bluuebunny/crossref_metadata_2025_split huggingface dataset:
Functional analysis of the Zygosaccharomyces rouxii Fps1p homologue
Authors: Tang Xue‐Ming , Kayingo Gerald , Prior Bernard A. 
Published: June 2005

AbstractThe osmotolerant yeast Zygosaccharomyces rouxii accumulates the polyols glycerol and D‐arabitol intracellularly in response to hyperosmotic stress, but the membrane transport proteins regulating polyol accumulation have not been studied. We have cloned and characterized a FPS1 homologue in Z. rouxii NRRL Y2547, and its sequence revealed a 2709 bp open reading frame encoding a peptide of 692 deduced amino acids with 56.9% identity to the Saccharomyces cerevisiae Fps1p. The role of this putative membrane channel protein in polyol accumulation and release during osmoregulation was investigated. The Z. rouxii FPS1 (ZrFPS1) complemented the S. cerevisiae fps1Δ growth defect and glycerol release upon hypo‐osmotic shock. Deletion of ZrFPS1 did not affect growth on glycerol as sole carbon source, suggesting that other transport proteins are involved in the uptake of glycerol. However, mutants lacking ZrFPS1 exhibited a significant decrease in glycerol and D‐arabitol efflux and poor growth during hypo‐osmotic conditions, suggesting that ZrFPS1 might be involved in D‐arabitol transport in addition to glycerol. This is the first demonstration of a yeast gene that affects D‐arabitol transport. The full‐length ZrFPS1 gene sequence including upstream promoter has been deposited in the public database under Accession No. AY488133. Copyright © 2005 John Wiley & Sons, Ltd.
New drug‐resistant cassettes for gene disruption and epitope tagging in Schizosaccharomyces pombe
Authors: Sato Masamitsu , Dhut Susheela , Toda Takashi 
Published: June 2005

AbstractWe describe new heterologous modules for PCR‐based gene targeting in the fission yeast Schizosaccharomyces pombe. Two bacterial genes, hph and nat, which display dominant drug‐resistance phenotypes, are used as new selectable markers in these modules. Both genes have been used successfully in the budding yeast Saccharomyces cerevisiae, in which hph confers resistance to hygromycin B, while nat confers nourseothricin resistance (Goldstein and McCusker, 1999). Vector modules for gene disruption and C‐terminal tagging with 3HA, 13Myc and GFP(S65T) are constructed using previously constructed pFA6a–MX6–derived plasmids (Bähler et al., 1998; Wach et al., 1997). In combination with the existing systems that are based upon the G418‐resistance gene (kan), triple gene deletions or tags could be constructed. In addition a vector for one‐step integration of a monomeric RFP (mRFP) to the C‐terminus of proteins of interest is developed. Finally, oligonucleotides that allow a simple marker switch from kan to hph or nat, and vice versa, are described. The new constructs developed here should facilitate post‐genomic molecular analysis of protein functions in fission yeast. Copyright © 2005 John Wiley & Sons, Ltd.
Multiple solutions of stick and separation type in the Signorini model with Coulomb friction
Authors: Hild P. 
Published: June 2005

AbstractThis paper proves the existence of multiple solutions to the Coulomb friction problem with Signorini contact conditions in continuum linear elasticity. We consider a body lying on a rigid foundation and we propose a method in order to exhibit two solutions to the frictional contact problem when the friction coefficient is large enough: one solution which separates from the foundation and another one which remains stuck on the foundation. We apply the method to the simple class of problems with triangular bodies and linear displacement fields and we describe the cases in which such multiple solutions exist. Denoting by μ the friction coefficient, we come to the conclusion that such nonuniqueness cases may appear when μ>1.
The conjugate gradient algorithm applied to quaternion valued matrices
Authors: Opfer G. 
Published: June 2005

AbstractQuaternions are a tool used to describe motions of rigid bodies in ℝ3, (Kuipers, [15]). An interesting application is the topic of moving surfaces (Traversoni, [21]), where quaternion interpolation is used which requires solving equations with quaternion coefficients. In this paper we investigate the well known conjugate gradient algorithm (cg‐algorithm) introduced by Hestenes and Stiefel [10] applied to quaternion valued, hermitean, positive definite matrices. We shall show, that the features known from the real case are still valid in the quaternion case. These features are: error propagation, early stopping, cg‐algorithm as iterative process with error estimates, applicability to indefinite matrices. We have to present some basic facts about quaternions and about matrices with quaternion entries, in particular, about eigenvalues of such matrices. We also present some numerical examples of quaternion systems solved by the cg‐algorithm.
Experimental validation of simulated plate deformations caused by shock waves
Authors: Stoffel M. 
Published: June 2005

