bluuebunny/crossref_metadata_2025 huggingface dataset:
MODELING PRODUCTION OF SOME HIGH-MASS SECONDARIES IN HEAVY-ION COLLISIONS
Authors: DE BHASKAR , BHATTACHARYYA S.
Published: May 2004

In the light of a newly proposed phenomenological model offered by the combinational approach, we attempt to interpret with a modest degree of success the measured data on production of the pT-spectra of the lambda (Λ) baryons and phi (Φ) mesons in some heavy-ion collisions. The choices of the specific varieties for the present study are influenced by the two factors: (i) availability of data in [Formula: see text] reactions at some high energies and also in a few heavy-ion collisions at several energies; and (ii) the status and importance of the specific particle(s) from various physical considerations.
MICROSCOPIC STUDY OF BACKBENDING PHENOMENA IN 126-132Ce
Authors: DEVI RANI , BHAT R. K. , KHOSA S. K.
Published: May 2004

126-132 Ce isotopes, which exhibit enhanced collective behavior and occurrence of first backbend around 10+, are studied in the Variation after Projection (VAP) and Cranked Hartree–Bogoliubov (CHB) frameworks. The pairing plus-quadrupole-quadrupole (PQQ) interaction is employed as an effective interaction. The yrast spectra, B(E2) transition probabilities and variation of moment of inertia versus cranking frequency are studied. Our results show that the backbending arises as a result of the sudden alignment of a pair of protons in the h11/2 subshell.
STRONG ABSORPTION MODEL STUDIES OF PION-NUCLEUS SCATTERING AROUND THE Δ RESONANCE
Authors: SARKER DIPIKA RANI , BEGUM L. , RAHMAN MD. A. , SEN GUPTA H. M.
Published: May 2004

Angular distribution data on the elastic scattering of pions are studied on several nuclei around the Δ resonance in terms of the three-parameter strong absorption model of Frahn and Venter. The parameters thus obtained are used in the analyses of inelastic scattering of pions leading to the lowest as well as higher lying 2+ and 3- states, and the corresponding deformation parameters are extracted.
THE MOVING FRICTION CONE APPROACH FOR THREE-DIMENSIONAL CONTACT SIMULATIONS
Authors: WRIGGERS PETER , KRSTULOVIĆ-OPARA LOVRE
Published: June 2004

A finite element contact approach based on the Moving Friction Cone (MFC) formulation is presented herein. The formulation is based on the contact constraint described using a single gap vector. Such a simplification, in comparison with the standard approach where normal and tangential gap vectors are used, results in significantly simpler, shorter and faster element code. The associated penalty is formulated to include large deformations and displacements. Within this approach a triangular contact element is developed using a high abstract mathematical level of symbolic description. Using this technique, a consistent linearization is obtained which leads to quadratic rates of convergence. Furthermore, the new technique results in algorithmic robustness, fast evaluation time, as well as a compact element code.
DEBONDING IN COMPOSITE MICROSTRUCTURES WITH MORPHOLOGICAL VARIATIONS
Authors: LI SHANHU , GHOSH SOMNATH
Published: June 2004

This paper describes the development of the Voronoi cell finite element model (VCFEM) with interfacial decohesion for simulating debonding induced microstructural damage in fiber reinforced composites. Normal and tangential cohesive zone models at the matrix-fiber interface are used to describe the onset and growth of damage along the inclusion-matrix interface. It is shown that the initiation and especially the propagation of debonding depends not only on the total cohesive energy, but also on the shape of the traction-displacement curve. The model is used to study the influence of various local morphological parameters on damage evolution by interfacial debonding. A special function of various geometric parameters is developed to predict the location of debonding in microstructures with varying morphology. Various numerical examples are solved to establish the effectiveness of the model.
FRACTURE MECHANICS ANALYSIS OF MULTI-LAYER PLAIN WEAVE FABRIC LAMINATES WITH TRANSVERSE CRACKS AT CRYOGENIC TEMPERATURES
Authors: TAKEDA TOMO , SHINDO YASUHIDE , NARITA FUMIO
Published: June 2004

This paper presents the stress intensity factors for internal and edge cracks in multi-layer glass/epoxy plain weave fabric laminates subjected to uniaxial tension load at cryogenic temperatures. Cracks are considered to have occurred in the transverse fiber bundles. Finite element analysis of the limiting case when the cracks extend to the interfaces between two fiber bundles is carried out. Special singular elements containing the exact stress singularity are used to model the singular stress field near the crack tip. Numerical results for the stress intensity factor at cryogenic temperatures are displayed graphically and discussed in detail.
EFFECT OF FRACTURE CRITERIA ON HIGH VELOCITY PERFORATION OF THIN BEAMS
Authors: TENG XIAOQING , WIERZBICKI TOMASZ
Published: June 2004

An adequate ductile fracture locus has to be developed to reasonably model crack initiation and propagation in high velocity impact. Most of the fracture loci in the literature were proposed on the basis of tensile tests while in high velocity impact cracks usually occur in the region where shear and compression are dominant. In this paper, perforation response of a thin beam struck by a rigid, blunt projectile moving at a high velocity is simulated using, respectively, uniform fracture strain, Johnson-Cook's, and Bao-Wierzbicki's fracture locus for 2024-T351 aluminum alloy. The former two predict that materials in the impacted area of the beam beneath the rigid mass fail layer by layer, which is not consistent with experimental observations. By contrary, Bao-Wierzbicki's fracture locus, which was developed from up-setting, shear and tensile tests, and covers the whole range of the stress triaxiality, is capable of capturing all of the features occurring in the whole failure process. Numerical results reveal that the beam would fail by shear plugging at a high impact velocity and by tensile tearing at a velocity near the ballistic limit.
EFFICIENT COMPUTATION OF MAGNETO-HYDRODYNAMIC PHENOMENA IN ASTROPHYSICS BY CCUP-MOCCT METHOD
Authors: OGATA YOUICHI , YABE TAKASHI , SHIBATA KAZUNARI , KUDOH TAKAHIRO
Published: June 2004

