammonia cycling occurs in vivo, it could act in concert with luminal K+cycling to facilitate AHL Na+reabsorption via NKCC2. With physiological ammonia, peritubular KCl also blunts NHE3 activity by inhibiting NH4+uptake on the Na-K-ATPase, and alkalinizing the cell.
A mathematical model of rat ascending Henle limb. III. Tubular function
Authors: Weinstein Alan M.
Published: November 2009

K+plays a catalytic role in AHL Na+reabsorption via Na+-K+-2Cl−cotransporter (NKCC2), recycling across luminal K+channels, so that luminal K+is not depleted. Based on models of the ascending Henle limb (AHL) epithelium, it has been hypothesized that NH4+may also catalyze luminal Na+uptake. This hypothesis requires that luminal NH4+not be depleted, implying replenishment via either direct secretion of NH4+, or NH3in parallel with a proton. In the present work, epithelial models of rat medullary and cortical AHL (Weinstein AM, Krahn TA. Am J Physiol Renal Physiol 298: F000–F000, 2009) are configured as tubules and examined in simulations of function in vitro and in vivo to assess the feasibility of a catalytic role for NH4+in Na+reabsorption. Modulation of Na+transport is also examined by peritubular K+concentration and by Bartter-type transport defects in NKCC2 (type 1), in luminal membrane K+channels (type 2), and in peritubular Cl−channels (type 3). It is found that a catalytic role for NH4+, which is significant in magnitude (relative to K+), is quantitatively realistic, in terms of uptake via NKCC2, and in terms of luminal membrane ammonia backflux. Simulation of a 90% NKCC2 defect is predicted to double distal Na+delivery; it is also predicted to increase distal acid delivery (principally as NH4+). With doubling of medullary K+, the model predicts a 30% increase in distal Na+delivery, but in this case there is a decrease in AHL acidification. This effect of peritubular K+on proton secretion appears to be akin to type 3 Bartter's pathophysiology, in which there is decreased peritubular HCO3−exit, cytosolic alkalinization, and a consequent decrease in luminal proton secretion by NHE3. One consequence of overlapping and redundant roles for K+and NH4+, is a blunted impact of luminal membrane K+permeability on overall Na+reabsorption, so that type 2 Bartter pathophysiology is not well captured by the model.
Cadmium-induced DNA damage triggers G2/M arrest via chk1/2 and cdc2 in p53-deficient kidney proximal tubule cells
Authors: Bork Ulrich , Lee Wing-Kee , Kuchler Anna , Dittmar Thomas , Thévenod Frank
Published: November 2009

Carcinogenesis is a multistep process that is frequently associated with p53 inactivation. The class 1 carcinogen cadmium (Cd2+) causes renal cancer and is known to inactivate p53. G2/mitosis (M) arrest contributes to stabilization of p53-deficient mutated cells, but its role and regulation in Cd2+-exposed p53-deficient renal cells are unknown. In p53-inactivated kidney proximal tubule (PT) cells, comet assay experiments showed that Cd2+(50–100 μM) induced DNA damage within 1–6 h. This was associated with peak formation of reactive oxygen species (ROS) at 1–3 h, measured with dihydrorhodamine 123, and G2/M cell cycle arrest at 6 h, which were abolished by the antioxidant α-tocopherol (100 μM). Cd2+-induced G2/M arrest was enhanced approximately twofold on release from cell synchronization (double thymidine block or nocodazole) and resulted in approximately twofold increase of apoptosis, indicating that G2/M arrest mirrors DNA damage and toxicity. The Chk1/2 kinase inhibitor UCN-01 (0.3 μM), which relieves G2/M transition block, abolished Cd2+-induced G2arrest and increased apoptosis. This was accompanied by prevention of Cd2+-induced cyclin-dependent kinase cdc2 phosphorylation at tyrosine 15, as shown by immunofluorescence microscopy and immunoblotting. The data indicate that in p53-inactivated PT cells Cd2+-induced ROS formation and DNA damage trigger signaling of checkpoint activating kinases ataxia telangiectasia-mutated kinase (ATM) and ataxia telangiectasia and Rad3-related kinase (ATR) to cause G2/M arrest. This may promote survival of premalignant PT cells and Cd2+carcinogenesis.
Lovastatin-induced cholesterol depletion affects both apical sorting and endocytosis of aquaporin-2 in renal cells
Authors: Procino G. , Barbieri C. , Carmosino M. , Rizzo F. , Valenti G. , Svelto M.
Published: November 2009