AbstractIn the present paper measured and simulated vibrations of viscoplastic plates under impulsive loading are compared to each other. The aim is to determine how accurately the measured deformations can be calculated by the chosen constitutive and structural theories. A first‐order shear deformation shell theory assuming small strains and moderate rotations and viscoplastic laws are applied. In the experimental part of this study short time measurement techniques are applied to shock tubes in order to record fast loading processes and plate deformations.
A geometric treatment of Jellett's egg
Authors: Bou‐Rabee N.M. , Marsden J.E. , Romero L.A. 
Published: June 2005

AbstractThis paper explains and gives a global analysis of the “rising egg” phenomenon. The main tools that are used in this analysis are derived from the theory of dissipation‐induced instabilities, adiabatic invariants, and LaSalle's invariance principle. The analysis is done within the framework of a specific model of the egg as a prolate spheroid, with its equations of motion derived from Newtonian mechanics. The paper begins by considering the linear and nonlinear stability of the non‐risen and risen states of the spheroid corresponding to the initial and final state of the rising egg phenomenon. The asymptotic state of the spheroid is determined by an adiabatic momentum invariant. Because the symmetry associated with this adiabatic invariant coincides with the symmetry associated with the Jellett invariant in the tippe top, we call this quantity the Jellett momentum map. Linear theory shows that the spectral stability of the non‐risen state is determined by a cubic polynomial. The spectral stability of the risen state is governed by the modified Maxwell‐Bloch equations – a normal form that appears in the problem of tippe top inversion and that was studied previously by the authors. A generalization of the energy‐momentum method that includes adiabatic momentum invariants provides explicit criteria for the existence of an orbit connecting these states. In particular, it is shown that if the risen state is stable, the spheroid rises all the way.
Microarchitectured cellular solids – the hunt for statically determinate periodic trusses
Authors: Hutchinson R.G. , Fleck N.A. 
Published: June 2005

AbstractThe mechanical properties of open‐cell metallic foams and periodic lattice materials are explained by a structural analysis of their parent pin‐jointed truss structures. A matrix method of analysis is presented in order to elucidate whether a periodic truss structure can collapse by macroscopic strain producing mechanisms, or by periodic collapse mechanisms which induce zero macroscopic strain to first order. It is shown that the planar Kagome truss is of the latter type, and is consequently stiff. The in‐plane stiffness of the 2D Kagome grid and the bending stiffness of the 3D Kagome double‐layer grid (KDLG) are determined for elastic members. An alternative, statically determinate, double‐layer grid is derived from the octet truss, and is referred to as the modified octet truss (MOT). This structure has faces comprising a hexagonal grid and a semi‐regular triangular grid, and is much less stiff than the Kagome double‐layer grid. Both structures have morphing capability due to their static and kinematic determinacy.
Reproduction strategy in an island population of yellow‐necked mice
Authors: Bujalska Gabriela , Grüm Leszek 
Published: June 2005

AbstractA population of yellow‐necked mice, Apodemus flavicollis, inhabiting Crabapple Island (NE Poland) was sampled from 1994–2002. The catch‐mark‐release method was applied. Sexually mature males and females (including pregnant ones) as well as immatures of each sex were identified. During the study period 3,036 mice were caught 10,672 times. The number of mice caught varied from 6 individuals (April 1999) to 272 (July 1996). The number of both mature females and mature males increased linearly with population size. Differences in the reproductive strategies of yellow‐necked mouse and bank voles, Clethrionomys glareolus, are discussed. The respective strategies led to high variability in the population size of mice and much less variability in the case of the voles during the breeding season.
Biosynthesis of agmatine in isolated mitochondria and perfused rat liver: studies with 15N-labelled arginine
Authors: HORYN Oksana , LUHOVYY Bohdan , LAZAROW Adam , DAIKHIN Yevgeny , NISSIM Ilana , YUDKOFF Marc , NISSIM Itzhak 
Published: June 2005