We proved that the CIP (Constrained Interpolation Profile/Cubic Interpolated Pseudoparticle)-MOCCT (Method of Characteristics/Constrained Transport) is capable of treating MHD phenomena using a mesh several times coarser than the conventional schemes. Comparing the present method with the modified Lax-Wendroff methods in the Parker instability in two and three dimensions, the superiority of the CIP scheme has been demonstrated from its low numerical phase error and damping rate. In addition, we employ the CIP-CUP (CIP-combined unified procedure/CCUP) method that solves the Poisson equation for pressure in order to make the present scheme more stable. This method is able to treat the pressure scale height having just one grid, which is five times coarser than the conventional scheme, as well as the magnetic reconnection, which has been described with a coarse grid.
MULTISCALE NUMERICAL METHODS FOR SINGULARLY PERTURBED CONVECTION-DIFFUSION EQUATIONS
Authors: PARK PETER J. , HOU THOMAS Y.
Published: June 2004

We present an efficient and robust approach in the finite element framework for numerical solutions that exhibit multiscale behavior, with applications to singularly perturbed convection-diffusion problems. The first type of equation we study is the convection-dominated convection-diffusion equation, with periodic or random coefficients; the second type of equation is an elliptic equation with singularities due to discontinuous coefficients and non-smooth boundaries. In both cases, standard methods for purely hyperbolic or elliptic problems perform poorly due to sharp boundary and internal layers in the solution.

We propose a framework in which the finite element basis functions are designed to capture the local small-scale behavior correctly. When the structure of the layers can be determined locally, we apply the multiscale finite element method, in which we solve the corresponding homogeneous equation on each element to capture the small scale features of the differential operator. We demonstrate the effectiveness of this method by computing the enhanced diffusivity scaling for a passive scalar in the cellular flow. We also carry out the asymptotic error analysis for its convergence rate and perform numerical experiments for verification. For a random flow with nonlocal layer structure, we use a variational principle to gain additional information in our attempt to design asymptotic basis functions. We also apply the same framework for elliptic equations with discontinuous coefficients or non-smooth boundaries. In that case, we construct local basis function near singularities using infinite element method in order to resolve extreme singularity. Numerical results on problems with various singularities confirm the efficiency and accuracy of this approach.
GENERALIZED FINITE ELEMENT METHODS — MAIN IDEAS, RESULTS AND PERSPECTIVE
Authors: BABUŠKA IVO , BANERJEE UDAY , OSBORN JOHN E.
Published: June 2004

This paper is an overview of the main ideas of the Generalized Finite Element Method (GFEM). We present the basic results, experiences with, and potentials of this method. GFEM is a generalization of the classical Finite Element Method — in its h, p, and h-p versions — as well as of the various forms of meshless methods used in engineering.
SINGULAR ENRICHMENT FINITE ELEMENT METHOD FOR ELASTODYNAMIC CRACK PROPAGATION
Authors: BELYTSCHKO TED , CHEN HAO
Published: June 2004

An enrichment technique for accurately modeling two dimensional crack propagation within the framework of the finite element method is presented. The technique uses an enriched basis that spans the asymptotic dynamic crack-tip solution. The enrichment functions and their spatial derivatives are able to exactly reproduce the asymptotic displacement field and strain field for a moving crack. The stress intensity factors for Mode I and Mode II are taken as additional degrees of freedom. An explicit time integration scheme is used to solve the resulting discrete equations. Numerical simulations of linear elastodynamic problems are reported to demonstrate the accuracy and potential of the technique.
Hydroxyl radical activation of a Ca2+-sensitive nonselective cation channel involved in epithelial cell necrosis
Authors: Simon Felipe , Varela Diego , Eguiguren Ana Luisa , Díaz Laín F. , Sala Francisco , Stutzin Andrés
Published: June 2004

In a previous work the involvement of a fenamate-sensitive Ca2+-activated nonselective cation channel (NSCC) in free radical-induced rat liver cell necrosis was demonstrated ( 5 ). Therefore, we studied the effect of radical oxygen species and oxidizing agents on the gating behavior of a NSCC in a liver-derived epithelial cell line (HTC). Single-channel currents were recorded in HTC cells by the excised inside-out configuration of the patch-clamp technique. In this cell line, we characterize a 19-pS Ca2+-activated, ATP- and fenamate-sensitive NSCC nearly equally permeable to monovalent cations. In the presence of Fe2+, exposure of the intracellular side of NSCC to H2O2 increased their open probability ( Po) by ∼40% without affecting the unitary conductance. Desferrioxamine as well as the hydroxyl radical (·OH) scavenger MCI-186 inhibited the effect of H2O2, indicating that the increase in Po was mediated by ·OH. Exposure of the patch membrane to the oxidizing agent 5,5′-dithio- bis-2-nitrobenzoic acid (DTNB) had a similar effect to ·OH. The increase in Po induced by ·OH or DTNB was not reverted by preventing formation or by DTNB washout, respectively. However, the reducing agent dithiothreitol completely reversed the effects on Po of both ·OH and DTNB. A similar increase in Po was observed by applying the physiological oxidizing molecule GSSG. Moreover, GSSG-oxidized channels showed enhanced sensitivity to Ca2+. The effect of GSSG was fully reversed by GSH. These results suggest an intracellular site(s) of action of oxidizing agents on cysteine targets on the fenamate-sensitive NSCC protein implicated in epithelial cell necrosis.
CREB trans-activates the murine H+-K+-ATPase α2-subunit gene
Authors: Xu Xiangyang , Zhang Wenzheng , Kone Bruce C.
Published: June 2004