Vasopressin causes the redistribution of the water channel aquaporin-2 (AQP2) from cytoplasmic storage vesicles to the apical plasma membrane of collecting duct principal cells, leading to urine concentration. The molecular mechanisms regulating the selective apical sorting of AQP2 are only partially uncovered. In this work, we investigate whether AQP2 sorting/trafficking is regulated by its association with membrane rafts. In both MCD4 cells and rat kidney, AQP2 preferentially associated with Lubrol WX-insoluble membranes regardless of its presence in the storage compartment or at the apical membrane. Block-and-release experiments indicate that 1) AQP2 associates with detergent-resistant membranes early in the biosynthetic pathway; 2) strong cholesterol depletion delays the exit of AQP2 from the trans-Golgi network. Interestingly, mild cholesterol depletion promoted a dramatic accumulation of AQP2 at the apical plasma membrane in MCD4 cells in the absence of forskolin stimulation. An internalization assay showed that AQP2 endocytosis was clearly reduced under this experimental condition. Taken together, these data suggest that association with membrane rafts may regulate both AQP2 apical sorting and endocytosis.
Novel Potassium Channel Blocker, 4-AP-3-MeOH, Inhibits Fast Potassium Channels and Restores Axonal Conduction in Injured Guinea Pig Spinal Cord White Matter
Authors: Sun Wenjing , Smith Daniel , Fu Yan , Cheng Ji-Xin , Bryn Steven , Borgens Richard , Shi Riyi
Published: November 2009

We have demonstrated that 4-aminopyridine-3-methanol (4-AP-3-MeOH), a 4-aminopyridine derivative, significantly restores axonal conduction in stretched spinal cord white-matter strips and shows no preference in restoring large and small axons. This compound is 10 times more potent when compared with 4-AP and other derivatives in restoring axonal conduction. Unlike 4-AP, 4-AP-3-MeOH can restore axonal conduction without changing axonal electrophysiological properties. In addition, we also have confirmed that 4-AP-3-MeOH is indeed an effective blocker of IA based on patch-clamp studies using guinea pig dorsal root ganglia cells. Furthermore, we have also provided the critical evidence to confirm the unmasking of potassium channels following mechanical injury. Taken together, our data further supports and implicates the role of potassium channels in conduction loss and its therapeutic value as an effective target for intervention to restore function in spinal cord trauma. Furthermore, due to its high potency and possible low side effect of impacting electrophysiological properties, 4-AP-3-MeOH is perhaps the optimal choice in reversing conduction block in spinal cord injury compared with other derivatives previously reported from this group.
Heterogeneity of Membrane Properties in Sympathetic Preganglionic Neurons of Neonatal Mice: Evidence of Four Subpopulations in the Intermediolateral Nucleus
Authors: Zimmerman Amanda , Hochman Shawn
Published: November 2009

Spinal cord sympathetic preganglionic neurons (SPNs) integrate activity from descending and sensory systems to determine the final central output of the sympathetic nervous system. The intermediolateral column (IML) has the highest number and density of SPNs and, within this region, SPN somas are found in distinct clusters within thoracic and upper lumbar spinal segments. Whereas SPNs exhibit a rostrocaudal gradient of end-target projections, individual clusters contain SPNs with diverse functional roles. Here we explored diversity in the electrophysiological properties observed in Hb9-eGFP–identified SPNs in the IML of neonatal mice. Overall, mouse SPN intrinsic membrane properties were comparable with those seen in other species. A wide range of values was obtained for all measured properties (up to a 10-fold difference), suggesting that IML neurons are highly differentiated. Using linear regression we found strong correlations between many cellular properties, including input resistance, rheobase, time constant, action potential shape, and degree of spike accommodation. The best predictor of cell function was rheobase, which correlated well with firing frequency–injected current ( f– I) slopes as well as other passive and active membrane properties. The range in rheobase suggests that IML neurons have a recruitment order with stronger synaptic drives required for maximal recruitment. Using cluster analysis, we identified at least four subpopulations of SPNs, including one with a long time constant, low rheobase, and high f– I gain. We thus propose that the IML contains populations of neurons that are differentiable by their membrane properties and hypothesize they represent diverse functional classes.
Saccadic Compensation for Smooth Eye and Head Movements During Head-Unrestrained Two-Dimensional Tracking
Authors: Daye P. M. , Blohm G. , Lefèvre P.
Published: November 2009