An important but unresolved question is whether mammalian mitochondria metabolize arginine to agmatine by the ADC (arginine decarboxylase) reaction. 15N-labelled arginine was used as a precursor to address this question and to determine the flux through the ADC reaction in isolated mitochondria obtained from rat liver. In addition, liver perfusion system was used to examine a possible action of insulin, glucagon or cAMP on a flux through the ADC reaction. In mitochondria and liver perfusion, 15N-labelled agmatine was generated from external 15N-labelled arginine. The production of 15N-labelled agmatine was time- and dose-dependent. The time-course of [U-15N4]agmatine formation from 2 mM [U-15N4]arginine was best fitted to a one-phase exponential curve with a production rate of approx. 29 pmol·min−1·(mg of protein)−1. Experiments with an increasing concentration (0– 40 mM) of [guanidino-15N2]arginine showed a Michaelis constant Km for arginine of 46 mM and a Vmax of 3.7 nmol·min−1·(mg of protein)−1 for flux through the ADC reaction. Experiments with broken mitochondria showed little changes in Vmax or Km values, suggesting that mitochondrial arginine uptake had little effect on the observed Vmax or Km values. Experiments with liver perfusion demonstrated that over 95% of the effluent agmatine was derived from perfusate [guanidino-15N2]arginine regardless of the experimental condition. However, the output of 15N-labelled agmatine (nmol·min−1·g−1) increased by approx. 2-fold (P&lt;0.05) in perfusions with cAMP. The findings of the present study provide compelling evidence that mitochondrial ADC is present in the rat liver, and suggest that cAMP may stimulate flux through this pathway.
Nop53p is a novel nucleolar 60S ribosomal subunit biogenesis protein
Authors: SYDORSKYY Yaroslav , DILWORTH David J. , HALLORAN Brendan , YI Eugene C. , MAKHNEVYCH Taras , WOZNIAK Richard W. , AITCHISON John D. 
Published: June 2005

Ribosome biogenesis in Saccharomyces cerevisiae occurs primarily in a specialized nuclear compartment termed the nucleolus within which the rRNA genes are transcribed by RNA polymerase I into a large 35 S rRNA precursor. The ensuing association/dissociation and catalytic activity of numerous trans-acting protein factors, RNAs and ribosomal proteins ultimately leads to the maturation of the precursor rRNAs into 25, 5.8 and 18 S rRNAs and the formation of mature cytoplasmic 40 and 60 S ribosomal subunits. Although many components involved in ribosome biogenesis have been identified, our understanding of this essential cellular process remains limited. In the present study we demonstrate a crucial role for the previously uncharacterized nucleolar protein Nop53p (Ypl146p) in ribosome biogenesis. Specifically, Nop53p appears to be most important for biogenesis of the 60 S subunit. It physically interacts with rRNA processing factors, notably Cbf5p and Nop2p, and co-fractionates specifically with pre-60 S particles on sucrose gradients. Deletion or mutations within NOP53 cause significant growth defects and display significant 60 S subunit deficiencies, an imbalance in the 40 S:60 S ratio, as revealed by polysome profiling, and defects in progression beyond the 27 S stage of 25 S rRNA maturation during 60 S biogenesis.
A new type of scorpion Na+-channel-toxin-like polypeptide active on K+ channels
Authors: SRAIRI-ABID Najet , GUIJARRO Joseba Iñaki , BENKHALIFA Rym , MANTEGAZZA Massimo , CHEIKH Amani , BEN AISSA Manel , HAUMONT Pierre-Yves , DELEPIERRE Muriel , EL AYEB Mohamed 
Published: June 2005

We have purified and characterized two peptides, named KAaH1 and KAaH2 (AaH polypeptides 1 and 2 active on K+ channels, where AaH stands for Androctonus australis Hector), from the venom of A. australis Hector scorpions. Their sequences contain 58 amino acids including six half-cysteines and differ only at positions 26 (Phe/Ser) and 29 (Lys/Gln). Although KAaH1 and KAaH2 show important sequence similarity with anti-mammal β toxins specific for voltage-gated Na+ channels, only weak β-like effects were observed when KAaH1 or KAaH2 (1 μM) were tested on brain Nav1.2 channels. In contrast, KAaH1 blocks Kv1.1 and Kv1.3 channels expressed in Xenopus oocytes with IC50 values of 5 and 50 nM respectively, whereas KAaH2 blocks only 20% of the current on Kv1.1 and is not active on Kv1.3 channels at a 100 nM concentration. KAaH1 is thus the first member of a new subfamily of long-chain toxins mainly active on voltage-gated K+ channels. NMR spectra of KAaH1 and KAaH2 show good dispersion of signals but broad lines and poor quality. Self-diffusion NMR experiments indicate that lines are broadened due to a conformational exchange on the millisecond time scale. NMR and CD indicate that both polypeptides adopt a similar fold with α-helical and β-sheet structures. Homology-based molecular models generated for KAaH1 and KAaH2 are in accordance with CD and NMR data. In the model of KAaH1, the functionally important residues Phe26 and Lys29 are close to each other and are located in the α-helix. These residues may constitute the so-called functional dyad observed for short α-KTx scorpion toxins in the β-sheet.
C/EBPα activates the transcription of triacylglycerol hydrolase in 3T3-L1 adipocytes
Authors: WEI Enhui , LEHNER Richard , VANCE Dennis E. 
Published: June 2005