Despite its key role in potassium homeostasis, transcriptional control of the H+-K+-ATPase α2-subunit (HKα2) gene in the collecting duct remains poorly characterized. cAMP increases H+-K+-ATPase activity in the collecting duct, but its role in activating HKα2 transcription has not been explored. Previously, we demonstrated that the proximal 177 bp of the HKα2 promoter confers basal collecting duct-selective expression. This region contains several potential cAMP/Ca2+-responsive elements (CRE). Accordingly, we examined the participation of CRE-binding protein (CREB) in HKα2 transcriptional control in murine inner medullary collecting duct (mIMCD)-3 cells. Forskolin and vasopressin induced HKα2 mRNA levels, and CREB overexpression stimulated the activity of HKα2 promoter-luciferase constructs. Serial deletion analysis revealed that CREB inducibility was retained in a construct containing the proximal 100 bp of the HKα2 promoter. In contrast, expression of a dominant negative inhibitor (A-CREB) resulted in 60% lower HKα2 promoter-luciferase activity, suggesting that constitutive CREB participates in basal HKα2 transcriptional activity. A constitutively active CREB mutant (CREB-VP16) strongly induced HKα2 promoter-luciferase activity, whereas overexpression of CREBdLZ-VP16, which lacks the CREB DNA-binding domain, abolished this activation. In vitro DNase I footprinting and gel shift/supershift analysis of the proximal promoter with recombinant glutathione S-transferase (GST)-CREB-1 and mIMCD-3 cell nuclear extracts revealed sequence-specific DNA-CREB-1 complexes at −86/−60. Mutation at three CRE-like sequences within this region abolished CREB-1 DNA-binding activity and abrogated CREB-VP16 trans-activation of the HKα2 promoter. In contrast, mutation of the neighboring −104/−94 κβ element did not alter CREB-VP16 trans-activation of the HKα2 promoter. Thus CREB-1, binding to one or more CRE-like elements in the −86/−60 region, trans-activates the HKα2 gene and may represent an important link between rapid and delayed effects of cAMP on HKα2 activity.
Imaging endoplasmic reticulum calcium with a fluorescent biosensor in transgenic mice
Authors: Hara Manami , Bindokas Vytautas , Lopez James P. , Kaihara Kelly , Landa Luis R. , Harbeck Mark , Roe Michael W.
Published: June 2004

The use of biosynthetic fluorescent sensors is an important new approach for imaging Ca2+ in cells. Genetically encoded indicators based on green fluorescent protein, calmodulin, and fluorescence resonance energy transfer (FRET) have been utilized to measure Ca2+ in nonmammalian transgenic organisms and provide information about the organization and regulation of Ca2+ signaling events in vivo. However, expression of biosynthetic FRET-based Ca2+ indicators in transgenic mammals has proven to be problematic. Here, we report transgenic expression of an endoplasmic reticulum (ER) Ca2+ biosensor in mouse pancreas. We targeted expression of a yellow cameleon3.3er (YC3.3er) transgene with mouse insulin I promoter. YC3.3er protein expression was limited to pancreatic β-cells within islets of Langerhans and absent in the exocrine pancreas and other tissues. Animals developed and matured normally; sensor expression was unaffected by age. Glucose tolerance in transgenic mice was also unaffected, indicating the transgenic biosensor did not impair endocrine pancreas function. ER Ca2+ responses after administration of thapsigargin, carbachol, and glucose were measured in individual β-cells of intact islets using confocal microscopy and confirmed the function of the biosensor. We conclude that controlling transgene transcription with a cell-specific promoter permits transgenic expression of FRET-based Ca2+ sensors in mammals and that this approach will facilitate real-time optical imaging of signal transduction events in living tissues.
A key angiogenic role of monocyte chemoattractant protein-1 in hemangioendothelioma proliferation
Authors: Gordillo Gayle M. , Onat Duygu , Stockinger Michael , Roy Sashwati , Atalay Mustafa , Beck F. Michael , Sen Chandan K.
Published: June 2004

Angiomatous lesions are common in infants and children. Hemangioendotheliomas (HE) represent one type of these lesions. Endothelial cell proliferation and the development of vascular/blood cell-filled spaces are inherent in the growth of HE. Therefore, understanding mechanisms that regulate the proliferation of these lesions should provide key insight into mechanisms regulating angiogenesis. A murine model was used to test the significance of monocyte chemoattractant protein (MCP)-1 in HE proliferation. EOMA cells, a cell line derived from a spontaneously arising murine HE, generate these lesions with 100% efficiency when injected subcutaneously into syngeneic mice. MCP-1 produced by EOMA cells recruit macrophages, which were shown to induce angiogenic behavior in EOMA cells by stimulating transwell migration and inducing sprout formation on type I collagen gels. When EOMA cells were injected into MCP-1−/− mice, only 50% of the mice developed tumors, presumably because the low levels of MCP-1 expressed by the injected EOMA cells were enough to overcome any host deficits of this chemokine. When EOMA cells were coinjected with a neutralizing antibody to MCP-1, tumors failed to develop in any of the treated mice, including syngeneic 129P3, C57Bl/6 (wild type), and MCP-1−/−. These results present the first evidence that MCP-1 is required for HE proliferation and may promote the growth of these lesions by stimulating angiogenic behavior of endothelial cells. This study has produced the first in vivo evidence of a complete response for any neoplasm, specifically a vascular proliferative lesion, to anti-MCP-1 therapy in animals with intact immune systems.
Regional rheological differences in locomoting neutrophils
Authors: Yanai M. , Butler J. P. , Suzuki T. , Sasaki H. , Higuchi H.
Published: June 2004