Spatial updating is the ability to keep track of the position of world-fixed objects while we move. In the case of vision, this phenomenon is called spatial constancy and has been studied in head-restraint conditions. During head-restrained smooth pursuit, it has been shown that the saccadic system has access to extraretinal information from the pursuit system to update the objects' position in the surrounding environment. However, during head-unrestrained smooth pursuit, the saccadic system needs to keep track of three different motor commands: the ocular smooth pursuit command, the vestibuloocular reflex (VOR), and the head movement command. The question then arises whether saccades compensate for these movements. To address this question, we briefly presented a target during sinusoidal head-unrestrained smooth pursuit in darkness. Subjects were instructed to look at the flash as soon as they saw it. We observed that subjects were able to orient their gaze to the memorized (and spatially updated) position of the flashed target generally using one to three successive saccades. Similar to the behavior in the head-restrained condition, we found that the longer the gaze saccade latency, the better the compensation for intervening smooth gaze displacements; after about 400 ms, 62% of the smooth gaze displacement had been compensated for. This compensation depended on two independent parameters: the latency of the saccade and the eye contribution to the gaze displacement during this latency period. Separating gaze into eye and head contributions, we show that the larger the eye contribution to the gaze displacement, the better the overall compensation. Finally, we found that the compensation was a function of the head oscillation frequency and we suggest that this relationship is linked to the modulation of VOR gain. We conclude that the general mechanisms of compensation for smooth gaze displacements are similar to those observed in the head-restrained condition.
Lack of outcome benefit and clopidogrel “resistance”
Authors: Serebruany Victor
Published: November 2009

Impaired response to clopidogrel, or “resistance” is a cornerstone concept for justification of more aggressive antiplatelet regimens, and development of new more potent drugs. There are over 1,000 citations (although predominantly reviews, or case reports) in MEDLINE related to clopidogrel “resistance”, while about 100 of them attempted to link low response to adverse clinical outcomes. However, most of these studies are woefully small, and not randomised. The TRITON trial assessed head-to-head novel antiplatelet agent prasugrel versus clopidogrel in patients with acute coronary syndromes. This study was the first in a decade to challenge clopidogrel monopoly, and to indirectly test the “resistance” hypothesis. The primary endpoint was the rate of cardiovascular death, non-fatal myocardial infarction, or stroke, and occurred in 12.1% of patients treated with clopidogrel, and 9.9% of patients randomised to prasugrel, suggesting impressive vascular outcome benefit of prasugrel over clopidogrel. However, the Food and Drug Administration (FDA) presented more balanced, and realistic outlook on TRITON. While very early periprocedural benefit exists, long-term prasugrel therapy yielded identical to clopidogrel vascular outcomes among 13,608 TRITON patients challenging the postulate that clopidogrel “resistance” phenomenon is clinically relevant. Despite the fact that prasugrel 10 mg/daily cause 2.5 times more potent platelet inhibition than conventional clopidogrel 75 mg/daily, with fewer patients exhibiting broad response variability, and/or antiplatelet “resistance”, the vascular benefit beyond acute phase was identical. Keeping in mind growing over time bleeding, cancer, and mortality risks associated with chronic prasugrel use, small observational studies should be judged with skepticism as hypothesis-generating, pending confirmation in randomised trials.
Feature Selection in Simple Neurons: How Coding Depends on Spiking Dynamics
Authors: Famulare Michael , Fairhall Adrienne
Published: November 2009

The relationship between a neuron's complex inputs and its spiking output defines the neuron's coding strategy. This is frequently and effectively modeled phenomenologically by one or more linear filters that extract the components of the stimulus that are relevant for triggering spikes and a nonlinear function that relates stimulus to firing probability. In many sensory systems, these two components of the coding strategy are found to adapt to changes in the statistics of the inputs in such a way as to improve information transmission. Here, we show for two simple neuron models how feature selectivity as captured by the spike-triggered average depends on both the parameters of the model and the statistical characteristics of the input.
A Moving Bump in a Continuous Manifold: A Comprehensive Study of the Tracking Dynamics of Continuous Attractor Neural Networks
Authors: Fung C. C. Alan , Wong K. Y. Michael , Wu Si
Published: November 2009