TGH (triacylglycerol hydrolase) catalyses the lipolysis of intracellular stored triacylglycerol. To explore the mechanisms that regulate TGH expression in adipose tissue, we studied the expression of TGH during the differentiation of 3T3-L1 adipocytes. TGH mRNA and protein levels increased dramatically in 3T3-L1 adipocytes compared with pre-adipocytes. Electrophoretic mobility shift assays demonstrated enhanced binding of nuclear proteins of adipocytes to the distal murine TGH promoter region (−542/−371 bp), yielding one adipocyte-specific migrating complex. Competitive and supershift assays demonstrated that the distal TGH promoter fragment bound C/EBPα (CCAAT/enhancer-binding protein α). Transient transfections of different mutant TGH promoter–luciferase constructs into 3T3-L1 adipocytes and competitive electromobility shift assays showed that the C/EBP-binding elements at positions −470/−459 bp and −404/−390 bp are important for transcriptional activation. Co-transfection with C/EBPα cDNA and TGH promoter constructs in 3T3-L1 pre-adipocytes demonstrated that C/EBPα increased TGH promoter activity. Ectopic expression of C/EBPα in NIH 3T3 cells activated TGH mRNA expression without causing differentiation into adipocytes. These experiments directly link increased TGH expression in adipocytes to transcriptional regulation by C/EBPα. This is the first evidence that C/EBPα participates directly in the regulation of an enzyme associated with lipolysis.
YB-1 represses AP1-dependent gene transactivation and interacts with an AP-1 DNA sequence
Authors: SAMUEL Shaija , TWIZERE Jean-Claude , BERNSTEIN Lori R. 
Published: June 2005

Involvement of the AP-1 (activator protein-1) transcription factor has been demonstrated previously in the regulation of cell proliferation and cell-cycle progression, in the control of cell migration, invasion and metastasis, and in signal transduction, stress responsiveness, DNA replication and DNA repair. YB-1 (Y-box-binding protein-1) has also been implicated in many of these processes. However, the mechanism by which YB-1 mediates these processes is poorly understood. In the present study, we report that overexpression of a transfected gene encoding YB-1 in human HeLa cervical carcinoma cells significantly represses the transactivation of a minimal AP-1 reporter construct in response to the tumour promoter PMA. YB-1 also represses mRNA expression and PMA-induced promoter transactivation of the endogenous AP-1 target gene encoding matrix metalloproteinase-12 (metalloelastase). YB-1 transrepression of both the minimal and matrix metalloproteinase-12 promoter reporter constructs is dependent on the AP-1 sequence. To identify new nuclear proteins that bind specifically to the AP-1 DNA-binding site, we devised a DNA-affinity-chromatography-based assay termed NAPSTER (nucleotide-affinity preincubation specificity test of recognition) and discovered a 49 kDa protein from human cancer cells that binds in a sequence-specific manner to the AP-1 DNA sequence. By tandem MS fragmentation sequencing analyses we determined that p49 is a YB-1. Immunoblotting of the NAPSTER-purified p49 protein using anti-YB-1 antibodies confirmed YB-1 binding to the AP-1 DNA sequence, as did gel mobility-supershift assays using YB-1 antibodies. This is the first report of YB-1 transrepression and interaction at the AP-1 DNA-binding site.
Glucosamine induces cell-cycle arrest and hypertrophy of mesangial cells: implication of gangliosides
Authors: MASSON Elodie , WIERNSPERGER Nicolas , LAGARDE Michel , BAWAB Samer El 
Published: June 2005