Intracellular rheology is a useful probe of the mechanisms underlying spontaneous or chemotactic locomotion and transcellular migration of leukocytes. We characterized regional rheological differences between the leading, body, and trailing regions of isolated, adherent, and spontaneously locomoting human neutrophils. We optically trapped intracellular granules and measured their displacement for 500 ms after a 100-nm step change in the trap position. Results were analyzed in terms of simple viscoelasticity and with the use of structural damping (stress relaxation follows a power law in time). Structural damping fit the data better than did viscoelasticity. Regional viscoelastic stiffness and viscosity or structural damping storage and loss moduli were all significantly lower in leading regions than in pooled body and/or trailing regions (the latter were not significantly different). Structural damping showed similar levels of elastic and dissipative stresses in body and/or trailing regions; leading regions were significantly more fluidlike (increased power law exponent). Cytoskeletal disruption with cytochalasin D or nocodazole made body and/or trailing regions ∼50% less elastic and less viscous. Cytochalasin D completely suppressed pseudopodial formation and locomotion; nocodazole had no effect on leading regions. Neither drug changed the dissipation-storage energy ratio. These results differ from those of studies of neutrophils and other cell types probed at the cell membrane via β2-integrin receptors, which suggests a distinct role for the cell cortex or focal adhesion complexes. We conclude that 1) structural damping well describes intracellular rheology, and 2) while not conclusive, the significantly more fluidlike behavior of the leading edge supports the idea that intracellular pressure may be the origin of motive force in neutrophil locomotion.
Signal transduction of betacellulin in growth and migration of vascular smooth muscle cells
Authors: Mifune Mizuo , Ohtsu Haruhiko , Suzuki Hiroyuki , Frank Gerald D. , Inagami Tadashi , Utsunomiya Hirotoshi , Dempsey Peter J. , Eguchi Satoru
Published: June 2004

Epidermal growth factor (EGF) family ligands have been implicated in cardiovascular diseases because of their enhanced expression in vascular lesions and their promoting effects on growth and migration of vascular smooth muscle cells (VSMCs). Betacellulin (BTC), a novel EGF family ligand, has been shown to be expressed in atherosclerotic lesions and to be a potent growth factor of VSMCs. However, the molecular mechanisms downstream of BTC involved in mediating vascular remodeling remain largely unknown. Therefore, the aim of this study was to examine the effects of BTC on signal transduction, growth, and migration in VSMCs. We found that BTC stimulated phosphorylation of EGF receptor (EGFR) at Tyr1068, which was completely blocked by an EGFR kinase inhibitor, AG-1478. BTC also phosphorylated ErbB2 at Tyr877, Tyr1112, and Tyr1248 and induced association of ErbB2 with EGFR, suggesting their heterodimerization in VSMCs. In postreceptor signal transduction, BTC stimulated phosphorylation of extracellular signal-regulated kinase (ERK)1/2, Akt, and p38 mitogen-activated protein kinase (MAPK). Moreover, BTC stimulated proliferation and migration of VSMCs. ERK and Akt inhibitors suppressed migration markedly and proliferation partially, whereas the p38 inhibitor suppressed migration partially but not proliferation. In addition, we found the presence of endogenous BTC in conditioned medium of VSMCs and an increase of BTC on angiotensin II stimulation. In summary, BTC promotes growth and migration of VSMCs through activation of EGFR, ErbB2, and downstream serine/threonine kinases. Together with the expression and processing of endogenous BTC in VSMCs, our results suggest a critical involvement of BTC in vascular remodeling.
FFAs are not involved in regulation of gluconeogenesis and glycogenolysis in adults with uncomplicated P. falciparum malaria
Authors: van Thien Huynh , Weverling G. J. , Ackermans M. T. , canh Hung Nguyen , Endert E. , Kager P. A. , Sauerwein H. P.
Published: May 2004

In normal subjects, elevation of plasma free fatty acid (FFA) levels stimulates gluconeogenesis (GNG) and inhibits glycogenolysis (GLY). In adults with uncomplicated Plasmodium falciparum malaria, GNG is increased and GLY decreased. To test the hypothesis that FFAs are regulators of GNG and GLY in uncomplicated falciparum malaria, we investigated the effect of inhibition of lipolysis by acipimox in 12 patients with uncomplicated falciparum malaria. Six of them were given acipimox, and six served as controls. Also as controls, six matched healthy subjects were studied on two occasions with and without acipimox. After 16 h of fasting, glucose production and GNG were significantly higher in the malaria patients compared with the healthy controls ( P = 0.003 and <0.0001, respectively), whereas GLY was significantly lower ( P < 0.001), together with elevated plasma concentrations of cortisol and glucagon. During the study, glucose production in patients declined over time ( P < 0.0001), without a statistically significant difference between the acipimox-treated and untreated patients. In controls, however, with acipimox the decline was less outspoken compared with nontreated controls ( P = 0.005). GNG was unchanged over time in patients as well as in healthy controls, and no influence of acipimox was found. In patients, GLY declined over time ( P < 0.001), without a difference between acipimox-treated and untreated patients. In contrast, in controls treated with acipimox, no change over time was found, which was statistically different from the decline in untreated controls ( P = 0.002). In conclusion, in falciparum malaria, FFAs are not involved in regulation of glucose production, nor of GNG or GLY.
AMP kinase is not required for the GLUT4 response to exercise and denervation in skeletal muscle
Authors: Holmes Burton F. , Lang David B. , Birnbaum Morris J. , Mu James , Dohm G. Lynis
Published: June 2004