Understanding how the dynamics of a neural network is shaped by the network structure and, consequently, how the network structure facilitates the functions implemented by the neural system is at the core of using mathematical models to elucidate brain functions. This study investigates the tracking dynamics of continuous attractor neural networks (CANNs). Due to the translational invariance of neuronal recurrent interactions, CANNs can hold a continuous family of stationary states. They form a continuous manifold in which the neural system is neutrally stable. We systematically explore how this property facilitates the tracking performance of a CANN, which is believed to have clear correspondence with brain functions. By using the wave functions of the quantum harmonic oscillator as the basis, we demonstrate how the dynamics of a CANN is decomposed into different motion modes, corresponding to distortions in the amplitude, position, width, or skewness of the network state. We then develop a perturbation approach that utilizes the dominating movement of the network's stationary states in the state space. This method allows us to approximate the network dynamics up to an arbitrary accuracy depending on the order of perturbation used. We quantify the distortions of a gaussian bump during tracking and study their effects on tracking performance. Results are obtained on the maximum speed for a moving stimulus to be trackable and the reaction time for the network to catch up with an abrupt change in the stimulus.
Convolutional Networks Can Learn to Generate Affinity Graphs for Image Segmentation
Authors: Turaga Srinivas C. , Murray Joseph F. , Jain Viren , Roth Fabian , Helmstaedter Moritz , Briggman Kevin , Denk Winfried , Seung H. Sebastian
Published: November 2009

Many image segmentation algorithms first generate an affinity graph and then partition it. We present a machine learning approach to computing an affinity graph using a convolutional network (CN) trained using ground truth provided by human experts. The CN affinity graph can be paired with any standard partitioning algorithm and improves segmentation accuracy significantly compared to standard hand-designed affinity functions.

We apply our algorithm to the challenging 3D segmentation problem of reconstructing neuronal processes from volumetric electron microscopy (EM) and show that we are able to learn a good affinity graph directly from the raw EM images. Further, we show that our affinity graph improves the segmentation accuracy of both simple and sophisticated graph partitioning algorithms.

In contrast to previous work, we do not rely on prior knowledge in the form of hand-designed image features or image preprocessing. Thus, we expect our algorithm to generalize effectively to arbitrary image types.
Spiking Neural Networks for Cortical Neuronal Spike Train Decoding
Authors: Fang Huijuan , Wang Yongji , He Jiping
Published: November 2009

Recent investigation of cortical coding and computation indicates that temporal coding is probably a more biologically plausible scheme used by neurons than the rate coding used commonly in most published work. We propose and demonstrate in this letter that spiking neural networks (SNN), consisting of spiking neurons that propagate information by the timing of spikes, are a better alternative to the coding scheme based on spike frequency (histogram) alone. The SNN model analyzes cortical neural spike trains directly without losing temporal information for generating more reliable motor command for cortically controlled prosthetics. In this letter, we compared the temporal pattern classification result from the SNN approach with results generated from firing-rate-based approaches: conventional artificial neural networks, support vector machines, and linear regression. The results show that the SNN algorithm can achieve higher classification accuracy and identify the spiking activity related to movement control earlier than the other methods. Both are desirable characteristics for fast neural information processing and reliable control command pattern recognition for neuroprosthetic applications.
A Simulation Study Investigating the Impact of Dendritic Morphology and Synaptic Topology on Neuronal Firing Patterns
Authors: Chen Jen-Yung
Published: November 2009

In the brain, complex information interactions among neurons span several spatial and temporal scales, making it extremely difficult to identify the principles governing neural information processing. In this study, we used computational models to investigate the impact of dendritic morphology and synaptic topology on patterns of neuronal firing. We first constructed Hodgkin-Huxley-type neuron models that possessed dendrites with different morphological features. We then simulated the responses of these neurons to a number of spatiotemporal input patterns. The similarity between neuronal responses to different patterned inputs was effectively evaluated by a novel combination of metric space analysis and multidimensional scaling analyses. The results showed that neurons with different morphological or anatomical features exhibit differences in stimulus-specific temporal encoding and firing reliability. These findings support the idea that in addition to biophysical membrane properties, the dendritic morphology and the synaptic topology of a neuron can play a significant role in neuronal information processing and may directly contribute to various brain functions.