Alterations in proliferation and hypertrophy of renal mesangial cells are typical features of diabetic nephropathy. The HP (hexosamine pathway) has been proposed as a biochemical hypothesis to explain microvascular alterations due to diabetic nephropathy; however, involvement of HP in the regulation of mesangial cell growth or hypertrophy has been poorly studied. Although gangliosides are known to regulate cell proliferation, their potential role in mesangial cell-growth perturbations has hardly been explored. In the present study, we investigated the effects of the HP activation, mimicked by GlcN (glucosamine) treatment, on mesangial cell growth and hypertrophy and the potential implication of gangliosides in these processes. Our results indicate that GlcN induced hypertrophy of mesangial cells, as measured by an increase in the protein/cell ratio, and it caused cell-cycle arrest by an increase in the expression of cyclin-dependent kinase inhibitor p21Waf1/Cip1. Furthermore, GlcN treatment resulted in a massive increase in the levels of gangliosides GM2 and GM1. Treatment of cells with exogenous GM2 and GM1 reproduced the effects of 0.5 mM GlcN on p21Waf1/Cip1 expression, cell-cycle arrest and hypertrophy, suggesting that gangliosides GM2 and GM1 are probably involved in mediating GlcN effects. These results document a new role of the HP in the regulation of mesangial cell growth and hypertrophy. They also suggest a potential new mechanism of action of the HP through modulation of ganglioside levels.
Interaction of U-box E3 ligase SNEV with PSMB4, the β7 subunit of the 20 S proteasome
Authors: LÖSCHER Marlies , FORTSCHEGGER Klaus , RITTER Gustav , WOSTRY Martina , VOGLAUER Regina , SCHMID Johannes A. , WATTERS Steven , RIVETT A. Jennifer , AJUH Paul , LAMOND Angus I. , KATINGER Hermann , GRILLARI Johannes 
Published: June 2005

Recognition of specific substrates for degradation by the ubiquitin–proteasome pathway is ensured by a cascade of ubiquitin transferases E1, E2 and E3. The mechanism by which the target proteins are transported to the proteasome is not clear, but two yeast E3s and one mammalian E3 ligase seem to be involved in the delivery of targets to the proteasome, by escorting them and by binding to the 19 S regulatory particle of the proteasome. In the present study, we show that SNEV (senescence evasion factor), a protein with in vitro E3 ligase activity, which is also involved in DNA repair and splicing, associates with the proteasome by directly binding to the β7 subunit of the 20 S proteasome. Upon inhibition of proteasome activity, SNEV does not accumulate within the cells although its co-localization with the proteasome increases significantly. Since immunofluorescence microscopy also shows increased co-localization of SNEV with ubiquitin after proteasome inhibition, without SNEV being ubiquitinated by itself, we suggest that SNEV shows E3 ligase activity not only in vitro but also in vivo and escorts its substrate to the proteasome. Since the yeast homologue of SNEV, Prp19, also interacts with the yeast β7 subunit of the proteasome, this mechanism seems to be conserved during evolution. Therefore these results support the hypothesis that E3 ligases might generally be involved in substrate transport to the proteasome. Additionally, our results provide the first evidence for a physical link between components of the ubiquitin–proteasome system and the spliceosome.
Mechanism of feedback regulation of insulin receptor substrate-1 phosphorylation in primary adipocytes
Authors: HERS Ingeborg , TAVARÉ Jeremy M. 
Published: June 2005

Serine and threonine phosphorylation of IRS-1 (insulin receptor substrate-1) has been reported to decrease its ability to be tyrosine-phosphorylated by the insulin receptor. Insulin itself may negatively regulate tyrosine phosphorylation of IRS-1 through a PI3K (phosphoinositide 3-kinase)-dependent feedback pathway. In the present study, we examined the regulation and role of IRS-1 serine phosphorylation in the modulation of IRS-1 tyrosine phosphorylation in physiologically relevant cells, namely freshly isolated primary adipocytes. We show that insulin-stimulated phosphorylation of Ser312 and Ser616 in IRS-1 was relatively slow, with maximal phosphorylation achieved after 20 and 5 min respectively. The effect of insulin on phosphorylation of both these sites required the activation of PI3K and the MAPKs (mitogen-activated protein kinases) ERK1/2 (extracellular-signal-regulated kinase 1 and 2), but not the activation of mTOR (mammalian target of rapamycin)/p70S6 kinase, JNK (c-Jun N-terminal kinase) or p38MAPK. Although inhibition of PI3K and ERK1/2 both substantially decreased insulin-stimulated phosphorylation of Ser312 and Ser616, only wortmannin enhanced insulin-stimulated tyrosine phosphorylation of IRS-1. Furthermore, inhibition of mTOR/p70S6 kinase, JNK or p38MAPK had no effect on insulin-stimulated IRS-1 tyrosine phosphorylation. The differential effect of inhibition of ERK1/2 on insulin-stimulated IRS-1 phosphorylation of Ser312/Ser616 and tyrosine indicates that these events are independent of each other and that phosphorylation of Ser312/Ser616 is not responsible for the negative regulation of IRS-1 tyrosine phosphorylation mediated by PI3K in primary adipocytes.