An acute bout of exercise increases muscle GLUT4 mRNA in mice, and denervation decreases GLUT4 mRNA. AMP-activated protein kinase (AMPK) activity in skeletal muscle is also increased by exercise, and GLUT4 mRNA is increased in mouse skeletal muscle after treatment with AMPK activator 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside(AICAR). These findings suggest that AMPK activation might be responsible for the increase in GLUT4 mRNA expression in response to exercise. To investigate the role of AMPK in GLUT4 regulation in response to exercise and denervation, transgenic mice with a mutated AMPK α-subunit (dominant negative; AMPK-DN) were studied. GLUT4 did not increase in AMPK-DN mice that were treated with AICAR, demonstrating that muscle AMPK is inactive. Exercise (two 3-h bouts of treadmill running separated by 1 h of rest) increased GLUT4 mRNA in both wild-type and AMPK-DN mice. Likewise, denervation decreased GLUT4 mRNA in both wild-type and AMPK-DN mice. GLUT4 mRNA was also increased by AICAR treatment in both the innervated and denervated muscles. These data demonstrate that AMPK is not required for the response of GLUT4 mRNA to exercise and denervation.
Cold-induced PGC-1α expression modulates muscle glucose uptake through an insulin receptor/Akt-independent, AMPK-dependent pathway
Authors: Oliveira Rachel L. G. S. , Ueno Mirian , de Souza Cláudio T. , Pereira-da-Silva Márcio , Gasparetti Alessandra L. , Bezzera Rosangela M. N. , Alberici Luciane C. , Vercesi Aníbal E. , Saad Mario J. A. , Velloso Lício A.
Published: June 2004

Peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) participates in control of expression of genes involved in adaptive thermogenesis, muscle fiber type differentiation, and fuel homeostasis. The objective of the present study was to evaluate the participation of cold-induced PGC-1α expression in muscle fiber type-specific activity of proteins that belong to the insulin-signaling pathway. Rats were exposed to 4°C for 4 days and acutely treated with insulin in the presence or absence of an antisense oligonucleotide to PGC-1α. Cold exposure promoted a significant increase of PGC-1α and uncoupling protein-3 protein expression in type I and type II fibers of gastrocnemius muscle. In addition, cold exposure led to higher glucose uptake during a hyperinsulinemic clamp, which was accompanied by higher expression and membrane localization of GLUT4 in both muscle fiber types. Cold exposure promoted significantly lower insulin-induced tyrosine phosphorylation of the insulin receptor (IR) and Ser473phosphorylation of acute transforming retrovirus thymoma (Akt) and an insulin-independent increase of Thr172phosphorylation of adenosine 5′-monophosphate-activated protein kinase (AMPK). Inhibition of PGC-1α expression in cold-exposed rats by antisense oligonucleotide treatment diminished glucose clearance rates during a hyperinsulinemic clamp and reduced expression and membrane localization of GLUT4. Reduction of PGC-1α expression resulted in no modification of insulin-induced tyrosine phosphorylation of the IR and Ser473phosphorylation of Akt. Finally, reduction of PGC-1α resulted in lower Thr172phosphorylation of AMPK. Thus cold-induced hyperexpression of PGC-1α participates in control of skeletal muscle glucose uptake through a mechanism that controls GLUT4 expression and subcellular localization independent of the IR and Akt activities but dependent on AMPK.
Regulation of full-length and truncated growth hormone (GH) receptor by GH in tissues oflit/litor bovine GH transgenic mice
Authors: Iida Keiji , del Rincon Juan P. , Kim Dong-Sun , Itoh Emina , Coschigano Karen T. , Kopchick John J. , Thorner Michael O.
Published: June 2004

Two truncated isoforms of growth hormone (GH) receptor (GHR) were identified in mice and in humans. The proteins encoded by these isoforms lack most of the intracellular domain of the GHR and inhibit GH action in a dominant negative fashion. We have quantified the mRNAs encoding the GHR isoforms in mouse tissues by use of real-time RT-PCR and examined the effect of GH excess or deficiency on regulation of mRNA levels of the GHR isoforms in vivo. In the liver, the truncated GHR mRNAs (mGHR-282 and mGHR-280) were 0.5 and <0.1%, respectively, the level of full-length GHR (mGHR-fl). In skeletal muscle, the values were 2–3 and 0.1–0.5% of mGHR-fl, respectively, and in subcutaneous fat, the values were 3–5 and 0.1–0.5% of mGHR-fl, respectively. The bovine GH transgenic mice showed a significant increase of mGHR-fl in liver but a significant decrease in skeletal muscle, with no difference in subcutaneous fat when compared with control mice. The lit/lit mice showed a significant decrease of mGHR-fl in liver, no difference of mGHR-fl in muscle, and a significant increase of mGHR-fl in subcutaneous fat when compared with lit/+ mice. The mRNA of mGHR-282 was regulated in parallel with mGHR-fl in all tissues of all mice examined, whereas that of mGHR-280 was not changed in either GH-excess or GH-deficient states. In conclusion, two truncated isoforms of GHR mRNAs were detected in liver, skeletal muscle, and subcutaneous fat of mice. The ratio of GHR-tr to GHR-fl mRNA was tissue specific and not affected by chronic excess or deficiency of GH.
Critical role of vitamin D in sulfate homeostasis: regulation of the sodium-sulfate cotransporter by 1,25-dihydroxyvitamin D3
Authors: Bolt Merry J. G. , Liu Wenhua , Qiao Guilin , Kong Juan , Zheng Wei , Krausz Thomas , Cs-Szabo Gabriella , Sitrin Michael D. , Li Yan Chun
Published: June 2004

As the fourth most abundant anion in the body, sulfate plays an essential role in numerous physiological processes. One key protein involved in transcellular transport of sulfate is the sodium-sulfate cotransporter NaSi-1, and previous studies suggest that vitamin D modulates sulfate homeostasis by regulating NaSi-1 expression. In the present study, we found that, in mice lacking the vitamin D receptor (VDR), NaSi-1 expression in the kidney was reduced by 72% but intestinal NaSi-1 levels remained unchanged. In connection with these findings, urinary sulfate excretion was increased by 42% whereas serum sulfate concentration was reduced by 50% in VDR knockout mice. Moreover, levels of hepatic glutathione and skeletal sulfated proteoglycans were also reduced by 18 and 45%, respectively, in the mutant mice. Similar results were observed in VDR knockout mice after their blood ionized calcium levels and rachitic bone phenotype were normalized by dietary means, indicating that vitamin D regulation of NaSi-1 expression and sulfate metabolism is independent of its role in calcium metabolism. Treatment of wild-type mice with 1,25-dihydroxyvitamin D3or vitamin D analog markedly stimulated renal NaSi-1 mRNA expression. These data provide strong in vivo evidence that vitamin D plays a critical role in sulfate homeostasis. However, the observation that serum sulfate and skeletal proteoglycan levels in normocalcemic VDR knockout mice remained low in the absence of rickets and osteomalacia suggests that the contribution of sulfate deficiency to development of rickets and osteomalacia is minimal.
Na+-dependent neutral amino acid transporters A, ASC, and N of the blood-brain barrier: mechanisms for neutral amino acid removal
Authors: O'Kane Robyn L. , Viña Juan R. , Simpson Ian , Hawkins Richard A.
Published: June 2004

Four Na+-dependent transporters of neutral amino acids (NAA) are known to exist in the abluminal membranes (brain side) of the blood-brain barrier (BBB). This article describes the kinetic characteristics of systems A, ASC, and N that, together with the recently described Na+-dependent system for large NAA (Na+-LNAA), provide a basis for understanding the functional organization of the BBB. The data demonstrate that system A is voltage dependent (3 positive charges accompany each molecule of substrate). Systems ASC and N are not voltage dependent. Each NAA is a putative substrate for at least one system, and several NAA are transported by as many as three. System A transports Pro, Ala, His, Asn, Ser, and Gln; system ASC transports Ser, Gly, Met, Val, Leu, Ile, Cys, and Thr; system N transports Gln, His, Ser, and Asn; Na+-LNAA transports Leu, Ile, Val, Trp, Tyr, Phe, Met, Ala, His, Thr, and Gly. Together, these four systems have the capability to actively transfer every naturally occurring NAA from the extracellular fluid (ECF) to endothelial cells and thence to the circulation. The existence of facilitative transport for NAA (L1) on both membranes provides the brain access to essential NAA. The presence of Na+-dependent carriers on the abluminal membrane provides a mechanism by which NAA concentrations in the ECF of brain are maintained at ∼10% of those of the plasma.
Modeling of lipid and protein depletion during total starvation
Authors: Caloin Michel
Published: June 2004

This study presents a model describing lipid and protein depletion of an individual facing total starvation. The model distinguishes two compartments of body mass: a metabolic compartment and a structural compartment. It is considered that the lipids and the proteins of the metabolic compartment ensure the totality of physiological functions. The main assumptions of the model lie in the definitions of lipid mass and protein mass of the metabolic compartment, which are related to total lipid mass and total body mass, respectively. Under these assumptions, for a given individual, the ratio of lipid and protein utilization rates is proportional to the adiposity. The model accounts for the protein sparing observed at high adiposity levels and enables us to discuss the individual's survival in relation to the levels of lipid and protein depletion. The time course of changes in lipid and protein depletion rates can be calculated by introducing the energy expenditure of the individual. In simulations, it was assumed that specific energy expenditure was constant during starvation and that mortality occurred at a critical level of protein depletion. The most characteristic results derived from these simulations concern the kinetics of protein depletion, which depend markedly on initial adiposity. Accordingly, in obese subjects, the rate of protein losses remains fairly constant during fasting, whereas it increases from the onset of the fast in lean subjects, in agreement with experimental observations. In the model, protein and lipid depletion rates are both proportional to energy expenditure, which needs to be confirmed from complementary data.
Intramyocellular lipid content in type 2 diabetes patients compared with overweight sedentary men and highly trained endurance athletes
Authors: van Loon Luc J. C. , Koopman René , Manders Ralph , van der Weegen Walter , van Kranenburg Gerrit P. , Keizer Hans A.
Published: June 2004

Recent evidence suggests that intramyocellular lipid (IMCL) accretion is associated with obesity and the development of insulin resistance and/or type 2 diabetes. However, trained endurance athletes are markedly insulin sensitive, despite an elevated mixed muscle lipid content. In an effort to explain this metabolic paradox, we compared muscle fiber type-specific IMCL storage between populations known to have elevated IMCL deposits. Immunofluorescence microscopy was performed on muscle biopsies obtained from eight highly trained endurance athletes, eight type 2 diabetes patients, and eight overweight, sedentary men after an overnight fast. Mixed muscle lipid content was substantially greater in the endurance athletes (4.0 ± 0.4% area lipid stained) compared with the diabetes patients and the overweight men (2.3 ± 0.4 and 2.2 ± 0.5%, respectively). More than 40% of the greater mixed muscle lipid content was attributed to a higher proportion type I muscle fibers (62 ± 8 vs. 38 ± 3 and 33 ± 7%, respectively), which contained 2.8 ± 0.3-fold more lipid than the type II fibers. The remaining difference was explained by a significantly greater IMCL content in the type I muscle fibers of the trained athletes. Differences in IMCL content between groups or fiber types were accounted for by differences in lipid droplet density, not lipid droplet size. IMCL distribution showed an exponential increase in lipid content from the central region toward the sarcolemma, which was similar between groups and fiber types. In conclusion, IMCL contents can be substantially greater in trained endurance athletes compared with overweight and/or type 2 diabetes patients. Because structural characteristics and intramyocellular distribution of lipid aggregates seem to be similar between groups, we conclude that elevated IMCL deposits are unlikely to be directly responsible for inducing insulin resistance.
Combined ingestion of protein and carbohydrate improves protein balance during ultra-endurance exercise
Authors: Koopman René , Pannemans Daphne L. E. , Jeukendrup Asker E. , Gijsen Annemie P. , Senden Joan M. G. , Halliday David , Saris Wim H. M. , van Loon Luc J. C. , Wagenmakers Anton J. M.
Published: June 2004

The aims of this study were to compare different tracer methods to assess whole body protein turnover during 6 h of prolonged endurance exercise when carbohydrate was ingested throughout the exercise period and to investigate whether addition of protein can improve protein balance. Eight endurance-trained athletes were studied on two different occasions at rest (4 h), during 6 h of exercise at 50% of maximal O2uptake (in sequential order: 2.5 h of cycling, 1 h of running, and 2.5 h of cycling), and during subsequent recovery (4 h). Subjects ingested carbohydrate (CHO trial; 0.7 g CHO·kg−1·h−1) or carbohydrate/protein beverages (CHO + PRO trial; 0.7 g CHO·kg−1·h−1and 0.25 g PRO·kg−1·h−1) at 30-min intervals during the entire study. Whole body protein metabolism was determined by infusion of l-[1-13C]leucine, l-[2H5]phenylalanine, and [15N2]urea tracers with sampling of blood and expired breath. Leucine oxidation increased from rest to exercise [27 ± 2.5 vs. 74 ± 8.8 (CHO) and 85 ± 9.5 vs. 200 ± 16.3 mg protein·kg−1·h−1(CHO + PRO), P < 0.05], whereas phenylalanine oxidation and urea production did not increase with exercise. Whole body protein balance during exercise with carbohydrate ingestion was negative (−74 ± 8.8, −17 ± 1.1, and −72 ± 5.7 mg protein·kg−1·h−1) when l-[1-13C]leucine, l-[2H5]phenylalanine, and [15N2]urea, respectively, were used as tracers. Addition of protein to the carbohydrate drinks resulted in a positive or less-negative protein balance (−32 ± 16.3, 165 ± 4.6, and 151 ± 13.4 mg protein·kg−1·h−1) when l-[1-13C]leucine, l-[2H5]phenylalanine, and [15N2]urea, respectively, were used as tracers. We conclude that, even during 6 h of exhaustive exercise in trained athletes using carbohydrate supplements, net protein oxidation does not increase compared with the resting state and/or postexercise recovery. Combined ingestion of protein and carbohydrate improves net protein balance at rest as well as during exercise and postexercise recovery.
V-type ATPase is involved in biogenesis of GLUT4 vesicles
Authors: Malikova Marina , Shi Jun , Kandror Konstantin V.
Published: June 2004

Proton pumps participate in several aspects of endocytic protein trafficking. However, their involvement specifically in the GLUT4 pathway has been a matter of great controversy. Here, we report that incubation of 3T3-L1 adipocytes with specific inhibitors of V-type ATPase, concanamycin A and bafilomycin A1, inhibits insulin-regulated glucose transport and results in accumulation of GLUT4 in heavy, rapidly sedimenting intracellular membranes. Correspondingly, the amount of small responsive GLUT4 vesicles in concanamycin A- and bafilomycin A1-treated cells is decreased. We conclude that these drugs block translocation of GLUT4 in adipose cells by inhibiting formation of small insulin-responsive vesicles on donor intracellular membranes. At the same time, proton pump inhibitors do not affect insulin-dependent translocation of preexisting vesicles or GLUT4 sorting in recycling endosomes. On the contrary, wortmannin acutely inhibits insulin-dependent translocation of the preexisting vesicles but has no effect on vesicle formation.
Insulin stimulates fatty acid transport by regulating expression of FAT/CD36 but not FABPpm
Authors: Chabowski Adrian , Coort Susan L. M. , Calles-Escandon Jorge , Tandon Narendra N. , Glatz Jan F. C. , Luiken Joost J. F. P. , Bonen Arend
Published: June 2004

Because insulin has been shown to stimulate long-chain fatty acid (LCFA) esterification in skeletal muscle and cardiac myocytes, we investigated whether insulin increased the rate of LCFA transport by altering the expression and the subcellular distribution of the fatty acid transporters FAT/CD36 and FABPpm. In cardiac myocytes, insulin very rapidly increased the expression of FAT/CD36 protein in a time- and dose-dependent manner. During a 2-h period, insulin (10 nM) increased cardiac myocyte FAT/CD36 protein by 25% after 60 min and attained a maximum after 90–120 min (+40–50%). There was a dose-dependent relationship between insulin (10−12to 10−7M) and FAT/CD36 expression. The half-maximal increase in FAT/CD36 protein occurred at 0.5 × 10−9M insulin, and the maximal increase occurred at 10−9to 10−8M insulin (+40–50%). There were similar insulin-induced increments in FAT/CD36 protein in cardiac myocytes (+43%) and in Langendorff-perfused hearts (+32%). In contrast to FAT/CD36, insulin did not alter the expression of FABPpm protein in either cardiac myocytes or the perfused heart. By use of specific inhibitors of insulin-signaling pathways, it was shown that insulin-induced expression of FAT/CD36 occurred via the PI 3-kinase/Akt insulin-signaling pathway. Subcellular fractionation of cardiac myocytes revealed that insulin not only increased the expression of FAT/CD36, but this hormone also targeted some of the FAT/CD36 to the plasma membrane while concomitantly lowering the intracellular depot of FAT/CD36. At the functional level, the insulin-induced increase in FAT/CD36 protein resulted in an increased rate of palmitate transport into giant vesicles (+34%), which paralleled the increase in plasmalemmal FAT/CD36 (+29%). The present studies have shown that insulin regulates protein expression of FAT/CD36, but not FABPpm, via the PI 3-kinase/Akt insulin-signaling pathway.
Neuropeptide Y antagonism reduces reflex cutaneous vasoconstriction in humans
Authors: Stephens Dan P. , Saad Adham R. , Bennett Lee Ann T. , Kosiba Wojciech A. , Johnson John M.
Published: June 2004

Previous studies have provided evidence of a non-noradrenergic contributor to reflex cutaneous vasoconstriction in humans but did not identify the transmitter responsible. To test whether neuropeptide Y (NPY) has a role, in two series of experiments we slowly reduced whole body skin temperature (TSK) from 34.5 to 31.7°C. In protocol 1, Ringer solution and the NPY receptor antagonist BIBP-3226 alone were delivered intradermally via microdialysis. In protocol 2, yohimbine plus propranolol (Yoh + Pro), Yoh + Pro in combination with BIBP-3226, and Ringer solution were delivered to antagonize locally the vasomotor effects of NPY and norepinephrine. Blood flow was measured by laser Doppler flowmetry (LDF). Mean arterial blood pressure (MAP) was monitored at the finger (Finapres). In protocol 1, cutaneous vascular conductance (CVC) fell by 45%, to 55.1 ± 5.6% of baseline at control sites ( P < 0.05). At BIBP-3226-treated sites, CVC fell by 34.1% to 65.9 ± 5.0% ( P < 0.05; P < 0.05 between sites). In protocol 2, during body cooling, CVC at control sites fell by 32.6%, to 67.4 ± 4.3% of baseline; at sites treated with Yoh + Pro, CVC fell by 18.7%, to 81.3 ± 4.4% of baseline ( P < 0.05 vs. baseline; P < 0.05 vs. control) and did not fall significantly at sites treated with BIBP-3226 + Yoh + Pro ( P > 0.05; P < 0.05 vs. other sites). After cooling, exogenous norepinephrine induced vasoconstriction at control sites ( P < 0.05) but not at sites treated with Yoh + Pro + BIBP-3226 ( P > 0.05). These results indicate that NPY participates in sympathetically mediated cutaneous vasoconstriction in humans during whole body cooling.
Increased cell death in osteopontin-deficient cardiac fibroblasts occurs by a caspase-3-independent pathway
Authors: Zohar Ron , Zhu Baoqian , Liu Peter , Sodek Jaro , McCulloch C. A.
Published: June 2004

Reperfusion-induced oxidative injury to the myocardium promotes activation and proliferation of cardiac fibroblasts and repair by scar formation. Osteopontin (OPN) is a proinflammatory cytokine that is upregulated after reperfusion. To determine whether OPN enhances fibroblast survival after exposure to oxidants, cardiac fibroblasts from wild-type (WT) or OPN-null (OPN−/−) mice were treated in vitro with H2O2to model reperfusion injury. Within 1 h, membrane permeability to propidium iodide (PI) was increased from 5 to 60% in OPN−/−cells but was increased to only 20% in WT cells. In contrast, after 1–8 h of treatment with H2O2, the percent of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)-stained cells was more than twofold higher in WT than OPN−/−cells. Electron microscopy of WT cells treated with H2O2showed chromatin condensation, nuclear fragmentation, and cytoplasmic and nuclear shrinkage, which are consistent with apoptosis. In contrast, H2O2-treated OPN−/−cardiac fibroblasts exhibited cell and nuclear swelling and membrane disruption that are indicative of cell necrosis. Treatment of OPN−/−and WT cells with a cell-permeable caspase-3 inhibitor reduced the percentage of TUNEL staining by more than fourfold in WT cells but decreased staining in OPN−/−cells by ∼30%. Although the percentage of PI-permeable WT cells was reduced threefold, the percent of PI-permeable OPN−/−cells was not altered. Restoration of OPN expression in OPN−/−fibroblasts reduced the percentage of PI-permeable cells but not TUNEL staining after H2O2treatment. Thus H2O2-induced cell death in OPN-deficient cardiac fibroblasts is mediated by a caspase-3-independent, necrotic pathway. We suggest that the increased expression of OPN in the myocardium after reperfusion may promote fibrosis by protecting cardiac fibroblasts from cell death.
Expression of cardiac troponin T with COOH-terminal truncation accelerates cross-bridge interaction kinetics in mouse myocardium
Authors: Stelzer Julian E. , Patel Jitandrakumar R. , Olsson M. Charlotte , Fitzsimons Daniel P. , Leinwand Leslie A. , Moss Richard L.
Published: June 2004

Transgenic mice expressing an allele of cardiac troponin T (cTnT) with a COOH-terminal truncation (cTnTtrunc) exhibit severe diastolic and mild systolic dysfunction. We tested the hypothesis that contractile dysfunction in myocardium expressing low levels of cTnTtrunc (i.e., <5%) is due to slowed cross-bridge kinetics and reduced thin filament activation as a consequence of reduced cross-bridge binding. We measured the Ca2+ sensitivity of force development [pCa for half-maximal tension generation (pCa50)] and the rate constant of force redevelopment ( ktr) in cTnTtrunc and wild-type (WT) skinned myocardium both in the absence and in the presence of a strong-binding, non-force-generating derivative of myosin subfragment-1 (NEM-S1). Compared with WT mice, cTnTtrunc mice exhibited greater pCa50, reduced steepness of the force-pCa relationship [Hill coefficient ( nH)], and faster ktr at submaximal Ca2+ concentration ([Ca2+]), i.e., reduced activation dependence of ktr. Treatment with NEM-S1 elicited similar increases in pCa50 and similar reductions in nH in WT and cTnTtrunc myocardium but elicited greater increases in ktr at submaximal activation in cTnTtrunc myocardium. Contrary to our initial hypothesis, cTnTtrunc appears to enhance thin filament activation in myocardium, which is manifested as significant increases in Ca2+-activated force and the rate of cross-bridge attachment at submaximal [Ca2+]. Although these mechanisms would not be expected to depress systolic function per se in cTnTtrunc hearts, they would account for slowed rates of myocardial relaxation during early diastole.